Abstract:

Based on 1∶50,000 size gravity and magnetic data of Shiwu faulted depression in Songliao Basin，twenty-one major faults in Shiwu faulted depression were determined by methods of frequency domain transformation in gravity and magnetic field，discrete 2D wavelet transformation，correlation filtration and anomalies stripping. The faults in basement of Shiwu faulted depression were determined，and could be divided into the following four groups, Shangshutai big fault zone(F1)，Bawu fracture zone(F2)，Jinshan fault zone(F3) and Dayushu fault zone(F4). Shangshutai fault in western border of Shiwu faulted depression and a series of faults in NE direction inside the depression consist of  the structure of basement faults in Shiwu depression.On the whole，Shangshutai fault develops as a segment of a circle in planar configuration，and its direction is NE in its north，SN in the middle，and SW in the south. Three fault groups of F2，F3 and F4 are determined as normal fault in NE direction in Shiwu faulted depression，moreover，the trend of these normal faults are coincide with the northern segment of fault F1，hence，these four fault groups would become into being in a same tectonic stress field, and the four main faults compose of the basement of Shiwu faulted depression. The results provide a significant evidence for prospecting hydrocarbon of the basement.

Key words: fault, gravity and magnetic anomaly, anomalies stripping, structure frame of the crystalline basement, Shiwu faulted depression, Songliao basin