Abstract:Based on the periodic variation of tidal forces,outgoing longwave radiation(OLR)data from the FY-3E satellite were used to analyze the daily variations of OLR from June 30 to August 30 in 2023 over a large area(17°N～55°N,73°E～136°E)of the Chinese mainland.In addition,correlations between tidal forces,OLR,and the MS5.5 earthquake that occurred in Pingyuan County,Dezhou on August 6,2023 were discussed.Analysis of OLR changes and the synchronous tidal force cycle revealed that:①During the periods without earthquake tidal force changes(cycles A and B before the earthquake and D after the earthquake),OLR exhibited no significant variations near the epicenter,whereas continuous OLR anomalies were observed during the earthquake period(cycle C),accompanied by continuous variation in tidal force from trough to peak to trough.OLR anomalies show the stage characteristics of initial warming,strengthening,peak attenuation,and gradual calming,which are synchronous in time.②OLR anomalies were closely distributed around the Liaocheng-lankou fault,indicating that seismic tectonic movement was the main cause of OLR anomalies associated with the earthquake,and the evolution of OLR anomalies during the earthquake represent the radiation of seismic tectonic stress changes.③The earthquake occurred near the peak phase point of cycle C,synchronous with the enhanced characteristics of the OLR anomalies.Therefore,when accumulated seismic tectonic stress exceeded the critical state of rock fracture and sliding,the sudden change in the size and direction of the tidal force promoted the instability of the Liaocheng-lankou fault and induced the earthquake.These results also show that the OLR products of the FY-3E satellite are useful for identifying seismic infrared anomalies.

Abstract:At 11:16 am on June 8,2024,a magnitude 3.5 earthquake occurred in Youxi County,Sanming City,Fujian Province.After the earthquake,the Fujian Earthquake Agency quickly activated a Level V emergency response and dispatched a post-earthquake field work investigation team to the affected area.In cooperation with earthquake and emergency management departments at the city and county levels,the team conducted intensity surveys at 35 survey points within the earthquake-affected area.The surveys enabled determination of the macroscopic intensity and macroscopic epicenter,as well as delineation of the isoseismal contour of macroscopic intensity.Using drone technology,the investigation identified brick-concrete structures and column-and-tie timber frame structures as the predominant housing types in the earthquake-stricken areas.Based on these findings,further analysis was conducted to identify weak points in seismic fortification and potential safety hazards in rural residential buildings in the affected areas.

Abstract:Seismic geology,bands,gaps,and energy;the spatiotemporal distribution of seismic activity;and the frequency of small earthquakes were used to track the characteristics of the seismic activity in southern Jiangxi and its adjacent areas(23.66°N～27.20°N,113.50°E～118.84°E).Earthquakes of magnitude 4.0 or higher in the region were synchronous with earthquakes of magnitude 5.0 or higher in the southeast coastal seismic zone.Earthquakes of magnitude 2.5 or higher have appeared in the surrounding area since 2018.Earthquakes of magnitude 3.0 or higher have occurred in belts since 2020;the clustering of moderate earthquakes has increased,and earthquakes of magnitude 4.0～5.0 have not occurred,indicating a state of energy accumulation.In July 2016,the southeastern coastal seismic zone entered the fifth active phase since 1900,with active earthquakes of magnitude 5.0 or higher.Southern Jiangxi and its adjacent areas are involved.A risk exists of earthquakes of magnitude 5.0 or higher occurring in the next 1～3 years,and special attention should be paid to seismic activity in the border areas of Jiangxi,Guangdong,and Fujian.

Abstract:To investigate the changes of geoelectric field observation data quality of increasing the burial depth of LGB-3 solid non-polarized electrodes at Wujiahe station from 3.5 m to 5 m in November 2018,a comparative analysis was conducted using relevant data collected during 2015 to 2023.The results indicate the following:Increasing the electrode burial depth had no significant effect on the correlation coefficients,and no clear positive or negative correlation was observed between electrode depth and the geoelectric field components in different lateral directions.Daily difference analysis revealed improved data stability and an overall enhancement in observation quality following the increased burial depth.Analysis of daily average dynamic curve showed that,during periods of frequent irrigation and rainfall from April to Spetember,both the frequency and amplitude of disturbances were significantly reduced,suggesting improved resistance to environmental interference.

