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Sample records for 3d seismic refraction

  1. Structure of the Lesser Antilles subduction forearc and backstop from 3D seismic refraction tomography

    NASA Astrophysics Data System (ADS)

    Evain, Mikael; Galve, Audrey; Charvis, Philippe; Laigle, Mireille; Kopp, Heidrun; Bécel, Anne; Weinzierl, Wolfgang; Hirn, Alfred; Flueh, Ernst R.; Gallart, Josep

    2013-09-01

    In 2007 the Sismantilles II experiment was conducted to constrain structure and seismicity in the central Lesser Antilles subduction zone. The seismic refraction data recorded by a network of 27 OBSs over an area of 65 km × 95 km provide new insights on the crustal structure of the forearc offshore Martinique and Dominica islands. The tomographic inversion of first arrival travel times provides a 3D P-wave velocity model down to 15 km. Basement velocity gradients depict that the forearc is made up of two distinct units: A high velocity gradient domain named the inner forearc in comparison to a lower velocity gradient domain located further trenchward named the outer forearc. Whereas the inner forearc appears as a rigid block uplifted and possibly tilted as a whole to the south, short wavelength deformations of the outer forearc basement are observed, beneath a 3 to 6 km thick sedimentary pile, in relation with the subduction of the Tiburon Ridge and associated seafloor reliefs. North, offshore Dominica Island, the outer forearc is 70 km wide. It extends as far as 180 km to the east of the volcanic front where it acts as a backstop on which the accretionary wedge developed. Its width decreases strongly to the south to terminate offshore Martinique where the inner forearc acts as the backstop. The inner forearc is likely the extension at depth of the Mesozoic magmatic crust outcropping to the north in La Désirade Island and along the scarp of the Karukera Spur. The outer forearc could be either the eastern prolongation of the inner forearc, but the crust was thinned and fractured during the past tectonic history of the area or by recent subduction processes, or an oceanic terrane more recently accreted to the island arc.

  2. tomo3d: a new 3-D joint refraction and reflection travel-time tomography code for active-source seismic data

    NASA Astrophysics Data System (ADS)

    Meléndez, A.; Korenaga, J.; Sallares, V.; Ranero, C. R.

    2012-12-01

    We present the development state of tomo3d, a code for three-dimensional refraction and reflection travel-time tomography of wide-angle seismic data based on the previous two-dimensional version of the code, tomo2d. The core of both forward and inverse problems is inherited from the 2-D version. The ray tracing is performed by a hybrid method combining the graph and bending methods. The graph method finds an ordered array of discrete model nodes, which satisfies Fermat's principle, that is, whose corresponding travel time is a global minimum within the space of discrete nodal connections. The bending method is then applied to produce a more accurate ray path by using the nodes as support points for an interpolation with beta-splines. Travel time tomography is formulated as an iterative linearized inversion, and each step is solved using an LSQR algorithm. In order to avoid the singularity of the sensitivity kernel and to reduce the instability of inversion, regularization parameters are introduced in the inversion in the form of smoothing and damping constraints. Velocity models are built as 3-D meshes, and velocity values at intermediate locations are obtained by trilinear interpolation within the corresponding pseudo-cubic cell. Meshes are sheared to account for topographic relief. A floating reflector is represented by a 2-D grid, and depths at intermediate locations are calculated by bilinear interpolation within the corresponding square cell. The trade-off between the resolution of the final model and the associated computational cost is controlled by the relation between the selected forward star for the graph method (i.e. the number of nodes that each node considers as its neighbors) and the refinement of the velocity mesh. Including reflected phases is advantageous because it provides a better coverage and allows us to define the geometry of those geological interfaces with velocity contrasts sharp enough to be observed on record sections. The code also

  3. TOMO3D: 3-D joint refraction and reflection traveltime tomography parallel code for active-source seismic data—synthetic test

    NASA Astrophysics Data System (ADS)

    Meléndez, A.; Korenaga, J.; Sallarès, V.; Miniussi, A.; Ranero, C. R.

    2015-10-01

    We present a new 3-D traveltime tomography code (TOMO3D) for the modelling of active-source seismic data that uses the arrival times of both refracted and reflected seismic phases to derive the velocity distribution and the geometry of reflecting boundaries in the subsurface. This code is based on its popular 2-D version TOMO2D from which it inherited the methods to solve the forward and inverse problems. The traveltime calculations are done using a hybrid ray-tracing technique combining the graph and bending methods. The LSQR algorithm is used to perform the iterative regularized inversion to improve the initial velocity and depth models. In order to cope with an increased computational demand due to the incorporation of the third dimension, the forward problem solver, which takes most of the run time (˜90 per cent in the test presented here), has been parallelized with a combination of multi-processing and message passing interface standards. This parallelization distributes the ray-tracing and traveltime calculations among available computational resources. The code's performance is illustrated with a realistic synthetic example, including a checkerboard anomaly and two reflectors, which simulates the geometry of a subduction zone. The code is designed to invert for a single reflector at a time. A data-driven layer-stripping strategy is proposed for cases involving multiple reflectors, and it is tested for the successive inversion of the two reflectors. Layers are bound by consecutive reflectors, and an initial velocity model for each inversion step incorporates the results from previous steps. This strategy poses simpler inversion problems at each step, allowing the recovery of strong velocity discontinuities that would otherwise be smoothened.

  4. tomo3d: a new 3-D joint refraction and reflection travel-time tomography code for active-source seismic data

    NASA Astrophysics Data System (ADS)

    Meléndez, A.; Korenaga, J.; Sallarès, V.; Ranero, C. R.

    2012-04-01

    We present the development state of tomo3d, a code for three-dimensional refraction and reflection travel-time tomography of wide-angle seismic data based on the previous two-dimensional version of the code, tomo2d. The core of both forward and inverse problems is inherited from the 2-D version. The ray tracing is performed by a hybrid method combining the graph and bending methods. The graph method finds an ordered array of discrete model nodes, which satisfies Fermat's principle, that is, whose corresponding travel time is a global minimum within the space of discrete nodal connections. The bending method is then applied to produce a more accurate ray path by using the nodes as support points for an interpolation with beta-splines. Travel time tomography is formulated as an iterative linearized inversion, and each step is solved using an LSQR algorithm. In order to avoid the singularity of the sensitivity kernel and to reduce the instability of inversion, regularization parameters are introduced in the inversion in the form of smoothing and damping constraints. Velocity models are built as 3-D meshes, and velocity values at intermediate locations are obtained by trilinear interpolation within the corresponding pseudo-cubic cell. Meshes are sheared to account for topographic relief. A floating reflector is represented by a 2-D grid, and depths at intermediate locations are calculated by bilinear interpolation within the corresponding square cell. The trade-off between the resolution of the final model and the associated computational cost is controlled by the relation between the selected forward star for the graph method (i.e. the number of nodes that each node considers as its neighbors) and the refinement of the velocity mesh. Including reflected phases is advantageous because it provides a better coverage and allows us to define the geometry of those geological interfaces with velocity contrasts sharp enough to be observed on record sections. The code also

  5. 3-D Tomography Study of Seismic Refraction/Wide-Angle Reflection Data Across the Variscides, SW Ireland

    NASA Astrophysics Data System (ADS)

    O'Reilly, B. M.; Landes, M.; Readman, P. W.; Shannon, P. M.; Prodehl, C.

    2002-12-01

    The VARNET-96 seismic experiment acquired three seismic refraction/wide-angle reflection profiles in order to examine the crustal structure in the south-west of Ireland. 170 seismic stations were used on 300 recording sites. The shotpoint geometry was designed to allow for both in-line and off-line fan shot recordings on the three profiles. A total of 34 water shots was fired. Results from 3-D raytrace and inversion modelling illustrate the pervasive lateral heterogeneity of the study area south of the Shannon Estuary. Palaeozoic strata at the south coast are about 5-6 km thick associated with the sedimentary infill of the Munster and South Munster Basins. To the north, shallow upper crust in the vicinity of the Killarney-Mallow Fault Zone is followed by a 3-4 km thick sedimentary succession in the Dingle-Shannon Basin. A zone of high-velocity upper crust (6.4-6.6 km/s) beneath the South Munster Basin correlates with a gravity high between the Kenmare-Killarney and the Leinster Granite gravity lows. Other high-velocity zones were found beneath Dingle Bay and the Kenmare River region and may be associated with the deep traces of the Killarney-Mallow Fault Zone and the Cork-Kenmare Line. The 3-D velocity model was taken as a basis for the computation of PmP reflected arrivals from the crust-mantle boundary. The Moho depth varies from about 28-29 km at the south coast to about 32-33 km beneath the Dingle-Shannon Basin, the region where the 2-D inline model shows a south-dipping reflector in the upper mantle. Pervasive Variscan deformation appears to be confined to the sedimentary and upper crustal structure and has not deformed the entire crust supporting a thin-skinned tectonic model for Variscan deformation. Deep-crustal variations only occur where they can be correlated with major tectonic features such as the Caledonian Iapetus Suture near the Shannon Estuary. The shallowing of the Moho towards the coast may result from Mesozoic crustal extension in the adjacent

  6. 3-D Seismic Interpretation

    NASA Astrophysics Data System (ADS)

    Moore, Gregory F.

    2009-05-01

    This volume is a brief introduction aimed at those who wish to gain a basic and relatively quick understanding of the interpretation of three-dimensional (3-D) seismic reflection data. The book is well written, clearly illustrated, and easy to follow. Enough elementary mathematics are presented for a basic understanding of seismic methods, but more complex mathematical derivations are avoided. References are listed for readers interested in more advanced explanations. After a brief introduction, the book logically begins with a succinct chapter on modern 3-D seismic data acquisition and processing. Standard 3-D acquisition methods are presented, and an appendix expands on more recent acquisition techniques, such as multiple-azimuth and wide-azimuth acquisition. Although this chapter covers the basics of standard time processing quite well, there is only a single sentence about prestack depth imaging, and anisotropic processing is not mentioned at all, even though both techniques are now becoming standard.

  7. 3D crustal seismic velocity model for the Gulf of Cadiz and adjacent areas (SW Iberia margin) based on seismic reflection and refraction profiles

    NASA Astrophysics Data System (ADS)

    Lozano, Lucía; Cantavella, Juan Vicente; Barco, Jaime; Carranza, Marta; Burforn, Elisa

    2016-04-01

    The Atlantic margin of the SW Iberian Peninsula and northern Morocco has been subject of study during the last 30 years. Many seismic reflection and refraction profiles have been carried out offshore, providing detailed information about the crustal structure of the main seafloor tectonic domains in the region, from the South Portuguese Zone and the Gulf of Cadiz to the Abyssal Plains and the Josephine Seamount. The interest to obtain a detailed and realistic velocity model for this area, integrating the available data from these studies, is clear, mainly to improve real-time earthquake hypocentral location and for tsunami and earthquake early warning. Since currently real-time seismic location tools allow the implementation of 3D velocity models, we aim to generate a full 3D crustal model. For this purpose we have reviewed more than 50 profiles obtained in different seismic surveys, from 1980 to 2008. Data from the most relevant and reliable 2D seismic velocity published profiles were retrieved. We first generated a Moho depth map of the studied area (latitude 32°N - 41°N and longitude 15°W - 5°W) by extracting Moho depths along each digitized profile with a 10 km spacing, and then interpolating this dataset using ordinary kriging method and generating the contour isodepth map. Then, a 3D crustal velocity model has been obtained. Selected vertical sections at different distances along each profile were considered to retrieve P-wave velocity values at each interface in order to reproduce the geometry and the velocity gradient within each layer. A double linear interpolation, both in distance and depth, with sampling rates of 10 km and 1 km respectively, was carried out to generate a (latitude, longitude, depth, velocity) matrix. This database of all the profiles was interpolated to obtain the P-wave velocity distribution map every kilometer of depth. The new 3D velocity model has been integrated in NonLinLoc location program to relocate several representative

  8. Crustal high-velocity anomaly at the East European Craton margin in SE Poland (TESZ) modelled by 3-D seismic tomography of refracted and reflected arrivals

    NASA Astrophysics Data System (ADS)

    Środa, Piotr; Dec, Monika

    2016-04-01

    The area of Trans-European Suture Zone in SE Poland represents a contact of major tectonic units of different consolidation age - from the Precambrian East European Craton, through Palaeozoic West European Platform to Cenozoic Carpathian orogen. The region was built by several phases of crustal accretion, which resulted in a complex collage of tectonic blocks. In 2000, this region was studied by several seismic wide-angle profiles of CELEBRATION 2000 experiment, providing a dense coverage of seismic data in SE Poland and allowing for detailed investigations of the crustal structure and properties in this area. Beneath the marginal part of the EEC, the 2-D modelling of in-line data form several CELEBRATION profiles revealed a prominent high P-wave velocity anomaly in the upper crust, with Vp of 6.7-7.1 km/s, starting at 10-16 km depth (e.g., Środa et al., 2006). Anomalously high velocities are observed in the area located approximately beneath Lublin trough, to the NE of Teisseyre-Tornquist Zone. Based on 3-D tomography of first arrivals of in- and off-line CELEBRATION 2000 recordings (Malinowski et al., 2008), elevated velocities are also reported in the same area and seem to continue to the SW, off the craton margin. Gravimetric modelling also revealed anomalously high density in the same region at similar depths. High seismic velocities and densities are interpreted as indicative for a pronounced mafic intrusion, possibly related to extensional processes at the EEC margin. Previous 3-D models of the high-velocity intrusion were based on first arrivals (crustal refractions) only. In this study, also off-line reflections (not modelled up to now) are used, in order to enlarge the data set and to better constrain the geometry and properties of the velocity anomaly. A code for 3-D joint tomographic inversion of refracted and reflected arrivals, with model parametrization allowing for velocity discontinuities was used (Rawlinson, 2007). With this approach, besides the

  9. Fully 3D refraction correction dosimetry system

    NASA Astrophysics Data System (ADS)

    Manjappa, Rakesh; Sharath Makki, S.; Kumar, Rajesh; Mohan Vasu, Ram; Kanhirodan, Rajan

    2016-02-01

    The irradiation of selective regions in a polymer gel dosimeter results in an increase in optical density and refractive index (RI) at those regions. An optical tomography-based dosimeter depends on rayline path through the dosimeter to estimate and reconstruct the dose distribution. The refraction of light passing through a dose region results in artefacts in the reconstructed images. These refraction errors are dependant on the scanning geometry and collection optics. We developed a fully 3D image reconstruction algorithm, algebraic reconstruction technique-refraction correction (ART-rc) that corrects for the refractive index mismatches present in a gel dosimeter scanner not only at the boundary, but also for any rayline refraction due to multiple dose regions inside the dosimeter. In this study, simulation and experimental studies have been carried out to reconstruct a 3D dose volume using 2D CCD measurements taken for various views. The study also focuses on the effectiveness of using different refractive-index matching media surrounding the gel dosimeter. Since the optical density is assumed to be low for a dosimeter, the filtered backprojection is routinely used for reconstruction. We carry out the reconstructions using conventional algebraic reconstruction (ART) and refractive index corrected ART (ART-rc) algorithms. The reconstructions based on FDK algorithm for cone-beam tomography has also been carried out for comparison. Line scanners and point detectors, are used to obtain reconstructions plane by plane. The rays passing through dose region with a RI mismatch does not reach the detector in the same plane depending on the angle of incidence and RI. In the fully 3D scanning setup using 2D array detectors, light rays that undergo refraction are still collected and hence can still be accounted for in the reconstruction algorithm. It is found that, for the central region of the dosimeter, the usable radius using ART-rc algorithm with water as RI matched

  10. Fully 3D refraction correction dosimetry system.

    PubMed

    Manjappa, Rakesh; Makki, S Sharath; Kumar, Rajesh; Vasu, Ram Mohan; Kanhirodan, Rajan

    2016-02-21

    The irradiation of selective regions in a polymer gel dosimeter results in an increase in optical density and refractive index (RI) at those regions. An optical tomography-based dosimeter depends on rayline path through the dosimeter to estimate and reconstruct the dose distribution. The refraction of light passing through a dose region results in artefacts in the reconstructed images. These refraction errors are dependant on the scanning geometry and collection optics. We developed a fully 3D image reconstruction algorithm, algebraic reconstruction technique-refraction correction (ART-rc) that corrects for the refractive index mismatches present in a gel dosimeter scanner not only at the boundary, but also for any rayline refraction due to multiple dose regions inside the dosimeter. In this study, simulation and experimental studies have been carried out to reconstruct a 3D dose volume using 2D CCD measurements taken for various views. The study also focuses on the effectiveness of using different refractive-index matching media surrounding the gel dosimeter. Since the optical density is assumed to be low for a dosimeter, the filtered backprojection is routinely used for reconstruction. We carry out the reconstructions using conventional algebraic reconstruction (ART) and refractive index corrected ART (ART-rc) algorithms. The reconstructions based on FDK algorithm for cone-beam tomography has also been carried out for comparison. Line scanners and point detectors, are used to obtain reconstructions plane by plane. The rays passing through dose region with a RI mismatch does not reach the detector in the same plane depending on the angle of incidence and RI. In the fully 3D scanning setup using 2D array detectors, light rays that undergo refraction are still collected and hence can still be accounted for in the reconstruction algorithm. It is found that, for the central region of the dosimeter, the usable radius using ART-rc algorithm with water as RI matched

  11. 3D Elastic Seismic Wave Propagation Code

    1998-09-23

    E3D is capable of simulating seismic wave propagation in a 3D heterogeneous earth. Seismic waves are initiated by earthquake, explosive, and/or other sources. These waves propagate through a 3D geologic model, and are simulated as synthetic seismograms or other graphical output.

  12. Automating Shallow 3D Seismic Imaging

    SciTech Connect

    Steeples, Don; Tsoflias, George

    2009-01-15

    Our efforts since 1997 have been directed toward developing ultra-shallow seismic imaging as a cost-effective method applicable to DOE facilities. This report covers the final year of grant-funded research to refine 3D shallow seismic imaging, which built on a previous 7-year grant (FG07-97ER14826) that refined and demonstrated the use of an automated method of conducting shallow seismic surveys; this represents a significant departure from conventional seismic-survey field procedures. The primary objective of this final project was to develop an automated three-dimensional (3D) shallow-seismic reflection imaging capability. This is a natural progression from our previous published work and is conceptually parallel to the innovative imaging methods used in the petroleum industry.

  13. 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.

  14. Refraction Correction in 3D Transcranial Ultrasound Imaging

    PubMed Central

    Lindsey, Brooks D.; Smith, Stephen W.

    2014-01-01

    We present the first correction of refraction in three-dimensional (3D) ultrasound imaging using an iterative approach that traces propagation paths through a two-layer planar tissue model, applying Snell’s law in 3D. This approach is applied to real-time 3D transcranial ultrasound imaging by precomputing delays offline for several skull thicknesses, allowing the user to switch between three sets of delays for phased array imaging at the push of a button. Simulations indicate that refraction correction may be expected to increase sensitivity, reduce beam steering errors, and partially restore lost spatial resolution, with the greatest improvements occurring at the largest steering angles. Distorted images of cylindrical lesions were created by imaging through an acrylic plate in a tissue-mimicking phantom. As a result of correcting for refraction, lesions were restored to 93.6% of their original diameter in the lateral direction and 98.1% of their original shape along the long axis of the cylinders. In imaging two healthy volunteers, the mean brightness increased by 8.3% and showed no spatial dependency. PMID:24275538

  15. 3D refractive index measurements of special optical fibers

    NASA Astrophysics Data System (ADS)

    Yan, Cheng; Huang, Su-Juan; Miao, Zhuang; Chang, Zheng; Zeng, Jun-Zhang; Wang, Ting-Yun

    2016-09-01

    A digital holographic microscopic chromatography-based approach with considerably improved accuracy, simplified configuration and performance stability is proposed to measure three dimensional refractive index of special optical fibers. Based on the approach, a measurement system is established incorporating a modified Mach-Zehnder interferometer and lab-developed supporting software for data processing. In the system, a phase projection distribution of an optical fiber is utilized to obtain an optimal digital hologram recorded by a CCD, and then an angular spectrum theory-based algorithm is adopted to extract the phase distribution information of an object wave. The rotation of the optic fiber enables the experimental measurements of multi-angle phase information. Based on the filtered back projection algorithm, a 3D refraction index of the optical fiber is thus obtained at high accuracy. To evaluate the proposed approach, both PANDA fibers and special elliptical optical fiber are considered in the system. The results measured in PANDA fibers agree well with those measured using S14 Refractive Index Profiler, which is, however, not suitable for measuring the property of a special elliptical fiber.

  16. 3-D seismic imaging of complex geologies

    SciTech Connect

    Womble, D.E.; Dosanjh, S.S.; VanDyke, J.P.; Oldfield, R.A.; Greenberg, D.S.

    1995-02-01

    We present three codes for the Intel Paragon that address the problem of three-dimensional seismic imaging of complex geologies. The first code models acoustic wave propagation and can be used to generate data sets to calibrate and validate seismic imaging codes. This code reported the fastest timings for acoustic wave propagation codes at a recent SEG (Society of Exploration Geophysicists) meeting. The second code implements a Kirchhoff method for pre-stack depth migration. Development of this code is almost complete, and preliminary results are presented. The third code implements a wave equation approach to seismic migration and is a Paragon implementation of a code from the ARCO Seismic Benchmark Suite.

  17. 3-D seismic imaging of complex geologies

    NASA Astrophysics Data System (ADS)

    Womble, David E.; Dosanjh, Sudip S.; Vandyke, John P.; Oldfield, Ron A.; Greenberg, David S.

    We present three codes for the Intel Paragon that address the problem of three-dimensional seismic imaging of complex geologies. The first code models acoustic wave propagation and can be used to generate data sets to calibrate and validate seismic imaging codes. This code reported the fastest timings for acoustic wave propagation codes at a recent SEG (Society of Exploration Geophysicists) meeting. The second code implements a Kirchhoff method for pre-stack depth migration. Development of this code is almost complete, and preliminary results are presented. The third code implements a wave equation approach to seismic migration and is a Paragon implementation of a code from the ARCO Seismic Benchmark Suite.

  18. Relocation of Groningen seismicity using refracted waves

    NASA Astrophysics Data System (ADS)

    Ruigrok, E.; Trampert, J.; Paulssen, H.; Dost, B.

    2015-12-01

    The Groningen gas field is a giant natural gas accumulation in the Northeast of the Netherlands. The gas is in a reservoir at a depth of about 3 km. The naturally-fractured gas-filled sandstone extends roughly 45 by 25 km laterally and 140 m vertically. Decades of production have led to significant compaction of the sandstone. The (differential) compaction is thought to have reactivated existing faults and being the main driver of induced seismicity. Precise earthquake location is difficult due to a complicated subsurface, and that is the likely reason, the current hypocentre estimates do not clearly correlate with the well-known fault network. The seismic velocity model down to reservoir depth is quite well known from extensive seismic surveys and borehole data. Most to date earthquake detections, however, were made with a sparse pre-2015 seismic network. For shallow seismicity (<5 km depth) horizontal source-receiver distances tend to be much larger than vertical distances. Consequently, preferred source-receiver travel paths are refractions over high-velocity layers below the reservoir. However, the seismic velocities of layers below the reservoir are poorly known. We estimated an effective velocity model of the main refracting layer below the reservoir and use this for relocating past seismicity. We took advantage of vertical-borehole recordings for estimating precise P-wave (refraction) onset times and used a tomographic approach to find the laterally varying velocity field of the refracting layer. This refracting layer is then added to the known velocity model, and the combined model is used to relocate the past seismicity. From the resulting relocations we assess which of the faults are being reactivated.

  19. Seismic refraction analysis: the path forward

    USGS Publications Warehouse

    Haines, Seth S.; Zelt, Colin; Doll, William

    2012-01-01

    Seismic Refraction Methods: Unleashing the Potential and Understanding the Limitations; Tucson, Arizona, 29 March 2012 A workshop focused on seismic refraction methods took place on 29 May 2012, associated with the 2012 Symposium on the Application of Geophysics to Engineering and Environmental Problems. This workshop was convened to assess the current state of the science and discuss paths forward, with a primary focus on near-surface problems but with an eye on all applications. The agenda included talks on these topics from a number of experts interspersed with discussion and a dedicated discussion period to finish the day. Discussion proved lively at times, and workshop participants delved into many topics central to seismic refraction work.

  20. Application of 3D reflection seismic methods to mineral exploration

    NASA Astrophysics Data System (ADS)

    Urosevic, Milovan

    2013-04-01

    Seismic exploration for mineral deposits is often tested by excessively complex structures, regolith heterogeneity, intrinsically low signal to noise ratio, ground relief and accessibility. In brown fields, where the majority of the seismic surveys have been conducted, existing infrastructure, old pits and tailings, heavy machinery in operation, mine drainage and other mine related activities are further challenging the application of seismic methods and furthermore increasing its cost. It is therefore not surprising that the mining industry has been reluctant to use seismic methods, particularly 3D for mineral exploration, primarily due to the high cost, but also because of variable performance, and in some cases ambiguous interpretation results. However, shallow mineral reserves are becoming depleted and exploration is moving towards deeper targets. Seismic methods will be more important for deeper investigations and may become the primary exploration tool in the near future. The big issue is if we have an appropriate seismic "strategy" for exploration of deep, complex mineral reserves. From the existing case histories worldwide we know that massive ore deposits (VMS, VHMS) constitute the best case scenario for the application of 3D seismic. Direct targeting of massive ore bodies from seismic has been documented in several case histories. Sediment hosted deposits could, in some cases, can also produce a detectable seismic signature. Other deposit types such as IOCG and skarn are much more challenging for the application of seismic methods. The complexity of these deposits requires new thinking. Several 3D surveys acquired over different deposit types will be presented and discussed.

  1. Imaging thin-bed reservoirs with 3-D seismic

    SciTech Connect

    Hardage, B.A.

    1996-12-01

    This article explains how a 3-D seismic data volume, a vertical seismic profile (VSP), electric well logs and reservoir pressure data can be used to image closely stacked thin-bed reservoirs. This interpretation focuses on the Oligocene Frio reservoir in South Texas which has multiple thin-beds spanning a vertical interval of about 3,000 ft.

  2. 3D seismic imaging, example of 3D area in the middle of Banat

    NASA Astrophysics Data System (ADS)

    Antic, S.

    2009-04-01

    3D seismic imaging was carried out in the 3D seismic volume situated in the middle of Banat region in Serbia. The 3D area is about 300 km square. The aim of 3D investigation was defining geology structures and techtonics especially in Mesozoik complex. The investigation objects are located in depth from 2000 to 3000 m. There are number of wells in this area but they are not enough deep to help in the interpretation. It was necessary to get better seismic image in deeper area. Acquisition parameters were satisfactory (good quality of input parameters, length of input data was 5 s, fold was up to 4000 %) and preprocessed data was satisfied. GeoDepth is an integrated system for 3D velocity model building and for 3D seismic imaging. Input data for 3D seismic imaging consist of preprocessing data sorted to CMP gathers and RMS stacking velocity functions. Other type of input data are geological information derived from well data, time migrated images and time migrated maps. Workflow for this job was: loading and quality control the input data (CMP gathers and velocity), creating initial RMS Velocity Volume, PSTM, updating the RMS Velocity Volume, PSTM, building the Initial Interval Velocity Model, PSDM, updating the Interval Velocity Model, PSDM. In the first stage the attempt is to derive initial velocity model as simple as possible as.The higher frequency velocity changes are obtained in the updating stage. The next step, after running PSTM, is the time to depth conversion. After the model is built, we generate a 3D interval velocity volume and run 3D pre-stack depth migration. The main method for updating velocities is 3D tomography. The criteria used in velocity model determination are based on the flatness of pre-stack migrated gathers or the quality of the stacked image. The standard processing ended with poststack 3D time migration. Prestack depth migration is one of the powerful tool available to the interpretator to develop an accurate velocity model and get

  3. A comparative study between a rectilinear 3-D seismic survey and a concentric-circle 3-D seismic survey

    SciTech Connect

    Maldonado, B.; Hussein, H.S.

    1994-12-31

    Due to the rectilinear nature of the previous 3D seismic survey, the details necessary for proper interpretation were absent. Theoretically, concentric 3D seismic technology may provide an avenue for gaining more and higher quality data coverage. Problems associated with recording a rectilinear 3D seismic grid over the salt dome in this area have created the need to investigate the use of such procedures as the concentric-circle 3D seismic acquisition technique. The difficulty of imaging salt dome flanks with conventional rectilinear 3D seismic may be a result of the inability to precisely predict the lateral velocity-field variation adjacent to both salt and sediments. The dramatic difference in the interval velocities of salt and sediments causes the returning ray to severely deviate from being a hyperbolic path. This hampers the ability to predict imaging points near the salt/sediment interface. Perhaps the most difficult areas to image with rectilinear seismic surveys are underneath salt overhangs. Modeling suggests that a significant increase in the number of rays captured from beneath a salt overhang can be achieved with the concentric-circle method. This paper demonstrates the use of the ``circle shoot`` on a survey conducted over a salt dome in the Gulf of Mexico. A total of 80 concentric circles cover an area which is equivalent to 31,000 acres. The final post-stack data were sorted into bins with dimensions of 25 meters by 25 meters. A comparison of 3D rectilinear shooting vs. 3D concentric circle shooting over the same area will show an improvement in data quality and signal-to-noise characteristics.

  4. 3-D seismic exploration in the Ames hole

    SciTech Connect

    Ainsworth, K.R.

    1995-09-01

    The Ames Crater of Major County, Oklahoma has been one of the more controversial drilling projects to emerge in the Mid-Continent province in this decade. Within the crater, dolomitic and granodiorite breccias produce substantial quantities of oil and gas within structurally controlled accumulations. To understand the structural complexities of the crater, Continental Resources, in partnership with other Ames operators, acquired 3-D seismic data in four separate acquisition projects across various exploratory and development projects across the crater. Integrated seismic and subsurface control revealed four separate features within the principal crater floor oil and gas accumulation. Using the 3-D data as a lead tool, these companies identified and developed a significant number of commercial tests within the limits of the seismic surveys. Although the tool generally proved to be successful, reservoir variability, velocity variations, and interpretational errors resulted in some non-commercial and dry tests.

  5. Imaging fault zones using 3D seismic image processing techniques

    NASA Astrophysics Data System (ADS)

    Iacopini, David; Butler, Rob; Purves, Steve

    2013-04-01

    Significant advances in structural analysis of deep water structure, salt tectonic and extensional rift basin come from the descriptions of fault system geometries imaged in 3D seismic data. However, even where seismic data are excellent, in most cases the trajectory of thrust faults is highly conjectural and still significant uncertainty exists as to the patterns of deformation that develop between the main faults segments, and even of the fault architectures themselves. Moreover structural interpretations that conventionally define faults by breaks and apparent offsets of seismic reflectors are commonly conditioned by a narrow range of theoretical models of fault behavior. For example, almost all interpretations of thrust geometries on seismic data rely on theoretical "end-member" behaviors where concepts as strain localization or multilayer mechanics are simply avoided. Yet analogue outcrop studies confirm that such descriptions are commonly unsatisfactory and incomplete. In order to fill these gaps and improve the 3D visualization of deformation in the subsurface, seismic attribute methods are developed here in conjunction with conventional mapping of reflector amplitudes (Marfurt & Chopra, 2007)). These signal processing techniques recently developed and applied especially by the oil industry use variations in the amplitude and phase of the seismic wavelet. These seismic attributes improve the signal interpretation and are calculated and applied to the entire 3D seismic dataset. In this contribution we will show 3D seismic examples of fault structures from gravity-driven deep-water thrust structures and extensional basin systems to indicate how 3D seismic image processing methods can not only build better the geometrical interpretations of the faults but also begin to map both strain and damage through amplitude/phase properties of the seismic signal. This is done by quantifying and delineating the short-range anomalies on the intensity of reflector amplitudes

  6. A Geo-referenced 3D model of the Juan de Fuca Slab and associated seismicity

    USGS Publications Warehouse

    Blair, J.L.; McCrory, P.A.; Oppenheimer, D.H.; Waldhauser, F.

    2011-01-01

    We present a Geographic Information System (GIS) of a new 3-dimensional (3D) model of the subducted Juan de Fuca Plate beneath western North America and associated seismicity of the Cascadia subduction system. The geo-referenced 3D model was constructed from weighted control points that integrate depth information from hypocenter locations and regional seismic velocity studies. We used the 3D model to differentiate earthquakes that occur above the Juan de Fuca Plate surface from earthquakes that occur below the plate surface. This GIS project of the Cascadia subduction system supersedes the one previously published by McCrory and others (2006). Our new slab model updates the model with new constraints. The most significant updates to the model include: (1) weighted control points to incorporate spatial uncertainty, (2) an additional gridded slab surface based on the Generic Mapping Tools (GMT) Surface program which constructs surfaces based on splines in tension (see expanded description below), (3) double-differenced hypocenter locations in northern California to better constrain slab location there, and (4) revised slab shape based on new hypocenter profiles that incorporate routine depth uncertainties as well as data from new seismic-reflection and seismic-refraction studies. We also provide a 3D fly-through animation of the model for use as a visualization tool.

  7. Targeted infill drilling at Stratton field using 3-D seismic

    SciTech Connect

    Suydam, J.R.; Reitz, D.T.

    1994-12-31

    Stratton field is located on the Vicksburg flexure trend in Nueces and Kleberg Counties, South Texas. It has produced more than 2.8 Tcf of gas since 1937 from Frio fluvial/deltaic sandstones and Vicksburg shallow-marine sandstones. The field is a combination stratigraphic and faulted structural trap, and contains numerous highly compartmentalized sandstone reservoirs. Continuous infield drilling is required to keep the field producing, and 3-D seismic data have been used to select the best locations for these wells. In 1992, an 8-mi{sup 2} seismic survey was completed in the southern end of the field, and the resulting structural interpretation presented many more fault traps than were apparent in the 2-D seismic interpretation. So far, all of the new wells drilled within the survey have encountered untapped compartments enclosed by fault traps. Furthermore, fault cuts in the new wells have always been within 20 ft of the position predicted by seismic data.

  8. Advanced computational tools for 3-D seismic analysis

    SciTech Connect

    Barhen, J.; Glover, C.W.; Protopopescu, V.A.

    1996-06-01

    The global objective of this effort is to develop advanced computational tools for 3-D seismic analysis, and test the products using a model dataset developed under the joint aegis of the United States` Society of Exploration Geophysicists (SEG) and the European Association of Exploration Geophysicists (EAEG). The goal is to enhance the value to the oil industry of the SEG/EAEG modeling project, carried out with US Department of Energy (DOE) funding in FY` 93-95. The primary objective of the ORNL Center for Engineering Systems Advanced Research (CESAR) is to spearhead the computational innovations techniques that would enable a revolutionary advance in 3-D seismic analysis. The CESAR effort is carried out in collaboration with world-class domain experts from leading universities, and in close coordination with other national laboratories and oil industry partners.

  9. NORTH HILL CREEK 3-D SEISMIC EXPLORATION PROJECT

    SciTech Connect

    Marc T. Eckels; David H. Suek; Denise H. Harrison; Paul J. Harrison

    2004-05-06

    Wind River Resources Corporation (WRRC) received a DOE grant in support of its proposal to acquire, process and interpret fifteen square miles of high-quality 3-D seismic data on non-allotted trust lands of the Uintah and Ouray (Ute) Indian Reservation, northeastern Utah, in 2000. Subsequent to receiving notice that its proposal would be funded, WRRC was able to add ten square miles of adjacent state and federal mineral acreage underlying tribal surface lands by arrangement with the operator of the Flat Rock Field. The twenty-five square mile 3-D seismic survey was conducted during the fall of 2000. The data were processed through the winter of 2000-2001, and initial interpretation took place during the spring of 2001. The initial interpretation identified multiple attractive drilling prospects, two of which were staked and permitted during the summer of 2001. The two initial wells were drilled in September and October of 2001. A deeper test was drilled in June of 2002. Subsequently a ten-well deep drilling evaluation program was conducted from October of 2002 through March 2004. The present report discusses the background of the project; design and execution of the 3-D seismic survey; processing and interpretation of the data; and drilling, completion and production results of a sample of the wells drilled on the basis of the interpreted survey. Fifteen wells have been drilled to test targets identified on the North Hill Creek 3-D Seismic Survey. None of these wildcat exploratory wells has been a dry hole, and several are among the best gas producers in Utah. The quality of the data produced by this first significant exploratory 3-D survey in the Uinta Basin has encouraged other operators to employ this technology. At least two additional 3-D seismic surveys have been completed in the vicinity of the North Hill Creek Survey, and five additional surveys are being planned for the 2004 field season. This project was successful in finding commercial oil, natural gas

  10. 3D Seismic Reflection Experiment over the Galicia Deep Basin

    NASA Astrophysics Data System (ADS)

    Sawyer, D. S.; Jordan, B.; Reston, T. J.; Minshull, T. A.; Klaeschen, D.; Ranero, C.; Shillington, D. J.; Morgan, J. K.

    2014-12-01

    In June thru September, 2013, a 3D reflection and a long offset seismic experiment were conducted at the Galicia rifted margin by investigators from the US, UK, Germany, and Spain. The 3D multichannel experiment covered 64 km by 20 km (1280 km2), using the RV Marcus Langseth. Four streamers 6 km long were deployed at 12.5 m hydrophone channel spacing. The streamers were 200 m apart. Two airgun arrays, each 3300 cu in, were fired alternately every 37.5 m, to collectively yield a 400 m wide sail line consisting of 8 CMP lines at 50 m spacing. The long offset seismic experiment included 72 short period OBS's deployed below the 3D reflection survey box. Most of the instruments recorded all the shots from the airgun array shots. The 3D seismic box covered a variety of geologic features. The Peridotite Ridge (PR), is associated with the exhumation of upper mantle rocks to the seafloor during the final stage of the continental separation between the Galicia Bank and the Grand Banks of Newfoundland. The S reflector is present below most of the continental blocks under the deep Galicia basin. S is interpreted to be a low-angle detachment fault formed late in the rifting process, and a number of rotated fault block basins and ranges containing pre and syn-rift sediments. Initial observations from stacked 3D seismic data, and samples of 2D pre-stack time migrated (PSTM) 3D seismic data show that the PR is elevated above the present seafloor in the South and not exposed through the seafloor in the North. The relative smoothness of the PR surface for the entire 20 km N-S contrasts with the more complex, shorter wavelength, faulting of the continental crustal blocks to the east. The PR does not seem to show offsets or any apparent internal structure. The PSTM dip lines show substantial improvement for the structures in the deep sedimentary basin East of the PR. These seem to extend the S reflector somewhat farther to the West. The migrated data show a substantial network of

  11. Targeted infill drilling at Stratton Field using 3-D seismic

    SciTech Connect

    Suydam, J.; Reitz, D.

    1994-09-01

    Stratton field is located on the Vicksburg flexure trend in Nueces and Kleberg counties, south Texas. It has produced over 2.8 tcf of gas since 1937 from Frio fluvial/deltaic sandstones and Vicksburg shallow marine sandstones. The field is a combination stratigraphic and faulted structural trap, and contains numerous highly compartmentalized sandstone reservoirs. Continuous infield drilling is required to keep the field producing, and 3-D seismic data have been used to select the best locations for these wells. In 1992, the Bureau of Economic Geology shot an 8-mi{sup 2} survey in the southern end of the field, and the resulting structural interpretation presented many more fault traps that were not apparent in the 2-D seismic interpretation. So far, all of the new wells drilled within the survey have encountered untapped compartments enclosed by fault traps. Furthermore, fault cuts in the new wells have always been within 20 ft of the position predicted by seismic data.

  12. 3D seismic imaging on massively parallel computers

    SciTech Connect

    Womble, D.E.; Ober, C.C.; Oldfield, R.

    1997-02-01

    The ability to image complex geologies such as salt domes in the Gulf of Mexico and thrusts in mountainous regions is a key to reducing the risk and cost associated with oil and gas exploration. Imaging these structures, however, is computationally expensive. Datasets can be terabytes in size, and the processing time required for the multiple iterations needed to produce a velocity model can take months, even with the massively parallel computers available today. Some algorithms, such as 3D, finite-difference, prestack, depth migration remain beyond the capacity of production seismic processing. Massively parallel processors (MPPs) and algorithms research are the tools that will enable this project to provide new seismic processing capabilities to the oil and gas industry. The goals of this work are to (1) develop finite-difference algorithms for 3D, prestack, depth migration; (2) develop efficient computational approaches for seismic imaging and for processing terabyte datasets on massively parallel computers; and (3) develop a modular, portable, seismic imaging code.

  13. 3D Seismic Reflection Experiment Over the Galicia Deep Basin

    NASA Astrophysics Data System (ADS)

    Sawyer, Dale; Jordan, Brian; Tesi Sanjurjo, Mari; Alexanian, Ara; Morgan, Julia; Shillington, Donna; Reston, Timothy; Minshull, Timothy; Klaeschen, Dirk; Ranero, César

    2014-05-01

    In June thru September, 2013, a 3D reflection and a long offset seismic experiment were conducted at the Galicia rifted margin by investigators from the US, UK, Germany, and Spain. The 3D multichannel experiment covered 64 km by 20 km (1280 km2), using the RV Marcus Langseth. Four streamers 6 km long were deployed at 12.5 m hydrophone channel spacing. The streamers were 200 m apart. Two airgun arrays, each 3300 cu in, were fired alternately every 37.5 m, to collectively yield a 400 m wide sail line consisting of 8 CMP lines at 50 m spacing. The long offset seismic experiment included 72 short period OBS's deployed below the 3D reflection survey box. Most of the instruments recorded all the shots from the airgun array shots. The 3D seismic box covered a variety of geologic features. The Peridotite Ridge (PR), is associated with the exhumation of upper mantle rocks to the seafloor during the final stage of the continental separation between the Galicia Bank and the Grand Banks of Newfoundland. The S reflector is present below most of the continental blocks under the deep Galicia basin. S is interpreted to be a low-angle detachment fault formed late in the rifting process, and a number of rotated fault block basins and ranges containing pre and syn-rift sediments. Initial observations from stacked, but not yet migrated, 3D seismic data show that the PR is elevated above the present seafloor in the South and not exposed through the seafloor in the North. The relative smoothness of the PR surface for the entire 20 km N-S contrasts with the more complex, shorter wavelength, faulting of the continental crustal blocks to the east. The PR does not seem to show offsets or any apparent internal structure. However, migration will be required to see internal structure of the PR. Between the PR and the western most rifted continental crustal blocks, is a sedimentary basin about as wide as the PR and very different from the sedimentary basins bounded by the continental crustal

  14. Exploration 3-D Seismic Field Test/Native Tribes Initiative

    SciTech Connect

    Carroll, Herbert B.; Chen, K.C.; Guo, Genliang; Johnson, W.I.; Reeves,T.K.; Sharma,Bijon

    1999-04-27

    To determine current acquisition procedures and costs and to further the goals of the President's Initiative for Native Tribes, a seismic-survey project is to be conducted on Osage tribal lands. The goals of the program are to demonstrate the capabilities, costs, and effectiveness of 3-D seismic work in a small-operator setting and to determine the economics of such a survey. For these purposes, typical small-scale independent-operator practices are being followed and a shallow target chose in an area with a high concentration of independent operators. The results will be analyzed in detail to determine if there are improvements and/or innovations which can be easily introduced in field-acquisition procedures, in processing, or in data manipulation and interpretation to further reduce operating costs and to make the system still more active to the small-scale operator.

  15. Exploring the seismic expression of fault zones in 3D seismic volumes

    NASA Astrophysics Data System (ADS)

    Iacopini, David; Butler, Rob; Purves, Steve

    2016-04-01

    Mapping and understanding distributed deformation is a major challenge for the structural interpretation of seismic data. However, volumes of seismic signal disturbance with low signal/noise ratio are systematically observed within 3D seismic datasets around fault systems. These seismic disturbance zones (SDZ) are commonly characterized by complex perturbations of the signal and occur at the sub-seismic to seismic scale. They may store important information on deformation distributed around those larger scale structures that may be readily interpreted in conventional amplitude displays of seismic data scale. We introduce a method to detect fault-related disturbance zones and to discriminate between this and other noise sources such as those associated with the seismic acquisition (footprint noise). Two case studies, from the Taranaki basin and deep-water Niger delta are presented. These resolve structure within SDZs using tensor and semblance attributes along with conventional seismic mapping. The tensor attribute is more efficient in tracking volumes containing structural displacements while structurally-oriented semblance coherency is commonly disturbed by small waveform variations around the fault throw. We propose a workflow to map and cross-plot seismic waveform signal properties extracted from the seismic disturbance zone as a tool to investigate the seismic signature and explore seismic facies of a SDZ.

  16. Exploring the seismic expression of fault zones in 3D seismic volumes

    NASA Astrophysics Data System (ADS)

    Iacopini, D.; Butler, R. W. H.; Purves, S.; McArdle, N.; De Freslon, N.

    2016-08-01

    Mapping and understanding distributed deformation is a major challenge for the structural interpretation of seismic data. However, volumes of seismic signal disturbance with low signal/noise ratio are systematically observed within 3D seismic datasets around fault systems. These seismic disturbance zones (SDZ) are commonly characterized by complex perturbations of the signal and occur at the sub-seismic (10 s m) to seismic scale (100 s m). They may store important information on deformation distributed around those larger scale structures that may be readily interpreted in conventional amplitude displays of seismic data. We introduce a method to detect fault-related disturbance zones and to discriminate between this and other noise sources such as those associated with the seismic acquisition (footprint noise). Two case studies from the Taranaki basin and deep-water Niger delta are presented. These resolve SDZs using tensor and semblance attributes along with conventional seismic mapping. The tensor attribute is more efficient in tracking volumes containing structural displacements while structurally-oriented semblance coherency is commonly disturbed by small waveform variations around the fault throw. We propose a workflow to map and cross-plot seismic waveform signal properties extracted from the seismic disturbance zone as a tool to investigate the seismic signature and explore seismic facies of a SDZ.

  17. Frio, Yegua objectives of E. Texas 3D seismic

    SciTech Connect

    1996-07-01

    Houston companies plan to explore deeper formations along the Sabine River on the Texas and Louisiana Gulf Coast. PetroGuard Co. Inc. and Jebco Seismic Inc., Houston, jointly secured a seismic and leasing option from Hankamer family et al. on about 120 sq miles in Newton County, Tex., and Calcasieu Parish, La. PetroGuard, which specializes in oilfield rehabilitation, has production experience in the area. Historic production in the area spans three major geologic trends: Oligocene Frio/Hackberry, downdip and mid-dip Eocene Yegua, and Eocene Wilcox. In the southern part of the area, to be explored first, the trends lie at 9,000--10,000 ft, 10,000--12,000 ft, and 14,000--15,000 ft, respectively. Output Exploration Co., an affiliate of Input/Output Inc., Houston, acquired from PetroGuard and Jebco all exploratory drilling rights in the option area. Output will conduct 3D seismic operations over nearly half the acreage this summer. Data acquisition started late this spring. Output plans to use a combination of a traditional land recording system and I/O`s new RSR 24 bit radio telemetry system because the area spans environments from dry land to swamp.

  18. Northern California Seismic Attenuation: 3-D Qp and Qs models

    NASA Astrophysics Data System (ADS)

    Eberhart-Phillips, D. M.

    2015-12-01

    The northern California crust exhibits a wide range of rock types and deformation processes which produce pronounced heterogeneity in regional attenuation. Using local earthquakes, 3-D Qp and Qs crustal models have been obtained for this region which includes the San Andreas fault system, the Central Valley, the Sierra Nevada batholith, and the Mendocino subduction volcanic system. Path attenuation t* values were determined from P and S spectra of 959 spatially distributed earthquakes, magnitude 2.5-6.0 from 2005-2014, using 1254 stations from NCEDC networks and IRIS Mendocino and Sierra Nevada temporary arrays. The t* data were used in Q inversions, using existing hypocenters and 3-D velocity models, with basic 10-km node spacing. The uneven data coverage was accounted for with linking of nodes into larger areas in order to provide useful Q images across the 3-D volume. The results at shallow depth (< 2 km) show very low Q in the Sacramento Delta, the Eureka area, and parts of the Bay Area. In the brittle crust, fault zones that have high seismicity exhibit low Q. In the lower crust, low Q is observed along fault zones that have large cumulative displacement and have experienced grain size reduction. Underlying active volcanic areas, low Q features are apparent below 20-km depth. Moderately high Q is associated with igneous rocks of the Sierra Nevada and Salinian block, while the Franciscan subduction complex shows moderately low Q. The most prominent high Q feature is related to the Great Valley Ophiolite.

  19. The Northern Walker Lane Seismic Refraction Experiment

    NASA Astrophysics Data System (ADS)

    Louie, J. N.; Smith, S. B.; Thelen, W.; Scott, J. B.; Clark, M.

    2002-12-01

    We are developing a three-dimensional reference seismic velocity model for the western Great Basin region of Nevada and eastern California. The northern Walker Lane had not been characterized well by previous work. In May 2002 we collected a new crustal refraction profile from Battle Mountain, Nev. across western Nevada, the Reno area, Lake Tahoe, and the northern Sierra to Auburn, Calif. Mine blasts and earthquakes were recorded by 199 Texan instruments (loaned by the PASSCAL Instrument Center) extending across this more than 450-km-long transect. The seismic sources at the eastern end were mining blasts at Barrick's GoldStrike pit. We recorded additional blasts at the Florida Canyon and other mines between Lovelock and Battle Mountain, Nevada. The GoldStrike mine produced several ripple-fired blasts using 10,000-40,000 kg of ANFO each. First arrivals from the larger blasts are obvious to distances exceeding 250 km in the raw records. A M2.4 earthquake near Bridgeport, Calif. also produced pickable P-wave arrivals across at least half the transect, providing fan-shot data. We recorded only during working hours, and so missed an M4 earthquake that occurred at night. Events of M2 occurred during our recording to the west on the San Andreas fault near Pinnacles, Calif.; M3 events occurred near Portola and Mammoth Lakes, Calif. Arrivals from M5 events in the Mariana and Kuril Islands also appear in the records. Time-picks from these earthquakes may be possible after more work on synthetic-time modeling, data filtering, and display. We plan to record blasts at quarries in the western Sierra in future experiments, for a direct refraction reversal. We will compare our time picks against times generated from regional velocity models, to identify potential crustal and upper-mantle velocity anomalies. Such anomalies may be associated with the Battle Mountain heat-flow high, the northern Walker Lane belt, or the northern Sierran block.

  20. Label-free characterization of white blood cells by measuring 3D refractive index maps

    PubMed Central

    Yoon, Jonghee; Kim, Kyoohyun; Park, HyunJoo; Choi, Chulhee; Jang, Seongsoo; Park, YongKeun

    2015-01-01

    The characterization of white blood cells (WBCs) is crucial for blood analyses and disease diagnoses. However, current standard techniques rely on cell labeling, a process which imposes significant limitations. Here we present three-dimensional (3D) optical measurements and the label-free characterization of mouse WBCs using optical diffraction tomography. 3D refractive index (RI) tomograms of individual WBCs are constructed from multiple two-dimensional quantitative phase images of samples illuminated at various angles of incidence. Measurements of the 3D RI tomogram of WBCs enable the separation of heterogeneous populations of WBCs using quantitative morphological and biochemical information. Time-lapse tomographic measurements also provide the 3D trajectory of micrometer-sized beads ingested by WBCs. These results demonstrate that optical diffraction tomography can be a useful and versatile tool for the study of WBCs. PMID:26504637

  1. Seismic refraction survey of the ANS preferred site

    SciTech Connect

    Davis, R.K. ); Hopkins, R.A. ); Doll, W.E. )

    1992-02-01

    Between September 19, 1991 and October 8, 1991 personnel from Martin Marietta Energy Systems, Inc. (Energy Systems), Automated Sciences Group, Inc., and Marrich, Inc. performed a seismic refraction survey at the Advanced Neutron Source (ANS) preferred site. The purpose of this survey was to provide estimates of top-of-rock topography, based on seismic velocities, and to delineate variations in rock and soil velocities. Forty-four seismic refraction spreads were shot to determine top-of-rock depths at 42 locations. Nine of the seismic spreads were shot with long offsets to provide 216 top-of-rock depths for 4 seismic refraction profiles. The refraction spread locations were based on the grid for the ANS Phase I drilling program. Interpretation of the seismic refraction data supports the assumption that the top-of-rock surface generally follows the local topography. The shallow top-of-rock interface interpreted from the seismic refraction data is also supported by limited drill information at the site. Some zones of anomalous data are present that could be the result of locally variable weathering, a localized variation in shale content, or depth to top-of-rock greater than the site norm.

  2. Recognizing Basement Fault Reactivation in 3D Seismic Datasets

    NASA Astrophysics Data System (ADS)

    Imber, J.; McCaffrey, K.; Holdsworth, R.; England, R.; Freeman, S.; Dore, T.; Geldjvik, G.

    2003-04-01

    3D seismic data are now widely used for hydrocarbon exploration and production, and because of its ability to image sub-surface structures, the technology represents one of the most important conceptual advances in the Earth Sciences in recent years. It provides an important tool capable of addressing fundamental questions concerning the way in which fault systems evolve in the continental crust, the effects of inherited crustal weakness on rifting style and the control of fault networks on reservoir properties. Preliminary analyses of published offshore seismic data demonstrate that there are quantifiable differences in the geometric evolution and growth of "thin-skinned" normal fault systems in which there is no direct basement involvement compared to those developed above little- and highly-reactivated basement structures. Reactivated fault systems are characterised by rapid strain localisation and fault lengths that are controlled by up-dip propagation of basement structures (Walsh et al. 2002). Thus, fault growth during reactivation is likely to be achieved by increasing cumulative displacement with negligible lateral propagation. Important questions remain, however, concerning the way in which faults grow and localise displacement during the earliest stages of reactivation. In particular, we have little detailed understanding of the extent to which basement fault geometry (e.g. polarity, segmentation) influences the pattern of faulting observed in the cover sequence, the kinematics of up-dip fault propagation and/or linkage, or the degree of displacement localisation at low bulk strains. Normal faults that developed in response to glacial retreat on the NE Atlantic Margin reactivate pre-existing Mesozoic, Caledonian and/or Precambrian structures and are characterised by low displacements (throws typically 100--101 m), thus representing the earliest stages in the development of a reactivated fault system. Spectacular images of postglacial and underlying

  3. Barren Acidic Soil Assessment using Seismic Refraction Survey

    NASA Astrophysics Data System (ADS)

    Tajudin, S. A. A.; Abidin, M. H. Z.; Madun, A.; Zawawi, M. H.

    2016-07-01

    Seismic refraction method is one of the geophysics subsurface exploration techniques used to determine subsurface profile characteristics. From past experience, seismic refraction method is commonly used to detect soil layers, overburden, bedrock, etc. However, the application of this method on barren geomaterials remains limited due to several reasons. Hence, this study was performed to evaluate the subsurface profile characteristics of barren acidic soil located in Ayer Hitam, Batu Pahat, Johor using seismic refraction survey. The seismic refraction survey was conducted using ABEM Terraloc MK 8 (seismograph), a sledge hammer weighing 7 kg (source) and 24 units of 10 Hz geophones (receiver). Seismic data processing was performed using OPTIM software which consists of SeisOpt@picker (picking the first arrival and seismic configureuration data input) and SeisOpt@2D (generating 2D image of barren acidic soil based on seismic velocity (primary velocity, Vp) distribution). It was found that the barren acidic soil profile consists of three layers representing residual soil (Vp= 200-400 m/s) at 0-2 m, highly to completely weathered soil (Vp= 500-1800 m/s) at 3-8 m and shale (Vp= 2100-6200 m/s) at 9-20 m depth. Furthermore, result verification was successfully done through the correlation of seismic refraction data based on physical mapping and the geological map of the study area. Finally, it was found that the seismic refraction survey was applicable for subsurface profiling of barren acidic soil as it was very efficient in terms of time, cost, large data coverage and sustainable.

  4. Application of seismic-refraction techniques to hydrologic studies

    USGS Publications Warehouse

    Haeni, F.P.

    1988-01-01

    During the past 30 years, seismic-refraction methods have been used extensively in petroleum, mineral, and engineering investigations and to some extent for hydrologic applications. Recent advances in equipment, sound sources, and computer interpretation techniques make seismic refraction a highly effective and economical means of obtaining subsurface data in hydrologic studies. Aquifers that can be defined by one or more high-seismic-velocity surface, such as (1) alluvial or glacial deposits in consolidated rock valleys, (2) limestone or sandstone underlain by metamorphic or igneous rock, or (3) saturated unconsolidated deposits overlain by unsaturated unconsolidated deposits, are ideally suited for seismic-refraction methods. These methods allow economical collection of subsurface data, provide the basis for more efficient collection of data by test drilling or aquifer tests, and result in improved hydrologic studies. This manual briefly reviews the basics of seismic-refraction theory and principles. It emphasizes the use of these techniques in hydrologic investigations and describes the planning, equipment, field procedures, and interpretation techniques needed for this type of study. Further-more, examples of the use of seismic-refraction techniques in a wide variety of hydrologic studies are presented.

  5. Application of seismic-refraction techniques to hydrologic studies

    USGS Publications Warehouse

    Haeni, F.P.

    1986-01-01

    Seismic-refraction methods have been extensively used in petroleum, mineral, and engineering investigations and to some extent, for hydrologic applications during the past 30 years. Recent advances in equipment, sound sources, and computer-interpretation techniques make seismic-refraction methods a highly effective and economical means of obtaining subsurface data in hydrologic studies. Aquifers that can be defined by one or more high seismic-velocity surfaces, such as alluvial or glacial deposits in consolidated rock valleys, limestone or sandstone underlain by metamorphic or igneous rock, or saturated unconsolidated deposits overlain by unsaturated unconsolidated deposits, are ideally suited for applying seismic-refraction methods. These methods allow the economical collection of subsurface data and provide the basis for more efficient collection of subsurface data by test drilling or aquifer tests and results in improved hydrologic studies. This manual briefly reviews the basics of seismic refraction theory and principles. It emphasizes the use of this technique in hydrologic investigations and describes the planning, equipment, field procedures, and interpretation techniques needed for this type of study. Examples of the use of seismic refraction techniques in a wide variety of hydrologic studies are presented. (USGS)

  6. Intraplate Seismicity and Lithospheric Strength as Inferred from 3D Seismic Models

    NASA Astrophysics Data System (ADS)

    Mooney, W. D.; Pollitz, F. F.; Ritsema, J.

    2014-12-01

    Focal mechanism studies and other stress indicators indicate that intraplate earthquakes in central and eastern North America are consistent with an ENE-WSW compressive stress field that acts on existing faults. Here we argue that either locally thinned lithosphere (as beneath the Reelfoot Rift, central US) or regional lithospheric thinning (as beneath the edge of the North American craton or the rifted continental margin) constitutes zones of relatively low lithospheric strength where crustal strain accumulates. We use seismic surface waves to determine the 3D shear-wave seismic velocity structure of the lithosphere, and find that the Reelfoot Rift is underlain by a zone with low mantle seismic velocities that extends to at least 200 km depth. Thus, the Reelfoot Rift, which hosts the New Madrid Seismic Zone, is unique among North American paleo-rifts in term of the properties in the mantle. We hypothesize that this low-velocity mantle volume is weaker than its surroundings and that the Reelfoot Rift consequently has relatively lower elastic plate thickness that would tend to concentrate tectonic stress within this zone. On a continental scale, the 3D velocity model clearly identifies an approximately 220-km-thick, high seismic velocity lithospheric root beneath the North America craton which has a low rate of crustal seismicity and very few events with Mw≥6. We attribute the relatively aseismic nature of the craton to dry, cold conditions within the cratonic lower crust and mantle lithosphere. Conversely, we find that a high proportion of intraplate events are concentrated around the pronounced lateral gradient in lithospheric thickness that surrounds the craton. We attribute this observation to a lateral decrease in lithospheric strength at the edge of the North American craton. This relationship between intraplate seismicity and lithospheric properties is apparent in maps that compare regional and continental lithospheric thickness with crustal seismicity. We

  7. Microseismic monitoring of soft-rock landslide: contribution of a 3D velocity model for the location of seismic sources.

    NASA Astrophysics Data System (ADS)

    Floriane, Provost; Jean-Philippe, Malet; Cécile, Doubre; Julien, Gance; Alessia, Maggi; Agnès, Helmstetter

    2015-04-01

    Characterizing the micro-seismic activity of landslides is an important parameter for a better understanding of the physical processes controlling landslide behaviour. However, the location of the seismic sources on landslides is a challenging task mostly because of (a) the recording system geometry, (b) the lack of clear P-wave arrivals and clear wave differentiation, (c) the heterogeneous velocities of the ground. The objective of this work is therefore to test whether the integration of a 3D velocity model in probabilistic seismic source location codes improves the quality of the determination especially in depth. We studied the clay-rich landslide of Super-Sauze (French Alps). Most of the seismic events (rockfalls, slidequakes, tremors...) are generated in the upper part of the landslide near the main scarp. The seismic recording system is composed of two antennas with four vertical seismometers each located on the east and west sides of the seismically active part of the landslide. A refraction seismic campaign was conducted in August 2014 and a 3D P-wave model has been estimated using the Quasi-Newton tomography inversion algorithm. The shots of the seismic campaign are used as calibration shots to test the performance of the different location methods and to further update the 3D velocity model. Natural seismic events are detected with a semi-automatic technique using a frequency threshold. The first arrivals are picked using a kurtosis-based method and compared to the manual picking. Several location methods were finally tested. We compared a non-linear probabilistic method coupled with the 3D P-wave model and a beam-forming method inverted for an apparent velocity. We found that the Quasi-Newton tomography inversion algorithm provides results coherent with the original underlaying topography. The velocity ranges from 500 m.s-1 at the surface to 3000 m.s-1 in the bedrock. For the majority of the calibration shots, the use of a 3D velocity model

  8. How effective can optical-CT 3D dosimetry be without refractive fluid matching?

    PubMed Central

    Rankine, L; Oldham

    2013-01-01

    Achieving accurate optical CT 3D dosimetry without the use of viscous refractive index (RI) matching fluids would greatly increase convenience. Software has been developed to simulate optical CT 3D dosimetry for a range of scanning configurations including parallel-beam, point and converging light sources. For each configuration the efficacy of 3 refractive media were investigated: air, water, and a fluid closely matched to Presage (RI = 1.00, 1.33 and 1.49 respectively). The results revealed that the useable radius of the dosimeter (i.e. where data was within 2% of truth) reduced to 68% for water-matching, and 31% for dry-scanning in air. Point source incident ray geometry produced slightly more favourable results, although variation between the three geometries was relatively small. The required detector size however, increased by a factor six for dry-scanning, introducing cost penalties. For applications where dose information is not required in the periphery, some dry and low-viscous matching configurations may be feasible. PMID:24454520

  9. 3D Modelling of Seismically Active Parts of Underground Faults via Seismic Data Mining

    NASA Astrophysics Data System (ADS)

    Frantzeskakis, Theofanis; Konstantaras, Anthony

    2015-04-01

    During the last few years rapid steps have been taken towards drilling for oil in the western Mediterranean sea. Since most of the countries in the region benefit mainly from tourism and considering that the Mediterranean is a closed sea only replenishing its water once every ninety years careful measures are being taken to ensure safe drilling. In that concept this research work attempts to derive a three dimensional model of the seismically active parts of the underlying underground faults in areas of petroleum interest. For that purpose seismic spatio-temporal clustering has been applied to seismic data to identify potential distinct seismic regions in the area of interest. Results have been coalesced with two dimensional maps of underground faults from past surveys and seismic epicentres, having followed careful reallocation processing, have been used to provide information regarding the vertical extent of multiple underground faults in the region of interest. The end product is a three dimensional map of the possible underground location and extent of the seismically active parts of underground faults. Indexing terms: underground faults modelling, seismic data mining, 3D visualisation, active seismic source mapping, seismic hazard evaluation, dangerous phenomena modelling Acknowledgment This research work is supported by the ESPA Operational Programme, Education and Life Long Learning, Students Practical Placement Initiative. References [1] Alves, T.M., Kokinou, E. and Zodiatis, G.: 'A three-step model to assess shoreline and offshore susceptibility to oil spills: The South Aegean (Crete) as an analogue for confined marine basins', Marine Pollution Bulletin, In Press, 2014 [2] Ciappa, A., Costabile, S.: 'Oil spill hazard assessment using a reverse trajectory method for the Egadi marine protected area (Central Mediterranean Sea)', Marine Pollution Bulletin, vol. 84 (1-2), pp. 44-55, 2014 [3] Ganas, A., Karastathis, V., Moshou, A., Valkaniotis, S., Mouzakiotis

  10. High-resolution 3D seismic model of the crustal and uppermost mantle structure in Poland

    NASA Astrophysics Data System (ADS)

    Grad, Marek; Polkowski, Marcin; Ostaficzuk, Stanisław R.

    2016-01-01

    In the area of Poland a contact between the Precambrian and Phanerozoic Europe and the Carpathians has a complicated structure and a complex P-wave velocity of the sedimentary cover, crystalline crust, Moho depth and the uppermost mantle. The geometry of the uppermost several kilometers of sediments is relatively well recognized from over 100,000 boreholes. The vertical seismic profiling (VSP) from 1188 boreholes provided detailed velocity data for regional tectonic units and for stratigraphic successions from Permian to the Tertiary and Quaternary deposits. These data, however, do not provide information about the velocity and basement depth in the central part of the Trans-European suture zone (TESZ) and in the Carpathians. So, the data set is supplemented by 2D velocity models from 32 deep seismic sounding refraction profiles which also provide information about the crust and uppermost mantle. Together with the results of other methods: vertical seismic profiling, magnetotelluric, allow for the creation of a detailed, high-resolution 3D model for the entire Earth's crust and the uppermost mantle down to a depth of 60 km. The thinnest sedimentary cover in the Mazury-Belarus anteclise is only 0.3 to 1 km thick, which increases to 7 to 8 km along the East European Craton (EEC) margin, and 9 to 12 km in the TESZ. The Variscan domain is characterized by a 1-4 km thick sedimentary cover, while the Carpathians are characterized by very thick sedimentary layers, up to about 20 km. The crystalline crust is differentiated and has a layered structure. The crust beneath the West European Platform (WEP; Variscan domain) is characterized by P-wave velocities of 5.8-6.6 km/s. The upper and middle crusts beneath the EEC are characterized by velocities of 6.1-6.6 km/s, and are underlain by a high velocity lower crust with a velocity of about 7 km/s. A general decrease in velocity is observed from the older to the younger tectonic domains. The TESZ is associated with a steep dip

  11. 3-D seismic velocity and attenuation structures in the geothermal field

    SciTech Connect

    Nugraha, Andri Dian; Syahputra, Ahmad; Fatkhan,; Sule, Rachmat

    2013-09-09

    We conducted delay time tomography to determine 3-D seismic velocity structures (Vp, Vs, and Vp/Vs ratio) using micro-seismic events in the geothermal field. The P-and S-wave arrival times of these micro-seismic events have been used as input for the tomographic inversion. Our preliminary seismic velocity results show that the subsurface condition of geothermal field can be fairly delineated the characteristic of reservoir. We then extended our understanding of the subsurface physical properties through determining of attenuation structures (Qp, Qs, and Qs/Qp ratio) using micro-seismic waveform. We combined seismic velocities and attenuation structures to get much better interpretation of the reservoir characteristic. Our preliminary attanuation structures results show reservoir characterization can be more clearly by using the 3-D attenuation model of Qp, Qs, and Qs/Qp ratio combined with 3-D seismic velocity model of Vp, Vs, and Vp/Vs ratio.

  12. 3-D visualisation and interpretation of seismic attributes extracted from large 3-D seismic datasets: Subregional and prospect evaluation, deepwater Nigeria

    SciTech Connect

    Sola, M.; Haakon Nordby, L.; Dailey, D.V.; Duncan, E.A. )

    1996-01-01

    High resolution 3-D visualization of horizon interpretation and seismic attributes from large 3-D seismic surveys in deepwater Nigeria has greatly enhanced the exploration team's ability to quickly recognize prospective segments of subregional and prospect specific scale areas. Integrated workstation generated structure, isopach and extracted horizon consistent, interval and windowed attributes are particularly useful in illustrating the complex structural and stratigraphical prospectivity of deepwater Nigeria. Large 3-D seismic volumes acquired over 750 square kilometers can be manipulated within the visualization system with attribute tracking capability that allows for real time data interrogation and interpretation. As in classical seismic stratigraphic studies, pattern recognition is fundamental to effective depositions facies interpretation and reservoir model construction. The 3-D perspective enhances the data interpretation through clear representation of relative scale, spatial distribution and magnitude of attributes. In deepwater Nigeria, many prospective traps rely on an interplay between syndepositional structure and slope turbidite depositional systems. Reservoir systems in many prospects appear to be dominated by unconfined to moderately focused slope feeder channel facies. These units have spatially complex facies architecture with feeder channel axes separated by extensive interchannel areas. Structural culminations generally have a history of initial compressional folding with late in extensional collapse and accommodation faulting. The resulting complex trap configurations often have stacked reservoirs over intervals as thick as 1500 meters. Exploration, appraisal and development scenarios in these settings can be optimized by taking full advantage of integrating high resolution 3-D visualization and seismic workstation interpretation.

  13. 3-D visualisation and interpretation of seismic attributes extracted from large 3-D seismic datasets: Subregional and prospect evaluation, deepwater Nigeria

    SciTech Connect

    Sola, M.; Haakon Nordby, L.; Dailey, D.V.; Duncan, E.A.

    1996-12-31

    High resolution 3-D visualization of horizon interpretation and seismic attributes from large 3-D seismic surveys in deepwater Nigeria has greatly enhanced the exploration team`s ability to quickly recognize prospective segments of subregional and prospect specific scale areas. Integrated workstation generated structure, isopach and extracted horizon consistent, interval and windowed attributes are particularly useful in illustrating the complex structural and stratigraphical prospectivity of deepwater Nigeria. Large 3-D seismic volumes acquired over 750 square kilometers can be manipulated within the visualization system with attribute tracking capability that allows for real time data interrogation and interpretation. As in classical seismic stratigraphic studies, pattern recognition is fundamental to effective depositions facies interpretation and reservoir model construction. The 3-D perspective enhances the data interpretation through clear representation of relative scale, spatial distribution and magnitude of attributes. In deepwater Nigeria, many prospective traps rely on an interplay between syndepositional structure and slope turbidite depositional systems. Reservoir systems in many prospects appear to be dominated by unconfined to moderately focused slope feeder channel facies. These units have spatially complex facies architecture with feeder channel axes separated by extensive interchannel areas. Structural culminations generally have a history of initial compressional folding with late in extensional collapse and accommodation faulting. The resulting complex trap configurations often have stacked reservoirs over intervals as thick as 1500 meters. Exploration, appraisal and development scenarios in these settings can be optimized by taking full advantage of integrating high resolution 3-D visualization and seismic workstation interpretation.

  14. 2D seismic residual statics derived from refraction interferometry

    NASA Astrophysics Data System (ADS)

    Zhang, Chao; Zhang, Jie

    2016-07-01

    Refraction traveltimes have long been applied for deriving long-wavelength statics solutions. These traveltimes are also applied for the derivation of residual statics, but they must be sufficiently accurate at short wavelengths. In this study, we present a seismic residual statics method that applies interferometric theory to produce four stacked virtual refraction gathers with a significantly improved signal-to-noise ratio. These gathers are composed of forward and backward virtual refraction gathers for receivers and shots. By picking the first arrivals on these four gathers followed by the application of a set of refraction equations, reliable residual statics solutions can be derived. This approach can help deal with noisy data and also avoid using traveltime picks from shot gathers. We demonstrate the approach by applying it to synthetic data as well as real data.

  15. Investigating a clay landslide site using 3D P-wave reflection seismics in Lilla Edet, Sweden

    NASA Astrophysics Data System (ADS)

    Lundberg, E.; Malehmir, A.; Juhlin, C.; Bastani, M.

    2012-04-01

    Landslides are one of the most commonly occurring natural disasters. Global damages range in the billions of dollars and cost hundreds of lives each year; Sweden is not an exception. The main objectives of this geohazard-related project are (1) to improve the understanding of the geometrical shape and structure of clay areas, (2) to develop tools for monitoring changes in their geometry and physical properties as critical factors for landslide triggering, and (3) to provide robust analytical methods for assessing risks associated with clay landslides both in short and long terms. The project is sponsored by the Geoscientists Without Borders (GWB) Program of the Society of Exploration Geophysicists and is multidisciplinary, involving several geophysical methods such as ground gravity and magnetics, geoelectrics, controlled source/radio magnetotellurics, as well as reflection/refraction seismic methods (both P- and S-wave source and receivers). The test site is located on the shoreline of the Göta river that runs from lake Vänern to Göteborg on the southwest coast. The Göta river is the largest river in Sweden and follows the Götaälv Zone, which is an approximately 4 km wide fault zone dipping towards the west. The 3D seismic survey covers a large landslide scar that occurred about 30-40 years ago. The main objective of the 3D seismic is to image the bedrock topography in detail and possibly define layering in the sediments above. The 3D seismic data were acquired in September 2011 using a weight-drop source, 4 m geophone spacing and 20 m line spacing with the source activated at most geophone positions. Ten lines with 60 geophones on each line were shot in two overlapping patches. The preliminary results are encouraging and depict the bedrock topography at 100-150 ms or about 70-100 m. The central line in the 3D seismic survey is overlapped by a longer 2D reflection seismic profile, acquired using a dynamite source. The 2D reflection stack, as well as a travel

  16. 3D P-wave velocity structure of the deep Galicia rifted margin: A first analysis of the Galicia 3D wide-angle seismic dataset

    NASA Astrophysics Data System (ADS)

    Bayrakci, Gaye; Minshull, Timothy A.; Davy, Richard G.; Karplus, Marianne S.; Kaeschen, Dirk; Papenberg, Cord; Krabbenhoeft, Anne; Sawyer, Dale; Reston, Timothy J.; Shillington, Donna J.; Ranero, César R.

    2014-05-01

    Galicia 3D, a reflection-refraction and long offset seismic experiment was carried out from May through September 2013, at the Galicia rifted margin (in the northeast Atlantic Ocean, west of Spain) as a collaboration between US, UK, German and Spanish groups. The 3D multichannel seismic acquisition conducted by R/V Marcus Langseth covered a 64 km by 20 km (1280 km2) zone where the main geological features are the Peridotite Ridge (PR), composed of serpentinized peridotite and thought be upper mantle exhumed to the seafloor during rifting, and the S reflector which has been interpreted to be a low angle detachment fault overlain by fault bounded, rotated, continental crustal blocks. In the 3D box, two airgun arrays of 3300 cu.in. were fired alternately (in flip-flop configuration) every 37.5 m. All shots are recorded by 44 short period four component ocean bottom seismometers (OBS) and 26 ocean bottom hydrophones (OBH) deployed and recovered by R/V Poseidon, as well as four 6 km hydrophone streamers with 12.5 m channel spacing towed by R/V Marcus Langseth. We present the preliminary results of the first arrival time tomography study which is carried out with a subset of the wide-angle dataset, in order to generate a 3D P-wave velocity volume for the entire depth sampled by the reflection data. After the relocation of OBSs and OBHs, an automatic first-arrival time picking approach is applied to a subset of the dataset, which comprises more than 5.5 million source-receiver pairs. Then, the first-arrival times are checked visually, in 3-dimensions. The a priori model used for the first-arrival time tomography is built up using information from previous seismic surveys carried out at the Galicia margin (e.g. ISE, 1997). The FAST algorithm of Zelt and Barton (1998) is used for the first-arrival time inversion. The 3D P-wave velocity volume can be used in interpreting the reflection dataset, as a starting point for migration, to quantify the thinning of the crustal layers

  17. Assessing a 3D smoothed seismicity model of induced earthquakes

    NASA Astrophysics Data System (ADS)

    Zechar, Jeremy; Király, Eszter; Gischig, Valentin; Wiemer, Stefan

    2016-04-01

    As more energy exploration and extraction efforts cause earthquakes, it becomes increasingly important to control induced seismicity. Risk management schemes must be improved and should ultimately be based on near-real-time forecasting systems. With this goal in mind, we propose a test bench to evaluate models of induced seismicity based on metrics developed by the CSEP community. To illustrate the test bench, we consider a model based on the so-called seismogenic index and a rate decay; to produce three-dimensional forecasts, we smooth past earthquakes in space and time. We explore four variants of this model using the Basel 2006 and Soultz-sous-Forêts 2004 datasets to make short-term forecasts, test their consistency, and rank the model variants. Our results suggest that such a smoothed seismicity model is useful for forecasting induced seismicity within three days, and giving more weight to recent events improves forecast performance. Moreover, the location of the largest induced earthquake is forecast well by this model. Despite the good spatial performance, the model does not estimate the seismicity rate well: it frequently overestimates during stimulation and during the early post-stimulation period, and it systematically underestimates around shut-in. In this presentation, we also describe a robust estimate of information gain, a modification that can also benefit forecast experiments involving tectonic earthquakes.

