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Satellite Laser Ranging (SLR) technology is one of the main technologies in the field of space geodesy, it has played an extremely important role in laser ranging data application and research. As a commonly used geodynamic satellites, the main contribution of LAGEOS and LAGEOS-2 is the solution of orbit determination and station coordinates. At present, there are 8 analysis centers of the International Laser Ranging Service (ILRS) to release the precise orbit products for the two LAGEOS satellites. However, there is currently no relevant research on the analysis of the consistency of these orbits. So, the authors would evaluate the accuracies of them, and the results show that the orbital accuracies of the two LAGEOS satellites are 3 ∼ 5 cm. SLR is regarded as one of the important input data of the International Terrestrial Reference Frame (ITRF), the analysis center of ILRS provides weekly solutions of station coordinates for ITRF. But, due to the limitation of SLR observation conditions, for example most observations of Chinese SLR stations can be made at night, and laser ranging test cannot be conducted in rainy days, the orbit solution of the seven-day arc may have the problem of less data. Therefore, this paper proposed a method for computing the station coordinates based on long arc orbit determination, and we developed the LAODGEO software (Long Arc Orbit Determination Software for Geodynamic Satellite), which is used to solve the orbits of two LAGEOS satellites and station coordinates of five SLR stations in China. The results show that the obtained orbital precision is basically superior to 3.70 cm, and the 3DRMS values between station coordinates solved by us and the coordinates published by SLRF2014 are mostly smaller than 0.013 m, which is consistent with research results domestic and overseas. [ABSTRACT FROM AUTHOR]

Volcano deformation monitoring is one of the most widely studied research topics by using interferometric synthetic aperture radar (InSAR). In the new open and big SAR data era, the development of data processing methods, and interdisciplinary integration have pushed volcanic study into a new stage. This paper reviews the studies of volcano monitoring and parameter inversion based on InSAR. First, we introduce the principle of InSAR, the advanced InSAR time series methods, and the main error sources. Then, we summarize the commonly used classical analytical and numerical models in volcanic deformation modeling. We select several cases to introduce the specific InSAR applications in studying volcanic tectonic dynamic mechanisms including magma transfer, eruption, degassing and hydrothermal activity. Finally, we summarize the current status of volcanic deformation monitoring in China and the future advances of InSAR volcano geodesy. [ABSTRACT FROM AUTHOR]

The contribution presents the representative research progress on global static gravity field modeling, regional geoid/quasigeoid determination, vertical datum study, as well as the theory, algorithm and software for gravity field study in China from 2019 to 2023, which are the highlights of the chapter 6 "Progress in Earth Gravity Model and Vertical Datum" in the "2019-2023 China National Report on Geodesy" that submitted to the International Association of Geodesy(IAG). In addition, suggestions are proposed to promote the research in the fields of earth gravity field, geoid/quasigeoid and vertical datumin China according to trends of international geodesy and related disciplines. [ABSTRACT FROM AUTHOR]

Modern geodetic technologies, including high-precision ground-based gravity measurements, satellite gravimetry, satellite altimetry, Global Navigation Satellite Systems (GNSS), and Interferometric Synthetic Aperture Radar(InSAR), offer a wealth of observations for monitoring global hydrological processes with exceptional accuracy and spatio-temporal resolutions. Mass redistribution and Earth's surface deformation over land related to global and regional water cycling can be inferred from modern gravimetry, altimetry, GNSS, and InSAR techniques. Hydrogeodesy becomes an emerging field of geodesy aiming to analyze the changes of water in the Earth system. The paper introduces the China's advances in hydrogeodesy in recent years. It brings together multiple geodetic teams' work from China, showcasing the application of modern geodetic technologies in the field of hydrology, including research on terrestrial water storage, groundwater storage, glaciers/ice sheets, and reservoir water storage. [ABSTRACT FROM AUTHOR]

The ocean accounts for approximately 71% of the total area of the Earth. Whether it is studying the shape of the Earth itself through geodesy or the future development of earth system science, strengthening the construction of ocean geodesy disciplines and innovating ocean geodetic observation technologies have evident theoretical and practical significance. In recent years, the discipline of ocean geodesy in China has been continuously developing and growing, and notable breakthroughs have been made in ocean satellite geodesy and seafloor geodetic observation technology. Research on ocean geodetic observation models and algorithms has also made great progress. [ABSTRACT FROM AUTHOR]

