震前地下水中硫化氢气体的短临前兆特征

本文以实际震例为依据,叙述了天山地震带中强地震前地下水中硫化氢气体的短临异常特征。以硫化氢气体为例,对地下气体的地震前兆机理进行了粗浅的讨论。指出中强地震前,硫化氢气体普遍出现短期异常变化,临震突变现象也比较清楚。硫化氢气体在短临异常阶段的特征具有动力过程(应力应变能的预释放)的突发性、气量增长的突变性和异常时间的短促性。文中还对前兆近场和前兆远场在不同孕震阶段中的受力状态和异常特征进行了分析。认为主破裂前的加速蠕滑和微破裂以及由此而产生的超声振动和低频形变波的传播是临震前地下水中硫化氢气、氡气和其他气体浓度普遍增高的主要原因。

PRECURSORY CHARACTERISTICS OF HYDROGEN SULFIDE IN GROUND WATER IMMEDIATELY BEFORE EARTHQUAKES

In this paper,based on the abundant seismic facts,the abnormal fea-tures of hydrogen sulfide in ground water immediately before the occuran-ce of moderate and strong earthquakes in the Tianshan seismic zone are described.A preliminary discussion on the seismic precursory mechanism of underground gases is made.It is noted that,before moderate and stro-ng earthquakes,as a general rule,abnormal changes with hydrogen sulfi-de for a short period of time take place.Mutation phenomena immediate-ly before earthquakes are also obviously observed.Characteristics of hyd-rogen sulfide during the period immediately before earthquakes are as fol-lows:the suddeness of dynamic process (pre-release of stress strain ener-gy),the mutation characteristics of gas amount increase and the short duration of the abnormal stage.Besides,here also an analysis for the sta-te of subjection to forces and the abnormal characteristics of the precu-rsory near fields and far from fields in various stages of earthquake preg-nancy is made.It is considered that the accelerated creep slipping and the appearance of microcracks prior to that of main cracks and the propaga-tion of supersonic vibrations and lowfrequency deformation waves produc-ed therefrom is the main reason for the universal increase in the concent-ration of hydrogen sulfide,radon and other gases in ground water shortly before earthqukes.In recent years,hydrogen sulfide has become one of the main indices used for predicting earthquakes,and good results have been obtained.