地震地质 ›› 2018, Vol. 40 ›› Issue (3): 523-538.DOI: 10.3969/j.issn.0253-4967.2018.03.002

• 研究论文 • 上一篇    下一篇

重庆荣昌地区注水诱发地震的时空分布特征

王志伟1, 王小龙2, 马胜利1, 雷兴林1,3, 刘培洵1   

  1. 1. 中国地震局地质研究所, 地震动力学国家重点实验室, 北京 100029;
    2. 重庆市地震局, 重庆 401147;
    3. 日本产业技术综合研究所, 筑波 305-8567
  • 收稿日期:2017-06-29 修回日期:2018-02-02 出版日期:2018-06-20 发布日期:2018-07-21
  • 作者简介:王志伟,男,1990年出生,2017年于中国地震局地质研究所获固体地球物理专业硕士学位,从事构造物理学研究,E-mail:wangzw90th@163.com。
  • 基金资助:
    地震科技近期重点突破方向专项(JH-16-50)资助

DETAILED TEMPORAL-SPATIAL DISTRIBUTION OF INDUCED EARTHQUAKES BY WATER INJECTION IN RONGCHANG, CHONGQING

WANG Zhi-wei1, WANG Xiao-long2, MA Sheng-li1, LEI Xing-lin1,3, LIU Pei-xun1   

  1. 1. State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China;
    2. Chongqing Earthquake Administration, Chongqing 401147, China;
    3. Geological Survey of Japan, AIST, Tsukuba, 305-8567, Japan
  • Received:2017-06-29 Revised:2018-02-02 Online:2018-06-20 Published:2018-07-21

摘要: 基于区域固定地震台站和6套流动加密台站的观测资料,对重庆荣昌地区2008年10月—2011年7月期间的地震活动性进行了分析。在双差定位的基础上,采用匹配定位方法(M&L)对微小地震进行检测与定位;采用CAP(Cut and Paste)方法,反演获得了ML≥3.5地震的震源机制解。在此基础上,分析地震活动的时空分布特征、震源特征及其与地质构造的关系,并讨论了2010年9月10日ML5.1地震前后的小震活动特征。通过匹配定位方法共检测到3 354次微地震事件,约为中国地震台网中心地震目录的5倍,震级集中于ML-1.0~1.0之间,震源深度大部分处于2~4km范围内;震级-频次统计分析表明,地震目录更加完整,震级下限从ML1.0降低到ML0.3。地震活动主要集中在几条隐伏断层附近,并具有从注水井向外扩展的特征;9次ML≥3.5地震震源机制解均为逆断层型,与该区区域应力场协调,并与已有断层性质一致,表明地震活动与注水活动导致已有断层的再活动有关。而发震断层方向、倾角及滑动角散布范围较大表明流体孔隙压力增加对局部应力场有较大影响,使不同产状的断层活化。ML5.1地震发生之前,地震活动首先表现为时间上丛集,空间上分布于大部分发震断层段上,随后出现了约3月的平静期,这与基于实验结果提出的"蠕滑-均匀化"机制一致,可能是断层亚失稳的一种表现形式,但这种解释需要进一步的工作论证。

关键词: 地震定位, 微地震检测, 震源机制, 诱发地震, 荣昌

Abstract: Based on the seismic data collected from regional permanent stations and 6 temporal stations, we analyzed the seismic activity from October 2008 to July 2011 in Rongchang area. On the basis of HypoDD relocated results, we used Match&Locate method to detect and located the micro-earthquakes. We obtained the focal mechanism solutions of some earthquakes with ML ≥ 3.5 by using CAP method. Then we analyzed the temporal-spatial distribution of earthquakes and discussed the characteristics of micro-seismicity before the ML5.1 earthquake occurring on September 10, 2010. We totally detected 3 354 micro-earthquake events, which are nearly 5 times of the earthquakes in the seismic catalog issued by China Earthquake Networks Center. The magnitude of the detected events is mostly from ML-1 to 1, and the focal depth is from 2 to 4km. The magnitude-frequency analysis shows that the catalog completeness is obviously improved after adding the detected earthquakes, with the lowest magnitude decreasing from ML1.0 to 0.3. The earthquakes hypocenters are mainly clustered along faults or buried faults and in a dominant depth range consistent with the depth of injection wells, and also show a tendency of lateral extension from injection wells. The focal mechanism solutions of 9 earthquakes of ML ≥ 3.5 presented reverse faulting, as the same as the preexisting faults, indicating that earthquakes were surely related to reactivation of the faults. The strike, dip and rate of the causative faults separated in wide ranges, which indicates not only obvious changes in structure and strike of preexisting faults but also the effect of increasing pore pressure on the local stress field. Before the ML5.1 earthquake on September 10 of 2010, seismicity firstly showed clustering in time and covered the most part of the seismogenic fault in space. Then an obvious seismic quiescence occurred and lasted about 3 months. The phenomenon is consistent with the mechanism of creep sliding and resistance-uniformization along the fault zone, suggested on the basis of laboratory experiments, and it may be one of patterns of sub-instability along fault zone. However, such explanation needs to be further confirmed.

Key words: earthquake relocation, microearthquake detection, focal mechanism, induced earthquake, Rongchang

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