HR: 0830h
AN: S31F-0828 [PDF]
TI: Evidence of a Subducting Slab Beneath Taiwan From a Joint Observation of Seismic Waveforms and Travel
Times
AU: * Chen, P
EM: bob@earth.sinica.edu.tw
AF: Institute of Earth Sciences,
Academia Sinica, 128 Academia Road,
Sec 2, Nankang, Taipei, 115
Taiwan
AU: Huang, B
EM: hwbs@earth.sinica.edu.tw
AF: Institute of Earth Sciences,
Academia Sinica, 128 Academia Road,
Sec 2, Nankang, Taipei, 115
Taiwan
AU: Liang, W
EM: wtl@earth.sinica.edu.tw
AF: Institute of Earth Sciences,
Academia Sinica, 128 Academia Road,
Sec 2, Nankang, Taipei, 115
Taiwan
AB:
We propose that the effects
of a near-receiver slab is straightforward to observe
with a seismic array.
While this proposal is globally applicable,
the application on data of
the "Broadband Array in Taiwan for Seismology
(BATS)" is significant for local studies.
The Tonga-Kermadec earthquakes
exhibit consistently
negative travel time anomalies and
reduced P wave amplitudes
for stations in central Taiwan,
suggesting the presence of
an aseismic subducted slab.
This suggestion is enhanced by
the correlations of amplitude ratios
with earthquake latitudes,
which can be seen for station as north as 24.3\deg (TDCB).
The more reduction in amplitudes for earthquakes
with more negative latitudes
is consistent with the southward propagation
of the "arc-continent collision".
In an attempt to seek for the "equivalent planar slab",
we model the joint observations of
travel time anomalies and amplitude
reductions for stations SSLB and TPUB, using 2-D pseudospectrum method.
The probable range of slab extent to produce
the observations (without corrections for station effects)
of both stations is 400 km long, 4% velocity anomalies
to 500 km long, 3% velocity anomalies.
DE: 7200 SEISMOLOGY
DE: 7203 Body wave propagation
DE: 8100 TECTONOPHYSICS
DE: 8123 Dynamics, seismotectonics
SC: Seismology [S]
MN: 2003 Fall Meeting