Attenuation of Seismic Waves in the Near-Source Region
Abstract
Consider a model of elastic wave propagation through a material permeated by a dilute ensemble of cracks. The excitation strains are large enough to cause the cracks to grow either by fatigue or by stress corrosion. As the cracks grow, energy is removed from the excitation. The dominant mechanism of growth, and hence for absorption, is creep in the slip-weakening zone at the edges of the cracks. Because of non-linearity, the attenuation in the time domain in this case is significantly waveform dependent. For harmonic excitation and narrow bandwidth detection, 1/Q varies as the cube of the excitation amplitude and is independent of the frequency. For broad band impulsive excitation and detection, an equivalent transfer function for the attenuation has a Q which varies as the first power of the frequency for low frequencies, both for simulated explosion and extended noisy waveshapes. Keywords: Attenuation, Fatigue crack growth, Stress corrosion.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 14, 1989
- Accession Number
- ADA226814
Entities
People
- Leon Knopoff
Organizations
- University of California, Los Angeles