One of the key goals of geodesy is to study the fine structure of the Earth's gravity field and construct a high-resolution gravity field model (GFM). Aiming at the current insufficient resolution problem of the EIGEN_6C4 model, the refined ultra-high degree models EIGEN_3660 and EIGEN_5480 are determined with a spectral expansion approach in this study, which is to augment EIGEN_6C4 model using topographic potential models (TPMs). A comparative spectral evaluation for EIGEN_6C4, EIGEN_3660, and EIGEN_5480 models indicates that the gravity field spectral powers of EIGEN_3660 and EIGEN_5480 models outperform the EIGEN_6C4 model after degree 2000. The augmented models EIGEN_3660 and EIGEN_5480 are verified using the deflection of the vertical (DOV) of China and Colorado, gravity data from Australia and mainland America, and GNSS/leveling in China. The validation results indicate that the accuracy of EIGEN_3660 and EIGEN_5480 models in determining height anomaly, DOV, and gravity anomaly outperform the EIGEN_6C4 model, and the EIGEN_5480 model has optimal accuracy. The accuracy of EIGEN_5480 model in determining south–north component and east–west component of the DOV in China has been improved by about 21.1% and 23.1% compared to the EIGEN_6C4 model, respectively. In the mountainous Colorado, the accuracy of EIGEN_5480 model in determining south–north component and east–west component of the DOV has been improved by about 28.2% and 35.2% compared to EIGEN_6C4 model, respectively. In addition, gravity value comparison results in Australia and mainland America indicate that the accuracy of the EIGEN_5480 model for deriving gravity anomalies is improved by 16.5% and 11.3% compared to the EIGEN_6C4 model, respectively. [ABSTRACT FROM AUTHOR]

The International Association of Geodesy (IAG) aims to establish the International Height Reference System (IHRS) as one of its primary scientific objectives. Central to the realization of the IHRS is global vertical datum unification, which requires the connection of existing local vertical height reference systems (VHS) robustly and consistently. However, conventional methods are not suitable for estimating the offsets between two distant local height systems. In this paper, we propose a framework for connecting two local VHSs using ultraprecise clock frequency signal links between satellites and ground stations, referred to as the satellite frequency signal transmission (SFST) approach. The SFST approach allows for the direct determination of the geopotential and height differences between two ground datum stations without any location restrictions between the two VHSs. The simulation results show that the VHSs of China and the US can be unified with an accuracy of several centimeters, provided that the stability of atomic clocks used on-board the satellite and at on-ground datum locations reaches 4.8 × 10 − 17 τ − 1 / 2 for an averaging time τ (in seconds). We conclude that the SFST approach shows promise for achieving centimeter-level accuracy in unifying the global vertical height datum and represents a new paradigm for the realization of the IHRS. [ABSTRACT FROM AUTHOR]

Simple Summary: Oaks (Quercus spp.) are a major component of subtropical and temperate forests in the Northern Hemisphere. There are approximately 464 species, and they are dominant tree species in ecosystems. Oaks have a long history of cultivation in Europe, North America, and other continents. They are also cultivated and distributed in most provinces of China. In this paper, Quercus germplasm resource distribution, ecological adaptability, and utilization are explored. All evidence indicates that oaks have been widely distributed since ancient times and have greater functional value than other species in the Fagaceae family. This review will provide a deeper understanding of oak conservation, development, and utilization in China. Oaks exhibit unique biological characteristics and high adaptability to complex climatic and soil conditions. They are widely distributed across various regions, spanning 40 degrees latitude and 75 degrees longitude. The total area of oak forest in China is 16.72 million hm2. There are 60 lineages of Quercus in China, including 49 species, seven varieties, and four subgenera. Archaeological data indicate that oaks were already widely distributed in ancient times, and they are dominant trees in vast regions of China's forests. In addition, the acorn was an important food for ancestral humans, and it has accompanied human civilization since the early Paleolithic. Diverse oak species are widely distributed and have great functional value, such as for greening, carbon sequestration, industrial and medicinal uses, and insect rearing. Long-term deforestation, fire, diseases, and pests have led to a continuous decline in oak resources. This study discusses the Quercus species and their distribution in China, ecological adaptation, and the threats facing the propagation and growth of oaks in a changing world. This will give us a better understanding of Quercus resources, and provide guidance on how to protect and better utilize germplasm resources in China. The breeding of new varieties, pest control, and chemical and molecular research also need to be strengthened in future studies. [ABSTRACT FROM AUTHOR]

