基于加密观测的金沙江下游水库区速度结构成像

引用本文

张娜, 赵翠萍, 李春宏, 周连庆. 基于加密观测的金沙江下游水库区速度结构成像[J]. 地震地质, 2019,41(6): 1380-1394.
ZHANG Na, ZHAO Cui-ping, LI Chun-hong, ZHOU Lian-qing. VELOCITY STRUCTURE TOMOGRAPHY OF REGIONS DOWNSTREAM THE JINSHA RIVER BASED ON DENSE OBSERVATION[J]. SEISMOLOGY AND GEOLOGY, 2019,41(6): 1380-1394. 复制到剪切板

DOI:10.3969/j.issn.0253-4967.2019.06.005
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基于加密观测的金沙江下游水库区速度结构成像

张娜^1,²⁾, 赵翠萍^1),^*, 李春宏¹⁾, 周连庆¹⁾

1)中国地震局地震预测研究所, 北京　100036

2)山西省地震局, 太原　030021

*通讯作者: 赵翠萍, 研究员, E-mail: zhaocp@cea-ies.ac.cn。

〔作者简介〕张娜, 女, 1992年生, 2018年于中国地震局地震预测研究所获地球物理学专业硕士学位, 现主要从事地震学研究, 电话: 18834821722, E-mail: 15201562933@163.com。

收稿日期: 2018-02-28

基金项目: 中国地震局地震预测研究所基本科研业务专项“川滇菱形块体南部深部构造与水库地震危险性研究”(2015IES0103)、中国地震局地震预测研究所基本科研业务专项“典型库区蓄水前后地震活动监测和水库地震活动特征研究”(2015IES010303)和中国地震局地球物理研究所基本科研业务专项(DQJB16B05)共同资助

摘要

文中使用2013年8月—2016年12月金沙江下游水库台网42个台站记录到的7⁴65个地震事件的到时数据, 采用双差层析成像方法, 反演得到了金沙江下游水库区地震震源参数及周围地区分辨率达0.1°的地壳三维速度结构。在研究区2~6km深的浅层, P、 S波沿小江断裂北段呈现低速异常特征, S波的低速异常尤其显著, 在小江断裂带东、西两侧出现了明显的低速区, 说明浅层低速区的分布与研究区的地形、岩性分布以及金沙江流经区域对应较好。自6km深处开始, P波在小江断裂北段东侧形成了沿昭通、会泽-彝良断裂的NE向高速条带, S波在莲峰断裂、包谷垴-小河断裂、昭通-鲁甸断裂和会泽-彝良断裂所围限的区域内呈现高速分布。以小江断裂为界, 在深度10km以上的浅层, 包括宁会断裂在内的小江断裂西侧, V_P呈现显著的低速异常, 而小江断裂东侧则为高速。小江断裂带自北至南呈现显著的 V_P低值, 且北段的低速异常相对显著, 在巧家附近低速异常区的深度达15km。白鹤滩大坝下方呈现显著的 V_P低速分布, 深度至5km。大坝周围的地震在低速一侧由浅至深形成了条带。乌东德大坝下方为稳定的高速分布。重定位结果显示: 研究区内震源深度<20km的地震优势分布在15km以浅, 在小江断裂带东、西两侧的麻塘断裂、大朵断裂以及会泽县附近的重定位事件出现了比较明显的近EW向分布, 与该区域内主要大型断裂的NE走向不同。鲁甸地震序列的震源深度<15km, 优势分布在10km以浅, 地震序列的优势分布方向为近EW和SN向, 在2个优势方向上2a内发生的余震分别形成了长约40km、 20km的条带。

关键词: 小江断裂带北段; 双差层析成像; 三维速度结构; 鲁甸 M6.5地震

中图分类号:P315.2 文献标志码:A 文章编号:0253-4967(2019)06-1380-15

VELOCITY STRUCTURE TOMOGRAPHY OF REGIONS DOWNSTREAM THE JINSHA RIVER BASED ON DENSE OBSERVATION

ZHANG Na^1,²⁾, ZHAO Cui-ping¹⁾, LI Chun-hong¹⁾, ZHOU Lian-qing¹⁾

1)Institute of Earthquake Forecasting, China Earthquake Administration, Beijing　100036, China

2)Shanxi Earthquake Agency, Taiyuan　030021, China

Abstract

In this paper, the double difference seismic tomography method is applied to the phase arrival times of 7465 seismic events to determine the hypocenter parameters of events as well as detailed 3D velocity structure at the northern segment of Xiaojiang Fault and its surrounding area. The data was recorded by 42 stations of the Jinshajiang River network from August 2013 to November 2016. At 2~6km, V_P and V_S present low velocity anomalies along the northern segment of Xiaojiang Fault, and the V_S anomaly is especially remarkable. On both sides of the Xiaojiang Fault, there also exist obvious P and S wave low velocity areas. These low velocity areas correspond to the terrain, lithology distribution and the watershed of Jinsha River at shallower layer in the study area. Starting from 6km, a NE-directed high V_P band along Zhaotong-Ludian and Huize-Yiliang Fault is formed on the eastern side of the northern segment of Xiaojiang Fault. V_S also shows the high value in the area bounded by Lianfeng Fault, Baogunao-Xiaohe Fault and Huize-Yiliang Fault. Above 10km depth, to the west side of the Xiaojiang Fault including the Ninghui Fault, V_P shows a significant low-velocity anomaly, while to the east side it presents high velocity feature. The Xiaojiang fault zone shows a significant low V_P from north to south in the study region, and the low velocity anomaly in the northern segment is relatively significant, especially the low velocity anomaly area reaches 15km deep around Qiaojia area. Beneath the Baihetan Dam, a significant low V_P area reaching to 5km deep is found. The earthquakes around the dam formed a strip from shallow to deep on the low-velocity area side. Whereas, a stable high-velocity area is found under the Wudongde Dam. The events relocation result shows that: all the focal depths in the study area are shallower than 20km, and the predominant focal depth is within 15km. Different from the NE-trending of the major faults in the study area, the relocated seismic events are obviously distributed nearly east-west along Matang Fault and Daduo Fault and the region around Huize. The focal depths of M_S6.5 Ludian earthquake sequences are shallower than 15km, and mostly less than 10km. The aftershocks within 2a after the Ludian M6.5 earthquake form two predominant bands of about 40km and 20km along near EW and SN direction, respectively.

Keyword: northern segment of Xiaojiang Fault and its surrounding area; double difference seismic tomography; 3D velocity structure; Ludian M_S6.5 earthquake

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0 引言

金沙江下游建设了乌东德、白鹤滩、溪洛渡和向家坝4座世界级巨型梯级水库, 规模相当于2个三峡水库, 在中国具有非常重要的民生和经济意义。其中, 已建成但尚未蓄水的乌东德、白鹤滩水库和已经运行的溪洛渡水库坐落在本文的研究区域(26° ~27.8° N, 102° ~104° E)内。白鹤滩水电站位于研究区中心, 其上游与乌东德梯级电站相接, 下游尾水与溪洛渡梯级电站相连, 是金沙江下游河段4个梯级开发的第2级。溪洛渡水库最大坝高278m, 正常蓄水位600m, 库容1.27× 10¹⁰m³; 白鹤滩水库最大坝高289m, 正常蓄水位825m, 库容2.06× 10¹⁰m³, 是中国目前库容最大的水电站之一; 乌东德水电站距白鹤滩水电站180km, 最大坝高265m, 初设蓄水位(海拔)975m, 总库容约5.863× 10⁹m³。

金沙江下游梯级电站中的溪洛渡、向家坝先后于2012年10月、 2013年5月蓄水, 蓄水后水库区周边区域地震活动增强。为加强金沙江下游地区的地震活动监测, 开展白鹤滩水库蓄水前后高精度的地震活动时空特征、深浅介质结构等对比研究, 沿金沙江下游架设了26个加密台站, 与四川、云南区域地震台网、中国地震局地球物理研究所布设的 “ 巧家台阵” 组成了覆盖溪洛渡— 白鹤滩— 乌东德段的观测台阵, 本文称之为 “ 金沙江下游水库台网” 。该台网平均台间距< 20km, 监测能力可达0.3级, 仪器采样率为100sps。由于Zhang等(2003)提出的双差层析成像方法(TomoDD)具有能够获得更加精细的震源区速度结构和地震定位结果的显著优势, 近年来该方法已被广泛应用于有密集观测数据的水库区的结构研究(Dixit et al., 2014; 罗佳宏等, 2016), 以揭示库区介质受水库蓄水的影响及库区地震发生的介质环境等。为获得白鹤滩水库区蓄水前的精细速度结构, 为今后开展对比研究奠定基础, 本文利用金沙江下游水库区台网的观测数据, 采用TomoDD方法, 进行了金沙江下游水库及其周边区域的震源定位和三维速度结构成像研究。