  18. A 3D seismic tomography of the Lesser Antilles Subduction Zone offshore Dominica and Martinique islands

    NASA Astrophysics Data System (ADS)

    Evain, Mikaël.; Galve, Audrey; Charvis, Philippe; Laigle, Mireille; Flueh, Ernst; Weinzierl, Wolfgang

    2010-05-01

    Along the eastern border of the Caribbean plate the Lesser Antilles islands form an active volcanic arc above the Atlantic subducting lithosphere. The crustal structure of this convergent margin is presented here from first arrival tomographic inversion of a 3D wide-angle seismic dataset acquired offshore Dominica and Martinique islands by a network of 27 Ocean Bottom Seismometers (OBS). The resulting 3D velocity model shows good resolution from 7-8 km down to ~15 km depth in a 150 km x 150 km area. Though our study area is located at the northern termination of one of the world's largest accretionary prisms we still observe about 5 to 7 km of sediment (v< 4 km/s) in the southeastern corner of our model. Our network is centered on a remarkable bathymetric feature: the Arawak Basin, a 6 km deep basin trending NW-SE, filled with 3 km of sediment on average. The western side of the Arawak Basin is bordered at depth by a basement high, highlighted by the rise of the 6.0-6.5 km/s velocity contours up to 2 km below seafloor. To the east of the Arawak Basin, below the accretionary prism, SW-NE cross-sections show two successive rises of velocity contours from 4.0 to 6.0 km/s. The first one, also clearly seen on the MCS data, is coincident with the eastern border of the Arawak Basin, while the second one seems located ~30 km to the East, below the thick accretionary prism. We interpret these highs as basement uplifts associated with the subduction of the Tiburon ridge. We do not sample the interplate contact mainly due to high seismic attenuation in the accretionary wedge. More insight into the geometry of this contact may arise from the processing of a ~285 km long wide-angle refraction/reflection profile parallel to the convergence that cross our 3D velocity model in its middle and continues across the entire subduction complex. Preliminary tomographic results from this dataset recorded by 45 densely spaced OBS confirm the observations described above. This new 2D line

  19. Geological characterisation of complex reservoirs using 3D seismic: Case studies

    NASA Astrophysics Data System (ADS)

    Benaissa, Zahia; Benaïssa, Abdelkader; Seghir Baghaoui, Mohamed; Bendali, Mohamed; Chami, Adel; Khelifi Touhami, Médina; Ouadfeul, Sid Ali; Boudella, Amar

    2014-05-01

    3D seismic allows getting a set of numerous closely-spaced seismic lines that provide a high spatially sampled measure of subsurface reflectivity. It leads to an accurate interpretation of seismic reflection data, which is one of the most important stages of a successful hydrocarbons exploration, especially in the reservoirs characterised by complex geological setting. We present here two case studies pertaining to two Algerian hydrocarbon fields. Considering the positive results obtained from 2D seismic interpretation, several wells were drilled. Some of them have proved dry, due certainly to inaccurate seismic interpretation because of non standard geological context. For the first case, the high quality of the 3D seismic data allowed to reveal, on all the inlines and crosslines, the existence of paleovalleys under the top of the Ordovician (unit IV) reservoir. The mapping of these paleovalleys clearly showed that the dry well, contrary to the other wells, was implanted outside paleovalleys. This fact was confirmed by the analysis of well data. The second case study concerns the problem of andesitic eruptive deposits on the top of the Ordovician reservoir, which condition the geometry and continuity of this reservoir and cause uncertainties in the mapping of the Hercynian unconformity. Well data associated with 3D seismic response shows that eruptive deposits generate high impedance anomaly because of the high density and velocity of andesites. We used this information to interpret these eruptive rocks as being responsible of high impedance anomalies, inside the Ordovician reservoir, on the impedance volume generated from the 3D seismic data. A 3D extraction of the anomalies allowed an accurate localisation of the andesites. So, it appears, according to these two case studies, that for an efficient recovery of hydrocarbons, we have to rely, first of all, on an accurate seismic interpretation before we use microscopic measurements. 3D seismic, once again, remains

  20. Best fit refractive index of matching liquid for 3D NIPAM gel dosimeters using optical CT

    NASA Astrophysics Data System (ADS)

    Chen, Chin-Hsing; Wu, Jay; Hsieh, Bor-Tsung; Chen, De-Shiou; Wang, Tzu-Hwei; Chien, Sou-Hsin; Chang, Yuan-Jen

    2014-11-01

    The accuracy of an optical computed tomography (CT)-based dosimeter is significantly affected by the refractive index (RI) of the matching liquid. Mismatched RI induces reflection and refraction as the laser beam passes through the gel phantom. Moreover, the unwanted light rays collected by the photodetector produce image artifacts after image reconstruction from the collected data. To obtain the best image quality, this study investigates the best-fit RI of the matching liquid for a 3D NIPAM gel dosimeter. The three recipes of NIPAM polymer gel used in this study consisted of 5% gelatin, 5% NIPAM and 3% N,N'-methylene bisacrylamide, which were combined with three compositions (5, 10, and 20 mM) of Tetrakis (hydroxymethyl) phosphonium chloride. Results were evaluated using a quantitative evaluation method of the gamma evaluation technique. Results showed that the best-fit RI for the non-irradiated NIPAM gel ranges from 1.340 to 1.346 for various NIPAM recipes with sensitivities ranging from 0.0113 to 0.0227. The greatest pass rate of 88.00% is achieved using best-fit RI=1.346 of the matching liquid. The adoption of mismatching RI decreases the gamma pass rate by 2.63% to 16.75% for all three recipes of NIPAM gel dosimeters. In addition, the maximum average deviation is less than 0.1% for the red and transparent matching liquids. Thus, the color of the matching liquid does not affect the measurement accuracy of the NIPAM gel dosimeter, as measured by optical CT.

  1. Label-free 3D refractive-index acquisition by micro-manipulations of cells in suspension (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Shaked, Natan T.

    2016-03-01

    Our latest methods for non-invasive label-free acquisition of the three-dimensional (3-D) refractive-index maps of live cells in suspension are reviewed. These methods are based on the acquisition of off-axis interferograms of single or multiple cells in suspension from different angles using an external interferometric module, while fully rotating each cell using micro-manipulations. The interferometric projections are processed via computed tomographic phase microscopy reconstruction technique, which considers optical diffraction effects, into the 3-D refractive-index structure of the suspended cell. Till now, tomographic phase microscopy was obtained by acquiring a series of interferograms of the light transmitted through the sample in different angles by either using an entire sample rotation, or patch clamping a single cell, which is invasive to the cells, or alternatively, using various angles of illumination, which causes a limited acceptance angle, and an incomplete 3-D Fourier spectrum. In contrast, our methods allow fast acquisition with full angular range, and thus obtain an accurate 3-D refractive-index map of the imaged cell. By inspection of the 3-D refractive-index distribution of cells in suspension, the proposed methods can be useful for high-throughput, label-free characterization of biological processes and cellular transformations from healthy to pathological conditions.

  2. 3-D Seismic Experimentation and Advanced Processing/Inversion Development for Investigations of the Shallow Subsurface

    SciTech Connect

    Levander, Alan R.

    2004-12-01

    Under ER63662, 3-D Seismic Experimentation and Advanced Processing/Inversion Development for Investigations of the Shallow Subsurface, we have completed a number of subprojects associated with the Hill Air Force Base (HAFB) high resolution 3-D reflection/tomography dataset.

  3. Optical-CT 3D Dosimetry Using Fresnel Lenses with Minimal Refractive-Index Matching Fluid

    PubMed Central

    Bache, Steven; Malcolm, Javian; Adamovics, John; Oldham, Mark

    2016-01-01

    Telecentric optical computed tomography (optical-CT) is a state-of-the-art method for visualizing and quantifying 3-dimensional dose distributions in radiochromic dosimeters. In this work a prototype telecentric system (DFOS—Duke Fresnel Optical-CT Scanner) is evaluated which incorporates two substantial design changes: the use of Fresnel lenses (reducing lens costs from $10-30K t0 $1-3K) and the use of a ‘solid tank’ (which reduces noise, and the volume of refractively matched fluid from 1ltr to 10cc). The efficacy of DFOS was evaluated by direct comparison against commissioned scanners in our lab. Measured dose distributions from all systems were compared against the predicted dose distributions from a commissioned treatment planning system (TPS). Three treatment plans were investigated including a simple four-field box treatment, a multiple small field delivery, and a complex IMRT treatment. Dosimeters were imaged within 2h post irradiation, using consistent scanning techniques (360 projections acquired at 1 degree intervals, reconstruction at 2mm). DFOS efficacy was evaluated through inspection of dose line-profiles, and 2D and 3D dose and gamma maps. DFOS/TPS gamma pass rates with 3%/3mm dose difference/distance-to-agreement criteria ranged from 89.3% to 92.2%, compared to from 95.6% to 99.0% obtained with the commissioned system. The 3D gamma pass rate between the commissioned system and DFOS was 98.2%. The typical noise rates in DFOS reconstructions were up to 3%, compared to under 2% for the commissioned system. In conclusion, while the introduction of a solid tank proved advantageous with regards to cost and convenience, further work is required to improve the image quality and dose reconstruction accuracy of the new DFOS optical-CT system. PMID:27019460

  4. Optical-CT 3D Dosimetry Using Fresnel Lenses with Minimal Refractive-Index Matching Fluid.

    PubMed

    Bache, Steven; Malcolm, Javian; Adamovics, John; Oldham, Mark

    2016-01-01

    Telecentric optical computed tomography (optical-CT) is a state-of-the-art method for visualizing and quantifying 3-dimensional dose distributions in radiochromic dosimeters. In this work a prototype telecentric system (DFOS-Duke Fresnel Optical-CT Scanner) is evaluated which incorporates two substantial design changes: the use of Fresnel lenses (reducing lens costs from $10-30K t0 $1-3K) and the use of a 'solid tank' (which reduces noise, and the volume of refractively matched fluid from 1 ltr to 10 cc). The efficacy of DFOS was evaluated by direct comparison against commissioned scanners in our lab. Measured dose distributions from all systems were compared against the predicted dose distributions from a commissioned treatment planning system (TPS). Three treatment plans were investigated including a simple four-field box treatment, a multiple small field delivery, and a complex IMRT treatment. Dosimeters were imaged within 2 h post irradiation, using consistent scanning techniques (360 projections acquired at 1 degree intervals, reconstruction at 2mm). DFOS efficacy was evaluated through inspection of dose line-profiles, and 2D and 3D dose and gamma maps. DFOS/TPS gamma pass rates with 3%/3mm dose difference/distance-to-agreement criteria ranged from 89.3% to 92.2%, compared to from 95.6% to 99.0% obtained with the commissioned system. The 3D gamma pass rate between the commissioned system and DFOS was 98.2%. The typical noise rates in DFOS reconstructions were up to 3%, compared to under 2% for the commissioned system. In conclusion, while the introduction of a solid tank proved advantageous with regards to cost and convenience, further work is required to improve the image quality and dose reconstruction accuracy of the new DFOS optical-CT system.

  5. Optical-CT 3D Dosimetry Using Fresnel Lenses with Minimal Refractive-Index Matching Fluid.

    PubMed

    Bache, Steven; Malcolm, Javian; Adamovics, John; Oldham, Mark

    2016-01-01

    Telecentric optical computed tomography (optical-CT) is a state-of-the-art method for visualizing and quantifying 3-dimensional dose distributions in radiochromic dosimeters. In this work a prototype telecentric system (DFOS-Duke Fresnel Optical-CT Scanner) is evaluated which incorporates two substantial design changes: the use of Fresnel lenses (reducing lens costs from $10-30K t0 $1-3K) and the use of a 'solid tank' (which reduces noise, and the volume of refractively matched fluid from 1 ltr to 10 cc). The efficacy of DFOS was evaluated by direct comparison against commissioned scanners in our lab. Measured dose distributions from all systems were compared against the predicted dose distributions from a commissioned treatment planning system (TPS). Three treatment plans were investigated including a simple four-field box treatment, a multiple small field delivery, and a complex IMRT treatment. Dosimeters were imaged within 2 h post irradiation, using consistent scanning techniques (360 projections acquired at 1 degree intervals, reconstruction at 2mm). DFOS efficacy was evaluated through inspection of dose line-profiles, and 2D and 3D dose and gamma maps. DFOS/TPS gamma pass rates with 3%/3mm dose difference/distance-to-agreement criteria ranged from 89.3% to 92.2%, compared to from 95.6% to 99.0% obtained with the commissioned system. The 3D gamma pass rate between the commissioned system and DFOS was 98.2%. The typical noise rates in DFOS reconstructions were up to 3%, compared to under 2% for the commissioned system. In conclusion, while the introduction of a solid tank proved advantageous with regards to cost and convenience, further work is required to improve the image quality and dose reconstruction accuracy of the new DFOS optical-CT system. PMID:27019460

  6. SCEC/CME CyberShake: Probabilistic Seismic Hazard Analysis Using 3D Seismic Waveform Modeling

    NASA Astrophysics Data System (ADS)

    Callaghan, S.; Maechling, P. J.; Cui, Y.; Faerman, M.; Field, E.; Graves, R.; Gupta, N.; Gupta, V.; Jordan, T. H.; Kesselman, C.; Mehta, G.; Okaya, D.; Vahi, K.; Zhao, L.

    2005-12-01

    Researchers on the SCEC Community Modeling Environment (SCEC/CME) Project are calculating Probabilistic Seismic Hazard Curves for several sites in the Los Angeles area. The hazard curves calculated in this study use Intensity Measure Relationships (IMRs) based on 3D ground motion simulations rather than on attenuation relationships. State-of-the-art Probabilistic Seismic Hazard Analysis (PSHA) is currently conducted using IMRs that use empirically-based attenuation relationships. These attenuation relationships represent relatively simple analytical models based on the regression of observed data. However, it is widely believed that significant improvements in SHA will rely on the use of more physics-based, waveform modeling. In fact, a more physics-based approach to PSHA was endorsed in a recent assessment of earthquake science by National Research Council (2003). In order to introduce the use of 3D seismic waveform modeling into PSHA hazard curve calculations, the SCEC/CME CyberShake group is integrating state-of-the-art PSHA software tools (OpenSHA), SCEC-developed geophysical models (SCEC CVM3.0), validated anelastic wave modeling (AWM) software, and state-of-the-art computational technologies including high performance computing and grid-based scientific workflows in an effort to develop an OpenSHA-compatible 3D waveform-based IMR component. This will allow researchers to combine a new class of waveform-based IMRs with the large number of existing PSHA components, such as Earthquake Rupture Forecasts (ERF's), that are currently implemented in the OpenSHA system. To calculate a probabilistic hazard curve for a site of interest, we use the OpenSHA implementation of the NSHMP-2002 ERF and identify all ruptures within 200km of the site of interest. For each of these ruptures, we convert the NSHMP-2002 rupture definition into one, or more, Ruptures with Slip Time History (Rupture Variations) using newly developed Rupture Generator software. Strain Green Tensors are

  7. Epikarstic storage and doline structural characterization with time-lapse geophysics (seismic refraction & electrical resistivity)

    NASA Astrophysics Data System (ADS)

    Valois, R.; Galibert, P.; Guérin, R.; Mendes, M.; Plagnes, V.

    2011-12-01

    Karst formations are one of the most challenging environments in terms of groundwater, engineering and environmental issues. Geophysical methods can provide useful subsurface information in karst regions concerning groundwater vulnerability assessment, exploitation or hazard estimation. First, dolines are studied as preferential pathways for the protection of karstic aquifer in south France. Geophysics helps to characterize lateral and underground morphologies of such objects and is able to detect doline hidden by the soil cover too. Electrical resistivity and seismic refraction tomographies provide information about dolines filling and could help to propose a genesis scenario. Time-lapse resistivity measurements show that the studied doline is more vulnerable to infiltration on its sides than at its centre. The epikarst could be defined as a perched aquifer above the massive carbonate rocks; it constitutes a highly fractured zone, which water stock capacities. So, the epikarst was investigated with 3D seismic refraction and results show an important velocity anisotropy linked to the fracturing and weathering of the dolostone. The 3D model presents also some large heterogeneities: a corridor with highly weathered dolostone and an unweathered pinnacle. The corridor is probably situated on vertical joints, which have conducted aggressive water. The associated weathering with residual weathered-rock keeping its initial volume could create a "ghost-rock" corridor. So, the epikarst in the dolostones of the Causse du Larzac (France) seems to be composed by "ghost-rock" developed around a specific direction of fractures. Time-lapse electrical resistivity and seismic refraction velocity were carried out on this epikarst to observe the influence of water saturation on the measurements. The results show important variations for both seismic and electrical methods and are localized in the first 6 m: in the weathered zone. So, time-lapse measurements could more easily identify

  8. Time-lapse 3-D seismic imaging of shallow subsurface contaminant flow.

    PubMed

    McKenna, J; Sherlock, D; Evans, B

    2001-12-01

    This paper presents a physical modelling study outlining a technique whereby buoyant contaminant flow within water-saturated unconsolidated sand was remotely monitored utilizing the time-lapse 3-D (TL3-D) seismic response. The controlled temperature and pressure conditions, along with the high level of acquisition repeatability attainable using sandbox physical models, allow the TL3-D seismic response to pore fluid movement to be distinguished from all other effects. TL3-D seismic techniques are currently being developed to monitor hydrocarbon reserves within producing reservoirs in an endeavour to improve overall recovery. However, in many ways, sandbox models under atmospheric conditions more accurately simulate the shallow subsurface than petroleum reservoirs. For this reason, perhaps the greatest application for analogue sandbox modelling is to improve our understanding of shallow groundwater and environmental flow mechanisms. Two fluid flow simulations were conducted whereby air and kerosene were injected into separate water-saturated unconsolidated sand models. In both experiments, a base 3-D seismic volume was recorded and compared with six later monitor surveys recorded while the injection program was conducted. Normal incidence amplitude and P-wave velocity information were extracted from the TL3-D seismic data to provide visualization of contaminant migration. Reflection amplitudes displayed qualitative areal distribution of fluids when a suitable impedance contrast existed between pore fluids. TL3-D seismic reflection tomography can potentially monitor the change in areal distribution of fluid contaminants over time, indicating flow patterns. However, other research and this current work have not established a quantifiable relationship between either normal reflection amplitudes and attenuation and fluid saturation. Generally, different pore fluids will have unique seismic velocities due to differences in compressibility and density. The predictable

  9. 3D seismic data interpretation of Boonsville Field, Texas

    NASA Astrophysics Data System (ADS)

    Alhakeem, Aamer Ali

    The Boonsville field is one of the largest gas fields in the US located in the Fort Worth Basin, north central Texas. The highest potential reservoirs reside in the Bend Conglomerate deposited during the Pennsylvanian. The Boonsville data set is prepared by the Bureau of Economic Geology at the University of Texas, Austin, as part of the secondary gas recovery program. The Boonsville field seismic data set covers an area of 5.5 mi2. It includes 38 wells data. The Bend Conglomerate is deposited in fluvio-deltaic transaction. It is subdivided into many genetic sequences which include depositions of sandy conglomerate representing the potential reserves in the Boonsville field. The geologic structure of the Boonsville field subsurface are visualized by constructing structure maps of Caddo, Davis, Runaway, Beans Cr, Vineyard, and Wade. The mapping includes time structure, depth structure, horizon slice, velocity maps, and isopach maps. Many anticlines and folds are illustrated. Karst collapse features are indicated specially in the lower Atoka. Dipping direction of the Bend Conglomerate horizons are changing from dipping toward north at the top to dipping toward east at the bottom. Stratigraphic interpretation of the Runaway Formation and the Vineyard Formation using well logs and seismic data integration showed presence of fluvial dominated channels, point bars, and a mouth bar. RMS amplitude maps are generated and used as direct hydrocarbon indicator for the targeted formations. As a result, bright spots are indicated and used to identify potential reservoirs. Petrophysical analysis is conducted to obtain gross, net pay, NGR, water saturation, shale volume, porosity, and gas formation factor. Volumetric calculations estimated 989.44 MMSCF as the recoverable original gas in-place for a prospect in the Runaway and 3.32 BSCF for a prospect in the Vineyard Formation.

  10. Recovering physical property information from subduction plate boundaries using 3D full-waveform seismic inversion

    NASA Astrophysics Data System (ADS)

    Bell, R. E.; Morgan, J. V.; Warner, M.

    2013-12-01

    Our understanding of subduction margin seismogenesis has been revolutionised in the last couple of decades with the discovery that the size of the seismogenic zone may not be controlled simply by temperature and a broad spectrum of seismic behaviour exists from stick-slip to stable sliding. Laboratory and numerical experiments suggest that physical properties, particularly fluid pressure may play an important role in controlling the seismic behaviour of subduction margins. Although drilling can provide information on physical properties along subduction thrust faults at point locations at relatively shallow depths, correlations between physical properties and seismic velocity using rock physics relationships are required to resolve physical properties along the margin and down-dip. Therefore, high resolution seismic velocity models are key to recovering physical property information at subduction plate boundaries away from drill sites. 3D Full waveform inversion (FWI) is a technique pioneered by the oil industry to obtain high-resolution high-fidelity models of physical properties in the sub-surface. 3D FWI involves the inversion of low-frequency (>2 to <7 Hz), early arriving (principally transmitted) seismic data, to recover the macro (intermediate to long-wavelength) velocity structure. Although 2D FWI has been used to improve velocity models of subduction plate boundaries before, 3D FWI has not yet been attempted. 3D inversions have superior convergence and accuracy, as they sample the subsurface with multi-azimuth multiply-crossing wavefields. In this contribution we perform a suite of synthetic tests to investigate if 3D FWI could be used to better resolve physical property information along subduction margin plate boundaries using conventionally collected 3D seismic data. We base our analysis on the Muroto Basin area of the Nankai margin and investigate if the acquisition parameters and geometry of the subduction margin render 3D seismic data collected across

  11. Modeling and validation of a 3D velocity structure for the Santa Clara Valley, California, for seismic-wave simulations

    USGS Publications Warehouse

    Hartzell, S.; Harmsen, S.; Williams, R.A.; Carver, D.; Frankel, A.; Choy, G.; Liu, P.-C.; Jachens, R.C.; Brocher, T.M.; Wentworth, C.M.

    2006-01-01

    A 3D seismic velocity and attenuation model is developed for Santa Clara Valley, California, and its surrounding uplands to predict ground motions from scenario earthquakes. The model is developed using a variety of geologic and geophysical data. Our starting point is a 3D geologic model developed primarily from geologic mapping and gravity and magnetic surveys. An initial velocity model is constructed by using seismic velocities from boreholes, reflection/refraction lines, and spatial autocorrelation microtremor surveys. This model is further refined and the seismic attenuation is estimated through waveform modeling of weak motions from small local events and strong-ground motion from the 1989 Loma Prieta earthquake. Waveforms are calculated to an upper frequency of 1 Hz using a parallelized finite-difference code that utilizes two regions with a factor of 3 difference in grid spacing to reduce memory requirements. Cenozoic basins trap and strongly amplify ground motions. This effect is particularly strong in the Evergreen Basin on the northeastern side of the Santa Clara Valley, where the steeply dipping Silver Creek fault forms the southwestern boundary of the basin. In comparison, the Cupertino Basin on the southwestern side of the valley has a more moderate response, which is attributed to a greater age and velocity of the Cenozoic fill. Surface waves play a major role in the ground motion of sedimentary basins, and they are seen to strongly develop along the western margins of the Santa Clara Valley for our simulation of the Loma Prieta earthquake.

  12. Gray-level transformation and Canny edge detection for 3D seismic discontinuity enhancement

    NASA Astrophysics Data System (ADS)

    Di, Haibin; Gao, Dengliang

    2014-11-01

    In a 3D seismic survey, detecting seismic discontinuities is vital to robust structural and stratigraphic analysis in the subsurface. Previous methods have difficulty highlighting subtle discontinuities from seismic data in cases where the local amplitude variation is of non-zero mean. This study proposes implementing a gray-level transformation and the Canny edge detector for improved imaging of discontinuities. Specifically, the new process transforms seismic signals to be of zero mean and helps amplify subtle discontinuities, leading to an enhanced visualization for structural and stratigraphic details. Applications to various 3D seismic datasets demonstrate that the new algorithm helps better define channels, faults, and fractures than the traditional similarity, amplitude gradient, and semblance attributes.

  13. Crustal density structure in northwestern South America derived from analysis and 3-D modeling of gravity and seismicity data

    NASA Astrophysics Data System (ADS)

    Sanchez-Rojas, J.; Palma, M.

    2014-11-01

    This paper presents a three-dimensional (3-D) interpretation of new gravity and seismicity datasets for northern South America. A 3-D forward density model was constructed on the basis of deep wide-angle seismic refraction sections, Moho depth from receiver functions, and surface geology. Density values were estimated from published borehole data for sediments by using empirical velocity-density functions and considering mineralogical-chemical composition variations under typical pressure-temperature conditions for upper and lower crustal rocks. The modeled 3-D density structure was kept as simple as possible. The continental and oceanic plates were formed by two sedimentary bodies, one crustal body, and one mantle lithosphere body overlying a sub-lithospheric mantle. The Caribbean plate was modeled with an atypical crustal thickness of ~ 18 km (including sediments). The geometry of the Caribbean plate was modeled using a combination of gravity modeling and analyses of the seismicity and focal-mechanism solutions. Intermediate seismicity and the orientation of the T-axes appeared aligned along the predicted position of the slab. As a result, the estimated slab dip angle under Maracaibo and the Mérida Andes was ~ 15° and increases up to ~ 20° after 100 km depth. The model shows two orientations in the slab strike: ~ N150°E ± 5 in western Colombia and southward underneath the Maracaibo block. The modeling results suggest that the northern South American upper and lower crusts are relatively light and the density of the Caribbean crust is typical for an oceanic crust.

  14. Poor boy 3D seismic effort yields South Central Kentucky discovery

    SciTech Connect

    Hanratty, M.

    1996-11-04

    Clinton County, Ky., is on the eastern flank of the Cincinnati arch and the western edge of the Appalachian basin and the Pine Mountain overthrust. Clinton County has long been known for high volume fractured carbonate wells. The discovery of these fractured reservoir, unfortunately, has historically been serendipitous. The author currently uses 2D seismic and satellite imagery to design 3D high resolution seismic shoots. This method has proven to be the most efficient and is the core of his program. The paper describes exploration methods, seismic acquisition, well data base, and seismic interpretation.

  15. Understanding North Texas Seismicity: A Joint Analysis of Seismic Data and 3D Pore Pressure Modeling

    NASA Astrophysics Data System (ADS)

    DeShon, H. R.; Hornbach, M. J.; Ellsworth, W. L.; Oldham, H. R.; Hayward, C.; Stump, B. W.; Frohlich, C.; Olson, J. E.; Luetgert, J. H.

    2014-12-01

    In November 2013, a series of earthquakes began along a mapped ancient fault system near Azle, Texas. The Azle events are the third felt earthquake sequence in the Fort Worth (Barnett Shale) Basin since 2008, and several production and injection wells in the area are drilled to depths near the recent seismic activity. Understanding if and/or how injection and removal of fluids in the crystalline crust reactivates faults have important implications for seismology, the energy industry, and society. We assessed whether the Azle earthquakes were induced using a joint analysis of the earthquake data, subsurface geology and fault structure, and 3D pore pressure modeling. Using a 12-station temporary seismic deployment, we have recorded and located >300 events large enough to be recorded on multiple stations and 1000s of events during periods of swarm activity. High-resolution locations and focal mechanisms indicate that events occurred on NE-SW trending, steeply dipping normal faults associated with the southern end of the Newark East Fault Zone with hypocenters between 2-8 km depth. We considered multiple causes that might have changed stress along this system. Earthquakes resulting from natural processes, though perhaps unlikely in this historically inactive region, can be neither ruled out nor confirmed due to lack of information on the natural stress state of these faults. Analysis of lake and groundwater variations near Azle showed that no significant stress changes occurred prior to or during the earthquake sequence. In contrast, analysis of pore-pressure models shows that the combination of formation water production and wastewater injection near the fault could have caused pressure increases that induced earthquakes on near-critically stressed faults.

  16. 3-D photo-patterning of refractive index structures in photosensitive thin film materials

    DOEpatents

    Potter, Jr., Barrett George; Potter, Kelly Simmons

    2002-01-01

    A method of making a three-dimensional refractive index structure in a photosensitive material using photo-patterning. The wavelengths at which a photosensitive material exhibits a change in refractive index upon exposure to optical radiation is first determined and then a portion of the surface of the photosensitive material is optically irradiated at a wavelength at which the photosensitive material exhibits a change in refractive index using a designed illumination system to produce a three-dimensional refractive index structure. The illumination system can be a micro-lenslet array, a macroscopic refractive lens array, or a binary optic phase mask. The method is a single-step, direct-write procedure to produce a designed refractive index structure.

  17. High refractive index immersion liquid for superresolution 3D imaging using sapphire-based aplanatic numerical aperture increasing lens optics.

    PubMed

    Laskar, Junaid M; Shravan Kumar, P; Herminghaus, Stephan; Daniels, Karen E; Schröter, Matthias

    2016-04-20

    Optically transparent immersion liquids with refractive index (n∼1.77) to match the sapphire-based aplanatic numerical aperture increasing lens (aNAIL) are necessary for achieving deep 3D imaging with high spatial resolution. We report that antimony tribromide (SbBr3) salt dissolved in liquid diiodomethane (CH2I2) provides a new high refractive index immersion liquid for optics applications. The refractive index is tunable from n=1.74 (pure) to n=1.873 (saturated), by adjusting either salt concentration or temperature; this allows it to match (or even exceed) the refractive index of sapphire. Importantly, the solution gives excellent light transmittance in the ultraviolet to near-infrared range, an improvement over commercially available immersion liquids. This refractive-index-matched immersion liquid formulation has enabled us to develop a sapphire-based aNAIL objective that has both high numerical aperture (NA=1.17) and long working distance (WD=12  mm). This opens up new possibilities for deep 3D imaging with high spatial resolution. PMID:27140083

  18. High refractive index immersion liquid for superresolution 3D imaging using sapphire-based aplanatic numerical aperture increasing lens optics.

    PubMed

    Laskar, Junaid M; Shravan Kumar, P; Herminghaus, Stephan; Daniels, Karen E; Schröter, Matthias

    2016-04-20

    Optically transparent immersion liquids with refractive index (n∼1.77) to match the sapphire-based aplanatic numerical aperture increasing lens (aNAIL) are necessary for achieving deep 3D imaging with high spatial resolution. We report that antimony tribromide (SbBr3) salt dissolved in liquid diiodomethane (CH2I2) provides a new high refractive index immersion liquid for optics applications. The refractive index is tunable from n=1.74 (pure) to n=1.873 (saturated), by adjusting either salt concentration or temperature; this allows it to match (or even exceed) the refractive index of sapphire. Importantly, the solution gives excellent light transmittance in the ultraviolet to near-infrared range, an improvement over commercially available immersion liquids. This refractive-index-matched immersion liquid formulation has enabled us to develop a sapphire-based aNAIL objective that has both high numerical aperture (NA=1.17) and long working distance (WD=12  mm). This opens up new possibilities for deep 3D imaging with high spatial resolution.

  19. Seismic source inversion using Green's reciprocity and a 3-D structural model for the Japanese Islands

    NASA Astrophysics Data System (ADS)

    Simutė, S.; Fichtner, A.

    2015-12-01

    We present a feasibility study for seismic source inversions using a 3-D velocity model for the Japanese Islands. The approach involves numerically calculating 3-D Green's tensors, which is made efficient by exploiting Green's reciprocity. The rationale for 3-D seismic source inversion has several aspects. For structurally complex regions, such as the Japan area, it is necessary to account for 3-D Earth heterogeneities to prevent unknown structure polluting source solutions. In addition, earthquake source characterisation can serve as a means to delineate existing faults. Source parameters obtained for more realistic Earth models can then facilitate improvements in seismic tomography and early warning systems, which are particularly important for seismically active areas, such as Japan. We have created a database of numerically computed 3-D Green's reciprocals for a 40°× 40°× 600 km size area around the Japanese Archipelago for >150 broadband stations. For this we used a regional 3-D velocity model, recently obtained from full waveform inversion. The model includes attenuation and radial anisotropy and explains seismic waveform data for periods between 10 - 80 s generally well. The aim is to perform source inversions using the database of 3-D Green's tensors. As preliminary steps, we present initial concepts to address issues that are at the basis of our approach. We first investigate to which extent Green's reciprocity works in a discrete domain. Considering substantial amounts of computed Green's tensors we address storage requirements and file formatting. We discuss the importance of the initial source model, as an intelligent choice can substantially reduce the search volume. Possibilities to perform a Bayesian inversion and ways to move to finite source inversion are also explored.

  20. Land 3D-seismic data: Preprocessing quality control utilizing survey design specifications, noise properties, normal moveout, first breaks, and offset

    USGS Publications Warehouse

    Raef, A.

    2009-01-01

    The recent proliferation of the 3D reflection seismic method into the near-surface area of geophysical applications, especially in response to the emergence of the need to comprehensively characterize and monitor near-surface carbon dioxide sequestration in shallow saline aquifers around the world, justifies the emphasis on cost-effective and robust quality control and assurance (QC/QA) workflow of 3D seismic data preprocessing that is suitable for near-surface applications. The main purpose of our seismic data preprocessing QC is to enable the use of appropriate header information, data that are free of noise-dominated traces, and/or flawed vertical stacking in subsequent processing steps. In this article, I provide an account of utilizing survey design specifications, noise properties, first breaks, and normal moveout for rapid and thorough graphical QC/QA diagnostics, which are easy to apply and efficient in the diagnosis of inconsistencies. A correlated vibroseis time-lapse 3D-seismic data set from a CO2-flood monitoring survey is used for demonstrating QC diagnostics. An important by-product of the QC workflow is establishing the number of layers for a refraction statics model in a data-driven graphical manner that capitalizes on the spatial coverage of the 3D seismic data. ?? China University of Geosciences (Wuhan) and Springer-Verlag GmbH 2009.

  1. Areal 3-D seismic technique for reservoir delineation: Case history from offshore Niger Delta

    SciTech Connect

    Idowu, A.O. )

    1993-02-01

    In the 1950s, early exploration period in the Niger Delta witnessed the use of 2-D (two dimensional) seismic reflection method which adequate for imaging large subsurface geologic features including growth faulting and roll-over anticlines. This technique involves the Common-Depth-Point method (CDP) which acquires a plane of seismic information in distance along the surface and in time into the geological section, and is used to improve the signal-to-noise (S/N) ratio, to remove multiples and consequently give a representation of the subsurface particularly if the data are collected up- or downdip. By mid-1980s, the obvious geological structures have, in general, been discovered and it became necessary to adopt a more sophisticated technique such as the 3-D (three dimensional) seismic method to delineate more subtle reservoirs and resolve complex fault patterns in order to aid exploration as well as facilitate efficient field development. The case history discussed in this paper involves the use of areal 3-D seismic method for delineating the reservoir characterization of the O-field located in a shallow water area of the western Niger Delta. The areal 3-D seismic technique is superior to the earlier CDP method in that a cube of seismic data can be collected in two dimensions in space and one in time by a variety of techniques including the swath seismic shooting pattern adopted for gathering the 3-D data for the O-field's reservoir which involves the line of sources. The objective is to adequately sample the subsurface so that changes in various parameters such as the amplitude phase or power in the siesmic signal or velocity of propagation can be mapped areally and interpreted as an indication of changes in the physical properties of the rock matrix.

  2. Automatic detection of karstic sinkholes in seismic 3D images using circular Hough transform

    NASA Astrophysics Data System (ADS)

    Heydari Parchkoohi, Mostafa; Keshavarz Farajkhah, Nasser; Salimi Delshad, Meysam

    2015-10-01

    More than 30% of hydrocarbon reservoirs are reported in carbonates that mostly include evidence of fractures and karstification. Generally, the detection of karstic sinkholes prognosticate good quality hydrocarbon reservoirs where looser sediments fill the holes penetrating hard limestone and the overburden pressure on infill sediments is mostly tolerated by their sturdier surrounding structure. They are also useful for the detection of erosional surfaces in seismic stratigraphic studies and imply possible relative sea level fall at the time of establishment. Karstic sinkholes are identified straightforwardly by using seismic geometric attributes (e.g. coherency, curvature) in which lateral variations are much more emphasized with respect to the original 3D seismic image. Then, seismic interpreters rely on their visual skills and experience in detecting roughly round objects in seismic attribute maps. In this paper, we introduce an image processing workflow to enhance selective edges in seismic attribute volumes stemming from karstic sinkholes and finally locate them in a high quality 3D seismic image by using circular Hough transform. Afterwards, we present a case study from an on-shore oilfield in southwest Iran, in which the proposed algorithm is applied and karstic sinkholes are traced.

  3. Identifying High Potential Well Targets with 3D Seismic and Mineralogy

    SciTech Connect

    Mellors, R. J.

    2015-10-30

    Seismic reflection the primary tool used in petroleum exploration and production, but use in geothermal exploration is less standard, in part due to cost but also due to the challenges in identifying the highly-permeable zones essential for economic hydrothermal systems [e.g. Louie et al., 2011; Majer, 2003]. Newer technology, such as wireless sensors and low-cost high performance computing, has helped reduce the cost and effort needed to conduct 3D surveys. The second difficulty, identifying permeable zones, has been less tractable so far. Here we report on the use of seismic attributes from a 3D seismic survey to identify and map permeable zones in a hydrothermal area.

  4. Integrating 3D seismic curvature and curvature gradient attributes for fracture characterization: Methodologies and interpretational implications

    SciTech Connect

    Gao, Dengliang

    2013-03-01

    In 3D seismic interpretation, curvature is a popular attribute that depicts the geometry of seismic reflectors and has been widely used to detect faults in the subsurface; however, it provides only part of the solutions to subsurface structure analysis. This study extends the curvature algorithm to a new curvature gradient algorithm, and integrates both algorithms for fracture detection using a 3D seismic test data set over Teapot Dome (Wyoming). In fractured reservoirs at Teapot Dome known to be formed by tectonic folding and faulting, curvature helps define the crestal portion of the reservoirs that is associated with strong seismic amplitude and high oil productivity. In contrast, curvature gradient helps better define the regional northwest-trending and the cross-regional northeast-trending lineaments that are associated with weak seismic amplitude and low oil productivity. In concert with previous reports from image logs, cores, and outcrops, the current study based on an integrated seismic curvature and curvature gradient analysis suggests that curvature might help define areas of enhanced potential to form tensile fractures, whereas curvature gradient might help define zones of enhanced potential to develop shear fractures. In certain fractured reservoirs such as at Teapot Dome where faulting and fault-related folding contribute dominantly to the formation and evolution of fractures, curvature and curvature gradient attributes can be potentially applied to differentiate fracture mode, to predict fracture intensity and orientation, to detect fracture volume and connectivity, and to model fracture networks.

  5. Advancing New 3D Seismic Interpretation Methods for Exploration and Development of Fractured Tight Gas Reservoirs

    SciTech Connect

    James Reeves

    2005-01-31

    In a study funded by the U.S. Department of Energy and GeoSpectrum, Inc., new P-wave 3D seismic interpretation methods to characterize fractured gas reservoirs are developed. A data driven exploratory approach is used to determine empirical relationships for reservoir properties. Fractures are predicted using seismic lineament mapping through a series of horizon and time slices in the reservoir zone. A seismic lineament is a linear feature seen in a slice through the seismic volume that has negligible vertical offset. We interpret that in regions of high seismic lineament density there is a greater likelihood of fractured reservoir. Seismic AVO attributes are developed to map brittle reservoir rock (low clay) and gas content. Brittle rocks are interpreted to be more fractured when seismic lineaments are present. The most important attribute developed in this study is the gas sensitive phase gradient (a new AVO attribute), as reservoir fractures may provide a plumbing system for both water and gas. Success is obtained when economic gas and oil discoveries are found. In a gas field previously plagued with poor drilling results, four new wells were spotted using the new methodology and recently drilled. The wells have estimated best of 12-months production indicators of 2106, 1652, 941, and 227 MCFGPD. The latter well was drilled in a region of swarming seismic lineaments but has poor gas sensitive phase gradient (AVO) and clay volume attributes. GeoSpectrum advised the unit operators that this location did not appear to have significant Lower Dakota gas before the well was drilled. The other three wells are considered good wells in this part of the basin and among the best wells in the area. These new drilling results have nearly doubled the gas production and the value of the field. The interpretation method is ready for commercialization and gas exploration and development. The new technology is adaptable to conventional lower cost 3D seismic surveys.

  6. Prestack reverse time migration for 3D marine reflection seismic data

    SciTech Connect

    Jang, Seonghyung; Kim, Taeyoun

    2015-03-10

    Prestack reverse time migration (RTM) is a method for imaging the subsurface using the inner product of wavefield extrapolation in shot domain and in receiver domain. It is well known that RTM is better for preserving amplitudes and phases than other prestack migrations. Since 3D seismic data is huge data volume and it needs heavy computing works, it requires parallel computing in order to have a meaningful depth image of the 3D subsurface. We implemented a parallelized version of 3D RTM for prestack depth migration. The results of numerical example for 3D SEG/EAGE salt model showed good agreement with the original geological model. We applied RTM to offshore 3D seismic reflection data. The study area is 12 × 25 km with 120 survey lines. Shot and receiver spacing is 25 m and 12.5 m. The line spacing is 100 m. Shot gathers were preprocessed to enhance signal to noise ratio and velocity model was calculated from conventional stack velocity. Both of them were used to obtain 3D image using RTM. The results show reasonable subsurface image.

  7. P-Cable: New High-Resolution 3D Seismic Acquisition Technology

    NASA Astrophysics Data System (ADS)

    Planke, Sverre; Berndt, Christian; Mienert, Jürgen; Bünz, Stefan; Eriksen, Frode N.; Eriksen, Ola K.

    2010-05-01

    We have developed a new cost-efficient technology for acquisition of high-resolution 3D seismic data: the P-Cable system. This technology is very well suited for deep water exploration, site surveys, and studies of shallow gas and fluid migration associated with gas hydrates or leaking reservoirs. It delivers unparalleled 3D seismic images of subsurface sediment architectures. The P-Cable system consists of a seismic cable towed perpendicular to a vessel's steaming direction. This configuration allows us to image an up to 150 m wide swath of the sub-surface for each sail line. Conventional 3D seismic technology relies on several very long streamers (up to 10 km long streamers are common), large sources, and costly operations. In contrast, the P-Cable system is light-weight and fast to deploy from small vessels. Only a small source is required as the system is made for relatively shallow imaging, typically above the first water-bottom multiple. The P-Cable system is particularly useful for acquisition of small 3D cubes, 10-50 km2, in focus areas, rather than extensive mapping of large regions. The rapid deployment and recovery of the system makes it possible to acquire several small cubes (10 to 30 km2) with high-resolution (50-250 Hz) seismic data in during one cruise. The first development of the P-Cable system was a cooperative project achieved by Volcanic Basin Petroleum Research (VBPR), University of Tromsø, National Oceanography Centre, Southampton, and industry partners. Field trials using a 12-streamer system were conducted on sites with active fluid-leakage systems on the Norwegian-Barents-Svalbard margin, the Gulf of Cadiz, and the Mediterranean. The second phase of the development introduced digital streamers. The new P-Cable2 system also includes integrated tow and cross cables for power and data transmission and improved doors to spread the larger cross cable. This digital system has been successfully used during six cruises by the University of Troms

  8. Identification Of Rippability And Bedrock Depth Using Seismic Refraction

    SciTech Connect

    Ismail, Nur Azwin; Saad, Rosli; Nawawi, M. N. M; Muztaza, Nordiana Mohd; El Hidayah Ismail, Noer; Mohamad, Edy Tonizam

    2010-12-23

    Spatial variability of the bedrock with reference to the ground surface is vital for many applications in geotechnical engineering to decide the type of foundation of a structure. A study was done within the development area of Mutiara Damansara utilising the seismic refraction method using ABEM MK8 24 channel seismograph. The geological features of the subsurface were investigated and velocities, depth to the underlying layers were determined. The seismic velocities were correlated with rippability characteristics and borehole records. Seismic sections generally show a three layer case. The first layer with velocity 400-600 m/s predominantly consists of soil mix with gravel. The second layer with velocity 1600-2000 m/s is suggested to be saturated and weathered area. Both layers forms an overburden and generally rippable. The third layer represents granite bedrock with average depth and velocity 10-30 m and >3000 m/s respectively and it is non-rippable. Steep slope on the bedrock are probably the results of shear zones.

  9. 3D Seismic Experimentation and Advanced Processing/Inversion Development for Investigations of the Shallow Subsurface

    SciTech Connect

    Levander, Alan Richard; Zelt, Colin A.

    2015-03-17

    The work plan for this project was to develop and apply advanced seismic reflection and wide-angle processing and inversion techniques to high resolution seismic data for the shallow subsurface to seismically characterize the shallow subsurface at hazardous waste sites as an aid to containment and cleanup activities. We proposed to continue work on seismic data that we had already acquired under a previous DoE grant, as well as to acquire additional new datasets for analysis. The project successfully developed and/or implemented the use of 3D reflection seismology algorithms, waveform tomography and finite-frequency tomography using compressional and shear waves for high resolution characterization of the shallow subsurface at two waste sites. These two sites have markedly different near-surface structures, groundwater flow patterns, and hazardous waste problems. This is documented in the list of refereed documents, conference proceedings, and Rice graduate theses, listed below.

  10. 3-D Seismic Tomographic Modelling of the North-Western Spitsbergen Area

    NASA Astrophysics Data System (ADS)

    Czuba, W.

    2015-12-01

    Deep seismic sounding measurements were performed in the continent-ocean transition zone of the north-western Svalbard continental margin in 1976 - 1999 in an international co-operation. Seismic energy (airgun and TNT shots) was recorded by land (onshore) seismic stations, ocean bottom seismometers (OBS), and ocean bottom hydrophone systems (OBH). Data from archival and modern seismic profiles were altogether used for 3-D tomographic inversion using JIVE3D software. The modelling area was chosen to be a rectangle of 420 x 330 km (Fig.). The results are similar to the earlier 2-D modelling, supplemented by off-line information from the profiles and the SPITS permanent station, giving a 3-D image of the crustal structure and Moho interface shape. The continental crust thins to the west and north. A minimum depth of about 6 km to the Moho discontinuity was found east of the Molloy Deep and in the Knipovich Ridge. The Moho interface deepens to about 30 km beneath the continental crust of Spitsbergen.

  11. ActiveSeismoPick3D - automatic first arrival determination for large active seismic arrays

    NASA Astrophysics Data System (ADS)

    Paffrath, Marcel; Küperkoch, Ludger; Wehling-Benatelli, Sebastian; Friederich, Wolfgang

    2016-04-01

    We developed a tool for automatic determination of first arrivals in active seismic data based on an approach, that utilises higher order statistics (HOS) and the Akaike information criterion (AIC), commonly used in seismology, but not in active seismics. Automatic picking is highly desirable in active seismics as the number of data provided by large seismic arrays rapidly exceeds of what an analyst can evaluate in a reasonable amount of time. To bring the functionality of automatic phase picking into the context of active data, the software package ActiveSeismoPick3D was developed in Python. It uses a modified algorithm for the determination of first arrivals which searches for the HOS maximum in unfiltered data. Additionally, it offers tools for manual quality control and postprocessing, e.g. various visualisation and repicking functionalities. For flexibility, the tool also includes methods for the preparation of geometry information of large seismic arrays and improved interfaces to the Fast Marching Tomography Package (FMTOMO), which can be used for the prediction of travel times and inversion for subsurface properties. Output files are generated in the VTK format, allowing the 3D visualization of e.g. the inversion results. As a test case, a data set consisting of 9216 traces from 64 shots was gathered, recorded at 144 receivers deployed in a regular 2D array of a size of 100 x 100 m. ActiveSeismoPick3D automatically checks the determined first arrivals by a dynamic signal to noise ratio threshold. From the data a 3D model of the subsurface was generated using the export functionality of the package and FMTOMO.

  12. 3D Porosity Estimation of the Nankai Trough Sediments from Core-log-seismic Integration

    NASA Astrophysics Data System (ADS)

    Park, J. O.

    2015-12-01

    The Nankai Trough off southwest Japan is one of the best subduction-zone to study megathrust earthquake fault. Historic, great megathrust earthquakes with a recurrence interval of 100-200 yr have generated strong motion and large tsunamis along the Nankai Trough subduction zone. At the Nankai Trough margin, the Philippine Sea Plate (PSP) is being subducted beneath the Eurasian Plate to the northwest at a convergence rate ~4 cm/yr. The Shikoku Basin, the northern part of the PSP, is estimated to have opened between 25 and 15 Ma by backarc spreading of the Izu-Bonin arc. The >100-km-wide Nankai accretionary wedge, which has developed landward of the trench since the Miocene, mainly consists of offscraped and underplated materials from the trough-fill turbidites and the Shikoku Basin hemipelagic sediments. Particularly, physical properties of the incoming hemipelagic sediments may be critical for seismogenic behavior of the megathrust fault. We have carried out core-log-seismic integration (CLSI) to estimate 3D acoustic impedance and porosity for the incoming sediments in the Nankai Trough. For the CLSI, we used 3D seismic reflection data, P-wave velocity and density data obtained during IODP (Integrated Ocean Drilling Program) Expeditions 322 and 333. We computed acoustic impedance depth profiles for the IODP drilling sites from P-wave velocity and density data. We constructed seismic convolution models with the acoustic impedance profiles and a source wavelet which is extracted from the seismic data, adjusting the seismic models to observed seismic traces with inversion method. As a result, we obtained 3D acoustic impedance volume and then converted it to 3D porosity volume. In general, the 3D porosities show decrease with depth. We found a porosity anomaly zone with alteration of high and low porosities seaward of the trough axis. In this talk, we will show detailed 3D porosity of the incoming sediments, and present implications of the porosity anomaly zone for the

  13. Complex Crustal Structure Beneath Western Turkey Revealed by 3D Seismic Full Waveform Inversion (FWI)

    NASA Astrophysics Data System (ADS)

    Cubuk-Sabuncu, Yesim; Taymaz, Tuncay; Fichtner, Andreas

    2016-04-01

    We present a 3D radially anisotropic velocity model of the crust and uppermost mantle structure beneath the Sea of Marmara and surroundings based on the full waveform inversion method. The intense seismic activity and crustal deformation are observed in the Northwest Turkey due to transition tectonics between the strike-slip North Anatolian Fault (NAF) and the extensional Aegean region. We have selected and simulated complete waveforms of 62 earthquakes (Mw > 4.0) occurred during 2007-2015, and recorded at (Δ < 10°) distances. Three component earthquake data is obtained from broadband seismic stations of Kandilli Observatory and Earthquake Research Center (KOERI, Turkey), Hellenic Unified Seismic Network (HUSN, Greece) and Earthquake Research Center of Turkey (AFAD-DAD). The spectral-element solver of the wave equation, SES3D algorithm, is used to simulate seismic wave propagation in 3D spherical coordinates (Fichtner, 2009). The Large Scale Seismic Inversion Framework (LASIF) workflow tool is also used to perform full seismic waveform inversion (Krischer et al., 2015). The initial 3D Earth model is implemented from the multi-scale seismic tomography study of Fichtner et al. (2013). Discrepancies between the observed and simulated synthetic waveforms are determined using the time-frequency misfits which allows a separation between phase and amplitude information (Fichtner et al., 2008). The conjugate gradient optimization method is used to iteratively update the initial Earth model when minimizing the misfit. The inversion is terminated after 19 iterations since no further advances are observed in updated models. Our analysis revealed shear wave velocity variations of the shallow and deeper crustal structure beneath western Turkey down to depths of ~35-40 km. Low shear wave velocity anomalies are observed in the upper and mid crustal depths beneath major fault zones located in the study region. Low velocity zones also tend to mark the outline of young volcanic

  14. Estimating the detectability of faults in 3D-seismic data - A valuable input to Induced Seismic Hazard Assessment (ISHA)

    NASA Astrophysics Data System (ADS)

    Goertz, A.; Kraft, T.; Wiemer, S.; Spada, M.

    2012-12-01

    In the past several years, some geotechnical operations that inject fluid into the deep subsurface, such as oil and gas development, waste disposal, and geothermal energy development, have been found or suspected to cause small to moderate sized earthquakes. In several cases the largest events occurred on previously unmapped faults, within or in close vicinity to the operated reservoirs. The obvious conclusion drawn from this finding, also expressed in most recently published best practice guidelines and recommendations, is to avoid injecting into faults. Yet, how certain can we be that all faults relevant to induced seismic hazard have been identified, even around well studied sites? Here we present a probabilistic approach to assess the capability of detecting faults by means of 3D seismic imaging. First, we populate a model reservoir with seed faults of random orientation and slip direction. Drawing random samples from a Gutenberg-Richter distribution, each seed fault is assigned a magnitude and corresponding size using standard scaling relations based on a circular rupture model. We then compute the minimum resolution of a 3D seismic survey for given acquisition parameters and frequency bandwidth. Assuming a random distribution of medium properties and distribution of image frequencies, we obtain a probability that a fault of a given size is detected, or respectively overlooked, by the 3D seismic. Weighting the initial Gutenberg-Richter fault size distribution with the probability of imaging a fault, we obtain a modified fault size distribution in the imaged volume from which we can constrain the maximum magnitude to be considered in the seismic hazard assessment of the operation. We can further quantify the value of information associated with the seismic image by comparing the expected insured value loss between the image-weighted and the unweighted hazard estimates.

  15. GPU-based rapid reconstruction of cellular 3D refractive index maps from tomographic phase microscopy (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Dardikman, Gili; Shaked, Natan T.

    2016-03-01

    We present highly parallel and efficient algorithms for real-time reconstruction of the quantitative three-dimensional (3-D) refractive-index maps of biological cells without labeling, as obtained from the interferometric projections acquired by tomographic phase microscopy (TPM). The new algorithms are implemented on the graphic processing unit (GPU) of the computer using CUDA programming environment. The reconstruction process includes two main parts. First, we used parallel complex wave-front reconstruction of the TPM-based interferometric projections acquired at various angles. The complex wave front reconstructions are done on the GPU in parallel, while minimizing the calculation time of the Fourier transforms and phase unwrapping needed. Next, we implemented on the GPU in parallel the 3-D refractive index map retrieval using the TPM filtered-back projection algorithm. The incorporation of algorithms that are inherently parallel with a programming environment such as Nvidia's CUDA makes it possible to obtain real-time processing rate, and enables high-throughput platform for label-free, 3-D cell visualization and diagnosis.

  16. Application of Plenoptic PIV for 3D Velocity Measurements Over Roughness Elements in a Refractive Index Matched Facility

    NASA Astrophysics Data System (ADS)

    Thurow, Brian; Johnson, Kyle; Kim, Taehoon; Blois, Gianluca; Best, Jim; Christensen, Ken

    2014-11-01

    The application of Plenoptic PIV in a Refractive Index Matched (RIM) facility housed at Illinois is presented. Plenoptic PIV is an emerging 3D diagnostic that exploits the light-field imaging capabilities of a plenoptic camera. Plenoptic cameras utilize a microlens array to measure the position and angle of light rays captured by the camera. 3D/3C velocity fields are determined through application of the MART algorithm for volume reconstruction and a conventional 3D cross-correlation PIV algorithm. The RIM facility is a recirculating tunnel with a 62.5% aqueous solution of sodium iodide used as the working fluid. Its resulting index of 1.49 is equal to that of acrylic. Plenoptic PIV was used to measure the 3D velocity field of a turbulent boundary layer flow over a smooth wall, a single wall-mounted hemisphere and a full array of hemispheres (i.e. a rough wall) with a k/ δ ~ 4.6. Preliminary time averaged and instantaneous 3D velocity fields will be presented. This material is based upon work supported by the National Science Foundation under Grant No. 1235726.

  17. An ocean-bottom hydrophone recorder for seismic refraction experiments

    NASA Astrophysics Data System (ADS)

    Sinha, M. C.; Owen, T. R. E.; Mason, M.

    1981-06-01

    A new and inexpensive pop-up ocean-bottom hydrophone recorder has been developed for use in seismic refraction experiments. It is capable of operating in water depths of up to 4000 m and in very rugged topography, and uses an acoustic command system built by the U.K. Institute of Oceanographic Sciences for recovery. The instrument is mounted in an inexpensive cylindrical pressure case based on commercially available extruded aluminium alloy tubing, and uses glass spheres and syntactic foam for buoyancy. Hydrophone and clock signals are frequency modulated and recorded on tape cassettes, with a recording duration of three hours allowing up to 18 programmed shot windows. The prototype has made seven free descents on the Mid-Atlantic ridge and in the Gulf of Oman, and successfully recorded shots under operational conditions for the first time in September 1979. The total component cost of the prototype was £2740 (1979 prices).

  18. Combining sequence stratigraphy with 3-D seismic imaging in low-accommodation basins

    SciTech Connect

    Hardage, B.A.; Carr, D.L.; Simmons, J.L. Jr.

    1995-12-31

    Pennsylvania-age rocks in several areas of the Midcontinent of the United States were deposited in low-accommodation basinal settings, that is, in basinal areas where only modest verticle reliefs could accept the sediment influx. Many thin Pennsylvanian sequences in these low-accommodation environments exhibit severe lateral heterogeneity because they have been extensively reworked by repeated transgressions and regressions of a fluctuating sea. Consequently, the distinctive geometries of relic depositional features (such as meandering channels) tend to be distorted or even totally destroyed, as compared with how such geometries appear in high-accommodation basins where depositional topography, once buried, is rarely exposed to destructive processes. Our objectives are to show examples of 3-D seismic images of several depositional topographies in a moderate- to low-accommodation basin and to explain how these thin sequences can be identified in well control and interpreted in 3-D seismic data volumes.

  19. Imaging of 3-D seismic velocity structure of Southern Sumatra region using double difference tomographic method

    SciTech Connect

    Lestari, Titik; Nugraha, Andri Dian

    2015-04-24

    Southern Sumatra region has a high level of seismicity due to the influence of the subduction system, Sumatra fault, Mentawai fault and stretching zone activities. The seismic activities of Southern Sumatra region are recorded by Meteorological Climatological and Geophysical Agency (MCGA’s) Seismograph network. In this study, we used earthquake data catalog compiled by MCGA for 3013 events from 10 seismic stations around Southern Sumatra region for time periods of April 2009 – April 2014 in order to invert for the 3-D seismic velocities structure (Vp, Vs, and Vp/Vs ratio). We applied double-difference seismic tomography method (tomoDD) to determine Vp, Vs and Vp/Vs ratio with hypocenter adjustment. For the inversion procedure, we started from the initial 1-D seismic velocity model of AK135 and constant Vp/Vs of 1.73. The synthetic travel time from source to receiver was calculated using ray pseudo-bending technique, while the main tomographic inversion was applied using LSQR method. The resolution model was evaluated using checkerboard test and Derivative Weigh Sum (DWS). Our preliminary results show low Vp and Vs anomalies region along Bukit Barisan which is may be associated with weak zone of Sumatran fault and migration of partial melted material. Low velocity anomalies at 30-50 km depth in the fore arc region may indicated the hydrous material circulation because the slab dehydration. We detected low seismic seismicity in the fore arc region that may be indicated as seismic gap. It is coincides contact zone of high and low velocity anomalies. And two large earthquakes (Jambi and Mentawai) also occurred at the contact of contrast velocity.

  20. 3-D Characterization of Seismic Properties at the Smart Weapons Test Range, YPG

    NASA Astrophysics Data System (ADS)

    Miller, Richard D.; Anderson, Thomas S.; Davis, John C.; Steeples, Don W.; Moran, Mark L.

    2001-10-01

    The Smart Weapons Test Range (SWTR) lies within the Yuma Proving Ground (YPG), Arizona. SWTR is a new facility constructed specifically for the development and testing of futuristic intelligent battlefield sensor networks. In this paper, results are presented for an extensive high-resolution geophysical characterization study at the SWTR site along with validation using 3-D modeling. In this study, several shallow seismic methods and novel processing techniques were used to generate a 3-D grid of earth seismic properties, including compressional (P) and shear (S) body-wave speeds (Vp and Vs), and their associated body-wave attenuation parameters (Qp, and Qs). These experiments covered a volume of earth measuring 1500 m by 300 m by 25 m deep (11 million cubic meters), centered on the vehicle test track at the SWTR site. The study has resulted in detailed characterizations of key geophysical properties. To our knowledge, results of this kind have not been previously achieved, nor have the innovative methods developed for this effort been reported elsewhere. In addition to supporting materiel developers with important geophysical information at this test range, the data from this study will be used to validate sophisticated 3-D seismic signature models for moving vehicles.

  1. Multi-hole seismic modeling in 3-D space and cross-hole seismic tomography analysis for boulder detection

    NASA Astrophysics Data System (ADS)

    Cheng, Fei; Liu, Jiangping; Wang, Jing; Zong, Yuquan; Yu, Mingyu

    2016-11-01

    A boulder stone, a common geological feature in south China, is referred to the remnant of a granite body which has been unevenly weathered. Undetected boulders could adversely impact the schedule and safety of subway construction when using tunnel boring machine (TBM) method. Therefore, boulder detection has always been a key issue demanded to be solved before the construction. Nowadays, cross-hole seismic tomography is a high resolution technique capable of boulder detection, however, the method can only solve for velocity in a 2-D slice between two wells, and the size and central position of the boulder are generally difficult to be accurately obtained. In this paper, the authors conduct a multi-hole wave field simulation and characteristic analysis of a boulder model based on the 3-D elastic wave staggered-grid finite difference theory, and also a 2-D imaging analysis based on first arrival travel time. The results indicate that (1) full wave field records could be obtained from multi-hole seismic wave simulations. Simulation results describe that the seismic wave propagation pattern in cross-hole high-velocity spherical geological bodies is more detailed and can serve as a basis for the wave field analysis. (2) When a cross-hole seismic section cuts through the boulder, the proposed method provides satisfactory cross-hole tomography results; however, when the section is closely positioned to the boulder, such high-velocity object in the 3-D space would impact on the surrounding wave field. The received diffracted wave interferes with the primary wave and in consequence the picked first arrival travel time is not derived from the profile, which results in a false appearance of high-velocity geology features. Finally, the results of 2-D analysis in 3-D modeling space are comparatively analyzed with the physical model test vis-a-vis the effect of high velocity body on the seismic tomographic measurements.

  2. Tracking Paths of Ocean Source Ambient Seismic Noise into, and through, the 3D Earth

    NASA Astrophysics Data System (ADS)

    Reading, A. M.; Gal, M.; Morse, P. E.; Koper, K. D.; Hemer, M. A.; Rawlinson, N.; Salmon, M.; De Kool, M.; Kennett, B. L. N.

    2014-12-01

    Array measurements of seismic noise (microseisms) are emerging as independent observables that inform our knowledge of ocean storms. Using an improved implementation of IAS Capon analysis, we can infer the location and amplitude of multiple sources of seismic noise over multiple decades. For the Southern Ocean, we can use seismic records to assist in identifying shifting patterns of ocean storms. Thus we can investigate topics such as the disparity between wave height trends identified using calibrated satellite records, which appear to be in increasing over multiple decades, and wave heights measured directly using a wave-rider buoy, which does not show a significant change over the same time frame. The passage of wave energy from the water column to the solid Earth, and through the 3D Earth to the seismic array must be tracked effectively. In this contribution, we focus on understanding the passage of seismic noise through the 3D Earth. In particular, we investigate path deviations from 1D Earth models for body waves sources from a variety of locations in the Southern Ocean recorded at Australian seismic arrays. We also investigate path deviations of surface waves travelling across the Australian continent, using the AusREM Earth model. We also appraise other factors affecting the interpretation of slowness, backazimuth and amplitude from seismic array records. These include the effect of the bathymetry-related transfer function controlling energy entering the solid Earth from the water column and the impact of local geology at the site of the seismic array. For a season of storms in the southern hemisphere winter, we simulate the path of energy from a representative range of locations to Australia seismic arrays. We employ a wavefront tracking technique, fast marching, that can support heterogeneous structure and the consideration of multiple arrivals. We find that storms in some locations are subject to a much larger deviation from the expected path of energy

  3. Emplacement of pyroclastic deposits offshore Montserrat: Insights from 3D seismic data

    NASA Astrophysics Data System (ADS)

    Karstens, J.; Crutchley, G. J.; Berndt, C.; Talling, P. J.; Watt, S. F. L.; Hühnerbach, V.; Le Friant, A.; Lebas, E.; Trofimovs, J.

    2013-05-01

    During the current (1995-present) eruptive phase of the Soufrière Hills volcano on Montserrat, voluminous pyroclastic flows entered the sea off the eastern flank of the island, resulting in the deposition of well-defined submarine pyroclastic lobes. Previously reported bathymetric surveys documented the sequential construction of these deposits, but could not image their internal structure, the morphology or extent of their base, or interaction with the underlying sediments. We show, by combining these bathymetric data with new high-resolution three dimensional (3D) seismic data, that the sequence of previously detected pyroclastic deposits from different phases of the ongoing eruptive activity is still well preserved. A detailed interpretation of the 3D seismic data reveals the absence of significant (> 3 m) basal erosion in the distal extent of submarine pyroclastic deposits. We also identify a previously unrecognized seismic unit directly beneath the stack of recent lobes. We propose three hypotheses for the origin of this seismic unit, but prefer an interpretation that the deposit is the result of the subaerial flank collapse that formed the English's Crater scarp on the Soufrière Hills volcano. The 1995-recent volcanic activity on Montserrat accounts for a significant portion of the sediments on the southeast slope of Montserrat, in places forming deposits that are more than 60 m thick, which implies that the potential for pyroclastic flows to build volcanic island edifices is significant.

  4. Sequence stratigraphy and 3-D seismic imaging in low-accommodation basins

    SciTech Connect

    Hardage, B.A.; Carr, D.L.; Hamilton, D.S.; Simmons, J.L. Jr. )

    1996-01-01

    Pennsylvanian-age rocks in several areas of the Midcontinent of the United States were deposited in low-accommodation basinal settings. Many sequences in these low-accommodation environments exhibit severe lateral heterogeneity because they have been extensively reworked by repeated transgressions and regressions. Consequently, the distinctive geometries of relic depositional features tend to be distorted or totally destroyed, in contrast to such geometries in high-accommodation basins where depositional topography, once buried, is rarely exposed to erosional processes. Our objective is to show how these thin and obscure low-accommodation sequences can be identified in well control and interpreted in 3-D seismic data volumes. Numerous, deep-rooted karst-collapse zones affected the areal continuity of many sequences in some Midcontinent basins. We combine sequence stratigraphy with 3-D seismic imaging to document that many of these karst-collapse zones originate at deep Ellenburger ( ) levels and then extend vertically for a distance of 2,000 ft (600 m) or more into Pennsylvanian-age rocks. We also offer evidence that properly chosen seismic attributes, calculated in thin, accurately defined seismic time windows that correspond to log-defined sequences, show compartmented reservoir facies in low-accommodation basins.

  5. Sequence stratigraphy and 3-D seismic imaging in low-accommodation basins

    SciTech Connect

    Hardage, B.A.; Carr, D.L.; Hamilton, D.S.; Simmons, J.L. Jr.

    1996-12-31

    Pennsylvanian-age rocks in several areas of the Midcontinent of the United States were deposited in low-accommodation basinal settings. Many sequences in these low-accommodation environments exhibit severe lateral heterogeneity because they have been extensively reworked by repeated transgressions and regressions. Consequently, the distinctive geometries of relic depositional features tend to be distorted or totally destroyed, in contrast to such geometries in high-accommodation basins where depositional topography, once buried, is rarely exposed to erosional processes. Our objective is to show how these thin and obscure low-accommodation sequences can be identified in well control and interpreted in 3-D seismic data volumes. Numerous, deep-rooted karst-collapse zones affected the areal continuity of many sequences in some Midcontinent basins. We combine sequence stratigraphy with 3-D seismic imaging to document that many of these karst-collapse zones originate at deep Ellenburger (?) levels and then extend vertically for a distance of 2,000 ft (600 m) or more into Pennsylvanian-age rocks. We also offer evidence that properly chosen seismic attributes, calculated in thin, accurately defined seismic time windows that correspond to log-defined sequences, show compartmented reservoir facies in low-accommodation basins.

  6. Thrust fault growth within accretionary wedges: New Insights from 3D seismic reflection data

    NASA Astrophysics Data System (ADS)

    Orme, H.; Bell, R. E.; Jackson, C. A. L.

    2015-12-01

    The shallow parts of subduction megathrust faults are typically thought to be aseismic and incapable of propagating seismic rupture. The 2011 Tohoku-Oki earthquake, however, ruptured all the way to the trench, proving that in some locations rupture can propagate through the accretionary wedge. An improved understanding of the structural character and physical properties of accretionary wedges is therefore crucial to begin to assess why such anomalously shallow seismic rupture occurs. Despite its importance, we know surprisingly little regarding the 3D geometry and kinematics of thrust network development in accretionary prisms, largely due to a lack of 3D seismic reflection data providing high-resolution, 3D images of entire networks. Thus our current understanding is largely underpinned by observations from analogue and numerical modelling, with limited observational data from natural examples. In this contribution we use PSDM, 3D seismic reflection data from the Nankai margin (3D Muroto dataset, available from the UTIG Academic Seismic Portal, Marine Geoscience Data System) to examine how imbricate thrust fault networks evolve during accretionary wedge growth. Previous studies have reported en-echelon thrust fault geometries from the NW part of the dataset, and have related this complex structure to seamount subduction. We unravel the evolution of faults within the protothrust and imbricate thrust zones by interpreting multiple horizons across faults and measuring fault displacement and fold amplitude along-strike; by doing this, we are able to investigate the three dimensional accrual of strain. We document a number of local displacement minima along-strike of faults, suggesting that, the protothrust and imbricate thrusts developed from the linkage of smaller, previously isolated fault segments. We also demonstrate that the majority of faults grew upward from the décollement, although there is some evidence for downward fault propagation. Our observations

  7. Initial Look at 3d Seismic Data Acquired Over the Galicia Margin

    NASA Astrophysics Data System (ADS)

    Sawyer, D. S.; Reston, T. J.; Shillington, D. J.; Minshull, T. A.; Klaeschen, D.; Morgan, J. K.

    2013-12-01

    In June thru September, 2013, a 3D reflection and long offset seismic experiment was conducted at the Galicia rifted margin by investigators from the US, UK, Germany, and Spain. The 3D multichannel experiment covered 64 km by 20 km (1280 km2), using the RV Marcus Langseth. Four streamers 6 km long were deployed at 12.5 m hydrophone channel spacing. The streamers were 200 m apart. Two airgun arrays, each 3300 cu in, were fired alternately every 37.5 m, to collectively yield a 400 m wide sail line consisting of 8 CMP lines at 50 m spacing. The long offset seismic experiment included 72 short period OBS's deployed below the 3D reflection survey box. Most of the instruments recorded all the shots from the airgun array shots. A few of the instruments were deployed twice, once to densify the instruments on a single profile and then to be moved into the full array. Finally, 6 of the OBS's were deployed on a profile extending 90 km to the west of the 3D box, in order to use combined MCS and OBS data to locate the boundary between the oceanic crust and exhumed upper mantle. The 3D seismic box covered a variety of geologic features including the Peridotite Ridge (PR) associated with the exhumation of upper mantle rocks to the seafloor, the S reflector interpreted to be a low-angle detachment fault formed late in the rifting process, and a number of rotated fault block basins and ranges containing pre- and syn-rift sediments. Initial observations, based only on 2D seismic dip lines (albeit 400 m apart), show the along strike variation of the PR: ~1050 m higher than adjacent basement in the South of the 3D box and much increased in size, ~2200 m high in the North. Some cross-sections of the PR show apparent internal structure that may help identify the emplacement mechanism of the feature and its relationship with the boundary between rifted continental crust blocks and exhumed upper mantle rocks. To the immediate East and West of the PR there are strong negative

  8. 2D and 3D Refraction Based X-ray Imaging Suitable for Clinical and Pathological Diagnosis

    SciTech Connect

    Ando, Masami; Bando, Hiroko; Ueno, Ei

    2007-01-19

    The first observation of micro papillary (MP) breast cancer by x-ray dark-field imaging (XDFI) and the first observation of the 3D x-ray internal structure of another breast cancer, ductal carcinoma in-situ (DCIS), are reported. The specimen size for the sheet-shaped MP was 26 mm x 22 mm x 2.8 mm, and that for the rod-shaped DCIS was 3.6 mm in diameter and 4.7 mm in height. The experiment was performed at the Photon Factory, KEK: High Energy Accelerator Research Organization. We achieved a high-contrast x-ray image by adopting a thickness-controlled transmission-type angular analyzer that allows only refraction components from the object for 2D imaging. This provides a high-contrast image of cancer-cell nests, cancer cells and stroma. For x-ray 3D imaging, a new algorithm due to the refraction for x-ray CT was created. The angular information was acquired by x-ray optics diffraction-enhanced imaging (DEI). The number of data was 900 for each reconstruction. A reconstructed CT image may include ductus lactiferi, micro calcification and the breast gland. This modality has the possibility to open up a new clinical and pathological diagnosis using x-ray, offering more precise inspection and detection of early signs of breast cancer.

  9. Training toward Advanced 3D Seismic Methods for CO2 Monitoring, Verification, and Accounting

    SciTech Connect

    Christopher Liner

    2012-05-31

    The objective of our work is graduate and undergraduate student training related to improved 3D seismic technology that addresses key challenges related to monitoring movement and containment of CO{sub 2}, specifically better quantification and sensitivity for mapping of caprock integrity, fractures, and other potential leakage pathways. We utilize data and results developed through previous DOE-funded CO{sub 2} characterization project (DE-FG26-06NT42734) at the Dickman Field of Ness County, KS. Dickman is a type locality for the geology that will be encountered for CO{sub 2} sequestration projects from northern Oklahoma across the U.S. midcontinent to Indiana and Illinois. Since its discovery in 1962, the Dickman Field has produced about 1.7 million barrels of oil from porous Mississippian carbonates with a small structural closure at about 4400 ft drilling depth. Project data includes 3.3 square miles of 3D seismic data, 142 wells, with log, some core, and oil/water production data available. Only two wells penetrate the deep saline aquifer. In a previous DOE-funded project, geological and seismic data were integrated to create a geological property model and a flow simulation grid. We believe that sequestration of CO{sub 2} will largely occur in areas of relatively flat geology and simple near surface, similar to Dickman. The challenge is not complex geology, but development of improved, lower-cost methods for detecting natural fractures and subtle faults. Our project used numerical simulation to test methods of gathering multicomponent, full azimuth data ideal for this purpose. Our specific objectives were to apply advanced seismic methods to aide in quantifying reservoir properties and lateral continuity of CO{sub 2} sequestration targets. The purpose of the current project is graduate and undergraduate student training related to improved 3D seismic technology that addresses key challenges related to monitoring movement and containment of CO{sub 2

  10. 3D High-Resolution Seismic Imaging of Fluid Flow Anomalies on the Norwegian Continental Shelf

    NASA Astrophysics Data System (ADS)

    Planke, S.; Eriksen, F. N.; Eriksen, O. K.; Myklebust, R.; Stokke, H. H.

    2015-12-01

    Fluid flow anomalies are common on the Norwegian Continental Shelf. Such features are imaged by multiple P-Cable high resolution seismic 2D lines and 3D cubes in the Norwegian Barents Sea. P-Cable is a high resolution 3D seismic system consisting of multiple streamers attached to a cross cable that is towed perpendicular to the vessels steaming direction. The short offset, high frequency source and closely spaced streamers facilitates for excellent vertical and horizontal resolution that provides key information for understanding the sub-surface. Recent data have been broadband processed, and the method has proven to enhance the imaging of the sub-surface significantly. Barents Sea P-Cable surveys have targeted shallow fluid anomalies in the uppermost ca. 500 meters of the sub-surface. New data have been acquired in 2012, 2014 and 2015. The most recent data focus on the southeast part of the Norwegian Barents Sea where P-Cable data give a new insight into the subsurface not provided by conventional seismic data in the region. Geologically, the Barents Sea region is characterized by Paleozoic and Mesozoic siliciclastic successions overlaid in most areas by a thin cover of Cenozoic glacial sediments. Hydrocarbon-rich Jurassic and Triassic sequences are locally situated in the shallow sub-surface as a result of extensive late Cenozoic uplift and erosion. The unloading has been reported to reactivate and create new faults in addition to initiate further migration of fluids in the sub-surface (Chand et al., 2012). The presence of shallow hydrocarbon systems creates an optimal setting for imaging fluid flow anomalies with high resolution 3D seismic data. The Barents Sea P-Cable data image a range of fluid related features such as cross-cutting reflections and bright spots, chimney structures, acoustic masking, pockmarks and mud volcanoes.

  11. Technological Advancements: Seismic Refraction on the Pajarito Plateau, Northern New Mexico.

    SciTech Connect

    Nisengard, J. E.; Ferguson, J. F.; Hinz, E.; Isaacson, J.; Gauthier, Rory P.

    2005-01-01

    Geophysical techniques can be used for non-invasive surveys at archaeological sites. Seismic refraction is one such technology that has many potential applications, although it has been under-utilized. It is an inexpensive, efficient way to characterize subsurface deposits, especially at sites in shallow contexts over bedrock. Archaeologists and geophysicists participating in the Summer of Applied Geophysics Experience (SAGE), from Los Alamos National Laboratory (LANL), and Bandelier National Monument are working together to characterize Ancestral Pueblo (A.D. 1200 to 1600) sites. We present the results from three seismic refraction surveys and provide an overview of how seismic refraction works.

