3D Kirchhoff depth migration algorithm: A new scalable approach for parallelization on multicore CPU based cluster

NASA Astrophysics Data System (ADS)

Rastogi, Richa; Londhe, Ashutosh; Srivastava, Abhishek; Sirasala, Kirannmayi M.; Khonde, Kiran

2017-03-01

In this article, a new scalable 3D Kirchhoff depth migration algorithm is presented on state of the art multicore CPU based cluster. Parallelization of 3D Kirchhoff depth migration is challenging due to its high demand of compute time, memory, storage and I/O along with the need of their effective management. The most resource intensive modules of the algorithm are traveltime calculations and migration summation which exhibit an inherent trade off between compute time and other resources. The parallelization strategy of the algorithm largely depends on the storage of calculated traveltimes and its feeding mechanism to the migration process. The presented work is an extension of our previous work, wherein a 3D Kirchhoff depth migration application for multicore CPU based parallel system had been developed. Recently, we have worked on improving parallel performance of this application by re-designing the parallelization approach. The new algorithm is capable to efficiently migrate both prestack and poststack 3D data. It exhibits flexibility for migrating large number of traces within the available node memory and with minimal requirement of storage, I/O and inter-node communication. The resultant application is tested using 3D Overthrust data on PARAM Yuva II, which is a Xeon E5-2670 based multicore CPU cluster with 16 cores/node and 64 GB shared memory. Parallel performance of the algorithm is studied using different numerical experiments and the scalability results show striking improvement over its previous version. An impressive 49.05X speedup with 76.64% efficiency is achieved for 3D prestack data and 32.00X speedup with 50.00% efficiency for 3D poststack data, using 64 nodes. The results also demonstrate the effectiveness and robustness of the improved algorithm with high scalability and efficiency on a multicore CPU cluster.

Uncertainty analysis of depth predictions from seismic reflection data using Bayesian statistics

NASA Astrophysics Data System (ADS)

Michelioudakis, Dimitrios G.; Hobbs, Richard W.; Caiado, Camila C. S.

2018-06-01

Estimating the depths of target horizons from seismic reflection data is an important task in exploration geophysics. To constrain these depths we need a reliable and accurate velocity model. Here, we build an optimum 2-D seismic reflection data processing flow focused on pre-stack deghosting filters and velocity model building and apply Bayesian methods, including Gaussian process emulation and Bayesian History Matching, to estimate the uncertainties of the depths of key horizons near the Deep Sea Drilling Project (DSDP) borehole 258 (DSDP-258) located in the Mentelle Basin, southwest of Australia, and compare the results with the drilled core from that well. Following this strategy, the tie between the modelled and observed depths from DSDP-258 core was in accordance with the ±2σ posterior credibility intervals and predictions for depths to key horizons were made for the two new drill sites, adjacent to the existing borehole of the area. The probabilistic analysis allowed us to generate multiple realizations of pre-stack depth migrated images, these can be directly used to better constrain interpretation and identify potential risk at drill sites. The method will be applied to constrain the drilling targets for the upcoming International Ocean Discovery Program, leg 369.

Processing and attenuation of noise in deep seismic-reflection data from the Gulf of Maine

USGS Publications Warehouse

Hutchinson, D.R.; Lee, M.W.

1989-01-01

The U.S. Geological Survey deep crustal studies reflection profile across the Gulf of Maine off southeastern New England was affected by three sources of noise: side-scattered noise, multiples, and 20-Hz whale sounds. The special processing most effective in minimizing this noise consisted of a combination of frequency-wavenumber (F-K) filtering, predictive deconvolution, and spectral whitening, each applied in the shot domain (prestack). Application of the F-K filter to remove side-scatter noise in the poststack domain resulted in a much poorer quality profile. The prestack noise suppression processing techniques resulted in a reflection profile with good signal-to-noise ratios and reliable strong reflections, especially at depths equivalent to the lower crust (24-34 km). Certain geologic features, such as a buried rift basin and a crustal fault are resolved much better within the upper crust after this processing. Finite difference migration of these data using realistic velocities produced excellent results. Migration was essential to distinguish between abundant dipping and subhorizontal reflections in the lower crust as well as to show an essentially transparent upper mantle. ?? 1989 Kluwer Academic Publishers.

Angle-domain common-image gathers from anisotropic Gaussian beam migration and its application to anisotropy-induced imaging errors analysis

NASA Astrophysics Data System (ADS)

Han, Jianguang; Wang, Yun; Yu, Changqing; Chen, Peng

2017-02-01

An approach for extracting angle-domain common-image gathers (ADCIGs) from anisotropic Gaussian beam prestack depth migration (GB-PSDM) is presented in this paper. The propagation angle is calculated in the process of migration using the real-value traveltime information of Gaussian beam. Based on the above, we further investigate the effects of anisotropy on GB-PSDM, where the corresponding ADCIGs are extracted to assess the quality of migration images. The test results of the VTI syncline model and the TTI thrust sheet model show that anisotropic parameters ɛ, δ, and tilt angle 𝜃, have a great influence on the accuracy of the migrated image in anisotropic media, and ignoring any one of them will cause obvious imaging errors. The anisotropic GB-PSDM with the true anisotropic parameters can obtain more accurate seismic images of subsurface structures in anisotropic media.

Reverse time migration by Krylov subspace reduced order modeling

NASA Astrophysics Data System (ADS)

Basir, Hadi Mahdavi; Javaherian, Abdolrahim; Shomali, Zaher Hossein; Firouz-Abadi, Roohollah Dehghani; Gholamy, Shaban Ali

2018-04-01

Imaging is a key step in seismic data processing. To date, a myriad of advanced pre-stack depth migration approaches have been developed; however, reverse time migration (RTM) is still considered as the high-end imaging algorithm. The main limitations associated with the performance cost of reverse time migration are the intensive computation of the forward and backward simulations, time consumption, and memory allocation related to imaging condition. Based on the reduced order modeling, we proposed an algorithm, which can be adapted to all the aforementioned factors. Our proposed method benefit from Krylov subspaces method to compute certain mode shapes of the velocity model computed by as an orthogonal base of reduced order modeling. Reverse time migration by reduced order modeling is helpful concerning the highly parallel computation and strongly reduces the memory requirement of reverse time migration. The synthetic model results showed that suggested method can decrease the computational costs of reverse time migration by several orders of magnitudes, compared with reverse time migration by finite element method.

Imaging Shallow Salt With 3D Refraction Migration

NASA Astrophysics Data System (ADS)

Vanschuyver, C. J.; Hilterman, F. J.

2005-05-01

In offshore West Africa, numerous salt walls are within 200 m of sea level. Because of the shallowness of these salt walls, reflections from the salt top can be difficult to map, making it impossible to build an accurate velocity model for subsequent pre-stack depth migration. An accurate definition of salt boundaries is critical to any depth model where salt is present. Unfortunately, when a salt body is very shallow, the reflection from the upper interface can be obscured due to large offsets between the source and near receivers and also due to the interference from multiples and other near-surface noise events. A new method is described using 3D migration of the refraction waveforms which is simplified because of several constraints in the model definition. The azimuth and dip of the refractor is found by imaging with Kirchhoff theory. A Kirchhoff migration is performed where the traveltime values are adjusted to use the CMP refraction traveltime equation. I assume the sediment and salt velocities to be known such that once the image time is specified, then the dip and azimuth of the refraction path can be found. The resulting 3D refraction migrations are in excellent depth agreement with available well control. In addition, the refraction migration time picks of deeper salt events are in agreement with time picks of the same events on the reflection migration.

Pre-stack depth migration in an anisotropic crystalline environment at the COSC-1 borehole, central Sweden

NASA Astrophysics Data System (ADS)

Simon, H.; Buske, S.; Hedin, P.; Juhlin, C.; Krauß, F.; Giese, R.

2017-12-01

The Scandinavian Caledonides represent a well preserved deeply eroded Palaeozoic orogen, formed by the collision of the two palaeocontinents Baltica and Laurentia. Today, after four hundred million years of erosion along with uplift and extension during the opening of the North Atlantic Ocean, the geological structure in central western Sweden consists of allochthons, underlying autochthonous units, and the shallow west-dipping décollement that separates the two and is associated with Cambrian black shales. The project Collisional Orogeny in the Scandinavian Caledonides (COSC) aims to investigate these structures and their physical conditions with two approximately 2.5 km deep fully cored scientific boreholes in central Sweden. The first borehole COSC-1 was successfully drilled in 2014 and obtained a continuous cored section through the highly deformed Seve Nappe. After drilling was completed several surface and borehole based seismic experiments were conducted. The data from a multi-azimuthal walkaway VSP in combination with long offset surface lines was used to image the structures in the vicinity of the borehole. Clear differences in vertical and horizontal P-wave velocities made it necessary to also account for anisotropy. The resulting VTI velocity model provides the basis for subsequent application of seismic imaging approaches. An anisotropic eikonal solver was used to calculate the traveltimes needed for Kirchhoff-based pre-stack depth migration methods. The resulting images were compared to the corresponding migration results based on an isotropic velocity model. Both images are dominated by strong and clear reflections, however, they appear more continuous and better focused in the anisotropic result. Most of the dominant reflections originate below the bottom of the borehole and therefore they are probably situated within the Precambrian basement. They might represent dolerite intrusions or deformation zones of Caledonian or pre-Caledonian age.

A new scheme for velocity analysis and imaging of diffractions

NASA Astrophysics Data System (ADS)

Lin, Peng; Peng, Suping; Zhao, Jingtao; Cui, Xiaoqin; Du, Wenfeng

2018-06-01

Seismic diffractions are the responses of small-scale inhomogeneities or discontinuous geological features, which play a vital role in the exploitation and development of oil and gas reservoirs. However, diffractions are generally ignored and considered as interference noise in conventional data processing. In this paper, a new scheme for velocity analysis and imaging of seismic diffractions is proposed. Two steps compose of this scheme in our application. First, the plane-wave destruction method is used to separate diffractions from specular reflections in the prestack domain. Second, in order to accurately estimate migration velocity of the diffractions, the time-domain dip-angle gathers are derived from a Kirchhoff-based angle prestack time migration using separated diffractions. Diffraction events appear flat in the dip-angle gathers when imaged above the diffraction point with selected accurate migration velocity for diffractions. The selected migration velocity helps to produce the desired prestack imaging of diffractions. Synthetic and field examples are applied to test the validity of the new scheme. The diffraction imaging results indicate that the proposed scheme for velocity analysis and imaging of diffractions can provide more detailed information about small-scale geologic features for seismic interpretation.

Fallon, Nevada FORGE Seismic Reflection Profiles

DOE Data Explorer

Blankenship, Doug; Faulds, James; Queen, John; Fortuna, Mark

2018-02-01

Newly reprocessed Naval Air Station Fallon (1994) seismic lines: pre-stack depth migrations, with interpretations to support the Fallon FORGE (Phase 2B) 3D Geologic model. Data along seven profiles (>100 km of total profile length) through and adjacent to the Fallon site were re-processed. The most up-to-date, industry-tested seismic processing techniques were utilized to improve the signal strength and coherency in the sedimentary, volcanic, and Mesozoic crystalline basement sections, in conjunction with fault diffractions in order to improve the identification and definition of faults within the study area.

Steep-dip seismic imaging of the shallow San Andreas Fault near Parkfield

USGS Publications Warehouse

Hole, J.A.; Catchings, R.D.; St. Clair, K.C.; Rymer, M.J.; Okaya, D.A.; Carney, B.J.

2001-01-01

Seismic reflection and refraction images illuminate the San Andreas Fault to a depth of 1 kilometer. The prestack depth-migrated reflection image contains near-vertical reflections aligned with the active fault trace. The fault is vertical in the upper 0.5 kilometer, then dips about 70° to the southwest to at least 1 kilometer subsurface. This dip reconciles the difference between the computed locations of earthquakes and the surface fault trace. The seismic velocity cross section shows strong lateral variations. Relatively low velocity (10 to 30%), high electrical conductivity, and low density indicate a 1-kilometer-wide vertical wedge of porous sediment or fractured rock immediately southwest of the active fault trace.

Wide-angle Marine Seismic Refraction Imaging of Vertical Faults: Pre-Stack Turning Wave Migrations of Synthetic Data and Implications for Survey Design

NASA Astrophysics Data System (ADS)

Miller, N. C.; Lizarralde, D.; McGuire, J.; Hole, J. A.

2006-12-01

We consider methodologies, including survey design and processing algorithms, which are best suited to imaging vertical reflectors in oceanic crust using marine seismic techniques. The ability to image the reflectivity structure of transform faults as a function of depth, for example, may provide new insights into what controls seismicity along these plate boundaries. Turning-wave migration has been used with success to image vertical faults on land. With synthetic datasets we find that this approach has unique difficulties in the deep ocean. The fault-reflected crustal refraction phase (Pg-r) typically used in pre-stack migrations is difficult to isolate in marine seismic data. An "imagable" Pg-r is only observed in a time window between the first arrivals and arrivals from the sediments and the thick, slow water layer at offsets beyond ~25 km. Ocean- bottom seismometers (OBSs), as opposed to a long surface streamer, must be used to acquire data suitable for crustal-scale vertical imaging. The critical distance for Moho reflections (PmP) in oceanic crust is also ~25 km, thus Pg-r and PmP-r are observed with very little separation, and the fault-reflected mantle refraction (Pn-r) arrives prior to Pg-r as the observation window opens with increased OBS-to-fault distance. This situation presents difficulties for "first-arrival" based Kirchoff migration approaches and suggests that wave- equation approaches, which in theory can image all three phases simultaneously, may be more suitable for vertical imaging in oceanic crust. We will present a comparison of these approaches as applied to a synthetic dataset generated from realistic, stochastic velocity models. We will assess their suitability, the migration artifacts unique to the deep ocean, and the ideal instrument layout for such an experiment.

Splay fault branching from the Hikurangi subduction shear zone: Implications for slow slip and fluid flow

NASA Astrophysics Data System (ADS)

Plaza-Faverola, A.; Henrys, S.; Pecher, I.; Wallace, L.; Klaeschen, D.

2016-12-01

Prestack depth migration data across the Hikurangi margin, East Coast of the North Island, New Zealand, are used to derive subducting slab geometry, upper crustal structure, and seismic velocities resolved to ˜14 km depth. We investigate the potential relationship between the crustal architecture, fluid migration, and short-term geodetically determined slow slip events. The subduction interface is a shallow dipping thrust at <7 km depth near the trench and steps down to 14 km depth along an ˜18 km long ramp, beneath Porangahau Ridge. This apparent step in the décollement is associated with splay fault branching and coincides with a zone of maximum slip (90 mm) inferred on the subduction interface during slow slip events in June and July 2011. A low-velocity zone beneath the plate interface, updip of the plate interface ramp, is interpreted as fluid-rich overpressured sediments capped with a low permeability condensed layer of chalk and interbedded mudstones. Fluid-rich sediments have been imbricated by splay faults in a region that coincides with the step down in the décollement from the top of subducting sediments to the oceanic crust and contribute to spatial variation in frictional properties of the plate interface that may promote slow slip behavior in the region. Further, transient fluid migration along splay faults at Porangahau Ridge may signify stress changes during slow slip.

Imaging of 2-D multichannel land seismic data using an iterative inversion-migration scheme, Naga Thrust and Fold Belt, Assam, India

NASA Astrophysics Data System (ADS)

Jaiswal, Priyank; Dasgupta, Rahul

2010-05-01

We demonstrate that imaging of 2-D multichannel land seismic data can be effectively accomplished by a combination of reflection traveltime tomography and pre-stack depth migration (PSDM); we refer to the combined process as "the unified imaging". The unified imaging comprises cyclic runs of joint reflection and direct arrival inversion and pre-stack depth migration. From one cycle to another, both the inversion and the migration provide mutual feedbacks that are guided by the geological interpretation. The unified imaging is implemented in two broad stages. The first stage is similar to the conventional imaging except that it involves a significant use of velocity model from the inversion of the direct arrivals for both datuming and stacking velocity analysis. The first stage ends with an initial interval velocity model (from the stacking velocity analysis) and a corresponding depth migrated image. The second stage updates the velocity model and the depth image from the first stage in a cyclic manner; a single cycle comprises a single run of reflection traveltime inversion followed by PSDM. Interfaces used in the inversion are interpretations of the PSDM image in the previous cycle and the velocity model used in PSDM is from the joint inversion in the current cycle. Additionally in every cycle interpreted horizons in the stacked data are inverted as zero-offset reflections for constraining the interfaces; the velocity model is maintained stationary for the zero-offset inversion. A congruency factor, j, which measures the discrepancy between interfaces from the interpretation of the PSDM image and their corresponding counterparts from the inversion of the zero-offset reflections within assigned uncertainties, is computed in every cycle. A value of unity for jindicates that images from both the inversion and the migration are equivalent; at this point the unified imaging is said to have converged and is halted. We apply the unified imaging to 2-D multichannel seismic data from the Naga Thrust and Fold Belt (NTFB), India, were several exploratory wells in the last decade targeting sub-thrust leads in the footwall have failed. This failure is speculatively due to incorrect depth images which are in turn attributed to incorrect velocity models that are developed using conventional methods. The 2-D seismic data in this study is acquired perpendicular to the trend of the NTFB where the outcropping hanging wall has a topographic culmination. The acquisition style is split-spread with 30 m shot and receiver spacing and a nominal fold of 90. The data are recorded with a sample interval of 2 ms. Overall the data have a moderate signal-to-noise ratio and a broad frequency bandwidth of 8-80 Hz. The seismic line contains the failed exploratory well in the central part. The final results from unified imaging (both the depth image and the corresponding velocity model) suggest presence of a triangle zone, which was previously undiscovered. Conventional imaging had falsely portrayed the triangle zone as structural high which was interpreted as an anticline. As a result, the exploratory well, meant to target the anticline, met with pressure changes which were neither expected nor explained. The unified imaging results not only explain the observations in the well but also reveal new leads in the region. The velocity model from unified imaging was also found to be adequate for frequency-domain full-waveform imaging of the hanging wall. Results from waveform inversion are further corroborated by the geological interpretation of the exploratory well.

Image of the Moho across the continent-ocean transition, US east coast

DOE Office of Scientific and Technical Information (OSTI.GOV)

Holbrook, W.S.; Purdy, G.M.; Reiter, E.C.

1992-03-01

Strong wide-angle reflections from the Moho were recorded by ocean-bottom seismic instruments during the 1988 Carolina Trough multichannel seismic experiment, in an area where the Moho is difficult to detect with vertical-incidence seismic data. Prestack depth migration of these reflections has enabled the construction of a seismic image of the Moho across the continent-ocean transition of a sedimented passive margin. The Moho rises across the margin at a slope of 10{degree}-12{degree}, from a depth of about 33 km beneath the continental shelf to 20 km beneath the outer rise. This zone of crustal thinning defines a distinct, 60-70-km-wide continent-ocean transitionmore » zone. The authors interpret the Moho in the Carolina Trough as a Jurassic feature, formed by magmatic intrusion and underplating during the rifting of Pangea.« less

Uncertainty analysis of depth predictions from seismic reflection data using Bayesian statistics

NASA Astrophysics Data System (ADS)

Michelioudakis, Dimitrios G.; Hobbs, Richard W.; Caiado, Camila C. S.

2018-03-01

Estimating the depths of target horizons from seismic reflection data is an important task in exploration geophysics. To constrain these depths we need a reliable and accurate velocity model. Here, we build an optimum 2D seismic reflection data processing flow focused on pre - stack deghosting filters and velocity model building and apply Bayesian methods, including Gaussian process emulation and Bayesian History Matching (BHM), to estimate the uncertainties of the depths of key horizons near the borehole DSDP-258 located in the Mentelle Basin, south west of Australia, and compare the results with the drilled core from that well. Following this strategy, the tie between the modelled and observed depths from DSDP-258 core was in accordance with the ± 2σ posterior credibility intervals and predictions for depths to key horizons were made for the two new drill sites, adjacent the existing borehole of the area. The probabilistic analysis allowed us to generate multiple realizations of pre-stack depth migrated images, these can be directly used to better constrain interpretation and identify potential risk at drill sites. The method will be applied to constrain the drilling targets for the upcoming International Ocean Discovery Program (IODP), leg 369.

Seismic Imaging and Characterization of Bright Spots in the West Bohemia Seismic Zone (Germany and Czech Republic)

NASA Astrophysics Data System (ADS)

Alexandrakis, C.; Schreiter, L.; Hlousek, F.; Jusri, T.; Buske, S.

2017-12-01

In crystalline environments, imaging faults, layer boundaries and small scale structures is challenging due to the complex geometry of the structures themselves and the influence of the hardrock environment on the seismic wavefield. Optimally designed active seismic surveys and careful processing can produce a clear image of the subsurface structures. However, if little is known about the local geology and tectonic state of the area, the imaged reflections can be difficult to interpret. This is the case in the West Bohemia Seismic Zone, located along the border of Germany and Czech Republic. This geodynamically active area is spotted with springs and gas vents, and frequently experiences low magnitude seismic swarms. The most active region is located in the Cheb basin and coincides with the junction of a northwest trending fault with a north-south trending shear zone, making for a structurally complex hardrock setting. In the early 1990s, two long-offset reflection seismic profiles were collected along the boundary of the Cheb basin: MVE-90 along the northern edge, and 9HR-91 in the east. These profiles were recently reprocessed using Kirchhoff PreStack Depth Migration, revealing high amplitude reflections, or bright spots, that correlate to nearby seismicity. Several studies have hypothesized that the 9HR-91 bright spots image a fluid trap, where mantle-sourced fluids accumulate, thereby facilitating slip on the faults and triggering the swarms. However, the exact nature of the bright spots remains an open question. They may be a change in lithology and/or porosity, an infilled vein or an impermeable fault. We aim to answer this question by first using Coherency-Based PreStack Depth Migration to produce detailed images of the bright spots. We then forward model the waveforms guided by the reflection coefficients in order to derive rock-physical parameters. Finally, the best-fitting models are interpreted in terms of their possible relationship to the West Bohemia swarms.

A method of directly extracting multiwave angle-domain common-image gathers

NASA Astrophysics Data System (ADS)

Han, Jianguang; Wang, Yun

2017-10-01

Angle-domain common-image gathers (ADCIGs) can provide an effective way for migration velocity analysis and amplitude versus angle analysis in oil-gas seismic exploration. On the basis of multi-component Gaussian beam prestack depth migration (GB-PSDM), an alternative method of directly extracting multiwave ADCIGs is presented in this paper. We first introduce multi-component GB-PSDM, where a wavefield separation is proceeded to obtain the separated PP- and PS-wave seismic records before migration imaging for multiwave seismic data. Then, the principle of extracting PP- and PS-ADCIGs using GB-PSDM is presented. The propagation angle can be obtained using the real-value travel time of Gaussian beam in the course of GB-PSDM, which can be used to calculate the incidence and reflection angles. Two kinds of ADCIGs can be extracted for the PS-wave, one of which is P-wave incidence ADCIGs and the other one is S-wave reflection ADCIGs. In this paper, we use the incident angle to plot the ADCIGs for both PP- and PS-waves. Finally, tests of synthetic examples show that the method introduced here is accurate and effective.

Interpretation of a 3D Seismic-Reflection Volume in the Basin and Range, Hawthorne, Nevada

NASA Astrophysics Data System (ADS)

Louie, J. N.; Kell, A. M.; Pullammanappallil, S.; Oldow, J. S.; Sabin, A.; Lazaro, M.

2009-12-01

A collaborative effort by the Great Basin Center for Geothermal Energy at the University of Nevada, Reno, and Optim Inc. of Reno has interpreted a 3d seismic data set recorded by the U.S. Navy Geothermal Programs Office (GPO) at the Hawthorne Army Depot, Nevada. The 3d survey incorporated about 20 NNW-striking lines covering an area of approximately 3 by 10 km. The survey covered an alluvial area below the eastern flank of the Wassuk Range. In the reflection volume the most prominent events are interpreted to be the base of Quaternary alluvium, the Quaternary Wassuk Range-front normal fault zone, and sequences of intercalated Tertiary volcanic flows and sediments. Such a data set is rare in the Basin and Range. Our interpretation reveals structural and stratigraphic details that form a basis for rapid development of the geothermal-energy resources underlying the Depot. We interpret a map of the time-elevation of the Wassuk Range fault and its associated splays and basin-ward step faults. The range-front fault is the deepest, and its isochron map provides essentially a map of "economic basement" under the prospect area. There are three faults that are the most readily picked through vertical sections. The fault reflections show an uncertainty in the time-depth that we can interpret for them of 50 to 200 ms, due to the over-migrated appearance of the processing contractor’s prestack time-migrated data set. Proper assessment of velocities for mitigating the migration artifacts through prestack depth migration is not possible from this data set alone, as the offsets are not long enough for sufficiently deep velocity tomography. The three faults we interpreted appear as gradients in potential-field maps. In addition, the southern boundary of a major Tertiary graben may be seen within the volume as the northward termination of the strong reflections from older Tertiary volcanics. Using a transparent volume view across the survey gives a view of the volcanics in full, providing a clear picture of prominent structures. Potential drill targets and areas of development are defined within the data volume by the intersections of the fault surfaces with the tracked, strong stratigraphic reflections. Target volumes for drilling and development are defined by the intersections of the faults and bright-spot stratigraphy, and their uncertainty bounds. There are a few such intersections present within the 3d volume. Analyzing seismic attributes gives the opportunity to identify characteristics common in geothermal environments.

Fracture identification based on remote detection acoustic reflection logging

NASA Astrophysics Data System (ADS)

Zhang, Gong; Li, Ning; Guo, Hong-Wei; Wu, Hong-Liang; Luo, Chao

2015-12-01

Fracture identification is important for the evaluation of carbonate reservoirs. However, conventional logging equipment has small depth of investigation and cannot detect rock fractures more than three meters away from the borehole. Remote acoustic logging uses phase-controlled array-transmitting and long sound probes that increase the depth of investigation. The interpretation of logging data with respect to fractures is typically guided by practical experience rather than theory and is often ambiguous. We use remote acoustic reflection logging data and high-order finite-difference approximations in the forward modeling and prestack reverse-time migration to image fractures. First, we perform forward modeling of the fracture responses as a function of the fracture-borehole wall distance, aperture, and dip angle. Second, we extract the energy intensity within the imaging area to determine whether the fracture can be identified as the formation velocity is varied. Finally, we evaluate the effect of the fracture-borehole distance, fracture aperture, and dip angle on fracture identification.

Correlation Between Geological Stuctures and Gas Hydrate amount Offshore the South Shetland Island — Preliminary Results

NASA Astrophysics Data System (ADS)

Loreto, M. F.; Tinivella, U.; Accaino, F.; Giustiniani, M.

2010-05-01

Sediments of the accretionary prism, present along the continental margin of the Peninsula Antarctica SW of Elephant Island, are filled by gas hydrates as evidenced by a strong BSR. A multidisciplinary geophysical dataset, represented by seismic data, multibeam, chirp profiles, CTD and core samples, was acquired during three oceanographic cruises. The estimation of gas hydrate and free gas concentrations is based on the P-wave velocity analysis. In order to extract a detailed and reliable velocity field, we have developed and optimized a procedure that includes the pre-stack depth migration to determine, iteratively and with a layer stripping approach method, the velocity field and the depth-migrated seismic section. The final velocity field is then translated in terms of gas hydrate and free gas amounts by using theoretical approaches. Several seismic sections have been processed in the investigated area. The final 2D velocity sections have been translated in gas-phase concentration sections, considering the gas distribution within sediments both uniformly and patchly distributed. The free gas layer is locally present and, consequently, the base of the free gas reflector was identified only in some lines or part of them. The hydrate layer shows important lateral variations of hydrate concentration in correspondence of geological features, such as faults and folds. The intense fluid migration along faults and different fluid accumulation in correspondence of geological structures can control the gas hydrate concentration and modify the geothermal field in the surrounding area.

Imaging Faults in Carbonate Reservoir using Full Waveform Inversion and Reverse Time Migration of Walkaway VSP Data

NASA Astrophysics Data System (ADS)

Takam Takougang, E. M.; Bouzidi, Y.

2016-12-01

Multi-offset Vertical Seismic Profile (walkaway VSP) data were collected in an oil field located in a shallow water environment dominated by carbonate rocks, offshore the United Arab Emirates. The purpose of the survey was to provide structural information of the reservoir, around and away from the borehole. Five parallel lines were collected using an air gun at 25 m shot interval and 4 m source depth. A typical recording tool with 20 receivers spaced every 15.1 m, and located in a deviated borehole with an angle varying between 0 and 24 degree from the vertical direction, was used to record the data. The recording tool was deployed at different depths for each line, from 521 m to 2742 m depth. Smaller offsets were used for shallow receivers and larger offsets for deeper receivers. The lines merged to form the input dataset for waveform tomography. The total length of the combined lines was 9 km, containing 1344 shots and 100 receivers in the borehole located half-way down. Acoustic full waveform inversion was applied in the frequency domain to derive a high resolution velocity model. The final velocity model derived after the inversion using the frequencies 5-40 Hz, showed good correlation with velocities estimated from vertical incidence VSP and sonic log, confirming the success of the inversion. The velocity model showed anomalous low values in areas that correlate with known location of hydrocarbon reservoir. Pre-stack depth Reverse time migration was then applied using the final velocity model from waveform inversion and the up-going wavefield from the input data. The final estimated source signature from waveform inversion was used as input source for reverse time migration. To save computational memory and time, every 3 shots were used during reverse time migration and the data were low-pass filtered to 30 Hz. Migration artifacts were attenuated using a second order derivative filter. The final migration image shows a good correlation with the waveform tomography velocity model, and highlights a complex network of faults in the reservoir, that could be useful in understanding fluid and hydrocarbon movements. This study shows that the combination of full waveform tomography and reverse time migration can provide high resolution images that can enhance interpretation and characterization of oil reservoirs.

Seismic depth imaging of sequence boundaries beneath the New Jersey shelf

NASA Astrophysics Data System (ADS)

Riedel, M.; Reiche, S.; Aßhoff, K.; Buske, S.

2018-06-01

Numerical modelling of fluid flow and transport processes relies on a well-constrained geological model, which is usually provided by seismic reflection surveys. In the New Jersey shelf area a large number of 2D seismic profiles provide an extensive database for constructing a reliable geological model. However, for the purpose of modelling groundwater flow, the seismic data need to be depth-converted which is usually accomplished using complementary data from borehole logs. Due to the limited availability of such data in the New Jersey shelf, we propose a two-stage processing strategy with particular emphasis on reflection tomography and pre-stack depth imaging. We apply this workflow to a seismic section crossing the entire New Jersey shelf. Due to the tomography-based velocity modelling, the processing flow does not depend on the availability of borehole logging data. Nonetheless, we validate our results by comparing the migrated depths of selected geological horizons to borehole core data from the IODP expedition 313 drill sites, located at three positions along our seismic line. The comparison yields that in the top 450 m of the migrated section, most of the selected reflectors were positioned with an accuracy close to the seismic resolution limit (≈ 4 m) for that data. For deeper layers the accuracy still remains within one seismic wavelength for the majority of the tested horizons. These results demonstrate that the processed seismic data provide a reliable basis for constructing a hydrogeological model. Furthermore, the proposed workflow can be applied to other seismic profiles in the New Jersey shelf, which will lead to an even better constrained model.

Practical Implementation of Prestack Kirchhoff Time Migration on a General Purpose Graphics Processing Unit

NASA Astrophysics Data System (ADS)

Liu, Guofeng; Li, Chun

2016-08-01

In this study, we present a practical implementation of prestack Kirchhoff time migration (PSTM) on a general purpose graphic processing unit. First, we consider the three main optimizations of the PSTM GPU code, i.e., designing a configuration based on a reasonable execution, using the texture memory for velocity interpolation, and the application of an intrinsic function in device code. This approach can achieve a speedup of nearly 45 times on a NVIDIA GTX 680 GPU compared with CPU code when a larger imaging space is used, where the PSTM output is a common reflection point that is gathered as I[ nx][ ny][ nh][ nt] in matrix format. However, this method requires more memory space so the limited imaging space cannot fully exploit the GPU sources. To overcome this problem, we designed a PSTM scheme with multi-GPUs for imaging different seismic data on different GPUs using an offset value. This process can achieve the peak speedup of GPU PSTM code and it greatly increases the efficiency of the calculations, but without changing the imaging result.

Seismic stratigraphy and deformational styles of the offshore Cyrenaica (Libya) and bordering Mediterranean Ridge

NASA Astrophysics Data System (ADS)

Yem, Lionel Mbida; Camera, Laurent; Mascle, Jean; Ribodetti, Alessandra

2011-04-01

Off northwest Libya the Cyrenaica foreland basin domain and its Pan-African continental crust, which constitute the African promontory, are overthrusted by the Mediterranean Ridge Complex. The thrust belt contact and its seismic stratigraphy have been analysed using pre-stack depth-migrated multichannel seismic (MCS) lines recorded during the MEDISIS survey (2002). The geometry and sedimentary distribution analysis through the wedge-top depocentres allow reconstruction of schematic cross-sections of the tectono-sedimentary wedge that includes two major thrust sequences separated by an apparently poorly deformed transition zone. Based on time-space variation of several piggyback basins, we propose that these thrust sequences relate to distinct phases of shortening. (1) A first event, which probably occurred just prior to the Messinian crisis in latest Miocene (Tortonian times?) and (2) A second event, that has finally led to the present-day overthrusting of the Mediterranean Ridge over the Libyan continental slope.

Acoustic Reverse Time Migration of the Cascadia Subduction Zone Dataset

NASA Astrophysics Data System (ADS)

Jia, L.; Mallick, S.

2017-12-01

Reverse time migration (RTM) is a wave-equation based migration method, which provides more accurate images than ray-based migration methods, especially for the structures in deep areas, making it an effective tool for imaging the subduction plate boundary. In this work, we extend the work of Fortin (2015) and applied acoustic finite-element RTM on the Cascadia Subduction Zone (CSZ) dataset. The dataset was acquired by Cascadia Open-Access Seismic Transects (COAST) program, targeting the megathrust in the central Cascadia subduction zone (Figure 1). The data on a 2D seismic reflection line that crosses the Juan de Fuca/North American subduction boundary off Washington (Line 5) were pre-processed and worked through Kirchhoff prestack depth migration (PSDM). Figure 2 compares the depth image of Line 5 of the CSZ data using Kirchhoff PSDM (top) and RTM (bottom). In both images, the subducting plate is indicated with yellow arrows. Notice that the RTM image is much superior to the PSDM image by several aspects. First, the plate boundary appears to be much more continuous in the RTM image than the PSDM image. Second, the RTM image indicates the subducting plate is relatively smooth on the seaward (west) side between 0-50 km. Within the deformation front of the accretionary prism (50-80 km), the RTM image shows substantial roughness in the subducting plate. These features are not clear in the PSDM image. Third, the RTM image shows a lot of fine structures below the subducting plate which are almost absent in the PSDM image. Finally, the RTM image indicates that the plate is gently dipping within the undeformed sediment (0-50 km) and becomes steeply dipping beyond 50 km as it enters the deformation front of the accretionary prism. Although the same conclusion could be drawn from the discontinuous plate boundary imaged by PSDM, RTM results are far more convincing than the PSDM.

Characterization of intrabasin faulting and deformation for earthquake hazards in southern Utah Valley, Utah, from high-resolution seismic imaging

USGS Publications Warehouse

Stephenson, William J.; Odum, Jack K.; Williams, Robert A.; McBride, John H.; Tomlinson, Iris

2012-01-01

We conducted active and passive seismic imaging investigations along a 5.6-km-long, east–west transect ending at the mapped trace of the Wasatch fault in southern Utah Valley. Using two-dimensional (2D) P-wave seismic reflection data, we imaged basin deformation and faulting to a depth of 1.4 km and developed a detailed interval velocity model for prestack depth migration and 2D ground-motion simulations. Passive-source microtremor data acquired at two sites along the seismic reflection transect resolve S-wave velocities of approximately 200 m/s at the surface to about 900 m/s at 160 m depth and confirm a substantial thickening of low-velocity material westward into the valley. From the P-wave reflection profile, we interpret shallow (100–600 m) bedrock deformation extending from the surface trace of the Wasatch fault to roughly 1.5 km west into the valley. The bedrock deformation is caused by multiple interpreted fault splays displacing fault blocks downward to the west of the range front. Further west in the valley, the P-wave data reveal subhorizontal horizons from approximately 90 to 900 m depth that vary in thickness and whose dip increases with depth eastward toward the Wasatch fault. Another inferred fault about 4 km west of the mapped Wasatch fault displaces horizons within the valley to as shallow as 100 m depth. The overall deformational pattern imaged in our data is consistent with the Wasatch fault migrating eastward through time and with the abandonment of earlier synextensional faults, as part of the evolution of an inferred 20-km-wide half-graben structure within Utah Valley. Finite-difference 2D modeling suggests the imaged subsurface basin geometry can cause fourfold variation in peak ground velocity over distances of 300 m.

Cordilleran front range structural features in northwest Montana interpreted from vintage seismic reflection data

NASA Astrophysics Data System (ADS)

Porter, Mason C.; Rutherford, Bradley S.; Speece, Marvin A.; Mosolf, Jesse G.

2016-04-01

Industry seismic reflection data spanning the Rocky Mountain Cordillera front ranges of northwest Montana were reprocessed and interpreted in this study. Five seismic profiles represent 160 km of deep reflection data collected in 1983 that span the eastern Purcell anticlinorium, Rocky Mountain Trench (RMT), Rocky Mountain Basal Décollement (RMBD), and Lewis thrust. The data were reprocessed using modern techniques including refraction statics, pre-stack time migration (PSTM), and pre- and post-stack depth migration. Results indicate the RMBD is 8-13 km below the Earth's surface and dip 3-10° west. Evidence for the autochthonous Mesoproterozoic Belt and basal Cambrian rocks beneath the RMBD is present in all of the profiles and appears to extend east of the RMT. The Lewis thrust was identified in the seismic profiles and appears to sole into the RMBD east of the RMT. The RMT fault system has a dip displacement of 3-4 km and forms a half graben filled with 1 km of unconsolidated Tertiary sedimentary deposits. The RMT and adjacent Flathead fault systems are interpreted to be structurally linked and may represent a synthetic, en echelon fault system.

Structure of the California Coast Ranges and San Andreas Fault at SAFOD from seismic waveform inversion and reflection imaging

USGS Publications Warehouse

Bleibinhaus, F.; Hole, J.A.; Ryberg, T.; Fuis, G.S.

2007-01-01

A seismic reflection and refraction survey across the San Andreas Fault (SAF) near Parkfield provides a detailed characterization of crustal structure across the location of the San Andreas Fault Observatory at Depth (SAFOD). Steep-dip prestack migration and frequency domain acoustic waveform tomography were applied to obtain highly resolved images of the upper 5 km of the crust for 15 km on either side of the SAF. The resulting velocity model constrains the top of the Salinian granite with great detail. Steep-dip reflection seismic images show several strong-amplitude vertical reflectors in the uppermost crust near SAFOD that define an ???2-km-wide zone comprising the main SAF and two or more local faults. Another prominent subvertical reflector at 2-4 km depth ???9 km to the northeast of the SAF marks the boundary between the Franciscan terrane and the Great Valley Sequence. A deep seismic section of low resolution shows several reflectors in the Salinian crust west of the SAF. Two horizontal reflectors around 10 km depth correlate with strains of seismicity observed along-strike of the SAF. They represent midcrustal shear zones partially decoupling the ductile lower crust from the brittle upper crust. The deepest reflections from ???25 km depth are interpreted as crust-mantle boundary. Copyright 2007 by the American Geophysical Union.

Anatomy of the western Java plate interface from depth-migrated seismic images

NASA Astrophysics Data System (ADS)

Kopp, H.; Hindle, D.; Klaeschen, D.; Oncken, O.; Reichert, C.; Scholl, D.

2009-11-01

Newly pre-stack depth-migrated seismic images resolve the structural details of the western Java forearc and plate interface. The structural segmentation of the forearc into discrete mechanical domains correlates with distinct deformation styles. Approximately 2/3 of the trench sediment fill is detached and incorporated into frontal prism imbricates, while the floor sequence is underthrust beneath the décollement. Western Java, however, differs markedly from margins such as Nankai or Barbados, where a uniform, continuous décollement reflector has been imaged. In our study area, the plate interface reveals a spatially irregular, nonlinear pattern characterized by the morphological relief of subducted seamounts and thicker than average patches of underthrust sediment. The underthrust sediment is associated with a low velocity zone as determined from wide-angle data. Active underplating is not resolved, but likely contributes to the uplift of the large bivergent wedge that constitutes the forearc high. Our profile is located 100 km west of the 2006 Java tsunami earthquake. The heterogeneous décollement zone regulates the friction behavior of the shallow subduction environment where the earthquake occurred. The alternating pattern of enhanced frictional contact zones associated with oceanic basement relief and weak material patches of underthrust sediment influences seismic coupling and possibly contributed to the heterogeneous slip distribution. Our seismic images resolve a steeply dipping splay fault, which originates at the décollement and terminates at the sea floor and which potentially contributes to tsunami generation during co-seismic activity.

Anatomy of the western Java plate interface from depth-migrated seismic images

USGS Publications Warehouse

Kopp, H.; Hindle, D.; Klaeschen, D.; Oncken, O.; Reichert, C.; Scholl, D.

2009-01-01

Newly pre-stack depth-migrated seismic images resolve the structural details of the western Java forearc and plate interface. The structural segmentation of the forearc into discrete mechanical domains correlates with distinct deformation styles. Approximately 2/3 of the trench sediment fill is detached and incorporated into frontal prism imbricates, while the floor sequence is underthrust beneath the d??collement. Western Java, however, differs markedly from margins such as Nankai or Barbados, where a uniform, continuous d??collement reflector has been imaged. In our study area, the plate interface reveals a spatially irregular, nonlinear pattern characterized by the morphological relief of subducted seamounts and thicker than average patches of underthrust sediment. The underthrust sediment is associated with a low velocity zone as determined from wide-angle data. Active underplating is not resolved, but likely contributes to the uplift of the large bivergent wedge that constitutes the forearc high. Our profile is located 100 km west of the 2006 Java tsunami earthquake. The heterogeneous d??collement zone regulates the friction behavior of the shallow subduction environment where the earthquake occurred. The alternating pattern of enhanced frictional contact zones associated with oceanic basement relief and weak material patches of underthrust sediment influences seismic coupling and possibly contributed to the heterogeneous slip distribution. Our seismic images resolve a steeply dipping splay fault, which originates at the d??collement and terminates at the sea floor and which potentially contributes to tsunami generation during co-seismic activity. ?? 2009 Elsevier B.V.

Multi-Mode 3D Kirchhoff Migration of Receiver Functions at Continental Scale With Applications to USArray

NASA Astrophysics Data System (ADS)

Millet, F.; Bodin, T.; Rondenay, S.

2017-12-01

The teleseismic scattered seismic wavefield contains valuable information about heterogeneities and discontinuities inside the Earth. By using fast Receiver Function (RF) migration techniques such as classic Common Conversion Point (CCP) stacks, one can easily interpret structural features down to a few hundred kilometers in the mantle. However, strong simplifying 1D assumptions limit the scope of these methods to structures that are relatively planar and sub-horizontal at local-to-regional scales, such as the Lithosphere-Asthenosphere Boundary and the Mantle Transition Zone discontinuities. Other more robust 2D and 2.5D methods rely on fewer assumptions but require considerable, sometime prohibitive, computation time. Following the ideas of Cheng (2017), we have implemented a simple fully 3D Prestack Kirchhoff RF migration scheme which uses the FM3D fast Eikonal solver to compute travel times and scattering angles. The method accounts for 3D elastic point scattering and includes free surface multiples, resulting in enhanced images of laterally varying dipping structures, such as subducted slabs. The method is tested for subduction structures using 2.5D synthetics generated with Raysum and 3D synthetics generated with specfem3D. Results show that dip angles, depths and lateral variations can be recovered almost perfectly. The approach is ideally suited for applications to dense regional datasets, including those collected across the Cascadia and Alaska subduction zones by USArray.

Traveltime computation and imaging from rugged topography in 3D TTI media

NASA Astrophysics Data System (ADS)

Liu, Shaoyong; Wang, Huazhong; Yang, Qinyong; Fang, Wubao

2014-02-01

Foothill areas with rugged topography are of great potential for oil and gas seismic exploration, but subsurface imaging in these areas is very challenging. Seismic acquisition with larger offset and wider azimuth is necessary for seismic imaging in complex areas. However, the scale anisotropy in this case must be taken into account. To generalize the pre-stack depth migration (PSDM) to 3D transversely isotropic media with vertical symmetry axes (VTI) and tilted symmetry axes (TTI) from rugged topography, a new dynamic programming approach for the first-arrival traveltime computation method is proposed. The first-arrival time on every uniform mesh point is calculated based on Fermat's principle with simple calculus techniques and a systematic mapping scheme. In order to calculate the minimum traveltime, a set of nonlinear equations is solved on each mesh point, where the group velocity is determined by the group angle. Based on the new first-arrival time calculation method, the corresponding PSDM and migration velocity analysis workflow for 3D anisotropic media from rugged surface is developed. Numerical tests demonstrate that the proposed traveltime calculation method is effective in both VTI and TTI media. The migration results for 3D field data show that it is necessary to choose a smooth datum to remove the high wavenumber move-out components for PSDM with rugged topography and take anisotropy into account to achieve better images.

Generalized migration in frequency-wavenumber domain (MGF-K) in anisotropic media

NASA Astrophysics Data System (ADS)

Kostecki, Andrzej; Półchłopek, Anna

2013-06-01

In this paper, the background of MGF-K migration in dual domain (wavenumber-frequency K-F and space-time) in anisotropic media is presented. Algorithms for poststack (zero-offset) and prestack migration are based on downward extrapolation of acoustic wavefield by shift-phase with correction filter for lateral variability of medium's parameters. In anisotropic media, the vertical wavenumber was determined from full elastic wavefield equations for two dimensional (2D) tilted transverse isotropy (TTI) model. The method was tested on a synthetic wavefield for TTI anticlinal model (zero-offset section) and on strongly inhomogeneous vertical transverse isotropy (VTI) Marmousi model. In both cases, the proper imaging of assumed media was obtained.

Seismic reflection images of the central California coast ranges and the tremor region of the San-Andreas-Fault system near Cholame

NASA Astrophysics Data System (ADS)

Gutjahr, Stine; Buske, Stefan

2010-05-01

The SJ-6 seismic reflection profile was acquired in 1981 over a distance of about 180 km from Morro Bay to the Sierra Nevada foothills in South Central California. The profile runs across several prominent fault systems, e.g. the Riconada Fault (RF) in the western part as well as the San Andreas Fault (SAF) in its central part. The latter includes the region of increased tremor activity near Cholame, as reported recently by several authors. We have recorrelated the original field data to 26 seconds two-way traveltime which allows us to image the crust and uppermost mantle down to approximately 40 km depth. A 3D tomographic velocity model derived from local earthquake data (Thurber et al., 2006) was used and Kirchhoff prestack depth migration as well as Fresnel-Volume-Migration were applied to the data set. Both imaging techniques were implemented in 3D by taking into account the true shot and receiver locations. The imaged subsurface volume itself was divided into three separate parts to correctly account for the significant kink in the profile line near the SAF. The most prominent features in the resulting images are areas of high reflectivity down to 30 km depth in particular in the central western part of the profile corresponding to the Salinian Block between the RF and the SAF. In the southwestern part strong reflectors can be identified that are dipping slightly to the northeast at depths of around 15-25 km. The eastern part consists of west dipping sediments at depths of 2-10 km that form a syncline structure in the west of the eastern part. The resulting images are compared to existing interpretations (Trehu and Wheeler, 1987; Wentworth and Zoback, 1989; Bloch et al., 1993) and discussed in the frame of the suggested tremor locations in that area.

Development of Vertical Cable Seismic System for Hydrothermal Deposit Survey (2) - Feasibility Study

NASA Astrophysics Data System (ADS)

Asakawa, E.; Murakami, F.; Sekino, Y.; Okamoto, T.; Mikada, H.; Takekawa, J.; Shimura, T.

2010-12-01

In 2009, Ministry of Education, Culture, Sports, Science and Technology(MEXT) started the survey system development for Hydrothermal deposit. We proposed the Vertical Cable Seismic (VCS), the reflection seismic survey with vertical cable above seabottom. VCS has the following advantages for hydrothermal deposit survey. . (1) VCS is an effective high-resolution 3D seismic survey within limited area. (2) It achieves high-resolution image because the sensors are closely located to the target. (3) It avoids the coupling problems between sensor and seabottom that cause serious damage of seismic data quality. (4) Various types of marine source are applicable with VCS such as sea-surface source (air gun, water gun etc.) , deep-towed or ocean bottom sources. (5) Autonomous recording system. Our first experiment of 2D/3D VCS surveys has been carried out in Lake Biwa, JAPAN. in November 2009. The 2D VCS data processing follows the walk-away VSP, including wave field separation and depth migration. The result gives clearer image than the conventional surface seismic. Prestack depth migration is applied to 3D data to obtain good quality 3D depth volume. Uncertainty of the source/receiver poisons in water causes the serious problem of the imaging. We used several transducer/transponder to estimate these positions. The VCS seismic records themselves can also provide sensor position using the first break of each trace and we calibrate the positions. We are currently developing the autonomous recording VCS system and planning the trial experiment in actual ocean to establish the way of deployment/recovery and the examine the position through the current flow in November, 2010. The second VCS survey will planned over the actual hydrothermal deposit with deep-towed source in February, 2011.

High resolution crustal image of South California Continental Borderland: Reverse time imaging including multiples

NASA Astrophysics Data System (ADS)

Bian, A.; Gantela, C.

2014-12-01

Strong multiples were observed in marine seismic data of Los Angeles Regional Seismic Experiment (LARSE).It is crucial to eliminate these multiples in conventional ray-based or one-way wave-equation based depth image methods. As long as multiples contain information of target zone along travelling path, it's possible to use them as signal, to improve the illumination coverage thus enhance the image quality of structural boundaries. Reverse time migration including multiples is a two-way wave-equation based prestack depth image method that uses both primaries and multiples to map structural boundaries. Several factors, including source wavelet, velocity model, back ground noise, data acquisition geometry and preprocessing workflow may influence the quality of image. The source wavelet is estimated from direct arrival of marine seismic data. Migration velocity model is derived from integrated model building workflow, and the sharp velocity interfaces near sea bottom needs to be preserved in order to generate multiples in the forward and backward propagation steps. The strong amplitude, low frequency marine back ground noise needs to be removed before the final imaging process. High resolution reverse time image sections of LARSE Lines 1 and Line 2 show five interfaces: depth of sea-bottom, base of sedimentary basins, top of Catalina Schist, a deep layer and a possible pluton boundary. Catalina Schist shows highs in the San Clemente ridge, Emery Knoll, Catalina Ridge, under Catalina Basin on both the lines, and a minor high under Avalon Knoll. The high of anticlinal fold in Line 1 is under the north edge of Emery Knoll and under the San Clemente fault zone. An area devoid of any reflection features are interpreted as sides of an igneous plume.

Identifying structural styles in Colombia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilson, W.P.; Van Nieuwenhuise, R.E.; Steuer, M.R.

1996-08-01

Much of our understanding of the Earth is from the study of surface geology and seismic, but many surface structures are responses to deformation which occurred below sedimentary layers. The practice within the petroleum industry is to use top-down processes of analyzing the surface to understand the subsurface, and observed surface structural styles tend to influence seismic interpretations. Yet many conditions which influenced the structural styles seen at the surface are different at depth. Since seismic is a time representation of the Earth, many interpretation pitfalls may exist within areas of complex geology. Also, its reliability decreases with depth andmore » with increasing geologic complexity. Forward modeling and pre-stack depth migration technologies are used to provide true depth images of the seismic data. Even with these advances in seismic imaging technology, the interpreter needs to incorporate additional data into the interpretation. Accurate structural identification requires the interpreter to integrate seismic with surface geology, remote sensing, gravity, magnetic data, geochemistry, fault-plane solutions from earthquakes, and regional tectonic studies. Incorporating these types of data into the interpretation will help us learn how basement is involved in the deformation of overlying sediments. A study of the Eastern Cordillera of Colombia shows the deformation to be dominantly transpressional in style. Euler deconvolution of the areomagnetic data shows a highly fractured basement, steep fault lineaments, en echelon structures, and complex fault patterns, all of which would be typical of wrench-type deformation. Available surface geology, regional studies, earthquake data, and forward modeling support this interpretation.« less

Subduction Zone Dewatering at the Southern End of New Zealand's Hikurangi Margin - Insights from 2D Seismic Tomography

NASA Astrophysics Data System (ADS)

Crutchley, G. J.; Klaeschen, D.

2016-12-01

The southern end of New Zealand's Hikurangi subduction margin is characterised by highly-oblique convergence as it makes a southward transition into a right-lateral transform plate boundary. Long-offset seismic data that cross part of the offshore portion of this transition zone give new insight into the nature of the margin. We have carried out two-dimensional pre-stack depth migrations with an iterative reflection tomography to update the velocity field on two seismic lines in this area. The depth-migrated sections show much-improved imaging of faulting within the wedge, and the seismic velocities themselves give clues about the distribution of gas and/or overpressured regions at the plate boundary and within the overlying wedge. A fascinating observation is a major splay fault that has been (or continues to be) a preferred dewatering pathway through the wedge, evidenced by a thermal anomaly that has left its mark on the overlying gas hydrate layer. Another interesting observation is a thick and laterally extensive low velocity zone beneath the subduction interface, which might have important implications for the long-term mechanical stability of the interface. Our on-going work on these data is focused on amplitude versus offset analysis in an attempt to better understand the nature of the subduction interface and also the shallower gas hydrate system. This study is an example of how distinct disturbances of the gas hydrate system can provide insight into subduction zone fluid flow processes that are important for understanding wedge stability and ultimately earthquake hazard.

New insights into the North Taranaki Basin from New Zealand's first broadband 3D survey

NASA Astrophysics Data System (ADS)

Uzcategui, Marjosbet; Francis, Malcolm; Kong, Wai Tin Vincent; Patenall, Richard; Fell, Dominic; Paxton, Andrea; Allen, Tristan

2016-06-01

The Taranaki Basin is the only hydrocarbon producing basin in New Zealand. The North Taranaki Basin has widespread two-dimensional (2D) seismic coverage and numerous wells that have not encountered commercial accumulations. This is attributed to the structural complexity in the central graben and the absence of necessary information to help understand the basin's evolution. An active petroleum system has been confirmed by hydrocarbon shows and non-commercial oil and gas discoveries (Karewa-1 and Kora-1). A broadband long offset three-dimensional (3D) seismic survey was acquired and processed by Schlumberger in 2013 to evaluate the hydrocarbon potential of the North Taranaki Basin. Innovative acquisition techniques were combined with advanced processing and imaging methods. Raypath distortions and depth uncertainty were significantly reduced by processing through tilted transverse isotropy (TTI) anisotropic Kirchhoff prestack depth migration with a geologically constrained velocity model. The survey provided the necessary information to understand the petroleum system and provide evidence for material hydrocarbon accumulations. In this investigation, we assessed the hydrocarbon potential of the North Taranaki Basin using the newly acquired data. 3D seismic interpretation and amplitude-versus-offset (AVO) analysis support the renewed potential of the basin and demonstrate effectiveness of these technologies that together can achieve encouraging results for hydrocarbon exploration.

Methane Hydrate Concentrations at GC955 and WR313 Drilling Sites in the Gulf of Mexico Determined from Seismic Prestack Waveform Inversion

NASA Astrophysics Data System (ADS)

Fortin, W.; Goldberg, D.; Küçük, H. M.

2016-12-01

Gas hydrates are naturally occurring compounds, which, at a molecular scale, are lattice structures of ice embedded with various gas molecules in the lattice voids. Volumetric estimates of associated hydrocarbons vary greatly due to the difficulty in remotely estimating hydrate concentrations in marine sediments but embedded hydrocarbon stores are thought to represent a significant portion of global deposits. The unstable nature of methane hydrates has been linked to submarine landslides and the subsequent release of large quantities of methane can accelerate global climate change. Understanding the details of gas hydrate systems is important for potential economic production and assessing natural hazards risks. Seismic reflection techniques are uniquely capable of detecting gas hydrates. Often, hydrate layers appear as bottom simulating reflectors (BSRs); however, BSRs are not present everywhere gas hydrates are known to occur. Using recently reprocessed prestack time migrated data and prestack waveform inversion (PWI) techniques, we produce velocity models at high vertical and horizontal resolution in order to investigate the presence of gas hydrates in the Gulf of Mexico. Coupling our PWI results with known velocity-property relationships and data from nearby well controls, we determine the viability of recently collected high-resolution seismic data and outline small-scale heterogeneities at GC955 and WR313. We outline where PWI techniques are capable of identifying gas hydrates in seismic reflection data where BSRs are not present.

Prestack Waveform Inversion and Well Log Examination at GC955 and WR313 in the Gulf of Mexico for Estimation of Methane Hydrate Concentrations

NASA Astrophysics Data System (ADS)

Fortin, W.; Goldberg, D.; Kucuk, H. M.

2017-12-01

Gas hydrates are naturally occurring compounds, which, at a molecular scale, are lattice structures of ice embedded with various gas molecules in the lattice voids. Volumetric estimates of associated hydrocarbons vary greatly due to the difficulty in remotely estimating hydrate concentrations in marine sediments but embedded hydrocarbon stores are thought to represent a significant portion of global deposits. Inherent hydrate instabilities obscure our understanding of and complicates processes related to resource extraction and hydrate response to disturbances in the local environment. Understanding the spatial extent and variability of hydrate deposits have important implications for potential economic production, climate change, and assessing natural hazards risks. Seismic reflection techniques are capable of determining the extent of gas hydrate deposits, often through the observation of bottom simulating reflectors (BSRs). However, BSRs are not present everywhere gas hydrates exist. Using high resolution prestack time migrated seismic data and prestack waveform inversion (PWI) we produce highly resolved velocity models and compare them to co-located well logs. Coupling our PWI results with velocity-porosity relationships and nearby well control, we map hydrate properties at GC955 and WR313. Integrating small scale heterogeneities and variations along the velocity model with in-situ measurements, we develop a workflow aimed to quantify hydrate concentrations observed in seismic data over large areas in great detail regardless of the existence of a BSR.

Common reflection point migration and velocity analysis for anisotropic media

NASA Astrophysics Data System (ADS)

Oropeza, Ernesto V.

An efficient Kirchhoff-style prestack depth migration, called 'parsimonious' migration was developed a decade ago for isotropic 2D and 3D media. The common-reflection point (CRP) migration velocity analysis (MVA) was developed later for isotropic media. The isotropic parsimonious migration produces incorrect images when the media is actually anisotropic. Similarly, isotropic CRP MVA produces incorrect inversions when the medium is anisotropic. In this study both parsimonious depth migration and common-reflection point migration velocity analysis are extended for application to 2D tilted transversely isotropic (TTI) media and illustrated with synthetic P-wave data. While the framework of isotropic parsimonious migration may be retained, the extension to TTI media requires redevelopment of each of the numerical components, including calculation of the phase and group velocity for TTI media, development of a new two-point anisotropic ray tracer, and substitution of an initial-angle and anisotropic shooting ray-trace algorithm to replace the isotropic one. The 2D model parameterization consists of Thomsen's parameters (Vpo, epsilon, delta) and the tilt angle of the symmetry axis of the TI medium. The parsimonious anisotropic migration algorithm is successfully applied to synthetic data from a TTI version of the Marmousi-2 model. The quality of the image improves by weighting the impulse response by the calculation of the anisotropic Fresnel radius. The accuracy and speed of this migration makes it useful for anisotropic velocity model building. The common-reflection point migration velocity analysis for TTI media for P-waves includes (and inverts for) Vpo, epsilon, and delta. The orientation of the anisotropic symmetry axis have to be constrained. If it constrained orthogonal to the layer bottom (as it conventionally is), it is estimated at each CRP and updated at each iteration without intermediate picking. The extension to TTI media requires development of a new inversion procedure to include Vpo, epsilon, and delta in the perturbations. The TTI CRP MVA is applied to a single layer to demonstrate its feasibility. Errors in the estimation of the orientation of the symmetry axis larger that 5 degrees affect the inversion of epsilon and delta while Vpo is less sensitive to this parameter. The TTI CRP MVA is also applied to a version of the TTI BP model by layer stripping so one group of CRPs are used do to inversion top to bottom, constraining the model parameter after each previous group of CRPs converges. Vpo, delta and the orientation of the anisotropic symmetry axis (constrained orthogonal to the local reflector orientation) are successfully inverted. epsilon is less well constrained by the small acquisition aperture in the data .

High-resolution seismic imaging of the Kevitsa mafic-ultramafic Cu-Ni-PGE hosted intrusion, northern Finland

NASA Astrophysics Data System (ADS)

Malehmir, Alireza; Koivisto, Emilia; Wjins, Chris; Tryggvason, Ari; Juhlin, Christopher

2014-05-01

Kevitsa, in northern Finland, is a large nickel/copper ore body hosted by a massive mafic-ultramafic intrusion with measured and indicated resources of 240 million tons (cutoff 0.1%) grading 0.30% Ni and 0.41% Cu. Mining started in 2012 with an open pit that will extend down to about 550-600 m depth. The expected mine life is more than 20 years. Numerous boreholes are available in the area, but the majority of them are shallow and do not provide a comprehensive understanding of the dimensions of the intrusion. However, a number of boreholes do penetrate the basal contact of the intrusion. Most of these are also shallow and concentrated at the edge of the intrusion. A better knowledge of the geometry of the intrusion would provide a framework for near-mine and deep exploration in the area, but also a better understanding of the geology. Exact mapping of the basal contact of the intrusion would also provide an exploration target for the contact-type mineralization that is often more massive and richer in Ni-Cu than the disseminated mineralization away from the contact. With the objective of better characterizing the intrusion, a series of 2D profiles were acquired followed by a 3D reflection survey that covered an area of about 3 km by 3 km. Even though the geology is complex and the seismic P-wave velocity ranges between 5 to 8 km/s, conventional processing results show gently- to steeply-dipping reflections from depths of approximately 2 km to as shallow as 100 m. Many of these reflections are interpreted to originate from either fault systems or internal magmatic layering within the Kevitsa main intrusion. Correlations between the 3D surface seismic data and VSP data, based upon time shifts or phase changes along the reflections, support the interpretation that numerous faults are imaged in the volume. Some of these faults cross the planned open-pit mine at depths of about 300-500 m, and it is, therefore, critical to map them for mine planning. The seismic 3D volume better represents the geology around the mine and in the vicinity of the known deposit, while the 2D seismic profiles were designed to provide information on larger-scale structures in the area. Both the 2D and 3D seismic data were used to create a 3D lithological and structural model of the entire complex. Information on the dimensions of the ore-bearing Kevitsa intrusion can be used for more effective exploration in the area. The base of the intrusion is particularly clear in the northern and western sectors of the seismic data. Toward the east, the base is mostly defined by disruption of the reflectors internal to the intrusion. Recent tests using prestack migration methods on the 3D data show partial improvements in the image, especially at shallow depths. 3D seismic tomography has also been performed and the results indicate low velocity zones crossing the open pit that can be interpreted as zones of weakness. Future studies will focus on using the tomography results as the input velocity field for prestack depth migration of the 3D data and also improving the 3D geological model of the study area. Acknowledgments: FQM, GTK, HiSeis and Vibrometric

Inverse-Ray Imaging of Gas Hydrates Along a MCS/OBS Profile at the Continental Slope Offshore SW Taiwan

NASA Astrophysics Data System (ADS)

Wang, T. K.; Chen, C.; Yang, B.; Lee, C.

2006-12-01

Prevalence of gas hydrates offshore SW Taiwan has been proposed due to lots of bottom-simulated reflectors (BSR) appeared on the seismic data. In this paper, we analyze a MCS/OBS profile with intensive BSR signals at the continental slope of the northern South China Sea. Firstly, MCS data with 160 channels collected by R/V Maurice-Ewing in September 1995 is re-processed through vertical velocity analysis, horizon velocity analysis, and prestack depth migration. Then, OBS data collected by the first Micro-OBS survey from NTOU team in August 2005 is analyzed through travel-time inversion of reflected and refracted arrivals for which the initial model is constructed from the MCS result. Finally, a novel technique of inverse reflected rays by considering both MCS and OBS data is applied for layer-stripping imaging of sedimentary layers. Velocity models imaged from three methods are confirmed the prevalence of BSR at 100-400 m depth below the sea floor along the whole profile. Relatively smooth sedimentary layers are observed below the lower slope of the continent whereas several mud diapers are imaged below the upper slope of the continent. Above the mud diapers, we find gas hydrates with high velocity of about 1.9-2.1 km/s and thickness of about 100 m immediately above the strong BSR. Similarly, near the mud diapers, free gas with low velocity of about 1.4-1.7 km/s and thickness of about 200 m is imaged. Migration of free gas through diapirism may result in lots of gas hydrates accumulated below the upper slope of the continent offshore SW Taiwan.

Origin of a crustal splay fault and its relation to the seismogenic zone and underplating at the erosional north Ecuador-south Colombia oceanic margin

NASA Astrophysics Data System (ADS)

Collot, J.-Y.; Agudelo, W.; Ribodetti, A.; Marcaillou, B.

2008-12-01

Splay faults within accretionary complexes are commonly associated with the updip limit of the seismogenic zone. Prestack depth migration of a multichannel seismic line across the north Ecuador-south Colombia oceanic margin images a crustal splay fault that correlates with the seaward limit of the rupture zone of the 1958 (Mw 7.7) tsunamogenic subduction earthquake. The splay fault separates 5-6.6 km/s velocity, inner wedge basement rocks, which belong to the accreted Gorgona oceanic terrane, from 4 to 5 km/s velocity outer wedge rocks. The outer wedge is dominated by basal tectonic erosion. Despite a 3-km-thick trench fill, subduction of 2-km-high seamount prevented tectonic accretion and promotes basal tectonic erosion. The low-velocity and poorly reflective subduction channel that underlies the outer wedge is associated with the aseismic, décollement thrust. Subduction channel fluids are expected to migrate upward along splay faults and alter outer wedge rocks. Conversely, duplexes are interpreted to form from and above subducting sediment, at ˜14- to 15-km depths between the overlapping seismogenic part of the splay fault and the underlying aseismic décollement. Coeval basal erosion of the outer wedge and underplating beneath the apex of inner wedge control the margin mass budget, which comes out negative. Intraoceanic basement fossil listric normal faults and a rift zone inverted in a flower structure reflect the evolution of the Gorgona terrane from Cretaceous extension to likely Eocene oblique compression. The splay faults could have resulted from tectonic inversion of listric normal faults, thus showing how inherited structures may promote fluid flow across margin basement and control seismogenesis.

Development of Vertical Cable Seismic System

NASA Astrophysics Data System (ADS)

Asakawa, E.; Murakami, F.; Sekino, Y.; Okamoto, T.; Ishikawa, K.; Tsukahara, H.; Shimura, T.

2011-12-01

In 2009, Ministry of Education, Culture, Sports, Science and Technology(MEXT) started the survey system development for Hydrothermal deposit. We proposed the Vertical Cable Seismic (VCS), the reflection seismic survey with vertical cable above seabottom. VCS has the following advantages for hydrothermal deposit survey. (1) VCS is an efficient high-resolution 3D seismic survey in limited area. (2) It achieves high-resolution image because the sensors are closely located to the target. (3) It avoids the coupling problems between sensor and seabottom that cause serious damage of seismic data quality. (4) Because of autonomous recording system on sea floor, various types of marine source are applicable with VCS such as sea-surface source (GI gun etc.) , deep-towed or ocean bottom source. Our first experiment of 2D/3D VCS surveys has been carried out in Lake Biwa, JAPAN, in November 2009. The 2D VCS data processing follows the walk-away VSP, including wave field separation and depth migration. Seismic Interferometry technique is also applied. The results give much clearer image than the conventional surface seismic. Prestack depth migration is applied to 3D data to obtain good quality 3D depth volume. Seismic Interferometry technique is applied to obtain the high resolution image in the very shallow zone. Based on the feasibility study, we have developed the autonomous recording VCS system and carried out the trial experiment in actual ocean at the water depth of about 400m to establish the procedures of deployment/recovery and to examine the VC position or fluctuation at seabottom. The result shows that the VC position is estimated with sufficient accuracy and very little fluctuation is observed. Institute of Industrial Science, the University of Tokyo took the research cruise NT11-02 on JAMSTEC R/V Natsushima in February, 2011. In the cruise NT11-02, JGI carried out the second VCS survey using the autonomous VCS recording system with the deep towed source provided by Institute of Industrial Science, the University of Tokyo. It generates high frequency acoustic waves around 1kHz. The acquired VCS data clearly shows the reflections and currently being processed for imaging the subsurface structure.

Seismic imaging and velocity structure around the JFAST drill site in the Japan Trench: low Vp, high Vp/ Vs in the transparent frontal prism

NASA Astrophysics Data System (ADS)

Nakamura, Yasuyuki; Kodaira, Shuichi; Cook, Becky J.; Jeppson, Tamara; Kasaya, Takafumi; Yamamoto, Yojiro; Hashimoto, Yoshitaka; Yamaguchi, Mika; Obana, Koichiro; Fujie, Gou

2014-12-01

Seismic image and velocity models were obtained from a newly conducted seismic survey around the Integrated Ocean Drilling Program (IODP) Japan Trench Fast Drilling Project (JFAST) drill site in the Japan Trench. Pre-stack depth migration (PSDM) analysis was applied to the multichannel seismic reflection data to produce an accurate depth seismic profile together with a P wave velocity model along a line that crosses the JFAST site location. The seismic profile images the subduction zone at a regional scale. The frontal prism where the drill site is located corresponds to a typically seismically transparent (or chaotic) zone with several landward-dipping semi-continuous reflections. The boundary between the Cretaceous backstop and the frontal prism is marked by a prominent landward-dipping reflection. The P wave velocity model derived from the PSDM analysis shows low velocity in the frontal prism and velocity reversal across the backstop interface. The PSDM velocity model around the drill site is similar to the P wave velocity model calculated from the ocean bottom seismograph (OBS) data and agrees with the P wave velocities measured from the core experiments. The average Vp/ Vs in the hanging wall sediments around the drill site, as derived from OBS data, is significantly larger than that obtained from core sample measurements.

Sea level history in 3D: Data acquisition and processing for an ultra-high resolution MCS survey across IODP Expedition 313 drillsite

NASA Astrophysics Data System (ADS)

Nedimovic, M. R.; Mountain, G. S.; Austin, J. A., Jr.; Fulthorpe, C.; Aali, M.; Baldwin, K.; Bhatnagar, T.; Johnson, C.; Küçük, H. M.; Newton, A.; Stanley, J.

2015-12-01

In June-July 2015, we acquired the first 3D/2D hybrid (short/long streamer) multichannel seismic (MCS) reflection dataset. These data were collected simultaneously across IODP Exp. 313 drillsites, off New Jersey, using R/V Langsethand cover ~95% of the planned 12x50 km box. Despite the large survey area, the lateral and vertical resolution for the 3D dataset is almost a magnitude of order higher than for data gathered for standard petroleum exploration. Such high-resolution was made possible by collection of common midpoint (CMP) lines whose combined length is ~3 times the Earth's circumference (~120,000 profile km) and a source rich in high-frequencies. We present details on the data acquisition, ongoing data analysis, and preliminary results. The science driving this project is presented by Mountain et al. The 3D component of this innovative survey used an athwartship cross cable, extended laterally by 2 barovanes roughly 357.5 m apart and trailed by 24 50-m P-Cables spaced ~12.5 m with near-trace offset of 53 m. Each P-Cable had 8 single hydrophone groups spaced at 6.25 m for a total of 192 channels. Record length was 4 s and sample rate 0.5 ms, with no low cut and an 824 Hz high cut filter. We ran 77 sail lines spaced ~150 m. Receiver locations were determined using 2 GPS receivers mounted on floats and 2 compasses and depth sensors per streamer. Streamer depths varied from 2.1 to 3.7 m. The 2D component used a single 3 km streamer, with 240 9-hydrophone groups spaced at 12.5 m, towed astern with near-trace offset of 229 m. The record length was 4 s and sample rate 0.5 ms, with low cut filter at 2 Hz and high cut at 412 Hz. Receiver locations were recorded using GPS at the head float and tail buoy, combined with 12 bird compasses spaced ~300 m. Nominal streamer depth was 4.5 m. The source for both systems was a 700 in3 linear array of 4 Bolt air guns suspended at 4.5 m towing depth, 271.5 m behind the ship's stern. Shot spacing was 12.5 m. Data analysis to prestack time migration is being carried out by Absolute Imaging, a commercial company. The shipboard QC analysis and brute stacks indicate that the final product will be superb. Key advantages of the hybrid 3D/2D dataset are: (1) Velocity control from the 2D long-streamer data combined with the ultra-high resolution of the P-Cable 3D dataset; (2) Opportunity for prestack and poststack attribute analysis.

Integrated Reflection Seismic Monitoring and Reservoir Modeling for Geologic CO2 Sequestration

DOE Office of Scientific and Technical Information (OSTI.GOV)

John Rogers

The US DOE/NETL CCS MVA program funded a project with Fusion Petroleum Technologies Inc. (now SIGMA) to model the proof of concept of using sparse seismic data in the monitoring of CO{sub 2} injected into saline aquifers. The goal of the project was to develop and demonstrate an active source reflection seismic imaging strategy based on deployment of spatially sparse surface seismic arrays. The primary objective was to test the feasibility of sparse seismic array systems to monitor the CO{sub 2} plume migration injected into deep saline aquifers. The USDOE/RMOTC Teapot Dome (Wyoming) 3D seismic and reservoir data targeting themore » Crow Mountain formation was used as a realistic proxy to evaluate the feasibility of the proposed methodology. Though the RMOTC field has been well studied, the Crow Mountain as a saline aquifer has not been studied previously as a CO{sub 2} sequestration (storage) candidate reservoir. A full reprocessing of the seismic data from field tapes that included prestack time migration (PSTM) followed by prestack depth migration (PSDM) was performed. A baseline reservoir model was generated from the new imaging results that characterized the faults and horizon surfaces of the Crow Mountain reservoir. The 3D interpretation was integrated with the petrophysical data from available wells and incorporated into a geocellular model. The reservoir structure used in the geocellular model was developed using advanced inversion technologies including Fusion's ThinMAN{trademark} broadband spectral inversion. Seal failure risk was assessed using Fusion's proprietary GEOPRESS{trademark} pore pressure and fracture pressure prediction technology. CO{sub 2} injection was simulated into the Crow Mountain with a commercial reservoir simulator. Approximately 1.2MM tons of CO{sub 2} was simulated to be injected into the Crow Mountain reservoir over 30 years and subsequently let 'soak' in the reservoir for 970 years. The relatively small plume developed from this injection was observed migrating due to gravity to the apexes of the double anticline in the Crow Mountain reservoir of the Teapot dome. Four models were generated from the reservoir simulation task of the project which included three saturation models representing snapshots at different times during and after simulated CO{sub 2} injection and a fully saturated CO{sub 2} fluid substitution model. The saturation models were used along with a Gassmann fluid substitution model for CO{sub 2} to perform fluid volumetric substitution in the Crow Mountain formation. The fluid substitution resulted in a velocity and density model for the 3D volume at each saturation condition that was used to generate a synthetic seismic survey. FPTI's (Fusion Petroleum Technologies Inc.) proprietary SeisModelPRO{trademark} full acoustic wave equation software was used to simulate acquisition of a 3D seismic survey on the four models over a subset of the field area. The simulated acquisition area included the injection wells and the majority of the simulated plume area.« less

Joint Optimization of Vertical Component Gravity and Seismic P-wave First Arrivals by Simulated Annealing

NASA Astrophysics Data System (ADS)

Louie, J. N.; Basler-Reeder, K.; Kent, G. M.; Pullammanappallil, S. K.

2015-12-01

Simultaneous joint seismic-gravity optimization improves P-wave velocity models in areas with sharp lateral velocity contrasts. Optimization is achieved using simulated annealing, a metaheuristic global optimization algorithm that does not require an accurate initial model. Balancing the seismic-gravity objective function is accomplished by a novel approach based on analysis of Pareto charts. Gravity modeling uses a newly developed convolution algorithm, while seismic modeling utilizes the highly efficient Vidale eikonal equation traveltime generation technique. Synthetic tests show that joint optimization improves velocity model accuracy and provides velocity control below the deepest headwave raypath. Detailed first arrival picking followed by trial velocity modeling remediates inconsistent data. We use a set of highly refined first arrival picks to compare results of a convergent joint seismic-gravity optimization to the Plotrefa™ and SeisOpt® Pro™ velocity modeling packages. Plotrefa™ uses a nonlinear least squares approach that is initial model dependent and produces shallow velocity artifacts. SeisOpt® Pro™ utilizes the simulated annealing algorithm and is limited to depths above the deepest raypath. Joint optimization increases the depth of constrained velocities, improving reflector coherency at depth. Kirchoff prestack depth migrations reveal that joint optimization ameliorates shallow velocity artifacts caused by limitations in refraction ray coverage. Seismic and gravity data from the San Emidio Geothermal field of the northwest Basin and Range province demonstrate that joint optimization changes interpretation outcomes. The prior shallow-valley interpretation gives way to a deep valley model, while shallow antiformal reflectors that could have been interpreted as antiformal folds are flattened. Furthermore, joint optimization provides a clearer image of the rangefront fault. This technique can readily be applied to existing datasets and could replace the existing strategy of forward modeling to match gravity data.

Some practical aspects of prestack waveform inversion using a genetic algorithm: An example from the east Texas Woodbine gas sand

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mallick, S.

1999-03-01

In this paper, a prestack inversion method using a genetic algorithm (GA) is presented, and issues relating to the implementation of prestack GA inversion in practice are discussed. GA is a Monte-Carlo type inversion, using a natural analogy to the biological evolution process. When GA is cast into a Bayesian framework, a priori information of the model parameters and the physics of the forward problem are used to compute synthetic data. These synthetic data can then be matched with observations to obtain approximate estimates of the marginal a posteriori probability density (PPD) functions in the model space. Plots of thesemore » PPD functions allow an interpreter to choose models which best describe the specific geologic setting and lead to an accurate prediction of seismic lithology. Poststack inversion and prestack GA inversion were applied to a Woodbine gas sand data set from East Texas. A comparison of prestack inversion with poststack inversion demonstrates that prestack inversion shows detailed stratigraphic features of the subsurface which are not visible on the poststack inversion.« less

Enhanced Seismic Imaging of Turbidite Deposits in Chicontepec Basin, Mexico

NASA Astrophysics Data System (ADS)

Chavez-Perez, S.; Vargas-Meleza, L.

2007-05-01

We test, as postprocessing tools, a combination of migration deconvolution and geometric attributes to attack the complex problems of reflector resolution and detection in migrated seismic volumes. Migration deconvolution has been empirically shown to be an effective approach for enhancing the illumination of migrated images, which are blurred versions of the subsurface reflectivity distribution, by decreasing imaging artifacts, improving spatial resolution, and alleviating acquisition footprint problems. We utilize migration deconvolution as a means to improve the quality and resolution of 3D prestack time migrated results from Chicontepec basin, Mexico, a very relevant portion of the producing onshore sector of Pemex, the Mexican petroleum company. Seismic data covers the Agua Fria, Coapechaca, and Tajin fields. It exhibits acquisition footprint problems, migration artifacts and a severe lack of resolution in the target area, where turbidite deposits need to be characterized between major erosional surfaces. Vertical resolution is about 35 m and the main hydrocarbon plays are turbidite beds no more than 60 m thick. We also employ geometric attributes (e.g., coherent energy and curvature), computed after migration deconvolution, to detect and map out depositional features, and help design development wells in the area. Results of this workflow show imaging enhancement and allow us to identify meandering channels and individual sand bodies, previously undistinguishable in the original seismic migrated images.

Multivariate Formation Pressure Prediction with Seismic-derived Petrophysical Properties from Prestack AVO inversion and Poststack Seismic Motion Inversion

NASA Astrophysics Data System (ADS)

Yu, H.; Gu, H.

2017-12-01

A novel multivariate seismic formation pressure prediction methodology is presented, which incorporates high-resolution seismic velocity data from prestack AVO inversion, and petrophysical data (porosity and shale volume) derived from poststack seismic motion inversion. In contrast to traditional seismic formation prediction methods, the proposed methodology is based on a multivariate pressure prediction model and utilizes a trace-by-trace multivariate regression analysis on seismic-derived petrophysical properties to calibrate model parameters in order to make accurate predictions with higher resolution in both vertical and lateral directions. With prestack time migration velocity as initial velocity model, an AVO inversion was first applied to prestack dataset to obtain high-resolution seismic velocity with higher frequency that is to be used as the velocity input for seismic pressure prediction, and the density dataset to calculate accurate Overburden Pressure (OBP). Seismic Motion Inversion (SMI) is an inversion technique based on Markov Chain Monte Carlo simulation. Both structural variability and similarity of seismic waveform are used to incorporate well log data to characterize the variability of the property to be obtained. In this research, porosity and shale volume are first interpreted on well logs, and then combined with poststack seismic data using SMI to build porosity and shale volume datasets for seismic pressure prediction. A multivariate effective stress model is used to convert velocity, porosity and shale volume datasets to effective stress. After a thorough study of the regional stratigraphic and sedimentary characteristics, a regional normally compacted interval model is built, and then the coefficients in the multivariate prediction model are determined in a trace-by-trace multivariate regression analysis on the petrophysical data. The coefficients are used to convert velocity, porosity and shale volume datasets to effective stress and then to calculate formation pressure with OBP. Application of the proposed methodology to a research area in East China Sea has proved that the method can bridge the gap between seismic and well log pressure prediction and give predicted pressure values close to pressure meassurements from well testing.

Seismic Investigations of the Murci Geothermal Field (Southern Tuscany, Italy): Preliminary Results

NASA Astrophysics Data System (ADS)

Riedel, M.; Alexandrakis, C.; Buske, S.

2013-12-01

The Monte Amiata region in the Southern Tuscany, Central Italy, describes a volcanic complex with great significance in terms of the regional fresh water supply, mining and geothermal power generation. Mainly for the latter purpose, the volcanic area of Mt Amiata has been the subject of extensive geological and geophysical research (e.g. Dini et al., 2010 and references therein). The insights from these studies have led to successful geothermal production in the Mt Amiata region since the early 1960s (e.g. Batini et al., 2003). Today's most important reservoirs in this area are the Bagnore and the Piancastagnaio fields which are both operated by the company Enel Green Power. The work presented here deals with the Murci area, another potential reservoir located about 10 km southwest of the Mt Amiata volcanic complex. Therefore, in order to get a more detailed understanding of this area, five reflection seismic profiles were carried out. We have performed on three of them a preliminary depth-migrated images, through Kirchhoff prestack depth migration (KPSDM). The vital point of depth migration algorithms is the accuracy of the velocity model that is used for the backpropagation of the seismic data. Therefore, we derived a suitable 1D starting model from nearby well logs and VSP measurements. In order to remove the large topography effects along the profiles, we then utilized first-arrival tomography for each seismic line. For the following processing we incorporated these 2D tomographic results into our starting model which compensates for static effects and improves the resolution in the near-surface area. The velocity models were then used in the application of KPSDM to the seismic data for each profile, respectively. The resulting preliminary images show a zone of high seismic reflectivity, known as the 'K-horizon' (e.g. Brogi, 2008), and could improve its geological interpretation. These promising results encourage us to proceed with deeper migration velocity analysis which will reveal more details about the structures of the Murci area. Batini, F. et al., 2003: Geological features of Larderello-Travale and Mt. Amiata geothermal areas (southern Tuscany, Italy), Episodes, 26, 239-244. Brogi, A., 2008. The structure of the Monte Amiata volcano-geothermal area (Northern Apennines, Italy): Neogene-Quaternary compression versus extension, Int J Earth Sci (Geol Rundsch) (2008) 97:677-703 Dini, I. et al., 2010. Geological Evaluation of the Base of the Mt. Amiata Volcanic Complex (Tuscany, Italy), Procedings World Geothermal Congress 2010, Bali, Indonesia, April 2010.

Imaging exhumed lower continental crust in the distal Jequitinhonha basin, Brazil

NASA Astrophysics Data System (ADS)

Loureiro, A.; Schnürle, P.; Klingelhöfer, F.; Afilhado, A.; Pinheiro, J.; Evain, M.; Gallais, F.; Dias, N. A.; Rabineau, M.; Baltzer, A.; Benabdellouahed, M.; Soares, J.; Fuck, R.; Cupertino, J. A.; Viana, A.; Matias, L.; Moulin, M.; Aslanian, D.; Vinicius Aparecido Gomes de Lima, M.; Morvan, L.; Mazé, J. P.; Pierre, D.; Roudaut-Pitel, M.; Rio, I.; Alves, D.; Barros Junior, P.; Biari, Y.; Corela, C.; Crozon, J.; Duarte, J. L.; Ducatel, C.; Falcão, C.; Fernagu, P.; Le Piver, D.; Mokeddem, Z.; Pelleau, P.; Rigoti, C.; Roest, W.; Roudaut, M.; Salsa Team

2018-07-01

Twelve combined wide-angle refraction and coincident multi-channel seismic profiles were acquired in the Jequitinhonha-Camamu-Almada, Jacuípe, and Sergipe-Alagoas basins, NE Brazil, during the SALSA experiment in 2014. Profiles SL11 and SL12 image the Jequitinhonha basin, perpendicularly to the coast, with 15 and 11 four-channel ocean-bottom seismometers, respectively. Profile SL10 runs parallel to the coast, crossing profiles SL11 and SL12, imaging the proximal Jequitinhonha and Almada basins with 17 ocean-bottom seismometers. Forward modelling, combined with pre-stack depth migration to increase the horizontal resolution of the velocity models, indicates that sediment thickness varies between 3.3 km and 6.2 km in the distal basin. Crustal thickness at the western edge of the profiles is of around 20 km, with velocity gradients indicating a continental origin. It decreases to less than 5 km in the distal basin, with high seismic velocities and gradients, not compatible with normal oceanic crust nor exhumed upper mantle. Typical oceanic crust is never imaged along these about 200 km-long profiles and we propose that the transitional crust in the Jequitinhonha basin is a made of exhumed lower continental crust.

Seismic structure from multi-channel seismic reflection and wide-angle data of Transect 0E in the Southern Gulf of California

NASA Astrophysics Data System (ADS)

Paramo, P.; Holbrook, W.; Brown, H.; Lizarralde, D.; Fletcher, J.; Umhoefer, P.; Kent, G.; Harding, A.; Gonzalez, A.; Axen, G.

2005-12-01

We present a velocity model from wide-angle data along with coincident prestack depth migration sections from seismic reflection data collected in the southern Gulf of California. Transect 0E runs NE to SW from the hills of Sierra Madre in mainland Mexico near Mazatlan to approximately 115 km into Gulf of California waters. Wide-angle data were recorded by 9 ocean bottom seismometers, deployed by the R/V New Horizon and 10 Reftek seismometers located along onshore extension of the transect. The average spacing for the OBS and Refteks is ~12 km and shots were fired from the R/V Maurice Ewing at 150 m intervals. Transect 0E crosses what it is believed to be extended continental crust and lies in the initial direction of extension characteristic of the proto-gulf. Preliminary results from the velocity model show upper crustal velocities of 6.1-6.3 km/s and lower crustal velocities of 6.7-7.0 km/s along the entire transect. Seismic velocities and crustal thicknesses observed along transect 0E are characteristic of non-volcanic margins.

Insights into crustal structure of the Eastern North American Margin from community multichannel seismic and potential field data

NASA Astrophysics Data System (ADS)

Davis, J. K.; Becel, A.; Shillington, D. J.; Buck, W. R.

2017-12-01

In the fall of 2014, the R/V Marcus Langseth collected gravity, magnetic, and reflection seismic data as part of the Eastern North American Margin Community Seismic Experiment. The dataset covers a 500 km wide section of the Mid-Atlantic passive margin offshore North Carolina, which formed after the Mesozoic breakup of the supercontinent Pangaea. Using these seismic and potential field data, we present observations and interpretations along two cross margin and one along-margin profiles. Analyses and interpretations are conducted using pre-stack depth migrated reflection seismic profiles in conjunction with forward modeling of shipboard gravity and magnetic anomalies. Preliminary interpretations of the data reveal variations in basement character and structure across the entire transition between continental and oceanic domains. These interpretations help provide insight into the origin and nature of the prominent East Coast and Blake Spur magnetic anomalies, as well as the Inner Magnetic Quiet Zone which occupies the domain between the anomalies. Collectively, these observations can aid in deciphering the rift-to-drift transition during the breakup of North America and West Africa and formation of the Central Atlantic.

Analysis of the Pre-stack Split-Step Migration Operator Using Ritz Values

NASA Astrophysics Data System (ADS)

Kaplan, S. T.; Sacchi, M. D.

2009-05-01

The Born approximation for the acoustic wave-field is often used as a basis for developing algorithms in seismic imaging (migration). The approximation is linear, and, as such, can be written as a matrix-vector multiplication (Am=d). In the seismic imaging problem, d is seismic data (the recorded wave-field), and we aim to find the seismic reflectivity m (a representation of earth structure and properties) so that Am=d is satisfied. This is the often studied inverse problem of seismic migration, where given A and d, we solve for m. This can be done in a least-squares sense, so that the equation of interest is, AHAm = AHd. Hence, the solution m is largely dependent on the properties of AHA. The imaging Jacobian J provides an approximation to AHA, so that J-1AHA is, in a broad sense, better behaved then AHA. We attempt to quantify this last statement by providing an analysis of AHA and J-1AHA using their Ritz values, and for the particular case where A is built using a pre-stack split-step migration algorithm. Typically, one might try to analyze the behaviour of these matrices using their eigenvalue spectra. The difficulty in the analysis of AHA and J-1AHA lie in their size. For example, a subset of the relatively small Marmousi data set makes AHA a complex valued matrix with, roughly, dimensions of 45 million by 45 million (requiring, in single-precision, about 16 Peta-bytes of computer memory). In short, the size of the matrix makes its eigenvalues difficult to compute. Instead, we compute the leading principal minors of similar tridiagonal matrices, Bk=Vk-1AHAVk and Ck = Uk-1 J-1 AHAUk. These can be constructed using, for example, the Lanczos decomposition. Up to some value of k it is feasible to compute the eigenvalues of Bk and Ck which, in turn, are the Ritz values of, respectively, AHA and J-1 AHA, and may allow us to make quantitative statements about their behaviours.

Velocity analysis of simultaneous-source data using high-resolution semblance—coping with the strong noise

NASA Astrophysics Data System (ADS)

Gan, Shuwei; Wang, Shoudong; Chen, Yangkang; Qu, Shan; Zu, Shaohuan

2016-02-01

Direct imaging of simultaneous-source (or blended) data, without the need of deblending, requires a precise subsurface velocity model. In this paper, we focus on the velocity analysis of simultaneous-source data using the normal moveout-based velocity picking approach.We demonstrate that it is possible to obtain a precise velocity model directly from the blended data in the common-midpoint domain. The similarity-weighted semblance can help us obtain much better velocity spectrum with higher resolution and higher reliability compared with the traditional semblance. The similarity-weighted semblance enforces an inherent noise attenuation solely in the semblance calculation stage, thus it is not sensitive to the intense interference. We use both simulated synthetic and field data examples to demonstrate the performance of the similarity-weighted semblance in obtaining reliable subsurface velocity model for direct migration of simultaneous-source data. The migrated image of blended field data using prestack Kirchhoff time migration approach based on the picked velocity from the similarity-weighted semblance is very close to the migrated image of unblended data.

