Ground deformation is a key parameter in interpreting precursory stress and strain patterns and provides valuable information for seismic studies. Interferometric Synthetic Aperture Radar (InSAR) is a robust technique capable of measuring such deformations with high precision. In this study, we applied Persistent Scatterer InSAR (PS-InSAR) and Small Baseline Subset InSAR (SBAS-InSAR) techniques to analyze surface deformation patterns prior to the M_W7.8 Türkiye earthquakes. A total of 40 Sentinel-1 SAR images in ascending mode (path-014) were used, covering the period from January 2022 to May 2023 with a 12-day repeat cycle, both before and after the February 6, 2023, seismic events. The area near the M_W7.8 earthquake epicenter exhibited deformation rates ranging from - 42.9 mm/yr to +44.3 mm/yr based on PS-InSAR, while SBAS-InSAR indicated deformation in the range of - 58.5 mm/yr to +47.7 mm/yr for the same location. The line-of-sight (LOS) deformation from the PS-SBAS merged analysis ranged from - 43.4 mm/yr to +36.0 mm/yr. The integration of PS-InSAR and SBAS-InSAR provided greater reliability than single-method techniques. Several parameters were analyzed, including the PS-SBAS merged time series, wavelet power spectrum analysis of deformation values near the epicenter, and the first principal component (PC1) of wavelet coefficients, to identify precursory deformation before the earthquake. The PS-SBAS merged time series showed progressive phase decorrelation during the months preceding the event, indicating pre-seismic ground deformation. The wavelet power spectrum of the LOS deformation showed consistently high power from October 2022 to May 2023, suggesting abnormal pre-seismic activity. Furthermore, the monthly rate of change of wavelet PC1 revealed a declining trend prior to the earthquake, followed by an increase afterward. These observations point toward the potential for small-area precursory deformation monitoring using multitemporal InSAR techniques.

The Palu-Koro Fault is one of the most active left-lateral strike-slip faults in Indonesia. This study integrates gravity data (GGMPlus), GNSS measurements, and seismic analysis to better understand the fault structure and tectonic behavior. The results show that the high First Horizontal Derivative (FHD) value along the fault corresponds to a sharp density gradient related to high tectonic activities. The secondary fault branches and lineaments can also be identified from Tilt Derivative (TDR), emphasizing the fault system's complexity. GNSS data from the INA-CORS network reveals patterns with notable extensional dilatation rates exceeding 100 nanostrain/year in pull-apart basins and compressional zones displaying significant uplift potential. Shear strain measurements highlight regions with deformation rates exceeding 250 nanostrain/year, particularly in the central Palu-Koro Fault segment. Seismicity clustering analysis indicates shallow to intermediate-depth earthquakes along the fault, majority at depths 20-30 km, reflecting lateral tectonic forces align with strike-slip Palu-Koro Fault activities. The integration of gravity, GNSS, and seismicity results critical insights into the fault's heterogeneity, deformation processes, and potential for large seismic events, contributing to enhanced hazard risk assessment and mitigation strategies in this geologically dynamic region.

On 28 March 2025, a shallow devastating strike-slip earthquake with a moment magnitude (M_W) of 7.7 struck Mandalay, the second-largest city in Myanmar, marking the most powerful seismic event in this region over the past century. The event holds significant implications for understanding regional tectonic evolution. In this study, we utilize spaceborne interferometric synthetic aperture radar (InSAR) data and pixel offset observations in both azimuth and range directions to capture the co-seismic surface deformations associated with this earthquake, which depict clear surface ruptures extending approximately 500 km. We develop a three-segment fault slip model to estimate the detailed slip distribution of the 2025 Myanmar event. The inversion results demonstrate that a three-segment fault model with dip angles varying from 70° to 88° can effectively produce the observed coseismic surface deformation. Our analysis reveals that the earthquake is dominated by right-lateral strike-slip motions within the top 12 km of the crust. Notably, the maximum slip of 4.6 m is observed at the ground surface, suggesting no significant shallow slip deficit occurred. Furthermore, the 2025 M_W7.7 earthquake appears to have filled a previously identified seismic gap along the southern segment of the Sagaing fault. Coulomb stress transfer modeling indicates that coseismic slip on the northern segment has promoted the subsequent failure of the two southern segments. We estimate a recurrence interval of large-magnitude earthquakes (M_W > 7) of approximately 104-131 years for the seismogenic fault based on the coseismic and interseismic released seismic moments. The significant scarcity of aftershocks within the supershear rupture zone, coupled with the relatively low moment-scaled radiated energy, provides compelling evidence for supershear rupture propagation along the Sagaing fault during this earthquake.

