Variation of Q value before and after the 1999 Xiuyan, Liaoning Province, M =5.4 earthquake on the basis of analysis on attenuation dispersion of P waves |
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Authors: | Liu Xi-qiang Sun Qing-wen Li Hong Shi Yu-yan Ji Ai-dong and Wang Feng-ji |
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Institution: | (1) Earthquake Administration of Shandong Province, 250014 Ji’nan, China |
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Abstract: | A method for determining medium quality factor is developed on the basis of analyzing the attenuation dispersion of the arrived
first period P wave. In order to enhance signal to noise ratio, improve the resolution in measurement and reduce systematic
error we applied the data resampling technique. The group velocity delay of P wave was derived by using an improved multi-filtering
method. Based on a linear viscoelastic relaxation model we deduced the medium quality factor Q
m, and associated error with 95% confidence level. Applying the method to the seismic record of the Xiuyan M=5.4 earthquake sequences we obtained the following result: (1) High Q
m started to appear from Nov. 9, 1999. The events giving the deduced high Q
m value clustered in a region with their epicenter distances being between 32 and 46 km to the Yingkou station. This Q
m
versus distance observation obviously deviates from the normal trend of Q
m linearly increasing with distance. (2) The average Q
m before the 29 Dec. 1999 M=5.4 earthquake is 460, while the average Q
m between the M=5.4 event and the 12 Jan. 2000 M=5.1 earthquake is 391, and the average Q
m after the M=5.1 event is 204.
Foundation item: State Key Project of Science and Technology during the Tenth Five-year Plan (2004BA601B01-03-01). |
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Keywords: | P wave data resampling multi-filtering anelasticity of medium inversion of meidium quality factor Q m variation before and after earthquake |
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