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The objective of this project is to construct regional wave (Pg, Sn, and Lg) attenuation models for the crust and upper mantle throughout the Iranian plateau and surrounding regions. This research should increase ray path coverage of critical areas and help to create robust regional phase amplitude and attenuation models. We have combined our Iranian data set with our existing Middle Eastern Lg waveform database. These two data sets, combined, give us reasonably good coverage of the northern Middle East. We have created a catalog of seismic events in and around Iran with reliable source spectra as well as tested regional phase attenuation maps for the Zagros and Iranian plateau. We have developed an Sn attenuation model using two station measurements of Q for regional phase Sn (0.1 to 0.5 Hz) and for high frequency Sn (0.5 to 2 Hz). We have also processed Pg waveforms in order to obtain robust estimates of Qp in the crust within the Iranian plateau. For most of the phases we see moderately high attenuation within the plateau and less attenuation along the Zagros mountains. This project is the first to use two station and reverse two station methods to measure attenuation of phases such as Pg and Sn., The original document contains color images.

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 distribution of natural earthquakes and the fact that countries run separate national seismic networks without well-developed data-sharing agreements. We report here on a variety of scientific efforts to enhance knowledge of the lithospheric velocity structure in the Middle East, making use of data from national networks in Saudi Arabia, Oman, and Kuwait to improve seismic location accuracy for events throughout the region. Collaborative seismology engagements with research institutes in the Middle East have produced several important findings. Studies of regional seismic structure revealed that the Arabian Shield and the Arabian Platform have fundamental differences in velocity structure. The earth?s crust is relatively thicker than average in Kuwait and Iraq as a result of the Mesopotamian Foredeep, characterized by 8-10 km thick sediments. Ophiolites dominate the southeastern margin of the Arabian Peninsula, where the crust is thicker and seismic velocities are faster. In Kuwait seismic activity is intensified near oil fields, and seismic source parameters show that this activity comes from tectonic events. This work is informed by continuous or event-based regional seismic data obtained from 68 seismic stations from national networks, and this number is expected to grow in the future. A current effort is focused on using regional seismic data to develop better and more accurate seismic magnitude scales based on coda for stations in these national networks. Data and derived measurements from stations are integrated into lithospheric velocity and attenuation models to increase resolution, improve event location accuracy and source parameter determination, and advance tectonic understanding of the region., Published in the Proceedings of the 2012 Monitoring Research Review - Ground-Based Nuclear Explosion Monitoring Technologies, 18-20 September 2012, Albuquerque, NM. Volume I. Sponsored by the Air Force Research Laboratory (AFRL) and the National Nuclear Security Administration (NNSA). U.S. Government or Federal Rights License

The Magnitude and Distance Amplitude Correction (MDAC) methodology of corrects ratios of regional phase amplitudes for source, path, and site effects and has proven effective for event identification. The MDAC formulation includes a term that describes the earthquake source scaling as the apparent stress variation with magnitude. In almost all regions there is evidence for non-self similar source scaling. The behavior of earthquake source scaling has been the topic of significant debate in the earthquake source community mainly because current methods require substantial path, site, and source radiation pattern corrections that ultimately yield large variance of the apparent stress. A new, state-of-the-art methodology, the coda ratio technique, provides unprecedented estimates for corner frequency and apparent stress drop, roughly 3 times less variance than conventional methods using a minimal number of stations and events. Within broad regions it is likely that apparent stress varies with location due to lateral variations in regional stress field, rheology, and degree of tectonic activity. Currently MDAC assumes a single linear apparent stress scaling with moment for a given region, but if there is a priori information on lateral variations in apparent stress, then this can be used to lower the amplitude ratio scatter and increase the discrimination capability. The coda ratio methodology has been applied to a variety of tectonic regions and clear distinctions between each of them have been found., The original document contains color images. Published in The Proceedings of the 2011 Monitoring Research Review Ground-Based Nuclear Explosion Monitoring Technologies, 13 15 September 2011, Tucson, AZ, Volume I, pp 495-502. Government Purpose Rights.

