Active Faults Exploration And Research On Associated Activity Of The Shawan Fault Zone

The Shawan fault zone is important in the Pearl River Delta, because of the long extension and the large area of threaten, restricting the urban development of Guangzhou, Foshan, and other cities nearby. In order to guide the local earthquake disaster work, it is significant to master the law of the Shawan fault zone development, for judging the current activity.This study carried out a series of active fault detection, after the regional geological information have been collected, such as surface survey, trenching, geophysical prospecting, soil radon measurement, drilling, dating analysis. Based on the result of active fault detection, this study finished activity analysis from the active fault landform, fault gas, dating, earthquake etc. According to the analysis results, the Shawan fault zone have been summarized in the process of formation and evolution.The conclusion:(1)The control of the Shawan fault zone on the modern landform of the Pearl River Delta is weak. Meanwhile, the largest magnitude earthquake triggered by the fault zone is not more than 6, at the stage of earthquake level. Under these frame, the activity of the Shawan fault zone is not strong.(2)This phenomenon, which shows compression torsion, tension shear superimposed on the fracture outcrops, indicates that the Shawan fault zone active multi period through the numbers of tectonic events. According to the result of survey, geophysical exploration, drilling, trenching, this paper found that only the branch of the zone, Zini-Lingshan fault(F013) has obviously Quaternary activity in the Shibaluohan hill, Dagang town. Dating proved that F013 is active in this area from the early Late Pleistocene and middle date. But the other branches can not be evaluated for active fault, without the phenomenon, the fault in Quaternary strata, and the evidence by dating.(3)Based on the analysis result of fault gas, this research found that F007, the main fracture of the Shawan fault zone, is more active than the east one, F008, F010. Combined with the situation that F013,at the west of F007, shows the most significant activity in Quaternary of the fault zone in current, it may indicate the activity law of the each branch of the fault zone. This hypothesis needs to be further verified.(4)The Shawan fault zone formed in the Cretaceous(Yanshan movement), enhanced activity in the Paleogene, controlled the basal geomorphology formation of the Pearl River Delta in the Neogene(the second act of Himalayan movement), weakened, enhanced, then weakened in the Quaternary, performed weak fault in the recent.