鄂尔多斯块体东南缘现今的变形特征与构造模式探讨

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刘瑞春, 张锦, 郭文峰, 陈慧, 郑亚迪, 成诚. 鄂尔多斯块体东南缘现今的变形特征与构造模式探讨[J]. 地震地质, 2021,43(3):540-558.
LIU Rui-chun, ZHANG Jin, GUO Wen-feng, CHEN Hui, ZHENG Ya-di, CHENG Cheng. STUDY ON THE RECENT DEFORMATION CHARACTERISTIC AND STRUCTURAL DEFORMATION MODEL OF THE SOUTH-EASTERN MARGIN OF ORDOS BLOCK[J]. SEISMOLOGY AND GEOLOGY, 2021,43(3):540-558. 复制到剪切板

DOI:10.3969/j.issn.0253-4967.2021.03.005
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鄂尔多斯块体东南缘现今的变形特征与构造模式探讨

刘瑞春^1,^2,³⁾, 张锦¹⁾, 郭文峰^2,³⁾, 陈慧^2,³⁾, 郑亚迪^2,³⁾, 成诚^2,³⁾

1)太原理工大学, 太原 030024

2)山西省地震局, 太原 030021

3)太原大陆裂谷动力学国家野外科学观测研究站, 太原 030021

〔作者简介〕刘瑞春, 男, 1982年生, 2007年于长安大学获大地测量与测量工程专业硕士学位, 高级工程师, 主要研究方向为大地测量与地壳形变应用, 电话:0351-5610585, E-mail:wavelet1982@163.com。

收稿日期:2020-10-30 修回日期:2021-01-14

基金项目:中国地震局地震预测研究所基本科研业务专项(2017IES0101)、山西省科技攻关项目(20140313023-1)和山西省地震局科研项目(SBK-2121)共同资助

摘要

鄂尔多斯块体东南缘是中国大陆西部碰撞挤压到东部伸展拉张动力学转换的关键地区, 其新构造运动以强烈的差异升降运动为主, 在该区开展空间高分辨率的地壳垂直运动观测尤为重要。文中基于Radarsat-2宽模式影像, 采用干涉图堆叠(Stacking)技术获得了研究区的空间高分辨LOS向平均形变速率场, 并与研究区域内长期观测的GPS连续站数据开展对比分析。在此基础上, 利用倾滑断层位错模型、粒子群算法(PSO)反演了主要断裂的滑动速率和闭锁深度, 结果表明:1)利用干涉图堆叠(Stacking)技术得到的研究区年尺度地壳形变场具有较高的精度, 且区域地壳短期形变与长期形变具有一致性。 2)鄂尔多斯东南缘的构造和非构造形变相互叠加, 构造形变主要发生在活动断裂附近, 与断层滑动速率和闭锁深度有关。非构造形变主要发生在盆地内部的第四纪地层, 与含水层厚度和地下水开采量有关, 最大量级>5cm/a。 3)中条山北麓断裂和峨嵋台地北缘断裂的滑动速率为0.37mm/a和0.74mm/a, 闭锁深度为3.4km和4.3km, 可能表明断裂在最后一次强震发生后还未完全闭锁, 现今以浅部活动为主。峨嵋台地南缘断裂的滑动速率为0.47mm/a, 闭锁深度为0.95km, 表明断层现今可能以蠕滑活动为主。 4)鄂尔多斯地块的逆时针旋转和秦岭山地的向E挤出逃逸, 形成了鄂尔多斯东南缘以走滑-伸展转换为特征的似三联点构造区。

关键词: 鄂尔多斯东南缘; InSAR; GPS; 滑动速率; 闭锁深度; 构造变形模型

中图分类号:P315.2 文献标志码:A 文章编号:0253-4967(2021)03-0540-19

STUDY ON THE RECENT DEFORMATION CHARACTERISTIC AND STRUCTURAL DEFORMATION MODEL OF THE SOUTH-EASTERN MARGIN OF ORDOS BLOCK

LIU Rui-chun^1,^2,³⁾, ZHANG Jin¹⁾, GUO Wen-feng^2,³⁾, CHEN Hui^2,³⁾, ZHENG Ya-di^2,³⁾, CHENG Cheng^2,³⁾

1)Taiyuan University of Technology, Taiyuan 030024, China

2)Shanxi Earthquake Agency, Taiyuan 030021, China

3)National Continental Rift Valley Dynamics Observatory of Taiyuan, Taiyuan 030021, China

Abstract

The southeastern margin of the Ordos block is a key area for dynamic transformation from collision and compression in the western part of the Chinese mainland to extension in the east, and also is the junction of the NE-SW trending structure in the north and near the E-W trending structure in the south of the North China block. The tectonic activity in the southeastern margin of the Ordos block is intense. In this region, the Houma-Yuncheng section is a noteworthy area for medium- and long-term large earthquake risk determined by China Earthquake Administration, which involves three tectonic units:Linfen Basin, Yuncheng Basin and Emei Platform. The potential seismogenic faults include the Hancheng Fault, the southern margin fault of Emei Platform and the piedmont fault of Zhongtiao Mountains. Because the neotectonic movement in this region is mainly dominated by strong differential movement, it is important to estimate the fault kinematics parameters based on the high-resolution vertical crustal movement observation constraints.
Fault locking depth and slip rate are important indicators to judge the risk of future earthquakes. When the accumulation time of fault seismic moment and fault length are given, the larger fault locking depth and higher slip rate will cause the greater energy accumulation and stronger future earthquakes risk of the fault. Based on the traditional leveling and GPS data, previous studies found that the southeastern margin of the Ordos block is perhaps experiencing strong tectonic movement. However, the measuring point density of the above technical means is difficult to satisfy the quantitative study of the current activity characteristics of specific faults. Therefore, the interferogram stacking technique is used to obtain the spatial high-resolution InSAR average deformation rate field of the study area based on the Radarsat -2 wide-mode image in this paper firstly. At the same time, the three-component velocity of GPS continuous station in the study area is projected into the radar line of sight direction. After unifying the reference datum, comparative analysis was conducted to evaluate the accuracy and reliability of InSAR results. The results show that the standard deviation of the difference between the short-term InSAR and the long-term GPS observation values is 2.7mm. The annual crustal deformation field obtained by using the interferogram stacking technology in the study area has a high accuracy, which can reflect the characteristics of regional crustal movement. It also indicates that the regional crustal short-term deformation is consistent with the long-term deformation. Secondly, the dip-slip fault dislocation model and particle swarm optimization(PSO)were used to invert the main fault slip rate and locking depth, the inversion was repeated 1 000 times, and the optimum estimate of parameters was obtained by statistical analysis of results and uncertainty. The fault slip rate and locking depth data approximately obey the normal distribution, and the stability is good; the dip angles of faults are skewed but concentrated. The above results show that the fault movement parameters obtained from InSAR deformation field inversion are reliable and can be used for regional tectonic movement analysis. Finally, based on the data of regional geological structure, fault slip rate, fault locking depth and present seismic activity, this paper analyzes the variation characteristics of InSAR deformation field, and discusses the fault tectonic movement mode, future seismic risk and regional tectonic deformation pattern in the southeastern margin of Ordos. The results show that the tectonic and nontectonic deformations are superimposed on the southeastern margin of Ordos. Tectonic deformation mainly occurs near active faults, which is related to fault slip rate and closure depth. Nontectonic deformation mainly occurs in the Quaternary strata inside the basin, which is related to the thickness of the aquifer and the amount of groundwater extraction, and the maximum can reach 5cm/a. The slip rate of the fault at the northern foot of the Zhongtiao Mountains and the northern margin of the Emei Platform is 0.37mm/a and 0.74mm/a, and the blocking depth is 3.4km and 4.3km, which are relatively shallow. It may indicate that the fault was not completely closed after the last strong earthquake and is dominated by shallow seismic activity. The slip rate of the fault on the southern margin of the Emei Platform is 0.47mm/a, and the closure depth is 0.95km, indicating that the faults are mainly creepy. The counterclockwise rotation of the Ordos block and the eastward extrusion and escape of the Qinling Mountains formed a quasi-triple junction structural area on the southeastern margin of Ordos, characterized by strike-slip-extension transition.

