The rapid determination of the seismogenic fault plane after a large earthquake has important reference value for the determination of post-earthquake seismic activity trend. In this study, firstly, the source mechanism data of the 2024 Wushi Ms7.1 earthquake sequence in Xinjiang, China were collected, the central solution for multiple source mechanism solutions of the same earthquake are estimated, and the focal mechanism nodal plane clustering analysis are performed. The two clusters are obtained after removing the noise point of nodal plane, in which the cluster with smaller standard deviation may be the seismogenic fault plane of the M_S7.1 earthquake. Then, in order to further verify the possible seismogenic fault plane through the relationship of the fault plane and the stress field, we collected the historical seismic source mechanism data in Wushi earthquake source region, and inverted the tectonic stress field. The stress field shows northwest-southeast compressive stress and near-vertical tensile stress. By projecting the stress field onto the two cluster centroid of nodal planes obtained from clustering analysis, it was found that the cluster centroid of nodal planes with less standard error subject larger shear stress, and the normal stress also supports its rupture. Comprehensive analysis with other information, we preferred the seismogenic fault of the 2024 Wushi M_S7.1 earthquake is and north-west dipping, low dip angle fault with strike of 245.14°and the dip of 45.67°.

This article utilizes the Total Electron Content (TEC) data measured by the GPS stations of the Chinese Mainland Crustal Movement Observation Network (referred to as the “Crustal Network” hereafter) to establish an empirical ionospheric model for the Beijing-Tianjin-Hebei region. By incorporating solar flux and geomagnetic activity data, the performance of the model is enhanced. The study develops a functional model for the diurnal, seasonal variation, and geomagnetic effect components of the ionospheric TEC, using a nonlinear least squares method to fit the coefficients. A multi-parameter empirical fusion model is proposed-the Ionospheric TEC Beijing-Tianjin-Hebei Region Model (MEFM-ITBTHR) - to predict the ionospheric TEC in the Beijing-Tianjin-Hebei region. Results indicate that the MEFM-ITBTHR model fits the modeling dataset well. The performance of the MEFM-ITBTHR model is further analyzed through geographical variation, seasonal variation, and geomagnetic disturbance analysis. Results demonstrate that in the Beijing-Tianjin-Hebei region, the MEFM-ITBTHR model exhibits better forecasting accuracy, linear correlation, and model precision for measured TEC across different latitudes, seasons, and geomagnetic disturbances compared to the IRI2020 and NeQuick2 models. The regional TEC empirical model constructed in this study provides a new method for ionospheric delay correction for GNSS single-frequency users and holds significant reference value for establishing other new and improving existing empirical ionospheric models.

This article uses two methods, slug test and tide inversion, to calculate the permeability coefficient of Wang 3 Well, Baodi New Well, and Ninghe Well at different periods. Comparing the calculation results, we find that the results obtained by using two methods are comparable in overall magnitude, and the trend of change is consistent. Especially for observation wells in aquifers with stable development and good continuity, the calculation results of the two methods are closer. The permeability coefficient estimated by slug test mainly reflects the permeability characteristics of the local aquifer around the wellbore during the short-term water flow process. The permeability coefficient estimated by tide inversion reflects the average permeability of a large range of aquifers over a long period of time. Therefore, in the analysis of coseismic response and abnormal verification of water pumping (injection) interference, using slug tests to estimate the permeability coefficient of the well aquifer is more reasonable, and it is more reasonable to use tide inversion to estimate the permeability coefficient in analyzing regional stress field changes. We analyze the characteristics and causes of water level and permeability change characteristics and causes of the three observation wells, as well as, we mechanism of water level coseismic response in Wang 3 Well and Baodi New Well to the Maduo M7.4 earthquake in Qinghai Province on May 22, 2021, and the impact mechanism of the Maduo earthquake to water level in Ninghe Well. We find that factors, such as stress accumulation, pumping or injection water, and seismic wave propagation, can affect the permeability of aquifer medium. Moreover, the propagation process of seismic waves has different impacts on different aquifer medium, and the response characteristics and mechanisms of observation wells with the same aquifer lithology to the same earthquake are also different.

According to the M_S5.1 earthquake in Dengta, Liaoning Province on January 23, 2013, the variation of ATSCTF (Additional Tectonic Stress Caused by Tidal Force) at the epicenter (41.5°N, 123.2°E) was calculated for 5 weeks before the earthquake and 3 weeks after the earthquake (from December 16, 2012 to February 15, 2013) using the ATSCTF calculation model. When the earthquake occurred, the vertical component of ATSCTF was near the high phase point, indicating that tidal force had an inducing effect on the normal fault strike-slip earthquake. The low phase points of the ATSCTF cycle (December 19, January 4, January 18, February 2) were taken as the background, and the subsequent data of each cycle were subtracted from the background day by day. The variation of ATSCTF of the seismogenic period is C cycle. In space, the OLR of the epicenter and its southern area shows a significant continuous increase before the earthquake, and in time, it experiences an evolution process of initial micro-anomaly→anomaly strengthening→peak→attenuation→earthquake→quiet, which is consistent with the infrared radiation characteristics of the mechanical evolution process of rock stress loading-rupture: initial fretting rupture→expansion rupture→stress locking→earthquake outbreak→quiet. It shows that the tidal force has an inducing effect on the active fault in a critical state, and OLR is the radiation characterization of the seismic tectonic stress and strain process.