  12. 3D seismic data reconstruction based on complex-valued curvelet transform in frequency domain

    NASA Astrophysics Data System (ADS)

    Zhang, Hua; Chen, Xiaohong; Li, Hongxing

    2015-02-01

    Traditional seismic data sampling must follow the Nyquist Sampling Theorem. However, the field data acquisition may not meet the sampling criteria due to missing traces or limits in exploration cost, causing a prestack data reconstruction problem. Recently researchers have proposed many useful methods to regularize the seismic data. In this paper, a 3D seismic data reconstruction method based on the Projections Onto Convex Sets (POCS) algorithm and a complex-valued curvelet transform (CCT) has been introduced in the frequency domain. In order to improve reconstruction efficiency and reduce the computation time, the seismic data are transformed from the t-x-y domain to the f-x-y domain and the data reconstruction is processed for every frequency slice during the reconstruction process. The selection threshold parameter is important for reconstruction efficiency for each iteration, therefore an exponential square root decreased (ESRD) threshold is proposed. The experimental results show that the ESRD threshold can greatly reduce iterations and improve reconstruction efficiency compared to the other thresholds for the same reconstruction result. We also analyze the antinoise ability of the CCT-based POCS reconstruction method. The example studies on synthetic and real marine seismic data showed that our proposed method is more efficient and applicable.

  13. Accelerating POCS interpolation of 3D irregular seismic data with Graphics Processing Units

    NASA Astrophysics Data System (ADS)

    Wang, Shu-Qin; Gao, Xing; Yao, Zhen-Xing

    2010-10-01

    Seismic trace interpolation is necessary for high-resolution imaging when the acquired data are not adequate or when some traces are missing. Projection-onto-convex-sets (POCS) interpolation can gradually recover missing traces with an iterative algorithm, but its computational cost in a 3D CPU-based implementation is too high for practical applications. We present a computing scheme to speedup 3D POCS interpolation with graphics processing units (GPUs). We accelerate the most time-consuming part of the 3D POCS algorithm (i.e. Fourier transforms) by taking advantage of a GPU-based Fourier transform library. Other parts are fine-tuned to maximize the utilization of GPU computing resources. We upload the whole input data set to the global memory of the GPUs and reuse it until the final result is obtained. This can avoid low-bandwidth data transfer between CPU and GPUs. We minimize the number of intermediate 3D arrays to save GPU global memory by optimizing the algorithm implementation. This allows us to handle a much larger input data set. When reducing the runtime of our GPU implementation, the coalescing of global memory access and the 3D CUFFT library provides us with the greatest performance improvements. Numerical results show that our scheme is 3-29× times faster than the optimized CPU-based implementation, depending on the size of 3D data set. Our GPU computing scheme allows a significant reduction of computational cost and would facilitate 3D POCS interpolation for practical applications.

  14. 3D Numerical Simulation on the Sloshing Waves Excited by the Seismic Shacking

    NASA Astrophysics Data System (ADS)

    Zhang, Lin; Wu, Tso-Ren

    2016-04-01

    In the event of 2015 Nepal earthquake, a video clip broadcasted worldwide showed a violent water spilling in a hotel swimming pool. This sloshing phenomenon indicates a potential water loss in the sensitive facilities, e.g. the spent fuel pools in nuclear power plant, has to be taken into account carefully under the consideration of seismic-induced ground acceleration. In the previous studies, the simulation of sloshing mainly focused on the pressure force on the structure by using a simplified Spring-Mass Method developed in the field of solid mechanics. However, restricted by the assumptions of plane water surface and limited wave height, significant error will be made in evaluating the amount of water loss in the tank. In this paper, the computational fluid dynamical model, Splash3D, was adopted for studying the sloshing problem accurately. Splash3D solved 3D Navier-Stokes Equation directly with Large-Eddy Simulation (LES) turbulent closure. The Volume-of-fluid (VOF) method with piecewise linear interface calculation (PLIC) was used to track the complex breaking water surface. The time series acceleration of a design seismic was loaded to excite the water. With few restrictions from the assumptions, the accuracy of the simulation results were improved dramatically. A series model validations were conducted by compared to a 2D theoretical solution, and a 3D experimental data. Good comparisons can be seen. After the validation, we performed the simulation for considering a sloshing case in a rectangular water tank with a dimension of 12 m long, 8 m wide, 8 m deep, which contained water with 7 m in depth. The seismic movement was imported by considering time-series acceleration in three dimensions, which were about 0.5 g to 1.2 g in the horizontal directions, and 0.3 g to 1 g in the vertical direction. We focused the discussions on the kinematics of the water surface, wave breaking, velocity field, pressure field, water force on the side walls, and, most

  15. Seismic Response of 3D Steel Buildings considering the Effect of PR Connections and Gravity Frames

    PubMed Central

    Haldar, Achintya; López-Barraza, Arturo; Rivera-Salas, J. Luz

    2014-01-01

    The nonlinear seismic responses of 3D steel buildings with perimeter moment resisting frames (PMRF) and interior gravity frames (IGF) are studied explicitly considering the contribution of the IGF. The effect on the structural response of the stiffness of the beam-to-column connections of the IGF, which is usually neglected, is also studied. It is commonly believed that the flexibility of shear connections is negligible and that 2D models can be used to properly represent 3D real structures. The results of the study indicate, however, that the moments developed on columns of IGF can be considerable and that modeling buildings as plane frames may result in very conservative designs. The contribution of IGF to the lateral structural resistance may be significant. The contribution increases when their connections are assumed to be partially restrained (PR). The incremented participation of IGF when the stiffness of their connections is considered helps to counteract the no conservative effect that results in practice when lateral seismic loads are not considered in IGF while designing steel buildings with PMRF. Thus, if the structural system under consideration is used, the three-dimensional model should be used in seismic analysis and the IGF and the stiffness of their connections should be considered as part of the lateral resistance system. PMID:24995357

  16. Detection of ancient morphology and potential hydrocarbon traps using 3-D seismic data and attribute analysis

    SciTech Connect

    Heggland, R.

    1995-12-31

    This paper presents the use of seismic attributes on 3D data to reveal Tertiary and Cretaceous geological features in Norwegian block 9/2. Some of the features would hardly be possible to map using only 2D seismic data. The method which involves a precise interpretation of horizons, attribute analysis and manipulation of colour displays, may be useful when studying morphology, faults and hydrocarbon traps. The interval of interest in this study was from 0 to 1.5 s TWT. Horizontal displays (timeslices and attribute maps), seemed to highlight very nicely geological features such as shallow channels, fractures, karst topography and faults. The attributes used for mapping these features were amplitude, total reflection energy (a volume or time interval attribute), dip and azimuth. The choice of colour scale and manipulation of colour displays were also critical for the results. The data examples clearly demonstrate how it is possible to achieve a very detailed mapping of geological features using 3D seismic data and attribute analysis. The results of this study were useful for the understanding of hydrocarbon migration paths and hydrocarbon traps.

  17. Seismic response of 3D steel buildings considering the effect of PR connections and gravity frames.

    PubMed

    Reyes-Salazar, Alfredo; Bojórquez, Edén; Haldar, Achintya; López-Barraza, Arturo; Rivera-Salas, J Luz

    2014-01-01

    The nonlinear seismic responses of 3D steel buildings with perimeter moment resisting frames (PMRF) and interior gravity frames (IGF) are studied explicitly considering the contribution of the IGF. The effect on the structural response of the stiffness of the beam-to-column connections of the IGF, which is usually neglected, is also studied. It is commonly believed that the flexibility of shear connections is negligible and that 2D models can be used to properly represent 3D real structures. The results of the study indicate, however, that the moments developed on columns of IGF can be considerable and that modeling buildings as plane frames may result in very conservative designs. The contribution of IGF to the lateral structural resistance may be significant. The contribution increases when their connections are assumed to be partially restrained (PR). The incremented participation of IGF when the stiffness of their connections is considered helps to counteract the no conservative effect that results in practice when lateral seismic loads are not considered in IGF while designing steel buildings with PMRF. Thus, if the structural system under consideration is used, the three-dimensional model should be used in seismic analysis and the IGF and the stiffness of their connections should be considered as part of the lateral resistance system.

  18. Seismic response of 3D steel buildings considering the effect of PR connections and gravity frames.

    PubMed

    Reyes-Salazar, Alfredo; Bojórquez, Edén; Haldar, Achintya; López-Barraza, Arturo; Rivera-Salas, J Luz

    2014-01-01

    The nonlinear seismic responses of 3D steel buildings with perimeter moment resisting frames (PMRF) and interior gravity frames (IGF) are studied explicitly considering the contribution of the IGF. The effect on the structural response of the stiffness of the beam-to-column connections of the IGF, which is usually neglected, is also studied. It is commonly believed that the flexibility of shear connections is negligible and that 2D models can be used to properly represent 3D real structures. The results of the study indicate, however, that the moments developed on columns of IGF can be considerable and that modeling buildings as plane frames may result in very conservative designs. The contribution of IGF to the lateral structural resistance may be significant. The contribution increases when their connections are assumed to be partially restrained (PR). The incremented participation of IGF when the stiffness of their connections is considered helps to counteract the no conservative effect that results in practice when lateral seismic loads are not considered in IGF while designing steel buildings with PMRF. Thus, if the structural system under consideration is used, the three-dimensional model should be used in seismic analysis and the IGF and the stiffness of their connections should be considered as part of the lateral resistance system. PMID:24995357

  19. 3D Seismic Flexure Analysis for Subsurface Fault Detection and Fracture Characterization

    NASA Astrophysics Data System (ADS)

    Di, Haibin; Gao, Dengliang

    2016-10-01

    Seismic flexure is a new geometric attribute with the potential of delineating subtle faults and fractures from three-dimensional (3D) seismic surveys, especially those overlooked by the popular discontinuity and curvature attributes. Although the concept of flexure and its related algorithms have been published in the literature, the attribute has not been sufficiently applied to subsurface fault detection and fracture characterization. This paper provides a comprehensive study of the flexure attribute, including its definition, computation, as well as geologic implications for evaluating the fundamental fracture properties that are essential to fracture characterization and network modeling in the subsurface, through applications to the fractured reservoir at Teapot Dome, Wyoming (USA). Specifically, flexure measures the third-order variation of the geometry of a seismic reflector and is dependent on the measuring direction in 3D space; among all possible directions, flexure is considered most useful when extracted perpendicular to the orientation of dominant deformation; and flexure offers new insights into qualitative/quantitative fracture characterization, with its magnitude indicating the intensity of faulting and fracturing, its azimuth defining the orientation of most-likely fracture trends, and its sign differentiating the sense of displacement of faults and fractures.

  20. A seismic modelling environment as a research and teaching tool for 3-D subsurface modelling

    NASA Astrophysics Data System (ADS)

    Burford, Dennis J.; Ger, Larry; Blake, Edwin H.; de Wit, Maarten J.; Doucouré, C. Moctar; Hart, Roger J.

    Early geological modelling and visualisation techniques were limited to manual cross-sections or isometric perspectives. Computer modelling has automated this task to a certain degree, but traditional approaches do not allow iterative validation during the modelling process. When the structure is complex and data sparse, as is often the case in geology, interactive 3-D modelling techniques should be employed that can interrogate new and existing data, guided by the geological experience of the modeller. Using the Vredefort dome in South Africa as a case study, we describe a Seismic Modelling Environment (SME) to demonstrate the potential of this type of computer-based modelling and geological visualisation. SME offers a novel approach to interactive 3-D modelling of complex geological structures using an extension of sweep representations and user-controlled forward modelling with seismic analysis for validation. Incorporation of validation techniques allows early confirmation or rejection of models. Tested by a group of third-year geology students, SME's iterative construction and exploration of a 3-D model clearly provided users with a superior understanding through visualisation. SME has, therefore, potential both as an educational as well as a research tool.

  1. Saudi Arabian seismic deep-refraction profiles; final project report

    USGS Publications Warehouse

    Healy, J.H.; Mooney, W.D.; Blank, H.R.; Gettings, M.E.; Kohler, W.M.; Lamson, R.J.; Leone, L.E.

    1983-01-01

    In February 1978 a seismic deep-refraction profile was recorded by the U.S. Geological Survey along a 1000-km line across the Arabian Shield in western Saudi Arabia. The line begins in Mesozoic cover rocks near Riyadh on the Arabian Platform, leads southwesterly across three major Precambrian tectonic provinces, traverses Cenozoic rocks of the coastal plain near Jizan (Tihamat-Asir), and terminates at the outer edge of the Farasan Bank in the southern Red Sea. More than 500 surveyed recording sites were occupied, including 19 in the Farasan Islands. Six shot points were used: five on land, with most charges placed below the water table in drill holes, and one at sea, with charges placed on the sea floor and detonated from a ship. Slightly more than 61 metric tons of explosives were used in 19 discrete firings. Seismic energy was recorded by 100 newly-developed portable seismic stations deployed in approximately 200 km-long arrays for each firing. Each station consisted of a standard 2-Hz vertical component geophone coupled to a self-contained analog recording instrument equipped with a magnetic-tape cassette. In this final report, we fully document the field and data-processing procedures and present the final seismogram data set as both a digital magnetic tape and as record sections for each shot point. Record sections include a normalized set of seismograms, reduced at 6 km/s, and a true-amplitude set, reduced at 8 km/s, which have been adjusted for amplifier gain, individual shot size, and distance from the shot point. Appendices give recorder station and shot information, digital data set descriptions, computer program listings, arrival times used in the interpretation, and a bibliography of reports published as a result of this project. We used two-dimensional ray-tracing techniques in the data analysis, and our interpretation is based primarily on horizontally layered models. The Arabian Shield is composed, to first-order, of two layers, each about 20 km

  2. 3D Full Seismic Waveform Tomography of NW Turkey and Surroundings

    NASA Astrophysics Data System (ADS)

    Cubuk, Yesim; Fichtner, Andreas; Taymaz, Tuncay

    2015-04-01

    Northward collision of the Arabian plate with the Eurasian plate, and interaction of the motion between dynamic processes originated from the subduction of the African plate beneath the Aegean generated very complex tectonic structures in the study region. Western Turkey is among one of the most active extensional regions in the world and the study area is mainly located where the extensional Aegean and the right-lateral strike-slip North Anatolian Fault Zone (NAFZ) intersects. Therefore, the tectonic framework of the NW Turkey and the Marmara region is mainly characterized by the transition between the strike-slip tectonics to the extensional tectonics. The Sea of Marmara region has been subjected to several active and passive seismic investigations, nevertheless the accurate knowledge on the heterogeneity in the crust and upper mantle beneath the study area still remains enigmatic. On small-scale tomography problems, seismograms strongly reflect the effects of heterogeneities and the scattering properties of the Earth. Thus, the knowledge of high-resolution seismic imaging with an improved 3D radially anisotropic crustal model of the NW Turkey will enable better localization of earthquakes, identification of faults as well as the improvement of the seismic hazard assessment. For this purpose, we aim to develop 3D radially anisotropic subsurface structure of the Sea of Marmara and NW Turkey crust based on full waveform adjoint tomography method. The earthquake data were principally obtained from the Kandilli Observatory and Earthquake Research Institute (KOERI) and Earthquake Research Center (AFAD-DAD) database. In addition to this, some of the seismic waveform data extracted from the Hellenic Unified Seismic Network (HUSN) stations that are located within our study region were also used in this study. We have selected and simulated waveforms of earthquakes with magnitudes 4.0 ≤ Mw ≤ 6.7 occurred in the period between 2007-2014 to determine the 3D velocity

  3. Parallel 3D Simulation of Seismic Wave Propagation in the Structure of Nobi Plain, Central Japan

    NASA Astrophysics Data System (ADS)

    Kotani, A.; Furumura, T.; Hirahara, K.

    2003-12-01

    We performed large-scale parallel simulations of the seismic wave propagation to understand the complex wave behavior in the 3D basin structure of the Nobi Plain, which is one of the high population cities in central Japan. In this area, many large earthquakes occurred in the past, such as the 1891 Nobi earthquake (M8.0), the 1944 Tonankai earthquake (M7.9) and the 1945 Mikawa earthquake (M6.8). In order to mitigate the potential disasters for future earthquakes, 3D subsurface structure of Nobi Plain has recently been investigated by local governments. We referred to this model together with bouguer anomaly data to construct a detail 3D basin structure model for Nobi plain, and conducted computer simulations of ground motions. We first evaluated the ground motions for two small earthquakes (M4~5); one occurred just beneath the basin edge at west, and the other occurred at south. The ground motions from these earthquakes were well recorded by the strong motion networks; K-net, Kik-net, and seismic intensity instruments operated by local governments. We compare the observed seismograms with simulations to validate the 3D model. For the 3D simulation we sliced the 3D model into a number of layers to assign to many processors for concurrent computing. The equation of motions are solved using a high order (32nd) staggered-grid FDM in horizontal directions, and a conventional (4th-order) FDM in vertical direction with the MPI inter-processor communications between neighbor region. The simulation model is 128km by 128km by 43km, which is discritized at variable grid size of 62.5-125m in horizontal directions and of 31.25-62.5m in vertical direction. We assigned a minimum shear wave velocity is Vs=0.4km/s, at the top of the sedimentary basin. The seismic sources for the small events are approximated by double-couple point source and we simulate the seismic wave propagation at maximum frequency of 2Hz. We used the Earth Simulator (JAMSTEC, Yokohama Inst) to conduct such

  4. An Integrated Multi-component Processing and Interpretation Framework for 3D Borehole Seismic Data

    SciTech Connect

    M. Karrenbach

    2004-04-01

    This report covers the October 2003 until March 2004 time period. Work has continued successfully on several tasks 1 through 7. Most of these tasks have been executed independently. Due to availability of manpower during that time period we progressed steadily and completed some of the tasks, while others are still on going. We achieved the goals that we had set up in the task schedule. Reviewing the results of this work period indicates that our plan is on schedule and we did not encounter any unforeseen problems. The work plan will continue as projected. Several independent tasks pursuant the statement of project objectives have been executed simultaneously and are still on-going. This report summarizes the selection, test processing and test flow generation of a relevant 3D borehole seismic high-resolution test dataset. This multi-component data set is suitable for future use in this project due to data quality and unique acquisition characteristics. This report shows initial processing results that supported the data selection scheduled for Task 1. Use of real data is augmented by the creating a 3D layered synthetic geologic model in which multi-component 3D borehole seismic data were generated using 3D ray tracing. A gridded surface representation of the reflection interfaces as well as fully populated velocity grids were generated and archived. The model consists of a moderately dipping geologic setting with horizon undulations. A realistic velocity variation is used in between the three layers. Acquisition was simulated from a set of equidistant source locations at the surface of the model, while a close to vertical VSP well was used to capture the wave field data. The source pattern was close to a staggered grid pattern. Multi-component particle displacements were recorded every 50 ft down with an array length of 4,000 ft. P-P as well as P-S reflections were specified in the resulting wave field. We ensured a large enough aperture with enough fine sampling

  5. Technological advances cut collection costs for offshore 3-D seismic exploration

    SciTech Connect

    Lyle, D.

    1995-07-01

    New work in data collection and processing promises to lower costs drastically for offshore 3-D seismic work. Cost for offshore 3-D work was always a bargain. Since offshore is government property, operators don`t have to pay access fees to landowners. Collection crews don`t have to work around barns, houses and mountains. In spite of that bargain cost, the operator still has to foot the bill for boats, crews, and a tremendous application of computer power. The boats, crews and computer power still are there, but the costs are dropping. The major players in this business in the Gulf of Mexico are Western Geophysical Co., Geco Prakla, Petroleum Geo-Services (PGS) and Digicon Geophysical Corp., and they all know that technology allows them to raise their profit margins while lowering costs to clients.

  6. 3-D Seismic Exploration Project, Ute Indian Tribe, Uintah and Ouray Reservation, Uintah County, Utah

    SciTech Connect

    Eckels, Marc T.

    2002-09-09

    The objectives of this North Hill Creek 3-D seismic survey were to: (1) cover as large an area as possible with available budget; (2) obtain high quality data throughout the depth range of the prospective geologic formations of 2,000' to 12,000' to image both gross structures and more subtle structural and stratigraphic elements; (3) overcome the challenges posed by a hard, reflective sandstone that cropped out or was buried just a few feet below the surface under most of the survey area; and (4) run a safe survey.

  7. Complex patterns of faulting revealed by 3D seismic data at the West Galicia rifted margin

    NASA Astrophysics Data System (ADS)

    Reston, Timothy; Cresswell, Derren; Sawyer, Dale; Ranero, Cesar; Shillington, Donna; Morgan, Julia; Lymer, Gael

    2015-04-01

    The west Galicia margin is characterised by crust thinning to less than 3 km, well-defined fault blocks, which overlie a bright reflection (the S reflector) generally interpreted as a tectonic Moho. The margin exhibits neither voluminous magmatism nor thick sediment piles to obscure the structures and the amount of extension. As such is represents an ideal location to study the process of continental breakup both through seismic imaging and potentially through drilling. Prestack depth migration of existing 2D profiles has strongly supported the interpretation of the S reflector as both a detachment and as the crust-mantle boundary; wide-angle seismic has also shown that the mantle beneath S is serpentinised. Despite the quality of the existing 2D seismic images, a number of competing models have been advanced to explain the formation of this margin, including sequential faulting, polyphase faulting, multiple detachments and the gravitational collapse of the margin over exhumed mantle. As these models, all developed for the Galicia margin, have been subsequently applied to other margins, distinguishing between them has implications not only for the structure of the Galicia margin but for the process of rifting through to breakup more generally. To address these issues in summer of 2013 we collected a 3D combined seismic reflection and wide-angle dataset over this margin. Here we present some of the results of ongoing processing of the 3D volume, focussing on the internal structure of some of the fault blocks that overlies the S detachment. 2D processing of the data shows a relatively simple series of tilted fault block, bound by west-dipping faults that detach downwards onto the bright S reflector. However, inspection of the 3D volume produced by 3D pre-stack time migration reveals that the fault blocks contain a complex set of sedimentary packages, with strata tilted to the east, west, north and south, each package bound by faults. Furthermore, the top of crustal

  8. 3D seismic attribute-assisted analysis of microseismic events in the Marcellus Shale

    NASA Astrophysics Data System (ADS)

    Hart, Ariel Kelton

    Microseismic monitoring is often used during the process of oil and gas exploitation to monitor seismicity that may be triggered by hydraulic fracturing, a common practice in the Appalachian Basin. Anthropogenically-induced minor upward fracture growth is not uncommon in the Marcellus shale; however, in the area of study, significant microseismic activity was registered above the target zone. In order to ascertain whether out-of-zone growth might have been predictable and identify which areas are more likely to experience brittle failure first, 3D seismic and microseismic data were analyzed with a focus on better understanding variations in the acoustic properties associated with unconventional naturally fractured reservoirs. Ant Tracking was used to identify areas of increased local seismic discontinuity, as these areas are generally more intensely deformed and may represent zones of increased fracture intensity. Ant Tracking results reveal discontinuities in the Marcellus are oriented approximately at N52E and N41W; discontinuities do not coincide with N25E trending folds apparent in the 3D seismic, but tend to follow deeper structural trends instead. These discontinuity orientations are interpreted to be a result of continued movement on deeper faults throughout the Paleozoic; these faults possibly acted as seed points for fractures further upsection and potentially led to the precipitation of the large N25E trending imbricate backthrusts seen in the 3D seismic. The reservoir's response to hydraulic fracturing also provided insights into local stress anisotropy and into optimal well and stage spacing needed to maximize drainage area and locate additional wells during the field development phase. Microseismic, well, and pump data used to gauge the reservoir's response to a hydraulic fracture treatment indicated that the number of stages, lateral length, total proppant volume, and fracture energy heavily influence how a well produces. SHmax in the area is oriented

  9. 3D insight into fault geometries, deformation, and fluid-migration within the Hosgri Fault Zone offshore central California: Results from high-resolution 3D seismic data

    NASA Astrophysics Data System (ADS)

    Kluesner, J.; Brothers, D. S.; Johnson, S. Y.; Watt, J. T.

    2015-12-01

    High-resolution 3D seismic P-Cable data and advanced seismic attribute analyses were used to detect and interpret complex strike-slip fault geometries, deformation patterns, and fluid-pathways across a portion of the Hosgri Fault Zone (HFZ) offshore central California. Combination of the fault attribute results with structural analysis provides 3D insight into the geometry and internal structure of restraining and releasing bends, step-over zones, fault convergence zones, and apparent paired fault bends. The 3D seismic volume covers a 13.7 km2 region along the HFZ offshore of Point Sal and was collected in 2012 as part of the PG&E Central California Seismic Imaging Project (PG&E, 2014). Application of the fault attribute workflow isolated and delineated fault strands within the 3D volume. These results revealed that the northern and southern edges of the survey region are characterized by single fault strands that exhibit an approximate 6° change in strike across the 3D volume. Between these single faults strands is a complex network of fault splays, bends, stepovers, and convergence zones. Structural analysis reveals that the southern portion of the HFZ in the region is characterized by transtensional deformation, whereas transpressional-related folding dominates the central and northern portions of the HFZ. In the central region, convergence of the Lions Head Fault from the southeast results in an apparent impinging block, leading to development of a "paired fault bend" to the west. Combination of the fault and "chimney" attribute results indicates a strong connection between faults and fluid-migration pathways. Fluid-pathways are concentrated along discrete faults in the transtensional zones, but appear to be more broadly distributed amongst fault bounded anticlines and structurally controlled traps in the transpressional zones.

  10. 3D interpretation of SHARAD radargram data using seismic processing routines

    NASA Astrophysics Data System (ADS)

    Kleuskens, M. H. P.; Oosthoek, J. H. P.

    2009-04-01

    Ground penetrating radar on board a satellite has entered the field of planetary geology. Two radars enable subsurface observations of Mars. In 2003, ESA launched the Mars Express equipped with MARSIS, a low frequency radar which was able to detect only the base of the ice caps. Since December 2006, the Shallow Radar (SHARAD) of Agenzia Spaziale Italiana (ASI) on board the NASA Mars Reconnaissance Orbiter (MRO) is active in orbit around Mars. The SHARAD radar covers the frequency band between 15 and 25 MHz. The vertical resolution is about 15 m in free space. The horizontal resolution is 300-1000 m along track and 1500-8000 m across track. The radar penetrates the subsurface of Mars up to 2 km deep, and is capable of detecting multiple reflections in the ice caps of Mars. Considering the scarcity of planetary data relative to terrestrial data, it is essential to combine all available types of data of an area of interest. Up to now SHARAD data has only been interpreted separately as 2D radargrams. The Geological Survey of the Netherlands has decades of experience in interpreting 2D and 3D seismic data of the Dutch subsurface, especially for the 3D interpretation of reservoir characteristics of the deeper subsurface. In this abstract we present a methodology which can be used for 3D interpretation of SHARAD data combined with surface data using state-of-the art seismic software applied in the oil and gas industry. We selected a region that would be most suitable to demonstrate 3D interpretation. The Titania Lobe of the North Polar ice cap was selected based on the abundancy of radar data and the complexity of the ice lobe. SHARAD data is released to the scientific community via the Planetary Data System. It includes ‘Reduced Data Records' (RDR) data, a binary format which contains the radargram. First the binary radargram data and corresponding coordinates were combined and converted to the commonly used seismic seg-y format. Second, we used the reservoir

  11. New results from a 3D seismic academic dataset across the west Galicia margin

    NASA Astrophysics Data System (ADS)

    Lymer, Gaël; Cresswell, Derren; Reston, Tim; Stevenson, Carl; Sawyer, Dale

    2016-04-01

    The west Galicia margin (western Spain) is a magma-poor margin and has limited sedimentary cover, providing ideal conditions to study the processes of continental extension and break-up through seismic imaging. The margin is characterised by hyper-extended continental crust, well defined rotated faults blocks with associated syn-kinematic sedimentary wedges, and exhumed serpentinized continental mantle. Faulted blocks overlie a bright reflection, the S reflector, generally interpreted as both a detachment and the crust-mantle boundary. But open questions remain concerning the role of the S detachment in extension leading to breakup. To study further the S reflection and its role in continental breakup, a new 3D high-resolution multi-channel seismic dataset has been acquired over the Galicia margin during summer 2013. It consists in 800 inlines and 5000 crosslines distributed on a ~680 km2 areal. This 3D dataset is thus the largest academic one of its kind. It extends across the edge of the continental crust and captures the 3D nature of extension and break-up of the northern Atlantic continental margins. Here we present some results from our interpretations of the 3D volume, which allow various horizons, including the base of the post-rift sedimentary cover, the top basement and the S reflector, to be mapped out in 3D. These maps provide 3D views of the margin structure and also reveal the texture of each horizon. We also focus on the internal structure of some of the faulted blocks through interpretation of the crustal normal faults. The main normal faults are generally connected downward on the S reflector, revealing strong interactions between crustal thinning and the S. The half-grabens and the fault blocks are dominantly N-S oriented, but the crustal structures vary both along strike and cross strike. We particularly observe an intriguingly NW-SE trend, highlighted by a pronounced low within the crest of the fault blocks. We also observe this trend from

  12. SEISVIZ3D: Stereoscopic system for the representation of seismic data - Interpretation and Immersion

    NASA Astrophysics Data System (ADS)

    von Hartmann, Hartwig; Rilling, Stefan; Bogen, Manfred; Thomas, Rüdiger

    2015-04-01

    The seismic method is a valuable tool for getting 3D-images from the subsurface. Seismic data acquisition today is not only a topic for oil and gas exploration but is used also for geothermal exploration, inspections of nuclear waste sites and for scientific investigations. The system presented in this contribution may also have an impact on the visualization of 3D-data of other geophysical methods. 3D-seismic data can be displayed in different ways to give a spatial impression of the subsurface.They are a combination of individual vertical cuts, possibly linked to a cubical portion of the data volume, and the stereoscopic view of the seismic data. By these methods, the spatial perception for the structures and thus of the processes in the subsurface should be increased. Stereoscopic techniques are e. g. implemented in the CAVE and the WALL, both of which require a lot of space and high technical effort. The aim of the interpretation system shown here is stereoscopic visualization of seismic data at the workplace, i.e. at the personal workstation and monitor. The system was developed with following criteria in mind: • Fast rendering of large amounts of data so that a continuous view of the data when changing the viewing angle and the data section is possible, • defining areas in stereoscopic view to translate the spatial impression directly into an interpretation, • the development of an appropriate user interface, including head-tracking, for handling the increased degrees of freedom, • the possibility of collaboration, i.e. teamwork and idea exchange with the simultaneous viewing of a scene at remote locations. The possibilities offered by the use of a stereoscopic system do not replace a conventional interpretation workflow. Rather they have to be implemented into it as an additional step. The amplitude distribution of the seismic data is a challenge for the stereoscopic display because the opacity level and the scaling and selection of the data have to

  13. Validating 3D Seismic Velocity Models Using the Spectral Element Method

    NASA Astrophysics Data System (ADS)

    Maceira, M.; Rowe, C. A.; Allen, R. M.; Obrebski, M. J.

    2010-12-01

    As seismic instrumentation, data storage and dissemination and computational power improve, seismic velocity models attempt to resolve smaller structures and cover larger areas. However, it is unclear how accurate these velocity models are and, while the best models available are used for event determination, it is difficult to put uncertainties on seismic event parameters. Model validation is typically done using resolution tests that assume the imaging theory used is accurate and thus only considers the impact of the data coverage on resolution. We present the results of a more rigorous approach to model validation via full three-dimensional waveform propagation using Spectral Element Methods (SEM). This approach makes no assumptions about the theory used to generate the models but require substantial computational resources. We first validate 3D tomographic models for the Western USA generated using both ray-theoretical and finite-frequency methods. The Dynamic North America (DNA) Models of P- and S- velocity structure (DNA09-P and DNA09-S) use teleseismic body-wave traveltime residuals recorded at over 800 seismic stations provided by the Earthscope USArray and regional seismic networks. We performed systematic computations of synthetics for the dataset used to generate the DNA models. Direct comparison of these synthetic seismograms to the actual observations allows us to accurately assess and validate the models. Implementation of the method for a densely instrumented region such as that covered by the DNA model provides a useful testbed for the validation methods that we will subsequently apply to other, more challenging study areas.

  14. 3D geometry of the strain-field at transform plate boundaries: Implications for seismic rupture

    SciTech Connect

    Bodin, P.; Bilham, R. |

    1994-11-01

    We examine the amplitude and distribution of slip on vertical frictionless faults in the zone of concentrated shear strain that is characteristic of transform plate boundaries. We study both a 2D and a 3D approximation to this strain field. Mean displacements on ruptures within the zone of concentrated shear strain are proportional to the shear strain at failure when they are short, and are limited by plate displacements since the last major earthquake when they are long. The transition between these two behaviors occurs when the length of the dislocation approaches twice the thickness of the seismogenic crust, approximately the breadth of the zone of concentrated shear strain observed geodetically at transform plate boundaries. This result explains the observed non-linear scaling relation between seismic moment and rupture length. A geometrical consequence of the 3D model, in which the strain-field tapers downward, is that moderate earthquakes with rupture lengths similar to the thickness of the crust tend to slip more at depth than near the surface. Seismic moments estimated from surface slip in moderate earthquakes (M less than or equal to 7) will thus be underestimated. Shallow creep, if its along-strike dimension is extensive, can reduce a surface slip deficit that would otherwise develop on faults on which M less than 7 events are typical. In the absence of surface creep or other forms of off-fault deformation great earthquakes may be necessary features of transform boundaries with downward-tapering strain-fields.

  15. Effect of damping and yielding on the seismic response of 3D steel buildings with PMRF.

    PubMed

    Reyes-Salazar, Alfredo; Haldar, Achintya; Rodelo-López, Ramon Eduardo; Bojórquez, Eden

    2014-01-01

    The effect of viscous damping and yielding, on the reduction of the seismic responses of steel buildings modeled as three-dimensional (3D) complex multidegree of freedom (MDOF) systems, is studied. The reduction produced by damping may be larger or smaller than that of yielding. This reduction can significantly vary from one structural idealization to another and is smaller for global than for local response parameters, which in turn depends on the particular local response parameter. The uncertainty in the estimation is significantly larger for local response parameter and decreases as damping increases. The results show the limitations of the commonly used static equivalent lateral force procedure where local and global response parameters are reduced in the same proportion. It is concluded that estimating the effect of damping and yielding on the seismic response of steel buildings by using simplified models may be a very crude approximation. Moreover, the effect of yielding should be explicitly calculated by using complex 3D MDOF models instead of estimating it in terms of equivalent viscous damping. The findings of this paper are for the particular models used in the study. Much more research is needed to reach more general conclusions.

  16. Effect of Damping and Yielding on the Seismic Response of 3D Steel Buildings with PMRF

    PubMed Central

    Haldar, Achintya; Rodelo-López, Ramon Eduardo; Bojórquez, Eden

    2014-01-01

    The effect of viscous damping and yielding, on the reduction of the seismic responses of steel buildings modeled as three-dimensional (3D) complex multidegree of freedom (MDOF) systems, is studied. The reduction produced by damping may be larger or smaller than that of yielding. This reduction can significantly vary from one structural idealization to another and is smaller for global than for local response parameters, which in turn depends on the particular local response parameter. The uncertainty in the estimation is significantly larger for local response parameter and decreases as damping increases. The results show the limitations of the commonly used static equivalent lateral force procedure where local and global response parameters are reduced in the same proportion. It is concluded that estimating the effect of damping and yielding on the seismic response of steel buildings by using simplified models may be a very crude approximation. Moreover, the effect of yielding should be explicitly calculated by using complex 3D MDOF models instead of estimating it in terms of equivalent viscous damping. The findings of this paper are for the particular models used in the study. Much more research is needed to reach more general conclusions. PMID:25097892

  17. 3-D seismic improves structural mapping of a gas storage reservoir (Paris basin)

    SciTech Connect

    Huguet, F. ); Pinson, C. )

    1993-09-01

    In the Paris basin, anticlinal structures with closure of no more than 80 m and surface area of a few km[sup 2] are used for underground gas storage. At Soings-en-Sologne, a three-dimensional (3-D) survey (13 km[sup 2]) was carried out over such a structure to establish its exact geometry and to detail its fault network. Various reflectors were picked automatically on the migrated data: the top of the Kimmeridgian, the top of the Bathoinian and the base of the Hettangian close to the top of the reservoir. The isochron maps were converted into depth using data from 12 wells. Horizon attributes (amplitude, dip, and azimuth) were used to reconstruct the fault's pattern with much greater accuracy than that supplied by interpretation from previous two-dimensional seismic. The Triassic and the Jurassic are affected by two systems of conjugate faults (N10-N110, inherited from the Hercynian basement and N30-N120). Alternating clay and limestone are the cause of numerous structural disharmonies, particularly on both sides of the Bathonian. Ridges associated with N30-N120 faults suggest compressive movements contemporaneous with the tertiary events. The northern structure in Soings-en-Sologne thus appear to be the result of polyphased tectonics. Its closure (25 m), which is associated either with dips or faults, is described in detail by 3-D seismic, permitting more accurate forecast of the volume available for gas storage.

  18. Effect of damping and yielding on the seismic response of 3D steel buildings with PMRF.

    PubMed

    Reyes-Salazar, Alfredo; Haldar, Achintya; Rodelo-López, Ramon Eduardo; Bojórquez, Eden

    2014-01-01

    The effect of viscous damping and yielding, on the reduction of the seismic responses of steel buildings modeled as three-dimensional (3D) complex multidegree of freedom (MDOF) systems, is studied. The reduction produced by damping may be larger or smaller than that of yielding. This reduction can significantly vary from one structural idealization to another and is smaller for global than for local response parameters, which in turn depends on the particular local response parameter. The uncertainty in the estimation is significantly larger for local response parameter and decreases as damping increases. The results show the limitations of the commonly used static equivalent lateral force procedure where local and global response parameters are reduced in the same proportion. It is concluded that estimating the effect of damping and yielding on the seismic response of steel buildings by using simplified models may be a very crude approximation. Moreover, the effect of yielding should be explicitly calculated by using complex 3D MDOF models instead of estimating it in terms of equivalent viscous damping. The findings of this paper are for the particular models used in the study. Much more research is needed to reach more general conclusions. PMID:25097892

  19. DEVELOPMENT OF A 400 LEVEL 3C CLAMPED DOWNHOLE SEISMIC RECEIVER ARRAY FOR 3D BOREHOLE SEISMIC IMAGING OF GAS RESERVOIRS

    SciTech Connect

    Bjorn N.P Paulsson

    2002-05-01

    Borehole seismology is the highest resolution geophysical imaging technique available to the oil and gas industry for characterization and monitoring of oil and gas reservoirs. However, the industry's ability to economically do high resolution 3D imaging of deep and complex gas reservoirs using borehole seismology is currently frustrated by the lack of the acquisition technology necessary to record the large volumes of the high frequency, high signal-to-noise-ratio borehole seismic data needed to do 3D imaging. This proposal takes direct aim at this shortcoming. P/GSI is developing a 400 level 3C clamped downhole seismic receiver array for borehole seismic 3D imaging. This array will remove the acquisition barrier to record the necessary volumes of data to do high resolution 3D VSP or 3D cross well seismic imaging. 3D VSP and long range Cross-Well Seismology (CWS) are two of the borehole seismic techniques that will allow the Gas industry to take the next step in their quest for higher resolution images of the gas reservoirs. Today only a fraction of the original Oil or Gas in place is produced when reservoirs are considered depleted. This is primarily due to our lack of understanding of the detailed compartmentalization of the oil and gas reservoirs. The 400 level 3C borehole seismic receiver array will allow for economic use of 3D borehole seismic imaging for reservoir characterization and monitoring. By using 3C surface seismic or borehole seismic sources the 400 level receiver array will furthermore facilitate 9C reservoir imaging. The 9C borehole seismic data will provide P, SH and SV information for imaging of the complex deep gas reservoirs and allow quantitative prediction of the rock and the fluid types. The data quality and the data volumes from a 400 level 3C array will allow us to develop the data processing technology necessary for high resolution reservoir imaging.

  20. DEVELOPMENT OF A 400 LEVEL 3C CLAMPED DOWNHOLE SEISMIC RECEIVER ARRAY FOR 3D BOREHOLE SEISMIC IMAGING OF GAS RESERVOIRS

    SciTech Connect

    Bjorn N.P. Paulsson

    2002-09-01

    Borehole seismology is the highest resolution geophysical imaging technique available to the oil and gas industry for characterization and monitoring of oil and gas reservoirs. However, the industry's ability to economically do high resolution 3D imaging of deep and complex gas reservoirs using borehole seismology is currently frustrated by the lack of the acquisition technology necessary to record the large volumes of the high frequency, high signal-to-noise-ratio borehole seismic data needed to do 3D imaging. This proposal takes direct aim at this shortcoming. P/GSI is developing a 400 level 3C clamped downhole seismic receiver array for borehole seismic 3D imaging. This array will remove the acquisition barrier to record the necessary volumes of data to do high resolution 3D VSP or 3D cross well seismic imaging. 3D VSP and long range Cross-Well Seismology (CWS) are two of the borehole seismic techniques that will allow the Gas industry to take the next step in their quest for higher resolution images of the gas reservoirs. Today only a fraction of the original Oil or Gas in place is produced when reservoirs are considered depleted. This is primarily due to our lack of understanding of the detailed compartmentalization of the oil and gas reservoirs. The 400 level 3C borehole seismic receiver array will allow for economic use of 3D borehole seismic imaging for reservoir characterization and monitoring. By using 3C surface seismic or 3C borehole seismic sources the 400 level receiver array will furthermore facilitate 9C reservoir imaging. The 9C borehole seismic data will provide P, SH and SV information for imaging of the complex deep gas reservoirs and allow quantitative prediction of the rock and the fluid types. The data quality and the data volumes from a 400 level 3C array will allow us to develop the data processing technology necessary for high resolution reservoir imaging.

  1. 3D refraction correction and extraction of clinical parameters from spectral domain optical coherence tomography of the cornea.

    PubMed

    Zhao, Mingtao; Kuo, Anthony N; Izatt, Joseph A

    2010-04-26

    Capable of three-dimensional imaging of the cornea with micrometer-scale resolution, spectral domain-optical coherence tomography (SDOCT) offers potential advantages over Placido ring and Scheimpflug photography based systems for accurate extraction of quantitative keratometric parameters. In this work, an SDOCT scanning protocol and motion correction algorithm were implemented to minimize the effects of patient motion during data acquisition. Procedures are described for correction of image data artifacts resulting from 3D refraction of SDOCT light in the cornea and from non-idealities of the scanning system geometry performed as a pre-requisite for accurate parameter extraction. Zernike polynomial 3D reconstruction and a recursive half searching algorithm (RHSA) were implemented to extract clinical keratometric parameters including anterior and posterior radii of curvature, central cornea optical power, central corneal thickness, and thickness maps of the cornea. Accuracy and repeatability of the extracted parameters obtained using a commercial 859nm SDOCT retinal imaging system with a corneal adapter were assessed using a rigid gas permeable (RGP) contact lens as a phantom target. Extraction of these parameters was performed in vivo in 3 patients and compared to commercial Placido topography and Scheimpflug photography systems. The repeatability of SDOCT central corneal power measured in vivo was 0.18 Diopters, and the difference observed between the systems averaged 0.1 Diopters between SDOCT and Scheimpflug photography, and 0.6 Diopters between SDOCT and Placido topography.

  2. Waveform Tomography and its Application to Marine Seismic Refraction Data

    NASA Astrophysics Data System (ADS)

    Nag, S.; Canales, J.

    2008-05-01

    We explore the applicability of two-dimensional seismic waveform tomography to conventional deep-water, long- offset (10s of kilometers) seismic refraction experiments in which ocean-bottom receivers and sea-surface sources are usually spaced several kilometers and a few 100s of meters apart, respectively. In particular, we test the application of waveform tomography to ocean-bottom seismometer (hydrophone) data collected along the rift valley of the Mid-Atlantic Ridge near 26°N in the vicinity of the active TAG hydrothermal system, which is thought to be located on the hanging wall of an active oceanic detachment fault [e.g., Canales et al., Geochem. Geophys. Geosyst., 8, Q08004, 2007]. If successful, waveform tomography could provide detailed velocity information related to fluid flow and alternation along the fault zone that cannot be obtained from traveltime tomography analyses. We use the frequency-domain, elastic-wave equation approach of R.G. Pratt [Geophysics, 64, 888-901, 1999]. Initial data processing consisted of spherical divergence corrections, wavelet shaping and predictive deconvolution using a special design and application window data to obtain a smooth, random amplitude spectrum sans the bubble pulse. Other processing steps included filtering, windowing and offset-dependent amplitude normalization with respect to forward modeled synthetics. Forward modeling is done via the central-difference scheme of finite difference method with the primary modeling parameters being the boundary conditions, time-domain damping parameter to prevent wraparound energy, appropriate quality factor and dispersion coefficient. Source and velocity inversion is done at selected frequencies using "efficient waveform inversion" [Sirgue and Pratt, Geophysics, 69, 231-248 2004] to minimize the misfit of data residuals via the gradient method. Inversion parameters (offset weighting, depth tapering, gradient wave-number filtering and masking) were tested and decided on a

  3. Seismic characteristics of central Brazil crust and upper mantle: A deep seismic refraction study

    USGS Publications Warehouse

    Soares, J.E.; Berrocal, J.; Fuck, R.A.; Mooney, W.D.; Ventura, D.B.R.

    2006-01-01

    A two-dimensional model of the Brazilian central crust and upper mantle was obtained from the traveltime interpretation of deep seismic refraction data from the Porangatu and Cavalcante lines, each approximately 300 km long. When the lines were deployed, they overlapped by 50 km, forming an E-W transect approximately 530 km long across the Tocantins Province and western Sa??o Francisco Craton. The Tocantins Province formed during the Neoproterozoic when the Sa??o Francisco, the Paranapanema, and the Amazon cratons collided, following the subduction of the former Goia??s ocean basin. Average crustal VP and VP/VS ratios, Moho topography, and lateral discontinuities within crustal layers suggest that the crust beneath central Brazil can be associated with major geological domains recognized at the surface. The Moho is an irregular interface, between 36 and 44 km deep, that shows evidences of first-order tectonic structures. The 8.05 and 8.23 km s-1 P wave velocities identify the upper mantle beneath the Porangatu and Cavalcante lines, respectively. The observed seismic features allow for the identification of (1) the crust has largely felsic composition in the studied region, (2) the absence of the mafic-ultramafic root beneath the Goia??s magmatic arc, and (3) block tectonics in the foreland fold-and-thrust belt of the northern Brasi??lia Belt during the Neoproterozoic. Seismic data also suggested that the Bouguer gravimetric discontinuities are mainly compensated by differences in mass distribution within the lithospheric mantle. Finally, the Goia??s-Tocantins seismic belt can be interpreted as a natural seismic alignment related to the Neoproterozoic mantle domain. Copyright 2006 by the American Geophysical Union.

  4. Testing & Validating: 3D Seismic Travel Time Tomography (Detailed Shallow Subsurface Imaging)

    NASA Astrophysics Data System (ADS)

    Marti, David; Marzan, Ignacio; Alvarez-Marron, Joaquina; Carbonell, Ramon

    2016-04-01

    A detailed full 3 dimensional P wave seismic velocity model was constrained by a high-resolution seismic tomography experiment. A regular and dense grid of shots and receivers was use to image a 500x500x200 m volume of the shallow subsurface. 10 GEODE's resulting in a 240 channels recording system and a 250 kg weight drop were used for the acquisition. The recording geometry consisted in 10x20m geophone grid spacing, and a 20x20 m stagered source spacing. A total of 1200 receivers and 676 source points. The study area is located within the Iberian Meseta, in Villar de Cañas (Cuenca, Spain). The lithological/geological target consisted in a Neogen sedimentary sequence formed from bottom to top by a transition from gyspum to silstones. The main objectives consisted in resolving the underground structure: contacts/discontinuities; constrain the 3D geometry of the lithology (possible cavities, faults/fractures). These targets were achieved by mapping the 3D distribution of the physical properties (P-wave velocity). The regularly space dense acquisition grid forced to acquire the survey in different stages and with a variety of weather conditions. Therefore, a careful quality control was required. More than a half million first arrivals were inverted to provide a 3D Vp velocity model that reached depths of 120 m in the areas with the highest ray coverage. An extended borehole campaign, that included borehole geophysical measurements in some wells provided unique tight constraints on the lithology an a validation scheme for the tomographic results. The final image reveals a laterally variable structure consisting of four different lithological units. In this methodological validation test travel-time tomography features a high capacity of imaging in detail the lithological contrasts for complex structures located at very shallow depths.

  5. Q AS A LITHOLOGICAL/HYDROCARBON INDICATOR: FROM FULL WAVEFORM SONIC TO 3D SURFACE SEISMIC

    SciTech Connect

    Jorge O. Parra; C.L. Hackert; L. Wilson; H.A. Collier; J. Todd Thomas

    2006-03-31

    The goal of this project was to develop a method to exploit viscoelastic rock and fluid properties to greatly enhance the sensitivity of surface seismic measurements to the presence of hydrocarbon saturation. To reach the objective, Southwest Research Institute scientists used well log, lithology, production, and 3D seismic data from an oil reservoir located on the Waggoner Ranch in north central Texas. The project was organized in three phases. In the first phase, we applied modeling techniques to investigate seismic- and acoustic-frequency wave attenuation and its effect on observable wave attributes. We also gathered existing data and acquired new data from the Waggoner Ranch field, so that all needed information was in place for the second phase. During the second phase, we developed methods to extract attenuation from borehole acoustic and surface seismic data. These methods were tested on synthetic data constructed from realistic models and real data. In the third and final phase of the project, we applied this technology to a full data set from the Waggoner site. The results presented in this Final Report show that geological conditions at the site did not allow us to obtain interpretable results from the Q processing algorithm for 3D seismic data. However, the Q-log processing algorithm was successfully applied to full waveform sonic data from the Waggoner site. A significant part of this project was technology transfer. We have published several papers and conducted presentations at professional conferences. In particular, we presented the Q-log algorithm and applications at the Society of Exploration Geophysicists (SEG) Development and Production Forum in Austin, Texas, in May 2005. The presentation attracted significant interest from the attendees and, at the request of the SEG delegates, it was placed on the Southwest Research Institute Internet site. The presentation can be obtained from the following link: http://www.swri.org/4org/d15/elecsys

  6. Next-generation seismic experiments - II: wide-angle, multi-azimuth, 3-D, full-waveform inversion of sparse field data

    NASA Astrophysics Data System (ADS)

    Morgan, Joanna; Warner, Michael; Arnoux, Gillean; Hooft, Emilie; Toomey, Douglas; VanderBeek, Brandon; Wilcock, William

    2016-02-01

    3-D full-waveform inversion (FWI) is an advanced seismic imaging technique that has been widely adopted by the oil and gas industry to obtain high-fidelity models of P-wave velocity that lead to improvements in migrated images of the reservoir. Most industrial applications of 3-D FWI model the acoustic wavefield, often account for the kinematic effect of anisotropy, and focus on matching the low-frequency component of the early arriving refractions that are most sensitive to P-wave velocity structure. Here, we have adopted the same approach in an application of 3-D acoustic, anisotropic FWI to an ocean-bottom-seismometer (OBS) field data set acquired across the Endeavour oceanic spreading centre in the northeastern Pacific. Starting models for P-wave velocity and anisotropy were obtained from traveltime tomography; during FWI, velocity is updated whereas anisotropy is kept fixed. We demonstrate that, for the Endeavour field data set, 3-D FWI is able to recover fine-scale velocity structure with a resolution that is 2-4 times better than conventional traveltime tomography. Quality assurance procedures have been employed to monitor each step of the workflow; these are time consuming but critical to the development of a successful inversion strategy. Finally, a suite of checkerboard tests has been performed which shows that the full potential resolution of FWI can be obtained if we acquire a 3-D survey with a slightly denser shot and receiver spacing than is usual for an academic experiment. We anticipate that this exciting development will encourage future seismic investigations of earth science targets that would benefit from the superior resolution offered by 3-D FWI.

  7. Significant reserve additions from oligocene Hackberry Sands utilizing 3-D seismic, upper Texas and Louisiana Gulf Coast

    SciTech Connect

    Zamboras, R.L.

    1995-10-01

    The Oligocene Hackberry sands of the Hackberry Embayment represent a complex and elusive exploration target. 3-D seismic evaluation along the headward erosional limits of the embayment provides a reconstructive framework of tectonic and sedimentation patterns which facilitate hydrocarbon exploration. The 3-D seismic along the Orange County, Texas portion of the Oligocene Hackberry trend indicates: (1) similarities of Hackberry structural and depositional setting to that of the underlying Eocene Yegua Formation; (2) four distinct cyclical sedimentation episodes associated with basin floor slump faulting: (3) the usefulness of seismic attributes as direct hydrocarbon indicators, and (4) the potential for significant oil and gas reserves additions in a mature trend. The Hackberry embayment represents a microcosm of the basin structural and depositional processes. Utilizing 3-D seismic to lower risk and finding cost will renew interest in trends such as the Hackberry of the Upper Texas-Louisiana Gulf Coast.

  8. Near-surface velocity structure from borehole and refraction seismic surveys

    SciTech Connect

    Parry, D.; Lawton, D.C.

    1994-12-31

    Seismic refraction and borehole reflection data have been used in conjunction with other geophysical tools to characterize the near-surface geology in the vicinity of a shallow well near Calgary, Alberta. The investigated section is comprised primarily of glacial tills and gravels. Seismic waves generated in the lower gravel units travel as compressional waves up to the till/gravel interface, where they are converted to shear waves upon transmission. Velocity structure from a reverse vertical seismic profile (RVSP) survey agrees closely with that from refraction surveying.

  9. Analysis of Paleokarst Sinkholes in the Arkoma Basin using 3-D Seismic

    NASA Astrophysics Data System (ADS)

    Kumbalek, Michael

    Paleokarst features are important to understand, both with regards to research geologists and to the petroleum industry. In terms of geology, understanding paleokarst features can yield more information about the depositional and surface environments of past times, and how diagenetic alteration affected the environment during the formation of karst features. In the petroleum industry, paleokarst features can have positive or negative consequence resulting in a potential reservoir with enhanced porosity due to the paleokarst features, or as a geo-hazard to prepare for or avoid when drilling. Inspired by issues faced when drilling in the Ft. Worth basin, this study utilizes multiple 3-D seismic surveys and subsurface well control to map paleokarsts within the Viola Limestone in the Arkoma Basin. Calculated seismic attribute volumes used to identify paleokarst sinkholes within the Viola Group include coherency and curvature attributes. ImageJ software was used to aid in counting and measuring paleokarst sinkholes identified using seismic mapping, coherency, and curvature attribute volumes. In addition to mapping, a cumulative distribution plot was produced from the diameters of the seismically mapped paleokarst sinkholes, allowing for an estimate to be made as to what the total amount of paleokarst sinkholes are within the study area. The methods detailed in this study proved to be effective in mapping and analyzing paleokarst sinkholes within the Viola Group. The paleokarst sinkholes mapped were determined to have been formed on the outer edge of the Southern Oklahoma aulacogen, as a result of the Sylvan/Viola unconformity. In addition to this, it has been determined that these paleokarst sinkholes are linked in formation to visually similar paleokarst sinkholes located in the Ellenburger Group in the Fort Worth Basin.

  10. High-resolution 3D seismic investigation of giant seafloor craters in the Barents Sea

    NASA Astrophysics Data System (ADS)

    Waage, Malin; Bünz, Stefan; Andreassen, Karin

    2016-04-01

    Multiple giant craters exist on the seafloor in an area of ~ 100 km2 east of Bear Island Trough in the west-central Barents Sea. It has been hypothesized that these craters might have been caused by gas eruptions following the last deglaciation. Gas seepage from the seafloor occurs abundantly in this area. The crater area is still likely to represent one of the largest hot-spots for shallow marine methane release in the arctic. In summer 2015, we acquired high-resolution P-Cable 3D seismic data in this area covering several of the craters and their associated pingo structures. Due to the shallow and hard Triassic bedrock, penetration of the seismic signals is limited to approximately 450 ms bsf. The crater structures are up to 1 km wide and 40 m deep. Pingo structures occur on the rim of some of the craters and are up to 700 m wide and up to 15 m high above the surrounding seafloor. The 3D seismic data reveals faults, fracture networks and weakness zone that resemble pipes or similar vertical, focused fluid-flow structures in the Triassic sedimentary rocks below the craters. The principal orientation of the faults is in a ~ NW-SE direction that coincides with regional faulting from Permo-Triassic extension. The seismic data also show high-amplitude anomalies beneath some of representing shallow gas accumulations that might be the intermediate source of the gas seepage. This might suggest that craters are caused by high pressured gas that migrated from deeper petroleum systems and accumulated in the shallow Triassic rocks during the last glaciation. Previous work indicate that craters of similar size are likely a cause of enormous blow-outs of gas. Our study discusses the formation mechanisms and timing of these potential blow-out craters and whether they formed during the last deglaciation, when this area was likely quite unstable as severe glacial erosion caused localized high isostatic rebound rates here. We also investigate the role of gas hydrates that might

  11. Development of seismic anisotropy during subduction-induced 3D mantle flow

    NASA Astrophysics Data System (ADS)

    Faccenda, M.; capitanio, F. A.

    2012-12-01

    Subduction zones are convergent margins where the rigid lithosphere sinks into the Earth's mantle inducing complex 3D flow patterns. Seismic anisotropy generated by strain-induced lattice/crystal preferred orientation (LPO/CPO) of intrinsically anisotropic minerals is commonly used to study flow in the mantle and its relations with plate motions. As the development of seismic anisotropy due to upper and lower plate motions occurs at depths and timescales such that it is not directly observable, numerical modelling provides a useful tool to investigate these processes. We computed the seismic anisotropy of dry olivine-enstatite aggregates due to strain-induced LPO in 3D mechanical models of dynamic subduction by using, respectively, D-Rex and Underworld. Subsequently, FSTRACK was used to compute seismogram synthetics and SKS splitting patterns. We found that for relatively narrow subducting plates, retreat motions are maximized producing strong subslab trench-parallel anisotropy. Here, synthetic data reproduce quite well the observations in analogous subduction systems like Calabria and South Sandwich, where the fast azimuths orients parallel to the trench in the forearc and follow the toroidal flow patterns on the slab edges. Furthermore, we found that the amount of anisotropy is proportional to the amount of subduction, while it does not depend on the rate at which the plate subducts. On the other hand, larger subducting plates subducts mainly by plate advance, favoring poloidal motions and trench-perpendicular anisotropy. Additional Earth-like plate geometries involving along-trench variation of the subducting plate age that induces differential slab retreat motions are considered. We also tested different olivine fabrics (A, B, C, E type), yielding distinct SKS splitting patterns that may help to constrain the composition of the upper mantle. Although more sophisticated numerical modelling taking into account temperature-dependent mantle rock rheologies and P

  12. 3-D Seismic Imaging of Sedimentary Underplating at the Corner of the Cascadia Mantle Wedge

    NASA Astrophysics Data System (ADS)

    Calvert, A. J.; Preston, L. A.; Farahbod, A. M.

    2010-12-01

    In several subduction zones, teleseismic surveys have identified landward dipping zones with anomalously low seismic velocities at depths >20 km, which are interpreted to be the subducting oceanic crust. In the Cascadia subduction zone, two teleseismic profiles (CAFE and POLARIS) lie in an area of dense seismicity and mostly within a group of active source, crustal-scale seismic surveys that were acquired between 1995 and 1999. A 3-D P wave velocity model, which extends to depths as great as 65 km, has been derived by an integrated tomographic inversion of the areally distributed earthquakes and active source data. To identify the low velocity zone in the velocity model, we compare coincident linear sections extracted from the model with the P and S wave velocity perturbations derived from the teleseismic data. Given the uncertainties in the analysis of the different datasets, it is probable that the analyses of the teleseismic data and the tomographic inversion of local seismic travel time data have identified the same landward dipping low velocity zone. In the 3-D tomographic velocity model, the low velocity zone, which can be traced along strike between the two 2-D teleseismic surveys, outcrops in the Olympic Mountains where rocks of the accretionary wedge have been exhumed. The oceanic crust, which is located by PmP reflections, underlies the more shallowly dipping low velocity zone. At depths of 35-40 km, the low velocity zone separates from the descending plate and decreases in amplitude. The plate interface may be located at the top of the basaltic oceanic crust, i.e. near the base of the low velocity zone, but the boundary between the two plates could also be a vertically distributed shear zone corresponding to the deeper part of the low velocity region. At depth, the low velocity zone corresponds to previously identified seismic reflections, which we suggest represent rocks sheared at, or immediately above, the inter-plate boundary. The seismic reflectors

  13. An Integrated Multi-component Processing and Interpretation Framework for 3D Borehole Seismic Data

    SciTech Connect

    M. Karrenbach

    2004-10-15

    This report covers the April 2004-September 2004 time period. Work has been performed successfully on several tasks 1 through 16. Part of this work has been reported in 15418R03. Most of portions of these tasks have been executed independently. We progressed steadily and completed some of the sub-tasks, while others are still on going. We achieved the goals that we had set up in the task schedule. Reviewing the results of this work period indicates that our plan is solid and we did not encounter any unforeseen problems. The work plan will continue as scheduled. A midyear review will be presented in November or December 2004. Several independent tasks pursuant the statement of project objectives have been executed simultaneously and are still on-going. Use of real seismic test data is augmented by the creation a 3D ray tracing synthetic test data. We used the previously constructed 3D layered model and simulated data acquisition from a set of circular source locations at the surface of the model, while a close to vertical VSP well was used to capture the wave field data. The source pattern was optimized with respect to Fresnel zone width at the target depth. Multi-component particle displacements were recorded every 50 ft down with an array length of 4,000 ft. P-P as well as P-S reflections were specified in the resulting wave field. We ensured a large enough aperture with enough fine sampling to perform advanced processing, imaging and analysis tests in the future during this project. We constantly improved the interfacing of our software libraries with newly designed 3C display classes and mechanisms. We used the previously implemented 3C Work Bench tool as the primary prototyping tool. This work bench allows to load as well as manipulate and display data items in a flexible manner. We continued to demonstrate its basic functionality by loading source maps, horizons, seismic and velocity volumes, well logs into the tool, performing basic QC steps as is necessary

  14. Crustal structure beneath the eastern Swiss Alps derived from seismic refraction data

    NASA Astrophysics Data System (ADS)

    Ye, S.; Ansorge, J.; Kissling, E.; Mueller, St.

    1995-02-01

    The eastern part of the Swiss Central Alps is densely covered by a network of seismic refraction and wide-angle reflection profiles recorded mostly parallel to the tectonic strike of the Alps and along the newly acquired N-S-oriented European Geotraverse (EGT). To obtain a well-constrained crustal transect along the EGT an initial model was constructed from information based mainly on the coincident reflection seismic profile of the Swiss National Research Program NFP20 and short-range observations of the EGT data for the shallow structure and on the along-strike wide-angle profiles for the deep structure. The refinement of the initial model by 2-D raytracing during the subsequent interpretation of the EGT data leads to a detailed P-wave velocity distribution of the crustal cross-section beneath the Central Swiss Alps and its adjacent areas. In general, the distinctly layered crustal structure below the Alpine foreland thickens considerably as the Alps are approached, reaching a maximum thickness of nearly 60 km below the Insubric Line. The upper and middle crust has velocities between 6.0 and 6.2 km/s. Except for the area below the southern part of the Molasse Basin and the Helvetic nappes a distinct lower crust with a relatively low velocity of 6.5-6.6 km/s is found. Below the Penninic nappes the lower crust thickens remarkably, merging probably with the high-velocity zone of 6.6 km/s at a depth of about 21 km, which has been interpreted as the top of the indenting lower crust of the Adriatic promontory of the African plate. A clear vertical offset between the smoothly south-dipping European and the more rapidly rising Adriatic crust-mantle boundaries is found. The complex structures of the upper crust beneath the Alps caused by the nappe tectonics can only be partly resolved by the refraction seismic data. A south-dipping high-velocity zone within the Penninic nappe pile and a reflector beneath the northern front of the Aar Massif can possibly be interpreted as

  15. Lithology Cubes and Geobodies from 3D Seismic Data - a Gulf of Mexico Case Study

    NASA Astrophysics Data System (ADS)

    Shelander, D. L.; Zhang, L.; Jacob, C.; Biles, N. E.

    2012-12-01

    Seismic data can be expressed in terms of lithology by utilizing a conversion process which was applied in a case study from the Gulf of Mexico shelf. This process uses rock physics analyses from well data to establish relationships between observed lithology/pore fluid types and physical properties that can be inverted from pre-stack seismic data, e.g. acoustic impedance, P-wave/S-wave velocity ratio (Vp/Vs), and density. Saturation of water (Sw) and volume of shale (Vshale) limits were used to define four lithology/fluid classes (litho-class) in terms of the physical properties; hydrocarbon (HC) sand, wet sand, shaly sand, and shale. Bayesian derived probability density functions (PDFs) for each litho-class were calculated from well log computations of acoustic impedance, Vp/Vs, and density. Using the PDFs, probability cubes for the individual lithologies are calculated from the seismic derived acoustic impedance, Vp/Vs, and density cubes. LithoCube probability cubes are calculated for 4 different litho-classes, and used to determine two additional cubes, a maximum probability cube and a ClassCube. Thus, six LithoCube volumes were generated: ClassCube (comprising the 4 litho-classes, plus an undefined class, assigned based on the highest probability for each sample), Maximum Probability (the value of the highest probability found for each sample, values 0-1.0), Probability of shale (values 0-1.0), Probability of shaly sand (values 0-1.0), Probability of wet sand (values 0-1.0), and Probability of HC sand (values 0 -1.0) The ClassCube provides a quick look, indicating which of the 4 lithology types is most probable for any one sample in the 3D cubes. The Probability for HC sand cube is very useful because it shows probability levels for HC sand occurrence. For example with the four litho-classes, probability for the HC sand may be as high as 1.0, or as low as 0.26. For 0.26 values, the probabilities for the other 3 litho-classes can be 0.25, 0.25 and 0.24. Both of

  16. Imaging 3D seismic velocity along the seismogenic zone of Algarve region (southern Portugal)

    NASA Astrophysics Data System (ADS)

    Rocha, João.; Bezzeghoud, Mourad; Caldeira, Bento; Dias, Nuno; Borges, José; Matias, Luís.; Dorbath, Catherine; Carrilho, Fernando

    2010-05-01

    The present seismic tomographic study is focused around Algarve region, in South of Portugal. To locate the seismic events and find the local velocity structure of epicentral area, the P and S arrival times at 38 stations are used. The data used in this study were obtained during the Algarve campaign which worked from January/2006 to July/2007. The preliminary estimate of origin times and hypocentral coordinates are determined by the Hypoinverse program. Linearized inversion procedure was applied to comprise the following two steps: 1) finding the minimum 1D velocity model using Velest and 2) simultaneous relocation of hypocenters and determination of local velocity structure. The velocity model we have reached is a 10 layer model which gave the lowest RMS, after several runnings of eight different velocity models that we used "a priori". The model parameterization assumes a continuous velocity field between 4.5 km/s and 7.0 km/s until 30 km depth. The earth structure is represented in 3D by velocity at discrete points, and velocity at any intervening point is determined by linear interpolation among the surrounding eight grid points. A preliminary analysis of the resolution capabilities of the dataset, based on the Derivative Weight Sum (DWS) distribution, shows that the velocity structure is better resolved in the West part of the region between the surface to15 km. The resulting tomographic image has a prominent low-velocity anomaly that shows a maximum decrease in P-wave velocity in the first 12 kms in the studied region. We also identified the occurrence of local seismic events of reduced magnitude not catalogued, in the neighbourhood of Almodôvar (low Alentejo). The spatial distribution of epicentres defines a NE-SW direction that coincides with the strike of the mapped geological faults of the region and issued from photo-interpretation. Is still expectable to refine the seismicity of the region of Almodôvar and establish more rigorously its role in the

  17. 3-D full waveform inversion of seismic data; Part I. Theory

    SciTech Connect

    Lee, Ki Ha

    2003-05-12

    Full waveform inversion of seismic data is a challenging subject partly because of the lack of precise knowledge of the source. Since currently available approaches involve some form of approximations to the source, inversion results are subject to the quality and the choice of the source information used. A new full waveform inversion scheme has been introduced (Lee and Kim, 2003) using normalized wavefield for simple two-dimensional (2-D) scalar problems. The method does not require source information, so potential inversion errors due to source estimation may be eliminated. A gather of seismic traces is first Fourier-transformed into the frequency domain and a normalized wavefield is obtained for each trace in the frequency domain. Normalization is done with respect to the frequency response of a reference trace selected from the gather, so the complex-valued normalized wavefield is source-independent and dimensionless. The inversion algorithm minimizes misfits between measured normalized wavefield and numerically computed normalized wavefield. In this paper the full waveform inversion is extended to three-dimensional (3-D) problems.

  18. LLNL's 3-D A Priori Model Constraints and Uncertainties for Improving Seismic Location

    SciTech Connect

    Flanagan, M P; Myers, S C; Schultz, C A; Pasyanos, M E; Bhattacharyya, J

    2000-07-14

    Accurate seismic event location is key to monitoring the Comprehensive Nuclear-Test-Ban Treaty (CTBT) and is largely dependent on our understanding of the crust and mantle velocity structure. This is particularly challenging in aseismic regions, devoid of calibration data, which leads us to rely on a priori constraints on the velocities. We investigate our ability to improve seismic event location in the Middle East, North Africa, and the Former Soviet Union (ME/NA/FSU) by using a priori three-dimensional (3-D) velocity models in lieu of more commonly used one dimensional (1-D) models. Event locations based on 1-D models are often biased, as they do not account for significant travel-time variations that result from heterogeneous crust and mantle; it follows that 3-D velocity models have the potential to reduce this bias. Here, we develop a composite 3-D model for the ME/NA/FSU regions. This fully 3-D model is an amalgamation of studies ranging from seismic reflection to geophysical analogy. Our a priori model specifies geographic boundaries and velocity structures based on geology, tectonics, and seismicity and information taken from published literature, namely a global sediment thickness map of 1{sup o} resolution (Laske and Masters, 1997), a regionalized crustal model based on geology and tectonics (Sweeney and Walter, 1998; Bhattacharyya et al., 2000; Walter et al., 2000), and regionalized upper mantle (RUM) models developed from teleseismic travel times (Gudmundsson and Sambridge, 1998). The components of this model were chosen for the complementary structures they provide. The 1{sup o} sediment map and regionalized crustal model provide detailed structures and boundaries not available in the more coarse 5{sup o} models used for global-scale studies. The RUM models offer improved resolution over global tomography, most notably above depths of 300 km where heterogeneity is greatest; however, we plan to test other published upper mantle models of both P- and S

  19. Refining seismic parameters in low seismicity areas by 3D trenching: The Alhama de Murcia fault, SE Iberia

    NASA Astrophysics Data System (ADS)

    Ferrater, Marta; Ortuño, Maria; Masana, Eulàlia; Pallàs, Raimon; Perea, Hector; Baize, Stephane; García-Meléndez, Eduardo; Martínez-Díaz, José J.; Echeverria, Anna; Rockwell, Thomas K.; Sharp, Warren D.; Medialdea, Alicia; Rhodes, Edward J.

    2016-06-01

    Three-dimensional paleoseismology in strike-slip faults with slip rates less than 1 mm per year involves a great methodological challenge. We adapted 3D trenching to track buried channels offset by the Alhama de Murcia seismogenic left-lateral strike-slip fault (SE Iberia). A fault net slip of 0.9 ± 0.1 mm/yr was determined using statistical analysis of piercing lines for one buried channel, whose age is constrained between 15.2 ± 1.1 ka and 21.9-22.3 cal BP. This value is larger and more accurate than the previously published slip rates for this fault. The minimum number of five paleo-earthquakes identified since the deposition of dated layers suggests a maximum average recurrence interval of approximately 5 ka. The combination of both seismic parameters yields a maximum slip per event between 5.3 and 6.3 m. We show that accurately planned trenching strategies and data processing may be key to obtaining robust paleoseismic parameters in low seismicity areas.

  20. An optimal transport approach for seismic tomography: application to 3D full waveform inversion

    NASA Astrophysics Data System (ADS)

    Métivier, L.; Brossier, R.; Mérigot, Q.; Oudet, E.; Virieux, J.

    2016-11-01

    the L 2 distance, in 2D and 3D contexts.

  1. 3D Euler deconvolution in the New Madrid seismic zone (eastern US)

    NASA Astrophysics Data System (ADS)

    Arroucau, P.; Vlahovic, G.; Powell, C. A.

    2011-12-01

    The seismicity of intraplate continental interiors is one of the most challenging -though a bit overlooked- research topics in seismology. The most famous of those is undoubtedly the New Madrid seismic zone (NMSZ), named after the city of New Madrid, Missouri, that was destroyed by one of the three M>7.0 earthquakes that occurred in central United States during the winter 1811-1812. After two centuries, there is still no consensus about what caused that crisis, how it is related to the current moderate magnitude activity of that region, and how likely it is that similarly large events will occur again in a near future in the NMSZ or in its vicinity. As often in such geodynamic settings, a key question is the role of structural reactivation in the current stress field. As modern earthquakes of the NMSZ mostly occur in the Precambrian basement, below the Mississippi embayment sedimentary cover and at such depths that no deformation is observed at the surface, almost no direct observation is available about faults segments that would be responsible for that seismicity. Yet the activity of the NMSZ is known to coincide with a Precambrian failed rift, the Reelfoot rift, whose geometry is mostly inferred from potential field data. In this work, we apply 3D Euler deconvolution to the total magnetic intensity field of the NMSZ. Euler deconvolution is a technique commonly used in exploration geophysics to determine the depth of magnetic sources and more generally to produce depth-to-basement maps and image deep structures buried beneath non-magnetic sedimentary cover. We obtain basement topography maps that we compare with previously published maps and with the earthquake distribution in the NMSZ.

  2. Surface amplitude data: 3D-seismic for interpretation of sea floor geology (Louisiana Slope)

    SciTech Connect

    Roberts, H.H.

    1996-09-01

    Proliferation of 3D-seismic in support of hydrocarbon exploration/production has created new data for improved interpretation of sea floor and shallow subsurface geology. Processing of digital seismic data to enhance amplitude anomalies produces information for improved assessment of geohazards and identification of sensitive benthic communities protected by environmental regulations. Coupled with high resolution acoustic data and direct observation/sampling using a manned research submersible, surface amplitude maps add critical interpretive information for identification of sea floor features. Non-reflective zones (acoustic wipeouts) are associated with many slope features. Mud diapirs, mud mounds, mud volcanoes, gas-changed sediments, gas hydrates, slump deposits, carbonate hardgrounds, and various types of carbonate mounds are all features that exhibit this common response on high resolution seismic profiles. Amplitude data help make specific identifications. Since 1988, submersible data from mid-to-upper slope features (Garden Banks, Green Canyon, and Mississippi Canyon lease block areas) have been analyzed with conventional high resolution acoustic data and 313-amplitude extraction maps. Areas of rapid venting of sediment and hydrocarbon-charged formation fluids are clearly distinguishable from mud diapirs and areas of carbonate mounds (slow seepage). Gas hydrates occur as mounds and mounded zones along faults; products of moderate flux rates below (approx.) 500 in water depths. Gas hydrates function as stored trophic resources that support sensitive chemosynthetic communities. Amplitude extraction maps clearly identify these features by a strong low impedance amplitude anomaly. Refinement and {open_quotes}field calibration{close_quotes} of the surface amplitude extraction method may eventually lead to a new standard for evaluating geohazards and sensitive benthic communities.

  3. Modeling the Coast Mountains Batholith, British Columbia, Canada with 3D Seismic Tomography

    NASA Astrophysics Data System (ADS)

    Quinonez, S. M.; Olaya, J. C.; Miller, K. C.; Romero, R.; Velasco, A. A.; Harder, S. H.; Cerda, I.

    2011-12-01

    The Coast Mountains Batholith on the west coast of British Columbia, Canada comprises a series of granitic to tonalitic plutons; where felsic continental crust is generated from the subduction of mafic oceanic crust by partial melting and fractionation, leaving ultra-mafic roots. In July of 2009, a large controlled-source experiment was conducted along a 400km east - west transect from Bella Bella into central British Columbia. Student volunteers from multiple universities deployed 1,800 one-component and 200 three-component geophones plus 2400 Texan data recorders with 200-m spacing intervals and shot spacing at 30-km. The 18-point sources ranged from 160 to 1,000 kg of high explosive. The geoscience component of the NSF-funded Cyber-ShARE project at UTEP focuses on fusing models developed from different data sets to develop 3-D Earth models. Created in 2007, the Cyber-ShARE Center brings together experts in computer science, computational mathematics, education, earth science, and environmental science. We leverage the Cyber-ShARE work to implement an enhanced 3-D finite difference tomography approach for P-wave delays times (Hole, 1992) with a graphical user interface and visualization framework. In particular, to account for model sensitivity to picked P-wave arrival times, we use a model fusion approach (Ochoa et al., 2010) to generate a model with the lowest RMS residual that a combination of a set of Monte Carlo sample models. In order to make the seismic tomography process more interactive at many points, visualizations of model perturbation at each iteration will help to troubleshoot when a model is not converging to highlight where the RMS residual values are the highest to pinpoint where changes need to be made to achieve model convergence. Finally, a model of the upper mantle using 3-D P-wave tomography will be made to determine the location of these ultra-mafic roots.

  4. New 3D seismicity maps using chromo-stereoscopy with two alternative freewares

    NASA Astrophysics Data System (ADS)

    Okamoto, Y.