Superresolution near-field imaging with surface waves

NASA Astrophysics Data System (ADS)

Fu, Lei; Liu, Zhaolun; Schuster, Gerard

2018-02-01

We present the theory for near-field superresolution imaging with surface waves and time reverse mirrors (TRMs). Theoretical formulae and numerical results show that applying the TRM operation to surface waves in an elastic half-space can achieve superresolution imaging of subwavelength scatterers if they are located less than about 1/2 of the shear wavelength from the source line. We also show that the TRM operation for a single frequency is equivalent to natural migration, which uses the recorded data to approximate the Green's functions for migration, and only costs O(N4) algebraic operations for post-stack migration compared to O(N6) operations for natural pre-stack migration. Here, we assume the sources and receivers are on an N × N grid and there are N2 trial image points on the free surface. Our theoretical predictions of superresolution are validated with tests on synthetic data. The field-data tests suggest that hidden faults at the near surface can be detected with subwavelength imaging of surface waves by using the TRM operation if they are no deeper than about 1/2 the dominant shear wavelength.

Structural interpretation and physical property estimates based on COAST 2012 seismic reflection profiles offshore central Washington, Cascadia subduction zone

NASA Astrophysics Data System (ADS)

Webb, S. I.; Tobin, H. J.; Everson, E. D.; Fortin, W.; Holbrook, W. S.; Kent, G.; Keranen, K. M.

2014-12-01

The Cascadia subduction zone has a history of large magnitude earthquakes, but a near-total lack of plate interface seismicity, making the updip limit of the seismogenic zone difficult to locate. In addition, the central Cascadia accretionary prism is characterized by an extremely low wedge taper angle, landward vergent initial thrusting, and a flat midslope terrace between the inner and outer wedges, unlike most other accretionary prisms (e.g. the Nankai Trough, Japan). The Cascadia Open Access Seismic Transect (COAST) lines were shot by R/V Marcus Langseth in July of 2012 off central Washington to image this subduction zone. Two trench-parallel and nine trench-perpendicular lines were collected. In this study, we present detailed seismic interpretation of both time- and depth-migrated stacked profiles, focused on elucidating the deposition and deformation of both pre- and syn-tectonic sediment in the trench and slope. Distribution and timing of sediments and their deformation is used to unravel the evolution of the wedge through time. Initially, interpretation of the time-sections is carried out to support the building of tomographic velocity models to aid in the pre-stack depth migration (PSDM) of selected lines. In turn, we use PSDM velocity models to estimate porosity and pore pressure conditions at the base of the wedge and across the basal plate interface décollement where possible, using established velocity-porosity transforms. Interpretation in this way incorporates both accurate structural relationships and robust porosity models to document wedge development and present-day stress state, in particular regions of potential overpressure. Results shed light on the origin and evolution of the mid-slope terrace and the low taper angle for the forearc wedge. This work may shed light ultimately on the position of the potential updip limit of the seismogenic zone beneath the wedge.

Splay Fault Branching from the Hikurangi Subduction Shear Zone: Implications for Slow Slip and Fluid Flow

NASA Astrophysics Data System (ADS)

Henrys, S. A.; Plaza-Faverola, A. A.; Pecher, I. A.; Klaeschen, D.; Wallace, L.

2016-12-01

Seismic reflection data along the East Coast of the New Zealand North Island are used to map the offshore character and geometry of the central Hikurangi subduction thrust and outer wedge in a region of short term ( 2-3 weeks duration) geodetically determined slow-slip events (SSEs). Pre-stack depth migration of line 05CM-38 was used to derive subducting slab geometry and upper crustal structure together with a Vp image of the crust that is resolved to 14 km depth. The subduction interface is a shallow dipping thrust at < 7 km deep near the trench and steps down to 14 km depth along an approximately 18 km long ramp, beneath Porangahau Ridge. This bend in the subducted plate is associated with splay fault branching and coincides with the zone of maximum slip (90 mm) inferred on the subduction interface during slow slip events in June and July 2011. We infer that the step down in the décollement transfers slip on the plate interface from the top of subducting sediments to the oceanic crust and drives underplating beneath the inner margin of central Hikurangi margin. Low-velocity subducting sediments (LVZ) beneath the plate interface, updip of the plate interface ramp, are interpreted as being capped with a low permeability condensed layer of chalk and interbedded mudstones. We interpret this LVZ as fluid-rich overpressured sediments that have been displaced and later imbricated by splay faults in a region that may mark the up-dip transition from seismic to aseismic behavior. Further, we hypothesize that fluids derived from the overpressured sediment are channeled along splay faults to the shallow sub-seafloor near Porangahau Ridge where seafloor seepage and an upwarping of the gas hydrate Bottom-Simulating Reflector have been documented.

Application of 3D full waveform inversion on real marine data sets

NASA Astrophysics Data System (ADS)

Plessix, Rene-Edouard

2010-05-01

Full waveform inversion (FWI) was proposed more than 25 years. Over the last ten years, several real 2D examples have been published showing the potential and the difficulties of this approach. The application of acoustic FWI to sizeable real 3D data sets became possible a few year ago thanks to the increase of computer power. The developments in seismic acquisition are also an enabler to FWI that works best with wide aperture data sets and low frequencies. In this way, the Ocean Bottom Seismometer (OBS) or Ocean Bottom Cable (OBC) data sets are well suited since they often contain long offsets, wide azimuth and low frequencies. In this presentation, I will describe the results we obtained by inverting a deep-water OBS data set from the Gulf of Mexico. The data set contains offsets up to 17 km. A classic multiscale FWI was applied starting at 2 Hz. FWI helps to reveal shallow gas accumulations that were difficult to capture with classic reflection traveltime inversion. The presence of these gas accumulations was also supported by a visco-acoustic FWI and an inversion for the quality factor. This result illustrates the power of FWI to image the shallow structures where diving waves propagate. Detecting these shallow velocity anomalies is not only important for imaging but also for hazard analysis, for instance, during a well planning. Analysis of the isotropic FWI results showed that some of the reflected energy was not correctly interpreted, since after pre-stack migration the common image gathers were not flat. In fact, FWI tries to interpret both reflected and refracted energy. Since the sediments in the Gulf of Mexico are anisotropic, the reflected and refracted waves may travel with a different velocity. We then carried out a VTI (Vertical Transversely Isotropic) FWI with a fixed ratio between the NMO (Normal MoveOut) velocity and the horizontal velocity. This ratio was found by traveltime inversion and is spatially varying. Migrating with the velocity found by VTI FWI led to a better image even for the sediments beneath the salt at 6 km depth. This improvement at those depths however strongly depends on the accuracy of the initial model since FWI works in a (non-linear) migration mode at that depth with this acquisition. Depending on the permission to publish, I may also discuss some results obtained with a more traditional narrow azimuth streamer data sets.

Accretion in the wake of terrane collision: The Neogene accretionary wedge off Kenai Peninsula, Alaska

USGS Publications Warehouse

Fruehn, J.; von Huene, Roland E.; Fisher, M.A.

1999-01-01

Subduction accretion and repeated terrane collision shaped the Alaskan convergent margin. The Yakutat Terrane is currently colliding with the continental margin below the central Gulf of Alaska. During the Neogene the terrane's western part was subducted after which a sediment wedge accreted along the northeast Aleutian Trench. This wedge incorporates sediment eroded from the continental margin and marine sediments carried into the subduction zone on the Pacific plate. Prestack depth migration was performed on six seismic reflection lines to resolve the structure within this accretionary wedge and its backstop. The lateral extent of the structures is constrained by high-resolution swath bathymetry and seismic lines collected along strike. Accretionary structure consists of variably sized thrust slices that were deformed against a backstop during frontal accretion and underplating. Toward the northeast the lower slope steepens, the wedge narrows, and the accreted volume decreases notwith-standing a doubling of sediments thickness in the trench. In the northeasternmost transect, near the area where the terrane's trailing edge subducts, no frontal accretion is observed and the slope is eroded. The structures imaged along the seismic lines discussed here most likely result from progressive evolution from erosion to accretion, as the trailing edge of the Yakutat Terrane is subducting.

Baseline seismic survey for the 2nd offshore methane hydrate production test in the Eastern Nankai Trough

NASA Astrophysics Data System (ADS)

Teranishi, Y.; Inamori, T.; Kobayashi, T.; Fujii, T.; Saeki, T.; Takahashi, H.; Kobayashi, F.

2017-12-01

JOGMEC carries out seismic monitoring surveys before and after the 2nd offshore methane hydrate (MH) production test in the Eastern Nankai Trough and evaluates MH dissociation behavior from the time-lapse seismic response. In 2016, JOGMEC deployed Ocean Bottom Cable (OBC) system provided by OCC in the Daini Atsumi Knoll with water depths of 900-1100 m. The main challenge of the seismic survey was to optimize the cable layout for ensuring an effective time-lapse seismic detectability while overcoming the following two issues: 1. OBC receiver lines were limited to only two lines. It was predicted that the imaging of shallow reflectors would suffer from lack of continuity and resolution due to this limitation of receiver lines. 2. The seafloor and shallow sedimentary layers including monitoring target are dipping to the Northwest direction. It was predicted that the refection points would laterally shift to up-dip direction (Southeast direction). In order to understand the impact of the issues above, the seismic survey was designed with elastic wave field simulation. The reflection seismic survey for baseline data was conducted in August 2016. A total of 70 receiver stations distributed along one cable were deployed successfully and a total of 9952 shots were fired. After the baseline seismic survey, the hydrophone and geophone vertical component datasets were processed as outlined below: designaturing, denoising, surface consistent deconvolution and surface consistent amplitude correction. High-frequency imaging with Reverse Time Migration (RTM) was introduced to these data sets. Improvements in imaging from the RTM are remarkable compared to the Kirchhoff migration and the existing Pre-stack time migration with 3D marine surface seismic data obtained and processed in 2002, especially in the following parts. The MH concentrated zone which has complex structures. Below the Bottom Simulating Reflector (BSR) which is present as a impedance-contrast boundary

Seismic Migration Imaging of the Mantle Transition Zone Beneath Continental US with Receiver Functions

NASA Astrophysics Data System (ADS)

Zhang, H.; Schmandt, B.

2017-12-01

The mantle transition zone has been widely studied by multiple sub-fields in geosciences including seismology, mineral physics and geodynamics. Due to the relatively high water storage capacity of olivine polymorphs (wadsleyite and ringwoodite) inside the transition zone, it is proposed to be a potential geochemical water reservoir that may contain one or more ocean masses of water. However, there is an ongoing debate about the hydration level of those minerals and how it varies from place to place. Considering that dehydration melting, which may happen during mantle flow across phase transitions between hydrated olivine polymorphs, may be seismically detectable, large-scale seismic imaging of heterogeneous scattering in the transition zone can contribute to the debate. To improve our understanding of the properties of the mantle transition zone and how they relate to mantle flow across its boundaries, it is important to gain an accurate image with large spatial coverage. The accuracy is primarily limited by the density of broadband seismic data and the imaging algorithms applied to the data, while the spatial coverage is limited by the availability of wide-aperture (>500 km) seismic arrays. Thus, the emergence of the USArray seismic data set (www.usarray.org) provides a nearly ideal data source for receiver side imaging of the mantle transition zone due to its large aperture ( 4000 km) with relatively small station spacing ( 70 km), which ensures that the transition zone beneath it is well sampled by teleseismic waves. In total, more than 200,000 P to S receiver functions will be used for imaging structures in depth range of 300 km to 800 km beneath the continental US with an improved 3D Kirchhoff pre-stacking migration method. The method uses 3-D wave fronts calculated for P and S tomography models to more accurately calculate point scattering coefficients and map receiver function lag times to 3-D position. The new images will help resolve any laterally sporadic or dipping interfaces that may be present at transition zone depths. The locations of sporadic velocity decreases will be compared with mantle flow models to evaluate the possibility of dehydration melting.

Evidence for Patchy Sediment Underthrusting and a Strong, Drained Outer Accretionary Wedge in Central Cascadia: Implications for Dynamic Slip Conditions

NASA Astrophysics Data System (ADS)

Tobin, H. J.; Webb, S. I.

2017-12-01

The central Cascadia subduction zone forearc in the region offshore Washington, where a hot, young incoming plate is covered by a 2-3 km thick sedimentary sequence, features a wide, very narrowly-tapered outer accretionary wedge composed of landward vergent thrust sheets. Longstanding questions for this region include the position and host-rock environment of the plate boundary décollement fault, the thickness of sedimentary strata underthrust beneath the wedge with the downgoing plate, and the effective stress or pore fluid pressure condition in the wedge and along its base. We have analyzed nine multichannel seismic lines of the 2012 COAST multi-channel seismic reflection survey using both time- and depth- migrated seismic sections for structural interpretation. Results show that there is evidence for two parallel décollement levels, with up to 200 - 500 meters thickness of a mostly-underthrust sequence in places, but which is absent entirely in others. This patchy distribution is mapped and related to features of the overlying wedge structure. We also analyzed the seismic interval velocity distribution produced during pre-stack depth migration imaging, and used it to compute estimated porosity, pore fluid pressure, and effective stress via empirical physical properties transforms. We find that the wedge shows evidence for at most only modest, localized excess pore pressure, and instead most of the wedge appears to be at near-hydrostatic, drained condition. Modest overpressure ratios of up to only 0.15 are detected, localized in the footwalls of thrust splays. We find no evidence for overpressure zones in the underthrust sequence below the upper décollement, in contrast to findings from several other wedges worldwide. Taken together, the accretionary wedge structure and apparent low pore pressure condition here is consistent with a mechanically strong wedge overlying a base that is very weak, at least transiently. By analogy with recent work from Sumatra, Tohoku, and elsewhere, we speculate that this is potentially conducive to efficient propagation of megathrust slip to the deformation front in large earthquakes.

Time-lapse seismic waveform modelling and attribute analysis using hydromechanical models for a deep reservoir undergoing depletion

NASA Astrophysics Data System (ADS)

He, Y.-X.; Angus, D. A.; Blanchard, T. D.; Wang, G.-L.; Yuan, S.-Y.; Garcia, A.

2016-04-01

Extraction of fluids from subsurface reservoirs induces changes in pore pressure, leading not only to geomechanical changes, but also perturbations in seismic velocities and hence observable seismic attributes. Time-lapse seismic analysis can be used to estimate changes in subsurface hydromechanical properties and thus act as a monitoring tool for geological reservoirs. The ability to observe and quantify changes in fluid, stress and strain using seismic techniques has important implications for monitoring risk not only for petroleum applications but also for geological storage of CO2 and nuclear waste scenarios. In this paper, we integrate hydromechanical simulation results with rock physics models and full-waveform seismic modelling to assess time-lapse seismic attribute resolution for dynamic reservoir characterization and hydromechanical model calibration. The time-lapse seismic simulations use a dynamic elastic reservoir model based on a North Sea deep reservoir undergoing large pressure changes. The time-lapse seismic traveltime shifts and time strains calculated from the modelled and processed synthetic data sets (i.e. pre-stack and post-stack data) are in a reasonable agreement with the true earth models, indicating the feasibility of using 1-D strain rock physics transform and time-lapse seismic processing methodology. Estimated vertical traveltime shifts for the overburden and the majority of the reservoir are within ±1 ms of the true earth model values, indicating that the time-lapse technique is sufficiently accurate for predicting overburden velocity changes and hence geomechanical effects. Characterization of deeper structure below the overburden becomes less accurate, where more advanced time-lapse seismic processing and migration is needed to handle the complex geometry and strong lateral induced velocity changes. Nevertheless, both migrated full-offset pre-stack and near-offset post-stack data image the general features of both the overburden and reservoir units. More importantly, the results from this study indicate that integrated seismic and hydromechanical modelling can help constrain time-lapse uncertainty and hence reduce risk due to fluid extraction and injection.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silva, M.A.; Osorio, M.; Sharp, A.

LASMO started exploration in the Espinal Block within the Upper Magdalena Valley of Colombia in 1987. Since then six exploration wells have been drilled within the block which have resulted in four New Field Wildcat successes. Two of these successes have been in subthrust configurations. This presentation shall describe the exploration and appraisal techniques used to delimit the Venganza Field which was the first subthrust field discovery made in Colombia. The first stages of our exploration for the subthrust trap were conventional seismic surveying, and structural modelling using the excellent geological outcrop data. These led to the formulation of themore » Venganza prospect which comprised tilted Late Cretaceous Guadalupe sandstones overthrusted by stratigraphically older Villeta shales. The Venganza Prospect was drilled in 1991 and encountered the reservoir as expected directly beneath the thrust plane, and produced oil at 5800 barrels/day on test. Subsequent to the Venganza-1 discovery, further seismic data were acquired and processed using pre-stack depth migration. These new data {open_quotes}verified{close_quotes} the Venganza geological model, and formed the basis for appraisal drilling. The Venganza-2 appraisal well, drilled 4 km to the north of the successful exploration well, was dry and indicated that the subthrust trap configuration was much more subtle than first anticipated. The presentation shall then demonstrate the evolution of our understanding of the subthrust trap configuration and the evolution of our search techniques for it.« less

Slab Penetration vs. Slab Stagnation: Mantle Reflectors as an Indicator

NASA Astrophysics Data System (ADS)

Okeler, A.; Gu, Y. J.; Schultz, R.; Contenti, S. M.

2011-12-01

Subducting oceanic lithosphere along convergent margins may stagnate near the base of the upper mantle or penetrate into the lower mantle. These dynamic processes cause extensive thermal and compositional variations, which can be observed in terms of impedance contrast (reflectivity) and topography of mantle transition zone (MTZ) discontinuities, i.e., 410- and 660-km discontinuities. In this study, we utilize ~ 15000 surface-reflected shear waves (SS) and their precursory arrivals (S410S and S660S) to analyze subduction related deformations on mantle reflectivity structure. We apply pre-stack, time-to-depth migration technique to SS precursors, and move weak underside reflections using PREM-predicted travel-time curves. Common Mid-point gathers are formed to investigate structure under the western Pacific, south America, and Mediterranean convergent boundaries. In general, mantle reflectivity structures are consistent with previous seismic tomography models. In regions of slab penetration (e.g., southern Kurile arc, Aegean Sea), our results show 1) a substantial decrease in S660S amplitude, and 2) strong lower mantle reflector(s) at ~ 900 km depth. These reflective structures are supported by zones of high P and S velocities extending into the lower mantle. Our 1-D synthetic simulations suggest that the decreasing S660S amplitudes are, at least partially, associated with shear wave defocusing due to changes in reflector depth (by ±20 km) within averaging bin. Assuming a ~500 km wide averaging area, a dipping reflector with 6-8 % slope can reduce the amplitude of a SS precursor by ~50%. On the other hand, broad depressions with strong impedance contrast at the base of the MTZ characterize the regions of slab stagnation, such as beneath the Tyrrhenian Sea and northeastern China. For the latter region, substantial topography on the 660-km discontinuity west of the Wadati-Benioff zone suggests that the stagnant part of the Pacific plate across Honshu arc is not nearly as flat as previously suggested.

Fine-scale thermohaline ocean structure retrieved with 2-D prestack full-waveform inversion of multichannel seismic data: Application to the Gulf of Cadiz (SW Iberia)

NASA Astrophysics Data System (ADS)

Dagnino, D.; Sallarès, V.; Biescas, B.; Ranero, C. R.

2016-08-01

This work demonstrates the feasibility of 2-D time-domain, adjoint-state acoustic full-waveform inversion (FWI) to retrieve high-resolution models of ocean physical parameters such as sound speed, temperature and salinity. The proposed method is first described and then applied to prestack multichannel seismic (MCS) data acquired in the Gulf of Cadiz (SW Iberia) in 2007 in the framework of the Geophysical Oceanography project. The inversion strategy flow includes specifically designed data preconditioning for acoustic noise reduction, followed by the inversion of sound speed in the shotgather domain. We show that the final sound speed model has a horizontal resolution of ˜ 70 m, which is two orders of magnitude better than that of the initial model constructed with coincident eXpendable Bathy Thermograph (XBT) data, and close to the theoretical resolution of O(λ). Temperature (T) and salinity (S) are retrieved with the same lateral resolution as sound speed by combining the inverted sound speed model with the thermodynamic equation of seawater and a local, depth-dependent T-S relation derived from regional conductivity-temperature-depth (CTD) measurements of the National Oceanic and Atmospheric Administration (NOAA) database. The comparison of the inverted T and S models with XBT and CTD casts deployed simultaneously to the MCS acquisition shows that the thermohaline contrasts are resolved with an accuracy of 0.18oC for temperature and 0.08 PSU for salinity. The combination of oceanographic and MCS data into a common, pseudo-automatic inversion scheme allows to quantitatively resolve submeso-scale features that ought to be incorporated into larger-scale ocean models of oceans structure and circulation.

Constraints on Shallow Crustal Structure across the San Andreas Fault Zone, Coachella Valley, Southern California: Results from the Salton Seismic Imaging Project (SSIP)

NASA Astrophysics Data System (ADS)

Hernandez, A.; Persaud, P.; Bauer, K.; Stock, J. M.; Fuis, G. S.; Hole, J. A.; Goldman, M.

2015-12-01

The strong influence of basin structure and crustal heterogeneities on seismic wave propagation suggests that these factors should be included in calculations of strong ground shaking. Knowledge of the shallow subsurface is thus essential for an accurate seismic hazard estimate for the densely populated Coachella Valley, the region north of the potential M7.8 rupture near the Salton Sea. Using SSIP data, we analyzed first arrivals from nine 65-911 kg explosive shots recorded along a profile in the Coachella Valley in order to evaluate the interpretation of our 2D tomographic results and give added details on the structural complexity of the shallow crust. The line extends 37 km from the Peninsular Ranges to the Little San Bernardino Mountains crossing the major strands of the San Andreas Fault Zone. We fit traveltime curves to our picks with forward modeling ray tracing, and determined 1D P-wave velocity models for traveltime arrivals east and west of each shot, and a 2D model for the line. We also inferred the geometry of near-vertical faults from the pre-stack line migration method of Bauer et al. (2013). In general, the 1D models east of individual shots have deeper basement contacts and lower apparent velocities, ~5 km/s at 4 km depth, whereas the models west of individual shots have shallower basement and velocities up to 6 km/s at 2 km depth. Mismatches in basement depths (assuming 5-6 km/s) between individual 1D models indicate a shallowly dipping basement, deepening eastward towards the Banning Fault and shoaling abruptly farther east. An east-dipping structure in the 2D model also gives a better fit than horizontal layers. Based on high velocity zones derived from traveltimes at 9-20 km from the western end of the line, we included an offset from ~2 km to 4 km depth near the middle of the line, which significantly improved the 2D model fit. If fault-related, this offset could represent the Garnet Hill Fault if it continues southward in the subsurface.

Natural Gas Hydrates Estimation Using Seismic Inversion and Rock Physics

NASA Astrophysics Data System (ADS)

Dutta, N.; Dai, J.; Kleinberg, R.; Xu, H.

2005-05-01

Gas hydrate drilling worldwide indicates that the formation of gas hydrates in shallow sediments tends to increase P- and S-wave velocities of the hosting rocks. Rock physics models of gas hydrates provide the links between velocity anomalies and gas hydrate concentration. In this abstract, we evaluate the numerical predictions of some of the major rock physics models of gas hydrates and validate those with well log data from the Mallik and Blake Ridge wells. We find that a model in which the gas hydrate is a part of the rock framework produces results that are consistent with well log data. To enhance the accuracy of seismic estimation, we adopt a five-step, integrated workflow that enables us to identify and quantify gas hydrates in the deepwater Gulf of Mexico (GOM). It includes: 1) Reprocessing conventional 3D seismic data at high resolution using an amplitude-preserving flow with prestack time migration, 2) A detailed stratigraphic evaluation to identify potential hydrate zones, 3) Seismic attribute analysis to further delineate anomalous zones, 4) Full waveform prestack inversion to characterize acoustic properties of gas hydrates in 1D (Mallick, 1995; Mallick, 1999) and map in 3D using hybrid inversion techniques (Dutta, 2002; Mallick and Dutta, 2002), and 5) Quantitative estimation of gas hydrate saturation using rock property models. We illustrate the procedure using 3D seismic data, and estimate gas hydrate saturation in the study area in the GOM.

A Hybrid Seismic Inversion Method for V P/V S Ratio and Its Application to Gas Identification

NASA Astrophysics Data System (ADS)

Guo, Qiang; Zhang, Hongbing; Han, Feilong; Xiao, Wei; Shang, Zuoping

2018-03-01

The ratio of compressional wave velocity to shear wave velocity (V P/V S ratio) has established itself as one of the most important parameters in identifying gas reservoirs. However, considering that seismic inversion process is highly non-linear and geological conditions encountered may be complex, a direct estimation of V P/V S ratio from pre-stack seismic data remains a challenging task. In this paper, we propose a hybrid seismic inversion method to estimate V P/V S ratio directly. In this method, post- and pre-stack inversions are combined in which the pre-stack inversion for V P/V S ratio is driven by the post-stack inversion results (i.e., V P and density). In particular, the V P/V S ratio is considered as a model parameter and is directly inverted from the pre-stack inversion based on the exact Zoeppritz equation. Moreover, anisotropic Markov random field is employed in order to regularise the inversion process as well as taking care of geological structures (boundaries) information. Aided by the proposed hybrid inversion strategy, the directional weighting coefficients incorporated in the anisotropic Markov random field neighbourhoods are quantitatively calculated by the anisotropic diffusion method. The synthetic test demonstrates the effectiveness of the proposed inversion method. In particular, given low quality of the pre-stack data and high heterogeneity of the target layers in the field data, the proposed inversion method reveals the detailed model of V P/V S ratio that can successfully identify the gas-bearing zones.

Intelligent inversion method for pre-stack seismic big data based on MapReduce

NASA Astrophysics Data System (ADS)

Yan, Xuesong; Zhu, Zhixin; Wu, Qinghua

2018-01-01

Seismic exploration is a method of oil exploration that uses seismic information; that is, according to the inversion of seismic information, the useful information of the reservoir parameters can be obtained to carry out exploration effectively. Pre-stack data are characterised by a large amount of data, abundant information, and so on, and according to its inversion, the abundant information of the reservoir parameters can be obtained. Owing to the large amount of pre-stack seismic data, existing single-machine environments have not been able to meet the computational needs of the huge amount of data; thus, the development of a method with a high efficiency and the speed to solve the inversion problem of pre-stack seismic data is urgently needed. The optimisation of the elastic parameters by using a genetic algorithm easily falls into a local optimum, which results in a non-obvious inversion effect, especially for the optimisation effect of the density. Therefore, an intelligent optimisation algorithm is proposed in this paper and used for the elastic parameter inversion of pre-stack seismic data. This algorithm improves the population initialisation strategy by using the Gardner formula and the genetic operation of the algorithm, and the improved algorithm obtains better inversion results when carrying out a model test with logging data. All of the elastic parameters obtained by inversion and the logging curve of theoretical model are fitted well, which effectively improves the inversion precision of the density. This algorithm was implemented with a MapReduce model to solve the seismic big data inversion problem. The experimental results show that the parallel model can effectively reduce the running time of the algorithm.

High-resolution near-surface velocity model building using full-waveform inversion—a case study from southwest Sweden

NASA Astrophysics Data System (ADS)

Adamczyk, A.; Malinowski, M.; Malehmir, A.

2014-06-01

Full-waveform inversion (FWI) is an iterative optimization technique that provides high-resolution models of subsurface properties. Frequency-domain, acoustic FWI was applied to seismic data acquired over a known quick-clay landslide scar in southwest Sweden. We inverted data from three 2-D seismic profiles, 261-572 m long, two of them shot with small charges of dynamite and one with a sledgehammer. To our best knowledge this is the first published application of FWI to sledgehammer data. Both sources provided data suitable for waveform inversion, the sledgehammer data containing even wider frequency spectrum. Inversion was performed for frequency groups between 27.5 and 43.1 Hz for the explosive data and 27.5-51.0 Hz for the sledgehammer. The lowest inverted frequency was limited by the resonance frequency of the standard 28-Hz geophones used in the survey. High-velocity granitic bedrock in the area is undulated and very shallow (15-100 m below the surface), and exhibits a large P-wave velocity contrast to the overlying normally consolidated sediments. In order to mitigate the non-linearity of the inverse problem we designed a multiscale layer-stripping inversion strategy. Obtained P-wave velocity models allowed to delineate the top of the bedrock and revealed distinct layers within the overlying sediments of clays and coarse-grained materials. Models were verified in an extensive set of validating procedures and used for pre-stack depth migration, which confirmed their robustness.

Improving GPR Surveys Productivity by Array Technology and Fully Automated Processing

NASA Astrophysics Data System (ADS)

Morello, Marco; Ercoli, Emanuele; Mazzucchelli, Paolo; Cottino, Edoardo

2016-04-01

The realization of network infrastructures with lower environmental impact and the tendency to use digging technologies less invasive in terms of time and space of road occupation and restoration play a key-role in the development of communication networks. However, pre-existing buried utilities must be detected and located in the subsurface, to exploit the high productivity of modern digging apparatus. According to SUE quality level B+ both position and depth of subsurface utilities must be accurately estimated, demanding for 3D GPR surveys. In fact, the advantages of 3D GPR acquisitions (obtained either by multiple 2D recordings or by an antenna array) versus 2D acquisitions are well-known. Nonetheless, the amount of acquired data for such 3D acquisitions does not usually allow to complete processing and interpretation directly in field and in real-time, thus limiting the overall efficiency of the GPR acquisition. As an example, the "low impact mini-trench "technique (addressed in ITU - International Telecommunication Union - L.83 recommendation) requires that non-destructive mapping of buried services enhances its productivity to match the improvements of new digging equipment. Nowadays multi-antenna and multi-pass GPR acquisitions demand for new processing techniques that can obtain high quality subsurface images, taking full advantage of 3D data: the development of a fully automated and real-time 3D GPR processing system plays a key-role in overall optical network deployment profitability. Furthermore, currently available computing power suggests the feasibility of processing schemes that incorporate better focusing algorithms. A novel processing scheme, whose goal is the automated processing and detection of buried targets that can be applied in real-time to 3D GPR array systems, has been developed and fruitfully tested with two different GPR arrays (16 antennas, 900 MHz central frequency, and 34 antennas, 600 MHz central frequency). The proposed processing scheme take advantage of 3D data multiplicity by continuous real time data focusing. Pre-stack reflection angle gathers G(x, θ; v) are computed at nv different velocities (by the mean of Kirchhoff depth-migration kernels, that can naturally cope with any acquisition pattern and handle irregular sampling issues). It must be noted that the analysis of pre-stack reflection angle gathers plays a key-role in automated detection: targets are identified and the best local propagation velocities are recovered through a correlation estimate computed for all the nv reflection angle gathers. Indeed, the data redundancy of 3D GPR acquisitions highly improves the proposed automatic detection reliability. The goal of real-time automated processing has been pursued without the need of specific high performance processing hardware (a simple laptop is required). Moreover, the automatization of the entire surveying process allows to obtain high quality and repeatable results without the need of skilled interpreters. The proposed acquisition procedure has been extensively tested: more than 100 Km of acquired data prove the feasibility of the proposed approach.

Optimizing the design of vertical seismic profiling (VSP) for imaging fracture zones over hardrock basement geothermal environments

NASA Astrophysics Data System (ADS)

Reiser, Fabienne; Schmelzbach, Cedric; Maurer, Hansruedi; Greenhalgh, Stewart; Hellwig, Olaf

2017-04-01

A primary focus of geothermal seismic imaging is to map dipping faults and fracture zones that control rock permeability and fluid flow. Vertical seismic profiling (VSP) is therefore a most valuable means to image the immediate surroundings of an existing borehole to guide, for example, the placing of new boreholes to optimize production from known faults and fractures. We simulated 2D and 3D acoustic synthetic seismic data and processed it through to pre-stack depth migration to optimize VSP survey layouts for mapping moderately to steeply dipping fracture zones within possible basement geothermal reservoirs. Our VSP survey optimization procedure for sequentially selecting source locations to define the area where source points are best located for optimal imaging makes use of a cross-correlation statistic, by which a subset of migrated shot gathers is compared with a target or reference image from a comprehensive set of source gathers. In geothermal exploration at established sites, it is reasonable to assume that sufficient à priori information is available to construct such a target image. We generally obtained good results with a relatively small number of optimally chosen source positions distributed over an ideal source location area for different fracture zone scenarios (different dips, azimuths, and distances from the surveying borehole). Adding further sources outside the optimal source area did not necessarily improve the results, but rather resulted in image distortions. It was found that fracture zones located at borehole-receiver depths and laterally offset from the borehole by 300 m can be imaged reliably for a range of the different dips, but more source positions and large offsets between sources and the borehole are required for imaging steeply dipping interfaces. When such features cross-cut the borehole, they are particularly difficult to image. For fracture zones with different azimuths, 3D effects are observed. Far offset source positions contribute less to the image quality as fracture zone azimuth increases. Our optimization methodology is best suited for designing future field surveys with a favorable benefit-cost ratio in areas with significant à priori knowledge. Moreover, our optimization workflow is valuable for selecting useful subsets of acquired data for optimum target-oriented processing.

The Flemish Cap - Goban Spur conjugate margins: New evidence of asymmetry

NASA Astrophysics Data System (ADS)

Gerlings, J.; Louden, K. E.; Minshull, T. A.; Nedimović, M. R.

2011-12-01

The combined results of deep multichannel seismic (MCS) and refraction/wide-angle reflection seismic (R/WAR) profiles across the Flemish Cap-Goban Spur conjugate margin pair will be presented to help constrain rifting and breakup processes. Both profiles cross magnetic anomaly 34 and extend into oceanic crust, which makes it possible to observe the complete extensional history from continental rifting through the formation of initial oceanic crust. Kirchhoff poststack time and prestack time and depth migration images of the Flemish Cap MCS data are produced using a velocity model constructed from the MCS and R/WAR data. These new images show improved continuity of the Moho under the thick continental crust of Flemish Cap. The basement morphology image is sharper and reflections observed in the thin crust of the transition zone are more coherent. A basement high at the seaward-most end of the transition zone now displays clear diapiric features. To compare the two margins, the existing migrated MCS data across Goban Spur has been time-to-depth converted using the R/WAR velocity model of the margin. These reimaged seismic profiles demonstrate asymmetries in continental rifting and breakup with a complex transition to oceanic spreading: (1) During initial phases of rifting, the Flemish Cap margin displays a sharper necking profile than that of the Goban Spur margin. (2) Within the ocean-continent-transition zone, constraints from S-wave velocities on both margins indentifies previously interpreted oceanic crust as thinned continental crust offshore Flemish Cap in contrast with primarily serpentinized mantle offshore Goban Spur. (3) Continental breakup and initial seafloor spreading occur in a complex, asymmetric manner where the initial ~50 km of oceanic crust appears different on the two margins. Offshore Flemish Cap, both R/WAR and MCS results indicate a sharp boundary immediately seaward of a ridge feature, where the basement morphology becomes typical of slow seafloor spreading. There are no significant changes in either reflectivity or velocity seaward toward magnetic anomaly 34. On the Goban Spur margin in marked contrast, the basement morphology landward of magnetic anomaly 34 is shallower and has lower relief, and the velocity model indicates a diffuse change between the transitional crust and seafloor spreading. The results from these two very different conjugate margins emphasize the importance of having both types of seismic data from both conjugate margins when interpreting the geodynamic processes.

Pressure as a limit to bloater (Coregonus hoyi) vertical migration

USGS Publications Warehouse

TeWinkel, Leslie M.; Fleischer, Guy W.

1998-01-01

Observations of bloater vertical migration showed a limit to the vertical depth changes that bloater experience. In this paper, we conducted an analysis of maximum differences in pressure encountered by bloater during vertical migration. Throughout the bottom depths studied, bloater experienced maximum reductions in swim bladder volume equal to approximately 50-60% of the volume in midwater. The analysis indicated that the limit in vertical depth change may be related to a maximum level of positive or negative buoyancy for which bloater can compensate using alternative mechanisms such as hydrodynamic lift. Bloater may be limited in the extent of migration by either their depth of neutral buoyancy or the distance above the depth of neutral buoyancy at which they can still maintain their position in the water column. Although a migration limit for the bloater population was evident, individual distances of migration varied at each site. These variations in migration distances may indicate differences in depths of neutral buoyancy within the population. However, in spite of these variations, the strong correlation between shallowest depths of migration and swim bladder volume reduction across depths provides evidence that hydrostatic pressure limits the extent of daily vertical movement in bloater.

Seismic imaging of the Main Frontal Thrust in Nepal reveals a shallow décollement and blind thrusting

NASA Astrophysics Data System (ADS)

Almeida, Rafael V.; Hubbard, Judith; Liberty, Lee; Foster, Anna; Sapkota, Soma Nath

2018-07-01

Because great earthquakes in the Himalaya have an average recurrence interval exceeding 500 yr, most of what we know about past earthquakes comes from paleoseismology and tectonic geomorphology studies of the youngest fault system there, the Main Frontal Thrust (MFT). However, these data are sparse relative to fault segmentation and length, and interpretations are often hard to validate in the absence of information about fault geometry. Here, we image the upper two km of strata in the vicinity of the fault tip of the MFT in central Nepal (around the town of Bardibas) applying a pre-stack migration approach to two new seismic reflection profiles that we interpret using quantitative fault-bend folding theory. Our results provide direct evidence that a shallow décollement produces both emergent (Patu thrust) and blind (Bardibas thrust) fault strands. We show that the décollement lies about 2 km below the land surface near the fault tip, and steps down to a regional 5 km deep décollement level to the north. This implies that there is significant variation in the depth of the décollement. We demonstrate that some active faults do not reach the surface, and therefore paleoseismic trenching alone cannot characterize the earthquake history at these locations. Although blind, these faults have associated growth strata that allow us to infer their most recent displacement history. We present the first direct evidence of fault dip on two fault strands of the MFT at depth that can allow terrace uplift measurements to be more accurately converted to fault slip. We identify a beveled erosional surface buried beneath Quaternary sediments, indicating that strath surface formation is modulated by both climate-related base level changes and tectonics. Together, these results indicate that subsurface imaging, in conjunction with traditional paleoseismological tools, can best characterize the history of fault slip in the Himalaya and other similar thrust fault systems.

Vertical Cable Seismic Survey for Hydrothermal Deposit

NASA Astrophysics Data System (ADS)

Asakawa, E.; Murakami, F.; Sekino, Y.; Okamoto, T.; Ishikawa, K.; Tsukahara, H.; Shimura, T.

2012-04-01

The vertical cable seismic is one of the reflection seismic methods. It uses hydrophone arrays vertically moored from the seafloor to record acoustic waves generated by surface, deep-towed or ocean bottom sources. Analyzing the reflections from the sub-seabed, we could look into the subsurface structure. This type of survey is generally called VCS (Vertical Cable Seismic). Because VCS is an efficient high-resolution 3D seismic survey method for a spatially-bounded area, we proposed the method for the hydrothermal deposit survey tool development program that the Ministry of Education, Culture, Sports, Science and Technology (MEXT) started in 2009. We are now developing a VCS system, including not only data acquisition hardware but data processing and analysis technique. Our first experiment of VCS surveys has been carried out in Lake Biwa, JAPAN in November 2009 for a feasibility study. Prestack depth migration is applied to the 3D VCS data to obtain a high quality 3D depth volume. Based on the results from the feasibility study, we have developed two autonomous recording VCS systems. After we carried out a trial experiment in the actual ocean at a water depth of about 400m and we carried out the second VCS survey at Iheya Knoll with a deep-towed source. In this survey, we could establish the procedures for the deployment/recovery of the system and could examine the locations and the fluctuations of the vertical cables at a water depth of around 1000m. The acquired VCS data clearly shows the reflections from the sub-seafloor. Through the experiment, we could confirm that our VCS system works well even in the severe circumstances around the locations of seafloor hydrothermal deposits. We have, however, also confirmed that the uncertainty in the locations of the source and of the hydrophones could lower the quality of subsurface image. It is, therefore, strongly necessary to develop a total survey system that assures a accurate positioning and a deployment techniques. We have carried out two field surveys in FY2011. One is a 3D survey with a boomer for a high-resolution surface source and the other one for an actual field survey in the Izena Cauldron an active hydrothermal area in the Okinawa Trough. Through these surveys, the VCS will become a practical exploration tool for the exploration of seafloor hydrothermal deposits.

Full 40 km crustal reflection seismic datasets in several Indonesian basins

NASA Astrophysics Data System (ADS)

Dinkelman, M. G.; Granath, J. W.; Christ, J. M.; Emmet, P. A.; Bird, D. E.

2010-12-01

Long offset, deep penetration regional 2D seismic data sets have been acquired since 2002 by GX Technology in a number of regions worldwide (www.iongeo.com/Data_Libraries/Spans/). Typical surveys consist of 10+ lines located to image specific critical aspects of basin structure. Early surveys were processed to 20 km, but more recent ones have extended to 40-45 km from 16 sec records. Pre-stack time migration is followed by pre-stack depth migration using gravity and in some cases magnetic modeling to constrain the velocity structure. We illustrate several cases in the SE Asian and Australasian area. In NatunaSPAN™ two generations of inversion can be distinguished, one involving Paleogene faults with Neogene inversion and one involving strike slip-related uplift in the West Natuna Basin. Crustal structure in the very deep Neogene East Natuna Basin has also been imaged. The JavaSPAN™ program traced Paleogene sediments onto oceanic crust of the Flores Sea, thus equating back arc spreading there to the widespread Eocene extension. It also imaged basement in the Makassar Strait beneath as much as 6 km of Cenozoic sedimentary rocks that accumulated Eocene rift basins (the North and South Makassar basins) on the edge of Sundaland, the core of SE Asia. The basement is seismically layered: a noisy upper crust overlies a prominent 10 km thick transparent zone, the base of which marks another change to slightly noisier reflectivity. Eocene normal faults responsible for the opening of extensional basins root in the top of the transparent layer which may be Moho or a brittle-ductile transition within the extended continental crust. Of particular significance is the first image of thick Precambrian basins comprising the bulk of continental crust under the Arafura Sea in the ArafuraSPAN™ program. Four lines some 1200 km long located between Australia and New Guinea on the Arafura platform image a thin Phanerozoic section overlying a striking Precambrian basement composed of sedimentary and burial metamorphosed sedimentary rock that we divide into two packages on the basis of seismic character. The upper is 8-15 km of undeformed late Precambrian sediments the top of which ties Eocambrian rocks in wells in offshore New Guinea. This package appears to correlate to the Wessel Group in northern Australia. The lower package is composed of 10-15 km of strongly bedded, presumably burial metamorphosed rocks that make up the bulk of the lower crust. These may equate to any of a number of northern Australian Mesoproterozoic basins. This lower package offlaps ‘pods’ of seismically transparent basement (?Paleoproterozoic or Archean) that make up at most the lowermost 15 km of the 40 km PSDM line. Both Precambrian packages appear to be craton-margin sedimentary wedges, the younger overlapping the older. The SE extent of the lowermost package is deformed in a thrust system which may mark the event that detached it from its original underlying oceanic or transitional crust during cratonization. The SPAN programs are important new data sets to clarify and in some cases solve outstanding problems in basin architecture and tectonic evolution.

Do Daphnia use metalimnetic organic matter in a north temperate lake? An analysis of vertical migration

USGS Publications Warehouse

Brosseau, Chase Julian; Cline, Timothy J.; Cole, Jonathan J.; Hodgson, James R.; Pace, Michael L.; Weidel, Brian C.

2012-01-01

Diel vertical migration of zooplankton is influenced by a variety of factors including predation, food, and temperature. Research has recently shifted from a focus on factors influencing migration to how migration affects nutrient cycling and habitat coupling. Here we evaluate the potential for Daphnia migrations to incorporate metalimnetic productivity in a well-studied northern Wisconsin lake. We use prior studies conducted between 1985 and 1990 and current diel migration data (2008) to compare day and night Daphnia vertical distributions with the depth of the metalimnion (between the thermocline and 1% light depth). Daphnia migrate from a daytime mean residence depth of between about 1.7 and 2.5 m to a nighttime mean residence depth of between 0 and 2.0 m. These migrations are consistent between the prior period and current measurements. Daytime residence depths of Daphnia are rarely deep enough to reach the metalimnion; hence, metalimnetic primary production is unlikely to be an important resource for Daphnia in this system.

Resolution enhancement of robust Bayesian pre-stack inversion in the frequency domain

NASA Astrophysics Data System (ADS)

Yin, Xingyao; Li, Kun; Zong, Zhaoyun

2016-10-01

AVO/AVA (amplitude variation with an offset or angle) inversion is one of the most practical and useful approaches to estimating model parameters. So far, publications on AVO inversion in the Fourier domain have been quite limited in view of its poor stability and sensitivity to noise compared with time-domain inversion. For the resolution and stability of AVO inversion in the Fourier domain, a novel robust Bayesian pre-stack AVO inversion based on the mixed domain formulation of stationary convolution is proposed which could solve the instability and achieve superior resolution. The Fourier operator will be integrated into the objective equation and it avoids the Fourier inverse transform in our inversion process. Furthermore, the background constraints of model parameters are taken into consideration to improve the stability and reliability of inversion which could compensate for the low-frequency components of seismic signals. Besides, the different frequency components of seismic signals can realize decoupling automatically. This will help us to solve the inverse problem by means of multi-component successive iterations and the convergence precision of the inverse problem could be improved. So, superior resolution compared with the conventional time-domain pre-stack inversion could be achieved easily. Synthetic tests illustrate that the proposed method could achieve high-resolution results with a high degree of agreement with the theoretical model and verify the quality of anti-noise. Finally, applications on a field data case demonstrate that the proposed method could obtain stable inversion results of elastic parameters from pre-stack seismic data in conformity with the real logging data.

Updated mapping and seismic reflection data processing along the Queen Charlotte fault system, southeast Alaska

NASA Astrophysics Data System (ADS)

Walton, M. A. L.; Gulick, S. P. S.; Haeussler, P. J.; Rohr, K.; Roland, E. C.; Trehu, A. M.

2014-12-01

The Queen Charlotte Fault (QCF) is an obliquely convergent strike-slip system that accommodates offset between the Pacific and North America plates in southeast Alaska and western Canada. Two recent earthquakes, including a M7.8 thrust event near Haida Gwaii on 28 October 2012, have sparked renewed interest in the margin and led to further study of how convergent stress is accommodated along the fault. Recent studies have looked in detail at offshore structure, concluding that a change in strike of the QCF at ~53.2 degrees north has led to significant differences in stress and the style of strain accommodation along-strike. We provide updated fault mapping and seismic images to supplement and support these results. One of the highest-quality seismic reflection surveys along the Queen Charlotte system to date, EW9412, was shot aboard the R/V Maurice Ewing in 1994. The survey was last processed to post-stack time migration for a 1999 publication. Due to heightened interest in high-quality imaging along the fault, we have completed updated processing of the EW9412 seismic reflection data and provide prestack migrations with water-bottom multiple reduction. Our new imaging better resolves fault and basement surfaces at depth, as well as the highly deformed sediments within the Queen Charlotte Terrace. In addition to re-processing the EW9412 seismic reflection data, we have compiled and re-analyzed a series of publicly available USGS seismic reflection data that obliquely cross the QCF. Using these data, we are able to provide updated maps of the Queen Charlotte fault system, adding considerable detail along the northernmost QCF where it links up with the Chatham Strait and Transition fault systems. Our results support conclusions that the changing geometry of the QCF leads to fundamentally different convergent stress accommodation north and south of ~53.2 degrees; namely, reactivated splay faults to the north vs. thickening of sediments and the upper crust to the south. We also highlight areas where additional data are needed and would be ideal targets for future study.

Imaging of Ultra-Wideband Georadar Data

NASA Astrophysics Data System (ADS)

ferguson, Robert; Yedlin, Matthew; Pichot, Christian; Dauvignac, Jean-Yves; Fortino, Nicolas; Gaffet, Stéphane

2013-04-01

We present a methodology for georadar acquisition and processing that returns superior images of the subsurface for low cost. Georadar data were acquired in March 2011 in the anti-blast tunnel within the Inter-Disciplinary Underground Science & Technology Laboratory at the Laboratoire Souterrain a Bas Bruit (LSBB, http://lsbb.oca.eu), Rustrel, France. The georadar data from LSBB were acquired with an exponentially tapered slot antenna (ETSA) of the Vivaldi type. The ETSA is connected to an Agilent vector network analyzer and it operates between 150 MHz to 2 GHz with a noise floor of -120 dB. One of the most interesting technical aspects of the recordings is the use of both a conventional bistatic recording geometry (the source / receiver offset is about 65 cm) and what we will call a monostatic recording geometry where the emitting antenna is also the receiving antenna. The monostatic (reflection) data and bistatic (transmission) data are recorded complex numbers and each recorded number is a stack of monochromatic wave measurements. This system is reported to have a number of outstanding attributes including long depth of resolution due to it's wide bandwidth. Compared to other systems it has a greater dynamic range plus low distortion, and this is achieved with low-noise, low-loss cables and shielding with ultra-wideband absorbers. The resulting monostatic georadargrams are a true, zero-offset recording geometry, and so zero-offset migration (imaging that is based on the exploding reflector concept) returns a high accuracy image for low cost. To restore reflection attenuation due to the low Q factor associated with georadar, we apply nonstationary, Gabor-domain deconvolution. We find that amplitude attenuation is restored and phase distortion is corrected. The improved accuracy of our methodology is established first through direct comparison of our Gabor-deconvolved data with conventional, stationary deconvolution where we find that the nonstationary result is superior. Then, using a bistatic data set for an imaging comparison, we show that ZOM ( Zero-Offset Migration) applied to the bistatic data introduces spurious reflection imagery in the upper 50 cm, but that PSDM (Pre-Stack Depth Migration) of the bistatic data returns an image that is similar to ZOM of the monostatic data. The bistatic data were acquired coincident with the monostatic acquisition and have a source / receiver offset of 65 cm. Thus, imaging accuracy associated with PSDM is achieved using ZOM at 1/100 the computational cost. In the deeper section of our dataset, we find that the ZOM image using the monostatic data returns a significantly improved image than PSDM of the bistatic data. This is unexpected, but perhaps the difference is a phenomenon that is due to out-of-plane reflections and that 2D PSDM is rightly defocussing out-of-plane energy. We feel that subsequent 3D data acquisition could resolve this difference.

Continental break-up history of a deep magma-poor margin based on seismic reflection data (northeastern Gulf of Aden margin, offshore Oman)

NASA Astrophysics Data System (ADS)

Autin, Julia; Leroy, Sylvie; Beslier, Marie-Odile; d'Acremont, Elia; Razin, Philippe; Ribodetti, Alessandra; Bellahsen, Nicolas; Robin, Cécile; Al Toubi, Khalfan

2010-02-01

Rifting between Arabia and Somalia started around 35 Ma followed by spreading at 17.6 Ma in the eastern part of the Gulf of Aden. The first-order segment between Alula-Fartak and Socotra-Hadbeen fracture zones is divided into three second-order segments with different structure and morphology. Seismic reflection data were collected during the Encens Cruise in 2006 on the northeastern margin. In this study, we present the results of Pre-Stack Depth Migration of the multichannel seismic data from the western segment, which allows us to propose a tectono-stratigraphic model of the evolution of this segment of the margin from rifting to the present day. The chronological interpretation of the sedimentary sequences is mapped out within relation to the onshore observations and existing dating. After a major development of syn-rift grabens and horsts, the deformation localized where the crust is the thinnest. This deformation occurred in the distal margin graben (DIM) at the northern boundary of the ocean-continent transition (OCT) represented by the OCT ridge. At the onset of the OCT formation differential uplift induced a submarine landslide on top of the deepest tilted block and the crustal deformation was restricted to the southern part of the DIM graben, where the continental break-up finally occurred. Initial seafloor spreading was followed by post-rift magmatic events (flows, sills and volcano-sedimentary wedge), whose timing is constrained by the analysis of the sedimentary cover of the OCT ridge, correlated with onshore stratigraphy. The OCT ridge may represent exhumed serpentinized mantle intruded by post-rift magmatic material, which modified the OCT after its emplacement.

Geophysical Characterization for Potential Carbon Dioxide Sequestration in the Black Warrior Basin of Alabama

NASA Astrophysics Data System (ADS)

Goodliffe, A. M.; Harris, W.; Rutter, R. S.; Clark, P.; Pashin, J. C.; Esposito, R. A.

2011-12-01

The southeastern US is a leading producer of carbon dioxide emissions in large part due to the high number of coal-fired power plants in the region. As part of a Department of Energy (DOE) National Energy Technology Laboratory (NETL) funded geological characterization project we have collected a number of geophysical data sets that characterize the Black Warrior Basin in the vicinity of the Alabama Power Gorgas Steam Plant in Walker County, Alabama. These geophysical data sets are important for extending the results from our 8000-foot characterization hole throughout the basin. Two 5-mile seismic reflection profiles processed through pre-stack time migration image the Cambrian through Pennsylvanian stratigraphy in the basin. The major injection targets in the saline reservoirs of the Hartselle Sandstone, Tuscumbia Limestone, Stones River Group and Knox Group. Initial examination of the data show that it is well suited for techniques such as Amplitude Versus Offset (AVO) analysis and inversion with the downhole data. Multiple offset vertical seismic profiles (VSP) image the formations close to and at multiple azimuths away from the drill hole. These VSPs also provide an important link to the seismic reflection profiles, which pass a little less than a mile to the north of the drill hole. Three shallow microseismic wells in the vicinity of the main drill hole have 3-component geophones cemented at depths of 50, 150, and 250 foot. These wells, designed to record small magnitude seismic events resulting from low-volume water injection, are important for characterizing the local fracture pathways and stress fields. Downhole gravity data complements the usual suite of downhole tools by imaging density variations deeper into the formations and ensuring that the identified saline reservoirs are not locally discontinuous.

How the gas hydrate system gives insight into subduction wedge dewatering processes in a zone of highly-oblique convergence on the southern Hikurangi margin of New Zealand

NASA Astrophysics Data System (ADS)

Crutchley, Gareth; Klaeschen, Dirk; Pecher, Ingo; Henrys, Stuart

2017-04-01

The southern end of New Zealand's Hikurangi subduction margin is characterised by highly-oblique convergence as it makes a southward transition into a right-lateral transform plate boundary at the Alpine Fault. Long-offset seismic data that cross part of the offshore portion of this transition zone give new insight into the nature of the plate boundary. We have carried out 2D pre-stack depth migrations, with an iterative reflection tomography to update the velocity field, on two seismic lines in this area to investigate fluid flow processes that have implications for the mechanical stability of the subduction interface. The results show distinct and focused fluid expulsion pathways from the subduction interface to the shallow sub-surface. For example, on one of the seismic lines there is a clear disruption of the gas hydrate system at its intersection with a splay fault - a clear indication of focused fluid release from the subduction interface. The seismic velocities derived from tomography also highlight a broad, pronounced low velocity zone beneath the deforming wedge that we interpret as a thick zone of gas-charged fluids that may have important implications for the long-term frictional stability of the plate boundary in this area. The focused flow upward toward the seafloor has the potential to result in the formation of concentrated gas hydrate deposits. Our on-going work on these data will include amplitude versus offset analysis in an attempt to better characterise the nature of the subduction interface, the fluids in that region, and also the shallower gas hydrate system.

Shear Wave Splitting analysis of borehole microseismic reveals weak azimuthal anisotropy hidden behind strong VTI fabric of Lower Paleozoic shales in northern Poland

NASA Astrophysics Data System (ADS)

Gajek, Wojciech; Verdon, James; Malinowski, Michał; Trojanowski, Jacek

2017-04-01

Azimuthal anisotropy plays a key-role in hydraulic fracturing experiments, since it provides information on stress orientation and pre-existing fracture system presence. The Lower Paleozoic shale plays in northern Poland are characterized by a strong (15-18%) Vertical Transverse Isotropy (VTI) fabric which dominates weak azimuthal anisotropy being of order of 1-2%. A shear wave travelling in the subsurface after entering an anisotropic medium splits into two orthogonally polarized waves travelling with different velocities. Splitting parameters which can be assessed using a microseismic array are polarization of the fast shear wave and time delay between two modes. Polarization of the fast wave characterizes the anisotropic system on the wave path while the time delay is proportional to the magnitude of anisotropy. We employ Shear Wave Splitting (SWS) technique using a borehole microseismic dataset collected during a hydraulic stimulation treatment located in northern Poland, to image fracture strike masked by a strong VTI signature. During the inversion part, the VTI background parameters were kept constant using information from 3D seismic (VTI model used for pre-stack depth migration). Obtained fracture azimuths averaged over fracturing stages are consistent with the available XRMI imager logs from the nearby vertical well, however they are different from the large-scale maximum stress direction (by 40-45 degrees). Inverted Hudson's crack density (ca. 2%) are compatible with the low shear-wave anisotropy observed in the cross-dipole sonic logs (1-2%). This work has been funded by the Polish National Centre for Research and Development within the Blue Gas project (No BG2/SHALEMECH/14). Data were provided by the PGNiG SA. Collaboration with University of Bristol was supported within TIDES COST Action ES1401.

Sub-basalt Imaging of Hydrocarbon-Bearing Mesozoic Sediments Using Ray-Trace Inversion of First-Arrival Seismic Data and Elastic Finite-Difference Full-Wave Modeling Along Sinor-Valod Profile of Deccan Syneclise, India

NASA Astrophysics Data System (ADS)

Talukdar, Karabi; Behera, Laxmidhar

2018-03-01

Imaging below the basalt for hydrocarbon exploration is a global problem because of poor penetration and significant loss of seismic energy due to scattering, attenuation, absorption and mode-conversion when the seismic waves encounter a highly heterogeneous and rugose basalt layer. The conventional (short offset) seismic data acquisition, processing and modeling techniques adopted by the oil industry generally fails to image hydrocarbon-bearing sub-trappean Mesozoic sediments hidden below the basalt and is considered as a serious problem for hydrocarbon exploration in the world. To overcome this difficulty of sub-basalt imaging, we have generated dense synthetic seismic data with the help of elastic finite-difference full-wave modeling using staggered-grid scheme for the model derived from ray-trace inversion using sparse wide-angle seismic data acquired along Sinor-Valod profile in the Deccan Volcanic Province of India. The full-wave synthetic seismic data generated have been processed and imaged using conventional seismic data processing technique with Kirchhoff pre-stack time and depth migrations. The seismic image obtained correlates with all the structural features of the model obtained through ray-trace inversion of wide-angle seismic data, validating the effectiveness of robust elastic finite-difference full-wave modeling approach for imaging below thick basalts. Using the full-wave modeling also allows us to decipher small-scale heterogeneities imposed in the model as a measure of the rugose basalt interfaces, which could not be dealt with ray-trace inversion. Furthermore, we were able to accurately image thin low-velocity hydrocarbon-bearing Mesozoic sediments sandwiched between and hidden below two thick sequences of high-velocity basalt layers lying above the basement.

The Messinian evaporites in the Levant Basin: lithology, deformation and its evolution

NASA Astrophysics Data System (ADS)

Feng, Ye; Steinberg, Josh; Reshef, Moshe

2017-04-01

The lithological composition of the Messinian evaporite in the Levant Basin remains controversial and salt deformation mechanisms are still not fully understood, due to the lack of high resolution 3D depth seismic data and well logs that record the entire evaporite sequence. We demonstrate how 3D Pre-stack depth migration (PSDM) and intra-salt tomography can lead to improved salt imaging. Using 3D PSDM seismic data with great coverage and deepwater well log data from recently drilled boreholes, we reveal intra-salt reflective units associated with thin clastic layers and a seismic transparent background consisting of uniform pure halite. Structural maps of all internal reflectors are generated for stratigraphy and attributes analysis. High amplitude fan structures in the lowermost intra-salt reflector are observed, which may indicate the source of the clastic formation during the Messinian Salinity Crisis (MSC). The Messinian evaporite in the Levant Basin comprises six units; the uppermost unit thickens towards the northwest, whereas the other units are uniform in thickness. The top of salt (TS) horizon is relatively horizontal, while all other intra-salt reflectors and base of salt (BS) dip towards the northwest. Different seismic attributes are used for identification of intra-salt deformation patterns. Maximum curvature maps show NW-striking thrust faults on the TS and upper intra-salt units, and dip azimuth maps are used to show different fold orientations between the TS and intra-salt units, which indicate a two-phase deformation mechanism: basin NW tilting as syn-depositional phase and NNE spreading of Plio-Pleistocene overburden as post-depositional phase. RMS amplitude maps are used to identify a channelized system on the TS. An evaporite evolution model during the MSC of the Levant Basin is therefore established based on all the observations. Finally the mechanical properties of the salts will be utilized to explore salt deformation in the Levant Basin. Feng, Y. E., & Reshef, M. (2016). The Eastern Mediterranean Messinian salt-depth imaging and velocity analysis considerations. Petroleum Geoscience, 22(4), 2-19. doi:http://dx.doi.org/10.1144/petgeo2015-088 Feng, Y. E., Yankelzon, A., Steinberg, J., & Reshef, M. (2016). Lithology and characteristics of the Messinian evaporite sequence of the deep Levant Basin, eastern Mediterranean. Marine Geology, 376, 118-131. doi:http://dx.doi.org/10.1016/j.margeo.2016.04.004

Crustal shortening followed by extensional collapse of the Cordilleran orogenic belt in northwestern Montana: Evidence from vintage seismic reflection profiles acquired in the Swan Range and Swan Valley

NASA Astrophysics Data System (ADS)

Rutherford, B. S.; Speece, M. A.; Stickney, M. C.; Mosolf, J. G.

2013-12-01

Reprocessing of one 24-fold (96 channel) and four 30-fold (120 channel) 2D seismic reflection profiles have revealed crustal scale reflections in the Swan Range and adjacent Swan River Valley of northwestern Montana. The five reprocessed profiles constitute 142.6 of the 303.3 linear km acquired in 1983-84 by Techo of Denver, Colorado. The four 30-fold profiles used helicopter-assisted dynamite shooting (Poulter method) and the 24-fold profile used the Vibroseis method. Acquisition parameters were state of the art for the time. The Swan Range lies east of the Rocky Mountain Trench and is part of the Cordilleran foreland thrust belt where the Lewis thrust system emplaced a thick slab of Proterozoic Belt Supergroup strata eastward and over Paleozoic and Mesozoic rocks during the Late Cretaceous to early Paleocene Laramide orogeny. Deeply drilled borehole data are absent within the study area; however, we generated a synthetic seismogram from the Arco-Marathon 1 Paul Gibbs well (total depth=5418 m), located approximately 70 km west of the reprocessed profiles, and correlated the well data to surface seismic profiles. Large impedance contrasts in the log data are interpreted to be tholeiitic Moyie sills within the Prichard Formation argillite (Lower Belt), which produce strong reflection events in regional seismic sections and result in highly reflective, east-dipping events in the reprocessed profiles. We estimate a depth of 10 km (3 to 3.5 seconds) to the basal detachment of the Lewis thrust sheet. The décollement lies within Belt Supergroup strata to the west of the Swan River Valley before contacting unreflective, west-dipping crystalline basement beneath the Swan Range--a geometry that results in a wedge of eastward-thinning, autochthonous Belt rocks. Distinct fault-plane signatures from the west-dipping, range-bounding Swan fault--produced by extensional collapse of the over-thickened Cordillera--are not successfully imaged. However, reflections from Cenozoic half-graben fill suggest up to 1.5 km of Cenozoic basin filling sediments are present. Refraction tomography velocity modeling of distinct refracted arrivals, prevalent in the gathers, constrain a half-graben geometry for the Swan Valley. Signal attenuation within the low-velocity valley fill make correlation of reflectors at the depth of the décollement impossible underneath the Swan Valley. Prestack depth migration of the sections is anticipated to improve geometric constraints on major structural features of the Swan Range and Swan Valley.

Crustal structure and tectonic deformation of the southern Ecuadorian margin

NASA Astrophysics Data System (ADS)

Calahorrano, Alcinoe; Collot, Jean-Yves; Sage, Françoise; Ranero, César R.

2010-05-01

Multichannel seismic lines acquired during the SISTEUR cruise (2000) provide new constraints on the structure and deformation of the subduction zone at the southern Ecuadorian margin, from the deformation front to the continental shelf of the Gulf of Guayaquil. The pre-stack depth migrated images allows to characterise the main structures of the downgoing and overriding plates and to map the margin stratigraphy in order to propose a chronology of the deformation, by means of integrating commercial well data and industry seismic lines located in the gulf area. The 100-km-long seismic lines show the oceanic Nazca plate underthrusting the South American plate, as well as the subduction channel and inter-plate contact from the deformation front to about 90 km landward and ~20 km depth. Based on seismic structure we identify four upper-plate units, consisting of basement and overlaying sedimentary sequences A, B and C. The sedimentary cover varies along the margin, being few hundreds of meters thick in the lower and middle slope, and ~2-3 km thick in the upper slope. Exceptionally, a ~10-km -thick basin, here named Banco Peru basin, is located on the upper slope at the southernmost part of the gulf. This basin seems to be the first evidence of the Gulf of Guayaquil opening resulting from the NE escaping of the North Andean Block. Below the continental shelf, thick sedimentary basins of ~6 to 8 km occupy most of the gulf area. Tectonic deformation across most of the upper-plate is dominated by extensional regime, locally disturbed by diapirism. Compression evidences are restricted to the deformation front and surrounding areas. Well data calibrating the seismic profiles indicate that an important portion of the total thickness of the sedimentary coverage of the overriding plate are Miocene or older. The data indicate the extensional deformation resulting from the NE motion of the North Andean Block and the opening of the Gulf of Guayaquil, evolves progressively in age from the southern edge of the gulf near Banco Peru, where main subsidence seems to be Miocene or older, toward the northern limit, where high subsidence rates are early Pleistocene.

Seismic Velocity Variation and Evolution of the Upper Oceanic Crust across the Mid-Atlantic Ridge at 1.3°S

NASA Astrophysics Data System (ADS)

Jian, H.; Singh, S. C.

2017-12-01

The oceanic crust that covers >70% of the solid earth is formed at mid-ocean ridges, but get modified as it ages. Understanding the evolution of oceanic crust requires investigations of crustal structures that extend from zero-age on the ridge axis to old crust. In this study, we analyze a part of a 2000-km-long seismic transect that crosses the Mid-Atlantic Ridge segment at 1.3°S, south of the Chain transform fault. The seismic data were acquired using a 12-km-long multi-sensor streamer and dense air-gun shots. Using a combination of downward continuation and seismic tomography methods, we have derived a high-resolution upper crustal velocity structure down to 2-2.5 km depth below the seafloor, from the ridge axis to 3.5 Ma on both sides of the ridge axis. The results demonstrate that velocities increase at all depths in the upper crust as the crust ages, suggesting that hydrothermal precipitations seal the upper crustal pore spaces. This effect is most significant in layer 2A, causing a velocity increase of 0.5-1 km/s after 1-1.5 Ma, beyond which the velocity increase is very small. Furthermore, the results exhibit a significant decrease in both the frequency and amplitude of the low-velocity anomalies associated with faults beyond 1-1.5 Ma, when faults become inactive, suggesting a linkage between the sealing of fault space and the extinction of hydrothermal activity. Besides, the off-axis velocities are systematically higher on the eastern side of the ridge axis compared to on the western side, suggesting that a higher hydrothermal activity should exist on the outside-corner ridge flank than on the inside-corner flank. While the tomography results shown here cover 0-3.5 Ma crust, the ongoing research will further extend the study area to older crust and also incorporating pre-stack migration and full waveform inversion methods to improve the seismic structure.

Seismic Reflection Imaging of the Heat Source of an Ultramafic-Hosted Hydrothermal System (Rainbow, Mid-Atlantic Ridge 36° 10-17'N)

NASA Astrophysics Data System (ADS)

Canales, J. P.; Dunn, R. A.; Sohn, R. A.; Horning, G.; Arai, R.; Paulatto, M.

2015-12-01

Most of our understanding of hydrothermal systems and the nature of their heat sources comes from models and observations at fast and intermediate spreading ridges. In these settings, hydrothermal systems are mainly located within the axial zone of a spreading segment, hosted in basaltic rock, and primarily driven by heat extracted from crystallization of crustal melt sills. In contrast, hydrothermal systems at slow-spreading ridges like the Mid-Atlantic Ridge (MAR) show a great variety of venting styles and host-rock lithology, and are located in diverse tectonic settings like axial volcanic ridges, non-transform discontinuities (NTDs), the foot of ridge valley walls, and off-axis inside corner highs. Among MAR systems, the Rainbow hydrothermal field (RHF) stands out as an end-member of this diversity: an ultramafic-hosted system emitting H2 and CH4-rich fluids at high temperatures and high flow rates, which suggests a magmatic heat source despite the lack of evidence for recent volcanism and its location within an NTD with presumably low magma budget. We present 2D multichannel seismic reflection images across the Rainbow massif from the NSF-funded MARINER multidisciplinary geophysical study that reveal, for the first time, the magmatic system driving hydrothermal circulation in an ultramafic setting. Data were acquired in 2013 onboard the RV M. Langseth with an 8-km-long hydrophone streamer. The images have been obtained from pre-stack depth migrations using a regional 3D P-wave velocity model from a coincident controlled-source seismic tomography experiment using ocean bottom seismometers. Our images show a complex magmatic system centered beneath the RHF occupying an areal extent of ~3.7x6 km2, with partially molten sills ranging in depth between ~3.4 km and ~6.9 km below the seafloor. Our data also image high-amplitude dipping reflections within the massif coincident with strong lateral velocity gradients that may arise from detachment fault planes, lithological contacts, and/or alteration boundaries. Our results are an important step towards understanding the interactions of detachment faulting, magmatic intrusion, and hydrothermal circulation.

Data-driven Green's function retrieval and application to imaging with multidimensional deconvolution

NASA Astrophysics Data System (ADS)

Broggini, Filippo; Wapenaar, Kees; van der Neut, Joost; Snieder, Roel

2014-01-01

An iterative method is presented that allows one to retrieve the Green's function originating from a virtual source located inside a medium using reflection data measured only at the acquisition surface. In addition to the reflection response, an estimate of the travel times corresponding to the direct arrivals is required. However, no detailed information about the heterogeneities in the medium is needed. The iterative scheme generalizes the Marchenko equation for inverse scattering to the seismic reflection problem. To give insight in the mechanism of the iterative method, its steps for a simple layered medium are analyzed using physical arguments based on the stationary phase method. The retrieved Green's wavefield is shown to correctly contain the multiples due to the inhomogeneities present in the medium. Additionally, a variant of the iterative scheme enables decomposition of the retrieved wavefield into its downgoing and upgoing components. These wavefields then enable creation of a ghost-free image of the medium with either cross correlation or multidimensional deconvolution, presenting an advantage over standard prestack migration.

Near-surface Imaging of a Maya Plaza Complex using Ground-Penetrating Radar

NASA Astrophysics Data System (ADS)

Aitken, J. A.; Stewart, R. R.

2005-05-01

The University of Calgary has conducted a number of ground-penetrating radar surveys at a Maya archaeological site. The purpose of the study is to discern the near-surface structure and stratigraphy of the plaza, and to assist the archaeologists in focusing their excavation efforts. The area of study is located in Belize, Central America at the ancient Maya site of Maax Na. Flanked by structures believed to be temples to the north and west, the archaeologists were interested in determining how many levels of plaza were built and if there was any discernable slope to the plaza. Over the last three years, both 2-D lines and 3-D grids were acquired at the plaza using a Sensors and Software Inc. Noggin Plus system at an antenna frequency of 250 MHz. The processing flow consisted of the application of gain, various filtering techniques and a diffraction stack migration using Reflexw. Interpolation of the gridded data was investigated using simple averaging, F-K migration, pre-stack migration and inversion techniques. As this study has evolved over different field seasons, measured velocities appear to change with the saturation level of the shallow section. Velocity measurements ranged from 0.058 - .106 m/ns during the wet conditions encountered in 2002 and 2004, while velocities of 1.22 - 1.40 m/ns were measured in the drought of 2003. The GPR images to date indicate continuous and interpretable images of the subsurface, showing evidence of structure, discontinuities and amplitude variations. A number of interesting anomalies have been identified, and prioritized for excavation.

Estimating the free gas content in Baltic Sea sediments using compressional wave velocity from marine seismic data

NASA Astrophysics Data System (ADS)

Tóth, Zsuzsanna; Spiess, Volkhard; Mogollón, José M.; Jensen, Jørn Bo

2014-12-01

A 2-D high-resolution velocity field was obtained from marine seismic data to quantify free gas content in shallow muddy sediments at in situ pressure and temperature. The velocities were acquired applying Migration Velocity Analysis on prestack time-migrated data. Compressional wave velocities are highly sensitive to free gas as very small amounts of gas can cause a significant decrease in the medium velocity. The analyzed profile crosses a depression filled with organic-rich Holocene mud in the Bornholm Basin, Baltic Sea. The interval velocity field reveals two low-velocity patches, which extend from the reversed polarity reflections marking the top of the gassy sediment layer down to the base of the Holocene mud. Average interval velocities within the gassy mud are lower than the seafloor migration velocity by up to ˜500 m/s. This decrease, using a geoacoustic model, is caused by an average 0.046% gas volume fraction. The interval velocities in individual cells of the velocity field are reduced to ˜200 m/s predicting up to 3.4% gas content. The velocity field is limited in resolution due to velocity determination at and between reflections; however, together with the stratigraphic interpretation, geological units containing free gas could be identified. Shallow gas occurs vertically throughout most of the Holocene mud in the gassy area. Comparison with biogeochemical studies at other Baltic Sea sites suggests that the distribution of free gas is likely to be patchy in the sediment, but the gas concentration may peak below the sulfate-methane transition zone and gradually decrease below.

Reply to “Comment on ‘Near-surface location, geometry, and velocities of the Santa Monica fault zone, Los Angeles, California’ by R. D. Catchings, G. Gandhok, M. R. Goldman, D. Okaya, M. J. Rymer, and G. W. Bawden” by T. L. Pratt and J. F. Dolan

USGS Publications Warehouse

Catchings, Rufus D.; Rymer, Michael J.; Goldman, Mark R.; Bawden, Gerald W.

2010-01-01

In a comment on our 2008 paper (Catchings, Gandhok, et al., 2008) on the Santa Monica fault in Los Angeles, California, Pratt and Dolan (2010) (herein referred to as P&D) cite numerous objections to our work, inferring that our study is flawed. However, as shown in our reply, their objections contradict their own published works, published works of others, and proven seismic methodologies. Rather than responding to each repeated invalid objection, we address their objections by topic in the subsequent sections.In Catchings, Gandhok, et al. (2008), we presented high-resolution seismic-reflection images that showed two near-surface faults in the upper 50 m beneath the grounds of the Wadsworth Veterans Administration Hospital (WVAH). Although P&D suggest we effectively duplicated their seismic acquisition, our survey was not a duplication of their efforts. Rather, we conducted a seismic-imaging survey over a similar profile as Pratt et al. (1998) but used a different data acquisition system and different data processing methods to evaluate methods of seismically imaging blind faults in the wake of the 17 January 1994 M 6.7 Northridge earthquake. We used an acquisition method that provides both tomographic seismic velocities and reflection images. Our combined-data approach allowed for shallower imaging (∼2.5 m minimum) than the ∼20-m minimum of Pratt et al. (1998), clearer images of the fault zone, and more accurate depth determinations (rather than time images). In processing the reflection images, we used prestack depth migration, which is generally accepted as the only proper imaging method for imaging subsurface structures with strong lateral velocity variations (Versteeg, 1993), a condition shown to exist at the WVAH site. We correlated our reflection images with refraction tomography images, borehole lithology, and velocity data, Interferometric Synthetic Aperture Radar images, and changes in groundwater depths. Except for some minor differences, our seismic-reflection images coincide with previously published seismic-reflection images by Dolan and Pratt (1997) and Pratt et al. (1998), and a paleoseismic study by Dolan et al. (2000). Principal differences among our interpretations and those of Pratt et al. (1998) relate to the upper 20 m and the south side of the fault, which Pratt et al. (1998) did not clearly image. In contrast, our seismic images included structures on both sides of the fault zone from about 2.5 m depth to about 100 m depth at WVAH, allowing us to interpret more details.

Time-lapse processing of 2D seismic profiles with testing of static correction methods at the CO2 injection site Ketzin (Germany)

NASA Astrophysics Data System (ADS)

Bergmann, Peter; Yang, Can; Lüth, Stefan; Juhlin, Christopher; Cosma, Calin

2011-09-01

The Ketzin project provides an experimental pilot test site for the geological storage of CO2. Seismic monitoring of the Ketzin site comprises 2D and 3D time-lapse experiments with baseline experiments in 2005. The first repeat 2D survey was acquired in 2009 after 22 kt of CO2 had been injected into the Stuttgart Formation at approximately 630 m depth. Main objectives of the 2D seismic surveys were the imaging of geological structures, detection of injected CO2, and comparison with the 3D surveys. Time-lapse processing highlighted the importance of detailed static corrections to account for travel time delays, which are attributed to different near-surface velocities during the survey periods. Compensation for these delays has been performed using both pre-stack static corrections and post-stack static corrections. The pre-stack method decomposes the travel time delays of baseline and repeat datasets in a surface consistent manner, while the latter cross-aligns baseline and repeat stacked sections along a reference horizon. Application of the static corrections improves the S/N ratio of the time-lapse sections significantly. Based on our results, it is recommended to apply a combination of both corrections when time-lapse processing faces considerable near-surface velocity changes. Processing of the datasets demonstrates that the decomposed solution of the pre-stack static corrections can be used for interpretation of changes in near-surface velocities. In particular, the long-wavelength part of the solution indicates an increase in soil moisture or a shallower groundwater table in the repeat survey. Comparison with the processing results of 2D and 3D surveys shows that both image the subsurface, but with local variations which are mainly associated to differences in the acquisition geometry and source types used. Interpretation of baseline and repeat stacks shows that no CO2 related time-lapse signature is observable where the 2D lines allow monitoring of the reservoir. This finding is consistent with the time-lapse results of the 3D surveys, which show an increase in reflection amplitude centered around the injection well. To further investigate any potential CO2 signature, an amplitude versus offset (AVO) analysis was performed. The time-lapse analysis of the AVO does not indicate the presence of CO2, as expected, but shows signs of a pressure response in the repeat data.

Joint Stochastic Inversion of Pre-Stack 3D Seismic Data and Well Logs for High Resolution Hydrocarbon Reservoir Characterization

NASA Astrophysics Data System (ADS)

Torres-Verdin, C.

2007-05-01

This paper describes the successful implementation of a new 3D AVA stochastic inversion algorithm to quantitatively integrate pre-stack seismic amplitude data and well logs. The stochastic inversion algorithm is used to characterize flow units of a deepwater reservoir located in the central Gulf of Mexico. Conventional fluid/lithology sensitivity analysis indicates that the shale/sand interface represented by the top of the hydrocarbon-bearing turbidite deposits generates typical Class III AVA responses. On the other hand, layer- dependent Biot-Gassmann analysis shows significant sensitivity of the P-wave velocity and density to fluid substitution. Accordingly, AVA stochastic inversion, which combines the advantages of AVA analysis with those of geostatistical inversion, provided quantitative information about the lateral continuity of the turbidite reservoirs based on the interpretation of inverted acoustic properties (P-velocity, S-velocity, density), and lithotype (sand- shale) distributions. The quantitative use of rock/fluid information through AVA seismic amplitude data, coupled with the implementation of co-simulation via lithotype-dependent multidimensional joint probability distributions of acoustic/petrophysical properties, yields accurate 3D models of petrophysical properties such as porosity and permeability. Finally, by fully integrating pre-stack seismic amplitude data and well logs, the vertical resolution of inverted products is higher than that of deterministic inversions methods.

Partial diel migration: A facultative migration underpinned by long-term inter-individual variation.

PubMed

Harrison, Philip M; Gutowsky, Lee F G; Martins, Eduardo G; Patterson, David A; Cooke, Steven J; Power, Michael

2017-09-01

The variations in migration that comprise partial diel migrations, putatively occur entirely as a consequence of behavioural flexibility. However, seasonal partial migrations are increasingly recognised to be mediated by a combination of reversible plasticity in response to environmental variation and individual variation due to genetic and environmental effects. Here, we test the hypothesis that while partial diel migration heterogeneity occurs primarily due to short-term within-individual flexibility in behaviour, long-term individual differences in migratory behaviour also underpin this migration variation. Specifically, we use a hierarchical behavioural reaction norm approach to partition within- and among-individual variation in depth use and diel plasticity in depth use, across short- and long-term time-scales, in a group of 47 burbot (Lota lota) tagged with depth-sensing acoustic telemetry transmitters. We found that within-individual variation at the among-dates-within-seasons and among-seasons scale, explained the dominant proportion of phenotypic variation. However, individuals also repeatedly differed in their expression of migration behaviour over the 2 year study duration. These results reveal that diel migration variation occurs primarily due to short-term within-individual flexibility in depth use and diel migration behaviour. However, repeatable individual differences also played a key role in mediating partial diel migration. These findings represent a significant advancement of our understanding of the mechanisms generating the important, yet poorly understood phenomena of partial diel migration. Moreover, given the pervasive occurrence of diel migrations across aquatic taxa, these findings indicate that individual differences have an important, yet previously unacknowledged role in structuring the temporal and vertical dynamics of aquatic ecosystems. © 2017 The Authors. Journal of Animal Ecology © 2017 British Ecological Society.

Habitat use by fishes of Lake Superior. II. Consequences of diel habitat use for habitat linkages and habitat coupling in nearshore and offshore waters

USGS Publications Warehouse

Gorman, Owen T.; Yule, Daniel L.; Stockwell, Jason D.

2012-01-01

Diel migration patterns of fishes in nearshore (15–80 m depth) and offshore (>80 m) waters of Lake Superior were examined to assess the potential for diel migration to link benthic and pelagic, and nearshore and offshore habitats. In our companion article, we described three types of diel migration: diel vertical migration (DVM), diel bank migration (DBM), and no diel migration. DVM was expressed by fishes migrating from benthopelagic to pelagic positions and DBM was expressed by fishes migrating horizontally from deep to shallow waters at night. Fishes not exhibiting diel migration typically showed increased activity by moving from benthic to benthopelagic positions within demersal habitat. The distribution and biomass of fishes in Lake Superior was characterized by examining 704 bottom trawl samples collected between 2001 and 2008 from four depth zones: ≤40, 41–80, 81–160, and >160 m. Diel migration behaviors of fishes described in our companion article were applied to estimates of areal biomass (kg ha−1) for each species by depth zone. The relative strength of diel migrations were assessed by applying lake area to areal biomass estimates for each species by depth zone to yield estimates of lake-wide biomass (metric tonnes). Overall, species expressing DVM accounted for 83%, DBM 6%, and non-migration 11% of the total lake-wide community biomass. In nearshore waters, species expressing DVM represented 74% of the biomass, DBM 25%, and non-migration 1%. In offshore waters, species expressing DVM represented 85%, DBM 1%, and non-migration 14% of the biomass. Of species expressing DVM, 83% of total biomass occurred in offshore waters. Similarly, 97% of biomass of non-migrators occurred in offshore waters while 83% of biomass of species expressing DBM occurred in nearshore waters. A high correlation (R2 = 0.996) between lake area and community biomass by depth zone resulted in 81% of the lake-wide biomass occurring in offshore waters. Accentuating this nearshore-offshore trend was one of increasing estimated total areal biomass of the fish community with depth zone, which ranged from 13.71 kg ha−1 at depths ≤40 m to 18.81 kg ha−1 at depths >160 m, emphasizing the importance of the offshore fish community to the lake ecosystem. The prevalence of diel migration expressed by Lake Superior fishes increases the potential of fish to link benthic and pelagic and shallow and deepwater habitats. These linkages enhance the potential for habitat coupling, a condition where habitats become interconnected and interdependent through transfers of energy and nutrients. Habitat coupling facilitates energy and nutrient flow through a lake ecosystem, thereby increasing productivity, especially in large lakes where benthic and pelagic, and nearshore and offshore habitats are often well separated. We propose that the application of biomass estimates to patterns of diel migration in fishes can serve as a useful metric for assessing the potential for habitat linkages and habitat coupling in lake ecosystems, and provide an important indicator of ecosystem health and function. The decline of native Lake Trout and ciscoes and recent declines in exotic Alewife and Rainbow Smelt populations in other Great Lakes have likely reduced the capacity for benthic-pelagic coupling in these systems compared to Lake Superior. We recommend comparing the levels and temporal changes in diel migration in other Great Lakes as a means to assess changes in the relative health and function of these ecosystems.

The Application of Depth Migration for Processing GPR Data

NASA Astrophysics Data System (ADS)

Hoai Trung, Dang; Van Giang, Nguyen; Thanh Van, Nguyen

2018-03-01

Migration methods play a significant role in processing ground penetrating radar data. Beside recovering the true image of subsurface structures from the prior designed velocity model and the raw GPR data, the migration algorithm could be an effective tool in bulding real environmental velocity model. In this paper, we have proposed one technique using energy diagram extracted from migrated data as a criterion of looking for the correct velocity. Split Step Fourier migration, a depth migration, is chosen for facing the challenge where the velocity varies laterally and vertically. Some results verified on field data on Vietnam show that migrated sections with calculated velocity from energy diagram have the best quality.

The impact of small irrigation diversion dams on the recent migration rates of steelhead and redband trout (Oncorhynchus mykiss)

USGS Publications Warehouse

Weigel, Dana E.; Connolly, Patrick J.; Powell, Madison S.

2013-01-01

Barriers to migration are numerous in stream environments and can occur from anthropogenic activities (such as dams and culverts) or natural processes (such as log jams or dams constructed by beaver (Castor canadensis)). Identification of barriers can be difficult when obstructions are temporary or incomplete providing passage periodically. We examine the effect of several small irrigation diversion dams on the recent migration rates of steelhead (Oncorhynchus mykiss) in three tributaries to the Methow River, Washington. The three basins had different recent migration patterns: Beaver Creek did not have any recent migration between sites, Libby Creek had two-way migration between sites and Gold Creek had downstream migration between sites. Sites with migration were significantly different from sites without migration in distance, number of obstructions, obstruction height to depth ratio and maximum stream gradient. When comparing the sites without migration in Beaver Creek to the sites with migration in Libby and Gold creeks, the number of obstructions was the only significant variable. Multinomial logistic regression identified obstruction height to depth ratio and maximum stream gradient as the best fitting model to predict the level of migration among sites. Small irrigation diversion dams were limiting population interactions in Beaver Creek and collectively blocking steelhead migration into the stream. Variables related to stream resistance (gradient, obstruction number and obstruction height to depth ratio) were better predictors of recent migration rates than distance, and can provide important insight into migration and population demographic processes in lotic species.

Corrugations on the S Reflector West of Spain: Kinematic Implications

NASA Astrophysics Data System (ADS)

Lymer, G.; Cresswell, D.; Reston, T. J.; Stevenson, C.; Bull, J.; Sawyer, D. S.

2016-12-01

The west Galicia margin (western Spain) provides favourable conditions to study the processes of continental extension and break-up through seismic imaging. Beneath the tilted fault blocks of the margin is a bright reflection, the S reflector, which is interpreted to be a detachment and the crust-mantle boundary. However questions remain concerning the role of the S during extension and in the mechanisms of breakup. To better understand the role of the S in continental breakup, a 3D multi-channel seismic dataset was acquired over the Galicia margin in summer 2013. It has been processed through to prestack time migration in collaboration with Repsol followed by depth conversion using velocities extracted from new velocity models based on wide-angle data across the Galicia margin and applied to a structural interpretation of the fault block structure. The faults that bound the present-day tilted blocks detach downward onto the S, suggesting that the S is a rooted detachment surface that formed late in the rifting history of the Galicia margin. The fact that the syn-tectonic sediments related to the block bounding faults represent only the latest part of the syn-rift units also supports a late development of the S detachment. The map of the S reveals a series of linear and parallel low ridges and troughs, also evident on the amplitude map of S, that are neither velocity distortions nor artefacts. We interpret these as slip surface "corrugations" and relate them to the slip direction during the rifting. The orientation of the corrugations changes oceanward, from E-W to ESE-WNW. It either suggests that slip on S was diachronous and that the extension direction changed as it migrated oceanward, or that the extension can be described as a clockwise rotation of the COT about a pole located 80km north of the 3D volume, just west of the northern Galicia Bank. There the edges of the Galicia Bank and the Galicia Escarpment appear in the bathymetry as a "V" shape opening to the south, which is reliable to a rotation of the area. Such a rotation is also consistent with the southward increasing internal deformation of some of the basement blocks along the margin. In either case it reveals the 3D complexity of the extension processes leading to breakup.

Slope tomography based on eikonal solvers and the adjoint-state method

NASA Astrophysics Data System (ADS)

Tavakoli F., B.; Operto, S.; Ribodetti, A.; Virieux, J.

2017-06-01

Velocity macromodel building is a crucial step in the seismic imaging workflow as it provides the necessary background model for migration or full waveform inversion. In this study, we present a new formulation of stereotomography that can handle more efficiently long-offset acquisition, complex geological structures and large-scale data sets. Stereotomography is a slope tomographic method based upon a semi-automatic picking of local coherent events. Each local coherent event, characterized by its two-way traveltime and two slopes in common-shot and common-receiver gathers, is tied to a scatterer or a reflector segment in the subsurface. Ray tracing provides a natural forward engine to compute traveltime and slopes but can suffer from non-uniform ray sampling in presence of complex media and long-offset acquisitions. Moreover, most implementations of stereotomography explicitly build a sensitivity matrix, leading to the resolution of large systems of linear equations, which can be cumbersome when large-scale data sets are considered. Overcoming these issues comes with a new matrix-free formulation of stereotomography: a factored eikonal solver based on the fast sweeping method to compute first-arrival traveltimes and an adjoint-state formulation to compute the gradient of the misfit function. By solving eikonal equation from sources and receivers, we make the computational cost proportional to the number of sources and receivers while it is independent of picked events density in each shot and receiver gather. The model space involves the subsurface velocities and the scatterer coordinates, while the dips of the reflector segments are implicitly represented by the spatial support of the adjoint sources and are updated through the joint localization of nearby scatterers. We present an application on the complex Marmousi model for a towed-streamer acquisition and a realistic distribution of local events. We show that the estimated model, built without any prior knowledge of the velocities, provides a reliable initial model for frequency-domain FWI of long-offset data for a starting frequency of 4 Hz, although some artefacts at the reservoir level result from a deficit of illumination. This formulation of slope tomography provides a computationally efficient alternative to waveform inversion method such as reflection waveform inversion or differential-semblance optimization to build an initial model for pre-stack depth migration and conventional FWI.

Development of a 3D VHR seismic reflection system for lacustrine settings - a case study in Lake Geneva, Switzerland

NASA Astrophysics Data System (ADS)

Scheidhauer, M.; Dupuy, D.; Marillier, F.; Beres, M.

