关中地区地震活动规律及其与构造活动的关系研究

【作者】 杨建军；

【导师】 吴汉宁；

【作者基本信息】 西北大学 ， 地球探测与信息技术， 2006， 博士

【摘要】 本文在对关中地区区域构造及重磁异常特征的分析基础上,根据陕西省地震台网监测资料及西安地区微地震台网监测成果,从地震的空间分布特征、周期性、迁移现象、重复性、强度、频度、b值分析等方面,对区域地震活动特征、关中地区地震活动规律进行了分析研究,关中地区地震活动主要受北东—北东东向、北西向、东西向三组方向的断裂控制,震源深度多为5—25公里,均属浅源地震,历史地震表现为东强西弱,东部的汾渭地震带表现出较强的地震活动性,近代地震活动主要以微震或小震为主,存在着8—10年的活动周期,近期表现出西强东弱的趋势,地震的频度与地震最大震级呈互补关系,未来的几年间,地震频度会有所减少,强度会增大,将有可能发生4级左右的地震,推测在2040年左右,关中地区将进入地震高潮期,届时将可能有5—6级左右的地震发生。 对地震与构造形变、主要断裂带、地壳及上地幔、地裂缝、温泉和地热、电性结构等关系进行了分析研究,通过震源机制解、地震等烈度线、地应力测量、断层位移测量及模拟试验等成果,分析了关中地区的地应力状态,从关中盆地的动力学机制,对该区的地震成因机制进行了探讨,认为与关中盆地长轴平行的NE和NEE向的水平挤压力、与盆地长轴方向垂直的水平张力及地幔上涌力三组力的作用,加之壳内高导层这一有利的介质环境,是导致关中地区地震发生的主要原因。 以古城西安为中心,对地震影响场进行了探讨,对关中地区及邻区地震危险性地段进行了趋势预测,在关中地区划分出7个地震危险性地段,即临潼—长安段,华县—蓝田段,朝邑段,灞河段、韩城段、陇县段、武功段,这些地震危险性地段是近期乃至今后相当长的时期内地震监测的重点区域。对西安地区的区域地壳稳定性进行了评价和分区,采用模糊数学中的模糊聚类分析方法,对西安市区域地壳稳定性进行了模糊评判,根据模糊评判结果,提出西安市城市建设应向西部和西南部发展等建议。更多还原

【Abstract】 Activity character of regional earthquake and earthquake movement law are researched in this paper on the base of analyzing regional structure and gravity-magnetic abnormity characteristics. The analyzing aboved is made from earthquake’s space distributing, periodicity, migration phenomenon, repetition, strength, frequency, b value etc., according to data of earthquake station net in Shaanxi Province and microseisms station net watching results in Xi’an area. 3 group faults which are NEE, NW and EW direction control earthquake activities in Guanzhong area. Epicenter depth mostly is 5-25km and in shallow-focus earthquake. Earthquake in east area of Guanzhong was stronger and weaker in the West in history. Fen-Wei earthquake belt showed more activity. Microseisms and small seisms is main movement in recent earthquake, it has 8-10years’ period of movement and show the trend that they are strong in the West but weaker in the East. And frequency and biggest magnitude of earthquake is supplement each other. In next years earthquake frequency will lessen but strength enhance, about M4. It presumes there is earthquake climax period in Guanzhong area in 2040 and M5-6 earthquake is happened at that time.Analyzing the relation between earthquake and structure distortion, main fault belt, crust, upper mantle, ground fracture, hotspring, geotherm, conductance frame, stress state in Guanzhong area is analyzed with earthquake mechanism, isoseismal line, crustal stress measure, fault displacement measure, and simulating test results. Earthquake formation mechanism is discussed with dynamics mechanism in Guanzhong base. There are 3 forces and a good medium environment, which are main reasons caused earthquake happened in Guanzhong area. The first force is NE and NEE level extrusion one which is parallel with long axis of Guanzhong base. The second one is level strain which is vertical with long axis of the base. The third one is mantle upper emerging. High conductive layer is a good medium environment.There is trend forecast of earthquake fatalness of Guanzhong area and near, taking Xi’an city as the center and discussing earthquake infection. 7 earthquake danger parts are ploted in this area, which is Lintong- Chang’an district, Huaxian-Lantian district, Chaoyi district, Bahe district, Hancheng district, Longxian district, Wugong district. They are key regions for earthquake watching in recent even long period time. Region stability of Xi’an city is evaluated , carved up and judged with fuzzy clustering analyzing of maths. Xi’an city development trend should be in the direction of the West and the Southwest according to analyzing results aboved.更多还原