We present a new harmonic development of the long-periodic band of the Earth tide-generating potential (TGP). It updates the corresponding part of the previous TGP expansion, KSM03, and includes 38 terms of period longer than about 18 years (yr) and amplitude not less than 10^-8 m²·s^-2. The development is made through a modified spectral analysis of the TGP numerical values tabulated over more than 30000 yr (13201 BC-17191 AD). The latest JPL NASA's long-term numerical ephemeris DE441 is used to source the Moon, the Sun, and major planets' coordinates. For comparison, the KSM03 series was done on the basis of an older DE406 ephemeris and over a shorter time interval of 2000 yr (1000-3000). As a result of using an extended time span, several new long-periodic waves in the Earth TGP were found and most of the other terms are updated. In particular, a relatively large term of amplitude of 3 × 10^-5 m²·s^-2 and a period of approximately 7.4 kyr is revealed. Several new waves of period close to 18.61 yr (the period of the lunar nodal cycle, LNC) are separated from the main LNC term. The effect of the general precession in longitude (of a 25.7 kyr period) on the Earth TGP for the first time is evaluated. As a result, a number of updated TGP terms include the precession rate in their arguments. A new catalogue of the long-periodic terms in the Earth TGP spectrum in both standard HW95 and KSM03 format is released.

In the past, the free-air gradient - 308.6 × 10^-8 s^-2 was used as the vertical gravity gradient of the measuring point in gravity data processing, which resulted in inaccurate instrument height corrections. To investigate the influence of using the vertical gravity gradient, theoretical gradients of the Jinzhai baseline field in the Dabie Mountains were calculated using DEM data and WGM2012 gravity anomaly data. Adjustment results were compared with those using the free-air gradient. Using the theoretically calculated vertical gravity gradient correction improved the scale factor calibration precision by an average of 0.00007. The average precision of gravity adjustment results under different datum controls increased from 2.23 × 10^-8 m/s² to 1.45 × 10^-8 m/s². In a single-datum control adjustment, the maximum effect of the actual vertical gravity gradient on datum transfer is 8.7 × 10^-8 m/s², while the effect without it is as low as 9.0 × 10^-8 m/s² and as high as 27.5 × 10^-8 m/s². In a multi-datum system, using the actual vertical gravity gradient yields the best results. Even with the three-datum control adjustment, the average effect of the free-air gradient correction on the results reaches 3.9 × 10^-8 m/s². Therefore, incorporating measured or theoretically calculated vertical gravity gradients into gravity data processing is essential for significantly enhancing its accuracy and precision.

On January 20, 2025, an M_W6.0 earthquake occurred in Chiayi County, southwestern Taiwan, China. In this study, we utilize Sentinel-1 data to investigate the coseismic ground displacement and fault slip model of this event. Here, we present the geodetic fault model of the 2025 Chiayi earthquake. While both east-dipping and west-dipping fault models can adequately reproduce the InSAR observations, the east-dipping model was found to better align with the quasi-east-west and quasi-vertical deformation fields derived from decomposing Interferometric Synthetic Aperture Radar (InSAR) ascending and descending orbits, the characteristics of interseismic deformation, and the tectonic features of the seismic region. The best-fitting east-dipping uniform-slip model shows that the seismogenic fault is characterized as a reverse slip striking 336.2°, dipping northeastward. The fault's upper boundary is buried at a depth of 8.0 km, with a dip angle of 27.6° and a slip angle of 61.6°. Calculations of Coulomb stress changes reveal that regions experiencing positive changes are primarily concentrated at the northeast and southwest extremities of the Chiayi earthquake rupture, as well as in the northwest and southeast lobes flanking the rupture zone.

The Gravity Recovery and Climate Experiment (GRACE) Level-2 products, i.e., monthly gravity field models expressed in spheric harmonic (SH) coefficients, have been released in several versions since 2002. In this study, we analyze the extraction of co-seismic signals associated with the 2004 Sumatra-Andaman M_W9.1 earthquake, using GRACE data from four versions, namely the RL01, RL04, RL05, and RL06, provided by the Center for Space Research (CSR), University of Texas at Austin. Results indicate that the co-seismic signals extracted from later versions of GRACE data are less affected by noise. Moreover, the earliest RL01 vision can also reflect the co-seismic gravity-change signals of the 2004 Sumatra-Andaman earthquake. In particular, we find that the spatial pattern of the co-seismic signals extracted from the RL04 version of GRACE data exhibits significant distortion, which is probably due to the large errors introduced in the processing of the atmosphere and ocean models in the gravity field inversion. Comparison between the dislocation model prediction and GRACE observation suggests that the GRACE results from later versions are more consistent with the model prediction. In addition, the dislocation models with stronger constraints from near-field measurements during the fault-slip inversion provide a more consistent prediction with the GRACE observation. The uncertainty estimation of GRACE data over the global oceanic region reveals that the noise levels gradually decrease from the earlier to later versions, with the RMSs of 7.1, 4.9, 2.4, and 2.1 μGal (with 300 km spatial smoothing) for the RL01, RL04, RL05, and RL06 versions, respectively.

