Earthquake-induced potential landslides are commonly estimated using landslide susceptibility maps. Nevertheless, the fault location is not identified and the ground motion caused by it is unavailable in the map. Thus...Earthquake-induced potential landslides are commonly estimated using landslide susceptibility maps. Nevertheless, the fault location is not identified and the ground motion caused by it is unavailable in the map. Thus, potential coseismic landslides for a specific fault motion-induced earthquake could not be predicted using the map. It is meaningful to incorporate the fault location and ground motion characteristics into the landslide predication model. A new method for a specific fault motion-induced coseismic landslide prediction model using GIS （Geographic Information System） is proposed herein. Location of mountain ridges, slope gradients over 45~, PVGA （Peak Vertical Ground Accelerations） exceeded o.15 g, and PHGA （Peak Horizontal Ground Accelerations） exceeded o.25 g of slope units were representing locations that initiated landslides during the 1999 Chi-Chi earthquake in Taiwan. These coseismic landslide characteristics were used to identify areas where landslides occurred during Meishan fault motion-induced strong ground motions in Chiayi County in Taiwan. The strong ground motion （over 8 Gal in the database, 1 Gal = 0.0l m/s2, and 1 g = 981 GaD characteristics were evaluated by the fault length, site distance to the fault, and topography, and their attenuation relations are presented in GIS. The results of the analysis show that coseismic landslide areas could be identified promptly using GIS. The earthquake intensity and focus depthhave visible effects on ground motion. The shallower the focus depth, the larger the magnitude increase of the landslides. The GIS-based landslide predication method is valuable combining the geomorphic characteristics and ground motion attenuation relationships for a potential region landslide hazard assessment and in disaster mitigation planning.展开更多
Rupture directivity effect causes spatial variation in strong ground motion parameters. It causes difference between the strike- normal （V.） and strike-parallel （Vp） components of horizontal ground motion amplitud...Rupture directivity effect causes spatial variation in strong ground motion parameters. It causes difference between the strike- normal （V.） and strike-parallel （Vp） components of horizontal ground motion amplitudes. These variations become significant for strong ground motion velocity and the authors have developed a modification to define directivity effect factor to account for the effect of rupture directivity in empirical velocity attenuation relations which are based on modeling Silakhor earthquake, using finite element method by ANSYS. The ground motion parameters that are modified include ratio of Vn/Vp component of horizontal velocity and Vn component to average horizontal velocity （V）. The ratio of Vn to Vp is large in both the forward directivity direction, where velocity is larger, and in the backward directivity direction, where velocity is smaller. Therefore the authors expected that the Vn/Vp was mainly controlled by directivity angle. Also the variation of fault normal velocity to average horizontal velocity ratio by directivity angle （0） is defined from earthquake modeling. It shows Vn/V is controlled by directivity angle, distance between the site, epicenter and rupture length. This ratio has the same trend in Silakhor earthquake strong ground velocity data. In this paper the equation for Vn/Vp variations by directivity angle is recommended. The authors used Somervill et al. （1997） directivity model parameters as （R/L） cos2 ~ to define directivity effect on Vn/V ratio and therefore directivity factor is determined to account in near field empirical strong ground velocity attenuation relationships.展开更多
基金supported in part by the Taiwan Science & Technology Center for Disaster Reduction of Chinese Taipei
文摘Earthquake-induced potential landslides are commonly estimated using landslide susceptibility maps. Nevertheless, the fault location is not identified and the ground motion caused by it is unavailable in the map. Thus, potential coseismic landslides for a specific fault motion-induced earthquake could not be predicted using the map. It is meaningful to incorporate the fault location and ground motion characteristics into the landslide predication model. A new method for a specific fault motion-induced coseismic landslide prediction model using GIS （Geographic Information System） is proposed herein. Location of mountain ridges, slope gradients over 45~, PVGA （Peak Vertical Ground Accelerations） exceeded o.15 g, and PHGA （Peak Horizontal Ground Accelerations） exceeded o.25 g of slope units were representing locations that initiated landslides during the 1999 Chi-Chi earthquake in Taiwan. These coseismic landslide characteristics were used to identify areas where landslides occurred during Meishan fault motion-induced strong ground motions in Chiayi County in Taiwan. The strong ground motion （over 8 Gal in the database, 1 Gal = 0.0l m/s2, and 1 g = 981 GaD characteristics were evaluated by the fault length, site distance to the fault, and topography, and their attenuation relations are presented in GIS. The results of the analysis show that coseismic landslide areas could be identified promptly using GIS. The earthquake intensity and focus depthhave visible effects on ground motion. The shallower the focus depth, the larger the magnitude increase of the landslides. The GIS-based landslide predication method is valuable combining the geomorphic characteristics and ground motion attenuation relationships for a potential region landslide hazard assessment and in disaster mitigation planning.
文摘Rupture directivity effect causes spatial variation in strong ground motion parameters. It causes difference between the strike- normal （V.） and strike-parallel （Vp） components of horizontal ground motion amplitudes. These variations become significant for strong ground motion velocity and the authors have developed a modification to define directivity effect factor to account for the effect of rupture directivity in empirical velocity attenuation relations which are based on modeling Silakhor earthquake, using finite element method by ANSYS. The ground motion parameters that are modified include ratio of Vn/Vp component of horizontal velocity and Vn component to average horizontal velocity （V）. The ratio of Vn to Vp is large in both the forward directivity direction, where velocity is larger, and in the backward directivity direction, where velocity is smaller. Therefore the authors expected that the Vn/Vp was mainly controlled by directivity angle. Also the variation of fault normal velocity to average horizontal velocity ratio by directivity angle （0） is defined from earthquake modeling. It shows Vn/V is controlled by directivity angle, distance between the site, epicenter and rupture length. This ratio has the same trend in Silakhor earthquake strong ground velocity data. In this paper the equation for Vn/Vp variations by directivity angle is recommended. The authors used Somervill et al. （1997） directivity model parameters as （R/L） cos2 ~ to define directivity effect on Vn/V ratio and therefore directivity factor is determined to account in near field empirical strong ground velocity attenuation relationships.
