Download or read book Seismic Discrimination of Earthquakes and Explosions with Application to the Southwestern United States written by D. H. VON Seggern and published by . This book was released on 1979 with total page 247 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study examines seismic discrimination between underground nuclear explosions and earthquakes in the Southwestern United States. A thorough review of theoretical and applied research on this problem, especially as it relates to that region, is presented first, followed by a presentation of the seismic discrimination parameters computed for a suite of events in the Southwest and a series of experiments with multi-dimensional discrimination. Review of past work finds some theoretical support for successful discrimination based upon several distinct measurements on seismic recordings. Although negative first motion and presence of pP both indicate a natural earthquake source, they cannot be found confidently in many cases. The relative level of shear-wave and Love-wave phases should be a good classification parameter. The long-period P spectrum of explosions should be diminished due to the surface interaction and consequent cancellation by pP. The region under study extends from California to the southern Rocky Mountains and from roughly 40 degrees N to the Gulf of California. A region of high seismicity, it is also a complex region encompassing several tectonic provinces, including the Basin-Range Province where the Nevada Test Site is located. In general, seismic discriminant parameters obtained from the recordings reflected the theoretical expectations of earthquake-explosion differences. Path-station effects were large for every parameter, especially for short-period data.

Download or read book Energy Research Abstracts written by and published by . This book was released on 1989 with total page 992 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Seismic Discrimination Between Earthquakes and Explosions in the Middle East and North Africa written by and published by . This book was released on 1997 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: The recently signed Comprehensive Test Ban Treaty provides for an international network of primary and auxiliary seismic monitoring stations (IMS) to verify its compliance. Calibration is required to confidently use these stations to identify and discriminate between earthquakes, mine-related events and clandestine nuclear explosions, particularly for small to moderate seismic events recorded regionally at only a few stations. Given the lack of regional recordings of underground nuclear tests in most of the world, we are making use of mining and industrial explosions to test discriminants. For example we use the Multimax compiled dataset of small earthquakes and quarry explosions in Israel to test regional discriminants at local distances with mixed results. Further complicating calibration is the fact that many INK sites have not yet been installed and others have very short operating histories. When IMS data is available, there is often a lack of independent information (ground truth) on the seismic sources. Here we describe a procedure for calibrating stations with limited data and apply it to the IMS auxiliary station MDT in Morocco. Data was initially available for three months in 1990 when MDT was operated as part of MEDNET. An event detector was run over the continuous data and regional events identified and roughly located using S-P time and back azimuth. The procedure uses spatial and temporal clustering to identify ''known'' mine blasts. The spatial clustering is done using the waveform correlation technique of Harris (1991) to find events with similar sources and locations. Temporal clustering looks at the time of day and repetition in time of events with the mine blasts occurring during working hours and days repeatedly over a period of time. A set of ''known'' earthquakes is also determined using location, time of day, distribution in time and size criteria. With these independent libraries of identified seismic events, we evaluate promising regional discriminants such as high frequency P/Lg. We also examine distance and path effects on the discriminants. Preliminary results indicate high frequency P/Lg provides some separation between mine blasts and earthquakes at MDT.

Download or read book Investigations Into Seismic Discrimination Between Earthquakes Chemical Explosions and Nuclear Explosions written by and published by . This book was released on 1995 with total page 227 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this report we describe some results of investigations on a problem of discrimination between nuclear explosions, chemical explosions and earthquakes, carried out in the Complex Seismological Expedition of the Joint Institute of Physics of the Earth of the Russian Academy of Sciences. Records of underground nuclear explosions from the Semipalatinsk test site, and from region the Pre-Caspian depression, and also records of nearby chemical explosions and earthquakes were processed. We analysed records of permanent and temporary stations, located mainly in the North Tien Shan, northern Kazakhstan and Urals regions. We studied the influence of regional conditions on the effectiveness of seismic monitoring of nuclear explosions. Various amplitude criteria of the discrimination between explosions and earthquakes are considered. We analyzed possibilities to discriminate different source types using spectral-temporal characteristics of seismograms. The nature of some wave types, recorded at region distances, is investigated. We consider possibilities of discrimination between nuclear and chemical explosions and earthquakes using analysis of characteristics of irregular waves. We outline future investigations, connected with the study of the unique set of seismograms kept in the CSE.