1 地震和构造背景

研究区(图1a)位于川滇菱形块体东缘, 属于地质构造不稳定的地区, 该区地质构造背景复杂、构造活动性强(徐锡伟等, 2003)。印度板块持续向欧亚板块的NE向俯冲碰撞导致现今川滇地块向SSE沿喜马拉雅东构造顺时针旋转, 在块体运动过程中华南地块以稳定被动地块的形式阻挡川滇地块的EW和SSE向挤压。研究区内发育许多规模巨大、内部结构复杂的断裂(图1b), 如大凉山断裂、则木河断裂和小江断裂北段(巧家— 东川段)等走向NNW或SN向的深大断裂及NE走向的巧家-莲峰、昭通-鲁甸、会泽-彝良等活动断裂。这些断裂带从活动构造性质及规模上看均具有发生强震、大震的能力(闻学泽等, 2013)。断裂活动对地貌起着重要的控制作用, 金沙江在则木河断裂南段、小江断裂北段及莲峰断裂等多处沿断裂发育, 大坝以南、以北分属于不同的断裂构造。以金沙江(小江断裂北段)为界, 研究区东、西两侧分属不同的构造块体。巧家-莲峰、昭通-鲁甸2条NE向断裂带属于川滇块体-华南地块边界带, 亦是大凉山次级块体与华南地块之间的边界带。位于研究区中心的白鹤滩水电站正好在大凉山SN向构造带的南段、凉山构造带东侧与莲峰-巧家构造带相加持的三角形区域内。

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图 1 研究区域地质构造背景及历史M_S6以上地震
a 白色实线框为研究区。 b 英文字母代表主要的断裂带: DLSF 大凉山断裂; ZMF 则木河断裂; XJF 小江断裂; LFF 莲峰断裂; ZT-LDF 昭通-鲁甸断裂; HZ-YLF 会泽-彝良断裂; NHF 宁会断裂; BGN-XHNF 包谷垴-小河断裂; MT 麻塘断裂; DDF 大朵断裂。黑色矩形代表水库大坝: WDD 乌东德水库; BHT 白鹤滩水库。红色实心圆为研究区内6级以上的地震分布Fig. 1 Tectonic background and M_S≥ 6.0 earthquakes of the study area.

现代构造应力场的研究结果表明, 川滇地块应力场以水平作用为主, 主压应力优势方位为NNW(谢富仁等, 2004; 刘平江等, 2007; Luo et al., 2016)。本研究区历史上发生6级以上地震11次, 其中2次7级以上地震, 分别是1933年发生于小江断裂上的云南东川7.5级和1850年发生于则木河断裂的四川西昌7.5级地震。历史中强震主要集中在则木河-小江断裂带上, 2000AD以来主要沿NE向的昭通-鲁甸断裂及其周边发生, 以中等强度地震为主。如2003年鲁甸M_S5.0和M_S5.2地震、 2004年鲁甸M_S5.6地震等。 2014年8月3日鲁甸M6.5地震发生于昭通、莲峰断裂带之间NW走向的包谷垴断裂(徐锡伟等, 2014)。

2 数据及处理

金沙江下游水库区台网分布如图 2所示。我们对金沙江下游水库台网中42个台站2013年8月31日— 2016年12月13日的观测数据进行处理(巧家台阵观测数据的时间范围为2013年8月— 2015年12月)。首先进行震相和事件识别, 采用基于川滇三维模型的盖格定位方法, 得到了7⁴65个事件的初始定位结果和大量震相数据, 用于本文的进一步研究。

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	图 2 金沙江下游水库区台网分布图黑色实心矩形为水库位置; 三角形为台站; 红色实心三角形为YLTV台Fig. 2 The distribution of seismic stations in the downstream of Jinsha River.

2.1 初始速度模型

在速度成像反演过程中, 一维速度模型影响着三维反演结果的合理性。本文从金沙江下游水库台网的7465个观测数据中选择了最大方位空隙角≤ 180° 、 P波观测数目最少为8的地震事件共824个, 首先进行最小一维速度模型反演(Kissling et al., 1994)。由于YLTV台位于研究区的中心(图2), 记录的地震到时资料丰富, 反演过程中选择其为参考台站。分别以研究区内前人通过人工地震方法获得的测震剖面(熊绍柏等, 1986; 徐涛等, 2014)及CRUST1.0(Laske et al., 2013)速度模型作为最小一维速度模型反演的初始速度模型。使用相同的P波数据并设置相同的反演参数进行20次迭代反演, 得到最小一维速度模型。反演结果(图3)表明, 不同输入模型的反演结果在深度≥ 4km处均收敛于同样的速度, 深度< 4km时由于地震深度分布的不均性导致结果较为发散。其中, 使用CRUST1.0速度模型作为初始模型反演得到的最小一维速度模型的走时均方根残差和数据方差均最小, 均方根残差从1.014s降至 0.455s, 方差从1.405s²降至0.284s²。同时, 为验证结果的准确性, 再以添加± 15%扰动的CRUST1.0模型(图3)作为输入模型进行扰动性实验, 得到的2种速度模型基本都收敛于最小一维速度模型, 说明迭代反演得到的最小一维速度模型是准确且稳定的。最终确定以CRUST1.0模型为输入的反演结果即最小一维速度模型作为双差成像采用的初始速度模型(图 3中的红色实线)。

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	图 3 最小一维速度反演结果Fig. 3 The inversion results of the minimum 1-D velocity model.

2.2 双差成像数据处理

在反演过程中, 将研究区域划分为水平方向间隔为0.1° 的网格, 垂向层位深度设置为0km、 1km、 2km、 4km、 6km、 8km、 10km、 15km、 20km和80km, 选取近白鹤滩水库大坝的点位(26.9° N, 103.0° E)为反演坐标原点。从7465个原始数据中剔除一些明显异常的震相, 最后所用数据的震相、走时如图4a所示。根据研究区内地震事件的分布特点、射线路径的分布情况(图4b), 设置事件到台站的最大距离为200km, 每个事件的最大邻居数为30, 事件对之间的最小和最大间距为0.1km和10km。最终用于反演的台站数为42个, 实际参加反演的地震事件为6328个, P波记录63099条, S波记录65612条, P波、 S波绝对到时差数据121472个, 双差数据1250868个。

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	图 4 参加反演到时数据的时距曲线及射线分布 a P、 S波时距曲线, 其中绿色线内为实际反演中所用的震相; b 实际参加反演的6³28个事件的震中、射线分布Fig. 4 Time-distance curve and raypath of the data used in inversion.

双差层析成像采用LSQR(Least Square QR factorization)算法进行速度结构和地震定位的联合反演, 在LSQR反演过程中阻尼因子和平滑参数共同约束反演结果, 其中平滑因子约束慢度的变化量, 而阻尼因子则同时约束着地震位置和慢度的变化量。 LSQR以总走时残差L2范数为目标函数进行迭代求解(Zhang et al., 2003), 故需要分别对慢度变化量的L2范数、地震位置和慢度变化量的L2范数进行权衡分析, 以得到平滑因子和阻尼因子。本文选择L曲线法进行权衡分析, 选取最优的正则化参数参加反演, 如图 5所示。最终选定的阻尼因子和平滑参数分别为15和500。反演进行过程中对不同的数据采用不同的加权方案, 开始时为绝对数据赋予较大权重以反演整体的速度结构, 之后为相对走时数据赋予较大权重以更好地约束震源区的速度结构。由于在联合反演中速度的收敛快于地震位置, 因此在实际反演过程中每次联合反演之后单独进行1次定位反演。迭代次数根据走时残差不再减小为准则, 最后经过10次迭代, 绝对数据的RMS残差从 0.386s 降至 0.193s, 加权数据的RMS残差从 0.998s 降至 0.141s。

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	图 5 利用L曲线法选择最佳的平滑因子和阻尼参数 a L 曲线选择平滑因子为15; b 平滑因子为15时阻尼参数的取值为500Fig. 5 Best parameter of smooth and damp selected by L curve method.

