Dectecting And 3D Geological Modeling Of Active Fault In Nansha District,Guangzhou

The basement tectonics of Nansha District,Guangzhou City,is mainly a fault block tectonic system formed by the northwest-oriented Baini-Shawan Fault and the north-east-oriented NanshaDongguan Fault,which intersect each other and control the formation and evolution of the Pearl River Delta Basin together with other surrounding fault zones(groups).These fault zones(groups)are still active and have brought many earthquakes to the Pearl River Delta region in the past.The Quaternary loose sedimentary layer,bedrock weathering crust,and hidden bedrock constitute the subsurface shallow geological environment in Nansha area,and the active fractures in this layer are very likely to affect the construction of underground space and generate a lot of engineering geological and environmental problems.The use of three-dimensional(3D)geological modeling means can visually reflect the geological structure and help to understand and analyze the spatial characteristics of active faults.In this study,two major active fault zones(groups)in Nansha District were studied,and the basic characteristics of the faults of the main branch faults in the study area were identified on the basis of extensive data collection.The 3D spatial characteristics and activity characteristics of active faults in the study area were detected and analyzed by means of field geological survey,physical prospecting,drilling and 3D geological modeling.And based on the investigation and analysis results,tectonic stability zoning of the study area was carried out and engineering construction suggestions were made.The main results and understanding obtained are as follows:1.A geological database was established by collecting a large amount of geological data,especially the shallow drilling data.Different gridding interpolation methods were selected for different formats of data.In Voxler 3D visualization platform,the 3D model construction of borehole,stratum and section was realized.2.The north-west oriented Baini-Shawan Fault Zone in the area is highly active.The earliest formation of this fault was in the Cretaceous period,and the latest evidence of activity is that the fault cut through the Late Pleistocene triangular layer,indicating that its activity occurred between8 ka-10 ka ago.The surface outcrops of the Nansha-Dongguan Fault Group in the north-east direction indicate that the mechanical properties of the fault are tensional in the early stage and compressional-torsional in the later stage.There are some differences in the time,period,mode and size of each branch of the rupture activity.North-East fault is misplaced The north-west trending rupture,therefore,it is inferred that the rupture was formed at least before the Early Cretaceous,and the activity of the rupture weakened significantly in the Late Pleistocene,but did not stop,and the latest activity may have occurred between 6 ka-10 ka ago.3.The cross-cutting relationships between the faults and between the faults and strata reflected by the 3D geological model are used to classify the fault activity in Nansha area and to zone the regional tectonic stability.The general characteristics of the tectonic stability of Nansha area were obtained,and suggestions on the suitability of engineering construction and facility protection were made for each partition.