重庆地区历史地震等震线长轴方位分布综合分析

Comprehensive Analysis of the Distribution of Isoseismal Curve Major Axis Directions of Historical Earthquakes in Chongqing Area

摘要:

统计了重庆地区历史地震等震线长轴方位分布，主要为NE向。通过对地震活动、活动断裂分布、震源机制解的统计特征分析，指出历史地震等震线长轴方位与活动断裂的走向、震源机制解的一个节面走向基本保持一致，三者之间可相互印证。在地震应急工作中可快速建立等震线模型，从而确定灾区面积。

Abstract:

In this study，the isoseismal curve major axis directions of historical earthquakes were counted in the Chongqing area，and the dominant direction was identified.The seismic activity in this area can be roughly divided into two NE strips the route that include one along the Huayingshan fault zone and the other along the Qiyaoshan-Jinfushan fault zone.The Chongqing area is a moderate earthquake region.The historical earthquake space distribution indicates that earthquake occurred in the belt boundary fault of two or three structural units in and NE of the axis of the anticline.The NE fracture structure is dominant in Chongqing area，and the seismogenic structure of most Chongqing earthquakes is a NE-trending fault zone.Rongchang is an earthquake-prone zone in the Chongqing area，which includes seismogenic tectonic earthquakes in the Huayingshan fault zone.On the basis of focal mechanism analysis of Chongqing and adjacent areas，the potential of the seismogenic structure was examined，to provide a basis for evaluating the earthquake isoseismal curve major axis direction. Through the collection of focal mechanism solutions of moderate-strong earthquakes in this area，determination of a composite mechanism solution of small earthquakes，calculation of the focal mechanism of small and moderate earthquakes in Rongchang area，and analysis of the focal mechanism solution features，it is concluded that the tensile principal stress axes and the principal compressive stress axis are nearly horizontal in the area of the modern tectonic stress field，the principal compressive stress is.NW-SE，and the tensile principal stress is NNE-SSW.The predominant distribution of the historical earthquake isoseismal curve major axis direction is NE trending.Through the analysis of the seismic activity and active faults，it was determined that the direction of major axis orientation and active fault lines nearby show better consistency.This result indicates that despite the uncertainty in historical isoseismals for detailed records，the statistical results of long-range distribution for Chongqing，which is a moderate earthquake area，can be used to determine the local seismogenic structure and for seismic rupture location research.A section of the strike of the focal mechanism solution was consistent with the macroseismic intensity survey data obtained by the isoseismal map of long axis direction.After the earthquake，the location of the earthquake epicenter can be evaluated，and the direction of the long axis of the isoseismal can be obtained through the magnitude to develop an isoseismal model for rapid determination of the scope of the disaster.The isoseismal curve major axis direction of historical earthquakes，active faults, and the nodal plane of the focal mechanism solution in the Chongqing area are essentially consistent and can be confirmed by cross correlation.