摘要
2013年4月20日和7月22日先后发生了四川芦山7.0级和甘肃岷县6.6级地震。这两次地震前天水地电台地电阻率的井下观测资料都出现明显的短临异常变化,其中芦山地震前11天地电阻率NS道、EW道、N45°W道出现同步异常,表现为明显波动变化;岷县地震前约40天地电阻率三道出现异常,测值出现明显波动变化。
The earth resistivity observation station in Tianshui,China,is located in the northern region of the Qinling latitudinal tectonic belt,which is the western settlement zone of the Neocathaysian structural system and includes the southward-insertion portion of Qilianshan-Luliangshan-Helanshan front arc structural system and the southern edge of the Weihe fault.This area exhibits a clear diamond structure with an N-E,N-W,and E-W configuration,in which seismic activity is frequent and epicenter location varies.The station has an altitude of 1 150 m,average humidity of approximately 63％,and annual average temperature of 18 ℃.The polar region of this area includes Ⅰ-and Ⅱ-grade terraces of the Yongchuan River.During the past five years,two larger earthquakes have occurred in this region including the Lushan M7.0 earthquake on April 20,2013,and the Minxian-Zhangxian M6.6 earthquake on July 22,2013.The epicenters of these two earthquakes were 550 km and 200 km,respectively,from Tianshui station.Prior to their occurrences,the earth resistivity observation data of Tianshui station showed obvious short-term anomalies that differed in morphology and amplitude.Eleven days prior to the Lushan earthquake,the N-S,E-W,and N45°W channels of the deep well observing system showed clear synchronous abnormal changes,which remained for 11 days following the earthquake.Forty days prior to the Minxian-Zhangxin earthquake,the 7.05±0.01 normal value of the E-W channel showed intermittent fluctuation anomalies of approximately ± ±0.02.Although both earthquakes occurred in the S-N seismic belt,the Lushan earthquake occurred in the Longmenshan fault zone,and the Minxian-Zhangxian earthquake occurred in the Lintan-Tanchang fault zone.
出处
《地震工程学报》
CSCD
北大核心
2013年第4期816-818,共3页
China Earthquake Engineering Journal
基金
中国地震局兰州地震研究所地震科技发展基金野外站基金(2013096)
关键词
四川芦山7
0级地震
甘肃岷县6
6级地震
地电阻率
井下观测系统
异常分析
Lushan M7.0 earthquake in Sichuan
Minxian M6.6 earthquake in Gansu
earth resistivity
deep well observing system
anomaly analysis