The study utilized GNSS observation data from 1999 to 2024 to investigate the crustal deformation characteristics near the epicenter of the Dingri earthquake. The results show that the GNSS horizontal velocity value at the Dingri earthquake epicenter is about 25.9 mm/year, and the vertical velocity value is close to zero. The vertical velocity field indicates that most of the study area is subsiding, while the rift area is uplifting, and the Shenzha-Dingjie fault zone is in an uplifting area with a significant uplift gradient. The maximum shear strain rate and the second invariant of the strain tensor at the epicenter are 36 × 10^-9/year and 56 × 10^-9/year, respectively. The surface expansion rate field suggests that the earthquake occurred in a region of compressive deformation. The historical earthquake stress change distribution indicates that the Coulomb stress change loading value at the epicenter of the Dingri earthquake is 1.549 bar, exceeding the stress triggering threshold. This indicates that historical earthquakes promoted the occurrence of this event. The central and western sections of the South Tibetan Detachment System fault zone and the middle section of the Shenzha-Dingjie fault zone are located in high-strain value areas and postseismic stress loading regions. The seismic risk in this region should be closely monitored in the future.

On March 28, 2025, an M_W7.7 earthquake struck Myanmar, with the epicenter located in the central segment of the Qinghai-Xizang-Yunnan-Myanmar-Indonesia η-type structure. This region hosts a series of active faults, including the right-lateral Sagaing Fault and the Red River Fault in southwestern Yunnan. Based on the fault geometry model published by Zhang et al. and the Crust1.0 layered medium model, this study simulates the co-seismic and post-seismic Coulomb stress changes at depths of 5, 10, and 15 km on the main fault zones within the study area. The results indicate that the earthquake was dominated by Coulomb stress unloading, with localized loading observed at the northern and southern ends of the rupture. On the Sagaing Fault, Coulomb stress changes were dominated by unloading: average decreases ranged from - 2.4 to - 4.7 bar across all depths and timescales, indicating a low likelihood of large-scale rupture on that fault. However, in the northern segment of the rupture, localized stress loading exceeded the critical threshold of 0.1 bar, suggesting a possible enhancement of local seismic hazard. In southwestern Yunnan, co-seismic Coulomb stress loading at all depths ranged from - 0.37 × 10^-2 to 1.8 × 10^-2 bar. Post-seismic stress changes were minor, with a maximum of 3.2 × 10^-3 bar. These results imply that the M_W7.7 event induced only subtle adjustments to the long-term tectonic stress field in southwestern Yunnan; nevertheless, the presence of stress-loading regions within seismic gaps warrants continued attention to potential hazard.

As the largest ice sheet storage area in the world, Antarctica's gravity field characteristics are key data for studying ice sheet mass balance, sea level changes, and polar resource exploration. However, current gravity field modeling in polar regions faces two major challenges: First, the satellite orbital inclination limit (e.g., the GOCE mission has observation gaps within the latitude circle of 83.3°), which causes ill-posed problems in satellite gravity inversion. Although some studies have improved this using methods like Tikhonov regularization and spherical cap regularization, the applicability of different regularization methods in polar regions lacks systematic evaluation. Second, multi-source gravity data have frequency band limitations, and the study of frequency band characteristics in combined gravity models is relatively scarce. To address these issues, this paper utilizes international Antarctic airborne gravity datasets, including AntGG and PolarGap. It systematically evaluates the accuracy of six satellite gravity field models (such as DIR_R6 and GOCO06s) and five combined gravity models (such as EGM2008 and XGM2019e) in Antarctica, from both spatial and spectral perspectives. The study reveals the error distribution characteristics of different models in Antarctica and further quantifies the contribution characteristics of each model in different frequency bands. The results show that global gravity field models exhibit lower quality within the polar gap at the 83.3°S latitude circle, and introducing additional measurement data combined with regularization methods can significantly improve their accuracy. Additionally, among the combined gravity field models, the XGM2019e_2159 model performs best in Antarctica, and the inclusion of satellite altimetry data significantly improves its quality in oceanic regions. The findings of this study will provide experimental references for data selection and gravity field model optimization in Antarctic gravity field research.