    2011-12-01

    Seismicity maps play a key role in an introduction of geosciences studies or outreach programs. Various techniques are used in order to show earthquakes in a three dimensional field. To use "chromo-stereoscopy" is our simple and easier-making solution. The Chroma Depth 3D Glasses are employed for this purpose. The glasses consist of two transparent blazed grating films covered with a paper holder and cost a little (1 US$). Looking through these glasses, the colored chart turns into three dimensional perspective due to the mechanism that the color codes make a depth dimension with dispersion. We use two complementary freewares to make maps, the GMT (Generic Mapping Tools, Wessel and Smith.1988) and the POV-Ray (Persistence of Vision Pty. Ltd. 2004). The two softwares have their own advantages; the GMT is specialized for map making with simple scripts, while the POV-Ray produces realistic 3D rendering images with more complicated scripts. The earthquakes are plotted with the rainbow color codes depending on their depths in a black background as printed or PC images. Therefore, the red colored shallow earthquakes are float in front and blue colored ones sink deeper. This effect is so amazing that the students who first wear these glasses are strongly moved and fascinated with this simple mechanism. The data used here are from JMA seismicity catalogue and USGS (ANSS) catalogue. The POV-Ray version needs coastline data, so we got them from the Coastline Extractor (NGDC) web site. Also, the POR-Ray has no function to draw lines in three dimensions, so we had to make some trials for showing them in relief. The main target of our map is "the Wadati-Beniof zone", in which the sub-ducting oceanic plate surface is fringed by deeper earthquakes colored yellow, green to blue. The active volcanic regions such as the Hawaii islands or the active fault regions such as the San Andreas Fault are also effective targets of our method. However, since their shallow complicated seismic

  5. 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

  6. Las Vegas Basin Seismic Response Project: Preliminary Results From Seismic Refraction Experiments, Las Vegas, NV.

    NASA Astrophysics Data System (ADS)

    Zaragoza, S. A.; Snelson, C. M.; Harder, S. H.; Kaip, G.; Luke, B.; Buck, B. J.; Hanson, A. D.

    2002-12-01

    In May and September 2002, seismic refraction data were acquired in the Las Vegas basin. Located in the southern Basin and Range province, the cities of Las Vegas, North Las Vegas, and Henderson sit atop a fault-bounded basin with a depth of up to 5 km and basin dimensions of roughly 60 km wide (east-west) by 50 km in length (north-south). Previous isostatic gravity, seismic reflection, and aeromagnetic studies indicate that a series of sub-basins exist beneath the unconsolidated basin fill, with the deepest sub-basin occurring 5 km west of the fault block bounding the eastern edge of the basin (Frenchman Mountain). The basin is significantly deeper along its northern extremity, following the path of the fault block bounding the northern edge of the basin (Las Vegas Valley Shear Zone), and along the western edge of Frenchman Mountain. Recent, paleoseismic studies have indicated that faults in the Las Vegas region have the potential for an earthquake of M6.5 to 7.0. It is estimated that a M6.9 earthquake in the basin could produce about 11 billion dollars in damage and a significant number of deaths and/or injuries. In addition, an equivalent or larger event in the Death Valley fault zone, 150 km distance, would also be devastating to the metropolitan area of approximately 1.5 million residents. Therefore, it is essential to understand the seismic hazard posed to the Las Vegas region. This project is part of a larger collaborative effort to characterize the basin and its response to ground shaking. The University of Nevada, Las Vegas with assistance from the University of Texas at El Paso, students from UNLV and UTEP, volunteers from the community and several students from Centennial High school deployed 432 portable seismic recorders ("Texans") throughout the valley. Shot point locations were located at three quarries in the valley, one to the north, one to the east and one to the southwest. The profiles cross the Las Vegas Valley Shear zone as well as a prominent

  7. Development of a 400 Level 3C Clamped Downhole Seismic Receiver Array for 3D Borehole Seismic Imaging of Gas Reservoirs

    SciTech Connect

    Bjorn N.P. Paulsson

    2005-08-21

    Borehole seismology is the highest resolution geophysical imaging technique available today to the oil and gas industry for characterization and monitoring of oil and gas reservoirs. However, the industry's ability to economically do high resolution 3D imaging of deep and complex gas reservoirs using borehole seismology is currently hampered by the lack of the acquisition technology necessary to record the large volumes of the high frequency, high signal-to-noise-ratio borehole seismic data needed to do 3D imaging. This project takes direct aim at this shortcoming by developing a 400 level 3C clamped downhole seismic receiver array, and accompanying software, for borehole seismic 3D imaging. This large borehole seismic array will remove the technical acquisition barrier for recording the necessary volumes of data to do high resolution 3D VSP or 3D cross well seismic imaging. Massive 3D VSP{reg_sign} and long range Cross-Well Seismology (CWS) are two of the borehole seismic techniques that will allow the Gas industry to take the next step in their quest for higher resolution images of the gas reservoirs for the purpose of improving the recovery of the natural gas resources. Today only a fraction of the original Oil or Gas in place is produced when reservoirs are considered depleted. This is primarily due to our lack of understanding of the detailed compartmentalization of the oil and gas reservoirs. The 400 level 3C borehole seismic receiver array will allow for the economic use of 3D borehole seismic imaging for reservoir characterization and monitoring by allowing the economic recording of the required large data volumes that have a sufficiently dense spatial sampling. By using 3C surface seismic or 3C borehole seismic sources the 400 level receiver arrays will furthermore allow 3D reservoir imaging using 9C data. The 9C borehole seismic data will provide P, SH and SV information for imaging of the complex deep gas reservoirs and allow quantitative prediction of

  8. Development of a 400 Level 3C Clamped Downhole Seismic Receiver Array for 3D Borehole Seismic Imaging of Gas Reservoirs

    SciTech Connect

    Bjorn N.P Paulsson

    2006-05-05

    Borehole seismology is the highest resolution geophysical imaging technique available today to the oil and gas industry for characterization and monitoring of oil and gas reservoirs. However, the industry's ability to economically do high resolution 3D imaging of deep and complex gas reservoirs using borehole seismology is currently hampered by the lack of the acquisition technology necessary to record the large volumes of the high frequency, high signal-to-noise-ratio borehole seismic data needed to do 3D imaging. This project takes direct aim at this shortcoming by developing a 400 level 3C clamped downhole seismic receiver array, and accompanying software, for borehole seismic 3D imaging. This large borehole seismic array will remove the technical acquisition barrier for recording the necessary volumes of data to do high resolution 3D VSP or 3D cross well seismic imaging. Massive 3D VSP{reg_sign} and long range Cross-Well Seismology (CWS) are two of the borehole seismic techniques that will allow the Gas industry to take the next step in their quest for higher resolution images of the gas reservoirs for the purpose of improving the recovery of the natural gas resources. Today only a fraction of the original Oil or Gas in place is produced when reservoirs are considered depleted. This is primarily due to our lack of understanding of the detailed compartmentalization of the oil and gas reservoirs. The 400 level 3C borehole seismic receiver array will allow for the economic use of 3D borehole seismic imaging for reservoir characterization and monitoring by allowing the economic recording of the required large data volumes that have a sufficiently dense spatial sampling. By using 3C surface seismic or 3C borehole seismic sources the 400 level receiver arrays will furthermore allow 3D reservoir imaging using 9C data. The 9C borehole seismic data will provide P, SH and SV information for imaging of the complex deep gas reservoirs and allow quantitative prediction of

  9. Development of a 400 Level 3C Clamped Downhole Seismic Receiver Array for 3D Borehole Seismic Imaging of Gas Reservoirs

    SciTech Connect

    Bjorn N. P. Paulsson

    2005-09-30

    Borehole seismology is the highest resolution geophysical imaging technique available today to the oil and gas industry for characterization and monitoring of oil and gas reservoirs. However, the industry's ability to economically do high resolution 3D imaging of deep and complex gas reservoirs using borehole seismology is currently hampered by the lack of the acquisition technology necessary to record the large volumes of the high frequency, high signal-to-noise-ratio borehole seismic data needed to do 3D imaging. This project takes direct aim at this shortcoming by developing a 400 level 3C clamped downhole seismic receiver array, and accompanying software, for borehole seismic 3D imaging. This large borehole seismic array will remove the technical acquisition barrier for recording the necessary volumes of data to do high resolution 3D VSP or 3D cross well seismic imaging. Massive 3D VSP{reg_sign} and long range Cross-Well Seismology (CWS) are two of the borehole seismic techniques that will allow the Gas industry to take the next step in their quest for higher resolution images of the gas reservoirs for the purpose of improving the recovery of the natural gas resources. Today only a fraction of the original Oil or Gas in place is produced when reservoirs are considered depleted. This is primarily due to our lack of understanding of the detailed compartmentalization of the oil and gas reservoirs. The 400 level 3C borehole seismic receiver array will allow for the economic use of 3D borehole seismic imaging for reservoir characterization and monitoring by allowing the economic recording of the required large data volumes that have a sufficiently dense spatial sampling. By using 3C surface seismic or 3C borehole seismic sources the 400 level receiver arrays will furthermore allow 3D reservoir imaging using 9C data. The 9C borehole seismic data will provide P, SH and SV information for imaging of the complex deep gas reservoirs and allow quantitative prediction of

  10. DEVELOPMENT OF A 400 LEVEL 3C CLAMPED DOWNHOLE SEISMIC RECEIVER ARRAY FOR 3D BOREHOLE SEISMIC IMAGING OF GAS RESERVOIRS

    SciTech Connect

    Bjorn N.P. Paulsson

    2004-12-31

    Borehole seismology is the highest resolution geophysical imaging technique available today to the oil and gas industry for characterization and monitoring of oil and gas reservoirs. However, the industry's ability to economically do high resolution 3D imaging of deep and complex gas reservoirs using borehole seismology is currently frustrated by the lack of the acquisition technology necessary to record the large volumes of the high frequency, high signal-to-noise-ratio borehole seismic data needed to do 3D imaging. This project takes direct aim at this shortcoming by developing a 400 level 3C clamped downhole seismic receiver array, and accompanying software, for borehole seismic 3D imaging. This large borehole seismic array will remove the technical acquisition barrier for recording the necessary volumes of data to do high resolution 3D VSP or 3D cross well seismic imaging. Massive 3D VSP{reg_sign} and long range Cross-Well Seismology (CWS) are two of the borehole seismic techniques that will allow the Gas industry to take the next step in their quest for higher resolution images of the gas reservoirs for the purpose of improving the recovery of the natural gas resources. Today only a fraction of the original Oil or Gas in place is produced when reservoirs are considered depleted. This is primarily due to our lack of understanding of the detailed compartmentalization of the oil and gas reservoirs. The 400 level 3C borehole seismic receiver array will allow for the economic use of 3D borehole seismic imaging for reservoir characterization and monitoring by allowing the economic recording of the required large data volumes that have a sufficiently dense spatial sampling. By using 3C surface seismic or 3C borehole seismic sources the 400 level receiver arrays will furthermore allow 3D reservoir imaging using 9C data. The 9C borehole seismic data will provide P, SH and SV information for imaging of the complex deep gas reservoirs and allow quantitative prediction of

  11. DEVELOPMENT OF A 400 LEVEL 3C CLAMPED DOWNHOLE SEISMIC RECEIVER ARRAY FOR 3D BOREHOLE SEISMIC IMAGING OF GAS RESERVOIRS

    SciTech Connect

    Bjorn N.P. Paulsson

    2005-03-31

    Borehole seismology is the highest resolution geophysical imaging technique available today to the oil and gas industry for characterization and monitoring of oil and gas reservoirs. However, the industry's ability to economically do high resolution 3D imaging of deep and complex gas reservoirs using borehole seismology is currently hampered by the lack of the acquisition technology necessary to record the large volumes of the high frequency, high signal-to-noise-ratio borehole seismic data needed to do 3D imaging. This project takes direct aim at this shortcoming by developing a 400 level 3C clamped downhole seismic receiver array, and accompanying software, for borehole seismic 3D imaging. This large borehole seismic array will remove the technical acquisition barrier for recording the necessary volumes of data to do high resolution 3D VSP or 3D cross well seismic imaging. Massive 3D VSP{reg_sign} and long range Cross-Well Seismology (CWS) are two of the borehole seismic techniques that will allow the Gas industry to take the next step in their quest for higher resolution images of the gas reservoirs for the purpose of improving the recovery of the natural gas resources. Today only a fraction of the original Oil or Gas in place is produced when reservoirs are considered depleted. This is primarily due to our lack of understanding of the detailed compartmentalization of the oil and gas reservoirs. The 400 level 3C borehole seismic receiver array will allow for the economic use of 3D borehole seismic imaging for reservoir characterization and monitoring by allowing the economic recording of the required large data volumes that have a sufficiently dense spatial sampling. By using 3C surface seismic or 3C borehole seismic sources the 400 level receiver arrays will furthermore allow 3D reservoir imaging using 9C data. The 9C borehole seismic data will provide P, SH and SV information for imaging of the complex deep gas reservoirs and allow quantitative prediction of

  12. DEVELOPMENT OF A 400 LEVEL 3C CLAMPED DOWNHOLE SEISMIC RECEIVER ARRAY FOR 3D BOREHOLE SEISMIC IMAGING OF GAS RESERVOIRS

    SciTech Connect

    Bjorn N.P. Paulsson

    2004-06-30

    Borehole seismology is the highest resolution geophysical imaging technique available today to the oil and gas industry for characterization and monitoring of oil and gas reservoirs. However, the industry's ability to economically do high resolution 3D imaging of deep and complex gas reservoirs using borehole seismology is currently frustrated by the lack of the acquisition technology necessary to record the large volumes of the high frequency, high signal-to-noise-ratio borehole seismic data needed to do 3D imaging. This project takes direct aim at this shortcoming by developing a 400 level 3C clamped downhole seismic receiver array, and accompanying software, for borehole seismic 3D imaging. This large borehole seismic array will remove the technical acquisition barrier for recording the necessary volumes of data to do high resolution 3D VSP or 3D cross well seismic imaging. 3D VSP and long range Cross-Well Seismology (CWS) are two of the borehole seismic techniques that will allow the Gas industry to take the next step in their quest for higher resolution images of the gas reservoirs for the purpose of improving the recovery of the natural gas resources. Today only a fraction of the original Oil or Gas in place is produced when reservoirs are considered depleted. This is primarily due to our lack of understanding of the detailed compartmentalization of the oil and gas reservoirs. The 400 level 3C borehole seismic receiver array will allow for the economic use of 3D borehole seismic imaging for reservoir characterization and monitoring by allowing the economic recording of the required large data volumes that have a sufficiently dense spatial sampling. By using 3C surface seismic or 3C borehole seismic sources the 400 level receiver array will furthermore allow 3D reservoir imaging using 9C data. The 9C borehole seismic data will provide P, SH and SV information for imaging of the complex deep gas reservoirs and allow quantitative prediction of the rock and the

  13. DEVELOPMENT OF A 400 LEVEL 3C CLAMPED DOWNHOLE SEISMIC RECEIVER ARRAY FOR 3D BOREHOLE SEISMIC IMAGING OF GAS RESERVOIRS

    SciTech Connect

    Bjorn N.P. Paulsson

    2002-12-01

    Borehole seismology is the highest resolution geophysical imaging technique available today to the oil and gas industry for characterization and monitoring of oil and gas reservoirs. However, the industry's ability to economically do high resolution 3D imaging of deep and complex gas reservoirs using borehole seismology is currently frustrated by the lack of the acquisition technology necessary to record the large volumes of the high frequency, high signal-to-noise-ratio borehole seismic data needed to do 3D imaging. This project takes direct aim at this shortcoming by developing a 400 level 3C clamped downhole seismic receiver array, and accompanying software, for borehole seismic 3D imaging. This large borehole seismic array will remove the technical acquisition barrier for recording the necessary volumes of data to do high resolution 3D VSP or 3D cross well seismic imaging. 3D VSP and long range Cross-Well Seismology (CWS) are two of the borehole seismic techniques that will allow the Gas industry to take the next step in their quest for higher resolution images of the gas reservoirs for the purpose of improving the recovery of the natural gas resources. Today only a fraction of the original Oil or Gas in place is produced when reservoirs are considered depleted. This is primarily due to our lack of understanding of the detailed compartmentalization of the oil and gas reservoirs. The 400 level 3C borehole seismic receiver array will allow for the economic use of 3D borehole seismic imaging for reservoir characterization and monitoring by allowing the economic recording of the required large data volumes that have a sufficiently dense spatial sampling. By using 3C surface seismic or 3C borehole seismic sources the 400 level receiver array will furthermore allow 3D reservoir imaging using 9C data. The 9C borehole seismic data will provide P, SH and SV information for imaging of the complex deep gas reservoirs and allow quantitative prediction of the rock and the

  14. DEVELOPMENT OF A 400 LEVEL 3C CLAMPED DOWNHOLE SEISMIC RECEIVER ARRAY FOR 3D BOREHOLE SEISMIC IMAGING OF GAS RESERVOIRS

    SciTech Connect

    Bjorn N.P. Paulsson

    2004-05-31

    Borehole seismology is the highest resolution geophysical imaging technique available today to the oil and gas industry for characterization and monitoring of oil and gas reservoirs. However, the industry's ability to economically do high resolution 3D imaging of deep and complex gas reservoirs using borehole seismology is currently frustrated by the lack of the acquisition technology necessary to record the large volumes of the high frequency, high signal-to-noise-ratio borehole seismic data needed to do 3D imaging. This project takes direct aim at this shortcoming by developing a 400 level 3C clamped downhole seismic receiver array, and accompanying software, for borehole seismic 3D imaging. This large borehole seismic array will remove the technical acquisition barrier for recording the necessary volumes of data to do high resolution 3D VSP or 3D cross well seismic imaging. 3D VSP and long range Cross-Well Seismology (CWS) are two of the borehole seismic techniques that will allow the Gas industry to take the next step in their quest for higher resolution images of the gas reservoirs for the purpose of improving the recovery of the natural gas resources. Today only a fraction of the original Oil or Gas in place is produced when reservoirs are considered depleted. This is primarily due to our lack of understanding of the detailed compartmentalization of the oil and gas reservoirs. The 400 level 3C borehole seismic receiver array will allow for the economic use of 3D borehole seismic imaging for reservoir characterization and monitoring by allowing the economic recording of the required large data volumes that have a sufficiently dense spatial sampling. By using 3C surface seismic or 3C borehole seismic sources the 400 level receiver array will furthermore allow 3D reservoir imaging using 9C data. The 9C borehole seismic data will provide P, SH and SV information for imaging of the complex deep gas reservoirs and allow quantitative prediction of the rock and the

  15. DEVELOPMENT OF A 400 LEVEL 3C CLAMPED DOWNHOLE SEISMIC RECEIVER ARRAY FOR 3D BOREHOLE SEISMIC IMAGING OF GAS RESERVOIRS

    SciTech Connect

    Bjorn N.P Paulsson

    2003-09-01

    Borehole seismology is the highest resolution geophysical imaging technique available today to the oil and gas industry for characterization and monitoring of oil and gas reservoirs. However, the industry's ability to economically do high resolution 3D imaging of deep and complex gas reservoirs using borehole seismology is currently frustrated by the lack of the acquisition technology necessary to record the large volumes of the high frequency, high signal-to-noise-ratio borehole seismic data needed to do 3D imaging. This project takes direct aim at this shortcoming by developing a 400 level 3C clamped downhole seismic receiver array, and accompanying software, for borehole seismic 3D imaging. This large borehole seismic array will remove the technical acquisition barrier for recording the necessary volumes of data to do high resolution 3D VSP or 3D cross well seismic imaging. 3D VSP and long range Cross-Well Seismology (CWS) are two of the borehole seismic techniques that will allow the Gas industry to take the next step in their quest for higher resolution images of the gas reservoirs for the purpose of improving the recovery of the natural gas resources. Today only a fraction of the original Oil or Gas in place is produced when reservoirs are considered depleted. This is primarily due to our lack of understanding of the detailed compartmentalization of the oil and gas reservoirs. The 400 level 3C borehole seismic receiver array will allow for the economic use of 3D borehole seismic imaging for reservoir characterization and monitoring by allowing the economic recording of the required large data volumes that have a sufficiently dense spatial sampling. By using 3C surface seismic or 3C borehole seismic sources the 400 level receiver array will furthermore allow 3D reservoir imaging using 9C data. The 9C borehole seismic data will provide P, SH and SV information for imaging of the complex deep gas reservoirs and allow quantitative prediction of the rock and the

  16. DEVELOPMENT OF A 400 LEVEL 3C CLAMPED DOWNHOLE SEISMIC RECEIVER ARRAY FOR 3D BOREHOLE SEISMIC IMAGING OF GAS RESERVOIRS.

    SciTech Connect

    Bjorn N.P Paulsson

    2003-01-01

    Borehole seismology is the highest resolution geophysical imaging technique available today to the oil and gas industry for characterization and monitoring of oil and gas reservoirs. However, the industry's ability to economically do high resolution 3D imaging of deep and complex gas reservoirs using borehole seismology is currently frustrated by the lack of the acquisition technology necessary to record the large volumes of the high frequency, high signal-to-noise-ratio borehole seismic data needed to do 3D imaging. This project takes direct aim at this shortcoming by developing a 400 level 3C clamped downhole seismic receiver array, and accompanying software, for borehole seismic 3D imaging. This large borehole seismic array will remove the technical acquisition barrier for recording the necessary volumes of data to do high resolution 3D VSP or 3D cross well seismic imaging. 3D VSP and long range Cross-Well Seismology (CWS) are two of the borehole seismic techniques that will allow the Gas industry to take the next step in their quest for higher resolution images of the gas reservoirs for the purpose of improving the recovery of the natural gas resources. Today only a fraction of the original Oil or Gas in place is produced when reservoirs are considered depleted. This is primarily due to our lack of understanding of the detailed compartmentalization of the oil and gas reservoirs. The 400 level 3C borehole seismic receiver array will allow for the economic use of 3D borehole seismic imaging for reservoir characterization and monitoring by allowing the economic recording of the required large data volumes that have a sufficiently dense spatial sampling. By using 3C surface seismic or 3C borehole seismic sources the 400 level receiver array will furthermore allow 3D reservoir imaging using 9C data. The 9C borehole seismic data will provide P, SH and SV information for imaging of the complex deep gas reservoirs and allow quantitative prediction of the rock and the

  17. DEVELOPMENT OF A 400 LEVEL 3C CLAMPED DOWNHOLE SEISMIC RECEIVER ARRAY FOR 3D BOREHOLE SEISMIC IMAGING OF GAS RESERVOIRS

    SciTech Connect

    Bjorn N.P. Paulsson

    2004-09-30

    Borehole seismology is the highest resolution geophysical imaging technique available today to the oil and gas industry for characterization and monitoring of oil and gas reservoirs. However, the industry's ability to economically do high resolution 3D imaging of deep and complex gas reservoirs using borehole seismology is currently frustrated by the lack of the acquisition technology necessary to record the large volumes of the high frequency, high signal-to-noise-ratio borehole seismic data needed to do 3D imaging. This project takes direct aim at this shortcoming by developing a 400 level 3C clamped downhole seismic receiver array, and accompanying software, for borehole seismic 3D imaging. This large borehole seismic array will remove the technical acquisition barrier for recording the necessary volumes of data to do high resolution 3D VSP or 3D cross well seismic imaging. Massive 3D VSP{reg_sign} and long range Cross-Well Seismology (CWS) are two of the borehole seismic techniques that will allow the Gas industry to take the next step in their quest for higher resolution images of the gas reservoirs for the purpose of improving the recovery of the natural gas resources. Today only a fraction of the original Oil or Gas in place is produced when reservoirs are considered depleted. This is primarily due to our lack of understanding of the detailed compartmentalization of the oil and gas reservoirs. The 400 level 3C borehole seismic receiver array will allow for the economic use of 3D borehole seismic imaging for reservoir characterization and monitoring by allowing the economic recording of the required large data volumes that have a sufficiently dense spatial sampling. By using 3C surface seismic or 3C borehole seismic sources the 400 level receiver arrays will furthermore allow 3D reservoir imaging using 9C data. The 9C borehole seismic data will provide P, SH and SV information for imaging of the complex deep gas reservoirs and allow quantitative prediction of

  18. DEVELOPMENT OF A 400 LEVEL 3C CLAMPED DOWNHOLE SEISMIC RECEIVER ARRAY FOR 3D BOREHOLE SEISMIC IMAGING OF GAS RESERVOIRS

    SciTech Connect

    Bjorn N.P. Paulsson

    2003-12-01

    Borehole seismology is the highest resolution geophysical imaging technique available today to the oil and gas industry for characterization and monitoring of oil and gas reservoirs. However, the industry's ability to economically do high resolution 3D imaging of deep and complex gas reservoirs using borehole seismology is currently frustrated by the lack of the acquisition technology necessary to record the large volumes of the high frequency, high signal-to-noise-ratio borehole seismic data needed to do 3D imaging. This project takes direct aim at this shortcoming by developing a 400 level 3C clamped downhole seismic receiver array, and accompanying software, for borehole seismic 3D imaging. This large borehole seismic array will remove the technical acquisition barrier for recording the necessary volumes of data to do high resolution 3D VSP or 3D cross well seismic imaging. 3D VSP and long range Cross-Well Seismology (CWS) are two of the borehole seismic techniques that will allow the Gas industry to take the next step in their quest for higher resolution images of the gas reservoirs for the purpose of improving the recovery of the natural gas resources. Today only a fraction of the original Oil or Gas in place is produced when reservoirs are considered depleted. This is primarily due to our lack of understanding of the detailed compartmentalization of the oil and gas reservoirs. The 400 level 3C borehole seismic receiver array will allow for the economic use of 3D borehole seismic imaging for reservoir characterization and monitoring by allowing the economic recording of the required large data volumes that have a sufficiently dense spatial sampling. By using 3C surface seismic or 3C borehole seismic sources the 400 level receiver array will furthermore allow 3D reservoir imaging using 9C data. The 9C borehole seismic data will provide P, SH and SV information for imaging of the complex deep gas reservoirs and allow quantitative prediction of the rock and the

  19. DEVELOPMENT OF A 400 LEVEL 3C CLAMPED DOWNHOLE SEISMIC RECEIVER ARRAY FOR 3D BOREHOLE SEISMIC IMAGING OF GAS RESERVOIRS

    SciTech Connect

    Bjorn N.P Paulsson

    2003-07-01

    Borehole seismology is the highest resolution geophysical imaging technique available today to the oil and gas industry for characterization and monitoring of oil and gas reservoirs. However, the industry's ability to economically do high resolution 3D imaging of deep and complex gas reservoirs using borehole seismology is currently frustrated by the lack of the acquisition technology necessary to record the large volumes of the high frequency, high signal-to-noise-ratio borehole seismic data needed to do 3D imaging. This project takes direct aim at this shortcoming by developing a 400 level 3C clamped downhole seismic receiver array, and accompanying software, for borehole seismic 3D imaging. This large borehole seismic array will remove the technical acquisition barrier for recording the necessary volumes of data to do high resolution 3D VSP or 3D cross well seismic imaging. 3D VSP and long range Cross-Well Seismology (CWS) are two of the borehole seismic techniques that will allow the Gas industry to take the next step in their quest for higher resolution images of the gas reservoirs for the purpose of improving the recovery of the natural gas resources. Today only a fraction of the original Oil or Gas in place is produced when reservoirs are considered depleted. This is primarily due to our lack of understanding of the detailed compartmentalization of the oil and gas reservoirs. The 400 level 3C borehole seismic receiver array will allow for the economic use of 3D borehole seismic imaging for reservoir characterization and monitoring by allowing the economic recording of the required large data volumes that have a sufficiently dense spatial sampling. By using 3C surface seismic or 3C borehole seismic sources the 400 level receiver array will furthermore allow 3D reservoir imaging using 9C data. The 9C borehole seismic data will provide P, SH and SV information for imaging of the complex deep gas reservoirs and allow quantitative prediction of the rock and the

  20. DEVELOPMENT OF A 400 LEVEL 3C CLAMPED DOWNHOLE SEISMIC RECEIVER ARRAY FOR 3D BOREHOLE SEISMIC IMAGING OF GAS RESERVOIRS

    SciTech Connect

    Bjorn N.P. Paulsson

    2004-05-01

    Borehole seismology is the highest resolution geophysical imaging technique available today to the oil and gas industry for characterization and monitoring of oil and gas reservoirs. However, the industry's ability to economically do high resolution 3D imaging of deep and complex gas reservoirs using borehole seismology is currently frustrated by the lack of the acquisition technology necessary to record the large volumes of the high frequency, high signal-to-noise-ratio borehole seismic data needed to do 3D imaging. This project takes direct aim at this shortcoming by developing a 400 level 3C clamped downhole seismic receiver array, and accompanying software, for borehole seismic 3D imaging. This large borehole seismic array will remove the technical acquisition barrier for recording the necessary volumes of data to do high resolution 3D VSP or 3D cross well seismic imaging. 3D VSP and long range Cross-Well Seismology (CWS) are two of the borehole seismic techniques that will allow the Gas industry to take the next step in their quest for higher resolution images of the gas reservoirs for the purpose of improving the recovery of the natural gas resources. Today only a fraction of the original Oil or Gas in place is produced when reservoirs are considered depleted. This is primarily due to our lack of understanding of the detailed compartmentalization of the oil and gas reservoirs. The 400 level 3C borehole seismic receiver array will allow for the economic use of 3D borehole seismic imaging for reservoir characterization and monitoring by allowing the economic recording of the required large data volumes that have a sufficiently dense spatial sampling. By using 3C surface seismic or 3C borehole seismic sources the 400 level receiver array will furthermore allow 3D reservoir imaging using 9C data. The 9C borehole seismic data will provide P, SH and SV information for imaging of the complex deep gas reservoirs and allow quantitative prediction of the rock and the

  1. Development of a High-Resolution Shallow Seismic Refraction Tomography System at the Monterey Bay Aquarium Research Institute

    NASA Astrophysics Data System (ADS)

    Henthorn, R.; Caress, D. W.; Chaffey, M. R.; McGill, P. R.; Kirkwood, W. J.; Burgess, W. C.

    2009-12-01

    and model the shallow seismic velocity structure using 2D or 3D tomographic inversion algorithms. The target experimental scale of subsurface sections ranges from 100m across and 20m deep to 1km across and 200m deep. Given the approximately 3 kHz center-frequency and a source shot spacing of less than a meter, the best achievable resolution of subsurface structure will be about 1 meter. Both the target scale and resolution is ultimately determined by the receiver spacing used in the experiment. Although the combination of chirp sonar technology, high frequency OBHs, ROV operational capabilities, and tomographic inversion algorithms is novel, all of the relevant technologies are mature and available. Moreover, this capability will be readily exportable to oceanographic institutions and programs with access to operational ROVs.

  2. 3D Discontinuous Galerkin elastic seismic wave modeling based upon a grid injection method

    NASA Astrophysics Data System (ADS)

    Monteiller, V.

    2015-12-01

    Full waveform inversion (FWI) is a seismic imaging method that estimates thesub-surface physical properties with a spatial resolution of the order of thewavelength. FWI is generally recast as the iterative optimization of anobjective function that measures the distance between modeled and recordeddata. In the framework of local descent methods, FWI requires to perform atleast two seismic modelings per source and per FWI iteration.Due to the resulting computational burden, applications of elastic FWI have been usuallyrestricted to 2D geometries. Despite the continuous growth of high-performancecomputing facilities, application of 3D elastic FWI to real-scale problemsremain computationally too expensive. To perform elastic seismic modeling with a reasonable amount of time, weconsider a reduced computational domain embedded in a larger background modelin which seismic sources are located. Our aim is to compute repeatedly thefull wavefield in the targeted domain after model alteration, once theincident wavefield has been computed once for all in the background model. Toachieve this goal, we use a grid injection method referred to as the Total-Field/Scattered-Field (TF/SF) technique in theelectromagnetic community. We implemented the Total-Field/Scattered-Field approach in theDiscontinuous Galerkin Finite Element method (DG-FEM) that is used to performmodeling in the local domain. We show how to interface the DG-FEM with any modeling engine (analytical solution, finite difference or finite elements methods) that is suitable for the background simulation. One advantage of the Total-Field/Scattered-Field approach is related to thefact that the scattered wavefield instead of the full wavefield enter thePMLs, hence making more efficient the absorption of the outgoing waves at theouter edges of the computational domain. The domain reduction in which theDG-FEM is applied allows us to use modest computational resources opening theway for high-resolution imaging by full

  3. The 3D crustal structure of Northeastern Tibetan area from seismic tomography

    NASA Astrophysics Data System (ADS)

    Sun, Anhui

    2015-04-01

    The Northeastern Tibetan region is located in the border area of three sub-plates in China, i.e. the Tibetan plateau, North China block and Xinjiang block. Effected simultaneously by the extrusion driven by the India-Eurasia plat collision and the blockage of the Ordos basin, this area has complex geology, strong tectonics activities and suffered from several large historic earthquakes, such as the Haiyuan earthquake (M8.6) in 1920, the Gulang earthquake (M8.0) in 1927. To enhance our understanding of the crustal structure and the interaction between different tectonic blocks of this region, we conduct a three-dimensional (3D) tomographic study by using the arrival time date recorded by regional seismic network. We used 101101 P and 103313 S wave arrival times from 11650 local earthquakes during 1970 to 2013 recorded by 154 permanent seismic stations of the local Seismic Network, installed over five provinces in China, i.e. Gansu, Ningxia, Qinghai, Shanxi, Neimenggu. We first established a 1D primary crustal model from LITHO1.0, an updated crust and lithospheric model of the Earth by weighted averaging. To better performer ray tracing, our inversion involved three discontinuities (including the Moho) with depth variation over the mantle derived from LITHO1.0. Detailed three-dimensional seismic velocity (Vp and Vs) structures of the crust of the Northeastern Tibetan are determined with a horizontal resolution of about 35 km and a depth resolution of 6-20 km. The Poisson's ratio (σ) structure was also estimated after obtained Vp and Vs structures. We detected low-velocity anomalies in the lower crust and relative high-velocity anomalies in the upper crust beneath the Longmenshan faults zone, which are in good agreement with the results of most previous geophysical studies. Our results revealed clear different velocity variation beneath both sides of different tectonic blocks. In addition, we found the correlation between our tomographic result and previous

  4. 3D Seismic and Magnetic characterization of the Borax Lake Hydrothermal System in the Alvord Desert, southeastern Oregon.

    NASA Astrophysics Data System (ADS)

    Hess, S.; Bradford, J.; Lyle, M.; Routh, P.; Liberty, L.; Donaldson, P.

    2004-05-01

    As part of an interdisciplinary project aiming to study the link between the physical characteristics of hydrothermal systems and biota that occupy those systems, we are conducting a detailed geophysical characterization of an active hydrothermal system. The Borax Lake Hydrothermal System (BLHS), consisting of Borax Lake and the surrounding hot springs. BLHS is located near the center of the Alvord Basin in southeastern Oregon. The Alvord Basin is a north-south trending graben in the Northern Great Basin bounded by the Steens Mountains to the west and the Trout Creek Mountains to the east. We conducted a 2D seismic survey to characterize the geologic structure of the basin, a high-resolution 3D seismic survey to characterize the geologic structure of the BLHS, and a high-resolution 3D magnetic survey to characterize any lineaments in the bedrock that might control fluid flow in the BLHS. Previous results from the 2D seismic survey show a mid-basin basement high aligned approximately with the hot springs. In this study we present the results from the high-resolution 3D seismic and magnetic survey of the BLHS. We acquired the 3D seismic data using an SKS rifle and 240 channel recording system. The seismic survey covers approximately 90,000 sq. m with a maximum inline offset aperture of 225 m, crossline aperture of 75 m, and 360 degree azimuthal coverage. The coincidental magnetic survey was collected using a Geometrics 858G cesium vapor magnetometer. We designed both surveys to span nearly 100 active hydrothermal springs, including an approximately 50 m stepover in the trend of the surface expression of the hot springs. After preliminary processing, the 3D seismic data show continuous reflections up to 300 ms (~ 480 m). The initial interpretation of features seen in the 3D data cube include: normal faults dipping to the east and west, near-surface disturbances that are consistent with the trend of the hot springs, and significant near surface velocity anomalies

  5. Joint inversion of 3-D seismic, gravimetric and magnetotelluric data for sub-basalt imaging in the Faroe-Shetland Basin

    NASA Astrophysics Data System (ADS)

    Heincke, B.; Moorkamp, M.; Jegen, M.; Hobbs, R. W.

    2012-12-01

    collected along parallel lines by a shipborne gradiometer and the marine MT data set is composed of 41 stations that are distributed over the whole investigation area. Logging results from a borehole located in the central part of the investigation area enable us to derive parameter relationships between seismic velocities, resistivities and densities that are adequately describe the rock property behaviors of both the basaltic lava flows and sedimentary layers in this region. In addition, a 3-D reflection seismic survey covering the central part allows us to incorporate the top of basalt and other features as constraints in the joint inversions and to evaluate the quality of the final results. Literature: D. Colombo, M. Mantovani, S. Hallinan, M. Virgilio, 2008. Sub-basalt depth imaging using simultaneous joint inversion of seismic and electromagnetic (MT) data: a CRB field study. SEG Expanded Abstract, Las Vegas, USA, 2674-2678. M. Jordan, J. Ebbing, M. Brönner, J. Kamm , Z. Du, P. Eliasson, 2012. Joint Inversion for Improved Sub-salt and Sub-basalt Imaging with Application to the More Margin. EAGE Expanded Abstracts, Copenhagen, DK. M. Moorkamp, B. Heincke, M. Jegen, A.W.Roberts, R.W. Hobbs, 2011. A framework for 3-D joint inversion of MT, gravity and seismic refraction data. Geophysical Journal International, 184, 477-493.

  6. 3D-seismic observations of Late Pleistocene glacial dynamics on the central West Greenland margin

    NASA Astrophysics Data System (ADS)

    Hofmann, Julia; Knutz, Paul; Cofaigh, Colm Ó.

    2016-04-01

    Fast-flowing ice streams and outlet glaciers exert a major control on glacial discharge from contemporary and palaeo ice sheets. Improving our understanding of the extent and dynamic behaviour of these palaeo-ice streams is therefore crucial for predictions of the response of ice sheets to present and future climate warming and the associated implications for global sea level. This poster presents results from two 3D-seismic surveys located on the shelf adjoining the Disko Bay trough-mouth fan (TMF), one of the largest glacial outlet systems in Greenland. Located at the seaward terminus of the c. 370 km long cross-shelf Disko Trough, the Disko Bay TMF was generated by highly efficient subglacial sediment delivery onto the continental slopes during repeated ice-stream advances. A variety of submarine glacial landform assemblages are recognised on the seabed reflecting past ice-stream activity presumably related to glacial-interglacial cycles. The 3D-seismic volumes cover the shallow banks located north and south of the Disko Trough. The focus of this study is the seabed and the uppermost stratigraphic interval associated with the Late Stage of TMF development, presumably covering the late Pleistocene (Hofmann et al., submitted). Seabed morphologies include multiple sets of ridges up to 20 m high that extend in NW-SE direction for c. 30 km, and cross-cutting curvilinear furrows with maximum lengths of c. 9 km and average depths of c. 4.5 m. Back-stepping, arcuate scarps facing NW define the shelf break on the northern survey, comprising average widths of c. 4.5 km and incision depths of c. 27.5 m. The large transverse ridge features on the southern survey are likely ice-marginal and are interpreted as terminal moraine ridges recording the existence of a shelf-edge terminating, grounded Late Weichselian ice sheet. The furrows, most prominent on the outer shelf adjoining the shallow banks and partly incising the moraine ridges, are interpreted as iceberg ploughmarks

  7. 3D multicomponent seismic characterization of a clastic reservoir in the Middle Magdalena Valley Basin, Colombia

    NASA Astrophysics Data System (ADS)

    Velasquez-Espejo, Antonio Jose

    The main goal of this research is to characterize the combined structural-stratigraphic trap of the Tenerife Field in the Middle Magdalena Valley Basin (MMVB), Colombia. For the first time in Colombia the structural and quantitative interpretation of modern three-dimensional multicomponent (3D-3C) seismic imaging enables a geometric description, a kinematic interpretation of the structural styles, and the facies distribution of the reservoir. A seismic petrophysics work-flow to better achieve the seismic well-tie. Edited and check-shot calibrated P-wave sonic logs were obtained and coefficients of the Gardner and Castagna equations were calibrated to match the density and shear-wave velocity depth trends for the basin. Seismic modeling was performed to evaluate the PP and PS seismic response of the reservoir interval (Mugrosa Formation). The structural interpretation methodology involves a 3D fault-correlation and horizon picking for both PP- and PS-PSTM data volumes. Geometric attributes such as coherence and curvature were used to enhance the structural discontinuities. The main unconformity of the Middle Eocene (MEU) was interpreted, and an attribute-assisted interpretation of the reservoir was conducted in detail. While P-wave data provided most of the structural interpretation, converted-wave data provide a better understanding of the faults. Traditionally, compressive thrust-propagation folds and tectonic inversion have been considered as the main mechanisms controlling the deformation in the MMVB. However, the new interpretation shown in this work provides a different structural concept that involves two major structural styles: 1. Under the MEU the Late Cretaceous and Early Paleocene deformation, dominated by east-verging thrust and partially inverted Mesozoic normal faults, is preserved. Associated folds exhibit a north-south strike, and their structural development is controlled by a long-lived structural element that dominates the area (the Infantas

  8. Evolution of Submarine Gullies on a Prograding Slope: Insights from 3D Seismic Reflection Data

    NASA Astrophysics Data System (ADS)

    Shumaker, L.; Jobe, Z. R.

    2014-12-01

    Submarine gullies are common features on continental slopes on both passive and active margins, but the processes dictating gully formation and the role of gullies in deep-water sediment transport are topics of debate. The geometries of gullies can provide clues to understanding the processes by which they initiate and grow, particularly when considered in the context of surrounding submarine geomorphology. Further confidence in these interpretations can be gained by tracking the temporal history of gullies with evolution of the continental margin. The 500 km2 Tui 3D seismic survey from the Taranaki Basin, New Zealand, shows continental slope gullies and other channel features in a ~1 km-thick package of prograding shelf-slope clinoforms that developed over Pliocene-Pleistocene time. This dataset allows for documentation of gullies over ~3 Ma, through numerous cycles of initiation and burial. For this study, we manually interpreted clinoform packages to generate 'paleo-seafloor' surfaces that provide context such as position of the shelf edge, slope gradient and azimuth, and relative progradation and aggradation magnitudes. Gully geometries were obtained from detailed seismic interpretation guided by semblance and RMS amplitude imaging on these surfaces. Gullies are low sinuosity, with widths ranging from ~50-150 m and depths from a few tens to <100 m. Gullies are observed to grow in width and relief downslope without evidence for aggradational confinement (levees), and in some cases form gully 'complexes' hundreds of m wide in the lower slope region. These complexes are present through >150 m of stratigraphy, indicating that they are long-lived features on the slope. This further indicates that the frequency of flows along the gullies was enough to maintain their topographic expression during slope progradation and aggradation, and suggests that gullies play an integral role in transport processes on the slope.

  9. Comparative velocity structure of active Hawaiian volcanoes from 3-D onshore-offshore seismic tomography

    USGS Publications Warehouse

    Park, J.; Morgan, J.K.; Zelt, C.A.; Okubo, P.G.; Peters, L.; Benesh, N.

    2007-01-01

    We present a 3-D P-wave velocity model of the combined subaerial and submarine portions of the southeastern part of the Island of Hawaii, based on first-arrival seismic tomography of marine airgun shots recorded by the onland seismic network. Our model shows that high-velocity materials (6.5-7.0??km/s) lie beneath Kilauea's summit, Koae fault zone, and the upper Southwest Rift Zone (SWRZ) and upper and middle East Rift Zone (ERZ), indicative of magma cumulates within the volcanic edifice. A separate high-velocity body of 6.5-6.9??km/s within Kilauea's lower ERZ and upper Puna Ridge suggests a distinct body of magma cumulates, possibly connected to the summit magma cumulates at depth. The two cumulate bodies within Kilauea's ERZ may have undergone separate ductile flow seaward, influencing the submarine morphology of Kilauea's south flank. Low velocities (5.0-6.3??km/s) seaward of Kilauea's Hilina fault zone, and along Mauna Loa's seaward facing Kao'iki fault zone, are attributed to thick piles of volcaniclastic sediments deposited on the submarine flanks. Loihi seamount shows high-velocity anomalies beneath the summit and along the rift zones, similar to the interpreted magma cumulates below Mauna Loa and Kilauea volcanoes, and a low-velocity anomaly beneath the oceanic crust, probably indicative of melt within the upper mantle. Around Kilauea's submarine flank, a high-velocity anomaly beneath the outer bench suggests the presence of an ancient seamount that may obstruct outward spreading of the flank. Mauna Loa's southeast flank is also marked by a large, anomalously high-velocity feature (7.0-7.4??km/s), interpreted to define an inactive, buried volcanic rift zone, which might provide a new explanation for the westward migration of Mauna Loa's current SWRZ and the growth of Kilauea's SWRZ. ?? 2007 Elsevier B.V. All rights reserved.

  10. A 3D S-wave model of the Valhall subsurface from ambient seismic noise tomography

    NASA Astrophysics Data System (ADS)

    Mordret, A.; Landes, M.; Shapiro, N.; Singh, S. C.; Roux, P.

    2013-12-01

    We present a depth inversion of Scholte wave group and phase velocity maps obtained from cross-correlation of 6.5 hours of noise data from the Valhall Life of Field Seismic (LoFS) network. We computed 2 690 040 vertical-vertical component cross-correlations from the 2320 available sensors, turning each sensor into a virtual source emitting Scholte waves. We used a traditional straight-ray surface-wave tomography to compute the group velocity map. The phase velocity maps have been computed using the Eikonal tomography method. For every virtual source, we measured the Scholte wave phase travel times to all other stations and interpolated them on a regular grid. This phase travel-time surface is inverted into phase velocity map via applying the eikonal equation. The contributions from all 2320 virtual sources are stacked to create the final phase velocity map of the Valhall subsurface. Scholte wave isotropic phase velocity maps at periods between 0.65 s and 1.6 s show a coherent geomorphological pattern dominated by paleo-channels in the shallower part. We also retrieved the azimuthal anisotropy and its lateral variations showing a characteristic elliptical pattern around the central exploitation platform. The inversion of these maps in depth using the Neighbourhood Algorithm allowed us to create a high resolution 3D S-wave model of the first 600 m of the Valhall subsurface and to precise the locations of geological structures at depth. These results would have important implication for shear wave statics and monitoring of sea-floor subsidence due to oil extraction. The 3D model could also be a good candidate for a starting model used in full-waveform inversions.

  11. Investigations into the feasibility of optical-CT 3D dosimetry with minimal use of refractively matched fluids

    SciTech Connect

    Chisholm, Kelsey; Miles, Devin; Rankine, Leith; Oldham, Mark

    2015-05-15

    Purpose: In optical-CT, the use of a refractively matched polyurethane solid-tank in place of a fluid bath has the potential to greatly increase practical convenience, reduce cost, and possibly improve the efficacy of flood corrections. This work investigates the feasibility of solid-tank optical-CT imaging for 3D dosimetry through computer simulation. Methods: A MATLAB ray-tracing simulation platform, ScanSim, was used to model a parallel-source telecentric optical-CT imaging system through a polyurethane solid-tank containing a central cylindrical hollow into which PRESAGE radiochromic dosimeters can be placed. A small amount of fluid fills the 1–5 mm gap between the dosimeter and the walls of the tank. The use of the solid-tank reduces the required amount of fluid by approximately 97%. To characterize the efficacy of solid-tank, optical-CT scanning simulations investigated sensitivity to refractive index (RI) mismatches between dosimeter, solid-tank, and fluid, for a variety of dosimeter (RI = 1.5–1.47) and fluid (RI = 1.55–1.0) combinations. Efficacy was evaluated through the usable radius (r{sub u}) metric, defined as the fraction of the radius of the dosimeter where measured dose is predicted to be within 2% of the ground truth entered into the simulation. Additional simulations examined the effect of increasing gap size (1–5 mm) between the dosimeter and solid-tank well. The effects of changing the lens tolerance (0.5°–5.0°) were also investigated. Results: As the RI mismatch between the dosimeter and solid-tank increased from 0 to 0.02, the usable radius decreased from 97.6% to 50.2%. The optimal fluid RI decreased nonlinearly from 1.5 to 1.34 as the mismatch increased and was up to 9% lower than the tank. Media mismatches between the dosimeter and solid-tank also exacerbate the effects of changing the gap size, with no easily quantifiable relationship with usable radius. Generally, the optimal fluid RI value increases as gap size increases and

  12. High-Resolution Seismic Reflection and Refraction Imaging of the Hayward Fault in Fremont, Alameda County, California

    NASA Astrophysics Data System (ADS)

    Everson, E. D.; Rymer, M. J.; Goldman, M. R.; Catchings, R. D.

    2007-12-01

    In July 2007, the U.S. Geological Survey acquired a 60-m-long seismic reflection and refraction profile across the main trace of the Hayward fault in Fremont Central Park, Fremont, California. The profile was designed to determine the geometry, seismic velocities, and possible structural complexities of the fault. The study was along a part of the surface rupture of the 1868 M 7.0 Hayward earthquake. We used single-element, 40-Hz vertical geophones placed at 1-m intervals along the profile with 0.5-m lateral offset from the shot points, also with 1-m intervals. Seismic sources were generated by multiple sledgehammer blows at each shot point. Data were recorded unfiltered in the field on a Geometrics Strataview RX-60 seismograph at a sampling rate of 0.5 ms for 2 s. Geophone locations were measured in 3D using differential GPS. We developed a velocity model using the Hole (1992) code to invert P-wave first arrivals of the refraction data. Seismic P-wave velocities range from about 200 m/s near the surface to approximately 800 m/s at a depth of 13 to 16 m. The velocity model was then applied to the reflection data to develop an unmigrated common depth point (CDP) stack. The reflection data indicate the presence of at least three fault strands in an approximately 20-m-wide zone. We believe the three strands define an upwardly flaring 'flower structure', with the central strand being the main strand of the Hayward fault. The three strands project to merge at a depth of about 150 m; the overall dip of the fault zone in the upper 100 m is to the northeast, at about 88 degrees.

  13. 3D Seismic Reflection Data: Has the Geological Hubble Retained Its Focus?

    NASA Astrophysics Data System (ADS)

    Jackson, Christopher

    2016-04-01

    In their seminal paper in 2002, Joe Cartwright and Mads Huuse referred to 3D seismic reflection data as the 'Geological Hubble', illustrating how these data had the potential to revolutionise our understanding of the genesis and evolution of sedimentary basins. 14 years on, I will here outline just some of the key recent advances made in our understanding of basin structure and stratigraphy, focusing on: (i) the intrusion and extrusion of igneous rocks; (ii) salt tectonics, with particular emphasis on intrasalt structure and the kinematics and mechanics of diapirism; (iii) the geometry and growth of normal faults; and (iv) the structure and emplacement of mass-transport complexes (MTCs). I will stress that future advances at least partly relies on hydrocarbon exploration companies and government agencies continuing to make their data freely available via easy-to-access data portals. I will issue a clarion call to academics, stressing that 'geodynamicists', sedimentologists, structural geologists and geomorphologists, amongst others, can benefit from utilising what I believe are currently an underused data type.

  14. Seismic 3D modelling of VHMS deposits: case studies from Pyhäsalmi and Vihanti, Finland

    NASA Astrophysics Data System (ADS)

    Heinonen, Suvi; Heikkinen, Pekka; Kukkonen, Ilmo; Snyder, David

    2013-04-01

    from the known deposit of Pyhäsalmi. Heterogeneous geological surroundings and an unfavourable shape of the ore deposit mask the seismic signal originating from the ore-host rock contact. Based on these experiences, hardrock seismic exploration is most efficiently done through geological 3D-modeling in which determination of a favourable geological setting for ore is used to target drill holes instead of only hunting bright spots. In both study areas seismic data has increased the knowledge about areal geological structures, continuation of ore-hosting lithologies in depth and also helped to understand better the tectonic evolution of the area. These studies show that 3D modelling of seismic profiles is efficient in improving geological understanding of the structures controlling the ore deposits in thus guiding exploration efforts.

  15. Effect of 3-D viscoelastic structure on post-seismic relaxation from the 2004 M = 9.2 Sumatra earthquake

    USGS Publications Warehouse

    Pollitz, F.; Banerjee, P.; Grijalva, K.; Nagarajan, B.; Burgmann, R.

    2008-01-01

    The 2004 M=9.2 Sumatra-Andaman earthquake profoundly altered the state of stress in a large volume surrounding the ???1400 km long rupture. Induced mantle flow fields and coupled surface deformation are sensitive to the 3-D rheology structure. To predict the post-seismic motions from this earthquake, relaxation of a 3-D spherical viscoelastic earth model is simulated using the theory of coupled normal modes. The quasi-static deformation basis set and solution on the 3-D model is constructed using: a spherically stratified viscoelastic earth model with a linear stress-strain relation; an aspherical perturbation in viscoelastic structure; a 'static'mode basis set consisting of Earth's spheroidal and toroidal free oscillations; a "viscoelastic" mode basis set; and interaction kernels that describe the coupling among viscoelastic and static modes. Application to the 2004 Sumatra-Andaman earthquake illustrates the profound modification of the post-seismic flow field at depth by a slab structure and similarly large effects on the near-field post-seismic deformation field at Earth's surface. Comparison with post-seismic GPS observations illustrates the extent to which viscoelastic relaxation contributes to the regional post-seismic deformation. ?? Journal compilation ?? 2008 RAS.

  16. 3-D Seismic Images of Mud Volcano North Alex, West-Nile Delta, Egypt

    NASA Astrophysics Data System (ADS)

    Bialas, Joerg; Klaeschen, Dirk; Papenberg, Cord; Gehrmann, Romina; Sommer, Malte

    2010-05-01

    Mud volcanoes within shelf areas are the bathymetric expression of mobilized overpressured sediments causing a feature of possible instability within the slope. Such a scene is given in the West-Nile Delta offshore Alexandria, Egypt at 700 m water depth, ,which was studied during a RWE Dea funded research project. The West Nile Delta forms part of the source of the large turbiditic Nile Deep Sea Fan. Since the late Miocene sediments have formed an up to 10 km thick pile, which includes about 1 - 3 km of Messinian evaporates. The sediment load of the overburden implies strong overpressures and salt-related tectonic deformation. Both are favourable for fluid migration towards the seafloor guided by the fractured margin. Deep-cutting channel systems like the Rosetta channel characterize the continental slope. Bathymetric expressions of slides and numerous mud volcanoes in the area are expressions of active processes, which contribute to the ongoing modification of the slope. The western deltaic system, Rosetta branch, has formed an 80 km wide continental shelf. Here at 700 m water depth the mud volcano North Alex developed his circular bathymetric feature, which proved to be an active gas and mud-expelling structure. A grid of 2-D seismic profiles did reveal a large set of faults located within the main mud volcano as well as surrounding the structure. Internal faults are mainly related to episodic mud expulsion processes and continuous gas and fluid production. Deep cutting external faults surround the structure in a half circle shape. They can be tracked up to the seafloor indicating ongoing tectonic activity of the slope area. A recently build 3-D acquisition system (funded by RWE Dea) suitable for mid-size research vessels was applied to collect an active seismic cube of the mud volcano. Based on the P-Cable design 11 parallel streamers (each 12.5 m long with 1.5 m group interval) were used to record shots of a single 210 cinch GI airgun. Based on GPS positions of

  17. CO2 mass estimation visible in time-lapse 3D seismic data from a saline aquifer and uncertainties

    NASA Astrophysics Data System (ADS)

    Ivanova, A.; Lueth, S.; Bergmann, P.; Ivandic, M.

    2014-12-01

    At Ketzin (Germany) the first European onshore pilot scale project for geological storage of CO2 was initiated in 2004. This project is multidisciplinary and includes 3D time-lapse seismic monitoring. A 3D pre-injection seismic survey was acquired in 2005. Then CO2 injection into a sandstone saline aquifer started at a depth of 650 m in 2008. A 1st 3D seismic repeat survey was acquired in 2009 after 22 kilotons had been injected. The imaged CO2 signature was concentrated around the injection well (200-300 m). A 2nd 3D seismic repeat survey was acquired in 2012 after 61 kilotons had been injected. The imaged CO2 signature further extended (100-200 m). The injection was terminated in 2013. Totally 67 kilotons of CO2 were injected. Time-lapse seismic processing, petrophysical data and geophysical logging on CO2 saturation have allowed for an estimate of the amount of CO2 visible in the seismic data. This estimate is dependent upon a choice of a number of parameters and contains a number of uncertainties. The main uncertainties are following. The constant reservoir porosity and CO2 density used for the estimation are probably an over-simplification since the reservoir is quite heterogeneous. May be velocity dispersion is present in the Ketzin reservoir rocks, but we do not consider it to be large enough that it could affect the mass of CO2 in our estimation. There are only a small number of direct petrophysical observations, providing a weak statistical basis for the determination of seismic velocities based on CO2 saturation and we have assumed that the petrophysical experiments were carried out on samples that are representative for the average properties of the whole reservoir. Finally, the most of the time delay values in the both 3D seismic repeat surveys within the amplitude anomaly are near the noise level of 1-2 ms, however a change of 1 ms in the time delay affects significantly the mass estimate, thus the choice of the time-delay cutoff is crucial. In spite

  18. Thrust fault segmentation and downward fault propagation in accretionary wedges: New Insights from 3D seismic reflection data

    NASA Astrophysics Data System (ADS)

    Orme, Haydn; Bell, Rebecca; Jackson, Christopher

    2016-04-01

    The shallow parts of subduction megathrust faults are typically thought to be aseismic and incapable of propagating seismic rupture. The 2011 Tohoku-Oki earthquake, however, ruptured all the way to the trench, proving that in some locations rupture can propagate through the accretionary wedge. An improved understanding of the structural character and physical properties of accretionary wedges is therefore crucial to begin to assess why such anomalously shallow seismic rupture occurs. Despite its importance, we know surprisingly little regarding the 3D geometry and kinematics of thrust network development in accretionary prisms, largely due to a lack of 3D seismic reflection data providing high-resolution, 3D images of entire networks. Thus our current understanding is largely underpinned by observations from analogue and numerical modelling, with limited observational data from natural examples. In this contribution we use PSDM, 3D seismic reflection data from the Nankai margin (3D Muroto dataset, available from the UTIG Academic Seismic Portal, Marine Geoscience Data System) to examine how imbricate thrust fault networks evolve during accretionary wedge growth. We unravel the evolution of faults within the protothrust and imbricate thrust zones by interpreting multiple horizons across faults and measuring fault displacement and fold amplitude along-strike; by doing this, we are able to investigate the three dimensional accrual of strain. We document a number of local displacement minima along-strike of faults, suggesting that, the protothrust and imbricate thrusts developed from the linkage of smaller, previously isolated fault segments. Although we often assume imbricate faults are likely to have propagated upwards from the décollement we show strong evidence for fault nucleation at shallow depths and downward propagation to intersect the décollement. The complex fault interactions documented here have implications for hydraulic compartmentalisation and pore

  19. Archive report for most USGS seismic refraction investigations conducted between 1978 and 1991

    USGS Publications Warehouse

    Murphy, Janice M.

    2000-01-01

    In 1978, the U.S. Geological Survey (USGS) began acquiring seismic refraction data throughout the U.S. and Saudi Arabia. Numerous professional papers have been published in the literature and the technical details and goals for most of these surveys have been described in USGS Open-file reports (Table 1). This report describes the archiving of the data.

  20. San Francisco Bay Area Velocity Structure From Controlled-Source Seismic Refraction Imaging

    NASA Astrophysics Data System (ADS)

    Goldman, M. R.; Catchings, R. D.; Steedman, C. E.; Gandhok, G.; Boatwright, J.; Rymer, M. J.

    2004-12-01

    To better understand the velocities and structures of the crust and upper mantle in the San Francisco Bay area, we developed 2-D tomographic velocity models along four seismic refraction profiles acquired along and across the bay area in the early 1990's. The four profiles extended from (1) Hollister to Inverness along the San Francisco and Marin Peninsulas (~200 km long), (2) Hollister to Santa Rosa along the East Bay (~220 km long), (3) the Pacific Ocean to Livermore crossing the bay (~100 km long), and (4) the Pacific Ocean to the western Santa Clara Valley (~25 km long), centered on the epicenter of the1989 M. 6.9 Loma Prieta earthquake. Velocity models were not previously developed for three of the seismic profiles, and the previously developed model for the fourth profile (Catchings and Kohler, 1996) did not include some of the currently available seismic data. The profiles along the bay image structures from the near surface to about 25 km depth, and they show velocity anomalies associated with the major faults (San Andreas, Hayward, Rodgers Creek, Calaveras) and basins along the profile. Velocities range from about 2 km/s in the basins to about 7 km/s at the Moho, which dips southward along both sides of the bay. The cross bay profile shows velocity anomalies associated with six fault zones between the Pacific Ocean and the Livermore Valley and higher upper-crustal velocities (~6.2 km/s) between the San Andreas and Hayward faults than to the southwest (~5 km/s) or northeast (~4 km/s) of those faults. The Loma Prieta profile shows velocities ranging from 2 km/s to 6 km/s in the upper 5 km, with the highest velocities in the epicentral region of the 1989 Loma Prieta earthquake. A pronounced, northeast-dipping, low-velocity zone is located beneath the surface expression of the San Andreas fault zone, but other fault zones along the profile show high-velocity anomalies beneath their surface expressions. Collectively, the velocity images show the complexity of

  1. 3D seismic imaging around the 2.5 km deep COSC-1 scientific borehole, central Sweden

    NASA Astrophysics Data System (ADS)

    Hedin, Peter; Juhlin, Christopher; Buske, Stefan

    2015-04-01

    Following the successful completion of the COSC-1 drilling campaign, a number of geophysical investigations have been performed in and around the 2.5 km deep borehole. Three different seismic experiments were conducted simultaneously in the fall of 2014 to take advantage of the same source points; 1) a Vertical Seismic Profile (VSP) in the borehole, 2) three 2D seismic profiles across the borehole, and 3) a limited 3D seismic survey (presented here). The latter is the first 3D seismic survey on land in Scandinavia to target the Caledonian Nappes and will allow mapping a small part of the Seve Nappe Complex (SNC) in 3D. Furthermore, it will allow extrapolation of results from downhole logging, core analysis and other seismic surveys to structures surrounding the borehole. A total number of 429 receivers (10 Hz single component geophones) were planted with 20 m separation along 7 lines spaced 200 m apart. The total area with receivers covered approximately 1.5 km2 and was centered on the drill site. A combination of a mechanical source (a rock breaking hydraulic hammer, near offsets) and explosive charges (0.5 kg fired at 3.5 - 5 m depth, far offsets) were used. The source points were activated along roads radiating outwards from the COSC-1 drill site in a star pattern. The nominal shot spacing was 20 m (vibrating source) or 80 m (explosives) and maximum horizontal offset was about 5.75 km. The high-grade metamorphic SNC is well known from previous 2D seismic studies to be a highly reflective unit. However, due to the complex 3D geometry and lithological variation within the unit, it has not been clearly imaged. The new 3D data provide a means to image these structures in more detail and to follow the lithological and structural interfaces observed in the core into the surrounding unit. Preliminary results from the 3D processing and correlation with borehole data will be presented.

  2. Well log analysis to assist the interpretation of 3-D seismic data at Milne Point, north slope of Alaska

    USGS Publications Warehouse

    Lee, Myung W.

    2005-01-01

    In order to assess the resource potential of gas hydrate deposits in the North Slope of Alaska, 3-D seismic and well data at Milne Point were obtained from BP Exploration (Alaska), Inc. The well-log analysis has three primary purposes: (1) Estimate gas hydrate or gas saturations from the well logs; (2) predict P-wave velocity where there is no measured P-wave velocity in order to generate synthetic seismograms; and (3) edit P-wave velocities where degraded borehole conditions, such as washouts, affected the P-wave measurement significantly. Edited/predicted P-wave velocities were needed to map the gas-hydrate-bearing horizons in the complexly faulted upper part of 3-D seismic volume. The estimated gas-hydrate/gas saturations from the well logs were used to relate to seismic attributes in order to map regional distribution of gas hydrate inside the 3-D seismic grid. The P-wave velocities were predicted using the modified Biot-Gassmann theory, herein referred to as BGTL, with gas-hydrate saturations estimated from the resistivity logs, porosity, and clay volume content. The effect of gas on velocities was modeled using the classical Biot-Gassman theory (BGT) with parameters estimated from BGTL.

  3. Tectonics Of Eastern Offshore Trinidad Based On Integration Of BOLIVAR 2D Seismic Lines With Industry 3D Seismic Surveys

    NASA Astrophysics Data System (ADS)

    Soto, M. D.; Mann, P.; Wood, L. J.

    2004-12-01

    New MCS lines in the eastern offshore area of Trinidad augmented by existing 3D seismic surveys by industry provide new insights into complex, strain partitioning produced along this segment of the South America-Caribbean plate boundary. Two major tectonosequences are imaged separated by a Middle Miocene angular unconformity known from wells and mapping in Trinidad. A thick section of deep-marine carbonate and clastic rocks are cleanly truncated by the Middle Miocene unconformity and are chaotically deformed along vertical to northwest-dipping thrust faults. This shortening event reflects a major pulse of pre-Middle Miocene southeastward overthrusting of the Caribbean arc over the passive margin of South America. An upper 2-7-km-thick tectonosequence consisting of late Miocene-Quaternary shelf-related sandstone and shale was deposited by the nearby Orinoco delta. This section is folded to lesser degree and deformed by the sub-vertical, right-lateral Central Range fault zone (CRFZ), known from GPS studies to accommodate 12 mm/yr, of the total 20 mm/yr of interplate motion. Deep, continuous reflec-tors are observed at a depth of 12-17 km beneath eastern Trinidad are correlated with authochthonous, late Cretaceous-early Tertiary carbonate and clastic rocks of the South American passive margin. The Darien fault southeast of the CRFZ accommodates active shortening, elevates passive margin rocks to the surface in Trinidad, and forms the northeastern limit of a large, 12-km-thick foreland basin (Columbus basin) that extends onshore.

  4. Development of a 400 Level 3C Clamped Downhole Seismic Receiver Array for 3D Borehole Seismic Imaging of Gas Reservoirs

    SciTech Connect

    Bjorn N. P. Paulsson

    2006-09-30

    Borehole seismology is the highest resolution geophysical imaging technique available today to the oil and gas industry for characterization and monitoring of oil and gas reservoirs. However, the industry's ability to perform high resolution 3D imaging of deep and complex gas reservoirs using borehole seismology has been hampered by the lack of acquisition technology necessary to record large volumes of high frequency, high signal-to-noise-ratio borehole seismic data. This project took aim at this shortcoming by developing a 400 level 3C clamped downhole seismic receiver array, and accompanying software, for borehole seismic 3D imaging. This large borehole seismic array has removed the technical acquisition barrier for recording the data volumes necessary to do high resolution 3D VSP and 3D cross-well seismic imaging. Massive 3D VSP{reg_sign} and long range Cross-Well Seismology (CWS) are two of the borehole seismic techniques that promise to take the gas industry to the next level in their quest for higher resolution images of deep and complex oil and gas reservoirs. Today only a fraction of the oil or gas in place is produced when reservoirs are considered depleted. This is primarily due to our lack of understanding of detailed compartmentalization of oil and gas reservoirs. In this project, we developed a 400 level 3C borehole seismic receiver array that allows for economic use of 3D borehole seismic imaging for reservoir characterization and monitoring. This new array has significantly increased the efficiency of recording large data volumes at sufficiently dense spatial sampling to resolve reservoir complexities. The receiver pods have been fabricated and tested to withstand high temperature (200 C/400 F) and high pressure (25,000 psi), so that they can operate in wells up to 7,620 meters (25,000 feet) deep. The receiver array is deployed on standard production or drill tubing. In combination with 3C surface seismic or 3C borehole seismic sources, the 400

  5. Seismic Hazard Maps for Seattle, Washington, Incorporating 3D Sedimentary Basin Effects, Nonlinear Site Response, and Rupture Directivity

    USGS Publications Warehouse

    Frankel, Arthur D.; Stephenson, William J.; Carver, David L.; Williams, Robert A.; Odum, Jack K.; Rhea, Susan

    2007-01-01

    This report presents probabilistic seismic hazard maps for Seattle, Washington, based on over 500 3D simulations of ground motions from scenario earthquakes. These maps include 3D sedimentary basin effects and rupture directivity. Nonlinear site response for soft-soil sites of fill and alluvium was also applied in the maps. The report describes the methodology for incorporating source and site dependent amplification factors into a probabilistic seismic hazard calculation. 3D simulations were conducted for the various earthquake sources that can affect Seattle: Seattle fault zone, Cascadia subduction zone, South Whidbey Island fault, and background shallow and deep earthquakes. The maps presented in this document used essentially the same set of faults and distributed-earthquake sources as in the 2002 national seismic hazard maps. The 3D velocity model utilized in the simulations was validated by modeling the amplitudes and waveforms of observed seismograms from five earthquakes in the region, including the 2001 M6.8 Nisqually earthquake. The probabilistic seismic hazard maps presented here depict 1 Hz response spectral accelerations with 10%, 5%, and 2% probabilities of exceedance in 50 years. The maps are based on determinations of seismic hazard for 7236 sites with a spacing of 280 m. The maps show that the most hazardous locations for this frequency band (around 1 Hz) are soft-soil sites (fill and alluvium) within the Seattle basin and along the inferred trace of the frontal fault of the Seattle fault zone. The next highest hazard is typically found for soft-soil sites in the Duwamish Valley south of the Seattle basin. In general, stiff-soil sites in the Seattle basin exhibit higher hazard than stiff-soil sites outside the basin. Sites with shallow bedrock outside the Seattle basin have the lowest estimated hazard for this frequency band.

  6. New insights into the earliest Quaternary environments in the Central North Sea from 3D seismic

    NASA Astrophysics Data System (ADS)

    Lamb, Rachel; Huuse, Mads; Stewart, Margaret; Brocklehurst, Simon H.

    2014-05-01

    In the past the transition between an unconformable surface in the south to a conformable horizon towards the north has made identification and mapping the base-Quaternary in the central North Sea difficult (Sejrup et al 1991; Gatliff et al 1994). However recent integration of biostratigraphy, pollen analysis, paleomagnetism and amino acid analysis in the Dutch and Danish sectors (Rasmussen et al 2005; Kuhlmann et al 2006) has allowed greater confidence in the correlation to the region 3D seismic datasets and thus has allowed the base-Quaternary to be mapped across the entire basin. The base-Quaternary has been mapped using the PGS MegaSurvey dataset from wells in the Danish Sector along the initially unconformable horizon and down the delta front into the more conformable basin giving a high degree of confidence in the horizon pick. The revised base-Quaternary surface reaches a depth of 1248 ms TWT with an elongate basin shape which is significantly deeper than the traditionally mapped surface. Using RMS amplitudes and other seismic attributes the revised base-Quaternary has been investigated along the horizon and in time slice to interpret the environments of the earliest Quaternary prior to the onset of glaciation. Combined with analysis of aligned elongate furrows over 10 km long, 100 m wide and 100 m deep suggest a deep marine environment in an almost enclosed basin with persistent strong NW-SE bottom currents in the deepest parts. Pockmarks were formed by the escape of shallow gas on the sides of a small delta in the eastern part of the basin. The progradation of large deltas from both the north and south into the basin make up the majority of the deposition of sediment into the basin. Key Words: base-Quaternary; seismic interpretation; paleoenvironments References: Gatliff, R.W, Richards, P.C, Smith, K, Graham, C.C, McCormac, M, Smith, N.J.P, Long, D, Cameron, T.D.J, Evans, D, Stevenson, A.G, Bulat, J, Ritchie, J.D, (1994) 'United Kingdom offshore regional

  7. 3D Seismic Studies of Igneous Intrusions, Taranaki Basin, off-shore west New Zealand

    NASA Astrophysics Data System (ADS)

    Harbor, R. L.; Chrisitiansen, E. H.; Keach, R. W.

    2008-12-01

    Several off-shore volcano-plutonic complexes are imaged in a detailed 3D seismic survey acquired by Pogo New Zealand/Plains Exploration. The new data provide insight into the sizes, shapes, and wall rock deformation associated with the emplacement of plutons. The seismic survey, conducted in 2005, covers 1700 km2 and was processed with modern techniques used in hydrocarbon exploration. The images and structures have to be interpreted with care because of distortions caused by "velocity pull ups" created by the large seismic wave velocity contrast between sediment and igneous rock. The magmatic rocks may be part of the Mohakatino Volcanic Centre (15 to 1.5 Ma) that intrudes and partially fills the Taranaki graben, which began to form in the Cretaceous. Imaged plutons range from less than 1 to as much as 12 km across. The intrusions are steep-sided and do not resemble sills, but their bases are poorly resolved. The top of the largest complex is sharply delineated and marked by multiple apophyses as much as 2 km across and hundreds of meters high. Deformation along the sides of the intrusion is dominated by of a faulted rim anticline, with apparent dips of 45° or higher. Dips decrease rapidly away from the intrusion but doming extends several hundred meters from the margins. A series of high-angle faults fan out from the margin of the pluton and cut the folded strata along the margin. These faults terminate against the margins of the intrusion, extend as much as 1 pluton diameter away from the margin, and then merge with "regional" faults that are part of the Taranaki graben. Offset along these radiating faults is on the order of a few hundred meters. Strata on the top of the complex are thinned but are deformed into a faulted dome with an amplitude of about 1 km. Steep, dip-slip faults form a semi-radial pattern in the roof rocks but are strongly controlled by the regional stress field as many of the faults are sub-parallel to those that form the graben. The longest

  8. Structure of the Lesser Antilles subduction zone from seismic refraction tomography

    NASA Astrophysics Data System (ADS)

    Charvis, P.; Evain, M.; Galve, A.; Laigle, M.; Ruiz Fernandez, M.; Kopp, H.; Hirn, A.; Flueh, E. R.; Party, T.

    2011-12-01

    In 2007, two wide-angle seismic experiments were conducted to constrain the structure of the central Lesser Antilles subduction zone. During the Sismantilles II experiment, seismic refraction data recorded by a network of 27 OBSs over an area of more than 6000 km2 provide new insights on the crustal structure of the forearc offshore Martinique and Dominica islands. The tomographic inversion of first arrival travel times provides a 3D P-wave velocity model down to 15 km. Basement velocity gradient shows the forearc made of two distinct units: A high velocity gradient domain named the inner forearc in comparison to a lower velocity gradient domain located further trenchward named the outer forearc. The inner forearc is likely the extension at depth of the Mesozoic magmatic crust outcropping to the north in La Désirade Island and along the scarp of the Karukera spur and then represent the eastern limit of the Caribbean Plateau. The outer forearc probably consists of magmatic rocks of a similar origin. It could be either part of the margin of the Caribbean Plateau, like the inner forearc, but the crust was thinned and fractured during the past tectonic history of the area or by recent subduction processes, or an oceanic terrane more recently accreted to the island arc. Whereas the inner forearc appears as a rigid block uplifted and tilted as a whole to the south, short wavelength deformations of the outer forearc basement are observed, beneath a 3 to 6 km thick sedimentary pile, in relation with the subduction of the Tiburon ridge and associated seamounts. North, offshore Dominica Island, the outer forearc is 70 km wide. It extends as far as 180 km to the east of the volcanic front where it acts as a backstop on which the accretionary wedge developed. Its width decreases strongly to the south to terminate offshore Martinique where the inner forearc acts as the backstop. Two dense wide-angle seismic refraction lines, shot during the Trail experiment (2007) provides a 2

  9. Seismic refraction studies on the acoustic basement in the continental shelf of the East Sea, Korea

    SciTech Connect

    Kim, K.Y.; Kim, H.J.; Han, S.J.

    1996-12-31

    Critically refracted seismic waves can be utilized in elucidation of physical properties of a high-impedance acoustic basement, where reflection methods are not effective in general. Quality factor Q was estimated for the high-impedance acoustic basement in the continental shelf of the East Sea, Korea. Various pre-processing steps for the estimation included static correction for gun delay, geometric correction, data interpolation, and Fourier transform. Based on the constant Q model, quality factor was computed for the uppermost layer within the basement using the spectral-ratio method. The computation gives values between 10.4 and 13.6, which fall under the range for water-saturated clastic sedimentary rocks. Using seismic events refracted from the layer boundaries within the acoustic basement in the study area, sedimentary layers were successfully defined. A short window AGC (automatic gain control) is an effective tool to reveal existence of the refraction boundaries. Based on a model for horizontal layers, refraction velocity and thickness were computed for each layer under a short seismic line of 3.75 km long in the continental shelf. From four distinct linear events, three layers were interpreted under the water body of 150 m deep. The computed thickness is 275 m for the top layer and 200 m for the middle one. The corresponding refraction velocities are approximately 3,900 m/s and 5,100 m/s, respectively. The refraction event from the top of the lowest layer suggests that its phase velocity is greater than 6,400 m/s.