Download or read book Geophysical Abstracts written by and published by . This book was released on 1985 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Application of a Combined Source Model for Seismic Discrimination written by Helmut Y. A. Hsiao and published by . This book was released on 1978 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this study has been to use the observed long-period teleseismic surface wave data of earthquakes and presumed underground explosions to determine the source mechanisms and to use these source mechanism estimates to discriminate between the two classes of events. In order to demonstrate this purpose, fifteen events have been selected and analyzed for the Russian Eastern Kazakh (EKZ) region, central and northern Eurasia, and the United States Nevada Test Site (NTS). The observation stations available for this study included the Seismic Research Observatories (SRO), Abbreviated Seismic Research Observatories (ASRO), the High Gain Long-Period (HGLP) stations (the same as the previous VLPE), and existing VELANET arrays. For a fair comparison of explosion and earthquake events, both have been treated in the same way by using the combined source model which combines a point explosive source and a point double-couple source. In order to cut down computer expenses and widen the searching rangge of some parameters, a binary exhaustive search method was applied to modify the amplitude spectral fitting process without any constraint. The results obtained from this modified process gave very good spectral fits for most events and lowered the minimum residual fitting error of each event.

Download or read book Regional Seismic Discrimination Optimization With and Without Nuclear Test Data written by W. R. Walter and published by . This book was released on 2005 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: The western U.S. has abundant natural seismicity, historic nuclear explosion data, and widespread mine blasts, making it a good testing ground to study the performance of regional source-type discrimination techniques. We have assembled and measured a large set of these events to systematically explore how to best optimize discrimination performance. Nuclear explosions can be discriminated from a background of earthquakes using regional phase (Pn, Pg, Sn, Lg) amplitude measures such as high frequency P/S ratios. The discrimination performance is improved if the amplitudes can be corrected for source size and path length effects. We show good results are achieved using earthquakes alone to calibrate for these effects with the MDAC technique (Walter and Taylor, 2001). We show significant further improvement is then possible by combining multiple MDAC amplitude ratios using an optimized weighting technique such as Linear Discriminant Analysis (LDA). However this requires data or models for both earthquakes and explosions. In many areas of the world regional distance nuclear explosion data is lacking, but mine blast data is available. Mine explosions are often designed to fracture and/or move rock, giving them different frequency and amplitude behavior than contained chemical shots, which seismically look like nuclear tests. Here we explore discrimination performance differences between explosion types, the possible disparity in the optimization parameters that would be chosen if only chemical explosions were available and the corresponding effect of that disparity on nuclear explosion discrimination. There are a variety of additional techniques in the literature also having the potential to improve regional high frequency P/S discrimination. We explore two of these here: three-component averaging and maximum phase amplitude measures. Typical discrimination studies use only the vertical component measures and for some historic regional nuclear records these are all that are available. However S-waves are often better recorded on the horizontal components and some studies have shown that using a three-component average or a vertical-P/horizontal-S or other three-component measure can improve discrimination over using the vertical alone (e.g. Kim et al. 1997; Bowers et al 2001). Here we compare the performance of vertical and three-component measures on the western U.S. test set. A complication in regional discrimination is the variation in P and S-wave propagation with region. The dominantly observed regional high frequency S-wave can vary with path between Sn and Lg in a spatially complex way. Since the relative lack of high frequency S-waves is the signature of an explosion, failing to account for this could lead to misidentifying an earthquake as an explosion. The regional P phases Pn and Pg vary similarly with path and also with distance, with Pg sometimes being a strong phase at near regional distances but not far regional. One way to try and handle these issues is to correct for all four regional phases but choose the phase with the maximum amplitude. A variation on this strategy is to always use Pn but choose the maximum S phase (e.g. Bottone et al. 2002). Here we compare the discrimination performance of several different (max P)/(max S) measures to vertical, three-component and multivariate measures. Our preliminary results show that multivariate measures perform much better than single ratios, though transportability of the LDA weights between regions is an issue. Also in our preliminary results, we do not find large discrimination performance improvements with three-component averages and maximum phase amplitude measures compared to using the vertical component alone.

Download or read book Investigations Into Seismic Discrimination Between Earthquakes Chemical Explosions and Nuclear Explosions written by L. V. Antonova and published by . This book was released on 1995 with total page 227 pages. Available in PDF, EPUB and Kindle. Book excerpt: We analyzed possibilities to discriminate different source types using spectral-temporal characteristics of seismograms. The nature of some wave types, recorded at regional distances, is investigated. We consider possibilities of discrimination between nuclear and chemical explosions and earthquakes using analysis of characteristics of irregular waves. We outline future investigations, connected with the study of the unique set of seismograms kept in the CSE.

