山东乳山地震序列震源机制解一致性参数特征

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刘方斌, 曲均浩, 李亚军, 范晓易, 苗庆杰. 山东乳山地震序列震源机制解一致性参数特征[J]. 地震地质, 2018,40(5): 1086-1099.
LIU Fang-bin, QU Jun-hao, LI Ya-jun, FAN Xiao-yi, MIAO Qing-jie. RESEARCH ON CHARACTERISTICS OF THE FOCAL MECHANISM SOLUTIONS CONSISTENCY OF RUSHAN EARTHQUAKE SEQUENCE, SHANDONG PROVINCE[J]. SEISMOLOGY AND GEOLOGY, 2018,40(5): 1086-1099. 复制到剪切板

DOI:10.3969/j.issn.0253-4967.2018.05.009
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山东乳山地震序列震源机制解一致性参数特征

刘方斌^1,², 曲均浩^1,^3,^*, 李亚军¹, 范晓易¹, 苗庆杰¹

1山东省地震局, 济南 250014

2兰州大学, 西部环境教育部重点实验室, 兰州 730000

3中国地震局地质研究所, 北京 100029

*通讯作者: 曲均浩, 博士, 高级工程师, 主要从事数字地震学应用及余震活动机理研究, E-mail: gisqjh@126.com。

〔作者简介〕刘方斌, 男, 1989年生, 2014年于中国地震局兰州地震研究所获构造地质学专业硕士学位, 工程师, 现主要从事数字地震学应用及地震序列研究, 电话: 0531-58622065, E-mail: liufangbin8908@163.com。

收稿日期: 2017-06-20

基金项目: 中国地震局星火计划项目(XH16025)、中国地震局三结合项目(CEA-JC/3JH-171601)和山东省地震局科技创新团队基金(SDST-07-2018)联合资助

摘要

采用双差定位法对乳山台阵记录到的 M_L≥1.0的1418个地震事件(2014年5月7日—2016年12月31日)进行重新定位, 利用P波初动和CAP方法对研究区内 M_L≥1.5地震进行震源机制解反演, 根据震源机制解资料进行应力张量反演, 从而分析乳山地区应力状态以及震源机制一致性参数时空特征。结果显示: 1)乳山地震序列沿NWW-SEE向展布, 形成长约4km、宽约3km的矩形活动带; 2)推测乳山地震序列发震断层走向为NWW-SEE、近直立、以走滑运动为主兼具一定逆倾滑分量; 3)采用自助线性应力反演(LSIB)方法得到乳山地区主压应力轴方向为25°, 倾角10°; 中等应力方向为286°, 倾角45°; 主张应力方向为125°, 倾角43°; 4)乳山地震序列的震源机制一致性参数随时间变化整体呈现平稳状态, 地震发生的空间位置与震源参数一致性空间分布关系较为吻合。

关键词: 乳山地震序列; 双差定位; 震源机制解; 一致性参数

中图分类号:P315.72⁺7 文献标志码:0253-4967(2018)05-1086-14 文章编号:0253-4967(2018)05-1086-14

RESEARCH ON CHARACTERISTICS OF THE FOCAL MECHANISM SOLUTIONS CONSISTENCY OF RUSHAN EARTHQUAKE SEQUENCE, SHANDONG PROVINCE

LIU Fang-bin^1,², QU Jun-hao^1,³, LI Ya-jun¹, FAN Xiao-yi¹, MIAO Qing-jie¹

1)Shandong Earthquake Agency, Jinan 250014, China

2)Key Laboratory of Western China’s Environment System, Ministry of Education, Lanzhou University, Lanzhou 730000, China;

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

Abstract

Many small earthquakes occurred intensively and continuously and formed an earthquake sequence after the M_L3.8 earthquake happened at Rushan County, Shandong Province on October 1, 2013. Up to March, 2017, more than 13000 events have been recorded, with 3429 locatable shocks, of which 31 events with M_L≥3.0. This sequence is rarely seen in East China for its extraordinary long duration and the extremely high frequency of aftershocks. To track the developing tendency of the earthquake sequence accurately, 20 temporary seismometers were arranged to monitor the sequence activities around the epicenter of the sequence since May 6, 2014.
Firstly, this paper adopts double difference method to relocate the 1418 earthquakes of M_L≥1.0 recorded by temporary seismometers in the Rushan earthquake sequence(May 7, 2014 to December 31, 2016), the result shows that the Rushan earthquake sequence mainly extends along NWW-SEE and forms a rectangular activity belt of about 4km long and 3km wide. In addition, the seismogenic fault of Rushan earthquake sequence stretches along NWW-SEE with nearly vertical strike-slip movement and a small amount of thrust component.
Then we apply the P-wave initial motion and CAP to invert the focal mechanism of earthquakes with M_L≥1.5 in the study area. The earthquakes can be divided into several categories, including 3 normal fault earthquakes(0.9%), 3 normal-slip earthquakes(0.9%), 229 strike-slip earthquakes(65.8%), 18 thrust fault earthquakes(5.2%), 37 thrust-slip earthquakes(10.6%)and 58 undefined(16.6%). Most earthquakes had a strike-slip mechanism in Rushan(65.8%), which is one of the intrinsic characteristics of the stress field.
According to the focal mechanism solutions, we further utilized the LSIB method(Linear stress inversion bootstrap)to invert the stress tensor of Rushan area. The result shows that the azimuth and plunge of three principal stress( σ₁, σ₂, σ₃) axes are 25°, 10°; 286°, 45°; 125°, 43°, respectively. Based on the stress field inversion results, we calculated the focal mechanism solutions consistency parameter( θ)and the angle( θ₁)between σ₁ and P axis. The trend lines of θ and θ₁ were relatively stable with small fluctuation near the average line over time. Furthermore, the earthquake sequence can be divided into three stages based on θ and θ₁ values. The first stage is before September 16, 2014, and the variation of the θ and θ₁ values is relatively smooth with short period. All focal mechanism solutions of the three M_L≥3.0 earthquakes exhibited consistence. The second stage started from September 16, 2014 to July 1, 2015, the fluctuation range of θ and θ₁ values is larger than that of the first stage with a relative longer period. The last stage is after July 1, 2015, values of θ and θ₁ gradually changed to a periodic change, three out of the four M_L≥3.0 earthquakes(strike-slip type)displayed a good consistency.
Spatially, earthquakes occurred mainly in green, yellow-red regions, and the focal mechanism parameters consistency θ was dominant near the green region(around the average value), which presents a steady state, and the spatial locations are concordant with the distribution of θ value. Moreover, all of M_L≥3.0 earthquakes are located in the transitional region from the mean value to lower value area or region below the mean value area, which also indicates the centralized stress field of the region.

Keyword: Rushan earthquake sequence; double difference location; focal mechanism solution; consistency parameter

文章图片

0 引言

2013年10月1日在山东威海市乳山市(36.83° N, 121.70° E)发生M_L3.8地震, 之后中小地震不断, 发生多次M_L≥ 4.0地震。截至2017年3月, 已记录地震13i093次, 其中可定位地震3i429次, M_L≥ 3.0地震31次。与历史地震序列相比, 该区域从未出现过如此高频、时间持久的地震序列活动(曲均浩等, 2015)(图1)。

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	图1 乳山地震序列M-t图Fig. 1 M-t plot of Rushan earthquake sequence.

