Co-seismic surface ruptures produced by the 2005 Pakistan M_w7.6 earthquake in the Muzaffarabad area, revealed by QuickBird imagery data

摘要

High-resolution QuickBird imagery data have been used to analyse and detect the co-seismic surface ruptures produced by the 2005 Pakistan M_w7.6 earthquake in the Muzaffarabad area. The analytical results and interpretations of the QuickBird images reveal that the co-seismic surface ruptures are mostly concentrated on the pre-existing active faults striking northwest-southeast. Most of co-seismic surface ruptures show a deformation feature of compressional cracks having a right-stepping echelon geometric pattern. Individual cracks vary from metre order to 1-km in length, generally 10 to 100 m. In the northern Muzaffarabad city, an east-west striking co-seismic surface zone of ～ 1 km length occurred in the jog area between two northwest-southeast striking surface rupture zones. A strong damage zone along which all buildings completely collapsed is concentrated in a deformation zone of ～60m wide on the uplift side of the east-west striking surface rupture zone. Large-scale landslides caused by strong ground motion are mostly constricted on the uplift side along the co-seismic surface rupture zones. The deformation features and spatial distribution patterns of the co-seismic surface ruptures and the ground motion direction indicate that the co-seismic fault that triggered the 2005 Pakistan M_w 7.6 earthquake is a thrust fault with a right-lateral slip component.