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The gravity-geological method (GGM) is an approach that utilizes marine gravity anomalies (GAs) and shipborne bathymetric data to invert seafloor topography by resolving short-wavelength GAs through the Bouguer Plate approximation. Such an approximation ignores the non-linear effects caused by surrounding seafloor topographical undulations that actually exist in short-wavelength GAs, and thus leaving the space for further modification of GGM. This study thoroughly derives the relationship between seafloor topography and GA, as well as the formula of GGM. Then, we propose a self-adaptive method to improve the accuracy of the inversion significantly: the enhanced GGM (EGGM). The method uses the equivalent mass line method to approximate the non-linear gravitational effects of the surrounding seafloor topography to correct the short-wavelength GAs. By introducing two optimal density contrast parameters, EGGM has been designed to effectively integrate the combined effects of various non-linear factors to a certain extent. The accuracy of the seafloor topography models, produced with a spatial resolution of 1′ × 1′, was evaluated over the study area (132°E–136°E, 36°N–40°N) located in the Sea of Japan. The results indicate that the accuracy of EGGM has a relative improvement of 13.73 per cent compared to that of GGM in the overall study area, while the accuracy of both models is higher than that of the SIO_unadjusted model. The study further investigated the feasibility and stability of EGGM by examining the accuracy of both GGM and EGGM in various water depth ranges and areas with diverse terrain characteristics. [ABSTRACT FROM AUTHOR]

The Sumatran Fault Zone (SFZ) of the Indonesian island of Sumatra, which is broken up into 19 fault segments, accommodates much of the trench-parallel component of the oblique convergence between the Indo-Australian and Sunda plates. To understand the potential hazard of SFZ earthquakes to the local population, we investigate slip rates and locking depths of three SFZ segments in southern Sumatra using previously unpublished data from our Sumatran Fault Monitoring (SuMo) campaign Global Positioning System (GPS) network. We model the GPS data using a 2-D interseismic dislocation model optimized using a Bayesian approach. For the Musi segment of the SFZ, we find that slip rates ranging from 10 to 22 mm yr−1 and locking depths from 1 to 20 km fit the data similarly well, suggesting a lack of resolution for the SuMo network in this segment. For the Manna and Kumering segments where the resolution is better, the estimated slip rates are 18 [12–22, 95 per cent confidence intervals] mm yr−1 and 12 [9–15] mm yr−1, respectively, while the estimated locking depths are 29 [15–47] km and 5 [3–16] km, respectively. The deep locking depth estimated for the Manna segment can be explained by the large station gap in this segment. Considering the uncertainty, all the estimated slip rates from our study remains aligned with the SFZ's average slip rate of ∼15 mm yr−1, which was previously derived using updated geological slip rates and geodetic block modelling of the entire SFZ. Our results support the idea that the forearc sliver west of the SFZ behaves as a rigid microplate. [ABSTRACT FROM AUTHOR]

On 16 April 2013, an M w = 7.7 earthquake struck the border of Iran and Pakistan in the central part of the Makran subduction zone with a reported depth of 80 km by USGS. This rare event in this poorly instrumented region helps to shed light on the kinematics of the subducting slab. We investigate source parameters of the Saravan intraslab normal earthquake using RADARSAT-2 SAR images in three ascending tracks, nine permanent GNSS sites and teleseismic data. The maximum coseismic displacement occurred at the SRVN GNSS station with 54.1 mm southeast horizontal and 42.7 mm upward vertical displacements. The coseismic ascending InSAR displacement maps illustrate a continuous and smooth NE-trending elliptical shape deformation pattern with a maximum of ∼29 cm of displacement away from the satellite. We use 25 broad-band teleseismic P-waveforms to estimate the focal mechanism of the main shock. A joint uniform inversion of InSAR, GNSS and teleseismic data reveals a NW-dipping SW-striking fault and a primarily normal-faulting earthquake with a minor right-lateral strike-slip component. The static slip distribution of the InSAR coseismic maps localizes variable slip at depths between 50 and 81 km with a maximum amplitude >3 m at 60–75.5 km depth, rupturing the oceanic crust of the subducted slab. The kinematic slip distribution exhibits a well-constrained slip pattern with a nucleation depth of 65 km. The source time function indicates that the earthquake reaches its maximum moment tensor release at ∼8 and ∼16 s. The NE-trend of the Saravan earthquake slip pattern, the orientation of the volcanic arc, and the distribution of the intraslab intermediate-depth normal earthquakes provide new insights into slab geometry in the central Makran subduction zone. We suggest that the slab bending at the hinge of subducting Arabian Plate is oblique along a NE–SW direction parallel to the volcanic arc rather than the shoreline or deformation front, and it is likely to be the reason for an oblique volcanic arc in the Makran subduction zone. These new constraints on the Makran slab geometry will help further studies in establishing realistic coupling maps for seismic hazard assessment. [ABSTRACT FROM AUTHOR]

• The software supports space geodetic data processing, precise positioning and orbit determination, and multi-source fusion navigation. • The core computational engines are written using C++ language and apply efficiency optimization algorithms such as parallel computing, with modular structure, cross-platform capabilities and efficient performance. • The software provides both client and server functions for high-precision navigation services, and centimeter-level multi-source fusion navigation can be achieved in urban scenarios though the integrated system of PPP-RTK/MEMS/VIS/LiDAR. The software platform named GNSS + REsearch, Application and Teaching (GREAT) has been designed and developed by Wuhan University for satellite geodesy and multi-source fusion navigation. GREAT is a comprehensive software platform based on C++ language, with modular structure, cross-platform capabilities and efficient performance. The software mainly focuses on space geodetic data processing, precise positioning and orbit determination, and multi-source fusion navigation. With the integration of multiple space geodetic techniques at observation level, GREAT can achieve the determination of global geodetic parameters. Meanwhile, GREAT can also achieve real-time precise orbit and clock determination by processing GNSS data from globally distributed stations, and the accuracies are about 3–6 cm for orbit and 0.1–0.4 ns for clock. Based on high-precision orbit and clock products, centimeter-level onboard positioning accuracies can be achieved with PPP-RTK in open-sky scenarios. Furthermore, centimeter-level multi-source fusion navigation can be achieved in urban scenarios though the integrated system of PPP-RTK/MEMS/VIS/LiDAR. Additionally, efficiency optimization algorithms such as parallel computing are applied to enable the software to handle the data-intensive and calculation-intensive situations. [ABSTRACT FROM AUTHOR]

SUMMARY: The prominent Pamir plateau holds considerable significance in comprehending the processes of Asian continental collisional orogeny. However, due to harsh natural conditions and low seismic activity within the Pamir hinterland, our understanding of this region remains deficient. Recent major events and the accumulation of geodetic observations present a rare opportunity for us to get insights into the tectonic activities and orogenic processes occurring in this region. First, employing Sentinel-1 and Advanced Land Observation Satellite (ALOS)-2 Synthetic Aperture Radar (SAR) images, we acquire coseismic displacements associated with the most recent earthquakes in 2015 and 2023. Subsequently, we conduct the source models inversion with the constraints of surface displacements based on a finite-fault model. Our results reveal displacements ranging from −0.8 to 0.8 m for the 2015 Mw 7.2 Tajik earthquake and −0.25 to 0.25 m for the 2023 Mw 6.9 Murghob event, respectively. The optimal three-segment model for the 2015 event ruptured a fault length of 89 km with a surface rupture extending 59 km along the Sarez–Karakul fault (SKF), characterized predominantly by left-lateral strike-slip motion, with a maximum slip of 3.5 m. Meanwhile, our preferred uniform slip model suggests that the 2023 event ruptured an unmapped fault in the southern Pamir region with a strike angle of 31° and a dip angle of 76.8°. The distributed slip model indicates that the 2023 event ruptured a fault length of 32 km, resulting in an 8 km surface rupture. This event is characterized by left-lateral strike slip, with a peak slip of 2.2 m. Secondly, the Coulomb stress calculations demonstrate that the 2023 event was impeded by the 2015 event. Finally, interseismic Global Positioning System data revel a relative motion of 3.4–5.7 mm yr−1 in the N-S component and 3.2–3.8 mm yr−1 in the E-W component along the SKF in the Pamir hinterland, respectively. These N-S direction strike-slip activities and slip behaviours support an ongoing strong shear and extension in the Pamir regime, which is a response to the oblique convergence between the Indian and Eurasian plates. [ABSTRACT FROM AUTHOR]

Atmospheric rivers (ARs) deliver significant and essential precipitation to the western United States (US) with consequential interannual variability. The intensity and frequency of ARs strongly influence reservoir levels, mountain snowpack, and groundwater recharge, which are key drivers of water‐resource availability and natural hazards. Between October 2022 and April 2023, western states experienced exceptionally heavy precipitation from several families of powerful ARs. Using observations of surface‐loading deformation from Global Navigation Satellite Systems, we find that terrestrial water‐storage gains exceeded 100% of normal within vital California watersheds. Independent water‐storage solutions derived from different data‐analysis and inversion methods provide an important measure of precision. The sustained storage increases, which we show are closely associated with ARs at daily‐to‐weekly timescales, alleviated both meteorological and hydrological drought conditions in the region, with a lag in hydrological‐drought improvements. Quantifying water‐storage recovery associated with extreme precipitation after drought advances understanding of an increasingly variable hydrologic cycle. Plain Language Summary: Human communities in the western United States rely on seasonal mountain snowpack and precipitation for agriculture, industry, and the civilian water supply. Over the past two decades, increasingly severe drought conditions have plagued western states. In this study, we investigate gains in water storage related to recent atmospheric rivers, which are long and narrow corridors of atmospheric moisture associated with extreme precipitation, using an interdisciplinary approach called hydrogeodesy. Hydrogeodesy uses satellite‐ and ground‐based sensors to track subtle changes in the shape of the Earth and its gravity field caused by the redistribution of water through the Earth system. By treating the Earth as a natural scale, we can infer how much water is gained or lost from a particular area over time. Advancing our understanding of water‐resource availability, the Earth's water cycle, and the Earth's changing climate is critical for improving water‐resource management, sustaining natural ecosystems, and mitigating natural hazards. Key Points: We use surface deformation to assess changes in terrestrial water storage (TWS) associated with families of strong atmospheric rivers (ARs) in 2022–2023Large jumps in mountain water storage from ARs spurred recoveries from major California droughts in 2012–2015 and 2019–2022Early‐season water‐storage gains, driven by ARs, nearly equal precipitation inputs, indicating extensive reservoir recharge [ABSTRACT FROM AUTHOR]

