In order to study the stress state at the source region of the M5.1 earthquake occurred on July 12, 2020, a dense array was deployed in this area after the earthquake. 96 focal mechanism solutions and a fine crustal stress field of 0.25°×0.25° were obtained by using 20505 P-wave first motion polarity data in the earthquake source region and its adjacent area. The results show that: The focal mechanism of small earthquakes in the Guye earthquake region of Tangshan is mainly strike-slip type, followed by normal-fault type. The P-axis is NNE oriented with large of the plunge angle, while the T-axis NNW oriented with smaller plunge angle. Moreover, we found that there is a certain angle of deflection in the P-axis azimuth in the area near the Luanxian-Laoting fault, that is, from the NEE—SWW oriented deflection on the west side of the fault to the NW—SE oriented deflection on the east side of the fault, indicating the division of the stress field by the reverse-normal activity of the Luanxian-Laoting fault. The solution and analysis of the focal mechanism and stress field of small earthquakes can provide reference for further research in this area, especially in the area near the Luanxian-Laoting fault.

The Chuan No.05 well, located in the Sichuan-Yunnan region, is a seismic observation well located at the west end of the Xigeda-Yuanmou fault. The statistical data of the coseismic response of the well show that the response time of the well dynamic ground water level is 1~85 min and the response amplitude is 1~29 mm. The response modes include oscillation type, pulse type, step-change type and step-change-oscillation type. By calculating the seismic distribution range and the seismic energy density of the well, the seismic reflection ability of the well is analyzed. The results show that when the epicentral distance (r) and magnitude (M) meet the relation logr≤0.95M-3.35, the dynamic ground water level of the Chuan No.05 wells more likely to have a coseismic response. For earthquakes above M_S8.0, the well has a significant ability to reflect earthquakes, and the variation range of water level is greatly constrained by the magnitude and epicenter distance. It is found that the energy density e(r) of the dynamic ground water level for the response of the Chuan No.05 is in the range of 10^-6~10^-2 J/m³, and when the energy density e(r)≥10^-3 J/m³, the water temperature can produce post-seismic step change.

Following the 2019 Jingxi M_S5.2 earthquake in Guangxi, the Debao M_S4.8 earthquake occurred in western Guangxi on August 4, 2021. To investigate the enhancement of seismicity in western Guangxi and determine whether there were any abnormal changes related to the earthquake before it occurred. In this paper, the R-value scoring method is used to analyze the abnormal characteristics and evaluate the prediction efficiency of the vertical displacement of the DF microseism signals and the absolute value of the monthly extreme rate at Pingxiang station. The results show that earthquakes with magnitudes greater than M_S4.0 within a 400 km radius of the Pingxiang station are more likely to occur during periods of high vertical displacement, which frequently coincide with typhoon seasons. These earthquakes are also likely to occur during the transition from low to high vertical displacement values. The 2021 Debao M_S4.8 earthquake occurred during a period when vertical displacement gradually increased from a low value of 0.1×10^-6 m to 0.15×10^-6 m. The results of annual scale prediction efficiency show that, with a monthly rate threshold (S₀) of 0.00039×10^-6 m per month, the optimal value (R_M) was 0.29. The duration of anomalies before the 2021 Debao earthquake lasted 8 months, comparable to the optimal prediction duration of 6 months as determined by the R-value evaluation method. When discussing the accumulation pattern of the R-value with the accumulation of seismic cases, it was found that new seismic cases can improve the optimal prediction strategy, with the threshold gradually converging to 0.00039×10^-6 m per month~0.00031×10^-6 m per month, the optimal forecast duration gradually converging to 6~10 months, and the R-value gradually converging to 0.29~0.31. Comparing with other gPhone gravity stations in Guangxi, it was found that during the 2021 Debao M_S4.8 earthquake, the short-term increase in vertical displacement at Pingxiang station before the earthquake was related to the enhancement of DF pulsation signals excited by the typhoon. The possibility of earthquakes was high when the typhoon path was orthogonal to the coastline of China. This study provides empirical insights and references for predicting the occurrence period of M_S4.0 and above earthquakes in western Guangxi in the future.

Utilizing the seismic travel-time catalog of Alaska from 2000 to 2016 provided by the International Seismological Centre (ISC), this study employs eikonal equation-based seismic tomography to invert the three-dimensional velocity structure of the subsurface in southern Alaska, resulting in a high-resolution P-wave velocity model for the region. The results reveal strong heterogeneity in the crustal structure. The low-speed anomalies in the crust align well with geological structures such as surface sedimentary basins. Distinct high-velocity anomalies are observed in the upper mantle, corresponding to the subducting Pacific plate. Above this high-velocity anomaly, a thin layer of low-velocity anomalies is present, presumably the Yakutat microplate subducting into the North American plate. The 2018 M_W7.1 Anchorage earthquake occurred at the boundary of this microplate, possibly triggered by relative motions between the subducting plate and the overriding plate. Beneath Spur Volcano, significant low-velocity anomalies are evident, possibly indicating the formation of magma channels and magma chambers characterized by strong low-velocity anomalies, influenced by the upwelling of fluids released by partial melt and dehydration of material during plate subduction. Conversely, high-velocity anomalies dominate beneath Redoubt Volcano, and the high-velocity anomaly representing the subducting slab is discontinuous, possibly suggesting plate tearing. The fluids released by the dehydration of the subducting plate, as well as the upward movement of high-temperature, partially-molten material along inclined channels, provide the material and energy sources for surface volcanic activity.

