Magnetic Surveying of the Chaochou Fault

• Main Authors: Sheng-Wen Chen, 陳聖文
• Other Authors: Charles Lewis
• Format: Others
• Language: en_US
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/89496944914203758548

碩士 === 國立成功大學 === 資源工程學系碩博士班 === 93 === 　The Chaochou fault, the western-most basement-involved thrust faultexpressed at the surface in southern Taiwan, overrides paleo deep-seated normal faults and therefore becomes a high-angle thrust fault near the surface with certain splay faults due to the partitioning of energy. The horizontal component of this energy generates a left-lateral strike slip movement near the surface, and deep-seated extensional faulting provides a ramp. A décollement could be approximately 7 km deep with a throw of 6 km on the west-vergent upthrust Chaochou fault. West of this western-most Chaochou thrust fault,there appears to be a sequence of normal faults in pre-Miocene basement. 　This interpretation results from surveying of the Earth’s total intensity magnetic field combined with gravity, seismic, well log and geologic data in order to better delineate an outline of the basement setting of this N-S trending fault. Magnetic surveying involved seven E-W profiles traversing the fault from north to south, and the magnetic results indicate the Chaochou fault is a west-vergent upthrust fault with a magnetic signature throw of 40 nT. Bouguer gravity data shows a pronounced minimum with a throw of 50 mgal that is indicative of the Chaochou fault as well. Satellite images and topographic maps clearly show the N-S 80 km linear surface trace of the Chaochou fault that divides the older metamorphic rocks of the Central Range on the east from younger sediments of Coastal Plains on the west. 　This major active fault was chosen for this magnetic study, not only because of these significant characteristics mentioned above, but also due to the Chaochou fault being located in a complex tectonic setting of the transfer collision zone between the continental Eurasia and the oceanic Philippine plates. 　Magnetic surveying tied to other geophysical data has been demonstrated to be an appropriate way to better characterize an active basement-involved fault at relatively in expensive cost.