2003-04-01

For better understanding of geologic processes in complex lacustrine settings, detailed information on geologic features is required. In many cases, the 3D seismic method may be the only appropriate approach. The aim of this work is to develop an efficient very high-resolution 3D seismic reflection system for lake studies. In Lake Geneva, Switzerland, near the city of Lausanne, past high-resolution investigations revealed a complex fault zone, which was subsequently chosen for testing our new system of three 24-channel streamers and integrated differential GPS (dGPS) positioning. A survey, carried out in 9 days in August 2001, covered an area of 1500^om x 675^om and comprised 180 CMP lines sailed perpendicular to the fault strike always updip, since otherwise the asymmetric system would result in different stacks for opposite directions. Accurate navigation and shot spacing of 5^om is achieved with a specially developed navigation and shot-triggering software that uses differential GPS onboard and a reference base close to the lake shore. Hydrophone positions could be accurately (<^o0.5^om) calculated with the aid of three additional dGPS antennas mounted on rafts attached to the streamer tails. Towed at a distance of only 75^om behind the vessel, they allowed determination of possible feathering due to cross-line currents or small course variations. The multi-streamer system uses two retractable booms deployed on each side of the boat and rest on floats. They separate the two outer streamers from the one in the center by a distance of 7.5^om. Combined with a receiver spacing of 2.5^om, the bin dimension of the 3D data becomes 3.75^om in cross-line and 1.25^om in inline direction. Potential aliasing problems from steep reflectors up to 30^o within the fault zone motivated the use of a 15/15 cu. in. double-chamber bubble-canceling Mini G.I. air gun (operated at 80^obars and 1^om depth). Although its frequencies do not exceed 650^o Hz, it combines a penetration of non-aliased signal to depths of 400^om with a best vertical resolution of 1.15^om. The multi-streamer system allows acquisition of high quality data, which already after conventional 3D processing show particularly clear images of the fault zone and the overlying sediments in all directions. Prestack depth migration can further improve data quality and is more appropriate for subsequent geologic interpretation.

30 CFR 250.175 - When may the Regional Supervisor grant an SOO?

Code of Federal Regulations, 2011 CFR

2011-07-01

... required under paragraph (b)(2) of this section must include full 3-D depth migration beneath the salt...) Includes full 3-D depth migration over the entire lease area. (3) Before requesting the suspension, you...

Vertical migration and nighttime distribution of adult bloaters in Lake Michigan

USGS Publications Warehouse

TeWinkel, Leslie M.; Fleischer, Guy W.

1999-01-01

The vertical migration and nighttime vertical distribution of adult bloaters Coregonus hoyi were investigated during late summer in Lake Michigan using acoustics simultaneously with either midwater or bottom trawling. Bloaters remained on or near bottom during the day. At night, bloaters were distributed throughout 30-65 m of water, depending on bottom depth. Shallowest depths of migration were not related to water temperature or incident light. Maximum distances of migration increased with increasing bottom depth. Nighttime midwater densities ranged from 0.00 to 6.61 fish/1,000 mA? and decreased with increasing bottom depth. Comparisons of length distributions showed that migrating and nonmigrating bloaters did not differ in size. However, at most sites, daytime bottom catches collected a greater proportion of larger individuals compared with nighttime midwater or bottom catches. Mean target strengths by 5-m strata indicated that migrating bloaters did not stratify by size in the water column at night. Overall, patterns in frequency of empty stomachs and mean digestive state of prey indicated that a portion of the bloater population fed in the water column at night. Bloater diet composition indicated both midwater feeding and bottom feeding. In sum, although a portion of the bloater population fed in the water column at night, bloaters were not limited to feeding at this time. This research confirmed that bloaters are opportunistic feeders and did not fully support the previously proposed hypothesis that bloater vertical migration is driven by the vertically migrating macroinvertebrate the opossom shrimp Mysis relicta.

30 CFR 250.175 - When may the Regional Supervisor grant an SOO?

Code of Federal Regulations, 2012 CFR

2012-07-01

... paragraph (b)(2) of this section must include full 3-D depth migration beneath the salt sheet and over the...) Includes full 3-D depth migration over the entire lease area. (3) Before requesting the suspension, you...

30 CFR 250.175 - When may the Regional Supervisor grant an SOO?

Code of Federal Regulations, 2014 CFR

2014-07-01

... paragraph (b)(2) of this section must include full 3-D depth migration beneath the salt sheet and over the...) Includes full 3-D depth migration over the entire lease area. (3) Before requesting the suspension, you...

30 CFR 250.175 - When may the Regional Supervisor grant an SOO?

Code of Federal Regulations, 2013 CFR

2013-07-01

... paragraph (b)(2) of this section must include full 3-D depth migration beneath the salt sheet and over the...) Includes full 3-D depth migration over the entire lease area. (3) Before requesting the suspension, you...

Habitat use by fishes of Lake Superior. I. Diel patterns of habitat use in nearshore and offshore waters of the Apostle Islands region

USGS Publications Warehouse

Gorman, O.T.; Yule, D.L.; Stockwell, J.D.

2012-01-01

Diel patterns of distribution of fishes in nearshore (15–80 m depth) and offshore (>80 m) waters of the Apostle Islands region of Lake Superior were described using bottom trawls, mid-water trawls, and acoustic gear during day and night sampling. These data revealed three types of diel migration: diel vertical migration (DVM), diel bank migration (DBM), and no migration. DVM was expressed by fishes migrating from benthopelagic to pelagic strata and DBM was expressed by fishes migrating horizontally from deeper waters in the day to shallower waters at night while remaining within the benthopelagic stratum. Most fishes that did not exhibit diel migration showed increased nighttime densities as a result of increased activity and movement from benthic to benthopelagic strata. Rainbow Smelt (Osmerus mordax), Cisco (Coregonus artedi), Bloater (C. hoyi), Kiyi (C. kiyi), juvenile Trout-Perch (Percopsis omiscomaycus), and adult siscowet (Salvelinus namaycush siscowet) exhibited DVM. Lake Whitefish (C. clupeaformis), lean Lake Trout (Salvelinus namaycush namaycush), and juvenile siscowet exhibited DBM. Adult Trout-Perch and adult Pygmy Whitefish (Prosopium coulteri) exhibited a mixture of DBM and DVM. Burbot (Lota lota), Slimy Sculpin (Cottus cognatus), Spoonhead Sculpin (C. ricei), and Deepwater Sculpin (Myoxocephalus thompsonii) did not exhibit diel migration, but showed evidence of increased nocturnal activity. Ninespine Stickleback (Pungitius pungitius) exhibited a mixture of DVM and non-migration. Juvenile Pygmy Whitefish did not show a diel change in density or depth distribution. Species showing ontogenetic shifts in depth distribution with larger, adult life stages occupying deeper waters included, Rainbow Smelt, lean and siscowet Lake Trout, Lake Whitefish, Pygmy Whitefish, Ninespine Stickleback and Trout-Perch. Of these species, siscowet also showed an ontogenetic shift from primarily DBM as juveniles to primarily DVM as adults. Across all depths, fishes expressing DVM accounted for 73% of the total estimated community areal biomass (kg ha−1) while those expressing DBM accounted for 25% and non-migratory species represented 2% of the biomass. The proportion of total community biomass exhibiting DVM increased with depth, from 59% to 95% across ≤30 m to >90 m depth zones. Along the same depth gradient, the proportion of total community biomass exhibiting DBM declined from 40% to 1%, while non-migrators increased from 1% to 4%. These results indicate that DVM and DBM behaviors are pervasive in the Lake Superior fish community and potentially provide strong linkages that effect coupling of benthic and pelagic and nearshore and offshore habitats.

Seismic imaging of gas hydrates in the northernmost South China sea

NASA Astrophysics Data System (ADS)

Wang, Tan K.; Yang, Ben Jhong; Deng, Jia-Ming; Lee, Chao-Shing; Liu, Char-Shine

2010-03-01

Horizon velocity analysis and pre-stack depth migration of seismic profiles collected by R/V Maurice Ewing in 1995 across the accretionary prism off SW Taiwan and along the continental slope of the northernmost South China Sea were implemented for identifying gas hydrates. Similarly, a survey of 32 ocean-bottom seismometers (OBS), with a spacing of about 500 m, was conducted for exploring gas hydrates on the accretionary prism off SW Taiwan in April 2006. Travel times of head wave, refraction, reflection and converted shear wave identified from the hydrophone, vertical and horizontal components of these OBS data were applied for imaging P-wave velocity and Poisson’s ratio of hydrate-bearing sediments. In the accretionary prism off SW Taiwan, we found hydrate-bearing sediment, with a thickness of about 100-200 m, a relatively high P-wave velocity of 1.87-2.04 km/s and a relatively low Poisson’s ratio of 0.445-0.455, below anticlinal ridges near imbricate emergent thrusts in the drainage system of the Penghu and Kaoping Canyons. Free-gas layer, with a thickness of about 30-120 m, a relatively low P-wave velocity of 1.4-1.8 km/s and a relatively high Poisson’s ratio (0.47-0.48), was also observed below most of the bottom-simulating reflectors (BSR). Subsequently, based on rock physics of the three-phase effective medium, we evaluated the hydrate saturation of about 12-30% and the free-gas saturation of about 1-4%. The highest saturation (30% and 4%) of gas hydrates is found below anticlines due to N-S trending thrust-bounded folds and NE-SW thrusting and strike-slip ramps in the lower slope of the accretionary prism. We suggest that fluid may have migrated through the relay-fault array due to decollement folding and gas hydrates have been trapped in anticlines formed by the basement rises along the thrust faults. In contrast, in the rifted continental margin of the northernmost South China Sea, P-wave velocities of 1.9-2.2 km/s and 1.3-1.6 km/s, and thicknesses of about 50-200 m and 100-200 m, respectively, for a hydrate layer and a free-gas layer were imaged below the remnant and erosional ridges in the upper continental slope. High P-wave velocity of hydrate-bearing sediment below erosional ridges may also indicate high saturation of hydrates there. Normal faults due to rifting in the South China continental crust may have provided conduits for gas migration below the erosional ridges where P-wave velocity of hydrate-bearing sediment in the passive continental margin of the northernmost South China Sea is greater than that in the active accretionary prism off SW Taiwan.

Prestack density inversion using the Fatti equation constrained by the P- and S-wave impedance and density

NASA Astrophysics Data System (ADS)

Liang, Li-Feng; Zhang, Hong-Bing; Dan, Zhi-Wei; Xu, Zi-Qiang; Liu, Xiu-Juan; Cao, Cheng-Hao

2017-03-01

Simultaneous prestack inversion is based on the modified Fatti equation and uses the ratio of the P- and S-wave velocity as constraints. We use the relation of P-wave impedance and density (PID) and S-wave impedance and density (SID) to replace the constant Vp/Vs constraint, and we propose the improved constrained Fatti equation to overcome the effect of P-wave impedance on density. We compare the sensitivity of both methods using numerical simulations and conclude that the density inversion sensitivity improves when using the proposed method. In addition, the random conjugate-gradient method is used in the inversion because it is fast and produces global solutions. The use of synthetic and field data suggests that the proposed inversion method is effective in conventional and nonconventional lithologies.

Blocky inversion of multichannel elastic impedance for elastic parameters

NASA Astrophysics Data System (ADS)

Mozayan, Davoud Karami; Gholami, Ali; Siahkoohi, Hamid Reza

2018-04-01

Petrophysical description of reservoirs requires proper knowledge of elastic parameters like P- and S-wave velocities (Vp and Vs) and density (ρ), which can be retrieved from pre-stack seismic data using the concept of elastic impedance (EI). We propose an inversion algorithm which recovers elastic parameters from pre-stack seismic data in two sequential steps. In the first step, using the multichannel blind seismic inversion method (exploited recently for recovering acoustic impedance from post-stack seismic data), high-resolution blocky EI models are obtained directly from partial angle-stacks. Using an efficient total-variation (TV) regularization, each angle-stack is inverted independently in a multichannel form without prior knowledge of the corresponding wavelet. The second step involves inversion of the resulting EI models for elastic parameters. Mathematically, under some assumptions, the EI's are linearly described by the elastic parameters in the logarithm domain. Thus a linear weighted least squares inversion is employed to perform this step. Accuracy of the concept of elastic impedance in predicting reflection coefficients at low and high angles of incidence is compared with that of exact Zoeppritz elastic impedance and the role of low frequency content in the problem is discussed. The performance of the proposed inversion method is tested using synthetic 2D data sets obtained from the Marmousi model and also 2D field data sets. The results confirm the efficiency and accuracy of the proposed method for inversion of pre-stack seismic data.

The Sunda-Banda Arc Transition: New Insights From Marine Wide-Angle Seismic Data

NASA Astrophysics Data System (ADS)

Planert, L.; Shulgin, A.; Kopp, H.; Mueller, C.; Flueh, E.; Lueschen, E.; Engels, M.; Dayuf Jusuf, M.

2007-12-01

End of 2006, RV SONNE cruise SO190 SINDBAD (Seismic and Geoacoustic Investigations along the Sunda- Banda Arc Transition) went south of the Indonesian archipelago to acquire various geophysical datasets between 112 °E and 122 °E. The main goal of the project is to investigate the modifications of the lower plate (variability in the plate roughness, transition from oceanic to continental lower plate) and their effects on the tectonics of the upper plate (development of an outer high and forearc basin, accretionary and erosive processes). The tectonic style changes in neighboring margin segments from an oceanic plate-island arc subduction along the eastern Sunda margin to a continental plate-island arc collision along the Banda margin. Moreover, the character of the incoming oceanic plate varies from the rough topography in the area where the Roo Rise is subducting off eastern Java, to the smooth oceanic seafloor of the Argo- Abyssal Plain subducting off Bali, Lombok, and Sumbawa. In order to cover the entire variations of the lower plate, seven seismic refraction profiles were conducted along four major north-south oriented corridors of the margin, at 113 °E, 116 °E, 119 °E, and 121 °E, as well as three profiles running perpendicular to the major corridors. A total of 239 ocean bottom hydrophone and seismometer deployments were successfully recovered. Shooting was conducted along 1020 nm of seismic profiles using a G-gun cluster of 64 l. Here, we present velocity models obtained by applying a tomographic approach which jointly inverts for refracted and reflected phases. Additional geometry and velocity information for the uppermost layers, obtained by prestack depth migration of multichannel seismic reflection data (see poster of Mueller et al. in this session), is incorporated into our models and held fixed during the iterations. geomar.de/index.php?id=sindbad

High-resolution seismic survey for the characterization of planned PIER-ICDP fluid-monitoring sites in the Eger Rift zone

NASA Astrophysics Data System (ADS)

Simon, H.; Buske, S.

2017-12-01

The Eger Rift zone (Czech Republic) is a intra-continental non-volcanic region and is characterized by outstanding geodynamic activities, which result in earthquake swarms and significant CO2 emanations. Because fluid-induced stress can trigger earthquake swarms, both natural phenomena are probably related to each other. The epicentres of the earthquake swarms cluster at the northern edge of the Cheb Basin. Although the location of the cluster coincides with the major Mariánské-Lázně Fault Zone (MLFZ) the strike of the focal plane indicates another fault zone, the N-S trending Počátky-Plesná Zone (PPZ). Isotopic analysis of the CO2-rich fluids revealed a significant portion of upper mantle derived components, hence a magmatic fluid source in the upper mantle was postulated. Because of these phenomena, the Eger Rift area is a unique site for interdisciplinary drilling programs to study the fluid-earthquake interaction. The ICDP project PIER (Probing of Intra-continental magmatic activity: drilling the Eger Rift) will set up an observatory, consisting of five monitoring boreholes. In preparation for the drilling, the goal of the seismic survey is the characterization of the projected fluid-monitoring drill site at the CO2 degassing mofette field near Hartoušov. This will be achieved by a 6 km long profile with dense source and receiver spacing. The W-E trending profile will cross the proposed drill site and the surface traces of MLFZ and PPZ. The outcome of the seismic survey will be a high-resolution structural image of potential reflectors related to these fault zones. This will be achieved by the application of advanced pre-stack depth migration methods and a detailed P-wave velocity distribution of the area obtained from first arrival tomography. During interpretation of the seismic data, a geoelectrical resistivity model, acquired along the same profile line, will provide important constraints, especially with respect to fluid pathways.

The 1946 Unimak Tsunami Earthquake Area: revised tectonic structure in reprocessed seismic images and a suspect near field tsunami source

USGS Publications Warehouse

Miller, John J.; von Huene, Roland E.; Ryan, Holly F.

2014-01-01

In 1946 at Unimak Pass, Alaska, a tsunami destroyed the lighthouse at Scotch Cap, Unimak Island, took 159 lives on the Hawaiian Islands, damaged island coastal facilities across the south Pacific, and destroyed a hut in Antarctica. The tsunami magnitude of 9.3 is comparable to the magnitude 9.1 tsunami that devastated the Tohoku coast of Japan in 2011. Both causative earthquake epicenters occurred in shallow reaches of the subduction zone. Contractile tectonism along the Alaska margin presumably generated the far-field tsunami by producing a seafloor elevation change. However, the Scotch Cap lighthouse was destroyed by a near-field tsunami that was probably generated by a coeval large undersea landslide, yet bathymetric surveys showed no fresh large landslide scar. We investigated this problem by reprocessing five seismic lines, presented here as high-resolution graphic images, both uninterpreted and interpreted, and available for the reader to download. In addition, the processed seismic data for each line are available for download as seismic industry-standard SEG-Y files. One line, processed through prestack depth migration, crosses a 10 × 15 kilometer and 800-meter-high hill presumed previously to be basement, but that instead is composed of stratified rock superimposed on the slope sediment. This image and multibeam bathymetry illustrate a slide block that could have sourced the 1946 near-field tsunami because it is positioned within a distance determined by the time between earthquake shaking and the tsunami arrival at Scotch Cap and is consistent with the local extent of high runup of 42 meters along the adjacent Alaskan coast. The Unimak/Scotch Cap margin is structurally similar to the 2011 Tohoku tsunamigenic margin where a large landslide at the trench, coeval with the Tohoku earthquake, has been documented. Further study can improve our understanding of tsunami sources along Alaska’s erosional margins.

High precision gas hydrate imaging of small-scale and high-resolution marine sparker multichannel seismic data

NASA Astrophysics Data System (ADS)

Luo, D.; Cai, F.

2017-12-01

Small-scale and high-resolution marine sparker multi-channel seismic surveys using large energy sparkers are characterized by a high dominant frequency of the seismic source, wide bandwidth, and a high resolution. The technology with a high-resolution and high-detection precision was designed to improve the imaging quality of shallow sedimentary. In the study, a 20KJ sparker and 24-channel streamer cable with a 6.25m group interval were used as a seismic source and receiver system, respectively. Key factors for seismic imaging of gas hydrate are enhancement of S/N ratio, amplitude compensation and detailed velocity analysis. However, the data in this study has some characteristics below: 1. Small maximum offsets are adverse to velocity analysis and multiple attenuation. 2. Lack of low frequency information, that is, information less than 100Hz are invisible. 3. Low S/N ratio since less coverage times (only 12 times). These characteristics make it difficult to reach the targets of seismic imaging. In the study, the target processing methods are used to improve the seismic imaging quality of gas hydrate. First, some technologies of noise suppression are combined used in pre-stack seismic data to suppression of seismic noise and improve the S/N ratio. These technologies including a spectrum sharing noise elimination method, median filtering and exogenous interference suppression method. Second, the combined method of three technologies including SRME, τ-p deconvolution and high precision Radon transformation is used to remove multiples. Third, accurate velocity field are used in amplitude energy compensation to highlight the Bottom Simulating Reflector (short for BSR, the indicator of gas hydrates) and gas migration pathways (such as gas chimneys, hot spots et al.). Fourth, fine velocity analysis technology are used to improve accuracy of velocity analysis. Fifth, pre-stack deconvolution processing technology is used to compensate for low frequency energy and suppress of ghost, thus formation reflection characteristics are highlighted. The result shows that the small-scale and high resolution marine sparker multi-channel seismic surveys are very effective in improving the resolution and quality of gas hydrate imaging than the conventional seismic acquisition technology.

On the temperature dependence of Na migration in thin SiO 2 films during ToF-SIMS O 2+ depth profiling

NASA Astrophysics Data System (ADS)

Krivec, Stefan; Detzel, Thomas; Buchmayr, Michael; Hutter, Herbert

2010-10-01

The detection of Na in insulating samples by means of time of flight-secondary ion mass spectrometry (ToF-SIMS) depth profiling has always been a challenge. In particular the use of O 2+ as sputter species causes a severe artifact in the Na depth distribution due to Na migration under the influence of an internal electrical filed. In this paper we address the influence of the sample temperature on this artifact. It is shown that the transport of Na is a dynamic process in concordance with the proceeding sputter front. Low temperatures mitigated the migration process by reducing the Na mobility in the target. In the course of this work two sample types have been investigated: (i) A Na doped PMMA layer, deposited on a thin SiO 2 film. Here, the incorporation behavior of Na into SiO 2 during depth profiling is demonstrated. (ii) Na implanted into a thin SiO 2 film. By this sample type the migration behavior could be examined when defects, originating from the implantation process, are present in the SiO 2 target. In addition, we propose an approach for the evaluation of an implanted Na profile, which is unaffected by the migration process.

Can lagrangian models reproduce the migration time of European eel obtained from otolith analysis?

NASA Astrophysics Data System (ADS)

Rodríguez-Díaz, L.; Gómez-Gesteira, M.

2017-12-01

European eel can be found at the Bay of Biscay after a long migration across the Atlantic. The duration of migration, which takes place at larval stage, is of primary importance to understand eel ecology and, hence, its survival. This duration is still a controversial matter since it can range from 7 months to > 4 years depending on the method to estimate duration. The minimum migration duration estimated from our lagrangian model is similar to the duration obtained from the microstructure of eel otoliths, which is typically on the order of 7-9 months. The lagrangian model showed to be sensitive to different conditions like spatial and time resolution, release depth, release area and initial distribution. In general, migration showed to be faster when decreasing the depth and increasing the resolution of the model. In average, the fastest migration was obtained when only advective horizontal movement was considered. However, faster migration was even obtained in some cases when locally oriented random migration was taken into account.

An efficient implementation of 3D high-resolution imaging for large-scale seismic data with GPU/CPU heterogeneous parallel computing

NASA Astrophysics Data System (ADS)

Xu, Jincheng; Liu, Wei; Wang, Jin; Liu, Linong; Zhang, Jianfeng

2018-02-01

De-absorption pre-stack time migration (QPSTM) compensates for the absorption and dispersion of seismic waves by introducing an effective Q parameter, thereby making it an effective tool for 3D, high-resolution imaging of seismic data. Although the optimal aperture obtained via stationary-phase migration reduces the computational cost of 3D QPSTM and yields 3D stationary-phase QPSTM, the associated computational efficiency is still the main problem in the processing of 3D, high-resolution images for real large-scale seismic data. In the current paper, we proposed a division method for large-scale, 3D seismic data to optimize the performance of stationary-phase QPSTM on clusters of graphics processing units (GPU). Then, we designed an imaging point parallel strategy to achieve an optimal parallel computing performance. Afterward, we adopted an asynchronous double buffering scheme for multi-stream to perform the GPU/CPU parallel computing. Moreover, several key optimization strategies of computation and storage based on the compute unified device architecture (CUDA) were adopted to accelerate the 3D stationary-phase QPSTM algorithm. Compared with the initial GPU code, the implementation of the key optimization steps, including thread optimization, shared memory optimization, register optimization and special function units (SFU), greatly improved the efficiency. A numerical example employing real large-scale, 3D seismic data showed that our scheme is nearly 80 times faster than the CPU-QPSTM algorithm. Our GPU/CPU heterogeneous parallel computing framework significant reduces the computational cost and facilitates 3D high-resolution imaging for large-scale seismic data.

Regulating the migration of smooth muscle cells by a vertically distributed poly(2-hydroxyethyl methacrylate) gradient on polymer brushes covalently immobilized with RGD peptides.

PubMed

Wu, Sai; Du, Wang; Duan, Yiyuan; Zhang, Deteng; Liu, Yixiao; Wu, Bingbing; Zou, Xiaohui; Ouyang, Hongwei; Gao, Changyou

2018-05-30

The gradient localization of biological cues is of paramount importance to guide directional migration of cells. In this study, poly(2-hydroxyethyl methacrylate-co-glycidyl methacrylate)-block- poly(2-hydroxyethyl methacrylate) (P(HEMA-co-GMA)-b-PHEMA) brushes with a uniform underneath P(HEMA-co-GMA) layer and a gradient thickness of PHEMA blocks were prepared by using surface-initiated atom-transfer radical polymerization and a dynamically controlled polymerization process. The polymer chains were subsequently functionalized with the cell-adhesive arginine-glycine-aspartic acid (RGD) peptides by reaction with the glycidyl groups, and their structures and properties were characterized by X-ray photoelectron spectrometry (XPS), quartz crystal microbalance with dissipation (QCM-D) and air contact angle. Adhesion and migration processes of smooth muscle cells (SMCs) were then studied. Compared with those on the sufficiently exposed RGD surface, the cell adhesion and mobility were well maintained when the RGD peptides were localized at 18.9 nm depth, whereas the adhesion, spreading and migration rate of SMCs were significantly impaired when the RGD peptides were localized at a depth of 38.4 nm. On the RGD depth gradient surface, the SMCs exhibited preferential orientation and enhanced directional migration toward the direction of reduced thickness of the second PHEMA brushes. Half of the cells were oriented within ± 30° to the x-axis direction, and 72% of the cells moved directionally at the optimal conditions. Cell adhesion strength, arrangement of cytoskeleton, and gene and protein expression levels of adhesion-related proteins were studied to corroborate the mechanisms, demonstrating that the cell mobility is regulated by the complex and synergetic intracellular signals resulted from the difference in surface properties. Cell migration is of paramount importance for the processes of tissue repair and regeneration. So far, the gradient localization of biological cues perpendicular to the substrate, which is the usual case for the biological signaling molecules to locate in ECM in vivo, has been scarcely studied, and has not been used to guide the directional migration of cells. In this study, we prepare a depth gradient of RGD peptides along the polymer chains, which is used to guide the directional migration of SMCs after a second hydrophilic bock is prepared in a gradient manner. For the first time the directional migration of SMCs is achieved under the guidance of a depth gradient of RGD ligands. The mechanisms of different cell migration abilities are further discussed based on the results of cell adhesion, cell adhesion force, cytoskeleton alignment and expression of relative proteins and genes. This work paves a new strategy by fabricating a gradient polymer brushes with immobilized bioactive molecules to dominate the directional cell migration, and elucidates the mechanisms underlining the biased migration along RGD depth localization gradients, shedding a light for the design of novel biomaterials to control and guide cell migration and invasion. Copyright © 2018 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Migrating slow slip detected by slow and repeating earthquakes along the Nankai trough, Japan

NASA Astrophysics Data System (ADS)

Uchida, N.; Obara, K.; Takagi, R.; Asano, Y.

2017-12-01

In the western part of the Nankai trough region, successive occurrences of deep non-volcanic tremors and shallow very low frequency earthquakes (VLFEs) associated with long-term slow slip events (SSEs) are reported in 2003 and 2010. To understand the link between the two seismic slow earthquakes, we identify small repeating earthquake in and around the region from the waveform similarity of earthquakes observed by NIED Hi-net. The result shows the repeaters are located in 15-30 km depth that is in between the depth range of the shallow VLFEs (depth <=15 km) and deep SSEs (depth>= 25km). They are also located outside of the source area of the 1946 Mw8.3 Nankai earthquake, consistent with the hypothesis that repeaters occur due to stress concentration to a locked patch by aseismic slip (creep) in the surrounding area. The long-term trend of aseismic slip estimated from the repeaters shows that the slip rate were faster during 2-3 years period before the 2003 and 2010 episodes. We also found short-term (days to month) accelerations of aseismic slip during the episode of 2010 that migrated toward north. The migration detected from repeaters follows shallow migration of VLFEs and precedes the deep migration of tremors. Therefore we consider that during the period of the long-term SSE of 3 years period, short-term slow slip migrated about 300 km length in 1 month from shallower and south part to deeper and north part of the plate boundary near the edge of the slip area of the Nankai earthquake. Such long-distance migration probably related to large-scale locking of plate boundary that is responsible to the Nankai earthquake and the interseismic stress concentration to the locked area.

Development of Vertical Cable Seismic System (2)

NASA Astrophysics Data System (ADS)

Asakawa, E.; Murakami, F.; Tsukahara, H.; Ishikawa, K.

2012-12-01

The vertical cable seismic is one of the reflection seismic methods. It uses hydrophone arrays vertically moored from the seafloor to record acoustic waves generated by surface, deep-towed or ocean bottom sources. Analyzing the reflections from the sub-seabed, we could look into the subsurface structure. This type of survey is generally called VCS (Vertical Cable Seismic). Because VCS is an efficient high-resolution 3D seismic survey method for a spatially-bounded area, we proposed the method for the hydrothermal deposit survey tool development program that the Ministry of Education, Culture, Sports, Science and Technology (MEXT) started in 2009. We are now developing a VCS system, including not only data acquisition hardware but data processing and analysis technique. Our first experiment of VCS surveys has been carried out in Lake Biwa, JAPAN in November 2009 for a feasibility study. Prestack depth migration is applied to the 3D VCS data to obtain a high quality 3D depth volume. Based on the results from the feasibility study, we have developed two autonomous recording VCS systems. After we carried out a trial experiment in the actual ocean at a water depth of about 400m and we carried out the second VCS survey at Iheya Knoll with a deep-towed source. In this survey, we could establish the procedures for the deployment/recovery of the system and could examine the locations and the fluctuations of the vertical cables at a water depth of around 1000m. The acquired VCS data clearly shows the reflections from the sub-seafloor. Through the experiment, we could confirm that our VCS system works well even in the severe circumstances around the locations of seafloor hydrothermal deposits. We have carried out two field surveys in 2011. One is a 3D survey with a boomer for a high-resolution surface source and the other one for an actual field survey in the Izena Cauldron an active hydrothermal area in the Okinawa Trough. Through these surveys, we have confirmed that the uncertainty in the locations of the source and of the hydrophones in water could lower the quality of subsurface image. It is, therefore, strongly necessary to develop a total survey system that assures an accurate positioning and a deployment techniques. In case of shooting on sea surface, GPS navigation system are available, but in case of deep-towed source or ocean bottom source, the accuracy of shot position with SSBL/USBL is not sufficient for the very high-resolution imaging as requested for the SMS survey. We will incorporate the accurate LBL navigation systems with VCs. The LBL navigation system has been developed by IIS of the University of Tokyo. The error is estimated less than 10cm at the water depth of 3000m. Another approach is that the shot points can be calculated using the first break of the VCS after the VCS locations are estimated by slant-ranging from the sea surface. Our VCS system has been designed as a survey tool for hydrothermal deposit, but it will be also applicable for deep water site surveys or geohazard assessment such as active faults.

Numerical simulation of bubble plumes and an analysis of their seismic attributes

NASA Astrophysics Data System (ADS)

Li, Canping; Gou, Limin; You, Jiachun

2017-04-01

To study the bubble plume's seismic response characteristics, the model of a plume water body has been built in this article using the bubble-contained medium acoustic velocity model and the stochastic medium theory based on an analysis of both the acoustic characteristics of a bubble-contained water body and the actual features of a plume. The finite difference method is used for forward modelling, and the single-shot seismic record exhibits the characteristics of a scattered wave field generated by a plume. A meaningful conclusion is obtained by extracting seismic attributes from the pre-stack shot gather record of a plume. The values of the amplitude-related seismic attributes increase greatly as the bubble content goes up, and changes in bubble radius will not cause seismic attributes to change, which is primarily observed because the bubble content has a strong impact on the plume's acoustic velocity, while the bubble radius has a weak impact on the acoustic velocity. The above conclusion provides a theoretical reference for identifying hydrate plumes using seismic methods and contributes to further study on hydrate decomposition and migration, as well as on distribution of the methane bubble in seawater.

The diel migrations and distributions within a Mesopelagic community in the North East Atlantic. 1. Introduction and sampling procedures

NASA Astrophysics Data System (ADS)

Roe, H. S. J.; Angel, M. V.; Badcock, J.; Domanski, P.; James, P. T.; Pugh, P. R.; Thurston, M. H.

(i) This paper is an introduction to a series of papers describing the diel migrations and interrelationships of a mesopelagic community in the northeast Atlantic. (ii) The biological and physical background to the sampling area is described. (iii) There was little physical structure in the water column to a depth of 1000 m. (iv) The influence of Mediterranean water was detectable at varying depths between 550 and 800 m during the sampling programme. The possibility of mesoscale activity at these depths is discussed. (v) The sampling programme is described. Using the I.O.S. rectangular midwater trawl, the RMT 1 + 8, one hour samples were taken at 4 depth horizons, 100, 250, 450 and 600 m. Each depth was fished continuously for 48 hr. (vi) Additional non-quantitative surface samples, and surface light measurements were made throughout the RMT 1 + 8 sampling period. (vii) 97 hauls were made and the data for fish, decapod Crustacea, mysids, euphausiids, amphipods, copepods, ostracods, siphonophores, medusae, cteniphores and chaetognaths analysed. (viii) General results in terms of total numbers and numbers of species taken by the RMT 1 and the RMT 8 are described. (ix) The populations at 100 and 250 m showed more diel variation than those at 450 and 600 m, but the proportions of individual species and groups changed continuously at all depths. (x) These changes are due to diel vertical migrations. The migrations of most species only involved a part of their populations.

Pre-stack separation of PP and split PS waves in HTI media

NASA Astrophysics Data System (ADS)

Lu, Jun; Wang, Yun; Yang, Yuyong; Chen, Jingyi

2017-07-01

Separation of PP and split PS waves in transversely isotropic media with a horizontal axis of symmetry is crucial for imaging subsurface targets and for fracture prediction in a multicomponent seismic survey using P-wave sources. In conventional multicomponent processing, when a low velocity zone is present near the surface, it is often assumed that the vertical Z-component mainly records P modes and that the horizontal X- and Y-components record S modes, including split PS waves. However, this assumption does not hold when the ubiquitous presence of azimuthal anisotropy makes near surface velocity structures more complicated. Seismic wavefields recorded in each component therefore generally represent a complex waveform formed by PP and split PS waves, seriously distorting velocity analysis and seismic imaging. Most previous studies on wave separation have tended to separate P and S modes using pre-stack data and to separate split S modes using post-stack sections, under the assumption of orthogonal polarization. However, split S modes can hardly maintain their original orthogonal polarizations during propagation to the surface due to stratigraphic heterogeneity. Here, without assuming orthogonal polarization, we present a method for pre-stack separation of PP, PS1 and PS2 waves using all three components. The core of our method is the rotation of wave vectors from the Cartesian coordinate system established by Z-, R- and T-axes to a coordinate system established by the true PP-, PS1- and PS2-wave vector directions. Further, we propose a three-component superposition approach to obtain base wave vectors for the coordinate system transformation. Synthetic data testing results confirm that the performance of our wave separation method is stable under different noise levels. Application to field data from Southwest China reveals the potential of our proposed method.

Geographic differences in vertical connectivity in the Caribbean coral Montastraea cavernosa despite high levels of horizontal connectivity at shallow depths.

PubMed

Serrano, X; Baums, I B; O'Reilly, K; Smith, T B; Jones, R J; Shearer, T L; Nunes, F L D; Baker, A C

2014-09-01

The deep reef refugia hypothesis proposes that deep reefs can act as local recruitment sources for shallow reefs following disturbance. To test this hypothesis, nine polymorphic DNA microsatellite loci were developed and used to assess vertical connectivity in 583 coral colonies of the Caribbean depth-generalist coral Montastraea cavernosa. Samples were collected from three depth zones (≤10, 15-20 and ≥25 m) at sites in Florida (within the Upper Keys, Lower Keys and Dry Tortugas), Bermuda, and the U.S. Virgin Islands. Migration rates were estimated to determine the probability of coral larval migration from shallow to deep and from deep to shallow. Finally, algal symbiont (Symbiodinium spp.) diversity and distribution were assessed in a subset of corals to test whether symbiont depth zonation might indicate limited vertical connectivity. Overall, analyses revealed significant genetic differentiation by depth in Florida, but not in Bermuda or the U.S. Virgin Islands, despite high levels of horizontal connectivity between these geographic locations at shallow depths. Within Florida, greater vertical connectivity was observed in the Dry Tortugas compared to the Lower or Upper Keys. However, at all sites, and regardless of the extent of vertical connectivity, migration occurred asymmetrically, with greater likelihood of migration from shallow to intermediate/deep habitats. Finally, most colonies hosted a single Symbiodinium type (C3), ruling out symbiont depth zonation of the dominant symbiont type as a structuring factor. Together, these findings suggest that the potential for shallow reefs to recover from deep-water refugia in M. cavernosa is location-specific, varying among and within geographic locations likely as a consequence of local hydrology. © 2014 John Wiley & Sons Ltd.

Preliminary 3d depth migration of a network of 2d seismic lines for fault imaging at a Pyramid Lake, Nevada geothermal prospect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frary, R.; Louie, J.; Pullammanappallil, S.

Roxanna Frary, John N. Louie, Sathish Pullammanappallil, Amy Eisses, 2011, Preliminary 3d depth migration of a network of 2d seismic lines for fault imaging at a Pyramid Lake, Nevada geothermal prospect: presented at American Geophysical Union Fall Meeting, San Francisco, Dec. 5-9, abstract T13G-07.

Acquisition, Processing, and Analysis of Continuous Multi-Offset GPR Data for Problems in Hydrogeophysics: Is it Worth the Cost? (Invited)

NASA Astrophysics Data System (ADS)

Bradford, J. H.

2009-12-01

Commercial development of multi-channel ground-penetrating radar (GPR) systems has made acquisition of continuous multi-offset (CMO) data more cost effective than ever. However, additional operator training, equipment costs, field and analysis time, and computation requirements necessarily remain substantially higher than conventional fixed offset GPR surveys. The choice to conduct a CMO survey is a target driven optimization problem where in many cases the added value outweighs the additional cost. Drawing examples from surface water, groundwater, snow, and glacier hydrology, I demonstrate a range of information that can be derived from CMO data with particular emphasis on estimating material properties of relevance to hydrological problems. Careful data acquisition is key to accurate property measurements. CMO geometries can be constructed with a single-channel system although with a significant loss of time and personnel efficiency relative to modern multi-channel systems. Using procedures such as common-midpoint stacking and pre-stack velocity filtering, it is possible to substantially improve the signal-to-noise ratio in GPR reflection images. However, the primary advantage of CMO data is dense sampling of a wide aperture of travelpaths through the subsurface. These data provide the basis for applying tomographic imaging techniques. Reflection velocity tomography in the pre-stack migration domain provides a robust approach to constructing accurate and detailed electromagnetic velocity models. These models in turn are used in conjunction with petrophysical models to estimate hydrologic properties such as porosity. Additionally, we can utilize the velocity models in conjunction with analysis of the frequency dependent attenuation to evaluate real and complex dielectric permittivity. The real and complex components of dielectric permittivity may have differing sensitivity to different components of the hydrologic system. Understanding this behavior may lead to improved understanding of relevant lithologic properties such as bulk clay content or fluid chemical composition during biodegradation of hydrocarbon contaminants. In addition to velocity tomography, CMO data enable reflection attenuation difference tomography. While time-lapse attenuation difference tomography using crosswell GPR transmission data is a well established technique for imaging conductive tracers in groundwater systems, it is not common for reflection data. Numerical examples based on a realistic aquifer model show that surface data can provide resolution of conductive tracer zones that is comparable to cross well data, thereby minimizing the need for invasive and expensive boreholes.

Characteristic Analysis of Air-gun Source Wavelet based on the Vertical Cable Data

NASA Astrophysics Data System (ADS)

Xing, L.

2016-12-01

Air guns are important sources for marine seismic exploration. Far-field wavelets of air gun arrays, as a necessary parameter for pre-stack processing and source models, plays an important role during marine seismic data processing and interpretation. When an air gun fires, it generates a series of air bubbles. Similar to onshore seismic exploration, the water forms a plastic fluid near the bubble; the farther the air gun is located from the measurement, the more steady and more accurately represented the wavelet will be. In practice, hydrophones should be placed more than 100 m from the air gun; however, traditional seismic cables cannot meet this requirement. On the other hand, vertical cables provide a viable solution to this problem. This study uses a vertical cable to receive wavelets from 38 air guns and data are collected offshore Southeast Qiong, where the water depth is over 1000 m. In this study, the wavelets measured using this technique coincide very well with the simulated wavelets and can therefore represent the real shape of the wavelets. This experiment fills a technology gap in China.

The Continent-Ocean transition across the Galicia margin: First observations from the Galicia 3D volume

NASA Astrophysics Data System (ADS)

Lymer, Gaël; Cresswell, Derren; Reston, Tim; Stevenson, Carl; Bull, Jon; Sawyer, Dale; Morgan, Julia

2017-04-01

The west Galicia margin has been at the forefront 2D models of breakup subsequently applied to other margins. In summer 2013, a 3D multi-channel seismic dataset was acquired over the Galicia margin with the aim to revisit the margin from a 3D perspective and understand processes of continental extension and break-up through seismic imaging. The volume has been processed through to prestack time migration, followed by depth conversion using velocities extracted from new velocity models based on wide-angle data. Our first interpretations have shown that the most recent block-bounding faults detach downward on a bright reflector, the S reflector, corresponding to a rooted detachment fault and locally the crust-mantle boundary. The 3D topographic and amplitude maps of the S reveal a series of slip surface "corrugations" whose orientation changes oceanward from E-W to ESE-WNW and that we relate to the slip direction during the rifting. We now focus our investigations on the distal part of the S, just east of the Peridotite Ridge, a ridge of exhumed serpentinized mantle. While the S is mainly a continuous surface beneath the continental crust, it suddenly loses its reflectivity oceanward nearby the eastern flank of the ridge. It is likely that the S stops abruptly because it has been offset for almost 1 STWTT by some landward-dipping faults associated with the development of the ridge. This configuration is particularly defendable in the north of the dataset. The implication would be that in this area, the S is shallow and lies below very thin or inexistent basement, thus providing an ideal target for ODP drilling. Alternatively, the S could be intensively segmented by small-offset, but abundant, west-dipping normal faults that root downward on a persistent landward dipping fault that bounds the eastern flank of the ridge. Such a dissection of the S could also explain its lack of reflectivity nearby the ridge; similar reduced reflectivity is locally observed in other parts of the 3D volume in the vicinity of the faults that bound the continental crustal blocks. The implication would be that the S is still located at depth below intensively broken slices of crust and stops against the eastern flank of the Peridotite Ridge. Both cases show that rifting to break-up was a complex and time-variant 3D process that involved several generations of faulting, including late potential landward-dipping structures that controlled the development of the peridotite ridge.

The Porcupine Basin: from rifting to continental breakup

NASA Astrophysics Data System (ADS)

Reston, Timothy; Gaw, Viola; Klaeschen, Dirk; McDermott, Ken

2015-04-01

Southwest of Ireland, the Porcupine Basin is characterized by axial stretching factors that increase southward to values greater than six and typical of rifted margins. As such, the basin can be regarded as a natural laboratory to investigate the evolution and symmetry of rifting leading towards continental separation and breakup, and in particular the processes of mantle serpentinisation, and the onset of detachment faulting. We have processed through to prestack depth migration a series of E-W profiles crossing the basin at different axial stretching factors and linked by a N-S profile running close to the rift axis. Our results constrain the structure of the basin and have implications for the evolution of rifted margins. In the north at a latitude of 52.25N, no clear detachment is imaged, although faults do appear to cut down into the mantle, so that serpentinisation may have started. Further south (51.75N), a bright reflection (here named P) cuts down to the west from the base of the sedimentary section, is overlain by small fault blocks and appears to represent a detachment fault. P may in part follow the top of partially serpentinized mantle: this interpretation is consistent with gravity modelling, with numerical models of crustal embrittlement and mantle serpentinization during extension and with wide-angle data (see posters of Prada and of Watremez). Furthermore, P closely resembles the S reflection west of Iberia, where such serpentinites are well documented. P develops where the crust was thinned to less than 3 km during rifting, again similar to S. Although overall the basin remains symmetrical, the consistent westward structural dip of the detachment implies that, at high stretching factors, extension became asymmetric. Analysis of the depth sections suggests that the detachment may have been active as a rolling hinge rooting at low-angle beneath the Porcupine Bank, consistent with the presence of a footwall of serpentinites. This requires very weak fault rocks, such as serpentinites. Reconstructions suggest that the detachment developed after the onset of serpentinisation and thus represents late stage of faulting within a complex polyphase rift history. Farther south still, a N-S running profile shows that P cuts up to form the top of the basement, and locally forms the top of what we interpret as exhumed mantle, since buried by postrift sediments. Thus detachment here appear to have been both responsible for the late-stage extension of the crust and the unroofing of the mantle. The same processes are likely to have occurred at magma poor rifted margins.

The crustal characteristics at syn- and/or post-rifting in eastern Shikoku basin by seismic reflection survey

NASA Astrophysics Data System (ADS)

Yamashita, M.; Takahashi, N.; Kodaira, S.; Takizawa, K.; No, T.; Miura, S.; Kaneda, Y.

2008-12-01

Imaging of the arc-backarc transition zone is important in relation to the backarc opening process. Shikoku Basin locates between the Kyushu-Palau Ridge and the Izu-Ogasawara Arc, which is an important area to reveal the opening evolution of the backarc basins as a part of the growth process of the Philippine Sea. The Shikoku Basin was in the backarc rifting and spreading stage during about 30-15 Ma (e.g. Okino et al., 1994). High P-wave velocity lower crust is identified in arc-backarc transition zone by refraction survey using OBSs (Takahashi et al., 2007). Japan Agency for Marine-Earth Science and Technology (JAMSTEC) carried out multi-channel seismic reflection (MCS) survey using 12,000 cu.in. air gun and 5 km streamer with 204 ch hydrophones in the Izu-Ogasawara region since 2004. We extracted and mapped the crustal characteristics from poststack and prestack depth migrated profiles. According to obtained profiles, the deformation structure with share component is recognized in arc-backarc transition zone, which located eastern side of Shikoku Basin from Zenisu Ridge to about 500 km south. The maximum width of this deformation zone is about 100 km. The relative displacement of horizon is little; however, it is strongly deformed from upper crust beneath seafloor. This deformation zone indicates the post- rifting activity in east side of Shikoku Basin. On the other hand, some knolls are indicated along the en- echelon arrangement from Izu-Ogasawara arc. Ishizuka et al. (2003) reported post-rifting volcanism with Miocene age in en-echelon arrangement. A part of these knolls are estimated to penetrate at syn-rifting and/or post-rifting stage in backarc opening. By comparing the both side of arc-backarc transition zone, we elucidate syn- and post-rifting effect in Shikoku Basin. We also carried out high density MCS surveys in Shikoku Basin in order to IODP proposal site for reconstruction of magmatic processes since Oligocene in rear arc. In this survey, we use new tuned airgun array with total capacity of 7,800 cu. in. for high resolution imaging. Preliminary result shows that the proposed site is covered with thick sediments, and acoustic basement is seen at depth of 1.5-2 km (1.5-2 sec in two way traveltime) from sea bottom, a part of which is discontinuous. Many clear reflectors can be observed within sediments, some of which corresponding to those identified in previous MCS lines.

Glacially-derived overpressure in the northeastern Alaskan subduction zone: combined tomographic and morphometric analysis of shallow sediments on the Yakutat shelf and slope, Gulf of Alaska

NASA Astrophysics Data System (ADS)

Clary, W. A.; Worthington, L. L.; Scuderi, L. A.; Daigle, H.; Swartz, J. M.

2017-12-01

The Pamplona zone fold and thrust belt is the offshore expression of convergence and shallow subduction of the Yakutat microplate beneath North America in the northeastern Alaska subduction zone. The combination of convergent tectonics and glaciomarine sedimentary processes create patterns of deformation and deposition resulting in a shallow sedimentary sequence with varying compaction, fluid pressure, and fault activity. We propose that velocity variations observed in our tomographic analysis represent long-lived fluid overpressure due to loading by ice sheets and sediments. Regions with bathymetric and stratigraphic evidence of recent ice sheets and associated sedimentation should be collocated with evidence of overpressure (seismic low velocity zones) in the shallow sediments. Here, we compare a velocity model with shelf seismic stratigraphic facies and modern seafloor morphology. To document glacially derived morphology we use high resolution bathymetry to identify channel and gully networks on the western Yakutat shelf-slope then analyze cross-channel shape indices across the study area. We use channel shape index measurements as a proxy of recent ice-proximal sedimentation based on previously published results that proposed a close correlation. Profiles taken at many locations were fitted with a power function and assigned a shape - U-shape channels likely formed proximal to recent ice advances. Detailed velocity models were created by a combination of streamer tomography and pre-stack depth migration velocities with seismic data including: a 2008 R/V Langseth dataset from the St. Elias Erosion and Tectonics Project (STEEP); and a 2004 high-resolution R/V Ewing dataset. Velocity-porosity-permeability relationships developed using IODP Expedition 341 drilling data inform interpretation and physical properties analyses of the shallow sediments. Initial results from a 35 km profile extending SE seaward of the Bering glacier and subparallel to the Bering trough suggest a spatial relationship between the extent of U-shaped profiles and low-velocity shallow sediments. Towards the SE end of the model we observe a large overlap of U-shaped indices, and a shallow low-velocity zone in the mapped extent of the last glacial maximum suggestive of overpressure due to loading by ice sheet activity.

Fault linkage and continental breakup

NASA Astrophysics Data System (ADS)

Cresswell, Derren; Lymer, Gaël; Reston, Tim; Stevenson, Carl; Bull, Jonathan; Sawyer, Dale; Morgan, Julia

2017-04-01

The magma-poor rifted margin off the west coast of Galicia (NW Spain) has provided some of the key observations in the development of models describing the final stages of rifting and continental breakup. In 2013, we collected a 68 x 20 km 3D seismic survey across the Galicia margin, NE Atlantic. Processing through to 3D Pre-stack Time Migration (12.5 m bin-size) and 3D depth conversion reveals the key structures, including an underlying detachment fault (the S detachment), and the intra-block and inter-block faults. These data reveal multiple phases of faulting, which overlap spatially and temporally, have thinned the crust to between zero and a few km thickness, producing 'basement windows' where crustal basement has been completely pulled apart and sediments lie directly on the mantle. Two approximately N-S trending fault systems are observed: 1) a margin proximal system of two linked faults that are the upward extension (breakaway faults) of the S; in the south they form one surface that splays northward to form two faults with an intervening fault block. These faults were thus demonstrably active at one time rather than sequentially. 2) An oceanward relay structure that shows clear along strike linkage. Faults within the relay trend NE-SW and heavily dissect the basement. The main block bounding faults can be traced from the S detachment through the basement into, and heavily deforming, the syn-rift sediments where they die out, suggesting that the faults propagated up from the S detachment surface. Analysis of the fault heaves and associated maps at different structural levels show complementary fault systems. The pattern of faulting suggests a variation in main tectonic transport direction moving oceanward. This might be interpreted as a temporal change during sequential faulting, however the transfer of extension between faults and the lateral variability of fault blocks suggests that many of the faults across the 3D volume were active at least in part simultaneously. Alternatively, extension may have varied in direction spatially if it were a rotation about a pole located to the north.

Migration of fallout radiocaesium in a grassland soil from 1986 to 2001. Part I: activity-depth profiles of (134)Cs and (137)Cs.

PubMed

Schimmack, W; Schultz, W

2006-09-15

The temporal changes of the vertical distribution of (134)Cs (deposited by the Chernobyl fallout in 1986) and (137)Cs (deposited by the Chernobyl and the global fallout) in the soil were investigated at an undisturbed Bavarian grassland site in Germany. At ten sampling dates between 1986 and 2001, the activity density of (134)Cs and (137)Cs was determined in various soil layers down to 80 cm depth. In 2001, the small-scale spatial variability of the radiocaesium activity was determined by sampling five plots within 10 m(2) (coefficient of variation about 20% for the upper soil layers). Between 1987 and 1990, substantial changes of the activity-depth profiles were observed. The percentage depth distributions of (134)Cs and (137)Cs were rather similar. The 50%-depth of the accumulated activity increased from 2.4 cm in 1988 to 5.3 cm in 2001 for (134)Cs and from 2.7 to 5.8 cm for (137)Cs. This indicates that at the study site the migration data of Chernobyl-derived (137)Cs can be estimated by those of total (137)Cs. In the second part of this study, the activity-depth profiles will be evaluated by the convection-dispersion model [Schimmack, W, Feria Márquez, F. Migration of fallout radiocaesium in a grassland soil from 1986 to 2001. Part II: Evaluation of the activity-depth profiles by transport models. Sci Total Environ 2006-this issue].

Weather conditions associated with autumn migration by mule deer in Wyoming.

PubMed

Rittenhouse, Chadwick D; Mong, Tony W; Hart, Thomas

2015-01-01

Maintaining ecological integrity necessitates a proactive approach of identifying and acquiring lands to conserve unfragmented landscapes, as well as evaluating existing mitigation strategies to increase connectivity in fragmented landscapes. The increased use of highway underpasses and overpasses to restore connectivity for wildlife species offers clear conservation benefits, yet also presents a unique opportunity to understand how weather conditions may impact movement of wildlife species. We used remote camera observations (19,480) from an existing wildlife highway underpass in Wyoming and daily meteorological observations to quantify weather conditions associated with autumn migration of mule deer in 2009 and 2010. We identified minimal daily temperature and snow depth as proximate cues associated with mule deer migration to winter range. These weather cues were consistent across does and bucks, but differed slightly by year. Additionally, extreme early season snow depth or cold temperature events appear to be associated with onset of migration. This information will assist wildlife managers and transportation officials as they plan future projects to maintain and enhance migration routes for mule deer.

Migration Pathways, Behavioural Thermoregulation and Overwintering Grounds of Blue Sharks in the Northwest Atlantic

PubMed Central

Campana, Steven E.; Dorey, Anna; Fowler, Mark; Joyce, Warren; Wang, Zeliang; Yashayaev, Igor

2011-01-01

The blue shark Prionace glauca is the most abundant large pelagic shark in the Atlantic Ocean. Although recaptures of tagged sharks have shown that the species is highly migratory, migration pathways towards the overwintering grounds remain poorly understood. We used archival satellite pop-up tags to track 23 blue sharks over a mean period of 88 days as they departed the coastal waters of North America in the autumn. Within 1–2 days of entering the Gulf Stream (median date of 21 Oct), all sharks initiated a striking diel vertical migration, taking them from a mean nighttime depth of 74 m to a mean depth of 412 m during the day as they appeared to pursue vertically migrating squid and fish prey. Although functionally blind at depth, calculations suggest that there would be a ∼2.5-fold thermoregulatory advantage to swimming and feeding in the markedly cooler deep waters, even if there was any reduced foraging success associated with the extreme depth. Noting that the Gulf Stream current speeds are reduced at depth, we used a detailed circulation model of the North Atlantic to examine the influence of the diving behaviour on the advection experienced by the sharks. However, there was no indication that the shark diving resulted in a significant modification of their net migratory pathway. The relative abundance of deep-diving sharks, swordfish, and sperm whales in the Gulf Stream and adjacent waters suggests that it may serve as a key winter feeding ground for large pelagic predators in the North Atlantic. PMID:21373198

Evaluating geophysical lithology determination methods in the central offshore Nile Delta, Egypt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nada, H.; Shrallow, J.

1994-12-31

Two post stack and one prestack geophysical techniques were used to extract lithology and fluid information from seismic data. The purpose of this work was to evaluate the effectiveness of such methods in helping to find more hydrocarbons and reduce exploration risk in Egypt`s Nile Delta. Amplitude Variations with Offset (AVO) was used as a direct hydrocarbon indicator. CDP gathers were sorted into common angle gathers. The angle traces from 0--10 degrees were stacked to form a near angle stack and those from 30--40 degrees were stacked to form a far angle stack. Comparison of the far and near anglemore » stacks indicate areas which have seismic responses that match gas bearing sand models in the Pliocene and Messinian. Seismic Sequence Attribute mapping was used to measure the reflectivity of a seismic sequence. The specific sequence attribute measured in this study was the Maximum Absolute Amplitude of the seismic reflections within a sequence. Post stack seismic inversion was used to convert zero phase final migrated data to pseudo acoustic impedance data to interpret lithology from seismic data. All three methods are useful in the Nile Delta for identifying sand prone areas, but only AVO can be used to detect fluid content.« less

Walkaway-VSP survey using distributed optical fiber in China oilfield

NASA Astrophysics Data System (ADS)

Wu, Junjun; Yu, Gang; Zhang, Qinghong; Li, Yanpeng; Cai, Zhidong; Chen, Yuanzhong; Liu, Congwei; Zhao, Haiying; Li, Fei

2017-10-01

Distributed acoustic sensing (DAS) is a new type of replacement technology for geophysical geophone. DAS system is similar to high-density surface seismic geophone array. In the stage of acquisition, DAS can obtain the full well data with one shot. And it can provide enhanced vertical seismic profile (VSP) imaging and monitor fluids and pressures changes in the hydrocarbon production reservoir. Walkaway VSP data acquired over a former producing well in north eastern China provided a rich set of very high quality data. A standard VSP data pre-processing workflow was applied, followed by pre-stack Kirchhoff time migration. In the DAS pre-processing step we were faced with additional and special challenges: strong coherent noise due to cable slapping and ringing along the borehole casing. The single well DAS Walkaway VSP images provide a good result with higher vertical and lateral resolution than the surface seismic in the objective area. This paper reports on lessons learned in the handling of the wireline cable and subsequent special DAS data processing steps developed to remediate some of the practical wireline deployment issues. Optical wireline cable as a conveyance of fiber optic cables for VSP in vertical wells will open the use of the DAS system to much wider applications.

Nonanadromous fish passage in highway culverts.

DOT National Transportation Integrated Search

1995-01-01

Highway culverts may hinder the normal migrations of various trout species in wild trout streams, due to increased flow velocity, shallow water depths, increased turbulence, and perching. This can impede migrational movements, affecting the genetic d...

The Sun, Moon, Wind, and Biological Imperative–Shaping Contrasting Wintertime Migration and Foraging Strategies of Adult Male and Female Northern Fur Seals (Callorhinus ursinus)

PubMed Central

Sterling, Jeremy T; Springer, Alan M.; Iverson, Sara J.; Johnson, Shawn P.; Pelland, Noel A.; Johnson, Devin S.; Lea, Mary-Anne; Bond, Nicholas A.

2014-01-01

Adult male and female northern fur seals (Callorhinus ursinus) are sexually segregated in different regions of the North Pacific Ocean and Bering Sea during their winter migration. Explanations for this involve interplay between physiology, predator-prey dynamics, and ecosystem characteristics, however possible mechanisms lack empirical support. To investigate factors influencing the winter ecology of both sexes, we deployed five satellite-linked conductivity, temperature, and depth data loggers on adult males, and six satellite-linked depth data loggers and four satellite transmitters on adult females from St. Paul Island (Bering Sea, Alaska, USA) in October 2009. Males and females migrated to different regions of the North Pacific Ocean: males wintered in the Bering Sea and northern North Pacific Ocean, while females migrated to the Gulf of Alaska and California Current. Horizontal and vertical movement behaviors of both sexes were influenced by wind speed, season, light (sun and moon), and the ecosystem they occupied, although the expression of the behaviors differed between sexes. Male dive depths were aligned with the depth of the mixed layer during daylight periods and we suspect this was the case for females upon their arrival to the California Current. We suggest that females, because of their smaller size and physiological limitations, must avoid severe winters typical of the northern North Pacific Ocean and Bering Sea and migrate long distances to areas of more benign environmental conditions and where prey is shallower and more accessible. In contrast, males can better tolerate often extreme winter ocean conditions and exploit prey at depth because of their greater size and physiological capabilities. We believe these contrasting winter behaviors 1) are a consequence of evolutionary selection for large size in males, important to the acquisition and defense of territories against rivals during the breeding season, and 2) ease environmental/physiological constraints imposed on smaller females. PMID:24722344

The sun, moon, wind, and biological imperative-shaping contrasting wintertime migration and foraging strategies of adult male and female northern fur seals (Callorhinus ursinus).

PubMed

Sterling, Jeremy T; Springer, Alan M; Iverson, Sara J; Johnson, Shawn P; Pelland, Noel A; Johnson, Devin S; Lea, Mary-Anne; Bond, Nicholas A

2014-01-01

Adult male and female northern fur seals (Callorhinus ursinus) are sexually segregated in different regions of the North Pacific Ocean and Bering Sea during their winter migration. Explanations for this involve interplay between physiology, predator-prey dynamics, and ecosystem characteristics, however possible mechanisms lack empirical support. To investigate factors influencing the winter ecology of both sexes, we deployed five satellite-linked conductivity, temperature, and depth data loggers on adult males, and six satellite-linked depth data loggers and four satellite transmitters on adult females from St. Paul Island (Bering Sea, Alaska, USA) in October 2009. Males and females migrated to different regions of the North Pacific Ocean: males wintered in the Bering Sea and northern North Pacific Ocean, while females migrated to the Gulf of Alaska and California Current. Horizontal and vertical movement behaviors of both sexes were influenced by wind speed, season, light (sun and moon), and the ecosystem they occupied, although the expression of the behaviors differed between sexes. Male dive depths were aligned with the depth of the mixed layer during daylight periods and we suspect this was the case for females upon their arrival to the California Current. We suggest that females, because of their smaller size and physiological limitations, must avoid severe winters typical of the northern North Pacific Ocean and Bering Sea and migrate long distances to areas of more benign environmental conditions and where prey is shallower and more accessible. In contrast, males can better tolerate often extreme winter ocean conditions and exploit prey at depth because of their greater size and physiological capabilities. We believe these contrasting winter behaviors 1) are a consequence of evolutionary selection for large size in males, important to the acquisition and defense of territories against rivals during the breeding season, and 2) ease environmental/physiological constraints imposed on smaller females.

Buoyancy characteristics of the bloater (Coregonus hoyi) in relation to patterns of vertical migration and acoustic backscattering

USGS Publications Warehouse

Fleischer, Guy W.; TeWinkel, Leslie M.

1998-01-01

Acoustic studies in Lake Michigan found that bloaters (Coregonus hoyi) were less reflective per size than the other major pelagic species. This difference in in situ acoustic backscattering could indicate that the deep-water bloaters have compressed swimbladders for much of their vertical range with related implications on buoyancy. To test this hypothesis, the buoyancy characteristics of bloaters were determined with fish placed in a cage that was lowered to bottom and monitored with an underwater camera. We found bloaters were positively buoyant near surface, neutrally buoyant at intermediate strata, and negatively buoyant near bottom. This pattern was consistent for the range of depths bloaters occur. The depth of neutral buoyancy (near the 50-n strata) corresponds with the maximum extent of vertical migration for bloaters observed in acoustic surveys. Fish below this depth would be negatively buoyant which supports our contention that bloaters deeper in the water column have compressed swimbladders. Understanding the buoyancy characteristics of pelagic fishes will help to predict the effects of vertical migration on target strength measurement and confirms the use of acoustics as a tool to identify and quantify the ecological phenomenon of vertical migration.

Migration Decision-Making among Mexican Youth: Individual, Family, and Community Influences

ERIC Educational Resources Information Center

Tucker, Christine M.; Torres-Pereda, Pilar; Minnis, Alexandra M.; Bautista-Arredondo, Sergio A.

2013-01-01

We explored migration decisions using in-depth, semistructured interviews with male and female youth ages 14 to 24 (n = 47) from two Mexican communities, one with high and one with low U.S. migration density. Half were return migrants and half were nonmigrants with relatives in the United States. Migrant and nonmigrant youth expressed different…

The impact of Hurricane Sandy on the shoreface and inner shelf of Fire Island, New York: large bedform migration but limited erosion

USGS Publications Warehouse

Goff, John A.; Flood, Roger D.; Austin, James A.; Schwab, William C.; Christensen, Beth A.; Browne, Cassandra M.; Denny, Jane F.; Baldwin, Wayne E.

2015-01-01

We investigate the impact of superstorm Sandy on the lower shoreface and inner shelf offshore the barrier island system of Fire Island, NY using before-and-after surveys involving swath bathymetry, backscatter and CHIRP acoustic reflection data. As sea level rises over the long term, the shoreface and inner shelf are eroded as barrier islands migrate landward; large storms like Sandy are thought to be a primary driver of this largely evolutionary process. The “before” data were collected in 2011 by the U.S. Geological Survey as part of a long-term investigation of the Fire Island barrier system. The “after” data were collected in January, 2013, ~two months after the storm. Surprisingly, no widespread erosional event was observed. Rather, the primary impact of Sandy on the shoreface and inner shelf was to force migration of major bedforms (sand ridges and sorted bedforms) 10’s of meters WSW alongshore, decreasing in migration distance with increasing water depth. Although greater in rate, this migratory behavior is no different than observations made over the 15-year span prior to the 2011 survey. Stratigraphic observations of buried, offshore-thinning fluvial channels indicate that long-term erosion of older sediments is focused in water depths ranging from the base of the shoreface (~13–16 m) to ~21 m on the inner shelf, which is coincident with the range of depth over which sand ridges and sorted bedforms migrated in response to Sandy. We hypothesize that bedform migration regulates erosion over these water depths and controls the formation of a widely observed transgressive ravinement; focusing erosion of older material occurs at the base of the stoss (upcurrent) flank of the bedforms. Secondary storm impacts include the formation of ephemeral hummocky bedforms and the deposition of a mud event layer.

Seasonal migration and environmental conditions of Pacific halibut Hippoglossus stenolepis, elucidated from pop-up archival transmitting (PAT) tags

USGS Publications Warehouse

Loher, Timothy; Seitz, Andrew C.

2006-01-01

Pop-up archival transmitting (PAT) tags were used to study the fall migration of halibut in the Gulf of Alaska (GOA). We tagged 6 Pacific halibut Hippoglossus stenolepis on summer feeding grounds in the eastern GOA and another 6 in the western GOA from June 13 to August 6, 2002. The tags were programed to be released from the fish on January 15, 2003, at the height of the winter spawning season: 10 tags successfully detached, transmitted archived environmental data (depth and temperature), and generated accurate latitude–longitude coordinates shortly after pop-up; 2 tags deployed off SE Alaska were lost. The tags revealed that 6 fish had moved a considerable distance (>200 km) between tagging and pop-up, and all of these had moved northward to some extent. The longest of the observed migrations was from the southern Alaska Peninsula to Yakutat Bay, a linear displacement of 1153 km; 4 fish showed little evidence of geographic displacement, exhibiting migrations that ranged only from 30 to 69 km. Although 2 fish had moved inshore by the end of the tagging period, all other fish had moved offshore regardless of their overall migration distance. The precise timing of offshore movements varied, beginning as early as August and as late as January. These observations generally corroborate conventional tagging, indicating migration of halibut toward winter spawning grounds in the northern GOA, and movement of fish to deep water in fall. However, no single stereotypic migration behavior was apparent, and a variety of vertical movement patterns and temperature profiles were observed. Halibut spent most time in waters of 5 to 7°C, but experienced temperatures ranging from 2.6 to 11.6°C. Depth observations ranged from 0 to 736 m, with summertime activity concentrated in depths from 0 to 400 m, and halibut that exhibited offshore movement were typically observed at 300 to 700 m by mid-winter. Vertical movement (short-period changes in depth) varied among fish and over time, with some fish displaying little vertical activity, others displaying short periods of activity, and still others displaying considerable activity throughout their time at liberty.

Diel Vertical Migration Thresholds of Karenia brevis (Dinophyceae).

EPA Science Inventory

Light and nutrient availability change throughout dinoflagellate diel vertical migration (DVM) and/or with subpopulation location in the water column along the west Florida shelf. Typically, the vertical depth of the shelf is greater than the distance a subpopulation can vertical...

Light penetration structures the deep acoustic scattering layers in the global ocean.

PubMed

Aksnes, Dag L; Røstad, Anders; Kaartvedt, Stein; Martinez, Udane; Duarte, Carlos M; Irigoien, Xabier

2017-05-01

The deep scattering layer (DSL) is a ubiquitous acoustic signature found across all oceans and arguably the dominant feature structuring the pelagic open ocean ecosystem. It is formed by mesopelagic fishes and pelagic invertebrates. The DSL animals are an important food source for marine megafauna and contribute to the biological carbon pump through the active flux of organic carbon transported in their daily vertical migrations. They occupy depths from 200 to 1000 m at daytime and migrate to a varying degree into surface waters at nighttime. Their daytime depth, which determines the migration amplitude, varies across the global ocean in concert with water mass properties, in particular the oxygen regime, but the causal underpinning of these correlations has been unclear. We present evidence that the broad variability in the oceanic DSL daytime depth observed during the Malaspina 2010 Circumnavigation Expedition is governed by variation in light penetration. We find that the DSL depth distribution conforms to a common optical depth layer across the global ocean and that a correlation between dissolved oxygen and light penetration provides a parsimonious explanation for the association of shallow DSL distributions with hypoxic waters. In enhancing understanding of this phenomenon, our results should improve the ability to predict and model the dynamics of one of the largest animal biomass components on earth, with key roles in the oceanic biological carbon pump and food web.

Origin and migration of hydrocarbon gases and carbon dioxide, Bekes Basin, southeastern Hungary

USGS Publications Warehouse

Clayton, J.L.; Spencer, C.W.; Koncz, I.; Szalay, A.

1990-01-01

The Bekes Basin is a sub-basin within the Pannonian Basin, containing about 7000 m of post-Cretaceous sedimentary rocks. Natural gases are produced from reservoirs (Precambrian to Tertiary in age) located on structural highs around the margins of the basin. Gas composition and stable carbon isotopic data indicate that most of the flammable gases were derived from humic kerogen contained in source rocks located in the deep basin. The depth of gas generation and vertical migration distances were estimated using quantitative source rock maturity-carbon isotope relationships for methane compared to known Neogene source rock maturity-depth relationships in the basin. These calculations indicate that as much as 3500 m of vertical migration has occured in some cases. Isotopically heavy (> - 7 > 0) CO2 is the predominant species present in some shallow reservoirs located on basin-margin structural highs and has probably been derived via long-distance vertical and lateral migration from thermal decompositon of carbonate minerals in Mesozoic and older rocks in the deepest parts of the basin. A few shallow reservoirs (< 2000m) contain isotopically light (-50 to -60%0) methane with only minor amounts of C2+ homologs (< 3% v/v). This methane is probably mostly microbial in origin. Above-normal pressures, occuring at depths greater than 1800 m, are believed to be the principal driving force for lateral and vertical gas migration. These pressures are caused in part by active hydrocarbon generation, undercompaction, and thermal decomposition of carbonates. 

Vertical migration of Karenia brevis in the northeastern Gulf of Mexico observed from glider measurements.

PubMed

Hu, Chuanmin; Barnes, Brian B; Qi, Lin; Lembke, Chad; English, David

2016-09-01

The toxic marine dinoflagellate, Karenia brevis (the species responsible for most of red tides or harmful algal blooms in the Gulf of Mexico), is known to be able to swim vertically to adapt to the light and nutrient environments, nearly all such observations have been made through controlled experiments using cultures. Here, using continuous 3-dimensional measurements by an ocean glider across a K. brevis bloom in the northeastern Gulf of Mexico between 1 and 8 August 2014, we show the vertical migration behavior of K. brevis. Within the bloom where K. brevis concentration is between 100,000 and 1,000,000cellsL -1 , the stratified water shows a two-layer system with the depth of pycnocline ranging between 14-20m and salinity and temperature in the surface layer being <34.8 and >28°C, respectively. The bottom layer shows the salinity of >36 and temperature of <26°C. The low salinity is apparently due to coastal runoff, as the top layer also shows high amount of colored dissolved organic matter (CDOM). Within the top layer, chlorophyll-a fluorescence shows clear diel changes in the vertical structure, an indication of K. brevis vertical migration at a mean speed of 0.5-1mh -1 . The upward migration appears to start at sunrise at a depth of 8-10m, while the downward migration appears to start at sunset (or when surface light approaches 0) at a depth of ∼2m. These vertical migrations are believed to be a result of the need of K. brevis cells for light and nutrients in a stable, stratified, and CDOM-rich environment. Copyright © 2016 Elsevier B.V. All rights reserved.

Simple dielectric mixing model in the monitoring of CO2 leakage from geological storage aquifer

NASA Astrophysics Data System (ADS)

Abidoye, L. K.; Bello, A. A.

2017-03-01

The principle of the dielectric mixing for multiphase systems in porous media has been employed to investigate CO2-water-porous media system and monitor the leakage of CO2, in analogy to scenarios that can be encountered in geological carbon sequestration. A dielectric mixing model was used to relate the relative permittivity for different subsurface materials connected with the geological carbon sequestration. The model was used to assess CO2 leakage and its upward migration, under the influences of the depth-dependent characteristics of the subsurface media as well as the fault-connected aquifers. The results showed that for the upward migration of CO2 in the subsurface, the change in the bulk relative permittivity (εb) of the CO2-water-porous media system clearly depicts the leakage and movement of CO2, especially at depth shallower than 800 m. At higher depth, with higher pressure and temperature, the relative permittivity of CO2 increases with pressure, while that of water decreases with temperature. These characteristics of water and supercritical CO2, combine to limit the change in the εb, at higher depth. Furthermore, it was noted that if the pore water was not displaced by the migrating CO2, the presence of CO2 in the system increases the εb. But, with the displacement of pore water by the migrating CO2, it was shown how the εb profile decreases with time. Owing to its relative simplicity, composite dielectric behaviour of multiphase materials can be effectively deployed for monitoring and enhancement of control of CO2 movement in the geological carbon sequestration.

Upward migration of Vesuvius magma chamber over the past 20,000 years.

PubMed

Scaillet, B; Pichavant, M; Cioni, R

2008-09-11

Forecasting future eruptions of Vesuvius is an important challenge for volcanologists, as its reawakening could threaten the lives of 700,000 people living near the volcano. Critical to the evaluation of hazards associated with the next eruption is the estimation of the depth of the magma reservoir, one of the main parameters controlling magma properties and eruptive style. Petrological studies have indicated that during past activity, magma chambers were at depths between 3 and 16 km (refs 3-7). Geophysical surveys have imaged some levels of seismic attenuation, the shallowest of which lies at 8-9 km depth, and these have been tentatively interpreted as levels of preferential magma accumulation. By using experimental phase equilibria, carried out on material from four main explosive events at Vesuvius, we show here that the reservoirs that fed the eruptive activity migrated from 7-8 km to 3-4 km depth between the ad 79 (Pompeii) and ad 472 (Pollena) events. If data from the Pomici di Base event 18.5 kyr ago and the 1944 Vesuvius eruption are included, the total upward migration of the reservoir amounts to 9-11 km. The change of preferential magma ponding levels in the upper crust can be attributed to differences in the volatile content and buoyancy of ascending magmas, as well as to changes in local stress field following either caldera formation or volcano spreading. Reservoir migration, and the possible influence on feeding rates, should be integrated into the parameters used for defining expected eruptive scenarios at Vesuvius.

Radiocesium distribution along the slope in the Iput river basin as a tracer of the contaminant secondary migration

NASA Astrophysics Data System (ADS)

Korobova, Elena; Romanov, Sergey; Beriozkin, Victor; Dogadkin, Nikolay

2016-04-01

The main goal of the study performed in 2014-2015 at the test site located in the abandoned zone of the Iput river basin was to study detailed patterns of Cs-137 redistribution along the terrace slope and the adjacent floodplain depression almost 30 years after the Chernobyl accident. Cs-137 surface activity was measured with the help of modified field gamma-spectrometer Violinist III (USA) in a grid 2 m x 2 m within the test plot sized 10 m x 24 m. Gamma-spectrometry was accompanied by topographical survey. Cs-137 depth distribution was studied by soil core sampling in increments of 2 cm and 5 cm down to 40 cm depth. Cs-137 activity in soil samples was measured in laboratory conditions by Nokia gamma-spectrometer. The results showed distinct natural dissimilarity of Cs-137 surface activity within the undisturbed soil of slope. Cs-137 depth migration in successive soil cores marked different patterns correlated with the position in relief. In particular cores Cs-137 depth variation correlated with water regime that shows that the processes of secondary distribution of Cs-137 along the slope obviously depend upon water migration. The finding is important for understanding of regularities in patterns of radiocesium spatial distribution.

Beach recovery capabilities after El Niño 2015–2016 at Ensenada Beach, Northern Baja California

NASA Astrophysics Data System (ADS)

Ruiz de Alegría-Arzaburu, Amaia; Vidal-Ruiz, Jesús Adrián

2018-06-01

This study investigates the recovery capabilities of a single-barred beach in the Pacific Mexican coast before and after the 2015-2016 El Niño winter. Concurrent hydrodynamic and morphological data collected over a 3-year period (August 2014-2017) were analysed to determine the subaerial-subtidal volumetric exchange and cross-shore subtidal sandbar migrations, in relation to the incident wave forcing. The beach presented a seasonal seaward and landward sandbar migration cycle. The sandbar migrated offshore during the energetic waves between November and February, and onshore during the milder wave period in spring, until welding to the subaerial beach around May. The transfer of sediment towards the subaerial section continued over the summer, reaching a complete recovery by September/October. Prior to El Niño, the subaerial beach successfully recovered by the end of summer 2015 through the landward sandbar migration process. The 2015-2016 energetic winter waves caused a subaerial volume loss of 140 m3 m-1 (from October 2015 to March 2016), more than twice the amount eroded in the other winters, and the sandbar moved further offshore and to deeper depths (3-4 m) than the winter before. In addition, the energetic 2015-2016 winter waves lasted for 2 months longer than in other years, making the 2016 spring shorter. Consequently, during the onshore migration, the sandbar was unable of reaching shallow depths, and a large portion of sand remained in the subtidal beach. The subaerial beach recovered 60 and 65% of the loss in the 2016 and 2017 summers, respectively. It is concluded that the landward migration process of the sandbar during the spring is critical to ensure a full subaerial beach recovery over the mild wave period in summer. The recovery capabilities of the subaerial beach will depend on the cross-shore distance and depth where the sandbar is located, and on the duration of mild wave conditions required for the sandbar to migrate onshore.

Beach recovery capabilities after El Niño 2015-2016 at Ensenada Beach, Northern Baja California

NASA Astrophysics Data System (ADS)

Ruiz de Alegría-Arzaburu, Amaia; Vidal-Ruiz, Jesús Adrián

2018-05-01

This study investigates the recovery capabilities of a single-barred beach in the Pacific Mexican coast before and after the 2015-2016 El Niño winter. Concurrent hydrodynamic and morphological data collected over a 3-year period (August 2014-2017) were analysed to determine the subaerial-subtidal volumetric exchange and cross-shore subtidal sandbar migrations, in relation to the incident wave forcing. The beach presented a seasonal seaward and landward sandbar migration cycle. The sandbar migrated offshore during the energetic waves between November and February, and onshore during the milder wave period in spring, until welding to the subaerial beach around May. The transfer of sediment towards the subaerial section continued over the summer, reaching a complete recovery by September/October. Prior to El Niño, the subaerial beach successfully recovered by the end of summer 2015 through the landward sandbar migration process. The 2015-2016 energetic winter waves caused a subaerial volume loss of 140 m3 m-1 (from October 2015 to March 2016), more than twice the amount eroded in the other winters, and the sandbar moved further offshore and to deeper depths (3-4 m) than the winter before. In addition, the energetic 2015-2016 winter waves lasted for 2 months longer than in other years, making the 2016 spring shorter. Consequently, during the onshore migration, the sandbar was unable of reaching shallow depths, and a large portion of sand remained in the subtidal beach. The subaerial beach recovered 60 and 65% of the loss in the 2016 and 2017 summers, respectively. It is concluded that the landward migration process of the sandbar during the spring is critical to ensure a full subaerial beach recovery over the mild wave period in summer. The recovery capabilities of the subaerial beach will depend on the cross-shore distance and depth where the sandbar is located, and on the duration of mild wave conditions required for the sandbar to migrate onshore.

Enhanced migration of polychlorodibenzo-p-dioxins and furans in the presence of pentachlorophenol-treated oil in soil around utility poles: screening model validation.

PubMed

Bulle, Cécile; Samson, Réjean; Deschênes, Louise

2010-03-01

Field samples were collected around six pentachlorophenol (PCP)-treated wooden poles (in clay, organic soil, and sand) to evaluate the vertical migration of polychlorodibenzo-p-dioxins and furans (PCDD/Fs). Soils were characterized, PCDD/Fs, C(10)-C(50), and PCP were analyzed for seven composite samples located at a depth from 0 to 100 cm and at a distance from 0 to 50 cm from each pole. Concentrations of PCDD/Fs measured in organic soils were the highest (maximum 1.2E + 05 pg toxic equivalent TEQ/g soil), followed by clay (maximum 3.8E + 04 pg TEQ/g soil) and sand (maximum 1.8E + 04 pg TEQ/g soil). Model predictions, including the influence of wood treatment oil, were validated using measured concentration values in soils around poles. The model predicts a migration of PCDD/Fs due to the migration of oil, which differs depending on the type of soil: in clay, 90% of PCDD/Fs are predicted to remain in the first 29 cm, whereas in sand, 80 to 90% of the emitted PCDD/Fs are predicted to migrate deeper than 185 cm. For the organic soil, the predicted migration depth varies from 90 to 155 cm. This screening model allows evaluating the danger of microcontaminated sites around PCP-treated wooden poles: from a risk assessment perspective, in the case of organic soil and clay, no PCDD/F contamination is to be expected below the pole, but high levels of PCDD/Fs can be found in the first 2 m below the surface. For sand, however, significantly lower levels of PCDD/Fs were predicted in the surface soil, while the migration depth remains elevated, posing an inherent danger of aquifer contamination under the pole.

Spontaneous correction of pathologic tooth migration and reduced infrabony pockets following nonsurgical periodontal therapy: a case report.

PubMed

Sato, Shuichi; Ujiie, Hisashi; Ito, Koichi

2004-10-01

This case report describes the spontaneous correction of pathologic tooth migration and reduced infrabony pockets after nonsurgical periodontal therapy. A 3-mm diastema between the maxillary incisors was closed completely, and the mandibular teeth, which had migrated pathologically, returned to the optimal position. Clinical evaluation showed a significant reduction in probing depth, with increased clinical attachment and bone deposition demonstrated radiologically.

The Dynamics of Vertical Migration in the Oceanic Gulf of Mexico after Deepwater Horizon: Active Linkage of Large Vertebrates and Deep-Pelagic Nekton

NASA Astrophysics Data System (ADS)

Sutton, T.; Cook, A.; Frank, T. M.; Boswell, K. M.; Vecchione, M.; Judkins, H.; Romero, I.

2016-02-01

Toothed whales, smaller cetaceans, seabirds, and epipelagic gamefishes rely on deep-pelagic (meso- and bathypelagic) nekton as primary or secondary prey. This trophic interaction is mediated by downward and upward vertical movements (e.g., sperm whale diving and lanternfishes migration, respectively). This interaction also links particle-feeding lower trophic levels with top predators in a manner that spans the gamut of depth domains. This is particularly important with respect to a whole-water column disturbance such as the Deepwater Horizon oil spill (DWHOS). Here we present highly resolved vertical distribution and migration data collected during a large-scale, NOAA-supported, deep-pelagic (0-1500 m) survey in 2011, along with data collected during ongoing GoMRI-supported DEEPEND consortium surveys. The deep-pelagic nekton community of the Gulf of Mexico is a complex mixture of migrating, non-migrating, and partially migrating assemblages that connect surface waters with depths in excess of 1000 m. Major patterns of vertical distribution for 400+ species of fishes, cephalopods, and macrocrustaceans, the primary prey of many important species of oceanic vertebrates living near-surface, will be summarized and quantified with the goal of highlighting potential vectors of anthropogenic contamination transfer in the deep-pelagial, the Gulf's largest ecosystem.

Migrations and swimming capabilities of endangered pallid sturgeon (Scaphirhynchus albus) to guide passage designs in the fragmented Yellowstone River

USGS Publications Warehouse

Braaten, P. J.; Elliott, Caroline M.; Rhoten, Jason C.; Fuller, D. B.; McElroy, Brandon J.

2015-01-01

Fragmentation of the Yellowstone River is hypothesized to preclude recruitment of endangered Scaphirhynchus albus (pallid sturgeon) by impeding upstream spawning migrations and access to upstream spawning areas, thereby limiting the length of free-flowing river required for survival of early life stages. Building on this hypothesis, the reach of the Yellowstone River affected by Intake Diversion Dam (IDD) is targeted for modification. Structures including a rock ramp and by-pass channel have been proposed as restoration alternatives to facilitate passage. Limited information on migrations and swimming capabilities of pallid sturgeon is available to guide engineering design specifications for the proposed structures. Migration behavior, pathways (channel routes used during migrations), and swimming capabilities of free-ranging wild adult pallid sturgeon were examined using radiotelemetry, and complemented with hydraulic data obtained along the migration pathways. Migrations of 12–26% of the telemetered pallid sturgeon population persisted to IDD, but upstream passage over the dam was not detected. Observed migration pathways occurred primarily through main channel habitats; however, migrations through side channels up to 3.9 km in length were documented. The majority of pallid sturgeon used depths of 2.2–3.4 m and mean water velocities of 0.89–1.83 m/s while migrating. Results provide inferences on depths, velocities, and habitat heterogeneity of reaches successfully negotiated by pallid sturgeon that may be used to guide designs for structures facilitating passage at IDD. Passage will provide connectivity to potential upstream spawning areas on the Yellowstone River, thereby increasing the likelihood of recruitment for this endangered species.

Migration of air bubbles in ice under a temperature gradient, with application to “Snowball Earth”

NASA Astrophysics Data System (ADS)

Dadic, Ruzica; Light, Bonnie; Warren, Stephen G.

2010-09-01

To help characterize the albedo of "sea glaciers" on Snowball Earth, a study of the migration rates of air bubbles in freshwater ice under a temperature gradient was carried out in the laboratory. The migration rates of air bubbles in both natural glacier ice and laboratory-grown ice were measured for temperatures between -36°C and -4°C and for bubble diameters of 23-2000 μm. The glacier ice was sampled from a depth near close-off (74 m) in the JEMS2 ice core from Summit, Greenland. Migration rates were measured by positioning thick sections of ice on a temperature gradient stage mounted on a microscope inside a freezer laboratory. The maximum and minimum migration rates were 5.45 μm h-1 (K cm-1)-1 at -4°C and 0.03 μm h-1 (K cm-1)-1 at -36°C. Besides a strong dependence on temperature, migration rates were found to be proportional to bubble size. We think that this is due to the internal air pressure within the bubbles, which may correlate with time since close-off and therefore with bubble size. Migration rates show no significant dependence on bubble shape. Estimates of migration rates computed as a function of bubble depth within sea glaciers indicate that the rates would be low relative to the predicted sublimation rates, such that the ice surface would not lose its air bubbles to net downward migration. It is therefore unlikely that air bubble migration could outrun the advancing sublimation front, transforming glacial ice to a nearly bubble-free ice type, analogous to low-albedo marine ice.

Estuarine retention of larvae of the crab Rhithropanopeus harrisii

NASA Astrophysics Data System (ADS)

Cronin, Thomas W.

1982-08-01

Larvae of estuarine organisms continually face possible export from the parent estuary. Retention of larvae of the estuarine crab Rhithropanopeus harrisii was investigated in the upper Newport River estuary, North Carolina. All of the developmental stages occurred in the same area of the estuary with similar horizontal distributions, and the concentrations of intermediate and late stages were not greatly reduced from those of the first larval stage. This was strong evidence for the continuous retention of larvae in the upper estuary. To determine mechanisms by which retention might be effected, field studies of the vertical distributions and migrations of these larvae were made. The four zoeal stages had similar but complex vertical migration patterns, which varied from study to study. These migrations centered on the depth of no net flow, reducing longitudinal transport during development. Cross-spectral analysis of the larval migrations and the environmental cycles of light, salinity and current speed revealed that each of these external cycles affected larval depth. Megalopae of R. harrisii also migrated vertically, but they were present in much lower concentrations than the zoeal stages, an indication of a change to benthic existence in this final larval form.

New tools for subsurface imaging of 3D seismic Node data in hydrocarbon exploration =

NASA Astrophysics Data System (ADS)

Benazzouz, Omar

A aquisicao de dados sismicos de reflexao multicanal 3D/4D usando Ocean Bottom NODES de 4 componentes constitui atualmente um sector de importancia crescente no mercado da aquisicao de dados reflexao sismica marinha na industria petrolifera. Este tipo de dados permite obter imagens de sub-superficie de alta qualidade, com baixos niveis de ruido, banda larga, boa iluminacao azimutal, offsets longos, elevada resolucao e aquisicao de tanto ondas P como S. A aquisicao de dados e altamente repetitiva e portanto ideal para campanhas 4D. No entanto, existem diferencas significativas na geometria de aquisicao e amostragem do campo de ondas relativamente aos metodos convencionais com streamers rebocados a superficie, pelo que e necessario desenvolver de novas ferramentas para o processamento deste tipo de dados. Esta tese investiga tres aspectos do processamento de dados de OBSs/NODES ainda nao totalmente resolvidos de forma satisfatoria: a deriva aleatoria dos relogios internos, o posicionamento de precisao dos OBSs e a implementacao de algoritmos de migracao prestack 3D em profundidade eficientes para obtencao de imagens precisas de subsuperficie. Foram desenvolvidos novos procedimentos para resolver estas situacoes, que foram aplicados a dados sinteticos e a dados reais. Foi desenvolvido um novo metodo para deteccao e correccao de deriva aleatoria dos relogios internos, usando derivadas de ordem elevada. Foi ainda desenvolvido um novo metodo de posicionamento de precisao de OBSs usando multilateracao e foram criadas ferramentas de interpolacao/extrapolacao dos modelos de velocidades 3D de forma a cobrirem a extensao total area de aquisicao. Foram implementados algoritmos robustos de filtragem para preparar o campo de velocidades para o tracado de raios e minimizar os artefactos na migracao Krichhoff pre-stack 3D em profundidade. Os resultados obtidos mostram um melhoramento significativo em todas as situacoes analisadas. Foi desenvolvido o software necessario para o efeito e criadas solucoes computacionais eficientes. As solucoes computacionais desenvolvidas foram integradas num software standard de processamento de sismica (SPW) utilizado na industria, de forma a criar, conjuntamente com as ferramentas ja existentes, um workflow de processamento integrado para dados de OBS/NODES, desde a aquisicao e controle de qualidade a producao dos volumes sismicos migrados pre-stack em profundidade.

The lead (Pb) isotope signature, behaviour and fate of traffic-related lead pollution in roadside soils in The Netherlands.

PubMed

Walraven, N; van Os, B J H; Klaver, G Th; Middelburg, J J; Davies, G R

2014-02-15

In this study the origin, behaviour and fate of anthropogenic Pb in sandy roadside soils were assessed by measuring soil characteristics, Pb isotope composition and content. In 1991 and 2003 samples were taken at different depth intervals at approximately 8 and 75 m from two highways in The Netherlands. The Pb isotope composition of the litter layer ((206)Pb/(207)Pb=1.12-1.14) differs from the deeper soil samples ((206)Pb/(207)Pb=1.20-1.21). Based on a mixing model it is concluded that the samples contain two Pb sources: natural Pb and anthropogenic Pb, the latter mainly derived from gasoline. (206)Pb/(207)Pb ratios demonstrate that the roadside soils were polluted to a depth of ~15 cm. Within this depth interval, anthropogenic Pb content is associated with organic matter. Although Pb pollution only reached a depth of ~15 cm, this does not mean that the topsoils retain all anthropogenic Pb. Due to the low pH and negligible binding capacity of soils at depths >15 cm, anthropogenic Pb migrated towards groundwater after reaching depths of >15 cm. The Pb isotope composition of the groundwater ((206)Pb/(207)Pb=1.135-1.185) establishes that groundwater is polluted with anthropogenic Pb. The contribution of anthropogenic Pb to the groundwater varies between ~30 and 100%. Based on the difference in soil Pb content and Pb isotope compositions over a period of 12 years, downward Pb migration is calculated to vary from 72 ± 95 to 324 ± 279 mg m(-2)y(-1). Assuming that the downward Pb flux is constant over time, it is calculated that 35-90% of the atmospherically delivered Pb has migrated to the groundwater. Copyright © 2013 Elsevier B.V. All rights reserved.

Quantitative geophysical investigations at the Diamond M field, Scurry County, Texas

NASA Astrophysics Data System (ADS)

Davogustto Cataldo, Oswaldo Ernesto

The Diamond M field over the Horseshoe Atoll reservoir of west Texas has produced oil since 1942. Even with some 210 well penetrations, complex reservoir compartmentalization has justified an ongoing drilling program with three wells drilled within the last three years. Accurate reservoir characterization requires accurate description of the geometry, geological facies, and petrophysical property distribution ranging from core, through log to the seismic scale. The operator has conducted a careful logging and coring process including dipole sonic logs in addition to acquiring a modern 3D vertical phone - vertical vibrator "P-wave" seismic data volume and an equivalent size 2-component by 2-componet "S-wave" seismic data volume. I analyze these data at different scales, integrating them into a whole. I begin with core analysis of the petrophysical properties of the Horseshoe Atoll reservoir. Measuring porosity, permeability, NMR T2 relaxation and velocities (Vp and Vs) as a function of pressure and find that porosity measurements are consistent when measured with different techniques. When upscaled, these measurements are in excellent agreement with properties measured at the log scale. Together, these measurements provide a lithology-porosity template against which I correlate my seismic P- and S-impedance measurements. Careful examination of P- and S-impedances as well as density from prestack inversion of the P-wave survey of the original time migrated gathers showed lower vertical resolution for S-impedance and density. These latter two parameters are controlled by the far-offset data, which suffers from migration stretch. I address this shortcoming by applying a recently developed non-stretch NMO technique which not only improved the bandwidth of the data but also resulted in inversions that better match the S-impedance and density well log data. The operator hypothesized that 2C by 2C S-wave data would better delineate lithology than conventional P-wave seismic data. Although introduced in the mid-1980s, 2C by 2C data are rarely acquired, with most surveys showing less vertical resolution than conventional (and prior to slip-sweep technology more economically acquired) P-wave data. Initial processing by the service company showed a comparable, but lower frequency, image for the "transverse" component, and poor images for the "radial" component. Although the dipole sonic logs did not indicate the presence of significant anisotropy, shear wave splitting is readily observed on the surface seismic stacks. I therefore developed a prestack Alford rotation algorithm that minimizes the cross-talk between components, resulting vertical resolution comparable to the P-wave data, and independent measure of lithology, and also a direct measure of the direction of the principal axes of anisotropy. The direction of azimuthal anisotropy is aligned N45E consistent with the regional maximum horizontal stress axis obtained from the world stress map database. On average, the Cisco Formation appears 10% thicker on the slow shear (S2) volume than on the fast shear (S1 ) volume and between 70% and 100% thicker on the P-wave volume. Cross-plotting cumulative production against the various seismic attributes, I find a strong negative correlation to S-impedance and P-impedance. Zones of low S-impedance and low P-impedance correlate to better producing wells. More quantitative correlation will require the analysis of the role fractures versus porosity contribute to production.

Vertical migration of plutonium-239 + -240, americium-241 and caesium-137 fallout in a forest soil under spruce.

PubMed

Bunzl, K; Kracke, W; Schimmack, W

1992-03-01

The vertical activity distributions of fallout 238Pu, 239+240Pu, 241Am, 134Cs and 137Cs in a forest soil (Hapludult) were determined at several locations in a spruce stand separately according to their origin (global fallout or Chernobyl fallout). To determine the rate of migration of these radionuclides in each soil horizon, the observed depth profiles of the radionuclides were evaluated with a compartment model. In the top organic horizons (LOf1 and Of2), the migration rates for all radionuclides from both sources were above 0.5 cm per year. In the Oh horizon the migration rates observed for global fallout Pu, Am and Cs were similar (0.2-0.4 cm per year). Compared with Pu, however, the mobility of Am is slightly, but statistically significantly, enhanced. The highest rate in this layer was found for Chernobyl-derived radiocaesium (2 cm per year). In the layers of the mineral horizon (depth 0-2, 2-5 and 5-10 cm) the observed migration rates were very similar for global fallout Pu (0.08-0.7 cm per year) and Am (0.1-2 cm per year). In comparison, the migration rate of global fallout radiocaesium was about half in each layer. The highest rate was observed again for Chernobyl-derived radiocaesium (0.5-3 cm per year).

How to choose a subset of frequencies in frequency-domain finite-difference migration

NASA Astrophysics Data System (ADS)

Mulder, W. A.; Plessix, R.-E.

2004-09-01

Finite-difference migration with the two-way wave equation can be accelerated by an order of magnitude if the frequency domain rather than the time domain is used. This gain is mainly accomplished by using a subset of the available frequencies. The implicit assumption is that the data have a certain amount of redundancy in the frequency domain. The choice of frequencies cannot be arbitrary. If the frequencies are chosen with a constant increment and their spacing is too large, the well-known wrap-around that occurs when transforming back to the time domain will also show up in the migration to the depth domain, albeit in a more subtle way. Because migration involves propagation in a given background velocity model and summation over shots and receivers, the effects of wrap-around may disappear even when the Nyquist theorem is not obeyed. We have studied these effects analytically for the constant-velocity case and determined sampling conditions that avoid wrap-around artefacts. The conditions depend on the velocity, depth of the migration grid and offset range. They show that the spacing between subsequent frequencies can be larger than the inverse of the time range prescribed by the Nyquist theorem. A 2-D example has been used to test the validity of these conditions for a more realistic velocity model. Finite-difference migration with the one-way wave equation shows a similar behaviour.

Dune migration in a steep, coarse-bedded stream

USGS Publications Warehouse

Dinehart, Randy L.

1989-01-01

During 1986 and 1987, migrating bed forms composed of coarse sand and fine gravel (d50=1.8 to 9.1 mm) were documented in the North Fork Toutle River at Kid Valley, Washington, at flow velocities ranging from 1.6 to 3.4 m s−1 and depths of 0.8 to 2.2 m. The bed forms (predominantly lower regime dunes) were studied with a sonic depth sounder transducer suspended in the river at a stationary point. Twelve temporal depth-sounding records were collected during storm runoff and nearly steady, average streamflow, with record durations ranging from 37 to 261 min. Waveform height was defined by dune front heights, which ranged from 12 to 70 cm. A weak correlation between flow depth and the standard deviation of bed elevation was noted. Dune front counts and spectral analyses of the temporal records showed that dune crests passed the observation point every 2 to 5 min. Dunes were often superposed on larger bed forms with wave periods between 10 and 30 min. Gradual changes in waveform height and periodicity occurred over several hours during storm runoff. The processes of dune growth and decay were both time-dependent and affected by changes in streamflow. Rates of migration for typical dunes were estimated to be 3 cm s−1, and dune wavelengths were estimated to be 6 to 7 m.

3D receiver function Kirchhoff depth migration image of Cascadia subduction slab weak zone

NASA Astrophysics Data System (ADS)

Cheng, C.; Allen, R. M.; Bodin, T.; Tauzin, B.

2016-12-01

We have developed a highly computational efficient algorithm of applying 3D Kirchhoff depth migration to telesismic receiver function data. Combine primary PS arrival with later multiple arrivals we are able to reveal a better knowledge about the earth discontinuity structure (transmission and reflection). This method is highly useful compare with traditional CCP method when dipping structure is met during the imaging process, such as subduction slab. We apply our method to the reginal Cascadia subduction zone receiver function data and get a high resolution 3D migration image, for both primary and multiples. The image showed us a clear slab weak zone (slab hole) in the upper plate boundary under Northern California and the whole Oregon. Compare with previous 2D receiver function image from 2D array(CAFE and CASC93), the position of the weak zone shows interesting conherency. This weak zone is also conherent with local seismicity missing and heat rising, which lead us to think about and compare with the ocean plate stucture and the hydralic fluid process during the formation and migration of the subduction slab.

Transoceanic migration, spatial dynamics, and population linkages of white sharks.

PubMed

Bonfil, Ramón; Meÿer, Michael; Scholl, Michael C; Johnson, Ryan; O'Brien, Shannon; Oosthuizen, Herman; Swanson, Stephan; Kotze, Deon; Paterson, Michael

2005-10-07

The large-scale spatial dynamics and population structure of marine top predators are poorly known. We present electronic tag and photographic identification data showing a complex suite of behavioral patterns in white sharks. These include coastal return migrations and the fastest known transoceanic return migration among swimming fauna, which provide direct evidence of a link between widely separated populations in South Africa and Australia. Transoceanic return migration involved a return to the original capture location, dives to depths of 980 meters, and the tolerance of water temperatures as low as 3.4 degrees C. These findings contradict previous ideas that female white sharks do not make transoceanic migrations, and they suggest natal homing behavior.

Deep crustal structure of the northeastern margin of the Arabian plate from seismic and gravity data

NASA Astrophysics Data System (ADS)

Pilia, Simone; Ali, Mohammed; Watts, Anthony; Keats, Brook; Searle, Mike

2017-04-01

The United Arab Emirates-Oman mountains constitute a 700 km long, 50 km wide compressional orogenic belt that developed during the Cainozoic on an underlying extensional Tethyan rifted margin. It contains the world's largest and best-exposed thrust sheet of oceanic crust and upper mantle (Semail Ophiolite), which was obducted onto the Arabian rifted continental margin during the Late Cretaceous. Although the shallow structure of the UAE-Oman mountain belt is reasonably well known through the exploitation of a diverse range of techniques, information on deeper structure remains little. Moreover, the mechanisms by which dense oceanic crustal and mantle rocks are emplaced onto less dense and more buoyant continental crust are still controversial and remain poorly understood. The focus here is on an active-source seismic and gravity E-W transect extending from the UAE-mountain belt to the offshore. Seismic refraction data were acquired using the survey ship M/V Hawk Explorer, which was equipped with a large-volume airgun array (7060 cubic inches, 116 liters). About 400 air gun shots at 50-second time interval were recorded on land by eight broadband seismometers. In addition, reflection data were acquired at 20 seconds interval and recorded by a 5-km-long multichannel streamer. Results presented here include an approximately 85 km long (stretching about 35 km onshore and 50 km offshore) P-wave velocity crustal profile derived by a combination of forward modelling and inversion of both diving and reflected wave traveltimes using RAYINVR software. We employ a new robust algorithm based on a Monte Carlo approach (VMONTECARLO) to address the velocity model uncertainties. We find ophiolite seismic velocities of about 5.5 km/s and a thick sedimentary package in the offshore. Furthermore, the velocity model reveals a highly stretched crust with the Moho discontinuity lying at about 20 km. A prestack depth-migrated profile (about 50 km long) coincident with the offshore part of the refraction profile shows a thick sequence (up to about 10 km) of seaward dipping sediments that are offset by a number of listric (normal) faults, some of which intersect the seabed and so reflect recent tectonic activity. The trend of the Bouguer anomaly provides further constraints on the deeper structure of the margin and appears to confirm the presence of a stretched crust.

Uniquely Acquired Vintage Seismic Reflection Data Reveal the Stratigraphic and Tectonic History of the Montana Disturbed Belt, USA

NASA Astrophysics Data System (ADS)

Speece, M. A.; Link, C. A.; Stickney, M.

2011-12-01

In 1983 and 1984 Techco of Denver, Colorado, acquired approximately 302 linear kilometers of two-dimensional (2D) seismic reflection data in Flathead and Lake Counties, Montana, USA, as part of an initiative to identify potential drilling targets beneath the Swan and Whitefish Mountain Ranges and adjacent basins of northwestern Montana. These seismic lines were collected in the Montana Disturbed Belt (MDB) or Montana thrust belt along the western edge of Glacier National Park in mountainous terrain with complicated subsurface structures including thrust faults and folds. These structures formed during the Laramide Orogeny as sedimentary rocks of the Precambrian Belt Supergroup were thrust eastward. Later, during the Cenozoic, high-angle normal faults produced prominent west-facing mountain scarps of the Mission, Swan and Whitefish mountains. The 1983 data set consisted of two profiles of 24-fold (96-channels) Vibroseis data and four profiles of 24-fold (96-channels) helicopter-assisted dynamite data. The dynamite data were collected using the Poulter Method in which explosives were placed on poles and air shots were recorded. The 1983 dynamite profiles extend from southwest to northeast across the Whitefish Mountain Range to the edge of Glacier National Park and the Vibroseis data were collected along nearby roadways. The 1984 data set consists of four profiles of 30-fold (120-channels) helicopter-assisted dynamite data that were also collected using the Poulter Method. The 1984 profiles cross the Swan Mountain Range between Flathead Lake and Glacier National Park. All of these data sets were recently donated to Montana Tech and subsequently recovered from nine-track tape. Conventionally processed seismic stacked sections from the 1980s of these data show evidence of a basement decollement that separates relatively undeformed basement from overlying structures of the MDB. Unfortunately, these data sets have not been processed using modern seismic processing techniques including linear noise suppression of the air wave and ground roll, refraction statics, and prestack migration. Reprocessing of these data using state-of-the-art seismic reflection processing techniques will provide a detailed picture of the stratigraphy and tectonic framework for this region. Moreover, extended correlations of the Vibroseis records to Moho depths might reveal new insights on crustal thickness and provide a framework for understanding crustal thickening during the Laramide Orogeny as well as later Cenozoic extension.

Observing Migration and Burial of Unexploded Ordnance in the Nearshore Environment with Instrumented Surrogates

NASA Astrophysics Data System (ADS)

Bruder, B. L.; Cristaudo, D.; Puleo, J. A.

2016-12-01

Prior to 1972, it was legal and common practice to unload unexploded ordnance (UXO) into the ocean. Only 60-100 miles off the US coast alone there are 72 dumping sites where it is estimated 31 million pounds of UXO lie. As recently as 2015, UXO have been found not only in the nearshore environment, but on populated beaches. Thus, understanding the migration and burial of these objects is not only of oceanographic interest, but a matter of public safety. The presented project evaluates the efficacy of instrumented UXO surrogates for observing munition migration and burial. Instrumented surrogates were exposed to near prototype scale wave conditions over a mobile bed at the Littoral Warfare Environment at Aberdeen Test Center, MD. Surrogates were deployed in the swash zone, inner and outer surf zones. Dependent on munition size, surrogates housed multiple suites of self-logging sensors. Sensor suites included different combinations of inertial motion units, ultra-wideband tracking tags, pressure transducers, shock recorders, and photocells. Preliminary results show sensor suites can resolve various types of surrogate movement. Pressure transducers accurately record ambient wave conditions as well as changes in mean depth due to surrogate migration. Inertial motion units resolve munition accelerations for rolling and translational motion. Inertial motion unit data is used to estimate trajectory as well when coupled with mean depth and bathymetric data. Photocells, which measure ambient light, resolve munition burial as well as serve as proxies for surrounding environmental conditions such as suspended sediment and water depth. The presented project will continue to utilize and couple surrogate sensor data to resolve munition movement and burial under different conditions. Knowledge of munition migration helps focus UXO detection and recovery, conserving US military and coastal resources.

Coalbed methane accumulation and dissipation patterns: A Case study of the Junggar Basin, NW China

NASA Astrophysics Data System (ADS)

Li, Xin; Fu, Xuehai; Yang, Xuesong; Ge, Yanyan; Quan, Fangkai

2018-07-01

The Junggar Basin is a potential replacement area of coalbed methane (CBM) development in China. To improve the efficiency of CBM exploration, we investigated CBM accumulation and dissipation patterns of coal profiles located in the northwestern, southern, eastern, and central Junggar Basin based on the following criteria: burial depth, hydrogeological zone, CBM origin, CBM phase, and CBM migration type. We identified four types of CBM accumulation patterns: (1) a self-sourcing CBM pattern containing adsorbed gas of biogenic origin from shallow-depth coal within a weak runoff zone; (2) an endogenic migration pattern containing adsorbed gas of thermogenic origin from the medium and deep coals within a stagnant zone; (3) an exogenic migration pattern containing adsorbed gas of thermogenic origin from deep coal within a stagnant zone; and (4) an exogenic migration pattern containing adsorbed and free gas of thermogenic origin from ultra-deep coal within a stagnant zone. We also identified two types of CBM dissipation patterns: (1) shallow-depth coal within a runoff zone with mixed origin CBM; and (2) shallow and medium-deep coal seams with mixed origin CBM. CBM migration in low-rank coals was more substantial than that adsorbed in high-rank coal. CBM in shallow coal could easily escape, in the absence of closed structures or hydrogeological seals. CBM reservoirs occurred in deep coal where oversaturated gas may accumulate. Future exploration should focus on gas-water sealing structures in shallow coalbeds. CBM that occurred in adsorbed and free phases and other unconventional natural gas dominated by free gas in the coal stratum should be co-explored and co-developed.

An application of LOTEM around salt dome near Houston, Texas

NASA Astrophysics Data System (ADS)

Paembonan, Andri Yadi; Arjwech, Rungroj; Davydycheva, Sofia; Smirnov, Maxim; Strack, Kurt M.

2017-07-01

A salt dome is an important large geologic structure for hydrocarbon exploration. It may seal a porous reservoir of rocks that form petroleum reservoirs. Several techniques such as seismic, gravity, and electromagnetic including magnetotelluric have successfully yielded salt dome interpretation. Seismic has difficulties seeing through the salt because the seismic energy gets trapped by the salt due to its high velocity. Gravity and electromagnetics are more ideal methods. Long Offset Transient Electromagnetic (LOTEM) and Focused Source Electromagnetic (FSEM) were tested over a salt dome near Houston, Texas. LOTEM data were recorded at several stations with varying offset, and the FSEM tests were also made at some receiver locations near a suspected salt overhang. The data were processed using KMS's processing software: First, for assurance, including calibration and header checking; then transmitter and receiver data are merged and microseismic data is separated; Finally, data analysis and processing follows. LOTEM processing leads to inversion or in the FSEM case 3D modeling. Various 3D models verify the sensitivity under the salt dome. In addition, the processing was conducted pre-stack, stack, and post-stack. After pre-stacking, the noise was reduced, but showed the ringing effect due to a low-pass filter. Stacking and post-stacking with applying recursive average could reduce the Gibbs effect and produce smooth data.

Fine Scale Baleen Whale Behavior Observed via Tagging Over Daily Time Scales

DTIC Science & Technology

2012-09-30

right whales and sei whales) and the diel vertical migration behavior of their copepod prey. I hypothesize that (1) right whales track the diel...vertical migration of copepods by feeding near the bottom during the day and at the surface at night, and (2) sei whales are unable to feed on copepods at...depth during the day, and are therefore restricted to feeding on copepods at the surface only. Because copepod diel vertical migration is variable

Fine Scale Baleen Whale Behavior Observed via Tagging Over Daily Time Scales

DTIC Science & Technology

2013-09-30

sei whales) and the diel vertical migration behavior of their copepod prey. I hypothesize that (1) right whales track the diel vertical migration of... copepods by feeding near the bottom during the day and at the surface at night, and (2) sei whales are unable to feed on copepods at depth during the...day, and are therefore restricted to feeding on copepods at the surface only. Because copepod diel vertical migration is variable over time (days to

The influence of oceanographic features on the foraging behavior of the olive ridley sea turtle Lepidochelys olivacea along the Guiana coast

NASA Astrophysics Data System (ADS)

Chambault, Philippine; de Thoisy, Benoît; Heerah, Karine; Conchon, Anna; Barrioz, Sébastien; Dos Reis, Virginie; Berzins, Rachel; Kelle, Laurent; Picard, Baptiste; Roquet, Fabien; Le Maho, Yvon; Chevallier, Damien

2016-03-01

The circulation in the Western Equatorial Atlantic is characterized by a highly dynamic mesoscale activity that shapes the Guiana continental shelf. Olive ridley sea turtles (Lepidochelys olivacea) nesting in French Guiana cross this turbulent environment during their post-nesting migration. We studied how oceanographic and biological conditions drove the foraging behavior of 18 adult females, using satellite telemetry, remote sensing data (sea surface temperature, sea surface height, current velocity and euphotic depth), simulations of micronekton biomass (pelagic organisms) and in situ records (water temperature and salinity). The occurrence of foraging events throughout migration was located using Residence Time analysis, while an innovative proxy of the hunting time within a dive was used to identify and quantify foraging events during dives. Olive ridleys migrated northwestwards using the Guiana current and remained on the continental shelf at the edge of eddies formed by the North Brazil retroflection, an area characterized by low turbulence and high micronekton biomass. They performed mainly pelagic dives, hunting for an average 77% of their time. Hunting time within a dive increased with shallower euphotic depth and with lower water temperatures, and mean hunting depth increased with deeper thermocline. This is the first study to quantify foraging activity within dives in olive ridleys, and reveals the crucial role played by the thermocline on the foraging behavior of this carnivorous species. This study also provides novel and detailed data describing how turtles actively use oceanographic structures during post-nesting migration.

Microgrooved Polymer Substrates Promote Collective Cell Migration To Accelerate Fracture Healing in an in Vitro Model.

PubMed

Zhang, Qing; Dong, Hua; Li, Yuli; Zhu, Ye; Zeng, Lei; Gao, Huichang; Yuan, Bo; Chen, Xiaofeng; Mao, Chuanbin

2015-10-21

Surface topography can affect cell adhesion, morphology, polarity, cytoskeleton organization, and osteogenesis. However, little is known about the effect of topography on the fracture healing in repairing nonunion and large bone defects. Microgrooved topography on the surface of bone implants may promote cell migration into the fracture gap to accelerate fracture healing. To prove this hypothesis, we used an in vitro fracture (wound) healing assay on the microgrooved polycaprolactone substrates to study the effect of microgroove widths and depths on the osteoblast-like cell (MG-63) migration and the subsequent healing. We found that the microgrooved substrates promoted MG-63 cells to migrate collectively into the wound gap, which serves as a fracture model, along the grooves and ridges as compared with the flat substrates. Moreover, the groove widths did not show obvious influence on the wound healing whereas the smaller groove depths tended to favor the collective cell migration and thus subsequent healing. The microgrooved substrates accelerated the wound healing by facilitating the collective cell migration into the wound gaps but not by promoting the cell proliferation. Furthermore, microgrooves were also found to promote the migration of human mesenchymal stem cells (hMSCs) to heal the fracture model. Though osteogenic differentiation of hMSCs was not improved on the microgrooved substrate, collagen I and minerals deposited by hMSCs were organized in a way similar to those in the extracellular matrix of natural bone. These findings suggest the necessity in using microgrooved implants in enhancing fracture healing in bone repair.

Frequency-domain elastic full waveform inversion using encoded simultaneous sources

NASA Astrophysics Data System (ADS)

Jeong, W.; Son, W.; Pyun, S.; Min, D.

2011-12-01

Currently, numerous studies have endeavored to develop robust full waveform inversion and migration algorithms. These processes require enormous computational costs, because of the number of sources in the survey. To avoid this problem, the phase encoding technique for prestack migration was proposed by Romero (2000) and Krebs et al. (2009) proposed the encoded simultaneous-source inversion technique in the time domain. On the other hand, Ben-Hadj-Ali et al. (2011) demonstrated the robustness of the frequency-domain full waveform inversion with simultaneous sources for noisy data changing the source assembling. Although several studies on simultaneous-source inversion tried to estimate P- wave velocity based on the acoustic wave equation, seismic migration and waveform inversion based on the elastic wave equations are required to obtain more reliable subsurface information. In this study, we propose a 2-D frequency-domain elastic full waveform inversion technique using phase encoding methods. In our algorithm, the random phase encoding method is employed to calculate the gradients of the elastic parameters, source signature estimation and the diagonal entries of approximate Hessian matrix. The crosstalk for the estimated source signature and the diagonal entries of approximate Hessian matrix are suppressed with iteration as for the gradients. Our 2-D frequency-domain elastic waveform inversion algorithm is composed using the back-propagation technique and the conjugate-gradient method. Source signature is estimated using the full Newton method. We compare the simultaneous-source inversion with the conventional waveform inversion for synthetic data sets of the Marmousi-2 model. The inverted results obtained by simultaneous sources are comparable to those obtained by individual sources, and source signature is successfully estimated in simultaneous source technique. Comparing the inverted results using the pseudo Hessian matrix with previous inversion results provided by the approximate Hessian matrix, it is noted that the latter are better than the former for deeper parts of the model. This work was financially supported by the Brain Korea 21 project of Energy System Engineering, by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2010-0006155), by the Energy Efficiency & Resources of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government Ministry of Knowledge Economy (No. 2010T100200133).

Learning US History in an Age of Globalization and Transnational Migration

ERIC Educational Resources Information Center

An, Sohyun

2009-01-01

This paper examines US Korean youth's perspectives on US history and the impact of their sociocultural backgrounds, particularly their migration status, on their historical interpretations. Based on in-depth interviews with 42 US Korean high school students, the study opens up the question of diversity within an ethnic group, while it also begins…

Floating Migration, Education, and Globalization in the US Caribbean

ERIC Educational Resources Information Center

Gonzalez, Mirerza; Rios-Villarini, Nadjah

2012-01-01

This article follows a research project that collects oral histories of bilingual education teachers from Puerto Rico who migrated to the US Virgin Islands in the late twentieth century. The teachers' oral histories are used as a case study that provides in-depth analysis of competing discourses related to education and globalization in these two…

Influence of forest and rangeland management on anadromous fish habitat in Western North America: habitat requirements of anadromous salmonids.

Treesearch

D.W. Reiser; T.C. Bjornn

1979-01-01

Habitat requirements of anadromous and some resident salmonid fishes have been described for various life stages, including upstream migration of adults, spawning, incubation, and juvenile rearing. Factors important in the migration of adults are water temperature, minimum water depth, maximum water velocity, turbidity, dissolved oxygen, and...

Migration Decision-Making among Mexican Youth: Individual, Family, and Community Influences

PubMed Central

Tucker, Christine M.; Torres-Pereda, Pilar; Minnis, Alexandra M.; Bautista-Arredondo, Sergio A.

2013-01-01

We explored migration decisions using in-depth, semi-structured interviews with male and female youth ages 14 to 24 (n=47) from two Mexican communities, one with high and one with low U.S. migration density. Half were return migrants and half were non-migrants with relatives in the U.S. Migrant and non-migrant youth expressed different preferences, especially in terms of education and their ability to wait for financial gain. Reasons for migration were mostly similar across the two communities; however, the perceived risk of the migration journey was higher in the low density migration community while perceived opportunities in Mexico were higher in the high density migration community. Reasons for return were related to youths’ initial social and economic motivations for migration. A greater understanding of factors influencing migration decisions may provide insight into the vulnerability of immigrant youth along the journey, their adaptation process in the U.S., and their reintegration in Mexico. PMID:23626401

Migration Decision-Making among Mexican Youth: Individual, Family, and Community Influences.

PubMed

Tucker, Christine M; Torres-Pereda, Pilar; Minnis, Alexandra M; Bautista-Arredondo, Sergio A

2013-05-07

We explored migration decisions using in-depth, semi-structured interviews with male and female youth ages 14 to 24 (n=47) from two Mexican communities, one with high and one with low U.S. migration density. Half were return migrants and half were non-migrants with relatives in the U.S. Migrant and non-migrant youth expressed different preferences, especially in terms of education and their ability to wait for financial gain. Reasons for migration were mostly similar across the two communities; however, the perceived risk of the migration journey was higher in the low density migration community while perceived opportunities in Mexico were higher in the high density migration community. Reasons for return were related to youths' initial social and economic motivations for migration. A greater understanding of factors influencing migration decisions may provide insight into the vulnerability of immigrant youth along the journey, their adaptation process in the U.S., and their reintegration in Mexico.

Timing of seasonal migration in mule deer: effects of climate, plant phenology, and life-history characteristics

USGS Publications Warehouse

Monteith, Kevin L.; Bleich, Vernon C.; Stephenson, Thomas R.; Pierce, Beck M.; Conner, Mary M.; Klaver, Robert W.; Bowyer, R. Terry

2011-01-01

Phenological events of plants and animals are sensitive to climatic processes. Migration is a life-history event exhibited by most large herbivores living in seasonal environments, and is thought to occur in response to dynamics of forage and weather. Decisions regarding when to migrate, however, may be affected by differences in life-history characteristics of individuals. Long-term and intensive study of a population of mule deer (Odocoileus hemionus) in the Sierra Nevada, California, USA, allowed us to document patterns of migration during 11 years that encompassed a wide array of environmental conditions. We used two new techniques to properly account for interval-censored data and disentangle effects of broad-scale climate, local weather patterns, and plant phenology on seasonal patterns of migration, while incorporating effects of individual life-history characteristics. Timing of autumn migration varied substantially among individual deer, but was associated with the severity of winter weather, and in particular, snow depth and cold temperatures. Migratory responses to winter weather, however, were affected by age, nutritional condition, and summer residency of individual females. Old females and those in good nutritional condition risked encountering severe weather by delaying autumn migration, and were thus risk-prone with respect to the potential loss of foraging opportunities in deep snow compared with young females and those in poor nutritional condition. Females that summered on the west side of the crest of the Sierra Nevada delayed autumn migration relative to east-side females, which supports the influence of the local environment on timing of migration. In contrast, timing of spring migration was unrelated to individual life-history characteristics, was nearly twice as synchronous as autumn migration, differed among years, was related to the southern oscillation index, and was influenced by absolute snow depth and advancing phenology of plants. Plasticity in timing of migration in response to climatic conditions and plant phenology may be an adaptive behavioral strategy, which should reduce the detrimental effects of trophic mismatches between resources and other life-history events of large herbivores. Failure to consider effects of nutrition and other life-history traits may cloud interpretation of phenological patterns of mammals and conceal relationships associated with climate change.

Political motivations for intra-European migration

PubMed Central

Flipo, Aurore

2016-01-01

Motivations for migrating within the European Union have mainly been attributed to economic, career and lifestyle choices. This article suggests that political dissatisfaction is also an important motivator of recent intra-European migration. In our analysis of in-depth interviews with Romanian migrants in Spain and with Spanish migrants in Norway, we found a common emphasis on the political dimensions of their decision to migrate. In the interviews, the economic component of migration was often related to bad governance and negative perceptions of the state. The similarities of Spanish and Romanian migration narratives are especially striking because Spain and Romania represent substantially different migratory, political and economic contexts. However, migration is more obviously intertwined with conventional acts of political protest in the Spanish case. We suggest that differences in democratic contexts are pivotal in people’s reactions to and framing of their deep dissatisfaction with domestic politics, as found in many European countries today. PMID:28751786

Political motivations for intra-European migration.

PubMed

Bygnes, Susanne; Flipo, Aurore

2017-08-01

Motivations for migrating within the European Union have mainly been attributed to economic, career and lifestyle choices. This article suggests that political dissatisfaction is also an important motivator of recent intra-European migration. In our analysis of in-depth interviews with Romanian migrants in Spain and with Spanish migrants in Norway, we found a common emphasis on the political dimensions of their decision to migrate. In the interviews, the economic component of migration was often related to bad governance and negative perceptions of the state. The similarities of Spanish and Romanian migration narratives are especially striking because Spain and Romania represent substantially different migratory, political and economic contexts. However, migration is more obviously intertwined with conventional acts of political protest in the Spanish case. We suggest that differences in democratic contexts are pivotal in people's reactions to and framing of their deep dissatisfaction with domestic politics, as found in many European countries today.

Oxygen and Temperature Effects on Vertically Migrating Animals in Oxygen Minimum Zones

NASA Astrophysics Data System (ADS)

Seibel, B.

2016-02-01

Large populations of oceanic nekton and zooplankton undergo daily migrations from shallow water at night to depths greater than 200 m during the daytime. In some regions, these migrations cross extreme gradients of temperature, oxygen and carbon dioxide. Oxygen minimum zones (OMZs) are extensive and characterized by deep-water (100-800 m) oxygen partial pressures that would be lethal to most marine organisms, yet are tolerated by vertical migrators. Climate change is predicted to further deplete oxygen, and measurable reductions in oxygen have already been documented in some regions. Increases in shallow water temperature and carbon dioxide are occurring simultaneously. Oxygen levels and temperature are important drivers of biodiversity and distribution, and documented changes in community structure and function are reportedly associated with OMZ expansion and warming. Here I answer fundamental questions concerning zooplankton distributions, adaptations, and functions in oxygen minimum zones. In particular I report that metabolic suppression is a common strategy that facilitates diel occupancy of extreme hypoxia in many oceanic taxa. Anaerobic metabolic pathways play a minimal role in compensating for reduced aerobic ATP production. Numerous epigenetic mechanisms lead to reductions in energetically costly cellular processes, such as transcription and translation. Total metabolism is reduced by 50% or more during exposure to levels of hypoxia that characterize the daytime habitat for most vertically-migrating zooplankton. I further show that many migrators approach their upper thermal maximum in shallow water at night. Thus expanding OMZs and global warming may together compress the habitable depth range for many species.

Moho Depth Variations in the Northeastern North China Craton Revealed by Receiver Function Imaging

NASA Astrophysics Data System (ADS)

Zhang, P.; Chen, L.; Yao, H.; Fang, L.

2016-12-01

The North China Craton (NCC), one of the oldest cratons in the world, has attracted wide attention in Earth Science for decades because of the unusual Mesozoic destruction of its cratonic lithosphere. Understanding the deep processes and mechanism of this craton destruction demands detailed knowledge about the deep structure of the region. In this study, we used two-year teleseismic receiver function data from the North China Seismic Array consisting of 200 broadband stations deployed in the northeastern NCC to image the Moho undulation of the region. A 2-D wave equation-based poststack depth migration method was employed to construct the structural images along 19 profiles, and a pseudo 3D crustal velocity model of the region based on previous ambient noise tomography and receiver function study was adopted in the migration. We considered both the Ps and PpPs phases, but in some cases we also conducted PpSs+PsPs migration using different back azimuth ranges of the data, and calculated the travel times of all the considered phases to constrain the Moho depths. By combining the structure images along the 19 profiles, we got a high-resolution Moho depth map beneath the northeastern NCC. Our results broadly consist with the results of previous active source studies [http://www.craton.cn/data], and show a good correlation of the Moho depths with geological and tectonic features. Generally, the Moho depths are distinctly different on the opposite sides of the North-South Gravity Lineament. The Moho in the west are deeper than 40 km and shows a rapid uplift from 40 km to 30 km beneath the Taihang Mountain Range in the middle. To the east in the Bohai Bay Basin, the Moho further shallows to 30-26 km depth and undulates by 3 km, coinciding well with the depressions and uplifts inside the basin. The Moho depth beneath the Yin-Yan Mountains in the north gradually decreases from 42 km in the west to 25 km in the east, varying much smoother than that to the south.

Kerr-gated picosecond Raman spectroscopy and Raman photon migration of equine bone tissue with 400-nm excitation

NASA Astrophysics Data System (ADS)

Morris, Michael D.; Goodship, Allen E.; Draper, Edward R. C.; Matousek, Pavel; Towrie, Michael; Parker, Anthony W.

2004-07-01

We show that Raman spectroscopy with visible lasers, even in the deep blue is possible with time-gated Raman spectroscopy. A 4 picosec time gate allows efficient fluorescence rejection, up to 1000X, and provides almost background-free Raman spectra with low incident laser power. The technology enables spectroscopy with better than 10X higher scattering efficiency than is possible with the NIR (785 nm and 830 nm) lasers that are conventionally used. Raman photon migration is shown to allow depth penetration. We show for the first time that Kerr-gated Raman spectra of bone tissue with blue laser excitation enables both fluorescence rejection and depth penetration.

Vertical distribution, composition and migratory patterns of acoustic scattering layers in the Canary Islands

NASA Astrophysics Data System (ADS)

Ariza, A.; Landeira, J. M.; Escánez, A.; Wienerroither, R.; Aguilar de Soto, N.; Røstad, A.; Kaartvedt, S.; Hernández-León, S.

2016-05-01

Diel vertical migration (DVM) facilitates biogeochemical exchanges between shallow waters and the deep ocean. An effective way of monitoring the migrant biota is by acoustic observations although the interpretation of the scattering layers poses challenges. Here we combine results from acoustic observations at 18 and 38 kHz with limited net sampling in order to unveil the origin of acoustic phenomena around the Canary Islands, subtropical northeast Atlantic Ocean. Trawling data revealed a high diversity of fishes, decapods and cephalopods (152 species), although few dominant species likely were responsible for most of the sound scattering in the region. We identified four different acoustic scattering layers in the mesopelagic realm: (1) at 400-500 m depth, a swimbladder resonance phenomenon at 18 kHz produced by gas-bearing migrant fish such as Vinciguerria spp. and Lobianchia dofleini, (2) at 500-600 m depth, a dense 38 kHz layer resulting primarily from the gas-bearing and non-migrant fish Cyclothone braueri, and to a lesser extent, from fluid-like migrant fauna also inhabiting these depths, (3) between 600 and 800 m depth, a weak signal at both 18 and 38 kHz ascribed either to migrant fish or decapods, and (4) below 800 m depth, a weak non-migrant layer at 18 kHz which was not sampled. All the dielly migrating layers reached the epipelagic zone at night, with the shorter-range migrations moving at 4.6 ± 2.6 cm s - 1 and the long-range ones at 11.5 ± 3.8 cm s - 1. This work reduces uncertainties interpreting standard frequencies in mesopelagic studies, while enhances the potential of acoustics for future research and monitoring of the deep pelagic fauna in the Canary Islands.

Winter range arrival and departure of white-tailed deer in northeastern Minnesota

USGS Publications Warehouse

Nelson, M.E.

1995-01-01

I analyzed 364 spring and 239 fall migrations by 194 white-tailed deer (Odocoileus virginianus) from 1975 to 1993 in northeastern Minnesota to determine the proximate cause of arrivals on and departures from winter ranges. The first autumn temperatures below -7?C initiated fall migrations for 14% (95% confidence interval (CI) = 0-30) of female deer prior to snowfall in three autumns, but only 2% remained on winter ranges. During 14 autumns, the first temperatures below -7?C coincidental with snowfalls elicited migration in 45% (95% CI = 34-57) of females, and 91 % remained on winter ranges. Arrival dates failed to correlate with independent variables of temperature and snow depth, precluding predictive modeling of arrival on winter ranges. During 13 years, a mean of 80% of females permanently arrived on winter ranges by 31 December. Mean departure dates from winter ranges varied annually (19 March - 4 May) and between winter ranges (14 days) and according to snow depth (15-cm differences). Only 15 - 41 % of deer departed when snow depths were> 30 cm but 80% had done so by the time of lO-cm depths. Mean weekly snow depths in March (18-85 cm) and mean temperature in April (0.3 -8.1 ?c) explained most of the variation in mean departure dates from two winter ranges (Ely, R2 = 0.87, P < 0.0005, n = 19 springs; Isabella, R2 = 0.85, P = 0.0001, n = 12 springs). Mean differences between observed mean departure dates and mean departure dates predicted from equations ranged from 3 days (predictions within the study area) to 8 days (predictions for winter ranges 100-440 km distant).

A wave equation migration method for receiver function imaging: 2. Application to the Japan subduction zone

NASA Astrophysics Data System (ADS)

Chen, Ling; Wen, Lianxing; Zheng, Tianyu

2005-11-01

The newly developed wave equation poststack depth migration method for receiver function imaging is applied to study the subsurface structures of the Japan subduction zone using the Fundamental Research on Earthquakes and Earth's Interior Anomalies (FREESIA) broadband data. Three profiles are chosen in the subsurface imaging, two in northeast (NE) Japan to study the subducting Pacific plate and one in southwest (SW) Japan to study the Philippine Sea plate. The descending Pacific plate in NE Japan is well imaged within a depth range of 50-150 km. The slab image exhibits a little more steeply dipping angle (˜32°) in the south than in the north (˜27°), although the general characteristics between the two profiles in NE Japan are similar. The imaged Philippine Sea plate in eastern SW Japan, in contrast, exhibits a much shallower subduction angle (˜19°) and is only identifiable at the uppermost depths of no more than 60 km. Synthetic tests indicate that the top 150 km of the migrated images of the Pacific plate is well resolved by our seismic data, but the resolution of deep part of the slab images becomes poor due to the limited data coverage. Synthetic tests also suggest that the breakdown of the Philippine Sea plate at shallow depths reflects the real structural features of the subduction zone, rather than caused by insufficient coverage of data. Comparative studies on both synthetics and real data images show the possibility of retrieval of fine-scale structures from high-frequency contributions if high-frequency noise can be effectively suppressed and a small bin size can be used in future studies. The derived slab geometry and image feature also appear to have relatively weak dependence on overlying velocity structure. The observed seismicity in the region confirms the geometries inferred from the migrated images for both subducting plates. Moreover, the deep extent of the Pacific plate image and the shallow breakdown of the Philippine Sea plate image are observed to correlate well with the depth extent of the seismicity beneath NE and SW Japan. Such a correlation supports the inference that the specific appearance of slabs and intermediate-depth earthquakes are a consequence of temperature-dependent dehydration induced metamorphism occurring in the hydrated descending oceanic crust.

Crustal structure of the Sunda-Banda arc transition: results from marine geophysical investigations offshore eastern Indonesia

NASA Astrophysics Data System (ADS)

Planert, L.; Shulgin, A.; Kopp, H.; Lueschen, E.; Mueller, C.; Flueh, E.; Djajadihardja, Y.; Engels, M.

2009-04-01

The Sunda-Banda arc transition, the easternmost portion of the Indonesian convergent margin, presents a probably unique natural laboratory to study lower plate variability and related upper plate deformation in the so-called ‘subduction factory' for a deeper understanding of forearc evolution. In neighboring margin segments, we can observe strong changes of the incoming plate (transition from an oceanic to a continental lower plate, increasing plate age to the East, presence/absence of an oceanic plateau, variability in plate roughness) as well as a wide range of corresponding forearc structures, including large sedimentary basins and an accretionary prism/outer arc high of variable size and shape. During RV Sonne cruise SO190 in 2006 (SINDBAD: Seismic and Geoacoustic Investigations along the Sunda-Banda Arc Transition), we acquired a combination of seismic wide-angle OBH/OBS refraction, multichannel streamer and gravity data in order to study the seismic velocity structure of the subducting crust and the overriding island arc along a number of trench normal corridors located between 113°E and 121°E. Additionally, a number of trench parallel profiles were conducted which mainly focus on the internal structure of the large sedimentary basins and which were also intended for further clarifying the type of underlying forearc crust and mantle respectively. We used a tomographic approach for refracted and reflected phases to obtain seismic velocity models which again were used for prestack depth-migration of the MCS data. In turn, we incorporated the highly resolved sedimentary portions as a priori structure in our tomography. The results show the seismic velocity structure of the incoming plate, starting 100 km seaward of the trench, and the adjoining forearc down to depths of 20-28 km, i.e. well into the upper mantle, and at the same time fit the gravity data very well, using simple velocity-density relations. In the Argo abyssal plain, the models show 8.0-8.5 km thick oceanic crust. The velocities in the crust and uppermost mantle are reduced within distances of ~50 km seaward of the trench, which coincides with the onset of normal faulting on the incoming oceanic plate. Anomalously low mantle velocities of 7.5 km/s directly beneath the Moho are possibly due to the intrusion of seawater and subsequent serpentinisation of mantle peridotite. Landward of the trench in the outer arc high, velocities do not exceed 5.5 km/s down to the top of the subducting slab, which can be traced over ~70 km length beneath the forearc down to ~13 km depth. The plate boundary is of irregular shape, obviously imprinted by the complex deformation of the oceanic basement prior to subduction, which is further amplified as response to thrusting/downbending of the dissected oceanic blocks. Offshore Lombok island, our models reveal the geometry of the Lombok basin as well as the forearc Moho in ~16 km depth. Reduced upper mantle velocities suggest a hydrated shallow mantle wedge for this corridor. Further east offshore Sumba island, where the Java trench terminates and the transition to the collisional regime further east occurs, our models show a subducting oceanic plate of similar thickness and structure. But different to the situation offshore Lombok, we find no evidence for a shallow mantle wedge beneath the forearc; crustal-type velocities are found down to depths of ~20 km. The different forearc regime is most likely related to the collision with the Sumba block. Our results give a detailed view into the complex structure in both the deeper and shallower portions of this convergent margin.

The Mechanics of Single Cell and Collective Migration of Tumor Cells

PubMed Central

Lintz, Marianne; Muñoz, Adam; Reinhart-King, Cynthia A.

2017-01-01

Metastasis is a dynamic process in which cancer cells navigate the tumor microenvironment, largely guided by external chemical and mechanical cues. Our current understanding of metastatic cell migration has relied primarily on studies of single cell migration, most of which have been performed using two-dimensional (2D) cell culture techniques and, more recently, using three-dimensional (3D) scaffolds. However, the current paradigm focused on single cell movements is shifting toward the idea that collective migration is likely one of the primary modes of migration during metastasis of many solid tumors. Not surprisingly, the mechanics of collective migration differ significantly from single cell movements. As such, techniques must be developed that enable in-depth analysis of collective migration, and those for examining single cell migration should be adopted and modified to study collective migration to allow for accurate comparison of the two. In this review, we will describe engineering approaches for studying metastatic migration, both single cell and collective, and how these approaches have yielded significant insight into the mechanics governing each process. PMID:27814431

Epithelial-mesenchymal transition transcription factors control pluripotent adult stem cell migration in vivo in planarians

PubMed Central

Abnave, Prasad; Aboukhatwa, Ellen; Kosaka, Nobuyoshi; Thompson, James; Hill, Mark A.

2017-01-01

Migration of stem cells underpins the physiology of metazoan animals. For tissues to be maintained, stem cells and their progeny must migrate and differentiate in the correct positions. This need is even more acute after tissue damage by wounding or pathogenic infection. Inappropriate migration also underpins metastasis. Despite this, few mechanistic studies address stem cell migration during repair or homeostasis in adult tissues. Here, we present a shielded X-ray irradiation assay that allows us to follow stem cell migration in planarians. We demonstrate the use of this system to study the molecular control of stem cell migration and show that snail-1, snail-2 and zeb-1 EMT transcription factor homologs are necessary for cell migration to wound sites and for the establishment of migratory cell morphology. We also observed that stem cells undergo homeostatic migration to anterior regions that lack local stem cells, in the absence of injury, maintaining tissue homeostasis. This requires the polarity determinant notum. Our work establishes planarians as a suitable model for further in-depth study of the processes controlling stem cell migration in vivo. PMID:28893948

Pre-stack full-waveform inversion of multichannel seismic data to retrieve thermohaline ocean structure. Application to the Gulf of Cadiz (SW Iberia).

NASA Astrophysics Data System (ADS)

Dagnino, Daniel; Jiménez Tejero, Clara-Estela; Meléndez, Adrià; Gras, Clàudia; Sallarès, Valentí; Ranero, César R.

2016-04-01

This work demonstrates the feasibility to retrieve high-resolution models of oceanic physical parameters by means of 2D adjoint-state full-waveform inversion (FWI). The proposed method is applied to pre-stack multi-channel seismic (MCS) data acquired in the Gulf of Cadiz (SW Iberia) in the framework of the EU GO (Geophysical Oceanography) project in 2006. We first design and apply a specific data processing flow that allows reducing data noise without modifying trace amplitudes. This step is shown to be essential to obtain accurate results due to the low signal-to-noise ratio (SNR) of water layer reflections, which are typically three-to-four orders of magnitude weaker than those in solid earth. Second, we propose new techniques to improve the inversion results by reducing the artefacts appearing in the gradient and misfit as a consequence of the low SNR. We use a weight and filter operator to focus in the regions where the gradient is reliable. The source wavelet is then inverted together with the sound speed. We demonstrate the efficiency of the proposed method and inversion strategy retrieving a 2D sound speed model along a 50 km-long MCS profile collected in the Gulf of Cadiz during the GO experiment. In this region, the Mediterranean outflow entrains the Atlantic waters, creating a salinity complex thermohaline structure that can be measured by a difference in acoustic impedance. The inverted sound speed model have a resolution of 75m for the horizontal direction, which is two orders of magnitude better than the models obtained using conventional, probe-based oceanographic techniques. In a second step, temperature and salinity are derived from the sound speed by minimizing the difference between the inverted and the theoretical sound speed estimated using the thermodynamic equation of seawater (TEOS-10 software). To apply the TEOS-10 we first calculate a linear-fitting between temperature and salinity using regional data from the National Oceanic and Atmospheric Administration (NOAA) compilation. Pressure is calculated from latitude and depth. In the final step, salinity is calculated using the Temperature-Salinity relation and the previously estimated temperature. The comparison of the inverted temperature, salinity model with measures from XBT and CTD probes deployed simultaneously to the MCS data acquisition shows that the accuracy of the inverted models is ˜0.15°C for temperature and ˜0.1psu for salinity.

Multiliteracies on Instant Messaging in Negotiating Local, Translocal, and Transnational Affiliations: A Case of an Adolescent Immigrant

ERIC Educational Resources Information Center

Lam, Wan Shun Eva

2009-01-01

Through an in-depth case study of the instant messaging practices of an adolescent girl who had migrated to the United States from China, this qualitative investigation examines the development of multiliteracies in the context of transnational migration and new media of communication. Data consisted of screen recordings of the youth's digital…

Deep scattering layer migration and composition: observations from a diving saucer.

PubMed

Barham, E G

1966-03-18

The distribution of a myctophid fish and physonect siphonophores observed during dives in the Soucoupe off Baja California closely correlates with scattering layers recorded simultaneously with a 12-kcy/sec echo sounder. These organisms were observed while they were migrating vertically, and at their night and daytime levels. They are capable of rapid, extensive changes in depth.

Vertical distributions and diel migrations of Euthecosomata in the northwest Sargasso Sea

NASA Astrophysics Data System (ADS)

Wormuth, John H.

1981-12-01

Vertical distributions and seasonal variations in abundance of nine abundant or frequent pteropod species or subspecies in the northwest Sargasso Sea are described. Factor analyses yielded two groups, diel migrators and non-migrators. In terms of water column abundances, tows taken in August and November are similar, as are tows in December and April. Most species show significant within-species agreement in depth distribution over the year but high variability in abundance. Regression analyses using environmental parameters as independent variables show significant correlations of species abundances with temperature.

Revealing small-scale diffracting discontinuities by an optimization inversion algorithm

NASA Astrophysics Data System (ADS)

Yu, Caixia; Zhao, Jingtao; Wang, Yanfei

2017-02-01

Small-scale diffracting geologic discontinuities play a significant role in studying carbonate reservoirs. The seismic responses of them are coded in diffracted/scattered waves. However, compared with reflections, the energy of these valuable diffractions is generally one or even two orders of magnitude weaker. This means that the information of diffractions is strongly masked by reflections in the seismic images. Detecting the small-scale cavities and tiny faults from the deep carbonate reservoirs, mainly over 6 km, poses an even bigger challenge to seismic diffractions, as the signals of seismic surveyed data are weak and have a low signal-to-noise ratio (SNR). After analyzing the mechanism of the Kirchhoff migration method, the residual of prestack diffractions located in the neighborhood of the first Fresnel aperture is found to remain in the image space. Therefore, a strategy for extracting diffractions in the image space is proposed and a regularized L 2-norm model with a smooth constraint to the local slopes is suggested for predicting reflections. According to the focusing conditions of residual diffractions in the image space, two approaches are provided for extracting diffractions. Diffraction extraction can be directly accomplished by subtracting the predicted reflections from seismic imaging data if the residual diffractions are focused. Otherwise, a diffraction velocity analysis will be performed for refocusing residual diffractions. Two synthetic examples and one field application demonstrate the feasibility and efficiency of the two proposed methods in detecting the small-scale geologic scatterers, tiny faults and cavities.

Generation and migration of petroleum in the Mahakam delta, Indonesia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Durand, B.; Bessereau, G.; Doligez, B.

1988-08-01

The Mahakam delta, located east of Kalimantan, Indonesia, contains sediments of Miocene-Pliocene age. Their thickness may reach more than 8,000 m in places, and sections which have been drilled are generally overpressured below 3,000 to 4,000 m. Petroleum was formed essentially from a kerogen originating in terrestrial land plants grown in an equatorial climate. The kerogen may occur either dispersed in clays or concentrated in humic coal beds. Petroleum potential (oil and gas) of this kerogen at the beginning of catagenesis is 200-250 mg HC/g organic carbon on the average (as measured by Rock-Eval pyrolysis) but is highly variable aroundmore » this mean value (100-400 mg HC/g organic carbon approximately). Although the kerogen is of terrestrial origin, the kerogen-containing sediments have the capacity to produce and expel oil at depth, as shown by large quantities of oil pooled in sandy reservoirs together with gas in a relatively small area. Depth of top oil kitchen varies from 2,500 to 4,000 m and is greater in synclines than on top of structures. Present isotherms follow more or less the same pattern. Migration is very recent and is till at work. Light hydrocarbons have migrated farther from their source than heavy ones did. Thus condensate in pooled gas and the density of pooled oil tend to increase with depth. These variations of oil and gas compositions along secondary and tertiary migration routes are likely to be provoked by evaporative fractionation processes.« less

Migratory behavior of eastern North Pacific gray whales tracked using a hydrophone array

PubMed Central

Helble, Tyler A.; D’Spain, Gerald L.; Weller, David W.; Wiggins, Sean M.; Hildebrand, John A.

2017-01-01

Eastern North Pacific gray whales make one of the longest annual migrations of any mammal, traveling from their summer feeding areas in the Bering and Chukchi Seas to their wintering areas in the lagoons of Baja California, Mexico. Although a significant body of knowledge on gray whale biology and behavior exists, little is known about their vocal behavior while migrating. In this study, we used a sparse hydrophone array deployed offshore of central California to investigate how gray whales behave and use sound while migrating. We detected, localized, and tracked whales for one full migration season, a first for gray whales. We verified and localized 10,644 gray whale M3 calls and grouped them into 280 tracks. Results confirm that gray whales are acoustically active while migrating and their swimming and acoustic behavior changes on daily and seasonal time scales. The seasonal timing of the calls verifies the gray whale migration timing determined using other methods such as counts conducted by visual observers. The total number of calls and the percentage of calls that were part of a track changed significantly over both seasonal and daily time scales. An average calling rate of 5.7 calls/whale/day was observed, which is significantly greater than previously reported migration calling rates. We measured a mean speed of 1.6 m/s and quantified heading, direction, and water depth where tracks were located. Mean speed and water depth remained constant between night and day, but these quantities had greater variation at night. Gray whales produce M3 calls with a root mean square source level of 156.9 dB re 1 μPa at 1 m. Quantities describing call characteristics were variable and dependent on site-specific propagation characteristics. PMID:29084266

Migratory behavior of eastern North Pacific gray whales tracked using a hydrophone array.

PubMed

Guazzo, Regina A; Helble, Tyler A; D'Spain, Gerald L; Weller, David W; Wiggins, Sean M; Hildebrand, John A

2017-01-01

Eastern North Pacific gray whales make one of the longest annual migrations of any mammal, traveling from their summer feeding areas in the Bering and Chukchi Seas to their wintering areas in the lagoons of Baja California, Mexico. Although a significant body of knowledge on gray whale biology and behavior exists, little is known about their vocal behavior while migrating. In this study, we used a sparse hydrophone array deployed offshore of central California to investigate how gray whales behave and use sound while migrating. We detected, localized, and tracked whales for one full migration season, a first for gray whales. We verified and localized 10,644 gray whale M3 calls and grouped them into 280 tracks. Results confirm that gray whales are acoustically active while migrating and their swimming and acoustic behavior changes on daily and seasonal time scales. The seasonal timing of the calls verifies the gray whale migration timing determined using other methods such as counts conducted by visual observers. The total number of calls and the percentage of calls that were part of a track changed significantly over both seasonal and daily time scales. An average calling rate of 5.7 calls/whale/day was observed, which is significantly greater than previously reported migration calling rates. We measured a mean speed of 1.6 m/s and quantified heading, direction, and water depth where tracks were located. Mean speed and water depth remained constant between night and day, but these quantities had greater variation at night. Gray whales produce M3 calls with a root mean square source level of 156.9 dB re 1 μPa at 1 m. Quantities describing call characteristics were variable and dependent on site-specific propagation characteristics.

Spatial delineation, fluid-lithology characterization, and petrophysical modeling of deepwater Gulf of Mexico reservoirs though joint AVA deterministic and stochastic inversion of three-dimensional partially-stacked seismic amplitude data and well logs

NASA Astrophysics Data System (ADS)

Contreras, Arturo Javier

This dissertation describes a novel Amplitude-versus-Angle (AVA) inversion methodology to quantitatively integrate pre-stack seismic data, well logs, geologic data, and geostatistical information. Deterministic and stochastic inversion algorithms are used to characterize flow units of deepwater reservoirs located in the central Gulf of Mexico. A detailed fluid/lithology sensitivity analysis was conducted to assess the nature of AVA effects in the study area. Standard AVA analysis indicates that the shale/sand interface represented by the top of the hydrocarbon-bearing turbidite deposits generate typical Class III AVA responses. Layer-dependent Biot-Gassmann analysis shows significant sensitivity of the P-wave velocity and density to fluid substitution, indicating that presence of light saturating fluids clearly affects the elastic response of sands. Accordingly, AVA deterministic and stochastic inversions, which combine the advantages of AVA analysis with those of inversion, have provided quantitative information about the lateral continuity of the turbidite reservoirs based on the interpretation of inverted acoustic properties and fluid-sensitive modulus attributes (P-Impedance, S-Impedance, density, and LambdaRho, in the case of deterministic inversion; and P-velocity, S-velocity, density, and lithotype (sand-shale) distributions, in the case of stochastic inversion). The quantitative use of rock/fluid information through AVA seismic data, coupled with the implementation of co-simulation via lithotype-dependent multidimensional joint probability distributions of acoustic/petrophysical properties, provides accurate 3D models of petrophysical properties such as porosity, permeability, and water saturation. Pre-stack stochastic inversion provides more realistic and higher-resolution results than those obtained from analogous deterministic techniques. Furthermore, 3D petrophysical models can be more accurately co-simulated from AVA stochastic inversion results. By combining AVA sensitivity analysis techniques with pre-stack stochastic inversion, geologic data, and awareness of inversion pitfalls, it is possible to substantially reduce the risk in exploration and development of conventional and non-conventional reservoirs. From the final integration of deterministic and stochastic inversion results with depositional models and analogous examples, the M-series reservoirs have been interpreted as stacked terminal turbidite lobes within an overall fan complex (the Miocene MCAVLU Submarine Fan System); this interpretation is consistent with previous core data interpretations and regional stratigraphic/depositional studies.

A comparison of mesopelagic mesozooplankton community structure in the subtropical and subarctic North Pacific Ocean

NASA Astrophysics Data System (ADS)

Steinberg, Deborah K.; Cope, Joseph S.; Wilson, Stephanie E.; Kobari, T.

2008-07-01

Mesopelagic mesozooplankton communities of an oligotrophic (Hawaii Ocean Time series-HOT station ALOHA) and a mesotrophic (Japanese time-series station K2) environment in the North Pacific Ocean are compared as part of a research program investigating the factors that control the efficiency of particle export to the deep sea (VERtical Transport In the Global Ocean—VERTIGO). We analyzed zooplankton (>350 μm) collected from net tows taken between 0 and 1000 m at each site to investigate the biomass size structure and the abundance of the major taxonomic groups in discrete depth intervals throughout the water column. Biomass of zooplankton at K2 over all depths was approximately an order of a magnitude higher than at ALOHA, with a significantly higher proportion of the biomass at K2 in the larger (>2 mm) size classes. This difference was mostly due to the abundance at K2 of the large calanoid copepods Neocalanus spp. and Eucalanus bungii, which undergo ontogenetic (seasonal) vertical migration. The overall strength of diel vertical migration was higher at K2, with a mean night:day biomass ratio in the upper 150 m of 2.5, vs. a ratio of 1.7 at ALOHA. However, the amplitude of the diel migration (change in weighted mean depth between day and night) was higher at ALOHA for all biomass size classes, perhaps due to deeper light penetration causing deeper migration to avoid visual predators. A number of taxa known to feed on suspended or sinking detritus showed distinct peaks in the mesopelagic zone, which affects particle transport efficiency at both sites. These taxa include calanoid and poecilostomatoid (e.g., Oncaea spp.) copepods, salps, polychaetes, and phaeodarian radiolaria at K2, harpacticoid copepods at ALOHA, and ostracods at both sites. We found distinct layers of carnivores (mainly gelatinous zooplankton) in the mesopelagic at K2 including chaetognaths, hydrozoan medusae, polychaetes, and gymnosome pteropods, and, in the upper mesopelagic zone, of ctenophores and siphonophores; at both sites a mesopelagic layer of hyperiid amphipods was found. The large population of ontogenetically migrating calanoid copepods is likely supporting large carnivorous populations at depth at K2. The contrasting zooplankton taxonomic structure at the two sites helps explain the higher efficiency of the biological pump at K2. Factors responsible for increased transport efficiency at K2 include rapid transport of POC via larger fecal pellets produced by zooplankton at K2, and enhanced active carbon export at K2 vs. ALOHA, due to the greater strength of diel vertical migration and to additional ontogenetic migration at K2.

Reverse time migration in tilted transversely isotropic media

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Linbing; Rector III, James W.; Hoversten, G. Michael

2004-07-01

This paper presents a reverse time migration (RTM) method for the migration of shot records in tilted transversely isotropic (TTI) media. It is based on the tilted TI acoustic wave equation that was derived from the dispersion relation. The RTM is a full depth migration allowing for velocity to vary laterally as well as vertically and has no dip limitations. The wave equation is solved by a tenth-order finite difference scheme. Using 2D numerical models, we demonstrate that ignoring the tilt angle will introduce both lateral and vertical shifts in imaging. The shifts can be larger than 0.5 wavelength inmore » the vertical direction and 1.5 wavelength in the lateral direction.« less

The linkage of life course, migration, health, and aging: health in adults and elderly Mexican migrants.

PubMed

de Oca, Verónica Montes; García, Telésforo Ramírez; Sáenz, Rogelio; Guillén, Jennifer

2011-10-01

Migration is a phenomenon that impacts individuals throughout the life course. Particularly, Mexican elderly migrants show evidence of lifetime accumulations of the effects of migration on health conditions. Examine how the relationship between historical time and individual time explains different factors impacting the health of Mexican adult and elderly migrants in Mexico and the United States. Data from in-depth interviews with Mexican migrants living in selected locations in Mexico and the United States were used to illustrate the links between life course conditions, aging, migration, and health outcomes. According to this theoretical perspective and the data, historical time, age at migration, and the conditions under which the migration trajectory developed, show different impacts on the health and quality of life of the elderly, as revealed through analysis of labor experience, disease and accidents, medical service, health treatment, transnational networks, and family formation.

Seismic Modeling of the Alasehir Graben, Western Turkey

NASA Astrophysics Data System (ADS)

Gozde Okut, Nigar; Demirbag, Emin

2014-05-01

The purpose of this study is to develop a depth model to make synthetic seismic reflection sections, such as stacked and migrated sections with different velocity models. The study area is east-west trending Alasehir graben which is one of the most prominent structure in the western Anatolia, proved to have geothermal energy potential by researchers and exploration companies. Geological formations were taken from Alaşehir-1 borehole drilled by Turkish Petroleum Corporation (Çiftçi, 2007) and seismic interval velocities were taken from check-shots in the same borehole (Kolenoǧlu-Demircioǧlu, 2009). The most important structure is the master graben bounding fault (MGBF) in the southern margin of the Alasehir graben. Another main structure is the northern bounding fault called the antithetic fault of the MGBF with high angle normal fault characteristic. MGBF is a crucial contact between sedimentary cover and the metamorphic basement. From basement to the surface, five different stratigraphic units constitute graben fill . All the sedimentary units thicknesses get thinner from the southern margin to the northern margin of the Alasehir graben displaying roll-over geometry. A commercial seismic data software was used during modeling. In the first step, a 2D velocity/depth model was defined. Ray tracing was carried out with diffraction option to produce the reflection travel times. The reflection coefficients were calculated and wavelet shaping was carried out by means of band-pass filtering. Finally synthetic stacked section of the Alasehir graben was obtained. Then, migrated sections were generated with different velocity models. From interval velocities, average and RMS velocities were calculated for the formation entires to test how the general features of the geological model may change against different seismic models after the migration. Post-stack time migration method was used. Pseudo-velocity analysis was applied at selected CDP locations. In theory, seismic migration moves events to their correct spatial locations and collapse energy from diffractions back to their scattering points. This features of migration can be distinguished in the migrated sections. When interval velocities used, all the diffractions are removed and fault planes can be seen clearly. When average velocities used, MGBF plane extends to greater depths. Additionally, slope angles and locations of antithetic faults in the northern margin of the graben changes. When RMS velocities used, a migrated section was obtained for which to make an interpretation was quite hard, especially for the main structures along the northern margin and reflections related to formations.

Impacts of ontogenetically migrating copepods on downward carbon flux in the western subarctic Pacific Ocean

NASA Astrophysics Data System (ADS)

Kobari, Toru; Steinberg, Deborah K.; Ueda, Ai; Tsuda, Atsushi; Silver, Mary W.; Kitamura, Minoru

2008-07-01

To evaluate the impacts of ontogenetically (seasonally) migrating copepods on carbon transport to the mesopelagic zone, we investigated depth distribution, population structure, and feeding activity of the ontogentic copepod community in the western subarctic Pacific Ocean from day-night pairs of zooplankton samples down to 1000 m during the VERtical Transport In the Global Ocean (VERTIGO) program. Over the 31 July-16 August 2005 study period, the biomass of Neocalanus cristatus and Neocalanus plumchrus predominated in the near surface waters, while Neocalanus flemingeri was already dormant at depth. We observed a strong diel migration for Metridia pacifica, and a seasonal downward migration for Eucalanus bungii. Based on gut pigment analysis, ingestion rate of the copepod community was 214-375 mg C m -2 day -1, which was equal to 26-37% of the concurrent primary production. However, comparison of grazing estimated from gut pigments to calculated carbon demand of the copepod community indicates that phytoplankton comprised 37-59% of the ingested carbon. Thus, the copepod community appears to have also relied on detritus and microzooplankton for their nutrition, likely because primary production during this time was dominated by picophytoplankton too small to be grazed by these large copepods. Fecal pellet flux by the copepod community was estimated to account for 141-223% of the sedimentary particulate organic carbon (POC) flux at 150 m, suggesting considerable fragmentation and consumption of pellets in the upper layers. Fecal pellets alone were adequate to meet copepod carbon demand in the surface 0-150 m layer. Active carbon flux by diel migration of M. pacifica (respiration, egestion, and mortality) was 4-17 mg C m -2 day -1, equal to 6-44% of sedimentary POC flux at 150 m. Active carbon flux by N. flemingeri ontogenetic migration (i.e., respiration and mortality at depth) contributed 246 mg C m -2 year -1, equal to 9% of sedimentary POC flux at 1000 m. The imminent downward migration of N. cristatus and N. plumchrus would lead to an additional ontogenetic carbon flux on the order of 1719 mg C m -2 year -1. Copepod fecal pellet transport and active transport by diel and ontogenetic migration are thus important carbon fluxes during a season dominated by small phytoplankton, and ontogenetic migrants in the subarctic Pacific Ocean play a relatively more important role in active carbon flux compared with other open-ocean regions.

Epithelial-mesenchymal transition transcription factors control pluripotent adult stem cell migration in vivo in planarians.

PubMed

Abnave, Prasad; Aboukhatwa, Ellen; Kosaka, Nobuyoshi; Thompson, James; Hill, Mark A; Aboobaker, A Aziz

2017-10-01

Migration of stem cells underpins the physiology of metazoan animals. For tissues to be maintained, stem cells and their progeny must migrate and differentiate in the correct positions. This need is even more acute after tissue damage by wounding or pathogenic infection. Inappropriate migration also underpins metastasis. Despite this, few mechanistic studies address stem cell migration during repair or homeostasis in adult tissues. Here, we present a shielded X-ray irradiation assay that allows us to follow stem cell migration in planarians. We demonstrate the use of this system to study the molecular control of stem cell migration and show that snail-1 , snail-2 and zeb-1 EMT transcription factor homologs are necessary for cell migration to wound sites and for the establishment of migratory cell morphology. We also observed that stem cells undergo homeostatic migration to anterior regions that lack local stem cells, in the absence of injury, maintaining tissue homeostasis. This requires the polarity determinant notum Our work establishes planarians as a suitable model for further in-depth study of the processes controlling stem cell migration in vivo . © 2017. Published by The Company of Biologists Ltd.

Contribution of seismic processing to put up the scaffolding for the 3-dimensional study of deep sedimentary basins: the fundaments of trans-national 3D modelling in the project GeoMol

NASA Astrophysics Data System (ADS)

Capar, Laure

2013-04-01

Within the framework of the transnational project GeoMol geophysical and geological information on the entire Molasse Basin and on the Po Basin are gathered to build consistent cross-border 3D geological models based on borehole evidence and seismic data. Benefiting from important progress in seismic processing, these new models will provide some answers to various questions regarding the usage of subsurface resources, as there are geothermal energy, CO2 and gas storage, oil and gas production, and support decisions-making to national and local administrations as well as to industries. More than 28 000 km of 2D seismic lines are compiled reprocessed and harmonized. This work faces various problems like the vertical drop of more than 700 meters between West and East of the Molasse Basin and to al lesser extent in the Po Plain, the heterogeneities of the substratum, the large disparities between the period and parameters of seismic acquisition, and depending of their availability, the use of two types of seismic data, raw and processed seismic data. The main challenge is to harmonize all lines at the same reference level, amplitude and step of signal processing from France to Austria, spanning more than 1000 km, to avoid misfits at crossing points between seismic lines and artifacts at the country borders, facilitating the interpretation of the various geological layers in the Molasse Basin and Po Basin. A generalized stratigraphic column for the two basins is set up, representing all geological layers relevant to subsurface usage. This stratigraphy constitutes the harmonized framework for seismic reprocessing. In general, processed seismic data is available on paper at stack stage and the mandatory information to take these seismic lines to the final stage of processing, the migration step, are datum plane and replacement velocity. However several datum planes and replacement velocities were used during previous processing projects. Our processing sequence is to first digitize the data, to have them in SEG-Y format. The second step is to apply some post-stack processing to obtain a good data quality before the final migration step. The third step is the final migration, using optimized migration velocities and the fourth step is the post-migration processing. In case of raw seismic data, the mandatory information for processing is made accessible, like from observer logs, coordinates and field seismic data. The processing sequence in order to obtain the final usable version of the seismic line is based on a pre-stack time migration. A complex processing sequence is applied. One main issue is to deal with the significant changes in the topography along the seismic lines and in the first twenty meter layer, this low velocity zone (LVZ) or weathered zone, where some lateral velocity variations occur and disturb the wave propagation, therefore the seismic signal. In seismic processing, this matter is solved by using the static corrections which allow removing these effects of lateral velocity variations and the effects of topography. Another main item is the good determination of root mean square velocities for migration, to improve the final result of seismic processing. Within GeoMol, generalized 3D velocity models of stack velocities are calculated in order to perform a rapid time-depth conversion. In final, all seismic lines of the project GeoMol will be at the same level of processing, the migration level. But to tie all these lines, a single appropriate datum plane and replacement velocity for the entire Molasse Basin and Po Plain, respectively, have to be carefully set up, to avoid misties at crossing points. The reprocessing and use of these 28 000 km of seismic lines in the project GeoMol provide the pivotal database to build a 3D framework model for regional subsurface information on the Alpine foreland basins (cf. Rupf et al. 2013, EGU2013-8924). The project GeoMol is co-funded by the Alpine Space Program as part of the European Territorial Cooperation 2007-2013. The project integrates partners from Austria, France, Germany, Italy, Slovenia and Switzerland and runs from September 2012 to June 2015. Further information on www.geomol.eu The GeoMol seismic interpretation team: Roland Baumberger (swisstopo), Agnès BRENOT (BRGM), Alessandro CAGNONI (RLB), Renaud COUËFFE (BRGM), Gabriel COURRIOUX (BRGM), Chiara D'Ambrogi (ISPRA), Chrystel Dezayes (BRGM), Charlotte Fehn (LGRB), Sunseare GABALDA (BRGM), Gregor Götzl (GBA), Andrej Lapanje (GeoZS), Stéphane MARC (BRGM), Alberto MARTINI (RER-SGSS), Fabio Carlo Molinari (RER-SGSS), Edgar Nitsch (LGRB), Robert Pamer (LfU BY), Marco PANTALONI (ISPRA), Sebastian Pfleiderer (GBA), Andrea PICCIN (RLB), (Nils Oesterling (swisstopo), Isabel Rupf (LGRB), Uta Schulz (LfU BY), Yves SIMEON (BRGM), Günter SÖKOL (LGRB), Heiko Zumsprekel (LGRB)

Short-range, overpressure-driven methane migration in coarse-grained gas hydrate reservoirs

DOE PAGES

Nole, Michael; Daigle, Hugh; Cook, Ann E.; ...

2016-08-31

Two methane migration mechanisms have been proposed for coarse-grained gas hydrate reservoirs: short-range diffusive gas migration and long-range advective fluid transport from depth. Herein we demonstrate that short-range fluid flow due to overpressure in marine sediments is a significant additional methane transport mechanism that allows hydrate to precipitate in large quantities in thick, coarse-grained hydrate reservoirs. Two-dimensional simulations demonstrate that this migration mechanism, short-range advective transport, can supply significant amounts of dissolved gas and is unencumbered by limitations of the other two end-member mechanisms. Here, short-range advective migration can increase the amount of methane delivered to sands as compared tomore » the slow process of diffusion, yet it is not necessarily limited by effective porosity reduction as is typical of updip advection from a deep source.« less

Short-range, overpressure-driven methane migration in coarse-grained gas hydrate reservoirs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nole, Michael; Daigle, Hugh; Cook, Ann E.

Two methane migration mechanisms have been proposed for coarse-grained gas hydrate reservoirs: short-range diffusive gas migration and long-range advective fluid transport from depth. Herein we demonstrate that short-range fluid flow due to overpressure in marine sediments is a significant additional methane transport mechanism that allows hydrate to precipitate in large quantities in thick, coarse-grained hydrate reservoirs. Two-dimensional simulations demonstrate that this migration mechanism, short-range advective transport, can supply significant amounts of dissolved gas and is unencumbered by limitations of the other two end-member mechanisms. Here, short-range advective migration can increase the amount of methane delivered to sands as compared tomore » the slow process of diffusion, yet it is not necessarily limited by effective porosity reduction as is typical of updip advection from a deep source.« less

Seafloor morphology in the different domains of the Calabrian Arc subduction complex - Ionian Sea

NASA Astrophysics Data System (ADS)

Riminucci, F.; Polonia, A.; Torelli, L.; Mussoni, P.

2010-05-01

The Calabrian Arc (CA) is a subduction system that develops along the African-Eurasian plate boundary in the Ionian Sea and connects the E-W trending Sicilian Maghrebian belt with the NW-SE trending Southern Apennines. The first systematic geophysical investigation in the offshore region of the CA was conducted during the 70's by the Institute of Marine Geology (now ISMAR) with the R/V 'Bannock' [1]. In the last 30 years, further geophysical data (high penetration multichannel seismics, CHIRP and multibeam data) has been acquired in the offshore of the CA, down to the Ionian Abyssal Plain. The integrated interpretation of the existing geophysical data [2] has outlined the regional architecture of the subduction complex, the main tectonic features absorbing plate motion and variation of seafloor morphology in the different structural domains. Pre-stack depth migrated seismic profiles has revealed that the accretionary complex is constituted by two distinct wedges whose geometry, structural style and seafloor morphology widely vary. The outermost accretionary wedge has been emplaced in post-messinian times. It is a salt-bearing complex as pointed out by the internal structure of the wedge (acoustically transparent assemblage), very low taper angle and high seismic velocities. The seafloor shows a rough morphology, short wavelength folds and depressions superimposed on a rather constant gentle regional slope. Landward of the outer wedge, the evaporites are no longer present and the transition to the clastic rock assemblage is reflected in a different structural architecture, which shows steeper slopes and a succession of topographic scarps separated by sedimentary basins and mid slope terraces. The topographic scarps are controlled in depth by a series of high angle landward dipping reflectors, that we interpreted as out of sequence thrust faults absorbing shortening at the rear of the wedge. Landward of the inner wedge a mid slope terrace develops (inner plateau) between 1300 and 1600 m water depth. It is a relatively flat area of variable width ranging from 10 to 50 Km, represented by the forearc basin and the innermost accretionary wedge. Seafloor morphology is related to small undulation of the seafloor. A thick section of Plio-Quaternary and Messinian sediments is present below the flat terrace. Sediments appear to be folded and, in some regions highly disrupted along local sub-circular structures that affect the seafloor morphology as well. Geometry and seismic facies of these sub-circular swells rising from the surrounding suggest they are diapiric structures. Variation of seafloor morphology is strictly related to the progression of structural domains within the Calabrian Arc subduction complex. The integrated analysis of seafloor morphology and structural style through an integrated approach involving the interpretation of seismic data at different scales has been carried out in order to outline relationships between shallow tectonic processes and deep structures. Moreover, the analysis of morphobathymetric and seismic data, combined with well targeted sediment samples has the potential to reveal relationships between tectonics, sedimentation and fluid flow in the different portions of the accretionary wedge. References: 1 - Rossi S., Sartori R. 1981. A seismic reflection study of the External Calabrian Arc in the Northern Ionian Sea (Eastern Mediterranean). Marine Geoph. Res., 4, 403-426. 2 - Polonia A. et al., The Calabrian Arc subduction complex: plate convergence, active faults, and mud diapirism. New results from the CALAMARE-2008 cruise (N/R CNR Urania). Submitted to G3.

Diurnal vertical migration of Cochlodinium polykrikoides during the red tide in Korean coastal sea waters.

PubMed

Kim, Young Sug; Jeong, Chang Su; Seong, Gi Tak; Han, In Sung; Lee, Young Sik

2010-09-01

The diurnal vertical migration of Cochlodinium polykrikoides (C. polykrikoides), which caused a red tide in the Korean coastal waters of the East Sea/Sea of Japan in September 2003, was examined by determining the time-dependent changes in the density of living cells in relation to the depth of the water column. The ascent of this species into the surface layer (depth of water 2 m) occurred during 1400-1500. The descent started at 1600 and a high distribution rate (86%) at 15-20 m was observed at 0300. During the ascent, the cells were widely distributed at each depth level from 0600 hr and at 0800-1100, the cells were primarily distributed in the middle layer (0-6 m). The concentration of dissolved inorganic nitrogen was generally < or = 2.86 micromol l(-1), but at 1400-1500, the concentration in the surface layer reduced to < or = 0.14 micromol l(-1). Moreover, the concentration gradually increased as the depth increased to > or = 5 m. These results showed that the nutrient-consumption rate associated with the proliferation of C. polykrikoides during a red tide is more influenced by the inorganic-nitrogen resources ratherthan the inorganic-phosphorus compounds.

Residual depth anomalies and the origin of the Australian-Antarctic discordance zone

NASA Astrophysics Data System (ADS)

Marks, Karen M.; Vogt, Peter R.; Hall, Stuart A.

1990-10-01

A new, high resolution depth anomaly map covering the anomalously deep and rough Australian-Antarctic Discordance (AAD) has been constructed using crustal ages derived from a detailed aeromagnetic survey. The map shows a large, arcuate-shaped, negative depth anomaly that is centered on the Southeast Indian Ridge and trends NNE across the Australian plate (SSE across the Antarctic plate). Within this broad scale feature, two prominent depth anomaly lows are observed at 45°S, 128°E (the northern flank) and 54°S, 125°E (the southern flank). Both lows are associated with 15 Ma oceanic crust. The observed depth anomaly patterns are compared with the distinctive patterns predicted by coldspot, downwelling limbs of convection cells, and thin crust models of the discordance source. The observed depth anomaly does not result from absolute plate motions over a fixed coldspot source because the predicted ENE trend on the Antarctic plate is not in agreement with the SSE trend observed. The symmetric arrangement of the large-scale depth anomaly and prominent lows about the ridge axis suggests instead a source that has varied in strength but remained located at the ridge axis as the ridge migrated northeastward in the absolute reference frame. The organized pattern of elongated depth anomaly highs and lows predicted for upper mantle convection (cells) is not evident in the observed depth anomaly map. Thus a convergence of downwelling limbs of convection cells beneath the discordance is not indicated. If the source of cooler upwelling that produces less magma and hence thin crust has not varied over time, nor migrated along the ridge, then the predicted depth anomaly would persist unchanged with distance from the ridge axis, and trend in the direction of relative plate motion (parallel to fracture zones). The observed depth anomaly trends obliquely across fracture zones and changes in both amplitude and location relative to the ridge axis, and is therefore not consistent with cool upwelling producing thin crust. To explain the features of the depth anomaly map, we propose that asthenospheric material flowing from the Amsterdam hotspot in the west, and the Balleny and Tasmantid hotspots in the east, collides within the discordance. Propagating rifts converging on the AAD provide evidence for such asthenospheric flow. Attenuated shear velocities beneath the George V fracture zone complex, and lavas geochemically identical to those from propagating rifts associated with hotspots, suggest a thermal anomaly producing additional asthenospheric flow east of the AAD. The increased flow and greater proximity of the discordance to the thermal anomaly and hotspots to the east produce a higher pressure gradient, and hence greater driving force, which results in a westward migration of the collision zone with time. Seafloor spreading over the westward moving collision zone has produced the observed arcuate-shaped anomaly with the accompanying oblique depth anomaly trends. We cannot decipher from depth anomalies alone whether the converging flows downwell within the AAD or simply mix with upwelling materials.

Coupling MAST-1D, a sediment routing model for channel-floodplain complexes, with channel migration relationships to predict reach-averaged river morphodynamics. Preliminary results

NASA Astrophysics Data System (ADS)

Viparelli, E.; Eke, E. C.; Lauer, J. W.

2017-12-01

Sediment exchange between the channel and floodplain can occur via meander migration, overbank deposition or erosion, and changes in channel geometry. Depending on channel and floodplain history, floodplains can act either as sources or sinks of bed material and/or wash load. Here we present preliminary modeling results that explicitly account for the feedbacks between the changes in floodplain geometry and sediment size distribution and the changes in channel geometry and migration. These results are obtained by coupling the Morphodynamics And Sediment Tracers in 1D (MAST-1D) program with the results of meander migration studies linking the bankfull flow depth and mean velocity to channel migration, sinuosity and channel geometry. MAST-1D is a numerical model built to describe grain size specific transport of sediment and tracers and the long-term - i.e. decadal and longer - evolution of channel floodplain complexes. MAST-1D differs from other 1D numerical models because it allows for 1) uneven exchange of sediment and tracers between the river channel and the floodplain, 2) temporal changes in channel geometry, bed elevation and floodplain thickness, which result in changes in the channel hydraulic capacity, and 3) temporal changes of size distribution and tracer content in the floodplain, in the load and in the underlying substrate. Under conditions of constant base level, water and sediment supply, the system evolves toward a steady state wherein the amount of sediment deposited through point bar deposition and overbank sedimentation is balanced by the erosion of sediment from the floodplain through lateral migration. The current formulation couples MAST-1D with empirical channel migration relationships that link bankfull flow depth and mean velocity to channel migration, sinuosity and channel geometry. Future development of this preliminary work will involve a fully coupled MAST-1D model with a standard meander migration model that will allow for the building of floodplain stratigraphy and tracking of the position of the meandering channel in space and time.

Compressible magma/mantle dynamics: 3-D, adaptive simulations in ASPECT

NASA Astrophysics Data System (ADS)

Dannberg, Juliane; Heister, Timo

2016-12-01

Melt generation and migration are an important link between surface processes and the thermal and chemical evolution of the Earth's interior. However, their vastly different timescales make it difficult to study mantle convection and melt migration in a unified framework, especially for 3-D global models. And although experiments suggest an increase in melt volume of up to 20 per cent from the depth of melt generation to the surface, previous computations have neglected the individual compressibilities of the solid and the fluid phase. Here, we describe our extension of the finite element mantle convection code ASPECT that adds melt generation and migration. We use the original compressible formulation of the McKenzie equations, augmented by an equation for the conservation of energy. Applying adaptive mesh refinement to this type of problems is particularly advantageous, as the resolution can be increased in areas where melt is present and viscosity gradients are high, whereas a lower resolution is sufficient in regions without melt. Together with a high-performance, massively parallel implementation, this allows for high-resolution, 3-D, compressible, global mantle convection simulations coupled with melt migration. We evaluate the functionality and potential of this method using a series of benchmarks and model setups, compare results of the compressible and incompressible formulation, and show the effectiveness of adaptive mesh refinement when applied to melt migration. Our model of magma dynamics provides a framework for modelling processes on different scales and investigating links between processes occurring in the deep mantle and melt generation and migration. This approach could prove particularly useful applied to modelling the generation of komatiites or other melts originating in greater depths. The implementation is available in the Open Source ASPECT repository.

Electronic tags and genetics explore variation in migrating steelhead kelts (oncorhynchus mykiss), Ninilchik river, Alaska

USGS Publications Warehouse

Nielsen, J.L.; Turner, S.M.; Zimmerman, C.E.

2011-01-01

Acoustic and archival tags examined freshwater and marine migrations of postspawn steelhead kelts (Oncorhynchus mykiss) in the Ninilchik River, Alaska, USA. Postspawn steelhead were captured at a weir in 2002-2005. Scale analysis indicated multiple migratory life histories and spawning behaviors. Acoustic tags were implanted in 99 kelts (2002-2003), and an array of acoustic receivers calculated the average speed of outmigration, timing of saltwater entry, and duration of residency in the vicinity of the river mouth. Ocean migration data were recovered from two archival tags implanted in kelts in 2004 (one male and one female). Archival tags documented seasonal differences in maximum depth and behavior with both fish spending 97% of time at sea <6 m depth (day and night). All study fish were double tagged with passive integrated transponder (PIT) tags implanted in the body cavity. Less than 4% of PIT tags were retained in postspawn steelhead. Molecular genetics demonstrated no significant differences in genetic population structure across years or among spawning life history types, suggesting a genetically panmictic population with highly diverse life history characteristics in the Ninilchik River.

Migration depths of juvenile Chinook salmon and steelhead relative to total dissolved gas supersaturation in a Columbia River reservoir

USGS Publications Warehouse

Beeman, J.W.; Maule, A.G.

2006-01-01

The in situ depths of juvenile salmonids Oncorhynchus spp. were studied to determine whether hydrostatic compensation was sufficient to protect them from gas bubble disease (GBD) during exposure to total dissolved gas (TDG) supersaturation from a regional program of spill at dams meant to improve salmonid passage survival. Yearling Chinook salmon O. tshawytscha and juvenile steelhead O. mykiss implanted with pressure-sensing radio transmitters were monitored from boats while they were migrating between the tailrace of Ice Harbor Dam on the Snake River and the forebay of McNary Dam on the Columbia River during 1997-1999. The TDG generally decreased with distance from the tailrace of the dam and was within levels known to cause GBD signs and mortality in laboratory bioassays. Results of repeated-measures analysis of variance indicated that the mean depths of juvenile steelhead were similar throughout the study area, ranging from 2.0 m in the Snake River to 2.3 m near the McNary Dam forebay. The mean depths of yearling Chinook salmon generally increased with distance from Ice Harbor Dam, ranging from 1.5 m in the Snake River to 3.2 m near the forebay. Juvenile steelhead were deeper at night than during the day, and yearling Chinook salmon were deeper during the day than at night. The TDG level was a significant covariate in models of the migration depth and rates of each species, but no effect of fish size was detected. Hydrostatic compensation, along with short exposure times in the area of greatest TDG, reduced the effects of TDG exposure below those generally shown to elicit GBD signs or mortality. Based on these factors, our results indicate that the TDG limits of the regional spill program were safe for these juvenile salmonids.

Using Water Depth Sensors and High-resolution Topographic Mapping to Inform Wetland Management at a Globally Important Stopover Site for Migratory Shorebirds

NASA Astrophysics Data System (ADS)

Schaffer-Smith, D.; Swenson, J. J.; Reiter, M. E.; Isola, J. E.

2017-12-01

Over 50% of western hemisphere shorebird species are in decline due to ongoing habitat loss and habitat degradation. Wetland dependent shorebirds prefer shallowly flooded habitats (water depth <5cm), yet most wetlands are not managed to optimize shallow areas. In-situ water depth measurements and microtopography data coupled with satellite image analysis can assist in understanding habitat suitability patterns at broad spatial scales. We generated detailed bathymetry, and estimated spatial daily water depths, the proportion of wetland area providing flooded habitat within the optimal depth range, and the volume of water present in 23 managed wetlands in the Sacramento Valley of California, a globally important shorebird stopover site. Using 30 years of satellite imagery, we estimated suitable habitat extent across the landscape under a range of climate conditions. While spring shorebird abundance has historically peaked in early April, we found that maximum optimal habitat extent occurred after mid-April. More than 50% of monitored wetlands provided limited optimal habitat (<5% of total wetland extent) during the peak of migration between mid-March and mid-April. Furthermore, the duration of suitable habitat presence was fleeting; only 4 wetlands provided at least 10 consecutive days with >5% optimal habitat during the peak of migration. Wetlands with a higher percent clay content and lower topographic variability were more likely to provide a greater extent and duration of suitable habitat. We estimated that even in a relatively wet El-Nino year as little as 0.01%, to 10.72% of managed herbaceous wetlands in the Sacramento Valley provided optimal habitat for shorebirds at the peak of migration in early April. In an extreme drought year, optimal habitat decreased by 80% compared to a wet year Changes in the timing of wetland irrigation and drawdown schedules and the design of future wetland restoration projects could increase the extent and duration of optimal flooded habitat for migratory shorebirds, without significant increases in overall water use requirements.

High-velocity basal sediment package atop oceanic crust, offshore Cascadia: Impacts on plate boundary processes and fluid migration

NASA Astrophysics Data System (ADS)

Peterson, D. E.; Keranen, K. M.

