Informatics Publishing Limited

R. K. Singh ¹, Rajesh Prakash ¹, A. K. Shukla ¹, A. K. Bhatnagar ¹, H. N. Srivastava ²

Affiliations
1 India Meteorological Department, New Delhi - 110 003, IN
2 128, Pocket-A, Sarita Vihar, New Delhi - 110 044, IN

Abstract

Seismicity pattern has been examined prior to the occurrence of the six earthquakes (M ≥ 54) during the period 1965 to 2005. This includes the damaging earthquake of Gilgit 1972 Pattan 1974 and Muzaffarabad earthquake 2005. The results were interpreted with reference to (i) pattern of occurrence of past earthquakes (ii) energy released event wise and cumulative energy released year wise. It was interesting to note that all these earthquakes were preceded by quiescence followed by increase in seismicity before the occurrence of main earthquake. An alternative interpretation of the data prior to the occurrence of the great Muzaffarabad earthquake (October 2005) suggested a sequence of double quiescence as reported in Uttarkashi (1991) and Chamoli (1999) earthquakes in Uttaranchal. The focal mechanism solution of an earthquake during February 2004 and October 2005 revealed significant changes in the orientation of P and T axis. It was interesting to find that the value of 'b' in Gutenberg-Richter frequency magnitude relationship decreased markedly during 1985-1994 and almost recovered prior to the occurrence of Great Muzaffarabad earthquake m accordance with the Dilantancy Diffusion model of earthquakes.

Keywords

Seismicity Pattern, Muzaffarabad Earthquake, B-value.

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