Download or read book A Discrimination Analysis of Regional Seismic Data Recorded at Tonto Forest Observatory from Nevada Test Site Explosions and Nearby Earthquakes written by J. R. Murphy and published by . This book was released on 1981 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt: The principal objectives of the research reported here are to identify any diagnostic differences between regional seismic phases produced by earthquakes and underground nuclear explosions and to assess their applicability to events occurring in various regions of the U.S.S.R. Two approaches are used: one employs traditional time-domain amplitude and period measurements to compare the relative excitation of various regional phases for earthquakes and explosions, while the second focuses on more sophisticated measurement or processing techniques such as spectral ratios or narrow-band filtering to extract information about frequency differences in the signals generated by the two types of events. The research reported here was directed at identification of discriminants based on measurements of seismic phases at regional distances from a well-controlled set of Western U.S. explosions and nearby earthquakes. The set includes more than 50 Nevada Test Site events (explosions and nearby earthquakes) recorded at the Tonto Forest Observatory in Arizona. The investigation included spectral analyses of the short-period regional phases, Pn, Pg, and Lg which follows-up a previously reported study of time-domain characteristics of these phases. In addition, the current study includes an analysis of the time-domain characteristics of the long-period data from the Nevada Test Site event set, with particular emphasis on the potential applicability of the Ms/mb discriminant to the identification of small events (mb

Download or read book Discrimination of Earthquakes and Chemical Explosions with a Regional Network written by Peder Johansson and published by . This book was released on 1987 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Research Required to Support Comprehensive Nuclear Test Ban Treaty Monitoring written by National Research Council and published by National Academies Press. This book was released on 1997-08-01 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt: On September 24, 1996, President Clinton signed the Comprehensive Nuclear Test Ban Treaty at the United Nations Headquarters. Over the next five months, 141 nations, including the four other nuclear weapon statesâ€"Russia, China, France, and the United Kingdomâ€"added their signatures to this total ban on nuclear explosions. To help achieve verification of compliance with its provisions, the treaty specifies an extensive International Monitoring System of seismic, hydroacoustic, infrasonic, and radionuclide sensors. This volume identifies specific research activities that will be needed if the United States is to effectively monitor compliance with the treaty provisions.

Download or read book Government Reports Annual Index written by and published by . This book was released on 1987 with total page 954 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book EMPIRICAL OBSERVATIONS OF EARTHQUAKE EXPLOSION DISCRIMINATION USING P written by and published by . This book was released on 2007 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: We continue exploring methodologies to improve earthquake-explosion discrimination using regional amplitude ratios such as P/S. The earliest simple source models predicted P/S wave amplitudes for explosions should be much larger than for earthquakes across the body wave spectrum. However empirical observations show the separation of explosions from earthquakes using regional P/S amplitudes is strongly frequency dependent, with relatively poor separation at low frequencies (≈ 1 Hz) and relatively good separation at high frequencies (> ≈3 Hz). We demonstrate this using closely located pairs of earthquakes and explosions recorded on common, publicly available stations at test sites around the world e.g. Nevada, Lop Nor, Novaya Zemlya, Semipalatinsk, India, Pakistan, and North Korea. We show this pattern appears to have little dependence on the point source variability revealed by longer period surface wave modeling. For example regional waveform modeling shows strong tectonic release from the May 1998 India test in contrast with very little tectonic release in the recent North Korea test, but the P/S discrimination behavior is similar in both events, using the limited regional data available. While accepted explosion P-wave models have been available for many years, the frequency behavior of the P/S discriminant has inspired a variety of competing models to explain how explosions generate S-waves. We briefly review some of these models in the context of the P/S discriminant observations. One hypothesis is that S-waves are generated mainly from conversion of P-waves and surface waves, so S-waves from explosions can be predicted from the P-wave models via a frequency dependent transfer function. A different hypothesis is that significant generation of S-waves comes from the CLVD (compensated linear vector dipole) component created by spall above the explosion. A recent model by Fisk (2006) shows the explosion S-wave spectra can be modeled using the P-wave spectra with the corner frequency reduced by the ratio of the wave velocities, which seems to imply a direct generation of S-waves in the source region. We examine a number of nuclear tests from around the world in light of these models. Given the importance of depth on some of the model predictions we reexamine some of the overburied explosions in Nevada. We also look at chemical explosions, including dedicated single shots at different depths and mining shots at adjacent open pit and underground mines to look at depth effects. Finally we examine a subset of Nevada data with signal above noise up to 16 Hz to determine if discrimination performance saturates at frequencies around 6 Hz as some models predict, or continues to improve at higher frequencies.