  10. Characterization of gas hydrate distribution using conventional 3D seismic data in the Pearl River Mouth Basin, South China Sea

    USGS Publications Warehouse

    Wang, Xiujuan; Qiang, Jin; Collett, Timothy S.; Shi, Hesheng; Yang, Shengxiong; Yan, Chengzhi; Li, Yuanping; Wang, Zhenzhen; Chen, Duanxin

    2016-01-01

    A new 3D seismic reflection data volume acquired in 2012 has allowed for the detailed mapping and characterization of gas hydrate distribution in the Pearl River Mouth Basin in the South China Sea. Previous studies of core and logging data showed that gas hydrate occurrence at high concentrations is controlled by the presence of relatively coarse-grained sediment and the upward migration of thermogenic gas from the deeper sediment section into the overlying gas hydrate stability zone (BGHSZ); however, the spatial distribution of the gas hydrate remains poorly defined. We used a constrained sparse spike inversion technique to generate acoustic-impedance images of the hydrate-bearing sedimentary section from the newly acquired 3D seismic data volume. High-amplitude reflections just above the bottom-simulating reflectors (BSRs) were interpreted to be associated with the accumulation of gas hydrate with elevated saturations. Enhanced seismic reflections below the BSRs were interpreted to indicate the presence of free gas. The base of the BGHSZ was established using the occurrence of BSRs. In areas absent of well-developed BSRs, the BGHSZ was calculated from a model using the inverted P-wave velocity and subsurface temperature data. Seismic attributes were also extracted along the BGHSZ that indicate variations reservoir properties and inferred hydrocarbon accumulations at each site. Gas hydrate saturations estimated from the inversion of acoustic impedance of conventional 3D seismic data, along with well-log-derived rock-physics models were also used to estimate gas hydrate saturations. Our analysis determined that the gas hydrate petroleum system varies significantly across the Pearl River Mouth Basin and that variability in sedimentary properties as a product of depositional processes and the upward migration of gas from deeper thermogenic sources control the distribution of gas hydrates in this basin.

  11. 3-D seismic and offset VSP data for delineation of a horizontal well trajectory: Bloque IV, Lake Maracaibo

    SciTech Connect

    Barrientos, C.; Johnston, S.; Leon, K.; Stewart, L.; Bryant, I.D.

    1996-08-01

    3-D seismic data were combined with well data to provide the broad structural framework necessary to define a horizontal infill well location in the Lower Lagunillas reservoir of Bloque IV; however, the low vertical resolution of the data precluded detailed interpretation of the thin (c. 30 ft) target horizon. Horizon slices through the 3-D volume indicated lineations that might represent faults or flexures that are below resolution of the data. An offset VSP was recorded in the pilot well with a source location positioned so as to illuminate the planned well path. The frequency content of the VSP (up to 50 Hz) was much higher the dominant frequency of the surface seismic (10 Hz). The VSP provided indications of good reservoir continuity and possible improvement in reservoir quality downdip. The dip of the formation in the plane of the well path, a critical parameter for steering the well, was confirmed as close to 3 degrees. The well subsequently confirmed these indications. it appears that offset VSPs offer the potential to significantly reduce drilling risks associated with horizontal wells in Lake Maracaibo, even when 3-D surface seismic is already available.

  12. Stratigraphic Interpretation and Reservoir Implications of the Arbuckle Group (Cambrian-Ordovician) using 3D Seismic, Osage County, Oklahoma

    NASA Astrophysics Data System (ADS)

    Keeling, Ryan Marc

    The Arbuckle Group in northeastern Oklahoma consists of multiple carbonate formations, along with several relatively thin sandstone units. The group is a part of the "Great American Carbonate Bank" of the mid-continent and can be found regionally as far east as the Arkoma Basin in Arkansas, and as far west as the Anadarko Basin in Oklahoma. The Arbuckle is part of the craton-wide Sauk sequence, which is both underlain and overlain by regional unconformities. Arbuckle is not deposited directly on top of a source rock. In order for reservoirs within the Arbuckle to become charged with hydrocarbons, they must be juxtaposed against source rocks or along migration pathways. Inspired by the petroleum potential of proximal Arbuckle reservoirs and the lack of local stratigraphic understanding, this study aims to subdivide Arbuckle stratigraphy and identify porosity networks using 3D seismic within the study area of western Osage County, Oklahoma. These methods and findings can then be applied to petroleum exploration in Cambro-Ordovician carbonates in other localities. My research question is: Can the Arbuckle in SW Osage County be stratigraphically subdivided based on 3D seismic characteristics? This paper outlines the depositional environment of the Arbuckle, synthesizes previous studies and examines the Arbuckle as a petroleum system in Northeastern Oklahoma. The investigation includes an interpretation of intra-Arbuckle unconformities, areas of secondary porosity (specifically, sequence boundaries), and hydrocarbon potential of the Arbuckle Group using 3D seismic data interpretation with a cursory analysis of cored intervals.

  13. An open-source Matlab code package for improved rank-reduction 3D seismic data denoising and reconstruction

    NASA Astrophysics Data System (ADS)

    Chen, Yangkang; Huang, Weilin; Zhang, Dong; Chen, Wei

    2016-10-01

    Simultaneous seismic data denoising and reconstruction is a currently popular research subject in modern reflection seismology. Traditional rank-reduction based 3D seismic data denoising and reconstruction algorithm will cause strong residual noise in the reconstructed data and thus affect the following processing and interpretation tasks. In this paper, we propose an improved rank-reduction method by modifying the truncated singular value decomposition (TSVD) formula used in the traditional method. The proposed approach can help us obtain nearly perfect reconstruction performance even in the case of low signal-to-noise ratio (SNR). The proposed algorithm is tested via one synthetic and field data examples. Considering that seismic data interpolation and denoising source packages are seldom in the public domain, we also provide a program template for the rank-reduction based simultaneous denoising and reconstruction algorithm by providing an open-source Matlab package.

  14. High-resolution 3-D P wave attenuation structure of the New Madrid Seismic Zone using local earthquake tomography

    NASA Astrophysics Data System (ADS)

    Bisrat, Shishay T.; DeShon, Heather R.; Pesicek, Jeremy; Thurber, Clifford

    2014-01-01

    A three-dimensional (3-D), high-resolution P wave seismic attenuation model for the New Madrid Seismic Zone (NMSZ) is determined using P wave path attenuation (t*) values of small-magnitude earthquakes (MD < 3.9). Events were recorded at 89 broadband and short-period seismometers of the Cooperative New Madrid Seismic Zone Network and 40 short-period seismometers of the Portable Array for Numerical Data Acquisition experiment. The amplitude spectra of all the earthquakes are simultaneously inverted for source, path (t*), and site parameters. The t* values are inverted for QP using local earthquake tomography methods and a known 3-D P wave velocity model for the region. The four major seismicity arms of the NMSZ exhibit reduced QP (higher attenuation) than the surrounding crust. The highest attenuation anomalies coincide with areas of previously reported high swarm activity attributed to fluid-rich fractures along the southeast extension of the Reelfoot fault. The QP results are consistent with previous attenuation studies in the region, which showed that active fault zones and fractured crust in the NMSZ are highly attenuating.

  15. Fluid Flow Processes Study: from a 3D seismic data set in the Pointer Ridge offshore SW Taiwan

    NASA Astrophysics Data System (ADS)

    Han, Wei-Chung; Liu, Char-Shine; Chen, Liwen; Chi, Wu-Cheng; Lin, Che-Chuan

    2016-04-01

    This study analyzes a 3D seismic cube in the Pointer Ridge for understanding the fluid flow processes in subsurface. Pointer Ridge is a ridge situated on the passive China continental margin and is suggested as a potential prospect for future gas hydrate development. High methane flux rate, active gas venting and seismic chimneys have been observed in this area, which are direct evidences for active ongoing fluid migration processes. To find the possible fluid conduits and to understand how the fluids have migrated along those conduits, we firstly identify the structural and sedimentary features from this 3D seismic cube in our study area. Secondly, seismic attribute analyses are carried out for detecting fluid conduits and evaluating the contribution of recognized faults/fractures for fluid flow, respectively. Finally, we propose conceptual models to illustrate how fluids have migrated along those conduits to the seafloor and how those conduits have developed. The results show: 1) a major NE-SW striking normal fault (PR Fault) separates a depositional field on the hanging wall and a erosional field on the footwall; 2) the PR Fault zone itself and the chimneys in its footwall act as main conduits for focused fluid flow migrating to the seafloor; 3) the development of the chimneys in the Pointer Ridge area are highly controlled by the erosion and deposition processes. Since the ongoing fluid flow processes will increase the seafloor instabilities and the Pointer Ridge is a gas hydrate leaking site, our results could provide useful information for further risk evaluation.

  16. A combinatorial algorithm for the optimization of refraction seismics data inversion

    NASA Astrophysics Data System (ADS)

    Micciancio, Stefano

    1993-08-01

    The problem of data inversion in refraction seismics can be split in two parts: data first must be preprocessed in order to determine the travel-time curve; this essentially is a geometrical problem, complicated, however, by its pattern recognition aspects. Once the geometrical problem is solved, the second part, the inversion proper, is straightforward, as the soil layering model can be calculated according to well-known algorithms. The more difficult part of the problem is the former, which implies a type of pattern recognition; because of this type of difficulty, the geometrical part of the problem usually is committed to the skill of a human operator. This paper describes an algorithm exploiting combinatorial optimization techniques to automatize the pattern recognition part of the problem of data inversion in refraction seismics. The listing of a Pascal source program, implementing the algorithm proposed, is included.

  17. 3D joint inversion using seismic data and marine controlled-source electromagnetic data for evaluating gas hydrate concentrations

    NASA Astrophysics Data System (ADS)

    Kim, B.; Byun, J.; Seol, S. J.; Jeong, S.; Chung, Y.; Kwon, T.

    2015-12-01

    For many decades, gas hydrates have been received great attention as a potential source of natural gas. Therefore, the detailed information of structures of buried gas hydrates and their concentrations are prerequisite for the production for the gas hydrate as a reliable source of alternate energy. Recently, for this reason, a lot of gas hydrate assessment methods have been proposed by many researchers. However, it is still necessary to establish as new method for the further improvement of the accuracy of the 3D gas hydrate distribution. In this study, we present a 3D joint inversion method that provides superior quantitative information of gas hydrate distributions using 3D seismic data obtained by ocean-bottom cable (OBC) and marine controlled-source electromagnetic (CSEM) data. To verify our inversion method, we first built the general 3D gas hydrate model containing vertical methane-flow pathways. With the described model, we generated synthetic 3D OBC data and marine CSEM data using finite element modeling algorithms, respectively. In the joint inversion process, to obtain the high-resolution volumetric P-wave velocity structure, we applied the 3D full waveform inversion algorithm to the acquired OBC data. After that, the obtained P-wave velocity model is used as the structure constraint to compute cross-gradients with the updated resistivity model in the EM inversion process. Finally, petrophysical relations were applied to estimate volumetric gas hydrate concentrations. The proposed joint inversion process makes possible to obtain more precise quantitative gas hydrate assessment than inversion processes using only seismic or EM data. This technique can be helpful for accurate decision-making in gas hydrate development as well as in their production monitoring.

  18. A seismic refraction technique used for subsurface investigations at Meteor Crater, Arizona

    NASA Technical Reports Server (NTRS)

    Ackermann, H. D.; Godson, R. H.; Watkins, J. S.

    1975-01-01

    A seismic refraction technique for interpreting the subsurface shape and velocity distribution of an anomalous surface feature such as an impact crater is described. The method requires the existence of a relatively deep refracting horizon and combines data obtained from both standard shallow refraction spreads and distant offset shots by using the deep refractor as a source of initial arrivals. Results obtained from applying the technique to Meteor crater generally agree with the known structure of the crater deduced by other investigators and provide new data on an extensive fractured zone surrounding the crater. The breccia lens is computed to extend roughly 190 m below the crater floor, about 30 m less than the value deduced from early drilling data. Rocks around the crater are fractured as distant as 900 m from the rim crest and to a depth of at least 800 m beneath the crater floor.

  19. A New Generation of Large Seismic Refraction Experiments in Central Europe (1997-2003)

    NASA Astrophysics Data System (ADS)

    Guterch, A.; Grad, M.; Spicak, A.; Brueckl, E.; Hegedus, E.; Keller, G. R.; Thybo, H.

    2003-12-01

    Beginning in 1997, Central Europe has been covered by an unprecedented network of seismic refraction experiments. These experiments (POLONAISE'97, CELEBRATION 2000, ALP 2002, SUDETES 2003) have only been possible due a massive international cooperative effort. The total length of all profiles is about 19,000 km, and over 300 explosive sources were employed. The result is a network of seismic refraction profiles that extends along the Trans-European Suture Zone region of Poland and the Bohemian massif, Pannonian basin, trough the Carpathians and Alps to the Adriatic Sea and the Dinarides. As reflected in structures within these areas, Central Europe has experienced a complex tectonic history that includes the Caledonian, Variscan, and Alpine orogenies. The related TESZ region is a broad zone of deformation that extends across Europe from British Isles to the Black Sea region that formed as Europe was assembled from a complex collage of terranes during the late Palaeozoic. For example, the Bohemian massif is mostly located in the Czech Republic and is a large, complex terrane whose origin can be traced to northern Gondwana (Africa). These terranes were accreted along the margin of Baltica that was formed during the break-up of Rodinia. The tectonic evolution of this region shares many attributes with the Appalachian/Ouachita origin and is certainly of global important to studies in terrane tectonics and continental evolution. In southern Poland, several structural blocks are located adjacent to Baltica and were probably transported laterally along it similar to the Cenozoic movement of terranes along the western margin of North America. The younger Carpathian arc and Pannonian back-arc basin were also targeted by these experiments. Thickness of the crust in the area of investigations changes from 22-25 km in the Pannonian basin to about 55 km in the Trans-European Suture Zone in SE Poland. Together, these experiments are providing an unprecedented 3-D image of the

  20. Deep crustal structure of the Cascade Range and surrounding regions from seismic refraction and magnetotelluric data

    USGS Publications Warehouse

    Stanley, W.D.; Mooney, W.D.; Fuis, G.S.

    1990-01-01

    Several regional seismic refraction and magnetotelluric (MT) profiles have been completed across the Cascade Range and surrounding geologic provinces in California, Oregon, and Washington. Analysis of three MT and two seismic refraction profiles in Oregon and a coincident MT and refraction profile in northern California show a high degree of correlation between resistivity and velocity models. The main feature that is evident in both data sets is a highly conductive (2-20 ohm m) zone that occurs at depths of 6-20 km and largely within a midcrustal velocity layer of 6.4-6.6 km/s, overlying a lower crust with velocities of 7.0-7.4 km/s. Accretionary structures in the southern Washington Cascades have been shown to be related to stress release in the area of Mount St. Helens. In order to explain the similar structures in the MT and refraction models for Oregon and California, a model is proposed involving the effects of metamorphic zonation to produce the velocity structure, combined with metamorphically produced fluids and partial melt to produce the deep conductor. -from Authors

  1. Negative refraction and focusing analysis in a left-handed material slab and realization with a 3D photonic crystal structure

    NASA Astrophysics Data System (ADS)

    Ahmadlou, Majid; Kamarei, Mahmoud; Sheikhi, Mohammad Hossein

    2006-02-01

    The increasing interest in metamaterials and structures with negative refraction index requires a formulation capable of a full analysis of wave propagation in such materials and structures. Since two-dimensional (2D) problems have been largely explored in the literature, the natural step is a three-dimensional (3D) formulation of these structures. In this paper, (3D) formulation and simulation of a left-handed metamaterial slab using the finite-difference time domain (FDTD) method in conjunction with perfectly matched layers (PMLs) is presented, and also a (3D) photonic crystal (PC) based structure is presented as a candidate for replacing the left-handed medium slab to realize the negative index of refraction on natural dielectric substrates. The results of these simulations are compared with each other, and the resulting outputs of the developed model are in good agreement. The results demonstrate numerically the focusing of the field emitted from an omnidirectional line source placed in front of the slab and crystal. Both the source and the focus pattern are away from the slab interfaces at two sides of the slab to have a real, negative perfect image. The dimensions of the simulation domain are set to have both source and image in the resulted plots. The focus pattern shows the ability of a photonic crystal structure in making a true flat lens.

  2. Crustal structure of Shatsky Rise from joint refraction and reflection seismic tomography

    NASA Astrophysics Data System (ADS)

    Korenaga, J.; Sager, W. W.

    2011-12-01

    Shatsky Rise in the western Pacific is one of a few gigantic oceanic plateaus in the world, with a surface area of ˜ 4.8 ± 105~km2 (about the same size as California). In contrast to other large oceanic plateaus formed during the Cretaceous Quite Period, Shatsky Rise formed during the frequent reversals of magnetic polarity, allowing its tectonic environment to be resolved in detail. It was formed at a rapidly spreading ridge-ridge-ridge triple junction, so the effect of lithospheric lid on magma migration is expected to be minimal, thereby facilitating the petrological interpretation of its seismic structure in terms of parental mantle processes. In the summer of 2010, a seismic refraction survey combined with multichannel seismic profiling was conducted across Shatsky Rise. Twenty eight ocean-bottom seismometers were deployed along two crossing perpendicular lines, and all of the instruments were recovered successfully, yielding a large volume of high-quality wide-angle refraction and reflection data, with the source-receiver distance often exceeding 200~km. In this contribution, we present the P-wave velocity structure of the Shatsky Rise crust, which is constructed by joint refraction and reflection travel time tomography, and also discuss its implications for the origin of Shatsky Rise.

  3. Estimation and 3-D modeling of seismic parameters for fluvial systems

    SciTech Connect

    Brown, R.L.; Levey, R.A.

    1994-12-31

    Borehole measurements of parameters related to seismic propagation (Vp, Vs, Qp and Qs) are seldom available at all the wells within an area of study. Well logs and other available data can be used along with certain results from laboratory measurements to predict seismic parameters at wells where these measurements are not available. Next, three dimensional interpolation techniques based upon geological constraints can then be used to estimate the spatial distribution of geophysical parameters within a given environment. The net product is a more realistic model of the distribution of geophysical parameters which can be used in the design of surface and borehole seismic methods for probing the reservoir.

  4. Application of Cutting-Edge 3D Seismic Attribute Technology to the Assessment of Geological Reservoirs for CO2 Sequestration

    SciTech Connect

    Christopher Liner; Jianjun Zeng; Po Geng Heather King Jintan Li; Jennifer Califf; John Seales

    2010-03-31

    The goals of this project were to develop innovative 3D seismic attribute technologies and workflows to assess the structural integrity and heterogeneity of subsurface reservoirs with potential for CO{sub 2} sequestration. Our specific objectives were to apply advanced seismic attributes to aide in quantifying reservoir properies and lateral continuity of CO{sub 2} sequestration targets. Our study area is the Dickman field in Ness County, Kansas, a type locality for the geology that will be encountered for CO{sub 2} sequestration projects from northern Oklahoma across the U.S. midcontent to Indiana and beyond. Since its discovery in 1962, the Dickman Field has produced about 1.7 million barrels of oil from porous Mississippian carbonates with a small structural closure at about 4400 ft drilling depth. Project data includes 3.3 square miles of 3D seismic data, 142 wells, with log, some core, and oil/water production data available. Only two wells penetrate the deep saline aquifer. Geological and seismic data were integrated to create a geological property model and a flow simulation grid. We systematically tested over a dozen seismic attributes, finding that curvature, SPICE, and ANT were particularly useful for mapping discontinuities in the data that likely indicated fracture trends. Our simulation results in the deep saline aquifer indicate two effective ways of reducing free CO{sub 2}: (a) injecting CO{sub 2} with brine water, and (b) horizontal well injection. A tuned combination of these methods can reduce the amount of free CO{sub 2} in the aquifer from over 50% to less than 10%.

  5. Reducing disk storage of full-3D seismic waveform tomography (F3DT) through lossy online compression

    NASA Astrophysics Data System (ADS)

    Lindstrom, Peter; Chen, Po; Lee, En-Jui

    2016-08-01

    Full-3D seismic waveform tomography (F3DT) is the latest seismic tomography technique that can assimilate broadband, multi-component seismic waveform observations into high-resolution 3D subsurface seismic structure models. The main drawback in the current F3DT implementation, in particular the scattering-integral implementation (F3DT-SI), is the high disk storage cost and the associated I/O overhead of archiving the 4D space-time wavefields of the receiver- or source-side strain tensors. The strain tensor fields are needed for computing the data sensitivity kernels, which are used for constructing the Jacobian matrix in the Gauss-Newton optimization algorithm. In this study, we have successfully integrated a lossy compression algorithm into our F3DT-SI workflow to significantly reduce the disk space for storing the strain tensor fields. The compressor supports a user-specified tolerance for bounding the error, and can be integrated into our finite-difference wave-propagation simulation code used for computing the strain fields. The decompressor can be integrated into the kernel calculation code that reads the strain fields from the disk and compute the data sensitivity kernels. During the wave-propagation simulations, we compress the strain fields before writing them to the disk. To compute the data sensitivity kernels, we read the compressed strain fields from the disk and decompress them before using them in kernel calculations. Experiments using a realistic dataset in our California statewide F3DT project have shown that we can reduce the strain-field disk storage by at least an order of magnitude with acceptable loss, and also improve the overall I/O performance of the entire F3DT-SI workflow significantly. The integration of the lossy online compressor may potentially open up the possibilities of the wide adoption of F3DT-SI in routine seismic tomography practices in the near future.

  6. The application of seismic stratigraphic methods on exploration 3D seismic data to define a reservoir model in OPL 210, Deepwater Nigeria

    SciTech Connect

    Ragnhild, L.; Ventris, P.; Osahon, G.

    1995-08-01

    OPL 210 lies in deepwater on the northwestern flank of the Niger Delta. The partners in this block are Allied Energy and The Statoil and BP Alliance. The license has a 5 year initial exploration phase and carries a 2 well commitment. At present the database comprises a 1 x 1 km grid of 2D seismic across the block, and 450 sq. km of 3D in an area of special interest. A larger 3D survey is planned for 1995. Little is known about the reservoir in the deep water, but we expect our main target to be ponded slope and basin turbidites. As such the bulk of the shelf well data available has little or no relevance to the play type likely to be encountered. Prior to drilling, seismic stratigraphy has been one of several methods used to generate a consistent predictive reservoir model. The excellent quality and high resolution of the 3D data have allowed identification and detailed description of several distinctive seismic facies. These facies are described in terms of their internal geometries and stacking patterns. The geometries are then interpreted based on a knowledge of depositional processes from analog slope settings. This enables a predictive model to be constructed for the distribution of reservoir within the observed facies. These predictions will be tested by one of the first wells drilled in the Nigerian deepwater in mid 1995.

  7. Seismic refraction studies at the Painter Street bridge site, Rio Dell, California

    SciTech Connect

    Heuze, F.E.; Swift, R.P.

    1991-09-01

    This report summarizes the results of seismic refraction P- and S-wave measurements, at the site of the Painter Street bridge, in Rio Dell, California. The bridge is spanning highway US 101, 4 miles south of Fortuna, in northwestern California. This study was performed to provide an estimate of material properties for the foundation of the bridge, in support of a seismic stability analysis of the bridge performed at LLNL by D. McCallen. The Rio Dell region is seismically active and the Painter Street bridge is one of only 2 bridges of its type in California, instrumented for strong motion recordings. Measurements were made using a 12-channel Geometric/Nimbus ES 1210 Signal Enhancement Seismograph. 3 refs., 21 figs., 1 tab.

  8. Pennsylvanian Subsurface Sequence Stratigraphy Based on 3D Seismic and Wireline Data in Western Osage County, Oklahoma

    NASA Astrophysics Data System (ADS)

    West, Alexander

    The Pennsylvanian System in the Mid-Continent United States has been studied for nearly a century. In north central Oklahoma, the Pennsylvanian is primarily composed of cyclothems. These cyclothems are sequences of alternating carbonate, clastic, and shale members. Because of this, these zones can be difficult to differentiate. This project provides valuable insight into better understanding the Pennsylvanian System in western Osage County, Oklahoma. The scope of this project is to perform a subsurface study to produce a detailed interpretation of the depositional history and stratigraphy of Pennsylvanian sequences in western Osage County. This study features 3D seismic and well log investigations that will be used together for local and regional subsurface interpretations. The seismic surveys used in the project are the Wild Creek and Gray Horse 3D surveys in western Osage County. The well logs, digital and raster, provide respectable well control for western Osage County. Together, interpretations from the seismic data and well logs will be used to provide a better understanding of the subsurface stratigraphy and depositional history of Pennsylvanian sequences in western Osage County, Oklahoma.

  9. High-resolution 3D seismic imaging of a pull-apart basin in the Gulf of Cadiz

    NASA Astrophysics Data System (ADS)

    Crutchley, G.; Berndt, C.; Klaeschen, D.; Gutscher, M.

    2009-12-01

    In 2006, high-resolution 3D seismic data were acquired in the Gulf of Cadiz and the Mediterranean Sea aboard the RRS Charles Darwin as part of the HERMES (Hotspot Ecosystem Research on the Margins of European Seas) project. The P-Cable system, a cost-efficient set-up for fast acquisition of 3D seismic data on 12 single-channel streamers, was utilized to acquire seismic cubes at four different targets. Here, we present results from the second target - a WNW-ESE-oriented pull-apart basin in the southeastern Gulf of Cadiz. Initial processing has included: 1) spatial positioning of each recording channel from GPS data acquired on the outer two channels, 2) improved positioning of shot points and channels from the inversion of first arrival times, 3) application of a swell filter to improve reflection coherency, 4) CDP binning and stacking and 5) migration. The new data confirm that the southeastern Gulf of Cadiz north of the Rharb submarine valley is structurally controlled by numerous strike slip faults that were active until quite recently (within the resolution of the data). Given the location of this basin, between the extensional domain on the upper slope and the compressional toe of the accretionary wedge, we interpret the origin to be gravitational sliding on a detachment layer, possibly containing salt, but at this stage not imaged by our profiles.

  10. A web-based platform for simulating seismic wave propagation in 3D shallow Earth models with DEM surface topography

    NASA Astrophysics Data System (ADS)

    Luo, Cong; Friederich, Wolfgang

    2016-04-01

    Realistic shallow seismic wave propagation simulation is an important tool for studying induced seismicity (e.g., during geothermal energy development). However over a long time, there is a significant problem which constrains computational seismologists from performing a successful simulation conveniently: pre-processing. Conventional pre-processing has often turned out to be inefficient and unrobust because of the miscellaneous operations, considerable complexity and insufficiency of available tools. An integrated web-based platform for shallow seismic wave propagation simulation has been built. It is aiming at providing a user-friendly pre-processing solution, and cloud-based simulation abilities. The main features of the platform for the user include: revised digital elevation model (DEM) retrieving and processing mechanism; generation of multi-layered 3D shallow Earth model geometry (the computational domain) with user specified surface topography based on the DEM; visualization of the geometry before the simulation; a pipeline from geometry to fully customizable hexahedral element mesh generation; customization and running the simulation on our HPC; post-processing and retrieval of the results over cloud. Regarding the computational aspect, currently the widely accepted specfem3D is chosen as the computational package; packages using different types of elements can be integrated as well in the future. According to our trial simulation experiments, this web-based platform has produced accurate waveforms while significantly simplifying and enhancing the pre-processing and improving the simulation success rate.

  11. The use of exploration 3D seismic data to optimise oil exploration in OPL 210 deepwater, Nigeria

    SciTech Connect

    Nelson, L.C.; Lilletveit, R.; Sandvoll, T.

    1995-08-01

    Allied Energy and the Statoil and BP Alliance are currently partners in the OPL 210 license, in deepwater Nigeria. The license has a 5 year initial exploration phase which carries a two well commitment. To optimize the location of these wells in this challenging and costly drilling environment the partnership has decided to acquire extensive exploration 3D seismic data within the block. Interpretation of the first of two planned 3D surveys has led to a much clearer understanding of: (a) The structural segmentation of the prospect and thus a clearer idea of the likely hydrocarbon pool size. (b) The distribution of amplitude anomalies and thus, hopefully, a superior understanding of reservoir distribution and hydrocarbons. Here the limiting factor is clearly the lack of deepwater geophysical calibration, due to the absence of wells. Consequently, conclusions at this stage, are qualitative either than quantative. Combined with detailed seismic stratigraphic and high tech geophysical analysis, these two aspects will assist in the highgrading of segments in the prospect, prior to final decisions on the well locations. The first well, planned for 1995, will be one of the first wells drilled in the Nigerian deepwater area. Examples of both 2D and 3D data will be used to demonstrate the above and some of the first well results will be integrated into our interpretation to highlight how some of our perceptions may have changed.

  12. Seismicity patterns along the Ecuadorian subduction zone: new constraints from earthquake location in a 3-D a priori velocity model

    NASA Astrophysics Data System (ADS)

    Font, Yvonne; Segovia, Monica; Vaca, Sandro; Theunissen, Thomas

    2013-04-01

    To improve earthquake location, we create a 3-D a priori P-wave velocity model (3-DVM) that approximates the large velocity variations of the Ecuadorian subduction system. The 3-DVM is constructed from the integration of geophysical and geological data that depend on the structural geometry and velocity properties of the crust and the upper mantle. In addition, specific station selection is carried out to compensate for the high station density on the Andean Chain. 3-D synthetic experiments are then designed to evaluate the network capacity to recover the event position using only P arrivals and the MAXI technique. Three synthetic earthquake location experiments are proposed: (1) noise-free and (2) noisy arrivals used in the 3-DVM, and (3) noise-free arrivals used in a 1-DVM. Synthetic results indicate that, under the best conditions (exact arrival data set and 3-DVM), the spatiotemporal configuration of the Ecuadorian network can accurately locate 70 per cent of events in the frontal part of the subduction zone (average azimuthal gap is 289° ± 44°). Noisy P arrivals (up to ± 0.3 s) can accurately located 50 per cent of earthquakes. Processing earthquake location within a 1-DVM almost never allows accurate hypocentre position for offshore earthquakes (15 per cent), which highlights the role of using a 3-DVM in subduction zone. For the application to real data, the seismicity distribution from the 3-D-MAXI catalogue is also compared to the determinations obtained in a 1-D-layered VM. In addition to good-quality location uncertainties, the clustering and the depth distribution confirm the 3-D-MAXI catalogue reliability. The pattern of the seismicity distribution (a 13 yr record during the inter-seismic period of the seismic cycle) is compared to the pattern of rupture zone and asperity of the Mw = 7.9 1942 and the Mw = 7.7 1958 events (the Mw = 8.8 1906 asperity patch is not defined). We observe that the nucleation of 1942, 1958 and 1906 events coincides with

  13. Deep seismic refraction experiment in northeast Brazil: New constraints for Borborema province evolution

    NASA Astrophysics Data System (ADS)

    Lima, Marcus Vinicius A. G. de; Berrocal, Jesus; Soares, José E. P.; Fuck, Reinhardt A.

    2015-03-01

    The Borborema Province of northeastern Brazil is a major Proterozoic crustal province that, until now, has never been explored using deep crustal seismic methods. Here are reported the first results obtained from a high-quality seismic refraction/wide-angle reflection profile that has defined the internal seismic velocity structure and thickness of the crust in this region. Almost 400 recording stations were deployed in the Deep Seismic Refraction (DSR) experiment through an NW-SE ca. 900 km linear array and 19 shots were exploded at every 50 km along the line. Data from the 10 southeastern most shots of the seismic profile were processed in this work. The main features and geological structures crossed by the studied portion of the profile belong to the so-called Central Sub-province of the Borborema tectonic province. The crustal model obtained is compatible with a typical structure of extended crust. The model was essentially divided into three layers: upper crust, lower crust, and a half-space represented by the shallower portion of the mantle. The Moho is an irregular interface with depth ranging between 31.7 and 34.5 km, and beneath the Central Sub-province it varies from 31.5 to 33 km depth, where its limits are related to major crustal discontinuities. The distribution of velocities within the crust is heterogeneous, varying vertically from 5.7 to 6.3 km/s in the upper crust and from 6.45 to 6.9 km/s in the lower crust. From the average crustal velocity distribution it is evident that the Central Sub-province has seismic characteristics different from neighboring domains. The crust is relatively thin and crustal thickness variations in the profile are subtle due to stretching that occurred in the Cretaceous, during the fragmentation of Pangaea, opening of the South Atlantic Ocean and separation of South America from Africa.

  14. Three-dimensional seismic refraction tomography of the crustal structure at the ION site on the Ninetyeast Ridge, Indian Ocean

    NASA Astrophysics Data System (ADS)

    Schlindwein, Vera; Bönnemann, Christian; Reichert, Christian; Grevemeyer, Ingo; Flueh, Ernst

    2003-01-01

    We have performed a 3-D seismic refraction tomography of a 48 × 48 km2 area surrounding ODP site 757, which is planned to host an International Ocean Network (ION) permanent seismological observatory, called the Ninetyeast Ridge Observatory (NERO). The study area is located in the southern part of the Ninetyeast Ridge, the trail left by the Kerguelen hotspot on the Indian plate. The GEOMAR Research Centre for Marine Geosciences and the Federal Institute for Geosciences and Natural Resources acquired 18 wide-angle profiles recorded by 23 ocean bottom hydrophones during cruise SO131 of R/V Sonne in spring 1998. We apply a first arrival traveltime tomography technique using regularized inversion to recover the 3-D velocity structure relative to a 1-D background model that was constructed from a priori information and averaged traveltime data. The final velocity model revealed the crustal structure down to approximately 8 km depth. Resolution tests showed that structures with approximately 6 km horizontal extent can reliably be resolved down to that depth. The survey imaged the extrusive layer of the upper crust of the Ninetyeast Ridge, which varies in thickness between 3 and 4 km. A high-velocity anomaly coinciding with a positive magnetic anomaly represents a volcanic centre from which crust in this area is thought to have formed. A pronounced low-velocity anomaly is located underneath a thick sedimentary cover in a bathymetric depression. However, poor ray coverage of the uppermost kilometre of the crust in this area resulted in smearing of the shallow structure to a larger depth. Tests explicitly including the shallow low-velocity layer confirmed the existence of the deeper structure. The heterogeneity of the upper crust as observed by our study will have consequences for the waveforms of earthquake signals to be recorded by the future seismic observatory.

  15. Investigation into 3D earth structure and sources using full seismic waveforms

    NASA Astrophysics Data System (ADS)

    Covellone, Brian M.

    Seismograms are the result of the complex interactions between a seismic source, a propagation medium and the seismograph's response. Through the use of 3-dimensional modeling and full seismic waveform data, we quantify and minimize errors associated with the source and propagation medium within our data sets. We compile a new and unique earthquake catalog for the Middle East that is openly available to the public. We quantify the benefits of using a 3-dimensional model relative to a 1-dimensional model to minimizing error in earthquake moment tensors and identify where in the waveform 3-dimensional models outperform 1-dimensional models. Two new and unique 3-dimensional seismic wave speed models are computed for the Ontong Java plateau and eastern North American margin.Both models are significant improvements to the resolution of wave speed structures in the crust and upper mantle and provide new information for the evaluation of tectonic features.

  16. Using 3D Simulation of Elastic Wave Propagation in Laplace Domain for Electromagnetic-Seismic Inverse Modeling

    NASA Astrophysics Data System (ADS)

    Petrov, P.; Newman, G. A.

    2010-12-01

    -Fourier domain we had developed 3D code for full-wave field simulation in the elastic media which take into account nonlinearity introduced by free-surface effects. Our approach is based on the velocity-stress formulation. In the contrast to conventional formulation we defined the material properties such as density and Lame constants not at nodal points but within cells. This second order finite differences method formulated in the cell-based grid, generate numerical solutions compatible with analytical ones within the range errors determinate by dispersion analysis. Our simulator will be embedded in an inversion scheme for joint seismic- electromagnetic imaging. It also offers possibilities for preconditioning the seismic wave propagation problems in the frequency domain. References. Shin, C. & Cha, Y. (2009), Waveform inversion in the Laplace-Fourier domain, Geophys. J. Int. 177(3), 1067- 1079. Shin, C. & Cha, Y. H. (2008), Waveform inversion in the Laplace domain, Geophys. J. Int. 173(3), 922-931. Commer, M. & Newman, G. (2008), New advances in three-dimensional controlled-source electromagnetic inversion, Geophys. J. Int. 172(2), 513-535. Newman, G. A., Commer, M. & Carazzone, J. J. (2010), Imaging CSEM data in the presence of electrical anisotropy, Geophysics, in press.

  17. Delineating Potential Quick-clay Areas Using High-resolution Seismic Methods: Towards a 3D Model of an Area Prone to Slide in SW Sweden

    NASA Astrophysics Data System (ADS)

    Salas Romero, S.; Malehmir, A.; Snowball, I.

    2015-12-01

    Quick clay can liquefy under increased stress and is responsible for major landslides in Sweden, Norway and Canada, but despite extensive investigations delineating quick clay remains a challenge. As part of a large multidisciplinary project, this study focuses on an area prone to quick-clay landslides in SW Sweden. P- and S-wave seismic, electrical resistivity tomography, and RMT (radio-magnetotelluric) data obtained in 2011 (Malehmir et al. 2013) suggested the presence of a coarse-grained layer of variable thickness sandwiched between clays, with quick clay above. The coarse-grained layer was assumed to accelerate the formation of quick clay, influencing its thickness. Additional geophysical data (reflection and refraction seismic, and RMT) and studies of three boreholes drilled in 2013, with the aim to intersect the coarse-grained layer, extended the area covered in 2011. Here we report on four seismic profiles (total length 3.5 km) acquired in 2013, combined with side-scan and single channel reflection seismic data along a river, which was believed to be important in the context of quick-clay landslides. Wireless (50-1C-10 Hz and 24-3C-broadband) and cabled sensors (323-28 Hz), 4-10 m apart, were used for the data acquisition of the longest profile (nearly 2 km long). Dynamite, accelerated weight-drop and sledgehammer were used as seismic sources. Simultaneous data acquisition for two parallel profiles, about 300 m apart, provides additional information. Preliminary results delineate the bedrock and its undulation near and in the river. We believe that overlying reflections are caused by the coarse-grained materials, whose lateral extension is considerably larger than previously thought. This may imply a wider area containing quick clay and hence at risk of slope failure. The new data and previous results are combined to construct a high-resolution 3D subsurface model that focuses on the coarse-grained layer and potential quick-clay areas. Malehmir A, Bastani M

  18. 3D seismic geomorphology and geologic controls on gas hydrate accumulation mechanism in the Miyazaki-oki forearc basin, Japan

    NASA Astrophysics Data System (ADS)

    Komatsu, Y.; Kobayashi, T.; Fujii, T.

    2015-12-01

    The stratigraphy of the Miyazaki-oki forearc basin along the Southwest Japan Arc comprises the early Miocene to early Pleistocene Miyazaki Group and the Hyuganada Group. These groups comprise sediments (up to 5000 m) deposited in deep marine to shallow marine environments. Based on characteristics of well data outside seismic exploration area and stratigraphy of land areas, the Miyazaki Group was divided into four seismic units and the Hyuganada Group was divided into two seismic units. In this area, bottom-simulating reflectors (BSRs) have been widely observed and considered as representing lower boundaries of methane-hydrate-bearing deposits. However, the gas hydrate accumulation mechanism for this area is not yet well understood. We show the relation between sandy sediment distribution identified from the 3D seismic geomorphological analysis and methane hydrate occurrence to identify the accumulation mechanism. A submarine fan system was subdivided into four seismic facies: Submarine canyon complexes; Leveed channel complexes; Submarine fan complexes; Mass transport complexes (MTD). Depositional systems of target layers are characterized by a transition from submarine fan deposits (Miyazaki Group) to channel-levee deposits and MTD (Hyuganada Group). This transition of depositional environments is strongly influenced by global tectonics since early Miocene in the Southwest Japan Arc. A part of channel-fill located around structural wing and middle fan deposits above the BSR is inferred as sediments intercalated with sandy layers. We consider that these deposits contain methane hydrate because the sandy sediment distribution approximately coincides with a high-velocity zone as an indicator of gas hydrate. The comparison of the areal extent of the seismic facies and the mapped structural configuration, suggest that the gas hydrate accumulation represent combination structural-stratigraphic trap.

  19. Seismic attribute analysis for 3-D structural interpretation of the offshore South Marsh Island, Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Horozal, Senay; Lee, Gwang Hoon; Cukur, Deniz; Pigott, John D.

    2013-04-01

    Structural and seismic attribute analyses of 3-D seismic reflection data from southwest offshore South Marsh Island, Louisiana, Gulf of Mexico, reveal complex structures affected by salt tectonics triggered by interaction between salt, faults and rapid deltaic sedimentation on the shallow continental shelf. Salt exercises the main control on the sedimentary processes in the study area to move, to divert sediment, to create instability, and to block sediment transport pathways. The depths of salt range about 4,300 m (14,000 ft) to 6,500 m (21,600 ft). Salt is very deep and forms a thin sheet in the southwestern part of the area, whereas it rises to shallow depths, forming a dome in the central part. Salt is seen at relatively shallow stratigraphic levels in the northwest and south where it forms thin salt rollers. The margins of Miocene strata are deformed by salt movement and faulting in the study area. The study area is riddled by numerous normal faults which are mostly E-trending and some N- and NW-trending with southward gradual increase in growth factors. Eight main normal faults were interpreted from seismic data which are mostly E-trending S-dipping, and are accompanied by smaller secondary faults. Three of E-trending down-to-the-basin growth faults cut across the study area separating the area into four blocks. These faults form a stair-stepping structure in the south direction. Two conjugate-crossing normal faults are located over the central salt dome which may indicate active salt doming. Seismic attribute analysis was applied as output of seismic volumes, and horizon and time-slice maps in order to identify the structure of study area. These attribute volumes together with time- and horizon-slices gave amplitude anomalies at discontinuities (faults) and lithological changes (sand to shale, salt). Faults interpreted and mapped from seismic profiles and those identified by seismic attribute slices are compatible, therefore, seismic attribute analysis can

  20. A Robust MEMS Based Multi-Component Sensor for 3D Borehole Seismic Arrays

    SciTech Connect

    Paulsson Geophysical Services

    2008-03-31

    The objective of this project was to develop, prototype and test a robust multi-component sensor that combines both Fiber Optic and MEMS technology for use in a borehole seismic array. The use such FOMEMS based sensors allows a dramatic increase in the number of sensors that can be deployed simultaneously in a borehole seismic array. Therefore, denser sampling of the seismic wave field can be afforded, which in turn allows us to efficiently and adequately sample P-wave as well as S-wave for high-resolution imaging purposes. Design, packaging and integration of the multi-component sensors and deployment system will target maximum operating temperature of 350-400 F and a maximum pressure of 15000-25000 psi, thus allowing operation under conditions encountered in deep gas reservoirs. This project aimed at using existing pieces of deployment technology as well as MEMS and fiber-optic technology. A sensor design and analysis study has been carried out and a laboratory prototype of an interrogator for a robust borehole seismic array system has been assembled and validated.

  1. Combined interpretation of 3D seismic reflection attributes for geothermal exploration in the Polish Basin using self-organizing maps

    NASA Astrophysics Data System (ADS)

    Bauer, Klaus; Pussak, Marcin; Stiller, Manfred; Bujakowski, Wieslaw

    2014-05-01

    Self-organizing maps (SOM) are neural network techniques which can be used for the joint interpretation of multi-disciplinary data sets. In this investigation we apply SOM within a geothermal exploration project using 3D seismic reflection data. The study area is located in the central part of the Polish basin. Several sedimentary target horizons were identified at this location based on fluid flow rate measurements in the geothermal research well Kompina-2. The general objective is a seismic facies analysis and characterization of the major geothermal target reservoir. A 3D seismic reflection experiment with a sparse acquisition geometry was carried out around well Kompina-2. Conventional signal processing (amplitude corrections, filtering, spectral whitening, deconvolution, static corrections, muting) was followed by normal-moveout (NMO) stacking, and, alternatively, by common-reflection-surface (CRS) stacking. Different signal attributes were then derived from the stacked images including root-mean-square (RMS) amplitude, instantaneous frequency and coherency. Furthermore, spectral decomposition attributes were calculated based on the continuous wavelet transform. The resulting attribute maps along major target horizons appear noisy after the NMO stack and clearly structured after the CRS stack. Consequently, the following SOM-based multi-parameter signal attribute analysis was applied only to the CRS images. We applied our SOM work flow, which includes data preparation, unsupervised learning, segmentation of the trained SOM using image processing techniques, and final application of the learned knowledge. For the Lower Jurassic target horizon Ja1 we derived four different clusters with distinct seismic attribute signatures. As the most striking feature, a corridor parallel to a fault system was identified, which is characterized by decreased RMS amplitudes and low frequencies. In our interpretation we assume that this combination of signal properties can be

  2. Application of stacking and inversion techniques to three-dimensional wide-angle reflection and refraction seismic data of the Eastern Alps

    NASA Astrophysics Data System (ADS)

    Behm, Michael; Brückl, Ewald; Chwatal, Werner; Thybo, Hans

    2007-07-01

    We present new methods for the interpretation of 3-D seismic wide-angle reflection and refraction data with application to data acquired during the experiments CELEBRATION, 2000 and ALP 2002 in the area of the Eastern Alps and their transition to the surrounding tectonic provinces (Bohemian Massif, Carpathians, Pannonian domain, Dinarides). Data was acquired on a net of arbitrarily oriented seismic lines by simultaneous recording on all lines of seismic waves from the shots, which allows 2-D and 3-D interpretations. Much (80%) of the data set consists of crossline traces. Low signal to noise (S/N) ratio in the area of the young orogens decreases the quality of travel time picks. In these seismically heterogeneous areas it is difficult to assign clearly defined arrivals to the seismic phases, in particular on crossline record sections. In order to enhance the S/N ratio, signal detection and stacking techniques have been applied to enhance the Pg-, Pn- and PmP phases. Further, inversion methods have been developed for the interpretation of WAR/R-data, based on automated 1-D inversion (Pg) and the application of the delay time concept (Pn). The results include a 3-D velocity model of the crust based on Pg waves, time and depth maps of the Moho and a Pn-velocity map. The models based on stacked data are robust and provide a larger coverage, than models based on travel time picks from single-fold (unstacked) traces, but have relatively low resolution, especially near the surface. They were used as the basis for constructing models with improved resolution by the inversion of picks from single-fold data. The results correlate well with geological structures and show new prominent features in the Eastern Alps area and their surrounds. The velocity distribution in the crust has strong lateral variations and the Moho in the investigation area appears to be fragmented into three parts.

  3. 9C-3D seismic interpretation of the Bakken Formation, Banner Field, North Dakota

    NASA Astrophysics Data System (ADS)

    Comegys, Lillian R.

    The Bakken Petroleum System is a multi-reservoir play with estimated total undiscovered resources of 3.649 BBO oil and 1.85 TCF natural gas in the United States portion of the Williston Basin (Pollastro 2008). The presence of natural fractures in all three members of the Bakken Formation have been linked to high initial production (IP) and cumulative production from the Antelope Field and better reservoir potential in the Elm Coulee Field and Sanish Fields (Sturm and Gomez 2009; Honsberger 2012; Theloy 2011). Therefore, the ability of seismic data to determine the presence, orientation, and density of natural fractures is an important achievement for petroleum exploration and exploitation. The STAMPEDE 9-component seismic survey is located in Mountrail County, North Dakota, in the Banner Field, southeast of the Parshall and Sanish Fields. It is the goal of the Reservoir Characterization Project to analyze the structural influences on reservoir properties in the STAMPEDE survey area using the compressional and pure shear seismic volumes supplemented by the public well information available on the North Dakota Industrial Commission website. Fracturing induced by basement faulting and lithology changes is detectable using multicomponent seismic data in the Stampede seismic survey. Shear wave splitting analysis delineates zones of different fracture orientation and density. These areas correlate to interpreted fault intersections and the predicted area of increased fracture frequency based on facies changes in the Middle Bakken Member and its mechanical stratigraphy. Wrench fault mechanics are at work in the study area, creating isolated convergent and divergent stress regimes in the separate fault blocks. Main fault interpretations are based on shear wave isochron mapping, wireline log mapping, seismic panel observations. Fracture interpretations were made on the analysis of shear time and amplitude anisotropy maps and the correlation of a P-wave Velocity Variation

  4. 3-D Seismic Methods for Geothermal Reservoir Exploration and Assessment--Summary

    SciTech Connect

    Majer, E.L.

    2003-07-14

    A wide variety of seismic methods covering the spectrum from DC to kilohertz have been employed at one time or the other in geothermal environments. The reasons have varied from exploration for a heat source to attempting to find individual fractures producing hot fluids. For the purposes here we will assume that overall objective of seismic imaging is for siting wells for successful location of permeable pathways (often fracture permeability) that are controlling flow and transport in naturally fractured reservoirs. The application could be for exploration of new resources or for in-fill/step-out drilling in existing fields. In most geothermal environments the challenge has been to separate the ''background'' natural complexity and heterogeneity of the matrix from the fracture/fault heterogeneity controlling the fluid flow. Ideally one not only wants to find the fractures, but the fractures that are controlling the flow of the fluids. Evaluated in this work is current state-of-the-art surface (seismic reflection) and borehole seismic methods (Vertical Seismic Profiling (VSP), Crosswell and Single Well) to locate and quantify geothermal reservoir characteristics. The focus is on active methods; the assumption being that accuracy is needed for successful well siting. Passive methods are useful for exploration and detailed monitoring for in-fill drilling, but in general the passive methods lack the precision and accuracy for well siting in new or step out areas. In addition, MEQ activity is usually associated with production, after the field has been taken to a mature state, thus in most cases it is assumed that there is not enough MEQ activity in unproduced areas to accurately find the permeable pathways. The premise of this review is that there may new developments in theory and modeling, as well as in data acquisition and processing, which could make it possible to image the subsurface in much more detail than 15 years ago. New understanding of the effect of

  5. Ground-Truthing Seismic Refraction Tomography for Sinkhole Detection in Florida

    NASA Astrophysics Data System (ADS)

    Hiltunen, D. R.; Hudyma, N.; Quigley, T. P.; Samakur, C.

    2007-12-01

    In order to provide effective return of storm water runoff to the subsurface aquifer, the Florida Department of Transportation (FDOT) constructs detention basins adjacent to its transportation facilities. These basins serve as a collection point for runoff within a local drainage area, and the overburden soil above the aquifer provides a natural filter for contaminants in the surface runoff water. However, the geologic setting for many of these basins in Florida is karst, limestone bedrock at shallow depth, and the concentration of water flow in these basins leads to frequent development of sinkholes. These sinkholes are an environmental hazard, as they provide a direct, open conduit for contaminant-laden runoff water to return to the aquifer rather than percolate through the overburden soil. Consequently, FDOT is keenly interested in all aspects of sinkholes, including factors leading to formation, methods of early detection, and effective methods for rapid repair. Recently, FDOT has engaged in a research effort to evaluate the capabilities of a wide range of geophysical investigation tools with regard to detection of sinkhole-prone areas within sites being considered for construction of detention ponds. The geophysical techniques evaluated have included ground penetrating radar (GPR), multi- electrode electrical resistivity (MER), seismic MASW, and seismic refraction tomography. In addition to geophysical testing at the research sites, extensive traditional geotechnical site characterization has been conducted, including boring and sampling of soil and rock, standard penetration tests (SPT), and cone penetration tests (CPT). The proposed paper will evaluate the capabilities of seismic refraction tomography. Comparisons between refraction tomograms and borehole logs, SPT soundings, and CPT soundings suggest that the refraction method can map the laterally-variable top of bedrock surface typical of karst terrane. During a recent ground proving exercise at the

  6. Stochastic estimation of aquifer geometry using seismic refraction data with borehole depth constraints

    SciTech Connect

    Chen, J.; Hubbard, S.S.; Gaines, D.; Korneev, V.; Baker, G.; Watson, D.

    2010-09-01

    We develop a Bayesian model to invert surface seismic refraction data with depth constraints from boreholes for characterization of aquifer geometry and apply it to seismic and borehole datasets collected at the contaminated Oak Ridge National Laboratory site in Tennessee. Rather than the traditional approach of first inverting the seismic arrival times for seismic velocity and then using that information to aid in the spatial interpolation of wellbore data, we jointly invert seismic first arrival time data and wellbore-based information, such as depths of key lithological boundaries. We use a staggered-grid finite-difference algorithm with second order accuracy in time and fourth order accuracy in space to model seismic full waveforms and use an automated method to pick the first arrival times. We use Markov Chain Monte Carlo methods to draw many samples from the joint posterior probability distribution, on which we can estimate the key interfaces and their associated uncertainty as a function of horizontal location and depth. We test the developed method on both synthetic and field case studies. The synthetic studies show that the developed method is effective at rigorous incorporation of multiscale data and the Bayesian inversion reduces uncertainty in estimates of aquifer zonation. Applications of the approach to field data, including two surface seismic profiles located 620 m apart from each other, reveal the presence of a low-velocity subsurface zone that is laterally persistent. This geophysically-defined feature is aligned with the plume axis, suggesting it may serve as an important regional preferential flow pathway.

  7. Successful gas hydrate prospecting using 3D seismic - A case study for the Mt. Elbert prospect, Milne Point, North Slope Alaska

    USGS Publications Warehouse

    Inks, T.L.; Agena, W.F.

    2008-01-01

    In February 2007, the Mt. Elbert Prospect stratigraphic test well, Milne Point, North Slope Alaska encountered thick methane gas hydrate intervals, as predicted by 3D seismic interpretation and modeling. Methane gas hydrate-saturated sediment was found in two intervals, totaling more than 100 ft., identified and mapped based on seismic character and wavelet modeling.

  8. Cataloguing Seismic Waveform Properties Recorded With a 3D Network in a Gold Mine in South Africa

    NASA Astrophysics Data System (ADS)

    Julia, J.; Nyblade, A. A.; Gok, R.; Walter, W. R.; Linzer, L.; Durrheim, R. J.; Dirks, P.

    2007-12-01

    The SAVUKA gold mine is located in the northwestern edge of the Witwatersrand basin, a Late Archean (3.07- 2.71~Ga) intracratonic basin in South Africa that hosts the largest known gold-uranium-pyrite ore deposits in the world. Seismic events related to the mine activity span several orders of magnitude through a variety of sources that include mine blasts, pillar collapses, and faulting events. These events are systematically recorded and catalogued through an in-mine, 3D seismic network consisting of 20, three-component, short-period stations with natural frequencies ranging between 4.5 and 28.0~Hz and deployed as deep as ~3.5 km. After 5 months of seismic monitoring of the mine, we have been able to assemble a database of over 6000 events spanning magnitudes in the -2.5 < ML < 4.4 range. The potential of this unique data set for characterizing the detailed seismic properties of the basin and studying source properties of non-double couple events is explored through simple, first-pass analysis on the recorded waveforms. Moreover, the in-mine network is complemented by a small array of 4 broadband stations interspaced ~10~km apart on the surface of the mine, and by a number of AfricaArray stations in South Africa and neighboring countries located at regional distances (50- 1000~km) from the mine. The largest mine-induced events are clearly recorded at distances as far away from the mine as 450~km and provide a unique opportunity for studying the regional propagation of seismic phases as well as the structure of the cratonic crust underlying the basin.

  9. Interpretation of Late Cretaceous Volcanic Mounds and Surrounding Gulfian Series Formations Using 3D Seismic Data in Zavala County, Texas

    NASA Astrophysics Data System (ADS)

    Bennett, Laura Claire

    The Late Cretaceous Gulfian series is a prominent and important series across the State of Texas that has been extensively studied since the nineteenth century. It is composed of series of southeast-dipping shelf carbonates and clastics deposited on the northwest margin of the Gulf of Mexico Basin. In south Texas, the Gulfian series was deposited in the Rio Grande Embayment and Maverick Basin and is comprised of the Eagle Ford Group, Austin Group, Anacacho Limestone, San Miguel Formation, Olmos Formation, and Escondido Formation that crop out and continue basinward in the subsurface. Late Cretaceous volcanism formed volcanic mounds composed of altered palagonite tuff that are clustered into two fields, including the Uvalde Field centered in Zavala County. Using the Pedernales 3D seismic survey, located in east-central Zavala County, several volcanic mounds were identified and mapped without the use of well log data by identifying structures and characteristics associated with the volcanic mounds. Isolating these mounds through mapping enabled the mapping of the tops surrounding Gulfian formations, Lower Eagle Ford, Upper Eagle Ford, Austin, Anacacho, and San Miguel, for which time-structure, amplitude, similarity/coherency attribute, and isochron maps were generated. By using 3D seismic data, the volcanic mounds and their relation to surrounding rocks can be better interpreted.

  10. Microgravity Characterization of the Hontomín CO2 Storage Site (Spain). Integration with 3D Seismic Results

    NASA Astrophysics Data System (ADS)

    Ayarza, P.; Andres, J.; Alcalde, J.; Martí, D.; Marzán, I.; Martinez-Catalan, J. R.; Carbonell, R.; García Lobón, J. L.; Pérez Estaún, A.

    2014-12-01

    Hontomín hosts the first Spanish CO2storage Technology Development Plant. The area, located in the southern part of Mesozoic Basque-Cantabrian Basin, presents E-W and ESE-WNW faults formed during a Permian-Triassic extensional event. The latter were reactivated during the opening of the Bay of Biscay, while a new set of NNE-SSW faults developed. Fractures were reactivated again during the Alpine compression. The resulting configuration is a dome-like structure that includes the Mesozoic succession (Upper Triassic to Lower Cretaceous) and is crowned by Upper Cretaceous and Eocene rocks lying unconformably. The target injection pointis located at 1500 m depth, within a Jurassic carbonate saline formation. Several multidisciplinary studies have been carried out in Hontomín aiming to obtain a thorough geological characterization. Among these, a microgravity survey, acquired under the umbrella of the CIUDEN foundation, has provided us with a complete 3D image of the site. A 4x4 km2area, coincident with that surveyed by 3D seismic reflection, has been sampled using a dense grid with a station spacing of 100 m. The result is a high resolution Bouguer anomaly gravity map capable of offering insights into the subsurface geology down to the depth of the injection point. The application of mathematical procedures to the data has further enhanced its potential for interpretation. The calculated regional anomaly indicates that the dome structure strikes E-W to ENE-WSW, sub-parallel to a major fault: the South Fault, part of the Ubierna fault system. The resulting residual anomaly enhances a number of NW-SE features that have also been interpreted as faults and that can be observed after performing vertical and horizontal derivatives to the data. Calculation of the Euler solutions confirms the previous results and brings out a new NNW-SSE feature, namely the East Fault. Integration with 3D seismic data suggests that faults affect different levels of the sedimentary sequence

  11. Crustal structure in the eastern Colorado Plateaus Provence from seismic-refraction measurements

    USGS Publications Warehouse

    Roller, John C.

    1964-01-01

    A reversed seismic-refraction profile was recorded in the Colorado Plateaus Province from Hanksville, Utah, to Chinle, Arizona, The velocity of Pg is 6.2 km/sec, and the true velocity of Pn is 7.8 km/sec, Waves identified as reflections indicate that an intermediate layer in the crust has a velocity of approximately 6.8 km/sec. Thickness of the crust is 43 km at Chinle and 40 km at Hanksville. The Pn velocity in the Colorado Plateaus Province is the same as that in the Basin and Range Province, but is significantly lower than Pn in the High Plains of Colorado.

  12. Application of seismic refraction methods in groundwater modeling studies in New England ( USA).

    USGS Publications Warehouse

    Haeni, F.P.

    1986-01-01

    Seismic refraction studies were conducted over unconfined glacial aquifers in New England to determine: 1) depth of the underlying bedrock; 2) depth of the water table; 3) saturated thickness of the aquifer in areas not accessible to heavy drilling equipment; 4) areas where thick, unsaturated sediments overlie thickly saturated parts of the aquifer; and 5) locations of test holes and type of drilling equipment needed. These data were used in groundwater models and provided parameter values that required few adjustments during calibration. -from Author

  13. Crustal structure of Yunnan province, People's Republic of China, from seismic refraction profiles

    USGS Publications Warehouse

    Kan, R.-J.; Hu, H.-X.; Zeng, R.-S.; Mooney, W.D.; McEvilly, T.V.

    1986-01-01

    Seismic refraction, profiles in Yunnan Province, southwestern China, define the crustal structure in an area of active tectonics, on the southern end of the Himalaya-Burma arc. The crustal thickness ranges from 38 to 46 kilometers, and the relatively low mean crustal velocity indicates a crustal composition compatible with normal continental crust and consisting mainly of meta-sedimentary and silicic intrusive rocks, with little mafic or ultramafic component. This composition suggests a crustal evolution involving sedimentary processes on the flank of the Yangtze platform rather than the accretion of oceanic island arcs, as has been proposed. An anomalously low upper-mantle velocity observed on one profile, but not on another at right angles to it may indicate active tectonic processes in the mantle or seismic anisotropy.

  14. CRUSTAL STRUCTURE OF THE SOUTHERN CALAVERAS FAULT ZONE, CENTRAL CALIFORNIA, FROM SEISMIC REFRACTION INVESTIGATIONS.

    USGS Publications Warehouse

    Blumling, Peter; Mooney, Walter D.; Lee, W.H.K.

    1985-01-01

    A magnitude 5. 7 earthquake on August 6, 1979, within the Calaveras fault zone, near Coyote Lake of west-central California, motivated a seismic-refraction investigation in this area. A northwest-southeast profile along the fault, as well as two fan profiles across the fault were recorded to examine the velocity structure of this region. The analysis of the data reveals a complicated upper crustal velocity structure with strong lateral variations in all directions. Velocities within the fault zone were determined from the fan profiles. Near Anderson Lake, a pronounced delay of first arrivals on the fan records indicates a vertical 1- to 2-km-wide near-surface, low-velocity zone along the fault. Near Coyote Lake, the delays observed in the fan records correlate with two subsurface en-echelon fault planes which have been previously identified from lineations in the seismicity pattern. Refs.

  15. Crustal Structure of Yunnan Province, People's Republic of China, from Seismic Refraction Profiles.

    PubMed

    Kan, R J; Hu, H X; Zeng, R S; Mooney, W D; McEvilly, T V

    1986-10-24

    Seismic refraction, profiles in Yunnan Province, southwestern China, define the crustal structure in an area of active tectonics on the southern end of the Himalaya-Burma arc. The crustal thickness ranges from 38 to 46 kilometers, and the relatively low mean crustal velocity indicates a crustal composition compatible with normal continental crust and consisting mainly of meta-sedimentary and silicic intrusive rocks, with little mafic or ultramafic component. This composition suggests a crustal evolution involving sedimentary processes on the flank of the Yangtze platform rather than the accretion of oceanic island arcs, as has been proposed. An anomalously low upper-mantle velocity observed on one profile but not on another at right angles to it may indicate active tectonic processes in the mantle or seismic anisotropy.

  16. 3-D seismic data for field development: Landslide field case study

    SciTech Connect

    Raeuchle, S.K.; Carr, T.R.; Tucker, R.D. )

    1990-05-01

    The Landslide field is located on the extreme southern flank of the San Joaquin basin, approximately 25 mi south of Bakersfield, California. The field, discovered in 1985, has produced in excess 9 million bbl of oil with an estimated ultimate recovery of more than 13 MMBO. The Miocene Stevens sands, which form the reservoir units at Landslide field, are interpreted as a series of constructional submarine fan deposits. Deposition of the fans was controlled by paleotopography with an abrupt updip pinch-out of the sands to the southwest. The three-dimensional seismic data over the field was used to locate the bottom hole of the landslide 22X-30 development well as close to this abrupt updip pinchout as possible in order to maximize oil recovery. A location was selected two traces (330 ft) from the updip pinch-out as mapped on the seismic data. The well was successfully drilled during 1989, encountering 150 ft of net sand with initial production in excess of 1,500 bbl of oil/day. A pressure buildup test indicates the presence of a boundary approximately 200 ft from the well bore. This boundary is interpreted as the updip pinchout of the Stevens sands against the paleohigh. Based on examination of changes in amplitude, the absence or presence of reservoir-quality sand can be mapped across the paleohighs. Application of three-dimensional seismic data, integration with well data, and in particular reconstruction cuts tied closely to existing wells can be used to map the ultimate extent of the field and contribute to efficient development.

  17. 3D elastic full waveform inversion: case study from a land seismic survey

    NASA Astrophysics Data System (ADS)

    Kormann, Jean; Marti, David; Rodriguez, Juan-Esteban; Marzan, Ignacio; Ferrer, Miguel; Gutierrez, Natalia; Farres, Albert; Hanzich, Mauricio; de la Puente, Josep; Carbonell, Ramon

    2016-04-01

    Full Waveform Inversion (FWI) is one of the most advanced processing methods that is recently reaching a mature state after years of solving theoretical and technical issues such as the non-uniqueness of the solution and harnessing the huge computational power required by realistic scenarios. BSIT (Barcelona Subsurface Imaging Tools, www.bsc.es/bsit) includes a FWI algorithm that can tackle with very complex problems involving large datasets. We present here the application of this system to a 3D dataset acquired to constrain the shallow subsurface. This is where the wavefield is the most complicated, because most of the wavefield conversions takes place in the shallow region and also because the media is much more laterally heterogeneous. With this in mind, at least isotropic elastic approximation would be suitable as kernel engine for FWI. The current study explores the possibilities to apply elastic isotropic FWI using only the vertical component of the recorded seismograms. The survey covers an area of 500×500 m2, and consists in a receivers grid of 10 m×20 m combined with a 250 kg accelerated weight-drop as source on a displaced grid of 20 m×20 m. One of the main challenges in this case study is the costly 3D modeling that includes topography and substantial free surface effects. FWI is applied to a data subset (shooting lines 4 to 12), and is performed for 3 frequencies ranging from 15 to 25 Hz. The starting models are obtained from travel-time tomography and the all computation is run on 75 nodes of Mare Nostrum supercomputer during 3 days. The resulting models provide a higher resolution of the subsurface structures, and show a good correlation with the available borehole measurements. FWI allows to extend in a reliable way this 1D knowledge (borehole) to 3D.

  18. A western gray whale mitigation and monitoring program for a 3-D seismic survey, Sakhalin Island, Russia.

    PubMed

    Johnson, S R; Richardson, W J; Yazvenko, S B; Blokhin, S A; Gailey, G; Jenkerson, M R; Meier, S K; Melton, H R; Newcomer, M W; Perlov, A S; Rutenko, S A; Würsig, B; Martin, C R; Egging, D E

    2007-11-01

    The introduction of anthropogenic sounds into the marine environment can impact some marine mammals. Impacts can be greatly reduced if appropriate mitigation measures and monitoring are implemented. This paper concerns such measures undertaken by Exxon Neftegas Limited, as operator of the Sakhalin-1 Consortium, during the Odoptu 3-D seismic survey conducted during 17 August-9 September 2001. The key environmental issue was protection of the critically endangered western gray whale (Eschrichtius robustus), which feeds in summer and fall primarily in the Piltun feeding area off northeast Sakhalin Island. Existing mitigation and monitoring practices for seismic surveys in other jurisdictions were evaluated to identify best practices for reducing impacts on feeding activity by western gray whales. Two buffer zones were established to protect whales from physical injury or undue disturbance during feeding. A 1 km buffer protected all whales from exposure to levels of sound energy potentially capable of producing physical injury. A 4-5 km buffer was established to avoid displacing western gray whales from feeding areas. Trained Marine Mammal Observers (MMOs) on the seismic ship Nordic Explorer had the authority to shut down the air guns if whales were sighted within these buffers. Additional mitigation measures were also incorporated: Temporal mitigation was provided by rescheduling the program from June-August to August-September to avoid interference with spring arrival of migrating gray whales. The survey area was reduced by 19% to avoid certain waters <20 m deep where feeding whales concentrated and where seismic acquisition was a lower priority. The number of air guns and total volume of the air guns were reduced by about half (from 28 to 14 air guns and from 3,390 in(3) to 1,640 in(3)) relative to initial plans. "Ramp-up" (="soft-start") procedures were implemented. Monitoring activities were conducted as needed to implement some mitigation measures, and to assess

  19. Reducing Disk Storage of Full-3D Seismic Waveform Tomography (F3DT) Through Lossy Online Compression

    DOE PAGES

    Lindstrom, Peter; Chen, Po; Lee, En-Jui

    2016-05-05

    Full-3D seismic waveform tomography (F3DT) is the latest seismic tomography technique that can assimilate broadband, multi-component seismic waveform observations into high-resolution 3D subsurface seismic structure models. The main drawback in the current F3DT implementation, in particular the scattering-integral implementation (F3DT-SI), is the high disk storage cost and the associated I/O overhead of archiving the 4D space-time wavefields of the receiver- or source-side strain tensors. The strain tensor fields are needed for computing the data sensitivity kernels, which are used for constructing the Jacobian matrix in the Gauss-Newton optimization algorithm. In this study, we have successfully integrated a lossy compression algorithmmore » into our F3DT SI workflow to significantly reduce the disk space for storing the strain tensor fields. The compressor supports a user-specified tolerance for bounding the error, and can be integrated into our finite-difference wave-propagation simulation code used for computing the strain fields. The decompressor can be integrated into the kernel calculation code that reads the strain fields from the disk and compute the data sensitivity kernels. During the wave-propagation simulations, we compress the strain fields before writing them to the disk. To compute the data sensitivity kernels, we read the compressed strain fields from the disk and decompress them before using them in kernel calculations. Experiments using a realistic dataset in our California statewide F3DT project have shown that we can reduce the strain-field disk storage by at least an order of magnitude with acceptable loss, and also improve the overall I/O performance of the entire F3DT-SI workflow significantly. The integration of the lossy online compressor may potentially open up the possibilities of the wide adoption of F3DT-SI in routine seismic tomography practices in the near future.« less

  20. 3D imaging of the Corinth rift from a new passive seismic tomography and receiver function analysis

    NASA Astrophysics Data System (ADS)

    Godano, Maxime; Gesret, Alexandrine; Noble, Mark; Lyon-Caen, Hélène; Gautier, Stéphanie; Deschamps, Anne

    2016-04-01

    The Corinth Rift is the most seismically active zone in Europe. The area is characterized by very localized NS extension at a rate of ~ 1.5cm/year, the occurrence of frequent and intensive microseismic crises and occasional moderate to large earthquakes like in 1995 (Mw=6.1). Since the year 2000, the Corinth Rift Laboratory (CRL, http://crlab.eu) consisting in a multidisciplinary natural observatory, aims at understanding the mechanics of faulting and earthquake nucleation in the Rift. Recent studies have improved our view about fault geometry and mechanics within CRL, but there is still a critical need for a better knowledge of the structure at depth both for the accuracy of earthquake locations and for mechanical interpretation of the seismicity. In this project, we aim to analyze the complete seismological database (13 years of recordings) of CRL by using recently developed methodologies of structural imaging, in order to determine at the same time and with high resolution, the local 3D structure and the earthquake locations. We perform an iterative joint determination of 3D velocity model and earthquake coordinates. In a first step, P and S velocity models are determined using first arrival time tomography method proposed by Taillandier et al. (2009). It consists in the minimization of the cost function between observed and theoretical arrival times which is achieved by the steepest descent method (e.g. Tarantola 1987). This latter requires computing the gradient of the cost function by using the adjoint state method (Chavent 1974). In a second step, earthquakes are located in the new velocity model with a non-linear inversion method based on a Bayesian formulation (Gesret et al. 2015). Step 1 and 2 are repeated until the cost function no longer decreases. We present preliminary results consisting in: (1) the adjustement of a 1D velocity model that is used as initial model of the 3D tomography and (2) a first attempt of the joint determination of 3D velocity

  1. Rock formation characterization for carbon dioxide geosequestration: 3D seismic amplitude and coherency anomalies, and seismic petrophysical facies classification, Wellington and Anson-Bates Fields, Kansas, USA

    NASA Astrophysics Data System (ADS)

    Ohl, Derek; Raef, Abdelmoneam

    2014-04-01

    Higher resolution rock formation characterization is of paramount priority, amid growing interest in injecting carbon dioxide, CO2, into subsurface rock formations of depeleting/depleted hydrocarbon reservoirs or saline aquifers in order to reduce emissions of greenhouse gases. In this paper, we present a case study for a Mississippian carbonate characterization integrating post-stack seismic attributes, well log porosities, and seismic petrophysical facies classification. We evaluated changes in petrophysical lithofacies and reveal structural facies-controls in the study area. Three cross-plot clusters in a plot of well log porosity and acoustic impedance corroborated a Neural Network petrophysical facies classification, which was based on training and validation utilizing three petrophysically-different wells and three volume seismic attributes, extracted from a time window including the wavelet of the reservoir-top reflection. Reworked lithofacies along small-throw faults has been revealed based on comparing coherency and seismic petrophysical facies. The main objective of this study is to put an emphasis on reservoir characterization that is both optimized for and subsequently benefiting from pilot tertiary CO2 carbon geosequestration in a depleting reservoir and also in the deeper saline aquifer of the Arbuckle Group, south central Kansas. The 3D seismic coherency attribute, we calculated from a window embracing the Mississippian top reflection event, indicated anomalous features that can be interpreted as a change in lithofacies or faulting effect. An Artificial Neural Network (ANN) lithofacies modeling has been used to better understand these subtle features, and also provide petrophysical classes, which will benefit flow-simulation modeling and/or time-lapse seismic monitoring feasibility analysis. This paper emphasizes the need of paying greater attention to small-scale features when embarking upon characterization of a reservoir or saline-aquifer for CO2

  2. INCREASING OIL RECOVERY THROUGH ADVANCED REPROCESSING OF 3D SEISMIC, GRANT CANYON AND BACON FLAT FIELDS, NYE COUNTY, NEVADA

    SciTech Connect

    Eric H. Johnson; Don E. French

    2001-06-01

    Makoil, Inc., of Orange, California, with the support of the U.S. Department of Energy has reprocessed and reinterpreted the 3D seismic survey of the Grant Canyon area, Railroad Valley, Nye County, Nevada. The project was supported by Dept. of Energy Grant DE-FG26-00BC15257. The Grant Canyon survey covers an area of 11 square miles, and includes Grant Canyon and Bacon Flat oil fields. These fields have produced over 20 million barrels of oil since 1981, from debris slides of Devonian rocks that are beneath 3,500 to 5,000 ft of Tertiary syntectonic deposits that fill the basin of Railroad Valley. High-angle and low-angle normal faults complicate the trap geometry of the fields, and there is great variability in the acoustic characteristics of the overlying valley fill. These factors combine to create an area that is challenging to interpret from seismic reflection data. A 3D seismic survey acquired in 1992-93 by the operator of the fields has been used to identify development and wildcat locations with mixed success. Makoil believed that improved techniques of processing seismic data and additional well control could enhance the interpretation enough to improve the chances of success in the survey area. The project involved the acquisition of hardware and software for survey interpretation, survey reprocessing, and reinterpretation of the survey. SeisX, published by Paradigm Geophysical Ltd., was chosen as the interpretation software, and it was installed on a Dell Precision 610 computer work station with the Windows NT operating system. The hardware and software were selected based on cost, possible addition of compatible modeling software in the future, and the experience of consulting geophysicists in the Billings area. Installation of the software and integration of the hardware into the local office network was difficult at times but was accomplished with some technical support from Paradigm and Hewlett Packard, manufacturer of some of the network equipment. A

  3. Development of a State-Wide 3-D Seismic Tomography Velocity Model for California

    NASA Astrophysics Data System (ADS)

    Thurber, C. H.; Lin, G.; Zhang, H.; Hauksson, E.; Shearer, P.; Waldhauser, F.; Hardebeck, J.; Brocher, T.

    2007-12-01

    We report on progress towards the development of a state-wide tomographic model of the P-wave velocity for the crust and uppermost mantle of California. The dataset combines first arrival times from earthquakes and quarry blasts recorded on regional network stations and travel times of first arrivals from explosions and airguns recorded on profile receivers and network stations. The principal active-source datasets are Geysers-San Pablo Bay, Imperial Valley, Livermore, W. Mojave, Gilroy-Coyote Lake, Shasta region, Great Valley, Morro Bay, Mono Craters-Long Valley, PACE, S. Sierras, LARSE 1 and 2, Loma Prieta, BASIX, San Francisco Peninsula and Parkfield. Our beta-version model is coarse (uniform 30 km horizontal and variable vertical gridding) but is able to image the principal features in previous separate regional models for northern and southern California, such as the high-velocity subducting Gorda Plate, upper to middle crustal velocity highs beneath the Sierra Nevada and much of the Coast Ranges, the deep low-velocity basins of the Great Valley, Ventura, and Los Angeles, and a high- velocity body in the lower crust underlying the Great Valley. The new state-wide model has improved areal coverage compared to the previous models, and extends to greater depth due to the data at large epicentral distances. We plan a series of steps to improve the model. We are enlarging and calibrating the active-source dataset as we obtain additional picks from investigators and perform quality control analyses on the existing and new picks. We will also be adding data from more quarry blasts, mainly in northern California, following an identification and calibration procedure similar to Lin et al. (2006). Composite event construction (Lin et al., in press) will be carried out for northern California for use in conventional tomography. A major contribution of the state-wide model is the identification of earthquakes yielding arrival times at both the Northern California Seismic

  4. Calibration of 3D Upper Mantle Structure in Eurasia Using Regional and Teleseismic Full Waveform Seismic Data

    SciTech Connect

    Barbara Romanowicz; Mark Panning

    2005-04-23

    Adequate path calibrations are crucial for improving the accuracy of seismic event location and origin time, size, and mechanism, as required for CTBT monitoring. There is considerable information on structure in broadband seismograms that is currently not fully utilized. The limitations have been largely theoretical. the development and application to solid earth problems of powerful numerical techniques, such as the Spectral Element Method (SEM), has opened a new era, and theoretically, it should be possible to compute the complete predicted wavefield accurately without any restrictions on the strength or spatial extent of heterogeneity. This approach requires considerable computational power, which is currently not fully reachable in practice. We propose an approach which relies on a cascade of increasingly accurate theoretical approximations for the computation of the seismic wavefield to develop a model of regional structure for the area of Eurasia located between longitudes of 30 and 150 degrees E, and latitudes of -10 to 60 degrees North. The selected area is particularly suitable for the purpose of this experiment, as it is highly heterogeneous, presenting a challenge for calibration purposes, but it is well surrounded by earthquake sources and, even though they are sparsely distributed, a significant number of high quality broadband digital stations exist, for which data are readily accessible through IRIS (Incorporated Research Institutions for Seismology) and the FDSN (Federation of Digital Seismic Networks). The starting models used will be a combination of a-priori 3D models recently developed for this region, combining various geophysical and seismological data, and a major goal of this study will be to refine these models so as to fit a variety of seismic waveforms and phases.

