| 1974年和1979年江苏省溧阳两次中等强度地震的前兆性空区. |
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| 引用本文： | 魏光兴, 赵兴兰, 顾贞庆. 1983: 1974年和1979年江苏省溧阳两次中等强度地震的前兆性空区.. 地震学报, 5(1): 65-72. |
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| 作者姓名： | 魏光兴 赵兴兰 顾贞庆 |
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| 作者单位： | 山东省地震局 |
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| 摘 要： | 1974年4月22日、1979年7月9日在江苏省溧阳地区先后发生5.8级、6.3级(ML)两次地震.在这两次地震前约23个月,其周围200多公里范围内出现地震空区图象.1974年5.8级地震前16个月,在240公里范围内没有发生小地震;临近震前7个月空区活化,爆发一系列小地震.1979年6.3级地震前15个月,在100公里范围内和240公里范围外发生一些小地震,形成环形空区;临近地震前7个月,约200公里范围内均无小震活动.根据两次主震等震线,主、余震展布和震源机制结果认为,它们是在北东东向压应力和北北西向张应力作用下,发生在同一震源区的不同期共轭地震.两次地震空区图象的形成、发展和消失过程,描绘了区域应力持续作用下,中等均匀程度的地壳不均匀应变的演化过程.
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ON THE PRECURSORY SEISMIC GAPS BEFORE TWO MEDIUM-SIZE EARTHQUAKES OCCURRED IN 1974 AND 1979 IN LIYANG COUNTY,JIANGSU |
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| WEI GUANGXING, ZHAO XINGLAN, GU ZHENQINGcom sh advanc. 1983: ON THE PRECURSORY SEISMIC GAPS BEFORE TWO MEDIUM-SIZE EARTHQUAKES OCCURRED IN 1974 AND 1979 IN LIYANG COUNTY, JIANGSU. Acta Seismologica Sinica, 5(1): 65-72. |
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| Authors: | WEI GUANGXING ZHAO XINGLAN GU ZHENQINGcom sh advanc |
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| Affiliation: | Seismological Bureau of Shandong Province |
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| Abstract: | Two earthquakes (ML = 5.8 and 6.3) occurred in Liyang County, Jiangsu Province, on April 22, 1974 and July 9, 1979 respectively. Seismic gaps appeared within about 23 months before each of these two earthquakes in a region of about 200 km in radius around the epicenters. During 16 months before the 1974 earthquake of magnitude 5.8, not a single small earthquake occurred in an areas of radius 240 km around the mainshock. Seven months prior to the. mainshock, the gap began to be activated and a series of small shocks broke out. Fifteen months before the 1979 earthquake of magnitude 6.3, inside an area of radius 100 km and outside an area of radius 240 km, there occurred a number of small earthquakes, thus forming a doughnut-shaped seismic gap, while during 7 months before the mainshock no small earthquake occurred in an area of radius about 200 km.Based on the distribution pattern of the isoseismal lines of both mainshocks and their aftershocks as well as the focal mechanism solutions of the two earthquakes, it could be inferred that both earthquakes are the result of the action of compressive stress in the NEE direction and tensional stress in the NNW direction. They are conjugate earthquakes of the same focal region at two different times. The processes of formation, development and disappearance of both of the seismic gaps imply the process of evolution of the heterogeneous strain of the semi-homogeneous crust under the continuous action of the ambient regional stress field. |
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