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EARTHQUAKE ›› 2011, Vol. 31 ›› Issue (4): 98-107.

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Estimating the Boundary of Density Anomaly Source and Hazard Zone based on Gravity Variation before Earthquakes

CHEN Shi1, XU Wei-min1, ZHU Yi-qing2, JIANG Chang-sheng1, LU Hong-yan1, GUO Feng-yi1   

  1. 1. Institute of Geophysics, CEA, Beijing 100081, China;
    2. The Second Crust Mointoring and Application Center, CEA, Xi'an 710054, China
  • Received:2011-06-14 Revised:2011-07-08 Online:2011-10-31 Published:2021-09-09

Abstract: Repeated mobile gravity observation in China mainland has been one of the main technical means for monitoring earthquake precursors. Researches on mobile observation of gravity field before large earthquakes indicated that continuous variation of regional gravity field (increase or decrease) significantly related with large earthquake occurrences. In this paper, we carried out computation and transformation of theoretical gravity anomalies based on a 3-D tilt model. We found an effective method to determine the boundaries of density anomaly source. Moreover, analysis on the characteristics of the anomalies is based on a spatial correlation coefficient method. We further obtain a probability method to estimate the hazard zone. At last, we process and analyze mobile observations of gravity in eastern margin of Tibet Plateau from 1998 to 2005 by the preceding method. It is found that the location of anomaly gradient zone and the boundary of hypocentroid can be confirmed effectively. Combined with background gravity field and other information, we can obtain a probability estimate of earthquake hazard zone, which will be necessary to determine the risk region in annual earthquake consultation.

Key words: Density anomaly source, Seismic hazard zone, Gravity variation, Spatial correlation coefficient, Eastern margin of Tibet

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