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Download or read book Regional Seismic Discrimination Research at LLNL. written by and published by . This book was released on 1995 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book LLNL's Regional Seismic Discrimination Research written by and published by . This book was released on 1995 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book LLNL's Regional Model Calibration and Body-Wave Discrimination Research in the Former Soviet Union Using Peaceful Nuclear Explosions (PNEs). written by and published by . This book was released on 2000 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Long-range seismic profiles from Peaceful Nuclear Explosions (PNE) in the Former Soviet Union (FSU) provide a unique data set to investigate several important issues in regional Comprehensive Nuclear-Test-Ban Treaty (CTBT) monitoring. The recording station spacing (H"5 km) allows for extremely dense sampling of the propagation from the source to H"3300 km. This allows us to analyze the waveforms at local, near- and far-regional and teleseismic distances. These data are used to: (1) study the evolution of regional phases and phase amplitude ratios along the profile; (2) infer one-dimensional velocity structure along the profile; and (3) evaluate the spatial correlation of regional and teleseismic travel times and regional phase amplitude ratios. We analyzed waveform data from four PNE's (m{sub b} = 5.1-5.6) recorded along profile KRATON, which is an east-west trending profile located in northern Sibertil. Short-period regional discriminants, such as P/S amplitude ratios, will be essential for seismic monitoring of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) at small magnitudes (m{sub b}
Author : C. A. Schultz
Publisher :
ISBN 13 :
Total Pages : 10 pages
Book Rating : 4.:/5 (228 download)
Download or read book Wave Propagation Modeling Capabilities at LLNL: Applications to Regional Discrimination written by C. A. Schultz and published by . This book was released on 1995 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: The numerical synthesis of regional seismograms has become an integral part of Lawrence Livermore National Laboratory's (LLNL) seismic discrimination program. In this paper, we summarize our fundamental approaches to numerical modeling. Our capabilities currently include reflectivity, normal mode, boundary integral, and finite-difference modeling, along with hybrid approaches which utilize two or more of these techniques together. We apply these capabilities to the discriminant variability along three different arrays deployed during the Non- Proliferation Experiment (NPE). Phase amplitudes have been calculated for the approximately three hundred regional stations which recorded the NPE. The majority of these recordings were to the west of the NPE, along one profile of the Southern Sierra Continental Dynamics (SSCD) refraction profile. Based on the three profiles which made up the SSCD refraction experiment, traveltime tomography was utilized to develop a well constrained 3D velocity model across a profile which extends from the Basin and Range, through the southern Sierra Nevada range, the Great Valley, to the San Andreas fault zone in the coastal ranges. The western array of the NPE regional deployment consisted of 285 stations coincident with this SSCD profile. This resulted in phase and discriminant coverage along one of the most well constrained velocity profiles in the western United states. Our analysis shows that although there is amplification of Pg and Lg, Pn has some of the most dramatic variations in amplitude. In California, these amplifications coincide with the western flank of the Sierra Nevada, the eastern quarter of the Great Valley, and the coastal ranges. In Nevada, a dramatic amplification occurred in the Broken Hills volcanic region.
Author : T. J. Bennett
Publisher :
ISBN 13 :
Total Pages : 87 pages
Book Rating : 4.:/5 (227 download)
Download or read book Regional Discrimination Research written by T. J. Bennett and published by . This book was released on 1981 with total page 87 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this project is to systematically assess the potential of regional phases for discriminating earthquakes and nuclear explosions with particular emphasis on defining the applicability of such discriminants to events in various regions of the U.S.S.R. The first research approach employs more traditional, time domain amplitude and period measurements to compare the relative excitation of different regional phases from earthquakes and explosions. The second approach focuses on the evaluation of the capabilities of other measurement or processing techniques, such as spectral ratios or narrow-band filtering, to identify seismic sources using regional phases. The principal technical phases of the regional discrimination research effort are: (1) review and assess time and frequency domain characteristics of regional seismic phases and evaluate their dependency on source type, propagation path and station environment; (2) Develop a tentative set of source identification criteria based on information from regional phases; and (3) Test proposed regional discriminants on observed data to determine their capability to identify earthquakes and explosions in various tectonic and geologic settings.
