摘要
分析了延庆五里营井汶川M8.0地震和玉树M7.1地震数字化流体前兆观测资料,对比研究了五里营井流体在2次强震中的响应差异。结果显示,流体异常响应灵敏度与地震震级和观测点震中距有一定关系,地震震级越大,观测点距离震中越近,流体异常响应越灵敏。2次大震前流体前兆都观测到氦气释放活动最先出现异常反应,其释放强度与震级有关,震级越大,异常变化越强烈,其中汶川地震He浓度释放短期内出现较大变化可能与不断的强余震活动和大震后的构造调整有关。2次大震发生后,氦气异常释放反而增加明显,这一过程有异常He的贡献。这一方面可能与6—9月是年变过程有关,另一方面也可能与五里营井热储型气体释放特征有关,地震孕育发生过程中,有大量的深部来源He释放出来进入地热系统并改变整个组成,在时间上较断裂型气体释放晚,并且异常消失的时间也会晚得多。2次强震流体映震响应差异可能与2次地震深部构造背景和动力机制差异有关。处于南北地震带的汶川地震与观测点所在东部地区的关联强于青藏高原内部的玉树地震。氦气可能是观测点所在地区监测地下深部气体异常活动的灵敏指标。
The precursor response characteristics of digital fluid caused by Wenchuan M 8.0 and Yushu M 7.1 earthquakes are studied,and the response difference of the observations of Wuliying Well to the two strong earthquakes is compared.The result shows that the abnormal fluid response has a certain relationship with earthquake size and epicenter distance.The greater the earthquake,and the closer to the epicenter from the observatory,the more sensitive the response will be to fluid anomalies.Abnormal Helium release was the first to be observed before both strong earthquakes in the fluid precursor observation.The release intensity is related to earthquake magnitude,the larger the magnitude of earthquake,the stronger the abnormal change.The large change in He release in a short period after the Wenchuan earthquake may be related to continuous activity of strong aftershocks and the structural adjustment after the earthquake.Helium release increased significantly after both earthquakes,as contributed by the abnormal deep-sited Helium release.However,this process may be connected with the annual change from July to September on the one hand,and related to the hot-reservoir type gas release in Wuliying well on the other hand.In the earthquake preparation process,a large number of deep-derived Helium is released into the geothermal system and the entire composition is changed.Temporally,this gas release appears later than fault-type gas release,and the vanishing time of this anomaly is also much later.The response difference of fluid precursor to the two strong earthquakes may be related to differences of deep structural setting and dynamic mechanism.It also shows there is stronger correlation to the Wenchuan M 8.0 earthquake in South-North earthquake belt and North-China region than to the Yushu M 7.1 earthquake in internal Qinghai-Tibet Plateau.Helium gas can be a sensitive indicator for monitoring abnormal deep-gas activity of the region where the observation station locates.Hence,observation and research should be strengthened in the future.
出处
《地震地质》
EI
CSCD
北大核心
2011年第3期644-652,共9页
Seismology and Geology
基金
北京市地震局局长基金(2011)资助
关键词
地下流体
响应差异
强震
五里营井
underground fluid
response difference
strong earthquake
Wuliying Well