| Transitioning the Coda Methodology to Full 2-D for P and S Codas (Postprint) |
30 Dec 2011 |
8 pages |
| Authors:
Kevin M Mayeda; W S Phillips; Rengin Gok; Michael E Pasyanos; William R Walter; WESTON GEOPHYSICAL LEXINGTON MA
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 | 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 ... |
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| Estimating the Uncertainty and Predictive Capabilities of Three-Dimensional Earth Models |
30-Sep-2009 |
11 pages |
| Authors:
Stephen C Myers; Delaine T Reiter; William L Rodi; WESTON GEOPHYSICAL LEXINGTON MA
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| Many three-dimensional models of seismic velocity structure in Eurasia have been developed in recent years by the seismic nuclear monitoring community. Most of these models are not accompanied by quantitative estimates of uncertainty, either in the model velocities themselves or in geophysical observables predicted by the models (e.g., body-wave travel times). Moreover, the various 3D models produced by these studies have not been compared to one another for their predictive ... |
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| Incorporating Love- and Rayleigh-Wave Magnitudes, Unequal Earthquake and Explosion Variance Assumptions, and Intrastation Complexity for Improved Event Screening |
30 Sep 2009 |
11 pages |
| Authors:
Jessie L Bonner; Anastasia Stroujkova; Robert H Shumway; Robert B Herrmann; Dale N Anderson; WESTON GEOPHYSICAL LEXINGTON MA
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| Our objective is to improve seismic event screening using the properties of surface waves. We are accomplishing this through (1) the development of a Love-wave magnitude formula that is complementary to the Russell (2006) formula for Rayleigh waves and (2) quantifying differences in complexities and magnitude variances for earthquake and explosion-generated surface waves. We have applied the M(x) (VMAX) analysis (Bonner et al., 2006) using both Love and Rayleigh waves ... |
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| Quantification of Rock Damage from Small Explosions and Its Effect on Shear-Wave Generation |
15 Jun 2009 |
170 pages |
| Authors:
Mark Leidig; Jessie Bonner; Randolph J Martin; Peter Boyd; Jim Lewkowicz; WESTON GEOPHYSICAL LEXINGTON MA
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| Weston Geophysical Corp., New England Research, Inc., and several geotechnical consultants conducted the Vermont/New England Damage Experiment in central Vermont during July 2008. A series of five explosions using charges with yields of 135 and 270 lbs and three types of explosives were detonated in homogeneous, low fracture density granite. The goal of the experiment was to generate different amounts of rock damage around the source by using explosives with ... |
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| A New Regional 3-D Velocity Model for Asia from the Joint Inversion of P-Wave Travel Times and Surface-Wave Dispersion Data |
30-Sep-2008 |
10 pages |
| Authors:
Delaine T Reiter; William L Rodi; WESTON GEOPHYSICAL LEXINGTON MA
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| Accurate travel-time predictions for regional seismic phases are essential for locating small seismic events with the accuracy needed for nuclear monitoring decisions. Travel times calculated through a three-dimensional (3-D) Earth model have the best chance of achieving acceptable prediction errors, if the model is constrained by sufficient data. With this motivation, we have developed a self-consistent 3-D P and S velocity model of the crust and upper mantle in a ... |
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| Improved Phase Characterization of Far-Regional Body Wave Arrivals in Central Asia |
30-Sep-2008 |
11 pages |
| Authors:
Aaron Ferris; Delaine Reiter; Anastasia Stroujkova; WESTON GEOPHYSICAL LEXINGTON MA
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| At far-regional and near-teleseismic distances the early body-wave coda contains information that is potentially useful to monitoring seismologists. However, waveforms from this distance range are typically under-utilized because of propagation complexities that cause significant difficulties in seismogram interpretation. For example, the first approx. 20 seconds of a far-regional seismogram often include multi-pathed arrivals caused by the interaction of the wavefield with upper mantle discontinuities at 220 km, 410 km and ... |
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| Small-Event Yield and Source Characterization using |
30-Sep-2008 |
10 pages |
| Authors:
Kevin Mayeda; WESTON GEOPHYSICAL LEXINGTON MA
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| The mission of the Air Force Technical Applications Center (AFTAC) requires accurate yield estimation for nuclear explosions. Historically, the focus has been on larger yield events (m(b) > approx 4.5) using teleseismic body wave magnitudes and applying test-site-specific corrections for yield estimates. The regional coda methodology provides unprecedented stability and avoids test site bias because it is based upon absolute source spectra. Increasingly, however, there is interest in monitoring smaller ... |
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| Quantification of Rock Damage from Small Explosions and its Effect on Shear-Wave Generation: Phase I - Homogeneous Crystalline Rock |
30-Sep-2008 |
11 pages |
| Authors:
Mark Leidig; Peter Boyd; Randolph J Martin; James F Lewkowicz; Dorothy Richter; Robert Garfield; Jeffrey A Reid; Jessie L Bonner; WESTON GEOPHYSICAL LEXINGTON MA
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| We are currently conducting a one-year feasibility study to determine the most efficient way to characterize the damage from an explosive source and to identity the source(s) of shear wave generation. We hope to quantify crack nucleation and growth (Ashby and Sammis, 1990) as an S-wave generation mechanism in the far-field (Sammis, 2002) and to map the cone of damage (Patton et. al. 2005; Stevens et. al. 2003) above a ... |
