Analysis of seismicity-induced landslides due to the 8 October 2005 earthquake in Kashmir Himalaya

Abstract

Widespread landslides were reported in the devastating earthquake of 7.6 M w that occurred on 8 October 2005 with epicentre located within Hazara syntaxis, Kashmir Himalaya. As this area covers mostly inaccessible mountainous terrain, an attempt was made to detect and map landslides on medium to high resolution satellite data products such as Indian Cartosat-1 (PAN: 2.5 m resolution), Resourcesat-1 (LISS IV: 5.8 m multispectral), Landsat-TM (30 m multispectral) and ASTER (15 m multispectral). The extent of slope failures and landslides was mapped (776 landslides) based on subpixel registration, image interpretation and field investigation. The ground deformation cum damage survey revealed that the hanging wall side of the causative fault was severely affected and caused numerous earthquake-triggered landslides. The terrain parameters such as surface geology, slope gradient, slope aspect, curvature and relief classes were correlated with actual landslide occurrences and critical classes were identified. The statistical analysis of landslides inventory based on probability density function enabled estimation of earthquake magnitude and size of the largest landslide, which correspond well to the actual data. The study demonstrated extrapolation of total landslide affected area (67.36 km 2 ) from the partial inventory of landslides based on satellite image interpretation. Based on the volumetric estimation, average landslide thickness was determined to be around 6.9-7.7 m and total displaced mass available for erosion was also estimated to be around 0.34-0.5 2 km 3 .