Research On Concealed Faults Activity Of Quaternary In Nanshan District Shenzhen City

Active fault under the city is the direct cause of the urban earthquake and geological disaster.Due to the influence of the north east Wuhua-Shenzhen fault zone and the north west Pearl River Mouth Fault zone,the regional exist few active faults.Therefore,it is of great significance to ascertain fault spatial distribution and activity of the quaternary to provide scientific basis for urban construction and disaster prevention.Based on the distribution of known faults,the characteristics of regional geology and concealed fault detection in the city,the surrounding ground geological investigations,geophysical and drilling exploration,chronology analysis work are applied,specific as follows:?1?The outcrops in Nanshan peninsula exposed surface rupture activity traces and reflect the fault rock is a intense thermal metamorphic belt.Broken pieces,such as wide fracture rock outcrop zone thickness up to 15m thick silicide,cataclastic rock,without the appearance of new fracture.There is no evidence of fault perturbation and the upper quaternary sediments in both north and south.?2?According to the seismic and high-density electrical detection results of the secondary fault of Pearl River Mouth Fault zone F₄ and F₅,both faults have significant characteristics in the Shenzhen bay and Qianhai.The existence of F₄ fault is confirmed by the borehole profile,and the age dataing result show that it is a Holocene active fault.?3?The fault system spatially controls the Pearl River Mouth sag,which regionally cuts through northeast oriented fault and presents strong discontinuity.The NW fault was lately activated during the upper and middle Pleistocene,most of which were old fault with new movements.Recent movements appeared with obvious intervals.Movements apparently weakened during the Holocene and most secondary faults were hardly active or inactive.