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The overall mission of the National Center for Nuclear Security (NCNS) Source Physics Experiment (SPE-N) at the Nevada National Security Site (NNSS) near Las Vegas, Nevada is to improve upon and develop new physics based models for underground nuclear explosions using scaled, underground chemical explosions as proxies. Infrasound has been used for many years to study explosive sources both above and below ground. For most of these studies the explosions were single shot events located in different areas. With the SPE-N series of explosions, we have the unique and rare opportunity to study infrasound generated by a well-characterized source from the same borehole. This reduces the number of variables that must be accounted for when generating models using the acoustic data. At the time of submission, the first two explosive tests (SPE-N-1 and SPE-N-2) were successfully conducted on May 3 and October 25, 2011, respectively. SPE-N-1 had a yield of 0.1 tons at a depth of 60 m with a scaled depth of burial of 1,026 m. This explosion was used as a calibration shot as it was the first in the series. SPE-N-2 had a yield of 1 ton at a depth of 45 m, corresponding to a scaled depth of burial of 357 m. The acoustic amplitudes ranged from 0.5 Pa at 225 m, to not being detected after 1 km for the 0.1 ton shot; and 14 Pa at 225 m, to 0.1 Pa at 5 km for the 1 ton shot. This paper will focus on detailed acoustic observations from both of these tests as well as describe future work, including detailed modeling of infrasound generation at the surface in the area above the explosion., Published in the Proceedings of the 2012 Monitoring Research Review - Ground-Based Nuclear Explosion Monitoring Technologies, 18-20 September 2012, Albuquerque, NM. Volume II. Sponsored by the Air Force Research Laboratory (AFRL) and the National Nuclear Security Administration (NNSA). U.S. Government or Federal Rights License

We report on R&D that is enabling enhancements to the Bayesian Infrasound Source Location (BISL) method for infrasound event location. The focus of this effort is on improving BISL through the development and implementation of physics-based priors. Phase identification in BISL is incorporated through a prior probability density function on group velocity. We report on the development of a distance-dependent prior through a massive simulation effort that will be validated by a ground-truth data analysis effort. In addition to providing constraints for the prior Probability Density Function (PDF), this coupled effort is also providing constraints on the probability distributions that are used in the likelihood equations in BISL. We assess the enhancement in location precision using a dynamic prior, instead of the previous uniform prior, for some example events. Finally, we discuss efforts to improve the numerical implementation of BISL using Monte Carlo integration., Published in the Proceedings of the 2012 Monitoring Research Review - Ground-Based Nuclear Explosion Monitoring Technologies, 18-20 September 2012, Albuquerque, NM. Volume II. Sponsored by the Air Force Research Laboratory (AFRL) and the National Nuclear Security Administration (NNSA). U.S. Government or Federal Rights License

Detectors were assessed that distinguish infrasound signals from both correlated and uncorrelated noise. Approaches to this problem are implementation of the F-detector, which employs the F-statistic, and cross-correlation techniques separating correlated and uncorrelated signals. We tested a modified F-detector that applies an adaptive procedure to identify variations in correlated noise, thus reducing false alarms. Using the modified F-detector, the temporal variation in the adaptive nature of the detector for a number of sites was investigated. The sensitivity of the detection procedure to the adaptive window used to estimate the C parameter that characterizes the correlated noise and impacts the false alarm rate was tested. The C values are found to be stable over long time periods for inland arrays within but show variations under high wind velocity conditions for adaptive windows as short as 1 hour for arrays on islands or near the coast. In order to further understand variations in background noise, the 10th, 50th, and 90th percentile noise spectral densities were estimated. The noise estimates show a strong wind speed effect on acoustic noise; for example, the spread between the 10th and 90th percentiles is about 40 dB at 0.1 Hz., Presented at the conference on Monitoring Research Review: Ground-Based Nuclear Explosion Monitoring Technologies, held in Tucson, AZ on 13-15 September 2011. Published in the Proceedings of the conference on Monitoring Research Review: Ground-Based Nuclear Explosion Monitoring Technologies, v2 p798-807, 2011. Prepared in cooperation with Los Alamos National Laboratory and the Korea Institute of Geoscience and Mineral Resources.