2.3 解的分辨率测试

为判断在实际数据和网格模型下所采用的反演方法能否正确地反映出速度异常, 本文在反演开始前采用棋盘法测试解的分辨率。将研究区划分为0.1° × 0.1° 的网格, 对实际反演中的初始速度模型加± 5%的扰动得到棋盘格速度模型, 并将其作为理论速度模型, 利用其计算得到理论走时模型; 再使用实际反演中的初始速度模型和理论走时数据反演速度结构, 比较反演结果与检测板的相似程度以估计解的可靠性。根据图 6所示的棋盘测试结果可知, 在4~20km的深度上, 除边界外研究区的分辨率可以达到10km; 在浅层即0~2km的深度上, 棋盘测试结果仅在研究区中心区域可达10km的分辨率。

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	图 6 不同深度的棋盘测试结果 a P波棋盘测试结果; b S波棋盘测试结果Fig. 6 Checkerboard test results at each depth.

3 反演结果及讨论

在反演过程中每个节点的射线分布可以作为解的可靠性的一个估计。 DWS(Distributions of Derivative Weight)反映了一个模型参量周围的平均相对射线密度。 Scarfì 等(2007)的研究表明, 当DWS> 100时, 反演结果具有较高的可靠性。因此在下文结果讨论时, 重点讨论DWS> 100 的区域的速度值。

3.1 三维P波、 S波速度

根据三维速度反演结果(图7)可知, 研究区P、 S波的速度分布在各个深度上显示出较好的一致性变化特征。 P波速度结果显示, 在2km深处, 沿金沙江的小江断裂北段及其周边的巧家、宁南、会东、会泽等地均出现了显著的P波低速区域。由浅至深, 自4km深处起, 沿小江断裂北段分布的P波低速区范围开始缩小并变得离散; 宁南— 白鹤滩大坝— 巧家低速区自4km深处消失, 会东附近的低速异常则一直延续至15km深处。在4km、 6km、 8km深处, 研究区小江断裂东侧NE向的会泽-彝良断裂、昭通-鲁甸断裂及与莲峰断裂、昭通-鲁甸断裂相交的NW向包谷垴-小河断裂以高速异常为主, 而昭通-鲁甸断裂的鲁甸— 昭通段为整条断层上速度相对较低的一段。在10~15km深度范围内, NW向的包谷垴-小河断裂呈现低速, 并将处于高速区的昭通-鲁甸断裂截为2段, 高速分布逐渐占据了小江断裂北段东侧, 其中沿昭通-鲁甸断裂、会泽-彝良断裂的区域均为高速区。

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	图 7 不同深度的V_P、 V_S分布 a V_P分布; b V_S分布。黑色十字代表DWS> 100的节点; 红色五角星为鲁甸主震震中Fig. 7 V_P and V_S distribution at each depth.

S波速度结果显示, 在2km深处, 沿白鹤滩大坝— 东川之间的小江断裂带及其两侧呈现显著的S波低速分布。在4~6km深度范围内, 沿小江断裂北段分布的S波低速区范围开始离散。在其东侧, S波低速区被沿昭通、莲峰断裂展布的NE向高速区所取代, 仅在会泽盆地及鲁甸— 昭通段周围存在明显的低速区域, 这2个S波低速区一直延续至15km深处。沿小江断裂带及其西侧, 在宁南北— 巧家— 白鹤滩大坝及会东周围存在S波低速区。自6km起的下部区域, 宁南北— 巧家— 白鹤滩大坝的低速区在巧家附近消失, 而宁南北— 白鹤滩大坝及会东附近的低速分布一直延续到15km深处。

综上, 在研究区2~6km的浅层, 沿小江断裂北段(向N至白鹤滩大坝)及其西侧的范围, P、 S波低速异常特征相对较为显著, S波低速特征尤其显著。而自6km深处开始, 在金沙江东侧形成了沿昭通断裂、会泽-彝良断裂的NE向P波高速条带; S波在莲峰断裂、包谷垴-小河断裂、昭通-鲁甸断裂和会泽-彝良断裂所围限的区域内呈现高速特征。金沙江西侧宁南北— 白鹤滩大坝及会东附近、小江断裂东侧昭通-鲁甸断裂上的鲁甸— 昭通段及会泽盆地的低速区延续到了15km深处。

图 8给出了图9b中沿库区内几个典型断层走向剖面上的速度分布, 其中AA'剖面沿NE向穿过小江断裂, 其西侧为宁会断裂, 东侧为莲峰断裂, 白鹤滩大坝位于该剖面附近。由图8a可见, 5km以浅金沙江以西的宁会断裂低速异常显著, 同时白鹤滩大坝下方也为显著的P波低速分布区域, 一直延伸至5km深处, 该低速体似乎存在侵入高速区域的趋势。白鹤滩大坝周围的地震由浅至深沿低速区分布, 形成条带, S波的低速异常不明显。 BB’ 剖面也沿NE向穿过金沙江, 其东侧为昭通-鲁甸断裂带, 其西侧端部是乌东德大坝。由图8b可见, 以小江断裂为界, 以西为相对低速区域, 其东侧昭通-鲁甸断裂呈显著的高速。乌东德大坝下方是稳定的高速体。 CC’ 沿小江断裂带展布, 由图8c可见, 该剖面自北至南呈现显著的低V_P特征, 且与昭通-鲁甸断裂交会处以北的段低速异常显著, 尤其是在巧家附近的低速异常区, 其深度可达15km。此外, 地质研究表明, 自巧家盆地至蒙姑以南的小江口段, 小江断裂带沿金沙江谷地发育, 断层破碎带及影响带较宽, 尤其在后期遭受金沙江的强烈切割, 张性构造裂隙及边坡卸荷裂隙均在一定程度上发育。查阅中国 1︰50万地质图可发现, 小江断裂带及以西的岩性主要为砂岩、灰岩、白云岩以及碎屑岩等硬度较低、孔隙度较大的岩石。上述因素可能是金沙江下游及其周围浅层P、 S波速度较低的主要原因。而小江断裂带以东主要出露着大面积的峨眉山玄武岩, 与该处浅层为P、 S波高速区具有较好的一致性。本文的结果与其它地球物理场反演结果也有共同之处。吴建平等(2013)反演得到的整个小江断裂带及其周边0.25° 网格的P波速度结果显示, 在1km、 10km深度上, 小江断裂带内主要为低速异常, 其东侧为高速异常; 在20km以上的中下地壳, 其北段主要为高速异常。根据本文的结果(图7a), 可能自15km开始小江断裂北段已基本为P波高速区。

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	图 8 不同剖面上的V_P、 V_S分布 a— e为沿不同测线所做剖面, 测线位置分别为图9b中的AA'— EE'; 其中红色五角星代表2014年8月3日鲁甸M_S6.5地震; 沿测线投影的地震均为重定位结果Fig. 8 The distribution of V_P, V_S on vertical profiles.

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	图 9 重新定位前后的地震震中分布 a 初始震中位置分布与深度分布统计(红色方框内为鲁甸震源区); b 重新定位后震中位置分布与深度分布统计(AA'— EE'为测线位置)Fig. 9 Original and relocated epicenters in the study area.

国内外研究表明(杨卓欣等, 2013; Dixit et al., 2014; 周连庆, 2016), 水库蓄水之后, 水库区的断层裂隙带是库区蓄水后的主要导水通道, 叶秀薇等(2017)发现在新丰江库区地震多发生于导水通道的两侧。三峡水库蓄水后丛集性地震集中发生在岩性易于渗水、断裂与河流交会的区域(廖武林等, 2009; 马文涛等, 2010; 周连庆, 2016)。因此, 金沙江下游水库区需要重点关注岩性易于流体渗透、有较破碎断裂带可作为导水通道的区段, 其中白鹤滩大坝区域需要重点加强监测。

3.2 震源定位结果及鲁甸地震序列

我们得到了6120个地震事件的重定位结果(如图9), 重定位之后震源平均测定误差在SN、 EW和UD向分别为0.50km、0.40km和0.50km。重定位的结果显示, 研究区地震震源深度< 20km, 优势分布于15km及以浅范围内。由地震深度分布统计图可见, 重定位事件中94.7%的事件分布在0~15km的深度范围内, 且主要集中在5~10km范围内, 占震源深度≤ 15km的地震总数目的45.60%。而初始定位结果显示震源深度在0~15km范围内的地震占总地震数目的90.1%, 但其中深5~10km的地震数目只占35.03%。与初始震源位置相比, 地震更集中沿断层分布, 主要沿小江断裂北段、小江断裂东、西两侧的NWW向分支断裂以及鲁甸地震震源区分布。沿小江断裂北段金沙江分布的地震深度可达10km, 表明小江断裂带可能至少切穿上地壳。重定位之后的地震事件在小江断裂东、西两侧的麻塘断裂、大朵断裂和会泽县附近出现了比较明显的近EW向分布特征, 这些EW向分布的地震震源深度均约10km。

