从溧阳六级地震的前兆特征讨论中强震的预报问题

扬州～铜陵地震带位于大华北强震活动区和华南地震相对平静区的交接部位,中强震比较活跃。由于中强震震源应力场作用范围有限,时间不长,每个中强震的前兆有其相对的独立性——很少受大华北强震与本区其他中强震的影响。这就为检验前兆的准确性提供了较好的环境。1979年7月9日溧阳六级地震后经历了一年多时间的检验,我们将其较可靠的前兆

FORERUNNERS OF THE LIYANG EARTHQUAKE OF JULY 9,1979(Ms=6.0) AND ITS IMPLICATIONS ON PREDICTION OF MODERATE EARTHQUAKES

After the Liyang Earthquake (M_s=5.5) of April.22.1974,networks have been established in the epicentral area and its adjacent region for observing various possible forerunners,including seismic activity,crust deformation,parameters of underground water (Radon content,water le-vel,flow),geomagnetic and stress field variations.Because of these net-works some continuous data were obtained before the Liyang Earthquake (M_s=6.0),the more reliable ones of them have been collected basically in this paper.A preliminary study shows that the preparatory process of the Liyang Earthquake (6.0) can be divided into three stages:the 1^st stage began from early 1978 and is called medium-term anomaly,the 2^nd stage,called short-term anomaly,started in May,1979,the imminent anomaly (the 3^rd stage) appeared half a month before the earthquake.Majority of the anomalies appeared at distances of about 100 km from the epicenter,and a few between 1-200 km.Macro-phenomena (anomalous behaviour of animals,changes in parameters of underground water and so on) appeared near the epicentral region.The authors suggest that in order to predict moderate earthquakes,it is very important to identify the anomalous characters of each stage and to study the geological structures in the vicinity of the observing points at which the anomalies appeared.