On March 28, 2025, an MS7.9 earthquake occurred in the Himalayan-Myanmar Arc at the junction of the Indian Plate and the Eurasian Plate. Utilizing broadband waveform data provided by the Global Seismographic Network, this study adopted the W-phase method and the P-wave first-motion polarity method to invert the centroid-moment-tensor and fault plane solutions of this earthquake. Additionally, the far-field point source model, global attenuation model, and energy flux density method were used to determine the radiated energy of this earthquake. The energy-moment ratio, apparent stress, stress drop, and radiated energy enhancement factor were also calculated based on the measured seismic moment. The main findings are as follows: (1) this event was a strike-slip earthquake with steeply dipping faults. The focal mechanism solution yielded two nodal planes: Plane I (strike 358°, dip 70°, rake −175°) and Plane II (strike 266°, dip 85°, rake −20°). The seismic moment of 4.94 × 1020 N·m corresponds to a moment magnitude of 7.7. The centroid was located at 21.21°N and 95.92°E and a depth of 35.0 km. The centroid time was 35 s. (2) The radiated seismic energy was 2.6 × 1016 J, which was converted to an energy magnitude of 8.0, higher than the moment magnitude. (3) The energy-moment ratio was 5.3 × 10−5, apparent stress was 1.58 MPa, stress drop was 6.79 MPa, and radiated energy enhancement factor describing the complexity of fault rupture was calculated as 113. (4) In summary, the Myanmar earthquake is a strike-slip earthquake, characterized by steeply dipping faults and highly efficient energy release. Compared with earthquakes of the same magnitude, such earthquakes have a greater destructive power on local buildings and infrastructure, increasing the likelihood of severe disasters.

With the increasing depth and intensity of coal mining in China, non-natural seismic events occur more frequently, posing higher demands on mine safety and seismic monitoring. a core parameter in earthquake monitoring and hazard assessment, precise determination magnitude is essential for predicting and mitigating dynamic disasters. To address this, conducted 22 controlled blasting experiments in the Weihai Port area of Shandong Province, using a combination of fixed and mobile seismic stations to systematically investigate the attenuation characteristics of near-field seismic waves and to establish a regional calibration function for magnitude (ML). The calibration functions for both horizontal and vertical components derived through least-squares fitting, from which the corresponding local magnitude determination formula was developed. Results from the 22 blasting events indicate good consistency of single-station magnitudes, with small deviations compared to the magnitudes determined by the Shandong Seismic Network, satisfying the required accuracy for magnitude estimation. Overall, this study establishes a calibration function applicable within 5 km of Weihai blasting area, enhancing the consistency between magnitudes of blasting and natural earthquakes. The results provide a valuable reference for improving regional seismic monitoring systems and strengthening early warning capabilities for mine-related hazards.

The absence of a standardized magnitude determination framework in China’s coal mine microseismic (MS) monitoring networks has led to substantial discrepancies in magnitude estimates across different mines, as well as systematic deviations from the magnitudes reported by the China Earthquake Networks. These inconsistencies arise primarily from inconsistent methodologies, the complex high-frequency wave propagation characteristics and inappropriate application of regional attenuation models to near-field MS data. Together, these issues undermine the comparability, reliability, and practical utility of MS monitoring results. To address this challenge, we propose a unified magnitude calibration framework specifically designed for coal mine MS monitoring in China, with the goal of aligning MS magnitude estimates with national seismic standards. Based on data from 29 controlled underground blasting experiments conducted at four geologically distinct coal mines using hybrid monitoring networks (surface and underground sensors), we derived site-specific high-resolution calibration functions and calculated the corresponding event magnitudes. Our results revealed that while surface stations exhibit stable attenuation characteristics, underground propagation paths vary significantly between sites. Importantly, vertical component amplitudes showed equivalent reliability to horizontal components, enabling simplified processing approaches. For mines where blasting experiments were unfeasible, empirical average attenuation models were developed based on observational data from four coal mines. Finally, application of the model to a mining-induced high-energy event demonstrated improved magnitude consistency and largely eliminated systematic distance-dependent bias. These findings support the integration of the newly developed magnitude scales into existing mining-induced seismic monitoring systems, which can be calibrated through localized data accumulation. This integration systematically enhances monitoring effectiveness across two critical dimensions—disaster assessment accuracy and early warning timeliness—specifically tailored to address the prevention and control demands of rockbursts and other mining-induced seismic events.

