广西苍梧<em> M</em><sub>S</sub>5.4地震震源深度

引用本文

赵韬, 储日升, 倪四道, 王莹, 周勇, 曾祥方. 广西苍梧 M_S5.4地震震源深度 [J]. 地震地质, 2019,41(3): 619-632.
ZHAO Tao, CHU Ri-sheng, NI Si-dao, WANG Ying, ZHOU Yong, ZENG Xiang-fang. STUDY ON FOCAL DEPTH OF THE M_S5.4 CANGWU EARTHQUAKE IN GUANGXI [J]. SEISMOLOGY AND GEOLOGY, 2019,41(3): 619-632. 复制到剪切板

DOI:10.3969/j.issn.0253-4967.2019.03.006
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广西苍梧 M_S5.4地震震源深度

赵韬¹⁾, 储日升^2),^*, 倪四道²⁾, 王莹¹⁾, 周勇³⁾, 曾祥方²⁾

1)陕西省地震局, 西安 710068

2)中国科学院测量与地球物理研究所, 武汉 430077

3)南方科技大学, 深圳 518055

*通讯作者: 储日升, 男, 博士, 主要从事地震学研究, E-mail: chur@whigg.ac.cn。

〔作者简介〕赵韬, 男, 1989年生, 2017年于中国科学技术大学地球与空间科学学院获地质工程专业硕士学位, 工程师, 主要从事地震监测数字地震资料分析处理工作以及震源机制解快速产出方面的研究, 电话: 15929933676, E-mail: zhaotaowy@163.com。

收稿日期: 2017-11-01

基金项目: 中国地震局监测预报司测震台网青年骨干培养专项(20170623)和陕西省地震局启航与创新基金(201603)共同资助

摘要

2016年7月31日广西苍梧发生的 M_S5.4地震是广西测震台网自建立以来所记录到的区域内最强地震。不同机构对于此次事件给出的震源深度结果相差较大, 例如美国地质调查局(USGS)地震目录显示其深度为24.5km, 而全球矩心矩张量研究中心(Global CMT)测定的深度为15.6km。为了进一步准确确定广西苍梧地震的震源深度, 文中基于区域速度模型, 首先利用走时残差全局搜索法初步得到此次地震震源深度及误差范围, 然后使用CAP(Cut and Paste)方法反演苍梧地震震源机制, 在此基础上, 采用Rayleigh波振幅谱和sPL震相方法进一步约束了此次地震的震源深度。研究结果显示: 利用走时残差全局搜索法获得的苍梧 M_S5.4地震震源深度及误差范围为(13±3)km, CAP方法反演的深度为10km, Rayleigh波振幅谱测定深度结果为9~10km, sPL震相测定深度结果为10km, 最终确定广西苍梧 M_S5.4地震的震源深度约10km, 这表明此次事件仍为发生于上地壳的地震。本文结果同时表明, USGS地震目录在研究区的震源深度精度有待提高。

关键词: 震源深度; sPL震相; Rayleigh波振幅谱; 广西苍梧 M_S5.4地震

中图分类号:P315.63 文献标志码:A 文章编号:0253-4967(2019)03-0619-14

STUDY ON FOCAL DEPTH OF THE M_S5.4 CANGWU EARTHQUAKE IN GUANGXI

ZHAO Tao¹⁾, CHU Ri-sheng²⁾, NI Si-dao²⁾, WANG Ying¹⁾, ZHOU Yong³⁾, ZENG Xiang-fang²⁾

1)Earthquake Agency of Shaanxi Province, Xi'an 710068, China

2)Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan 430077, China

3)Department of Earth and Space Sciences, School of Science, Southern University of Science and Technology, Shenzhen 518055, China

Abstract

On July 31th, 2016, a magnitude 5.4 earthquake struck Cangwu Country, Guangxi Zhuang Autonomous Region, it was the largest earthquake recorded by Guangxi Seismological Network since it set up. The number of people affected by the earthquake had reached 20 000, and the direct economic losses caused by the earthquake were nearly 100 million Yuan.
After the earthquake, USGS provided a global earthquake catalog showing that the focal depth of Cangwu earthquake was about 24.5km. However, the result given by the Global Centroid Moment Tensor showed the focal depth of this earthquake was 15.6km. However, the result obtained by Xu Xiaofeng et al. using CAP method was 5.1km. It was clear that the focal depths of Cangwu earthquake given by different institutions were quite different from each other. However, accurate focal depth of the earthquake has important significance for exploring the tectonic mechanism near the epicenter, so it is necessary to further determine the more accurate depth of the Cangwu earthquake.
In order to further accurately determine the focal depth of Cangwu earthquake, we used the global search method for travel-time residual to calculate the focal depth of this earthquake and its error range, based on the regional velocity model, which is a one-dimensional velocity model of the Xianggui tectonic belt produced by the comprehensive geophysical profile. Then, we inverted the focal mechanism of this earthquake with the CAP method. Based on this, the focal depth of Cangwu M_S5.4 earthquake was further determined by the method of the Rayleigh surface wave amplitude spectrum and the sPL phase, respectively.
Computed results reveal that the focal depth of this earthquake and its error range from the travel-time residual global search method is about(13±3)km, the focal depth inverted by CAP method is about 10km, the focal depth from sPL phase is about 10km, and the focal depth from Rayleigh surface wave amplitude spectrum is about 9~10km. Finally, we confirmed that the focal depth of Cangwu M_S5.4 earthquake is about 10km, which indicates that this earthquake still occurred in the upper crust. In the case of low network density, the sPL phase and Rayleigh wave amplitude spectrum recorded by only 1 or 2 broadband stations could be used to obtain more accurate focal depth.
The focal depth's accuracy of Cangwu M_S5.4 earthquake in the USGS global earthquake catalog has yet to be improved. In the future, we should consider the error of the source parameters when using the USGS global earthquake catalog for other related research.

Keyword: focal depth; sPL phase; Rayleigh wave amplitude spectrum; Guangxi Cangwu M_S5.4 earthquake

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0 引言

2016年7月31日发生于广西苍梧的M_S5.4地震是广西测震台网建立以来所记录到的区域最大地震, 地震受灾人数达2万多人, 造成的直接经济损失近1亿元(周军学等, 2017)。此次地震发生在江南造山带与华夏地块的过渡区, 打破了东南沿海地震带5级地震长达16a的平静, 可能对东南沿海地震带乃至大陆东部地区6级地震活动具有指示意义。地震震中位于NNE向的贺街-夏郢断裂带附近, 该断裂带的信息在历史资料中无详细记录。地震发生后, 美国地质调查局(USGS)公布的全球正式地震目录显示本次地震的震源深度为24.5km, 全球矩心矩张量研究中心(Global CMT)给出的震源深度为15.6km, 而徐晓枫等(2017)利用CAP(Cut and Paste)方法反演得到的震源深度为5.1km(表1)。获得此次地震准确的震源深度对于探明贺街-夏郢断裂带附近的构造机制有着重要意义, 而各机构给出的震源深度存在显著差异, 因此需要进一步测定更加精确的结果。

表1 广西苍梧5.4级地震震源参数 Table1 Source parameters of Guangxi Cangwu M_S5.4 earthquake

震源深度是研究地下介质构造、孕震环境及地震成因的重要基础(陈立军, 2000; 张国民等, 2002; 石耀霖等, 2003; 朱艾斓等, 2008)。准确的震源深度是研究地震烈度的重要参数, 在震级相同的情况下, 震源深度越小则地表烈度越大, 地震带来的人员和财产损失往往也会增大(Gupta et al., 2013; 曹均锋等, 2015)。2012年9月7日11时19分, 云南彝良发生了5.7级地震, 1h后, 又发生1次5.6级地震, 2次地震共导致81人死亡, 约18万户、 74.4万余人受灾, 并给当地居民造成了重大的财产损失(冯新科等, 2015)。吕坚等(2013)通过深入研究发现, 这2次地震的震源深度均为6km左右, 震源深度较浅是此次彝良地震造成重大财产损失、惨重人员伤亡的重要原因之一。而2016年1月2日发生在黑龙江林口县的M6.4地震, 其震源深度达580km, 当地居民甚至没有感觉到地震的发生。

