Sample records for abstract high-quality seismic

  1. Data quality control and tools in passive seismic experiments exemplified on the Czech broadband seismic pool MOBNET in the AlpArray collaborative project

    NASA Astrophysics Data System (ADS)

    Vecsey, Luděk; Plomerová, Jaroslava; Jedlička, Petr; Munzarová, Helena; Babuška, Vladislav; AlpArray Working Group

    2017-12-01

    This paper focuses on major issues related to the data reliability and network performance of 20 broadband (BB) stations of the Czech (CZ) MOBNET (MOBile NETwork) seismic pool within the AlpArray seismic experiments. Currently used high-resolution seismological applications require high-quality data recorded for a sufficiently long time interval at seismological observatories and during the entire time of operation of the temporary stations. In this paper we present new hardware and software tools we have been developing during the last two decades while analysing data from several international passive experiments. The new tools help to assure the high-quality standard of broadband seismic data and eliminate potential errors before supplying data to seismological centres. Special attention is paid to crucial issues like the detection of sensor misorientation, timing problems, interchange of record components and/or their polarity reversal, sensor mass centring, or anomalous channel amplitudes due to, for example, imperfect gain. Thorough data quality control should represent an integral constituent of seismic data recording, preprocessing, and archiving, especially for data from temporary stations in passive seismic experiments. Large international seismic experiments require enormous efforts from scientists from different countries and institutions to gather hundreds of stations to be deployed in the field during a limited time period. In this paper, we demonstrate the beneficial effects of the procedures we have developed for acquiring a reliable large set of high-quality data from each group participating in field experiments. The presented tools can be applied manually or automatically on data from any seismic network.

  2. High-Quality Seismic Observations of Sonic Booms

    NASA Technical Reports Server (NTRS)

    Wurman, Gilead; Haering, Edward A., Jr.; Price, Michael J.

    2011-01-01

    The SonicBREWS project (Sonic Boom Resistant Earthquake Warning Systems) is a collaborative effort between Seismic Warning Systems, Inc. and NASA Dryden Flight Research Center. This project aims to evaluate the effects of sonic booms on Earthquake Warning Systems in order to prevent such systems from experiencing false alarms due to sonic booms. The airspace above the Antelope Valley, California includes the High Altitude Supersonic Corridor and the Black Mountain Supersonic Corridor. These corridors are among the few places in the US where supersonic flight is permitted, and sonic booms are commonplace in the Antelope Valley. One result of this project is a rich dataset of high-quality accelerometer records of sonic booms which can shed light on the interaction between these atmospheric phenomena and the solid earth. Nearly 100 sonic booms were recorded with low-noise triaxial MEMS accelerometers recording 1000 samples per second. The sonic booms had peak overpressures ranging up to approximately 10 psf and were recorded in three flight series in 2010 and 2011. Each boom was recorded with up to four accelerometers in various array configurations up to 100 meter baseline lengths, both in the built environment and the free field. All sonic booms were also recorded by nearby microphones. We present the results of the project in terms of the potential for sonic-boom-induced false alarms in Earthquake Warning Systems, and highlight some of the interesting features of the dataset.

  3. Abstract analysis method facilitates filtering low-methodological quality and high-bias risk systematic reviews on psoriasis interventions.

    PubMed

    Gómez-García, Francisco; Ruano, Juan; Aguilar-Luque, Macarena; Alcalde-Mellado, Patricia; Gay-Mimbrera, Jesús; Hernández-Romero, José Luis; Sanz-Cabanillas, Juan Luis; Maestre-López, Beatriz; González-Padilla, Marcelino; Carmona-Fernández, Pedro J; García-Nieto, Antonio Vélez; Isla-Tejera, Beatriz

    2017-12-29

    Article summaries' information and structure may influence researchers/clinicians' decisions to conduct deeper full-text analyses. Specifically, abstracts of systematic reviews (SRs) and meta-analyses (MA) should provide structured summaries for quick assessment. This study explored a method for determining the methodological quality and bias risk of full-text reviews using abstract information alone. Systematic literature searches for SRs and/or MA about psoriasis were undertaken on MEDLINE, EMBASE, and Cochrane database. For each review, quality, abstract-reporting completeness, full-text methodological quality, and bias risk were evaluated using Preferred Reporting Items for Systematic Reviews and Meta-analyses for abstracts (PRISMA-A), Assessing the Methodological Quality of Systematic Reviews (AMSTAR), and ROBIS tools, respectively. Article-, author-, and journal-derived metadata were systematically extracted from eligible studies using a piloted template, and explanatory variables concerning abstract-reporting quality were assessed using univariate and multivariate-regression models. Two classification models concerning SRs' methodological quality and bias risk were developed based on per-item and total PRISMA-A scores and decision-tree algorithms. This work was supported, in part, by project ICI1400136 (JR). No funding was received from any pharmaceutical company. This study analysed 139 SRs on psoriasis interventions. On average, they featured 56.7% of PRISMA-A items. The mean total PRISMA-A score was significantly higher for high-methodological-quality SRs than for moderate- and low-methodological-quality reviews. SRs with low-bias risk showed higher total PRISMA-A values than reviews with high-bias risk. In the final model, only 'authors per review > 6' (OR: 1.098; 95%CI: 1.012-1.194), 'academic source of funding' (OR: 3.630; 95%CI: 1.788-7.542), and 'PRISMA-endorsed journal' (OR: 4.370; 95%CI: 1.785-10.98) predicted PRISMA-A variability. Reviews with a

  4. Signal Quality and the Reliability of Seismic Observations

    NASA Astrophysics Data System (ADS)

    Zeiler, C. P.; Velasco, A. A.; Pingitore, N. E.

    2009-12-01

    The ability to detect, time and measure seismic phases depends on the location, size, and quality of the recorded signals. Additional constraints are an analyst’s familiarity with a seismogenic zone and with the seismic stations that record the energy. Quantification and qualification of an analyst’s ability to detect, time and measure seismic signals has not been calculated or fully assessed. The fundamental measurement for computing the accuracy of a seismic measurement is the signal quality. Several methods have been proposed to measure signal quality; however, the signal-to-noise ratio (SNR) has been adopted as a short-term average over the long-term average. While the standard SNR is an easy and computationally inexpensive term, the overall statistical significance has not been computed for seismic measurement analysis. The prospect of canonizing the process of cataloging seismic arrivals hinges on the ability to repeat measurements made by different methods and analysts. The first step in canonizing phase measurements has been done by the IASPEI, which established a reference for accepted practices in naming seismic phases. The New Manual for Seismological Observatory Practices (NMSOP, 2002) outlines key observations for seismic phases recorded at different distances and proposes to quantify timing uncertainty with a user-specified windowing technique. However, this added measurement would not completely remove bias introduced by different techniques used by analysts to time seismic arrivals. The general guideline to time a seismic arrival is to record the time where a noted change in frequency and/or amplitude begins. This is generally achieved by enhancing the arrivals through filtering or beam forming. However, these enhancements can alter the characteristics of the arrival and how the arrival will be measured. Furthermore, each enhancement has user-specified parameters that can vary between analysts and this results in reduced ability to repeat

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

    NASA Astrophysics Data System (ADS)

    Luo, D.; Cai, F.

    2017-12-01

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

  6. Improving Vintage Seismic Data Quality through Implementation of Advance Processing Techniques

    NASA Astrophysics Data System (ADS)

    Latiff, A. H. Abdul; Boon Hong, P. G.; Jamaludin, S. N. F.

    2017-10-01

    It is essential in petroleum exploration to have high resolution subsurface images, both vertically and horizontally, in uncovering new geological and geophysical aspects of our subsurface. The lack of success may have been from the poor imaging quality which led to inaccurate analysis and interpretation. In this work, we re-processed the existing seismic dataset with an emphasis on two objectives. Firstly, to produce a better 3D seismic data quality with full retention of relative amplitudes and significantly reduce seismic and structural uncertainty. Secondly, to facilitate further prospect delineation through enhanced data resolution, fault definitions and events continuity, particularly in syn-rift section and basement cover contacts and in turn, better understand the geology of the subsurface especially in regard to the distribution of the fluvial and channel sands. By adding recent, state-of-the-art broadband processing techniques such as source and receiver de-ghosting, high density velocity analysis and shallow water de-multiple, the final results produced a better overall reflection detail and frequency in specific target zones, particularly in the deeper section.

  7. Reporting quality of randomised controlled trial abstracts among high-impact general medical journals: a review and analysis

    PubMed Central

    Hays, Meredith; Andrews, Mary; Wilson, Ramey; Callender, David; O'Malley, Patrick G; Douglas, Kevin

    2016-01-01

    Objective The aim of this study was to assess adherence to the Consolidated Standards of Reporting Trials (CONSORT) for Abstracts by five high-impact general medical journals and to assess whether the quality of reporting was homogeneous across these journals. Design This is a descriptive, cross-sectional study. Setting Randomised controlled trial (RCT) abstracts in five high-impact general medical journals. Participants We used up to 100 RCT abstracts published between 2011 and 2014 from each of the following journals: The New England Journal of Medicine (NEJM), the Annals of Internal Medicine (Annals IM), The Lancet, the British Medical Journal (The BMJ) and the Journal of the American Medical Association (JAMA). Main outcome The primary outcome was per cent overall adherence to the 19-item CONSORT for Abstracts checklist. Secondary outcomes included per cent adherence in checklist subcategories and assessing homogeneity of reporting quality across the individual journals. Results Search results yielded 466 abstracts, 3 of which were later excluded as they were not RCTs. Analysis was performed on 463 abstracts (97 from NEJM, 66 from Annals IM, 100 from The Lancet, 100 from The BMJ, 100 from JAMA). Analysis of all scored items showed an overall adherence of 67% (95% CI 66% to 68%) to the CONSORT for Abstracts checklist. The Lancet had the highest overall adherence rate (78%; 95% CI 76% to 80%), whereas NEJM had the lowest (55%; 95% CI 53% to 57%). Adherence rates to 8 of the checklist items differed by >25% between journals. Conclusions Among the five highest impact general medical journals, there is variable and incomplete adherence to the CONSORT for Abstracts reporting checklist of randomised trials, with substantial differences between individual journals. Lack of adherence to the CONSORT for Abstracts reporting checklist by high-impact medical journals impedes critical appraisal of important studies. We recommend diligent assessment of adherence to reporting

  8. Reporting quality of randomised controlled trial abstracts among high-impact general medical journals: a review and analysis.

    PubMed

    Hays, Meredith; Andrews, Mary; Wilson, Ramey; Callender, David; O'Malley, Patrick G; Douglas, Kevin

    2016-07-28

    The aim of this study was to assess adherence to the Consolidated Standards of Reporting Trials (CONSORT) for Abstracts by five high-impact general medical journals and to assess whether the quality of reporting was homogeneous across these journals. This is a descriptive, cross-sectional study. Randomised controlled trial (RCT) abstracts in five high-impact general medical journals. We used up to 100 RCT abstracts published between 2011 and 2014 from each of the following journals: The New England Journal of Medicine (NEJM), the Annals of Internal Medicine (Annals IM), The Lancet, the British Medical Journal (The BMJ) and the Journal of the American Medical Association (JAMA). The primary outcome was per cent overall adherence to the 19-item CONSORT for Abstracts checklist. Secondary outcomes included per cent adherence in checklist subcategories and assessing homogeneity of reporting quality across the individual journals. Search results yielded 466 abstracts, 3 of which were later excluded as they were not RCTs. Analysis was performed on 463 abstracts (97 from NEJM, 66 from Annals IM, 100 from The Lancet, 100 from The BMJ, 100 from JAMA). Analysis of all scored items showed an overall adherence of 67% (95% CI 66% to 68%) to the CONSORT for Abstracts checklist. The Lancet had the highest overall adherence rate (78%; 95% CI 76% to 80%), whereas NEJM had the lowest (55%; 95% CI 53% to 57%). Adherence rates to 8 of the checklist items differed by >25% between journals. Among the five highest impact general medical journals, there is variable and incomplete adherence to the CONSORT for Abstracts reporting checklist of randomised trials, with substantial differences between individual journals. Lack of adherence to the CONSORT for Abstracts reporting checklist by high-impact medical journals impedes critical appraisal of important studies. We recommend diligent assessment of adherence to reporting guidelines by authors, reviewers and editors to promote transparency

  9. Utah's Regional/Urban ANSS Seismic Network---Strategies and Tools for Quality Performance

    NASA Astrophysics Data System (ADS)

    Burlacu, R.; Arabasz, W. J.; Pankow, K. L.; Pechmann, J. C.; Drobeck, D. L.; Moeinvaziri, A.; Roberson, P. M.; Rusho, J. A.

    2007-05-01

    The University of Utah's regional/urban seismic network (224 stations recorded: 39 broadband, 87 strong-motion, 98 short-period) has become a model for locally implementing the Advanced National Seismic System (ANSS) because of successes in integrating weak- and strong-motion recording and in developing an effective real-time earthquake information system. Early achievements included implementing ShakeMap, ShakeCast, point-to- multipoint digital telemetry, and an Earthworm Oracle database, as well as in-situ calibration of all broadband and strong-motion stations and submission of all data and metadata into the IRIS DMC. Regarding quality performance, our experience as a medium-size regional network affirms the fundamental importance of basics such as the following: for data acquisition, deliberate attention to high-quality field installations, signal quality, and computer operations; for operational efficiency, a consistent focus on professional project management and human resources; and for customer service, healthy partnerships---including constant interactions with emergency managers, engineers, public policy-makers, and other stakeholders as part of an effective state earthquake program. (Operational cost efficiencies almost invariably involve trade-offs between personnel costs and the quality of hardware and software.) Software tools that we currently rely on for quality performance include those developed by UUSS (e.g., SAC and shell scripts for estimating local magnitudes) and software developed by other organizations such as: USGS (Earthworm), University of Washington (interactive analysis software), ISTI (SeisNetWatch), and IRIS (PDCC, BUD tools). Although there are many pieces, there is little integration. One of the main challenges we face is the availability of a complete and coherent set of tools for automatic and post-processing to assist in achieving the goals/requirements set forth by ANSS. Taking our own network---and ANSS---to the next level

  10. [Quality of the structured abstracts presented at a congress].

    PubMed

    dos Santos, Edilson F; Pereira, Maurício G

    2007-01-01

    To assess and compare quality of abstracts presented at a medical congress (XIV Congresso da Sociedade Brasileira de Infectologia, November, 2005). The hypothesis is that material of better quality is chosen for oral presentation. All the 63 abstracts selected for oral presentation were compared with a random sample (n=63) of the 664 abstracts registered as poster presentations. Quality was measured by a structured questionnaire comprised of 33 criteria, distributed in eight categories: purpose, research design, setting, subjects, intervention, measurement, results and conclusions. The questionnaire was applied by one of the authors who were not blind to the objective of the study. The final score could range from 0 (bad) to 1 (excellent). Abstracts quality was considered moderately good. The overall mean quality scores were 0.60 and 0.62 respectively, for poster and oral presentation (p = 0.086). The criteria rated poorly were: subjects, variable measurements, location and conclusion. The tested hypothesis of better quality in abstracts selected for oral presentation has not been confirmed. It is recommended that organizers of the congresses the use of objective quality criteria to select the form of presentation while improving on quality.

  11. Development and evaluation of a quality score for abstracts

    PubMed Central

    Timmer, Antje; Sutherland, Lloyd R; Hilsden, Robert J

    2003-01-01

    Background The evaluation of abstracts for scientific meetings has been shown to suffer from poor inter observer reliability. A measure was developed to assess the formal quality of abstract submissions in a standardized way. Methods Item selection was based on scoring systems for full reports, taking into account published guidelines for structured abstracts. Interrater agreement was examined using a random sample of submissions to the American Gastroenterological Association, stratified for research type (n = 100, 1992–1995). For construct validity, the association of formal quality with acceptance for presentation was examined. A questionnaire to expert reviewers evaluated sensibility items, such as ease of use and comprehensiveness. Results The index comprised 19 items. The summary quality scores showed good interrater agreement (intra class coefficient 0.60 – 0.81). Good abstract quality was associated with abstract acceptance for presentation at the meeting. The instrument was found to be acceptable by expert reviewers. Conclusion A quality index was developed for the evaluation of scientific meeting abstracts which was shown to be reliable, valid and useful. PMID:12581457

  12. The data quality analyzer: A quality control program for seismic data

    NASA Astrophysics Data System (ADS)

    Ringler, A. T.; Hagerty, M. T.; Holland, J.; Gonzales, A.; Gee, L. S.; Edwards, J. D.; Wilson, D.; Baker, A. M.

    2015-03-01

    The U.S. Geological Survey's Albuquerque Seismological Laboratory (ASL) has several initiatives underway to enhance and track the quality of data produced from ASL seismic stations and to improve communication about data problems to the user community. The Data Quality Analyzer (DQA) is one such development and is designed to characterize seismic station data quality in a quantitative and automated manner. The DQA consists of a metric calculator, a PostgreSQL database, and a Web interface: The metric calculator, SEEDscan, is a Java application that reads and processes miniSEED data and generates metrics based on a configuration file. SEEDscan compares hashes of metadata and data to detect changes in either and performs subsequent recalculations as needed. This ensures that the metric values are up to date and accurate. SEEDscan can be run as a scheduled task or on demand. The PostgreSQL database acts as a central hub where metric values and limited station descriptions are stored at the channel level with one-day granularity. The Web interface dynamically loads station data from the database and allows the user to make requests for time periods of interest, review specific networks and stations, plot metrics as a function of time, and adjust the contribution of various metrics to the overall quality grade of the station. The quantification of data quality is based on the evaluation of various metrics (e.g., timing quality, daily noise levels relative to long-term noise models, and comparisons between broadband data and event synthetics). Users may select which metrics contribute to the assessment and those metrics are aggregated into a "grade" for each station. The DQA is being actively used for station diagnostics and evaluation based on the completed metrics (availability, gap count, timing quality, deviation from a global noise model, deviation from a station noise model, coherence between co-located sensors, and comparison between broadband data and synthetics

  13. Sensitivities Kernels of Seismic Traveltimes and Amplitudes for Quality Factor and Boundary Topography

    NASA Astrophysics Data System (ADS)

    Hsieh, M.; Zhao, L.; Ma, K.

    2010-12-01

    Finite-frequency approach enables seismic tomography to fully utilize the spatial and temporal distributions of the seismic wavefield to improve resolution. In achieving this goal, one of the most important tasks is to compute efficiently and accurately the (Fréchet) sensitivity kernels of finite-frequency seismic observables such as traveltime and amplitude to the perturbations of model parameters. In scattering-integral approach, the Fréchet kernels are expressed in terms of the strain Green tensors (SGTs), and a pre-established SGT database is necessary to achieve practical efficiency for a three-dimensional reference model in which the SGTs must be calculated numerically. Methods for computing Fréchet kernels for seismic velocities have long been established. In this study, we develop algorithms based on the finite-difference method for calculating Fréchet kernels for the quality factor Qμ and seismic boundary topography. Kernels for the quality factor can be obtained in a way similar to those for seismic velocities with the help of the Hilbert transform. The effects of seismic velocities and quality factor on either traveltime or amplitude are coupled. Kernels for boundary topography involve spatial gradient of the SGTs and they also exhibit interesting finite-frequency characteristics. Examples of quality factor and boundary topography kernels will be shown for a realistic model for the Taiwan region with three-dimensional velocity variation as well as surface and Moho discontinuity topography.

  14. High Voltage Seismic Generator

    NASA Astrophysics Data System (ADS)

    Bogacz, Adrian; Pala, Damian; Knafel, Marcin

    2015-04-01

    This contribution describes the preliminary result of annual cooperation of three student research groups from AGH UST in Krakow, Poland. The aim of this cooperation was to develop and construct a high voltage seismic wave generator. Constructed device uses a high-energy electrical discharge to generate seismic wave in ground. This type of device can be applied in several different methods of seismic measurement, but because of its limited power it is mainly dedicated for engineering geophysics. The source operates on a basic physical principles. The energy is stored in capacitor bank, which is charged by two stage low to high voltage converter. Stored energy is then released in very short time through high voltage thyristor in spark gap. The whole appliance is powered from li-ion battery and controlled by ATmega microcontroller. It is possible to construct larger and more powerful device. In this contribution the structure of device with technical specifications is resented. As a part of the investigation the prototype was built and series of experiments conducted. System parameter was measured, on this basis specification of elements for the final device were chosen. First stage of the project was successful. It was possible to efficiently generate seismic waves with constructed device. Then the field test was conducted. Spark gap wasplaced in shallowborehole(0.5 m) filled with salt water. Geophones were placed on the ground in straight line. The comparison of signal registered with hammer source and sparker source was made. The results of the test measurements are presented and discussed. Analysis of the collected data shows that characteristic of generated seismic signal is very promising, thus confirms possibility of practical application of the new high voltage generator. The biggest advantage of presented device after signal characteristics is its size which is 0.5 x 0.25 x 0.2 m and weight approximately 7 kg. This features with small li-ion battery makes

  15. Participation in the Apollo passive seismic experiment

    NASA Technical Reports Server (NTRS)

    Press, F.; Toksoez, M. N.; Dainty, A.

    1972-01-01

    Computer programs which were written to read digital tapes containing lunar seismic data were studied. Interpreting very early parts of the lunar seismogram as seismic body-wave phases enabled the determination of the structure of the outer part of the moon in the Fra Mauro region. The crust in the Fra Mauro region is 60 to 65 km-thick, overlaying a high velocity mantle. The crust is further divided into an upper part, 25 km thick, apparently made of material similar to the surficial basalts, and a lower part of seemingly different composition, possibly an anorthositic gabbro. The generation of the exceedingly long reverberating wave-train observed in lunar seismogram was also studied. This is believed to be due to an intense scattering layer with very high quality coefficient overlying a more homogeneous elastic medium. Titles and abstracts of related published papers are included.

  16. Method for determining formation quality factor from seismic data

    DOEpatents

    Taner, M. Turhan; Treitel, Sven

    2005-08-16

    A method is disclosed for calculating the quality factor Q from a seismic data trace. The method includes calculating a first and a second minimum phase inverse wavelet at a first and a second time interval along the seismic data trace, synthetically dividing the first wavelet by the second wavelet, Fourier transforming the result of the synthetic division, calculating the logarithm of this quotient of Fourier transforms and determining the slope of a best fit line to the logarithm of the quotient.

  17. Relationships between abstract features and methodological quality explained variations of social media activity derived from systematic reviews about psoriasis interventions.

    PubMed

    Ruano, J; Aguilar-Luque, M; Isla-Tejera, B; Alcalde-Mellado, P; Gay-Mimbrera, J; Hernandez-Romero, José Luis; Sanz-Cabanillas, J L; Maestre-López, B; González-Padilla, M; Carmona-Fernández, P J; Gómez-García, F; García-Nieto, A Vélez

    2018-05-24

    The aim of this study was to describe the relationship among abstract structure, readability, and completeness, and how these features may influence social media activity and bibliometric results, considering systematic reviews (SRs) about interventions in psoriasis classified by methodological quality. Systematic literature searches about psoriasis interventions were undertaken on relevant databases. For each review, methodological quality was evaluated using the Assessing the Methodological Quality of Systematic Reviews (AMSTAR) tool. Abstract extension, structure, readability, and quality and completeness of reporting were analyzed. Social media activity, which consider Twitter and Facebook mention counts, as well as Mendeley readers and Google scholar citations were obtained for each article. Analyses were conducted to describe any potential influence of abstract characteristics on review's social media diffusion. We classified 139 intervention SRs as displaying high/moderate/low methodological quality. We observed that abstract readability of SRs has been maintained high for last 20 years, although there are some differences based on their methodological quality. Free-format abstracts were most sensitive to the increase of text readability as compared with more structured abstracts (IMRAD or 8-headings), yielding opposite effects on their quality and completeness depending on the methodological quality: a worsening in low quality reviews and an improvement in those of high-quality. Both readability indices and PRISMA for Abstract total scores showed an inverse relationship with social media activity and bibliometric results in high methodological quality reviews but not in those of lower quality. Our results suggest that increasing abstract readability must be specially considered when writing free-format summaries of high-quality reviews, because this fact correlates with an improvement of their completeness and quality, and this may help to achieve broader

  18. Research on Seismic Wave Attenuation in Gas Hydrates Layer Using Vertical Cable Seismic Data

    NASA Astrophysics Data System (ADS)

    Wang, Xiangchun; Liang, Lunhang; Wu, Zhongliang

    2018-06-01

    Vertical cable seismic (VCS) data are the most suitable seismic data for estimating the quality factor Q values of layers under the sea bottom by now. Here the quality factor Q values are estimated using the high-precision logarithmic spectrum ratio method for VCS data. The estimated Q values are applied to identify the layers with gas hydrates and free gas. From the results it can be seen that the Q value in layer with gas hydrates becomes larger and the Q value in layer with free gas becomes smaller than layers without gas hydrates or free gas. Additionally, the estimated Q values are used for inverse Q filtering processing to compensate the attenuated seismic signal's high-frequency component. From the results it can be seen that the main frequency of seismic signal is improved and the frequency band is broadened, the resolution of the VCS data is improved effectively.

  19. The data quality analyzer: a quality control program for seismic data

    USGS Publications Warehouse

    Ringler, Adam; Hagerty, M.T.; Holland, James F.; Gonzales, A.; Gee, Lind S.; Edwards, J.D.; Wilson, David; Baker, Adam

    2015-01-01

    The quantification of data quality is based on the evaluation of various metrics (e.g., timing quality, daily noise levels relative to long-term noise models, and comparisons between broadband data and event synthetics). Users may select which metrics contribute to the assessment and those metrics are aggregated into a “grade” for each station. The DQA is being actively used for station diagnostics and evaluation based on the completed metrics (availability, gap count, timing quality, deviation from a global noise model, deviation from a station noise model, coherence between co-located sensors, and comparison between broadband data and synthetics for earthquakes) on stations in the Global Seismographic Network and Advanced National Seismic System.

  20. An interrupted time series analysis showed suboptimal improvement in reporting quality of trial abstract.

    PubMed

    Chhapola, Viswas; Tiwari, Soumya; Brar, Rekha; Kanwal, Sandeep Kumar

    2016-03-01

    To assess and compare the immediate and long-term change in reporting quality of randomized controlled trial (RCT) abstracts published in Pediatrics, The Journal of Pediatrics, and JAMA Pediatrics before and after the publication of Consolidated Standards of Reporting Trial (CONSORT)-abstract statement. Study had "Interrupted time-series" design. Eligible RCT abstracts were retrieved by PubMed search in two study periods from January 2003 to December 2007 (pre-CONSORT) and January 2010 to December 2014 (post-CONSORT). These abstracts were matched with the CONSORT checklist for abstracts. The primary outcome measure was CONSORT-abstract score defined as number of CONSORT items correctly reported divided by 18 and expressed as percentage. The mean percentage scores were used to compare reporting quality between pre- and post-CONSORT using segmented linear regression. A total of 424 RCT abstracts in pre-CONSORT and 467 in post-CONSORT were analyzed. A significant change in slope of regression line between two time periods (0.151 [confidence interval CI, 0.004-0.298], P = 0.044) was observed. Intercepts did not show a significant difference (-2.39 [CI, 4.93-0.157], P = 0.065). The overall reporting quality of RCT abstracts in the high-impact pediatrics journals was suboptimal (<50%); however, it improved when assessed over a 5-year period, implying slow but gradual adoption of guideline. Copyright © 2016 Elsevier Inc. All rights reserved.

  1. Seismic High Attenuation Beneath Southern New England Indicates High Asthenospheric Temperature and No Melt

    NASA Astrophysics Data System (ADS)

    Dong, M. T.; Menke, W. H.

    2017-12-01

    Seismic attenuation exhibits strong geographic variability in northeastern North America, with the highest values associated with the previously-recognized Northern Appalachian Anomaly (NAA) in southern New England. The shear wave quality factor at 100 km depth is 14s<25, the ratio of P-wave and S-wave quality factors is QP/Qs=1.2±0.03, and the frequency dependence parameter is α=0.39±0.025. The high values of Qp/Qs and α are compatible with laboratory measurements of unmelted rock and incompatible with widespread melting. The low Qs (high shear attenuation) implies high mantle temperatures ( 1550-1650°C) at 100 km depth (assuming no melt). Small-scale variations in attenuation suggests structural heterogeneity within the NAA, possibly due to lithospheric delamination caused by directional asthenospheric flow.

  2. High-resolution seismic reflection surveying with a land streamer

    NASA Astrophysics Data System (ADS)

    Cengiz Tapırdamaz, Mustafa; Cankurtaranlar, Ali; Ergintav, Semih; Kurt, Levent

    2013-04-01

    In this study, newly designed seismic reflection data acquisition array (land streamer) is utilized to image the shallow subsurface. Our acquisition system consist of 24 geophones screwed on iron plates with 2 m spacing, moving on the surface of the earth which are connected with fire hose. Completely original, 4.5 Kg weight iron plates provides satisfactory coupling. This land-streamer system enables rapid and cost effective acquisition of seismic reflection data due to its operational facilities. First test studies were performed using various seismic sources such as a mini-vibro truck, buffalo-gun and hammer. The final fieldwork was performed on a landslide area which was studied before. Data acquisition was carried out on the line that was previously measured by the seismic survey using 5 m geophone and shot spacing. This line was chosen in order to re-image known reflection patterns obtained from the previous field study. Taking penetration depth into consideration, a six-cartridge buffalo-gun was selected as a seismic source to achieve high vertical resolution. Each shot-point drilled 50 cm for gunshots to obtain high resolution source signature. In order to avoid surface waves, the offset distance between the source and the first channel was chosen to be 50 m and the shot spacing was 2 m. These acquisition parameters provided 12 folds at each CDP points. Spatial sampling interval was 1 m at the surface. The processing steps included standard stages such as gain recovery, editing, frequency filtering, CDP sorting, NMO correction, static correction and stacking. Furthermore, surface consistent residual static corrections were applied recursively to improve image quality. 2D F-K filter application was performed to suppress air and surface waves at relatively deep part of the seismic section. Results show that, this newly designed, high-resolution land seismic data acquisition equipment (land-streamer) can be successfully used to image subsurface. Likewise

  3. Does the CONSORT checklist for abstracts improve the quality of reports of randomized controlled trials on clinical pathways?

    PubMed

    Cui, Qi; Tian, Jinhui; Song, Xuping; Yang, Kehu

    2014-12-01

    The extension of the Consolidated Standards of Reporting Trials (CONSORT) statement provides reporting guidelines to improve the reporting quality of randomized controlled trials (RCTs). This present study was aim to assess the reporting quality of abstracts of RCTs on clinical pathway. Eight databases were searched from inception to November 2012 to identify RCTs. We extracted basic information and CONSORT items from abstracts. Each abstract was assessed independently by two reviewers. Statistical analyses were performed with SPSS 13.0. Level of significance was set at P < 0.05. 328 abstracts were included. 300 (91.5%) were published in Chinese, of which 292 were published on high impact factor journals. 28 English abstracts were all published on Science Citation Index (SCI) journals. (1) Intervention, objective and outcome were almost fully reported in all abstracts, while recruitment and funding were never reported. (2) There are nine items (P < 0.05) in Chinese that were of low quality compared with in English. There was statistically difference on total score between Chinese and English abstracts (P < 0.00001). (3) There was no difference in any items between high and low impact factor journal in China. (4) In SCI journals, there were significant changes in reporting for three items trial design (P = 0.026), harms (P = 0.039) and trial registration (P = 0.019) in different periods (pre- and post-CONSORT), but only the numbers of randomized (P = 0.003) changed in Chinese abstracts. The reporting quality of abstracts of RCTs on clinical pathway still should be improved. After the publication of CONSORT for abstracts guideline, the RCT abstracts reporting quality were improvement to some extent. The abstracts in Chinese journals showed non-adherence to the CONSORT for abstracts guidelines. © 2014 John Wiley & Sons, Ltd.

  4. SEER*Educate: Use of Abstracting Quality Index Scores to Monitor Improvement of All Employees.

    PubMed

    Potts, Mary S; Scott, Tim; Hafterson, Jennifer L

    2016-01-01

    Integral parts of the Seattle-Puget Sound's Cancer Surveillance System registry's continuous improvement model include the incorporation of SEER*Educate into its training program for all staff and analyzing assessment results using the Abstracting Quality Index (AQI). The AQI offers a comprehensive measure of overall performance in SEER*Educate, which is a Web-based application used to personalize learning and diagnostically pinpoint each staff member's place on the AQI continuum. The assessment results are tallied from 6 abstracting standards within 2 domains: incidence reporting and coding accuracy. More than 100 data items are aligned to 1 or more of the 6 standards to build an aggregated score that is placed on a continuum for continuous improvement. The AQI score accurately identifies those individuals who have a good understanding of how to apply the 6 abstracting standards to reliably generate high quality abstracts.

  5. Imaging the Danish Chalk Group with high resolution, 3-component seismics

    NASA Astrophysics Data System (ADS)

    Kammann, J.; Rasmussen, S. L.; Nielsen, L.; Malehmir, A.; Stemmerik, L.

    2016-12-01

    The Chalk Group in the Danish Basin forms important reservoirs to hydrocarbons as well as water resources, and it has been subject to several seismic studies to determine e.g. structural elements, deposition and burial history. This study focuses on the high quality seismic response of a survey acquired with an accelerated 45 kg weight drop and 3-component MEMS-based sensors and additional wireless vertical-type sensors. The 500 m long profile was acquired during one day close to a chalk quarry and chalk cliffs of the Stevns peninsula in eastern Denmark where the well-known K-T (Cretaceous-Tertiary) boundary and different chalk lithologies are well-exposed. With this simple and fast procedure we were able to achieve deep P-wave penetration to the base of the Chalk Group at about 900 m depth. Additionally, the CMP-processed seismic image of the vertical component stands out by its high resolution. Sedimentary features are imaged in the near-surface Danian, as well as in the deeper Maastrichtian and Upper Campanian parts of the Chalk Group. Integration with borehole data suggests that changes in composition, in particular clay content, correlate with changes in reflectivity of the seismic data set. While the pure chalk in the Maastrichtian deposits shows rather low reflectivity, succession enriched in clay appear to be more reflective. The integration of the mentioned methods gives the opportunity to connect changes in facies to the elastic response of the Chalk Group in its natural environmental conditions.

  6. High-resolution lithospheric imaging with seismic interferometry

    NASA Astrophysics Data System (ADS)

    Ruigrok, Elmer; Campman, Xander; Draganov, Deyan; Wapenaar, Kees

    2010-10-01

    In recent years, there has been an increase in the deployment of relatively dense arrays of seismic stations. The availability of spatially densely sampled global and regional seismic data has stimulated the adoption of industry-style imaging algorithms applied to converted- and scattered-wave energy from distant earthquakes, leading to relatively high-resolution images of the lower crust and upper mantle. We use seismic interferometry to extract reflection responses from the coda of transmitted energy from distant earthquakes. In theory, higher-resolution images can be obtained when migrating reflections obtained with seismic interferometry rather than with conversions, traditionally used in lithospheric imaging methods. Moreover, reflection data allow the straightforward application of algorithms previously developed in exploration seismology. In particular, the availability of reflection data allows us to extract from it a velocity model using standard multichannel data-processing methods. However, the success of our approach relies mainly on a favourable distribution of earthquakes. In this paper, we investigate how the quality of the reflection response obtained with interferometry is influenced by the distribution of earthquakes and the complexity of the transmitted wavefields. Our analysis shows that a reasonable reflection response could be extracted if (1) the array is approximately aligned with an active zone of earthquakes, (2) different phase responses are used to gather adequate angular illumination of the array and (3) the illumination directions are properly accounted for during processing. We illustrate our analysis using a synthetic data set with similar illumination and source-side reverberation characteristics as field data recorded during the 2000-2001 Laramie broad-band experiment. Finally, we apply our method to the Laramie data, retrieving reflection data. We extract a 2-D velocity model from the reflections and use this model to migrate the

  7. Seismic site-response characterization of high-velocity sites using advanced geophysical techniques: application to the NAGRA-Net

    NASA Astrophysics Data System (ADS)

    Poggi, V.; Burjanek, J.; Michel, C.; Fäh, D.

    2017-08-01

    The Swiss Seismological Service (SED) has recently finalised the installation of ten new seismological broadband stations in northern Switzerland. The project was led in cooperation with the National Cooperative for the Disposal of Radioactive Waste (Nagra) and Swissnuclear to monitor micro seismicity at potential locations of nuclear-waste repositories. To further improve the quality and usability of the seismic recordings, an extensive characterization of the sites surrounding the installation area was performed following a standardised investigation protocol. State-of-the-art geophysical techniques have been used, including advanced active and passive seismic methods. The results of all analyses converged to the definition of a set of best-representative 1-D velocity profiles for each site, which are the input for the computation of engineering soil proxies (traveltime averaged velocity and quarter-wavelength parameters) and numerical amplification models. Computed site response is then validated through comparison with empirical site amplification, which is currently available for any station connected to the Swiss seismic networks. With the goal of a high-sensitivity network, most of the NAGRA stations have been installed on stiff-soil sites of rather high seismic velocity. Seismic characterization of such sites has always been considered challenging, due to lack of relevant velocity contrast and the large wavelengths required to investigate the frequency range of engineering interest. We describe how ambient vibration techniques can successfully be applied in these particular conditions, providing practical recommendations for best practice in seismic site characterization of high-velocity sites.

  8. Estimation of gas hydrate saturation using isotropic and anisotropic models at the location selected after measurement of seismic quality factor

    NASA Astrophysics Data System (ADS)

    Mundhra, A.; Sain, K.; Shankar, U.

    2012-12-01

    The Indian National Gas Hydrate Program Expedition (NGHP) 01 discovered gas hydrate in unconsolidated sediments at several drilling sites along the continental margins of Krishna-Godavari Basin, India. Presence of gas hydrate reduces the attenuation of travelling seismic waves which can be measured by estimation of seismic quality factor (Dasgupta and Clark, 1998). Here, we use log spectral ratio method (Sain et al, 2009) to compute quality factor at three locations, among which two have strong and one has no bottom simulating reflector (BSR), along seismic cross-line near one of the drilling site. Interval quality factor for three submarine sedimentary layers bounded by seafloor, BSR, one reflector above and another reflector below the BSR has been measured. To compute quality factor, unprocessed pre-stack seismic data has been used to avoid any influence of processing sequence. We have estimated that interval quality factor lies within 200-220 in the interval having BSR while it varies within 90-100 in other intervals. Thereby, high interval quality factor ascertains that observed BSR is due to presence of gas hydrates. We have performed rock physics modelling by using isotropic and anisotropic models, to quantitatively estimate gas hydrate saturation at one of the location where an interval has high quality factor. Abruptly high measured resistivity and high P-wave velocity in the interval, leads to towering hydrate saturation (Archie,1942 and Helegrud et al, 1999) in comparison to lower gas hydrate saturations estimated by pressure core and chlorinity measurements. Overestimation of saturation is attributed to presence of near vertical fractures that are identified from logging-while-drilling resistivity images. We have carried out anisotropic modeling (Kennedy and Herrick, 2004 and Lee,2009) by incorporating fracture volume and fracture porosity to estimate hydrate saturation and have observed that modeled gas hydrate saturations agree with the lower gas

  9. Study for the quality assessment of abstracts presented to Italian public health national conferences: a six years survey.

    PubMed

    Castaldi, S; Colombo, A; D'Errico, R; Bert, F; Siliquini, R; Ceruti, M; Curti, S; Gaietta, M; Garavelli, E; Legouellec, L; Lovato, E; Martinese, M; Visco, F

    2013-01-01

    Oral and poster presentations at congresses are essential to spread scientific knowledge among the medical community. Many scientific societies have analyzed the quality of papers presented at their meetings but no information on abstracts' evaluation has been presented in Public Health field. This study aims to examine the quality of abstracts presented at annual meetings of Italian Public Health Society (SItI) in the period 2005-2010 through a validated checklist grid, evaluating eight dimensions: Inherency, Structure, Originality, Objectives, Study design, Sources, Results, Conclusions. Each item was scored from 0 to 3 points (max score: 24) and we used the average score in our study (15) as threshold of good quality. A multivariate analysis was performed in order to investigate predictors of score of abstracts presented. A total of 4,399 abstracts (1,172 oral communications, 3,227 posters) was examined. Around 60% were submitted by Universities and around 40% were from Central Italy. The highest quality was found in the fields of Vaccines (average score 18.9), Infectious Diseases (18) and in abstracts submitted by Universities (16.4). Predictors of lower quality identified were geographical area and affiliation (p= 0.002). Abstracts containing well-written Results, Conclusions and Objectives (3 points) were more likely to be of high quality(OR=55.6, OR=41.9, and OR=157.4; p>0.001) CONCLUSIONS: This is the first European study evaluating the quality of abstracts in the public health field. A reliable evaluation tool is fundamental to offer a transparent methodology of assessment and to improve the quality of research.

  10. Annual Quality Assurance Conference Abstracts by Barbara Marshik

    EPA Pesticide Factsheets

    25th Annual Quality Assurance Conference. Abstracts: Material and Process Conditions for Successful Use of Extractive Sampling Techniques and Certification Methods Errors in the Analysis of NMHC and VOCs in CNG-Based Engine Emissions by Barbara Marshik

  11. A high-resolution ambient seismic noise model for Europe

    NASA Astrophysics Data System (ADS)

    Kraft, Toni

    2014-05-01

    measurement precision (i.e. earthquake location), while considering this extremely complex boundary condition. To solve this problem I have developed a high-resolution ambient seismic noise model for Europe. The model is based on land-use data derived from satellite imagery by the EU-project CORINE in a resolution of 100x100m. The the CORINE data consists of several land-use classes, which, besides others, contain: industrial areas, mines, urban fabric, agricultural areas, permanent corps, forests and open spaces. Additionally, open GIS data for highways, and major and minor roads and railway lines were included from the OpenStreetMap project (www.openstreetmap.org). This data was divided into three classes that represent good, intermediate and bad ambient conditions of the corresponding land-use class based on expert judgment. To account for noise propagation away from its source a smoothing operator was applied to individual land-use noise-fields. Finally, the noise-fields were stacked to obtain an European map of ambient noise conditions. A calibration of this map with data of existing seismic stations Europe allowed me to estimate the expected noise level in actual ground motion units for the three ambient noise condition classes of the map. The result is a high-resolution ambient seismic noise map, that allows the network designer to make educated predictions on the expected noise level for arbitrary location in Europe. The ambient noise model was successfully tested in several network optimization projects in Switzerland and surrounding countries and will hopefully be a valuable contribution to improving the data quality of microseismic monitoring networks in Europe.

  12. pySeismicDQA: open source post experiment data quality assessment and processing

    NASA Astrophysics Data System (ADS)

    Polkowski, Marcin

    2017-04-01

    Seismic Data Quality Assessment is python based, open source set of tools dedicated for data processing after passive seismic experiments. Primary goal of this toolset is unification of data types and formats from different dataloggers necessary for further processing. This process requires additional data checks for errors, equipment malfunction, data format errors, abnormal noise levels, etc. In all such cases user needs to decide (manually or by automatic threshold) if data is removed from output dataset. Additionally, output dataset can be visualized in form of website with data availability charts and waveform visualization with earthquake catalog (external). Data processing can be extended with simple STA/LTA event detection. pySeismicDQA is designed and tested for two passive seismic experiments in central Europe: PASSEQ 2006-2008 and "13 BB Star" (2013-2016). National Science Centre Poland provided financial support for this work via NCN grant DEC-2011/02/A/ST10/00284.

  13. GDP: A new source for shallow high-resolution seismic exploration

    NASA Astrophysics Data System (ADS)

    Rashed, Mohamed A.

    2009-06-01

    Gas-Driven Piston (GDP) is a new source for shallow seismic exploration. This source works by igniting a small amount of gas inside a closed chamber connected to a vertical steel cylinder. The gas explosion drives a steel piston, mounted inside the cylinder, downward so that the piston's thick head hits a steel base at the end of the cylinder generating a strong shock wave into the ground. Experimental field tests conducted near Ismailia, Egypt, prove that the portable, inexpensive and environmentally benign GDP generates stronger seismic waves than the sledgehammer that is commonly used in shallow seismic exploration. Tests also show that GDP is a highly repeatable and controllable and that its seismic waves contain a good amount of high frequencies which makes the GDP an excellent source for shallow seismic exploration.

  14. High-resolution chirp seismic reflection data acquired from the Cap de Creus shelf and canyon area, Gulf of Lions, Spain in 2004

    USGS Publications Warehouse

    Grossman, Eric E.; Hart, Patrick E.; Field, Michael E.; Triezenberg, Peter

    2006-01-01

    Seismic reflection data were collected from the Cap de Creus shelf and canyon in the southwest portion of the Gulf of Lions in October 2004. The data were acquired using the U.S. Geological Survey`s (USGS) high-resolution Edgetech CHIRP 512i seismic reflection system aboard the R/V Oceanus. Data from the shipboard 3.5 kHz echosounder were also collected but are not presented here. The seismic reflection data were collected as part of EuroSTRATAFORM funded by the Office of Naval Research. In October 2004, more than 200 km of high resolution seismic reflection data were collected in water depths ranging 30 m - 600 m. All data were recorded with a Delph Seismic PC-based digital recording system and processed with Delph Seismic software. Processed sections were georeferenced into tiff images for digital archive, processing and display. Penetration ranged 20-80 m. The data feature high quality vertical cross-section imagery of numerous sequences of Quaternary seismic stratigraphy. 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. The data are of high quality and provide new information on the location and thickness of sediment deposits overlying a major erosion surface on the Cap de Creus shelf; they also provide new insight into sediment processes on the walls and in the channel of Cap de Creus Canyon. These data are under study by researchers at the US Geological Survey, the University of Barcelona, and Texas A and M University. Copies of the data are available to all researchers.

  15. Mini-Sosie high-resolution seismic method aids hazards studies

    USGS Publications Warehouse

    Stephenson, W.J.; Odum, J.; Shedlock, K.M.; Pratt, T.L.; Williams, R.A.

    1992-01-01

    The Mini-Sosie high-resolution seismic method has been effective in imaging shallow-structure and stratigraphic features that aid in seismic-hazard and neotectonic studies. The method is not an alternative to Vibroseis acquisition for large-scale studies. However, it has two major advantages over Vibroseis as it is being used by the USGS in its seismic-hazards program. First, the sources are extremely portable and can be used in both rural and urban environments. Second, the shifting-and-summation process during acquisition improves the signal-to-noise ratio and cancels out seismic noise sources such as cars and pedestrians. -from Authors

  16. A High-Resolution View of Global Seismicity

    NASA Astrophysics Data System (ADS)

    Waldhauser, F.; Schaff, D. P.

    2014-12-01

    We present high-precision earthquake relocation results from our global-scale re-analysis of the combined seismic archives of parametric data for the years 1964 to present from the International Seismological Centre (ISC), the USGS's Earthquake Data Report (EDR), and selected waveform data from IRIS. We employed iterative, multistep relocation procedures that initially correct for large location errors present in standard global earthquake catalogs, followed by a simultaneous inversion of delay times formed from regional and teleseismic arrival times of first and later arriving phases. An efficient multi-scale double-difference (DD) algorithm is used to solve for relative event locations to the precision of a few km or less, while incorporating information on absolute hypocenter locations from catalogs such as EHB and GEM. We run the computations on both a 40-core cluster geared towards HTC problems (data processing) and a 500-core HPC cluster for data inversion. Currently, we are incorporating waveform correlation delay time measurements available for events in selected regions, but are continuously building up a comprehensive, global correlation database for densely distributed events recorded at stations with a long history of high-quality waveforms. The current global DD catalog includes nearly one million earthquakes, equivalent to approximately 70% of the number of events in the ISC/EDR catalogs initially selected for relocation. The relocations sharpen the view of seismicity in most active regions around the world, in particular along subduction zones where event density is high, but also along mid-ocean ridges where existing hypocenters are especially poorly located. The new data offers the opportunity to investigate earthquake processes and fault structures along entire plate boundaries at the ~km scale, and provides a common framework that facilitates analysis and comparisons of findings across different plate boundary systems.

  17. Micro-seismicity in the Gulf of Cadiz: Is there a link between micro-seismicity, high magnitude earthquakes and active faults?

    NASA Astrophysics Data System (ADS)

    Silva, Sónia; Terrinha, Pedro; Matias, Luis; Duarte, João C.; Roque, Cristina; Ranero, César R.; Geissler, Wolfram H.; Zitellini, Nevio

    2017-10-01

    The Gulf of Cadiz seismicity is characterized by persistent low to intermediate magnitude earthquakes, occasionally punctuated by high magnitude events such as the M 8.7 1755 Great Lisbon earthquake and the M = 7.9 event of February 28th, 1969. Micro-seismicity was recorded during 11 months by a temporary network of 25 ocean bottom seismometers (OBSs) in an area of high seismic activity, encompassing the potential source areas of the mentioned large magnitude earthquakes. We combined micro-seismicity analysis with processing and interpretation of deep crustal seismic reflection profiles and available refraction data to investigate the possible tectonic control of the seismicity in the Gulf of Cadiz area. Three controlling mechanisms are explored: i) active tectonic structures, ii) transitions between different lithospheric domains and inherited Mesozoic structures, and iii) fault weakening mechanisms. Our results show that micro-seismicity is mostly located in the upper mantle and is associated with tectonic inversion of extensional rift structures and to the transition between different lithospheric/rheological domains. Even though the crustal structure is well imaged in the seismic profiles and in the bathymetry, crustal faults show low to negligible seismic activity. A possible explanation for this is that the crustal thrusts are thin-skinned structures rooting in relatively shallow sub-horizontal décollements associated with (aseismic) serpentinization levels at the top of the lithospheric mantle. Therefore, co-seismic slip along crustal thrusts may only occur during large magnitude events, while for most of the inter-seismic cycle these thrusts remain locked, or slip aseismically. We further speculate that high magnitude earthquake's ruptures may only nucleate in the lithospheric mantle and then propagate into the crust across the serpentinized layers.

  18. Seismic Data Archive Quality Assurance -- Analytics Adding Value at Scale

    NASA Astrophysics Data System (ADS)

    Casey, R. E.; Ahern, T. K.; Sharer, G.; Templeton, M. E.; Weertman, B.; Keyson, L.

    2015-12-01

    Since the emergence of real-time delivery of seismic data over the last two decades, solutions for near-real-time quality analysis and station monitoring have been developed by data producers and data stewards. This has allowed for a nearly constant awareness of the quality of the incoming data and the general health of the instrumentation around the time of data capture. Modern quality assurance systems are evolving to provide ready access to a large variety of metrics, a rich and self-correcting history of measurements, and more importantly the ability to access these quality measurements en-masse through a programmatic interface.The MUSTANG project at the IRIS Data Management Center is working to achieve 'total archival data quality', where a large number of standardized metrics, some computationally expensive, are generated and stored for all data from decades past to the near present. To perform this on a 300 TB archive of compressed time series requires considerable resources in network I/O, disk storage, and CPU capacity to achieve scalability, not to mention the technical expertise to develop and maintain it. In addition, staff scientists are necessary to develop the system metrics and employ them to produce comprehensive and timely data quality reports to assist seismic network operators in maintaining their instrumentation. All of these metrics must be available to the scientist 24/7.We will present an overview of the MUSTANG architecture including the development of its standardized metrics code in R. We will show examples of the metrics values that we make publicly available to scientists and educators and show how we are sharing the algorithms used. We will also discuss the development of a capability that will enable scientific researchers to specify data quality constraints on their requests for data, providing only the data that is best suited to their area of study.

  19. Reassessment of the Seismicity and seismic hazards of Libya

    NASA Astrophysics Data System (ADS)

    Ben Suleman, A.; Elmeladi, A.

    2009-04-01

    The tectonic evolution of Libya, located at the northern extreme of the African continent, has yielded a complex crustal structure that is composed of a series of basins and uplifts. The present day deformation of Libya is the result of the Eurasia-Africa continental collision. At the end of the year 2005, The Libyan National Seismological Network was established to monitor local, regional and teleseismic activities, as well as to provide high quality data for research projects both locally and on the regional and global scale. This study aims to discuss the seismicity of Libya by using the new data from the Libyan national seismological network and to focus on the seismic hazards. At first glance the seismic activity map shows dominant trends of seismicity with most of the seismic activity concentrated along the northern coastal areas. Four major seismic trends were quite noticeable. A first trend is a NW-SE direction coinciding with the eastern boarder of the Hun Graben. A second trend is also a NW-SE direction in the offshore area and might be a continuation of this trend. The other two trends were located in the western Gulf of Sirt and Cyrenaica platform. The rest of seismicity is diffuse either offshore or in land, with no good correlation with well-mapped faults. Detailed investigations of the Libyan seismicity indicates that the Libya has experienced earthquakes of varying magnitudes and that there is definitely a certain amount of seismic risk involved in engineering projects, particularly in the northern regions. Detailed investigation of the distribution of the Libyan earthquakes in space and time along with all other geological considerations suggested the classification of the country into four seismic zones with the Hun graben zone being the most seismically active zone.

  20. Astronomical Instrumentation Systems Quality Management Planning: AISQMP (Abstract)

    NASA Astrophysics Data System (ADS)

    Goldbaum, J.

    2017-12-01

    (Abstract only) The capability of small aperture astronomical instrumentation systems (AIS) to make meaningful scientific contributions has never been better. The purpose of AIS quality management planning (AISQMP) is to ensure the quality of these contributions such that they are both valid and reliable. The first step involved with AISQMP is to specify objective quality measures not just for the AIS final product, but also for the instrumentation used in its production. The next step is to set up a process to track these measures and control for any unwanted variation. The final step is continual effort applied to reducing variation and obtaining measured values near optimal theoretical performance. This paper provides an overview of AISQMP while focusing on objective quality measures applied to astronomical imaging systems.

  1. High-resolution seismic measurements at loamy dikes for monitoring high-water influences

    NASA Astrophysics Data System (ADS)

    Jaksch, Katrin; Giese, Rüdiger

    2010-05-01

    For the risk management of high-water events it is important to know how secure river dikes are. Even the structures of dikes are often unknown. Methods for the exploration of existing dikes and of their underground, for an evaluation of failure potential and strengthening requirements are needed. In the presented work, the potential of a high-resolution seismics to monitor the moisture penetration of dikes during flood periods was analyzed. To identify the extent of moisture penetration and to determine the structures of a loamy dike body would enable to determine the probability of a dike failure. Dikes made of loam show a different behavior of moisture penetration under high-water influence. The distribution and penetration of water is moderate compared to sandy dikes and resist longer high-water events. The water expands slowly in the dike body in all directions known as fingering. It should be analyzed how the moisture penetration from a dike can be displayed with seismic methods. The aim was to identify on the basis of seismic measurements the areas of moisture penetration within a dike during a flood and out of it to determine the probability of collapse of the dike. For that purpose the structures in the dike body should be determined in reference to the materials and his soil parameters like water content and porosity. A test facility was built for dikes including a regulation for the water level. This allowed the simulation of flood scenarios at dikes. Two dikes with different loam content were built in order to determine the failure mechanism of dikes. With a width of 8 meters at the basis they had nearly the dimension of river dikes. Seismic instrumentation was installed on both dike models. The seismic survey consists of three parallel receiver lines on the dike which recorded seismic signals emitted along the same lines, resulting in a 3D-seismic data set. The receivers were 3-component-geophones fixed in spikes, at the flooded side of the dike were

  2. High-Level Data-Abstraction System

    NASA Technical Reports Server (NTRS)

    Fishwick, P. A.

    1986-01-01

    Communication with data-base processor flexible and efficient. High Level Data Abstraction (HILDA) system is three-layer system supporting data-abstraction features of Intel data-base processor (DBP). Purpose of HILDA establishment of flexible method of efficiently communicating with DBP. Power of HILDA lies in its extensibility with regard to syntax and semantic changes. HILDA's high-level query language readily modified. Offers powerful potential to computer sites where DBP attached to DEC VAX-series computer. HILDA system written in Pascal and FORTRAN 77 for interactive execution.

  3. Large-scale seismic waveform quality metric calculation using Hadoop

    DOE PAGES

    Magana-Zook, Steven; Gaylord, Jessie M.; Knapp, Douglas R.; ...

    2016-05-27

    Here in this work we investigated the suitability of Hadoop MapReduce and Apache Spark for large-scale computation of seismic waveform quality metrics by comparing their performance with that of a traditional distributed implementation. The Incorporated Research Institutions for Seismology (IRIS) Data Management Center (DMC) provided 43 terabytes of broadband waveform data of which 5.1 TB of data were processed with the traditional architecture, and the full 43 TB were processed using MapReduce and Spark. Maximum performance of ~0.56 terabytes per hour was achieved using all 5 nodes of the traditional implementation. We noted that I/O dominated processing, and that I/Omore » performance was deteriorating with the addition of the 5th node. Data collected from this experiment provided the baseline against which the Hadoop results were compared. Next, we processed the full 43 TB dataset using both MapReduce and Apache Spark on our 18-node Hadoop cluster. We conducted these experiments multiple times with various subsets of the data so that we could build models to predict performance as a function of dataset size. We found that both MapReduce and Spark significantly outperformed the traditional reference implementation. At a dataset size of 5.1 terabytes, both Spark and MapReduce were about 15 times faster than the reference implementation. Furthermore, our performance models predict that for a dataset of 350 terabytes, Spark running on a 100-node cluster would be about 265 times faster than the reference implementation. We do not expect that the reference implementation deployed on a 100-node cluster would perform significantly better than on the 5-node cluster because the I/O performance cannot be made to scale. Finally, we note that although Big Data technologies clearly provide a way to process seismic waveform datasets in a high-performance and scalable manner, the technology is still rapidly changing, requires a high degree of investment in personnel, and will

  4. Large-scale seismic waveform quality metric calculation using Hadoop

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

    Magana-Zook, Steven; Gaylord, Jessie M.; Knapp, Douglas R.

    Here in this work we investigated the suitability of Hadoop MapReduce and Apache Spark for large-scale computation of seismic waveform quality metrics by comparing their performance with that of a traditional distributed implementation. The Incorporated Research Institutions for Seismology (IRIS) Data Management Center (DMC) provided 43 terabytes of broadband waveform data of which 5.1 TB of data were processed with the traditional architecture, and the full 43 TB were processed using MapReduce and Spark. Maximum performance of ~0.56 terabytes per hour was achieved using all 5 nodes of the traditional implementation. We noted that I/O dominated processing, and that I/Omore » performance was deteriorating with the addition of the 5th node. Data collected from this experiment provided the baseline against which the Hadoop results were compared. Next, we processed the full 43 TB dataset using both MapReduce and Apache Spark on our 18-node Hadoop cluster. We conducted these experiments multiple times with various subsets of the data so that we could build models to predict performance as a function of dataset size. We found that both MapReduce and Spark significantly outperformed the traditional reference implementation. At a dataset size of 5.1 terabytes, both Spark and MapReduce were about 15 times faster than the reference implementation. Furthermore, our performance models predict that for a dataset of 350 terabytes, Spark running on a 100-node cluster would be about 265 times faster than the reference implementation. We do not expect that the reference implementation deployed on a 100-node cluster would perform significantly better than on the 5-node cluster because the I/O performance cannot be made to scale. Finally, we note that although Big Data technologies clearly provide a way to process seismic waveform datasets in a high-performance and scalable manner, the technology is still rapidly changing, requires a high degree of investment in personnel, and will

  5. Large-scale seismic waveform quality metric calculation using Hadoop

    NASA Astrophysics Data System (ADS)

    Magana-Zook, S.; Gaylord, J. M.; Knapp, D. R.; Dodge, D. A.; Ruppert, S. D.

    2016-09-01

    In this work we investigated the suitability of Hadoop MapReduce and Apache Spark for large-scale computation of seismic waveform quality metrics by comparing their performance with that of a traditional distributed implementation. The Incorporated Research Institutions for Seismology (IRIS) Data Management Center (DMC) provided 43 terabytes of broadband waveform data of which 5.1 TB of data were processed with the traditional architecture, and the full 43 TB were processed using MapReduce and Spark. Maximum performance of 0.56 terabytes per hour was achieved using all 5 nodes of the traditional implementation. We noted that I/O dominated processing, and that I/O performance was deteriorating with the addition of the 5th node. Data collected from this experiment provided the baseline against which the Hadoop results were compared. Next, we processed the full 43 TB dataset using both MapReduce and Apache Spark on our 18-node Hadoop cluster. These experiments were conducted multiple times with various subsets of the data so that we could build models to predict performance as a function of dataset size. We found that both MapReduce and Spark significantly outperformed the traditional reference implementation. At a dataset size of 5.1 terabytes, both Spark and MapReduce were about 15 times faster than the reference implementation. Furthermore, our performance models predict that for a dataset of 350 terabytes, Spark running on a 100-node cluster would be about 265 times faster than the reference implementation. We do not expect that the reference implementation deployed on a 100-node cluster would perform significantly better than on the 5-node cluster because the I/O performance cannot be made to scale. Finally, we note that although Big Data technologies clearly provide a way to process seismic waveform datasets in a high-performance and scalable manner, the technology is still rapidly changing, requires a high degree of investment in personnel, and will likely

  6. Don't forget the posters! Quality and content variables associated with accepted abstracts at a national trauma meeting.

    PubMed

    Dossett, Lesly A; Fox, Erin E; del Junco, Deborah J; Zaydfudim, Victor; Kauffmann, Rondi; Shelton, Julia; Wang, Weiwei; Cioffi, William G; Holcomb, John B; Cotton, Bryan A

    2012-05-01

    As a primary venue for presenting research results, abstracts selected for presentation at national meetings should be of the highest scientific merit and research quality. It is uncertain to what degree this is achieved as the methodological quality of abstracts submitted to national surgical meetings has not been previously described. The objective of this study was to evaluate abstracts presented at a leading trauma meeting for methodological quality. All abstracts accepted for the 2009 American Association for the Surgery of Trauma meeting were reviewed and scored for methodological quality based on 10 criteria (scores, 0-10; 10 being the highest). Criteria were based on nationally published methodology guidelines. Two independent reviewers who were blinded to institution, region, and author reviewed each abstract. A total of 187 abstracts were accepted for presentation (67 oral and 120 posters). The most frequent clinical topics were shock/transfusion (23%), abdomen (12%), and nervous system (11%). Shock/transfusion abstracts were more common in the oral presentations (31% vs. 19%; p = 0.06). Abstracts from the northeast and south regions were the most common in both oral (26% and 29%) and posters (25% and 24%). Basic science accounted for 12% of accepted studies, while 51% were clinical and 28% were health services/outcomes. Only 8% of abstracts presented randomized data and only 11% reported null findings. Overall abstract scores ranged from 3 to 10 (median, 7; mean, 7.4). Abstracts selected for poster presentation had an overall higher score than those selected for oral presentation (7.4 ± 1.7 vs. 6.8 ± 1.7; p = 0.02). Although oral presentations traditionally receive the most attention and interest, the methodological quality of abstracts accepted for poster presentation equals (and sometimes exceeds) that of oral abstracts. Attendees of these national meetings should reconsider their time spent in viewing and visiting these poster sessions as with the

  7. Spots of Seismic Danger Extracted by Properties of Low-Frequency Seismic Noise

    NASA Astrophysics Data System (ADS)

    Lyubushin, Alexey

    2013-04-01

    A new method of seismic danger estimate is presented which is based on using properties of low-frequency seismic noise from broadband networks. Two statistics of noise waveforms are considered: multi-fractal singularity spectrum support width D and minimum normalized entropy En of squared orthogonal wavelet coefficients. The maps of D and En are plotted in the moving time window. Let us call the regions extracted by low values of D and high values of En as "spots of seismic danger" - SSD. Mean values of D and En are strongly anti-correlated - that is why statistics D and En extract the same SSD. Nevertheless their mutual considering is expedient because these parameters are based on different approaches. The physical mechanism which underlies the method is consolidation of small blocks of the Earth's crust into the large one before the strong earthquake. This effect has a consequence that seismic noise does not include spikes which are connected with mutual movements of small blocks. The absence of irregular spikes in the noise follows the decreasing of D and increasing of entropy En. The stability in space and size of the SSD provides estimates of the place and energy of the probable future earthquake. The increasing or decreasing of SSD size and minimum or maximum values of D and En within SSD allows estimate the trend of seismic danger. The method is illustrating by the analysis of seismic noise from broadband seismic network F-net in Japan [1-5]. Statistically significant decreasing of D allowed a hypothesis about approaching Japan to a future seismic catastrophe to be formulated at the middle of 2008. The peculiarities of correlation coefficient estimate within 1 year time window between median values of D and generalized Hurst exponent allowed to make a decision that starting from July of 2010 Japan come to the state of waiting strong earthquake [3]. The method extracted a huge SSD near Japan which includes the region of future Tohoku mega-earthquake and the

  8. Seismicity of Central Asia as Observed on Three IMS Stations

    DTIC Science & Technology

    2008-09-01

    and BVAR are all high-quality seismic arrays . Noise levels at the stations are generally acceptable for the period reviewed, except during the...following conditions: (1) a 4.5-Hz intermittent noise source at MKAR, (2) periodic high-frequency bursts on portions of the SONM array , and (3) a...seismic events (including single station events) observable on three central Asian IMS seismic array stations: Makanchi, Kazakhstan (MKAR); Songino

  9. Abstracting ICU Nursing Care Quality Data From the Electronic Health Record.

    PubMed

    Seaman, Jennifer B; Evans, Anna C; Sciulli, Andrea M; Barnato, Amber E; Sereika, Susan M; Happ, Mary Beth

    2017-09-01

    The electronic health record is a potentially rich source of data for clinical research in the intensive care unit setting. We describe the iterative, multi-step process used to develop and test a data abstraction tool, used for collection of nursing care quality indicators from the electronic health record, for a pragmatic trial. We computed Cohen's kappa coefficient (κ) to assess interrater agreement or reliability of data abstracted using preliminary and finalized tools. In assessing the reliability of study data ( n = 1,440 cases) using the finalized tool, 108 randomly selected cases (10% of first half sample; 5% of last half sample) were independently abstracted by a second rater. We demonstrated mean κ values ranging from 0.61 to 0.99 for all indicators. Nursing care quality data can be accurately and reliably abstracted from the electronic health records of intensive care unit patients using a well-developed data collection tool and detailed training.

  10. Seismic probing of continental subduction zones

    NASA Astrophysics Data System (ADS)

    Zhao, Liang; Xu, Xiaobing; Malusà, Marco G.

    2017-09-01

    High-resolution images of Earth's interior provide pivotal information for the understanding of a range of geodynamic processes, including continental subduction and exhumation of ultrahigh-pressure (UHP) metamorphic rocks. Here we present a synthesis of available global seismic observations on continental subduction zones, and selected examples of seismic probing from the European Alps, the Himalaya-Tibet and the Qinling-Dabie orogenic belts. Our synthesis and examples show that slabs recognized beneath exhumed continental UHP terranes generally have shallow dip angles (<45°) at depths <100 km, to become much steeper at depths >100 km. Slabs underlined by a clear high velocity anomaly from Earth's surface to the mantle are generally Cenozoic in age. Some of these slabs are continuous, whereas other continental subduction zones are located above discontinuous high velocity anomalies possibly suggesting slab breakoff. The density of seismic stations and the quality of recordings are of primary importance to get high-resolution images of the upper mantle to be used as a starting point to provide reliable geodynamic interpretations. In some cases, areas previously indicated as possible site of slab breakoff, such as the European Alps, have been later proven to be located above a continuous slab by using higher quality travel time data from denser seismic arrays. Discriminating between oceanic and continental slabs can be challenging, but valuable information can be provided by combining teleseismic tomography and receiver function analysis. The upper mantle beneath most continental UHP terranes generally shows complex seismic anisotropy patterns that are potentially preserved even in pre-Cenozoic subduction zones. These patterns can be used to provide information on continental slabs that are no longer highlighted by a clear high-velocity anomaly.

  11. Deriving an Abstraction Network to Support Quality Assurance in OCRe

    PubMed Central

    Ochs, Christopher; Agrawal, Ankur; Perl, Yehoshua; Halper, Michael; Tu, Samson W.; Carini, Simona; Sim, Ida; Noy, Natasha; Musen, Mark; Geller, James

    2012-01-01

    An abstraction network is an auxiliary network of nodes and links that provides a compact, high-level view of an ontology. Such a view lends support to ontology orientation, comprehension, and quality-assurance efforts. A methodology is presented for deriving a kind of abstraction network, called a partial-area taxonomy, for the Ontology of Clinical Research (OCRe). OCRe was selected as a representative of ontologies implemented using the Web Ontology Language (OWL) based on shared domains. The derivation of the partial-area taxonomy for the Entity hierarchy of OCRe is described. Utilizing the visualization of the content and structure of the hierarchy provided by the taxonomy, the Entity hierarchy is audited, and several errors and inconsistencies in OCRe’s modeling of its domain are exposed. After appropriate corrections are made to OCRe, a new partial-area taxonomy is derived. The generalizability of the paradigm of the derivation methodology to various families of biomedical ontologies is discussed. PMID:23304341

  12. Breakup magmatism on the Vøring Margin, mid-Norway: New insight from interpretation of high-quality 2D and 3D seismic reflection data

    NASA Astrophysics Data System (ADS)

    Abdelmalak, M. M.; Planke, S.; Millett, J.; Jerram, D. A.; Maharjan, D.; Zastrozhnov, D.; Schmid, D. W.; Faleide, J. I.; Svensen, H.; Myklebust, R.

    2017-12-01

    The Vøring Margin offshore mid-Norway is a classic volcanic rifted margin, characterized by voluminous Paleogene igneous rocks present on both sides of the continent-ocean boundary. The margin displays (1) thickened transitional crust with a well-defined lower crustal high-velocity body and prominent deep crustal reflections, the so-called T-Reflection, (2) seaward dipping reflector (SDR) wedges and a prominent northeast-trending escarpment on the Vøring Marginal High, and (3) extensive sill complexes in the adjacent Cretaceous Vøring Basin. During the last decade, new 2D and 3D industry seismic data along with improved processing techniques, such as broadband processing and noise reduction processing sequences, have made it possible to image and map the breakup igneous complex in much greater detail than previously possible. Our interpretation includes a combination of (1) seismic horizon picking, (2) integrated seismic-gravity-magnetic (SGM) interpretation, (3) seismic volcanostratigraphy, and (4) igneous seismic geomorphology. The results are integrated with published wide-angle seismic data, re-analyzed borehole data including new geochronology, and new geodynamic modeling of the effects of magmatism on the thermal history and subsidence of the margin. The extensive sill complexes and associated hydrothermal vent complexes in the Vøring Basin have a Paleocene-Eocene boundary age based on high-precision U/Pb dating combined with seismic mapping constraints. On the marginal high, our results show a highly variable crustal structure, with a pre-breakup configuration consisting of large-scale structural highs and sedimentary basins. These structures were in-filled and covered by basalt flows and volcanogenic sediments during the early stages of continental breakup in the earliest Eocene. Subsequently, rift basins developed along the continent-ocean boundary and where infilled by up to ca. 6 km thick basalt sequences, currently imaged as SDRs fed by a dike swarm

  13. Annotated bibliography, seismicity of and near the island of Hawaii and seismic hazard analysis of the East Rift of Kilauea

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

    Klein, F.W.

    1994-03-28

    This bibliography is divided into the following four sections: Seismicity of Hawaii and Kilauea Volcano; Occurrence, locations and accelerations from large historical Hawaiian earthquakes; Seismic hazards of Hawaii; and Methods of seismic hazard analysis. It contains 62 references, most of which are accompanied by short abstracts.

  14. Seismic Source Scaling and Discrimination in Diverse Tectonic Environments

    DTIC Science & Technology

    2009-09-30

    3349-3352. Imanishi, K., W. L. Ellsworth, and S. G. Prejean (2004). Earthquake source parameters determined by the SAFOD Pilot Hole seismic array ... seismic discrimination by performing a thorough investigation of* earthquake source scaling using diverse, high-quality datascts from varied tectonic...these corrections has a direct impact on our ability to identify clandestine explosions in the broad regional areas characterized by low seismicity

  15. Don’t forget the posters! Quality and content variables associated with accepted abstracts at a national trauma meeting

    PubMed Central

    Dossett, Lesly A.; Fox, Erin E.; del Junco, Deborah J.; Zaydfudim, Victor; Kauffmann, Rondi; Shelton, Julia; Wang, Weiwei; Cioffi, William G.; Holcomb, John B.; Cotton, Bryan A.

    2014-01-01

    BACKGROUND As a primary venue for presenting research results, abstracts selected for presentation at national meetings should be of the highest scientific merit and research quality. It is uncertain to what degree this is achieved as the methodological quality of abstracts submitted to national surgical meetings has not been previously described. The objective of this study was to evaluate abstracts presented at a leading trauma meeting for methodological quality. METHODS All abstracts accepted for the 2009 American Association for the Surgery of Trauma meeting were reviewed and scored for methodological quality based on 10 criteria (scores, 0–10; 10 being the highest). Criteria were based on nationally published methodology guidelines. Two independent reviewers who were blinded to institution, region, and author reviewed each abstract. RESULTS A total of 187 abstracts were accepted for presentation (67 oral and 120 posters). The most frequent clinical topics were shock/transfusion (23%), abdomen (12%), and nervous system (11%). Shock/transfusion abstracts were more common in the oral presentations (31% vs. 19%; p =0.06). Abstracts from the northeast and south regions were the most common in both oral (26% and 29%) and posters (25% and 24%). Basic science accounted for 12% of accepted studies, while 51% were clinical and 28% were health services/outcomes. Only 8% of abstracts presented randomized data and only 11% reported null findings. Overall abstract scores ranged from 3 to 10 (median, 7; mean, 7.4). Abstracts selected for poster presentation had an overall higher score than those selected for oral presentation (7.4 ±1.7 vs. 6.8 ±1.7; p =0.02). CONCLUSION Although oral presentations traditionally receive the most attention and interest, the methodological quality of abstracts accepted for poster presentation equals (and sometimes exceeds) that of oral abstracts. Attendees of these national meetings should reconsider their time spent in viewing and visiting

  16. Field test investigation of high sensitivity fiber optic seismic geophone

    NASA Astrophysics Data System (ADS)

    Wang, Meng; Min, Li; Zhang, Xiaolei; Zhang, Faxiang; Sun, Zhihui; Li, Shujuan; Wang, Chang; Zhao, Zhong; Hao, Guanghu

    2017-10-01

    Seismic reflection, whose measured signal is the artificial seismic waves ,is the most effective method and widely used in the geophysical prospecting. And this method can be used for exploration of oil, gas and coal. When a seismic wave travelling through the Earth encounters an interface between two materials with different acoustic impedances, some of the wave energy will reflect off the interface and some will refract through the interface. At its most basic, the seismic reflection technique consists of generating seismic waves and measuring the time taken for the waves to travel from the source, reflect off an interface and be detected by an array of geophones at the surface. Compared to traditional geophones such as electric, magnetic, mechanical and gas geophone, optical fiber geophones have many advantages. Optical fiber geophones can achieve sensing and signal transmission simultaneously. With the development of fiber grating sensor technology, fiber bragg grating (FBG) is being applied in seismic exploration and draws more and more attention to its advantage of anti-electromagnetic interference, high sensitivity and insensitivity to meteorological conditions. In this paper, we designed a high sensitivity geophone and tested its sensitivity, based on the theory of FBG sensing. The frequency response range is from 10 Hz to 100 Hz and the acceleration of the fiber optic seismic geophone is over 1000pm/g. sixteen-element fiber optic seismic geophone array system is presented and the field test is performed in Shengli oilfield of China. The field test shows that: (1) the fiber optic seismic geophone has a higher sensitivity than the traditional geophone between 1-100 Hz;(2) The low frequency reflection wave continuity of fiber Bragg grating geophone is better.

  17. Continuous, Large-Scale Processing of Seismic Archives for High-Resolution Monitoring of Seismic Activity and Seismogenic Properties

    NASA Astrophysics Data System (ADS)

    Waldhauser, F.; Schaff, D. P.

    2012-12-01

    Archives of digital seismic data recorded by seismometer networks around the world have grown tremendously over the last several decades helped by the deployment of seismic stations and their continued operation within the framework of monitoring earthquake activity and verification of the Nuclear Test-Ban Treaty. We show results from our continuing effort in developing efficient waveform cross-correlation and double-difference analysis methods for the large-scale processing of regional and global seismic archives to improve existing earthquake parameter estimates, detect seismic events with magnitudes below current detection thresholds, and improve real-time monitoring procedures. We demonstrate the performance of these algorithms as applied to the 28-year long seismic archive of the Northern California Seismic Network. The tools enable the computation of periodic updates of a high-resolution earthquake catalog of currently over 500,000 earthquakes using simultaneous double-difference inversions, achieving up to three orders of magnitude resolution improvement over existing hypocenter locations. This catalog, together with associated metadata, form the underlying relational database for a real-time double-difference scheme, DDRT, which rapidly computes high-precision correlation times and hypocenter locations of new events with respect to the background archive (http://ddrt.ldeo.columbia.edu). The DDRT system facilitates near-real-time seismicity analysis, including the ability to search at an unprecedented resolution for spatio-temporal changes in seismogenic properties. In areas with continuously recording stations, we show that a detector built around a scaled cross-correlation function can lower the detection threshold by one magnitude unit compared to the STA/LTA based detector employed at the network. This leads to increased event density, which in turn pushes the resolution capability of our location algorithms. On a global scale, we are currently building

  18. Sources of high frequency seismic noise: insights from a dense network of ~250 stations in northern Alsace (France)

    NASA Astrophysics Data System (ADS)

    Vergne, Jerome; Blachet, Antoine; Lehujeur, Maximilien

    2015-04-01

    Monitoring local or regional seismic activity requires stations having a low level of background seismic noise at frequencies higher than few tenths of Hertz. Network operators are well aware that the seismic quality of a site depends on several aspects, among them its geological setting and the proximity of roads, railways, industries or trees. Often, the impact of each noise source is only qualitatively known which precludes estimating the quality of potential future sites before they are tested or installed. Here, we want to take advantage of a very dense temporary network deployed in Northern Alsace (France) to assess the effect of various kinds of potential sources on the level of seismic noise observed in the frequency range 0.2-50 Hz. In September 2014, more than 250 seismic stations (FairfieldNodal@ Zland nodes with 10Hz vertical geophone) have been installed every 1.5 km over a ~25km diameter disc centred on the deep geothermal sites of Soultz-sous-Forêts and Rittershoffen. This region exhibits variable degrees of human imprints from quite remote areas to sectors with high traffic roads and big villages. It also encompasses both the deep sedimentary basin of the Rhine graben and the piedmont of the Vosges massif with exposed bedrock. For each site we processed the continuous data to estimate probability density functions of the power spectral densities. At frequencies higher than 1 Hz most sites show a clear temporal modulation of seismic noise related to human activity with the well-known variations between day and night and between weekdays and weekends. Moreover we observe a clear evolution of the spatial distribution of seismic noise levels with frequency. Basically, between 0.5 and 4 Hz the geological setting modulates the level of seismic noise. At higher frequencies, the amplitude of seismic noise appears mostly related to the distance to nearby roads. Based on road maps and traffic estimation, a forward approach is performed to model the induced

  19. The SISIFO project: Seismic Safety at High Schools

    NASA Astrophysics Data System (ADS)

    Peruzza, Laura; Barnaba, Carla; Bragato, Pier Luigi; Dusi, Alberto; Grimaz, Stefano; Malisan, Petra; Saraò, Angela; Mucciarelli, Marco

    2014-05-01

    For many years, the Italian scientific community has faced the problem of the reduction of earthquake risk using innovative educational techniques. Recent earthquakes in Italy and around the world have clearly demonstrated that seismic codes alone are not able to guarantee an effective mitigation of risk. After the tragic events of San Giuliano di Puglia (2002), where an earthquake killed 26 school children, special attention was paid in Italy to the seismic safety of schools, but mainly with respect to structural aspects. Little attention has been devoted to the possible and even significant damage to non-structural elements (collapse of ceilings, tipping of cabinets and shelving, obstruction of escape routes, etc..). Students and teachers trained on these aspects may lead to a very effective preventive vigilance. Since 2002, the project EDURISK (www.edurisk.it) proposed educational tools and training programs for schools, at primary and middle levels. More recently, a nationwide campaign aimed to adults (www.iononrischio.it) was launched with the extensive support of civil protection volounteers. There was a gap for high schools, and Project SISIFO was designed to fill this void and in particular for those schools with technical/scientific curricula. SISIFO (https://sites.google.com/site/ogssisifo/) is a multidisciplinary initiative, aimed at the diffusion of scientific culture for achieving seismic safety in schools, replicable and can be structured in training the next several years. The students, helped by their teachers and by experts from scientific institutions, followed a course on specialized training on earthquake safety. The trial began in North-East Italy, with a combination of hands-on activities for the measurement of earthquakes with low-cost instruments and lectures with experts in various disciplines, accompanied by specifically designed teaching materials, both on paper and digital format. We intend to raise teachers and students knowledge of the

  20. Method for determining formation quality factor from well log data and its application to seismic reservoir characterization

    DOEpatents

    Walls, Joel; Taner, M. Turhan; Dvorkin, Jack

    2006-08-08

    A method for seismic characterization of subsurface Earth formations includes determining at least one of compressional velocity and shear velocity, and determining reservoir parameters of subsurface Earth formations, at least including density, from data obtained from a wellbore penetrating the formations. A quality factor for the subsurface formations is calculated from the velocity, the density and the water saturation. A synthetic seismogram is calculated from the calculated quality factor and from the velocity and density. The synthetic seismogram is compared to a seismic survey made in the vicinity of the wellbore. At least one parameter is adjusted. The synthetic seismogram is recalculated using the adjusted parameter, and the adjusting, recalculating and comparing are repeated until a difference between the synthetic seismogram and the seismic survey falls below a selected threshold.

  1. MSNoise: a Python Package for Monitoring Seismic Velocity Changes using Ambient Seismic Noise

    NASA Astrophysics Data System (ADS)

    Lecocq, T.; Caudron, C.; Brenguier, F.

    2013-12-01

    Earthquakes occur every day all around the world and are recorded by thousands of seismic stations. In between earthquakes, stations are recording "noise". In the last 10 years, the understanding of this noise and its potential usage have been increasing rapidly. The method, called "seismic interferometry", uses the principle that seismic waves travel between two recorders and are multiple-scattered in the medium. By cross-correlating the two records, one gets an information on the medium below/between the stations. The cross-correlation function (CCF) is a proxy to the Green Function of the medium. Recent developments of the technique have shown those CCF can be used to image the earth at depth (3D seismic tomography) or study the medium changes with time. We present MSNoise, a complete software suite to compute relative seismic velocity changes under a seismic network, using ambient seismic noise. The whole is written in Python, from the monitoring of data archives, to the production of high quality figures. All steps have been optimized to only compute the necessary steps and to use 'job'-based processing. We present a validation of the software on a dataset acquired during the UnderVolc[1] project on the Piton de la Fournaise Volcano, La Réunion Island, France, for which precursory relative changes of seismic velocity are visible for three eruptions betwee 2009 and 2011.

  2. High vertical resolution crosswell seismic imaging

    DOEpatents

    Lazaratos, Spyridon K.

    1999-12-07

    A method for producing high vertical resolution seismic images from crosswell data is disclosed. In accordance with one aspect of the disclosure, a set of vertically spaced, generally horizontally extending continuous layers and associated nodes are defined within a region between two boreholes. The specific number of nodes is selected such that the value of a particular characteristic of the subterranean region at each of the nodes is one which can be determined from the seismic data. Once values are established at the nodes, values of the particular characteristic are assigned to positions between the node points of each layer based on the values at node within that layer and without regard to the values at node points within any other layer. A seismic map is produced using the node values and the assigned values therebetween. In accordance with another aspect of the disclosure, an approximate model of the region is established using direct arrival traveltime data. Thereafter, the approximate model is adjusted using reflected arrival data. In accordance with still another aspect of the disclosure, correction is provided for well deviation. An associated technique which provides improvements in ray tracing is also disclosed.

