Download or read book An Automated Local regional Seismic Event Detection and Location System Using Waveform Correlation written by Michell M. Withers and published by . This book was released on 1997 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book An Automated Local regional Seismic Event Detection and Location System Using Waveform Correlation written by Michell M. Withers and published by . This book was released on 1997 with total page 398 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Testing the Waveform Correlation Event Detection System written by and published by . This book was released on 1997 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: Waveform Correlation Event Detection System (WCEDS) prototypes have now been developed for both global and regional networks and the authors have extensively tested them to assess the potential usefulness of this technology for CTBT (Comprehensive Test Ban Treaty) monitoring. In this paper they present the results of tests on data sets from the IDC (International Data Center) Primary Network and the New Mexico Tech Seismic Network. The data sets span a variety of event types and noise conditions. The results are encouraging at both scales but show particular promise for regional networks. The global system was developed at Sandia Labs and has been tested on data from the IDC Primary Network. The authors have found that for this network the system does not perform at acceptable levels for either detection or location unless directional information (azimuth and slowness) is used. By incorporating directional information, however, both areas can be improved substantially suggesting that WCEDS may be able to offer a global detection capability which could complement that provided by the GA (Global Association) system in use at the IDC and USNDC (United States National Data Center). The local version of WCEDS (LWCEDS) has been developed and tested at New Mexico Tech using data from the New Mexico Tech Seismic Network (NMTSN). Results indicate that the WCEDS technology works well at this scale, despite the fact that the present implementation of LWCEDS does not use directional information. The NMTSN data set is a good test bed for the development of LWCEDS because of a typically large number of observed local phases and near network-wide recording of most local and regional events. Detection levels approach those of trained analysts, and locations are within 3 km of manually determined locations for local events.

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 Automated Seismic Event Location by Waveform Coherence Analysis written by Francesco Grigoli and published by . This book was released on 2013 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Automated location of seismic events is a very important task in microseismic monitoring operations as well for local and regional seismic monitoring. Since microseismic records are generally characterised by low signal-to-noise ratio, such methods are requested to be noise robust and sufficiently accurate. Most of the standard automated location routines are based on the automated picking, identification and association of the first arrivals of P and S waves and on the minimization of the residuals between theoretical and observed arrival times of the considered seismic phases. Although current methods can accurately pick P onsets, the automatic picking of the S onset is still problematic, especially when the P coda overlaps the S wave onset. In this thesis I developed a picking free automated method based on the Short-Term-Average/Long-Term-Average (STA/LTA) traces at different stations as observed data. I used the STA/LTA of several characteristic functions in order to increase the sensitiveness to the P wave and the S waves. For the P phases we use the STA/LTA traces of the vertical energy function, while for the S phases, we use the STA/LTA traces of the horizontal energy trace and then a more optimized characteristic function which is obtained using the principal component analysis technique. The orientation of the horizontal components can be retrieved by robust and linear approach of waveform comparison between stations within a network using seismic sources outside the network (chapter 2). To locate the seismic event, we scan the space of possible hypocentral locations and origin times, and stack the STA/LTA traces along the theoretical arrival time surface for both P and S phases. Iterating this procedure on a three-dimensional grid we retrieve a multidimensional matrix whose absolute maximum corresponds to the spatial and temporal coordinates of the seismic event. Location uncertainties are then estimated by perturbing the STA/LTA parameters (i.e the length of both long and short time windows) and relocating each event several times. In order to test the location method I firstly applied it to a set of 200 synthetic events. Then we applied it to two different real datasets. A first one related to mining induced microseismicity in a coal mine in the northern Germany (chapter 3). In this case we successfully located 391 microseismic event with magnitude range between 0.5 and 2.0 Ml. To further validate the location method I compared the retrieved locations with those obtained by manual picking procedure. The second dataset consist in a pilot application performed in the Campania-Lucania region (southern Italy) using a 33 stations seismic network (Irpinia Seismic Network) with an aperture of about 150 km (chapter 4). We located 196 crustal earthquakes (depth