震源深度也被广泛用于约束地震成因。随着人类社会的发展, 确定油气开采及地下注水与地震之间的关系, 对于社会的发展和科学研究而言意义重大。通过可靠的震中经纬度和精确的地震震源深度可以判断地震震群震源是否与地下注水井的位置具有对应性, 由此可判断地震震群是否由地下注水诱发(王小龙等, 2012; Ellsworth, 2013; Kim, 2013)。此外, 地震事件的全矩张量解中非双力偶成分所占比例也是鉴别地震成因的重要参数(刘俊清等, 2017)。

然而, 仅通过区域台网数据较难准确测定震源深度。虽然测震台站可在水平方向上较好地包围震中, 但是在垂向(深度方向)上测震台站仅位于震源上侧, 导致角度分布具有局限性(罗艳等, 2013; 郑勇等, 2017)。目前, 很多测震台网使用的震源参数测定方法主要基于Pg、 Sg震相的到时, 这种方法一般在震中距不超过1.4倍震源深度的范围内且有台站分布的情况下才能够获得精确的震源深度(Mori, 1991)。

如今, 越来越多的学者开始使用对深度敏感的震相来测定震源深度, 对于近震, 常使用sPg、 sPn、 sPmP和sPL震相来测定震源深度。sPg震相在震中距为60~100km的台站可被观测到(Langston, 1987; 吕坚等, 2012); sPmP震相在震中距为200~300km的区域才可记录到发育较好的波形(Bock et al., 1996; Ma, 2010); 而sPn震相能量较弱, 一般只有在中强地震时, 在震中距300km左右的区域才有可能被观测到(King, 1979; Zonno et al., 1984; Saikia, 2000); sPL震相为近震震相, 通常在震中距30~50km内可以被观测到(崇加军等, 2010)。此外, 还可以使用地震波形记录特征, 如Rayleigh波振幅谱(Aki et al., 2002)、 Rayleigh波与体波振幅比(罗艳等, 2010; 李志伟等, 2015)、 Love波频谱^①(①Pitarka A, Helmberger D V, 2009, Analysis and simulation of 3D scattering due to heterogeneous crustal structure and surface topography on regional phases; magnitude and discrimination, Report, AFRL-RV-HA-TR-2009-1058。)以及CAP和Rayleigh波振幅谱联合测定震源深度(Jia et al., 2017)。

本文以广西苍梧M_S5.4地震数字波形为基础, 基于区域速度模型, 首先利用走时残差全局搜索法初步得到苍梧M_S5.4地震的震源深度及误差范围, 然后使用CAP方法反演其震源机制, 在此基础上, 利用Rayleigh波振幅谱和sPL震相进一步测定苍梧地震的震源深度。

1 速度模型与方法

1.1 速度模型

本文使用的速度模型为郑圻森等(2003)使用地球物理综合剖面产出的湘桂构造带的一维速度模型。该模型主要通过人工地震测深剖面资料, 并参考重力反演和地震面波频散反演数据等得到, 是一个3层一维速度模型, 也是目前广西苍梧地区较为合理且使用较广的速度模型(表2)。

表2 广西苍梧地区速度模型 Table2 The crustal velocity model for Cangwu region

1.2 走时残差全局搜索法

朱元清等(1990)研究表明, Pn、 Pg震相走时差对震源深度有较高的敏感度, 在已知震中位置和地壳速度模型的情况下, 可以采用全局搜索法计算每个台站的Pn、 Pg理论走时差, 然后对比理论走时差和实际观测走时差以确定震源深度。

考虑到地震定位存在误差, 以中国地震台网中心编制的地震目录震中位置为搜索参考点, 将搜索空间划分为52 111个网格点, 其中水平方向的搜索范围为± 0.2° , 搜索间隔为0.01° , 深度的搜索范围为0~30km, 搜索间隔为1km。单个网格点的走时残差定义如下:

$T_{res} = \frac{1}{MN} \overset{M}{\sum_{i}} \overset{N}{\sum_{j}} | (P n_{j}^{*} - P g_{i}^{*}) - (P n_{j}^{^} - P g_{i}^{^}) | (1)$

式(1)中, 上角标 “ * ” 表示理论计算走时, 上角标 “ ^” 表示人工提取的走时。 N为Pn震相数, M为Pg震相数, 取最小走时残差点作为最优深度。当使用震中距≤ 60km的Pg震相和震中距160~300km的Pn震相时, 通过该方法得到的深度误差≤ 3km(宋秀青等, 2014)。

1.3 CAP方法

CAP方法(Zhao et al., 1994; Zhu et al., 1996)是一种使用体波和面波联合反演的方法。该方法把原始波形分为Pnl和Snl 2部分, 采用频率-波数方法(F-K)(Zhu et al., 2002)计算台站的格林函数, 利用格林函数得到合成地震图后, 为Pnl和Snl 波形分别赋予不同的权重, 通过格点搜索方法在空间搜索、拟合、反演地震事件的最佳震源机制。该方法分别对体波、面波进行拟合, 由此减小了深度模型及地壳横向不均匀性对反演结果的影响。

1.4 sPL震相法

sPL震相是从震源出发的上行SV波临界入射到地表后转换形成的P波, 主要沿着地表传播(图1)。其初动可能较直达S波更加尖锐, 能量在径向最强, 垂直向次之, 切向则最弱。但是随着震中距的增加衰减加快, sPL震相法基于sPL和Pg波的到时差计算深度, 因此减小了震中位置对深度结果的影响。同时, 由于sPL震相法使用近震数据(震中距30~50km), 在此震中距范围内其它反射震相(如PmP、 Pn等)还未出射, 故不易误认(崇加军等, 2010)。图 2为一维简单速度模型下震中距为40km的台站的理论震动图。从图中可以看出, sPL与Pg的走时差随着深度的变化呈线性变化, 前者能量在径向最强, 垂直向次之, 切向最弱。

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	图 1 均匀半空间下sPL震相传播路径示意图Fig. 1 Ray path of sPL and P wave for the model of half space.

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	图 2 sPL震相到时(红色虚线)随深度变化图Fig. 2 Three-component sPL phases arrival time for different focal depths.

1.5 Rayleigh波振幅谱法

Rayleigh波可以表示为

式中, $I_{1} = \overset{0}{\int_{- \infty}} ρ (z) [r_{1}^{2} (z) + r_{3}^{2} (z)] d z$ , c为相速度, U为群速度, k为对应波数, φ 为方位角, h为震源深度, r为震中距, r₁、 r₂和r₃为方程的正模解, ρ 为密度。在震源机制解确定的情况下, Rayleigh波的振幅谱只与震源深度有关, 因此对比不同震源深度下的Rayleigh波振幅谱可为震源深度提供有力的约束(Aki et al., 2002)。图 3给出了震中距为700km, 震源深度为7km、 9km和11km时的Rayleigh波理论震动图及3个深度的Rayleigh波振幅谱。从图中可以看出, Rayleigh波振幅谱频谱极小值的周期随着震源深度的增加而逐渐增大。因此, 利用Rayleigh波振幅谱可以更好地约束震源深度。

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图 3 震中距为700km时不同震源深度Rayleigh波理论震动图和振幅谱
绿色、红色和蓝色实线分别代表震源深度为7km、 9km和11km的结果。 a 第一行为垂向理论震动图, 第二行为0.01~0.1Hz带通滤波后的垂向理论震动图; b 不同震源深度下的Rayleigh波振幅谱Fig. 3 Comparison of synthetic waveforms and Rayleigh wave amplitude spectra at different focal depths of stations with epicentral distance of 700km.

2 结果与分析

2.1 利用走时残差全局搜索法确定苍梧地震震源深度

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	图 4 不同震源深度的走时残差分布图Fig. 4 Travel time residuals distribution map of different focal depths.