The Ordos Block is a critical component of the North China Craton (NCC), which is located at the northeastern edge of the Tibetan Plateau. Over the years, it has undergone complex tectonic evolution due to the influence of multiple factors, such as the India–Eurasia plate collision, the subduction of the Pacific Plate, and the southward movement of the Siberian Plate. To investigate the crustal structure and dynamic evolution of the northern margin of the Ordos Block, this study employs joint inversion of receiver functions and gravity data and then integrates results from geology, geophysics, and geodesy. The overall results indicate that the crustal thickness shows a thickening trend from south to north. The generally high Poisson’s ratio suggests that the crust is rich in silica or subjected to high crustal stress. Furthermore, the common conversion point (CCP) stacking results identify distinct layering in the subsurface structure of the northern margin, including the Conrad discontinuity and low-velocity zones, thus reflecting its complex deep structure. Driven by the eastward growth of the Tibetan Plateau and the northwestward subduction of the Pacific Plate, the block rotates counterclockwise, playing a significant role in the formation of surrounding rift basins. The abovementioned findings emphasize the influence of surrounding tectonic activities on the crustal structure and dynamics of the northern margin of the Ordos Block, thus highlighting the potential for strong earthquakes in the region. [ABSTRACT FROM AUTHOR]

Fault geometric complexity plays a critical role in earthquake rupture dimension. Fault bifurcations are commonly observed in earthquake geology, yet, robust kinematic rupture processes on bifurcated fault branches are largely missing, limiting our understanding of rupture dynamics and seismic hazard. Here, we holistically study the fault geometry and bilateral rupture of the 2021 Mw7.4 Maduo, China earthquake, that shows clear fault bifurcation near its eastern terminal. We integrate space geodesy imaging, back‐projection of high‐frequency teleseismic array waveforms, multiple point source and finite fault inversions, and constrain in detail the rupture process, in particular, through its fault bifurcation. Our models reveal a stable rupture speed of ∼2.5 km/s throughout the entire rupture and a simultaneous rupture through fault branches bifurcated at 20°. The rupture on bifurcated faults radiated more high‐frequency waves, especially from the stopping phases. The stopping phase on the southern branch likely stopped the rupture on the northern branch. Plain Language Summary: Earthquake is produced by sudden shear dislocation across the fault. The geometric complexity of fault structure, such as bend, step‐over, branching and bifurcation, play important roles in determining the final rupture dimension (hence the magnitude) of the earthquake, as they can easily produce stress heterogeneity on the faults. Although geological and recent space geodetic observations have well‐recorded the fault geometry complexity, detailed spatial and temporal evolution of rupture through such fault segments, especially fault bifurcations, are rarely well‐imaged. In this study, we integrate broadband seismic waveform and geodetic observations for the 2021 Mw7.4 Maduo earthquake in China, and process and model them with a set of tools, to produce a high resolution rupture model for the earthquake. The preferred model reveals a near constant rupture speed of 2.5 km/s throughout the entire rupture, and resolves the detailed rupture process through the bifurcated fault segments at its eastern terminal, where the termination of the rupture on the southern branch stopped the rupture on the northern branch. Key Points: Geodetic imaging, back‐projection, multiple point source and finite fault inversions are conducted for the Maduo earthquakeWe show a stable rupture speed (∼2.5 km/s) of the entire rupture and a simultaneous rupture through bifurcated fault branchesThe stopping phase on the southern branch likely stopped the rupture on the northern branch [ABSTRACT FROM AUTHOR]

Ultrawideband (UWB) is well-suited for indoor positioning due to its high resolution and good penetration through objects. The observation model of UWB positioning is nonlinear. As one of nonlinear filter algorithms, extended Kalman filter (EKF) is widely used to estimate the position. In practical applications, the dynamic estimation is subject to the outliers caused by gross errors. However, the EKF cannot resist the effect of gross errors. The innovation will become abnormally large and the performance and the reliability of the filter algorithm are inevitably influenced. In this study, a robust EKF (REKF) method accompanied by hypothesis test and robust estimation is proposed. To judge the validity of model, the global test based on Mahalanobis distance is implemented to assess whether the test statistical term exceeds the threshold for outlier detection. To reduce and eliminate the effects of the individual outlier, the robust estimation using scheme III of the Institute of Geodesy and Geophysics of China (IGGIII) based on local test of the normalized residual is performed. Meanwhile, three kinds of stochastic models for outliers are expressed by modeling the contaminated distributions. Furthermore, the simulation and measurement experiments are performed to verify the effectiveness and feasibility of the proposed REKF for resisting the outliers. Simulation experiment results are given to demonstrate that the outliers following all the three kinds of contaminated distributions can be detected. The proposed REKF can effectively control the influences of the outliers being treated as systematic errors and large variance random errors. When the outliers come from the thick-tailed distribution, the robust estimation does not play a role, and the REKF are equivalent to the EKF method. The measured experiment results show that the outliers will be generated in the nonline-of-sight environment whose impact is abnormally serious. The robust estimation can provide relatively reliable optimized residuals and control the influences of the outliers caused by gross errors. We can believe that the proposed REKF is effective to resist the effects of outliers and improves the positioning accuracy compared with least-squares (LS) and EKF method. Moreover, the adaptive filter and ranging error model should be considered to compensate the state model errors and ranging systematic errors respectively. Then, the measurement outliers will be detected more correctly, and the robust estimation will be used effectively. [ABSTRACT FROM AUTHOR]

