Download or read book Methods for Improving Seismic Event Location Processing written by and published by . This book was released on 2001 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Our research program consists of four components, each involving some aspect of multiple-event analysis: (1) high-precision waveform cross-correlation (WCC) for arrival time estimation, (2) robust event clustering, (3) waveform decomposition and source wavelet deconvolution reshaping, (4) double-difference (DD) multiple-event locations and tomography. Our research focused initially on the development and testing of these seismic analysis methods using 'ground-truth' (GT) datasets at different scales (local and regional), and is being followed by the application of these methods to a 'test bed' regional-distance seismic dataset, including tests on real-time and simulated real-time data streams. Here we highlight some of the more significant project achievements from components 1, 2 and 4.

Download or read book Methods of Improving Regional Seismic Event Locations written by and published by . This book was released on 2001 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this paper we investigate the effect that depth-dependent Source Specific Station Corrections (SSSC's) have on improving regional seismic event location accuracy. To accomplish this we have relocated events considered GT5 or less that occur within the region encompassed by Weston Geophysical's regional 3-D model of the India-Pakistan region (WINPAK3D) using different depth-dependent SSSC's. By comparing the hypocenters produced using SSSC's at different depths to the ground truth location, we have gained insight into the minimum number of depth-dependent SSSC's that must be implemented in current automatic processing routines for accurate and efficient regional event location. For a crustal earthquake, we generated SSSC's for a suite of depths by calculating travel times for WINPAK3D relative to the global IASPEI91 model (Kennett and Engdahl, 1991) to all regional stations. We then estimated the event hypocenter using the International Seismological Center (ISC) location as an initial hypocenter and two different but closely related methods of SSSC application and hypocenter location. For both location procedures, we compared the location derived from application of the different depth-dependent SSSC's to the ISC location in order to determine if there were significant differences in the hypocenters. Our initial results suggest that two SSSC's, one for the crust and one for the mantle, may be the minimum number of SSSC's to achieve the current goal in location accuracy in our study region.

Download or read book Advances in Seismic Event Location written by Cliffort H. Thurber and published by Springer Science & Business Media. This book was released on 2013-11-11 with total page 271 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advances in Seismic Event Location provides a broad overview of the fundamental issues involved in seismic event location, and presents a variety of state-of-the-art location methods and applications at a wide range of spatial scales. Three important themes in the book are: seismic monitoring for a Comprehensive Nuclear-Test-Ban Treaty (CTBT), seismic event location in three-dimensional Earth models, and methods for multiple-event location. Each chapter contains background material to help readers less familiar with the topics covered, as well as to provide abundant references for readers interested in probing deeper into a topic. However, most of the emphasis is on recent advances in methodology and their application. Audience: The book is intended primarily for academic and professional researchers and graduate students in seismology.

