Using earthquake catalogue, this study applied the Load-Unload Response Ratio (LURR) method to investigate anomalies preceding five M_S≥5.5 earthquakes (including three M_S≥6.0 earthquakes) in the northern segment of the North-South Seismic Belt during 2015—2023. LURR anomalies were identified within 300 km of each epicenter, with peak anomalies occurring approximately 5~20 months prior to the mainshocks. For the 2015 Alxa M_S5.8 and the 2016 Menyuan M_S6.4 events, dimensional analysis was used to quantify the magnitude and timing of the earthquakes and refine the epicentral locations from a forward-prediction perspective. The results indicate that the LURR method has considerable applicability for intermediate-term earthquake forecasting in complex tectonic settings. Our study provides new insights into seismogenic processes and regional seismic hazard assessment.

Based on the Yunnan earthquake sequence catalog from 1970 to 2024, this study selected 40 earthquake sequences of foreshock-mainshock and swarm (accounting for 1/3 of all sequences with M_S≥5.0) to explore their spatial distribution characteristics, as well as the temporal and magnitude relationships between the first significant earthquake and the first target earthquake. The results indicate that: ① Foreshock-mainshock and swarm-type earthquake sequences are mainly distributed in southwestern Yunnan and western-northwestern of Yunnan, while no such sequences occur in southeastern Yunnan. Earthquake cases with M_S≥7.0 are concentrated in western and southwestern of Yunnan. ② 67.5% of the first target earthquakes occurred within 10 days after the first significant earthquake, with 37.5% occurring within 24 hours. The probability of the first target earthquake occurring within 10 days exceeds 70% in central Yunnan and northwestern Yunnan. ③ Magnitude changes are primarily characterized by cross-magnitude-level escalation and equal-magnitude fluctuations. In western of Yunnan, there are no across-bracket downgrade seismic cases, and the proportion of cross-magnitude-level escalation is high. In central and northeastern of Yunnan, equal-magnitude fluctuations dominate. The research findings can provide a statistical basis for earthquake trend judgment in post-earthquake emergency response in Yunnan. Special attention should be paid to the risk of larger or comparable magnitude earthquakes occurring within 10 days in the original seismic area after a significant earthquake.

On January 8, 2022, at 01:45, an M_S6.9 earthquake occurred in Menyuan County, Haibei Prefecture, Qinghai Province. Based on the seismic waveform data from 38 seismic stations, we identified and located Very-Low-Frequency Earthquake (VLFE) occurring during the six days preceding the mainshock. The research adopts waveform envelope analysis and short-time Fourier transform techniques, combined with an envelope cross-correlation method for VLFEs location. Temporal sequence analysis was further applied to investigate the spatial evolution of the VLFEs. The results show that 12 VLFEs were identified in the three days prior to the Menyuan earthquake, all associated with activity along the seismogenic fault. Notably, the last event (VLFE12), with the largest magnitude (M2.34), occurred only 55 km from the mainshock epicenter, suggesting a close connection with the main shock. Compared with natural minor earthquakes, VLFEs were spatially closer to the seismogenic faults. These events can thus supplement the limitations of small earthquake analyses. In-depth research on the associated seismogenic characteristics between VLFE events and seismogenic faults plays an important role in determining the activity of the main fault before the earthquake and the location of the future epicenter.

When tectonic stress increases, the amplitudes of incoming seismic surface waves from outside the study area increase. This amplification is due to the low attenuation coefficient of crustal media, along with focusing effects caused by wave impedance contrasts. As a result, seismogenic zones can be identified through observations of temporal variations in disturbing surface wave amplitudes (DSWA). In this study, we analyzed data from vertical-pendulum (VP) tilt-meters deployed in northeastern China between 2016 and 2019. We used these data to calculate DSWA for offshore earthquakes. We derived normalized amplitudes using magnitude-amplitude scaling relations and set criteria for identifying anomalies. Time-correlation analysis revealed a short-term correspondence between normalized DSWA anomalies and M≥4 earthquakes in the region. Case studies, such as the 2018 Jilin Songyuan M5.7 earthquake, demonstrated a progressive transition from weak to strong in DSWA near epicenters. These results indicate DSWA anomalies can help constrain the timing and location of moderate to strong earthquakes. This is particularly useful in compressional tectonic settings such as northeastern, southwestern, and northwestern China.