On January 23, 2024, an M_S7.1 earthquake with a focal depth of 20 km occurred in Uqturpan County (78.63°E, 41.26°N), Xinjiang, China. In this paper, the multi electromagnetic anomalies, such as earth resistivity, geoelectric field, and geomagnetic field, within 500 km from the epicenter of the 2024 Uqturpan County M_S7.1 earthquake, are analyzed using morphological analysis, dominant azimuth, normalized change rate method, daily ratio of geomagnetic field, and vertical intensity polarization method. After excluding factors such as instrument operation, station observation environment, and space electromagnetic activity, it is considered that the annual change in earth resistivity occurred before the earthquake at Kalpin station within a range of about 70 km from the epicenter. The annual amplitude of the EW direction at the Kalpin earth resistivity station in 2023 was significantly less than the background, being the most prominent variation since 2014. The dominant azimuth angles of rock fissures in the long and short EW/NW geoelectric fields in Wenquan showed a decrease followed by an increase 8 months before the earthquake, and they shifted towards the direction of the Uqturpan County earthquake just before the event. The geomagnetic field exhibited abnormal changes in the vertical intensity polarization, the daily ratio of the vertical component, and the displacement of the geomagnetic low point 10 months, 57 days, 35 days, and 7 days before the earthquake, respectively. Additionally, the 2022—2023 mobile geomagnetic survey also showed anomalous variations in the region from Kalpin County to Akqi County. Finally, the temporal and spatial evolution characteristics of the multi-parameter electromagnetic anomalies during the 2024 Uqturpan M_S7.1 earthquake on January 23 are analyzed, and the causes of the precursors are discussed. These results can accumulate experiences and cases for earthquake prediction using the electromagnetic multi-parameter method in the future, and help to further optimize prediction indexes.

The calibration results of the BG2015R Radon measuring instrument using two different methods, namely the radon solid source and the radon chamber, were compared and analyzed. The results show that the calibration coefficient (K) obtained from calibrating the BG2015R Radon measuring instrument in the radon chamber at three different measuring points is 5%, larger than that obtained using the radon solid source. The repeatability of the radon chamber calibration was calculated at low concentration measurement points, while the repeatability of the radon solid source calibration was lower due to the higher measurement concentration. When calibrating the BG2015R Radon measuring instrument using the radon chamber, the relative inherent error was calculated using the calibration coefficients from three measurement points, allowing for a linear evaluation of the instrument’s response. However, when using the radon solid source calibration, repeated measurements were only made at a single measurement point, and the relative error was calculated from multiple calibration results, which did not allow for a linear evaluation.

We collected and processed multi-source observational data, including high-rate GNSS, near-field strong motion, and InSAR data, from the area surrounding the epicenter of the 2022 Menyuan M_W6.6 earthquake, to reveal the preliminary results of coseismic displacement waveforms and InSAR deformation fields. Using high-rate GNSS data to quickly obtain fault rupture characteristics, we found that the earthquake was left-lateral strike-slip. The Lenglongling fault exhibited a maximum slip of 3.9 m at a depth of approximately 1 km, while the Tuolaishan fault had a maximum slip of 2.1 m at a similar depth. By combining high-rate GNSS, near-field strong motion, and InSAR data in a joint inversion, the Lenglongling fault’s maximum slip was determined as 3.8 m at a depth of 3.2 km, and the Tuolaishan fault’s maximum slip was 1.2 m at a depth of 2 km. The inclusion of near-field strong motion data in the multi-source joint inversion provided more accurate results compared to existing inversions using only high-rate GNSS and InSAR data. Analysis of the rupture process and source time function indicated that the earthquake lasted 14 seconds, with energy release concentrated in the first 9.5 seconds. The seismic moment release rate peaked at 5 seconds and then gradually slowed down, with a total release of 1.33×10¹⁹ N·m, corresponding to a moment magnitude M_W6.63.

