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| Titel |
Crustal Structure Across Northern Taiwan Determined by the 2008 TAIGER Land Refraction Experiment Data |
| VerfasserIn |
Ching-Ching Lin, Bor-Shouh Huang, Ling-Yun Chiao |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250036582
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| Zusammenfassung |
| Taiwan is located along a segment of the convergent boundary between the Eurasian and
Philippine Sea plates. East of the island, the Philippine Sea plate has subducted northward
beneath the Eurasian Plate. The collision of two plates has generated the ongoing Taiwan
Orogen. Currently, seismic studies have given us some indications of the velocity structure
beneath Taiwan and the gravity data also have provided depth models of the MohoroviÄić
discontinuity. However, high-resolution images of the crust and upper mantle adjacent to the
boundary and detailed seismic velocity analyses are still insufficient in this region. The
experiment of the 2008 wide-angle seismic refraction from the project of Taiwan Integrated
Geodynamic Research (TAIGER) provided a valuable dataset to determine high
resolution image of the crust. We attempt to construct a two-dimensional model for
seismic velocity across the northern part of the island from P-wave arrival times of
TAIGER data. We selected data from the Transect 6 line. It is an onshore seismic
survey spanned approximate 100-km in northern Taiwan with receiver spacing in
200 meters and consists of five explosions with the dynamite from 750 to 3000
kilograms.
In this study, we employed the ray-tracing method for forward modeling which is
developed by Zelt and Smith in 1992. This popular and readily method is able to determine
depth and velocity simultaneously. By adjusting iteratively until the minimum of
root-mean-square misfits between observed and simulated travel times is achieved. In
addition, the normalized chi-squared, Ï2, is taken into account as well. In general, an
appropriate value of Ï2 is considered that the data have been fit suitably. Eventually, we can
thus obtain the optimal velocity model. During the modeling that we referred as
layer stripping, we first picked the initial arrivals to constrain the uppermost crustal
structure. We then traced ray paths from different layers respectively. In this way, we
could build up the whole velocity structure step by step. The preliminary results for
shallow structures indicate that this method yield results consistent with geological
structures and provide details for velocity with depths. Velocities at the uppermost crust
indicate strong lateral variations of P-wave velocities, ranging from 2.3 km/sec
to 4.4 km/sec and increase from 2.8 km/sec to 4.8 km/sec at the bottom of this
layer. The largest velocity gradient in this layer is under the Central Range. We
will continue our study for the deep layers to establish a detailed velocity models. |
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