为精确跟踪乳山地震序列的发展趋势, 山东省地震局于2014年5月6日在序列震中附近陆续架设了20个流动台站, 为获取地震序列的精确空间位置及活动特征提供了丰富的观测数据。本文基于2014年5月7日— 2016年12月31日期间乳山流动台(简称: 乳山台阵)记录的地震资料, 选取M_L≥ 1.0的1i418个地震事件采用双差定位法(Waldhauser et al., 2000)进行重新定位, 获取序列准确的空间分布; 通过P波初动方法(胡幸平等, 2008; 俞红玉等, 2013)计算研究区内346个1.5≤ M_L< 3.6地震的震源机制解, 对于2个M_L≥ 3.6地震采用CAP(Cut and Paste)方法(Zhu et al., 1996)进行计算; 最后根据震源机制解资料进行应力张量反演, 进而分析震源机制一致性参数的时空特征。

1 台站和数据

乳山台阵的架设对乳山地震序列形成全方位的包围(如图2), 为震源区地震定位及震源机制解的计算提供了宝贵的数据。本文采用Hyposat定位方法对2014年5月7日— 2016年12月31日期间记录的地震事件进行绝对定位, 共得到14i165次地震记录, 选取M_L≥ 1.0、震相数≥ 8的1i418个地震事件进行重定位, 选定348个M_L≥ 1.5地震进行震源机制解反演。为保证计算过程中观测报告震相数据的可靠性, 对Pg、 Sg震相时距曲线进行拟合, 剔除明显错误或者误差较大的震相, 其相关系数达0.997以上(图3)。

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	图2 研究区台站及震中分布图Fig. 2 Distribution map of stations and epicenters of Rushan area.

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	图3 乳山地震序列时距曲线Fig. 3 Travel time curves of Rushan earthquake sequence.

2 双差定位

双差定位法是1种高精度的相对定位算法(Waldhauser et al., 2000), 目前已被广泛应用于地震序列的重定位研究中(房立华等, 2013, 2014; Govoni et al., 2014; Fang et al., 2015)。本文综合对比Crust2.0及层析成像得到的胶东半岛地壳速度模型(张岭等, 2005; 李霞等, 2012; 曲均浩等, 2015), 选用不同模型关键深度的速度值作为本文初始模型的速度值(表1), 波速比设为1.73, 定位中事件对最大距离设为10km, 采用阻尼最小二乘法进行反演。定位共用到P波走时60i810个(72%), S波走时57i995个(72%)。通常情况下, P波到时的拾取往往比S波精确, 本文对P波震相数据权值赋为1.0、 S波震相为0.5, 经过6次迭代定位后残差由原来的0.003i2降低到0.000i5, 重新定位后计算得到1i393个结果(98.24%)。乳山地震序列时间窗较长, 双差定位所用的地震对数量明显增加, 提高了定位精度和重新定位后地震的数量。

表1 地壳P波速度模型 Table1 Crustal velocity model of P wave

图4为乳山地震序列重定位前后结果对比图, 重定位后地震展布线性趋势更加明显, 呈NWW-SEE向, 在震中区内形成1个长约4km、宽约3km的矩形密集活动带。根据郑建常等(2015)、曲均浩等(2015)基于CAP方法对乳山序列较大地震震源机制解的研究, 所得到的17个震源机制解中有16个节面优势走向为290° 左右, 与本文乳山台阵重定位结果地震展布方向基本一致。另外, 这一结果与郑建常等(2015)、曲均浩等(2018)采用双差定位法对乳山台阵记录的部分地震重定位结果也基本一致。

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	图4 乳山地震序列重定位前后震中分布红色圆圈为重定位结果, 黑色圆圈为绝对定位结果Fig. 4 The epicenter distribution before and after the relocation of Rushan earthquake sequence.

3 震源机制解分析

震源机制解不仅含有断层运动方式及震源破裂过程的信息, 而且还能够反映地震前后震源区应力变化状态, 为区域构造应力场研究提供重要依据(李金等, 2015)。虽然1次中小地震的震源机制解不足以反映区域应力场的概况, 但大量中小地震震源机制解的总体特征在一定程度上能够代表区域构造应力场的方向(许忠淮等, 1983)。

3.1 震源机制解反演

震源机制解是1种采用地震学方法来判别断层错动方式和地震发震机制的方法。在震源机制的求解过程中, P波初动法是计算中小地震震源机制比较常用的方法, 该方法有快速简便的优点, 但同时要求P波震相数据不能太少, 并且在震源球面上有足够的覆盖区域(崔效锋等, 2011)。而乳山台阵及增设的海岛台, 将震中位置包裹得较好, 可有效满足P波初动法的使用条件。本文采用许忠淮等(1983)提出的格点尝试法对1.5≤ M_L< 3.6地震求解P波初动震源机制解。计算过程中, 对于1次地震, 其初动数据要求至少有8个, 矛盾符号比均< 0.2, 共获得震源机制解346个。

CAP方法是将宽频带记录到的波形分成Pnl和面波2部分, 分别赋予不同的权重, 在给定速度模型的前提下采用频率-波数法(F-K)计算各个台站位置的格林函数, 由震源函数及格林函数合成理论波形, 将理论波形与实际观测波形进行互相关, 拟合出残差最小的机制解作为最终反演结果。其优点在于反演过程中完整地使用了波形记录, 全面地反映了震源信息, 对震源深度的反演起到很好的约束性。另外, 该方法允许各时间窗理论波形和观测波形进行相对滑动拟合, 大大减少了地壳速度结构模型对反演结果的影响, 降低了对台站数量和方位角分布的要求, 提高了信噪比和反演精度, 适用于震级略大的小地震及中、强地震震源机制解的研究(罗钧等, 2015), 本文2次3.6级以上地震的震源机制解均采用该方法求得。2014年5月7日— 2016年12月31日期间M_L3.0以上地震震源机制解见表2。

表2 乳山地震序列部分震源机制解 Table2 Part of focal mechanisms of Rushan earthquake sequence

根据Zoback(1992)对震源机制的分类标准(表3), 对上述震源机制进行分类统计。统计结果显示, 在348次M_L≥ 1.5地震震源机制解中, 有NF型3次(0.9%), NS型3次(0.9%), SS型229次(65.8%), TF型18次(5.2%), TS型37次(10.6%), UD型58次(16.6%)。为进一步研究乳山地震序列震源机制空间的分布特征, 将震源机制解按上述分类标准进行区分并投影在图5上, 从图中可见, 乳山地区沿着NWW-SEE向分布的走滑型地震具有频次上的绝对优势。

表3 震源机制解类型分类标准(引自Zoback, 1992) Table3 Classification standard of focal mechanism solutions(cited from Zoback, 1992)

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	图5 研究区震源机制分布图Fig. 5 Distribution of focal mechanism solutions of Rushan earthquake sequence.

3.2 震源机制各参数分析

本文采用统计方法展示震源机制解的各参数分布状态, 由于无法判断震源机制解中的2个节面哪个是断层面, 故对2个节面合并分析。图6为348个M_L≥ 1.5地震的震源机制解各参数的每10° 间隔的归一频度图。据走向显示, 节面主要集中在NWW-SEE向和近S向2个优势方向, 其中NWW-SEE向节面与本文序列重定位展布方向基本一致, 由此判定其应为乳山序列发震断层面, 这一结果与曲均浩等 $^{}$ 研究所得乳山地区层析成像结果相吻合。节面倾角频度分布中, 倾角几乎呈直立状态, 角域在60° ~90° , 尤以70° ~90° 居多。节面滑动角取-150° ~-30° 为正倾向滑动, 30° ~150° 为逆倾向滑动, 0° ± 30° 和150° ~180° 、 -150° ~-180° 为走向滑动。研究发现有72%的断层滑动角分布在走向滑动范围内, 20%为逆倾向, 仅有8%为正倾向滑动。根据滑动角和倾角的分布范围可推测乳山地震序列发震断层应以高角度的走滑运动为主, 兼具一定的逆倾滑分量。

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	图 6 震源机制解节面走向、倾角、滑动角归一频度图Fig. 6 Normalized frequency diagram of strike, dip and rake of focal mechanism solutions.

此外, 对上述震源机制解的P轴和T轴进行投影(图7), 结果发现: 不同类型的震源机制解的P轴和T轴的方向不同。其中, SS型(65.8%)和TS型(10.6%)P轴和T轴的方向具有相对较好的一致性, 呈NNE和SEE向分布; UD型(16.6%)P轴和T轴的方向分布相对杂乱; NF型和NS型整体占比较小(< 2%), 无法判断。尽管各类型的P轴和T轴方向各异, 但P轴总体优势方向为NNE— NEE向(图7a), T轴优势方向为SEE— SSE向(图7b), 两者呈现正交关系, 且轴向急剧调整的现象很少, 表明该区域构造应力场的优势方向分布具有相对均匀性和稳定性。另外, 从P、 T轴的倾角统计分析可以看出, 两者作用力呈现低角度, 主要集中在0° ~30° 。

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	图7 P、 T轴投影分布图Fig. 7 Projection direction chart of P and T axis.