China Chang'E-3 performed soft landing at the plains of Sinus Iridum on lunar surface on December 14th 2013 successfully; it opened a new window for observing lunar surface with radiometric tracking which many lunar scientific researchers always pursue for. Since July 2014, OCEL (Observing Chang'E-3 Lander with VLBI) project has been conducted jointly by IVS (International VLBI Service of Geodesy and Astrometry) and BACC (Beijing Aerospace Control Center), a global IVS R&D network augmented with two China Deep Space Stations configured for OCEL. This paper presents the current status and preliminary result of the OCEL and mainly focuses on determination of the lander position, which is about 7 meter in height and 14 meter in plane of lunar surface with respect to LRO (Lunar Reconnaissance Orbiter). Based on accuracy analysis, further optimized OCEL sessions will make use of this target-of-opportunity, the Chang'E-3 lunar lander, as long as it is working. With higher accurate radiometric observables, more prospective contribution to earth and lunar science is expected by combining with LLR. [ABSTRACT FROM AUTHOR]

We have developed a stable North China Reference Frame 2016 (NChina16) using five years of continuous GPS observations (2011.8–2016.8) from 12 continuously operating reference stations (CORS) fixed to the North China Craton. Applications of NChina16 in landslide and subsidence studies are illustrated in this article. A method for realizing a regional geodetic reference frame is introduced. The primary result of this study is the seven parameters for transforming Cartesian ECEF (Earth-Centered, Earth-Fixed) coordinates X, Y, and Z from the International GNSS Service Reference Frame 2008 (IGS08) to NChina16. The seven parameters include the epoch that is used to align the regional reference frame to IGS08 and the time derivatives of three translations and three rotations. The GIPSY-OASIS (V6.4) software package was used to obtain the precise point positioning (PPP) daily solutions with respect to IGS08. The frame stability of NChina16 is approximately 0.5 mm/year in both horizontal and vertical directions. This study also developed a regional model for correcting seasonal motions superimposed into the vertical component of the GPS-derived displacement time series. Long-term GPS observations (1999–2016) from five CORS in North China were used to develop the seasonal model. According to this study, the PPP daily solutions with respect to NChina16 could achieve 2–3 mm horizontal accuracy and 4–5 mm vertical accuracy after being modified by the regional model. NChina16 will be critical to study geodynamic problems in North China, such as earthquakes, faulting, subsidence, and landslides. The regional reference frame will be periodically updated every few years to mitigate degradation of the frame with time and be synchronized with the update of IGS reference frame. [ABSTRACT FROM AUTHOR]

Differences between seismic and geodetic strain rates can highlight regions of potential seismic hazard. In China, many of the most devastating historical and recent earthquakes have occurred around the margins of the Ordos Plateau. We construct an earthquake catalogue for the region that covers the 700 yr period from 1315 to 2015, and is thought to be complete for events with Ms > 6. We use Kostrov summations to determine a seismic strain rate tensor for each of the margins of the Ordos Plateau. We also use the latest campaign GPS data to calculate both a continuously varying geodetic strain rate field for the region and individual geodetic strain rate tensors for each of the plateau margins. We then compare our seismic and geodetic strain rate results to identify regions with seismic moment deficits and also calculate expected recurrence intervals from our geodetic moment rates. We find notable seismic strain rate deficits in northern Ningxia (to the west of the Ordos Plateau), in the Hetao and Linhe Grabens (to the north of the plateau), and in the Shanxi Grabens (to the northeast of the plateau). In theWeihe Graben (to the south of the plateau), although there is an overall seismic strain rate excess for the last 700 yr, there is some indication of relative quiescence for the last few centuries. Assuming no aseismic accommodation of deformation, these deficits indicate enhanced potential for large earthquakes in these regions in the future. Either temporal clustering of earthquakes or individual, large-magnitude events with long recurrence intervals could explain these patterns of moment release. Meanwhile, in southern Ningxia (to the southwest of the plateau) we find a seismic strain rate excess, indicating a likely lower level of seismic hazard in this region. In southern Ningxia and the Shanxi Grabens the pattern of strain suggested by the Kostrov summations is consistent with the geodetic strains. In northern Ningxia, the Hetao and Linhe Grabens, and the Weihe Graben--where there are fewer historical earthquakes and sparser GPS station coverage--the seismic and geodetic patterns of strain release are inconsistent. [ABSTRACT FROM AUTHOR]

