The 2005 Earthquake of Northern Pakistan (Magnitude 7. 6) occurred on 8 October 2005, slope failures were triggered at more than 2, 000 locations. Using a 90-m-resolution digital elevation model (DEM) , the authors determined that most of the slope failures occurred at the hanging walls of the reverse fault and that many large slope failures occurred near the reverse fault. In this paper, we selected 977 slope failures exceeding 250 m
2 in area (roughly 15 m x 15 m) that occurred within 4 km from a reverse fault, and we calculated the slope failure orientation using 15-m-resolution DEM derived from TERRA/Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data. It was confirmed that at least 30% of those slope failures occurred on slopes facing S or SW. Furthermore, it was confirmed that the slope failure orientation is consistent with the hanging wall-surface displacement (permanent displacement by the seismic faulting) data obtained by Environmental Satellite (ENVISAT) /Synthetic Aperture Radar (SAR) . According to oral accounts from residents recorded by other researchers, most of the surface displacement occurred immediately after the main shock. This suggests that the main factor in the orientation bias of slope failure is the orientation bias of surface displacement.
View full abstract