HR: 08:30h
AN: S21C-03    [Abstracts]
TI: Scaling and Complexity in Small Earthquakes - the Orinda Sequence
AU: * Hellweg, M
EM: peggy@seismo.berkeley.edu
AF: Berkeley Seismological Laboratory, U.C. Berkeley 215 McCone Hall #4760, Berkeley, CA 94720 United States
AB: On October 19 and 20, 2004, two earthquakes with ML 3.5 and 3.4 occurred ENE of Orinda, CA, almost directly below Berkeley Seismological Laboratory's (BSL) station BRIB (37.92 N, 122.15 W). The 3-component borehole geophone registered more than 4000 fore- and aftershocks the first week of the sequence, with magnitudes down to -2 and S-P times ranging from 0.58 to 0.72 s. Many of the events, including the ML 3.4 aftershock exhibit complexity. Some events have a second P-arrival between their P and S phases, while others occur as part of a rapid sequence with the new P wave following shortly after preceding event's S-wave. We estimate the extent of the source volume using S-P times and polarization, and investigate the spatial relationship between the subevents in the double and multiple earthquakes. Using time- and spectral-domain methods, we determine moment, energy and event radius to study their interrelationship for this cluster of events with magnitudes from -1.5 to 3.5.
DE: 7209 Earthquake dynamics (1242)
DE: 7215 Earthquake source observations (1240)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
SC: Seismology [S]
MN: Fall Meeting 2005