截至2016年12月, 2014年8月3日鲁甸M_S6.5地震序列(图9a中红色方框所示的范围为鲁甸震区)重定位前余震分布在图9a中的绿色方框内, 重定位的余震分布显示出更为明显的丛集性, 优势方向为基本垂直共轭分布的近EW和SN向条带, 与前人的重定位结果基本一致(房立华等, 2014; 王未来等, 2014)。但与主震后2个月内的余震图像不同的是, 2a多内的余震形成EW向长约40km、 SN向长约20km的条带(图9b中DD'、 EE'的位置)。鲁甸地震序列的震源深度< 15km, 优势分布在10km以浅的范围内。

4 结论

本研究利用2013年8月— 2016年12月金沙江下游水库台网42个台站记录到的7465个地震事件的P、 S波绝对到时数据以及相对到时数据, 采用双差层析成像方法对金沙江下游水库区震源参数和三维速度结构进行了联合反演, 首次得到了研究区2km、 4km、 6km、 8km、 10km、 15km深度、分辨率为0.1° 的速度结构。根据反演结果, 得到以下几点认识:

(1)在研究区深2~6km的浅层, 低速区与研究区地形、岩性分布以及金沙江流经的区域对应较好。沿小江断裂北段(北至白鹤滩大坝)P、 S波呈现低速异常特征, S波低速异常尤为显著。在金沙江下游的西侧, 存在宁南北— 巧家— 白鹤滩大坝及会东周围的P、 S波低速区, 自6km深处起, 宁南北— 巧家— 白鹤滩大坝低速区在巧家附近消失, 而会东周围的P、 S波低速区一直延续至15km深处。在金沙江东侧的会泽盆地及昭通-鲁甸断裂上的鲁甸— 昭通段, 自2km深处起存在2个明显的低速区, 且一直延续至15km深处。

(2)自6km深处开始, 在小江断裂带北段东侧形成了NE向沿昭通-鲁甸断裂、会泽-彝良断裂分布的P波高速条带。 S波在莲峰断裂、包谷垴-小河断裂、昭通-鲁甸断裂和会泽-彝良断裂所围限的区域内呈现高速特征, 这可能与峨眉山玄武岩喷发造成的大量基性和超基性幔源物质侵入地壳有关。

(3)以小江断裂为界, 在深10km以上的浅层, 小江断裂西侧包括宁会断裂在内的区域P波低速异常显著, 东侧则呈现高速特征。而小江断裂自北至南呈现显著的低V_P特征, 且与昭通-鲁甸断裂交会处以北的区域低速异常显著, 尤其在巧家附近低速异常区的深度达到15km。该区域V_S则较为稳定。

(4)白鹤滩大坝下方呈现明显的P波低速分布区域, 深度至5km。大坝周围的地震由浅至深沿低速区分布, 形成条带。而乌东德大坝下方是稳定的高速体。白鹤滩大坝尚未蓄水, 需关注该大坝周围的地震活动, 重点加强监测。

(5)研究区内发生地震的震源深度< 20km, 优势分布在15km以浅的地壳内部。地震主要集中分布在小江断裂北段、小江断裂东、西两侧NWW走向的分支断裂以及鲁甸地震震源区。沿小江断裂北段分布的地震深度可达10km, 表明小江断裂带可能至少切穿了上地壳。与该区域主要大型断裂的NE走向所不同的是, 重定位之后的地震事件在小江断裂东、西两侧的麻塘断裂、大朵断裂和会泽县附近出现了比较明显的近EW向分布, 这些EW向分布的地震震源深度均约10km。

(6)2014年8 月3日鲁甸M_S6.5地震的序列余震分布优势方向为近EW和SN向, 呈基本垂直的共轭分布, 2a内在这2个优势方向上的余震分别形成了长约40km、 20km的条带。鲁甸地震余震序列震源深度< 15km, 优势分布在10km以浅的范围内。

致谢中国地震局地球物理研究所许力生研究员提供了巧家台阵观测数据; 张海江老师提供了TomoDD软件; 审稿专家为本文提出了中肯的修改意见。在此一并表示感谢!

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[13]	徐涛, 张明辉, 田小波, 等. 2014. 丽江—清镇剖面上地壳速度结构及其与鲁甸 M_S6. 5地震孕震环境的关系[J]. 地球物理学报, 57(9): 3069—3079. doi: 106038/cjg20140932. XU Tao, ZHANG Ming-hui, TIAN Xiao-bo, et al. 2014. Upper crustal velocity of Lijiang-Qingzhen profile and its relationship with the seismogenic environment of the M_S6. 5 Ludian earthquake[J]. Chinese Journal of Geophysics, 57(9): 3069—3079(in Chinese). [本文引用:1]
[14]	杨卓欣, 刘宝峰, 王勤彩, 等. 2013. 新丰江库区上地壳三维细结构层析成像[J]. 地球物理学报, 56(4): 1177—1189. doi: 106038/cjg20130413. YANG Zhuo-xin, LIU Bao-feng, WANG Qin-cai, et al. 2013. Tomographic imaging of the upper crustal structure beneath the Xinfengjiang reservoir area[J]. Chinese Journal of Geophysics, 56(4): 1177—1189(in Chinese). [本文引用:1]
[15]	叶秀薇, 邓志辉, 黄元敏, 等. 2017. 新丰江水库中上地壳P波三维速度结构特征及库水的渗透影响[J]. 地球物理学报, 60(9): 3432—3444. YE Xiu-wei, DENG Zhi-hui, HUANG Yuan-min, et al. 2017. The characteristics of 3D P-wave velocity structure of middle-upper crust and reservoir water infiltration-diffusion in Xinfengjiang Reservoir of Guangdong[J]. Chinese Journal of Geophysics, 60(9): 3432—3444(in Chinese). [本文引用:1]
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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: 103969/j.issn.0253-4967.2014.04.01.

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.

... 5地震序列(图9a中红色方框所示的范围为鲁甸震区)重定位前余震分布在图9a中的绿色方框内, 重定位的余震分布显示出更为明显的丛集性, 优势方向为基本垂直共轭分布的近EW和SN向条带, 与前人的重定位结果基本一致(房立华等, 2014 ...

2007

0.0

... 刘平江等, 2007 ...

2009

0.0

廖武林, 张丽芬, 姚运生. 2009. 三峡水库地震活动特征研究[J]. 地震地质, 31(4): 707—714. doi: 103969/j. issn. 0253-4967. 2009. 04. 014.

LIAO

Wu-lin

, ZHANG

Li-fen

, YAO

Yun-sheng

. 2009. Characters of seismicity in the Three Gorges reservoir area[J]. Seismology and Geology, 31(4): 707—714(in Chinese).

Accurate earthquake location is of primary importance in studying the seismicity of reservoir area. The well known program Velest was used to inverse the minimum 1-D velocity,hypocenter location and station correction simultaneously.We selected 529 earthquakes,which were recorded at least by 10 stations each and whose max azimuth gap was less than 180?,to re-determine the velocity model and station corrections with three different initial models used by different researchers before.Using the 1-D minimum velocity model and station correction,we relocated 2138 earthquakes in the Three Gorges area.The average focal depth changes remarkably in different areas,as 5.6km in the area near Xiannvshan Fault,2.9km in the Xietan area and 2.6km in the Badong area.Divided by the depth of 5km,the b values are different,as 1.07,1.16 and 0.90 for all,shallower and deeper events respectively. The frequency of shallower or deeper events per 15 days increases with impounding.But that of the shallower ones drops quickly and the deeper attenuates slowly when water lever keeps stable.

1. Institute of Geophysics, China Earthquake Administration, Beijing 100081, China; 2. Institute of Seismology, China Earthquake Administration, Wuhan 430071, China

在已有速度模型的基础上,选取三峡水库区529个地震重新确定了速度模型和台站校正,并利用该结果对2 138次地震进行了定位。研究表明,在不同区域震源深度存在明显的差异,仙女山断裂附近的地震平均震源深度为5.6km,而巴东地区的地震平均震源深度为2.6km。以震源深度5km为界,浅于5km的地震的 b 值为1.16,而深于5km地震的 b 值为0.90,不同深度地震的频次变化与水位关系差异明显。

... 三峡水库蓄水后丛集性地震集中发生在岩性易于渗水、断裂与河流交会的区域(廖武林等, 2009 ...