  3. Quality of reporting of trial abstracts needs to be improved: using the CONSORT for abstracts to assess the four leading Chinese medical journals of traditional Chinese medicine.

    PubMed

    Wang, Ling; Li, Yulin; Li, Jing; Zhang, Mingming; Xu, Lin; Yuan, Wenming; Wang, Gang; Hopewell, Sally

    2010-07-08

    Due to language limitations, the abstract of journal article may be the only way for people of non-Chinese speaking countries to know about trials in traditional Chinese medicine (TCM). However, little is known about the reporting quality of these trial abstracts. Our study is to assess the reporting quality of abstracts of randomized controlled trials (RCT) published in four leading Chinese medical journals of TCM, and to identify any differences in reporting between the Chinese and English version of the same abstract publication. Two reviewers hand-searched the Chinese Journal of Integrated Traditional and Western Medicine, the Chinese Journal of Integrative Medicine, the China Journal of Chinese Materia Medica and the Chinese Acupuncture & Moxibustion for all abstracts of RCTs published between 2006 and 2007. Two reviewers independently assessed the reporting quality of the Chinese and English version of all eligible abstracts based on a modified version of the CONSORT for reporting randomised trials in journal and conference abstracts (CONSORT for abstracts). We identified a total of 345 RCTs of TCM with both a Chinese and English abstract. More than half of Chinese abstracts reported details of the trial participants (68%; 234/345), control group intervention (52%; 179/345), the number of participants randomized (73%; 253/345) and benefits when interpreting the trial results (55%; 190/345). Reporting of methodological quality or key features of trial design and trial results were poor; only 2% (7/345) included details of the trial design, 3% (11/345) defined the primary outcome, 5% (17/345) described the methods of random sequence generation, and only 4% (13/345) reported the number of participants analyzed. No abstracts provided details on allocation concealment and trial registration. The percentage agreement in reporting (between the Chinese and English version of the same abstract) ranged from 84% to 100% across individual checklist item. The reporting

  4. Quality of reporting of trial abstracts needs to be improved: using the CONSORT for abstracts to assess the four leading Chinese medical journals of traditional Chinese medicine

    PubMed Central

    2010-01-01

    Background Due to language limitations, the abstract of journal article may be the only way for people of non-Chinese speaking countries to know about trials in traditional Chinese medicine (TCM). However, little is known about the reporting quality of these trial abstracts. Our study is to assess the reporting quality of abstracts of randomized controlled trials (RCT) published in four leading Chinese medical journals of TCM, and to identify any differences in reporting between the Chinese and English version of the same abstract publication. Method Two reviewers hand-searched the Chinese Journal of Integrated Traditional and Western Medicine, the Chinese Journal of Integrative Medicine, the China Journal of Chinese Materia Medica and the Chinese Acupuncture & Moxibustion for all abstracts of RCTs published between 2006 and 2007. Two reviewers independently assessed the reporting quality of the Chinese and English version of all eligible abstracts based on a modified version of the CONSORT for reporting randomised trials in journal and conference abstracts (CONSORT for abstracts). Results We identified a total of 345 RCTs of TCM with both a Chinese and English abstract. More than half of Chinese abstracts reported details of the trial participants (68%; 234/345), control group intervention (52%; 179/345), the number of participants randomized (73%; 253/345) and benefits when interpreting the trial results (55%; 190/345). Reporting of methodological quality or key features of trial design and trial results were poor; only 2% (7/345) included details of the trial design, 3% (11/345) defined the primary outcome, 5% (17/345) described the methods of random sequence generation, and only 4% (13/345) reported the number of participants analyzed. No abstracts provided details on allocation concealment and trial registration. The percentage agreement in reporting (between the Chinese and English version of the same abstract) ranged from 84% to 100% across individual

  5. 2D - 3D high resolution seismic survey on the Sea of Marmara - Western High

    NASA Astrophysics Data System (ADS)

    Saritas, H.; Cifci, G.; Géli, L.; Thomas, Y.; Marsset, B.; Rochat, A.; Westbrook, G. K.; Ker, S.; Atgin, O.; Akhun ćoşkun, S. D.; Grall, C.; Henr, P.; Gürçay, S.; Okay, S.; ćoşkun, S.; Özkan, Ö.; Barın, B.

    2012-04-01

    In the Sea of Marmara the main strand of the NAF is made up of the Ganos (15km long), Central Marmara (150 km), and North Boundary (45 km) fault segment (Okay et al., 2000). The Central Marmara Fault crosses over The Western High which is located between Tekirdag and Central Marmara Basins. The Western High and Cinarcik Basin is one of the major regions of geological interest which is the area close to the NAF where evidence of gas hydrates and gas escapes have been observed during previous scientific cruises. To understand movement of the NAF and origin of the gas , collecting data was focused on these areas by the latter cruises. It started with TAMAM (Turkish-American Marmara Multichannel) cruise in July 2008 by R/V Koca Piri Reis which belongs to Dokuz Eylul University , and after that it continued with MARMESONET (Marmara Demonstration Mission Program supported by European Seafloor Observatory Network) in December 2009 by R/V Le Suroit which belongs to IFREMER. This cruise consisted of two leg; leg-1 was about collecting multibeam and AUV data, Leg-2 was about collecting High Resolution 3D Seismic data. The last cruise PirMarmara was carried out in June 2010 by R/V Koca Piri Reis , its aim was that collecting 2D High Resolution Seismic Data .These projects are grouped in ESONET MARMARA-DM Project. 3D seismic data provide detailed information about fault distribution and subsurface structures. Computer-based interpretation and display of 3D seismic data allow for more thorough analysis than 2D seismic data. The objectives of this survey are; find gas strata and gas hydrate formation location in the western high, geological description of this area, understand tectonical movement related to dextral strike slip North Anatolian fault, focus on the mud volcano in which close to NAF, find gas hydrate and origin of the existing gas , and location of the gas escaping, investigate the creation of the Marmara Sea concerning with Western High. Integrate good velocity

  6. High-resolution seismicity catalog of Italian peninsula in the period 1981-2015

    NASA Astrophysics Data System (ADS)

    Michele, M.; Latorre, D.; Castello, B.; Di Stefano, R.; Chiaraluce, L.

    2017-12-01

    In order to provide an updated reference catalog of Italian seismicity, the absolute location of the last 35 years (1981-2015) of seismic activity was computed with a three-dimensional VP and VS velocity model covering the whole Italian territory. The NonLinLoc code (Lomax et al., 2000), which is based on a probabilistic approach, was used to provide a complete and robust description of the uncertainties associated to the locations corresponding to the hypocentral solutions with the highest probability density. Moreover, the code using a finite difference approximation of the eikonal equation (Podvin and Lecomte, 1991), allows to manage very contrasted velocity models in the arrival time computation. To optimize the earthquakes location, we included the station corrections in the inverse problem. For each year, the number of available earthquakes depends on both the network detection capability and the occurrence of major seismic sequences. The starting earthquakes catalog was based on 2.6 million P and 1.9 million S arrival time picks for 278.607 selected earthquakes, recorded at least by 3 seismic stations of the Italian seismic network. The new catalog compared to the previous ones consisting of hypocentral locations retrieved with linearized location methods, shows a very good improvement as testified by the location parameters assessing the quality of the solution (i.e., RMS, azimuthal gap, formal error on horizontal and vertical components). In addition, we used the distance between the expected and the maximum likelihood hypocenter location to establish the unimodal (high-resolved location) or multimodal (poor-resolved location) character of the probability distribution. We used these parameters to classify the resulting locations in four classes (A, B, C and D) considering the simultaneous goodness of the previous parameters. The upper classes (A and B) include the 65% of the relocated earthquake, while the lowest class (D) only includes the 7% of the

  7. Anomalous concentrations of seismically triggered rock falls in Pacoima Canyon: Are they caused by highly susceptible slopes or local amplification of seismic shaking?

    USGS Publications Warehouse

    Harp, Edwin L.; Jibson, Randall W.

    2002-01-01

    Anomalously high concentrations of rock falls were triggered in Pacoima Canyon (Los Angeles, California) during the 1994 Northridge earthquake. Similar concentrations were also documented from the 1971 San Fernando earthquake. Using an engineering rock-mass classification that evaluates the susceptibility of rock slopes to seismic failure based on the fracture properties of a rock mass (in terms of a numerical "Q-value" that describes rock quality), the rock slopes in Pacoima Canyon were compared with rock slopes in sorrounding areas where topography and lithology are similar, but rock-fall concentrations from the earthquakes were much lower. A statistical comparison of Q-values from five sites surrounding Pacoima Canyon indicates that seismic susceptibilities are similar to those within Pacoima Canyon; differences in the characteristics of rock slopes between these sites are not sufficient to account for the relatively high concentrations of rock falls within Pacoima Canyon as compared to low concentrations elsewhere. By eliminating susceptibility differences as a cause, the most likely explanations for the differences in rock-fall concentrations is anomalously high shaking levels in Pacoima Canyon, possibly resulting from topographic amplification within the canyon.

  8. GNSS seismometer: Seismic phase recognition of real-time high-rate GNSS deformation waves

    NASA Astrophysics Data System (ADS)

    Nie, Zhaosheng; Zhang, Rui; Liu, Gang; Jia, Zhige; Wang, Dijin; Zhou, Yu; Lin, Mu

    2016-12-01

    High-rate global navigation satellite systems (GNSS) can potentially be used as seismometers to capture short-period instantaneous dynamic deformation waves from earthquakes. However, the performance and seismic phase recognition of the GNSS seismometer in the real-time mode, which plays an important role in GNSS seismology, are still uncertain. By comparing the results of accuracy and precision of the real-time solution using a shake table test, we found real-time solutions to be consistent with post-processing solutions and independent of sampling rate. In addition, we analyzed the time series of real-time solutions for shake table tests and recent large earthquakes. The results demonstrated that high-rate GNSS have the ability to retrieve most types of seismic waves, including P-, S-, Love, and Rayleigh waves. The main factor limiting its performance in recording seismic phases is the widely used 1-Hz sampling rate. The noise floor also makes recognition of some weak seismic phases difficult. We concluded that the propagation velocities and path of seismic waves, macro characteristics of the high-rate GNSS array, spatial traces of seismic phases, and incorporation of seismographs are all useful in helping to retrieve seismic phases from the high-rate GNSS time series.

  9. Reporting quality of randomised controlled trial abstracts on age-related macular degeneration health care: a cross-sectional quantification of the adherence to CONSORT abstract reporting recommendations.

    PubMed

    Baulig, Christine; Krummenauer, Frank; Geis, Berit; Tulka, Sabrina; Knippschild, Stephanie

    2018-05-22

    To assess the reporting quality of randomised controlled trial (RCT) abstracts on age-related macular degeneration (AMD) healthcare, to evaluate the adherence to the Consolidated Standards of Reporting Trials (CONSORT) statement's recommendations on minimum abstract information and to identify journal characteristics associated with abstract reporting quality. Cross-sectional evaluation of RCT abstracts on AMD healthcare. A PubMed search was implemented to identify RCT abstracts on AMD healthcare published in the English language between January 2004 and December 2013. Data extraction was performed by two parallel readers independently by means of a documentation format in accordance with the 16 items of the CONSORT checklist for abstracts. The total number of criteria fulfilled by an abstract was derived as primary endpoint of the investigation; incidence rate ratios (IRRs) with unadjusted 95% CI were estimated by means of multiple Poisson regression to identify journal and article characteristics (publication year, multicentre design, structured abstract recommendations, effective sample size, effective abstract word counts and journal impact factor) possibly associated with the total number of fulfilled items. 136 of 673 identified abstracts (published in 36 different journals) fulfilled all eligibility criteria. The median number of fulfilled items was 7 (95% CI 7 to 8). No abstract reported all 16 recommended items; the maximum total number was 14, the minimum 3 of 16 items. Multivariate analysis only demonstrated the abstracts' word counts as being significantly associated with a better reporting of abstracts (Poisson regression-based IRR 1.002, 95% CI 1.001 to 1.003). Reporting quality of RCT abstracts on AMD investigations showed a considerable potential for improvement to meet the CONSORT abstract reporting recommendations. Furthermore, word counts of abstracts were identified as significantly associated with the overall abstract reporting quality.

  10. Fast history matching of time-lapse seismic and production data for high resolution models

    NASA Astrophysics Data System (ADS)

    Jimenez Arismendi, Eduardo Antonio

    Integrated reservoir modeling has become an important part of day-to-day decision analysis in oil and gas management practices. A very attractive and promising technology is the use of time-lapse or 4D seismic as an essential component in subsurface modeling. Today, 4D seismic is enabling oil companies to optimize production and increase recovery through monitoring fluid movements throughout the reservoir. 4D seismic advances are also being driven by an increased need by the petroleum engineering community to become more quantitative and accurate in our ability to monitor reservoir processes. Qualitative interpretations of time-lapse anomalies are being replaced by quantitative inversions of 4D seismic data to produce accurate maps of fluid saturations, pore pressure, temperature, among others. Within all steps involved in this subsurface modeling process, the most demanding one is integrating the geologic model with dynamic field data, including 4Dseismic when available. The validation of the geologic model with observed dynamic data is accomplished through a "history matching" (HM) process typically carried out with well-based measurements. Due to low resolution of production data, the validation process is severely limited in its reservoir areal coverage, compromising the quality of the model and any subsequent predictive exercise. This research will aim to provide a novel history matching approach that can use information from high-resolution seismic data to supplement the areally sparse production data. The proposed approach will utilize streamline-derived sensitivities as means of relating the forward model performance with the prior geologic model. The essential ideas underlying this approach are similar to those used for high-frequency approximations in seismic wave propagation. In both cases, this leads to solutions that are defined along "streamlines" (fluid flow), or "rays" (seismic wave propagation). Synthetic and field data examples will be used

  11. Development of Vertical Cable Seismic System

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  12. Sled-Mounted Geophone Arrays for Near-Surface (0-4m) Seismic Profiling in Highly-attenuating Sedimentary Facies: Atchafalaya Basin Indian Bayou, Louisiana

    NASA Astrophysics Data System (ADS)

    Lorenzo, J. M.; Saanumi, A. A.; Westbrook, C. C.; Egnew, S. F.; Bentley, S. J.

    2004-12-01

    Towed land-geophone seismic arrays have the potential to increase markedly the efficiency for collecting near-surface (0-100m) high-resolution seismic data, but viable cases are few and have been limited to a narrow range of near-surface sedimentary facies. During November 2003 through June 2004 we conducted extensive seismic tests with traditional geophones mounted on low-cost Π -shaped sleds. We targeted human habitation surfaces within the upper few meters of a crevasse splay complex in the Atchafalaya Basin study area, Indian Bayou Wildlife Management Area, Louisiana, U.S. For seismic-to-core correlation, sealed, continuous test cores were run through a multi-sensor to test for magnetic susceptibility, bulk sediment density and electrical resistivity. We compared 24-channel seismic data using a variety of seismic source-receiver combinations. Sources comprised a 12-gauge pipe-gun, a 0.22 caliber-powered piston gun, an accelerated weight drop, and a small claw hammer. Commercial blanks, 2g-black-powder, and primer-only shells were fired by the pipe gun. Receivers included 100-Hz vertical-, and 14-Hz-horizontal-component geophones. For comparison, both ground-planted and geophones mounted on wooden and iron sleds 0.3 and 1.2m long respectively. Geophones mounted on steel sleds produced data of adequate quality. Whereas traditional ground-planted geophones showed better data quality, time and cost efficiency make mounted phones more feasible for regional studies as traditional arrays are prohibitively expensive. Because of the high seismic attenuation, only horizontal-component geophones mounted on heavy (9-kg) steel sleds provided useful data, although the shallowest reflection observed in the shear wave data came from a boundary at ~ 19m depth, too far below the target depth of 4-5 m. Instead, we forward-modeled refraction traveltime data to derive the acoustic and SH velocity structure.

  13. High resolution mapping of seismic properties across upper mantle discontinuities in the stagnant slab region beneath Korea

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Shen, X.; Song, T. R. A.; Lim, H.

    2016-12-01

    Plate tectonic processes operating over much of the Earth's history induce long-term mantle mixing of chemical heterogeneities, recycling of volatiles into the mantle and regulate basalt geochemistry. Fundamental questions relevant to the mantle transition zone concern the nature of phase transition, the distribution of chemical heterogeneities (e.g., harzburgite, basalt), the temperature gradient, as well as the degree and extent of hydration and melting. One particularly important question is how the slab stagnation may be influenced by hydration or/and basalt enrichment in the mantle transition zone. To help answer these questions, we aim to detail upper mantle seismic discontinuity properties, including the shear velocity contrast, the density contrast, the transition sharpness and the gradient using high quality receiver functions using broadband data in South Korea, which is located in the immediate vicinity of the imaged stagnant slab near northeast China. Our approach involves broadband observation and amplitude analysis of direct converted waves (Pds) and multiples (PpPds) from the 410 and 660 seismic discontinuities, following our previous effort in a similar analysis in China. We processed waveforms from 52 broadband seismic stations of the Korea seismic array using an automatic scheme to remove noisy waveforms and retained close to 12,000 high quality receiver functions. After gathering receiver functions as a function of epicentral distance, we perform slowness stacking of direct converted waves and the multiples, respectively, at several discrete frequency bands between 1 sec and 15 sec. To avoid interferences from other mantle waves (PP, PPP, PcP, PP410s, PP660s), we stack receive functions across epicentral distances of 74-90 (62-76) degrees for the 410 (660) seismic discontinuity and obtain amplitude estimates and uncertainties through the bootstrap method. To properly calibrate the amplitudes of receiver functions, we take into account the effect

  14. Seismic lateral prediction in chalky limestone reservoirs offshore Qatar

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

    Rubbens, I.B.H.M.; Murat, R.C.; Vankeulen, J.

    Following the discovery of non-structurally trapped oil accumulations in Cretaceous chalky reservoirs on the northern flank of the North Dome offshore QATAR, a seismic lateral prediction study was carried out for QATAR GENERAL PETROLEUM CORPORATION (Offshore Operations). The objectives of this study were to assist in the appraisal of these oil accumulations by predicting their possible lateral extent and to investigate if the technique applied could be used as a basis for further exploration of similar oil prospects in the area. Wireline logs of eight wells and some 1000 km of high quality seismic data were processed into acoustic impedancemore » (A.I.) logs and seismic A.I. sections. Having obtained a satisfactory match of the A.I. well logs and the A.I. of the seismic traces at the well locations, relationships were established by the use of well log data which allowed the interpretation of the seismic A.I. in terms of reservoir quality. Measurements of the relevant A.I. characteristics were then carried out by computer along all seismic lines and porosity distribution maps prepared for some of the reservoirs. These maps, combined with detailed seismic depth contour maps at reservoir tops, lead to definition of good reservoir development areas downdip from poor reservoir quality zones i.e. of the stratigraphic trap areas, and drilling locations could thus be proposed. The system remains to be adequately calibrated when core material becomes available in the area of study.« less

  15. High-resolution reflection seismic survey at a CCS site, Taiwan

    NASA Astrophysics Data System (ADS)

    Wang, Chien-Ying; Chung, Chen-Tung; Kuo, Hsuan-Yu; Wu, Ming-shyan; Kuo-Chen, Hao

    2017-04-01

    To control the effect of greenhouse gas on global warming, the reduction of carbon dioxide emission has become a significant international issue in recent years. The capture of carbon dioxide during its manufacturing and storing in adjacent areas are the most economical way. This research uses high-resolution seismic reflection survey to investigate the region around the world's largest coal-fired power plant at Taichung Port, Taiwan. We aim to detect proper geological structures and to evaluate the possible way to store carbon dioxide. This research uses reflection seismic survey with two mini-vibrators and 240 channels to investigate detailed underground structures. The total length of seismic lines is more than 20 kilometers. By aligning sequential seismic lines, we are able to correlate stratigraphic layers over a wide area. Two adjacent wells along the seismic line are used to identified possible formations. The TaiChung Power Plant (TCPP) at Taichung Port is our target which has more cross-tied seismic lines and a seismic line even extending into the sea water. We analyze these seismic profiles to establish the geological model for carbon dioxide storage and evaluate the possibility of storage systems. Furthermore, this research may prepare some baseline data for the future carbon dioxide injection monitoring. The result shows that the geological structures striking 8 degrees east of north and dipping 2.8 degrees to the east. This means that carbon dioxide will migrate toward the sea direction after injection. The structural layers are relatively flat without any sign of faults. Three carbon dioxide storage systems : Mushan Wuchihshan—Paling(bottom), Peiliao—Talu(middle) and Kueichulin—Chinshui(upper) system are identified. All has the proper reservoir with high porosity and capable caprocks more than 100 meters thick. The geological storage of carbon dioxide injected into TCPP site is a feasible, commercial and safe way to reduce the emission of carbon

  16. Visualization of volumetric seismic data

    NASA Astrophysics Data System (ADS)

    Spickermann, Dela; Böttinger, Michael; Ashfaq Ahmed, Khawar; Gajewski, Dirk

    2015-04-01

    Mostly driven by demands of high quality subsurface imaging, highly specialized tools and methods have been developed to support the processing, visualization and interpretation of seismic data. 3D seismic data acquisition and 4D time-lapse seismic monitoring are well-established techniques in academia and industry, producing large amounts of data to be processed, visualized and interpreted. In this context, interactive 3D visualization methods proved to be valuable for the analysis of 3D seismic data cubes - especially for sedimentary environments with continuous horizons. In crystalline and hard rock environments, where hydraulic stimulation techniques may be applied to produce geothermal energy, interpretation of the seismic data is a more challenging problem. Instead of continuous reflection horizons, the imaging targets are often steep dipping faults, causing a lot of diffractions. Without further preprocessing these geological structures are often hidden behind the noise in the data. In this PICO presentation we will present a workflow consisting of data processing steps, which enhance the signal-to-noise ratio, followed by a visualization step based on the use the commercially available general purpose 3D visualization system Avizo. Specifically, we have used Avizo Earth, an extension to Avizo, which supports the import of seismic data in SEG-Y format and offers easy access to state-of-the-art 3D visualization methods at interactive frame rates, even for large seismic data cubes. In seismic interpretation using visualization, interactivity is a key requirement for understanding complex 3D structures. In order to enable an easy communication of the insights gained during the interactive visualization process, animations of the visualized data were created which support the spatial understanding of the data.

  17. New seismic study begins in Puerto Rico

    USGS Publications Warehouse

    Tarr, A.C.

    1974-01-01

    A new seismological project is now underway in Puerto Rico to provide information needed for accurate assessment of the island's seismic hazard. The project should also help to increase understanding of the tectonics and geologic evolution of the Caribbean region. The Puerto Rico Seismic Program is being conducted by the Geological Survey with support provided by the Puerto Rico Water Resources Authority, an agency responsible for generation and distribution of electric power throughout the Commonwealth. The Program will include the installation of a network of high quality seismograph stations to monitor seismic activity on and around Puerto Rico. These stations will be distributed across the island to record the seismicity as uniformly as possible. The detection and accurate location of small earthquakes, as well as moderate magnitude shocks, will aid in mapping active seismic zones and in compiling frequency of occurrence statistics which ultimately wil be useful in seismic risk-zoning of hte island. 

  18. High-Resolution Seismic Imaging of Near-Surface Voids

    NASA Astrophysics Data System (ADS)

    Gritto, R.; Korneev, V. A.; Elobaid, E. A.; Mohamed, F.; Sadooni, F.

    2017-12-01

    A major hazard in Qatar is the presence of karst, which is ubiquitous throughout the country including depressions, sinkholes, and caves. Causes for the development of karst include faulting and fracturing where fluids find pathways through limestone and dissolve the host rock to form caverns. Of particular concern in rapidly growing metropolitan areas that expand in heretofore unexplored regions are the collapse of such caverns. Because Qatar has seen a recent boom in construction, including the planning and development of complete new sub-sections of metropolitan areas, the development areas need to be investigated for the presence of karst to determine their suitability for the planned project. We present a suite of seismic techniques applied to a controlled experiment to detect, locate and estimate the size of a karst analog in form of a man-made water shaft on the campus of Qatar University, Doha, Qatar. Seismic waves are well suited for karst detection and characterization. Voids represent high-contrast seismic objects that exhibit strong responses due to incident seismic waves. However, the complex geometry of karst, including shape and size, makes their imaging nontrivial. While karst detection can be reduced to the simple problem of detecting an anomaly, karst characterization can be complicated by the 3D nature of the problem of unknown scale, where irregular surfaces can generate diffracted waves of different kind. In our presentation, we employ a variety of seismic techniques to demonstrate the detection and characterization of a vertical water collection shaft analyzing the phase, amplitude and spectral information of seismic waves that have been scattered by the object. We use the reduction in seismic wave amplitudes and the delay in phase arrival times in the geometrical shadow of the vertical shaft to independently detect and locate the object in space. Additionally, we use narrow band-pass filtered data combining two orthogonal transmission surveys

  19. Conference presentation to publication: a retrospective study evaluating quality of abstracts and journal articles in medical education research.

    PubMed

    Stephenson, Christopher R; Vaa, Brianna E; Wang, Amy T; Schroeder, Darrell R; Beckman, Thomas J; Reed, Darcy A; Sawatsky, Adam P

    2017-11-09

    There is little evidence regarding the comparative quality of abstracts and articles in medical education research. The Medical Education Research Study Quality Instrument (MERSQI), which was developed to evaluate the quality of reporting in medical education, has strong validity evidence for content, internal structure, and relationships to other variables. We used the MERSQI to compare the quality of reporting for conference abstracts, journal abstracts, and published articles. This is a retrospective study of all 46 medical education research abstracts submitted to the Society of General Internal Medicine 2009 Annual Meeting that were subsequently published in a peer-reviewed journal. We compared MERSQI scores of the abstracts with scores for their corresponding published journal abstracts and articles. Comparisons were performed using the signed rank test. Overall MERSQI scores increased significantly for published articles compared with conference abstracts (11.33 vs 9.67; P < .001) and journal abstracts (11.33 vs 9.96; P < .001). Regarding MERSQI subscales, published articles had higher MERSQI scores than conference abstracts in the domains of sampling (1.59 vs 1.34; P = .006), data analysis (3.00 vs 2.43; P < .001), and validity of evaluation instrument (1.04 vs 0.28; P < .001). Published articles also had higher MERSQI scores than journal abstracts in the domains of data analysis (3.00 vs 2.70; P = .004) and validity of evaluation instrument (1.04 vs 0.26; P < .001). To our knowledge, this is the first study to compare the quality of medical education abstracts and journal articles using the MERSQI. Overall, the quality of articles was greater than that of abstracts. However, there were no significant differences between abstracts and articles for the domains of study design and outcomes, which indicates that these MERSQI elements may be applicable to abstracts. Findings also suggest that abstract quality is generally preserved

  20. High volcanic seismic b-values: Real or artefacts?

    NASA Astrophysics Data System (ADS)

    Roberts, Nick; Bell, Andrew; Main, Ian G.

    2015-04-01

    The b-value of the Gutenberg-Richter distribution quantifies the relative proportion of large to small magnitude earthquakes in a catalogue, in turn related to the population of fault rupture areas and the average slip or stress drop. Accordingly the b-value is an important parameter to consider when evaluating seismic catalogues as it has the potential to provide insight into the temporal or spatial evolution of the system, such as fracture development or changes in the local stress regime. The b-value for tectonic seismicity is commonly found to be close to 1, whereas much higher b-values are frequently reported for volcanic and induced seismicity. Understanding these differences is important for understanding the processes controlling earthquake occurrence in different settings. However, it is possible that anomalously high b-values could arise from small sample sizes, under-estimated completeness magnitudes, or other poorly applied methodologies. Therefore, it is important to establish a rigorous workflow for analyzing these datasets. Here we examine the frequency-magnitude distributions of volcanic earthquake catalogues in order to determine the significance of apparently high b-values. We first derive a workflow for computing the completeness magnitude of a seismic catalogue, using synthetic catalogues of varying shape, size, and known b-value. We find the best approach involves a combination of three methods: 'Maximum Curvature', 'b-value stability', and the 'Goodness-of-Fit test'. To calculate a reliable b-value with an error ≤0.25, the maximum curvature method is preferred for a 'sharp-peaked' discrete distribution. For a catalogue with a broader peak the b-value stability method is the most reliable with the Goodness-of-Fit test being an acceptable backup if the b-value stability method fails. We apply this workflow to earthquake catalogues from El Hierro (2011-2013) and Mt Etna (1999-2013) volcanoes. In general, we find the b-value to be equal to or

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

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

    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 mapmore » permeable zones in a hydrothermal area.« less

  2. High-Resolution Analysis of Seismicity Induced at Berlín Geothermal Field, El Salvador

    NASA Astrophysics Data System (ADS)

    Kwiatek, G.; Bulut, F.; Dresen, G. H.; Bohnhoff, M.

    2012-12-01

    We investigate induced microseismic activity monitored at Berlín Geothermal Field, El Salvador, during a hydraulic stimulation. The site was monitored for a time period of 17 months using thirteen 3-component seismic stations located in shallow boreholes. Three stimulations were performed in the well TR8A with a maximum injection rate and well head pressure of 160l/s and 130bar, respectively. For the entire time period of our analysis, the acquisition system recorded 581 events with moment magnitudes ranging between -0.5 and 3.7. The initial seismic catalog provided by the operator was substantially improved: 1) We re-picked P- and S-wave onsets and relocated the seismic events using the double-difference relocation algorithm based on cross-correlation derived differential arrival time data. Forward modeling was performed using a local 1D velocity model instead of homogeneous full-space. 2) We recalculated source parameters using the spectral fitting method and refined the results applying the spectral ratio method. We investigated the source parameters and spatial and temporal changes of the seismic activity based on the refined dataset and studied the correlation between seismic activity and production. The achieved hypocentral precision allowed resolving the spatiotemporal changes in seismic activity down to a scale of a few meters. The application of spectral ratio method significantly improved the quality of source parameters in a high-attenuating and complex geological environment. Of special interest is the largest event (Mw3.7) and its nucleation process. We investigate whether the refined seismic data display any signatures that the largest event is triggered by the shut-in of the well. We found seismic activity displaying clear spatial and temporal patterns that could be easily related to the amount of water injected into the well TR8A and other reinjection wells in the investigated area. The migration of seismicity outside of injection point is observed

  3. High temporal resolution mapping of seismic noise sources using heterogeneous supercomputers

    NASA Astrophysics Data System (ADS)

    Gokhberg, Alexey; Ermert, Laura; Paitz, Patrick; Fichtner, Andreas

    2017-04-01

    Time- and space-dependent distribution of seismic noise sources is becoming a key ingredient of modern real-time monitoring of various geo-systems. Significant interest in seismic noise source maps with high temporal resolution (days) is expected to come from a number of domains, including natural resources exploration, analysis of active earthquake fault zones and volcanoes, as well as geothermal and hydrocarbon reservoir monitoring. Currently, knowledge of noise sources is insufficient for high-resolution subsurface monitoring applications. Near-real-time seismic data, as well as advanced imaging methods to constrain seismic noise sources have recently become available. These methods are based on the massive cross-correlation of seismic noise records from all available seismic stations in the region of interest and are therefore very computationally intensive. Heterogeneous massively parallel supercomputing systems introduced in the recent years combine conventional multi-core CPU with GPU accelerators and provide an opportunity for manifold increase and computing performance. Therefore, these systems represent an efficient platform for implementation of a noise source mapping solution. We present the first results of an ongoing research project conducted in collaboration with the Swiss National Supercomputing Centre (CSCS). The project aims at building a service that provides seismic noise source maps for Central Europe with high temporal resolution (days to few weeks depending on frequency and data availability). The service is hosted on the CSCS computing infrastructure; all computationally intensive processing is performed on the massively parallel heterogeneous supercomputer "Piz Daint". The solution architecture is based on the Application-as-a-Service concept in order to provide the interested external researchers the regular access to the noise source maps. The solution architecture includes the following sub-systems: (1) data acquisition responsible for

  4. Oncology trial abstracts showed suboptimal improvement in reporting: a comparative before-and-after evaluation using CONSORT for Abstract guidelines.

    PubMed

    Ghimire, Saurav; Kyung, Eunjung; Lee, Heeyoung; Kim, Eunyoung

    2014-06-01

    The aims of this study were to evaluate the quality of randomized controlled trial (RCT) abstracts published in the field of oncology and identify characteristics associated with better reporting quality. All phase III trials published during 2005-2007 [before Consolidated Standards of Reporting Trials (CONSORT)] and 2010-2012 (after CONSORT) were searched electronically in MEDLINE/PubMed and retrieved for review using an 18-point overall quality score (OQS) for reporting based on the CONSORT for Abstract guidelines. Descriptive statistics followed by multivariate linear regression were used to identify features associated with improved reporting quality. The mean OQS was 8.2 (range: 5-13; 95% confidence interval (CI): 8.0, 8.3) and 9.9 (range: 5-18; 95% CI: 9.7, 10.2) in the pre- and post-CONSORT periods, respectively. The method for random sequence generation, allocation concealment, blinding details, and funding sources were missing in pre-CONSORT abstracts and insufficiently reported (<20%) in post-CONSORT abstracts. A high impact factor (P < 0.001) and the journal of publication (P < 0.001) were independent factors that were significantly associated with higher reporting quality on multivariate analysis. The reporting quality of RCT abstracts in oncology showed suboptimal improvement over time. Thus, stricter adherence to the CONSORT for Abstract guidelines is needed to improve the reporting quality of RCT abstracts published in oncology. Copyright © 2014 Elsevier Inc. All rights reserved.

  5. High-resolution image of Calaveras fault seismicity

    USGS Publications Warehouse

    Schaff, D.P.; Bokelmann, G.H.R.; Beroza, G.C.; Waldhauser, F.; Ellsworth, W.L.

    2002-01-01

    By measuring relative earthquake arrival times using waveform cross correlation and locating earthquakes using the double difference technique, we are able to reduce hypocentral errors by 1 to 2 orders of magnitude over routine locations for nearly 8000 events along a 35-km section of the Calaveras Fault. This represents ~92% of all seismicity since 1984 and includes the rupture zone of the M 6.2 1984 Morgan Hill, California, earthquake. The relocated seismicity forms highly organized structures that were previously obscured by location errors. There are abundant repeating earthquake sequences as well as linear clusters of earthquakes. Large voids in seismicity appear with dimensions of kilometers that have been aseismic over the 30-year time interval, suggesting that these portions of the fault are either locked or creeping. The area of greatest slip in the Morgan Hill main shock coincides with the most prominent of these voids, suggesting that this part of the fault may be locked between large earthquakes. We find that the Calaveras Fault at depth is extremely thin, with an average upper bound on fault zone width of 75 m. Given the location error, however, this width is not resolvably different from zero. The relocations reveal active secondary faults, which we use to solve for the stress field in the immediate vicinity of the Calaveras Fault. We find that the maximum compressive stress is at a high angle, only 13 from the fault normal, supporting previous interpretations that this fault is weak.

  6. Deepwater seismic acquisition technology

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

    Caldwell, J.

    1996-09-01

    Although truly new technology is not required for successful acquisition of seismic data in deep Gulf of Mexico waters, it is helpful to review some basic aspects of these seismic surveys. Additionally, such surveys are likely to see early use of some emerging new technology which can improve data quality. Because such items as depth imaging, borehole seismic, 4-D and marine 3-component recording were mentioned in the May 1996 issue of World Oil, they are not discussed again here. However, these technologies will also play some role in the deepwater seismic activities. What is covered in this paper are somemore » new considerations for: (1) longer data records needed in deeper water, (2) some pros and cons of very long steamer use, and (3) two new commercial systems for quantifying data quality.« less

  7. Engineering challenges of operating year-round portable seismic stations at high-latitude

    NASA Astrophysics Data System (ADS)

    Beaudoin, Bruce; Carpenter, Paul; Hebert, Jason; Childs, Dean; Anderson, Kent

    2017-04-01

    Remote portable seismic stations are, in most cases, constrained by logistics and cost. High latitude operations introduce environmental, technical and logistical challenges that require substantially more engineering work to ensure robust, high quality data return. Since 2006, IRIS PASSCAL has been funded by NSF to develop, deploy, and maintain a pool of polar specific seismic stations. Here, we describe our latest advancements to mitigate the challenges of high-latitude, year-round station operation. The IRIS PASSCAL program has supported high-latitude deployments since the late 1980s. These early deployments were largely controlled source, summer only experiments. In early 2000 PASSCAL users began proposing year-round deployments of broadband stations in some of the harshest environments on the planet. These early year-round deployments were stand-alone (no telemetry) stations largely designed to operate during summer months and then run as long as possible during the winter with hopes the stations would revive come following summer. In 2006 and in collaboration with UNAVCO, we began developing communications, power systems, and enclosures to extend recording to year-round. Since this initial effort, PASSCAL continued refinement to power systems, enclosure design and manufacturability, and real-time data communications. Several sensor and data logger manufacturers have made advances in cold weather performance and delivered newly designed instruments that have furthered our ability to successfully run portable stations at high-latitude with minimal logistics - reducing size and weight of instruments and infrastructure. All PASSCAL polar engineering work is openly shared through our website: www.passcal.nmt.edu/content/polar

  8. High Resolution Near Surface 3D Seismic Experiments: A Carbonate Platform vs. a Siliciclastic Sequence

    NASA Astrophysics Data System (ADS)

    Filippidou, N.; Drijkoningen, G.; Braaksma, H.; Verwer, K.; Kenter, J.

    2005-05-01

    Interest in high-resolution 3D seismic experiments for imaging shallow targets has increased over the past years. Many case studies presented, show that producing clear seismic images with this non-evasive method, is still a challenge. We use two test-sites where nearby outcrops are present so that an accurate geological model can be built and the seismic result validated. The first so-called natural field laboratory is located in Boulonnais (N. France). It is an upper Jurassic siliciclastic sequence; age equivalent of the source rock of N. Sea. The second one is located in Cap Blanc,to the southwest of the Mallorca island(Spain); depicting an excellent example of Miocene prograding reef platform (Llucmajor Platform); it is a textbook analog for carbonate reservoirs. In both cases, the multidisciplinary experiment included the use of multicomponent and quasi- or 3D seismic recordings. The target depth does not exceed 120m. Vertical and shear portable vibrators were used as source. In the center of the setups, boreholes were drilled and Vertical Seismic Profiles were shot, along with core and borehole measurements both in situ and in the laboratory. These two geologically different sites, with different seismic stratigraphy have provided us with exceptionally high resolution seismic images. In general seismic data was processed more or less following standard procedures, a few innovative techniques on the Mallorca data, as rotation of horizontal components, 3D F-K filter and addition of parallel profiles, have improved the seismic image. In this paper we discuss the basic differences as seen on the seismic sections. The Boulonnais data present highly continuous reflection patterns of extremenly high resolution. This facilitated a high resolution stratigraphic description. Results from the VSP showed substantial wave energy attenuation. However, the high-fold (330 traces ) Mallorca seismic experiment returned a rather discontinuous pattern of possible reflectors

  9. Artificial neural networks for defining the water quality determinants of groundwater abstraction in coastal aquifer

    NASA Astrophysics Data System (ADS)

    Lallahem, S.; Hani, A.

    2017-02-01

    Water sustainability in the lower Seybouse River basin, eastern Algeria, must take into account the importance of water quantity and quality integration. So, there is a need for a better knowledge and understanding of the water quality determinants of groundwater abstraction to meet the municipal and agricultural uses. In this paper, the artificial neural network (ANN) models were used to model and predict the relationship between groundwater abstraction and water quality determinants in the lower Seybouse River basin. The study area chosen is the lower Seybouse River basin and real data were collected from forty five wells for reference year 2006. Results indicate that the feed-forward multilayer perceptron models with back-propagation are useful tools to define and prioritize the important water quality parameters of groundwater abstraction and use. The model evaluation shows that the correlation coefficients are more than 95% for training, verification and testing data. The model aims to link the water quantity and quality with the objective to strengthen the Integrated Water Resources Management approach. It assists water planners and managers to better assess the water quality parameters and progress towards the provision of appropriate quantities of water of suitable quality.

  10. Seismic Waveform Modeling of Broadband Data From a Temporary High-Density Deployment in the Los Angeles Basin

    NASA Astrophysics Data System (ADS)

    Herrman, M.; Polet, J.

    2016-12-01

    A total of 73 broadband seismometers were deployed for a passive source seismic experiment called the Los Angeles Syncline Seismic Interferometry Experiment (LASSIE) from September to November of 2014. The purpose of this experiment was to collect high density seismic data for the Los Angeles Basin (LAB) to better understand basin structure and response. This research will use the data collected from LASSIE to assess and refine current velocity models of the LAB using a full waveform modeling approach. To this end we will compare seismograms recorded by LASSIE for a subset of the 53 earthquakes and quarry blasts located by the Southern California Seismic Network (SCSN) that occurred within or near the LAB during the deployment period to synthetic seismograms generated by the Frequency-Wavenumber (FK) code developed by Zhu and Rivera (2002). A first analysis of the data indicates that roughly 25 of the 53 events have waveforms with sufficiently high signal to noise ratio, providing approximately 500 seismograms that are of suitable quality for comparison. We observe significant changes in waveform characteristics between stations with a very small separation distance of approximately 1 km. Focal mechanisms for most of these events have been obtained from Dr. Egill Hauksson (personal communication). We will show comparisons between the broadband velocity waveforms recorded by stations across the LASSIE array and FK synthetics determined for a variety of 1D velocity models that have been developed for the LAB area (such as Hadley and Kanamori, 1977; Hauksson, 1989, 1995 and Magistrale, 1992). The results of these comparisons will be analyzed to provide additional constraints on the subsurface seismic velocity structure within the Los Angeles basin.

  11. 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

  12. Hydra—The National Earthquake Information Center’s 24/7 seismic monitoring, analysis, catalog production, quality analysis, and special studies tool suite

    USGS Publications Warehouse

    Patton, John M.; Guy, Michelle R.; Benz, Harley M.; Buland, Raymond P.; Erickson, Brian K.; Kragness, David S.

    2016-08-18

    This report provides an overview of the capabilities and design of Hydra, the global seismic monitoring and analysis system used for earthquake response and catalog production at the U.S. Geological Survey National Earthquake Information Center (NEIC). Hydra supports the NEIC’s worldwide earthquake monitoring mission in areas such as seismic event detection, seismic data insertion and storage, seismic data processing and analysis, and seismic data output.The Hydra system automatically identifies seismic phase arrival times and detects the occurrence of earthquakes in near-real time. The system integrates and inserts parametric and waveform seismic data into discrete events in a database for analysis. Hydra computes seismic event parameters, including locations, multiple magnitudes, moment tensors, and depth estimates. Hydra supports the NEIC’s 24/7 analyst staff with a suite of seismic analysis graphical user interfaces.In addition to the NEIC’s monitoring needs, the system supports the processing of aftershock and temporary deployment data, and supports the NEIC’s quality assurance procedures. The Hydra system continues to be developed to expand its seismic analysis and monitoring capabilities.

  13. TQM: A bibliography with abstracts. [total quality management

    NASA Technical Reports Server (NTRS)

    Gottlich, Gretchen L. (Editor)

    1992-01-01

    This document is designed to function as a special resource for NASA Langley scientists, engineers, and managers during the introduction and development of total quality management (TQM) practices at the Center. It lists approximately 300 bibliographic citations for articles and reports dealing with various aspects of TQM. Abstracts are also available for the majority of the citations. Citations are organized by broad subject areas, including case studies, customer service, senior management, leadership, communication tools, TQM basics, applications, and implementation. An introduction and indexes provide additional information on arrangement and availability of these materials.

  14. Deep-towed high resolution seismic imaging II: Determination of P-wave velocity distribution

    NASA Astrophysics Data System (ADS)

    Marsset, B.; Ker, S.; Thomas, Y.; Colin, F.

    2018-02-01

    The acquisition of high resolution seismic data in deep waters requires the development of deep towed seismic sources and receivers able to deal with the high hydrostatic pressure environment. The low frequency piezoelectric transducer of the SYSIF (SYstème Sismique Fond) deep towed seismic device comply with the former requirement taking advantage of the coupling of a mechanical resonance (Janus driver) and a fluid resonance (Helmholtz cavity) to produce a large frequency bandwidth acoustic signal (220-1050 Hz). The ability to perform deep towed multichannel seismic imaging with SYSIF was demonstrated in 2014, yet, the ability to determine P-wave velocity distribution wasn't achieved. P-wave velocity analysis relies on the ratio between the source-receiver offset range and the depth of the seismic reflectors, thus towing the seismic source and receivers closer to the sea bed will provide a better geometry for P-wave velocity determination. Yet, technical issues, related to the acoustic source directivity, arise for this approach in the particular framework of piezoelectric sources. A signal processing sequence is therefore added to the initial processing flow. Data acquisition took place during the GHASS (Gas Hydrates, fluid Activities and Sediment deformations in the western Black Sea) cruise in the Romanian waters of the Black Sea. The results of the imaging processing are presented for two seismic data sets acquired over gas hydrates and gas bearing sediments. The improvement in the final seismic resolution demonstrates the validity of the velocity model.

  15. High-resolution seismic-reflection data offshore of Dana Point, southern California borderland

    USGS Publications Warehouse

    Sliter, Ray W.; Ryan, Holly F.; Triezenberg, Peter J.

    2010-01-01

    The U.S. Geological Survey collected high-resolution shallow seismic-reflection profiles in September 2006 in the offshore area between Dana Point and San Mateo Point in southern Orange and northern San Diego Counties, California. Reflection profiles were located to image folds and reverse faults associated with the San Mateo fault zone and high-angle strike-slip faults near the shelf break (the Newport-Inglewood fault zone) and at the base of the slope. Interpretations of these data were used to update the USGS Quaternary fault database and in shaking hazard models for the State of California developed by the Working Group for California Earthquake Probabilities. This cruise was funded by the U.S. Geological Survey Coastal and Marine Catastrophic Hazards project. Seismic-reflection data were acquired aboard the R/V Sea Explorer, which is operated by the Ocean Institute at Dana Point. A SIG ELC820 minisparker seismic source and a SIG single-channel streamer were used. More than 420 km of seismic-reflection data were collected. This report includes maps of the seismic-survey sections, linked to Google Earth? software, and digital data files showing images of each transect in SEG-Y, JPEG, and TIFF formats.

  16. Imaging the Ferron Member of the Mancos Shale formation using reprocessed high-resolution 2-D seismic reflection data: Emery County, Utah

    USGS Publications Warehouse

    Taylor, D.J.

    2003-01-01

    Late in 1982 and early in 1983, Arco Exploration contracted with Rocky Mountain Geophysical to acquired four high-resolution 2-D multichannel seismic reflection lines in Emery County, Utah. The primary goal in acquiring this data was an attempt to image the Ferron Member of the Upper Cretaceous Mancos Shale. Design of the high-resolution 2-D seismic reflection data acquisition used both a short geophone group interval and a short sample interval. An explosive energy source was used which provided an input pulse with broad frequency content and higher frequencies than typical non-explosive Vibroseis?? sources. Reflections produced by using this high-frequency energy source when sampled at a short interval are usually able to resolve shallow horizons that are relatively thin compared to those that can be resolved using more typical oil and gas exploration seismic reflection methods.The U.S. Geological Survey-Energy Resources Program, Geophysical Processing Group used the processing sequence originally applied by Arco in 1984 as a guide and experimented with processing steps applied in a different order using slightly different parameters in an effort to improve imaging the Ferron Member horizon. As with the Arco processed data there are sections along all four seismic lines where the data quality cannot be improved upon, and in fact the data quality is so poor that the Ferron horizon cannot be imaged at all.Interpretation of the seismic and core hole data indicates that the Ferron Member in the study area represent a deltaic sequence including delta front, lower delta plain, and upper delta plain environments. Correlating the depositional environments for the Ferron Member as indicated in the core holes with the thickness of Ferron Member suggests the presence of a delta lobe running from the northwest to the southeast through the study area. The presence of a deltaic channel system within the delta lobe complex might prove to be an interesting conventional

  17. High resolution P-wave velocity structure beneath Northeastern Tibet from multiscale seismic tomography

    NASA Astrophysics Data System (ADS)

    Guo, B.; Gao, X.; Chen, J.; Liu, Q.; Li, S.

    2016-12-01

    The continuing collision of the northward advancing Indian continent with the Eurasia results in the high elevations and thickened Tibetan Plateau. Numerous geologic and geophysical studies engaged in the mechanics of the Tibetan Plateau deformation and uplift. Many seismic experiments were deployed in south and central Tibet, such as INDEPTH and Hi-climb, but very few in northeastern Tibet. Between 2013 and 2015, The China Seismic Array-experiment operated 670 broadband seismic stations with an average station spacing of 35km. This seismic array located in northeastern Tibet and covered the Qilian Mountains, Qaidam Basin, and part of Songpan-Ganzi, Gobi-Alashan, Yangzi, and Ordos. A new multiscale seismic traveltime tomography technique with sparsity constrains were used to map the upper mantle P-wave velocity structure beneath northeastern Tibet. The seismic tomography algorithm employs sparsity constrains on the wavelet representation velocity model via the L1-norm regularization. This algorithm can efficiently deal with the uneven-sampled volume, and give multiscale images of the model. Our preliminary results can be summarized as follows: 1) in the upper mantle down to 200km, significate low-velocity anomalies exist beneath the northeastern Tibet, and slight high-velocity anomalies beneath the Qaidam basin; 2) under Gobi-Alashan, Yangzi, and Ordos, high-velocity anomalies appear to extend to a depth of 250km, this high-velocity may correspond to the lithosphere; 3) there exist relative high-velocity anomalies at depth of 250km-350km underneath north Tibet, which suggests lithospheric delamination; 4) the strong velocity contrast between north Tibet and Yangzi, Gabi-Alashan is visible down to 200km, which implies the north Tibet boundary.

  18. Ambient seismic noise levels: A survey of the permanent and temporary seismographic networks in Morocco, North Africa

    NASA Astrophysics Data System (ADS)

    El Fellah, Y.; Khairy Abd Ed-Aal, A.; El Moudnib, L.; Mimoun, H.; Villasenor, A.; Gallart, J.; Thomas, C.; Elouai, D.; Mimoun, C.; Himmi, M.

    2013-12-01

    Abstract The results, of a conducted study carried out to analyze variations in ambient seismic noise levels at sites of the installed broadband stations in Morocco, North Africa, are obtained. The permanent and the temporary seismic stations installed in Morocco of the Scientific Institute ( IS, Rabat, Morocco), institute de Ciencias de la Tierra Jaume almera (ICTJA, Barcelona, Spain) and Institut für Geophysik (Munster, Germany) were used in this study. In this work, we used 23 broadband seismic stations installed in different structural domains covering all Morocco from south to north. The main purposes of the current study are: 1) to present a catalog of seismic background noise spectra for Morocco obtained from recently installed broadband stations, 2) to assess the effects of experimental temporary seismic vault construction, 3) to determine the time needed for noise at sites to stabilize, 4) to establish characteristics and origin of seismic noise at those sites. We calculated power spectral densities of background noise for each component of each broadband seismometer deployed in the different investigated sites and then compared them with the high-noise model and low-noise Model of Peterson (1993). All segments from day and night local time windows were included in the calculation without parsing out earthquakes. The obtained results of the current study could be used forthcoming to evaluate permanent station quality. Moreover, this study could be considered as a first step to develop new seismic noise models in North Africa not included in Peterson (1993). Keywords Background noise; Power spectral density; Model of Peterson; Scientific Institute; Institute de Ciencias de la Tierra Jaume almera; Institut für Geophysik

  19. Development of Towed Marine Seismic Vibrator as an Alternative Seismic Source

    NASA Astrophysics Data System (ADS)

    Ozasa, H.; Mikada, H.; Murakami, F.; Jamali Hondori, E.; Takekawa, J.; Asakawa, E.; Sato, F.

    2015-12-01

    The principal issue with respect to marine impulsive sources to acquire seismic data is if the emission of acoustic energy inflicts harm on marine mammals or not, since the volume of the source signal being released into the marine environment could be so large compared to the sound range of the mammals. We propose a marine seismic vibrator as an alternative to the impulsive sources to mitigate a risk of the impact to the marine environment while satisfying the necessary conditions of seismic surveys. These conditions include the repeatability and the controllability of source signals both in amplitude and phase for high-quality measurements. We, therefore, designed a towed marine seismic vibrator (MSV) as a new type marine vibratory seismic source that employed the hydraulic servo system for the controllability condition in phase and in amplitude that assures the repeatability as well. After fabricating a downsized MSV that requires the power of 30 kVA at a depth of about 250 m in water, several sea trials were conducted to test the source characteristics of the downsized MSV in terms of amplitude, frequency, horizontal and vertical directivities of the generated field. The maximum sound level satisfied the designed specification in the frequencies ranging from 3 to 300 Hz almost omnidirectionally. After checking the source characteristics, we then conducted a trial seismic survey, using both the downsized MSV and an airgun of 480 cubic-inches for comparison, with a streamer cable of 2,000m long right above a cabled earthquake observatory in the Japan Sea. The result showed that the penetration of seismic signals generated by the downsized MSV was comparable to that by the airgun, although there was a slight difference in the signal-to-noise ratio. The MSV could become a versatile source that will not harm living marine mammals as an alternative to the existing impulsive seismic sources such as airgun.

  20. Newberry Seismic Deployment Fieldwork Report

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

    Wang, J; Templeton, D C

    2012-03-21

    This report summarizes the seismic deployment of Lawrence Livermore National Laboratory (LLNL) Geotech GS-13 short-period seismometers at the Newberry Enhanced Geothermal System (EGS) Demonstration site located in Central Oregon. This Department of Energy (DOE) demonstration project is managed by AltaRock Energy Inc. AltaRock Energy had previously deployed Geospace GS-11D geophones at the Newberry EGS Demonstration site, however the quality of the seismic data was somewhat low. The purpose of the LLNL deployment was to install more sensitive sensors which would record higher quality seismic data for use in future seismic studies, such as ambient noise correlation, matched field processing earthquakemore » detection studies, and general EGS microearthquake studies. For the LLNL deployment, seven three-component seismic stations were installed around the proposed AltaRock Energy stimulation well. The LLNL seismic sensors were connected to AltaRock Energy Gueralp CMG-DM24 digitizers, which are powered by AltaRock Energy solar panels and batteries. The deployment took four days in two phases. In phase I, the sites were identified, a cavity approximately 3 feet deep was dug and a flat concrete pad oriented to true North was made for each site. In phase II, we installed three single component GS-13 seismometers at each site, quality controlled the data to ensure that each station was recording data properly, and filled in each cavity with native soil.« less

  1. Seismic High Attenuation Region Observed Beneath Southern New England From Teleseismic Body Wave Spectra: Evidence for High Asthenospheric Temperature Without Melt

    NASA Astrophysics Data System (ADS)

    Dong, Mingduo T.; Menke, William H.

    2017-11-01

    Seismic attenuation exhibits strong geographic variability in northeastern North America, with the highest values associated with the previously recognized Northern Appalachian Anomaly (NAA) in southern New England. The shear wave quality factor at 100 km depth is 14 < QS < 25, the ratio of P wave and S wave quality factors is QP/QS = 1.2 ± 0.03 (95%), and the frequency dependence parameter is α = 0.39 ± 0.025 (95%). The high values of QP/QS and α are compatible with laboratory measurements of unmelted rock and, in the case of α, incompatible with widespread melting. The low QS implies high mantle temperatures ( 1,550-1,650°C) at 100 km depth (assuming no melt). Small-scale variations in attenuation suggest structural heterogeneity within the NAA, possibly due to lithospheric delamination caused by asthenospheric flow.

  2. Automatic Seismic-Event Classification with Convolutional Neural Networks.

    NASA Astrophysics Data System (ADS)

    Bueno Rodriguez, A.; Titos Luzón, M.; Garcia Martinez, L.; Benitez, C.; Ibáñez, J. M.

    2017-12-01

    Active volcanoes exhibit a wide range of seismic signals, providing vast amounts of unlabelled volcano-seismic data that can be analyzed through the lens of artificial intelligence. However, obtaining high-quality labelled data is time-consuming and expensive. Deep neural networks can process data in their raw form, compute high-level features and provide a better representation of the input data distribution. These systems can be deployed to classify seismic data at scale, enhance current early-warning systems and build extensive seismic catalogs. In this research, we aim to classify spectrograms from seven different seismic events registered at "Volcán de Fuego" (Colima, Mexico), during four eruptive periods. Our approach is based on convolutional neural networks (CNNs), a sub-type of deep neural networks that can exploit grid structure from the data. Volcano-seismic signals can be mapped into a grid-like structure using the spectrogram: a representation of the temporal evolution in terms of time and frequency. Spectrograms were computed from the data using Hamming windows with 4 seconds length, 2.5 seconds overlapping and 128 points FFT resolution. Results are compared to deep neural networks, random forest and SVMs. Experiments show that CNNs can exploit temporal and frequency information, attaining a classification accuracy of 93%, similar to deep networks 91% but outperforming SVM and random forest. These results empirically show that CNNs are powerful models to classify a wide range of volcano-seismic signals, and achieve good generalization. Furthermore, volcano-seismic spectrograms contains useful discriminative information for the CNN, as higher layers of the network combine high-level features computed for each frequency band, helping to detect simultaneous events in time. Being at the intersection of deep learning and geophysics, this research enables future studies of how CNNs can be used in volcano monitoring to accurately determine the detection and

  3. Seismic Yield Estimates of UTTR Surface Explosions

    NASA Astrophysics Data System (ADS)

    Hayward, C.; Park, J.; Stump, B. W.

    2016-12-01

    Since 2007 the Utah Test and Training Range (UTTR) has used explosive demolition as a method to destroy excess solid rocket motors ranging in size from 19 tons to less than 2 tons. From 2007 to 2014, 20 high quality seismic stations within 180 km recorded most of the more than 200 demolitions. This provides an interesting dataset to examine seismic source scaling for surface explosions. Based upon observer records, shots were of 4 sizes, corresponding to the size of the rocket motors. Instrument corrections for the stations were quality controlled by examining the P-wave amplitudes of all magnitude 6.5-8 earthquakes from 30 to 90 degrees away. For each station recording, the instrument corrected RMS seismic amplitude in the first 10 seconds after the P-onset was calculated. Waveforms at any given station for all the observed explosions are nearly identical. The observed RMS amplitudes were fit to a model including a term for combined distance and station correction, a term for observed RMS amplitude, and an error term for the actual demolition size. The observed seismic yield relationship is RMS=k*Weight2/3 . Estimated yields for the largest shots vary by about 50% from the stated weights, with a nearly normal distribution.

  4. Influence of seismic diffraction for high-resolution imaging: applications in offshore Malaysia

    NASA Astrophysics Data System (ADS)

    Bashir, Yasir; Ghosh, Deva Prasad; Sum, Chow Weng

    2018-04-01

    Small-scale geological discontinuities are not easy to detect and image in seismic data, as these features represent themselves as diffracted rather than reflected waves. However, the combined reflected and diffracted image contains full wave information and is of great value to an interpreter, for instance enabling the identification of faults, fractures, and surfaces in built-up carbonate. Although diffraction imaging has a resolution below the typical seismic wavelength, if the wavelength is much smaller than the width of the discontinuity then interference effects can be ignored, as they would not play a role in generating the seismic diffractions. In this paper, by means of synthetic examples and real data, the potential of diffraction separation for high-resolution seismic imaging is revealed and choosing the best method for preserving diffraction are discussed. We illustrate the accuracy of separating diffractions using the plane-wave destruction (PWD) and dip frequency filtering (DFF) techniques on data from the Sarawak Basin, a carbonate field. PWD is able to preserve the diffraction more intelligently than DFF, which is proven in the results by the model and real data. The final results illustrate the effectiveness of diffraction separation and possible imaging for high-resolution seismic data of small but significant geological features.

  5. Water Quality Instructional Resources Information System (IRIS): A Compilation of Abstracts to Water Quality and Water Resources Materials. Supplement VIII.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus, OH. Information Reference Center for Science, Mathematics, and Environmental Education.

    Compiled are abstracts and indexes to selected print and non-print materials; related to wastewater treatment and water quality education and instruction, as well as materials related to pesticides, hazardous wastes, and public participation. Sources of abstracted/indexed materials include all levels of government, private concerns, and…

  6. High Temporal Resolution Mapping of Seismic Noise Sources Using Heterogeneous Supercomputers

    NASA Astrophysics Data System (ADS)

    Paitz, P.; Gokhberg, A.; Ermert, L. A.; Fichtner, A.

    2017-12-01

    The time- and space-dependent distribution of seismic noise sources is becoming a key ingredient of modern real-time monitoring of various geo-systems like earthquake fault zones, volcanoes, geothermal and hydrocarbon reservoirs. We present results of an ongoing research project conducted in collaboration with the Swiss National Supercomputing Centre (CSCS). The project aims at building a service providing seismic noise source maps for Central Europe with high temporal resolution. We use source imaging methods based on the cross-correlation of seismic noise records from all seismic stations available in the region of interest. The service is hosted on the CSCS computing infrastructure; all computationally intensive processing is performed on the massively parallel heterogeneous supercomputer "Piz Daint". The solution architecture is based on the Application-as-a-Service concept to provide the interested researchers worldwide with regular access to the noise source maps. The solution architecture includes the following sub-systems: (1) data acquisition responsible for collecting, on a periodic basis, raw seismic records from the European seismic networks, (2) high-performance noise source mapping application responsible for the generation of source maps using cross-correlation of seismic records, (3) back-end infrastructure for the coordination of various tasks and computations, (4) front-end Web interface providing the service to the end-users and (5) data repository. The noise source mapping itself rests on the measurement of logarithmic amplitude ratios in suitably pre-processed noise correlations, and the use of simplified sensitivity kernels. During the implementation we addressed various challenges, in particular, selection of data sources and transfer protocols, automation and monitoring of daily data downloads, ensuring the required data processing performance, design of a general service-oriented architecture for coordination of various sub-systems, and

  7. Global Seismic Cross-Correlation Results: Characterizing Repeating Seismic Events

    NASA Astrophysics Data System (ADS)

    Vieceli, R.; Dodge, D. A.; Walter, W. R.

    2016-12-01

    Increases in seismic instrument quality and coverage have led to increased knowledge of earthquakes, but have also revealed the complex and diverse nature of earthquake ruptures. Nonetheless, some earthquakes are sufficiently similar to each other that they produce correlated waveforms. Such repeating events have been used to investigate interplate coupling of subduction zones [e.g. Igarashi, 2010; Yu, 2013], study spatio-temporal changes in slip rate at plate boundaries [e.g. Igarashi et al., 2003], observe variations in seismic wave propagation velocities in the crust [e.g. Schaff and Beroza, 2004; Sawazaki et al., 2015], and assess inner core rotation [e.g. Yu, 2016]. The characterization of repeating events on a global scale remains a very challenging problem. An initial global seismic cross-correlation study used over 310 million waveforms from nearly 3.8 million events recorded between 1970 and 2013 to determine an initial look at global correlated seismicity [Dodge and Walter, 2015]. In this work, we analyze the spatial and temporal distribution of the most highly correlated event clusters or "multiplets" from the Dodge and Walter [2015] study. We examine how the distributions and characteristics of multiplets are effected by tectonic environment, source-station separation, and frequency band. Preliminary results suggest that the distribution of multiplets does not correspond to the tectonic environment in any obvious way, nor do they always coincide with the occurrence of large earthquakes. Future work will focus on clustering correlated pairs and working to reduce the bias introduced by non-uniform seismic station coverage and data availability. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  8. Water Quality Instructional Resources Information System (IRIS): A Compilation of Abstracts to Water Quality and Water Resources, Supplement XIV (1983).

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus, OH. Information Reference Center for Science, Mathematics, and Environmental Education.

    Compiled are abstracts and indexes to selected print and non-print materials related to wastewater treatment and water quality education and instruction, as well as materials related to pesticides, hazardous wastes, and public participation. Sources of abstracted/indexed materials include all levels of government, private concerns, and educational…

  9. Water Quality Instructional Resources Information System (IRIS): A Compilation of Abstracts to Water Quality and Water Resources Materials. Supplement XII.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus, OH. Information Reference Center for Science, Mathematics, and Environmental Education.

    Compiled are abstracts and indexes to selected print and non-print materials related to wastewater treatment and water quality education and instruction, as well as materials related to pesticides, hazardous wastes, and public participation. Sources of abstracted/indexed materials include all levels of government, private concerns, and educational…

  10. Water Quality Instructional Resources Information System (IRIS). A Compilation of Abstracts to Water Quality and Water Resources Materials. Supplement XVI.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus, OH. Information Reference Center for Science, Mathematics, and Environmental Education.

    Compiled are abstracts and indexes to selected print and non-print materials related to wastewater treatment and water quality education and instruction, as well as materials related to pesticides, hazardous wastes, and public participation. Sources of abstracted/indexed materials include all levels of government, private concerns, and educational…

  11. Water Quality Instructional Resources Information System (IRIS): A Compilation of Abstracts to Water Quality and Water Resources Materials. Supplement IX.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus, OH. Information Reference Center for Science, Mathematics, and Environmental Education.

    Compiled are abstracts and indexes to selected print and non-print materials related to wastewater treatment and water quality education and instruction, as well as materials related to pesticides, hazardous wastes, and public participation. Sources of abstracted/indexed materials include all levels of government, private concerns, and educational…

  12. Water Quality Instructional Resources Information System (IRIS). A Compilation of Abstracts to Water Quality and Water Resources Materials. Supplement XIII.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus, OH. Information Reference Center for Science, Mathematics, and Environmental Education.

    Compiled are abstracts and indexes to selected print and non-print materials related to wastewater treatment and water quality education and instruction, as well as materials related to pesticides, hazardous wastes, and public participation. Sources of abstracted/indexed materials include all levels of government, private concerns, and educational…

  13. Water Quality Instructional Resources Information System (IRIS). A Compilation of Abstracts to Water Quality and Water Resources Materials. Supplement XV.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus, OH. Information Reference Center for Science, Mathematics, and Environmental Education.

    Compiled are abstracts and indexes to selected print and non-print materials related to wastewater treatment and water quality education and instruction, as well as materials related to pesticides, hazardous wastes, and public participation. Sources of abstracted/indexed materials include all levels of government, private concerns, and educational…

  14. Water Quality Instructional Resources Information System (IRIS): A Compilation of Abstracts to Water Quality and Water Resources Materials. Supplement XI.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus, OH. Information Reference Center for Science, Mathematics, and Environmental Education.

    Compiled are abstracts and indexes to selected print and non-print materials related to wastewater treatment and water quality education and instruction, as well as materials related to pesticides, hazardous wastes, and public participation. Sources of abstracted/indexed materials include all levels of government, private concerns, and educational…

  15. Water Quality Instructional Resources Information System (IRIS): A Compilation of Abstracts to Water Quality and Water Resources Materials. Supplement X.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus, OH. Information Reference Center for Science, Mathematics, and Environmental Education.

    Compiled are abstracts and indexes to selected print and non-print materials related to wastewater treatment and water quality education and instruction, as well as materials related to pesticides, hazardous wastes, and public participation. Sources of abstracted/indexed materials include all levels of government, private concerns, and educational…

  16. Water Quality Instructional Resources Information System (IRIS). A Compilation of Abstracts to Water Quality and Water Resources Materials. Supplement XVII.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus, OH. Information Reference Center for Science, Mathematics, and Environmental Education.

    Compiled are abstracts and indexes to selected print and non-print materials related to wastewater treatment and water quality education and instruction, as well as materials related to pesticides, hazardous wastes, and public participation. Sources of abstracted/indexed materials include all levels of government, private concerns, and educational…

  17. Water Quality Instructional Resources Information System (IRIS): A Compilation of Abstracts to Water Quality and Water Resources Materials, Supplement XVIII.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus, OH. Information Reference Center for Science, Mathematics, and Environmental Education.

    Compiled are abstracts and indexes to selected print and non-print materials related to wastewater treatment and water quality education and instruction, as well as materials related to pesticides, hazardous wastes, and public participation. Sources of abstracted/indexed materials include all levels of government, private concerns, and educational…

  18. High-fidelity simulation capability for virtual testing of seismic and acoustic sensors

    NASA Astrophysics Data System (ADS)

    Wilson, D. Keith; Moran, Mark L.; Ketcham, Stephen A.; Lacombe, James; Anderson, Thomas S.; Symons, Neill P.; Aldridge, David F.; Marlin, David H.; Collier, Sandra L.; Ostashev, Vladimir E.

    2005-05-01

    This paper describes development and application of a high-fidelity, seismic/acoustic simulation capability for battlefield sensors. The purpose is to provide simulated sensor data so realistic that they cannot be distinguished by experts from actual field data. This emerging capability provides rapid, low-cost trade studies of unattended ground sensor network configurations, data processing and fusion strategies, and signatures emitted by prototype vehicles. There are three essential components to the modeling: (1) detailed mechanical signature models for vehicles and walkers, (2) high-resolution characterization of the subsurface and atmospheric environments, and (3) state-of-the-art seismic/acoustic models for propagating moving-vehicle signatures through realistic, complex environments. With regard to the first of these components, dynamic models of wheeled and tracked vehicles have been developed to generate ground force inputs to seismic propagation models. Vehicle models range from simple, 2D representations to highly detailed, 3D representations of entire linked-track suspension systems. Similarly detailed models of acoustic emissions from vehicle engines are under development. The propagation calculations for both the seismics and acoustics are based on finite-difference, time-domain (FDTD) methodologies capable of handling complex environmental features such as heterogeneous geologies, urban structures, surface vegetation, and dynamic atmospheric turbulence. Any number of dynamic sources and virtual sensors may be incorporated into the FDTD model. The computational demands of 3D FDTD simulation over tactical distances require massively parallel computers. Several example calculations of seismic/acoustic wave propagation through complex atmospheric and terrain environments are shown.

  19. Attenuation Characteristics of High Frequency Seismic Waves in Southern India

    NASA Astrophysics Data System (ADS)

    Sivaram, K.; Utpal, Saikia; Kanna, Nagaraju; Kumar, Dinesh

    2017-07-01

    We present a systematic study of seismic attenuation and its related Q structure derived from the spectral analysis of P-, S-waves in the southern India. The study region is separated into parts of EDC (Eastern Dharwar Craton), Western Dharwar Craton (WDC) and Southern Granulite Terrain (SGT). The study is carried out in the frequency range 1-20 Hz, using a single-station spectral ratio technique. We make use of about 45 earthquakes, recorded in a network of about 32 broadband 3-component seismograph-stations, having magnitudes ( M L) varying from 1.6 to 4.5, to estimate the average seismic body wave attenuation quality factors; Q P and Q S. Their estimated average values are observed to be fitting to the power law form of Q = Q 0 f n . The averaged power law relations for Southern Indian region (as a whole) are obtained as Q P = (95 ± 1.12) f (1.32±0.01); Q S = (128 ± 1.84) f (1.49±0.01). Based on the stations and recorded local earthquakes, for parts of EDC, WDC and SGT, the average power law estimates are obtained as: Q P = (97 ± 5) f (1.40±0.03), Q S = (116 ± 1.5) f (1.48±0.01) for EDC region; Q P = (130 ± 7) f (1.20±0.03), Q S = (103 ± 3) f (1.49±0.02) for WDC region; Q P = (68 ± 2) f (1.4±0.02), Q S = (152 ± 6) f (1.48±0.02) for SGT region. These estimates are weighed against coda Q ( Q C) estimates, using the coda decay technique, which is based on a weak backscattering of S-waves. A major observation in the study of body wave analysis is the low body wave Q ( Q 0 < 200), moderately high value of the frequency-exponent, ` n' (>0.5) and Q S/ Q P ≫ 1, suggesting lateral stretches of dominant scattering mode of seismic wave propagation. This primarily could be attributed to possible thermal anomalies and spread of partially fluid-saturated rock-masses in the crust and upper mantle of the southern Indian region, which, however, needs further laboratory studies. Such physical conditions might partly be correlated to the active seismicity and

  20. South-Central Tibetan Seismicity from HiCLIMB Seismic Array Data

    NASA Astrophysics Data System (ADS)

    Carpenter, S.; Nabelek, J.; Braunmiller, J.

    2010-12-01

    The HiCLIMB broadband passive seismic experiment (2002-2005) operated 233 sites along a 800-km long north-south array extending from the Himalayan foreland into the Central Tibetan Plateau and a flanking 350x350 km lateral array in southern Tibet and eastern Nepal. We use data from the experiment’s second phase (June 2004 to August 2005), when stations operated in Tibet, to locate earthquakes in south-central Tibet, a region with no permanent seismic network where little is known about its seismicity. We used the Antelope software for automatic detection and arrival time picking, event-arrival association and event location. Requiring a low detection and event association threshold initially resulted in ~110,000 declared events. The large database size rendered manual inspection unfeasible and we developed automated post-processing modules to weed out spurious detections and erroneous phase and event associations, which stemmed, e.g., from multiple coincident earthquakes within the array or misplaced seismicity from the great 2004 Sumatra earthquake. The resulting database contains ~32,000 events within 5° distance from the closest station. We consider ~7,600 events defined by more than 30 P and S arrivals well located and discuss them here. Seismicity in the subset correlates well with mapped faults and structures seen on satellite imagery attesting to high location quality. This is confirmed by non-systematic, kilometer-scale differences between automatic and manual locations for selected events. Seismicity in south-central Tibet is intense north of the Yarlung-Tsangpo Suture. Almost 90% of events occurred in the Lhasa Terrane mainly along north-south trending rifts. Vigorous activity (>4,800 events) accompanied two M>6 earthquakes in the Payang Basin (84°E), ~100 km west of the linear array. The Tangra-Yum Co (86.5°E) and Pumqu-Xianza (88°E) rifts were very active (~1,000 events) without dominant main shocks indicating swarm like-behavior possibly related

  1. Water Quality Instructional Resources Information System (IRIS): A Compilation of Abstracts to Water Quality and Water Resources Materials, Supplement 28, 1986.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus, OH. Information Reference Center for Science, Mathematics, and Environmental Education.

    Compiled are abstracts and indexes to selected print and nonprint materials related to wastewater treatment and water quality education and instruction, as well as materials related to pesticides, hazardous wastes, and public participation. Sources of abstracted/indexed materials include all levels of government, private concerns, and educational…

  2. Water Quality Instructional Resources Information System (IRIS): A Compilation of Abstracts to Water Quality and Water Resources Materials, Supplement 25 (1986).

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus, OH. Information Reference Center for Science, Mathematics, and Environmental Education.

    Compiled are abstracts and indexes to selected print and non-print materials related to wastewater treatment and water quality education and instruction, as well as materials related to hazardous wastes and public participation. Sources of abstracted/indexed materials include all levels of government, private concerns, and educational…

  3. Water Quality Instructional Resources Information System (IRIS): A Compilation of Abstracts to Water Quality and Water Resources Materials, Supplement 26, 1986.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus, OH. Information Reference Center for Science, Mathematics, and Environmental Education.

    Compiled are abstracts and indexes to selected print and non-print materials related to wastewater treatment and water quality education and instruction, as well as materials related to pesticides, hazardous wastes, and public participation. Sources of abstracted/indexed materials include all levels of governmental, private concerns, and…

  4. Development of the Multi-Level Seismic Receiver (MLSR)

    NASA Astrophysics Data System (ADS)

    Sleefe, G. E.; Engler, B. P.; Drozda, P. M.; Franco, R. J.; Morgan, Jeff

    1995-02-01

    The Advanced Geophysical Technology Department (6114) and the Telemetry Technology Development Department (2664) have, in conjunction with the Oil Recovery Technology Partnership, developed a Multi-Level Seismic Receiver (MLSR) for use in crosswell seismic surveys. The MLSR was designed and evaluated with the significant support of many industry partners in the oil exploration industry. The unit was designed to record and process superior quality seismic data operating in severe borehole environments, including high temperature (up to 200 C) and static pressure (10,000 psi). This development has utilized state-of-the-art technology in transducers, data acquisition, and real-time data communication and data processing. The mechanical design of the receiver has been carefully modeled and evaluated to insure excellent signal coupling into the receiver.

  5. High resolution seismic reflection profiling at Aberdeen Proving Grounds, Maryland

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

    Miller, R.D.; Xia, Jianghai; Swartzel, S.

    1996-11-01

    The effectiveness of shallow high resolution seismic reflection (i.e., resolution potential) to image geologic interfaces between about 70 and 750 ft at the Aberdeen Proving Grounds, Maryland (APG), appears to vary locally with the geometric complexity of the unconsolidated sediments that overlay crystalline bedrock. The bedrock surface (which represents the primary geologic target of this study) was imaged at each of three test areas on walkaway noise tests and CDP (common depth point) stacked data. Proven high resolution techniques were used to design and acquire data on this survey. Feasibility of the technique and minimum acquisition requirements were determined throughmore » evaluation and correlation of walkaway noise tests, CDP survey lines, and a downhole velocity check shot survey. Data processing and analysis revealed several critical attributes of shallow seismic data from APG that need careful consideration and compensation on reflection data sets. This survey determined: (1) the feasibility of the technique, (2) the resolution potential (both horizontal and vertical) of the technique, (3) the optimum source for this site, (4) the optimum acquisition geometries, (5) general processing flow, and (6) a basic idea of the acoustic variability across this site. Source testing involved an accelerated weight drop, land air gun, downhole black powder charge, sledge hammer/plate, and high frequency vibrator. Shallow seismic reflection profiles provided for a more detailed picture of the geometric complexity and variability of the distinct clay sequences (aquatards), previously inferred from drilling to be present, based on sparse drill holes and basewide conceptual models. The seismic data also reveal a clear explanation for the difficulties previously noted in correlating individual, borehole-identified sand or clay units over even short distances.« less

  6. Seismicity and seismic hazard in Sabah, East Malaysia from earthquake and geodetic data

    NASA Astrophysics Data System (ADS)

    Gilligan, A.; Rawlinson, N.; Tongkul, F.; Stephenson, R.

    2017-12-01

    While the levels of seismicity are low in most of Malaysia, the state of Sabah in northern Borneo has moderate levels of seismicity. Notable earthquakes in the region include the 1976 M6.2 Lahad Datu earthquake and the 2015 M6 Ranau earthquake. The recent Ranau earthquake resulted in the deaths of 18 people on Mt Kinabalu, an estimated 100 million RM ( US$23 million) damage to buildings, roads, and infrastructure from shaking, and flooding, reduced water quality, and damage to farms from landslides. Over the last 40 years the population of Sabah has increased to over four times what it was in 1976, yet seismic hazard in Sabah remains poorly understood. Using seismic and geodetic data we hope to better quantify the hazards posed by earthquakes in Sabah, and thus help to minimize risk. In order to do this we need to know about the locations of earthquakes, types of earthquakes that occur, and faults that are generating them. We use data from 15 MetMalaysia seismic stations currently operating in Sabah to develop a region-specific velocity model from receiver functions and a pre-existing surface wave model. We use this new velocity model to (re)locate earthquakes that occurred in Sabah from 2005-2016, including a large number of aftershocks from the 2015 Ranau earthquake. We use a probabilistic nonlinear earthquake location program to locate the earthquakes and then refine their relative locations using a double difference method. The recorded waveforms are further used to obtain moment tensor solutions for these earthquakes. Earthquake locations and moment tensor solutions are then compared with the locations of faults throughout Sabah. Faults are identified from high-resolution IFSAR images and subsequent fieldwork, with a particular focus on the Lahad Datau and Ranau areas. Used together, these seismic and geodetic data can help us to develop a new seismic hazard model for Sabah, as well as aiding in the delivery of outreach activities regarding seismic hazard

  7. Extending Automatic Parallelization to Optimize High-Level Abstractions for Multicore

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

    Liao, C; Quinlan, D J; Willcock, J J

    2008-12-12

    Automatic introduction of OpenMP for sequential applications has attracted significant attention recently because of the proliferation of multicore processors and the simplicity of using OpenMP to express parallelism for shared-memory systems. However, most previous research has only focused on C and Fortran applications operating on primitive data types. C++ applications using high-level abstractions, such as STL containers and complex user-defined types, are largely ignored due to the lack of research compilers that are readily able to recognize high-level object-oriented abstractions and leverage their associated semantics. In this paper, we automatically parallelize C++ applications using ROSE, a multiple-language source-to-source compiler infrastructuremore » which preserves the high-level abstractions and gives us access to their semantics. Several representative parallelization candidate kernels are used to explore semantic-aware parallelization strategies for high-level abstractions, combined with extended compiler analyses. Those kernels include an array-base computation loop, a loop with task-level parallelism, and a domain-specific tree traversal. Our work extends the applicability of automatic parallelization to modern applications using high-level abstractions and exposes more opportunities to take advantage of multicore processors.« less

  8. Association Between Study Quality and Publication Rates of Medical Education Abstracts Presented at the Society of General Internal Medicine Annual Meeting.

    PubMed

    Sawatsky, Adam P; Beckman, Thomas J; Edakkanambeth Varayil, Jithinraj; Mandrekar, Jayawant N; Reed, Darcy A; Wang, Amy T

    2015-08-01

    Studies reveal that 44.5% of abstracts presented at national meetings are subsequently published in indexed journals, with lower rates for abstracts of medical education scholarship. We sought to determine whether the quality of medical education abstracts is associated with subsequent publication in indexed journals, and to compare the quality of medical education abstracts presented as scientific abstracts versus innovations in medical education (IME). Retrospective cohort study. Medical education abstracts presented at the Society of General Internal Medicine (SGIM) 2009 annual meeting. Publication rates were measured using database searches for full-text publications through December 2013. Quality was assessed using the validated Medical Education Research Study Quality Instrument (MERSQI). Overall, 64 (44%) medical education abstracts presented at the 2009 SGIM annual meeting were subsequently published in indexed medical journals. The MERSQI demonstrated good inter-rater reliability (intraclass correlation range, 0.77-1.00) for grading the quality of medical education abstracts. MERSQI scores were higher for published versus unpublished abstracts (9.59 vs. 8.81, p = 0.03). Abstracts with a MERSQI score of 10 or greater were more likely to be published (OR 3.18, 95% CI 1.47-6.89, p = 0.003). ). MERSQI scores were higher for scientific versus IME abstracts (9.88 vs. 8.31, p < 0.001). Publication rates were higher for scientific abstracts (42 [66%] vs. 37 [46%], p = 0.02) and oral presentations (15 [23%] vs. 6 [8%], p = 0.01). The publication rate of medical education abstracts presented at the 2009 SGIM annual meeting was similar to reported publication rates for biomedical research abstracts, but higher than publication rates reported for medical education abstracts. MERSQI scores were associated with higher abstract publication rates, suggesting that attention to measures of quality--such as sampling, instrument validity, and data analysis

  9. Water Quality Instructional Resources Information System (IRIS): A Compilation of Abstracts to Water Quality and Water Resources Materials, Supplement 29, 1987.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus, OH. Information Reference Center for Science, Mathematics, and Environmental Education.

    Compiled are abstracts and indexes to selected print and non-print materials related to wastewater treatment and water quality education and instruction, as well as materials related to pesticides, hazardous wastes, and public participation. Sources of abstracted/indexed materials include all levels of government, private concerns, and educational…

  10. Water Quality Instructional Resources Information System (IRIS): A Compilation of Abstracts to Water Quality and Water Resources Materials, Supplement 23 (1985).

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus, OH. Information Reference Center for Science, Mathematics, and Environmental Education.