2.2 利用CAP方法反演广西苍梧地震震源机制解

利用CAP方法对广西苍梧地震的震源机制解进行反演, 反演时分别对观测波形和理论震动图的Pnl震相及面波波形进行0.05~0.15Hz及0.05~0.1Hz带通滤波, 设Pnl震相的权重为2, 面波部分的权重为1, 拟合结果显示苍梧地震的震源机制在深度为10km时拟合最好(图5), 最佳双力偶解节面Ⅰ 的走向为339° 、倾角为57° 、滑动角为-17° , 节面Ⅱ 的走向为78° 、倾角为75° 、滑动角为-145° 。将本文反演的苍梧地震震源机制结果与Harvard矩张量反演中心所给出的震源机制解结果进行比较, 可以看出两者较为一致(表3), 说明本文利用CAP方法得到的结果比较可靠。

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	图 5 苍梧地震波震源机制解反演结果Fig. 5 Inversion of focal mechanism and depth for the Cangwu earthquake.

表3 广西苍梧5.4级地震震源机制解 Table3 Focal mechanism of the M_S5.4 Cangwu earthquake

2.3 利用sPL震相确定广西苍梧地震震源深度

基于sPL震相的特征可知, 震中距为30~50km时比较容易清晰地观测到该震相。经过筛选, 最终选择震中距为38.46km、方位角为6.7° 的贺州台(HZS)进行sPL震相研究(图6)。

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	图 6 台站分布图Fig. 6 Station distribution map.

以1Hz为截止频率对旋转后的波形进行低通滤波。滤波后的sPL震相波形在径向分量上能量最强, 垂直向次之, 切向则很弱, 这一特征与上行SV波经全反射转换成沿地表传播的P波的记录特征相符(图7)。基于CAP方法反演的苍梧地震的震源机制解(表3), 结合苍梧地区的一维速度模型(表2), 使用F-K方法合成了贺州台震源深度为0~20km的理论震动图, 再以1Hz为截止频率对其进行低通滤波, 并将贺州台的实际观测波形与理论波形进行对比(图8)。结果显示, 在震中距固定的情况下, sPL震相只对深度敏感, 且贺州台的sPL震相和Pg震相的到时差约2.3s。对比观测波形和理论震动图可最终确定广西苍梧M_S5.4地震的震源深度约10km。

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	图 7 贺州台径向、切向、垂直向波形Fig. 7 Radial, tangential and vertical component waveforms recorded by the station HZS.

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	图 8 1Hz低通滤波后贺州台不同深度理论震动与实际波形对比图黑色实线代表理论震动图, 红色实线代表实际观测波形, 蓝色虚线代表sPL震相到时Fig. 8 Waveforms fitting between synthetic and observed seismograms of station HZS for different depths after 1Hz lowpass filtering.

2.4 利用Rayleigh波振幅谱测定广西苍梧地震震源深度

提取所有垂直向波形数据的Rayleigh波频散曲线, 挑选出其中具有明显频谱极小值点的台站。依据本次地震事件的波形数据共筛选出2个台站, 分别是南平东坑台(NPDK)和进贤台(JIX)。基于所得的震源机制解, 计算南平东坑台(NPDK)和进贤台(JIX)震源深度1~21km的Rayleigh波理论振幅谱, 将实际观测波形的Rayleigh波振幅谱和理论Rayleigh波振幅谱进行比对。结果显示, 南平东坑台(NPDK)在震源深度9km, 进贤台(JIX)在震源深度10km的情况下实际观测波形的Rayleigh波振幅谱与理论Rayleigh波振幅谱吻合程度较高, 故利用Rayleigh波振幅谱测定的广西苍梧M_S5.4地震震源深度为9~10km(图9)。

	Figure Option View Download New Window
	图 9 南平东坑台和进贤台Rayleigh波振幅谱拟合图红色虚线代表实际观测数据Rayleigh波振幅谱, 灰色实线分别代表不同深度(单位:km)的理论数据Rayleigh波振幅谱, 黑色实线代表最优震源深度的理论数据Rayleigh波振幅谱Fig. 9 The fitting map of Rayleigh wave amplitude spectrum of station NPDK and station JIX.

3 讨论

本文使用走时残差全局搜索法、 CAP法并基于sPL震相和Rayleigh波振幅谱对广西苍梧M_S5.4地震的震源深度进行测定, 结果显示: 走时残差全局搜索法给出的此次地震震源深度为(13± 3)km; CAP法和sPL震相法给出结果均为10km; Rayleigh波振幅谱法给出的结果为9~10km。走时残差全局搜索法与其它方法给出的震源深度定位结果相差3~4km。由于走时残差全局搜索法基于走时数据, 反映了震源体破裂起始点的位置, 而CAP、 sPL震相和Rayleigh波振幅谱法基于波形数据, 反映了震源体的质心深度, 两者在物理含义上有本质区别(张广伟等, 2014)。对于5级左右的中等地震而言, 震源体尺度一般为km量级, 考虑到定位方法的物理含义存在差别, 3~4km左右的误差可以接受。基于走时的定位方法在缺少震中距< 2倍震源深度的台站数据时, 震源深度误差较大, 而此情况对基于波形反演的震源深度测定方法影响较小。综上所述, 此次苍梧地震震源深度应为10km左右。

通过CAP、 sPL震相与Rayleigh波振幅谱获得的震源深度较为一致, 但也存在1km左右的差异, 这可能是由于本文使用的苍梧地区一维速度模型与地壳真实速度模型存在偏差所致。理论模型与实际模型存在误差, 可能会影响CAP方法的反演结果(孟庆君, 2013)。而sPL震相和Rayleigh波理论振幅谱法均使用了CAP方法反演的震源机制解, 因此震源机制解的误差也会对最终定位结果造成影响。有研究表明, 当速度模型误差为10%时, sPL震相法对于真实震源深度为10km的地震测量误差在1km左右(崇加军等, 2010)。

USGS测定的苍梧地震震源深度为24.5km, 该结果说明其为一个发生在下地壳的地震。和本文所用的走时残差全局搜索法相同, 在此次地震定位中, USGS也使用了走时数据, 两者在物理含义上是一致的, 均反映了震源体破裂起始点的位置。但我们认为本文通过走时残差全局搜索法获得的定位深度相对USGS给出的定位深度精度更高, 这主要是由于本文在定位中使用的是震中距≤ 300km的近震数据, 而USGS对此次地震进行定位时所选用台站的震中距最小为590km。由此可知, USGS给出的部分地震目录的震源深度精度有待进一步提高, 在使用USGS全球地震目录进行其它相关研究时需要考虑震源深度误差带来的影响(李志伟等, 2015)。Harvard矩张量解给出的此次地震的质心深度为15.6km, 与本文的给出的质心深度也有一定差别, 这主要是由于其反演时使用了全球均匀速度模型, 对震源深度最终反演结果有一定影响。

利用Rayleigh波振幅谱测定震源深度需要注意以下几点: 1)需要提取较为完整的振幅谱极小值曲线, 当台站记录没有明显频散及最小值时, 此方法不再适用; 2)Rayleigh波理论振幅谱计算严重依赖震源机制解的准确性, 因此在使用此方法进行震源深度测定时, 需要尽可能保证震源机制解的准确性。

2016年7月31日发生于广西苍梧的M_S5.4地震震中位于江南造山带向华夏地块过渡的区域, 震中位于NNE向的贺街-夏郢断裂带附近, 历史上此次地震震中附近100km内仅发生过1次5级以上地震, 与贺街-夏郢断裂带相关的基础研究资料缺乏, 无法对苍梧地震的发震机制作进一步分析。目前广西壮族自治区地震局正在开展针对贺街-夏郢断裂带的探测项目, 获取广西苍梧地震精确的震源深度对于进一步探明贺街-夏郢断裂带的构造有一定的参考价值。

4 结论

准确的震源深度对于研究地震的孕震机制、成因及地震烈度评估有着重要的作用, 但震源深度的测定是一个难题, 如何利用较少的地震信息测定震源深度更是研究者所关心的问题。本文利用走时残差全局搜索法、 CAP法、 sPL震相法和Rayleigh波振幅谱法对2016年7月31日发生于广西苍梧的M_S5.4地震的震源深度进行了测定, 结果表明, 广西苍梧地震的震源深度为10km左右, 仍为发生在上地壳的地震。在台网密度不高的情况下, 只利用1~2个宽频带台站记录到的sPL震相和Rayleigh波振幅谱就可以获得较为精确的震源深度。

USGS全球地震目录给出的此次地震的震源深度有着明显偏差。未来在使用USGS全球地震目录进行其它相关研究时, 应该考虑到震源参数的误差。本文仅仅针对广西苍梧地震进行了相关分析及研究, 对于USGS全球地震目录进行整体评估尚需更多震例予以补充。

致谢中国地震局地球物理研究所国家测震台网数据备份中心为本研究提供了丰富的地震波形数据; 审稿专家对本文提出了非常宝贵的意见及建议。在此一并表示感谢!

