The ongoing collision between the Indian plate and the Eurasian plate brings up N-S crustal shortening and thickening of the Tibet Plateau, but its dynamic mechanisms remain controversial yet. As one of the most tectonically active regions of the world, South-Eastern Tibet (SET) has been greatly paid attention to by many geoscientists. Here we present the latest three-dimensional GPS velocity field to constrain the present-day tectonic process of SET, which may highlight the complex vertical crustal deformation. Improved data processing strategies are adopted to enhance the strain patterns throughout SET. The crustal uplifting and subsidence are dominated by regional deep tectonic dynamic processes. Results show that the Gongga Shan is uplifting with 1–1.5 mm/yr. Nevertheless, an anomalous crustal uplifting of ~8.7 mm/yr and negative horizontal dilation rates of 40–50 nstrain/yr throughout the Longmenshan structure reveal that this structure is caused by the intracontinental subduction of the Yangtze Craton. The Xianshuihe-Xiaojiang fault is a major active sinistral strike-slip fault which strikes essentially and consistently with the maximum shear strain rates. These observations suggest that the upper crustal deformation is closely related with the regulation and coupling of deep material.

According to general relativity theory (GRT), the clock at a position with lower geopotential ticks slower than an identical one at a position with higher geopotential. Here, we provide a geopotential comparison using a non-transportable hydrogen clock and a transportable hydrogen clock for altitude transmission based on the two-way satellite time and frequency transfer (TWSTFT) technique. First, we set one hydrogen clock on the fifth floor and another hydrogen clock on the ground floor, with their height difference of 22.8 m measured by tape, and compared the time difference between these two clocks by TWSTFT for 13 days. Then, we set both clocks on the ground floor and compared the time difference between the two clocks for seven days for zero-baseline calibration (synchronization). Based on the measured time difference between the two clocks at different floors, we obtained the height difference 28.0 $\pm$ 5.4 m, which coincides well with the tape-measured result. This experiment provides a method of height propagation using precise clocks based on the TWSTFT technique.

The integration of the Global Positioning System (GPS) and the Inertial Navigation System (INS) based on Real-time Kinematic (RTK) and Single Point Positioning (SPP) technology have been applied as a powerful approach in kinematic positioning and attitude determination. However, the accuracy of RTK and SPP based GPS/INS integration mode will degrade visibly along with the increasing user-base distance and the quality of pseudo-range. In order to overcome such weaknesses, the tightly coupled integration between GPS Precise Point Positioning (PPP) and INS was proposed recently. Because of the rapid development of the multi-constellation Global Navigation Satellite System (multi-GNSS), we introduce the multi-GNSS into the tightly coupled integration of PPP and INS in this paper. Meanwhile, in order to weaken the impacts of the GNSS observations with low quality and the inaccurate state model on the performance of the multi-GNSS PPP/INS tightly coupled integration, the Helmert variance component estimation based adaptive Kalman filter is employed in the algorithm implementation. Finally, a set of vehicle-borne GPS + BeiDou + GLONASS and Micro-Electro-Mechanical-Systems (MEMS) INS data is analyzed to evaluate the performance of such algorithm. The statistics indicate that the performance of the multi-GNSS PPP/INS tightly coupled integration can be enhanced significantly in terms of both position accuracy and convergence time.

The Global Positioning System (GPS) derived bedrock displacements respond to multiple geophysical effects, ranging from surface elastic loads to tectonic sources or viscoelastic uplifts stemming from Earth’s viscous mantle. In this study, the GPS‐inferred vertical crustal velocities are rigorously estimated in mainland China. We integrate the GPS vertical velocity field with Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow‐On (GFO) data, adopting an empirical Spatial Structure Function (SSF), to image tectonic deformation in mainland China with respect to the International Terrestrial Reference Frame (ITRF) 2014. We present four profiles across China, which indicate that our new robust results are superior to kriging. Furthermore, we use the GRACE/GFO products to account for elastic deformation due to surface mass changes to isolate tectonic deformation signals at GPS sites within mainland China from 2002 to 2019. By integrating GPS and GRACE/GFO measurements, our results reveal the long‐term spatial patterns of vertical tectonic motion in different blocks in mainland China. We conclude that significant steep velocity gradients occur at tectonic block boundaries that are attributable to locking and elastic strain accumulation on active block boundary faults.

The inner core translational mode (₁S₁), known as the Slichter triplet, can provide important information particularly on the Earth's inner core and its dynamics. A time domain spectral analysis method, the optimal sequence estimation (OSE), is devised and applied to search for the Slichter modes. Applications of the OSE and the multistation experiment (MSE) technique for detection of the singlets of ₃S₁ and ₂S₁ show that both OSE and MSE can isolate their singlets, but OSE provides a higher signal‐to‐noise ratio. OSE also can completely isolate the modes ₀S₂ and ₁S₂. Using two superconducting gravimeter data sets from nine Global Geodynamic Project stations before and after the 2004 Sumatra earthquake, we search for the possible Slichter triplet via OSE and provide a simple validation using the product spectrum. We set two preliminary criteria in order to identify possible signals; results show three signals as candidates for the Slichter triplet, more likely in the data after the 2004 Sumatra earthquake. While choosing the most reasonable criteria needs further studies, we emphasize here the effectiveness of the OSE in searching for the Slichter modes rather than claiming actual detections.