The Outgoing Longwave Radiation (OLR) data were used in the predict of the seismic activity situation in the Chinese mainland from November 2023 to October 2024. The M_S6.2 earthquake occurred in Jishishan County, Linxia Prefecture, Gansu Province (35.70°N, 102.79°E), on December 18, 2023. For this earthquake case, the characterization of OLR daily variation was retrospectively analyzed over a wide range (17°N~55°N, 73°E~135°E) and long time series (before, during, and after the earthquake). The results show that: ① From November 10, 2023 to January 8, 2024, the tide in the dangerous area experienced four consecutive cycles of peak-valley-peak (A, B, C and D), and the earthquakes occurred near the valley phase of “C” cycle. According to the daily variation of OLR in in the Chinese mainland observed synchronously during the four tidal cycles, only in the “C” cycle, with the tide changing from high point to low point, a significant and isolated OLR anomaly area extending in the northeast direction appeared synchronously in the epicenter area. The time evolution of this anomaly area underwent a process of “micro-enhancement—enhancement—micro-attenuation—enhancement—quiet”, which was consistent with the temporal and spatial evolution characteristics of infrared radiation in each stage of the process of “micro-rupture—rupture—locking—accelerating rupture—rupture” under stress. ② The abnormal area is distributed around the epicenter. In terms of time, after the OLR anomaly in the study area was enhanced, it recovers to be calm in the A and B cycles of the short-term tracking, and the continuous enhancement occurs in the C cycle, followed by a brief recession on the 15th-17th, and an earthquake occurs after the re-enhancement on the 18th, and the post-earthquake anomaly gradually attenuates and tends to be calm. In space, the OLR anomaly area obtained by tracking is distributed in strips. This temporal and spatial dynamic difference of OLR is not only the “thermal” image representation of seismic tectonic stress state at different stages, but also shows that earthquake preparation is a dynamic development process. It is of great significance to improve the ability of earthquake spatial-temporal prediction by adhering to the remote sensing monitoring and prediction method combining long-term, medium-term, and short-term.

Based on the thermal infrared brightness temperature data from China’s geostationary satellite, wavelet analysis and relative power spectrum methods were employed to examine the thermal radiation changes before and after three moderate-strong earthquakes in East China, which were the Gaoyou M_S4.9 earthquake on July 20, 2012, the Pingyuan M_S5.5 earthquake on August 6, 2023, and the Feidong M_S4.7 earthquake on September 18, 2024. We obtained the temporal and spatial evolution plots of different frequencies and the relative power spectrum time series curves of the regions with significant changes. It was found that there are thermal infrared bright temperature anomalies before the three earthquakes. The anomalous radiation zone progressively evolves and expands along the fault proximal to the epicenter, exhibiting a consistent trend as it gradually converges towards the epicenter from farther to closer regions. The relative power spectrum amplitude during the anomalous period exceeds 4 and persists for a minimum of 20 days, significantly higher than the amplitudes observed during other periods of the year. The maximum recorded amplitude correlated positively with earthquake magnitude. The seismic events generally occurred within approximately one month following the anomaly onset; however, the characteristic period length exhibited no consistent relationship with the earthquakes.

