Study on gravity anomaly changes and crustal structure characteristics in Weihe Basin

Abstract

Based on the Earth Gravitational Model (EGM2008) and the global terrain model (ETOPO1), we calculate and obtain the free air gravity anomaly and Bouguer gravity anomaly in the Weihe Basin. The wavelet multi-scale analysis method is used to decompose the Bouguer gravity anomaly with 1st to 5th order wavelet detail and wavelet approximation. At the same time, based on the logarithmic power spectrum method, the average depth of the field source corresponding to the 1st to 5th order wavelet detail and approximation is calculated. The research results show that: (1) the wavelet approximation of Bouguer gravity anomaly of order 1st to 5th in the Weihe Basin corresponds to a field source depth of 12 to 84 km. From the wavelet approximation images, the basic pattern of different tectonic units in the study area can be clearly seen. (2) The field source depth corresponding to the wavelet detail of the 1st to 5th order Bouguer gravity anomalies in the Weihe Basin is 3 to 49 km. From the wavelet detail images, the characteristics of different tectonic divisions and fault distribution in the study area can be clearly seen. (3) Gravity anomaly gradient zones often correspond to relatively large-scale faults, such as the Longxian-Baoji fault, the northern Qinling fault, the Weihe fault, and the Huashan piedmont fault. In addition, from the wavelet detail images, the main structural units such as the Baoji uplift, the Xi'an sag, the Lishan uplift and the Gushi sag can be identified.