Download or read book The DOE Model for Improving Seismic Event Locations Using Travel Time Corrections written by and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The U.S. National Laboratories, under the auspices of the Department of Energy, have been tasked with improv- ing the capability of the United States National Data Center (USNDC) to monitor compliance with the Comprehen- sive Test Ban Trea~ (CTBT). One of the most important services which the USNDC must provide is to locate suspicious events, preferably as accurately as possible to help identify their origin and to insure the success of on-site inspections if they are deemed necessary. The seismic location algorithm used by the USNDC has the capability to generate accurate locations by applying geographically dependent travel time corrections, but to date, none of the means, proposed for generating and representing these corrections has proven to be entirely satisfactory. In this presentation, we detail the complete DOE model for how regional calibration travel time information gathered by the National Labs will be used to improve event locations and provide more realistic location error esti- mates. We begin with residual data and error estimates from ground truth events. Our model consists of three parts: data processing, data storage, and data retrieval. The former two are effectively one-time processes, executed in advance before the system is made operational. The last step is required every time an accurate event location is needed. Data processing involves applying non-stationary Bayesian kriging to the residwd data to densifi them, and iterating to find the optimal tessellation representation for the fast interpolation in the data retrieval task. Both the kriging and the iterative re-tessellation are slow, computationally-expensive processes but this is acceptable because they are performed off-line, before any events are to be located. In the data storage task, the densified data set is stored in a database and spatially indexed. Spatial indexing improves the access efficiency of the geographically-ori- ented data requests associated with event location. Finally, in the Data Retrieval phase, when an accurate location is needed, the densified data is retrieved and a quick interpolation is performed using natural neighbor interpolation with a gradient slope modification to guarantee continuous derivatives. To test our model, we use the residuals from a large set of synthetic events (441) that were created to have travel times consistent with the IASP91 radial base model plus perturbations of up to 2 seconds taken from spherical har- monic surfaces with randomly generated coefficients. Relocating these events using 3 stations with poor azimuthal coverage and IASP91 travel times alone yields dislocations of up 278 km with a mean value of 58 km. Using our model to apply travel time corrections we reduce the hugest dislocation to 151 km and the mean value to 13 km. Fur- ther, the error ellipses generated now accurately reflect the uncertainly associated with the composite model (base model + corrections), and as a result are small for events occurring near ground truth event points and large for events occurring where no calibration data is available.

Download or read book High resolution Seismic Exploration written by Qing-Zhong Li and published by SEG Books. This book was released on 2017-09-01 with total page 319 pages. Available in PDF, EPUB and Kindle. Book excerpt: Capitalizing on knowledge learned over decades and combining underlying theory with practical bases, this book presents a systematic analysis of the issues involved in high-resolution seismic exploration. Translated from the original Chinese edition published in 1993 by Petroleum Industry Press and now updated to reflect contemporary developments, the book is adept at clarifying the objectives and approaches toward better precision in seismic prospecting. It provides innovative views on fundamental concepts including: perspective resolution and perspective S/N; the empirical relationship between compressional velocity (Vp) and absorption coefficient (Q); constructing basin absorption models; understanding sand layer tracking; improving dynamic and static corrections of near-surface effects as well as deconvolution; achieving maximum effective bandwidth of seismic data; and regressive seismic impedance inversion. It is an excellent reference for those involved in seismic prospecting research, data processing, and geologic interpretation, and it is recommended for workers as well as professors and graduate students.

Download or read book The State of Art Techniques of Seismic Imaging for the Deep and Ultra deep Hydrocarbon Reservoirs written by Jianping Huang and published by Frontiers Media SA. This book was released on 2022-11-11 with total page 149 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Routine Data Processing in Earthquake Seismology written by Jens Havskov and published by Springer Science & Business Media. This book was released on 2010-06-16 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this book is to get a practical understanding of the most common processing techniques in earthquake seismology. The book deals with manual methods and computer assisted methods. Each topic will be introduced with the basic theory followed by practical examples and exercises. There are manual exercises entirely based on the printed material of the book, as well as computer exercises based on public domain software. Most exercises are computer based. The software used, as well as all test data are available from http://extras.springer.com. This book is intended for everyone processing earthquake data, both in the observatory routine and in connection with research. Using the exercises, the book can also be used as a basis for university courses in earthquake processing. Since the main emphasis is on processing, the theory will only be dealt with to the extent needed to understand the processing steps, however references will be given to where more extensive explanations can be found. Includes: • Exercises • Test data • Public domain software (SEISAN) available from http://extras.springer.com

Download or read book Improving Global Seismic Event Locations Using Source Receiver Reciprocity written by and published by . This book was released on 2000 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: The leading source of error in seismic event locations is travel time perturbations caused by three-dimensional Earth structure. The reciprocity of travel times between sources and receivers provides a method for testing the effectiveness of empirical methods for improving event locations that rely on nearby calibration events of known location. We apply this approach to travel time residuals obtained by Engdahl et al. (1998) for almost 100,000 teleseismic events. By analyzing the residual patterns at thousands of seismic stations of known location, we characterize the spatial coherence of station/event mislocation vectors. We find that, on average, calibration events are likely to improve locations only if they are located within 100 to 150 km of the target events. For 84 events of known location, we find that applying source-receiver reciprocity can significantly reduce location errors by correcting for the teleseismic residual pattern observed at stations close to the target events. These results have implications for efforts to improve event locations for nuclear explosion monitoring purposes.