The GRACE (Gravity Recovery and Climate Experiment) satellite, operational from its launch in 2002 until October 2017, documented critical changes in global terrestrial water storage, significantly advancing the fields of gravity field analysis, hydrological variations, and environmental monitoring. This study investigates the thematic evolution of 2,966 SCIE-indexed publications on GRACE satellite applications from 2002 to 2022, utilizing co-occurrence network mapping and complex network analysis. Our results indicate a steady growth in GRACE satellite application research, with early publications (2002-2004) achieving an average citation rate exceeding 100, underscoring their substantial impact. Keyword clustering identified four primary research themes: Hydrology and Water Resources, Atmospheric and Environmental Science, Geophysical and Temporal Analysis, and Polar and Glaciological Studies. Over time, these themes have expanded and deepened, transitioning from initial focuses on gravity field computations to hydrological applications, sea level studies, and more specific investigations into water resources, climate change, and advancements in satellite geodesy. Recent research has particularly concentrated on groundwater and water storage issues. Geographically, the United States leads in publication output, impact, and international collaborations, with China following in publication count and network centrality, albeit with potential for improved impact. European countries demonstrate significant influence and centrality within the cooperation network. The evolution index of the international cooperation network shows a significant increase in connectivity from 2002 to 2022, with closer cooperation between countries. There is notable growth in both the number and intensity of collaborations, as evidenced by the rising average degree and average weighted degree. Overall, these indices underscore the evolution towards a more connected and globally integrated research network in GRACE satellite research. Looking forward, technological advancements, enhanced international collaboration, and integration with other data sources will drive future research in GRACE satellite application research, with important implications for addressing global environmental and climate challenges. [ABSTRACT FROM AUTHOR]

The processing of hundreds of Synthetic Aperture Radar (SAR) images acquired by two satellite systems: Sentinel‐1 and COSMO‐SkyMed reveals a decade of ground deformation for a ∼0.5 km diameter area around the summit crater of the only active carbonatitic volcano on Earth: Ol Doinyo Lengai in Tanzania. Further decomposing ascending and descending orbits when the appropriate SAR data sets overlap allow us to interpret the imaged deformation as ground subsidence with a significant rate of ∼3.6 cm/yr for the pixels located just north of the summit crater. Using geodetic modeling and inverting the highest spatial resolution COSMO‐SkyMed data set, we show that the mechanism explaining this subsidence is most likely a deflating very shallow (≤1 km depth below the summit crater at the 95% confidence level) magma reservoir, consistent with geochemical‐petrological and seismo‐acoustic studies. Plain Language Summary: We used data from two satellite systems, Sentinel‐1 and Cosmo‐SkyMed, to study Ol Doinyo Lengai, the only active carbonatitic volcano on Earth located in Tanzania. We analyzed hundreds of radar satellite images over a decade to understand changes in the ground deformation. By separating data from different orbits of the satellites and comparing them, we found that the ground at the volcano's summit was sinking at a rate of approximately 3.6 cm per year. Through simple geodetic modeling, we concluded that this sinking was likely caused by a shallow deflating magma reservoir, less than one km deep below the summit. This conclusion aligns with other scientific studies focusing on the volcano's petrology and geophysics. Key Points: InSAR time series show a ∼0.5 km diameter subsiding area around the summit crater at Ol Doinyo LengaiThe subsidence is likely due to a deflating shallow magma reservoir (point‐source)The modeled reservoir is less than 1 km deep below the summit crater, consistent with geophysical and geochemical studies [ABSTRACT FROM AUTHOR]

Improving the accuracy of zenith tropospheric delay (ZTD) models is an important task. However, the existing ZTD models still have limitations, such as a lack of appropriate vertical adjustment function and being unsuitable for China, which has a complex climate and great undulating terrain. A new approach that considers the time-varying vertical adjustment and delicate diurnal variations of ZTD was introduced to develop a new grid ZTD model (NGZTD). The NGZTD model employed the Gaussian function and considered the seasonal variations of Gaussian coefficients to express the vertical variations of ZTD. The effectiveness of vertical interpolation for the vertical adjustment model (NGZTD-H) was validated. The root mean squared errors (RMSE) of the NGZTD-H model improved by 58% and 22% compared to the global pressure and temperature 3 (GPT3) model using ERA5 and radiosonde data, respectively. The NGZTD model's effectiveness for directly estimating the ZTD was validated. The NGZTD model improved by 22% and 31% compared to the GPT3 model using GNSS-derived ZTD and layered ZTD at radiosonde stations, respectively. Seasonal variations in Gaussian coefficients need to be considered. Using constant Gaussian coefficients will generate large errors. The NGZTD model exhibited outstanding advantages in capturing diurnal variations and adapting to undulating terrain. We analyzed and discussed the main error sources of the NGZTD model using validation of spatial interpolation accuracy. This new ZTD model has potential applications in enhancing the reliability of navigation, positioning, and interferometric synthetic aperture radar (InSAR) measurements and is recommended to promote the development of space geodesy techniques. [ABSTRACT FROM AUTHOR]

Tectonic plate motions feed the earthquake cycle—a process whereby stress along crustal faults slowly increases over decade– or century–long periods, to then suddenly drop during earthquakes. Steadiness of plate motions during such cycles has long been a central tenet in models of earthquake genesis and of faults seismic potential, and can be tested against measurements of contemporary plate motions available from Global Navigation Satellite Systems (GNSS). Here we present analyses of GNSS data from Central and Northern Italy that illuminate the motion of the Adria microplate over a period of 6 years preceding the MW 6.3, 6 April 2009 L'Aquila (Italy) earthquake. We show that the motion of the whole Adria microplate changed before the 2009 earthquake, and slowed down by around 20%. We demonstrate with quantitative models that the torque required upon Adria in order to drive such a kinematic change is consistent with what is imparted to Adria by temporal stress variations occurring during the late interseismic phase of the 2009 L'Aquila earthquake cycle. The inference that plate motions can be influenced by, and thus sensitive to, earthquake cycles offers an additional perspective to assessing the seismic potential of tectonic margins. Plain Language Summary: Earth's outer shell is divided into a number of units—the tectonic plates—that move relative to each other at rates of few mm to cm per year. These relative motions are at the origin of the slow accumulation, along tectonic margins, of energy that is later released suddenly via earthquakes—a decade/century–long process generally referred to as earthquake cycle. It is commonly assumed that plate motions remain steady over such cycles. This is a central assumption in virtually all models of earthquake origin and seismic hazard. The ability to measure via geodetic techniques the contemporary motions of tectonic plates over periods of few years makes it possible to test the assumption above against observations. Here we focus on the Adria microplate, a tectonic unit comprising the Northern and Central parts of Italy, and accommodating the motion of Africa toward Eurasia. We show that the geodetically–observed motion of Adria slowed down during the years immediately preceding the MW 6.3 earthquake that occurred on 6 April 2009 near the city of L'Aquila, Italy, which is located along the southwestern tectonic margin of Adria. We demonstrate that the force required to slow down the Adria motion is similar to that developing along the portion of crustal fault that later generated the 2009 L'Aquila earthquake. Key Points: Adria microplate motion observed from Global Navigation Satellite Systems data slowed down by around 20% in the years preceding the 2009 L'Aquila earthquakeThe slowdown is larger than what permitted by data uncertainties or the impact of data noise, and is thus deemed tectonically meaningfulThe Adria motion slowdown requires a force upon Adria consistent with that imparted to Adria by the interseismic stress gain prior to 2009 [ABSTRACT FROM AUTHOR]

Modelling of the movements at the interface of the Amur and Okhotsk plates within the Sakhalin Island was performed using repeated satellite measurements on the Sakhalin Island and the nearest continental zone for the period of 2016–2021, as well as previously published data. When modelling fault-block kinematics, well-known relations were used to calculate reverse movements for buried rectangular dislocations in an elastic medium, which were implemented in the TDEFNODE software package. In the process of modelling the movements, the measured horizontal components of GNSS (Global Navigation Satellite System) velocities, the boundary and the mutual kinematics of the Amur and Okhotsk plates relative to the North American Plate according to the NNR-MORVEL56 model were used as the input data. This approach revealed persistent deviations in the direction of the simulated displacements of the Earth's surface from the observed ones, which can be explained by the discrepancy between the a priori specified kinematics of the blocks and the observed movements. To eliminate the systematic discrepancy, it was necessary to allow the possibility of updating the mutual kinematics of the blocks. The repeated calculations, with the same input data but in a problem formulation that allowed refinement of block kinematics, led to suppression of systematic discrepancies between the model and measured displacements while retaining the random scatter. The movement parameters of the Amur and Okhotsk plates, which were refined during the modelling, show typical slight differences from the movement parameters of the corresponding large lithospheric plates (the Eurasian and North American plates), from which they are separated into independent blocks in modern constructions. The calculated locking coefficients in the Sakhalin segment of the interplate boundary reach maximal values at depths of 20–30 km. The obtained locking pattern at the plate interface is compared with the sources of the largest earthquakes in the last 30 years in the considered area, viz., Neftegorsk (May 27, 1995) and Uglegorsk (April 4, 2000) earthquakes, which are found to be associated with zones of maximal locking and a high locking gradient, both in the dip and strike directions. [ABSTRACT FROM AUTHOR]