Keyword: southeastern margin of Ordos block; InSAR; GPS; slip rate; locking depth; tectonic deformation model

文章图片

0 引言

鄂尔多斯块体东南缘是中国大陆西部碰撞挤压到东部伸展拉张动力学转换的关键地区, 也是华北块体北部的NE-SW向构造与南部的近EW向构造的交接部位(陆一锋等, 2012)。鄂尔多斯块体东南缘的构造活动强烈, 共记录到6级以上地震22次, 其中7级以上地震7次, 震级最大的是发生在其东部边缘的1303年洪洞8级地震和南部边缘的1556年华县8级地震(张学民等, 2004; 任雪梅等, 2010)。

鄂尔多斯块体东南缘的新生代断陷盆地自北向南分别为临汾、运城盆地, 在平面上呈弧形, 罗云山断裂、韩城断裂控制断陷盆地的西边界, 霍山断裂、大阳断裂和浮山断裂控制东边界, 中条山山前断裂和华山山前断裂则控制南边界。这些主干断裂在南部为NE走向, 以强烈的差异升降运动为主, 向N逐渐过渡为NNE走向, 以张性右旋剪切运动为主。此外, 在断陷盆地内还发育多组与边界断裂斜交的横向断裂, 规模较大的有峨嵋台地北缘断裂和峨嵋台地南缘断裂, 这些断裂与盆地边界断裂相互交会, 形成极其复杂的构造格局(图 1)。该区域的侯马—运城段是中国地震局确定的中长期大地震值得注意的地区(M7专项工作组, 2012), 涉及临汾盆地、运城盆地和峨嵋台地3个构造单元, 潜在发震断裂有韩城断裂、峨嵋台地南缘断裂和中条山山前断裂等。

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	图 1 鄂尔多斯块体东南缘的区域构造图Fig. 1 Regional tectonic map of southeastern margin of Ordos block.

在震间期的不同孕震阶段, 断层两侧的地壳形变状态存在一定差异, 这种差异与断裂带所处的孕震阶段关系密切(张培震等, 2009; 闻学泽等, 2014), 以形变资料约束反演震间断层运动学参数已成为断层中长期危险性分析的一种重要手段(张培震等, 2003)。 Hao等(2016)和Wang等(2020)分别给出了鄂尔多斯块体周缘多期水准和GPS资料平差结果, 发现鄂尔多斯块体东南缘存在一个显著的下降变形区, 可能反映该区域正在发生强烈的构造运动。然而, 水准测点主要沿交通线路走向布设, GPS测点仅位于几个主要的构造单元内, 测点密度目前仍难以满足针对具体断裂现今活动特性的定量研究需求。

为了进一步研究鄂尔多斯东南缘现今地壳的变形特征和主要断裂中—长期地震危险性, 探讨区域构造变形模式, 本文利用时序InSAR技术获得了研究区现今的空间高分辨率形变速率场, 并利用区域内长期观测的连续GPS监测结果开展InSAR形变场的精度评价, 在此基础上, 利用倾滑断裂位错模型结合粒子群算法(PSO)反演了部分主要断裂的闭锁深度和滑动速率, 为区域构造模式和中—长期地震危险性探讨提供现今地壳形变方面的证据。

1 时序InSAR技术及数据处理方法

1.1 时序InSAR技术及应用

InSAR技术可以通过大空间尺度的成像过程提取研究区域的整体形变特征。传统的D-InSAR技术以两轨法和三轨法为代表, 在消除地形相位的前提下, 能获取大范围面状、二维的地表形变信息, 它侧重于单次形变或两时刻的累积形变, 使用SAR图像少, 对干涉图像参数要求非常高, 且大气效应估计困难, 很难同形变信号分离(Zebker et al., 1992; Hanssen, 2001)。随着星载SAR的发展, 在相同试验区可积累大量重复轨道的SAR数据, 特别是近年来发展起来的干涉图堆叠(Stacking)技术(Zebker et al., 1997)、永久散射体(permannent scatterers)技术(Hooper et al., 2004)和小基线集(Small Baseline Subsets, SBAS)(Berardino et al., 2002)等时序D-InSAR技术削弱了常规InSAR测量中的轨道误差、外部DEM误差、大气相位延迟误差等, 拓展了InSAR技术的应用领域(季灵运等, 2015)。目前, 该技术在震间和同震地壳形变监测(单新建等, 2002; Fialko, 2006; Cavalié et al., 2008; 屈春燕等, 2011)、地壳演变与火山活动(Berardino et al., 2002)、城市地表沉降(汤益先等, 2006; 周志伟等, 2011)等方面得到了广泛应用。

1.2 SAR影像及数据处理方案

本研究选用9景Radarsat-2宽模式影像, 数据幅宽150km×150km, 分辨率为30m, 波长为5.6cm, 获取时间为2016年1月—11月。数据处理采用干涉图堆叠(Stacking)技术, 该方法基于一系列解缠的差分干涉图, 通过积累法估计线性速率, 可将大气及其他各种噪声降为 1/ $\sqrt[]{N}$ , N为干涉图的个数(Hanssen, 2001)。由于Radarsat-2影像工作在C波段, 不允许较长的空间垂直基线, 再加上研究区域的地形起伏较大, 垂直基线> 400m会造成较严重的空间失相干。在进行数据处理时, 对9景SAR影像给定垂直基线< 400m的限制, 然后进行自由组合干涉, 共得到9个可用的干涉对, 基线组合如图 2 所示。

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	图 2 InSAR干涉图组合与基线Fig. 2 Combination and baselines of InSAR interferograms.

利用GAMMA软件对每个符合条件的干涉对进行SAR信号成像、图像配准与干涉、外部DEM模拟、基线估计与精化、相干系数计算、干涉图自适应滤波和相位解缠。其中, 外部地形数据使用美国NASA(美国宇航局)公布的SRTM DEM。相位解缠采用最小费用流算法, 以运城市区附近为解缠起始区域, 仅对相干系数> 0.6的像元进行解缠。

为保证后续计算结果的可靠性, 在处理数据时, 采用基于局部条纹频谱的自适应滤波方法提高干涉图的相干性, 降低相位解缠误差(Nof et al., 2012)。针对含有基线误差的干涉对, 基于已有的DEM和观测解缠相位, 采用非线性最小二乘平差方法去除基线误差(Lu, 2007)。此外, 为了削弱噪声、增加相干性及检测相对大尺度的形变信息, 对干涉图进行了4:20的多视处理。

2 InSAR形变速率场分析

2.1 InSAR与GPS监测结果的对比分析

InSAR获取的雷达视线向(LOS)形变量是一个相对量, 且易受时空失相干的制约和大气延迟以及DEM误差等因素的影响, 部分地区监测结果的可靠性不确定, 我们可以利用研究区域内可靠性相对较高的同时段连续GPS观测数据评价InSAR结果的精度和可靠性。由于InSAR和GPS测量分别属于2种不同的测量系统, GPS与InSAR的测量结果无法进行直接对比(汪宝存等, 2015)。为此, 首先需将GPS三分量速率投影到InSAR的雷达视线向(LOS), 然后进行参考基准的统一, 才能对InSAR测量的可靠性进行分析与评价。

雷达视线向变形量与地面三维变形量的转换关系如式(1)所示(宋小刚等, 2015)。其中, $θ$ 为卫星入射角, $α$ 为卫星轨道方向的方位角, $d_{LOS}$ 为视线向形变量, $V_{LOS}$ 为测量误差(轨道误差、大气延迟、失相干和DEM误差等)。将Radarsat-2雷达侧视角 $(θ$ =26.06°)和卫星轨道方位角 $(α$ =191.18°)代入式(1)并将其转换为矩阵形式, 结果如式(2)所示。可以看出, 地表垂直向对LOS方向影响最大, EW向影响次之, 约为垂直向的二分之一; SN向影响最小, 不到垂直向的十分之一。 EW向和垂直向的影响相反, LOS形变的结果取决于绝对值较大的变形方向, 在某些区域难以单独利用InSAR数据判断地表形变是上升还是下降。

$d_{LOS} = \sin θ \cos (α - 3 π / 2) U_{N} + \sin θ \sin (α - 3 π / 2) U_{E} + \cos θ U_{U} + V_{LOS}$ (1)

$d_{LOS} = [\begin{array}{l} 0.085 i 4 & - 0.430 i 7 & 0.898 i 4 \end{array}] [\begin{array}{l} U_{N} \\ U_{E} \\ U_{U} \end{array}] + V_{LOS}$ (2)

在InSAR监测范围内有9个可用的连续GPS观测站点(图 3), 观测时间为2011年1月—2020年6月, 基于中国地震台网中心产出的站点位置时间序列, 在去除周期、阶跃等各种非构造干扰后, 估计了GPS站点在观测时段内的三分量位移速率, 并根据式(2)计算了其在LOS方向上的投影值。由于InSAR监测点不能与GPS站点完全重合, 本文以区域内的GPS站点位置为圆心, 将其半径1m内的所有InSAR测点的平均形变量与GPS的投影结果进行对比, 并采用GPS和InSAR观测值之间的多项式关系消除2种测量系统的偏差(宋小刚等, 2015), 同时实现参考基准的统一。回归方程为

$y = - 0.008 x^{2} - 0.08 x - 1.75$ (3)

式(3)中, y为GPS投影值, x为InSAR测量值。以GPS为基础调整对应的InSAR值, 对InSAR值进行补偿, 以实现InSAR与GPS观测值参考基准的统一。统一基准后的结果见表1。

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	图 3 鄂尔多斯地块东南缘的InSAR地壳形变场Fig. 3 The InSAR crustal deformation field of the southeastern margin of Ordos block.