Abstract:Conducting the dynamic analysis of buried pipelines subjected to seismic action poses a complex engineering challenge.A reliability analysis method based on probability density evolution and the equivalent extreme value distribution was developed in full consideration of the randomness inherent in ground motions.This method offers a probabilistic and statistical perspective for investigating the stochastic dynamic response and reliability of buried pipelines.The method was used to conduct the stochastic dynamic analysis and reliability assessment of pipeline displacement,and its validity was compared and confirmed against the Monte Carlo Simulation(MCS)method.The results demonstrate that the Generalized Probability Density Evolution Method(GPDEM)is an economical and efficient approach for use in seismic dynamic reliability analysis,with broad applicability in the dynamic reliability analysis of nonlinear structures under seismic actions.The displacements of buried pipelines are highly sensitive to seismic action,undergoing significant nonlinear changes,and pronounced horizontal reciprocating motions can exacerbate fatigue damage in pipelines.Furthermore,pipelines may gradually subside over time,posing a severe threat to their safe operation.To ensure the seismic safety of buried pipelines,it is crucial to assess their seismic performance by considering the randomness of ground motions.A single evaluation index is inadequate for accurately assessing the performance level of buried pipelines across all time states.Results show that a reliability analysis based on the GPDEM can reasonably characterize the evolution of the probability density function of the dynamic response of buried pipelines during seismic events,thereby providing a theoretical foundation for the seismic design of buried pipelines.

Abstract:Based on 12.5 m resolution ALOS_PALSAR DEM data and hydrology analysis tool in Arcgis10.6,the stream geomorphic indices such as slope,relief degree of the land surface(RDLS),hypsometric integral(HI)and stream length gradient(SL)along the Qujiang fault(QJF)were extracted to analyze the impact of several stream geomorphic indices on the QJF's tectonic activity.Previous studies divided the Qujiang fault into three segments:northwest(NW),middle,and southeast(SE),from which fluvial geomorphic indices were extracted.The average HI value of the NW segment is 0.34,and the average SL value is 334;the average HI value of the middle segment is 0.44,and the average SL value is 383;and the average HI value of the SE segment is 0.45,and the average SL value is 415.The results indicate that the middle and SE segments are more active than the NW segment.Through the comprehensive analysis of lithology,climate and tectonic activity in the QJF region,it is believed that tectonic activity is the primary factor influencing the development of stream geomorphology.Field investigations of typical landforms and outcrops were conducted to analyze the historical seismicity of the QJF and the geometry of the fault,and the results showed that the middle and SE segments are more seismically active than the NW segment.The results of the stream geomorphic indices in this paper are consistent with previous studies,indicating that the seismic hazard in the QJF's middle and SE segment requires further investigation.

Abstract:A total of 410 global seismic events with MS≥4.0 recorded by Ceke earthquake monitoring station in Inner Mongolia from January 2023 to April 2024 were selected and analyzed.The deviations between surface wave magnitudes measured by Ceke earthquake monitoring station and those reported in the official catalog of the China Earthquake Networks Center were calculated.The average value of the surface wave magnitude deviation between the two was found to be 0.15,with small overall deviation and high accuracy.Further analysis examined the relationship between the magnitude deviation factures such as event magnitude,epicentral distance,and azimuth.These findings were helpful in improving the accuracy and reliability of magnitude determination at Ceke earthquake monitoring station.

Abstract:The Wuling fold belt,located on the western part of the South China continent,far from the plate margin,has developed a typical fold-and-thrust system and its deep structural and tectonic features reflect the crustal shortening and deformation processes in the intra-continental environment.Using the three-component teleseismic waveform data recorded at the Hefeng seismic station in Hubei Province within the Wuling fold belt,we extracted the P-wave receiver functions and focused on analyzing the characteristics of the change of Ps phase in back azimuth of teleseismic events,which revealed the differences in crustal structure between the two sides of the Hefeng fault.The key findings are as follows:the difference in arrival times between Ps phase and the direct P wave was about 4.8 s for the SE-directed events,whereas it was about 5.5 s for the NW-directed events.The significant difference in the arrival times of the Ps phases reflects that the Hefeng fault is a regional fault that extends to the depth of the Moho.CCP imaging and H-κ scanning analyses revealed a sharp contrast in the crustal thickness on the two sides of the Hefeng fault,which is steeply increased from 30 km on the SE side to about more than 40 km on the NW side,and there is an obvious intra-crustal velocity discontinuity on the NW side of the Hefeng fault.These findings offer new constraints for further studies on the dynamic mechanisms and processes of intra-continental deformation in the Wuling Mountains.

