莫拉克风灾引发之山崩与区域地质构造之关系：以高屏溪上游为例  

Typhoon Morakot Triggered Landslides and Their Regional Geological Structures: Case from Kaoping River

作　　者：黃志杰(Chih-Chieh Huang) 張中白(Chung-Pai Chang) 張文和(Slawomir Jack Giletycz) 

出　　处：《災害防救科技與管理》

摘　　要：莫拉克台风於2009年8月8日侵台，短时间的强大降雨在全岛造成许多重大灾害，其中位於献肚山下的小林村在台风登台的第三天遭大规模的山崩完全掩埋，灾後我们在高屏溪上游的旗山溪与荖浓溪流域的崩塌区及周围山区进行了详细的地质调查，藉以探讨地质构造在台风诱发山崩中所扮演的角色。研究结果显示，小林村後山之地层层面与节理暨小断层共同构成一组向下坡倾斜之不利岩楔，此类岩楔在崩前已呈虚悬状态，在促崩事件之影响下，引发难以抑止之快速滑动。除了小林村地区，高屏溪流域其他地区的所有地质证据也都支持：地质构造是山崩发生的重要潜在因子。地层层面、断层及地形等基本条件，应广泛调查作为预测山崩发生可能性的重要参考依据。此外，根据断层擦痕测量资料计算，研究区域整体受到的主压应力大致为西北－东南向，这个方向的压应力也暗示此地区应普遍存在一组东西走向及西北－东南走向的共轭破裂，沿着破裂方向如有地形或地层条件配合，则极易产生山崩，此点是未来防灾或地质评估中值得特别注意的条件。Typhoon Morakot invading Taiwan on August 8th, 2009 caused numerous major disasters throughout the island. Hsiaolin village located at the foothills of Shiendu Shan on the third day typhoon existence was entirely buried by massive landslide. A detail field investigation focused on structural measurement, around whole the Hsiaolin landslide as well as its surrounding area and the drainage area of the Kaoping River, has been carried out in this study. In order to realize the landslide mechanism of regional settings, we focused on the affect of geological structures and stress analysis around the study area. Wedge failure had been observed at numerous outcrops, which produced by bedding and fault systems' inter-cutting at the dip-slope area of the mountains. Therefore, in some areas landslide could have happen even with relative stable condition. After a detailed investigation from Hsiaolin and all other landslides of the Kaoping drainage basin, we came to a conclusion that structure geological setting played a major role as a direct factor for creating the regional landslide. By considering the geometric correlation between geological structure, strata attitude and topography, an objective hazard map can be provided. Besides, based on the slickenside data measured from the fault planes of fresh outcrops, a NW-SE compressional tectonic regime can be reconstructed. Associated with this compression, a conjugated fault system, which is composed of an E-W striking right-lateral fault and a NW-SE striking left-lateral fault, is also expectable in all this area. This fault system caused the slope failure and easy to lead big landslide. The results derived from the structural analysis can also be applied for improving advanced estimations of other related studies.

关 键 词：莫拉克颱風 小林村 山崩 地質構造