Dynamic mechanism for horizontal deformation in part of North China area

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大规模GPS揭示中国现今地壳构造形变特征

利用全国260多个陆态网络连续站以及2 000多个陆态网络区域站2011—2015年观测数据,计算分析中国大陆现今整体地壳构造形变特征以及板内应变场空间分布特征。根据密集、大范围的GPS速度场可知中国大陆现今整体速度场依然呈现西强东弱的态势,其中最大值出现在喜马拉雅地区,一般速率在35~42mm/a之间,而川滇地区形成的右旋剪切带的形变特征最为醒目,其西南部最小速率在3~9mm/a之间,北部最大速率在17~23mm/a;由应变场的空间分布可以看出应力最大的地区主要是喜马拉雅、昆仑山中部、川滇地区的鲜水河断裂带、天山地区以及京津唐地区;东部沿海地区应变速率表现为东西拉张型,主要是由于2011年日本大地震对该地区的影响还未完全消退造成的。     

中国大陆现今水平形变动态特征

2001~2004大陆水平应变场大致沿玉树、阿尼玛沁、鲜水河、小江等断裂带形成一条由东西走向转为南北走向的应变高值带.2004~2007高值带向局部收缩,并维持前期高值.新疆于田M_S7.3、四川汶川M_S8.0分别位于该高值带的东段、西段剪应变梯度带上,具备大尺度形变背景.分析认为昆仑山M_S8.1对青藏高原内部块体、川滇块体的相对运动产生重大影响,导致震中两侧一系列断裂带附近区域水平差异运动处于较高水平,印尼M_S8.7地震则有利于上述区域应变能进一步积累.此外,2001~2004、2004~2007应变分布特征总体从无序趋向有序,体现构造应力场经历调整与再积累过程.现阶段太平洋板块、菲律宾板块俯冲作用可能有所增强.     

Horizontal movement and strain characteristics in Tianshan and its adjacent region with GPS deformation data

Introduction The Tianshan Mountain is the youngest cordillera in the present-day continental Asia, and its tectonic evolution is closely related to the collision and subduction between Indian Plate and Eurasian Plate in the Himalayas orogen since Cenozoic…     

Current horizontal strain field in Chinese mainland derived from GPS data

Introduction In the years when the reliable data could not be obtained and in the analysis of strain property and magnitude in history, the intensity, property and activity pattern of strain field were mainly inferred on the bases of geometric characters of surface traces and behaviors (especially the faults) as well as the characteristics of petrology (XIE, et al, 1993; Molnar, Tapponnier, 1975, 1977; Tapponnier, Molnar, 1977; FU, et al, 2000). However, they are the averaged results accumu…     

Quantitative analysis on tectonic deformation of active rupture zones

Introduction The Global Position System (GPS) may provide information about the crust movement of high precision in a large area, which significantly improve the capability of monitoring crustal movement over the area. In the last decade, studies on the global plate movement, the large scale block motions, the high-resolution crust movement of related monitored regions and tectonic de-formation fields have become the hotspot of spatial geodesy (ZHU et al, 2003; Wang et al, 2001; HUANG et…     

近几年山西断裂带水平形变的初步分析

以沿山西断裂带布设的GPS监测网的6期复测资料(1999~2004)所计算的近期趋势性运动速率为基础,获得了2005、2006年山西断裂带相对于近期趋势性运动的偏离结果。结果显示:(1)趋势性差异运动信息不显著,运动信息明显的点数只占十分之一,它们分别是S21、S20、S30和S33(位于太原以南),量级最大约6mm/a;(2)尽管单站趋势性运动信息不显著,但整体模拟计算表明,1999~2004年似乎有南北相对运动的迹象,相对变化最大约2.0mm/a;(3)2005年有偏离趋势运动的迹象,且背离趋势运动方向,最大量级约7mm;(4)截至2006年的累计偏离量最大约6mm;这表明2006年基本未发生累计偏离。由于变化相对平稳,这可能预示着山西断裂带内近期地震活动强度不太可能明显提高。     