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1975 with total page 978 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Improving Earthquake Explosion Discrimination Using Attenuation Models of the Crust and Upper Mantle written by and published by . This book was released on 2009 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the past year, we have made significant progress on developing and calibrating methodologies to improve earthquake-explosion discrimination using high-frequency regional P/S amplitude ratios. Closely-spaced earthquakes and explosions generally discriminate easily using this method, as demonstrated by recordings of explosions from test sites around the world. In relatively simple geophysical regions such as the continental parts of the Yellow Sea and Korean Peninsula (YSKP) we have successfully used a 1-D Magnitude and Distance Amplitude Correction methodology (1-D MDAC) to extend the regional P/S technique over large areas. However in tectonically complex regions such as the Middle East, or the mixed oceanic-continental paths for the YSKP the lateral variations in amplitudes are not well predicted by 1-D corrections and 1-D MDAC P/S discrimination over broad areas can perform poorly. We have developed a new technique to map 2-D attenuation structure in the crust and upper mantle. We retain the MDAC source model and geometrical spreading formulation and use the amplitudes of the four primary regional phases (Pn, Pg, Sn, Lg), to develop a simultaneous multi-phase approach to determine the P-wave and S-wave attenuation of the lithosphere. The methodology allows solving for attenuation structure in different depth layers. Here we show results for the P and S-wave attenuation in crust and upper mantle layers. When applied to the Middle East, we find variations in the attenuation quality factor Q that are consistent with the complex tectonics of the region. For example, provinces along the tectonically-active Tethys collision zone (e.g. Turkish Plateau, Zagros) have high attenuation in both the crust and upper mantle, while the stable outlying regions like the Indian Shield generally have low attenuation. In the Arabian Shield, however, we find that the low attenuation in this Precambrian crust is underlain by a high-attenuation upper mantle similar to the nearby Red Sea Rift. Applying this 2-D MDAC methodology with the new attenuation models can significantly improve earthquake-explosion discrimination using regional P/S amplitude ratios. We demonstrate applications of this technique, including a study at station NIL (Nilore, Pakistan) using broad area earthquakes and the 1998 Indian nuclear explosion using a number of regional amplitude ratio discriminants. We are currently applying the technique in the YSKP region as well.

Download or read book REGIONAL SEISMIC AMPLITUDE MODELING AND TOMOGRAPHY FOR EARTHQUAKE EXPLOSION DISCRIMINATION written by and published by . This book was released on 2008 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: We continue exploring methodologies to improve earthquake-explosion discrimination using regional amplitude ratios such as P/S in a variety of frequency bands. Empirically we demonstrate that such ratios separate explosions from earthquakes using closely located pairs of earthquakes and explosions recorded on common, publicly available stations at test sites around the world (e.g. Nevada, Novaya Zemlya, Semipalatinsk, Lop Nor, India, Pakistan, and North Korea). We are also examining if there is any relationship between the observed P/S and the point source variability revealed by longer period full waveform modeling (e. g. Ford et al 2008). For example, regional waveform modeling shows strong tectonic release from the May 1998 India test, in contrast with very little tectonic release in the October 2006 North Korea test, but the P/S discrimination behavior appears similar in both events using the limited regional data available. While regional amplitude ratios such as P/S can separate events in close proximity, it is also empirically well known that path effects can greatly distort observed amplitudes and make earthquakes appear very explosion-like. Previously we have shown that the MDAC (Magnitude Distance Amplitude Correction, Walter and Taylor, 2001) technique can account for simple 1-D attenuation and geometrical spreading corrections, as well as magnitude and site effects. However in some regions 1-D path corrections are a poor approximation and we need to develop 2-D path corrections. Here we demonstrate a new 2-D attenuation tomography technique using the MDAC earthquake source model applied to a set of events and stations in both the Middle East and the Yellow Sea Korean Peninsula regions. We believe this new 2-D MDAC tomography has the potential to greatly improve earthquake-explosion discrimination, particularly in tectonically complex regions such as the Middle East. Monitoring the world for potential nuclear explosions requires characterizing seismic events and discriminating between natural and man-made seismic events, such as earthquakes and mining activities, and nuclear weapons testing. We continue developing, testing, and refining size-, distance-, and location-based regional seismic amplitude corrections to facilitate the comparison of all events that are recorded at a particular seismic station. These corrections, calibrated for each station, reduce amplitude measurement scatter and improve discrimination performance. We test the methods on well-known (ground truth) datasets in the U.S. and then apply them to the uncalibrated stations in Eurasia, Africa, and other regions of interest to improve underground nuclear test monitoring capability.

Download or read book Seismic Discrimination by Harmonic Analysis Techniques written by William Rayoul Youngblood and published by . This book was released on 1972 with total page 85 pages. Available in PDF, EPUB and Kindle. Book excerpt: A large set of short period earthquake and underground nuclear explosion teleseismic signals (recorded at LASA) were analyzed using bands of the Discrete Fourier Transform coefficients and a pattern recognition system. The earthquakes, from several regions, ranged in magnitude from 4.1 to 6.1, and included shallow and deep events. The explosions ranged in magnitude from 4.7 to 6.3, and included US, Soviet, and French shots. Best results were 88.9% of the earthquakes and 100% of the explosions correctly identified. Furthermore, when deep and unknown depth earthquakes were excluded, only one earthquake was misidentified. (Author).