Tectonic Stress Redistribution Induced by Geothermal Gradient Difference: Numerical Modeling of Stress Around the Anninghe Seismic Gap in the Southeastern Tibetan Plateau

Rheological behavior in the Earth's deep crust controls the state of tectonic stresses in both shallow and deep layers. Heterogeneity of rheological motion caused by geothermal gradient differences can induce redistribution of tectonic stresses, which is directly related to seismic activity. In this study, the tectonic stresses around the Anninghe fault in southeastern Tibetan Plateau are analyzed using a numerical model that considers the horizontal heterogeneity of rheological properties caused by local geothermal gradient differences. The results show that the depth of the crust reaching a rheology-dominant state is below 12-15 km in warm areas with relatively high geothermal gradient and below 19-22 km in cold areas. Rheological heterogeneity induces the redistribution of internal stress and plays an important role in understanding the distribution of earthquakes and stress in seismogenic zones. The Anninghe fault north of Mianning presents relatively large stresses, while that south of Mianning demonstrates low stresses. The low stresses due to high geothermal gradients can explain the seismic gap and the low fault locking. Furthermore, rheological heterogeneity also influences the in situ rock stress in shallow layers and the gravity anomaly in the deep crust.