This study examines the ~ 200-km-long northwestern Xianshuihe fault zone (NWXFZ), southwestern China, using more than three decades of geodetic observations from fault-crossing short-baseline and short-leveling surveys at seven sites. These data enable estimates of creep rates and depths, and examination of the long-term slip behavior. The surface motion of the NWXFZ is dominated by sinistral creep, although sinistral, transverse, and vertical slip components show spatio-temporal variations. Combining these slip variations with data of earthquake rupture, coseismic slip, seismicity, fault geometry, and far-fault movement velocity, and using the velocity-and-state friction theory, our analysis indicates that the surface slip behavior of the NWXFZ is segmented along strike. The 1973 rupture section of this fault zone exhibits spatio-temporally variable slip behavior, showing time-decaying post-1973 afterslip on the northwestern and southeastern parts of the rupture at depths above 5.8 − 7.0 km with average sinistral-creep rates of 1.3 and 3.5 mm/yr, respectively, but being relocked in the central part of the rupture. The 1923/1981 rupture section is generally in locking state, with postseismic and interseismic sinistral-creep at 1.1 mm/yr on its central part at depths above 2.0–2.8 km. The 1893 rupture section has been tightly locked without creep since at least the early 1980s. The thickness of the shallow velocity-strengthening (or creep) layer and the restraining bend geometry of the NWXFZ are the key factors that control spatio-temporal variations in surface creep rates. Two surface-observed locked fault portions are located within two different restraining bends in the NWXFZ, both of which act as compressive asperities and hence have enabled the long-term locking of these portions. Creep along the NWXFZ has also been affected to varying degrees by M 6.5 − M w 9.2 earthquakes at distances of 50 − 3800 km from the fault zone. Most of these effects have been removed from our estimates of the long-term average creep rates. [ABSTRACT FROM AUTHOR]

On July 11, 1995, an Mw 6.8 earthquake struck eastern Myanmar near the Chinese border; hereafter referred to as the 1995 Myanmar–China earthquake. Coseismic surface displacements associated with this event are identified from JERS-1 (Japanese Earth Resources Satellite-1) SAR (Synthetic Aperture Radar) images. The largest relative displacement reached 60 cm in the line-of-sight direction. We speculate that a previously unrecognized dextral strike-slip subvertical fault striking NW–SE was responsible for this event. The coseismic slip distribution on the fault planes is inverted based on the InSAR-derived deformation. The results indicate that the fault slip was confined to two lobes. The maximum slip reached approximately 2.5 m at a depth of 5 km in the northwestern part of the focal region. The inverted geodetic moment was approximately Mw = 6.69, which is consistent with seismological results. The 1995 Myanmar–China earthquake is one of the largest recorded earthquakes that has occurred around the “bookshelf faulting” system between the Sagaing fault in Myanmar and the Red River fault in southwestern China. [ABSTRACT FROM AUTHOR]

Taking four influential Chinese surveying and mapping journals as the data source, 5863 papers published during the period of 2003-2013 were obtained. Using the method of bibliometrics and visual analysis, summarizing the surveying and mapping papers in the past ten years (2003-2013), research themes, authors, and geographical distribution were analyzed. In the study, the papers of geodesy, cartography and GIS are 59.9%, more than half of all the papers. We also determine that the core author group has 131 authors, mainly of whom are from big cities. 90% of top ten cities on the number of publishing papers are capital cities or municipalities directly under the central government. In conclusion, we found that the research focus was different every year, and the research content was richness, the content of geodesy, cartography and GIS were widely researched, and the development of surveying and mapping is imbalanced in China. [ABSTRACT FROM AUTHOR]