Automated classification of seismic events is critical for earthquake monitoring and explosion detection, particularly in tectonically active regions, such as North China, where the waveform features of earthquakes and explosions are highly similar. This study compared feature-based machine learning (ML) and image-based deep learning (DL) methods in event- and station-level classification frameworks. The dataset consisted of 1,847 events and more than 43,000 vertical-component waveforms with two input types, 40-dimensional feature vectors for ML and spectrogram images for DL. The results showed that the event-level models consistently outperformed the station-level models, achieving over 98% accuracy; the station-level models performed well above 94%. On the test set, the ML and DL models exhibited comparable performance; however, the ML models demonstrated better generalization and lower computational demands. In contrast, DL models required fewer manual interventions. The misclassification analysis revealed distinct error patterns across the model types, indicating potential complementarity. These findings highlight the importance of model choice based on the input type, data granularity, and generalization needs. Although DL models are well suited to automated processing, ML approaches provide more robust and efficient solutions for real-world deployment.

In studies related to crustal stress, the spatial distribution of three-dimensional stress is often described by the azimuth distribution of the maximum and minimum horizontal principal stresses. In this paper, we investigated whether the azimuth of the horizontal principal stress can indicate the azimuth of the three-dimensional principal stress. The results show that the azimuth of the horizontal principal stress does not always accurately indicate the azimuth of the three-dimensional principal stress, nor do the azimuths of the maximum and minimum horizontal principal stresses always correspond to the compressive and tensile axes of the three-dimensional stress. The azimuth of the maximum horizontal principal stress may be close to the azimuth of the σ_1 or σ_2 axis, while the azimuth of the minimum horizontal principal stress may be close to the azimuth of the σ_2 or σ_3 axis. The correspondence between the azimuths of the maximum or minimum horizontal principal stress axis and the three-dimensional principal stress axis, as well as the azimuth angle between them, is closely related to the inclination of the three-dimensional principal stress axis and the relative magnitudes of the three principal stresses (shape ratio). The results of this study imply that it is not feasible to use the azimuth of the horizontal principal stress to represent the azimuth of the three-dimensional principal stress without prior knowledge of the three-dimensional stress.

As coal reserves are exploited in deeper geological strata, the associated high stress and complex geological conditions lead to an increase in microseismic events. These events serve as precursor signatures for dynamic failure mechanisms—particularly stress-threshold-governed rock bursts—thereby introducing latent geotechnical risks to mining operations. Consequently, the deployment of microseismic monitoring systems in coal mines becomes critical. However, many of these systems in Chinese coal mines suffer from significant drawbacks due to maintenance and calibration deficiencies, inaccurate event location, and considerable errors in magnitude estimation. To address these issues and enhance the systems’ reliability and accuracy, we initiated controlled blasting experiments at the 6306 working face of the Dongtan Coal Mine. Here, we strategically deployed seismometers both at surface and underground locations near the blasting sites to capture the resultant seismic waves. Our analysis revealed substantial differences in waveform characteristics observed at surface versus underground stations. Specifically, waveforms recorded at surface stations demonstrate P-wave dominance near the source with high-amplitude, pulse-like signals, transitioning to prominent surface waves as the distance increases. In contrast, underground stations predominantly captured high-frequency P waves with shorter durations and more complex waveforms due to multipath propagation and source location discrepancies. The relocation results demonstrate that the double-difference location method is effective in achieving relatively high-accuracy event locations when utilizing both surface and underground data. Furthermore, we established a precise calibration function applicable to the Dongtan Coal Mine and determined the local magnitudes of eight blasting events. On the basis of these results, an empirical relationship between local magnitude and weights of explosives was preliminarily derived. These findings can help enhance the reliability of microseismic monitoring systems in coal mines, thereby contributing to safer mining operations.

