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广东省被视为少震、弱震区,但近两年来(1985.9—1987.7),在广东省老震区的阳江县,就发生了M_s3.2—5.0级地震共达11次之多,其中4级以上4次,有2次为5.0级。可见此期间该区的地震活动既不算“少”,也并不很“弱”,这是值得人们关注的。笔者发现,在多次阳江地震前,海口市ZK 26钻孔(Δ=260km)水化组分含量均有一定程度的相应变化,似乎是反映该区地震活动的灵敏点。本文仅就该区2次5级地震前该钻孔地下水中HCO_3~-、Cl~-、CO_2含量及pH值的变化情况作一报道。
Guangdong Province was regarded as a small earthquake and a weak earthquake area. However, in the past two years (1985.9-1987.7), a total of 11 earthquakes of magnitude M_s3.2-5.0 occurred in Yangjiang County, an old earthquake zone in Guangdong Province, of which 4 4 or above level, there are 2 to 5.0 level. It can be seen that the seismic activity in the area during this period was neither “less” nor “very weak”, which deserved people’s attention. Before the Yangjiang earthquake, the authors found that the hydrate content of ZK26 borehole (Δ = 260km) in Haikou City has a certain degree of corresponding changes, which seems to be a sensitive point reflecting the seismic activity in this area. This paper reports only the changes of HCO 3 -, Cl 2 -, CO 2 and pH in the groundwater before the M = 5 M5 earthquake in this area.