Abstract:With the increasing number of earthquake stations and scaling up of unmanned stations,the traditional operation and maintenance mode of stations is facing various challenges such as frequent power supply,communication,and instrument failures.To improve the quality of monitoring data and reduce the pressure of operation and maintenance work,Hebei Earthquake Agency relies on the catastrophe prevention project to implement intelligent upgrading of seismic stations across the entire province.An intelligent guarantee technology system for the normal operation of the station observation system has been constructed by integrating an intelligent power supply,battery pack,switch,and camera equipment.The intelligent power supply provides instrument power supply and remote monitoring,combined with the battery pack,it ensures continuous power supply in case of power interruption in the city and switch optimization for network communication stability,while the camera monitors the device status and environmental safety in real-time.Intelligent upgrading have enabled remote alarms for abnormal power supply at stations and power outages as well as restarts of web terminals,effectively shortening the fault recovery time.Reliable operation of the network communication equipment ensures data communication,which combined with the intelligent power management platform of the network center,achieves unified monitoring of station operation and maintenance across the entire province.In practice,intelligent upgradings have effectively improved the continuous operation capability,maintenance efficiency,and observation data continuity of station equipment,thereby providing strong technical support for the reliability and timeliness of the earthquake monitoring and early warning network in Hebei Province.

Abstract:To better analyze the seismic site effects in land reclamation areas and provide a scientific basis for earthquake-resistant engineering design,this study investigates the Dongjiang port land reclamation area in Tianjin.Integrated short-period flow seismometers were used to collect ground motion noise at the site,and the consistency of horizontal-to-vertical(H/V)spectral ratio peaks was analyzed using noise level and H/V ratio methods.Based on long-term observations at fixed points for 26 days,ground motion noise was recorded,and a normalized profile map was generated by converting the H/V curve data using a formula based on dominant frequency and depth.The analysis revealed unstable H/V peak values in the low-frequency range below depths of 50～200 m,suggesting that weak wave impedance interfaces caused by backfill soil exist in the shallow subsurface,with relatively distinct soft sediment interfaces near depths of 50～200 m.The dominant frequencies at the site range of 0.6～1.6 Hz,with amplification factors of 1.96～3.99.This study provides a useful reference for estimating site effects in the Dongjiang port land reclamation area.

Abstract:This article has summarized the shortcomings and deficiencies in the construction and operation of the earthquake monitoring station network of China,analyzes the trend of modernization development of the monitoring station network,and proposes measures and suggestions for upgrading and replacing the earthquake monitoring network of China from the perspective of a new development philosophy.It has also detailed the design and implementation of the national disaster prevention project.

Abstract:Long-period low-frequency waves in seismic records contain crucial information regarding the adjustment of crustal stress states and the mechanical properties of the medium and thus hold significant research value.However,their study was limited by the scarcity of systematic observations.Solid tides,as natural and stable long-period signal sources in geophysics,serve as key indicators for evaluating the low-frequency response performance of instru-ments.This study,based on the low-noise ultra-wideband reference station built at Chongli seismic station under the National Seismic Intensity Rapid Reporting and Early Warning Project,utilized the continuous observation data from the Trillium Horizon 360 ultra-broadband seismometer deployed there in December 2024 to systematically assess the instrument's recording capability of solid tides.The results indicate that the instrument can clearly record solid tides,with the observed curves exhibiting good consistency with the theoretical solid tides and relatively good correspondence with the deformation and tilt observations at the same site.This fully confirms the superior observation environment of the Chongli seismic station and demonstrates that the Trillium Horizon 360 seismometer possesses excellent capabilities in observing ultra-low-frequency long-period signals.This has significant implications for recording and studying long-period signals generated by the Earth's vibrations.