The significance of adjustment and computation studies has grown in recent years, influencing allied fields like arithmetic and satellite geodesy. This empirical study explores the effectiveness of various soft and traditional regression methods in correcting survey field data. Specifically, it investigates soft computing techniques such as back-propagation artificial neural network (BPANN), radial basis function artificial neural network (RBFANN), generalized regression artificial neural network (GRANN), and traditional regression methods like polynomial regression model (PRM) and least square regression (LSR) techniques. The study aims to fill the knowledge gap regarding soft computing strategies for modifying real-time kinematics (RTK) GPS field data and the ongoing debate between artificial intelligence techniques (ANN) and traditional methods on which technique offers the best results in modifying survey field data. Performance criteria, including horizontal displacement (HE), arithmetic mean error (AME), arithmetic mean square error (AMSE), minimum and maximum error values, and arithmetic standard deviation (ASD), were used to assess each model technique. Statistical analysis revealed that RBFANN, BPANN, and GRANN achieved superior accuracy compared to conventional techniques (PRM and LSR) in adjusting real-time kinematics GPS data. RBFANN outperformed BPANN and GRANN in terms of AME, AMSE, and ASD of their horizontal displacement. These findings suggest that soft computing techniques enhance real-time kinematics GPS field data adjustment, addressing critical issues in accurate positioning, particularly in Ghana. This study contributes to the knowledge base for developing an accurate geodetic datum in Ghana for national and local objectives. This will lay a foundation for the global determination of exact positions in Ghana. RBFANN emerges as a promising option for real-time kinematics GPS field data adjustment in topographic surveys. However, care should be taken to check issues of data overfitting. [ABSTRACT FROM AUTHOR]

The mass transport of volatiles on Mars represents a seasonally changing load on the surface of the planet. Like on Earth, as mass is redistributed across the planet, the surface responds in a complex manner becoming displaced downwards or upwards. The magnitude and extent of displacement depend on the properties of the load and mechanical properties of the planetary interior. Based on new estimates of the height variation of the seasonal polar caps (SPCs), we predict local surface displacements of up to tens of millimeters with a strong degree 1 signal throughout the Martian year. The long‐wavelength portion of the displacement is potentially observable, with a magnitude of a few millimeters, located away from the SPC where one could realistically measure it with a landed or orbital mission. We also model the direct contribution of this process to observable time variable gravity, where we find the zonal coefficients to be in line with previous measurements, although with a smaller magnitude. Future measurements of this displacement could be used to help elucidate the composition of the interior of Mars using this process as a probe into the Martian interior. Furthermore, more refined measurements of time‐variable gravity would be a powerful tool in constraining the pole‐to‐pole volatile cycle present on Mars. Plain Language Summary: Mars has seasons that are similar to Earth's because of its axial tilt. This causes the CO2 polar caps of Mars to grow and shrink depending on the time of year. This change in mass causes the surface of Mars to physically displace in response to the change in mass. The magnitude of this displacement is based upon the change in the height of the polar caps and the interior properties of Mars, as a more rigid planet would resist this displacement more. Using new estimates of the height variations, we model what the magnitude and pattern of the displacement look like across Mars. We find displacements of up to tens of millimeters at the poles and a few millimeters closer to the equator. Measurement of this displacement and changes in gravity could help determine the interior structure of Mars and alleviate conflicting models of how Mars formed. Modern landed instruments, such as a geodetic station, and orbital instruments, such as altimeters and interferometric synthetic aperture radar, have the capability to do this. Key Points: Global seasonal displacements of the surface of Mars are caused by the deposition and sublimation of CO2 at the polesWe find its magnitude to be as high as centimeters and evaluate the needed measurement precision to constrain the interior of MarsThis reported displacement and gravity perturbation could be measured by a dedicated geodetic instrument or time‐variable gravity mission [ABSTRACT FROM AUTHOR]

Seismic moment accumulation rate is a fundamental parameter for assessing seismic hazard. It can be estimated geodetically from either fault‐based modeling, or strain rate‐based calculations, where fault‐based models largely depend on the rheological layering and the number of faults. The strain‐rate method depends on an unknown (Kostrov) thickness used to convert strain rate into moment rate. In Part 1 of this study, we use three published fault‐based models from southern California to establish the value of the Kostrov thickness such that the total moment from the strain‐rate approach, calculated from the fault model‐predicted strain rate, matches the fault‐based approach. Constrained thickness estimates of 7.3, 9.7, and 11.5 km (6.4–13.0 km, including uncertainties) suggest that the 11 km value used in previous studies may be too large and a lower value may be more accurate. In Part 2 we use calibrated values of Kostrov thickness, along with the latest compilation of GNSS velocity data, to partition moment rate into on‐fault and off‐fault moment rate, where off‐fault varies from 32%–43% of the total moment rate. The largest uncertainty is related to the method used to interpolate sparse GNSS data. Lastly, we compare our estimates of total moment rate (mean: 2.13 ± 0.42 × 1019 Nm/yr) with the historical seismic catalog. Results suggest that including uncertainties in Kostrov thickness brings fault‐based geodetic moment rate closer to the seismic moment release (particularly when aseismic afterslip is accounted for), while the (uncertain) values of off‐fault moment rate push geodetic moment rates to be larger than seismic moment rates. Plain Language Summary: One commonly‐used method of evaluating the future earthquake potential of a known fault is to estimate the moment rate accumulating along that fault. In other words, one can estimate how much earthquake energy is accumulating over time, caused by the forces that propel plate boundary motion along fault systems. Two ways to do this are: (a) using detailed fault models of plate boundary motion, which are constrained by satellite‐based measurements of surface motion or (b) using those satellite‐based measurements directly through the estimation of regional strain rate. Here, we investigate the uncertainties present in the latter method by comparing previously published estimates of fault‐based moment rate, with their equivalent strain rate‐based versions. We estimate uncertainties related to the strain‐rate based method, which can lead to an over‐ or under‐estimation of earthquake potential on a given fault system. In addition, we explore the off‐fault moment rate accumulation in southern California which can help identify areas of enhanced moment accumulation and thus increased seismic hazard. Key Points: Previously published fault‐based models can constrain a Kostrov thickness range of 6.4–13.0 km, including uncertaintiesDifferences between strain rate moment estimates and fault‐based estimates suggest 32%–43% off‐fault moment rate in southern CaliforniaThe largest uncertainty in estimating moment rate from strain rate is the degree of smoothing used to estimate strain from geodetic data [ABSTRACT FROM AUTHOR]

The Global Navigation Satellite System—Acoustic ranging combination technique (GNSS-A) is a seafloor geodetic observation technique that achieves an accuracy of centimetres by combining high-rate GNSS data with acoustic ranging. The technique determines the seafloor position by acoustic ranging between the sea surface and multiple seafloor stations, using GNSS data from the sea surface station. Here, the gradient state of the underwater sound speed structure (SSS) is a significant source of error. The open-source software GARPOS can reduce the effect from underwater gradient structures by retrieving the underwater disturbance as a parameter projected onto the sea surface and seafloor. To evaluate the effects of underwater disturbances, a quantitative comparison of the model parameters is necessary. In this study, we developed a representation method to evaluate features of the ocean field. Here, the expression method was described in the order of a formulation and an interpretation in the case of a 2-D cross-section and extension to the case of an actual 3-D field. This method makes it possible to evaluate SSS states in the GNSS-A observations. As an example, we showed the correlation between the anomaly of the expressed ocean state and the anomaly of the seafloor station position, showing that this expression method is an effective index for correcting bias errors. Additionally, we used the data from sites located in the Kuroshio area, a strong current near Japan, to show that the ocean state can be quantitatively interpreted using this expression method. [ABSTRACT FROM AUTHOR]

The wide-swath altimeter satellite Surface Water and Ocean Topography (SWOT) will provide high spatiotemporal resolution sea surface heights (SSHs), which is crucial for studying the impact of observation errors on marine gravity recovery. This study uses simulated SWOT data to derive deflection of the vertical (DOV) and gravity anomalies in the northern South China Sea. We quantified the impact of SWOT errors on DOV and gravity anomalies, and analysed the contributions from different directions of geoid gradient. The results show that the geoid gradient in the cross-track direction significantly improves gravity field recovery by enhancing the precision of east component of DOV. For one-cycle SWOT observations, phase errors emerge as the most impactful error affecting both DOV and gravity anomalies, followed by random errors. 2-D Gaussian filtering and the tilt correction proposed in this study could effectively mitigate their impact. Using the corrected data for DOV computation, the precision in the east and north components improves by 75.32 and 46.80 per cent, respectively, while enhancing the accuracy of the gravity field by 70.23 per cent. For 17-cycle data, phase errors and random errors remain the predominant factors affecting DOV and gravity anomalies, but their impact diminishes with an increase in SWOT observations. Our results indicate that marine gravity accuracy improves by approximately 70 per cent compared to a single cycle. Whether for single-cycle or multicycle data, the impact of phase errors is roughly twice that of random errors. These data processing strategies can serve as valuable references for wide-swath altimeter data processing, aiming to advance the precision and resolution of marine gravity field recovery. [ABSTRACT FROM AUTHOR]