  5. Investigation of the presence of transverse anisotropy in the 3D baseline seismic data at Ketzin, Germany

    NASA Astrophysics Data System (ADS)

    Kruachanta, Mingkhwan; Ivandic, Monika; Juhlin, Christopher

    2015-04-01

    A 3D seismic baseline survey was acquired within the EU funded CO2SINK project at Ketzin, Germany in 2005. CO2 was injected at about 630-650 meters depth into the Stuttgart Formation. The formation is heterogeneous with lithological facies of channel sandstones interbedded with floodplain mudstones. It underlies an approximately 210 meters thick sequence of claystone, silty claystone and anhydrite of the Weser and Arnstadt Formations. Claystone is considered to be an intrinsic-type anisotropic medium due to the platy shape of clay minerals. A thick interval of claystone caprock may show seismic velocity variation with propagation angle or seismic anisotropy. In this study, the degree of anisotropy was assumed to be weak. The processing steps followed conventional seismic data processing, except for the velocity estimation used for the moveout correction. The velocity approximation used nonhyperbolic or 4th order moveout for transverse anisotropic (TI) media which was proposed by Alkhalifah (1997). The 4th order moveout velocity approximation used the zero-dip normal moveout velocity (V nmo) and eta (?) anisotropic parameter for the velocity correction as defined by the following equations. tx = √(t02+X2/Vnmo2-2? X4/vnmo2 / t2o[1+2?)X2/Vnmo2]) where ? = 12[ 2 ] VVh2- - 1 nmoand tx is the traveltime, to is traveltime at zero offset, X is the offset and V h is horizontal velocity. Preliminary results indicate the presence of anisotropy in the study area with an eta parameter ranging from -0.185 to +0.180. Moveout velocity corrected stacked sections show an improvement in the continuity of reflections in the shallow part of the survey (above 500 ms), whereas there is no significant difference in the deeper region.

  6. Improving Geologic and Engineering Models of Midcontinent Fracture and Karst-Modified Reservoirs Using New 3-D Seismic Attributes

    SciTech Connect

    Susan Nissen; Saibal Bhattacharya; W. Lynn Watney; John Doveton

    2009-03-31

    Our project goal was to develop innovative seismic-based workflows for the incremental recovery of oil from karst-modified reservoirs within the onshore continental United States. Specific project objectives were: (1) to calibrate new multi-trace seismic attributes (volumetric curvature, in particular) for improved imaging of karst-modified reservoirs, (2) to develop attribute-based, cost-effective workflows to better characterize karst-modified carbonate reservoirs and fracture systems, and (3) to improve accuracy and predictiveness of resulting geomodels and reservoir simulations. In order to develop our workflows and validate our techniques, we conducted integrated studies of five karst-modified reservoirs in west Texas, Colorado, and Kansas. Our studies show that 3-D seismic volumetric curvature attributes have the ability to re-veal previously unknown features or provide enhanced visibility of karst and fracture features compared with other seismic analysis methods. Using these attributes, we recognize collapse features, solution-enlarged fractures, and geomorphologies that appear to be related to mature, cockpit landscapes. In four of our reservoir studies, volumetric curvature attributes appear to delineate reservoir compartment boundaries that impact production. The presence of these compartment boundaries was corroborated by reservoir simulations in two of the study areas. Based on our study results, we conclude that volumetric curvature attributes are valuable tools for mapping compartment boundaries in fracture- and karst-modified reservoirs, and we propose a best practices workflow for incorporating these attributes into reservoir characterization. When properly calibrated with geological and production data, these attributes can be used to predict the locations and sizes of undrained reservoir compartments. Technology transfer of our project work has been accomplished through presentations at professional society meetings, peer-reviewed publications

  7. Electrical Resistivity, Seismic Refraction Tomography and Drilling Logs to Identify the Heterogeneity and the Preferential Flow in a Shallow Aquifer

    NASA Astrophysics Data System (ADS)

    Lachhab, A.

    2015-12-01

    The study site is located at the Center for Environmental Education and Research (CEER) at Susquehanna University. Electrical Resistivity and Seismic Refraction Tomography (ERT and SRT), as well as several pumping tests were performed to identify zones of heterogeneities and hydrogeophysical characteristics of a shallow unconfined aquifer. The combination of these methods was selected to study the local geology and the subsurface preferential pathways of groundwater flow. 22 Dipole-Dipole ERT transects with 56 electrodes each and 11 SRT transects with 24 geophones each were performed. Drilling logs of 5 observation wells located within the site were also used. All drilling logs showed clearly the heterogeneity of the aquifer when compared to each other. The combination of ERT and SRT indicated that a potential zone of preferential flow is present within the aquifer and can be accurately identified based on the approach adopted in this study. The drilling logs served to specifically identify the soil and the geological formations making the heterogeneity of the aquifer. 3D ERT and SRT block diagrams were generated to connect all formations shown in the 2D tomography profiles to visualize the pathways of preferential flow and non-conductive formations. While ERT has proven to show saturated areas of the subsurface, SRT was more effective in identifying the bedrock-soil discontinuity and other near surface formations contributing to the local heterogeneity.

  8. 3D seismic analysis of gravity-driven and basement influenced normal fault growth in the deepwater Otway Basin, Australia

    NASA Astrophysics Data System (ADS)

    Robson, A. G.; King, R. C.; Holford, S. P.

    2016-08-01

    We use three-dimensional (3D) seismic reflection data to analyse the structural style and growth of a normal fault array located at the present-day shelf-edge break and into the deepwater province of the Otway Basin, southern Australia. The Otway Basin is a Late Jurassic to Cenozoic, rift-to-passive margin basin. The seismic reflection data images a NW-SE (128-308) striking, normal fault array, located within Upper Cretaceous clastic sediments and which consists of ten fault segments. The fault array contains two hard-linked fault assemblages, separated by only 2 km in the dip direction. The gravity-driven, down-dip fault assemblage is entirely contained within the 3D seismic survey, is located over a basement plateau and displays growth commencing and terminating during the Campanian-Maastrichtian, with up to 1.45 km of accumulated throw (vertical displacement). The up-dip normal fault assemblage penetrates deeper than the base of the seismic survey, but is interpreted to be partially linked along strike at depth to major basement-involved normal faults that can be observed on regional 2D seismic lines. This fault assemblage displays growth initiating in the Turonian-Santonian and has accumulated up to 1.74 km of throw. Our detailed analysis of the 3D seismic data constraints post-Cenomanian fault growth of both fault assemblages into four evolutionary stages: [1] Turonian-Santonian basement reactivation during crustal extension between Australia and Antarctica. This either caused the upward propagation of basement-involved normal faults or the nucleation of a vertically isolated normal fault array in shallow cover sediments directly above the reactivated basement-involved faults; [2] continued Campanian-Maastrichtian crustal extension and sediment loading eventually created gravitational instability on the basement plateau, nucleating a second, vertically isolated normal fault array in the cover sediments; [3] eventual hard-linkage of fault segments in both fault

  9. Seismic refraction data constrain along-axis structure of the Mid-Cayman spreading center

    NASA Astrophysics Data System (ADS)

    Van Avendonk, H. J.; Hayman, N. W.; Harding, J.; Grevemeyer, I.; Peirce, C.; Dannowski, A.; Papenberg, C. A.

    2015-12-01

    The Mid-Cayman Spreading Center (MCSC) is an ultraslow (15 mm/yr) spreading ridge between the Caribbean and North American plates. From north to south the MCSC is just ~140 km long, as it is bounded to the north by the Oriente transform fault, and to the south by the Swan Islands and Walton fault systems. The neovolcanic zone is characterized by an axial valley with depths to 6000 m, and a few off-axis bathymetric highs that can be as shallow as 2000 m. The role of tectonic and magmatic processes in the creation of this bathymetric relief is not yet understood. In the 2015 CaySEIS experiment, a collaboration between German, US and UK scientists, we gathered ocean-bottom seismic refraction data along five lines across and parallel to the MCSC to determine its crustal structure. We here present the tomographic analysis of marine seismic refractions recorded along the spreading axis. The presence of thin crust here shows that the bathymetric relief of the MCSC is at least in part isostatically compensated. Much of the older ultraslow spread crust on the flanks of the MCSC may not have accreted along the deep axial valley, but it may instead have formed by exhumation of gabbros along extensional faults in the adjacent seafloor.

  10. Avalon terane in eastern coastal Maine: seismic refraction-wide- angle reflection data

    USGS Publications Warehouse

    Luetgert, J.; Mann, C.E.

    1990-01-01

    A 145-km-long seismic refraction line recorded parallel to the eastern coastline of Maine within the Avalon terrane provides information about the crustal velocity structure within the Avalon block and its relation to other Appalachian terranes. A crustal velocity model for the upper 8 km shows that, except for a thin surficial layer of velocity 5.0-5.3 km/s, upper crustal granites and country rocks have velocities in the range 6.0-6.3 km/s and gabbros have a 6.5 km/s velocity. To determine the lower crustal structure, deep reflections were analyzed by applying normal moveout corrections routinely used in reflection data processing. Major reflective boundaries at approximately 3-4, 7, and 10-11 s two-way traveltime are easily distinguished, and are similar to those observed in a near-vertical seismic reflection survey crossing the refraction profile at its southwestern end. The deepest reflections correspond to the crust-mantle boundary at a depth of 34-35 km. -from Authors

  11. Shallow seismic refraction used to map the hydrostratigraphy of Nukuoro Atoll, Micronesia

    NASA Astrophysics Data System (ADS)

    Ayers, Jerry F.

    1990-02-01

    Results from a shallow seismic-refraction survey on Nukuoro indicate that the distribution of fresh and brackish groundwater on that atoll island is controlled by a three-dimensional mosaic of carbonate facies. Each facies is characterized by a distinct seismic velocity which is dependent on the grain size, composition, and abundance of carbonate cement. The refraction survey further indicates that the upper saturated zone is composed of mostly unconsolidated sediments underlain by highly permeable, well-indurated limestone. The fresh-water lens and associated transition zone of fresh to saline groundwater occur within the upper unconsolidated sediments. Measurements of chloride-ion concentrations in water samples collected from sites across the island indicate an asymmetric fresh-water lens with the thickest part of the lens located near the lagoon shoreline. During the 1983 drought, saline water intruded into the island's central topographical depression where taro is cultivated. The intrusion was caused by tidal pumping (upward movement) of brackish water underlying a reef-flat plate, which forms a confining layer over a significant part of the island.

  12. 3-D seismic analysis of a carbonate platform in the Molasse Basin - reef distribution and internal separation with seismic attributes

    NASA Astrophysics Data System (ADS)

    von Hartmann, Hartwig; Buness, Hermann; Krawczyk, Charlotte M.; Schulz, Rüdiger

    2012-10-01

    Carbonate platforms differ from clastic sedimentary environments by a greater heterogeneity, so that key horizons for mapping and compartmentalisation of the reservoir are generally missing. We show that different seismic attributes help to compete with these difficulties and to identify different carbonate facies within the platform. The Upper Jurassic carbonate platform in Southern Germany in the Molasse Basin is a main exploration target for hydrogeothermal projects. Knowledge about the distribution of different carbonate facies within the platform, which is overprinted by faults, is important for a realistic reservoir simulation. The platform with an average thickness of 600 meters was artificially divided into four layers of equal thickness. Within each layer the characteristic seismic pattern was visualized by different attributes (travel time mapping, spectral decomposition), allowing additionally for further depositional classification. Within the uppermost layer the coral reef distribution could be mapped. The reefs form several complexes of up to 12 square kilometres in size. The surrounding slope and trough areas are identified as well. Within the platform , the distribution of sponge reefs could be visualized. They form either amalgamations in distinct areas, or are spread as small singular structures with diameters of approximately less than hundred meters. Comparing tectonic elements and reef distribution within the whole platform reveals that the early topography triggered the reef distribution, while these lithologic inhomogenities influenced later on the local shape of tectonic lineaments. The fault system which dominates the structural style in the area is visible in the different transformations but does not obscure the facies distribution, which hindered former interpretations of the data set. In this way a reservoir model can incorporate now the first time the reef distribution within an area.

  13. The Role of Faulting on the Growth of a Carbonate Platform: Evidence from 3D Seismic Analysis and Section Restoration

    NASA Astrophysics Data System (ADS)

    Nur Fathiyah Jamaludin, Siti; Pubellier, Manuel; Prasad Ghosh, Deva; Menier, David; Pierson, Bernard

    2014-05-01

    Tectonics in addition to other environmental factors impacts the growth of carbonate platforms and plays an important role in shaping the internal architecture of the platforms. Detailed of faults and fractures development and healing in carbonate environment have not been explored sufficiently. Using 3D seismic and well data, we attempt to reconstruct the structural evolution of a Miocene carbonate platform in Central Luconia Province, offshore Malaysia. Luconia Province is located in the NW coast of Borneo and has become one of the largest carbonate factories in SE Asia. Seismic interpretations including seismic attribute analysis are applied to the carbonate platform to discern its sedimentology and structural details. Detailed seismic interpretations highlight the relationships of carbonate deposition with syn-depositional faulting. Branching conjugate faults are common in this carbonate platform and have become a template for reef growth, attesting lateral facies changes within the carbonate environments. Structural restoration was then appropriately performed on the interpreted seismic sections based on sequential restoration techniques, and provided images different from those of horizon flattening methods. This permits us to compensate faults' displacement, remove recent sediment layers and finally restore the older rock units prior to the fault motions. It allows prediction of platform evolution as a response to faulting before and after carbonate deposition and also enhances the pitfalls of interpretation. Once updated, the reconstructions allow unravelling of the un-seen geological features underneath the carbonate platform, such as paleo-structures and paleo-topography which in turn reflects the paleo-environment before deformations took place. Interestingly, sections balancing and restoration revealed the late-phase (Late Oligocene-Early Miocene) rifting of South China Sea, otherwise difficult to visualize on seismic sections. Later it is shown that

  14. Calculating the Probability of Strong Ground Motions Using 3D Seismic Waveform Modeling - SCEC CyberShake

    NASA Astrophysics Data System (ADS)

    Gupta, N.; Callaghan, S.; Graves, R.; Mehta, G.; Zhao, L.; Deelman, E.; Jordan, T. H.; Kesselman, C.; Okaya, D.; Cui, Y.; Field, E.; Gupta, V.; Vahi, K.; Maechling, P. J.

    2006-12-01

    Researchers from the SCEC Community Modeling Environment (SCEC/CME) project are utilizing the CyberShake computational platform and a distributed high performance computing environment that includes USC High Performance Computer Center and the NSF TeraGrid facilities to calculate physics-based probabilistic seismic hazard curves for several sites in the Southern California area. Traditionally, probabilistic seismic hazard analysis (PSHA) is conducted using intensity measure relationships based on empirical attenuation relationships. However, a more physics-based approach using waveform modeling could lead to significant improvements in seismic hazard analysis. Members of the SCEC/CME Project have integrated leading-edge PSHA software tools, SCEC-developed geophysical models, validated anelastic wave modeling software, and state-of-the-art computational technologies on the TeraGrid to calculate probabilistic seismic hazard curves using 3D waveform-based modeling. The CyberShake calculations for a single probablistic seismic hazard curve require tens of thousands of CPU hours and multiple terabytes of disk storage. The CyberShake workflows are run on high performance computing systems including multiple TeraGrid sites (currently SDSC and NCSA), and the USC Center for High Performance Computing and Communications. To manage the extensive job scheduling and data requirements, CyberShake utilizes a grid-based scientific workflow system based on the Virtual Data System (VDS), the Pegasus meta-scheduler system, and the Globus toolkit. Probabilistic seismic hazard curves for spectral acceleration at 3.0 seconds have been produced for eleven sites in the Southern California region, including rock and basin sites. At low ground motion levels, there is little difference between the CyberShake and attenuation relationship curves. At higher ground motion (lower probability) levels, the curves are similar for some sites (downtown LA, I-5/SR-14 interchange) but different for

  15. Using twelve years of USGS refraction lines to calibrate the Brocher and others (1997) 3D velocity model of the Bay Area

    USGS Publications Warehouse

    Boatwright, John; Blair, Luke; Catchings, Rufus; Goldman, Mark; Perosi, Fabio; Steedman, Clare

    2004-01-01

    Campbell (1983) demonstrated that site amplification correlates with depths to the 1.0, 1.5, and 2.5 km/s S-wave velocity horizons. To estimate these depths for the Bay Area stations in the PEER/NGA database, we compare the depths to the 3.2 and 4.4 km/s P-wave velocities in the Brocher and others (1997) 3D velocity model with the depths to these horizons determined from 6 refraction lines shot in the Bay Area from 1991 to 2003. These refraction lines range from two recent 20 km lines that extend from Los Gatos to downtown San Jose, and from downtown San Jose into Alum Rock Park, to two older 200 km lines than run axially from Hollister up the San Francisco Peninsula to Inverness and from Hollister up the East Bay across San Pablo Bay to Santa Rosa. Comparison of these cross-sections with the Brocher and others (1997) model indicates that the 1.5 km/s S-wave horizon, which we correlate with the 3.2 km/s P-wave horizon, is the most reliable horizon that can be extracted from the Brocher and others (1997) velocity model. We determine simple adjustments to bring the Brocher and others (1997) 3.2 and 4.4 km/s P-wave horizons into an average agreement with the refraction results. Then we apply these adjustments to estimate depths to the 1.5 and 2.5 km/s S-wave horizons beneath the strong motion stations in the PEER/NGA database.

  16. 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

  17. 3-D seismic over the Fausse Pointe Field: A case history of acquisition in a harsh environment

    SciTech Connect

    Duncan, P.M.; Nester, D.C.; Martin, J.A.; Moles, J.R.

    1995-12-31

    A 50 square mile 3D seismic survey was successfully acquired over Fausse Point Field in the latter half of 1994. The geophysical and logistical challenges of this project were immense. The steep dips and extensive range of target depths required a large shoot area with a relatively fine sampling interval. The surface, while essentially flat, included areas of cane field, crawfish ponds, thick brush, swamp, open lakes and deep canals -- all typical of southern Louisiana. Planning and permitting of the survey began in late 1993. Field operations began in June 1994 and were complete in January 1995. Field personnel numbered 150 at the peak of operations. More than 19,000 crew hours were required to complete the job at a cost of over 5,000,000. The project was complete on time and on budget. The resulting images of the salt dome and surrounding rocks are not only beautiful but are revealing many opportunities for new hydrocarbon development.

  18. Cognitive 3D geological voxel modelling based on AEM and seismic data - a case from the southern part of Denmark

    NASA Astrophysics Data System (ADS)

    Jørgensen, Flemming; Møller, Rasmus R.; Sandersen, Peter B. E.; Høyer, Anne-Sophie

    2013-04-01

    The highly complex composition of the Quaternary and Tertiary near-surface deposits in Denmark is a challenging environment for 3D modelling. Geological elements like cross-cutting buried valleys, faults, glaciotectonic thrusts and folds, delta units and erosional unconformities are vital to identify and include in 3D geological models, but at the same time they all add to the complexity of the geological picture. Borehole data are rarely sufficient for the modelling; instead much more laterally dense data are needed. Airborne electromagnetic techniques therefore serve as perfect tools for providing an overview and spatial distribution of the geological elements and their composition. Such airborne surveys are perfectly supplemented by seismic data in order to map the stratigraphic framework within a model area. Translating airborne electromagnetic data to geology is a complicated task that requires a significant amount of geophysical and geological insight. It is necessary to implement thorough geological background knowledge in the interpretations while at the same time identify and acknowledge the inherent limitations of the method. In an area covering 730 km2 across the border between Germany and Denmark a combination of an airborne transient electromagnetic survey (3200 line km performed with the SkyTEM system) and a 38 km high-resolution 2D seismic survey has proven very successful for mapping geological elements like the above-mentioned. Although the south-westernmost part of the study area is saturated with saltwater and the TEM data therefore are influenced by increased electrical conductivity, the geology is still revealed here. Geological interpretations are supported by a high number of pre-existing seismic sections originating from hydrocarbon exploration and borehole data, though most of the borehole data and several of the seismic sections have very poor quality. A couple of new 300-m deep exploration boreholes have been drilled in order to obtain

  19. Acceleration of 3D Finite Difference AWP-ODC for seismic simulation on GPU Fermi Architecture

    NASA Astrophysics Data System (ADS)

    Zhou, J.; Cui, Y.; Choi, D.

    2011-12-01

    AWP-ODC, a highly scalable parallel finite-difference application, enables petascale 3D earthquake calculations. This application generates realistic dynamic earthquake source description and detailed physics-based anelastic ground motions at frequencies pertinent to safe building design. In 2010, the code achieved M8, a full dynamical simulation of a magnitude-8 earthquake on the southern San Andreas fault up to 2-Hz, the largest-ever earthquake simulation. Building on the success of the previous work, we have implemented CUDA on AWP-ODC to accelerate wave propagation on GPU platform. Our CUDA development aims on aggressive parallel efficiency, optimized global and shared memory access to make the best use of GPU memory hierarchy. The benchmark on NVIDIA Tesla C2050 graphics cards demonstrated many tens of speedup in single precision compared to serial implementation at a testing problem size, while an MPI-CUDA implementation is in the progress to extend our solver to multi-GPU clusters. Our CUDA implementation has been carefully verified for accuracy.

  20. High-resolution 3-D S-wave Tomography of upper crust structures in Yilan Plain from Ambient Seismic Noise

    NASA Astrophysics Data System (ADS)

    Chen, Kai-Xun; Chen, Po-Fei; Liang, Wen-Tzong; Chen, Li-Wei; Gung, YuanCheng

    2015-04-01

    The Yilan Plain (YP) in NE Taiwan locates on the western YP of the Okinawa Trough and displays high geothermal gradients with abundant hot springs, likely resulting from magmatism associated with the back-arc spreading as attested by the offshore volcanic island (Kueishantao). YP features NS distinctive characteristics that the South YP exhibits thin top sedimentary layer, high on-land seismicity and significant SE movements, relative those of the northern counterpart. A dense network (~2.5 km station interval) of 89 Texan instruments was deployed in Aug. 2014, covering most of the YP and its vicinity. The ray path coverage density of each 0.015 degree cells are greater than 150 km that could provide the robustness assessment of tomographic results. We analyze ambient noise signals to invert a high-resolution 3D S-wave model for shallow velocity structures in and around YP. The aim is to investigate the velocity anomalies corresponding to geothermal resources and the NS geological distinctions aforementioned. We apply the Welch's method to generate empirical Rayleigh wave Green's functions between two stations records of continuous vertical components. The group velocities of thus derived functions are then obtained by the multiple-filter analysis technique measured at the frequency range between 0.25 and 1 Hz. Finally, we implement a wavelet-based multi-scale parameterization technique to construct 3D model of S-wave velocity. Our first month results exhibit low velocity in the plain, corresponding existing sediments, those of whole YP show low velocity offshore YP and those of high-resolution south YP reveal stark velocity contrast across the Sanshin fault. Key words: ambient seismic noises, Welch's method, S-wave, Yilan Plain

  1. The growth of non-colinear normal fault systems; What can we learn from 3D seismic reflection data?

    NASA Astrophysics Data System (ADS)

    Reeve, Matthew T.; Bell, Rebecca E.; Duffy, Oliver B.; Jackson, Christopher A.-L.; Sansom, Eleanor

    2015-01-01

    Many rift zones exhibit a range of fault orientations, rather than simple colinear faults that strike orthogonal to the inferred least principal stress. The formation of non-colinear fault sets has implications for assessing rift-zone kinematics, as well as determining palaeo-stress state in extensional basins. Using 3D seismic reflection data, we deduce the likely mechanisms responsible for the formation of a population of non-colinear faults in the Måløy Slope area of the northern North Sea. Three basement-displacing fault populations exist on the Måløy Slope; (i) large (>1 km throw), N-S-striking faults, (ii) smaller (<250 m throw) N-S-striking faults and (iii) small (<250 m throw) NE-SW-striking faults. All were initiated in the Middle Jurassic. Coeval growth of these fault populations, and the apparent correlation between the NE-SW faults and a NE-SW-trending gravity and magnetic anomaly high lead us to suggest that the NE-SW faults are the result of deflection of the otherwise E-W-orientated least principal stress by NE-trending intrabasement weaknesses. Our study's results have implications for the large-scale kinematic evolution of the North Sea, arguing that major rotations in extension direction are not required to generate multiple fault sets locally or across the rift. This study also highlights the importance of using borehole-constrained 3D seismic data as a tool in understanding non-colinear fault growth, and its broader implications for regional tectonic history.

  2. Seismic fabric and 3-D structure of the southwestern intracontinental Palmyride fold belt, Syria

    SciTech Connect

    Chaimov, T.A.; Barazangi, M. ); Al-Saad, D.; Sawaf, T.; Khaddour, M. )

    1993-12-01

    The Palmyride fold belt, a 400 x 100 km transpressive belt in central Syria that is the northeastern arm of the Syrian arc, is the result of late Mesozoic and Cenozoic inversion of a late Paleozoic and Mesozoic, northeast-trending, linear intracontinental basin located within the northern Arabian platform. The southwestern Palmyrides, near the Dead Sea transform fault system and the Anti-Lebanon mountains, are characterized by short wavelength (5--10 km) en echelon folds separated by small intermontane basins that developed mainly in the Neogene to Holocene. A new three-dimensional data cube, 60 x 70 x 10 km, generated on a Landmark Graphics workstation and based on approximately 700 km of two-dimensional seismic reflection profiles, elucidates the structure of the upper 10 km of the crust in the southwestern Palmyrides. Visualization of the subsurface structure, which is represented by a prominent Upper Cretaceous reflection surface in the data cube, is augmented by topographical and Bouguer gravity data of the same region. Preexisting discontinuities, probable normal fault relicts of the Mesozoic Palmyride rift, likely controlled the development of individual Neogene thrusts. The new subsurface image shows important structural features not identified in outcrop. Short, west-northwest-trending transcurrent (or transfer) faults like the short, en echelon northeast-trending thrust faults and blind thrusts of the Palmyrides. A pervasive regional decollment is not observed, even though Triassic evaporites host local detachments. Unlike topographic relief, which only roughly resembles subsurface structures, the Bouguer gravity signature of the southwestern Palmyrides closely mimics underlying shallow geologic structures both on a large ([approximately]50 km wavelength) and a small ([approximately]5--10 km wavelength) scale. The structural analysis and many other recent studies of the region indicate minor right-lateral shear coupled with compression in the Palmyrides.

  3. Multi-step damped multichannel singular spectrum analysis for simultaneous reconstruction and denoising of 3D seismic data

    NASA Astrophysics Data System (ADS)

    Zhang, Dong; Chen, Yangkang; Huang, Weilin; Gan, Shuwei

    2016-10-01

    Multichannel singular spectrum analysis (MSSA) is an effective approach for simultaneous seismic data reconstruction and denoising. MSSA utilizes truncated singular value decomposition (TSVD) to decompose the noisy signal into a signal subspace and a noise subspace and weighted projection onto convex sets (POCS)-like method to reconstruct the missing data in the appropriately constructed block Hankel matrix at each frequency slice. However, there still exists some residual noise in signal space due to two major factors: the deficiency of traditional TSVD and the iteratively inserted observed noisy data during the process of weighted POCS like iterations. In this paper, we first further extend the recently proposed damped MSSA (DMSSA) for random noise attenuation, which is more powerful in distinguishing between signal and noise, to simultaneous reconstruction and denoising. Then combined with DMSSA, we propose a multi-step strategy, named multi-step damped MSSA (MS-DMSSA), to efficiently reduce the inserted noise during the POCS like iterations, thus can improve the final performance of simultaneous reconstruction and denoising. Application of the MS-DMSSA approach on 3D synthetic and field seismic data demonstrates a better performance compared with the conventional MSSA approach.

  4. 3-D seismic evidence of the effects of carbonate karst collapse on overlying clastic stratigraphy and reservoir compartmentalization

    SciTech Connect

    Hardage, B.A.; Carr, D.L.; Simmons, J.L. Jr.; Jons, R.A.; Lancaster, D.E.; Elphick, R.Y.; Pendleton, V.M.

    1996-09-01

    A multidisciplinary team, composed of stratigraphers, petrophysicists, reservoir engineers, and geophysicists, studied a portion of Boonsville gas field in the Fort Worth Basin of north-central Texas to determine how modern techniques can be combined to understand the mechanisms by which fluvio-deltaic depositional processes create reservoir compartmentalization in a low- to moderate-accommodation basin. An extensive database involving well logs, cores, production, and pressure data from more than 200 wells, 26 mi{sup 2} of 3-D seismic data, vertical seismic profiles, and checkshots was assembled to support this investigation. The authors found the most important geologic influence on stratigraphy and reservoir compartmentalization in this basin to be the existence of numerous karst collapse chimneys over the area covered. These near-vertical karst collapses originated in, or near, the deep Ordovician-age Ellenburger carbonate section and created vertical chimneys extending as high as 2,500 ft above their point of origin, causing significant disruptions in the overlying clastic strata.

  5. Analysis of time-structure of BSRs using 3D seismic data in the Eastern Nankai Trough, Japan

    NASA Astrophysics Data System (ADS)

    Nagakubo, S.; Inamori, T.; Kobayashi, T.; Fujii, T.

    2005-12-01

    According to the result of METI Exploratory Wells "Tokai-Oki to Kumano-nada" conducted in FY2003 in Japan, it is suggested that methane hydrate bearing layers in the Eastern Nanakai Trough distribute heterogeneously above BSRs (Bottom Simulating Reflectors). To understand the heterogeneity of distribution of methane hydrate bearing layers and explore concentrated hydrate bearing layers, we conducted a detailed analysis of time-structure map of BSR using 3D seismic survey data acquired in the Eastern Nankai Trough. Since P-wave velocity of hydrate bearing layers are high, it was expected that two-way-time from sea bottom to BSR is short above concentrated hydrate bearing layers compared to hydrate bearing zones. Although significant anomalies are recognized on time-structure map, it seems that anomalies are corresponding to heterogeneous thermal-structure in preference to distribution of hydrate bearing layers around surveyed area. It should be considered that these thermal anomalies are depending on fluid migration with hydrocarbons through faults, unconformities and permeable sand layers from deeper formations. Since occurrences of methane hydrates are strongly restricted by temperature and pressure, analysis of time-structure of BSR acquired by seismic data could be helpful to understand the accumulation mechanism of methane hydrates in sediments.

  6. Investigation of drilling failure of Well A1, E-Field, onshore Niger Delta, Nigeria, using 3-D seismic data

    NASA Astrophysics Data System (ADS)

    Akinmosin, A.; Oladele, S.; Oriade, O. F.

    2016-02-01

    This study aimed at investigating reasons for failure of Well A1 that is surrounded by hydrocarbon discoveries in onshore Niger delta with a view to propose optimal location for a new well through interpretation of new 3-D seismic data. Sands encountered by Well A1 were delineated and tied to seismic. Structural closure was mapped and reservoirs at various depths were stacked and sectioned. Porosity, Net to Gross, and Gross Rock Volume of the reservoirs were computed. Well A1 was correlated to a nearby Well K4 and a good correlation was observed. A fault assisted multi reservoirs Prospect-E with south-westerly shift with depth was delineated on the hanging wall of structure building E-Fault whose closing contours is expected to trap hydrocarbon. Petrophysical properties of the reservoirs range from fair to good. Well A1 either perforated prospect-E beneath the oil water contact, completely missed prospect-E or punctured the wet foot wall of E-fault. Consequently, Well A1 could not impact the objective sands and only able to produce water. Well A1 failed because of wrong surface positioning which unsuccessfully targeted the shifting reservoirs. A successful exploratory well in E-Field would be a gently south-westerly deviated well whose vertical section would encounter the shallower sands and deviated section targeting the deeper sands with surface location at about 1 km southeast of Well A1.

  7. Crustal structure of the Southern Rio Grande rift determined from seismic refraction profiling

    NASA Technical Reports Server (NTRS)

    Sinno, Y. A.; Keller, G. R.; Harder, S. H.; Daggett, P. H.; Morgan, P.

    1986-01-01

    As part of a major cooperative seismic experiment, a series of seismic refraction profiles have been recorded in south-central New Mexico with the goal of determining the crustal structure in the southern Rio Grande rift. The data gathered greatly expand the seismic data base in the area, and consist of three interlocking regional profiles: a reversed E-W line across the rift, an unreversed N-S axial line, and an unreversed SW-SE line. The reversed E-W line shows no significant dip along the Moho (32 km thick crust) and a 7.7 km/s Pn velocity. Results from the N-S axial line and the NW-SE line indicate an apparent Pn velocity of 7.95 km/s and significant dip along the Moho with crustal thinning toward the south and southeast. When interpreted together, these data indicate a crustal thinning in the southern rift of 4-6 km with respect to the northern rift and the adjacent Basin and Range province, and establish the regional Pn velocity to be approximately 7.7 km/s. These results suggest that the Rio Grande rift can be identified as a crustal feature separate and distinct from the Basin and Range province.

  8. Exploring the tecto-sedimentary history of the lower Kumano basin: insights from 3D seismic analysis

    NASA Astrophysics Data System (ADS)

    Ramirez, S. G.; Gulick, S. P.; Hayman, N. W.

    2013-12-01

    The Nankai accretionary margin is seismically active, representing a hazard for the people living along the southwestern Japanese shores. In an effort to better understand its behavior, 3D seismic and well data have been acquired in the area. We are using such data in order to address open research topics such as: the conditions for forearc basin initiation, the role of former slope basins and slope cover sediments in the formation of forearc basins and the role of changes in sedimentation as a major controlling factor in forearc basin evolution. New 3D maps of key surfaces that bound and lie within the lower Kumano basin help us illuminate these topics. The lower bounding surface, UC4, represents missing section between 5.6-3.8 Ma. Toward the SE UC4 is relatively undeformed, with some structures approximately parallel to the modern-day trench. In contrast, toward the NW UC4 is intensely deformed with two main synforms whose hinges are oriented 15 degrees to the modern-trench. The two synforms have similar wavelengths and amplitudes and define the thickest sediment accumulations in the lower Kumano basin. We hypothesize that UC4 had a protracted evolution with early synform (thrust-bound slope-basins?) followed by a change in the maximum strain/plate convergence direction. This change caused the structural trend observed to the SE. This interpretation is in agreement with previous independent estimations of block rotation based on paleomagnetic analysis of samples from core recovered in the area. The upper bounding surface of the lower Kumano basin, UC2, underlies 1.6 Ma and younger sediments. Its morphology resembles a much smoother and less deformed version of UC4. It is slightly tilted landward. Seaward, it pinches out against UC4. Between the two bounding surfaces we recognized a major unconformity that we called UC3a and that we were able to track through most of the studied part of the seismic volume. Morphologically, UC3a is very similar to UC2. We interpret

  9. Seismic images of the Brooks Range fold and thrust belt, Arctic Alaska, from an integrated seismic reflection/refraction experiment

    USGS Publications Warehouse

    Levander, A.; Fuis, G.S.; Wissinger, E.S.; Lutter, W.J.; Oldow, J.S.; Moore, T.E.

    1994-01-01

    We describe results of an integrated seismic reflection/refraction experiment across the Brooks Range and flanking geologic provinces in Arctic Alaska. The seismic acquisition was unusual in that reflection and refraction data were collected simultaneously with a 700 channel seismograph system deployed numerous times along a 315 km profile. Shot records show continuous Moho reflections from 0-180 km offset, as well as numerous upper- and mid-crustal wide-angle events. Single and low-fold near-vertical incidence common midpoint (CMP) reflection images show complex upper- and middle-crustal structure across the range from the unmetamorphosed Endicott Mountains allochthon (EMA) in the north, to the metamorphic belts in the south. Lower-crustal and Moho reflections are visible across the entire reflection profile. Travel-time inversion of PmP arrivals shows that the Moho, at 33 km depth beneath the North Slope foothills, deepens abruptly beneath the EMA to a maximum of 46 km, and then shallows southward to 35 km at the southern edge of the range. Two zones of upper- and middle-crustal reflections underlie the northern Brooks Range above ~ 12-15 km depth. The upper zone, interpreted as the base of the EMA, lies at a maximum depth of 6 km and extends over 50 km from the range front to the north central Brooks Range where the base of the EMA outcrops above the metasedimentary rocks exposed in the Doonerak window. We interpret the base of the lower zone, at ~ 12 km depth, to be from carbonate rocks above the master detachment upon which the Brooks Range formed. The seismic data suggest that the master detachment is connected to the faults in the EMA by several ramps. In the highly metamorphosed terranes south of the Doonerak window, the CMP section shows numerous south-dipping events which we interpret as a crustal scale duplex involving the Doonerak window rocks. The basal detachment reflections can be traced approximately 100 km, and dip southward from about 10-12 km

  10. Crustal Structure across The Southwest Longmenshan Fault Zone from Seismic Wide Angle Reflection/Refraction Profile

    NASA Astrophysics Data System (ADS)

    Tian, Xiaofeng; Wang, Fuyun; Wang, Shuaijun; Duan, Yonghong

    2014-05-01

    The Lushan eathquake, which epicenter and focal depth were at 30.308° N, 102.888° E, and 14.0 km, is the latest intense earthquake occurring in the southwest section of the Longmenshan fault zone after the Ms 8.0 Wenchuan earthquake in 2008. According to the emergency field observations, the slip distribution of the Lushan earthquake was concentrated at the hypocenter, and did not rupture to the surface(Chen et al, 2013). The rupture history constrained by inverting waveforms showed that the causative fault plane of the Lushan event is apparently not a simple extension of either the Pengguan fault or the Beichuan fault that ruptured during the 2008 Mw 8.0 Wenchuan earthquake. The focal mechanism using the Cut and Paste algorithm showed this event occurred on a high dip-angle fault, but its dip angle is not steep enough to rupture the surface. All these research is not independent on the heterogeneous crust structure of the Longmenshan fault zone. A 450 km-long wide-angle reflection/refraction profile executed during September and October 2013. This experiment have provided the best opportunities to obtain better knowledge of seismic structure and properties of crust and uppermost mantle beneath the Southwest Longmenshan fault zone. This seismic profile extends from the west Sichuan Plain, through the Longmenshan Fault zone, and into the west Sichuan Plateau. We observed clear Pg, refraction Phase from the upper crust, Pi1/Pi2/Pi3, reflection/refraction Phase from intra-crust, PmP, reflection from the Moho boundary, and the Pn phase, refraction Phase from uppermost mantle. We present a hybrid tomographic and layered velocity model of the crust and uppermost mantle along the profile. The final velocity model reveals large variations both in structure and velocity, and is demonstrated that a particular model has minimum structure. The model shows the crustal thickness of the region is very variable. The Moho topography varies more than 10km in the southwest

  11. Hydrodynamic properties of the basal aquifer of Santa Cruz Island using seismic refraction, Galapagos - Ecuador

    NASA Astrophysics Data System (ADS)

    Loaiza, S.; Fortin, J.; Adelinet, M.; Guéguen, Y.; Violette, S.

    2012-04-01

    Santa Cruz Island is the most inhabited of the Galapagos archipelago, Ecuador. It faces important water resource problems which might lead to a major impact on their unique and pristine ecosystem, Endangered World Heritage list (2007). The scarcity of geological and hydrological data combined with the difficulty of access for field measurements lead to a poor understanding of the island hydrogeology. The Island is formed by series of thick fractured basaltic lava flows dissected by faults. The low-lying, extensive "basal" aquifer is the unique groundwater body identified on the island. This basal aquifer is subjected to sea-water intrusion, which has been mapped from electrical resistivity imaging with an airborne electromagnetic SkyTEM survey (D'Ozouville et al. 2008). In order to better understand the hydrodynamic properties of the basal aquifer, we acquired, in summer 2011, geophysical data based on seismic refraction. The experiment was conducted on three study sites located at different altitudes above the see level (Beagle site altitude +7m , Mirador +20m, and Villacis +393m). The P-wave refraction data were obtained using 24 geophones (1 component) and an acquisition system Daklink III. A hammer was used as an energy source. This source was the most environmentally friendly source that could be obtained and used in the Galapagos Island. Geophone spacing for the spreads was 1.2 or 5 m depending on the site. From our geophysical data, we could identify the different geological layers that constitute this basal aquifer and to estimate the thickness of these layers. We could as well clearly see the water level in the aquifer. More interesting, we found a P-wave velocity of ~1600 m/s in the dry fractured basalt lava flow, and a P-wave velocity of ~2700 m/s in the water saturated fractured basalt lava flow. The same velocity values were obtained in the different sites. This tends to show that the elastic properties of the aquifer are homogeneous and isotropic (at

  12. Seismic refraction study of the continental edge off the eastern united states

    USGS Publications Warehouse

    Sheridan, R.E.; Grow, J.A.; Behrendt, John C.; Bayer, K.C.

    1979-01-01

    Three long, strike-parallel, seismic-refraction profiles were made on the continental shelf edge, slope and upper rise off New Jersey during 1975. The shelf edge line lies along the axis of the East Coast Magnetic Anomaly (ECMA), while the continental rise line lies 80 km seaward of the shelf edge. Below the unconsolidated sediments (1.7-3.6 km/sec), high-velocity sedimentary rocks (4.2-6.2 km/sec) were found at depths of 2.6-8.2 km and are inferred to be cemented carbonates. Although multichannel seismic-reflection profiles and magnetic depth-to-source data predicted the top of oceanic basement at 6-8 km beneath the shelf edge and 10-11 km beneath the rise, no refracted events occurred as first arrivals from either oceanic basement (layer 2, approximately 5.5 km/ sec) or the upper oceanic crust (layer 3A, approximately 6.8 km/sec). Second arrivals from 10.5 km depth beneath the shelf edge are interpreted as events from a 5.9 km/sec refractor within igneous basement. Other refracted events from either layers 2 or 3A could not be resolved within the complex second arrivals. A well-defined crustal layer with a compressional velocity of 7.1-7.2 km/sec, which can be interpreted as oceanic layer 3B, occurred at 15.8 km depth beneath the shelf and 12.9 km beneath the upper rise. A well-reversed mantle velocity of 8.3 km/sec was measured at 18-22 km depth beneath the upper continental rise. Comparison with other deep-crustal profiles along the continental edge of the Atlantic margin off the United States, specifically in the inner magnetically quiet zone, indicates that the compressional wave velocities and layer depths determined on the U.S.G.S. profiles are very similar to those of nearby profiles. This suggests that the layers are continuous and that the interpretation of the oceanic layer 3B under the shelf edge east of New Jersey implies progradation of the shelf outward over the oceanic crust in that area. This agrees with magnetic anomaly evidence which shows the

  13. Method for identifying subsurface fluid migration and drainage pathways in and among oil and gas reservoirs using 3-D and 4-D seismic imaging

    DOEpatents

    Anderson, Roger N.; Boulanger, Albert; Bagdonas, Edward P.; Xu, Liqing; He, Wei

    1996-01-01

    The invention utilizes 3-D and 4-D seismic surveys as a means of deriving information useful in petroleum exploration and reservoir management. The methods use both single seismic surveys (3-D) and multiple seismic surveys separated in time (4-D) of a region of interest to determine large scale migration pathways within sedimentary basins, and fine scale drainage structure and oil-water-gas regions within individual petroleum producing reservoirs. Such structure is identified using pattern recognition tools which define the regions of interest. The 4-D seismic data sets may be used for data completion for large scale structure where time intervals between surveys do not allow for dynamic evolution. The 4-D seismic data sets also may be used to find variations over time of small scale structure within individual reservoirs which may be used to identify petroleum drainage pathways, oil-water-gas regions and, hence, attractive drilling targets. After spatial orientation, and amplitude and frequency matching of the multiple seismic data sets, High Amplitude Event (HAE) regions consistent with the presence of petroleum are identified using seismic attribute analysis. High Amplitude Regions are grown and interconnected to establish plumbing networks on the large scale and reservoir structure on the small scale. Small scale variations over time between seismic surveys within individual reservoirs are identified and used to identify drainage patterns and bypassed petroleum to be recovered. The location of such drainage patterns and bypassed petroleum may be used to site wells.

  14. Method for identifying subsurface fluid migration and drainage pathways in and among oil and gas reservoirs using 3-D and 4-D seismic imaging

    DOEpatents

    Anderson, R.N.; Boulanger, A.; Bagdonas, E.P.; Xu, L.; He, W.

    1996-12-17

    The invention utilizes 3-D and 4-D seismic surveys as a means of deriving information useful in petroleum exploration and reservoir management. The methods use both single seismic surveys (3-D) and multiple seismic surveys separated in time (4-D) of a region of interest to determine large scale migration pathways within sedimentary basins, and fine scale drainage structure and oil-water-gas regions within individual petroleum producing reservoirs. Such structure is identified using pattern recognition tools which define the regions of interest. The 4-D seismic data sets may be used for data completion for large scale structure where time intervals between surveys do not allow for dynamic evolution. The 4-D seismic data sets also may be used to find variations over time of small scale structure within individual reservoirs which may be used to identify petroleum drainage pathways, oil-water-gas regions and, hence, attractive drilling targets. After spatial orientation, and amplitude and frequency matching of the multiple seismic data sets, High Amplitude Event (HAE) regions consistent with the presence of petroleum are identified using seismic attribute analysis. High Amplitude Regions are grown and interconnected to establish plumbing networks on the large scale and reservoir structure on the small scale. Small scale variations over time between seismic surveys within individual reservoirs are identified and used to identify drainage patterns and bypassed petroleum to be recovered. The location of such drainage patterns and bypassed petroleum may be used to site wells. 22 figs.

  15. Deep crustal structure of the Tuamotu plateau and Tahiti (French Polynesia) based on seismic refraction data

    NASA Astrophysics Data System (ADS)

    Patriat, Martin; Klingelhoefer, Frauke; Aslanian, Daniel; Contrucci, Isabelle; Gutscher, Marc-André; Talandier, Jacques; Avedik, Felix; Francheteau, Jean; Weigel, Wilfried

    2002-07-01

    In French Polynesia, the young (<5Ma) Society Islands appear to result from intraplate volcanism, while the old (>50 Ma) Tuamotu plateau was likely created at or near the ridge axis. The structure of the crust between those two archipelagoes is constrained by a 300 km long refraction seismic profile. Crustal and upper mantle arrivals recorded by 6 OBHs and 3 land stations were used to provide a 2D model of the crust. Results of our study, combined with that of Grevemeyer et al. [2001] show a slight flexure below the Tahiti apron, while a deep crustal root (21 km) underlies the Tuamotu plateau. These structures reflect the different modes of load emplacement and compensation mechanisms between these two volcanic edifices, consistent with an increasing elastic thickness of the oceanic lithosphere with age.

  16. Potential Geophysical Field Transformations and Combined 3D Modelling for Estimation the Seismic Site Effects on Example of Israel

    NASA Astrophysics Data System (ADS)

    Eppelbaum, Lev; Meirova, Tatiana

    2015-04-01

    It is well-known that the local seismic site effects may have a significant contribution to the intensity of damage and destruction (e.g., Hough et al., 1990; Regnier et al., 2000; Bonnefoy-Claudet et al., 2006; Haase et al., 2010). The thicknesses of sediments, which play a large role in amplification, usually are derived from seismic velocities. At the same time, thickness of sediments may be determined (or defined) on the basis of 3D combined gravity-magnetic modeling joined with available geological materials, seismic data and borehole section examination. Final result of such investigation is a 3D physical-geological model (PGM) reflecting main geological peculiarities of the area under study. Such a combined study needs in application of a reliable 3D mathematical algorithm of computation together with advanced methodology of 3D modeling. For this analysis the developed GSFC software was selected. The GSFC (Geological Space Field Calculation) program was developed for solving a direct 3-D gravity and magnetic prospecting problem under complex geological conditions (Khesin et al., 1996; Eppelbaum and Khesin, 2004). This program has been designed for computing the field of Δg (Bouguer, free-air or observed value anomalies), ΔZ, ΔX, ΔY , ΔT , as well as second derivatives of the gravitational potential under conditions of rugged relief and inclined magnetization. The geological space can be approximated by (1) three-dimensional, (2) semi-infinite bodies and (3) those infinite along the strike closed, L.H. non-closed, R.H. on-closed and open). Geological bodies are approximated by horizontal polygonal prisms. The program has the following main advantages (besides abovementioned ones): (1) Simultaneous computing of gravity and magnetic fields; (2) Description of the terrain relief by irregularly placed characteristic points; (3) Computation of the effect of the earth-air boundary by the method of selection directly in the process of interpretation; (4

  17. Crustal structure along the coast of California from seismic-refraction measurements

    USGS Publications Warehouse

    Healy, J.H.

    1962-01-01

    Two reversed seismic-refraction profiles were recorded between Los Angeles and San Francisco in 1961. The three shotpoints were located in Santa Monica Bay, offshore near San Francisco, and at Camp Roberts, about halfway between Los Angeles and San Francisco. The velocity of Pg along these profiles is 6.1 ± 0.1 km/sec, with possible exceptions near San Francisco and near Los Angeles, where the scatter in the arrival times indicates complex near-surface velocity variations. The velocity of Pn between Los Angeles and Camp Roberts is 8.2 ± 0.1 km/sec, and between Camp Roberts and San Francisco 8.0 ± 0.2 km/sec. There is no indication of an intermediate crustal layer in the traveltimes of first arrivals. Computed depths to the Mohorovicic discontinuity, if the crust consists of a single layer, are: 35 km at Los Angeles, 23 km at Camp Roberts, and 23 km at San Francisco. Refractions from crustal layers of intermediate velocity need not appear as first arrivals, and in the extreme, the depth to the Mohorovicic discontinuity may be one-third greater than the thickness of a one-layer crust.

  18. Crustal structure from San Francisco, California, to Eureka, Nevada, from seismic-refraction measurements

    USGS Publications Warehouse

    Eaton, Jerry P.

    1963-01-01

    Seismic-refraction measurements from chemical explosions near San Francisco, California, and Fallon and Eureka, Nevada, were made along a line extending nearly 700 km inland from San Francisco across the Coast Ranges, Great Valley, Sierra Nevada, and Basin and Range Province. The velocity of Pg in the Basin and Range Province was found to be 6.0 km/sec. Between Fallon and Eureka the velocity of Pn is 7.8 km/sec, and just east of the Sierra Nevada it is about 7.9 km/sec. Two prominent phases closely following the first arrival between 50 and 250 km from the source in the Basin and Range Province were interpreted as reflections from an intermediate layer and from the Mohorovicic discontinuity. The velocity of P in the possible intermediate layer, deduced from the reflected phases be cause the refracted wave expected from this layer is nowhere a first arrival, seems to be 6.6 km/sec at the top of the layer and probably increases with depth.

  19. Seismic refraction and GPR measurements of depth to bedrock: A case study from Randolph College, Virginia

    NASA Astrophysics Data System (ADS)

    Datta, A.; Pokharel, R.; Toteva, T.

    2007-12-01

    Randolph College is located in Lynchburg, VA, in the eastern edge of the Blue Ridge Mountains. Lynchburg city lies in the James River Synclinorium and consists of metasedimentary and metaigneous rocks. As part of College's plan to expand, a new soccer field will be build. For that purpose, part of a hill has to be excavated. Information was needed on the depth to the bedrock at the site. We conducted a seismic refraction experiment as part of an eight week summer research program for undergraduate students. We used 24 vertical geophones, spaced at 1.5 m interval. Our recording device was a 12 channel Geometrics geode (ES 3000). The source was an 8 pound sledge hummer. Source positions were chosen to be at 5, 10, 15 and 20 m on both sides of the array. We collected data along a tree line (in two segments) and across a hockey field. The data collected from the hockey field had very low signal to noise ratio and clear refraction arrivals. The other two acquisition lines were much noisier and difficult to interpret. Our results are consistent with data from seven bore holes in close proximity to the field site. We interpreted depth to bedrock to be between 4 and 12 m. The bedrock velocities are consistent with weathered gneiss. To improve the interpretation of the tree line records, we conducted a GPR survey. The preliminary radar images are showing highly heterogeneous subsurface with multiple point reflectors.

  20. Reactivating of a mature oil field in the Finca-Yopales area, Venezuela, Using 3-D seismic

    SciTech Connect

    Sanchez, M.; Betancourt, H.

    1996-08-01

    The area of Finca-Yopales is located in the Eastern Venezuelan Basin in the Anzoategui State where Corpoven has the Trico and Yopales Norte fields. Based on the interpretation of 134 km{sup 2} of 3-D seismic and the geologic interpretation from 145 wells in the area, we define a better geological and structural model. We were also able to map 6 seismic reflectors corresponding to the units A8, F7, L4U and SI from the Oficina Formation, U2 top of Merecure Formation and the top of the Cretaceous, in order to generate a fault plane for all the area which was converted to depth with a lineal relationship which was obtained from wells available. From this interpretation we obtain the structural levels B4, J2, M1 and U2 which are references for the area, those being regional and trangressive events. The main feature of the structure is a high at the southeast of the area and three fault systems of Cretaceous, Miocene and post-Miocene age. This area has been exploited for a long time, having more than 93% of the inactive drilled wells. The total production up to April, 1995 is 59.14 MMbls; the Trico field is the most prolific, with more than 95% of the production. The sands L`s, U`s, O`s and S`s are the most prospective. This paper present the evaluation of the area and the analysis of the reservoir where we increased the computed reserves.

  1. A 3D Seismic Velocity Model Offshore Southern California from Ambient Noise Tomography of the ALBACORE OBS Array

    NASA Astrophysics Data System (ADS)

    Kohler, M. D.; Bowden, D. C.; Tsai, V. C.; Weeraratne, D. S.

    2015-12-01

    The Pacific-North America plate boundary in Southern California extends far west of the coastline, and a 12-month ocean bottom seismometer (OBS) array spanned the western side of the plate boundary to image lithospheric seismic velocities. Velocities are modeled through stacked cross correlations of ambient noise data. Twelve months of continuous data were used from 22 OBS stations and ~30 coastal and island Southern California Seismic Network stations. Particular attention has been paid to improving signal-to-noise ratios in the noise correlations with OBS stations by removing the effects of instrument tilt and infragravity waves. Different applications of preprocessing techniques allow us to distinguish the fundamental and first higher order Rayleigh modes, especially in deep water OBS pairs where the water layer dominates crustal sensitivity of the fundamental mode. Standard time domain and frequency domain methods are used to examine surface wave dispersion curves for group and phase velocities between 5 and 50 second periods, and these are inverted for 3D velocity structure. The results define the transition in three dimensions from continental lithospheric structure in the near-shore region to oceanic structure west of the continental borderland. While the most prominent features of the model relate to thinning of the crust west of the Patton Escarpment, other notable anomalies are present north-to-south throughout the continental borderland and along the coast from the Los Angeles Basin to the Peninsular Ranges. The velocity model will help describe the region's tectonic history, as well as provide new constraints for determination of earthquake relocations and rupture styles.

  2. Shallow 3-D vertical seismic profiling around a contaminant withdrawal well on the Lawrence Livermore National Laboratory Site

    SciTech Connect

    Rector, J.; Bainer, R.; Milligan, P.; Tong, C.

    1997-01-30

    One of the major problems associated with ground water contaminant remediation is well placement. Optimal-placement of wells requires an accurate knowledge of geologic structure and stratigraphy in the near surface sediments and rock (0 to 100 m). Without the development of remote imaging provided by geophysical techniques, the required spacing between treatment wells may be less than 2 m in order to be confident that all contaminant reservoirs had been remediated. One method for characterizing geologic structure and stratigraphy in the near surface is vertical seismic profiling (VSP), a technique often used on deep exploration wells to calibrate surface seismic reflection data. For near-surface applications, VSP data can be acquired efficiently using an array of hydrophones lowered into a fluid-filled borehole (Milligan et al, 1997). In this paper we discuss the acquisition and processing of a 3-D VSP collected at a shallow remediation site located on the grounds of the Lawrence Livermore National Laboratory (LLNL) near Livermore, California. The site was used by the United States Navy as an air training base. At this time, initial releases of hazardous materials to the environment occurred in the form of solvents [volatile organic compounds (VOCs)] that were used for the cleaning of airplanes and their parts. Gasoline, diesel and other petroleum-based compounds are also known to have leaked into the ground. California Research and Development Company, a subsidy of Standard Oil, occupied the southeastern portion of the site from 1950 to 1954. The first releases of radioactive materials to the environment occurred at this time, with the beginning of testing of radioactive materials at the site. In 1952, LLNL acquired the site. Additional releases of VOCS, polychlorinated biphenyls (PCBs), metals, radionuclides (primarily tritium), gasoline and pesticides have occurred since. These releases were due to localized spills, landfills, surface impoundments, disposal pits

  3. Analyzing the subsurface structure using seismic refraction method: Case study STMKG campus

    SciTech Connect

    Wibowo, Bagus Adi; Ngadmanto, Drajat; Daryono

    2015-04-24

    A geophysic survey is performed to detect subsurface structure under STMKG Campus in Pondok Betung, South Tangerang, Indonesia, using seismic refraction method. The survey used PASI 16S24-U24. The waveform data is acquired from 3 different tracks on the research location with a close range from each track. On each track we expanded 24 geofons with spacing between receiver 2 meters and the total length of each track about 48 meters. The waveform data analysed using 2 different ways. First, used a seismic refractionapplication WINSISIM 12 and second, used a Hagiwara Method. From both analysis, we known the velocity of P-wave in the first and second layer and the thickness of the first layer. From the velocity and the thickness informations we made 2-D vertical subsurface profiles. In this research, we only detect 2 layers in each tracks. The P-wave velocity of first layer is about 200-500 m/s with the thickness of this layer about 3-6 m/s. The P-wave velocity of second layer is about 400-900 m/s. From the P-wave velocity data we interpreted that both layer consisted by similar materials such as top soil, soil, sand, unsaturated gravel, alluvium and clay. But, the P-wave velocity difference between those 2 layers assumed happening because the first layer is soil embankment layer, having younger age than the layer below.

  4. Analyzing the subsurface structure using seismic refraction method: Case study STMKG campus

    NASA Astrophysics Data System (ADS)

    Wibowo, Bagus Adi; Ngadmanto, Drajat; Daryono

    2015-04-01

    A geophysic survey is performed to detect subsurface structure under STMKG Campus in Pondok Betung, South Tangerang, Indonesia, using seismic refraction method. The survey used PASI 16S24-U24. The waveform data is acquired from 3 different tracks on the research location with a close range from each track. On each track we expanded 24 geofons with spacing between receiver 2 meters and the total length of each track about 48 meters. The waveform data analysed using 2 different ways. First, used a seismic refractionapplication WINSISIM 12 and second, used a Hagiwara Method. From both analysis, we known the velocity of P-wave in the first and second layer and the thickness of the first layer. From the velocity and the thickness informations we made 2-D vertical subsurface profiles. In this research, we only detect 2 layers in each tracks. The P-wave velocity of first layer is about 200-500 m/s with the thickness of this layer about 3-6 m/s. The P-wave velocity of second layer is about 400-900 m/s. From the P-wave velocity data we interpreted that both layer consisted by similar materials such as top soil, soil, sand, unsaturated gravel, alluvium and clay. But, the P-wave velocity difference between those 2 layers assumed happening because the first layer is soil embankment layer, having younger age than the layer below.

  5. Impact of 3-D seismic data on the Nigerian National Petroleum Corporation/Chevron Nigeria Limited joint venture development drilling program

    SciTech Connect

    Quam, S. )

    1993-09-01

    The Nigerian National Petroleum Corporation/Chevron Nigeria Limited joint venture has been acquiring three-dimensional (3-D) seismic data over its concessions since 1984. To date, 1700 km[sup 2] have been recorded and processed at a cumulative cost of US $39 million. During 1991 - 1992, 20 development wells were drilled based directly on new 3-D seismic interpretations. These wells have added 148 million bbl of oil in new recoverable reserves, and to date have added 37,000 bbl/day to the joint venture's production. In addition, the 3-D interpretations have resulted in a sizable inventory of wells for future development drilling. The new 3-D interpretations provided more accurate pictures of fault patterns, fluid contacts, channel trends, stratigraphic continuity, and velocity/amplitude anomalies. In addition, the 3-D data were invaluable in designing low risk, directional well trajectories to tap relatively thin oil legs under large gas caps. Wells often were programmed to hit several objectives at their respective gas/oil contacts, resulting in maximized net oil sand pays and reducing the risk of gas production. In order to do this, directional [open quotes]sharpshooting,[close quotes] accurate depth conversion of the seismic time maps, was critical. By using the 3-D seismic, checkshot, and sonic data to develop a variable velocity space, well-top prognoses within 50 ft at depths of 6,000-10,000 ft were possible, and were key to the success of the program. As the joint venture acreage becomes more mature, development wells will be drilled for smaller numbers of stacked objectives, and sometimes for single sands. Highly accurate 3-D interpretations and depth conversions will become even more critical in order to tap thinner pay zones in a cost-effect manner.

  6. Seafloor surface processes and subsurface paleo-channel unconformities mapped using multi-channel seismic and multi-beam sonar data from the Galicia 3D seismic experiment.

    NASA Astrophysics Data System (ADS)

    Gibson, J. C.; Shillington, D. J.; Sawyer, D. S.; Jordan, B.; Morgan, J. K.; Ranero, C.; Reston, T. J.

    2015-12-01

    In this study we use geophysical methods, stratigraphic relationships, and coring/drilling leg results to assess possible controls on deep-sea channel formation in order to further constrain paleo-channel (PC) and associated unconformity timing/source processes. A series of cut and fill PC are mapped in 3D multi-channel seismic (MCS) data and compared with multi-beam (MB) sonar bathymetry/backscatter data collected during the Galicia 3D survey with the R/V Marcus G. Langseth (2013). The MCS data were collected using four 6 km streamers spaced at 200 m resulting in 25 m x 25 m common mid-point bins within the ~67 km x 20 km 3D volume. The MB data were collected at an average depth of ~4900 m with a constrained swath width of 4.5 km resulting in 11.25x overlap while enabling 25-m bathymetry and 10-m backscatter grids. The PC lie below the mouth of a submarine canyon at the edge of the Galicia abyssal plain and cut pre/syn-rift sediments; they are bound by a rift block to the north and paleo-levees to the south (maximum height of ~180m). From drilling results, the most recent PC is late Miocene in age. In this study, four PC are traced into the basin as unconformities. Several of the PC/unconformities are tentatively correlated with previously interpreted Pyrenean orogeny/compressional Miocene/Oligocene tectonic events. However, one PC/unconformity within this interval has not been previously interpreted. In order test the hypothesis that the unconformities are the result of a significant change in base level indicated by a low shale/sand (SS) ratio, we use seismic surface attributes to calculate the SS ratio and trace the horizontal extent of the unconformities. Additionally, the MB/MCS seafloor morphology reveals sedimentary waves outboard of the canyon mouth. We use backscatter data to compare the extent of recent processes (e.g., Pleistocene glaciation/de-glaciation) with the unconformities by mapping the surface/shallow subsurface SS ratio (volume scattering).

  7. Seismic Refraction Surveys in Devils Lane and Cyclone Grabens, Canyonlands National Park, Utah

    NASA Astrophysics Data System (ADS)

    Kroeger, G. C.; Grosfils, E. B.; Schultz, R. A.; Reno, B. L.; Godchaux, J. D.

    2002-12-01

    Bounding fault offsets in the geologically young (60-70 ka) grabens of Canyonlands National Park have been estimated previously by adding measured scarp topography to estimates of sediment fill thickness beneath the graben floor. Published values of sediment fill thickness have ranged from 5-50 m with most estimates less than 20 m and most previous measured thickness in the 3-10 m range. We have conducted shallow seismic refraction surveys in two grabens, Devils Lane and Cyclone. Geophysical work in this remote area is difficult due to the lack of power or water supplies, the difficulty of vehicle transport over one of the most technical 4-wheel drive roads in Utah, and the environmentally sensitive nature of the cryptobiotic soils in the grabens. In Devils Lane graben, 10 24-channels spreads were employed in a 2 km long line along the axis of this 3 km long graben. A 15-station gravity survey was also conducted along the axis of this graben. Three separate seismic lines were used to sample the ends and center of Cyclone graben that is nearly twice as large as Devils Lane. The seismic data were modeled using iterative ray tracing. Our results from Devils Lane (Grosfils et al., JSG, in press) show a well-defined layer of basin sediment that deepens rapidly from the end of the graben, from depths of 30 m to over 90 m. Typical depths in the center of the graben range from 70-80 m. Under some portions of the line, the sediment thickness is so large that our cable lengths were not long enough to record the bedrock refraction, suggesting sediment thickness of over 100 m. Sediment velocities range from 700-900 m/s with underlying bedrock velocities averaging 3000 m/s. Our results from Cyclone graben are similar, with typical sediment thickness of 70-80 m in the center of the graben and abrupt shallowing at the ends of the graben. Our results indicate significantly thicker sediment fill than assumed in most previous studies and may necessitate revising estimates of both

  8. Segmentation of Hypocenters and 3-D Velocity Structure around the Kii Peninsula Revealed by Onshore and Offshore Seismic Observations

    NASA Astrophysics Data System (ADS)

    Akuhara, T.; Mochizuki, K.; Nakahigashi, K.; Yamada, T.; Shinohara, M.; Sakai, S.; Kanazawa, T.; Uehira, K.; Shimizu, H.

    2013-12-01

    The Philippine Sea Plate subducts beneath the Eurasian Plate at a rate of ~4 cm/year along the Nankai Trough, southwest of Japan. Around the Kii Peninsula, the rupture boundary of the historical Tonankai and Nankai large earthquakes is located, and previous researches have revealed along-strike segmentation of hypocenters [Mochizuki et al., 2010], P-wave anisotropy [Ishise et al., 2009], low frequency earthquake (LFE) distribution [e.g., Obara, 2010] and subduction depth of the Philippine Sea (PHS) Plate, or there may exist a split in the PHS Plate [Ide et al., 2010]. To investigate such segmentation, in our previous work we determined 3-D velocity structure and hypocenters using P- and S-wave arrival times of earthquakes recorded by both ocean bottom seismometers (OBSs) that were deployed from 2003 to 2007 and on-land stations [Akuhara et al., 2013]. As a result, it was discovered that Vp/Vs ratio is also segmented within the oceanic crust and at the bottom of the overriding plate, which coincides with the LFE distribution: segment A is located along the Kii Channel, segment B around the western Kii Peninsula, and segment C around the eastern Kii Peninsula. In segment B, Vp/Vs ratio is low within the oceanic crust and LFE cluster characterized by an anomalously small amount of cumulative slip, compared to the other LFE clusters around the Kii Peninsula, is located [Obara, 2010]. The difference of Vp/Vs ratio and LFE activity among segments were interpreted as difference of pore fluid pressure. In fact, similar segmentation can be seen in hypocenters: Segment A with concentrated seismicity in the oceanic mantle, segment B with that in the oceanic crust, and segment C with little seismicity. To derive characteristic patterns of the hypocenters, we conducted a cluster analysis of earthquakes based on waveform similarity represented by cross-correlation coefficients (CCs) [e.g., Cattaneo, 1999], in which we took varying structural site effects among the OBS stations

  9. Possible migration front of gas-related fluid inferred from 3D seismic in the eastern Nankai Trough

    NASA Astrophysics Data System (ADS)

    Otsuka, H.; Morita, S.; Tanahashi, M.; Ashi, J.; Nagakubo, S.

    2010-12-01

    High resolution 3D seismic survey, “Tokai-oki to Kumano-nada”, was conducted for methane hydrate exploration in the eastern Nankai Trough by METI in 2002. Our study focuses on a series of accordion-shaped reflectors with horizontal axis of fold back. They are connected to the edge of BSRs and alternate their polarities at every fold back hinge. We call the reflectors “Foldback Reflectors (FBRs)” in this study. Sedimentary horizons are successive across these series of reflectors with no fault displacement as a general rule. FBR generally corresponds to lateral seismic facies boundary between BSR distribution area and outside of the BSR area. The formation beneath the BSR shows dimmed facies characterized by relatively low amplitude and lack of high frequency components in contrast to outside of the BSR area with normal facies. Seismic velocity analysis suggests that FBRs correspond to velocity boundaries, where the dimmed faceis below the BSR coinsides with relatively low velocity. The polarities of FBRs are also consistent with such velocity changes. Such dimmed facies with low velocity and low amplitude anomaly suggests effects of gas components in the pore water. In this area, FBRs are mostly developed in the well-stratified formation but not in the area of frequent fractures and the area of major lateral lithological change. The observed FBRs are clustered in northern slope of the uplifted outer ridge, whereas few FBRs are developed in the southern slope of the outer ridge with frequent compressive and strike-slip deformations related to major fault systems including the Kodaiba faults and the Tokai faults. The estimated strike directions of each FBRs are probably controlled by the dip direction of crossing formation. Another important character of FBRs is that it never crosses major unconformities into lower strata. In addition, high amplitude layers are sometimes recognized at hinges of foldbacks convex to the outside of the BSR area. These high

  10. 3D crustal architecture of the Alps-Apennines join — a new view on seismic data

    NASA Astrophysics Data System (ADS)

    Schumacher, M. E.; Laubscher, H. P.

    1996-08-01

    Seismic data from the Alps-Apennines join have usually been interpreted in the form of 2D cross-sections, passing either through the Western Alps or the Ligurian Alps-Monferrato Apennines. However, the oblique SE-NW convergence of Adria and Europa and superimposed rotations imply a distinct 3D kinematic development around the Adriatic Indenter (AI), the westernmost spur of Adria. In order to develop kinematic models, data on motion at the different margins of AI must be coordinated. Along the northern margin, the dextrally transpressive Insubric line (IL) was active between 25 and 16 Ma (Insubric-Helvetic phase of Alpine orogeny). Contemporaneously, along the southern margin (Paleo-Apenninic phase), a complementary sinistral motion took place along the Villalvernia-Varzi line (VVL). It emplaced the Monferrato Apennines westward to the north of the Ligurian Alps by carrying them westward on top of AI. Between 14 and 6 Ma (Jura-Lombardic phase of Alpine orogeny) the Lombardic thrust belt developed on the northern margin of AI, now largely hidden under the Po plain. Its continuation to the southwest is impeded by older thrust masses along the Western Alps that consist largely of basement, their sediments having been eroded, as noted on the deep reflection line CROP ALPI-1 by earlier investigators. This line, moreover, contains a deep reflection band originating in the autochthonous Mesozoic of the Apenninic foredeep. In order to better visualize this origin and the relation of further elements identified on reflection lines around the northwestern end of the Monferrato Apennines, a 3D fence diagram was constructed. It helps in establishing a 3D structural-kinematic model of the Alps-Apennines join based on the kinematics of AI. This model features an underthrust of AI under the western Alps in the Paleo-Apenninic phase. In the course of this underthrust, the Paleo-Apenninic elements of the Monferrato moved under the marginal thrusts of the western Alps. Subsequent Neo

  11. Seismic attenuation structure of the Seattle Basin, Washington State from explosive-source refraction data

    USGS Publications Warehouse

    Li, Q.; Wilcock, W.S.D.; Pratt, T.L.; Snelson, C.M.; Brocher, T.M.

    2006-01-01

    We used waveform data from the 1999 SHIPS (Seismic Hazard Investigation of Puget Sound) seismic refraction experiment to constrain the attenuation structure of the Seattle basin, Washington State. We inverted the spectral amplitudes of compressional- and shear-wave arrivals for source spectra, site responses, and one- and two-dimensional Q-1 models at frequencies between 1 and 40 Hz for P waves and 1 and 10 Hz for S waves. We also obtained Q-1 models from t* values calculated from the spectral slopes of P waves between 10 and 40 Hz. One-dimensional inversions show that Qp at the surface is 22 at 1 Hz, 130 at 5 Hz, and 390 at 20 Hz. The corresponding values at 18 km depth are 100, 440, and 1900. Qs at the surface is 16 and 160 at 1 Hz and 8 Hz, respectively, increasing to 80 and 500 at 18 km depth. The t* inversion yields a Qp model that is consistent with the amplitude inversions at 20 and 30 Hz. The basin geometry is clearly resolved in the t* inversion, but the amplitude inversions only imaged the basin structure after removing anomalously high-amplitude shots near Seattle. When these shots are removed, we infer that Q-1 values may be ???30% higher in the center of the basin than the one-dimensional models predict. We infer that seismic attenuation in the Seattle basin will significantly reduce ground motions at frequencies at and above 1 Hz, partially countering amplification effects within the basin.

  12. New insights of the nature of the Porcupine Median Ridge using Refraction Seismic Data

    NASA Astrophysics Data System (ADS)

    Watremez, Louise; Prada, Manel; Minshull, Tim; O'Reilly, Brian; Chen, Chen; Reston, Tim; Wagner, Gerlind; Gaw, Viola; Klaeschen, Dirk; Shannon, Patrick

    2015-04-01

    The Porcupine Basin is a narrow V-shaped failed rifted basin of Permo-Triassic to Cenozoic age, with the main rifting phase in the Late Jurassic to Early Cretaceous. It is located offshore SW Ireland, showing increasing stretching factors from less than 1.5 to the North to more than 6 to the South. A ridge feature, the Porcupine Median Ridge, has been identified in the middle of the southernmost part of the basin. During the last three decades, this ridge has been successively interpreted as a volcanic structure, a diapir of partially serpentinized mantle, or a block of continental crust. Its nature is still remains debated today. The most recent study uses velocity analysis of long streamer seismic reflection data to support the volcanic ridge hypothesis. In this study we use refraction seismic data acquired across the Porcupine Basin to derive a better constrained P-wave velocity structure across the basin, and in particular across the Porcupine Median Ridge. We use the data from a 300 km long shot line recorded on 32 ocean-bottom seismometers and an inline land seismometer. This profile is oriented West-East and crosses the entire basin in its southernmost part. Thus, we image the deep structure of the thinnest part of the basin, the geometry of the continental thinning from margin to margin, with a central focus on the Porcupine Median Ridge. Analysis of P-wave and S-wave seismic arrivals, together with gravity modelling, gives new insights into the nature of this structure and allows for a better understanding of the rifting process of Porcupine Basin and its thermal state during the rifting. Defining the nature of the Porcupine Median Ridge will also give us more information about when the ridge formed and its role in rifting processes. This project is funded by the Irish Shelf Programme Study Group (ISPSG) of the Petroleum Infrastructure Programme (PIP).

  13. Hypocenter relocation using a fast grid search method and a 3-D seismic velocity model for the Sumatra region

    SciTech Connect

    Nugroho, Hendro; Widiyantoro, Sri; Nugraha, Andri Dian

    2013-09-09

    Determination of earthquake hypocenter in Indonesia conducted by the Meteorological, Climatological, and Geophysical Agency (MCGA) has still used a 1-D seismic velocity model. In this research, we have applied a Fast Grid Search (FGM) method and a 3-D velocity model resulting from tomographic imaging to relocate earthquakes in the Sumatran region. The data were taken from the MCGA data catalog from 2009 to 2011 comprising of subduction zone and on land fault earthquakes with magnitude greater than 4 Mw. Our preliminary results show some significant changes in the depths of the relocated earthquakes which are in general deeper than the depths of hypocenters from the MCGA data catalog. The residual times resulting from the relocation process are smaller than those prior to the relocation. Encouraged by these results, we will continue to conduct hypocenter relocation for all events from the MCGA data catalog periodically in order to produce a new data catalog with good quality. We hope that the new data catalog will be useful for further studies.

  14. 3-D seismic results in the discovery of significant reserves bypassed for 55 years in the Chocolate Bayou Field

    SciTech Connect

    Pennington, A.; Plant, C.; Davis, C.

    1994-12-31

    The Chocolate Bayou Field is located 25 miles south of Houston, in Southeast Brazoria County, Texas. Discovered in 1938, the field has produced over 2 trillion cubic feet of natural gas and 65 million barrels of oil from approximately 30 sands and 300 wellbores. The majority of the production is from the sands of the upper and middle Frio (Oligocene) section. Accumulation is found on structural highs on both the downthrown and upthrown side of a major basinward growth fault. A 3-D seismic survey was conducted over the field in 1988 in an effort to locate bypassed reserves. Interpretation of the data revealed and unexpected paleo structure associated with a buried and previously undetected counter-regional fault located almost 3 miles south of the structural crest at the Upper Frio level. Detailed structural and isochron mapping with adequate depth conversions indicated that the structure was prospective for trapping of the Lower Frio Sand which were well developed but wet under the Upper Frio structural crest. Although the feature was located on the absolute edge of the survey, the data were adequate to locate two wells which have now been completed in the Lower Frio (RA{sub 4}) section. The sands ranged in thickness from 65 to 115 feet of net pay with porosities from 27 to 30% with sustained production rates in excess of 10,000 million cubic feet of gas and 140 barrels of oil per day per completion.