There is a need for routine measurements of infrasound from earthquakes, in conjunction with modeling, to better constrain our understanding of the generation of infrasound from earthquakes, in particular the effect of source depth. Here, we first outline a systematic search for infrasound from earthquakes from a range of magnitudes. Based on our observations, earthquakes with Mw5 appear to be reliable sources of infrasound, independent of depth with the detection of infrasound at regional distances largely driven by path and receiver effects. We identified clear infrasound detections from large earthquakes as deep as 123 km. In contrast, earthquakes with Mw4 are poor infrasound sources and are unlikely to be detected regionally. In particular, we note that there has yet to be a conclusive detection from an earthquake with Mw3.0. Our results imply that magnitude, rather than depth, appears to be the dominant factor influencing the generation of infrasound from earthquakes. To understand these observations further, we have developed a coupled seismoacoustic modeling technique comprising a three-dimensional (3D) finite difference algorithm, Rayleigh integral, and time domain parabolic equation. By gluing these techniques together, we are modeling the generation and propagation of infrasound from earthquakes. The effect of depth on these simulations, with comparison to our observational dataset, is discussed., Published in the Proceedings of the 2011 Monitoring Research Review - Ground-Based Nuclear Explosion Monitoring Technologies, 13-15 September 2011, Tucson, AZ. Volume II. Sponsored by the Air Force Research Laboratory (AFRL) and the National Nuclear Security Administration (NNSA). U.S. Government or Federal Rights License

Physical insight into source properties that contribute to the generation of infrasound signals is critical to understanding the differences in atmospheric signals from near-surface explosions and earthquakes. This understanding provides the background for assessing the possibility of signal discrimination from these different source types. This research attempts to develop a dataset necessary to address these issues and to provide constraints to the development of a physical basis for signal generation. The data component of this study is supported by the operation and maintenance of nine infrasonic arrays by the University of Utah Seismograph Stations (UUSS). Each array consists of four elements with an aperture of 150 m, with one element being co-located with a seismic station. One of the goals of this project is the recording of infrasound from earthquakes of moderate size on multiple infrasound arrays in order to assess the location of the infrasound source and its sensitivity to source mechanism and depth, as well as the characteristics of the signal. We report on processing results using infrasound data for all ML 3 earthquakes in the UUSS catalog from January 1, 2007, through March 31, 2011. We then focus on multiarray recordings of infrasound data from a moderate-sized event (Mw 4.6) in Utah. This event occurred on January 3 2011, at 12:06:37 UTC, within a known seismically active belt along the western side of the Sevier Valley in the Tushar Mountains (in the proximity of the city of Circleville). The event was widely felt in the surrounding communities, had a normal faulting mechanism and a depth constrained, by full moment tensor estimation, between 5 and 9 km. The main shock and 85 aftershocks were recorded by Utah's regional seismic network. Epicentral infrasound from the main event was detected by six of the nine infrasonic arrays distributed throughout Utah., Published in the Proceedings of the 2011 Monitoring Research Review - Ground-Based Nuclear Explosion Monitoring Technologies, 13-15 September 2011, Tucson, AZ. Volume II, p743-754. Sponsored by the Air Force Research Laboratory (AFRL) and the National Nuclear Security Administration (NNSA). U.S. Government or Federal Rights License

