Research on Deformation Mode of the Longmenshan-Longriba Region Using GPS and Leveling Data

The Longmenshan-Longriba region is located on the eastern edge of the Tibetan Plateau, and is an ideal place to study the eastward extrusion and uplift mechanism of the plateau. Previous studies on this area mainly focused on tectonic activity and seismic hazard, with few studies giving its overall deformation characteristics and dynamic mechanism. This paper uses the latest dense GPS data, combined with precise Leveling data to analyze the kinematic characteristics and deformation mode of the Longmenshan fault zone (LMSF) and the Longriba fault zone (LRBF). The results show that both the Longmenshan fault zone and the Longriba fault zone have certain right-lateral strike-slip and thrusting, indicating that they play an important role in adjusting strain distribution and absorbing tectonic deformation;The strain-rate field on the Longriba fault zone is broadly distributed, suggesting that the deformation field is at least partially coupled;while the strain-rate field on the Longmenshan fault zone presents a non-uniform distribution, indicating different dynamic sources acting on segments. The high strain rate areas revealed in this study points us to the high-risk area for future earthquakes. The present-day vertical motion velocity field in the region obtained from Leveling and GPS data shows a mismatch between the regional deformation field and active tectonics, which can be explained by the incomplete coupling of deformation between the lower and upper crust.

结合GPS/Leveling和正高改正确定GPS常年观测站正高

利用精密几何水准测量结合GPS/Leveling方法计算韩国行政自治部管辖内30所GPS常年观测站天线基准点的正高。并联合进行对水准点和GPS常年观测站偏心点的重力测量,使用正高改正方法计算出其改正量,提高正高的精确度。

Present-day 3D deformation field of Northeast China,observed by GPS and leveling

A broad view of present-day 3D deformation field around the Northeast China region was derived from GPS and leveling observations. We draw the following conclusions： First, the Northeast China region moved towards northwest with an average velocity of 5 ram/a, with respect to South China. The entire Northeast China region was in a low strain state from the strain rate field. Second, we processed two periods of first- order leveling data in 1970s and 1990s, showing the vertical deformation of the Northeast China region is ＂uplift in western part and subsidence in eastern part＇

Comparative study on vertical deformation based on GPS and leveling data

The development of GPS(Global Positioning System) technology has led to increasingly widely and successful applications of GPS surveys for monitoring crustal movements. However, multi-period GPS survey solutions have not been applied in monitoring vertical crustal movements with normal backgrounds. In this paper, we carried out a comparative study on the vertical deformation of the comprehensive profile of the cross-fault zone in Shanyin, Shanxi province, China, based on GPS and precise leveling observation data for multiple time periods. The vertical deformation rates observed with repeating GPS survey are obviously different(over 20 mm/y at some sites) from those with repeating leveling survey within a relatively short period. However, the deviations in the vertical displacement between GPS and leveling in a long-term survey(over three years) showed good consistency at 3-4 mm/y at most sites, on GPS forced offset surveying and fixed survey instruments in a long-term survey(over three years). Therefore, GPS vertical displacement results can be applied to the study of vertical crustal movements.

复杂环境下结合EMD的GPS-IR水位反演方法

利用法国布雷斯特(Brest)港BRST测站和英国塞文大桥监测系统GNSS双频观测数据,分别在静态和高动态环境下进行GPS-IR水位反演,探究传统GNSS监测系统进行水位反演的可行性与精度.结果表明:L1波段反演精度高于L2波段;在静态场景下,GPS-IR水位反演结果与验潮站数据相关系数大于0.98,在高动态场景下,桥梁GPS-IR水位反演精度稍低.利用经验模态分解(EMD)方法对算法进行改进,提高了在桥梁复杂环境下GPS-IR水位反演结果的精度,均方根误差(RMSE)相比经典方法降低约50%.本文方法提高了GPS-IR技术在不同水域环境下的适用性,在水位监测中具有很好的应用前景.