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| Small-Event Yield and Source Characterization Using Local P and S-Wave Coda Source Spectra |
Sep 2008 |
10 pages |
| Authors:
Kevin Mayeda; WESTON GEOPHYSICAL LEXINGTON MA
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| The Air Force Technical Applications Center mission requires accurate yield estimation for nuclear explosions. Historically, focus has been on larger yield events using teleseismic body wave magnitudes and applying test site specific corrections for yield estimates. Regional coda methodology provides unprecedented stability and avoids test site bias as it is based upon absolute source spectra. There is interest in monitoring smaller events. However, these events may only be recorded with ... |
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| Regional P-Coda for Stable Estimates of Body Wave Magnitude: Application to Novaya Zemlya and Nevada Test Site Events |
15-Apr-2008 |
24 pages |
| Authors:
Kevin Mayeda; WESTON GEOPHYSICAL LEXINGTON MA
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| Regional seismic explosion monitoring requires the discrimination of small clandestine nuclear explosions from background earthquakes. most successful teleseismic discriminant, the so-called Ms:mb, discriminant, compares the long-period surface waves magnitude (Ms) with the period P-based body wave magnitude (mb). There are many studies underway to try and extend surface wave magnitude (Ms) estimation to re distances and smaller magnitudes. Another problem that is encountered is how to estimate mb so that ... |
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| Regional P-Coda for Stable Estimates of Body Wave Magnitude: Extending the M(s):m(b) Discriminant to Smaller Events |
Sep 2006 |
12 pages |
| Authors:
Kevin Mayeda; Jessie Bonner; Heather Hooper; WESTON GEOPHYSICAL LEXINGTON MA
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| The most successful teleseismic discriminant is M(s):m(b), and many studies are underway to try and extend surface wave magnitude (M(s)) estimation to regional distances. A problem that is encountered at regional distances and small magnitudes is how to estimate m(b) so that the M(s):m(b) discriminant is meaningful and consistent with teleseismic measures. Over the past several years, a regional S-coda wave methodology has been developed that provides for the lowest ... |
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| A Regional Seismic Experiment in India to Increase Knowledge of Velocity Structure |
MAY 2006 |
170 pages |
| Authors:
James F. Lewkowicz; Keith Priestley; Vinod Gaur; Jessie L. Bonner; Sara G. Russell; Delaine Ritter; Alessia Maggi; Supryio Mitra; WESTON GEOPHYSICAL LEXINGTON MA
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| Weston Geophysical Corporation, Cambridge University and India Institute of Astrophysics formed a consortium in 2000 to deploy a network of high-quality broadband seismometers distributed across India. This network began operation in April 2001, and is now fully operational providing important data for studies focusing on the characterization of the velocity structure and propagation of seismic waves throughout Southern Asia. Each station consists of a Guralp CMG-3TD digital output seismometer plus ... |
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| Development of a Regional 3-D Velocity Model of the Pakistan Region for Improved Seismic Event Location |
APR 2006 |
32 pages |
| Authors:
Delaine Reiter; Michelle Johnson; Anca Rosca; Camlynn Vincent; William Rodi; WESTON GEOPHYSICAL LEXINGTON MA
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| In this report, we detail the development of a new regional 3-D tomographic P-wave velocity model (WINPAK3D) of a region in Southern Asia centered on Pakistan. Our primary goal in developing a 3-0 model of the crust and upper mantle in this region is to improve regional seismic event location. A detailed initial Pn model was iteratively refined using a nonlinear, conjugate-gradients technique that adjusts the velocity model of model ... |
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| Calibration of the M(sub s):m(sub b) Discriminant at the International Monitoring System Array NVAR (PS-47) |
SEP 2005 |
94 pages |
| Authors:
Jessie L. Bonner; Sara A. Russell; Ileana M. Tibuleac; David Russell; David G. Harkrider; Delaine T. Reiter; Robert H. Shumway; Robert Herrmann; Eugene Herrin; WESTON GEOPHYSICAL LEXINGTON MA
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| Surface wave magnitude [M(sub s)] estimation for small events recorded at near-regional distances will often require a magnitude scale designed for Rayleigh waves with periods between 5 and 25 seconds. We have completed several studies aimed at examining the usefulness of existing and new formulas at estimating surface wave magnitudes at periods not restricted to approximately 20 seconds. In Chapter 1, we show that 7-second surface waves can be used ... |
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| Empirical Analysis Of A 3-D Pakistan Regionalized Velocity Model For Improved Seismic Event Locations |
Sep 2000 |
11 pages |
| Authors:
Michelle Bernard-Johnson; Shirley Rieven; Carolynn Vincent; Delaine Reiter; William Rodi; WESTON GEOPHYSICAL LEXINGTON MA
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| The objective of this project is to improve regional event location in Pakistan and the surrounding regions by developing a 3-D velocity model for the crust and upper mantle. The CTBT goal of 1000 km2 location accuracy for small events is dependent upon the availability of such models, which can be used to compute accurate travel times of regional seismic phases. Our approach is to refine an a priori 3-D ... |
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