英文篇名
Are We Ready by Learning from the Nature ? -From Geotechnical Engineering Perspective to Wenchuan Earthquake Related Issues
作者
林銘郎、董家鈞、胡植慶、劉桓吉、陳江准、孫思優、劉說安、李錫堤
關鍵字
汶川地震、龍門山斷裂帶、集集地震、車籠埔斷層、堰塞湖
摘要
四川省汶川地震的特色是規模大(MS8.0),地震斷層地表破裂跡長(推估長300公里)、主震持續時間久(推估達2分鐘)、震源淺(10-20公里)、破壞力強(死亡人數至2008/05/25止已超過六萬人)。引發這次地震的造震斷層是龍門山斷裂帶中的北川-映秀斷層。由於龍門山與成都盆地的關係,類似車籠埔斷層與台中盆地的關係;兩者都是位於板塊邊界活動構造變形前緣。映秀—北川斷層位置可能相當於台灣中部的水里坑-陳有蘭斷層,故推測尚未列入活動斷層的水里坑-陳有蘭斷層也有再活動之可能;而陳有蘭溪河谷兩岸地震衍生的二次災害現象與經驗正可能是岷江河谷兩岸及其他災區未來災害發展的境況模擬,皆值得進一步調查與探索。四川碧口土壩受震產生的下陷率略高於鯉頄潭大壩(集集地震),但皆與Seed-Lee-Idriss法的估算大致相符。根據福衛二號影像配合SRTM地形資料計算唐家山堰塞湖水位上升速率,與中國水利部估計相似。雖然地震發生的時間尚無法預測,但從汶川地震與集集地震的經驗得知,新期活動斷層的位置與規模是可以大致推測獲得,如果活動斷層位於人口密集的都會或山區附近,人們要如何因應?不幸地震災害發生,要如何緊急避難、減少災害損失?地震災後要如何選擇相對安全的場所進行復建等都是迫切而急須解決的課題。
英文摘要
The Wenchuan Earthquake of Ms 8.0 taken place in Sichuan, China is characterized by its extensive surface fault rupture, long duration time, shallow depth of hypocenter and more than 60000 casualties. Being one of these faults located within Longmen Shan thrust belt, the Beichuan fault gave rise to the Wenchuan Earthquake. Both Wenchuan Earthquake in China and Chichi Earthquake in Taiwan occurred in the leading deformation front of two active collisional plate boundaries. Similarities of the geological and geomorphological background between the Wenchuan Earthquake and the Chichi Earthquake promote the discussion of the geotechnical related issues by comparing these two cases in this article. Location of Beichuan fault in Longmen Shan thrust belt could be regarded as the Shuilikeng-Chenyulan Fault in central Taiwan, where might have the potential of reactivation. In the near future, the hazardous scenarios such as massive landslides, debris flows experienced in the Chenyulan stream area in Taiwan could also happen in Sichuan, China where had been heavily struck by Wenchuan Earthquake. The settlement ratio of Bi-kou Dam in China is similan to Li-yu-tan Dam in Taiwan, both are matching the calculation results by the Seed-Lee-Idriss method. The arising speed of water table in Tang-jia-shan dam-up lake estimated from CSRSR remote sensing images and SRTM data resemble that provided by the Ministry of Water Conservancy, China. Even though the earthquake prediction is still a challenge, based on the experience by analyzing Wenchuan Earthquake and Chichi Earthquake and their consequence on the humanity, the features of active faults and related seismic hazards can be properly evaluated. Once the active faults are found located near the urban area, it is important and urgent to establish appropriate emergency response and evacuation plans, as well as the mitigation design after disasters, in order to validly prevent damage and reduce loss.