Understanding Lg wave attenuation provides valuable insights into crustal properties such as temperature, partial melting, and fractures, making it a crucial tool for studying crustal material flow in tectonically active regions. Central-southwestern China, encompassing the eastern Tibetan Plateau, Sichuan Basin, Qinling Orogenic Belt, and nearby areas, is a key region for such research due to its complex tectonic activity driven by the collision between the Indian and Eurasian plates. However, many questions remain about the pathways and barriers that influence the eastward migration of crustal material from the Tibetan Plateau. To tackle these challenges, we treat unresolved 3-D structural effects in Lg spectral amplitude as Gaussian-distributed modeling errors. This approach supports our SVD-based inversion method, enabling reliable estimation of crustal attenuation and thorough evaluation of model resolution and reliability. By incorporating site response corrections into the traditional two-station (TS) method and integrating it with reversed two-station (RTS) and reversed two-event (RTE) techniques, we effectively minimized the impact of source and site effects, enhancing the accuracy of attenuation tomography. Utilizing over 34,000 Lg waveforms from 257 crustal earthquakes, we constructed a high-resolution broadband Lg wave attenuation model across a frequency range of 0.05–10.0 Hz. The findings reveal complex attenuation patterns that correlate with regional tectonic and crustal features, offering fresh insights into the pathways and barriers affecting the eastward flow of material from the Tibetan Plateau.

Studying the energy release characteristics of mining-induced earthquakes deepens our understanding of the mechanisms underlying such seismic events and thereby enhances safety measures in mining operations. To explore the energy release efficiency and mechanisms of mining-induced seismic events, we identified 59 earthquakes with magnitudes of 2.0 or above in China, which we determined to be mining-induced earthquakes on the basis of the publicly available earthquake catalog from the China Earthquake Networks. These events, which occurred between November 2014 and May 2023, were further studied by determining their seismic moment (M0) and radiated seismic energy (ER) via spectral inversion techniques. The main conclusions were as follows: (1) The energy release efficiency was assessed by determining the energy-to-moment ratio (Θ = log10(ER/M0)). The Θ values of mining-induced earthquakes significantly lower than those of natural tectonic earthquakes, indicating a lower energy release efficiency in mining-induced high-energy events. This difference was caused mainly by the reduced high-frequency energy in seismic waves produced by shallow mining-induced events. Additionally, the absence of near-field stations could restrict the detection of high-frequency energy directly emitted from the source. The variations in energy release efficiency between events were closely related to their seismic mechanisms and environmental conditions. (2) An empirical relationship between the moment magnitude MW and radiated seismic energy, expressed as log10(ER) = 1.5 MW + 2.35, was established for mining-induced earthquakes. (3) The energy release mechanism was analyzed by the S/P wave energy ratio. For most mining-induced events, these ratios were comparable to those of natural tectonic earthquakes, suggesting that tectonic forces dominated their seismic mechanisms. However, a few events displayed lower S/P wave energy ratios, indicating the potential presence of collapse or tensile components in their seismic mechanisms. (4) The energy release mechanism and focal mechanism of mining-induced earthquakes provide valuable insights into the causes of these events. This study contributes to a better understanding of the energy release and seismic mechanisms of high-energy earthquakes caused by mining activities and offers valuable insights for risk assessment and preventive measures.

At 14:20(Beijing time)on March 28,2025,a magnitude 7.9 earthquake struck the Mandalay region in central Myanmar.In response,the Institute of Geophysics,China Earthquake Administration,initiated a rapid scientific assessment involving multidisciplinary teams.Source parameters,focal mechanism,rupture process,and seismic radiated energy were estimated.According to the inferred source model,ground shaking intensity map and coseismic deformation field were simulated.The results indicate that the earthquake occurred along the Sagaing fault and was characterized by predominant right-lateral strike-slip motion.Both the moment energy ratio and the slowness parameter exceed global averages,suggesting a relatively high level of energy dissipation.The estimated intensity in the epicentral region may have reached or exceeded level X(on the Modified Mercalli Intensity scale),potentially affecting an area of approxi-mately three hundred thousand km2.Significant coseismic displacement was shown with the maximum horizontal offset reaching 1.09 m.