Abstract:The Urad Rear Banner region is located at the intersection of the Alxa,Ordos,and Yanshan blocks.Seismic activity in this area is influenced by changes in the tectonic stress field and is correlated with the occurrence of moderate to strong earthquakes.Since October 2022,the region has experienced a significant increase in small earthquake activity,exceeding background levels.In this study,we analyzed a seismic window within the Urad Rear Banner area.The cumulative frequency of earthquakes with a magnitude of M2.0 or greater in 180 days was used as the window-opening indicator.The target events were earthquakes with M≥5.0 events occurring along the northwestern edge of the Ordos block.Prediction effectiveness was evaluated using the R-value metric.By examining the distribution of R-values within the two-dimensional parameter space of the prediction window length and threshold,prediction rules were established based on the highest R-value.The results showed that the highest R-value was 0.43,with an optimal prediction window length of 200 days and an alarm threshold of eight events.Under these parameters,the frequency-based predic-tion indicator demonstrated good predictive performance and high reliability.

Abstract:The underground fluid observational data of Dian 02 well at Yuanmou seismic station from 2008 to 2024 were selected,and four types of interference were identified by comparison with normal observational data:technical system failure,site environmental,human factor,and other accidental interference.The prediction efficiency of the underground fluid observational data from Yuanmou seismic station was analyzed.The prediction efficiency R values of all underground fluid observational data of Yuanmou seismic station were calculated using the threshold,rate difference,trend turning,and annual change detection methods.The results showed that the water temperature,water level,and gas radon R values calculated using these four methods were all greater than 0,indicating that they have predictive significance.The prediction efficiency of the water temperature calculated using the rate difference method was R greater than R0,indicating predictive significance.The gaseous mercury R values calculated using the four methods were all less than 0,indicating that gaseous mercury had no effective predictive significance.

Abstract:Co-seismic response identification of fixed-point deformation data currently relies on manual selection,and no automatic co-seismic response detection method has yet been applied.This study proposes the first deep learning model for the co-seismic response detection of fixed-point deformation data in China,which is used to detect co-seismic response signals quickly and accurately on the second dataset of a single vertical pendulum broadband tiltmeter.The model was constructed using the transfer learning technique;it introduces three representative pre-trained models for earthquake detection in seismic data as feature extractors,migrates their knowledge and capabilities of earthquake detection in seismic data to fixed-point deformation data,and then designs and adapts supporting data converters and classifiers.Tests on real observational data showed that the model provided a good detection performance.The application of continuous data from Jixian station proved that the model was not only capable of detecting all the co-seismic response events recorded manually,but it also found events that were not recognized manually,with an accuracy rate of no less than 75%.Compared with traditional manual processing,the detection efficiency,detection capability,and consistency are greatly improved using this model.

Abstract:Using static water level observation data from Dehongfapa well and recorded co-seismic response events as the research objects,the operation,tidal factor,observation accuracy,and co-seismic response characteristics of the static water level observation data of Dehongfapa well were systematically analyzed.The results showed clear diurnal variations in the solid tide affecting the Dehongfapa well static water level,and the variation pattern showed obvious daily and semi-daily waves,the observational data were highly accurate and a strong tidal response ability was noted.The well exhibited a strong response to large earthquakes,and the static water level showed different co-seismic response patterns for different earthquakes,mainly in the form of oscillations.The variation range of the co-seismic response of the well water level was generally negatively correlated with the well-seismic distance and positively correlated with the magnitude,and the co-seismic response time was positively correlated with the well-seismic distance.Finally,the mechanism of the co-seismic response characteristics of the water level was comprehensively analyzed,and the related mechanism was preliminarily discussed in combination with the specific situation of Dehongfapa well.

Abstract:In recent years,multiple unidentified sounds have been heard in the Tongling area,and significant vibrations have been felt within structures.To conduct a time-frequency analysis of these unidentified sounds,this study used the time-frequency analysis method in the seismic event recognition system(SERS)developed by the Non-Natural Earthquake Research Laboratory of the Institute of Geophysics,China Earthquake Administration.Through using the SERS,a comparative analysis of time-frequency data and waveform characteristics was conducted between unidentified sound and natural earthquakes,mine explosions,and a chemical plant explosion event in the Tongling area.It was preliminarily determined that the unidentified sound originated from the ground or above.Field visits and investigations showed that when the unidentified sound occurred,no explosions,geological disasters,or other safety production accidents were observed in the city.It was thus concluded that the unidentified sound event was caused by human activity on the ground(or surface).This study provides a reference for using SERS to analyze the source of other non-natural earthquakes.