Monitoring absolute vertical land motions and absolute sea-level changes from GPS and tide gauges data over French Polynesia

In this study,we estimate the absolute vertical land motions at three tidal stations with collocated Global Navigation Satellite System(GNSS)receivers over French Polynesia during the period 2007-2020,and obtain,as ancillary results,estimates of the absolute changes in sea level at the same locations.To verify our processing approach to determining vertical motion,we first modeled vertical motion at the International GNSS Service(IGS)THTI station located in the capital island of Tahiti and compared our estimate with previous independent determinations,with a good agreement.We obtained the following estimates for the vertical land motions at the tide gauges:Tubuai island,Austral Archipelago-0.92±0.17 mm/yr,Vairao village,Tahiti Iti:-0.49±0.39 mm/yr,Rikitea,Gambier Archipelago-0.43±0.17 mm/yr.The absolute variations of the sea level are:Tubuai island,Austral Archipelago 5.25±0.60 mm/yr,Vairao village,Tahiti Iti:3.62±0.52 mm/yr,Rikitea,Gambier Archipelago 1.52±0.23 mm/yr.We discuss these absolute values in light of the values obtained from altimetric measurements and other means in French Polynesia.

Deformation Evolution Characteristics Revealed by GPS and Cross-fault Leveling Data before the M_S8. 0 Wenchuan Earthquake

Based on GPS velocity during 1999-2007,GPS baseline time series on large scale during1999-2008 and cross-fault leveling data during 1985-2008,the paper makes some analysis and discussion to study and summarize the movement,tectonic deformation and strain accumulation evolution characteristics of the Longmenshan fault and the surrounding area before the MS8. 0 Wenchuan earthquake,as well as the possible physical mechanism late in the seismic cycle of the Wenchuan earthquake. Multiple results indicate that:GPS velocity profiles show that obvious continuous deformation across the eastern Qinghai-Tibetan Plateau before the earthquake was distributed across a zone at least 500 km wide,while there was little deformation in Sichuan Basin and Longmenshan fault zone,which means that the eastern Qinghai-Tibetan Plateau provides energy accumulation for locked Longmenshan fault zone continuously. GPS strain rates show that the east-west compression deformation was larger in the northwest of the mid-northern segment of the Longmenshan fault zone,and deformation amplitude decreased gradually from far field to near fault zone,and there was little deformation in fault zone. The east-west compression deformation was significant surrounding the southwestern segment of the Longmenshan fault zone,and strain accumulation rate was larger than that of mid-northern segment.Fault locking indicates nearly whole Longmenshan fault was locked before the earthquake except the source of the earthquake which was weakly locked,and a 20 km width patch in southwestern segment between 12 km to 22. 5 km depth was in creeping state. GPS baseline time series in northeast direction on large scale became compressive generally from 2005 in the North-South Seismic Belt,which reflects that relative compression deformation enhances. The cross-fault leveling data show that annual vertical change rate and deformation trend accumulation rate in the Longmenshan fault zone were little,which indicates that vertical activity near the fault was very weak and the fault was tightly locked. According to analyses of GPS and cross-fault leveling data before the Wenchuan earthquake,we consider that the Longmenshan fault is tightly locked from the surface to the deep,and the horizontal and vertical deformation are weak surrounding the fault in relatively small-scale crustal deformation. The process of weak deformation may be slow,and weak deformation area may be larger when large earthquake is coming. Continuous and slow compression deformation across eastern Qinghai-Tibetan Plateau before the earthquake provides dynamic support for strain accumulation in the Longmenshan fault zone in relative large-scale crustal deformation.