4 震源机制一致性时空特征

震源机制一致性参数是区域构造应力场3个主应力轴 $\begin{matrix} (σ_{1} 、 σ_{2} 和 σ_{3}) \end{matrix}$ 与震源机制解P、 T、 B轴在三维空间的夹角之和, 其公式为

$θ = α + β + γ$

其中, θ 为震源机制一致性参数, 最大值为270° , 最小值为0° (刁桂苓等, 2004; 赵英萍等, 2004; 程万正等, 2006; 泽仁志玛等, 2009; 付虹等, 2011), α =∠σ ₁OP, β =∠σ ₂OB, γ =∠σ ₃OT(图8)。

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	图8 应力示意图Fig. 8 Stress schematic diagram.

任何1个地震序列都有发生、发展和衰退的过程, 前震或在震群中较大地震发生之前, 小震的震源机制相对一致性往往是地震活动性增强的标志, 而震源机制的相对紊乱往往伴随着余震或地震群活动的减弱, 鉴于此, 根据震源机制的一致性与否可以判断震群中最大地震是否已经发生(陈颙, 1978)。陈颙(1978)研究发现, 强震前中小地震震源机制解趋于一致性的现象时有发生, 并提出用前震震源机制的一致性来描述地震活动性。黄显良等(2015)采用P波、 SV波和SH波的极性和振幅比联合求解2014年安徽省金寨M_L3.9震群序列的震源机制解, 并得到该序列的震源一致性参数及P轴方位角随时间的变化关系。李丽等(2015)采用层状介质中点源位错模型的广义透射系数的快速算法和理论地震图拟合直达波最大振幅比来求解小震震源机制解, 计算了2001— 2012年山西地区281个中小地震的震源机制解, 分析了一致性参数时空分布与该地区中等地震活动的关系。李金等(2015)利用天山地震带306个震源机制解资料反演该区域应力场, 得出该区域震源机制一致性的时空分布与中强地震有一定关系。

本文利用上述348个中小地震的震源机制解作为输入数据, 采用Michael(1984, 1987)的自助线性应力反演(Linear stress inversion bootstrap, LSIB)方法计算乳山区域应力张量。在置信区间为95%情况下, 其最大主压应力 $σ_{1}$ 方位角为25° , 倾角10° ; 中等应力 $σ_{2}$ 方位角为286° , 倾角45° ; 最小主压应力 $σ_{3}$ 方位角为125° , 倾角43° 。

4.1 震源机制一致性时间分布特征

基于应力场反演结果, 计算了乳山地震序列348个M_L≥ 1.5地震震源机制解的P、 T、 B轴与平均区域应力场3个对应主应力轴的方位角差, 获得震源机制一致性参数值θ , 其时序变化分布如图9a所示。主压应力 $σ_{1}$ 通常较为稳定, 为此, 本文分析了区域应力场最大主应力轴 $σ_{1}$ 与震源机制解对应的主压应力P轴之间的夹角 $θ_{1}$ (图9b)。图中横轴按照地震先后顺序绘制, 各时间间隔不等长, 图中标注了M_L≥ 3.0地震及其震源机制解。

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	图9 震源机制一致性参数时序分布Fig. 9 Distribution of consistency parameter of focal mechanism solutions with time.

图中黑色虚线表示各小震震源机制解一致性参数的变化, 随机性较强, 数值变化区间较宽。参考前人(付虹等, 2011)的研究结论, 将均值作为控制线, 低于均值表示震源机制与构造应力场重合性较好, 构造应力场对该地区控制作用增强; 高于均值则控制作用减小。为便于分析变化趋势, 采用五点滑动平均法重新计算, 结果显示, 五点滑动平均法的趋势线在均值线附近波动, 曲线随时间的变化总体较平稳, 区内12次M_L≥ 3.0地震中有10次地震的 $θ$ 值(图9a)低于均值(165.58), 另外2个略高于低值。另外, 根据 $θ$ 和 $θ_{1}$ 值一致性的整体变化大致分为3个阶段:一是2014年9月16日之前, $θ$ 和 $θ_{1}$ 值变化幅度较为平缓且周期较短。该时段7次3.0级以上地震(SS型)的震源机制解具有一定的相似性。二是2014年9月16日— 2015年7月1日, $θ 和 θ_{1}$ 值波动幅度相对前一阶段较大、变化周期长, 共发生1次TS型地震。三是2015年7月1日之后, 该时段的 $θ 和 θ_{1}$ 值由先前的较大波动逐渐开始呈现周期性变化, 共发生4次3.0级以上地震, 其中3次SS型地震的 $θ 和 θ_{1}$ 值表现出较好的一致性。

4.2 震源机制一致性空间分布特征

图10为基于五点滑动平均法绘制的乳山地震序列M_L≥ 1.5中小地震震源机制一致性参数θ 等值线分布图, 展示了乳山地震序列与震源机制一致性参数空间异常的分布关系。由于地震主要集中发生在图4线框内位置, 框外的地震样本数偏少, 计算可信度不高, 因而本文着重探讨线框内的地震震源参数一致性。如图所示, 地震主要发生在绿色、黄红色及其交替区域, 震源机制一致性参数θ 整体上以绿色为主导(均值附近), 黄红色其次, 仅有少部分区域出现极低值, 一致性参数表现相对较为稳定, 地震发生的空间位置与震源参数一致性空间分布较为吻合, 研究区内M_L≥ 3.0地震均位于均值线向低值区过渡或低于均值的区域, 有效体现了区域应力场集中的结果。

	Figure Option View Download New Window
	图10 震源机制一致性参数空间分布黑色圆点 M_L≥ 1.5; 红色圆点 M_L≥ 3.0; 震源机制解同图9Fig. 10 Spatial distribution of consistency parameter of focal mechanism solutions.

5 结论

(1)利用双差定位对乳山台阵记录到的M_L1.0以上1i418个地震事件进行重新定位, 获得了1i393个定位结果。精定位后的地震主要分布在乳山断裂的SE侧, 沿NWW-SEE向展布, 空间上形成1个长约4km、宽约3km的矩形密集活动带。

(2)采用P波初动和CAP方法共反演得到348个M_L1.5以上地震的震源机制解, 综合各地震震源机制解走向参数及序列精定位展布方向, 可判断乳山序列发震断层为NWW-SEE向; 根据滑动角和倾角的分布范围可推测该断层应以高角度的走滑运动为主, 兼具一定的逆倾滑分量。

(3)根据震源机制解反演得到乳山区域平均应力场, 其主压应力方向为25° , 倾角10° ; 中等应力方向为286° , 倾角45° ; 主张应力方向为125° , 倾角43° 。

(4)基于应力场反演结果, 得到乳山地震序列348个M_L1.5以上地震震源机制一致性参数值 $θ$ 及区域应力场最大主应力轴与震源机制解对应主压应力P轴之间的夹角 $θ_{1} 。结果表明, θ 和 θ_{1}$ 值的趋势线随时间的变化总体较平稳, 地震发生的空间位置与震源参数一致性空间分布关系较为吻合, 表现出较好的一致性。

致谢在本文成文过程中, 甘肃省地震局袁道阳研究员和山东省地震局王志才研究员在发震构造方面给予了指导和建议, 山东省地震局李霞高级工程师对本文提出了宝贵意见, 中国地震局地球物理研究所冀战波博士对GMT进行了指导, 新疆维吾尔自治区地震局李金工程师对ZMAP软件方面给予了帮助, 两名审稿专家对本文提出的宝贵意见和建议, 在此一并致谢。文中图件采用GMT和ZMAP绘制。

The authors have declared that no competing interests exist.