The monitoring of hydrochemical ions in hot spring water is a method that can provide information on short-term precursory anomalies before earthquakes. By conducting dynamic monitoring of hydrochemical ions in water samples from Aiken Spring and Dachaidan Hot Spring (hereinafter referred to as AKQ and DCD, respectively) located on the frequently active fault zones in western Qinghai, and analyzing the correlation between the changes in hydrochemical ions of hot spring water and the occurrence of earthquakes in the surrounding area, the following results were obtained: ① The hydrochemical types of AKQ and DCD are Mg·Na-Cl·HCO₃ and Na-Cl, respectively. ② The δ¹⁸O and δD values of AKQ range from -11.48‰ to -9.45‰ and -74.67‰ to -66.93‰, respectively. Comparative analysis with the isotopic composition of atmospheric precipitation indicates that the main sources of recharge for the hot spring water in the study area are groundwater and atmospheric precipitation, with a recharge elevation of 3.0 to 3.4 km. ③ The water-rock reaction analysis shows that AKQ is immature water, while DCD is partially mature water. The estimated geothermal reservoir temperatures are 103.84℃ and 148.03℃, respectively, and the estimated depths of thermal circulation are 2679 m and 4816 m, respectively. ④ Taking earthquakes of magnitude 4.5 and above that occurred in the vicinity during the dynamic monitoring period of hydrochemical ions in AKQ and DCD as case studies, the average concentrations of Cl^-, Na⁺ and SO^2-₄ were used as background indicators, and concentrations exceeding the average value plus or minus two times the standard deviation were considered as short-term precursory anomaly indicators. The R-value scoring method was used to evaluate the effectiveness of the anomalies. The results show that the anomalies of AKQ have high predictive effectiveness for earthquakes of M4.5 or higher within a range of 1100 km, while the anomalies of DCD have high predictive effectiveness for earthquakes of magnitude 4.5 or higher within a range of 300 km. These anomalies have good reference value for earthquake prediction. ⑤ The short-term precursory anomaly change type of AKQ is a “decrease-recovery” pattern. The anomalies appear 10 days to 1 month before the earthquake and last for 9 to 50 days. For earthquakes within a 300 km range, the precursory anomalies last for 1 month to 50 days, and the earthquake usually occurs around the 20th day of the anomaly period. For earthquakes beyond a 300 km range, the precursory anomalies last for no more than 20 days and the earthquake occurs within 1 month after the anomaly ends. The short-term precursory anomaly change type of DCD is mainly characterized by “decrease-stable” or “decrease-recovery” patterns, with a few earthquakes showing an “increase-stable” pattern. The anomaly duration ranges from 3 days to 1 month, and the earthquake generally occurs within 1 month after the anomaly ends. ⑥ The main cause of the anomalies may be changes in the regional tectonic stress field before the earthquake, leading to fluid mixing or water-rock interaction, which in turn causes changes in hydrochemical ion concentrations. The persistence or recovery of the anomaly pattern may be related to whether the seismic stress is sufficiently released or a new water-rock reaction equilibrium is re-established, as well as whether the stress is permanently altered after the earthquake or if the fractures are blocked by mineral precipitation resulting from water-rock reactions.

This study utilizes water level and hydrochemical analysis data from 14 observation wells of the National Groundwater Monitoring Project in the southern segment of the Qingshui River Basin, Ningxia, China. Based on convolutional regression, spectral analysis, harmonic analysis, and water-rock equilibrium state methods, the confined nature of groundwater in the aquifer system of each well is comprehensively evaluated. The results indicate that wells 173 and 174 are unconfined groundwater, with close hydraulic connections to the external environment. The remaining 12 wells exhibit varying degrees of confined groundwater characteristics, being influenced not only by certain external hydraulic connections but also by deeper groundwater. These 14 wells in the region can serve as a valuable supplement for seismic precursor monitoring. In future seismic tracking, the dynamic characteristics of groundwater levels and hydrochemistry from these wells can be fully utilized to capture precursor anomalies associated with earthquake preparation processes.