Previous studies have shown that it is difficult to determine whether the 2015 Pishan earthquake occurred on a uniform fault or a ramp-flat fault with variable dip angles due to the similar goodness of data fit to coseismic and afterslip models on these two fault models. Here, we first present the InSAR deformation obtained from both ascending and descending orbits, covering the coseismic period and cumulative 5-yr period after the 2015 Pishan earthquake. We then determine the preferred fault geometry by the spatial distributions between the positive Coulomb failure stress change triggered by main shock and the afterslip. Based on the preferred fault model, we finally use a combined model to determine the contributions of elastic and viscoelastic deformation in the post-seismic deformation. We find that the Pishan earthquake prefers to occur on a ramp-flat fault, and the coseismic slip is mainly distributed at a depth of 9–13 km, with a maximum slip of about 1.3 m. The post-seismic deformation is primarily governed by afterslip, as the poroelastic rebound-induced deformation fails to account for the observed post-seismic deformation and the contributions from the viscoelastic relaxation mechanism can be considered negligible in the combined model. Moreover, the modelled stress-driven afterslip and observed kinematic afterslip have good consistency, and the difference between the root mean square error of the two afterslip models is only 4.3 mm. The results from the afterslip model indicate that both of the updip and downdip directions distribute the afterslip, and slip in the updip direction is greater than that of the downdip direction. Meanwhile, the maximum cumulative afterslip after 5 yr is approximately 0.26 m which is equivalent to a released seismic moment of a M w 6.47. [ABSTRACT FROM AUTHOR]

Movements and deformations of ground surface at the Almaz-Zhemchuzhina deposit are studied using surveying techniques. The source data in estimation of parameters and patterns of the stress–strain behavior were observations over the recent geodynamic movements using survey markers and GPS / GLONASS technologies. The proposed scientific approach and guidelines on the use of the studies of trend and cycling geodynamic movements made it possible to determine the natural stress–strain parameters and to accomplish zoning of the test area by the intensities of the movements. [ABSTRACT FROM AUTHOR]

Abstract—The geodynamics of Northern Eurasia has been analyzed based on repeated coordinate solutions for GNSS stations throughout the Russian Federation territory from 2015 to the present. Two sources of data were used for this purpose: observations at the stations of the Russian Fundamental Astro-Geodetic Network (FAGN) and stations of the International GNSS Service (IGS) with permanent satellite tracking. This data set allowed one to estimate correctness of the block kinematics of the Eurasian plate in three tectonic plate motion models: NUVEL-1A, NNR-MORVEL-56, and ITRF2014. The analysis of the misfits between the observed and model velocities has shown that these misfits have a systematic component in the vicinity of the East European Platform, which differs for each of three models. In addition to analyzing the block kinematics of the Eurasian Plate, we also evaluated its internal stability. For this purpose, we calculated the areal deformations of Northern Eurasia using the finite element method. To this end, the processing results of two original datasets were complemented by the results for the observation data from the global dataset of the Nevada Geodetic Laboratory. Besides interplate boundary deformations, which are consistent with existing ideas of the geodynamics of Northern Eurasia, the strain field analysis also revealed intraplate deformations distributed consistently with the configuration of the Northern Eurasia cratons. [ABSTRACT FROM AUTHOR]

Physical heights is one of the most important topics in physical geodesy. Their original concept, introduced in the 19-th century, defined physical heights as lengths of plumblines of the Earth's gravity field between the geoid and points of interest. There are orthometric heights of surface points, that have been traditionally estimated by spirit levelling and measured gravity; however, the knowledge of the density distribution of topographic masses (masses between the geoid and Earth's surface) is required that significantly affects their determinability. This was also the main reason why a new type of physical heights was proposed in the mid of the 20-th century. Normal heights approximate orthometric heights in a sense that the Earth's gravity field is replaced by the normal gravity field, an analytic model based on the theory of an equipotential ellipsoid. This height system has been introduced since that time in different countries in Europe and beyond. Contrary to the classical height system based on orthometric heights, its counterpart based on normal heights may have slightly different definitions. Moreover, normal heights are often defined as heights of points above the quasigeoid. This contribution reviews alternative definitions of normal heights and respective height systems. It is argued that both orthometric and normal heights refer to the geoid. In the case physical heights are estimated by satellite positioning, normal heights must be computed through the height anomaly estimated at each point of interest, whether it is below, at or above the Earth's surface. On the contrary, orthometric heights of all points along the same plumbline, be it below, at or above the Earth's surface, are estimated by introducing one value of the geoid height. Normal heights of surface points can be estimated by spirit levelling easier than orthometric heights as no topographic mass density hypothesis is required; however, one has to keep in mind the gravity field approximation used both for their definition and realization. [ABSTRACT FROM AUTHOR]

Interferometric synthetic aperture radar (InSAR) decorrelation that creates great challenges to phase unwrapping has been a critical issue for mapping large earthquake deformation. Some studies have proposed a 'remove-and-return model' solution to tackle this problem, but it has not been fully validated yet, and therefore has rarely been applied to real earthquake scenarios. In this study, we use the 2023 M w 7.8 and 7.6 earthquake doublet in Turkey and Syria as a case example to develop an iterative modelling method for InSAR-based coseismic mapping. We first derive surface deformation fields using Sentinel-1 offset tracking and Sentinel-2 optical image correlation, and invert them for an initial coseismic slip model, based on which we simulate InSAR coseismic phase measurements. We then remove the simulated phase from the actual Sentinel-1 phase and conduct unwrapping. The simulated phase is added back to the unwrapped phase to produce the final phase measurements. Comparing to the commonly used unwrapping method, our proposed approach can significantly improve coherence and reduce phase gradients, enabling accurate InSAR measurements. Combining InSAR, offset tracking and optical image correlation, we implement a joint inversion to obtain an optimal coseismic slip model. Our model shows that slip on the Çardak Fault is concentrated on a ∼100 km segment; to both ends, slip suddenly diminished. On the contrary, rupture on the East Anatolian Fault Zone propagated much longer as its geometry is fairly smooth. The iterative coseismic modelling method is proven efficient and can be easily applied to other continental earthquakes. [ABSTRACT FROM AUTHOR]

Plate-coupling estimates and previous seismicity indicate that portions of the Makran megathrust of southern Pakistan and Iran are partially coupled and have the potential to produce future magnitude 7+ earthquakes. However, the GPS observations needed to constrain coupling models are sparse and lead to an incomplete understanding of regional earthquake and tsunami hazard. In this study, we assess GPS velocities for plate coupling of the Makran subduction zone with specific attention to model resolution and the accretionary prism rheology. We use finite element model-derived Green's functions to invert for the interseismic slip deficit under both elastic and viscoelastic Earth assumptions. We use the model resolution matrix to characterize plate-coupling scenarios that are consistent with the limited spatial resolution afforded by GPS observations. We then forward model the corresponding tsunami responses at major coastal cities within the western Indian Ocean basin. Our plate-coupling results show potential segmentation of the megathrust with varying coupling from west to east, but do not rule out a scenario where the entire length of the megathrust could rupture in a single earthquake. The full subduction zone rupture scenarios suggest that the Makran may be able to produce earthquakes up to M w 9.2. The corresponding tsunami model from the largest earthquake event (M w 9.2) estimates maximum wave heights reaching 2–5 m at major port cities in the northern Arabian Sea region. Cities on the west coast of India are less affected (1–2 m). Coastlines bounding eastern Africa, and the Strait of Hormuz, are the least affected (<1 m). [ABSTRACT FROM AUTHOR]

This study acquires the coseismic deformation field and the high-frequency dynamic displacement of the M W 7.4 earthquake that occurred in Maduo, China, on 2021 May 22, based on the BeiDou Navigation Satellite System (BDS), and the comparison with the results obtained by the Global Positioning System (GPS) reveals that the two systems are certain differences in their ability to acquire the coseismic deformation field. The maximum difference in the horizontal coseismic deformation is <5 mm, and the maximum difference in the vertical coseismic deformation is 8.7 mm. The dynamic displacement waveforms of the 2021 M W 7.4 Maduo earthquake acquired by BDS and GPS are very similar, which confirms that BDS can acquire ground-shaking images with an accuracy comparable to that of GPS. Based on the empirical relationship equation of the peak ground displacement (PGD) and moment magnitude (M W), this study verifies and calculates both the M W of the 2021 M W 7.4 Maduo earthquake and the error and finds that the M W can be quickly and accurately obtained by using the empirical PGD and M W equations, and this M W value can be used as a supplementary means of calibrating the M W of the large earthquake early warning systems, which can be quickly determined by seismic wave data. Finally, by comparing the slip distributions inverted from the BDS and GPS coseismic deformation fields, this study finds that BDS is equally effective as GPS. [ABSTRACT FROM AUTHOR]

A major earthquake shook the Chinese county of Maduo, located in the Songpan-Ganzi terrane on the Tibetan Plateau, on 21 May 2021. Here, we investigate the post-seismic deformation process of this event, with the aim to understand the fault geometry, friction behaviour and regional rheology. To keep the self-consistency between co- and post-seismic deformation models, we first constrain the fault geometry and coseismic slip model of this event, which are directly used in modelling the post-seismic deformation. The coseimsic slip model reveals that the majority of coseismic slip is confined at the middle (3–15 km) of the brittle layer, leading to significant shallow slip deficit. Secondly, we obtain the post-seismic deformation in the first 450 d following the 2021 Maduo earthquake using the GPS and InSAR displacement time-series data. Thirdly, a combined model incorporating afterslip and viscoelastic relaxation is built to explain the observed post-seismic deformation. Our results suggest that the viscoelastic relaxation effect should be considered in the observation period, in order to avoid the unphysical deep afterslip in the ductile lower crustal layer. Combined analysis on viscosities inferred from this study and previous studies suggests a weak lower crust with steady-state viscosity of 1018–1019 Pa s beneath the Songpan-Ganzi terrane, which may give rise to the distributed shear deformation and the development of subparallel secondary faults within the terrane. Besides, the inferred afterslip on uppermost patches of the middle fault segment suggests a rate-strengthening frictional behaviour that may be related to the coseismic slip deficit and rupture arrest of the Maduo earthquake. [ABSTRACT FROM AUTHOR]

