嘉南地區孕震活動特性研究

Study on Property of Seismogenic Activity for Chianan Area

黃靖媛(JING-YUAN HUANG)

指導教授 ： 溫怡瑛

國立中正大學/理學院/地球與環境科學系地震研究所/碩士(2016年)

摘要

前人研究成果指出，嘉南地區之斷層系統在30年內有很高的破裂機率，這對於人口密集且集中的西半部區域產生極大的威脅。因此，本研究彙整中央氣象局的地震監測網(CWBSN)、國家地震工程研究中心(NCREE)與本系於2014年開始之雲嘉南地區地體動力整合研究而架設寬頻地震網(簡稱ITCH)於2008年11月至2015年6月的地震到時資料進行重新定位，期望能提高測站的包覆性得到更精確的定位結果與速度構造，並分析其對於應力反演之結果及其擬合度還有摩擦係數之間的關係為何，進一步了解嘉南地區的地震活動特性與其在地體構造上的意義。

本研究之結果包括：(i) 嘉南地區之震源機制解破裂方向與區域斷層型態及大地應力方向並不完全吻合，推測此區大多偏向走向滑移機制的特性與古正斷層系統造成之既有破裂面有關。(ii) 梅山斷層西南側之地震群集(陳厝寮斷層南側)由應力方向與破裂方向分析之擬合度得出較梅山斷層東側低之摩擦係數，推論與梅山斷層中段近期之低地震活動量，以及梅山斷層之特殊地表破裂形態有關。(iii) 嘉南地區孕震特性為：多分佈於深度範圍5~15公里處，且整個研究區域大地應力方向與摩擦係數的變化顯示嘉南地區的構造異質性，因而造就複雜的構造系統與地震活動特性。期望這些彙整的地震資料與分析結果能提供未來嘉南地區地震潛勢評估的有用參考。

關鍵字

應力分析 ； 地震活動 ； 嘉南地區

並列摘要

Previous study has suggested Chianan area as the region with higher probability to generate large earthquake in next 30 years. In this study, we collect the P and S arrival data (2008/11~2015/06) determined by the Central Weather Bureau (CWB) and two local seismic networks, which were operated by National Center for Research on Earthquake Engineering (NCREE) and Integration of geodynamic research in Chiayi area (ITCH) projected by National Chung Cheng University, respectively. Through applying the 3D relocation analysis and stress inversion, we attempt to further understand the properties of seismic activity and the implication of the tectonic structures in this area.

Our results show that: (i) The faulting mechanisms do not exactly correspond with the regional tectonic stress and active faults in this area. The primary strike-slip faulting mechanism might be related to the preexisting normal fault. (ii) The lowest friction coefficient was obtained in the southwest region to the Meishan fault with a value of 0.3. This might respond to the complicated fracture system of the Meishan fault. (iii) The seismic activities in Chianan area most range between 5 to 15 km depth, and the various friction coefficients (0.3~0.5) indicate the complex fault structure and heterogeneity in this region. We hope this integrated seismic data and study result can provide some helpful information for potential seismic-hazard assessment in Chinan area.

並列關鍵字

Seismic activity ； Chianan area ； Stress inversion

參考文獻

翁志傑、鄭凱謙、王維豪 (2011)，用GPS連續站監測九芎坑斷層活動特性與地區性訊號分析，中華民國地籍測量學會會刊30卷4期，1-16頁。

Byerlee, J. (1978), Friction of Rocks, Pure and Applied Geophysics, 116, 615-626.

Cai, H. T., H. Kuo-Chen, X. Jin; C. Y. Wang, B. S. Huang and H. Y. Yen (2015), A three-dimensional Vp, Vs, and Vp/Vs crustal structure in Fujian, Southeast China, from active and passive-source experiments, Journal of Asian Earth Sciences, 111, 517-527.

Chen, C. H., W. H. Wang and T. L. Teng (2001), 3-D Velocity structure around the source area of the Chi-Chi earthquake, 1999 Taiwan: before and after mainshock, Bull. Seism. Soc. Am., 91, 1010-1027.

Chang, S. H. and W. H. Wang (2006), Mechanical properties, slip and nucleation of the 1999 Chia-Yi earthquake: The question of static stress influence from the 1999 Chi-Chi earthquake, Terr. Atmos. Ocean. Sci., 17, 331-343.