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2015

0.0

... 曹均锋等, 2015) ...

2000

0.0

陈立军. 2000. 中国地震震源深度与强震活动状态研究[J]. 地震地质, 22(4): 360-370.

CHEN

Li-jun

. 2000. Research of focal depth and active state of the strong earthquake in China[J]. Seismology and Geology, 22(4): 360-370(in Chinese).

A detailed analysis is made for the earthquake data with focal depth since 1970 on the most regians of China. A hypothesis is poposed to explain the analysis results, which leads to a new concept on the overall situation of major earthquakes in China. It is suggested that major events of China are driven by the earthquakes with middle-depth ard deep-depth sources which occurred at four "hot spots" in 1970s, that are located at Jilin Province, Xindoukushi of Xinjiang, Taiwan, and Rikeze of Tibet. A process of earthquake chain composed of an active period (1970～1982), adjustment period (1983～1992) and waning period (1993～1999) has been completed. Althouth the last period is still under going, a new circle of the earthquake chain may be developing since the M 7.0 deep event of Jilin on April 8, 1999.

Seismological Bureau of Hunan Province, Changsha 41001

通过对中国绝大部分地区1970年以来有仪器测定震源深度的地震资料进行详细分析,提出了"地震地热说"的假说并对分析结果作出解释,得出了一个关于中国强震活动大形势的全新观念,认为中国强震活动受到地壳深部4个"热点"(吉林、新疆兴都库什、台湾和西藏日喀则等中深源震区)70年代强震活动的牵引,完成了一个由地震活动高潮期(1970～1982)、调整期(1983～1992)和消减期(1993～1999)所组成的地震链全过程。目前消减期尚未结束,但从1999年4月8日吉林7.0级深震开始,新的一轮地震链过程可能已在酝酿之中。

... 震源深度是研究地下介质构造、孕震环境及地震成因的重要基础(陈立军, 2000 ...

2010

0.0

崇加军, 倪四道, 曾祥方. 2010. sPL, 一个近距离确定震源深度的震相[J]. 地球物理学报, 53(11): 2620-2630.

CHONG

Jia-jun

, NI

Si-dao

, ZENG

Xiang-fang

. 2010. sPL, an effective seismic phase for determining focal depth at near distance[J]. Chinese Journal of Geophysics, 53(11): 2620-2630(in Chinese).

A seimic phase is often observed between P and S of continental earthquakes for epicentral distances less than 50km in regions with simple crustal structure. It is stronger on radial component than on vertical component, and its tangential amplitude is weak. The seismic phase is also less impulsive than P waves. From synthetic waveforms, we find that it is generated when S wave goes upward and is post-critically converted to P wave traveling along the free surface. It also may contain multiple conversion or reverberations of P wave near free surface. Because it results from coupling between S and P waves, we define this phase as sPL. For a half-space velocity model, sPL degenerates to surface P wave as defined by Aki and Richards, and it contains less high frequency energy due to its similar nature as head waves. But it may contain multiple reverberations of P wave near critical distance when there is substantial sub-surface velocity gradient. Waveform study shows that differential time between sPL and direct P is insensitive to epicentral distance, but increases almost linearly with the focal depth. It is used to determine the focal depths for a 2005 earthquake sequence in Jiujiang, China. Error analysis with synthetic waveforms indicates that 10% uncertainty in velocity structure will lead to depth error of about 2km or less. Focal depth from sPL has the advantage that it can be obtained from even only one seismic record in distance less than 50km and accurate epicentral distance is not required. It may help a lot to determine focal depth of small earthquakes with magnitude less than M3, thus will be helpful when only sparse seismic stations are available.

1. Mengcheng National Geophysical Observatory, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China; 2. CAS Key Laboratory of Dynamic Geodesy, Institute of Geodesy and Geophysics, Academy of Sciences, Wuhan 430077, China

实际地震波形观测表明,对于大陆结构相对简单的地壳中的地震而言,有一震相出现在P 波和S波之间.一般在30~50 km附近发育得较好,其能量主要集中在径向分量,而垂向分量的振幅相对径向要小,切向分量上的振幅很弱,且波形以低频为主,通常没有P波尖锐.在利用FK方法计算合成地震图的基础上,发现该震相是由S波入射到自由地表形成水平传播的P波(文献称为surface P wave,自由地表P波)或者包括S波入射到地表后形成的多次P波或其散射震相.由于该震相是由S波和P波之间耦合而形成,本文将其定义为sPL(s coupled into P) 震相.理论波形研究表明,sPL相对直达P波的到时差对震中距离不敏感,而随着震源深度的增加几乎呈线性增加,因此可以很好的约束震源深度.本文以2005年江西九江地震为例,证实了sPL确定震源深度的可行性和可靠性.在观测到sPL震相的情况下,离震源50 km以内的一个三分量地震台站的波形就可以帮助获得可靠的震源深度,而不需要精确的震中距离.由于sPL震相出现距离较近,对于较小(三级以上)的地震也可以应用,因此在稀疏台网布局情形下sPL对于确定中小地震深度应该具有很好的应用意义.

... sPL震相为近震震相, 通常在震中距30~50km内可以被观测到(崇加军等, 2010) ...

... 同时, 由于sPL震相法使用近震数据(震中距30~50km), 在此震中距范围内其它反射震相(如PmP、 Pn等)还未出射, 故不易误认(崇加军等, 2010) ...

... 有研究表明, 当速度模型误差为10%时, sPL震相法对于真实震源深度为10km的地震测量误差在1km左右(崇加军等, 2010) ...

2015

0.0

冯新科, 李志强, 李晓丽, 等. 2015. 彝良地震地质灾害特征及其空间分布分析[J]. 地震地质, 37(2): 555-564. doi: 103969/j. issn. 0253-4967. 2015. 02. 017.

FENG

Xin-ke

, LI

Zhi-qiang

, LI

Xiao-li

, et al. 2015. Characteristics of geological hazards in Yiliang earthquake and statistical analyses of their spatial distribution[J]. Seismology and Geology, 37(2): 555-564(in Chinese).

On September 7, 2012 at 11: 19 and 12: 16(Beijing time), two catastrophic earthquakes with M S 5.7 and M S 5.6 struck the junction area of Yiliang County, Yunnan Province and Weining County, Guizhou Province, China. The research result indicates that the September 7, 2012 Yiliang earthquake triggered a mass of secondary geological disasters. The spatial distribution of the Yiliang earthquake triggered geological disasters is presented in this paper, by field check and using visual interpretation of remote sensing imageries. The statistical analyses results of their spatial distribution indicate that there are about 213 geological hazards throughout an area of about 0.67km 2 , consisting of collapse, landslide, rolling stones and mud-rock flow etc. We analyzed five characteristic parameters of these geological disasters triggered by Yiliang earthquake using GIS spatial analyses, such as seismic intensity, the formation stratum, slope angle, distances to river system and distances to road, and investigated in depth the control effect of these influence factors on the earthquake-induced geological hazards. This study reveals that: 1)most of the earthquake-induced geological hazards occurred in the Carboniferous strata along the Luoze River; 2)seismic region with intensity Ⅷ within the study area is the high incidence area of geological disasters, and the geological hazards have positive correlation with seismic intensity; 3)the hazards are mostly distributed in the slope range between 20°~50°; 4)geological disasters are densely distributed in the distance of 500m to river system and road, and they have negative correlation with the distance.