表1 GPS投影值与InSAR观测值的比较 Table 1 Comparison between GPS projection and InSAR observations

统一参考基准后, 多数测点的InSAR短期观测值与GPS长期观测值的差值< 0.3cm(表1), 计算所得的标准差为0.27cm, 表明InSAR监测结果的精度和可靠性较高, 能够反映区域地壳运动特征, 同时也表明区域短期地壳运动与长期运动较为一致。其中, JIXI和WENX 2个点的差值稍大, 约为0.5cm, 可能由于GPS和InSAR的观测时间段不一致, 测点局部的非构造形变差异导致。

2.2 InSAR形变速率场的空间变化特征分析

图 3中的平均形变速率场覆盖的主要地质构造有运城、临汾盆地以及峨嵋台地、太行山和吕梁山隆起区, 主要断裂包括中条山北麓断裂、罗云山断裂、峨嵋台地南缘断裂和峨嵋台地北缘断裂。图像东、西两侧的太行山、吕梁山隆起区由于地势陡峭、植被覆盖茂密, 短波长的C波段难以穿透植被冠层, 时间相干性保持能力弱, 雷达卫星成像的后向散射随着时间的推移会变得严重不相关, 同时由于与地形起伏相关的对流层垂直分层延迟相位的影响, 上述区域形变点较为稀疏, 形变结果误差相对较大。临汾、运城盆地和峨嵋台地及周边区域相对干燥且裸露, 受大气延迟和植被覆盖影响较小, 数据相干性较好, 形变点分布连续, 监测结果较为可信。

为辅助分析不同地质构造块体和断裂的形变速率变化特征, 绘制了1条跨越主要地质构造块体和活动断裂的变形剖面, 见图 3 中的CC'。剖面宽1km, 为便于分析, 将剖面跨越的活动断裂、地质构造块体名称以及地表高程标注于图 4 中。

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	图 4 鄂尔多斯地块东南缘的LOS向形变剖面 LYF 罗云山断裂; NEF 峨嵋山北麓断裂; SEF 峨嵋山南麓断裂; ZTF 中条山断裂Fig. 4 The LOS deformation profile of the southeastern margin of Ordos block.

研究区域的空间形变格局受到地质构造和地层特征的控制, 同时受地下水开采的显著影响(Yang et al., 2016)。以活动断裂为界, 山区和横向隆起区相对稳定、盆地相对下沉的总体形变格局反映了区域第四纪以来的继承性构造运动。峨嵋台地内部存在的局部下沉区可能与峨嵋台地被第四纪黄土覆盖有关(李振宏等, 2020)。

中条山和峨嵋台地隆起区的形变受地下水开采的影响不大, 这些台地0~2mm/a的隆起可能为长期的震间地壳运动(Zhao et al., 2018)。中条山北麓断裂控制运城盆地的南边界, 沿剖面CC'在断裂两盘的上升和下沉存在mm级的差异运动速率, 可能表明在监测时段内该段落存在一定的活动性。峨嵋台地北缘和南缘断裂分别控制临汾盆地的南边界和运城盆地的北边界, 2条断裂沿CC'剖面的差异运动较小, 在监测时段内剖面经过的段落相对稳定。

在临汾和运城盆地内部, 显著沉降区域主要位于中条山山前断裂和罗云山断裂上盘的冲积平原, 同时受到周边正断层控制。其中, 沉降最严重的夏县和永济地区地处中条山山前断裂上盘的涑水平原, 地下水类型为松散岩类孔隙水, 潜水含水层、潜水-承压含水层和承压含水层均为主要的地下水开采层(黄昕霞等, 2007)。地下水过量开采形成永久性地下水下降漏斗, 同时导致含水层的孔隙压力减小, 从而引发严重的地面沉降(姚亮, 2017)。因此, 中条山山前断裂上盘> 5cm/a的变形主要是由于地下水开采所导致的地面沉降。这种变形仅发生在浅地表区域, 变形量远大于基于地震地质方法得到的约1mm/a的断层倾滑速率(苗德雨等, 2014)以及区域水准测量所得到的最大为6~8mm/a的地壳垂直运动速率(Hao et al., 2016), 与断层活动由深部滑动和构造应力所驱动的机理完全不同(乔鑫等, 2019)。

3 鄂尔多斯东南缘断裂的滑动速率与闭锁深度反演

鄂尔多斯东南缘为典型的盆岭构造发育地区, 构造运动以垂直向为主(国家地震局鄂尔多斯周缘活动断裂系课题组, 1988), 通过Radarsat-2影像获得的LOS向形变量的65%是垂直向运动所贡献的, 适宜开展区域构造运动分析。利用地壳形变观测数据反演断层的运动参数主要有位错模型、块体运动模型及负位错模型。考虑到研究区断裂以正倾滑为主, 且块体规模不大, 我们没有把研究区作为整体模型, 仅通过 “ 刃型” 位错提出的倾滑断层震间形变数学表达式(Freund et al., 1976)做剖面反演。反演模型的表达式为

$u_{x} = \frac{s}{π} [\cos δ ta n^{- 1} (\frac{x}{d}) + \frac{\sin δ - \frac{x}{d} \cos δ}{1 + {(\frac{x}{d})}^{2}}]$ (4)

$u_{z} = - \frac{s}{π} [\sin δ ta n^{- 1} (\frac{x}{d}) + \frac{\cos δ + \frac{x}{d} \sin δ}{1 + {(\frac{x}{d})}^{2}}]$ (5)

其中, $u_{x}$ 为水平面垂直断层X方向的位移, $u_{z}$ 为垂直地面Z方向的位移, $s$ 为沿断层面倾滑的位移, $d$ 为断层闭锁深度, $δ$ 为断层倾角, $x$ 为观测点到断层的垂直距离。由于研究区断裂以正倾滑活动为主, 在研究时段内拉张和走滑分量很小, 此处忽略水平面平行和垂直于断层方向的位移, 将 $u_{z}$ 投影到LOS方向可得式(6)。式中, $θ$ 为SAR传感器的入射角。

$u_{LOS} = u_{z} \cos θ$ (6)

我们切取了鄂尔多斯东南缘3条主干断裂的InSAR形变剖面, 剖面见图 3 中的AA'、 BB'和DD', 剖面长15km, 宽1km。根据地震地质、现今大地测量的研究结果, 研究区震间地壳构造运动相对稳定, 一般不会超过2mm/a(司苏沛等, 2014; Zhao et al., 2018), 因此, 反演时将剖面线上绝对值> 2mm/a的形变点剔除。同时, 为避免局部速率陡变点对拟合结果的影响, 对形变速率剖面进行平滑处理, 沿剖面线按0.2km的窗口计算形变速率的平均值(乔鑫等, 2019)。反演时, 根据区域已有的大地震震源深度和地震精定位研究结果(蔡妍等, 2014), 将断裂的闭锁深度设定为0~30km。研究区断层多为高角度正断层, 倾角一般为40°~80°(国家地震局“ 鄂尔多斯周缘活动断裂系” 课题组, 1988), 据此将断层的倾角范围设为30°~90°。由于断层倾角不为90°时, 地表位移曲线中心不对称, 同时考虑到断层位置难以准确确定, 反演时设置了沿x坐标的偏移常数, 取值范围为-3~3km。

由于式(6)具有高度非线性特征, 无法确定参数的近似值, 直接利用最小二乘法反演容易使方程产生奇异而无解。为了解决这一问题, 本文使用带惯性权重的粒子群智能优化方法(Shi et al., 1999), 并采用惯性权重线性递减策略(刘杰等, 2010), 在搜索初期使各粒子以较大的步长在全局范围内探测较好的种子, 在搜索后期以较小的步长在极值点周围做精细搜索, 从而使算法有较大机率收敛于全局最优解。反演重复执行1i000次, 通过统计分析得到参数的最优估计结果和不确定性。反演和统计结果见表2和图 5, 剖面结果见图 6。

表2 断层参数的统计结果 Table 2 Statistical results of fault parameters

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	图 5 断层参数反演结果的统计分析矩形盒内部的红色横线代表中位数, 矩形盒上、下两端分别代表上、下四分位数, 红色十字代表异常值, 虚线表示正常值的分布区间Fig. 5 Statistical analysis of fault parameter inversion results.