Development of high-resolution seismic attenuation models of the Iranian Plateau and the Zagros Mountains is undertaken. Previous studies have suggested a complexity in crustal and uppermost mantle seismic attenuation structure as well as regional phase propagation characteristics beneath much of the Iranian Plateau and the surrounding regions. Regional seismic phases show strong lateral variability in amplitude and frequency content due to this very complex structure. Furthermore, due to a lack of two-dimensional seismic array data, much of the three-dimensional seismic structure and propagation characteristics of the crust, lithosphere and upper mantle remain unknown. Data collected by a series of deployments which consisted of approximately 140 temporary and permanent seismic stations in the Iranian Plateau and the Zagros Mountains is being used with a comprehensive set of techniques to develop and calibrate high-resolution regional phase attenuation models of the crust and upper mantle for a major portion of Arabian-Eurasian plate boundary. Validation of these results will include calibration with selected ground-truth events and comparison with existing amplitude models. A catalog of well located events that have reliable source spectra determined using coda will be created., Presented at the 2011 Monitoring Research Review: Ground-Based Nuclear Explosion Monitoring Technologies held in Tucson, AZ on 13-15 September 2011. Published in the Proceedings of the 2011 Monitoring Research Review: Ground-Based Nuclear Explosion Monitoring Technologies, v1 p153-160, 2012. The original document contains color images.

Small underground nuclear explosions need to be confidently detected and identified in regions of the world where they have never before occurred. We are developing a parametric model of the nuclear explosion seismic source spectrum derived from regional phases (Pn, Pg, Sn, and Lg) that is compatible with earthquake-based geometrical spreading and attenuation. Earthquake spectra are fit with a generalized version of the Brune spectrum, which is a three-parameter model that describes the long-period level, corner-frequency, and spectral slope at high-frequencies. Explosion spectra can be fit with similar spectral models whose parameters are then correlated with near-source geology and containment conditions. We observe a correlation of high gas-porosity (low strength) with increased spectral slope. However, there are trade-offs between the slope and corner-frequency, which we try to independently constrain using Mueller-Murphy relations and coda-ratio techniques. We complement our previous work that focused on the Nevada National Security Site (NNSS, formerly the Nevada Test Site) with data from explosions at the Semipalatinsk Test Site recorded at the Borovoye Geophysical Observatory (BRV). The BRV data archive allows for application of the parametric explosion model in a high-strength near-source geology. The relationship between the parametric equations and the geologic and containment conditions will assist in our physical understanding of the nuclear explosion source. The achievable goal of our parametric model development is to be able to predict observed local and regional distance seismic amplitudes for event identification and yield determination in regions with incomplete or no prior history of underground nuclear testing., Published in the Proceedings of the 2011 Monitoring Research Review - Ground-Based Nuclear Explosion Monitoring Technologies, 13-15 September 2011, Tucson, AZ. Volume I. Sponsored by the Air Force Research Laboratory (AFRL) and the National Nuclear Security Administration (NNSA). U.S. Government or Federal Rights License

We present the latest results on Lawrence Livermore National Laboratory's calibration efforts for seismic attenuation of regional body and surface waves that have application to many different areas of nuclear explosion monitoring. We have developed methods that use amplitude measurements of the direct regional phases (Pn, Pg, Sn Lg) to determine the attenuation structure of the lithosphere in Eurasia. The amplitudes are inverted simultaneously for attenuation parameters (Qp, Qs) of the crust and upper mantle, along with event source terms and station site terms. We are applying similar methodologies to coda amplitudes. Like direct waves, coda waves are subject to path-dependent variations in amplitudes. We see geographic similarities between the crustal shear-wave attenuation and the results from the coda attenuation. Calibration of coda in the Middle East and other areas is complicated by the fact that the dominant S-wave phase is either Sn or Lg depending on tectonic region, distance, and frequency. Over the past year, we have made great progress on the calibration of surface wave attenuation with the development of the Surface Wave Amplitude Processor (SWAP). With this tool, we are able to make surface wave amplitude measurements quickly, reliably, and consistently. We will be presenting a preliminary surface wave attenuation tomography of the Middle East. Regional attenuation models are directly applicable to event discrimination, such as high-frequency regional P/S discriminants (e.g., Pn/Lg, Pg/Lg, Pn/Sn) and longer period Ms:mb. Correcting the observed amplitudes for path-dependent variations reduces scatter in the earthquake population and increases separation from explosions. Better body-wave path corrections might even allow the extension of P/S discrimination to lower frequencies so long as true source differences between events exist at those frequencies., Published in the Proceedings of the 2011 Monitoring Research Review - Ground-Based Nuclear Explosion Monitoring Technologies, 13-15 September 2011, Tucson, AZ. Volume I. Sponsored by the Air Force Research Laboratory (AFRL) and the National Nuclear Security Administration (NNSA). U.S. Government or Federal Rights License

