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首页> 外文期刊>Journal of Asian earth sciences >Three-dimensional seismic attenuation structure beneath the Taiwan region and its tectonic implication
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Three-dimensional seismic attenuation structure beneath the Taiwan region and its tectonic implication

机译：台湾地区下方的三维地震衰减结构及其构造意义

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摘要

Three-dimensional (3-D) attenuation structures were determined for Taiwan region by inversion of earthquake intensity data set. The seismic intensity which is assumed to be a measure of the maximum acceleration of the S-wave at the seismic station is used to estimate the attenuation structure. The intensity data set consists of about 5500 intensity readings for 1410 earthquakes reported by the Central Weather Bureau of Taiwan from 1987 to 2010. The 3-D attenuation maps consisting of five layers were constructed to a depth of 74 km. The obtained model reveals the following features: first, a high absorption zone exists in the westernmost Okinawa trough. These high-attenuation anomalies seem to extend from upper crust to mantle beneath the Yilan Plain and Kueishantao Island. We interpret the high absorption zone as the presence of the relatively hot lower crust and uppermost mantle in response to the local opening of the Okinawa trough. Second, strong lateral variation of seismic attenuation is observed from the source region of the Chi-Chi earthquake in the central Taiwan. Most aftershocks were occurred beneath the Western Foothills which is characterized by a transition from high attenuation to low attenuation between the Chelungpu fault and Chuchih fault. However, the region east to the Chuchih fault is relatively quiescent. This study suggests that the high Vp/Vs and lateral variation of attenuation features existing beneath the Western Foothills could be associated with porous materials containing fluid which might affect the generation of the Chi-Chi earthquake.
机译：通过反演地震烈度数据集，确定了台湾地区的三维（3-D）衰减结构。被认为是地震台站S波最大加速度的量度的地震强度被用来估计衰减结构。强度数据集包括1987年至2010年台湾中央气象局报告的1410地震的约5500强度读数。构建了由五层组成的3-D衰减图，深度为74 km。获得的模型具有以下特征：首先，在最西端的冲绳海槽中存在一个高吸收带。这些高衰减异常似乎从上地壳一直延伸到宜兰平原和葵山套岛下方的地幔。我们将高吸收区解释为响应冲绳海槽的局部开放而存在的相对较热的下地壳和最上层的地幔。其次，从台湾中部的集集地震的震源区观察到地震衰减的强烈横向变化。大部分余震发生在西山麓丘陵以下，其特征是切龙普断裂与楚奇断裂之间从高衰减到低衰减的过渡。但是，楚奇断裂带以东的地区相对静止。这项研究表明，西山麓丘陵以下存在的高Vp / Vs和衰减特征的横向变化可能与含有流体的多孔材料有关，这可能会影响Chi-Chi地震的发生。

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