2017-12-01

Differences in fluid pressure and mechanical properties at megathrust boundaries in subduction zones have been proposed to create varying seismogenic behavior. In Cascadia, where large ruptures are possible but little seismicity occurs presently, new seismic transects across the deformation front (COAST cruise; Holbrook et al., 2012) image an unusually high-wavespeed sedimentary unit directly overlying oceanic crust. Wavespeed increases before sediments reach the deformation front, and the well-laminated unit, consistently of 1 km thickness, can be traced for 50 km beneath the accretionary prism before imaging quality declines. Wavespeed is modeled via iterative prestack time migration (PSTM) imaging and increases from 3.5 km/sec on the seaward end of the profile to >5.0 km/s near the deformation front. Landward of the deformation front, wavespeed is low along seaward-dipping thrust faults in the Quaternary accretionary prism, indicative of rapid dewatering along faults. The observed wavespeed of 5.5 km/sec just above subducting crust is consistent with porosity <5% (Erickson and Jarrard, 1998), possibly reflecting enhanced consolidation, cementation, and diagenesis as the sediments encounter the deformation front. Beneath the sediment, the compressional wavespeed of uppermost oceanic crust is 3-4 km/sec, likely reduced by alteration and/or fluids, lowest within a propagator wake. The propagator wake intersects the plate boundary at an oblique angle and changes the degree of hydration of the oceanic plate as it subducts within our area. Fluid flow out of oceanic crust is likely impeded by the low-porosity basal sediment package except along the focused thrust faults. Decollements are present at the top of oceanic basement, at the top of the high-wavespeed basal unit, and within sedimentary strata at higher levels; the decollement at the top of oceanic crust is active at the toe of the deformation front. The basal sedimentary unit appears to be mechanically strong, similar to observations from offshore Sumatra, where strongly consolidated sediments at the deformation front are interpreted to facilitate megathrust rupture to the trench (Hupers et al., 2017). A uniformly strong plate interface at Cascadia may inhibit microseismicity while building stress that is released in great earthquakes.

Working in the global world: looking for more modern workplace overseas

NASA Astrophysics Data System (ADS)

Joko Pitoyo, Agus

2018-04-01

International labor migration overseas is very complex and involves multiple dimensional issues, ranging from economic to social, political, and cultural issues. A very long history migration has affect the live of households which has been dependent very much on it, not only in economic terms but also in broader aspects.This research aim is to understand the history and process of international labor migration from the District of Ponorogo. The research was done using mixed method design, combining quantitative and qualitative approaches. Firstly, a survey was done by involving about a thousand households and followed with qualitative method applying in-depth interviews and FGDs to sub-samples households and some key informants. The results have shown that intergenerational migration has established in Ponogoro. There has been an expansion of destination countries with the establishment of many international migration routes. Migrant workers from Ponorogo have traveled to very distant continents and to more modern countries.

Gas migration through Opouawe Bank at the Hikurangi margin offshore New Zealand

NASA Astrophysics Data System (ADS)

Koch, Stephanie; Schroeder, Henning; Haeckel, Matthias; Berndt, Christian; Bialas, Joerg; Papenberg, Cord; Klaeschen, Dirk; Plaza-Faverola, Andreia

2016-06-01

This study presents 2D seismic reflection data, seismic velocity analysis, as well as geochemical and isotopic porewater compositions from Opouawe Bank on New Zealand's Hikurangi subduction margin, providing evidence for essentially pure methane gas seepage. The combination of geochemical information and seismic reflection images is an effective way to investigate the nature of gas migration beneath the seafloor, and to distinguish between water advection and gas ascent. The maximum source depth of the methane that migrates to the seep sites on Opouawe Bank is 1,500-2,100 m below seafloor, generated by low-temperature degradation of organic matter via microbial CO2 reduction. Seismic velocity analysis enabled identifying a zone of gas accumulation underneath the base of gas hydrate stability (BGHS) below the bank. Besides structurally controlled gas migration along conduits, gas migration also takes place along dipping strata across the BGHS. Gas migration on Opouawe Bank is influenced by anticlinal focusing and by several focusing levels within the gas hydrate stability zone.

"Right Here is the Gateway": Mobility, Sex Work Entry and HIV Risk Along the Mexico-U.S. Border.

PubMed

Goldenberg, Sm; Silverman, Js; Engstrom, D; Bojorquez-Chapela, I; Strathdee, Sa

2014-08-01

Women comprise an increasing proportion of migrants. Many voluntarily migrate for sex work or practice survival sex, while others may be trafficked for sexual exploitation. To investigate how the context of mobility shapes sex work entry and HIV risk, we conducted in-depth interviews with formerly trafficked women currently engaged in sex work (n=31) in Tijuana, Mexico and their service providers (n=7) in Tijuana and San Diego, USA from 2010-2011. Women's experiences of coerced and deceptive migration, deportation as forced migration, voluntary mobility, and migration to a risk environment illustrate that circumstances driving and resulting from migration shape vulnerability to sex trafficking, voluntary sex work entry, and HIV risk. Findings suggest an urgent need for public health and immigration policies that provide integrated support for deported and/or recently arrived female migrants. Policies to prevent sex trafficking and assist trafficked females must also consider the varying levels of personal agency involved in migration and sex work entry.

“Right Here is the Gateway”: Mobility, Sex Work Entry and HIV Risk Along the Mexico-U.S. Border

PubMed Central

Goldenberg, SM; Silverman, JS; Engstrom, D; Bojorquez-Chapela, I; Strathdee, SA

2013-01-01

Women comprise an increasing proportion of migrants. Many voluntarily migrate for sex work or practice survival sex, while others may be trafficked for sexual exploitation. To investigate how the context of mobility shapes sex work entry and HIV risk, we conducted in-depth interviews with formerly trafficked women currently engaged in sex work (n=31) in Tijuana, Mexico and their service providers (n=7) in Tijuana and San Diego, USA from 2010–2011. Women’s experiences of coerced and deceptive migration, deportation as forced migration, voluntary mobility, and migration to a risk environment illustrate that circumstances driving and resulting from migration shape vulnerability to sex trafficking, voluntary sex work entry, and HIV risk. Findings suggest an urgent need for public health and immigration policies that provide integrated support for deported and/or recently arrived female migrants. Policies to prevent sex trafficking and assist trafficked females must also consider the varying levels of personal agency involved in migration and sex work entry. PMID:25346548

Glyphosate transport through weathered granite soils under irrigated and non-irrigated conditions--Barcelona, Spain.

PubMed

Candela, Lucila; Caballero, Juan; Ronen, Daniel

2010-05-15

The transport of Glyphosate ([N-phosphonomethyl] glycine), AMPA (aminomethylphosphonic acid, CH(6)NO(3)P), and Bromide (Br(-)) has been studied, in the Mediterranean Maresme area of Spain, north of Barcelona, where groundwater is located at a depth of 5.5m. The unsaturated zone of weathered - granite soils was characterized in adjacent irrigated and non-irrigated experimental plots where 11 and 10 boreholes were drilled, respectively. At the non irrigated plot, the first half of the period was affected by a persistent and intense rainfall. After 69 days of application residues of Glyphosate up to 73.6 microgg(-1) were detected till a depth of 0.5m under irrigated conditions, AMPA, analyzed only in the irrigated plot was detected till a depth of 0.5m. According to the retardation coefficient of Glyphosate as compared to that of Br(-) for the topsoil and subsoil (80 and 83, respectively) and the maximum observed migration depth of Br(-) (2.9 m) Glyphosate and AMPA should have been detected till a depth of 0.05 m only. Such migration could be related to the low content of organic matter and clays in the soils; recharge generated by irrigation and heavy rain, and possible preferential solute transport and/or colloidal mediated transport. Copyright 2010 Elsevier B.V. All rights reserved.

Using a Convection Model to Predict Altitudes of White Stork Migration Over Central Israel

NASA Astrophysics Data System (ADS)

Shamoun-Baranes, Judy; Liechti, Olivier; Yom-Tov, Yoram; Leshem, Yossi

Soaring migrants such as storks, pelicans and large birds of prey rely on thermal convection during migration. The convection model ALPTHERM was designed to predict the onset, strength, duration and depth of thermal convection for varying topographies for glider pilots, based on atmospheric conditions at midnight. We tested ALPTHERM predictions as configured for two topographies of central Israel, the Coastal Plains and the Judean and Samarian Mountains in order to predict altitudes of migrating white storks (Ciconia ciconia). Migrating flocks of white storks were tracked with a motorized glider, to measure maximum altitudes of migration during spring 2000. A significant positive correlation was found between the maximum daily altitudes of migration measured and the predicted upper boundary of thermal convection for the Coastal Plains and Samarian Mountains. Thirty-minute predictions for the Coastal Plains and Samarian Mountains correlated positively with measured maximum migration altitudes per thermal. ALPTHERM forecasts can be used to alter flight altitudes in both civil and especially military aviation and reduce the hazard of serious aircraft collisions with soaring migrants.

Seismic Azimuthal Anisotropy of the Lower Paleozoic Shales in Northern Poland: can we reliably detect it?

NASA Astrophysics Data System (ADS)

Cyz, Marta; Malinowski, Michał

2017-04-01

Analysis of the azimuthal anisotropy is an important aspect of characterization the Lower Paleozoic shale play in northern Poland, since it can be used to map pre-existing fracture networks or help in optimal placement of the horizontal wells. Previous studies employed Velocity versus Azimuth (VVAz) method and found that this anisotropy is weak - on the order of 1-2%, only locally - close to major fault zones - being higher (ca. 7%). This is consistent with the recent re-interpretation of the cross-dipole sonic data, which indicates average shear wave anisotropy of 1%. The problem with the VVAz method is that it requires good definition of the interval, for which the analysis is made and it should be minimum 100 ms thick. In our case, the target intervals are thin - upper reservoir (Lower Silurian Jantar formation) is 15 m thick, lower reservoir (Upper Ordovician Sasino formation) is 25 m thick. Therefore, we prefer to use the Amplitude vs Azimuth (AVAz) method, which can be applied on a single horizon (e.g. the base of the reservoir). However, the AVAz method depends critically on the quality of the seismic data and preservation of amplitudes during processing. On top of the above mentioned issues, physical properties of the Lower Paleozoic shales from Poland seem to be unfavourable for detecting azimuthal anisotropy. For example, for both target formations, parameter g=(Vs/Vp)2 is close to 0.32, which implies that the anisotropy expressed by the anisotropic gradient in the dry (i.e. gas-filled fractures) case is close to zero. In case of e.g. the Bakken Shale, g is much higher (0.38-0.4), leading to a detectable anisotropic signature even in the dry case. Modelling of the synthetic AVAz response performed using available well data suggested that anisotropic gradient in the wet (fluid-filled) case should be detectable even in case of the weak anisotropy (1-2%). This scenario is consistent with the observation, that the studied area is located in the liquid/condensate window. Promising results of the synthetic modelling allowed us to perform analysis on the real data: a subset (52.8 km2) of a large modern wide-azimuth 3D seismic survey from northern Poland. The seismic data were pre-stack depth migrated using full-azimuth non-sectored type migration algorithm, providing excellent input for AVAz. We perform both the classical Ruger and Fourier Coefficients AVAz. Results of the AVAz analysis of the real data correlate to some extent with the earlier VVAz results, both in terms of the anisotropy magnitude and orientation. Despite the weak anisotropy, obtained orientations are more or less consistent with the available image (XRMI) logs from the vertical wells. This work has been funded by the Polish National Centre for Research and Development within the Blue Gas project (No BG2/SHALEMECH/14). Data were provided by the PGNiG SA. We thank CGG GeoSoftware for the donation of the Hampson-Russell ProAZ software.

Opportunistic acoustic recordings of (potential) orangeback flying squid Sthenoteuthis pteropus in the Central Eastern Atlantic

NASA Astrophysics Data System (ADS)

Peña, Marian; Villanueva, Roger; Escánez, Alejandro; Ariza, Alejandro

2018-03-01

Squids are fast swimmers that are difficult to catch by nets and to record with echosounders in the open ocean. A rare detection of orangeback flying squid Sthenoteuthis pteropus in the Central Eastern Atlantic Ocean off the coast of Senegal was accomplished during the MAFIA oceanographic survey carried out between Brazil and the Canary Islands in April 2015. Although net sampling did not yield any subadult or adult individuals, dozens were visually detected from the vessel jumping out of the water at night and displaying their characteristic dorsal photophore patch. A few squids were caught with fishing lines and identified at the species level. The acoustic echograms revealed distinctive previously unobserved acoustic echotraces that seemed to be caused by those squids, which were the only new species detected at that station (over a bottom depth ranging from 4010 to 5215 m, between 10° 45‧ N 22° 41‧ W and 10° 53‧ N 22° 40‧ W). The acoustic response and swimming behaviour shown by those echotraces reinforced this hypothesis. The (potentially) squid recordings dove rapidly (0.19 m/s to 0.48 m/s) from around 10 m below the mesopelagic fish layer, which had migrated to the subsurface at night (35 m depth), to depths of 70-95 m, and swam upward, apparently attacking fish from below. The morning squid migration to deeper waters (250-300 m) was also recorded acoustically. Downward movements of squid swimming at speeds of 0.22 m/s were calculated from the echogram, while the mesopelagic migrating fish swam at 0.27 m/s reaching 250 m depth. Sv120 - Sv38 averaged 2.7 ± 3.2 dB for the squid echotraces while the mesopelagic layer showed values of -8.8 ± 0.9 dB. These ranges agreed with values in the literature and from theoretical models. This study provides more insight into the migrating behaviour of oceanic squids, a species group that is poorly represented in the acoustic literature due to challenges in studying them.

Sandwave Morphologies and Dynamics in a Continental Shelf Environment : Example of the Banc du Four (western Brittany, France)

NASA Astrophysics Data System (ADS)

Franzetti, M.; Garlan, T.; Le Roy, P.; Delacourt, C.; Cancouët, R.; Graindorge, D.; Deschamps, A.

2011-12-01

Marine sand dunes and sandbanks are mainly observed in continental tidal shelves (North Sea, South China Sea, North Atlantic America) and may be highly dynamic (for example up to 75 m/y in the Marsdiep inlet). So they may pose a potential risk to offshore installations and shipping. Multitemporal mapping of sandwaves, necessary to mitigate this hazard, is complicated by their dynamic character, which is still poorly understood especially in the offshore domain. In consequence, these structures are often defined as moribund at depths greater than 30 meters. The aim of this investigation is to study evolution of deeper (110 meters) complex set of sand bedforms : "Banc du Four" located in the Iroise Sea. The study area is exposed to strong tidal currents and storm waves at the junction of the Northeast Atlantic Ocean and the Western English Channel, conditions favorable to sediment dynamics. The bathymetric data, which form the basis of this study, are two Digital Terrain Modeling's (DTM's) derived from MultiBeam Echosounder (MBES) surveys : "Pourquoi-Pas?" oceanographic research vessel (R/V) in February 2009 (5 meters resolution DTM) and R/V "Albert Lucas" in August 2010 (2 meters resolution DTM). Sandwave parameters (water depth, shape, wavelength, height, symmetry index, ...) have been derived from the 2009 bathymetric data. The Banc du Four is characterized by a large sandbank (45 meters height and 2 km width) flanked by dune fields. The morphological characteristics of the dunes vary greatly (range 30 to 110 meters depth, 40 meters maximal height, 600 meters maximal width, symmetrical to asymmetrical, ...). However, this complexity can be explained by the involved sandwave dynamic (range 0 to 30 meters per year migration velocity). Spatial correlation method, applied on the two DTM's, are used to measure the migration rate. The high migration rates for deeper giant dunes bring to light the dynamic sandwave existence at depths exceeding 30-40 meters, contrary to previously accepted models. Dune asymmetry is proportional to migration rates and the lee side is always oriented towards the direction of movement. These relationships confirm the observations reported in the literature for shallower structures.

Study on immobilization and migration of nuclide u in superficial soil of uranium tailings pond

NASA Astrophysics Data System (ADS)

Chang, Zhe; Zhou, Shukui

2017-05-01

The uranium tailings in southern China was used as the object of study to study the fixation and migration characteristics of nuclide U in shallow tailings. The results showed that the precipitation of tailings in the tailings soil was not linearly related to the depth during the acid rain leaching process. Tailings soil in the role of fixatives, when the lime as a fixative, the tailings of different soil uranium in 20 days after the re-precipitation. However, when lime and ammonium phosphate were used as fixing agents, the cumulative precipitation of U had a significant effect, and the migration of uranium was inhibited.

Walker Ranch 3D seismic images

DOE Data Explorer

Robert J. Mellors

2016-03-01

Amplitude images (both vertical and depth slices) extracted from 3D seismic reflection survey over area of Walker Ranch area (adjacent to Raft River). Crossline spacing of 660 feet and inline of 165 feet using a Vibroseis source. Processing included depth migration. Micro-earthquake hypocenters on images. Stratigraphic information and nearby well tracks added to images. Images are embedded in a Microsoft Word document with additional information. Exact location and depth restricted for proprietary reasons. Data collection and processing funded by Agua Caliente. Original data remains property of Agua Caliente.

Complex vertical migration of larvae of the ghost shrimp, Nihonotrypaea harmandi, in inner shelf waters of western Kyushu, Japan

NASA Astrophysics Data System (ADS)

Tamaki, Akio; Mandal, Sumit; Agata, Yoshihiro; Aoki, Ikumi; Suzuki, Toshikazu; Kanehara, Hisao; Aoshima, Takashi; Fukuda, Yasushi; Tsukamoto, Hideshi; Yanagi, Tetsuo

2010-01-01

The position of meroplanktonic larvae in the water column with depth-dependent current velocities determines horizontal transport trajectories. For those larvae occurring in inner shelf waters, little is known about how combined diel and tidally-synchronized vertical migration patterns shift ontogenetically. The vertical migration of larvae of Nihonotrypaea harmandi (Decapoda: Thalassinidea: Callianassidae) was investigated in mesotidal, inner shelf waters of western Kyushu, Japan in July-August 2006. The larval sampling at seven depth layers down to 60 m was conducted every 3 h for 36 h in a 68.5-m deep area 10 km off a major coastal adult habitat. Within a 61-65-m deep area 5-7.5 km off the adult habitat, water temperature, salinity, chlorophyll a concentration, and photon flux density were measured, and water currents there were characterized from harmonic analysis of current meter data collected in 2008. The water column was stratified, with pycnocline, chlorophyll a concentration maximum, and 2% of photon flux density at 2 m, recorded at around 22-24 m. The stratified residual currents were detected in their north component, directed offshore and onshore in the upper and lower mixed layers, respectively. More than 87% of larvae occurred between 20 m and 60 m, producing a net onshore transport of approximately 1.3 km d -1. At the sunset flooding tide, all zoeal-stage larvae ascended, which could further promote retention (1.4-km potential onshore transport in 3 h). The actual onshore transport of larvae was detected by observing their occurrence pattern in a shallow embayment area with the adult habitat for 24 h in October 1994. However, ontogenetic differences in the vertical migration pattern in inner shelf waters were also apparent, with the maximum mean positions of zoeae deepening with increasing stages. Zoeae I and II performed a reverse diel migration, with their minimum and maximum depths being reached around noon and midnight, respectively. Zoeae IV and V descended continuously. Zoeae III had behaviors that were intermediate to those of the earlier- and later-stage zoeae. Postlarvae underwent a normal diel migration (nocturnal ascent) regardless of tides, with the deepest position (below 60 m and/or on the bottom) during the day. These findings give a new perspective towards how complex vertical migration patterns in meroplanktonic larvae enable their retention in inner shelf waters before the final entry of postlarvae into their natal populations.

Integrating seismic reflection and geological data and interpretations across an internal basement massif: The southern Appalachian Pine Mountain window, USA

USGS Publications Warehouse

McBride, J.H.; Hatcher, R.D.; Stephenson, W.J.; Hooper, R.J.

2005-01-01

The southern Appalachian Pine Mountain window exposes 1.1 Ga Grenvillian basement and its metasedimentary Paleozoic(?) cover through the allochthonous Inner Piedmont. The issue of whether the crustal block inside the window was either transported above the master Appalachian (late Alleghanian) de??collement or is an autochthonous block that was overridden by the de??collement has been debated for some time. New detrital zircon geochronologic data from the cover rocks inside the window suggest this crustal block was derived from Gondwana but docked with Laurentia before the Alleghanian event. Reprocessed deep seismic reflection data from west-central Georgia (pre- and poststack noise reduction, amplitude variation analysis, and prestack depth migration) indicate that a significant band of subhorizontal reflections occurs almost continuously beneath the window collinear with the originally recognized de??collement reflections north of the window. A marked variation in the de??collement image, from strong and coherent north of the window to more diffuse directly beneath the window, is likely a partial consequence of the different geology between the Inner Piedmont and the window. The more diffuse image beneath the window may also result from imaging problems related to changes in topography and fold of cover (i.e., signal-to-noise ratio). Two alternative tectonic models for the Pine Mountain window can partially account for the observed variation in the de??collement reflectivity. (1) The Pine Mountain block could be truncated below by a relatively smooth continuation of the de??collement. The window would thus expose an allochthonous basement duplex or horse-block thrust upward from the south along the Late Proterozoic rifted continental margin. (2) The window represents localized exhumation of autochthonous basement and cover along a zone of distributed intrabasement shearing directly beneath the window. Either model is viable if only reflector geometry is considered; model (1) is favored if both geometry and kinematics of Blue Ridge-Piedmont thrust sheet emplacement are incorporated. In either model, the southern margin of the window merges to the west with the Iapetan early Alleghanian Central Piedmont suture, which juxtaposes North American-affinity Piedmont rocks to the north and exotic Panafrican rocks of the Carolina (Avalon) terrane to the south. Immediately south of the window, this suture dips southward and merges in the lower crust with the late Alleghanian suture joining the Appalachians with Gondwana. ?? 2005 Geological Society of America.

Scars of the Farallon Plate in the High Plains Revealed by 3D Wavefield Imaging with the Earthscope Transportable Array

NASA Astrophysics Data System (ADS)

Pavlis, G. L.; Yang, X.

2012-12-01

We used P to S conversion data from the Earthscope Automated Receiver function Survey (EARS) to image the upper mantle from the west coast to the Mississippi River. We used 178,300 radial and transverse receiver function estimates that survived automated editing procedures defined by EARS. Processing delays by EARS limited the data to the period through April 5, 2012. We processed these data with a three-component, fully three-dimensional, prestack, wavefield imaging procedure that we have referred to previously as plane-wave migration. Previous results with earlier generations of the EARS data and the same technique revealed the presence of a continuous, east-dipping horizon throughout the entire Cordillera between a depth of approximately 200-450 km with hints of penetration of this horizon through the 410 km discontinuity. This surface was interpreted as a marker on the top of the actively subducting Juan de Fuca/Farallon slab through cross-validation with all published body wave tomography models derived from USArray data. The new results reveal a surprisingly similar feature under the high plains. We observe a high-amplitude, east-dipping horizon that begins near the Rocky Mountain front and intersects the 410 km discontinuity at approximately the longitude of the Kansas-Missouri border. The lateral extent of this feature, however, is more limited. It disappears to the north around the Kansas-Nebraska border and to the south within central Texas. This region corresponds closely with the "big break" defined in tomography models of Sigloch (2011. She interpreted this feature as a residual signature of a westward jump of the Farallon slab at the close of the Laramide orogeny that is commonly viewed as a period of flat-slab subduction. We suggest the feature we image is equivalent to the east-dipping feature presently seen under the Cordillera. The feature imaged in the Cordillera can be directly linked to active processes. If a comparable process maintains what we see in the high plains it may mark a boundary where the cratonic keel is overriding the mantle above the transition zone along a zone of deformation originally created in the Laramide. This may be an explanation of the elevated topography of the high plains. An alternative explanation is we are seeing a residual scar from the Laramide, but that would require this region of the mantle to have been static for the order of 70 Myr and that the craton moves over the mantle along a thin deformation zone.

Deep-pelagic (0-3000 m) fish assemblage structure over the Mid-Atlantic Ridge in the area of the Charlie-Gibbs Fracture Zone

NASA Astrophysics Data System (ADS)

Cook, April B.; Sutton, Tracey T.; Galbraith, John K.; Vecchione, Michael

2013-12-01

Only a miniscule fraction of the world’s largest volume of living space, the ocean’s midwater biome, has ever been sampled. As part of the International Census of Marine Life field project on Mid-Atlantic Ridge ecosystems (MAR-ECO), a discrete-depth trawling survey was conducted in 2009 aboard the NOAA FSV Henry B. Bigelow to examine the pelagic faunal assemblage structure and distribution over the Charlie-Gibbs Fracture Zone (CGFZ) of the northern Mid-Atlantic Ridge. Day/night sampling at closely spaced stations allowed the first characterization of diel vertical migration of pelagic nekton over the MAR-ECO study area. Discrete-depth sampling from 0-3000 m was conducted using a Norwegian “Krill” trawl with five codends that were opened and closed via a pre-programmed timer. Seventy-five species of fish were collected, with a maximum diversity and biomass observed between depths of 700-1900 m. A gradient in sea-surface temperature and underlying watermasses, from northwest to southeast, was mirrored by a similar gradient in ichthyofaunal diversity. Using multivariate analyses, eight deep-pelagic fish assemblages were identified, with depth as the primary discriminatory variable. Strong diel vertical migration (DVM) of the mesopelagic fauna was a prevalent feature of the study area, though the numerically dominant fish, Cyclothone microdon (Gonostomatidae), exhibited a broad (0-3000 m) vertical distribution and did not appear to migrate on a diel basis. Three patterns of vertical distribution were observed in the study area: (a) DVM of mesopelagic, and possibly bathypelagic, taxa; (b) broad vertical distribution spanning meso- and bathypelagic depths; and (c) discrete vertical distribution within a limited depth range. Overall species composition and rank order of abundance of fish species agreed with two previous expeditions to the CGFZ (1982-1983 and 2004), suggesting some long-term consistency in the ichthyofaunal composition of the study area, at least in the summer. Frequent captures of putative bathypelagic fishes, shrimps, and cephalopods in the epipelagic zone (0-200 m) were confirmed. The results of this expedition reveal distributional patterns unlike those previously reported for open-ocean ecosystems, with the implication of increased transfer efficiency of surface production to great depths in the mid-North Atlantic.

Using geographic distribution of well-screen depths and hydrogeologic conditions to identify areas of concern for contaminant migration through inactive supply wells

NASA Astrophysics Data System (ADS)

Gailey, Robert M.

2018-02-01

Contaminant migration through inactive supply wells can negatively affect groundwater quality and the combined effects from groups of such wells may cause greater impacts. Because the number of wells in many basins is often large and the geographic areas involved can be vast, approaches are needed to estimate potential impacts and focus limited resources for investigation and corrective measures on the most important areas. One possibility is to evaluate the geographic distribution of well-screen depths relative to hydrogeologic conditions and assess where contaminant migration through wells may be impacting groundwater quality. This approach is demonstrated for a geographically extensive area in the southern Central Valley of California, USA. The conditions that lead to wells acting as conduits for contaminant migration are evaluated and areas where the problem likely occurs are identified. Although only a small fraction of all wells appear to act as conduits, potential impacts may be significant considering needs to control nonpoint-source pollution and improve drinking water quality for rural residents. Addressing a limited number of areas where contaminant migration rates are expected to be high may cost-effectively accomplish the most beneficial groundwater quality protection and improvement. While this work focuses on a specific region, the results indicate that impacts from groups of wells may occur in other areas with similar conditions. Analyses similar to that demonstrated here may guide efficient investigation and corrective action in such areas with benefits occurring for groundwater quality. Potential benefits may justify expenditures to develop the necessary data for performing the analyses.

Migration and diving behavior of Centrophorus squamosus in the NE Atlantic. Combining electronic tagging and Argo hydrography to infer deep ocean trajectories

NASA Astrophysics Data System (ADS)

Rodríguez-Cabello, Cristina; González-Pola, Cesar; Sánchez, Francisco

2016-09-01

A total of nine leafscale gulper sharks Centrophorus squamosus (Bonnaterre, 1788), were tagged with pop-up, satellite, archival, transmitting tags (PSAT) in the Marine Protected Area (MPA) of El Cachucho (Le Danois Bank) located in waters to the north of Spain, (NE Atlantic). Tags provided data on time, pressure and temperature that were used to examine movement patterns and diving behavior. Data collected from Argo floats in the study area have been used to devise a simple geolocation algorithm to infer the probable routes followed by this species. Tag release points revealed that C. squamosus moved both to the west (Galician waters) and to the north (Porcupine Bank) from the tagging area, suggesting well defined preferred pathways. The inferred trajectories indicated that sharks alternate periods constrained to specific geographical regions with quick and prompt movements covering large distances. Two sharks made conspicuous diurnal vertical migrations being at shallower depths around midnight and at maximum depths at midday, while other sharks did not make vertical migrations. Vertical movements were done smoothly and independently of the fish swimming long-distances or resting in the area. Overall results confirm that this species is highly migratory, supporting speeds of 20 nautical miles.day-1 and well capable to swim and make vertical migrations well above the abyssal plain.

Distribution of melt along the East Pacific Rise 9°50'N from amplitude variation with angle (AVA) of incidence technique

NASA Astrophysics Data System (ADS)

Marjanovic, M.; Carton, H. D.; Carbotte, S. M.; Mutter, J. C.; Nedimovic, M. R.; Canales, J.

2012-12-01

Multichannel seismic (MCS) data collected in 2008 along the crest of the East Pacific Rise (EPR) 8°20'-10°10'N offer an excellent opportunity for studying along-axis variations in seismic properties of the mid-crustal magma sill imaged at ˜1.6 km below seafloor and inferring along-axis variations in the physical properties of this melt body. Locally, pre-stack data show a clear decrease in the amplitude of the P-wave reflection off the top of the magma sill as a function of angle of incidence, an observation reminiscent of the amplitude response of some hydrocarbon-saturated reservoirs, which may imply that within these regions the sill contains fully molten material. In oil and gas exploration, a technique known as amplitude variation with angle of incidence (AVA) analysis has been developed to derive reservoir properties from amplitude behavior. One such method, developed recently, uses intercept (derived from near-angle of incidence information, A) vs. slope (derived from mid-angle of incidence information, B) as seismic attributes to infer reservoir properties. Here, for the first time, we apply this approach to the mid-ocean ridge environment to infer variations in melt content of the axial magma sill. Using the presence of a converted P- to S- phase at the AMC as the first-order proxy for melt, we limit the application of AVA analysis to the region between ~9°30' and 10°00'N along the EPR axis. Prior to conducting the AVA analysis properly, data preparation steps are required (Kirchhoff pre-stack time migration, Radon filtering, velocity analysis of the AMC event for its accurate normal move-out correction, conversion of CMP gathers from offset domain to angle of incidence domain, and near and mid angle stacking were carried out here) and an interpretation scheme adequate for the mid-ocean ridge environment is established. The individual regions for conducting the A vs. B AVA analysis were based on previously-defined small-scale segmentation of the axial magma sill. The AVA behavior suggests the presence of melt within the four segments (each 5 to 10 km in length) spanning between ~9°42.3'N and 9°56.2'N. Drainage related to the 2005-06 eruption appears to be limited to a narrow area (~500 m in length) centered at 9°50.6'N. Furthermore, data from the 9°53'N area shows increased scatter of the seismic attributes A and B that can be explained by the anomalous density/velocity relationship for iron-enriched rocks; within this same region, seafloor lavas show a relatively higher concentration of Fe. The intercept vs. slope AVA method tested here thus seems a very promising tool for the study of mid-ocean ridge magma systems.

Diel and seasonal movement pattern of the dusky grouper Epinephelus marginatus inside a marine reserve.

PubMed

Koeck, Barbara; Pastor, Jérémy; Saragoni, Gilles; Dalias, Nicolas; Payrot, Jérôme; Lenfant, Philippe

2014-03-01

Temporal movement patterns and spawning behaviour of the dusky grouper Epinephelus marginatus were investigated using depth and temperature sensors combined to acoustic telemetry. Results showed that these fish are year-round resident, remaining inside the fully protected area of the marine reserve of Cerbère-Banyuls (65 ha) and display a diurnal activity pattern. Records from depth sensors revealed that groupers range inside small, distinct, and individual territories. Individual variations in habitat depth are only visible on a seasonal scale, i.e., between the spawning season and the rest of the year. In fact, during summer months when the seawater temperature exceeded 20 °C, tagged groupers made vertical spawning migrations of 4-8 m in amplitude. These vertical migrations are characteristic of the reproductive behaviour of dusky groupers, during which they release their gametes. The results are notable for the implementation of management rules in marine protected areas, such as reduced navigation speed, boating or attendance during spawning season. Copyright © 2013 Elsevier Ltd. All rights reserved.

Chagas Disease, Migration and Community Settlement Patterns in Arequipa, Peru

PubMed Central

Gilman, Robert H.; Cornejo del Carpio, Juan G.; Naquira, Cesar; Bern, Caryn; Levy, Michael Z.

2009-01-01

Background Chagas disease is one of the most important neglected tropical diseases in the Americas. Vectorborne transmission of Chagas disease has been historically rare in urban settings. However, in marginal communities near the city of Arequipa, Peru, urban transmission cycles have become established. We examined the history of migration and settlement patterns in these communities, and their connections to Chagas disease transmission. Methodology/Principal Findings This was a qualitative study that employed focus group discussions and in-depth interviews. Five focus groups and 50 in-depth interviews were carried out with 94 community members from three shantytowns and two traditional towns near Arequipa, Peru. Focus groups utilized participatory methodologies to explore the community's mobility patterns and the historical and current presence of triatomine vectors. In-depth interviews based on event history calendars explored participants' migration patterns and experience with Chagas disease and vectors. Focus group data were analyzed using participatory analysis methodologies, and interview data were coded and analyzed using a grounded theory approach. Entomologic data were provided by an ongoing vector control campaign. We found that migrants to shantytowns in Arequipa were unlikely to have brought triatomines to the city upon arrival. Frequent seasonal moves, however, took shantytown residents to valleys surrounding Arequipa where vectors are prevalent. In addition, the pattern of settlement of shantytowns and the practice of raising domestic animals by residents creates a favorable environment for vector proliferation and dispersal. Finally, we uncovered a phenomenon of population loss and replacement by low-income migrants in one traditional town, which created the human settlement pattern of a new shantytown within this traditional community. Conclusions/Significance The pattern of human migration is therefore an important underlying determinant of Chagas disease risk in and around Arequipa. Frequent seasonal migration by residents of peri-urban shantytowns provides a path of entry of vectors into these communities. Changing demographic dynamics of traditional towns are also leading to favorable conditions for Chagas disease transmission. Control programs must include surveillance for infestation in communities assumed to be free of vectors. PMID:20016830

Seismic velocity estimation from time migration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cameron, Maria Kourkina

2007-01-01

This is concerned with imaging and wave propagation in nonhomogeneous media, and includes a collection of computational techniques, such as level set methods with material transport, Dijkstra-like Hamilton-Jacobi solvers for first arrival Eikonal equations and techniques for data smoothing. The theoretical components include aspects of seismic ray theory, and the results rely on careful comparison with experiment and incorporation as input into large production-style geophysical processing codes. Producing an accurate image of the Earth's interior is a challenging aspect of oil recovery and earthquake analysis. The ultimate computational goal, which is to accurately produce a detailed interior map of themore » Earth's makeup on the basis of external soundings and measurements, is currently out of reach for several reasons. First, although vast amounts of data have been obtained in some regions, this has not been done uniformly, and the data contain noise and artifacts. Simply sifting through the data is a massive computational job. Second, the fundamental inverse problem, namely to deduce the local sound speeds of the earth that give rise to measured reacted signals, is exceedingly difficult: shadow zones and complex structures can make for ill-posed problems, and require vast computational resources. Nonetheless, seismic imaging is a crucial part of the oil and gas industry. Typically, one makes assumptions about the earth's substructure (such as laterally homogeneous layering), and then uses this model as input to an iterative procedure to build perturbations that more closely satisfy the measured data. Such models often break down when the material substructure is significantly complex: not surprisingly, this is often where the most interesting geological features lie. Data often come in a particular, somewhat non-physical coordinate system, known as time migration coordinates. The construction of substructure models from these data is less and less reliable as the earth becomes horizontally nonconstant. Even mild lateral velocity variations can significantly distort subsurface structures on the time migrated images. Conversely, depth migration provides the potential for more accurate reconstructions, since it can handle significant lateral variations. However, this approach requires good input data, known as a 'velocity model'. We address the problem of estimating seismic velocities inside the earth, i.e., the problem of constructing a velocity model, which is necessary for obtaining seismic images in regular Cartesian coordinates. The main goals are to develop algorithms to convert time-migration velocities to true seismic velocities, and to convert time-migrated images to depth images in regular Cartesian coordinates. Our main results are three-fold. First, we establish a theoretical relation between the true seismic velocities and the 'time migration velocities' using the paraxial ray tracing. Second, we formulate an appropriate inverse problem describing the relation between time migration velocities and depth velocities, and show that this problem is mathematically ill-posed, i.e., unstable to small perturbations. Third, we develop numerical algorithms to solve regularized versions of these equations which can be used to recover smoothed velocity variations. Our algorithms consist of efficient time-to-depth conversion algorithms, based on Dijkstra-like Fast Marching Methods, as well as level set and ray tracing algorithms for transforming Dix velocities into seismic velocities. Our algorithms are applied to both two-dimensional and three-dimensional problems, and we test them on a collection of both synthetic examples and field data.« less

Time-domain least-squares migration using the Gaussian beam summation method

NASA Astrophysics Data System (ADS)

Yang, Jidong; Zhu, Hejun; McMechan, George; Yue, Yubo

2018-04-01

With a finite recording aperture, a limited source spectrum and unbalanced illumination, traditional imaging methods are insufficient to generate satisfactory depth profiles with high resolution and high amplitude fidelity. This is because traditional migration uses the adjoint operator of the forward modeling rather than the inverse operator. We propose a least-squares migration approach based on the time-domain Gaussian beam summation, which helps to balance subsurface illumination and improve image resolution. Based on the Born approximation for the isotropic acoustic wave equation, we derive a linear time-domain Gaussian beam modeling operator, which significantly reduces computational costs in comparison with the spectral method. Then, we formulate the corresponding adjoint Gaussian beam migration, as the gradient of an L2-norm waveform misfit function. An L1-norm regularization is introduced to the inversion to enhance the robustness of least-squares migration, and an approximated diagonal Hessian is used as a preconditioner to speed convergence. Synthetic and field data examples demonstrate that the proposed approach improves imaging resolution and amplitude fidelity in comparison with traditional Gaussian beam migration.

Time-domain least-squares migration using the Gaussian beam summation method

NASA Astrophysics Data System (ADS)

Yang, Jidong; Zhu, Hejun; McMechan, George; Yue, Yubo

2018-07-01

With a finite recording aperture, a limited source spectrum and unbalanced illumination, traditional imaging methods are insufficient to generate satisfactory depth profiles with high resolution and high amplitude fidelity. This is because traditional migration uses the adjoint operator of the forward modelling rather than the inverse operator. We propose a least-squares migration approach based on the time-domain Gaussian beam summation, which helps to balance subsurface illumination and improve image resolution. Based on the Born approximation for the isotropic acoustic wave equation, we derive a linear time-domain Gaussian beam modelling operator, which significantly reduces computational costs in comparison with the spectral method. Then, we formulate the corresponding adjoint Gaussian beam migration, as the gradient of an L2-norm waveform misfit function. An L1-norm regularization is introduced to the inversion to enhance the robustness of least-squares migration, and an approximated diagonal Hessian is used as a pre-conditioner to speed convergence. Synthetic and field data examples demonstrate that the proposed approach improves imaging resolution and amplitude fidelity in comparison with traditional Gaussian beam migration.

Transfer of fallout radionuclides derived from Fukushima NPP accident: 1 year study on transfer of radionuclides through hydrological processes

NASA Astrophysics Data System (ADS)

Onda, Yuichi; Kato, Hiroaki; Patin, Jeremy; Yoshimura, Kazuya; Tsujimura, Maki; Wakahara, Taeko; Fukushima, Takehiko

2013-04-01

Previous experiences such as Chernobyl Nuclear Power Plant accident have confirmed that fallout radionuclides on the ground surface migrate through natural environment including soils and rivers. Therefore, in order to estimate future changes in radionuclide deposition, migration process of radionuclides in forests, soils, ground water, rivers should be monitored. However, such comprehensive studies on migration through forests, soils, ground water and rivers have not been conducted so far. Here, we present the following comprehensive investigation was conducted to confirm migration of radionuclides through natural environment including soils and rivers. 1)Study on depth distribution of radiocaesium in soils within forests, fields, and grassland 2)Confirmation of radionuclide distribution and investigation on migration in forests 3)Study on radionuclide migration due to soil erosion under different land use 4)Measurement of radionuclides entrained from natural environment including forests and soils 5)Investigation on radionuclide migration through soil water, ground water, stream water, spring water under different land use 6)Study on paddy-to-river transfer of radionuclides through suspended sediments 7)Study on river-to-ocean transfer of radionuclides via suspended sediments 8)Confirmation of radionuclide deposition in ponds and reservoirs

Intimate partner violence and forced migration during pregnancy: Structural constraints to women's agency.

PubMed

Turan, Janet M; Hatcher, Abigail M; Romito, Patrizia; Mangone, Emily; Durojaiye, Modupeoluwa; Odero, Merab; Camlin, Carol S

2016-01-01

Little is known about migration during pregnancy related to intimate partner violence (IPV). In this paper, we examine issues of agency in relation to pregnant women's migrations in a high HIV prevalence area of Kenya. We qualitatively explored forced migration among pregnant women, using data from in-depth interviews, focus groups and IPV screening forms. To quantitatively examine migration during pregnancy, we analysed data from a prospective study of 614 pregnant women. The qualitative data revealed that women had varied responses to violence in pregnancy, with some being able to leave the marital home voluntarily as a strategy to escape violence. Others were 'sent packing' from their marital homes when they dared to exercise autonomy, in some cases related to HIV status. Quantitative analyses revealed that pregnant women who migrated were more educated, less likely to be living with a partner and had fewer children than other women. Migration among pregnant women in Kenya illustrates the complexity of understanding women's agency in the context of IPV. The findings indicate that there is not a dichotomy between 'victim' and 'agent', but rather a complex dynamic between and within pregnant women, who may sequentially or simultaneously experience aspects of victimhood and/or agentic response.

Migration velocity analysis using residual diffraction moveout: a real-data example

NASA Astrophysics Data System (ADS)

Gonzalez, Jaime A. C.; de Figueiredo, José J. S.; Coimbra, Tiago A.; Schleicher, Jörg; Novais, Amélia

2016-08-01

Unfocused seismic diffraction events carry direct information about errors in the migration-velocity model. The residual-diffraction-moveout (RDM) migration-velocity-analysis (MVA) method is a recent technique that extracts this information by means of adjusting ellipses or hyperbolas to uncollapsed migrated diffractions. In this paper, we apply this method, which has been tested so far only on synthetic data, to a real data set from the Viking Graben. After application of a plane-wave-destruction (PWD) filter to attenuate the reflected energy, the diffractions in the real data become interpretable and can be used for the RDM method. Our analysis demonstrates that the reflections need not be completely removed for this purpose. Beyond the need to identify and select diffraction events in post-stack migrated sections in the depth domain, the method has a very low computational cost and processing time. To reach an acceptable velocity model of comparable quality as one obtained with common-midpoint (CMP) processing, only two iterations were necessary.

Seasonal changes in partial, reverse diel vertical migrations of cisco Coregonus artedi.

PubMed

Ahrenstorff, T D; Hrabik, T R

2016-09-01

The objectives of this study were to (1) document changes in partial, reverse diel vertical migrations (DVM) patterns of cisco Coregonus artedi in Ten Mile Lake, MN, U.S.A., throughout the year and (2) evaluate the mechanisms that may cause shifts in migration behaviour. Results indicated that C. artedi vertical distributions remained deep in the water column during the day and night of the spring and autumn, which was related to a low risk, low reward strategy. During summer, a partial migration occurred where a portion of the population remained deeper according to the low risk, low reward strategy, while the other portion performed a more extensive high risk, high reward reverse DVM. In winter, C. artedi did not migrate because there were only low risk, low reward conditions present at all depths. The extensive partial, reverse DVM during summer probably increased the growth potential of C. artedi, helping individuals survive in a lake with low zooplankton prey resources. © 2016 The Fisheries Society of the British Isles.

The diel vertical migration patterns and individual swimming behavior of overwintering sprat Sprattus sprattus

NASA Astrophysics Data System (ADS)

Solberg, Ingrid; Kaartvedt, Stein

2017-02-01

We addressed the behavioral patterns and DVM dynamics of sprat overwintering in a Norwegian fjord (150 m) with increasing hypoxia by depth. An upward-facing echosounder deployed at the bottom and cabled to shore provided 4 months of continuous acoustic data. This enabled detailed studies of individual behavior, specifically allowing assessment of individual vertical migrations at dusk and dawn in relation to light, analysis of so-called rise-and-sink swimming, and investigation of the sprat' swimming activity and behavior in severely hypoxic waters. Field campaigns supplemented the acoustic studies. The acoustic records showed that the main habitat for sprat was the upper ∼65 m where oxygen concentrations were ⩾0.7 mL O2 L-1. The sprat schooled at ∼50 m during daytime and initiated an upward migration about 1 h prior to sunset. While some sprat migrated to surface waters, other individuals interrupted the ascent when at ∼20-30 m, and returned to deeper waters ∼20-50 min after sunset. Sprat at depth was on average larger, yet individuals made excursions to- and from upper layers. Sprat were swimming in a "rise and sink" pattern at depth, likely related to negative buoyancy. Short-term dives into waters with less than 0.45 mL O2 L-1 were interpreted as feeding forays for abundant overwintering Calanus spp. The deep group of sprat initiated a dawn ascent less than 1 h before sunrise, ending at 20-30 m where they formed schools. They subsequently returned to deeper waters about ∼20 min prior to sunrise. Measurements of surface light intensities indicated that the sprat experienced lower light levels in upper waters at dawn than at dusk. The vertical swimming speed varied significantly between the behavioral tasks. The mixed DVM patterns and dynamic nocturnal behavior of sprat persisted throughout winter, likely shaped by individual strategies involving optimized feeding and predator avoidance, as well as relating to temperature, hypoxia and negative buoyancy.

Morphological adjustments in a meandering reach of the middle Yangtze River caused by severe human activities

NASA Astrophysics Data System (ADS)

Zhou, Meirong; Xia, Junqiang; Lu, Jinyou; Deng, Shanshan; Lin, Fenfen

2017-05-01

In the past 50 years, the Shishou reach in the middle Yangtze River underwent significant channel evolution owing to the implementation of an artificial cutoff, the construction of bank revetment works and the operation of the Three Gorges Project (TGP). Based on the measured hydrological data and topographic data, the processes of channel evolution in this reach were investigated mainly from the adjustments in planform and cross-sectional geometries. The variation in planform geometry obtained in this study indicates that (i) the artificial cutoff at Zhongzhouzi caused the river regime to adjust drastically, with the mean rate of thalweg migration at reach scale of 42.0 m/a over the period 1966-1975; (ii) then the effect of this artificial cutoff reduced gradually, with the mean migration rate decreasing to < 30 m/a in 1975-1993, while it increased to > 40 m/a owing to the occurrence of high water levels in 1993-1998; and (iii) the average annual rate of thalweg migration decreased to 29.3 m/a because of the impacts of various bank protection engineering and the TGP operation during the period 2002-2015. However, remarkable thalweg migration processes still occurred in local regions after the TGP operation, which resulted in significant bankline migration in local reaches of Beimenkou, Shijiatai, and Tiaoxiankou. In addition, the adjustments of bankfull channel geometry were investigated at section and reach scales after the TGP operation. Calculated results show that lateral channel migration in this reach was restricted by various river regulation works and that channel evolution was mainly characterized by an increase in bankfull depth and cross-sectional area. Empirical relationships were developed between the reach-scale bankfull dimensions (depth and area), the bankfull widths at specified sections, and the previous 5-year average fluvial erosion intensity during flood seasons, with high correlation degrees between them being obtained.

Modelling Waterfall Retreat in Heterogenous Bedrock

NASA Astrophysics Data System (ADS)

Attal, M.; Hodge, R. A.; Williams, R.; Baynes, E.

2016-12-01

Bedrock rivers are the mediators of environmental change through mountainous landscapes. In response to an increase in uplift rate for example, a "knickpoint" (often materialised as a waterfall) will propagate upstream, separating a domain downstream where the river and its adjacent hillslopes have steepened in response to the change from a "relict" domain upstream which is adjusted to the conditions before the change (Crosby and Whipple 2006). Many studies assume that knickpoint propagation rate scales with drainage area, based on the stream power theory. However, recent studies in a range of locations have found no obvious relationship between knickpoint retreat rate and drainage area, potentially resulting from the stream power law neglecting (i) the influence of sediment on the processes associated with waterfall migration and (ii) thresholds for bedrock detachment (Cook et al. 2013; Mackey et al. 2014; DiBiase et al. 2015; Baynes et al. 2015; Brocard et al. 2016). In this study, we develop a 1D model of waterfall retreat in horizontally bedded bedrock with varying joint spacing. In the model, knickpoint migration is based on two rules: a waterfall will start migrating once the threshold flow depth (a function of knickpoint height and joint spacing) has been exceeded (Lamb and Dietrich 2009), and the migration rate will then be a function of the water-depth-to-waterfall-height ratio, based on experimental results by Baynes (2015). Using a hydrograph based on a Poisson rectangular pulse rainfall simulator (Tucker and Bras 2001), we demonstrate the importance of structure in controlling the speed at which waterfalls migrate but also their number and the length over which they are distributed (Fig. 1). The model is applied to the Jökulsá á Fjöllum, NE Iceland, where rapid migration of waterfalls as a result of discrete events has been identified (Baynes et al. 2015), using new constraints on joint spacing derived from high resolution lidar survey of the gorge walls.

Variations in Melt Generation and Migration along the Aleutian Arc (Invited)

NASA Astrophysics Data System (ADS)

Plank, T. A.; Van Keken, P. E.

2013-12-01

The generation and ascent of mantle melt beneath volcanic arcs sets the course for how magmas differentiate to form the continental crust and erupt explosively from volcanoes. Although the basic framework of melting at subduction zones is understood to involve the convective influx of hot mantle (Tp ≥ 1300°C) and advective transport of water-rich fluids from the subducting slab, the P-T paths that melts follow during melt generation and migration are still not well known. The Aleutian Arc provides an opportunity to explore the conditions of mantle melting in the context of volcanoes that span an unusually large range in the depth to the slab, from Seguam island, with among the shallowest depths to the slab worldwide (~65 km, [1]) to Bogoslof island, behind the main volcanic front and twice the depth to the slab (~130 km). Here we combine thermal models tuned to Aleutian subduction parameters [after 2] with petrological estimates of the T and P of mantle-melt equilibration, using a major element geothermometer [3] and estimates of H2O and fO2 from olivine-hosted melt inclusion measurements [4] for basaltic magmas from 6 volcanoes in the central Aleutians (Korovin, Seguam, Bogoslof, Pakushin, Akutan, Shishaldin). We find mantle-melt equilibration conditions to vary systematically as a function of the depth to the slab, from 30 km and 1220°C (for Seguam) to 60 km and 1300°C (for Bogoslof). Such shallow depths, which extend up to the Moho, define a region perched well above the hot core of the mantle wedge predicted from thermal models, even considering the shallow depths of slab-mantle coupling (< 60 km) required to supply hot mantle beneath Seguam. Thus, even though the greatest melt production will occur in the hot core of the wedge (50-100 km depth), melts apparently ascend and re-equilibrate in the shallowest mantle. Volcanoes that overlie the greatest depth to the slab, and lie furthest from the wedge corner, stall at greater depths (~60 km), at the base of the conductive upper plate (i.e., lithosphere). The conductive lid and isotherms shallow toward the wedge corner. This leads to shallower depths of melt equilibration at shallower depths to the slab. A second effect is infiltration of melt into the thinning lithosphere, likely due to the increase in strain-rate toward the wedge corner, which favors melt segregation, migration, and shallow equilibration [5]. Such a process is developed most beneath Seguam, where melts collect at the Moho (~ 30km), but are still > 1200°C. Such equilibration depths in the uppermost mantle (30-60 km) and temperatures typical of the base of the conductive lid appear to characterize most modeled primary arc magmas [6], and point to a final re-setting point in the mantle that controls the composition of bulk arc crust. [1] Syracuse & Abers, 2006, G3. [2] Syracuse, van Keken, Abers, (2010) PEPI. [3] Lee, Luffi, Plank, Dalton, Leeman (2009) EPSL. [4] Zimmer et al. (2010) J.Pet. [5] Holzman & Kendall (2010). [6] Ruscitto et al. (2012) G3.

Seismic data enhancement and regularization using finite offset Common Diffraction Surface (CDS) stack

NASA Astrophysics Data System (ADS)

Garabito, German; Cruz, João Carlos Ribeiro; Oliva, Pedro Andrés Chira; Söllner, Walter

2017-01-01

The Common Reflection Surface stack is a robust method for simulating zero-offset and common-offset sections with high accuracy from multi-coverage seismic data. For simulating common-offset sections, the Common-Reflection-Surface stack method uses a hyperbolic traveltime approximation that depends on five kinematic parameters for each selected sample point of the common-offset section to be simulated. The main challenge of this method is to find a computationally efficient data-driven optimization strategy for accurately determining the five kinematic stacking parameters on which each sample of the stacked common-offset section depends. Several authors have applied multi-step strategies to obtain the optimal parameters by combining different pre-stack data configurations. Recently, other authors used one-step data-driven strategies based on a global optimization for estimating simultaneously the five parameters from multi-midpoint and multi-offset gathers. In order to increase the computational efficiency of the global optimization process, we use in this paper a reduced form of the Common-Reflection-Surface traveltime approximation that depends on only four parameters, the so-called Common Diffraction Surface traveltime approximation. By analyzing the convergence of both objective functions and the data enhancement effect after applying the two traveltime approximations to the Marmousi synthetic dataset and a real land dataset, we conclude that the Common-Diffraction-Surface approximation is more efficient within certain aperture limits and preserves at the same time a high image accuracy. The preserved image quality is also observed in a direct comparison after applying both approximations for simulating common-offset sections on noisy pre-stack data.

The consequences of Ireland's culture of medical migration.

PubMed

Humphries, Niamh; Crowe, Sophie; McDermott, Cian; McAleese, Sara; Brugha, Ruairi

2017-12-28

In recent years, Ireland has experienced a large-scale, outward migration of doctors. This presents a challenge for national policy makers and workforce planners seeking to build a self-sufficient medical workforce that trains and retains enough doctors to meet demand. Although, traditionally, medical migration has been considered beneficial to the Irish health system, austerity has brought a greater level of uncertainty to the health system and, with it, a need to reappraise the professional culture of migration and its impact on the Irish health system. This paper illustrates how a culture of migration informs career and migration plans. It draws on quantitative data-registration and migration data from source and destination countries-and qualitative data-in-depth interviews with 50 doctors who had undertaken postgraduate medical training in Ireland. Of 50 respondents, 42 highlighted the importance of migration. The culture of medical migration rests on two assumptions-that international training/experience is beneficial to all doctors and that those who emigrate will return to Ireland with additional skills and experience. This assumption of return is challenged by a new generation of doctors whose professional lives have been shaped by globalisation and by austerity. Global comparisons reveal the comparatively poor working conditions, training and career opportunities in Ireland and the relative attractiveness of a permanent career abroad. In light of these changes, there is a need to critically appraise the culture of medical migration to determine if and in what circumstances migration is appropriate to the needs of the Irish health system. The paper considers the need to reappraise the culture of medical migration and the widespread emigration that it promotes.

Habitat Parameters for Oxygen Minimum Zone Copepods from the Eastern Tropical North Pacific

NASA Astrophysics Data System (ADS)

Wishner, K. F.; Outram, D.; Grassian, B.

2016-02-01

Oxygen minimum zones (OMZs) affect zooplankton distributions and may be expanding in worldwide spatial and vertical extent from climate change. We studied zooplankton (especially copepod) distributions in the Eastern Tropical North Pacific (ETNP) OMZ, using day-night vertically-stratified MOCNESS tows (0-1000m). Habitat parameters (temperature, oxygen, depth) were defined for abundant copepod species and groups. Zooplankton layers, with a unique suite of species, occurred at upper and lower OMZ oxyclines. At the mesopelagic lower oxycline, there was a layer with a characteristic species assemblage and a sharp 10X biomass increase compared to nearby depths. The lower oxycline layer occurred within a narrow very low oxygen concentration (2µM). At two stations with different OMZ vertical extents, the lower oxycline layer depth changed with OMZ thickness, remaining at the same oxygen concentration but different temperature. Life history habitat (diapause depth, temperature) of the copepod Eucalanus inermis was also affected. In the upper water column at the two stations, large diel vertical migrators (fish, euphausiids) descended to taxon-specific daytime depths in the mid OMZ, regardless of oxygen level, but copepod species distributions showed more variability and sensitivity to habitat parameters. We predict that, with moderate OMZ expansion, the lower oxycline community will likely shift depth, thus re-distributing midwater biomass, species, and processes. In the upper water column, large vertical migrator distributions may be less affected, while smaller taxa (copepods) will likely be sensitive to habitat changes. At some point, the ability to withstand these changes may be exceeded for particular taxa, with consequences for assemblages, trophic webs, and export. In keeping with the session theme, we hope to compare our oceanic findings with others' results from coastal hypoxic situations.

Migration stopover ecology of western avian populations: A southwestern migration workshop

USGS Publications Warehouse

Skagen, Susan K.; Melcher, Cynthia P.; Hazelwood, Rob

2004-01-01

Workshop participants discussed a coordinated approach for addressing immediate research needs regarding migration patterns and crucial stopover sites and types. They envisioned a three­-tiered, coordinated approach: (1) long-term research to address effects of climate change and other large-scale patterns, (2) intensive, short-term survey and monitoring efforts using a stratified random design within habitats of interest to elucidate regional patterns of distribution and habitat use, and (3) research conducted at existing survey and banding sites to address more in-depth questions (e.g., rates of lipid deposition, microhabitat use, isotope analyses). There was considerable interest in developing common research proposals to blend the broad expertise represented at this workshop. A second meeting is recommended to build on the momentum of these discussions, to facilitate collaborations, and further the goals of integrated approaches to broadscale research on migration stopover ecology. 

Predictive modeling of freezing and thawing of frost-susceptible soils.

DOT National Transportation Integrated Search

2015-09-01

Frost depth is an essential factor in design of various transportation infrastructures. In frost : susceptible soils, as soils freezes, water migrates through the soil voids below the freezing line : towards the freezing front and causes excessive he...

Deep low-frequency earthquake activities during the failed magmatic eruptions of Mts. Iwate and Fuji, Japan

NASA Astrophysics Data System (ADS)

Nakamichi, H.; Hamaguchi, H.; Ukawa, M.; Tanaka, S.; Ueki, S.; Nishimura, T.

2008-12-01

I review deep low-frequency earthquake (DLF) activities during the failed magmatic eruptions of Mts. Iwate and Fuji, Japan. Volcanic unrests at Mts. Iwate and Fuji were observed in 1998-1999 and 2000-2001, respectively. Several hundred DLFs occurred during the unrest at Mt. Iwate; the number of DLFs in a normal year is less than or equal to 10. The DLF activity at Mt. Fuji increased sharply during the period from September 2000 to May 2001. The frequency of DLFs at Mt. Fuji during the DLF swarm was 20 times higher than that during normal activity. The DLFs of Mts. Iwate and Fuji show non-DC source mechanisms and suggest fluid motion at the focal regions. The DLF hypocenters of Mt. Fuji defined an ellipsoid with a diameter of 5 km; their focal depths are 11-16 km. The ellipsoid was centered 3 km northeast of the summit, and its major axis was directed in the northwest-southeast direction. The center of the ellipsoid gradually migrated upward, and 2-3 km in the northwest direction during 1998-2001. The migration of the DLFs reflects the volcanic fluid migration associated with a northwest-southeast-oriented dike beneath Mt. Fuji. The DLFs of Mt. Iwate were located at intermediate depths (5-12 km) beneath the summit and at deep depths (31-37 km) in the regions located 10 km south and 10 km northeast of the summit. In April 1998, the frequency of DLFs increased five days before an increase in the occurrence of shallow volcanic earthquakes at Mt. Iwate. Hypocenter migration of the DLFs at intermediate depths was observed from April 1998 to September 1998. New fumarole activity in the western region of Mt. Iwate commenced in 1999. These observations indicate that DLFs at Mts. Fuji and Iwate have common features in their activities and source mechanisms. But, shallow volcanic activities at these two volcanoes were much different: strong shallow seismic activity and volcano inflations as well as a new formation of fumarolic area were observed at Mt. Iwate, while such shallow activities were not detected at Mt. Fuji. Although it is still unknown what mechanisms control their magma supply systems, we may say that activation of DLF beneath active volcanoes does not always accompany magma intrusions in the shallow volcano edifice.

Confined Li ion migration in the silicon-graphene complex system: An ab initio investigation

NASA Astrophysics Data System (ADS)

Wang, Guoqing; Xu, Bo; Shi, Jing; Lei, Xueling; Ouyang, Chuying

2018-04-01

Silicon-Carbon complex systems play an important role in enhancing the performance of Si-based anode materials for Li ion batteries. In this work, the Li migration property of the Silicon-Graphene (Si-Gr) complex systems are investigated by using first-principles calculations. Especially, the effects of graphene coating on the migration of Li ions are discussed in detail. The distance between Si surface and graphene in the Si-Gr system significantly affects the lateral migration of Li ions. With the decrease of the distance from 4.715 to 3.844 Å, the energy barrier of Li ion migration also decreases from 0.115 to 0.067 eV, which are all lower than that of the case without graphene d(0.135 eV). However, smaller distance (3.586 Å) brings the high energy barrier (0.237 eV). Through AIMD calculations, it is found that the graphene coating in the Si-Gr complex system would result in the larger intercalation depths, more uniform distributions, and higher migration coefficients of Li ions. Further calculations of migration coefficients of Li ions at different temperature are used to obtained the activation energy for Li ions migration in the Si-Gr system, which is as low as 0.028 eV. This low activation energy shows that it is easy for Li ions migrating in the Si-Gr system. Our study provided the basically information to understand the migration mechanism of Li ions in Si-C system.

Depth distribution of radiocesium in Fukushima paddy fields and implications for ongoing decontamination works

NASA Astrophysics Data System (ADS)

Lepage, H.; Evrard, O.; Onda, Y.; Lefèvre, I.; Laceby, J. P.; Ayrault, S.

2014-09-01

Large quantities of radiocesium were deposited across a 3000 km2 area northwest of the Fukushima Dai-ichi nuclear power plant after the March 2011 accident. Although many studies have investigated the fate of radiocesium in soil in the months following the accident, the potential migration of this radioactive contaminant in rice paddy fields requires further examination after the typhoons that occurred in this region. Such investigations will help minimize potential human exposure in rice paddy fields or transfer of radioactive contaminants from soils to rice. Radionuclide activity concentrations and organic content were analysed in 10 soil cores sampled from paddy fields in November 2013, 20 km north of the Fukushima power plant. Our results demonstrate limited depth migration of radiocesium with the majority concentrated in the uppermost layers of soils (< 5 cm). More than 30 months after the accident, 81.5 to 99.7% of the total 137Cs inventories was still found within the < 5 cm of the soil surface, despite cumulative rainfall totalling 3300 mm. Furthermore, there were no significant correlations between radiocesium migration depth and total organic carbon content. We attributed the maximum depth penetration of 137Cs to maintenance (grass cutting - 97% of 137Cs in the upper 5 cm) and farming operations (tilling - 83% of 137Cs in the upper 5 cm). As this area is exposed to erosive events, ongoing decontamination works may increase soil erodibility. We therefore recommend the rapid removal of the uppermost - contaminated - layer of the soil after removing the vegetation to avoid erosion of contaminated material during the subsequent rainfall events. Remediation efforts should be concentrated on soils characterised by radiocesium activities > 10 000 Bq kg-1 to prevent the contamination of rice. Further analysis is required to clarify the redistribution of radiocesium eroded on river channels.

The diving behaviour of green turtles undertaking oceanic migration to and from Ascension Island: dive durations, dive profiles and depth distribution.

PubMed

Hays, G C; Akesson, S; Broderick, A C; Glen, F; Godley, B J; Luschi, P; Martin, C; Metcalfe, J D; Papi, F

2001-12-01

Satellite telemetry was used to record the submergence duration of green turtles (Chelonia mydas) as they migrated from Ascension Island to Brazil (N=12 individuals) while time/depth recorders (TDRs) were used to examine the depth distribution and dive profiles of individuals returning to Ascension Island to nest after experimental displacement (N=5 individuals). Satellite telemetry revealed that most submergences were short (<5 min) but that some submergences were longer (>20 min), particularly at night. TDRs revealed that much of the time was spent conducting short (2-4 min), shallow (approximately 0.9-1.5 m) dives, consistent with predictions for optimisation of near-surface travelling, while long (typically 20-30 min), deep (typically 10-20 m) dives had a distinctive profile found in other marine reptiles. These results suggest that green turtles crossing the Atlantic do not behave invariantly, but instead alternate between periods of travelling just beneath the surface and diving deeper. These deep dives may have evolved to reduce silhouetting against the surface, which would make turtles more susceptible to visual predators such as large sharks.

Fluid source inferred from strontium isotopes in pore fluid and carbonate recovered during Expedition 337 off Shimokita, Japan

NASA Astrophysics Data System (ADS)

Hong, W.; Moen, N.; Haley, B. A.

2013-12-01

IODP Expedition 337 was designed to understand the relationship between a deep-buried (2000 meters below seafloor) hydrocarbon reservoir off the Shimokita peninsula (Japan), and the microbial community that this carbon reservoir sustains at such depth. Understanding sources and pathways of flow of fluids that carry hydrocarbons, nutrients, and other reduced components is of particular interest to fulfilling the expedition objectives, since this migrating fluid supports microbial activity not only of the deep-seated communities but also to the shallow-dwelling organisms. To this aim, the concentration and isotopic signature of Sr can be valuable due to that it is relatively free from biogenic influence and pristine in terms of drill fluid contamination. From the pore water Sr profile, concentration gradually increases from 1500 to 2400 mbsf. The depth where highest Sr concentration is observed corresponds to the depths where couple layers of carbonate were observed. Such profile suggests an upward-migrating fluid carries Sr from those deep-seated carbonate layers (>2400 mbsf) to shallower sediments. To confirm this inference, pore water, in-situ formation fluid, and carbonate samples were analyzed for Sr isotopes to investigate the fluid source.

The use of a Phosphate-Based Migrating Corrosion Inhibitor to Repair Reinforced Concrete Elements Contaminated by Chlorides

NASA Astrophysics Data System (ADS)

Tittarelli, Francesca; Mobili, Alessandra; Bellezze, Tiziano

2017-08-01

The use of sodium monofluorophosphate (MFP) was experimented as migrator inhibiting treatment against corrosion of reinforced concrete elements induced by chlorides. The results show that sodium monofluorophosphate, applied by surface impregnation, is able to slow down reinforcement corrosion only for reinforcing steel bars with concrete cover not thicker than 1 cm. This limitation is most probably due to the difficulty, with the type of application adopted, in making MFP to reach concentrations high enough to inhibit the corrosive process at greater depths from the impregnation surface.

Detailed Crustal Geometry of the Continental Collision between India and Eurasia: Constraints from Deep Seismic Reflection Profiles across the Yarlung-Zangbo Suture, Tibet, at 88°E

NASA Astrophysics Data System (ADS)

Gao, R.; Li, W.; Guo, X.; Li, H.; Lu, Z.; He, R.; Zeng, L.; Klemperer, S. L.; Huang, X.

2016-12-01

The Tibetan plateau was created by continental collision between India and Eurasia and their ongoing convergence. The extent of subduction of Indian crust is central to our understanding the geodynamics of continental collision. However, owing to the lack of high-resolution data on the crustal-scale geometry of the Himalayan collision zone, the thickness of Indian crust subducting beneath the Yarlung-Zangbo Suture has been poorly known. Here we present two new deep seismic reflection profiles, respectively 100-km and 60-km long, across the central part of the Yarlung-Zangbo suture at c. 88°E (Figure 1). Seismic data processing used the CGG, ProMAX, and GeoEast systems. Processing included tomographic static correction, true-amplitude recovery, frequency analysis, filter-parameter tests, surface-consistent-amplitude corrections, surface-consistent deconvolution, coherent noise suppression, random noise attenuation, human-computer interactive velocity analysis, residual statics correction, Kirchhoff pre-stack time migration incorporating the rugged topography, and post-stack polynomial fitting to remove noise. Our two profiles both trace the Main Himalayan Thrust continuously from the mid-crust to deep beneath southern Tibet. Together with prominent Moho reflections at the base of the double-normal-thickness crust, the geometry of the subducting Indian crust is well defined. Both profiles image a limited extent of the Indian crust beneath southern Tibet and indicate that north-dipping Indian crust and south-dipping Lhasa crust converge beneath the Xietongmen region, above the remnant mantle suture. Figure 1. Geological map of the Xietongmen Region, south Tibet. The deep seismic reflection profile is shown as a solid red line, the location of big shots are shown as black stars.

Intimate Partner Violence and Forced Migration during Pregnancy: Structural Constraints to Women’s Agency

PubMed Central

Turan, Janet M.; Hatcher, Abigail M.; Romito, Patrizia; Mangone, Emily; Durojaiye, Modupeoluwa; Odero, Merab; Camlin, Carol S.

2015-01-01

Little is known about migration during pregnancy related to intimate partner violence (IPV). In this paper, we examine issues of agency in relation to pregnant women’s migrations in a high HIV prevalence area of Kenya. We qualitatively explored forced migration among pregnant women, using data from in-depth interviews, focus groups, and IPV screening forms. To quantitatively examine migration during pregnancy, we analyzed data from a prospective study of 614 pregnant women. The qualitative data revealed that women had varied responses to violence in pregnancy, with some being able to leave the marital home voluntarily as a strategy to escape violence. Others were ‘sent packing’ from their marital homes when they dared to exercise autonomy, in some cases related to HIV status. Quantitative analyses revealed that pregnant women who migrated were more educated, less likely to be living with a partner, and had fewer children than other women. Migration among pregnant women in Kenya illustrates the complexity of understanding women’s agency in the context of IPV. The findings indicate that there is not a dichotomy between “victim” and “agent”, but rather a complex dynamic between and within pregnant women, who may sequentially or simultaneously experience aspects of victimhood and/or agentic response. PMID:25996287

Travelling light: white sharks (Carcharodon carcharias) rely on body lipid stores to power ocean-basin scale migration

PubMed Central

Del Raye, Gen; Jorgensen, Salvador J.; Krumhansl, Kira; Ezcurra, Juan M.; Block, Barbara A.

2013-01-01

Many species undertake long-distance annual migrations between foraging and reproductive areas. Such migrants depend on the efficient packaging, storage and utilization of energy to succeed. A diverse assemblage of organisms accomplishes this through the use of lipid reserves; yet, it remains unclear whether the migrations of elasmobranchs, which include the largest gill breathers on Earth, depend on such a mechanism. We examine depth records from pop-up satellite archival tags to discern changes in buoyancy as a proxy for energy storage in Eastern Pacific white sharks, and assess whether lipid depletion fuels long-distance (approx. 4000 km) migrations. We develop new algorithms to assess body condition, buoyancy and drift rate during drift dives and validate the techniques using a captive white shark. In the wild, we document a consistent increase in drift rate over the course of all migrations, indicating a decrease in buoyancy caused by the depletion of lipid reserves. These results comprise, to our knowledge, the first assessment of energy storage and budgeting in migrating sharks. The methods provide a basis for further insights into using electronic tags to reveal the energetic strategies of a wide range of elasmobranchs. PMID:23864595

Pressure and temperature interactions on aerobic metabolism in migrating silver eels: results in vitro.

PubMed

Scaion, D; Vettier, A; Sébert, P

2008-01-01

The European eel (Anguilla anguilla) migrates (6000 km) from European coast towards the supposed spawning area: the Sargasso Sea. This intensive and sustained swimming activity is performed without feeding and by using essentially red muscle i.e. aerobic metabolism. Temperature and hydrostatic pressure vary during migration and have known effects on energy metabolism, mainly on mitochondrial functioning. We raise the question about the existence of a pressure-temperature combination that optimizes energy metabolism. We have measured the maximal oxygen consumption (MO2) of red muscle fibres of silver eel (migrating stage) in a temperature range (5 to 25 degrees C) covering what can be reasonably expected during the migration. We have combined (random order) three temperatures (5, 15, 25 degrees C) with 5 different pressures steps from 0.1 to 10.1 MPa (corresponding to depths from surface to 1000 m). The results show that when an adequate temperature is chosen as a reference, pressure effects and pressure sensitivity depend on the temperature. Based on the fact that energy budget is limited in migrating eels, we consider that the best conditions are low temperature and high pressure.

Migration, violence, and safety among migrant sex workers: a qualitative study in two Guatemalan communities.

PubMed

Rocha-Jiménez, Teresita; Brouwer, Kimberly C; Silverman, Jay G; Morales-Miranda, Sonia; Goldenberg, Shira M

2016-09-01

Despite reports of high levels of violence among women migrants in Central America, limited evidence exists regarding the health and safety of migrant sex workers in Central America. This study is based on 16 months of field research (November 2012-February 2014), including ethnographic fieldwork, in-depth interviews, and focus groups conducted with 52 internal and international migrant female sex workers in Tecún Umán and Quetzaltenango, Guatemala, key transit and destination communities for both international and internal migrants. The analysis explored migration-related determinants of susceptibility to violence experienced by migrant sex workers across different phases of migration. Violence in home communities and economic considerations were key drivers of migration. Unsafe transit experiences (eg undocumented border crossings) and negative interactions with authorities in destination settings (eg extortion) contributed to migrant sex workers' susceptibility to violence, while enhanced access to information on immigration policies and greater migration and sex work experience were found to enhance agency and resilience. Findings suggest the urgent need for actions that promote migrant sex workers' safety in communities of origin, transit, and destination, and programmes aimed at preventing and addressing human rights violations within the context of migration and sex work.

a Comparative Case Study of Reflection Seismic Imaging Method

NASA Astrophysics Data System (ADS)

Alamooti, M.; Aydin, A.

2017-12-01

Seismic imaging is the most common means of gathering information about subsurface structural features. The accuracy of seismic images may be highly variable depending on the complexity of the subsurface and on how seismic data is processed. One of the crucial steps in this process, especially in layered sequences with complicated structure, is the time and/or depth migration of seismic data.The primary purpose of the migration is to increase the spatial resolution of seismic images by repositioning the recorded seismic signal back to its original point of reflection in time/space, which enhances information about complex structure. In this study, our objective is to process a seismic data set (courtesy of the University of South Carolina) to generate an image on which the Magruder fault near Allendale SC can be clearly distinguished and its attitude can be accurately depicted. The data was gathered by common mid-point method with 60 geophones equally spaced along an about 550 m long traverse over a nearly flat ground. The results obtained from the application of different migration algorithms (including finite-difference and Kirchhoff) are compared in time and depth domains to investigate the efficiency of each algorithm in reducing the processing time and improving the accuracy of seismic images in reflecting the correct position of the Magruder fault.

Nurse migration and health workforce planning: Ireland as illustrative of international challenges.

PubMed

Humphries, Niamh; Brugha, Ruairi; McGee, Hannah

2012-09-01

Ireland began actively recruiting nurses internationally in 2000. Between 2000 and 2010, 35% of new recruits into the health system were non-EU migrant nurses. Ireland is more heavily reliant upon international nurse recruitment than the UK, New Zealand or Australia. This paper draws on in-depth interviews (N=21) conducted in 2007 with non-EU migrant nurses working in Ireland, a quantitative survey of non-EU migrant nurses (N=337) conducted in 2009 and in-depth interviews conducted with key stakeholders (N=12) in late 2009/early 2010. Available primary and secondary data indicate a fresh challenge for health workforce planning in Ireland as immigration slows and nurses (both non-EU and Irish trained) consider emigration. Successful international nurse recruitment campaigns obviated the need for health workforce planning in the short-term, however the assumption that international nurse recruitment had 'solved' the nursing shortage was short-lived and the current presumption that nurse migration (both emigration and immigration) will always 'work' for Ireland over-plays the reliability of migration as a health workforce planning tool. This article analyses Ireland's experience of international nurse recruitment 2000-2010, providing a case study which is illustrative of health workforce planning challenges faced internationally. Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.

Constrained Adherable Area of Nanotopographic Surfaces Promotes Cell Migration through the Regulation of Focal Adhesion via Focal Adhesion Kinase/Rac1 Activation.

PubMed

Lim, Jiwon; Choi, Andrew; Kim, Hyung Woo; Yoon, Hyungjun; Park, Sang Min; Tsai, Chia-Hung Dylan; Kaneko, Makoto; Kim, Dong Sung

2018-05-02

Cell migration is crucial in physiological and pathological processes such as embryonic development and wound healing; such migration is strongly guided by the surrounding nanostructured extracellular matrix. Previous studies have extensively studied the cell migration on anisotropic nanotopographic surfaces; however, only a few studies have reported cell migration on isotropic nanotopographic surfaces. We herein, for the first time, propose a novel concept of adherable area on cell migration using isotropic nanopore surfaces with sufficient nanopore depth by adopting a high aspect ratio. As the pore size of the nanopore surface was controlled to 200, 300, and 400 nm in a fixed center-to-center distance of 480 nm, it produced 86, 68, and 36% of adherable area, respectively, on the fabricated surface. A meticulous investigation of the cell migration in response to changes in the constrained adherable area of the nanotopographic surface showed 1.4-, 1.5-, and 1.6-fold increase in migration speeds and a 1.4-, 2-, and 2.5-fold decrease in the number of focal adhesions as the adherable area was decreased to 86, 68, and 36%, respectively. Furthermore, a strong activation of FAK/Rac1 signaling was observed to be involved in the promoted cell migration. These results suggest that the reduced adherable area promotes cell migration through decreasing the FA formation, which in turn upregulates FAK/Rac1 activation. The findings in this study can be utilized to control the cell migration behaviors, which is a powerful tool in the research fields involving cell migration such as promoting wound healing and tissue repair.

Health, migration and border management: analysis and capacity-building at Europe's borders.

PubMed

Hollings, Jennifer; Samuilova, Mariya; Petrova-Benedict, Roumyana

2012-04-01

Three key elements were analysed in Hungary, Poland and Slovakia as a basis for strengthening the capacity of staff and structures related to health, migration and border management: public health concerns linked to migration, health needs and rights of migrants and the occupational health of staff. This IOM project was implemented through an in-depth situation analysis as well as the development of training modules and public health guidelines. Findings indicate a paucity of existing data, gaps in the health care for migrants and few existing tools for border officials and health professionals. Sets of training modules were developed for each of these groups, including common modules on migration and the right to health and intercultural communication, as well as targeted health modules. The guidelines promote good practices in the context of border management and detention. The EU is working towards a common immigration policy and integrated border management; however, a harmonized approach to migration and health is still lacking. Further research and piloting of the developed materials is needed to fully establish an adaptable, common toolkit.

Validating proposed migration equation and parameters' values as a tool to reproduce and predict 137Cs vertical migration activity in Spanish soils.

PubMed

Olondo, C; Legarda, F; Herranz, M; Idoeta, R

2017-04-01

This paper shows the procedure performed to validate the migration equation and the migration parameters' values presented in a previous paper (Legarda et al., 2011) regarding the migration of 137 Cs in Spanish mainland soils. In this paper, this model validation has been carried out checking experimentally obtained activity concentration values against those predicted by the model. This experimental data come from the measured vertical activity profiles of 8 new sampling points which are located in northern Spain. Before testing predicted values of the model, the uncertainty of those values has been assessed with the appropriate uncertainty analysis. Once establishing the uncertainty of the model, both activity concentration values, experimental versus model predicted ones, have been compared. Model validation has been performed analyzing its accuracy, studying it as a whole and also at different depth intervals. As a result, this model has been validated as a tool to predict 137 Cs behaviour in a Mediterranean environment. Copyright © 2017 Elsevier Ltd. All rights reserved.

Safety and feasibility of breast lesion localization using magnetic seeds (Magseed): a multi-centre, open-label cohort study.

PubMed

Harvey, James R; Lim, Yit; Murphy, John; Howe, Miles; Morris, Julie; Goyal, Amit; Maxwell, Anthony J

2018-06-01

Wire localization has several disadvantages, notably wire migration and difficulty scheduling the procedure close to surgery. Radioactive seed localization overcomes these disadvantages, but implementation is limited due to radiation safety requirements. Magnetic seeds potentially offer the logistical benefits and transcutaneous detection equivalence of a radioactive seed, with easier implementation. This study was designed to evaluate the feasibility and safety of using magnetic seeds for breast lesion localization. A two-centre open-label cohort study to assess the feasibility and safety of magnetic seed (Magseed) localization of breast lesions. Magseeds were placed under radiological guidance into women having total mastectomy surgery. The primary outcome measure was seed migration distance. Secondary outcome measures included accuracy of placement, ease of transcutaneous detection, seed integrity and safety. Twenty-nine Magseeds were placed into the breasts of 28 patients under ultrasound guidance. There was no migration of the seeds between placement and surgery. Twenty-seven seeds were placed directly in the target lesion with the other seeds being 2 and 3 mm away. All seeds were detectable transcutaneously in all breast sizes and at all depths. There were no complications or safety issues. Magnetic seeds are a feasible and safe method of breast lesion localization. They can be accurately placed, demonstrate no migration in this feasibility study and are detectable in all sizes and depths of breast tissue. Now that safety and feasibility have been demonstrated, further clinical studies are required to evaluate the seed's effectiveness in wide local excision surgery.

Characterization of potential transport pathways and implications for groundwater management near an anticline in the Central Basin area, Los Angeles County, California

USGS Publications Warehouse

Ponti, Daniel J.; Wagner, Brian J.; Land, Michael; Landon, Matthew K.

2014-01-01

The Central Groundwater Basin (Central Basin) of southern Los Angeles County includes ~280 mi2 of the Los Angeles Coastal Plain and serves as the primary source of water for more than two million residents. In the Santa Fe Springs–Whittier–Norwalk area, located in the northeastern part of the basin, several sources of volatile organic compounds have been identified. The volatile organic compunds are thought to have contributed to a large, commingled contaminant plume in groundwater that extends south-southwest downgradient from the Omega Chemical Corporation Superfund Site across folded geologic strata, known as the Santa Fe Springs Anticline. A multifaceted study—that incorporated a three-dimensional sequence-stratigraphic geologic model, two-dimensional groundwater particle-tracking simulations, and new groundwater chemistry data—was conducted to gain insight into the geologic and hydrologic controls on contaminant migration in the study area and to assess the potential for this shallow groundwater contamination to migrate into producing aquifer zones. Conceptual flow models were developed along a flow-parallel cross section based on the modeled stratigraphic architecture, observed geochemistry, and numerical model simulations that generally agree with observed water levels and contaminant distributions. These models predict that contaminants introduced into groundwater at shallow depths near the Omega Chemical Corporation Superfund Site and along the study cross section will likely migrate downgradient to depths intercepted by public supply wells. These conclusions, however, are subject to limitations and simplifications inherent in the modeling approaches used, as well as a significant scarcity of available geologic and hydrogeochemical information at depth and in the downgradient parts of the study area.

Geology and habitat of oil in Ras Budran field, Gulf of Suez, Egypt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chowdhary, L.R.; Taha, S.

1987-10-01

The Ras Budran structure at the deepest mappable seismic reflector, the top of the Kareem Formation (middle Miocene), is a broad northeast-southwest-trending anticlinal feature with an anomalous strike nearly at right angles to the main Gulf of Suez trend. Oil is produced from three units of Nubian Formation sandstone from a depth of 11,000-12,000 ft (3352-3657 m). The lower unit of Paleozoic age averages 10% porosity and has up to 200 md in-situ permeability. Wells completed in this unit produce up to 2000 BOPD. In contrast, the sands to the upper two units of the Early Cretaceous have 15-20% porositymore » and up to 700 md permeability. Wells completed in this unit produce 6000-8000 BOPD. The Ras Budran structure was formed primarily during an intra-Rudeis tectonic phase (lower Miocene). Oil migration for accumulation in the structure started in the late Miocene or Pliocene when the Santonian Brown Limestone and the Eocene Thebes Formation, the main source beds in the Gulf of Suez, reached the threshold of oil generation at a burial depth of approximately 10,000 ft (3048 m). At this depth, the organic matter in the source beds had a high transformation ratio (0.10 to 0.15), high yields of C/sub 15+/ soluble organic matter and C/sub 15+/ saturated hydrocarbons, vitrinite reflectance (R/sub 0/) of 0.62%, and a time-temperature index (TTI) value of 15. Oil migration from mature source beds in adjoining lows into low-potential Nubian reservoirs is easily explained by fault planes that acted as conduits for oil migration. 16 figures, 3 tables.« less

Depth profiling of Pu, 241Am and 137Cs in soils from southern Belarus measured by ICP-MS and alpha and gamma spectrometry.

PubMed

Boulyga, Sergei F; Zoriy, Myroslav; Ketterer, Michael E; Becker, J Sabine

2003-08-01

The depth distribution of plutonium, americium, and 137Cs originating from the 1986 accident at the Chernobyl Nuclear Power Plant (NPP) was investigated in several soil profiles in the vicinity from Belarus. The vertical migration of transuranic elements in soils typical of the 30 km relocation area around Chernobyl NPP was studied using inductively coupled plasma mass spectrometry (ICP-MS), alpha spectrometry, and gamma spectrometry. Transuranic concentrations in upper soil layers ranged from 6 x 10(-12) g g(-1) to 6 x 10(-10) g g(-1) for plutonium and from 1.8 x 10(-13) g g(-1) to 1.6 x 10(-11) g g(-1) for americium. These concentrations correspond to specific activities of (239+240)Pu of 24-2400 Bq kg(-1) and specific activity of 241Am of 23-2000 Bq kg(-1), respectively. Transuranics in turf-podzol soil migrate slowly to the deeper soil layers, thus, 80-95%, of radionuclide inventories were present in the 0-3 cm intervals of turf-podzol soils collected in 1994. In peat-marsh soil migration processes occur more rapidly than in turf-podzol and the maximum concentrations are found beneath the soil surface (down to 3-6 cm). The depth distributions of Pu and Am are essentially identical for a given soil profile. (239+240)Pu/137Cs and 241Am/137Cs activity ratios vary by up to a factor of 5 at some sites while smaller variations in these ratios were observed at a site close to Chernobyl, suggesting that 137Cs is dominantly particle associated close to Chernobyl but volatile species of 137Cs are of relatively greater importance at the distant sites.

Distribution, abundance, and feeding ecology of decapods in the Arabian Sea, with implications for vertical flux

NASA Astrophysics Data System (ADS)

Mincks, Sarah L.; Bollens, Stephen M.; Madin, Laurence P.; Horgan, Erich; Butler, Mari; Kremer, Patricia M.; Craddock, James E.

Macrozooplankton and micronekton samples were collected on two cruises in the Arabian Sea conducted during the Spring Intermonsoon period (May) and the SW Monsoon period (August) of 1995. Discrete depth samples were collected down to depths of 1000-1500 m. Quantitative gut content analyses were performed on four species of decapod shrimps, Gennadas sordidus, Sergia filictum, Sergia creber, and Eupasiphae gilesii, as well as on the pelagic crab Charybdis smithii. Of the shrimps, only S. filictum and S. creber increased significantly in abundance between the Spring Intermonsoon and SW Monsoon seasons. These four species were found at all depths sampled, and most did not appear to be strong vertical migrators. G. sordidus and S. filictum did appear to spread upward at night, especially during the SW Monsoon, but this movement did not include the entire population. S. creber showed signs of diel vertical migration only in some areas. All four shrimp species except, to some degree, S. creber lived almost exclusively within the oxygen minimum zone (150-1000 m), and are likely to have respiratory adaptations that allow them to persist under such conditions. Feeding occurred at all depths throughout these species' ranges, but only modest feeding occurred in the surface layer (0-150 m). G. sordidus appeared to feed continuously throughout the day and night. Estimated contribution of fecal material to vertical flux ranged from <0.01-2.1% of particulate flux at 1000 m for the shrimps and 1.8-3.0% for C. smithii.

Migration Imaging of the Java Subduction Zones

NASA Astrophysics Data System (ADS)

Dokht, Ramin M. H.; Gu, Yu Jeffrey; Sacchi, Mauricio D.

2018-02-01

Imaging of tectonically complex regions can greatly benefit from dense network data and resolution enhancement techniques. Conventional methods in the analysis of SS precursors stack the waveforms to obtain an average discontinuity depth, but smearing due to large Fresnel zones can degrade the fine-scale topography on the discontinuity. To provide a partial solution, we introduce a depth migration algorithm based on the common scattering point method while considering nonspecular diffractions from mantle transition zone discontinuities. Our analysis indicates that, beneath the Sunda arc, the depth of the 410 km discontinuity (the 410) is elevated by 30 km and the 660 km discontinuity (the 660) is depressed by 20-40 km; the region of the strongest anticorrelation is correlated with the morphology of the subducting Indo-Australian slab. In eastern Java, a "flat" 410 coincides with a documented slab gap, showing length scales greater than 400 km laterally and 200 km vertically. This observation could be explained by the arrival of a buoyant oceanic plateau at the Java trench at approximately 8 Ma ago, which may have caused a temporary cessation of subduction and formed a tear in the subducting slab. Our results highlight contrasting depths of the 410 and 660 along the shallow-dipping slab below the Banda trench. The 660, however, becomes significantly uplifted beneath the Banda Sea, which is accompanied by enhanced reflection amplitudes. We interpret these observations as evidence for a subslab low-velocity zone, possibly related to the lower mantle upwelling beneath the subducting slab.

Locating the depth of magma supply for volcanic eruptions, insights from Mt. Cameroon

PubMed Central

Geiger, Harri; Barker, Abigail K.; Troll, Valentin R.

2016-01-01

Mt. Cameroon is one of the most active volcanoes in Africa and poses a possible threat to about half a million people in the area, yet knowledge of the volcano’s underlying magma supply system is sparse. To characterize Mt. Cameroon’s magma plumbing system, we employed mineral-melt equilibrium thermobarometry on the products of the volcano’s two most recent eruptions of 1999 and 2000. Our results suggest pre-eruptive magma storage between 20 and 39 km beneath Mt. Cameroon, which corresponds to the Moho level and below. Additionally, the 1999 eruption products reveal several shallow magma pockets between 3 and 12 km depth, which are not detected in the 2000 lavas. This implies that small-volume magma batches actively migrate through the plumbing system during repose intervals. Evolving and migrating magma parcels potentially cause temporary unrest and short-lived explosive outbursts, and may be remobilized during major eruptions that are fed from sub-Moho magma reservoirs. PMID:27713494

Locating the depth of magma supply for volcanic eruptions, insights from Mt. Cameroon.

PubMed

Geiger, Harri; Barker, Abigail K; Troll, Valentin R

2016-10-07

Mt. Cameroon is one of the most active volcanoes in Africa and poses a possible threat to about half a million people in the area, yet knowledge of the volcano's underlying magma supply system is sparse. To characterize Mt. Cameroon's magma plumbing system, we employed mineral-melt equilibrium thermobarometry on the products of the volcano's two most recent eruptions of 1999 and 2000. Our results suggest pre-eruptive magma storage between 20 and 39 km beneath Mt. Cameroon, which corresponds to the Moho level and below. Additionally, the 1999 eruption products reveal several shallow magma pockets between 3 and 12 km depth, which are not detected in the 2000 lavas. This implies that small-volume magma batches actively migrate through the plumbing system during repose intervals. Evolving and migrating magma parcels potentially cause temporary unrest and short-lived explosive outbursts, and may be remobilized during major eruptions that are fed from sub-Moho magma reservoirs.

