地震地质 ›› 2015, Vol. 37 ›› Issue (4): 966-981.DOI: 10.3969/j.issn.0253-4967.2015.04.003

• 地震预测方法专题 • 上一篇    下一篇

郯庐断裂带山东段震源参数及应力状态

王鹏, 郑建常, 刘希强, 徐长朋, 李霞   

  1. 山东省地震局, 济南 250102
  • 收稿日期:2015-10-29 出版日期:2015-12-20 发布日期:2016-01-28
  • 通讯作者: 郑建常
  • 作者简介:王鹏, 男, 1983年生, 2009年于中国地震局地球物理研究所获固体地球物理学专业硕士学位, 工程师, 现在主要从事地震活动性和数字地震学方面的研究, 电话: 0531-58622027, E-mail: wangpengeq@163.com。
  • 基金资助:

    地震科技星火计划(XH15026)和中国地震局震情跟踪青年课题项目(2015010106)共同资助。

research of source parameters and stress state in shandong segment of tanlu fault zone

WANG Peng, ZHENG Jian-chang, LIU Xi-qiang, XU Chang-peng, LI Xia   

  1. Earthquake Administration of Shandong Province, Jinan 250102, China
  • Received:2015-10-29 Online:2015-12-20 Published:2016-01-28

摘要:

利用山东数字地震台网记录到的2007—2014年的郯庐断裂带山东段ML≥1.0小震的震源机制解和视应力值, 借助三角形图解法和平均力轴张量法, 并结合b值等参数, 综合分析了该区近年的应力状态。研究结果表明: 郯庐断裂带山东段的主应力场方向为NEE-SWW向, 是受西太平洋板块的俯冲作用和印度板块与欧亚板块挤压作用的共同影响的结果; 震源错动类型以走滑型为主, 逆冲型和正断型次之; 通过视应力的时空演化图像看到郯庐断裂带山东段视应力值从2008年汶川地震之后呈现总体减弱的趋势, 而空间上视应力分布很不均匀, 高应力主要集中在安丘段和郯城—莒县段, 尤其是安丘段出现了小震级高视应力的情况, 同时安丘段的b值也显示同样的高应力, 低b值反映高应力, 低频度反映低应力释放, 表明安丘段可能正在积累较高的应力, 处于断层闭锁阶段。

关键词: 震源机制解, 视应力, 三角形图解法, 力轴张量法, 郯庐断裂带山东段, 应力状态

Abstract:

In recent years, there have been few researches and analysis published on the seismic activity and stress state in Shandong segment of Tanlu fault zone using digital seismological methods such as seismic apparent stress, focal mechanism solution and so on. In this paper, source parameters such as focal mechanism solutions and apparent stress are calculated using the waveform data of ML≥1 moderate-small earthquakes in Shandong segment of Tanlu fault zone recorded by Shandong digital seismic network since 2007. According to focal mechanism solutions, a statistical analysis is done on the focal dislocation types in the study area using triangle graphical method, and the results show that the faulting in this area is mainly of strike-slip mechanism, and there are less thrust and normal mechanism. Calculation with the mean stress tensor method illustrates that the direction of mean principle stress of Shandong segment of Tanlu fault zone is NEE-SWW, which is the result of the combined effect of the subduction of West Pacific plate and the extrusion of Indian plate to Eurasian plate; the small dip angle indicates that the mode of action of stress is nearly horizontal, and the direction of principal stress axis is nearly perpendicular to the Tanlu fault zone. Under the action of such compressive stress field, dislocation is not likely to occur and the stress accumulation is enhanced on both sides of the fault. The apparent stress is calculated using the source spectral parameters method. Apparent stress has positive correlation with the magnitude and increases with the increased magnitude. So we get apparent stress difference by subtracting the empirical fitting value from the apparent stress. By removing the impact of magnitude, and according to the temporal-spatial evolution image of apparent stress difference, we found that the apparent stress in Shandong segment of Tanlu fault zone generally has a trend of decrease starting from the Wenchuan earthquake in 2008, and the spatial distribution of apparent stress in the region is very uneven. Combined with the spatial distribution of b values, the result shows that high stress is mainly located in Anqiu segment and Tancheng-Juxian segment, especially in Anqiu segment where small magnitude earthquakes appeared accompanying with the high stress. Low b-value means high stress and low frequency means low stress release, which indicates that Anqiu segment might accumulate higher stress and is at the fault locking stage. The research will provide new data for better understanding the present active feature and stress state of the Shandong segment of the Tanlu fault zone.

Key words: focal mechanism solutions, apparent stress, triangle graphical method, average stress tensor, Shandong segment of Tanlu fault zone, stress state

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