The identification of a signature relating depth to a remotely recorded infrasound signal requires a dataset of earthquakes, recorded infrasonically, with well-constrained depths. Although the premise is simple, five significant complications arise: (1) Earthquakes can generate infrasound via a variety of processes, which have occasionally been confused in past studies due to the complexity of the process; (2) mining explosions are efficient infrasound generators and can be mistaken for earthquakes; (3) coherent noise on infrasound arrays can be confused with transient signals; (4) atmospheric path effects must be adequately accounted for; and (5) seismic estimates of depth trade-off with origin time without a measurement in the near-epicentral region. This study provides a comprehensive framework for addressing these limitations, building on a focused study of the Wells, Nevada earthquake sequence that was performed as part of the previous year of this research effort (Arrowsmith et al., 2009). Such an approach is necessary to robustly identify a depth signature within a signal that incorporates various source, path, and receiver effects. In addition, we outline a complementary seismo-acoustic modeling approach, also being explored as part of this study, which should provide insight into the physical basis of an infrasonic depth signature., Published in Proceedings of the 2010 Monitoring Research Review - Ground-Based Nuclear Explosion Monitoring Technologies, 21-23 September 2010, Orlando, FL. Volume II. Sponsored by the Air Force Research Laboratory (AFRL) and the National Nuclear Security Administration (NNSA). U.S. Government or Federal Rights License

Understanding the source properties responsible for infrasound generation is critical to developing a seismo-acoustic data discriminant to distinguish between near-surface explosions and earthquakes. The regional seismicity, complex topography, open-pit quarries, and subsurface mining in the Utah region create a unique setting for the study of near-field infrasound. The Utah network has been operating three permanent infrasound arrays collocated with seismic stations NOQ (2006), BGU (2007), and EPU (2007). Additionally, four new arrays were installed and collocated with existing seismic stations BRPU, FSUT, HWUT, and WMUT. This summer three additional arrays will be collocated at stations LCMT, PSUT, and RCJ. Each array consists of four infrasound sensors with an average spacing of 100 m, recording at 100 samples/s, and all data is telemetered to the University of Utah in near-real-time. This increased array coverage provides greater likelihood for independent locations of infrasound sources using crossing backazimuth estimates. The data from the arrays are being processed with InfraMonitor which generates lists of detections and catalogs of located infrasound sources. Once processing is complete, the detections will be used to correlate and model the infrasound generation by earthquakes utilizing preexisting earthquake scaling relations dependent on depth, magnitude, and mechanism. The observations made during this study will contribute to refining the source excitation model for infrasound., Published in Proceedings of the 2010 Monitoring Research Review - Ground-Based Nuclear Explosion Monitoring Technologies, 21-23 September 2010, Orlando, FL. Volume II. Sponsored by the Air Force Research Laboratory (AFRL) and the National Nuclear Security Administration (NNSA). U.S. Government or Federal Rights License

This work is intended to provide automated methodology for processing seismic and infrasound data from seismo-acoustic arrays and apply the methodology to regional networks for validation with ground truth information. In the initial year of the project automated techniques for detecting, associating and locating infrasound signals were developed. Recently, the location procedure has been cast into a Bayesian framework. Work this year has focused on assessment of sets of robust regional infrasound signals in order to optimize the location algorithms. Quantification of the importance of model and empirical travel times, backazimuth estimation (including errors) and signal detectability have all been undertaken and are reported. Two specific studies are reported. Infrasound from a static rocket test conducted at Promontory, Utah on11/01/2007, was observed on USArray seismographs up to a distance of 600 km. Signal durations were broadly consistent with the duration of the test, 123 s, and signal envelopes correlated with variations in thrust in some cases. The effect of adding Gaussian noise to wind profiles is investigated for the purpose of phase identification. It is shown that all observations can be predicted through the combination of simulations using different noise levels, suggesting that a probabilistic approach to phase identification is possible. These results have important implications for how atmospheric models might be utilized in source location in particular how they might be implemented into the Bayesian location framework of Modrak et al. (2010). The deterministic dependence of infrasound propagation on the season and path environment was quantified by the analysis of more than 1,000 repetitive infrasonic ground-truth events at an active, open-pit mine in Korea over 2 years., Published in Proceedings of the 2010 Monitoring Research Review - Ground-Based Nuclear Explosion Monitoring Technologies, 21-23 September 2010, Orlando, FL. Volume II p667-677. Sponsored by the Air Force Research Laboratory (AFRL) and the National Nuclear Security Administration (NNSA). U.S. Government or Federal Rights License