The south-eastern offshore of the Boso Peninsula in Japan periodically experiences short-term slow slip events (SSEs) every few years. On 2018 June, an SSE occurred with the maximum surface horizontal displacement reaching up to 4.7 cm by according to the operational global navigation satellite system (GNSS) network. This study performed a time-series analysis of interferometric synthetic aperture radar (InSAR) with Sentinel-1 SAR images to investigate detailed spatial pattern of surface displacements caused by the SSE. With the assistance of an atmospheric delay correction with a regional numerical weather model output, the InSAR time-series analysis successfully captured displacement signals in three paths, whose maximum amplitudes in line-of-sight directions were 1.46, 1.86 and −0.80 cm. A checkerboard test revealed that the resolution of the slip inversion was higher when InSAR was used than that using GNSS, especially in and around the inland. The slip inversion with the actual displacement data derived from the InSAR time-series analysis was performed with the L-curve optimization, showing that the estimated slip area was concentrated offshore south-eastward from the Boso Peninsula with the maximum slip of 5 cm and the estimated moment magnitude of 6.4. As similar to previous SSEs in the Boso Peninsula, a seismic swarm simultaneously occurred in the downdip area adjacent to the estimated slip with the SSE occurrence, suggesting a different friction characteristics between them. This study demonstrates usefulnesses of the InSAR observation for capturing detailed spatial characteristics of small-displacement events like SSEs and of the hybrid use of the externally derived delay correction with the time-series analysis to improve the displacement detection accuracy. [ABSTRACT FROM AUTHOR]

Earthquake source parameters can be estimated using seismological observations, but the identification of the fault responsible is often complicated by location uncertainties and the inherent ambiguity between nodal planes. Satellite Interferometric Synthetic Aperture Radar (InSAR) can be used to observe ground deformation and model fault geometry but is limited by climate conditions (water vapour) and ground coverage (dense vegetation). In the tropics, the atmosphere is dynamic and most regions are densely vegetated, making detecting coseismic deformation challenging. Here, we perform a systematic inspection of coseismic interferograms from Sentinel-1 SAR images, to assess their suitability for detecting coseismic deformation in Costa Rica. Using data from the seismological network, we target seven earthquakes between 2016 and 2020 with depths |$\le \, 20$| km and magnitudes M w 5.3–6.2. For each event, we use the seismic parameters to compute line-of-sight displacements for ascending and descending geometries and for both nodal planes and generate 12- and 24-d coseismic interferograms where available. We obtain interferograms with coseismic displacement signals for three of the seven earthquakes. We invert the geodetic data to retrieve the earthquake source parameters but the lack of offshore geodetic coverage causes trade-offs between parameters and large uncertainties. The Jacó and Golfito earthquakes likely occurred on the subduction interface and the geodetic locations were 6–9 km closer to the coast than previous seismic estimates. The Burica earthquake occurred on a shallow steeply dipping thrust fault in the outer forearc. For the other earthquakes, no coseismic deformation was detected due to atmospheric noise or poor coherence. These results demonstrate the suitability of 12-d Sentinel-1 interferograms for monitoring shallow earthquakes of magnitude > M w 5.7 in Central America. This approach can be used to begin a surface deformation catalogue for the region, which will ultimately help improve the understanding of active deformation processes and improve hazard maps. [ABSTRACT FROM AUTHOR]

On December 18, 2023, the MS 6.2 Jishishan earthquake occurred in the northeastern region of the Qinghai-Xizang Plateau, causing heavy casualties and property damage in Gansu and Qinghai Provinces. In this study, we integrate space imaging geodesy, finite fault inversion, and back-projection methods to decipher its rupture property, including fault geometry, coseismic slip distribution, rupture direction, and propagation speed. The results reveal that the seismogenic fault dips to the southwest at an angle of 29°. The major slip asperity is dominated by reverse slip and is concentrated within a depth range of 7-16 km, which explains the significant uplift near the epicenter observed by both the Sentinel-1 ascending and descending InSAR data. Moreover, the teleseismic array waveforms indicate a northwest propagating rupture with an overall slow rupture velocity of ~1.91 km/s (AK array) or 1.01 km/s (AU array). [ABSTRACT FROM AUTHOR]

To improve the accuracy of monthly temporal gravity field models for Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GRACE-FO) mission, a new series named HUST-Grace2024 is determined based on the updated L1B dataset (GRACE L1B RL03 & GRACE-FO L1B RL04) and the newest atmosphere and ocean de-aliasing product (AOD1B RL07). Compared to the previous HUST temporal gravity field model releases, we made some improvements on both updating background models and processing chain as follows. (1) During the satellite onboard events, the intersatellite pointing angles are calculated to pinpoint the outliers in K-band range rates (KBRRs) and accelerometer observations. To exclude outliers, the advisable threshold is respectively 50 mrad for KBRRs and 20 mrad for accelerations. (2) To relieve the impacts of KBRR noise in different frequencies, a hybrid data weighting method is proposed. Kinematic empirical parameters are used to reduce the low frequency noise, while a stochastic model is designed to relieve the impacts of random noise above 10 mHz. (3) a fully-populated scale factor matrix is used to improve the quality of accelerometer calibration. Analysis in spectral and spatial domain is then implemented, which demonstrates that HUSTGrace2024 has a noticeable reduction of 10% to 30% in noise level and remains consistent amplitudes over 48 basins in singal content compared with the official GRACE and GRACE-FO solutions. These evaluations confirm that our aforementioned efforts lead to a better temporal gravity field series. [ABSTRACT FROM AUTHOR]

The potential for future earthquakes on faults is often inferred from inversions of geodetically derived surface velocities for locking on faults using kinematic models such as block models. This can be challenging in complex deforming zones with many closely spaced faults or where deformation is not readily described with block motions. Furthermore, surface strain rates are more directly related to coupling on faults than surface velocities. We present a methodology for estimating slip deficit rate directly from strain rate and apply it to New Zealand for the purpose of incorporating geodetic data in the 2022 revision of the New Zealand National Seismic Hazard Model. The strain rate inversions imply slightly higher slip deficit rates than the preferred geologic slip rates on sections of the major strike‐slip systems including the Alpine Fault, the Marlborough Fault System and the northern part of the North Island Fault System. Slip deficit rates are significantly lower than even the lowest geologic estimates on some strike‐slip faults in the southern North Island Fault System near Wellington. Over the entire plate boundary, geodetic slip deficit rates are systematically higher than geologic slip rates for faults slipping less than one mm/yr but lower on average for faults with slip rates between about 5 and 25 mm/yr. We show that 70%–80% of the total strain rate field can be attributed to elastic strain due to fault coupling. The remaining 20%–30% shows systematic spatial patterns of strain rate style that is often consistent with local geologic style of faulting. Plain Language Summary: The potential for future earthquakes on faults is often inferred from velocities of the ground surface derived from satellite geodesy, but this approach can be challenging in complex deforming zones with many closely spaced faults. We present a new methodology for estimating the rate at which energy is accumulating on faults using measurements of surface strain rates. The method is applied to New Zealand for the purpose of incorporating geodetic data in the 2022 revision of the New Zealand National Seismic Hazard Model. We show that 70%–80% of the total deformation field can be attributed to energy accumulation on known active faults while the source of the remaining 20%–30% remains unknown. Along some of the major faults in New Zealand we find some important differences in rates of energy accumulation from what is expected from geologic data. Estimated rates are significantly lower than even the lowest geologic estimates on some faults in the fault system near highly‐populated Wellington. Key Points: We develop a method to invert geodetically derived strain rates for slip deficit rates on faultsWe find small but systematic differences between slip deficit rates and geologic slip ratesAbout 70%–80% of the surface strain can be attributed to elastic strain due to coupling on faults [ABSTRACT FROM AUTHOR]

The Gravity Recovery and Climate Experiment (GRACE) and its successor, GRACE Follow-On (GRACE-FO), have revolutionized the approach to monitoring global mass variations. However, the presence of several gaps, notably the continuous 11-month gap between the two missions, has generated a disruption in observations and hindered the analysis and application of the data. To address this problem, we have proposed a spectral domain gap-filling approach based on principal component analysis (PCA). Our simulation experiments demonstrate that the PCA gap-filling technique has significant potential to successfully reconstruct global mass variation and accurately capture real signals for most basins with an accuracy of less than 2 cm. When applied to actual missing data, our methodology delivers highly consistent results with previously published filling approaches, such as singular spectrum analysis and improved multichannel singular spectrum analysis method, for most of the global basins. Noteworthy, in the case of the Nelson basin, our PCA gap-filling method outperforms other methods in capturing seasonal signals and the return to a normal level of the terrestrial water storage changes in 2018. A comparison in the spectral domain indicates that the accuracy of the PCA-filling output is comparable to the original GRACE(-FO) data. Moreover, our method exhibits high generality, allowing for direct application to continuous GRACE(-FO) data without other additional data processing and without differentiating the types of missing data. Therefore, the proposed PCA gap-filling method offers exciting opportunities to guarantee the continuity of global mass change observations and benefit subsequent applications that require continuous data records. [ABSTRACT FROM AUTHOR]

