HR: 0800h
AN: DI51A-0288    [Abstracts]
TI: Determination of Rupture Velocities of Deep-focus Earthquakes Using Combination of Teleseismic and Regional Data
AU: * Park, S
EM: suncheon@eqh.dpri.kyoto-u.ac.jp
AF: Kyoto University Pioneering Research Unit for Next Generation, Kyoto University, Gokasho, Uji, 611-0011, Japan
AU: Mori, J
EM: mori@eqh.dpri.kyoto-u.ac.jp
AF: Earthquake Hazards Division, Disaster Prevention Research Institute, Kyoto University, Gokasho, Uji, 611-0011, Japan
AB: Although rupture velocity is an important parameter in understanding the physics of the earthquake source, it is often difficult to determine. For shallow earthquakes, not only seismic waveform data but also geodetic or surface displacement data are frequently available, so that they can be constraints for the estimation of source parameters including rupture velocity. However these closely observed data are not available for deep-focus earthquakes and this fact makes it more difficult to accurately estimate earthquake source parameters. One common method to estimate rupture velocity of deep-focus earthquakes is to use relative locations between the hypocenter and subevents, using time differences between the initiation and later phases in waveforms depending on the direction from the source to stations. This method has many uncertainties especially when it is difficult to pick the arrivals from subevents in the waveforms and when the event has a simple source time function. Another method is with seismic waveform inversions, which also often used for shallow earthquakes. This, however, does not have strong constraints on the fault dimension and rupture velocity because of the trade- off between them. To estimate rupture velocities of deep-focus earthquakes with better resolution, we used a new method, which is combination of teleseismic waveform inversion and forward modeling of regional data. We first carried out teleseismic waveform inversions for rupture velocities of 0.5 \symbol{"7E} 6 km/s on both nodal planes obtained by Harvard CMT solutions, varying grid size for the change of rupture velocity. Next, forward modeling of regional data was performed with each slip distribution obtained by teleseismic inversions, using empirical Green function method. Then we estimated the rupture velocity when the synthetics calculated by forward modeling best explain the observed regional data. Using this method we were able to estimate the rupture velocities of three deep-focus earthquakes surrounding Japan. The estimated rupture velocities are about 1 \symbol{"7E} 2 km/s, which are equivalent to 20 \symbol{"7E} 40 % of shear wave velocity. These values of rupture velocities are quite slow, compared to typical values for shallow earthquakes, which are 70 \symbol{"7E} 80 % of shear wave velocity.
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 7200 SEISMOLOGY
DE: 7203 Body waves
SC: Study of the Earth's Deep Interior [DI]
MN: 2007 Fall Meeting