Creep or Seismicity in the Salt Range of Pakistan?
S.P. Satyabala(1), Masato Furuya(2) and Roger Bilham(3)
(1) National Geophysical Research Institute, Uppal Road, HYDERABAD - 500 007, India
(2) The University of Tokyo, Tokyo, Japan., Tokyo, Japan., Japan
(3) University of Colorardo at Boulder, Colorado, COLORADO, United States
Several geological/geophysical studies suggest southward movement of the Potwar plateau relative to and on to the Indian Shield at a rate of ~1 cm/yr. As the plateau appears to act as a rigid block, this motion must be taken up on faults bordering the Potwar plateau, the Kalabagh re-entrant and the Kohat plateau e.g. the western edge of the Potwar Plateau is bounded by strike-slip zones across which we expect to find a long-term slip rate of the same order. A rate of motion of 1-cm/year implies that creep steadily dissipates potential energy from the Himalayan collision. Zero implies a locked detachment with the possibility of future damaging seismicity. We analyzed nearly 100 ERS-1/2 and several ENVISAT SAR images covering the Kalabagh Fault on the western end of the Salt Ranges to form interferograms spanning different time intervals. The interferograms show little or no movement across the fault indicating that surface creep is absent across the fault. The fault dips to the east so that in the absence of surface creep, slip at depth is expected. This should manifest as a shear signal over a distance of 10-30 km to the east of the fault. Further work is being carried out to look for a possible shear signal east of the Kalabagh fault. The interferograms have also captured coseismic deformation due to a moderate earthquake consistent with slip on the decollement.
Keywords: ESA European
Space Agency - Agence spatiale europeenne,
observation de la terre, earth observation,
satellite remote sensing,
teledetection, geophysique, altimetrie, radar,
chimique atmospherique, geophysics, altimetry, radar,