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.
Daily resolution data retrieved from the 1243 ground-based Global Positioning System (GPS) stations in Japan are utilized to expose surface displacements before the destructive M9 Tohoku-Oki earthquake (March 11, 2011). Variations in the residual GPS data, in which effects of the long-term plate movements, short-term noise and frequency-dependent variations have been removed through a band-pass filter via the Hilbert–Huang transform, are compared with parameters of the focal mechanism associated with the Tohoku-Oki earthquake for validation. Analytical results show that the southward movements, which were deduced from the residual displacements and agree with the strike of the rupture fault, became evident on the 65th day before the Tohoku-Oki earthquake. This observation suggests that the shear stress played an important role in the seismic incubation period. The westward movements, which are consistent with the angle of the maximum horizontal compressive stress, covered entire Japan and formed an impeded area (142°E, 42°N) about 75 km away from the epicenter on the 47th day prior to the earthquake. The horizontal displacements integrated with the vertical movements from the residual GPS data are very useful to construct comprehensive images in diagnosing the surface deformation from destructive earthquakes along the subduction zone.  相似文献   

2.
Greek-Turkish boundary near the cities Kos and Bodrum has been shaken on July 20, 2017 by a Mw6.6 earthquake. The mainshock is located offshore and did not generate an on-land surface rupture. Analyzing pre- and post-earthquake continuous/survey-type static GPS observations, we investigated co-seismic surface displacements at 20 sites to characterize source parameters and slip-distribution of the mainshock. Fault plane solutions as well as co-seismic slip distribution have been acquired through the inversion of co-seismic GPS displacements modeling the event as elastic dislocations in a half space. Fault plane solution shows a southward dipping normal-type fault segment extending a depth down to ~12 km, which remains within the brittle upper crust. Results from the distributed slip inversion show that the mainshock activated a ~65 km fault section, which has three high slip patches, namely western, central and eastern patches, where the coseismic slips reach up to 13, 26, and 5 cm, respectively. This slip pattern indicates that the pre-earthquake coupling, which is storing the slip deficit, occurred on these three patches.  相似文献   

3.
The 26th January 2001 Bhuj earthquake occurred in the Kachchh Rift Basin which has a long history of major earthquakes. Great Triangulation Survey points (GTS) were first installed in the area in 1856–60 and some of these were measured using Global Positioning System (GPS) in the months of February and July 2001. Despite uncertainties associated with repairs and possible reconstruction of points in the past century, the re-measurements reveal pre-seismic, co-seismic and post-seismic deformation related to Bhuj earthquake. More than 25 Μ-strain contraction north of the epicenter appears to have occurred in the past 140 years corresponding to a linear convergence rate of approximately 10 mm/yr across the Rann of Kachchh. Motion of a single point at Jamnagar 150 km south of the epicenter in the 4 years prior to the earthquake, and GTS-GPS displacements in Kathiawar suggests that pre-seismic strain south of the epicenter was small and differs insignificantly from that measured elsewhere in India. Of the 20 points measured within 150 km of the epicenter, 12 were made at existing GTS points which revealed epicentral displacements of up to 1 m, and strain changes exceeding 30 Μ-strain. Observed displacements are consistent with reverse co-seismic slip. Re-measurements in July 2001 of one GTS point (Hathria) and eight new points established in February reveal post-seismic deformation consistent with continued slip on the Bhuj rupture zone.  相似文献   

4.
We explore the use of high-rate GPS, strong-motion records and their joint use for earthquake monitoring, the data collected during 2011 Mw 9.0 Tohoku earthquake was studied. We compared the recorded co-seismic movement, analyzed the displacements in both time-frequency domain. Meanwhile, the comparison of P wave detection was shown and the dynamic velocity waves were discussed. The results suggest that the GPS-only solution is good for low-frequency signal, and the strong-motion-only solution is good for high-frequency signal, thus, the integration of two datasets best complement the advantages of each, more details of co-seismic motions and broader frequency band of seismic signals. This is crucial for earthquake monitoring and early warning.  相似文献   

5.
李煜航  崔笃信  郝明 《地球科学》2015,40(10):1767-1780
GPS测量可以提供高精度的时空图像, 但前任对比研究尚未深入.通过使用线性球面块体模型理论, 在前人针对活动块体研究的基础上, 建立青藏高原东北缘地区三维块体几何模型.以1999—2007年的GPS水平速度场数据作为约束, 反演得到青藏高原东北缘的主要活动断裂长期滑动速率和广义海原断裂带的空间亏损滑动分布及其耦合变化.上述结果为青藏高原东北缘现今运动变形的动力学和强震中-长期危险性预测研究提供了约束和参考.   相似文献   

6.
The Killari earthquake of September 29, 1993 (Mw=6.2) in peninsular India triggered several aftershocks that were recorded by a network of 21 stations. We computed the change in regional static stress caused by coseismic slip on the earthquake rupture and correlated it with the aftershocks with a view to constrain some of the rupture parameters of this earthquake. We evaluated the six available estimates of fault plane solutions for this earthquake and concluded that reverse slip on a 42° dipping, N112° trending fault, which extends up to the surface from a depth of 7 km, produces maximum correlation between the increased static stress and aftershock distribution. Our analysis suggests that the majority of coseismic slip occurred on the part of the rupture that lies in the depth range of 3–6.5 km.  相似文献   

7.
中国大陆现今构造变形GPS观测数据与速度场   总被引：64，自引：6，他引：58  
王琪  张培震  马宗晋 《地学前缘》2002,9(2):415-429
利用 1991— 1999年间 36 2个全球定位系统 (GPS)测站的观测资料 ,初步获得了中国大陆及周边地区现今地壳水平运动的统一速度场。该速度场主要涵盖青藏高原 ,天山 ,塔里木、川滇 ,河西走廊 ,福建东南沿海等重要构造活动区 ,测定精度总体优于 2～ 3mm/a ,速度场站点的分布和测定精度基本上满足中国大陆现今构造变形和动力学研究的需求。现代大地测量第一次比较全面、定量地展示出中国大陆在周边板块作用下大幅度构造变形的图像 ,为模拟大陆岩石圈动力过程提供了基础性的运动学约束条件。  相似文献   

8.
Global Positioning System (GPS) technologies have been frequently applied for the purpose of landslide monitoring. A local stable reference frame is essential for precisely interpreting landslide movements derived from GPS observations. In this study, we define a stable reference frame using over 5 years of continuous GPS data collected from eight permanent GPS stations in the Puerto Rico and Virgin Islands (PRVI) region. The realization of the Stable Puerto Rico and Virgin Islands Reference Frame (SPRVIRF) is defined in terms of a 14-parameter Helmert transformation from the International Global Navigation Satellite System (GNSS) Service Reference Frame of 2008 (IGS08). SPRVIRF is aligned with the IGS08 at epoch 2013.0. The GIPSY/OASIS (V6.2) software package, which employs the precise point positioning (PPP) with single receiver phase ambiguity resolution, was used to calculate position coordinates within IGS08. Through the combined use of the PPP post-processing method and SPRVIRF, it is practical and easy to conduct millimeter accuracy landslide monitoring by a single technician with a single GPS unit. SPRVIRF provides a precise common reference frame in the PRVI region that can be used for a broad range of research applications, such as delineating long-term landslide creeping, studying ground deformation associated with subsidence, fault creep, hydrologic loading and microplate motions, and monitoring long-term deformation of critical structures, such as dams, high-rise buildings, and long-span bridges.  相似文献   

9.
The M w 8.6 Indian Ocean earthquake occurred on April 11, 2012 near the NW junction of three plates viz. Indian, Australian and Sunda plate, which caused widespread coseismic displacements and Coulomb stress changes. We analyzed the GPS data from three IGS sites PBRI, NTUS & COCO and computed the coseismic horizontal displacements. In order to have in-depth understanding of the physics of earthquake processes and probabilistic hazard, we estimated the coseismic displacements and associated Coulomb stress changes from two rectangular parallel fault geometries, constrained by Global Positioning System (GPS) derived coseismic displacements. The Coulomb stress changes following the earthquake found to be in the range of 5 to ?4 bar with maximum displacement of ～11 m near the epicenter. We find that most of the aftershocks occurred in the areas of increased Coulomb stress and concentrated in three clusters. The temporal variation of the aftershocks, not conformed to modified Omori’s law, speculating poroelastic processes. It is also ascertained that the spatio-temporal transient stress changes may promote the occurrence of the subsequent earthquakes and enhance the seismic risk in the region.  相似文献   

10.
Nowadays many continuously operating reference stations (CORS) network were established in Middle East to improve the surveying tasks. Establishing such geodetic control networks can be a costly business where multiple stations should be occupied simultaneously and post-processed with scientific software. Recently, precise point positioning (PPP) provides precise positioning values that may be an alternative to precise relative processing. The current research aims to investigate that PPP has a potential as a reliable absolute positioning technique operational simplicity as well as to investigate the capability of PPP approach to be a low cost alternative to the conventional positioning methods used in position determination of core networks stations. In comparison with common relative GPS techniques, the costs are reduced; because no base stations and no simultaneous observations are necessary, no need for control network maintenance which could be the most defective factors that Egypt HARN network suffered from. To see the feasibility study of using PPP for precise determination of the CORS, 14 days of GNSS data for the 14 Kuwait integrated with 27 IGS stations were processed by Bernese software to calculate the precise coordinates of Kuwaiti CORS network in the latest terrestrial geodetic frame. Three days of these data were processed by Trimble business center software and using PPP approach to calculate the precise coordinates of Kuwait network. In the current research, a comparable investigation was carried out between the coordinates obtained from Bernese software, Trimble business center, and PPP approach. The comparison proved high level of agreement between the coordinates which confirm that PPP approach can be applied for establishment of CORS network.  相似文献   

11.
A detailed study of the Earth tide effects on the GPS kinematic/static positioning is presented in this paper by using theoretical Earth tide computation and practical GPS data processing. Tidal effects could reach up to 30 cm in Denmark and Greenland depending on the measuring time and the position of reference station. With a baseline less than 80 km, the difference of the Earth tide effects could reach more than 5 mm. So, in precise applications of GPS positioning, the Earth tide effect has to be taken into account even for a relative small local GPS network. Several examples are given for demonstrating that the Earth tide effects can be viewed by GPS surveying. They are given through static GPS data static processing, static GPS data kinematic processing, and airborne kinematic GPS data processing. In these cases, the Earth tide effects can be subtracted from the GPS results. The determination of tidal parameter through static GPS data kinematic processing has also been tested.  相似文献   

12.
A Mw 6.3 magnitude earthquake occurred on October 6, 2008 in southern Damxung County within the N–S trending Yangyi graben, which forms the northern section of the Yadong-Gulu rift of south-central Tibet. The earthquake had a maximum intensity of IX at the village of Yangyi (also Yangying) (29°43.3′N; 90°23.6′E) and resulted in 10 deaths and 60 injured in this sparsely populated region. Field observations and focal mechanism solutions show normal fault movement occurred along the NNE-trending western boundary fault of the Yangyi graben, in agreement with the felt epicenter, pattern of the isoseismal contours, and distribution of aftershocks. The earthquake and its tectonic relations were studied in detail to provide data on the seismic hazard to the nearby city of Lhasa.The Damxung earthquake is one of the prominent events along normal and strike-slip faults that occurred widely about Tibet before and after the 2008 Mw 7.9 magnitude Wenchuan earthquake. Analysis of these recent M ? 5.0 earthquake sequences demonstrate a kinematic relation between the normal, strike-slip, and reverse causative fault movements across the region. These earthquakes are found to be linked and the result of eastward extrusion of two large structural blocks of central Tibet. The reverse and oblique-slip surface faulting along the Longmenshan thrust belt at the eastern margin of the Tibetan Plateau causing the Wenchuan earthquake, was the result of eastward directed compression and crustal shortening due to the extrusion. Prior to it, east–west extensional deformation indicated by normal and strike-slip faulting events across central Tibet, had led to a build up of the compression to the east. The subsequent renewal of extensional deformational events in central Tibet appears related to some drag effect due to the crustal shortening of the Wenchuan event. Unraveling the kinematical relation between these earthquake swarms is a very helpful approach for understanding the migration of strong earthquakes across Tibet.  相似文献   

13.
Spatial-temporal patterns of aftershocks of the 2001 Mw7.7 Bhuj earthquake during 2001–2008 reveal a northward spatial migration of seismic activity in the Kachchh seismic zone, which could be related with the loading stresses caused by the continued occurrences of aftershocks on the north Wagad fault (NWF), the causative fault of the 2001-mainshock. Aiming at explaining the observed northward migration of activity, we modelled the Coulomb failure stress change (DCFS) produced by the 2001-mainshock, the 2006 Mw5.6 Gedi fault (GF) and the 2007 Mw4.5 Allah bund fault (ABF) events on optimally oriented plane. A strong correlation between occurrences of earthquakes and regions of increased DCFS is obtained on the associated three faults i.e. NWF, ABF and GF. Predicted DCFS on the GF increased by 0.9 MPa at 3 km depth, where the 7th March 2006 Mw5.6 event occurred, whereas predicted DCFS on the ABF increased by 0.07 MPa at 30 km depth, where the 15th December 2007 Mw4.5 event occurred. Focal mechanism solutions of three events on the ABF have been estimated using the iterative inversion of broadband data from 5–10 stations, which are also constrained by the first P-motion data from 8–12 stations. These focal mechanism solutions for the ABF events reveal a dominant reverse movement with a strike-slip component along a preferred northwest or northeast dipping plane (∼50–70°). Focal mechanisms of the events on all the three fault zones reveal an N-S oriented P- axis or maximum principal stress in the region, which agrees with the prevailing N-S compression over the Indian plate. It is apparent that the northward migration of the static stress changes from the NWF, resulting from the occurrence 2001 Bhuj mainshock, might have caused the occurrence of the events on the GF and ABF during 2006–08.  相似文献   

14.
Earthquakes cause static stress perturbations in the nearby crust and mantle. Obeying rheological laws, this stress relaxes in a time frame of months to years with the spatial extent of few km to hundreds of km. While postseismic relaxation associated with major inter-plate earthquakes is well established, there have been few opportunities to explore its occurrence following intraplate earthquakes. The M w 7.6 Bhuj earthquake on January 26, 2001 in western India is considered to be an intraplate event and provided a unique opportunity to examine post-earthquake relaxation processes sufficiently away from plate boundaries. To study the characteristics of transient postseismic deformation, six Global Positioning System campaigns were made at 14 sites. The postseismic transients were delineated after removing plate motions from the position time series. Postseismic deformation has been observed at all the sites in the study area. During 2001?C2007, the site closest to the epicenter exhibited postseismic deformation of about 30 and 25?mm in the north and east components, respectively. Time series of the NS and EW components of the postseismic transients can be fitted to both logarithmic and exponential functions. Close to the epicenter, the logarithmic function fits well to the initial transient, and an exponential function fits well to the later phases. The remaining sites (located east and west of the epicentral region) exhibited significantly diminished north?Csouth relaxation. Rapidly decaying afterslip and poroelastic mechanisms seem to be responsible for postseismic relaxation in the vicinity of epicenter during the initial period subsequent to the Bhuj earthquake. Postseismic relaxation by viscoelastic flow below the seismogenic zone seems to affect displacements across the entire Bhuj region. This paper presents the characteristics of postseismic transients and deformation processes in the scenario of the highly heterogeneous crust in the Bhuj region.  相似文献   

15.
GPS PPP技术用于滑坡监测的试验与结果分析   总被引：1，自引：0，他引：1  
王利  张勤  黄观文  涂锐  张双成 《岩土力学》2014,35(7):2118-2124
为了研究全球定位系统(GPS)精密单点定位(PPP)技术用于滑坡等地质灾害监测时可能达到的精度和可靠性等问题,结合某类滑坡的大型物理模型试验,在滑坡体上布设了若干GPS监测点进行连续实时动态监测,利用PPP技术对该滑坡从稳定、开始滑动直至产生破坏的全过程监测数据进行了处理与分析,并与GPS单历元差分定位、载波相位实时差分定位技术监测结果进行了对比。结果表明:GPS PPP技术监测结果的内符合精度约为10 mm,外符合精度约为40 mm,且GPS PPP技术具有一些差分GPS无法比拟的优势,如无需基准站支持、作业成本低、效率高、可直接获取监测点在国际地球参考框架下的绝对坐标等。该技术完全可用于滑坡等地质灾害的实时动态监测和预警。  相似文献   

16.
The 12 September 2007 great Bengkulu earthquake (M w 8.4) occurred on the west coast of Sumatra about 130 km SW of Bengkulu. The earthquake was followed by two strong aftershocks of M w 7.9 and 7.0. We estimate coseismic offsets due to the mainshock, derived from near-field Global Positioning System (GPS) measurements from nine continuous SuGAr sites operated by the California Institute of Technology (Caltech) group. Using a forward modelling approach, we estimated slip distribution on the causative rupture of the 2007 Bengkulu earthquake and found two patches of large slip, one located north of the mainshock epicenter and the other, under the Pagai Islands. Both patches of large slip on the rupture occurred under the island belt and shallow water. Thus, despite its great magnitude, this earthquake did not generate a major tsunami. Further, we suggest that the occurrence of great earthquakes in the subduction zone on either side of the Siberut Island region, might have led to the increase in static stress in the region, where the last great earthquake occurred in 1797 and where there is evidence of strain accumulation.  相似文献   

17.
The Mw 9.3 Sumatra earthquake of December 26, 2004 caused extensive coseismic displacements globally, measurements of which were made essentially using modern geodetic techniques. This earthquake induced considerable perturbation in stress distribution as far as ∼8000 km away from the epicenteral region, which is tending to relax to its normal rates as seen from postseismic transient deformation. The monitoring of crustal displacements from strategically located sites using GPS provides coseismic as well as postseismic deformation that facilitates the understanding of the fault geometry, elastic thickness, postseismic relaxation mechanisms, rheology and earthquake recurrence time interval.We investigated coseismic and postseismic GPS derived displacements in Indian region together with the GPS data collected from Andaman and Sumatra region. It is found that while EW displacements are significantly large in peninsular India, those in the region to the north of Central India Tectonic Zone (CITZ) are relatively small. We could delineate the postseismic transients from position time series and interpreted them in terms of viscoelastic relaxation. It is inferred that the postseismic deformation is characterized by a power-law viscoelastic flow in the mantle. In Indian peninsula region, the timescale parameter of the exponential decay (τ = 250 days) would require an extremely low viscosity for the upper mantle. Relying on the prevailing coseismic and postseismic displacement fields, the present study also reflects upon the contemporary litho-tectonics of the Indian sub-continent.  相似文献   

18.
根据同震位移GPS观测数据, 利用有限元法反演了2011年3月11日本MW9.0级地震的断层滑移模式。在此基础上, 计算了日本MW9.0级地震引起的同震位移场和应力场, 给出了位移和应力的分布, 分析了他们的变化规律并与实测结果进行了对比。计算结果表明: 日本MW9.0级地震的静态断层滑移量最大可达25 m。地震引起断层上盘向东位移, 最大位移在震中附近, 可达24.25 m, 日本东北地区向东位移最大可达6 m。震后地表隆起, 隆起幅度可达5.6 m, 隆起的最高点也在震中附近。日本东北地区东海岸附近有一下沉带, 下沉量可达0.8 m。同震地表位移的计算值与GPS测量结果基本一致。地震引起应力变化, 导致震后应力下降。应力变化是不均匀的, 在震中附近约为9.9 MPa, 在深处可达32 MPa, 在日本东北地区地表应力变化小于4.4 MPa。地震引起的应力变化主要是水平应力, 垂直应力基本不变。  相似文献   

19.
Abstract: Dextral-slip thrust movement of the Songpan-Garzê terrain over the Sichuan block caused the Ms 8.0 Wenchuan earthquake of May 12, 2008 and offset the Central Longmenshan Fault (CLF) along a distance of ~250 km. Displacement along the CLF changes from Yingxiu to Qingchuan. The total oblique slip of up to 7.6 m in Yingxiu near the epicenter of the earthquake, decreases northeastward to 5.3 m, 6.6 m, 4.4 m, 2.5 m and 1.1 m in Hongkou, Beichuan, Pingtong, Nanba and Qingchuan, respectively. This offset apparently occurred during a sequence of four reported seismic events, EQ1–EQ4, which were identified by seismic inversion of the source mechanism. These events occurred in rapid succession as the fault break propagated northeastward during the earthquake. Variations in the plunge of slickensides along the CLF appear to match these events. The Mw 7.5 EQ1 event occurred during the first 0–10 s along the Yingxiu-Hongkou section of the CLF and is characterized by 1.7 m vertical slip and vertical slickensides. The Mw 8.0 EQ2 event, which occurred during the next 10–42 s along the Yingxiu-Yanziyan section of the CLF, is marked by major dextral-slip with minor thrust and slickensides plunging 25°–35° southwestward. The Mw 7.5 EQ3 event occurred during the following 42–60 s and resulted in dextral-slip and slickensides plunging 10° southwestward in Beichuan and plunging 73° southwestward in Hongkou. The Mw 7.7 EQ4 event, which occurred during the final 60–95 s along the Beichuan-Qingchuan section of the CLF, is characterized by nearly equal values of dextral and vertical slips with slickensides plunging 45°–50° southwestward. These seismic events match and evidently controlled the concentrations of landslide dams caused by the Wenchuan earthquake in Longmenshan Mountains.  相似文献   

20.
Hastaoglu  K. O.  Sanli  D. U. 《Natural Hazards》2011,58(3):1275-1294
GPS is frequently used in the monitoring of natural hazards and other geophysical phenomena. Landslide monitoring is one such area in which various GPS methods are tested and various systematic error sources are introduced. In previous studies, one error source introduced on rapid static GPS was the effect of large height differences in GPS positions. In this study, we further investigate how GPS velocities/slip rates are affected by large station height differences when rapid static surveying is used. In order to demonstrate the influences, we used static GPS measurements from the Koyulhisar landslide in central Turkey. Comparison of rapid static GPS solutions with static GPS solutions using BERNESE 5.0 indicates that systematic biases occur in the estimated rapid static GPS deformation rates when the station height difference is large between baseline points. The effect is more significant on the vertical component, whereas it is negligible on the horizontal components. When reducing the height difference between the reference station and the rover stations, rapid static solutions from 15-min sessions show high correlation and similar deformation rates with static positioning solutions.  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