ESTIMATION OF HIGH-FREQUENCY WAVE RADIATION AREAS ON THE FAULT PLANE OF THE 1995 HYOGO-KEN NANBU EARTHQUAKE BY THE ENVELOPE INVERSION OF ACCELERATION SEISMOGRAMS
Y. Kakehi et al., ESTIMATION OF HIGH-FREQUENCY WAVE RADIATION AREAS ON THE FAULT PLANE OF THE 1995 HYOGO-KEN NANBU EARTHQUAKE BY THE ENVELOPE INVERSION OF ACCELERATION SEISMOGRAMS, Journal of Physics of the Earth, 44(5), 1996, pp. 505-517
We estimated the high-frequency wave radiation process on the fault pl
ane of the 1995 Hyogo-ken Nanbu earthquake (M-JMA = 7.2), which was a
strike slip event along active inland faults, by the envelope inversio
n of strong-motion acceleration seismograms. The horizontal extent of
the region that radiated high-frequency (2-10 Hz) waves is about 45 km
. which matches the source region estimated from the inversion of stro
ng-motion displacement waveforms. High-frequency waves were mainly rad
iated at the periphery of this source region, while a clear gap of rad
iation was seen in the center. Along the Nojima fault, both high- and
low-frequency wave radiation were large. This is explained by the fact
that the rupture broke the ground surface here. High-frequency waves
were also radiated at the step-over of faults between Awaji Island and
the Kobe area. The step-over is interpreted to have behaved as a geom
etrical barrier and generated high-frequency waves when ruptured. The
radiation of high-frequency waves in the northeastern part from the hy
pocenter to Kobe was small in the large moment release areas estimated
From the displacement waveform inversion, and large at their peripher
ies. This suggests these high-frequency waves were slopping phases fro
m the subevents corresponding to the large moment release areas. The e
xtent of the source region of high-frequency waves roughly matches tha
t of the heavily damaged areas. We inferred that the strong high-frequ
ency waves that came directly from the source was one of the causes of
the heavy damage to low-rise structures.