芦山地震、汶川地震与龙门山地区水汽异常

WATER VAPOR ANOMALIES RELATED TO THE LUSHAN AND WENCHUAN EARTHQUAKES IN THE LONGMENSHAN MOUNTAINS AREA

对龙门山地区水汽动态的分析研究表明,在2013年芦山MS7.0地震和2008年汶川MS8.0地震前,龙门山地区大气相对湿度异常频次都出现了先逐年下降,然后快速回升的过程;下降时间较长,10a以上,上升时间较短,1～2a;震中位于异常频次相对下降和上升幅度都是最大的中心或邻近区域.在地震孕育中期阶段发生水汽异常趋势变化的原因可能是由于岩层裂隙的张合、地下流体的运动和地热能的变化,影响地面温度和潜热交换的速度所致.在地震孕育的中长期阶段（10a～几a）,地壳岩石受压缩变形,孔隙、裂隙不断闭合或减少,由地下释放的热水、热汽减少,潜热交换速度也随之降低,相对湿度异常频次表现为逐年下降的趋势.在地震孕育的中短期阶段,地壳岩石变形进一步加大,可能导致微破裂不断扩展,由地下释放的热水、热汽由减少转为增加,潜热交换速度由降低转为迅速增加,相对湿度异常频度也表现出由逐年下降转为突发的快速上升.

Studies of air relative humidity dynamic process in Longmenshan Mountains area,Sichuan,southwcstern China show that,before the 2013 Lushan MS7.0 earthquake and the 2008 Wenchuan MS8.0 earthquake,the annual frequency of air relative humidity anomalies appeared to decrease year by year in the initial period,and then increased quickly.The fall time is longer,often more than 10 years,and the rise time is short,about 1 ～2 years.The epicenters are located in or near the area where the anomaly frequency of air relative humidity declined most and increased more than other regions.The tendency transition of the annual frequency of air relative humidity anomalies in the middleterm period of earthquake preparation is probably due to the opening and closing of rock fracture,underground fluid movement and geothermal energy release,which cause the change of ground temperature and latent heat exchange rate.In the medium and long-term period of earthquake preparation（10 to several years）,the crust rock is under compression deformation,the rock pores and fissures are continuously closed or reduced,the releasing of underground hot water or hot vapor decreases,and the latent heat exchange rate has also decreased,therefore the relative humidity anomaly frequency shows a declining trend.Whereas in the medium and short-term period of the earthquake preparation,as the crustal rock deformation increases further,which may lead to micro fractures expanding,and the underground hot water and hot vapor by releasing will turn from decreasing to increasing,the latent heat exchange rate changes from reducing to rapidly increasing,and the relative humidity anomaly frequency also shows a transition from decreasing year by year to a rapid increase in burst.