HR: 0830h
AN: S21D-0336    [PDF]
TI: Relative Location of Multiple Events Using Empirical Green Functions
AU: * Fischer, T
EM: tomas@ig.cas.cz
AF: Geophysical Institute, Academy of Science of the Czech Republic, Bocni II/1401, Praha 4, 14131 Czech Republic
AB: Some events of the earthquake swarms occurring in NW-Bohemia, Czech Republic, display complex waveforms indicating a complicated rupture process. The method of empirical Green function deconvolution has shown that relative source time functions of these ML=2..3 earthquakes consist of several single events whose origin times and perhaps also other source parameters may differ. To find the parameters of individual single events, which build up the multiple event, a new method of modeling the waveforms of complex events with the use of empirical Green functions was designed. The waveform of a complex event is considered as a sum of waveforms of several single events with different moments, origin times and hypocenter coordinates. To construct a waveform of each single event composing the multiple event a source-time function of a triangular shape and a waveform of a near small event as an empirical Green function is used. Assuming similar focal mechanisms of the sub-events and of the "Green event", the method searches for coordinates and origin times of the sub-events and for their relative seismic moments. The relative position and timing of the sub-events give insight into the process of rupture propagation of swarm events yielding constraints for the rupture velocity, which helps to test the causal relation of the sub-events. Application of the method to the waveforms of the year 2000 swarm has shown that it is possible to distinguish hypocenters of sub-events whose relative distance exceeds 50m. The comparison of the relative position of the sub-events with their focal mechanisms indicated if they correspond to an interrupted rupture growth or likely belong to parallel cracks.
DE: 7209 Earthquake dynamics and mechanics
DE: 7215 Earthquake parameters
DE: 7260 Theory and modeling
SC: Seismology [S]
MN: 2003 Fall Meeting