利用空间大地测量资料研究临汾盆地及边界断裂形变场演化特征

基于临汾盆地及其周缘的GPS和In SAR观测资料,通过计算最大主应变、最小主应变、面应变等水平形变特征量以及罗云山断裂(南段)上盘雷达视线向形变速率,综合研究汶川M 8.0地震前后临汾盆地及边界断裂现今地壳形变特征。结果显示:汶川M 8.0地震的发生引起临汾盆地及周缘形变场的动态调整,罗云山断裂南段至峨嵋台地北缘断裂应变率场由弱张性活动转为较强的压性活动状态,最大面应变率由1.5×10-8/a变为-3.1×10-8/a,SBAS-In SAR结果同时显示,罗云山断裂(南段)上盘于2009年起由下降转为隆起,在形变场动态调整过程中发生河津M 4.8地震,之后该区域应变率场恢复背景状态;汶川M 8.0地震有利于在山西断陷带南段北东东向断裂间形成压性应变积累,对河津地M 4.8地震的发生可能具有促进作用。     

The deformation pattern and fault rate in the Tianshan Mountains inferred from GPS observations

Based on GPS measurements conducted from 1992 to 2006, we present the current crustal movement velocity field for approximately 400 sites in the Tianshan Mountains and their adjacent areas, and estimate slip rates on the major faults using a 2-D elastic dislocation model. Our studies show slip rates within the range of 1―4 mm/a on the NW-SE trending strike-slip faults (such as Talas-Fergana fault) in the Tianshan Mountains. We also found the slip rates on the approximately WE-SN trending gently-dipping detachment fault vary from 10―13 mm/a for the southwest Tianshan Mountains to 2―5 mm/a for the eastern Tianshan Mountains, and to 6―12 mm/a for the Kyrgrz Tianshan. The GPS velocity field reveals that the total convergence is not uniformly distributed across the Tianshan Mountains, with 80%―90% of the N-S shortening absorbed along the southern and northern edges, and relatively little deformation accommodated within the interior. This first-order feature of strain pattern is explained best by underthrusting of adjacent blocks beneath the Tianshan Mountains along a basal detachment fault. We found the occurrence of historical M7―8 earthquakes somewhere in the locked ramp that connects the creeping and locking segments of the detachment, thereby resulting in elastic strain concentration and accumulation around it. The elastic strain confined in the upper crustal layer above the detachment ultimately releases through infrequent great earthquakes in the Tianshan Mountains, resulting in considerable folding and faulting at their margins. The Tianshan Mountains propagated outward and rose progressively as a wedge-shaped block.     

GPS水平形变面应变率梯度与强震危险区关系探讨

全球定位系统(GPS)观测和信息处理技术的发展, 为获取高精度地壳水平运动和相关的应用研究提供了良好的基础． 应用中国地壳运动观测网络中心提供的1999—2007年GPS水平形变速率观测结果, 研究了地壳水平形变面应变率梯度与强震发生的关系, 探索了地震中长期预测对强震危险区的判识方法． 结果表明, 中国大陆2001—2011年发生的大部分M_S6.8以上强震, 地震地点均位于面应变梯度高-低值过渡区与块体边界带相交汇的部位; GPS面应变率梯度可以作为中长期强震危险区判识的一种方法, 与最大剪应变率分布相比, 缩小了强震孕育地点的判识范围． 文章最后给出了中国大陆地区未来10年或稍长时间的强震危险区.     

基于GPS的华北地区地壳水平形变特征研究

利用中国大陆构造环境监测网络2009、2011年2期的GPS数据资料,计算得到华北地区相对于稳定的欧亚板块的区域水平速度场。根据水平速度场,基于连续变形假说,采用三角形方法计算了区域应变场特征值,并用GMT绘制了其分布图像。结合地震地质资料对该区的地壳水平形变特征进行分析研究,得出了有意义的结论:(1)水平相对运动与应变率场分布显示,板块交界处的断裂带及其附近区域地壳运动差异显著,应变率量值较为突出;(2)山西断陷带的活动方式与地质结果具有差异性;(3)区内最大剪应变、面膨胀的高值区主要位于环渤海的京津唐地区、山西断陷带中南部及郯庐断裂带中南段。     

