scholarly journals Mantle Heterogeneities and the SCEC Reference Three-Dimensional Seismic Velocity Model Version 3

2003 ◽  
Vol 93 (2) ◽  
pp. 757-774 ◽  
Author(s):  
M. D. Kohler
Keyword(s):  
Seismic Velocity ◽  
Three Dimensional ◽  
Velocity Model ◽  
Model Version ◽  
Mantle Heterogeneities

scholarly journals Antarctic Upper Mantle Rheology

2021 ◽  
pp. M56-2020-19
Author(s):  
E. R. Ivins ◽  
W. van der Wal ◽  
D. A. Wiens ◽  
A. J. Lloyd ◽  
L. Caron
Keyword(s):  
Wave Velocity ◽  
Upper Mantle ◽  
Effective Viscosity ◽  
Seismic Velocity ◽  
Imaging Techniques ◽  
Three Dimensional ◽  
Velocity Model ◽  
Mantle Flow ◽  
S Wave ◽  
Velocity Changes

AbstractThe Antarctic mantle and lithosphere are known to have large lateral contrasts in seismic velocity and tectonic history. These contrasts suggest differences in the response time scale of mantle flow across the continent, similar to those documented between the northeastern and southwestern upper mantle of North America. Glacial isostatic adjustment and geodynamical modeling rely on independent estimates of lateral variability in effective viscosity. Recent improvements in imaging techniques and the distribution of seismic stations now allow resolution of both lateral and vertical variability of seismic velocity, making detailed inferences about lateral viscosity variations possible. Geodetic and paleo sea-level investigations of Antarctica provide quantitative ways of independently assessing the three-dimensional mantle viscosity structure. While observational and causal connections between inferred lateral viscosity variability and seismic velocity changes are qualitatively reconciled, significant improvements in the quantitative relations between effective viscosity anomalies and those imaged by P- and S-wave tomography have remained elusive. Here we describe several methods for estimating effective viscosity from S-wave velocity. We then present and compare maps of the viscosity variability beneath Antarctica based on the recent S-wave velocity model ANT-20 using three different approaches.

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

2020 ◽  
Author(s):  
Michael L. Begnaud ◽  
Stephen C. Myers ◽  
Brian Young ◽  
James R. Hipp ◽  
Doug Dodge ◽  
...  
Keyword(s):  
Travel Time ◽  
Seismic Velocity ◽  
Three Dimensional ◽  
Computer Software ◽  
Velocity Model ◽  
Travel Times ◽  
Crust And Upper Mantle ◽  
Data Set ◽  
Earth Models ◽  
Regional Phases

Abstract 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).

scholarly journals A California Statewide Three-Dimensional Seismic Velocity Model from Both Absolute and Differential Times

2010 ◽  
Vol 100 (1) ◽  
pp. 225-240 ◽  
Author(s):  
G. Lin ◽  
C. H. Thurber ◽  
H. Zhang ◽  
E. Hauksson ◽  
P. M. Shearer ◽  
...  
Keyword(s):  
Seismic Velocity ◽  
Three Dimensional ◽  
Velocity Model

Seismic velocity models for heat zones in Athabasca tar sands

Geophysics ◽  
1990 ◽  
Vol 55 (8) ◽  
pp. 1108-1112 ◽  
Author(s):  
Larry R. Lines ◽  
Ronald Jackson ◽  
James D. Covey
Keyword(s):  
Seismic Velocity ◽  
Three Dimensional ◽  
Velocity Model ◽  
Steam Injection ◽  
P Wave ◽  
Injection Velocity ◽  
Low Velocity ◽  
Borehole Data ◽  
Tar Sands ◽  
Velocity Models

Recent laboratory and field studies indicate that the P-wave velocity in Athabasca tar sands decreases when temperature increases during steam injection. In this paper we derive time variant velocity models from seismic traveltime inversions of both reflection and borehole data. Prior to steam injection, three‐dimensional (3-D) reflector velocity‐depth models are established using image‐ray conversions of traveltimes to depth. The changes in velocity due to steam injection are modeled by inverting traveltime data from seismic monitor surveys after steam injection and comparing these results to velocities computed prior to steam injection. Velocity models are essentially determined by traveltimes from the 3-D seismic reflection survey. The surface‐to‐wellbore data traveltimes show the expected delay caused by steam injection but do not significantly alter the velocity model produced by reflection traveltimes. For seismic monitor surveys, low‐velocity zones show a very good correlation with zones of temperature increase at injector well positions. The results indicate that velocity models obtained from seismic traveltimes may prove useful in detecting steam fronts in tar sands.

scholarly journals Three‐Dimensional Basin and Fault Structure From a Detailed Seismic Velocity Model of Coachella Valley, Southern California

2019 ◽  
Vol 124 (5) ◽  
pp. 4728-4750
Author(s):  
Rasheed Ajala ◽  
Patricia Persaud ◽  
Joann M. Stock ◽  
Gary S. Fuis ◽  
John A. Hole ◽  
...  
Keyword(s):  
Southern California ◽  
Seismic Velocity ◽  
Three Dimensional ◽  
Velocity Model ◽  
Fault Structure ◽  
Coachella Valley
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