HR: 11:05h
AN: T22A-04    [Abstracts]
TI: The Effect of Bandwidth Limitations on the Inference of Slip-Weakening and Energy Parameters from Seismograms
AU: * Spudich, P
EM: spudich@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Road, Menlo Park, CA 94025 United States
AU: Guatteri, M
EM: Mariagiovanna_Guatteri@swissre.com
AF: Swiss Re, 175 King St., Armonk, NY 10504 United States
AB: Numerous researchers have obtained estimates of slip-weakening distance Dc and fracture energy for recent earthquakes. Dc is often observed to be a significant fraction of the total slip and tends to correlate with total slip. While these observations may well be true of real earthquakes, we show that low-pass filtering of strong motion seismograms can also produce some of these effects in inverted rupture models. We test the accuracy of Dc estimates by calculating them in low-pass filtered versions of models A and B of Guatteri and Spudich (2000). Models A and B are two different rupture models for a hypothetical M6.5 earthquake, and they have nearly identical rupture time, slip, and stress drop distributions, as well as nearly identical predicted seismograms, but Dc for model B is about twice that for model A. By low-pass filtering slip models A and B at 1.0 Hz, we simulate the blurring effects of band-limited waveform inversions on these slip models. At each point on a fault, Dc' is defined to be the slip at the time of the peak slip speed at that point. Low-pass filtering the slip models causes an upward bias in Dc inferred from stress-slip curves, and it causes an artificial correlation between Dc' and the total slip. Low-pass filtering might also bias fracture energy high and radiated energy low. These biases should be considered when interpreting Dc derived from band-limited slip models of real earthquakes.
DE: 7209 Earthquake dynamics and mechanics
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting