乌恰伽师地区GPS地壳运动监测网研究

通过对乌恰、伽师地区GPS监测网进行的6期复测，结合周边地区的IGS站数据，计算得到了该区50多个GPS点位在ITRF2000下的最新运动速率及相对欧亚板块(在NNR-NUVEL 1A地质模型下)的运动速率，由此得到了该区的现今地壳形变速率图．结果表明GPS站主要运动方向为北北西，基本上与天山褶皱带走向正交，形成对天山的正向挤压．同时对乌恰一伽师(20021225 Ms5．8)及伽师一巴楚(20030224 Ms6．8)地震前后的地壳运动进行了应变计算及分析，得出大震前震中及邻近地区会大面积产生高剪应变集中区的结论．     

中国大陆地壳现今运动的GPS测量结果与初步分析

利用中国大陆及周边地区1991－2000年间一系列全球定位系统（GPS）观测资料，计算了340个GPS站点的位移速率，得到了统一的中国大陆现今地壳运动速率场。这些站主要集中于青藏高原及其周缘的喜马拉雅、、川滇、河西走廊、阿尔金、天山，以及华北、福建东南沿海等主要构造活动区。固定测站速率精度优于1mm/a，流动测站速率精度优于3mm/a。根据GPS结果对中国大陆现今地壳运动的状况进行了分析。     

1976年唐山MS7.8地震同震及现今形变特征

基于1976年唐山M_S7.8地震的同震位移和现今GPS速度结果, 本文分析了该地震的同震破裂参数、 同震应变释放分布及其现今应变积累特征． 对唐山同震位移二维位错解析公式的拟合结果显示, 唐山地震前的断层闭锁深度约为18—23 km, 断层倾角可能介于74°—90°之间, 同震位错量约为3.1—3.4 m． 在同震过程中沿发震断层表现出显著的右旋错动特征, 在发震断层两侧沿NE向表现出左旋应变释放特征． 在本文现有的GPS测站密度和精度情况下, 尚无法识别出现今阶段沿唐山断裂的明显蠕滑特征． 唐山同震应变释放和现今GPS应变率积累结果均显示, 唐山断裂SE侧的剪切形变(速率)量值大于其NW侧, 同震与现今阶段的形变量值相差约1000倍．      

GPS约束下九寨沟地区断裂带现今运动速率的非连续接触模拟研究

以中国地壳运动观测网络2009—2013年GPS观测数据为边界条件,使用非连续接触有限元技术构建九寨沟地区二维有限元模型,在不确定性分析的基础之上,计算区内主要断裂带现今运动速率。研究结果表明:在巴颜喀拉块体整体近于NE向的推挤过程中,九寨沟地区的塔藏断裂、虎牙断裂、树正断裂均呈现为较高的左旋走滑兼具挤压的现今运动特征;岷江断裂、龙日坝断裂和龙门山断裂则呈现为右旋走滑兼有挤压的运动特性。结合区域主应变率计算结果,发现九寨沟地区仍然具有较高的应变积累背景。树正断裂作为2017年8月8日九寨沟M7.0地震的发震断层,其现今左旋滑动速率为3.0 mm/a,与东昆仑断裂带玛沁—玛曲段附近的左旋走滑速率4.1mm/a基本匹配,说明该断裂可能是东昆仑断裂带东端分支断裂之一,而东昆仑断裂与虎牙断裂之间的历史地震空区可能已被九寨沟地震事件贯通。     

鲜水河断裂带北段GPS测量及其运动特征

鲜水河GPS监测网由18个沿鲜水河断裂带分布的点组成．1991年对该网进行了首次观测,1996和2000年进行了两期整网复测．本利用该网199l和2000年的二期GPS观测资料结合川西地区20世纪70年代以来的常规大地测量资料,计算给出了这一强震活动带现今运动图像：由测区的北西虾拉沱测点到南东的乾宁测点水平位移速率逐渐增大,而断层两盘的相对运动不明显．表明利用短边GPS测量可有效监视活动断裂带两侧一定区域的地壳运动．对比有形变测量资料以来川西地区6级以上地震分布的特点,认为可根据鲜水河断裂带断层两盘的相对运动和跨越断层的地壳整体运动的强弱这两种运动图像来研究区域强震的活动特征．     

2008年于田7.3级地震前西昆仑地形变的GPS初步研究

利用GPS观测资料计算并获取了2008年新疆西昆仑地区于田7.3级地震发生前的现今地壳运动速度场,通过速度场分布研究了区域内主要断层的活动速率.结果表明:震中以南的龙木错断裂呈左旋走滑性质的运动特征,走滑速率为1.2～2.5 mm/a;震中以北的阿尔金左旋走滑断裂滑动速率为5 mm/a;震中北西面的康西瓦断裂的左旋走滑平均速率约为3～7 mm/a.区域应变场分布一定程度上受断裂带分布的影响.7.3级地震就位于断裂活动交汇的部位和最大剪应变率高值区的边缘.     

利用GPS数据探讨北天山东段现今地壳应变场演化特征——重新认识2016年呼图壁MS6.2地震

利用2009—2011、2011—2013、2013—2015年GPS形变资料,借助最小二乘配置方法、位移与应变的偏导关系,计算获得北天山东部应变场的动态演化结果,重新认识北天山东段构造区的现今活动特征,探讨应变场三个周期空间分布特征与2016年呼图壁6.2级地震的内部联系。结果表明:(1)区域地壳运动速率与应变场强度在时间上表现为“弱-强-弱”的变化特征,主应变率以NNW或NNE向的主压应变为主,第一、三周期N-S向主压应变较小,约(1~2)×10^-8/a,第二周期变化显著增强,约(1~6)×10^-8/a,第三周期滑动速率显示北天山东段呈“强[(2.2±0.4) mm/a]-弱(不明显)-强[(3.0±1.0) mm/a]”的右旋走滑特征;(2)地震可能更易发生在面应变率场等值线四象限中心区域或正、负过渡区的高密度梯度带内部,这可能是地震孕育过程中利用GPS资料观测到的形变前兆;(3)强震更易发生在剪应变率(最大剪应变率)的高值区或边缘区;(4)相对于面应变率与最大剪应变率等应变场物理量,主应变率更适用于在块体运动方向与性质上给出解释。     

焉耆盆地北缘断裂全新世滑动速率及地震危险性

天山是典型的陆内再生造山带,研究其现今内部断裂的变形特征和活动速率对于认识整个天山造山带的应变分配方式和变形过程具有重要意义。现今天山活动构造的研究大部分集中在天山两侧向盆地扩展的前缘部分,然而对于天山内部活动构造的定量化研究并不多见。该研究聚焦于南天山与其内部山间盆地之间的边界断裂——焉耆盆地北缘断裂,通过野外地质调查可将该断裂分为东西2段,其中东段逆冲断错了一系列山前洪积扇,形成了线性明显的陡坎地貌。通过利用高精度差分GPS对23组断层陡坎的测量,发现其垂向位移大致可分为1.9m、2.4m和3.0m 3组,推测单次地震的同震位移量为0.5~0.6m。其中保存于3.0m左右陡坎的地貌面为区域性地貌面,通过利用原地宇宙成因核素测定该地貌面的暴露年龄约为5ka,这与博斯腾湖沉积物所记录到冷暖气候交替的时间段相符,说明气候的冷暖变化控制了南天山前地貌面的形成和废弃。结合断层陡坎高度及地貌面年龄可得焉耆盆地北缘断裂东段5ka以来的倾滑速率为0.6~0.7mm/a,SN向的地壳缩短速率约为0.4mm/a,垂向滑动速率约为0.5mm/a。依据地震矩计算公式评估焉耆盆地北缘具有发生7.5级强震的可能性。该研究为认识现今天山的变形过程和变形方式提供定量化的数据支持,对于理解天山内部的强震发生地点和地震危险性具有重要的现实意义。     

新疆帕米尔东北侧地区现今地壳运动的GPS监测研究

通过加密帕米尔东北侧地区的GPS监测网并进行复测,结合周边地区的IGS站数据,计算得到了该地区40多个GPS点位运动速率,由此得到了该地区的现今地壳形变速率图及GPS基准站的时间序列。结果表明：各GPS站主要运动方向为北北西,基本上与天山褶皱带走向正交,即形成对天山的正向挤压。伽师附近及其西南区的运动形态与周邻测站有所不同,表明伽师地区的构造变形与近几年地震活动有某种关联。环塔里木盆地周边点在各区内的速率变化较小,方向也基本一致,说明塔里木盆地内部变形较小或基本不变形。     

2016年青海门源MS6.4地震震前应变积累及同震变形特征

2016年1月21日青海省门源县发生了M_S6.4地震, 发震断裂为冷龙岭北侧断裂, 震中位置与1986年门源6.4级地震相同。 本文收集了本次地震震中及其周边区域1999—2015年GPS观测资料, 解算了GPS速度场、 跨断裂连续观测站基线时间序列和应变率场。 结果显示, 祁连山断裂带为一条宽度约60 km的连续变形带。 在断裂带南侧地壳运动以顺时针旋转为主, 运动量值没有显著差异; 跨过断裂带到达其北部之后, 地壳运动量值明显减小, 显示出该断裂带的强烈活动特征。 冷龙岭断裂左旋走滑速率为6.17±0.41 mm/a, 挤压速率为1.83±0.38 mm/a, 断层闭锁深度为22.1±3.1 km。 利用GPS连续观测站数据解算的地震同震位移显示, 震中西南侧26.8 km处的青海门源(QHME)测站记录到了明显同震位移, 其水平运动方向为北东向, 与逆冲为主的震源机制解一致。     

Research on present crustal deformation in the southern Tianshan (Jiashi) region by GPS geodesy

IntroductionSinceaMs=6.9earthquakeoccurredinArtux,Xinjiang,ChinaonMarchl9,l996,7earth-quakeswithmagnitudeofMs>6werefollowedsuccessivelynearbyJiashi,southemnanshan.Thephenomenonthatagroupofstrongearthquakes(Jiashiearthquakeswann)concentratedwithinashorterperiodoflyearormoreisanunprecedentedeventsincetheinstrUmentalrecordofseis-micityinthecontinent,drawingconsiderableattentionofseismologists.TheJiashiearthquakeswarmhaPpenedonthenortheastemflankofthewestCmsyntaxofHimalayancollisionbeltwheret…     

2020年3月23日新疆拜城5.0级和7月13日霍城5.0级地震总结

2020年3月23日和7月13日,新疆天山中部地区分别发生拜城5.0级和霍城5.0级地震,其中拜城5.0级地震发生在南天山地震带中段,霍城5.0级地震发生在北天山地震带西段。系统总结2次地震前出现的地震活动和地球物理观测异常,结果表明：①拜城5.0级地震：震前主要存在5级地震成组和尼勒克钻孔应变中短期异常;②霍城5.0级地震：震前中短期异常比较丰富,存在3级以上地震带状分布、地震发生率指数、D值、调制比、b值异常,而地球物观测则以形变异常为主,主要出现在震中附近区域。综合分析认为：①拜城5.0级地震前地震活动异常较少,地球物理观测以趋势异常为主,短期指示意义不明确;②霍城5.0级地震前具有中短期预测意义的地震活动和地球物理异常较为丰富,为后续中强地震的发生提供了判定依据。     

天山地震带主要活动断层现今的滑动速率及其地震矩亏损

文中收集了1999—2015年天山地震带及其周边地区的GNSS数据,计算得到了速度场结果,并利用弹性块体模型计算了研究区域内各块体的闭锁深度和主要断层的滑动速率。研究结果表明:南天山断裂带西段的迈丹断裂的缩短速率处于高值状态,达(-6.3±1.9) mm/a,高于南天山东段;北天山断裂带西段的缩短速率同样高于东段。利用主要断裂带的滑动速率计算出各地震带的地震矩积累变化及1900年以来的地震矩释放变化量,以分析地震矩亏损分布,结果显示北天山山前断裂、迈丹断裂、额尔齐斯断裂带北段和喀什河断裂西段存在较大的地震矩亏损,具有孕育7级以上地震的潜能,而北轮台断裂、柯坪断裂带中段则呈现地震矩盈余状态,在未来的一段时间内不具备发生强震的可能。     

最小二乘配置下的天山地区应变场特征分布

利用已有的GPS观测数据,借助球面最小二乘配置方法对天山地区的GPS速度场进行研究,得到了研究区域应变场的空间分布特征．其最大主压应变表明,大地震多发生在主压应变快速交替变化的地带,主压应变最大值主要分布于西南天山与帕米尔弧及塔里木西北交汇的地区,强地震(M7.0—8.0)基本发生在该区域．面膨胀值表明天山地区应变呈挤压收缩的特征．      

我国西部地震群体活动特征研究

在对我国西部本世纪第五个地震活跃幕以来地震群体活动时空强演变规律回顾的基础上,研究了近１～２年中强地震的分布特点,结合大地形变的演变状况,对本区地震活动进行了研究,并认为本区处于本活跃幕末的翘尾活动阶段。     

DEFORMATION CHARACTERISTICS AND KINEMATIC PARAMETERS INVERSION OF HAIYUAN FAULT ZONE BASED ON TIME SERIES INSAR

Located at the bend of the northeastern margin of Qinghai-Tibet Plateau, the Haiyuan fault zone is a boundary fault of the stable Alashan block, the stable Ordos block and the active Tibet block, and is the most significant fault zone for the tectonic deformation and strong earthquake activity. In 1920, a M8.5 earthquake occurred in the eastern segment of the fault, causing a surface rupture zone of about 240km. After that, the segment has been in a state of calmness in seismic activity, and no destructive earthquakes of magnitude 6 or above have occurred. Determining the current activity of the Haiyuan fault zone is very important and necessary for the analysis and assessment of its future seismic hazard. To study activity of the Haiyuan fault zone, the degree of fault coupling and the future seismic hazard, domestic and foreign scholars have carried out a lot of research using geology methods and GPS geodetic techniques, but these methods have certain limitations. The geology method is a traditional classical method of fault activity research, but dislocation measurement can only be performed on a local good fault outcrop. There are a limited number of field measurement points and the observation results are not equally limited depending on the sampling location and sampling method. The distribution of GPS stations is sparse, especially in the near-fault area, there is almost no GPS data. Therefore, the spatial resolution of the deformation field features obtained by GPS is low, and there are certain limitations in the kinematic parameter inversion using this method. In this study, we obtain the average InSAR line-of-sight deformation field from the Maomaoshan section to the mid-1920s earthquake rupture segment of the Haiyuan earthquake in the period from 2003 to 2010 based on the PSInSAR technique. The results show that there are obvious differences between the slip rates of the two walls of the fault in the north and the south, which are consistent with the motion characteristics of left-lateral strike-slip in the Haiyuan fault zone. Through the analysis of the high-density cross-fault deformation rate profile of the Laohushan segment, it is determined that the creep length is about 19km. Based on the two-dimensional arctangent model, the fault depth and deep slip rate of different locations in the Haiyuan fault zone are obtained. The results show that the slip rate and the locking depth of the LHS segment change significantly from west to east, and the slip rate decreases from west to east, decreasing from 7.6mm/a in the west to 4.5mm/a in the easternmost. The western part of the LHS segment and the middle part are in a locked state. The western part has a locking depth of 4.2~4.4km, and the middle part has a deeper locking depth of 6.9km, while the eastern part is less than 1km, that is, the shallow surface is creeping, and the creep rate is 4.5~4.8mm/a. On the whole, the 1920 earthquake's rupture segment of the Haiyuan fault zone is in a locked state, and both the slip rate and the locking depth are gradually increased from west to east. The slip rate is increased from 3.2mm/a in the western segment to 5.4mm/a in the eastern segment, and the locking depth is increased from 4.8km in the western segment to 7.5km in the eastern segment. The results of this study refine the understanding of the slip rate and the locking depth of the different segments of the Haiyuan fault zone, and provide reference information for the investigation of the strain accumulation state and regional seismic hazard assessment of different sections of the fault zone.     