Satellite altimetry provides major data sources for marine gravity recovery, and typical altimetry derived models, for example, DTU21 and SS V32.1, were usually released with 1 arcmin × 1 arcmin gridding interval. Their true resolution is much lower than the nominal ∼2 km level. By contrast, the in situ ship-borne measurements are considered to have better short-wavelength resolution. In this paper, we aim to propose a new method to fully utilize satellite altimetry data and ship-borne measurements, namely the frequency-domain fusion method, and give certain analysis of new method along with two spatial-domain fusion methods. Comprehensive analysis is focus on four aspects: gravity signals in fusion images, numerical verifications, power spectra, as well as coherence analysis. Initial evaluation indicates that, first, the frequency-domain fusion method has advantage in flexibility, since it can autonomously select dominant bands to fuse different data sets. Secondly, the new method retains medium-long wavelength signals from altimetry-derived model and effectively incorporate dominant short-wavelength signals of in-situ measurements, while the spatial-domain methods are essentially full-wavelength fusion and inevitably diminish the role of satellite altimetry. To some extent, the new method maximize the positive contribution of satellite altimetry measurements and efficiently exploit the benefits of ship-borne data. Finally, verification experiments were similarly designed in three regions with different amount and ratio of ship-borne data to thoroughly evaluate various methods. In two regions with gridded and dense along-cruise ship-borne data, the average accuracy of this frequency-domain fusion results is improved by 0.346 and 0.613 mGal, respectively. In a region with sparse ship-borne data, we still recommend using spatial-domain fusion methods since the new method is unable to align ship-borne data with model grid. It is concluded from the above analysis that the new method effectively incorporates the short-wavelength signals from ship-borne data into the altimetry-derived gravity field model, and it is significant that the new method maximizes the application of advantageous bands from different data sources. [ABSTRACT FROM AUTHOR]

High‐resolution present‐day earth surface deformation maps from satellites provide important data constraints, which help us better understand tectonic processes and analyze seismic hazards. Here, we use Sentinel‐1 Radar images (2014–2020) and accurate positioning measurements (2009–2019) to get a high‐resolution three‐dimensional earth surface velocity map for the northeastern Tibetan Plateau, and we invert the slip rate and coupling ratio of major regional faults. We find ∼4 mm/yr uplift along an arc from the Qilianshan to Lajishan, relative to the neighboring low‐elevation area to the east, which indicates ongoing rapid orogeny. We find transient deformation along the Laohushan and 1920 M8.5 Haiyuan rupture segments of the Haiyuan fault, whereas the western Haiyuan, southern Liupanshan, central Lajishan and central‐western West Qinling faults are essentially locked above 15–20 km, suggesting a potentially high seismic hazard. Plain Language Summary: The northeast Tibetan Plateau, which is impeded by the tectonically stable Ordos block, continues to grow in response to the far‐field India‐Eurasia collision. This region has several large‐scale active faults that hosted some destructive earthquakes in the last 100 years. Although intensively studied, the fault kinematics of those seismogenic faults are still not clear, mainly because of poor observational constraints. Hence, high‐resolution present‐day deformation maps are essential to answering this question, either of scientific or societal concern. We provide satellite‐based ground deformation rate maps with mm‐accuracy for this region. They show shallow fault creep along some segments of the Haiyuan fault which is better constrained than previous results, active tectonic uplift in the Lajishan. Our work gives new constraints for the seismic hazard for the Northeastern Tibetan Plateau case. Key Points: We derive a new high‐resolution three‐dimensional present‐day deformation map for the Northeastern Tibetan PlateauGeodetic data reveals ongoing rapid uplift along an accurate orogenic belt from the eastern Qilianshan and LajishanNew constraints for the seismic hazard analysis for the Northeastern Tibetan Plateau [ABSTRACT FROM AUTHOR]

More than 20 yr of measurement data of the gravity missions GRACE (Gravity Recovery And Climate Experiment) and GRACE-FO (GRACE-Follow-On) allow detailed investigations of long-term trends in continental terrestrial water storage (TWS). However, the spatial resolution of conventional GRACE/GRACE-FO data products is limited to a few hundred kilometres which restrains from investigating hydrological trends at smaller spatial scales. In this study GRACE and GRACE-FO data have been used to calculate TWS trends with maximized spatial resolution. Conventionally, GRACE/GRACE-FO is presented as a series of either unconstrained gravity fields post-processed with spatial low pass filters or constrained inversions commonly known as Mascon products. This paper demonstrates that both approaches to suppress spatially correlated noise are mathematically equivalent. Moreover, we demonstrate that readily inverting all available sensor data from GRACE/GRACE-FO for a single TWS trend map, together with annual variations and a mean gravity field, provides additional spatial detail not accessible from the standard products. The variable trade-off between spatial and temporal resolution as a unique feature of satellite gravimetry allows for gravity products that are tailored towards specific geophysical applications. We show additional signal content in terms of long-term water storage trends for four dedicated examples (Lake Victoria, Northwest India, Bugachany Reservoir and High Plains Aquifer) for which external information from other remote sensing instruments corroborates the enhanced spatial resolution of the new mean-field trend product. [ABSTRACT FROM AUTHOR]

We successfully detected widely distributed ground displacements for the 2023 Kahramanmaraş, Turkey, earthquakes by conducting interferometric synthetic aperture radar (InSAR) analyses using a ScanSAR observation mode. Major deformation extended approximately 350 and 150 km along the southern and northern strands bifurcating in the west of the East Anatolian Fault, produced by the main shock and the largest aftershock. The deformation map reveals that the ruptures propagated on the Erkenek, Pazarcık and Amanos segments on the southern strand and the Çardak segment on the northern strand. The fault plane of the northern strand bends approximately 45° at both edges with Z-shaped crank geometry. The bending fault at the western edge runs just along the Çardak segment but does not reach the Savrun segment, while at the eastern edge it deviates from known active faults such as Sürgü, Malatya faults and Doğansehır fault zone. A 3-D displacement map demonstrates that almost pure left-lateral fault motions were distributed along the two strands, with little vertical deformation. The moment magnitudes estimated from the slip distribution model were 7.82 and 7.66 for the southern and northern strands, respectively, with the Erkenek and Çardak segments having the largest released seismic moments on each strand, corresponding to approximately 31 and 57 per cent of the total, respectively. The Coulomb Failure Function change values indicate that the main shock can promote the largest aftershock with a standard value of the effective friction coefficient. Additionally, the unclamping effect controlled by the frictional property of the rock was a key factor in pulling the trigger of the seismic event on the northern strand. The historically accumulated and released seismic energies were imbalanced for the Pazarcık and Erkenek segments, suggesting that the 2023 event does not support a simple characteristic earthquake model; rather, it may be consistent with a supercycle model, in which the slip remnants from the characteristic earthquakes have been historically accumulated as coupling on a fault and released as huge earthquakes at longer intervals. [ABSTRACT FROM AUTHOR]

With strong technology improvement, especially GNSS, coordinate transformation has become an essential tool in everyday practice. For this reason, it is beneficial to have a good understanding of the mathematical process of coordinate transformation, as well as the method for calculating transformation parameters. The purpose of this article is to provide a detailed explanation of the coordinate transformation procedure and the calculation of transformation parameters for seven transformation models: 3-parameter, 5-parameter standard and abridged, 7-parameter, 8-parameter, 9-parameter, and 12-parameter. For each transformation model, a basic transformation equation, a procedure for calculating transformation parameters, inverse expression for reversible transformation, as well as characteristics of each model are provided. As an addition, for each model, a numerical example of calculating transformation parameters for the territory of the Republic of Croatia is provided. Additionally, for the example of the 7-parameter transformation, importance of reversible transformation, rotation convention, as well as the form of the rotation matrix used during transformation are demonstrated. [ABSTRACT FROM AUTHOR]

The receiver tracking error stochastic (RTES) model can improve GNSS precise point positioning (PPP) performance under ionospheric scintillation. However, it relies on scintillation products derived from ionospheric scintillation monitoring receivers (ISMRs), which means the RTES model cannot be used for abundant geodetic GNSS receivers. In this study, we propose an improved RTES, referred to as Impr_RTES model, to mitigate scintillation effects on geodetic GNSS receivers at low latitudes, where severe scintillation frequently occurs. In the Impr_RTES model, the tracking error variances at the output of code delay locked loop are calculated by using the index S4c, and these of phase locked loop are modeled by using the rate of total electron content index (ROTI) and S4c. Both S4c and ROTI can be derived from geodetic GNSS receivers. The performance of the Impr_RTES model is validated by using the data sets from ISMR and geodetic receivers, respectively. Using one month of GPS data collected at HNLW station installed with ISMR in Hainan of China from 1 to 28 February in 2023, statistical results indicate that the PPP solution based on Impr_RTES model can improve the positioning accuracy by approximately 22.6%, 23.8%, and 30.2% in the east, north, and up directions, respectively, over the elevation angle stochastic (EAS) model. Meanwhile, the positioning performance of Impr_RTES PPP is comparable to that of RTES PPP. For the GPS data from geodetic receivers, experimental results suggest that compared with EAS, the Impr_RTES model can obviously mitigate scintillation effects on PPP. Plain Language Summary: Ionospheric irregularities in the ionosphere can lead to rapid and random fluctuations in the amplitude and phase of GNSS signals transmitted through them, which is known as ionospheric scintillation. It can degrade GNSS precise point positioning (PPP) accuracy. The receiver tracking error stochastic (RTES) model can mitigate scintillation effects on GNSS PPP. However, this model is established by using the scintillation index S4 and the dedicated parameters products released by the ionospheric scintillation monitoring receivers (ISMRs). Compared with GNSS tracking stations installed with geodetic receivers, the number of the ISMR stations is very limited in the world. This study proposes an improved RTES (Impr_RTES) model for the geodetic receivers to mitigate scintillation effects of low latitudes on GNSS PPP. Using GPS data sets collected by both ISMR and geodetic receivers, experimental results indicate that the Impr_RTES can significantly improve positioning accuracy under ionospheric scintillation conditions. Key Points: Current receiver tracking error stochastic (RTES) model relies on ionospheric scintillation monitoring receiver productsImproved RTES model based on geodetic GNSS receiver is established to mitigate scintillation effects on precise point positioning (PPP)Positioning accuracy of GNSS PPP based on Improved RTES model is better than that of PPP based on elevation angle stochastic model [ABSTRACT FROM AUTHOR]