Pre-earthquake assessment of landslide hazards has become one of the important means to reduce secondary disasters of earthquakes. Since its construction, more than 500 earthquakes have occurred in the Jiaokou Reservoir area of Ningbo (as of 2021), China, where seismic activity is relatively active and has certain potential for moderate earthquakes, but no earthquake-triggered landslide hazard assessment has been conducted. In this study, the simplified Newmark method was used to assess the distribution of high-risk areas of earthquake-triggered landslides in the Jiaokou Reservoir area under a scenario earthquake of M_S5.5. The study shows that the high-risk areas of earthquake-triggered landslides are relatively concentrated in the central and southern parts of the study area, and there are also some high-risk areas of earthquake-triggered landslides around the reservoir area. The potential earthquake-triggered landslides have a limited impact on buildings and population in the area. The roads leading to the earthquake’s epicenter are largely unaffected by potential landslides. However, there are certain risks of small-scale landslides and falling rocks on two sections of the road located about 1 km and 1.5 km from the dam site on the right bank of the reservoir. The reliability of earthquake-triggered landslide risk assessments can be enhanced by utilizing large-scale geological maps, selecting appropriate physical and mechanical parameters for rock-soil masses, and improving earthquake-triggered landslide inventories, among other measures. When combined with targeted field investigations, these preliminary assessments of earthquake geological disasters can provide a highly reliable technical support for regional earthquake prevention and disaster reduction efforts.

The quantitative analysis of sedimentary layer amplification effects can provide fundamental data for seismic hazard assessment and source parameter inversion. Calculating the amplitude ratio of seismic waves directly from seismic observation records at different depths within sedimentary layers, eliminates the need for modeling the sedimentary layer structure and site conditions, and avoids errors caused by structural uncertainties. This approach serves as an effective means to analyze sedimentary layer amplification effects. Taking the Tianjin Plain as the study region, this research utilizes seismic record data from borehole velocimeters of the Tianjin Seismic Network and surface accelerometers of the earthquake early warning network (operational since June 2021) at co-located observation sites. The workflow involves: ① using waveform cross-correlation to pick up the direct P-wave and S-wave phases, as well as the travel-time differences of corresponding surface-reflected phases; ② calculating the horizontal S-wave relative amplitude ratio from the amplitudes of direct body waves at the surface and borehole levels; ③ deriving the spatial distributions of P-wave to S-wave velocity ratios (V_P/V_S) and S-wave relative amplification factors. Based on the relative amplification factors of seismic waves, the study further determines the magnitude differences and correction values between surface and borehole stations, and analyzes the factors influencing velocity ratios and relative amplitude ratios. The results show that: ① the V_P/V_S velocity ratios in the study area range from 4.5 to 5.8, with a spatial distribution characterized by relatively higher values in southern Tianjin and lower values in the central region; ② the relative amplitude ratios range from 0.88 to 2.65, exhibiting a spatial pattern of smaller values in southwestern Tianjin and larger values in the central and eastern regions; ③ in southwestern Tianjin, the magnitudes calculated from surface accelerometers and borehole velocimeters are essentially consistent and require no correction. For other regions, the magnitudes from surface accelerometers align well with those from borehole velocimeters after subtracting 0.3. By comparing the spatial distributions of velocity ratios and relative amplitude ratios with regional tectonic features, sedimentary layer thickness distribution, meteorological factors, groundwater levels, and surface subsidence, we find that shallow tectonic structures and meteorological factors have weaker correlations with the results. In contrast, changes in groundwater levels causing variations in sedimentary layer saturation and surface subsidence causing compaction of sedimentary layers can explain the spatial distribution characteristics of seismic ground motion in sedimentary layers. This paper speculates that changes in groundwater levels and the associated changes in surface subsidence rates may be an important factor influencing the spatial distribution characteristics of velocity ratios and relative amplitude ratios.