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	图 6 断层变形剖面及倾滑断层模型拟合结果 AA'、 BB'、 DD'分别为峨嵋台地南缘断裂、中条山北麓断裂和峨嵋台地北缘断裂的形变剖面及拟合结果; 红色圆圈为断层LOS向的平均变形速率, 灰色点为断层剖面LOS向的变形速率Fig. 6 Fault deformation profiles and fitting results of dip-slip fault model.

用箱线图统计上述方法反演得到的断层参数(图 5), 各参数的中位数和均值列于表2。结果显示, 断层滑动速率、闭锁深度的中位数分别在0~1mm/a和0~5km之间, 中位数与均值相同, 反演结果的异常值数量< 12个, 数据近似服从正态分布, 反演稳定性较好; 断层倾角的中位数与均值存在一定差异, 反演结果的异常值数量为6~57个, 为偏态分布, 但有明显的分布集中趋势。下面对每条断层的3个参数进行逐一分析。

断裂倾滑速率的中位数分别为0.74mm/a、 0.47mm/a和0.37mm/a, 参数的平均值与中位数相同。极小和极大值分别为0.69mm/a和0.79mm/a、 0.34mm/a和0.60mm/a、 0.34mm/a和0.46mm/a, 上、下四分位间距均< 0.06mm/a, 反演结果仅存在6~11个异常值, 表明数据集中程度较高, 稳定性较好。

断裂闭锁深度的中位数分别为3.4km、 0.95km和4.3km, 参数的平均值与中位数相同。极小和极大值分别为2.8km和4.1km、 0.3km和2.0km、 3.7km和5.0km, 上、下四分位间距均< 0.3km, 反演结果仅存在6~11个异常值, 表明数据集中程度较高, 反演稳定性较好。

断裂倾角的中位数分别为64.8°、 87.6°和30.6°, 参数的平均值与中位数有一定差异, 差值在0.8°~7.5°之间。参数的极小和极大值分别为59.5°和71.6°、 70.5°和90.0°、 30.0°和33.9°, 上、下四分位间距< 3.3°, 反演结果存在12~57个异常值, 表明数据有一定的集中度, 但反演稳定性略差。

4 分析与讨论

4.1 与已有InSAR结果的对比分析

将InSAR形变结果与Yang等(2016)的结果进行对比, 2个形变场整体具有较好的一致性, 均监测到中条山山前断裂的夏县附近和罗云山断裂的新绛县附近存在2个沉降区, 最大形变量均> 5cm/a(图 3), 说明本文的数据处理结果较为可靠, 同时也说明该区域是一个地表形变复杂的地区, 形变场具有多尺度性和不均匀性。

与Yang等(2016)的结果相比, 本文使用的Radarsat-2宽模式影像在EW向的覆盖范围更广, 较完整地揭示了中条山山前断裂西段的形变特征。中条山断裂西段的永济地区于2016年发生了明显的下沉形变, 靠近断裂处的形变量达2~5cm/a, 这个量级的形变是由较长时期地质资料获得的断层滑动速率的7~10倍(程绍平等, 2002; 司苏沛等, 2014)。本研究时段的监测结果显示, 该区域的沉降范围已超过中条山断裂夏县段, 值得关注。本研究时段内, 夏县和新绛县附近2个沉降区的形变范围和量级均没有继续发展, 可能与近年来这2个地区大力实施的关井压采及地下水综合治理工程有关(姚亮, 2017)。

Yang等(2016)发现位于临汾盆地罗云山断裂南段的河津地区存在一个由于地下水回升驱动的隆升异常变形区, 2009年2月—2010年10月累计回升4cm。本研究给出的该区域2016年的形变结果表明, 区域地表变形已趋于稳定, 未出现明显隆升和沉降。

4.2 断裂的滑动速率、闭锁深度与地震危险性

断裂上的地震矩累积率以及未来发生地震的震级与断层滑动速率、闭锁深度成正比(Ward, 1994; Savage et al., 1997)。当积累时间和断层长度一定时, 断层的闭锁深度越大、滑动速率越高, 则积累的能量就越大; 如果闭锁深度接近于零, 断层将只发生蠕滑而不会积累应变能。因此, 断层的闭锁深度和滑动速率是判断未来地震危险性的重要指标(崔笃信等, 2019)。

鄂尔多斯东南缘的侯马—运城地区为历史地震破裂空区(M7专项工作组, 2012), 有地震台网记录以来, 该区震群非常活跃, 发生的11次M≥4.0地震近一半表现为震群活动, 垣曲震群最大的主震震级达到M5.5, 可能表明该区域介质很不均匀, 但作用力十分集中(Mogi, 1963), 其强震危险性值得关注。下文将对研究区主要断层的滑动速率、闭锁深度与地震危险性进行讨论。

峨嵋台地北缘断裂:该断裂为临汾-侯马盆地与峨嵋台地隆起之间的边界断裂, 总体走向NEE, 全长约120km, 中段活动性最强, 最后一次古地震事件距今约46ka, 震级约达7.5级(陈国顺等, 1993; 徐伟等, 2016)。 1970年以来, 该断裂附近发生的最大地震为1989年侯马M4.9地震。反演结果显示, 该断裂中段的垂直滑动速率约为0.37mm/a, 与地质学在此处测定的晚更新世晚期以来滑动速率≥0.36mm/a的结果一致(徐伟等, 2014)。断裂在此处的闭锁深度为4.3km, 具有积累中等强度地震应变能的条件。

峨嵋台地南缘断裂:该断裂为峨嵋台地与运城盆地之间的边界断裂, 全长约130km, 走向NEE, 为正倾滑断层, 早更新世活动强烈, 全新世期间趋于稳定(郭春彬, 2019)。 1970年以来, 该断裂附近仅发生若干次震级约为M3.0的地震。该断裂的滑动速率在地质上没有确切的结果, 基于InSAR剖面资料反演得到的滑动速率约为0.47mm/a, 略大于峨嵋台地北缘断裂。断裂的闭锁深度为0.95km, 现今可能以蠕滑活动为主。

中条山北麓断裂:该断裂是运城盆地东界和南界的主控断裂, 全长140km, 根据走向、活动性等差异可分为韩阳段、解州段和夏县段3个段落, 解州段为晚更新世以来滑动速率最大的段落(国家地震局 “ 鄂尔多斯周缘活动断裂系” 课题组, 1988; 程绍平等, 2002)。断裂全新世以来发生过3次古地震事件, 最大震级> 8级(邓起东等, 1992; 司苏沛等, 2014; 王怡然等, 2015)。 1970年以来, 该断裂附近发生的最大地震为1998年永济M4.6地震。基于InSAR剖面资料反演得到解州段的滑动速率为0.74mm/a, 与物探和探槽资料揭示的(0.75±0.05)mm/a的平均滑动速率一致(司苏沛等, 2014)。中条山北麓断裂解州段的闭锁深度为3.4km, 可能表明断裂在最后一次强震后还没有完全闭锁, 主要以浅部活动为主。

4.3 鄂尔多斯东南缘的构造变形模型

华北地区的新构造运动受控于印欧碰撞产生的远场效应和岩石圈地幔的上涌。青藏高原东北缘地块的持续推挤及其构造应力的向E传递导致鄂尔多斯地块逆时针旋转和秦岭山地向E挤出逃逸(李延兴等, 2003; 张培震等, 2003)。该挤出构造动力过程主导了汾渭裂谷系的走滑拉分及其沿山西地堑系的NE向扩展(张岳桥等, 2019)。

鄂尔多斯东南缘弧形拉张区地处鄂尔多斯地块、华北平原地块与华南地块的交接区, 3个相关块体分别以(5.7±0.1)mm/a、 (5.5±0.1)mm/a和(7.5±0.1)mm/a的平均速率整体向E—SE向移动(Wang et al., 2020)。 3个相关构造支中, 秦岭北缘断裂带主要为左旋拉张性质, 拉张速率从西段向东段逐渐增大(李延兴等, 2003; 崔笃信等, 2019); 忻定-太原-临汾断陷盆地带主要包括忻定盆地、太原盆地和临汾盆地, 具有右旋拉张性质; 渭河盆地北缘断裂带的主要活动性质为拉张。

上述块体及构造带的相互作用和运动转换, 在西安—运城—临汾一带形成了较为复杂的三角形交接构造(图 7), 这种交接构造为中国大陆内部典型的似三联点构造(田勤俭等, 1998)。在似三联点附近, 一系列断裂将三角形交接区分成多个条块, 条块间的相对运动可通过边界断裂的活动表现。秦岭构造带作为一个地壳通道, 其向E挤出导致汾渭地堑系的走滑拉张和NE向扩展, 形成了由楔形的临汾盆地和鄂尔多斯东南缘弧形拉张区组成的走滑-伸展转换系统(张岳桥等, 2019)。

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	图 7 鄂尔多斯东南缘的似三联点及相关构造(田勤俭等, 1998)Fig. 7 Quasi triple junction and related structures in southeastern margin of Ordos block(TIAN Qin-jian et al., 1998).

