2016 Mw 6.4 美濃地震地動參數及受損建築物的關係研究

Abstract

2016年2月6日臺灣高雄市美濃區發生震矩規模 (Moment magnitude, Mw) 6.4地震，造成117人死亡與超過600件以上受損建築物，是臺灣在1999年集集地震 (Mw =7.6) 後災情最嚴重的地震事件。因此本研究希望透過美濃地震PGA、PGV與受損建築物資料建立迴歸關係式，分析兩者關聯性，在下一次面對災害性地震時，提供災防相關單位評估可能造成的損失。 1999年集集地震地動參數與受損建築物間的迴歸關係式已經被前人建立。由於2010年起，臺灣採用新的地震後建築災損評估，從以往的全倒(Totally collapsed)與半倒(Partially collapsed)改為紅單(red-tagged)與黃單(yellow-tagged)，故有重新探討其關聯性之必要。「紅單」意義為建築物的主要結構受損或傾斜達一定程度而發生危險，必須修建或可能拆除；「黃單」則代表建築物的次要結構或鄰近建築物傾斜達一定程度而發生危險，其不需拆除只要經過補強後，確定安全無虞即可取消列管。由於臺灣已經佈放高密度的地震站，於2016年美濃地震發生時提供充足且良好的地震紀錄，加上臺南市政府在地震後統計詳盡的災損資料，這是一個很好的機會來重建適用於新法規的迴歸式。 本研究使用資料採用交通部中央氣象局自由場強地動觀測網(Taiwan Strong Motion Instrumentation Program, TSMIP)的強地動紀錄，分為最大地動加速度(Peak Ground Acceleration, PGA)與積分後所獲得的最大地動速度(Peak Ground Velocity, PGV)。建築災損資料則使用臺南市政府資料開放平台各行政區紅單及黃單的調查結果。 根據2016年美濃地震的分析結果，本研究得到與前人文獻不同的觀察。研究結果顯示，PGA對應紅單率與黃單率的相關性比PGV高。經過調查後發現，受損建築物的總樓層數大約70%為三層樓以下。因此PGA與災損率的高相關性可能主要與本次地震事件的受損建築物為低矮樓房有關。

The relationships between ground motion parameters (including peak ground acceleration, PGA；peak ground velocity, PGV) and building damages are crucial to estimate the possible seismic losses for future destructive earthquakes. One of such relationships had been established based on the case of the 1999 Chi-Chi earthquake (Mw=7.6). Since 2010, a new assessment system of seismic damaged buildings had been adopted in Taiwan. Damaged buildings are now classified into two categories, yellow-tagged buildings (secondary structural damage) are amendable and red-tagged buildings (major structural damage) may need to rebuild. Our main goal is to renew the relationship to better reflect the current status in Taiwan, both in the buildings and assessment system. The 2016 Meinong earthquake (Mw=6.4) caused the most damaging buildings in Taiwan since the 1999 Chi-Chi earthquake. Excellent seismic data was recorded from the Taiwan Strong Motion Instrumentation Program (TSMIP) and detailed damage statistics were sorted by Tainan city government. It’s an opportunity to combine ground motion data with building assessments for the new regression relationship. From the results, we find out that in the Meinong earthquake, the PGA seems to possess a higher correlation to the building damages, contrary to the previous studies. Further investigation suggests that it may be due to the biased sample size to the damaged buildings, that is, most of the damaged buildings tend to be lower.