Application of Waveform Modeling to Determine Focal Mechanisms of the 1993 Tapu Earthquake and Its Aftershocks

Abstract

To determine the focal mechanisms of the 1993 Tapu earthquake sequence by applying the multiple station moment tensor inversion is the main objective of this paper. Digital strong motion seismograms recorded at short distance are used. The realistic layered model obtained by Ho and Shin (1994) is slightly modified to calculate the Green¡¦s functions and then the synthetic waveforms for moment tensor inversion.
Both fault plane solutions decomposed from moment tensor and the depth cross-section of aftershocks show that the were two earthquake sequences from 15, December 1993 to 30 January 1994. The first earthquake sequence was mainly for1ned by the Tapu main earthquake (ML=5.7). The focal depths were distributed between 10.0 and 17.0 km. The ruptural process was characterized by a westward dipping thrust fault. The second earthquake sequence occurred after 3, January 1994 and was located 20 km north of the first. The mainshock (ML=4.4) and aftershocks of the second sequence were located shallowly between 3.0 and 8.0 km. The fault plane solutions show a vertical normal faulting of southern dipping with a left-lateral component.

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