福州市活断层探测与地震危险性评价

Active Faults Exploration and Seismic Hazard Assessment in Fuzhou City

大量震例研究表明 ,活动断层产生的直下型地震对城市的破坏非常严重 ,应用先进有效的地质与地球物理探测技术 ,准确地探明城市之下及附近活动断层分布 ,确定直下型地震的震源和危害性是我国城市减灾工作面临的一个非常急迫的实际问题。《福州市活断层探测与地震危险性评价》项目作为中国地震局全国城市活动断层探测的试点与示范项目于 2 0 0 1年初开始实施 ,2 0 0 4年 8月通过中国地震局的验收。项目围绕解决城市范围内的断裂定位、定年、定性、深部背景、地震危险性和危害性及防震减灾对策等一系列科学问题 ,通过“初查与目标区主要活断层鉴定”、“深部地震构造环境探测”、“地震活断层鉴定与危险性评价”、“地震活断层的详细探测”、“地震活断层危害性评价”和“活断层地理信息系统建设”等阶段的探测和评价工作 ,同时在福州市城、郊区全面开展壤中气汞、土壤汞、气氡、地质雷达、多道直流电法、瞬变电磁法、浅层地震折射法、浅层地震反射法、勘探震源效果对比、用于建立福州盆地埋藏第四系 (标准 )剖面的钻探等多种手段的试验探测 ,总结各种试验探测的技术指标和实践经验 ,在活断层的综合试验探测、定位定年、地震危险性和危害性评价等方面取得了下列成果与结论 :(1)福州市活断层综合试验探测成?

A mass of earthquake researches indicate that earthquake directly beneath cities induced by active faults devastates cities seriously. So it is a urgent issue for disaster mitigation of cities in China to explore the distribution of active faults beneath and near the city, and identify the epicenter of earthquake directly beneath cities and hazard. As a testing and demonstrating project of active fault exploration of the whole country of China Earthquake Administration, the project, named “Active Faults Exploration and Seismic Hazard Assessment of Fuzhou City”, was begun in the early of 2001 and passed the check of China Earthquake Administration in August, 2004. Surrounding the goals of the project, resolving a serial of scientific issues such as fault orientation, dating, property identification, depth setting, seismic hazard and harm, through several stages explorations and evaluations including “primary exploration and identification of major active faults in target region”, “exploration of the setting of deep seismic tectonics”, “detailed exploration of active faults”, “seismic harm assessment of active faults”, and constructing of geography information system of active faults”, a lot of methods used in the exploration such as absorbed mercury, free mercury, radon in soil, geology radar, multi-channel direct current, transient electromagnetic, shallow seismic refraction and reflectibility, effect contrast of various seismic source, and testing exploration of drill hole used to construct the buried Quarternary standard section of the Fuzhou basin, to sum up the technical index and experiences of different testing explorations, a serial fruits and conclusions can be drawn about synthesis testing exploration of active fault, orientation and dating, seismic hazard and harm assessment: 1.The fruit of synthesis testing exploration in Fuzhou city indicates that it is a best combined method for active fault exploration (orientation), seismic hazard and harm assessment (dating and determining character) and that of basing on sufficient collection, arranging and analysis the data of relative geology, geophysics and drill holes etc, regarding geochemical exploration as forerunner “scout” to identify the possible location of active fault, sallow seismic exploration as major exploration method, eclectromagnetic exploration as supplement, and the Quaternary section or strata sequence of drilling and different geophysic data of logging as method to correct and validate the data above, combined with the exposed faults or trenches, paleoearthquake investigation, contrast of drill core strata, stratigraphic sequence, absolute ages and related ages of sporopollen analysis of two sides of concealed fault etc; 2.The Fuzhou basin locates in the tectonic setting with the medium intensity seismic hazard, there is Taiwan dynamical antenna has weak effect to it; 3.The activity of major faults is weak in the Fuzhou basin, all of target faults are not Holocene faults by identification, in which the Bayishuiku-Shanggan fault and the Minhou-Nanyu fault are at least inactive faults since middle of late Pleistocene, else are inactive faults since late Pleistocene; 4.There is not the deep tectonic setting which induce directly beneath and strong devastating earthquake in depth of the Fuzhou basin, the Changle-Zhaoan fault near Fuzhou will be a seismic source region which effect Fuzhou city in the future. 5.There is hazard that moderately strong earthquake related with major faults of the Fuzhou basin, but the probability occurring earthquake is small. 6.There is weak seismic harm in the Fuzhou basin, and it is anticipated that there will be not surface rupture. 7.The first active fault GIS is constructed, there are a lot of function such as information inquiry and display, the management, analysis and treatment of data, consultation and service etc.