临汾盆地内部发育有多组断裂, NNE—NE向右旋走滑断裂控制盆地的边界, 近EW或NW向左旋正走滑断裂控制盆地内部的次级构造单元。鄂尔多斯东南缘弧形拉张区由多个子凹陷组成, 包括西安凹陷、固市凹陷、运城盆地和灵宝盆地等, 其沉积-沉降主体受南缘和东南缘边界伸展断裂控制, 形成盆-山地貌(张岳桥等, 2019), 其新构造运动的一个特点是由SW向NE逐渐减弱, 位于最南端的秦岭北缘断裂带活动性最强, 中条山山前断裂、峨嵋台地南缘和北缘断裂的活动性逐渐变弱。

5 结论

本文利用干涉图堆叠(Stacking)技术处理了2016年1月—11月的9景Radarsat-2宽模式影像, 获取了鄂尔多斯东南缘空间高分辨率InSAR形变速率场, 并在此基础上通过反演分析了主干断裂的闭锁深度、滑动速率和地震危险性, 具体结论如下:

(1)采用干涉图堆叠(Stacking)技术可有效获取研究区空间高分辨率的高精度地壳形变场, 且利用InSAR技术获得的区域地壳短期形变与GPS获得的长期形变具有一致性。

(2)鄂尔多斯东南缘的临汾、运城盆地构造和非构造形变相互叠加。构造形变主要发生在活动断裂附近, 与断层的滑动速率和闭锁深度有关; 非构造形变主要发生在盆地内的第四纪地层, 空间上具有差异性, 与含水层厚度和地下水开采量有关, 最大幅度> 5cm/a。

(3)InSAR资料揭示的中条山北缘断裂、峨嵋台地北缘和南缘断裂的滑动速率< 1mm/a、闭锁深度< 5km, 现今可能主要以浅部活动或蠕滑活动为主。

(4)鄂尔多斯地块的逆时针旋转和秦岭山地的向E挤出逃逸, 在鄂尔多斯东南缘的西安—运城—临汾一带形成了以走滑-伸展转换为特征的似三联点构造区。

致谢中国地震台网中心王阅兵高级工程师提供了GNSS站点位移时间序列, 在此表示衷心感谢!

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2019

0.0

... 因此, 断层的闭锁深度和滑动速率是判断未来地震危险性的重要指标(崔笃信等, 2019) ...

... 崔笃信等, 2019) ...

2014

0.0

蔡妍, 吴建平, 房立华, 等. 2014. 鄂尔多斯东缘地震重定位及拉张盆地过渡区的地震分布特征[J]. 地球物理学报, 57(4):1079—1090.

CAI

Yan

, WU

Jian-ping

, FANG

Li-hua

, et al. 2014. Relocation of the earthquakes in the eastern margin of Ordos block and their tectonic implication in the transition zones of extensional basin[J]. Chinese Journal of Geophysics, 57(4):1079—1090(in Chinese).

Using the double-difference earthquake location algorithm, we relocated the earthquakes in the eastern margin of Ordos block (34 degrees N-41 degrees N, 110 degrees E-115 degrees E) from 2008-2012. After relocation, the accuracy of the earthquakes is improved, and the epicenters are more concentrated. The focal depth within the basins in the eastern margin of Ordos block is shallow, mostly less than 13 km. It is shown that the focal depth deepens from inside to the ends of the basin, particularly in the northern end of Taiyuan and Linfen basin, and E' mei mesa between Yuncheng and Linfen basin, with the focal depth up to about 20 similar to 25 km. It is considered that with the circumstance of the thinned crust and upwelling mantle, the thermal effects reduce the thickness of the brittle layer in the crust, which shallows the maximum focal depth; the transverse uplifts between basins are subjected to some forces, such as shear-compression stress from the regional stress field and horizontal compression from upwelling mantle inside the basins. In this case, it is easy to produce stress concentration in the contact zones between the transverse uplifts and basins, which may induce earthquakes. Due to the change in thickness of the brittle layer, the focal depth. deepens in the transition zone from basins to the transverse uplifts. The earthquakes in the northeastern margin of Ordos block are diffuse, and the focal depth is relatively shallow, which may be related to the large-scale thermal effect from mantle and the decreasing of the brittle layer thickness. According to the spatial distribution of the earthquakes, we discussed the characteristics of the faults in some basins.

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

利用双差地震定位方法对鄂尔多斯东缘地区（34°N—41°N，110°E—115°E）2008年1月—2012年12月的中小地震进行了重新定位.重定位后，定位精度得到改善，震中分布更加集中.鄂尔多斯东缘拉张盆地内部震源深度较浅，大多小于13 km，向盆地两端震源深度有加深的趋势，特别是太原盆地北端，临汾盆地北端，以及运城与临汾盆地之间的峨眉台地，震源深度可达20~25 km左右.我们认为盆地内部地壳减薄，上地幔上隆，热作用导致地壳内部脆性层减薄，致使最大震源深度变浅；盆地之间的横向隆起区受区域应力场挤压剪切作用以及盆地内部上地幔上拱产生的水平向挤压力作用等，在横向隆起区与盆地接触带易产生应力集中，导致地震的发生，由于受脆性层厚度变化等的影响，在盆地向横向隆起区过渡部位出现震源深度加深的现象.鄂尔多斯东北缘地区地震分布弥散、震源深度相对较浅，可能与源自地幔的大范围深部热作用以及地壳脆性层厚度减薄有关.根据地震的空间分布特征，对部分盆地内部的断层特征进行了讨论.

... 反演时, 根据区域已有的大地震震源深度和地震精定位研究结果(蔡妍等, 2014), 将断裂的闭锁深度设定为0~30km ...

2002

0.0

程绍平, 杨桂枝. 2002. 山西中条山断裂带的晚第四纪分段模型[J]. 地震地质, 24(3):289—302.

CHENG

Shao-ping

, YANG

Gui-zhi

. 2002. Late Quaternary segmentation model of the Zhongtiaoshan Fault, Shanxi Province[J]. Seismology and Geology, 24(3):289—302(in Chinese).

