首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
We estimate interseismic coupling on the subducting plate interface in the Tokai area, central Japan, by inverting two geodetic data sets. The data record surface motion between March 1996 to May 2000; one represents vertical motion deduced from the leveling observations and the other is the horizontal velocity field deduced from GPS observations. In the inversion, we employed the analytical solutions of surface displacement due to a triangular dislocation element embedded in a homogeneous elastic half space in order to represent the curved plate interface. The vertical data show that the most strongly coupled portion of the subduction interface is concentrated beneath Omaezaki Cape, while the horizontal data show strongest coupling in the shallower region of the subducting plate interface. The estimated maximum value of coupling from the horizontal data is 40 mm/year, while that from vertical data is 25 mm/year.  相似文献   

2.
Land subsidence was first observed in Shanghai nearly a century ago, in 1921. Land subsidence attributed to groundwater extraction has been severe in China and is still occurring. Recent subsidence and associated earth fissures occurring since 2000 in three principal regions—the North China Plain, Fenwei Basin and Yangtze Delta—are introduced, and historical subsidence in these areas is briefly summarized. The subsidence-affected area in these regions with cumulative subsidence greater than or equal to 200 mm is more than 90,000 km2 and covers 22 provinces (cities), which include intensively developed and densely populated areas. Earth fissures accompanying the subsidence create significant geohazards; more than 1,000 earth fissures have been identified in the North China Plain, Fenwei Basin and Yangtze Delta. Effective land-subsidence-monitoring networks, that include continuous global positioning system (GPS) stations, repeat GPS and leveling surveys of geodetic benchmarks, InSAR, borehole extensometers, and groundwater observation wells, have been established in these three subsidence-affected areas. Mitigation measures and administrative means have been implemented in some areas, with good results in the Yangtze Delta area.  相似文献   

3.
In 2006, a cooperation project between China Geological Survey and the Geological Survey of Canada started the monitoring of the landslide along the deep-cut valley in the western Sichuan using integrated GPS and InSAR observation at the Jiaju landslide. Both GPS and InSAR techniques provided complementary measurements with the GPS providing horizontal movement and InSAR providing vertical motion. Meanwhile, InSAR images demonstrate also an effective tool to recognize new landslides in complex steep mountain region. The GPS observations provide continuous monitoring data while InSAR data provide monthly measurements. The differential InSAR results show a deformation information that divided the Jiaju landslide to two areas, the north and south parts. The north part is sliding greater than the southern part in spatial domain. The sliding was faster in 2008 than that in 2006 in time domain, suggesting a gradual increased acceleration over time. The GPS displacement data during the past 2  years show the northern part slid horizontally 55–207 mm/a and vertically −23 mm/a, while the southern part slid horizontally 12–34 mm/a; and the vertical displacement mainly moved downward 0.05 to 12 mm/a. On average, the observations from December of 2006 to January of 2008 indicate that the northern part is sliding at 41.6 mm/a horizontally and 43.9 mm/a vertically, while the southern part is sliding at 16.1 mm/a horizontally and 17.5 mm/a vertically. The data acquired through the GPS and InSAR are generally comparable. Geological survey revealed some secondary landslides, cracks, and fissures within the deformation of the Jiaju landslide that could be induced by following factors: surface water drainage, river erosion, and slope cutting and overloading.  相似文献   

