The conjoining and interfering influence of the Circum‐Pacific zone and the Tethys‐Himalayan zone make China a country of intense intracontinental seismicity. Here we provide three new quantitatively assessed products and use them to better constrain seismic hazards in China. First, we process ~2,700 Global Positioning System (GPS) data spanning 1996–2017 provided by the Crustal Movement Observation Network of China (CMONOC) network and the Nevada Geodetic Laboratory. To produce a robust tectonic velocity solution, we implement a data editing scheme to account for 8 Mw ≥ 7 earthquakes to reduce the influence of transient phenomena. The solution is then rotated into a consistent reference frame with 10 other published velocity sources surrounding mainland China. Second, we calculate a new geodetic strain rate model using an optimal mesh grid definition of 0.4° × 0.4° determined jointly by the Nyquist frequency method and checkerboard tests. We evaluate and validate the geodetic strain rate results from both a statistical (i.e., based on the Bayesian factor) and quantitative (i.e., based on the comparison with the 2‐D analytical strain rate result) approaches. Third, we use our new geodetic strain rate model to estimate seismicity rates.

The Sichuan Province comprises the cratonic Sichuan Basin and the eastern Tibetan Plateau separated by the recently activated Longmen Shan fault zone, thus providing a natural laboratory to study interseismic and postseismic processes. In this work we compute a new regional geodetic velocity solution from most of the continuous Global Navigation Satellite Systems (GNSS)/GPS data available in the Sichuan Province that we assess for transient postseismic deformation. For 11 continuous sites in close proximity to the Wenchuan 2008 event epicenter that were operational during the Wenchuan event we find an average short‐term relaxation time of 11 days with maximum amplitude of 6.6 mm for the postseismic transient and no resolvable long‐term transient. Using tests for block rigidity guided by previous kinematic studies we elucidate a longer‐term transient in GNSS/GPS observations collected after the Wenchuan event that spans an extensive region of the eastern Tibetan Plateau. We correct for transients, produce an updated secular velocity field, and revise the kinematics of the region using elastic block modeling. Our results indicate that predicted slip rates are in good agreement with both geological and GNSS/GPS velocity profile‐derived results, and we resolve two independent blocks with the expanded GNSS/GPS data set. Our constraints on the spatial extent of long‐term postseismic deformation support models of ductile lower crust in the eastern margin of the Tibetan Plateau.

The Xianshuihe‐Xiaojiang fault system (XXFS) plays a crucial role in accommodating relative motions of the south China block and the expanding Tibetan Plateau. Compared to the narrow southern and northern segments of the XXFS, the central section (also referred to as the Daliangshan mountain area) is broader and dissected by a network of faults. Geologic studies suggest that three major NNW trending faults may dominate slip partitioning of more recent faults in this region. However, due to accessibility issues, sparse geodetic studies have constrained geodetic fault slip rates with contradictory results. In this study, we use 17 new Global Navigation Satellite System sites combined with existing solutions to investigate slip partitioning of the region. We derive a tectonic velocity solution, develop a block kinematic model constrained by Euler pole clustering technique, and calculate geodetic fault slip rates to compare with geologic fault slip rates. We confirm that the Anninghe‐Daliangshan sliver (ADS) is a distinct, rigid block, and we resolve a new, rigid Daliangshan‐Yingjing‐Mabian block (DYB). Kinematic modeling predicts long‐term slip rates that suggest both the ADS and the DYB partition (~10.0–12.0 mm/year) relative motion between the Tibetan Plateau and south China block in the central XXFS, reconciling geologic observations. We suggest that both the continuum and microplate deformation patterns are present in our study area, of which the local tectonics is better explained by the microplate model, but scale of the kinematics makes its motion more consistent with the continuum model.

This study analyzed the total electron content (TEC) observed by 337 ground‐based Global Navigation Satellite System (GNSS) receivers over China and South Asia, the critical frequency of the ionospheric F₂ layer (f_oF₂) and its height (h_mF₂) recorded by the ionosonde at Puer (22.7°N, 101.05°E, 72% obscuration), Yunnan province, during and after the annular solar eclipse on June 21, 2020. The observations show that the eclipse induced not only a daytime major depression but also nighttime perturbations in the ionosphere. The TEC perturbed intermittently from noon to midnight between 85° and 125°E on the eclipse day. The positive and negative changes of the prereversal enhancement respectively occur in the nearby longitudinal sectors of 100°and 115°E. The TEC perturbations behave as a terminator wave that propagates in a northwestward direction after sunset.

Geostationary BeiDou satellites monitor the total electron content (TEC) in the ionosphere over certain locations 24 hr per day without interruption and act as ionosphere‐based seismometers. The system detected perturbations in TEC before both the M6.1 Dali and M7.3 Qinghai earthquakes that occurred during the night of 21–22 May 2021. The TEC perturbations reside mainly over an area within a distance of ∼700 km from the epicenters of the earthquakes. The standing waves revealed the persistence of a subsurface wave source before the occurrences of the earthquakes, which differs from the co‐seismic ionospheric distributions propagating away from the epicenters. The resident waves in TEC and ground vibrations share a frequency of ∼0.004 Hz, which can be attributed to the resonant coupling between the lithosphere and ionosphere.

Periodic signals replaced noise that was found in continuous seismic data, particularly in the nighttime, from the broadband seismometer at the MVP-LAI (monitoring vibrations and perturbations in the lithosphere, atmosphere and ionosphere) system before the occurrence of the Luxian earthquake on 16 September 2021. A short distance of ~150 km between the MVP-LAI system and the epicenter of the Luxian earthquake suggests the periodic singles as promising seismo-phenomena, due to that the radius of the earthquake preparation zone is ~380 km for an M6 event. Integration of geophysical parameters, including atmospheric pressure, vertical electric field, radon concentration, groundwater level and precipitation, at the MVP-LAI system provides an excellent opportunity for studying the seismo-LAI coupling associated with the Luxian earthquake. Analytical results show that ground vibrations, atmospheric pressure and total electron content varied from ~10⁻³ to ~10⁻² Hz before the Luxian earthquake. The seismo-LAI coupling in the relatively low frequency band (~10⁻³ Hz) can be referred to as the acoustic-gravity waves triggered by the amplified ground vibrations. In contrast, the seismo-LAI coupling in a relatively high frequency band (~10⁻² Hz) would be caused by micro-cracks and/or the high-mode natural frequency that further drives changes of TEC due to the atmospheric resonance.