利用GPS觀測資料及塊體模型分析台灣中部及北部地區地殼變形

Analysis of Crustal Deformation in Central and Northern Taiwan Using Block Modeling with GPS Observations

李其芳(Chi-Fang Lee)

指導教授 ： 張午龍

國立中央大學/地球科學學院/地球科學系/碩士(2015年)

摘要

台灣地區因處歐亞板塊與菲律賓海板塊碰撞邊界，因此構造活動劇烈，地震活動度也相當高。GPS觀測紀錄顯示，水平地表運動由西部麓山帶至西部平原速度降低約30 mm/yr，代表此區正經歷很快的壓縮應變。本研究利用三維塊體模型及GPS紀錄到的地表速度場評估台灣中部及北部地區17條斷層的震間滑移情形及地震潛勢。使用的GPS資料包含2006-2013間由262個連續站及498個移動式測站的位移測量值。研究區域內劃分成23個塊體，並利用地調所公布之17條活動斷層當成塊體邊界。本研究結果顯示區域內長期滑移速率及滑移虧損率較高( >10 mm/yr)的斷層大都為南北走向的西部麓山帶斷層，包含車籠埔、大尖山及觸口斷層，此外梅山斷層亦有較大的滑移速率及滑移虧損率。另外本研究利用二維斷層模型同時逆推大甲─彰化、車籠埔、及大茅埔─雙冬斷層的震間滑移。結果顯示較高的滑移速率(約20 mm/yr)落在大茅埔─雙冬斷層上，且滑脫面上的滑移速率約33 mm/yr。本研究的三維塊體與二維斷層模型一致顯示西部麓山帶的斷層滑移速率大於變形前緣，且測地矩率較高之斷層也同樣落在西部麓山帶斷層上。推論在台灣中部地區西部麓山帶斷層面上的能量累積速率較快，未來短時間內發生地震的潛勢也較高。

關鍵字

全球衛星定位系統 ； 塊體模型 ； 地震潛勢

並列摘要

Taiwan locates in a high seismic activity belt of the southeastern Asia. In central Taiwan, many large earthquakes occurred in historic time, such as the 1906 Meishan (ML= 7.1), the 1935 Hsinchu-Taichung (ML=7.1), and the 1999 Chi-Chi (Mw= 7.6) earthquakes. GPS horizontal velocities, in addition, also show a shortening rate of about 30 mm/yr across the Central Range to the Deformation Front in the central Taiwan. In this study, we employed a method of block modeling to study the interseismic behavior, evaluate slip deficits and earthquake potential of all activity faults which published by CGS in this area. We use the 2006-2013 GPS observations from 262 continuous and 498 campaign stations and set our model with 23 blocks and 17 boundary faults for the study area. In this study, we set two models. One of model only considered block rotation and fault coupling effect, and another added internal strain in our model. We first calculated the geodetic long-term slip rates, which reflect relative motion between blocks, and the slip deficit rates, which reflect interseismic fault coupling, of the boundary faults. Our elastic model results revealed large rates of slip deficit (>10 mm/yr) occur on the N-S trended Chelungpu─Tachienshan─Chukou faults of the Western Foothill rather than the Tachia─Changhua fault of the Deformation Front. In addition, we also used Monte Carlo method to set a 2-D model fault model cross Tachia─Changhua, Chelungpu and Tamaopu─Shuangtung fault. The result shows that higher slip rate of 20 mm/yr on Tamaopu─Shuangtung fault, and smaller on Tachia─Changhua fault. As a result, we think this kind N-S trended faults have relatively high earthquake potential due to the fast absorption of contracted strain energy across the Western Foothill of Taiwan. For 100 years recurrent interval, the magnitude of larger than Mw 6 earthquake might occur on the most of fault in the study area, and the top five of magnitude are consistent of N-S trended faults on western Foothills belt.

並列關鍵字

GPS ； Block model ； Earthquake potential

參考文獻

丁權 (2012). 新竹地區活動斷層特性研究，碩士論文，國立台灣大學地質科學系，共182頁。

石再添、鄧國雄、張瑞津、石慶得和楊貴三 (1986) 台灣活斷層的地形學研究。

中央地質調查所 (2010) 台灣活動斷層分布圖。

吳明賢、王明惠、周學良、李元偉、翁榮南、胡錦城和王乾盈 (2011) 台灣西南海域義竹斷層是否為古第三紀台南盆地的邊界斷層？，石油季刊，第47卷 第一期，第1-19頁。

邱紀瑜 (2011) 利用GPS觀測資料探討台北地區之地殼變形，碩士論文，國立中央大學地球物理研究所，共126頁。