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

Abstract

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 ∼60 m 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.

Acknowledgements

We thank Dr Q. A. Hassan of the University of Tokyo and Mr S. Takatsu of CTI (Construction Technology Institute) for kindly providing the field photographs. We are very grateful to the University of Maryland Global Land Cover Facility for releasing Landsat ETM+ images (http://www.glcf.umiacs.umd.edu/index.shtml), National Aeronautics and Space Administration (NASA) Shuttle Radar Topography Mission Project for SRTM data (http://www2.jpl.nasa.gov/srtm/), the International Seismological Centre for earthquake data (http://www.isc.ac.uk/index.html), and C. B. Ramsey for OxCal version 3.10 program (http://www.rlaha.ox.ac.uk/O/oxcal.php). This work was supported by the Nuclear and Industrial Safety Agency, Japan and the Science Project (Project No. 18340158 for A. Lin) of the Ministry of Education, Culture, Sports, Science and Technology of Japan.