    Compiled are abstracts and indexes to selected print and non-print materials related to wastewater treatment and water quality education and instruction, as well as materials related to pesticides, hazardous wastes, and public participation. Sources of abstracted/indexed materials include all levels of government, private concerns, and educational…

  11. Water Quality Instructional Resources Information System (IRIS): A Compilation of Abstracts to Water Quality and Water Resources Materials, Supplement XIX (1984).

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus, OH. Information Reference Center for Science, Mathematics, and Environmental Education.

    Compiled are abstracts and indexes to selected print and non-print materials related to wastewater treatment and water quality education and instruction, as well as materials related to pesticides, hazardous wastes, and public participation. Sources of abstracted/indexed materials include all levels of government, private concerns, and educational…

  12. Water Quality Instructional Resources Information System (IRIS): A Compilation of Abstracts to Water Quality and Water Resources Materials, Supplement XX (1984).

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus, OH. Information Reference Center for Science, Mathematics, and Environmental Education.

    Compiled are abstracts and indexes to selected print and non-print materials related to wastewater treatment and water quality education and instruction, as well as materials related to pesticides, hazardous wastes, and public participation. Sources of abstracted/indexed materials include all levels of government, private concerns, and educational…

  13. Water Quality Instructional Resources Information System (IRIS): A Compilation of Abstracts to Water Quality and Water Resources Materials, Supplement 22 (1985).

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus, OH. Information Reference Center for Science, Mathematics, and Environmental Education.

    Compiled are abstracts and indexes to selected print and non-print materials related to wastewater treatment and water quality education and instruction, as well as materials related to pesticides, hazardous wastes, and public participation. Sources of abstracted/indexed materials include all levels of government, private concerns, and educational…

  14. Water Quality Instructional Resources Information System (IRIS): A Compilation of Abstracts to Water Quality and Water Resources Materials, Supplement 21 (1985).

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus, OH. Information Reference Center for Science, Mathematics, and Environmental Education.

    Compiled are abstracts and indexes to selected print and non-print materials related to wastewater treatment and water quality education and instruction, as well as materials related to pesticides, hazardous wastes, and public participation. Sources of abstracted/indexed materials include all levels of government, private concerns, and educational…

  15. Water Quality Instructional Resources Information System (IRIS): A Compilation of Abstracts to Water Quality and Water Resources Materials, Supplement 27, 1986.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus, OH. Information Reference Center for Science, Mathematics, and Environmental Education.

    Compiled are abstracts and indexes to selected print and non-print materials related to wastewater treatment and water quality education and instruction, as well as materials related to pesticides, hazardous wastes, and public participation. Sources of abstracted/indexed materials include all levels of government, private concerns, and educational…

  16. Extracting physical parameters from marine seismic data: New methods in seismic oceanography and velocity inversion

    NASA Astrophysics Data System (ADS)

    Fortin, Will F. J.

    The utility and meaning of a geophysical dataset is dependent on good interpretation informed by high-quality data, processing, and attribute examination via technical methodologies. Active source marine seismic reflection data contains a great deal of information in the location, phase, and amplitude of both pre- and post-stack seismic reflections. Using pre- and post-stack data, this work has extracted useful information from marine reflection seismic data in novel ways in both the oceanic water column and the sub-seafloor geology. In chapter 1 we develop a new method for estimating oceanic turbulence from a seismic image. This method is tested on synthetic seismic data to show the method's ability to accurately recover both distribution and levels of turbulent diffusivity. Then we apply the method to real data offshore Costa Rica where we observe lee waves. Our results find elevated diffusivities near the seafloor as well as above the lee waves five times greater than surrounding waters and 50 times greater than open ocean diffusivities. Chapter 2 investigates subsurface geology in the Cascadia Subduction Zone and outlines a workflow for using pre-stack waveform inversion to produce highly detailed velocity models and seismic images. Using a newly developed inversion code, we achieve better imaging results as compared to the product of a standard, user-intensive method for building a velocity model. Our results image the subduction interface ~30 km farther landward than previous work and better images faults and sedimentary structures above the oceanic plate as well as in the accretionary prism. The resultant velocity model is highly detailed, inverted every 6.25 m with ~20 m vertical resolution, and will be used to examine the role of fluids in the subduction system. These results help us to better understand the natural hazards risks associated with the Cascadia Subduction Zone. Chapter 3 returns to seismic oceanography and examines the dynamics of nonlinear

  17. Application of seismic interferometric migration for shallow seismic high precision data processing: A case study in the Shenhu area

    NASA Astrophysics Data System (ADS)

    Wei, Jia; Liu, Huaishan; Xing, Lei; Du, Dong

    2018-02-01

    The stability of submarine geological structures has a crucial influence on the construction of offshore engineering projects and the exploitation of seabed resources. Marine geologists should possess a detailed understanding of common submarine geological hazards. Current marine seismic exploration methods are based on the most effective detection technologies. Therefore, current research focuses on improving the resolution and precision of shallow stratum structure detection methods. In this article, the feasibility of shallow seismic structure imaging is assessed by building a complex model, and differences between the seismic interferometry imaging method and the traditional imaging method are discussed. The imaging effect of the model is better for shallow layers than for deep layers because coherent noise produced by this method can result in an unsatisfactory imaging effect for deep layers. The seismic interference method has certain advantages for geological structural imaging of shallow submarine strata, which indicates continuous horizontal events, a high resolution, a clear fault, and an obvious structure boundary. The effects of the actual data applied to the Shenhu area can fully illustrate the advantages of the method. Thus, this method has the potential to provide new insights for shallow submarine strata imaging in the area.

  18. Seismic definition of Lower Cretaceous delta, south Whale subbasin, offshore Newfoundland

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

    Jayasinghe, N.R.; Stokes, R.E.

    1986-05-01

    Recognition of stratigraphic traps in areas where previous prospects were structural is a trend attributable partly to the availability of new, high-quality seismic data. In the South Whale subbasin, offshore Newfoundland, Canada, such a change in exploration philosophy is presently being evaluated. Exploratory drilling offshore eastern Canada began in 1966 in the South Whale subbasin. By the end of 1973, 13 wells were drilled in this subbasin; however, lack of success discouraged further drilling. These wells evaluated large, salt-related structures, well defined by seismic data. Although an adequate reservoir was encountered in a number of these wells, faulting associated withmore » halokinesis may have resulted in petroleum migration out of the reservoir. Interpretation of recently acquired high-quality seismic data indicate a delta in the Lower Cretaceous Missisauga Formation in the study area. Seismic dip sections across the delta show a shingled progradation pattern suggesting a wave-dominated depositional environment. The delta comprises approximately 400 km/sup 2/, with closure in the eastern half. Data from wells in the area indicate that adequate source and sealing beds could be present. Furthermore, rocks of similar age in the nearby Avalon basin contain significant petroleum accumulations, the most notable being within the Hibernia oil field.« less

  19. Borehole prototype for seismic high-resolution exploration

    NASA Astrophysics Data System (ADS)

    Giese, Rüdiger; Jaksch, Katrin; Krauß, Felix; Krüger, Kay; Groh, Marco; Jurczyk, Andreas

    2014-05-01

    Target reservoirs for the exploitation of hydrocarbons or hot water for geothermal energy supply can comprise small layered structures, for instance thin layers or faults. The resolution of 2D and 3D surface seismic methods is often not sufficient to determine and locate these structures. Borehole seismic methods like vertical seismic profiling (VSP) and seismic while drilling (SWD) use either receivers or sources within the borehole. Thus, the distance to the target horizon is reduced and higher resolution images of the geological structures can be achieved. Even these methods are limited in their resolution capabilities with increasing target depth. To localize structures more accuracy methods with higher resolution in the range of meters are necessary. The project SPWD -- Seismic Prediction While Drilling aims at s the development of a borehole prototype which combines seismic sources and receivers in one device to improve the seismic resolution. Within SPWD such a prototype has been designed, manufactured and tested. The SPWD-wireline prototype is divided into three main parts. The upper section comprises the electronic unit. The middle section includes the upper receiver, the upper clamping unit as well as the source unit and the lower clamping unit. The lower section consists of the lower receiver unit and the hydraulic unit. The total length of the prototype is nearly seven meters and its weight is about 750 kg. For focusing the seismic waves in predefined directions of the borehole axis the method of phased array is used. The source unit is equipped with four magnetostrictive vibrators. Each can be controlled independently to get a common wave front in the desired direction of exploration. Source signal frequencies up to 5000 Hz are used, which allows resolutions up to one meter. In May and September 2013 field tests with the SPWD-wireline prototype have been carried out at the KTB Deep Crustal Lab in Windischeschenbach (Bavaria). The aim was to proof the

  20. High-resolution seismic data regularization and wavefield separation

    NASA Astrophysics Data System (ADS)

    Cao, Aimin; Stump, Brian; DeShon, Heather

    2018-04-01

    We present a new algorithm, non-equispaced fast antileakage Fourier transform (NFALFT), for irregularly sampled seismic data regularization. Synthetic tests from 1-D to 5-D show that the algorithm may efficiently remove leaked energy in the frequency wavenumber domain, and its corresponding regularization process is accurate and fast. Taking advantage of the NFALFT algorithm, we suggest a new method (wavefield separation) for the detection of the Earth's inner core shear wave with irregularly distributed seismic arrays or networks. All interfering seismic phases that propagate along the minor arc are removed from the time window around the PKJKP arrival. The NFALFT algorithm is developed for seismic data, but may also be used for other irregularly sampled temporal or spatial data processing.

  1. High-resolution seismic-reflection data collected on R/V S.P. LEE: L9-84-CP, Marshall Islands to Hawaii

    USGS Publications Warehouse

    Schwab, William C.; Bailey, Norman G.

    1984-01-01

    The U.S. Geological Survey (USGS) R/V S.P. LEE (cruise L9-84-CP) left Majuro, Radak chain of the Marshall Islands on July 28, 1984, cruised over the Mid-Pacific Mountains, and reached Hawaii on August 15, 1984. The main objectives of the cruise were to study the distribution and composition of ferromanganese-oxide crusts in the Marshall Islands and to retrieve a current meter/sediment trap mooring deployed in October 1983 on Horizon Guyot, Mid-Pacific Mountains (USGS LS-83-HW cruise). The quality of the geophysical data collected is generally good. However, the declivity of some seamount, atoll, and guyot flanks are too large to allow high-quality resolution from the surface-towed systems that were used.The navigation system used was an integrated satellite-navigation/LORAN-C (in Mid-Pacific Mountains)/dead-reckoning system that was updated by radar when possible. A total of 5410 km of 12-kHz and 3.5-kHz seismic-reflection data and 730 km of 80-in3 to 148-in3 airgun seismic-reflection data were collected. The original records can be seen and studied at the USGS offices at Woods Hole, MA 02543. Microfilm copies of the seismic-reflection data can be purchased only from the National Geophysical Data Center, NOAA/EDIS/NGDC, 325 Broadway, Boulder, CO 80303.

  2. Mesozoic and Cenozoic structural evolution of North Oman: New insights from high-quality 3D seismic from the Lekhwair area

    NASA Astrophysics Data System (ADS)

    Bazalgette, Loïc; Salem, Hisham

    2018-06-01

    This paper highlights the role of Triassic-Jurassic extension and late Cretaceous compression in the Mesozoic-Cenozoic (Alpine) structuring of North Oman. The syn/post-Mesozoic regional structural evolution is usually documented as a succession of two stages of deformation. The Alpine 1 phase, late Cretaceous in age, occurred in association with two ophiolite obduction stages (Semail and Masirah ophiolites). It was characterised by strike slip to extensional deformation in the North Oman foreland basin sub-surface. The Alpine 2 phase, Miocene in age, was related to the continental collision responsible for both the Zagros orogen and the uplift of the Oman Mountains. The Alpine 2 deformation was transpressional to compressional. Observation and interpretation of good quality 3D seismic in the Lekhwair High area enabled the distinction of two earlier phases. Early Mesozoic extension occurred concomitantly with the regional Triassic to Jurassic rifting, developing Jurassic-age normal faults. Late Cretaceous compression occurred prior to the main Alpine 1 phase and triggered the inversion of Jurassic-seated normal faults as well as the initiation of compressional folds in the Cretaceous overburden. These early phases have been ignored or overlooked as part of the North Oman history although they are at the origin of structures hosting major local and regional hydrocarbon accumulations.

  3. Seismic Tomography and the Development of a State Velocity Profile

    NASA Astrophysics Data System (ADS)

    Marsh, S. J.; Nakata, N.

    2017-12-01

    Earthquakes have been a growing concern in the State of Oklahoma in the last few years and as a result, accurate earthquake location is of utmost importance. This means using a high resolution velocity model with both lateral and vertical variations. Velocity data is determined using ambient noise seismic interferometry and tomography. Passive seismic data was acquired from multiple IRIS networks over the span of eight years (2009-2016) and filtered for earthquake removal to obtain the background ambient noise profile for the state. Seismic Interferometry is applied to simulate ray paths between stations, this is done with each possible station pair for highest resolution. Finally the method of seismic tomography is used to extract the velocity data and develop the state velocity map. The final velocity profile will be a compilation of different network analyses due to changing station availability from year to year. North-Central Oklahoma has a dense seismic network and has been operating for the past few years. The seismic stations are located here because this is the most seismically active region. Other parts of the state have not had consistent coverage from year to year, and as such a reliable and high resolution velocity profile cannot be determined from this network. However, the Transportable Array (TA) passed through Oklahoma in 2014 and provided a much wider and evenly spaced coverage. The goal of this study is to ultimately combine these two arrays over time, and provide a high quality velocity profile for the State of Oklahoma.

  4. Water Quality Instructional Resources Information System (IRIS): A Compilation of Abstracts to Water Quality and Water Resources Materials, Supplement 24 (l985).

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus, OH. Information Reference Center for Science, Mathematics, and Environmental Education.

    Compiled are abstracts and indexes to selected print and non-print materials related to wastewater treatment and water quality education and instruction, as well as materials related to pesticides, hazardous wastes, and public participation. Sources of abstracted/indexed materials include all levels of government, private concerns, and educational…

  5. Water Quality Instructional Resources Information System (IRIS): A Compilation of Abstracts to Water Quality and Water Resources materials. Supplement 31, 1987.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus, OH. Information Reference Center for Science, Mathematics, and Environmental Education.

    The Environmental Quality Instructional Resources Center in Columbus, Ohio, acquires, reviews, indexes, and announces both print (books, modules, units, etc.) and non-print (films, slides, video tapes, etc.) materials related to water quality and water resources education and instruction. This publication contains abstracts and indexes to selected…

  6. Water Quality Instructional Resources Information System (IRIS): A Compilation of Abstracts to Water Quality and Water Resources Materials, Supplement 30, 1987.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus, OH. Information Reference Center for Science, Mathematics, and Environmental Education.

    The Environmental Quality Instructional Resources Center acquires, reviews, indexes, and announces both print (books, modules, units, etc.) and non-print (films, slides, video tapes, etc.) materials related to water quality and water resources education and instruction. This publication contains abstracts and indexes to selected materials related…

  7. Can high seismic b-values be explained solely by poorly applied methodology?

    NASA Astrophysics Data System (ADS)

    Roberts, Nick; Bell, Andrew; Main, Ian

    2015-04-01

    The b-value of the Gutenberg-Richter distribution quantifies the relative proportion of large to small magnitude earthquakes in a catalogue, in turn related to the population of fault rupture areas and the average slip or stress drop. Accordingly the b-value is an important parameter to consider when evaluating seismic catalogues as it has the potential to provide insight into the temporal or spatial evolution of the system, such as fracture development or changes in the local stress regime. The b-value for tectonic seismicity is commonly found to be close to 1, whereas much higher b-values are frequently reported for volcanic and induced seismicity. Understanding these differences is important for understanding the processes controlling earthquake occurrence in different settings. However, it is possible that anomalously high b-values could arise from small sample sizes, under-estimated completeness magnitudes, or other poorly applied methodologies. Therefore, it is important to establish a rigorous workflow for analyzing these datasets. Here we examine the frequency-magnitude distributions of volcanic earthquake catalogues in order to determine the significance of apparently high b-values. We first derive a workflow for computing the completeness magnitude of a seismic catalogue, using synthetic catalogues of varying shape, size, and known b-value. We find the best approach involves a combination of three methods: 'Maximum Curvature', 'b-value stability', and the 'Goodness-of-Fit test'. To calculate a reliable b-value with an error ≤0.25, the maximum curvature method is preferred for a 'sharp-peaked' discrete distribution. For a catalogue with a broader peak the b-value stability method is the most reliable with the Goodness-of-Fit test being an acceptable backup if the b-value stability method fails. We apply this workflow to earthquake catalogues from El Hierro (2011-2013) and Mt Etna (1999-2013) volcanoes. In general, we find the b-value to be equal to or

  8. High resolution seismic stratigraphy of Tampa Bay, Florida

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

    Tihansky, A.B.; Hine, A.C.; Locker, S.D.

    1993-03-01

    Tampa Bay is one of two large embayments that interrupt the broad, regional nature of the carbonate ramp of the west coast of the Florida carbonate platform. It is believed to have formed as a result of preferential dissolution of the Cenozoic limestones beneath it. Highly reactive freshwater systems became hydrologically focused in the bay region as the surface and groundwater systems established themselves during sea-level lowstands. This weakening of the underlying limestone resulted in extensive karstification, including warping, subsidence, sinkhole and spring formation. Over 120 miles of high resolution seismic reflection data were collected within Tampa Bay. This recordmore » has been tied into 170 core borings taken from within the bay. This investigation has found three major seismic stratigraphic sequences beneath the bay. The lowermost sequence is probably of Miocene age. Its surface is highly irregular due to erosion and dissolution and exhibits a great deal of vertical relief as well as gentler undulations or warping. Much of the middle sequence consists of low angle clinoforms that gently downlap and fill in the underlying karst features. The uppermost sequence is a discontinuous unit comprised of horizontal to low angle clinoforms that are local in their extent. The recent drainage and sedimentation patterns within the bay area are related to the underlying structure controlled by the Miocene karst activity.« less

  9. Engineering for Autonomous Seismic Stations at the IRIS PASSCAL Instrument Center

    NASA Astrophysics Data System (ADS)

    Anderson, K. R.; Carpenter, P.; Beaudoin, B. C.; Parker, T.; Hebert, J.; Childs, D.; Chung, P.; Reusch, A. M.

    2015-12-01

    The NSF funded Incorporated Research Institutions for Seismology (IRIS) through New Mexico Tech operates the PASSCAL Instrument Center (PIC) in Socorro New Mexico. The engineering effort at the PIC seeks to optimize seismic station operations for all portable experiments, include those in extremely remote and harsh polar environments. Recent advances have resulted in improved station design, allowing improved operational efficiencies, data quality return and reduction in station logistics associated with installation, maintenance and decommissioning of stations. These include: Battery and power system designs. Incorporating primary Lithium Thionyl Chloride (LTC) technology with rechargeable Lithium Iron Phosphate (LiFePO4) batteries allows systems to operate in areas with long-term solar autonomy (high latitudes). Development includes charge controller systems to switch between primary and secondary technologies efficiently. Enclosures: Engineered solutions to efficiently manage waste heat, maintain operational environment and provide light-weight and durable housing for seismic instrumentation. Communications: In collaboration with Xeos Technologies Inc., we deliver Iridium-based SOH/Command and Control telemetry as well as full bandwidth seismic data communications in high latitude environments at low power requirements. Smaller-lighter-instrumentation: Through the GEOICE MRI, we are working with Nanometrics on next generation "all-in-one" seismic systems that can be deployed in polar environments - easing logistics, minimizing installation time and improving data quality return for these expensive deployments. All autonomous station designs are openly and freely available at the IRIS PASSCAL webpage (www.passcal.nmt.edu/polar/design-drawings). More information on GEOICE and data quality from various seismometer emplacements will be presented in other posters at this AGU meeting.

  10. Seismicity near a Highly-Coupled Patch in the Central Ecuador Subduction Zone

    NASA Astrophysics Data System (ADS)

    Regnier, M. M.; Segovia, M.; Font, Y.; Charvis, P.; Galve, A.; Jarrin, P.; Hello, Y.; Ruiz, M. C.; Pazmino, A.

    2017-12-01

    The temporary onshore-offshore seismic network deployed during the 2-years period of the OSISEC project provides an unprecedented, detailed and well-focused image of the seismicity for magnitudes as low as 2.0 in the Central Ecuadorian subduction zone. Facing the southern border of the Carnegie Ridge, a shallow and discrete highly-coupled patch is correlated to the subduction of a large oceanic relief. No large earthquake is known in this area that is experiencing recurrent seismic swarms and slow slip events. The shallow and locked subduction interface shows no evidence of background seismicity that instead occurred down dip of the coupled patch where it is possibly controlled by structural features of the overriding plate. We show a clear spatial correlation between the background microseismicity, the down dip extension of the locked patch at 20 km depth and the geology of the upper plate. The dip angle of the interplate contact zone, defined by a smooth interpolation through the hypocenters of thrust events, is consistent with a progressive increase from 6° to 25° from the trench to 20 km depth. Offshore, a seismic swarm, concomitant with a slow slip event rupturing the locked area, highlights the reactivation of secondary active faults that developed within the thickened crust of the subducting Carnegie Ridge, at the leading edge of a large oceanic seamount. No seismicity was detected near the plate interface suggesting that stress still accumulates at small and isolated asperities

  11. Toward uniform probabilistic seismic hazard assessments for Southeast Asia

    NASA Astrophysics Data System (ADS)

    Chan, C. H.; Wang, Y.; Shi, X.; Ornthammarath, T.; Warnitchai, P.; Kosuwan, S.; Thant, M.; Nguyen, P. H.; Nguyen, L. M.; Solidum, R., Jr.; Irsyam, M.; Hidayati, S.; Sieh, K.

    2017-12-01

    Although most Southeast Asian countries have seismic hazard maps, various methodologies and quality result in appreciable mismatches at national boundaries. We aim to conduct a uniform assessment across the region by through standardized earthquake and fault databases, ground-shaking scenarios, and regional hazard maps. Our earthquake database contains earthquake parameters obtained from global and national seismic networks, harmonized by removal of duplicate events and the use of moment magnitude. Our active-fault database includes fault parameters from previous studies and from the databases implemented for national seismic hazard maps. Another crucial input for seismic hazard assessment is proper evaluation of ground-shaking attenuation. Since few ground-motion prediction equations (GMPEs) have used local observations from this region, we evaluated attenuation by comparison of instrumental observations and felt intensities for recent earthquakes with predicted ground shaking from published GMPEs. We then utilize the best-fitting GMPEs and site conditions into our seismic hazard assessments. Based on the database and proper GMPEs, we have constructed regional probabilistic seismic hazard maps. The assessment shows highest seismic hazard levels near those faults with high slip rates, including the Sagaing Fault in central Myanmar, the Sumatran Fault in Sumatra, the Palu-Koro, Matano and Lawanopo Faults in Sulawesi, and the Philippine Fault across several islands of the Philippines. In addition, our assessment demonstrates the important fact that regions with low earthquake probability may well have a higher aggregate probability of future earthquakes, since they encompass much larger areas than the areas of high probability. The significant irony then is that in areas of low to moderate probability, where building codes are usually to provide less seismic resilience, seismic risk is likely to be greater. Infrastructural damage in East Malaysia during the 2015

  12. ANZA Seismic Network- From Monitoring to Science

    NASA Astrophysics Data System (ADS)

    Vernon, F.; Eakin, J.; Martynov, V.; Newman, R.; Offield, G.; Hindley, A.; Astiz, L.

    2007-05-01

    The ANZA Seismic Network (http:eqinfo.ucsd.edu) utilizes broadband and strong motion sensors with 24-bit dataloggers combined with real-time telemetry to monitor local and regional seismicity in southernmost California. The ANZA network provides real-time data to the IRIS DMC, California Integrated Seismic Network (CISN), other regional networks, and the Advanced National Seismic System (ANSS), in addition to providing near real-time information and monitoring to the greater San Diego community. Twelve high dynamic range broadband and strong motion sensors adjacent to the San Jacinto Fault zone contribute data for earthquake source studies and continue the monitoring of the seismic activity of the San Jacinto fault initiated 24 years ago. Five additional stations are located in the San Diego region with one more station on San Clemente Island. The ANZA network uses the advance wireless networking capabilities of the NSF High Performance Wireless Research and Education Network (http:hpwren.ucsd.edu) to provide the communication infrastructure for the real-time telemetry of Anza seismic stations. The ANZA network uses the Antelope data acquisition software. The combination of high quality hardware, communications, and software allow for an annual network uptime in excess of 99.5% with a median annual station real-time data return rate of 99.3%. Approximately 90,000 events, dominantly local sources but including regional and teleseismic events, comprise the ANZA network waveform database. All waveform data and event data are managed using the Datascope relational database. The ANZA network data has been used in a variety of scientific research including detailed structure of the San Jacinto Fault Zone, earthquake source physics, spatial and temporal studies of aftershocks, array studies of teleseismic body waves, and array studies on the source of microseisms. To augment the location, detection, and high frequency observations of the seismic source spectrum from local

  13. 2D Seismic Reflection Data across Central Illinois

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

    Smith, Valerie; Leetaru, Hannes

    interpretation of the Mt. Simon and Knox sections difficult. The data quality also gradually decreased moving westward across the state. To meet evolving project objectives, in 2012 the seismic data was re-processed using different techniques to enhance the signal quality thereby rendering a more coherent seismic profile for interpreters. It is believed that the seismic degradation could be caused by shallow natural gas deposits and Quaternary sediments (which include abandoned river and stream channels, former ponds, and swamps with peat deposits) that may have complicated or changed the seismic wavelet. Where previously limited by seismic coverage, the seismic profiles have provided valuable subsurface information across central Illinois. Some of the interpretations based on this survey included, but are not limited to: - Stratigraphy generally gently dips to the east from Morgan to Douglas County. - The Knox Supergroup roughly maintains its thickness. There is little evidence for faulting in the Knox. However, at least one resolvable fault penetrates the entire Knox section. - The Eau Claire Formation, the primary seal for the Mt. Simon Sandstone, appears to be continuous across the entire seismic profile. - The Mt. Simon Sandstone thins towards the western edge of the basin. As a result, the highly porous lowermost Mt. Simon section is absent in the western part of the state. - Overall basement dip is from west to east. - Basement topography shows evidence of basement highs with on-lapping patterns by Mt. Simon sediments. - There is evidence of faults within the lower Mt. Simon Sandstone and basement rock that are contemporaneous with Mt. Simon Sandstone deposition. These faults are not active and do not penetrate the Eau Claire Shale. It is believed that these faults are associated with a possible failed rifting event 750 to 560 million years ago during the breakup of the supercontinent Rodinia.« less

  14. Classifying seismic noise and sources from OBS data using unsupervised machine learning

    NASA Astrophysics Data System (ADS)

    Mosher, S. G.; Audet, P.

    2017-12-01

    The paradigm of plate tectonics was established mainly by recognizing the central role of oceanic plates in the production and destruction of tectonic plates at their boundaries. Since that realization, however, seismic studies of tectonic plates and their associated deformation have slowly shifted their attention toward continental plates due to the ease of installation and maintenance of high-quality seismic networks on land. The result has been a much more detailed understanding of the seismicity patterns associated with continental plate deformation in comparison with the low-magnitude deformation patterns within oceanic plates and at their boundaries. While the number of high-quality ocean-bottom seismometer (OBS) deployments within the past decade has demonstrated the potential to significantly increase our understanding of tectonic systems in oceanic settings, OBS data poses significant challenges to many of the traditional data processing techniques in seismology. In particular, problems involving the detection, location, and classification of seismic sources occurring within oceanic settings are much more difficult due to the extremely noisy seafloor environment in which data are recorded. However, classifying data without a priori constraints is a problem that is routinely pursued via unsupervised machine learning algorithms, which remain robust even in cases involving complicated datasets. In this research, we apply simple unsupervised machine learning algorithms (e.g., clustering) to OBS data from the Cascadia Initiative in an attempt to classify and detect a broad range of seismic sources, including various noise sources and tremor signals occurring within ocean settings.

  15. Overcoming barriers to high performance seismic design using lessons learned from the green building industry

    NASA Astrophysics Data System (ADS)

    Glezil, Dorothy

    NEHRP's Provisions today currently governing conventional seismic resistant design. These provisions, though they ensure the life-safety of building occupants, extensive damage and economic losses may still occur in the structures. This minimum performance can be enhanced using the Performance-Based Earthquake Engineering methodology and passive control systems like base isolation and energy dissipation systems. Even though these technologies and the PBEE methodology are effective reducing economic losses and fatalities during earthquakes, getting them implemented into seismic resistant design has been challenging. One of the many barriers to their implementation has been their upfront costs. The green building community has faced some of the same challenges that the high performance seismic design community currently faces. The goal of this thesis is to draw on the success of the green building industry to provide recommendations that may be used overcome the barriers that high performance seismic design (HPSD) is currently facing.

  16. Incorporating seismic phase correlations into a probabilistic model of global-scale seismology

    NASA Astrophysics Data System (ADS)

    Arora, Nimar

    2013-04-01

    We present a probabilistic model of seismic phases whereby the attributes of the body-wave phases are correlated to those of the first arriving P phase. This model has been incorporated into NET-VISA (Network processing Vertically Integrated Seismic Analysis) a probabilistic generative model of seismic events, their transmission, and detection on a global seismic network. In the earlier version of NET-VISA, seismic phase were assumed to be independent of each other. Although this didn't affect the quality of the inferred seismic bulletin, for the most part, it did result in a few instances of anomalous phase association. For example, an S phase with a smaller slowness than the corresponding P phase. We demonstrate that the phase attributes are indeed highly correlated, for example the uncertainty in the S phase travel time is significantly reduced given the P phase travel time. Our new model exploits these correlations to produce better calibrated probabilities for the events, as well as fewer anomalous associations.

  17. Sublake geologic structure from high-resolution seismic-reflection data from four sinkhole lakes in the Lake Wales Ridge, Central Florida

    USGS Publications Warehouse

    Tihansky, A.B.; Arthur, J.D.; DeWitt, D.W.

    1996-01-01

    Seismic-reflection profiles from Lake Wales, Blue Lake, Lake Letta, and Lake Apthorp located along the Lake Wales Ridge in central Florida provide local detail within the regional hydrogeologic framework as described by litho- and hydrostratigraphic cross sections. Lakes located with the mantled karst region have long been considered to be sinkhole lakes, originating from subsidence activity. High-resolution seismic- reflection data confirm this origin for these four lakes. The geologic framework of the Lake Wales Ridge has proven to be a suitable geologic setting for continuous high-resolution seismic-reflection profiling in lakes; however, the nature of the lake-bottom sediments largely controls the quality of the seismic data. In lakes with significant organic-rich bottom deposits, interpretable record was limited to areas where organic deposits were minimal. In lakes with clean, sandy bottoms, the seismic-reflection methods were highly successful in obtaining data that can be correlated with sublake subsidence features. These techniques are useful in examining sublake geology and providing a better understanding of how confining units are affected by subsidence in a region where their continuity is of significant importance to local lake hydrology. Although local geologic control around each lake generally corresponds to the regional geologic framework, local deviations from regional geologic trends occur in sublake areas affected by subsidence activity. Each of the four lakes examined represents a unique set of geologic controls and provides some degree of structural evidence of subsidence activity. Sublake geologic structures identified include: (1) marginal lake sediments dipping into bathymetric lows, (2) lateral discontinuity of confining units including sags and breaches, (3) the disruption and reworking of overlying unconsolidated siliciclastic sediments as they subside into the underlying irregular limestone surface, and (4) sublake regions where

  18. Variability of High Resolution Vp/Vs and Seismic Velocity Structure Along the Nicaragua/Costa Rica Segment of the Middle America Subduction Zone

    NASA Astrophysics Data System (ADS)

    Moore-Driskell, M. M.; DeShon, H. R.

    2012-12-01

    Previous studies of subduction zone earthquakes have shown that fault conditions control earthquake rupture and behavior. There are many potential properties that may vary along the subduction margin that could cause fault zone variability, including plate age, temperature, and/or geometry, convergence rate, state of hydration, overriding geology, subducting sediment packages, or subducting seamounts/ridges. The Nicaragua/Costa Rica segment of the Middle America subduction zone is highly variable along strike and down dip. We use this margin to examine how these variable conditions affect earthquake behavior by determining local ratios of compressional to shear wave velocities (Vp/Vs) and detailed seismic velocity structure. Vp/Vs is one of the best tools available to reliably define fault conditions because it is directly related to the Poisson's ratio of the fault material, and it is sensitive to the presence of fluids and changing permeability. Thus with well-resolved near source Vp/Vs measurements we can infer composition and/or high fluid pressures. Here, we use a technique developed by Lin and Shearer (2007) to determine local Vp/Vs in small areas (~2 x 2 x 2 km) with high seismicity. Within the seismogenic zone, we find the margin to be highly variable along strike in Vp/Vs and seismic velocity. These changes correlate to documented variability in incoming plate properties. Increased Vp/Vs is associated with intraplate earthquakes along Nicaragua and northern Costa Rica. We compare our results with other geophysical studies including new high-resolution images of seismic velocity structure, an extensive catalog of high quality relocated events, apparent stress calculations, coupling, and SSE/NVT occurrence. A better understanding of the connection between fault properties and earthquake behavior gives insight into the role of fluids in seismogenesis, the spectrum of earthquake rupture, and possible hazard at subduction zones.

  19. Water Quality Instructional Resources Information System (IRIS): A Compilation of Abstracts to Water Quality and Water Resources Materials.

    ERIC Educational Resources Information Center

    Office of Water Program Operations (EPA), Cincinnati, OH. National Training and Operational Technology Center.

    Presented is a compilation of over 3,000 abstracts on print and non-print materials related to water quality and water resources education. Entries are included from all levels of governmental sources, private concerns, and educational institutions. Each entry includes: title, author, cross references, descriptors, and availability. (CLS)

  20. National Seismic Network of Georgia

    NASA Astrophysics Data System (ADS)

    Tumanova, N.; Kakhoberashvili, S.; Omarashvili, V.; Tserodze, M.; Akubardia, D.

    2016-12-01

    Georgia, as a part of the Southern Caucasus, is tectonically active and structurally complex region. It is one of the most active segments of the Alpine-Himalayan collision belt. The deformation and the associated seismicity are due to the continent-continent collision between the Arabian and Eurasian plates. Seismic Monitoring of country and the quality of seismic data is the major tool for the rapid response policy, population safety, basic scientific research and in the end for the sustainable development of the country. National Seismic Network of Georgia has been developing since the end of 19th century. Digital era of the network started from 2003. Recently continuous data streams from 25 stations acquired and analyzed in the real time. Data is combined to calculate rapid location and magnitude for the earthquake. Information for the bigger events (Ml>=3.5) is simultaneously transferred to the website of the monitoring center and to the related governmental agencies. To improve rapid earthquake location and magnitude estimation the seismic network was enhanced by installing additional 7 new stations. Each new station is equipped with coupled Broadband and Strong Motion seismometers and permanent GPS system as well. To select the sites for the 7 new base stations, we used standard network optimization techniques. To choose the optimal sites for new stations we've taken into account geometry of the existed seismic network, topographic conditions of the site. For each site we studied local geology (Vs30 was mandatory for each site), local noise level and seismic vault construction parameters. Due to the country elevation, stations were installed in the high mountains, no accessible in winter due to the heavy snow conditions. To secure online data transmission we used satellite data transmission as well as cell data network coverage from the different local companies. As a result we've already have the improved earthquake location and event magnitudes. We

  1. Integration of P- and SH-wave high-resolution seismic reflection and micro-gravity techniques to improve interpretation of shallow subsurface structure: New Madrid seismic zone

    USGS Publications Warehouse

    Bexfield, C.E.; McBride, J.H.; Pugin, Andre J.M.; Ravat, D.; Biswas, S.; Nelson, W.J.; Larson, T.H.; Sargent, S.L.; Fillerup, M.A.; Tingey, B.E.; Wald, L.; Northcott, M.L.; South, J.V.; Okure, M.S.; Chandler, M.R.

    2006-01-01

    Shallow high-resolution seismic reflection surveys have traditionally been restricted to either compressional (P) or horizontally polarized shear (SH) waves in order to produce 2-D images of subsurface structure. The northernmost Mississippi embayment and coincident New Madrid seismic zone (NMSZ) provide an ideal laboratory to study the experimental use of integrating P- and SH-wave seismic profiles, integrated, where practicable, with micro-gravity data. In this area, the relation between "deeper" deformation of Paleozoic bedrock associated with the formation of the Reelfoot rift and NMSZ seismicity and "shallower" deformation of overlying sediments has remained elusive, but could be revealed using integrated P- and SH-wave reflection. Surface expressions of deformation are almost non-existent in this region, which makes seismic reflection surveying the only means of detecting structures that are possibly pertinent to seismic hazard assessment. Since P- and SH-waves respond differently to the rock and fluid properties and travel at dissimilar speeds, the resulting seismic profiles provide complementary views of the subsurface based on different levels of resolution and imaging capability. P-wave profiles acquired in southwestern Illinois and western Kentucky (USA) detect faulting of deep, Paleozoic bedrock and Cretaceous reflectors while coincident SH-wave surveys show that this deformation propagates higher into overlying Tertiary and Quaternary strata. Forward modeling of micro-gravity data acquired along one of the seismic profiles further supports an interpretation of faulting of bedrock and Cretaceous strata. The integration of the two seismic and the micro-gravity methods therefore increases the scope for investigating the relation between the older and younger deformation in an area of critical seismic hazard. ?? 2006 Elsevier B.V. All rights reserved.

  2. Quality of reporting in abstracts of randomized controlled trials published in leading journals of periodontology and implant dentistry: a survey.

    PubMed

    Faggion, Clovis Mariano; Giannakopoulos, Nikolaos Nikitas

    2012-10-01

    Most readers, reviewers, and editors rely on abstracts to decide whether to assess the full text of an article. A research abstract should, therefore, be as informative as possible. The standard of reporting in abstracts of randomized controlled trials (RCTs) in periodontology and implant dentistry has not yet been assessed. The objectives of this review are: 1) to assess the quality of reporting in abstracts of RCTs in periodontology and implant dentistry, and 2) to investigate changes in the quality of reporting by comparing samples from different periods. The authors searched the PubMed electronic database, independently and in duplicate, for abstracts of RCTs published in seven leading journals of periodontology and implant dentistry from 2005 to 2007 and from 2009 to 2011. The quality of reporting in selected abstracts with reference to the CONSORT (Consolidated Standards of Reporting Trials) for Abstracts checklist published in January 2008 was assessed independently and in duplicate. Cohen κ statistic was used to determine the extent of agreement of the reviewers. Pearson χ(2) test and/or Fisher exact test were used to assess differences in reporting in the two samples. Level of significance was set at P <0.05. Three hundred ninety-two abstracts are included in this review. Three items (intervention, objective, and conclusions) were almost fully reported in both samples. In contrast, other items (randomization, trial registration, and funding) were never reported. There were significant changes in reporting for only two items, trial design and title (items better reported in the pre- and post-CONSORT samples, respectively). Most topics, however, were similarly poorly reported in both samples of abstracts. The quality of reporting in abstracts of RCTs in periodontology and implant dentistry can be improved. Authors should follow the CONSORT for Abstracts guidelines, and journal editors should promote clear rules to improve authors' adherence to these

  3. The Budget Guide to Seismic Network Management

    NASA Astrophysics Data System (ADS)

    Hagerty, M. T.; Ebel, J. E.

    2007-05-01

    Regardless of their size, there are certain tasks that all seismic networks must perform, including data collection and processing, earthquake location, information dissemination, and quality control. Small seismic networks are unlikely to possess the resources -- manpower and money -- required to do much in-house development. Fortunately, there are a lot of free or inexpensive software solutions available that are able to perform many of the required tasks. Often the available solutions are all-in-one turnkey packages designed and developed for much larger seismic networks, and the cost of adapting them to a smaller network must be weighed against the ease with which other, non-seismic software can be adapted to the same task. We describe here the software and hardware choices we have made for the New England Seismic Network (NESN), a sparse regional seismic network responsible for monitoring and reporting all seismicity within the New England region in the northeastern U.S. We have chosen to use a cost-effective approach to monitoring using free, off-the-shelf solutions where available (e.g., Earthworm, HYP2000) and modifying freeware solutions when it is easier than trying to adapt a large, complicated package. We have selected for use software that is: free, likely to receive continued support from the seismic or, preferably, larger internet community, and modular. Modularity is key to our design because it ensures that if one component of our processing system becomes obsolete, we can insert a suitable replacement with few modifications to the other modules. Our automated event detection, identification and location system is based on a wavelet transform analysis of station data that arrive continuously via TCP/IP transmission over the internet. Our system for interactive analyst review of seismic events and remote system monitoring utilizes a combination of Earthworm modules, Perl cgi-bin scripts, Java, and native Unix commands and can now be carried out via

  4. Seismic Ecology

    NASA Astrophysics Data System (ADS)

    Seleznev, V. S.; Soloviev, V. M.; Emanov, A. F.

    The paper is devoted to researches of influence of seismic actions for industrial and civil buildings and people. The seismic actions bring influence directly on the people (vibration actions, force shocks at earthquakes) or indirectly through various build- ings and the constructions and can be strong (be felt by people) and weak (be fixed by sensing devices). The great number of work is devoted to influence of violent seismic actions (first of all of earthquakes) on people and various constructions. This work is devoted to study weak, but long seismic actions on various buildings and people. There is a need to take into account seismic oscillations, acting on the territory, at construction of various buildings on urbanized territories. Essential influence, except for violent earthquakes, man-caused seismic actions: the explosions, seismic noise, emitted by plant facilities and moving transport, radiation from high-rise buildings and constructions under action of a wind, etc. can exert. Materials on increase of man- caused seismicity in a number of regions in Russia, which earlier were not seismic, are presented in the paper. Along with maps of seismic microzoning maps to be built indicating a variation of amplitude spectra of seismic noise within day, months, years. The presence of an information about amplitudes and frequencies of oscillations from possible earthquakes and man-caused oscillations in concrete regions allows carry- ing out soundly designing and construction of industrial and civil housing projects. The construction of buildings even in not seismically dangerous regions, which have one from resonance frequencies coincident on magnitude to frequency of oscillations, emitted in this place by man-caused objects, can end in failure of these buildings and heaviest consequences for the people. The practical examples of detail of engineering- seismological investigation of large industrial and civil housing projects of Siberia territory (hydro power

  5. Micro-seismicity and seismic moment release within the Coso Geothermal Field, California

    USGS Publications Warehouse

    Kaven, Joern; Hickman, Stephen H.; Davatzes, Nicholas C.

    2014-01-01

    We relocate 16 years of seismicity in the Coso Geothermal Field (CGF) using differential travel times and simultaneously invert for seismic velocities to improve our knowledge of the subsurface geologic and hydrologic structure. We expand on our previous results by doubling the number of relocated events from April 1996 through May 2012 using a new field-wide 3-D velocity model. Relocated micro-seismicity sharpens in many portions of the active geothermal reservoir, likely defining large-scale fault zones and fluid pressure compartment boundaries. However, a significant fraction of seismicity remains diffuse and does not cluster into sharply defined structures, suggesting that permeability is maintained within the reservoir through distributed brittle failure. The seismic velocity structure reveals heterogeneous distributions of compressional (Vp) and shear (Vs) wave speed, with Vs generally higher in the Main Field and East Flank and Vp remaining relatively uniform across the CGF, but with significant local variations. The Vp/Vs ratio appears to outline the two main producing compartments of the reservoir at depths below mean ground level of approximately 1 to 2.5 km, with a ridge of relatively high Vp/Vs separating the Main Field from the East Flank. Detailed analyses of spatial and temporal variations in earthquake relocations and cumulative seismic moment release in the East Flank reveal three regions with persistently high rates of seismic activity. Two of these regions exhibit sharp, stationary boundaries at the margins of the East Flank that likely represent barriers to fluid flow and advective heat transport. However, seismicity and moment release in a third region at the northern end of the East Flank spread over time to form an elongated NE to SW structure, roughly parallel both to an elongated cluster of seismicity at the southern end of the East Flank and to regional fault traces mapped at the surface. Our results indicate that high

  6. High-frequency seismic signals associated with glacial earthquakes in Greenland

    NASA Astrophysics Data System (ADS)

    Olsen, K.; Nettles, M.

    2017-12-01

    Glacial earthquakes are magnitude 5 seismic events generated by iceberg calving at marine-terminating glaciers. They are characterized by teleseismically detectable signals at 35-150 seconds period that arise from the rotation and capsize of gigaton-sized icebergs (e.g., Ekström et al., 2003; Murray et al., 2015). Questions persist regarding the details of this calving process, including whether there are characteristic precursory events such as ice slumps or pervasive crevasse opening before an iceberg rotates away from the glacier. We investigate the high-frequency seismic signals produced before, during, and after glacial earthquakes. We analyze a set of 94 glacial earthquakes that occurred at three of Greenland's major glaciers, Jakobshavn Isbræ, Helheim Glacier, and Kangerdlugssuaq Glacier, from 2001 - 2013. We employ data from the GLISN network of broadband seismometers around Greenland and from short-term seismic deployments located close to the glaciers. These data are bandpass filtered to 3 - 10 Hz and trimmed to one-hour windows surrounding known glacial earthquakes. We observe elevated amplitudes of the 3 - 10 Hz signal for 500 - 1500 seconds spanning the time of each glacial earthquake. These durations are long compared to the 60 second glacial-earthquake source. In the majority of cases we observe an increase in the amplitude of the 3 - 10 Hz signal 200 - 600 seconds before the centroid time of the glacial earthquake and sustained high amplitudes for up to 800 seconds after. In some cases, high-amplitude energy in the 3 - 10 Hz band precedes elevated amplitudes in the 35 - 150 s band by 300 seconds. We explore possible causes for these high-frequency signals, and discuss implications for improving understanding of the glacial-earthquake source.

  7. Building a Smartphone Seismic Network

    NASA Astrophysics Data System (ADS)

    Kong, Q.; Allen, R. M.

    2013-12-01

    We are exploring to build a new type of seismic network by using the smartphones. The accelerometers in smartphones can be used to record earthquakes, the GPS unit can give an accurate location, and the built-in communication unit makes the communication easier for this network. In the future, these smartphones may work as a supplement network to the current traditional network for scientific research and real-time applications. In order to build this network, we developed an application for android phones and server to record the acceleration in real time. These records can be sent back to a server in real time, and analyzed at the server. We evaluated the performance of the smartphone as a seismic recording instrument by comparing them with high quality accelerometer while located on controlled shake tables for a variety of tests, and also the noise floor test. Based on the daily human activity data recorded by the volunteers and the shake table tests data, we also developed algorithm for the smartphones to detect earthquakes from daily human activities. These all form the basis of setting up a new prototype smartphone seismic network in the near future.

  8. Identification of ground motion features for high-tech facility under far field seismic waves using wavelet packet transform

    NASA Astrophysics Data System (ADS)

    Huang, Shieh-Kung; Loh, Chin-Hsiung; Chen, Chin-Tsun

    2016-04-01

    Seismic records collected from earthquake with large magnitude and far distance may contain long period seismic waves which have small amplitude but with dominant period up to 10 sec. For a general situation, the long period seismic waves will not endanger the safety of the structural system or cause any uncomfortable for human activity. On the contrary, for those far distant earthquakes, this type of seismic waves may cause a glitch or, furthermore, breakdown to some important equipments/facilities (such as the high-precision facilities in high-tech Fab) and eventually damage the interests of company if the amplitude becomes significant. The previous study showed that the ground motion features such as time-variant dominant frequencies extracted using moving window singular spectrum analysis (MWSSA) and amplitude characteristics of long-period waves identified from slope change of ground motion Arias Intensity can efficiently indicate the damage severity to the high-precision facilities. However, embedding a large hankel matrix to extract long period seismic waves make the MWSSA become a time-consumed process. In this study, the seismic ground motion data collected from broadband seismometer network located in Taiwan were used (with epicenter distance over 1000 km). To monitor the significant long-period waves, the low frequency components of these seismic ground motion data are extracted using wavelet packet transform (WPT) to obtain wavelet coefficients and the wavelet entropy of coefficients are used to identify the amplitude characteristics of long-period waves. The proposed method is a timesaving process compared to MWSSA and can be easily implemented for real-time detection. Comparison and discussion on this method among these different seismic events and the damage severity to the high-precision facilities in high-tech Fab is made.

  9. High-resolution seismic reflection to delineate shallow gas in Eastern Kansas

    USGS Publications Warehouse

    Miller, R.D.; Watney, W.L.; Begay, D.K.; Xia, J.

    2000-01-01

    Unique amplitude characteristics of shallow gas sands within Pennsylvanian clastic-carbonate dominated sequences are discernible on high-resolution seismic reflection data in eastern Kansas. Upward grading sequences of sand into shale represent a potential gas reservoir with a low-impedence acoustic contrast at the base of the encasing layer. The gas sand and encasing shale, which define the gas reservoir studied here, are part of an erosional incised valley where about 30 m of carbonates and shale have been replaced by sandstone and shale confined to the incised valley. These consolidated geologic settings would normally possess high impedence gas sand reservoirs as defined by abrupt contacts between the gas sand and encasing shale. Based orr core and borehole logs, the gas sand studied here grades from sand into shale in a fashion analogous to that observed in classic low-impedance environments. Amplitude and phase characteristics of high-resolution seismic data across this approximately 400-m wide gas sand are indicative of a low-impedance reservoir. Shot gathers possess classic amplitude with offsett-dependent characteristics which are manifeted on the stacked section as "bright spots." Dominant Frequencies of around 120 Hz allow detection of several reflectors within the 30+ meters of sand/shale that make up this localized gas-rich incised valley fill. The gradational nature of the trapping mechanism observed in this gas reservoir would make detection with conventional seismic reflection methods unlikely.

  10. Two applications of time reversal mirrors: seismic radio and seismic radar.

    PubMed

    Hanafy, Sherif M; Schuster, Gerard T

    2011-10-01

    Two seismic applications of time reversal mirrors (TRMs) are introduced and tested with field experiments. The first one is sending, receiving, and decoding coded messages similar to a radio except seismic waves are used. The second one is, similar to radar surveillance, detecting and tracking a moving object(s) in a remote area, including the determination of the objects speed of movement. Both applications require the prior recording of calibration Green's functions in the area of interest. This reference Green's function will be used as a codebook to decrypt the coded message in the first application and as a moving sensor for the second application. Field tests show that seismic radar can detect the moving coordinates (x(t), y(t), z(t)) of a person running through a calibration site. This information also allows for a calculation of his velocity as a function of location. Results with the seismic radio are successful in seismically detecting and decoding coded pulses produced by a hammer. Both seismic radio and radar are highly robust to signals in high noise environments due to the super-stacking property of TRMs. © 2011 Acoustical Society of America

  11. Seismic Technology Adapted to Analyzing and Developing Geothermal Systems Below Surface-Exposed High-Velocity Rocks Final Report

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

    Hardage, Bob A.; DeAngelo, Michael V.; Ermolaeva, Elena

    The objective of our research was to develop and demonstrate seismic data-acquisition and data-processing technologies that allow geothermal prospects below high-velocity rock outcrops to be evaluated. To do this, we acquired a 3-component seismic test line across an area of exposed high-velocity rocks in Brewster County, Texas, where there is high heat flow and surface conditions mimic those found at numerous geothermal prospects. Seismic contractors have not succeeded in creating good-quality seismic data in this area for companies who have acquired data for oil and gas exploitation purposes. Our test profile traversed an area where high-velocity rocks and low-velocity sedimentmore » were exposed on the surface in alternating patterns that repeated along the test line. We verified that these surface conditions cause non-ending reverberations of Love waves, Rayleigh waves, and shallow critical refractions to travel across the earth surface between the boundaries of the fast-velocity and slow-velocity material exposed on the surface. These reverberating surface waves form the high level of noise in this area that does not allow reflections from deep interfaces to be seen and utilized. Our data-acquisition method of deploying a box array of closely spaced geophones allowed us to recognize and evaluate these surface-wave noise modes regardless of the azimuth direction to the surface anomaly that backscattered the waves and caused them to return to the test-line profile. With this knowledge of the surface-wave noise, we were able to process these test-line data to create P-P and SH-SH images that were superior to those produced by a skilled seismic data-processing contractor. Compared to the P-P data acquired along the test line, the SH-SH data provided a better detection of faults and could be used to trace these faults upward to the boundaries of exposed surface rocks. We expanded our comparison of the relative value of S-wave and P-wave seismic data for

  12. Geographical coincidence of high heat flow, high seismicity, and upwelling, with hydrocarbon deposits, phosphorites, evaporites, and uranium ores.

    PubMed

    Libby, L M; Libby, W F

    1974-10-01

    Oil deposits occur in deep sediments, and appear to be organic matter that has been transformed through the action of geothermal heat and pressure. Deep sediments, rich in biological remains, are created by ocean upwelling, caused in part by high geothermal heat flow through the sea bottom. Such regions correlate with enhanced seismic activity. We look for correlations of seismicity, high heat flux, petroleum, uranium, phosphates, and salts, deposited from abundant plant life. These may be useful in discovering more petroleum and coal. We estimate that the known world reserves of petroleum and coal are about 10(-4) of the total of buried biogenic carbon.

  13. Geographical Coincidence of High Heat Flow, High Seismicity, and Upwelling, with Hydrocarbon Deposits, Phosphorites, Evaporites, and Uranium Ores

    PubMed Central

    Libby, L. M.; Libby, W. F.

    1974-01-01

    Oil deposits occur in deep sediments, and appear to be organic matter that has been transformed through the action of geothermal heat and pressure. Deep sediments, rich in biological remains, are created by ocean upwelling, caused in part by high geothermal heat flow through the sea bottom. Such regions correlate with enhanced seismic activity. We look for correlations of seismicity, high heat flux, petroleum, uranium, phosphates, and salts, deposited from abundant plant life. These may be useful in discovering more petroleum and coal. We estimate that the known world reserves of petroleum and coal are about 10-4 of the total of buried biogenic carbon. Images PMID:16592185

  14. Evaluation of seismic testing for quality assurance of lime-stabilized soil.

    DOT National Transportation Integrated Search

    2013-08-01

    This study sought to determine the technical feasibility of using seismic techniques to measure the : laboratory and field seismic modulus of lime-stabilized soils (LSS), and to compare/correlate test results : from bench-top (free-free resonance) se...

  15. PQLX: A seismic data quality control system description, applications, and users manual

    USGS Publications Warehouse

    McNamara, Daniel E.; Boaz, Richard I.

    2011-01-01

    We present a detailed description and users manual for a new tool to evaluate seismic station performance and characteristics by providing quick and easy transitions between visualizations of the frequency and time domains. The software is based on the probability density functions (PDF) of power spectral densities (PSD) (McNamara and Buland, 2004) and builds on the original development of the PDF stand-alone software system (McNamara and Boaz, 2005) and the seismological data viewer application PQL (IRIS-PASSCAL Quick Look) and PQLII (available through the IRIS PASSCAL program: http://www.passcal.nmt.edu/content/pql-ii-program-viewing-data). With PQLX (PQL eXtended), computed PSDs are stored in a MySQL database, allowing a user to access specific time periods of PSDs (PDF subsets) and time series segments through a GUI-driven interface. The power of the method and software lies in the fact that there is no need to screen the data for system transients, earthquakes, or general data artifacts, because they map into a background probability level. In fact, examination of artifacts related to station operation and episodic cultural noise allow us to estimate both the overall station quality and a baseline level of Earth noise at each site. The output of this analysis tool is useful for both operational and scientific applications. Operationally, it is useful for characterizing the current and past performance of existing broadband stations, for conducting tests on potential new seismic station locations, for evaluating station baseline noise levels (McNamara and others, 2009), for detecting problems with the recording system or sensors, and for evaluating the overall quality of data and metadata. Scientifically, the tool allows for mining of PSDs for investigations on the evolution of seismic noise (for example, Aster and others, 2008; and Aster and others, 2010) and other phenomena. Currently, PQLX is operational at several organizations including the USGS National

  16. Abstracting event-based control models for high autonomy systems

    NASA Technical Reports Server (NTRS)

    Luh, Cheng-Jye; Zeigler, Bernard P.

    1993-01-01

    A high autonomy system needs many models on which to base control, management, design, and other interventions. These models differ in level of abstraction and in formalism. Concepts and tools are needed to organize the models into a coherent whole. The paper deals with the abstraction processes for systematic derivation of related models for use in event-based control. The multifaceted modeling methodology is briefly reviewed. The morphism concepts needed for application to model abstraction are described. A theory for supporting the construction of DEVS models needed for event-based control is then presented. An implemented morphism on the basis of this theory is also described.

  17. Extraction of Pn seismic signals from air-gun shots recorded by the Cascadia Amphibious seismic experiment

    NASA Astrophysics Data System (ADS)

    Rathnayaka, S.; Gao, H.

    2017-12-01

    The goal of this study is to extract Pn (head wave) seismic waveforms recorded by both offshore and onshore (broadband and short period) seismic stations and evaluate the data quality. Two offshore active-source seismic experiments, MGL 1211 and MGL 1212, were conducted from 13th June to 24th July 2012, during the first year deployment of the Cascadia Initiative Amphibious Array. In total, we choose 110 ocean bottom seismometers and 209 inland stations that are located along the entire Cascadia subduction zone. We first remove the instrument response, and then explore the potential frequency ranges and the diurnal effect. We make the common receiver gathering for each seismic station and filter the seismic waveforms at multiple frequency bands, ranging from 3-5 Hz, 5-10 Hz, 10-20 Hz, to 20-40 Hz, respectively. To quantitatively evaluate the data quality, we calculate the signal-to-noise ratio (SNR) of the waveforms for usable stations that record clear Pn arrivals at multiple frequency bands. Our results show that most offshore stations located at deep water (>1.5 km) record clear air-gun shot signals at frequencies higher than 3 Hz and up to 550 km away from the source. For most stations located on the shallow continental shelf, the seismic recordings appear much noisier at all the frequencies compared to stations at deep water. Three general trends are observed for the SNR distribution; First, the SNR ratio increases from lower to higher frequency bands; Second, the ratio decreases with the increasing source-to-receiver distance; And third, the ratio increases from shallow to deep water. We also observe a rough negative relationship of the signal-to-noise ratio with the thickness of the marine sediment. Only 5 inland stations record clear air-gun shot arrivals up to 200 km away from the source. More detailed data quality analysis with more results will also be present.

  18. Focused fluid-flow processes through high-quality bathymetric, 2D seismic and Chirp data from the southern parts of the Bay of Biscay, France

    NASA Astrophysics Data System (ADS)

    Baudon, Catherine; Gillet, Hervé; Cremer, Michel

    2013-04-01

    High-quality bathymetric, 2D seismic and Chirp data located in the southern parts of the Bay of Biscay, France, collected by the University of Bordeaux 1 (Cruises ITSAS 2, 2001; PROSECAN 3, 2006 and SARGASS, 2010) have recently been compiled. The survey area widely covers the Capbreton Canyon, which lies on the boundary between two major structural zones: the Aquitanian passive margin to the North, and the Basque-Cantabrian margin to the South which corresponds to the offshore Pyrenean front. The dataset revealed a large number of key seafloor features potentially associated with focused fluid-flow processes and subsurface sediment-remobilization. Focused fluid migration through sub-seabed sediments is a common phenomenon on continental margins worldwide and has widespread implications from both industrial and fundamental perspectives, from seafloor marine environmental issues to petroleum exploration and hazard assessments. Our study analyses the relationships between seafloor features, deeper structures and fluid migration through the Plio-Quaternary sedimentary pile. The geometrical characteristics, mechanisms of formation and kinematics of four main groups of seabed features have been investigated. (i) A 150km2 field of pockmarks can be observed on the Basque margin. These features are cone-shaped circular or elliptical depressions that are either randomly distributed as small pockmarks (diameter < 20m) or aligned in trains of large pockmarks (ranging from 200 to 600m in diameter) along shallow troughs leading downstream to the Capbreton Canyon. Seismic data show that most pockmarks reach the seabed through vertically staked V-shaped features but some are buried and show evidence of lateral migration through time. (ii) A second field of widely-spaced groups of pockmarks pierce the upper slope of the Aquitanian margin. These depressions are typically a few hundred meters in diameter and seem to be preferentially located in the troughs or on the stoss sides of

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

    NASA Astrophysics Data System (ADS)

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

    2018-04-01

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

  20. Time-dependent seismic tomography of the Coso geothermal area, 1996-2004

    USGS Publications Warehouse

    Julian, B.R.; Foulger, G.R.

    2005-01-01

    The permanent 18-station network of three-component digital seismometers at the seismically active Coso geothermal area, California, provides high-quality microearthquake (MEQ) data that are well suited to investigating temporal variations in structure related to processes within the geothermal reservoir. A preliminary study [Julian, et al., 2003; Julian, et al., 2004] comparing data from 1996 and 2003 found significant variations in the ratio of the seismic wave-speeds, Vp/Vs, at shallow depths over this time interval. This report describes results of a more detailed study of each year from 1996 through 2004.

  1. Evaluation and developmental studies of possible active seismic experiments during the post-Apollo period

    NASA Technical Reports Server (NTRS)

    Kovach, R. L.

    1974-01-01

    Seismic velocity studies pertinent to the lunar crust and mantle are briefly summarized. The compressional and shear wave velocities in loose aggregates are discussed along with the effects of temperature on seismic velocity in compacted powders. Abstracts of papers concerning the lunar structure are included.

  2. Composite Earthquake Catalog of the Yellow Sea for Seismic Hazard Studies

    NASA Astrophysics Data System (ADS)

    Kang, S. Y.; Kim, K. H.; LI, Z.; Hao, T.

    2017-12-01

    The Yellow Sea (a.k.a West Sea in Korea) is an epicontinental and semi-closed sea located between Korea and China. Recent earthquakes in the Yellow Sea including, but not limited to, the Seogyuckryulbi-do (1 April 2014, magnitude 5.1), Heuksan-do (21 April 2013, magnitude 4.9), Baekryung-do (18 May 2013, magnitude 4.9) earthquakes, and the earthquake swarm in the Boryung offshore region in 2013, remind us of the seismic hazards affecting east Asia. This series of earthquakes in the Yellow Sea raised numerous questions. Unfortunately, both governments have trouble in monitoring seismicity in the Yellow Sea because earthquakes occur beyond their seismic networks. For example, the epicenters of the magnitude 5.1 earthquake in the Seogyuckryulbi-do region in 2014 reported by the Korea Meteorological Administration and China Earthquake Administration differed by approximately 20 km. This illustrates the difficulty with seismic monitoring and locating earthquakes in the region, despite the huge effort made by both governments. Joint effort is required not only to overcome the limits posed by political boundaries and geographical location but also to study seismicity and the underground structures responsible. Although the well-established and developing seismic networks in Korea and China have provided unprecedented amount and quality of seismic data, high quality catalog is limited to the recent 10s of years, which is far from major earthquake cycle. It is also noticed the earthquake catalog from either country is biased to its own and cannot provide complete picture of seismicity in the Yellow Sea. In order to understand seismic hazard and tectonics in the Yellow Sea, a composite earthquake catalog has been developed. We gathered earthquake information during last 5,000 years from various sources. There are good reasons to believe that some listings account for same earthquake, but in different source parameters. We established criteria in order to provide consistent

  3. 4-D High-Resolution Seismic Reflection Monitoring of Miscible CO2 Injected into a Carbonate Reservoir

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

    Richard D. Miller; Abdelmoneam E. Raef; Alan P. Byrnes

    2007-06-30

    The objective of this research project was to acquire, process, and interpret multiple high-resolution 3-D compressional wave and 2-D, 2-C shear wave seismic data in the hopes of observing changes in fluid characteristics in an oil field before, during, and after the miscible carbon dioxide (CO{sub 2}) flood that began around December 1, 2003, as part of the DOE-sponsored Class Revisit Project (DOE No.DE-AC26-00BC15124). Unique and key to this imaging activity is the high-resolution nature of the seismic data, minimal deployment design, and the temporal sampling throughout the flood. The 900-m-deep test reservoir is located in central Kansas oomoldic limestonesmore » of the Lansing-Kansas City Group, deposited on a shallow marine shelf in Pennsylvanian time. After 30 months of seismic monitoring, one baseline and eight monitor surveys clearly detected changes that appear consistent with movement of CO{sub 2} as modeled with fluid simulators and observed in production data. Attribute analysis was a very useful tool in enhancing changes in seismic character present, but difficult to interpret on time amplitude slices. Lessons learned from and tools/techniques developed during this project will allow high-resolution seismic imaging to be routinely applied to many CO{sub 2} injection programs in a large percentage of shallow carbonate oil fields in the midcontinent.« less

  4. Seismic Design of a Single Bored Tunnel: Longitudinal Deformations and Seismic Joints

    NASA Astrophysics Data System (ADS)

    Oh, J.; Moon, T.

    2018-03-01

    The large diameter bored tunnel passing through rock and alluvial deposits subjected to seismic loading is analyzed for estimating longitudinal deformations and member forces on the segmental tunnel liners. The project site has challenges including high hydrostatic pressure, variable ground profile and high seismic loading. To ensure the safety of segmental tunnel liner from the seismic demands, the performance-based two-level design earthquake approach, Functional Evaluation Earthquake and Safety Evaluation Earthquake, has been adopted. The longitudinal tunnel and ground response seismic analyses are performed using a three-dimensional quasi-static linear elastic and nonlinear elastic discrete beam-spring elements to represent segmental liner and ground spring, respectively. Three components (longitudinal, transverse and vertical) of free-field ground displacement-time histories evaluated from site response analyses considering wave passage effects have been applied at the end support of the strain-compatible ground springs. The result of the longitudinal seismic analyses suggests that seismic joint for the mitigation measure requiring the design deflection capacity of 5-7.5 cm is to be furnished at the transition zone between hard and soft ground condition where the maximum member forces on the segmental liner (i.e., axial, shear forces and bending moments) are induced. The paper illustrates how detailed numerical analyses can be practically applied to evaluate the axial and curvature deformations along the tunnel alignment under difficult ground conditions and to provide the seismic joints at proper locations to effectively reduce the seismic demands below the allowable levels.

  5. Hanford Quarter Seismic Report - 98C Seismicity On and Near the Hanford Site, Pasco Basin, Washington: April 1, 1998 Through June 30, 1998

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

    DC Hartshorn, SP Reidel, AC Rohay

    1998-10-23

    Hanford Seismic Monitoring provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network (HSN) for the U.S. Department of Energy and its contractors. The staff also locates aud identifies sources of seismic activity and monitors changes in the hi~orical pattern of seismic activity at the Hanford Site. The data are. compiled archived, and published for use by the Hanford Site for waste management Natural Phenomena Hazards assessments, and engineering design and construction. In addition, the seismic monitoring organization works with the Hanford Site Emergency Services Organization to provide assistance in the event of zinmore » earthquake on the Hanford Site. The HSN and Ihe Eastern Washington Regional Network (EN/RN) consist-of 42 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Monitoring staff. The operational rate for the third quarter of FY 1998 for stations in the HSN was 99.99%. The operational rate for the third quarter of FY 1998 for stations of the EWRN was 99.95%. For the third quarter of FY 1998, the acquisition computer triggered 133 times. Of these triggers 11 were local earthquakes: 5 (45Yo) in the Columbia River Basalt Group, 2(1 8%) in the pre-basalt sediments, and 4 (36%) in the crystalline basement. The geologic and tectonic environments where these earthquakes occurred are discussed in this report.« less

  6. Hanford Quarter Seismic Report - 98C Seismicity On and Near the Hanford Site, Pasco Basin, Washington: April 1, 1998 Through June 30, 1998

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

    DC Hartshorn, SP Reidel, AC Rohay.

    1998-10-23

    Hanford Seismic Monitoring provides an uninterrupted collection of high-quality raw and processed seismic data from the Hanford Seismic Network (HSN) for the U.S. Department of Energy and its contractors. The staff also locates aud identifies sources of seismic activity and monitors changes in the hi orical pattern of seismic activity at the Hanford Site. The data are. compiled archived, and published for use by the Hanford Site for waste management Natural Phenomena Hazards assessments, and engineering design and construction. In addition, the seismic monitoring organization works with the Hanford Site Emergency Services Organization to provide assistance in the event ofmore » zin earthquake on the Hanford Site. The HSN and Ihe Eastern Washington Regional Network (EN/RN) consist-of 42 individual sensor sites and 15 radio relay sites maintained by the Hanford Seismic Monitoring staff. The operational rate for the third quarter of FY 1998 for stations in the HSN was 99.99%. The operational rate for the third quarter of FY 1998 for stations of the EWRN was 99.95%. For the third quarter of FY 1998, the acquisition computer triggered 133 times. Of these triggers 11 were local earthquakes: 5 (45Yo) in the Columbia River Basalt Group, 2(1 8%) in the pre-basalt sediments, and 4 (36%) in the crystalline basement. The geologic and tectonic environments where these earthquakes occurred are discussed in this report.« less

  7. High-resolution seismic constraints on flow dynamics in the oceanic asthenosphere.

    PubMed

    Lin, Pei-Ying Patty; Gaherty, James B; Jin, Ge; Collins, John A; Lizarralde, Daniel; Evans, Rob L; Hirth, Greg

    2016-07-28

    Convective flow in the mantle and the motions of tectonic plates produce deformation of Earth's interior, and the rock fabric produced by this deformation can be discerned using the anisotropy of the seismic wave speed. This deformation is commonly inferred close to lithospheric boundaries beneath the ocean in the uppermost mantle, including near seafloor-spreading centres as new plates are formed via corner flow, and within a weak asthenosphere that lubricates large-scale plate-driven flow and accommodates smaller scale convection. Seismic models of oceanic upper mantle differ as to the relative importance of these deformation processes: seafloor spreading fabric is very strong just beneath the crust-mantle boundary (the Mohorovičić discontinuity, or Moho) at relatively local scales, but at the global and ocean-basin scales, oceanic lithosphere typically appears weakly anisotropic when compared to the asthenosphere. Here we use Rayleigh waves, recorded across an ocean-bottom seismograph array in the central Pacific Ocean (the NoMelt Experiment), to provide unique localized constraints on seismic anisotropy within the oceanic lithosphere-asthenosphere system in the middle of a plate. We find that azimuthal anisotropy is strongest within the high-seismic-velocity lid, with the fast direction coincident with seafloor spreading. A minimum in the magnitude of azimuthal anisotropy occurs within the middle of the seismic low-velocity zone, and then increases with depth below the weakest portion of the asthenosphere. At no depth does the fast direction correlate with the apparent plate motion. Our results suggest that the highest strain deformation in the shallow oceanic mantle occurs during corner flow at the ridge axis, and via pressure-driven or buoyancy-driven flow within the asthenosphere. Shear associated with motion of the plate over the underlying asthenosphere, if present, is weak compared to these other processes.

  8. Using Seismic Interferometry to Investigate Seismic Swarms

    NASA Astrophysics Data System (ADS)

    Matzel, E.; Morency, C.; Templeton, D. C.

    2017-12-01

    Seismicity provides a direct means of measuring the physical characteristics of active tectonic features such as fault zones. Hundreds of small earthquakes often occur along a fault during a seismic swarm. This seismicity helps define the tectonically active region. When processed using novel geophysical techniques, we can isolate the energy sensitive to the fault, itself. Here we focus on two methods of seismic interferometry, ambient noise correlation (ANC) and the virtual seismometer method (VSM). ANC is based on the observation that the Earth's background noise includes coherent energy, which can be recovered by observing over long time periods and allowing the incoherent energy to cancel out. The cross correlation of ambient noise between a pair of stations results in a waveform that is identical to the seismogram that would result if an impulsive source located at one of the stations was recorded at the other, the Green function (GF). The calculation of the GF is often stable after a few weeks of continuous data correlation, any perturbations to the GF after that point are directly related to changes in the subsurface and can be used for 4D monitoring.VSM is a style of seismic interferometry that provides fast, precise, high frequency estimates of the Green's function (GF) between earthquakes. VSM illuminates the subsurface precisely where the pressures are changing and has the potential to image the evolution of seismicity over time, including changes in the style of faulting. With hundreds of earthquakes, we can calculate thousands of waveforms. At the same time, VSM collapses the computational domain, often by 2-3 orders of magnitude. This allows us to do high frequency 3D modeling in the fault region. Using data from a swarm of earthquakes near the Salton Sea, we demonstrate the power of these techniques, illustrating our ability to scale from the far field, where sources are well separated, to the near field where their locations fall within each other

  9. High-resolution seismic stratigraphy of an Holocene lacustrine delta in western Lake Geneva (Switzerland)

    USGS Publications Warehouse

    Baster, I.; Girardclos, S.; Pugin, A.; Wildi, W.

    2003-01-01

    A high-resolution seismic survey was conducted in western Lake Geneva on a small delta formed by the Promenthouse, the Asse and the Boiron rivers. This dataset provides information on changes in the geometry and sedimentation patterns of this delta from Late-glacial to Present. The geometry of the deposits of the lacustrine delta has been mapped using 300-m spaced grid lines acquired with a 12 kHz Echosounder subbottom profiler. A complete three dimensional image of the sediment architecture was reconstructed through seismic stratigraphic analysis. Six different delta lobes have been recognized in the prodelta area. Depositional centers and lateral extension of the delta have changed through time, indicating migration and fluctuation of river input as well as changes in lake currents and wind regime from the time of glacier retreat to the Present. The delta slope is characterized by a high instability causing stumps developing and by the accumulation of biogenic gas that prevents seismic penetration.

  10. Salton Trough Post-seismic Afterslip, Viscoelastic Response, and Contribution to Regional Hazard

    NASA Astrophysics Data System (ADS)

    Parker, J. W.; Donnellan, A.; Lyzenga, G. A.

    2012-12-01

    The El Mayor-Cucapah M7.2 April 4 2010 earthquake in Baja California may have affected accumulated hazard to Southern California cities due to loading of regional faults including the Elsinore, San Jacinto and southern San Andreas, faults which already have over a century of tectonic loading. We examine changes observed via multiple seismic and geodetic techniques, including micro seismicity and proposed seismicity-based indicators of hazard, high-quality fault models, the Plate Boundary Observatory GNSS array (with 174 stations showing post-seismic transients with greater than 1 mm amplitude), and interferometric radar maps from UAVSAR (aircraft) flights, showing a network of aseismic fault slip events at distances up to 60 km from the end of the surface rupture. Finite element modeling is used to compute the expected coseismic motions at GPS stations with general agreement, including coseismic uplift at sites ~200 km north of the rupture. Postseismic response is also compared, with GNSS and also with the CIG software "RELAX." An initial examination of hazard is made comparing micro seismicity-based metrics, fault models, and changes to coulomb stress on nearby faults using the finite element model. Comparison of seismicity with interferograms and historic earthquakes show aseismic slip occurs on fault segments that have had earthquakes in the last 70 years, while other segments show no slip at the surface but do show high triggered seismicity. UAVSAR-based estimates of fault slip can be incorporated into the finite element model to correct Coloumb stress change.

  11. Recent Progress of Seismic Observation Networks in Japan

    NASA Astrophysics Data System (ADS)

    Okada, Y.

    2013-04-01

    Before the occurrence of disastrous Kobe earthquake in 1995, the number of high sensitivity seismograph stations operated in Japan was nearly 550 and was concentrated in the Kanto and Tokai districts, central Japan. In the wake of the Kobe earthquake, Japanese government has newly established the Headquarters for Earthquake Research Promotion and started the reconstruction of seismic networks to evenly cover the whole Japan. The basic network is composed of three seismographs, i.e. high sensitivity seismograph (Hi-net), broadband seismograph (F-net), and strong motion seismograph (K-NET). A large majority of Hi-net stations are also equipped with a pair of strong motion sensors at the bottom of borehole and the ground surface (KiK-net). A plenty of high quality data obtained from these networks are circulated at once and is producing several new seismological findings as well as providing the basis for the Earthquake Early Warning system. In March 11, 2011, "Off the Pacific coast of Tohoku Earthquake" was generated with magnitude 9.0, which records the largest in the history of seismic observation in Japan. The greatest disaster on record was brought by huge tsunami with nearly 20 thousand killed or missing people. We are again noticed that seismic observation system is quite poor in the oceanic region compared to the richness of it in the inland region. In 2012, NIED has started the construction of ocean bottom seismic and tsunami observation network along the Japan Trench. It is planned to layout 154 stations with an average spacing of 30km, each of which is equipped with an accelerometer for seismic observation and a water pressure gauge for tsunami observation. We are expecting that more rapid and accurate warning of earthquake and tsunami becomes possible by this observing network.

  12. Next Generation Seismic Imaging; High Fidelity Algorithms and High-End Computing

    NASA Astrophysics Data System (ADS)

    Bevc, D.; Ortigosa, F.; Guitton, A.; Kaelin, B.

    2007-05-01

    uniquely powerful computing power of the MareNostrum supercomputer in Barcelona to realize the promise of RTM, incorporate it into daily processing flows, and to help solve exploration problems in a highly cost-effective way. Uniquely, the Kaleidoscope Project is simultaneously integrating software (algorithms) and hardware (Cell BE), steps that are traditionally taken sequentially. This unique integration of software and hardware will accelerate seismic imaging by several orders of magnitude compared to conventional solutions running on standard Linux Clusters.

  13. Research on Influencing Factors and Generalized Power of Synthetic Artificial Seismic Wave

    NASA Astrophysics Data System (ADS)

    Jiang, Yanpei

    2018-05-01

    Start your abstract here… In this paper, according to the trigonometric series method, the author adopts different envelope functions and the acceleration design spectrum in Seismic Code For Urban Bridge Design to simulate the seismic acceleration time history which meets the engineering accuracy requirements by modifying and iterating the initial wave. Spectral analysis is carried out to find out the the distribution law of the changing frequencies of the energy of seismic time history and to determine the main factors that affect the acceleration amplitude spectrum and energy spectrum density. The generalized power formula of seismic time history is derived from the discrete energy integral formula and the author studied the changing characteristics of generalized power of the seismic time history under different envelop functions. Examples are analyzed to illustrate that generalized power can measure the seismic performance of bridges.

  14. The Nature of Spontaneity in High Quality Mathematics Learning Experiences

    ERIC Educational Resources Information Center

    Williams, Gaye

    2004-01-01

    Spontaneity has been linked to high quality learning experiences in mathematics (Csikszentmihalyi & Csikszentmihalyi, 1992; Williams, 2002).This paper shows how spontaneity can be identified by attending to the nature of social elements in the process of abstracting (Dreyfus, Hershkowitz, & Schwarz, 2001). This process is elaborated…

  15. New comprehensive standard seismic noise models and 3D seismic noise variation for Morocco territory, North Africa, obtained using seismic broadband stations

    NASA Astrophysics Data System (ADS)

    El Fellah, Younes; El-Aal, Abd El-Aziz Khairy Abd; Harnafi, Mimoun; Villaseñor, Antonio

    2017-05-01

    In the current work, we constructed new comprehensive standard seismic noise models and 3D temporal-spatial seismic noise level cubes for Morocco in north-west Africa to be used for seismological and engineering purposes. Indeed, the original global standard seismic noise models published by Peterson (1993) and their following updates by Astiz and Creager (1995), Ekström (2001) and Berger et al. (2003) had no contributing seismic stations deployed in North Africa. Consequently, this preliminary study was conducted to shed light on seismic noise levels specific to north-west Africa. For this purpose, 23 broadband seismic stations recently installed in different structural domains throughout Morocco are used to study the nature and characteristics of seismic noise and to create seismic noise models for Morocco. Continuous data recorded during 2009, 2010 and 2011 were processed and analysed to construct these new noise models and 3D noise levels from all stations. We compared the Peterson new high-noise model (NHNM) and low-noise model (NLNM) with the Moroccan high-noise model (MHNM) and low-noise model (MLNM). These new noise models are comparable to the United States Geological Survey (USGS) models in the short period band; however, in the period range 1.2 s to 1000 s for MLNM and 10 s to 1000 s for MHNM display significant variations. This variation is attributed to differences in the nature of seismic noise sources that dominate Morocco in these period bands. The results of this study have a new perception about permanent seismic noise models for this spectacular region and can be considered a significant contribution because it supplements the Peterson models and can also be used to site future permanent seismic stations in Morocco.

  16. High Resolution SAR Imaging Employing Geometric Features for Extracting Seismic Damage of Buildings

    NASA Astrophysics Data System (ADS)

    Cui, L. P.; Wang, X. P.; Dou, A. X.; Ding, X.

    2018-04-01

    Synthetic Aperture Radar (SAR) image is relatively easy to acquire but difficult for interpretation. This paper probes how to identify seismic damage of building using geometric features of SAR. The SAR imaging geometric features of buildings, such as the high intensity layover, bright line induced by double bounce backscattering and dark shadow is analysed, and show obvious differences texture features of homogeneity, similarity and entropy in combinatorial imaging geometric regions between the un-collapsed and collapsed buildings in airborne SAR images acquired in Yushu city damaged by 2010 Ms7.1 Yushu, Qinghai, China earthquake, which implicates a potential capability to discriminate collapsed and un-collapsed buildings from SAR image. Study also shows that the proportion of highlight (layover & bright line) area (HA) is related to the seismic damage degree, thus a SAR image damage index (SARDI), which related to the ratio of HA to the building occupation are of building in a street block (SA), is proposed. While HA is identified through feature extraction with high-pass and low-pass filtering of SAR image in frequency domain. A partial region with 58 natural street blocks in the Yushu City are selected as study area. Then according to the above method, HA is extracted, SARDI is then calculated and further classified into 3 classes. The results show effective through validation check with seismic damage classes interpreted artificially from post-earthquake airborne high resolution optical image, which shows total classification accuracy 89.3 %, Kappa coefficient 0.79 and identical to the practical seismic damage distribution. The results are also compared and discussed with the building damage identified from SAR image available by other authors.

  17. Diffraction Seismic Imaging of the Chalk Group Reservoir Rocks

    NASA Astrophysics Data System (ADS)

    Montazeri, M.; Fomel, S.; Nielsen, L.

    2016-12-01

    In this study we investigate seismic diffracted waves instead of seismic reflected waves, which are usually much stronger and carry most of the information regarding subsurface structures. The goal of this study is to improve imaging of small subsurface features such as faults and fractures. Moreover, we focus on the Chalk Group, which contains important groundwater resources onshore and oil and gas reservoirs in the Danish sector of the North Sea. Finding optimum seismic velocity models for the Chalk Group and estimating high-quality stacked sections with conventional processing methods are challenging tasks. Here, we try to filter out as much as possible of undesired arrivals before stacking the seismic data. Further, a plane-wave destruction method is applied on the seismic stack in order to dampen the reflection events and thereby enhance the visibility of the diffraction events. After this initial processing, we estimate the optimum migration velocity using diffraction events in order to obtain a better resolution stack. The results from this study demonstrate how diffraction imaging can be used as an additional tool for improving the images of small-scale features in the Chalk Group reservoir, in particular faults and fractures. Moreover, we discuss the potential of applying this approach in future studies focused on such reservoirs.

  18. Seismic-wave attenuation associated with crustal faults in the New Madrid seismic zone

    USGS Publications Warehouse

    Hamilton, R.M.; Mooney, W.D.

    1990-01-01

    The attenuation of upper crustal seismic waves that are refracted with a velocity of about 6 kilometers per second varies greatly among profiles in the area of the New Madrid seismic zone in the central Mississippi Valley. The waves that have the strongest attenuation pass through the seismic trend along the axis of the Reelfoot rift in the area of the Blytheville arch. Defocusing of the waves in a low-velocity zone and/ or seismic scattering and absorption could cause the attenuation; these effects are most likely associated with the highly deformed rocks along the arch. Consequently, strong seismic-wave attenuation may be a useful criterion for identifying seismogenic fault zones.

