BEMD of Gravity and Magnetic Anomalies and Its Application in the Gangdise Belt's Crustal Structure

Crustal structure is one of the main targets of deep geophysical exploration in the Qinghai-Tibet Plateau. In this paper, the bi-dimensional empirical mode decomposition (BEMD) separation method combined with power spectrum analysis is studied, and it is applied to the separation of gravity and magnetic anomalies in the Gangdise belt. The model test results show that the method can separate the superimposed anomalies and obtain a reliable estimation of the source depth. The decomposition results in the study area show that the bouguer and the RTP magnetic anomalies can be divided into three anomalies which are induced by three equivalent layer sources from shallow to deep. The deep gravity and magnetic fields are characterized by the north-south partition and the east-west block. It is proved that the Qinghai-Tibet Plateau is formed by splicing the terrains along the north-south direction and after its formation, it is continuously pushed northward by the Indian plate unevenly, which makes the material properties of the Himalayan terrain and the Gangdise terrain have significant differences in deep from east to west bounded by 88°E and 93°-95°E. It is inferred that the low density body is discontinuous in east-west direction and the low density body in the middle and east of the study area is cut by the Yarlung Zangbo suture zone.