The project objectives are: first, transition the 1D coda methodology to a full 2D capability, including both P-coda and S-coda, including the ability to account for frequency-dependent phase blockage, as well as 2D variations in peak envelope velocity and site-transfer corrections; second, improve upon the way amplitude measurements are made and tie to an absolute scale. Existing data holdings are being leveraged at both institutions and also new results used that stem from local background coda models, earthquake source scaling studies, and more-sophisticated scattering models in the literature., Presented at the 2011 Monitoring Research Review Ground-Based Nuclear Explosion Monitoring Technologies, in Tucson, AZ on 13-15 Sep 2011 and published in proceedings of the same, v1 p127-131. Prepared in cooperation with Los Alamos National Laboratory and Lawrence Livermore National Laboratory. The original document contains color images.

We demonstrated that SPL waveform data, together with associated phases, are able to constrain crustal and upper mantle seismic wave velocity structures. Forward modeling is done using a reflectivity algorithm and optimization is carried out using an algorithm called very fast simulated annealing (VFSA). The code runs efficiently on multiple processors using MPI routines., Published in Proceedings of the 2010 Monitoring Research Review - Ground-Based Nuclear Explosion Monitoring Technologies, 21-23 September 2010, Orlando, FL. Volume I. Sponsored by the Air Force Research Laboratory (AFRL) and the National Nuclear Security Administration (NNSA). U.S. Government or Federal Rights License

In this project, we have developed and exploited a unique seismic dataset to address the characteristics of small seismic events and the associated seismic signals observed at local ( 200 km) and regional ( 2000 km) distances. The dataset has been developed using mining-induced events from three deep gold mines in South Africa recorded on in-mine networks ( 1 km) composed of tens of high-frequency sensors, a network of four broadband stations installed as part of this project at the surface around the mines (1-10 km), and a network of existing broadband seismic stations at local/regional distances (50-1000 km) from the mines. The final dataset includes (i) 2 years (2007 and 2008) of continuous recording by the surface broadband array and (ii) tens of thousands of mine tremors in the -3.4 ML 4.4 local magnitude range recorded by high-frequency in-mine geophones. Events with positive magnitudes are generally well recorded by the surface-mine stations, while magnitudes of 3.0 and larger are seen at regional distances (up to 600 km) in high-pass filtered recordings. Significant effort has been devoted to quality control of the in-mine, high-frequency data gathered during this effort. The quality control consisted of (i) identification and analysis of outliers among the P- and S-wave travel-time picks reported by the in-mine network operator and (ii) verification of sensor orientations. The outliers have been identified through a Wadati filter developed during this project that searches for the largest subset of P- and S-wave travel-time picks consistent with a medium of uniform wave-speed. We have also detected that trigger times were mistakenly reported as origin times by the in-mine network operator, and corrections have been obtained from the intercept times in the Wadati diagrams. Sensor orientations have been verified by correlating empirically and theoretically rotated P-, SV-, and SH- waveforms., Published in Proceedings of the 2010 Monitoring Research Review - Ground-Based Nuclear Explosion Monitoring Technologies, 21-23 September 2010, Orlando, FL. Volume I. Sponsored by the Air Force Research Laboratory (AFRL) and the National Nuclear Security Administration (NNSA). U.S. Government or Federal Rights License

