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Hot asthenospheric upwelling and intense intraplate seismicity in eastern North China Craton: Insights from isostatic gravity anomalies.

Vasanthi A.

GONDWANA RESEARCH

https://doi.org/10.1016/j.gr.2026.01.004 

Gravity data from a Global Gravity Model over the North China Craton (NCC) were analysed using the Finite Element Method developed at CSIR-NGRI to understand the cause of strong intraplate earthquakes in this region. Historic earthquakes such as the 1975 Haicheng (M 7.3) and 1976 Tangshan (M 7.8) exemplify the potential for large future earthquakes within this reworked cratonic domain. The results show a strong positive isostatic residual gravity anomaly over the Eastern Block of the NCC, suggesting widespread subsurface magmatic intrusion related to upwelling of hot asthenospheric mantle. Notably, all major historical earthquakes with magnitude greater than 7 are located within this gravity-high region. In addition, 2.5D gravity modelling indicates significant thinning of the lithosphere beneath this area. In addition, high heat flow (>80 mW/m²) and reduced lithospheric strength suggest active thermal and mechanical weakening below this region, which collectively promote strain accumulation driving frequent large intraplate earthquakes.

Fig: Isostatic residual gravity high over eastern North China Craton, marked by clustered M>7 earthquakes and high heat flow, aligns with Profile AA', indicating asthenospheric upwelling, lithospheric thinning and magma underplating.

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