At 09:05 on January 7,2025(Beijing time),a magnitude 6.8 earthquake occurred in Dingri,Xizang Autonomous Region.The Institute of Geophysics,China Earthquake Administration launched a rapid earthquake emergency response after the earthquake,and organized researchers in relevant fields to estimate the source parameters,source mechanism,rupture process,and seismic radiation energy of the earthquake.The aftershock sequence was repositioned,and seismic intensity maps and InSAR coseismic deformation field simulations were conducted based on the source rupture process.The results indicate that the earthquake occurred on the west side of the Dengmocuo fault in the Shenzha-Dingjie fault system,with a main normal fault mechanism and a duration of about 20 seconds.It also exhibited asymmetric bilateral rupture characteristics,with the rupture mainly extending northward and most likely reaching the surface.Aftershocks are mainly distributed in a nearly north-south direction,with focal depths concentrated between 5～23 km.The seismic intensity in the extreme earthquake zone may reach seismic intensity IX or above,and the possible affected area may exceed 30000 km2.This earthquake caused significant surface coseismic displacement,with a maximum horizontal displacement of 0.29 m and a vertical displacement of-0.75 m.

Radiated seismic energy is a quantitative characteristic of an earthquake that depends not only on the initial and final stresses, but also on the rupture history, and reflects the dynamic characteristics of the source. The seismic wave energy radiated per unit of seismic moment, or energy-moment ratio, represents the balance between the stress drop, source rupture velocity, and variation in the shear wave velocity. Earthquakes with a high energy-moment ratio thus release strain energy more rapidly. The accurate and rapid determination of radiated seismic energy and the energy-moment ratio play an important role in seismic hazard assessment, quantitative earthquake research, and engineering seismology research. In this study, waveform data from the Global Seismographic Network were used to measure the dynamic source parameters of an earthquake that occurred on January 7, 2025, in Dingri, Xizang, with the radiated energy, energy-moment ratio, slowness parameter, and apparent stress investigated. Static source parameters such as the seismic moment and moment magnitude were also determined. The main results were as follows: (1) the radiated energy of the earthquake was 9.73×1014 J, corresponding to an energy magnitude ME of 7.1, with a source rupture time of 24 s; (2) the focal mechanism was normal faulting, with the seismic moment of 4.98×1019 N·m corresponding to a moment magnitude MW of 7.1. Nodal plane I was focused at 191°/32°/−67° while plane II was at 344°/60°/−104°, and the centroid depth was 12.3 km; (3) the energy-moment ratio of the earthquake was 1.95×10–5, the slowness parameter was −4.71, and the apparent stress was 0.59 MPa. The energy-moment ratio was thus higher than the average for normal fault earthquakes on the Chinese mainland. In conclusion, the results indicated that the 2025 earthquake was a normal fault earthquake with relatively high energy release efficiency and significant potential for damage to local buildings and the infrastructure, as verified by the severe damage to ground structures and significant casualties nearby.

Stress field inversion based on focal mechanisms requires accurate identification of seismogenic faults from the two nodal planes given by the focal mechanism, and then obtaining the stress field by fitting the slip direction of the seismogenic faults. However, current techniques and methods cannot guarantee that seismogenic faults can be accurately identified from all focal mechanisms. Therefore, a small fraction of the auxiliary fault planes are included in the fault data used for stress field inversion, and to what extent does the presence of this fraction of pseudo faults cause the reconstructed stress field to deviate from the actual stress field? In this paper, we have shown through synthetic experiments that the incorrect selection of faults for part of the focal mechanisms may cause the reconstructed stress direction and the relative magnitude of the principal stresses ( R) to deviate significantly from the actual situation. The amount of deviation in the reconstructed stress field is mainly related to three factors, which are the actual stress R value, the fraction of focal mechanisms that incorrectly selected faults, and the noise level contained in the focal mechanisms. When the actual stress R value is around the median, the only way to accurately reconstruct the R value is to accurately select the fault planes. When the actual stress R value is relatively small, accurate selection of the fault plane helps to accurately reconstruct the stress orientation. Therefore, accurate selection of faults from the focal mechanisms can ensure that the orientation and R value of the stress field can be accurately reconstructed under different background stress fields, which is important for reasonable interpretation of tectonic movement based on the reconstructed stress field.

