Analysis of a deep ``non-double couple'' earthquake using very broadband data,
Kuge, K., and H. Kawakatsu
Geophys. Res. Lett., 17,
227-230, 1990.
Abstract
We analyze the source mechanism of a deep earthquake
beneath Japan on January 1, 1984 (9:03 40.1sec,
136.80oE, 33.62oN, depth=386.0km,
mb=6.4, ISC),
whose Harvard centroid moment tensor (CMT) solution
significantly deviates from a double couple mechanism.
The broadband P-wave ground displacement records show
the presence of several distinct phases whose relative amplitudes vary
among the stations.
We perform very broadband waveform analyses
over four different frequency bands:
CMT inversion (surface waves 4~5mHz) and long-period body waves
(12~20mHz)),
first motion using the long-period P and SH waveforms (~0.04Hz),
and broadband P-wave waveform analysis (0.03~1Hz).
We postulate and show that the large non double couple solution observed at
long periods (>25sec) is a manifestation of the presence of several subevents
with different double couple mechanisms in a single rupture sequence.