王少坡^1,2,,
罗纲^3,4,,,
史亚男⁵,
解孟雨⁶,
魏东平^1,2
1. 中国科学院计算地球动力学重点实验室, 北京 100049
2. 中国科学院大学地球与行星科学学院, 北京 100049
3. 武汉大学测绘学院, 武汉 430079
4. 武汉大学地球空间环境与大地测量教育部重点实验室, 武汉 430079
5. 中国石油大学(北京)地球科学学院, 北京 102249
6. 中国地震台网中心, 北京 100045

基金项目: 国家自然科学基金项目（41474086，41874115）和中国科学院于国家外国专家局创新团队国际合作伙伴计划项目（KZZD-EW-TZ-19）资助


详细信息

作者简介: 王少坡, 男, 1991年生, 博士研究生, 主要从事板块应力场及数值模拟研究.E-mail:wangshaopo14@mails.ucas.ac.cn

通讯作者: 罗纲, 男, 1977年生, 教授, 主要从事地球动力学数值模拟研究.E-mail:gluo@sgg.whu.edu.cn

中图分类号: P313

收稿日期:2019-06-13
修回日期:2020-01-08
上线日期:2020-04-05

Seismic b-value and stress field characteristics in the eastern subduction zone of Okhotsk micro-plate

WANG ShaoPo^1,2,,
LUO Gang^3,4,,,
SHI YaNan⁵,
XIE MengYu⁶,
WEI DongPing^1,2
1. Key Laboratory of Computational Geodynamics, Chinese Academy of Sciences, Beijing 100049, China
2. College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
3. School of Geodesy and Geomantic, Wuhan University, Wuhan 430079, China
4. Key Laboratory of Geospace Environment and Geodesy, Ministry of Education, Wuhan University, Wuhan 430079, China
5. College of Geosciences, China University of Petroleum, Beijing 102249, China
6. China Earthquake Networks Center, Beijing 100045, China


More Information

Corresponding author: LUO Gang,E-mail:gluo@sgg.whu.edu.cn

MSC: P313

--> Received Date: 13 June 2019
Revised Date: 08 January 2020
Available Online: 05 April 2020


摘要
摘要:古登堡-里克特震级-频度关系式中的b值与剪切应力（或偏应力）大小被认为存在着负相关的关系，因此b值常被用作估算区域应力大小的指标.本文利用1970-2018年鄂霍次克微板块东部俯冲带区域的地震目录，使用最大似然法对该区域的b值进行空间扫描，得到了该区域沿海沟走向不同区域及不同深度的b值分布，进而调查与分析其应力状态及地球动力学特征.结果显示不同俯冲区域的b值分布具有4个共同特征：1）地壳范围内的高b值特征，表明其剪切应力较低；2）俯冲板片与上覆板块耦合强烈的区域b值较低，表明该位置剪切应力较高；3）弧前区域b值较高，表明其剪切应力较低；4）海沟东侧的太平洋板块与软流层接触的区域b值较高，表明该位置剪切应力较低.上述这些b值分布结果及其剪切应力分布，是能够与俯冲带的地球动力学结构与特征相关联的.我们也发现在水平方向上，在浅部区域（0~40 km深度范围），勘察加地区的剪切应力相对于北日本地区和千岛地区更低；在更深的区域（40~80 km深度范围），千岛地区弧前区域的剪切应力较低.由本文俯冲带区域力平衡估算得到的俯冲接触面上的剪应力大小能够解释鄂霍次克微板块东部俯冲带不同接触界面上的b值大小及其分布差异.本文得到的日本海沟附近区域平均b值在大地震前后的时间变化揭示了该区域震间、震前和震后的应力演化过程.
关键词: 震级-频度/
b值/
鄂霍次克微板块/
俯冲带/
应力场

Abstract:The b value in the Gutenberg-Richter relation is believed to be negatively correlated with the magnitude of shear stress (or deviatoric stress). Hence b value is often used as an index to estimate the level of regional stress. Based on the seismic catalog data in the eastern subduction zone of Okhotsk micro-plate from 1970 to 2018, we used the maximum likelihood method to calculate the regional b values, and obtained the distributions of b values in different regions along the trench strike and different depths, We used the b-value map to investigate and analyze the regional stress states and geodynamic characteristics. The results show four common characteristics:1) a higher b value exists in the crust indicating a lower shear stress here; 2) the locations where the subducting and overriding plates are strongly coupled have a lower b value, indicating a higher shear stress here; 3) the b value is higher in the forearc, reflecting the lower shear stress in this region; 4) on the east side of the trench, the contacting regions between the lithosphere of Pacific plate and its underlying asthenosphere have a higher b-value, suggesting a lower shear stress at these locations. The distribution of shear stress estimated from the distribution of b value in the subduction zone can be explained by the regional geodynamic structures and characteristics. We also find that in the horizontal direction, the shear stress in Kamchatka region is smaller than that in the northern Japan region and the Kuril region within the shallow region (0~40 km); in the deeper region (40~80 km), the shear stress in the forearc of the Kuril region is relatively small. The shear stress on the subduction contact surface calculated from the force quilibrium in this study can explain the b-value magnitude and its distribution at the contact surface in different regions of the eastern subduction zone of the Okhotsk micro-plate. The temporal variation of our calculated average b values near the Japan Trench before and after the 2011 M9.1 Tohoku-Oki earthquake can explain the stress evolution process during interseismic, preseismic and postseismic phases.
Key words:Magnitude-frequency/
b-value/
Okhotsk micro-plate/
Subduction zone/
Stress field



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