Small underground nuclear explosions need to be confidently detected and identified in regions of the world where they have never occurred. We are developing a parametric model of the nuclear explosion seismic source spectrum derived from regional phases (Pn, Pg, Sn, and Lg) that is compatible with earthquake-based geometrical spreading and attenuation. Earthquake spectra are fit with a generalized version of the Brune spectrum, which is a three-parameter model that describes the long-period level, corner-frequency, and spectral slope at high frequencies. These parameters are then correlated with near-source geology and containment conditions. There is a correlation of high gas-porosity (low strength) with increased spectral slope. However, there are trade-offs between the slope and corner-frequency, which we try to independently constrain using Mueller-Murphy relations and coda-ratio techniques. The relationship between the parametric equations and the geologic and containment conditions will assist in our physical understanding of the nuclear explosion source. The achievable goal of our parametric model development is to be able to predict observed local and regional distance seismic amplitudes for event identification and yield determination in regions with incomplete or no prior history of underground nuclear testing., Published in Proceedings of the 2010 Monitoring Research Review - Ground-Based Nuclear Explosion Monitoring Technologies, 21-23 September 2010, Orlando, FL. Volume I. Sponsored by the Air Force Research Laboratory (AFRL) and the National Nuclear Security Administration (NNSA). U.S. Government or Federal Rights License

It is well known that one-dimensional models do a poor job of predicting both regional amplitudes and travel-times over large and tectonically complicated regions. As a result regional discrimination methods (e.g., high-frequency P/S, Ms:mb) and magnitude estimates (e.g. coda magnitude) can perform poorly when applied over broad regions. The careful calibration of the earth's attenuation structure is critical to the universal application of event discrimination and yield estimation methods down to very small magnitudes. We have developed and are continuing to improve methods that use the direct amplitudes of the major regional phases (Pn, Pg, Sn, Lg) to determine the attenuation structure of the lithosphere in the Middle East and East Asia. The amplitudes are inverted simultaneously for attenuation parameters (Qp, Qs) of the crust and upper mantle, event source terms, and station site terms, which ensures that parameters, such as seismic moment and apparent stress, are consistent across each phase. We are using these models to correct observed amplitudes for path-dependent variations due to earth structure. Amplitude corrections can be demonstrated to improve high-frequency regional P/S discriminants (e.g., Pn/Lg, Pg/Lg, Pn/Sn) by reducing scatter in the earthquake population and increasing separation from explosions. Better path corrections allow the extension of discrimination to lower frequencies so long as true source differences between events exist at those frequencies. We are applying similar methodologies to coda amplitudes with the goal of improving magnitude and yield estimation. While coda waves average over large regions and have less variation than direct phases, they too are subject to path-dependent variations in amplitudes. Furthermore, they can be sensitive to changes in the dominant phase (e.g., Sn vs. Lg) over broad regions. We report on our efforts for the 2-D calibration of coda amplitudes in the Middle East., Published in Proceedings of the 2010 Monitoring Research Review - Ground-Based Nuclear Explosion Monitoring Technologies, 21-23 September 2010, Orlando, FL. Volume I. Sponsored by the Air Force Research Laboratory (AFRL) and the National Nuclear Security Administration (NNSA). U.S. Government or Federal Rights License

The Caucasus-Caspian region is part of the Alpine-Himalayan collision belt and is an area of complex structure accompanied by large variations in seismic wave velocities. Using data from 29 new broadband seismic stations in the region as well as data from a temporary (1999-2001) deployment in eastern Turkey, a unified velocity structure is developed using teleseismic receiver functions and surface waves. Joint inversion of surface wave group dispersion curves generated from ambient noise with receiver functions show that crustal thickness varies from 34 to 52 km in the region. The thickest crust is in Lesser Caucasus and the thinnest is in the Arabian Plate. Thin crust is also observed near the Caspian. The lithospheric mantle in the Greater Caucasus and the Kura depression is faster than the Anatolian Plateau and Lesser Caucasus. This possibly indicates the presence of cold lithosphere. The lower crust is slowest in the northeastern part of the Anatolian Plateau where Holocene volcanoes are located. Fundamental mode Rayleigh wave phase velocities are determined at periods between 20 and 145 seconds. We observe a relatively high velocity zone located in the upper mantle under the Kura basin and the western part of Caspian Sea that is continuous to the Moho. The images show very low velocities beneath the eastern Anatolian plateau implying the existence of a partially molten asthenospheric material underlying a very thin lithosphere. Using a two-station method, both Lg and Pg attenuation is measured and tomograpically inverted to yield attenuation maps. Efficient Lg propagation is observed throughout much of the Arabian plate. Moderate Lg Q is observed in the Lesser Caucasus and Kura Basin while low Lg Q is observed in the East Anatolian plateau. Pg shows highly variable propagation throughout the region., The original document contains color images.