Convergent plate boundaries are often characterized by widely deformed zones, where coexisting tectonic processes and variable fault kinematics can occur. Here, we quantify this variability along the Africa‐Eurasia deformed boundary in southern Italy, based on the evaluation of geodetic strain rate by recent space geodesy observations and plate motions, which are integrated by main geometric properties of detected faults in the area. We propose a compilation of 160 known faults. We use numerical methods to predict fault kinematics and net slip rate, due to the geodetic deformation field with the inclusion of fault strain accommodation. The obtained tectonic setting is compared with the observable, showing a fault rake agreement of the 73%, which allows us to consider this approach potentially favorable to improve the knowledge of fault kinematics along diffuse plate boundaries, when fault properties are not directly available. Plain Language Summary: A boundary between two plates is not a single line but it is often a large area with diffuse deformation, simultaneous tectonic processes and complex geodynamics. Here, we analyze the Africa‐Eurasia convergent and deformed boundary in southern Italy, central Mediterranean, where the lineaments along which crustal blocks move, the faults, show variable motion directions. We integrated the data describing the accurate displacement of the Earth's surface coming from recent satellite observations and from global plate motion models, together with geometric characteristics of 160 known faults, which we compiled for the purpose of computing the deformation field, that is, the geodetic strain rate, and kinematics along the faults of the area, using numerical methods. The procedure to integrate geodetic and geological observed data allows us to model crustal deformation both offshore and onshore the study area, and the agreement of the 73% between observed versus predicted fault kinematics suggests that this approach can help to investigate tectonics deformation along diffuse plate boundaries worldwide, when fault properties cannot be directly observed. Key Points: We combine 392 recent Global navigation satellite system rates and the geometry of 160 faults of southern Italy to compute new strain rate field using numerical methodsWe present fault kinematics of the region and compare it to reference literatureWe obtain a tectonic setting which suggests this approach is useful to investigate fault kinematics along diffuse plate boundaries [ABSTRACT FROM AUTHOR]

The coastal environment represents a resource from both a natural and economic point of view, but it is subject to continuous transformations due to climate change, human activities, and natural risks. Remote sensing techniques have enormous potential in monitoring coastal areas. However, one of the main tasks is accurately identifying the boundary between waterbodies such as oceans, seas, lakes or rivers, and the land surface. The aim of this research is to evaluate the accuracy of coastline extraction using different datasets. The images used come from UAV-RGB and the Landsat-9 and Sentinel-2 satellites. The method applied for extracting the coast feature involves a first phase of application of the Normalized Difference Water Index (NDWI), only for satellite data, and consequent application of the maximum likelihood classification, with automatic vectorization. To carry out a direct comparison with the extracted data, a coastline obtained through a field survey using a Global Navigation Satellite System (GNSS) device was used. The results are very satisfactory as they meet the minimum requirements specified by the International Hydrographic Organization (IHO) S-44. Both the UAV and the Sentinel-2 reach the maximum order, called the Exclusive order (Total Horizontal Uncertainty (THU) of 5 m with a confidence level of 95%), while the Landsat-9 falls into the Special order (THU of 10 m with a confidence level of 95%). [ABSTRACT FROM AUTHOR]

Earthquake swarms represent a particular mode of seismicity, not directly related to the occurrence of large earthquakes (e.g., aftershocks) but rather driven by external forcing such as aseismic deformation or fluid migration in fault systems. Sometimes their occurrence overlaps with observable geodetic signals in space and time, indicating a direct link. However, the low resolution of geodetic observations tends to obscure the small scale spatial and temporal dynamics of swarms. In this work, we automatically extract clusters of seismicity related to the 2014 Alto Tiberina swarm sequence (Italy) using an unsupervised clustering approach that exploits space and time information of the seismicity. The quantitative characterization of each cluster indicates that the overall swarm is composed of spatially and temporally confined (sub) swarms each of which could potentially be driven by small‐scale aseismic deformation process. This observation aligns with similar findings during slow slip events in subduction zones. Plain Language Summary: An earthquake swarm is characterized by an elevated rate of earthquake occurrences in a specific region, surpassing the typical seismic activity, without being preceded by a major seismic event. Earthquake swarms are thought to be driven by mechanisms like slow deformation or the migration of fluids. In this study we take a closer look into the seismicity of an earthquake swarm in the Apennines in Italy, exploiting unsupervised machine learning methods. This approach indicates that the swarm sequence consists of a general, smooth increase in seismicity, occasionally punctuated by short accelerations of seismic activity. The subsequent analysis of the accelerated seismicity suggests a connection with several small, slow deformation processes that collectively constitute a large‐scale deformation process, as measured by geodetic data. Key Points: Combining hierarchical and density‐based clustering enables to automatically separate background and clustered seismicityThe quantitative analysis of the extracted clusters reveals a swarm‐like characterThe swarm‐like clusters further indicate relations to aseismic processes [ABSTRACT FROM AUTHOR]

Satellite Laser Ranging (SLR) is an established technique providing very accurate position measurements of satellites in Earth orbit. However, despite decades of development, it remains a complex and expensive technology, which impedes its further growth to new applications and users. The miniSLR implements a complete SLR system within a small, transportable enclosure. Through this design, costs of ownership can be reduced significantly, and the process of establishing a new SLR site is greatly simplified. A number of novel technical solutions have been implemented to achieve a good laser ranging performance despite the small size and simplified design. Data from the initial six months of test operation have been used to generate a first estimation of the system performance. The data include measurements to many of the important SLR satellites, such as Lageos, Etalon and most of the geodetic and Earth observation missions in LEO. It is shown that the miniSLR achieves sub-centimetre accuracy, comparable with conventional SLR systems. The miniSLR is an engineering station in the International Laser Ranging Service and supplies data to the community. Continuous efforts are undertaken to further improve the system operation and stability. [ABSTRACT FROM AUTHOR]

Marmara Region hosts a substantial part of the inhabitants in Turkey, more than 30 per cent of the total population in the cities of Istanbul, Bursa and Kocaeli. This region has experienced several large earthquakes in the past and is still under threat of destructive earthquakes in the future. There, subparallel strands of the North Anatolian Fault (NAF) expand into the region, distributing the earthquake hazards across the whole region. Thus, it is a key issue to investigate how the tectonic process is distributed between these subparallel strands to discriminate their individual earthquake hazards. In this context, we used GPS slip rates to quantify the slip partitioning of the subparallel strands of the fault system. In addition to available slip rates compiled by Bulut et al. and Kreemer et al. we analysed 71 GPS sites (51 continuous and 20 campaign-based) to intensify the GPS network in the region. GPS observations reveal 81.7, 7.7 and 10.7 per cent slip ratios for northern, middle and southern strands. These ratios are also verified by the time series analysis of continuous GPS stations, leading us to the conclusion that the northern strand of the NAF hosts substantially shorter recurrence periods and, therefore, in the long term, the highest earthquake hazard in the Marmara Region. [ABSTRACT FROM AUTHOR]

We study the 2016 January 21 (⁠|${{{M}}}_{\rm{w}}$|  5.9) and 2022 January 8 (⁠|${{{M}}}_{\rm{w}}$|  6.7) earthquake sequence that struck the Menyuan region in northwest China's Qinghai province. These two earthquakes are destructive events that occurred around/on the Lenglongling fault (LLLF). Here, we derive the line-of-sight displacement fields of the two earthquakes using Interferometric Synthetic Aperture Radar (InSAR) measurements of Sentinel-1 SAR data, and map the range and horizontal offset fields of the 2022 event using Sentinel-1 amplitude images and Planet-Lab optical images. Based on the offset maps, we determine the detailed surface rupture trace of the 2022 event. We perform slip inversions for the two earthquakes on triangle fault patches whose size increases with depth. Results show that the western branch segment of the 2022 event has a ∼0.5-m normal dip-slip motion. This result contradicts previous inferences on dip-slip sense of this branch segment. We identify a left-stepping fault structure with a ∼5-km step width in the transition zone between the Tuolaishan fault (TLSF) and LLLF, which may serve as a kinematic barrier to prevent further propagation of seismic rupture along the TLSF. Stress calculation shows that a stress drop of ∼0.4 bar produced by the 2016 event on a ∼5-km long LLLF segment may act as a negative stress barrier to suppress rupture propagation of the 2022 event toward the southeast of the LLLF. [ABSTRACT FROM AUTHOR]

High quality Interferometric Synthetic Aperture Radar (InSAR) interferograms are essential for determining surface deformation from InSAR time-series. However, InSAR interferograms are usually polluted by spatially correlated errors (SCEs), especially the unmodelled atmospheric phase delays. To mitigate spatially correlated errors and improve the quality of InSAR interferograms, we propose a new approach to incorporate the Global Navigation Satellite System (GNSS) data from continuously operating reference stations for enhancing InSAR interferograms via modelling SCEs as signals and solving the signals together with the systematic parameters using least squares collocation (LSC), which is referred to as the LSC-GInSAR approach. Our improvement for the GInSAR method of Neely et al. can correct more SCEs. The Sentinel-1 data over the southern Central Valley of California, USA, are processed with our LSC-GInSAR approach, which is compared to the GInSAR approach. The performance of the LSC-GInSAR approach is evaluated by external GNSS displacements. The results show that the LSC-GInSAR approach can effectively mitigate medium-to-long-wavelength SCEs. The displacements resolved by LSC-GInSAR are more consistent with the cGNSS observations than those resolved by GInSAR, with an average root mean square improvement of 14.3 per cent. In addition, the LSC-GInSAR approach reduced the average standard deviations of all 276 InSAR interferograms from 14.2 to 11.0 mm compared to that of the GInSAR approach. [ABSTRACT FROM AUTHOR]

