Influence of geological factors on the kinematics of the neighboring Jiufengershan and Hungtsaiping landslides trigged by Chi-Chi earthquake

• Main Authors: Wang-Ru Lee, 李旺儒
• Other Authors: Jia-Jyun Dong
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/77qpd3

碩士 === 國立中央大學 === 應用地質研究所 === 94 === The Chi-Chi Earthquake (Mw=7.6) of September 21, 1999 triggered many landslides in central Taiwan. Two of these landslides, Hungtsaiping and Jiufengershan were gigantic landslides. The distance between these two landslides is 2km. The kinematic of these two landslides is significant different. Jiufengershan landslide was a catastrophic rockslide-avalanche and the Hungtsaiping landslide was relatively slow-moving. This research explores the geological factors accounts for the differences. Factors such as the characteristics of strong-motion, geology and geomorphology were considered in the study. Based on the site investigation, the mechanism of Hungtsaiping landslide is studied. The sliding area is 88.6ha. Three slid masses(slid mass A, slid mass B, slid mass C) are identified. Thick colluvium sliding along bedding plane of shale are also identified. An analysis of 12 strong-motion records collected in the concern area showed that the distribution of horizontal pseudostatic coefficients and earthquake energy ratio were anisotropic. The principal direction of strong-motion is mostly in the E/W~ESE/WNW trending. The maximum permanent displacements computed using the strong-motion records and a modified sliding-block method were also direction-dependent and oriented in the trend of E/W~ESE/WNW. This direction is perpendicular to the trend of the main geological structures of the studied area. The back calculated friction angle that corresponds to a critical land mass displacement for the Jiufengershan landslide is about 2.6º larger than that of Hungtsaiping landslide. The material on the sliding surface in Jiufengershan should be more velocity-dependent than that of the Hungtsaiping landslide according to the back calculations. The difference of the friction angles of the sliding surface of two study landslides. The difference of the friction angles of the sliding surface of two study landslides is oriented from the different slid materials. The importance of direction-dependent strong-motion, slope aspect, and mechanical properties of sliding surface on the kinematics of two nearby deep-seated landslides is demonstrated.