时钟不准情形地震精确定位研究 以2011年1月19日安庆地震序列为例

包丰; 倪四道; 赵建和; 谢军; 陈伟文; 曾祥方

doi:10.3969/j.issn.0253-3782.2013.02.003

时钟不准情形地震精确定位研究以2011年1月19日安庆地震序列为例

包丰^1,2,
倪四道^2, ,,
赵建和³,
谢军¹,
陈伟文¹,
曾祥方¹

1.
中国合肥 230026 中国科学技术大学地球和空间科学学院蒙城地球物理国家野外科学观测研究站
2.
中国武汉 430077 中国科学院测量与地球物理研究所大地测量与地球动力学国家重点实验室
3.
中国合肥 230031 安徽省地震局

基金项目: 国家自然科学基金(NSFC40821160549， NSFC41074032)、中国科学院知识创新工程(KZCX2-YW-116-01)和地震行业基金(200808078)共同资助.

详细信息

通讯作者:
倪四道,E-mail:sdni@whigg.ac.cn

中图分类号: P315.3
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出版历程
- 收稿日期: 2012-02-14
- 修回日期: 2012-08-02
- 发布日期: 2013-02-28

Anqing earthquake; double-difference earthquake location algorithm; instrumental clock error; sPL; S-P arrival time difference

1.
Mengcheng National Geophysical Observatory, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China
2.
State Key Laboratory of Geodesy and Earth’s Dynamics, Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan 430077, China
3.
Earthquake Administration of Anhui Province, Hefei 230031, China

摘要

摘要: 通过余震序列的精确定位可以较为准确地刻画主震破裂区的时空变化规律. 为了减小仪器时钟误差对地震定位精度的影响，本文基于2011年1月19日安庆地震流动台站的S-P到时差，通过主事件和双差地震定位法得到较为准确的主震位置和余震序列时空分布，并评估了仪器时钟误差；又通过对sPL近震深度震相的分析，得到了余震序列较为可靠的深度分布. 结果表明，安庆地震发生在宿松—枞阳断裂带附近，余震序列大体近水平分布在5 km深度，呈长1.5 km、宽1 km、高0.3 km的薄板状展布；从时空分布来看，随着时间的推移余震序列似乎有往北东方向扩展的趋势. 研究表明，基于S-P到时差的定位方法可以有效消除时钟不准确带来的影响，为中小地震和余震序列活动性的研究提供可靠的定位结果.
- 安庆地震 /
- 双差地震定位法 /
- 时钟误差 /
- sPL深度震相 /
- S-P到时差
Abstract: Accurate locations of aftershocks are helpful for understanding rupture process of the main shock. In order to suppress the impact of instrumental clock error, the arrival-time differences between S and P by the temporary seismic array installed after the 19 January 2011 Anqing earthquake were used to reconstruct the travel-time data of P and S and more accurate locations of the main shock and aftershocks were obtained by using master event and double-difference earthquake location algorithm; an algorithm was proposed to estimate the range of clock error; more reliable depth distribution of the aftershocks was also obtained via analysing sPL, a depth phase at near epicentral distance. The result shows that the Anqing earthquake occurred near Susong--Zongyang fault zone, and the aftershocks concentrated nearly horizontally in the depth range of about 5 km, spreading in the shape of a thin slab around 1.5 km long, 1.0 km wide and 0.3 km thick; the sequence tended to spread northeastward as time went on. The study suggests that earthquake location based on S--P arrival-time difference method can effectively eliminate the influence of clock error, providing reliable results for moderate, minor earthquakes and aftershocks.
- Anqing earthquake /
- double-difference earthquake location algorithm /
- instrumental clock error /
- sPL /
- S-P arrival time difference

HTML全文

图 1 绝对到时初始定位和双差法重新定位的结果 (a) A-A′剖面深度分布图； (b) B-B′剖面深度分布图； (c) 余震序列的震中分布图.空心圆为绝对到时初定的余震序列，实心圆为双差法重新定位的余震序列，实三角为流动台站的分布，实心星号为CENC速报的主震位置 ①，空心星号为CENC正式的主震位置 ②

Figure 1. Location by using absolute arrival time earthquake location method and double-difference earthquake location method (a) Depth distribution along A-A′; (b) Depth distribution along B-B′; (c) Epicenter distribution of aftershocks. Open circles represent aftershocks located by absolute arrival time earthquake location method,solid dots indicate aftershocks relocated by double-difference earthquake location method,solid triangles denote temporary stations used,solid star shows location of the main shock preliminarily reported by CENC,and open star shows final location of the main shock by CENC

下载: 全尺寸图片幻灯片

图 2 台阵整体时钟误差E的时间演化图．黑点表示余震事件

Figure 2. Variation of array system clock error with time. Black dots indicate aftershocks

下载: 全尺寸图片幻灯片

图 3 安庆地震序列重新定位结果 (a) 主事件相对定位方法对主震重新定位; (b) A-A′剖面深度分布； (c) B-B′剖面深度分布； (d) 安庆地震序列重新定位的震中分布．图(a)中，三角形为相对定位所用台站的分布，星号为主震相对定位的最终结果；图(b)—(d)中，空心圆为初定的余震序列，绿色实心圆为2011年1月21日18时之前双差重新定位的余震序列,蓝色倒三角为1月21日18时—25日双差重新定位的余震序列，正三角为流动台分布，实心星号为CENC速报的主震位置①，空心星号为CENC正式的主震位置^① ，红色方框为主事件相对定位后主震的位置

Figure 3. Result of the relocated Anqing earthquake sequence (a) Relocation of the main shock by using master event relative location method; (b) Depth distribution along A-A′ ; (c) Depth distribution along B-B′ ; (d) Epicenter distribution of the relocated Anqing earthquake sequence. In figure (a),triangles are permanent stations used,and star represents the main shock; In figures (b),(c) and (d),open circles represent aftershocks located primarily by using absolute arrival time earthquake location method,green solid circles represent aftershocks relocated by using double-difference earthquake location method before 18:00 on Jan. 21,2011 blue inverted triangles are aftershocks relocated by using double-difference earthquake location method from 18:00 on Jan. 21 to Jan. 25,regular triangles denote temporary stations,solid and open stars denote the same as in Fig.1,red square represents the main shock relocated by using master event relative location method

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图 4 sPL震相识别(以M_L2.0以上余震为例)．图中 Z为垂向分向，R为径向分向，T为切向分向． sPL在径向上强，且比较不尖锐

Figure 4. Identification of sPL phase,with aftershocks of M_L≥2.0 as example. Z is vertical component,R is radial component,and T is tangential component. sPL is strong and lumpy on the radial component as compared to P or S wave

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图 5 通过sPL震相估计地震序列的深度 (a) M_L1.0以上余震的实测sPL-P到时差演变； (b) 不同震源深度下 sPL-P的理论到时差与震中距的关系

Figure 5. Determination of focal depth by using sPL (a) Measured sPL-P arrival-time differences of M_L≥1.0 aftershocks; (b) Relation between theoretical sPL-P arrival-time difference and epicentral distance at different focal depths

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表 1 流动台阵记录的1.5级以上余震（引自CEDC统一目录^③）

Table 1 M≥1.5 aftershocks recorded by the temporary seismic array (from uniform catalog of CEDC)

下载: 导出CSV

表 2 定位使用的一维地壳速度模型

Table 2 1D crustal velocity model

下载: 导出CSV

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