摘要
大同6.1级地震前,地磁前兆异常在时间、空间和强度等方面沿一定构造部位展现出有规律的分布。其中日变低点位移异常分界线沿燕山阴山断裂带、太行山山前断裂带、秦岭褶断带和南北地震带形成一个闭合圈。地磁流动磁测、地电、形变、水化学、地下水和地应力等前兆异常在两个条带上——北京以西至呼和浩特与北京以南至邯郸一带明显地呈条状分布。这些异常密集的地带恰好是日变低点位移分界线所通过的燕山带和太行山山前断裂带的一部分地段。而远离分界线所通过的那部分地段的前兆异常明显地减弱。这种情况表明被某些地质构造带分隔开来的地壳块体,在地震前可能发生一定程度的运动,致使某些构造带内的介质发生物理性质的变化。此外,大同地震前,这些前兆异常在时间序列上显示出具有中、短、临的前兆特点。
Before the Datong 6.1 earthquake, geomagnetc precursory anomalies showed a regular distribution along certain structures in time, space and εemplitude. Among them, the boundary line of anomaly of low—point move-ment of daily variation formed a closed ring along yanshan—Yingshan fault zone, the piedmont fault zone of Taihang mountain, Qinling fold fault zone and South—North seismic zone. The precursory anonalies of mobile geomagnetic observation, telluric current, deformation, bydrochemistry, groundwater and terrestrial stress, were on two belts, Beiging-Huhehote and Beijng-Handan, obviously showing a band-like distribution. The region concentrated with these anomalies is just one part of Yanshah fault zone and the piedmont fault zone of Taihang mountain through which the boundray line of low-point movement of daily variation passed, but the precursory anomalies far from the boundary line were obvrously decreased. This indicates that, in the crustal blocks which were separated by some tectonic zones, movement to a certain extent may take place beforc an earthquake, resulting in variatron of physical property of media in some tectonic znoes. Furthermore, prior to the Datong earthquake, these precursory anomalies showed the characteristics of mid-term, short-term and imminent precursors in time series.
出处
《华北地震科学》
北大核心
1991年第4期89-99,共11页
North China Earthquake Sciences
