The Characteristics of Microtremors at the Site of SMART1 Array

羅東強震儀陣列區微地動的特性

黃文紀(Win-Gee Huang) ； 葉永田(Yeong-Tein Yeh)

《Terrestrial, Atmospheric and Oceanic Sciences》 1卷3期 (1990/09) Pp. 225-242

摘要

1982年7月12，13和15日，我們在羅東强震儀陣列區（簡稱SMART1），利用三個位置不同的小型陣列，從事了數次的微地動測記，以期對該地區的地動雜訊有所了解。本文是利用頻率－波數(Frequency-Wavenumber)的分析方法，研究微地動的來源與特性。分析結果顯示：在頻帶0.6赫至1.84赫之間，微地動的來源可能由東側太平洋海岸浪潮所造成，且微地動的特性是表面波。由微地動的速度頻散曲線我們也大略推測陣列區的地下構造。由地表至深度300公尺左右，大致可分成二個層次，第一層的厚度約為110公尺，其S波的速度約為是380公尺／秒至500公尺／秒。第二層的厚度約為200公尺其S波的速度為700公尺／秒至850公尺／秒。

並列摘要

In this study, three microtremor observations were conducted in theSMART1 area, on July 12,13 and 15,1982.The data, in each observation, were recorded by a small circular array of about 460m in diameter. The array consisted of 9receivers spaces from 100 to 400 meters apart. The origin and characteristics of microtremors were investigated by the technique of high-resolution frequency-wavenumber (f-k) analysis. Our results show that microtremors, in the frequency range of0.72 to 1.84 Hz, may be caused by the effects of the Pacific Ocean tide on the coast to the east of the Lanyang plain. The microtremors are composed of surface waves. Two-layer subsurface velocity structures are also estimated from the resulting dispersion curves. The top layer is about 112m thick with an S-wave velocity of 390-500m s^(-1). The second layer is about 188 m thick with an S-wave velocity of 690-850m s^(-1)