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 an...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.展开更多
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 ...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.展开更多
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...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.展开更多
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 mov...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.展开更多
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 focu...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.展开更多
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 no...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＇展开更多
The Global Geopotential Models (GGMs) of GOCE (Gravity Recovery and steady- state Ocean Circulation Explorer) differ globally as well as regionally in their accuracy and resolution based on the maximum degree and orde...The Global Geopotential Models (GGMs) of GOCE (Gravity Recovery and steady- state Ocean Circulation Explorer) differ globally as well as regionally in their accuracy and resolution based on the maximum degree and order (d/o) of the fully normalized spherical harmonic (SH) coefficients, which express each GGM. The main idea of this study is to compare the free-air gravity anomalies and quasi geoid heights determined from several recent GOCE-based GGMs with the corresponding ones from the Earth Gravitational Model 2008 (EGM2008) over Egypt on the one hand and with ground-based measurements on the other hand. The results regarding to the comparison of GOCE-based GGMs with terrestrial gravity and GPS/levelling data provide better improvement with respect to EGM2008. The 4th release GOCE-based GGM developed with the use of space-wise solution strategy (SPW_R4) approximates the gravity field well over the Egyptian region. The SPW_R4 model is accordingly suggested as a reference model for recovering the long wavelength (up to SH d/o 200) components of quasi geoid heights when modelling the gravimetric quasi-geoid over the Egypt. Finally, three types of transformation models: Four-, Five- and Seven-parameter transformations have been applied to reduce the data biases and to provide a better fitting of quasi geoid heights obtained from the studied GOCE-based GGMs to those from GPS/levelling data. These models reveal that the standard deviation of vertical datum over Egypt is at the level of about 32 cm.展开更多
The absolute rate of mean sea level of Xiamen area is derived from the data of Xiamen tide gauge station and Xiamen GPS fiducial station of crustal movement observation network of China（CMONC）. The height variation ...The absolute rate of mean sea level of Xiamen area is derived from the data of Xiamen tide gauge station and Xiamen GPS fiducial station of crustal movement observation network of China（CMONC）. The height variation is discussed deeply in this paper, h is shown that height has periodic variations. So the rate of vertical land movement can not be precisely obtained only from several GPS campaigns. It is pointed out that the vertical crustal movement of tide gauge station should be monitored by using long-term continuous GPS observations.展开更多
To realize the data synchronization between the inertial measurement unit （IMU） and the global positioning system （GPS）, the synchronization technology in the IMU/GPS integrated measurement system of vehicle motio...To realize the data synchronization between the inertial measurement unit （IMU） and the global positioning system （GPS）, the synchronization technology in the IMU/GPS integrated measurement system of vehicle motion parameters is studied. According to the characteristics of the output signals of the IMU and the GPS, without the IMU synchronization signal, the synchronization circuit based on CPLD is designed and developed, which need not alter the configurations of the IMU and GPS. Experiments of measuring vehicle motion parameters, which rely on the synchronization circuit to realize IMU/GPS data synchronization, are made. The driving routes in experiments comprise a curve and a straight line. Experimental results show that the designed circuit can accurately measure the synchronization time difference and the IMU period, and can effectively solve the data synchronization in IMU/GPS integration. Furthermore, the IMU/GPS integrated measurement system based on the synchronization circuit can measure and calculate many vehicle motion parameters in high frequency mode.展开更多
To improve the performance of the traditional map matching algorithms in freeway traffic state monitoring systems using the low logging frequency GPS （global positioning system） probe data, a map matching algorithm ...To improve the performance of the traditional map matching algorithms in freeway traffic state monitoring systems using the low logging frequency GPS （global positioning system） probe data, a map matching algorithm based on the Oracle spatial data model is proposed. The algorithm uses the Oracle road network data model to analyze the spatial relationships between massive GPS positioning points and freeway networks, builds an N-shortest path algorithm to find reasonable candidate routes between GPS positioning points efficiently, and uses the fuzzy logic inference system to determine the final matched traveling route. According to the implementation with field data from Los Angeles, the computation speed of the algorithm is about 135 GPS positioning points per second and the accuracy is 98.9%. The results demonstrate the effectiveness and accuracy of the proposed algorithm for mapping massive GPS positioning data onto freeway networks with complex geometric characteristics.展开更多
基金the University of French Polynesiafunding by several successive“Decision Aide a la Recherche”(DAR)grants to the Geodesy Observatory of Tahiti from the French Space Agency(CNES)+2 种基金fundings from the local government of French Polynesia(Observatoire Polynesien du Rechauffement Climatique)funding by“National Natural Science Foundation of China”(Grand No.41931075)funding by“the Fundamental Research Funds for the Central Universities"(Grand No.2042022kf1198)。
文摘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.
基金supported by the China National Special Fund for Earthquake Scientific Research in Public Interest(201508009)
文摘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.
文摘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.
基金supported by the National Key R&D Program of China(2018YFC1503606 2017YFC1500502)Earthquake Tracking Task(2019010215)
文摘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.
文摘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.
基金supported by the Spark Programs of Earthquake Sciences(XH14069Y)the Special Earthquake Research Project of the China Earthquake Administration(201208009)
文摘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＇
文摘The Global Geopotential Models (GGMs) of GOCE (Gravity Recovery and steady- state Ocean Circulation Explorer) differ globally as well as regionally in their accuracy and resolution based on the maximum degree and order (d/o) of the fully normalized spherical harmonic (SH) coefficients, which express each GGM. The main idea of this study is to compare the free-air gravity anomalies and quasi geoid heights determined from several recent GOCE-based GGMs with the corresponding ones from the Earth Gravitational Model 2008 (EGM2008) over Egypt on the one hand and with ground-based measurements on the other hand. The results regarding to the comparison of GOCE-based GGMs with terrestrial gravity and GPS/levelling data provide better improvement with respect to EGM2008. The 4th release GOCE-based GGM developed with the use of space-wise solution strategy (SPW_R4) approximates the gravity field well over the Egyptian region. The SPW_R4 model is accordingly suggested as a reference model for recovering the long wavelength (up to SH d/o 200) components of quasi geoid heights when modelling the gravimetric quasi-geoid over the Egypt. Finally, three types of transformation models: Four-, Five- and Seven-parameter transformations have been applied to reduce the data biases and to provide a better fitting of quasi geoid heights obtained from the studied GOCE-based GGMs to those from GPS/levelling data. These models reveal that the standard deviation of vertical datum over Egypt is at the level of about 32 cm.
文摘The absolute rate of mean sea level of Xiamen area is derived from the data of Xiamen tide gauge station and Xiamen GPS fiducial station of crustal movement observation network of China（CMONC）. The height variation is discussed deeply in this paper, h is shown that height has periodic variations. So the rate of vertical land movement can not be precisely obtained only from several GPS campaigns. It is pointed out that the vertical crustal movement of tide gauge station should be monitored by using long-term continuous GPS observations.
文摘To realize the data synchronization between the inertial measurement unit （IMU） and the global positioning system （GPS）, the synchronization technology in the IMU/GPS integrated measurement system of vehicle motion parameters is studied. According to the characteristics of the output signals of the IMU and the GPS, without the IMU synchronization signal, the synchronization circuit based on CPLD is designed and developed, which need not alter the configurations of the IMU and GPS. Experiments of measuring vehicle motion parameters, which rely on the synchronization circuit to realize IMU/GPS data synchronization, are made. The driving routes in experiments comprise a curve and a straight line. Experimental results show that the designed circuit can accurately measure the synchronization time difference and the IMU period, and can effectively solve the data synchronization in IMU/GPS integration. Furthermore, the IMU/GPS integrated measurement system based on the synchronization circuit can measure and calculate many vehicle motion parameters in high frequency mode.
文摘To improve the performance of the traditional map matching algorithms in freeway traffic state monitoring systems using the low logging frequency GPS （global positioning system） probe data, a map matching algorithm based on the Oracle spatial data model is proposed. The algorithm uses the Oracle road network data model to analyze the spatial relationships between massive GPS positioning points and freeway networks, builds an N-shortest path algorithm to find reasonable candidate routes between GPS positioning points efficiently, and uses the fuzzy logic inference system to determine the final matched traveling route. According to the implementation with field data from Los Angeles, the computation speed of the algorithm is about 135 GPS positioning points per second and the accuracy is 98.9%. The results demonstrate the effectiveness and accuracy of the proposed algorithm for mapping massive GPS positioning data onto freeway networks with complex geometric characteristics.