Institute of Geology, China Earthquake Administration, Beijing 100029, China

2012年9月7日11时19分和12时16分在云南省彝良县与贵州省威宁县交界处相继发生5.7级和5.6级地震(简称 "9 ·07"彝良地震), 此次地震诱发了大量的次生地质灾害, 文中基于现场调查和遥感影像目视解译的方法得到了彝良地震地质灾害的空间分布图, 并对其分布特征做了分析。统计结果表明, 此次地震诱发的地质灾害约213处, 总面积约为0.67km 2 , 地质灾害类型多样, 但以崩塌、滚石为主。利用GIS空间分析功能, 对此次地震诱发地质灾害的所在烈度区、地层、坡度和距水系、道路的距离等5个影响因子进行统计分析, 深入揭示了影响因子对地震诱发地质灾害的控制作用。结果表明, 此次地震诱发的次生地质灾害: 1)多发生于沿洛泽河一带的石炭系内; 2)多发生在Ⅷ度区内, 且与烈度呈正相关关系; 3)主要分布在坡度20°~50°范围; 4)密集发生在距水系、道路的距离为500m内的区域, 且与距水系、道路的距离呈负相关关系。

... 4万余人受灾, 并给当地居民造成了重大的财产损失(冯新科等, 2015) ...

2015

0.0

李志伟, 黄志斌, 王晓欣, 等. 2015. USGS地震目录中4~5级震源深度异常地震可靠性初步研究: 以南北地震带若干地震为例[J]. 地球物理学报, 58(4): 1236-1250. doi: 106038/cjg20150412.

Zhi-wei

, HUANG

Zhi-bin

, WANG

Xiao-xin

, et al. 2015. A study on the reliability of M4~5 earthquakes with anomalous focal depth in the USGS earthquake catalog: Several earthquakes in the North-South Seismic Belt[J]. Chinese Journal of Geophysics, 58(4): 1236-1250(in Chinese).

The USGS earthquake catalog indicates that a few earthquakes with >30 km focal depths occurred in the North-South Seismic Belt of China. Whether these focal depths are reliable or not is an important issue for the studies on the seismogenic mechanism, lithosphere strength and tectonic implications. The focal depths of five M 4~5 earthquakes in the North-South Seismic Belt are carefully studied with broadband three-component waveforms from local and regional stations.With the traveltime difference between first P and sPL depth phase, the qualitative relations between the focal depth and the short-period Rayleigh wave (Rg wave), the amplitude ratio of Rg/P, and the focal mechanism inversion by Cut and Paste (CAP) methods, the focal depths of five M 4~5 earthquakes in the North-South Seismic Belt are accurately determined. Synthetic seismic waveforms are calculated by frequency-wavenumber (FK) method. In the CAP method, three-component waveforms from local and regional stations with good azimuthal distributions are used to invert for the focal mechanisms and focal depth. The Pnl and surface wave are separately fitted to avoid the effects of the lateral variations of the crustal structure. The grid search scheme is used in the CAP method to find the best-fit focal depth and focal mechanisms. For the Rg wave, when the earthquakes have shallow focal depth (e.g., M 4.7 earthquake in Huining, Ningxia (10~11 km), the M 4.8 earthquake in Fumin, Yunnan (11~12 km) and the M 4.7 earthquake in Huidong, Sichuan (8~9 km), are all within 8~12 km. The differences in focal depth from the sPL depth phase and the CAP method are about 2~3 km, which should be accurate enough to confirm that the earthquakes occurred in the upper or mid-lower crust. In contrast, the focal depths of all three earthquakes are greater than 30 km (31, 33 and 46 km depth) in the USGS earthquake catalog, which mistakenly means the three earthquakes all occurred in the mid-lower crust rather than upper crust. For the M 4.6 and M 4.9 earthquake in Longchang, Sichuan, the focal depth from sPL depth phase is about 1~2 km, which is shallower than the focal depth of 4 km from the CAP method. The independent result from amplitude ratio of Rg/P is ~2 km, which is close to the results from the sPL depth phase. Since there is 2~3 km difference in the focal depth between results from the sPL depth phase, Rg/P and the CAP method, we inferred that the regional 1-D velocity model used in the synthetic waveform calculation in the CAP method could induce the bias on the focal depth due to the thick low-velocity sediments and/or strong lateral variations in the upper crustal structure. In contrast, the sPL depth phase method is not strongly affected by the bias of the velocity model. Therefore, for the extremely shallow earthquakes, the sPL depth phase and the amplitude ratio of Rg/P methods should be used to identify the focal depth rather than the CAP method only. In final, the focal depths of the M 4.6 and M 4.9 earthquake in Longchang, Sichuan should be 1~2 km, which belong to the extremely shallow earthquakes. There is still large bias in the USGS earthquake catalog compared to the focal depth of 10 km for the two earthquakes.It's meaningful to determine the focal depth with seismic waveforms at only one or two local stations for the regions with sparse seismic stations. With the sPL depth phase, the Rg wave, and the CAP methods, the focal depths of 5 M 4~5 earthquakes in the North-South Seismic Belt are accurately determined. The focal depths of three earthquakes are within 8~12 km, and the focal depth of the other two earthquakes are 1~2 km, which indicates quite large discrepancies with the focal depths of the USGS earthquake catalog. Therefore, at least in the North-South Seismic Belt of China, the M 4~5 earthquakes with deeper focal depths (e.g.,>30 km) in the USGS earthquake catalog need be further studied to identify their accuracy.

1. State Key Laboratory of Geodesy and Earth's Dynamics, Institute of Geodesy and Geophysics, Chinese Academy of Sciences, Wuhan 430077, China; 2. China Earthquake Networks Center, Beijing 100045, China; 3. Institute of Geophysics, China Earthquake Administration, Beijing 100081, China; 4. Mengcheng National Geophysical Observatory, University of Science and Technology of China, Hefei 230026, China

在南北地震带地区,USGS全球地震目录中存在一些震源深度大于30 km的地震.这些地震的震源深度是否可靠,对于研究这一地区的孕震机制、岩石圈强度和构造演化等科学问题具有重要意义.本文以南北地震带2012年发生的5个4~5级地震为例,利用区域地震台网的波形数据,基于sPL深度震相、短周期瑞利面波以及CAP等独立方法测定了其震源深度.结果表明:sPL深度震相和CAP方法给出的震源深度比较一致,差别小于2~3 km,能够得到比较可靠的震源深度;短周期瑞利面波及其与P波振幅比也确定了地震震源深度较浅的特征.本文研究结果显示:宁夏会宁4.7级、云南富民4.8级和四川会东4.7级地震的震源深度约为8~12 km左右,仍为发生于上地壳的地震,USGS地震目录给出的30 km甚至更深的震源深度存在明显偏差;对于四川隆昌4.6和4.9级地震,本文给出的震源深度为1~2 km,属于极浅源地震,USGS地震目录给出的10 km和35 km的震源深度结果尚需进一步改进.

... 李志伟等, 2015)、 Love波频谱^①(①Pitarka A, Helmberger D V, 2009, Analysis and simulation of 3D scattering due to heterogeneous crustal structure and surface topography on regional phases ...

... 由此可知, USGS给出的部分地震目录的震源深度精度有待进一步提高, 在使用USGS全球地震目录进行其它相关研究时需要考虑震源深度误差带来的影响(李志伟等, 2015) ...

2017

0.0

... 此外, 地震事件的全矩张量解中非双力偶成分所占比例也是鉴别地震成因的重要参数(刘俊清等, 2017) ...

2010

0.0

... , 2002)、 Rayleigh波与体波振幅比(罗艳等, 2010 ...

2013

0.0

罗艳, 曾祥方, 倪四道. 2013. 震源深度测定方法研究进展[J]. 地球物理学进展, 28(5): 2309-2321.

LUO

Yan

, ZENG

Xiang-fang

, NI

Si-dao

. 2013. Progress on the determination of focal depth[J]. Progress in Geophysics, 28(5): 2309-2321(in Chinese).

The focal depth is an important parameter of seismology. It plays a key role in fast earthquake hazard evaluation and seismogenic research. It, however, is a challenge to determine focal depth with high precision. Most popular location methods base on arrival time of seismic wave. Due to seismic network coverage and seismic velocity heterogeneity, such methods are difficult to obtain high resolution result. The information extracted from seismic waveform, such as amplitude, polarization, spectrum, provides efficient constraint on depth even with sparse network. After a simple review of location methods based on arrival time, we pay more attention on methods based on depth phase, and provide several application examples.

