碩士 / 國立臺灣大學 / 海洋研究所 / 100 / Historical record of significant disastrous earthquakes (Mw>8) has mostly been regarded as megathrust earthquakes that slipped along the interface of underthrusting plate and overriding plate. This kind of thrust is thought to be the seismogenic zone of the great earthquakes. Stresses between two plates can be easily accumulated in this zone, and sea floor may rupture during the co-seismic slip of the megathrust, generating great tsunami. Previous studies have reported that a major out-of-sequence thrust is present in the accretionary wedge south of Taiwan, thus megathrust earthquakes could be generated in the Manila subduction zone south of Taiwan. This research analyzes 4 large-offset seismic profile data collected during the TAIGER survey in 2009 for the purpose of investigating the deep structures of the Manila subduction zone. Advanced processing techniques have been employed to eliminate the multiple energy on the seismic profile that improves the quality of the deep crust images.
Manila subduction system is located between the Philippine Sea Plate and the Eurasian Plate. This subduction system can be divided into four major tectonic features from west to east: Manila Trench, accretionary wedge, North Luzon Trough and Luzon volcanic arc. The accretionary wedge can be further divided into a lower slope domain and an upper slope domain by a major out-of-sequence thrust. Duplex structure produced by underplating processes may exist below the upper slope domain, as inferred by the roof thrust reflection. Decollement has clearly been observed below the lower slope domain of the accretionary wedge. The range of the decollement increases from south to north, inferring that the continental materials were carrying into the subduction zone and the subduction angle is decreasing from south to north.
This study has identified two or three thrusts branching out from the megathrust and not connected to the decollement. These thrusts may extend to the sea floor, and they are so-called megasplay faults. There is no obvious change on the branching point and megasplay fault position from subduction to incipient collision. The existence of the gigantic thrust represents this area have high potential of seismic and tsunami threat.
| Identifer | oai:union.ndltd.org:TW/100NTU05279021 |
| Date | January 2012 |
| Creators | Che-Ping Chuang, 莊哲平 |
| Contributors | Char-shine Liu, 劉家瑄 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 84 |
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