Download or read book LLNL Middle East and North Africa Research Database written by and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Lawrence Livermore National Laboratory (LLNL) Comprehensive Nuclear-Test-Ban Treaty Research and Development (CTBT R and D) program has made significant progress populating a comprehensive seismic research database (RDB) for seismic events and derived research products in the Middle East and North Africa (MENA). Our original ME/NA study region has enlarged and is now defined as an area including the Middle East, Africa, Europe, Southwest Asia, the Former Soviet Union and the Scandinavian/Arctic region. The LLNL RDB will facilitate calibration of all International Monitoring System (IMS) stations (primary and auxiliary) or their surrogates (if not yet installed) as well as a variety of gamma stations. The RDB provides not only a coherent framework in which to store and organize large volumes of collected seismic waveforms and associated event parameter information, but also provides an efficient data processing/research environment for deriving location and discrimination correction sur faces and capabilities. In order to accommodate large volumes of data from many sources with diverse formats the RDB is designed to be flexible and extensible in addition to maintaining detailed quality control information and associated metadata. Station parameters, instrument responses, phase pick information, and event bulletins were compiled and made available through the RDB. For seismic events in the MENA region occurring between 1976 and 1999, we have systematically assembled, quality checked and organized event waveforms; continuous seismic data from 1990 to present are archived for many stations. Currently, over 11,400 seismic events and 1.2 million waveforms are maintained in the RDB and made readily available to researchers. In addition to open sources of seismic data, we have established collaborative relationships with several ME/NA countries that have yielded additional ground truth and broadband waveform data essential for regional calibration and capability studies. Additional data and ground truth from other countries are also currently being sought. Research results, along with descriptive metadata are stored and organized within the LLNL RDB and prepared for delivery and integration into the Department of Energy (DOE) Knowledge Base (KB). Deliverables consist of primary data products (raw materials for calibration) and derived products (distilled from the organized raw seismological data). By combining travel-time observations, event characterization studies, and regional wave-propagation studies of the LLNL CTBT research team for ground truth events and regional events, we have assembled a library of ground truth information, event location correction surfaces, tomographic models and mine explosion histories required to support the ME/NA regionalization program. Corrections and parameters distilled from the LLNL RDB provide needed contributions to the KB for the MENA region and will enable the United States National Data Center (NDC) to effectively verify CTBT compliance. The LLNL portion of the DOE KB supports critical NDC pipeline functions in detection, location, feature extraction, discrimination, and analyst review in the Middle East and North Africa.
Author : W. R. Walter
Publisher :
ISBN 13 :
Total Pages : 12 pages
Book Rating : 4.:/5 (316 download)
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.
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ISBN 13 :
Total Pages : 11 pages
Book Rating : 4.:/5 (713 download)
Download or read book LLNL Middle East and North Africa and Former Soviet Union Research Database written by and published by . This book was released on 2000 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Lawrence Livermore National Laboratory (LLNL) Ground-Based Nuclear Explosion Monitoring (GNEM) R & D program has made significant progress populating a comprehensive Seismic Research Knowledge Base (SRKB) and deriving calibration parameters for the Middle East and North Africa (ME/NA) and Former Soviet Union (FSU) regions. The LLNL SRKB provides not only a coherent framework in which to store and organize very large volumes of collected seismic waveforms, associated event parameter information, and spatial contextual data, but also provides an efficient data processing/research environment for deriving location and discrimination correction surfaces. The SRKB is a flexible and extensible framework consisting of a relational database (RDB), Geographical Information System (GIS), and associated product/data visualization and data management tools. This SRKB framework is designed to accommodate large volumes of data (over 2 million waveforms from 20,000 events) in diverse formats from many sources (both LLNL derived research and integrated contractor products) in addition to maintaining detailed quality control and metadata. Using the SRKB framework, we are combining travel-time observations, event characterization studies, and regional tectonic models to assemble a library of ground truth information and phenomenology (e.g. travel-time and amplitude) correction surfaces required for support of the ME/NA and FSU regionalization program. Corrections and parameters distilled from the LLNL SRKB provide needed contributions to the DOE Knowledge Base (DOE KB) for the ME/NA and FSU regions and will help improve monitoring for underground nuclear testing. The LLNL research products will facilitate calibration of International Monitoring System (IMS) stations (primary and auxiliary), their surrogates (if not yet installed) and selected gamma stations necessary to complete the above tasks in the ME/NA and FSU regions.