Estimation of Subsidence in Po Delta Area (Northern Italy) by Integration of GPS Data, High-Precision Leveling and Archival Orthometric Elevations

Subsidence in a deformation area can be measured in various ways, examples being conventional high-precision leveling, differential InSAR and multi-temporal GPS surveys. Integration of methods can improve results, and is crucial to extract high-precision data. In particular, orthometric and ellipsoid elevations, surveyed at different moments in time, can be compared to yield information on vertical movements when geoid anomalies are known. However, a data checking procedure must be applied if archival orthometric elevations are used, because long-term measurements for many historical benchmarks may have been lost and/or replaced with other points, but at different elevations. This type of checking can be carried out over an area without gravimetric anomalies by modeling geoid undulations and vertical displacements in the time-span used for analysis, excluding points with anomalous values. This procedure was tested and applied in the Po Delta area (northern Italy), historically subject to high subsidence rates: the leveling benchmarks of 1983 were measured with the GPS technique in 2008. After checking of archival data and transformation from ellipsoid to orthometric elevations, comparisons of the same points and interpolations on the study area provided a subsidence map for the 1983-2008 period.

GPS三角高程测量方法的应用与解析

GPS三角高程方法是一种比较特殊的测量高程方法。本文通过对现有的测量方法和理念进行大体的概括和总结,对该方法的适合条件进行了简单的归纳,并将其原理和所处的背景以及现实意义进行简单的分析和探讨,利用实践得到的数据加以证明。原理介绍中涵盖了GPS三角高程测量的方法^([1]);通过计算公式推导出GPS三角高程的测量高差^([2]);介绍了精度和误差的相关要求和约束;涉及应用到的高程系统。对上述内容进行了系统的阐述、说明,最终证明GPS三角高程测量方法能够满足四等水准测量的精度要求,适用于特定地理条件下完成高程测量任务。

联合GPS和InSAR研究海原-六盘山断裂现今的地壳变形特征

海原—六盘山构造区为青藏高原东北部构造变形最为显著的区域之一,历史强震活动频繁,是研究青藏高原NE向扩展的重要窗口和地震孕育过程的理想场所。文中处理了跨海原-六盘山断裂2014—2020年期间2个轨道的时序Sentinel-1A/B SAR数据,获得了该区域InSAR视线向现今的地壳形变场。融合公开发表的近十多年时间尺度的水平GPS地壳运动速度场,获得了研究区高密度地壳水平形变场。对比GPS、水准和InSAR观测结果,以及GPS-InSAR融合的高密度水平形变场,分析讨论了该区域的地壳形变、应变场特征及其与构造之间的对应关系。主要结论如下:1)GPS和InSAR观测表明,1920年海原8.5级大地震的震后黏弹性松弛效应在海原断裂南侧至今仍较为明显;2)GPS-InSAR高分辨率水平形变场表明,狭义海原断裂左旋滑动速率的递减主要发生在中东段,而中西段递减并不显著,可能与海原断裂向六盘山断裂之间由左旋走滑向逆冲推覆构造转换有关;3)六盘山断裂中—南段的地壳垂直形变和水平形变场特征均显示,该段断裂可能处于强震孕育的中晚期,根据反演得到的断层运动参数和地震地质资料,估算六盘山断裂中—南段发生强震的最大矩震级约达7.5级;4)研究区应变积累较快的区域主要集中在海原断裂附近和海原断裂—香山-天景山断裂之间的左旋剪切区,香山-天景山断裂东南段的应变率场和周围相比明显偏小,存在应变不匹配现象,可能与强震孕育有关。

基于EGM2008模型的GPS水准拟合方法应用研究——以尼泊尔西北部山区某水电站测量工程为例

常规GPS水准拟合方法被广泛应用于测量工程中,但其具有精度不够高的缺陷。对此,文章针对尼泊尔西北部山区某水电站测量工程中水准测量施测困难的问题,结合算例对基于EGM2008重力场模型的GPS水准拟合方法进行研究,并且与传统的GPS水准拟合方法进行对比。结果表明,在尼泊尔山区某水电站高程控制测量中,该方法的测量精度相对传统水准拟合方法有很大提高,且该方法能够满足四等水准测量的要求。

基于GPS与GLONASS信噪比反演海平面高度研究

为研究GPS和GLONASS各波段反演海平面高度中精度及时间分辨率等问题,选取SC02站2019年124—130年积日GPS L_(1) L_(2)波段及GLONASS G_(1) G_(2)波段SNR数据,采用多项式方法分解复合信号得到反射信号,利用LSP进行频谱分析,反演得到海平面高度。以该站附近验潮仪数据为真值,对GPS及GLONASS数据反演结果的精度及时间分辨率进行对比分析。结果表明:1)GPS与GLONASS均可用于海平面高度反演;2)GPS L_(1)波段反演结果精度与时间分辨率高于L_(2)波段;3)GPS与GLONASS可联合对海平面高度进行反演,且时间分辨率将会得到极大提升;4)GPS及GLONASS反演结果中均存在系统误差,在后续研究过程中需针对该方面进一步研究。

基于GPS-水准联合监测技术的特大跨径桥梁控制测量研究

随着现代化建设进程的推进,跨径为几千米甚至十几千米的特大跨海桥梁日益增多,常规的控制网构建方案能否满足如此大尺寸桥梁工程施工的精度要求逐渐引起了建设行业的重视。本文以台州湾跨海大桥为例,在严格遵循测量原则的前提下提出了监测方案,并采用GPS技术及水准测量完成了平面控制测量和高程控制测量。结果表明,二等GPS控制网最弱边为TZQ5-TZQ6,相对精度为1/505000,控制网反算边长与实测边长的绝对误差在5 mm以内,最大相对误差1/140800,二等水准测量每千米水准测量偶然中误差为±0.29 mm,闭合差为0.5 mm,测量精度均满足相关规范的要求。本文所采用的控制网点位布设方法、监测方案及遵循原则等均能为建立特大跨海桥梁高精度控制网提供参考。

吐哈盆地胜北洼陷中下侏罗统水西沟群天文旋回地层划分

根据自然伽马测井数据,对吐哈盆地胜北洼陷沁探1井中下侏罗统水西沟群开展旋回地层学分析和沉积噪声模拟,并利用识别出的地层中的米兰科维奇旋回信号来研究地球轨道周期对湖平面变化的驱动作用,进而进行天文旋回地层划分。研究结果表明:①吐哈盆地胜北洼陷中下侏罗统水西沟群在自然伽马曲线中可识别出12.8~51.1 m,3.0~11.9 m,1.1~3.6 m和1.3~2.4 m的沉积旋回,比例关系为21.0∶5.0∶1.5∶1.0。根据天文调谐与相关系数估算出水西沟群沉积速率为3.3~11.7 cm·ka-1。②天文调谐后的时间域序列显示水西沟群长偏心率周期为405 ka、短偏心率周期为99~131 ka、斜率周期为32.6~35.0 ka、岁差周期为20.0~24.8 ka,证明吐哈盆地中下侏罗统沉积过程受到米兰科维奇旋回控制。沁探1井八道湾组(未钻穿)、三工河组和西山窑组的持续时间分别为3.0±0.1 Ma,4.1±0.1 Ma和9.0±0.1 Ma。③地球轨道旋回对陆相湖盆的湖平面升降具有明显的驱动作用,沁探1井水西沟群的沉积噪声模拟证明了~1.5 Ma超长周期可控制台北凹陷早—中侏罗世湖平面的变化。

川西南下寒武统筇竹寺组页岩旋回地层学研究

[目的]四川盆地下寒武统的泥页岩不仅包含重要的环境生命演化信息,同时也是我国当前页岩气勘探开发的重点层位,对其开展精细地层年代学研究具有生产及科研的双重价值。[方法]为了更准确地探明四川盆地下寒武统筇竹寺组黑色页岩层序沉积特征,对川西南地区金页1井筇竹寺组页岩地层开展了旋回地层学研究。[结果与结论](1)通过分析不同测井曲线测井响应特征,认为钾元素测井序列是最适合古环境、古气候的替代指标。(2)将钾元素深度序列进行频谱分析和滑动窗口频谱分析,识别出偏心率和斜率周期(405 kyr,131 kyr,95 kyr,36.4 kyr,28.2 kyr);并结合相关系数分析,以不同沉积速率为限,将整段曲线划分为四段,分别进行405 kyr长偏心率周期的带通滤波;以周缘地区的年代地层年龄526.86±0.16 Ma为年龄控制点,建立了金页1井筇竹寺组的“浮动”天文年代标尺。(3)筇竹寺组共记录了29个长偏心率周期,四段地层的最优沉积速率分别为2.5,2.9,3.4和4.8 cm/kyr。(4)以405 kyr的轨道调谐为基础的沉积噪音模型DYNOT及ρ1曲线重建了筇竹寺组沉积时期相对海平面变化曲线;以该曲线为理论参照,在筇竹寺组中划分了4个三级层序,识别出4个最大海泛面及与之对应的T-R旋回;4个三级层序的沉积时限从下到上为3.18,2.03,2.97和3.63 Ma,分别包含了8个,5个,7个和9个长偏心率周期。(5)海平面变化曲线的低值对应了全球碳同位素负偏,推测是由于海平面的下降引起的有机质发生氧化,并向海水释放碳同位素偏轻的无机碳,形成碳同位素负偏。

GPS桥梁高程控制测量

本文提出利用江河每边岸上相邻水准点间的高程异常差进行ＧＰＳ高程拟合，避免了两岸未统一高程系统对拟合参数的影响，经虎门大桥实验验证，在海面宽３ｋｍ多的两岸上获得的高程系统差的精度满足特大型公路桥梁的高程控制要求，这对沿海平坦地区的铁路桥梁跨河水准测量都有参考作用。

GPS在农田土地平整地形测量中应用的初步研究

根据测量的田面高程数据和估算的平地土方量,对GPS测量技术的田间应用效果进行评价,利用统计方法对比分析定点GPS与水准仪测量的高程数据,初步探讨车载行进速度对GPS测量精度的影响,分析采用GPS技术替代人工水准仪测量方法的可行性。结果表明,基于定点GPS数据和水准仪测量结果绘制的田面微地形状况具有较好的相似性,两者间具有相同的测量精度。车载行进速度对GPS测量精度的影响是明显的,慢速下的GPS测量精度高于快速下的相应结果,低速且匀速的车辆行驶方式是确保该法测量精度的重要措施。在农田土地平整作业中,利用先进的GPS技术替代传统的人工水准仪测量方法对田面高程进行测量具有较好的可行性。

利用GPS监测地面沉降的精度分析

为了监测天津地区的地面沉降,配合精密水准测量,1995年布设了一个GPS监测网,每年的10-11月进行一次精密GPS测量,并与同期进行的精密水准复测的垂直形变结果进行比较研究。根据1995-2004连续十年GPS大地高与精密水准测量观测数据对比研究,验证了GPS监测地面沉降的精度,从理论和实践上论证了GPS大地高变化完全可以像精密水准测量一样高精度获取水准测量点的沉降值,从而得出在地面沉降监测中GPS测量可用于监测地面沉降的结论。

基于GPSPPK/PPP的长距离潮位测量

GPS RTK技术在近距离潮位测量中已得到了应用,但因无线电传播距离的局限,难以实施长距离潮位测量。给出了基于GPS载波相位后处理技术(post processing kinematic,PPK)和精密单点定位技术(pre-cise point positioning,PPP)的长距离潮位测量的思想和方法,并通过实验对其进行了验证,取得了良好的效果。

GPS测量地面沉降的可靠性及精度分析

根据对1995～2004连续10年的GPS大地高与精密水准测量数据的对比研究，验证了两种方法的实际精度，结果表明：GPS大地高变化完全可以像精密水准测量一样高精度地获取水准测量点的沉降值，可用于地面沉降监测。