The 2013 Mw6.8 Lushan, China earthquake occurred in the southwestern end of the Longmenshan fault zone. We jointly invert local strong motion data and geodetic measurements of coseismic surface deformation, including GPS and InSAR, to obtain a robust model of the rupture process of the 2013 Lushan earthquake. Our joint inversion best model involves the rupture of two opposing faults during the Lushan earthquake, a main fault and a secondary fault. It is only when the secondary fault is included that both the GPS and InSAR measurements are fit along with the near-field strong motion. Over 75% of the computed moment was released in slip on the main fault segment, a northwest dipping, listric thrust fault, with buried thrust and dextral strike-slip at hypocenter depths, and with only minor slip closer to the surface. The secondary fault mainly involved oblique thrust slip or pure dextral strike-slip at shallower depths, and accounts for just under 24% of the moment released in the Lushan earthquake. Coulomb stress changes of about 0.5 MPa on the secondary fault segment at the time coseismic slip initiated on that fault indicate that slip was likely triggered by the coseismic slip on the main blind thrust fault. Our coseismic slip model is consistent with a sub-horizontal and east–west to southeast–northwest trending most compressive stress. Our inferred coseismic slip model is also consistent with previous GPS derived models of strain accumulation on the Longmenshan fault system. [ABSTRACT FROM AUTHOR]

• A maximum eigenvalue detection (MED) based method is used for ionospheric anomaly detection, which possesses mathematical verifiability and simplicity. • The MED method demonstrates its sensitivity to ionospheric anomalies by comparing and presenting ROTI, S4, CSC and TEC. • The statistical results show the seasonal and daily variations at low latitudes in China, spatial differences between north and south China. A discussion of a simulation application is also presented in the paper. At low latitudes in China, local ionospheric anomalies are frequent and difficult to capture, posing positioning errors and safety risks to GNSS users. This leads to conservative error bounds in GNSS augmentation systems. For example, in Satellite Based Augmentation System (SBAS), the presence of under-sampled regions and the ionospheric instability at low latitudes can result in an over-conservative error bound, i.e., Grid Ionospheric Vertical Error (GIVE) with reduced availability. Ionospheric irregularity detectors could be used to exclude anomalies from the grid model to share the integrity risk and tighten the GIVE. The detection method needs to have theoretical validity and sensitivity to small local anomalies. However, current irregularity detectors are designed for Ionospheric Grid Point (IGP), dealing with wide-area spatial anomalies. The problem of decreased availability resulting from the over-conservative error bound caused by the frequent local ionospheric anomalies is unsolved, especially at low latitudes and the equatorial region. To further enhance the GNSS performance, the applicability analysis of a maximum eigenvalue-based ionospheric irregularity detector, which is sensitive to local-scale spatial anomalies, is presented. The detection capability of MED for ionospheric anomalies is demonstrated by theory, cases, statistics, and simulation applications. This method can also be used for ionospheric monitoring in geodesy or geophysics. [ABSTRACT FROM AUTHOR]

The article highlights the Expert Assessment Workshop on "Decadal Climate Variability and Cross-Scale Interactions" held by the International Commission on Climate (ICCL) of the International Association of Meteorology and Atmospheric Sciences (IAMAS) of the International Union of Geodesy and Geophysics (IUGG) in Beijing, China on April 16-17, 2013. Topics of the workshop include interdecadal Pacific oscillation (IPO), anthropogenic climate change above natural decadal, and the Asian monsoon.

Total petroleum hydrocarbon (TPH) pollution in oilfield soils is a worldwide environmental problem. In this study, we analysed the spatial variation of residual TPH components and the ecological risk they pose. The soils of five selected oilfields in China, across 11 degrees of latitude and 17 degrees of longitude were selected for the investigation. The results showed that the non-zonal composition of the residual TPHs in the soil was similar to the that of the crude oil input. Principal component analysis (PCA) suggested that the effect of zonal environmental factors explained 81.5% of the variability in the residual indexes of saturated and aromatic hydrocarbons. The first principal component, the soil clay and organic matter, correlated positively with the residual TPH index. The second principal component, the accumulated temperature, however, correlated negatively with the residual TPH index in the soil. Moreover, the application of the soil quality index (SoQI) and a Monte Carlo simulation for estimating the residual TPH content suggested that the ecological risk caused by residual TPHs in the soil decreased when the oilfield latitude and clay and organic matter content in the oilfield soil were lower. This study provides a basis for the assessment and monitoring of ecological risk in oilfield soils worldwide. [Display omitted] • Spatial eco-risks of residual soil TPH are assessed using soil quality index. • Non-zonal crude oil properties affected the compositions of residual soil TPH. • Zonal environmental factors influenced the concentrations of residual soil TPH. [ABSTRACT FROM AUTHOR]