2016

0.0

罗佳宏, 马文涛. 2016. 三峡库区上地壳速度结构初步研究[J]. 地震地质, 38(2): 329—341. doi: 103969/j. issn. 0253-4967. 2016. 02. 008.

LUO

Jia-hong

, MA

Wen-tao

. 2016. A preliminary study on upper crustal velocity structure in the Three Gorges reservoir area[J]. Seismology and Geology, 38(2): 329—341(in Chinese).

In this paper, using the double difference tomography method, the P wave and S wave velocity structures of the earth's crust beneath the Three Gorges Reservoir are inversed based on the high-resolution seismic data of seismological stations recorded from March 2009 to December 2010. According to the research results, the P wave and S wave crust velocity zones in the Three Gorges Reservoir area show a high V P value area and a V S value area with value low in the lower part and high in the upper part, distributing respectively at both sides of Shennongxi River to western Xietan in the north of Badong and near the outlet of the Xiangxi River at the northern section on Xiannvshan Fault. In the region from the two sides of Shennong River in the north of Badong to the western Xietan, microseisms are distributed in three zones in near east-west direction, with steep and north-dipping sections, spreading along the high-to-low velocity transition zone of the P and S wave. On the northern section of Xiannvshan Fault, small earthquakes are distributed along the NNW-trending Xiannvshan Fault, and the geological section reveals a steep and linear distribution along the transitional zone between the high V P value area and the V S value that is low in the upper and high in the lower part. Joint inversion results show a good consistency of the planes of the microseisms with the distribution of active faults.

Key Laboratory of Active Tectonics and Volcano, Institute of Geology, China Earthquake Administration, Beijing 100029, China

文中利用三峡加密观测台网记录的2009年3月到2010年12月高精度地震数据，使用双差层析成像方法，联合反演了三峡库区上地壳的震源位置参数和三维上地壳P波和S波速度结构。研究结果显示，三峡库区上地壳P波速度和S波速度区域出现2个高 V P 值、上低下高 V S 值区，分别在巴东北部神农溪两岸-泄滩西区域和仙女山断裂带北段香溪河口附近。巴东北部神农溪两岸-泄滩西区域，较小地震的平面分布呈3条近EW向的条带，剖面陡立、向N倾，沿着P波和S波高、低速过渡带分布；香溪河口附近地震沿NNW向的仙女山断裂带分布，地质剖面显示出地震陡立线性分布，沿着高 V P 值、上低下高 V S 值区的过渡带展布，联合反演得到的微震面与断裂构造分布具有较好的一致性。

... 罗佳宏等, 2016), 以揭示库区介质受水库蓄水的影响及库区地震发生的介质环境等 ...

2010

0.0

马文涛, 徐长朋, 李海鸥, 等. 2010. 长江三峡水库诱发地震加密观测及地震成因初步分析[J]. 地震地质, 32(4): 552—563. doi: 103969/j. issn. 0253-4967. 201004. 003.

Wen-tao

, XU

Chang-peng

, LI

Hai-ou

, et al. 2010. Intensive observation of reservoir-induced earthquake and preliminary analysis on the causes of earthquakes in Three Gorges Reservoir[J]. Seismology and Geology, 32(4): 552—563(in Chinese).

In accordance with the requirements of "Eleventh Five-Year" national scientific and technological support projects,an intensive seismic observation network consisting of 26 seismic stations was established at the Three Gorges Reservoir area in the section of Hubei Province in March 2009(21 short-period seismographs,5 broadband digital seismographs).From March to December,2009,2995 M L -0.8～2.9 earthquakes were observed during the trial impounding of the Three Gorges Reservoir(water level rose from 145m to 172.8m).Using the double difference earthquake location algorithm,2837 earthquakes were relocated precisely.The results show: The pattern of small local earthquake swarms in Three Gorges Reservoir area took on a linear distribution or mass-like cluster distribution,the mass-like clusters of events were generally within the distance of 5km from waterfront,and the linear distribution of the earthquakes could be extended to a distance of 16 kilometers away from waterfront.In Hubei section of Three Gorges Reservoir,earthquakes were mainly concentrated in the northern end of Xiannüfeng and Jiuwanxi Fault in the vicinity of the Xiangxihe river,and along the banks of the Yangtze river at the east of Xietan village and at Shenlongxi area on the northern bank in Badong region;the focal depths were less than 10km,and 4km in average.Earthquake frequency of the reservoir region had a positive correlation with reservoir water level fluctuation,indicating that the seismicity belonged to the reservoir induced earthquakes.Along the Shenlong river in the reservoir area,earthquakes showed three linear distributions in the northern Badong County,which was related to karst distribution.There are underground rivers along carbonate strata.When reservoir was impounded,water permeated into the underground rivers,thus inducing earthquakes.Earthquakes in the areas on the cross-river segment of Xiannüfeng Fault,the Jiuwanxi Fault and at the areas west of Xietan,Shazhen and Xizhen,may be related to the softening of discontinuities,such as the Nukou Fault,the Xiannüfeng Fault or the bedding joints,etc.,which would lead to failure of rock masses,thus,inducing earthquakes.However,convincing conclusions about the triggering mechanism still need further study.In addition,in the areas south of Wenhua and Yanglin of Zigui County and at Rangkou town east of Badong county,there are mining-induced earthquakes at the mines nearby.And on the shores of the reservoir,there are some collapse earthquakes.

1. National Center for Active Fault Studies, Institute of Geology, China Earthquake Administration, Beijing 100029, China; 2. Earthquake Administration of Shandong Province, Jinan 250014, China; 3. Handan Seismic Station, Earthquake Administration of Hebei Province, Handan 056001, China

从2009年3月起在长江三峡水库湖北段建立了26个地震台站组成的加密台网。2009年3—12月记录到2995次 M L -0.8～2.9地震。利用双差定位软件重新确定了2837次地震的精确位置。结果显示:长江三峡水库库区小震震群分布图像呈线性分布或团块状丛集分布,团块状丛集一般在距离库水边5km范围内,地震线性分布可以延伸到距库水边16km远的地方;长江三峡水库湖北段地震主要集中分布在香溪河附近的仙女山断裂北端及九湾溪断裂、泄滩乡以西的长江两岸和巴东北岸神龙溪及附近地区,震源深度<10km,平均在4km左右;库区地震活动频次与库水位升降过程正相关,说明属于水库诱发地震。巴东库区神龙溪两岸地震明显呈现出3条线性分布,通过对比该地区碳酸盐岩的分布特征,发现是由于水库蓄水后,库水从神龙溪两岸等地下暗河渗入而诱发地震的;而仙女山断裂过江段、九湾溪断裂和泄滩乡、沙镇溪镇西部地区等的地震可能与仙女山断裂带、牛口断裂或顺层解理等不连续结构面软化,导致岩体失稳而诱发了水库地震,但诱发机制仍需要进一步详细研究才能获得令人信服的结论。另外,在秭归县文化南和杨林、巴东县东壤口镇以东等地存在着煤矿开采引起的矿山诱发地震,在长江三峡库区两岸存在着一些塌陷地震。

... 马文涛等, 2010 ...

2013

0.0

闻学泽, 杜方, 易桂喜, 等. 2013. 川滇交界东段昭通、莲峰断裂带的地震危险背景[J]. 地球物理学报, 56(10): 3361—3372. doi: 106038/cjg20131012.

WEN

Xue-ze

, DU

Fang

, YI

Gui-xi

, et al. 2013. Earthquake potential of the Zhaotong and Lianfeng fault zones of the eastern Sichuan-Yunnan border region[J]. Chinese Journal of Geophysics, 56(10): 3361—3372(in Chinese).

