HR: 0800h
AN: S41A-0228    [Abstracts]
TI: Mapping Large Structures Using the Shallow Reflection Seismics
AU: * Wang, C
EM: wangcy@cc.ncu.edu.tw
AF: Institute of Geophysics, National Central University, No.300, Jhongda Rd., Jhongli City, 32001, Taiwan
AB: The shallow reflection seismics is designed to map shallow structures, say, above a depth of 1000m. The method has the merits of efficiency, high-resolution, and most important, cost-effective. It is a small system, as comparing with the oil-exploration seismics, however, which is affordable by a regular institute and can be used to study relatively large structures to a certain extent. This report describes a case to detect an active fault in Central Taiwan. This fault is unclear in the surface geology. Eight profiles across the major fault are used to map this 20 km long fault. Two concepts from the shallow reflection seismics are applied: 1) Several short lines, each 400m long and 1km apart, are aligned to compose a profile with several km long. 2) High resolution factors are kept, such as small geophone intervals (2m or 4m), high-frequency and high-power sources. A large channel number (e.g., 192) is needed to extend the receiver spray range, which helps to cover larger depths. This results in "1 sec" records which can trace detailed shallow structures as well as the parts as deep as 2000m. The "1 sec" reflection seismics is demonstrated to be a powerful tool to extend the surface geologic observation to substantial depths. The method is cheap and efficient, thus, can be applied extensively as a useful tool to aid the regional geologic mapping.
DE: 0935 Seismic methods (3025, 7294)
DE: 0994 Instruments and techniques
DE: 3260 Inverse theory
DE: 7260 Theory
DE: 7294 Seismic instruments and networks (0935, 3025)
SC: Seismology [S]
MN: 2007 Fall Meeting