Detecting the timing and amount of deformation is critical for understanding the physical causes and eventually warning of possible landslide hazards. Monitoring of deformation of structures and ground surface displacements during landslides can be accomplished by using different types of systems and techniques. Besides geotechnical or physical techniques, remote sensing techniques can be classified as satellite techniques, photogrammetric techniques, geodetic techniques, ground based techniques, and so on. To study and govern growing geological disasters in China, especially in the Three Gorges area, Three Gorges Research Center for Geo-hazard (TGRG) is establishing an infra structure to effectively and comprehensively analyze the mechanism of landslide deformation, focused on the Huangtupo landslide, using of various advanced monitoring systems and techniques. In this article, the framework and latest advances of integration of multi remote sensing techniques in the infrastructure are presented. Different remote sensing techniques, data processing and integrating methods, and the latest results are discussed in detail. At last, reviews on current work and suggestions for further work are put forward. [ABSTRACT FROM AUTHOR]

Abstract: Determining the slip-rate history along the right-lateral Karakorum fault (KF) is fundamental to understanding its present-day kinematic role in the deformation of Tibet. Geodetic and geologic studies suggest slip-rates of 0–11mm/yr along this structure. Whether slip-rate variability exists along strike and/or time, or simply results from different measuring techniques/timescales, remains unknown. In order to constrain slip-rates within a timescale of 200ka, we studied fluvial and glacial geomorphic features that are right-laterally or vertically offset by the fault by varying amounts from 7±1m to 430±30m and up to 53±5m, respectively. We constrained their ages using 10Be surface exposure dating on 141 quartz-rich samples collected on 4 lateral moraines and at 3 alluvial sites along the southernmost segment of the KF (Menshi–Kailas basin) and along the Gurla Mandhata detachment fault in the Pulan graben. From the 30° fault bend at Baer (80.5°E) to Mount Kailas area, the slip-rate along the KF is >7.1+3.2/−1.7 mm/yr at Menshi and >7.9+3.2/−2.5 mm/yr at Kailas (slip on two parallel fault strands). In the Pulan graben, the normal fault slip-rate is >1.6+0.4/−0.3 mm/yr. Our data suggest that the Quaternary slip-rate along the southern KF does not decrease eastward but is constant along strike for at least 200km, from >5–11mm/yr in the Gar basin further north to >7–8mm/yr in the Menshi–Kailas basin. Because no expected along-strike slip-rate gradient is observed, it implies that the KF does not end at the Kailas but must extend where the slip rate decreases, i.e. eastward along the Yarlung Zangbo suture and southward along the Gurla Mandhata–Humla fault system. [Copyright &y& Elsevier]

SUMMARY In 2001 November a magnitude 7.8 earthquake ruptured a 400 km long portion of the Kunlun fault, northeastern Tibet. In this study, we analyse over five years of post-seismic geodetic data and interpret the observed surface deformation in terms of stress relaxation in the thick Tibetan lower crust. We model GPS time-series (first year) and InSAR line of sight measurements (years two to five) and infer that the most likely mechanism of post-seismic stress relaxation is time-dependent distributed creep of viscoelastic material in the lower crust. Since a single relaxation time is not sufficient to model the observed deformation, viscous flow is modelled by a lower crustal Burgers rheology, which has two material relaxation times. The optimum model has a transient viscosity 9 × 1017 Pa s, steady-state viscosity 1 × 1019 Pa s and a ratio of long term to Maxwell shear modulus of 2:3. This model gives a good fit to GPS stations south of the Kunlun Fault, while displacements at stations north of the fault are over-predicted. We attribute this asymmetry in the GPS residual to lateral heterogeneity in rheological structure across the southern margin of the Qaidam Basin, with thinner crust/higher viscosities beneath the basin than beneath the Tibetan Plateau. Deep afterslip localized in a shear zone beneath the fault rupture gives a reasonable match to the observed InSAR data, but the slip model does not fit the earlier GPS data well. We conclude that while some localized afterslip likely occurred during the early post-seismic phase, the bulk of the observed deformation signal is due to viscous flow in the lower crust. To investigate regional variability in rheological structure, we also analyse post-seismic displacements following the 1997 Manyi earthquake that occurred 250 km west of the Kokoxili rupture. We find that viscoelastic properties are the same as for the Kokoxili area except for the transient viscosity, which is 5 × 1017 Pa s. The viscosities estimated for the Manyi and Kokoxili areas are consistent with constraints obtained from other earthquakes in the northwest and south central parts of the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