At 22:37 on December 2, 2023 (Beijing time), a M7.6 earthquake occurred in the eastern waters of Mindanao，Philippines. The Institute of Geophysics, China Earthquake Administration initiated the response mechanism after this earthquake and organized geophysics researchers to estimate the source parameters, focal mechanism，rupture process and earthquake radiation energy of this earthquake. Based on the source model, the Shakemap and the coseismic deformation field simulation are carried out. Product results demonstrate that this earthquake occurred on the subduction zone slab where the Philippine Sea Plate collided with the Eurasian Plate/Sunda Block. This earthquake is of dominant thrusting mechanism. The energy was concentrated and released in the first 40 seconds. The maximum slip of the fault rupture is up to 7 m. The efficiency of the earthquake source in radiating seismic energy is low and the slowness coefficient is slightly lower than the average level of the global same moment magnitude earthquake, and the feeling of the earthquake is relatively weak. The earthquake intensity in the extreme seismic area possibly reaches more than Ⅸ, and the approximate disaster range is up to 27000 km2. This earthquake caused apparent coseismic displacement with the maximum displacements reaching 0.6 m and 1.2 m in the horizontal and vertical directions respectively. Comprehensive analysis shows that this earthquake can’t produce a large-scale tsunami.

At 23:59 on December 18, 2023 (Beijing time), a M6.2 earthquake occurred in the Gansu Province of Jishishan. The Institute of Geophysics，China Earthquake Administration initiated the response mechanism after this earthquake and organized geophysics researchers to estimate the source parameters, focal mechanism, rupture process, earthquake radiation energy and earthquake relocation of this earthquake. Based on the source model, the Shakemap and the coseismic deformation field simulation are carried out. The results demonstrate that the earthquake is of dominant thrusting mechanism. The energy was concentrated and released in the first 8 seconds. The earthquake intensity in the extreme seismic area possibly exceeded Ⅷ, resulting in an estimated disaster range of approximately 6000 km2. This earthquake caused apparent horizontal coseismic displacement with maximum displacements reaching 7.8 cm and 15.8 cm.

震源特征可通过震源参数量化,震后快速测定震源参数,对于研究区域构造特征、地震的震源性质和孕育演化过程、开展震害评估和地震应急响应都具有重要意义.本研究采用区域地震台网和全球地震台网提供的宽频带波形资料,使用近震全波形反演方法得到了 2022年1月8日青海门源Ms6.9地震的地震矩、矩震级和震源机制解等静态震源参数,并测定了地震辐射能量、能量震级和破裂持续时间等动态震源参数.结果显示:(1)本次地震为一次高倾角的走滑型地震,震源机制解节面Ⅰ走向194°、倾角87°、滑动角175°,节面Ⅱ走向285°、倾角85°、滑动角3°,地震矩为8.5X1018N·m,转化成矩震级为6.6,矩心深度为3 km.结合动态震源参数,可确定节面Ⅱ为地震断层面;(2)地震辐射能量为4.3×1014J,转化成能量震级为6.8,高于矩震级;(3)地震呈现双侧破裂特征,破裂持续时间为11 s;(4)能矩比为5.1×10-5,视应力为1.53 MPa,应力降为6.58 MPa,描述断层破裂复杂度的辐射能量增强因子为34;(5)综合本文结果,可认为门源地震属于一次断层倾角较高、能量释放效率偏高的走滑型地震.与同样震级的地震相比,这样的地震一般会造成比较严重的灾害.

After the occurrence of the 2008 Wenchuan M w 7.9 earthquake, the Longmen-Shan fault zone exhibits highly active seismicity. In the years between 2008 and 2022, successive moderate magnitude aftershocks followed in the region. In this study, we used high-quality seismic data from the National Earthquake Data Center of China to estimate the source parameters of 184 moderate magnitude events ( M w 3.9–6.2) in the Longmen-Shan Fault zone. The dataset comprised the aftershocks of two sequences that occurred in the area, including the 2008 Wenchuan earthquake sequence and the 2013 Lushan earthquake sequence. They have been classified according to their focal mechanism. First, our results suggested that the values of apparent stress varied from approximately 0.1–11 MPa, which are higher than the global average. The strike-slip earthquakes have the highest average apparent stress among the types of earthquakes. The above results indicate that the moderately high levels of energy release from earthquakes in this region could result in high ground shaking potential. This behavior may be associated with the high stress accumulation and the strong deformation characteristics in the intraplate environment of the Longmen-Shan Fault zone. The values of the stress drop vary from approximately 0.24–39 MPa and appear to show a slightly increasing trend with the seismic moment. The stress drop level of the Lushan earthquake sequence is higher than the mean value of intraplate earthquakes, while the Wenchuan earthquake sequence is typical of intraplate earthquakes. Second, we investigate the radiated energy enhancement factor (REEF) to quantify the source complexities. The results show that the earthquakes have REEF values between 1.2 and 7.1, and most events are consistent with expectations based on the Brune ω -square model. There exist differences in the source complexity of earthquakes within the source area, and the average ω -square source model could result in an unreliable estimate of the radiated seismic energy of some events. The observation of moderate magnitude earthquakes suggests that the availability of different source parameters will help us to assess the seismic hazard and predict the shaking potential in the earthquake area.