This study collected ground motion intensity attenuation relationships for Chongqing and its adjacent regions. Selected intensity attenuation models were transformed using regional bedrock strong-motion data, and regression analysis was performed to derive region-specific ground motion attenuation relationships. The derived model was then validated using strong-motion recordings from the M6.8 Luding earthquake in Sichuan. Compared with other regional studies, the proposed model exhibits lower near-field saturation peak ground acceleration (PGA) and a more rapid attenuation trend in the far field, indicating that ground motion attenuation characteristics are closely related to regional seismicity and geological structures. Additionally, the stochastic finite-fault method was employed to simulate historical earthquakes in Qianjiang. The simulated spatial distribution showed good agreement with field investigation results, further supporting the applicability of the proposed attenuation model to historical events. This study provides valuable data support for seismic design of major engineering structures and post-earthquake disaster assessment in the region, demonstrating its practical engineering significance.

In China, earthquake prediction follows a progressive refinement approach across four temporal scales: long-term, medium-term, short-term, and imminent (referred to as “long-medium-short-imminent”). As a continuation of medium term prediction for 1~3 years, medium-short term prediction focuses on the annual to imminent stages. Within the framework of medium-short term earthquake prediction operations, the primary task of electromagnetic (EM) methods is to analyze and identify anomalies with predictive significance across annual to imminent scales, providing a scientific basis for nationwide comprehensive earthquake prediction. Another mission of EM methods is to conduct medium-short term earthquake predictions based on the correlation mechanisms between EM anomalies and seismogenic processes, as well as the established earthquake prediction strategies. The EM-based medium-short term prediction involves two main tasks. The first is annual-scale prediction. This work is primarily conducted during annual consultations, involving predicting the locations and magnitudes of potential moderate-to-strong earthquakes in the coming year. The second is short-term to imminent prediction. This work is carried out in weekly and monthly consultations. The aim of short-term to imminent prediction is to dynamically assess the urgency of an earthquake occurrence based on the evolving stages of anomalies. This approach aligns with China’s overarching earthquake prediction strategy. Spatially, it employs the principle of “field-to-source and source-to-field” analysis (identifying seismic sources through regional field anomalies and vice versa), while temporally adhering to the “long-medium-short-imminent” progressive refinement. Technically, the prediction process begins with evaluating background anomalies (e.g., apparent resistivity, geoelectric field, and geomagnetic field variations) to identify concentrated zones for potential locations and magnitudes. Subsequently, abrupt changes (short-term to imminent anomalies) within or near the predicted regions are dynamically monitored. Most of the anomaly analysis relies on quantitative methods, though prediction criteria are mainly empirical, derived from historical case studies. While some anomalies exhibit clear links to the late stage of seismogenic processes, others require further investigation. This paper reviews the technical methodologies, anomalous characteristics, and underlying mechanisms involved in EM-based medium-short term earthquake prediction, aiming to stimulate future advancements in earthquake prediction based on electromagnetic observations.

This paper reviews the development process and current application status of geoelectric field data in the field of earthquake prediction in China over the past 60 years. It elaborates in detail on the evolution of the geoelectric field observation system from its early stage to modern digital and multi-pole distance observation. It analyzes the normal variation characteristics of the geoelectric field, the methods for extracting pre-earthquake anomalies, and application examples in earthquake prediction practice. At the same time, it discusses the existing problems and challenges in current research and offers insights into future development trends. Through comprehensive analysis of multi-source data, it aims to fully present the important value and development prospects of geoelectric field data in the field of earthquake prediction, and provide references for subsequent research.

In 2023, the CEA proposed to establish the IASPEI Commission for the Rapid Interdisciplinary Investigation of significant Earthquakes (Comm. RI²sE). In 2025, the IASPEI resolution adopted the establishment of the Comm. RI²sE. This paper briefly summarizes the related discussion and communication, especially those in Berlin, Beijing, Antalya, Windhock, Shenyang, and Lisbon, recording the evolution of ideas with the discussion, which also provides the commission with suggestions.