探討隱沒板塊孕震構造對臺灣北部地區強地動之影響

The Assessment of Strong-Ground Motion Impact to The North Taiwan Forinter- and Intra-Plate Earthquakes

顏銀桐(Yin-Tung Yen) ； 楊世緯(Shih-Wei Yang) ； 鄭錦桐(Chin-Tung Cheng)

《災害防救科技與管理學刊》 3卷1期 (2014/03) Pp. 25-40

https://doi.org/10.6149/JDM.2014.0301.02

摘要

隱沒板塊孕震構造可分為板塊內部與板塊介面兩類型，本研究利用經驗格林函數法，探討兩者影響場址強地動的差異，發現板塊內部地震所造成之強地動值高於板塊介面地震，緣於板塊內部地震的強地動產生區域面積（斷層破裂面積）較小，其應力降約為70至120bar；而板塊介面地震的面積大，對應之應力降約為35至40bar。再者，透過數值模擬所獲得之最大地表加速度強地動值，與實際觀測值以及透過強地動衰減式所推估者進行比較，發現應力降較小的板塊介面地震，其實際觀測值與數值模擬成果均落在強地動衰減式推估之平均值範圍內，而應力降較大的板塊內部地震，部分實際觀測值與數值模擬成果則高於強地動衰減式推估之平均值之上，顯示強地動衰減式對於應力降較大地震的PGA值有低估之現象。本研究之分析結果顯示地震防災評估時，應予以強調與重視板塊內部地震之強地動表現。

關鍵字

板塊內部地震 ； 板塊介面地震 ； 經驗格林函數法 ； 衰減式

並列摘要

In this study, we estimated the strongmotion generation area (SMGA) and stress drop for inter- and intra-plateearthquakes using empirical Green's function method to depict their characteristics. Observed peak ground accelerations (PGA) for subduction zoneearthquakes show significant diversity in PGA between intra-plateearthquakes and inter-plate earthquakes. Analyzed results show that the intra-plateearthquakes have smaller SMGA and larger stress drop than inter-plateearthquakes. The stress drop derived from intra-plate earthquakes and inter-plateearthquakes is 70 to 120 bar and 35 to 40 bar, respectively. The PGA of synthetic seismogram forboth inter-plate earthquakes and intra-plate earthquakes are similar to the observation ones. Comparing to the PGA estimated from ground motion prediction equation (GMPE), the standarddeviations of observation and the PGA of synthetic seismogram for inter-plate earthquakes are inone sigma, but the ones for intra-plate earthquake are larger than one sigma, suggesting that the GMPE has an underestimation to large stressdrop of intra-plate earthquakes, which should be paid more attentionin seismic hazard assessment and earthquake hazard mitigation.

並列關鍵字

Inter-plate earthquake ； Intra-plate earthquake ； Subduction zone ； Empirical green's function ； Ground motion prediction equation (GMPE)

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