Download or read book Advanced Time Series Analysis in Geosciences written by Flavio Cannavo’ and published by Frontiers Media SA. This book was released on 2021-05-12 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Extreme Environmental Events written by Robert A. Meyers and published by Springer Science & Business Media. This book was released on 2010-11-03 with total page 1273 pages. Available in PDF, EPUB and Kindle. Book excerpt: Extreme Environmental Events is an authoritative single source for understanding and applying the basic tenets of complexity and systems theory, as well as the tools and measures for analyzing complex systems, to the prediction, monitoring, and evaluation of major natural phenomena affecting life on earth. These phenomena are often highly destructive, and include earthquakes, tsunamis, volcanoes, climate change,, and weather. Early warning, damage, and the immediate response of human populations to these phenomena are also covered from the point of view of complexity and nonlinear systems. In 61 authoritative, state-of-the art articles, world experts in each field apply such tools and concepts as fractals, cellular automata, solitons game theory, network theory, and statistical physics to an understanding of these complex geophysical phenomena.

Download or read book The Waveform Correlation Event Detection System Project Phase I written by and published by . This book was released on 1996 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt: A study using long-period seismic data showed that seismic events can be detected and located based on correlations of processed waveform profiles with the profile expected for an event. In this technique both time and space are discretized and events are found by forming profiles and calculating correlations for all time-distance points. events are declared at points with large correlations. In the first phase of the Waveform Correlation Event Detection System (WCEDS) Project at Sandia Labs we have developed a prototype automatic event detection system based on Shearer's work which shows promise for treaty monitoring applications. Many modifications have been made to meet the requirements of the monitoring environment. A new full matrix multiplication has been developed which can reduce the number of computations needed for the data correlation by as much as two orders of magnitude for large grids. New methodology has also been developed to deal with the problems caused by false correlations (sidelobes) generated during the correlation process. When an event has been detected, masking matrices are set up which will mask all correlation sidelobes due to the event, allowing other events with intermingled phases to be found. This process is repeated until a detection threshold is reached. The system was tested on one hour of Incorporated Research Institutions for Seismology (IRIS) broadband data and built all 4 of the events listed in the National Earthquake Information Center (NEIC) Preliminary Determination of Epicenters (PDE) which were observable by the IRIS network. A continuous execution scheme has been developed for the system but has not yet been implemented. Improvements to the efficiency of the code are in various stages of development. Many refinements would have to be made to the system before it could be used as part of an actual monitoring system, but at this stage we know of no clear barriers which would prevent an eventual implementation of the system.

Download or read book Instrumentation in Earthquake Seismology written by Jens Havskov and published by Springer Science & Business Media. This book was released on 2010-02-11 with total page 365 pages. Available in PDF, EPUB and Kindle. Book excerpt: Here is unique and comprehensive coverage of modern seismic instrumentation, based on the authors’ practical experience of a quarter-century in seismology and geophysics. Their goal is to provide not only detailed information on the basics of seismic instruments but also to survey equipment on the market, blending this with only the amount of theory needed to understand the basic principles. Seismologists and technicians working with seismological instruments will find here the answers to their practical problems. Instrumentation in Earthquake Seismology is written to be understandable to the broad range of professionals working with seismological instruments and seismic data, whether students, engineers or seismologists. Whether installing seismic stations, networks and arrays, working and calibrating stationary or portable instruments, dealing with response information, or teaching about seismic instruments, professionals and academics now have a practical and authoritative sourcebook. Includes: SEISAN and SEISLOG software systems that are available from http://extras.springer.com and http://www.geo.uib.no/seismo/software/software.html

Download or read book Energy Research Abstracts written by and published by . This book was released on 1988 with total page 1684 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Advances in Studies of Heterogeneities in the Earth s Lithosphere written by Yehuda Ben-Zion and published by Pageoph Topical Volumes. This book was released on 2006-04-19 with total page 388 pages. Available in PDF, EPUB and Kindle. Book excerpt: This second special issue is in honor of Keiiti Aki. It focuses on recent advances in quantifying and interpreting heterogeneities in lithosperic structures and earthquake behavior. The volume provides a combination of reviews, methodological studies and applications on topics related to Aki's pioneering contributions. The discussed subjects include research associated with dynamic earthquake rupture. It also includes material on Aki and a list of his publications.