Based on the observed waveform data of the regional digital seismic networks, the gCAP inversion method is used in three-dimensional space to obtain the centroid fine position of the Helingeer M_L4.5 earthquake on March 30, 2020, which is 40.131°N, 111.922°E, and the depth is 13 km. The strike/dip/slip of the first nodal plane are 279°/41°/-27° and those of the second nodal plane are 30°/72°/-127°. The moment magnitude is M_W3.98. The double-difference method named HypoDD algorithm is used to relocate the main shock and aftershock sequences, and the relocation results of 19 seismics events are obtained. The results show that the focal parameters of main shock are 111.858°E and 40.136°N, and the focal depth is 11.718 km. The aftershock sequences are bilaterally extended along NW—SE direction and the subsurface rupture length is 4.6 km. The depth profile shows that the main shock is located in the middle of the aftershock area. The main rupture extends upward and downward simultaneously, and the depth distribution of the sequence ranges from 4 km to 17 km. The 20 sets of measurement results show that the NW-trending nodal plane Ⅰ is the seismogenic fault plane. Based on the research results of the geological structure of the focal area, the tectonic stress field and the three-dimensional crustal structure of the aftershock sequence distribution area, it is inferred that the seismogenic fault of the Helingeer M_L4.5 earthquake is a NW-trending buried fault and the event is a left-lateral strike-slip mechanism with normal fault component. The earthquake occurred in the transition zone of high and low wave velocity conversion in the crust, which is located on the side of the high velocity body. Comprehensive analysis shows that influx of fluid materials plays an important role in triggering the earthquake event, and the complex fault structure not only provides pathways for fluid migration, but also controls the occurrence of earthquakes and the spatial distribution of seismic sequences.

Capability of dynamic rupture propagation along stepover of strike-slip fault controls the possible size of earthquake rupture. The effects of heterogenous initial stress on dynamic rupture propagation are significant. In the study, we integrate a dynamic rupture propagation model with a static stress perturbance model to construct a heterogenous stress field along strike-slip fault. Then, we investigate the influence of static stress perturbance produced by previous rupture on subsequent rupture near stepover along a strike-slip fault. Our two-dimensional numerical results show that static stress perturbance produced by previous rupture improve the capability of rupture propagating across stepover in the subsequent event significantly even the stepover arrested previous rupture. The influence of various high initial stress on rupture propagation across stepover along a strike-slip is insignificant. Rupture with various high initial stress can propagate across stepover of similar width. Larger stress drop and smaller fault strength ration (S) can improve the capability of rupture over stepover with larger width. So, static stress perturbance produced by previous events should not be ignored when studying the cascading rupture behavior along fault segmentations.

Classification of non-natural seismic events is one of the daily tasks of the seismic monitoring business. This research is mainly aimed at the classification of earthquakes, explosions and mining-induced earthquakes. On the basis of the research results of seismic wave data processing, feature extraction and artificial intelligence comprehensive classification, a seismic event recognition software (SERS) with good portability, expansibility and independent intellectual property rights is developed based on the Qt development framework and combined with Python, Matlab and other programming languages. The software can be deployed on different operating systems and consists of seven modules: seismic data import module, data processing module, feature extraction module, comprehensive classification module, feature analysis module, yield estimation module, and result analysis module. The software integrates various time-frequency feature extraction techniques and artificial intelligence classification methods, to form a comprehensive process for classifying the seismic events. The built-in classification models in the software have an accuracy rate exceeding 90% and a wide range of applications. It has been applied in a number of earthquake monitoring departments, achieved favorable outcomes and enhanced the capability for rapid analysis of non-natural earthquakes.

In this paper, the local area of North China (32°N~42°N, 114°E~122°E) was chosen as studied region. Regarding the 2023 Shandong Pingyuan M_S5.5 earthquake, 2021 Dafeng Sea area M_S5.0 earthquake and 2020 Hebei Guye M_S5.1 earthquake as the target earthquakes, the Pattern Informatics (PI) method was applied to the retrospective research on the forecasting seismic activity risk of the three earthquakes. With parameters of forecasting window length 5 years and grid size 0.5°×0.5°/1.0°×1.0°, the period from 2019 to 2027 of successive hotspot forecasting window images sliding year by year were obtained. The results show that PI hotspot effect with the grid size 1.0°×1.0 ° is better than 0.5°×0.5°. And it has a good indication effect on the location of Pingyuan and Dafeng sea area earthquakes. When the time window length and the absolute value of the normalization threshold increasing, only a few windows have effective hotspots for the Guye earthquake. But no parameter model that can simultaneously cover the epicenter grid of the three earthquakes has been found. There is a risk of M_S≥5.0 earthquake in the Bohai Rim region of the Tan-Lu fault zone in the following 3~4 years, which the PI hotspots under different parameter models indicating. The results of this paper can provide certain reference significance about seismic hazard analysis of M_S≥5.0 earthquake for local area of North China.

