2006年云南盐津5.1级双震的监测与研究
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摘要
利用2006年云南省盐津两次5.1级地震现场流动台网的近场地震监测资料,结合云南区域地震台网地震波资料进行精确定位,给出了盐津地震主、余震的震源参数,并分析讨论了这两次地震的震源过程。结果显示,这两次地震处于同一构造区,发震构造为NE向断裂,主破裂走向约N53°E,倾向NW,倾角约80°,断层性质为走滑型。断层破裂长度约9km,宽度约3km,破裂面深度3～9km,断层走向与宏观等震线长轴方向基本一致。震源参数研究表明,盐津震区地震矩为109～1016N.m,震源破裂半径为90～300m,应力降为0.0002～32MPa。高应力降地震事件主要发生在5～10km深度范围内,表明该深度区是盐津地震的主要活动区。定位结果还显示,第1次地震的破裂面在深度7～9km之间为余震空白区,认为该空白区是盐津地震主破裂面上的障碍体,第2次地震将障碍体贯穿。地震破裂面障碍体的存在是盐津震区发生两次地震的主要成因,说明地震空白区图像对地震预测具有十分重要的意义。
Two M5.1 earthquakes occurred in Yanjin,Yunnan,China,in 2006.We located the events with high precision,solved the source parameters of the Yanjin earthquake sequences,and discussed the rupture processes of the Yanjin doublet by using the near-field and regional seismic waveforms.The result shows that the two M5.1 earthquakes lie in the same tectonic region.The main fracture at depth 3-9 km is strike slip with a dimension about 9 km×3 km approximately,a strike about N53°E,and a dip about 80°.The strike of the fracture is consistent with that of the long axis of isoseismals.The seismic moment,rupture radius and stress drop are 109-1016 N·m,90-300 m and 0.000 2-32 MPa respectively in the seismic area.The events with higher stress drop concentrated at depth 5-10 km,so this depth range is the main active zone of the Yanjin earthquakes.The spatial distribution of the aftershocks displays that the main rupture plane of the former M5.1 earthquake has an absent-shock zone at depth 7-9 km,which is regarded as the asperity on main rupture plane,and the following M5.1 earthquake ruptured through the asperity.This suggests that the asperity on the rupture plane resulted in the Yanjin double shocks.So the absent-shock zone mapping is important for earthquake prediction.
Two M5.1 earthquakes occurred in Yanjin,Yunnan,China,in 2006.We located the events with high precision,solved the source parameters of the Yanjin earthquake sequences,and discussed the rupture processes of the Yanjin doublet by using the near-field and regional seismic waveforms.The result shows that the two M5.1 earthquakes lie in the same tectonic region.The main fracture at depth 3-9 km is strike slip with a dimension about 9 km×3 km approximately,a strike about N53°E,and a dip about 80°.The strike of the fracture is consistent with that of the long axis of isoseismals.The seismic moment,rupture radius and stress drop are 109-1016 N·m,90-300 m and 0.000 2-32 MPa respectively in the seismic area.The events with higher stress drop concentrated at depth 5-10 km,so this depth range is the main active zone of the Yanjin earthquakes.The spatial distribution of the aftershocks displays that the main rupture plane of the former M5.1 earthquake has an absent-shock zone at depth 7-9 km,which is regarded as the asperity on main rupture plane,and the following M5.1 earthquake ruptured through the asperity.This suggests that the asperity on the rupture plane resulted in the Yanjin double shocks.So the absent-shock zone mapping is important for earthquake prediction.
引文
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时振梁,张少泉,赵国荣,等.1992.地震工作手册[S].北京:地震出版社,135-136.
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叶建庆,秦嘉政.2001.数字地震记录震源参数测定[G]//毛玉平,万登堡.2000年云南姚安6.5级地震.昆明:云南科技出版社:55-99.
叶建庆,秦嘉政,蔡绍平,等.2002a.永胜地震观测与研究[J].地震研究.25(B):64-73.
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B a kun W H.1984.Seismic moments,local magnitudes,and coda-du-ration magnitudes for earthquakes in central California[J].BSSA,74:439-458.
安艺敬一,理查兹P G著.1986.定量地震学——理论和方法(第二卷)[M].北京:地震出版社.
非明伦,周光全,谢英情,等.2006.盐津5.1级地震现场调查与烈度分布[J].地震研究.29(4):411-417.
李立平,叶建庆,谢庆茵.1990.澜沧—耿马地震震源动力学参数研究[J].地震研究,13(3):223-233.
李一正,Bakun W H,金亚夫,等.1985.滇西地区震级与地震矩标度[J].地震研究,8(6):617-632.
秦嘉政,阚荣举.1986.用近震尾波估算昆明及其周围地区的Q值和地震矩[J].地球物理学报,29(2):145-156.
秦嘉政,李白基,叶建庆,等.2000.用数字记录资料测定腾冲火山区的微震参数[J].地震研究.23(2):124-132
秦嘉政,叶建庆,钱晓东,等.2003a.2000年姚安地震的震源参数[J].地球物理学报.46(5):633-641.
秦嘉政,叶建庆,蔡绍平,等.2003b.云南姚安—永胜地震近源数字地震观测与现代新参数报告[M].北京:地震出版社.
秦嘉政,叶建庆,蔡绍平,等.2005.云南大姚地震近源数字地震观测与现代新参数报告[M].北京:地震出版社.
时振梁,张少泉,赵国荣,等.1992.地震工作手册[S].北京:地震出版社,135-136.
叶建庆,秦嘉政.2000.火山区数字地震观测[G]//皇甫岗,姜朝松.腾冲火山研究.昆明:云南科技出版社:176-231.
叶建庆,秦嘉政.2001.数字地震记录震源参数测定[G]//毛玉平,万登堡.2000年云南姚安6.5级地震.昆明:云南科技出版社:55-99.
叶建庆,秦嘉政,蔡绍平,等.2002a.永胜地震观测与研究[J].地震研究.25(B):64-73.
叶建庆,苏有锦,刘学军,等.2002b.2001年云南中强地震序列震源参数[J].地震研究.25(2):115-123.
B a kun W H.1984.Seismic moments,local magnitudes,and coda-du-ration magnitudes for earthquakes in central California[J].BSSA,74:439-458.
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