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1978

0.0

陈颙. 1978. 用震源机制一致性作为描述地震活动性的新参数[J]. 地球物理学报, 21(2): 142—159.

CHEN

Yong

. 1978. Consistency of focal mechanism as a new parameter in describing seismic activity[J]. Chinese Journal of Geophysics, 21(2): 142—159(in Chinese).

From the point of view of focal mechanism, characteristics of foreshocks, aftershocks and earthquake swarms are analysed, based on observations of some of the strong earthquakes occurred in recent years. It is pointed out that there are considerable differences between the three. A "Group Parameter" - Consistency of focal mechanism has been suggested to describe the seismicity of a group of earthquakes and we try to make it more or less quantitative. It is emphasized that to identify the consistancy of focal mechanism for a group of earthquakes, one may find quick and convenient by just analysing the wave form of the seismic records. Besides, in this paper, some examples are also given for the assessment of earthquake risk by using the parameter mentioned above.

本文根据近年来的一些强震震例,从震源机制角度分析了前震、余震和地震群的不同特点,指出在震源机制的一致程度方面,前震、余震和地震群有明显的差别,提出了描述一群地震活动性方面的一个“群体”参数——震源机制一致性,并试图给这个参数定量化.本文强调判断一群地震震源机制一致性时,用地震记录波形鉴别法常常是迅速方便的,还给出了一些用震源机制一致性参数确定地震危险性的实例.

... 任何1个地震序列都有发生、发展和衰退的过程, 前震或在震群中较大地震发生之前, 小震的震源机制相对一致性往往是地震活动性增强的标志, 而震源机制的相对紊乱往往伴随着余震或地震群活动的减弱, 鉴于此, 根据震源机制的一致性与否可以判断震群中最大地震是否已经发生(陈颙, 1978) ...

... 陈颙(1978)研究发现, 强震前中小地震震源机制解趋于一致性的现象时有发生, 并提出用前震震源机制的一致性来描述地震活动性 ...

2006

0.0

程万正, 阮祥, 张永久. 2006. 川滇次级地块震源机制解类型与一致性参数[J]. 地震学报, 28(6): 561—573.

CHENG

Wan-zheng

, RUAN

Xiang

, ZHANG

Yong-jiu

. 2006. Types of focal mechanism solutions and parameter consistency of the sub blocks in Sichuan and Yunnan Provinces[J]. Acta Seismologica Sinica, 28(6): 561—573(in Chinese).

... 程万正等, 2006 ...

2011

0.0

崔效锋, 胡幸平, 俞春泉, 等. 2011. 汶川地震序列震源机制解研究[J]. 北京大学学报: 自然科学版, 47(6): 1063—1072.

CUI

Xiao-feng

, HU

Xing-ping

, YU

Chun-quan

, et al. 2011. Research on focal mechanism solutions of Wenchuan earthquake sequence[J]. Acta Scientiarum Naturalium Universitatis Pekinensis, 47(6): 1063—1072(in Chinese).

Based on the initial P wave polarity of digital wave form data given by Chinese National Seismic Network, regional seismic network, temporary seismic networks as well as some IRIS stations, employing the improved grid point test method, 121 reliable focal mechanism solutions of Wenchuan earthquake sequence (M 4.0) are determined. The results show that the initial rupture of mainshock is purely thrust. The aftershocks of Wenchuan earthquake sequence are mostly thrust or strike-slip, and there is a characteristic of subsection distribution. The P axes shows a dominant distribution in the directions of NWW-SEE and NEE-SWW.

利用2008年5月12日至8月7日包括国家地震台网、地方区域地震台网和流动地震台网在内的1023个地震台站及IRIS台站的数字地震波形记录资料, 读取P波初动极性, 并采用改进的格点尝试法对汶川地震序列震源机制解进行求解, 给出121个4.0级以上质量可靠的震源机制解。根据求解结果发现: 汶川Ms 8.0级主震P波初动解为纯逆冲型; 汶川余震序列震源机制解绝大部分是逆冲型或走滑型地震, 并具有分段分布特征; 其P轴方位有两个优势分布方向: 北西西?南东东向和北东东?南西西向。

... 在震源机制的求解过程中, P波初动法是计算中小地震震源机制比较常用的方法, 该方法有快速简便的优点, 但同时要求P波震相数据不能太少, 并且在震源球面上有足够的覆盖区域(崔效锋等, 2011) ...

2004

0.0

刁桂苓, 赵英萍, 啜永清, 等. 2004. 大同晚期强余震前震源机制解的一致性特征[J]. 内陆地震, 18(3): 202—206.

DIAO

Gui-ling

, ZHAO

Ying-ping

, CHUAI

Yong-qing

, et al. 2004. Coherence characteristics of focal mechanism solutions of later-period strong aftershocks[J]. Inland Earthquake, 18(3): 202—206(in Chinese).

取层状介质中一点源位错模型,由计算综合地震图得到P、S各自最大振幅,通过其最大振幅比值与观测资料拟合的方式来确定震源机制.大同遥测地震台网较好地记录了大同地震序列的大量小震.经系统地查阅台网和周围其他台站1990-2002年的全部记录,读取垂直向的P、S最大振幅数据,反演计算得到620个小地震的震源机制解.这些解的优势取向和华北构造应力场的方向相同.定义各个震源机制解的P、N、T轴和构造应力场的3个应力主轴在3维空间的夹角之和为一致性参数,发现在1991年和1999年发生的晚期强余震前2-8个月,一致性参数出现显著的下降.我们认为,这是具有短期预测意义的现象.

... (刁桂苓等, 2004 ...

2013

0.0

房立华, 吴建平, 王未来, 等. 2013. 四川芦山 M_S7. 0地震及其余震序列重定位[J]. 科学通报, 58(20): 1901—1909.

FANG

Li-hua

, WU

Jian-ping

, WANG

Wei-lai

, et al. 2013. Relocation of mainshock and aftershock sequences of M_S7. 0 Sichuan Lushan earthquake[J]. Chinese Science Bulletin, 58(20): 1901—1909(in Chinese).

使用三维速度模型, 测定了2013年4月20日四川芦山 M s7.0级地震的主震位置. 使用双差方法对芦山地震的主震和2464个余震序列进行了重定位, 获得了2405个地震的重定位结果, 平均定位误差在E-W, N-S, U-D方向分别为0.30, 0.29和0.59 km. 主震位置为30.291°N, 102.983°E, 震源深度为17.6 km. 余震展布长度约35 km, 宽度约16 km, 震源深度的优势分布范围在10~20 km之间, 浅部地震很少. 震源深度剖面显示断层面向北西倾斜, 浅部倾角较陡, 深部略缓, 表现为“铲形”逆冲断层的特征. 尽管余震震中主要沿双石-大川断裂地表出露位置的两侧分布, 但根据震源深度剖面推测的芦山地震的发震构造可能为其东侧的一条盲逆冲断层. 重定位结果揭示, 余震区存在一条向南东倾斜的余震带, 它与发震断层相交成y字型, 推测它是逆冲推覆构造中常见的反冲断层, 芦山地震触发了这条反冲断层的活动.

... , 2000), 目前已被广泛应用于地震序列的重定位研究中(房立华等, 2013, 2014 ...

2014

0.0

房立华, 吴建平, 王未来, 等. 2014. 云南鲁甸 M_S6. 5地震余震重定位及其发震构造[J]. 地震地质, 36(4): 1173—1185. doi: DOI: 103969/j. issn. 0253-4967. 2014. 04. 019.

FANG

Li-hua

, WU

Jian-ping

, WANG

Wei-lai

, et al. 2014. Relocation of the aftershock sequence of the M_S6. 5 Ludian earthquake and its seismogenic structure[J]. Seismology and Geology, 36(4): 1173—1185(in Chinese).

We integrated two-month phase data recorded by Yunnan Seismic Network, Zhaotong Seismic Network, Qiaojia Seismic Array and temporal stations deployed around the Ludian earthquake source region and relocated the aftershock sequence of the Ludian earthquake. The locations of 1 750 aftershocks were determined using double-difference location algorithm. The relocation result shows that the aftershock distribution has two predominant directions, to the southeast and southwest, and shows itself as an asymmetric conjugate shape. The lengths of the two aftershock strips are about 16km. The angle between the two strips is about 100°. Aftershock distribution shows that the seismogenic fault of the Ludian earthquake is a high-angle strike-slip fault. The mainshock is located at the middle at southwest of the two aftershock strips. Early aftershocks are distributed mainly along the NW-SE direction, perpendicular to the Zhaotong-Ludian Fault. The aftershocks located to the southwest of the mainshock may be triggered by the mainshock. According to the aftershock distribution and its relations with neighboring faults, focal mechanism of the mainshock, the long axis orientation of seismic intensity map, and distribution of landslides, we speculate that the seismogenic fault is the Baogunao-Xiaohe Fault. There are significant differences not only in seismic activity, deep velocity structure, but also the block movement direction and rate on both sides of the Baogunao-Xiaohe Fault. The northward expansion of aftershock activity may be blocked by the high-velocity anomaly zone located on the north side of the Baogunao-Xiaohe Fault.

1. Institute of Geophysics, China Earthquake Administration, Beijing 100081, China; 2. Guangdong Earthquake Administration, Guangzhou 510070, China

整合了鲁甸震区周边的云南省地震台网、昭通市地震台网、巧家台阵, 以及流动台站2个月的震相观测数据, 对鲁甸地震序列进行了重新定位, 得到了1 750个地震的震源参数.重定位结果显示, 余震有2个优势分布方向, 分别为SE向和SW向, 具有不对称的共轭分布特征.2个余震条带的展布长度相当, 约为16km, 夹角约100°.余震分布显示鲁甸地震的发震断层为高倾角的走滑断层.主震位于2个余震条带中间略偏西南的位置, 早期余震主要沿NW-SE向垂直于昭通-鲁甸断裂分布, 主震西南侧的余震可能为后期触发的.根据余震分布与周边断层的关系、主震震源机制、烈度分布的长轴方位, 以及滑坡分布等资料, 认为鲁甸地震的发震断层为NW向的包谷垴-小河断裂.包谷垴-小河断裂南北两侧无论是在地震活动、深部速度结构, 还是块体运动方向和速率方面都存在显著差异, 断裂北侧的高速异常可能是阻止余震向北继续扩展的主要原因.

... , 2000), 目前已被广泛应用于地震序列的重定位研究中(房立华等, 2013, 2014 ...

2011

0.0

付虹, 王绍晋, 李丽, 等. 2011. 滇中地区震源机制一致性参数时空分布与强震活动[J]. 地震研究, 34(2): 113—118.

Hong

, WANG

Shao-jin

, LI

, et al. 2011. Spatial-temporal distribution of the parameters of the focal mechanism and strong seismicity in Central Yunnan[J]. Journal of Seismological Research, 34(2): 113—118(in Chinese).

利用云南数字地震台网记录到的地震直达波Pg、Sg振幅资料,采用层状介质中点源位错模型的广义透射系数的快速算法,计算理论地震图的Pg、Sg最大振幅比值,将其与观测值拟合,反演得到1999年至2009年11月14日滇中地区206个中小地震的震源机制解,计算震源机制解应力主轴与相应的区域构造应力场主轴之间的一致性参数,分析震源机制一致性参数时空分布与强震活动的关系。分析表明,强震发生前3年至数月,强震震源区附近出现多个震源释放应力场与区域应力场一致或接近的中小地震,强震就发生在中小震震源机制一致性参数低值分布区内或其边缘附近。

... 付虹等, 2011), #cod#x003b1 ...

... 参考前人(付虹等, 2011)的研究结论, 将均值作为控制线, 低于均值表示震源机制与构造应力场重合性较好, 构造应力场对该地区控制作用增强 ...

2008

0.0

胡幸平, 俞春泉, 陶开, 等. 2008. 利用P波初动资料求解汶川地震及其强余震震源机制解[J]. 地球物理学报, 51(6): 1711—1718.

Xing-ping

, YU

Chun-quan

, TAO

Kai

, et al. 2008. Focal mechanism solutions of Wenchuan earthquake and its strong aftershocks obtained from initial P wave polarity analysis[J]. Chinese Journal of Geophysics, 51(6): 1711—1718(in Chinese).

We firstly read out initial P wave polarity from the digital wave form data given by Chinese national seismic networks, regional seismic network, temporary seismic network as well as some IRIS stations. Then employing grid point test method we obtain Focal Mechanism Solution of the great Wenchuan earthquake, which measured at 8.0 M S occurred at 14∶28 CST on May 12, 2008 in Sichuan province of China as well as those of some of its strong aftershocks ( M ≥ 5.0). This group of focal mechanism solutions are very important complement of 9 optimized double-couple solutions published by Harvard university.

通过查阅国家地震台网、各省区域地震台网和流动地震台网，以及IRIS数据中心给出的一些国际台站的数字波形记录，读取P波初动方向，利用格点尝试法计算了2008年5月12日汶川8.0级（ M S ）特大地震以及其后发生的部分强余震（44次）的震源机制解.这组震源机制解是对哈佛大学已公布的9个地震的最佳双力偶解的很好补充.

... 通过P波初动方法(胡幸平等, 2008 ...

2015

0.0

... 黄显良等(2015)采用P波、 SV波和SH波的极性和振幅比联合求解2014年安徽省金寨M_L3 ...

2015

0.0

李金, 周龙泉, 龙海英, 等. 2015. 天山地震带(中国境内)震源机制一致性参数的时空特征[J]. 地震地质, 37(3): 792—803. doi: DOI: 103969/j. issn. 0253-4967. 2015. 03. 010.

Jin

, ZHOU

Long-quan

, LONG

Hai-ying

, et al. 2015. Spatial-temporal characteristics of the focal mechanism consistency parameter in Tianshan(within Chinese territory)seismic zone[J]. Seismology and Geology, 37(3): 792—803(in Chinese).

Based on 306 focal mechanism solutions of M S ≥3.5 earthquakes from 2003 to 2014 in Tianshan seismic zone, we divide the Tianshan seismic zone into grids of certain size and use multiple focal mechanism solutions around each grid node to do the stress tensor inversion, and then calculate the temporal and spatial distribution of the focal mechanism consistency parameter for each grid node. On this basis the stress state of the Tianshan seismic zone is analyzed and the relationship between temporal and spatial distribution of focal mechanism consistency parameter and strong earthquakes is discussed. The result shows that the principal compressive stress of Tianshan is quite similar to the former research result; the P axis of the whole Tianshan is mainly in NS direction and in NNE and NNW in localized areas. There is a corresponding relationship between the temporal-spatial distribution of the focal mechanism consistency parameter and the strong earthquakes; strong earthquakes in the middle-east area of Tianshan Mountains often occur in the low value zones of focal mechanism consistency parameter or near the edge of the zones. Since the second half of 2011, the focal mechanism consistency parameter in the middle-east area of Tianshan Mountains presents a process from disorder to consistency, which corresponds to the group activity of strong earthquakes in Xinjiang in this period; the focal mechanism consistency parameter in the southern section of Tianshan also decreased before 2008 Wuqia M S 6.9 earthquake. In addition, we can see from the b -value image of Tianshan that earthquakes with magnitude larger than 5 occur mostly in the relatively low b value area.

基于天山地震带2003—2014年306个 M S 3.5以上的震源机制解资料, 将天山地震带划分为一定的网格, 利用每个网格节点及其周围一定范围内的多个震源机制解进行应力张量反演; 计算各节点震源机制一致性参数的时空分布, 在此基础上研究了天山地震带的应力状态, 以及震源机制一致性参数时空分布与中强以上地震活动的关系.结果表明, 反演获得的天山地震带主应力与早期研究结果具有相似性, 整个天山地震带主应力轴以SN向为主, 局部区域呈现NNE、NNW向.震源机制一致性时空分布与天山地震带中强地震的发生具有一定的对应关系, 天山中东段地区中强地震大多发生在震源机制一致性参数低值分布区或其边缘附近.2011年下半年以来, 天山中东段地区震源机制一致性参数总体呈现由紊乱到一致的过程, 与该时段内新疆地区中强地震的成组活动相互对应; 2008年乌恰6.9级强震前, 南天山西段震源机制一致性参数也明显下降; 此外, 从计算得到的天山地震带 b 值图像来看, 2003年以来5级以上中强地震多分布于 b 值相对较低的区域.