Cathaysian Block and Jiangnan Orogenic Belt are located on the active continental margin, and the deformation mode of the lithosphere in this region is of great significance for studying the subduction of the Pacific Sea and Philippine Sea Plates into Eurasia. The anisotropy of SKS waves to indicate the direction of material flow in the upper mantle is a powerful means to study the deformation of the deep lithosphere. Based on the teleseismic waveforms from 23 fixed stations in Zhejiang Province, shear wave splitting measurements were conducted to analyze the anisotropic characteristics of different blocks in the Cathaysian Block and the northern part of the Jiangnan Orogenic Belt. The results showed the fast polarization of the middle and lower reaches of the Yangtze River Metallogenic Belt is 70.0°, with a splitting time of 0.58 s; the fast polarization of the southeastern part of the orogenic belt is -60.7°, with a splitting time of 0.89 s; the fast polarization of the Cathaysian Block is -65.0°, with a splitting time of 0.90 s. The study suggests that the mantle under the middle and lower reaches of the Yangtze Metallogenic Belt flows parallel to the metallogenic belt. The mantle under the southeastern part of the Cathaysian Block and Jiangnan Orogenic Belt flows along NW—SE to NWW—SEE. The deep boundary between the Jiangnan Orogenic Belt and Cathaysian Block is likely located in the Qin-Hang Junction Zone, which is closer to the Yangtze block.

The Tibetan Plateau and its surrounding areas not only are characterized by intense seismic activity, but also experience various types of geological disasters, including landslides, ice avalanches, snow avalanches, debris flows, and glacial lake outburst floods. These disasters result from the rapid downward movement of debris such as rocks and glaciers, and are influenced by factors such as tectonic movements and environmental changes. From a seismological perspective, these geological hazards are considered to be the result of a unidirectional force acting on mountain slopes, with seismic waves providing crucial information about the source parameters and processes of these hazards. This paper systematically reviews the recent advances in the study of landslide-type geological hazards by compiling previous studies and summarizes the basic principles of using seismic waves to study landslide sources. The 2017 Maoxian landslide is selected as a case study, and seismic waveform records are subjected to time-frequency analysis, force-time function inversion, and other calculations. The analysis process is refined through the comparison of timelines and optimization of station data selection. The results indicate that the Maoxian landslide process includes three stages: pre-sliding initiation, main sliding, and post-sliding adjustment, with a total duration of approximately 123 seconds. The main sliding process comprises acceleration and deceleration phases, with a maximum velocity of about 54 m/s and a maximum horizontal displacement of about 2 km. Low-frequency signals are significant during the acceleration phase, while high-frequency signals are significantly enhanced during the deceleration sliding process, revealing the comprehensive impact of changes in slope gradient, debris composition, and sliding friction. With the continuous improvement of seismic observation and data processing technology, the ability of seismic waves to identify landslides is gradually enhanced, which helps to improve the monitoring capability of landslide-type geological hazards.

The pull-apart basin is an important derived structure in strike-slip faults, and its formation is closely related to fault activity. In this paper, a small pull-apart basin, which developed in the western section of the Altyn Tagh fault near the macro epicenter of the 1924 Minfeng M_S7.3 double earthquakes, was taken as the research object. Based on the high-resolution digital elevation model obtained from the GF-7 satellite stereo image pair and the principle of sediment volume conservation, the volume change during the formation process of the pull apart basin was systematically obtained, and the pull value of the basin was calculated to be 391 m. Near-surface Optically Stimulated Luminescence (OSL) samples of the diluvial platform, where the basin locates, are collected and measured, and the result shows that the basin formation age is (14.53±0.6) ka, so the fault slip rate of this section is 12.9~14.0 mm/a. The normal fault profile is discovered in the pull-apart basin. Combined the study of stratigraphic sedimentary sequences and the OSL results, it reveales at least two seismic displacement events since 7.15 ka, and the last one is likely related to the 1924 Minfeng double earthquakes.

The occurrence of an earthquake is instantaneous and destructive, which may cause serious disaster to human society. Therefore, the development of relevant theories and methods for earthquake prediction is of great significance. In this study, classical back propagation (BP) neural network and variational mode decomposition (VMD) technology are combined to develop a new VMD-BP earthquake prediction model. Four VMD-BP models were constructed to predict the time, magnitude, and location (latitude and longitude) of earthquakes. For each entry in the earthquake catalog, four features other than the depth of the earthquake source are considered: time difference, magnitude, latitude, and longitude. The past five adjacent seismic events was used as the input to the VMD-BP model, and the next seismic event was used as the output. The model was empirically analyzed in the Sichuan and Xizang regions. By comparing the prediction performance of the models, it is concluded that the VMD-BP model has better prediction accuracy and goodness of fit than the BP model. It illustrates that the VMD-based model can make more accurate earthquake prediction, which will provide useful references for future in-depth research on earthquake prediction.

