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Pure and Applied Geophysics

, Volume 164, Issue 10, pp 1963–1983 | Cite as

Source Parameters of the Deadly Mw 7.6 Kashmir Earthquake of 8 October, 2005

  • Prantik Mandal
  • R. K. Chadha
  • N. Kumar
  • I. P. Raju
  • C. Satyamurty
Article

Abstract

During the last six years, National Geophysical Research Institute, Hyderabad has established a semi-permanent seismological network of 5–8 broadband seismographs and 10–20 accelerographs in the Kachchh seismic zone, Gujarat with a prime objective to monitor the continued aftershock activity of the 2001 Mw 7.7 Bhuj mainshock. The reliable and accurate broadband data for the 8 October Mw 7.6 2005 Kashmir earthquake and its aftershocks from this network as well as Hyderabad Geoscope station enabled us to estimate the group velocity dispersion characteristics and one-dimensional regional shear velocity structure of the Peninsular India. Firstly, we measure Rayleigh-and Love-wave group velocity dispersion curves in the period range of 8 to 35 sec and invert these curves to estimate the crustal and upper mantle structure below the western part of Peninsular India. Our best model suggests a two-layered crust: The upper crust is 13.8 km thick with a shear velocity (Vs) of 3.2 km/s; the corresponding values for the lower crust are 24.9 km and 3.7 km/sec. The shear velocity for the upper mantle is found to be 4.65 km/sec. Based on this structure, we perform a moment tensor (MT) inversion of the bandpass (0.05–0.02 Hz) filtered seismograms of the Kashmir earthquake. The best fit is obtained for a source located at a depth of 30 km, with a seismic moment, Mo, of 1.6 × 1027 dyne-cm, and a focal mechanism with strike 19.5°, dip 42°, and rake 167°. The long-period magnitude (MA ~ Mw) of this earthquake is estimated to be 7.31. An analysis of well-developed sPn and sSn regional crustal phases from the bandpassed (0.02–0.25 Hz) seismograms of this earthquake at four stations in Kachchh suggests a focal depth of 30.8 km.

Keywords

Source parameters interplate seismicity centroid moment tensor solutions regional phases long-period magnitude 

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Copyright information

© Birkhäuser Verlag, Basel, 2007

Authors and Affiliations

  • Prantik Mandal
    • 1
  • R. K. Chadha
    • 1
  • N. Kumar
    • 1
  • I. P. Raju
    • 1
  • C. Satyamurty
    • 1
  1. 1.National Geophysical Research InstituteHyderabadIndia

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