Clayey injection veins and pseudotachylyte from two boreholes penetrating the Chelungpu Fault, Taiwan: Their implications for the contrastive seismic slip behaviors during the 1999 Chi‐Chi earthquake
Clayey injection veins and pseudotachylyte from two boreholes penetrating the Chelungpu Fault, Taiwan: Their implications for the contrastive seismic slip behaviors during the 1999 Chi‐Chi earthquake
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DOI：
10.1111/j.1440-1738.2004.00455.x
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发表时间：
2005-03
期刊：
影响因子：
1.5
通讯作者：
K. Otsuki;Takayuki Uduki;Nobuaki Monzawa;Hidemi Tanaka
中科院分区：
文献类型：
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作者：
K. Otsuki;Takayuki Uduki;Nobuaki Monzawa;Hidemi Tanaka
摘要1999年台湾集集大地震中发生的地震滑动在车笼埔断层沿着的不同区域表现出不同的行为：北部发生了一个大而平滑的滑动，而南部发生了一个相对较小的与高频地震波辐射有关的滑动。对穿越车笼埔地震断层的北方（丰源）和南方（南头）浅孔岩芯样品进行了分析。北方场地的断层带以与粘土质注入脉有关的软粘土质物质为特征。这表明，在古地震滑动事件中，断裂带受到加压，因此发生了有效的弹性流体动力润滑。相反，南部的断层岩是古老的假玄武玻璃岩，被重复的古代地震滑动事件震碎。许多假玄武玻璃碎片的统计分析表明，摩擦熔融的程度往往是低的。在这种情况下，地震滑动受到高粘度熔融层的机械屏障的限制。这些对比断层岩是由重复的古代地震滑动事件产生的，但在1999年集集地震期间可能也发生了两种相应的摩擦机制，从而导致了南北的对比滑动行为。
Abstract The seismic slip that occurred during the 1999 Chi‐Chi earthquake in Taiwan showed contrastive behaviors in different regions along the Chelungpu Fault: A large and smooth slip occurred in the north, while a relatively small slip associated with high‐frequency seismic wave radiation occurred in the south. The core samples from shallow boreholes at northern (Fengyuan) and southern (Nantou) sites penetrating the seismic Chelungpu Fault were analyzed. The fault zones at the northern site are characterized by soft clayey material associated with clayey injection veins. This suggests that the fault zones were pressurized during ancient seismic slip events, and hence the elastohydrodynamic lubrication occurred effectively. In contrast, the fault rock from the southern site is old pseudotachylyte that has been shattered by repeated ancient seismic slip events. Statistical analysis of many pseudotachylyte fragments reveals that the degree of frictional melting tended to be low. In this case, the seismic slip is restrained by the mechanical barrier of a highly viscous melt layer. These contrastive fault rocks were produced by repeated ancient seismic slip events, but the two corresponding mechanisms of friction are likely to have also occurred during the 1999 Chi‐Chi earthquake, thus causing the contrastive slip behaviors in the north and south.