  19. Expected Seismicity and the Seismic Noise Environment of Europa

    NASA Astrophysics Data System (ADS)

    Panning, Mark P.; Stähler, Simon C.; Huang, Hsin-Hua; Vance, Steven D.; Kedar, Sharon; Tsai, Victor C.; Pike, William T.; Lorenz, Ralph D.

    2018-01-01

    Seismic data will be a vital geophysical constraint on internal structure of Europa if we land instruments on the surface. Quantifying expected seismic activity on Europa both in terms of large, recognizable signals and ambient background noise is important for understanding dynamics of the moon, as well as interpretation of potential future data. Seismic energy sources will likely include cracking in the ice shell and turbulent motion in the oceans. We define a range of models of seismic activity in Europa's ice shell by assuming each model follows a Gutenberg-Richter relationship with varying parameters. A range of cumulative seismic moment release between 1016 and 1018 Nm/yr is defined by scaling tidal dissipation energy to tectonic events on the Earth's moon. Random catalogs are generated and used to create synthetic continuous noise records through numerical wave propagation in thermodynamically self-consistent models of the interior structure of Europa. Spectral characteristics of the noise are calculated by determining probabilistic power spectral densities of the synthetic records. While the range of seismicity models predicts noise levels that vary by 80 dB, we show that most noise estimates are below the self-noise floor of high-frequency geophones but may be recorded by more sensitive instruments. The largest expected signals exceed background noise by ˜50 dB. Noise records may allow for constraints on interior structure through autocorrelation. Models of seismic noise generated by pressure variations at the base of the ice shell due to turbulent motions in the subsurface ocean may also generate observable seismic noise.

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  1. High-resolution seismic reflection survey at Dover AFB: A comparison of three seismic sources

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

    Cardimona, S.; Kadinsky-Cade, K.; Miller, R.

    1996-11-01

    In June of 1995, the Earth Sciences Division of the Air Force Phillips Lab, with survey equipment from the University of Delaware and assisted by the Kansas Geological Survey and Elohi Geophysics, conducted a geophysical site characterization of the SERDP-funded Groundwater Remediation Field Lab (GRFL) located at Dover AFB, Delaware and administered by Applied Research Associates for USAF Armstrong Lab. Seismic data were collected in order to (1) compare the results using three different compressional sources and (2) cover the field site well enough to characterize the seismic response of the shallow subsurface. This paper will focus primarily on themore » first of these two goals. Seismic data were collected along three north-south profiles set 10 meters apart, each profile with a different compressional source: a 5.5kg sledgehammer, a 12-gauge firing rod from Betsy Seisgun Inc. shooting 150 grain blanks, and a portable piezoelectrically driven vibrator, developed by Elohi Geophysics, operating with a 90Hz-450Hz sweep. An east-west cross line was collected using the sledgehammer source in order to tie the three profiles together. A laser theodolite provided station location and elevation control. The primary targets were the water table (that had been marked on maps at a depth of about 3 meters) and a sand-clay interface at about 15 meters depth. We collected 24-channel CMP data using a half meter spacing of both source and 100Hz geophones. Field C after initial walkaway noise testing with each source did not show any one source to be outstanding A practical early result of the seismic survey showed the water table to be at just over 10 meters. We have associated the strongest reflection event with the water-table interface. Seismic data comparison in this study is based on spectral content, total energy and signal-to-noise ratios, as well as a discussion of coherency of the primary reflection event at the water table.« less

  2. SISYPHUS: A high performance seismic inversion factory

    NASA Astrophysics Data System (ADS)

    Gokhberg, Alexey; Simutė, Saulė; Boehm, Christian; Fichtner, Andreas

    2016-04-01

    In the recent years the massively parallel high performance computers became the standard instruments for solving the forward and inverse problems in seismology. The respective software packages dedicated to forward and inverse waveform modelling specially designed for such computers (SPECFEM3D, SES3D) became mature and widely available. These packages achieve significant computational performance and provide researchers with an opportunity to solve problems of bigger size at higher resolution within a shorter time. However, a typical seismic inversion process contains various activities that are beyond the common solver functionality. They include management of information on seismic events and stations, 3D models, observed and synthetic seismograms, pre-processing of the observed signals, computation of misfits and adjoint sources, minimization of misfits, and process workflow management. These activities are time consuming, seldom sufficiently automated, and therefore represent a bottleneck that can substantially offset performance benefits provided by even the most powerful modern supercomputers. Furthermore, a typical system architecture of modern supercomputing platforms is oriented towards the maximum computational performance and provides limited standard facilities for automation of the supporting activities. We present a prototype solution that automates all aspects of the seismic inversion process and is tuned for the modern massively parallel high performance computing systems. We address several major aspects of the solution architecture, which include (1) design of an inversion state database for tracing all relevant aspects of the entire solution process, (2) design of an extensible workflow management framework, (3) integration with wave propagation solvers, (4) integration with optimization packages, (5) computation of misfits and adjoint sources, and (6) process monitoring. The inversion state database represents a hierarchical structure with

  3. High seismic velocity (7.x) lower crustal layers in cratonic North America: a view from xenoliths and EarthScope seismic data

    NASA Astrophysics Data System (ADS)

    Mahan, K. H.; Barnhart, K. R.; Schulte-Pelkum, V.; Blackburn, T.; Bowring, S. A.; Dudas, F. O.

    2010-12-01

    Continental crust worldwide has local areas with a lowermost layer characterized by unusually high seismic P velocities of over 7 km/s. The presence (or absence) of these high-velocity layers, as well as their thickness, composition and degree of heterogeneity, can have a profound influence on the rheological properties and behavior of the lower crust. These data also provide fundamental information about lithospheric growth and destruction processes. In North America, high-velocity layers have been inferred for portions of a significant number of seismic refraction lines, as well as from surface wave and receiver function studies. However, the 2-D and localized nature of most existing studies leave many open questions regarding the full spatial extent of these layers (e.g. correlations with Archean vs Proterozoic terranes, collisional or accretionary boundaries, rift zones or plume tracks, etc.). EarthScope’s USArray provides an exceptional opportunity to improve our knowledge of the distribution of 7.x layers in North America. Similarly, xenoliths provide a complimentary opportunity to investigate compositional, geochronological, and petrophysical characteristics of the lower crust in selected areas. In Montana and Wyoming, where seismic experiments reveal an anomalously thick (up to 25 km) 7.x layer, our studies emphasize the heterogeneity in modes of formation, physical properties, and age of the lower crust. We highlight an example from xenoliths exhumed by Eocene minettes from the Great Falls Tectonic Zone in central Montana. The suite includes mafic garnet granulites, mafic eclogite, and felsic granulites with peak pressures of 0.8-1.5+ GPa, consistent with derivation from depths of 28-55+ km. Multiple samples preserve evidence for prograde burial and some are polymetamorphic. One sample (likely a restite from melted supracrustal material) contains evidence for an early mid-crustal metamorphic event followed by an increase in pressure from <0.8 to >1.0 GPa

  4. The reporting quality of meta-analysis results of systematic review abstracts in periodontology and implant dentistry is suboptimal.

    PubMed

    Polychronopoulou, Argy

    2014-12-01

    Assessment of the quality of reporting in abstracts of systematic reviews with meta-analyses in periodontology and implant dentistry. Faggion CM Jr., Liu J, Huda F, Atieh M. J Periodontal Res 2014; 49(2):137-42. Argy Polychronopoulou, DDS, MS, ScM, ScD PURPOSE/QUESTION: What is the reporting quality of meta-analysis results of abstracts of systematic reviews in periodontology and implant dentistry journals? The authors received no funding for this study Meta-epidemiological study Level 3: Other evidence Not applicable. Copyright © 2014 Elsevier Inc. All rights reserved.

  5. 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.

  6. A Fiber-Optic Borehole Seismic Vector Sensor System for Geothermal Site Characterization and Monitoring

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

    Paulsson, Bjorn N.P.; Thornburg, Jon A.; He, Ruiqing

    2015-04-21

    shown that the system can record events at magnitudes much smaller than M-2.6 at frequencies up to 2,000 Hz. The sensors have also proved to be about 100 times more sensitive than the regular coil geophones that are used in borehole seismic systems today. The fiber optic seismic sensors have furthermore been qualified to operate at temperatures over 300°C (572°F). Simultaneously with the fiber optic based seismic 3C vector sensors we are using the lead-in fiber to acquire Distributed Acoustic Sensor (DAS) data from the surface to the bottom of the vector array. While the DAS data is of much lower quality than the vector sensor data it provides a 1 m spatial sampling of the downgoing wavefield which will be used to build the high resolution velocity model which is an essential component in high resolution imaging and monitoring.« less

  7. High Resolution Vertical Seismic Profile from the Chicxulub IODP/ICDP Expedition 364 Borehole: Wave Speeds and Seismic Reflectivity.

    NASA Astrophysics Data System (ADS)

    Nixon, C.; Kofman, R.; Schmitt, D. R.; Lofi, J.; Gulick, S. P. S.; Christeson, G. L.; Saustrup, S., Sr.; Morgan, J. V.

    2017-12-01

    We acquired a closely-spaced vertical seismic profile (VSP) in the Chicxulub K-Pg Impact Crater drilling program borehole to calibrate the existing surface seismic profiles and provide complementary measurements of in situ seismic wave speeds. Downhole seismic records were obtained at spacings ranging from 1.25 m to 5 m along the borehole from 47.5 m to 1325 mwsf (meters wireline below sea floor) (Fig 1a) using a Sercel SlimwaveTM geophone chain (University of Alberta). The seismic source was a 30/30ci Sercel Mini GI airgun (University of Texas), fired a minimum of 5 times per station. Seismic data processing used a combination of a commercial processing package (Schlumberger's VISTA) and MatlabTM codes. The VSP displays detailed reflectivity (Fig. 1a) with the strongest reflection seen at 600 mwsf (280 ms one-way time), geologically corresponding to the sharp contact between the post-impact sediments and the target peak ring rock, thus confirming the pre-drilling interpretations of the seismic profiles. A two-way time trace extracted from the separated up-going wavefield matches the major reflection both in travel time and character. In the granitic rocks that form the peak ring of the Chicxulub impact crater, we observe P-wave velocities of 4000-4500 m/s which are significantly less than the expected values of granitoids ( 6000 m/s) (Fig. 1b). The VSP measured wave speeds are confirmed against downhole sonic logging and in laboratory velocimetry measurements; these data provide additional evidence that the crustal material displaced by the impact experienced a significant amount of damage. Samples and data provided by IODP. Samples can be requested at http://web.iodp.tamu.edu/sdrm after 19 October 2017. Expedition 364 was jointly funded by ECORD, ICDP, and IODP with contributions and logistical support from the Yucatan State Government and UNAM. The downhole seismic chain and wireline system is funded by grants to DRS from the Canada Foundation for Innovation and

  8. BDS Precise Point Positioning for Seismic Displacements Monitoring: Benefit from the High-Rate Satellite Clock Corrections

    PubMed Central

    Geng, Tao; Su, Xing; Fang, Rongxin; Xie, Xin; Zhao, Qile; Liu, Jingnan

    2016-01-01

    In order to satisfy the requirement of high-rate high-precision applications, 1 Hz BeiDou Navigation Satellite System (BDS) satellite clock corrections are generated based on precise orbit products, and the quality of the generated clock products is assessed by comparing with those from the other analysis centers. The comparisons show that the root mean square (RMS) of clock errors of geostationary Earth orbits (GEO) is about 0.63 ns, whereas those of inclined geosynchronous orbits (IGSO) and medium Earth orbits (MEO) are about 0.2–0.3 ns and 0.1 ns, respectively. Then, the 1 Hz clock products are used for BDS precise point positioning (PPP) to retrieve seismic displacements of the 2015 Mw 7.8 Gorkha, Nepal, earthquake. The derived seismic displacements from BDS PPP are consistent with those from the Global Positioning System (GPS) PPP, with RMS of 0.29, 0.38, and 1.08 cm in east, north, and vertical components, respectively. In addition, the BDS PPP solutions with different clock intervals of 1 s, 5 s, 30 s, and 300 s are processed and compared with each other. The results demonstrate that PPP with 300 s clock intervals is the worst and that with 1 s clock interval is the best. For the scenario of 5 s clock intervals, the precision of PPP solutions is almost the same to 1 s results. Considering the time consumption of clock estimates, we suggest that 5 s clock interval is competent for high-rate BDS solutions. PMID:27999384

  9. BDS Precise Point Positioning for Seismic Displacements Monitoring: Benefit from the High-Rate Satellite Clock Corrections.

    PubMed

    Geng, Tao; Su, Xing; Fang, Rongxin; Xie, Xin; Zhao, Qile; Liu, Jingnan

    2016-12-20

    In order to satisfy the requirement of high-rate high-precision applications, 1 Hz BeiDou Navigation Satellite System (BDS) satellite clock corrections are generated based on precise orbit products, and the quality of the generated clock products is assessed by comparing with those from the other analysis centers. The comparisons show that the root mean square (RMS) of clock errors of geostationary Earth orbits (GEO) is about 0.63 ns, whereas those of inclined geosynchronous orbits (IGSO) and medium Earth orbits (MEO) are about 0.2-0.3 ns and 0.1 ns, respectively. Then, the 1 Hz clock products are used for BDS precise point positioning (PPP) to retrieve seismic displacements of the 2015 Mw 7.8 Gorkha, Nepal, earthquake. The derived seismic displacements from BDS PPP are consistent with those from the Global Positioning System (GPS) PPP, with RMS of 0.29, 0.38, and 1.08 cm in east, north, and vertical components, respectively. In addition, the BDS PPP solutions with different clock intervals of 1 s, 5 s, 30 s, and 300 s are processed and compared with each other. The results demonstrate that PPP with 300 s clock intervals is the worst and that with 1 s clock interval is the best. For the scenario of 5 s clock intervals, the precision of PPP solutions is almost the same to 1 s results. Considering the time consumption of clock estimates, we suggest that 5 s clock interval is competent for high-rate BDS solutions.

  10. Reevaluation of the Seismicity and seismic hazards of Northeastern Libya

    NASA Astrophysics Data System (ADS)

    Ben Suleman, abdunnur; Aousetta, Fawzi

    2014-05-01

    Libya, located at the northern margin of the African continent, underwent many episodes of orogenic activities. These episodes of orogenic activities affected and shaped the geological setting of the country. This study represents a detailed investigation that aims to focus on the seismicity and its implications on earthquake hazards of Northeastern Libya. At the end of year 2005 the Libyan National Seismological Network starts functioning with 15 stations. The Seismicity of the area under investigation was reevaluated using data recorded by the recently established network. The Al-Maraj earthquake occurred in May 22nd 2005was analyzed. This earthquake was located in a known seismically active area. This area was the sight of the well known 1963 earthquake that kills over 200 people. Earthquakes were plotted and resulting maps were interpreted and discussed. The level of seismic activity is higher in some areas, such as the city of Al-Maraj. The offshore areas north of Al-Maraj seem to have higher seismic activity. It is highly recommended that the recent earthquake activity is considered in the seismic hazard assessments for the northeastern part of Libya.

  11. Seismic Prediction While Drilling (SPWD): Seismic exploration ahead of the drill bit using phased array sources

    NASA Astrophysics Data System (ADS)

    Jaksch, Katrin; Giese, Rüdiger; Kopf, Matthias

    2010-05-01

    In the case of drilling for deep reservoirs previous exploration is indispensable. In recent years the focus shifted more on geological structures like small layers or hydrothermal fault systems. Beside 2D- or 3D-seismics from the surface and seismic measurements like Vertical Seismic Profile (VSP) or Seismic While Drilling (SWD) within a borehole these methods cannot always resolute this structures. The resolution is worsen the deeper and smaller the sought-after structures are. So, potential horizons like small layers in oil exploration or fault zones usable for geothermal energy production could be failed or not identified while drilling. The application of a device to explore the geology with a high resolution ahead of the drill bit in direction of drilling would be of high importance. Such a device would allow adjusting the drilling path according to the real geology and would minimize the risk of discovery and hence the costs for drilling. Within the project SPWD a device for seismic exploration ahead of the drill bit will be developed. This device should allow the seismic exploration to predict areas about 50 to 100 meters ahead of the drill bit with a resolution of one meter. At the GFZ a first prototype consisting of different units for seismic sources, receivers and data loggers has been designed and manufactured. As seismic sources four standard magnetostrictive actuators and as receivers four 3-component-geophones are used. Every unit, actuator or geophone, can be rotated in steps of 15° around the longitudinal axis of the prototype to test different measurement configurations. The SPWD prototype emits signal frequencies of about 500 up to 5000 Hz which are significant higher than in VSP and SWD. An increased radiation of seismic wave energy in the direction of the borehole axis allows the view in areas to be drilled. Therefore, every actuator must be controlled independently of each other regarding to amplitude and phase of the source signal to

  12. Highly Integrated Quality Assurance – An Empirical Case

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

    Drake Kirkham; Amy Powell; Lucas Rich

    2011-02-01

    Highly Integrated Quality Assurance – An Empirical Case Drake Kirkham1, Amy Powell2, Lucas Rich3 1Quality Manager, Radioisotope Power Systems (RPS) Program, Idaho National Laboratory, P.O. Box 1625 M/S 6122, Idaho Falls, ID 83415-6122 2Quality Engineer, RPS Program, Idaho National Laboratory 3Quality Engineer, RPS Program, Idaho National Laboratory Contact: Voice: (208) 533-7550 Email: Drake.Kirkham@inl.gov Abstract. The Radioisotope Power Systems Program of the Idaho National Laboratory makes an empirical case for a highly integrated Quality Assurance function pertaining to the preparation, assembly, testing, storage and transportation of 238Pu fueled radioisotope thermoelectric generators. Case data represents multiple campaigns including the Pluto/New Horizons mission,more » the Mars Science Laboratory mission in progress, and other related projects. Traditional Quality Assurance models would attempt to reduce cost by minimizing the role of dedicated Quality Assurance personnel in favor of either functional tasking or peer-based implementations. Highly integrated Quality Assurance adds value by placing trained quality inspectors on the production floor side-by-side with nuclear facility operators to enhance team dynamics, reduce inspection wait time, and provide for immediate, independent feedback. Value is also added by maintaining dedicated Quality Engineers to provide for rapid identification and resolution of corrective action, enhanced and expedited supply chain interfaces, improved bonded storage capabilities, and technical resources for requirements management including data package development and Certificates of Inspection. A broad examination of cost-benefit indicates highly integrated Quality Assurance can reduce cost through the mitigation of risk and reducing administrative burden thereby allowing engineers to be engineers, nuclear operators to be nuclear operators, and the cross-functional team to operate more efficiently. Applicability of this

  13. Adding seismic broadband analysis to characterize Andean backarc seismicity in Argentina

    NASA Astrophysics Data System (ADS)

    Alvarado, P.; Giuliano, A.; Beck, S.; Zandt, G.

    2007-05-01

    Characterization of the highly seismically active Andean backarc is crucial for assessment of earthquake hazards in western Argentina. Moderate-to-large crustal earthquakes have caused several deaths, damage and drastic economic consequences in Argentinean history. We have studied the Andean backarc crust between 30°S and 36°S using seismic broadband data available from a previous ("the CHARGE") IRIS-PASSCAL experiment. We collected more than 12 terabytes of continuous seismic data from 22 broadband instruments deployed across Chile and Argentina during 1.5 years. Using free software we modeled full regional broadband waveforms and obtained seismic moment tensor inversions of crustal earthquakes testing for the best focal depth for each event. We also mapped differences in the Andean backarc crustal structure and found a clear correlation with different types of crustal seismicity (i.e. focal depths, focal mechanisms, magnitudes and frequencies of occurrence) and previously mapped terrane boundaries. We now plan to use the same methodology to study other regions in Argentina using near-real time broadband data available from the national seismic (INPRES) network and global seismic networks operating in the region. We will re-design the national seismic network to optimize short-period and broadband seismic station coverage for different network purposes. This work is an international effort that involves researchers and students from universities and national government agencies with the goal of providing more information about earthquake hazards in western Argentina.

  14. Data Quality Control of the French Permanent Broadband Network in the RESIF Framework

    NASA Astrophysics Data System (ADS)

    Grunberg, Marc; Lambotte, Sophie; Engels, Fabien; Dretzen, Remi; Hernandez, Alain

    2014-05-01

    In the framework of the RESIF (Réseau Sismologique et géodésique Français) project, a new information system is being setting up, allowing the improvement of the management and the distribution of high quality data from the different elements of RESIF and the associated networks. Within this information system, EOST (in Strasbourg) is in charge of collecting real-time permanent broadband seismic waveform, and performing Quality Control on these data. The real-time and validated data set are pushed to the French National Distribution Center (Isterre/Grenoble) in order to make them publicly available. Furthermore EOST hosts the BCSF-ReNaSS, in charge of the French metropolitan seismic bulletin. This allows to benefit from some high-end quality control based on the national and world-wide seismicity. Here we present first the real-time seismic data flow from the stations of the French National Broad Band Network to EOST, and then, the data Quality Control procedures that were recently installed, including some new developments. The data Quality Control consists in applying a variety of subprocesses to check the consistency of the whole system and process from the stations to the data center. This allows us to verify that instruments and data transmission are operating correctly. Moreover analysis of the ambient noise helps to characterize intrinsic seismic quality of the stations and to identify other kind of disturbances. The deployed Quality Control consist in a pipeline that starts with low-level procedures : check the real-time miniseed data file (file naming convention, data integrity), check for inconsistencies between waveform and meta-data (channel name, sample rate, etc.), compute waveform statistics (data availability, gap/overlap, mean, rms, time quality, spike). It is followed by some high-level procedures such as : power spectral density computation (PSD), STA/LTA computation to be correlated to the seismicity, phases picking and stations magnitudes

  15. 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.

  16. Seismic Attenuation Structure and Intraplate Deformation

    NASA Astrophysics Data System (ADS)

    Bezada, M.; Kowalke, S.; Smale, J.

    2017-12-01

    It has been suggested that intraplate deformation and seismicity is localized at weak zones in the lithosphere and at rheological boundaries. Comparisons of intraplate deformation regions with mantle seismic velocity structure suggest a correlation, but are not universally accepted as compelling evidence. We present P-wave attenuation models built from records of teleseismic deep-focus earthquakes in three different regions that show significant correlation between attenuation structure and intraplate seismicity and deformation. In the eastern United States, the New Madrid, Wabash Valley, Eastern Tennessee, Central Virginia, and Carolina seismic zones all occur at or near the edges of high-Q (low attenuation) regions. In Spain, intraplate seismicity is absent from high-Q regions but relatively abundant in surrounding low-Q regions where intraplate orogeny is also observed. In Australia, where our model resolution is relatively poor owing to sparse and uneven station coverage, the Petermann and Alice Springs intraplate orogens occur near the edge of a high-Q feature roughly coinciding with the undeformed Amadeus basin. Our results suggest that lithospheric structure exerts important controls on the localization of intraplate deformation and seismicity and that seismic attenuation is a useful proxy for lithospheric strength.

  17. Very-long-period seismic signals - filling the gap between deformation and seismicity

    NASA Astrophysics Data System (ADS)

    Neuberg, Jurgen; Smith, Paddy

    2013-04-01

    Good broadband seismic sensors are capable to record seismic transients with dominant wavelengths of several tens or even hundreds of seconds. This allows us to generate a multi-component record of seismic volcanic events that are located in between the conventional high to low-frequency seismic spectrum and deformation signals. With a much higher temporal resolution and accuracy than e.g. GPS records, these signals fill the gap between seismicity and deformation studies. In this contribution we will review the non-trivial processing steps necessary to retrieve ground deformation from the original velocity seismogram and explore which role the resulting displacement signals have in the analysis of volcanic events. We use examples from Soufriere Hills volcano in Montserrat, West Indies, to discuss the benefits and shortcomings of such methods regarding new insights into volcanic processes.

  18. Lithospheric strucutre and relationship to seismicity beneath the Southeastern US using reciever functions

    NASA Astrophysics Data System (ADS)

    Cunningham, E.; Lekic, V.

    2017-12-01

    Despite being on a passive margin for millions of years, the Southeastern United States (SEUS) contains numerous seismogenic zones with the ability to produce damaging earthquakes. However, mechanisms controlling these intraplate earthquakes are poorly understood. Recently, Biryol et al. 2016 use P-wave tomography suggest that upper mantle structures beneath the SEUS correlate with areas of seismicity and seismic quiescence. Specifically, thick and fast velocity lithosphere beneath North Carolina is stable and indicative of areas of low seismicity. In contrast, thin and slow velocity lithosphere is weak, and the transition between the strong and weak lithosphere may be correlated with seismogenic zones found in the SEUS. (eg. Eastern Tennessee seismic zone and the Central Virginia seismic zone) Therefore, I systematically map the heterogeneity of the mantle lithosphere using converted seismic waves and quantify the spatial correlation between seismicity and lithospheric structure. The extensive network of seismometers that makes up the Earthscope USArray combined with the numerous seismic deployments in the Southeastern United States allows for unprecedented opportunity to map changes in lithospheric structure across seismogenic zones and seismic quiescent regions. To do so, I will use both P-to-s and S-to-p receiver functions (RFS). Since RFs are sensitive to seismic wavespeeds and density discontinuities with depth, they particularly useful for studying lithospheric structure. Ps receiver functions contain high frequency information allowing for high resolution, but can become contaminated by large sediment signals; therefore, I removed sediment multiples and correct for time delays of later phases using the method of Yu et. al 2015 which will allow us to see later arriving phases associated with lithospheric discontinuities. S-to-p receiver functions are not contaminated by shallow layers, making them ideal to study deep lithospheric structures but they can

  19. Challenges in Assessing Seismic Hazard in Intraplate Europe

    NASA Astrophysics Data System (ADS)

    Hintersberger, E.; Kuebler, S.; Landgraf, A.; Stein, S. A.

    2014-12-01

    Intraplate regions are often characterized by scattered, clustered and migrating seismicity and the occurrence of low-strain areas next to high-strain ones. Increasing evidence for large paleoearthquakes in such regions together with population growth and development of critical facilities, call for better assessments of earthquake hazards. Existing seismic hazard assessment for intraplate Europe is based on instrumental and historical seismicity of the past 1000 years, as well some active fault data. These observations face important limitations due to the quantity and quality of the available data bases. Even considering the long record of historical events in some populated areas of Europe, this time-span of thousand years likely fails to capture some faults' typical large-event recurrence intervals that are in the order of tens of thousands of years. Paleoseismology helps lengthen the observation window, but only produces point measurements, and preferentially in regions suspected to be seismically active. As a result, the expected maximum magnitudes of future earthquakes are quite uncertain, likely to be underestimated, and earthquakes are likely to occur in unexpected locations. These issues in particular arise in the heavily populated Rhine Graben and Vienna Basin areas, and in considering the hazard to critical facilities like nuclear power plants posed by low-probability events.

  20. Lithospheric Models of the Middle East to Improve Seismic Source Parameter Determination/Event Location Accuracy

    DTIC Science & Technology

    2012-09-01

    State Award Nos. DE-AC52-07NA27344/24.2.3.2 and DOS_SIAA-11-AVC/NMA-1 ABSTRACT The Middle East is a tectonically complex and seismically...active region. The ability to accurately locate earthquakes and other seismic events in this region is complicated by tectonics , the uneven...and seismic source parameters show that this activity comes from tectonic events. This work is informed by continuous or event-based regional

  1. Water Quality Instructional Resources Information System (IRIS): A Compilation of Abstracts to Water Quality and Water Resources Materials. Includes May 1979 edition and Supplements 1-15.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus, OH. Information Reference Center for Science, Mathematics, and Environmental Education.

    Compiled are abstracts and indexes to selected print and non-print materials related to wastewater treatment and water quality education and instruction, as well as materials related to pesticides, hazardous wastes, and public participation. Sources of abstracts/indexed materials include all levels of government, private concerns, and educational…

  2. One Decade of Induced Seismicity in Basel, Switzerland: A Consistent High-Resolution Catalog Obtained by Template Matching

    NASA Astrophysics Data System (ADS)

    Herrmann, M.; Kraft, T.; Tormann, T.; Scarabello, L.; Wiemer, S.

    2017-12-01

    Induced seismicity at the site of the Basel Enhanced Geothermal System (EGS) continuously decayed for six years after injection had been stopped in December 2006. Starting in May 2012, the Swiss Seismological Service was detecting a renewed increase of induced seismicity in the EGS reservoir to levels last seen in 2007 and reaching magnitudes up to ML2.0. Seismic monitoring at this EGS site is running for more than ten years now, but the details of the long-term behavior of its induced seismicity remained unexplored because a seismic event catalog that is consistent in detection sensitivity and magnitude estimation did not exist.We have created such a catalog by applying our matched filter detector to the 11-year-long seismic recordings of a borehole station at 2.7km depth. Based on 3'600 located earthquakes of the operator's borehole-network catalog, we selected about 2'500 reasonably dissimilar templates using waveform clustering. This large template set ensures an adequate coverage of the diversity of event waveforms which is due to the reservoir's highly complex fault system and the close observation distance. To cope with the increased computational demand of scanning 11-years of data with 2'500 templates, we parallelized our detector to run on a high-performance computer of the Swiss National Supercomputing Centre.We detect more than 200'000 events down to ML-2.5 during the six-day-long stimulation in December 2006 alone. Previously, only 13'000 detections found by an amplitude-threshold-based detector were known for this period. The high temporal and spatial resolution of this new catalog allows us to analyze the statistics of the induced Basel earthquakes in great detail. We resolve spatio-temporal variations of the seismicity parameters (a- and b-value) that have not been identified before and derive the first high-resolution temporal evolution of the seismic hazard for the Basel EGS reservoir.In summer 2017, our detector monitored the 10-week pressure

  3. Joint interpretation of seismic tomography and new magnetotelluric results provide evidence for support of high topography in the Southern Rocky Mountains and High Plains of eastern Colorado, USA

    NASA Astrophysics Data System (ADS)

    Feucht, D. W.; Sheehan, A. F.; Bedrosian, P.

    2015-12-01

    A recent magnetotelluric (MT) survey in central Colorado, USA, when interpreted alongside existing seismic tomography, reveals potential mechanisms of support for high topography both regionally and locally. Broadband and long period magnetotelluric data were collected at twenty-three sites along a 330 km E-W profile across the Southern Rocky Mountains and High Plains of central North America as part of the Deep RIFT Electrical Resistivity (DRIFTER) experiment. Remote-reference data processing yielded high quality MT data over a period range of 100 Hz to 10,000 seconds. A prominent feature of the regional geo-electric structure is the Denver Basin, which contains a thick package of highly conductive shales and porous sandstone aquifers. One-dimensional forward modeling was performed on stations within the Denver Basin to estimate depth to the base of this shallow conductor. Those estimates were then used to place a horizontal penalty cut in the model mesh of a regularized two-dimensional inversion. Two-dimensional modeling of the resistivity structure reveals two major anomalous regions in the lithosphere: 1) a high conductivity region in the crust under the tallest peaks of the Rocky Mountains and 2) a lateral step increase in lithospheric resistivity beneath the plains. The Rocky Mountain crustal anomaly coincides with low seismic wave speeds and enhanced heat flow and is thus interpreted as evidence of partial melt and/or high temperature fluids emplaced in the crust by tectonic activity along the Rio Grande Rift. The lateral variation in the mantle lithosphere, while co-located with a pronounced step increase in seismic velocity, appears to be a gradational boundary in resistivity across eastern Colorado and could indicate a small degree of compositional modification at the edge of the North American craton. These inferred conductivity mechanisms, namely crustal melt and modification of mantle lithosphere, likely contribute to high topography locally in the

  4. Advanced Seismic While Drilling System

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

    Robert Radtke; John Fontenot; David Glowka

    A breakthrough has been discovered for controlling seismic sources to generate selectable low frequencies. Conventional seismic sources, including sparkers, rotary mechanical, hydraulic, air guns, and explosives, by their very nature produce high-frequencies. This is counter to the need for long signal transmission through rock. The patent pending SeismicPULSER{trademark} methodology has been developed for controlling otherwise high-frequency seismic sources to generate selectable low-frequency peak spectra applicable to many seismic applications. Specifically, we have demonstrated the application of a low-frequency sparker source which can be incorporated into a drill bit for Drill Bit Seismic While Drilling (SWD). To create the methodology ofmore » a controllable low-frequency sparker seismic source, it was necessary to learn how to maximize sparker efficiencies to couple to, and transmit through, rock with the study of sparker designs and mechanisms for (a) coupling the sparker-generated gas bubble expansion and contraction to the rock, (b) the effects of fluid properties and dynamics, (c) linear and non-linear acoustics, and (d) imparted force directionality. After extensive seismic modeling, the design of high-efficiency sparkers, laboratory high frequency sparker testing, and field tests were performed at the University of Texas Devine seismic test site. The conclusion of the field test was that extremely high power levels would be required to have the range required for deep, 15,000+ ft, high-temperature, high-pressure (HTHP) wells. Thereafter, more modeling and laboratory testing led to the discovery of a method to control a sparker that could generate low frequencies required for deep wells. The low frequency sparker was successfully tested at the Department of Energy Rocky Mountain Oilfield Test Center (DOE RMOTC) field test site in Casper, Wyoming. An 8-in diameter by 26-ft long SeismicPULSER{trademark} drill string tool was designed and manufactured

  5. The Quality of Reporting of Abstracts in Physical Therapy Literature is Suboptimal: Cross-Sectional, Bibliographic Analysis.

    PubMed

    Richter, Randy R; Sebelski, Chris A; Austin, Tricia M

    2016-09-01

    The quality of abstract reporting in physical therapy literature is unknown. The purpose of this study was to provide baseline data for judging the future impact of the 2010 Consolidated Standards of Reporting Trials statement specifically referencing the 2008 Consolidated Standards of Reporting Trials statement for reporting of abstracts of randomized controlled trials across and between a broad sample and a core sample of physical therapy literature. A cross-sectional, bibliographic analysis was conducted. Abstracts of randomized controlled trials from 2009 were retrieved from PubMed, PEDro, and CENTRAL. Eligibility was determined using PEDro criteria. For outcomes measures, items from the Consolidated Standards of Reporting Trials statement for abstract reporting were used for assessment. Raters were not blinded to citation details. Using a computer-generated set of random numbers, 150 abstracts from 112 journals comprised the broad sample. A total of 53 abstracts comprised the core sample. Fourteen of 20 Consolidated Standards of Reporting Trials items for both samples were reported in less than 50% of the abstracts. Significantly more abstracts in the core sample reported (% difference core - broad; 95% confidence interval) title (28.4%; 12.9%-41.2%), blinding (15.2%; 1.6%-29.8%), setting (47.6%; 32.4%-59.4%), and confidence intervals (13.1%; 5.0%-25.1%). These findings provide baseline data for determining if continuing efforts to improve abstract reporting are heeded.

  6. The performance of the stations of the Romanian seismic network in monitoring the local seismic activity

    NASA Astrophysics Data System (ADS)

    Ardeleanu, Luminita Angela; Neagoe, Cristian

    2014-05-01

    The seismic survey of the territory of Romania is mainly performed by the national seismic network operated by the National Institute for Earth Physics of Bucharest. After successive developments and upgrades, the network consists at present of 123 permanent stations equipped with high quality digital instruments (Kinemetrics K2, Quantera Q330, Quantera Q330HR, PS6-24 and Basalt digitizers) - 102 real time and 20 off-line stations - which cover the whole territory of the country. All permanent stations are supplied with 3 component accelerometers (episenzor type), while the real time stations are in addition provided with broadband (CMG3ESP, CMG40T, KS2000, KS54000, KS2000, CMG3T, STS2) or short period (SH-1, S13, Mark l4c, Ranger, GS21, L22_VEL) velocity sensors. Several communication systems are currently used for the real time data transmission: an analog line in UHF band, a line through GPRS (General Packet Radio Service), a dedicated line through satellite, and a dedicated line provided by the Romanian Special Telecommunication Service. During the period January 1, 2006 - June 30, 2013, 5936 shallow depth seismic events - earthquakes and quarry blasts - with local magnitude ML ≥ 1.2 were localized on the Romanian territory, or in its immediate vicinity, using the records of the national seismic network; 1467 subcrustal earthquakes (depth ≥ 60 km) with magnitude ML ≥ 1.9 were also localized in the Vrancea region, at the bend of the Eastern Carpathians. The goal of the present study is to evaluate the individual contribution of the real time seismic stations to the monitoring of the local seismicity. The performance of each station is estimated by taking into consideration the fraction of events that are localised using the station records, compared to the total number of events of the catalogue, occurred during the time of station operation. Taking into account the nonuniform space distribution of earthquakes, the location of the site and the recovery

  7. A New Design of Seismic Stations Deployed in South Tyrol

    NASA Astrophysics Data System (ADS)

    Melichar, P.; Horn, N.

    2007-05-01

    When designing the seismic network in South Tyrol, the seismic service of Austria and the Civil defense in South Tyrol combined more that 10 years experience in running seismic networks and private communication systems. In recent years the high data return rate of > 99% and network uptime of > 99.% is achieved by the combination of high quality station design and equipment, and the use of the Antelope data acquisition and processing software which comes with suite of network monitoring & alerting tools including Nagios, etc. The new Data Center is located in city of Bolzano and is connected to the other Data Centers in Austria, Switzerland, and Italy for data back up purposes. Each Data Center uses also redundant communication system if the primary system fails. When designing the South Tyrol network, new improvements were made in seismometer installations, grounding, lighting protection and data communications in order to improve quality of data recorded as well as network up-time, and data return. The new 12 stations are equipped with 6 Channels Q330+PB14f connected to STS2 + EpiSensor sensor. One of the key achievements was made in the grounding concept for the whole seismic station - and aluminum boxes were introduced which delivered Faraday cage isolation. Lightning protection devices are used for the equipment inside the aluminum housing where seismometer and data logger are housed. For the seismometer cables a special shielding was introduced. The broadband seismometer and strong-motion sensor are placed on a thick glass plate and therefore isolated from the ground. The precise seismometer orientation was done by a special groove on the glass plate and in case of a strong earthquake; the seismometer is tide up to the base plate. Temperature stability was achieved by styrofoam sheets inside the seismometer aluminum protection box.

  8. Cloud Computing Services for Seismic Networks

    NASA Astrophysics Data System (ADS)

    Olson, Michael

    This thesis describes a compositional framework for developing situation awareness applications: applications that provide ongoing information about a user's changing environment. The thesis describes how the framework is used to develop a situation awareness application for earthquakes. The applications are implemented as Cloud computing services connected to sensors and actuators. The architecture and design of the Cloud services are described and measurements of performance metrics are provided. The thesis includes results of experiments on earthquake monitoring conducted over a year. The applications developed by the framework are (1) the CSN---the Community Seismic Network---which uses relatively low-cost sensors deployed by members of the community, and (2) SAF---the Situation Awareness Framework---which integrates data from multiple sources, including the CSN, CISN---the California Integrated Seismic Network, a network consisting of high-quality seismometers deployed carefully by professionals in the CISN organization and spread across Southern California---and prototypes of multi-sensor platforms that include carbon monoxide, methane, dust and radiation sensors.

  9. Assessment of the quality of reporting in abstracts of systematic reviews with meta-analyses in periodontology and implant dentistry.

    PubMed

    Faggion, C M; Liu, J; Huda, F; Atieh, M

    2014-04-01

    Proper scientific reporting is necessary to ensure the correct interpretation of study results by readers. The main objective of this study was to assess the quality of reporting in abstracts of systematic reviews (SRs) with meta-analyses in periodontology and implant dentistry. Differences in reporting of abstracts in Cochrane and paper-based reviews were also assessed. The PubMed electronic database and the Cochrane database for SRs were searched on November 11, 2012, independently and in duplicate, for SRs with meta-analyses related to interventions in periodontology and implant dentistry. Assessment of the quality of reporting was performed independently and in duplicate, taking into account items related to the effect direction, numerical estimates of effect size, measures of precision, probability and consistency. We initially screened 433 papers and included 146 (127 paper-based and 19 Cochrane reviews, respectively). The direction of evidence was reported in two-thirds of the abstracts while strength of evidence and measure of precision (i.e., confidence interval) were reported in less than half the selected abstracts. Measures of consistency such as I(2) statistics were reported in only 5% of the selected sample of abstracts. Cochrane abstracts reported the limitations of evidence and precision better than paper-based ones. Two items ("meta-analysis" in title and abstract, respectively), were nevertheless better reported in paper-based abstracts. Abstracts of SRs with meta-analyses in periodontology and implant dentistry currently have no uniform standard of reporting, which may hinder readers' understanding of study outcomes. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  10. 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

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

    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.

  11. Illuminating Asset Value through New Seismic Technology

    NASA Astrophysics Data System (ADS)

    Brandsberg-Dahl, S.

    2007-05-01

    evaluate technologies and subsequently encourage vendor activity to develop and deploy a commercial system. The 3D seismic method exploded into general usage in the 1990's. Our industry delivered 3D cheaper and faster, improving quality through improved acquisition specifications and new processing technology. The need to mitigate business risks in highly material subsalt plays led BP to explore the technical limits of the seismic method, testing novel acquisition techniques to improve illumination and signal to noise ratio. These were successful and are applicable to analogue seismic quality problems globally providing breakthroughs in illuminating previously hidden geology and hydrocarbon reservoirs. A focused business challenge, smart risk taking, investment in people and computing capability, partnerships, and rapid implementation are key themes that will be touched on through out the talk.

  12. Nitrogen Plasma Optimization for High-Quality Dilute Nitrides

    DTIC Science & Technology

    2005-02-01

    Available online 1 February 2005Abstract Growth of GaInNAs by molecular beam epitaxy (MBE) generally requires a nitrogen plasma, which complicates growth...InGaAs and InGaAsP lasers. This paper addresses several of the challenges of plasma-assisted molecular beam epitaxy (MBE) of high-quality dilute nitrides...A.L. Holmes, Using beam flux monitor as Langmuir probe for plasma-assisted molecular beam epitaxy , J. Vac. Sci. Technol. B, in press.

  13. Quality assurance of the gene ontology using abstraction networks.

    PubMed

    Ochs, Christopher; Perl, Yehoshua; Halper, Michael; Geller, James; Lomax, Jane

    2016-06-01

    The gene ontology (GO) is used extensively in the field of genomics. Like other large and complex ontologies, quality assurance (QA) efforts for GO's content can be laborious and time consuming. Abstraction networks (AbNs) are summarization networks that reveal and highlight high-level structural and hierarchical aggregation patterns in an ontology. They have been shown to successfully support QA work in the context of various ontologies. Two kinds of AbNs, called the area taxonomy and the partial-area taxonomy, are developed for GO hierarchies and derived specifically for the biological process (BP) hierarchy. Within this framework, several QA heuristics, based on the identification of groups of anomalous terms which exhibit certain taxonomy-defined characteristics, are introduced. Such groups are expected to have higher error rates when compared to other terms. Thus, by focusing QA efforts on anomalous terms one would expect to find relatively more erroneous content. By automatically identifying these potential problem areas within an ontology, time and effort will be saved during manual reviews of GO's content. BP is used as a testbed, with samples of three kinds of anomalous BP terms chosen for a taxonomy-based QA review. Additional heuristics for QA are demonstrated. From the results of this QA effort, it is observed that different kinds of inconsistencies in the modeling of GO can be exposed with the use of the proposed heuristics. For comparison, the results of QA work on a sample of terms chosen from GO's general population are presented.

  14. The Pollino Seismic Sequence: Activated Graben Structures in a Seismic Gap

    NASA Astrophysics Data System (ADS)

    Rößler, Dirk; Passarelli, Luigi; Govoni, Aladino; Bindi, Dino; Cesca, Simone; Hainzl, Sebatian; Maccaferri, Francesco; Rivalta, Eleonora; Woith, Heiko; Dahm, Torsten

    2015-04-01

    mapped for the area. Consistent with mapped faults, the seismicity interested both eastwards and westwards dipping normal faults that define the geometry of seismically active graben-like structures. At least one cluster shows an additional spatio-temporal migration with spreading hypocentres similar to other swarm areas with fluid-triggering mechanisms. The static Coulomb stress change transferred by the largest shock onto the swarm area and on the CF cannot explain the observed high seismicity rate. We study the evolution of the frequency-size distribution of the events and the seismicity rate changes. We find that the majority of the earthquakes cannot be justified as aftershocks (directly related to the tectonics or to earthquake-earthquake interaction) and are best explained by an additional forcing active over the entire sequence. Our findings are consistent with the action of fluids (e.g. pore-pressure diffusion) triggering seismicity on pre-loaded faults. Additional aseismic release of tectonic strain by transient, slow slip is also consistent with our analysis. Analysis of deformation time series may clarify this point in future studies.

  15. Assessment of the Vibrations Effects Caused by Technical Seismicity Due to the Railway traffic on High-sensitivity Machinery

    NASA Astrophysics Data System (ADS)

    Papán, Daniel; Valašková, Veronika; Demeterová, Katarína

    2016-10-01

    The numerical and experimental approach in structural dynamics problems is more and more current nowadays. This approach is applied and solved in many research and developing institutions of the all the world. Vibrations effect caused by passing trains used in manufacturing facilities can affect the quality of the production activity. This effect is possible to be solved by a numerical or an experimental way. Numerical solution is not so financially and time demanding. The main aim of this article is to focus on just experimental measurement of this problem. In this paper, the case study with measurement due to cramped conditions realized in situ is presented. The case study is located close to railway. The vibration effect caused by passing trains on the high-sensitivity machinery contained in this object were observed. The structure was a high-sensitivity machine that was placed in a construction process. For the measurements, the high-sensitivity standard vibrations equipment was used. The assessments of measurements’ results were performed for the technological conditions and Slovak Standard Criteria. Both of these assessments were divided to amplitude and frequency domain. The amplitude criterion is also divided to peak particle velocity and RMS (Root Mean Square). Frequency domain assessment were realised using the frequency response curves obtained from high-sensitivity machinery manufacturer. The frequency limits are established for each axis of triaxle system. The measurement results can be predicted if the vibration have to be reduced. Measurement implemented in the production hall should obtain materials to determine the seismic loading and response of production machinery caused by technical seismicity.

  16. Seismic Noise Analysis and Reduction through Utilization of Collocated Seismic and Atmospheric Sensors at the GRO Chile Seismic Network

    NASA Astrophysics Data System (ADS)

    Farrell, M. E.; Russo, R. M.

    2013-12-01

    gain insight into how local atmospheric conditions couple with the ground to generate seismic noise, and to explore strategies for reducing this noise post data collection. Comparison of spectra of atmospheric data streams to the three broadband seismic channels for continuous signals recorded during May and June of 2013 shows high coherence between infrasound signals and time variation of air pressure (dP/dt) that we calculated from the air pressure data stream. Coherence between these signals is greatest for the east-west component of the seismic data in northern Chile. Although coherence between seismic, infrasound, and dP/dt is lower for all three seismic channels at other GRO Chile stations, for some of the data streams coherence can jump as much as 6 fold for certain frequency bands, with a common 3-fold increase for periods shorter than 10 seconds and the occasional 6-fold increase at long or very long periods.

  17. High-Resolution Seismic-Reflection and Marine Magnetic Data Along the Hosgri Fault Zone, Central California

    USGS Publications Warehouse

    Sliter, Ray W.; Triezenberg, Peter J.; Hart, Patrick E.; Watt, Janet T.; Johnson, Samuel Y.; Scheirer, Daniel S.

    2009-01-01

    The U.S. Geological Survey (USGS) collected high-resolution shallow seismic-reflection and marine magnetic data in June 2008 in the offshore areas between the towns of Cayucos and Pismo Beach, Calif., from the nearshore (~6-m depth) to just west of the Hosgri Fault Zone (~200-m depth). These data are in support of the California State Waters Mapping Program and the Cooperative Research and Development Agreement (CRADA) between the Pacific Gas & Electric Co. and the U.S. Geological Survey. Seismic-reflection and marine magnetic data were acquired aboard the R/V Parke Snavely, using a SIG 2Mille minisparker seismic source and a Geometrics G882 cesium-vapor marine magnetometer. More than 550 km of seismic and marine magnetic data was collected simultaneously along shore-perpendicular transects spaced 800 m apart, with an additional 220 km of marine magnetometer data collected across the Hosgri Fault Zone, resulting in spacing locally as smallas 400 m. This report includes maps of the seismic-survey sections, linked to Google Earth software, and digital data files showing images of each transect in SEG-Y, JPEG, and TIFF formats, as well as preliminary gridded marine-magnetic-anomaly and residual-magnetic-anomaly (shallow magnetic source) maps.

  18. Natural Gas Hydrates Estimation Using Seismic Inversion and Rock Physics

    NASA Astrophysics Data System (ADS)

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

    2005-05-01

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

  19. Vertical Cable Seismic Survey for Hydrothermal Deposit

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  20. Open Source Tools for Seismicity Analysis

    NASA Astrophysics Data System (ADS)

    Powers, P.

    2010-12-01

    The spatio-temporal analysis of seismicity plays an important role in earthquake forecasting and is integral to research on earthquake interactions and triggering. For instance, the third version of the Uniform California Earthquake Rupture Forecast (UCERF), currently under development, will use Epidemic Type Aftershock Sequences (ETAS) as a model for earthquake triggering. UCERF will be a "living" model and therefore requires robust, tested, and well-documented ETAS algorithms to ensure transparency and reproducibility. Likewise, as earthquake aftershock sequences unfold, real-time access to high quality hypocenter data makes it possible to monitor the temporal variability of statistical properties such as the parameters of the Omori Law and the Gutenberg Richter b-value. Such statistical properties are valuable as they provide a measure of how much a particular sequence deviates from expected behavior and can be used when assigning probabilities of aftershock occurrence. To address these demands and provide public access to standard methods employed in statistical seismology, we present well-documented, open-source JavaScript and Java software libraries for the on- and off-line analysis of seismicity. The Javascript classes facilitate web-based asynchronous access to earthquake catalog data and provide a framework for in-browser display, analysis, and manipulation of catalog statistics; implementations of this framework will be made available on the USGS Earthquake Hazards website. The Java classes, in addition to providing tools for seismicity analysis, provide tools for modeling seismicity and generating synthetic catalogs. These tools are extensible and will be released as part of the open-source OpenSHA Commons library.

  1. Romanian Data Center: A modern way for seismic monitoring

    NASA Astrophysics Data System (ADS)

    Neagoe, Cristian; Marius Manea, Liviu; Ionescu, Constantin

    2014-05-01

    The main seismic survey of Romania is performed by the National Institute for Earth Physics (NIEP) which operates a real-time digital seismic network. The NIEP real-time network currently consists of 102 stations and two seismic arrays equipped with different high quality digitizers (Kinemetrics K2, Quanterra Q330, Quanterra Q330HR, PS6-26, Basalt), broadband and short period seismometers (CMG3ESP, CMG40T, KS2000, KS54000, KS2000, CMG3T,STS2, SH-1, S13, Mark l4c, Ranger, gs21, Mark l22) and acceleration sensors (Episensor Kinemetrics). The data are transmitted at the National Data Center (NDC) and Eforie Nord (EFOR) Seismic Observatory. EFOR is the back-up for the NDC and also a monitoring center for the Black Sea tsunami events. NIEP is a data acquisition node for the seismic network of Moldova (FDSN code MD) composed of five seismic stations. NIEP has installed in the northern part of Bulgaria eight seismic stations equipped with broadband sensors and Episensors and nine accelerometers (Episensors) installed in nine districts along the Danube River. All the data are acquired at NIEP for Early Warning System and for primary estimation of the earthquake parameters. The real-time acquisition (RT) and data exchange is done by Antelope software and Seedlink (from Seiscomp3). The real-time data communication is ensured by different types of transmission: GPRS, satellite, radio, Internet and a dedicated line provided by a governmental network. For data processing and analysis at the two data centers Antelope 5.2 TM is being used running on 3 workstations: one from a CentOS platform and two on MacOS. Also a Seiscomp3 server stands as back-up for Antelope 5.2 Both acquisition and analysis of seismic data systems produce information about local and global parameters of earthquakes. In addition, Antelope is used for manual processing (event association, calculation of magnitude, creating a database, sending seismic bulletins, calculation of PGA and PGV, etc.), generating

  2. On Strong Positive Frequency Dependencies of Quality Factors in Local-Earthquake Seismic Studies

    NASA Astrophysics Data System (ADS)

    Morozov, Igor B.; Jhajhria, Atul; Deng, Wubing

    2018-03-01

    Many observations of seismic waves from local earthquakes are interpreted in terms of the frequency-dependent quality factor Q( f ) = Q0 f^{η } , where η is often close to or exceeds one. However, such steep positive frequency dependencies of Q require careful analysis with regard to their physical consistency. In particular, the case of η = 1 corresponds to frequency-independent (elastic) amplitude decays with time and consequently requires no Q-type attenuation mechanisms. For η > 1, several problems with physical meanings of such Q-factors occur. First, contrary to the key premise of seismic attenuation, high-frequency parts of the wavefield are enhanced with increasing propagation times relative to the low-frequency ones. Second, such attenuation cannot be implemented by mechanical models of wave-propagating media. Third, with η > 1, the velocity dispersion associated with such Q(f) occurs over unrealistically short frequency range and has an unexpected oscillatory shape. Cases η = 1 and η > 1 are usually attributed to scattering; however, this scattering must exhibit fortuitous tuning into the observation frequency band, which appears unlikely. The reason for the above problems is that the inferred Q values are affected by the conventional single-station measurement procedure. Both parameters Q 0 and are apparent, i.e., dependent on the selected parameterization and inversion method, and they should not be directly attributed to the subsurface. For η ≈ 1, parameter Q 0 actually describes the frequency-independent amplitude decay in access of some assumed geometric spreading t -α , where α is usually taken equal one. The case η > 1 is not allowed physically and could serve as an indicator of problematic interpretations. Although the case 0 < η < 1 is possible, its parameters Q 0 and may also be biased by the measurement procedure. To avoid such difficulties of Q-based approaches, we recommend measuring and interpreting the amplitude-decay rates

  3. The Project Serapis: High Resolution Seismic Imagingof The Campi Flegrei Caldera Structure

    NASA Astrophysics Data System (ADS)

    Zollo, A.; Virieux, J.; Capuano, P.; Chiarabba, C.; de Franco, R.; Makris, J.; Michelini, A.; Musacchio, G.; Serapis Group

    expected NE-SW and SE-NW structural trends and it has been designed to get 2D/3D images of the crustal structure at a regional scale. A denser 2D network of 35 OBSs has been deployed in the bay of Pozzuoli aimed at detecting and modeling reflected/converted waves from 1 the possible shallow to deep discontinuities beneath the Campi Flegrei caldera. The main target of this particular receiver lay-out is the detailed imaging of the magma chamber top, expected at 4-5 km depth, according to temperature measurements in wells and sparse seismic observations. About 5000 shots have been performed dur- ing the SERAPIS experiment, at an average spatial spacing of 125 m, for a total ship travel path of 620 km. All of the seismic lines have been re-sampled at least twice, using a staggered configuration, which results in a smaller source spacing (less than 65m). In the gulf of Pozzuoli the source array had a geometry of a 5x5 km grid, slightly shifted south with respect to the OBS array. Seismic signals produced by air- guns have been well detected up to 50-60 km distance and the whole Campi Flegrei, Ischia and Procida on-land networks have recorded high quality seismograms pro- duced by the gridded source array in the bay of Pozzuoli. Due to the extended and very dense source and receiver arrays used for SERAPIS, this campaign can provide an innovative contribution to the accurate reconstruction of the Campi Flegrei caldera structure and to the definition of its feeding system at depth. *SERAPIS group: Auger Emmanuel, Bernard Marie-Lise, Bobbio Antonella, Bonagura Mariateresa, Cantore Luciana, Convertito Vincenzo, D'Auria Luca, De Matteis Raffaella, Emolo Anto- nio, Festa Gaetano, Gasparini Paolo, Giberti Grazia, Herrero Andre, Improta Luigi, Lancieri Maria Flora, Nielsen Stefan, Nisii Vincenzo, Russo Guido, Satriano Clau- dio, Simini Mariella, Vassallo Maurizio, Bruno Pier Paolo, Buonocunto Ciro, Capello Marco, Del Pezzo Edoardo, Galluzzo Danilo, Gaudiosi Germana, Giuliana Alessio

  4. NIED seismic moment tensor catalogue for regional earthquakes around Japan: quality test and application

    NASA Astrophysics Data System (ADS)

    Kubo, Atsuki; Fukuyama, Eiichi; Kawai, Hiroyuki; Nonomura, Ken'ichi

    2002-10-01

    We have examined the quality of the National Research Institute for Earth Science and Disaster Prevention (NIED) seismic moment tensor (MT) catalogue obtained using a regional broadband seismic network (FREESIA). First, we examined using synthetic waveforms the robustness of the solutions with regard to data noise as well as to errors in the velocity structure and focal location. Then, to estimate the reliability, robustness and validity of the catalogue, we compared it with the Harvard centroid moment tensor (CMT) catalogue as well as the Japan Meteorological Agency (JMA) focal mechanism catalogue. We found out that the NIED catalogue is consistent with Harvard and JMA catalogues within the uncertainty of 0.1 in moment magnitude, 10 km in depth, and 15° in direction of the stress axes. The NIED MT catalogue succeeded in reducing to 3.5 the lower limit of moment magnitude above which the moment tensor could be reliably estimated. Finally, we estimated the stress tensors in several different regions by using the NIED MT catalogue. This enables us to elucidate the stress/deformation field in and around the Japanese islands to understand the mode of deformation and applied stress. Moreover, we identified a region of abnormal stress in a swarm area from stress tensor estimates.

  5. Demonstration of improved seismic source inversion method of tele-seismic body wave

    NASA Astrophysics Data System (ADS)

    Yagi, Y.; Okuwaki, R.

    2017-12-01

    Seismic rupture inversion of tele-seismic body wave has been widely applied to studies of large earthquakes. In general, tele-seismic body wave contains information of overall rupture process of large earthquake, while the tele-seismic body wave is inappropriate for analyzing a detailed rupture process of M6 7 class earthquake. Recently, the quality and quantity of tele-seismic data and the inversion method has been greatly improved. Improved data and method enable us to study a detailed rupture process of M6 7 class earthquake even if we use only tele-seismic body wave. In this study, we demonstrate the ability of the improved data and method through analyses of the 2016 Rieti, Italy earthquake (Mw 6.2) and the 2016 Kumamoto, Japan earthquake (Mw 7.0) that have been well investigated by using the InSAR data set and the field observations. We assumed the rupture occurring on a single fault plane model inferred from the moment tensor solutions and the aftershock distribution. We constructed spatiotemporal discretized slip-rate functions with patches arranged as closely as possible. We performed inversions using several fault models and found that the spatiotemporal location of large slip-rate area was robust. In the 2016 Kumamoto, Japan earthquake, the slip-rate distribution shows that the rupture propagated to southwest during the first 5 s. At 5 s after the origin time, the main rupture started to propagate toward northeast. First episode and second episode correspond to rupture propagation along the Hinagu fault and the Futagawa fault, respectively. In the 2016 Rieti, Italy earthquake, the slip-rate distribution shows that the rupture propagated to up-dip direction during the first 2 s, and then rupture propagated toward northwest. From both analyses, we propose that the spatiotemporal slip-rate distribution estimated by improved inversion method of tele-seismic body wave has enough information to study a detailed rupture process of M6 7 class earthquake.

  6. Evaluation of the Seismic Hazard in Venezuela with a revised seismic catalog that seeks for harmonization along the country borders

    NASA Astrophysics Data System (ADS)

    Rendon, H.; Alvarado, L.; Paolini, M.; Olbrich, F.; González, J.; Ascanio, W.

    2013-05-01

    Probabilistic Seismic Hazard Assessment is a complex endeavor that relies on the quality of the information that comes from different sources: the seismic catalog, active faults parameters, strain rates, etc. Having this in mind, during the last several months, the FUNVISIS seismic hazard group has been working on a review and update of the local data base that form the basis for a reliable PSHA calculation. In particular, the seismic catalog, which provides the necessary information that allows the evaluation of the critical b-value, which controls how seismic occurrence distributes with magnitude, has received particular attention. The seismic catalog is the result of the effort of several generations of researchers along the years; therefore, the catalog necessarily suffers from the lack of consistency, homogeneity and completeness for all ranges of magnitude over any seismic study area. Merging the FUNVISIS instrumental catalog with the ones obtained from international agencies, we present the work that we have been doing to produce a consistent seismic catalog that covers Venezuela entirely, with seismic events starting from 1910 until 2012, and report the magnitude of completeness for the different periods. Also, we present preliminary results on the Seismic Hazard evaluation that takes into account such instrumental catalog, the historical catalog, updated known fault geometries and its correspondent parameters, and the new seismic sources that have been defined accordingly. Within the spirit of the Global Earthquake Model (GEM), all these efforts look for possible bridges with neighboring countries to establish consistent hazard maps across the borders.

  7. High-resolution diapycnal mixing map of the Alboran Sea thermocline from seismic reflection images

    NASA Astrophysics Data System (ADS)

    Mojica, Jhon F.; Sallarès, Valentí; Biescas, Berta

    2018-06-01

    The Alboran Sea is a dynamically active region where the salty and warm Mediterranean water first encounters the incoming milder and cooler Atlantic water. The interaction between these two water masses originates a set of sub-mesoscale structures and a complex sequence of processes that entail mixing close to the thermocline. Here we present a high-resolution map of the diapycnal diffusivity around the thermocline depth obtained using acoustic data recorded with a high-resolution multichannel seismic system. The map reveals a patchy thermocline, with spots of strong diapycnal mixing juxtaposed with areas of weaker mixing. The patch size is of a few kilometers in the horizontal scale and of 10-15 m in the vertical one. The comparison of the obtained maps with the original acoustic images shows that mixing tends to concentrate in areas where internal waves, which are ubiquitous in the surveyed area, become unstable and shear instabilities develop, enhancing energy transfer towards the turbulent regime. These results are also compared with others obtained using more conventional oceanographic probes. The values estimated based on the seismic data are within the ranges of values obtained from oceanographic data analysis, and they are also consistent with reference theoretical values. Overall, our results demonstrate that high-resolution seismic systems allow the remote quantification of mixing at the thermocline depth with unprecedented resolution.

  8. 1-D seismic velocity model and hypocenter relocation using double difference method around West Papua region

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

    Sabtaji, Agung, E-mail: sabtaji.agung@gmail.com, E-mail: agung.sabtaji@bmkg.go.id; Indonesia’s Agency for Meteorological, Climatological and Geophysics Region V, Jayapura 1572; Nugraha, Andri Dian, E-mail: nugraha@gf.itb.ac.id

    2015-04-24

    West Papua region has fairly high of seismicity activities due to tectonic setting and many inland faults. In addition, the region has a unique and complex tectonic conditions and this situation lead to high potency of seismic hazard in the region. The precise earthquake hypocenter location is very important, which could provide high quality of earthquake parameter information and the subsurface structure in this region to the society. We conducted 1-D P-wave velocity using earthquake data catalog from BMKG for April, 2009 up to March, 2014 around West Papua region. The obtained 1-D seismic velocity then was used as inputmore » for improving hypocenter location using double-difference method. The relocated hypocenter location shows fairly clearly the pattern of intraslab earthquake beneath New Guinea Trench (NGT). The relocated hypocenters related to the inland fault are also observed more focus in location around the fault.« less

  9. 4-D High-Resolution Seismic Reflection Monitoring of Miscible CO2 Injected into a Carbonate Reservoir

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

    Richard D. Miller; Abdelmoneam E. Raef; Alan P. Byrnes

    2005-09-01

    The objective of this research project is to acquire, process, and interpret multiple high-resolution 3-D compressional wave and 2-D, 2-C shear wave seismic data to observe changes in fluid characteristics in an oil field before, during, and after the miscible carbon dioxide (CO{sub 2}) flood that began around December 1, 2003, as part of the DOE-sponsored Class Revisit Project (DOE DE-AC26-00BC15124). Unique and key to this imaging activity is the high-resolution nature of the seismic data, minimal deployment design, and the temporal sampling throughout the flood. The 900-m-deep test reservoir is located in central Kansas oomoldic limestones of the Lansing-Kansasmore » City Group, deposited on a shallow marine shelf in Pennsylvanian time. After 18 months of seismic monitoring, one baseline and six monitor surveys clearly imaged changes that appear consistent with movement of CO{sub 2} as modeled with fluid simulators.« less

  10. Utilization of Screw Piles in High Seismicity Areas of Cold and Warm Permafrost

    DOT National Transportation Integrated Search

    2010-07-01

    This work was performed in support of the AUTC project Utilization of Screw Piles in : High Seismicity Areas of Cold and Warm Permafrost under the direction of PI Dr. Kenan : Hazirbaba. Surface wave testing was performed at 30 sites in the City...

  11. ASDF: An Adaptable Seismic Data Format with Full Provenance

    NASA Astrophysics Data System (ADS)

    Smith, J. A.; Krischer, L.; Tromp, J.; Lefebvre, M. P.

    2015-12-01

    In order for seismologists to maximize their knowledge of how the Earth works, they must extract the maximum amount of useful information from all recorded seismic data available for their research. This requires assimilating large sets of waveform data, keeping track of vast amounts of metadata, using validated standards for quality control, and automating the workflow in a careful and efficient manner. In addition, there is a growing gap between CPU/GPU speeds and disk access speeds that leads to an I/O bottleneck in seismic workflows. This is made even worse by existing seismic data formats that were not designed for performance and are limited to a few fixed headers for storing metadata.The Adaptable Seismic Data Format (ASDF) is a new data format for seismology that solves the problems with existing seismic data formats and integrates full provenance into the definition. ASDF is a self-describing format that features parallel I/O using the parallel HDF5 library. This makes it a great choice for use on HPC clusters. The format integrates the standards QuakeML for seismic sources and StationXML for receivers. ASDF is suitable for storing earthquake data sets, where all waveforms for a single earthquake are stored in a one file, ambient noise cross-correlations, and adjoint sources. The format comes with a user-friendly Python reader and writer that gives seismologists access to a full set of Python tools for seismology. There is also a faster C/Fortran library for integrating ASDF into performance-focused numerical wave solvers, such as SPECFEM3D_GLOBE. Finally, a GUI tool designed for visually exploring the format exists that provides a flexible interface for both research and educational applications. ASDF is a new seismic data format that offers seismologists high-performance parallel processing, organized and validated contents, and full provenance tracking for automated seismological workflows.

  12. The seismic project of the National Tsunami Hazard Mitigation Program

    USGS Publications Warehouse

    Oppenheimer, D.H.; Bittenbinder, A.N.; Bogaert, B.M.; Buland, R.P.; Dietz, L.D.; Hansen, R.A.; Malone, S.D.; McCreery, C.S.; Sokolowski, T.J.; Whitmore, P.M.; Weaver, C.S.

    2005-01-01

    In 1997, the Federal Emergency Management Agency (FEMA), National Oceanic and Atmospheric Administration (NOAA), U.S. Geological Survey (USGS), and the five western States of Alaska, California, Hawaii, Oregon, and Washington joined in a partnership called the National Tsunami Hazard Mitigation Program (NTHMP) to enhance the quality and quantity of seismic data provided to the NOAA tsunami warning centers in Alaska and Hawaii. The NTHMP funded a seismic project that now provides the warning centers with real-time seismic data over dedicated communication links and the Internet from regional seismic networks monitoring earthquakes in the five western states, the U.S. National Seismic Network in Colorado, and from domestic and global seismic stations operated by other agencies. The goal of the project is to reduce the time needed to issue a tsunami warning by providing the warning centers with high-dynamic range, broadband waveforms in near real time. An additional goal is to reduce the likelihood of issuing false tsunami warnings by rapidly providing to the warning centers parametric information on earthquakes that could indicate their tsunamigenic potential, such as hypocenters, magnitudes, moment tensors, and shake distribution maps. New or upgraded field instrumentation was installed over a 5-year period at 53 seismic stations in the five western states. Data from these instruments has been integrated into the seismic network utilizing Earthworm software. This network has significantly reduced the time needed to respond to teleseismic and regional earthquakes. Notably, the West Coast/Alaska Tsunami Warning Center responded to the 28 February 2001 Mw 6.8 Nisqually earthquake beneath Olympia, Washington within 2 minutes compared to an average response time of over 10 minutes for the previous 18 years. ?? Springer 2005.

  13. High seismic attenuation at a mid-ocean ridge reveals the distribution of deep melt.

    PubMed

    Eilon, Zachary C; Abers, Geoffrey A

    2017-05-01

    At most mid-ocean ridges, a wide region of decompression melting must be reconciled with a narrow neovolcanic zone and the establishment of full oceanic crustal thickness close to the rift axis. Two competing paradigms have been proposed to explain melt focusing: narrow mantle upwelling due to dynamic effects related to in situ melt or wide mantle upwelling with lateral melt transport in inclined channels. Measurements of seismic attenuation provide a tool for identifying and characterizing the presence of melt and thermal heterogeneity in the upper mantle. We use a unique data set of teleseismic body waves recorded on the Cascadia Initiative's Amphibious Array to simultaneously measure seismic attenuation and velocity across an entire oceanic microplate. We observe maximal differential attenuation and the largest delays ([Formula: see text] s and δ T S ~ 2 s) in a narrow zone <50 km from the Juan de Fuca and Gorda ridge axes, with values that are not consistent with laboratory estimates of temperature or water effects. The implied seismic quality factor ( Q s ≤ 25) is among the lowest observed worldwide. Models harnessing experimentally derived anelastic scaling relationships require a 150-km-deep subridge region containing up to 2% in situ melt. The low viscosity and low density associated with this deep, narrow melt column provide the conditions for dynamic mantle upwelling, explaining a suite of geophysical observations at ridges, including electrical conductivity and shear velocity anomalies.

  14. Midplate seismicity exterior to former rift-basins

    USGS Publications Warehouse

    Dewey, J.W.

    1988-01-01

    Midplate seismicity associated with some former rift-zones is distributed diffusely near, but exterior to, the rift basins. This "basin-exterior' seismicity cannot be attributed to reactivation of major basin-border faults on which uppercrustal extension was concentrated at the time of rifting, because the border faults dip beneath the basins. The seismicity may nonetheless represent reactivation of minor faults that were active at the time of rifting but that were located outside of the principal zones of upper-crustal extension; the occurrence of basin-exterior seismicity in some present-day rift-zones supports the existence of such minor basin-exterior faults. Other hypotheses for seismicity exterior to former rift-basins are that the seismicity reflects lobes of high stress due to lithospheric-bending that is centered on the axis of the rift, that the seismicity is localized on the exteriors of rift-basins by basin-interiors that are less deformable in the current epoch than the basin exteriors, and that seismicity is localized on the basin-exteriors by the concentration of tectonic stress in the highly elastic basin-exterior upper-crust. -from Author

  15. High-resolution seismic reflection profiling for mapping shallow aquifers in Lee County, Florida

    USGS Publications Warehouse

    Missimer, T.M.; Gardner, Richard Alfred

    1976-01-01

    High-resolution continuous seismic reflection profiling equipment was utilized to define the configuration of sedimentary layers underlying part of Lee County, Florida. About 45 miles (72 kilometers) of profile were made on the Caloosahatchee River Estuary and San Carlos Bay. Two different acoustic energy sources, a high resolution boomer and a 45-electrode high resolution sparker, both having a power input of 300 joules, were used to obtain both adequate penetration and good resolution. The seismic profiles show that much of the strata of middle Miocene to Holocene age apparently are extensively folded but not faulted. Initial interpretations indicate that: (1) the top of the Hawthorn Formation (which contains the upper Hawthorn aquifer) has much relief due chiefly to apparent folding; (2) the limestone, sandstone, and unconsolidated sand and phosphorite, which together compose the sandstone aquifer, appear to be discontinuous; (3) the green clay unit of the Tamiami Formation contains large scale angular beds dipping eastward; and (4) numerous deeply cut alluvium-filled paleochannels underlie the Caloosahatchee River. (Woodard-USGS)

  16. Physics based simulation of seismicity induced in the vicinity of a high-pressure fluid injection

    NASA Astrophysics Data System (ADS)

    McCloskey, J.; NicBhloscaidh, M.; Murphy, S.; O'Brien, G. S.; Bean, C. J.

    2013-12-01

    High-pressure fluid injection into subsurface is known, in some cases, to induce earthquakes in the surrounding volume. The increasing importance of ';fracking' as a potential source of hydrocarbons has made the seismic hazard from this effect an important issue the adjudication of planning applications and it is likely that poor understanding of the process will be used as justification of refusal of planning in Ireland and the UK. Here we attempt to understand some of the physical controls on the size and frequency of induced earthquakes using a physics-based simulation of the process and examine resulting earthquake catalogues The driver for seismicity in our simulations is identical to that used in the paper by Murphy et al. in this session. Fluid injection is simulated using pore fluid movement throughout a permeable layer from a high-pressure point source using a lattice Boltzmann scheme. Diffusivities and frictional parameters can be defined independently at individual nodes/cells allowing us to reproduce 3-D geological structures. Active faults in the model follow a fractal size distribution and exhibit characteristic event size, resulting in a power-law frequency-size distribution. The fluid injection is not hydraulically connected to the fault (i.e. fluid does not come into physical contact with the fault); however stress perturbations from the injection drive the seismicity model. The duration and pressure-time function of the fluid injection can be adjusted to model any given injection scenario and the rate of induced seismicity is controlled by the local structures and ambient stress field as well as by the stress perturbations resulting from the fluid injection. Results from the rate and state fault models of Murphy et al. are incorporated to include the effect of fault strengthening in seismically quite areas. Initial results show similarities with observed induced seismic catalogues. Seismicity is only induced where the active faults have not been

  17. Abstract analogical reasoning in high-functioning children with autism spectrum disorders.

    PubMed

    Green, Adam E; Kenworthy, Lauren; Mosner, Maya G; Gallagher, Natalie M; Fearon, Edward W; Balhana, Carlos D; Yerys, Benjamin E

    2014-12-01

    Children with autism spectrum disorders (ASD) exhibit a deficit in spontaneously recognizing abstract similarities that are crucial for generalizing learning to new situations. This may contribute to deficits in the development of appropriate schemas for navigating novel situations, including social interactions. Analogical reasoning is the central cognitive mechanism that enables typically developing children to understand abstract similarities between different situations. Intriguingly, studies of high-functioning children with ASD point to a relative cognitive strength in basic, nonabstract forms of analogical reasoning. If this analogical reasoning ability extends to abstract analogical reasoning (i.e., between superficially dissimilar situations), it may provide a bridge between a cognitive capability and core ASD deficits in areas such as generalization and categorization. This study tested whether preserved analogical reasoning abilities in ASD can be extended to abstract analogical reasoning, using photographs of real-world items and situations. Abstractness of the analogies was determined via a quantitative measure of semantic distance derived from latent semantic analysis. Children with ASD performed as well as typically developing children at identifying abstract analogical similarities when explicitly instructed to apply analogical reasoning. Individual differences in abstract analogical reasoning ability predicted individual differences in a measure of social function in the ASD group. Preliminary analyses indicated that children with ASD, but not typically developing children, showed an effect of age on abstract analogical reasoning. These results provide new evidence that children with ASD are capable of identifying abstract similarities through analogical reasoning, pointing to abstract analogical reasoning as a potential lever for improving generalization skills and social function in ASD. © 2014 International Society for Autism Research, Wiley

  18. Seismic reflection imaging of shallow oceanographic structures

    NASA Astrophysics Data System (ADS)

    Piété, Helen; Marié, Louis; Marsset, Bruno; Thomas, Yannick; Gutscher, Marc-André

    2013-05-01

    Multichannel seismic (MCS) reflection profiling can provide high lateral resolution images of deep ocean thermohaline fine structure. However, the shallowest layers of the water column (z < 150 m) have remained unexplored by this technique until recently. In order to explore the feasibility of shallow seismic oceanography (SO), we reprocessed and analyzed four multichannel seismic reflection sections featuring reflectors at depths between 10 and 150 m. The influence of the acquisition parameters was quantified. Seismic data processing dedicated to SO was also investigated. Conventional seismic acquisition systems were found to be ill-suited to the imaging of shallow oceanographic structures, because of a high antenna filter effect induced by large offsets and seismic trace lengths, and sources that typically cannot provide both a high level of emission and fine vertical resolution. We considered a test case, the imagery of the seasonal thermocline on the western Brittany continental shelf. New oceanographic data acquired in this area allowed simulation of the seismic acquisition. Sea trials of a specifically designed system were performed during the ASPEX survey, conducted in early summer 2012. The seismic device featured: (i) four seismic streamers, each consisting of six traces of 1.80 m; (ii) a 1000 J SIG sparker source, providing a 400 Hz signal with a level of emission of 205 dB re 1 μPa @ 1 m. This survey captured the 15 m thick, 30 m deep seasonal thermocline in unprecedented detail, showing images of vertical displacements most probably induced by internal waves.

  19. Abstracts of Research Papers 1970.

    ERIC Educational Resources Information Center

    Drowatzky, John N., Ed.

    This publication includes the abstracts of 199 research papers presented at the 1970 American Association for Health, Physical Education, and Recreation convention in Seattle, Washington. Abstracts from symposia on environmental quality education, obesity, motor development, research methods, and laboratory equipment are also included. Each…

  20. The underground seismic array of Gran Sasso (UNDERSEIS), central Italy

    NASA Astrophysics Data System (ADS)

    Scarpa, R.; Muscente, R.; Tronca, F.; Fischione, C.; Rotella, P.; Abril, M.; Alguacil, G.; Martini, M.; de Cesare, W.

    2003-04-01

    Since early May, 2002, a small aperture seismic array has been installed in the underground Physics Laboratories of Gran Sasso, located near seismic active faults of central Apennines, Italy. This array is presently composed by 21 three-component short period seismic stations (Mark L4C-3D), with average distance 90 m and semi-circular aperture of 400 m x 600 m. It is intersecting a main seismogenic fault where the presence of slow earthquakes has been recently detected through two wide band geodetic laser interferometers. The underground Laboratories are shielded by a limestone rock layer having 1400 m thickness. Each seismometer is linked, through a 24 bits A/D board, to a set of 6 industrial PC via a serial RS-485 standard. The six PC transmit data to a server through an ethernet network. Time syncronization is provided by a Master Oscillator controlled by an atomic clock. Earthworm package is used for data selection and transmission. High quality data have been recorded since May 2002, including local and regional earthquakes. In particular the 31 October, 2002, Molise (Mw=5.8 earthquake) and its aftershocks have been recorded at this array. Array techniques such as polarisation and frequency-slowness analyses with the MUSIC noise algorithm indicate the high performance of this array, as compared to the national seismic network, for identifying the basic source parameters for earthquakes located at distance of few hundreds of km.

  1. The Iquique 2014 sequence: understanding its nucleation and propagation from the seismicity evolution

    NASA Astrophysics Data System (ADS)

    Fuenzalida, A.; Rietbrock, A.; Woollam, J.; Tavera, H.; Ruiz, S.

    2017-12-01

    The Northern Chile and Southern Peru region is well known for its high seismic hazard due to the lack of recent major ruptures along long segments of the subduction interface. For this reason the 2014 Iquique Mw 8.1 earthquake that occurred in the Northern Chile seismic gap was expected and high quality seismic and geodetic networks were operating at the time of the event recording the precursory phase of a mega-thrust event with unprecedented detail. In this study we used seismic data collected during the 2014 Iquique sequence to generate a detailed earthquake catalogue. This catalogue consists of more than 15,000 events identified in Northern Chile during the period between 1/3/14 and 31/5/14 and provides full coverage of the immediate foreshock sequence, the main-shock and early after-shock series. The initial catalogue was obtained by automatic data processing and only selecting events with at least two associate S phases to improve the reliability of initial locations. Subsequently, this subset of events was automatically processed again using an optimized STA/LTA triggering algorithm for both P and S-waves and constraining the detection times by estimated arrival times at each station calculated for the preliminary locations. Finally, all events were relocated using a recently developed 1D velocity model and associated station corrections. For events Mw 4 or larger that occurred between the 15/3/14 and 10/04/14, we estimated it regional moment tensor by full-waveform inversion. Our results confirm the seismic activation of the upper plate during the foreshock sequence, as well highlight a crustal activity on the fore-arc during the aftershock series. The seismicity distribution was compared to the previous inter-seismic coupling studies obtained in the region, in which we observe interplay between high and low coupling areas, which are correlated to the seismicity rate. The spatial distribution of the seismicity and the complexities on the mechanisms observed

  2. Apollo 14 and 16 Active Seismic Experiments, and Apollo 17 Lunar Seismic Profiling

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Seismic refraction experiments were conducted on the moon by Apollo astronauts during missions 14, 16, and 17. Seismic velocities of 104, 108, 92, 114 and 100 m/sec were inferred for the lunar regolith at the Apollo 12, 14, 15, 16, and 17 landing sites, respectively. These data indicate that fragmentation and comminution caused by meteoroid impacts has produced a layer of remarkably uniform seismic properties moonwide. Brecciation and high porosity are the probable causes of the very low velocities observed in the lunar regolith. Apollo 17 seismic data revealed that the seismic velocity increases very rapidly with depth to 4.7 km/sec at a depth of 1.4 km. Such a large velocity change is suggestive of compositional and textural changes and is compatible with a model of fractured basaltic flows overlying anorthositic breccias. 'Thermal' moonquakes were also detected at the Apollo 17 site, becoming increasingly frequent after sunrise and reaching a maximum at sunset. The source of these quakes could possibly be landsliding.

  3. The theory and method of variable frequency directional seismic wave under the complex geologic conditions

    NASA Astrophysics Data System (ADS)

    Jiang, T.; Yue, Y.

    2017-12-01

    It is well known that the mono-frequency directional seismic wave technology can concentrate seismic waves into a beam. However, little work on the method and effect of variable frequency directional seismic wave under complex geological conditions have been done .We studied the variable frequency directional wave theory in several aspects. Firstly, we studied the relation between directional parameters and the direction of the main beam. Secondly, we analyzed the parameters that affect the beam width of main beam significantly, such as spacing of vibrator, wavelet dominant frequency, and number of vibrator. In addition, we will study different characteristics of variable frequency directional seismic wave in typical velocity models. In order to examine the propagation characteristics of directional seismic wave, we designed appropriate parameters according to the character of direction parameters, which is capable to enhance the energy of the main beam direction. Further study on directional seismic wave was discussed in the viewpoint of power spectral. The results indicate that the energy intensity of main beam direction increased 2 to 6 times for a multi-ore body velocity model. It showed us that the variable frequency directional seismic technology provided an effective way to strengthen the target signals under complex geological conditions. For concave interface model, we introduced complicated directional seismic technology which supports multiple main beams to obtain high quality data. Finally, we applied the 9-element variable frequency directional seismic wave technology to process the raw data acquired in a oil-shale exploration area. The results show that the depth of exploration increased 4 times with directional seismic wave method. Based on the above analysis, we draw the conclusion that the variable frequency directional seismic wave technology can improve the target signals of different geologic conditions and increase exploration depth with little

  4. Bayesian identification of multiple seismic change points and varying seismic rates caused by induced seismicity

    NASA Astrophysics Data System (ADS)

    Montoya-Noguera, Silvana; Wang, Yu

    2017-04-01

    The Central and Eastern United States (CEUS) has experienced an abnormal increase in seismic activity, which is believed to be related to anthropogenic activities. The U.S. Geological Survey has acknowledged this situation and developed the CEUS 2016 1 year seismic hazard model using the catalog of 2015 by assuming stationary seismicity in that period. However, due to the nonstationary nature of induced seismicity, it is essential to identify change points for accurate probabilistic seismic hazard analysis (PSHA). We present a Bayesian procedure to identify the most probable change points in seismicity and define their respective seismic rates. It uses prior distributions in agreement with conventional PSHA and updates them with recent data to identify seismicity changes. It can determine the change points in a regional scale and may incorporate different types of information in an objective manner. It is first successfully tested with simulated data, and then it is used to evaluate Oklahoma's regional seismicity.

  5. 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

  6. Streaks, multiplets, and holes: High-resolution spatio-temporal behavior of Parkfield seismicity

    USGS Publications Warehouse

    Waldhauser, F.; Ellsworth, W.L.; Schaff, D.P.; Cole, A.

    2004-01-01

    Double-difference locations of ???8000 earthquakes from 1969-2002 on the Parkfield section of the San Andreas Fault reveal detailed fault structures and seismicity that is, although complex, highly organized in both space and time. Distinctive features of the seismicity include: 1) multiple recurrence of earthquakes of the same size at precisely the same location on the fault (multiplets), implying frictional or geometric controls on their location and size; 2) sub-horizontal alignments of hypocenters along the fault plane (streaks), suggestive of rheological transitions within the fault zone and/or stress concentrations between locked and creeping areas; 3) regions devoid of microearthquakes with typical dimensions of 1-5 km (holes), one of which contains the M6 1966 Parkfield earthquake hypocenter. These features represent long lived structures that persist through many cycles of individual event. Copyright 2004 by the American Geophysical Union.

  7. MUSTANG: A Community-Facing Web Service to Improve Seismic Data Quality Awareness Through Metrics

    NASA Astrophysics Data System (ADS)

    Templeton, M. E.; Ahern, T. K.; Casey, R. E.; Sharer, G.; Weertman, B.; Ashmore, S.

    2014-12-01

    IRIS DMC is engaged in a new effort to provide broad and deep visibility into the quality of data and metadata found in its terabyte-scale geophysical data archive. Taking advantage of large and fast disk capacity, modern advances in open database technologies, and nimble provisioning of virtual machine resources, we are creating an openly accessible treasure trove of data measurements for scientists and the general public to utilize in providing new insights into the quality of this data. We have branded this statistical gathering system MUSTANG, and have constructed it as a component of the web services suite that IRIS DMC offers. MUSTANG measures over forty data metrics addressing issues with archive status, data statistics and continuity, signal anomalies, noise analysis, metadata checks, and station state of health. These metrics could potentially be used both by network operators to diagnose station problems and by data users to sort suitable data from unreliable or unusable data. Our poster details what MUSTANG is, how users can access it, what measurements they can find, and how MUSTANG fits into the IRIS DMC's data access ecosystem. Progress in data processing, approaches to data visualization, and case studies of MUSTANG's use for quality assurance will be presented. We want to illustrate what is possible with data quality assurance, the need for data quality assurance, and how the seismic community will benefit from this freely available analytics service.

  8. Learnings from the Monitoring of Induced Seismicity in Western Canada over the Past Three Years

    NASA Astrophysics Data System (ADS)

    Yenier, E.; Moores, A. O.; Baturan, D.; Spriggs, N.

    2017-12-01

    In response to induced seismicity observed in western Canada, existing public networks have been densified and a number of private networks have been deployed to closely monitor the earthquakes induced by hydraulic fracturing operations in the region. These networks have produced an unprecedented volume of seismic data, which can be used to map pre-existing geological structures and understand their activation mechanisms. Here, we present insights gained over the past three years from induced seismicity monitoring (ISM) for some of the most active operators in Canada. First, we discuss the benefits of high-quality ISM data sets for making operational decisions and how their value largely depends on choice of instrumentation, seismic network design and data processing techniques. Using examples from recent research studies, we illustrate the key role of robust modeling of regional source, attenuation and site attributes on the accuracy of event magnitudes, ground motion estimates and induced seismicity hazard assessment. Finally, acknowledging that the ultimate goal of ISM networks is assisting operators to manage induced seismic risk, we share some examples of how ISM data products can be integrated into existing protocols for developing effective risk management strategies.

  9. Effect of dewatering on seismic performance of multi-anchor wall due to high ground water level

    NASA Astrophysics Data System (ADS)

    Kobayashi, Makoto; Miura, Kinya; Konami, Takeharu; Hayashi, Taketo; Sato, Hiroki

    2017-10-01

    Previous research reported that the ground water in the backfill of reinforced soil wall made it deteriorate. According to the damage investigation of Great East Earthquake 2011, the reinforced soil structure due to high ground water level by seismic wave were deformed remarkably. Some of them classified ultimate limit state or restorability limit state. However, more than 90% of reinforced soil structure, which suffered from this earthquake, were classified into no damage condition. Therefore, it is necessary that the seismic behaviors of multi-anchor wall due to seepage flow should be clarified in order to adopt the performance-based design in such reinforced soil structure. In this study, a series of centrifugal shaking table tests were conducted to investigate the seismic behavior of multi-anchor wall due to high ground water level. The reinforced drainage pipes were installed into the backfill in order to verify the dewatering effect and additional reinforcement. Furthermore, to check only the dewatering effect, the model tests was carried out with several ground water table that was modeled the case reinforced drainage pipes installed. The test results show unique behavior of reinforced region that moved integrally. This implies that the reinforced region has been behaved as if it became one mass, and this behavior make this structure increase seismic performance. Thus, the effectiveness of dewatering was observed remarkably because of decreasing the inertial force during earthquake.

  10. Elasticity of ferropericlase and seismic heterogeneity in the Earth's lower mantle: Ferropericlase High Pressure-Temperature Elasticity

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

    Yang, Jing; Lin, Jung-Fu; Jacobsen, Steven D.

    2016-12-16

    Deciphering the origin of seismic heterogeneity has been one of the major challenges in understanding the geochemistry and geodynamics of the deep mantle. Fully anisotropic elastic properties of constituent minerals at relevant pressure-temperature conditions of the lower mantle can be used to calculate seismic heterogeneity parameters in order to better understand chemically and thermally induced seismic heterogeneities. In this study, the single-crystal elastic properties of ferropericlase (Mg0.94Fe0.06)O were measured using Brillouin spectroscopy and X-ray diffraction at conditions up to 50 GPa and 900 K. The velocity-density results were modeled using third-order finite-strain theory and thermoelastic equations along a representative geothermmore » to investigate high pressure-temperature and compositional effects on the seismic heterogeneity parameters. Our results demonstrate that from 660 to 2000 km, compressional wave anisotropy of ferropericlase increased from 4% to 9.7%, while shear wave anisotropy increased from 9% to as high as 22.5%. The thermally induced lateral heterogeneity ratio (RS/P = ∂lnVS/∂lnVP) of ferropericlase was calculated to be 1.48 at ambient pressure but decreased to 1.43 at 40 GPa along a representative geotherm. The RS/P of a simplified pyrolite model consisting of 80% bridgmanite and 20% ferropericlase was approximately 1.5, consistent with seismic models at depths from 670 to 1500 km, but showed an increased mismatch at lower mantle depths below ~1500 km. This discrepancy below mid-lower mantle could be due to either a contribution from chemically induced heterogeneity or the effects of the Fe spin transition in the deeper parts of the Earth's lower mantle.« less

  11. First approximations in avalanche model validations using seismic information

    NASA Astrophysics Data System (ADS)

    Roig Lafon, Pere; Suriñach, Emma; Bartelt, Perry; Pérez-Guillén, Cristina; Tapia, Mar; Sovilla, Betty

    2017-04-01

    Avalanche dynamics modelling is an essential tool for snow hazard management. Scenario based numerical modelling provides quantitative arguments for decision-making. The software tool RAMMS (WSL Institute for Snow and Avalanche Research SLF) is one such tool, often used by government authorities and geotechnical offices. As avalanche models improve, the quality of the numerical results will depend increasingly on user experience on the specification of input (e.g. release and entrainment volumes, secondary releases, snow temperature and quality). New model developments must continue to be validated using real phenomena data, for improving performance and reliability. The avalanches group form University of Barcelona (RISKNAT - UB), has studied the seismic signals generated from avalanches since 1994. Presently, the group manages the seismic installation at SLF's Vallée de la Sionne experimental site (VDLS). At VDLS the recorded seismic signals can be correlated to other avalanche measurement techniques, including both advanced remote sensing methods (radars, videogrammetry) and obstacle based sensors (pressure, capacitance, optical sender-reflector barriers). This comparison between different measurement techniques allows the group to address the question if seismic analysis can be used alone, on more additional avalanche tracks, to gain insight and validate numerical avalanche dynamics models in different terrain conditions. In this study, we aim to add the seismic data as an external record of the phenomena, able to validate RAMMS models. The seismic sensors are considerable easy and cheaper to install than other physical measuring tools, and are able to record data from the phenomena in every atmospheric conditions (e.g. bad weather, low light, freezing make photography, and other kind of sensors not usable). With seismic signals, we record the temporal evolution of the inner and denser parts of the avalanche. We are able to recognize the approximate position

  12. Seismic and Geodetic Monitoring of the Nicoya, Costa Rica, Seismic Gap

    NASA Astrophysics Data System (ADS)

    Protti, M.; Gonzalez, V.; Schwartz, S.; Dixon, T.; Kato, T.; Kaneda, Y.; Simila, G.; Sampson, D.

    2007-05-01

    The Nicoya segment of the Middle America Trench has been recognized as a mature seismic gap with potential to generate a large earthquake in the near future (it ruptured with large earthquakes in 1853, 1900 and 1950). Low level of background seismicity and fast crustal deformation of the forearc are indicatives of strong coupling along the plate interface. Given its high seismic potential, the available data and especially the fact that the Nicoya peninsula extends over large part of the rupture area, this gap was selected as one of the two sites for a MARGINS-SEIZE experiment. With the goal of documenting the evolution of loading and stress release along this seismic gap, an international effort involving several institutions from Costa Rica, the United States and Japan is being carried out for over a decade in the region. This effort involves the installation of temporary and permanent seismic and geodetic networks. The seismic network includes short period, broad band and strong motion instruments. The seismic monitoring has provided valuable information on the geometry and characteristics of the plate interface. The geodetic network includes temporary and permanent GPS stations as well as surface and borehole tiltmeters. The geodetic networks have helped quantify the extend and degree of coupling. A continuously recording, three- station GPS network on the Nicoya Peninsula, Costa Rica, recorded what we believe is the first slow slip event observed along the plate interface of the Costa Rica subduction zone. We will present results from these monitoring networks. Collaborative international efforts are focused on expanding these seismic and geodetic networks to provide improved resolution of future creep events, to enhanced understanding of the mechanical behavior of the Nicoya subduction segment of the Middle American Trench and possibly capture the next large earthquake and its potential precursor deformation.

  13. Seismic Structure of Perth Basin (Australia) and surroundings from Passive Seismic Deployments

    NASA Astrophysics Data System (ADS)

    Issa, N.; Saygin, E.; Lumley, D. E.; Hoskin, T. E.

    2016-12-01

    We image the subsurface structure of Perth Basin, Western Australia and surroundings by using ambient seismic noise data from 14 seismic stations recently deployed by University of Western Australia (UWA) and other available permanent stations from Geoscience Australia seismic network and the Australian Seismometers in Schools program. Each of these 14 UWA seismic stations comprises a broadband sensor and a high fidelity 3-component 10 Hz geophone, recording in tandem at 250 Hz and 1000 Hz. The other stations used in this study are equipped with short period and broadband sensors. In addition, one shallow borehole station is operated with eight 3 component geophones at depths of between 2 and 44 m. The network is deployed to characterize natural seismicity in the basin and to try and identify any microseismic activity across Darling Fault Zone (DFZ), bounding the basin to the east. The DFZ stretches to approximately 1000 km north-south in Western Australia, and is one of the longest fault zones on the earth with a limited number of detected earthquakes. We use seismic noise cross- and auto-correlation methods to map seismic velocity perturbations across the basin and the transition from DFZ to the basin. Retrieved Green's functions are stable and show clear dispersed waveforms. Travel times of the surface wave Green's functions from noise cross-correlations are inverted with a two-step probabilistic framework to map the absolute shear wave velocities as a function of depth. The single station auto-correlations from the seismic noise yields P wave reflectivity under each station, marking the major discontinuities. Resulting images show the shear velocity perturbations across the region. We also quantify the variation of ambient seismic noise at different depths in the near surface using the geophones in the shallow borehole array.

  14. Seismic evidence for multiple-stage exhumation of high/ultrahigh pressure metamorphic rocks in the eastern Dabie orogenic belt

    NASA Astrophysics Data System (ADS)

    Luo, Yinhe; Zhao, Kaifeng; Tang, Chi-Chia; Xu, Yixian

    2018-05-01

    The Dabie-Sulu orogenic belt in China contains one of the largest exposures of high and ultrahigh pressure (HP and UHP) metamorphic rocks in the world. The origin of HP/UHP metamorphic rocks and their exhumation to the surface in this belt have attracted great interest in the geologic community because the study of exhumation history of HP/UHP rocks helps to understand the process of continental-continental collision and the tectonic evolution of post-collision. However, the exhumation mechanism of the HP-UHP rocks to the surface is still contentious. In this study, by deploying 28 broadband seismic stations in the eastern Dabie orogenic belt and combining seismic data from 40 stations of the China National Seismic Network (CNSN), we image the high-resolution crustal isotropic shear velocity and radial anisotropy structure using ambient noise tomography. Our high-resolution 3D models provide new information about the exhumation mechanism of HP/UHP rocks and the origin of two dome structures.

  15. Output-only modal dynamic identification of frames by a refined FDD algorithm at seismic input and high damping

    NASA Astrophysics Data System (ADS)

    Pioldi, Fabio; Ferrari, Rosalba; Rizzi, Egidio

    2016-02-01

    The present paper deals with the seismic modal dynamic identification of frame structures by a refined Frequency Domain Decomposition (rFDD) algorithm, autonomously formulated and implemented within MATLAB. First, the output-only identification technique is outlined analytically and then employed to characterize all modal properties. Synthetic response signals generated prior to the dynamic identification are adopted as input channels, in view of assessing a necessary condition for the procedure's efficiency. Initially, the algorithm is verified on canonical input from random excitation. Then, modal identification has been attempted successfully at given seismic input, taken as base excitation, including both strong motion data and single and multiple input ground motions. Rather than different attempts investigating the role of seismic response signals in the Time Domain, this paper considers the identification analysis in the Frequency Domain. Results turn-out very much consistent with the target values, with quite limited errors in the modal estimates, including for the damping ratios, ranging from values in the order of 1% to 10%. Either seismic excitation and high values of damping, resulting critical also in case of well-spaced modes, shall not fulfill traditional FFD assumptions: this shows the consistency of the developed algorithm. Through original strategies and arrangements, the paper shows that a comprehensive rFDD modal dynamic identification of frames at seismic input is feasible, also at concomitant high damping.

  16. Seismic monitoring at Deception Island volcano (Antarctica): Recent advances

    NASA Astrophysics Data System (ADS)

    Carmona, E.; Almendros, J.; Martín, R.; Cortés, G.; Alguacil, G.; Moreno, J.; Martín, B.; Martos, A.; Serrano, I.; Stich, D.; Ibáñez, J. M.

    2012-04-01

    at Deception Island since 2008. In the current survey we collaborate with the Spanish Army to add another permanent station that will be able to send to the IAG-UGR seismic information about the activity of the volcano during the winter, using a communications satellite (SPAINSAT). These advances simplify the field work and the data acquisition procedures, and allow us to obtain high-quality seismic data in real-time. These improvements have a very important significance for a better and faster interpretation of the seismo-volcanic activity and assessment of the volcanic hazards at Deception Island volcano.

  17. When probabilistic seismic hazard climbs volcanoes: the Mt. Etna case, Italy - Part 1: Model components for sources parameterization

    NASA Astrophysics Data System (ADS)

    Azzaro, Raffaele; Barberi, Graziella; D'Amico, Salvatore; Pace, Bruno; Peruzza, Laura; Tuvè, Tiziana

    2017-11-01

    The volcanic region of Mt. Etna (Sicily, Italy) represents a perfect lab for testing innovative approaches to seismic hazard assessment. This is largely due to the long record of historical and recent observations of seismic and tectonic phenomena, the high quality of various geophysical monitoring and particularly the rapid geodynamics clearly demonstrate some seismotectonic processes. We present here the model components and the procedures adopted for defining seismic sources to be used in a new generation of probabilistic seismic hazard assessment (PSHA), the first results and maps of which are presented in a companion paper, Peruzza et al. (2017). The sources include, with increasing complexity, seismic zones, individual faults and gridded point sources that are obtained by integrating geological field data with long and short earthquake datasets (the historical macroseismic catalogue, which covers about 3 centuries, and a high-quality instrumental location database for the last decades). The analysis of the frequency-magnitude distribution identifies two main fault systems within the volcanic complex featuring different seismic rates that are controlled essentially by volcano-tectonic processes. We discuss the variability of the mean occurrence times of major earthquakes along the main Etnean faults by using an historical approach and a purely geologic method. We derive a magnitude-size scaling relationship specifically for this volcanic area, which has been implemented into a recently developed software tool - FiSH (Pace et al., 2016) - that we use to calculate the characteristic magnitudes and the related mean recurrence times expected for each fault. Results suggest that for the Mt. Etna area, the traditional assumptions of uniform and Poissonian seismicity can be relaxed; a time-dependent fault-based modeling, joined with a 3-D imaging of volcano-tectonic sources depicted by the recent instrumental seismicity, can therefore be implemented in PSHA maps

  18. High-resolution seismic reflection/refraction images near the outer margin of the Chesapeake Bay impact crater, York-James Peninsula, southeastern Virginia

    USGS Publications Warehouse

    Catchings, R.D.; Saulter, D.E.; Powars, D.S.; Goldman, M.R.; Dingler, J.A.; Gohn, G.S.; Schindler, J.S.; Johnson, G.H.

    2001-01-01

    Powars and Bruce (1999) showed that the Chesapeake Bay region of southeastern Virginia was the site of an asteroid or comet impact during the late Eocene, approximately 35 million years ago (Fig. 1). Initial borehole and marine seismic-reflection data revealed a 90-km-diameter impact structure, referred to as the Chesapeake Bay Impact Crater (CBIC), that lies buried beneath the southern Chesapeake Bay and surrounding Virginia Coastal Plain (Powars and Bruce, Figs. 1b). Stratigraphic correlations among a series of boreholes suggest that the impact disrupted basement rock and the overlying Cretaceous through middle Eocene deltaic and marine sediments. The CBIC truncates important regional sedimentary aquifer systems and possibly caused differential flushing of connate seawater. Therefore, the CBIC affects the present-day ground-water quantity and quality in the rapidly growing Hampton Roads region of southeastern Virginia. Impact-generated faults in the basement rock may be the sources of small-to-moderate earthquakes that have been occurred around the perimeter of the impact structure over the past few hundred years (Johnson et al., 1998). Powars and Bruce (1999) suggest that 150 m to 490 m of relatively undisturbed, post-impact Coastal-Plain sediments overlie the impact-disrupted sediments and basement rocks west of Chesapeake Bay. Their interpretation of marine seismic data, released from Texaco and Exxon, revealed a central 38-km-wide, 1.6-km-deep disrupted zone in the basement rocks (inner basin), which is surrounded by a 21- to 31-km-wide, 1- km-deep annular trough. Steep rim escarpments surround these features, which they mapped regionally as the outer and inner margins (rims) of the CBIC (Fig. 1b). The outer margin is a slumped terrace zone that has a 120- to 305-m-high gullied escarpment and varies in width from 0.8 to 3.2 km. However, the geographic bounds of the CBIC, its effects on the regional aquifer systems, and the distribution of impact generated

  19. Induced Seismicity from different sources in Italy: how to interpret it?

    NASA Astrophysics Data System (ADS)

    Pastori, M.; De Gori, P.; Piccinini, D.; Bagh, S.; Improta, L.; Chiarabba, C.

    2015-12-01

    Typically the term "induced seismicity" is used to refer minor earthquakes and tremors caused by human activities that alter the stresses and strains on the Earth's crust. In the last years, the interest in the induced seismicity related to fluids (oil and gas, and geothermal resources) extraction or injection is increased, because it is believed to be responsible to enucleate earthquakes. Possible sources of induced seismicity are not only represented by the oil and gas production but also, i.e., by changes in the water level of artificial lakes. The aim of this work is to show results from two different sources, wastewater injection and changes in the water level of an artificial reservoir (Pertusillo lake), that can produce induced earthquakes observed in the Val d'Agri basin (Italy) and to compare them with variation in crustal elastic parameters. Val d'Agri basin in the Apennines extensional belt hosts the largest oilfield in onshore Europe and is bordered by NW-SE ­trending fault systems. Most of the recorded seismicity seems to be related to these structures. We correlated the seismicity rate, injection curves and changes in water levels with temporal variations of Vp/Vs and anisotropic parameters of the crustal reservoirs and in the nearby area. We analysed about 983 high-quality recordings occurred from 2002 to 2014 in Val d'Agri basin from temporary and permanent network held by INGV and ENI corporate. 3D high-precision locations and manual-revised P- and S-picking are used to estimate anisotropic parameters (delay time and fast direction polarization) and Vp/Vs ratio. Seismicity is mainly located in two areas: in the SW of the Pertusillo Lake, and near the Eni Oil field (SW and NE of the Val d'Agri basin respectively). Our correlations well recognize the seismicity diffusion process, caused by both water injection and water level changes; these findings could help to model the active and pre-existing faults failure behaviour.

  20. National Earthquake Information Center Seismic Event Detections on Multiple Scales

    NASA Astrophysics Data System (ADS)

    Patton, J.; Yeck, W. L.; Benz, H.; Earle, P. S.; Soto-Cordero, L.; Johnson, C. E.

    2017-12-01

    The U.S. Geological Survey National Earthquake Information Center (NEIC) monitors seismicity on local, regional, and global scales using automatic picks from more than 2,000 near-real time seismic stations. This presents unique challenges in automated event detection due to the high variability in data quality, network geometries and density, and distance-dependent variability in observed seismic signals. To lower the overall detection threshold while minimizing false detection rates, NEIC has begun to test the incorporation of new detection and picking algorithms, including multiband (Lomax et al., 2012) and kurtosis (Baillard et al., 2014) pickers, and a new bayesian associator (Glass 3.0). The Glass 3.0 associator allows for simultaneous processing of variably scaled detection grids, each with a unique set of nucleation criteria (e.g., nucleation threshold, minimum associated picks, nucleation phases) to meet specific monitoring goals. We test the efficacy of these new tools on event detection in networks of various scales and geometries, compare our results with previous catalogs, and discuss lessons learned. For example, we find that on local and regional scales, rapid nucleation of small events may require event nucleation with both P and higher-amplitude secondary phases (e.g., S or Lg). We provide examples of the implementation of a scale-independent associator for an induced seismicity sequence (local-scale), a large aftershock sequence (regional-scale), and for monitoring global seismicity. Baillard, C., Crawford, W. C., Ballu, V., Hibert, C., & Mangeney, A. (2014). An automatic kurtosis-based P-and S-phase picker designed for local seismic networks. Bulletin of the Seismological Society of America, 104(1), 394-409. Lomax, A., Satriano, C., & Vassallo, M. (2012). Automatic picker developments and optimization: FilterPicker - a robust, broadband picker for real-time seismic monitoring and earthquake early-warning, Seism. Res. Lett. , 83, 531-540, doi: 10

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

    NASA Astrophysics Data System (ADS)

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

    2018-02-01

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

  2. The use of vertical seismic profiles in seismic investigations of the earth

    USGS Publications Warehouse

    Balch, Alfred H.; Lee, M.W.; Miller, J.J.; Ryder, Robert T.

    1982-01-01

    During the past 8 years, the U.S. Geological Survey has conducted an extensive investigation on the use of vertical seismic profiles (VSP) in a variety of seismic exploration applications. Seismic sources used were surface air guns, vibrators, explosives, marine air guns, and downhole air guns. Source offsets have ranged from 100 to 7800 ft. Well depths have been from 1200 to over 10,000 ft. We have found three specific ways in which VSPs can be applied to seismic exploration. First, seismic events observed at the surface of the ground can be traced, level by level, to their point of origin within the earth. Thus, one can tie a surface profile to a well log with an extraordinarily high degree of confidence. Second, one can establish the detectability of a target horizon, such as a porous zone. One can determine (either before or after surface profiling) whether or not a given horizon or layered sequence returns a detectable reflection to the surface. The amplitude and character of the reflection can also be observed. Third, acoustic properties of a stratigraphic sequence can be measured and sometimes correlated to important exploration parameters. For example, sometimes a relationship between apparent attenuation and sand percentage can be established. The technique shows additional promise of aiding surface exploration indirectly through studies of the evolution of the seismic pulse, studies of ghosts and multiples, and studies of seismic trace inversion techniques. Nearly all current seismic data‐processing techniques are adaptable to the processing of VSP data, such as normal moveout (NMO) corrections, stacking, single‐and multiple‐channel filtering, deconvolution, and wavelet shaping.

  3. Landslide seismic magnitude

    NASA Astrophysics Data System (ADS)

    Lin, C. H.; Jan, J. C.; Pu, H. C.; Tu, Y.; Chen, C. C.; Wu, Y. M.

    2015-11-01

    Landslides have become one of the most deadly natural disasters on earth, not only due to a significant increase in extreme climate change caused by global warming, but also rapid economic development in topographic relief areas. How to detect landslides using a real-time system has become an important question for reducing possible landslide impacts on human society. However, traditional detection of landslides, either through direct surveys in the field or remote sensing images obtained via aircraft or satellites, is highly time consuming. Here we analyze very long period seismic signals (20-50 s) generated by large landslides such as Typhoon Morakot, which passed though Taiwan in August 2009. In addition to successfully locating 109 large landslides, we define landslide seismic magnitude based on an empirical formula: Lm = log ⁡ (A) + 0.55 log ⁡ (Δ) + 2.44, where A is the maximum displacement (μm) recorded at one seismic station and Δ is its distance (km) from the landslide. We conclude that both the location and seismic magnitude of large landslides can be rapidly estimated from broadband seismic networks for both academic and applied purposes, similar to earthquake monitoring. We suggest a real-time algorithm be set up for routine monitoring of landslides in places where they pose a frequent threat.

  4. Seismic hazard in Hawaii: High rate of large earthquakes and probabilistics ground-motion maps

    USGS Publications Warehouse

    Klein, F.W.; Frankel, A.D.; Mueller, C.S.; Wesson, R.L.; Okubo, P.G.

    2001-01-01

    The seismic hazard and earthquake occurrence rates in Hawaii are locally as high as that near the most hazardous faults elsewhere in the United States. We have generated maps of peak ground acceleration (PGA) and spectral acceleration (SA) (at 0.2, 0.3 and 1.0 sec, 5% critical damping) at 2% and 10% exceedance probabilities in 50 years. The highest hazard is on the south side of Hawaii Island, as indicated by the MI 7.0, MS 7.2, and MI 7.9 earthquakes, which occurred there since 1868. Probabilistic values of horizontal PGA (2% in 50 years) on Hawaii's south coast exceed 1.75g. Because some large earthquake aftershock zones and the geometry of flank blocks slipping on subhorizontal decollement faults are known, we use a combination of spatially uniform sources in active flank blocks and smoothed seismicity in other areas to model seismicity. Rates of earthquakes are derived from magnitude distributions of the modem (1959-1997) catalog of the Hawaiian Volcano Observatory's seismic network supplemented by the historic (1868-1959) catalog. Modern magnitudes are ML measured on a Wood-Anderson seismograph or MS. Historic magnitudes may add ML measured on a Milne-Shaw or Bosch-Omori seismograph or MI derived from calibrated areas of MM intensities. Active flank areas, which by far account for the highest hazard, are characterized by distributions with b slopes of about 1.0 below M 5.0 and about 0.6 above M 5.0. The kinked distribution means that large earthquake rates would be grossly under-estimated by extrapolating small earthquake rates, and that longer catalogs are essential for estimating or verifying the rates of large earthquakes. Flank earthquakes thus follow a semicharacteristic model, which is a combination of background seismicity and an excess number of large earthquakes. Flank earthquakes are geometrically confined to rupture zones on the volcano flanks by barriers such as rift zones and the seaward edge of the volcano, which may be expressed by a magnitude

  5. Seismic Symphonies

    NASA Astrophysics Data System (ADS)

    Strinna, Elisa; Ferrari, Graziano

    2015-04-01

    The project started in 2008 as a sound installation, a collaboration between an artist, a barrel organ builder and a seismologist. The work differs from other attempts of sound transposition of seismic records. In this case seismic frequencies are not converted automatically into the "sound of the earthquake." However, it has been studied a musical translation system that, based on the organ tonal scale, generates a totally unexpected sequence of sounds which is intended to evoke the emotions aroused by the earthquake. The symphonies proposed in the project have somewhat peculiar origins: they in fact come to life from the translation of graphic tracks into a sound track. The graphic tracks in question are made up by copies of seismograms recorded during some earthquakes that have taken place around the world. Seismograms are translated into music by a sculpture-instrument, half a seismograph and half a barrel organ. The organ plays through holes practiced on paper. Adapting the documents to the instrument score, holes have been drilled on the waves' peaks. The organ covers about three tonal scales, starting from heavy and deep sounds it reaches up to high and jarring notes. The translation of the seismic records is based on a criterion that does match the highest sounds to larger amplitudes with lower ones to minors. Translating the seismogram in the organ score, the larger the amplitude of recorded waves, the more the seismogram covers the full tonal scale played by the barrel organ and the notes arouse an intense emotional response in the listener. Elisa Strinna's Seismic Symphonies installation becomes an unprecedented tool for emotional involvement, through which can be revived the memory of the greatest disasters of over a century of seismic history of the Earth. A bridge between art and science. Seismic Symphonies is also a symbolic inversion: the instrument of the organ is most commonly used in churches, and its sounds are derived from the heavens and

  6. Data Quality Parameters and Web Services Facilitate User Access to Research-Ready Seismic Data

    NASA Astrophysics Data System (ADS)

    Trabant, C. M.; Templeton, M. E.; Van Fossen, M.; Weertman, B.; Ahern, T. K.; Casey, R. E.; Keyson, L.; Sharer, G.

    2016-12-01

    IRIS Data Services has the mission of providing efficient access to a wide variety of seismic and related geoscience data to the user community. With our vast archive of freely available data, we recognize that there is a constant challenge to provide data to scientists and students that are of a consistently useful level of quality. To address this issue, we began by undertaking a comprehensive survey of the data and generating metrics measurements that provide estimates of data quality. These measurements can inform the scientist of the level of suitability of a given set of data for their scientific investigation. They also serve as a quality assurance check for network operators, who can act on this information to improve their current recording or mitigate issues with already recorded data and metadata. Following this effort, IRIS Data Services is moving forward to focus on providing tools for the scientist that make it easier to access data of a quality and characteristic that suits their investigation. Data that fulfill this criterion are termed "research-ready". In addition to filtering data by type, geographic location, proximity to events, and specific time ranges, we will offer the ability to filter data based on specific quality assessments. These include signal-to-noise ratio measurements, data continuity, timing quality, absence of channel cross-talk, and potentially many other factors. Our goal is to ensure that the user receives only the data that meets their specifications and will not require extensive review and culling after delivery. We will present the latest developments of the MUSTANG automated data quality system and introduce the Research-Ready Data Sets (RRDS) service. Together these two technologies serve as a data quality assurance ecosystem that will provide benefit to the scientific community by aiding efforts to readily find appropriate and suitable data for use in any number of objectives.

  7. Comparison of smoothing methods for the development of a smoothed seismicity model for Alaska and the implications for seismic hazard

    NASA Astrophysics Data System (ADS)

    Moschetti, M. P.; Mueller, C. S.; Boyd, O. S.; Petersen, M. D.

    2013-12-01

    In anticipation of the update of the Alaska seismic hazard maps (ASHMs) by the U. S. Geological Survey, we report progress on the comparison of smoothed seismicity models developed using fixed and adaptive smoothing algorithms, and investigate the sensitivity of seismic hazard to the models. While fault-based sources, such as those for great earthquakes in the Alaska-Aleutian subduction zone and for the ~10 shallow crustal faults within Alaska, dominate the seismic hazard estimates for locations near to the sources, smoothed seismicity rates make important contributions to seismic hazard away from fault-based sources and where knowledge of recurrence and magnitude is not sufficient for use in hazard studies. Recent developments in adaptive smoothing methods and statistical tests for evaluating and comparing rate models prompt us to investigate the appropriateness of adaptive smoothing for the ASHMs. We develop smoothed seismicity models for Alaska using fixed and adaptive smoothing methods and compare the resulting models by calculating and evaluating the joint likelihood test. We use the earthquake catalog, and associated completeness levels, developed for the 2007 ASHM to produce fixed-bandwidth-smoothed models with smoothing distances varying from 10 to 100 km and adaptively smoothed models. Adaptive smoothing follows the method of Helmstetter et al. and defines a unique smoothing distance for each earthquake epicenter from the distance to the nth nearest neighbor. The consequence of the adaptive smoothing methods is to reduce smoothing distances, causing locally increased seismicity rates, where seismicity rates are high and to increase smoothing distances where seismicity is sparse. We follow guidance from previous studies to optimize the neighbor number (n-value) by comparing model likelihood values, which estimate the likelihood that the observed earthquake epicenters from the recent catalog are derived from the smoothed rate models. We compare likelihood

  8. Comparison of smoothing methods for the development of a smoothed seismicity model for Alaska and the implications for seismic hazard

    USGS Publications Warehouse

    Moschetti, Morgan P.; Mueller, Charles S.; Boyd, Oliver S.; Petersen, Mark D.

    2014-01-01

    In anticipation of the update of the Alaska seismic hazard maps (ASHMs) by the U. S. Geological Survey, we report progress on the comparison of smoothed seismicity models developed using fixed and adaptive smoothing algorithms, and investigate the sensitivity of seismic hazard to the models. While fault-based sources, such as those for great earthquakes in the Alaska-Aleutian subduction zone and for the ~10 shallow crustal faults within Alaska, dominate the seismic hazard estimates for locations near to the sources, smoothed seismicity rates make important contributions to seismic hazard away from fault-based sources and where knowledge of recurrence and magnitude is not sufficient for use in hazard studies. Recent developments in adaptive smoothing methods and statistical tests for evaluating and comparing rate models prompt us to investigate the appropriateness of adaptive smoothing for the ASHMs. We develop smoothed seismicity models for Alaska using fixed and adaptive smoothing methods and compare the resulting models by calculating and evaluating the joint likelihood test. We use the earthquake catalog, and associated completeness levels, developed for the 2007 ASHM to produce fixed-bandwidth-smoothed models with smoothing distances varying from 10 to 100 km and adaptively smoothed models. Adaptive smoothing follows the method of Helmstetter et al. and defines a unique smoothing distance for each earthquake epicenter from the distance to the nth nearest neighbor. The consequence of the adaptive smoothing methods is to reduce smoothing distances, causing locally increased seismicity rates, where seismicity rates are high and to increase smoothing distances where seismicity is sparse. We follow guidance from previous studies to optimize the neighbor number (n-value) by comparing model likelihood values, which estimate the likelihood that the observed earthquake epicenters from the recent catalog are derived from the smoothed rate models. We compare likelihood

  9. Seismic Imager Space Telescope

    NASA Technical Reports Server (NTRS)

    Sidick, Erkin; Coste, Keith; Cunningham, J.; Sievers,Michael W.; Agnes, Gregory S.; Polanco, Otto R.; Green, Joseph J.; Cameron, Bruce A.; Redding, David C.; Avouac, Jean Philippe; hide

    2012-01-01

    capabilities, to improved management of earthquake risk, and to improved public safety policies. The position of the spacecraft, its high optical quality, large field of view, and large field of regard will make it an ideal platform for other scientific studies. The same data could be simply reused for other studies. If different data, such as multi-spectral data, is required, additional instruments could share the telescope.

  10. High resolution seismic stratigraphy and Mass Transport Deposits of the proximal continental margin, offshore Quarteira, South Portugal: Preliminary Results.

    NASA Astrophysics Data System (ADS)

    Duarte, Débora; Santos, Joana; Terrinha, Pedro; Brito, Pedro; Noiva, João; Ribeiro, Carlos; Roque, Cristina

    2017-04-01

    More than 300 nautical miles of multichannel seismic reflection data were acquired in the scope of the ASTARTE project (Assessment Strategy and Risk Reduction for Tsunamis in Europe), off Quarteira, Algarve, South Portugal. The main goal of this very high resolution multichannel seismic survey was to obtain high-resolution images of the sedimentary record to try to discern the existence of high energy events, possibly tsunami backwash deposits associated with large magnitude earthquakes generated at the Africa-Eurasia plate boundary This seismic dataset was processed at the Instituto Português do Mar e da Atmosfera (IPMA), with the SeisSpace PROMAX Seismic Processing software. A tailor-made processing flow was applied, focusing in the removal of the seafloor multiple and in the enhancement of the superficial layers. A sparker source, using with 300 J of energy and a fire rate of 0,5 s was used onboard Xunauta, an 18 m long vessel. The preliminary seismostratigraphic interpretation of the Algarve ASTARTE seismic dataset allowed the identification of a complex sequence seismic units of progradational and agradational bodies as well as Mass Transported Deposits (MTD). The MTD package of sediments has a very complex internal structure, 20m of thickness, is apparently spatially controlled by an escarpment probably associated to past sea level low stands. The MTD covers across an area, approximately parallel to an ancient coastline, with >30 km (length) x 5 km (across). Acknowledgements: This work was developed as part of the project ASTARTE (603839 FP7) supported by the grant agreement No 603839 of the European Union's Seventh. The Instituto Portugues do Mar e da Atmosfera acknowledges support by Landmark Graphics (SeisWorks) via the Landmark University Grant Program.

  11. Seismic Structural Setting of Western Farallon Basin, Southern Gulf of California, Mexico.

    NASA Astrophysics Data System (ADS)

    Pinero-Lajas, D.; Gonzalez-Fernandez, A.; Lopez-Martinez, M.; Lonsdale, P.

    2007-05-01

    Data from a number of high resolution 2D multichannel seismic (MCS) lines were used to investigate the structure and stratigraphy of the western Farallon basin in the southern Gulf of California. A Generator-Injector air gun provided a clean seismic source shooting each 12 s at a velocity of 6 kts. Each signal was recorded during 6- 8 s, at a sampling interval of 1 ms, by a 600 m long digital streamer with 48 channels and a spacing of 12.5 m. The MCS system was installed aboard CICESE's (Centro de Investigacion Cientifica y de Educacion Superior de Ensenada) 28 m research vessel Francisco de Ulloa. MCS data were conventionally processed, to obtain post- stack time-migrated seismic sections. The MCS seismic sections show a very detailed image of the sub-bottom structure up to 2-3 s two-way travel time (aprox. 2 km). We present detailed images of faulting based on the high resolution and quality of these data. Our results show distributed faulting with many active and inactive faults. Our study also constrains the depth to basement near the southern Baja California eastern coast. The acoustic basement appears as a continuous feature in the western part of the study area and can be correlated with some granite outcrops located in the southern Gulf of California islands. To the East, near the center of the Farallon basin, the acoustic basement changes, it is more discontinuous, and the seismic sections show a number of diffracted waves.

  12. Very-high-resolution seismic and magnetic investigations of a chemical munition dumpsite in the Baltic Sea

    NASA Astrophysics Data System (ADS)

    Missiaen, Tine; Feller, Pascal

    2008-09-01

    Very-high-resolution (VHR) seismic and magnetic investigations were carried out over a chemical munition dumpsite in the Bornholm Basin, south-western Baltic Sea. The main goal of the investigations was to image the shallow internal structure of the dumpsite and to map the lateral and vertical distribution of the dumped war material. The shallow geology was imaged in great detail on the seismic data. Seven seismic-stratigraphic units were identified, related to different stages in the Holocene and late-glacial history. A large number of diapir-like features were observed that most likely represent fluid expulsion phenomena. Four shipwrecks were identified in the dumpsite area. The wrecks have partly sunk into the soft upper sediments, their height above the sea floor reaching no more than 2 m. Seismic and magnetic data indicate the presence of a large number of buried objects. In most cases there is a good correlation between the seismic and magnetic data sets. The objects are generally buried no deeper than 1 to 2 m. Their size varies between 1.5 and 5 m, occasionally up to 10 m. Shallow pits in the sea bed are likely due to the impact of dumping. The data confirm the wide variety of dumped war material ranging from bombs and shells to encasements and containers. The distribution of the buried objects seems rather heterogeneous, with locally high object concentrations surrounded by areas of lower object density. The results of this case study demonstrate the benefit of complementary, concurrent geophysical investigations for munition dumpsite research. Finally this will yield a better assessment of the current status of the dumpsite and the possible ecological risks related to the dumped war material.

  13. 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.

  14. Romanian Educational Seismic Network Project

    NASA Astrophysics Data System (ADS)

    Tataru, Dragos; Ionescu, Constantin; Zaharia, Bogdan; Grecu, Bogdan; Tibu, Speranta; Popa, Mihaela; Borleanu, Felix; Toma, Dragos; Brisan, Nicoleta; Georgescu, Emil-Sever; Dobre, Daniela; Dragomir, Claudiu-Sorin

    2013-04-01

    Romania is one of the most active seismic countries in Europe, with more than 500 earthquakes occurring every year. The seismic hazard of Romania is relatively high and thus understanding the earthquake phenomena and their effects at the earth surface represents an important step toward the education of population in earthquake affected regions of the country and aims to raise the awareness about the earthquake risk and possible mitigation actions. In this direction, the first national educational project in the field of seismology has recently started in Romania: the ROmanian EDUcational SEISmic NETwork (ROEDUSEIS-NET) project. It involves four partners: the National Institute for Earth Physics as coordinator, the National Institute for Research and Development in Construction, Urban Planning and Sustainable Spatial Development " URBAN - INCERC" Bucharest, the Babeş-Bolyai University (Faculty of Environmental Sciences and Engineering) and the software firm "BETA Software". The project has many educational, scientific and social goals. The main educational objectives are: training students and teachers in the analysis and interpretation of seismological data, preparing of several comprehensive educational materials, designing and testing didactic activities using informatics and web-oriented tools. The scientific objective is to introduce into schools the use of advanced instruments and experimental methods that are usually restricted to research laboratories, with the main product being the creation of an earthquake waveform archive. Thus a large amount of such data will be used by students and teachers for educational purposes. For the social objectives, the project represents an effective instrument for informing and creating an awareness of the seismic risk, for experimentation into the efficacy of scientific communication, and for an increase in the direct involvement of schools and the general public. A network of nine seismic stations with SEP seismometers

  15. Seismic assessment of Technical Area V (TA-V).

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

    Medrano, Carlos S.

    The Technical Area V (TA-V) Seismic Assessment Report was commissioned as part of Sandia National Laboratories (SNL) Self Assessment Requirement per DOE O 414.1, Quality Assurance, for seismic impact on existing facilities at Technical Area-V (TA-V). SNL TA-V facilities are located on an existing Uniform Building Code (UBC) Seismic Zone IIB Site within the physical boundary of the Kirtland Air Force Base (KAFB). The document delineates a summary of the existing facilities with their safety-significant structure, system and components, identifies DOE Guidance, conceptual framework, past assessments and the present Geological and Seismic conditions. Building upon the past information and themore » evolution of the new seismic design criteria, the document discusses the potential impact of the new standards and provides recommendations based upon the current International Building Code (IBC) per DOE O 420.1B, Facility Safety and DOE G 420.1-2, Guide for the Mitigation of Natural Phenomena Hazards for DOE Nuclear Facilities and Non-Nuclear Facilities.« less

  16. Weighted stacking of seismic AVO data using hybrid AB semblance and local similarity

    NASA Astrophysics Data System (ADS)

    Deng, Pan; Chen, Yangkang; Zhang, Yu; Zhou, Hua-Wei

    2016-04-01

    The common-midpoint (CMP) stacking technique plays an important role in enhancing the signal-to-noise ratio (SNR) in seismic data processing and imaging. Weighted stacking is often used to improve the performance of conventional equal-weight stacking in further attenuating random noise and handling the amplitude variations in real seismic data. In this study, we propose to use a hybrid framework of combining AB semblance and a local-similarity-weighted stacking scheme. The objective is to achieve an optimal stacking of the CMP gathers with class II amplitude-variation-with-offset (AVO) polarity-reversal anomaly. The selection of high-quality near-offset reference trace is another innovation of this work because of its better preservation of useful energy. Applications to synthetic and field seismic data demonstrate a great improvement using our method to capture the true locations of weak reflections, distinguish thin-bed tuning artifacts, and effectively attenuate random noise.

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

    NASA Astrophysics Data System (ADS)

    Yu, H.; Gu, H.

    2017-12-01

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

  18. Modernization of the Caltech/USGS Southern California Seismic Network

    NASA Astrophysics Data System (ADS)

    Bhadha, R.; Devora, A.; Hauksson, E.; Johnson, D.; Thomas, V.; Watkins, M.; Yip, R.; Yu, E.; Given, D.; Cone, G.; Koesterer, C.

    2009-12-01

    performance and metadata availability. We will improve existing software to facilitate the update of metadata, and to improve the interoperability between SeisNetWatch and our database of metadata. The improved software will also be made available to other regional networks as part of the CISN software distribution. These upgrades, will greatly improve the robustness of the SCSN, and facilitate higher quality and more reliable earthquake monitoring than was available before in southern California. The modernized SCSN will contribute to more coordinated search and rescue as well as economic resilience following a major earthquake by providing accurate earthquake information, and thus facilitate rapid deployment of field crews and rapid business resumption. Further, advances in seismological research will be facilitated by the high quality seismic data that will be collected in one of the most seismically active areas in the contiguous US.

  19. Peru Subduction Zone Seismic Experiment (PeruSZE): Preliminary Results From a Seismic Network Between Mollendo and Lake Titicaca, Peru.

    NASA Astrophysics Data System (ADS)

    Guy, R.; Stubailo, I.; Skinner, S.; Phillips, K.; Foote, E.; Lukac, M.; Aguilar, V.; Tavera, H.; Audin, L.; Husker, A.; Clayton, R.; Davis, P. M.

    2008-12-01

    This work describes preliminary results from a 50 station broadband seismic network recently installed from the coast to the high Andes in Peru. UCLA's Center for Embedded Network Sensing (CENS) and Caltech's Tectonic Observatory are collaborating with the IRD (French L'Institut de Recherche pour le Developpement) and the Institute of Geophysics, in Lima Peru in a broadband seismic experiment that will study the transition from steep to shallow slab subduction. The currently installed line has stations located above the steep subduction zone at a spacing of about 6 km. In 2009 we plan to install a line of 50 stations north from this line along the crest of the Andes, crossing the transition from steep to shallow subduction. A further line from the end of that line back to the coast, completing a U shaped array, is in the planning phase. The network is wirelessly linked using multi-hop network software designed by computer scientists in CENS in which data is transmitted from station to station, and collected at Internet drops, from where it is transmitted over the Internet to CENS each night. The instrument installation in Peru is almost finished and we have been receiving data daily from 10 stations (out of total 50) since June 2008. The rest are recording on-site while the RF network is being completed. The software system provides dynamic link quality based routing, reliable data delivery, and a disruption tolerant shell interface for managing the system from UCLA without the need to travel to Peru. The near real-time data delivery also allows immediate detection of any problems at the sites. We are building a seismic data and GPS quality control toolset that would greatly minimize the station's downtime by alerting the users of any possible problems.

  20. High resolution seismic imaging of faults beneath Limón Bay, northern Panama Canal, Republic of Panama

    USGS Publications Warehouse

    Pratt, Thomas L.; Holmes, Mark; Schweig, Eugene S.; Gomberg, Joan S.; Cowan, Hugh A.

    2003-01-01

    High-resolution seismic reflection profiles from Limo??n Bay, Republic of Panama, were acquired as part of a seismic hazard investigation of the northern Panama Canal region. The seismic profiles image gently west and northwest dipping strata of upper Miocene Gatu??n Formation, unconformably overlain by a thin (<20 m) sequence of Holocene muds. Numerous faults, which have northeast trends where they can be correlated between seismic profiles, break the upper Miocene strata. Some of the faults have normal displacement, but on many faults, the amount and type of displacement cannot be determined. The age of displacement is constrained to be Late Miocene or younger, and regional geologic considerations suggest Pliocene movement. The faults may be part of a more extensive set of north- to northeast-trending faults and fractures in the canal region of central Panama. Low topography and the faults in the canal area may be the result of the modern regional stress field, bending of the Isthmus of Panama, shearing in eastern Panama, or minor deformation of the Panama Block above the Caribbean subduction zone. For seismic hazard analysis of the northern canal area, these faults led us to include a source zone of shallow faults proximal to northern canal facilities. ?? 2003 Elsevier B.V. All rights reserved.

  1. Seismic imaging of the oil and geothermal reservoirs using the induced seismicity

    NASA Astrophysics Data System (ADS)

    Zhang, H.; Toksoz, M. N.; Fehler, M.

    2011-12-01

    It is known that microseismicity can be induced in the oil field due to the stress change caused by oil/gas production. Similarly, injection of high-pressure fluids into the reservoir can also induce microseismicity. Due to the proximity of induced seismicity to the reservoir, in some cases, it may be advantageous to use induced seismicity to image the reservoir. The seismic stations for monitoring the induced seismicity are usually sparse. Conventional travel time tomography using travel times from seismic events to stations may not be applicable because of poor ray coverage outside the source region. In comparison, the double-difference tomography method of Zhang and Thurber (2003) that uses the differential travel times is able to image the reservoir by avoiding determining the velocity structure outside the source region. In this study, we present two case studies of applying double-difference tomography to induced seismicity monitored by borehole stations. In the case of an oil field in Oman, five closely spaced monitoring wells are used to monitor microseismicity induced by gas production. In each well, multiple seismic sensors are positioned from depths 750 m - 1250 m and about 2000 events are selected for tomography. Reservoir imaging shows encouraging results in identifying structures and velocity changes within reservoir layers. Clear velocity contrast was seen across the major northeast-southwest faults. Low Vp, low Vs and low Vp/Vs anomalies are mainly associated with the gas production layer. For the case of the Soultz Enhanced Geothermal System at Soultz-sous-Forets, France, we used travel time data from the September and October 1993 hydraulic stimulations, where only four borehole stations are available. The results showed that the S-wave velocity structure correlated well with seismicity and showed low velocity zones at depths between 2900 and 3300 meters, where fluid was believed to have infiltrated the reservoir. We also attempt time

  2. Martian seismicity

    NASA Technical Reports Server (NTRS)

    Phillips, Roger J.; Grimm, Robert E.

    1991-01-01

    The design and ultimate success of network seismology experiments on Mars depends on the present level of Martian seismicity. Volcanic and tectonic landforms observed from imaging experiments show that Mars must have been a seismically active planet in the past and there is no reason to discount the notion that Mars is seismically active today but at a lower level of activity. Models are explored for present day Mars seismicity. Depending on the sensitivity and geometry of a seismic network and the attenuation and scattering properties of the interior, it appears that a reasonable number of Martian seismic events would be detected over the period of a decade. The thermoelastic cooling mechanism as estimated is surely a lower bound, and a more refined estimate would take into account specifically the regional cooling of Tharsis and lead to a higher frequency of seismic events.

  3. Ischia Island: Historical Seismicity and Dynamics

    NASA Astrophysics Data System (ADS)

    Carlino, S.; Cubellis, E.; Iannuzzi, R.; Luongo, G.; Obrizzo, F.

    2003-04-01

    The seismic energy release in volcanic areas is a complex process and the island of Ischia provides a significant scenario of historical seismicity. This is characterized by the occurence of earthquakes with low energy and high intensity. Information on the seismicity of the island spans about eight centuries, starting from 1228. With regard to effects, the most recent earthquake of 1883 is extensively documented both in the literature and unpublished sources. The earthquake caused 2333 deaths and the destruction of the historical and environmental heritage of some areas of the island. The most severe damage occurred in Casamicciola. This event, which was the first great catastrophe after the unification of Italy in the 1860s (Imax = XI degree MCS), represents an important date in the prevention of natural disasters, in that it was after this earthquake that the first Seismic Safety Act in Italy was passed by which lower risk zones were identified for new settlements. Thanks to such detailed analysis, reliable modelling of the seismic source was also obtained. The historical data onwards makes it possible to identify the area of the epicenter of all known earthquakes as the northern slope of Monte Epomeo, while analysis of the effects of earthquakes and the geological structures allows us to evaluate the stress fields that generate the earthquakes. In a volcanic area, interpretation of the mechanisms of release and propagation of seismic energy is made even more complex as the stress field that acts at a regional level is compounded by that generated from migration of magmatic masses towards the surface, as well as the rheologic properties of the rocks dependent on the high geothermic gradient. Such structural and dynamic conditions make the island of Ischia a seismic area of considerable interest. It would appear necessary to evaluate the expected damage caused by a new event linked to the renewal of dynamics of the island, where high population density and the

  4. Is Seismically Determined Q an Intrinsic Material Property?

    NASA Astrophysics Data System (ADS)

    Langston, C. A.

    2003-12-01

    The seismic quality factor, Q, has a well-defined physical meaning as an intrinsic material property associated with a visco-elastic or a non-linear stress-strain constitutive relation for a material. Measurement of Q from seismic waves, however, involves interpreting seismic wave amplitude and phase as deviations from some ideal elastic wave propagation model. Thus, assumptions in the elastic wave propagation model become the basis for attributing anelastic properties to the earth continuum. Scientifically, the resulting Q model derived from seismic data is no more than a hypothesis that needs to be verified by other independent experiments concerning the continuum constitutive law and through careful examination of the truth of the assumptions in the wave propagation model. A case in point concerns the anelasticity of Mississippi embayment sediments in the central U.S. that has important implications for evaluation of earthquake strong ground motions. Previous body wave analyses using converted Sp phases have suggested that Qs is ~30 in the sediments based on simple ray theory assumptions. However, detailed modeling of 1D heterogeneity in the sediments shows that Qs cannot be resolved by the Sp data. An independent experiment concerning the amplitude decay of surface waves propagating in the sediments shows that Qs must be generally greater than 80 but is also subject to scattering attenuation. Apparent Q effects seen in direct P and S waves can also be produced by wave tunneling mechanisms in relatively simple 1D heterogeneity. Heterogeneity is a general geophysical attribute of the earth as shown by many high-resolution data sets and should be used as the first litmus test on assumptions made in seismic Q studies before a Q model can be interpreted as an intrinsic material property.

  5. Three-Dimensional Anisotropic Acoustic and Elastic Full-Waveform Seismic Inversion

    NASA Astrophysics Data System (ADS)

    Warner, M.; Morgan, J. V.

    2013-12-01

    Three-dimensional full-waveform inversion is a high-resolution, high-fidelity, quantitative, seismic imaging technique that has advanced rapidly within the oil and gas industry. The method involves the iterative improvement of a starting model using a series of local linearized updates to solve the full non-linear inversion problem. During the inversion, forward modeling employs the full two-way three-dimensional heterogeneous anisotropic acoustic or elastic wave equation to predict the observed raw field data, wiggle-for-wiggle, trace-by-trace. The method is computationally demanding; it is highly parallelized, and runs on large multi-core multi-node clusters. Here, we demonstrate what can be achieved by applying this newly practical technique to several high-density 3D seismic datasets that were acquired to image four contrasting sedimentary targets: a gas cloud above an oil reservoir, a radially faulted dome, buried fluvial channels, and collapse structures overlying an evaporate sequence. We show that the resulting anisotropic p-wave velocity models match in situ measurements in deep boreholes, reproduce detailed structure observed independently on high-resolution seismic reflection sections, accurately predict the raw seismic data, simplify and sharpen reverse-time-migrated reflection images of deeper horizons, and flatten Kirchhoff-migrated common-image gathers. We also show that full-elastic 3D full-waveform inversion of pure pressure data can generate a reasonable shear-wave velocity model for one of these datasets. For two of the four datasets, the inclusion of significant transversely isotropic anisotropy with a vertical axis of symmetry was necessary in order to fit the kinematics of the field data properly. For the faulted dome, the full-waveform-inversion p-wave velocity model recovers the detailed structure of every fault that can be seen on coincident seismic reflection data. Some of the individual faults represent high-velocity zones, some represent

  6. Characteristics of Induced and Tectonic Seismicity in Oklahoma Based on High-precision Earthquake Relocations and Focal mechanisms

    NASA Astrophysics Data System (ADS)

    Aziz Zanjani, F.; Lin, G.

    2016-12-01

    Seismic activity in Oklahoma has greatly increased since 2013, when the number of wastewater disposal wells associated with oil and gas production was significantly increased in the area. An M5.8 earthquake at about 5 km depth struck near Pawnee, Oklahoma on September 3, 2016. This earthquake is postulated to be related with the anthropogenic activity in Oklahoma. In this study, we investigate the seismic characteristics in Oklahoma by using high-precision earthquake relocations and focal mechanisms. We acquire the seismic data between January 2013 and October 2016 recorded by the local and regional (within 200 km distance from the Pawnee mainshock) seismic stations from the Incorporated Research Institutions for Seismology (IRIS). We relocate all the earthquakes by applying the source-specific station term method and a differential time relocation method based on waveform cross-correlation data. The high-precision earthquake relocation catalog is then used to perform full-waveform modeling. We use Muller's reflection method for Green's function construction and the mtinvers program for moment tensor inversion. The sensitivity of the solution to the station and component distribution is evaluated by carrying out the Jackknife resampling. These earthquake relocation and focal mechanism results will help constrain the fault orientation and the earthquake rupture length. In order to examine the static Coulomb stress change due to the 2016 Pawnee earthquake, we utilize the Coulomb 3 software in the vicinity of the mainshock and compare the aftershock pattern with the calculated stress variation. The stress change in the study area can be translated into probability of seismic failure on other parts of the designated fault.

  7. Study of seismic response and vibration control of High voltage electrical equipment damper based on TMD

    NASA Astrophysics Data System (ADS)

    Liu, Chuncheng; Wang, Chongyang; Mao, Long; Zha, Chuanming

    2016-11-01

    Substation high voltage electrical equipment such as mutual inductor, circuit interrupter, disconnecting switch, etc., has played a key role in maintaining the normal operation of the power system. When the earthquake disaster, the electrical equipment of the porcelain in the transformer substation is the most easily to damage, causing great economic losses. In this paper, using the method of numerical analysis, the establishment of a typical high voltage electrical equipment of three dimensional finite element model, to study the seismic response of a typical SF6 circuit breaker, at the same time, analysis and contrast the installation ring tuned mass damper (TMD damper for short), by changing the damper damping coefficient and the mass block, install annular TMD vibration control effect is studied. The results of the study for guiding the seismic design of high voltage electrical equipment to provide valuable reference.

  8. Small aperture seismic arrays for studying planetary interiors and seismicity

    NASA Astrophysics Data System (ADS)

    Schmerr, N. C.; Lekic, V.; Fouch, M. J.; Panning, M. P.; Siegler, M.; Weber, R. C.

    2017-12-01

    Seismic arrays are a powerful tool for understanding the interior structure and seismicity across objects in the Solar System. Given the operational constraints of ground-based lander investigations, a small aperture seismic array can provide many of the benefits of a larger-scale network, but does not necessitate a global deployment of instrumentation. Here we define a small aperture array as a deployment of multiple seismometers, with a separation between instruments of 1-1000 meters. For example, small aperture seismic arrays have been deployed on the Moon during the Apollo program, the Active Seismic Experiments of Apollo 14 and 16, and the Lunar Seismic Profiling Experiment deployed by the Apollo 17 astronauts. Both were high frequency geophone arrays with spacing of 50 meters that provided information on the layering and velocity structure of the uppermost kilometer of the lunar crust. Ideally such arrays would consist of instruments that are 3-axis short period or broadband seismometers. The instruments must have a sampling rate and frequency range sensitivity capable of distinguishing between waves arriving at each station in the array. Both terrestrial analogs and the data retrieved from the Apollo arrays demonstrate the efficacy of this approach. Future opportunities exist for deployment of seismic arrays on Europa, asteroids, and other objects throughout the Solar System. Here we will present both observational data and 3-D synthetic modeling results that reveal the sensing requirements and the primary advantages of a small aperture seismic array over single station approach. For example, at the smallest apertures of < 1 m, we constrain that sampling rates must exceed 500 Hz and instrument sensitivity must extend to 100 Hz or greater. Such advantages include the improved ability to resolve the location of the sources near the array through detection of backazimuth and differential timing between stations, determination of the small-scale structure

  9. TexNet seismic network performance and reported seismicity in West Texas

    NASA Astrophysics Data System (ADS)

    Savvaidis, A.; Lomax, A.; Aiken, C.; Young, B.; Huang, D.; Hennings, P.

    2017-12-01

    In 2015, the Texas State Legislature began funding the Texas Seismological Network (TexNet). Since then, 22 new permanent broadband three-component seismic stations have been added to 17 existing stations operated by various networks [US, N4, IM]. These stations together with 4 auxiliary stations, i.e. long term deployments of 20 sec portable stations, were deployed to provide a baseline of Texas seismicity. As soon as the deployment of the new permanent stations took place in West Texas, TexNet was able to detect and characterize smaller magnitude events than was possible before, i.e. M < 2.5. As a consequence, additional portable stations were installed in the area in order to better map the current seismicity level. During the different stages of station deployment, we monitored the seismic network performance and its ability to detect earthquake activity. We found that a key limitation to the network performance is industrial noise in West Texas. For example, during daytime, phase picking and event detection rates are much lower than during nighttime at noisy sites. Regarding seismicity, the high density portable station deployment close to the earthquake activity minimizes hypocentral location uncertainties. In addition, we examined the effects of different crustal velocity models in the area of study on hypocentral location using the local network first arrivals. Considerable differences in location were obtained, which shows the importance of local networks and/or reliable crustal velocity models for West Texas. Given the levels of seismicity in West Texas, a plan to continuously monitor the study area is under development.

  10. Seismic hazard assessment of Syria using seismicity, DEM, slope, active tectonic and GIS

    NASA Astrophysics Data System (ADS)

    Ahmad, Raed; Adris, Ahmad; Singh, Ramesh

    2016-07-01

    In the present work, we discuss the use of an integrated remote sensing and Geographical Information System (GIS) techniques for evaluation of seismic hazard areas in Syria. The present study is the first time effort to create seismic hazard map with the help of GIS. In the proposed approach, we have used Aster satellite data, digital elevation data (30 m resolution), earthquake data, and active tectonic maps. Many important factors for evaluation of seismic hazard were identified and corresponding thematic data layers (past earthquake epicenters, active faults, digital elevation model, and slope) were generated. A numerical rating scheme has been developed for spatial data analysis using GIS to identify ranking of parameters to be included in the evaluation of seismic hazard. The resulting earthquake potential map delineates the area into different relative susceptibility classes: high, moderate, low and very low. The potential earthquake map was validated by correlating the obtained different classes with the local probability that produced using conventional analysis of observed earthquakes. Using earthquake data of Syria and the peak ground acceleration (PGA) data is introduced to the model to develop final seismic hazard map based on Gutenberg-Richter (a and b values) parameters and using the concepts of local probability and recurrence time. The application of the proposed technique in Syrian region indicates that this method provides good estimate of seismic hazard map compared to those developed from traditional techniques (Deterministic (DSHA) and probabilistic seismic hazard (PSHA). For the first time we have used numerous parameters using remote sensing and GIS in preparation of seismic hazard map which is found to be very realistic.

  11. Seismicity of Cascade Volcanoes: Characterization and Comparison

    NASA Astrophysics Data System (ADS)

    Thelen, W. A.

    2016-12-01

    Here we summarize and compare the seismicity around each of the Very High Threat Volcanoes of the Cascade Range of Washington, Oregon and California as defined by the National Volcanic Early Warning System (NVEWS) threat assessment (Ewert et al., 2005). Understanding the background seismic activity and processes controlling it is critical for assessing changes in seismicity and their implications for volcanic hazards. Comparing seismicity at different volcanic centers can help determine what critical factors or processes affect the observed seismic behavior. Of the ten Very High Threat Volcanoes in the Cascade Range, five volcanoes are consistently seismogenic when considering earthquakes within 10 km of the volcanic center or caldera edge (Mount Rainier, Mount St. Helens, Mount Hood, Newberry Caldera, Lassen Volcanic Center). Other Very High Threat volcanoes (South Sister, Mount Baker, Glacier Peak, Crater Lake and Mount Shasta) have comparatively low rates of seismicity and not enough recorded earthquakes to calculate catalog statistics. Using a swarm definition of 3 or more earthquakes occurring in a day with magnitudes above the largest of the network's magnitude of completenesses (M 0.9), we find that Lassen Volcanic Center is the "swarmiest" in terms of percent of seismicity occurring in swarms, followed by Mount Hood, Mount St. Helens and Rainier. The predominance of swarms at Mount Hood may be overstated, as much of the seismicity is occurring on surrounding crustal faults (Jones and Malone, 2005). Newberry Caldera has a relatively short record of seismicity since the permanent network was installed in 2011, however there have been no swarms detected as defined here. Future work will include developing discriminates for volcanic versus tectonic seismicity to better filter the seismic catalog and more precise binning of depths at some volcanoes so that we may better consider different processes. Ewert J. W., Guffanti, M. and Murray, T. L. (2005). An

  12. Mammoth Mountain, California broadband seismic experiment

    NASA Astrophysics Data System (ADS)

    Dawson, P. B.; Pitt, A. M.; Wilkinson, S. K.; Chouet, B. A.; Hill, D. P.; Mangan, M.; Prejean, S. G.; Read, C.; Shelly, D. R.

    2013-12-01

    Mammoth Mountain is a young cumulo-volcano located on the southwest rim of Long Valley caldera, California. Current volcanic processes beneath Mammoth Mountain are manifested in a wide range of seismic signals, including swarms of shallow volcano-tectonic earthquakes, upper and mid-crustal long-period earthquakes, swarms of brittle-failure earthquakes in the lower crust, and shallow (3-km depth) very-long-period earthquakes. Diffuse emissions of C02 began after a magmatic dike injection beneath the volcano in 1989, and continue to present time. These indications of volcanic unrest drive an extensive monitoring effort of the volcano by the USGS Volcano Hazards Program. As part of this effort, eleven broadband seismometers were deployed on Mammoth Mountain in November 2011. This temporary deployment is expected to run through the fall of 2013. These stations supplement the local short-period and broadband seismic stations of the Northern California Seismic Network (NCSN) and provide a combined network of eighteen broadband stations operating within 4 km of the summit of Mammoth Mountain. Data from the temporary stations are not available in real-time, requiring the merging of the data from the temporary and permanent networks, timing of phases, and relocation of seismic events to be accomplished outside of the standard NCSN processing scheme. The timing of phases is accomplished through an interactive Java-based phase-picking routine, and the relocation of seismicity is achieved using the probabilistic non-linear software package NonLinLoc, distributed under the GNU General Public License by Alomax Scientific. Several swarms of shallow volcano-tectonic earthquakes, spasmodic bursts of high-frequency earthquakes, a few long-period events located within or below the edifice of Mammoth Mountain and numerous mid-crustal long-period events have been recorded by the network. To date, about 900 of the ~2400 events occurring beneath Mammoth Mountain since November 2011 have

  13. Seismic Characterization of EGS Reservoirs

    NASA Astrophysics Data System (ADS)

    Templeton, D. C.; Pyle, M. L.; Matzel, E.; Myers, S.; Johannesson, G.

    2014-12-01

    To aid in the seismic characterization of Engineered Geothermal Systems (EGS), we enhance the traditional microearthquake detection and location methodologies at two EGS systems. We apply the Matched Field Processing (MFP) seismic imaging technique to detect new seismic events using known discrete microearthquake sources. Events identified using MFP are typically smaller magnitude events or events that occur within the coda of a larger event. Additionally, we apply a Bayesian multiple-event seismic location algorithm, called MicroBayesLoc, to estimate the 95% probability ellipsoids for events with high signal-to-noise ratios (SNR). Such probability ellipsoid information can provide evidence for determining if a seismic lineation could be real or simply within the anticipated error range. We apply this methodology to the Basel EGS data set and compare it to another EGS dataset. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  14. High frequency seismic monitoring of debris flows at Chalk Cliffs (CO), USA

    NASA Astrophysics Data System (ADS)

    Coviello, Velio; Kean, Jason; Smith, Joel; Coe, Jeffrey; Arattano, Massimo; McCoy, Scott

    2015-04-01

    A growing number of studies adopt passive seismic monitoring techniques to investigate slope instabilities and landslide processes. These techniques are attractive and convenient because large areas can be monitored from a safe distance. This is particularly true when the phenomena under investigation are rapid and infrequent mass movements like debris flows. Different types of devices are used to monitor debris flow processes, but among them ground vibration detectors (GVDs) present several, specific advantages that encourage their use. These advantages include: (i) the possibility to be installed outside the channel bed, (ii) the high adaptability to different and harsh field conditions, and (iii) the capability to detect the debris flow front arrival tens of seconds earlier than contact and stage sensors. Ground vibration data can provide relevant information on the dynamics of debris flows such as timing and velocity of the main surges. However, the processing of the raw seismic signal is usually needed, both to obtain a more effective representation of waveforms and to decrease the amount of data that need to be recorded and analyzed. With this objective, the methods of Amplitude and Impulses are commonly adopted to transform the raw signal to a 1-Hz signal that allows for a more useful representation of the phenomenon. In that way, peaks and other features become more visible and comparable with data obtained from other monitoring devices. In this work, we present the first debris flows seismic recordings gathered in the Chalk Cliffs instrumented basin, central Colorado, USA. In May 2014, two 4.5-Hz, three-axial geophones were installed in the upper part of the catchment. Seismic data are sampled at 333 Hz and then recorded by a standalone recording unit. One geophone is directly installed on bedrock, the other one mounted on a 1-m boulder partially buried in colluvium. This latter sensor integrates a heavily instrumented cross-section consisting of a 225 cm2

  15. Combined Application of Shallow Seismic Reflection and High-resolution Refraction Exploration Approach to Active Fault Survey, Central Orogenic Belt, China

    NASA Astrophysics Data System (ADS)

    Lin, S.; Luo, D.; Yanlin, F.; Li, Y.

    2016-12-01

    Shallow Seismic Reflection (SSR) is a major geophysical exploration method with its exploration depth range, high-resolution in urban active fault exploration. In this paper, we carried out (SSR) and High-resolution refraction (HRR) test in the Liangyun Basin to explore a buried fault. We used NZ distributed 64 channel seismic instrument, 60HZ high sensitivity detector, Geode multi-channel portable acquisition system and hammer source. We selected single side hammer hit multiple overlay, 48 channels received and 12 times of coverage. As there are some coincidence measuring lines of SSR and HRR, we chose multi chase and encounter observation system. Based on the satellite positioning, we arranged 11 survey lines in our study area with total length for 8132 meters. GEOGIGA seismic reflection data processing software was used to deal with the SSR data. After repeated tests from the aspects of single shot record compilation, interference wave pressing, static correction, velocity parameter extraction, dynamic correction, eventually got the shallow seismic reflection profile images. Meanwhile, we used Canadian technology company good refraction and tomographic imaging software to deal with HRR seismic data, which is based on nonlinear first arrival wave travel time tomography. Combined with drilling geological profiles, we explained 11 measured seismic profiles. Results show 18 obvious fault feature breakpoints, including 4 normal faults of south-west, 7 reverse faults of south-west, one normal fault of north-east and 6 reverse faults of north-east. Breakpoints buried depth is 15-18 meters, and the inferred fault distance is 3-12 meters. Comprehensive analysis shows that the fault property is reverse fault with northeast incline section, and fewer branch normal faults presenting southwest incline section. Since good corresponding relationship between the seismic interpretation results, drilling data and SEM results on the property, occurrence, broken length of the fault

  16. The assessment of seismic hazard for Gori, (Georgia) and preliminary studies of seismic microzonation

    NASA Astrophysics Data System (ADS)

    Gogoladze, Z.; Moscatelli, M.; Giallini, S.; Avalle, A.; Gventsadze, A.; Kvavadze, N.; Tsereteli, N.

    2016-12-01

    Seismic risk is a crucial issue for South Caucasus, which is the main gateway between Asia and Europe. The goal of this work is to propose new methods and criteria for defining an overall approach aimed at assessing and mitigating seismic risk in Georgia. In this reguard seismic microzonation represents a highly useful tool for seismic risk assessmentin land management, for design of buildings or structures and for emergency planning.Seismic microzonation assessment of local seismic hazard,which is a component of seismicity resulting from specific local characteristics which cause local amplification and soil instability, through identification of zones with seismically homogeneous behavior. This paper presents the results of preliminary study of seismic microzonation of Gori, Georgia. Gori is and is located in the Shida Kartli region and on both sides of Liachvi and Mtkvari rivers, with area of about 135 km2around the Gori fortress. Gori is located in Achara-Trialeti fold-thrust belt, that is tectonically unstable. Half of all earthquakes in Gori area with magnitude M≥3.5 have happened along this fault zone and on basis of damage caused by previous earthquakes, this territory show the highest level of risk (the maximum value of direct losses) in central part of the town. The seismic microzonation map of level 1 for Gori was carried out using: 1) Already available data (i.e., topographic map and boreholes data), 2) Results of new geological surveys and 3) Geophysical measurements (i.e., MASW and noise measurements processed with HVSR technique). Our preliminary results highlight the presence of both stable zones susceptible to local amplifications and unstable zones susceptible to geological instability. Our results are directed to establish set of actions aimed at risk mitigation before initial onset of emergency, and to management of the emergency once the seismic event has occurred. The products obtained, will contain the basic elements of an integrated system

  17. Georgia-Armenia Transboarder seismicity studies

    NASA Astrophysics Data System (ADS)

    Godoladze, T.; Tvaradze, N.; Javakishvili, Z.; Elashvili, M.; Durgaryan, R.; Arakelyan, A.; Gevorgyan, M.

    2012-12-01

    In the presented study we performed Comprehensive seismic analyses for the Armenian-Georgian transboarder active seismic fault starting on Armenian territory, cutting the state boarder and having possibly northern termination on Adjara-Triealeti frontal structure in Georgia. In the scope of International projects: ISTC A-1418 "Open network of scientific Centers for mitigation risk of natural hazards in the Southern Caucasus and Central Asia" and NATO SfP- 983284 Project "Caucasus Seismic Emergency Response" in Akhalkalaki (Georgia) seismic center, Regional Summer school trainings and intensive filed investigations were conducted. Main goal was multidisciplinary study of the Javakheti fault structure and better understanding seismicity of the area. Young scientists from Turkey, Armenia, Azerbaijan and Georgia were participated in the deployment of temporal seismic network in order to monitor seisimity on the Javakheti highland and particularly delineate fault scarf and identify active seismic structures. In the scope of international collaboration the common seismic database has been created in the southern Caucasus and collected data from the field works is available now online. Javakheti highland, which is located in the central part of the Caucasus, belongs to the structure of the lesser Caucasus and represents a history of neotectonic volcanism existed in the area. Jasvakheti highland is seismicalu active region devastating from several severe earthquakes(1088, 1283, 1899…). Hypocenters located during analogue network were highly scattered and did not describe real pattern of seismicity of the highland. We relocated hypocenters of the region and improved local velocity model. The hypocenters derived from recently deployed local seismic network in the Javakheti highland, clearly identified seismically active structures. Fault plane solutions of analogue data of the Soviet times have been carefully analyzed and examined. Moment tensor inversion were preformed

  18. Design and development of digital seismic amplifier recorder

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

    Samsidar, Siti Alaa; Afuar, Waldy; Handayani, Gunawan, E-mail: gunawanhandayani@gmail.com

    2015-04-16

    A digital seismic recording is a recording technique of seismic data in digital systems. This method is more convenient because it is more accurate than other methods of seismic recorders. To improve the quality of the results of seismic measurements, the signal needs to be amplified to obtain better subsurface images. The purpose of this study is to improve the accuracy of measurement by amplifying the input signal. We use seismic sensors/geophones with a frequency of 4.5 Hz. The signal is amplified by means of 12 units of non-inverting amplifier. The non-inverting amplifier using IC 741 with the resistor values 1KΩmore » and 1MΩ. The amplification results were 1,000 times. The results of signal amplification converted into digital by using the Analog Digital Converter (ADC). Quantitative analysis in this study was performed using the software Lab VIEW 8.6. The Lab VIEW 8.6 program was used to control the ADC. The results of qualitative analysis showed that the seismic conditioning can produce a large output, so that the data obtained is better than conventional data. This application can be used for geophysical methods that have low input voltage such as microtremor application.« less

  19. Mobile seismic exploration

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

    Dräbenstedt, A., E-mail: a.draebenstedt@polytec.de, E-mail: rembe@iei.tu-clausthal.de, E-mail: ulrich.polom@liag-hannover.de; Seyfried, V.; Cao, X.

    2016-06-28

    Laser-Doppler-Vibrometry (LDV) is an established technique to measure vibrations in technical systems with picometer vibration-amplitude resolution. Especially good sensitivity and resolution can be achieved at an infrared wavelength of 1550 nm. High-resolution vibration measurements are possible over more than 100 m distance. This advancement of the LDV technique enables new applications. The detection of seismic waves is an application which has not been investigated so far because seismic waves outside laboratory scales are usually analyzed at low frequencies between approximately 1 Hz and 250 Hz and require velocity resolutions in the range below 1 nm/s/√Hz. Thermal displacements and air turbulence have critical influences to LDVmore » measurements at this low-frequency range leading to noise levels of several 100 nm/√Hz. Commonly seismic waves are measured with highly sensitive inertial sensors (geophones or Micro Electro-Mechanical Sensors (MEMS)). Approaching a laser geophone based on LDV technique is the topic of this paper. We have assembled an actively vibration-isolated optical table in a minivan which provides a hole in its underbody. The laser-beam of an infrared LDV assembled on the optical table impinges the ground below the car through the hole. A reference geophone has detected remaining vibrations on the table. We present the results from the first successful experimental demonstration of contactless detection of seismic waves from a movable vehicle with a LDV as laser geophone.« less

  20. Seismic Wavefield Imaging of Long-Period Ground Motion in the Tokyo Metropolitan Area, Japan

    NASA Astrophysics Data System (ADS)

    Nagao, H.; Kano, M.; Nagata, K.; Ito, S. I.; Sakai, S.; Nakagawa, S.; Hori, M.; Hirata, N.

    2017-12-01

    Long-period ground motions due to large earthquakes can cause devastating disasters, especially in urbanized areas located on sedimentary basins. To assess and mitigate such damage, it is essential to rapidly evaluate seismic hazards for infrastructures, which can be simulated by seismic response analyses that use waveforms at the base of each infrastructure as an input ground motion. The present study reconstructs the seismic wavefield in the Tokyo metropolitan area located on the Kanto sedimentary basin, Japan, from seismograms of the Metropolitan Seismic Observation network (MeSO-net). The obtained wavefield fully explains the observed waveforms in the frequency band of 0.10-0.20 Hz. This is attributed to the seismic wavefield imaging technique proposed by Kano et al. (2017), which implements the replica exchange Monte Carlo method to simultaneously estimate model parameters related to the subsurface structure and source information. Further investigation shows that the reconstructed seismic wavefield lower than 0.30 Hz is of high quality in terms of variance reduction (VR), which quantifies a misfit in waveforms but that the VR rapidly worsens in higher frequencies. Meanwhile, the velocity response spectra show good agreement with observations up to 0.90 Hz in terms of the combined goodness of fit (CGOF), which is a measure of misfit in the velocity response spectra. Inputting the reconstructed wavefield into seismic response analyses, we can rapidly assess the overall damage to infrastructures immediately after a large earthquake.

  1. High-precision mapping of seismicity in the 2014 Bárdarbunga volcanic episode

    NASA Astrophysics Data System (ADS)

    Vogfjörd, Kristín S.; Hensch, Martin; Gudmundsson, Gunnar B.; Jónsdóttir, Kristín

    2015-04-01

    The Bárdarbunga volcano and its associated fissure swarm in Iceland's Eastern volcanic zone is a highly active system with over 20 eruptions in the last 11 centuries. The location of this active volcano and much of the fissure swarm under several hundred metres thick ice gives rise to multiple hazards, including explosive, subglacial eruptions and associated subglacial floods (jökulhlaups), as well as fissure eruptions extruding large volumes of lava. After a decade of increasing seismic activity, volcanic unrest at Bárdarbunga suddenly escalated into a minor subglacial eruption on 16 August 2014. In the following weeks seismic activity soared and surface deformation of tens of cm were observed, caused by rifting and a dyke intrusion, which propagated 48 km northward from the central volcano (Sigmundsson et al., 2014). The dyke propagation stopped just outside the glacial margin and ended in a fissure eruption at Holuhraun at the end of August. At the time of writing the eruption is ongoing, having extruded a lava volume of over 1 km3 and released high rates of SO2 into the atmosphere. Over twenty thousand microearthquakes have been recorded. Initially most were in the dyke, but after the first two weeks the activity around the caldera rim increased and over 70 shallow earthquakes with MW > 5 have been located along the caldera rim accompanied by caldera subsidence. At the onset of the unrest on 16 August, the seismicity was located in the caldera and north of the caldera rim, but already in the first few hours the activity propagated out of the caldera to the SE. Still, the activity continued for a few days in the fissure swarm to the NE of the rim. High-precision earthquake locations in the propagating dyke have revealed its very detailed, planar rifting segments, with the events distributed over a 3-4 km depth range, and mostly between 6 and 9 km. These very planar event distributions are highly unusual in volcanic areas and strongly suggest rifting of

  2. Features of Radiation and Propagation of Seismic Waves in the Northern Caucasus: Manifestations in Regional Coda

    NASA Astrophysics Data System (ADS)

    Kromskii, S. D.; Pavlenko, O. V.; Gabsatarova, I. P.

    2018-03-01

    Based on the Anapa (ANN) seismic station records of 40 earthquakes ( M W > 3.9) that occurred within 300 km of the station since 2002 up to the present time, the source parameters and quality factor of the Earth's crust ( Q( f)) and upper mantle are estimated for the S-waves in the 1-8 Hz frequency band. The regional coda analysis techniques which allow separating the effects associated with seismic source (source effects) and with the propagation path of seismic waves (path effects) are employed. The Q-factor estimates are obtained in the form Q( f) = 90 × f 0.7 for the epicentral distances r < 120 km and in the form Q( f) = 90 × f1.0 for r > 120 km. The established Q( f) and source parameters are close to the estimates for Central Japan, which is probably due to the similar tectonic structure of the regions. The shapes of the source parameters are found to be independent of the magnitude of the earthquakes in the magnitude range 3.9-5.6; however, the radiation of the high-frequency components ( f > 4-5 Hz) is enhanced with the depth of the source (down to h 60 km). The estimates Q( f) of the quality factor determined from the records by the Sochi, Anapa, and Kislovodsk seismic stations allowed a more accurate determination of the seismic moments and magnitudes of the Caucasian earthquakes. The studies will be continued for obtaining the Q( f) estimates, geometrical spreading functions, and frequency-dependent amplification of seismic waves in the Earth's crust in the other regions of the Northern Caucasus.

  3. Patterned basal seismicity shows sub-ice stream bedforms

    NASA Astrophysics Data System (ADS)

    Barcheck, C. G.; Tulaczyk, S. M.; Schwartz, S. Y.