Author : L. V. Antonova
Publisher :
ISBN 13 :
Total Pages : 227 pages
Book Rating : 4.:/5 (52 download)
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.
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ISBN 13 :
Total Pages : 12 pages
Book Rating : 4.:/5 (682 download)
Download or read book LLNL Identification Program written by and published by . This book was released on 2001 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: LLNL identification research is focused on the problem of correctly discriminating small-magnitude explosions from a background of earthquakes, mining tremors, and other events. The goal is to reduce the variance within the population of each type of event, while increasing the separation between the explosions and the other event types. We address this problem for both broad categories of seismic waves: body waves and surface waves. First, we map out the effects of propagation and source size in advance so that they can be accounted for and removed from observed events. This can dramatically reduce the population variance. Second, we try to optimize the measurement process to improve the separation between population types. For body waves we focus on the identification power of the short-period regional phases Pn, Pg, Sn and Lg, which can often be detected down to very small magnitudes. Many studies have shown that particular ratios of these phases, such as 6-to 8-Hz Pn/Lg, can effectively discriminate between closely located explosions and earthquakes. To extend this discrimination power over broad areas, we use our revised Magnitude and Distance Amplitude Correction (MDAC2) procedure. This joint source and path model fits the observed spectra and removes magnitude and distance trends from the data. The MDAC residuals are kriged to provide full 2-D path corrections by phase and frequency band. The MDAC residuals allow the exploration of all possible ratios and multivariate combinations of ratios for their discrimination power. We also make use of the MDAC spectra and the noise spectra to determine the expected detectability of each phase and use that to optimize the multivariate discriminants as a function of location. We quantify the discrimination power using the misidentified event trade-off curves and an equi-probable measure. We evaluate the correction surfaces using a cross-validation technique. The result is an end-to-end validation and discrimination performance measure for each station analyzed, and a set of measurement algorithms and correction surfaces that greatly improves discrimination. For surface waves we continue to make improvements in our regional group velocity tomography models. We have recently expanded our Rayleigh and Love wave dispersion measurements from the Middle East and North Africa into the European Arctic. The resulting tomography models now cover all of western Eurasia and provide high-resolution maps of group velocity from 10-to 100-seconds period. The maps also provide estimates of the expected phase spectra of new events that can be used in phase-match filters to compress the expected signals and improve the signal-to-noise ratio on surface wave magnitude (Ms) estimates. Phase match filters in combination with regional Ms formulas can significantly lower the threshold at which Ms can be measured, extending the Ms-mb discriminant. We have measured Ms in western Eurasia for thousands of events at tens of stations, with and without phase match filtering, and found a marked improvement in discrimination. Finally we are exploring the Ms-yield relation for the explosions in the dataset with announced yields.