1. Institute of Earthquake Science, China Earthquake Administration, Beijing 100036, China; 2. Key laboratory of computational geodynamics, CAS, University of Chinese Academy of Sciences, Beijing 100049, China; 3. State Key Laboratory of geodesy and earth's dynamics, Institute of Geodesy and Geophysi, Chinese Academy of Sciences, Wuhan 430077, China

震源深度是地震学研究的关键参数之一,在地震灾害快速评估、孕震机理研究等方面具有重要意义,但是稀疏台网中震源深度的精确测定一直是难点.基于地震波到时信息是测定震源深度的常用方法,但极大地受限于台网密度及速度结构复杂性,测定精度不高.而利用P、S、面波等主要震相及深度震相的振幅、偏振、频谱等信息,即使在稀疏台网中也可以精确测定震源深度.本文在回顾基于到时及基于波形的震源深度测定方法的基础上,重点阐述了利用深度震相测定震源深度的方法原理,并将这些方法应用于实际地震的震源深度研究,给出了几个高精度测定典型地震震源深度的观测实例.

... 虽然测震台站可在水平方向上较好地包围震中, 但是在垂向(深度方向)上测震台站仅位于震源上侧, 导致角度分布具有局限性(罗艳等, 2013 ...

2012

0.0

吕坚, 曾文敬, 谢祖军, 等. 2012. 2011年9月10日瑞昌-阳新4. 6级地震的震源破裂特征与区域强震危险性[J]. 地球物理学报, 55(11): 3625-3633. doi: 106038/j. issn. 0001-5733. 2012. 11. 011.

LÜ

Jian

, ZENG

Wen-jing

, XIE

Zu-jun

, et al. 2012. Rupture characteristics of the M_S4. 6 Ruichang-Yangxin earthquake of Sep. 102011 and the strong earthquake risk in the region[J]. Chinese Journal of Geophysics, 55(11): 3625-3633(in Chinese).

Based on the records of regional digital seismic networks, we relocated precisely the M(s)4.6 Ruichang-Yangxin earthquake sequence of Sep. 10, 2011 with the HYPODD method, and obtained the focal depth and focal mechanism of the M(s)4.6 main-shock with the "Cut and Paste" (CAP) method. In order to determine the focal depth, we combined with local depth phases like sPg, PmP, and sPmP to research it,and further discussed the rupture characteristics of the event and the strong earthquake risk in the region. Our result shows that the focal depth of the M(s)4.6 Ruichang-Yangxin earthquake is 15 +/- 2 km and the best double couple solution is 30 degrees, 86 degrees, and -169 degrees for strike, dip, and slip angles respectively with the other nodal plane of 299 degrees, 79 degrees and -4 degrees. Combining with the rupture characteristics and the geologic settings in the region, we infer that the event is caused by the Ruichang-Wuxue fault which is the Tangcheng-Lujiang fault buried in the seismic zone. The Ruichang-Yangxin earthquake occurred in the east of the middle and lower Yangtze River fault-block, the M-s >= 5.5 earthquakes in the region show the obvious features of seismic grouping activity, and the recent significant earthquakes mostly occurred on the Tangcheng-Lujiang fault or its adjacent fault, which shows the tendency of accelerating energy release. So we should pay more attention to the risk of about M6 earthquake in the region in the future years.

[Lu Jian; Zeng Wen-Jing; Zeng Xin-Fu; Deng Hui; Hu Rui; Li Bin; Li Yu-Ze] Earthquake Adm Jiangxi Prov, Nanchang 330039, Peoples R China.;[Xie Zu-Jun] Chinese Acad Sci, State Key Lab Geodesy & Earths Dynam, Inst Geodesy & Geophys, Wuhan 430077, Peoples R China.;[Zhang Yong] China Earthquake Adm, Beijing 100036, Peoples R China.

基于区域数字地震台网记录,采用HYPODD方法精确定位了2011年9月10日瑞昌—阳新地震序列的震源位置,采用CAP方法反演得到了4.6级主震的震源深度和震源机制解,并结合区域深度震相sPg、PmP和sPmP对主震震源深度进行了进一步确定,随后探讨了这次地震的震源破裂特征和所在区域的强震危险性.结果显示:瑞昌—阳新4.6级地震的震源深度为15±2 km,震源机制解为节面Ⅰ走向30°,倾角86°,滑动角-169°,节面Ⅱ走向299°,倾角79°,滑动角-4°,发震构造为郯城—庐江断裂带往震区延伸隐伏的瑞昌—武穴断裂;本次地震发生在长江中下游断块东部,所在区域的5.5级以上地震具有明显的成组活动特征,近期显著地震集中发生在郯城—庐江断裂带南段及其分支断裂上,地震能量有加速释放的趋势,未来十年左右该区域存在发生6级左右强震的可能性.

... 吕坚等, 2012) ...

2013

0.0

吕坚, 郑秀芬, 肖健, 等. 2013. 2012年9月7日云南彝良 M_S5. 7、 M_S5. 6地震震源破裂特征与发震构造研究[J]. 地球物理学报, 56(8): 2645-2654. doi: 106038/cjg20130814.

LÜ

Jian

, ZHENG

Xiu-fen

, XIAO

Jian

, et al. 2013. Rupture characteristics and seismogenic structures of the M_S5. 7 and M_S5. 6 Yiliang earthquakes of Sep. 7, 2012[J]. Chinese Journal of Geophysics, 56(8): 2645-2654(in Chinese).

Based on the records of CSN and regional digital seismic networks, we obtained the focal depth and focal mechanism of the M(s)5. 7 and M(s)5. 6 Yiliang earthquakes of Sep. 7,2012 with the "Cut and Paste" (CAP) method, and used the teleseismic depth phases like P, P-p, and P-s from IRIS records to determine the focal depth. Further, we analyzed the rupture characteristics and seismogenic structures of the Yiliang earthquakes combining with the earthquake epicenters, seismic intensity, and geologic settings in the region. Our result shows that the best double couple solution of the M(s)5. 7 event is 243 degrees,62 degrees, and 149 degrees for strike, dip, and rake angles respectively, the other nodal plane is 349 degrees,63 degrees, and 32 degrees; for the M(s)5. 6 event the solution is 241 degrees,37 degrees,162 degrees with the other nodal plane of 346 degrees, 79 degrees and 54 degrees. We infer that both of the M(s)5. 7 and M(s)5. 6 earthquakes occurred on the NE striking Shimen fault and the focal depths of the events are about 6 km, the released seismic energy was concentrated in shallower crust which is an important reason for the serious seismic damage in the region.

Lu Jian 1 ;Xiao Jian 1 ;Zeng Xin-Fu 1 ;Li Bin 1 ;Dong Fei-Fei 1 ;Zheng Xiu-Fen 2 ;Xie Zu-Jun 3 ;

基于中国国家和区域数字地震台网记录,采用CAP方法反演了2012年9月7日云南彝良5.7、5.6级地震的震源机制解和震源深度,并利用IRIS提供的远震记录深度震相(P、 P P、 S P)进一步确定了震源深度,最后结合地震序列分布、地震烈度分布和区域地质背景讨论了发震构造.结果显示彝良5.7级地震的震源机制解为节面I走向243°、倾角62°、滑动角149°,节面Ⅱ走向349°、倾角63°、滑动角32°;5.6级地震的震源机制解为节面I走向241°、倾角37°、滑动角162°,节面Ⅱ走向346°、倾角79°、滑动角54°,这两次地震的发震构造均为NE走向的石门断裂,震源矩心深度均为6 km左右,表明地震的能量释放主要发生在地壳浅部,这也是导致震区严重灾害的一个重要原因.

... 吕坚等(2013)通过深入研究发现, 这2次地震的震源深度均为6km左右, 震源深度较浅是此次彝良地震造成重大财产损失、惨重人员伤亡的重要原因之一 ...

2013

0.0

... 理论模型与实际模型存在误差, 可能会影响CAP方法的反演结果(孟庆君, 2013) ...