基于GPS应变与震源机制解应力反演喜马拉雅构造带现今地壳形变特征

喜马拉雅构造带及其临近区域是印度板块与欧亚大陆板块挤压碰撞的前缘地带.本文利用GPS实测速度场与震源机制解数据分别计算了研究区域现今地壳岩石圈表面的GPS应变场及岩石圈内部的主应力分布,研究了印度板块持续挤压作用下板块边界带地壳岩石圈现今地壳形变的空间分布特征.结果显示,南北向的剧烈挤压变形与东西向的拉伸变形是现今青藏高原南缘地壳岩石圈的主要变形特征.其中南北向的地壳挤压变形主要集中在主前缘冲断带与雅鲁藏布江缝合带之间.东西方向上,南北走向的亚东—谷露断裂是区域地壳东西向伸展变形的重要分界断裂.75°E是研究区域地壳形变的另一条显著不连续边界,其西侧地壳主压应变强度低、方向弥散且最大主压应力方向一致性较差,而东侧地壳主压应变方向与主压应力方向以及地壳水平运动速度场方向均具有较好的一致性.布格重力异常的小波多尺度辨析结果显示该分界带与循喜马拉雅西构造结楔入欧亚大陆的印度板块密切相关.     

西藏南部地区现今构造变形分析

近十多年来藏南地区GPS网的多期观测结果为研究其构造变形提供了精确数据。本文将该区划分为冈底斯、西喜马拉雅、中喜马拉雅、拉萨4个块体,建立了各块体的弹性运动模型。以藏北高原的旋转框架为参考基准,得到藏南地区的水平形变场和应变场,分析形变场和应变场的空间变化,发现藏南地区存在强烈的S-N向挤压缩短变形,同时也有明显的E-W向伸展变形。南北边界之间的平均缩短速率16.9±2.5mm/a,大约吸收了印度与欧亚汇聚速率的42.4%。在雅鲁藏布江缝合线与班公错—嘉黎断裂之间,从80°E到90°E,地壳E—W向的伸展速率16.3±2.4mm/a。因此,藏南地区现今构造变形是以挤压缩短为主,S-N向挤压缩短与E—W伸展共存的复合变形模式。印度板块向欧亚板块的俯冲推挤是该区域变形的主要驱动力,重力作用对其变形也有重要贡献。     

Present-day horizontal deformation status of continental China and its driving mechanism

Based on velocity data of 933 GPS sites and using the methods of Ordinary Kriging interpolation and shape function derivation, this study has obtained the strain rate field of continental China in the spherical coordinates. In comparison with previous research results, it is found that such a strain rate field can be described by both the continuous deformation and block motions in the continent. The Tibetan Plateau and Tianshan region are characterized by continuous deformation which is distributed across the whole area. Within the blocks of South China, Tarim, Ordos, and Northeast China, little crustal deformation and deformation occurs primarily on the faults along their boundaries, which can be explained by the model of block motion. In other regions, such as the Yinshan-Yanshan block, North China block, and East Shandong-Yellow Sea, deformation patterns can be explained by both models. Besides, from southwest to northeast of continental China, there are three remarkable extensional zones of NW trending. These results imply that the NNE directed push of the India plate is the primary driving force accounting for the internal deformation of continental China. It produces the uplift, hori-zontal shortening and vertical thickening of the Tibetan Plateau as well as radiation-like material extru-sion. Of these extruded materials, one part accommodates the eastward "escape" of other blocks, generating convergence and compression of western China and widespread extension and local com-plicated deformation in eastern China under the joint action of the surrounding settings. The other part opens a corridor between the South China block and Tibetan Plateau, flowing toward southeast to the Myanmar range arc and filling the gap there which is produced by back-arc extension due to plate subduction.     