Author : Douglas R. Baumgardt
Publisher :
ISBN 13 :
Total Pages : 87 pages
Book Rating : 4.:/5 (227 download)
Download or read book Case Studies of Seismic Discrimination Problems and Regional Discriminant Transportability written by Douglas R. Baumgardt and published by . This book was released on 1995 with total page 87 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report describes case studies of regional seismic discriminants, using the Intelligent Seismic Event Identification System (ISEIS), and addresses issues related to the transportability of regional discriminants. Some of the key results of this study include: (1) Observations of large Lg waves from mine blasts. (2) Investigation of the P/S frequency-dependence discriminant. (3)The importance of signal decorrelation in the generation of spectral scalloping by ripple fired mine blasts. (4) Path corrections for the Lg spectral ratio discriminant using a simple anelastic attenuation model. Also described in this report is a discrimination study of the January 5, 1995 Urals mine event. Because there were no nearby earthquakes or blasts in the Urals mine region, recordings of the event at regional station ARU were compared with WMQ recordings of Chinese nuclear blasts and earthquakes at comparable distance, but in a different geographic and tectonic region. This comparison indicated that the January 3, 1995 event had Pn/Lg amplitude ratios more comparable to Chinese earthquakes than nuclear explosions. Based on the analysis of Pn/Lg ratios at NORESS and comparison those produced by PNEs in the same region recorded at NORSAR, we conclude that the January 3, 1995 event produced much stronger shear waves (Sn, Lg) relative to P than did nuclear blasts. We conclude that the event was probably a mine tremor or collapse.
Author : Michael A. Chinnery
Publisher :
ISBN 13 :
Total Pages : 81 pages
Book Rating : 4.:/5 (227 download)
Download or read book Seismic Discrimination written by Michael A. Chinnery and published by . This book was released on 1977 with total page 81 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report describes 23 investigations in the field of seismic discrimination. These are grouped as follows: regional seismic studies (13 contributions), miscellaneous studies (6 contributions), and recent developments in our data and computer systems (4 contributions). (Author).
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ISBN 13 :
Total Pages : 38 pages
Book Rating : 4.:/5 (951 download)
Download or read book Probabilistic Seismic Hazards Update for LLNL. written by and published by . This book was released on 2016 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fugro Consultants, Inc. (FCL) completed the Probabilistic Seismic Hazard Analysis (PSHA) performed for Building 332 at the Lawrence Livermore National Laboratory (LLNL), near Livermore, CA. The study performed for the LLNL site includes a comprehensive review of recent information relevant to the LLNL regional tectonic setting and regional seismic sources in the vicinity of the site and development of seismic wave transmission characteristics. The Seismic Source Characterization (SSC), documented in Project Report No. 2259-PR-02 (FCL, 2015b), and Ground Motion Characterization (GMC), documented in Project Report No. 2259-PR-06 (FCL, 2015a) were developed in accordance with ANS/ANSI 2.29- 2008 Level 2 PSHA guidelines. The ANS/ANSI 2.29-2008 Level 2 PSHA framework is documented in Project Report No. 2259-PR-05 (FCL, 2016a). The Hazard Input Document (HID) for input into the PSHA developed from the SSC and GMC is presented in Project Report No. 2259-PR-04 (FCL, 2016b). The site characterization used as input for development of the idealized site profiles including epistemic uncertainty and aleatory variability is presented in Project Report No. 2259-PR-03 (FCL, 2015c). The PSHA results are documented in Project Report No. 2259-PR-07 (FCL, 2016c).
Author :
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ISBN 13 :
Total Pages : 50 pages
Book Rating : 4.:/5 (227 download)
Download or read book Investigation of Regional Seismic Discrimination Issues for Small Or Decoupled Nuclear Explosions written by and published by . This book was released on 1994 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goals of lowering the seismic threshold for underground nuclear explosions to magnitudes near 2.5 m sob o and extending the capability to other geographical regions will require utilization of regional stations for detection and identification. However, regional techniques have seldom been tested on small nuclear explosions. Therefore, S-CUBED is conducting a research program aimed at the identification problems associated with small or decoupled nuclear explosions near a low monitoring threshold (e.g. 1-kt fully decoupled or about 2.5 mb). Initial efforts have focused on using source scaling procedures to scale down records from larger explosions and produce representative seismograms at ARPA regional array stations. The scaled signals embedded in typical background noise at the station enable an assessment of capabilities for different regional signal analysis methods at the lower thresholds. Our preliminary findings are that useful far-regional signals from small or decoupled nuclear explosions may be constrained to very limited high-frequency bands, which may limit the capabilities of some regional detection and identification techniques.