This work is intended to provide automated methodology for processing seismic and infrasound data from seismo-acoustic arrays and to apply the methodology to regional networks for validation with ground truth information. As reported last year, the project has developed automated techniques for detecting, associating and locating infrasound signals. Work reported this year focuses on refinement of both the detection and location component of the program. Ground truth information developed on the Korean Peninsula is further used to refine the methodology. New location developments are underway. We are incorporating an infrasonic grid-search location method into a Bayesian framework that provides conditional probabilities on the location given the observed data (inter-array time delays and backazimuths) and a prior distribution. The prior provides ancillary information on the event location, which can be as simple as empirical bounds on backazimuth deviations and group velocities. However, we are investigating extending this simple approach through the use of a 3D ray-tracing algorithm to impose more specific constraints based on available atmospheric specifications. Finally a set of ground truth seismo-acoustic events have been developed for the Korean Peninsula and include a large number of events from a limestone quarry in the Republic of Korea. In-mine seismic and acoustic observations provide the basis of the detailed ground truth. These events occur daily with multiple events on active days and span nearly two years, providing the basis of assessing spatial and temporal variations in propagation path, including variations in backazimuth as well as phase and group velocity. The reported analyses of these data provide empirical bounding constraints for the location algorithm that is under development., Presented at the conference on Monitoring Research Review 2009 (MRR-2009): Ground-Based Nuclear Explosion Monitoring Technologies, held in Tucson, AZ, on 21-23 Sep 2009. Published in the proceedings of the conference, v1 p706-713, 2009. Prepared in cooperation with Los Alamos National Laboratory (LANL); Korea Institute of Geoscience and Mineral Resources; and Southern Methodist University. Sponsored in part by National Nuclear Security Administration (NNSA). The original document contains color images. All DTIC reproductions will be in black and white.

Seismo-acoustic measurements provide an opportunity to quantify natural and man-made sources that are at or near the Earth's surface. We have operated three acoustic arrays collocated with seismometers from the University of Utah Seismograph Stations (BGU, EPU, NOQ). We report on progress in three separate areas of research related to these seismo-acoustic databases. The first topic investigates seismo-acoustic signals from the Wells, Nevada earthquake that occurred on February 21, 2008 at 14:16:02 UTC (Mw 6.0). The detailed research and interpretation of this event has been conducted under a separate effort (Arrowsmith et al., 2009c, these Proceedings). The focus in this work is on the data acquisition and highlighting the sources of seismo-acoustic signals that can be observed on regional seismo-acoustic arrays. This event was well recorded by many seismic stations, including the EarthScope Transportable Array (TA) stations, and was also recorded by three infrasonic arrays in Utah (BGU, EPU, NOQ), one in Nevada (NVIAR), and one in Wyoming (PD1AR). The waveforms recorded from the Wells sequence (main event and aftershocks) at the five infrasonic arrays are characterized by complex signals that correspond to: (1) P and 5 arrivals, a result of the coupling-to-air of the seismic waves that traveled to the vicinity of the infrasonic stations (local infrasound); (2) a secondary source of infrasound between the source and receiver; and (3) epicentral infrasound (acoustic energy that was generated by the ground motion at the epicenter and traveled through the atmosphere to the arrays at air sound speed). The second area of work focuses on characterizing acoustic to seismic coupling. In August 2007, infrasound microphones were added at Earthscope stations PI3A, M13A, M14A, and N12A as part of an experiment to record 40,000 lb explosions at the Utah Test and Training Range on Hill Air Force Base (AFB)., Prepared in collaboration with University of Utah Seismograph Stations, Korea Institute of Geoscience and Mineral Resources, and Los Alamos National Laboratory. Proposal no. BAA08-65. 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, v1 p230-238. The original document contains color images. All DTIC reproductions will be in black and white.