4.
The Thompson River valley, south of Ashcroft in British Columbia, Canada, has experienced several landslides since the mid-1800s. The national railways that run along the valley cross a number of these landslides. All the landslides occur in glacial deposits, typically sliding on weak clay layers. Some have failed rapidly to very rapidly and are currently inactive or showing deformation rates from a few millimeters to centimeters per year. An evaluation of satellite InSAR (Interferometric Synthetic Aperture Radar) using RADARSAT-2 images between September 2013 and November 2015 provides new insight into landslide displacements in the Thompson River valley. This information enhances the ongoing hazard management of unstable terrain. This paper presents the comparison of the InSAR measurements with other instrumentation (GPS and ShapeAccelArrays? -SAA) installed at one moving landslide and then addresses the extent and magnitude of the slope movements observed. InSAR was found to provide similar displacement values to those measured otherwise. The stable location showed displacements of +/?1 mm with an average near zero during the whole monitoring period. Six areas of slope movement were identified within the study area, all within or adjacent to the footprints of past landslides. The average line of sight (LOS) displacement rates range between 11 and 39 mm/year. Most of the landslides exhibited seasonal variations in velocity that corresponds to changes in river elevation in the valley.  相似文献   

5.
David Verdonck   《Tectonophysics》2005,395(3-4):179-191
Active horizontal and vertical deformation in western Washington is modeled using an inverse dislocation model. The modeling technique uses published horizontal crustal velocities, derived from campaign and continuous GPS data, and uplift rates, calculated from repeated historical leveling surveys. The plate interface is represented by both screw and edge dislocations divided into segments. The rate of slip deficit accumulation on each segment is estimated by inverting the surface deformation data using a linear least squares procedure. The model predicts the data well, with an overall RMS residual of 0.85 mm/year. The horizontal residual vectors show no discernable pattern and no significant uniform regional strain and rigid rotations can be identified. The estimated slip deficit accumulation rates suggest that the plate interface is locked in a broad region beneath the coastline and possibly partially locked further downdip. The maximum slip deficit rate was estimated at 32.1±1.9 mm/year or approximately 91% of the plate convergence rate. The partially locked zone appears to be accumulating slip deficit at 8.2±1.9 mm/year.  相似文献   

6.
青藏高原的隆升是新生代最壮观的地质事件,关于青藏高原隆升研究一直是地学界的研究焦点.河流阶地的发育记录了丰富的构造运动和气候变化的信息,近年来被广泛应用于构造运动和气候演变的研究,但前人研究的河流阶地基本分布在青藏高原的周缘,阶地的形成可能是气候与构造运动共同作用的结果.本文通过高分辨率卫星影像的解译,在青藏高原内部的西昆仑阿什库勒地区发现了多达七级的河流阶地.对该处河流阶地结构、沉积特征、几何特征的研究表明该阶地是典型的构造成因阶地.野外利用全站仪对河流阶地地貌形态进行了精细的测量,获得了各级阶地的拔河高度分别为4～5m(T1)、9～ 10m(T2)、16 ～ 18m(T3)、28～31m(T4)、45～48m(T5).通过宇宙成因核素10Be测年方法对各级阶地面的暴露年龄进行了测定,获得了各级阶地的形成时代分别为7.7±0.7ka(T1)、32.7±3.lka (T2)、53.6±2.5ka(T3)、115.7±23.2ka(T4)、166.8±10.4ka (T5)、19.5±8.5ka (T6).由此确定了晚第四纪166.8ka以来不同时期的河流下切速率总体介于0.2～0.35mm/yr,该速率代表了青藏高原西北部晚第四纪166.8ka以来的平均隆升速率.  相似文献   

7.
The Upper Rhine graben is a north–northeast trending rift system, which belongs to the European Cenozoic rift system. Today, the southern part of the graben is seismically still active. Earthquakes of magnitude 5 have a recurrence time of approximately 30 years. In order to monitor and to determine the displacements in the study area, GPS measurements have been carried out in two campaigns (1999 and 2000), and observations of the available permanent stations have been processed in 2002. Owing to the small size of deformations expected, high accuracy requirements must be met by the GPS processing. In order to achieve these requirements, precise antenna modeling has been introduced into the processing. As expected the short time span has not enabled to detect significant displacements from the GPS measurements. The deformation analysis shows that the horizontal displacement rates do not exceed 1 mm/year, which is compatible with the geological information. Owing to the fact that the accuracy of positioning with GPS for the vertical coordinates is lower than for the horizontal coordinates, the determination of vertical displacements has been carried out using the leveling technique. In the area of Freiburg, first-order and second-order leveling lines have been chosen for the detection of local displacements on the Weinstetten, on the Lehen-Schönberg and on the Main Border Fault (MBF). Some sections of these faults are still active today. Significant vertical displacements have been observed at the Weinstetten fault in the area of Bad Krozingen and on the MBF in Freiburg. The displacement rates (1925–1984) are 0.17±0.01 mm/year and 0.25±0.02 mm/year respectively. The results agree very well with the results of seismotectonic investigations, and show that ongoing displacements can be found on the northern part of the Lehen-Schönberg fault in the vicinity of Eichstetten, and on the MBF in the vicinity of Freiburg.  相似文献   

8.
David Verdonck   《Tectonophysics》2006,417(3-4):221-230
Data from 29 tide gauges and 113 pairs of first and second order leveling lines are analyzed to determine the pattern of vertical deformation in the Pacific Northwest of the United States. The data span nearly 100 years and represent the interseismic elastic deformation related to the great earthquake cycle. Uplift rates calculated from leveling surveys are adjusted to a model surface in the tidal reference frame using a robust, weighted, linear, least square technique. Rapid uplift occurs in two distinct broad regions along the coast separated by a narrow zone of slow subsidence. Vertical deformation rates range from > 4 mm/year of uplift on southern Vancouver Island to > 2 mm/year of subsidence in northern coastal Oregon. The deformation pattern is consistent with the results of previous studies and subduction models.  相似文献   

9.
通过对西藏海拔最高、面积最大湖泊-纳木错周缘湖相沉积、湖岸堤的野外调查和湖岸阶地的水准测量,发现在纳木错沿岸拔湖48m以下,发育有6级湖岸阶地,拔湖48~139.2m发育有高位湖相沉积。湖相沉积物的同位素测年结果表明,纳木错湖泊发育与藏北高原东南部古大湖演化可划分为3个阶段:①116~37kaB.P.间的古大湖期;②37~30kaB.P.间的外流湖期;③30kaB.P.以来的纳木错期。根据纳木错晚更新世以来湖相沉积中粘土矿物的X光衍射分析结果,以及采用比值法、高岭石法和衍射峰法的研究,探讨了粘土矿物所显示的环境变化信息。粘土矿物成分变化表明,该区已具备了寒温带干旱、半干旱区的气候环境特征。为研究青藏高原的湖泊演化、气候变化、古地理变迁及其隆升过程等提供了新资料。   相似文献   

10.
A continuous GPS measurement site, ISRR, at Gandhinagar (Western India), documented ~?5 mm/year of surface subsidence rate during 2009–2016. Preliminary modelling using an analytical solution indicates that the observed surface subsidence rate at the ISRR site is consistent with the ground water depletion reported from Gandhinagar. An assessment of data from GPS sites at Lucknow and Varanasi in the Indo-Gangetic plains in Northern India does not indicate any significant subsidence at these sites which is also consistent with the in situ observations of insignificant depletion of ground water in the region.  相似文献   

11.
The Himalayan region has been studied extensively during the past few decades in terms of present ongoing deformations. Various models have been proposed for the evolution of the Himalaya to explain the cause of earthquake occurrences and to understand the seismotectonics of the Himalayan collision zone. However, the information on displacements from field geodetic surveys is still too scarce in time and spatial domains so as to provide convincing evidences. Moreover, classical Probabilistic Seismic Hazard Approaches also fail due to paucity of data in higher magnitude range, thus emphasizing the need of spatial level displacement measurements. It is in this context that the present study has been carried out to estimate the surface displacement in a seismically active region of the Himalaya between Ganga and Yamuna Tear using Differential SAR interferometry. Three single-look complex images, obtained from ASAR sensor onboard ENVISAT satellite, have been used. A displacement rate of 8?C10?mm per year in N15°E direction of Indian plate has been obtained in this three-pass SAR interferometry study. It has been noted that the estimated convergence rate using Differential SAR interferometry technique is relatively low in comparison with those obtained from previous classical studies. The reported low convergence rate may be due to occurrence of silent/quite earthquakes, aseismic slip, differential movement of Delhi Hardwar ridge, etc. Therefore, in view of the contemporary seismicity and conspicuous displacements, a study of long-term observations of this surface movement has been recommended in future through a time-series SAR interferometry analysis.  相似文献   

12.
The focus of this study is investigation of land subsidence in Semarang city Indonesia with the use of Interferometry Synthetic Aperture Radar (InSAR) of ALOS–PALSAR satellite. We processed 22 ascending SAR images during January 2007 to January 2009 plus two descending SAR images acquired on 6 June 2006 and 17 June 2007. The time series analysis of interferometry was performed by using 12 pairs of interferogram relative to 21 January 2007 and 8 pairs of interferogram relative 24 January 2008. The topographic phase contribution was removed using the 3-arcsec (90 m) Shuttle Radar Topography Mission (SRTM), Digital Elevation Model (DEM). We performed precision baseline estimation to vanish the fringes from baseline effect between master and slave data. In order to investigate the contribution of horizontal movement in our analysis, we constructed two interferograms of ascending orbit and descending orbit. The time series results exhibited that the area is subsiding continuously without a significant seasonal effect during January 2007 to January 2009. The land subsidence observed from InSAR data is approximately up to 8 cm/year. Three cross sections on image displacement show the extreme land subsidence occurred especially along the coastal area and lowland area where this area is considered as industrial with high-density settlements, consuming a lot of groundwater, and land is changed from agriculture and cultivation purposes to industrial estates and house. Our result also shows a consistency with historical pattern of subsidence measured by leveling data. The results highlight the potential use of InSAR measurements to provide better constraints for land subsidence in Semarang city Indonesia.  相似文献   

13.
We compare new and literature data concerning the integrated deformation rate since 18 ka for the central Apennines with deformation rate data derived from a 6-year GPS campaign. We constructed topographic profiles across the majority of the active faults in the area. We derived deformation rate data from displaced post-glacial sediments and slopes associated with the last major glacial retreat that occurred in the region about 18 kyr ago. Paleoseismic investigations in this region clearly show that offset of these features is the cumulative effect of repeated surface faulting earthquakes with magnitudes in the range 5.5 ≤ Ms ≤ 7.0. A cumulative throw-rate diagram, incorporating both our values and the values extracted from the literature (i.e., previously published trenching studies, scarp profiles and offset terraces), is presented providing a regional picture of the spatial deformation rate distribution in the central Apennines, during the latest Pleistocene and Holocene. By converting cumulative throw-rates into heave rates, we calculate maximum extension rates of ca. 2 mm/year at the location of the same transect where 6 ± 2 mm/year has been measured with GPS over 6 years. This discrepancy between geodetic and geological fault slip-rate data implies that we have to be cautious whenever we use GPS data for seismic hazard assessment purposes or when attempting to reconstruct the tectonic processes in an area, because geodetic data may be unrepresentative of the longer-term deformation rates. On the other hand, this discrepancy may provide insights into the mechanics of the seismic cycle. We discuss various scenarios that may explain the mis-match between long-term and short-term measurements.  相似文献   

14.
阴山位于河套断陷带北部,晚新生代以来,构造运动非常活跃,阴山持续不断隆起,河套随之不断下陷,作为地貌响应之一,阴山河谷中发育了一系列河流阶地。本文通过详细的野外地质调查,结合地貌学、沉积学及年代学方面的研究,厘定了阴山西段河谷普遍发育的4~5级河流阶地;并利用光释光(OSL)测年方法,恢复了其堆积-下切历史,建立了河流阶地年代框架:T4、T3、T2、T1级阶地大致形成时间分别为58.00ka BP、46.25ka BP、32.19ka BP、15.79ka BP之后;分析了本区河流阶地的成因:阴山的构造隆升为本区河流下切提供动力基础,是形成河流阶地的主要驱动力,气候变化通过改变水流流量与沉积物通量的比率影响阶地的堆积-下切行为的转换,是河流阶地形成的重要影响因素;进而利用河流侵蚀速率差异性讨论了晚更新世以来阴山西段的构造隆升模式:51.61~41.28ka BP之间,阴山西段隆升以中部高于东西部的穹窿式差异性隆升为主,23.22ka BP之后,阴山西段的隆升区段差异性减小,趋向于整体隆升。  相似文献   

15.
为了对河北省承德市滦平县张百湾镇周台子村铁矿区进行形变调查和监测,消除安全隐患,在时序CSInSAR（相干散射体InSAR）技术的基础上,开发了48景Sentinel1数据的DSCSInSAR（融合分布式散射体和相干散射体InSAR）技术。该方法首先采用AD (Anderson Darling)检验对同质像素点进行识别,然后基于协方差矩阵特征值分解算法对最优相位进行估计,最终通过时序形变解算得到铁矿区的地表形变结果。研究结果表明：研究区的年平均形变速率范围为-34.50~24.50 mm/a;大部分矿区都存在不同程度的沉降,其中周台子村和路边附近矿区沉降量较大,窑岭沟矿区出现明显抬升现象,最大沉降量和最大抬升量分别达到了34.00和24.03 mm,其形变结果与当地4个GPS监测点结果一致。与CSInSAR技术相比,DS CSInSAR技术极大提高了目标点的密度和干涉图的质量。  相似文献   

16.
We investigated the long-term reclamation settlement of Chek Lap Kok Airport, Hong Kong, one of the largest reclamation projects worldwide. An advanced InSAR technique was applied to two independent ASAR data sets along ascending (25 scenes) and descending (22 scenes) orbits acquired between 2003 and 2008, and allowed us to generate deformation velocity maps and displacement time series for the investigated area. Intercomparison of deformation velocity results from the two ASAR data sets and their validation against leveling survey measurements were carried out in order to assess accuracy and reliability of the InSAR observations. The intercomparison and validation results demonstrated the potential of elaborate InSAR processes on local-scale areas to monitor and detect a long-term residual settlement in such complex reclamation area. The InSAR-derived deformation velocity maps showed a fair stability in areas of the two original rocky islands of Chek Lap Kok and Lam Chau, and on most of the buildings at the site due to foundation on piles reaching the granite bedrock, whereas a generally moderate (3–7 mm/year) to strong (> 10 mm/year) and spatially variable settlement trend was detected in the majority of reclamation areas of the airport. The consistent relationship we found between the observed settlement pattern and the underlying geological conditions suggested that this recoded differential settlement was mainly related to the variations in thickness and soil properties of both the fill materials and the alluvial deposits below the reclamation. A geological and geotechnical interpretation of the lithostratigraphy of the alluvial deposits beneath the reclamation implied that the relatively large settlement rate measured up to 2008 was resulted from a still active primary consolidation process.  相似文献   

17.
Thirty-two tephra layers were identified in the time-interval 313–366 ka (Marine Isotope Stages 9–10) of the Quaternary lacustrine succession of the Fucino Basin, central Italy. Twenty-seven of these tephra layers yielded suitable geochemical material to explore their volcanic origins. Investigations also included the acquisition of geochemical data of some relevant, chronologically compatible proximal units from Italian volcanoes. The record contains tephra from some well-known eruptions and eruptive sequences of Roman and Roccamonfina volcanoes, such as the Magliano Romano Plinian Fall, the Orvieto–Bagnoregio Ignimbrite, the Lower White Trachytic Tuff and the Brown Leucitic Tuff. In addition, the record documents eruptions currently undescribed in proximal (i.e. near-vent) sections, suggesting a more complex history of the major eruptions of the Colli Albani, Sabatini, Vulsini and Roccamonfina volcanoes between 313 and 366 ka. Six of the investigated tephra layers were directly dated by single-crystal-fusion 40Ar/39Ar dating, providing the basis for a Bayesian age–depth model and a reassessment of the chronologies for both already known and dated eruptive units and for so far undated eruptions. The results provide a significant contribution for improving knowledge on the peri-Tyrrhenian explosive activity as well as for extending the Mediterranean tephrostratigraphical framework, which was previously based on limited proximal and distal archives for that time interval.  相似文献   

18.
Various hypotheses have been put forth in relation to the land uplift of Fennoscandia, which is well documented both by geological and geodetic observations. Most modern authors attribute the present uplift to an isostatic rebound of the earth after the last deglaciation. Recent information on the gravity field, both from the satellite data and land survey measurements is examined to ascertain whether the Fennoscandian uplift is associated with a gravity minimum and a mass deficit. Free air anomalies correlate well with the central area of uplift and predict a remaining uplift of about 100 m. Results of secular gravity measurements are inconclusive. Seismicity of Fennoscandia does not show a close association with the area of maximum uplift. Different rheological models proposed for the mantle below the Fennoscandian shield are reviewed and it is shown that the available data on the rates of uplift for the last 9000 years are more compatible with a low-viscosity (1020 P) asthenosphere of 100–200 km thickness.  相似文献   

19.
帕米尔造山带是印度-欧亚大陆会聚带的西构造结。木吉断层作为中-西帕米尔与东帕米尔的最北部边界转换断层,其运动性质和滑动速率的准确限定对于理解帕米尔现今应力状态和运动学特征等具有重要意义。本文以木吉断层东段布拉克村北位错特征显著的冰碛台地(39.2020°N,74.3910°E)为研究对象,基于高分辨率卫星影像解译、野外地质地貌调查、差分GPS测量和冰川漂砾宇宙成因核素10Be暴露测年,获得布拉克北冰碛台地形成(16.8±3.5 ka)以来木吉断层的累积右旋位错量、垂直位错量、南北向拉张量以及最小速率分别为约190 m、105±12 m、34±12 m和11.3±2.4 mm/a、6.3±1.5 mm/a、2.0±0.8 mm/a;三者的比值约为6:3:1,水平向的总滑动速率为11.5±2.3 mm/a。与位于断层中部近乎纯走滑的阿克萨依处相比,木吉断层在布拉克北以右旋走滑为主的同时,具有明显的正断分量。断层在布拉克北的水平向总滑动速率11.5±2.3 mm/a与阿克萨依处右旋走滑速率的最大值(9.4±0.9 mm/a)大致相当;因此尽管断层沿走向的运动性质发生了显著变化,其水平向滑动速率大致保持恒定。  相似文献   

20.
Man's interest in the dynamics of the earth's crust goes back several centuries. Ekman recently pointed out the theory of post-glacial uplift in Fennoscandia. In the 15th century, towns along the Baltic-Sea experienced receding of the sea. In this century, Bowie had started a program for repeating surveys in seismically active regions. Wegeners' hypothesis of Continental Drift aroused the interest of scientists. In January 1985, Walter Sullivan traced the evolution from Wegener's continental drift through plate tectonics to the latest suggestion of the formation of continents from “terranes”. Spatial techniques. Laser Ranging, VLBI, GPS have given geodesists the ability to monitor continental drift, intracontinental deformations and other phenomena.

Along faults, such as the San Andreas Fault, the conventional geodetic approach to deformation has been to use a linear concept, except for episodic events such as earthquakes and so on.

Wayne Thatcher's model on the declining strain rate is justified if sufficient geodetic data, well distributed, are available. Strain components can be computed from distortion patterns which might develop when an earlier survey is adjusted to be made consistent with a later survey. There exists a correlation of the movement of the instantaneous pole of rotation with the energy release of all earthquakes.  相似文献   


设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号