Preliminary results on kinematic model of tectonic blocks derived from high precision GPS observations in Southwest China

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Determination of active units with different kinematic property and their activity pattern in North China based on the data from GPS remeasurements

IntroductionWith the most feasible and powerful technical support provided by the high-precision GPS measurement for the study on horizontal crustal deformation, the obtainment of various-scale horizontal movement data and its study over the whole world is now in the ascendant, and its applicable fields is now expanding successively. In China, besides the GPS monitoring networks for different applications arranged by many agencies and departments, the key scientific project Crustal Movement…     

RESEARCH ON ACTIVITY OF ZHANGJIAKOU-BOHAI FAULT ZONE BASED ON GPS OBSERVATIONS

The northwestern section of the Zhangjiakou-Bohai fault zone starts in the west of Zhangjiakou, extending southeast through Huailai, Shunyi and Tianjin and entering into the Bohai Sea, with a width up to several tens of kilometers, narrow in the west and wide in the east. The Neogene-Quaternary has extended in the northwest and southeast direction, forming a large regional active structure. There are many earthquakes of magnitude 7 or above in the history on the Zhangjiakou-Bohai fault zone and it is also a strong earthquake activity zone in eastern China. Therefore, the modern tectonic activities of this fault zone have an important impact on regional seismic hazard, and are of great significance for earthquake prediction and disaster reduction. In this paper, using the mobile GPS station observation data of 1999, 2007, 2009, 2011, 2013 and 2015, and with the rigid-linear elastic block motion model equation proposed by LI Yan-xing, the horizontal deformation rate and strain rate of the Zhangjiakou-Bohai fault zone of the five adjacent periods of 1999-2007, 2007-2009, 2009-2011, 2011-2013 and 2013-2015 were calculated, the tectonic activity characteristics and evolution of the fault zone were studied. The results show that in the five periods, the average deformation rate of the Zhangjiakou-Bohai fault zone is 1. 74mm/a, the left-lateral strike-slip rate is 1.59mm/a, and the compression rate is -0.59mm/a. The Zhangjiakou-Bohai fault zone is characterized by left-lateral strike-slip and compression on the whole, and the left-lateral strike-slip rate is greater than the compression rate at each period. The strike-slip rate is significantly greater than the compression rate, indicating that the activity of Zhangjiakou-Bohai fault zone is dominated by left-lateral strike-slip faulting with compression. The minimum principal strain rate of the Zhangjiakou-Bohai fault zone in the five periods varies from -12.06×10^-9/a to -4.62×10^-9/a, and the average minimum principal strain axis direction is N63.9°E, with little change in direction. The maximum principal strain rate varies from 1.55×10^-9/a to 5.99×10^-9/a, and the average maximum principal strain axis direction is N333.9°W, the direction does not change much. The strike of the Zhangjiakou-Bohai fault zone is NWW(the overall strike is calculated by N300°W), and the normal strain rate of the fault zone is -5.87×10^-9/a(being compressional), and the shear strain rate is 12.70×10^-9/a. The shear strain rate on the fault zone is about twice the value of the normal strain rate, and the shear strain rate of the fault zone is greater than the normal strain rate, which indicates the shear stress of the 5 periods of 1999-2007, 2007-2009, 2009-2011, 2011-2013 and 2013-2015 is relatively significant, suggesting that the fault plain is dominated by left-lateral shear stress. This suggests that the Japan 3·11 earthquake has little effect on the deformation strain of the Zhangjiakou-Bohai fault zone, and it does not change the nature of activity of the fault zone. The tectonic activity is still inheriting. Since the tectonic activity of the Zhangjiakou-Bohai fault zone has gradually decreased after the Japan 3·11 earthquake, the deformation strain evolution trend has gradually returned to a unified consistent state. Therefore, the deformation strain state of the Zhangjiakou-Bohai fault zone does not have the condition for strong earthquakes.     