Download or read book Improving the Fundamental Understanding of Regional Seismic Signal Processing with a Unique Western U S Dataset written by K. Smith and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This project has built a unique historic database of regional distance nuclear explosion, earthquake, and mine-related digital broadband seismograms for the western United States (US). The emphasis is on data from Lawrence Livermore National Laboratory (LLNL)-managed stations MNA, ELK, KNB and LAC that recorded many nuclear tests and nearby earthquakes in broadband digital form since 1980, along with a small number of earlier events that were digitized from tapes. Through the generous cooperation of Sandia National Laboratory (SNL) we have also included waveforms from their Leo Brady network (BMN, DWN, LDS, NEL, TON). In addition we include data from other open broadband stations in the western US with long operating histories and/or ties to the International Monitoring System (IMS) (e.g. PFO, YKA, CMB, NEW, DUG, ANMO, TUC). These waveforms are associated with a reconciled catalog of events and station response information to facilitate analysis. The goal is to create a high-quality database that can be used in the future to analyze fundamental regional monitoring issues such as detection, location, magnitude, and discrimination. In the first stage of the project, we collected six different regional network catalogs from the University of Nevada, Reno (UNR), to provide accurate independent location information for events on the Nevada Test Site (NTS) and in the surrounding region. We have used National Nuclear Security Administration (NNSA)-developed software to reconcile these catalogs with each other and to incorporate them into a set of larger continental scale (CNSS, see http://www.cnss.org; USGS mining catalog compiled by Jim Dewey) and global scale (PDE, REB, ISC) catalogs. Finally, we incorporate the best catalogs of NTS nuclear event locations and source properties (Springer et al. 2002). The result is a single catalog of preferred origins, source information, and station information. Concurrently, we collected continuous seismic data from open stations and recovered and reformatted old event segmented data from the LLNL and SNL managed stations for past nuclear tests and earthquakes. We then used the preferred origin catalog to extract waveforms from continuous data and associate event segmented waveforms within the database. The result is a well-organized regional western US dataset with hundreds of nuclear tests, thousands of mining explosions and hundreds of thousands of earthquakes. In the second stage of the project we have chosen a subset of approximately 125 events that are well located and cover a range of magnitudes, source types, and locations. Ms. Flori Ryall, an experienced seismic analyst is reviewing this dataset. She is picking all arrival onsets with quantitative uncertainties and making note of data problems (timing errors, glitches, dropouts) and issues. The resulting arrivals and comments will then be loaded into the database for future researcher use. During the summer of 2003 we will be carrying out some analysis and quality control on this subset. It is anticipated that this set of consistently picked, independently located data will provide an effective test set for regional sparse station location algorithms. In addition, because the set will include nuclear tests, earthquakes, and mine-related events, each with related source parameters, it will provide a valuable test set for regional discrimination and magnitude estimation as well. A final relational database of these approximately 125 events in the high quality subset will be put onto a CD-ROM and distributed for other researchers to use in benchmarking regional algorithms after the conclusion of the project.

Download or read book Methods for Improving Seismic Event Location Processing written by and published by . This book was released on 2004 with total page 41 pages. Available in PDF, EPUB and Kindle. Book excerpt: Our research program consisted 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, and (4) double-difference (DD) multiple-event location 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 was followed by the application of these methods to real-time and simulated real-time data streams. Results of our project include an improved algorithm for WCC, a new method for validating WCC data using the bispectrum, real-time systems for event clustering and relocation, and a new method of seismic tomography utilizing absolute and differential arrival time data.

