Major Earthquakes by Rheological Diapirism of Crust-Mantle Material-Evidence from Satellite Gravity Data

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Abstract

Satellite gravity field data recovered by digital global models with 2-180 to 2-360 order are mainly originated from the density variation in the depth of 18-36 km, at which epicenters of most major structural earthquakes are located. Therefore, satellite gravity data can make great contribution to earthquake research. The author made a detailed analysis on the satellite gravity data over Wenchuan, Motuo, Zhongba, Jiashi of Western China and Taiwan area, where earthquakes more than magnitude of 6 took place in recent decades. It is surprising that the gravity field patterns over these areas are extremely similar, which is characterized by 1, paired positive and negative anomaly; 2, epicenters usually located between the pairs where gradient of gravity field is the steepest; 3, value of positive peak increases and its width decreases at higher order field; 4, distance between positive and negative peak varies in different tectonic background; 5, different styles of crust-mantle material diapirism in different stress fields. Geologically, rheological diapirism of high-density crust-mantle material provides a reasonable explanation to this unique pattern. The proposed high-density growth index is a measurement of density increase from deep to shallow. The passways of diapirism for high-density crust-mantle plastic material may be formed by the crust faults or giant fault zones and detachment stratum. The heterogeneity of crust-mantle material reflects the complexity of dynamic processes in continental plate tectonics. © 2009 China University of Geosciences (Beijing) and Peking University.

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Qi, F. (2009). Major Earthquakes by Rheological Diapirism of Crust-Mantle Material-Evidence from Satellite Gravity Data. Dixue Qianyuan/ Earth Science Frontiers, 16(3), 282–293. https://doi.org/10.1016/S1872-5791(08)60093-7

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