The NE-trending Zhaotong and Lianfeng fault zones of the eastern Sichuan-Yunnan border region are poorly studied on earthquake issues. To know whether the two fault zones have seismic potential for strong and major earthquakes, we make a comprehensive study by integrating multidisciplinary data of active tectonics and regional dynamics, distribution of relocated small earthquakes and focal mechanism solutions, historical earthquake rupture-areas, GPS deformation field, modern seismicity and its parameter patterns, etc. Our study shows that the Zhaotong and Lianfeng fault zones are a part of the boundary separating the Sichuan-Yunnan block and the South China block, and also the margin between the active and deformed secondary faulted block of Daliangshan and the relatively stable South China block. Structurally, the fault zones appear as two parallel and southeastward thrusting fault zones with the currently right-lateral strike-slip faulting along with significant thrusting components. Along the Zhaotong fault zone the time without major earthquakes is proved to have been over 1700 years at least, and a seismic gap exists there. The GPS deformation patterns suggest that the Zhaotong and Lianfeng fault zones have locked in different degrees. Also, several areas of low b-values or high stress exist on the Zhaotong fault zone near Ludian and on the southern segment of the Lianfeng fault zone. A locked or highly stressed fault segment of the Zhaotong fault zone between Ludian and Yiliang has been identified from low b-values and lack of current small earthquakes, and the moment magnitude for a maximum potential event on this fault segment is estimated to be about M(w)7. 4. We therefore conclude that mid- to long-term seismic potential for strong or major earthquakes exists on the Zhaotong fault zone. But, the seismic potential of the Lianfeng fault zone still needs to be studied further.

Yang Pan-Xin 1 ;Xiong Ren-Wei 1 ;Liu Xiao-Xia 1 ;Liu Qi 1 ;Wen Xue-Ze 1,2 ;Du Fang 2 ;Yi Gui-Xi 2 ;Long Feng 2 ;Fan Jun 2 ;

川滇交界东段NE向昭通、莲峰断裂带的研究程度较低.为了了解该断裂带是否存在发生强震/大地震的危险背景,我们基于区域活动构造与动力学、重新定位的小震分布和震源机制解、历史地震破裂区、GPS形变场、现代地震活动及其参数图像等多学科的信息进行综合研究.结果表明:昭通、莲峰断裂带是川滇-华南活动块体/地块边界带的一部分,也是活动及变形的大凉山次级块体与相对稳定的华南地块之间的边界带;结构上表现为2个平行展布、朝南东推覆的断裂带,现今运动为带有显著逆冲分量的右旋走滑性质.沿昭通断裂带无大地震的时间至少为1700 余年,目前存在地震空区.GPS变形图像反映昭通、莲峰断裂带已不同程度闭锁.另外,昭通断裂带的鲁甸附近以及莲峰断裂带的南段分别存在异常低 b 值区或高应力区.已由低 b 值区和小震空白区识别出昭通断裂带上的鲁甸—彝良之间存在高应力闭锁段,并估计出其潜在地震的最大矩震级为 M W 7.4.本研究因此认为昭通断裂带存在发生强震/大地震的中-长期危险背景, 而莲峰断裂带的危险性还需进一步研究.

... 这些断裂带从活动构造性质及规模上看均具有发生强震、大震的能力(闻学泽等, 2013) ...

2013

0.0

吴建平, 杨婷, 王未来, 等. 2013. 小江断裂带周边地区三维P波速度结构及其构造意义[J]. 地球物理学报, 56(7): 2257—2267. doi: 106038/cjg20130713.

Jian-ping

, YANG

Ting

, WANG

Wei-lai

, et al. 2013. Three dimensional P-wave velocity structure around XiaoJiang fault system and its tectonic implications[J]. Chinese Journal of Geophysics, 56(7): 2257—2267(in Chinese).

As the southeastern margin of Tibetan Plateau, Xiaojiang fault system plays an important role in the lateral escape of Tibetan Plateau materials. In this paper, 3-D P-wave velocity structure in Xiaojiang fault system and its surrounding areas was imaged by using travel time data from permanent seismic stations and a dense temporal seismic array. The results show that in the upper and middle crust, Xiaojiang fault system mainly represents low velocity, while high velocity anomalies exist to its east. In the middle and lower crust, a low velocity anomaly is shown in the central area of Xiaojiang fault system, and high velocity anomalies exist both in the northern and southern areas. The northern high velocity anomaly near Panzhihua extends from lower crust to the surface, and the southern one in the lower crust extends to the upper mantle. We consider that the low velocity anomaly in the central area of Xiaojiang fault system is caused by high temperature derived from upper mantle. The high velocity anomalies in the northern area are most likely related to the late Paleozoic mantle plume activity which caused a large amount of basic and ultrabasic mantle material intruded into the crust. These high velocity anomalies, with greater mechanical strength, play a certain impediment to southward escaping of Tibetan Plateau materials, and lead to the rapid uplift of the northern sub-block of the Sichuan-Yunnan active block. The north-dipping high velocity anomaly in the southern area is a further barrier for southward extrusion of Sichuan-Yunnan active block, leading to strong deformation and high rate of seismicity within the low velocity area in the overlying upper and middle crust. Meantime, this high velocity block contributes to stabilization in the upper mantle, which causes mantle materials of its southern region less affected by the southward escape of Tibetan Plateau materials.

Jian-Ping, Wu 1 ;Ting, Yang 1 ;Wei-Lai, Wang 1 ;Yue-Hong, Ming 1 ;Tian-Zhong, Zhang 1 ;

作为青藏高原的东南边界,小江断裂带在高原物质的侧向逃逸中发挥着重要的作用.本文利用流动地震台阵及固定台站的走时观测资料,对小江断裂带及周边区域的壳幔三维P波速度结构进行了研究.结果表明,在中上地壳,小江断裂带内部主要为低速异常,其东侧主要为高速异常.在中下地壳,小江断裂带中部为低速异常,北部和南部主要为高速异常,其中北部的高速异常可延伸到地表附近,南部的高速异常可一直延伸到上地幔.我们推测,小江断裂带中部的低速异常与深部热作用有关;北部的高速异常可能是晚古生代地幔柱活动导致大量基性和超基性幔源物质侵入地壳引起的,它的存在对青藏高原物质向南逃逸起到了一定的阻挡作用,可能是导致川滇活动块体北部次级块体快速抬升的重要因素;南部顶界面向北倾斜的高速异常体对川滇活动块体向南滑移起到了进一步的阻挡作用,导致其上覆的中上地壳低速异常区发生较强的变形和强烈的地震活动,同时在上地幔深度范围起到了稳定的作用,使其南部区域的介质受青藏高原物质向南挤出的影响明显减小.

... 吴建平等(2013)反演得到的整个小江断裂带及其周边0 ...

2014

0.0

王未来, 吴建平, 房立华, 等. 2014. 2014年云南鲁甸 M_S6. 5地震序列的双差定位[J]. 地球物理学报, 57(9): 3042—3051. doi: 106038/cjg20140929.

WANG

Wei-lai

, WU

Jian-ping

, FANG

Li-hua

, et al. 2014. Double difference location of the Ludian M_S6. 5 earthquake sequences in Yunnan Province in 2014[J]. Chinese Journal of Geophysics, 57(9): 3042—3051(in Chinese).

The earthquake sequences within sixteen days of the Ludian M(s)6.5 earthquake in Yunnan province are relocated by double difference algorithm. The relocation results show that the mainshock is located at 27.11 degrees N, 103.350 degrees E and the focal depth is about 15 km; the earthquake sequences are distributed dominantly "L"-shaped in the SSE and EW direction, and show nearly vertical focal depth distribution, indicating it is a strike-slip earthquake and has two rupture planes in different directions. Although the Ludian M(s)6.5 earthquake occurs near the NE-directed Zhaotong fault and its back thrust faults (Longshu fault and Dayandong fault), these faults are thrust faults and cannot be the seismogenic fault. This earthquake occurs in the junction region where multiple faults are distributed in radial pattern; the SSE-directed rupture branch has coincident strike with the Baogu' nao fault, while the nearly EW-directed rupture branch has coincident strike with the south part of the Xiaohe fault. The Ludian M(s)6.5 earthquake may have connected the Baoguinao fault and the Xiaohe fault in depth.

[Wang Wei-Lai; Wu Jian-Ping; Fang Li-Hua; Lai Gui-Juan] China Earthquake Adm, Inst Geophys, Beijing 100081, Peoples R China.

本文采用双差定位方法对云南鲁甸 M S 6.5地震震后16天的地震序列进行重定位研究.重定位结果显示，主震位于27.11°N，103.35°E，震源深度约15 km；地震序列主要呈“L”形优势分布，分为SSE向和近EW向两支，并均呈现近垂直的震源分布特征，显示此次地震为走滑型，并存在两个不同方向的破裂面.虽然此次地震发生于NE向昭通断裂及其反冲断裂（龙树断裂、大岩洞断裂）附近，但这些断裂均为逆冲型断裂，被排除了作为发震断裂的可能性；鲁甸地震发生在呈放射性分布的多条断裂的交汇部位，SSE向破裂分支与包谷垴断裂的方向一致，近EW向破裂分支与小河断裂南端的走向一致. 鲁甸地震可能已将包谷垴断裂和小河断裂在深部贯通.