Recent event identification efforts at Los Alamos National Laboratory (LANL) have focused on mining event ground-truth data collection in central Asia and testing far-local to near-regional discriminants using earthquakes, mining explosions, and single-charge chemical explosions. Our mining event efforts have identified over 20 mines and more than 1,000 mining explosions from around the former Soviet nuclear test site (KTS) in eastern Kazakhstan. Using the Kazakh National Data Centre (KNDC) bulletin from 2002 to 2007 and waveforms recorded at station KURK and array MKAR, we combined time-of-day seismic-event analysis, waveform cross correlations, seismic-event location methods, and image analysis to identify active mines. From our previous, but more limited studies, we had assumed mining explosions in eastern Kazakhstan occur only between about 8 AM and 8 PM local time. However, our latest study, using several thousand events, reveals that some mines shoot near midnight local time. Thus, we concluded that only during the hours of 21, 22, and 23 GMT (3, 4, and 5 AM local time) can we assume that the small events from this region are probable earthquakes. Using this assumption, we selected 8 events within about 250 km of station KURK as earthquakes, and we selected about 250 mining explosions from three mines for discrimination analyses. In addition, we gathered all available depth-of-burial (DOB), hole-closing, and tunnel-closing single-charge chemical explosions that occurred at KTS from 1997 to 2000 and were recorded at KURK. The single-charge chemical events occurred within about 125 km of KURK. From published reports, we have flagged three of these events as fully contained. For the mining events, we do not know the shooting practices, such as delayed-firing along rows of shotholes. Using the events described above, we tested spectral-ratio and phase-ratio body-wave amplitude discriminants., Presented at the Conference on Monitoring Research Review: Ground-Based Nuclear Explosion Monitoring Technologies (30th), held in Portsmouth, VA, on 23-25 Sep 2008. Published in the Proceedings of the Conference on Monitoring Research Review, p615-624, 2008. Sponsored in part by the Air Force Research Laboratory (AFRL). The original document contains color images.

With the recent increase of regional infrasound deployments, there is a need for tools that can be applied to networks of infrasound arrays in order to generate robust event catalogs. We present a new tool for regional infrasound monitoring that performs signal detection, association, and event location for networks of infrasound arrays. First, an algorithm for robust signal detection is presented, which utilizes an adaptive noise hypothesis, compensating for variable ambient noise. We show that the adaptive detection scheme performs significantly better than standard detection schemes in the presence of correlated noise. Next, we present a robust method for the association and location of infrasound events recorded at multiple arrays. A Matlab toolbox with a GUI interface, InfraMonitor 1.0, has been developed that incorporates this suite of algorithms for regional infrasound monitoring. An outline of the InfraMonitor 1.0 package is presented. A computer demonstration of InfraMonitor 1.0 will be available at the 2008 Monitoring Research Review meeting., Presented at Proceedings of the Monitoring Research Review: Ground-Based Nuclear Explosion Monitoring Technologies (30th), held in Portsmouth, VA on 23-25 Sep 2008. Published in Proceedings of the Monitoring Research Review: Ground-Based Nuclear Explosion Monitoring Technologies (30th), p837-843, 2008. Sponsored by the Air Force Research Laboratory (AFRL). The original document contains color images. Proposal no. BAA05-07.

The two main objectives of this work are to (1) develop an automated method for processing seismic and infrasound data from multiple seismo-acoustic arrays, and (2) to apply the method to a regional network of arrays for validation. The project involves development of automated techniques for detecting, associating, and locating infrasound signals at single and multiple arrays and then combining the processed results with similar automated procedures for seismic signals. This approach differs from most existing systems that typically depend on late association or data fusion after events are formed. Regional infrasound and seismo-acoustic events are automatically detected, associated and located using seismo-acoustic stations in Utah. We utilize the InfraMonitor toolbox, recently developed at Los Alamos National Laboratory (LANL), in collaboration with Southern Methodist University (SMU). The toolbox comprises an adaptive F-detector - which accounts for real ambient noise, and a robust signal association/event location algorithm. Seismic signals, obtained using a statistically based short-term average/long-term average (STA/LTA) detector, are associated with infrasound events obtained by InfraMonitor. A thorough ground-truth survey using satellite observations and independent data provides the basis for event identification. An analyst reviews automatic results in order to make a preliminary assessment of the number of false associations. We report on the numbers, distributions and sources of reviewed infrasound and seismo-acoustic events detected by Utah seismo-acoustic stations. Case studies of selected events provide examples of the infrasonic and seismo-acoustic records from regional events., Presented at the Conference on Ground-Based Nuclear Explosion Monitoring Technologies (30th), held in Portsmouth, VA, on 23-25 Sep 2008. Published in the proceedings of the conference in Monitoring Research Review, v1 p844-852, 2008. Prepared in cooperation with Southern Methodist University; University of Utah Seismograph Stations; and Korea Institute of Geosciences and Mineral Resources. The original document contains color images. All DTIC reproductions will be in black and white.