The Zhongtiaoshan Fault, southern Shanxi is an active fault in the southeastern part of the active fault system around Ordos Massif, being the boundary between the Yuncheng Faulted basin and the Zhongtiaoshan Faulted Mountain. The recent study about fault activity indicates that it has a lower level of activity and a relatively long recurrence interval of faulting. On the basis of this understanding, a further study is carried out on the segmentation of the Zhongtiaoshan Fault, while the late Quaternary segmentation model and its quantitative parameters are provided in the light of evidence from tectonic discontinuity, tectonic geomorphology, trench paleoseismology, and fault kinematics. The Zhongtiaoshan Fault runs from the northern piedmont to the western piedmont of the Zhongtiaoshan Mountains, with a length of 137km, a general strike of NE-NEE, and a dip angle of 58°～75°, being a high angle normal fault. On one hand, the northern piedmont part of the fault exhibits a big curve convex southeast; and on the other hand, the western piedmont part of the fault intersects with its northern piedmont part at an angle of 120°. By these two major tectonic discontinuities, the Zhongtiaoshan Fault can be divided into three geometric segments from northeast to southwest:the Xiaxian segment, the Xiezhou segment, and the Hanyang segment. The major tectonic discontinuities persistently control the Cenozoic sedimentation in the Yuncheng Faulted Basin. The Xiezhou segment of the Yuncheng Faulted Basin was the depocenter not only of Tertiary system but also of Quaternary system. Morphometric analysis has indicated that the elevation profile of divides and geomorphic characteristics of drainage system in the Zhongtiaoshan Mountains, such as length and gradient index of stream, as well as evolution of its mountain front, have apparent segmented variations, showing an along strike tectonic inhomogeneity caused by long term faulting. The quantitative parameters, such as long term slip rate, displacement per event, age of the last event, and average recurrence interval obtained from the studies of trench paleoseismology and fault kinematics are indicative of segmented differences in late Quaternary fault behavior of the Zhongtiaoshan Fault. In summary, the Zhongtiaoshan Fault is a typical fault exhibiting relatively long recurrence intervals. The surface rupturing events revealed in the trenches correspond to strong earthquakes of magnitude 7.7～8.1, which were separated by a quiescence period of 12,000 years for the Xiezhou segment, and 50,000～85,000 years for the Xiaxian and Hanyang segments. For the Zhongtiaoshan Fault, the only segment that was active during the Holocene epoch is the Xiezhou segment, which has the fastest long term slip rate, the biggest displacement per event, and the shortest average recurrence interval among the three segments. The Holocene activity of this segment might be attributed to the growth and strong activity of the secondary faults of the Zhongtiaoshan Fault since at latest the middle Pleistocene, inducing the frequent rupturing on the main fault. The occurrence of such a type of fault as the Zhongtiaoshan Fault with a relatively long recurrence interval(10 4 years)in the active fault system around the Ordos Massif implies the inhomogeneity of the movement of the Ordos Massif as a whole. The segmentation model and its quantitative parameters proposed in this paper may provide basic materials for seismic risk evaluation.

Institute of Geology, China Seismological Bureau, Beijing 100029, China

山西南部的中条山断裂是鄂尔多斯断块周边活动断裂系东南部分的1条断裂.有关断层活动性的最新研究结果表明,中条山断裂的活动性水平较低且重复间隔较长.在这个认识的基础上,根据构造不连续性、构造地貌学、探槽古地震学和断层运动学证据,进一步提出了晚第四纪中条山断裂的分段模型及其定量参数.

... 中条山断裂西段的永济地区于2016年发生了明显的下沉形变, 靠近断裂处的形变量达2~5cm/a, 这个量级的形变是由较长时期地质资料获得的断层滑动速率的7~10倍(程绍平等, 2002 ...

... 程绍平等, 2002) ...

1993

0.0

... 5级(陈国顺等, 1993 ...

1992

0.0

... 8级(邓起东等, 1992 ...

1988

0.0

... 3 鄂尔多斯东南缘断裂的滑动速率与闭锁深度反演鄂尔多斯东南缘为典型的盆岭构造发育地区, 构造运动以垂直向为主(国家地震局鄂尔多斯周缘活动断裂系课题组, 1988), 通过Radarsat-2影像获得的LOS向形变量的65%是垂直向运动所贡献的, 适宜开展区域构造运动分析 ...

... 研究区断层多为高角度正断层, 倾角一般为40°~80°(国家地震局#cod#x0201c ...

... 中条山北麓断裂:该断裂是运城盆地东界和南界的主控断裂, 全长140km, 根据走向、活动性等差异可分为韩阳段、解州段和夏县段3个段落, 解州段为晚更新世以来滑动速率最大的段落(国家地震局 #cod#x0201c ...

2019

0.0

... 峨嵋台地南缘断裂:该断裂为峨嵋台地与运城盆地之间的边界断裂, 全长约130km, 走向NEE, 为正倾滑断层, 早更新世活动强烈, 全新世期间趋于稳定(郭春彬, 2019) ...

2007

0.0

... 其中, 沉降最严重的夏县和永济地区地处中条山山前断裂上盘的涑水平原, 地下水类型为松散岩类孔隙水, 潜水含水层、潜水-承压含水层和承压含水层均为主要的地下水开采层(黄昕霞等, 2007) ...

2015

0.0

季灵运, 刘立炜, 郝明. 2015. 利用InSAR技术研究滇西南镇康-永德地区现今地壳形变特征[J]. 地震研究, 38(1):84—89.

Ling-yun

, LIU

Li-wei

, HAO

Ming

. 2015. Crustal deformation characteristic of Zhenkang-Yongde region in southwest Yunnan observed by InSAR technology[J]. Seismological Research, 38(1):84—89(in Chinese).

... , 2002)等时序D-InSAR技术削弱了常规InSAR测量中的轨道误差、外部DEM误差、大气相位延迟误差等, 拓展了InSAR技术的应用领域(季灵运等, 2015) ...

2020

0.0

... 峨嵋台地内部存在的局部下沉区可能与峨嵋台地被第四纪黄土覆盖有关(李振宏等, 2020) ...

2003

0.0

... 青藏高原东北缘地块的持续推挤及其构造应力的向E传递导致鄂尔多斯地块逆时针旋转和秦岭山地向E挤出逃逸(李延兴等, 2003 ...

... 3个相关构造支中, 秦岭北缘断裂带主要为左旋拉张性质, 拉张速率从西段向东段逐渐增大(李延兴等, 2003 ...

2010

0.0

... , 1999), 并采用惯性权重线性递减策略(刘杰等, 2010), 在搜索初期使各粒子以较大的步长在全局范围内探测较好的种子, 在搜索后期以较小的步长在极值点周围做精细搜索, 从而使算法有较大机率收敛于全局最优解 ...

2012

0.0

陆一锋, 徐鸣洁, 王良书, 等. 2012. 鄂尔多斯东南缘地区的地壳结构[J]. 科学通报, 57(1):59—64.

Yi-feng

, XU

Ming-jie

, WANG

Liang-shu

, et al. 2012. Crustal structure in the southeastern margin of Ordos[J]. Chinese Science Bulletin, 57(1):59—64(in Chinese).

利用布置在鄂尔多斯东南缘地区的地震台阵记录的远震资料数据, 采用接收函数方法研究这一地区的地壳厚度和地壳结构. 研究结果显示, 各台站下方的Moho 震相可以被清楚地识别,Moho 深度向东南方向逐渐变浅, 从鄂尔多斯块体内部的43 km 一直减小到邻近秦岭北缘的30km 左右. 地壳结构和Moho 形态特征在横向上表现出明显的差异性, 在研究区可以分为4 个部分:(Ⅰ) 在鄂尔多斯块体内部, Moho 平缓连续, 深度在40 km左右, 具有稳定克拉通地壳的特征;(Ⅱ) 渭河-山西地堑, Moho 出现上隆, 上隆幅度3 km 左右, 地壳减薄, 可能是由上地幔物质上涌引起的; (Ⅲ) 熊耳-伏牛山地区, Moho 平缓连续, 深度在36~33 km 之间, 往东南方向逐渐变浅,地壳结构相对简单; (Ⅳ) 邻近秦岭北缘的的河淮盆地, Moho 呈现出强烈的不连续特征, 横向结构差异明显, 平均深度约31 km. 另外, 位于构造边界的两个台站(st11 和st18)的下方, Moho 呈现明显的不连续现象, 可能受到边界断裂的影响. 研究结果表明鄂尔多斯东南缘地区地壳结构在横向上有很大的差异和变化, 对研究鄂尔多斯东南缘地区不同块体间的相互关系具有重要的意义.

... 0 引言鄂尔多斯块体东南缘是中国大陆西部碰撞挤压到东部伸展拉张动力学转换的关键地区, 也是华北块体北部的NE-SW向构造与南部的近EW向构造的交接部位(陆一锋等, 2012) ...

2012

0.0

... 运城段是中国地震局确定的中长期大地震值得注意的地区(M7专项工作组, 2012), 涉及临汾盆地、运城盆地和峨嵋台地3个构造单元, 潜在发震断裂有韩城断裂、峨嵋台地南缘断裂和中条山山前断裂等 ...

... 运城地区为历史地震破裂空区(M7专项工作组, 2012), 有地震台网记录以来, 该区震群非常活跃, 发生的11次M≥4 ...

2014

0.0

... 这种变形仅发生在浅地表区域, 变形量远大于基于地震地质方法得到的约1mm/a的断层倾滑速率(苗德雨等, 2014)以及区域水准测量所得到的最大为6~8mm/a的地壳垂直运动速率(Hao et al ...

2019

0.0

... , 2016), 与断层活动由深部滑动和构造应力所驱动的机理完全不同(乔鑫等, 2019) ...

... 2km的窗口计算形变速率的平均值(乔鑫等, 2019) ...

2011

0.0

... 屈春燕等, 2011)、地壳演变与火山活动(Berardino et al ...

2010

0.0

... 任雪梅等, 2010) ...