... 王未来等, 2014) ...

2004

0.0

谢富仁, 崔效锋, 赵建涛, 等. 2004. 中国大陆及邻区现代构造应力场分区[J]. 地球物理学报, 47(4): 654—662. doi: 103321/j. issn: 0001-5733. 2004. 04. 016.

XIE

Fu-ren

, CUI

Xiao-feng

, ZHAO

Jian-tao

, et al. 2004. Regional division of the recent tectonic stress field in China and adjacent areas[J]. Chinese Journal of Geophysics, 47(4): 654—662(in Chinese).

On the basis of the “Basic database of crustal stress environment in China”, this paper summarizes the basic characteristics of recent tectonic stress field in China and adjacent areas, proposes the principle of dividing the tectonic stress districts. The recent tectonic stress field of China and adjacent areas is classified into four classes: The characteristic of the first order tectonic stress district shows uniformity and stability in large areas and long time. This stress field is mostly controlled by the geometry character of plate boundary and the force acting on plate boundary. The stress action of second order tectonic stress district shows coherence in a relatively large area. This stress field is controlled by regional block interaction. The stress regime of the third order tectonic stress district shows comparability in finite areas. This stress field is mostly influenced by interior block interaction inside the areas. The stress character (direction, intensity, structure, etc) of the forth order stress district shows better coherence. This stress field is mostly controlled by block and fault interaction. The paper preliminarily analyzes the dynamic environment which controlled the recent tectonic stress field in China and adjacent areas.

Institute of Crustal Dynamics, China Earthquake Administration, Beijing 100085, China

以“中国大陆地壳应力环境基础数据库”资料为基础，总结了中国大陆及邻区现代构造应力场的基本特征，提出了划分构造应力分区的原则，将中国大陆及邻区现代构造应力场划为四级应力区. 指出一级构造应力区主要受板块边界的几何特征和作用在边界上的力所控制，应力作用在大范围和长时间内保持均匀和稳定；二级构造应力区受控于区域块体间的相互作用，在较大区域范围内应力作用具有较强的相关性；三级构造应力区受控于区域内部块体间的相互作用，在一定区域范围内应力结构具有相似性；四级构造应力区受控于块体和断裂相互作用的影响，其应力性状(方向、强度、结构等)一致性较好. 论文还初步分析了控制中国大陆及邻区现代构造应力场分布的动力学环境.

... 现代构造应力场的研究结果表明, 川滇地块应力场以水平作用为主, 主压应力优势方位为NNW(谢富仁等, 2004 ...

1986

0.0

熊绍柏, 滕吉文, 尹周勋, 等. 1986. 攀西构造带南部地壳与上地幔结构的爆炸地震研究[J]. 地球物理学报, 29(3): 235—244.

XIONG

Shao-bai

, TENG

Ji-wen

, YIN

Zhou-xun

, et al. 1986. Explosion seismological study of the structure of the crust and upper mantle at southern part of the Panxi tectonic belt[J]. Chinese Journal of Geophysics, 29(3): 235—244(in Chinese).

The Institute of Geophysics, Academia Sinica conducted some experiments of seismic refraction profiling crossing the Panzhihua region in 1984. The Panzhihua region is located at the southern part of the Panxi tectonic belt. We have analyzed six record sections for the W-E profile which extends 350 km. The results are as follows: （1） The crust of the Panxi region can be divided into three main layers Avith thicknesses of about 20, 20, and 15km respectively. （2） The thickness and the average velocity of the whole crust is 55km and 6.22 km/s respectively. （3） There is a high-velocity rock body near the surface of the axial area of the tectonic belt, and it is probably related to the enrichment of the Panzhihua type sefstr（?）mite in this district. （4） There is a low-velocity zone with a thickness of about 9-14 km a,t the lower part of the midcrust. The top of this low-velocity zone is located at about 23-27 km deep from the surface. The consistence of this result with the distribution of earthquake foci and the depth of Curie isotherm indicates that the existence of the low-velocity zone maybe related to the thermal state of the crust medium. （5） There are several faults which reach into the upper mantle and a high-velocity interlayer at the top of the lower crust. These may signify intrusion of the mantle substance into the crust. （6） A velocity VPn of 7.62-7.90 km/s at the uppermost mantle is consistent with that of recent continental rifting zone. After comparison with other regions in the world, we infer that the Panxi region is perhaps a paleorift zone, but it was strongly transformed by later period's tec-togenesis.

Institute of Geophysics, Academia Sinica

根据1984年攀西地区南部爆炸地震折射剖面资料的研究结果表明,本区的地壳厚度约为55km,且可分为20km、20km和15km厚的三个主要构造层。地壳的平均P波速度为6.22km/s。在深度23—27km之下的中地壳下部有一个厚9—14km的P波低速区,这一结果与其它地球物理观测资料相当吻合。上地幔顶部的P波速度为7.62—7.90km/s,与现代大陆裂谷区或构造活动地区的P_n波速度一致。另外,位于构造带轴部地区的渡口市一带,上地壳中有一高速岩体,下地壳中有高速夹层以及有些断裂带可能延伸到上地幔顶部,均表明地壳中曾经有地幔物质侵入。通过研究,我们推断这个地区有可能是一个被后期构造运动强烈改造过的、至今仍保留有一些裂谷构造残迹的古裂谷带。

... 分别以研究区内前人通过人工地震方法获得的测震剖面(熊绍柏等, 1986 ...

2014

0.0

徐锡伟, 江国焰, 于贵华, 等. 2014. 鲁甸6. 5级地震发震断层判定及其构造属性讨论[J]. 地球物理学报, 57(9): 3060—3068. doi: 106038/cjg20140931.

Xi-wei

, JIANG

Guo-yan

, YU

Gui-hua

, et al. 2014. Discussion on seismogenic fault of the Ludian M_S6. 5 earthquake and its tectonic attribution[J]. Chinese Journal of Geophysics, 57(9): 3060—3068(in Chinese).

The Ludian 6. 5 earthquake occurred in the marginal zone between the eastern Tibetan Plateau and the Yangtze Craton owing to southeastward motion of the Sichuan-Yunnan rhombic block. Although no surface rupture zone was observed during the emergency scientific investigation in the epicenter, the spatial linear distribution of the aftershocks recorded by a local seismic network, with the dominated axial azimuth of the earthquake intensities and earthquake ground fissures, displays that the seismogenic fault of the Ludian earthquake is a NW-trending left-lateral strike-slip fault, named as the Baogunao-Xiaohe fault, which may belong to the southern termination of the Daliangshan fault. Coulomb stress calculation shows that the occurrence of this earthquake uploads the adjacent active fault systems and the seismic risk for the historical seismic gaps could not be ignored.

[Xu Xi-Wei; Jiang Guo-Yan; Yu Gui-Hua; Wu Xi-Yan] China Earthquake Adm, Key Lab Act Tecton & Volcano, Inst Geol, Beijing 100029, Peoples R China.;[Zhang Jian-Guo; Li Xi] Yunnan Earthquake Adm, Kunming 650224, Peoples R China.

鲁甸6.5级地震是川滇菱形块体南南东向运动在青藏高原东缘与华南地块相互作用边界变形带上发生的一次中等强度地震.尽管野外应急科学考察没有发现明显的地震地表破裂带，但云南昭通防震减灾局局域地震台网记录到的余震条带状分布、震后科学考察获得的地震烈度长轴方位和极震区地震裂缝等显示出发震断层为NW向包谷垴—小河断裂，左旋走滑性质，属大凉山断裂南端部组成部分；库仑应力计算表明，鲁甸地震可对周边活动断层系历史地震空段产生应力加载作用，其地震危险性不容忽视.

... 5地震发生于昭通、莲峰断裂带之间NW走向的包谷垴断裂(徐锡伟等, 2014) ...

2003

0.0

... 1 地震和构造背景研究区(图1a)位于川滇菱形块体东缘, 属于地质构造不稳定的地区, 该区地质构造背景复杂、构造活动性强(徐锡伟等, 2003) ...