We investigate the slip distribution of the 2008 May 12 Wenchuan M 7.9 earthquake using GPS data and InSAR measurements under a linear inversion scheme, with emphasis on the effect of three factors, including constraint on rake, different discretizations, and layered elastic model. Within our inversion parameterization context, we find the most influential factor would be constraint on rake. Without constraint on rake, the slip model seems physically wrong under the depth of 15 km, due to the limited depth resolution of the geodetic data used, especially the one orbit of InSAR measurements. Thus it is necessary to add a priori to the slip rake to obtain a reasonable fault source model. Different discretizations of the subfault patches have a notable impact on the slip distribution. Also, the layered elastic model predicts more slip at depth than does the half-space model, by about 15-20 per cent. The characteristics of slip distribution established through our inversions include some points as follows: (1) the most reliable results would be expected at depth range of 0-15 km; (2) three peak-slip asperities are inverted, at Yingxiu county (near epicentre), Yuejiashan county, and Beichuan county, respectively; (3) the inverted rake along the Yingxiu-Beichuan fault changes from dominantly thrusting motion at the southwest segments to dominant right-lateral or even pure right-lateral strike slip at the northeast segments, and (4) only thrust slip is occurred on the Guanxian-Jiangyou fault. [ABSTRACT FROM AUTHOR]

For more than two decades the slip rate along the active, left-slip Altyn Tagh fault of northwestern Tibet has been disputed, with millennial rates reported to be as much as three times faster than those determined geodetically. This problem is signifi cant because the total offset, plate-boundary length, and age of the Altyn Tagh fault make it the most important single structure accommodating India-Asia convergence north of the Himalayas. Here we show that the central Altyn Tagh fault slipped at only 14-9 mm/a over the past 4-6 ka by tightly bracketing the age of a displaced fl uvial terrace riser at Yuemake (88.51°E, 38.19°N). This result contradicts previous latest Quaternary rates and is consistent with those derived from geodetic, paleoseismic, and geologic measurements, and thus resolves the long-standing dispute over the latest Quaternary slip rate along the longest active strike-slip fault in Tibet. [ABSTRACT FROM AUTHOR]

Observations of relative motion in a geodetic network in Ladakh, India, and across southern Tibet indicate slow shear on the Karakorum fault, rapid east-west extension across the whole of southern Tibet, and constant arc-normal convergence between India and southern Tibet along the Himalayan arc. Measurements of ten campaign-style and six permanent sites with global positioning system (GPS) precise geodesy provide these bounds on the style and rates of the large-scale deformation in the Tibet-Himalaya region. Divergence between sites at Leh, Ladakh, India, and Shiquanhe, western Tibet, as well as slow relative motion among sites within the Ladakh network, limit right-lateral slip parallel to the Karakorum fault to only 3.4 ± 5 mm/yr. This low rate concurs with a recent estimate of 3–4 mm/yr for Late Holocene time, but disagrees with the much higher rate of 30-35 mm/yr that has been used to argue for plate-like behavior of the Tibetan Plateau. Convergence between Ladakh and the Indian subcontinent at 18.8 ± 3 mm/yr at 224° ± 17° (1σ) differs little from estimates of convergence across the central segment of the Himalaya. Finally, lengthening of the baseline between Leh, Ladakh, and Lhasa (in southeastern Tibet) at 17.8 ± 1 mm/yr or between Leh and Bayi (farther to the southeast) at 18 ± 3 mm/yr, is consistent with an extrapolation of rates of east-west extension of the Tibetan Plateau based both on shorter GPS baselines (e.g., Lhasa-Simikot) and on diverging slip vectors of earthquakes in the Himalaya. We interpret these results to indicate that Tibet behaves more like a fluid than like a plate. [ABSTRACT FROM AUTHOR]

The article focuses on various topics related to geodesy. Nominations for the Young Authors Award to be given by the International Association of Geodesy (IAG) will be accepted until March 1, 2013. The International Symposium on Space Geodesy and Earth System (SGES2012) was conducted in Shanghai, China from August 18 to 21, 2012. A review of the book "Where on Earth Are We? Using the Sky for Mapping the Nordic Countries 1500-2000," by Martin Ekman, is presented.

Discusses the theory and methods to determine the geocenter variations by space geodetic techniques in China. Terrestrial reference frame; Description on the techniques.