利用GPS与环境负荷形变数据研究台风引起的垂向地表位移

台风造成的强降雨、低气压、海面高度变化均会引起地表的形变.本文利用中国大陆构造环境监测网（陆态网）7个GPS台站每日的垂向位移和环境负荷形变模型分析2018年9月10—26日台风"山竹"期间不同负荷引起的区域垂向地表形变.结果表明,台风期间大气负荷和非潮汐海洋负荷垂向形变最大分别达到5.1 mm和-9.2 mm.模型能较好地反映河流区域地表水文负荷变化造成的垂向形变,但不同模型之间存在系统偏差.由于缺少地下水等信息,模型反映负荷长期形变效应的效果不佳,且形变的量级明显小于GPS观测的结果.迅速增加的水文负荷使北海GPS站从开始下沉到最低点（-15.6 mm）5天的下沉量达到25.7 mm;珠海、广州GPS站均观测到河流汇水作用造成地表的二次下沉,且珠海站一周后才抬升到正常位置;湛江和北海GPS站能较好地反映河流水位变化,相关系数分别为-0.66和-0.50.研究结果表明,相比于形变模型,GPS能更有效地监测台风短期水文负荷形变,可为台风洪水等灾害监测与预报提供有用的信息.     

陕西中部地区跨断层垂直形变与水平应变相关性分析

利用陕西中部地区近年来跨断层垂直形变资料和由GPS结果给出的水平最大剪应变场资料, 对2005年度会商中提出的8处跨断层形变异常点位置, 插值拟合出其水平应变值, 并与垂直形变数据进行相关性分析发现, 临潼-长安断裂垂直形变和水平应变正相关显著; 口镇-关山断裂与华山山前断裂呈现负相关; 岐山-马召断裂北段正相关显著, 而中段与南段相关性差。 这可能是由于这些断裂以及各段受力情况不同造成的, 其中口镇-关山断裂东段和岐山-马召断裂北段近年来垂直运动幅度大活动强烈, 应加以特别关注。     

Determination of active units with different kinematic property and their activity pattern in North China based on the data from GPS remeasurements

Based on the high-accuracy data obtained from the GPS measurements carried out in 1992, 1995 and 1996, the isochronous active units with different kinematic property inside the North China area have been distinguished, 4 active units and 1 transition zone with distinct differential movement have been determined. They are Ordos-Yinshan unit, Yanshan unit, Shanxi-Hebei-Shandong (Jin-Ji-Lu) unit, Jiaodong-Liaoning-Shandong (Jiao-Liao-Lu) unit and Yanshan-Hebei (Yan-Ji) transition zone. The relative movements among the neighboring units in this period have been given. 1 The compressive movement between Ordos-Yinshan unit and Yanshan unit is not obvious with an amount of 0.4±1.3 mm/a. 2 Jin-Ji-Lu unit moves E40°S off the Ordos-Yinshan unit and the magnitude is 4.4±1.0 mm/a. 3 Relative to the Yan-Ji transition zone of differential movement, Yanshan unit shifts W38°N with a value of 2.4±1.3 mm/a and Jin-Ji-Lu unit moves eastward 35° by south with an amount of 2.3±0.9 mm/a. 4 Jin-Ji-Lu unit has a tensional left-lateral movement of 4.7±1.4 mm/a in the direction of E37°S relative to Yanshan unit. 5 Some area near Tanlu belt which is located in the southern part of Jin-Ji-Lu block has a southward movement 14° by west with a magnitude of 1.5±1.1 mm/a off the Jin-Ji-Lu unit. 6 Relative to Jin-Ji-Lu unit, Jiao-Liao-Lu unit has a trend of clockwise movement with a tensional right-lateral motion at the north end which neighbors Yanshan unit and a compressive motion at the south end. It should be noted that the errors given in the paper are obtained based on the divergence among the displacements of the sites in the unit, rather than the value calculated from the displacement error of the sites. The analyzed results indicate that: 1 Shanxi tectonic zone and Yan-Ji transition zone are the major tectonic active zones to show the frame and magnitude of interior relative movement in North China area, and others are the secondary tectonic active zones; 2 The complete horizontal deformation in the North China area is not homogeneous nor successive; 3 The kinetic model of North China area might be "mantle dragging plus boundary coupling". Foundation item: The National Key Basic Research Project Mechanism and Prediction of Continental Earthquakes (G1998040700).