The objectives of this study are to improve low-magnitude (concentrating on M2.5-5) regional seismic discrimination by performing a thorough investigation of earthquake source scaling using diverse, high-quality datasets from varied tectonic regions. Local-to-regional high-frequency discrimination requires an estimate of how Q earthquakes scale with size. Walter and Taylor (2001) developed the Magnitude and Distance Amplitude Corrections (MDAC) method to empirically account for these effects through regional calibration. The accuracy of these corrections has a direct impact on our ability to identify clandestine explosions in the broad regional areas characterized by low seismicity. Unfortunately our knowledge at small magnitudes (i.e., mb < -4.0) is poorly resolved, and source scaling remains a subject of on-going debate in the earthquake seismology community. Recently there have been a number of empirical studies suggesting scaling of micro-earthquakes is non-self-similar, yet there are an equal number of compelling studies that would suggest otherwise. It is not clear whether different studies obtain different results because they analyse different earthquakes, or because they use different methods. We investigate earthquake sources and scaling from different tectonic settings, comparing direct and coda wave analysis methods that both make use of Empirical Green's Function (EGF) earthquakes to remove path effects. We develop improved versions of the two methods, and then apply them to a range of data sets., Prepared in collaboration with Weston Geophysics Corporation and Lawrence Livermore National Laboratories. Proposal no. BAA06-70. Presented at Monitoring Research Review - Ground-Based Nuclear Explosion Monitoring Technologies, MRR 2009, Tuscon, AZ on 21-23 Sep 2009; published in proceedings of the same, v3 p419-429. The original document contains color images. All DTIC reproductions will be in black and white.

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 Magnitude Distance Amplitude Correction (MDAC) technique (Walter and Taylor, 2001) 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., Published in the Proceedings of the Monitoring Research Review: Ground-Based Nuclear Explosion Monitoring Technologies (30th) held in Portsmouth, VA on 23-25 Sep 2008, p702-711, 2008. The original document contains color images.

The southwest edge of Eurasia is a tectonically and structurally complex region that includes the Caspian and Black Sea basins, the Caucasus Mountains, and the high plateaus south of the Caucasus. Using data from 25 broadband stations located in the region, new estimates of crustal and upper mantle thickness, velocity structure, and attenuation are being developed. Receiver functions have been determined for all stations. Depth to Moho is estimated using slant stacking of the receiver functions, forward modeling, and inversion. Moho depths along the Caspian and in the Kura Depression are in general poorly constrained using only receiver functions due to thick sedimentary basin sediments. The best fitting models suggest a low velocity upper crust with Moho depths ranging from 30 to 40 km. Crustal thicknesses increase in the Greater Caucasus with Moho depths of 40 to 50 km. Pronounced variations with azimuth of source are observed indicating 3D structural complexity and upper crustal velocities are higher than in the Kura Depression to the south. In the Lesser Caucasus, south and west of the Kura Depression, the crust is thicker (40 to 50 km) and upper crustal velocities are higher. Work is underway to refine these models with the event-based surface wave dispersion and ambient-noise correlation measurements from continuous data. Regional phase (Lg and Pg) attenuation models as well as blockage maps for Pn and Sn are being developed. Two methods are used to estimate Q: the two-station method to estimate inter-station Q and the reversed, two-station, two-event method. The results are then inverted to create Lg and Pg Q maps. Initial results suggest substantial variations in both Pg and Lg Q in the region. A zone of higher Pg Q extends west from the Caspian between the Lesser and Greater Caucasus, and a narrow area of higher Lg Q is observed., Presented at the Monitoring Research Review (30th): Ground-Based Nuclear Explosion Monitoring Technologies held in Portsmouth, VA on 23-25 Sep 2008. Published in the Proceedings of the Monitoring Research Review (30th): Ground-Based Nuclear Explosion Monitoring Technologies, v1 p142-150, 2008. Sponsored in part by Department of Energy. The original document contains color images. All DTIC reproductions will be in black and white.

