The Characteristics of Microtremors at the Site of SMART1 Array


In this study, three microtremor observations were conducted in the SMART! area, on July 12, 13 and 15, 1982. The data, in each observa­ tion, were recorded by a small circular array of about 460 m in diam­ eter. The array consisted of 9 receivers spaces om 100 to 400 meters apart. The origin and characteristics of micratremors were investigated by the technique of high-resolution frequency-wavenumber (f-k) anal­ ysis. Our results show that microtremors, in the frequency range of 0.72 to 1.84 Hz, may be caused by the e ects of the Paci c Ocean tide on the coast to the east of the Lanyang plain. The microtremors are composed of sur ce waves. Two-layer subsur ce velocity structures are also estimated from the resulting dispersion curves. The top layer is about 112 m thick with an S-wave velocity of 390-500 m s-1. The second layer is about 188 m thick with an S-wave velocity of 690-850 m s-1.

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