... 3 震源机制解分析震源机制解不仅含有断层运动方式及震源破裂过程的信息, 而且还能够反映地震前后震源区应力变化状态, 为区域构造应力场研究提供重要依据(李金等, 2015) ...

... 李金等(2015)利用天山地震带306个震源机制解资料反演该区域应力场, 得出该区域震源机制一致性的时空分布与中强地震有一定关系 ...

2015

0.0

李丽, 宋美琴, 刘素珍, 等. 2015. 山西地区震源机制一致性参数时空特征分析[J]. 地震, 35(2): 43—50.

, SONG

Mei-qin

, LIU

Su-zhen

, et al. 2015. Spatial-temporal characteristics of the consistency parameter of focal mechanisms in Shanxi area[J]. Earthquake, 35(2): 43—50(in Chinese).

摘　要：利用山西数字地震台网记录到的中小地震波形资料,采用层状介质中点源位错模型的广义透射系数的快速算法和理论地震图拟合直达波最大振幅比来求取小震震源机制解的方法,计算了2001年—2012年山西地区281个中小地震震源机制解,根据优势分布得到山西地区现今平均构造应力场分布,计算震源机制解应力主轴与相应的区域构造应力场主轴之间的震源机制一致性参数,分析一致性参数时空分布与中等地震活动的关系。结果显示,2001年以来山西5次ML≥5.0地震前均有震源机制趋于一致性现象,震中分布在一致性参数低值附近或高低值过渡区域。

... 李丽等(2015)采用层状介质中点源位错模型的广义透射系数的快速算法和理论地震图拟合直达波最大振幅比来求解小震震源机制解, 计算了2001#cod#x02014 ...

2012

0.0

李霞, 刘希强, 李亚军, 等. 2012. 山东及邻区地震的重新定位及其与活动构造的关系[J]. 中国地震, 28(4): 381—392.

Xia

, LIU

Xi-qiang

, LI

Ya-jun

, et al. 2012. Relocation of earthquakes in Shand ong and its neighboring areas in China and relationship between their tectonics[J]. Earthquake Research in China, 28(4): 381—392(in Chinese).

... 李霞等, 2012 ...

2015

0.0

罗钧, 赵翠萍, 周连庆. 2015. 2013年8月香格里拉德钦-得荣 M_S5. 9地震序列震源机制与应力场特征[J]. 地球物理学报, 58(2): 424—435.

LUO

Jun

, ZHAO

Cui-ping

, ZHOU

Lian-qing

. 2015. Focal mechanisms and stress field of the Shangri-La Deqen, Yunnan Province-Derong, Sichuan Province M_S5. 9 earthquake sequence in August, 2013[J]. Chinese Journal of Geophysics, 58(2): 424—435(in Chinese).

No M S >5 earthquakes have been observed in the northwestern boundary of the Sichuan-Yunnan Block, the Jinshajiang fault and the Deqen-Zhongdian-Daju fault systems, since 1976. The M S 5.1 earthquake and the M S 5.9 earthquake, which sequentially took place in Shangri-La Deqen,Yunnan province-Derong Sichuan province on April 28 th , 2013 and April 31 th , 2013, supplement apparent gaps of the focal mechanisms spatial distributions image of Sichuan-Yunnan Block boundary fault systems and also provide important date for further researches in terms of both faulting activities and tectonic stress field characteristics. Using digitally broadband seismic records, we determined focal mechanisms of 10 moderate earthquakes ( M S >4) in this M S 5.9 and M S 5.1 earthquake sequence. The focal mechanism solutions then supply data for the analyses of seismogenic fault activities and investigations of focal mechanisms and stress field characteristics in the Sichuan-Yunnan region. Regional broadband seismic records of China Seismograph Network were used to determine the focal mechanisms and focal depths of the M S 5.9 earthquake, M S 5.1 earthquake and other M S >4 events by the whole wave inversion method called the Cut-and-Paste method. The Focal Mechanism Stress Inversion method was introduced to estimate the local crust stress field of the source region. Combining our researches of focal mechanisms of moderate and large earthquakes in recent years with the geologic structures, aftershock distributions, intensity features and geodynamic backgrounds, we analyzed the characteristics of focal mechanisms and stress field of this earthquake sequence. The following results are obtained from focal mechanisms and stress field solutions of the M S 5.9, M S 5.1 earthquake sequence: (1) The M S 5.9 earthquake and M S 5.1 earthquake are normal faulting events, so are other eight M S >4 aftershocks. Results show seismogenic fault is a northwest-west striking active fault. The fault solutions of the M S 5.9 and M S 5.1 earthquakes are strike 299°, dip 53°, rake -73° and strike 290°, dip 55°, rake -72°respectively. (2) Spatial distributions of T -axes and P -axes of the M S 5.9 and M S 5.1 events are exhibited similar, whereas, the orientations of these two axes of the M s 5.9 aftershocks deviate from the ones of the main event in the following two days and relocate to the ones that are similar with the main event later, indicating an obvious stress readjustment process in the seismic source region. (3) The maximum principal axes (maximum compression) are perpendicularly oriented in northwest-southeast and the minimum principal axes (minimum compression) are horizontally in north-northeast-south-southwest, leading to an obvious normal-faulting active region. These distributions are consistent with the trending of the surface maximum principal tensile stress field derived from the geodetic observations. (4) Combined our previous focal mechanisms determination, it can be concluded that the Shangri-La sub-block and the Baoshan sub-block are two interior regions in the Sichuan-Yunnan Block which are obviously under the normal-faulting regimes. However, the fault nodal planes and P -axes and T -axes strike differently in each boundary fault system. The orientations of nodal planes exhibit a clockwise rotation, with a gradual change from trending east-west in the northern section of the Jinshajiang fault and the middle section of the Litang fault to trending northwest-west in the Deqen-Zhongdian-Daju fault then to trending nearly north-south in the southwestern section of the Lijiang-Xiaojinhe fault and the northern margin of the Baoshan sub-block. The T -axes are correspondingly oriented in north-south or north-northwest-south-southeast further to northeast-southwest then to east-west or northeast-east-southwest-west, suggesting that stress states in these boundary faults are not consistent under the normal faulting regimes. In sum, this M S 5.9, M S 5.1 earthquake sequence is an apparent normal-faulting sequence. The stress field of seismic source experienced distinct stress readjustments during the development process of the whole sequence. Solutions of focal mechanisms of the Sichuan-Yunnan region in recent years show that the Shangri-La sub-block and the Baoshan sub-block are primarily under normal faulting stress patterns which are dominated by the horizontally tensile stress field. While the changes of the nodal planes and T -axes orientations in each boundary fault system indicate the existed influences of the sub-blocks interactions, terrain diversities under the background tectonic stress field.

