The use of local and regional S-wave coda is shown to provide stable amplitude ratios that better constrain source differences between event pairs. We first compared amplitude ratio performance between local and near-regional S and coda waves in the San Francisco Bay region for moderate-sized events, then applied the coda spectral ratio method to the 1999 Hector Mine mainshock and its larger aftershocks. We find: (1) Average amplitude ratio standard deviations using coda are 0.05 to 0.12, roughly a factor of 3 smaller than direct S-waves for 0.2 f 15.0 Hz; (2) Coda spectral ratios for the 7.0 Hector Mine earthquake and its aftershocks show a clear departure from self-similarity, consistent with other studies using the same datasets; (3) Event-pairs (Greens function and target events) can be separated by 25 km for coda amplitudes without any appreciable degradation, in sharp contrast to direct waves.
Berkeley Seismological Laboratory
215 McCone Hall, UC Berkeley, Berkeley, CA 94720-4760
Questions or comments? Send e-mail: firstname.lastname@example.org
© 2007, The Regents of the University of California