Download or read book Seismic Event Locations Using Multiple Phases written by A. C. Chang and published by . This book was released on 1985 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work evaluates the utility of a travel travel Covariance Matrix Method (COVMTX) for the improvement of the location of seismic events at regional distances using both Pn and Pg arrival times. Correlations between Pn and Pg travel time residuals are determined for the data set. The correlation of Pn and Pg times, rho sub PnPg for signals received at the same station from the same event was found to be very poor, less than 0.3 in all computations. The Covariance Matrix Method did not improve the results, possibly because the systematic bias due to the clustering of stations is small for the particular network of stations used in the relocation. Nevertheless, the method is still valuable because we must weight each signal differently, especially when multiple phases are used. The Simultaneous Inversion Method often resulted in erroneous depth estimates because the inversion for the depth dependent terms a sub Pn and a sub Pg in the linear travel time formula t = a + b delta may end up with some unacceptable values. By restricting the inversion for the a coefficients, the relocation resulted in the best results. This restriction is similar to the Successive Determinations Method devised by Chang et al. (1981), because it only improves the velocities or the b coefficients. This results suggests that a successive determinations approach may be very useful in locations using later phases, where large local variations in travel times are noted but are unpredictable prior to the location.

Download or read book Relative Seismic Event Location and Size Estimation Contributions to Earthquake Analysis and Seismic Discrimination at Local Distances written by Jonas Kintner and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Improving estimates of seismic source parameters is fundamental for understanding earthquake processes and enhancing current seismic event monitoring capabilities. In this dissertation I address several scientific challenges regarding the characterization (location, magnitude, etc.) of seismic events. Better source characterization allows us to relate seismic activity to observed surface deformation and to the broader tectonic implications of hazardous earthquakes. From a seismological perspective, I extend recently-developed surface-wave based methods to characterize seismic events across a wider range of tectonic environments, event sizes, station distributions, noise environments, and seismic source types. The first study documented is focused on constraining the relative locations and sizes of moderate-magnitude earthquakes in the 2013-2014 Minab sequence, Iran. We combinedsurface-wave cross correlation measurements, surface-wave spectra, and teleseismic body-wave modeling to constrain epicentroid locations, magnitudes, and depths. The results show that at least in some cases, we can use distant observations to improve the precision of relative earthquake epicentroid locations and magnitudes of remote earthquake sequences in tectonically complex regions. An appendix documents the results from relative relocations across the broad region including and surrounding Iran.Also included is a study of the 2014-15 Bushkan earthquake sequence, Iran. For this moderate-magnitude, shallow event, we used a combination of surface wave analysis, body wave modeling, and InSAR observations to characterize the mainshock and larger aftershocks. This study illuminates the opportunities provided by joint analysis of geodetic and seismological observations from modest-magnitude, shallow earthquakes in remote regions.Next I describe a study in which we characterize earthquake activity along the northwestern Caribbean plate boundary. We analyzed the earthquake processes along this margin by computing precise relative locations and magnitudes of moderate sized earthquakes from 1976 to 2018, and comparing the source-time functions and finite-fault models of the two largest recent earthquakes in the region. The relocation analysis allows us to improve relative event locations that help define the seismically active portions of the plate boundary more clearly. The finite-fault rupture models suggest that the large earthquakes along this strike-slip system may be influenced by faulting asperities and/or restraining bend features. The fourth study is an extension of the relative event location and magnitude estimation methods used in previous analyses. We estimate precise relative locations and magnitudes of small industrial explosions across Pennsylvania, USA using local and near-regional short-period shear-wave observations. The analysis is an effective illustration of the use of cross correlation of local-distance observations to compute high precision relative location and magnitude estimates of low-yield seismic sources.The final analysis described is an investigation of the potential to discriminate between earthquakes, mine blasts, and single shot borehole explosions using the amplitude ratio between local-distance (