Geophysical models constitute an important component of calibration for nuclear explosion monitoring. In order to keep them relevant to current monitoring problems, we have enhanced the models in several different ways. We will focus on discussing several of the enhancements here. We have significantly improved upon our surface wave model by expanding the region of the existing model of Eurasia and North Africa, south to cover all of Africa and north to cover the polar region into Alaska and Canada. We have also improved on our coverage in existing regions by including station-station dispersion paths based on ambient seismic noise. Surface waves are also being used to derive the crust and upper mantle velocity structure of these regions, including important parameters such as crustal thickness, upper mantle velocity, and lithospheric thickness. We will be comparing some of these results to other estimates of these parameters. We demonstrate some of the latest enhancements that we have made regarding stochastic models. For instance, we have been using the Markov Chain Monte Carlo (MCMC) technique to produce stochastic models in the Yellow Sea - Korean Peninsula (YSKP) region. By including more data sets (Love wave dispersion curves, gravity) and more data from the existing data sets (more travel times, more receiver functions, more Rayleigh wave dispersion curves), we have improved the lateral resolution of the model from 2 degrees to 1 degree. We will discuss some details of the methodology as well as features of the model. Finally, we will focus the last section on research to move beyond past and current 1-D, 2-D, and 2 -D methods and discuss some of the ongoing efforts to transition to fully 3-D models., Presented at the Monitoring Research Review: Ground-Based Nuclear Explosion Monitoring Technologies (29th) held in Denver, CO on 25-27 Sep 2007. Published in Proceedings of the Monitoring Research Review: Ground-Based Nuclear Explosion Monitoring Technologies (29th), p195-204, Sep 2007. The original document contains color images.

We continue exploring methodologies to improve earthquake-explosion discrimination using regional amplitude ratios such as P/S (ratio of P- and/or S-wave energy). 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 (tilde 1 Hz) and relatively good separation at high frequencies (greater than tilde 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., Presented at the Monitoring Research Review: Ground-Based Nuclear Explosion Monitoring Technologies Conference (29th) held in Denver, CO on 25-27 September 2007. Published in the Proceedings of the Monitoring Research Review: Ground-Based Nuclear Explosion Monitoring Technologies Conference (29th), p684-693, September 2007. The original document contains color images.

In this project, we are developing and exploiting a unique seismic data set to address the characteristics of small seismic events and the associated seismic signals observed at local (< 200 km) and regional (< 2000 km) distances. The data set is being developed using mining-induced events from 3 deep gold mines in South Africa recorded on in-mine networks (< 1 km) comprised of hundreds of high-frequency sensors, a network of broadband seismic stations installed as part of this project at the surface around the mines (1 - 50 km), and a network of existing broadband seismic stations at local and regional distances (50 - 1000 km) from the mines. The final data set will contain: (1) events spanning 5 orders of magnitude (M from approximately -1 to 3) well recorded at a wide range of local and regional distances, (2) events from a range of source depths (0 - 4 km), and (3) events from a variety of source types correlated with in-mine information such as pillar collapse and shear failure. Six months of data has been collected so far from the broadband seismic networks, and three months from the in-mine networks. We are exploiting the data set to improve U.S. operational capabilities to monitor for low-yield nuclear tests by analyzing the mining-induced events in a number of ways. We are gathering and analyzing events with M > 2.5, as well as some selected smaller events, including point explosions (mine blasts), mine-related stress release, mining activities, and shallow earthquakes. We are creating cataloged information on origin times and locations ground truth 0 (GT0), source parameters, focal mechanisms, coda-derived source spectra, coda magnitudes, local-to-regional phase propagation characteristics, relative P and S excitation, source apparent stress variation, and local-to-regional body-wave amplitude ratios that can discriminate between the different source categories., Presented at the Monitoring Research Review (29th): Ground-Based Nuclear Explosion Monitoring Technologies held in Denver, Colorado on 25-27 September 2007. Published in the Proceedings of the Monitoring Research Review (29th): Ground-Based Nuclear Explosion Monitoring Technologies, p185-194, 2007. Sponsored by the National Nuclear Security Administration (NNSA) and the Air Force Research Laboratory (AFRL). The original document contains color images.