  15. Potential Geophysical Field Transformations and Combined 3D Modelling for Estimation the Seismic Site Effects on Example of Israel

    NASA Astrophysics Data System (ADS)

    Eppelbaum, Lev; Meirova, Tatiana

    2015-04-01

    It is well-known that the local seismic site effects may have a significant contribution to the intensity of damage and destruction (e.g., Hough et al., 1990; Regnier et al., 2000; Bonnefoy-Claudet et al., 2006; Haase et al., 2010). The thicknesses of sediments, which play a large role in amplification, usually are derived from seismic velocities. At the same time, thickness of sediments may be determined (or defined) on the basis of 3D combined gravity-magnetic modeling joined with available geological materials, seismic data and borehole section examination. Final result of such investigation is a 3D physical-geological model (PGM) reflecting main geological peculiarities of the area under study. Such a combined study needs in application of a reliable 3D mathematical algorithm of computation together with advanced methodology of 3D modeling. For this analysis the developed GSFC software was selected. The GSFC (Geological Space Field Calculation) program was developed for solving a direct 3-D gravity and magnetic prospecting problem under complex geological conditions (Khesin et al., 1996; Eppelbaum and Khesin, 2004). This program has been designed for computing the field of Δg (Bouguer, free-air or observed value anomalies), ΔZ, ΔX, ΔY , ΔT , as well as second derivatives of the gravitational potential under conditions of rugged relief and inclined magnetization. The geological space can be approximated by (1) three-dimensional, (2) semi-infinite bodies and (3) those infinite along the strike closed, L.H. non-closed, R.H. on-closed and open). Geological bodies are approximated by horizontal polygonal prisms. The program has the following main advantages (besides abovementioned ones): (1) Simultaneous computing of gravity and magnetic fields; (2) Description of the terrain relief by irregularly placed characteristic points; (3) Computation of the effect of the earth-air boundary by the method of selection directly in the process of interpretation; (4

  16. Joint inversion of Multi-frequency Electromagnetic Induction and Seismic Refraction Data For Improved Near Surface Characterization

    NASA Astrophysics Data System (ADS)

    Elwaseif, M.

    2015-12-01

    We present a joint inversion routine between multi-frequency Electromagnetic (EM) induction and seismic refraction data that is based on using both cross-gradients and disconnect constraints. The joint inverse problem was solved using an iterative nonlinear least-squares formulation. Following each iteration, the cross gradient constraint enforces structural similarities between the EM and seismic models, whereas the disconnect constraint enforces sharp boundaries between different strata within the EM model. The locations of boundaries within the EM model are assumed to be consistent with the locations of user-defined velocity contours in the seismic model. We tested our method on a challenging synthetic EM and seismic model scenario that contains water-bearing zones as well as positively and negatively correlated model parameter values. In addition, we applied our method to GEM-2 and seismic refraction field data sets acquired along a 28-m-long profile in Laramie (WY), and we precisely recorded the locations where ground surface resistivity and velocity likely changes along that line. Unlike the results of separate EM and seismic inversions and the results of joint inversion based only on a cross-gradient constraint, our method was able to detect the water-bearing zones. In addition, it better captured ground surface changes in the field data set.

  17. 3D geological to geophysical modelling and seismic wave propagation simulation: a case study from the Lalor Lake VMS (Volcanogenic Massive Sulphides) mining camp

    NASA Astrophysics Data System (ADS)

    Miah, Khalid; Bellefleur, Gilles

    2014-05-01

    The global demand for base metals, uranium and precious metals has been pushing mineral explorations at greater depth. Seismic techniques and surveys have become essential in finding and extracting mineral rich ore bodies, especially for deep VMS mining camps. Geophysical parameters collected from borehole logs and laboratory measurements of core samples provide preliminary information about the nature and type of subsurface lithologic units. Alteration halos formed during the hydrothermal alteration process contain ore bodies, which are of primary interests among geologists and mining industries. It is known that the alteration halos are easier to detect than the ore bodies itself. Many 3D geological models are merely projection of 2D surface geology based on outcrop inspections and geochemical analysis of a small number of core samples collected from the area. Since a large scale 3D multicomponent seismic survey can be prohibitively expensive, performance analysis of such geological models can be helpful in reducing exploration costs. In this abstract, we discussed challenges and constraints encountered in geophysical modelling of ore bodies and surrounding geologic structures from the available coarse 3D geological models of the Lalor Lake mining camp, located in northern Manitoba, Canada. Ore bodies in the Lalor lake VMS camp are rich in gold, zinc, lead and copper, and have an approximate weight of 27 Mt. For better understanding of physical parameters of these known ore bodies and potentially unknown ones at greater depth, we constructed a fine resolution 3D seismic model with dimensions: 2000 m (width), 2000 m (height), and 1500 m (vertical depth). Seismic properties (P-wave, S-wave velocities, and density) were assigned based on a previous rock properties study of the same mining camp. 3D finite-difference elastic wave propagation simulation was performed in the model using appropriate parameters. The generated synthetic 3D seismic data was then compared to

  18. Mapping the North Sea base-Quaternary: using 3D seismic to fill a gap in the geological record

    NASA Astrophysics Data System (ADS)

    Lamb, Rachel; Huuse, Mads; Stewart, Margaret; Brocklehurst, Simon H.

    2014-05-01

    The identification and mapping of the base-Quaternary boundary in the central parts of the North Sea is problematic due to the change from an unconformable transition between Pliocene and Pleistocene deltaic deposits in the southern North Sea to a conformable one further north (Sejrup et al 1991; Gatliff et al 1994). The best estimates of the transition use seismic reflection data to identify a 'crenulated reflector' (Buckley 2012), or rely on correlating sparse biostratigraphy (Cameron et al 1987). Recent integration of biostratigraphy, pollen analysis, paleomagnetism and amino acid analysis in the Dutch and Danish sectors (Rasmussen et al 2005; Kuhlmann et al 2006) allows greater confidence in the correlation to a regional 3D seismic dataset and show that the base-Quaternary can be mapped across the entire basin. The base-Quaternary has been mapped using the PGS MegaSurvey dataset from wells in the Danish Sector along the initially unconformable horizon and down the delta front into the more conformable basin giving a high degree of confidence in the horizon pick. The mapped horizon is presented here alongside the difference between this new interpretation and the previously interpreted base-Quaternary (Buckley 2012). The revised base-Quaternary surface reaches a depth of 1248 ms TWT or approximately 1120 m (assuming average velocity of 1800 m/s) showing an elongate basin shape that follows the underlying structure of the Central Graben. The difference between the revised base-Quaternary and the traditional base-Quaternary reaches a maximum of over 600 ms TWT or approximately 540 m in the south-west with over 300 ms TWT or approximately 270 m at the Josephine well (56° 36.11'N, 2° 27.09'E) in the centre of the basin. Mapping this new base-Quaternary allows for the interpretation of the paleo-envionrment during the earliest Quaternary. Seismic attribute analysis indicates a deep water basin with sediment deposition from multiple deltas and redistribution by deep

  19. Rock formation characterization for CO2-EOR and carbon geosequestration; 3D seismic amplitude and coherency anomalies, Wellington Field, Kansas, USA

    USGS Publications Warehouse

    Ohl, D.; Raef, A.; Watnef, L.; Bhattacharya, S.

    2011-01-01

    In this paper, we present a workflow for a Mississipian carbonates characterization case-study integrating post-stack seismic attributes, well-logs porosities, and seismic modeling to explore relating changes in small-scale "lithofacies" properties and/or sub-seismic resolution faulting to key amplitude and coherency 3D seismic attributes. The main objective of this study is to put emphasis on reservoir characterization that is both optimized for and subsequently benefiting from pilot tertiary CO2-EOR in preparation for future carbon geosequestration in a depleting reservoir and a deep saline aquifer. The extracted 3D seismic coherency attribute indicated anomalous features that can be interpreted as a lithofacies change or a sub-seismic resolution faulting. A 2D finite difference modeling has been undertaken to understand and potentially build discriminant attributes to map structural and/or lithofacies anomalies of interest especially when embarking upon CO2-EOR and/or carbon sequestration monitoring and management projects. ?? 2011 Society of Exploration Geophysicists.

  20. Lithospheric structure beneath Central Europe from the POLONAISE'97, CELEBRATION 2000, ALP 2002, and SUDETES 2003 seismic refraction experiments

    NASA Astrophysics Data System (ADS)

    Guterch, A.; Grad, M.; Keller, G. R.

    2005-12-01

    Beginning in 1997, Central Europe between the Baltic and Adriatic Seas, has been covered by an unprecedented network of seismic refraction experiments POLONAISE'97, CELEBRATION 2000, ALP 2002, and SUDETES 2003, have only been possible due to a massive international consortium consisted of more than 30 institutions from 16 countries in Europe and North America. The majority of recording instruments was provided by the IRIS/PASSCAL Instrument Center and the University of Texas at El Paso (USA), and several other countries also provided instrumentation. Total length of seismic profiles in all experiments is about 20,000 km. The main results of these experiments are: 1) the delineation of the deep structure of the southwestern margin of the East European Craton (southern Baltica) and its relationship to younger terranes; delineation of the major terranes and crustal blocks in the Trans European Suture Zone; determination of the structural framework of the Pannonian basin; elucidation of the deep structure and evolution of the Western Carpathian Mountains and Eastern Alps; determination of the structural relationships between the structural elements of the Bohemian massif and adjacent features; construction of 3-D models of the lithospheric structure; and evaluation and develop geodynamic models for the tectonic evolution of the region. Experiment Working Groups Members: K. Aric, M. Behm, E. Brueckl, W. Chwatal, H. Grassl, S. Hock, V. Hoeck, F. Kohlbeck, E.-M. Rumpfhuber, Ch. Schmid, R. Schmoller, C. Tomek, Ch. Ullrich, F.Weber (Austria), A.A. Belinsky (Belarus), I. Asudeh, R. Clowes, Z. Hajnal (Canada), F. Sumanova (Croatia), M. Broz , P. Hrubcova, M. Korn, O. Karousova, J. Malek, A. Spicak (Czech Republic), S.L. Jensen, P. Joergensen, H. Thybo (Denmark), K. Komminaho, U. Luosto, T. Tiira, J. Yliniemi (Finland), F. Bleibinhaus, R. Brinkmann, B. Forkmann, H. Gebrande, H. Geissler, A. Hemmann, G. Jentzsch, D. Kracke, A. Schulze, K. Schuster (Germany), T. Bodoky, T

  1. Enhancing Monitoring of Recharge-Related Environmental Remediation Processes Using Time-Lapse Seismic Refraction

    NASA Astrophysics Data System (ADS)

    Gaines, D. P.; Baker, G. S.; Hubbard, S. S.; Watson, D. B.; Jardine, P. M.

    2008-12-01

    The application of time-lapse seismic methods has typically been constrained to large-scale geologic investigations associated with petroleum exploration and exploitation; however, there is growing interest in monitoring near-surface phenomena (e.g., fluid flow in fractured or karstic geologic media, hydraulic recharge, and near-surface anthropogenic manipulations) using time-lapse seismic methods. In order to demonstrate the feasibility of detailed time-lapse seismic refraction tomography (TLSRT), we have monitored a perched water table at Oak Ridge National Laboratory (ORNL) Y-12 site in conjunction with a multi- disciplinary investigation of the fate and transport of contaminants. Due to remnant anthropogenic alterations of the site (i.e., replacement of 0-7 meters of contaminated soil with poorly sorted limestone gravel fill during construction of a seepage basin cap), the near surface hydrology is extremely complex and is hypothesized to have a large influence on infiltration, contaminant distribution, and contaminant remobilization. Understanding the impact of recharge-related flow and transport processes is especially important in regions that are subjected to significant precipitation events, such as at the ORNL Y-12 site. Here, TLSRT techniques are used to monitor the changing geometry of a perched water table located near the covered seepage basin, while coincident time-lapse surface electrical resistivity (TLERT) measurements are used to monitor changes in total dissolved solids due to recharge-related dilution. Data are collected at multiple time intervals (i.e., daily, weekly, monthly, yearly) and at varying stages in the evolution of the perch zone. The resulting seismic data are processed using wavepath eikonal tomography (WET) and differenced to identify areas of variable velocity associated with a change in saturation. The differenced tomograms correlate with discrete point water table measurements; however, the highly variable water table at this

  2. 3D-Seismic images reveal the external structure of igneous intrusions, off-shore New Zealand

    NASA Astrophysics Data System (ADS)

    Christiansen, E. H.; Luke, J.; Keach, R. W., II

    2011-12-01

    Several volcano-plutonic complexes are imaged in a 3D seismic survey by Pogo New Zealand/Plains Exploration. The data provide insight into the sizes, shapes, and wall rock deformation associated with emplacement of plutons. The magmatic rocks are part of the Mohakatino Volcanic Centre (15 to 1.6 Ma) that intrudes and partially fills the Taranaki graben. Imaged plutons range from >1 to 12 km across. The large intrusions are steep-sided and do not resemble sills, but their bases are poorly resolved. The top of the complex is sharply delineated and marked by multiple apophyses as much as 2 km across and hundreds of meters high. Deformation along the sides of the intrusion is dominated by highly attenuated dipping strata with apparent dips >45°. Dips decrease away from the intrusion but doming extends several hundred meters from the margins. High-angle faults fan out from the margin of the pluton and cut the folded strata along the margin. These faults terminate against the intrusion, extend as much as 1 pluton diameter away from the margin, and then merge with regional normal faults that are part of the graben. Offset along these faults is on the order of a few hundred meters. Strata on the top of the complex are thinned and deformed into a faulted dome with an amplitude of about 1 km. Steep, dip-slip faults form a semi-radial pattern in the roof rocks but their orientations are strongly controlled by the regional stress field as many of the faults are sub-parallel to those that form the graben. The longest roof faults are about the same length as the diameter of the pluton and cut through approximately 1 km of overlying strata, but offset gradually diminishes vertically away from the top of the intrusion. The pluton appears to be composite and formed from multiple, steep-sided intrusions as evidenced by the complex margins, roof domes, and multiple apophyses. Small sills are apparent several hundreds of meters above the top of the main complex. Multiple episodes of

  3. Reconciling deep seismic refraction and reflection data from the grenvillian-appalachian boundary in western New England

    USGS Publications Warehouse

    Hughes, S.; Luetgert, J.H.; Christensen, N.I.

    1993-01-01

    The Grenvillian-Appalachian boundary is characterized by pervasive mylonitic deformation and retrograde alteration of a suite of imbricated allochthonous and parautochthonous gneisses that were thrust upon the Grenvillian continental margin during the lower Paleozoic. Seismic reflection profiling across this structural boundary zone reveals prominent dipping reflectors interpreted as overthrust basement slices (parautochthons) of the Green Mountain Anticlinorium. In contrast, a seismic refraction study of the Grenvillian-Appalachian boundary reveals a sub-horizontally layered seismic velocity model that is difficult to reconcile with the pronounced sub-vertical structures observed in the Green mountains. A suite of rock samples was collected from the Green Mountain Anticlinorium and measured at high pressures in the laboratory to determine the seismic properties of these allochthonous and parautochthonous gneisses. The laboratory-measured seismic velocities agree favorably with the modelled velocity structure across the Grenvillian-Appalachian boundary suggesting that the rock samples are reliable indicators of the rock mass as whole. Samples of the parautochthonous Grenvillian basement exposed in the Green Mountains have lower velocities, by about 0.5 km/s, than lithologically equivalent units exposed in the eastern Adirondack Highlands. Velocity reduction in the Green Mountain parautochthons can be accounted for by retrograde metamorphic alteration (hydration) of the paragneisses. Seismic anisotropies, ranging from 2 to 12%, in the mylonitized Green Mountain paragneisses may also contribute to the observation of lower seismic velocities, where the direction of ray propagation is normal to the foliation. The velocity properties of the Green Mountain paragneisses are thus insufficiently different from the mantling Appalachian allochthons to permit their resolution by the Ontario-New York-New England seismic refraction profile. ?? 1993.

  4. Characterization of the crust of Maine by seismic reflection and refraction

    SciTech Connect

    Stewart, D.B.; Luetgert, J.H.; Unger, J.D.; Phillips, J.D.

    1985-01-01

    Major structural features of the crust of Main and adjacent Quebec appear in both seismic reflection and refraction profiles gathered in 1983 and 1984 through US-Canada cooperative experiments and associated gravity, magnetic, and geologic studies. Excepting gabbroic plutons, the upper crust is sialic throughout Maine with velocity 5.7-6.3 km/sec; below approx.22 km, velocity increases to 6.8-7.2 km/sec. Crustal thinning, from 40 km in the NW to 35 km in the SE, accounts for all the increase in the regional gravity field to the SE. The crust-mantle transition is gradational but yields multiple strong Moho reflections and clear Pn arrivals. Seismic data permit five different kinds of continental crust (terranes) to be characterized. The terranes are separated by boundaries that penetrate most of the crust. No ancient oceanic crust was identified. In northwestern Maine, crust II with the Chain Lakes Massif and superposed ophiolite was obducted in the Taconian orogeny onto sialic (Grenville.) Crust I. Crust II is in steep contact with high grade sialic metamorphic rocks of crust III approx.10 km SE of the NW border of the Merrimack synclinorium. The contact is covered by approx.12 km of Silurian and Devonian metasedimentary rocks. Crust III contacts crust IV along the Norumbega fault zone; high grade Precambrian and lower Paleozoic metasedimentary rocks thrust southeastward make up the upper part of crust IV. Crust IV contacts crust V along the Turtle Head fault zone in Penobscot Bay. In Crust V approx.12 km of bimodal Lower Paleozoic volcanic rocks cover Precambrian rocks at medium grade. The irregular shapes of granitic plutons were determined to depths of 6-10 km.

  5. Models of crustal thickness for South America from seismic refraction, receiver functions and surface wave tomography

    NASA Astrophysics Data System (ADS)

    Assumpção, Marcelo; Feng, Mei; Tassara, Andrés; Julià, Jordi

    2013-12-01

    An extensive compilation of crustal thicknesses is used to develop crustal models in continental South America. We consider point crustal thicknesses from seismic refraction experiments, receiver function analyses, and surface-wave dispersion. Estimates of crustal thickness derived from gravity anomalies were only included along the continental shelf and in some areas of the Andes to fill large gaps in seismic coverage. Two crustal models were developed: A) by simple interpolation of the point estimates, and B) our preferred model, based on the same point estimates, interpolated with surface-wave tomography. Despite gaps in continental coverage, both models reveal interesting crustal thickness variations. In the Andean range, the crust reaches 75 km in Southern Peru and the Bolivian Altiplano, while crustal thicknesses seem to be close to the global continental average (~ 40 km) in Ecuador and southern Colombia (despite high elevations), and along the southern Andes of Chile-Argentina (elevation lower than 2000 m). In the stable continental platform the average thickness is 38 ± 5 km (1-st. deviation) and no systematic differences are observed among Archean-Paleoproterozoic cratons, NeoProterozoic fold belts, and low-altitude intracratonic sedimentary basins. An exception is the Borborema Province (NE Brazil) with crust ~ 30-35 km thick. Narrow belts surrounding the cratons are suggested in central Brazil, parallel to the eastern and southern border of the Amazon craton, and possibly along the TransBrasiliano Lineament continuing into the Chaco basin, where crust thinner than 35 km is observed. In the sub-Andean region, between the mid-plate cratons and the Andean cordillera, the crust tends to be thinner (~ 35 km) than the average crust in the stable platform, a feature possibly inherited from the old pre-Cambrian history of the continent. We expect that these crustal models will be useful for studies of isostasy, dynamic topography, and crustal evolution of the

  6. Landslide characterization using P- and S-wave seismic refraction tomography - The importance of elastic moduli

    NASA Astrophysics Data System (ADS)

    Uhlemann, S.; Hagedorn, S.; Dashwood, B.; Maurer, H.; Gunn, D.; Dijkstra, T.; Chambers, J.

    2016-11-01

    In the broad spectrum of natural hazards, landslides in particular are capable of changing the landscape and causing significant human and economic losses. Detailed site investigations form an important component in the landslide risk mitigation and disaster risk reduction process. These investigations usually rely on surface observations, discrete sampling of the subsurface, and laboratory testing to examine properties that are deemed representative of entire slopes. Often this requires extensive interpolations and results in large uncertainties. To compliment and extend these approaches, we present a study from an active landslide in a Lias Group clay slope, North Yorkshire, UK, examining combined P- and S-wave seismic refraction tomography (SRT) as a means of providing subsurface volumetric imaging of geotechnical proxies. The distributions of seismic wave velocities determined from SRT at the study site indicated zones with higher porosity and fissure density that are interpreted to represent the extent and depth of mass movements and weathered bedrock zones. Distinguishing the lithological units was facilitated by deriving the Poisson's ratio from the SRT data as saturated clay and partially saturated sandy silts showed distinctively different Poisson's ratios. Shear and Young's moduli derived from the SRT data revealed the weak nature of the materials in active parts of the landslide (i.e. 25 kPa and 100 kPa respectively). The SRT results are consistent with intrusive (i.e. cone penetration tests), laboratory, and additional geoelectrical data from this site. This study shows that SRT forms a cost-effective method that can significantly reduce uncertainties in the conceptual ground model of geotechnical and hydrological conditions that govern landslide dynamics.

  7. 3-D seismic velocity structure of the crust and the uppermost mantle in the northeastern Japan Arc

    NASA Astrophysics Data System (ADS)

    Zhao, Dapeng; Horiuchi, Shigeki; Hasegawa, Akira

    1990-09-01

    3-D seismic velocity structure of the crust and the uppermost mantle beneath the northeastern Japan Arc is investigated by using arrival time data from local earthquakes. We use a velocity model composed of three layers corresponding to the upper crust, the lower crust and the uppermost mantle, respectively. Taking into account the observed regional variation of P n-velocity, the uppermost mantle is further divided into three parts by two P n-velocity boundaries near the coasts of the Japan Sea and the Pacific Ocean. The velocities within the upper crust, the lower crust and the three parts of the uppermost mantle are assumed to be constant. Locations of two P n-velocity boundaries and depth distributions of the Conrad and the Moho discontinuities are expressed by continuous functions of unknown parameters. Station corrections and hypocenters are also introduced to be unknowns. These unknown parameters are determined by inverting arrival time data of P- and S-wave first arrivals and clear later arrivals of P g- and P ∗-waves. The P n-velocity boundary between the land and the Pacific Ocean is located approximately along the Pacific coastline and that between the land and the Japan Sea is nearly along the Japan Sea coastline. The Conrad and the Moho discontinuities are at depths ranging from 14 to 20 km and from 27 to 36 km, respectively. The Conrad and the Moho depths have similar spatial distributions. They are deep beneath the land and become shallower toward the western and the eastern coastlines. Beneath the land, they are shallow in the central part of the Tohoku District and become deeper toward both the north and the south directions. In the north, they become shallow again.

  8. Shallow Gas and Gas Hydrates in the Barents Sea Imaged by High-Resolution 3D Seismic Data

    NASA Astrophysics Data System (ADS)

    Planke, S.; Eriksen, O.; Eriksen, F. N.; Bunz, S.; Berndt, C.

    2012-12-01

    Shallow gas and gas hydrates are potential hazards for the petroleum industry, but may also represent future resources. Detailed mapping of shallow gas and gas hydrates is important to reduce drilling risks, to exploit hydrocarbon resources, and to better understand procesesse of gas migration and accumulation. We have collected two high resolution 3D seismic cubes of 10-20 km2 in areas with shallow gas in the Barents Sea. The cubes were acquired using the P-Cable system in water depths of 300-500 m with the vessel R/V Jan Mayen. The data were processed using the RadexPro software and a standard sequence including geometry, tide corrections, binning, filtering, and migration. Two main sedimentary sequences are present in the data, a sub-horizontal glacial package overlying a westward-dipping Paleogene sequence. The seabed is characterized by up to 15 m deep glacial ploughmarks. An upper regional unconformity (URU) separates the glacial and Paleogene sediments. Three levels of high-amplitude reflections are interpreted as evidence of shallow gas. Minor gas accumulations are present as semi-circular anomalies within the glacial sequence and as north-south trending anomalies just below the URU. More extensive gas accumulations are found within the Paleogene sediments, and the top gas reflections are clearly cross-cutting the dipping Paleogene sequence. Several paleo-pockmarks are interpreted within the glacial sequence, whereas no pockmarks are identified on the seafloor. The gas is interpreted to be sealed by overlying gas hydrates. Gas hydrate models show that pure methane is outside the gas hydrate stability field in the surveyed region, but within the gas hydrate stability field if methane is mixed with minor amounts of higher-order hydrocarbons (ethane and propane).

  9. Frequency-dependent traveltime tomography for near-surface seismic refraction data

    NASA Astrophysics Data System (ADS)

    Zelt, Colin A.; Chen, Jianxiong

    2016-10-01

    -structure regularization techniques to address the issue of model non-uniqueness. For synthetic data, the estimated FDTT models are shown to be more accurate than the corresponding infinite-frequency-derived models. Both 2-D and 3-D applications of FDTT to real data from a near-surface study yield estimated models that contain more structure than the corresponding infinite-frequency-derived models. Applications of FDTT without regularization demonstrate the potential of the WDVS-derived sensitivity kernels to provide a natural smoothing of the velocity model and thereby allow the data alone to determine the final model structure.

  10. Frequency-dependent traveltime tomography for near-surface seismic refraction data

    NASA Astrophysics Data System (ADS)

    Zelt, Colin A.; Chen, Jianxiong

    2016-07-01

    -structure regularization techniques to address the issue of model nonuniqueness. For synthetic data, the estimated FDTT models are shown to be more accurate than the corresponding infinite-frequency-derived models. Both 2-D and 3-D applications of FDTT to real data from a near-surface study yield estimated models that contain more structure than the corresponding infinite-frequency-derived models. Applications of FDTT without regularization demonstrate the potential of the WDVS-derived sensitivity kernels to provide a natural smoothing of the velocity model and thereby allow the data alone to determine the final model structure.

  11. Structure of the San Andreas fault zone at SAFOD from a seismic refraction survey

    USGS Publications Warehouse

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

    2006-01-01

    Refraction traveltimes from a 46-km long seismic survey across the San Andreas Fault were inverted to obtain two-dimensional velocity structure of the upper crust near the SAFOD drilling project. The model contains strong vertical and lateral velocity variations from <2 km/s to ???6 km/s. The Salinian terrane west of the San Andreas Fault has much higher velocity than the Franciscan terrane east of the fault. Salinian basement deepens from 0.8 km subsurface at SAFOD to ???2.5 km subsurface 20 km to the southwest. A strong reflection and subtle velocity contrast suggest a steeply dipping fault separating the Franciscan terrane from the Great Valley Sequence. A low-velocity wedge of Cenozoic sedimentary rocks lies immediately southwest of the San Andreas Fault. This body is bounded by a steep fault just northeast of SAFOD and approaches the depth of the shallowest earthquakes. Multiple active and inactive fault strands complicate structure near SAFOD. Copyright 2006 by the American Geophysical Union.

  12. 3-D reconstruction and virtual ductoscopy of high-grade ductal carcinoma in situ of the breast with casting type calcifications using refraction-based X-ray CT.

    PubMed

    Ichihara, Shu; Ando, Masami; Maksimenko, Anton; Yuasa, Tetsuya; Sugiyama, Hiroshi; Hashimoto, Eiko; Yamasaki, Katsuhito; Mori, Kensaku; Arai, Yoshinori; Endo, Tokiko

    2008-01-01

    Stereomicroscopic observations of thick sections, or three-dimensional (3-D) reconstructions from serial sections, have provided insights into histopathology. However, they generally require time-consuming and laborious procedures. Recently, we have developed a new algorithm for refraction-based X-ray computed tomography (CT). The aim of this study is to apply this emerging technology to visualize the 3-D structure of a high-grade ductal carcinomas in situ (DCIS) of the breast. The high-resolution two-dimensional images of the refraction-based CT were validated by comparing them with the sequential histological sections. Without adding any contrast medium, the new CT showed strong contrast and was able to depict the non-calcified fine structures such as duct walls and intraductal carcinoma itself, both of which were barely visible in a conventional absorption-based CT. 3-D reconstruction and virtual endoscopy revealed that the high-grade DCIS was located within the dichotomatous branches of the ducts. Multiple calcifications occurred in the necrotic core of the continuous DCIS, resulting in linear and branching (casting type) calcifications, a hallmark of high-grade DCIS on mammograms. In conclusion, refraction-based X-ray CT approaches the low-power light microscopic view of the histological sections. It provides high quality slice data for 3-D reconstruction and virtual ductosocpy.

  13. 3D seismic detection of shallow faults and fluid migration pathways offshore Southern Costa Rica: Application of neural-network meta-attributes

    NASA Astrophysics Data System (ADS)

    Kluesner, J. W.; Silver, E. A.; Nale, S. M.; Bangs, N. L.; McIntosh, K. D.

    2013-12-01

    We employ a seismic meta-attribute workflow to detect and analyze probable faults and fluid-pathways in 3D within the sedimentary section offshore Southern Costa Rica. During the CRISP seismic survey in 2011 we collected an 11 x 55 km grid of 3D seismic reflection data and high-resolvability EM122 multibeam data, with coverage extending from the incoming plate to the outer-shelf. We mapped numerous seafloor seep indicators, with distributions ranging from the lower-slope to ~15 km landward of the shelf break [Kluesner et al., 2013, G3, doi:10.1002/ggge.20058; Silver et al., this meeting]. We used the OpendTect software package to calculate meta-attribute volumes from the 3D seismic data in order to detect and visualize seismic discontinuities in 3D. This methodology consists of dip-steered filtering to pre-condition the data, followed by combining a set of advanced dip-steered seismic attributes into a single object probability attribute using a user-trained neural-network pattern-recognition algorithm. The parameters of the advanced seismic attributes are set for optimal detection of the desired geologic discontinuity (e.g. faults or fluid-pathways). The product is a measure of probability for the desired target that ranges between 0 and 1, with 1 representing the highest probability. Within the sedimentary section of the CRISP survey the results indicate focused fluid-migration pathways along dense networks of intersecting normal faults with approximately N-S and E-W trends. This pattern extends from the middle slope to the outer-shelf region. Dense clusters of fluid-migration pathways are located above basement highs and deeply rooted reverse faults [see Bangs et al., this meeting], including a dense zone of fluid-pathways imaged below IODP Site U1413. In addition, fault intersections frequently show an increased signal of fluid-migration and these zones may act as major conduits for fluid-flow through the sedimentary cover. Imaged fluid pathways root into high

  14. Along-axis crustal structure of the Porcupine Basin from seismic refraction data modelling

    NASA Astrophysics Data System (ADS)

    Prada, Manel; Watremez, Louise; Chen, Chen; O'Reilly, Brian; Minshull, Tim; Reston, Tim; Wagner, Gerlind; Gaws, Viola; Klaschen, Dirk; Shannon, Patrick

    2016-04-01

    The Porcupine Basin is a tongue-shaped offshore basin SW of Ireland that formed during the opening of the North Atlantic Ocean. Its history of development involved several rifting and subsidence phases during the Late Paleozoic and Cenozoic, with a particular major rift phase occurring in Late Jurassic-Early Cretaceous times. Previous work, focused on subsidence analysis, showed that stretching factors (β) in the northern part of the basin are < 1.5 and increase significantly southwards, where they were estimated to be > 6. However, recent studies based on seismic reflection and refraction profiles concluded that β in places along the basin axis were significantly higher, and suggested the presence of major crustal faulting and uppermost mantle serpentinization in the basin. Constraining β and the processes related to the formation of the basin will provide insights into aspects such as the tectonic response to lithospheric extension and the thermal evolution of the basin. Here we present the tomography results of five wide-angle seismic (WAS) profiles acquired across and along the basin axis. We used a travel time inversion method to model the WAS data and obtain P-wave velocity (Vp) models of the crust and uppermost mantle, together with the geometry of the main geological interfaces along each of these lines. Coincident seismic reflection profiles to each WAS line were also used to integrate the tectonic structure with the Vp model. These results improved constrains on the location of the base of the crust and allow to estimate maximum β (βmax) along each profile. The analysis shows that βmax values in the northern part of the basin are 5-6 times larger than estimates based on subsidence analysis. Towards the south, βmax increases up to 10, but then rapidly decreases to 3.3 southwards. These values are well within the range of crustal extension at which the crust becomes entirely brittle at magma-poor margins allowing the formation of major crustal

  15. Multicomponent, 3-D, and High-Resolution 2-D Seismic Characterization of Gas Hydrate Study Sites in the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Haines, S. S.; Hart, P. E.; Ruppel, C. D.; Collett, T. S.; Shedd, W.; Lee, M. W.; Miller, J.

    2012-12-01

    High saturations of gas hydrates have been identified within coarse-grained sediments in the Green Canyon 955 and Walker Ridge 313 lease blocks of the deepwater northern Gulf of Mexico. The thickness, lateral extent, and hydrate saturations in these deposits are constrained by geological and geophysical data and state-of-the-art logging-while-drilling information obtained in multiple boreholes at each site during a 2009 expedition. Presently lacking are multicomponent seismic data that can provide a thorough understanding of the in-situ compressional and shear seismic properties of the hydrate-bearing sediments. Such data may represent an important tool for future characterization of gas hydrate resources. To address this data gap, the U.S. Geological Survey, the U.S. Department of Energy, and the Bureau of Ocean Energy Management will collaborate on a 20-day research expedition to acquire wide-angle ocean bottom seismometer and high-resolution vertical incidence 2-D seismic data at the study sites. In preparation for this mid-2013 expedition, we have analyzed existing industry 3-D seismic data, along with numerically modeled multicomponent data. The 3-D seismic data allow us to identify and rank specific survey targets and can be combined with the numerical modeling results to determine optimal survey line orientation and acquisition parameters. Together, these data also provide a more thorough understanding of the gas hydrate systems at these two sites.

  16. Mid-Ocean Ridge Mantle Processes Constrained by the FAIM Seismic Refraction Experiment

    NASA Astrophysics Data System (ADS)

    Collins, J. A.; Lizarralde, D.; Gaherty, J. B.; Hirth, G.; Kim, S.

    2003-12-01

    The seismic structure (e.g. velocity, velocity gradients, anisotropy) of the shallow upper mantle of oceanic lithosphere constrains the degree of melt extraction at mid-ocean ridges and the shear deformation of the lithosphere. The variation of fine-scale structure with depth is difficult to resolve with teleseismic data but, with some notable exceptions, seismic refraction techniques - which have excellent depth resolution - have not been used to elucidate oceanic upper mantle structure. Here we report further results from the FAIM (Far-offset Active-source Imaging of the Mantle) seismic refraction experiment conducted along an 800-km-long flow-line transect and a 150-km-long ridge-parallel transect in the western north Atlantic. Sixteen short-period, vertical-component ocean-bottom seismometers (OBS) were deployed along the spreading-parallel transect in 3-km-separated pairs spaced 80-120 km apart, and 3 OBS were deployed orthogonal to the primary transect to a maximum distance of 350 km. Shot spacing was 1 km. Coherent P-wave arrivals were observed to 350-km distance, and the amplitude of this phase and its increasing and fast apparent-velocity suggest that energy is propagating to ˜24 km depth below the Moho. Two-dimensional travel-time analyses predict velocities of ˜8.25-8.55 km/s over the uppermost 24 km of the mantle on the flow-line-parallel transect and velocities of ˜8.05-8.25 km/s over the uppermost 10 km of the mantle on the ridge-parallel transect. At face value, these values indicate P-wave anisotropy is at least ˜3.0% throughout the upper 10 km of the mantle. However, velocities in only two orthogonal directions cannot constrain the precise direction and magnitude of anisotropy. To improve this estimate we analyzed the travel times of P-waves with good signal to noise from shots at ranges of 75-250 km, with an azimuth range spanning ˜100\\deg. When plotted as a function of propagation azimuth, these travel times display a strong variation, with

  17. Mapping the megathrust beneath the northern Gulf of Alaska using wide-angle seismic reflection/refraction profiles

    SciTech Connect

    Brocher, T.M.; Fuis, G.S.; Fisher, M.A.; Plafker, G.; Moses, M.J.; Taber, J.J. ); Christensen, N.I. . Dept. of Earth and Atmospheric Sciences)

    1993-04-01

    In the northern Gulf of Alaska and Prince William Sound, wide-angle seismic reflection/refraction profiling, earthquake studies, and laboratory measurements of physical properties are used to determine the geometry of the Prince William and Yakutat terranes, and the subducting Pacific plate. In this complex region, the Yakutat terrane is underthrust beneath the Prince William terrane, and both terranes are interpreted to be underlain by the Pacific plate. Wide-angle seismic reflection/refraction profiles recorded along 5 seismic lines are used to unravel this terrane geometry. Modeled velocities in the upper crust of the Prince William terrane (to 18-km depth) agree closely with laboratory velocity measurements of Orca Group phyllites and quartzofeldspathic graywackes (the chief components of the Prince William terrane) to hydrostatic pressures as high as 600 MPa (6 KBAR). An interpretation consistent with these data extends the Prince William terrane to at least 18-km depth. A landward dipping reflection at depths of 16--24 km is interpreted as the base of the Prince William terrane. This reflector corresponds to the top of the Wadati-Benioff zone seismicity and is interpreted as the megathrust. Beneath this reflector is a 6.9-km/s refractor, that is strongly reflective and magnetic, and is interpreted to be gabbro in Eocene age oceanic crust of the underthrust Yakutat terrane. Both wide-angle seismic and magnetic anomaly data indicate that the Yakutat terrane has been underthrust beneath the Prince William terrane for at least a few hundred kilometers. Wide-angle seismic data are consistent with a 9 to 10[degree] landward dip of the subducting Pacific plate, distinctly different from the inferred average 3 to 4[degree] dip of the overlying 6.9-km/s refractor and Wadati-Benioff seismic zone. The preferred interpretation of the geophysical data is that one composite plate, composed of the Pacific and Yakutat plates, is subducting beneath southern Alaska.

  18. Constraining Subsurface Structure and Composition Using Seismic Refraction Surveys of Proglacial Valleys in the Cordillera Blanca, Peru

    NASA Astrophysics Data System (ADS)

    Glas, R. L.; Lautz, L.; McKenzie, J. M.; Mark, B. G.; Baker, E. A.; Aubry-Wake, C.; Somers, L. D.; Wigmore, O.

    2015-12-01

    As tropical glaciers rapidly recede in response to climate change, the storage and discharge of groundwater will play an increasing role in regulating river baseflow, particularly during the dry season, when stream flow is currently sustained predominantly by glacial melt. Little is understood regarding the hydrogeologic processes controlling base flow characteristics of low-gradient proglacial valleys of the Cordillera Blanca in Northwestern Peru, which has the world's highest density of tropical glaciers. To better understand the processes of groundwater storage and discharge in proglacial meadows, we completed seismic refraction surveys in three representative valleys of the Cordillera Blanca range: the Quilcayhuanca, Yanamarey, and Pachacoto valleys. The locations of survey transects were chosen based on locations of previous sediment core sampling, GPR lines, and quantification of groundwater-surface water interaction derived from dye and temperature tracing experiments. The seismic surveys consisted of 48 vertical component geophones with 2.5 m spacing. Across the three representative valleys a total of 15 surveys were conducted, covering a distance of 1800 m in cross, down, and oblique-valley directions. Preliminary interpretation of the seismic refraction data indicates a maximum imaging depth of 16 m below land surface, and a transition from glacio-lacustrine sediments to buried saturated talus at a depth of 6 m in the Quilcayhuanca valley. The organic-rich glacio-lacustrine sediments in the Yanamarey valley have seismic velocities ranging from 300 to 800 m/s and are >16 m in thickness at mid- valley. Weathered metasedimentary bedrock in the Pachacoto valley was imaged at ~5 m below the valley surface, exhibiting a p-wave velocity of 3400 m/s. The knowledge of hydrogeologic structure derived from seismic refraction surveys will provide crucial boundary conditions for future groundwater models of the valleys of the Cordillera Blanca.

  19. Joint environmental assessment for Chevron USA, Inc. and Santa Fe Energy Resources, Inc.: Midway Valley 3D seismic project, Kern County, California

    SciTech Connect

    1996-10-01

    The proposed Midway Valley 3D Geophysical Exploration Project covers approximately 31,444 aces of private lands, 6,880 acres of Department of Energy (DOE) Lands within Naval Petroleum Reserve 2 (NPR2) and 3,840 acres of lands administered by the Bureau of Land Management (BLM), in western Kern County, California. This environmental assessment (EA) presents an overview of the affected environment within the project area using results of a literature review of biological field surveys previously conducted within or adjacent to a proposed 3D seismic project. The purpose is to provide background information to identify potential and known locations of sensitive wildlife and special status plant species within the proposed seismic project area. Biological field surveys, following agency approved survey protocols, will be conducted during October through November 1996 to acquire current resources data to provide avoidance as the project is being implemented in the field.

  20. Magma Migration Through the Continental Crust - 3-D Seismic and Thermo-mechanical Constraints on Sites of Crustal Contamination

    NASA Astrophysics Data System (ADS)

    Wilson, M.; Wheeler, W.

    2002-12-01

    Current understanding of the processes and pathways by which magma travels from its mantle source, through the crust to the Earth's surface is limited by the lack of continuously exposed sections through "fossil" magmatic systems. We report results from a 50 x 30 km 3-D seismic reflection survey of part of the Voring rifted continental margin of Norway which provide the first detailed images of an entire crustal magmatic plumbing system, from a Moho-level magma chamber, through complexes of sills and dykes in the mid to upper crust, to lavas and vent fields extruded at the early Tertiary paleosurface. The Voring margin of Norway formed during a period of Late Cretaceous to early Tertiary (Eocene) continental break-up when Greenland rifted away from Eurasia, resulting in the opening the NE Atlantic Ocean. Rifting was accompanied by widespread magmatic activity, inferred to be related to the impingement of the Iceland mantle plume on the base of the continental lithosphere. Regionally, magma migration occurred in at least two pulses: 62-59 Ma (main initial phase) and 57-54 Ma (continental break-up phase). Wide-angle seismic experiments indicate the presence of a laccolith-like "high-velocity body" (HVB) in the lower crust beneath most of the outer Voring Basin with P-wave velocities (Vp 7.1-7.4 km/s) characteristic of basaltic igneous rocks, overlying typical mantle rocks with Vp of over 8 km/s. The HVB locally reaches 8 km thickness and at break-up (54 Ma) measured 300 km x 500 km - corresponding to a volume of 450,000 cubic km of basaltic magma. It is interpreted as a magmatic underplate formed over a period of several million years as rising basaltic magmas ponded at the Moho at their level of neutral buoyancy. A laterally extensive sill complex (1000 m thick) occurs at the interface between thinned crystalline basement and the overlying Mesozoic sedimentary sequence. This is interpreted as one of the main intra-crustal magma storage reservoirs and is the most

  1. 3D seismic analysis of the Collyhurst Sandstone: implications for CO2 sequestration in the East Irish Sea Basin

    NASA Astrophysics Data System (ADS)

    Gamboa, Davide; Williams, John; Kirk, Karen; Gent, Christopher; Bentham, Michelle; Fellgett, Mark; Schofield, David

    2016-04-01

    Carbon Capture and Storage (CCS) is a vital technology towards low-carbon energy resources and the mitigation of global warming trends induced by rising CO2 levels in the atmosphere. The East Irish Sea Basin (EISB) is a key area for CCS in the western UK, having high CO2 storage potentials in explored hydrocarbon fields and in saline aquifers within the Permo-Triassic Sherwood Sandstone Formation. However, the theoretical storage potential of the EISB could be poorly estimated as the reservoir-prone Lower Permian formations are not considered in detail by current estimations. This work aims to fill this gap, focusing on the characterisation of the Lower Permian Collyhurst Sandstone Formation as a viable storage unit. The potential for CO2 storage is estimated as the total volume/area of suitable closures that are isolated by structural traps, occurring at depths suitable for CO2 injection and containment (>800m). Detailed structural and stratigraphic interpretations were made using 3D seismic data to assess the storage potential of the Collyhurst Sandstone Formation in the southern EISB. The basin strata is compartmentalised by numerous N-S trending faults. A higher degree of compartmentalisation occurs within regional anticlines where elongated tilted blocks are observed, bound by predominantly west-dipping faults that induce a variable offset of the Collyhurst Sandstone strata. Contrastingly, higher lateral continuity of this formation is observed within graben basins were faults are less frequent and with minor offset, thus potentially creating larger storage closures. Fault dip orientation in the grabens is variable, with west and east dipping faults occurring as a function of large east-dipping listric faults. This study was complemented by the stress modelling of the interpreted faults in order to assess the risk of CO2 leakage. Analysis of borehole breakouts observed in four approximately vertical wells in the EISB suggest a maximum horizontal stress

  2. Numerical dispersion, stability, and phase-speed for 3D time-domain finite-difference seismic wave propagation algorithms

    NASA Astrophysics Data System (ADS)

    Haney, M. M.; Aldridge, D. F.; Symons, N. P.

    2005-12-01

    Numerical solution of partial differential equations by explicit, time-domain, finite-difference (FD) methods entails approximating temporal and spatial derivatives by discrete function differences. Thus, the solution of the difference equation will not be identical to the solution of the underlying differential equation. Solution accuracy degrades if temporal and spatial gridding intervals are too large. Overly coarse spatial gridding leads to spurious artifacts in the calculated results referred to as numerical dispersion, whereas coarse temporal sampling may produce numerical instability (manifest as unbounded growth in the calculations as FD timestepping proceeds). Quantitative conditions for minimizing dispersion and avoiding instability are developed by deriving the dispersion relation appropriate for the discrete difference equation (or coupled system of difference equations) under examination. A dispersion relation appropriate for FD solution of the 3D velocity-stress system of isotropic elastodynamics, on staggered temporal and spatial grids, is developed. The relation applies to either compressional or shear wave propagation, and reduces to the proper form for acoustic propagation in the limit of vanishing shear modulus. A stability condition and a plane-wave phase-speed formula follow as consequences of the dispersion relation. The mathematical procedure utilized for the derivation is a modern variant of classical von Neumann analysis, and involves a 4D discrete space/time Fourier transform of the nine, coupled, FD updating formulae for particle velocity vector and stress tensor components. The method is generalized to seismic wave propagation within anelastic and poroelastic media, as well as sound wave propagation within a uniformly-moving atmosphere. A significant extension of the approach yields a stability condition for wave propagation across an interface between dissimilar media with strong material contrast (e.g., the earth's surface, the seabed

  3. Study of iron deposit using seismic refraction and resistivity in Carajás Mineral Province, Brazil

    NASA Astrophysics Data System (ADS)

    Nogueira, Pedro Vencovsky; Rocha, Marcelo Peres; Borges, Welitom Rodrigues; Silva, Adalene Moreira; Assis, Luciano Mozer de

    2016-10-01

    This work comprises the acquisition, processing and interpretation of 2D seismic shallow refraction (P-wave) and resistivity profiles located in the iron ore deposit of N4WS, Carajás Mineral Province (CMP), northern Brazil. The geophysical methods were used to identify the boundaries of the iron ore deposit. Another objective was to evaluate the potentiality of these geophysical methods in that geological context. In order to validate the results, the geophysical lines were located to match a geological borehole line. For the seismic refraction, we used 120 channels, spaced by 10 m, in a line of 1190 m, with seven shot points. The resistivity method used in the acquisition was the electrical resistivity imaging, with pole-pole array, in order to reach greater depths. The resistivity line had a length of 1430 m, with 10 m spacing between electrodes. The seismic results produced a model with two distinct layers. Based on the velocities values, the first layer was interpreted as altered rocks, and the second layer as more preserved rocks. It was not possible to discriminate different lithologies with the seismic method inside each layer. From the resistivity results, a zone of higher resistivity (> 3937 Ω·m) was interpreted as iron ore, and a region of intermediate resistivity (from 816 to 2330 Ω·m) as altered rocks. These two regions represent the first seismic layer. On the second seismic layer, an area with intermediated resistivity values (from 483 to 2330 Ω·m) was interpreted as mafic rocks, and the area with lower resistivity (< 483 Ω·m) as jaspilite. Our results were compared with geological boreholes and show reasonable correlation, suggesting that the geophysical anomalies correspond to the main variations in composition and physical properties of rocks.

  4. Earthquake relocation using a 3D a-priori geological velocity model from the western Alps to Corsica: Implication for seismic hazard

    NASA Astrophysics Data System (ADS)

    Béthoux, Nicole; Theunissen, Thomas; Beslier, Marie-Odile; Font, Yvonne; Thouvenot, François; Dessa, Jean-Xavier; Simon, Soazig; Courrioux, Gabriel; Guillen, Antonio

    2016-02-01

    The region between the inner zones of the Alps and Corsica juxtaposes an overthickened crust to an oceanic domain, which makes difficult to ascertain the focal depth of seismic events using routine location codes and average 1D velocity models. The aim of this article is to show that, even with a rather lose monitoring network, accurate routine locations can be achieved by using realistic 3D modelling and advanced location techniques. Previous earthquake tomography studies cover the whole region with spatial resolutions of several tens of kilometres on land, but they fail to resolve the marine domain due to the absence of station coverage and sparse seismicity. To overcome these limitations, we first construct a 3D a-priori P and S velocity model integrating known geophysical and geological information. Significant progress has been achieved in the 3D numerical modelling of complex geological structures by the development of dedicated softwares (e.g. 3D GeoModeller), capable at once of elaborating a 3D structural model from geological and geophysical constraints and, possibly, of refining it by inversion processes (Calcagno et al., 2008). Then, we build an arrival-time catalogue of 1500 events recorded from 2000 to 2011. Hypocentres are then located in this model using a numerical code based on the maximum intersection method (Font et al., 2004), updated by Theunissen et al. (2012), as well as another 3D location technique, the NonLinLoc software (Lomax and Curtis, 2001). The reduction of arrival-time residuals and uncertainties (dh, dz) with respect to classical 1D locations demonstrates the improved accuracy allowed by our approach and confirms the coherence of the 3D geological model built and used in this study. Our results are also compared with previous works that benefitted from the installation of dense temporary networks surrounding the studied epicentre area. The resulting 3D location catalogue allows us to improve the regional seismic hazard assessment

  5. Characterization of fracture reservoirs using static and dynamic data: From sonic and 3D seismic to permeability distribution. Annual report, March 1, 1996--February 28, 1997

    SciTech Connect

    Parra, J.O.; Collier, H.A.; Owen, T.E.

    1997-06-01

    In low porosity, low permeability zones, natural fractures are the primary source of permeability which affect both production and injection of fluids. The open fractures do not contribute much to porosity, but they provide an increased drainage network to any porosity. They also may connect the borehole to remote zones of better reservoir characteristics. An important approach to characterizing the fracture orientation and fracture permeability of reservoir formations is one based on the effects of such conditions on the propagation of acoustic and seismic waves in the rock. The project is a study directed toward the evaluation of acoustic logging and 3D-seismic measurement techniques as well as fluid flow and transport methods for mapping permeability anisotropy and other petrophysical parameters for the understanding of the reservoir fracture systems and associated fluid dynamics. The principal application of these measurement techniques and methods is to identify and investigate the propagation characteristics of acoustic and seismic waves in the Twin Creek hydrocarbon reservoir owned by Union Pacific Resources (UPR) and to characterize the fracture permeability distribution using production data. This site is located in the overthrust area of Utah and Wyoming. UPR drilled six horizontal wells, and presently UPR has two rigs running with many established drill hole locations. In addition, there are numerous vertical wells that exist in the area as well as 3D seismic surveys. Each horizontal well contains full FMS logs and MWD logs, gamma logs, etc.

  6. A crustal structure study of Jordan derived from seismic refraction data

    NASA Astrophysics Data System (ADS)

    El-Isa, Z.; Mechie, J.; Prodehl, C.; Makris, J.; Rihm, R.

    1987-07-01

    The interpretation of a deep seismic refraction study in Jordan, performed in May 1984, shows that much of the country is underlain by continental crust, 32-35 km thick, and normal mantle with a velocity of 8.0-8.2 km/s. In the Aqaba region, southwest and central Jordan, east of Wadi Araba, the crustal thickness is of the order of 32-35 km, while in the Amman region it is not less than 35 km. In southeast Jordan the crust thickens to at least 37 km in what is probably the transition to the Arabian Shield type of crust. The boundaries between the upper and lower crust at about 20 km depth and the lower crust and uppermost mantle are probably transition zones. The upper crystalline crust has velocities of 5.8-6.5 km/s while the lower crust has velocities greater than or around 6.65 km/s. While the crystalline basement is exposed in southwest Jordan and is at a depth of 2-2.5 km north of Amman, it is at a depth of not less than 5 km in central Jordan. A comparison of the crustal type and structure of Jordan and the adjacent Dead Sea rift with that of the Black Forest and the Rhine valley yields a striking resemblance. The situation of the Jordan-Dead Sea rift is explained in terms of the continental crust of Arabia rifting in preference to the thin (?oceanic) crust of the Mediterranean Sea.

  7. Seismic-refraction measurements of crustal structure between Nevada Test Site and Ludlow, California

    USGS Publications Warehouse

    Gibbs, J.F.; Roller, J.C.

    1964-01-01

    Seismic-refraction measurements from nuclear and chemical explosions were made along a line from the Nevada Test Site (NTS) to Ludlow, California, and additional recordings from nuclear explosions were made southward toward Calexico, California. The time of first arrivals from the Ludlow shotpoint is expressed as T0 = 0.00 + Δ/2.50 (assumed), T1 = 1.00 + Δ6.10, T2 = 2.81 + Δ/6.80, and T3 = 5.48 + ~7.76, where T is in seconds and distance Δ is in km. First arrival times from NTS fit the lines T1 = 0.74 + Δ/6.10, T2 = 2.81 + Δ/6.80 (assumed), T3 = 6.70 + Δ/8.04 to a distance of 265 km, beyond 265 km T3 = 5.83 + Δ/7.75. The difference in the apparent velocities of the Pn (T3) arrival is caused by variations in the dip of the Mohorovicic discontinuity. The thickness of the successive layers at NTS are H0 s 1.0 km (V0 ~ 2.5 km/sec), H1 = 13 km (v1 = 6.1 km/sec), and H2 = 20 km (v2 = 6.8 km/ sec); the total crustal thickness is 34 km. The successive crustal layers at Ludlow have a thickness of H0 = 1.4 km, H1 = 13 km, and H2 = 13 km; the total crustal thickness is 27 km.

  8. Deep structure of Porcupine Basin and nature of the Porcupine Median Ridge from seismic refraction tomography

    NASA Astrophysics Data System (ADS)

    Watremez, L.; Chen, C.; Prada, M.; Minshull, T. A.; O'Reilly, B.; Reston, T. J.; Wagner, G.; Gaw, V.; Klaeschen, D.; Shannon, P.

    2015-12-01

    The Porcupine Basin is a narrow V-shaped failed rifted basin located offshore SW Ireland. It is of Permo-Triassic to Cenozoic age, with the main rifting phase in the Late Jurassic to Early Cretaceous. Porcupine Basin is a key study area to learn about the processes of continental extension and to understand the thermal history of this rifted basin. Previous studies show increasing stretching factors, from less than 1.5 to the North to more than 6 to the South. A ridge feature, the Porcupine Median Ridge, has been identified in the middle of the southernmost part of the basin. During the last three decades, this ridge has been successively interpreted as a volcanic structure, a diapir of partially serpentinized mantle, or a block of continental crust. Its nature still remains debated today. In this study, we use arrival times from refractions and wide-angle reflections in the sedimentary, crustal and mantle layers to image the crustal structure of the thinnest part of the basin, the geometry of the continental thinning from margin to margin, and the Porcupine Median Ridge. The final velocity model is then compared with coincident seismic reflection data. We show that (1) the basin is asymmetric, (2) P-wave velocities in the uppermost mantle are lower than expected for unaltered peridotites, implying upper-mantle serpentinisation, (3) the nature of Porcupine Median Ridge is probably volcanic, and (4) the amount of thinning is greater than shown in previous studies. We discuss the thermal implications of these results for the evolution of this rift system and the processes leading to the formation of failed rifts. This project is funded by the Irish Shelf Petroleum Studies Group (ISPSG) of the Irish Petroleum Infrastructure Programme Group 4.

  9. Seismic-refraction measurements of crustal structure between Santa Monica Bay and Lake Mead

    USGS Publications Warehouse

    Roller, John C.; Healy, John H.

    1963-01-01

    A reversed seismic-refraction profile was recorded between Santa Monica Bay, California, and Lake Mead, Nevada, during November 1961. Depth to the Mohorovicic discontinuity was determined to be approximately 29 km at Santa Monica Bay, 36 km under the Transverse Ranges, 26 km under the Mojave Desert, and 30 km at Lake Mead. Prominent events on the seismograms in the distance range 30 to 150 km are interpreted as reflections from the Mohorovicic discontinuity and from a crustal layer of intermediate velocity. These reflected events are used to make a detailed interpretation of crustal structure. The velocity of compressional waves in the mantle immediately below the Mohorovicic discontinuity was determined to be 7.8 km/sec. The velocity of compressional waves in the intermediate layer is near 7.0 km/sec. The apparent velocity of the direct arrival in the crustal rocks near the surface is 6.l km/sec north-east of Santa Monica Bay, and 6.1 km/sec southwest of Lake Mead. The higher apparent velocity for the direct arrival from Santa Monica Bay seems to be the result of thinning toward the east of low-velocity rocks near the surface. These low-velocity near-surface rocks are Cenozoic sedimentary rocks and fractured and weathered granitic and metamorphic rocks. The velocity of Sg was determined to be 3.4. km/sec near Lake Mead. A prominent phase with apparent velocity of 6.3 to 6.4 km/sec was recorded at distances beyond 200 km. This phase is identified as P and is interpreted as a reflection from the intermediate layer. Amplitude measurements support the conclusion that the P phase is a reflected arrival.

  10. Comparison of P- and S-wave velocity profiles obtained from surface seismic refraction/reflection and downhole data

    USGS Publications Warehouse

    Williams, R.A.; Stephenson, W.J.; Odum, J.K.

    2003-01-01

    High-resolution seismic-reflection/refraction data were acquired on the ground surface at six locations to compare with near-surface seismic-velocity downhole measurements. Measurement sites were in Seattle, WA, the San Francisco Bay Area, CA, and the San Fernando Valley, CA. We quantitatively compared the data in terms of the average shear-wave velocity to 30-m depth (Vs30), and by the ratio of the relative site amplification produced by the velocity profiles of each data type over a specified set of quarter-wavelength frequencies. In terms of Vs30, similar values were determined from the two methods. There is <15% difference at four of the six sites. The Vs30 values at the other two sites differ by 21% and 48%. The relative site amplification factors differ generally by less than 10% for both P- and S-wave velocities. We also found that S-wave reflections and first-arrival phase delays are essential for identifying velocity inversions. The results suggest that seismic reflection/refraction data are a fast, non-invasive, and less expensive alternative to downhole data for determining Vs30. In addition, we emphasize that some P- and S-wave reflection travel times can directly indicate the frequencies of potentially damaging earthquake site resonances. A strong correlation between the simple S-wave first-arrival travel time/apparent velocity on the ground surface at 100 m offset from the seismic source and the Vs30 value for that site is an additional unique feature of the reflection/refraction data that could greatly simplify Vs30 determinations. ?? 2003 Elsevier Science B.V. All rights reserved.

  11. Galicia3D seismic volume: Connections between the western termination of the S reflector and eastern termination of the Peridotite Ridge

    NASA Astrophysics Data System (ADS)

    Sawyer, Dale; Jordan, Brian; Morgan, Julia; Shillington, Donna; Reston, Timothy; Ranero, Cesar

    2015-04-01

    In June thru September, 2013, a 3D reflection and a long offset seismic experiment were conducted at the Galicia rifted margin by investigators from the US, UK, Germany, and Spain. The 3D multichannel experiment covered 64 km by 20 km (1280 km2), using the RV Marcus Langseth. Four streamers 6 km long were deployed at 12.5 m hydrophone channel spacing. The streamers were 200 m apart. Two airgun arrays, each 3300 cu in, were fired alternately every 37.5 m, to collectively yield a 400 m wide sail line consisting of 8 CMP lines at 50 m spacing. We draw attention to the region from the Peridotite Ridge, PR, (on the west) and the western terminus of the S reflector (on the east). The S reflector is generally thought to separate continental crust and pre- and syn-rift sediment above, and serpentinized upper mantle below. In 2D and 3D seismic reflection data, the S reflector is very bright, generally horizontal, and is terminated very abruptly at the western end. The latter is particularly clear in the 3D volume. It is about 10-15 km wide between the end of the S reflector and the midpoint of the PR. In this interval, there appear to be fault bounded blocks that may be either continental crust or pre- or syn-rift sediments. The PR is a virtually straight, N-S ridge, without apparent fault offsets. The crest of the PR is at about 4800 mbsl at the S extent and is at 6070 mbsl at the N extent of the 3D volume. The crest is approximately linear in map view or N-S extent. Both sides, East and West of the PR, appear to show landslides and other mass wasting during the late stage of the syn-rifting interval. The PR rarely shows internal seismic structure in 2D and 3D. Most importantly, under the basin to the east of the PR there are substantially more recognizable structures connecting the S reflector and the PR. These were much less interpretable in previous 2D seismic profiles.

  12. Ryukyu Subduction Zone: 3D Geodynamic Simulations of the Effects of Slab Shape and Depth on Lattice-Preferred Orientation (LPO) and Seismic Anisotropy

    NASA Astrophysics Data System (ADS)

    Tarlow, S.; Tan, E.; Billen, M. I.

    2015-12-01

    At the Ryukyu subduction zone, seismic anisotropy observations suggest that there may be strong trench-parallel flow within the mantle wedge driven by complex 3D slab geometry. However, previous simulations have either failed to account for 3D flow or used the infinite strain axis (ISA) approximation for LPO, which is known to be inaccurate in complex flow fields. Additionally, both the slab depth and shape of the Ryukyu slab are contentious. Development of strong trench-parallel flow requires low viscosity to decouple the mantle wedge from entrainment by the sinking slab. Therefore, understanding the relationship between seismic anisotropy and the accompanying flow field will better constrain the material and dynamic properties of the mantle near subduction zones. In this study, we integrate a kinematic model for calculation of LPO (D-Rex) into a buoyancy-driven, instantaneous 3D flow simulation (ASPECT), using composite non-Newtonian rheology to investigate the dependence of LPO on slab geometry and depth at the Ryukyu Trench. To incorporate the 3D flow effects, the trench and slab extends from the southern tip of Japan to the western edge of Taiwan and the model region is approximately 1/4 of a spherical shell extending from the surface to the core-mantle boundary. In the southern-most region we vary the slab depth and shape to test for the effects of the uncertainties in the observations. We also investigate the effect of adding locally hydrated regions above the slab that affect both the mantle rheology and development of LPO through the consequent changes in mantle flow and dominate (weakest) slip system. We characterize how changes in the simulation conditions affect the LPO within the mantle wedge, subducting slab and sub-slab mantle and relate these to surface observations of seismic anisotropy.

  13. Data report for seismic refraction surveys conducted from 1980 to 1982 in the Livermore Valley and the Santa Cruz Mountains, California

    USGS Publications Warehouse

    Williams, Angela J.; Brocher, Thomas M.; Mooney, Walter D.; Boken, Annette

    1999-01-01

    We provide documentation for two seismic refraction profiles acquired by the U.S. Geological Survey in the San Francisco Bay area between 1980 and 1982 in Livermore Valley and the Santa Cruz Mountains. We also include the waveforms and travel times from five aftershocks of the April 1980 Livermore earthquake that were recorded on temporary seismic stations and that have not been published. Although seismic refraction profiles from the 1980 Livermore study have been published, none of the other data for this experiment, including shot times and locations, receiver locations, data quality, and travel times, have been reported. Similarly, such data from the 1981 to 1982 seismic refraction survey in the Santa Cruz Mountains included here have not been published. The first-arrival travel times from these profiles are reported in the hope that they can be used for three-dimensional velocity models in the San Francisco Bay area, particularly for the Livermore Valley and Santa Cruz Mountains.

  14. Determination of porosity and facies trends in a complex carbonate reservoir, by using 3-D seismic, borehole tools, and outcrop geology

    SciTech Connect

    Zacharakis, T.G. Jr.; Comet, J.N.; Murillo, A.A.

    1996-08-01

    Mesozoic carbonate reservoirs are found in the Mediterranean Sea, off the east coast of Spain. A wide variation of porosities are found in the core samples and logs: vuggy, breccia, fractures, and cavern porosity. In addition, complex Tertiary carbonate geometries include olistostromes, breccia bodies, and reef buildups, which are found on top of Mesozoic carbonates. Predicting the porosity trends within these oil productive reservoirs requires an understanding of how primary porosity was further enhanced by secondary processes, including fractures, karstification, and dolomitization in burial conditions. Through an extensive investigation of field histories, outcrop geology, and seismic data, a series of basic reservoir styles have been identified and characterized by well log signature and seismic response. The distribution pattern of the different reservoirs styles is highly heterogeneous, but by integrating subsurface data and outcrop analogs, it is possible to distinguish field-scale and local patterns of both vertical and local variations in reservoir properties. Finally, it is important to quantify these reservoir properties through the study of seismic attributes, such as amplitude variations, and log responses at the reservoir interval. By incorporating 3-D seismic data, through the use of seismic inversion, it is possible to predict porosity trends. Further, the use of geostatistics can lead to the prediction of reservoir development within the carbonate facies.

  15. The Galicia 3D experiment: an Introduction.

    NASA Astrophysics Data System (ADS)

    Reston, Timothy; Martinez Loriente, Sara; Holroyd, Luke; Merry, Tobias; Sawyer, Dale; Morgan, Julia; Jordan, Brian; Tesi Sanjurjo, Mari; Alexanian, Ara; Shillington, Donna; Gibson, James; Minshull, Tim; Karplus, Marianne; Bayracki, Gaye; Davy, Richard; Klaeschen, Dirk; Papenberg, Cord; Ranero, Cesar; Perez-Gussinye, Marta; Martinez, Miguel

    2014-05-01

    In June and July 2013, scientists from 8 institutions took part in the Galicia 3D seismic experiment, the first ever crustal -scale academic 3D MCS survey over a rifted margin. The aim was to determine the 3D structure of a critical portion of the west Galicia rifted margin. At this margin, well-defined tilted fault blocks, bound by west-dipping faults and capped by synrift sediments are underlain by a bright reflection, undulating on time sections, termed the S reflector and thought to represent a major detachment fault of some kind. Moving west, the crust thins to zero thickness and mantle is unroofed, as evidence by the "Peridotite Ridge" first reported at this margin, but since observed at many other magma-poor margins. By imaging such a margin in detail, the experiment aimed to resolve the processes controlling crustal thinning and mantle unroofing at a type example magma poor margin. The experiment set out to collect several key datasets: a 3D seismic reflection volume measuring ~20x64km and extending down to ~14s TWT, a 3D ocean bottom seismometer dataset suitable for full wavefield inversion (the recording of the complete 3D seismic shots by 70 ocean bottom instruments), the "mirror imaging" of the crust using the same grid of OBS, a single 2D combined reflection/refraction profile extending to the west to determine the transition from unroofed mantle to true oceanic crust, and the seismic imaging of the water column, calibrated by regular deployment of XBTs to measure the temperature structure of the water column. We collected 1280 km2 of seismic reflection data, consisting of 136533 shots recorded on 1920 channels, producing 260 million seismic traces, each ~ 14s long. This adds up to ~ 8 terabytes of data, representing, we believe, the largest ever academic 3D MCS survey in terms of both the area covered and the volume of data. The OBS deployment was the largest ever within an academic 3D survey.

  16. Use of 3D Seismic Azimuthal Iso-Frequency Volumes for the Detection and Characterization of High Porosity/Permeability Zones in Carbonate Reservoirs

    NASA Astrophysics Data System (ADS)

    Toelle, Brian E.

    Among the most important properties controlling the production from conventional oil and gas reservoirs is the distribution of porosity and permeability within the producing geologic formation. The geometry of the pore space within these reservoirs, and the permeability associated with this pore space geometry, impacts not only where production can occur and at what flow rates but can also have significant influence on many other rock properties. Zones of high matrix porosity can result in an isotropic response for certain reservoir properties whereas aligned porosity/permeability, such as open, natural fracture trends, have been shown to result in reservoirs being anisotropic in many properties. The ability to identify zones within a subsurface reservoir where porosity/permeability is significantly higher and to characterize them according to their geometries would be of great significance when planning where new boreholes, particularly horizontal boreholes, should be drilled. The detection and characterization of these high porosity/permeability zones using their isotropic and anisotropic responses may be possible through the analysis of azimuthal (also referred to as azimuth-limited) 3D seismic volumes. During this study the porosity/permeability systems of a carbonate, pinnacle reef within the northern Michigan Basin undergoing enhanced oil recovery were investigated using selected seismic attributes extracted from azimuthal 3D seismic volumes. Based on the response of these seismic attributes an interpretation of the geometry of the porosity/permeability system within the reef was made. This interpretation was supported by well data that had been obtained during the primary production phase of the field. Additionally, 4D seismic data, obtained as part of the CO2 based EOR project, supported reservoir simulation results that were based on the porosity/permeability interpretation.

  17. An evaluation of applicability of seismic refraction method in identifying shallow archaeological features A case study at archaeological site

    NASA Astrophysics Data System (ADS)

    Jahangardi, Morteza; Hafezi Moghaddas, Naser; Keivan Hosseini, Sayyed; Garazhian, Omran

    2015-04-01

    We applied the seismic refraction method at archaeological site, Tepe Damghani located in Sabzevar, NE of Iran, in order to determine the structures of archaeological interests. This pre-historical site has special conditions with respect to geographical location and geomorphological setting, so it is an urban archaeological site, and in recent years it has been used as an agricultural field. In spring and summer of 2012, the third season of archaeological excavation was carried out. Test trenches of excavations in this site revealed that cultural layers were often disturbed adversely due to human activities such as farming and road construction in recent years. Conditions of archaeological cultural layers in southern and eastern parts of Tepe are slightly better, for instance, in test trench 3×3 m²1S03, third test trench excavated in the southern part of Tepe, an adobe in situ architectural structure was discovered that likely belongs to cultural features of a complex with 5 graves. After conclusion of the third season of archaeological excavation, all of the test trenches were filled with the same soil of excavated test trenches. Seismic refraction method was applied with12 channels of P geophones in three lines with a geophone interval of 0.5 meter and a 1.5 meter distance between profiles on test trench 1S03. The goal of this operation was evaluation of applicability of seismic method in identification of archaeological features, especially adobe wall structures. Processing of seismic data was done with the seismic software, SiesImager. Results were presented in the form of seismic section for every profile, so that identification of adobe wall structures was achieved hardly. This could be due to that adobe wall had been built with the same materials of the natural surrounding earth. Thus, there is a low contrast and it has an inappropriate effect on seismic processing and identifying of archaeological features. Hence the result could be that application of

  18. A high-resolution seismic reflection/refraction study of the Chugach- Peninsular terrane boundary, southern Alaska

    USGS Publications Warehouse

    Brocher, T.M.; Fisher, M.A.; Geist, E.L.; Christensen, N.I.

    1989-01-01

    We present results from a high-resolution seismic refraction analysis of the shallow (approximately 2 km) crustal structure along the 107-km-long Trans-Alaska Crustal Transect Chugach reflection line in southern Alaska and a comparison with laboratory measurements of field samples. The refraction analysis includes the two-dimensional interpretation of several thousand first- and secondary-arrival travel times digitized from 1024-channel split-spread common shot gathers. The velocity model derived from this analysis better defines the location and geometry of terrane boundaries than does the normal incidence reflection section and agrees well with surface mapping of lithologies. Furthermore, the model predicts travel times within 100 ms of the reflection times recorded from the base of the Quaternary on the Chugach reflection section. -from Authors

  19. Seismic refraction profile, Kingdom of Saudi Arabia: field operations, instrumentation, and initial results

    USGS Publications Warehouse

    Blank, H. Richard; Healy, J.H.; Roller, John; Lamson, Ralph; Fisher, Fred; McClearn, Robert; Allen, Steve

    1979-01-01

    In February 1978 a seismic deep-refraction profile was recorded by the USGS along a 1000-km line across the Arabian Shield in western Saudi Arabia. The line begins in Paleozoic and Mesozoic cover rocks near Riyadh on the Arabian Platform, leads southwesterly across three major Precambrian tectonic provinces, traverses Cenozoic rocks of the coastal plain near Jizan (Tihamat Asir), and terminates at the outer edge of the Farasan Bank in the southern Red Sea. More than 500 surveyed recording sites were occupied, including 19 in the Farasan Islands. Six shot points were used--five on land, with charges placed mostly below water table in drill holes, and one at sea, with charges placed on the sea floor and fired from a ship. The total charge consumed was slightly in excess of 61 metric tons in 21 discrete firings. Seismic energy was recorded by means of a set of 100 newly developed portable seismic stations. Each station consists of a standard 2-Hz vertical geophone coupled to a self-contained analog recording instrument equipped with a magnetic-tape cassette. The stations were deployed in groups of 20 by five observer teams, each generally consisting of two scientist-technicians and a surveyor-guide. On the day prior to deployment, the instruments were calibrated and programmed for automatic operation by means of a specially designed device called a hand-held tester. At each of ten pre-selected recording time windows on a designated firing day, the instruments were programmed to turn on, stabilize, record internal calibration signals, record the seismic signals at three levels of amplification, and then deactivate. After the final window in the firing sequence, all instruments were retrieved and their data tapes removed for processing. A specially designed, field tape- dubbing system was utilized at shot point camps to organize and edit data recorded on the cassette tapes. The main functions of this system are to concatenate all data from each shot on any given day

  20. A high-resolution 3D seismic velocity model of the 2010 Mw 8.8 Maule, Chile earthquake rupture zone using land & OBS networks

    NASA Astrophysics Data System (ADS)

    Hicks, S. P.; Rietbrock, A.; Ryder, I. M.; Miller, M.; Lee, C.

    2013-12-01

    Knowledge of seismic properties along a subduction megathrust can shed light on the composition and structure of rocks along the fault. By comparing seismic velocity structure with models of interseismic locking, co-seismic slip and afterslip, we can begin to understand how physical properties may affect fault dynamics throughout the subduction seismic cycle. The Maule earthquake, which hit the coast of central Chile in 2010, is the 6th largest earthquake ever recorded, rupturing a 500 x 80 km area of the Chilean megathrust. Published models demonstrate a complex bilateral rupture, with most co-seismic slip occurring to the north of the mainshock epicentre, although significant slip likely stopped short of the trench and the continental Moho. Here, we show a new high-resolution 3D velocity model (vp and vp/vs ratio) of the central Chilean margin Our velocity model is based on manually picked P- and S-wave arrival times from 670 aftershocks recorded by the International Maule Aftershock Deployment (IMAD) network. Seismic properties of the marine forearc are poorly understood in subduction zones, but by incorporating picks from two ocean-bottom seismometer (OBS) networks, we can resolve the velocity structure of the megathrust as far as the trench. In total, the catalogue used for the tomographic inversion yields a total of ~50,000 high quality P- and S-wave picks. We analyse the quality of our model by analysis of the resolution matrix and by testing characteristic models. The 3D velocity model shows the main structures associated within a subduction forearc: the marine forearc basin (vp < 6.0 km/s), continental mantle (vp > 7.5 km/s), and subducting oceanic crust (vp ~ 7.7 km/s). The plate interface is well defined by relocated aftershock seismicity. P-wave velocities along the megathrust range from 6.5 km/s beneath the marine forearc to 7.7 km/s at the intersection of the megathrust with the continental Moho. We infer several high vp anomalies within the South

  1. The crustal structure of the axis of the Great Valley, California, from seismic refraction measurements

    USGS Publications Warehouse

    Holbrook, W.S.; Mooney, W.D.

    1987-01-01

    In 1982 the U.S. Geological Survey collected six seismic refraction profiles in the Great Valley of California: three axial profiles with a maximum shot-to-receiver offset of 160 km, and three shorter profiles perpendicular to the valley axis. This paper presents the results of two-dimensional raytracing and synthetic seismogram modeling of the central axial profile. The crust of the central Great Valley is laterally heterogeneous along its axis, but generally consists of a sedimentary section overlying distinct upper, middle, and lower crustal units. The sedimentary rocks are 3-5 km thick along the profile, with velocities increasing with depth from 1.6 to 4.0 km/s. The basement (upper crust) consists of four units: 1. (1) a 1.0-1.5 km thick layer of velocity 5.4-5.8 km/s, 2. (2) a 3-4 km thick layer of velocity 6.0-6.3 km/s, 3. (3) a 1.5-3.0 km thick layer of velocity 6.5-6.6 km/s, and 4. (4) a laterally discontinuous, 1.5 km thick layer of velocity 6.8-7.0 km/s. The mid-crust lies at 11-14 km depth, is 5-8 km thick, and has a velocity of 6.6-6.7 km/s. On the northwest side of our profile the mid-crust is a low-velocity zone beneath the 6.8-7.0 km/s lid. The lower crust lies at 16-19 km depth, is 7-13 km thick, and has a velocity of 6.9-7.2 km/s. Crustal thickness increases from 26 to 29 km from NW to SE in the model. Although an unequivocal determination of crustal composition is not possible from P-wave velocities alone, our model has several geological and tectonic implications. We interpret the upper 7 km of basement on the northwest side of the profile as an ophiolitic fragment, since its thickness and velocity structure are consistent with that of oceanic crust. This fragment, which is not present 10-15 km to the west of the refraction profile, is probably at least partially responsible for the Great Valley gravity and magnetic anomalies, whose peaks lie about 10 km east of our profile. The middle and lower crust are probably gabbroic and the product of

  2. Using Seismic Refraction and Ground Penetrating Radar (GPR) to Characterize the Valley Fill in Beaver Meadows, Rocky Mountain National Park

    NASA Astrophysics Data System (ADS)

    Kramer, N.; Harry, D. L.; Wohl, E. E.

