三维复杂速度结构中深发地震的双差分定位

江国明; 赵大鹏; 张贵宾

三维复杂速度结构中深发地震的双差分定位

江国明^{1, 2,},
赵大鹏³,
张贵宾²

1.
中国地质大学地下信息探测技术与仪器教育部重点实验室, 北京 100083
2.
中国地质大学地球物理与信息技术学院, 北京 100083
3.
日本东北大学地球物理系, 仙台 980-8578

基金项目:

地下信息探测技术与仪器教育部重点实验室开放课题项目 GDL0806

“863”计划重大项目 2006AA06A202

“863”计划重大项目 2006AA06A203

详细信息

作者简介:
江国明（1979—），博士，主要从事天然地震层析成像方面的研究. E-mail：jiang_guoming@cugb.edu.cn

中图分类号: P631
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出版历程
- 收稿日期: 2009-06-10
- 刊出日期: 2009-11-25

Locating Deep Earthquakes in Complex 3-D Velocity Structure Using a Modified Double-Difference Location Method

1.
Key Laboratory of Geo-Detection of Ministry of Education, China University of Geosciences, Beijing 100083, China
2.
School of Geophysics and Information Technology, China University of Geosciences, Beijing 100083, China
3.
Department of Geophysics, Tohoku University, Sendai 980-8578, Japan

摘要

摘要: 双差分地震定位法采用了一维射线追踪法和直角坐标系, 不适合于复杂速度模型中的地震定位.本研究采用三维射线追踪技术和球坐标系改进了双差分定位法, 扩大了它的应用范围.为了检验新方法的可行性和准确性, 以日本海地区下方的深发地震为研究对象, 通过对比4种复杂速度模型中双差分定位结果, 分析速度结构对双差分定位的影响.结果表明, 改进后的双差分定位法受速度结构变化的影响较小, 而且当震源区的速度模型越接近真实速度结构时, 定位结果的精度越高, 这为利用深发地震研究地球深部构造奠定了基础.
- 地震 /
- 双差分定位 /
- 三维速度模型 /
- 日本海
Abstract: The double-difference (DD) earthquake location algorithm cannot be used to locate earthquakes in the complex 3-D velocity models because it adopts a 1-D ray tracing technique and the Cartesian coordinates. In this study, we have improved the DD location method by adopting a 3-D ray tracing method and the spherical coordinates, and thus extended the range of its applications. To testify the feasibility and the precision of this new method, we have relocated the deep earthquakes that occurred beneath the Japan Sea, and analyzed the effect of velocity models by comparing the relocation results in four kinds of 3-D velocity models. Our results show that the improved DD location method is less affected by the velocity model, and the closer the velocity structure in the hypocenter to the real one is, the higher the location precision is. The improved DD location technique would be very useful for studying the mantle structure by using data from deep earthquakes.
- earthquakes /
- double-difference location /
- 3-D velocity model /
- Japan Sea

HTML全文

图 1 球坐标系及震源扰动示意图

空心五角星表示某一深发震源的位置.纬度、经度和深度的单位分别为rad和km.θ表示震源的纬度

Fig. 1. A hypocenter perturbation in the spherical coordinates

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图 2 震中和地震观测台站位置分布

a.空心圆圈和黑色正方形分别代表78个深发地震的震中和816个地震观测台站; 等深线代表太平洋俯冲板块的上边界深度, km (Zhao et al., 1997); b.横坐标表示震源位置相对于板块上边界的距离, 纵坐标表示震源深度

Fig. 2. Distribution of epicenters and seismic stations used in this study

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图 3 J-B速度模型和三维速度模型纵剖面示意图

a.3条虚线自上而下分别代表康氏面、莫霍面和~410 km间断面; b.白色箭头表示太平洋板块俯冲的方向

Fig. 3. 1-D J-B velocity model and 3-D velocity model in the vertical direction

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图 4 阻尼系数折中曲线图

Fig. 4. Trade-off curve of determining the optimal damping parameter (arrow)

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图 5 定位次数与走时残差均方根之间的关系

Fig. 5. Number of earthquake relocation versus the root-mean-square (RMS) travel-time residual

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图 6 震源参数随定位次数的变化情况

左图和右图分别表示定位后的震源相对于E^new的发震时刻和空间位置的变化, 每个柱状图中, 每条“柱”的宽度分别为0.1 s (发震时刻变化量) 和1 km (震源位置变化量), 即横坐标, 而高度则表示在每个分段内的地震个数占总数的百分比, 即纵坐标.右侧的60%表示每个子图中纵坐标的最大值, 而最小值默认为0%

Fig. 6. Changes in hypocenter parameters with the iteration number of earthquake relocations

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图 7 在模型1中每个震源定位前后的对比

a.纬度方向; b.经度方向; c.深度方向; d.空间距离; e.发震时刻; 空心圆圈和五角星分别代表78个深发地震定位前和定位后的位置及发震时刻与E^new之间的偏差

Fig. 7. Comparison of each hypocenter parameter before and after relocation in Model 1

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图 8 不同速度模型中的定位结果对比柱状

CT和DD分别代表常规定位和双差分定位.左图和右图分别表示定位后的震源相对于E^new的发震时刻和空间位置的变化

Fig. 8. Histogram of relocated hypocenters in different velocity models

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表 1 不同速度模型中的速度扰动值

Table 1. Velocity perturbation (in %) in different velocity models (see text for details)

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