1. Institute of Geophysics, China Earthquake Administration, Beijing 100081, China; 2. Key Laboratory of Earthquake Prediction, Institute of Earthquake Science, CEA, Beijing 100036, China

利用中国区域台网地震波形记录,采用CAP方法反演了香格里拉德钦(位于云南省)—得荣(属于四川省)2013年8月28日 M S 5.1、8月31日 M S 5.9地震及8次 M S >4余震的震源双力偶断层面解和震源质心深度.结合震区地质构造、余震分布、烈度分布、动力学背景等资料,分析了此次地震序列的震源机制和应力场特征.反演结果表明,此次地震序列为节面倾角倾斜的正断层型地震,发震断层为NWW向活动构造带.序列中最大地震 M S 5.9和次大地震 M S 5.1地震的破裂节面分别为走向299°、倾角53°、滑动角-73°;走向290°、倾角55°、滑动角-72°.震源区受到强烈的水平拉张力、垂直挤压力作用. M S 5.9地震后续余震 T、P 轴方位角随时间变化强烈,表明 M S 5.9地震后震源区应力调整作用明显.震源区应力场反演结果显示,地震发生的构造带上最大主拉应力为NNE-SSW向,最大主压应力为NW-SE向,与GPS观测所反映的地表最大主应力分布方向基本一致,表明震源区的应力状态可能主要受到背景大尺度构造应力场的控制.此次地震序列填充了川滇地区震源机制及应力场的空间分布图像,1976年以来可靠的震源机制解资料表明香格里拉次级块体是川滇块体及周边区域显著的拉张作用区域.香格里拉次级块体和保山次级块体正断层地震的断层节面及震源应力轴分布的空间变化,与GPS观测反映的地表最大主拉应力分布较一致,其空间分布特征反映了在青藏高原物质挤出背景下,块体之间相互作用、地势差异等作用对构造活动的影响.

... 另外, 该方法允许各时间窗理论波形和观测波形进行相对滑动拟合, 大大减少了地壳速度结构模型对反演结果的影响, 降低了对台站数量和方位角分布的要求, 提高了信噪比和反演精度, 适用于震级略大的小地震及中、强地震震源机制解的研究(罗钧等, 2015), 本文2次3 ...

2015

0.0

曲均浩, 蒋海昆, 李金, 等. 2015. 2013—2014年山东乳山地震序列发震构造初探[J]. 地球物理学报, 58(6): 1954—1962.

Jun-hao

, JIANG

Hai-kun

, LI

Jin

, et al. 2015. Preliminary study for seismogenic structure of the Rushan earthquake sequence in 2013—2014[J]. Chinese Journal of Geophysics, 58(6): 1954—1962(in Chinese).

采用结合波形互相关技术的双差定位方法,对2013—2014年山东乳山地震序列重新定位,通过CAP及P波初动方法确定乳山序列较大地震的震源机制,在此基础上初步探讨乳山地震序列发震构造.结果显示,乳山序列呈现NW向展布,地震密集分布在8km×3km范围,震源深度分布在4~10km,4~7km区间相对集中.较大地震震源机制的节面Ⅰ方向与序列地震优势分布方向基本一致.综合考虑精确定位结果及较大地震震源机制,并结合震区附近地震资料,初步推测乳山地震序列发震断层为NW方向、近直立的走滑型隐伏断裂.

... 与历史地震序列相比, 该区域从未出现过如此高频、时间持久的地震序列活动(曲均浩等, 2015)(图1) ...

... 曲均浩等, 2015), 选用不同模型关键深度的速度值作为本文初始模型的速度值(表1), 波速比设为1 ...

... 根据郑建常等(2015)、曲均浩等(2015)基于CAP方法对乳山序列较大地震震源机制解的研究, 所得到的17个震源机制解中有16个节面优势走向为290#cod#x000b0 ...

2018

0.0

曲均浩, 刘方斌, 郑建常, 等. 2018. 乳山地震序列区域台网及台阵定位结果对比[J]. 震灾防御技术, 13(1): 149—157.

Jun-hao

, LIU

Fang-bin

, ZHENG

Jian-chang

, et al. 2018. Comparision of location of Rushan seismic sequence between region network and array network[J]. Technology for Earthquake Disaster Prevention, 13(1): 149—157(in Chinese).

... 另外, 这一结果与郑建常等(2015)、曲均浩等(2018)采用双差定位法对乳山台阵记录的部分地震重定位结果也基本一致 ...

1983

0.0

许忠淮, 阎明, 赵仲和. 1983. 由多个小地震推断的华北地区构造应力场的方向[J]. 地震学报, 5(3): 268—279.

Zhong-huai

, YAN

Ming

, ZHAO

Zhong-he

. 1983. Evaluation of the direction of tectonic stress in North China from recorded data of a large number of small earthquakes[J]. Acta Seismologica Sinica, 5(3): 268—279(in Chinese).

利用1966—1978年间华北地区区域地震台记录的5级以下地震的初动方向,通过求平均节面解推断出13个分区的地壳构造应力场的主应力轴方向.通过数值试验论证了利用多个断层面随机取向的地震的 P、B、T 轴推断构造应力主轴方向的可能性.讨论了在推断构造应力场方向时,利用多个小地震资料比利用大地震资料所具有的优越性.用尝试法对所有可能解的三维参数空间以5°×5°×5°的间隔进行了扫描搜索,改进了扫描方法,节省了计算时间.

... 虽然1次中小地震的震源机制解不足以反映区域应力场的概况, 但大量中小地震震源机制解的总体特征在一定程度上能够代表区域构造应力场的方向(许忠淮等, 1983) ...

... 本文采用许忠淮等(1983)提出的格点尝试法对1 ...

2013

0.0

俞红玉, 陶开, 蔡晨, 等. 2013. 东日本大地震地震序列的震源机制解特征及其动力学意义[J]. 地球物理学报, 56(8): 2655—2669.

Hong-yu

, TAO

Kai

, CAI

Chen

, et al. 2013. Focal mechanism solutions of the Tohoku-Oki earthquake sequence and their geodynamical implications[J]. Chinese Journal of Geophysics, 56(8): 2655—2669(in Chinese).

The stress state of Japan Sea region and its evolution are both concerned greatly by geoscientists. In this paper, we study Harvard CMT solutions of the March 11, 2011 Tohoku-Oki Earthquake sequence from March 11th, 2011 to March 15th, 2012 by cluster analysis and find that they might be roughly sorted to four groups. The first group are low-angle thrust events, which are the same as the main shock and are mostly interplate events. The second group events are normal-fault earthquakes with principal extensional direction roughly pointing to E-W direction. Most of these earthquakes were located in the fore-arc uplift region of the Pacific plate, while some others occurred in the fore-arc accretionary wedge. The third group events are also normal-fault events mainly occurred in the fore-arc accretionary wedge though their principal extensional directions roughly parallel the Japan Trench. The forth group are reverse earthquakes with principal compressional directions roughly along N-S direction. We observe that Harvard CMT solutions of 2011 Tohoku-Oki earthquake sequence are obviously different from before. They show that Tohoku-Oki Earthquake sequence have released most of elastic energy in the main shock area. As a result, Pacific Plate and North America Plate have decoupled in the main rupture zone, which lowered the E-W compressional stress in Japan Sea and Northeastern China. However, Japan Sea Subduction Zone has not completely decoupled with North American Plate, even though the stress level in this region is lowered now. We claim that releasing of accumulated stress in the region of Japan Sea and Northeast China could lower the seismic hazard of roughly E-W direction compressive events, while tend to increase the activity of NNE-SSW strike-slip events as well as the volcanism, especially in Honshu. The characteristics of the Focal Mechanism Solutions of the Tohoku-Oki Earthquake Sequence remind us that stress state as well as evolution of Japan Sea might depend to some extent on coupling state between Pacific Plate and North American Plate. Long-lasting weak coupling might lead to re-opening of Japan Sea Basin because it will not only guarantee a relatively extensional environment, but also provide necessary water to deep depth.

日本本州及其邻近区域的应力状态以及弧后盆地的演化机制一直是人们所关注的问题.本文对2011年3月11日东日本大地震地震序列(2011年3月11日至2012年3月15日)的哈佛双力偶解进行了聚类分析,得到五种类型的震源机制解:与主震类型一致的低倾角逆断层型地震;主张应力方向垂直于日本海沟走向的正断层型地震;主张应力方向平行于日本海沟走向的正断层型地震;主压应力方向平行于日本海沟走向的逆断层型地震;包括走滑型地震在内的其他类型地震.东日本大地震地震序列中发生在弧前增生楔地震的震源机制解与大地震发生之前地震的震源机制解特征有显著区别,反映出该地区的应力状态与震前相比有较大改变.东日本大地震及其前震释放了附近区域的累积弹性应力,主震破裂区附近太平洋板块和其上覆板块接近完全解耦,降低了日本海盆地、中国东北地区的近东西向挤压应力水平.不过,整个本州岛东部区域太平洋板块和其上覆板块并没有完全解耦,但应力水平并不高.我们认为,日本海及中国东北应力水平的降低会使该区域的近东西向挤压型地震的危险性降低,而使NNE-SSW走向的走滑型地震活动性增强.同时,火山活动性也会增强.尤其是本州岛地区,存在近期火山爆发的可能性.东日本大地震地震序列的震源机制解特征还提示我们,日本海的应力状态及日本海的演化可能在一定程度上取决于太平洋板块和上覆板块的耦合状态.持续的弱耦合将不仅使得弧后大范围的地区保持岩浆上涌所必须的拉伸应力环境,而且还会因弧前隆起区发育大量正断层型地震而向深部提供促使岩浆生成所必须的水,因而造成日本海的再次扩张.

