A Study of Potential Destructive Earthquakes (ML ≥ 6.0) in Taiwan：On Seismogenic and Statistic Aspects
Date Issued
2014
Date
2014
Author(s)
Chen, Chi-Hsuan
Abstract
There are 33 active faults announced by Central Geological Survey, Taiwan (CGS, 2010), and they almost located in the Western Foothill, Western Coastal Plain, and Eastern Rift Valley area. Due to the limitation of advanced surveys and the complexity in mountain area, the evidences of active faults never easy to discovered, however, over 50 % of ML ≥ 6.0 inland earthquakes in the past century occurred in the Central Range area of Taiwan. To better understand the seismogenesis, we attempted to distinct the relationships between surface structure and seismological structure by earthquake geology in this dissertation. Earthquake geology is the study of the causality, source parameters, deformation feature, and recurrence of earthquakes within the crustal scale. In this study, we found the four ML ≥ 6.0 earthquakes from 2010 to June 2013 in Central Range correlated with the uplift of velocity structures. The seismic clusters extend to mid-lower crust represents the crust is undergoing thick-skinned deformation in Central Taiwan. Furthermore, a statistic study was also carried out to calculate the recurrence probability of ML ≥ 6.0 earthquakes. We ultimately summarized the achievements for respective projects, and their important for seismic hazard assessment.
The dissertation mainly consists of three projects. In the first, we re-examined source parameters of the 2012 Wutai earthquake in southern Taiwan, which is essential for earthquake geology study. After the 2010 ML 6.4 Jiasian earthquake caused extensive damage in southern Taiwan, deep, complicated structures were revealed. This earthquake provided us an opportunity to further investigate related tectonic issues and hazard mitigation. Together with recent relative large earthquakes (e.g. 2010 Jiasian and 2010 Taoyuan earthquakes) in southern Taiwan, we also delineated a picture of their tectonic environment. The more deeply relocated Wutai earthquake implied the involvement of the lower crust and that the blind thrust system in this region could go deeper.
In the second project, we studied the velocity structures of Central Taiwan by using the newly developed joint-inversion algorithm and seismological data. Although the previous tomographic results in Taiwan have been compatible with the tectonic interpretation, seldom local scale structures are discussed in advanced. Most tomography were P-wave velocities, or with Vp/Vs ratio jointly, but few for S-wave velocities. Therefore, we attempted to provide a new velocity structure of Vp, Vs, and Vp/Vs. The results show that seismicity is bounded by the pop-up velocity structure. The spatial geometry of Lishan Fault in the crustal scale was first revealed by the retrieved tomography. A high velocity body is exhumed to the west under the eastern Hsuehshan Range and right stop by the Lishan Fault on the east, demonstrating that the orogenic thrust system developed in central Taiwan is controlled by the Lishan Fault.
In the third project, we further expand the long-term forecasting model in Taiwan area. The time intervals between a series of events (the inter-occurrence periods) are stationary with an identical temporal distribution after an elimination of aftershocks. Based on the goodness-of-fit testing between a few models and observation, we suggested the use of the Gamma distribution in modeling this variable, earthquake inter-occurrence periods, for the study region. Accordingly, unified relationship was constructed, and statistical limitations of sparse sampling for devastating earthquakes (such as M ≥ 6.0 or 7.0) could be resolved.
Subjects
霧臺地震
南投地震
梨山斷層
造山運動
基盤上拱
地震統計
地震機率
SDGs
Type
thesis
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