Analysis of central western Europe deformation using GPS and seismic data

The kinematic field of central western Europe is characterized by relatively small movements (around 1–2 mm/year) and diffuse seismicity with earthquakes occurring mostly in the shallow crust (within 15 km), prevalently concentrated along the Alps and the European Cenozoic Rift System (ECRIS). In order to study and constrain the current crustal kinematic field we reconstructed the velocity and the strain field using permanent GPS stations, belonging to different networks (AGNES, EUREF, REGAL, RGP). The 2D strain rate tensor has been calculated using the method of least-squares collocation. Our results show that the area of maximum compression is located along the Alpine chain, where maximum values of 7 ± 2 nstrain/year are found, while maximum extension is measured between the Armorican Massif and the Massif Central, where values of 4 ± 2 nstrain/year are reached.The earthquakes with M > 3.0, have been used to estimate the seismic strain rates, while the style of the seismic deformation was reconstructed from the fault plane solutions (FPS) available from the literature. Relatively high values of seismic strain rates (around 10 nstrain/year) are measured along the Alpine Chain and the ECRIS. Results obtained by geodetic and seismic data are quite in agreement and reflect the different tectonic evolution of the geological features characterizing the area of study. The orientation of the compressional geodetic and seismic strain axes are NW-SE in most of the area of study, on account of the action of plate boundary forces. A rotation of the same axes to N-S direction along the eastern Alps, possibly related to the Adria convergence, is found.     

2011年日本东北地区太平洋近海地震对亚洲板块及韩国大地控制网的影响分析

本研究分析了2011年3月11日发生的M_w9.0日本东北地区太平洋近海地震对亚洲地区和韩国国内GPS卫星常年跟踪站的位移影响.为此,利用了日本东北地区太平洋近海地震发生前后两周(2011年3月4日到3月18日)的GPS站点数据,包括震中附近地区(韩国,中国,中国台湾地区,日本和俄罗斯)55个GPS卫星常年跟踪站和284个IGS 全球跟踪站,并采用GAMIT/GLOBK软件进行处理和平差,估算出所有GPS站点的同震形变.结果显示,日本东北地区太平洋近海地震引起的同震形变影响在亚洲地区比较明显,包括日本和附近国家,距离震中2702 km的中国武汉(WUHN)站也观测到同震形变.为精确分析日本东北地区太平洋近海地震对韩国国家大地控制网的影响,通过GAMIT/GLOBK软件计算出韩国GPS卫星常年跟踪站之间的基线长度变形,并分析出弹性变形量.结果表明:大部分GPS站点均向震中方向膨胀,且向震中的垂直方向收缩.由日本东北地区太平洋近海地震导致的最大剪应变达到韩国国家大地控制网年均变形率的约7倍,对韩国的地壳产生14.5~57.7 mm的水平位移,并导致韩国国家大地控制网产生弹性变形.因此,在不及时更新维护韩国国家大地控制网的情况下,GPS测量成果将会发生最大20 mm的位置误差.     