Model Parameterization and P-wave AVA Direct Inversion for Young's Impedance

NASA Astrophysics Data System (ADS)

Zong, Zhaoyun; Yin, Xingyao

2017-05-01

AVA inversion is an important tool for elastic parameters estimation to guide the lithology prediction and "sweet spot" identification of hydrocarbon reservoirs. The product of the Young's modulus and density (named as Young's impedance in this study) is known as an effective lithology and brittleness indicator of unconventional hydrocarbon reservoirs. Density is difficult to predict from seismic data, which renders the estimation of the Young's impedance inaccurate in conventional approaches. In this study, a pragmatic seismic AVA inversion approach with only P-wave pre-stack seismic data is proposed to estimate the Young's impedance to avoid the uncertainty brought by density. First, based on the linearized P-wave approximate reflectivity equation in terms of P-wave and S-wave moduli, the P-wave approximate reflectivity equation in terms of the Young's impedance is derived according to the relationship between P-wave modulus, S-wave modulus, Young's modulus and Poisson ratio. This equation is further compared to the exact Zoeppritz equation and the linearized P-wave approximate reflectivity equation in terms of P- and S-wave velocities and density, which illustrates that this equation is accurate enough to be used for AVA inversion when the incident angle is within the critical angle. Parameter sensitivity analysis illustrates that the high correlation between the Young's impedance and density render the estimation of the Young's impedance difficult. Therefore, a de-correlation scheme is used in the pragmatic AVA inversion with Bayesian inference to estimate Young's impedance only with pre-stack P-wave seismic data. Synthetic examples demonstrate that the proposed approach is able to predict the Young's impedance stably even with moderate noise and the field data examples verify the effectiveness of the proposed approach in Young's impedance estimation and "sweet spots" evaluation.

Prediction of shale prospectivity from seismically-derived reservoir and completion qualities: Application to a shale-gas field, Horn River Basin, Canada

NASA Astrophysics Data System (ADS)

Mo, Cheol Hoon; Lee, Gwang H.; Jeoung, Taek Ju; Ko, Kyung Nam; Kim, Ki Soo; Park, Kyung-sick; Shin, Chang Hoon

2018-04-01

Prospective shale plays require a combination of good reservoir and completion qualities. Total organic carbon (TOC) is an important reservoir quality and brittleness is the most critical condition for completion quality. We analyzed seismically-derived brittleness and TOC to investigate the prospectivity of the Horn River Group shale (the Muskwa, Otter Park, Evie shales) of a shale-gas field in the western Horn River Basin, British Columbia, Canada. We used the λρ-μρ brittleness template, constructed from the mineralogy-based brittleness index (MBI) and elastic logs from two wells, to convert the λρ and μρ volumes from prestack seismic inversion to the volume for the brittleness petrotypes (most brittle, intermediate, and least brittle). The probability maps of the most brittle petrotype for the three shales were generated from Bayesian classification, based on the λρ-μρ template. The relationship between TOC and P-wave and S-wave velocity ratio (VP/VS) at the wells allowed the conversion of the VP/VS volume from prestack inversion to the TOC volume, which in turn was used to construct the TOC maps for the three shales. Increased TOC is correlated with high brittleness, contrasting with the commonly-held understanding. Therefore, the prospectivity of the shales in the study area can be represented by high brittleness and increased TOC. We propose a shale prospectivity index (SPI), computed by the arithmetic average of the normalized probability of the most brittle petrotype and the normalized TOC. The higher SPI corresponds to higher production rates in the Muskwa and Evie shales. The areas of the highest SPI have not been fully tested. The future drilling should be focused on these areas to increase the economic viability of the field.

Facies Modeling Using 3D Pre-Stack Simultaneous Seismic Inversion and Multi-Attribute Probability Neural Network Transform in the Wattenberg Field, Colorado

NASA Astrophysics Data System (ADS)

Harryandi, Sheila

The Niobrara/Codell unconventional tight reservoir play at Wattenberg Field, Colorado has potentially two billion barrels of oil equivalent requiring hundreds of wells to access this resource. The Reservoir Characterization Project (RCP), in conjunction with Anadarko Petroleum Corporation (APC), began reservoir characterization research to determine how to increase reservoir recovery while maximizing operational efficiency. Past research results indicate that targeting the highest rock quality within the reservoir section for hydraulic fracturing is optimal for improving horizontal well stimulation through multi-stage hydraulic fracturing. The reservoir is highly heterogeneous, consisting of alternating chalks and marls. Modeling the facies within the reservoir is very important to be able to capture the heterogeneity at the well-bore scale; this heterogeneity is then upscaled from the borehole scale to the seismic scale to distribute the heterogeneity in the inter-well space. I performed facies clustering analysis to create several facies defining the reservoir interval in the RCP Wattenberg Field study area. Each facies can be expressed in terms of a range of rock property values from wells obtained by cluster analysis. I used the facies classification from the wells to guide the pre-stack seismic inversion and multi-attribute transform. The seismic data extended the facies information and rock quality information from the wells. By obtaining this information from the 3D facies model, I generated a facies volume capturing the reservoir heterogeneity throughout a ten square mile study-area within the field area. Recommendations are made based on the facies modeling, which include the location for future hydraulic fracturing/re-fracturing treatments to improve recovery from the reservoir, and potential deeper intervals for future exploration drilling targets.

Life history of the deep-sea cephalopod family Histioteuthidae in the western Mediterranean

NASA Astrophysics Data System (ADS)

Quetglas, Antoni; de Mesa, Aina; Ordines, Francesc; Grau, Amàlia

2010-08-01

The life cycle of the two species of the deep-sea family Histioteuthidae inhabiting the Mediterranean Sea ( Histioteuthis reversa and Histioteuthis bonnellii) was studied from monthly samples taken throughout the year during daytime hours by bottom trawl gears. A small sample of individuals found floating dead on the sea surface was also analyzed. Both species were caught exclusively on the upper slope at depths greater than 300 m. Their frequency of occurrence increased with depth and showed two different peaks, at 500-600 m and 600-700 m depth in H. bonnellii and H. reversa, respectively, which might indicate spatial segregation. Maturity stages were assigned using macroscopic determination and confirmed with histological analyses. Although mature males were caught all year round, no mature females were found, which suggests that their sexual maturation in the western Mediterranean takes place deeper than the maximum depth sampled (800 m). In fact, the increase in mean squid size with increasing depth in H. reversa indicates an ontogenetic migration to deeper waters. The individuals of both species found floating dead on the sea surface were spent females which had a relatively large cluster of small atresic eggs and a small number of remaining mature eggs scattered in the ovary and mantle cavity. The sizes of these females were clearly larger than the largest individuals caught with bottom trawls. A total of 12 and 7 different types of prey, belonging to three major taxonomic groups (crustaceans, osteichthyes and cephalopods), were identified in the stomach contents of H. reversa and H. bonnellii, respectively. In both species fishes were by far the main prey followed by crustaceans, whereas cephalopods were found only occasionally. The preys identified, mainly myctophids and natantian crustaceans, indicate that both histioteuthids base their diet on pelagic nictemeral migrators.

Post-deposition early-phase migration and retention behavior of radiocesium in a litter-mineral soil system in a Japanese deciduous forest affected by the Fukushima nuclear accident.

PubMed

Koarashi, Jun; Nishimura, Syusaku; Nakanishi, Takahiro; Atarashi-Andoh, Mariko; Takeuchi, Erina; Muto, Kotomi

2016-12-01

The fate of radiocesium ( 137 Cs) derived from the Fukushima nuclear accident and associated radiation risks are largely dependent on its migration and retention behavior in the litter-soil system of Japanese forest ecosystems. However, this behavior has not been well quantified. We established field lysimeters in a Japanese deciduous broad-leaved forest soon after the Fukushima nuclear accident to continuously monitor the downward transfer of 137 Cs at three depths: the litter-mineral soil boundary and depths of 5 cm and 10 cm in the mineral soil. Observations were conducted at two sites within the forest from May 2011 to May 2015. Results revealed similar temporal and depth-wise variations in 137 Cs downward fluxes for both sites. The 137 Cs downward fluxes generally decreased year by year at all depths, indicating that 137 Cs was rapidly leached from the forest-floor litter layer and was then immobilized in the upper (0-5 cm) mineral soil layer through its interaction with clay minerals. The 137 Cs fluxes also showed seasonal variation, which was in accordance with variations in the throughfall and soil temperature at the sites. There was no detectable 137 Cs flux at a depth of 10 cm in the mineral soil in the third and fourth years after the accident. The decreased inventory of mobile (or bioavailable) 137 Cs observed during early stages after deposition indicates that the litter-soil system in the Japanese deciduous forest provides only a temporary source for 137 Cs recycling in plants. Copyright © 2016 Elsevier Ltd. All rights reserved.

Rhythmic behaviour of marine benthopelagic species and the synchronous dynamics of benthic communities

NASA Astrophysics Data System (ADS)

Aguzzi, Jacopo; Sbragaglia, Valerio; Tecchio, Samuele; Navarro, Joan; Company, Joan B.

2015-01-01

Light-intensity cycles drive the relentless motion of species in the oceans, and water column migrants may cyclically make contact with the seabed, hence influencing the temporal dynamism of benthic ecosystems. The influence of light on this process remains largely unknown to date. In this study, we focus on the occurrence of day-night changes in benthic communities on the western Mediterranean continental shelf (100 m depth) and slope (400 m depth) as a potential result of a behaviourally sustained benthopelagic coupling. We analysed fluctuations in species abundance based on trawling at hourly intervals over a 4-day period as a proxy of activity rhythms at the seabed. We also measured light in situ to assess how the depth-related decrease of its intensity influences species rhythms and the occurrence of the putative benthopelagic synchronisation. Temporal similarities in the catch patterns for different species were screened by dendrogram analysis. On the continental shelf, species performing diel migrations (i.e., over a 24 h period) that were either vertical (i.e., benthopelagic) or horizontal across depths (i.e., nektobenthic) clustered together separately from the more sedentary endobenthic and epibenthic species. At the same depth, waveform analysis showed a significant diurnal increase in the catch of water column species and benthic species at night. Such coupling was absent on the continental slope, where light intensity was several orders of magnitude lower than that on the shelf. Our data indicate that diel activity rhythms, which are well known for vertical pelagic migrators, are also evident in the benthos. We discuss the role of light as a major evolutionary driver shaping the composition and biodiversity of benthic communities via visual predation.

Ocean Heat Content Reveals Secrets of Fish Migrations

PubMed Central

Luo, Jiangang; Ault, Jerald S.; Shay, Lynn K.; Hoolihan, John P.; Prince, Eric D.; Brown, Craig A.; Rooker, Jay R.

2015-01-01

For centuries, the mechanisms surrounding spatially complex animal migrations have intrigued scientists and the public. We present a new methodology using ocean heat content (OHC), a habitat metric that is normally a fundamental part of hurricane intensity forecasting, to estimate movements and migration of satellite-tagged marine fishes. Previous satellite-tagging research of fishes using archival depth, temperature and light data for geolocations have been too coarse to resolve detailed ocean habitat utilization. We combined tag data with OHC estimated from ocean circulation and transport models in an optimization framework that substantially improved geolocation accuracy over SST-based tracks. The OHC-based movement track provided the first quantitative evidence that many of the tagged highly migratory fishes displayed affinities for ocean fronts and eddies. The OHC method provides a new quantitative tool for studying dynamic use of ocean habitats, migration processes and responses to environmental changes by fishes, and further, improves ocean animal tracking and extends satellite-based animal tracking data for other potential physical, ecological, and fisheries applications. PMID:26484541

Horizontal and vertical movements of Caribbean reef sharks (Carcharhinus perezi): conservation implications of limited migration in a marine sanctuary

PubMed Central

Howey, Lucy A.; Tolentino, Emily R.; Jordan, Lance K. B.; Ruppert, Jonathan L. W.; Brooks, Edward J.

2017-01-01

Despite the ecological and economic importance of the Caribbean reef shark (Carcharhinus perezi), little data exist regarding the movements and habitat use of this predator across its range. We deployed 11 pop-up satellite archival tags on Caribbean reef sharks captured in the northeast Exuma Sound, The Bahamas, to assess their horizontal and vertical movements throughout the water column. Sharks showed high site fidelity to The Bahamas suggesting Bahamian subpopulations remain protected within the Bahamian Shark Sanctuary. Depth data indicate that Caribbean reef sharks spent a significant proportion (72–91%) of their time above 50 m in narrow vertical depth bands, which varied considerably on an individual basis. This may be indicative of high site fidelity to specific bathymetric features. Animals exhibited three broadly categorized sporadic off-bank excursions (more than 50 m excursions) down to a depth of 436.1 m, which were more frequent during the night. These deeper excursions during night may be indicative of foraging in relation to prey on mesophotic reefs, as well as diel-vertically migrating prey from the deeper meso- and bathypelagic zones. These vertical movements suggest that Caribbean reef sharks can be significant vectors of ecosystem connectivity further warranting holistic multi-system management and conservation approaches. PMID:28386422

A molecular and isotopic study of the organic matter from the Paris Basin, France

NASA Technical Reports Server (NTRS)

Lichtfouse, E.; Albrecht, P.; Behar, F.; Hayes, J. M.

1994-01-01

Thirteen Liassic sedimentary rocks of increasing depth and three petroleums from the Paris Basin were studied for 13C/12C isotopic compositions and biological markers, including steranes, sterenes, methylphenanthrenes, methylanthracenes, and triaromatic steroids. The isotopic compositions of n-alkanes from mature sedimentary rocks and petroleums fall in a narrow range (2%), except for the deepest Hettangian rock and the Trias petroleum, for which the short-chain n-alkanes are enriched and depleted in 13C, respectively. Most of the molecular parameters increase over the 2000-2500 m depth range, reflecting the transformation of the organic matter at the onset of petroleum generation. In this zone, carbonate content and carbon isotopic composition of carbonates, as well as molecular parameters, are distinct for the Toarcian and Hettangian source rocks and suggest a migration of organic matter from these two formations. Two novel molecular parameters were defined for this task: one using methyltriaromatic steroids from organic extracts; the other using 1-methylphenanthrene and 2-methylanthracene from kerogen pyrolysates. The anomalous high maturity of the Dogger petroleum relative to the maturity-depth trend of the source rocks is used to estimate the minimal vertical distance of migration of the organic matter from the source rock to the reservoir.

Horizontal and vertical movements of Caribbean reef sharks (Carcharhinus perezi): conservation implications of limited migration in a marine sanctuary.

PubMed

Shipley, Oliver N; Howey, Lucy A; Tolentino, Emily R; Jordan, Lance K B; Ruppert, Jonathan L W; Brooks, Edward J

2017-02-01

Despite the ecological and economic importance of the Caribbean reef shark ( Carcharhinus perezi ), little data exist regarding the movements and habitat use of this predator across its range. We deployed 11 pop-up satellite archival tags on Caribbean reef sharks captured in the northeast Exuma Sound, The Bahamas, to assess their horizontal and vertical movements throughout the water column. Sharks showed high site fidelity to The Bahamas suggesting Bahamian subpopulations remain protected within the Bahamian Shark Sanctuary. Depth data indicate that Caribbean reef sharks spent a significant proportion (72-91%) of their time above 50 m in narrow vertical depth bands, which varied considerably on an individual basis. This may be indicative of high site fidelity to specific bathymetric features. Animals exhibited three broadly categorized sporadic off-bank excursions (more than 50 m excursions) down to a depth of 436.1 m, which were more frequent during the night. These deeper excursions during night may be indicative of foraging in relation to prey on mesophotic reefs, as well as diel-vertically migrating prey from the deeper meso- and bathypelagic zones. These vertical movements suggest that Caribbean reef sharks can be significant vectors of ecosystem connectivity further warranting holistic multi-system management and conservation approaches.

Migrating pattern of deformation prior to the Tohoku-Oki earthquake revealed by GRACE data

NASA Astrophysics Data System (ADS)

Panet, Isabelle; Bonvalot, Sylvain; Narteau, Clément; Remy, Dominique; Lemoine, Jean-Michel

2018-05-01

Understanding how and when far-field continuous motions lead to giant subduction earthquakes remains a challenge. An important limitation comes from an incomplete description of aseismic mass fluxes at depth along plate boundaries. Here we analyse Earth's gravity field variations derived from GRACE satellite data in a wide space-time domain surrounding the Mw 9.0 2011 Tohoku-Oki earthquake. We show that this earthquake is the extreme expression of initially silent deformation migrating from depth to the surface across the entire subduction system. Our analysis indeed reveals large-scale gravity and mass changes throughout three tectonic plates and connected slabs, starting a few months before March 2011. Before the Tohoku-Oki earthquake rupture, the gravity variations can be explained by aseismic extension of the Pacific plate slab at mid-upper mantle depth, concomitant with increasing seismicity in the shallower slab. For more than two years after the rupture, the deformation propagated far into the Pacific and Philippine Sea plate interiors, suggesting that subduction accelerated along 2,000 km of the plate boundaries in March 2011. This gravitational image of the earthquake's long-term dynamics provides unique information on deep and crustal processes over intermediate timescales, which could be used in seismic hazard assessment.

Characterizing Lithospheric Thickness in Australia using Ps and Sp Scattered Waves

NASA Astrophysics Data System (ADS)

Ford, H. A.; Fischer, K. M.; Rychert, C. A.

2008-12-01

The purpose of this study is to constrain the morphology of the lithosphere-asthenosphere boundary throughout Australia using scattered waves. Prior surface wave studies have shown a correlation between lithospheric thickness and the three primary geologic provinces of Australia, with the shallowest lithosphere located beneath the Phanerozoic province to the east, and the thicker lithosphere located beneath the Proterozoic and Archean regions. To determine lithospheric thickness, waveform data from twenty permanent broadband stations spanning mainland Australia and the island of Tasmania were analyzed using Ps and Sp migration techniques. Waveform selection for each station was based on epicentral distance (35° to 80° for Ps and 55° to 80° for Sp), and event depth (no greater than 300 km for Sp). For both Ps and Sp a simultaneous deconvolution was performed on the data for each of the twenty stations, and the resulting receiver function for each station was migrated to depth. Data were binned with epicentral distance to differentiate direct discontinuity phases from crustal reverberations (for Ps) and other teleseismic arrivals (for Sp). Early results in both Ps and Sp show a clear Moho discontinuity at most stations in addition to sharp, strong crustal reverberations seen in many of the Ps images. In the eastern Phanerozoic province, a strong negative phase at 100-105 km is evident in Ps for stations CAN and EIDS. The negative phase lies within a depth range that corresponds to the negative velocity gradient between fast lithosphere and slow asthenosphere imaged by surface waves. We therefore think that it is the lithosphere- asthenosphere boundary. On the island of Tasmania, a negative phase at 70-75 km in Ps images at stations TAU and MOO also appears to be the lithosphere-asthenosphere boundary. In the Proterozoic and Archean regions of the Australian continent, initial results for both Ps and Sp migration indicate clear crustal phases, but significantly more complicated signals at mantle depths. However, at some stations along the southern edge of the thick sub-cratonic lithosphere (previously imaged by surface waves) phases exist which may represent a lithosphere-asthenosphere boundary at depths of 110-115 km. Constraining the relationship of lithospheric thickness to the age and tectonic history of the overlying crust in Australia is important for better understanding the long term evolution of the continent.

Induced migration of endothelial cells into 3D scaffolds by chemoattractants secreted by pro-inflammatory macrophages in situ.

PubMed

Li, Xuguang; Dai, Yuankun; Shen, Tao; Gao, Changyou

2017-06-01

Cell migration in scaffolds plays a crucial role in tissue regeneration, which can better mimic cell behaviors in vivo . In this study, a novel model has been proposed on controlling 3D cell migration in porous collagen-chitosan scaffolds with various pore structures under the stimulation of inflammatory cells to mimic the angiogenesis process. Endothelial cells (ECs) cultured atop the scaffolds in the Transwell molds which were placed into a well of a 24-well culture plate were promoted to migrate into the scaffolds by chemoattractants such as vascular endothelial growth factor (VEGF) and tumor necrosis factor-alpha (TNF-α) secreted by the pro-inflammatory macrophages incubated in the well culture plate. The phenotype of macrophages was mediated by 50 ng/ml interferon-gamma (IFN-γ) and different concentrations of lipopolysaccharide (LPS, 150-300 ng/ml). The cell migration depth had a positive correlation with LPS concentration, and thereby the TNF-α concentration. The ECs migrated easier to a deeper zone of the scaffolds prepared at - 10ºC (187 μm in pore diameter) than that at - 20ºC (108 μm in pore diameter) as well. The method provides a useful strategy to study the 3D cell migration, and is helpful to reveal the vascularization process during wound healing in the long run.

Induced migration of endothelial cells into 3D scaffolds by chemoattractants secreted by pro-inflammatory macrophages in situ

PubMed Central

Li, Xuguang; Dai, Yuankun; Shen, Tao

2017-01-01

Abstract Cell migration in scaffolds plays a crucial role in tissue regeneration, which can better mimic cell behaviors in vivo. In this study, a novel model has been proposed on controlling 3D cell migration in porous collagen-chitosan scaffolds with various pore structures under the stimulation of inflammatory cells to mimic the angiogenesis process. Endothelial cells (ECs) cultured atop the scaffolds in the Transwell molds which were placed into a well of a 24-well culture plate were promoted to migrate into the scaffolds by chemoattractants such as vascular endothelial growth factor (VEGF) and tumor necrosis factor-alpha (TNF-α) secreted by the pro-inflammatory macrophages incubated in the well culture plate. The phenotype of macrophages was mediated by 50 ng/ml interferon-gamma (IFN-γ) and different concentrations of lipopolysaccharide (LPS, 150–300 ng/ml). The cell migration depth had a positive correlation with LPS concentration, and thereby the TNF-α concentration. The ECs migrated easier to a deeper zone of the scaffolds prepared at − 10ºC (187 μm in pore diameter) than that at − 20ºC (108 μm in pore diameter) as well. The method provides a useful strategy to study the 3D cell migration, and is helpful to reveal the vascularization process during wound healing in the long run. PMID:28596912

Cross-shelf transport of pink shrimp larvae: Interactions of tidal currents, larval vertical migrations and internal tides

USGS Publications Warehouse

Criales, Maria M.; Browder, Joan A.; Mooers, C.N.K.; Robblee, M.B.; Cardenas, H.; Jackson, Thomas L.

2007-01-01

Transport and behavior of pink shrimp Farfantepenaeus duorarum larvae were investigated on the southwestern Florida (SWF) shelf of the Gulf of Mexico between the Dry Tortugas spawning grounds and Florida Bay nursery grounds. Stratified plankton samples and hydrographic data were collected at 2 h intervals at 3 stations located on a cross-shelf transect. At the Marquesas station, midway between Dry Tortugas and Florida Bay, internal tides were recognized by anomalously cool water, a shallow thermocline with strong density gradients, strong current shear, and a high concentration of pink shrimp larvae at the shallow thermocline. Low Richardson numbers occurred at the pycnocline depth, indicating vertical shear instability and possible turbulent transport from the lower to the upper layer where myses and postlarvae were concentrated. Analysis of vertically stratified plankton suggested that larvae perform vertical migrations and the specific behavior changes ontogenetically; protozoeae were found deeper than myses, and myses deeper than postlarvae. Relative concentrations of protozoea in the upper, middle and bottom layers were consistent with a diel vertical migration, whereas that of postlarvae and myses were consistent with the semidiurnal tides in phase with the flood tide. Postlarvae, the shallowest dwellers that migrate with a semidiurnal periodicity, experienced the largest net onshore flux and larval concentrations were highly correlated with the cross-shelf current. These results provide the first evidence of an onshore tidal transport (a type of selective tidal stream transport, STST), in decapod larvae migrating in continental shelf waters offshore, ca. 100 km from the coast and at a depth of 20 m, while approaching the coastal nursery grounds. Longer time series would be necessary to establish whether internal tides play any role in the larval onshore transport of this species and determine if the STST is the dominant onshore transport mechanism.

40 CFR 265.280 - Closure and post-closure.

Code of Federal Regulations, 2013 CFR

2013-07-01

..., including amount, frequency, and pH of precipitation; (5) Geological and soil profiles and surface and subsurface hydrology of the site, and soil characteristics, including cation exchange capacity, total organic..., concentration, and depth of migration of hazardous waste constituents in the soil as compared to their...

40 CFR 265.280 - Closure and post-closure.

Code of Federal Regulations, 2012 CFR

2012-07-01

..., including amount, frequency, and pH of precipitation; (5) Geological and soil profiles and surface and subsurface hydrology of the site, and soil characteristics, including cation exchange capacity, total organic..., concentration, and depth of migration of hazardous waste constituents in the soil as compared to their...

40 CFR 265.280 - Closure and post-closure.

Code of Federal Regulations, 2014 CFR

2014-07-01

..., including amount, frequency, and pH of precipitation; (5) Geological and soil profiles and surface and subsurface hydrology of the site, and soil characteristics, including cation exchange capacity, total organic..., concentration, and depth of migration of hazardous waste constituents in the soil as compared to their...

40 CFR 265.280 - Closure and post-closure.

Code of Federal Regulations, 2010 CFR

2010-07-01

..., including amount, frequency, and pH of precipitation; (5) Geological and soil profiles and surface and subsurface hydrology of the site, and soil characteristics, including cation exchange capacity, total organic..., concentration, and depth of migration of hazardous waste constituents in the soil as compared to their...

40 CFR 265.280 - Closure and post-closure.

Code of Federal Regulations, 2011 CFR

2011-07-01

..., including amount, frequency, and pH of precipitation; (5) Geological and soil profiles and surface and subsurface hydrology of the site, and soil characteristics, including cation exchange capacity, total organic..., concentration, and depth of migration of hazardous waste constituents in the soil as compared to their...

Peridote-water interaction generating migration pathways of H2-rich fluids in subduction context: Common processes in the ophiolites of Oman, New-Caledonia, Philippines and Turkey

NASA Astrophysics Data System (ADS)

Deville, E. P.; Prinzhofer, A.; Pillot, D.; Vacquand, C.; Sissmann, O.

2010-12-01

The occurrence of H2 flows which were punctually known notably in the ophiolites of Oman, Zambales (Philippines) and Antalya (Turkey) appears to be a widespread phenomenon in these major peridotite massifs associated with ancient or active subduction processes. Similar H2-rich gas flows have been discovered also in the peridotite of New-Caledonia. H2 concentrations are locally high (commonly 60 to90% in Oman). H2 is frequently degassing in hyperalkaline springs but the highest flows were found directly expelled from fractures in the peridotites. Obviously, within the fracture systems, gas and associated hyperalkaline water separate at shallow depth close to the top of the upper aquifer level. Locally high flows of gas migrate vertically in the fractures, whereas water with degassing H2 tends to migrate laterally in the fracture network toward the creeks where most of the hyperalkaline springs are found. The genesis of natural H2 is interpreted as the result of the interaction, at depth, between ultrabasic mantle rocks in the upper plate and water expelled by the subducted sediments by oxidation of metals (Fe2+, Mn2+) and reduction of water during serpentinisation. CH4 is commonly associated to the H2-rich fluids and it is interpreted as the result of the reduction of available CO2 at depth. N2 is also commonly associated to the H2-rich fluids in the ophiolites, whereas N2 flows (within H2) were found in the subducted sediments (below the sole décollement of the peridotite) where it can be observed (Oman and New-Caledonia). Within the peridotites, the hyperalkaline water is rich in ions OH- and Ca2+ and characterized by high pH (between 11 and 12). Most alkaline springs are found in the vicinity of major faults and/or lithological discontinuities like the basal décollement of the ophiolites and the peridotite-gabbro contact (Moho). This hyperalkaline water migration induces a chain of diagenetic reactions starting at depth within the fracture systems by the precipitation of Mg-carbonates (dolomite, magnesite) and continuing up to the surface where it leads mostly to the precipitation of Ca-carbonates (calcite, aragonite), and brucite. This chain of diagenetic reactions is associated with the capture and sequestration of the atmospheric CO2 during the precipitation of the carbonates.

Ring-Shaped Microlanes and Chemical Barriers as a Platform for Probing Single-Cell Migration.

PubMed

Schreiber, Christoph; Segerer, Felix J; Wagner, Ernst; Roidl, Andreas; Rädler, Joachim O

2016-05-31

Quantification and discrimination of pharmaceutical and disease-related effects on cell migration requires detailed characterization of single-cell motility. In this context, micropatterned substrates that constrain cells within defined geometries facilitate quantitative readout of locomotion. Here, we study quasi-one-dimensional cell migration in ring-shaped microlanes. We observe bimodal behavior in form of alternating states of directional migration (run state) and reorientation (rest state). Both states show exponential lifetime distributions with characteristic persistence times, which, together with the cell velocity in the run state, provide a set of parameters that succinctly describe cell motion. By introducing PEGylated barriers of different widths into the lane, we extend this description by quantifying the effects of abrupt changes in substrate chemistry on migrating cells. The transit probability decreases exponentially as a function of barrier width, thus specifying a characteristic penetration depth of the leading lamellipodia. Applying this fingerprint-like characterization of cell motion, we compare different cell lines, and demonstrate that the cancer drug candidate salinomycin affects transit probability and resting time, but not run time or run velocity. Hence, the presented assay allows to assess multiple migration-related parameters, permits detailed characterization of cell motility, and has potential applications in cell biology and advanced drug screening.

Migration, violence, and safety among migrant sex workers: A qualitative study in two Guatemalan communities

PubMed Central

Rocha-Jiménez, Teresita; Brouwer, Kimberly C.; Silverman, Jay G.; Morales-Miranda, Sonia

2016-01-01

Despite reports of high levels of violence among women migrants in Central America, limited evidence exists regarding the health and safety of migrant sex workers in Central America. This study is based on 16 months of field research (November 2012–February 2015), including ethnographic fieldwork, in-depth interviews, and focus groups conducted with 52 internal and international migrant female sex workers in Tecún Úman and Quetzaltenango, Guatemala, key transit and destination communities for both international and internal migrants. The analysis explored migration-related determinants of susceptibility to violence experienced by migrant sex workers across different phases of migration. Violence in home communities and economic considerations were key drivers of migration. Unsafe transit experiences (e.g., undocumented border crossings) and negative interactions with authorities in destination settings (e.g., extortion) contributed to migrant sex workers’ susceptibility to violence, while enhanced access to information on immigration policies and greater migration and sex work experience were found to enhance agency and resilience. Findings suggest an urgent need for actions that promote migrant sex workers’ safety in communities of origin, transit, and destination, and programmes aimed at preventing and addressing human rights violations within the context of migration and sex work. PMID:27439656

Dynamics of cells function on laser cell-chip system

NASA Astrophysics Data System (ADS)

Kushibiki, Toshihiro; Sano, Tomoko; Ishii, Katsunori; Yoshihashi-Suzuki, Sachiko; Awazu, Kunio

2006-02-01

A new type of cell-cultivation system based on laser processing has been developed for the on-chip cultivation of living cells. We introduce a "laser cell-chip", on which migration of cells, such as stem cells, tumor cells or immunocompetent cells, can be observed. A sheet prepared from epoxy resin was processed by KrF excimer laser (248 nm, 1.6 J/cm2) for preparation of microgrooved surfaces with various groove width, spacing, and depth. A laser cell-chip can make kinetic studies of cell migration depending on the concentration gradient of a chemoattractant. In this study, megakaryocytes were used for the migration on a groove of laser cell-chip by the concentration gradient of the stromal cell derived factor 1 (SDF-1/CXCL12). SDF-1/CXCL12 plays an important and unique role in the regulation of stem/progenitor cell trafficking. A megakaryocyte was migrated on a groove of laser cell-chip depending on the optical concentration gradient of SDF-1/CXCL12. Since SDF-1/CXCL12-induced migration of mature megakaryocyte was known to increase the platelet production in the bone marrow extravascular space, the diagnosis of cell migration on laser cell-chip could provide a new strategy to potentially reconstitute hematopoiesis and avoid life-threatening hemorrhage after myelosuppression or bone marrow failure.

Transfer of fallout radionuclides derived from Fukushima NPP accident: 1 year study on transfer of radionuclides through geomorphic processes

NASA Astrophysics Data System (ADS)

Onda, Y.; Kato, H.; Fukushima, T.; Wakahara, T.; Kita, K.; Takahashi, Y.; Sakaguchi, A.; Tanaka, K.; Yamashiki, Y.; Yoshida, N.

2012-12-01

After the Fukushima Daiichi Nuclear Power Plant acciden, fallout radionuclides on the ground surface will transfer through geomorphic processes. Therefore, in order to estimate future changes in radionuclide deposition, migration process of radionuclides in forests, soils, ground water, rivers, and entrainment from trees and soils should be confirmed. We (FMWSE group) was funded by MEXT, Japanese government, and 1 year following monitoring has been conducted about 1 year. 1 Migration study of radionuclides in natural environment including forests and rivers 1) Study on depth distribution of radiocaesium in soils within forests, fields, and grassland. 2) Confirmation of radionuclide distribution and investigation on migration in forests. 3) Study on radionuclide migration due to soil erosion under different land use. 4) Measurement of radionuclides entrained from natural environment including forests and soils. 2 Migration study of radionuclides through hydrological cycle such as soil water, rivers, lakes and ponds, ground water. 1) Investigation on radionuclide migration through soil water, ground water, stream water, spring water under different land use. 2) Study on paddy-to-river transfer of radionuclides through suspended sediment. 3) Study on river-to-ocean transfer of radionuclides via suspended sediment. 4) Confirmation of radionuclide deposition in ponds and reservoirs. We will present how and where the fallout radionulides transfter through geomorphic processes.

Polarizability of Six-Helix Bundle and Triangle DNA Origami and Their Escape Characteristics from a Dielectrophoretic Trap.

PubMed

Gan, Lin; Camacho-Alanis, Fernanda; Ros, Alexandra

2015-12-15

DNA nanoassemblies, such as DNA origamis, hold promise in biosensing, drug delivery, nanoelectronic circuits, and biological computing, which require suitable methods for migration and precision positioning. Insulator-based dielectrophoresis (iDEP) has been demonstrated as a powerful migration and trapping tool for μm- and nm-sized colloids as well as DNA origamis. However, little is known about the polarizability of origami species, which is responsible for their dielectrophoretic migration. Here, we report the experimentally determined polarizabilities of the six-helix bundle origami (6HxB) and triangle origami by measuring the migration times through a potential landscape exhibiting dielectrophoretic barriers. The resulting migration times correlate to the depth of the dielectrophoretic potential barrier and the escape characteristics of the origami according to an adapted Kramer's rate model, allowing their polarizabilities to be determined. We found that the 6HxB polarizability is larger than that of the triangle origami, which correlates with the variations in charge density of both origamis. Further, we discuss the orientation of both origami species in the dielectrophoretic trap and discuss the influence of diffusion during the escape process. Our study provides detailed insight into the factors contributing to the migration through dielectrophoretic potential landscapes, which can be exploited for applications with DNA and other nanoassemblies based on dielectrophoresis.

Space-time migration patterns and risk of HIV acquisition in rural South Africa

PubMed Central

Dobra, Adrian; Bärnighausen, Till; Vandormael, Alain; Tanser, Frank

2017-01-01

Objective: To quantify the space-time dimensions of human mobility in relationship to the risk of HIV acquisition. Methods: We used data from the population cohort located in a high HIV prevalence, rural population in KwaZulu-Natal, South Africa (2000–2014). We geolocated 8006 migration events (representing 1 028 782 km traveled) for 17 743 individuals (≥15 years of age) who were HIV negative at baseline and followed up these individuals for HIV acquisition (70 395 person-years). Based on the complete geolocated residential history of every individual in this cohort, we constructed two detailed time-varying migration indices. We then used interval-censored Cox proportional hazards models to quantify the relationship between the migration indices and the risk of HIV acquisition. Results: In total, 17.4% of participants migrated at least once outside the rural study community during the period of observation (median migration distance = 107.1 km, interquartile range 18.9–387.5). The two migration indices were highly predictive of hazard of HIV acquisition (P < 0.01) in both men and women. Holding other factors equal, the risk of acquiring HIV infection increased by 50% for migration distances of 40 km (men) and 109 km (women). HIV acquisition risk also increased by 50% when participants spent 44% (men) and 90% (women) of their respective time outside the rural study community. Conclusion: This in-depth analysis of a population cohort in a rural sub-Saharan African population has revealed a clear nonlinear relationship between distance migrated and HIV acquisition. Our findings show that even relatively short-distance migration events confer substantial additional risk of acquisition. PMID:27755099

Heavy metal migration in soils and rocks at historical smelting sites.

PubMed

Maskall, J; Whitehead, K; Thornton, I

1995-09-01

The vertical migration of metals through soils and rocks was investigated at five historical lead smelting sites ranging in age between 220 and 1900 years. Core samples were taken through metal-contaminated soils and the underlying strata. Concentration profiles of lead and zinc are presented from which values for the distances and rates of migration have been derived. Slag-rich soil horizons contain highly elevated metal concentrations and some contamination of underlying strata has occurred at all sites. However, the amounts of lead and zinc that have migrated from soils and been retained at greater depths are comparatively low. This low metal mobility in contaminated soils is partly attributed to the elevation of soil pH by the presence of calcium and carbonate originating from slag wastes and perhaps gangue minerals. Distances and rates of vertical migration were higher at those sites with soils underlain by sandstone than at those with soils underlain by clay. For sites with the same parent material, metal mobility appears to be increased at lower soil pH. The mean migration rates for lead and zinc reach maxima of 0.75 and 0.46 cm yr(-1) respectively in sandstone at Bole A where the elements have moved mean distances of 4.3 and 2.6 m respectively. There is some evidence that metal transport in the sandstone underlying Bole A and Cupola B occurs preferentially along rock fractures. The migration of lead and zinc is attenuated by subsurface clays leading to relatively low mean migration rates which range from 0.03 to 0.31 cm yr(-1) with many values typical of migration solely by diffusion. However, enhanced metal migration in clays at Cupola A suggest a preferential transport mechanism possibly in cracks or biopores.

How biophysical interactions associated with sub- and mesoscale structures and migration behavior affect planktonic larvae of the spiny lobster in the Juan Fernández Ridge: A modeling approach

NASA Astrophysics Data System (ADS)

Medel, Carolina; Parada, Carolina; Morales, Carmen E.; Pizarro, Oscar; Ernst, Billy; Conejero, Carlos

2018-03-01

The Juan Fernández Ridge (JFR) is a chain of topographical elevations in the eastern South Pacific (∼33-35°S, 76-81.5°W). Rich in endemic marine species, this ridge is frequently affected by the arrival of mesoscale eddies originating in the coastal upwelling zone off central-southern Chile. The impacts of these interactions on the structure and dynamics of the JFR pelagic system have, however, not been addressed yet. The present model-based study is focused on the coupled influence of mesoscale-submesoscale processes and biological behavior (i.e., diel vertical migration) on the horizontal distribution of planktonic larvae of the spiny lobster (Jasus frontalis) around the JFR waters. Two case studies were selected from a hydrodynamic Regional Ocean Modeling System to characterize mesoscale and submesoscale structures and an Individual-based model (IBM) to simulate diel vertical migration (DVM) and its impact on the horizontal distribution and the patchiness level. DVM behavior of these larvae has not been clearly characterized, therefore, three types of vertical mechanisms were assessed on the IBM: (1) no migration (LG), (2) a short migration (0-50 m depth, DVM1), and (3) a long migration (10-200 m depth, DVM2). The influence of physical properties (eddy kinetic energy, stretching deformation and divergence) on larval aggregation within meso and submesoscale features was quantified. The patchiness index assessed for mesoscale and submesoscale structures showed higher values in the mesoscale than in the submesoscale. However, submesoscale structures revealed a higher accumulation of particles by unit of area. Both vertical migration mechanisms produced larger patchiness indices compared to the no migration experiment. DVM2 was the one that showed by far the largest aggregation of almost all the aggregation zones. Larval concentrations were highest in the submesoscale structures; these zones were characterized by low eddy kinetic energy, negative stretching deformation, and slight convergence. Stretching deformation flow appeared to be triggered by the eddy-eddy interactions and the Robinson Island barrier effect, and it likely promotes the aggregation of the spiny lobster larvae in the Juan Fernández system. These results highlighted the importance of the coupled effect of physical (mesoscale and submesoscale oceanographic features) and biological processes (DVM) in the generation of larval patchiness and concentration of spiny lobster larvae around the JFR, which could be key for their survival and retention in those waters.

Oxygen minimum zone: An important oceanographic habitat for deep-diving northern elephant seals, Mirounga angustirostris.

PubMed

Naito, Yasuhiko; Costa, Daniel P; Adachi, Taiki; Robinson, Patrick W; Peterson, Sarah H; Mitani, Yoko; Takahashi, Akinori

2017-08-01

Little is known about the foraging behavior of top predators in the deep mesopelagic ocean. Elephant seals dive to the deep biota-poor oxygen minimum zone (OMZ) (>800 m depth) despite high diving costs in terms of energy and time, but how they successfully forage in the OMZ remains largely unknown. Assessment of their feeding rate is the key to understanding their foraging behavior, but this has been challenging. Here, we assessed the feeding rate of 14 female northern elephant seals determined by jaw motion events (JME) and dive cycle time to examine how feeding rates varied with dive depth, particularly in the OMZ. We also obtained video footage from seal-mounted videos to understand their feeding in the OMZ. While the diel vertical migration pattern was apparent for most depths of the JME, some very deep dives, beyond the normal diel depth ranges, occurred episodically during daylight hours. The midmesopelagic zone was the main foraging zone for all seals. Larger seals tended to show smaller numbers of JME and lower feeding rates than smaller seals during migration, suggesting that larger seals tended to feed on larger prey to satisfy their metabolic needs. Larger seals also dived frequently to the deep OMZ, possibly because of a greater diving ability than smaller seals, suggesting their dependency on food in the deeper depth zones. Video observations showed that seals encountered the rarely reported ragfish ( Icosteus aenigmaticus ) in the depths of the OMZ, which failed to show an escape response from the seals, suggesting that low oxygen concentrations might reduce prey mobility. Less mobile prey in OMZ would enhance the efficiency of foraging in this zone, especially for large seals that can dive deeper and longer. We suggest that the OMZ plays an important role in structuring the mesopelagic ecosystem and for the survival and evolution of elephant seals.

A link between deformation history and the orientation of reflective structures in the 2.68-2.83 Ga Opatica belt of the Canadian Superior Province

NASA Astrophysics Data System (ADS)

Bellefleur, G.; Calvert, A. J.; Chouteau, M. C.

1997-07-01

True three-dimensional reflector orientations can be derived from prestack seismic reflection data where a seismic profile is particularly crooked. This is accomplished by estimating a measure of coherency along travel time trajectories defined by the azimuth, dip, and depth of a reflector and the medium velocity. Results from Lithoprobe line 48, located in the Opatica belt of the Archean Superior Province, differentiate reflectors with two distinct orientations, which coincide with the attitudes of two deformational fabrics mapped at surface. Assuming a connection between reflectivity and strain induced by tectonic processes, the reflectors with NNE strikes and shallow dips toward the east are correlated with surface evidence for early west vergent thrusting in the Opatica belt. Other reflectors, which strike ENE-WSW and dip shallowly to the north and to the south, indicate that most of the reflectors in the southern Opatica and beneath the Abitibi greenstone belt at middle and lower crustal levels formed during a later, approximately N-S shortening event. Mantle reflections previously interpreted as a relict suture of an Archean subduction zone dip to the north at around 30°-45° and are also associated with this N-S event. The distribution of reflector orientations estimated at the crooked parts of line 48 indicates that much of the Opatica crust was reworked during the N-S shortening event, although a region of the middle and lower crust, characterized by the earlier D1 reflectors, is preserved in the central part of the belt.

A New Finite Difference Q-compensated RTM Algorithm in Tilted Transverse Isotropic (TTI) Media

NASA Astrophysics Data System (ADS)

Zhou, T.; Hu, W.; Ning, J.

2017-12-01

Attenuating anisotropic geological body is difficult to image with conventional migration methods. In such kind of scenarios, recorded seismic data suffer greatly from both amplitude decay and phase distortion, resulting in degraded resolution, poor illumination and incorrect migration depth in imaging results. To efficiently obtain high quality images, we propose a novel TTI QRTM algorithm based on Generalized Standard Linear Solid model combined with a unique multi-stage optimization technique to simultaneously correct the decayed amplitude and the distorted phase velocity. Numerical tests (shown in the figure) demonstrate that our TTI QRTM algorithm effectively corrects migration depth, significantly improves illumination, and enhances resolution within and below the low Q regions. The result of our new method is very close to the reference RTM image, while QRTM without TTI cannot get a correct image. Compared to the conventional QRTM method based on a pseudo-spectral operator for fractional Laplacian evaluation, our method is more computationally efficient for large scale applications and more suitable for GPU acceleration. With the current multi-stage dispersion optimization scheme, this TTI QRTM method best performs in the frequency range 10-70 Hz, and could be used in a wider frequency range. Furthermore, as this method can also handle frequency dependent Q, it has potential to be applied in imaging deep structures where low Q exists, such as subduction zones, volcanic zones or fault zones with passive source observations.

Observations of Munitions Mobility During a Nor'easter at Wallops Island

NASA Astrophysics Data System (ADS)

Swann, C.; Frank, D. P.; Braithwaite, E. F., III; Hagg, R. K.; Calantoni, J.

2017-12-01

Unexploded ordnance (or munitions) may migrate, bury, or become exposed over time, and may pose a hazard to both humans and environment. Understanding the behavior of munitions under various wave and current conditions is central to management and remediation of contaminated underwater sites. We embedded Inertial Measurement Units (IMUs) into inert replicas of large caliber munitions (81 mm - 155 mm), herein referred to as `smart munitions'. Several smart munitions were deployed in the field with IMUs logging at 16 Hz continuously. Simultaneously the local hydrodynamic conditions were monitored to correlate any resulting munitions mobility. Here, we present the response of the smart munitions to wave and current conditions observed during a nor'easter off the coast of Wallops Island, Virginia USA in about 10 m water depth. During the nor'easter, peak significant wave heights of 2.8 m were observed in 10 m water depth. Over a roughly 10-hour period, an 81 mm smart munition migrated approximately 206 ft in a net onshore direction. Displacement and heading of the migrated smart munition were estimated by divers during the recovery. Integration of the trajectory of motion for the smart munition using a custom signal processing algorithm was in good agreement with the diver measurements. Discussion will focus on the relationship of the local sediment type and the potential for munitions mobility.

Lateral Erosion Encourages Vertical Incision in a Bimodal Alluvial River

NASA Astrophysics Data System (ADS)

Gran, K. B.

2015-12-01

Sand can have a strong impact on gravel transport, increasing gravel transport rates by orders of magnitude as sand content increases. Recent experimental work by others indicates that adding sand to an armored bed can even cause armor to break-up and mobilize. These two elements together help explain observations from a bimodal sand and gravel-bedded river, where lateral migration into sand-rich alluvium breaks up the armor layer, encouraging further incision into the bed. Detailed bedload measurements were coupled with surface and subsurface grain size analyses and cross-sectional surveys in a seasonally-incised channel carved into the upper alluvial fan of the Pasig-Potrero River at Mount Pinatubo, Philippines. Pinatubo erupted in 1991, filling valleys draining the flanks of the volcano with primarily sand-sized pyroclastic flow debris. Twenty years after the eruption, sand-rich sediment inputs are strongly seasonal, with most sediment input to the channel during the rainy season. During the dry season, flow condenses from a wide braided planform to a single-thread channel in most of the upper basin, extending several km onto the alluvial fan. This change in planform creates similar unit discharge ranges in summer and winter. Lower sediment loads in the dry season drive vertical incision until the bed is sufficiently armored. Incision proceeds downstream in a wave, with increasing sediment transport rates and decreasing grain size with distance downstream, eventually reaching a gravel-sand transition and return to a braided planform. Incision depths in the gravel-bedded section exceeded 3 meters in parts of a 4 km-long study reach, a depth too great to be explained by predictions from simple winnowing during incision. Instead, lateral migration into sand-rich alluvium provides sufficient fine sediment to break up the armor surface, allowing incision to start anew and increasing the total depth of the seasonally-incised valley. Lateral migration is recorded in a series of inset terraces within the valley. The importance of sand on channel behavior thus extends beyond transport rates, affecting the depth of incision and volume of material excavated during a rainy to dry season transition.

Fracture Development within the Karaha-Telaga Bodas Geothermal Field, Indonesia

USGS Publications Warehouse

Nemcok, M.; Moore, J.N.; Allis, R.; McCulloch, J.

2002-01-01

Karaha-Telaga Bodas is a partially vapor-dominated geothermal system located in an active volcano in western Java. More than 2 dozen geothermal wells have been drilled to depths of 3 km. Detailed paragenetic and fluid-inclusion studies have defined liquid-dominated, transitional and vapor-dominated stages in the evolution of this system. The liquid-dominated stage was initiated by shallow magma intrusion into the base of the volcanic cone. Lava and pyroclastic flows capped a geothermal system. The uppermost andesite flows were only weakly fractured due to the insulating effect of the intervening altered pyroclastics, which absorbed the deformation. Shear and tensile fractures were filled with carbonates at shallow depths and by quartz, epidote and actinolite at depths and temperatures over 1km and 300??C. The system underwent numerous local cycles of overpressuring, which are marked by subhorizontal tensile fractures, anastomosing tensile fractures and implosion breccias. The development of the liquid system was interrupted by a catastrophic drop in fluid pressures. As the fluids boiled in response to this pressure drop, chalcedony and quartz were deposited in fractures having the largest apertures and steep dips. The orientations of these fractures indicate that the escaping overpressured fluids used the shortest possible paths to the surface. Vapor-dominated conditions were initiated within a vertical chimney over the still hot intrusion. As pressures declined these conditions spread outward. Downward migration of the chimney occurred as the intrusion cooled and the brittle-ductile transition migrated to greater depths. Condensate that formed at the top of the vapor-dominated zone percolated downward and lowsalinity meteoric water entered the marginal parts of the system. Calcite, anhydrite, and fluorite precipitated in fractures upon heating. A progressive sealing of the fractures occurred, resulting in the downward migration of the cap rock. In response to decreasing pore pressures in the expanding vapor zone, the fracture system within the vapor-dominated reservoir progressively collapsed, leaving only residual permeability, with apertures supported by asperities or propping breccia. In places, the fractures have completely collapsed where normal stresses acting on the fracture walls exceeded the compressive strength of the wall rock.

Subtractive Schooling and Betrayal

ERIC Educational Resources Information Center

Valenzuela, Angela

2008-01-01

To address the theme of this special issue--namely, the major challenges faced by teacher education in an increasing global society--the author finds herself returning to her earlier work. This return-intellectual-migration gives depth and meaning to the experience of immigration and speaks to the sensibilities (or lack thereof) that many teachers…

Migration, foraging, and residency patterns for Northern Gulf loggerheads: implications of local threats and international movements

USGS Publications Warehouse

Hart, Kristen M.; Lamont, Margaret M.; Sartain-Iverson, Autumn R.; Fujisaki, Ikuko

2014-01-01

Northern Gulf of Mexico (NGoM) loggerheads (Caretta caretta) make up one of the smallest subpopulations of this threatened species and have declining nest numbers. We used satellite telemetry and a switching state-space model to identify distinct foraging areas used by 59 NGoM loggerheads tagged during 2010–2013. We tagged turtles after nesting at three sites, 1 in Alabama (Gulf Shores; n = 37) and 2 in Florida (St. Joseph Peninsula; n = 20 and Eglin Air Force Base; n = 2). Peak migration time was 22 July to 9 August during which >40% of turtles were in migration mode; the mean post-nesting migration period was 23.0 d (±13.8 d SD). After displacement from nesting beaches, 44 turtles traveled to foraging sites where they remained resident throughout tracking durations. Selected foraging locations were variable distances from tagging sites, and in 5 geographic regions; no turtles selected foraging sites outside the Gulf of Mexico (GoM). Foraging sites delineated using 50% kernel density estimation were located a mean distance of 47.6 km from land and in water with mean depth of −32.5 m; other foraging sites, delineated using minimum convex polygons, were located a mean distance of 43.0 km from land and in water with a mean depth of −24.9 m. Foraging sites overlapped with known trawling activities, oil and gas extraction activities, and the footprint of surface oiling during the 2010 Deepwater Horizon oil spill (n = 10). Our results highlight the year-round use of habitats in the GoM by loggerheads that nest in the NGoM. Our findings indicate that protection of females in this subpopulation requires both international collaborations and management of threats that spatially overlap with distinct foraging habitats.

Migration, foraging, and residency patterns for Northern Gulf loggerheads: implications of local threats and international movements.

PubMed

Hart, Kristen M; Lamont, Margaret M; Sartain, Autumn R; Fujisaki, Ikuko

2014-01-01

Northern Gulf of Mexico (NGoM) loggerheads (Caretta caretta) make up one of the smallest subpopulations of this threatened species and have declining nest numbers. We used satellite telemetry and a switching state-space model to identify distinct foraging areas used by 59 NGoM loggerheads tagged during 2010-2013. We tagged turtles after nesting at three sites, 1 in Alabama (Gulf Shores; n = 37) and 2 in Florida (St. Joseph Peninsula; n = 20 and Eglin Air Force Base; n = 2). Peak migration time was 22 July to 9 August during which >40% of turtles were in migration mode; the mean post-nesting migration period was 23.0 d (±13.8 d SD). After displacement from nesting beaches, 44 turtles traveled to foraging sites where they remained resident throughout tracking durations. Selected foraging locations were variable distances from tagging sites, and in 5 geographic regions; no turtles selected foraging sites outside the Gulf of Mexico (GoM). Foraging sites delineated using 50% kernel density estimation were located a mean distance of 47.6 km from land and in water with mean depth of -32.5 m; other foraging sites, delineated using minimum convex polygons, were located a mean distance of 43.0 km from land and in water with a mean depth of -24.9 m. Foraging sites overlapped with known trawling activities, oil and gas extraction activities, and the footprint of surface oiling during the 2010 Deepwater Horizon oil spill (n = 10). Our results highlight the year-round use of habitats in the GoM by loggerheads that nest in the NGoM. Our findings indicate that protection of females in this subpopulation requires both international collaborations and management of threats that spatially overlap with distinct foraging habitats.

Hypoxia Tolerance and Metabolic Suppression in Oxygen Minimum Zone Euphausiids: Implications for Ocean Deoxygenation and Biogeochemical Cycles.

PubMed

Seibel, Brad A; Schneider, Jillian L; Kaartvedt, Stein; Wishner, Karen F; Daly, Kendra L

2016-10-01

The effects of regional variations in oxygen and temperature levels with depth were assessed for the metabolism and hypoxia tolerance of dominant euphausiid species. The physiological strategies employed by these species facilitate prediction of changing vertical distributions with expanding oxygen minimum zones and inform estimates of the contribution of vertically migrating species to biogeochemical cycles. The migrating species from the Eastern Tropical Pacific (ETP), Euphausia eximia and Nematoscelis gracilis, tolerate a Partial Pressure (PO2) of 0.8 kPa at 10 °C (∼15 µM O2) for at least 12 h without mortality, while the California Current species, Nematoscelis difficilis, is incapable of surviving even 2.4 kPa PO2 (∼32 µM O2) for more than 3 h at that temperature. Euphausia diomedeae from the Red Sea migrates into an intermediate oxygen minimum zone, but one in which the temperature at depth remains near 22 °C. Euphausia diomedeae survived 1.6 kPa PO2 (∼22 µM O2) at 22 °C for the duration of six hour respiration experiments. Critical oxygen partial pressures were estimated for each species, and, for E. eximia, measured via oxygen consumption (2.1 kPa, 10 °C, n = 2) and lactate accumulation (1.1 kPa, 10 °C). A primary mechanism facilitating low oxygen tolerance is an ability to dramatically reduce energy expenditure during daytime forays into low oxygen waters. The ETP and Red Sea species reduced aerobic metabolism by more than 50% during exposure to hypoxia. Anaerobic glycolytic energy production, as indicated by whole-animal lactate accumulation, contributed only modestly to the energy deficit. Thus, the total metabolic rate was suppressed by ∼49-64%. Metabolic suppression during diel migrations to depth reduces the metabolic contribution of these species to vertical carbon and nitrogen flux (i.e., the biological pump) by an equivalent amount. Growing evidence suggests that metabolic suppression is a widespread strategy among migrating zooplankton in oxygen minimum zones and may have important implications for the economy and ecology of the oceans. The interacting effects of oxygen and temperature on the metabolism of oceanic species facilitate predictions of changing vertical distribution with climate change. © The Author 2016. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. For permissions please email: journals.permissions@oup.com.

Transport and biodegradation of creosote compounds in clayey till, a field experiment

NASA Astrophysics Data System (ADS)

Broholm, Kim; Nilsson, Bertel; Sidle, Roy C.; Arvin, Erik

2000-02-01

The transport and biodegradation of 12 organic compounds (toluene, phenol, o-cresol, 2,6-, 3,5-dimethylphenol, naphthalene, 1-methylnaphthalene, benzothiophene, dibenzofuran, indole, acridine, and quinoline) were studied at a field site located on the island of Funen, Denmark, where a clayey till 10-15 m deep overlies a sandy aquifer. The upper 4.8 m of till is highly fractured and the upper 2.5 m contains numerous root and worm holes. A 1.5-2 m thick sand lens is encountered within the till at a depth of 4.8 m. Sampling points were installed at depths of 2.5 m, 4 m, and in the sand lens (5.5 m) to monitor the downward migration of a chloride tracer and the organic compounds. Water containing organic compounds and chloride was infiltrated into a 4 m×4.8 m basin at a rate of 8.8 m 3 day -1 for 7 days. The mass of naphthalene relative to chloride was 0.39-0.98 for the sampling points located at a depth of 2.5 m, 0.11-0.61 for the sampling points located at a depth of 4 m, and 0-0.02 for the sampling points located in the sand lens. A similar pattern was observed for eight organic compounds for which reliable results were obtained (toluene, phenol, o-cresol, 2,6-, 3,5-dimethylphenol, 1-methylnaphthalene, benzothiophene, and quinoline). This shows that the organic compounds were attenuated during the downward migration through the till despite the high infiltration rate. The attenuation process may be attributed to biodegradation.

Testing pop-up satellite tags as a tool for identifying critical habitat for Pacific halibut (Hippoglossus stenolepis) in the Gulf of Alaska

USGS Publications Warehouse

Seitz, Andrew C.; Wilson, Derek; Nielsen, Jennifer L.

2002-01-01

To maintain healthy commercial and sport fisheries for Pacific halibut (Hippoglossus stenolepis), critical habitat must be defined by determining life history patterns on a daily and seasonal basis. Pop-up satellite archival transmitting (PSAT) tags provide a fisheries-independent method of collecting environmental preference data (depth and ambient water temperature) as well as daily geolocation estimates based on ambient light conditions. In this study, 14 adult halibut (107-165 cm FL) were tagged and released with PSAT tags in and around Resurrection Bay, Alaska. Commercial fishermen recovered two tags, while five tags transmitted data to ARGOS satellites. Horizontal migration was not consistent among fish as three halibut remained in the vicinity of release while four traveled up to 358 km from the release site. Vertical migration was not consistent among fish and over time, but they spent most their time between 150-350 m. The minimum and maximum depths reached by any of the halibut were 2m and 502m, respectively. The fish preferred water temperatures of roughly 6 °C while experiencing ambient temperatures between 4.3 °C and 12.2 °C. Light attenuation with depth prevented existing geolocation software and light sensing hardware from accurately estimating geoposition, however, information from temperature, depth, ocean bathymetry, and pop-off locations provided inference on fish movement in the study area. PSAT tags were a viable tool for determining daily and seasonal behavior and identifying critical halibut habitat, which will aid fisheries managers in future decisions regarding commercial and sport fishing regulations.

Feeding ecology of mesopelagic zooplankton of the subtropical and subarctic North Pacific Ocean determined with fatty acid biomarkers

NASA Astrophysics Data System (ADS)

Wilson, S. E.; Steinberg, D. K.; Chu, F.-L. E.; Bishop, J. K. B.

2010-10-01

Mesopelagic zooplankton may meet their nutritional and metabolic requirements in a number of ways including consumption of sinking particles, carnivory, and vertical migration. How these feeding modes change with depth or location, however, is poorly known. We analyzed fatty acid (FA) profiles to characterize zooplankton diet and large particle (>51 μm) composition in the mesopelagic zone (base of euphotic zone -1000 m) at two contrasting time-series sites in the subarctic (station K2) and subtropical (station ALOHA) Pacific Ocean. Total FA concentration was 15.5 times higher in zooplankton tissue at K2, largely due to FA storage by seasonal vertical migrators such as Neocalanus and Eucalanus. FA biomarkers specific to herbivory implied a higher plant-derived food source at mesotrophic K2 than at oligotrophic ALOHA. Zooplankton FA biomarkers specific to dinoflagellates and diatoms indicated that diatoms, and to a lesser extent, dinoflagellates were important food sources at K2. At ALOHA, dinoflagellate FAs were more prominent. Bacteria-specific FA biomarkers in zooplankton tissue were used as an indicator of particle feeding, and peaks were recorded at depths where known particle feeders were present at ALOHA (e.g., ostracods at 100-300 m). In contrast, depth profiles of bacterial FA were relatively constant with depth at K2. Diatom, dinoflagellate, and bacterial biomarkers were found in similar proportions in both zooplankton and particles with depth at both locations, providing additional evidence that mesopelagic zooplankton consume sinking particles. Carnivory indices were higher and increased significantly with depth at ALOHA, and exhibited distinct peaks at K2, representing an increase in dependence on other zooplankton for food in deep waters. Our results indicate that feeding ecology changes with depth as well as by location. These changes in zooplankton feeding ecology from the surface through the mesopelagic zone, and between contrasting environments, have important consequences for the quality and quantity of organic material available to deeper pelagic and benthic food webs, and for organic matter sequestration.

Efficiency of two-way weirs and prepositioned electrofishing for sampling potamodromous fish migrations

USGS Publications Warehouse

Favrot, Scott D.; Kwak, Thomas J.

2016-01-01

Potamodromy (i.e., migration entirely in freshwater) is a common life history strategy of North American lotic fishes, and efficient sampling methods for potamodromous fishes are needed to formulate conservation and management decisions. Many potamodromous fishes inhabit medium-sized rivers and are mobile during spawning migrations, which complicates sampling with conventional gears (e.g., nets and electrofishing). We compared the efficiency of a passive migration technique (resistance board weirs) and an active technique (prepositioned areal electrofishers; [PAEs]) for sampling migrating potamodromous fishes in Valley River, a southern Appalachian Mountain river, from March through July 2006 and 2007. A total of 35 fish species from 10 families were collected, 32 species by PAE and 19 species by weir. Species richness and diversity were higher for PAE catch, and species dominance (i.e., proportion of assemblage composed of the three most abundant species) was higher for weir catch. Prepositioned areal electrofisher catch by number was considerably higher than weir catch, but biomass was lower for PAE catch. Weir catch decreased following the spawning migration, while PAEs continued to collect fish. Sampling bias associated with water velocity was detected for PAEs, but not weirs, and neither gear demonstrated depth bias in wadeable reaches. Mean fish mortality from PAEs was five times greater than that from weirs. Catch efficiency and composition comparisons indicated that weirs were effective at documenting migration chronology, sampling nocturnal migration, and yielding samples unbiased by water velocity or habitat, with low mortality. Prepositioned areal electrofishers are an appropriate sampling technique for seasonal fish occupancy objectives, while weirs are more suitable for quantitatively describing spawning migrations. Our comparative results may guide fisheries scientists in selecting an appropriate sampling gear and regime for research, monitoring, conservation, and management of potamodromous fishes.

Phosphorus vertical migration in aquic brown soil and light chernozem under different phosphorous application rate: a soil column leaching experiment.

PubMed

Zhao, Muqiu; Chen, Xin; Shi, Yi; Zhou, Quanlai; Lu, Caiyan

2009-01-01

A soil column leaching experiment was conducted to study the vertical migration of phosphorus in aquic brown soil and light chernozem under different phosphorus fertilization rates. The results showed that total dissolved phosphorus concentration in the leachates from the two soils was nearly the same, but dissolved inorganic phosphorus concentration was obviously different. In all fertilization treatments, aquic brown soil had a higher content of phosphorus in calcium chloride extracts compared with light chernozem. But Olsen phosphorus content was higher at the soil depth beneath 0-20 cm, and increased with increasing phosphorus application rate.

Magma migration at the onset of the 2012-13 Tolbachik eruption revealed by Seismic Amplitude Ratio Analyses

NASA Astrophysics Data System (ADS)

Taisne, B.; Caudron, C.; Kugaenko, Y.; Saltykov, V.

2015-12-01

In contrast of the 1975-76 Tolbachik eruption, the 2012-2013 Tolbachik eruption was not preceded by any striking change in seismic activity. By processing the Klyuchevskoy volcano group seismic data with the Seismic Amplitude Ratio Analysis (SARA) method, we gain insights into the dynamics of magma transfer prior to this important eruption. We highlighted a clear migration of the source of the microseismicity within the seismic swarm, starting 20 hours before the reported eruption onset (05:15 UTC, 26 November 2012). This migration proceeded in different phases and ended when eruptive tremor, corresponding to lava extrusion, was recorded (at ~11:00 UTC, 27 November 2012). In order to get a first order approximation of the location of the magma, we compare the calculated seismic intensity ratios with the theoretical ones. As expected, the observations suggest a migration toward the eruptive vent. However, we explain the pre-eruptive observed ratios by a vertical migration under the northern slope of Plosky Tolbachik volcano that would interact at shallower depth with an intermediate storage region and initiate the lateral migration toward the eruptive vents. Another migration is also captured by this technique and coincides with a seismic swarm that started 16-20 km to the south of Plosky Tolbachik at 20:31 UTC on November 28 and lasted for more than 2 days. This seismic swarm is very similar to the seismicity preceding the 1975-76 Tolbachik eruption and can be considered as a possible aborted eruption.

A model for migration and accumulation of hydrocarbons in the Thamama and Arab reservoirs in Abu Dhabi, U.A.E.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hawas, M.F.; Takezaki, H.

1995-08-01

The distribution of hydrocarbons in the Lower Cretaceous Thamama Group and Upper Jurassic Arab Formation in Abu Dhabi is influenced by the development of the intervening Hith anhydrites. The geochemical analysis of Thamama and Arab hydrocarbons indicate that they were generated from a common source rock: the Upper Jurassic Diyab Formation. Studies carried out on the Miocene sabkha anhydrites in the coastal flat west of Abu Dhabi supported a model for vertical migration through the Hith anhydrites under certain conditions. The established model implies that the Diyab oil and gas had migrated essentially vertically and individually which means that themore » oil migrated prior to the gas and their distribution is controlled by the differential sealing potential of the anhydrites at each migration phase: a Hith anhydrite bed of more than 30 feet (ft.) thick was a perfect seal for hydrocarbon migration into the Arab reservoirs. In this case, oils could not break through to the overlying Thamama group. But where the anhydride bed thicknesses dropped below 30 ft. thick, this permitted oil migration through to the overlying Thamama reservoirs during the oil generation phase in the Turonian time. At a later stage, with additional depth of burial and progressive diagenesis anhydrite beds as thin as 8 ft. thick became effective seals. These controlled the distribution of the gas during the gas generation phase in the Eocene time.« less

"She mixes her business": HIV transmission and acquisition risks among female migrants in western Kenya.

PubMed

Camlin, Carol S; Kwena, Zachary A; Dworkin, Shari L; Cohen, Craig R; Bukusi, Elizabeth A

2014-02-01

Migration and HIV research in sub-Saharan Africa has focused on HIV risks to male migrants, yet women's levels of participation in internal migration have met or exceeded those of men in the region. Moreover, studies that have examined HIV risks to female migrants found higher risk behavior and HIV prevalence among migrant compared to non-migrant women. However, little is known about the pathways through which participation in migration leads to higher risk behavior in women. This study aimed to characterize the contexts and processes that may facilitate HIV acquisition and transmission among migrant women in the Kisumu area of Nyanza Province, Kenya. We used qualitative methods, including 6 months of participant observation in women's common migration destinations and in-depth semi-structured interviews conducted with 15 male and 40 female migrants selected from these destinations. Gendered aspects of the migration process may be linked to the high risks of HIV observed in female migrants - in the circumstances that trigger migration, livelihood strategies available to female migrants, and social features of migration destinations. Migrations were often precipitated by household shocks due to changes in marital status (as when widowhood resulted in disinheritance) and gender-based violence. Many migrants engaged in transactional sex, of varying regularity, from clandestine to overt, to supplement earnings from informal sector trading. Migrant women are at high risk of HIV transmission and acquisition: the circumstances that drove migration may have also increased HIV infection risk at origin; and social contexts in destinations facilitate having multiple sexual partners and engaging in transactional sex. We propose a model for understanding the pathways through which migration contributes to HIV risks in women in high HIV prevalence areas in Africa, highlighting potential opportunities for primary and secondary HIV prevention at origins and destinations, and at key 'moments of vulnerability' in the migration process. Copyright © 2013 Elsevier Ltd. All rights reserved.

“She mixes her business”: HIV transmission and acquisition risks among female migrants in western Kenya

PubMed Central

Camlin, Carol S.; Kwena, Zachary A.; Dworkin, Shari L.; Cohen, Craig R.; Bukusi, Elizabeth A.

2014-01-01

Migration and HIV research in sub-Saharan Africa has focused on HIV risks to male migrants, yet women’s levels of participation in internal migration have met or exceeded those of men in the region. Moreover, studies that have examined HIV risks to female migrants found higher risk behavior and HIV prevalence among migrant compared to non-migrant women. However, little is known about the pathways through which participation in migration leads to higher risk behavior in women. This study aimed to characterize the contexts and processes that may facilitate HIV acquisition and transmission among migrant women in the Kisumu area of Nyanza Province, Kenya. We used qualitative methods, including 6 months of participant observation in women’s common migration destinations and in-depth semi-structured interviews conducted with 15 male and 40 female migrants selected from these destinations. Gendered aspects of the migration process may be linked to the high risks of HIV observed in female migrants— in the circumstances that trigger migration, livelihood strategies available to female migrants, and social features of migration destinations. Migrations were often precipitated by household shocks due to changes in marital status (as when widowhood resulted in disinheritance) and gender-based violence. Many migrants engaged in transactional sex, of varying regularity, from clandestine to overt, to supplement earnings from informal sector trading. Migrant women are at high risk of HIV transmission and acquisition: the circumstances that drove migration may have also increased HIV infection risk at origin; and social contexts in destinations facilitate having multiple sexual partners and engaging in transactional sex. We propose a model for understanding the pathways through which migration contributes to HIV risks in women in high HIV prevalence areas in Africa, highlighting potential opportunities for primary and secondary HIV prevention at origins and destinations, and at key ‘moments of vulnerability’ in the migration process. PMID:24565152

CENPI is overexpressed in colorectal cancer and regulates cell migration and invasion.

PubMed

Ding, Na; Li, Rongxin; Shi, Wenhao; He, Cui

2018-06-21

Centromere protein I (CENPI),an important member of centromere protein family, has been suggest to serve as a oncogene in breast cancer, but the clinical significance and biological function of CENPI in colorectal cancer (CRC) is still unclear. In our results, we found CENPI was overexpressed in CRC tissues and cells, and associated with clinical stage, tumor depth, lymph node metastasis, distant metastasis and differentiation in CRC patients. However, there was no significant association between CENPI protein expression and overall survival time in colon cancer patients and rectal cancer patients through analyzing TCGA survival data. Moreover, CENPI mRNA and protein were increased in metastatic lymph nodes compared with primary CRC tissues. Down-regulation of CENPI expression suppresses CRC cell migration, invasion and epithelial mesenchymal transition process. In conclusion, CENPI is overexpressed in CRC and functions as oncogene in modulating CRC cell migration, invasion and EMT process. Copyright © 2018. Published by Elsevier B.V.

In vitro action of progestogens on sperm migration in human cervical mucus;.

PubMed

Kesserü, E; Camacho-Ortega, P; Laudahn, G; Schopflin, G

1975-01-01

The presence of progestogens in the cervical mucus suppresses and arrests sperm penetration. Using the Kremer technique, the effects of in vitro released progesterone, d-norgestrel, and cyproterone acetate were studied by inserting silicone rubber threads bearing the respective compounds into capillary tubes containing cervical mucus. Control tubes were fitted with nonmedicated silicone rubber threads. After 24 hours of incubation, the sperm migration test was carried out to evaluate penetration depth, qualitative motility, and proportion of motile forms. Progesterone produced the greatest alterations. Migration was arrested within 30 minutes, the distance reached was consistently less than 2 cm, and sperm were completely immobile at 24 hours. D-norgestrel also exhibited a distinct spermiostatic effect, but it was not as intense as that of progesterone. Cyproterone acetate was practically effective during the first 120 minutes and produced alterations only in the qualitative and proportional motility.

Transnational Intergenerationalities: Cultural Learning in Polish Migrant Families and Its Implications for Pedagogy

ERIC Educational Resources Information Center

Sime, Daniela; Pietka-Nykaza, Emilia

2015-01-01

In this qualitative study, we examine the impact of family migration on intergenerational learning, especially in relation to the transmission of cultural values and practices. Drawing on data collected through in-depth case studies with migrant Polish children and their parents, we explore the influence of intergenerationality on children's…

Electrokinetic Strength Enhancement of Concrete

NASA Technical Reports Server (NTRS)

Cardenas, Henry E. (Inventor)

2016-01-01

A method and apparatus for strengthening cementitious concrete by placing a nanoparticle carrier liquid in contact with a first surface of a concrete section and inducing a current across the concrete section at sufficient magnitude and for sufficient time that nanoparticles in the nanoparticle carrier liquid migrate through a significant depth of the concrete section.

Electrokenitic Corrosion Treatment of Concrete

NASA Technical Reports Server (NTRS)

Cardenas, Henry E (Inventor)

2015-01-01

A method and apparatus for strengthening cementitious concrete by placing a nanoparticle carrier liquid in contact with a first surface of a concrete section and inducing a current across the concrete section at sufficient magnitude and for sufficient time that nanoparticles in the nanoparticle carrier liquid migrate through a significant depth of the concrete section.

Structural and magnetic depth profiles of magneto-ionic heterostructures beyond the interface limit

DOE PAGES

Gilbert, Dustin A.; Grutter, Alexander J.; Arenholz, Elke; ...

2016-07-22

Electric field control of magnetism provides a promising route towards ultralow power information storage and sensor technologies. The effects of magneto-ionic motion have been prominently featured in the modification of interface characteristics. Here, we demonstrate magnetoelectric coupling moderated by voltage-driven oxygen migration beyond the interface in relatively thick AlO x/GdO x/Co(15 nm) films. Oxygen migration and Co magnetization are quantitatively mapped with polarized neutron reflectometry under electro-thermal conditioning. The depth-resolved profiles uniquely identify interfacial and bulk behaviours and a semi-reversible control of the magnetization. Magnetometry measurements suggest changes in the microstructure which disrupt long-range ferromagnetic ordering, resulting in an additionalmore » magnetically soft phase. X-ray spectroscopy confirms changes in the Co oxidation state, but not in the Gd, suggesting that the GdO x transmits oxygen but does not source or sink it. These results together provide crucial insight into controlling magnetism via magneto-ionic motion, both at interfaces and throughout the bulk of the films.« less

Emigration and development: the case of a Bangladeshi village.

PubMed

Rahman, M M

2000-01-01

This article examines the developmental consequences of international labor migration in a Bangladeshi village. The data are from the Hoglakandi, a village 30 km southeast of Dhaka, capital of Bangladesh. A structured questionnaire with both open-ended and closed category questions was used among 50 Singapore returnees, supplemented with additional in-depth interviews. International labor migration has often been seen by many sending countries as a short cut development because of its role in unemployment relief, balance of payments relief, and capital formation of national level. The study argues that the causes and effects of emigration can better be understood only when the process is placed within its local context, since what may prove to be advantageous at the national level may prove to be detrimental to a household or community or vice-versa. It demonstrates how the contribution of labor migration is merely the transformation of labor into a structural component of the international political economy. The Hoglakandi experience reveals that labor migration does not fuel the local economy from an external pipeline of remittances and skill acquisition, rather it drains local resources that retard the development.

The impact of forced migration on the mental health of the elderly: a scoping review.

PubMed

Virgincar, Ashwini; Doherty, Shannon; Siriwardhana, Chesmal

2016-06-01

The worldwide elderly population fraction is increasing, with the greatest rise in developing countries. Older adults affected by conflict and forced migration mainly taking place in developing countries may be particularly vulnerable to poor mental health due to other age-specific risk factors. This review aims to explore global evidence on the effect of conflict-induced forced migration on the mental health of older adults. Seven bibliographic databases were searched. The title and abstract of 797 results were reviewed for qualitative and quantitative studies meeting inclusion and exclusion criteria. Six studies were selected for the in-depth review. Five papers assessed mental health in older adult populations displaced as refugees. One paper assessed mental health of older adults with varying immigration status. This review highlights the dearth of evidence about the impact of forced migration on the mental health of older adults. Further research is needed to explore the risk factors and processes that contribute to adverse mental health outcomes among older adult populations. This is essential to the development of interventions for this vulnerable and at-risk population, particularly in resource-poor settings.

Seasonal and diel movements of white sturgeon in the lower columbia river

USGS Publications Warehouse

Parsley, M.J.; Popoff, N.D.; Van Der Leeuw, B. K.; Wright, C.D.

2008-01-01

Continuous monitoring of the movements and depths used by white sturgeon Acipenser transmontanus with acoustic telemetry technologies in the lower Columbia River provided information on diel and seasonal migrations, local movements, and site fidelity. White sturgeon moved to shallower water at night and showed greater activity, inferred from rates of movement, than during daytime. The extent of local movement within a season was variable among fish; some fish readily moved among habitats while the movements of others were more constrained. White sturgeon were absent from the study area (river kilometers 45-52) during winter and returned from upstream during the spring, confirming an upstream seasonal migration in the fall and downstream migration in spring. The return of individual fish and reoccupation of areas previously inhabited showed that some white sturgeon exhibit site fidelity. This work shows that studies seeking to characterize habitat for white sturgeon need to be cognizant of diel migrations and site fidelity. We urge caution in the use of limited fish location data to describe habitats if diel activities and fine-scale movements are not known.

Imaging the internal structure of fluid upflow zones with detailed digital Parasound echosounder surveys

NASA Astrophysics Data System (ADS)

Spiess, V.; Zuehlsdorff, L.; von Lom-Keil, H.; Schwenk, T.

2001-12-01

Sites of venting fluids both with continuous and episodic supply often reveal complex surface and internal structures, which are difficult to image and cause problems to transfer results from local sampling towards a structural reconstruction and a quantification of (average) flux rates. Detailed acoustic and seismic surveys would be required to retrieve this information, but also an appropriate environment, where fluid migration can be properly imaged from contrasts to unaffected areas. Hemipelagic sediments are most suitable, since typically reflectors are coherent and of low lateral amplitude variation and structures are continuous over distances much longer than the scale of fluid migration features. During RV Meteor Cruise M473 and RV Sonne Cruise SO 149 detailed studies were carried out in the vicinity of potential fluid upflow zones in the Lower Congo Basin at 5oS in 3000 m water depth and at the Northern Cascadia Margin in 1000 m water depth. Unexpected sampling of massive gas hydrates from the sea floor as well as of carbonate concretions, shell fragments and different liveforms indicated active fluid venting in a typically hemipelagic realm. The acoustic signature of such zones includes columnar blanking, pockmark depressions at the sea floor, association with small offset faults (< 1m). A dedicated survey with closely spaced grid lines was carried out with the Parasound sediment echosounder (4 kHz), which data were digitally acquired with the ParaDigMA System for further processing and display, to image the spatial structure of the upflow zones. Due to the high data density amplitudes and other acoustic properties could be investigated in a 3D volume and time slices as well as reflector surfaces were analyzed. Pronounced lateral variations of reflection amplitudes within a complex pattern indicate potential pathways for fluid/gas migration and occurrences of near-surface gas hydrate deposits, which may be used to trace detailed surface evidence from side scan sonar imaging down to depth and support dedicated sampling.

Pteropod Ecology and Physiology in Relation to Natural Variability in Carbonate Chemistry

NASA Astrophysics Data System (ADS)

Lawson, G. L.; Maas, A. E.; Wang, A. Z.; Bergan, A. J.; Wiebe, P. H.; Blanco-Bercial, L.; Lavery, A.; Copley, N. J.

2016-02-01

The thecosomatous pteropods are a group of aragonite-shelled zooplankton thought to be particularly vulnerable to ocean acidification. We seek to gain insight into both basic questions of pteropod biology and potential responses to ocean acidification by combining field sampling with shipboard experimental manipulations, capitalizing on natural spatial variability in modern-day carbonate chemistry between and within the Atlantic and Pacific Oceans. Two cruises were conducted, in 2011 and 2012, along open-ocean transects running between 35 and 50°N in the NW Atlantic and NE Pacific; strong differences in environmental conditions exist between these regions, as well as along the Pacific transect, notably in aragonite compensation and oxygen minimum depths. The transects overlapped with portions of WOCE/CLIVAR lines A20 and P17N and measurements of carbonate chemistry provided insight into rates of chemical change as well as information on the pteropods' chemical environment. The abundance and diversity of pteropods varied substantially within and between the study regions. Depth-stratified net sampling during day and night indicated that multiple pteropod species undertook the typical diel vertical migration employed by many zooplankton species as an anti-predation strategy; the amplitude of this migration differed among species as well as within sub-populations of certain cosmopolitan species found in both oceans. Shipboard experiments of short-duration (<18 hrs, intended to mimic the duration of diel vertical migrations to depth) exposing eight species of pteropod to high CO2 and low O2 found no effect of CO2 alone on metabolic rate and an effect of low O2 or interactive effect of CO2 and O2 only in two Atlantic species not known to naturally encounter low oxygen in their biogeographic range. The implications of these various findings to our understanding of the response of pteropods to environmental change will be discussed.

Plutonium Particle Migration in the Shallow Vadose Zone: The Nevada Test Site as an Analog Site

NASA Astrophysics Data System (ADS)

Hunt, J. R.; Smith, D. K.

2004-12-01

The upper meter of the vadose zone in desert environments is the horizon where wastes have been released and human exposure is determined through dermal, inhalation, and food uptake pathways. This region is also characterized by numerous coupled processes that determine contaminant transport, including precipitation infiltration, evapotranspiration, daily and annual temperature cycling, dust resuspension, animal burrowing, and geochemical weathering reactions. While there is considerable interest in colloidal transport of minerals, pathogenic organisms, and contaminants in the vadose zone, there are limited field sites where the actual occurrence of contaminant migration can be quantified over the appropriate spatial and temporal scales of interest. At the US Department of Energy Nevada Test Site, there have been numerous releases of radionuclides since the 1950's that have become field-scale tracer tests. One series of tests was the four safety shots conducted in an alluvial valley of Area 11 in the 1950's. These experiments tested the ability of nuclear materials to survive chemical explosions without initiating fission reactions. Four above-ground tests were conducted and they released plutonium and uranium on the desert valley floor with only one of the tests undergoing some fission. Shortly after the tests, the sites were surveyed for radionuclide distribution on the land surface using aerial surveys and with depth. Additional studies were conducted in the 1970's to better understand the fate of plutonium in the desert that included studies of depth distribution and dust resuspension. More recently, plutonium particle distribution in the soil profile was detected using autoradiography. The results to date demonstrate the vertical migration of plutonium particles to depths in excess of 30 cm in this arid vadose zone. While plutonium migration at the Nevada Test Site has been and continues to be a concern, these field experiments have become analog sites for the release of radiological materials potentially important to consequence management investigations. In particular, these 50-year old experiments with long and detailed site investigations under relative undisturbed conditions offer insights into transport pathways that must be represented in simulation models that evaluate responses to radiological dispersal devices (RDDs). A compilation of the available site characterization data suggests additional experimental and modeling programs that can ultimately quantify the fate of contaminant particles released at the soil surface.

[Effects of fertilization method and nitrogen application rate on soil nitrogen vertical migration in a Populus xeuramericana cv. 'Guariento' plantation].

PubMed

Dai, Teng-fei; Xi, Ben-ye; Yan, Xiao-li; Jia, Li-ming

2015-06-01

A field experiment was conducted to investigate the effects of fertilization methods, i.e., drip (DF) and furrow fertilization (GF), and nitrogen (N) application rates (25, 50, 75 g N · plant(-1) · time(-1)) on the dynamics of soil N vertical migration in a Populus x euramericana cv. 'Guariento' plantation. The results showed that soil NH4(+)-N and NO3(-)-N contents decreased with the increasing soil depth under different fertilization methods and N application rates. In the DF treatment, soil NH4(+)-N and NO3(-)-N were mainly concentrated in the 0-40 cm soil layer, and their contents ascended firstly and then descended, reaching their maximum values at the 5th day (211.1 mg · kg(-1)) and 10th day (128.8 mg · kg(-1)) after fertilization, respectively. In the GF treatment, soil NH4(+)-N and NO3(-)-N were mainly concentrated in the 0-20 cm layer, and the content of soil NO3(-)-N rose gradually and reached its maximum at the 20th day (175.7 mg · kg(-1)) after fertilization, while the NH4(+)-N content did not change significantly after fertilization. Overall, N fertilizer had an effect within 20 days in the DF treatment, and more than 20 days in the GF treatment. In the DF treatment, the content and migration depth of soil NH4(+)-N and NO3(-)-N increased with the N application rate. In the GF treatment, the NO3(-)-N content increased with the N application rate, but the NH4(+)-N content was not influenced. Under the DF treatment, the hydrolysis rate, nitrification rate and migration depth of urea were higher or larger than that under the GF treatment, and more N accumulated in deep soil as the N application rate increased. Considering the distribution characteristics of fine roots and soil N, DF would be a better fertilization method in P. xeuramericana cv. 'Guariento' plantation, since it could supply N to larger distribution area of fine roots. When the N application rate was 50 g · tree(-1) each time, nitrogen mainly distributed in the zone of fine roots and had no risk of deep leaching, consequently improving the fertilizer utilization efficiency.

Mechanisms of sediment transport to shoreline salients onshore of fringing coral reefs

NASA Astrophysics Data System (ADS)

Hansen, J.; Cuttler, M.; Traykovski, P.; Lowe, R.; Buckley, M. L.; Storlazzi, C. D.; Rosenberger, K. J.

2016-12-01

Shoreline salients, often extending several hundred metres seaward relative to the adjacent shoreline, are a common morphological feature found in the lee of many fringing coral reefs globally. However, the physical mechanisms that govern the formation and equilibrium dynamics of these salients remains poorly understood. A recent field experiment in NW Australia at Ningaloo Reef examined the mechanism of sediment delivery to a salient that extends 700 m seaward onshore of a 4 km long fringing reef that sits 2 km offshore. The experimental array consisted of wave, water level, and velocity measurements at >20 sites from 20 m depth offshore of the reef, the reef crest, and numerous sites throughout the 3 m depth lagoon shoreward of the reef. Two sites within the lagoon, one each side of the salient, also measured the migration of 0.5 m wavelength, 0.1 m high sand ripples using horizontal and vertically mounted echo sounders. Consistent with existing theory, mean (wave-averaged) flows in the lagoon shoreward of the reef and along the shoreline were divergent up to 0.2 m/s, corresponding to the circulation pattern resulting from wave breaking induced setup on the reef and associated mass flux into the lagoon, and seaward return flow through two lateral channels. These divergent alongshore mean flows are inconsistent the accreted shoreline morphology. However, the two sites that measured ripple properties and migration showed consistent migration in the local (salient following) onshore direction up to 2 m/day (mean 0.14 m/day across the two sites) resulting in onshore sediment fluxes as large as 200 kg/m/day (mean 10.1 kg/m/day) assuming ripple migration equates to net bedload transport. Despite the considerable infragravity energy within the lagoon ( 50% of the energy spectrum) the 0.5 m wavelength ripples were suborbital based on the orbital diameter of the 0.2-0.5 m high short waves which enter the lagoon via refraction through the lateral channels and incomplete dissipation over the reef. These preliminary results indicate that onshore ripple migration of biogenic sediment generated by the coral reef from short waves within the lagoon is the primary source of sediment to the salient. Additional analyses will focus on the hydrodynamic mechanisms responsible for the variable rate of migration.

Characterizing leachate contamination in a landfill site using Time Domain Electromagnetic (TDEM) imaging

NASA Astrophysics Data System (ADS)

Baawain, Mahad S.; Al-Futaisi, Ahmed M.; Ebrahimi, A.; Omidvarborna, Hamid

2018-04-01

Time Domain Electromagnetic (TDEM) survey as well as drilling investigations were conducted to identify possible contamination of a dumping site in an unsaturated zone located in Barka, Oman. The method was applied to evaluate conductivity of the contaminated plumes in hot and arid/semiarid region, where high temperatures commonly ranged between 35 and 50 °C. The drilling investigation was carried out over the survey area to verify the geophysical results. The low-resistivity zone (<80 Ωm), encountered near the subsurface, indicated plume migration caused by liquid waste disposal activities. The combination of TDEM survey results with the lithology of piezometers showed that higher resistivity (>90 Ωm) was correlated with compacted or cemented gravels and cobbles, particularly that of medium dense to very dense gravels and cobbles. Additionally, the TDEM profiles suggested that the plume migration followed a preferential flow path. The resistivity range 40-80 Ωm considered as contaminated areas; however, the drilling results showed the close resistivity domain in the depth >70 m below water table for some profiles (BL1, BL2, BL3, BL4 and BL5). The combined results of drilling wells, piezometers, and TDEM apparent resistivity maps showed a coincidence of the migrated leachate plume and water table. Predicted zone of the probable contamination was located at the depth of around 65 m and horizontal offset ranges 0-280 m, 80-240 m, and 40-85 m in the sounding traverses of BL4, BL6 and BL7, respectively.

Seasonal variation in the flux of euthecosomatous pteropods collected in a deep sediment trap in the Sargasso Sea

NASA Astrophysics Data System (ADS)

Almogi-Labin, A.; Hemleben, Ch.; Deuser, W. G.

1988-03-01

A 4-year series of sediment trap samples from a depth of 3.2 km in the Sargasso Sea (32°05'N, 64°15'W) has revealed seasonal variations in the flux of euthecosomatous pteropods. Total pteropod flux is related to seasonal variations of the total particulate and organic carbon flux with a lag of 1-1.5 months. High flux of pteropods (>200 specimens m -2 day -1) occurs in late winter to mid-summer. Shells of individual pteropod species arrive in deep water in a seasonal succession similar to that in the living assemblage. Peak fluxes of Styliola subula, Clio pyramidata and Limacina bulimoides were recorded from February to May. Limacina inflata, Limacina lesueuri and Cuvierina columnella entered the trap in maximum numbers from April to mid-August. Creseis virgula conica and C. acicula were most abundant from June to late August. The latter two are non-migrating, epipelagic pteropods and comprise <10% of the assemblage. Diel migrators dominate the pteropod assemblage (92%). During the summer months they appear to migrate at greater depth, without reaching the surface water. Although many young are produced, only a small fraction, about 4% in the case of L. inflata and L. bulimoides, survives and reaches maturity. Adult shell size of L. inflata and L. bulimoides varies seasonally, reaching maximum size during spring, probably in response to increasing food availability.