Download or read book The Mechanism of Induced Seismicity written by Cezar I. Trifu and published by Birkhäuser. This book was released on 2012-12-06 with total page 632 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book An Integrated Approach to Seismic Event Location 2 Sources of Location Uncertainty for Teleseismic and Local Network Data written by and published by . This book was released on 1994 with total page 57 pages. Available in PDF, EPUB and Kindle. Book excerpt: The locations of seismic events determined from travel times by independent agencies differ for at least three reasons, including differences in picking of or availability of the phases, effects produced by individual structural peculiarities of each station, and systematic mislocations caused by the choice of the travel time model used for relocation. The present study evaluates earthquake locations for events in thin geographically diverse regions chosen to represent a broad spectrum of location problems. These are: Macquarie Ridge; Bucaramanga, Colombia; and Efate, Vanuatu. The evaluation methods include a comparison of locations reported by different agencies, an analysis of the sources of the variance of travel-time residuals, and a determination of the volume of groups of events thought to originate from a common source region. For the data analyzed it appears that station-dependent effects are a more significant source of location differences than are effects related to picking phase arrivals or choice of velocity model. Also, this study finds many situations where it seems inappropriate to utilize the strategy of minimizing travel time variance to improve location quality. Seismic event location, Seismic strain, Seismic discrimination.

Download or read book Advances and Applications of Passive Seismic Source Characterization written by Lei Li and published by Frontiers Media SA. This book was released on 2023-10-09 with total page 167 pages. Available in PDF, EPUB and Kindle. Book excerpt: Source characterization is a fundamental task of passive seismic monitoring. Spatial-temporal evolution of both, point sources and finite-fault source, provides essential information for timely seismic hazard management and advanced analysis of the seismicity in the monitored areas. In the last few decades, the rise of dense seismic arrays, increase of high-performance computing resources, and development of advanced array-based techniques lead to studies using recorded wavefields in great detail. Full waveform inversion can invert passive seismic source parameters with an iterative framework, which connects the delay-and-sum imaging technique and kernel-based inversion strategy. Moreover, emerging technologies like distributed acoustic sensing and machine learning also have great potential in advancing passive seismic imaging and source characterization. Besides, non-earthquake sources and ambient noise, as unconventional and passive sources, are also undergoing rapid development in infrastructure monitoring and subsurface imaging, due to the emergence of sensitive sensors and modern techniques like seismic interferometry.

Download or read book Regional Model Calibration For Improving Seismic Location written by and published by . This book was released on 2000 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: Accurate seismic event location is integral to the effective monitoring of the Comprehensive Nuclear-Test-Ban Treaty (CTBT), as well as being a fundamental component of earthquake source characterization. To account for the effects of crustal and mantle structure on seismic travel times, and to improve seismic event location in the Middle East and North Africa (MENA), we are developing a set of radially heterogeneous and azimuthally invariant traveltime models of the crust and upper mantle for each MENA seismic station. We begin by developing an average one-dimensional velocity model that minimizes the P-phase travel-time residuals from regional through teleseismic distance at each station. To do this we (1) generate a suite of 1-D velocity models of the earth, (2) compute travel times through the 1-D models using a tau-p formulation to produce standard travel-time tables, and (3) minimize the root-mean-square (rms) residuals between the P-phase arrivals predicted by each model and a groomed set of ISC P-phase arrival times (Engdahl et al., 1998). Once we have an average one-dimensional velocity model that minimizes the P-phase travel-time residuals for all distances, we repeat steps 1 through 3, systematically perturbing the travel-time model and using a grid search procedure to optimize models within regional, upper mantle, and teleseismic distance ranges. Regionalized models are combined into one two-dimensional model, using indicator functions and smoother methodologies to reduce distance and depth discontinuity artifacts between the individual models. Preliminary results of this study at a subset of MENA stations show that we are improving predictability with these models. Cross-validating the travel-time predictions with an independent data set demonstrates a marked reduction in the variance of the travel-time model error distributions. We demonstrate the improvement provided by these 2-D models by relocating the 1991 Racha aftershock sequence.