Download or read book Seismic Surface Waves in a Laterally Inhomogeneous Earth written by V.I. Keilis-Borok and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: Surface waves form the longest and strongest portion of a seismic record excited by explosions and shallow earthquakes. Traversing areas with diverse geologic structures, they 'absorb' information on the properties of these areas which is best retlected in dispersion, the dependence of velocity on frequency. The other prop erties of these waves - polarization, frequency content, attenuation, azimuthal variation of the amplitude and phase - arc also controlled by the medium between the source and the recording station; some of these are affected by the properties of the source itself and by the conditions around it. In recent years surface wave seismology has become an indispensable part of seismological practice. The maximum amplitude in the surface wave train of virtually every earthquake or major explosion is being measured and used by all national and international seismological surveys in the determination of the most important energy parameter of a seismic source, namely, the magnitude M,. The relationship between M, and the body wave magnitude fI1t, is routinely employed in identification of underground nuclear explosions. Surface waves of hundreds of earthquakes recorded every year are being analysed to estimate the seismic moment tensor of earthquake sources, to determine the periods of free oscillations of the Earth, to construct regional dispersion curves from which in turn the crustal and upper mantle structure in various areas is derived, and to evaluate the dissipative parameters of the mantle material.

Download or read book Earthquake Early Warning Systems written by Paolo Gasparini and published by Springer Science & Business Media. This book was released on 2007-08-10 with total page 363 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book provides information on the major EEW systems in operation and on the state-of-the-art of the different blocks forming an EW system: the rapid detection and estimation of the earthquake’s focal parameters, the signal transmission, the engineering interface and the information reliability/false alarm problem. It is the first time that so many aspects of EEW systems have been specifically focused upon within a single book.

Download or read book Integrated Seismic Event Detection and Location by Advanced Array Processing written by and published by . This book was released on 2007 with total page 95 pages. Available in PDF, EPUB and Kindle. Book excerpt: The principal objective of this two-year study is to develop and test a new advanced, automatic approach to seismic detection/location using array processing. We address a strategy to obtain significantly improved precision in the location of low-magnitude events compared with current fully-automatic approaches, combined with a low false alarm rate. We have developed and evaluated a prototype automatic system which uses as a basis regional array processing with fixed, carefully calibrated, site-specific parameters in conjuction with improved automatic phase onset time estimation. We have in parallel developed tools for Matched Field Processing for optimized detection and source-region identification of seismic signals. This narrow-band procedure aims to mitigate some of the causes of difficulty encountered using the standard array processing system, specifically complicated source-time histories of seismic events and shortcomings in the plane-wave approximation for seismic phase arrivals at regional arrays.