2014

0.0

徐涛, 张明辉, 田小波, 等. 2014. 丽江—清镇剖面上地壳速度结构及其与鲁甸 M_S6. 5地震孕震环境的关系[J]. 地球物理学报, 57(9): 3069—3079. doi: 106038/cjg20140932.

Tao

, ZHANG

Ming-hui

, TIAN

Xiao-bo

, et al. 2014. Upper crustal velocity of Lijiang-Qingzhen profile and its relationship with the seismogenic environment of the M_S6. 5 Ludian earthquake[J]. Chinese Journal of Geophysics, 57(9): 3069—3079(in Chinese).

On August 3, 2014, an M(s)6.5 earthquake occurred in Ludian County, Yunnan. The. Ludian earthquake ruptured along the NE-oriented Zhaotong - Lianfeng fault zone, western margin of the Yangtze block. However, there was no seismic sounding profile across the Zhaotong Lianfeng fault zone up to now. Since the distance from Lijiang - Panzhihua - Qingzhen active source seismic sounding profile to the Ludian earthquake source region is within 50 km, we can handle the wide-angle seismic data to reveal the upper crustal velocity structure in this area, and provide the velocity model of upper crust for the earthquake locating and focal mechanism inversion of Ludian earthquake sequence, etc. The velocity profile shows that the crustal velocity around the Xiaojiang fault is lower than its periphery, thus the rheological strength of the upper crust beneath the Xiaojiang fault is speculated to be weaker than its surrounding areas. Considering the high strain rate along the Xiaojiang fault, it is possible to accumulate great strain and strong stress in the Xiaojiang fault zone and its surrounding faults. Thus we should pay attention to the potential risk of strong earthquakes on the Xiaojiang fault and its nearby Ludian - Zhaotong fault.

[Xu Tao; Zhang Ming-Hui; Tian Xiao-Bo; Bai Zhi-Ming; Wu Cheng-Long; Zhang Zhong-Jie; Teng Ji-Wen] Chinese Acad Sci, State Key Lab Lithospher Evolut, Inst Geol & Geophys, Beijing 100029, Peoples R China.;[Zhang Ming-Hui; Wu Cheng-Long] Univ Chinese Acad Sci, Beijing 100049, Peoples R China.;[Zheng Yong] Chinese Acad Sci, State Key Lab Geodesy & Earths Dynam, Inst Geodesy & Geophys, Wuhan 430077, Peoples R China.

2014年8月3日，云南省昭通—鲁甸地区发生 M S 6.5级地震，造成了重大的人员伤亡和财产损失.鲁甸震区位于扬子块体的西缘，小江断裂带的东侧北东向的昭通—莲峰断裂带内.由于至今没有穿越该断裂带的人工源深地震测深剖面，而丽江—攀枝花—清镇650 km长深地震测深剖面距离鲁甸主震区不超过50 km，利用宽角地震资料的初至波震相，通过有限差分反演揭示该地区上地壳速度结构，可以为鲁甸震区的地震定位、地震孕育机制等提供深部速度模型.速度剖面显示：剖面结晶基底厚度平均为2 km左右；小江断裂带速度较低，东西两侧的速度较高；因此小江断裂带区域地壳强度比较低，加上断裂两侧的应变速率很高，所以小江断裂带和旁边的鲁甸—昭通断裂带，未来具有发生较大地震的可能，值得关注.

... 徐涛等, 2014)及CRUST1 ...

2013

0.0

杨卓欣, 刘宝峰, 王勤彩, 等. 2013. 新丰江库区上地壳三维细结构层析成像[J]. 地球物理学报, 56(4): 1177—1189. doi: 106038/cjg20130413.

YANG

Zhuo-xin

, LIU

Bao-feng

, WANG

Qin-cai

, et al. 2013. Tomographic imaging of the upper crustal structure beneath the Xinfengjiang reservoir area[J]. Chinese Journal of Geophysics, 56(4): 1177—1189(in Chinese).

A three-dimensional temporary seismic array with 50 stations was deployed in an approximately 50 km X 40 km region around the Xinfengjiang reservoir to receive seismic waves generated by artificial sources from different azimuths. The local earthquakes occurred in the area from March 2009 to May 2010 were recorded by 20 stations of the seismic array and 5 permanent seismic stations. With the inversion method without model blocks, both reflection waves generated by the artificial sources from Moho at critical distances and direct waves from local earthquakes are used to reconstruct the 3-D images of P,S velocity and V-P/V-S perturbation of the upper crust under the seismic array. The results show that the upper crust structures below the Xinfengjiang reservoir area have significant differences between the eastern and the western region. The structure is complicated in the east of the reservoir where the faults intersect mutually. Under the reservoir, the NNW striking Shijiao-Xingang-Baitian fault zone has complex lithology and structural features, and from Xingang to Shuangtang, it probably extends down to 8 km depth. The fault zone of nearly NE direction cuts crust deep. There are through shallower and deeper high-velocity ratio zones in both the canyon and near the east of the Xinfengjiang dam, especially in the western deep water canyon region of Xinfengjiang dam, along the river there is a steep fault fracture zone. The high-velocity ratio zones provide a good channel for water infiltration. The west of reservoir is a relatively stable tectonic region, where intact and hard granite rock with low permeability has been affected little by reservoir water. The occurrence of Xinfengjiang reservoir-induced earthquakes is closely related to the deep structure environment. The upper crustal medium property in the canyon and near the east of the dam is obviously laterally heterogeneous. The micro earthquakes are located in the specific parts of medium physical property and structure. It is suggested that the "soft" and "hard" staggered media environment possibly leads to occurrence of dip-slip normal fault type micro earthquakes.

Yang Zhuo-Xin 1 ;Liu Bao-Feng 1 ;Zhang Xian-Kang 1 ;Wang Qin-Cai 2 ;Zhao Cui-Ping 2 ;Chen Zhang-Li 2 ;

在新丰江库区布设一个范围约50 km×40 km、由50个地震临时台站组成的观测台阵,接收来自不同方位的人工震源产生的莫霍界面反射波;台阵中的20个台站和5个区域固定台还对2009年3月至2010年5月发生在库区的地方震进行了观测.本文联合利用人工地震莫霍面反射波走时和天然地震直达波走时,采用连续模型反演技术重建了库区上地壳P波、S波慢度扰动和 V p / V s 扰动分布图像.研究结果表明:新丰江库区东、西部地区上地壳结构存在明显的差异.库区东部地区构造复杂,多条断裂在该区呈交叉状分布.北西向的石角—新港—白田断裂带在库区段内具有复杂的岩性和构造特征,该断裂带在新港至双塘一线可能延伸至地下8 km左右;近北东向的断裂带切割地壳较深.峡谷区及大坝以东附近地区存在上、下贯通的波速比高值区,尤其是大坝以西的深水峡谷区,存在一条顺河走向的陡倾角断层裂隙带,为库水渗透提供了良好通道.库区西部地区为相对稳定构造区,完整坚硬的花岗岩体透水性能较差,受库水渗透影响很小.新丰江水库诱发地震的形成与深部构造环境密切相关.峡谷区及大坝以东附近地区上地壳介质性质呈现明显的横向不均匀性,微震分布在介质物性结构的特定部位,"软"、"硬"交错的介质环境是倾滑正断层型微小震产生的可能原因.

... 国内外研究表明(杨卓欣等, 2013 ...

2017

0.0

... 周连庆, 2016), 水库蓄水之后, 水库区的断层裂隙带是库区蓄水后的主要导水通道, 叶秀薇等(2017)发现在新丰江库区地震多发生于导水通道的两侧 ...

2016

0.0

... 周连庆, 2016), 水库蓄水之后, 水库区的断层裂隙带是库区蓄水后的主要导水通道, 叶秀薇等(2017)发现在新丰江库区地震多发生于导水通道的两侧 ...

... 周连庆, 2016) ...

2014

0.0

... 由于Zhang等(2003)提出的双差层析成像方法(TomoDD)具有能够获得更加精细的震源区速度结构和地震定位结果的显著优势, 近年来该方法已被广泛应用于有密集观测数据的水库区的结构研究(Dixit et al ...

... Dixit et al ...

1994

0.0

... 、 P波观测数目最少为8的地震事件共824个, 首先进行最小一维速度模型反演(Kissling et al ...

2013

0.0

... 0(Laske et al ...

2016

0.0

... Luo et al ...

2007

0.0

2003

0.0

... LSQR以总走时残差L2范数为目标函数进行迭代求解(Zhang et al ...