2002

0.0

... 目前, 该技术在震间和同震地壳形变监测(单新建等, 2002 ...

2014

0.0

... 根据地震地质、现今大地测量的研究结果, 研究区震间地壳构造运动相对稳定, 一般不会超过2mm/a(司苏沛等, 2014 ...

... 司苏沛等, 2014) ...

... 司苏沛等, 2014 ...

... 05)mm/a的平均滑动速率一致(司苏沛等, 2014) ...

2015

0.0

宋小刚, 申星, 姜宇, 等. 2015. 通过InSAR与GPS数据融合获取汶川地震同震三维形变场[J]. 地震地质, 37(1):222—231. doi:10.3969/j.issn.0253-4967.2015.17.

SONG

Xiao-gang

, SHEN

Xing

, JIANG

, et al. 2015. Coseismic 3D deformation field acquisition of the Wenchuan earthquake based on InSAR and GPS data[J]. Seismology and Geology, 37(1):222—231(in Chinese).

The variance component estimation method (VCEM) in generalized surveying adjustment theory, which realizes optimal weights allocation for different data sources, is applied to jointly invert two independent datasets, InSAR and GPS, for 3-D deformation field acquisition in this paper. Illustrated by the case of the Wenchuan earthquake, 3-D deformation field in high coherent area near the fault is achieved by using this method, which shows clearly a whole picture for the locations of right-lateral and thrust components movements generated by the earthquake. The 3-D deformation results are quantitatively consistent with GPS observations with RMS errors less than 5cm in 3-D directions, which demonstrates the feasibility to acquire precise 3-D deformation field by employing VCEM to fuse independent deformation datasets.

1 State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China; 2 School of Geosciences, China University of Petroleum(East China), Qingdao 266580, China

针对InSAR与GPS 两类独立的观测数据, 利用广义测量平差理论中方差分量估计法, 合理分配权重, 有效地融合了这两类观测数据, 从而估算出了地表在三维方向上的形变场。以四川汶川地震为例, 利用InSAR干涉测量结果和一定数量的GPS观测值, 通过该方法获取了地震断层两侧高相干区域上三维形变场, 清晰地显示了汶川地震的逆冲和右旋走滑分量的位置分布整体特征。结果表明, 在EW、SN和UD方向上地表形变量与GPS结果能够很好地吻合, 融合结果在三维方向上的均方根误差均不超过5cm, 证明了该方法能够得到精度较高的地震同震三维形变场, 也揭示了利用方差分量估计法对相互独立数据之间有效融合的可行性。

... 雷达视线向变形量与地面三维变形量的转换关系如式(1)所示(宋小刚等, 2015) ...

... 由于InSAR监测点不能与GPS站点完全重合, 本文以区域内的GPS站点位置为圆心, 将其半径1m内的所有InSAR测点的平均形变量与GPS的投影结果进行对比, 并采用GPS和InSAR观测值之间的多项式关系消除2种测量系统的偏差(宋小刚等, 2015), 同时实现参考基准的统一 ...

2006

0.0

... , 2002)、城市地表沉降(汤益先等, 2006 ...

1998

0.0

... 临汾一带形成了较为复杂的三角形交接构造(图 7), 这种交接构造为中国大陆内部典型的似三联点构造(田勤俭等, 1998) ...

2015

0.0

... 由于InSAR和GPS测量分别属于2种不同的测量系统, GPS与InSAR的测量结果无法进行直接对比(汪宝存等, 2015) ...

2015

0.0

王怡然, 李有利, 闫冬冬, 等. 2015. 中条山北麓断裂中南段全新世地震事件的初步研究[J]. 地震地质, 37(1):1—12. doi:10.3969/j.issn.0253-4967.2015.01.

WANG

Yi-ran

, LI

You-li

, YAN

Dong-dong

, et al. 2015. Holocene paleoseismology of the middle and south segments of the north Zhongtiaoshan fault zone, Shanxi[J]. Seismology and Geology, 37(1):1—12(in Chinese).

Shanxi Graben System(SGS)is a NNE-trending tectonic system located in the eastern and southern edges of Ordos Block and between Yinshan tectonic zone and Qinling tectonic zone. Composited with a series of NNE-, NE-trending graben basins, SGS is an important seismic zone in North China. Yuncheng Basin locates in the southern end of SGS, and is the deepest basin of the system. It is a half-graben with a shallow northern part and a deep southern part. As the south and east boundary of Yuncheng Basin, the North Zhongtiaoshan Fault Zone(NZFZ)played a key role in the development of the topology and tectonics setting of Yuncheng Basin. NZFZ is a normal fault zone, NE- to NEE-trending and 130km long. This fault zone can be divided into 3 segments:the south, the middle, and the north segment, and there are no historical M ≥7, but only 3 M =6 have taken place. Previous study suggests that the tectonic activity in this area is low and the earthquake interval is relatively long; seismic activity in the north and south segments is the weakest:the earthquake recurrence interval in the north segment is >50ka and it has not been active for >50ka, the interval of the south segment is ～12ka and its last movement is about 7ka ago. Our work tells a different story:based on thorough fieldwork, satellite imagery analysis, and trench investigation, we found that there have been multiple earthquake events taking place in all of the 3 segments during Holocene. This study includes two trenches that locate in the south and middle segments of NZFZ, each of them renders 3 paleo-earthquake events:a 10 570～8 010a BP event, an around 6 670～6 550a BP event, and a 2 110～320a BP event in TC-1; a 7 930～11 300a BP event, a 4 800～6 010a BP event, and a 2 680a BP event in TC-2. Through comparing these events with other 2 trenches in the middle segment of NZFZ(a XTC trench that renders a 19 980a BP event and a 8 570～7 780a BP event with >2.2m vertical displacement; a XLC trench that renders a 8 980～7 340a BP event with ～1.8m vertical displacement), we identified:a 8 570～8 010a BP event which broke through both middle and south segment of NZFZ with a largest known vertical displacement of >2.2m and 95km surface rupture, a 4 800～6 010a BP and a 2 110～320a BP event with 7～30km surface ruptures and largest known vertical displacements of 0.7m and 1.2m, respectively. The recurrence interval of these events is about 3 500a. Calculated with empirical formula of normal fault in North China, the magnitude of the 8 570～8 010a BP earthquake should be at least 8.0, and the magnitudes of the 4 800～6 010a BP and 2 110～320a BP events are both ≈7.0. These findings suggest that, as a Holocene active fault zone which made up with multiple faults, the middle and south segments of NZFZ have shown strong seismic activity and have triggered multiple earthquake events during the Holocene. Contrary to previous study, the activity of south segment might not be the weakest, and it is possible that the south segment is more seismic active than the middle segment.

College of Urban and Environmental Science, Peking University, Beijing 100871, China

通过对中条山北麓断裂进行探槽研究, 揭露了全新世以来, 断裂中段和南段的3次古地震事件, 包括1次发生在8 570～8 010a BP、贯通断裂中段和南段的8级以上特大地震, 以及4 800～6 010a BP和2 110～320a BP发生的2次7级左右的大地震, 地震复发间隔约为3 500a。研究表明, 中条山北麓断裂的南段和中段在全新世发生过多次活动, 活动性较强。

... 王怡然等, 2015) ...

2014

0.0

... 闻学泽等, 2014), 以形变资料约束反演震间断层运动学参数已成为断层中长期危险性分析的一种重要手段(张培震等, 2003) ...

2016

0.0

... 徐伟等, 2016) ...

2014

0.0

徐伟, 高战武, 杨源源. 2014. 山西峨眉台地北缘断裂晚第四纪活动性[J]. 地震地质, 36(4):1064—1076. doi:10.3969/j.issn.0253-4967.2014.04.011.

Wei

, GAO

Zhan-wu

, YANG

Yuan-yuan

. 2014. Late Quaternary activity research of the northern marginal fault of Emei platform, Shanxi Province[J]. Seismology and Geology, 36(4):1064—1076(in Chinese).