The Huoshan seismic window in Anhui Province, as an index of well-evaluated earthquake prediction efficiency, with R>R0 (R=0.26, R₀=0.204), plays an important role in the study of earthquake situation in Anhui and its neighboring areas. The summary of historical earthquake cases shows that when earthquakes M_L≥1.0 cumulative frequency within three months in Huoshan seismic window exceeds 40, the window opening anomaly appears, which has predictive significance for the earthquakes of M_S3.5 within 100 km, M_S4.0 within 250 km, M_S5.0 within 500 km and M_S6.0 or above beyond 500 km in the next year. Since 1970, only 7 earthquakes have been missed by this index, including the 2018 Henan Gushi Ms3.6 and 2019 Hubei Yingcheng Ms4.9 earthquakes before which small earthquakes in Huoshan seismic window area were enhanced and earthquakes M_L≥1.0 cumulative frequency within three months was close to the anomaly threshold. Small earthquakes are dense in Huoshan seismic window area, and there may be overlapping interference of waveforms lead to many identified earthquakes. Match and Locate (M&L) method was applied to detect small earthquakes in Huoshan seismic window during April 2017 and April to September 2019, so as to obtain a more complete earthquake catalog and re-analyze the prediction efficiency of Huoshan seismic window. The result shows that, based on the more complete earthquake catalog after detection, the Huoshan seismic window anomaly has not missed the 2018 Henan Gushi M_S3.6 earthquake and 2019 Hubei Yingcheng M_S4.9 earthquake, with R>R0 (R=0.30, R₀=0.196), and the dominant occurrence time of the earthquake corresponding to this anomaly is in 9 months. The development of this research indicates that the M&L method is practical in the small earthquake detection of Huoshan seismic window and can be applied as a conventional processing method in the subsequent study of Huoshan seismic window, to obtain a more complete earthquake catalog and provide data support for earthquake prediction study.

In recent years, the geomagnetic observation data from the Hongshan observatory have repeatedly shown abnormal variations due to vehicle interference, which has seriously affected the completeness of the data. Based on field experiments conducted at the Hongshan observatory, this paper focuses on analyzing the impact characteristics of light trucks and other types of vehicles on geomagnetic observation data during their transit on roads. The results indicate that the interference effect on observation data caused by vehicles is closely related to the materials they are made of, the greater the magnetic susceptibility of a vehicle's material, the greater the distance of influence. The intensity of the interference decreases gradually with the increase of distance and the interference effects of light trucks at 300 m from the measurement point and heavy trucks at 120 m from the measurement point basically disappear. The theoretical values of interference magnitude for light trucks are well aligned with the experimental results, whereas for heavy trucks, there is a significant discrepancy between the theoretical and experimental values. This difference may also be related to the variations in construction, size, volume, and design among different types of vehicles. By examining the patterns exhibited by the various components of the observation data under vehicle interference, it is preliminarily inferred that the interference magnetic field generated by the vehicles is characterized by a dipolar magnetic field with a magnetic axis parallel to the ground. Additionally, spectral analysis shows that both the D and H components exhibit distinct spectral peaks during the vehicles are in motion, with higher frequencies corresponding to higher vehicle speeds. This study provides meaningful evidence for the future identification of vehicular interference effects in geomagnetic observation data.

In order to improve the measurement accuracy of the signal detection circuit of differential capacitive sensors, this paper proposes a method that combines Delta-Sigma modulation technology with differential capacitive sensors to create a new type of signal detection system. This signal detection method places differential capacitive sensors, preamplifiers, and phase sensitive detection circuits within a Delta-Sigma feedback loop, forming a large feedback loop. By deriving the system transfer function of the detection circuit, we analyzed the technical advantages of using Delta-Sigma modulation technology in this detection method a circuit board and tested it. The research results indicate that the digital output of the signal detection method proposed in this article has a high correlation with the magnitude and direction of the deviation of the center plate from the equilibrium position, which has a good promoting effect on further improving the measurement accuracy of the differential capacitive sensor detection circuit.

Based on the observed seismograms from the regional broadband digital seismic network, the multi-point source seismic moment tensor inversion method is employed to perform the seismic moment tensor inversion for the 2023 Jishishan M_S6.2 main earthquake in Gansu province, China. The results show that the NE dipping nodal surface (strike 312°, dip 48°, and rake 76°) of the focal mechanism solution is the seismogenic fault. The majority of seismic moments are released from the source to the ground surface along the direction of the slip vector of the focal mechanism solution (azimuth 236°, plunge 40.5°), and the main rupture lasts about 5.8 s. At the same time, the secondary bilateral rupture occurred on the fault plane in the rupture zone of the earthquake.