Relationship between the lithosphere effective elastic thickness and earthquake distribution in the northeastern margin of the Tibetan Plateau
The lithosphere effective elastic thickness(Te)represents the comprehensive mechanical strength of the lithosphere,which is of great significance for understanding the seismogenic environment of regional deep structure.The geological structure of the northeast margin of the Tibetan Plateau is complex and strong earthquake activity occurs frequently.We aim to further understand the mechanical properties of the deep lithosphere in the region and its relationship with seismic activity.This article uses the Fan wavelet spectral method to calculate the effective elastic thickness(Te)and load ratio(F)of the lithosphere on the northeastern edge of the Tibetan Plateau through joint inversion of admittance and correlation.WGM2012 gravity anomaly,ETOPO1 topography,and CRUST1.0 model are used.The results show that Te in the whole study area is obviously high in the east and low in the west.Te in the Qinghai-Tibet block changes dramatically.The high value(＞40 km)in the west and the low value(＜20 km)in the east coexist.Te in the Ordos block is relatively high(＞30 km)and changes smoothly.The load ratio F is locally high in the southwest.The load ratio F of the Bayan Har and the Qiangtang blocks are relatively high(＞0.5),indicating that the underground load is the main load.While other blocks are relatively low(＜0.2),indicating that the surface load is the main load.The Ordos block has stable structure,strong lithosphere and high Te value;the internal tectonic activity is weak,the lateral change of deep material density is small,the load on the lithosphere is mainly from surface,so the load ratio F is small.The east of Qaidam block and the east of Bayan Har block may have lower crustal flow,with weak lithosphere and low Te values.The load ratio F in the interior of the Bayan Har block and the Xianshuihe fault is high,and the load on the lithosphere is mainly from underground,which may be caused by the large lateral changes in the deep lithosphere because of the eastward flow of crustal materials.By comparing and analyzing the corresponding relationship between Te and Te gradient,F and F gradient and the earthquake in the study area,it is found that the earthquake generally occurs in the area with relatively low Te,large Te gradient and large F gradient.The earthquakes with small magnitude mostly occur in the area with relatively small F,and the strong earthquakes with magnitude above 6 mostly occur in the area with F about 0.1 and 0.8.Therefore,the area where the lithosphere effective elastic thickness Te is thin,Te gradient and F gradient are large is more prone to earthquakes.
Effective elastic thicknessLoad ratioGravity anomalyEarthquake distribution
万方数据
维普