    2017-12-01

    Patterns in seismicity emanating from the bottom of fast-moving ice streams and glaciers may indicate localized patches of higher basal resistance— sometimes called 'sticky spots', or otherwise varying basal properties. These seismogenic basal areas resist an unknown portion of the total driving stress of the Whillans Ice Plain (WIP), in West Antarctica, but may play an important role in the WIP stick-slip cycle and ice stream slowdown. To better understand the mechanism and importance of basal seismicity beneath the WIP, we analyze seismic data collected by a small aperture (< 3km) network of 8 surface and 5 borehole seismometers installed in the main central sticky spot of the WIP. We use a network beamforming technique to detect and roughly locate thousands of small (magnitude < 0), local basal micro-earthquakes in Dec 2014, and we compare the resulting map of seismicity to ice bottom depth measured by airborne radar. The number of basal earthquakes per area within the network is spatially heterogeneous, but a pattern of two 400m wide streaks of high seismicity rates is evident, with >50-500 earthquakes detected per 50x50m grid cell in 2 weeks. These seismically active streaks are elongated approximately in the ice flow direction with a spacing of 750m. Independent airborne radar measurements of ice bottom depth from Jan 2013 show a low-amplitude ( 5m) undulation in the basal topography superposed on a regional gradient in ice bottom depth. The flow-perpendicular wavelength of these low-amplitude undulations is comparable to the spacing of the high seismicity bands, and the streaks of high seismicity intersect local lows in the undulating basal topography. We interpret these seismic and radar observations as showing seismically active sub-ice stream bedforms that are low amplitude and elongated in the direction of ice flow, comparable to the morphology of mega scale glacial lineations (MSGLs), with high basal seismicity rates observed in the MSGL troughs

  4. Monitoring Instrument Performance in Regional Broadband Seismic Network Using Ambient Seismic Noise

    NASA Astrophysics Data System (ADS)

    Ye, F.; Lyu, S.; Lin, J.

    2017-12-01

    In the past ten years, the number of seismic stations has increased significantly, and regional seismic networks with advanced technology have been gradually developed all over the world. The resulting broadband data help to improve the seismological research. It is important to monitor the performance of broadband instruments in a new network in a long period of time to ensure the accuracy of seismic records. Here, we propose a method that uses ambient noise data in the period range 5-25 s to monitor instrument performance and check data quality in situ. The method is based on an analysis of amplitude and phase index parameters calculated from pairwise cross-correlations of three stations, which provides multiple references for reliable error estimates. Index parameters calculated daily during a two-year observation period are evaluated to identify stations with instrument response errors in near real time. During data processing, initial instrument responses are used in place of available instrument responses to simulate instrument response errors, which are then used to verify our results. We also examine feasibility of the tailing noise using data from stations selected from USArray in different locations and analyze the possible instrumental errors resulting in time-shifts used to verify the method. Additionally, we show an application that effects of instrument response errors that experience pole-zeros variations on monitoring temporal variations in crustal properties appear statistically significant velocity perturbation larger than the standard deviation. The results indicate that monitoring seismic instrument performance helps eliminate data pollution before analysis begins.

  5. Report of reprocessing of reflection seismic profile X-5 Waste Isolation Pilot Plant site, Eddy County, New Mexico

    USGS Publications Warehouse

    Miller, John J.

    1983-01-01

    Seismic reflection profile X-5 exhibits a 7,700 ft long anomalous zone of poor quality to nonexistent reflections between shotpoints 100 and 170, compared to the high-quality, flat-lying, coherent reflections on either side. Results from drill holes in the area suggest 'layer cake' geology with no detectable abnormalities such as faults present. In an attempt to determine whether the anomalous zone of the seismic profile is an artifact or actually indicates a geologic condition, the data were extensively reprocessed using state-of-the-art processing techniques and the following conclusions were made: 1. The field-recorded data in the anomalous zone are of poor quality due to surface conditions and recording parameters used. 2. Reprocessing shows reflectors throughout the anomalous zone at all levels. However, it cannot prove that the reflectors are continuous throughout the anomalous zone. 3. Significant improvement in data quality may be achieved if the line is reshot using carefully determined recording parameters.

  6. Estimation of seismic quality factor: Artificial neural networks and current approaches

    NASA Astrophysics Data System (ADS)

    Yıldırım, Eray; Saatçılar, Ruhi; Ergintav, Semih

    2017-01-01

    The aims of this study are to estimate soil attenuation using alternatives to traditional methods, to compare results of using these methods, and to examine soil properties using the estimated results. The performances of all methods, amplitude decay, spectral ratio, Wiener filter, and artificial neural network (ANN) methods, are examined on field and synthetic data with noise and without noise. High-resolution seismic reflection field data from Yeniköy (Arnavutköy, İstanbul) was used as field data, and 424 estimations of Q values were made for each method (1,696 total). While statistical tests on synthetic and field data are quite close to the Q value estimation results of ANN, Wiener filter, and spectral ratio methods, the amplitude decay methods showed a higher estimation error. According to previous geological and geophysical studies in this area, the soil is water-saturated, quite weak, consisting of clay and sandy units, and, because of current and past landslides in the study area and its vicinity, researchers reported heterogeneity in the soil. Under the same physical conditions, Q value calculated on field data can be expected to be 7.9 and 13.6. ANN models with various structures, training algorithm, input, and number of neurons are investigated. A total of 480 ANN models were generated consisting of 60 models for noise-free synthetic data, 360 models for different noise content synthetic data and 60 models to apply to the data collected in the field. The models were tested to determine the most appropriate structure and training algorithm. In the final ANN, the input vectors consisted of the difference of the width, energy, and distance of seismic traces, and the output was Q value. Success rate of both ANN methods with noise-free and noisy synthetic data were higher than the other three methods. Also according to the statistical tests on estimated Q value from field data, the method showed results that are more suitable. The Q value can be estimated

  7. High-Resolution Seismic Reflection Imaging of the Reelfoot Fault, New Madrid, Missouri

    NASA Astrophysics Data System (ADS)

    Rosandich, B.; Harris, J. B.; Woolery, E. W.

    2017-12-01

    Earthquakes in the Lower Mississippi Valley are mainly concentrated in the New Madrid Seismic Zone and are associated with reactivated faults of the Reelfoot Rift. Determining the relationship between the seismogenic faults (in crystalline basement rocks) and deformation at the Earth's surface and in the shallow subsurface has remained an active research topic for decades. An integrated seismic data set, including compressional (P-) wave and shear (S-) wave seismic reflection profiles, was collected in New Madrid, Missouri, across the "New Madrid" segment of the Reelfoot Fault, whose most significant rupture produced the M 7.5, February 7, 1812, New Madrid earthquake. The seismic reflection profiles (215 m long) were centered on the updip projection of the fault, which is associated with a surface drainage feature (Des Cyprie Slough) located at the base of a prominent east-facing escarpment. The seismic reflection profiles were collected using 48-channel (P-wave) and 24-channel (S-wave) towable landsteamer acquisition equipment. Seismic energy was generated by five vertical impacts of a 1.8-kg sledgehammer on a small aluminum plate for the P-wave data and five horizontal impacts of the sledgehammer on a 10-kg steel I-beam for the S-wave data. Interpretation of the profiles shows a west-dipping reverse fault (Reelfoot Fault) that propagates upward from Paleozoic sedimentary rocks (>500 m deep) to near-surface Quaternary sediments (<10 m deep). The hanging wall of the fault is anticlinally folded, a structural setting almost identical to that imaged on the Kentucky Bend and Reelfoot Lake segments (of the Reelfoot Fault) to the south.

  8. Construction of High School Students' Abstraction Levels in Understanding the Concept of Quadrilaterals

    ERIC Educational Resources Information Center

    Budiarto, Mega Teguh; Khabibah, Siti; Setianingsih, Rini

    2017-01-01

    The purpose of this study was to examine the abstraction thinking or the vertical reorganization activity of mathematical concepts of high school students while taking account of the abstraction that was constructed earlier, and the socio-cultural background. This study was qualitative in nature with task-based interviews as the method of…

  9. Crustal seismicity in central Chile

    NASA Astrophysics Data System (ADS)

    Barrientos, S.; Vera, E.; Alvarado, P.; Monfret, T.

    2004-06-01

    Both the genesis and rates of activity of shallow intraplate seismic activity in central Chile are poorly understood, mainly because of the lack of association of seismicity with recognizable fault features at the surface and a poor record of seismic activity. The goal of this work is to detail the characteristics of seismicity that takes place in the western flank of the Andes in central Chile. This region, located less than 100 km from Santiago, has been the site of earthquakes with magnitudes up to 6.9, including several 5+ magnitude shocks in recent years. Because most of the events lie outside the Central Chile Seismic Network, at distances up to 60 km to the east, it is essential to have adequate knowledge of the velocity structure in the Andean region to produce the highest possible quality of epicentral locations. For this, a N-S refraction line, using mining blasts of the Disputada de Las Condes open pit mine, has been acquired. These blasts were detected and recorded as far as 180 km south of the mine. Interpretation of the travel times indicates an upper crustal model consisting of three layers: 2.2-, 6.7-, and 6.1-km thick, overlying a half space; their associated P wave velocities are 4.75-5.0 (gradient), 5.8-6.0 (gradient), 6.2, and 6.6 km/s, respectively. Hypocentral relocation of earthquakes in 1986-2001, using the newly developed velocity model, reveals several regions of concentrated seismicity. One clearly delineates the fault zone and extensions of the strike-slip earthquake that took place in September 1987 at the source of the Cachapoal River. Other regions of activity are near the San José volcano, the source of the Maipo River, and two previously recognized lineaments that correspond to the southern extension of the Pocuro fault and Olivares River. A temporary array of seismographs, installed in the high Maipo River (1996) and San José volcano (1997) regions, established the hypocentral location of events with errors of less than 1 km

  10. Seismicity and Crustal Anisotropy Beneath the Western Segment of the North Anatolian Fault: Results from a Dense Seismic Array

    NASA Astrophysics Data System (ADS)

    Turkelli, N.; Teoman, U.; Altuncu Poyraz, S.; Cambaz, D.; Mutlu, A. K.; Kahraman, M.; Houseman, G. A.; Rost, S.; Thompson, D. A.; Cornwell, D. G.; Utkucu, M.; Gülen, L.

    2013-12-01

    The North Anatolian Fault (NAF) is one of the major strike slip fault systems on Earth comparable to San Andreas Fault in some ways. Devastating earthquakes have occurred along this system causing major damage and casualties. In order to comprehensively investigate the shallow and deep crustal structure beneath the western segment of NAF, a temporary dense seismic network for North Anatolia (DANA) consisting of 73 broadband sensors was deployed in early May 2012 surrounding a rectangular grid of by 70 km and a nominal station spacing of 7 km with the aim of further enhancing the detection capability of this dense seismic array. This joint project involves researchers from University of Leeds, UK, Bogazici University Kandilli Observatory and Earthquake Research Institute (KOERI), and University of Sakarya and primarily focuses on upper crustal studies such as earthquake locations (especially micro-seismic activity), receiver functions, moment tensor inversions, shear wave splitting, and ambient noise correlations. To begin with, we obtained the hypocenter locations of local earthquakes that occured within the DANA network. The dense 2-D grid geometry considerably enhanced the earthquake detection capability which allowed us to precisely locate events with local magnitudes (Ml) less than 1.0. Accurate earthquake locations will eventually lead to high resolution images of the upper crustal structure beneath the northern and southern branches of NAF in Sakarya region. In order to put additional constraints on the active tectonics of the western part of NAF, we also determined fault plane solutions using Regional Moment Tensor Inversion (RMT) and P wave first motion methods. For the analysis of high quality fault plane solutions, data from KOERI and the DANA project were merged. Furthermore, with the aim of providing insights on crustal anisotropy, shear wave splitting parameters such as lag time and fast polarization direction were obtained for local events recorded

  11. A Deep-towed Digital Multichannel Seismic Streamer For Very High-resolution Studies Of Marine Subsurface Structures

    NASA Astrophysics Data System (ADS)

    Breitzke, M.; Bialas, J.; Inggas Working Group

    A deep-towed digital multichannel seismic streamer and side scan sonar system has been developed to collect marine seismic data with a very high lateral in- and cross- line resolution particularly in regions of special interest for gas hydrate research. As marine seismic sources conventional air-, GI or waterguns will be shot close to the sea surface. A depressor of about 2 tons weight ensures the slightly buoyant deep-towed system to keep in depth. The streamer is a modular digital system which can be operated in water depths up to 6000 m. At this stage of development, it consists of a 50 m lead-in cable towed behind the side scan sonar fish and 26 single nodes for each channel. Each node houses a sin- gle hydrophone, low- and high-cut filter, preamplifier and 24-bit AD converter. Three special engineering nodes additionally include a pressure sensor and compass which provide information on the depth of the node and on its geographical position relative to the ship. Nodes are interchangeable and can arbitrarily be connected by cables of 1 or 6.5 m length. A minimum sample interval of 0.25 ms allows to use sufficiently high- frequency seismic sources to guarantee both a very high vertical and lateral resolution. Data are stored both underwater on a linux-based PC with 120 GB storage capacity installed in a pressure vessel mounted on the side scan sonar fish, and onboard on a PC running a data acquisition program and a DLT device. Data are transferred between underwater and onboard systems via telemetry controlled by a second linux-based PC onboard, using coaxial cable or fibre optic technology. The exact position of the side scan sonar fish is determined by the ultra-short base line (USBL) Posidonia system. It mainly consists of a hull-mounted acoustic unit (antenna) and a responder mounted on the side scan sonar fish. Additionally, the three engineering nodes measure the depth and heading of the streamer at three positions relative to the side scan sonar fish. All

  12. 3D architecture modeling of reservoir compartments in a Shingled Turbidite Reservoir using high-resolution seismic data and sparse well control, example from Mars {open_quotes}Pink{close_quotes} reservoir, Mississippi Canyon Area, Gulf of Mexico

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

    Chapin, M.A.; Mahaffie, M.J.; Tiller, G.M.

    1996-12-31

    Economics of most deep-water development projects require large reservoir volumes to be drained with relatively few wells. The presence of reservoir compartments must therefore be detected and planned for in a pre-development stage. We have used 3-D seismic data to constrain large-scale, deterministic reservoir bodies in a 3-D architecture model of Pliocene-turbidite sands of the {open_quotes}E{close_quotes} or {open_quotes}Pink{close_quotes} reservoir, Prospect Mars, Mississippi Canyon Areas 763 and 807, Gulf of Mexico. Reservoir compartmentalization is influenced by stratigraphic shingling, which in turn is caused by low accommodation space predentin the upper portion of a ponded seismic sequence within a salt withdrawal mini-basin.more » The accumulation is limited by updip onlap onto a condensed section marl, and by lateral truncation by a large scale submarine erosion surface. Compartments were suggested by RFT pressure variations and by geochemical analysis of RFT fluid samples. A geological interpretation derived from high-resolution 3-D seismic and three wells was linked to 3-D architecture models through seismic inversion, resulting in a reservoir all available data. Distinguishing subtle stratigraphical shingles from faults was accomplished by detailed, loop-level mapping, and was important to characterize the different types of reservoir compartments. Seismic inversion was used to detune the seismic amplitude, adjust sandbody thickness, and update the rock properties. Recent development wells confirm the architectural style identified. This modeling project illustrates how high-quality seismic data and architecture models can be combined in a pre-development phase of a prospect, in order to optimize well placement.« less

  13. 3D architecture modeling of reservoir compartments in a Shingled Turbidite Reservoir using high-resolution seismic data and sparse well control, example from Mars [open quotes]Pink[close quotes] reservoir, Mississippi Canyon Area, Gulf of Mexico

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

    Chapin, M.A.; Mahaffie, M.J.; Tiller, G.M.

    1996-01-01

    Economics of most deep-water development projects require large reservoir volumes to be drained with relatively few wells. The presence of reservoir compartments must therefore be detected and planned for in a pre-development stage. We have used 3-D seismic data to constrain large-scale, deterministic reservoir bodies in a 3-D architecture model of Pliocene-turbidite sands of the [open quotes]E[close quotes] or [open quotes]Pink[close quotes] reservoir, Prospect Mars, Mississippi Canyon Areas 763 and 807, Gulf of Mexico. Reservoir compartmentalization is influenced by stratigraphic shingling, which in turn is caused by low accommodation space predentin the upper portion of a ponded seismic sequence withinmore » a salt withdrawal mini-basin. The accumulation is limited by updip onlap onto a condensed section marl, and by lateral truncation by a large scale submarine erosion surface. Compartments were suggested by RFT pressure variations and by geochemical analysis of RFT fluid samples. A geological interpretation derived from high-resolution 3-D seismic and three wells was linked to 3-D architecture models through seismic inversion, resulting in a reservoir all available data. Distinguishing subtle stratigraphical shingles from faults was accomplished by detailed, loop-level mapping, and was important to characterize the different types of reservoir compartments. Seismic inversion was used to detune the seismic amplitude, adjust sandbody thickness, and update the rock properties. Recent development wells confirm the architectural style identified. This modeling project illustrates how high-quality seismic data and architecture models can be combined in a pre-development phase of a prospect, in order to optimize well placement.« less

  14. The Caucasus Seismic Network (CNET): Seismic Structure of the Greater and Lesser Caucasus

    NASA Astrophysics Data System (ADS)

    Sandvol, E. A.; Mackey, K. G.; Nabelek, J.; Yetermishli, G.; Godoladze, T.; Babayan, H.; Malovichko, A.

    2017-12-01

    The Greater Caucasus are a portion of the Alpine-Himalayan mountain belt that has undergone rapid uplift in the past 5 million years, thus serving as a unique natural laboratory to study the early stages of orogenesis. Relatively lower resolution seismic velocity models of this region show contradictory lateral variability. Furthermore, recent waveform modeling of seismograms has clearly demonstrated the presence of deep earthquakes (with a maximum hypocentral depth of 175 km) below the Greater Caucasus. The region has been largely unexplored in terms of the detailed uppermost mantle and crustal seismic structure due in part to the disparate data sets that have not yet been merged as well as key portions being sparsely instrumented. We have established collaborative agreements across the region. Building on these agreements we recently deployed a major multi-national seismic array across the Greater Caucasus to address fundamental questions about the nature of continental deformation in this poorly understood region. Our seismic array has two components: (1) a grid of stations spanning the entire Caucasus and (2) two seismic transects consisting of stations spaced at distances of less than 10 km that cross the Greater Caucasus. In addition to the temporary stations, we are working to integrate data from the national networks to produce high resolution images of the seismic structure. Using data from over 106 new seismic stations in Azerbaijan, Armenia, Russia, and Georgia, we hope to gain a better understanding of the recent uplift ( 5 Ma) of the Greater Caucasus and the nature of seismogenic deformation in the region.

  15. Seismic Anisotropy of Soft Sands, Offshore Western AUstralia

    NASA Astrophysics Data System (ADS)

    Urosevic, M.; Gurevich, B.

    2007-05-01

    Seismic anisotropy is commonly measured in sand shale environment. Intrinsic polar anisotropy of the shale and its effect on seismic data processing and analysis is well established and reasonably well understood. In sandstone, azimuthal anisotropy is often detected and is typically connected to an in situ stress regime and the brittleness of the rock. This type of anisotropy, commonly referred to as fractured induced anisotropy, has been widely and extensively studied as it directly affects both permeability and the strength of the rock. Hence fracture induced anisotropy is not only important for hydrocarbon exploration but also for geotechnical studies, underground mining, etc. Interestingly, in the last few years azimuthal anisotropy has also been detected in soft, poorly consolidated clean sands, mainly by cross-dipole sonic log measurements. This is somewhat surprising as in such soft, typically highly porous and permeable rocks stress induced fractures are unlikely to be abundant. In this study we analyse the anisotropy in such sand class using well-log measurements, three-component VSP data, as well as 2D and 3D surface seismic (reflection) data. High-quality cross-dipole sonic log measurements showed significant shear wave splitting over unconsolidated, highly porous and permeable sand interval. The shear wave anisotropy was computed to be around 10-15%. This is commonly seen as an indication that the rock is fractured and that the fractures are likely to be open. However, image log data over the same sand section suggested dilute most likely non-conductive fractures. Analysis of the shear wave splitting in VSP data also suggested low fracture density. The frequency content of the direct fast and slow shear waves on the VSP data was very similar, not supporting the presence of open fluid saturated fractures. Unfortunately, the evidence from the VSP data is not very compelling because the reservoir is thin compared to the wavelength and sampling interval of

  16. Classifying elephant behaviour through seismic vibrations.

    PubMed

    Mortimer, Beth; Rees, William Lake; Koelemeijer, Paula; Nissen-Meyer, Tarje

    2018-05-07

    Seismic waves - vibrations within and along the Earth's surface - are ubiquitous sources of information. During propagation, physical factors can obscure information transfer via vibrations and influence propagation range [1]. Here, we explore how terrain type and background seismic noise influence the propagation of seismic vibrations generated by African elephants. In Kenya, we recorded the ground-based vibrations of different wild elephant behaviours, such as locomotion and infrasonic vocalisations [2], as well as natural and anthropogenic seismic noise. We employed techniques from seismology to transform the geophone recordings into source functions - the time-varying seismic signature generated at the source. We used computer modelling to constrain the propagation ranges of elephant seismic vibrations for different terrains and noise levels. Behaviours that generate a high force on a sandy terrain with low noise propagate the furthest, over the kilometre scale. Our modelling also predicts that specific elephant behaviours can be distinguished and monitored over a range of propagation distances and noise levels. We conclude that seismic cues have considerable potential for both behavioural classification and remote monitoring of wildlife. In particular, classifying the seismic signatures of specific behaviours of large mammals remotely in real time, such as elephant running, could inform on poaching threats. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

  17. Wind seismic noise introduced by external infrastructure: field data and transfer mechanism

    NASA Astrophysics Data System (ADS)

    Martysevich, Pavel; Starovoyt, Yuri

    2017-04-01

    Background seismic noise generated by wind was analyzed at six co-located seismic and infrasound arrays with the use of the wind speed data. The main factors affecting the noise level were identified as (a) external structures as antenna towers for intrasite communication, vegetation and heavy solar panels fixtures, (b) borehole casing and (c) local lithology. The wind-induced seismic noise peaks in the spectra can be predicted by combination of inverted pendulum model for antenna towers and structures used to support solar panels, free- or clamped-tube resonance of the borehole casing and is dependent on the type of sedimentary upper layer. Observed resonance frequencies are in agreement with calculated clamped / free tube modes for towers and borehole casings. Improvement of the seismic data quality can be achieved by minimizing the impact of surrounding structures close to seismic boreholes. The need and the advantage of the borehole installation may vanish and appear to be even not necessary at locations with non-consolidated sediments because the impact of surrounding structures on seismic background may significantly deteriorate the installation quality and therefore the detection capability of the array. Several IMS arrays where the radio telemetry antennas are used for data delivery to the central site may benefit from the redesign of the intrasite communication system by its substitute with the fiber-optic net as less harmful engineering solution.

  18. Origin and Formation of Giant Mounds in Lake Ladoga (Russia) from High-Resolution Seismic Reflection Data

    NASA Astrophysics Data System (ADS)

    Gromig, R.; Lebas, E.; Krastel, S.; Averes, T.; Wagner, B.; Melles, M.; Fedorov, G.

    2017-12-01

    In the framework of the German-Russian project `PLOT - Paleolimnological Transect' (for an overview of the project see Gromig et al., this meeting), a pilot seismic survey was carried out in Lake Ladoga (Russia) in late summer 2013. In total, 1500 km of seismic reflection profiles have been acquired using a mini-GI gun and a 32-channel seismic streamer. The high-resolution of the seismic data allows us to document in detail the sedimentary processes that occurred in the lake during the preglacial and postglacial history. The seismic stratigraphic architecture of the lake shows, from top to bottom, acoustically well-stratified Holocene muds overlaying rather transparent postglacial varves. These sediment successions are usually bordered by a hard reflector underneath, which may represent coarse-grained sediments or a till. The nature of the material composing the uppermost units have been tied to coring information from core Co1309, which was retrieved during the same survey. Of particular interest, are the single to composite, giant (kilometer-scale) mounds directly overlying the hard reflector. Internal architecture of the mounds reveals a complex formation history, with mound types showing significant structural deformation of different degrees; and other mound types showing a central deformation area, which strongly contrasts with the titled reflections or undisturbed stratification visible at the edges. The deepest seismic unit underlying the mounds is characterized by well-bedded, tilted reflectors in the southeastern part of the lake, while clear synclines are identified in the northwestern part of the lake. An erosional truncation separates the deepest unit from the overlying ones. In the work presented here, we focus on the understanding of the origin and the formation of the giant mounds with respect to the glacial history of Lake Ladoga.

  19. Distributions of high-velocity lower crust and seismic anisotropy across the continental U.S.: Integration of seismic, xenolith, and surface geologic data to address lithospheric dynamics and history

    NASA Astrophysics Data System (ADS)

    Schulte-Pelkum, V.; Mahan, K. H.; Shen, W.; Stachnik, J.; Caine, J. S.; Russo, R.

    2017-12-01

    Continental crust contains an integrated record of its tectonic history in its composition and preserved rock deformation fabrics. In this contribution, we highlight efforts to synthesize aspects of both of these records for the North American continent employing a variety of seismic and geologic data. We used EarthScope and pre-existing active source seismic data and selected xenolith studies to map the distribution of high-velocity lower crust, indicating mafic or garnet-bearing material, across the U.S. and assess its relationship to proposed emplacement and loss mechanisms such as under- and intraplating, collision, extension, heating, cooling, hydration, and delamination. Thin layers of high-velocity crust related to regional processes are found scattered throughout the continent. Thicker layers in large areas are found in the central and eastern U.S. in areas with thick crust, bounded roughly by the Rocky Mountain Front, which cuts across Proterozoic provinces. Hence, the difference between the two domains may reflect garnet growth with aging of continental crust in much of the central and eastern U.S., while conditions in the western U.S. appear unfavorable for growth and maintenance of thick layers of high-velocity garnet-bearing lower crust. In new research, we aim to complete a synthesis of seismic data and structural geologic data to derive constraints on the deformation history of the continent. EarthScope data have already been used to image seismic anisotropy from local scales along brittle faults and ductile shear zones to regional and continent-wide scales. These studies used multiple methods sensitive to different anisotropic parameters over a range of depths from shallow through deep crust and into the lithospheric mantle. Regional- to continent-wide comparisons of these results to geological data are currently hampered by a lack of large-scale geological data compilations. Our research seeks to facilitate ingestion of existing digital structural

  20. Citizen Science Seismic Stations for Monitoring Regional and Local Events

    NASA Astrophysics Data System (ADS)

    Zucca, J. J.; Myers, S.; Srikrishna, D.

    2016-12-01

    The earth has tens of thousands of seismometers installed on its surface or in boreholes that are operated by many organizations for many purposes including the study of earthquakes, volcanos, and nuclear explosions. Although global networks such as the Global Seismic Network and the International Monitoring System do an excellent job of monitoring nuclear test explosions and other seismic events, their thresholds could be lowered with the addition of more stations. In recent years there has been interest in citizen-science approaches to augment government-sponsored monitoring networks (see, for example, Stubbs and Drell, 2013). A modestly-priced seismic station that could be purchased by citizen scientists could enhance regional and local coverage of the GSN, IMS, and other networks if those stations are of high enough quality and distributed optimally. In this paper we present a minimum set of hardware and software specifications that a citizen seismograph station would need in order to add value to global networks. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  1. Pennsylvanian Tyler stratigraphic seismic concepts

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

    Moore, C.E.; Archer, R.J.

    Recent drilling in the Rattler Butte area of central Montana has renewed interest in the Pennsylvanian Tyler Formation as a drilling objective. New production in this area, coupled with the surrounding well density, provides an ideal situation for further development of Tyler stratigraphic-seismic exploration concepts and methods. Both geologic and geophysical Tyler thickness maps have proven to be useful tools in delineating eroded Heath and subsequent lower Tyler deposition. Seismic modeling has revealed a series of possible Tyler-Heath erosional edge characteristics, providing another tool for Tyler-Heath boundary definition. In modeling specific seismic sand signatures, it was found that seismic charactermore » and amplitude are dependent upon both formation thickness and lithology. Detailed mapping of the study area also revealed a new environmental interpretation of the Tyler. Unlike the fluvial system to the north, the Tyler regime in the Rattler Butte area appears to have fluctuated among fluvial, deltaic, and marine systems. Two hydrocarbon occurrence patterns have been noted within the Tyler: (1) although reservoir quality sands are present throughout the Tyler, those within the lower Tyler are more likely to contain hydrocarbons, and (2) close proximity to the Tyler-Heath erosional edge increases the chances of discovering oil-filled Tyler sands. Combined use of these exploration tools should greatly enhance the chances for successful lower Tyler exploration.« less

  2. The Olmsted fault zone, southernmost Illinois: A key to understanding seismic hazard in the northern new Madrid seismic zone

    USGS Publications Warehouse

    Bexfield, C.E.; McBride, J.H.; Pugin, Andre J.M.; Nelson, W.J.; Larson, T.H.; Sargent, S.L.

    2005-01-01

    Geological deformation in the northern New Madrid seismic zone, near Olmsted, Illinois (USA), is analyzed using integrated compressional-wave (P) and horizontally polarized-wave (SH) seismic reflection and regional and dedicated borehole information. Seismic hazards are of special concern because of strategic facilities (e.g., lock and dam sites and chemical plants on the Ohio River near its confluence with the Mississippi River) and because of alluvial soils subject to high amplification of earthquake shock. We use an integrated approach starting with lower resolution, but deeper penetration, P-wave reflection profiles to identify displacement of Paleozoic bedrock. Higher resolution, but shallower penetration, SH-wave images show deformation that has propagated upward from bedrock faults into Pleistocene loess. We have mapped an intricate zone more than 8 km wide of high-angle faults in Mississippi embayment sediments localized over Paleozoic bedrock faults that trend north to northeast, parallel to the Ohio River. These faults align with the pattern of epicenters in the New Madrid seismic zone. Normal and reverse offsets along with positive flower structures imply a component of strike-slip; the current stress regime favors right-lateral slip on northeast-trending faults. The largest fault, the Olmsted fault, underwent principal displacement near the end of the Cretaceous Period 65 to 70 million years ago. Strata of this age (dated via fossil pollen) thicken greatly on the downthrown side of the Olmsted fault into a locally subsiding basin. Small offsets of Tertiary and Quaternary strata are evident on high-resolution SH-wave seismic profiles. Our results imply recent reactivation and possible future seismic activity in a critical area of the New Madrid seismic zone. This integrated approach provides a strategy for evaluating shallow seismic hazard-related targets for engineering concerns. ?? 2005 Elsevier B.V. All rights reserved.

  3. High-resolution seismic reflection survey near SPR surface collapse feature at Weeks Island, Louisiana

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

    Miller, R.D.; Xia, J.; Harding, R.S. Jr.

    1994-12-31

    Shallow high resolution 2-D and 3-D seismic reflection techniques are assisting in the subsurface delineation of a surface collapse feature (sinkhole) at Weeks Island, Louisiana. Seismic reflection surveys were conducted in March 1994. Data from walkaway noise tests were used to assist selection of field recording parameters. The top of the salt dome is about 180 ft below ground surface at the sinkhole. The water table is an estimated 90 ft below the ground surface. A single coherent reflection was consistently recorded across the entire area of the survey, although stacking velocity and spectral content of the event varied. Onmore » the basis of observed travel times and stacking velocities, the coherent reflection event appears to originate above the top of the salt, possibly at or near the water table. Identification of this reflector will be made form borehole investigations currently planned for the sinkhole site. A depression or time sag in this reflection event is clearly evident in both the 2-D and 3-D seismic data in the immediate vicinity of the sinkhole. The time sag appears to be related to the subsurface structure of the reflector and not to near surface topography or velocity effects. Elsewhere in the survey area, observed changes in reflection travel times and wavelet character appear to be related to subsurface geologic structure. These seismic observations may assist in predicting where future sinkholes will develop after they have been tied to borehole data collected at the site.« less

  4. Questa Baseline and Pre-Mining Ground-Water Quality Investigation. 1. Depth to Bedrock Determinations Using Shallow Seismic Data Acquired in the Straight Creek Drainage Near Red River, New Mexico

    USGS Publications Warehouse

    Powers, Michael H.; Burton, Bethany L.

    2004-01-01

    In late May and early June of 2002, the U.S. Geological Survey (USGS) acquired four P-wave seismic profiles across the Straight Creek drainage near Red River, New Mexico. The data were acquired to support a larger effort to investigate baseline and pre-mining ground-water quality in the Red River basin (Nordstrom and others, 2002). For ground-water flow modeling, knowledge of the thickness of the valley fill material above the bedrock is required. When curved-ray refraction tomography was used with the seismic first arrival times, the resulting images of interval velocity versus depth clearly show a sharp velocity contrast where the bedrock interface is expected. The images show that the interpreted buried bedrock surface is neither smooth nor sharp, but it is clearly defined across the valley along the seismic line profiles. The bedrock models defined by the seismic refraction images are consistent with the well data.

  5. High-resolution seismic-reflection profiles and sidescan-sonar records collected on Block Island Sound by U.S. Geological Survey, R/V ASTERIAS, cruise AST 81-2

    USGS Publications Warehouse

    Needell, S. W.; Lewis, R.S.

    1982-01-01

    Cruise AST 81-2 was conducted aboard the R/V ASTERIAS during September 10-18, 1981, in Block Island Sound by the U.S. Geological Survey. It was funded in part by the Connecticut Geological and Natural History Survey. The purpose of the study was to define and map the geology and shallow structure, to determine the geologic framework and late Tertiary to Holocene history, and to identify and map any potential geologic hazards of Block Island Sound.The survey was conducted using an EG&G Uniboom seismic system and an EDO Western sidescan-sonar system. Seismic signals were band-passed between 400 and 4,000 Hz and were recorded at a quarter-second sweep rate. Sidescan sonographs were collected at a 100-m scan range to each side of the ship track. In all, 702 km of seismic-reflection profiles and 402 km of sidescan-sonar records were collected. Navigation was by Loran-C, and the ship position was recorded at 5-minute intervals. Seismic-reflection profiling is continuous and good in quality. Sidescan-sonar records are varied in quality; coverage was intermittent and eventu­ally terminated owing to difficulties with the recorder.Original records can be seen and studied at the U.S. Geological Survey Data Library at Woods Hole, MA 02543. Microfilm copies of the seismic-reflection pro­files and the sidescan sonographs can be purchased only from the National Geo­physical and Solar-Terrestrial Data Center, NOAA/EDIS/NGSDC, Code D621, 325 Broad­way, Boulder, CO 80303 (telephone 303-497-6338).

  6. Seismic excitation by space shuttles

    USGS Publications Warehouse

    Kanamori, H.; Mori, J.; Sturtevant, B.; Anderson, D.L.; Heaton, T.

    1992-01-01

    Shock waves generated by the space shuttles Columbia (August 13, 1989), Atlantis (April 11, 1991) and Discovery (September 18, 1991) on their return to Edwards Air Force Base, California, were recorded by TERRAscope (Caltech's broadband seismic network), the Caltech-U.S.G.S Southern California Seismic Network (SCSN), and the University of Southern California (USC) Los Angeles Basin Seismic Network. The spatial pattern of the arrival times exhibits hyperbolic shock fronts from which the path, velocity and altitude of the space shuttle could be determined. The shock wave was acoustically coupled to the ground, converted to a seismic wave, and recorded clearly at the broadband TERRAscope stations. The acoustic coupling occurred very differently depending on the conditions of the Earth's surface surrounding the station. For a seismic station located on hard bedrock, the shock wave (N wave) was clearly recorded with little distortion. Aside from the N wave, very little acoustic coupling of the shock wave energy to the ground occurred at these sites. The observed N wave record was used to estimate the overpressure of the shock wave accurately; a pressure change of 0.5 to 2.2 mbars was obtained. For a seismic station located close to the ocean or soft sedimentary basins, a significant amount of shock wave energy was transferred to the ground through acoustic coupling of the shock wave and the oceanic Rayleigh wave. A distinct topography such as a mountain range was found effective to couple the shock wave energy to the ground. Shock wave energy was also coupled to the ground very effectively through large man made structures such as high rise buildings and offshore oil drilling platforms. For the space shuttle Columbia, in particular, a distinct pulse having a period of about 2 to 3 seconds was observed, 12.5 s before the shock wave, with a broadband seismograph in Pasadena. This pulse was probably excited by the high rise buildings in downtown Los Angeles which were

  7. Seismic evidence for mass-transport deposits and BSR occurrence on the forearc region along the central Ryukyu Islands, Japan

    NASA Astrophysics Data System (ADS)

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

    2017-12-01

    Mass-transport deposits (MTDs) are widely observed from many continental margins and are a significant component of both slope and basin-floor settings. Although MTDs are typically mud-prone, some MTDs above certain porosity thresholds can act as important hydrocarbon reservoirs. MTDs associated with gas hydrate occurrence in the Ulleung basin were documented. The recovery of gas hydrate by drilling and piston coring has confirmed the gas hydrate accumulations in the basin. Gas hydrate dissociation may have played a role in the slide-initiation at the Storegga Slide offshore Norway. In this study, to identify the gas hydrate reservoir potential of MTDs, we focus on seismic characteristics (seismic facies, attributes, and velocity) of MTDs associated with bottom simulating reflectors (BSR). Our study area is in the forearc region along the central Ryukyu Islands (southeast Japan). In this area, BSR have been widely observed. However, the studies were insufficient for the evaluation of gas hydrate due to poor-quality 2-D seismic data. We use high-quality 3-D seismic volumes in water depths ranging from approximately 150 to 2000 m between Okinawa Island and Miyako Island. BSR in the eastern region of the study area was interpreted within Neogene to Quaternary MTDs. Strata in MTDs are correlated with the upper Shimajiri group based on the characteristics of well data outside of the seismic exploration area and stratigraphy of land areas. The Shimajiri group is composed of homogeneous siltstone intercalated with lenticular, thin-bedded, fine sandstone. Their group is water-dissolved gas reservoir in Okinawa Island and Miyako Island. On our seismic data, MTDs are shown as chaotic, poorly discontinuous strata of low amplitude, partially continuous moderate- to high-amplitude reflections. The seismic velocity profile shows a relative increase in MTD intervals above the BSR, similar to gas hydrate-bearing sediments. It is also indicative of over-consolidation that was

  8. Relationship between the upper mantle high velocity seismic lid and the continental lithosphere

    NASA Astrophysics Data System (ADS)

    Priestley, Keith; Tilmann, Frederik

    2009-04-01

    The lithosphere-asthenosphere boundary corresponds to the base of the "rigid" plates - the depth at which heat transport changes from advection in the convecting deeper upper mantle to conduction in the shallow upper mantle. Although this boundary is a fundamental feature of the Earth, mapping it has been difficult because it does not correspond to a sharp change in temperature or composition. Various definitions of the lithosphere and asthenosphere are based on the analysis of different types of geophysical and geological observations. The depth to the lithosphere-asthenosphere boundary determined from these different observations often shows little agreement when they are applied to the same region because the geophysical and geological observations (i.e., seismic velocity, strain rate, electrical resistivity, chemical depletion, etc.) are proxies for the change in rheological properties rather than a direct measure of the rheological properties. In this paper, we focus on the seismic mapping of the upper mantle high velocity lid and low velocity zone and its relationship to the lithosphere and asthenosphere. We have two goals: (a) to examine the differences in how teleseismic body-wave travel-time tomography and surface-wave tomography image upper mantle seismic structure; and (b) to summarise how upper mantle seismic velocity structure can be related to the structure of the lithosphere and asthenosphere. Surface-wave tomography provides reasonably good depth resolution, especially when higher modes are included in the analysis, but lateral resolution is limited by the horizontal wavelength of the long-period surface waves used to constrain upper mantle velocity structure. Teleseismic body-wave tomography has poor depth resolution in the upper mantle, particularly when no strong lateral contrasts are present. If station terms are used, features with large lateral extent and gradual boundaries are attenuated in the tomographic image. Body-wave models are not

  9. Seismic link at plate boundary

    NASA Astrophysics Data System (ADS)

    Ramdani, Faical; Kettani, Omar; Tadili, Benaissa

    2015-06-01

    Seismic triggering at plate boundaries has a very complex nature that includes seismic events at varying distances. The spatial orientation of triggering cannot be reduced to sequences from the main shocks. Seismic waves propagate at all times in all directions, particularly in highly active zones. No direct evidence can be obtained regarding which earthquakes trigger the shocks. The first approach is to determine the potential linked zones where triggering may occur. The second step is to determine the causality between the events and their triggered shocks. The spatial orientation of the links between events is established from pre-ordered networks and the adapted dependence of the spatio-temporal occurrence of earthquakes. Based on a coefficient of synchronous seismic activity to grid couples, we derive a network link by each threshold. The links of high thresholds are tested using the coherence of time series to determine the causality and related orientation. The resulting link orientations at the plate boundary conditions indicate that causal triggering seems to be localized along a major fault, as a stress transfer between two major faults, and parallel to the geothermal area extension.

  10. Assessing the seismic risk potential of South America

    USGS Publications Warehouse

    Jaiswal, Kishor; Petersen, Mark D.; Harmsen, Stephen; Smoczyk, Gregory M.

    2016-01-01

    We present here a simplified approach to quantifying regional seismic risk. The seismic risk for a given region can be inferred in terms of average annual loss (AAL) that represents long-term value of earthquake losses in any one year caused from a long-term seismic hazard. The AAL are commonly measured in the form of earthquake shaking-induced deaths, direct economic impacts or indirect losses caused due to loss of functionality. In the context of South American subcontinent, the analysis makes use of readily available public data on seismicity, population exposure, and the hazard and vulnerability models for the region. The seismic hazard model was derived using available seismic catalogs, fault databases, and the hazard methodologies that are analogous to the U.S. Geological Survey’s national seismic hazard mapping process. The Prompt Assessment of Global Earthquakes for Response (PAGER) system’s direct empirical vulnerability functions in terms of fatality and economic impact were used for performing exposure and risk analyses. The broad findings presented and the risk maps produced herein are preliminary, yet they do offer important insights into the underlying zones of high and low seismic risks in the South American subcontinent. A more detailed analysis of risk may be warranted by engaging local experts, especially in some of the high risk zones identified through the present investigation.

  11. ON-SITE CAVITY LOCATION-SEISMIC PROFILING AT NEVADA TEST SITE

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

    Forbes, C.B.; Peterson, R.A.; Heald, C.L.

    1961-10-25

    Experimental seismic studies were conducted at the Nevada Test Site for the purpose of designing and evaluating the most promising seismic techniques for on-site inspection. Post-explosion seismic profiling was done in volcanic tuff in the vicinity of the Rainier and Blanca underground explosions. Pre-explosion seismic profiling was done over granitic rock outcrops in the Climax Stock area, and over tuff at proposed location for Linen and Orchid. Near surface velocity profiling techniques based on measurements of seismic time-distance curves gave evidence of disturbances in near surface rock velocities over the Rainier and Refer als0 to abstract 30187. Blanca sites. Thesemore » disturbances appear to be related to near surface fracturing and spallation effects resulting from the reflection of the original intense compression wave pulse at the near surface as a tension pulse. Large tuned seismometer arrays were used for horizontal seismic ranging in an attempt to record back-scattered'' or reflected seismic waves from subsurface cavities or zones of rock fracturing around the underground explosions. Some possible seismic events were recorded from the near vicinities of the Rainier and Blanca sites. However, many more similar events were recorded from numerous other locations, presumably originating from naturally occurring underground geological features. No means was found for discriminating between artificial and natural events recorded by horizontal seismic ranging, and the results were, therefore, not immediately useful for inspection purposes. It is concluded that in some instances near surface velocity profiling methods may provide a useful tool in verifying the presence of spalled zones above underground nuclear explosion sites. In the case of horizontal seismic ranging it appears that successful application would require development of satisfactory means for recognition of and discrimination against seismic responses to naturally occurring geological

  12. Background noise model development for seismic stations of KMA

    NASA Astrophysics Data System (ADS)

    Jeon, Youngsoo

    2010-05-01

    The background noise recorded at seismometer is exist at any seismic signal due to the natural phenomena of the medium which the signal passed through. Reducing the seismic noise is very important to improve the data quality in seismic studies. But, the most important aspect of reducing seismic noise is to find the appropriate place before installing the seismometer. For this reason, NIMR(National Institution of Meteorological Researches) starts to develop a model of standard background noise for the broadband seismic stations of the KMA(Korea Meteorological Administration) using a continuous data set obtained from 13 broadband stations during the period of 2007 and 2008. We also developed the model using short period seismic data from 10 stations at the year of 2009. The method of Mcmara and Buland(2004) is applied to analyse background noise of Korean Peninsula. The fact that borehole seismometer records show low noise level at frequency range greater than 1 Hz compared with that of records at the surface indicate that the cultural noise of inland Korean Peninsula should be considered to process the seismic data set. Reducing Double Frequency peak also should be regarded because the Korean Peninsula surrounded by the seas from eastern, western and southern part. The development of KMA background model shows that the Peterson model(1993) is not applicable to fit the background noise signal generated from Korean Peninsula.

  13. The orthorhombic to high-P monoclinic phase transition in Mg-Fe Pyroxenes: Can it produce a seismic discontinuity?

    NASA Astrophysics Data System (ADS)

    Woodland, Alan B.

    The orthorhombic to high-P monoclinic phase transition in (Mg,Fe)SiO3 pyroxene with a mantle-relevant composition (XFs = 0.1) is expected to occur at ˜300 km depth [Woodland and Angel, 1997]. However, the divariant nature of the phase transition in the Mg-Fe system leaves the question open as to whether this transition occurs over a narrow enough pressure interval to cause a seismic discontinuity. New experimental results with binary Mg-Fe pyroxenes constrain the divariant loop to be 0.2 GPa wide at the composition of XFs = 0.4 and on the order of 0.15 GPa for a mantle-relevant composition. This implies that the phase transition will be complete over a depth interval of about 5-6 km in the mantle and it is concluded that the divariant loop of the orthorhombic to high-P monoclinic phase transition in (Mg,Fe)SiO3 pyroxene is indeed narrow enough to produce a “jump” in seismic velocities. The experimentally observed metastable behavior of orthopyroxene could further reduce the effective depth interval of this phase transition. The expected location of this phase transition coincides with a small magnitude seismic discontinuity, the “X-discontinuity”, occasionally observed in seismic profiles at ˜300 km depth, and thus provides a viable petrologic explanation for the origin of this discontinuity, if it truly exists.

  14. Data Quality Control of the French Permanent Broadband Network in the RESIF Framework.

    NASA Astrophysics Data System (ADS)

    Grunberg, M.; Lambotte, S.; Engels, F.

    2014-12-01

    In the framework of the RESIF (Réseau Sismologique et géodésique Français) project, a new information system is setting up, allowing the improvement of the management and the distribution of high quality data from the different elements of RESIF. Within this information system, EOST (in Strasbourg) is in charge of collecting real-time permanent broadband seismic waveform, and performing Quality Control on these data. The real-time and validated data set are pushed to the French National Distribution Center (Isterre/Grenoble) to make them publicly available. Furthermore EOST hosts the BCSF-ReNaSS, in charge of the French metropolitan seismic bulletin. This allows to benefit from some high-end quality control based on the national and world-wide seismicity. Here we present the real-time seismic data flow from the stations of the French National Broad Band Network to EOST, and then, the data Quality Control procedures that were recently installed, including some new developments.The data Quality Control consists in applying a variety of processes to check the consistency of the whole system from the stations to the data center. This allows us to verify that instruments and data transmission are operating correctly. Moreover, time quality is critical for most of the scientific data applications. To face this challenge and check the consistency of polarities and amplitudes, we deployed several high-end processes including a noise correlation procedure to check for timing accuracy (intrumental time errors result in a time-shift of the whole cross-correlation, clearly distinct from those due to change in medium physical properties), and a systematic comparison of synthetic and real data for teleseismic earthquakes of magnitude larger than 6.5 to detect timing errors as well as polarity and amplitude problems.

  15. Validating induced seismicity forecast models—Induced Seismicity Test Bench

    NASA Astrophysics Data System (ADS)

    Király-Proag, Eszter; Zechar, J. Douglas; Gischig, Valentin; Wiemer, Stefan; Karvounis, Dimitrios; Doetsch, Joseph

    2016-08-01

    Induced earthquakes often accompany fluid injection, and the seismic hazard they pose threatens various underground engineering projects. Models to monitor and control induced seismic hazard with traffic light systems should be probabilistic, forward-looking, and updated as new data arrive. In this study, we propose an Induced Seismicity Test Bench to test and rank such models; this test bench can be used for model development, model selection, and ensemble model building. We apply the test bench to data from the Basel 2006 and Soultz-sous-Forêts 2004 geothermal stimulation projects, and we assess forecasts from two models: Shapiro and Smoothed Seismicity (SaSS) and Hydraulics and Seismics (HySei). These models incorporate a different mix of physics-based elements and stochastic representation of the induced sequences. Our results show that neither model is fully superior to the other. Generally, HySei forecasts the seismicity rate better after shut-in but is only mediocre at forecasting the spatial distribution. On the other hand, SaSS forecasts the spatial distribution better and gives better seismicity rate estimates before shut-in. The shut-in phase is a difficult moment for both models in both reservoirs: the models tend to underpredict the seismicity rate around, and shortly after, shut-in.

  16. Using Antelope and Seiscomp in the framework of the Romanian Seismic Network

    NASA Astrophysics Data System (ADS)

    Marius Craiu, George; Craiu, Andreea; Marmureanu, Alexandru; Neagoe, Cristian

    2014-05-01

    The National Institute for Earth Physics (NIEP) operates a real-time seismic network designed to monitor the seismic activity on the Romania territory, dominated by the Vrancea intermediate-depth (60-200 km) earthquakes. The NIEP real-time network currently consists of 102 stations and two seismic arrays equipped with different high quality digitizers (Kinemetrics K2, Quanterra Q330, Quanterra Q330HR, PS6-26, Basalt), broadband and short period seismometers (CMG3ESP, CMG40T, KS2000, KS54000, KS2000, CMG3T, STS2, SH-1, S13, Mark l4c, Ranger, Gs21, Mark 22) and acceleration sensors (Episensor Kinemetrics). The primary goal of the real-time seismic network is to provide earthquake parameters from more broad-band stations with a high dynamic range, for more rapid and accurate computation of the locations and magnitudes of earthquakes. The Seedlink and AntelopeTM program packages are completely automated Antelope seismological system is run at the Data Center in Măgurele. The Antelope data acquisition and processing software is running for real-time processing and post processing. The Antelope real-time system provides automatic event detection, arrival picking, event location, and magnitude calculation. It also provides graphical displays and automatic location within near real time after a local, regional or teleseismic event has occurred SeisComP 3 is another automated system that is run at the NIEP and which provides the following features: data acquisition, data quality control, real-time data exchange and processing, network status monitoring, issuing event alerts, waveform archiving and data distribution, automatic event detection and location, easy access to relevant information about stations, waveforms, and recent earthquakes. The main goal of this paper is to compare both of these data acquisitions systems in order to improve their detection capabilities, location accuracy, magnitude and depth determination and reduce the RMS and other location errors.

  17. Generalized model of seismic pulse

    NASA Astrophysics Data System (ADS)

    Rabinovich, E. V.; Filipenko, N. Y.; Shefel, G. S.

    2018-05-01

    The paper presents data on a pulse model, suitable for generalizing models of known seismic pulses. It is shown that for each of the known models it is possible to obtain a very accurate quadratic approximation using the proposed model. For example, the fragment of a real seismic trace is approximated by a pulses set formed on the basis of the proposed model, with a high accuracy.

  18. Integrating sequence stratigraphy and rock-physics to interpret seismic amplitudes and predict reservoir quality

    NASA Astrophysics Data System (ADS)

    Dutta, Tanima

    This dissertation focuses on the link between seismic amplitudes and reservoir properties. Prediction of reservoir properties, such as sorting, sand/shale ratio, and cement-volume from seismic amplitudes improves by integrating knowledge from multiple disciplines. The key contribution of this dissertation is to improve the prediction of reservoir properties by integrating sequence stratigraphy and rock physics. Sequence stratigraphy has been successfully used for qualitative interpretation of seismic amplitudes to predict reservoir properties. Rock physics modeling allows quantitative interpretation of seismic amplitudes. However, often there is uncertainty about selecting geologically appropriate rock physics model and its input parameters, away from the wells. In the present dissertation, we exploit the predictive power of sequence stratigraphy to extract the spatial trends of sedimentological parameters that control seismic amplitudes. These spatial trends of sedimentological parameters can serve as valuable constraints in rock physics modeling, especially away from the wells. Consequently, rock physics modeling, integrated with the trends from sequence stratigraphy, become useful for interpreting observed seismic amplitudes away from the wells in terms of underlying sedimentological parameters. We illustrate this methodology using a comprehensive dataset from channelized turbidite systems, deposited in minibasin settings in the offshore Equatorial Guinea, West Africa. First, we present a practical recipe for using closed-form expressions of effective medium models to predict seismic velocities in unconsolidated sandstones. We use an effective medium model that combines perfectly rough and smooth grains (the extended Walton model), and use that model to derive coordination number, porosity, and pressure relations for P and S wave velocities from experimental data. Our recipe provides reasonable fits to other experimental and borehole data, and specifically

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  20. Geophysical Studies Based on Gravity and Seismic Data of Tule Desert, Meadow Valley Wash, and California Wash Basins, Southern Nevada

    USGS Publications Warehouse

    Scheirer, Daniel S.; Page, William R.; Miller, John J.

    2006-01-01

    Gravity and seismic data from Tule Desert, Meadow Valley Wash, and California Wash, Nevada, provide insight into the subsurface geometry of these three basins that lie adjacent to rapidly developing areas of Clark County, Nevada. Each of the basins is the product of Tertiary extension accommodated with the general form of north-south oriented, asymmetrically-faulted half-grabens. Geophysical inversion of gravity observations indicates that Tule Desert and Meadow Valley Wash basins are segmented into subbasins by shallow, buried basement highs. In this study, basement refers to pre-Cenozoic bedrock units that underlie basins filled with Cenozoic sedimentary and volcanic units. In Tule Desert, a small, buried basement high inferred from gravity data appears to be a horst whose placement is consistent with seismic reflection and magnetotelluric observations. Meadow Valley Wash consists of three subbasins separated by basement highs at structural zones that accommodated different styles of extension of the adjacent subbasins, an interpretation consistent with geologic mapping of fault traces oblique to the predominant north-south fault orientation of Tertiary extension in this area. California Wash is a single structural basin. The three seismic reflection lines analyzed in this study image the sedimentary basin fill, and they allow identification of faults that offset basin deposits and underlying basement. The degree of faulting and folding of the basin-fill deposits increases with depth. Pre-Cenozoic units are observed in some of the seismic reflection lines, but their reflections are generally of poor quality or are absent. Factors that degrade seismic reflector quality in this area are rough land topography due to erosion, deformed sedimentary units at the land surface, rock layers that dip out of the plane of the seismic profile, and the presence of volcanic units that obscure underlying reflectors. Geophysical methods illustrate that basin geometry is more

  1. Seismic hazard estimation of northern Iran using smoothed seismicity

    NASA Astrophysics Data System (ADS)

    Khoshnevis, Naeem; Taborda, Ricardo; Azizzadeh-Roodpish, Shima; Cramer, Chris H.

    2017-07-01

    This article presents a seismic hazard assessment for northern Iran, where a smoothed seismicity approach has been used in combination with an updated seismic catalog and a ground motion prediction equation recently found to yield good fit with data. We evaluate the hazard over a geographical area including the seismic zones of Azerbaijan, the Alborz Mountain Range, and Kopeh-Dagh, as well as parts of other neighboring seismic zones that fall within our region of interest. In the chosen approach, seismic events are not assigned to specific faults but assumed to be potential seismogenic sources distributed within regular grid cells. After performing the corresponding magnitude conversions, we decluster both historical and instrumental seismicity catalogs to obtain earthquake rates based on the number of events within each cell, and smooth the results to account for the uncertainty in the spatial distribution of future earthquakes. Seismicity parameters are computed for each seismic zone separately, and for the entire region of interest as a single uniform seismotectonic region. In the analysis, we consider uncertainties in the ground motion prediction equation, the seismicity parameters, and combine the resulting models using a logic tree. The results are presented in terms of expected peak ground acceleration (PGA) maps and hazard curves at selected locations, considering exceedance probabilities of 2 and 10% in 50 years for rock site conditions. According to our results, the highest levels of hazard are observed west of the North Tabriz and east of the North Alborz faults, where expected PGA values are between about 0.5 and 1 g for 10 and 2% probability of exceedance in 50 years, respectively. We analyze our results in light of similar estimates available in the literature and offer our perspective on the differences observed. We find our results to be helpful in understanding seismic hazard for northern Iran, but recognize that additional efforts are necessary to

  2. Seismicity, faulting, and structure of the Koyna-Warna seismic region, Western India from local earthquake tomography and hypocenter locations

    NASA Astrophysics Data System (ADS)

    Dixit, Madan M.; Kumar, Sanjay; Catchings, R. D.; Suman, K.; Sarkar, Dipankar; Sen, M. K.

    2014-08-01

    Although seismicity near Koyna Reservoir (India) has persisted for ~50 years and includes the largest induced earthquake (M 6.3) reported worldwide, the seismotectonic framework of the area is not well understood. We recorded ~1800 earthquakes from 6 January 2010 to 28 May 2010 and located a subset of 343 of the highest-quality earthquakes using the tomoDD code of Zhang and Thurber (2003) to better understand the framework. We also inverted first arrivals for 3-D Vp, Vs, and Vp/Vs and Poisson's ratio tomography models of the upper 12 km of the crust. Epicenters for the recorded earthquakes are located south of the Koyna River, including a high-density cluster that coincides with a shallow depth (<1.5 km) zone of relatively high Vp and low Vs (also high Vp/Vs and Poisson's ratios) near Warna Reservoir. This anomalous zone, which extends near vertically to at least 8 km depth and laterally northward at least 15 km, is likely a water-saturated zone of faults under high pore pressures. Because many of the earthquakes occur on the periphery of the fault zone, rather than near its center, the observed seismicity-velocity correlations are consistent with the concept that many of the earthquakes nucleate in fractures adjacent to the main fault zone due to high pore pressure. We interpret our velocity images as showing a series of northwest trending faults locally near the central part of Warna Reservoir and a major northward trending fault zone north of Warna Reservoir.

  3. Active seismic experiment

    NASA Technical Reports Server (NTRS)

    Kovach, R. L.; Watkins, J. S.; Talwani, P.

    1972-01-01

    The Apollo 16 active seismic experiment (ASE) was designed to generate and monitor seismic waves for the study of the lunar near-surface structure. Several seismic energy sources are used: an astronaut-activated thumper device, a mortar package that contains rocket-launched grenades, and the impulse produced by the lunar module ascent. Analysis of some seismic signals recorded by the ASE has provided data concerning the near-surface structure at the Descartes landing site. Two compressional seismic velocities have so far been recognized in the seismic data. The deployment of the ASE is described, and the significant results obtained are discussed.

  4. Advantages of wet work for near-surface seismic reflection

    USGS Publications Warehouse

    Miller, R.D.; Markiewicz, R.D.; Rademacker, T.R.; Hopkins, R.; Rawcliffe, R.J.; Paquin, J.

    2007-01-01

    Benefits of shallow water settings (0.1 to 0.5 m) are pronounced on shallow, high-resolution seismic reflection images and, for examples discussed here, range from an order of magnitude increased signal-to-noise ratio to resolution potential elevated by more than 8 times. Overall data quality of high-resolution seismic reflection data at three sites notorious for poor near-surface reflection returns was improved by coupling the source and/or receivers to a well sorted and fully saturated surface. Half-period trace-to-trace static offsets evident in reflections from receivers planted into a creek bank were eliminated by moving the geophones to the base of a shallow creek at the toe of the bank. Reflections from a dipping bedrock were recorded with a dominant frequency approaching 1 KHz from hydrophones in 0.5 m of water at the toe of a dam using a hammer impact source. A tamper impacted by a dead blow hammer in a shallow (10-20 cm) deep creek produced reflections with a dominant frequency over 400 Hz at depths as shallow as 6 ms. ?? 2007 Society of Exploration Geophysicists.

  5. Seismic Performance of Self-Consolidating Concrete Bridge Columns : Research Brief

    DOT National Transportation Integrated Search

    2017-09-01

    Rectangular bridge columns in high seismic areas require high amounts of confining steel. Self-consolidating concrete is ideal for the construction of concrete members with high steel congestion. However, there is lack of data on the seismic performa...

  6. Signal-to-noise ratio application to seismic marker analysis and fracture detection

    NASA Astrophysics Data System (ADS)

    Xu, Hui-Qun; Gui, Zhi-Xian

    2014-03-01

    Seismic data with high signal-to-noise ratios (SNRs) are useful in reservoir exploration. To obtain high SNR seismic data, significant effort is required to achieve noise attenuation in seismic data processing, which is costly in materials, and human and financial resources. We introduce a method for improving the SNR of seismic data. The SNR is calculated by using the frequency domain method. Furthermore, we optimize and discuss the critical parameters and calculation procedure. We applied the proposed method on real data and found that the SNR is high in the seismic marker and low in the fracture zone. Consequently, this can be used to extract detailed information about fracture zones that are inferred by structural analysis but not observed in conventional seismic data.

  7. Towards a more comprehensive usage of reflection seismic in near-surface characterization

    NASA Astrophysics Data System (ADS)

    Blouin, M.; Gloaguen, E.; Bellefleur, G.; Pugin, A.

    2014-12-01

    For more than a decade, research groups such as the Geological Survey of Canada built the interest for near-surface reflection seismic by proposing small vibrating sources and three components (3C) landstreamers. Developments in the instrumentation combined with extensive use of shear-wave profiling to image stratigraphy of unconsolidated environments at high resolution got this geophysical method more versatile, more accurate, increased cost effectiveness and allowed to cover greater distance per day. With those major upgrades as a starting point and in a context of regional aquifer characterization in St-Lawrence Lowlands in the province of Quebec, Canada, the present study propose a workflow to further enhance reflection seismic usage for near-surface characterization. First, as high resolution near surface surveys require small shot intervals and multiple channels on three axis, a lot of the acquisition information is received under a raw form yielding to unproductive quality control (QC). Hence, a tool was developed to process data "on the fly" and allow adequate real-time QC and on-site decision making. The algorithm was constructed in a Python environment and is accessible through a graphical user interface where the user is prompted for geometry parameters inputs and desired processing flow steps. Second, at the scale of seismic wavelengths, fine grain and poorly consolidated sediments such as marine clay of the St-Lawrence Lowlands can be viewed as a homogeneous medium presenting anisotropy. This section of the study showed that such geological settings yield to significant seismic velocity variations with angle of propagation that should not be ignore for normal move-out correction, migration or time to depth conversion. Finally, accurate delineation of stratigraphic horizons is an important task of any environmental or hydrogeological characterization study. A methodology was put forward to help integrate geophysical measurements with geological

  8. Modeling Wide-Angle Seismic Data from the Hi-CLIMB Experiment in Tibet

    NASA Astrophysics Data System (ADS)

    Nowack, R. L.; Griffin, J. D.; Tseng, T.; Chen, W.

    2009-12-01

    Using data from local and regional events recorded by the Hi-CLIMB array in Tibet, we utilize seismic attributes, including arrival times, Hilbert amplitudes and pulse frequencies, to constrain structures of seismic wave speed and attenuation in the crust and the upper mantle in western China. We construct more than 30 high-quality, regional seismic profiles, and select 14 of these, which show excellent crustal and Pn arrivals, for further analysis. Travel-times from events at regional distances constrain large-scale velocity structures, and four close-in events provide further details on crustal structure. We use the 3-D ray tracer, CRT, to model the travel-times. Initial results indicate that the Moho beneath the Lhasa terrane of southern Tibet is over 73 km deep with a high Pn speed of about 8.2 km/s. In contrast, the Qiangtang terrane farther north shows a thinner crust, by up to 10 km, and a low Pn speed of 7.8-7.9 km/s. Preliminary estimates of upper mantle velocity gradients are between .003 and .004 km/s per km, consistent with previous results by Phillips et al. (2007). We also use P to SV conversions from teleseismic earthquakes to independently constrain variations in speeds of Pn and depths of the Moho. For instance, amplitudes of the SsPmP phase, when its last reflection off the Moho is near-critical, are particularly sensitive to the contrast in seismic wave speeds across the crust-mantle interface; and results from these additional data are consistent with those from modeling of travel-times. Additional seismic attributes, extracted from wave-trains containing Pn and major crustal phases, are being compared with results of numerical modeling based on the spectral element method and asymptotic calculations in laterally varying media, where both lateral and vertical gradients in seismic wave speeds can strongly affect Pn amplitudes and pulse frequencies.

  9. Pick- and waveform-based techniques for real-time detection of induced seismicity

    NASA Astrophysics Data System (ADS)

    Grigoli, Francesco; Scarabello, Luca; Böse, Maren; Weber, Bernd; Wiemer, Stefan; Clinton, John F.

    2018-05-01

    The monitoring of induced seismicity is a common operation in many industrial activities, such as conventional and non-conventional hydrocarbon production or mining and geothermal energy exploitation, to cite a few. During such operations, we generally collect very large and strongly noise-contaminated data sets that require robust and automated analysis procedures. Induced seismicity data sets are often characterized by sequences of multiple events with short interevent times or overlapping events; in these cases, pick-based location methods may struggle to correctly assign picks to phases and events, and errors can lead to missed detections and/or reduced location resolution and incorrect magnitudes, which can have significant consequences if real-time seismicity information are used for risk assessment frameworks. To overcome these issues, different waveform-based methods for the detection and location of microseismicity have been proposed. The main advantages of waveform-based methods is that they appear to perform better and can simultaneously detect and locate seismic events providing high-quality locations in a single step, while the main disadvantage is that they are computationally expensive. Although these methods have been applied to different induced seismicity data sets, an extensive comparison with sophisticated pick-based detection methods is still missing. In this work, we introduce our improved waveform-based detector and we compare its performance with two pick-based detectors implemented within the SeiscomP3 software suite. We test the performance of these three approaches with both synthetic and real data sets related to the induced seismicity sequence at the deep geothermal project in the vicinity of the city of St. Gallen, Switzerland.

  10. Micro-seismic imaging using a source function independent full waveform inversion method

    NASA Astrophysics Data System (ADS)

    Wang, Hanchen; Alkhalifah, Tariq

    2018-03-01

    At the heart of micro-seismic event measurements is the task to estimate the location of the source micro-seismic events, as well as their ignition times. The accuracy of locating the sources is highly dependent on the velocity model. On the other hand, the conventional micro-seismic source locating methods require, in many cases manual picking of traveltime arrivals, which do not only lead to manual effort and human interaction, but also prone to errors. Using full waveform inversion (FWI) to locate and image micro-seismic events allows for an automatic process (free of picking) that utilizes the full wavefield. However, full waveform inversion of micro-seismic events faces incredible nonlinearity due to the unknown source locations (space) and functions (time). We developed a source function independent full waveform inversion of micro-seismic events to invert for the source image, source function and the velocity model. It is based on convolving reference traces with these observed and modeled to mitigate the effect of an unknown source ignition time. The adjoint-state method is used to derive the gradient for the source image, source function and velocity updates. The extended image for the source wavelet in Z axis is extracted to check the accuracy of the inverted source image and velocity model. Also, angle gathers is calculated to assess the quality of the long wavelength component of the velocity model. By inverting for the source image, source wavelet and the velocity model simultaneously, the proposed method produces good estimates of the source location, ignition time and the background velocity for synthetic examples used here, like those corresponding to the Marmousi model and the SEG/EAGE overthrust model.

  11. Observations and modeling of seismic background noise

    USGS Publications Warehouse

    Peterson, Jon R.

    1993-01-01

    The preparation of this report had two purposes. One was to present a catalog of seismic background noise spectra obtained from a worldwide network of seismograph stations. The other purpose was to refine and document models of seismic background noise that have been in use for several years. The second objective was, in fact, the principal reason that this study was initiated and influenced the procedures used in collecting and processing the data.With a single exception, all of the data used in this study were extracted from the digital data archive at the U.S. Geological Survey's Albuquerque Seismological Laboratory (ASL). This archive dates from 1972 when ASL first began deploying digital seismograph systems and collecting and distributing digital data under the sponsorship of the Defense Advanced Research Projects Agency (DARPA). There have been many changes and additions to the global seismograph networks during the past twenty years, but perhaps none as significant as the current deployment of very broadband seismographs by the U.S. Geological Survey (USGS) and the University of California San Diego (UCSD) under the scientific direction of the IRIS consortium. The new data acquisition systems have extended the bandwidth and resolution of seismic recording, and they utilize high-density recording media that permit the continuous recording of broadband data. The data improvements and continuous recording greatly benefit and simplify surveys of seismic background noise.Although there are many other sources of digital data, the ASL archive data were used almost exclusively because of accessibility and because the data systems and their calibration are well documented for the most part. Fortunately, the ASL archive contains high-quality data from other stations in addition to those deployed by the USGS. Included are data from UCSD IRIS/IDA stations, the Regional Seismic Test Network (RSTN) deployed by Sandia National Laboratories (SNL), and the TERRAscope network

  12. Method of synthesis of abstract images with high self-similarity

    NASA Astrophysics Data System (ADS)

    Matveev, Nikolay V.; Shcheglov, Sergey A.; Romanova, Galina E.; Koneva, Ð.¢atiana A.

    2017-06-01

    Abstract images with high self-similarity could be used for drug-free stress therapy. This based on the fact that a complex visual environment has a high affective appraisal. To create such an image we can use the setup based on the three laser sources of small power and different colors (Red, Green, Blue), the image is the pattern resulting from the reflecting and refracting by the complicated form object placed into the laser ray paths. The images were obtained experimentally which showed the good therapy effect. However, to find and to choose the object which gives needed image structure is very difficult and requires many trials. The goal of the work is to develop a method and a procedure of finding the object form which if placed into the ray paths can provide the necessary structure of the image In fact the task means obtaining the necessary irradiance distribution on the given surface. Traditionally such problems are solved using the non-imaging optics methods. In the given case this task is very complicated because of the complicated structure of the illuminance distribution and its high non-linearity. Alternative way is to use the projected image of a mask with a given structure. We consider both ways and discuss how they can help to speed up the synthesis procedure for the given abstract image of the high self-similarity for the setups of drug-free therapy.

  13. Application of seismic-refraction techniques to hydrologic studies

    USGS Publications Warehouse

    Haeni, F.P.

    1986-01-01

    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 surfaces, 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 applying seismic-refraction methods. These methods allow the 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 this technique in hydrologic investigations and describes the planning, equipment, field procedures, and intrepretation techniques needed for this type of study.Examples of the use of seismic-refraction techniques in a wide variety of hydrologic studies are presented.

  14. 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.

  15. Progressive Seismic Failure, Seismic Gap, and Great Seismic Risk across the Densely Populated North China Basin

    NASA Astrophysics Data System (ADS)

    Yin, A.; Yu, X.; Shen, Z.

    2014-12-01

    Although the seismically active North China basin has the most complete written records of pre-instrumentation earthquakes in the world, this information has not been fully utilized for assessing potential earthquake hazards of this densely populated region that hosts ~200 million people. In this study, we use the historical records to document the earthquake migration pattern and the existence of a 180-km seismic gap along the 600-km long right-slip Tangshan-Hejian-Cixian (THC) fault zone that cuts across the North China basin. The newly recognized seismic gap, which is centered at Tianjin with a population of 11 million people and ~120 km from Beijing (22 million people) and Tangshan (7 million people), has not been ruptured in the past 1000 years by M≥6 earthquakes. The seismic migration pattern in the past millennium suggests that the epicenters of major earthquakes have shifted towards this seismic gap along the THC fault, which implies that the 180- km gap could be the site of the next great earthquake with M≈7.6 if it is ruptured by a single event. Alternatively, the seismic gap may be explained by aseismic creeping or seismic strain transfer between active faults.

  16. Time-Independent Annual Seismic Rates, Based on Faults and Smoothed Seismicity, Computed for Seismic Hazard Assessment in Italy

    NASA Astrophysics Data System (ADS)

    Murru, M.; Falcone, G.; Taroni, M.; Console, R.

    2017-12-01

    In 2015 the Italian Department of Civil Protection, started a project for upgrading the official Italian seismic hazard map (MPS04) inviting the Italian scientific community to participate in a joint effort for its realization. We participated providing spatially variable time-independent (Poisson) long-term annual occurrence rates of seismic events on the entire Italian territory, considering cells of 0.1°x0.1° from M4.5 up to M8.1 for magnitude bin of 0.1 units. Our final model was composed by two different models, merged in one ensemble model, each one with the same weight: the first one was realized by a smoothed seismicity approach, the second one using the seismogenic faults. The spatial smoothed seismicity was obtained using the smoothing method introduced by Frankel (1995) applied to the historical and instrumental seismicity. In this approach we adopted a tapered Gutenberg-Richter relation with a b-value fixed to 1 and a corner magnitude estimated with the bigger events in the catalogs. For each seismogenic fault provided by the Database of the Individual Seismogenic Sources (DISS), we computed the annual rate (for each cells of 0.1°x0.1°) for magnitude bin of 0.1 units, assuming that the seismic moments of the earthquakes generated by each fault are distributed according to the same tapered Gutenberg-Richter relation of the smoothed seismicity model. The annual rate for the final model was determined in the following way: if the cell falls within one of the seismic sources, we merge the respective value of rate determined by the seismic moments of the earthquakes generated by each fault and the value of the smoothed seismicity model with the same weight; if instead the cells fall outside of any seismic source we considered the rate obtained from the spatial smoothed seismicity. Here we present the final results of our study to be used for the new Italian seismic hazard map.

  17. Near-surface, marine seismic-reflection data defines potential hydrogeologic confinement bypass in a tertiary carbonate aquifer, southeastern Florida

    USGS Publications Warehouse

    Cunningham, Kevin J.; Walker, Cameron; Westcott, Richard L.

    2012-01-01

    Approximately 210 km of near-surface, high-frequency, marine seismic-reflection data were acquired on the southeastern part of the Florida Platform between 2007 and 2011. Many high-resolution, seismic-reflection profiles, interpretable to a depth of about 730 m, were collected on the shallow-marine shelf of southeastern Florida in water as shallow as 1 m. Landward of the present-day shelf-margin slope, these data image middle Eocene to Pleistocene strata and Paleocene to Pleistocene strata on the Miami Terrace. This high-resolution data set provides an opportunity to evaluate geologic structures that cut across confining units of the Paleocene to Oligocene-age carbonate rocks that form the Floridan aquifer system.Seismic profiles image two structural systems, tectonic faults and karst collapse structures, which breach confining beds in the Floridan aquifer system. Both structural systems may serve as pathways for vertical groundwater flow across relatively low-permeability carbonate strata that separate zones of regionally extensive high-permeability rocks in the Floridan aquifer system. The tectonic faults occur as normal and reverse faults, and collapse-related faults have normal throw. The most common fault occurrence delineated on the reflection profiles is associated with karst collapse structures. These high-frequency seismic data are providing high quality structural analogs to unprecedented depths on the southeastern Florida Platform. The analogs can be used for assessment of confinement of other carbonate aquifers and the sealing potential of deeper carbonate rocks associated with reservoirs around the world.

  18. Understanding Seismic Anisotropy in Hunt Well of Fort McMurray, Canada

    NASA Astrophysics Data System (ADS)

    Malehmir, R.; Schmitt, D. R.; Chan, J.

    2014-12-01

    Seismic imaging plays vital role in geothermal systems as a sustainable energy resource. In this paper, we acquired and processed zero-offset and walk-away VSP and logging as well as surface seismic in Athabasca oil sand area, Alberta. Seismic data were highly processed to make better image geothermal system. Through data processing, properties of natural fractures such as orientation and width were studied and high probable permeable zones were mapped along the deep drilled to the depth of 2363m deep into crystalline basement rocks. In addition to logging data, seismic data were processed to build a reliable image of underground. Velocity analysis in high resolution multi-component walk-away VSP informed us about the elastic anisotropy in place. Study of the natural and induced fracture as well as elastic anisotropy in the seismic data, led us to better map stress regime around the well bore. The seismic image and map of fractures optimizes enhanced geothermal stages through hydraulic stimulation. Keywords: geothermal, anisotropy, VSP, logging, Hunt well, seismic

  19. Seismic risk assessment and application in the central United States

    USGS Publications Warehouse

    Wang, Z.

    2011-01-01

    Seismic risk is a somewhat subjective, but important, concept in earthquake engineering and other related decision-making. Another important concept that is closely related to seismic risk is seismic hazard. Although seismic hazard and seismic risk have often been used interchangeably, they are fundamentally different: seismic hazard describes the natural phenomenon or physical property of an earthquake, whereas seismic risk describes the probability of loss or damage that could be caused by a seismic hazard. The distinction between seismic hazard and seismic risk is of practical significance because measures for seismic hazard mitigation may differ from those for seismic risk reduction. Seismic risk assessment is a complicated process and starts with seismic hazard assessment. Although probabilistic seismic hazard analysis (PSHA) is the most widely used method for seismic hazard assessment, recent studies have found that PSHA is not scientifically valid. Use of PSHA will lead to (1) artifact estimates of seismic risk, (2) misleading use of the annual probability of exccedance (i.e., the probability of exceedance in one year) as a frequency (per year), and (3) numerical creation of extremely high ground motion. An alternative approach, which is similar to those used for flood and wind hazard assessments, has been proposed. ?? 2011 ASCE.

  20. Seismic data acquisition through tubing

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

    Buettner, H M; Jervis, M

    1999-07-01

    We have collected good quality crosswell seismic data through production tubing in active oil fields at realistic interwell distances (300 ft). The data were collected at the Aera Cymric field (1998) and at a Chevron site (1997); both located in the Central Valley of California. The Aera data were used to produce travel-time tomographic images of the interwell region. Both sites have similar geology, namely siliceous shale (diatomite) with moderate to highly attenuating reservoir rocks. In addition we confirmed modeling predictions that typical tubing attenuation losses are on the order of 12 dB. We expect that the use of strongermore » sources and tube wave suppression will allow for crosswell imaging at realistic distances even for low Q or high noise situations. We are searching for an industrial partner now for a data collection in the gas wells of the San Juan Basin or South Texas.« less

  1. Sub-crustal seismic activity beneath Klyuchevskoy Volcano

    NASA Astrophysics Data System (ADS)

    Carr, M. J.; Droznina, S.; Levin, V. L.; Senyukov, S.

    2013-12-01

    Seismic activity is extremely vigorous beneath the Klyuchevskoy Volcanic Group (KVG). The unique aspect is the distribution in depth. In addition to upper-crustal seismicity, earthquakes take place at depths in excess of 20 km. Similar observations are known in other volcanic regions, however the KVG is unique in both the number of earthquakes and that they occur continuously. Most other instances of deep seismicity beneath volcanoes appear to be episodic or transient. Digital recording of seismic signals started at the KVG in early 2000s.The dense local network reliably locates earthquakes as small as ML~1. We selected records of 20 earthquakes located at depths over 20 km. Selection was based on the quality of the routine locations and the visual clarity of the records. Arrivals of P and S waves were re-picked, and hypocentral parameters re-established. Newl locations fell within the ranges outlined by historical seismicity, confirming the existence of two distinct seismically active regions. A shallower zone is at ~20 km depth, and all hypocenters are to the northeast of KVG, in a region between KVG and Shiveluch volcano. A deeper zone is at ~30 km, and all hypocenters cluster directly beneath the edifice of the Kyuchevskoy volcano. Examination of individual records shows that earthquakes in both zones are tectonic, with well-defined P and S waves - another distinction of the deep seismicity beneath KVG. While the upper seismic zone is unquestionably within the crust, the provenance of the deeper earthquakes is enigmatic. The crustal structure beneath KVG is highly complex, with no agreed-upon definition of the crust-mantle boundary. Rather, a range of values, from under 30 to over 40 km, exists in the literature. Similarly, a range of velocity structures has been reported. Teleseismic receiver functions (RFs) provide a way to position the earthquakes with respect to the crust-mantle boundary. We compare the differential travel times of S and P waves from deep

  2. The Mohorovičić discontinuity beneath the continental crust: An overview of seismic constraints

    NASA Astrophysics Data System (ADS)

    Carbonell, Ramon; Levander, Alan; Kind, Rainer

    2013-12-01

    The seismic signature of the Moho from which geologic and tectonic evolution hypotheses are derived is to a large degree a result of the seismic methodology which has been used to obtain the image. Seismic data of different types, passive source (earthquake) broad-band recordings, and controlled source seismic refraction, densely recorded wide-angle deep seismic reflection, and normal incidence reflection (using VibroseisTM, explosives, or airguns), have contributed to the description of the Moho as a relatively complex transition zone. Of critical importance for the quality and resolution of the seismic image are the acquisition parameters, used in the imaging experiments. A variety of signatures have been obtained for the Moho at different scales generally dependent upon bandwidth of the seismic source. This variety prevents the development of a single universally applicable interpretation. In this way source frequency content, and source and sensor spacing determine the vertical and lateral resolution of the images, respectively. In most cases the different seismic probes provide complementary data that gives a fuller picture of the physical structure of the Moho, and its relationship to a petrologic crust-mantle transition. In regional seismic studies carried out using passive source recordings the Moho is a relatively well defined structure with marked lateral continuity. The characteristics of this boundary change depending on the geology and tectonic evolution of the targeted area. Refraction and wide-angle studies suggest the Moho to be often a relatively sharp velocity contrast, whereas the Moho in coincident high quality seismic reflection images is often seen as the abrupt downward decrease in seismic reflectivity. The origin of the Moho and its relation to the crust-mantle boundary is probably better constrained by careful analysis of its internal details, which can be complex and geographically varied. Unlike the oceanic Moho which is formed in a

  3. Seismic imaging of post-glacial sediments - test study before Spitsbergen expedition

    NASA Astrophysics Data System (ADS)

    Szalas, Joanna; Grzyb, Jaroslaw; Majdanski, Mariusz

    2017-04-01

    This work presents results of the analysis of reflection seismic data acquired from testing area in central Poland. For this experiment we used total number of 147 vertical component seismic stations (DATA-CUBE and Reftek "Texan") with accelerated weight drop (PEG-40). The profile was 350 metres long. It is a part of pilot study for future research project on Spitsbergen. The purpose of the study is to recognise the characteristics of seismic response of post-glacial sediments in order to design the most adequate survey acquisition parameters and processing sequence for data from Spitsbergen. Multiple tests and comparisons have been performed to obtain the best possible quality of seismic image. In this research we examine the influence of receiver interval size, front mute application and surface wave attenuation attempts. Although seismic imaging is the main technique we are planning to support this analysis with additional data from traveltime tomography, MASW and other a priori information.

  4. Seismic tomography as a tool for measuring stress in mines

    USGS Publications Warehouse

    Scott, Douglas F.; Williams, T.J.; Denton, D.K.; Friedel, M.J.

    1999-01-01

    Spokane Research Center personnel have been investigating the use of seismic tomography to monitor the behavior of a rock mass, detect hazardous ground conditions and assess the mechanical integrity of a rock mass affected by mining. Seismic tomography can be a valuable tool for determining relative stress in deep, >1,220-m (>4,000-ft), underground pillars. If high-stress areas are detected, they can be destressed prior to development or they can be avoided. High-stress areas can be monitored with successive seismic surveys to determine if stress decreases to a level where development can be initiated safely. There are several benefits to using seismic tomography to identify high stress in deep underground pillars. The technique is reliable, cost-effective, efficient and noninvasive. Also, investigators can monitor large rock masses, as well as monitor pillars during the mining cycle. By identifying areas of high stress, engineers will be able to assure that miners are working in a safer environment.Spokane Research Center personnel have been investigating the use of seismic tomography to monitor the behavior of a rock mass, detect hazardous ground conditions and assess the mechanical integrity of a rock mass affected by mining. Seismic tomography can be a valuable tool for determining relative stress in deep, >1,200-m (>4,000-ft), underground pillars. If high-stress areas are detected, they can be destressed prior to development or they can be avoided. High-stress areas can be monitored with successive seismic surveys to determine if stress decreases to a level where development can be initiated safely. There are several benefits to using seismic tomography to identify high stress in deep underground pillars. The technique is reliable, cost-effective, efficient and noninvasive. Also, investigators can monitor large rock masses, as well as monitor pillars during the mining cycle. By identifying areas of high stress. engineers will be able to assure that miners are

  5. High resolution seismic tomography imaging of Ireland with quarry blast data

    NASA Astrophysics Data System (ADS)

    Arroucau, P.; Lebedev, S.; Bean, C. J.; Grannell, J.

