| 研究生: |
楊政穎 Young, Chang-In |
|---|---|
| 論文名稱: |
台灣地震規模≧6前之活動性研究 Seismic activity before M≧6 earthquake in Taiwan |
| 指導教授: |
饒瑞鈞
Rau, Ruey-Juin |
| 學位類別: |
碩士 Master |
| 系所名稱: |
理學院 - 地球科學系 Department of Earth Sciences |
| 論文出版年: | 2016 |
| 畢業學年度: | 104 |
| 語文別: | 中文 |
| 論文頁數: | 180 |
| 中文關鍵詞: | 地震活動性 、逆斷層 、走向滑移斷層 |
| 外文關鍵詞: | seismic activity, reverse fault, strike slip fault |
| 相關次數: | 點閱:74 下載:8 |
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台灣位於聚合型板塊的邊界較容易產生大地震,若能了解大地震之前的現象並藉由此現象來預測大地震對台灣社會有相當大的幫助,Wu and Chiao (1999)發現在集集地震之前幾個月會有地震活動性下降的情況,因此假設主震之前地震活動性可能會有變化。本研究針對全台灣規模大於或等於6的地震做為研究對象,探討主震之前的地震活動性以及造成地震活動性變化的原因並定義出每個主震的發震構造、破裂區域。先用主震規模將理論的破裂區域面積求出,再根據主震之後幾個月的餘震分佈定義出破裂區域的長寬比率和相對位置,再以破裂區域為範圍去觀察主震之前的地震活動性變化,取主震之前四到五年的前震畫出地震數目隨時間的變化圖。本研究分為三種狀況來探討,分別為主震之前地震活動性上升、下降、沒有太大的變化。將每個主震之前地震活動性的變化為何定義完後,再去定義每個主震之前地震活動性變化的上升期和下降期以及地震數目上升或下降的百分比,接著畫出每個主震的所在位置,發現全台灣的大地震主要分佈在三個區域分別為西部褶皺逆衝帶、琉球島弧隱沒帶、東部碰撞帶,因此本研究將深入探討這三個區域內的斷層種類以及內部小斷層的相對位置。逆斷層在應變累積到接近主震發生時斷層上盤錯動的速率會下降,應變累積速率會下降,所以主震之前的地震活動性會下降,走向滑移斷層在應變累積到接近主震發生時,應變會累積在和主要斷層平行的小斷層,應變累積速率會上升,所以主震之前的地震活動性會上升。分析完48個主震之前四到五年地震活動性變化之後,得到的結果為逆斷層引發的主震中,主震之前地震活動性下降佔73.33%,所以逆斷層引發的主震之前地震活動性多為下降,走向滑移斷層引發的主震中,主震之前地震活動性上升佔56.25%,所以走向滑移斷層引發的主震之前地震活動性多為上升,和之前的假設吻合。
關鍵字:地震活動性、逆斷層、走向滑移斷層
Taiwan is located at the convergent plate boundary, so there are many large magnitude earthquakes in Taiwan. If we can know the precursor phenomena before large earthquake, it will be helpful for Taiwan society. This study uses 48 earthquakes (M≧6) from 1991 to 2014 to analyze the seismicity before the main shock in Taiwan. The proportion of seismic activity increased before main shock in the Ryukyu island arc subduction zone is larger than the fold and thrust belt in western Taiwan. Besides, the proportion of seismic activity decreased before main shock in the fold and thrust belt in western Taiwan is larger than Ryukyu island arc subduction zone. The seismicity of reverse fault decreases before the main shock. The seismicity of strike-slip fault increases before the main shock.
Key word: seismic activity, reverse fault, strike-slip fault.
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