Short term earthquake prediction is both a focus and challenge in earthquake research. Due to the incomplete understanding of the mechanism of earthquake occurrence, which involves multiple disciplines such as crustal movement, rock mechanics, and geophysics, studying short-term earthquake prediction is also a challenge and exploration for these scientific problems. Submitting earthquake short-term prediction cards to the earthquake management department is an important way to participate in earthquake short-term prediction work. In order to analyze the effectiveness of earthquake short-term prediction cards and accumulate experience in earthquake short-term prediction, this article systematically compiles the prediction cards related to Sichuan region from January 2016 to June 2023, briefly describes the basis for important prediction opinions, and discusses the improvement method of earthquake prediction card disposal process, to provide reference for earthquake short-term prediction work.

Hydrogeochemical anomalies in hot spring water can reveal short-term precursory anomalies before earthquakes, yet there remains divergent understanding the significance of the anomalies in different chemical components. This study presents a two-year continuous observation of major elements and isotopes in three hot springs located within 150 kilometers of the epicenter of the Longyang M_S5.2 earthquake that occurred on May 2^nd, 2023.The results reveal synchronous anomalies(δ18O、 δD、 SO^2-₄、 Cl^-)around three months (93~120 d) before the earthquake at the Eryuanniujie hot spring, characterized by deep water circulation and intense water-rock interactions. The Jiancao hot spring exhibited anomalies in volatile components (Cl^-) 112 days before the earthquake, likely influenced by deep-seated gases. Conversely, anomalies in major ions appeared approximately one month (36~43 d) before the earthquake at the Lianchangping hot spring, where shallow water circulation and pronounced mineral dissolution effects are observed. The hydrological and geochemical precursory anomalies in these three hot springs suggest that chlorine, as a volatile element, can carry more profound information, making it an advantageous indicator of short-term earthquake precursors. The simultaneous anomalies in multiple chemical components provide clearer earthquake indications. The timing of anomalies correlates with the depth of water circulation: anomalies in deeper circulating hot spring water appeared approximately three months before the earthquake, while those in shallower circulating hot springs occurred about one month prior. Comparative analysis of the post-seismic trends in the Eryuan Niujie hot spring following the 21^st May, 2021 Yangbi M_S6.4 earthquake indicates that hot springs within the same fault system as moderate earthquakes undergo disrupted water circulation and re-established a new equilibrium after them. Therefore, the background values of hot spring water following moderate earthquakes must be re-evaluated in the context of the specific tectonic settings.

Medium-term earthquake prediction plays a vital role in China’s progressive forecasting system, which integrates the mid-long term earthquake prediction. It enables dynamic monitoring of long-term trend predictions and key seismic hazard zone forecasts, applies these results to annual forecasting, and provides a reliable scientific basis for short-term forecasts. The task of dynamically monitoring long-term trends and location predictions is undertaken by the Expert Group on Tracking Earthquake Situations within the General Seismic Trend. The main tasks of tracking earthquake situations within the general seismic trend include: ① Determining seismic activity trends and main active zones for the next 1—3 years or longer. This involves forecasting changes in seismic trends (e.g., increases or decreases) in Chinese mainland, predicting the highest activity levels (maximum magnitude and frequency of M7 earthquakes), and identifying major active zones of strong earthquake based on a synthesis of national seismic trends and key tectonic zone analyses. ② Assessing the urgency of earthquake occurrences in key seismic risk zones identified on a 10-year scale for the next three years. The foundation of earthquake trend and key area prediction primarily includes phase activity, anomalies in seismic activity, regional crustal deformation, and the state of regional crustal stress. While the data processing, analysis, and calculation methods employed are quantitative, the underlying approach generally relies on empirical prediction methods derived from historical earthquake cases. The identification of long-term hazardous areas relies on probabilistic predictions derived from physical models of seismic sources. Similarly, the medium-term assessment of earthquake urgency builds upon the principles of long-term prediction, incorporating dynamic tracking of fault movement, fault stress states, and seismic source anomalies. Overall, this approach combines probabilistic predictions based on seismic source models with empirical predictions derived from earthquake indicators. This study systematically presents the conceptual framework and technical system for tracking seismic trends over the next 1—3 years and assessing the urgency of long-term hazardous zones in the continental region of China. It provides a brief overview of various prediction methods, covering basic principles, technical approaches, and medium-term anomalous characteristics. Finally, based on the practice of medium-term prediction and recent research progress, the study highlights the research needs for understanding the gestation and occurrence processes of strong continental earthquakes, their precursor mechanisms, and outlines future prospects for earthquake research in China. From a business perspective, it is hoped that the development direction of medium-term forecasting can be further clarified through the phased summarization of the technical system, tracking concepts, and forecasting methods. From a scientific perspective, the development of medium-term prediction identifies basic scientific and technological needs, including the integration of field and source concepts, foundational theoretical frameworks, and key issues in earthquake dynamics. These efforts are expected to contribute to basic research in earthquake prediction and the advancement of forecasting practices.