Based on the 1:50 000 geological mapping of active fault, the paper investigates the stratum, topography and faulted landforms of the northern marginal fault of Emei Platform, and preliminarily divides the northern marginal fault of Emei Platform into three sections by two stepovers near Tanjiazhuang Village and Nanliu Village according to different fault activity of each section. At west of Tanjiazhuang Village is a loess platform, and the high terrain scarp can be seen from the northern margin. The height of scarp decreases progressively and the slope becomes gentle westwards at the place between Nanchi Village and Xikang Village, and to the place near Xiaoliang town, we cannot see obvious terrain scarps. The faulted sections can only be seen in the gullies which cross the terrain scarp at the south of Guozhuang Village and Tanjiazhuang Village. The fault dislocates the Pliocene red clay and the middle Pleistocene Lishi loess and covered by Malan loess; continuous paleosoil can be seen across the terrain scarp in some gullies. These indicate that in this section the fault was active in the early middle Pleistocene and its activity becomes weaker or no longer active after that. The fault in the section between Tanjiazhuang Village and Nanliu Village can be divided into three parts by Shidian Village and Jinming Village, which are named, from west to east in sequence according to each faulted landform, the northern marginal fault of lacustrine terrace, the piedmont fault of Zijin Mountain and the northern marginal fault of loess platform. The fault transition area between each part is continuous and the fault is in linear distribution, so we see the whole fault section as having the same activity. In this section the Holocene diluvial fan is faulted. At least two plaeoearthquake events happened since Holocene, and the latest activity is in (2.00～1.29) ka BP according to Renzhuang trench and Jinsha trench, which can be well compared with former researches. The fault slip rate is over 0.33mm/a in the section south of Maguduo Village and is more than 0.36mm/a according to Renzhuang trench since the later period of the late Pleistocene. In the section between Nanliu Village and Xizhangpo Village, the fault distributes along the frontal edge of the diluvial platform and is covered by thick loess. A 50～200m high linear terrain scarp formed due to the activity of fault can be seen along the frontal edge especially in the part between Xunwang Village and Xulu Village. At north of Wuzhai Village, the height of scarp decreases progressively and to the place near Xizhangpo Village, the terrain scarp cannot be seen clearly. In this section, Malan loess is faulted, which indicates that this fault section has been active since the late Pleistocene, but the evidence of Holocene fault activity has not been obtained yet due to the non-development of Holocene stratum. The fault slip rate is no less than 0.1mm/a since the late Pleistocene according to the faulted section at south of Xunwang Village.

1. China Earthquake Disaster Prevention Center, Beijing 100029, China; 2. Anhui Earthquake Administration, Hefei 230031, China

通过1/5万活断层地质填图, 对山西峨嵋台地北缘断裂晚第四纪活动性进行了详细研究.以谭家庄、南柳附近的2个阶区为界, 将断裂分为西、中、东3段.谭家庄以西该断裂中更新世早期有过活动, 之后未见明显活动迹象.谭家庄至南柳之间断裂晚更新世以来活动强烈, 全新世仍有活动, 最新活动发生在(2.00～1.29)ka BP, 晚更新世晚期以来滑动速率≥0.36mm/a.南柳至西彰坡段晚更新世以来活动明显, 尚未发现全新世活动的直接证据, 晚更新世以来断层滑动速率≥0.1mm/a.

... 36mm/a的结果一致(徐伟等, 2014) ...

2017

0.0

... 地下水过量开采形成永久性地下水下降漏斗, 同时导致含水层的孔隙压力减小, 从而引发严重的地面沉降(姚亮, 2017) ...

... 本研究时段内, 夏县和新绛县附近2个沉降区的形变范围和量级均没有继续发展, 可能与近年来这2个地区大力实施的关井压采及地下水综合治理工程有关(姚亮, 2017) ...

2003

0.0

... 闻学泽等, 2014), 以形变资料约束反演震间断层运动学参数已成为断层中长期危险性分析的一种重要手段(张培震等, 2003) ...

... 张培震等, 2003) ...

2009

0.0

... 在震间期的不同孕震阶段, 断层两侧的地壳形变状态存在一定差异, 这种差异与断裂带所处的孕震阶段关系密切(张培震等, 2009 ...

2004

0.0

... 鄂尔多斯块体东南缘的构造活动强烈, 共记录到6级以上地震22次, 其中7级以上地震7次, 震级最大的是发生在其东部边缘的1303年洪洞8级地震和南部边缘的1556年华县8级地震(张学民等, 2004 ...

2019

0.0

... 该挤出构造动力过程主导了汾渭裂谷系的走滑拉分及其沿山西地堑系的NE向扩展(张岳桥等, 2019) ...

... 秦岭构造带作为一个地壳通道, 其向E挤出导致汾渭地堑系的走滑拉张和NE向扩展, 形成了由楔形的临汾盆地和鄂尔多斯东南缘弧形拉张区组成的走滑-伸展转换系统(张岳桥等, 2019) ...

... 鄂尔多斯东南缘弧形拉张区由多个子凹陷组成, 包括西安凹陷、固市凹陷、运城盆地和灵宝盆地等, 其沉积-沉降主体受南缘和东南缘边界伸展断裂控制, 形成盆-山地貌(张岳桥等, 2019), 其新构造运动的一个特点是由SW向NE逐渐减弱, 位于最南端的秦岭北缘断裂带活动性最强, 中条山山前断裂、峨嵋台地南缘和北缘断裂的活动性逐渐变弱 ...

2011

0.0

... 周志伟等, 2011)等方面得到了广泛应用 ...

2002

0.0

... , 2004)和小基线集(Small Baseline Subsets, SBAS)(Berardino et al ...

... 屈春燕等, 2011)、地壳演变与火山活动(Berardino et al ...

2008

0.0

... Cavali#cod#x000e9 ...

2006

0.0

... Fialko, 2006 ...

1976

0.0

... 位错提出的倾滑断层震间形变数学表达式(Freund et al ...

2001

0.0

... Hanssen, 2001) ...

... 数据处理采用干涉图堆叠(Stacking)技术, 该方法基于一系列解缠的差分干涉图, 通过积累法估计线性速率, 可将大气及其他各种噪声降为 1/ N, N为干涉图的个数(Hanssen, 2001) ...

2016

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... Hao等(2016)和Wang等(2020)分别给出了鄂尔多斯块体周缘多期水准和GPS资料平差结果, 发现鄂尔多斯块体东南缘存在一个显著的下降变形区, 可能反映该区域正在发生强烈的构造运动 ...

2004

0.0

... , 1997)、永久散射体(permannent scatterers)技术(Hooper et al ...

2007

0.0

... 针对含有基线误差的干涉对, 基于已有的DEM和观测解缠相位, 采用非线性最小二乘平差方法去除基线误差(Lu, 2007) ...

1963

0.0

... 5, 可能表明该区域介质很不均匀, 但作用力十分集中(Mogi, 1963), 其强震危险性值得关注 ...

2012

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... 为保证后续计算结果的可靠性, 在处理数据时, 采用基于局部条纹频谱的自适应滤波方法提高干涉图的相干性, 降低相位解缠误差(Nof et al ...

1997

0.0

... Savage et al ...

1999

0.0

... 为了解决这一问题, 本文使用带惯性权重的粒子群智能优化方法(Shi et al ...

2020

0.0

... SE向移动(Wang et al ...

1994

0.0

... 2 断裂的滑动速率、闭锁深度与地震危险性断裂上的地震矩累积率以及未来发生地震的震级与断层滑动速率、闭锁深度成正比(Ward, 1994 ...

2016

0.0

... 研究区域的空间形变格局受到地质构造和地层特征的控制, 同时受地下水开采的显著影响(Yang et al ...

... 1 与已有InSAR结果的对比分析将InSAR形变结果与Yang等(2016)的结果进行对比, 2个形变场整体具有较好的一致性, 均监测到中条山山前断裂的夏县附近和罗云山断裂的新绛县附近存在2个沉降区, 最大形变量均#cod#x0003E ...

... 与Yang等(2016)的结果相比, 本文使用的Radarsat-2宽模式影像在EW向的覆盖范围更广, 较完整地揭示了中条山山前断裂西段的形变特征 ...

... Yang等(2016)发现位于临汾盆地罗云山断裂南段的河津地区存在一个由于地下水回升驱动的隆升异常变形区, 2009年2月#cod#x02014 ...

1997

0.0

... 随着星载SAR的发展, 在相同试验区可积累大量重复轨道的SAR数据, 特别是近年来发展起来的干涉图堆叠(Stacking)技术(Zebker et al ...

1992

0.0

... 传统的D-InSAR技术以两轨法和三轨法为代表, 在消除地形相位的前提下, 能获取大范围面状、二维的地表形变信息, 它侧重于单次形变或两时刻的累积形变, 使用SAR图像少, 对干涉图像参数要求非常高, 且大气效应估计困难, 很难同形变信号分离(Zebker et al ...

2018

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... 中条山和峨嵋台地隆起区的形变受地下水开采的影响不大, 这些台地0~2mm/a的隆起可能为长期的震间地壳运动(Zhao et al ...

... Zhao et al ...