Interpretation of intensity attenuation relation of 1905 Kangra earthquake with epicentral distance and magnitude in the Northwest Himalayan region |
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Authors: | G K Ghosh A K Mahajan |
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Institution: | (1) Wadia Institute of Himalayan Geology, 33, GMS Road, Dehradun, India;(2) Indian Institute of Technology Roorkee, Rookree, India |
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Abstract: | Seismic intensity information of historical earthquake of NW Himalayas has been utilized for evaluating the attenuation of
the intensity with the epicentral distance. Purposefully, the observed intensity of big historical earthquake may implicitly
incorporate some site effects arising due to the near surface geology or deposited soil. The isoseismal map of the 1905 Kangra
earthquake yields an area of perceptibility defined by the intensity VII (RF Scale), which is mainly elongated in the NNW-SSE
direction. However, the higher isoseismals of intensity VIII and IX are more symmetrical and elongated in the SE direction.
These isoseismals are more compressed in the northeast and northwest direction indicating fast attenuation characteristics,
which may be either due to the presence of any transverse geotectonic feature or change in lithology. In the present study
the regression relation has been derived to incorporate the attenuation of intensity with variable magnitudes at different
epicentral distances. The derived attenuation relation is useful for assessing damage of a potential future earthquake (earthquake
scenario-based planning purposes) for the Kangra region, Northwest Himalaya. The derived relation is mentioned below:
I(R,Ms) = 2.856 + 1.31*Ms - 0.0017 * R - 0.9598*ln(R)I(R,Ms) = 2.856 + 1.31*Ms - 0.0017 * R - 0.9598*\ln (R) |
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