Arroyo channel head evolution in a flash-flood-dominated discontinuous ephemeral stream system

USGS Publications Warehouse

DeLong, Stephen B.; Johnson, Joel P.L.; Whipple, Kelin X.

2014-01-01

We study whether arroyo channel head retreat in dryland discontinuous ephemeral streams is driven by surface runoff, seepage erosion, mass wasting, or some combination of these hydrogeomorphic processes. We monitored precipitation, overland flow, soil moisture, and headcut migration over several seasonal cycles at two adjacent rangeland channel heads in southern Arizona. Erosion occurred by headward retreat of vertical to overhanging faces, driven dominantly by surface runoff. No evidence exists for erosion caused by shallow-groundwater–related processes, even though similar theater-headed morphologies are sometimes attributed to seepage erosion by emerging groundwater. At our field site, vertical variation in soil shear strength influenced the persistence of the characteristic theater-head form. The dominant processes of erosion included removal of grains and soil aggregates during even very shallow (1–3 cm) overland flow events by runoff on vertical to overhanging channel headwalls, plunge-pool erosion during higher-discharge runoff events, immediate postrunoff wet mass wasting, and minor intra-event dry mass wasting on soil tension fractures developing subparallel to the headwall. Multiple stepwise linear regression indicates that the migration rate is most strongly correlated with flow duration and total precipitation and is poorly correlated with peak flow depth or time-integrated flow depth. The studied channel heads migrated upslope with a self-similar morphologic form under a wide range of hydrological conditions, and the most powerful flash floods were not always responsible for the largest changes in landscape form in this environment. 

Array-Based Receiver Function Analysis of the Subducting Juan de Fuca Plate Beneath the Mount St. Helens Region and its Implications for Subduction Geometry and Metamorphism

NASA Astrophysics Data System (ADS)

Mann, M. E.; Abers, G. A.; Creager, K. C.; Ulberg, C. W.; Crosbie, K.

2017-12-01

Mount St. Helens (MSH) is unusual as a prolific arc volcano located 50 km towards the forearc of the main Cascade arc. The iMUSH (imaging Magma Under mount St. Helens) broadband deployment featured 70 seismometers at 10-km spacing in a 50-km radius around MSH, spanning a sufficient width for testing along-strike variation in subsurface geometry as well as deep controls on volcanism in the Cascade arc. Previous estimates of the geometry of the subducting Juan de Fuca (JdF) slab are extrapolated to MSH from several hundred km to the north and south. We analyze both P-to-S receiver functions and 2-D Born migrations of the full data set to locate the upper plate Moho and the dip and depth of the subducting slab. The strongest coherent phase off the subducting slab is the primary reverberation (Ppxs; topside P-to-S reflection) from the Moho of the subducting JdF plate, as indicated by its polarity and spatial pattern. Migration images show a dipping low velocity layer at depths less than 50 km that we interpret as the subducting JdF crust. Its disappearance beyond 50 km depth may indicate dehydration of subducting crust or disruption of high fluid pressures along the megathrust. The lower boundary of the low velocity zone, the JdF Moho, persists in the migration image to depths of at least 90 km and is imaged at 74 km beneath MSH, dipping 23 degrees. The slab surface is 68 km beneath MSH and 85 km beneath Mount Adams volcano to the east. The JdF Moho exhibits 10% velocity contrasts as deep as 85 km, an observation difficult to reconcile with simple models of crustal eclogitization. The geometry and thickness of the JdF crust and upper plate Moho is consistent with similar transects of Cascadia and does not vary along strike beneath iMUSH, indicating a continuous slab with no major disruption. The upper plate Moho is clear on the east side of the array but it disappears west of MSH, a feature we interpret as a result of both serpentinization of the mantle wedge and a westward increase in wavespeed of the continental crust. The seismically-imaged surface of the subducting JdF slab at 68 km beneath MSH is the shallowest yet documented beneath an arc volcano. Combined with the inference of serpentinization in the mantle wedge, this geometry presents a problem in that vertical mantle melt migration seems unfeasible, yet mantle melts contribute to erupted MSH magmas.

Porewater methane transport within the gas vesicles of diurnally migrating Chaoborus spp.: An energetic advantage

NASA Astrophysics Data System (ADS)

McGinnis, Daniel F.; Flury, Sabine; Tang, Kam W.; Grossart, Hans-Peter

2017-03-01

Diurnally-migrating Chaoborus spp. reach populations of up to 130,000 individuals m-2 in lakes up to 70 meters deep on all continents except Antarctica. Linked to eutrophication, migrating Chaoborus spp. dwell in the anoxic sediment during daytime and feed in the oxic surface layer at night. Our experiments show that by burrowing into the sediment, Chaoborus spp. utilize the high dissolved gas partial pressure of sediment methane to inflate their tracheal sacs. This mechanism provides a significant energetic advantage that allows the larvae to migrate via passive buoyancy rather than more energy-costly swimming. The Chaoborus spp. larvae, in addition to potentially releasing sediment methane bubbles twice a day by entering and leaving the sediment, also transport porewater methane within their gas vesicles into the water column, resulting in a flux of 0.01-2 mol m-2 yr-1 depending on population density and water depth. Chaoborus spp. emerging annually as flies also result in 0.1-6 mol m-2 yr-1 of carbon export from the system. Finding the tipping point in lake eutrophication enabling this methane-powered migration mechanism is crucial for ultimately reconstructing the geographical expansion of Chaoborus spp., and the corresponding shifts in the lake’s biogeochemistry, carbon cycling and food web structure.

Biodiversity, Community and Trophic Structure of the Suprabenthos of the Gulf of Cádiz-Guadalquivir Estuary Coupled System: Linking Pelagic-Benthic and Terrestrial-Marine Ecosystems.

NASA Astrophysics Data System (ADS)

Vilas, C.

2016-02-01

Suprabenthos biodiversity and species densities on both offshore and coastal systems are largely unknown. Main components like mysids, euphasiids or amphipods are omnivorous and constitute a major dietary component for many benthic and pelagic fishes, mammals, cephalopods and decapods. Despite their relevant ecological role linking pelagic-benthic food webs, suprabenthos have been chronically undersampled and their components underrepresented and underestimated in food web models. Many pelagic and demersal species of high commercial and ecological interest at the Gulf of Cádiz (GoC) feed at a bottom scattering layer identified from 0 to 200 m depth and up to 50 km from coast, related to the Guadalquivir Estuary (GE) influence coastal area, and present life history cycles based on a sequential use of habitats from GoC to GE nursery area, may be adapted to match the horizontal migrations of key suprabenthos prey species. In order to understand the ecological mechanisms through which the GE-GoC coupled ecosystem would influence the recruitment of these fishery resources, the suprabenthos was sampled by suprabenthic sldege (200 μm) from the shallow estuary to 75 m depth during June, August and November of 2013. We identified up to 300 species (H index 0.4-2-9 and Beta diversity 0.55), being copepods, molluscs, cumacea, cladocera, poliquets, decapods, mysids and amphipods the most important groups by biomass (mg/m3), finding densities up to 32.9 mg/m3 for copepods, 6 for mysids and up to 100 mg/m3 for decapods. Multivariate analysis determines depth as the most important variable explaining community structure, decreasing biodiversity with depth, while for sites at depths < 30 m the community changes seasonal. Fatty acid analysis of different group sizes is revealing interesting trophic links. Some prey copepods and mysid species show seasonal horizontal migrations between GoC and GE, connecting terrestrial and marine ecosystems.

Hydraulic and biological analysis of the passability of select fish species at the U.S. Geological Survey streamgaging weir at Blackwells Mills, New Jersey

USGS Publications Warehouse

Haro, Alexander J.; Mulligan, Kevin; Suro, Thomas P.; Noreika, John; McHugh, Amy

2017-10-16

Recent efforts to advance river connectivity for the Millstone River watershed in New Jersey have led to the evaluation of a low-flow gauging weir that spans the full width of the river. The methods and results of a desktop modelling exercise were used to evaluate the potential ability of three anadromous fish species (Alosa sapidissima [American shad], Alosa pseudoharengus [alewife], and Alosa aestivalis [blueback herring]) to pass upstream over the U.S. Geological Survey Blackwells Mills streamgage (01402000) and weir on the Millstone River, New Jersey, at various streamflows, and to estimate the probability that the weir will be passable during the spring migratory season. Based on data from daily fishway counts downstream from the Blackwells Mills streamgage and weir between 1996 and 2014, the general migratory period was defined as April 14 to May 28. Recorded water levels and flow data were used to theoretically estimate water depths and velocities over the weir, as well as flow exceedances occurring during the migratory period.Results indicate that the weir is a potential depth barrier to fish passage when streamflows are below 200 cubic feet per second using a 1-body-depth criterion for American shad (the largest fish among the target species). Streamflows in that range occur on average 35 percent of the time during the migratory period. An increase of the depth criterion to 2 body depths causes the weir to become a possible barrier to passage when flows are below 400 cubic feet per second. Streamflows in that range occur on average 73 percent of the time during the migration season. Average cross-sectional velocities at several points along the weir do not seem to be limiting to the fish migration, but maximum theoretical velocities estimated without friction loss over the face of the weir could be potentially limiting.

Seismic processes and migration of magma during the Great Tolbachik Fissure Eruption of 1975-1976 and Tolbachik Fissure Eruption of 2012-2013, Kamchatka Peninsula

NASA Astrophysics Data System (ADS)

Fedotov, S. A.; Slavina, L. B.; Senyukov, S. L.; Kuchay, M. S.

2015-12-01

Seismic and volcanic processes in the area of the northern group of volcanoes (NGV) in Kamchatka Peninsula that accompanied the Great Tolbachik Fissure Eruption (GTFE) of 1975-1976 and the Tolbachik Fissure Eruption (TFE, or "50 let IViS" due to anniversary of the Institute of Volcanology and Seismology, Far East Branch, Russian Academy of Sciences) of 2012-2013 and the seismic activity between these events are considered. The features of evolution of seismic processes of the major NGV volcanoes (Ploskii Tolbachik, Klyuchevskoy, Bezymannyi, and Shiveluch) are revealed. The distribution of earthquakes along depth, their spatial and temporal migration, and the relation of seismic and volcanic activity are discussed. The major features of seismic activity during the GTFE preparation and evolution and a development of earthquake series preceding the origin of the northern and southern breaks are described. The character of seismic activity between the GTFE and TFE is shown. The major peculiarities of evolution of seismic activity preceding and accompanying the TFE are described. The major magma sources and conduits of the NGV volcanoes are identified, as is the existence of a main conduit in the mantle and a common intermediate source for the entire NGV, the depth of which is 25-35 km according to seismic data. The depth of a neutral buoyancy layer below the NGV is 15-20 km and the source of areal volcanism of magnesian basalts northeast of the Klyuchevskoy volcano is located at depth of ~20 km. These data support the major properties of a 2010 geophysical model of magmatic feeding system of the Klyuchevskoy group of volcanoes. The present paper covers a wider NGV area and is based on the real experimental observations.

The impact of migration on the sexual health, behaviours and attitudes of Central and East European gay/bisexual men in London.

PubMed

Mole, Richard C M; Parutis, Violetta; Gerry, Christopher J; Burns, Fiona M

2014-02-01

Building on an earlier quantitative study which found that gay/bisexual men from Central and Eastern Europe were at greater risk of sexual ill health following migration to the UK, the aim of this qualitative study is to explore how the process of migration itself may have influenced the migrants' sexual behaviour and attitudes. To address these questions, we conducted 17 in-depth interviews in London with gay/bisexual male migrants from Central and Eastern Europe, drawing on Fisher and Fisher's Information-Motivation-Behavioral Skills model as an interpretive framework. We find that the sexual behaviours of our respondents have been significantly influenced by the process of migration itself. In particular, extricating themselves from the traditional systems of social control in their home societies and having greater access to gay venues in London resulted in their increased sexual activity, particularly in the first phase of migration. High-risk sexual behaviour was found to be a factor of sexual mixing, the use of commercial sex and perceptions of risk in the UK vis-á-vis Central and Eastern Europe, with each of these factors also influenced by the process of migration. Risk-prevention behaviour depended upon the possession of appropriate risk-prevention information, motivation to use condoms and appropriate behavioural skills, with the latter two factors in particular influenced by social mores in the home country and the UK. The interviews suggested a number of migration-related factors that increased the STI and HIV risk for these migrants. A number of potentially important policy recommendations stem from our analysis.

Impacts of an underwater high voltage DC power cable on fish migration movements in the San Francisco Bay.

NASA Astrophysics Data System (ADS)

Wyman, M. T.; Kavet, R.; Klimley, A. P.

2016-02-01

There is an increasingly strong interest on a global scale in offshore renewable energy production and transportation. However, there is concern that the electromagnetic fields (EMF) produced by these underwater cables may alter the behavior and physiology of marine species. Despite this concern, few studies have investigated these effects in free-living species. In 2009, a 85 km long high-voltage DC (HVDC) power cable was placed within the San Francisco Bay, running parallel, then perpendicular to, the migration route of anadromous species moving from the inland river system to the oceans. In this study, we assess the impacts of this HVDC cable on the migration behaviors of EMF-sensitive fish, including juvenile salmonids (Chinook salmon, Oncorhynchus tshawytscha, and steelhead trout, Oncorhynchus mykiss) and adult green sturgeon, Acipenser medirostris. Acoustic telemetry techniques were used to track fish migration movements through the San Francisco Bay both before and after the cable was activated; individuals implanted with acoustic transmitters were detected on cross-channel hydrophone arrays at key locations in the system. Magnetic fields were surveyed and mapped at these locations using a transverse gradiometer, and models of the cable's magnetic field were developed that closely matched the empirically measured values. Here, we present our analyses on the relationships between migration-related behavioral metrics (e.g., percent of successful migrations, duration of migration, time spent near vs. far from cable location, etc.) and environmental parameters, such as cable activation and load level, local magnetic field levels, depth, and currents.

30 CFR 717.14 - Backfilling and grading of road cuts, mine entry area cuts, and other surface work areas.

Code of Federal Regulations, 2012 CFR

2012-07-01

... order to prevent water pollution and sustained combustion, and to minimize adverse effects on plant growth and land uses. Where necessary to protect against upward migration of salts, exposure by erosion, to provide an adequate depth for plant growth, or to otherwise meet local conditions, the regulatory...

30 CFR 717.14 - Backfilling and grading of road cuts, mine entry area cuts, and other surface work areas.

Code of Federal Regulations, 2014 CFR

2014-07-01

... order to prevent water pollution and sustained combustion, and to minimize adverse effects on plant growth and land uses. Where necessary to protect against upward migration of salts, exposure by erosion, to provide an adequate depth for plant growth, or to otherwise meet local conditions, the regulatory...

30 CFR 717.14 - Backfilling and grading of road cuts, mine entry area cuts, and other surface work areas.

Code of Federal Regulations, 2013 CFR

2013-07-01

... order to prevent water pollution and sustained combustion, and to minimize adverse effects on plant growth and land uses. Where necessary to protect against upward migration of salts, exposure by erosion, to provide an adequate depth for plant growth, or to otherwise meet local conditions, the regulatory...

Boundaries, Work and Identity Practices: Being "'Asian" Migrant Educational Workers

ERIC Educational Resources Information Center

Joseph, Cynthia

2014-01-01

This article draws on the concept of boundaries in understanding the identity practices of a group of Malaysian skilled migrant women working in the Australian education sector. Drawing on in-depth interviews with these women on their migration and work experiences, the author explores the concept of boundary work within an educational framework.…

Pronounced Shear Velocity Asymmetry in the Mantle Across the Juan de Fuca Ridge and Curious Lack of Features at the Gorda Ridge

NASA Astrophysics Data System (ADS)

Bell, S. W.; Ruan, Y.; Forsyth, D. W.

2015-12-01

With new Rayleigh-wave tomography results, we have detected a clear and strong asymmetry in the shear velocity structure of the Juan de Fuca ridge. Concentrated in a relatively thin layer with a depth range of ~30-60km, there lies a region of very low shear velocity, with velocities ranging from ~3.8km/s to 4.0km/s. Such low velocities provide strong evidence for the presence of partial melt. This low-velocity region is highly asymmetric, extending much further west than east of the ridge. Especially at shallow depths of ~35 km, this low-velocity region is concentrated just west of the southern portion of the ridge. Peaking near the Axial Seamount, the youngest of the Cobb-Eickelberg Seamounts, it extends south to the region around the small Vance Seamounts just north of the junction with the Blanco Fracture Zone. The Juan de Fuca plate is relatively stationary in the hotspot reference frame, and the Juan de Fuca ridge migrates westward in the hotspot reference frame. Seamounts are overwhelmingly concentrated on the western flank of the ridge, and an asymmetric upwelling driven by migration in the hotspot reference frame has been proposed to explain the seamount asymmetry (i.e. Davis and Karsten, 1986). Our velocity asymmetry, which matches the seamount asymmetry, provides evidence for this asymmetric upwelling and its connection to migration in the absolute hotspot reference frame. In the shear velocity results, the Gorda ridge displays a remarkable lack of features, with no clearly identifiable expression in the subsurface velocity. There is evidence of a broad low-velocity feature beneath Gorda beginning at a depth of ~150 km, but no clear shallow features can be tied to the ridge. At the depths we can resolve (~25-250km), the anisotropy beneath and within the Juan de Fuca plate is small, indicating a deep source of the shear wave splitting results (Bodmer et al., in press), which indicate a fast axis aligned with the Juan de Fuca plate's absolute motion. Around the Gorda ridge, we observe clear East-West fast axis orientation on both the Pacific Plate and the Gorda portion of the Juan de Fuca Plate.

X-Ray Fluorescence Solvent Detection at the Substrate-Adhesive Interface

NASA Technical Reports Server (NTRS)

Wurth, Laura; Evans, Kurt; Weber, Bart; Headrick, Sarah

2005-01-01

With environmental regulations limiting the use of volatile organic compounds, low-vapor pressure solvents have replaced traditional degreasing solvents for bond substrate preparation. When used to clean and prepare porous bond substrates such as phenolic composites, low vapor pressure solvents can penetrate deep into substrate pore networks and remain there for extended periods. Trapped solvents can interact with applied adhesives either prior to or during cure, potentially compromising bond properties. Currently, methods for characterizing solvent time-depth profiles in bond substrates are limited to bulk gravimetric or sectioning techniques. While sectioning techniques such as microtome allow construction of solvent depth profiles, their depth resolution and reliability are limited by substrate type. Sectioning techniques are particularly limited near the adhesive-substrate interface where depth resolution is further limited by adhesive-substrate hardness and, in the case of a partially cured adhesive, mechanical properties differences. Additionally, sectioning techniques cannot provide information about lateral solvent diffusion. Cross-section component mapping is an alternative method for measuring solvent migration in porous substrates that eliminates the issues associated with sectioning techniques. With cross-section mapping, the solvent-wiped substrate is sectioned perpendicular rather than parallel to the wiped surface, and the sectioned surface is analyzed for the solvent or solvent components of interest using a two-dimensional mapping or imaging technique. Solvent mapping can be performed using either direct or indirect methods. With a direct method, one or more solvent components are mapped using red or Raman spectroscopy together with a moveable sample stage and/or focal plane array detector. With an indirect method, an elemental "tag" not present in the substrate is added to the solvent before the substrate is wiped. Following cross sectioning, the tag element can then be mapped by its characteristic x-ray emission using either x-ray fluorescence, or electron-beam energy-and wavelength-dispersive x-ray spectrometry. The direct mapping techniques avoid issues of different diffusion or migration rates of solvents and elemental tags, while the indirect techniques avoid spectral resolution issues in cases where solvents and substrates have adjacent or overlapping peaks. In this study, cross-section component indirect mapping is being evaluated as a method for measuring migration of d-limonene based solvents in glass-cloth phenolic composite (GCP) prior to and during subsequent bonding and epoxy adhesive cure.

Cross-correlation least-squares reverse time migration in the pseudo-time domain

NASA Astrophysics Data System (ADS)

Li, Qingyang; Huang, Jianping; Li, Zhenchun

2017-08-01

The least-squares reverse time migration (LSRTM) method with higher image resolution and amplitude is becoming increasingly popular. However, the LSRTM is not widely used in field land data processing because of its sensitivity to the initial migration velocity model, large computational cost and mismatch of amplitudes between the synthetic and observed data. To overcome the shortcomings of the conventional LSRTM, we propose a cross-correlation least-squares reverse time migration algorithm in pseudo-time domain (PTCLSRTM). Our algorithm not only reduces the depth/velocity ambiguities, but also reduces the effect of velocity error on the imaging results. It relieves the accuracy requirements on the migration velocity model of least-squares migration (LSM). The pseudo-time domain algorithm eliminates the irregular wavelength sampling in the vertical direction, thus it can reduce the vertical grid points and memory requirements used during computation, which makes our method more computationally efficient than the standard implementation. Besides, for field data applications, matching the recorded amplitudes is a very difficult task because of the viscoelastic nature of the Earth and inaccuracies in the estimation of the source wavelet. To relax the requirement for strong amplitude matching of LSM, we extend the normalized cross-correlation objective function to the pseudo-time domain. Our method is only sensitive to the similarity between the predicted and the observed data. Numerical tests on synthetic and land field data confirm the effectiveness of our method and its adaptability for complex models.

Impact of parental migration on psychosocial well-being of children left behind: a qualitative study in rural China.

PubMed

Zhao, Chenyue; Wang, Feng; Zhou, Xudong; Jiang, Minmin; Hesketh, Therese

2018-06-15

Tens of millions of rural "left-behind children (LBC)" in China grow up experiencing prolonged separation from their migrant worker parents. This study aimed to explore how children are affected by parental migration, from the perspectives of children, parents, and grandparents, focusing on the experiences of prolonged parent-child separation and relationship dynamics in the extended family. Qualitative in-depth interviews were conducted in a migrant-sending rural area of eastern China. Participants included 25 children (aged 7 to 14), 17 parents, and 13 grandparents, from 30 families, as well as 24 key informants from the communities. Data analysis followed a grounded theory approach. The results showed that despite the original purpose of benefiting children, parental migration resulted in challenges in child psychosocial well-being, due to the emotional impacts from prolonged parent-child separation. Parental absence also led to inadequate care and support for left-behind children. The negative effects of parental migration may be exacerbated by other vulnerabilities such as parents' divorce, poverty and grandparent caregivers' frailty. Concerns about child well-being made some migrants decide to return home permanently, because of the altered trade-offs of migration. Prolonged separation following migration often disrupts parent-child relationships and results in psychosocial difficulties in LBC, especially among those who live with multiple adversities in the family. Community-based interventions may help migrant parents and co-resident caregivers to better engage children and promote their resilience.

Avulsion vs Continuous Shifting: the Dynamics of Delta Distributary Channels Controlled by Basin Water Depth

NASA Astrophysics Data System (ADS)

Muto, T.; Naruse, H.

2015-12-01

An open question in the experimental study of surface processes is how basin water depth controls the dynamics of delta distributary channels. A recently suggested idea as to the issue is that, if a set of peculiar conditions is assumed, all of delta progradation, channel migration, alluvial aggradation and attainment of, or how close to, alluvial grade can be given by an identical formula with the same numerical value that is specified with dimensionless basin water depth. As one step ahead from this notion, we here report the finding obtained from a new series of tank experiments that basin water depth can also affect the modes by which active distributary channels change their locations, i.e. which one of avulsion and continuous shifting is predominant over the other. The results of the experiments clearly indicate that continuous shifting tends to become more predominant over avulsion as basin water depth increases. This tendency is related to a progressive decrease/increase in rate of alluvial aggradation which directly controls avulsion frequency. The present experimental notion can be examined with stratigraphic records of river deltas that accumulated with increasing or decreasing basin water depth.

Characterization and quantification of geochemical reaction rates in mine waste piles using unsaturated zone gases

NASA Astrophysics Data System (ADS)

Birkham, T.; Hendry, J.; Kirkland, R.; Bradley, S.; Mendoza, C.; Wassenaar, L.

2003-04-01

From 1997 to the present, we have installed and monitored 240 gas probes (maximum depth of 43 m) in unsaturated waste rock, overburden and tailings piles at a uranium mine in northern Saskatchewan, Canada and an oil sands mine in northern Alberta, Canada. Depth profiles of O2, CO2, N2 and CH4 pore-gas concentrations, temperature, and moisture content were measured in the field and used to characterize and quantifyin situ geochemical reaction rates. An innovative field-portable GC system has been developed to monitor pore-gas concentrations. At most sites, gas migration has been attributed to diffusion. At sites where advective transport may be important, subsurface total pressure measurements have been used to assess the contribution of advection to gas migration. The stable isotopes of molecular O2 (16O2 and 18O16O) and C in CO2 (12CO2 and 13CO2) have also been measured and modeled. At the uranium mine, the modelling of the O2, CO2, δ18OO2, and δ13CCO2 depth profiles was used to identify an alternative mechanism of O2 consumption and CO2 production in mine waste-rock piles. At the oil sands mine, a complex and unique system involving O2, CO2, and CH4 fluxes in the unsaturated zone and across the capillary fringe has been identified and is currently being modeled.

The influence of larval migration and dispersal depth on potential larval trajectories of a deep-sea bivalve

NASA Astrophysics Data System (ADS)

McVeigh, Doreen M.; Eggleston, David B.; Todd, Austin C.; Young, Craig M.; He, Ruoying

2017-09-01

Many fundamental questions in marine ecology require an understanding of larval dispersal and connectivity, yet direct observations of larval trajectories are difficult or impossible to obtain. Although biophysical models provide an alternative approach, in the deep sea, essential biological parameters for these models have seldom been measured empirically. In this study, we used a biophysical model to explore the role of behaviorally mediated migration from two methane seep sites in the Gulf of Mexico on potential larval dispersal patterns and population connectivity of the deep-sea mussel ;Bathymodiolus; childressi, a species for which some biological information is available. Three possible larval dispersal strategies were evaluated for larvae with a Planktonic Larval Duration (PLD) of 395 days: (1) demersal drift, (2) dispersal near the surface early in larval life followed by an extended demersal period before settlement, and (3) dispersal near the surface until just before settlement. Upward swimming speeds varied in the model based on the best data available. Average dispersal distances for simulated larvae varied between 16 km and 1488 km. Dispersal in the upper water column resulted in the greatest dispersal distance (1173 km ± 2.00), followed by mixed dispersal depth (921 km ± 2.00). Larvae originating in the Gulf of Mexico can potentially seed most known seep metapopulations on the Atlantic continental margin, whereas larvae drifting demersally cannot (237 km ± 1.43). Depth of dispersal is therefore shown to be a critical parameter for models of deep-sea connectivity.

Tectonic Inversion Along the Algerian and Ligurian Margins: On the Insight Provided By Latest Seismic Processing Techniques Applied to Recent and Vintage 2D Offshore Multichannel Seismic Data

NASA Astrophysics Data System (ADS)

Schenini, L.; Beslier, M. O.; Sage, F.; Badji, R.; Galibert, P. Y.; Lepretre, A.; Dessa, J. X.; Aidi, C.; Watremez, L.

2014-12-01

Recent studies on the Algerian and the North-Ligurian margins in the Western Mediterranean have evidenced inversion-related superficial structures, such as folds and asymmetric sedimentary perched basins whose geometry hints at deep compressive structures dipping towards the continent. Deep seismic imaging of these margins is difficult due to steep slope and superficial multiples, and, in the Mediterranean context, to the highly diffractive Messinian evaporitic series in the basin. During the Algerian-French SPIRAL survey (2009, R/V Atalante), 2D marine multi-channel seismic (MCS) reflection data were collected along the Algerian Margin using a 4.5 km, 360 channel digital streamer and a 3040 cu. in. air-gun array. An advanced processing workflow has been laid out using Geocluster CGG software, which includes noise attenuation, 2D SRME multiple attenuation, surface consistent deconvolution, Kirchhoff pre-stack time migration. This processing produces satisfactory seismic images of the whole sedimentary cover, and of southward dipping reflectors in the acoustic basement along the central part of the margin offshore Great Kabylia, that are interpreted as inversion-related blind thrusts as part of flat-ramp systems. We applied this successful processing workflow to old 2D marine MCS data acquired on the North-Ligurian Margin (Malis survey, 1995, R/V Le Nadir), using a 2.5 km, 96 channel streamer and a 1140 cu. in. air-gun array. Particular attention was paid to multiple attenuation in adapting our workflow. The resulting reprocessed seismic images, interpreted with a coincident velocity model obtained by wide-angle data tomography, provide (1) enhanced imaging of the sedimentary cover down to the top of the acoustic basement, including the base of the Messinian evaporites and the sub-salt Miocene series, which appear to be tectonized as far as in the mid-basin, and (2) new evidence of deep crustal structures in the margin which the initial processing had failed to reveal.

Study on diesel vertical migration characteristics and mechanism in water-bearing sand stratum using an automated resistivity monitoring system.

PubMed

Pan, Yuying; Jia, Yonggang; Wang, Yuhua; Xia, Xin; Guo, Lei

2018-02-01

Oil spills frequently occur on both land and sea. Petroleum in mobile phase will cause serious pollution in the sediment and can form a secondary pollution source. Therefore, it is very important to study the migration of petroleum in sediments ideally in a rapid and simplified approach. The release of diesel was simulated using fine beach sand to construct a model aquifer, and dynamic monitoring was carried out using an automated monitoring system including a resistivity probe originally developed by our research group. The mobile phase migration fronts were determined accurately using wavelet analysis method combined with resistivity curve method. Then, a relationship between resistivity and the joint oil-water content was established. The main conclusions were as follows. The seepage velocity of the diesel with high mobility at the initial stage of infiltration was faster, followed by a period when gravity seepage was dominant, and finally a redistribution period at the later stage, which was mainly an oil-water displacement process. The resistivity trends for diesel infiltration in different water-saturated soil layers varied with depth. The resistivity in the vadose zone fluctuated significantly, increasing initially and later decreasing. The resistivity change in the capillary zone was relatively small and constant in the initial stage; then, it increased and subsequently decreased. The resistivity in the saturated zone was basically unchanged with depth, and the value became slightly larger than the background value over time. Overall, for a large volume of mobile phase diesel leakage, the arrival migration fronts can be detected by wavelet analysis combined with resistivity curves. The thickness of the oil slick in the capillary zone can be estimated by resistivity changes. The relationships between resistivity and both the moisture content and oil-water joint saturation are in agreement with the linear models. The research results provide basic data and a new data processing method for monitoring of contaminated sites following major oil spills using the resistivity method.

Limits to benthic feeding by eiders in a vital Arctic migration corridor due to localized prey and changing sea ice

USGS Publications Warehouse

Lovvorn, James R.; Rocha, Aariel R.; Jewett, Stephen C.; Dasher, Douglas; Oppel, Steffen; Powell, Abby

2015-01-01

Four species of threatened or declining eider ducks that nest in the Arctic migrate through the northeast Chukchi Sea, where anticipated industrial development may require prioritizing areas for conservation. In this nearshore corridor (10–40 m depth), the eiders’ access to benthic prey during the spring is restricted to variable areas of open water within sea ice. For the most abundant species, the king eider (Somateria spectabilis), stable isotopes in blood cells, muscle, and potential prey indicate that these eiders ate mainly bivalves when traversing this corridor. Bivalves there were much smaller than the same taxa in deeper areas of the northern Bering Sea, possibly due to higher mortality rates caused by ice scour in shallow water; future decrease in seasonal duration of fast ice may increase this effect. Computer simulations suggested that if these eiders forage for >15 h/day, they can feed profitably at bivalve densities >200 m−2 regardless of water depth or availability of ice for resting. Sampling in 2010–2012 showed that large areas of profitable prey densities occurred only in certain locations throughout the migration corridor. Satellite data in April–May over 13 years (2001–2013) indicated that access to major feeding areas through sea ice in different segments of the corridor can vary from 0% to 100% between months and years. In a warming and increasingly variable climate, unpredictability of access may be enhanced by greater effects of shifting winds on unconsolidated ice. Our results indicate the importance of having a range of potential feeding areas throughout the migration corridor to ensure prey availability in all years. Spatial planning of nearshore industrial development in the Arctic, including commercial shipping, pipeline construction, and the risk of released oil, should consider these effects of high environmental variability on the adequacy of habitats targeted for conservation.

Limits to benthic feeding by eiders in a vital Arctic migration corridor due to localized prey and changing sea ice

NASA Astrophysics Data System (ADS)

Lovvorn, James R.; Rocha, Aariel R.; Jewett, Stephen C.; Dasher, Douglas; Oppel, Steffen; Powell, Abby N.

2015-08-01

Four species of threatened or declining eider ducks that nest in the Arctic migrate through the northeast Chukchi Sea, where anticipated industrial development may require prioritizing areas for conservation. In this nearshore corridor (10-40 m depth), the eiders' access to benthic prey during the spring is restricted to variable areas of open water within sea ice. For the most abundant species, the king eider (Somateria spectabilis), stable isotopes in blood cells, muscle, and potential prey indicate that these eiders ate mainly bivalves when traversing this corridor. Bivalves there were much smaller than the same taxa in deeper areas of the northern Bering Sea, possibly due to higher mortality rates caused by ice scour in shallow water; future decrease in seasonal duration of fast ice may increase this effect. Computer simulations suggested that if these eiders forage for >15 h/day, they can feed profitably at bivalve densities >200 m-2 regardless of water depth or availability of ice for resting. Sampling in 2010-2012 showed that large areas of profitable prey densities occurred only in certain locations throughout the migration corridor. Satellite data in April-May over 13 years (2001-2013) indicated that access to major feeding areas through sea ice in different segments of the corridor can vary from 0% to 100% between months and years. In a warming and increasingly variable climate, unpredictability of access may be enhanced by greater effects of shifting winds on unconsolidated ice. Our results indicate the importance of having a range of potential feeding areas throughout the migration corridor to ensure prey availability in all years. Spatial planning of nearshore industrial development in the Arctic, including commercial shipping, pipeline construction, and the risk of released oil, should consider these effects of high environmental variability on the adequacy of habitats targeted for conservation.

Migration, Foraging, and Residency Patterns for Northern Gulf Loggerheads: Implications of Local Threats and International Movements

PubMed Central

Hart, Kristen M.; Lamont, Margaret M.; Sartain, Autumn R.; Fujisaki, Ikuko

2014-01-01

Northern Gulf of Mexico (NGoM) loggerheads (Caretta caretta) make up one of the smallest subpopulations of this threatened species and have declining nest numbers. We used satellite telemetry and a switching state-space model to identify distinct foraging areas used by 59 NGoM loggerheads tagged during 2010–2013. We tagged turtles after nesting at three sites, 1 in Alabama (Gulf Shores; n = 37) and 2 in Florida (St. Joseph Peninsula; n = 20 and Eglin Air Force Base; n = 2). Peak migration time was 22 July to 9 August during which >40% of turtles were in migration mode; the mean post-nesting migration period was 23.0 d (±13.8 d SD). After displacement from nesting beaches, 44 turtles traveled to foraging sites where they remained resident throughout tracking durations. Selected foraging locations were variable distances from tagging sites, and in 5 geographic regions; no turtles selected foraging sites outside the Gulf of Mexico (GoM). Foraging sites delineated using 50% kernel density estimation were located a mean distance of 47.6 km from land and in water with mean depth of −32.5 m; other foraging sites, delineated using minimum convex polygons, were located a mean distance of 43.0 km from land and in water with a mean depth of −24.9 m. Foraging sites overlapped with known trawling activities, oil and gas extraction activities, and the footprint of surface oiling during the 2010 Deepwater Horizon oil spill (n = 10). Our results highlight the year-round use of habitats in the GoM by loggerheads that nest in the NGoM. Our findings indicate that protection of females in this subpopulation requires both international collaborations and management of threats that spatially overlap with distinct foraging habitats. PMID:25076053

Forage quantity estimation from MERIS using band depth parameters

NASA Astrophysics Data System (ADS)

Ullah, Saleem; Yali, Si; Schlerf, Martin

Saleem Ullah1 , Si Yali1 , Martin Schlerf1 Forage quantity is an important factor influencing feeding pattern and distribution of wildlife. The main objective of this study was to evaluate the predictive performance of vegetation indices and band depth analysis parameters for estimation of green biomass using MERIS data. Green biomass was best predicted by NBDI (normalized band depth index) and yielded a calibration R2 of 0.73 and an accuracy (independent validation dataset, n=30) of 136.2 g/m2 (47 % of the measured mean) compared to a much lower accuracy obtained by soil adjusted vegetation index SAVI (444.6 g/m2, 154 % of the mean) and by other vegetation indices. This study will contribute to map and monitor foliar biomass over the year at regional scale which intern can aid the understanding of bird migration pattern. Keywords: Biomass, Nitrogen density, Nitrogen concentration, Vegetation indices, Band depth analysis parameters 1 Faculty of Geo-Information Science and Earth Observation (ITC), University of Twente, The Netherlands

Tracking the Subsurface Signal of Decadal Climate Warming to Quantify Vertical Groundwater Flow Rates

NASA Astrophysics Data System (ADS)

Bense, V. F.; Kurylyk, B. L.

2017-12-01

Sustained ground surface warming on a decadal time scale leads to an inversion of thermal gradients in the upper tens of meters. The magnitude and direction of vertical groundwater flow should influence the propagation of this warming signal, but direct field observations of this phenomenon are rare. Comparison of temperature-depth profiles in boreholes in the Veluwe area, Netherlands, collected in 1978-1982 and 2016 provided such direct measurement. We used these repeated profiles to track the downward propagation rate of the depth at which the thermal gradient is zero. Numerical modeling of the migration of this thermal gradient "inflection point" yielded estimates of downward groundwater flow rates (0-0.24 m a-1) that generally concurred with known hydrogeological conditions in the area. We conclude that analysis of inflection point depths in temperature-depth profiles impacted by surface warming provides a largely untapped opportunity to inform sustainable groundwater management plans that rely on accurate estimates of long-term vertical groundwater fluxes.

Transnational labour migration and the politics of care in the Southeast Asian family

PubMed Central

Hoang, Lan Anh; Yeoh, Brenda S.A.; Wattie, Anna Marie

2012-01-01

Recent increases in female labour migration in and from Asia have triggered a surge of interest in how the absence of the mother and wife for extended periods of time affects the left-behind family, particularly children, in labour-sending countries. While migration studies in the region have shown that the extended family, especially female relatives, is often called on for support in childcare during the mother’s absence it is not yet clear how childcare arrangements are made. Drawing on in-depth interviews with non-parent carers of left-behind children in Indonesia and Vietnam, the paper aims to unveil complexities and nuances around care in the context of transnational labour migration. In so doing it draws attention to the enduring influence of social norms on the organisation of family life when women are increasingly drawn into the global labour market. By contrasting a predominantly patrilineal East Asian family structure in Vietnam with what is often understood as a bilateral South-East Asian family structure in Indonesia, the paper seeks to provide interesting comparative insights into the adaptive strategies that the transnational family pursues in order to cope with the reproductive vacuum left behind by the migrant mother. PMID:22984293

Female streetwalkers' perspectives on migration and HIV/STI risks in a changing economic and social environment: a qualitative study in Shanghai, China.

PubMed

Huang, Z Jennifer; Hu, Dier; Chang, Ruth; Zaccaro, Heather; Iguchi, Martin; Zheng, Huang; He, Na

2015-01-01

China's 30-year economic boom has created a unique social and economic market for commercial sex, as well as for a workforce of migrant women from rural China. This qualitative study explores the impact of the rapidly changing social and economic environment on migration patterns, knowledge of sexually transmitted infections (STIs), STI risk behaviours and health beliefs among female streetwalkers in Shanghai. Qualitative data were collected in 2010 through semi-structured in-depth interviews with 16 streetwalkers to characterise their migration passages, sexual health and behaviours, and peer networks. Many streetwalkers reported histories of childhood impoverishment, of family or partner violence or trauma, of migration consistent with the timeline and routes of economic development and of a scarcity in health, social or economic support. Their knowledge of the prevention and treatment of HIV and STIs was limited. They had little bargaining power on condom use and the majority resorted to vaginal douching and self-management with antibiotics as preventative measures. The study identifies streetwalkers' perspectives on the changing environment, their options and actions and, finally, HIV/STI risks that were unique to this hidden population.

Migrating swarms of brittle-failure earthquakes in the lower crust beneath Mammoth Mountain, California

USGS Publications Warehouse

Shelly, D.R.; Hill, D.P.

2011-01-01

Brittle-failure earthquakes in the lower crust, where high pressures and temperatures would typically promote ductile deformation, are relatively rare but occasionally observed beneath active volcanic centers. Where they occur, these earthquakes provide a rare opportunity to observe volcanic processes in the lower crust, such as fluid injection and migration, which may induce brittle faulting under these conditions. Here, we examine recent short-duration earthquake swarms deep beneath the southwestern margin of Long Valley Caldera, near Mammoth Mountain. We focus in particular on a swarm that occurred September 29-30, 2009. To maximally illuminate the spatial-temporal progression, we supplement catalog events by detecting additional small events with similar waveforms in the continuous data, achieving up to a 10-fold increase in the number of locatable events. We then relocate all events, using cross-correlation and a double-difference algorithm. We find that the 2009 swarm exhibits systematically decelerating upward migration, with hypocenters shallowing from 21 to 19 km depth over approximately 12 hours. This relatively high migration rate, combined with a modest maximum magnitude of 1.4 in this swarm, suggests the trigger might be ascending CO2 released from underlying magma.

Snow-mediated ptarmigan browsing and shrub expansion in arctic Alaska

Treesearch

Ken D. Tape; Rachel Lord; Hans-Peter Marshall; Roger W. Ruess

2010-01-01

Large, late-winter ptarmigan migrations heavily impact the shoot, plant, and patch architecture of shrubs that remain above the snow surface. Ptarmigan browsing on arctic shrubs was assessed in the vicinity of Toolik Lake, on the north side of the Brooks Range in Alaska. Data were collected in early May 2007, at maximum snow depth, after the bulk of the ptarmigan...

"If Only I Did Not Have That Label Attached to Me": Foregrounding Self-Positioning and Intersectionality in the Experiences of Immigrant and Refugee Youth

ERIC Educational Resources Information Center

Fruja Amthor, Ramona

2017-01-01

In order to bring forth the specific intricacies of the migration experience among comparatively understudied immigrant and refugee youth, this article bridges an intersectionality framework with multicultural education scholars' calls to flexibility and fluidity in conceptualizing culture and identity. Drawing on in-depth interviews, the analysis…

Large scale patterns in vertical distribution and behaviour of mesopelagic scattering layers

NASA Astrophysics Data System (ADS)

Klevjer, T. A.; Irigoien, X.; Røstad, A.; Fraile-Nuez, E.; Benítez-Barrios, V. M.; Kaartvedt., S.

2016-01-01

Recent studies suggest that previous estimates of mesopelagic biomasses are severely biased, with the new, higher estimates underlining the need to unveil behaviourally mediated coupling between shallow and deep ocean habitats. We analysed vertical distribution and diel vertical migration (DVM) of mesopelagic acoustic scattering layers (SLs) recorded at 38 kHz across oceanographic regimes encountered during the circumglobal Malaspina expedition. Mesopelagic SLs were observed in all areas covered, but vertical distributions and DVM patterns varied markedly. The distribution of mesopelagic backscatter was deepest in the southern Indian Ocean (weighted mean daytime depth: WMD 590 m) and shallowest at the oxygen minimum zone in the eastern Pacific (WMD 350 m). DVM was evident in all areas covered, on average ~50% of mesopelagic backscatter made daily excursions from mesopelagic depths to shallow waters. There were marked differences in migrating proportions between the regions, ranging from ~20% in the Indian Ocean to ~90% in the Eastern Pacific. Overall the data suggest strong spatial gradients in mesopelagic DVM patterns, with implied ecological and biogeochemical consequences. Our results suggest that parts of this spatial variability can be explained by horizontal patterns in physical-chemical properties of water masses, such as oxygen, temperature and turbidity.

Selective placement disposal of drilling fluids in west Texas

DOE Office of Scientific and Technical Information (OSTI.GOV)

McFarland, M.L.

1988-01-01

Burial of spent drilling fluids used in petroleum and natural gas exploration was evaluated as an alternative disposal technique for reducing surface soil contamination in western Texas. Simulated reserve pits were constructed to provide burial depths of 30, 90, and 150 cm below the surface, with orderly replacement of stockpiled subsoil and topsoil. Movement of soluble salts and heavy metals from drilling fluids into the overlying soil was monitored over a 20-month period. The effects of depth of drilling fluid burial on establishment, yields, and chemical composition of transplanted fourwing saltbush (Atriplex canescens (Pursh) Nutt.) and buffalograss (Buchloe dactyloides (Nutt.)more » Engelm.) were determined for two growing seasons. Sodium, Ca{sup +2}, and Cl{sup {minus}} were the dominant mobile ions, while migration of Mg{sup +2}, K{sup +}, and SO{sub 4}{sup {minus}2} was observed to a lesser degree. Exchangeable sodium percentages in the 15-cm zone immediately above drilling fluid ranged from 1.9 to 19.0 after 20 months. Total concentrations of Ba, Cr, Cu, Ni, and Zn were greater in drilling fluids than in native soil, but there was no evidence of migration of these metals into overlying soil.« less

Large scale patterns in vertical distribution and behaviour of mesopelagic scattering layers.

PubMed

Klevjer, T A; Irigoien, X; Røstad, A; Fraile-Nuez, E; Benítez-Barrios, V M; Kaartvedt, S

2016-01-27

Recent studies suggest that previous estimates of mesopelagic biomasses are severely biased, with the new, higher estimates underlining the need to unveil behaviourally mediated coupling between shallow and deep ocean habitats. We analysed vertical distribution and diel vertical migration (DVM) of mesopelagic acoustic scattering layers (SLs) recorded at 38 kHz across oceanographic regimes encountered during the circumglobal Malaspina expedition. Mesopelagic SLs were observed in all areas covered, but vertical distributions and DVM patterns varied markedly. The distribution of mesopelagic backscatter was deepest in the southern Indian Ocean (weighted mean daytime depth: WMD 590 m) and shallowest at the oxygen minimum zone in the eastern Pacific (WMD 350 m). DVM was evident in all areas covered, on average ~50% of mesopelagic backscatter made daily excursions from mesopelagic depths to shallow waters. There were marked differences in migrating proportions between the regions, ranging from ~20% in the Indian Ocean to ~90% in the Eastern Pacific. Overall the data suggest strong spatial gradients in mesopelagic DVM patterns, with implied ecological and biogeochemical consequences. Our results suggest that parts of this spatial variability can be explained by horizontal patterns in physical-chemical properties of water masses, such as oxygen, temperature and turbidity.

VERTICAL MIGRATION OF RADIONUCLIDES IN THE VICINITY OF THE CHERNOBYL CONFINEMENT SHELTER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farfan, E.; Jannik, T.; Marra, J.

2011-10-01

Studies on vertical migration of Chernobyl-origin radionuclides in the 5-km zone of the Chernobyl Nuclear Power Plant (ChNPP) in the area of the Red Forest experimental site were completed. Measurements were made by gamma spectrometric methods using high purity germanium (HPGe) detectors with beryllium windows. Alpha-emitting isotopes of plutonium were determined by the measurement of the x-rays from their uranium progeny. The presence of {sup 60}Co, {sup 134,137}Cs, {sup 154,155}Eu, and {sup 241}Am in all soil layers down to a depth of 30 cm was observed. The presence of {sup 137}Cs and {sup 241}Am were noted in the area containingmore » automorphous soils to a depth of 60 cm. In addition, the upper soil layers at the test site were found to contain {sup 243}Am and {sup 243}Cm. Over the past ten years, the {sup 241}Am/{sup 137}Cs ratio in soil at the experimental site has increased by a factor of 3.4, nearly twice as much as would be predicted based solely on radioactive decay. This may be due to 'fresh' fallout emanating from the ChNPP Confinement Shelter.« less

Effluent migration from septic tank systems in two different lithologies, Broward County, Florida

USGS Publications Warehouse

Waller, B.G.; Howie, Barbara; Causaras, C.R.

1987-01-01

Two septic tank test sites, one in sand and one in limestone, in Broward County, Florida, were analyzed for effluent migration. Groundwater from shallow wells, both in background areas and hydraulically down-gradient of the septic tank system, was sampled during a 16-month period from April 1983 through August 1984. Water quality indicators were used to determine the effluent affected zone near the septic tank systems. Specific conductance levels and concentrations of chloride, sulfate, ammonium, and nitrate indicated effluent movement primarily in a vertical direction with abrupt dilution as it moved down-gradient. Effluent was detected in the sand to a depth more than 20 ft below the septic tank outlet, but was diluted to near background conditions 50 ft down-gradient from the tank. Effluent in the limestone was detected in all three observation wells to depths exceeding 25 ft below the septic tank outlet and was diluted, but still detectable, 40 ft down-gradient. The primary controls on effluent movement from septic tank systems in Broward County are the lithology and layering of the geologic materials, hydraulic gradients, and the volume and type of use the system receives. (Author 's abstract)

Sunda-Banda Arc Transition: Marine Multichannel Seismic Profiling

NASA Astrophysics Data System (ADS)

Lueschen, E.; Mueller, C.; Kopp, H.; Djajadihardja, Y.; Ehrhardt, A.; Engels, M.; Lutz, R.; Planert, L.; Shulgin, A.; Working Group, S.

2008-12-01

After the Indian Ocean Mw 9.3 earthquake and tsunami on December 26, 2004, intensive research activities focussed on the Sunda Arc subduction system offshore Sumatra. For this area a broad database is now available interpreted in terms of plate segmentation and outer arc high evolution. In contrast, the highly active easternmost part of this subduction system, as indicated by the south of Java Mw 7.7 earthquake and tsunami on July 17, 2006, has remained almost unexplored until recently. During RV SONNE cruise SO190 from October until December 2006 almost 5000 km of marine geophysical profiles have been acquired at the eastern Sunda Arc and the transition to the Banda Arc. The SINDBAD project (Seismic and Geoacoustic Investigations along the Sunda-Banda Arc Transition) comprises 30-fold multichannel reflection seismics with a 3-km streamer, wide-angle OBH/OBS refraction seismics for deep velocity control (see poster of Shulgin et al. in this session), swath bathymetry, sediment echosounder, gravimetric and geomagnetic measurements. We present data and interpretations of several 250-380 km long, prestack depth-migrated seismic sections, perpendicular to the deformation front, based on velocity models from focussing analysis and inversion of OBH/OBS refraction data. We focus on the variability of the lower plate and the tectonic response of the overriding plate in terms of outer arc high formation and evolution, forearc basin development, accretion and erosion processes at the base of the overriding plate. The subducting Indo-Australian Plate is characterized by three segments: i) the Roo Rise with rough topography offshore eastern Java ii) the Argo Abyssal Plain with smooth oceanic crust offshore Bali, Lombok, and Sumbawa, and iii) the Scott Plateau with continental crust colliding with the Banda island arc. The forearc responds to differences in the incoming oceanic plate with the absence of a pronounced forearc basin offshore eastern Java and with development of the 4000 m deep forearc Lombok Basin offshore Bali, Lombok, and Sumbawa. The eastern termination of the Lombok Basin is formed by Sumba Island, which shows evidence for recent uplift, probably associated with the collision of the island arc with the continental Scott Plateau. The Sumba area represents the transition from subduction to collision. Our seismic profiles image the bending of the oceanic crust seaward of the trench and associated normal faulting. Landward of the trench, they image the subducting slab beneath the outer arc high, where the former bending-related normal faults appear to be reactivated as reverse faults introducing vertical displacements in the subducting slab. The accretionary prism and the outer arc high are characterized by an ocean-verging system of imbricate thrust sheets with major thrust faults connecting seafloor and detachment. Compression results in shortening and steepening of the imbricated thrust sheets building up the outer arc high. Tilted piggy-back basins and downlaps of tilted sediments in the southern Lombok forearc basin indicate ongoing uplift of the entire outer arc high, abrupt displacements, and recent tectonic activity.

Seismic imaging of a transform segment of the Maranhão-Barreirinhas-Ceará margin, NW Brazil

NASA Astrophysics Data System (ADS)

Schnurle, Philippe; Moulin, Maryline; Gallais, Flora; Afilhado, Alexandra; Afonso Dias, Nuno; Soares, José; Loureiro, Afonso; Fuck, Reinhardt; Cupertino, José; Viana, Adriano; Matias, Luís; Evain, Mikael; Aslanian, Daniel

2017-04-01

The structure of the North-East equatorial Brazilian margin was investigated during the MAGIC (Margins of brAzil, Ghana and Ivory Coast) seismic experiment, a project conducted by IFREMER (Institut Francais de Recherche pour l'Exploration de la Mer), UnB (University of Brasilia), FCUL (Faculdade de Ciências da Universidade de Lisboa) and Petrobras. The survey consists of 5 deep seismic profiles totaling 1900 km of marine multi-channel seismic reflection and wide angle acquisition with 143 deployments of short-period OBS's from the IFREMER pool. Three of the profiles were extended into land using Land Seismic Stations (LSS) from the Brazilian pool at a total of 50 points. This study focuses on the MC1 and MC5 wide-angle profiles: MC5 spans NW-SE 720 km in length, from the São Paulo Double Fracture Zone to the Borborema-Cearà margin. MC-1 spans parallel east of MC5, 360 km in length, in the presumed oceanic domain. Our main objective is to understand the fundamental processes which lead to the thinning and finally to the breakup of the continental crust in a specific context of a pull-apart system with two strike-slip borders. The experiment was devised to obtain the 2D structure along the profiles from joint pre-stack depth migration of the reflection data, and tomography and forward modeling of the OBS records. Along the MC1/MC5 wide-angle transects, 5 major sectors are identified: - the São Paulo Double Fracture Zone and the volcanic line associated to the southern São Paulo strike-slip zone presenting a 4.5 km thick volcano-sedimentary basin on top of a 5.5 km thick basement; - the intermediate domain, formed by the 4.5 km thick Basin III, the 7.5 km thick Basin II (interleaved by a 0.5-1 km thick volcanic layer), and the 5.5 km thick Basin I composing the continental slope. While the crust remains about 6 km thick, its acoustic velocity evolves from two-layer typical (4.8-6 km/s and 6.1-6.8 km/s) beneath Basin III to two-layer high velocity (6.1-6.8 km/s and 7.2-7.4 km/s) beneath Basin II and I, interpreted as exhumed lower continental crust; - to the east, the oceanic crust, evolves to an 2 layers crust 5 km thick, characterized by typical oceanic crustal velocities and also overlain by 5.5 km of sedimentary deposits, spanning between the two main fracture zones that fringe the Maranhão-Barreirinhas-Ceará segment; - the 50 km wide necking zone, forming the Parnaiba Platform and associated Ceará Basins, where the upper and lower crust thin abruptly; - the Medio Coreaù and Ceará Central thrust belt, where the unthinned continental crust thickness reaches 32 km. Keywords: North-East equatorial Brazil, transform margin, deep seismic structure

Estimation of the tritium retention in ITER tungsten divertor target using macroscopic rate equations simulations

NASA Astrophysics Data System (ADS)

Hodille, E. A.; Bernard, E.; Markelj, S.; Mougenot, J.; Becquart, C. S.; Bisson, R.; Grisolia, C.

2017-12-01

Based on macroscopic rate equation simulations of tritium migration in an actively cooled tungsten (W) plasma facing component (PFC) using the code MHIMS (migration of hydrogen isotopes in metals), an estimation has been made of the tritium retention in ITER W divertor target during a non-uniform exponential distribution of particle fluxes. Two grades of materials are considered to be exposed to tritium ions: an undamaged W and a damaged W exposed to fast fusion neutrons. Due to strong temperature gradient in the PFC, Soret effect’s impacts on tritium retention is also evaluated for both cases. Thanks to the simulation, the evolutions of the tritium retention and the tritium migration depth are obtained as a function of the implanted flux and the number of cycles. From these evolutions, extrapolation laws are built to estimate the number of cycles needed for tritium to permeate from the implantation zone to the cooled surface and to quantify the corresponding retention of tritium throughout the W PFC.

The Chaoborus pump: Migrating phantom midge larvae sustain hypolimnetic oxygen deficiency and nutrient internal loading in lakes.

PubMed

Tang, Kam W; Flury, Sabine; Grossart, Hans-Peter; McGinnis, Daniel F

2017-10-01

Hypolimnetic oxygen demand in lakes is often assumed to be driven mainly by sediment microbial processes, while the role of Chaoborus larvae, which are prevalent in eutrophic lakes with hypoxic to anoxic bottoms, has been overlooked. We experimentally measured the respiration rates of C. flavicans at different temperatures yielding a Q 10 of 1.44-1.71 and a respiratory quotient of 0.84-0.98. Applying the experimental data in a system analytical approach, we showed that migrating Chaoborus larvae can significantly add to the water column and sediment oxygen demand, and contribute to the observed linear relationship between water column respiration and depth. The estimated phosphorus excretion by Chaoborus in sediment is comparable in magnitude to the required phosphorus loading for eutrophication. Migrating Chaoborus larvae thereby essentially trap nutrients between the water column and the sediment, and this continuous internal loading of nutrients would delay lake remediation even when external inputs are stopped. Copyright © 2017 Elsevier Ltd. All rights reserved.

Nurses, Inc.: expansion and commercialization of nursing education in the Philippines.

PubMed

Masselink, Leah E; Lee, Shoou-Yih Daniel

2010-07-01

Exporting nurses has been a long-standing economic strategy for the Philippine government, despite the fact that the Philippines' domestic health system is weak and existing supplies of health workers are poorly distributed. This study explores the role of nursing schools as "migrant institutions" in expanding and commercializing nursing education and perpetuating the link between nursing education and migration. Data were collected primarily via in-depth interviews of key informants (nursing school administrators and policymakers) in the Philippines. Results suggest that nursing schools have expanded migration opportunities by making nursing educational available to more students and more diverse student populations. Also, some nursing schools have acted to control the licensure and recruitment processes by establishing commercial relationships with licensure exam review centers and recruitment agencies. These activities perpetuate the culture of migration in the country's nursing profession and indirectly contribute to declining quality of nursing education, misuse of scarce resources, corruption in the nursing sector, and exacerbation of existing health workforce imbalances. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Marine turtles used to assist Austronesian sailors reaching new islands.

PubMed

Wilmé, Lucienne; Waeber, Patrick O; Ganzhorn, Joerg U

2016-02-01

Austronesians colonized the islands of Rapa Nui, Hawaii, the Marquesas and Madagascar. All of these islands have been found to harbor Austronesian artifacts and also, all of them are known nesting sites for marine turtles. Turtles are well known for their transoceanic migrations, sometimes totalling thousands of miles, between feeding and nesting grounds. All marine turtles require land for nesting. Ancient Austronesians are known to have had outstanding navigation skills, which they used to adjust course directions. But these skills will have been insufficient to locate tiny, remote islands in the vast Indo-Pacific oceans. We postulate that the Austronesians must have had an understanding of the marine turtles' migration patterns and used this knowledge to locate remote and unknown islands. The depth and speed at which marine turtles migrate makes following them by outrigger canoes feasible. Humans have long capitalized on knowledge of animal behavior. Copyright © 2015 Académie des sciences. Published by Elsevier SAS. All rights reserved.

Unexpected Positive Buoyancy in Deep Sea Sharks, Hexanchus griseus, and a Echinorhinus cookei

PubMed Central

Nakamura, Itsumi; Meyer, Carl G.; Sato, Katsufumi

2015-01-01

We do not expect non air-breathing aquatic animals to exhibit positive buoyancy. Sharks, for example, rely on oil-filled livers instead of gas-filled swim bladders to increase their buoyancy, but are nonetheless ubiquitously regarded as either negatively or neutrally buoyant. Deep-sea sharks have particularly large, oil-filled livers, and are believed to be neutrally buoyant in their natural habitat, but this has never been confirmed. To empirically determine the buoyancy status of two species of deep-sea sharks (bluntnose sixgill sharks, Hexanchus griseus, and a prickly shark, Echinorhinus cookei) in their natural habitat, we used accelerometer-magnetometer data loggers to measure their swimming performance. Both species of deep-sea sharks showed similar diel vertical migrations: they swam at depths of 200–300 m at night and deeper than 500 m during the day. Ambient water temperature was around 15°C at 200–300 m but below 7°C at depths greater than 500 m. During vertical movements, all deep-sea sharks showed higher swimming efforts during descent than ascent to maintain a given swimming speed, and were able to glide uphill for extended periods (several minutes), indicating that these deep-sea sharks are in fact positively buoyant in their natural habitats. This positive buoyancy may adaptive for stealthy hunting (i.e. upward gliding to surprise prey from underneath) or may facilitate evening upward migrations when muscle temperatures are coolest, and swimming most sluggish, after spending the day in deep, cold water. Positive buoyancy could potentially be widespread in fish conducting daily vertical migration in deep-sea habitats. PMID:26061525

Unexpected Positive Buoyancy in Deep Sea Sharks, Hexanchus griseus, and a Echinorhinus cookei.

PubMed

Nakamura, Itsumi; Meyer, Carl G; Sato, Katsufumi

2015-01-01

We do not expect non air-breathing aquatic animals to exhibit positive buoyancy. Sharks, for example, rely on oil-filled livers instead of gas-filled swim bladders to increase their buoyancy, but are nonetheless ubiquitously regarded as either negatively or neutrally buoyant. Deep-sea sharks have particularly large, oil-filled livers, and are believed to be neutrally buoyant in their natural habitat, but this has never been confirmed. To empirically determine the buoyancy status of two species of deep-sea sharks (bluntnose sixgill sharks, Hexanchus griseus, and a prickly shark, Echinorhinus cookei) in their natural habitat, we used accelerometer-magnetometer data loggers to measure their swimming performance. Both species of deep-sea sharks showed similar diel vertical migrations: they swam at depths of 200-300 m at night and deeper than 500 m during the day. Ambient water temperature was around 15°C at 200-300 m but below 7°C at depths greater than 500 m. During vertical movements, all deep-sea sharks showed higher swimming efforts during descent than ascent to maintain a given swimming speed, and were able to glide uphill for extended periods (several minutes), indicating that these deep-sea sharks are in fact positively buoyant in their natural habitats. This positive buoyancy may adaptive for stealthy hunting (i.e. upward gliding to surprise prey from underneath) or may facilitate evening upward migrations when muscle temperatures are coolest, and swimming most sluggish, after spending the day in deep, cold water. Positive buoyancy could potentially be widespread in fish conducting daily vertical migration in deep-sea habitats.

Field-scale sulfur hexafluoride tracer experiment to understand long distance gas transport in the deep unsaturated zone

USGS Publications Warehouse

Walvoord, Michelle Ann; Andraski, Brian J.; Green, Christopher T.; Stonestrom, David A.; Striegl, Robert G.

2014-01-01

A natural gradient SF6 tracer experiment provided an unprecedented evaluation of long distance gas transport in the deep unsaturated zone (UZ) under controlled (known) conditions. The field-scale gas tracer test in the 110-m-thick UZ was conducted at the U.S. Geological Survey’s Amargosa Desert Research Site (ADRS) in southwestern Nevada. A history of anomalous (theoretically unexpected) contaminant gas transport observed at the ADRS, next to the first commercial low-level radioactive waste disposal facility in the United States, provided motivation for the SF6 tracer study. Tracer was injected into a deep UZ borehole at depths of 15 and 48 m, and plume migration was observed in a monitoring borehole 9 m away at various depths (0.5–109 m) over the course of 1 yr. Tracer results yielded useful information about gas transport as applicable to the spatial scales of interest for off-site contaminant transport in arid unsaturated zones. Modeling gas diffusion with standard empirical expressions reasonably explained SF6 plume migration, but tended to underpredict peak concentrations for the field-scale experiment given previously determined porosity information. Despite some discrepancies between observations and model results, rapid SF6 gas transport commensurate with previous contaminant migration was not observed. The results provide ancillary support for the concept that apparent anomalies in historic transport behavior at the ADRS are the result of factors other than nonreactive gas transport properties or processes currently in effect in the undisturbed UZ.

Reef Fish Community Biomass and Trophic Structure Changes across Shallow to Upper-Mesophotic Reefs in the Mesoamerican Barrier Reef, Caribbean

PubMed Central

Gress, Erika; Wright, Georgina; Exton, Dan A.; Rogers, Alex D.

2016-01-01

Mesophotic coral ecosystems (MCEs; reefs 30-150m depth) are of increased research interest because of their potential role as depth refuges from many shallow reef threats. Yet few studies have identified patterns in fish species composition and trophic group structure between MCEs and their shallow counterparts. Here we explore reef fish species and biomass distributions across shallow to upper-MCE Caribbean reef gradients (5-40m) around Utila, Honduras, using a diver-operated stereo-video system. Broadly, we found reef fish species richness, abundance and biomass declining with depth. At the trophic group level we identified declines in herbivores (both total and relative community biomass) with depth, mostly driven by declines in parrotfish (Scaridae). Piscivores increased as a proportion of the community with increased depth while, in contrast to previous studies, we found no change in relative planktivorous reef fish biomass across the depth gradient. In addition, we also found evidence of ontogenetic migrations in the blue tang (Acanthurus coeruleus), striped parrotfish (Scarus iserti), blue chromis (Chromis cyanea), creole wrasse (Clepticus parrae), bluehead wrasse (Thalassoma bifasciatum) and yellowtail snapper (Ocyurus chrysurus), with a higher proportion of larger individuals at mesophotic and near-mesophotic depths than on shallow reefs. Our results highlight the importance of using biomass measures when considering fish community changes across depth gradients, with biomass generating different results to simple abundance counts. PMID:27332811

Seismic Migration Imaging of the Crust and Upper Mantle Discontinuity Structure beneath Southern Taiwan

NASA Astrophysics Data System (ADS)

Liu, Y.-S.; Kuo, B.-Y.

2009-04-01

Taiwan is located in the convergent plate boundary zone where the Philippine Sea plate has obliquely collided on the Asian continental margin, initiating the arc-continent collision and subsequent mountain-building in Taiwan. Receiver function has been a powerful tool to image seismic velocity discontinuity structure in the crust and upper mantle which can help illuminate the deep dynamic process of active Taiwan orogeny. In this study, we adopt backprojection migration processing of teleseismic receiver functions to investigate the crust and upper mantle discontinuities beneath southern Taiwan, using the data from Southern Taiwan Transect Seismic Array (STTA), broadband stations of Central Weather Bureau (CWB), Broadband Array in Taiwan for Seismology (BATS), and Taiwan Integrated Geodynamics Research (TAIGER). This composite east-west trending linear array has the aperture of about 150 km with the station spacing of ~5-10 km. Superior to the common midpoint (CMP) stack approach, the migration can properly image the dipping, curved, or laterally-varying topography of discontinuous interfaces which very likely exist under the complicated tectonic setting of Taiwan. We first conduct synthetic experiments to test the depth and lateral resolution of migration images based on the WKBJ synthetic waveforms calculated from available source and receiver distributions. We will next construct the 2-D migration image under the array to reveal the topographic variation of the Moho and lithosphere discontinuities beneath southern Taiwan.

Migration of South African health workers: the extent to which financial considerations influence internal flows and external movements

PubMed Central

2013-01-01

Background The loss of human resource capacity has had a severe impact on the health system in South Africa. This study investigates the causes of migration focussing on the role of salaries and benefits. Health professionals from public, private and non-governmental (NGO) health facilities located in selected peri–urban and urban areas in KwaZulu-Natal, South Africa were surveyed about their current positions and attitudes toward migration. Methods The study uses cross-sectional data collected in 2009. A total of 694 health professionals (430 in the public sector, 133 in the NGO sector and 131 in the private sector) were surveyed. An additional 11 health professionals were purposively selected for in-depth interviews. Odds ratios with 95% confidence intervals were calculated to determine whether salaries influenced HWs decisions to migrate. Results HWs decision to move was not positively associated with lower salaries. It was found, instead, that the consideration to move was determined by other factors including age, levels of stress experienced and the extent to which they were satisfied at their current place of work. Conclusions The OSD appears to have lowered the risk of HWs migrating due to low salaries. However, the results also indicate that the South African Department of Health needs to improve working conditions for HWs within the public health sector to assist in retention. PMID:23919539

Migration of antioxidants from polylactic acid films, a parameter estimation approach: Part I - A model including convective mass transfer coefficient.

PubMed

Samsudin, Hayati; Auras, Rafael; Burgess, Gary; Dolan, Kirk; Soto-Valdez, Herlinda

2018-03-01

A two-step solution based on the boundary conditions of Crank's equations for mass transfer in a film was developed. Three driving factors, the diffusion (D), partition (K p,f ) and convective mass transfer coefficients (h), govern the sorption and/or desorption kinetics of migrants from polymer films. These three parameters were simultaneously estimated. They provide in-depth insight into the physics of a migration process. The first step was used to find the combination of D, K p,f and h that minimized the sums of squared errors (SSE) between the predicted and actual results. In step 2, an ordinary least square (OLS) estimation was performed by using the proposed analytical solution containing D, K p,f and h. Three selected migration studies of PLA/antioxidant-based films were used to demonstrate the use of this two-step solution. Additional parameter estimation approaches such as sequential and bootstrap were also performed to acquire a better knowledge about the kinetics of migration. The proposed model successfully provided the initial guesses for D, K p,f and h. The h value was determined without performing a specific experiment for it. By determining h together with D, under or overestimation issues pertaining to a migration process can be avoided since these two parameters are correlated. Copyright © 2017 Elsevier Ltd. All rights reserved.

Kurdish men's experiences of migration-related mental health issues.

PubMed

Taloyan, Marina; Al-Windi, Ahmad; Johansson, Leena Maria; Saleh-Stattin, Nuha

2011-10-01

The migration process may impose stress on the mental health of immigrants. To describe the experiences of immigrant men of Kurdish ethnicity during and after migration to Sweden with regard to mental health issues. Using the grounded theory method, we conducted a focus group interview with four Kurdish men and in-depth individual interviews with 10 other Kurdish men. A model with two major themes and interlinked categories was developed. The themes were (1) protective factors for good mental health (sense of belonging, creation and re-creation of Kurdish identity, sense of freedom, satisfaction with oneself) and (2) risk factors for poor mental health (worry about current political situation in the home country, yearning, lack of sense of freedom, dissatisfaction with Swedish society). The study provides insights into the psychological and emotional experiences of immigrant men of Kurdish ethnicity during and after migration to Sweden. It is important for primary health care providers to be aware of the impact that similar migration-related and life experiences have on the health status of immigrants, and also to be aware that groups are comprised of unique individuals with differing experiences and reactions to these experiences. The findings highlight the common themes of the men's experiences and suggest ways to ameliorate mental health issues, including feeling like one is seen as an individual, is a full participant in society, and can contribute to one's own culture.

Migration of South African health workers: the extent to which financial considerations influence internal flows and external movements.

PubMed

George, Gavin; Atujuna, Millicent; Gow, Jeff

2013-08-06

The loss of human resource capacity has had a severe impact on the health system in South Africa. This study investigates the causes of migration focussing on the role of salaries and benefits. Health professionals from public, private and non-governmental (NGO) health facilities located in selected peri-urban and urban areas in KwaZulu-Natal, South Africa were surveyed about their current positions and attitudes toward migration. The study uses cross-sectional data collected in 2009. A total of 694 health professionals (430 in the public sector, 133 in the NGO sector and 131 in the private sector) were surveyed. An additional 11 health professionals were purposively selected for in-depth interviews. Odds ratios with 95% confidence intervals were calculated to determine whether salaries influenced HWs decisions to migrate. HWs decision to move was not positively associated with lower salaries. It was found, instead, that the consideration to move was determined by other factors including age, levels of stress experienced and the extent to which they were satisfied at their current place of work. The OSD appears to have lowered the risk of HWs migrating due to low salaries. However, the results also indicate that the South African Department of Health needs to improve working conditions for HWs within the public health sector to assist in retention.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lefeuvre, F.E.; Wrolstad, K.H.; Zou, Ke Shan

Total and Unocal estimated sand-shale ratios in gas reservoirs from the upper Tertiary clastics of Myanmar. They separately used deterministic pre-stack and statistical post-stack seismic attribute analysis calibrated at two wells to objectively extrapolate the lithologies and reservoir properties several kilometers away from the wells. The two approaches were then integrated and lead to a unique distribution of the sands and shales in the reservoir which fit in the known regional geological model. For the sands, the fluid distributions (gas and brine) were also estimated as well as the porosity, water saturation, thickness and clay content of the sands. Thismore » was made possible by using precise elastic modeling based on the Biot-Gassmann equation in order to integrate the effects of reservoir properties on seismic signatures.« less

A Closer Look at the Junior Doctor Crisis in the United Kingdom's National Health Services: Is Emigration Justifiable?

PubMed

Teo, Wendy Zi Wei

2018-07-01

This article attempts to tackle the ethically and morally troubling issue of emigration of physicians from the United Kingdom, and whether it can be justified. Unlike most research that has already been undertaken in this field, which looks at migration from developing countries to developed countries, this article takes an in-depth look at the migration of physicians between developed countries, in particular from the United Kingdom (UK) to other developed countries such as Canada, Australia, New Zealand, and the United States (US). This examination was written in response to a current and critical crisis in the National Health Service (NHS), where impending contract changes may bring about a potential exodus of junior doctors.

Seasonal Modulation of Earthquake Swarm Activity Near Maupin, Oregon

NASA Astrophysics Data System (ADS)

Braunmiller, J.; Nabelek, J.; Trehu, A. M.

2012-12-01

Between December 2006 and November 2011, the Pacific Northwest Seismic Network (PNSN) reported 464 earthquakes in a swarm about 60 km east-southeast of Mt. Hood near the town of Maupin, Oregon. Relocation of forty-five MD≥2.5 earthquakes and regional moment tensor analysis of nine 3.3≤Mw≤3.9 earthquakes reveals a north-northwest trending, less than 1 km2 sized active fault patch on a 70° west dipping fault. At about 17 km depth, the swarm occurred at or close to the bottom of the seismogenic crust. The swarm's cumulative seismic moment release, equivalent to an Mw=4.4 earthquake, is not dominated by a single shock; it is rather mainly due to 20 MD≥3.0 events, which occurred throughout the swarm. The swarm started at the southern end and, during the first 18 months of activity, migrated to the northwest at a rate of about 1-2 m/d until reaching its northern terminus. A 10° fault bend, inferred from locations and fault plane solutions, acted as geometrical barrier that temporarily halted event migration in mid-2007 before continuing north in early 2008. The slow event migration points to a pore pressure diffusion process suggesting the swarm onset was triggered by fluid inflow into the fault zone. At 17 km depth, triggering by meteoritic water seems unlikely for a normal crustal permeability. The double couple source mechanisms preclude a magmatic intrusion at the depth of the earthquakes. However, fluids (or gases) associated with a deeper, though undocumented, magma injection beneath the Cascade Mountains, could trigger seismicity in a pre-stressed region when they have migrated upward and reached the seismogenic crust. Superimposed on overall swarm evolution, we found a statistically significant annual seismicity variation, which is likely surface driven. The annual seismicity peak during spring (March-May) coincides with the maximum snow load on the near-by Cascades. The load corresponds to a surface pressure variation of about 6 kPa, which likely causes an annual peak-to-peak vertical displacement of about 1 cm at GPS sites in the Cascades and GPS signals that decay with increasing distance from the Cascades. Stress changes due to loading and unloading of snow pack in the Cascades can act in two ways to instantaneously enhance seismicity. For a strike-slip fault roughly parallel to the trend of the load and 10s of km away from it, normal stress decreases slightly leading to slight fault unclamping. The load also leads to simultaneous compression of fluid conduits at greater depth driving fluids rapidly upward into the swarm source region. The small, temporally variable stress changes on the order of a few kPa or less seem to be adequate to modulate seismicity by varying fault normal stresses and controlling fluid injection into a critically stressed fault zone. The swarm region has been quiet since February 2012 suggesting stresses on the fault have been nearly completely released.

The challenges in using UAV and plane imagery to quantify channel change in sandy braided rivers

NASA Astrophysics Data System (ADS)

Strick, Robert; Ashworth, Philip; Best, James; Lane, Stuart; Nicholas, Andrew; Parsons, Daniel; Sambrook Smith, Gregory; Simpson, Christopher; Unsworth, Christopher

2017-04-01

The development of numerical models of river morpho-dynamics is hampered by the lack of high-resolution data at multiple time and space scales for model validation. Such data are especially challenging to obtain for sand-bed braided rivers that typically have multiple channels of varying depth and contain rapidly migrating low-relief bar-lobes and dunes. This paper reports on the efforts to meet these challenges using repeat UAV surveys and plane sorties to quantify morphological change and bedform migration rates along the South Saskatchewan River, Canada. The South Saskatchewan River, near Outlook (SK Province) is 600 m wide with very well sorted medium sand (D50 = 0.3 mm) and negligible clay. The Gardiner Dam, 20 km upstream of the study reach, traps much of the very fine sediment so that the waters are clear at low flow and therefore the river bed is entirely visible. Fieldwork campaigns in 2015 and 2016 captured: (i) 1:5000 aerial colour photographs over a 17.5 km reach; (ii) high temporal frequency repeat imagery, obtained using quadcopter and fixed-wing UAV platforms for multiple 100 x 500 m sub-reaches. Plane images were processed via Structure from Motion (SfM) photogrammetric techniques using Pix4D and supporting ArcGIS and Global Mapper analysis. The resulting point cloud was corrected for tilt and filtered in MATLAB at multiple spatial scales to remove noise. Elevations in sub-aqueous zones were obtained using a statistical model, relating image brightness to water depth, developed using single beam echo-sounder data collected near to the flight time. The final DSM for the plane imagery combines these two methods and has a 0.5 m spatial resolution with vertical accuracy of 6 cm. UAV imagery is also processed using Pix4D with application of a diffraction water depth correction, required due to the lower flight height, and gives a resulting vertical accuracy of 2 cm. Initial results highlight the following issues: (i) there are a series of technical challenges associated with the definition of the emergent/submergent boundaries, low texture areas, accounting for pixel 'discolouration' by algal mats and flooded vegetation, pixel colour saturation at water depths > 2 m, and shadow effects in the lee of large dune bedforms; (ii) tracking of individual dunes using orthophoto mosaics is relatively easy but migration rates are spatially highly variable; (iii) morphological changes to individual dunes as they migrate present difficulties for converting to bedload transport rates; (iv) the basic components of the braided planform stay in-tact during each flood year unless there is an extreme flood when the whole braided morphology is reset. This paper will give more details on the processing workflow, the technical challenges and associated solutions, and the potential application of the data generated for validation of a 2D morpho-dynamic model of sand-bed braided river evolution.

Predicted bulk composition of petroleum generated by Lower Cretaceous Wealden black shales, Lower Saxony Basin, Germany

NASA Astrophysics Data System (ADS)

Ziegs, Volker; Mahlstedt, Nicolaj; Bruns, Benjamin; Horsfield, Brian

2015-09-01

The Berriasian Wealden Shale provides the favourable situation of possessing immature to overmature source rock intervals due to differential subsidence within the Lower Saxony Basin. Hydrocarbon generation kinetics and petroleum physical properties have been investigated on four immature Wealden Shale samples situated in different depth intervals and following the PhaseKinetics approach of di Primio and Horsfield (AAPG Bull 90(7):1031-1058, 2006). Kinetic parameters and phase prediction were applied to a thermally calibrated 1D model of the geodynamic evolution at the location of an overmature well. The immature source rocks of all depth intervals comprise kerogen type I being derived from the lacustrine algae Botryococcus braunii. Bulk kinetics of the lower three depth intervals (sample 2-4) can be described by one single activation energy E a, typical for homogeneous, lacustrine organic matter (OM), whereas sample 1 from the uppermost interval shows a slightly broader E a distribution which hints to a more heterogeneous, less stable OM, but still of lacustrine origin. Predicted physical properties of the generated petroleum fluids are characteristic of variably waxy, black oil possessing GOR's below 100 Sm3/Sm3 and saturations pressures below 150 bar. Petroleum fluids from the more heterogeneous OM-containing sample 1 can always be described by slightly higher values. Based on the occurrence of paraffinic, free hydrocarbons in the uppermost horizon of the overmature well and gas/condensate in the lower 3 depth intervals, two scenarios have been discussed. From the first and least realistic scenario assuming no expulsion from the source rock, it can be deduced that phase separation in the course of uplift can only have occurred in the uppermost interval containing the slightly less stable OM but not in the lower intervals being composed of a more stable OM. Therefore and taking secondary cracking into account, all depth intervals should contain gas/condensate. The free hydrocarbons in the upper horizon are interpreted as impregnation from migrated hydrocarbons. The second scenario assumes nearly complete expulsion due to fracturing by the so-called generation overpressure (Mann et al. in Petroleum and basin evolution. Springer, Berlin, 1997). The expelled petroleum might migrate into lower pressurised source rock horizons and reach bubble-point pressures leading to the exsolution of gas and "precipitation" of very high molecular weight bitumen unable to migrate. Subsequent burial of the latter in the course of the basin evolution would lead to secondary cracking and remaining pyrobitumen explaining the high amounts of pyrobitumen in the overmature well Ex-B and relatively enhanced TOC contents at such high maturity levels.

Recent Findings on the Nature of Episodic Tremor and Slip Along the Northern Cascadia Margin

NASA Astrophysics Data System (ADS)

Dragert, H.; Wang, K.; Kao, H.

2008-12-01

Episodic Tremor and Slip (ETS), as observed along the northern Cascadia margin, has been defined empirically as repeated, transient ground motions at a plate margin, roughly opposite to longer-term interseismic deformation, occurring synchronously with low-frequency, emergent seismic signals. Although the exact causal processes are still a matter of debate, recent improvements in the monitoring of these transient events provide clearer constraints for the location and the migration of both tremor and slip. In areal distribution, the tremors continue to occur in a band overlying the 25 to 55 km depth contours of the nominal subducting plate interface. The previously reported extended depth distribution of tremor is also observed for the most recent tremor episodes, as is the coincidence of peak tremor activity with a band of seismic reflectors that is commonly interpreted to be positioned above the plate interface. In these episodes, tremors migrate along strike of the subduction zone from the southeast to the northwest at speeds ranging from 5 to 13 km/day. Tremor data also show changes in migration speed during the course of a single episode. No systematic migration in depth has yet been resolved. Denser GPS monitoring and the introduction of borehole strainmeters have also led to a better definition of the ETS surface deformations patterns, including those derived from the vertical GPS component. Inversion of the GPS data, constrained by limiting slip to the currently accepted plate interface, results in an area of slip that parallels the strike of the subduction zone, overlapping with but narrower than the band of tremor distribution and displaced slightly seaward. Inversion constrained by a shallower occurrence of slip, on or near the reflector band, results in a broader distribution of slip with reduced magnitudes. This would be more commensurate with the wider distribution of tremor. The current GPS deformation data are unable to tell whether the slip could be distributed over a thick shear zone. However, the time series of borehole strain indicate that the along-strike propagating slip patch likely has a sharp propagating front, supporting the notion that slip occurs along a thin slip zone or a single decollement. Consequently, a working model for ETS is that the dominant slip occurs repeatedly along a well-defined weak zone but the synchronous tremor occurs not only within this zone but also in a surrounding volume whose material properties have been altered by an abundance of fluids and the presence of high pore pressures.

Moonlight Drives Ocean-Scale Mass Vertical Migration of Zooplankton during the Arctic Winter.

PubMed

Last, Kim S; Hobbs, Laura; Berge, Jørgen; Brierley, Andrew S; Cottier, Finlo

2016-01-25

In extreme high-latitude marine environments that are without solar illumination in winter, light-mediated patterns of biological migration have historically been considered non-existent [1]. However, diel vertical migration (DVM) of zooplankton has been shown to occur even during the darkest part of the polar night, when illumination levels are exceptionally low [2, 3]. This paradox is, as yet, unexplained. Here, we present evidence of an unexpected uniform behavior across the entire Arctic, in fjord, shelf, slope and open sea, where vertical migrations of zooplankton are driven by lunar illumination. A shift from solar-day (24-hr period) to lunar-day (24.8-hr period) vertical migration takes place in winter when the moon rises above the horizon. Further, mass sinking of zooplankton from the surface waters and accumulation at a depth of ∼50 m occurs every 29.5 days in winter, coincident with the periods of full moon. Moonlight may enable predation of zooplankton by carnivorous zooplankters, fish, and birds now known to feed during the polar night [4]. Although primary production is almost nil at this time, lunar vertical migration (LVM) may facilitate monthly pulses of carbon remineralization, as they occur continuously in illuminated mesopelagic systems [5], due to community respiration of carnivorous and detritivorous zooplankton. The extent of LVM during the winter suggests that the behavior is highly conserved and adaptive and therefore needs to be considered as "baseline" zooplankton activity in a changing Arctic ocean [6-9]. VIDEO ABSTRACT. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Auger compositional depth profiling of the metal contact-TlBr interface

NASA Astrophysics Data System (ADS)

Nelson, A. J.; Swanberg, E. L.; Voss, L. F.; Graff, R. T.; Conway, A. M.; Nikolic, R. J.; Payne, S. A.; Kim, H.; Cirignano, L.; Shah, K.

2015-08-01

Degradation of room temperature operation of TlBr radiation detectors with time is thought to be due to electromigration of Tl and Br vacancies within the crystal as well as the metal contacts migrating into the TlBr crystal itself due to electrochemical reactions at the metal/TlBr interface. Scanning Auger electron spectroscopy (AES) in combination with sputter depth profiling was used to investigate the metal contact surface/interfacial structure on TlBr devices. Device-grade TlBr was polished and subjected to a 32% HCl etch to remove surface damage and create a TlBr1-xClx surface layer prior to metal contact deposition. Auger compositional depth profiling results reveal non-equilibrium interfacial diffusion after device operation in both air and N2 at ambient temperature. These results improve our understanding of contact/device degradation versus operating environment for further enhancing radiation detector performance.

Committing to Keep Illinois Students In-State: Understanding College Choice, Student Migration Patterns, and Retention Strategies

ERIC Educational Resources Information Center

Dean, Diane R.; Hunt, Erika L.; Smith, Ryan

2006-01-01

This report, sponsored by the Illinois Board of Higher Education and the Center for the Study of Education Policy at Illinois State University, presents in-depth multi-method research and analysis on what matters to Illinois students and their families when choosing a college, why so many students are leaving the state, where they are going, and…

"Even Though I Am Married, I Have a Dream": Constructing L2 Gendered Identities through Narratives of Departure and Arrival

ERIC Educational Resources Information Center

Giroir, Shannon

2014-01-01

This paper reports on the findings of a multiple case study to show how 3 women constructed meaning around the processes of L2 learning and migration and (re)constructed identities through their participation in new communities of practice (CoPs). Data sources include formal classroom observations, in-depth interviews, and the participants'…

Health services for reproductive tract infections among female migrant workers in industrial zones in Ha Noi, Viet Nam: an in-depth assessment

PubMed Central

2012-01-01

Background Rural-to-urban migration involves a high proportion of females because job opportunities for female migrants have increased in urban industrial areas. Those who migrate may be healthier than those staying in the village and they may benefit from better health care services at destination, but the 'healthy' effect can be reversed at destination due to migration-related health risk factors. The study aimed to explore the need for health care services for reproductive tract infections (RTIs) among female migrants working in the Sai Dong industrial zone as well as their services utilization. Methods The cross sectional study employed a mixed method approach. A cohort of 300 female migrants was interviewed to collect quantitative data. Two focus groups and 20 in-depth interviews were conducted to collect qualitative data. We have used frequency and cross-tabulation techniques to analyze the quantitative data and the qualitative data was used to triangulate and to provide more in-depth information. Results The needs for health care services for RTI were high as 25% of participants had RTI syndromes. Only 21.6% of female migrants having RTI syndromes ever seek helps for health care services. Barriers preventing migrants to access services were traditional values, long working hours, lack of information, and high cost of services. Employers had limited interests in reproductive health of female migrants, and there was ineffective collaboration between the local health system and enterprises. These barriers were partly caused by lack of health promotion programs suitable for migrants. Most respondents needed more information on RTIs and preferred to receive these from their employers since they commonly work shifts - and spend most of their day time at work. Conclusion While RTIs are a common health problem among female migrant workers in industrial zones, female migrants had many obstacles in accessing RTI care services. The findings from this study will help to design intervention models for RTI among this vulnerable group such as communication for behavioural impact of RTI health care, fostered collaboration between local health care services and employer enterprises, and on-site service (e.g. local or enterprise health clinics) strengthening. PMID:22369718

The properties of the lunar regolith at Chang'e-3 landing site: A study based on LPR data

NASA Astrophysics Data System (ADS)

Feng, J.; Su, Y.; Xing, S.; Ding, C.; Li, C.

2015-12-01

In situ sampling from surface is difficult in the exploration of planets and sometimes radar sensing is a better choice. The properties of the surface material such as permittivity, density and depth can be obtained by a surface penetrating radar. The Chang'e-3 (CE-3) landed in the northern Mare Imbrium and a Lunar Penetrating Radar (LPR) is carried on the Yutu rover to detect the shallow structure of the lunar crust and the properties of the lunar regolith, which will give us a close look at the lunar subsurface. We process the radar data in a way which consist two steps: the regular preprocessing step and migration step. The preprocessing part includes zero time correction, de-wow, gain compensation, DC removal, geometric positioning. Then we combine all radar data obtained at the time the rover was moving, and use FIR filter to reduce the noise in the radar image with a pass band frequency range 200MHz-600MHz. A normal radar image is obtained after the preprocessing step. Using a nonlinear least squares fitting method, we fit the most hyperbolas in the radar image which are caused by the buried objects or rocks in the regolith and estimate the EM wave propagation velocity and the permittivity of the regolith. For there is a fixed mathematical relationship between dielectric constant and density, the density profile of the lunar regolith is also calculated. It seems that the permittivity and density at the landing site is larger than we thought before. Finally with a model of variable velocities, we apply the Kirchhoff migration method widely used in the seismology to transform the the unfocused space-time LPR image to a focused one showing the object's (most are stones) true location and size. From the migrated image, we find that the regolith depth in the landing site is smaller than previous study and the stone content rises rapidly with depth. Our study suggests that the landing site is a young region and the reworked history of the surface is short, which is consistent with crater density, showing the gradual formation of regolith by rock fracture during impact events.

