地球物理学进展 ›› 2019, Vol. 34 ›› Issue (5): 1743-1749.doi: 10.6038/pg2019CC0292

• 固体地球物理及空间物理学(大气、行星、地球动力学、重磁电及地震学、地热学) • 上一篇    下一篇

小震震源机制解反演芦山断层倾角

段虎荣1,2,陈胜雷1,2,李闰1,2,闫全超1,2   

  1. 1. 地理信息工程国家重点实验室,西安 710054
    2. 西安科技大学测绘科学与技术学院,西安 710054
  • 收稿日期:2018-11-12 修回日期:2019-07-05 出版日期:2019-10-28 发布日期:2019-10-28
  • 作者简介:段虎荣,男,1979年生,博士,副教授,研究方向为固体地球物理、大地测量反演.(E-mail: duanhurong@126.com)
  • 基金资助:
    地理信息工程国家重点实验室开放基金(SKLGIE2017-M-3-3);国家自然科学基金(41304013)

Inversion of Lushan fault dip angle by the focal mechanism solution of small earthquakes

DUAN Hu-rong1,2,CHEN Sheng-lei1,2,LI Run1,2,YAN Quan-chao1,2   

  1. 1. State Key Laboratory of Geo-information Engineering, Xi’an 710054, China;
    2. College of Geomatics,Xi’an University of Science and Technology, Xi’an 710054, China;
  • Received:2018-11-12 Revised:2019-07-05 Online:2019-10-28 Published:2019-10-28

摘要:

断层的几何形态控制着上盘地层的变形特征,断层运动模型的地球物理与大地测量反演依赖于断层几何参数的给定,而在几何参数中,断层倾角参数对反演结果的影响最为显著.为探索芦山地震与地表同震位移的关系,本文以分布在芦山地震断层周围的地震震源机制解为起算数据,运用地震矩张量理论反演得到芦山地震断层面倾角的平均值为42°.为了进一步精细化断层的几何结构,根据震源机制解分布的差异特征,沿断层走向与断层面宽度方向将其划分成为3×3断层模型.经计算发现断层南段、中段、北段的倾角均随深度增加而减小,在同一深度上,断层中段的倾角小于南段和北段的倾角,在8~12 km深度时,从南到北断层面的倾角分别为66.29°、51.10°、55.22°,在12~16 km深度时,从南到北断层面的倾角分别为44.67°、34.95°、43.40°,在16~20 km深度时,从南到北断层面的倾角分别为 42.00°、29.93°、31.11°.分别采用单一平面模型(1×1)与分段分层模型(3×3)计算地表同震位移,发现两个模型的计算结果具有较好的一致性.相对单一平面模型 (1×1) 而言,分段分层模型(3×3)的计算结果与GPS观测值符合性更好,由此表明本文给出的细化后断层更接近断层的真实形态.

关键词: 芦山地震, 震源机制解, 地震矩张量, 断层倾角

Abstract:

The geometric shape of the fault controls the deformation characteristics of the upper plate. Geophysical and geodetic inversion of fault motion model depends on the determination of fault geometric parameters. Among the geometric parameters, fault dip parameters have the most significant impact on the inversion results. In order to explore the relationship between Lushan earthquake and ground displacement, the focal mechanism solutions around Lushan earthquake faults are used as the starting data, and the average dip of fault plane of Lushan earthquake is 42 degrees by inversion of seismic moment tensor theory. In order to further refine the fault geometry, Lushan fault is divided into a 3×3 fault model along the fault strike and fault width direction, according to the difference characteristics of the focal mechanism solution distribution. It is found that the dip angles of the southern, middle and northern sections of the fault decrease with increasing depth. At the same depth, the dip angle of the middle fault is smaller than the dip angle of the southern and northern sections. At 8~12 km depth, the dip angles from the south to the north fault are 66.29°, 51.10°, and 55.22°, respectively. At 12~16 km depth, the dip angles from the south to the north fault plane are 44.67°, 34.95°, and 43.40°, respectively. At a depth of 16~20 km, the dip angles from the south to the north fault plane are 42.00°, 29.93°, 31.11°, respectively. We calculated the surface co seismic displacement using a single plane model (1×1) and a piecewise layered model (3×3), respectively, and found that the calculation results of the two models are in good agreement. For the single-plane model (1×1), the calculated results of the segmented layered model (3×3) are in better agreement with the GPS observations, which indicates that the refined faults given in this paper may be closer to the actual shape of the fault.

Key words: Lushan earthquake, Focal mechanism solution, Seismic moment tensor, Fault dip angle

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