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地震 ›› 2005, Vol. 25 ›› Issue (2): 26-32.

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张北地震前小震活动和余震序列精确定位及主震破裂方向的讨论

白玲1, 王勤彩2, 刁桂苓2, 张天中1, 赖晓玲3, 李松林3, 林碧苍4, 武巴特尔1   

  1. 1.中国地震局地球物理研究所, 北京 100081;
    2.河北省地震局, 河北 石家庄 050021;
    3.中国地震局地球物理勘探中心, 河南 郑州 450006;
    4.中国地震局震害防御司, 北京 100036)
  • 收稿日期:2004-09-20 修回日期:2004-11-22 出版日期:2005-04-30 发布日期:2021-11-10
  • 作者简介:白玲(1973-), 女, 辽宁锦州人, 2002年在读博士生, 主要从事数字地震学和地震参数等研究。
  • 基金资助:
    国家自然科学基金项目(49974006)

Accurate location of small earthquakes before Zhangbei Earthquake and aftershock sequence and discussion on the Rupture's direction of main event

BAI Ling1, WANG Qin-cai2, DIAO Gui-ling2, ZHANG Tian-zhong1, LAI Xiao-ling3, LI Song-lin3, LIN Bi-cang4, WU Bateer1   

  1. 1. Institute of Geophysics, CEA, Beijing 100081;
    2. Earthquake Administration of Hebei Province, Shijiazhuang 050021;
    3. Research Center of Exploration of Geophysics, CEA, Zhengzhou 450003;
    4. Department of Earthquake Disaster Prevention, CEA, Beijing 100036, China
  • Received:2004-09-20 Revised:2004-11-22 Online:2005-04-30 Published:2021-11-10

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摘要： 1970年至1998年1月10日张北地震前, 沿NWW向发生2级以上地震24次, 其分布相对集中, 呈条带状。 对华北台网所记上述地震的到时数据全部重新查图核对, 并补充了内蒙古台网5个台的数据以改善用于定位的台站分布, 并采用主地震定位法重新定位, 除一个地震外, 其余地震更加集中, 形成一小震条带。 1998年2月中国地震局地球物理勘探中心在张北震区架设10台短周期数字化地震仪, 记录了大量微震。 作者采用P波和S波到时差重新进行了震源定位, 得到184次微震的定位结果, 连同1998年1～2月张北震区3级以上地震事件定位结果一起勾画出6.2级地震的震源破裂带。 由张北地震震中向SEE向延伸存在由强震构成的张家口-渤海地震带。 根据精确定位结果, 结合修订后主震的震源机制、 宏观烈度分布和层析成像资料, 讨论了张北地震和小尺度地震带(震源破裂带)、 震前的中等尺度小震条带以及大尺度的张家口-渤海强震带的关系。

关键词: 张北地震, 震源破裂带, 小震条带, 精确定位

Abstract: Before the Zhangbei earthquake through the lst of Jan. 1970 to the 10th of Jan. 1998, 24 earthquakes with magnitude larger than ML2.0 occurred in the NWW direction of Zhangbei earthquake, they were relatively concentrated along a belt. The arrival times of all the events are checked from the seismograms recorded at North China telemetric seismograph network. Additional data are used from other 5 stations of Inner Mongolia telemetric seismograph network to improve the distribution of stations used in location. Those earthquakes are relocated using the main event location approach. All events became more closely except one, forming a seismic belt. Many micro-earthquakes along Zhangbei seismic zone are recorded by 10 short period seismographs employed by Research Center of Exploration of Geophysics in February 1998. We relocated 184 micro-earthquakes using the arrival time difference between P and S waves. These micro-earthquakes together with the relocated earthquakes with magnitude large than 3.0 occurred along Zhangbei seismic zone in January 1998 outline a focal rupture belt of M6.2 earthquake. There is Zhangjiakou-Bohai rupture belt, where many strong earthquakes occurred in history, extended along the SEE direction of Zhangbei earthquake epicenter. In this paper, the results of accurate location together with the corrected focal mechanism and the distribution of macroscopic intensity are used to discuss the relationship between Zhangbei earthquake and small scale focal rupture belt and intermediate scale weak earthquake belt before the main earthquake and large scale Zhangjiakou-Bohai strong earthquake belt.

Key words: Zhangbei earthquake, Focal rupture belt, Weak earthquake belt, Accurate location

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