    2017-12-01

    Local earthquake tomography is a well established tool to image geological structure at depth. That technique, however, is difficult to apply in slowly deforming regions, where local earthquakes are typically rare and of small magnitude, resulting in sparse data sampling. The natural earthquake seismicity of Ireland is very low. That due to quarry and mining blasts, on the other hand, is high and homogeneously distributed. As a consequence, and thanks to the dense and nearly uniform coverage achieved in the past ten years by temporary and permanent broadband seismological stations, the quarry blasts offer an alternative approach for high resolution seismic imaging of the crust and uppermost mantle beneath Ireland. We detected about 1,500 quarry blasts in Ireland and Northern Ireland between 2011 and 2014, for which we manually picked more than 15,000 P- and 20,000 S-wave first arrival times. The anthropogenic, explosive origin of those events was unambiguously assessed based on location, occurrence time and waveform characteristics. Here, we present a preliminary 3D tomographic model obtained from the inversion of 3,800 P-wave arrival times associated with a subset of 500 events observed in 2011, using FMTOMO tomographic code. Forward modeling is performed with the Fast Marching Method (FMM) and the inverse problem is solved iteratively using a gradient-based subspace inversion scheme after careful selection of damping and smoothing regularization parameters. The results illuminate the geological structure of Ireland from deposit to crustal scale in unprecedented detail, as demonstrated by sensitivity analysis, source relocation with the 3D velocity model and comparisons with surface geology.

  6. Fault Imaging with High-Resolution Seismic Reflection for Earthquake Hazard and Geothermal Resource Assessment in Reno, Nevada

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

    Frary, Roxanna

    2012-05-05

    The Truckee Meadows basin is situated adjacent to the Sierra Nevada microplate, on the western boundary of the Walker Lane. Being in the transition zone between a range-front normal fault on the west and northwest-striking right-lateral strike slip faults to the east, there is no absence of faulting in this basin. The Reno- Sparks metropolitan area is located in this basin, and with a signi cant population living here, it is important to know where these faults are. High-resolution seismic reflection surveys are used for the imaging of these faults along the Truckee River, across which only one fault wasmore » previously mapped, and in southern Reno near and along Manzanita Lane, where a swarm of short faults has been mapped. The reflection profiles constrain the geometries of these faults, and suggest additional faults not seen before. Used in conjunction with depth to bedrock calculations and gravity measurements, the seismic reflection surveys provide de nitive locations of faults, as well as their orientations. O sets on these faults indicate how active they are, and this in turn has implications for seismic hazard in the area. In addition to seismic hazard, the faults imaged here tell us something about the conduits for geothermal fluid resources in Reno.« less

  7. Seismic anisotropy in deforming salt bodies

    NASA Astrophysics Data System (ADS)

    Prasse, P.; Wookey, J. M.; Kendall, J. M.; Dutko, M.

    2017-12-01

    Salt is often involved in forming hydrocarbon traps. Studying salt dynamics and the deformation processes is important for the exploration industry. We have performed numerical texture simulations of single halite crystals deformed by simple shear and axial extension using the visco-plastic self consistent approach (VPSC). A methodology from subduction studies to estimate strain in a geodynamic simulation is applied to a complex high-resolution salt diapir model. The salt diapir deformation is modelled with the ELFEN software by our industrial partner Rockfield, which is based on a finite-element code. High strain areas at the bottom of the head-like strctures of the salt diapir show high amount of seismic anisotropy due to LPO development of halite crystals. The results demonstrate that a significant degree of seismic anisotropy can be generated, validating the view that this should be accounted for in the treatment of seismic data in, for example, salt diapir settings.

  8. Angola Seismicity MAP

    NASA Astrophysics Data System (ADS)

    Neto, F. A. P.; Franca, G.

    2014-12-01

    The purpose of this job was to study and document the Angola natural seismicity, establishment of the first database seismic data to facilitate consultation and search for information on seismic activity in the country. The study was conducted based on query reports produced by National Institute of Meteorology and Geophysics (INAMET) 1968 to 2014 with emphasis to the work presented by Moreira (1968), that defined six seismogenic zones from macro seismic data, with highlighting is Zone of Sá da Bandeira (Lubango)-Chibemba-Oncócua-Iona. This is the most important of Angola seismic zone, covering the epicentral Quihita and Iona regions, geologically characterized by transcontinental structure tectono-magmatic activation of the Mesozoic with the installation of a wide variety of intrusive rocks of ultrabasic-alkaline composition, basic and alkaline, kimberlites and carbonatites, strongly marked by intense tectonism, presenting with several faults and fractures (locally called corredor de Lucapa). The earthquake of May 9, 1948 reached intensity VI on the Mercalli-Sieberg scale (MCS) in the locality of Quihita, and seismic active of Iona January 15, 1964, the main shock hit the grade VI-VII. Although not having significant seismicity rate can not be neglected, the other five zone are: Cassongue-Ganda-Massano de Amorim; Lola-Quilengues-Caluquembe; Gago Coutinho-zone; Cuima-Cachingues-Cambândua; The Upper Zambezi zone. We also analyzed technical reports on the seismicity of the middle Kwanza produced by Hidroproekt (GAMEK) region as well as international seismic bulletins of the International Seismological Centre (ISC), United States Geological Survey (USGS), and these data served for instrumental location of the epicenters. All compiled information made possible the creation of the First datbase of seismic data for Angola, preparing the map of seismicity with the reconfirmation of the main seismic zones defined by Moreira (1968) and the identification of a new seismic

  9. First results of a high resolution reflection seismic survey of the Central Northern Venezuelan Shelf

    NASA Astrophysics Data System (ADS)

    Avila, J.; van Welden, A.; Audemard, F.; de Batist, M.; Beck, C.; Scientific Party, G.

    2008-05-01

    In September - November 2007 the first high resolution marine seismic campaign on the North-Central coast of Venezuela was carried out between Cabo Codera and Golfo Triste. The principal aim of this work was to characterize the active San Sebastian Fault (SSF) and to analyze Cenozoic sedimentation on the Venezuela shelf focusing on: i) effects of active tectonics and ii) coastal landslides/flashflood deposits related to 1999 Vargas catastrophic event or to similar phenomena. Data were acquired onboard R/V GUAIQUERI II from the Oceanographic Institute of the Oriente University. The seismic source was a "CENTIPEDE" sparker (RCGM) operated between 300 and 600 J, 1.3 kHz main frequency. We used a single-channel streamer with 10 hydrophones. In total, 49 seismic profiles were collected, with a cumulative length of 1000 km approximately. In these seismic profiles we identified and separated the deposits into three main units. Unit (U1) comprises low energy reflectors mainly dipping in southward direction (i.e. toward the coast bounded by the San Sebastian Fault). This unit also includes a number of isolated acoustic anomalies, which we tentatively interpret as coral reefs. Its top is defined as Basal Erosional Discontinuity (BED) onto which Unit 2 (U2) deposits are onlapping. U2 is acoustically well-stratified, with strong reflectors. Gradual variations in thickness and a wavy configuration allow us to interpret U2 as probably Quaternary current-related deposits. Last Unit (U3) was defined on the Venezuela shelf and corresponds to prograding sequences probably related to the terrigenous input of the Tuy River. Impact of eustatic fluctuations on these deposits are discussed. The data were also used to construct a simplified bathymetry of the studied area. The lateral transition from the western Cariaco-Tuy pull-apart basin to the (single) SSF was clearly imaged (mostly folds and gravity faults). The survey also displayed prograding sediments bodies in La Tortuga Shelf

  10. Two types of seismicity accompanying hydraulic fracturing in Harrison County, Ohio - implications for seismic hazard and seismogenic mechanism

    NASA Astrophysics Data System (ADS)

    Kozlowska, M.; Brudzinski, M.; Friberg, P. A.; Skoumal, R.; Baxter, N. D.; Currie, B.

    2017-12-01

    While induced seismicity in the United States has mainly been attributed to wastewater disposal, Eastern Ohio has provided cases of seismicity induced by both hydraulic fracturing (HF) and wastewater disposal. In this study, we investigate five cases of seismicity associated with HF in Harrison County, OH. Because of their temporal and spatial isolation from other injection activities, this provide an ideal setting for studying the relationships between high pressure injection and earthquakes. Our analysis reveals two distinct groups of seismicity. Deeper earthquakes occur in the Precambrian crystalline basement, reach larger magnitudes (M>2), have lower b-values (<1), and continue for weeks following stimulation shut down. Shallower earthquakes, on the other hand, occur in Paleozoic sedimentary rocks 400 m below HF, are limited to smaller magnitudes (M<1), have higher b-values (>1.5), and lack post-stimulation activity. We seek the physical explanation of observed difference in earthquakes character and hypothesize that the maturity of faults is the main factor determining sequences b-values. Based on published results of laboratory experiments and fault modeling, we interpret the deep seismicity as slip on more mature faults in the older crystalline rocks and the shallow seismicity as slip on immature faults in the younger, lower viscosity sedimentary rocks. This suggests that HF inducing seismicity on deeper, more mature faults poses higher seismic hazards. The analysis of water and gas production data from these wells suggests that wells inducing deeper seismicity produced more water than wells with shallow seismicity. This indicates more extensive hydrologic connections outside the target reservoir, which may explain why gas production drops more quickly for wells with deeper seismicity. Despite these indications that hydraulic pressure fluctuations induce seismicity, we also find only 2-3 hours between onset of stimulation of HF wells and seismicity that is

  11. Seismic measurements of the internal properties of fault zones

    USGS Publications Warehouse

    Mooney, W.D.; Ginzburg, A.

    1986-01-01

    The internal properties within and adjacent to fault zones are reviewed, principally on the basis of laboratory, borehole, and seismic refraction and reflection data. The deformation of rocks by faulting ranges from intragrain microcracking to severe alteration. Saturated microcracked and mildly fractured rocks do not exhibit a significant reduction in velocity, but, from borehole measurements, densely fractured rocks do show significantly reduced velocities, the amount of reduction generally proportional to the fracture density. Highly fractured rock and thick fault gouge along the creeping portion of the San Andreas fault are evidenced by a pronounced seismic low-velocity zone (LVZ), which is either very thin or absent along locked portions of the fault. Thus there is a correlation between fault slip behavior and seismic velocity structure within the fault zone; high pore pressure within the pronounced LVZ may be conductive to fault creep. Deep seismic reflection data indicate that crustal faults sometimes extend through the entire crust. Models of these data and geologic evidence are consistent with a composition of deep faults consisting of highly foliated, seismically anisotropic mylonites. ?? 1986 Birkha??user Verlag, Basel.

  12. Seismic signal and noise on Europa

    NASA Astrophysics Data System (ADS)

    Panning, Mark; Stähler, Simon; Bills, Bruce; Castillo Castellanos, Jorge; Huang, Hsin-Hua; Husker, Allen; Kedar, Sharon; Lorenz, Ralph; Pike, William T.; Schmerr, Nicholas; Tsai, Victor; Vance, Steven

    2017-10-01

    Seismology is one of our best tools for detailing interior structure of planetary bodies, and a seismometer is included in the baseline and threshold mission design for the upcoming Europa Lander mission. Guiding mission design and planning for adequate science return, though, requires modeling of both the anticipated signal and noise. Assuming ice seismicity on Europa behaves according to statistical properties observed in Earth catalogs and scaling cumulative seismic moment release to the moon, we can simulate long seismic records and estimate background noise and peak signal amplitudes (Panning et al., 2017). This suggests a sensitive instrument comparable to many broadband terrestrial instruments or the SP instrument from the InSight mission to Mars will be able to record signals, while high frequency geophones are likely inadequate. We extend this analysis to also begin incorporation of spatial and temporal variation due to the tidal cycle, which can help inform landing site selection. We also begin exploration of how chaotic terrane at the bottom of the ice shell and inter-ice heterogeneities (i.e. internal melt structures) may affect anticipated seismic observations using 2D numerical seismic simulations.M. P. Panning, S. C. Stähler, H.-H. Huang, S. D. Vance, S. Kedar, V. C. Tsai, W. T. Pike, R. D. Lorenz, “Expected seismicity and the seismic noise environment of Europa,” J. Geophys. Res., in revision, 2017.

  13. Using micro-seismicity and seismic velocities to map subsurface geologic and hydrologic structure within the Coso geothermal field, California

    USGS Publications Warehouse

    Kaven, Joern Ole; Hickman, Stephen H.; Davatzes, Nicholas C.

    2012-01-01

    Geothermal reservoirs derive their capacity for fluid and heat transport in large part from faults and fractures. Micro-seismicity generated on such faults and fractures can be used to map larger fault structures as well as secondary fractures that add access to hot rock, fluid storage and recharge capacity necessary to have a sustainable geothermal resource. Additionally, inversion of seismic velocities from micro-seismicity permits imaging of regions subject to the combined effects of fracture density, fluid pressure and steam content, among other factors. We relocate 14 years of seismicity (1996-2009) in the Coso geothermal field using differential travel times and simultaneously invert for seismic velocities to improve our knowledge of the subsurface geologic and hydrologic structure. We utilize over 60,000 micro-seismic events using waveform cross-correlation to augment to expansive catalog of P- and S-wave differential travel times recorded at Coso. We further carry out rigorous uncertainty estimation and find that our results are precise to within 10s of meters of relative location error. We find that relocated micro-seismicity outlines prominent, through-going faults in the reservoir in some cases. We also find that a significant portion of seismicity remains diffuse and does not cluster into more sharply defined major structures. The seismic velocity structure reveals heterogeneous distributions of compressional (Vp) and shear (Vs) wave speed, with Vp generally lower in the main field when compared to the east flank and Vs varying more significantly in the shallow portions of the reservoir. The Vp/Vs ratio appears to outline the two main compartments of the reservoir at depths of -0.5 to 1.5 km (relative to sea-level), with a ridge of relatively high Vp/Vs separating the main field from the east flank. In the deeper portion of the reservoir this ridge is less prominent. Our results indicate that high-precision relocations of micro-seismicity can provide

  14. A High-Resolution Seismic Survey Across the State Line fault, NV

    NASA Astrophysics Data System (ADS)

    Beachly, M.; Cox, C. M.; Saldana, S. C.; Snelson, C. M.; Taylor, W. J.; Robins, C.; Davis, R.; Stropky, M.; Phillips, R.; Cothrun, C.

    2007-12-01

    During the summer of 2007, an investigation of the faulting in Stewart Valley was under taken, located within the central Basin and Range province ~90 km west of Las Vegas, Nevada. The goal of this study was to resolve the seismic hazard potential of the State Line fault, a right-lateral strike-slip fault that runs the length of Stewart Valley. Four seismic reflection lines were acquired, two perpendicular and two parallel to the State Line fault. What is presented is an analysis of the western and eastern seismic lines parallel to the State Line fault. The western line was acquired utilizing a 144-channel geode system with each of the 4.5 Hz vertical geophones set out at 5 m intervals to form a 715 m long profile. The eastern line employed 120 of these geophones in a 595 m long profile. A mini-vibroseis served as the seismic source every ten meters, between geophones. The vibroseis was programmed to produce an 8 s linear sweep from 20-160 Hz. Three sweeps were recorded at each shot location without acquisition filters at a sampling rate of 0.5 ms. The three shot gathers were then stacked at each location to reduce noise. The data collected had minimal noise, although; during the processing of the eastern line a notch filtered was used to remove the 60 Hz noise created by adjacent power line. These lines, acquired parallel to the State Line fault, contain matching features that serve to determine how much lateral displacement the fault has undergone. The amount of the displacement can indicate how active the fault is, and thus, what magnitude of earthquake can be expected in the future. This will in turn contribute to determining the seismic hazard potential for southern Nevada. A preliminary interpretation of the seismic reflection sections indicates an average displacement of about 20 - 38 m with greater displacement in the deeper sections of the image. The shallow depth displacement calculations are consistent with previous work in the area. The State Line fault

  15. Full-waveform seismic tomography of the Vrancea, Romania, subduction region

    NASA Astrophysics Data System (ADS)

    Baron, Julie; Morelli, Andrea

    2017-12-01

    The Vrancea region is one of the few locations of deep seismicity in Europe. Seismic tomography has been able to map lithospheric downwelling, but has not been able yet to clearly discriminate between competing geodynamic interpretations of the geological and geophysical evidence available. We study the seismic structure of the Vrancea subduction zone, using adjoint-based, full-waveform tomography to map the 3D vP and vS structure in detail. We use the database that was built during the CALIXTO (Carpathian Arc Lithosphere X-Tomography) temporary experiment, restricted to the broadband sensors and local intermediate-depth events. We fit waveforms with a cross-correlation misfit criterion in separate time windows around the expected P and S arrivals, and perform 17 iterations of vP and vS model updates (altogether, requiring about 16 million CPU hours) before reaching stable convergence. Among other features, our resulting model shows a nearly vertical, high-velocity body, that overlaps with the distribution of seismicity in its northeastern part. In its southwestern part, a slab appears to dip less steeply to the NW, and is suggestive of ongoing - or recently concluded - subduction geodynamic processes. Joint inversion for vP and vS allow us to address the vP/vS ratio distribution, that marks high vP/vS in the crust beneath the Focsani sedimentary basin - possibly due to high fluid pressure - and a low vP/vS edge along the lower plane of the subducting lithosphere, that in other similar environment has been attributed to dehydration of serpentine in the slab. In spite of the restricted amount of data available, and limitations on the usable frequency pass-band, full-waveform inversion reveals its potential to improve the general quality of imaging with respect to other tomographic techniques - although at a sensible cost in terms of computing resources. Our study also shows that re-analysis of legacy data sets with up-to-date techniques may bring new, useful

  16. Evaluation of a dense seismic array for acquisition of high quality data in the ACROSS observation

    NASA Astrophysics Data System (ADS)

    Tsuruga, K.; Kunitomo, T.; Hasada, Y.; Kumazawa, M.; Shigeta, N.; Kasahara, J.

    2004-12-01

    ACROSS is an active monitoring methodology to detect any subtle temporal change of physical properties in the Earth's interior. We demonstrate the potentiality of the ACROSS observation with a dense sensor array. We have conducted a dense seismic array observation at the distance of 1 km from the ACROSS source since 2003. The array is composed of 36 three-component velocity seismometers buried at 1.8 m deep in an area 25 m square. All the data are recorded accurately referring to a GPS clock. We derived and analyzed a transfer function (TF) from the source to a receiver by the following steps: (1) evaluating a force vector as source characteristics, (2) converting the observed data to the displacement vectors by incorporating all the corrections of the instruments, (3) stacking the observed data for an enough time to suppress the temporal noise, (4) extracting ACROSS signal and evaluating noise level, (5) representing TF in a tensor form with the estimated errors, (6) slant-stacking with variable ray parameters, (7) estimating the travel times and amplitudes of the wave arrivals by Sompi Event Analysis (Hasada et al., 2001) and representing the result by a pulse sequence, and (8) deriving the polarization vector for each arrival to identify all the wave modes. We analyzed TF of SH-wave component from 16 to 20 Hz as an example. We obtained good quality TF with S/N ratio up to 104 by stacking for 12 days at the step (3). The spatial noise originated from the local heterogeneity around the array was eliminated by the step (6). Several arrivals were recognized within the time windows from 0.6 to 1.8 s. The maximum amplitude of event traces was detected at the travel time of 1.064 s with a ray parameter of 7.9x10-4 s/m. We also found the scattered waves probably generated by the heterogeneities around the array. The ACROSS dense array observation would provide a lot of information on the underground heterogeneities. Consequently, we have the important and challenging

  17. Strong S-wave attenuation and actively degassing magma beneath Taal volcano, Philippines, inferred from source location analysis using high-frequency seismic amplitudes

    NASA Astrophysics Data System (ADS)

    Kumagai, H.; Lacson, R. _Jr., Jr.; Maeda, Y.; Figueroa, M. S., II; Yamashina, T.

    2014-12-01

    Taal volcano, Philippines, is one of the world's most dangerous volcanoes given its history of explosive eruptions and its close proximity to populated areas. A key feature of these eruptions is that the eruption vents were not limited to Main Crater but occurred on the flanks of Volcano Island. This complex eruption history and the fact that thousands of people inhabit the island, which has been declared a permanent danger zone, together imply an enormous potential for disasters. The Philippine Institute of Volcanology and Seismology (PHIVOLCS) constantly monitors Taal, and international collaborations have conducted seismic, geodetic, electromagnetic, and geochemical studies to investigate the volcano's magma system. Realtime broadband seismic, GPS, and magnetic networks were deployed in 2010 to improve monitoring capabilities and to better understand the volcano. The seismic network has recorded volcano-tectonic (VT) events beneath Volcano Island. We located these VT events based on high-frequency seismic amplitudes, and found that some events showed considerable discrepancies between the amplitude source locations and hypocenters determined by using onset arrival times. Our analysis of the source location discrepancies points to the existence of a region of strong S-wave attenuation near the ground surface beneath the east flank of Volcano Island. This region is beneath the active fumarolic area and above sources of pressure contributing inflation and deflation, and it coincides with a region of high electrical conductivity. The high-attenuation region matches that inferred from an active-seismic survey conducted at Taal in 1993. Our results, synthesized with previous results, suggest that this region represents actively degassing magma near the surface, and imply a high risk of future eruptions on the east flank of Volcano Island.

  18. Preliminary interpretation of high resolution 3D seismic data from offshore Mt. Etna, Italy

    NASA Astrophysics Data System (ADS)

    Gross, F.; Krastel, S.; Chiocci, F. L.; Ridente, D.; Cukur, D.; Bialas, J.; Papenberg, C. A.; Crutchley, G.; Koch, S.

    2013-12-01

    In order to gain knowledge about subsurface structures and its correlation to seafloor expressions, a hydro-acoustic dataset was collected during RV Meteor Cruise M86/2 (December 2011/January 2012) in Messina Straits and offshore Mt. Etna. Especially offshore Mt. Etna, the data reveals an obvious connection between subsurface structures and previously known morphological features at the sea floor. Therefore a high resolution 3D seismic dataset was acquired between Riposto Ridge and Catania Canyon close to the shore of eastern Sicily. The study area is characterized by a major structural high, which hosts several ridge-like features at the seafloor. These features are connected to a SW-NE trending fault system. The ridges are bended in their NE-SW direction and host major escarpments at the seafloor. Furthermore they are located directly next to a massive amphitheater structure offshore Mt. Etna with slope gradients of up to 35°, which is interpreted as remnants of a massive submarine mass wasting event off Sicily. The new 3D seismic dataset allows an in depth analysis of the ongoing deformation of the east flank of Mt. Etna.

  19. OGS improvements in 2012 in running the Northeastern Italy Seismic Network: the Ferrara VBB borehole seismic station

    NASA Astrophysics Data System (ADS)

    Pesaresi, Damiano; Romanelli, Marco; Barnaba, Carla; Bragato, Pier Luigi; Durì, Giorgio

    2013-04-01

    The Centro di Ricerche Sismologiche (CRS, Seismological Research Center) of the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS, Italian National Institute for Oceanography and Experimental Geophysics) in Udine (Italy) after the strong earthquake of magnitude M=6.4 occurred in 1976 in the Italian Friuli-Venezia Giulia region, started to operate the Northeastern Italy Seismic Network: it currently consists of 17 very sensitive broad band and 18 simpler short period seismic stations, all telemetered to and acquired in real time at the OGS-CRS data center in Udine. Real time data exchange agreements in place with other Italian, Slovenian, Austrian and Swiss seismological institutes lead to a total number of about 100 seismic stations acquired in real time, which makes the OGS the reference institute for seismic monitoring of Northeastern Italy. The southwestern edge of the OGS seismic network stands on the Po alluvial basin: earthquake localization and characterization in this area is affected by the presence of soft alluvial deposits. OGS ha already experience in running a local seismic network in high noise conditions making use of borehole installations in the case of the micro-seismicity monitoring of a local gas storage site for a private company. Following the ML=5.9 earthquake that struck the Emilia region around Ferrara in Northern Italy on May 20, 2012 at 02:03:53 UTC, a cooperation of Istituto Nazionale di Geofisica e Vulcanologia, OGS, the Comune di Ferrara and the University of Ferrara lead to the reinstallation of a previously existing very broad band (VBB) borehole seismic station in Ferrara. The aim of the OGS intervention was on one hand to extend its real time seismic monitoring capabilities toward South-West, including Ferrara and its surroundings, and on the other hand to evaluate the seismic response at the site. We will describe improvements in running the Northeastern Italy Seismic Network, including details of the Ferrara VBB

  20. From Geodetic Imaging of Seismic and Aseismic Fault Slip to Dynamic Modeling of the Seismic Cycle

    NASA Astrophysics Data System (ADS)

    Avouac, Jean-Philippe

    2015-05-01

    Understanding the partitioning of seismic and aseismic fault slip is central to seismotectonics as it ultimately determines the seismic potential of faults. Thanks to advances in tectonic geodesy, it is now possible to develop kinematic models of the spatiotemporal evolution of slip over the seismic cycle and to determine the budget of seismic and aseismic slip. Studies of subduction zones and continental faults have shown that aseismic creep is common and sometimes prevalent within the seismogenic depth range. Interseismic coupling is generally observed to be spatially heterogeneous, defining locked patches of stress accumulation, to be released in future earthquakes or aseismic transients, surrounded by creeping areas. Clay-rich tectonites, high temperature, and elevated pore-fluid pressure seem to be key factors promoting aseismic creep. The generally logarithmic time evolution of afterslip is a distinctive feature of creeping faults that suggests a logarithmic dependency of fault friction on slip rate, as observed in laboratory friction experiments. Most faults can be considered to be paved with interlaced patches where the friction law is either rate-strengthening, inhibiting seismic rupture propagation, or rate-weakening, allowing for earthquake nucleation. The rate-weakening patches act as asperities on which stress builds up in the interseismic period; they might rupture collectively in a variety of ways. The pattern of interseismic coupling can help constrain the return period of the maximum- magnitude earthquake based on the requirement that seismic and aseismic slip sum to match long-term slip. Dynamic models of the seismic cycle based on this conceptual model can be tuned to reproduce geodetic and seismological observations. The promise and pitfalls of using such models to assess seismic hazard are discussed.

  1. Quantitative modeling of reservoir-triggered seismicity

    NASA Astrophysics Data System (ADS)

    Hainzl, S.; Catalli, F.; Dahm, T.; Heinicke, J.; Woith, H.

    2017-12-01

    Reservoir-triggered seismicity might occur as the response to the crustal stress caused by the poroelastic response to the weight of the water volume and fluid diffusion. Several cases of high correlations have been found in the past decades. However, crustal stresses might be altered by many other processes such as continuous tectonic stressing and coseismic stress changes. Because reservoir-triggered stresses decay quickly with distance, even tidal or rainfall-triggered stresses might be of similar size at depth. To account for simultaneous stress sources in a physically meaningful way, we apply a seismicity model based on calculated stress changes in the crust and laboratory-derived friction laws. Based on the observed seismicity, the model parameters can be determined by maximum likelihood method. The model leads to quantitative predictions of the variations of seismicity rate in space and time which can be used for hypothesis testing and forecasting. For case studies in Talala (India), Val d'Agri (Italy) and Novy Kostel (Czech Republic), we show the comparison of predicted and observed seismicity, demonstrating the potential and limitations of the approach.

  2. Development of Vertical Cable Seismic System (2)

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    The vertical cable seismic is one of the reflection seismic methods. It uses hydrophone arrays vertically moored from the seafloor to record acoustic waves generated by surface, deep-towed or ocean bottom sources. Analyzing the reflections from the sub-seabed, we could look into the subsurface structure. This type of survey is generally called VCS (Vertical Cable Seismic). Because VCS is an efficient high-resolution 3D seismic survey method for a spatially-bounded area, we proposed the method for the hydrothermal deposit survey tool development program that the Ministry of Education, Culture, Sports, Science and Technology (MEXT) started in 2009. We are now developing a VCS system, including not only data acquisition hardware but data processing and analysis technique. Our first experiment of VCS surveys has been carried out in Lake Biwa, JAPAN in November 2009 for a feasibility study. Prestack depth migration is applied to the 3D VCS data to obtain a high quality 3D depth volume. Based on the results from the feasibility study, we have developed two autonomous recording VCS systems. After we carried out a trial experiment in the actual ocean at a water depth of about 400m and we carried out the second VCS survey at Iheya Knoll with a deep-towed source. In this survey, we could establish the procedures for the deployment/recovery of the system and could examine the locations and the fluctuations of the vertical cables at a water depth of around 1000m. The acquired VCS data clearly shows the reflections from the sub-seafloor. Through the experiment, we could confirm that our VCS system works well even in the severe circumstances around the locations of seafloor hydrothermal deposits. We have carried out two field surveys in 2011. One is a 3D survey with a boomer for a high-resolution surface source and the other one for an actual field survey in the Izena Cauldron an active hydrothermal area in the Okinawa Trough. Through these surveys, we have confirmed that the

  3. Passive seismic imaging based on seismic interferometry: method and its application to image the structure around the 2013 Mw6.6 Lushan earthquake

    NASA Astrophysics Data System (ADS)

    Gu, N.; Zhang, H.

    2017-12-01

    Seismic imaging of fault zones generally involves seismic velocity tomography using first arrival times or full waveforms from earthquakes occurring around the fault zones. However, in most cases seismic velocity tomography only gives smooth image of the fault zone structure. To get high-resolution structure of the fault zones, seismic migration using active seismic data needs to be used. But it is generally too expensive to conduct active seismic surveys, even for 2D. Here we propose to apply the passive seismic imaging method based on seismic interferometry to image fault zone detailed structures. Seismic interferometry generally refers to the construction of new seismic records for virtual sources and receivers by cross correlating and stacking the seismic records on physical receivers from physical sources. In this study, we utilize seismic waveforms recorded on surface seismic stations for each earthquake to construct zero-offset seismic record at each earthquake location as if there was a virtual receiver at each earthquake location. We have applied this method to image the fault zone structure around the 2013 Mw6.6 Lushan earthquake. After the occurrence of the mainshock, a 29-station temporary array is installed to monitor aftershocks. In this study, we first select aftershocks along several vertical cross sections approximately normal to the fault strike. Then we create several zero-offset seismic reflection sections by seismic interferometry with seismic waveforms from aftershocks around each section. Finally we migrate these zero-offset sections to create seismic structures around the fault zones. From these migration images, we can clearly identify strong reflectors, which correspond to major reverse fault where the mainshock occurs. This application shows that it is possible to image detailed fault zone structures with passive seismic sources.

  4. Evaluation of induced seismicity forecast models in the Induced Seismicity Test Bench

    NASA Astrophysics Data System (ADS)

    Király, Eszter; Gischig, Valentin; Zechar, Jeremy; Doetsch, Joseph; Karvounis, Dimitrios; Wiemer, Stefan

    2016-04-01

    Induced earthquakes often accompany fluid injection, and the seismic hazard they pose threatens various underground engineering projects. Models to monitor and control induced seismic hazard with traffic light systems should be probabilistic, forward-looking, and updated as new data arrive. Here, we propose an Induced Seismicity Test Bench to test and rank such models. We apply the test bench to data from the Basel 2006 and Soultz-sous-Forêts 2004 geothermal stimulation projects, and we assess forecasts from two models that incorporate a different mix of physical understanding and stochastic representation of the induced sequences: Shapiro in Space (SiS) and Hydraulics and Seismics (HySei). SiS is based on three pillars: the seismicity rate is computed with help of the seismogenic index and a simple exponential decay of the seismicity; the magnitude distribution follows the Gutenberg-Richter relation; and seismicity is distributed in space based on smoothing seismicity during the learning period with 3D Gaussian kernels. The HySei model describes seismicity triggered by pressure diffusion with irreversible permeability enhancement. Our results show that neither model is fully superior to the other. HySei forecasts the seismicity rate well, but is only mediocre at forecasting the spatial distribution. On the other hand, SiS forecasts the spatial distribution well but not the seismicity rate. The shut-in phase is a difficult moment for both models in both reservoirs: the models tend to underpredict the seismicity rate around, and shortly after, shut-in. Ensemble models that combine HySei's rate forecast with SiS's spatial forecast outperform each individual model.

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

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

    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.

  6. Seismicity, faulting, and structure of the Koyna-Warna seismic region, Western India from local earthquake tomography and hypocenter locations

    USGS Publications Warehouse

    Dixit, Madan M.; Kumar, Sanjay; Catchings, Rufus D.; Suman, K.; Sarkar, Dipankar; Sen, M.K.

    2014-01-01

    Although seismicity near Koyna Reservoir (India) has persisted for ~50 years and includes the largest induced earthquake (M 6.3) reported worldwide, the seismotectonic framework of the area is not well understood. We recorded ~1800 earthquakes from 6 January 2010 to 28 May 2010 and located a subset of 343 of the highest-quality earthquakes using the tomoDD code of Zhang and Thurber (2003) to better understand the framework. We also inverted first arrivals for 3-D Vp, Vs, and Vp/Vs and Poisson's ratio tomography models of the upper 12 km of the crust. Epicenters for the recorded earthquakes are located south of the Koyna River, including a high-density cluster that coincides with a shallow depth (<1.5 km) zone of relatively high Vp and low Vs (also high Vp/Vs and Poisson's ratios) near Warna Reservoir. This anomalous zone, which extends near vertically to at least 8 km depth and laterally northward at least 15 km, is likely a water-saturated zone of faults under high pore pressures. Because many of the earthquakes occur on the periphery of the fault zone, rather than near its center, the observed seismicity-velocity correlations are consistent with the concept that many of the earthquakes nucleate in fractures adjacent to the main fault zone due to high pore pressure. We interpret our velocity images as showing a series of northwest trending faults locally near the central part of Warna Reservoir and a major northward trending fault zone north of Warna Reservoir.

  7. Estimating Strain Accumulation in the New Madrid and Wabash Valley Seismic Zones

    NASA Astrophysics Data System (ADS)

    Craig, T. J.; Calais, E.

    2014-12-01

    The mechanical behaviour -- and hence earthquake potential -- of faults in continental interiors is a question of critical importance for the resultant seismic hazard, but no consensus has yet been reached on this controversial topic. The debate has focused on the central and eastern United States, in particular the New Madrid Seismic Zone, struck by three magnitude 7 or greater earthquakes in 1811--1812, and to a lesser extent the Wabash Valley Seismic Zone just to the north. A key aspect of this issue is the rate at which strain is currently accruing on those faults in the plate interior, a quantity that remains debated. Understanding if the present-day strain rates indicate sufficient motion to account for the historical and paleoseismological earthquakes by steady-state fault behaviour, or if strain accumulation is time-dependent in this area, is critical for investigating the causative process driving this seismicity in the plate interior, and how regional strain reflects the interplay between stresses arising from different geological processes. Here we address this issue with an analysis of up to 14 years of continuous GPS data from a network of 200 sites in the central United States centred on the New Madrid and Wabash Valley seismic zones. We find that high-quality sites in these regions show motions that are consistently within the 95% confidence limit of zero deformation relative to a rigid background. These results place an upper bound on regional strain accrual of 0.2 mm/yr and 0.5 mm/yr in the New Madrid and Wabash Valley Seismic Zones, respectively. These results, together with increasing evidence for temporal clustering and spatial migration of earthquake sequences in continental interiors, indicate that either tectonic loading rates or fault properties vary with time in the NMSZ and possibly plate-wide.

  8. Gas and seismicity within the Istanbul seismic gap.

    PubMed

    Géli, L; Henry, P; Grall, C; Tary, J-B; Lomax, A; Batsi, E; Riboulot, V; Cros, E; Gürbüz, C; Işık, S E; Sengör, A M C; Le Pichon, X; Ruffine, L; Dupré, S; Thomas, Y; Kalafat, D; Bayrakci, G; Coutellier, Q; Regnier, T; Westbrook, G; Saritas, H; Çifçi, G; Çağatay, M N; Özeren, M S; Görür, N; Tryon, M; Bohnhoff, M; Gasperini, L; Klingelhoefer, F; Scalabrin, C; Augustin, J-M; Embriaco, D; Marinaro, G; Frugoni, F; Monna, S; Etiope, G; Favali, P; Bécel, A

    2018-05-01

    Understanding micro-seismicity is a critical question for earthquake hazard assessment. Since the devastating earthquakes of Izmit and Duzce in 1999, the seismicity along the submerged section of North Anatolian Fault within the Sea of Marmara (comprising the "Istanbul seismic gap") has been extensively studied in order to infer its mechanical behaviour (creeping vs locked). So far, the seismicity has been interpreted only in terms of being tectonic-driven, although the Main Marmara Fault (MMF) is known to strike across multiple hydrocarbon gas sources. Here, we show that a large number of the aftershocks that followed the M 5.1 earthquake of July, 25 th 2011 in the western Sea of Marmara, occurred within a zone of gas overpressuring in the 1.5-5 km depth range, from where pressurized gas is expected to migrate along the MMF, up to the surface sediment layers. Hence, gas-related processes should also be considered for a complete interpretation of the micro-seismicity (~M < 3) within the Istanbul offshore domain.

  9. Seismic Noise Characterization in the Northern Mississippi Embayment

    NASA Astrophysics Data System (ADS)

    Wiley, S.; Deshon, H. R.; Boyd, O. S.

    2009-12-01

    We present a study of seismic noise sources present within the northern Mississippi embayment near the New Madrid Seismic Zone (NMSZ). The northern embayment contains up to 1 km of unconsolidated coastal plain sediments overlying bedrock, making it an inherently noisy environment for seismic stations. The area is known to display high levels of cultural noise caused by agricultural activity, passing cars, trains, etc. We characterize continuous broadband seismic noise data recorded for the months of March through June 2009 at six stations operated by the Cooperative New Madrid Seismic Network. We looked at a single horizontal component of data during nighttime hours, defined as 6:15PM to 5:45AM Central Standard Time, which we determined to be the lowest amplitude period of noise for the region. Hourly median amplitudes were compared to daily average wind speeds downloaded from the National Oceanic and Atmospheric Administration. We find a correlation between time periods of increased noise and days with high wind speeds, suggesting that wind is likely a prevalent source of seismic noise in the area. The effects of wind on seismic recordings may result from wind induced tree root movement which causes ground motion to be recorded at the vaults located ~3m below ground. Automated studies utilizing the local network or the EarthScope Transportable Array, scheduled to arrive in the area in 2010-11, should expect to encounter wind induced noise fluctuations and must account for this in their analysis.

  10. Seismic Catalogue and Seismic Network in Haiti

    NASA Astrophysics Data System (ADS)

    Belizaire, D.; Benito, B.; Carreño, E.; Meneses, C.; Huerfano, V.; Polanco, E.; McCormack, D.

    2013-05-01

    The destructive earthquake occurred on January 10, 2010 in Haiti, highlighted the lack of preparedness of the country to address seismic phenomena. At the moment of the earthquake, there was no seismic network operating in the country, and only a partial control of the past seismicity was possible, due to the absence of a national catalogue. After the 2010 earthquake, some advances began towards the installation of a national network and the elaboration of a seismic catalogue providing the necessary input for seismic Hazard Studies. This paper presents the state of the works carried out covering both aspects. First, a seismic catalogue has been built, compiling data of historical and instrumental events occurred in the Hispaniola Island and surroundings, in the frame of the SISMO-HAITI project, supported by the Technical University of Madrid (UPM) and Developed in cooperation with the Observatoire National de l'Environnement et de la Vulnérabilité of Haiti (ONEV). Data from different agencies all over the world were gathered, being relevant the role of the Dominican Republic and Puerto Rico seismological services which provides local data of their national networks. Almost 30000 events recorded in the area from 1551 till 2011 were compiled in a first catalogue, among them 7700 events with Mw ranges between 4.0 and 8.3. Since different magnitude scale were given by the different agencies (Ms, mb, MD, ML), this first catalogue was affected by important heterogeneity in the size parameter. Then it was homogenized to moment magnitude Mw using the empirical equations developed by Bonzoni et al (2011) for the eastern Caribbean. At present, this is the most exhaustive catalogue of the country, although it is difficult to assess its degree of completeness. Regarding the seismic network, 3 stations were installed just after the 2010 earthquake by the Canadian Government. The data were sent by telemetry thought the Canadian System CARINA. In 2012, the Spanish IGN together

  11. Detecting Seismic Infrasound Signals on Balloon Platforms

    NASA Astrophysics Data System (ADS)

    Krishnamoorthy, S.; Komjathy, A.; Cutts, J. A.; Pauken, M.; Garcia, R.; Mimoun, D.; Jackson, J. M.; Kedar, S.; Smrekar, S. E.; Hall, J. L.

    2017-12-01

    The determination of the interior structure of a planet requires detailed seismic investigations - a process that entails the detection and characterization of seismic waves due to geological activities (e.g., earthquakes, volcanoes, etc.). For decades, this task has primarily been performed on Earth by an ever-expanding network of terrestrial seismic stations. However, on planets such as Venus, where the surface pressure and temperature can reach as high as 90 atmospheres and 450 degrees Celsius respectively, placing seismometers on the planet's surface poses a vexing technological challenge. However, the upper layers of the Venusian atmosphere are more benign and capable of hosting geophysical payloads for longer mission lifetimes. In order to achieve the aim of performing geophysical experiments from an atmospheric platform, JPL and its partners (ISAE-SUPAERO and California Institute of Technology) are in the process of developing technologies for detection of infrasonic waves generated by earthquakes from a balloon. The coupling of seismic energy into the atmosphere critically depends on the density differential between the surface of the planet and the atmosphere. Therefore, the successful demonstration of this technique on Earth would provide ample reason to expect success on Venus, where the atmospheric impedance is approximately 60 times that of Earth. In this presentation, we will share results from the first set of Earth-based balloon experiments performed in Pahrump, Nevada in June 2017. These tests involved the generation of artificial sources of known intensity using a seismic hammer and their detection using a complex network of sensors, including highly sensitive micro-barometers suspended from balloons, GPS receivers, geophones, microphones, and seismometers. This experiment was the first of its kind and was successful in detecting infrasonic waves from the earthquakes generated by the seismic hammer. We will present the first comprehensive analysis

  12. An Expedient but Fascinating Geophysical Chimera: The Pinyon Flat Seismic Strain Point Array

    NASA Astrophysics Data System (ADS)

    Langston, C. A.

    2016-12-01

    The combination of a borehole Gladwin Tensor Strain Meter (GTSM) and a co-located three component broadband seismometer (BB) can theoretically be used to determine the propagation attributes of P-SV waves in vertically inhomogeneous media such as horizontal phase velocity and azimuth of propagation through application of wave gradiometry. A major requirement for this to be successful is to have well-calibrated strain and seismic sensors to be able to rely on using absolute wave amplitude from both systems. A "point" seismic array is constructed using the PBO GTSM station B084 and co-located BB seismic stations from an open array experiment deployed by UCSD as well as PFO station at the Pinyon Flat facility. Site amplitude statics for all three ground motion components are found for the 14-element (13 PY stations + PFO), small aperture seismic array using data from 47 teleseisms recorded from 2014 until present. Precision of amplitude measurement at each site is better than 0.2% for vertical components, 0.5% for EW components, and 1% for NS components. Relative amplitudes among sites of the array are often better than 1% attesting to the high quality of the instrumentation and installation. The wavefield and related horizontal strains are computed for the location of B084 using a second order Taylor's expansion of observed waveforms from moderate ( M4) regional events. The computed seismic array areal, differential, and shear strains show excellent correlation in both phase and amplitude with those recorded by B084 when using the calibration matrix previously determined using teleseismic strains from the entire ANZA seismic network. Use of the GTSM-BB "point" array significantly extends the bandwidth of gradiometry calculations over the small-aperture seismic array by nearly two orders of magnitude from 0.5 Hz to 0.01 Hz. In principle, a seismic strain point array could be constructed from every PBO GTSM with a co-located seismometer to help serve earthquake early

  13. Analysis of induced seismicity at The Geysers geothermal field, California

    NASA Astrophysics Data System (ADS)

    Emolo, A.; Maercklin, N.; Matrullo, E.; Orefice, A.; Amoroso, O.; Convertito, V.; Sharma, N.; Zollo, A.

    2012-12-01

    Fluid injection, steam extraction, and reservoir stimulation in geothermal systems lead to induced seismicity. While in rare cases induced events may be large enough to pose a hazard, on the other hand the microseismicity provides information on the extent and the space-time varying properties of the reservoir. Therefore, microseismic monitoring is important, both for mitigation of unwanted effects of industrial operations and for continuous assessment of reservoir conditions. Here we analyze induced seismicity at The Geysers geothermal field in California, a vapor-dominated field with the top of the main steam reservoir some 1-3 km below the surface. Commercial exploitation began in the 1960s, and the seismicity increased with increasing field development. We focus our analyses on induced seismicity recorded between August 2007 and October 2011. Our calibrated waveform database contains some 15000 events with magnitudes between 1.0 and 4.5 and recorded by the LBNL Geysers/Calpine surface seismic network. We associated all data with events from the NCEDC earthquake catalog and re-picked first arrival times. Using selected events with at least 20 high-quality P-wave picks, we determined a minimum 1-D velocity model using VELEST. A well-constrained P-velocity model shows a sharp velocity increase at 1-2 km depth (from 3 to 5 km/s) and then a gradient-like trend down to about 5 km depth, where velocities reach values of 6-7 km/s. The station corrections show coherent, relatively high, positive travel time delays in the NW zone, thus indicating a strong lateral variation of the P-wave velocities. We determined an average Vp-to-Vs ratio of 1.67, which is consistent with estimates from other authors for the same time period. The events have been relocated in the new model using a non-linear probabilistic methods. The seismicity appears spatially diffused in a 15x10 km2 area elongated in NW-SE direction, and earthquake depths range between 0 and 6 km. As in previous

  14. Variabilities in probabilistic seismic hazard maps for natural and induced seismicity in the central and eastern United States

    USGS Publications Warehouse

    Mousavi, S. Mostafa; Beroza, Gregory C.; Hoover, Susan M.

    2018-01-01

    Probabilistic seismic hazard analysis (PSHA) characterizes ground-motion hazard from earthquakes. Typically, the time horizon of a PSHA forecast is long, but in response to induced seismicity related to hydrocarbon development, the USGS developed one-year PSHA models. In this paper, we present a display of the variability in USGS hazard curves due to epistemic uncertainty in its informed submodel using a simple bootstrapping approach. We find that variability is highest in low-seismicity areas. On the other hand, areas of high seismic hazard, such as the New Madrid seismic zone or Oklahoma, exhibit relatively lower variability simply because of more available data and a better understanding of the seismicity. Comparing areas of high hazard, New Madrid, which has a history of large naturally occurring earthquakes, has lower forecast variability than Oklahoma, where the hazard is driven mainly by suspected induced earthquakes since 2009. Overall, the mean hazard obtained from bootstrapping is close to the published model, and variability increased in the 2017 one-year model relative to the 2016 model. Comparing the relative variations caused by individual logic-tree branches, we find that the highest hazard variation (as measured by the 95% confidence interval of bootstrapping samples) in the final model is associated with different ground-motion models and maximum magnitudes used in the logic tree, while the variability due to the smoothing distance is minimal. It should be pointed out that this study is not looking at the uncertainty in the hazard in general, but only as it is represented in the USGS one-year models.

  15. Near Surface Seismic Hazard Characterization in the Presence of High Velocity Contrasts

    NASA Astrophysics Data System (ADS)

    Gribler, G.; Mikesell, D.; Liberty, L. M.

    2017-12-01

    We present new multicomponent surface wave processing techniques that provide accurate characterization of near-surface conditions in the presence of large lateral or vertical shear wave velocity boundaries. A common problem with vertical component Rayleigh wave analysis in the presence of high contrast subsurface conditions is Rayleigh wave propagation mode misidentification due to an overlap of frequency-phase velocity domain dispersion, leading to an overestimate of shear wave velocities. By using the vertical and horizontal inline component signals, we isolate retrograde and prograde particle motions to separate fundamental and higher mode signals, leading to more accurate and confident dispersion curve picks and shear wave velocity estimates. Shallow, high impedance scenarios, such as the case with shallow bedrock, are poorly constrained when using surface wave dispersion information alone. By using a joint inversion of dispersion and horizontal-to-vertical (H/V) curves within active source frequency ranges (down to 3 Hz), we can accurately estimate the depth to high impedance boundaries, a significant improvement compared to the estimates based on dispersion information alone. We compare our approach to body wave results that show comparable estimates of bedrock topography. For lateral velocity contrasts, we observe horizontal polarization of Rayleigh waves identified by an increase in amplitude and broadening of the horizontal spectra with little variation in the vertical component spectra. The horizontal spectra offer a means to identify and map near surface faults where there is no topographic or clear body wave expression. With these new multicomponent active source seismic data processing and inversion techniques, we better constrain a variety of near surface conditions critical to the estimation of local site response and seismic hazards.

  16. Seismic features and evolution of a late Miocene submarine channel system in the Yinggehai basin, northwestern South China Sea

    NASA Astrophysics Data System (ADS)

    Sun, H.; Jiang, T.; Wang, Z.; Zhang, Y.

    2014-12-01

    Submarine channel is one of key conduits for coarse terrigenous clastic sediments to abyssal plain, which provides the possibility for deepwater hydrocarbon exploration. Recently, a new high-quality 3D seismic data is acquired in south Yinggehai basin (YGHB) and the detailed interpretations on those seismic profiles as well as RMS amplitude attributes and variance slices reveal a submarine channel system developed in late Miocene, which could be supplied from Hainan Island via turbidity currents so that it would be filled with sand-rich turbidites as good hydrocarbon reservoir. Based on the integration between regional seismic survey and some boreholes, the investigations on its infilling architectures and depositional processes are carried out. The results show that it composes two converged submarine channels with two channelized submarine fans to their west and the main submarine channel (MSC) is characterized by a downstream increasing width and is infilled by sediments with high amplitude seismic facies, which could be originated from channelized submarine fans. Furthermore, the complicated depositional processes around the confluence region of these two channels are pointed out and the interactions between the submarine channel system and nearby channelized submarine fans are discussed. The detailed illustration on the seismic features and depositional processes of the subsurface submarine system provides us better understanding deepwater sedimentary dynamics and would be more benefit for the hydrocarbon exploration in similar deepwater area around the world.

  17. High Resolution Seismic Imaging of the Trench Canyon Fault Zone, Mono Lake, Northeastern California

    NASA Astrophysics Data System (ADS)

    Novick, M. W.; Jayko, A. S.; Roeske, S.; McClain, J. S.; Hart, P. E.; Boyle, M.

    2009-12-01

    High resolution seismic imaging of Mono Lake, located in northeastern California, has revealed an approximately northwest striking fault in the area to the west of aerially exposed Negit Volcano. This fault, henceforth referred to as the Trench Canyon Fault (TCF), has also been mapped onshore along a correlating strike as far north as Cedar Hill Volcano, located to the northeast of the lake on the California/Nevada border. Onshore, the TCF was mapped for approximately 10 kilometers using air photos, DEM images, and standard geologic pace and compass mapping techniques. The TCF post- dates the last glacial maximum, evidenced by the cutting of wave cut benches along Cedar Hill Volcano. Relict, non-historic shorelines, left by the steady evaporation of Mono Lake beginning approximately 13k, are also repeatedly cut by the fault. Additional evidence of fault presence includes sag ponds, pressure ridges, tectonically fractured rocks, and normal fault scarps found along strike. Offshore, DEM images show a northeast striking structure to the northwest of Negit Volcano, which is co-linear with the onshore TCF. High resolution seismic imaging of the structure, using an applied acoustic/SIG mini-sparker system, reveals steeply dipping Holocene sediments, as well as volcanic deposits from active vents which have erupted in the last 1000 years, offset by the fault. Detailed structural analysis of the previously unstudied Trench Canyon Fault (TFC) and faults in the Cedar Hill region of northern California, along with seismic studies of sediments beneath Mono Lake not only allow for a better comprehension of this minor fault system, but provide greater understanding of the larger and more complex Walker Lane Shear Zone. Fault analyses, combined and correlated with those from CHV, give a better understanding of how slip is transferred into the complicated Mina defection to the east, from the dextral and normal faults along the Sierra Nevada Range front.

  18. Seismic Imaging of the Source Physics Experiment Site with the Large-N Seismic Array

    NASA Astrophysics Data System (ADS)

    Chen, T.; Snelson, C. M.; Mellors, R. J.

    2017-12-01

    The Source Physics Experiment (SPE) consists of a series of chemical explosions at the Nevada National Security Site. The goal of SPE is to understand seismic wave generation and propagation from these explosions. To achieve this goal, we need an accurate geophysical model of the SPE site. A Large-N seismic array that was deployed at the SPE site during one of the chemical explosions (SPE-5) helps us construct high-resolution local geophysical model. The Large-N seismic array consists of 996 geophones, and covers an area of approximately 2 × 2.5 km. The array is located in the northern end of the Yucca Flat basin, at a transition from Climax Stock (granite) to Yucca Flat (alluvium). In addition to the SPE-5 explosion, the Large-N array also recorded 53 weight drops. Using the Large-N seismic array recordings, we perform body wave and surface wave velocity analysis, and obtain 3D seismic imaging of the SPE site for the top crust of approximately 1 km. The imaging results show clear variation of geophysical parameter with local geological structures, including heterogeneous weathering layer and various rock types. The results of this work are being incorporated in the larger 3D modeling effort of the SPE program to validate the predictive models developed for the site.

  19. Seismic low-frequency-based calculation of reservoir fluid mobility and its applications

    NASA Astrophysics Data System (ADS)

    Chen, Xue-Hua; He, Zhen-Hua; Zhu, Si-Xin; Liu, Wei; Zhong, Wen-Li

    2012-06-01

    Low frequency content of seismic signals contains information related to the reservoir fluid mobility. Based on the asymptotic analysis theory of frequency-dependent reflectivity from a fluid-saturated poroelastic medium, we derive the computational implementation of reservoir fluid mobility and present the determination of optimal frequency in the implementation. We then calculate the reservoir fluid mobility using the optimal frequency instantaneous spectra at the low-frequency end of the seismic spectrum. The methodology is applied to synthetic seismic data from a permeable gas-bearing reservoir model and real land and marine seismic data. The results demonstrate that the fluid mobility shows excellent quality in imaging the gas reservoirs. It is feasible to detect the location and spatial distribution of gas reservoirs and reduce the non-uniqueness and uncertainty in fluid identification.

  20. How Deep is Shallow? Improving Absolute and Relative Locations of Upper Crustal Seismicity in Switzerland

    NASA Astrophysics Data System (ADS)

    Diehl, T.; Kissling, E. H.; Singer, J.; Lee, T.; Clinton, J. F.; Waldhauser, F.; Wiemer, S.

    2017-12-01

    Information on the structure of upper-crustal fault systems and their connection with seismicity is key to the understanding of neotectonic processes. Precisely determined focal depths in combination with structural models can provide important insight into deformation styles of the upper crust (e.g. thin- vs. versus thick-skinned tectonics). Detailed images of seismogenic fault zones in the upper crust, on the other hand, will contribute to the assessment of the hazard related to natural and induced earthquakes, especially in regions targeted for radioactive waste repositories or geothermal energy production. The complex velocity structure of the uppermost crust and unfavorable network geometries, however, often hamper precise locations (i.e. focal depth) of shallow seismicity and therefore limit tectonic interpretations. In this study we present a new high-precision catalog of absolute locations of seismicity in Switzerland. High-quality travel-time data from local and regional earthquakes in the period 2000-2017 are used to solve the coupled hypocenter-velocity structure problem in 1D. For this purpose, the well-known VELEST inversion software was revised and extended to improve the quality assessment of travel-time data and to facilitate the identification of erroneous picks in the bulletin data. Results from the 1D inversion are used as initial parameters for a 3D local earthquake tomography. Well-studied earthquakes and high-quality quarry blasts are used to assess the quality of 1D and 3D relocations. In combination with information available from various controlled-source experiments, borehole data, and geological profiles, focal depths and associated host formations are assessed through comparison with the resolved 3D velocity structure. The new absolute locations and velocity models are used as initial values for relative double-difference relocation of earthquakes in Switzerland. Differential times are calculated from bulletin picks and waveform cross

  1. A reappraisal of seismic Q evaluated at Mt. Etna volcano. Receipt for the application to risk analysis

    NASA Astrophysics Data System (ADS)

    Del Pezzo, Edoardo; Bianco, Francesca; Giampiccolo, Elisabetta; Tusa, Giuseppina; Tuvé, Tiziana

    2015-01-01

    A new approach in dealing with seismic risk in the volcanic areas of Italy, by taking into account the possible occurrence of damaging pre- or syn-eruptive seismic events, is exciting the scientific interest and is actually the topic developed in several research projects funded by the European Community (e.g., UPStrat-MAFA, www.upstrat-mafa.ov.ingv.it/UPstrat/) and the Civil Defense Department of Italy. To achieve this goal, it is necessary to have a detailed knowledge of the local attenuation-distance relations. In the present paper, we make a survey of the estimates of the seismic quality factor of the medium reported in literature for the Etna area. In the framework of a similar paper published for the Campi Flegrei zone in Southern Italy, we first review the results on seismic attenuation already obtained for Etna and then apply a standard technique to separately measure intrinsic and scattering attenuation coefficients from passive seismic data recorded by the Etna seismological network. Indications are then given for the correct utilization of the attenuation parameters to obtain the best candidate quality factor Q to be used in this area for seismic risk purposes.

  2. Tunnel Detection Using Seismic Methods

    NASA Astrophysics Data System (ADS)

    Miller, R.; Park, C. B.; Xia, J.; Ivanov, J.; Steeples, D. W.; Ryden, N.; Ballard, R. F.; Llopis, J. L.; Anderson, T. S.; Moran, M. L.; Ketcham, S. A.

    2006-05-01

    Surface seismic methods have shown great promise for use in detecting clandestine tunnels in areas where unauthorized movement beneath secure boundaries have been or are a matter of concern for authorities. Unauthorized infiltration beneath national borders and into or out of secure facilities is possible at many sites by tunneling. Developments in acquisition, processing, and analysis techniques using multi-channel seismic imaging have opened the door to a vast number of near-surface applications including anomaly detection and delineation, specifically tunnels. Body waves have great potential based on modeling and very preliminary empirical studies trying to capitalize on diffracted energy. A primary limitation of all seismic energy is the natural attenuation of high-frequency energy by earth materials and the difficulty in transmitting a high- amplitude source pulse with a broad spectrum above 500 Hz into the earth. Surface waves have shown great potential since the development of multi-channel analysis methods (e.g., MASW). Both shear-wave velocity and backscatter energy from surface waves have been shown through modeling and empirical studies to have great promise in detecting the presence of anomalies, such as tunnels. Success in developing and evaluating various seismic approaches for detecting tunnels relies on investigations at known tunnel locations, in a variety of geologic settings, employing a wide range of seismic methods, and targeting a range of uniquely different tunnel geometries, characteristics, and host lithologies. Body-wave research at the Moffat tunnels in Winter Park, Colorado, provided well-defined diffraction-looking events that correlated with the subsurface location of the tunnel complex. Natural voids related to karst have been studied in Kansas, Oklahoma, Alabama, and Florida using shear-wave velocity imaging techniques based on the MASW approach. Manmade tunnels, culverts, and crawl spaces have been the target of multi-modal analysis

  3. Frozen Gaussian approximation for 3D seismic tomography

    NASA Astrophysics Data System (ADS)

    Chai, Lihui; Tong, Ping; Yang, Xu

    2018-05-01

    Three-dimensional (3D) wave-equation-based seismic tomography is computationally challenging in large scales and high-frequency regime. In this paper, we apply the frozen Gaussian approximation (FGA) method to compute 3D sensitivity kernels and seismic tomography of high-frequency. Rather than standard ray theory used in seismic inversion (e.g. Kirchhoff migration and Gaussian beam migration), FGA is used to compute the 3D high-frequency sensitivity kernels for travel-time or full waveform inversions. Specifically, we reformulate the equations of the forward and adjoint wavefields for the purpose of convenience to apply FGA, and with this reformulation, one can efficiently compute the Green’s functions whose convolutions with source time function produce wavefields needed for the construction of 3D kernels. Moreover, a fast summation method is proposed based on local fast Fourier transform which greatly improves the speed of reconstruction as the last step of FGA algorithm. We apply FGA to both the travel-time adjoint tomography and full waveform inversion (FWI) on synthetic crosswell seismic data with dominant frequencies as high as those of real crosswell data, and confirm again that FWI requires a more sophisticated initial velocity model for the convergence than travel-time adjoint tomography. We also numerically test the accuracy of applying FGA to local earthquake tomography. This study paves the way to directly apply wave-equation-based seismic tomography methods into real data around their dominant frequencies.

  4. Developments in Seismic Data Quality Assessment Using MUSTANG at the IRIS DMC

    NASA Astrophysics Data System (ADS)

    Sharer, G.; Keyson, L.; Templeton, M. E.; Weertman, B.; Smith, K.; Sweet, J. R.; Tape, C.; Casey, R. E.; Ahern, T.

    2017-12-01

    MUSTANG is the automated data quality metrics system at the IRIS Data Management Center (DMC), designed to help characterize data and metadata "goodness" across the IRIS data archive, which holds 450 TB of seismic and related earth science data spanning the past 40 years. It calculates 46 metrics ranging from sample statistics and miniSEED state-of-health flag counts to Power Spectral Densities (PSDs) and Probability Density Functions (PDFs). These quality measurements are easily and efficiently accessible to users through the use of web services, which allows users to make requests not only by station and time period but also to filter the results according to metric values that match a user's data requirements. Results are returned in a variety of formats, including XML, JSON, CSV, and text. In the case of PSDs and PDFs, results can also be retrieved as plot images. In addition, there are several user-friendly client tools available for exploring and visualizing MUSTANG metrics: LASSO, MUSTANG Databrowser, and MUSTANGular. Over the past year we have made significant improvements to MUSTANG. We have nearly complete coverage over our archive for broadband channels with sample rates of 20-200 sps. With this milestone achieved, we are now expanding to include higher sample rate, short-period, and strong-motion channels. Data availability metrics will soon be calculated when a request is made which guarantees that the information reflects the current state of the archive and also allows for more flexibility in content. For example, MUSTANG will be able to return a count of gaps for any arbitrary time period instead of being limited to 24 hour spans. We are also promoting the use of data quality metrics beyond the IRIS archive through our recent release of ISPAQ, a Python command-line application that calculates MUSTANG-style metrics for users' local miniSEED files or for any miniSEED data accessible through FDSN-compliant web services. Finally, we will explore how

  5. 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.

  6. Vertical Cable Seismic Survey for SMS exploration

    NASA Astrophysics Data System (ADS)

    Asakawa, Eiichi; Murakami, Fumitoshi; Tsukahara, Hotoshi; Mizohata, Shigeharu

    2014-05-01

    The Vertical Cable Seismic (VCS) survey is one of the reflection seismic methods. It uses hydrophone arrays vertically moored from the seafloor to record acoustic waves generated by sea-surface, deep-towed or ocean bottom sources. Analyzing the reflections from the sub-seabed, we could look into the subsurface structure. Because the VCS is an efficient high-resolution 3D seismic survey method for a spatially-bounded area, we proposed it for the SMS survey tool development program that the Ministry of Education, Culture, Sports, Science and Technology (MEXT) started in 2009. We have been developing the VCS survey system, including not only data acquisition hardware but data processing and analysis technique. We carried out several VCS surveys combining with surface towed source, deep towed source and ocean bottom source. The water depths of these surveys are from 100m up to 2100 m. Through these experiments, our VCS data acquisition system has been also completed. But the data processing techniques are still on the way. One of the most critical issues is the positioning in the water. The uncertainty in the positions of the source and of the hydrophones in water degraded the quality of subsurface image. GPS navigation system is available on sea surface, but in case of deep-towed source or ocean bottom source, the accuracy of shot position with SSBL/USBL is not sufficient for the very high-resolution imaging. We have developed a new approach to determine the positions in water using the travel time data from the source to VCS hydrophones. In 2013, we have carried out the second VCS survey using the surface-towed high-voltage sparker and ocean bottom source in the Izena Cauldron, which is one of the most promising SMS areas around Japan. The positions of ocean bottom source estimated by this method are consistent with the VCS field records. The VCS data with the sparker have been processed with 3D PSTM. It gives the very high resolution 3D volume deeper than two

  7. Wave equation datuming applied to marine OBS data and to land high resolution seismic profiling

    NASA Astrophysics Data System (ADS)

    Barison, Erika; Brancatelli, Giuseppe; Nicolich, Rinaldo; Accaino, Flavio; Giustiniani, Michela; Tinivella, Umberta

    2011-03-01

    One key step in seismic data processing flows is the computation of static corrections, which relocate shots and receivers at the same datum plane and remove near surface weathering effects. We applied a standard static correction and a wave equation datuming and compared the obtained results in two case studies: 1) a sparse ocean bottom seismometers dataset for deep crustal prospecting; 2) a high resolution land reflection dataset for hydrogeological investigation. In both cases, a detailed velocity field, obtained by tomographic inversion of the first breaks, was adopted to relocate shots and receivers to the datum plane. The results emphasize the importance of wave equation datuming to properly handle complex near surface conditions. In the first dataset, the deployed ocean bottom seismometers were relocated to the sea level (shot positions) and a standard processing sequence was subsequently applied to the output. In the second dataset, the application of wave equation datuming allowed us to remove the coherent noise, such as ground roll, and to improve the image quality with respect to the application of static correction. The comparison of the two approaches evidences that the main reflecting markers are better resolved when the wave equation datuming procedure is adopted.

  8. Effects of Regulation on Induced Seismicity in Southern Kansas

    NASA Astrophysics Data System (ADS)

    Rubinstein, J. L.; Ellsworth, W. L.; Dougherty, S. L.

    2016-12-01

    The appearance of seismicity concurrent with the expansion of oil and gas activities in southern Kansas since September 2012 suggests that industrial operations are inducing earthquakes there. Much of the seismicity can be related to high-rate injection wells within 5 km of the earthquakes. There is significant complexity to the situation, though. Some of the seismicity, including the 2014 M4.8 Milan earthquake, the largest earthquake to occur in the area, lies at least 10km from high-rate injection wells. Additionally, the presence of high-rate wells does not guarantee that there will be nearby seismicity. Many of the highest-rate injection wells are located to the southwest of our study area, where there is minimal seismicity. We have also seen changes in earthquake rates shortly following the March 2015 enactment of new limits on the rate of wastewater disposal in five areas in southern Kansas. Overall, the earthquake rate has decreased significantly since these rules went into place. In more detail, however, earthquake rates within the five areas decreased, but the rate outside the five zones increased. It is likely that fluid-pressure diffusion is responsible for the migration of seismicity outside the areas of reduced injection because there is little injection in the areas unaffected by the new injection rules. This increase is also a reminder that seismicity can persist long after the reduction or cessation of injection. In addition to the effect of the new injection rules, it is possible that the reduction in injection may be partially caused by economic factors that have resulted in a decrease in the production of oil and gas. We have yet to disentangle the effects of the new injection rules and the low prices of oil and gas on the induced seismicity in southern Kansas.

  9. Lunar seismic profiling experiment natural activity study

    NASA Technical Reports Server (NTRS)

    Duennebier, F. K.

    1976-01-01

    The Lunar Seismic Experiment Natural Activity Study has provided a unique opportunity to study the high frequency (4-20 Hz) portion to the seismic spectrum on the moon. The data obtained from the LSPE was studied to evaluate the origin and importance of the process that generates thermal moonquakes and the characteristics of the seismic scattering zone at the lunar surface. The detection of thermal moonquakes by the LSPE array made it possible to locate the sources of many events and determine that they are definitely not generated by astronaut activities but are the result of a natural process on the moon. The propagation of seismic waves in the near-surface layers was studied in a qualitative manner. In the absence of an adequate theoretical model for the propagation of seismic waves in the moon, it is not possible to assign a depth for the scattering layer. The LSPE data does define several parameters which must be satisfied by any model developed in the future.

  10. 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

  11. Monitoring the Transport of Sediment During Tropical Cyclones From High-frequency Seismic Noise in Two Rivers of La Réunion Island

    NASA Astrophysics Data System (ADS)

    Fontaine, F. R.; Gonzalez, A.; Burtin, A.; Barruol, G.; Recking, A.; Join, J. L.; Delcher, E.

    2016-12-01

    La Réunion Island is a basaltic shield volcano located in the western Indian Ocean. The island undergoes heavy annual precipitations during tropical depressions and cyclones. These rainfalls modify the stream dynamics and sediment transport of rivers. The transport of sediment participates to the erosion of the volcanic island, however, in situ characterization is difficult during high water stage. In the frame of the Rivière des Pluies project, we are deploying a temporary seismic network of 10 three-component broadband seismometers around two rivers: Rivière des Pluies and Rivière du Mât. The goal of the project is to monitor spatial and temporal variations of the river's bed-load during tropical cyclones with high-frequency noise. Meteorological and hydrological stations are installed at both rivers providing valuable data such as precipitations, water discharge and water level. We will also sample the bed surface grain size distribution by visual count to determine its influence on the seismic noise. We present preliminary results from two broadband seismic stations located near instrumented streams. SALA station from the temporary RHUM-RUM seismic network (http://www.rhum-rum.net/en/) was installed close to the Rivière du Mât and the permanent GEOSCOPE RER station is located close to the Rivière de l'Est. We analyzed the footprint of the cyclone Bejisa in January 2014. We observe a significant increase of the precipitation when the cyclone eye is 300 km close to the island followed by the increase of the water discharge. Simultaneously the seismic signal shows a sudden increase of the power spectral density visible above 1 Hz. Further investigations on the relationship between the seismic noise and the hydrological and meteorological parameters will help us quantifying the river bed-load.

  12. Long-term deformation in the Mississippi Embayment (Central USA) imaged by high-resolution seismic reflection data

    NASA Astrophysics Data System (ADS)

    Hao, Yanjun

    Large magnitude intraplate earthquakes are a puzzling exception to plate tectonic theory. Unlike earthquakes occurring along plate boundaries, large continental intraplate earthquakes are a rare occurrence and are often distributed over broad regions. Albeit rare, their occurrence can cause widespread damage because of the low attenuation of seismic energy typical of plate interiors [Hanks and Johnston, 1992]. In the Central USA, most of the recent tectonic intraplate seismicity concentrates along the New Madrid seismic zone (NMSZ), where three large (M>7) earthquakes occurred between 1811--1812 [Johnston and Schweig, 1996]. Here the low surface deformation rates [Calais and Stein, 2009] conflict with the elevated instrument-recorded seismicity and the occurrence of historical and prehistorical large magnitude events [Tuttle et al., 2002]. One of the promising hypotheses proposed to reconcile this apparent contradiction is that intraplate earthquakes may be temporally clustered, episodic or cyclic, and may migrate spatially at the regional or continental scale across multiple faults or fault systems. In order to test this hypothesis and to understand how and where the long-term deformation is accommodated in the Mississippi Embayment, Central USA, I utilize high-resolution seismic reflection data acquired by the Mississippi River Project [Magnani and McIntosh, 2009] and by a 2010 survey across the Meeman-Shelby fault [Magnani, 2011; Hao et al., 2013]. To identify the location of Quaternary deformation and characterize deformation history, I acquired, processed, and interpreted the seismic reflection data and integrated them with other available geophysical (e.g. seismicity, crustal and lithospheric models) and geological (e.g. magmatism and borehole) data. For my research, I focus on three regions in the Mississippi Embayment: 1) the Meeman-Shelby fault west of Memphis, Tennessee, 2) the eastern Reelfoot rift margin north of Memphis, Tennessee, and 3) the area in

  13. Seismic gradiometry using ambient seismic noise in an anisotropic Earth

    NASA Astrophysics Data System (ADS)

    de Ridder, S. A. L.; Curtis, A.

    2017-05-01

    We introduce a wavefield gradiometry technique to estimate both isotropic and anisotropic local medium characteristics from short recordings of seismic signals by inverting a wave equation. The method exploits the information in the spatial gradients of a seismic wavefield that are calculated using dense deployments of seismic arrays. The application of the method uses the surface wave energy in the ambient seismic field. To estimate isotropic and anisotropic medium properties we invert an elliptically anisotropic wave equation. The spatial derivatives of the recorded wavefield are evaluated by calculating finite differences over nearby recordings, which introduces a systematic anisotropic error. A two-step approach corrects this error: finite difference stencils are first calibrated, then the output of the wave-equation inversion is corrected using the linearized impulse response to the inverted velocity anomaly. We test the procedure on ambient seismic noise recorded in a large and dense ocean bottom cable array installed over Ekofisk field. The estimated azimuthal anisotropy forms a circular geometry around the production-induced subsidence bowl. This conforms with results from studies employing controlled sources, and with interferometry correlating long records of seismic noise. Yet in this example, the results were obtained using only a few minutes of ambient seismic noise.

  14. Characterization of granular flow dynamics from the generated high-frequency seismic signal: insights from laboratory experiments

    NASA Astrophysics Data System (ADS)

    Mangeney, A.; Farin, M.; de Rosny, J.; Toussaint, R.; Trinh, P. T.

    2017-12-01

    Landslides, rock avalanche and rockfalls represent a major natural hazard in steep environments. However, owing to the lack of visual observations, the dynamics of these gravitational events is still not well understood. A burning challenge is to deduce the landslide dynamics (flow potential energy, involved volume, particle size…) from the characteristics of the generated seismic signal (radiated seismic energy, maximum amplitude, frequencies,...). Laboratory experiments of granular columns collapse are conducted on an inclined plane. The seismic signal generated by the collapse is recorded by piezoelectric accelerometers sensitive in a wide frequency range (1 Hz - 56 kHz). The granular flow are constituted with steel beads of same diameter. We compare the dynamic parameters of the granular flows, deduced from the movie of the experiments, to the seismic parameters deduced from the measured seismic signals. The ratio of radiated seismic energy to potential energy lost is shown to slightly decrease with slope angle and is between 0.2% and 9%. It decreases as time, slope angle and flow volume increase and when the particle diameter decreases. These results explain the dispersion over several orders of magnitude of the seismic efficiency of natural landslides. We distinguish two successive phases of rise and decay in the time profiles if the amplitude of the seismic signal and of the mean frequency of the signal generated by the granular flows. The rise phase and the maximum are shown to be independent of the slope angle. The maximum seismic amplitude coincides with the maximum flow speed in the direction normal to the slope but not with the maximum downslope speed. We observe that the shape of the seismic envelope and frequencies as a function of time changes after a critical slope angle, between 10° and 15° with respect to the horizontal, with a decay phase lasting much longer as slope angle increases, due to a change in the flow regime, from a dense to a more

  15. OGS improvements in 2012 in running the North-eastern Italy Seismic Network: the Ferrara VBB borehole seismic station

    NASA Astrophysics Data System (ADS)

    Pesaresi, D.; Romanelli, M.; Barnaba, C.; Bragato, P. L.; Durì, G.

    2014-07-01

    The Centro di Ricerche Sismologiche (CRS, Seismological Research Centre) of the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS, Italian National Institute for Oceanography and Experimental Geophysics) in Udine (Italy) after the strong earthquake of magnitude M=6.4 occurred in 1976 in the Italian Friuli-Venezia Giulia region, started to operate the North-eastern Italy Seismic Network: it currently consists of 17 very sensitive broad band and 18 simpler short period seismic stations, all telemetered to and acquired in real time at the OGS-CRS data centre in Udine. Real time data exchange agreements in place with other Italian, Slovenian, Austrian and Swiss seismological institutes lead to a total number of about 100 seismic stations acquired in real time, which makes the OGS the reference institute for seismic monitoring of North-eastern Italy. The south-western edge of the OGS seismic network (Fig. 1) stands on the Po alluvial basin: earthquake localization and characterization in this area is affected by the presence of soft alluvial deposits. OGS ha already experience in running a local seismic network in high noise conditions making use of borehole installations in the case of the micro-seismicity monitoring of a local gas storage site for a private company. Following the ML = 5.9 earthquake that struck the Emilia region around Ferrara in Northern Italy on 20 May 2012 at 02:03:53 UTC, a cooperation of Istituto Nazionale di Geofisica e Vulcanologia, OGS, the Comune di Ferrara and the University of Ferrara lead to the reinstallation of a previously existing very broad band (VBB) borehole seismic station in Ferrara. The aim of the OGS intervention was on one hand to extend its real time seismic monitoring capabilities toward South-West, including Ferrara and its surroundings, and on the other hand to evaluate the seismic response at the site. We will describe improvements in running the North-eastern Italy Seismic Network, including details of

  16. Differences in the lithosphere seismic structure along the Brazilian continental margin in the South Atlantic from travel time seismic tomography

    NASA Astrophysics Data System (ADS)

    Peres Rocha, M.; Azevedo, P. A. D.; Assumpcao, M.; Franca, G. S.; Marotta, G. S.

    2016-12-01

    Results of the P-wave travel-time seismic tomography method allowed observing differences in the seismic behavior of the lithosphere along the Brazilian continental margin in the South Atlantic. High velocity anomalies have predominance in the northern portion, which extends from the Rio de Janeiro to Alagoas States (between latitudes -22.5 and -8.5), and low velocity anomalies in the southern portion, which extends from Rio de Janeiro to Rio Grande do Sul States (between latitudes -30 and -22.5). Low velocities coincide spatially with the offshore high seismicity areas, as indicated by Assumpção (1998) and at the high velocities with low seismicity regions. The high velocity anomalies at northern portion are related to the cratonic and low-stretched lithosphere of San Francisco block that was connected to the Congo block before the opening of the Atlantic Ocean. Low velocities can be assigned to more weakened lithosphere, where it started the South Atlantic Ocean opening process. The oldest lithosphere in the South Atlantic, indicated by the magnetic anomalies of the oceanic floor, is higher in the southern part than in the northern part, suggesting that the continents in this region were separating, while the northern region was still connected to Africa, which could explain the lithospheric stretching process.

  17. High frequency seismic signal generated by landslides on complex topographies: from point source to spatially distributed sources

    NASA Astrophysics Data System (ADS)

    Mangeney, A.; Kuehnert, J.; Capdeville, Y.; Durand, V.; Stutzmann, E.; Kone, E. H.; Sethi, S.

    2017-12-01

    During their flow along the topography, landslides generate seismic waves in a wide frequency range. These so called landquakes can be recorded at very large distances (a few hundreds of km for large landslides). The recorded signals depend on the landslide seismic source and the seismic wave propagation. If the wave propagation is well understood, the seismic signals can be inverted for the seismic source and thus can be used to get information on the landslide properties and dynamics. Analysis and modeling of long period seismic signals (10-150s) have helped in this way to discriminate between different landslide scenarios and to constrain rheological parameters (e.g. Favreau et al., 2010). This was possible as topography poorly affects wave propagation at these long periods and the landslide seismic source can be approximated as a point source. In the near-field and at higher frequencies (> 1 Hz) the spatial extent of the source has to be taken into account and the influence of the topography on the recorded seismic signal should be quantified in order to extract information on the landslide properties and dynamics. The characteristic signature of distributed sources and varying topographies is studied as a function of frequency and recording distance.The time dependent spatial distribution of the forces applied to the ground by the landslide are obtained using granular flow numerical modeling on 3D topography. The generated seismic waves are simulated using the spectral element method. The simulated seismic signal is compared to observed seismic data from rockfalls at the Dolomieu Crater of Piton de la Fournaise (La Réunion).Favreau, P., Mangeney, A., Lucas, A., Crosta, G., and Bouchut, F. (2010). Numerical modeling of landquakes. Geophysical Research Letters, 37(15):1-5.

  18. Automated classification of seismic sources in a large database: a comparison of Random Forests and Deep Neural Networks.

    NASA Astrophysics Data System (ADS)

    Hibert, Clement; Stumpf, André; Provost, Floriane; Malet, Jean-Philippe

    2017-04-01

    In the past decades, the increasing quality of seismic sensors and capability to transfer remotely large quantity of data led to a fast densification of local, regional and global seismic networks for near real-time monitoring of crustal and surface processes. This technological advance permits the use of seismology to document geological and natural/anthropogenic processes (volcanoes, ice-calving, landslides, snow and rock avalanches, geothermal fields), but also led to an ever-growing quantity of seismic data. This wealth of seismic data makes the construction of complete seismicity catalogs, which include earthquakes but also other sources of seismic waves, more challenging and very time-consuming as this critical pre-processing stage is classically done by human operators and because hundreds of thousands of seismic signals have to be processed. To overcome this issue, the development of automatic methods for the processing of continuous seismic data appears to be a necessity. The classification algorithm should satisfy the need of a method that is robust, precise and versatile enough to be deployed to monitor the seismicity in very different contexts. In this study, we evaluate the ability of machine learning algorithms for the analysis of seismic sources at the Piton de la Fournaise volcano being Random Forest and Deep Neural Network classifiers. We gather a catalog of more than 20,000 events, belonging to 8 classes of seismic sources. We define 60 attributes, based on the waveform, the frequency content and the polarization of the seismic waves, to parameterize the seismic signals recorded. We show that both algorithms provide similar positive classification rates, with values exceeding 90% of the events. When trained with a sufficient number of events, the rate of positive identification can reach 99%. These very high rates of positive identification open the perspective of an operational implementation of these algorithms for near-real time monitoring of

  19. Odors and Air Pollution: A Bibliography with Abstracts.

    ERIC Educational Resources Information Center

    Environmental Protection Agency, Research Triangle Park, NC. Office of Air Programs.

    The annotated bibliography presents a compilation of abstracts which deal with odors as they relate to air pollution. The abstracts are arranged within the following categories: Emission sources; Control methods; Measurement methods; Air quality measurements; Atmospheric interaction; Basic science and technology; Effects-human health;…

  20. Study on Seismicity of Sino-Mongolia Arc Areas

    NASA Astrophysics Data System (ADS)

    Xu, Guangyin; Wang, Suyun

    2016-04-01

    Using the earthquake catalogue from China, Mongolia and the global catalogue, the uniform catalogue of North China, Mongolia and adjacent areas, which is within the region 80-130°E, 40-55°N, has been established by Institute of Geophysics, China Earthquake Administration and Research Center of Astronomy and Geophysics, Mongolian Academy of Science for the seismic hazard analysis and seismic zoning map of Mongolia according to the following principles. 1) Earthquakes, which just exist in one catalogue, need to be verified further. If the earthquakes occurred in the country where the catalog comes from, then they will be adopted. If not, it should be checked with other more data. 2) The events that come from the three data sources have be checked and verified as followings. (1) The parameters of earthquakes that occurred in China will be taken from China catalog. (2)The parameters of earthquakes that occurred in Mongolia will be taken from Mongolia catalog. (3) The parameters of earthquakes that occurred in the adjacent areas will be taken from the global catalog by Song et al. According to the uniform catalogue, the seismicity of the North China, Mongolia and adjacent areas is analyzed, and the conclusions as followings are made. 1) The epicenter map can be roughly divided into two parts, bounded by the longitude line 105°E , in accordance with the "North-South Seismic Belt" of China. The seismicity is in a high level with many strong earthquakes in the west and is in a low level with little strong events in the east. 2) Most earthquakes are shallow-focus events, but there are also several middle or deep-focus events in the study area. 3) Earthquakes with magnitude greater than 5 are basically complete since 1450 A.D., and the seismicity of the study areas is in a high level since 1700 A. 4) Two seismic belts, Altay seismic belt and Bolnay-Baikal seismic belt, are determined according to the epicenters and tectonics. 5) The b-values of magnitude - frequency

  1. High resolution seismic reflection survey in the Gulf of Pozzuoli, Naples, Italy. An example of preliminary interpretation of seismic profiles.