Download or read book Seismic Data Analysis written by Özdoğan Yilmaz and published by SEG Books. This book was released on 2001 with total page 2065 pages. Available in PDF, EPUB and Kindle. Book excerpt: Expanding the author's original work on processing to include inversion and interpretation, and including developments in all aspects of conventional processing, this two-volume set is a comprehensive and complete coverage of the modern trends in the seismic industry - from time to depth, from 3D to 4D, from 4D to 4C, and from isotropy to anisotropy.

Download or read book Methods and Applications of Signal Processing in Seismic Network Operations written by Tetsuo Takanami and published by Springer. This book was released on 2014-03-12 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book deals with various theoretical and practical methods for real-time automatic signal processing in local (and regional) seismic networks and associated software developments, including extraction of small seismic signal from noisy observation by piecewise modeling and self-organizing state space modeling, determination of arrival time of S wave by locally multivariate stationary AT modeling, automatic interpretation of seismic signal by combining cumulativ sum and simulative annealing (CUSUM-SA), AR-filtering for local and teleseismic events, the currently high sensitivity seismic network running in Japan (Hi-net), PC-based computer package for automatic detection and location of earthquakes, real-time automatic seismic data-processing in seismic network running in eastern Sicily (Italy), the SIL (South Iceland Lowland) seismological data acquisition system and routine analysis in Iceland and Sweden.

Download or read book Interferometric Methods for Seismic Monitoring in Industrial Environments written by Philippe Dales and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: As the global demand for energy and natural resources continues to increase so does our interaction with Earth's near surface through resource extraction and waste injection. In monitoring these interaction, seismology plays a central role. The focus of this work is on improving the detection and localization of seismic sources, a fundamental problem in seismology. After discussing the strengths and limitations of existing methods for source detection and localization, I develop a solution based on a beamforming approach that uses cross-correlation functions in a maximum likelihood search for sources of seismic energy. I call this method InterLoc, short for `interferometric locator', and apply it to data recorded at two active underground mines to demonstrate its effectiveness in monitoring both impulsive sources and persistent sources. Next, I demonstrate how persistent seismic sources, typically seen as contaminants, can be used directly to measure small changes in the medium between a source and either source-station pairs. This method relies on the ability to locate and monitor source activity and then use this information to identify and select cross-correlation functions to isolate each source of interest. From the resulting cross-correlations, it is possible to measure small temporal changes in the waveforms. To demonstrate this method, I show how ore-crushers can be used to track the growth of a block cave by measuring changes in traveltimes due to ray paths having to circumvent the growing cave. In the final chapter I focus on the development of a processing framework for the detection and location of microseismic events recorded on dense (or large-N) surface arrays. The proposed framework involves: (1) data reduction; (2) dividing the array into smaller sub-arrays; (3) waveform processing within fixed time windows; (4) stacking of time windows selected based on each potential origin time and source location; and (6) combining the output from all sub-arrays to infer detections and locations of sources. This methodology is validated with synthetic data built to emulate a real dataset from a 10,050 node survey to evaluate the suitability of land for carbon sequestration. Based on the presence of very strong coherent contaminating sources and low rock quality, I am only able to detect sources with moment magnitude greater than -0.5. In the five hours of data processed there is no positive detections suggesting this could be a good site for carbon storage. More work is needed to improve the detection threshold and quantify risk based on event location and magnitude. In summary, my work demonstrates how the interference (via cross-correlation) and stacking of seismic waveforms can be combined in different ways to create effective solutions for problems faced by today's industries.