Accession Number : ADP204444

Title :   Loss of High Frequency Upon Propagation through Shock-Damaged Rock,

Corporate Author : CALIFORNIA INST OF TECH PASADENA SEISMOLOGICAL LAB

Personal Author(s) : Ahrens, Thomas J. ; Liu, Cangli

PDF Url : ADP204444

Report Date : 14 AUG 1995

Pagination or Media Count : 7

Abstract : The attenuation of stress waves in samples of gabbroic rock subjected to shock loading up to 11 GPa is studied. We determine the attenuation coefficients, alpha sub p, for samples with different damage parameters under dynamic strains of 2 x 10(exp -7) and at frequencies around 2 MHz using the ultrasonic pulse-echo method. A fit to the data yields the P-wave spatial attenuation coefficient versus damage parameter: alpha sub p = 40.9 D sub p - 30.5 D sub sq p2 (db/cm). Basing on O'Connell-Budiansky theory a relation between attenuation coefficient and crack density is derived. The predictions of alpha sub p and Q from Walsh's theory agrees well with the experiment results for the samples with different damage deficits and the Q's we measure are in the range of 10 to 20. These very low values give rise to the sharp decrease in high frequency seismic energy, as the stress-wave from an explosion leaves the source region.

Descriptors :   *SEISMIC DETECTION, *SEISMIC WAVES, *ARMS CONTROL, *NUCLEAR EXPLOSION DETECTION, *IGNEOUS ROCK, SYMPOSIA, MONITORING, SHOCK WAVES, UNDERGROUND EXPLOSIONS, STRAIN(MECHANICS), WAVE PROPAGATION, SEISMIC DISCRIMINATION, TREATIES, SEISMIC VELOCITY, ULTRASONIC TESTS, STRESS WAVES, PRIMARY WAVES(SEISMIC WAVES), Q FACTOR.

Subject Categories : Government and Political Science
      Geology, Geochemistry and Mineralogy
      Seismology
      Seismic Detection and Detectors
      Nuclear Weapons

Distribution Statement : APPROVED FOR PUBLIC RELEASE