Download or read book I Seismic Moment Tensor Analysis of Micro Earthquakes in an Evolving Fluid Dominated System II Ambient Noise Cross Correlation for Evaluating Velocity Structure and Instrument Orientations in a Geothermal Environment written by Avinash Nayak and published by . This book was released on 2017 with total page 201 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents a detailed analysis of recorded seismic waves in terms of their source and their propagation through the Earth in multiple scenarios. First, I investigate the source mechanisms of some highly unusual seismic events associated with the formation of a large sinkhole at Napoleonville salt dome, Assumption Parish, Louisiana in August 2012. I implemented a grid-search approach for automatic detection, location and moment tensor inversion of these events. First, the effectiveness of this technique is demonstrated using low frequency (0.1-0.2 Hz) displacement waveforms and two simple 1D velocity models for the salt dome and the surrounding sedimentary strata for computation of Green’s functions in the preliminary analysis. In the revised, and more detailed analysis, I use Green’s functions computed using a finite-difference wave propagation method and a 3D velocity model that incorporates the currently known approximate geometry of the salt dome and the overlying anhydrite-gypsum cap rock, and features a large velocity contrast between the high velocity salt dome and low velocity sediments overlying and surrounding it. I developed a method for source-type-specific inversion of moment tensors utilizing long-period complete waveforms and first-motion polarities, which is useful for assessing confidence and uncertainties in the source-type characterization of seismic events. I also established an empirical method to rigorously assess uncertainties in the centroid location, MW and the source type of the events at the Napoleonville salt dome through changing network geometry, using the results of synthetic tests with real seismic noise. During 24-31 July 2012, the events with the best waveform fits are primarily located at the western edge of the salt dome at most probable depths of ~0.3-0.85 km, close to the horizontal positions of the cavern and the future sinkhole. The data are fit nearly equally well by opening crack moment tensors in the high velocity salt medium or by isotropic volume-increase moment tensors in the low velocity sediment layers. The addition of more stations further constrains the events to slightly shallower depths and to the lower velocity media just outside the salt dome with preferred isotropic volume-increase moment tensor solutions. I find that Green’s functions computed with the 3D velocity model generally result in better fit to the data than Green’s functions computed with the 1D velocity models, especially for the smaller amplitude tangential and vertical components, and result in better resolution of event locations and event source type. The dominant seismicity during 24- 31 July 2012 is characterized by the steady occurrence of seismic events with similar locations and moment tensor solutions at a near-characteristic inter-event time. The steady activity is sometimes interrupted by tremor-like sequences of multiple events in rapid succession, followed by quiet periods of little of no seismic activity, in turn followed by the resumption of seismicity with a reduced seismic moment-release rate. The dominant volume- increase moment tensor solutions and the steady features of the seismicity indicate a crack- valve-type source mechanism possibly driven by pressurized natural gas. Accurate and properly calibrated velocity models are essential for the recovery of correct seismic source mechanisms. I retrieved empirical Green’s functions in the frequency range ~ 0.2–0.9 Hz for interstation distances ranging from ~1 to ~30 km (~0.22 to ~6.5 times the wavelength) at The Geysers geothermal field, northern California, from cross-correlation of ambient seismic noise recorded by a wide variety of sensors. I directly compared noise- derived Green’s functions with normalized displacement waveforms of complete single-force synthetic Green’s functions computed with various 1D and 3D velocity models using the frequency-wavenumber integration method, and a 3D finite-difference wave propagation method, respectively. These comparisons provide an effective means of evaluating the suitability of different velocity models to different regions of The Geysers, and assessing the quality of the sensors and the noise cross-correlations. In the T-Tangential, R-Radial, Z- Vertical reference frame, the TT, RR, RZ, ZR and ZZ components (first component: force direction, second component: response direction) of noise-derived Green’s functions show clear surface-waves and even body-wave phases for many station pairs. They are also broadly consistent in phase and relative inter-component amplitudes with the synthetic Green’s functions for the known local seismic velocity structure that was derived primarily from body wave travel-time tomography, even at interstation distances less than one wavelength. I also found anomalous large amplitudes in TR, TZ, RT and ZT components of noise-derived Green’s functions at small interstation distances (≲4 km) that can be attributed to ~10°-30° sensor misalignments at many stations inferred from analysis of longer period teleseismic waveforms. After correcting for sensor misalignments, significant residual amplitudes in these components for some longer interstation distance (≳ 8 km) paths are better reproduced by the 3D velocity model than by the 1D models incorporating known values and fast axis directions of crack-induced shear-wave anisotropy in the geothermal field. I also analyzed the decay of Fourier spectral amplitudes of the TT component of the noise-derived Green’s functions at 0.72 Hz with distance in terms of geometrical spreading and attenuation. While there is considerable scatter in the amplitudes of noise-derived Green’s functions, the average decay is consistent with the decay expected from the amplitudes of synthetic Green’s functions and with the decay of tangential component local-earthquake ground-motion amplitudes with distance at the same frequency.