    2010-12-01

    This study is one of the first to use near surface geophysical techniques to characterize the subsurface stratigraphy in a high alpine, low gradient valley with a past glacial history and to obtain a preliminary grasp on the impact of Holocene beaver activity. Approximately 1 km of seismic refraction data and 5 km of GPR data were collected in Beaver Meadows, Rocky Mountain National Park. An asymmetric wedge of sediment ranging in depth from 0-20 m transverse to the valley profile was identified using seismic refraction. Complementary analysis of the GPR data suggests that the valley fill can be subdivided into till deposited during the Pleistocene glaciations and alluvium deposited during the Holocene. Two main facies were identified in the GPR profiles through pattern recognition. Facie Fd, which consists of chaotic discontinuous reflectors with an abundance of diffractions, is interpreted to be glacial till. Facie Fc, which is a combination of packages of complex slightly continuous reflectors interfingered with continuous horizontal to subhorizontal reflectors, is interpreted to be post-glacial alluvium and includes overbank, pond and in-channel deposits. Fc consistently overlies Fd throughout the study area and is no more than 7 m thick in the middle of the valley. The thickness of Holocene sedimentation (<7 m) is much less than the total amount of valley fill identified in the seismic refraction survey (0-20 m). A subfacie of Fc, Fch, which has reflectors with long periods was identified within Fc and is interpreted to be ponded sediments. The spatial distribution of facie Fch, along with: slight topographical features resembling buried beaver dams, a high abundance of fine sediment including silts and clays, historical records of beavers, and the name "Beaver Meadows" all suggest that Holocene beaver activity played a large role in sediment accumulation at this site, despite the lack of surficial relict beaver dams containing wood.

  3. pySeismicFMM: Python based travel time calculation in regular 2D and 3D grids in Cartesian and geographic coordinates using Fast Marching Method

    NASA Astrophysics Data System (ADS)

    Polkowski, Marcin

    2016-04-01

    Seismic wave travel time calculation is the most common numerical operation in seismology. The most efficient is travel time calculation in 1D velocity model - for given source, receiver depths and angular distance time is calculated within fraction of a second. Unfortunately, in most cases 1D is not enough to encounter differentiating local and regional structures. Whenever possible travel time through 3D velocity model has to be calculated. It can be achieved using ray calculation or time propagation in space. While single ray path calculation is quick it is complicated to find the ray path that connects source with the receiver. Time propagation in space using Fast Marching Method seems more efficient in most cases, especially when there are multiple receivers. In this presentation a Python module pySeismicFMM is presented - simple and very efficient tool for calculating travel time from sources to receivers. Calculation requires regular 2D or 3D velocity grid either in Cartesian or geographic coordinates. On desktop class computer calculation speed is 200k grid cells per second. Calculation has to be performed once for every source location and provides travel time to all receivers. pySeismicFMM is free and open source. Development of this tool is a part of authors PhD thesis. National Science Centre Poland provided financial support for this work via NCN grant DEC-2011/02/A/ST10/00284.

  4. Refraction seismic studies in the Miami River, Whitewater River, and Mill Creek valleys, Hamilton and Butler Counties, Ohio

    USGS Publications Warehouse

    Watkins, Joel S.

    1963-01-01

    Between September 17 and November 9, 1962, the U.S. Geological Survey, in cooperation with Ohio Division of Water, Miami Conservancy District, and c,ty of Cincinnati, Ohio, co.,:ducted a refraction seismic study in Hamilton and Butler Counties, southwest Ohio. The area lies between Hamilton, Ohio, and the Ohio River and includes a preglacial valley now occupied by portions of the Miami River, Whitewater River, and Mill Creek. The valley is partially filled with glacial debris which yields large quantities of good-quality water. The object of the study was to determine the thickness of these glacial deposits and the shape of the preglacial valley.

  5. Saudi Arabian seismic-refraction profile: A traveltime interpretation of crustal and upper mantle structure

    USGS Publications Warehouse

    Mooney, W.D.; Gettings, M.E.; Blank, H.R.; Healy, J.H.

    1985-01-01

    The crustal and upper mantle compressional-wave velocity structure across the southwestern Arabian Shield has been investigated by a 1000-km-long seismic refraction profile. The profile begins in Mesozoic cover rocks near Riyadh on the Arabian Platform, trends southwesterly across three major Precambrian tectonic provinces, traverses Cenozoic rocks of the coastal plain near Jizan, and terminates at the outer edge of the Farasan Bank in the southern Red Sea. More than 500 surveyed recording sites were occupied, and six shot points were used, including one in the Red Sea. Two-dimensional ray-tracing techniques, used to analyze amplitude-normalized record sections indicate that the Arabian Shield is composed, to first order, of two layers, each about 20 km thick, with average velocities of about 6.3 km/s and 7.0 km/s, respectively. West of the Shield-Red Sea margin, the crust thins to a total thickness of less than 20 km, beyond which the Red Sea shelf and coastal plain are interpreted to be underlain by oceanic crust. A major crustal inhomogeneity at the northeast end of the profile probably represents the suture zone between two crustal blocks of different composition. Elsewhere along the profile, several high-velocity anomalies in the upper crust correlate with mapped gneiss domes, the most prominent of which is the Khamis Mushayt gneiss. Based on their velocities, these domes may constitute areas where lower crustal rocks have been raised some 20 km. Two intracrustal reflectors in the center of the Shield at 13 km depth probably represent the tops of mafic intrusives. The Mohorovic??ic?? discontinuity beneath the Shield varies from a depth of 43 km and mantle velocity of 8.2 km/s in the northeast to a depth of 38 km and mantle velocity of 8.0 km/s depth in the southwest near the Shield-Red Sea transition. Two velocity discontinuities occur in the upper mantle, at 59 and 70 km depth. The crustal and upper mantle velocity structure of the Arabian Shield is

  6. Saudi Arabian seismic-refraction profile: A traveltime interpretation of crustal and upper mantle structure

    NASA Astrophysics Data System (ADS)

    Mooney, W. D.; Gettings, M. E.; Blank, H. R.; Healy, J. H.

    1985-02-01

    The crustal and upper mantle compressional-wave velocity structure across the southwestern Arabian Shield has been investigated by a 1000-km-long seismic refraction profile. The profile begins in Mesozoic cover rocks near Riyadh on the Arabian Platform, trends southwesterly across three major Precambrian tectonic provinces, traverses Cenozoic rocks of the coastal plain near Jizan, and terminates at the outer edge of the Farasan Bank in the southern Red Sea. More than 500 surveyed recording sites were occupied, and six shot points were used, including one in the Red Sea. Two-dimensional ray-tracing techniques, used to analyze amplitude-normalized record sections indicate that the Arabian Shield is composed, to first order, of two layers, each about 20 km thick, with average velocities of about 6.3 km/s and 7.0 km/s, respectively. West of the Shield-Red Sea margin, the crust thins to a total thickness of less than 20 km, beyond which the Red Sea shelf and coastal plain are interpreted to be underlain by oceanic crust. A major crustal inhomogeneity at the northeast end of the profile probably represents the suture zone between two crustal blocks of different composition. Elsewhere along the profile, several high-velocity anomalies in the upper crust correlate with mapped gneiss domes, the most prominent of which is the Khamis Mushayt gneiss. Based on their velocities, these domes may constitute areas where lower crustal rocks have been raised some 20 km. Two intracrustal reflectors in the center of the Shield at 13 km depth probably represent the tops of mafic intrusives. The Mohorovičić discontinuity beneath the Shield varies from a depth of 43 km and mantle velocity of 8.2 km/s in the northeast to a depth of 38 km and mantle velocity of 8.0 km/s depth in the southwest near the Shield-Red Sea transition. Two velocity discontinuities occur in the upper mantle, at 59 and 70 km depth. The crustal and upper mantle velocity structure of the Arabian Shield is interpreted

  7. Joint 3D seismic travel time and full channel electrical resistivity inversion with cross gradient structure constraint

    NASA Astrophysics Data System (ADS)

    Gao, J.; Zhang, H.

    2015-12-01

    Near surface geophysical exploration for the purpose of engineering design or construction For this reason, geophysical imaging demands a higher resolution and a better quantitative interpretation. Seismic travel time tomography and direct current resistivity tomography are two main methods for the near surface survey. Because of the limited coverage of observation system and the complex physical relationship between physical parameters and observations, individual geophysical method suffers issues of non-uniqueness and resolution limitation to some degree. We have developed a joint inversion method to combine seismic travel time tomography and full channel resistivity tomography. For the full channel resistivity survey, it uses two electrodes for power supply and all the other electrodes for recording. Compared with the traditional resistivity method, it collects more data and has a better model converge. Our joint inversion strategy relies on the structure constraint enforced through minimizing cross gradients between seismic velocity and resistivity models (Gallardo, 2003). For resistivity tomography, sensitivity kernels are obtained through the adjoint method by solving the electrostatic field equation with the finite-difference method. For seismic travel time tomography, ray paths and travel times are calculated using the fast marching method. We have tested our joint inversion method for a 2D cross-hole problem where two small zones with high and low velocity/resistivity anomalies. Seismic/electrical sources/receivers are installed in two boreholes. For separate seismic inversion, the smearing effect is evident and two anomaly zones are distorted and misplaced. For separate electric resistivity inversion, although two anomaly zones are positioned correctly their values are not accurate. By joint inversion, two velocity anomaly zones are clearly imaged and the smearing effect is greatly reduced. In comparison, for the resistivity model, the two anomaly zones

  8. 3D Seismic Reflection Images of An Off-Axis Melt Lens And Its Associated Upper Crust Around 9°39'N, East Pacific Rise

    NASA Astrophysics Data System (ADS)

    Han, S.; Carton, H. D.; Carbotte, S. M.; Mutter, J. C.; Canales, J.; Nedimović, M. R.

    2011-12-01

    During the 3D multi-channel seismic (MCS) survey MGL0812 aboard the R/V Langseth, several mid-crust reflectors were discovered off axis on both flanks of the East Pacific Rise from 9°35.6-57.0'N. The reversed polarity of these off-axis reflections with respect to the seafloor and Moho reflections and the high attenuation of the crust detected beneath two of them in the north suggest that they arise from melts residing at the mid-crust level outside the axial low velocity zone (Canales et al. 2010). These off-axis melt lenses (OAML) are probable sites of off-axis volcanism and potential heat sources for localized hydrothermal circulation on the ridge flanks. We focus here on a prominent OAML discovered on the eastern flank around 9°39'N. Results from 1D travel time modeling and 2D streamer tomography of downward continued shot gathers show the presence of a thinner seismic layer 2A above the center of the OAML compared with its surrounding crust. We attribute this thinning to the effects of alteration associated with localized off-axis hydrothermal circulation driven by the OAML, where precipitation of secondary minerals infills pore space within the lower basalt section, leading to increased seismic velocities and thereby converting the lowermost seismic layer 2A into seismic layer 2B. To further constrain the respective 3D geometries of the OAML and the AMC, their spatial relations, and the spatial extent and shape of the region of altered upper crust associated with the OAML, we conduct 3D processing of a small MCS grid that encompasses most of this OAML, aimed at imaging both on- and off-axis melt lens events and the base of seismic layer 2A. This grid covers an ~4 km x 24 km area centered on the ridge crest between ˜9°37.5'-40'N and extending on both flanks, within which a third order ridge axis discontinuity and two high temperature hydrothermal vents identified during Alvin dives in 1991 and 1994 are present. The data were recorded by four 468-channel

  9. 2D and 3D seismic measurements to evaluate the collapse risk of an important prehistoric cave in soft carbonate rock

    NASA Astrophysics Data System (ADS)

    Leucci, Giovanni; De Giorgi, Lara

    2015-02-01

    The southern part of the Apulia region (the Salento peninsula) has been the site of at least fifteen collapse events due to sinkholes in the last twenty years. The majority of these occurred in "soft" carbonate rocks (calcarenites). Man-made and/or natural cavities are sometimes assets of historical and archaeological significance. This paper provides a methodology for the evaluation of sinkhole hazard in "soft" carbonate rocks, combining seismic and mine engineering methods.Acase study of a natural cavity which is called Grotta delle Veneri is illustrated. For this example the approach was: i) 2D and 3D seismic methods to study the physical-mechanical characteristics of the rock mass that constitutes the roof of the cave; and ii) scaled span empirical analysis in order to evaluate the instability of the crown pillar's caves.

  10. 3D seismic interpretation of subsurface eruptive centers in a Permian large igneous province, Tazhong Uplift, central Tarim Basin, NW China

    NASA Astrophysics Data System (ADS)

    Yang, Jiangfeng; Zhu, Wenbin; Guan, Da; Zhu, Beibei; Yuan, Liansheng; Xiang, Xuemei; Su, Jinbao; He, Jingwen; Wu, Xinhui

    2015-12-01

    A 1445-km2 high-resolution 3D seismic reflection dataset is used to analyze the Permian large igneous province in the subsurface of the Tazhong area in the central Tarim Basin in northwestern China. Constrained by the synthetic seismograms of four wells, the top and base of the igneous rocks were identified in the seismic data. Seven large volcanic craters, each >10 km2 in area, have been discovered via the application of coherency and amplitude attributes. The thickness and volume of the igneous rocks were obtained by time-depth transformation. In the study area, all of the igneous rocks, with thicknesses from 120 to 1133 m, were formed by eruptions in the Early Permian. These events produced huge erupted volumes (178 km3) and multiple closely spaced volcanic edifices (<13 km). These features suggest that the study area may be the part of the eruptive center of the Permian igneous rocks in the Tarim Basin.

  11. Combined analysis of 2-D electrical resistivity, seismic refraction and geotechnical investigations for Bukit Bunuh complex crater

    NASA Astrophysics Data System (ADS)

    Azwin, I. N.; Saad, Rosli; Saidin, Mokhtar; Nordiana, M. M.; Anderson Bery, Andy; Hidayah, I. N. E.

    2015-01-01

    Interest in studying impact crater on earth has increased tremendously due to its importance in geologic events, earth inhabitant history as well as economic value. The existences of few shock metamorphism and crater morphology evidences are discovered in Bukit Bunuh, Malaysia thus detailed studies are performed using geophysical and geotechnical methods to verify the type of the crater and characteristics accordingly. This paper presents the combined analysis of 2-D electrical resistivity, seismic refraction, geotechnical SPT N value, moisture content and RQD within the study area. Three stages of data acquisition are made starting with regional study followed by detailed study on West side and East side. Bulk resistivity and p-wave seismic velocity were digitized from 2-D resistivity and seismic sections at specific distance and depth for corresponding boreholes and samples taken. Generally, Bukit Bunuh shows the complex crater characteristics. Standard table of bulk resistivity and p-wave seismic velocity against SPT N value, moisture content and RQD are produce according to geological classifications of impact crater; inside crater, rim/slumped terrace and outside crater.

  12. High-resolution gravity and seismic-refraction surveys of the Smoke Tree Wash area, Joshua Tree National Park, California

    USGS Publications Warehouse

    Langenheim, Victoria E.; Rymer, Michael J.; Catchings, Rufus D.; Goldman, Mark R.; Watt, Janet T.; Powell, Robert E.; Matti, Jonathan C.

    2016-03-02

    We describe high-resolution gravity and seismic refraction surveys acquired to determine the thickness of valley-fill deposits and to delineate geologic structures that might influence groundwater flow beneath the Smoke Tree Wash area in Joshua Tree National Park. These surveys identified a sedimentary basin that is fault-controlled. A profile across the Smoke Tree Wash fault zone reveals low gravity values and seismic velocities that coincide with a mapped strand of the Smoke Tree Wash fault. Modeling of the gravity data reveals a basin about 2–2.5 km long and 1 km wide that is roughly centered on this mapped strand, and bounded by inferred faults. According to the gravity model the deepest part of the basin is about 270 m, but this area coincides with low velocities that are not characteristic of typical basement complex rocks. Most likely, the density contrast assumed in the inversion is too high or the uncharacteristically low velocities represent highly fractured or weathered basement rocks, or both. A longer seismic profile extending onto basement outcrops would help differentiate which scenario is more accurate. The seismic velocities also determine the depth to water table along the profile to be about 40–60 m, consistent with water levels measured in water wells near the northern end of the profile.

  13. 3-D Modeling for Upper Mantle Anisotropy Beneath Idaho-Oregon (IDOR) Region Using Sks Splitting Intensity Measurements from IDOR Passive Seismic Project Dataset

    NASA Astrophysics Data System (ADS)

    Hongsresawat, S.; Panning, M. P.; Russo, R. M.; Mocanu, V. I.; Stanciu, A. C.; Bremner, P. M.; Torpey, M. E.; VanDecar, J. C.

    2014-12-01

    We used data recorded at 86 broadband seismic stations of the IDOR Passive Seismic Project to determine upper mantle anisotropy across the suture along which Blue Mountain island-arc terranes accreted to North America during Cretaceous. This suture is currently associated with the Western Idaho Shear Zone (WISZ), a narrow, highly-deformed ductile fault that was the locus of both dextral strike-slip along, and subduction beneath, the Paleozoic margin of the North American craton. We measured shear wave splitting intensity (SI), a seismic observable that is suitable for use in 3-D inversions of upper mantle seismic anisotropy, to determine these fabrics beneath the IDOR network. SI fast-polarization directions are spatially coherent across the region, and fall into three main groups: a group with fast azimuths trending ENE-WSW, observed at stations in eastern Oregon and the NW-SE-striking western Snake River Plain; a group with E-W trending fast azimuths observed at stations along the WISZ and the Idaho Batholith, which outcrops immediately east of the suture zone; and a group with ENE-WSW trending fast azimuths observed at stations situated in the Basin-and-Range extended region of southeastern Idaho. SI delay times range from 0.46 to 1.85 seconds, with a mean of 1.1 s. We also used backazimuthal variations of SI at all stations to invert for for 3-D anisotropic fabric using the finite-frequency approach called vectorial tomography (Chevrot and Monteiller, 2009). Our preliminary results are consistent with alignment of upper mantle fabrics in the extension direction as Basin-and-Range extension propagates northward into less-extended regions of Idaho and Oregon.

  14. Analysis of ancient-river systems by 3D seismic time-slice technique: A case study in northeast Malay Basin, offshore Terengganu, Malaysia

    NASA Astrophysics Data System (ADS)

    Sulaiman, Noorzamzarina; Hamzah, Umar; Samsudin, Abdul Rahim

    2014-09-01

    Fluvial sandstones constitute one of the major clastic petroleum reservoir types in many sedimentary basins around the world. This study is based on the analysis of high-resolution, shallow (seabed to 500 m depth) 3D seismic data which generated three-dimensional (3D) time slices that provide exceptional imaging of the geometry, dimension and temporal and spatial distribution of fluvial channels. The study area is in the northeast of Malay Basin about 280 km to the east of Terengganu offshore. The Malay Basin comprises a thick (> 8 km), rift to post-rift Oligo-Miocene to Pliocene basin-fill. The youngest (Miocene to Pliocene), post-rift succession is dominated by a thick (1-5 km), cyclic succession of coastal plain and coastal deposits, which accumulated in a humid-tropical climatic setting. This study focuses on the Pleistocene to Recent (500 m thick) succession, which comprises a range of seismic facies analysis of the two-dimensional (2D) seismic sections, mainly reflecting changes in fluvial channel style and river architecture. The succession has been divided into four seismic units (Unit S1-S4), bounded by basin-wide strata surfaces. Two types of boundaries have been identified: 1) a boundary that is defined by a regionally-extensive erosion surface at the base of a prominent incised valley (S3 and S4); 2) a sequence boundary that is defined by more weakly-incised, straight and low-sinuosity channels which is interpreted as low-stand alluvial bypass channel systems (S1 and S2). Each unit displays a predictable vertical change of the channel pattern and scale, with wide low-sinuosity channels at the base passing gradationally upwards into narrow high-sinuosity channels at the top. The wide variation in channel style and size is interpreted to be controlled mainly by the sea-level fluctuations on the widely flat Sunda land Platform.

  15. 3D modelling of the active normal fault network in the Apulian Ridge (Eastern Mediterranean Sea): Integration of seismic and bathymetric data with implicit surface methods

    NASA Astrophysics Data System (ADS)

    Bistacchi, Andrea; Pellegrini, Caludio; Savini, Alessandra; Marchese, Fabio

    2016-04-01

    The Apulian ridge (North-eastern Ionian Sea, Mediterranean), interposed between the facing Apennines and Hellenides subduction zones (to the west and east respectively), is characterized by thick cretaceous carbonatic sequences and discontinuous tertiary deposits crosscut by a penetrative network of NNW-SSE normal faults. These are exposed onshore in Puglia, and are well represented offshore in a dataset composed of 2D seismics and wells collected by oil companies from the '60s to the '80s, more recent seismics collected during research projects in the '90s, recent very high resolution seismics (VHRS - Sparker and Chirp-sonar data), multibeam echosounder bathymetry, and sedimentological and geo-chronological analyses of sediment samples collected on the seabed. Faults are evident in 2D seismics at all scales, and their along-strike geometry and continuity can be characterized with multibeam bathymetric data, which show continuous fault scarps on the seabed (only partly reworked by currents and covered by landslides). Fault scarps also reveal the finite displacement accumulated in the Holocene-Pleistocene. We reconstructed a 3D model of the fault network and suitable geological boundaries (mainly unconformities due to the discontinuous distribution of quaternary and tertiary sediments) with implicit surface methods implemented in SKUA/GOCAD. This approach can be considered very effective and allowed reconstructing in details complex structures, like the frequent relay zones that are particularly well imaged by seafloor geomorphology. Mutual cross-cutting relationships have been recognized between fault scarps and submarine mass-wasting deposits (Holocene-Pleistocene), indicating that, at least in places, these features are coeval, hence the fault network should be considered active. At the regional scale, the 3D model allowed measuring the horizontal WSW-ENE stretching, which can be associated to the bending moment applied to the Apulian Plate by the combined effect

  16. Analysis of ancient-river systems by 3D seismic time-slice technique: A case study in northeast Malay Basin, offshore Terengganu, Malaysia

    SciTech Connect

    Sulaiman, Noorzamzarina; Hamzah, Umar; Samsudin, Abdul Rahim

    2014-09-03

    Fluvial sandstones constitute one of the major clastic petroleum reservoir types in many sedimentary basins around the world. This study is based on the analysis of high-resolution, shallow (seabed to 500 m depth) 3D seismic data which generated three-dimensional (3D) time slices that provide exceptional imaging of the geometry, dimension and temporal and spatial distribution of fluvial channels. The study area is in the northeast of Malay Basin about 280 km to the east of Terengganu offshore. The Malay Basin comprises a thick (> 8 km), rift to post-rift Oligo-Miocene to Pliocene basin-fill. The youngest (Miocene to Pliocene), post-rift succession is dominated by a thick (1–5 km), cyclic succession of coastal plain and coastal deposits, which accumulated in a humid-tropical climatic setting. This study focuses on the Pleistocene to Recent (500 m thick) succession, which comprises a range of seismic facies analysis of the two-dimensional (2D) seismic sections, mainly reflecting changes in fluvial channel style and river architecture. The succession has been divided into four seismic units (Unit S1-S4), bounded by basin-wide strata surfaces. Two types of boundaries have been identified: 1) a boundary that is defined by a regionally-extensive erosion surface at the base of a prominent incised valley (S3 and S4); 2) a sequence boundary that is defined by more weakly-incised, straight and low-sinuosity channels which is interpreted as low-stand alluvial bypass channel systems (S1 and S2). Each unit displays a predictable vertical change of the channel pattern and scale, with wide low-sinuosity channels at the base passing gradationally upwards into narrow high-sinuosity channels at the top. The wide variation in channel style and size is interpreted to be controlled mainly by the sea-level fluctuations on the widely flat Sunda land Platform.

  17. 3D seismic velocity structure in the rupture area of the 2014 M8.2 Iquique earthquake in Northern Chile

    NASA Astrophysics Data System (ADS)

    Woollam, Jack; Fuenzallida, Amaya; Garth, Tom; Rietbrock, Andreas; Ruiz, Sergio; Tavera, Hernando

    2016-04-01

    Seismic velocity tomography is one of the key tools in Earth sciences to image the physical properties of the subsurface. In recent years significant advances have been made to image the Chilean subductions zone, especially in the area of the 2010 M8.8 Maule earthquake (e.g. Hicks et al., 2014), providing much needed physical constraints for earthquakes source inversions and rupture models. In 2014 the M8.2 Iquique earthquake struck the northern part of the Chilean subduction zone in close proximity to the Peruvian boarder. The pre- and aftershock sequence of this major earthquake was recorded by a densified seismological network in Northern Chile and Southern Peru, which provides an excellent data set to study in depth the 3D velocity structure along the subduction megathrust. Based on an automatic event catalogue of nearly 10,000 events spanning the time period March to May 2014 we selected approximately 450 events for a staggered 3D inversion approach. Events are selected to guarantee an even ray coverage through the inversion volume. We only select events with a minimum GAP of 200 to improve depth estimates and therefore increase resolution in the marine forearc. Additionally, we investigate secondary arrivals between the P- and S-wave arrival to improve depth location. Up to now we have processed about 450 events, from which about 150 with at least 30 P- and S-wave observations have been selected for the subsequent 3D tomography. Overall the data quality is very high, which allows arrival time estimates better than 0.05s on average. We will show results from the 1D, 2D, and preliminary 3D inversions and discuss the results together with the obtained seismicity distribution.

  18. Full Three-Dimensional Approach: Seismic Structure of the Mantle Beneath Western Pacific Using 3-D Fréchet Kernels

    NASA Astrophysics Data System (ADS)

    Chen, L.; Zhao, L.; Jordan, T. H.

    2002-12-01

    We present a full three-dimensional (3-D) model of the shear-speed structure for the mantle beneath western Pacific Ocean. Over 800 three-component recordings of earthquakes (Mw > 5.5) from the seismic zones around the western Pacific rim to station HON/KIP in Hawaii, MIDW in Midway, MAT/MAJO and ERM in Japan, and GUMO in Mariana Island were processed to obtain ~20,000 frequency-dependent phase delays for various of seismic waves, including S, SS, upper-mantle guided and surface waves, and ScS reverberations. The 3-D Fréchet kernels for these delay times are computed by the coupled normal mode theory described by Zhao, Jordan, and Chapman (2000), and the measurements were inverted for a 3-D radially anisotropic shear-speed model using a linear Gaussian-Bayesian scheme. The model parameters include shear-speed variations throughout the mantle and perturbations to radial shear-wave anisotropy in the uppermost mantle. The resolving power of the inversion has been investigated through a series of checkerboard and other tests, which indicate that the horizontal and vertical resolving lengths of about 700 and 200 km or less in the upper mantle. Our results for the large-scale variations in the isotropic shear speeds are generally consistent with published global tomographic models. For example, the uppermost mantle (< 200 km depth) shows fast anomalies in the interior of the Pacific plate and slow anomalies in the marginal basins along the Pacific rim, while this pattern is reversed in the transition zone (400-700 km). Our model reveals greater lateral heterogeneity than the global models, especially in the 200-400 km depth range, suggesting a complex 3-D mantle flow in the western Pacific upper mantle.

  19. Crustal structure of the conjugate margins of the SW South China Sea from wide-angle refraction seismic data

    NASA Astrophysics Data System (ADS)

    Pichot, Thibaud; Delescluse, Matthias; Chamot-Rooke, Nicolas; Pubellier, Manuel; Qiu, Yan; Meresse, Florian; Sun, Gen; Savva, Dimitri; Wong, Kenny P.; Watremez, Louise; Auxiètre, Jean-Luc

    2014-05-01

    The South China Sea (SCS) is the largest marginal basin of SE Asia. While the NE part of the SCS northern margin exhibits ~400 km of extended continental crust, its SW part shows nearly 800 km of extended continental crust, which makes it one of the widest rifted margin in the world. The debate around the mechanisms of formation of such a wide margin is complicated by the lack of a long enough refraction seismic profile. In June 2011, Chinese and French scientists conducted a joint geophysical experiment on board the R/V Tan Bao across the SW sub-basin of the SCS. A 1000-km-long wide-angle refraction seismic profile was acquired along the conjugate margins using a total of 50 Ocean Bottom Seismometers (OBS). 41,100 first refraction and 6,622 PmP reflection arrival traveltimes have been picked. We performed a joint reflection and refraction traveltime tomography inversion to obtain a 2-D velocity model of the crustal and upper mantle structures. Based on this new tomographic model, we show that the northern and southern margins share common structural characteristics: (1) an average crustal thickness of only 12 km, barely varying along the 800 km-long conjugate margin width, and (2) crustal scale lateral velocity variations. These lateral variations correlate well with seismic reflection observations of the crustal structures. The upper-middle crust shows clear lateral velocity variations defining low velocity bodies (LVB) bounded by large-scale normal faults. Major sedimentary basins are located above the LVBs, interpreted as hanging-wall blocks. The Moho interface remains rather flat (less than 4°) over the extended domain, suggesting that large normal faults root in a ductile lower crust, allowing isostatic compensation of the large normal fault blocks. Along the northern margin, the wavelength of the LVBs decreases from 90 to 45 km as the total crust thins toward the Continent-Ocean Transition (COT). The COTs are narrow and slightly asymmetric: 60-km-long on

  20. Marine seismic refraction data indicate Mesozoic syn-rift volcanism and seafloor-spreading in the northwestern Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Eddy, Drew; van Avendonk, Harm; Christeson, Gail; Norton, Ian; Karner, Garry; Johnson, Chris; Kneller, Erik; Snedden, John

    2013-04-01

    The Gulf of Mexico is a small ocean basin that formed by continental rifting and seafloor-spreading between North America and the Yucatan Block during the Jurassic to early Cretaceous. The lack of good, deeply-penetrating geophysical data in the Gulf of Mexico has precluded prior reconstructions of the timing and location of the transition from rifting to seafloor-spreading, as well as the degree to which magmatism influenced these geological processes. To illuminate the deep structure of this enigmatic region, we acquired four marine seismic refraction profiles in the northern Gulf of Mexico from the shelf to deep water as part of the Fall 2010 Gulf of Mexico Basin Opening (GUMBO) project. Here, we present the data and resulting seismic velocity structures of two GUMBO profiles in the northwestern Gulf of Mexico. GUMBO Line 1 extends ~330 km offshore south Texas from Matagorda Island across Alaminos Canyon to the central Gulf. GUMBO Line 2 extends ~400 km from the shelf offshore western Louisiana across the Sigsbee Escarpment. On both lines, ocean-bottom seismometers at 10-km spacing recorded 150m-spaced airgun shots over offsets up to 80 km. We use travel times from these long-offset reflections and refractions to image seismic velocities in the sediments, crystalline crust, and upper mantle using a tomographic inversion. On average, seismic velocities increase with depth from 2 km/s near the seafloor to 5 km/s near the interpreted base of salt. On both profiles we observe a large amount of lateral heterogeneity in the sediments due to salt tectonics. The deeper seismic velocity structure along GUMBO Line 1 also exhibits substantial lateral heterogeneity (4.5 km/s to 7 km/s) that may be consistent with crystallization of thin, ultraslow-spreading oceanic crust alternating with emplacement of exhumed mantle lithosphere. If the basement here is indeed oceanic, the prominent magnetic anomaly along the Texas coastline may represent the expression of synrift volcanism

  1. 3D Anisotropic Velocity Structure beneath the Kii Peninsula from P-wave Traveltime Tomography: Diagnostics of Seismic Anisotropy in a Subduction Zone

    NASA Astrophysics Data System (ADS)

    Ishise, M.; Koketsu, K.; Miyake, H.

    2008-12-01

    Seismic anisotropy is one of key elements to understand geodynamics such as mantle convection, plate tectonics, and evolutional process of the crust. Thus, it is crucial to investigate seismic anisotropy in the subduction zone where various phenomena are attributed to dynamic processes caused by interaction among adjacent plates. Actually, recent studies of seismic anisotropy show that the determination of a 3D seismic anisotropy structure can be potential diagnostics of a geological lineament structure inside the crust, and probe earthquake rupture areas and rupture nucleation points. In this study, we have evaluated the three-dimensional (3D) P-wave anisotropic velocity structure in the Kii Peninsula, southwest Japan, as well as the isotropic velocity structure by P-wave travel times tomography. The study area lies on the Eurasian (Amulian) plate above the subducting Philippine Sea Plate. This belongs to an accretionary prism, which is being developed at the margin of the Asian Continent, and is characterized by E-W trending metamorphic belts including a segment of the active faults zone called the Median Tectonic Line (MTL). Additionally, the Kii Peninsula region is presumed to be source regions of megathrust earthquakes along the Nankai trough. The resultant images of both the isotropic and anisotropic tomography show that the upper crust is characterized by E-W trending structure similar to that of the geological structure over the peninsula region. Because deformation of the crust such as preferred mineral alignment and recrystallization associated with planar structures produces significant seismic anisotropy, the plausible factor of the crustal feature is interpreted as E-W orientation of the regional metamorphic belt. Furthermore, in the resultant tomographic image, the E-W trending pattern is found within the deeper crust. This fact indicates that the lineament structure is sustained in the deeper crust. Since our tomography has good resolution in the

  2. The comparison of DYNA3D to approximate solutions for a partially- full waste storage tank subjected to seismic loading

    SciTech Connect

    Zaslawsky, M.; Kennedy, W.N.

    1992-09-30

    Mathematical solutions to the problem consisting of a partially-full waste tank subjected to seismic loading, embedded in soil, is classically difficult in that one has to address: soil-structure interaction, fluid-structure interaction, non-linear behavior of material, dynamic effects. Separating the problem and applying numerous assumptions will yield approximate solutions. This paper explores methods for generating these solutions accurately.

  3. 3D Seismic Interpretation, Mechanical Stratigraphy and Production Analysis of the Marcellus Shale in Northern West Virginia

    NASA Astrophysics Data System (ADS)

    Kish, Mollie K.

    The Marcellus shale is one of the most developed unconventional shale gas reservoirs in the world with a calculated 84.5 trillion cubic feet in proved natural gas reserves in Pennsylvania and West Virginia. To better exploit this resource all geological aspects of the Marcellus shale are being studied. In this study, mechanical stratigraphy and interpreted seismic fracture zones within the Marcellus shale are examined. These geologic criteria are assessed for potential to impact gas production by analyzing the gas production of fourteen horizontal Marcellus shale wells within and around the study area. Mechanical stratigraphy is evaluated from the top of the Tully limestone to the base of the Onondaga limestone to assess vertical heterogeneity of brittleness within and around the Marcellus shale. Brittleness estimations are derived from petrophysical well logs including bulk density, shear velocity and compressional velocity. Mineralogy assessment is completed using Schlumberger's SpectroLithRTM gamma ray spectroscopy mineralogy logs. Elastic moduli including Young's modulus, Poisson's ratio and Lame's parameters are assessed in terms of brittleness and total organic content to develop constraints for areas of high brittleness and high total organic content. The constraints developed at the study well are compared to studies at four other unconventional shale gas sites. The results suggest that mechanical properties are variable and site dependent. Conclusive ranges for Poisson's ratio and Young's modulus constraints for areas of high brittleness and high total organic cannot be developed for an entire shale play but may be useful in local analyses. Seismic discontinuities were extracted from two three dimensional seismic surveys using a post-stack processing workflow that included Ant-Tracking. They are interpreted to be associated with small faults and fracture zones. The relationship between the number of seismic discontinuities intersecting horizontal wells in

  4. Method for inverting reflection trace data from 3-D and 4-D seismic surveys and identifying subsurface fluid and pathways in and among hydrocarbon reservoirs based on impedance models

    DOEpatents

    He, Wei; Anderson, Roger N.

    1998-01-01

    A method is disclosed for inverting 3-D seismic reflection data obtained from seismic surveys to derive impedance models for a subsurface region, and for inversion of multiple 3-D seismic surveys (i.e., 4-D seismic surveys) of the same subsurface volume, separated in time to allow for dynamic fluid migration, such that small scale structure and regions of fluid and dynamic fluid flow within the subsurface volume being studied can be identified. The method allows for the mapping and quantification of available hydrocarbons within a reservoir and is thus useful for hydrocarbon prospecting and reservoir management. An iterative seismic inversion scheme constrained by actual well log data which uses a time/depth dependent seismic source function is employed to derive impedance models from 3-D and 4-D seismic datasets. The impedance values can be region grown to better isolate the low impedance hydrocarbon bearing regions. Impedance data derived from multiple 3-D seismic surveys of the same volume can be compared to identify regions of dynamic evolution and bypassed pay. Effective Oil Saturation or net oil thickness can also be derived from the impedance data and used for quantitative assessment of prospective drilling targets and reservoir management.

  5. Method for inverting reflection trace data from 3-D and 4-D seismic surveys and identifying subsurface fluid and pathways in and among hydrocarbon reservoirs based on impedance models

    DOEpatents

    He, W.; Anderson, R.N.

    1998-08-25

    A method is disclosed for inverting 3-D seismic reflection data obtained from seismic surveys to derive impedance models for a subsurface region, and for inversion of multiple 3-D seismic surveys (i.e., 4-D seismic surveys) of the same subsurface volume, separated in time to allow for dynamic fluid migration, such that small scale structure and regions of fluid and dynamic fluid flow within the subsurface volume being studied can be identified. The method allows for the mapping and quantification of available hydrocarbons within a reservoir and is thus useful for hydrocarbon prospecting and reservoir management. An iterative seismic inversion scheme constrained by actual well log data which uses a time/depth dependent seismic source function is employed to derive impedance models from 3-D and 4-D seismic datasets. The impedance values can be region grown to better isolate the low impedance hydrocarbon bearing regions. Impedance data derived from multiple 3-D seismic surveys of the same volume can be compared to identify regions of dynamic evolution and bypassed pay. Effective Oil Saturation or net oil thickness can also be derived from the impedance data and used for quantitative assessment of prospective drilling targets and reservoir management. 20 figs.

  6. a Multiple Data Set Joint Inversion Global 3d P-Velocity Model of the Earth's Crust and Mantle for Improved Seismic Event Location

    NASA Astrophysics Data System (ADS)

    Ballard, S.; Begnaud, M. L.; Hipp, J. R.; Chael, E. P.; Encarnacao, A.; Maceira, M.; Yang, X.; Young, C. J.; Phillips, W.

    2013-12-01

    SALSA3D is a global 3D P wave velocity model of the Earth's crust and mantle developed specifically to provide seismic event locations that are more accurate and more precise than are locations from 1D and 2.5D models. In this paper, we present the most recent version of our model, for the first time jointly derived from multiple types of data: body wave travel times, surface wave group velocities, and gravity. The latter two are added to provide information in areas with poor body wave coverage, and are down-weighted in areas where body wave coverage is good. To constrain the inversions, we invoked empirical relations among the density, S velocity, and P velocity. We demonstrate the ability of the new SALSA3D model to reduce mislocations and generate statistically robust uncertainty estimates for a large set of realizations derived from a carefully chosen set of globally-distributed ground truth events. We obtain path-dependent travel time prediction uncertainties for our model by computing the full 3D model covariance matrix of our tomographic system and integrating the model slowness variance and covariance along paths of interest. This approach yields very low travel time prediction uncertainties for well-sampled paths through the Earth and higher uncertainties for paths that are poorly represented in the data set used to develop the model. While the calculation of path-dependent prediction uncertainties with this approach is computationally expensive, uncertainties can be pre-computed for a network of stations and stored in 3D lookup tables that can be quickly and efficiently interrogated using GeoTess software.

  7. Seismic reflection and refraction data acquired in Canada Basin, Northwind Ridge and Northwind Basin, Arctic Ocean in 1988, 1992 and 1993

    USGS Publications Warehouse

    Grantz, Arthur; Hart, Patrick E.; May, Steven D.

    2004-01-01

    Seismic reflection and refraction data were collected in generally ice-covered waters of the Canada Basin and the eastern part of the Chukchi Continental Borderland of the Amerasia Basin, Arctic Ocean, during the late summers of 1988, 1992, and 1993. The data were acquired from a Polar class icebreaker, the U.S. Coast Guard Cutter Polar Star, using a seismic reflection system designed by the U.S. Geological Survey (USGS). The northernmost data extend to 78? 48' N latitude. In 1988, 155 km of reflection data were acquired with a prototype system consisting of a single 195 cubic inch air gun seismic source and a two-channel hydrophone streamer with a 150-m active section. In 1992 and 1993, 500 and 1,900 km, respectively, of seismic reflection profile data were acquired with an improved six air gun, 674 to 1303 cubic inch tuned seismic source array and the same two-channel streamer. In 1993, a 12-channel streamer with a 150-m active section was used to record five of the reflection lines and one line was acquired using a three air gun, 3,000 cubic inch source. All data were recorded with a DFS-V digital seismic recorder. Processed sections feature high quality vertical incidence images to more than 6 km of sub-bottom penetration in the Canada Basin. Refraction data were acquired with U.S. Navy sonobuoys recorded simultaneously with the seismic reflection profiles. In 1988 eight refraction profiles were recorded with the single air gun, and in 1992 and 1993 a total of 47 refraction profiles were recorded with the six air gun array. The sonobuoy refraction records, with offsets up to 35 km, provide acoustic velocity information to complement the short-offset reflection data. The report includes trackline maps showing the location of the data, as well as both digital data files (SEG-Y) and images of all of the profiles.

  8. A groundwater model for the Spruce Hole aquifer, Durham, NH, based on a detailed seismic refraction survey

    SciTech Connect

    Kerwin, R.A. . Dept. of Earth Sciences)

    1993-03-01

    The town of Durham and the University of New Hampshire are interested in using the Spruce Hole aquifer as a municipal pumping well site. The goals of this project were to determine the approximate thickness and areal extent of the aquifer, to determine the hydrologic characteristics and capabilities of the aquifer (groundwater flow directions and transmissivities), and to simulate the effect that pumping of the aquifer may have on the delicate ecosystem of Spruce Hole bog. The Spruce Hole aquifer is a drift deposit composed of glacial till and stratified sand and gravel and is underlain by metasedimentary bedrock. A kettlehole bog with a unique ecosystem with rare plants and insects is located near the center of the deposit. The author conducted a 65 site seismic refraction survey of the Spruce Hole aquifer to estimate water table elevation, bedrock depth, and saturated thickness, as well as till elevations (seismic velocities between 1.9 km/s and 2.6 km/s) at many of the locations. One-dimensional (cross section) and two-dimensional (map view) transmissivity based finite-difference groundwater models were developed to simulate the groundwater flow of the system and to determine transmissivity values for the stratified drift. An average transmissivity for the aquifer at each grid point in the model was determined through data from wells, the seismic refraction survey, and by matching estimated water table values with those calculated by the model. This model has produced simulations that are plausible representations of the ground-water system of the aquifer. A better understanding of kettlehole bog/groundwater system can be gotten from this work.

  9. Beyond the Seafloor: a Plio-Pleistocene Archive of Glacial Geomorphology from Basin-Wide 3D Seismic Reflection Data on the Mid-Norwegian Shelf

    NASA Astrophysics Data System (ADS)

    Newton, A.; Huuse, M.

    2015-12-01

    Oil and gas exploration on the mid-Norwegian shelf has created an extensive geophysical and geological database. As such, this margin has become one of the most comprehensively studied formerly-glaciated continental margins in the world. Industrial operations have concentrated on the structure and geohazard potential of glacial sediments whilst academic work has looked at reconstructing environmental conditions during and since the Last Glacial Maximum (LGM). This has generally consisted of mapping seafloor glacial geomorphology and a limited number of shallow sediment cores. Despite the increasingly large volume of 3D seismic reflection data available across the majority of the shelf, only limited work has been carried out investigating the oldest glaciations. A Plio-Pleistocene archive of glacial-interglacial history is preserved offshore and represents a unique study site because of the availability of 100s of 3D seismic reflection datasets. This database allows numerous different glacial erosion events and glacial landforms to be imaged throughout the glacially-derived NAUST Formation. We present an inventory of glacial history for the mid-Norwegian shelf and review the implications for the glacial history of Northwest Europe. This record shows glacial landforms such as iceberg scours, mega-scale glacial lineations and grounding-zone wedges, each of which provides an insight into ice characteristics. Dating is limited to a few tentative dates based on side-wall core data but we infer a further dating chronology based on dated sediments from the Voring Plateau, fluctuations in the benthic δ18O derived global sea level record, interpretation of seismic facies and the overall architecture. Glacial evidence is present regularly throughout the stratigraphy with the earliest evidence for marine terminating ice found at the base of the NAUST Formation at ~2.8 Ma.

  10. Correlation of generation interval and scale of large-scale submarine landslides using 3D seismic data off Shimokita Peninsula, Northeast Japan

    NASA Astrophysics Data System (ADS)

    Nakamura, Yuki; Ashi, Juichiro; Morita, Sumito

    2016-04-01

    To clarify timing and scale of past submarine landslides is important to understand formation processes of the landslides. The study area is in a part of continental slope of the Japan Trench, where a number of large-scale submarine landslide (slump) deposits have been identified in Pliocene and Quaternary formations by analysing METI's 3D seismic data "Sanrikuoki 3D" off Shimokita Peninsula (Morita et al., 2011). As structural features, swarm of parallel dikes which are likely dewatering paths formed accompanying the slumping deformation, and slip directions are basically perpendicular to the parallel dikes. Therefore, parallel dikes are good indicator for estimation of slip directions. Slip direction of each slide was determined one kilometre grid in the survey area of 40 km x 20 km. The remarkable slip direction varies from Pliocene to Quaternary in the survey area. Parallel dike structure is also available for the distinguishment of the slump deposit and normal deposit on time slice images. By tracing outline of slump deposits at each depth, we identified general morphology of the overall slump deposits, and calculated the volume of the extracted slump deposits so as to estimate the scale of each event. We investigated temporal and spatial variation of depositional pattern of the slump deposits. Calculating the generation interval of the slumps, some periodicity is likely recognized, especially large slump do not occur in succession. Additionally, examining the relationship of the cumulative volume and the generation interval, certain correlation is observed in Pliocene and Quaternary. Key words: submarine landslides, 3D seismic data, Shimokita Peninsula

  11. 3D Reservoir Modeling of Semutang Gas Field: A lonely Gas field in Chittagong-Tripura Fold Belt, with Integrated Well Log, 2D Seismic Reflectivity and Attributes.

    NASA Astrophysics Data System (ADS)

    Salehin, Z.; Woobaidullah, A. S. M.; Snigdha, S. S.

    2015-12-01

    Bengal Basin with its prolific gas rich province provides needed energy to Bangladesh. Present energy situation demands more Hydrocarbon explorations. Only 'Semutang' is discovered in the high amplitude structures, where rest of are in the gentle to moderate structures of western part of Chittagong-Tripura Fold Belt. But it has some major thrust faults which have strongly breached the reservoir zone. The major objectives of this research are interpretation of gas horizons and faults, then to perform velocity model, structural and property modeling to obtain reservoir properties. It is needed to properly identify the faults and reservoir heterogeneities. 3D modeling is widely used to reveal the subsurface structure in faulted zone where planning and development drilling is major challenge. Thirteen 2D seismic and six well logs have been used to identify six gas bearing horizons and a network of faults and to map the structure at reservoir level. Variance attributes were used to identify faults. Velocity model is performed for domain conversion. Synthetics were prepared from two wells where sonic and density logs are available. Well to seismic tie at reservoir zone shows good match with Direct Hydrocarbon Indicator on seismic section. Vsh, porosity, water saturation and permeability have been calculated and various cross plots among porosity logs have been shown. Structural modeling is used to make zone and layering accordance with minimum sand thickness. Fault model shows the possible fault network, those liable for several dry wells. Facies model have been constrained with Sequential Indicator Simulation method to show the facies distribution along the depth surfaces. Petrophysical models have been prepared with Sequential Gaussian Simulation to estimate petrophysical parameters away from the existing wells to other parts of the field and to observe heterogeneities in reservoir. Average porosity map for each gas zone were constructed. The outcomes of the research

  12. The Effects of Chemically Distinct LLSVPs on the Geoid: the Results from Both 3-D Thermochemical Convection and Seismically Constrained Instantaneous Flow Models

    NASA Astrophysics Data System (ADS)

    Liu, X.; Zhong, S.

    2014-12-01

    The long-wavelength geoid anomalies provide important constraints on mantle dynamics and mantle viscosity structure. Hager and Ricard and their colleagues successfully reproduced the observed geoid using seismically imaged mantle structure as buoyancy force in an isochemical, whole mantle convection model. However, it has been generally agreed that the seismically observed large low shear velocity provinces (LLSVPs) underneath the Pacific and the Africa in the lower mantle are chemically distinct and likely more dense than the ambient mantle. In this study, we investigate how chemically distinct LLSVPs or chemical piles affect the geoid using both time-dependent thermochemical convection model and instantaneous flow model driven by buoyancy derived from seismic models. First, by conducting a series of 3D spherical thermochemical convection calculations, we found that the chemically dense piles above the CMB have a compensation effect on the geoid, and as a result, the total geoid is only controlled by the upper ~1600 km of the mantle. Second, we use buoyancy structure derived from seismic model Smean to study whether the observed geoid can be reproduced by considering the compensation effects of the LLSVPs. The geoid modeling requires a viscosity profile η and a seismic velocity to density scaling f. We define a four-layer viscosity model with viscosities for lithosphere η_lt, the upper mantle η_um, the transition zone η_tz, and the lower mantle η_lm. With a fixed η_lt of 20, we compute the geoid and search for η_um, η_tz, η_lm, and f that lead to the maximum variance reduction for the geoid. For the whole mantle, isochemical model, the best model with variance reduction of ~71% for degrees 2-9 has viscosities of 20, 0.5, 0.5, 35, for η_lt, η_um, η_tz, and η_lm, respectively, and the scaling f is 0.24. For the thermochemical model with the bottom 1000 km of structure removed, the best model has a viscosity profile of 20, 0.5, 0.5, 30 for the four

  13. Imaging Near-Surface Controls on Hot Spring Expression Using Shallow Seismic Refraction in Yellowstone National Park

    NASA Astrophysics Data System (ADS)

    Price, A. N.; Lindsey, C.; Fairley, J. P., Jr.; Larson, P. B.

    2015-12-01

    We used shallow seismic refraction to image near-surface materials in the vicinity of a small group of hot springs, located in the Morning Mist Springs area of Lower Geyser Basin, Yellowstone National Park, Wyoming. Seismic velocities in the area surveyed range from a low of 0.3 km/s to a high of approximately 2.5 km/s. The survey results indicate an irregular surface topography overlain by silty sediments. The observed seismic velocities are consistent with a subsurface model in which sorted sands and gravels, probably outwash materials from the Pinedale glaciation, are overlain by silts and fine sands deposited in the flat-lying areas of the Morning Springs area. These findings are supported by published geologic maps of the area and well logs from a nearby borehole. The near-surface materials appear to be saturated with discharging hydrothermal fluids of varying temperature, and interbedded with semi-lithified geothermal deposits (sinter). We hypothesize that the relatively low-conductivity deposits of fines at the surface may serve to confine a shallow, relatively low-temperature (sub-boiling) hydrothermal aquifer, and that the distribution of sinter in the shallow subsurface plays an important role in determining the geometry of hydrothermal discharge (hot springs) at the land surface. Few studies of the shallow controls on hot spring expression exist for the Yellowstone caldera, and the present study therefore offers a unique glimpse into near-subsurface fluid flow controls.

  14. 3-D architecture modeling using high-resolution seismic data and sparse well control: Example from the Mars {open_quotes}Pink{close_quotes} reservoir, Mississippi Canyon Area, Gulf of Mexico

    SciTech Connect

    Chapin, M.A.; Tiller, G.M.; Mahaffie, M.J.

    1996-12-31

    Economic considerations of the deep-water turbidite play, in the Gulf of Mexico and elsewhere, require large reservoir volumes to be drained by relatively few, very expensive wells. Deep-water development projects to date have been planned on the basis of high-quality 3-D seismic data and sparse well control. The link between 3-D seismic, well control, and the 3-D geological and reservoir architecture model are demonstrated here for Pliocene turbidite sands of the {open_quotes}Pink{close_quotes} reservoir, Prospect Mars, Mississippi Canyon Areas 763 and 807, Gulf of Mexico. This information was used to better understand potential reservoir compartments for development well planning.

  15. Regional seismic wavefield computation on a 3-D heterogeneous Earth model by means of coupled traveling wave synthesis

    USGS Publications Warehouse

    Pollitz, F.F.

    2002-01-01

    I present a new algorithm for calculating seismic wave propagation through a three-dimensional heterogeneous medium using the framework of mode coupling theory originally developed to perform very low frequency (f < ???0.01-0.05 Hz) seismic wavefield computation. It is a Greens function approach for multiple scattering within a defined volume and employs a truncated traveling wave basis set using the locked mode approximation. Interactions between incident and scattered wavefields are prescribed by mode coupling theory and account for the coupling among surface waves, body waves, and evanescent waves. The described algorithm is, in principle, applicable to global and regional wave propagation problems, but I focus on higher frequency (typically f ??????0.25 Hz) applications at regional and local distances where the locked mode approximation is best utilized and which involve wavefields strongly shaped by propagation through a highly heterogeneous crust. Synthetic examples are shown for P-SV-wave propagation through a semi-ellipsoidal basin and SH-wave propagation through a fault zone.

  16. Crustal structure from the Hecataeus Rise to the Levantine Basin, eastern Mediterranean, from seismic refraction and gravity modelling

    NASA Astrophysics Data System (ADS)

    Welford, J. Kim; Hall, J.; Rahimi, A.; Reiche, S.; Hübscher, C.; Louden, K.

    2015-12-01

    In 2010, a wide-angle seismic reflection/refraction profile was acquired along the Hecataeus Rise, an area of shallow seabed immediately south of Cyprus in the eastern Mediterranean. The profile crossed from the Hecataeus Rise, through the Cyprus Arc to the Levantine Basin beyond. Due to the short length of the profile and the corresponding lack of deep ray coverage, velocity modelling was complemented by gravity modelling to gain constraints on deep crustal structure. The resultant model reveals velocities for the Hecataeus Rise that show no evidence of shallow ophiolites like those seen on mainland Cyprus, and the velocities are not diagnostic of a unique crustal affinity. Low-velocity sediments make up at least 7 km of the upper structure of Hecataeus Rise and these sediments overlie a two-layered crust. From the gravity modelling, the combined sediments and crust of Hecataeus Rise appear to be thinner than the Eratosthenes Seamount block to the southwest. A high-velocity lower crustal block is modelled under the seaward edge of Hecataeus Rise and, based on the gravity modelling, is inferred to extend landwards beneath the Rise. Similar high-velocity blocks were identified on the southwestern edge of Hecataeus Rise along nearby refraction lines and were interpreted as remnant Tethyan oceanic crust, foundered in the Cyprus Arc, along which subduction has ceased in this area. Given the thin two-layered crust beneath a thick accumulation of sediments modelled for Hecataeus Rise, we interpret that Hecataeus Rise represents a collage of oceanic fragments, accreted together within the failed subduction zone. Outboard of the crust of Hecataeus Rise, a 5-km deep low-velocity basin, possibly an accretionary wedge, is imaged that appears to correspond with the Cyprus Arc deformation zone imaged on both coincident and along-strike seismic reflection lines. A similar and wider feature is observed on seismic refraction lines to the west and combined, these may be revealing

  17. Improved 3D seismic attribute mapping by CRS stacking instead of NMO stacking: Application to a geothermal reservoir in the Polish Basin

    NASA Astrophysics Data System (ADS)

    Pussak, Marcin; Bauer, Klaus; Stiller, Manfred; Bujakowski, Wieslaw

    2014-04-01

    Within a seismic reflection processing work flow, the common-reflection-surface (CRS) stack can be applied as an alternative for the conventional normal moveout (NMO) or the dip moveout (DMO) stack. The advantages of the CRS stack include (1) data-driven automatic determination of stacking operator parameters, (2) imaging of arbitrarily curved geological boundaries, and (3) significant increase in signal-to-noise (S/N) ratio by stacking far more traces than used in a conventional stack. In this paper we applied both NMO and CRS stackings to process a sparse 3D seismic data set acquired within a geothermal exploration study in the Polish Basin. The stacked images show clear enhancements in quality achieved by the CRS stack in comparison with the conventional stack. While this was expected from previous studies, we also found remarkable improvements in the quality of seismic attributes when the CRS stack was applied instead of the conventional stack. For the major geothermal target reservoir (Lower Jurassic horizon Ja1), we present a comparison between both stacking methods for a number of common attributes, including root-mean-square (RMS) amplitudes, instantaneous frequencies, coherency, and spectral decomposition attributes derived from the continuous wavelet transform. The attribute maps appear noisy and highly fluctuating after the conventional stack, and are clearly structured after the CRS stack. A seismic facies analysis was finally carried out for the Ja1 horizon using the attributes derived from the CRS stack by using self-organizing map clustering techniques. A corridor parallel to a fault system was identified, which is characterized by decreased RMS amplitudes and decreased instantaneous frequencies. In our interpretation, this region represents a fractured, fluid-bearing compartment within the sandstone reservoir, which indicates favorable conditions for geothermal exploitation.

  18. Deep structure of the crust beneath the Sea of Okhotsk inferred from 3D seismic density modeling

    NASA Astrophysics Data System (ADS)

    Piskarev, A. L.; Butsenko, V. V.; Poselov, V. A.; Savin, V. A.

    2012-05-01

    Potential field anomalies of the Sea of Okhotsk region are analyzed for compiling a map of the basement's tectonic structures. A 3D density model of the Earth's crust is constructed using seismogeological and experimental-petrophysical data, which made it possible to obtain a visual image of main structures of the region reflecting the observable geophysical anomalies. The obtained data allow a domain located in the central part of the Sea of Okhotsk beyond the limits of the exclusive economic zone of the Russian Federation to be considered as a natural continuation of the continental shelf since the latter is structurally similar to western Kamchatka. The deep structural boundaries rise beneath the large sedimentary Deryugin and Tinro basins, which is characteristic of petroliferous basins.

  19. Seismically Inferred Rupture Process of the 2011 Tohoku-Oki Earthquake by Using Data-Validated 3D and 2.5D Green's Tensor Waveforms

    NASA Astrophysics Data System (ADS)

    Okamoto, T.; Takenaka, H.; Hara, T.; Nakamura, T.; Aoki, T.

    2014-12-01

    We analyze "seismic" rupture process of the March 11, 2011 Tohoku-Oki earthquake (GCMT Mw9.1) by using a non-linear multi-time-window waveform inversion method. We incorporate the effect of the near-source laterally heterogeneous structure on the synthetic Green's tensor waveforms; otherwise the analysis may result in erroneous solutions [1]. To increase the resolution we use teleseismic and strong-motion seismograms jointly because the one-sided distribution of strong-motion station may cause reduced resolution near the trench axis [2]. We use a 2.5D FDM [3] for teleseismic P-waves and a full 3D FDM that incorporates topography, oceanic water layer, 3D heterogeneity and attenuation for strong-motions [4]. We apply multi-GPU acceleration by using the TSUBAME supercomputer in Tokyo Institute of Technology [5]. We "validated" the Green's tensor waveforms with a point-source moment tensor inversion analysis for a small (Mw5.8) shallow event: we confirm the observed waveforms are reproduced well with the synthetics.The inferred slip distribution using the 2.5D and 3D Green's functions has large slips (max. 37 m) near the hypocenter and small slips near the trench (figure). Also an isolated slip region is identified close to Fukushima prefecture. These features are similar to those obtained by our preliminary study [4]. The land-ward large slips and trench-ward small slips have also been reported by [2]. It is remarkable that we confirmed these features by using data-validated Green's functions. On the other hand very large slips are inferred close to the trench when we apply "1D" Green's functions that do not incorporate the lateral heterogeneity. Our result suggests the trench-ward large deformation that caused large tsunamis did not radiate strong seismic waves. Very slow slips (e.g., the tsunami earthquake), delayed slips and anelastic deformation are among the candidates of the physical processes of the deformation.[1] Okamoto and Takenaka, EPS, 61, e17-e20, 2009

  20. Seismic Velocity Structure Across the Quebrada and Gofar Oceanic Transform Faults from 2D Refraction Tomography - A Comparison of Faults with High and Low Seismic Slip Deficits

    NASA Astrophysics Data System (ADS)

    Roland, E. C.; McGuire, J. J.; Collins, J. A.; Lizarralde, D.

    2009-12-01

    We perform two 2-D tomographic inversions using data collected as a part of the Quebrada-Discovery-Gofar (QDG) Transform Fault Active/Passive Experiment. The QDG transform faults are located in the southern Pacific Ocean and offset the East Pacific Rise (EPR) at approximately 4° south. In the spring of 2008, two ~100 km refraction profiles were collected, each using 8 short period Ocean Bottom Seismometers (OBS) from OBSIP and over 900 shots from the RV Marcus Langseth, across the easternmost segments of the Quebrada and Gofar transform faults. The two refraction profiles are modeled using a 2-D tomographic code that allows joint inversion of the Pg, PmP, and Pn arrivals (Korenaga et al., 2000). Variations in crustal velocity and thickness, as well as the width and depth extent of a significant low velocity zone within and below the transform valley provide some insight into the material properties of each of the fault-zones. Reduced seismic velocities that are 0.5 to over 1.0 km/s slower than velocities associated with the oceanic crust outside the fault zone may indicate the highly fractured fault zone lithology. The low velocity zone associated with the Quebrada fault also extends to the south of the active fault zone, beneath a fossil fault trace. Because Gofar is offset by an intratransform spreading center, we are able to compare ‘normal’ oceanic crust produced at the EPR to the south of the fault with crust associated with the ~15 km intratransform spreading center to the north. These two high slip rate (14 cm/yr) faults look similar morphologically and demonstrate comparable microseismicity characteristics, however their abilities to generate large earthquakes differ significantly. Gofar generates large earthquakes (Mw ~6) regularly every few years, but in the past 24 years only one large (Mw 5.6) event has been reliably located on Quebrada. The contrasting seismic behavior of these faults represents the range of behavior observed in the global

  1. A preliminary summary of a seismic-refraction survey in the vicinity of the Tonto Forest Observatory, Arizona

    USGS Publications Warehouse

    Roller, J.C.; Jackson, W.H.; Warren, D.H.; Healy, J.H.

    1964-01-01

    The U.S. Geological Survey complete d a seismic-refraction survey in the vicinity of the Tonto Forest Seismological Observatory (T.F.S.O.) in April and May 1964. More than 1200 km of reversed profiles were surveyed to determine the crustal structure and crustal and upper mantle velocities in this area. The purpose of this work was to provide information on wave-propagation paths of seismic events recorded at T.F.S.O. and to improve the performance of the Observatory in locating and identifying these events. First arrivals indicate that the Mohorovicic discontinuity dips to the northeast by as much as 6 degrees under T.F.S.O., and may even be displaced vertically by as much as 5 km immediately north of the Observatory near the boundary of the Basin and Range a n d t he Colorado Plateau Provinces. A preliminary examination of the first arrivals indicates that the crust at T.F.S.O. is at least 30 km thick and is made up of at least two seismic layers. A thin veneer at the surface with a velocity of approximately 4 km/sec is underlain by a layer with a velocity of approximately 5.9 km/sec to 6.1 km/sec. An intermediate layer with velocity of 6.6 to 7.0 km/sec is probably present in the lower crust, but is not revealed by first arrivals. The velocity of seismic waves in the upper mantle is about 7.9 km/sec.

  2. The Effects of Chemically Distinct LLSVPs on the Geoid: the Results from Both 3-D Thermochemical Convection and Seismically Constrained Instantaneous Flow Models

    NASA Astrophysics Data System (ADS)

    Liu, Xi; Zhong, Shijie

    2015-04-01

    The long-wavelength geoid anomalies provide important constraints on mantle dynamics and mantle viscosity structure. Hager and Ricard and their colleagues successfully reproduced the observed geoid using seismically imaged mantle structure as buoyancy force in an isochemical, whole mantle convection model. However, it has been generally agreed that the seismically observed large low shear velocity provinces (LLSVPs) underneath the Pacific and the Africa in the lower mantle are chemically distinct and likely more dense than the ambient mantle. In this study, we investigate how chemically distinct LLSVPs or chemical piles affect the geoid using both time-dependent thermochemical convection model and instantaneous flow model driven by buoyancy derived from seismic models. First, by conducting a series of 3D spherical thermochemical convection calculations, we found that the chemically dense piles above the CMB have a compensation effect on the geoid, and as a result, the total geoid is only controlled by the upper ~1600 km of the mantle. Second, we use buoyancy structure derived from seismic models (e.g., Smean and other models) to study whether the observed geoid can be reproduced by considering the compensation effects of the LLSVPs. The geoid modeling requires a viscosity profile and a seismic velocity to density scaling f. We define a four-layer viscosity model with viscosities for lithosphere, the upper mantle, the transition zone, and the lower mantle . With a fixed non-dimensional lithospheric viscosity at 20, we compute the geoid and search for other three viscosity parameters and scaling parameter f that lead to the maximum variance reduction for the geoid. For the whole mantle, isochemical model, the best model with variance reduction of ~71% for degrees 2-9 has viscosities of 0.5, 0.5, and 35, for the upper mantle, transition zone, and lower mantle, respectively, and the scaling f is 0.24. For the thermochemical model with the bottom 1000 km of structure

  3. Structure and evolution of the Gulf of Mexico: New results from the GUMBO marine seismic refraction study

    NASA Astrophysics Data System (ADS)

    Van Avendonk, Harm; Christeson, Gail; Norton, Ian; Eddy, Drew; Karner, Garry; Johnson, Chris; Kneller, Erik

    2013-04-01

    Plate reconstructions of the Gulf of Mexico suggest that Jurassic rifting in the Gulf of Mexico proceeded with a counterclockwise opening between North America and Yucatan, though the timing is poorly constrained. Seismic reflection data provide a detailed record of salt deposition and post-rift sedimentation, but the underlying basement and Moho has thus far not been imaged in detail. Therefore, the evolution of these rifted margins is not well known. In the Fall of 2010 we deployed ocean-bottom seismometers (OBSs) along four transects in the northern Gulf of Mexico to obtain much-needed constraints on the crustal structure, as part of the GUMBO (GUlf of Mexico Basin Opening) project. We shot refraction data along these lines with an industry vessel. The four OBS refraction profiles are located 1) offshore south Texas, 2) offshore western Louisiana, 3) offshore Alabama, and 4) offshore western Florida. Each of these seismic transects was oriented perpendicular to the margin from the coast towards the central Gulf of Mexico. The purpose of this experiment design was to capture structural variations in the margins in the approximate rift direction, and to a lesser degree to find evidence for differences in the style of rifting along the strike of the margin. Such east-west variability could indicate a diachronous rifting history, a possible influence of CAMP magmatism in the rifting process, and/or structural control from the preexisting lithospheric fabric in southern North America. We used the GUMBO OBS data to construct seismic velocity models along the four profiles. Due to the large sediment influx in the western Gulf of Mexico, it is possible that the continent-ocean transition here lies beneath the coastal plain, such that we did not capture this boundary on our two western profiles. However, the crust that lies offshore Texas is clearly thinner than offshore Louisiana, which could indicate an eastward increase in magmatic output during the early opening of

  4. Oceanic Character of Sub-Salt Crust in the NW Gulf of Mexico (GOM) Using Seismic Refraction and Reflection Data

    NASA Astrophysics Data System (ADS)

    Karner, G. D.; Johnson, C. A.

    2015-12-01

    Significant renewed interest in the geological development of the NW GOM is exemplified by the acquisition of academic seismic refraction and oil industry seismic reflection data. There is agreement that the GOM formed by Jurassic separation of North America and Yucatan, but disagreements remain on the distribution and timing of extended continental versus oceanic crust. Van Avendonk et al. (Geology, v43, 2015) interpreted seismic refraction data from the 2010 "GUMBO" expedition as rifted continental crust thinned by large-scale extensional faulting and syn-rift magmatism beneath the NW GOM. However, seismic reflection evidence for this extension is non-existent, and diagnostic fault-controlled syn-rift packages are not resolved. A very different interpretation of basement type and basin evolution is possible by applying geological process linked to hyper-extended margin formation to the same data. We note: 1) Base salt and Moho interfaces are well imaged; top basement is not resolved. We interpret a pre-salt sedimentary sequence 5-10 km thick, with velocities up to 6 km/s; high velocities in this sequence likely relate to greenschist-facies metamorphism associated with early high heat flow and deep burial. 2) Velocities of 6-8 km/s characterize crystalline basement but do not uniquely determine crustal type (i.e., velocity does not equate to rock type). Lateral variations (0-8 km) in crustal thickness are consistent with slow/ultra-slow seafloor spreading. 3) The undeformed base salt reflector and pre-salt sediment sequence imply a post-kinematic setting and a substantial delay between breakup and Callovian salt deposition. 4) Liassic Central Atlantic breakup is kinematically linked to the GOM and related SDR magmatism. Inboard SDRs, observed on both conjugate margins of the GOM, imply outboard oceanic crust. Together, these observations are consistent with regional sub-salt basement of early-mid Jurassic slow/ultra-slow spreading oceanic crust, associated with

  5. Neoarchaean tectonic history of the Witwatersrand Basin and Ventersdorp Supergroup: New constraints from high-resolution 3D seismic reflection data

    NASA Astrophysics Data System (ADS)

    Manzi, Musa S. D.; Hein, Kim A. A.; King, Nick; Durrheim, Raymond J.

    2013-04-01

    First-order scale structures in the West Wits Line and West Rand goldfields of the Witwatersrand Basin (South Africa) were mapped using the high-resolution 3D reflection seismic method. Structural models constrain the magnitude of displacement of thrusts and faults, the gross structural architecture and Neoarchaean tectonic evolution of the West Rand and Bank fault zones, which offset the gold-bearing reefs of the basin. The merging of several 3D seismic surveys made clear the gross strato-structural architecture of the goldfields; a macroscopic fold-thrust belt is crosscut by a macroscopic extensional fault array. These are dissected, eroded and overlain by the Transvaal Supergroup above an angular unconformity. The seismic sections confirm that the West Rand Group (ca. 2985-2902 Ma) is unconformably overlain by the Central Rand Group (ca. 2902-2849 Ma), with tilting of the West Rand Group syn- to post-erosion at ca. 2.9 Ga. The seismic sections also confirm that an unconformable relationship exists between the Central Rand Group and the auriferous Ventersdorp Contact Reef (VCR), with an easterly-verging fold-thrust belt being initiated concomitant to deposition of the VCR at approximately 2.72 Ga. Fold-thrust formation included development of the (1) newly identified first-order scale Libanon Anticline, (2) Tandeka and Jabulani thrusts which displace the West Rand Group, and (3) parasite folds. The fold-thrust belt is crosscut by a macroscopic extensional fault array (or rift-like system of faults) which incepted towards the end of extrusion of the Ventersdorp lavas, and certainly during deposition of the Platberg Group (2709-2643 Ma) when a mantle plume may have heated the lithosphere. The West Rand and Bank fault zones formed at this time and include (1) the West Rand and Bank faults which are scissors faults; (2) second and third-order scale normal faults in the immediate footwall and hanging wall of the faults; (3) drag synclines, and (4) rollover anticlines.

  6. Shallow sediment and upper crustal structure beneath the Salton Sea as imaged by active source marine seismic refraction in conjunction with the Salton Seismic Imaging Project

    NASA Astrophysics Data System (ADS)

    Kell, A. M.; Sahakian, V. J.; Harding, A. J.; Kent, G.; Driscoll, N. W.

    2012-12-01

    In the spring of 2011 we expanded a campaign of marine seismic reflection efforts in the Salton Sea in conjunction with the Salton Seismic Imaging Project (SSIP) to collect active-source marine refraction data using Ocean Bottom Seismometers (OBSs) and a marine airgun. The Salton Trough presents an opportunity to study rifting processes similar to those seen in the Gulf of California, as well as the seismic hazards associated with the southern terminus of the San Andreas Fault (SAF). An areal array, comprised of 78 OBS deployments, was focused in the southern part of the sea but also included a line parallel to the San Andreas Fault (SAF) , line 1, extending then length of the sea, and a line perpendicular to the SAF, crossing the northern basin, line 7. These lines are collinear with high-resolution reflection profiles and existing chirp profiles. The OBS array was concentrated in the southern Salton Sea to investigate the pull-apart deformation reported by Brothers et al. (2009). Using the methods of Van Avendonk (2004) we seek to constrain upper crustal velocities in this region by travel-time tomography. Beginning with P-wave arrival times we trace the ray paths through the model space and invert for seismic velocities. By iterating from the forward picking to the inversion, we reduce the chi-squared error to produce a 2D depth profile of the seismic velocities while maintaining a stable model. Line 1 uses 38 OBSs and 470 shots from a 210 cu. in. airgun to model the upper 4 km beneath the Salton Sea. Velocities vary from 1.5 km/s in the upper 1 km to an apparent 4 km deep basement velocity of 5.5 km/s. Velocity variations with depth agree with major boundaries in the co-linear seismic reflection profiles and the divergence toward the south/fault structure is also captured in these early models. Preliminary results for line 7 show similarly varying velocities - 1.5 to 3 km/s in the upper 2 kilometers of the crust, to slightly over 4 km/s at 4 km depth. Further

  7. Simulations of wave propagation and disorder in 3D non-close-packed colloidal photonic crystals with low refractive index contrast.

    PubMed

    Glushko, O; Meisels, R; Kuchar, F

    2010-03-29

    The plane-wave expansion method (PWEM), the multiple-scattering method (MSM) and the 3D finite-difference time-domain method (FDTD) are applied for simulations of propagation of electromagnetic waves through 3D colloidal photonic crystals. The system investigated is not a "usual" artificial opal with close-packed fcc lattice but a dilute bcc structure which occurs due to long-range repulsive interaction between electrically charged colloidal particles during the growth process. The basic optical properties of non-close-packed colloidal PhCs are explored by examining the band structure and reflection spectra for a bcc lattice of silica spheres in an aqueous medium. Finite size effects and correspondence between the Bragg model, band structure and reflection spectra are discussed. The effects of size, positional and missing-spheres disorder are investigated. In addition, by analyzing the results of experimental work we show that the fabricated structures have reduced plane-to-plane distance probably due to the effect of gravity during growth.

  8. Earthquakes in Action: Incorporating Multimedia, Internet Resources, Large-scale Seismic Data, and 3-D Visualizations into Innovative Activities and Research Projects for Today's High School Students

    NASA Astrophysics Data System (ADS)

    Smith-Konter, B.; Jacobs, A.; Lawrence, K.; Kilb, D.

    2006-12-01

    The most effective means of communicating science to today's "high-tech" students is through the use of visually attractive and animated lessons, hands-on activities, and interactive Internet-based exercises. To address these needs, we have developed Earthquakes in Action, a summer high school enrichment course offered through the California State Summer School for Mathematics and Science (COSMOS) Program at the University of California, San Diego. The summer course consists of classroom lectures, lab experiments, and a final research project designed to foster geophysical innovations, technological inquiries, and effective scientific communication (http://topex.ucsd.edu/cosmos/earthquakes). Course content includes lessons on plate tectonics, seismic wave behavior, seismometer construction, fault characteristics, California seismicity, global seismic hazards, earthquake stress triggering, tsunami generation, and geodetic measurements of the Earth's crust. Students are introduced to these topics through lectures-made-fun using a range of multimedia, including computer animations, videos, and interactive 3-D visualizations. These lessons are further enforced through both hands-on lab experiments and computer-based exercises. Lab experiments included building hand-held seismometers, simulating the frictional behavior of faults using bricks and sandpaper, simulating tsunami generation in a mini-wave pool, and using the Internet to collect global earthquake data on a daily basis and map earthquake locations using a large classroom map. Students also use Internet resources like Google Earth and UNAVCO/EarthScope's Jules Verne Voyager Jr. interactive mapping tool to study Earth Science on a global scale. All computer-based exercises and experiments developed for Earthquakes in Action have been distributed to teachers participating in the 2006 Earthquake Education Workshop, hosted by the Visualization Center at Scripps Institution of Oceanography (http

  9. Basement configuration of on-land Kutch basin from seismic refraction studies and modeling of first arrival travel time skips

    NASA Astrophysics Data System (ADS)

    Prasad, B. Rajendra; Venkateswarlu, N.; Prasad, A. S. S. S. R. S.; Murthy, A. S. N.; Sateesh, T.

    2010-10-01

    The Kutch basin is one of the three (Narmada, Cambay and Kutch) major marginal rift basins that are close to each other in mid-western part of the Indian subcontinent. The seismic refraction and wide-angle reflection data were acquired and a first order velocity structure of the Kutch sedimentary basin along Jakhau-Mandvi, Mandvi-Mundra, Mundra-Adesar and Hamirpur-Halvad profiles is derived. The travel time skip phenomenon has been noticed in the travel time plots and record sections indicating presence of low velocity sediments. Derived two-dimensional velocity-depth models revealed a Mesozoic sedimentary sequence sandwiched between Tr