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ISBN 13 :
Total Pages : 13 pages
Book Rating : 4.:/5 (682 download)
Download or read book LLNL Middle East, North Africa and Western Eurasia Knowledge Base written by and published by . This book was released on 2001 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Lawrence Livermore National Laboratory (LLNL) Ground-Based Nuclear Event Monitoring (GNEM) program has made significant progress populating a comprehensive Seismic Research Knowledge Base (SRKB) and deriving calibration parameters for the Middle East, North Africa and Western Eurasia (ME/NA/WE) regions. The LLNL SRKB provides not only a coherent framework in which to store and organize very large volumes of collected seismic waveforms, associated event parameter information, and spatial contextual data, but also provides an efficient data processing/research environment for deriving location and discrimination correction surfaces. The SRKB is a flexible and extensible framework consisting of a relational database (RDB), Geographical Information System (GIS), and associated product/data visualization and data management tools. This SRKB framework is designed to accommodate large volumes of data (almost 3 million waveforms from 57,000 events) in diverse formats from many sources (both LLNL derived research and integrated contractor products), in addition to maintaining detailed quality control and metadata. We have developed expanded look-up tables for critical station parameter information (including location and response) and an integrated and reconciled event catalog data set (including specification of preferred origin solutions and associated phase arrivals) for the PDE, CMT, ISC, REB and selected regional catalogs. Using the SRKB framework, we are combining traveltime observations, event characterization studies, and regional tectonic models to assemble a library of ground truth information and phenomenology (e.g. travel-time and amplitude) correction surfaces required for support of the ME/NA/WE regionalization program. We also use the SRKB to integrate data and research products from a variety of sources, such as contractors and universities, to merge and maintain quality control of the data sets. Corrections and parameters distilled from the LLNL SRKB provide essential contributions to the National Nuclear Security Administration Knowledge Base (NNSA KB) for the ME/NA/WE region and will improve capabilities for underground nuclear test monitoring. The LLNL research products will facilitate calibration of International Monitoring System (IMS) stations (primary and auxiliary), their surrogates (if not yet installed) and selected gamma stations necessary to complete the ME/NA/WE regionalization efforts. In addition to an overview of selected individual research products, we present an overview of our visualization, integration, validation, and organizational processes. Development of these processes and the LLNL SRKB was necessitated by both the very large amount of data and information involved, over 2 terabytes, and the varied data and research result formats utilized. Products assembled, integrated and validated using the LLNL SRKB are grouped into 5 major categories: (1) Reference and contextual information; (2) Detection data; (3) Calibration and ground truth data; (4) Event location products; and (5) Event identification products.
Author : J. R. Murphy
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ISBN 13 :
Total Pages : 72 pages
Book Rating : 4.:/5 (227 download)
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
Author : Theron Bennett
Publisher :
ISBN 13 :
Total Pages : 78 pages
Book Rating : 4.:/5 (455 download)
Download or read book Seismic Discrimination with Regional Phase Spectral Ratios: Investigation of Transportability written by Theron Bennett and published by . This book was released on 1997 with total page 78 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Comprehensive Test Ban Treaty (CTBT) requires the location and identification of seismic events which might be associated with small potential underground nuclear explosion tests. For monitoring the CTBT at low magnitude thresholds, reliance must be placed on regional seismic measurements. Various regional discrimination techniques have been shown to be effective for identifying events in some areas, but the transportability of such methods into uncalibrated source areas remains a problem. This research developed procedures which could be useful for transporting regional phase spectral ratio discriminant measures by accounting for propagation path effects using prior knowledge of attenuation. We have found that by correcting for attenuation the scatter in Lg spectral ratio observations between stations could be reduced. However, these measurements still show considerable overlap between different source types which weakens the reliability of the discriminant. It might be possible to improve the reliability of regional phase spectral ratios by limiting effects of noise on the measurements by focusing on nearer stations, limiting the frequency band over which the ratios are formed.
