HR: 0800h
AN: S41B-0991    [Abstracts]
TI: Rupture geometry of microearthquakes inferred from analysis of multiple events
AU: * Fischer, T
EM: tomfis@ig.cas.cz
AF: Geophysical Institute Acad. Sci., Bocni II/1401, Prague, 14131 Czech Republic
AB: Complicated waveforms of some swarm earthquakes in West Bohemia, Central Europe indicate complicated rupture history and possible space separation of several subruptures. I obtained the position and timing of the subevents building up the multiple event by waveform modeling with the use of empirical Green's functions. In total 18 multiple events were successfully modeled as double or triple events with separate rupture positions. The separation of subsources reached 100 ms in time and 320 m in space. The relative positions of the subevents with respect to the geometry of the fault indicate that most of them occurred very close to the common fault plane that was activated during the swarm. The space-time separation of the subevents corresponds to a speed of 3.0 km/s, a value typical for rupture propagation of large earthquakes. The later subevents occur farther than the nominal rupture radius of the first subevent, and their mutual distance scales with magnitude. These observations suggest that the analyzed multiple-events share a common fault surface and that their subevents represent individual rupture episodes. The angular distribution of the position vectors of later subevents indicates that many of them result from a slip-parallel rupture growth, while some of the ruptures propagate upwards. The hypocenters of the multiple events are not distributed uniformly on the fault plane; their clustering indicates that some patches of the fault are more likely to generate a stick-slip failure than the others.
DE: 7215 Earthquake source observations (1240)
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
SC: Seismology [S]
MN: Fall Meeting 2005