    NASA Astrophysics Data System (ADS)

    D'Aniello, Elena; di Fiore, Vincenzo; Sacchi, Marco; Rapolla, Antonio

    2010-05-01

    During the cruise CAFE_07 - Leg 3 conducted in the Gulf of Naples and Pozzuoli in January 2008, on board of the R/V URANIA of the CNR it was carried out the acquisition of a grid of ca. 800 km of high-resolution multichannel reflection seismic profiles (Sacchi et al., 2009; Di Fiore et al., 2009). The aim of the cruise was the understanding of the stratigraphic-structural setting of the Pozzuoli Bay area, with specific reference to the major offshore volcanic features, such as Nisida Bank, Pentapalummo Bank, M.Dolce-Pampano Bank and Miseno Bank and others. The Gulf of Pozzuoli is placed in the Volcanic district of Campi Flegrei, an area of active volcanism located at North West of Naples city, along the Tyrrhenian margin, in an extensional collapsed area called Campanian Plain, filled by siliciclastic, epiclastic and volcaniclastic sediments, deposited during Late Pliocene and Quaternary. Several studies present in literature suggest a relation between volcanic system of Campi Flegrei and faults system; in particular, at the Gulf of Pozzuoli we can observe some volcanic banks and submarine volcanic edifices, as Pentapalummo, Nisida and Miseno Banks, are aligned along the NE-SW trending Magnaghi-Sebeto fault line, that separates the Bay of Naples into two sectors: the first, at NW of the Bay, characterized by volcanism activity and magnetic anomalies and the second, at SE of the bay, involved only by sedimentary activity, with the exceptions of the circular anomalies in the offshore of Torre del Greco city (Bruno et al., 2003; Secomandi et al., 2003); other volcanic hights are instead positioned along NW-SE structural discontinuities (Bruno, 2004). The magnetic and gravimetric analysis of the Bay of Naples confirms the tectonic control of the Campanian volcanism: we can observe a good correspondence of high magnetic anomalies with the main volcanic structures at the North-Western side of the bay, just the Gulf of Pozzuoli, where both NE-SW and NW-SE normal faults

  2. High-resolution seismic-reflection images across the ICDP-USGS Eyreville deep drilling site, Chesapeake Bay impact structure

    USGS Publications Warehouse

    Powars, David S.; Catchings, Rufus D.; Goldman, Mark R.; Gohn, Gregory S.; Horton, J. Wright; Edwards, Lucy E.; Rymer, Michael J.; Gandhok, Gini

    2009-01-01

    The U.S. Geological Survey (USGS) acquired two 1.4-km-long, high-resolution (~5 m vertical resolution) seismic-reflection lines in 2006 that cross near the International Continental Scientific Drilling Program (ICDP)-USGS Eyreville deep drilling site located above the late Eocene Chesapeake Bay impact structure in Virginia, USA. Five-meter spacing of seismic sources and geophones produced high-resolution images of the subsurface adjacent to the 1766-m-depth Eyreville core holes. Analysis of these lines, in the context of the core hole stratigraphy, shows that moderate-amplitude, discontinuous, dipping reflections below ~527 m correlate with a variety of Chesapeake Bay impact structure sediment and rock breccias recovered in the cores. High-amplitude, continuous, subhorizontal reflections above ~527 m depth correlate with the uppermost part of the Chesapeake Bay impact structure crater-fill sediments and postimpact Eocene to Pleistocene sediments. Reflections with ~20-30 m of relief in the uppermost part of the crater-fill and lowermost part of the postimpact section suggest differential compaction of the crater-fill materials during early postimpact time. The top of the crater-fill section also shows ~20 m of relief that appears to represent an original synimpact surface. Truncation surfaces, locally dipping reflections, and depth variations in reflection amplitudes generally correlate with the lithostrati-graphic and sequence-stratigraphic units and contacts in the core. Seismic images show apparent postimpact paleochannels that include the first possible Miocene paleochannels in the Mid-Atlantic Coastal Plain. Broad downwarping in the postim-pact section unrelated to structures in the crater fill indicates postimpact sediment compaction.

  3. Seismic Methods

    EPA Pesticide Factsheets

    Seismic methods are the most commonly conducted geophysical surveys for engineering investigations. Seismic refraction provides engineers and geologists with the most basic of geologic data via simple procedures with common equipment.

  4. 1D Seismic reflection technique to increase depth information in surface seismic investigations

    NASA Astrophysics Data System (ADS)

    Camilletti, Stefano; Fiera, Francesco; Umberto Pacini, Lando; Perini, Massimiliano; Prosperi, Andrea

    2017-04-01

    1D seismic methods, such as MASW Re.Mi. and HVSR, have been extensively used in engineering investigations, bedrock research, Vs profile and to some extent for hydrologic applications, during the past 20 years. Recent advances in equipment, sound sources and computer interpretation techniques, make 1D seismic methods highly effective in shallow subsoil modeling. Classical 1D seismic surveys allows economical collection of subsurface data however they fail to return accurate information for depths greater than 50 meters. Using a particular acquisition technique it is possible to collect data that can be quickly processed through reflection technique in order to obtain more accurate velocity information in depth. Furthermore, data processing returns a narrow stratigraphic section, alongside the 1D velocity model, where lithological boundaries are represented. This work will show how collect a single-CMP to determine: (1) depth of bedrock; (2) gravel layers in clayey domains; (3) accurate Vs profile. Seismic traces was processed by means a new software developed in collaboration with SARA electronics instruments S.r.l company, Perugia - ITALY. This software has the great advantage of being able to be used directly in the field in order to reduce the times elapsing between acquisition and processing.

  5. High-precision relocation of induced seismicity in the geothermal system below St. Gallen (Switzerland)

    NASA Astrophysics Data System (ADS)

    Diehl, Tobias; Kraft, Toni; Eduard, Kissling; Nicholas, Deichmann; Clinton, John; Wiemer, Stefan

    2014-05-01

    From July to November 2013 a sequence of more than 850 events, of which more than 340 could be located, was triggered in a planned hydrothermal system below the city of St. Gallen in eastern Switzerland. Seismicity initiated on July 14 and the maximum Ml in the sequence was 3.5, comparable in size with the Ml 3.4 event induced by stimulation below Basel in 2006. To improve absolute locations of the sequence, more than 1000 P and S wave arrivals were inverted for hypocenters and 1D velocity structure. Vp of 5.6-5.8 km/s and a Vp/Vs ratio of 1.82-1.9 in the source region indicate a limestone or shale-type composition and a comparison with a lithological model from a 3D seismic model suggests that the seismically active streak (height up to 400 m) is within the Mesozoic layer. To resolve the fine structure of the induced seismicity, we applied waveform cross-correlation and double-difference algorithms. The results image a NE-SW striking lineament, consistent with a left-lateral fault plane derived from first motion polarities and moment tensor inversions. A spatio-temporal analysis of the relocated seismicity shows that, during first acid jobs on July 17, microseismicity propagated towards southwest over the entire future Ml 3.5 rupture plane. The almost vertical focal plane associated with the Ml 3.5 event of July 20 is well imaged by the seismicity. The area of the ruptured fault is approximately 675x400 m. Seismicity images a change in focal depths along strike, which correlates with a kink or bend in the mapped fault system northeast of the Ml 3.5 event. This change might indicate structural differences or a segmentation of the fault. Following the Ml 3.5 event, seismicity propagated along strike to the northeast, in a region without any mapped faults, indicating a continuation of the fault segment. Seismicity on this segment occurred in September and October. A complete rupture of the NE segment would have the potential to produce a magnitude larger than 3

  6. Reflection and refraction seismic on the great Ancona landslide

    NASA Astrophysics Data System (ADS)

    Stucchi, E.; Mazzotti, A.

    2003-04-01

    The Adriatic coast in Italy is characterised by the occurrence of several landslide bodies, some of which of huge extension. Here we present the results of seismic refraction and reflection studies recently carried out on the Ancona Landslide, which is located immediately westward of the harbour city of Ancona, and interests an area of about 3.5 km^2 with a landslide front of 2 km. The acquired seismic profile crosses the entire landslide body and was performed employing land and marine sources and receivers. Thus it allows the simultaneous acquisition of marine-marine, marine-land, land-marine and land-land data. The most significant acquisition parameters are: nominal maximum source-receiver offset 600 m, receiver group interval 5 m, single airgun and small explosive charges as energy sources, profile length 1.5 km, average reflection coverage on land 4000% and at sea 20000%. Notwithstanding the significant noise contamination due to intense human activities (road, naval and railway traffic) in the area, the data shows good first breaks and reflections which we use for refraction and reflection processing. The refraction study makes use of GRM and other techniques (Lawton) and it leads to a good definition of the shallower landslide bodies but it is not able to depict the deeper decollement surface. It is also very useful in providing a detailed near surface velocity model that is crucial for the determination of accurate static corrections for the reflection data. High quality subsurface images are achieved by applying different processing sequences to the different sets (marine, land or land-marine) of reflection seismic data. The processing steps that turned out as more effective to the achievement of such a quality were the noise removal by means of FX and SVD filtering, the attenuation of the bubble effect for the marine source data, the ground roll attenuation and the computation of accurate statics. The outcomes of the refraction and reflection

  7. Paleoseismic potential of sublacustrine landslide records in a high-seismicity setting (south-central Alaska)

    USGS Publications Warehouse

    Praet, Nore; Moernaut, Jasper; Van Daele, Maarten; Boes, Evelien; Haeussler, Peter J.; Strupler, Michael; Schmidt, Sabine; Loso, Michael G.; De Batist, Marc

    2017-01-01

    Sublacustrine landslide stratigraphy is considered useful for quantitative paleoseismology in low-seismicity settings. However, as the recharging of underwater slopes with sediments is one of the factors that governs the recurrence of slope failures, it is not clear if landslide deposits can provide continuous paleoseismic records in settings of frequent strong shaking. To test this, we selected three lakes in south-central Alaska that experienced a strong historical megathrust earthquake (the 1964 Mw9.2 Great Alaska Earthquake) and exhibit high sedimentation rates in their main basins (0.2 cm yr-1 -1.0 cm yr-1). We present high-resolution reflection seismic data (3.5 kHz) and radionuclide data from sediment cores in order to investigate factors that control the establishment of a reliable landslide record. Seismic stratigraphy analysis reveals the presence of several landslide deposits in the lacustrine sedimentary infill. Most of these landslide deposits can be attributed to specific landslide events, as multiple landslide deposits sourced from different lacustrine slopes occur on a single stratigraphic horizon. We identify numerous events in the lakes: Eklutna Lake proximal basin (14 events), Eklutna Lake distal basin (8 events), Skilak Lake (7 events) and Kenai Lake (7 events). The most recent event in each basin corresponds to the historic 1964 megathrust earthquake. All events are characterized by multiple landslide deposits, which hints at a regional trigger mechanism, such as an earthquake (the synchronicity criterion). This means that the landslide record in each basin represents a record of past seismic events. Based on extrapolation of sedimentation rates derived from radionuclide dating, we roughly estimate a mean recurrence interval in the Eklutna Lake proximal basin, Eklutna Lake distal basin, Skilak Lake and Kenai Lake, at ~ 250 yrs, ~ 450 yrs, ~ 900 yrs and ~ 450 yrs, respectively. This distinct difference in recording can be explained by variations

  8. Probabilistic Seismic Hazard Analysis for Georgia

    NASA Astrophysics Data System (ADS)

    Tsereteli, N. S.; Varazanashvili, O.; Sharia, T.; Arabidze, V.; Tibaldi, A.; Bonali, F. L. L.; Russo, E.; Pasquaré Mariotto, F.

    2017-12-01

    Nowadays, seismic hazard studies are developed in terms of the calculation of Peak Ground Acceleration (PGA), Spectral Acceleration (SA), Peak Ground Velocity (PGV) and other recorded parameters. In the frame of EMME project PSH were calculated for Georgia using GMPE based on selection criteria. In the frame of Project N 216758 (supported by Shota Rustaveli National Science Foundation (SRNF)) PSH maps were estimated using hybrid- empirical ground motion prediction equation developed for Georgia. Due to the paucity of seismically recorded information, in this work we focused our research on a more robust dataset related to macroseismic data,and attempted to calculate the probabilistic seismic hazard directly in terms of macroseismicintensity. For this reason, we started calculating new intensity prediction equations (IPEs)for Georgia taking into account different sets, belonging to the same new database, as well as distances from the seismic source.With respect to the seismic source, in order to improve the quality of the results, we have also hypothesized the size of faults from empirical relations, and calculated new IPEs also by considering Joyner-Boore and rupture distances in addition to epicentral and hypocentral distances. Finally, site conditions have been included as variables for IPEs calculation Regarding the database, we used a brand new revised set of macroseismic data and instrumental records for the significant earthquakes that struck Georgia between 1900 and 2002.Particularly, a large amount of research and documents related to macroseismic effects of individual earthquakes, stored in the archives of the Institute of Geophysics, were used as sources for the new macroseismic data. The latter are reported in the Medvedev-Sponheuer-Karnikmacroseismic scale (MSK64). For each earthquake the magnitude, the focal depth and the epicenter location are also reported. An online version of the database, with therelated metadata,has been produced for the 69

  9. New Seismic Monitoring Station at Mohawk Ridge, Valles Caldera

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

    Roberts, Peter Morse

    Two new broadband digital seismic stations were installed in the Valles Caldera in 2011 and 2012. The first is located on the summit of Cerros del Abrigo (station code CDAB) and the second is located on the flanks of San Antonio Mountain (station code SAMT). Seismic monitoring stations in the caldera serve multiple purposes. These stations augment and expand the current coverage of the Los Alamos Seismic Network (LASN), which is operated to support seismic and volcanic hazards studies for LANL and northern New Mexico (Figure 1). They also provide unique continuous seismic data within the caldera that can bemore » used for scientific studies of the caldera’s substructure and detection of very small seismic signals that may indicate changes in the current and evolving state of remnant magma that is known to exist beneath the caldera. Since the installation of CDAB and SAMT, several very small earthquakes have already been detected near San Antonio Mountain just west of SAMT (Figure 2). These are the first events to be seen in that area. Caldera stations also improve the detection and epicenter determination quality for larger local earthquakes on the Pajarito Fault System east of the Preserve and the Nacimiento Uplift to the west. These larger earthquakes are a concern to LANL Seismic Hazards assessments and seismic monitoring of the Los Alamos region, including the VCNP, is a DOE requirement. Currently the next closest seismic stations to the caldera are on Pipeline Road (PPR) just west of Los Alamos, and Peralta Ridge (PER) south of the caldera. There is no station coverage near the resurgent dome, Redondo Peak, in the center of the caldera. Filling this “hole” is the highest priority for the next new LASN station. We propose to install this station in 2018 on Mohawk Ridge just east of Redondito, in the same area already occupied by other scientific installations, such as the MCON flux tower operated by UNM.« less

  10. Seismic Sources for the Territory of Georgia

    NASA Astrophysics Data System (ADS)

    Tsereteli, N. S.; Varazanashvili, O.

    2011-12-01

    The southern Caucasus is an earthquake prone region where devastating earthquakes have repeatedly caused significant loss of lives, infrastructure and buildings. High geodynamic activity of the region expressed in both seismic and aseismic deformations, is conditioned by the still-ongoing convergence of lithospheric plates and northward propagation of the Afro-Arabian continental block at a rate of several cm/year. The geometry of tectonic deformations in the region is largely determined by the wedge-shaped rigid Arabian block intensively intended into the relatively mobile Middle East-Caucasian region. Georgia is partner of ongoing regional project EMME. The main objective of EMME is calculation of Earthquake hazard uniformly with heights standards. One approach used in the project is the probabilistic seismic hazard assessment. In this approach the first parameter requirement is the definition of seismic source zones. Seismic sources can be either faults or area sources. Seismoactive structures of Georgia are identified mainly on the basis of the correlation between neotectonic structures of the region and earthquakes. Requirements of modern PSH software to geometry of faults is very high. As our knowledge of active faults geometry is not sufficient, area sources were used. Seismic sources are defined as zones that are characterized with more or less uniform seismicity. Poor knowledge of the processes occurring in deep of the Earth is connected with complexity of direct measurement. From this point of view the reliable data obtained from earthquake fault plane solution is unique for understanding the character of a current tectonic life of investigated area. There are two methods of identification if seismic sources. The first is the seimsotectonic approach, based on identification of extensive homogeneous seismic sources (SS) with the definition of probability of occurrence of maximum earthquake Mmax. In the second method the identification of seismic sources

  11. A seismic hazard uncertainty analysis for the New Madrid seismic zone

    USGS Publications Warehouse

    Cramer, C.H.

    2001-01-01

    A review of the scientific issues relevant to characterizing earthquake sources in the New Madrid seismic zone has led to the development of a logic tree of possible alternative parameters. A variability analysis, using Monte Carlo sampling of this consensus logic tree, is presented and discussed. The analysis shows that for 2%-exceedence-in-50-year hazard, the best-estimate seismic hazard map is similar to previously published seismic hazard maps for the area. For peak ground acceleration (PGA) and spectral acceleration at 0.2 and 1.0 s (0.2 and 1.0 s Sa), the coefficient of variation (COV) representing the knowledge-based uncertainty in seismic hazard can exceed 0.6 over the New Madrid seismic zone and diminishes to about 0.1 away from areas of seismic activity. Sensitivity analyses show that the largest contributor to PGA, 0.2 and 1.0 s Sa seismic hazard variability is the uncertainty in the location of future 1811-1812 New Madrid sized earthquakes. This is followed by the variability due to the choice of ground motion attenuation relation, the magnitude for the 1811-1812 New Madrid earthquakes, and the recurrence interval for M>6.5 events. Seismic hazard is not very sensitive to the variability in seismogenic width and length. Published by Elsevier Science B.V.

  12. Tourism sector preparedness in zones with a high seismic risk: Case study of the Capital Region of Japan

    NASA Astrophysics Data System (ADS)

    Lihui, W.; Wang, D.

    2017-12-01

    Japan is a country highly vulnerable to natural disasters, especially earthquakes. Tourism, as a strategic industry in Japan, is especially vulnerable to destructive earthquake disasters owing to the characteristics of vulnerability, sensitivity and substitutability. Here we aim to provide theoretical understanding of the perception and responses of tourism managers towards damaging disasters in tourism destinations with high seismic risks. We conducted surveys among the mangers of tourism businesses in the capital area of Japan in 2014 and applied structural equation modeling techniques to empirically test the proposed model with four latent variables, which are risk perception, threat knowledge, disaster preparedness and earthquake preparedness. Our results show that threat knowledge affects risk perception and disaster preparedness positively. In addition, disaster preparedness positively affects earthquake preparedness. However, the proposed paths from risk perception to disaster preparedness, risk perception to earthquake preparedness, and threat knowledge to earthquake preparedness were not statistically significant. Our results may provide references for policymakers in promoting crisis planning in tourism destination with high seismic risks.

  13. High Resolution Seismic Study of the Holocene Infill of the Elkhorn Slough, Central California

    EPA Science Inventory

    The seismic analysis of the sedimentary infill of the Elkhorn Slough, central California, reveals a succession of three main seismic units: U1, U2, U3, with their correspondent discontinuities d2, d3. These units are deposited over a paleorelief representing the channel location ...

  14. New Madrid seismic zone recurrence intervals

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

    Schweig, E.S.; Ellis, M.A.

    1993-03-01

    Frequency-magnitude relations in the New Madrid seismic zone suggest that great earthquakes should occur every 700--1,200 yrs, implying relatively high strain rates. These estimates are supported by some geological and GPS results. Recurrence intervals of this order should have produced about 50 km of strike-slip offset since Miocene time. No subsurface evidence for such large displacements is known within the seismic zone. Moreover, the irregular fault pattern forming a compressive step that one sees today is not compatible with large displacements. There are at least three possible interpretations of the observations of short recurrence intervals and high strain rates, butmore » apparently youthful fault geometry and lack of major post-Miocene deformation. One is that the seismological and geodetic evidence are misleading. A second possibility is that activity in the region is cyclic. That is, the geological and geodetic observations that suggest relatively short recurrence intervals reflect a time of high, but geologically temporary, pore-fluid pressure. Zoback and Zoback have suggested such a model for intraplate seismicity in general. Alternatively, the New Madrid seismic zone is geologically young feature that has been active for only the last few tens of thousands of years. In support of this, observe an irregular fault geometry associated with a unstable compressive step, a series of en echelon and discontinuous lineaments that may define the position of a youthful linking fault, and the general absence of significant post-Eocene faulting or topography.« less

  15. Induced seismicity and implications for CO2 storage risk

    NASA Astrophysics Data System (ADS)

    Gerstenberger, M. C.; Nicol, A.; Bromley, C.; Carne, R.; Chardot, L.; Ellis, S. M.; Jenkins, C.; Siggins, T.; Viskovic, P.

    2012-12-01

    We provide an overview of a recently completed report for the IEA GHG that represents a comprehensive review of current research and observations in induced seismicity, its risk to successful completion of Carbon Capture and Storage (CCS) projects and potential mitigation measures. We focus on two topics: a meta-analysis of related data from multiple injection projects around the globe and the implications of these data for CCS induced seismicity risk management. Published data have been compiled from injection and extraction projects around the globe to examine statistical relationships between possible controlling factors and induced seismicity. Quality control of such observational earthquake data sets is crucial to ensure robust results and issues with bias and completeness of the data set will be discussed. Analyses of the available data support previous suggestions that the locations, numbers and magnitudes of induced earthquakes are dependent on a range of factors, including the injection rate, total injected fluid volume, the reservoir permeability and the proximity of pre-existing faults. Increases in the injection rates and total volume of fluid injected, for example, typically raise reservoir pressures and increase the likelihood of elevated seismicity rates and maximum magnitudes of induced earthquakes. The risks associated with induced seismicity at CCS sites can be reduced and mitigated using a systematic and structured risk management programme. While precise forecasts of the expected induced seismicity may never be possible, a thorough risk management procedure should include some level of knowledge of the possible behaviour of induced seismicity. Risk management requires estimates of the expected magnitude, number, location and timing of potential induced earthquakes. Such forecasts should utilise site specific observations together with physical and statistical models that are optimised for the site. Statistical models presently show the most

  16. Seismicity Structure of the Downgoing Nazca Slab in Northern Chile

    NASA Astrophysics Data System (ADS)

    Sippl, C.; Schurr, B.

    2017-12-01

    We applied an automatized earthquake detection and location algorithm to 8 years of continuous seismic data from the IPOC network in Northern Chile, located in the forearc between about 18.5°S and 24°S. The resulting seismicity catalog contains more than 113k double-difference relocated earthquake hypocenters and features a completeness magnitude around 2.8. Despite the occurrence of two megathrust earthquakes with vigorous aftershock seismicity in the studied time period (the 2007 Tocopilla and the 2014 Iquique earthquakes), >60% of the retrieved seismicity is located in a highly active band of intermediate-depth earthquakes (80-120 km deep) within the downgoing Nazca slab.We obtain a triple seismic zone in the updip part of the slab, with the three parallel dipping planes corresponding to the plate interface, the oceanic Moho (ca. 8 km below the interface) and a third band in the mantle lithosphere 26-28 km beneath the slab top. The plate interface seismicity terminates abruptly at a depth of 55 km. At about 80-90 km depth, the remaining two planes of seismicity then merge into the single, 20 km thick cluster of vigorous seismicity mentioned above, which terminates at 120 km depth. This cluster is located directly beneath the volcanic arc and shows a pronounced kink in the slab dipping angle. Intra-slab seismicity is most likely related to metamorphic dehydration reactions, hence our high-resolution earthquake distribution can be considered a map of metamorphic reactions (although a possibly incomplete one, since not all reactions necessarily invoke seismicity). By correlating this distribution with isotherms from thermal models as well as geophysical imaging results from previous studies, we attempt to get a glimpse at the processes that produce the different patches of intraslab seismicity at intermediate depths.

  17. Induced Seismicity Potential of Energy Technologies

    NASA Astrophysics Data System (ADS)

    Hitzman, Murray

    2013-03-01

    Earthquakes attributable to human activities-``induced seismic events''-have received heightened public attention in the United States over the past several years. Upon request from the U.S. Congress and the Department of Energy, the National Research Council was asked to assemble a committee of experts to examine the scale, scope, and consequences of seismicity induced during fluid injection and withdrawal associated with geothermal energy development, oil and gas development, and carbon capture and storage (CCS). The committee's report, publicly released in June 2012, indicates that induced seismicity associated with fluid injection or withdrawal is caused in most cases by change in pore fluid pressure and/or change in stress in the subsurface in the presence of faults with specific properties and orientations and a critical state of stress in the rocks. The factor that appears to have the most direct consequence in regard to induced seismicity is the net fluid balance (total balance of fluid introduced into or removed from the subsurface). Energy technology projects that are designed to maintain a balance between the amount of fluid being injected and withdrawn, such as most oil and gas development projects, appear to produce fewer seismic events than projects that do not maintain fluid balance. Major findings from the study include: (1) as presently implemented, the process of hydraulic fracturing for shale gas recovery does not pose a high risk for inducing felt seismic events; (2) injection for disposal of waste water derived from energy technologies does pose some risk for induced seismicity, but very few events have been documented over the past several decades relative to the large number of disposal wells in operation; and (3) CCS, due to the large net volumes of injected fluids suggested for future large-scale carbon storage projects, may have potential for inducing larger seismic events.

  18. Temporal abstraction-based clinical phenotyping with Eureka!

    PubMed

    Post, Andrew R; Kurc, Tahsin; Willard, Richie; Rathod, Himanshu; Mansour, Michel; Pai, Akshatha Kalsanka; Torian, William M; Agravat, Sanjay; Sturm, Suzanne; Saltz, Joel H

    2013-01-01

    Temporal abstraction, a method for specifying and detecting temporal patterns in clinical databases, is very expressive and performs well, but it is difficult for clinical investigators and data analysts to understand. Such patterns are critical in phenotyping patients using their medical records in research and quality improvement. We have previously developed the Analytic Information Warehouse (AIW), which computes such phenotypes using temporal abstraction but requires software engineers to use. We have extended the AIW's web user interface, Eureka! Clinical Analytics, to support specifying phenotypes using an alternative model that we developed with clinical stakeholders. The software converts phenotypes from this model to that of temporal abstraction prior to data processing. The model can represent all phenotypes in a quality improvement project and a growing set of phenotypes in a multi-site research study. Phenotyping that is accessible to investigators and IT personnel may enable its broader adoption.

  19. Causality between expansion of seismic cloud and maximum magnitude of induced seismicity in geothermal field

    NASA Astrophysics Data System (ADS)

    Mukuhira, Yusuke; Asanuma, Hiroshi; Ito, Takatoshi; Häring, Markus

    2016-04-01

    Occurrence of induced seismicity with large magnitude is critical environmental issues associated with fluid injection for shale gas/oil extraction, waste water disposal, carbon capture and storage, and engineered geothermal systems (EGS). Studies for prediction of the hazardous seismicity and risk assessment of induced seismicity has been activated recently. Many of these studies are based on the seismological statistics and these models use the information of the occurrence time and event magnitude. We have originally developed physics based model named "possible seismic moment model" to evaluate seismic activity and assess seismic moment which can be ready to release. This model is totally based on microseismic information of occurrence time, hypocenter location and magnitude (seismic moment). This model assumes existence of representative parameter having physical meaning that release-able seismic moment per rock volume (seismic moment density) at given field. Seismic moment density is to be estimated from microseismic distribution and their seismic moment. In addition to this, stimulated rock volume is also inferred by progress of microseismic cloud at given time and this quantity can be interpreted as the rock volume which can release seismic energy due to weakening effect of normal stress by injected fluid. Product of these two parameters (equation (1)) provide possible seismic moment which can be released from current stimulated zone as a model output. Difference between output of this model and observed cumulative seismic moment corresponds the seismic moment which will be released in future, based on current stimulation conditions. This value can be translated into possible maximum magnitude of induced seismicity in future. As this way, possible seismic moment can be used to have feedback to hydraulic stimulation operation in real time as an index which can be interpreted easily and intuitively. Possible seismic moment is defined as equation (1), where D

  20. Preparing and presenting effective abstracts and posters in psychiatry

    PubMed Central

    Singh, Manpreet K.

    2014-01-01

    Presenting an abstract and a poster gives scientists from all fields, including psychiatry, an important opportunity to introduce their research to others. Researchers and mental health professionals at all levels of career development can use several media resources to assist them with the technical aspects of preparing an abstract or a poster. This article will focus on major principles associated with preparing and presenting an abstract and a poster at a scientific meeting. A literature search using NIH PubMed was conducted to identify peer and non-peer-reviewed articles that provide methods for effective abstract and poster presentation for the period of 1966 to June 2014. First, we review the purpose and relative importance of abstracts and posters in academic settings. Next, we describe the qualities of an effective abstract and poster and common pitfalls that may occur. Finally, we present a systematic approach to preparing and presenting an abstract and a poster in a scientific setting. Several sources consistently suggest that readability, organization, and succinctness are qualities that make an effective and successful abstract and poster. Mental health professionals in all stages of their career development may benefit from following these guidelines in presenting their scientific work. PMID:25085499

  1. Preparing and presenting effective abstracts and posters in psychiatry.

    PubMed

    Singh, Manpreet K

    2014-12-01

    Presenting an abstract and a poster gives scientists from all fields, including psychiatry, an important opportunity to introduce their research to others. Researchers and mental health professionals at all levels of career development can use several media resources to assist them with the technical aspects of preparing an abstract or a poster. This article will focus on major principles associated with preparing and presenting an abstract and a poster at a scientific meeting. A literature search using NIH PubMed was conducted to identify peer and nonpeer-reviewed articles that provide methods for effective abstract and poster presentation for the period of 1966 to June 2014. First, the author reviews the purpose and relative importance of abstracts and posters in academic settings. Next, the author describes the qualities of an effective abstract and poster and common pitfalls that may occur. Finally, the author presents a systematic approach to preparing and presenting an abstract and a poster in a scientific setting. Several sources consistently suggest that readability, organization, and succinctness are qualities that make an effective and successful abstract and poster. Mental health professionals in all stages of their career development may benefit from following these guidelines in presenting their scientific work.

  2. NSR&D Program Fiscal Year (FY) 2015 Call for Proposals Mitigation of Seismic Risk at Nuclear Facilities using Seismic Isolation

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

    Coleman, Justin

    2015-02-01

    Seismic isolation (SI) has the potential to drastically reduce seismic response of structures, systems, or components (SSCs) and therefore the risk associated with large seismic events (large seismic event could be defined as the design basis earthquake (DBE) and/or the beyond design basis earthquake (BDBE) depending on the site location). This would correspond to a potential increase in nuclear safety by minimizing the structural response and thus minimizing the risk of material release during large seismic events that have uncertainty associated with their magnitude and frequency. The national consensus standard America Society of Civil Engineers (ASCE) Standard 4, Seismic Analysismore » of Safety Related Nuclear Structures recently incorporated language and commentary for seismically isolating a large light water reactor or similar large nuclear structure. Some potential benefits of SI are: 1) substantially decoupling the SSC from the earthquake hazard thus decreasing risk of material release during large earthquakes, 2) cost savings for the facility and/or equipment, and 3) applicability to both nuclear (current and next generation) and high hazard non-nuclear facilities. Issue: To date no one has evaluated how the benefit of seismic risk reduction reduces cost to construct a nuclear facility. Objective: Use seismic probabilistic risk assessment (SPRA) to evaluate the reduction in seismic risk and estimate potential cost savings of seismic isolation of a generic nuclear facility. This project would leverage ongoing Idaho National Laboratory (INL) activities that are developing advanced (SPRA) methods using Nonlinear Soil-Structure Interaction (NLSSI) analysis. Technical Approach: The proposed study is intended to obtain an estimate on the reduction in seismic risk and construction cost that might be achieved by seismically isolating a nuclear facility. The nuclear facility is a representative pressurized water reactor building nuclear power plant (NPP

  3. Seismic Interface Waves in Coastal Waters: A Review

    DTIC Science & Technology

    1980-11-15

    Being at the low- 4 frequency end of classical sonar activity and at the high-frequency end of seismic research, the propagation of infrasonic energy...water areas. Certainly this and other seismic detection methods will never replace the highly-developed sonar techniques but in coastal waters they...for many sonar purposes [5, 85 to 90) shows that very simple bottom models may already be sufficient to make allowance for the influence of the sea

  4. Seismic attenuation and scattering tomography of rock samples using stochastic wavefields: linking seismology, volcanology, and rock physics.

    NASA Astrophysics Data System (ADS)

    Fazio, Marco; De Siena, Luca; Benson, Phillip

    2016-04-01

    Seismic attenuation and scattering are two attributes that can be linked with porosity and permeability in laboratory experiments. When measuring these two quantities using seismic waveforms recorder at lithospheric and volcanic scales the areas of highest heterogeneity, as batches of melt and zones of high deformation, produce anomalous values of the measured quantities, the seismic quality factor and scattering coefficient. When employed as indicators of heterogeneity and absorption in volcanic areas these anomalous effects become strong indicators of magma accumulation and tectonic boundaries, shaping magmatic chambers and conduit systems. We perform attenuation and scattering measurements and imaging using seismic waveforms produced in laboratory experiments, at frequencies ranging between the kHz and MHz. As attenuation and scattering are measured from the shape of the envelopes, disregarding phases, we are able to connect the observations with the micro fracturing and petrological quantities previously measured on the sample. Connecting the imaging of dry and saturated samples via these novel attributes with the burst of low-period events with increasing saturation and deformation is a challenge. Its solution could plant the seed for better relating attenuation and scattering tomography measurements to the presence of fluids and gas, therefore creating a novel path for reliable porosity and permeability tomography. In particular for volcanoes, being able to relate attenuation/scattering measurements with low-period micro seismicity could deliver new data to settle the debate about if both source and medium can produce seismic resonance.

  5. Homogenization of Electromagnetic and Seismic Wavefields for Joint Inverse Modeling

    NASA Astrophysics Data System (ADS)

    Newman, G. A.; Commer, M.; Petrov, P.; Um, E. S.

    2011-12-01

    A significant obstacle in developing a robust joint imaging technology exploiting seismic and electromagnetic (EM) wave fields is the resolution at which these different geophysical measurements sense the subsurface. Imaging of seismic reflection data is an order of magnitude finer in resolution and scale compared to images produced with EM data. A consistent joint image of the subsurface geophysical attributes (velocity, electrical conductivity) requires/demands the different geophysical data types be similar in their resolution of the subsurface. The superior resolution of seismic data results from the fact that the energy propagates as a wave, while propagation of EM energy is diffusive and attenuates with distance. On the other hand, the complexity of the seismic wave field can be a significant problem due to high reflectivity of the subsurface and the generation of multiple scattering events. While seismic wave fields have been very useful in mapping the subsurface for energy resources, too much scattering and too many reflections can lead to difficulties in imaging and interpreting seismic data. To overcome these obstacles a formulation for joint imaging of seismic and EM wave fields is introduced, where each data type is matched in resolution. In order to accomplish this, seismic data are first transformed into the Laplace-Fourier Domain, which changes the modeling of the seismic wave field from wave propagation to diffusion. Though high frequency information (reflectivity) is lost with this transformation, several benefits follow: (1) seismic and EM data can be easily matched in resolution, governed by the same physics of diffusion, (2) standard least squares inversion works well with diffusive type problems including both transformed seismic and EM, (3) joint imaging of seismic and EM data may produce better starting velocity models critical for successful reverse time migration or full waveform imaging of seismic data (non transformed) and (4

  6. Geomorphology and seismic risk

    NASA Astrophysics Data System (ADS)

    Panizza, Mario

    1991-07-01

    The author analyses the contributions provided by geomorphology in studies suited to the assessment of seismic risk: this is defined as function of the seismic hazard, of the seismic susceptibility, and of the vulnerability. The geomorphological studies applicable to seismic risk assessment can be divided into two sectors: (a) morpho-neotectonic investigations conducted to identify active tectonic structures; (b) geomorphological and morphometric analyses aimed at identifying the particular situations that amplify or reduce seismic susceptibility. The morpho-neotectonic studies lead to the identification, selection and classification of the lineaments that can be linked with active tectonic structures. The most important geomorphological situations that can condition seismic susceptibility are: slope angle, debris, morphology, degradational slopes, paleo-landslides and underground cavities.

  7. Optimized suppression of coherent noise from seismic data using the Karhunen-Loève transform

    NASA Astrophysics Data System (ADS)

    Montagne, Raúl; Vasconcelos, Giovani L.

    2006-07-01

    Signals obtained in land seismic surveys are usually contaminated with coherent noise, among which the ground roll (Rayleigh surface waves) is of major concern for it can severely degrade the quality of the information obtained from the seismic record. This paper presents an optimized filter based on the Karhunen-Loève transform for processing seismic images contaminated with ground roll. In this method, the contaminated region of the seismic record, to be processed by the filter, is selected in such way as to correspond to the maximum of a properly defined coherence index. The main advantages of the method are that the ground roll is suppressed with negligible distortion of the remnant reflection signals and that the filtering procedure can be automated. The image processing technique described in this study should also be relevant for other applications where coherent structures embedded in a complex spatiotemporal pattern need to be identified in a more refined way. In particular, it is argued that the method is appropriate for processing optical coherence tomography images whose quality is often degraded by coherent noise (speckle).

  8. Evaluation of high frequency ghost cavitation emissions for two different seismic air-gun arrays using numerical modelling

    NASA Astrophysics Data System (ADS)

    Khodabandeloo, Babak; Landrø, Martin

    2017-04-01

    Sound is deployed by marine mammals for variety of vital purposes such as finding food, communication, echolocation, etc. On the other hand human activities generate underwater noise. One major type of acoustic source is marine seismic acquisition which is carried out to image layers beneath the seabed exploiting reflected acoustic and elastic waves. Air-gun arrays are the most common and efficient marine seismic sources. Field measurements using broad band hydrophones have revealed that acoustic energies emitted by air-gun arrays contains frequencies from a few Hz up to tens of kHz. Frequencies below 200 Hz benefit seismic imaging and the rest is normally considered as wasted energy. On the other hand, the high frequency range (above 200 Hz) overlaps with hearing curves of many marine mammals and especially toothed whales and may have an impact on their behavior. A phenomenon called ghost cavitation is recently recognized to be responsible for a major part of these high frequencies (> 5 kHz). Acoustic pressure waves of individual air guns reflected from sea surface can cause the hydrostatic pressure to drop towards zero close to the source array. In these regions there is a high probability for water vapor cavity growth and subsequent collapse. We have simulated ghost cavitation cloud using numerical modelling and the results are validated by comparing with field measurements. The model is used to compare the amount of high frequency noise due to ghost cavitation for two different air gun arrays. Both of the arrays have three subarrays but the array distance for the one with 2730 in3 air volume is 6 meters and for the slightly bigger array (3250 in3 in air volume) the subarrays are separated by 8 meters. Simulation results indicate that the second array, despite larger subarray distance, generates stronger ghost cavitation signal.

  9. Teaching hands-on geophysics: examples from the Rū seismic network in New Zealand

    NASA Astrophysics Data System (ADS)

    van Wijk, Kasper; Simpson, Jonathan; Adam, Ludmila

    2017-03-01

    Education in physics and geosciences can be effectively illustrated by the analysis of earthquakes and the subsequent propagation of seismic waves in the Earth. Educational seismology has matured to a level where both the hard- and software are robust and user friendly. This has resulted in successful implementation of educational networks around the world. Seismic data recorded by students are of such quality that these can be used in classic earthquake location exercises, for example. But even ocean waves weakly coupled into the Earth’s crust can now be recorded on educational seismometers. These signals are not just noise, but form the basis of more recent developments in seismology, such as seismic interferometry, where seismic waves generated by ocean waves—instead of earthquakes—can be used to infer information about the Earth’s interior. Here, we introduce an earthquake location exercise and an analysis of ambient seismic noise, and present examples. Data are provided, and all needed software is freely available.

  10. Seismic-Reflection Technology Defines Potential Vertical Bypass in Hydrogeologic Confinement within Tertiary Carbonates of the Southeastern Florida Platform

    NASA Astrophysics Data System (ADS)

    Cunningham, K. J.; Walker, C.; Westcott, R. L.

    2011-12-01

    Continuous improvements in shallow-focused, high-resolution, marine seismic-reflection technology has provided the opportunity to evaluate geologic structures that breach confining units of the Floridan aquifer system within the southeastern Florida Platform. The Floridan aquifer system is comprised mostly of Tertiary platform carbonates. In southeastern Florida, hydrogeologic confinement is important to sustainable use of the Floridan aquifer system, where the saline lower part is used for injection of wastewater and the brackish upper part is an alternative source of drinking water. Between 2007 and 2011, approximately 275 km of 24- and 48-channel seismic-reflection profiles were acquired in canals of peninsular southeastern Florida, Biscayne Bay, present-day Florida shelf margin, and the deeply submerged Miami Terrace. Vertical to steeply dipping offsets in seismic reflections indicate faults, which range from Eocene to possible early Pliocene age. Most faults are associated with karst collapse structures; however, a few tectonic faults of early Miocene to early Pliocene age are present. The faults may serve as a pathway for vertical groundwater flow across relatively low-permeability carbonate strata that separate zones of regionally extensive high-permeability in the Floridan aquifer system. The faults may collectively produce a regional confinement bypass system. In early 2011, twenty seismic-reflection profiles were acquired near the Key Biscayne submarine sinkhole located on the seafloor of the Miami Terrace. Here the water depth is about 365 m. A steeply dipping (eastward) zone of mostly deteriorated quality of seismic-reflection data underlies the sinkhole. Correlation of coherent seismic reflections within and adjacent to the disturbed zone indicates a series of faults occur within the zone. It is hypothesized that upward movement of groundwater within the zone contributed to development of a hypogenic karst system and the resultant overlying sinkhole

  11. Seismic sequences in the Sombrero Seismic Zone

    NASA Astrophysics Data System (ADS)

    Pulliam, J.; Huerfano, V. A.; ten Brink, U.; von Hillebrandt, C.

    2007-05-01

    The northeastern Caribbean, in the vicinity of Puerto Rico and the Virgin Islands, has a long and well-documented history of devastating earthquakes and tsunamis, including major events in 1670, 1787, 1867, 1916, 1918, and 1943. Recently, seismicity has been concentrated to the north and west of the British Virgin Islands, in the region referred to as the Sombrero Seismic Zone by the Puerto Rico Seismic Network (PRSN). In the combined seismicity catalog maintained by the PRSN, several hundred small to moderate magnitude events can be found in this region prior to 2006. However, beginning in 2006 and continuing to the present, the rate of seismicity in the Sombrero suddenly increased, and a new locus of activity developed to the east of the previous location. Accurate estimates of seismic hazard, and the tsunamigenic potential of seismic events, depend on an accurate and comprehensive understanding of how strain is being accommodated in this corner region. Are faults locked and accumulating strain for release in a major event? Or is strain being released via slip over a diffuse system of faults? A careful analysis of seismicity patterns in the Sombrero region has the potential to both identify faults and modes of failure, provided the aggregation scheme is tuned to properly identify related events. To this end, we experimented with a scheme to identify seismic sequences based on physical and temporal proximity, under the assumptions that (a) events occur on related fault systems as stress is refocused by immediately previous events and (b) such 'stress waves' die out with time, so that two events that occur on the same system within a relatively short time window can be said to have a similar 'trigger' in ways that two nearby events that occurred years apart cannot. Patterns that emerge from the identification, temporal sequence, and refined locations of such sequences of events carry information about stress accommodation that is obscured by large clouds of

  12. Optimizing Multi-Station Template Matching to Identify and Characterize Induced Seismicity in Ohio

    NASA Astrophysics Data System (ADS)

    Brudzinski, M. R.; Skoumal, R.; Currie, B. S.

    2014-12-01

    high-quality reliable stations within pre-existing seismic networks and is therefore a cost-efficient monitoring strategy for identifying and characterizing potentially induced seismic sequences.

  13. Analysis of induced seismicity in geothermal reservoirs – An overview

    USGS Publications Warehouse

    Zang, Arno; Oye, Volker; Jousset, Philippe; Deichmann, Nicholas; Gritto, Roland; McGarr, Arthur F.; Majer, Ernest; Bruhn, David

    2014-01-01

    In this overview we report results of analysing induced seismicity in geothermal reservoirs in various tectonic settings within the framework of the European Geothermal Engineering Integrating Mitigation of Induced Seismicity in Reservoirs (GEISER) project. In the reconnaissance phase of a field, the subsurface fault mapping, in situ stress and the seismic network are of primary interest in order to help assess the geothermal resource. The hypocentres of the observed seismic events (seismic cloud) are dependent on the design of the installed network, the used velocity model and the applied location technique. During the stimulation phase, the attention is turned to reservoir hydraulics (e.g., fluid pressure, injection volume) and its relation to larger magnitude seismic events, their source characteristics and occurrence in space and time. A change in isotropic components of the full waveform moment tensor is observed for events close to the injection well (tensile character) as compared to events further away from the injection well (shear character). Tensile events coincide with high Gutenberg-Richter b-values and low Brune stress drop values. The stress regime in the reservoir controls the direction of the fracture growth at depth, as indicated by the extent of the seismic cloud detected. Stress magnitudes are important in multiple stimulation of wells, where little or no seismicity is observed until the previous maximum stress level is exceeded (Kaiser Effect). Prior to drilling, obtaining a 3D P-wave (Vp) and S-wave velocity (Vs) model down to reservoir depth is recommended. In the stimulation phase, we recommend to monitor and to locate seismicity with high precision (decametre) in real-time and to perform local 4D tomography for velocity ratio (Vp/Vs). During exploitation, one should use observed and model induced seismicity to forward estimate seismic hazard so that field operators are in a position to adjust well hydraulics (rate and volume of the

  14. The nature of crustal boundaries: combined interpretation of wide-angle and normal-incidence seismic data

    NASA Astrophysics Data System (ADS)

    Long, Roger E.; Matthews, Patricia A.; Graham, Daniel P.

    1994-04-01

    After a few seconds two-way traveltime, normal-incidence seismic reflection sections are composed mainly of assemblages of short reflections. Very rarely are seen continuous reflections that might correspond to the Moho or a mid-crustal discontinuity. The inferred continuity of these boundaries has traditionally come from refraction seismology. There is now a body of high quality, coincident wide-angle and normal-incidence seismic data that have been recorded with 50-100 m shot spacing and with high frequency sources (e.g. MOBIL, BABEL). The complexity and characteristics of the wide-angle arrivals seen on these data suggest that they do not originate from continuous boundaries. It is suggested that these arrivals are reflections from the same assemblage of short length reflectors that are responsible for normal-incidence reflections. Seismic velocities below the middle crust may (1) change corresponding to normal-incidence reflectivity, or (2) generally increase with depth with localised sills or lens structures of different velocity accounting for the observed reflections. Wide-angle arrivals that have traditionally been identified as reflections from crustal boundaries (e.g. the mid-crust and Moho) and which were considered indicative of a sharp velocity discontinuity from continuous boundaries, may instead result from a concentration of lamellae.

  15. Alaska Seismic Hazards Safety Commission

    Science.gov Websites

    State Employees ASHSC State of Alaska search Alaska Seismic Hazards Safety Commission View of Anchorage and Commissions Alaska Seismic Hazards Safety Commission (ASHSC) main contant Alaska Seismic Hazards Safety Commission logo Alaska Seismic Hazards Safety Commission (ASHSC) - Mission The Alaska Seismic

  16. Continuous monitoring of high-rise buildings using seismic interferometry

    NASA Astrophysics Data System (ADS)

    Mordret, A.; Sun, H.; Prieto, G. A.; Toksoz, M. N.; Buyukozturk, O.

    2016-12-01

    The linear seismic response of a building is commonly extracted from ambient vibration measurements. Seismic deconvolution interferometry performed on ambient vibration measurements can also be used to estimate the dynamic characteristics of a building, such as the velocity of shear-waves travelling inside the building as well as a damping parameter depending on the intrinsic attenuation of the building and the soil-structure coupling. The continuous nature of the ambient vibrations allows us to measure these parameters repeatedly and to observe their temporal variations. We used 2 weeks of ambient vibration recorded by 36 accelerometers installed in the Green Building on the Massachusetts Institute of Technology campus (Cambridge, MA) to continuously monitor the shear-wave speed and the attenuation factor of the building. Due to the low strain of the ambient vibrations, the observed changes are totally reversible. The relative velocity changes between a reference deconvolution function and the current deconvolution functions are measured with two different methods: 1) the Moving Window Cross-Spectral technique and 2) the stretching technique. Both methods show similar results. We show that measuring the stretching coefficient for the deconvolution functions filtered around the fundamental mode frequency is equivalent to measuring the wandering of the fundamental frequency in the raw ambient vibration data. By comparing these results with local weather parameters, we show that the relative air humidity is the factor dominating the relative seismic velocity variations in the Green Building, as well as the wandering of the fundamental mode. The one-day periodic variations are affected by both the temperature and the humidity. The attenuation factor, measured as the exponential decay of the fundamental mode waveforms, shows a more complex behaviour with respect to the weather measurements.

  17. Strain limits for concrete filled steel tubes in AASHTO seismic provisions.

    DOT National Transportation Integrated Search

    2013-08-01

    Reinforced concrete filled steel tubes (RCFSTs) are commonly used as bridge pipe piles in high seismic regions. The pipe piles in high : seismic regions. The pipe-piles consist of reinforced concrete encased in a steel tube. The steel tube is used as...

  18. Enhancement of seismic monitoring in hydrocarbon reservoirs

    NASA Astrophysics Data System (ADS)

    Caffagni, Enrico; Bokelmann, Götz

    2017-04-01

    Hydraulic Fracturing (HF) is widely considered as one of the most significant enablers of the successful exploitation of hydrocarbons in North America. Massive usage of HF is currently adopted to increase the permeability in shale and tight-sand deep reservoirs, despite the economical downturn. The exploitation success is less due to the subsurface geology, but in technology that improves exploration, production, and decision-making. This includes monitoring of the reservoir, which is vital. Indeed, the general mindset in the industry is to keep enhancing seismic monitoring. It allows understanding and tracking processes in hydrocarbon reservoirs, which serves two purposes, a) to optimize recovery, and b) to help minimize environmental impact. This raises the question of how monitoring, and especially seismic techniques could be more efficient. There is a pressing demand from seismic service industry to evolve quickly and to meet the oil-gas industry's changing needs. Nonetheless, the innovative monitoring techniques, to achieve the purpose, must enhance the characterization or the visualization of a superior-quality images of the reservoir. We discuss recent applications of seismic monitoring in hydrocarbon reservoirs, detailing potential enhancement and eventual limitations. The aim is to test the validity of these seismic monitoring techniques, qualitatively discuss their potential application to energy fields that are not only limited to HF. Outcomes from our investigation may benefit operators and regulators in case of future massive HF applications in Europe, as well. This work is part of the FracRisk consortium (www.fracrisk.eu), funded by the Horizon2020 research programme, whose aims is to help minimize the environmental footprint of the shale-gas exploration and exploitation.

  19. An Investigation of Seismicity for the West Sumatra Region Indonesia

    NASA Astrophysics Data System (ADS)

    Syafriani, S.

    2018-04-01

    The purpose of this research was to investigate the seismicity of the West Sumatra region in the coordinates area of 94° E – 104° E and 2° N - 4° S. Guttenberg-Richer magnitude-frequency relation and seismic risk have been computed. Historical data of earthquakes used from year of 1970 to 2017 with magnitude higher than 4. The study area was divided into 8 sub-regions based on seismotectonic characteristics, plate tectonic and geological models. The determination of seismotectonic characteristics was based on the level of seismic activity in a region (a value) and rock stress condition (b value). High a value was associated with high seismic activity, whereas high b values were associated with low stress rock conditions, and vice versa. Based on the calculation results, a and b values were obtained in the interval of 5.5-11.3 and 0.7-2. The highest b value was obtained in the sub region 5 (Nias islands), while the lowest b value was obtained in sub region 7 (the Mentawai islands). The sub region 7, Mentawai Islands was indicated as the seismic risk potential areas.

  20. Seismic array observations for monitoring phreatic eruptions in Iwojima Island, Japan

    NASA Astrophysics Data System (ADS)

    Ueda, H.; Kawaguchi, R.; Chiba, K.; Fujita, E.; Tanada, T.

    2015-12-01

    Iwojima is an active volcanic island located within a 10 km wide submarine caldera about 1250 km to the south of Tokyo, Japan. The volcanic activity is characterized by intensive earthquake activity associated with an island-wide uplift with high uplift rate (30~40 cm/year) and hydrothermal activity. In the last 10 years, phreatic eruptions took place in and near the island in 2012, 2013, and 2015. In such restless volcano, predictions and detections of occurrence points of phreatic eruptions are important for ensuring safety of residents. In the previous studies, we found that the earthquake activity of Iwojima highly correlates with the island wide large uplift, but the precursory activity of the phreatic eruption in 2012 was deviated from the correlation (Ueda et al. 2013 AGU Fall Meeting). For prediction of occurrence points of phreatic eruptions and investigation of the eruption mechanism, we began observation by seismic arrays at two areas in December 2014. The seismic arrays enable to locate epicenters of volcanic tremors, which are not well located by existing seismic stations. In May and June 2015, Japan Maritime Self-Defense Force stayed in Iwojima and a live camera of Japan Meteorological Agency found very small phreatic eruptions occurred at the northern beach. Existing seismic stations could not detect seismic signals related with the eruptions. The seismic array could detect weak seismic signals related with the eruptions. Although the seismic arrays could not detect precursory signals because of too small eruption, we expect the seismic arrays can detect precursory seismic signals suggesting occurrence points of small or medium-sized phreatic eruptions. The seismic arrays also detected epicenters of harmonic and monotonic tremors took place at an active fumarolic field in the north earthen part of Iwojima. The apparent velocity of seismic waves (~1km/s) strongly suggests that the tremors relate with hydrothermal activity near ground surface.

  1. Regional Characterization of Tokyo Metoropolitan area using a highly-dense seismic netwok(MeSO-net)

    NASA Astrophysics Data System (ADS)

    Hirata, N.; Nakagawa, S.; Sakai, S.; Panayotopoulos, Y.; Ishikawa, M.; Ishibe, T.; Kimura, H.; Honda, R.

    2014-12-01

    We have developed a dense seismic network, MeSO-net (Metropolitan Seismic Observation network), since 2007 in the greater Tokyo urban region under the Special Project for Earthquake Disaster Mitigation in Tokyo Metropolitan Area (FY2007-FY2011) and Special Project for Reducing Vulnerability for Urban Mega Earthquake Disasters (FY2012-FY2016)( Hirata et al., 2009). So far we have acquired more than 120TB continuous seismic data form MeSO-net which consists of about 300 seismic stations. Using MeSO-net data, we obtain clear P- and S- wave velocity tomograms (Nakagawa et al., 2010) and Qp, Qs tomograms (Panayotopoulos et al., 2014) which show a clear image of Philippine Sea Plate (PSP) and PAcific Plate (PAP). A depth to the top of PSP, 20 to 30 km beneath northern part of Tokyo bay, is about 10 km shallower than previous estimates based on the distribution of seismicity (Ishida, 1992). This shallower plate geometry changes estimations of strong ground motion for seismic hazards analysis within the Tokyo region. Based on elastic wave velocities of rocks and minerals, we interpreted the tomographic images as petrologic images. Tomographic images revealed the presence of two stepwise velocity increase of the top layer of the subducting PSP slab. Because strength of the serpentinized peridotite is not large enough for brittle fracture, if the area is smaller than previously estimated, a possible area of the large thrust fault on the upper surface of PSP can be larger than previously thought. Change of seismicity rate after the 2011 Tohoku-oki earthquake suggests change of stressing rate in greater Tokyo. Quantitative analysis of MeSO-net data shows significant increase of rate of earthquakes that have a fault orientation favorable to increasing Coulomb stress after the Tohoku-oki event.

  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. High-resolution seismic-reflection data from offshore northern California — Bolinas to Sea Ranch

    USGS Publications Warehouse

    Sliter, Ray W.; Johnson, Samuel Y.; Chin, John L.; Allwardt, Parker; Beeson, Jeffrey; Triezenberg, Peter J.

    2016-12-05

    The U.S. Geological Survey collected high-resolution seismic-reflection data in September 2009, on survey S-8-09-NC, offshore of northern California between Bolinas and Sea Ranch.The survey area spans about 125 km of California’s coast and extends around Point Reyes. Data were collected aboard the U.S. Geological Survey R/V Parke Snavely. Cumulatively, ~1,150 km of seismic-reflection data were acquired using a SIG 2mille minisparker. Subbottom acoustic depth of penetration spanned tens to several hundred meters and varied by location and underlying sediments and rock types.This report includes maps and a navigation file of the surveyed transects, utilizing Google Earth™ software, as well as digital data files showing images of each transect in SEG-Y and JPEG formats. The images of bedrock, sediment deposits, and tectonic structure provide geologic information that is essential to hazard assessment, regional sediment management, and coastal and marine spatial planning at Federal, State and local levels. This information is also valuable for future research on the geomorphic, sedimentary, tectonic, and climatic record of central California.

  4. High-resolution seismic-reflection images across the ICDP-USGS Eyreville deep drilling site, Chesapeake Bay impact structure

    USGS Publications Warehouse

    Powars, D.S.; Catchings, R.D.; Goldman, M.R.; Gohn, G.S.; Horton, J. Wright; Edwards, L.E.; Rymer, M.J.; Gandhok, G.

    2009-01-01

    The U.S. Geological Survey (USGS) acquired two 1.4-km-long, high-resolution (??5 m vertical resolution) seismic-reflection lines in 2006 that cross near the International Continental Scientifi c Drilling Program (ICDP)-USGS Eyreville deep drilling site located above the late Eocene Chesapeake Bay impact structure in Virginia, USA. Five-meter spacing of seismic sources and geophones produced high-resolution images of the subsurface adjacent to the 1766-m-depth Eyreville core holes. Analysis of these lines, in the context of the core hole stratigraphy, shows that moderateamplitude, discontinuous, dipping reflections below ??527 m correlate with a variety of Chesapeake Bay impact structure sediment and rock breccias recovered in the cores. High-amplitude, continuous, subhorizontal reflections above ??527 m depth correlate with the uppermost part of the Chesapeake Bay impact structure crater-fi ll sediments and postimpact Eocene to Pleistocene sediments. Refl ections with ??20-30 m of relief in the uppermost part of the crater-fi ll and lowermost part of the postimpact section suggest differential compaction of the crater-fi ll materials during early postimpact time. The top of the crater-fi ll section also shows ??20 m of relief that appears to represent an original synimpact surface. Truncation surfaces, locally dipping reflections, and depth variations in reflection amplitudes generally correlate with the lithostratigraphic and sequence-stratigraphic units and contacts in the core. Seismic images show apparent postimpact paleochannels that include the fi rst possible Miocene paleochannels in the Mid-Atlantic Coastal Plain. Broad downwarping in the postimpact section unrelated to structures in the crater fi ll indicates postimpact sediment compaction. ?? 2009 The Geological Society of America.

  5. Constraining Seismic Structure of Upper-Mantle Discontinuities: A New Approach Using High-Frequency Triplication Data

    NASA Astrophysics Data System (ADS)

    Ishii, M.; Park, S.

    2016-12-01

    Constraining elastic properties of the 410- and 660-km discontinuities is crucial for understanding the mantle composition and dynamics. One approach to study the transition zone is to use the "triplicated" arrivals of seismic data. These arrivals consist of three seismic phases that are sensitive to seismic structure slightly above, at, and below the discontinuity. Thus, these data are powerful tools in providing constraints on the depth and velocity jump of the discontinuities with consequences for the studies of mantle composition and relevant phase transitions. One of the most challenging aspects of using the triplication data, however, is to identify the three individual phases that arrive close in time. In order to separate the three phases, we apply Radon transform to short-period seismograms recorded by a dense array of stations. This approach unwraps the triplication pattern, and brings out the high-frequency information that is not easily accessible in the original form of data. Subsequent modeling of the unwrapped data allows velocity jump, depth, and width of the discontinuities to be obtained. This method is applied to study the transition zone around the Kuril subduction zone, a region northeast of Japan. We take advantage of the High-Sensitivity Seismograph Network in Japan that consists of more than 700 stations. These stations provide dense sampling in distance that allows us to capture the triplication pattern. The wave speeds immediately above and below the 410- and 660-km discontinuities as well as their depths and widths are constrained. In general, both discontinuities are depressed compared to the global average, and exhibit finite widths. The width estimates have implications on effects such as the existence of water or melt, and garnet transformations occurring at similar depths as the post-spinel transition.

  6. Detecting Seismic Activity with a Covariance Matrix Analysis of Data Recorded on Seismic Arrays

    NASA Astrophysics Data System (ADS)

    Seydoux, L.; Shapiro, N.; de Rosny, J.; Brenguier, F.

    2014-12-01

    Modern seismic networks are recording the ground motion continuously all around the word, with very broadband and high-sensitivity sensors. The aim of our study is to apply statistical array-based approaches to processing of these records. We use the methods mainly brought from the random matrix theory in order to give a statistical description of seismic wavefields recorded at the Earth's surface. We estimate the array covariance matrix and explore the distribution of its eigenvalues that contains information about the coherency of the sources that generated the studied wavefields. With this approach, we can make distinctions between the signals generated by isolated deterministic sources and the "random" ambient noise. We design an algorithm that uses the distribution of the array covariance matrix eigenvalues to detect signals corresponding to coherent seismic events. We investigate the detection capacity of our methods at different scales and in different frequency ranges by applying it to the records of two networks: (1) the seismic monitoring network operating on the Piton de la Fournaise volcano at La Réunion island composed of 21 receivers and with an aperture of ~15 km, and (2) the transportable component of the USArray composed of ~400 receivers with ~70 km inter-station spacing.

  7. High-quality cardiopulmonary resuscitation.

    PubMed

    Nolan, Jerry P

    2014-06-01

    The quality of cardiopulmonary resuscitation (CPR) impacts on outcome after cardiac arrest. This review will explore the factors that contribute to high-quality CPR and the metrics that can be used to monitor performance. A recent consensus statement from North America defined five key components of high-quality CPR: minimizing interruptions in chest compressions, providing compressions of adequate rate and depth, avoiding leaning on the chest between compressions, and avoiding excessive ventilation. Studies have shown that real-time feedback devices improve the quality of CPR and, in one before-and-after study, outcome from out-of-hospital cardiac arrest. There is evidence for increasing survival rates following out-of-hospital cardiac arrest and this is associated with increasing rates of bystander CPR. The quality of CPR provided by healthcare professionals can be improved with real-time feedback devices. The components of high-quality CPR and the metrics that can be measured and fed back to healthcare professionals have been defined by expert consensus. In the future, real-time feedback based on the physiological responses to CPR may prove more effective.

  8. Integration of high-resolution seismic and aeromagnetic data for earthquake hazards evaluations: An example from the Willamette Valley, Oregon

    USGS Publications Warehouse

    Liberty, L.M.; Trehu, A.M.; Blakely, R.J.; Dougherty, M.E.

    1999-01-01

    Aeromagnetic and high-resolution seismic reflection data were integrated to place constraints on the history of seismic activity and to determine the continuity of the possibly active, yet largely concealed Mount Angel fault in the Willamette Valley, Oregon. Recent seismic activity possibly related to the 20-km-long fault includes a swarm of small earthquakes near Woodburn in 1990 and the magnitude 5.6 Scotts Mills earthquake in 1993. Newly acquired aeromagnetic data show several large northwest-trending anomalies, including one associated with the Mount Angel fault. The magnetic signature indicates that the fault may actually extend 70 km across the Willamette Valley to join the Newberg and Gales Creek faults in the Oregon Coast Range. We collected 24-fold high-resolution seismic reflection data along two transects near Woodburn, Oregon, to image the offset of the Miocene-age Columbia River Basalts (CRB) and overlying sediments at and northwest of the known mapped extent of the Mount Angel fault. The seismic data show a 100-200-m offset in the CRB reflector at depths from 300 to 700 m. Folded or offset sediments appear above the CRB with decreasing amplitude to depths as shallow as were imaged (approximately 40 m). Modeling experiments based on the magnetic data indicate, however, that the anomaly associated with the Mount Angel fault is not caused solely by an offset of the CRB and overlying sediments. Underlying magnetic sources, which we presume to be volcanic rocks of the Siletz terrane, must have vertical offsets of at least 500 m to fit the observed data. We conclude that the Mount Angel fault appears to have been active since Eocene age and that the Gales Creek, Newberg, and Mount Angel faults should be considered a single potentially active fault system. This fault, as well as other parallel northwest-trending faults in the Willamette Valley, should be considered as risks for future potentially damaging earthquakes.

  9. Preliminary Results from the North Anatolian Fault Passive Seismic Experiment: Seismicity and Anisotropy

    NASA Astrophysics Data System (ADS)

    Biryol, C. B.; Ozacar, A.; Beck, S. L.; Zandt, G.

    2006-12-01

    The North Anatolian Fault (NAF) is one of the world's largest continental strike-slip faults. Despite much geological work at the surface, the deep structure of the NAF is relatively unknown. The North Anatolian Fault Passive Seismic Experiment is mainly focused on the lithospheric structure of this newly coalescing continental transform plate boundary. In the summer of 2005, we deployed 5 broadband seismic stations near the fault to gain more insight on the background seismicity, and in June 2006 we deployed 34 additional broadband stations along multiple transects crossing the main strand of the NAF and its splays. In the region, local seismicity is not limited to a narrow band near the NAF but distributed widely suggesting widespread continental deformation especially in the southern block. We relocated two of the largest events (M>4) that occurred close to our stations. Both events are 40-50km south of the NAF in the upper crust (6-9 km) along a normal fault with a strike-slip component that previously ruptured during the June 6, 2000 Orta-Cankiri earthquake (M=6.0). Preliminary analysis of SKS splitting for 4 stations deployed in 2005 indicates seismic anisotropy with delay times exceeding 1 sec. The fast polarization directions for these stations are primarily in NE-SW orientation, which remains uniform across the NAF. This direction is at a high angle to the surface trace of the fault and crustal velocity field, suggesting decoupling of lithosphere and mantle flow. Our SKS splitting observations are also similar to that observed from GSN station ANTO in central Turkey and stations across the Anatolian Plateau in eastern Turkey indicating relatively uniform mantle anisotropy throughout the region.

  10. Advances through collaboration: sharing seismic reflection data via the Antarctic Seismic Data Library System for Cooperative Research (SDLS)

    USGS Publications Warehouse

    Wardell, N.; Childs, J. R.; Cooper, A. K.

    2007-01-01

    The Antarctic Seismic Data Library System for Cooperative Research (SDLS) has served for the past 16 years under the auspices of the Antarctic Treaty (ATCM Recommendation XVI-12) as a role model for collaboration and equitable sharing of Antarctic multichannel seismic reflection (MCS) data for geoscience studies. During this period, collaboration in MCS studies has advanced deciphering the seismic stratigraphy and structure of Antarctica’s continental margin more rapidly than previously. MCS data compilations provided the geologic framework for scientific drilling at several Antarctic locations and for high-resolution seismic and sampling studies to decipher Cenozoic depositional paleoenvironments. The SDLS successes come from cooperation of National Antarctic Programs and individual investigators in “on-time” submissions of their MCS data. Most do, but some do not. The SDLS community has an International Polar Year (IPY) goal of all overdue MCS data being sent to the SDLS by end of IPY. The community science objective is to compile all Antarctic MCS data to derive a unified seismic stratigraphy for the continental margin – a stratigraphy to be used with drilling data to derive Cenozoic circum-Antarctic paleobathymetry maps and local-to-regional scale paleoenvironmental histories.

  11. Imaging the crustal structure of Haiti's transpressional fault system using seismicity and tomography

    NASA Astrophysics Data System (ADS)

    Possee, D.; Keir, D.; Harmon, N.; Rychert, C.; Rolandone, F.; Leroy, S. D.; Stuart, G. W.; Calais, E.; Boisson, D.; Ulysse, S. M. J.; Guerrier, K.; Momplaisir, R.; Prepetit, C.

    2017-12-01

    Oblique convergence of the Caribbean and North American plates has partitioned strain across an extensive transpressional fault system that bisects Haiti. Most recently the 2010, MW7.0 earthquake ruptured multiple thrust faults in southern Haiti. However, while the rupture mechanism has been well studied, how these faults are segmented and link to deformation across the plate boundary is still debated. Understanding the link between strain accumulation and faulting in Haiti is also key to future modelling of seismic hazards. To assess seismic activity and fault structures we used data from 31 broadband seismic stations deployed on Haiti for 16-months. Local earthquakes were recorded and hypocentre locations determined using a 1D velocity model. A high-quality subset of the data was then inverted using travel-time tomography for relocated hypocentres and 2D images of Vp and Vp/Vs crustal structure. Earthquake locations reveal two clusters of seismic activity, the first delineates faults associated with the 2010 earthquake and the second shows activity 100km further east along a thrust fault north of Lake Enriquillo (Dominican Republic). The velocity models show large variations in seismic properties across the plate boundary; shallow low-velocity zones with a 5-8% decrease in Vp and high Vp/Vs ratios of 1.85-1.95 correspond to sedimentary basins that form the low-lying terrain on Haiti. We also image a region with a 4-5% decrease in Vp and an increased Vp/Vs ratio of 1.80-1.85 dipping south to a depth of 20km beneath southern Haiti. This feature matches the location of a major thrust fault and suggests a substantial damage zone around this fault. Beneath northern Haiti a transition to lower Vp/Vs values of 1.70-1.75 reflects a compositional change from mafic facies such as the Caribbean large igneous province in the south, to arc magmatic facies associated with the Greater Antilles arc in the north. Our seismic images are consistent with the fault system across

  12. Seismic expression of Red Fork channels in Major and Kay Counties, Oklahoma

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

    Hanoch, C.A.

    1987-08-01

    This paper investigates the application of regional seismic to exploration and development Red Fork sands of the Cherokee Group, in Major and Kay Counties, Oklahoma. A computer-aided exploration system (CAEX) was used to justify the subtle seismic expressions with the geological interpretation. Modeling shows that the low-velocity shales are the anomalous rock in the Cherokee package, which is most represented by siltstone and thin sands. Because the Red Fork channel sands were incised into or deposited with laterally time-equivalent siltstones, no strong reflection coefficient is associated with the top of the sands. The objective sands become a seismic anomaly onlymore » when they cut into and replace a low-velocity shale. This knowledge allows mapping the channel thickness by interpreting the shale thickness from seismic data. A group shoot line in Major County, Oklahoma, has been tied to the geologic control, and the channel thicknesses have been interpreted assuming a detectable vertical resolution of 10 ft. A personal computer-based geophysical work station is used to construct velocity logs representative of the geology to produce forward-modeled synthetic seismic sections, and to display, in color, the seismic trace attributes. These synthetic sections are used as tools to compare with and interpret the seismic line and to evaluate the interpretative value of lowest cost, lesser quality data versus reprocessing or new data acquisition.« less

  13. A quantitative analysis of global intermediate and deep seismicity

    NASA Astrophysics Data System (ADS)

    Ruscic, Marija; Becker, Dirk; Le Pourhiet, Laetitita; Agard, Philippe; Meier, Thomas

    2017-04-01

    exhibiting higher ratios indicating stronger hydration of older slabs and consequently stronger seismic activity at depth in older and thicker slabs. Furthermore, older slabs show the tendency to larger b-values. This indicates stronger fragmentation of older slabs favoring smaller events. Between 50 km and 300 km depth, seismicity in subduction zones decays nearly exponentially with depth. However, the majority of subduction zones show between about 60 km and 100 km lower seismic activity than expected by an exponential decay. This observation correlates well with findings from petrological studies that rocks are rarely scraped off from the downgoing plate at these depths indicating low seismic coupling and low stresses at the plate interface in a depth range below the seismogenic zone and above 100 km depth were dehydration reactions become virulent. Interestingly, the percentage of this deficit becomes larger with plate age for event frequency (reduced number of events), but decreases for moment release (events have larger magnitudes). It is observed that the forearc high is located above the plate interface with reduced seismic coupling. The forearc high is thus an indication of upward directed return flow along the seismically decoupled plate interface. In addition, it is found that the topography of the forearc high is larger above shallow dipping slabs. A correlation of the depth dependent seismic behavior with the subduction or trench velocity is not observed for the investigated subduction zones. Plate age seems to be the dominating factor for properties of intermediate deep and deep seismicity.

  14. Sequence stratigraphy, seismic stratigraphy, and seismic structures of the lower intermediate confining unit and most of the Floridan aquifer system, Broward County, Florida

    USGS Publications Warehouse

    Cunningham, Kevin J.; Kluesner, Jared W.; Westcott, Richard L.; Robinson, Edward; Walker, Cameron; Khan, Shakira A.

    2017-12-08

    Deep well injection and disposal of treated wastewater into the highly transmissive saline Boulder Zone in the lower part of the Floridan aquifer system began in 1971. The zone of injection is a highly transmissive hydrogeologic unit, the Boulder Zone, in the lower part of the Floridan aquifer system. Since the 1990s, however, treated wastewater injection into the Boulder Zone in southeastern Florida has been detected at three treated wastewater injection utilities in the brackish upper part of the Floridan aquifer system designated for potential use as drinking water. At a time when usage of the Boulder Zone for treated wastewater disposal is increasing and the utilization of the upper part of the Floridan aquifer system for drinking water is intensifying, there is an urgency to understand the nature of cross-formational fluid flow and identify possible fluid pathways from the lower to upper zones of the Floridan aquifer system. To better understand the hydrogeologic controls on groundwater movement through the Floridan aquifer system in southeastern Florida, the U.S. Geological Survey and the Broward County Environmental Planning and Community Resilience Division conducted a 3.5-year cooperative study from July 2012 to December 2015. The study characterizes the sequence stratigraphy, seismic stratigraphy, and seismic structures of the lower part of the intermediate confining unit aquifer and most of the Floridan aquifer system.Data obtained to meet the study objective include 80 miles of high-resolution, two-dimensional (2D), seismic-reflection profiles acquired from canals in eastern Broward County. These profiles have been used to characterize the sequence stratigraphy, seismic stratigraphy, and seismic structures in a 425-square-mile study area. Horizon mapping of the seismic-reflection profiles and additional data collection from well logs and cores or cuttings from 44 wells were focused on construction of three-dimensional (3D) visualizations of eight

  15. Map of Pseudo-F-statistics of seismic noise parameters as an indicator of current seismic danger in Japan

    NASA Astrophysics Data System (ADS)

    Lyubushin, Alexey

    2016-04-01

    The problem of estimate of current seismic danger based on monitoring of seismic noise properties from broadband seismic network F-net in Japan (84 stations) is considered. Variations of the following seismic noise parameters are analyzed: multifractal singularity spectrum support width, generalized Hurst exponent, minimum Hölder-Lipschitz exponent and minimum normalized entropy of squared orthogonal wavelet coefficients. These parameters are estimated within adjacent time windows of the length 1 day for seismic noise waveforms from each station. Calculating daily median values of these parameters by all stations provides 4-dimensional time series which describes integral properties of the seismic noise in the region covered by the network. Cluster analysis is applied to the sequence of clouds of 4-dimensional vectors within moving time window of the length 365 days with mutual shift 3 days starting from the beginning of 1997 up to the current time. The purpose of the cluster analysis is to find the best number of clusters (BNC) from probe numbers which are varying from 1 up to the maximum value 40. The BNC is found from the maximum of pseudo-F-statistics (PFS). A 2D map could be created which presents dependence of PFS on the tested probe number of clusters and the right-hand end of moving time window which is rather similar to usual spectral time-frequency diagrams. In the paper [1] it was shown that the BNC before Tohoku mega-earthquake on March 11, 2011, has strongly chaotic regime with jumps from minimum up to maximum values in the time interval 1 year before the event and this time intervals was characterized by high PFS values. The PFS-map is proposed as the method for extracting time intervals with high current seismic danger. The next danger time interval after Tohoku mega-EQ began at the end of 2012 and was finished at the middle of 2013. Starting from middle of 2015 the high PFS values and chaotic regime of BNC variations were returned. This could be

  16. Development of seismic tomography software for hybrid supercomputers

    NASA Astrophysics Data System (ADS)

    Nikitin, Alexandr; Serdyukov, Alexandr; Duchkov, Anton

    2015-04-01

    Seismic tomography is a technique used for computing velocity model of geologic structure from first arrival travel times of seismic waves. The technique is used in processing of regional and global seismic data, in seismic exploration for prospecting and exploration of mineral and hydrocarbon deposits, and in seismic engineering for monitoring the condition of engineering structures and the surrounding host medium. As a consequence of development of seismic monitoring systems and increasing volume of seismic data, there is a growing need for new, more effective computational algorithms for use in seismic tomography applications with improved performance, accuracy and resolution. To achieve this goal, it is necessary to use modern high performance computing systems, such as supercomputers with hybrid architecture that use not only CPUs, but also accelerators and co-processors for computation. The goal of this research is the development of parallel seismic tomography algorithms and software package for such systems, to be used in processing of large volumes of seismic data (hundreds of gigabytes and more). These algorithms and software package will be optimized for the most common computing devices used in modern hybrid supercomputers, such as Intel Xeon CPUs, NVIDIA Tesla accelerators and Intel Xeon Phi co-processors. In this work, the following general scheme of seismic tomography is utilized. Using the eikonal equation solver, arrival times of seismic waves are computed based on assumed velocity model of geologic structure being analyzed. In order to solve the linearized inverse problem, tomographic matrix is computed that connects model adjustments with travel time residuals, and the resulting system of linear equations is regularized and solved to adjust the model. The effectiveness of parallel implementations of existing algorithms on target architectures is considered. During the first stage of this work, algorithms were developed for execution on

  17. Development of Deep-tow Autonomous Cable Seismic (ACS) for Seafloor Massive Sulfides (SMSs) Exploration.

    NASA Astrophysics Data System (ADS)

    Asakawa, Eiichi; Murakami, Fumitoshi; Tsukahara, Hitoshi; Saito, Shutaro; Lee, Sangkyun; Tara, Kenji; Kato, Masafumi; Jamali Hondori, Ehsan; Sumi, Tomonori; Kadoshima, Kazuyuki; Kose, Masami

    2017-04-01

    Within the EEZ of Japan, numerous surveys exploring ocean floor resources have been conducted. The exploration targets are gas hydrates, mineral resources (manganese, cobalt or rare earth) and especially seafloor massive sulphide (SMS) deposits. These resources exist in shallow subsurface areas in deep waters (>1500m). For seismic explorations very high resolution images are required. These cannot be effectively obtained with conventional marine seismic techniques. Therefore we have been developing autonomous seismic survey systems which record the data close to the seafloor to preserve high frequency seismic energy. Very high sampling rate (10kHz) and high accurate synchronization between recording systems and shot time are necessary. We adopted Cs-base atomic clock considering its power consumption. At first, we developed a Vertical Cable Seismic (VCS) system that uses hydrophone arrays moored vertically from the ocean bottom to record close to the target area. This system has been successfully applied to SMS exploration. Specifically it fixed over known sites to assess the amount of reserves with the resultant 3D volume. Based on the success of VCS, we modified the VCS system to use as a more efficient deep-tow seismic survey system. Although there are other examples of deep-tow seismic systems, signal transmission cables present challenges in deep waters. We use our autonomous recording system to avoid these problems. Combining a high frequency piezoelectric source (Sub Bottom Profiler:SBP) that automatically shots with a constant interval, we achieve the high resolution deep-tow seismic without data transmission/power cable to the board. Although the data cannot be monitored in real-time, the towing system becomes very simple. We have carried out survey trial, which showed the systems utility as a high-resolution deep-tow seismic survey system. Furthermore, the frequency ranges of deep-towed source (SBP) and surface towed sparker are 700-2300Hz and 10-200Hz

  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. The AlpArray-CASE project: temporary broadband seismic network deployment and characterization

    NASA Astrophysics Data System (ADS)

    Dasović, Iva; Molinari, Irene; Stipčević, Josip; Šipka, Vesna; Salimbeni, Simone; Jarić, Dejan; Prevolnik, Snježan; Kissling, Eduard; Clinton, John; Giardini, Domenico

    2017-04-01

    While the northern part of the Adriatic microplate will be accurately imaged within the AlpArray project, its central and southern parts deserve detailed studies to obtain a complete picture of its structure and evolution. The Adriatic microplate forms the upper plate in the Western and Central Alps whereas it forms the lower plate in the Apennines and the Dinarides. However, the tectonics of Adriatic microplate is not well constrained and remains controversial, especially with regard to its contact with the Dinarides. The primary goal of the Central Adriatic Seismic Experiment (CASE) is to provide high quality seismological data and to shed light on seismicity and 3D lithospheric structure of the central Adriatic microplate and its boundaries. The CASE project is an international AlpArray Complementary Experiment carried out by four institutions: Department of Earth Sciences and Swiss Seismological Service of ETH Zürich (CH), Department of Geophysics and Croatian Seismological Service of Faculty of Science at University of Zagreb (HR), Republic Hydrometeorological Service of Republic of Srpska (BIH) and Istituto Nazionale di Geofisica e Vulcanologia (I). It establishes a temporary seismic network, expected to be operational at least for one year, composed by existing permanent and temporary seismic stations operated by the institutions involved and newly deployed temporary seismic stations, installed in November and December 2016, provided by ETH Zürich and INGV: five in Croatia, four in Bosnia and Herzegovina and two in Italy. In this work, we present stations sites and settings and discuss their characteristics in terms of site-effects and noise level of each station. In particular, we analyse the power spectral density estimates in order to investigate major sources of noise and background noise.

  20. Time-marching multi-grid seismic tomography

    NASA Astrophysics Data System (ADS)

    Tong, P.; Yang, D.; Liu, Q.

    2016-12-01

    From the classic ray-based traveltime tomography to the state-of-the-art full waveform inversion, because of the nonlinearity of seismic inverse problems, a good starting model is essential for preventing the convergence of the objective function toward local minima. With a focus on building high-accuracy starting models, we propose the so-called time-marching multi-grid seismic tomography method in this study. The new seismic tomography scheme consists of a temporal time-marching approach and a spatial multi-grid strategy. We first divide the recording period of seismic data into a series of time windows. Sequentially, the subsurface properties in each time window are iteratively updated starting from the final model of the previous time window. There are at least two advantages of the time-marching approach: (1) the information included in the seismic data of previous time windows has been explored to build the starting models of later time windows; (2) seismic data of later time windows could provide extra information to refine the subsurface images. Within each time window, we use a multi-grid method to decompose the scale of the inverse problem. Specifically, the unknowns of the inverse problem are sampled on a coarse mesh to capture the macro-scale structure of the subsurface at the beginning. Because of the low dimensionality, it is much easier to reach the global minimum on a coarse mesh. After that, finer meshes are introduced to recover the micro-scale properties. That is to say, the subsurface model is iteratively updated on multi-grid in every time window. We expect that high-accuracy starting models should be generated for the second and later time windows. We will test this time-marching multi-grid method by using our newly developed eikonal-based traveltime tomography software package tomoQuake. Real application results in the 2016 Kumamoto earthquake (Mw 7.0) region in Japan will be demonstrated.