震群与大地震关系的研究(华北地区)
STUDY OF EARTHQUAKE SWARMS IN RELATION TO LARGE EARTHQUAKES (NORTH CHINA AREA)
-
摘要: 1956-1976二十年来,华北地区(106E 以东,33N 以北,42N 以南,黄海以西)共发生震群37次,其中1966年邢台地震后到1976年唐山地震前,震群次数比1956-1966增加三倍多,近十年来华北四次七级以上地震就是在震群活动水平不断增高的背景上出现的.从空间分布上来看,1967-1972年震群分布范围相对缩小,仅靠近大震震中;1974年后,震群活动区域明显扩大,唐山地震前不到半年的时间内,震群活动沿唐山地震震中的 NE-SW 和 NW-SE 方向上分别延伸达一千多公里.这种地震活动随时间由未来大震震中逐步向外扩散的现象,在几次历史大地震前也类似出现过,据此粗略估计平均扩散速度约为100公里/年.除上述特点外,还观测到大震发生前一、二年至数月,在距未来震中不太远处(百公里)常发生前兆震群.分析了前兆震群与一般震群在震源机制、震源动力学参数、b 值以及 P 和 S 波振幅比等方面可能存在的差异.初步结果表明:与一般震群相比,前兆震群具有较高的应力降.最后,简要地分析了易于发生前兆震群可能的物理和构造条件.Abstract: From 1956 to 1976, there occurred thirty-seven earthquake swarms in North China, (i.e. east of 106 E, north of 33N, south of 42 N and west of Yellow sea). Among these, the number of earthquake swarms occurred just after the 1966 Xingtai (邢台) Earthquake to the 1976 Tangshan (唐山) Earthquake is about three times more than the number of swarms occurred in the period of 1956-1966. During the last ten years, all of the large earthquakes (M>7.0) occurred on the background of a continuously increasing activities of earthquake swarms.In view of the spatial distribution, the scope of activity of earthquake swarms) is limited in smaller areas, close to the epicenters of future large earthquakes. However, since 1974, the swarm activity has been clearly enlarged in spatial distribution. Around the epicenter of the subsequent Tangshan Earthquake, both in the NE-SW and NW-SE directions it was lengthened by more than 1000 kms, in less than half a year before the earthquake.Such a phenomenon of seismic activity spreading out from the epicenter of the impending major earthquake with the lapse of time can also be noticed before several historical earthquakes, the average spreading rate may be roughly estimated as about 100 km/year.Besides, it is also observed that precursory earthquake swarms, appear several months to one or two years before the impending large earthquakes at a not too far distance (about 100 kms).The possible differences between the precursory earthquake swarms and the ordinary ones in focal mechanism, dynamic source parameters, b value as well as the amplitude ratios of P and S waves have-been analysed. Preliminary results show that the stress drops for precursory earthquake swarms are higher. Finally, the physical and tectonic conditions under which precursory swarms might be observed are briefly discussed.
-
-
[1] 関谷溥,群凳性地震と地震予知,地震予知研究ッンポジワム,1972
[2] 茂木清夫,地震活动と地震予知,地震予知ッンポジワム,1977
[3] M .Isliida, and H. Kanamori., The foresliock activity of the 1971 san fernaudo earthquake California, BSSA,68, 5,1265——1280,1978
[4] F. F. Evison, Precursory seismi;e sequences in mew Zealand,NZ Jour of Geology and Geo——physics,20,11129——141,1977.
[5] F. F. Evison, The precursory earthquake swarm, Phaysics of the earth and Planatary Interiors,15,19——23,1977
[6] 华北地区ML地震目录(1952——1974)地震出版社(待发表).
[7] 北京及邻区地震目录汇编,地震出版社(待发表).
[8] 张祖胜,唐山7.8级地震的地面形变,欧洲地震委员会地球物理年会报告,1978,斯特拉斯堡.
[9] 赛克斯,缓慢地震与应力重新分布,国外地震,3, 10——13, 1979
[10] 许忠淮等,京津唐张地区地震应力场的方向特征,地震学报,1, 2, 121——132, 1979
[11] 约翰逊,粘滑源参数和地震源参数,国外地震,4, 41——43, 1975
[12] T .Mikumo, Source process of deep and Intermediate eartliauakes as inferred from long——period P and S waveforms, Physics of the Earth, 19. 4. 303——320. 1971,
[13] 朱传镇等,海城地震前后微震震源参数和介质品质因子,地球物理学报,20, 3, 228——231, 1977.
[14] R. Green, A. McGarr, A comparison of the focal mechanism and aftersliock distribution of the Ceres South Africa earthquake of September 29, 1969, BSS9, 62, 3, 869——871, 1972
[15] 张之立等,唐山地震的破裂过程及其力学分析,地震学报,2,2,111——129.1980
[16] 邢台地震总结,地震出版社(待发表).
[17] 顾浩鼎等,1975, 2, 4.辽宁省海城地震的震源机制,地球物理学报,19, 4, 270——284, 1976.
[18] 吴开统等,海城地震序列的特征,地球物理学报,19, 2, 95——109, 1976.
[19] D. F'. Hill, A model of earthquake swarm J. G.R.82. 8. 1347——1352. 1977.[1] 関谷溥,群凳性地震と地震予知,地震予知研究ッンポジワム,1972
[2] 茂木清夫,地震活动と地震予知,地震予知ッンポジワム,1977
[3] M .Isliida, and H. Kanamori., The foresliock activity of the 1971 san fernaudo earthquake California, BSSA,68, 5,1265——1280,1978
[4] F. F. Evison, Precursory seismi;e sequences in mew Zealand,NZ Jour of Geology and Geo——physics,20,11129——141,1977.
[5] F. F. Evison, The precursory earthquake swarm, Phaysics of the earth and Planatary Interiors,15,19——23,1977
[6] 华北地区ML地震目录(1952——1974)地震出版社(待发表).
[7] 北京及邻区地震目录汇编,地震出版社(待发表).
[8] 张祖胜,唐山7.8级地震的地面形变,欧洲地震委员会地球物理年会报告,1978,斯特拉斯堡.
[9] 赛克斯,缓慢地震与应力重新分布,国外地震,3, 10——13, 1979
[10] 许忠淮等,京津唐张地区地震应力场的方向特征,地震学报,1, 2, 121——132, 1979
[11] 约翰逊,粘滑源参数和地震源参数,国外地震,4, 41——43, 1975
[12] T .Mikumo, Source process of deep and Intermediate eartliauakes as inferred from long——period P and S waveforms, Physics of the Earth, 19. 4. 303——320. 1971,
[13] 朱传镇等,海城地震前后微震震源参数和介质品质因子,地球物理学报,20, 3, 228——231, 1977.
[14] R. Green, A. McGarr, A comparison of the focal mechanism and aftersliock distribution of the Ceres South Africa earthquake of September 29, 1969, BSS9, 62, 3, 869——871, 1972
[15] 张之立等,唐山地震的破裂过程及其力学分析,地震学报,2,2,111——129.1980
[16] 邢台地震总结,地震出版社(待发表).
[17] 顾浩鼎等,1975, 2, 4.辽宁省海城地震的震源机制,地球物理学报,19, 4, 270——284, 1976.
[18] 吴开统等,海城地震序列的特征,地球物理学报,19, 2, 95——109, 1976.
[19] D. F'. Hill, A model of earthquake swarm J. G.R.82. 8. 1347——1352. 1977.
计量
- 文章访问数: 1108
- HTML全文浏览量: 20
- PDF下载量: 144
下载:
