RESEARCH ON ACTIVITIES OF THE GUDIAN FAULT IN SONGYUAN,JILIN PROVINCE

The Gudian Fault in the southwest of Songyuan is an important fault in the central depression of the Songliao Basin. It was recognized from the petroleum exploration data. Based on the data, we conducted shallow seismic exploration, drilling exploration, age determination(OSL) and topography measurement. The fault features and its motion characteristics are analyzed with the results of shallow seismic exploration. With stratigraphic correlation and optical stimulated luminescence dating, the latest active age of the fault is determined. The surface relief of the region to the southeast of the drilling site is relatively larger than surrounding places. An 800m long section across the fault was measured by GPSRTK, and the deformation amount across the zone was calculated. Four conclusions are drawn in this paper:(1) The Gudian Fault is arcuate in shape and shows a property of inverse fault with a length of about 66km in the reflection interface T1(bottom of the upper Cretaceous Nenjiang Group). (2) The middle part of the fault rupture is wider than the ends, narrowing or dying out outwards. According to this feature and the rupture of the bottom of the fourth segment of the upper Cretaceous Nenjiang Group, the fault can be divided into three segments, e.g. Daliba Village-Gaizijing-Guyang segment, Guyang-Shenjingzi-Julongshan Village segment and Julongshan Village-Caiyuanzi segment. (3) The yellow silt layer at the base of the upper Pleistocene series ((33.66±3.27) ka BP~50ka BP) is offset by the Gudian Fault, while the upper tawny silt layer is not influenced by the fault. Thus, the fault belongs to late Pleistocene active fault. (4) The amount of geomorphic deformation around Shenjingzi is 9m. The depth of the bottom of the upper Pleistocene series is 11m and the Huangshan Group of the mid Pleistocene series exposes to the southeast of the deformation zone. Therefore, the throw of the bottom of the upper Pleistocene series is about 20m at the sides of the deformation zone. In addition, the Qianguo M6(3/4) earthquake occurred in Songyuan area in 1119 AD. Though some studies have been done, arguments still exist on the seismogenic structure of the Qianguo M6(3/4) earthquake. Combined with others studies, Gudian Fault is considered as the seismogenic structure of the Qianguo M6(3/4) earthquake.