2003

0.0

石耀霖, 朱守彪. 2003. 中国大陆震源机制深度变化反映的地壳-地幔流变特征[J]. 地球物理学报, 46(3): 359-365.

SHI

Yao-lin

, ZHU

Shou-biao

. 2003. Contrast of rheology in the crust and mantle near Moho revealed by depth variation of earthquake mechanism in continental China[J]. Chinese Journal of Geophysics, 46(3): 359-365(in Chinese).

Rheology of continental lithosphere is an important, but not well resolved basic issue in geodynamics. There are observational and experimental evidences to support a model of strong mantle  ductile weak lower crust near the Moho; there are also evidences to support a contrast model of weak ductile mantle  strong crust. In this study, we use CMT data of Harvard with corrected focal depth to analyze the depth variation of plunge angle of principal stresses in continental China. It is found that the plunge angles of earthquakes are either nearly horizontal or close to vertical for very shallow earthquakes, while there are great varieties in the plunge angle in the middle and lower crust and in the mantle. This feature is distinctively different from that in the regions with weak ductile lower crust, where the plunge angles of principal stresses at the base of earthquake generation layer are found nearly horizontal or vertical similar to the case of very shallow earthquakes. It may indicate that both kinds of crustmantle rheology models exist in China. Therefore, detailed integrated study on regional lithospheric rheology is necessary.

The Graduate School of the Chinese Academy of Sciences, Beijing 100039, China

大陆岩石层流变性质是一个重要而又没有完善解决的问题：既存在支持Moho面附近为强地幔-流动弱地壳模式的实验和观测事实，也存在支持流动弱地幔-强地壳模式的观测事实. 本文利用哈佛震源机制矩张量解及有关震源深度资料，对我国震源机制随深度的变化进行分析，发现虽然表浅地震震源机制主应力轴倾角接近水平或竖直，但中、下地壳和上地幔震源机制主应力轴倾角则多样化. 这与某些存在柔性下地壳软弱层地区具有孕震层下缘震源机制主应力轴也接近水平或竖直的特征明显不同. 它可能表明上述两种壳-幔流变模式在我国均存在，对我国岩石层流变性质还需要分区进行更细致的多方面研究.

... 石耀霖等, 2003 ...

2014

0.0

... 3km(宋秀青等, 2014) ...

2012

0.0

... 通过可靠的震中经纬度和精确的地震震源深度可以判断地震震群震源是否与地下注水井的位置具有对应性, 由此可判断地震震群是否由地下注水诱发(王小龙等, 2012 ...

2017

0.0

... 6km, 而徐晓枫等(2017)利用CAP(Cut and Paste)方法反演得到的震源深度为5 ...

2014

0.0

张广伟, 雷建设, 梁姗姗, 等. 2014. 2014年8月3日云南鲁甸 M_S6. 5地震序列重定位与震源机制研究[J]. 地球物理学报, 57(9): 3018-3027. doi: 106038/cjg20140926.

ZHANG

Guang-wei

, LEI

Jian-she

, LIANG

Shan-shan

, et al. 2014. Relocations and focal mechanism solutions of the 3 August 2014 Ludian, Yunnan M_S6. 5 earthquake sequence[J]. Chinese Journal of Geophysics, 57(9): 3018-3027. doi:10.6038/cjg20140926(inChinese).

Using the double-difference algorithm, we relocated the Ludian M(s)6.5 mainshock and its 647 aftershocks during 3 to 7 August 2014 and finally obtained 471 relocated earthquakes. Our results show that the focal depth of main shock is 13.3 km, which is close to the initial rupture depth of the main shock. The aftershock sequence presents an asymmetric conjugate shape with lengths of 17 km in the EW direction and of 22 km in the NW direction. Small earthquakes are predominately located above 10 km depth, and extend toward the shallow parts above 10 km depth along the southeast and eastwest directions of conjugate faults from the main shock. In addition, distribution of small earthquakes also shows that the seismogenic fault has a high dip and is the NW Baogunao-Xiaohe fault that is one branch of the Zhaotong-Ludian fault. Because the mainshock centroid depth can provide important evidence for understanding the serious disaster caused by the mainshock, we determined 5 focal mechanism solutions (M-s >=-4.0) including the main shock using the gCAP(generalized Cut And Paste) method. Our results show that the centroid depth of the main shock is only 5 km, which is consistent with the 2 similar to 8 km depth of larger slip in the obtained rupturing process. The conjugate rupture and shallower centroid depth of main shock could be the important causes for the serious disaster of this earthquake.

[Zhang Guang-Wei; Lei Jian-She; Sun Chang-Qing] Inst Crustal Dynam, Key Lab Crustal Dynam, Beijing 100085, Peoples R China.;[Liang Shan-Shan] China Earthquake Networks Ctr, Beijing 100045, Peoples R China.

本研究采用双差定位法对2014年 8月3日至7日期间鲁甸 M S 6.5级主震及647个余震序列进行重新定位，得到471个重定位结果.结果显示，主震的震源深度为13.3 km，与破裂过程显示的初始破裂深度较为接近，余震序列呈现出近东西向-北西向的不对称共轭状分布，近东西向长约17 km，而北西向长约22 km，小震优势分布深度为10 km以上，且由主震处沿共轭断层分别向东南向和近东西向逐渐往10 km深度以上的浅部迁移.小震分布还展示出发震断层高倾角分布，且与昭通—鲁甸断裂分支断裂包谷垴—小河断裂活动相关.由于主震破裂的质心深度可为深入认识本次地震灾害严重提供重要证据，为此我们采用gCAP（generalized Cut And Paste）方法反演了包括主震在内共5个4.0级以上地震的震源机制解，结果显示主震质心深度仅约5.0 km，与已有破裂过程显示的较大滑移量处于2~8 km之间的深度一致.本次主震错断了互为共轭的两条断裂，这种共轭破裂模式与矩心深度较浅，可能为本次地震致灾严重的重要原因.

... 由于走时残差全局搜索法基于走时数据, 反映了震源体破裂起始点的位置, 而CAP、 sPL震相和Rayleigh波振幅谱法基于波形数据, 反映了震源体的质心深度, 两者在物理含义上有本质区别(张广伟等, 2014) ...

2002

0.0

张国民, 汪素云, 李丽, 等. 2002. 中国大陆地震震源深度及其构造含义[J]. 科学通报, 47(9): 663-668.

ZHANG

Guo-min

, WANG

Su-yun

, LI

, et al. 2002. Focal depth of earthquakes in Chinese mainland and its tectonic implications[J]. Chinese Science Bulletin, 47(9): 663-668(in Chinese).

对中国大陆地震的震源深度资料作了系统研究. 震源深度的研究, 对于探索地震孕育和发生的深部环境, 地震能量集结、释放的活动构造背景, 以及地壳内部构造变形及其力学属性等都有非常重要的意义. 以1970年1月~2000年5月期间中国大陆M L ≥2.0级并给出深度的31282次1和2类精度的浅源地震为基础, 研究了深度分布特征, 并采用网格滑动平均方法, 统计了网格内地震的平均深度. 结果表明, 中国大陆平均深度为(16±7)km, 东部地区为(13±6)km, 西部为(18±8)km, 东部比西部平均偏浅5 km. 我国大陆地震深度最大的地区是新疆西南部地区, 即塔里木地块的西端和西南缘. 震源深度与构造分区的关系密切, 青藏活动地块震源深度平均为(33±12) km. 新疆活动地块为(21±10) km, 华北为(14±7) km; 东北为(11±5) km; 华南为(10±4) km. 完整地块边界上的地震较深, 其中最明显的是塔里木盆地的西南缘、北缘; 准噶尔盆地的南边缘, 阿拉善地块的南边缘; 鄂尔多斯地块的东、西两侧以及四川盆地的西边缘. 在新生性的破裂带上地震偏浅, 如滇西南地震带及张渤地震带. 另外, 还根据我国震源深度分布特征, 讨论了壳幔(主要是地壳)力学行为、变形属性和破坏方式.

... 张国民等, 2002 ...

2003

0.0

... 1 速度模型本文使用的速度模型为郑圻森等(2003)使用地球物理综合剖面产出的湘桂构造带的一维速度模型 ...