To reveal the seismogenic mechanism of the Luding earthquake, we employed the 118 China Seismic Network stations to collect the P-wave polarity data from each station, which was then used in the P-wave first motion approach to calculate the focal mechanism solution of the M6.8 Luding earthquake that occurred on September 5, 2022. We have also studied the loading effect of tectonic stress on the Luding earthquake fault based on the stress field data for the research area. The results indicate that this earthquake was a strike-slip type, the nodal plane I: strike 167°, dip Angle 78°, slip Angle 2°; Nodal plane Ⅱ: strike 77°, dip Angle 88°, slip Angle 168°. The two fault planes’ instability coefficients of the Luding earthquake are examined considering the region’s background stress field’s condition. The nodal plane I in the Moho circle is discovered to practically coincide with the Coulomb failure line and the tangent point of the Moho circle, indicating that this nodal plane has a high instability coefficient compared to the nodal plane II. The conclusion is that the nodal plane I has a higher likelihood of being the seismogenic fault plane, which is congruent with the seismogenic fault plane suggested by the aftershock distribution, the earthquake radiation energy distribution of a single station, and seismic intensity distribution. The Luding earthquake’s focal mechanism is highly like the theoretical focal mechanism of the fault situated at the location where the Coulomb failure line intersects the Mohr circle, demonstrating that background stress is what caused the earthquake. The substantial fault instability and similarity between the solved and theoretical focal mechanisms make it easier to comprehend the loading effect of tectonic stress on the Luding earthquake fault.

Fault stability analysis plays an important role in assessing the potential hazard of faults and in studying the mechanism of earthquake occurrence. Fault stability depends on the magnitude of the normal and shear stresses imposed on the fault by the tectonic stress and rock friction, while the magnitude of the normal and shear stresses is related to the spatial orientation of the fault normal with respect to the three principal stress axes, so it is easier to understand the variation of fault stability with its orientation by expressing the stability of different faults in the principal axis coordinate system. In this paper, we first developed a method to plot the stability of faults with different orientations in the principal stress axis coordinate system, then investigated the influence of the magnitude of principal stresses and friction on fault instability, and reached the conclusion that the instability is mainly affected by the relative magnitude of principal stresses (shape ratio). Finally, we proposed to use fault stability as an indicator to evaluate the quality of inverted stress obtained from fault slip data or earthquake focal mechanisms, that is, to evaluate the reliability of the inverted stress according to the compatibility of stress and fault stability. It is described in detail in terms of measured fault slip data from two regions.

本文研究了锦屏一级水库蓄水前后发生在库区及其周围ML0.5以上的地震活动并进行了精定位,反演了 ML3.0以上71个地震事件的震源机制解,并通过计算比较了蓄水前后的应力场.结果表明:锦屏一级水库地震开始响应时间较长,应与第一阶段水位抬升有限,库水淹没范围尚未覆盖震群附近有关.淹没范围扩大至震群所在区域后地震活动大幅增加,之后几个阶段的蓄水过程和地震活动变化有较好的对应关系.蓄水后大量地震集中发生在木里藏族自治县葫芦沟附近,震源深度集中在6～14 km,与蓄水前相比震源深度变浅.除葫芦沟以外的区域震源机制解结果,P、T轴分布及区域应力场反演结果都与之前的研究结果相一致.葫芦沟附近震群的震源机制多为走滑型,P轴以NS向及NNW—SSE向为主,T轴以EW向及NEE—SWW向为主,区域应力场最大和最小主应力轴近水平,中间应力轴近直立,R值为0.5,与其他区域存在差异,其发震机制应受孔隙压扩散和水浸润弱化作用影响.