Regional Crustal Stability Evaluation In Wuhan City

Due to the continuous development and expansion of "Great Wuhan" city circle,Wuhan regional crustal stability has become one of the essential factors restricting its urbanization process.This paper takes the crust of Wuhan city as the research object,selects six influencing factors,such as Bouguer gravity anomaly gradient,active faults,seismic activity,ground motion peak acceleration,geological disasters,and surface engineering geological characteristics to establish an evaluation model.Using the combination of fuzzy mathematics theory and tomographic analysis method to quantify each index and assign weights,Wuhan City is divided into 8,916 calculation units.The regional crustal stability of Wuhan City is comprehensively evaluated by fuzzy mathematics and Wuhan City is classified as stable.Further,four levels of sub-stable,sub-unstable,and unstable,and a quantitative partition map are obtained.On the basis of data collection,this article systematically studies the main active faults and their activities in Wuhan,and analyzes their influence on the stability of the crust.Using Wuhan's historical earthquakes and modern earthquakes,the collected data of strong and small earthquakes are analyzed and preprocessed.The seismic activity parameter b is calculated,and its spatial distribution map is created,which is used for the regional crustal stability map and to compare and determine its reliability.The evaluation results of the regional crustal stability in Wuhan show that Wuhan is mainly stable and sub-stable(accounting for 71.19%),and the unstable area only accounts for 3.44%.Specifically,it is divided into 13 stability zones,3 unstable zones,5 sub-unstable zones,4 sub-stable zones,and 1 stable zone.The zoning results are consistent with the b-value spatial distribution map,ground motion zoning map,the results of earlier studies with high credibility.The regional crustal instability area is mainly controlled by the Xiangguang fault,the Yangtze River fault and the Tuanma fault.Geological disasters and Burg Gravity anomalies also have a significant impact on it.Wuhan is mainly controlled by the Xiangguang Fault and Tuanma Fault with two hidden fault zones,with weak activity,low earthquake magnitude,medium frequency,and good overall stability.The level of modern earthquakes is relatively low.Modern earthquakes are mainly concentrated in Xinzhou and Jiangxia districts.The low b-value areas are mainly concentrated in the northeast of the study area.The frequency of earthquakes is relatively higher than that of other areas in the study area,and energy is often released in the form of microseisms.The b-value in the central part is relatively high,and no strong earthquakes have occurred in history,indicating that the crustal stress accumulation level in the urban area of Wuhan is relatively low.In response to the evaluation results of the regional crustal stability in Wuhan,more detailed engineering geological stability investigations should be conducted.More studies should be carried out in unstable areas when municipal planning and major project site selection need to be decided.The evaluation results can provide a basis for the construction of the Yangtze River New Town planning area.