Calibration of Seismograph Network may meet Test Ban Treaty's monitoring needs

Firbas, Petr; Fuchs, Karl; Mooney, Walter D.

doi:10.1029/98eo00315

Cited by 12 publications

(10 citation statements)

References 4 publications

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“…Travel times of regional seismic phases are strongly affected by heterogeneity in the crust and uppermost mantle. To improve location accuracy, we can account for heterogeneity by constructing three‐dimensional models of seismic velocity [ Firbas et al , 1998; Johnson and Vincent , 2002; Murphy et al , 2002; Ritzwoller et al , 2003; Yang et al , 2004; Pasyanos et al , 2004], or regionally varying travel‐time models [ Bondar and North , 1999; Richards et al , 2003]. We can also use empirical methods based on ground‐truth (GT) information [ Schultz et al , 1998; Myers and Schultz , 2000], or, as many of these authors show, the two methods may be combined to take advantage of the strengths of both.…”

Section: Introductionmentioning

confidence: 99%

The use of interstation P wave arrival time differences to account for regional path variability

Phillips

Rowe

Steck

2005

Geophysical Research Letters

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[1] The difference between arrival times from one seismic event to a pair of receivers is largely insensitive to source location error when certain geometric conditions are met. Using catalog data from a Chinese regional network, we illustrate the use of arrival time differences to control data quality and to derive a two-dimensional map of P n velocity and relative site terms. The resulting velocity patterns follow regional geology closely, site terms reflect variations in crustal thickness, and both are consistent with previous work based on single ray methods. The model fits the time difference data to better than 1 s and we obtain a variance reduction of 75%. We believe that the continued development of time-difference techniques will lead to improved location accuracy and precision using regional network data. Citation: Phillips, W. S., C. A. Rowe, and L. K. Steck (2005), The use of interstation P wave arrival time differences to account for regional path variability, Geophys.

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Section: Introductionmentioning

confidence: 99%

The use of interstation P wave arrival time differences to account for regional path variability

Phillips

Rowe

Steck

2005

Geophysical Research Letters

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“…Note the reduction of uncertainty as depth reaches the interface depth (i.e., 0 km). For events below the interface, the crustal-leg uncertainty is entirely due (for Pn/Sn) or mostly due (for Pg/Lg) to the receiver-side leg of the ray path (Firbas et al 1998). Station GERES is located in a part of the tomography/validation data set where there are many ray paths for the various distance bins where (t i -t o ) is the observed travel time, and T oi,c , T oi,r , T oi,g are the calculated travel times for an event o, along ray path i, for the source crustal leg c, the receiver crustal leg r, and the mantle gradient portion g, and d i is the head-wave distance (km) for path i.…”

Section: Constructing a 2d Random Effects Model For Rsttmentioning

confidence: 99%

Correction to: Updates to the Regional Seismic Travel Time (RSTT) Model: 2. Path-dependent Travel-time Uncertainty

Begnaud

Anderson

Myers

et al. 2021

Pure Appl. Geophys.

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The regional seismic travel time (RSTT) model and software were developed to improve travel-time prediction accuracy by accounting for three-dimensional crust and upper mantle structure. Travel-time uncertainty estimates are used in the process of associating seismic phases to events and to accurately calculate location uncertainty bounds (i.e. event location error ellipses). We improve on the current distance-dependent uncertainty parameterization for RSTT using a random effects model to estimate slowness (inverse velocity) uncertainty as a mean squared error for each model parameter. The random effects model separates the error between observed slowness and model predicted slowness into bias and random components. The path-specific travel-time uncertainty is calculated by integrating these mean squared errors along a seismic-phase ray path. We demonstrate that event location error ellipses computed for a 90% coverage ellipse metric (used by the Comprehensive Nuclear-Test-Ban Treaty Organization International Data Centre (IDC)), and using the path-specific travel-time uncertainty approach, are more representative (median 82.5% ellipse percentage) of true location error than error ellipses computed using distance-dependent travel-time uncertainties (median 70.1%). We also demonstrate measurable improvement in location uncertainties using the RSTT method compared to the current station correction approach used at the IDC (median 74.3% coverage ellipse).

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“…Sn gradient values are mostly minimal and consistent for large areas. Changes in gradient values are different due both from the use of the Bayesloc data as well as different starting values For relocation of the 2309 validation events, we use the LocOO3D algorithm developed by Sandia National Laboratories [https://www.sandia.gov/ salsa3d/Software.html] (Ballard et al 2008(Ballard et al , 2009 which permits using standard 1D travel-time tables (e.g., iasp91, ak135), source-specific correction surfaces (SSSCs) for each IMS station and phase (Firbas et al 1998) (converted to GeoTess format), ray-bending through 3D models, and full RSTT models for travel-time prediction. All depths are fixed at the Bayesloc result to reduce the trade-off between depth and origin time.…”

Section: Figure 12mentioning

confidence: 99%

“…of International Monitoring System primary (red) and auxiliary (blue) seismic stations. Circles indicate which stations had original IDC source-specific stations corrections (IDC-SSSCs) defined for regional phases (Pn, Pg, Sn, Lg)(Firbas et al 1998)…”

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confidence: 99%

Updates to the Regional Seismic Travel Time (RSTT) Model: 1. Tomography

Begnaud

Myers

Young

et al. 2020

Pure Appl. Geophys.

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A function of global monitoring of nuclear explosions is the development of Earth models for predicting seismic travel times for more accurate calculation of event locations. Most monitoring agencies rely on fast, distance-dependent one-dimensional (1D) Earth models to calculate seismic event locations quickly and in near real-time. RSTT (Regional Seismic Travel Time) is a seismic velocity model and computer software package that captures the major effects of three-dimensional crust and upper mantle structure on regional seismic travel times, while still allowing for fast prediction speed (milliseconds). We describe updates to the RSTT model using a refined data set of regional phases (i.e., Pn, Pg, Sn, Lg) using the Bayesloc relative relocation algorithm. The tomographic inversion shown here acts to refine the previous RSTT public model (rstt201404um) and displays significant features related to areas of global tectonic complexity as well as further reduction in arrival residual values. Validation of the updated RSTT model demonstrates significant reduction in median epicenter mislocation (15.3 km) using all regional phases compared to the iasp91 1D model (22.1 km) as well as to the current station correction approach used at the Comprehensive Nuclear-Test-Ban Treaty Organization International Data Centre (18.9 km).

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Calibration of Seismograph Network may meet Test Ban Treaty's monitoring needs

Cited by 12 publications

References 4 publications

The use of interstation P wave arrival time differences to account for regional path variability

The use of interstation P wave arrival time differences to account for regional path variability

Correction to: Updates to the Regional Seismic Travel Time (RSTT) Model: 2. Path-dependent Travel-time Uncertainty

Updates to the Regional Seismic Travel Time (RSTT) Model: 1. Tomography

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