... 俞红玉等, 2013)计算研究区内346个1 ...

2005

0.0

张岭, 刘劲松, 郝天珧. 2005. 利用Ground-Truth资料和Messy GA方法反演渤海湾盆地及其邻区地壳P波速度模型[J]. 地球物理学进展, 20(1): 186—197.

ZHANG

Ling

, LIU

Jin-song

, HAO

Tian-yao

. 2005. Inverse crustal P-wave velocity model of Bohai Bay Basin and its adjacent area by using Messy GA with Ground-Truth data[J]. Progress in Geophysics, 20(1): 186—197(in Chinese).

收集了1978～2003年位于渤海湾盆地及其邻近地区(大体位于东经112°～122°,北纬34°～44°之间)所记录到的的总计10534个地震或人工爆破事件的Pn、Pg以及P波到时数据,运用GT5准则,从中挑选出相对精确和可信度较高,且具有代表性的的10个地震事件,使用MessyGA算法,分别反演了这10个地震事件所对应的一维地壳P波速度模型.反演的局部地壳模型与已知结果对应较好,基本反映了震中区的地壳速度结构特征.该方法原理简单,计算方便,可用于确定局部和区域的地壳速度模型.

... 0及层析成像得到的胶东半岛地壳速度模型(张岭等, 2005 ...

2004

0.0

赵英萍, 刁桂苓, 高景春, 等. 2004. 张北强余震前震源机制解的一致性特征[J]. 华北地震科学, 22(1): 1—4.

ZHAO

Ying-ping

, DIAO

Gui-ling

, GAO

Jing-chun

, et al. 2004. Consistency of the focal mechanisms before some strong aftershocks in Zhangbei earthquake series[J]. North China Earthquake Sciences, 22(1): 1—4(in Chinese).

取层状介质中一点源位错模型,由计算综合地震图得到、各自最大振幅,通过其最大振幅比值与观测资料拟合的方式来确定震源机制.我们系统地查阅了北京台网、河北台网的数字化记录并补充内蒙古的兴和临时台、集宁台和宝昌台1998年～1999年3月的记录,读取垂直向的、最大振幅数据,经反演计算得到145个小地震的震源机制解.这些解的优势取向和华北构造应力场的方向相同.定义各个震源机制解的P、N、T轴和构造应力场的3个应力主轴在三维空间的夹角之和为一致性参数,发现在1999年发生的强余震前一致性参数出现异常变化,我们认为这是具有预测意义的现象.

... 赵英萍等, 2004 ...

2015

0.0

郑建常, 曲利, 曲均浩, 等. 2015. 乳山震群大小台网地震定位的对比研究[J]. 地震地质, 37(4): 953—965. doi: DOI: 103969/j. issn. 0253—4967. 2015. 04. 002.

ZHENG

Jian-chang

, QU

Jun-hao

, et al. 2015. Comparison of locations of Rushan earthquake swarm from large and small network[J]. Seismology and Geology, 37(4): 953—965(in Chinese).

A notable swarm occurred in Rushan, Shandong Peninsula and its activities continue since Oct. 2013 till now. Up to Sept. 30, 2014, more than 7 000 events have been recorded, in which locatable shocks exceed 2000, and 18 events with M L ≥3.0. The swarm is rarely seen in East China for its extraordinary duration time and surprising high frequency of aftershocks. 18 temporary seismometers have been deployed around the swarm since May 6, 2014, and composed a seismic array for monitoring the swarm activities. Based on data from permanent networks and temporary array, we relocated the earthquake sequence by using hypoDD method. It has been shown that, there is obvious difference between permanent network results and temporary array results. The permanent network of Shandong has a relative large coverage gap(more than 200°)for this swarm. Its location results therefore should not be reliable. There are maybe other errors in the permanent network result due to some problems in the raw data, such as too few stations for most locatable events(3 stations), and relative lower proportion of located events in final result(74.3%, while 95.1% in temporary array result). It can be found by comparing location results from permanent network and temporary array that, using temporary array's data can improve the location accuracy significantly. The results of temporary array are: aftershocks distribution of Rushan swarm is in NWW direction, the dip-direction of fitted fault plane is SW, and the strike and dip angle agree with focal mechanism of the mainshock. Focal depths of aftershocks are at 4.5～8km; the swarm is restricted in a small area about 3km×3km×1km, and has some characteristics such as clustering, staged activities, and etc; the aftershock activities are in accord with crack growth behavior pattern, hence we deduced that there may be fluid intrusion in source area. Finally, we discussed the seismogenic structures and active mechanisms of this swarm combined with relative geologic knowledge. We draw some conclusions as follows: 1)Rushan swarm probably occurred at the boundary of rock bodies of Duogu Mountain and Haiyangsuo super-unit; 2)The seismogenic structure is a blind fault, which should be a part of adjacent Heishankuang-Jilincun Fault, or might be a new fault at rock body boundaries; 3)Rushan swarm might be an evidence for the existence of the disputed Shidao Fault.

山东乳山地区自2013年10月起发生震群活动, 并且持续至今(2014年10月); 截至2014年9月30日, 共记录到余震7 000多次, 其中可定位事件2 000多次, M L ≥3.0的18次, 其持续时间、活动频度为1970年以来华东地区罕见。2014年5月6日起, 陆续在现场布设了18个流动台, 持续对序列活动进行观测。基于固定台网和流动台阵的资料, 使用双差方法对地震序列进行重新定位。结果显示, 流动台阵定位结果与固定台网结果存在较大差别, 由于数据本身的问题, 固定台网结果可能存在一定的偏差。流动台阵精定位结果显示, 乳山震群的余震呈NWW向展布, 倾向SW, 与震源机制解结果一致; 余震震源深度较浅, 4.5～8km; 余震主要集中在3km×3km×1km很小的范围内密集活动, 并且具有阶段性、丛集性的特点, 余震活动符合裂纹扩展模式, 可能存在流体触发因素。最后结合有关地质资料对此次乳山震群的发震构造、性质以及震群的活动机理进行了探讨。

... 根据郑建常等(2015)、曲均浩等(2015)基于CAP方法对乳山序列较大地震震源机制解的研究, 所得到的17个震源机制解中有16个节面优势走向为290#cod#x000b0 ...

... 另外, 这一结果与郑建常等(2015)、曲均浩等(2018)采用双差定位法对乳山台阵记录的部分地震重定位结果也基本一致 ...

2009

0.0

... 泽仁志玛等, 2009 ...

2015

0.0

... Fang et al ...

2014

0.0

... Govoni et al ...

1984

0.0

... 本文利用上述348个中小地震的震源机制解作为输入数据, 采用Michael(1984, 1987)的自助线性应力反演(Linear stress inversion bootstrap, LSIB)方法计算乳山区域应力张量 ...

1987

0.0

2000

0.0

... 0的1i418个地震事件采用双差定位法(Waldhauser et al ...

... 2 双差定位双差定位法是1种高精度的相对定位算法(Waldhauser et al ...

1996

0.0

... 6地震采用CAP(Cut and Paste)方法(Zhu et al ...

1992

0.0

... 根据Zoback(1992)对震源机制的分类标准(表3), 对上述震源机制进行分类统计 ...