Methodologies for the detection, association, location and identification of infrasound sources at local, regional and global distances are discussed. In the first part of this paper we apply a new regional monitoring method to data from the Washington State seismo-acoustic network and identify 206 local and regional infrasonic events in a dataset comprising 28 days of data. We detect multiple signals from mining explosions at two sites in Washington State, including 5 events that were recorded in a regional seismic bulletin. We also automatically detect and associate signals from the March 9th 2005 eruption at Mount Saint Helens, and locate the event to be within 5 km of the caldera. The second part of this paper outlines a technique for identifying infrasound signals from large known events on a global scale. We apply the technique to data from International Monitoring System (IMS) infrasound arrays for three super-bolides occurring on September 3rd, 2004, over Antarctica; on October 7th, 2004, over the Indian Ocean; and on December 9th, 2006, over North Africa. For each bolide we observe signals at multiple infrasonic arrays, with observations at ranges from tilde 1,000 to tilde 13,000 km. We investigate the causes of the asymmetric distributions of observations and show that site-noise is a dominant effect up to a range of tilde 10,000 km. We discuss how the preliminary work outlined in this paper provides important constraints for the purpose of event identification at local, regional and global distances. For large events, we outline how the synthesis of local, regional and global infrasonic data would provide the optimum dataset for event location and identification., 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), p815-824, September 2007. The original document contains color images.

As more seismic and infrasound stations and arrays are deployed for nuclear explosion monitoring, catalogs of seismic events contain not only earthquakes, but many types of anthropogenic sources. Mining events are commonly recorded at regional distances by these stations, with the possibility of misidentification, (e.g., a legitimate mining explosion mistaken as nuclear). Additionally, a nuclear explosion could potentially be embedded in a mining explosion and be missed. Different discriminants have been utilized to separate mining events from natural seismicity with varying degrees of success. In this paper we present results of ongoing efforts to test several discriminants (amplitude ratios, time varying spectral analysis, time-of-day analysis, and infrasound) for two active mining regions: the Powder River Basin (PRB) in the western United States and the Altai-Sayan (AS) in Russia. The first phase of work on this contract has focused on using seismic and infrasound data in the PRB as a test bed for developing and assessing different mining explosion discriminants. This work is outlined in detail by Arrowsmith et al. (2006a, 2007). The results obtained indicate that phase amplitude discriminants, which have been found to be successful in separating earthquakes from nuclear explosions, do not separate earthquakes and mining explosions in this region, probably due to a combination of source and path effects. However, a time-varying spectral discriminant developed as part of this project was very successful at identifying the largest types of mining explosions (cast blasts). We also identified infrasound signals from large mining explosions in this region, suggesting good potential for the use of infrasound as an additional discriminant in this region when winds are favorable., Presented at the Monitoring Research Review (29th): Ground-Based Nuclear Explosion Monitoring Technologies held in Denver, Colorado on 25-27 Sep 2007. Published in the Proceedings of the Monitoring Research Review (29th): Ground-Based Nuclear Explosion Monitoring Technologies, p531-540, 2007. Sponsored by the Air Force Research Laboratory (AFRL). The original document contains color images.