Kinematics of the eastern part of the North Anatolian Fault Zone

The North Anatolian Fault Zone (NAFZ), which marks the boundary between Anatolia and the Eurasian plate, is one of the world's most seismically active structures. Although the eastern part of NAFZ has high seismic hazard, there is a lack of geodetic information about the present tectonics of this region. Even though many scientists would like to study this area, geographical and logistical problems make performing scientific research difficult. In order to investigate contemporary neotectonic deformation on the eastern NAFZ and in its neighborhood, a relatively dense Global Positioning System (GPS) monitoring network was established in 2003. Geodetic observations were performed in three GPS campaigns in an area of 350 km × 200 km with 12-month intervals. In addition, 14 new GPS stations were measured far from the deforming area. Since this region includes the intersection of the NAFZ and the East Anatolian Fault Zone (EAFZ), deformation is complex and estimating seismic hazard is difficult. One important segment is the Yedisu segment and it has not broken since the 1784 earthquake. After the 1992 Erzincan and 2003 Pulumur earthquakes, the Coulomb stress loading on the Yedisu segment of the NAFZ has increased significantly, emphasizing the need to monitor this region. We computed the horizontal velocity field with respect to Eurasia and strain rates field as well. GPS-derived velocities relative to Eurasia are in the range of 16–24 mm/year, which are consistent with the regional tectonics. The principal strain rates were derived from the velocity field. Results show that strain is accumulating between the NAFZ and EAFZ along small secondary fault branches such as the Ovacik Fault (OF).     

QUATERNARY FOLDING OF THE XIHU ANTICLINE BELT ALONG FORELAND BASIN OF NORTH TIANSHAN

Tianshan is one of the longest and most active intracontinental orogenic belts in the world. Due to the collision between Indian and Eurasian plates since Cenozoic, the Tianshan has been suffering from intense compression, shortening and uplifting. With the continuous extension of deformation to the foreland direction, a series of active reverse fault fold belts have been formed. The Xihu anticline is the fourth row of active fold reverse fault zone on the leading edge of the north Tianshan foreland basin. For the north Tianshan Mountains, predecessors have carried out a lot of research on the activity of the second and third rows of the active fold-reverse faults, and achieved fruitful results. But there is no systematic study on the Quaternary activities of the Xihu anticline zone. How is the structural belt distributed in space?What are the geometric and kinematic characteristics?What are the fold types and growth mechanism?How does the deformation amount and characteristics of anticline change?In view of these problems, we chose Xihu anticline as the research object. Through the analysis of surface geology, topography and geomorphology and the interpretation of seismic reflection profile across the anticline, we studied the geometry, kinematic characteristics, fold type and growth mechanism of the structural belt, and calculated the shortening, uplift and interlayer strain of the anticline by area depth strain analysis.
In this paper, by interpreting the five seismic reflection profiles across the anticline belt, and combining the characteristics of surface geology and geomorphology, we studied the types, growth mechanism, geometry and kinematics characteristics, and deformation amount of the fold. The deformation length of Xihu anticline is more than 47km from west to east, in which the hidden length is more than 14km. The maximum deformation width of the exposed area is 8.5km. The Xihu anticline is characterized by small surface deformation, simple structural style and symmetrical occurrence. The interpretation of seismic reflection profile shows that the deep structural style of the anticline is relatively complex. In addition to the continuous development of a series of secondary faults in the interior of Xihu anticline, an anticline with small deformation amplitude(Xihubei anticline)is continuously developed in the north of Xihu anticline. The terrain high point of Xihu anticline is located about 12km west of Kuitun River. The deformation amplitude decreases rapidly to the east and decreases slowly to the west, which is consistent with the interpretation results of seismic reflection profile and the calculation results of shortening. The Xihu anticline is a detachment fold with the growth type of limb rotation. The deformation of Xihu anticline is calculated by area depth strain analysis method. The shortening of five seismic reflection sections A, B, C, D and E is(650±70) m, (1 070±70) m, (780±50) m, (200±40) m and(130±30) m, respectively. The shortening amount is the largest near the seismic reflection profile B of the anticline, and decreases gradually along the strike to the east and west ends of the anticline, with a more rapidly decrease to the east, which indicates that the topographic high point is also a structural high point. The excess area caused by the inflow of external material or outflow of internal matter is between -0.34km² to 0.56km². The average shortening of the Xihubei anticline is between(60±10) m and(130±40) m, and the excess area caused by the inflow of external material is between 0.50km² and 0.74km². The initial locations of the growth strata at the east part is about 1.9~2.0km underground, and the initial location of the growth strata at the west part is about 3.7km underground. We can see the strata overlying the Xihu anticline at 3.3km under ground, the strata above are basically not deformed, indicating that this section of the anticline is no longer active.