Evidence of focused fluid flow associated to the gas hydrate wedge on the angolan margin

NASA Astrophysics Data System (ADS)

Casenave, Viviane; Imbert, Patrice; Gay, Aurélien

2013-04-01

The Lower Congo basin, offshore south west Africa, is a prolific petroleum province, which has been extensively investigated and exploited for more than 30 years. The study area is located above a producing oil and gas field, the hydrocarbons being trapped in turbidite channels on a tectonic horst. The work is based on the analysis of 3-D seismic and site survey data (2D AUV, grab samples and ROV photos) above a deeper oil and gas field called Moho. The analysis of this seismic data set reveals numerous evidence of focused fluid flow through the Mio-Pliocene interval, including present-day seafloor seep features and shallow buried paleo-seeps, indicating past activity of the system. The main fluid migration-related structures are the followings: 1. Stacked amplitude anomalies, interpreted as the result of vertical migrations of gas are pervasive. Most of these seep features seem to correspond to fossil events as they are interpreted as successive precipitation at the seafloor of patches of seep carbonates (MDAC, Methane Derived Authigenic Carbonates) stacked during the activity of a seep. 2. Another phenomenon of gas migration through the sediment pile is visible on the seismic data of the Moho area: it is the BSR (Bottom Simulating Reflector) located above a horst. The BSR is formed by 2 patches, which cover a small area about 1.5 km² for the largest and 0.5 km2 for the smallest. These two BSRs are located under a depth of water included between 600 and 700 m, into the BSR wedging area. 3. A 'spider morphology' is visible on the seafloor. It corresponds to depressions forming variable-sized furrows oriented slightly oblique to the slope dip direction, directly above the upslope limit of the BSR patches. ROV photos and movies from these furrows showed the presence of seep carbonates and of bacterial carpets, linked with methane leak at the seafloor. A similar 'spider morphology' was also identified in subsurface, at 20 ms under the seafloor, further down the slope, in present-day water depth ranging from 750 to 850 m. These buried depressions cover a stripe in that depth range all over the area covered by the 3D seismic data. These two observations, made both on the seafloor and on it subsurface, seem to correspond to the same phenomenon of fluid expulsion, for the views of the seismic morphology similarities, but in different periods. It is interpreted as a result of a downward migration of the BSR, because of the last sea-level rise, which would have meant an upslope migration of the intersection of the BSR with the seafloor. Based on the evidence of gas hydrate dissociation phenomenon in the Lower Congo Basin, the pinch-out of the BSR may be considered as a natural laboratory for investigating a possible massive greenhouse gas release due to global warming.

Sensitivity analysis of 1-D dynamical model for basin analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, S.

1987-01-01

Geological processes related to petroleum generation, migration and accumulation are very complicated in terms of time and variables involved, and it is very difficult to simulate these processes by laboratory experiments. For this reasons, many mathematic/computer models have been developed to simulate these geological processes based on geological, geophysical and geochemical principles. The sensitivity analysis in this study is a comprehensive examination on how geological, geophysical and geochemical parameters influence the reconstructions of geohistory, thermal history and hydrocarbon generation history using the 1-D fluid flow/compaction model developed in the Basin Modeling Group at the University of South Carolina. This studymore » shows the effects of some commonly used parameter such as depth, age, lithology, porosity, permeability, unconformity (eroded thickness and erosion time), temperature at sediment surface, bottom hole temperature, present day heat flow, thermal gradient, thermal conductivity and kerogen type and content on the evolutions of formation thickness, porosity, permeability, pressure with time and depth, heat flow with time, temperature with time and depth, vitrinite reflectance (Ro) and TTI with time and depth, and oil window in terms of time and depth, amount of hydrocarbons generated with time and depth. Lithology, present day heat flow and thermal conductivity are the most sensitive parameters in the reconstruction of temperature history.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bruno, Michael

Geomechanics Technologies has completed a detailed characterization study of the Wilmington Graben offshore Southern California area for large-scale CO₂ storage. This effort has included: an evaluation of existing wells in both State and Federal waters, field acquisition of about 175 km (109 mi) of new seismic data, new well drilling, development of integrated 3D geologic, geomechanics, and fluid flow models for the area. The geologic analysis indicates that more than 796 MMt of storage capacity is available within the Pliocene and Miocene formations in the Graben for midrange geologic estimates (P50). Geomechanical analyses indicate that injection can be conducted withoutmore » significant risk for surface deformation, induced stresses or fault activation. Numerical analysis of fluid migration indicates that injection into the Pliocene Formation at depths of 1525 m (5000 ft) would lead to undesirable vertical migration of the CO₂ plume. Recent well drilling however, indicates that deeper sand is present at depths exceeding 2135 m (7000 ft), which could be viable for large volume storage. For vertical containment, injection would need to be limited to about 250,000 metric tons per year per well, would need to be placed at depths greater than 7000ft, and would need to be placed in new wells located at least 1 mile from any existing offset wells. As a practical matter, this would likely limit storage operations in the Wilmington Graben to about 1 million tons per year or less. A quantitative risk analysis for the Wilmington Graben indicate that such large scale CO₂ storage in the area would represent higher risk than other similar size projects in the US and overseas.« less

Ammonium excretion and oxygen respiration of tropical copepods and euphausiids exposed to oxygen minimum zone conditions

NASA Astrophysics Data System (ADS)

Kiko, R.; Hauss, H.; Buchholz, F.; Melzner, F.

2015-10-01

Calanoid copepods and euphausiids are key components of marine zooplankton communities worldwide. Most euphausiids and several copepod species perform diel vertical migrations (DVMs) that contribute to the export of particulate and dissolved matter to midwater depths. In vast areas of the global ocean, and in particular in the eastern tropical Atlantic and Pacific, the daytime distribution depth of many migrating organisms corresponds to the core of the oxygen minimum zone (OMZ). At depth, the animals experience reduced temperature and oxygen partial pressure (pO2) and an increased carbon dioxide partial pressure (pCO2) compared to their near-surface nighttime habitat. Although it is well known that low oxygen levels can inhibit respiratory activity, the respiration response of tropical copepods and euphausiids to relevant pCO2, pO2 and temperature conditions remains poorly parameterized. Further, the regulation of ammonium excretion at OMZ conditions is generally not well understood. It was recently estimated that DVM-mediated ammonium supply considerably fuels bacterial anaerobic ammonium oxidation - a major loss process for fixed nitrogen in the ocean. These estimates were based on the implicit assumption that hypoxia or anoxia in combination with hypercapnia (elevated pCO2) does not result in a downregulation of ammonium excretion. Here we show that exposure to OMZ conditions can result in strong depression of respiration and ammonium excretion in calanoid copepods and euphausiids from the Eastern Tropical North Atlantic and the Eastern Tropical South Pacific. These physiological responses need to be taken into account when estimating DVM-mediated fluxes of carbon and nitrogen into OMZs.

Atlantic Sturgeon Spatial and Temporal Distribution in Minas Passage, Nova Scotia, Canada, a Region of Future Tidal Energy Extraction

PubMed Central

Stokesbury, Michael J. W.; Logan-Chesney, Laura M.; McLean, Montana F.; Buhariwalla, Colin F.; Redden, Anna M.; Beardsall, Jeffrey W.; Broome, Jeremy E.; Dadswell, Michael J.

2016-01-01

In the Bay of Fundy, Atlantic sturgeon from endangered and threatened populations in the USA and Canada migrate through Minas Passage to enter and leave Minas Basin. A total of 132 sub-adult and adult Atlantic sturgeon were tagged in Minas Basin during the summers of 2010–2014 using pressure measuring, uniquely coded, acoustic transmitters with a four or eight year life span. The aim of this study was to examine spatial and seasonal distribution of sturgeon in Minas Passage during 2010–2014 and test the hypothesis that, when present, Atlantic sturgeon were evenly distributed from north to south across Minas Passage. This information is important as tidal energy extraction using in-stream, hydrokinetic turbines is planned for only the northern portion of Minas Passage. Electronic tracking data from a total of 740 sturgeon days over four years demonstrated that Atlantic sturgeon used the southern portion of Minas Passage significantly more than the northern portion. Sturgeon moved through Minas Passage at depths mostly between 15 and 45 m (n = 10,116; mean = 31.47 m; SD = 14.88). Sturgeon mean swimming depth was not significantly related to bottom depth and in deeper regions they swam pelagically. Sturgeon predominately migrated inward through Minas Passage during spring, and outward during late summer-autumn. Sturgeon were not observed in Minas Passage during winter 2012–2013 when monitoring receivers were present. This information will enable the estimation of encounters of Atlantic sturgeon with in-stream hydrokinetic turbines. PMID:27383274

Organic sedimentation and genesis of petroleum in Mahakam Delta, Borneo

DOE Office of Scientific and Technical Information (OSTI.GOV)

Combaz, A.; de Matharel, M.

1978-09-01

The delta on the eastern coast of Kalimantan, Borneo, is a typical sedimentary-delta model for hydrocarbon accumulation. Because of a remarkable sedimentary continuity since the middle Miocene, three superimposed paleodeltas separated by two transgressive sequences are preserved. Several oil fields have been discovered in the area. Geochemical and microscopic studies of the organic material indicate a history of biochemical and catagenetic degradation, migration of the hydrocarbons generated, and their concentration in the sandstone reservoirs. The organic material in the source rocks generally is of continental and vegetal origin. The oils studied are highly paraffinic, increase in gravity with depth, andmore » have a very low sulfur content and a CPI close to 1. The oils of the two fields of Bekapai and Handil do not differ significantly, except that the degree of maturation of oil seems lower in Handil than in Bekapai. The characteristics of the source-rock chloroform extract are basically the same as those of the oils but the CPI is greater, between C25 and C29, and there is a higher proportion of alkanes in the extracts. The isoprenoid spectra, however, are very similar in both families of products. As a result it is concluded that the accumulations are probably not from source rocks in the vicinity of the reservoirs but originate at greater depths. The hydrocarbons could have migrated vertically about 3,000 m, chiefly along the faults present at both Bekapai and Handil. This process also could provoke the segregation of oils of increasing gravity with depth.« less

Predictive model for local scour downstream of hydrokinetic turbines in erodible channels

NASA Astrophysics Data System (ADS)

Musa, Mirko; Heisel, Michael; Guala, Michele

2018-02-01

A modeling framework is derived to predict the scour induced by marine hydrokinetic turbines installed on fluvial or tidal erodible bed surfaces. Following recent advances in bridge scour formulation, the phenomenological theory of turbulence is applied to describe the flow structures that dictate the equilibrium scour depth condition at the turbine base. Using scaling arguments, we link the turbine operating conditions to the flow structures and scour depth through the drag force exerted by the device on the flow. The resulting theoretical model predicts scour depth using dimensionless parameters and considers two potential scenarios depending on the proximity of the turbine rotor to the erodible bed. The model is validated at the laboratory scale with experimental data comprising the two sediment mobility regimes (clear water and live bed), different turbine configurations, hydraulic settings, bed material compositions, and migrating bedform types. The present work provides future developers of flow energy conversion technologies with a physics-based predictive formula for local scour depth beneficial to feasibility studies and anchoring system design. A potential prototype-scale deployment in a large sandy river is also considered with our model to quantify how the expected scour depth varies as a function of the flow discharge and rotor diameter.

Migration of Chemotactic Bacteria in Soft Agar: Role of Gel Concentration

PubMed Central

Croze, Ottavio A.; Ferguson, Gail P.; Cates, Michael E.; Poon, Wilson C.K.

2011-01-01

We study the migration of chemotactic wild-type Escherichia coli populations in semisolid (soft) agar in the concentration range C = 0.15–0.5% (w/v). For C≲0.35%, expanding bacterial colonies display characteristic chemotactic rings. At C = 0.35%, however, bacteria migrate as broad circular bands rather than sharp rings. These are growth/diffusion waves arising because of suppression of chemotaxis by the agar and have not been previously reported experimentally to our knowledge. For C = 0.4–0.5%, expanding colonies do not span the depth of the agar and develop pronounced front instabilities. The migration front speed is weakly dependent on agar concentration at C < 0.25%, but decreases sharply above this value. We discuss these observations in terms of an extended Keller-Segel model for which we derived novel transport parameter expressions accounting for perturbations of the chemotactic response by collisions with the agar. The model makes it possible to fit the observed front speed decay in the range C = 0.15–0.35%, and its solutions qualitatively reproduce the observed transition from chemotactic to growth/diffusion bands. We discuss the implications of our results for the study of bacteria in porous media and for the design of improved bacteriological chemotaxis assays. PMID:21806920

Measuring snow water equivalent from common-offset GPR records through migration velocity analysis

NASA Astrophysics Data System (ADS)

St. Clair, James; Holbrook, W. Steven

2017-12-01

Many mountainous regions depend on seasonal snowfall for their water resources. Current methods of predicting the availability of water resources rely on long-term relationships between stream discharge and snowpack monitoring at isolated locations, which are less reliable during abnormal snow years. Ground-penetrating radar (GPR) has been shown to be an effective tool for measuring snow water equivalent (SWE) because of the close relationship between snow density and radar velocity. However, the standard methods of measuring radar velocity can be time-consuming. Here we apply a migration focusing method originally developed for extracting velocity information from diffracted energy observed in zero-offset seismic sections to the problem of estimating radar velocities in seasonal snow from common-offset GPR data. Diffractions are isolated by plane-wave-destruction (PWD) filtering and the optimal migration velocity is chosen based on the varimax norm of the migrated image. We then use the radar velocity to estimate snow density, depth, and SWE. The GPR-derived SWE estimates are within 6 % of manual SWE measurements when the GPR antenna is coupled to the snow surface and 3-21 % of the manual measurements when the antenna is mounted on the front of a snowmobile ˜ 0.5 m above the snow surface.

Striations, duration, migration and tidal response in deep tremor.

PubMed

Ide, Satoshi

2010-07-15

Deep tremor in subduction zones is thought to be caused by small repeating shear slip events on the plate interface with significant slow components. It occurs at a depth of about 30 kilometres and provides valuable information on deep plate motion and shallow stress accumulation on the fault plane of megathrust earthquakes. Tremor has been suggested to repeat at a regular interval, migrate at various velocities and be modulated by tidal stress. Here I show that some time-invariant interface property controls tremor behaviour, using precise location of tremor sources with event duration in western Shikoku in the Nankai subduction zone, Japan. In areas where tremor duration is short, tremor is more strongly affected by tidal stress and migration is inhibited. Where tremor lasts longer, diffusive migration occurs with a constant diffusivity of 10(4) m(2) s(-1). The control property may be the ratio of brittle to ductile areas, perhaps determined by the influence of mantle wedge serpentinization on the plate interface. The spatial variation of the controlling property seems to be characterized by striations in tremor source distribution, which follows either the current or previous plate subduction directions. This suggests that the striations and corresponding interface properties are formed through the subduction of inhomogeneous structure, such as seamounts, for periods as long as ten million years.

Planet-disc interaction in laminar and turbulent discs

NASA Astrophysics Data System (ADS)

Stoll, Moritz H. R.; Picogna, Giovanni; Kley, Wilhelm

2017-07-01

In weakly ionised discs turbulence can be generated through the vertical shear instability (VSI). Embedded planets are affected by a stochastic component in the torques acting on them, which can impact their migration. In this work we study the interplay between a growing planet embedded in a protoplanetary disc and the VSI turbulence. We performed a series of 3D hydrodynamical simulations for locally isothermal discs with embedded planets in the mass range from 5 to 100 Earth masses. We study planets embedded in an inviscid disc that is VSI unstable, becomes turbulent, and generates angular momentum transport with an effective α = 5 × 10-4. This is compared to the corresponding viscous disc using exactly this α-value. In general we find that the planets have only a weak impact on the disc turbulence. Only for the largest planet (100 M⊕) does the turbulent activity become enhanced inside of the planet. The depth and width of a gap created by the more massive planets (30,100 M⊕) in the turbulent disc equal exactly that of the corresponding viscous case, leading to very similar torque strengths acting on the planet, with small stochastic fluctuations for the VSI disc. At the gap edges vortices are generated that are stronger and longer-lived in the VSI disc. Low mass planets (with Mp ≤ 10 M⊕) do not open gaps in the disc in either case, but generate for the turbulent disc an overdensity behind the planet that exerts a significant negative torque. This can boost the inward migration in VSI turbulent discs well above the Type I rate. Owing to the finite turbulence level in realistic 3D discs the gap depth will always be limited and migration will not stall in inviscid discs.

Hot, deep origin of petroleum: deep basin evidence and application

USGS Publications Warehouse

Price, Leigh C.

1978-01-01

Use of the model of a hot deep origin of oil places rigid constraints on the migration and entrapment of crude oil. Specifically, oil originating from depth migrates vertically up faults and is emplaced in traps at shallower depths. Review of petroleum-producing basins worldwide shows oil occurrence in these basins conforms to the restraints of and therefore supports the hypothesis. Most of the world's oil is found in the very deepest sedimentary basins, and production over or adjacent to the deep basin is cut by or directly updip from faults dipping into the basin deep. Generally the greater the fault throw the greater the reserves. Fault-block highs next to deep sedimentary troughs are the best target areas by the present concept. Traps along major basin-forming faults are quite prospective. The structural style of a basin governs the distribution, types, and amounts of hydrocarbons expected and hence the exploration strategy. Production in delta depocenters (Niger) is in structures cut by or updip from major growth faults, and structures not associated with such faults are barren. Production in block fault basins is on horsts next to deep sedimentary troughs (Sirte, North Sea). In basins whose sediment thickness, structure and geologic history are known to a moderate degree, the main oil occurrences can be specifically predicted by analysis of fault systems and possible hydrocarbon migration routes. Use of the concept permits the identification of significant targets which have either been downgraded or ignored in the past, such as production in or just updip from thrust belts, stratigraphic traps over the deep basin associated with major faulting, production over the basin deep, and regional stratigraphic trapping updip from established production along major fault zones.

DDT Vertical Migration and Formation of Accumulation Layer in Pesticide-Producing Sites.

PubMed

Liu, Li; Bai, Liping; Man, Changgeng; Liang, Wuhong; Li, Fasheng; Meng, Xiaoguang

2015-08-04

Soil samples were collected at various depths (0.5-21.5 m) from ten boreholes that were drilled with a SH-30 Model Rig, four of which were at a dicofol production site while six were at a dichlorodiphenyltrichloroethane (DDT) production site. In industrial sites, the shallow soils at depths of 0-2 m were mostly backfill soils, which cannot represent the contamination situation of the sites. The contaminated levels in the deep original soil can represent the situation in contaminated sites. All the soil samples investigated at the DDT and dicofol production sites were found to be seriously polluted. The contents of both DDT (0.6-6071 mg/kg) and dicofol (0.5-1440 mg/kg) were much higher at the dicofol production site than at the DDT production site (DDTs, 0.01-664.6 mg/kg; dicofol, <0.1 mg/kg), even in the deep soil. DDTs had a different distribution in the soil of the pesticide production site from that in the soil outside the sites and that in agricultural soils. The results of the investigation revealed that DDTs were easily enriched in cohesive soil and in the bottom zone of aquifers, where the concentration was higher than in above the layers. DDTs were found to be hard to degrade, and their degradation speed was slower than their vertical migration, despite the fact that hydrophobic DDTs did not migrate easily in soils. In the dicofol production site, the value of DDE/DDD cannot indicate the degradation condition of DDTs, nor can the value of (DDE + DDD)/DDT identify how long DDTs have remained in the soil. It is debatable that the half-life of DDT inputted to soils is about 20-30 years, maybe longer than the generally recognized time.

4D imaging of the source of ground deformation at Campi Flegrei caldera (Italy) during recent unrest episodes

NASA Astrophysics Data System (ADS)

D'Auria, L.; Giudicepietro, F.; Martini, M.; Lanari, R.

2011-12-01

Campi Flegrei caldera, has been affected in recent decades by three episodes of significant ground uplift. After the last crisis (1982-84), which was accompanied by strong seismicity, the ground has shown a general descending trend, occasionally interrupted by minor uplift episodes, together with low-magnitude volcano-tectonic and long-period seismicity. We assume that the source of minor ground deformations consists in a diffuse volumetric source, related to both thermoelastic and poroelastic strain. This is a reasonable assumption considering that Campi Flegrei are known to host a geothermal reservoir. We have inverted a DInSAR dataset spanning the interval 1995-2008. Results show that the geometry of the source is much more complex than previously recognized and, most important, it shows significant temporal variations, within few months. The deformation source, of the analyzed uplift episodes, starts with a volumetric expansion centered at a depth of about 5 km. The position of this volume is close to the caldera rims. Later the expansion migrates upward, reaching the surface along preferred paths, leading to the Solfatara area, located almost at the center of the caldera. This area is well known for its powerful geothermal emissions. During the upward migration, seismic long-period sources are activated. Their location is consistent with the path identified by the inversion of the DInSAR dataset. We infer, that this dynamics is linked to the injection of hot fluid batches, along the caldera rims and their upward migration, following preferential high permeability paths. Furthermore we have identified an injection episode which has not been previously recognized. The deformation source remains at depth slowly waning in few years. We show how this conceptual framework fits well with the observed geodetic, seismic and geochemical data.

Hydrogeologic characterization of an arid zone Radioactive Waste Management Site

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ginanni, J.M.; O`Neill, L.J.; Hammermeister, D.P.

1994-06-01

An in-depth subsurface site characterization and monitoring program for the soil water migration pathway has been planned, implemented, and completed to satisfy data requirements for a waiver from groundwater monitoring, for an exemption from liner leachate collections systems, and for different regulatory driven performance assessments. A traditional scientific approach has been taken to focus characterization and monitoring efforts. This involved developing a conceptual model of the hydrogeologic system and defining and testing hypotheses about this model. Specific hypotheses tested included: that the system was hydrologically heterogenous and anisotropic, and that recharge was very low or negligible. Mineralogical, physical, and hydrologicmore » data collected to test hypotheses has shown the hydrologic system to be remarkably homogenous and isotropic rather than heterogenous and anisotropic. Both hydrodynamic and environmental tracer approaches for estimating recharge have led to the conclusion that recharge from the Area 5 RWMS is not occurring in the upper region of the vadose zone, and that recharge at depth is extremely small or negligible. This demonstration of ``no migration of hazardous constituents to the water table satisfies a key requirement for both the groundwater monitoring waiver and the exemption from liner leachate collection systems. Data obtained from testing hypotheses concerning the soil water migration pathway have been used to refine the conceptual model of the hydrogeologic system of the site. These data suggest that the soil gas and atmospheric air pathways may be more important for transporting contaminants to the accessible environment than the soil water pathway. New hypotheses have been developed about these pathways, and characterization and monitoring activities designed to collect data to test these hypotheses.« less

Integrated exploration workflow in the south Middle Magdalena Valley (Colombia)

NASA Astrophysics Data System (ADS)

Moretti, Isabelle; Charry, German Rodriguez; Morales, Marcela Mayorga; Mondragon, Juan Carlos

2010-03-01

The HC exploration is presently active in the southern part of the Middle Magdalena Valley but only moderate size discoveries have been made up to date. The majority of these discoveries are at shallow depth in the Tertiary section. The structures located in the Valley are faulted anticlines charged by lateral migration from the Cretaceous source rocks that are assumed to be present and mature eastward below the main thrusts and the Guaduas Syncline. Upper Cretaceous reservoirs have also been positively tested. To reduce the risks linked to the exploration of deeper structures below the western thrusts of the Eastern Cordillera, an integrated study was carried out. It includes the acquisition of new seismic data, the integration of all surface and subsurface data within a 3D-geomodel, a quality control of the structural model by restoration and a modeling of the petroleum system (presence and maturity of the Cretaceous source rocks, potential migration pathways). The various steps of this workflow will be presented as well as the main conclusions in term of source rock, deformation phases and timing of the thrust emplacement versus oil maturation and migration. Our data suggest (or confirm) The good potential of the Umir Fm as a source rock. The early (Paleogene) deformation of the Bituima Trigo fault area. The maturity gap within the Cretaceous source rock between the hangingwall and footwall of the Bituima fault that proves an initial offset of Cretaceous burial in the range of 4.5 km between the Upper Cretaceous series westward and the Lower Cretaceous ones eastward of this fault zone. The post Miocene weak reactivation as dextral strike slip of Cretaceous faults such as the San Juan de Rio Seco fault that corresponds to change in the Cretaceous thickness and therefore in the depth of the thrust decollement.

Oxygen Isotope Variability within Nautilus Shell Growth Bands

PubMed Central

2016-01-01

Nautilus is often used as an analogue for the ecology and behavior of extinct externally shelled cephalopods. Nautilus shell grows quickly, has internal growth banding, and is widely believed to precipitate aragonite in oxygen isotope equilibrium with seawater. Pieces of shell from a wild-caught Nautilus macromphalus from New Caledonia and from a Nautilus belauensis reared in an aquarium were cast in epoxy, polished, and then imaged. Growth bands were visible in the outer prismatic layer of both shells. The thicknesses of the bands are consistent with previously reported daily growth rates measured in aquarium reared individuals. In situ analysis of oxygen isotope ratios using secondary ion mass spectrometry (SIMS) with 10 μm beam-spot size reveals inter- and intra-band δ18O variation. In the wild-caught sample, a traverse crosscutting 45 growth bands yielded δ18O values ranging 2.5‰, from +0.9 to -1.6 ‰ (VPDB), a range that is larger than that observed in many serial sampling of entire shells by conventional methods. The maximum range within a single band (~32 μm) was 1.5‰, and 27 out of 41 bands had a range larger than instrumental precision (±2 SD = 0.6‰). The results from the wild individual suggest depth migration is recorded by the shell, but are not consistent with a simple sinusoidal, diurnal depth change pattern. To create the observed range of δ18O, however, this Nautilus must have traversed a temperature gradient of at least ~12°C, corresponding to approximately 400 m depth change. Isotopic variation was also measured in the aquarium-reared sample, but the pattern within and between bands likely reflects evaporative enrichment arising from a weekly cycle of refill and replacement of the aquarium water. Overall, this work suggests that depth migration behavior in ancient nektonic mollusks could be elucidated by SIMS analysis across individual growth bands. PMID:27100183

Changing Melt-Migration Geometries with Crustal Depth: an Example From the Eastern Transverse Ranges.

NASA Astrophysics Data System (ADS)

Brown, K. L.; Paterson, S. R.; Barth, A. P.

2006-12-01

Detailed studies of North American Cordilleran sheeted plutons (Miller and Paterson, 2001; Mahan et al., 2003; Manduca et al., 1993) reveal that some have predominantly sub-vertical geometries, indicating construction within fundamentally vertical boundary zones in mid-crustal terrains. In contrast, the Bighorn sheeted complex of the eastern Transverse Ranges in southern California preserves fabrics that indicate a gently to moderately dipping geometry. Preliminary barometry shows that the eastern Transverse Ranges constitutes a tilted cross- section of the Mesozoic arc to depths of about 24 km. Whereas the shallow part of the tilted section is dominated by comparatively homogeneous Mesozoic plutons that intrude Proterozoic basement, the deeper part is dominated by mid-crustal sheeted plutons of Jurassic and Late Cretaceous age. Volumetrically dominant components of the western sheeted plutonic complex are biotite hornblende tonalite, granodiorite, and two mica-garnet granite sheets interlayered at meter to decimeter scale. Field observations indicate a transition from discordant plutons with weak magmatic fabrics to the contemporaneous deeper sheeted plutons with intense magmatic fabrics, suggesting that fabric intensity is related to pluton geometry and depth. Microscope investigations reveal that magmatic textures and fabrics are dominant in sheeted igneous rocks. Magmatic textures are defined by euhedral to subhedral plagioclase, hornblende, and biotite that do not show significant internal crystal-plastic deformation. Magmatic fabrics observable at the outcrop scale are defined by shape preferred orientations of euhedral to subhedral plagioclase, hornblende, and biotite grains. Although magmatic textures and fabrics are observed in all compositions, intense magmatic fabrics are prominent in granodiorite and fine-grained tonalite. Solid-state textures are defined by recrystallization of interstitial quartz and microfracturing of feldspar. Although the sheeted plutons were originally described as foliated metamorphic rocks, the preserved magmatic textures and fabrics suggest that this zone is melt dominated. In addition, the pluton geometries may be explained by changing melt-migration patterns with depth.

Oxygen isotope variability within Nautilus shell growth bands

DOE PAGES

Linzmeier, Benjamin J.; Kozdon, Reinhard; Peters, Shanan E.; ...

2016-04-21

Nautilus is often used as an analogue for the ecology and behavior of extinct externally shelled cephalopods. Nautilus shell grows quickly, has internal growth banding, and is widely believed to precipitate aragonite in oxygen isotope equilibrium with seawater. Pieces of shell from a wild-caught Nautilus macromphalus from New Caledonia and from a Nautilus belauensis reared in an aquarium were cast in epoxy, polished, and then imaged. Growth bands were visible in the outer prismatic layer of both shells. The thicknesses of the bands are consistent with previously reported daily growth rates measured in aquarium reared individuals. In situ analysis ofmore » oxygen isotope ratios using secondary ion mass spectrometry (SIMS) with 10 μm beam-spot size reveals inter- and intra-band δ 18O variation. In the wild-caught sample, a traverse crosscutting 45 growth bands yielded δ 18O values ranging 2.5‰, from +0.9 to -1.6 ‰ (VPDB), a range that is larger than that observed in many serial sampling of entire shells by conventional methods. The maximum range within a single band (~32 μm) was 1.5‰, and 27 out of 41 bands had a range larger than instrumental precision (±2 SD = 0.6‰). The results from the wild individual suggest depth migration is recorded by the shell, but are not consistent with a simple sinusoidal, diurnal depth change pattern. In addition, to create the observed range of δ 18O, however, this Nautilus must have traversed a temperature gradient of at least ~12°C, corresponding to approximately 400 m depth change. Isotopic variation was also measured in the aquarium-reared sample, but the pattern within and between bands likely reflects evaporative enrichment arising from a weekly cycle of refill and replacement of the aquarium water. Overall, this work suggests that depth migration behavior in ancient nektonic mollusks could be elucidated by SIMS analysis across individual growth bands.« less

Pop-up satellite archival tag effects on the diving behaviour, growth and survival of adult Atlantic salmon Salmo salar at sea.

PubMed

Hedger, R D; Rikardsen, A H; Thorstad, E B

2017-01-01

The effects of large, externally attached pop-up satellite archival tags (PSATs) were compared with those of small implanted data storage tags (DSTs) on adult Atlantic salmon Salmo salar during their ocean migration in regards to depth utilization, diving depth, diving rate, diving speed and temperatures experienced. Additionally the return rate and growth of individuals tagged with PSATs was compared with those of small acoustic tags and DSTs. Overall, the depth distribution of individuals tagged with PSATs was similar to that of those tagged with DSTs, reflecting the pelagic nature of S. salar at sea. Individuals tagged with PSATs, however, dived less frequently and to shallower depths, and dived and surfaced at slower velocities. Sea surface temperatures experienced by individuals tagged with PSATs were similar to those experienced by those tagged with DSTs for the same time of year, suggesting that there were no large differences in the ocean migration. Return rates did not depend on whether individuals were tagged with PSATs or not, indicating that survival at sea was not impacted by PSATs in comparison to small internal tags. Individuals tagged with PSATs, however, had a smaller increase in body mass than those tagged with acoustic tags or DSTs. It was concluded that PSATs are suitable for use in researching large-scale migratory behaviour of adult S. salar at sea, but that some effects on their behaviour from tagging must be expected. Effects of PSATs may be largest in the short term when S. salar are swimming in bursts at high speeds. Even though individuals tagged with PSATs performed deep and frequent dives, the results of this study suggest that untagged individuals would perform even deeper and more frequent dives than tagged individuals. © 2016 The Fisheries Society of the British Isles.

Modeling Rip Channel and Mega-Cusp Migration With XBeach

NASA Astrophysics Data System (ADS)

Orzech, M.; Thornton, E.; Reniers, A.; Macmahan, J.; O'Reilly, B.

2008-12-01

The relationship between alongshore rip channel migration and sediment transport is investigated using XBeach, a recently developed 2DH coastal erosion model. XBeach solves the nonlinear shallow water equations and accounts for the effects of breaking waves, wind, turbulent dispersion, and nonlinear bottom friction. It is similar to the more widely used Delft3D but focuses on morphological change to the beach and dune and includes the action of swash on a moving shoreline. Numerics have been simplified to increase model speed and ensure stability in shallow water. XBeach is first validated by recreating a three-year time series of alongshore rip migration patterns measured with video at Fort Ord, near Monterey, CA. The model is initialized with wave spectral data at 15m depth, provided by the Coastal Data Information Program (CDIP). Flow fields and transport patterns are then examined in detail over a single rip channel and mega-cusp to better understand the small scale processes associated with migration, and a range of simulations are conducted to quantify the effects on migration rates of varying wave height, incident angle, or tidal elevation. Results are presented from a four-month period of carefully monitored, accelerated shoreline erosion at the Fort Ord site, which followed the removal of a longstanding riprap barrier that had created a sand dune peninsula extending to the water's edge. Model-predicted erosion rates along the 300m stretch of shoreline are compared with dune retreat measurements for the period.

Reconsidering acculturation in dietary change research among Latino immigrants: challenging the preconditions of US migration

PubMed Central

Martínez, Airín D.

2012-01-01

BACKGROUND Dietary changes among Latino immigrants are often attributed to acculturation. Acculturation-diet research typically assumes that migration to the US is necessary for negative dietary changes to occur in Latino immigrants’ diets. OBJECTIVE The goal of this article is to demonstrate that extant acculturation research is not adequate in capturing changes in Latino immigrants’ diets. This is due to the role of globalization and transnational processes in modernizing their diets in Latin America. DESIGN Utilizing an interactionist cultural studies approach, this exploratory situational analysis based on 27 in-depth interviews with Latino immigrants, nutrition reports, and transnational food companies’ websites, examines how Latino immigrants were already engaging in negative dietary practices in their former country. RESULTS Latino immigrants who resided in urban areas in their former countries and migrated to the US on or after 2000 were fully engaged in negative dietary practices prior to migration. Such practices included consuming food outside of the home and integrating processed food into their cooking. Their dietary practices were also informed by nutrition discourses. The modernization of food production and consumption and the transnational transmission of nutrition are transnational processes changing Latino immigrants’ diets prior to migration. CONCLUSION Researchers should approach the study of dietary change among Latino immigrants in the US through a transnational perspective in order to avoid overlooking potential confounders such as current food insecurity, new socioeconomic positions as undocumented, low-income persons, and increased hours worked outside of the home. PMID:22731980

Gender, migration and urban development in Costa Rica: the case of Guanacaste.

PubMed

Chant, S

1991-01-01

Factors fueling urbanization in Guanacaste province, Costa Rica are explored and how the pattern of urban growth reflects gender divisions of labor is considered. Urbanization in Latin America has been due largely to the expansion of economic activities in urban centers, but in Guanacaste, rural employment persists among the poor. Towns in this peripheral province have witnessed no major expansion in urban-based employment opportunities. On the basis of an in-depth survey of urban dwellers in the province's 3 leading towns (Liberia, Canas, and Santa Cruz), an attempt is made to explain Guanacaste's urbanization. The 1st section discusses the migration, urbanization, and economic development in Costa Rica, as well as Guanacaste. The 2nd section provides the findings of the survey of 350 low-income, urban households in Guanacaste, focusing on the households' reported reasons for moving. Section 3 examines household survival strategies in the areas surveyed, paying close attention to gender and age selectivity of short-term out-migration to external labor markets. Section 4 interprets the apparent connection between gender-differentiated labor migration and the dominance of reproductive factors in household decisions to move to urban centers. Section 5 considers the implications of the migration patterns on women, while section 6 discusses the wider implications of the study. The study reveals that in Guanacaste, urbanization is more strongly linked to the reproductive (e.g., housing and welfare) needs of household survival than to productive (employment and income) needs.

What are Chinese nurses' experiences whilst working overseas? A narrative scoping review.

PubMed

Zhong, Yaping; McKenna, Lisa; Copnell, Beverley

2017-09-01

Transnational nurse migration has become an apparent attribute of the global nurse shortage and it is foreseeable that China will play an increasingly significant role in nurse exports. These nurses have unique cultural and professional needs throughout their journey of migration and in-depth analysis of Chinese migrant nurses' experiences is urgently required to manage and empower an ethnically diverse workforce. To synthesise Chinese migrant nurses' experiences by examining the findings of existing studies. Scoping review methods incorporating narrative synthesis were conducted. Arksey and O'Malley's five-stage scoping review framework was utilised to identify Chinese migrant nurses' experiences. 13 databases were searched, and 5009 articles were retrieved. After screening the titles and abstracts, 169 articles were assessed in full text for eligibility, and finally 22 articles plus 2 manually included ones, representing 19 discrete studies, were further analysed and synthesised with a three-step narrative synthesis. 13 qualitative studies, 5 quantitative studies and 1 mixed- methods study met inclusion criteria. Two main themes were identified. "Contexts and migration" comprised three subthemes: perceptions of nursing, original culture and nursing differences. "The self and migration" included four subthemes: initiating, transition, reality and future. This scoping review revealed the literature on Chinese migrant nurses and provided insight into their stories and circumstances. There were external factors which affected Chinese nurses' interpretations and choices. Throughout their migration journeys, they encountered various challenges and also successes. They responded with positive or negative behavioural and psychosocial changes. Copyright © 2017 Elsevier Ltd. All rights reserved.

Slug Test Characterization Results for Multi-Test/Depth Intervals Conducted During the Drilling of CERCLA Operable Unit OU UP-1 Wells 299-W19-48, 699-30-66, and 699-36-70B

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spane, Frank A.; Newcomer, Darrell R.

2010-06-15

This report presents test descriptions and analysis results for multiple, stress-level slug tests that were performed at selected test/depth intervals within three Operable Unit (OU) UP-1 wells: 299-W19-48 (C4300/Well K), 699-30-66 (C4298/Well R), and 699-36-70B (C4299/Well P). These wells are located within, adjacent to, and to the southeast of the Hanford Site 200-West Area. The test intervals were characterized as the individual boreholes were advanced to their final drill depths. The primary objective of the hydrologic tests was to provide information pertaining to the areal variability and vertical distribution of hydraulic conductivity with depth at these locations within the OUmore » UP-1 area. This type of characterization information is important for predicting/simulating contaminant migration (i.e., numerical flow/transport modeling) and designing proper monitor well strategies for OU and Waste Management Area locations.« less

Slug Test Characterization Results for Multi-Test/Depth Intervals Conducted During the Drilling of CERCLA Operable Unit OU ZP-1 Wells 299-W11-43, 299-W15-50, and 299-W18-16

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spane, Frank A.; Newcomer, Darrell R.

2010-06-21

The following report presents test descriptions and analysis results for multiple, stress level slug tests that were performed at selected test/depth intervals within three Operable Unit (OU) ZP-1 wells: 299-W11-43 (C4694/Well H), 299-W15-50 (C4302/Well E), and 299-W18-16 (C4303/Well D). These wells are located within south-central region of the Hanford Site 200-West Area (Figure 1.1). The test intervals were characterized as the individual boreholes were advanced to their final drill depths. The primary objective of the hydrologic tests was to provide information pertaining to the areal variability and vertical distribution of hydraulic conductivity with depth at these locations within the OUmore » ZP-1 area. This type of characterization information is important for predicting/simulating contaminant migration (i.e., numerical flow/transport modeling) and designing proper monitor well strategies for OU and Waste Management Area locations.« less

Can Vertical Migrations of Dinoflagellates Explain Observed Bioluminescence Patterns During an Upwelling Event in Monterey Bay, California?

DTIC Science & Technology

2012-01-25

concentration of their population , physical con- ditions (currents, temperature, strength of stratification , mixed layer depth etc.), light...REPORT DOCUMENTATION PAGE Form Approved OMB No. 07040188 The public reporting burden for this collection of information is estimated to average 1...completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of

Large scale patterns in vertical distribution and behaviour of mesopelagic scattering layers

PubMed Central

Klevjer, T. A.; Irigoien, X.; Røstad, A.; Fraile-Nuez, E.; Benítez-Barrios, V. M.; Kaartvedt., S.

2016-01-01

Recent studies suggest that previous estimates of mesopelagic biomasses are severely biased, with the new, higher estimates underlining the need to unveil behaviourally mediated coupling between shallow and deep ocean habitats. We analysed vertical distribution and diel vertical migration (DVM) of mesopelagic acoustic scattering layers (SLs) recorded at 38 kHz across oceanographic regimes encountered during the circumglobal Malaspina expedition. Mesopelagic SLs were observed in all areas covered, but vertical distributions and DVM patterns varied markedly. The distribution of mesopelagic backscatter was deepest in the southern Indian Ocean (weighted mean daytime depth: WMD 590 m) and shallowest at the oxygen minimum zone in the eastern Pacific (WMD 350 m). DVM was evident in all areas covered, on average ~50% of mesopelagic backscatter made daily excursions from mesopelagic depths to shallow waters. There were marked differences in migrating proportions between the regions, ranging from ~20% in the Indian Ocean to ~90% in the Eastern Pacific. Overall the data suggest strong spatial gradients in mesopelagic DVM patterns, with implied ecological and biogeochemical consequences. Our results suggest that parts of this spatial variability can be explained by horizontal patterns in physical-chemical properties of water masses, such as oxygen, temperature and turbidity. PMID:26813333

Origin of Amazon mudbanks along the northeastern coast of South America

USGS Publications Warehouse

Allison, M.A.; Lee, M.T.; Ogston, A.S.; Aller, R.C.

2000-01-01

Seismic profiles, sediment cores, and water column measurements were collected along the northeastern coast of Brazil to examine the origin of mudbanks in the Amazon coastal mud belt. These 10-60-km-long, shore-attached features previously had been observed to migrate along the 1200 km coast of the Guianas in response to wave forcing. CHIRP (3.5 kHz) seismic profiles of the shoreface and inner shelf located two mudbanks updrift of the previous eastern limit in French Guiana. 210Pb geochronology shows that these two banks are migrating to the northwest over a relict mud surface in 5-20 m water depth. The mudbanks are 3-4 m thick and are translating over a modern shoreface mud wedge deposited by previous mudbank passage in < 5 m water depth. Initial mudbank development is taking place on the intertidal and shallow subtidal mudflats at Cabo Cassipore, associated with an alongshore-accreting clinoform feature. Sediment trapping in this area is controlled by the nearshore presence of strong water column stratification produced by the enormous Amazon freshwater discharge on the shelf and by proximity to the Cassipore River estuary. Seasonal and decadal periods of sediment supply and starvation in this area likely are controlled by variations in northwest trade wind intensity. (C) 2000 Elsevier Science B.V.

The delineation of DNAPL in a heterogeneous unconsolidated aquifer using a hydro punch sampler and hydrophobic dye testing procedures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cirilli, J.; DeRose, N.

1995-09-01

The site is a pharmaceutical facility located in Newark, New Jersey. The facility which has been in operation for approximately 90 years, previously contained a 15,000 gallon underground tank used to store TCE. Upon the tanks removal in the early 1980`s the tank integrity was found to have been compromised. In compliance with the NJDEP Industrial Site Recovery Act, the responsible party was required to locate DNAPL in the aquifer. Due to TCE`s relative density, vertical migration to depths greater than 80 feet has occurred. Lateral migration over distances greater than 500 feet has been documented. Currently, the investigation hasmore » focused on the neighboring cemetery, where approximately 20 deep soil borings have been advanced at selected locations downslope of the TCE source area. The soil borings were drilled by mud rotary methods to a depth that was determined in the field to be proximal to the bottom of the heterogeneous unconsolidated aquifer. Continuous split spoon soil sampling for detailed geologic interpretation and field screening utilizing an organic vapor instrument was performed. The Hydro Punch (HP II) sampler was used in the aqueous sampling model to collect a discrete ground water sample from the interface between the aquifer and the till.« less

CE-QUAL-W2 Modeling of Head-of-Reservoir Conditions at Shasta Reservoir, California

NASA Astrophysics Data System (ADS)

Clancey, K. M.; Saito, L.; Svoboda, C.; Bender, M. D.; Hannon, J.

2014-12-01

Restoration of Chinook salmon and steelhead is a priority in the Sacramento River Basin since they were listed under the Endangered Species Act in 1989 and 1998, respectively. Construction of Shasta Dam and Reservoir obstructed fish migration, resulting in severe population declines. Efforts have been undertaken to restore the fisheries, including evaluation of opportunities for reintroducing Chinook salmon upstream of the dam and providing juvenile fish passage downstream past Shasta Dam. Shasta Reservoir and the Sacramento River and McCloud River tributaries have been modeled with CE-QUAL-W2 (W2) to assess hydrodynamic and temperature conditions with and without surface curtains to be deployed in the tributaries. Expected head-of-reservoir tributary conditions of temperature and water depth are being simulated under dry, median and wet year conditions. Model output is analyzed during months of downstream migration of fish from upstream Sacramento and McCloud River tributaries. W2 will be used to determine presence of favorable conditions for juvenile rearing with proposed surface temperature curtains. Evaluation of favorable conditions for fish includes assessment of water temperature, velocities, and depth. Preliminary results for head-of-reservoir conditions and the influence of temperature curtains modeled with W2 will be presented. Study findings may assist in formulation of juvenile fish passage alternatives for Shasta Lake.

Dual-vergence structure from multiple migration of widely spaced OBSs

NASA Astrophysics Data System (ADS)

Yelisetti, Subbarao; Spence, George D.; Scherwath, Martin; Riedel, Michael; Klaeschen, Dirk

2017-10-01

The detailed structure of the northern Cascadia basin and frontal ridge region was obtained using data from several widely spaced ocean bottom seismometers (OBSs). Mirror imaging was used in which the downgoing multiples (mirror signal) are migrated as they provide information about a much larger area than imaging with primary signal alone. Specifically, Kirchhoff time migration was applied to hydrophone and vertical geophone data. Our results indicate remarkable structures that were not observed on the northern Cascadia margin in previous single-channel or multi-channel seismic (MCS) data. Results show that, in these water depths (2.0-2.5 km), an OBS can image up to 5 km on either side of its position on the seafloor and hence an OBS spacing of 5 km is sufficient to provide a two-fold migration stack. Results also show the top of the igneous oceanic crust at 5-6 km beneath the seafloor using only a small airgun source (120 in.3). Specifically, OBS migration results clearly show the continuity of reflectors which enabled the identification of frontal thrusts and a main thrust fault. These faults indicate, for the first time on this margin, the presence of a dual-vergence structure. These kinds of structures have so far been observed in < 0.5% of modern convergent margins and could be related to horizontal compression associated with subduction and low basal shear stress resulting from over-pressure. Reanalysis of previous MCS data from this region augmented the OBS migration results and further suggests that the vergence switches from seaward to landward around central Vancouver Island. Furthermore, fault geometry analyses indicate that the total amount of shortening accommodated due to faulting and folding is about 3 km, which suggest that thrusting would have started at least ∼ 65 ky ago.

Photon migration through fetal head in utero using continuous wave, near infrared spectroscopy: clinical and experimental model studies

NASA Astrophysics Data System (ADS)

Ramanujam, Nirmala; Vishnoi, Gargi; Hielscher, Andreas H.; Rode, Martha; Forouzan, Iraj; Chance, Britton

2000-04-01

Near infrared (NIR) measurements were made from the maternal abdomen (clinical studies) and laboratory tissue phantoms (experimental studies) to gain insight into photon migration through the fetal head in utero. Specifically, a continuous wave spectrometer was modified and employed to make NIR measurements at 760 and 850 nm, at a large (10 cm) and small (2.5/4 cm) source-detector separation, simultaneously, on the maternal abdomen, directly above the fetal head. A total of 19 patients were evaluated, whose average gestational age and fetal head depth, were 37 weeks +/- 3 and 2.25 cm +/- 0.7, respectively. At the large source-detector separation, the photons are expected to migrate through both the underlying maternal and fetal tissues before being detected at the surface, while at the short source-detector separation, the photons are expected to migrate primarily through the superficial maternal tissues before being detected. Second, similar NIR measurements were made on laboratory tissue phantoms, with variable optical properties and physical geometries. The variable optical properties were obtained using different concentrations of India ink and Intralipid in water, while the variable physical geometries were realized by employing glass containers of different shapes and sizes. Third, the NIR measurements, which were made on the laboratory tissue phantoms, were compared to the NIR measurements made on the maternal abdomen to determine which tissue phantom best simulates the photon migration path through the fetal head in utero. The results of the comparison were used to provide insight into the optical properties and physical geometry of the maternal and fetal tissues in the photon migration path.

Ultrasound breast imaging using frequency domain reverse time migration

NASA Astrophysics Data System (ADS)

Roy, O.; Zuberi, M. A. H.; Pratt, R. G.; Duric, N.

2016-04-01

Conventional ultrasonography reconstruction techniques, such as B-mode, are based on a simple wave propagation model derived from a high frequency approximation. Therefore, to minimize model mismatch, the central frequency of the input pulse is typically chosen between 3 and 15 megahertz. Despite the increase in theoretical resolution, operating at higher frequencies comes at the cost of lower signal-to-noise ratio. This ultimately degrades the image contrast and overall quality at higher imaging depths. To address this issue, we investigate a reflection imaging technique, known as reverse time migration, which uses a more accurate propagation model for reconstruction. We present preliminary simulation results as well as physical phantom image reconstructions obtained using data acquired with a breast imaging ultrasound tomography prototype. The original reconstructions are filtered to remove low-wavenumber artifacts that arise due to the inclusion of the direct arrivals. We demonstrate the advantage of using an accurate sound speed model in the reverse time migration process. We also explain how the increase in computational complexity can be mitigated using a frequency domain approach and a parallel computing platform.

Oligocene to Holocene sediment drifts and bottom currents on the slope of Gabon continental margin (west Africa). Consequences for sedimentation and southeast Atlantic upwelling

NASA Astrophysics Data System (ADS)

Séranne, Michel; Nzé Abeigne, César-Rostand

1999-10-01

Seismic reflection profiles on the slope of the south Gabon continental margin display furrows 2 km wide and some 200 m deep, that develop normal to the margin in 500-1500 m water depth. Furrows are characterised by an aggradation/progradation pattern which leads to margin-parallel, northwestward migration of their axes through time. These structures, previously interpreted as turbidity current channels, display the distinctive seismic image and internal organisation of sediment drifts, constructed by the activity of bottom currents. Sediment drifts were initiated above a major Oligocene unconformity, and they developed within a Oligocene to Present megasequence of general progradation of the margin, whilst they are markedly absent from the underlying Late Cretaceous-Eocene aggradation megasequence. The presence of upslope migrating sediment waves, and the northwest migration of the sediment drifts indicate deposition by bottom current flowing upslope, under the influence of the Coriolis force. Such landwards-directed bottom currents on the slope probably represent coastal upwelling, which has been active along the west Africa margin throughout the Neogene.

In vivo imaging of cytotoxic T cell infiltration and elimination of a solid tumor.

PubMed

Boissonnas, Alexandre; Fetler, Luc; Zeelenberg, Ingrid S; Hugues, Stéphanie; Amigorena, Sebastian

2007-02-19

Although the immune system evolved to fight infections, it may also attack and destroy solid tumors. In most cases, tumor rejection is initiated by CD8(+) cytotoxic T lymphocytes (CTLs), which infiltrate solid tumors, recognize tumor antigens, and kill tumor cells. We use a combination of two-photon intravital microscopy and immunofluorescence on ordered sequential sections to analyze the infiltration and destruction of solid tumors by CTLs. We show that in the periphery of a thymoma growing subcutaneously, activated CTLs migrate with high instantaneous velocities. The CTLs arrest in close contact to tumor cells expressing their cognate antigen. In regions where most tumor cells are dead, CTLs resume migration, sometimes following collagen fibers or blood vessels. CTLs migrating along blood vessels preferentially adopt an elongated morphology. CTLs also infiltrate tumors in depth, but only when the tumor cells express the cognate CTL antigen. In tumors that do not express the cognate antigen, CTL infiltration is restricted to peripheral regions, and lymphocytes neither stop moving nor kill tumor cells. Antigen expression by tumor cells therefore determines both CTL motility within the tumor and profound tumor infiltration.

Factors associated with the process of adaptation among Pakistani adolescent females living in United States.

PubMed

Khuwaja, Salma A; Selwyn, Beatrice J; Mgbere, Osaro; Khuwaja, Alam; Kapadia, Asha; McCurdy, Sheryl; Hsu, Chiehwen E

2013-04-01

This study explored post-migration experiences of recently migrated Pakistani Muslim adolescent females residing in the United States. In-depth, semi-structured interviews were conducted with thirty Pakistani Muslim adolescent females between the ages of 15 and 18 years living with their families in Houston, Texas. Data obtained from the interviews were evaluated using discourse analysis to identify major reoccurring themes. Participants discussed factors associated with the process of adaptation to the American culture. The results revealed that the main factors associated with adaptation process included positive motivation for migration, family bonding, social support networks, inter-familial communication, aspiration of adolescents to learn other cultures, availability of English-as-second-language programs, participation in community rebuilding activities, and faith practices, English proficiency, peer pressure, and inter-generational conflicts. This study provided much needed information on factors associated with adaptation process of Pakistani Muslim adolescent females in the United States. The results have important implications for improving the adaptation process of this group and offer potential directions for intervention and counseling services.

Coastal leatherback turtles reveal conservation hotspot

PubMed Central

Robinson, Nathan J.; Morreale, Stephen J.; Nel, Ronel; Paladino, Frank V.

2016-01-01

Previous studies have shown that the world’s largest reptile – the leatherback turtle Dermochelys coriacea – conducts flexible foraging migrations that can cover thousands of kilometres between nesting sites and distant foraging areas. The vast distances that may be travelled by migrating leatherback turtles have greatly complicated conservation efforts for this species worldwide. However, we demonstrate, using a combination of satellite telemetry and stable isotope analysis, that approximately half of the nesting leatherbacks from an important rookery in South Africa do not migrate to distant foraging areas, but rather, forage in the coastal waters of the nearby Mozambique Channel. Moreover, this coastal cohort appears to remain resident year-round in shallow waters (<50 m depth) in a relatively fixed area. Stable isotope analyses further indicate that the Mozambique Channel also hosts large numbers of loggerhead turtles Caretta caretta. The rare presence of a resident coastal aggregation of leatherback turtles not only presents a unique opportunity for conservation, but alongside the presence of loggerhead turtles and other endangered marine megafauna in the Mozambique Channel, highlights the importance of this area as a marine biodiversity hotspot. PMID:27886262

Water recharge and solute transport through the vadose zone of fractured chalk under desert conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nativ, R.; Dahan, O.; Adar, E.

In the present study the inferred mechanism of groundwater recharge and contamination was studied using tracer concentrations in the fractured vadose zone of the Avdat chalk. The results of this study are important for an evaluation of groundwater contamination from existing and planned facilities in the northern Negev desert in Israel. This study focused on the vicinity of the Ramat Hovav industrial chemical complex in the northern Negev, which also includes the national site for hazardous waste. Water recharge and solute migration rates were examined in five core holes and one borehole which penetrate the entire vadose zone and enabledmore » the collection of rock samples for chemical and isotopic analyses, and an observation of fracture distribution with depth. Tritium profiles were used to estimate water percolation rates through the vadose zone, chloride profiles were used to assess the migration rate of nonreactive solutes, and bromide profiles were also used to evaluate the migration rate of nonreactive contaminants. Deuterium and oxygen 18 profiles were used to assess the evaporation of the infiltrating water at and near land surface.« less

"I won't be staying here for long": a qualitative study on the retention of migrant nurses in Ireland

PubMed Central

2009-01-01

Background Although international nurse recruitment campaigns have succeeded in attracting large numbers of migrant nurses to countries such as Ireland, where domestic supply has not kept pace with demand, the long-term success of such initiatives from a workforce planning perspective will depend on the extent to which these nurses can be retained in destination countries. Methods This paper draws on qualitative, in-depth interviews undertaken with 21 migrant nurses in Ireland, focusing specifically on their future migration intentions. Results Our findings indicate that more than half of the respondents are considering migration onwards, for the most part because the destination country has failed to provide them with sufficient stability, particularly in terms of citizenship and family reunification. In considering onward migration, factors outside the health system were of most concern to those interviewed. Conclusion This demonstrates the need for destination countries to take a broader and more long-term approach to international nurse recruitment, rather than regarding it as an inexpensive way to fill gaps within the health care system. PMID:19660106

Upper mantle structure across the Trans-European Suture Zone imaged by S-receiver functions

NASA Astrophysics Data System (ADS)

Knapmeyer-Endrun, Brigitte; Krüger, Frank; Geissler, Wolfram H.; Passeq Working Group

2017-01-01

We present a high-resolution study of the upper mantle structure of Central Europe, including the western part of the East European Platform, based on S-receiver functions of 345 stations. A distinct contrast is found between Phanerozoic Europe and the East European Craton across the Trans-European Suture Zone. To the west, a pronounced velocity reduction with depth interpreted as lithosphere-asthenosphere boundary (LAB) is found at an average depth of 90 km. Beneath the craton, no strong and continuous LAB conversion is observed. Instead we find a distinct velocity reduction within the lithosphere, at 80-120 km depth. This mid-lithospheric discontinuity (MLD) is attributed to a compositional boundary between depleted and more fertile lithosphere created by late Proterozoic metasomatism. A potential LAB phase beneath the craton is very weak and varies in depth between 180 and 250 km, consistent with a reduced velocity contrast between the lower lithosphere and the asthenosphere. Within the Trans-European Suture Zone, lithospheric structure is characterized by strong heterogeneity. A dipping or step-wise increase to LAB depth of 150 km is imaged from Phanerozoic Europe to 20-22° E, whereas no direct connection to the cratonic LAB or MLD to the east is apparent. At larger depths, a positive conversion associated with the lower boundary of the asthenosphere is imaged at 210-250 km depth beneath Phanerozoic Europe, continuing down to 300 km depth beneath the craton. Conversions from both 410 km and 660 km discontinuities are found at their nominal depth beneath Phanerozoic Europe, and the discontinuity at 410 km depth can also be traced into the craton. A potential negative conversion on top of the 410 km discontinuity found in migrated images is analyzed by modeling and attributed to interference with other converted phases.

Mississippi exploration field trials using microbial, radiometrics, free soil gas, and other techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moody, J.S.; Brown, L.R.; Thieling, S.C.

1995-12-31

The Mississippi Office of Geology has conducted field trials using the surface exploration techniques of geomicrobial, radiometrics, and free soil gas. The objective of these trials is to determine if Mississippi oil and gas fields have surface hydrocarbon expression resulting from vertical microseepage migration. Six fields have been surveyed ranging in depth from 3,330 ft to 18,500 ft. The fields differ in trapping styles and hydrocarbon type. The results so far indicate that these fields do have a surface expression and that geomicrobial analysis as well as radiometrics and free soil gas can detect hydrocarbon microseepage from pressurized reservoirs. Allmore » three exploration techniques located the reservoirs independent of depth, hydrocarbon type, or trapping style.« less

Plate tectonics and hotspots: the third dimension.

PubMed

Anderson, D L; Tanimoto, T; Zhang, Y S

1992-06-19

High-resolution seismic tomographic models of the upper mantle provide powerful new constraints on theories of plate tectonics and hotspots. Midocean ridges have extremely low seismic velocities to a depth of 100 kilometers. These low velocities imply partial melting. At greater depths, low-velocity and high-velocity anomalies record, respectively, previous positions of migrating ridges and trenches. Extensional, rifting, and hotspot regions have deep (> 200 kilometers) low-velocity anomalies. The upper mantle is characterized by vast domains of high temperature rather than small regions surrounding hotspots; the asthenosphere is not homogeneous or isothermal. Extensive magmatism requires a combination of hot upper mantle and suitable lithospheric conditions. High-velocity regions of the upper 200 kilometers of the mantle correlate with Archean cratons.

Pulsed remineralisation in the northwestern Mediterranean Sea: a hypothesis

NASA Astrophysics Data System (ADS)

Denis, Michel; Martin, Valérie; Momzikoff, André; Gondry, Geneviève; Stemmann, Lars; Demers, Serge; Gorsky, Gaby; Andersen, Valérie

2003-02-01

A general study of biogeochemical processes (DYNAPROC cruise) was conducted in May 1995 at a time-series station in the open northwestern Mediterranean Sea where horizontal advection was weak. Short-term variations of the vertical distributions of pico- and nanophytoplankton were investigated over four 36-h cycles, along with parallel determinations of metabolic CO 2 production rates and amino acid-containing colloid (AACC) concentrations at the chlorophyll maximum depth. The vertical (0-1000-m depth) distributions of (i) AACC, (ii) suspended particles and (iii) metabolic CO 2 production rate were documented during the initial and final stages of these 36-h cycles. This study was concerned with diel vertical migration (DVM) of zooplankton, which provided periodic perturbations. Accordingly, the time scale of the experimental work varied from a few hours to a few days. Although all distributions exhibited a periodic behaviour, AACC distributions were generally not linked to diel vertical migrations. In the subsurface layer, Synechococcus made the most abundant population and large variations in concentration were observed both at day and at night. The corresponding integrated (over the upper 90 m) losses of Synechococcus during one night pointed to a potential source of exported organic matter amounting to 534 mg C m -2. This study stresses the potential importance of organic matter export from the euphotic zone through the daily grazing activity of vertically migrating organisms, which would not be accounted for by measurements at longer time scales. The metabolic CO 2 production exhibited a peak of activity below 500 m that was shifted downward, apparently in a recurrent way and independently of the vertical distributions of AACC or of suspended particulate material. To account for this phenomenon, a «sustained wave train» hypothesis is proposed that combines the effect of the diel superficial faecal pellet production by swarming migrators and the repackaging activity of the nonmigrating midwater populations. Our results confirm the recent finding that the particulate compartment is not the major source of the observed instantaneous remineralisation rate and shed a new light on the fate of organic matter in the aphotic zone.

Area 2: Inexpensive Monitoring and Uncertainty Assessment of CO2 Plume Migration using Injection Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Srinivasan, Sanjay

2014-09-30

In-depth understanding of the long-term fate of CO₂ in the subsurface requires study and analysis of the reservoir formation, the overlaying caprock formation, and adjacent faults. Because there is significant uncertainty in predicting the location and extent of geologic heterogeneity that can impact the future migration of CO₂ in the subsurface, there is a need to develop algorithms that can reliably quantify this uncertainty in plume migration. This project is focused on the development of a model selection algorithm that refines an initial suite of subsurface models representing the prior uncertainty to create a posterior set of subsurface models thatmore » reflect injection performance consistent with that observed. Such posterior models can be used to represent uncertainty in the future migration of the CO₂ plume. Because only injection data is required, the method provides a very inexpensive method to map the migration of the plume and the associated uncertainty in migration paths. The model selection method developed as part of this project mainly consists of assessing the connectivity/dynamic characteristics of a large prior ensemble of models, grouping the models on the basis of their expected dynamic response, selecting the subgroup of models that most closely yield dynamic response closest to the observed dynamic data, and finally quantifying the uncertainty in plume migration using the selected subset of models. The main accomplishment of the project is the development of a software module within the SGEMS earth modeling software package that implements the model selection methodology. This software module was subsequently applied to analyze CO₂ plume migration in two field projects – the In Salah CO₂ Injection project in Algeria and CO₂ injection into the Utsira formation in Norway. These applications of the software revealed that the proxies developed in this project for quickly assessing the dynamic characteristics of the reservoir were highly efficient and yielded accurate grouping of reservoir models. The plume migration paths probabilistically assessed by the method were confirmed by field observations and auxiliary data. The report also documents the application of the software to answer practical questions such as the optimum location of monitoring wells to reliably assess the migration of CO₂ plume, the effect of CO₂-rock interactions on plume migration and the ability to detect the plume under those conditions and the effect of a slow, unresolved leak on the predictions of plume migration.« less

Fracture development within a stratovolcano: The Karaha-Telaga Bodas geothermal field, Java volcanic arc

USGS Publications Warehouse

Nemcok, M.; Moore, J.N.; Allis, R.; McCulloch, J.

2004-01-01

Karaha-Telaga Bodas, a vapour-dominated geothermal system located in an active volcano in western Java, is penetrated by more than two dozen deep geothermal wells reaching depths of 3 km. Detailed paragenetic and fluid-inclusion studies from over 1000 natural fractures define the liquid-dominated, transitional and vapour-dominated stages in the evolution of this system. The liquid-dominated stage was initiated by ashallow magma intrusion into the base of the volcanic cone. Lava and pyroclastic flows capped a geothermal system. The uppermost andesite flows were only weakly fractured due to the insulating effect of the intervening altered pyroclastics, which absorbed the deformation. Shear and tensile fractures that developed were filled with carbonates at shallow depths, and by quartz, epidote and actinolite at depths and temperatures over 1 km and 300??C. The system underwent numerous cycles of overpressuring, documented by subhorizontal tensile fractures, anastomosing tensile fracture patterns and implosion breccias. The development of the liquidsystem was interrupted by a catastrophic drop in fluid pressures. As the fluids boiled in response to this pressure drop, chalcedony and quartz were selectively deposited in fractures that had the largest apertures and steep dips. The orientations of these fractures indicate that the escaping overpressured fluids used the shortest possible paths to the surface. Vapour-dominated conditions were initiated at this time within a vertical chimney overlying the still hot intrusion. As pressures declined, these conditions spread outward to form the marginal vapour-dominated region encountered in the drill holes. Downward migration of the chimney, accompanied by growth of the marginal vapour-dominated regime, occurred as the intrusion cooled and the brittle-ductile transition migrated to greater depths. As the liquids boiled off, condensate that formed at the top of the vapour-dominated zone percolated downward and low-salinity meteoric water entered the marginal parts of the system. Calcite, anhydrite and fluorite precipitated in fractures on heating. Progressive sealing of the fractures resulted in the downward migration of the cap rock. In response to decreased pore pressure in the expanding vapour zone, walls of the fracture system within the vapour-dominated reservoir progressively collapsed. It left only residual permeability in the remaining fracture volume, with apertures supported only by asperities or propping breccia. In places where normal stresses acting on the fracture walls exceeded the compressive strength of the wall rock, the fractures have completely collapsed. Fractures within the present-day cap rock include strike- and oblique-slip faults, normal faults and tensile fractures, all controlled by a strike-slip stress regime. The reservoir is characterized by normal faults and tensile fractures controlled by a normal-fault stress regime. The fractures show no evidence that the orientation of the stress field has changed since fracture propagation began. Fluid migration in the lava and pyroclastic flows is controlled by fractures. Matrix permeability controls fluid flow in the sedimentary sections of the reservoir. Productive fractures are typically roughly perpendicular to the minimum compressive stress, ??3, and are prone to slip and dilation within the modern stress regime. ?? The Geological Society of London 2004.

Cadmium removal from urban stormwater runoff via bioretention technology and effluent risk assessment for discharge to surface water.

PubMed

Wang, Jianlong; Zhang, Pingping; Yang, Liqiong; Huang, Tao

2016-01-01

Bioretention technology, a low-impact development stormwater management measure, was evaluated for its ability to remove heavy metals (specifically cadmium, Cd) from urban stormwater runoff. Fine sand, zeolite, sand and quartz sand were selected as composite bioretention media. The effects of these materials on the removal efficiency, chemical forms, and accumulation and migration characteristics of Cd were examined in laboratory scale bioretention columns. Heretofore, few studies have examined the removal of Cd by bioretention. A five-step sequential extraction method, a single-contamination index method, and an empirical migration equation were used in the experiments. The average Cd removal efficiency of quartz sand approached 99%, and removal by the other media all exceeded 90%. The media types markedly affected the forms of Cd found in the columns as well as its vertical migration rate. The Cd accumulated in the four media was mainly in residual form; moreover, accumulation of Cd occurred mainly in the surface layer of the bioretention column. The migration depth of Cd in the four media increased with elapsed time, in the following sequence: zeolite>quartz sand>fine sand>sand. In contrast, the migration rate decreased with elapsed time, and the migration rate of Cd was lowest in sand (0.015 m per annum over the first ten years). The comprehensive risk index analysis indicated that the risk arising from Cd discharge to surface water was "intermediate", and that the degree of risk was lowest in sand, then quartz sand, zeolite, and fine sand in sequence. These results indicate that the adsorption and accumulation of Cd in the four media are more significant than the migration of Cd. In addition, the results of Cd risk assessment for the effluent indicate that each of the four media can serve as long-term adsorption material in a bioretention facility for purifying stormwater runoff. Copyright © 2016 Elsevier B.V. All rights reserved.

Upward nitrate transport by phytoplankton in oceanic waters: balancing nutrient budgets in oligotrophic seas.

PubMed

Villareal, Tracy A; Pilskaln, Cynthia H; Montoya, Joseph P; Dennett, Mark

2014-01-01

In oceanic subtropical gyres, primary producers are numerically dominated by small (1-5 µm diameter) pro- and eukaryotic cells that primarily utilize recycled nutrients produced by rapid grazing turnover in a highly efficient microbial loop. Continuous losses of nitrogen (N) to depth by sinking, either as single cells, aggregates or fecal pellets, are balanced by both nitrate inputs at the base of the euphotic zone and N2-fixation. This input of new N to balance export losses (the biological pump) is a fundamental aspect of N cycling and central to understanding carbon fluxes in the ocean. In the Pacific Ocean, detailed N budgets at the time-series station HOT require upward transport of nitrate from the nutricline (80-100 m) into the surface layer (∼0-40 m) to balance productivity and export needs. However, concentration gradients are negligible and cannot support the fluxes. Physical processes can inject nitrate into the base of the euphotic zone, but the mechanisms for transporting this nitrate into the surface layer across many 10s of m in highly stratified systems are unknown. In these seas, vertical migration by the very largest (10(2)-10(3) µm diameter) phytoplankton is common as a survival strategy to obtain N from sub-euphotic zone depths. This vertical migration is driven by buoyancy changes rather than by flagellated movement and can provide upward N transport as nitrate (mM concentrations) in the cells. However, the contribution of vertical migration to nitrate transport has been difficult to quantify over the required basin scales. In this study, we use towed optical systems and isotopic tracers to show that migrating diatom (Rhizosolenia) mats are widespread in the N. Pacific Ocean from 140°W to 175°E and together with other migrating phytoplankton (Ethmodiscus, Halosphaera, Pyrocystis, and solitary Rhizosolenia) can mediate time-averaged transport of N (235 µmol N m(-2) d(-1)) equivalent to eddy nitrate injections (242 µmol NO3 (-) m(-2) d(-1)). This upward biotic transport can close N budgets in the upper 250 m of the central Pacific Ocean and together with diazotrophy creates a surface zone where biological nutrient inputs rather than physical processes dominate the new N flux. In addition to these numerically rare large migrators, there is evidence in the literature of ascending behavior in small phytoplankton that could contribute to upward flux as well. Although passive downward movement has dominated models of phytoplankton flux, there is now sufficient evidence to require a rethinking of this paradigm. Quantifying these fluxes is a challenge for the future and requires a reexamination of individual phytoplankton sinking rates as well as methods for capturing and enumerating ascending phytoplankton in the sea.

Upward nitrate transport by phytoplankton in oceanic waters: balancing nutrient budgets in oligotrophic seas

PubMed Central

Pilskaln, Cynthia H.; Montoya, Joseph P.; Dennett, Mark

2014-01-01

In oceanic subtropical gyres, primary producers are numerically dominated by small (1–5 µm diameter) pro- and eukaryotic cells that primarily utilize recycled nutrients produced by rapid grazing turnover in a highly efficient microbial loop. Continuous losses of nitrogen (N) to depth by sinking, either as single cells, aggregates or fecal pellets, are balanced by both nitrate inputs at the base of the euphotic zone and N2-fixation. This input of new N to balance export losses (the biological pump) is a fundamental aspect of N cycling and central to understanding carbon fluxes in the ocean. In the Pacific Ocean, detailed N budgets at the time-series station HOT require upward transport of nitrate from the nutricline (80–100 m) into the surface layer (∼0–40 m) to balance productivity and export needs. However, concentration gradients are negligible and cannot support the fluxes. Physical processes can inject nitrate into the base of the euphotic zone, but the mechanisms for transporting this nitrate into the surface layer across many 10s of m in highly stratified systems are unknown. In these seas, vertical migration by the very largest (102–103 µm diameter) phytoplankton is common as a survival strategy to obtain N from sub-euphotic zone depths. This vertical migration is driven by buoyancy changes rather than by flagellated movement and can provide upward N transport as nitrate (mM concentrations) in the cells. However, the contribution of vertical migration to nitrate transport has been difficult to quantify over the required basin scales. In this study, we use towed optical systems and isotopic tracers to show that migrating diatom (Rhizosolenia) mats are widespread in the N. Pacific Ocean from 140°W to 175°E and together with other migrating phytoplankton (Ethmodiscus, Halosphaera, Pyrocystis, and solitary Rhizosolenia) can mediate time-averaged transport of N (235 µmol N m-2 d-1) equivalent to eddy nitrate injections (242 µmol NO3− m-2 d-1). This upward biotic transport can close N budgets in the upper 250 m of the central Pacific Ocean and together with diazotrophy creates a surface zone where biological nutrient inputs rather than physical processes dominate the new N flux. In addition to these numerically rare large migrators, there is evidence in the literature of ascending behavior in small phytoplankton that could contribute to upward flux as well. Although passive downward movement has dominated models of phytoplankton flux, there is now sufficient evidence to require a rethinking of this paradigm. Quantifying these fluxes is a challenge for the future and requires a reexamination of individual phytoplankton sinking rates as well as methods for capturing and enumerating ascending phytoplankton in the sea. PMID:24688877

Stratification by cyanobacteria in lakes: a dynamic buoyancy model indicates size limitations met by Planktothrix rubescens filaments.

PubMed

Walsby, Anthony E

2005-11-01

The ability of the Planktothrix rubescens to stratify in Lake Zürich is related to the size and shape of the cyanobacterial filaments. Detailed measurements made in the lake are used in a dynamic computer model of buoyancy regulation to investigate the vertical movements of filaments tracking the depth at which the irradiance would support neutral buoyancy. The movement of the filament lags behind the constantly changing target depth owing to (a) the time taken for the filament to respond to the irradiance by changing its density and (b) the time it takes to move by sinking down or floating up through the water column. The model simulates the stratification depth over a 5-month period of the summer from the continuous measurements of irradiance and weekly measurements of light attenuation and temperature, without any further adjustment over the period. Models using filaments of the size observed in Lake Zürich explain several details of the observed depth changes: smaller planktonic cyanobacteria (e.g. Limnothrix sp.) are unable to migrate fast enough and larger ones (e.g. Anabaena spp.) will overshoot and become entrained in the epilimnion. The model can be used to simulate recruitment of Planktothrix filaments from different depths after vernal stratification. Recruitment of filaments from depths down to 45 m will contribute to the metalimnetic population increase in early July.

Parameters on reconstructions of geohistory, thermal history, and hydrocarbon generation history in a sedimentary basin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cao, S.; Lerche, I.

1988-01-01

Geological processes related to petroleum generation, migration, and accumulation are very complicated in terms of time and variables involved, and are very difficult to simulate by laboratory experiments. For this reason, many mathematic/computer models have been developed to simulate these geological processes based on geological, geophysical, and geochemical principles. Unfortunately, none of these models can exactly simulate these processes because of the assumptions and simplifications made in these models and the errors in the input for the models. The sensitivity analysis is a comprehensive examination on how geological, geophysical, and geochemical parameters affect the reconstructions of geohistory, thermal history, andmore » hydrocarbon generation history. In this study, a one-dimensional fluid flow/compaction model has been used to run the sensitivity analysis. The authors will show the effects of some commonly used parameters such as depth, age, lithology, porosity, permeability, unconformity (time and eroded thickness), temperature at sediment surface, bottom hole temperature, present day heat flow, thermal gradient, thermal conductivity and kerogen type, and content on the evolutions of formation thickness, porosity, permeability, pressure with time and depth, heat flow with time, temperature with time and depth, vitrinite reflectance (R/sub 0/) and TTI with time and depth, oil window in terms of time and depth, and amount of hydrocarbon generated with time and depth.« less

Trace gas and vegetation feedback responses of Alaskan tussock tundra to long-term snow depth manipulations

NASA Astrophysics Data System (ADS)

Ebbs, L. M.; Taneva, L.; Sullivan, P.; Welker, J. M.

2009-12-01

Changes in the precipitation and temperature regimes in Northern Alaska are manifesting themselves through shifts in sea ice, vegetation traits, animal migration timing and hydrologic dynamics. Changes in precipitation and soil temperature result in changes in plant mineral nutrition, soil nutrient availability, trace gas exchanges and differential nutrient acquisition strategies by arctic plants. In this study, we report on the extent to which long-term increases in snow depth, along with reductions in snow depth alter the magnitudes and pattern of CO2 exchange, soil properties and vegetation traits. A doubling of snow depth (from ~0.5 to ~1.0m) results in a delay of the growing season by ~ 2 weeks, however, by peak season, the rates of CO2 exchange are 50% higher in areas which had experienced deeper snow depth levels. To the contrary, long-term reductions in snow depth results in accelerated rates of plant phenology, however CO2 exchange rates at peak season are 30% less than those areas under ambient snow cover in the preceding winter. Reduced snow depth areas had the coldest winter soil temperatures while the deeper areas had the warmest winter soil temperatures, which may partially explain the summer CO2 fluxes indirectly via different rates of winter N mineralization and differences in leaf N properties. Our results indicate that shifting fall, winter and spring when snow is the primary form of precipitation, may have profound effects on tussock tundra systems.

Magma intrusion near Volcan Tancitaro: Evidence from seismic analysis

DOE PAGES

Pinzon, Juan I.; Nunez-Cornu, Francisco J.; Rowe, Charlotte Anne

2016-11-17

Between May and June 2006, an earthquake swarm occurred near Volcan Tancítaro in Mexico, which was recorded by a temporary seismic deployment known as the MARS network. We located ~1000 events from this seismic swarm. Previous earthquake swarms in the area were reported in the years 1997, 1999 and 2000. We relocate and analyze the evolution and properties of the 2006 earthquake swarm, employing a waveform cross-correlation-based phase repicking technique. Hypocenters from 911 events were located and divided into eighteen families having a correlation coefficient at or above 0.75. 90% of the earthquakes provide at least sixteen phase picks. Wemore » used the single-event location code Hypo71 and the P-wave velocity model used by the Jalisco Seismic and Accelerometer Network to improve hypocenters based on the correlation-adjusted phase arrival times. We relocated 121 earthquakes, which show clearly two clusters, between 9–10 km and 3–4 km depth respectively. The average location error estimates are <1 km epicentrally, and <2 km in depth, for the largest event in each cluster. Depths of seismicity migrate upward from 16 to 3.5 km and exhibit a NE-SW trend. The swarm first migrated toward Paricutin Volcano but by mid-June began propagating back toward Volcán Tancítaro. In addition to its persistence, noteworthy aspects of this swarm include a quasi-exponential increase in the rate of activity within the first 15 days; a b-value of 1.47; a jug-shaped hypocenter distribution; a shoaling rate of ~5 km/month within the deeper cluster, and a composite focal mechanism solution indicating largely reverse faulting. As a result, these features of the swarm suggest a magmatic source elevating the crustal strain beneath Volcan Tancítaro.« less

Magma intrusion near Volcan Tancitaro: Evidence from seismic analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pinzon, Juan I.; Nunez-Cornu, Francisco J.; Rowe, Charlotte Anne

Between May and June 2006, an earthquake swarm occurred near Volcan Tancítaro in Mexico, which was recorded by a temporary seismic deployment known as the MARS network. We located ~1000 events from this seismic swarm. Previous earthquake swarms in the area were reported in the years 1997, 1999 and 2000. We relocate and analyze the evolution and properties of the 2006 earthquake swarm, employing a waveform cross-correlation-based phase repicking technique. Hypocenters from 911 events were located and divided into eighteen families having a correlation coefficient at or above 0.75. 90% of the earthquakes provide at least sixteen phase picks. Wemore » used the single-event location code Hypo71 and the P-wave velocity model used by the Jalisco Seismic and Accelerometer Network to improve hypocenters based on the correlation-adjusted phase arrival times. We relocated 121 earthquakes, which show clearly two clusters, between 9–10 km and 3–4 km depth respectively. The average location error estimates are <1 km epicentrally, and <2 km in depth, for the largest event in each cluster. Depths of seismicity migrate upward from 16 to 3.5 km and exhibit a NE-SW trend. The swarm first migrated toward Paricutin Volcano but by mid-June began propagating back toward Volcán Tancítaro. In addition to its persistence, noteworthy aspects of this swarm include a quasi-exponential increase in the rate of activity within the first 15 days; a b-value of 1.47; a jug-shaped hypocenter distribution; a shoaling rate of ~5 km/month within the deeper cluster, and a composite focal mechanism solution indicating largely reverse faulting. As a result, these features of the swarm suggest a magmatic source elevating the crustal strain beneath Volcan Tancítaro.« less

Modeling effluent distribution and nitrate transport through an on-site wastewater system.

PubMed

Hassan, G; Reneau, R B; Hagedorn, C; Jantrania, A R

2008-01-01

Properly functioning on-site wastewater systems (OWS) are an integral component of the wastewater system infrastructure necessary to renovate wastewater before it reaches surface or ground waters. There are a large number of factors, including soil hydraulic properties, effluent quality and dispersal, and system design, that affect OWS function. The ability to evaluate these factors using a simulation model would improve the capability to determine the impact of wastewater application on the subsurface soil environment. An existing subsurface drip irrigation system (SDIS) dosed with sequential batch reactor effluent (SBRE) was used in this study. This system has the potential to solve soil and site problems that limit OWS and to reduce the potential for environmental degradation. Soil water potentials (Psi(s)) and nitrate (NO(3)) migration were simulated at 55- and 120-cm depths within and downslope of the SDIS using a two-dimensional code in HYDRUS-3D. Results show that the average measured Psi(s) were -121 and -319 cm, whereas simulated values were -121 and -322 cm at 55- and 120-cm depths, respectively, indicating unsaturated conditions. Average measured NO(3) concentrations were 0.248 and 0.176 mmol N L(-1), whereas simulated values were 0.237 and 0.152 mmol N L(-1) at 55- and 120-cm depths, respectively. Observed unsaturated conditions decreased the potential for NO(3) to migrate in more concentrated plumes away from the SDIS. The agreement (high R(2) values approximately 0.97) between the measured and simulated Psi(s) and NO(3) concentrations indicate that HYDRUS-3D adequately simulated SBRE flow and NO(3) transport through the soil domain under a range of environmental and effluent application conditions.

Magma intrusion near Volcan Tancítaro: Evidence from seismic analysis

NASA Astrophysics Data System (ADS)

Pinzón, Juan I.; Núñez-Cornú, Francisco J.; Rowe, Charlotte A.

2017-01-01

Between May and June 2006, an earthquake swarm occurred near Volcan Tancítaro in Mexico, which was recorded by a temporary seismic deployment known as the MARS network. We located ∼1000 events from this seismic swarm. Previous earthquake swarms in the area were reported in the years 1997, 1999 and 2000. We relocate and analyze the evolution and properties of the 2006 earthquake swarm, employing a waveform cross-correlation-based phase repicking technique. Hypocenters from 911 events were located and divided into eighteen families having a correlation coefficient at or above 0.75. 90% of the earthquakes provide at least sixteen phase picks. We used the single-event location code Hypo71 and the P-wave velocity model used by the Jalisco Seismic and Accelerometer Network to improve hypocenters based on the correlation-adjusted phase arrival times. We relocated 121 earthquakes, which show clearly two clusters, between 9-10 km and 3-4 km depth respectively. The average location error estimates are <1 km epicentrally, and <2 km in depth, for the largest event in each cluster. Depths of seismicity migrate upward from 16 to 3.5 km and exhibit a NE-SW trend. The swarm first migrated toward Paricutin Volcano but by mid-June began propagating back toward Volcán Tancítaro. In addition to its persistence, noteworthy aspects of this swarm include a quasi-exponential increase in the rate of activity within the first 15 days; a b-value of 1.47; a jug-shaped hypocenter distribution; a shoaling rate of ∼5 km/month within the deeper cluster, and a composite focal mechanism solution indicating largely reverse faulting. These features of the swarm suggest a magmatic source elevating the crustal strain beneath Volcan Tancítaro.

Fish passage and abundance around grade control structures on incised streams

USGS Publications Warehouse

Thomas, J.T.; Papanicolaou, A.N.; Pierce, C.L.; Dermisis, D.C.; Litvan, M.E.; Larson, C.J.

2009-01-01

This paper summarizes research from separate studies of fish passage over weirs (Larson et al., 2004; Litvan, 2006; Litvan, et al., 2008a-c) and weir hydraulics (Papanicolaou and Dermisis, 2006; Papanicolaou and Dermisis, in press). Channel incision in the deep loess region of western Iowa has caused decreased biodiversity because streams have high sediment loads, altered flow regimes, lost habitat, and lost lateral connectivity with their former floodplains. In-stream grade control structures (GCS) are built to prevent further erosion, protect infrastructure, and reduce sediment loads. However, GCS can have a detrimental impact on fisheries abundance and migration, biodiversity, and longitudinal connectivity. Fish mark-recapture studies were performed on stretches of streams with and without GCS. GCS with vertical or 1:4 (rise/run) downstream slopes did not allow fish migration, but GCS with slopes ??? 1:15 did. GCS sites were characterized by greater proportions of pool habitat, maximum depths, fish biomass, slightly higher index of biotic integrity (IBI) scores, and greater macroinvertebrate abundance and diversity than non-GCS sites. After modification of three GCS, IBI scores increased and fish species exhibiting truncated distributions before were found throughout the study area. Another study examined the hydraulic performance of GCS to facilitate unimpeded fish passage by determining the mean and turbulent flow characteristics in the vicinity of the GCS via detailed, non-intrusive field tests. Mean flow depth (Y) and velocity (V) atop the GCS were critical for evaluating GCS performance. Turbulent flow measurements illustrated that certain GCS designs cause sudden constrictions which form eddies large enough to disorient fish. GCS with slopes ??? 1:15 best met the minimum requirements to allow catfish passage of a flow depth of ??? 0.31 m and a mean flow velocity of ??? 1.22 m/s. ?? 2009 ASCE.

A Cross-Shore Model of Barrier Island Migration over a Compressible Substrate

DTIC Science & Technology

2010-01-01

possibly become submerged (e.g., Penland and Boyd, 1981; Leather - man et al., 1982; McBride et al., 1995). Penland and Boyd (1981) defined three stages of...tð Þ + d tð Þð Þ2 " #1=2 for 1 30 ≤ tan β tð Þ≤ 1 5 ð11Þ in which ρ is the density of water, and the maximum dimensionless depth-integrated wave

The ARGOS system used for tracking gray whales

NASA Technical Reports Server (NTRS)

Mate, B. R.; Beaty, D.; Hoisington, C.; Kutz, R.; Mate, M. L.

1983-01-01

The development of satellite whale tags used to track gray whales in the eastern north Pacific Ocean is summarized. Two gray whales were radio-tagged in San Ignacio Lagoon (Mexico) and tracked on their northbound migration. One of the transmitters was modified to record and relay depth-of-dive information at 15 sec intervals throughout the course of the dive. Technical elements of data acquisition and analysis are outlined. The major biological findings are discussed.

Electric Field Stimulation Enhances Healing of Post-Traumatic Osteoarthritic Cartilage

DTIC Science & Technology

2016-10-01

analyzed using ANOVA with Tukey’s post -hoc test (pɘ.05). RESULTS: In study 1, a proportion of synovial fibroblasts migrated to a maximum depth of ~250...AWARD NUMBER: W81XWH-14-1-0591 TITLE: Electric Field Stimulation Enhances Healing of Post -Traumatic Osteoarthritic Cartilage PRINCIPAL...COVERED 30 Sep 2015 – 29 Sep 2016 4. TITLE AND SUBTITLE Cartilage 5a. CONTRACT NUMBER Electric Field Stimulation Enhances Healing of Post -Traumatic

Vertical distribution of hydraulic characteristics and water quality in three boreholes in the Galena-Platteville Aquifer at the Parson's Casket Hardware Superfund site, Belvidere, Illinois, 1990

USGS Publications Warehouse

Mills, P.C.

1993-01-01

The U.S. Geological Survey investigated contaminant migration in the Galena-Platteville aquifer at the Parson's Casket Hardware site in Belvidere, Ill. This report presents the results of the first phase of the investigation, from August through December 1990. A packer assembly was used to isolate various depth intervals in three 150-foot-deep boreholes in the dolomite aquifer. Aquifer-test data include vertical distributions of vertical hydraulic gradient, horizontal hydraulic conductivity (K), and response of water levels in observation wells to borehole pumping. Water-quality data include vertical distributions of field-measured properties and laboratory determinations of concentrations of volatile organic compounds (VOC's). vertical hydraulic gradients in the aquifer were downward. The downward gradients ranged from less than 0.01 to 0.37 foot/foot. The largest gradient was associated with an elevated-K interval at 115 to 125 feet below land surface. The hydraulic characteristics of strata within the aquifer seem to be generally consistent across the site. The strata can be subdivided into five hydraulic units with the following approximate depth ranges-and K's : (1) a 1- to 5-foot-thick weathered surface at about 35 feet below land surface, 1-200 ft/d (feet per day); (2) 35-80 feet, 0.05-0.5 ft/d; (3) 80-115 feet, 0.5 ft/d; (4) 115-125 feet, 0.5-10 ft/d; and (5) 125-150 feet, 0.5 ft/d. Water-level drawdowns were detected in one shallow bedrock observation well during pumping of some of the packed intervals in a nearby borehole, indicating that the degree of vertical connection between some intervals in the aquifer may be greater than that between others. During development pumping of one borehole, drawdowns were detected in a nearby well screened in the lower part of the overlying glacial-drift deposits, indicating hydraulic connection between the glacial drift aquifer and the bedrock aquifer. VOC's were detected throughout the upper half (about 150 feet ) of the bedrock aquifer beneath the site. The detected compounds were predominantly chlorinated ethenes and ethanes (maximum concentration was 570 ppb (parts per billion) of trichloroethylene. There was a positive correlation between concentrations of VOC's, specific conductance, and K. The distribution of VOC concentrations indicate that the low-K dolomite beds in the Galena-Platteville aquifer may impede the downward migration of the VOC's and that the high-K beds and fissures may provide pathways for the lateral migration of VOC's through the aquifer. Contaminant migration is possibly affected by ground-water flow through vertical fractures that connect shallow beds with deeper beds in the aquifer, thus explaining the detections of some VOC species at intermittent depths.

Nearshore bars and the break-point hypothesis

USGS Publications Warehouse

Sallenger, A.H.; Howd, P.A.

1989-01-01

The set of hypotheses calling for bar formation at the break point was tested with field data. During two different experiments, waves were measured across the surf zone coincident with the development of a nearshore bar. We use a criterion, based on the wave height to depth ratio, to determine the offshore limit of the inner surf zone. During the first experiment, the bar became better developed and migrated offshore while remaining well within the inner surf zone. During the second experiment, the surf zone was narrower and we cannot rule out the possibility of break point processes contributing to bar development. We conclude that bars are not necessarily coupled with the break point and can become better developed and migrate offshore while being in the inner surf zone landward from initial wave breaking in the outer surf zone. ?? 1989.

Imaging stem cell distribution, growth, migration, and differentiation in 3-D scaffolds for bone tissue engineering using mesoscopic fluorescence tomography.

PubMed

Tang, Qinggong; Piard, Charlotte; Lin, Jonathan; Nan, Kai; Guo, Ting; Caccamese, John; Fisher, John; Chen, Yu

2018-01-01

Regenerative medicine has emerged as an important discipline that aims to repair injury or replace damaged tissues or organs by introducing living cells or functioning tissues. Successful regenerative medicine strategies will likely depend upon a simultaneous optimization strategy for the design of biomaterials, cell-seeding methods, cell-biomaterial interactions, and molecular signaling within the engineered tissues. It remains a challenge to image three-dimensional (3-D) structures and functions of the cell-seeded scaffold in mesoscopic scale (>2 ∼ 3 mm). In this study, we utilized angled fluorescence laminar optical tomography (aFLOT), which allows depth-resolved molecular characterization of engineered tissues in 3-D to investigate cell viability, migration, and bone mineralization within bone tissue engineering scaffolds in situ. © 2017 Wiley Periodicals, Inc.