In space geodetic techniques, the mapping functions (MFs) provide the relationship between zenith and slant tropospheric delays. The MFs are determined under the assumption of spherically layered atmosphere. However, the atmosphere is not spherically layered, and the asymmetry should be considered. Therefore, tropospheric gradients are taken into account. Nevertheless, tropospheric gradients alone can not fully represent the deviation from a spherically layered atmosphere, and hence cm level errors arise especially for low elevation angles. In this study, we present new approaches to modify the wet MF to reduce mismodelling of tropospheric delays. The delays in the study were calculated using ray-tracing algorithm based on ECMWF's ERA5 dataset. We first analyzed the performances of the new approaches. Then, two Precise Point Positioning (PPP) simulation studies and a real case study were carried out for two different regions namely Germany and Türkiye. According to the results, the proposed approaches reduce the modelling errors up to by a factor 6 for both regions. Besides, simulation studies show that the approaches improve the accuracies of the ZTDs and heights. In the practical application however, we could not find a clear improvement in the PPP analyze and this might be related to the ERA5 which can not be regarded error-free. [ABSTRACT FROM AUTHOR]

In the determination of the Earth gravity field in satellite geodesy, the inclination functions represent the projection of data observed along the orbital plane of a satellite orbit into the sphere in the terrestial reference frame. The inclination functions in this work is studied from a group theoretical perspective. The inclination functions are proved to generate a representation of the SO(3) group. An orthogonal relation of the inclination functions is derived and some recurrence relations for the inclination functions are given, based on which an algorithm to calculate the inclination functions is proposed. [ABSTRACT FROM AUTHOR]

A tectonic Plate Motion Model (PMM) is essential for geodetic applications, while contributing to the understanding of geodynamic processes affecting the Earth's surface. We introduce a PMM derived from the horizontal velocities of 518 sites extracted from the ITRF2020 solution. These sites were chosen away from plate boundaries, Glacial Isostatic Adjustment regions, and other deforming zones. Unlike the ITRF2014‐PMM, which showed no significant Origin Rate Bias (ORB), velocities used to determine the ITRF2020‐PMM exhibit a statistically significant ORB (0.74 ± 0.09 mm/yr along the Z‐component). Users are advised to add the estimated ORB to the horizontal velocities predicted by the ITRF2020‐PMM rotation poles for full consistency with the ITRF2020. However, the predicted vertical velocities resulting from the addition of the ORB should be discarded. The overall precision with which the ITRF2020 velocity field is represented by the rigid ITRF2020‐PMM is at the level of 0.25 mm/yr WRMS. Plain Language Summary: The Earth's surface is divided in large and small tectonic plates, which evolve and move slowly over time, resulting in lateral displacements of the ground surface typically of the order of a few cm/yr. Because of the relative motion between tectonic plates, plate boundaries can be either divergent (when two plates move away from each other), convergent (when two plates collide) or transform (when two plates slide past each other). Plate motion models are used to quantify the relative motions of the plates with respect to each other, and are determined using geological data or observations collected by space geodesy instruments distributed over different plates at the Earth's surface. In the latter case, space geodesy observations from the four space geodetic techniques covering more than 40 years of data are analyzed to estimate the long‐term displacements (or velocities) of each instrument in a well defined and self‐consistent global reference frame. The derived velocity field is then used to estimate a comprehensive plate motion model (PMM). This article presents a PMM for 13 tectonic plates based on a subset of the velocity field from the recently released International Terrestrial Reference Frame 2020 (ITRF2020); see https://itrf.ign.fr/en/solutions/ITRF2020. Key Points: We derive a plate motion model for 13 tectonic plates from the ITRF2020 horizontal velocity fieldBuilt under the rigid‐plate motion hypothesis, the model represents the ITRF2020 velocity field with a precision of 0.25 mm/yr WRMSThe residual velocities would show a global northward motion if a translation rate was not included in the inversion model [ABSTRACT FROM AUTHOR]

The aim of the new generation of Global Geodetic Observing System is a millimeter-level accuracy in positioning, with a crucial role to be played by Global Navigation Satellites Systems (GNSS) in the Precise Point Positioning (PPP) mode. This is of course because GNSS constellations and receivers provide an efficient stand-alone technique with a homogeneous performance over large areas (positions, navigation and meteorology) when used in conjunction with the PPP mode, with also an ever-increasing data flow and different satellite line-of-sights. The requirement of accuracies reaching the millimeter or sub-millimeter implies a knowledge at this level of each line in the GNSS-PPP error budget, including, but not restricted to: clock biases, troposphere and ionosphere delays, multipath and ground deformations. In this review study, we consider this millimeter-/submillimeter level GNSS-PPP error budget, and possible mitigations and improvements in the frame of the existing global constellations: GPS, Galileo, GLONASS and BDS, in view of augmented constellations and/or Low Earth Orbit constellations, which will be available in the near future. We also pay a special attention to systematic biases that can/could exist between constellations. [ABSTRACT FROM AUTHOR]

Mass redistribution in the Earth system induce variations of the Earth's gravity field. Now, the time-varying gravity models from the Gravity Recovery and Climate Experiment (GRACE) mission can only estimate the large-scale gravity changes, so the high-resolution marine gravity trend (MGT) model is urgently required to detect small-scale Earth's mass migration. The sea level change is a significant response to marine gravity field change. Here, we propose to estimate the high-resolution MGT using the sea level trend (SLT). Firstly, the SLT model caused by marine mass change (MMC) on 5′ × 5′ grids covering the Bay of Bengal (BOB) is established based on multisatellite altimetry data and EN4 quality-controlled ocean data, named BOB_MMC_SLT. Then, the marine mass trend (MMT) is calculated using the BOB_MMC_SLT. The spherical harmonic function (SHF) method is applied to estimate MGT using the MMT, and this MGT model on 5′ × 5′ grids, named BOB_SHF_MGT, is used to study marine gravity changes and their associated geophysical processes. The results show that, the MGT mean of BOB_SHF_MGT is about 0.14 μGal yr−1, which indicates that marine gravity in BOB is rising. The earthquakes mainly occur in the southeastern BOB where MGT is obviously rising, which may be related to the increased density of the Burma Plate due to the subduction of the India Plate and the Australia Plate. BOB_SHF_MGT shows that the marine gravity rise rate is increasing from the 85°E ridge to Andaman–Nicobar ridge, with a maximum at the location where the India Plate subducts to the Burma Plate. The MGT model based on altimetry data constructed by SHF method is important for the study of small-scale mass migration near the subduction boundaries. [ABSTRACT FROM AUTHOR]

The tropospheric delay acquired by the Global Navigation Position System (GPS) Precise Point Positioning (PPP) is continuous and steady, less affected by rainfall. The Water Vapor Radiometer (WVR) can provide real‐time meteorological parameters but is more sensitive to high‐frequency information in troposphere. To explore the use of WVR‐retrieved tropospheric delay and assist other geodetic techniques for atmospheric correction, the tropospheric delay from WVR and co‐located GPS at Shanghai, Beijing, Kunming, and Urumqi stations in China are compared. For the inconsistent values of WVR‐PPP zenith wet delay, the variations of the tropospheric delay from WVR and GPS before and after the rainfall were statistically analyzed. The results suggest that, for the rain rate ranging from 0.1 to 50 mm/hr, the impact of rainfall on WVR could last from 10 min before to 30 min after the rainfall. With filtering WVR data based on meteorological parameters and rain rate, the zenith wet delay between WVR and PPP at Shanghai shows good consistency, the root mean square (RMS) is 6.11 mm, correlation is 0.997, and the RMS in the other three stations ranges from 16.35 to 25.16 mm (correlation ranges in 0.794–0.951). The analysis indicates that the tropospheric delay of WVR is reliable to be applied to space geodetic techniques correction in real‐time with filtering to reduce the effect of rainfall, water vapor, and liquid water variability. Key Points: Comparison of zenith wet delay(ZWD) from water vapor radiometer, co‐located GPS station observations in high temporal resolutionQuantitative analysis of the magnitude and duration of rainfall effects on the zenith wet delay from water vapor radiometer and GPSSuch data analysis and processing might be valuable for assimilating multi‐source data on tropospheric wet delay [ABSTRACT FROM AUTHOR]

Estimates of line-of-sight (LOS) displacements from Interferometric Synthetic Aperture Radar (InSAR) observations serve as the basis of the long-term monitoring of an operating natural gas storage site at Honor Rancho in California. An inversion algorithm is used to estimate the portion of the signal that is attributable to deformation within the gas storage reservoir, located at a depth of around 3 km. Removing this contribution produces residuals that are used to characterize the background variation is surface deformation at the gas storage facility and to determine a threshold that can signify unusually large residuals. An application to almost 7 yr of InSAR data, from 2011 until 2018, indicates that there are intervals of heightened residuals as well as brief episodes of anomalously large misfits. An examination of the spatial distributions of the individual residual LOS displacements indicates larger displacements in an alluvial valley just south of the reservoir, with rapid spatial variations in sign, indicating a rather shallow origin. Furthermore, the two anomalous events also involve rapid spatial variations in the LOS displacement residuals directly above the storage facility. The results demonstrate that the technique of extracting residuals after removing the reservoir signal is a useful approach, even in the case of this deep reservoir, and is a promising method for long-term monitoring.