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Title: Two Sources of Nonisotropic Radiation From Underground Explosions in Granite

Significant tangential ground motion observed during underground explosions makes it difficult to distinguish them from natural earthquakes. Such motion can be generated by the source geometry and emplacement conditions, by the heterogeneous nature of the rock mass (mechanical properties may vary in space due to the presence of cracks, joints, faults, and various geologic layers) and also by the nonuniform in situ stress state. The last mechanism is increasingly important with depth when the difference in main principal stresses becomes significant. This paper is focused on the role of material strength of the rock mass in generation of nonradial motion during explosions in prestressed media. Numerical modeling of underground chemical explosions in granite at various depths has been conducted to compare two possible mechanisms of shear wave generation. The first, caused by rock mass anisotropy, is important at shallow depth. The second is related to elastic-plastic relaxation around the cavity created by the explosion. As a result, tangential motions for these two mechanisms have different signatures.
Authors:
 [1]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Report Number(s):
LLNL-JRNL-733561
Journal ID: ISSN 2169-9313; TRN: US1800272
Grant/Contract Number:
AC52-07NA27344; W-7405-southern-48
Type:
Accepted Manuscript
Journal Name:
Journal of Geophysical Research. Solid Earth
Additional Journal Information:
Journal Volume: 122; Journal Issue: 11; Journal ID: ISSN 2169-9313
Publisher:
American Geophysical Union
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 54 ENVIRONMENTAL SCIENCES; underground explosions; jointed rock; cavity relaxation; tangential ground motion; anisotropy; shear waves
OSTI Identifier:
1411684
Alternate Identifier(s):
OSTI ID: 1408788