Crustal Structure Across Northern Taiwan Determined by the 2008 TAIGER Land Refraction Experiment Data
| Autor: | Ching-Ching Lin, 林青青 |
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| Rok vydání: | 2010 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 98 Taiwan is located along a segment of the convergent boundary between the Eurasian and the Philippine Sea plates. The collision of two plates has generated the ongoing Taiwan Orogeny. Until very recent, seismic studies have given us more information about the velocity structure beneath Taiwan, and gravity data have also been attempted to invert for at least the spatial variation of the depth of the Mohorovičić discontinuity. However, there have been some strong disagreements between them. High resolution images of the crust and detailed seismic velocity structures are still far from well constructed in this region. The experiment of the land seismic refraction from the project of Taiwan Integrated Geodynamic Research (TAIGER) provided a valuable dataset to determine high resolution image of the crust. We take advantage of the data to construct the two-dimensional velocity model across the northern part of the island from P-wave arrival times. 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. Forward ray-tracing is invoked iteratively to adjust the velocity variation until suitable fitting between observed and synthetic travel times are achieved. Because of using the first P-wave arrivals, the deepest ray path may propagate approximate 10-km deep. We used the actual elevations of stations for all of the travel-time calculations. Results from the forward modeling of Pg phases show that strong lateral variations of P-wave velocity in the uppermost crust. At the depth of 3-km, a wide range of velocities from 4.2 km/sec to 5.4 km/sec was obtained. At the distance 30-40 km of our model, there may be a fault bounded Western Foothills and Hsueshan Range. And we observed another boundary separated Hsueshan Range and Backbone Range at the distance about 80 km of our model. Overall, our model coincides with geological observations. To the east, a large velocity gradient appeared under the Eastern Central Range. The results provided a high resolution image beneath Transect 6 and could be very useful for future seismic and tectonic studies. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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