2009

0.0

郑秀芬, 欧阳飚, 张东宁, 等. 2009. “国家数字测震台网数据备份中心”技术系统建设及其对汶川大地震研究的数据支撑[J]. 地球物理学报, 52(5): 1412-1417. doi: 103969/j. issn. 0001-5733. 2009. 05. 031.

ZHENG

Xiu-fen

, OUYANG

Biao

, ZHANG

Dong-ning

, et al. 2009. Technical system construction of Data Backup Centre for China Seismograph Network and the data support to researches on the Wenchuan earthquake[J]. Chinese Journal of Geophysics, 52(5): 1412-1417(in Chinese).

The seismological observation system in China has experienced rapid development over the Tenth Five-year Plan period. The technical system construction of Data Backup Centre for China Seismograph Network is one of the most important parts of China Digital Seismological Observation Network program, which has been completed in Institute of Geophysics, China Earthquake Administration at the end of 2007. The data centre is capable of receiving near real-time continuous waveform data from more than 1000 permanent seismic stations, and also manipulating that data, including data quality control, data format converting, event data extraction by user order and data download service via internet. By now, we have supplied about 70 TB waveform data to over 70 researches of over 10 academic institutes and universities, especially the studies concerned with the Wenchuan great earthquake. The paper will give a brief introduction to the technical system construction, rapid response of data service to the Wenchuan earthquake studies, construction of automatic event-extracted system for rapid response of large earthquake in near real-time and data support to scientific researches.

1 Institute of Geophysics , China Earthquake Administration , Beijing 100081, China 2 China Earthquake Network Center, Beijing 100045, China

“十五”期间中国地震观测系统得到了迅速的发展, 中国地震局地球物理研究所于2007年底完成“中国数字地震观测网络”项目“国家数字测震台网数据备份中心”技术系统的建设.该数据备份中心可以准实时地接收并存储全国1000多个固定地震台站的信号，具备海量数据校验、数据格式转换、以用户定制方式截取地震事件波形数据和数据网络下载的功能.到目前为止，已累计为国内10多个科研单位开展的70多项研究提供了近70TB海量波形数据的服务，特别在快速开展的汶川特大地震震后相关研究中提供了重要的数据支撑和保障作用.本文介绍了“国家数字测震台网数据备份中心”技术系统建设、汶川特大地震数据服务快速响应、大地震快速响应波形数据自动截取系统建设，以及对地震学及相关科学研究的数据支持情况.

2017

0.0

... 郑勇等, 2017) ...

2017

0.0

... 4地震是广西测震台网建立以来所记录到的区域最大地震, 地震受灾人数达2万多人, 造成的直接经济损失近1亿元(周军学等, 2017) ...

2008

0.0

朱艾斓, 徐锡伟, 刁桂苓, 等. 2008. 汶川 M_S8. 0地震部分余震重新定位及地震构造初步分析[J]. 地震地质, 30(3): 759-767.

ZHU

Ai-lan

, XU

Xi-wei

, DIAO

Gui-ling

, et al. 2008. Relocation of the M_S8. 0 Wenchuan earthquake sequence in part: Preliminary seismotectonic analysis[J]. Seismology and Geology, 30(3): 759-767(in Chinese).

2741 aftershocks of the May 12,2008 M S 8.0 Wenchuan earthquake from May 12 to June 26 were relocated using the double difference algorithm to investigate tentatively the seismotectonic deformation and rupture process of the earthquake.Most relocated aftershocks occurred in the upper crust at depths of 0～20km,and fewer in the lower crust from depth of 25 to 40km,which may correspond to faulting in the lower crust.An aseismic layer appears beneath the Longmenshan thrust nappe zone between 20 and 25km depth after relocation,which may be correlated with the detachment for thrusting of the nappe zone.Spatial distribution of the relocated aftershocks and focal mechanism solutions show that the earthquake ruptured from south to north unilaterally with segmentation characteristics.The seismic belt formed by the aftershocks may be divided into two segments by the Gaochuan stepover in Anxian.The width of the seismic belt becomes narrower from south to north in map view,implying that the dip of the seismic fault may become steeper northward.The focal mechanism solutions suggest that rupturing in the south segment where the initial rupture point locates may be dominated by thrust slip with less component of strike slip,while it may have both thrust slip and dextral strike slip in the north segment.From Beichuan to the northeast end of the rupture zone,the seismic belt cannot be correlated with any fault in the north segment of the Longmenshan thrust nappe zone,even it cuts athwart the Qingchuan Fault.We can conclude that no controlling fault in the north segment of the Longmenshan thrust nappe zone was involved in earthquake generating and rupturing.The hypocenters in this part delineate a near vertical rupturing plane perpendicular to the strike of the seismic belt,and the focal mechanism solutions show great dextral strike slip component.

1. Earthquake Administration of Shanghai Municipality, Shanghai 200062, China; 2. National Center for Active Fault Studies, Institute of Geology, China Earthquake Administration, Beijing 100029, China; 3. Earthquake Administration of Hebei Province, Shijiazhuang 050021, China; 4. Earthquake Administration of Sichuan Province, Chengdu 610041, China; 5. China Seismic Network Center, Beijing 100045, China

利用双差地震定位法对5月12日汶川 M S 8.0地震至6月26日四川地震台网整理形成观测报告的2741个余震进行了重新定位。在此基础上,初步探讨了汶川地震的地震构造及其余震的破裂扩展。重新定位后震源深度主要分布在0～20km间的上地壳,25～40km的下地壳也有少量地震发生,与下地壳存在脆性变形的断裂活动相对应,在20～25km深度范围内的上下地壳之间存在一个明显的缺震层,推测其可能构成推覆构造的滑脱面。从震源分布与震源机制解在空间的变化上,地震破裂由南向北单侧破裂且存在明显的分段活动性,推测可能存在逆冲推覆与右旋走滑破裂相互转换的过程:逆冲推覆滑动主要发生在高川以南的段落上,震源机制解表现为以逆冲为主;地震破裂向北并未沿龙门山推覆构造带北段扩展,而是斜切青川断裂,震源分布刻画的结构面陡直,震源机制解表现为以右旋走滑错动为主。

... 朱艾斓等, 2008) ...

1990

0.0

... 2 走时残差全局搜索法朱元清等(1990)研究表明, Pn、 Pg震相走时差对震源深度有较高的敏感度, 在已知震中位置和地壳速度模型的情况下, 可以采用全局搜索法计算每个台站的Pn、 Pg理论走时差, 然后对比理论走时差和实际观测走时差以确定震源深度 ...

2002

0.0

... 此外, 还可以使用地震波形记录特征, 如Rayleigh波振幅谱(Aki et al ...

... 在震源机制解确定的情况下, Rayleigh波的振幅谱只与震源深度有关, 因此对比不同震源深度下的Rayleigh波振幅谱可为震源深度提供有力的约束(Aki et al ...

1996

0.0

... sPmP震相在震中距为200~300km的区域才可记录到发育较好的波形(Bock et al ...

2013

0.0

... Ellsworth, 2013 ...

2013

0.0

... 准确的震源深度是研究地震烈度的重要参数, 在震级相同的情况下, 震源深度越小则地表烈度越大, 地震带来的人员和财产损失往往也会增大(Gupta et al ...

2017

0.0

... )以及CAP和Rayleigh波振幅谱联合测定震源深度(Jia et al ...

2013

0.0

... Kim, 2013) ...

1979

0.0

... 而sPn震相能量较弱, 一般只有在中强地震时, 在震中距300km左右的区域才有可能被观测到(King, 1979 ...

1987

0.0

... sPg震相在震中距为60~100km的台站可被观测到(Langston, 1987 ...

2010

0.0

... Ma, 2010) ...

1991

0.0

... 4倍震源深度的范围内且有台站分布的情况下才能够获得精确的震源深度(Mori, 1991) ...

2000

0.0

... Saikia, 2000) ...

1994

0.0

... 3 CAP方法CAP方法(Zhao et al ...

1996

0.0

... Zhu et al ...

2002

0.0

... 该方法把原始波形分为Pnl和Snl 2部分, 采用频率-波数方法(F-K)(Zhu et al ...

1984

0.0

... Zonno et al ...