Abstract:A suitable crustal velocity model can help seismologists determine seismic accuracy. At present, the speed model used in the Liaoning network is a two-layer, average velocity model obtained from data of natural earthquakes and artificial blasting in South China. However, for some networks outside of South China, the crustal velocity model is obviously different from the South China model. Therefore, it is necessary to study the velocity model that conforms to the crustal structure in this area. In this study, based on phase analysis of the strong earthquakes that occurred in Liaoning Province in recent years, a more suitable, one-dimensional velocity model for the crustal structure in Liaoning has been calculated using the Hyposat method. The results show that the new model is better than the South China model in seismic positioning, and its time and epicentral differences are better than those of the South China model.

Abstract:Using GPS data for the Yinchuan Basin and adjacent regions, in this paper, we describe the characteristics of the current crustal horizontal movement. We investigated the tectonic dynamics and seismic risk in the Yinchuan Basin by analyzing the spatial distribution characteristics of the principal strain rate, surface expansion rate, maximum shear strain rate, and small earthquakes. The results show that the main movement of the eastern piedmont fault of Helanshan and the northern section of the Yellow River fault is extensional strike-slip, whereas the southern section of the Yellow River fault is dominated by strike-slip movement. The principal strain rate of the Yinchuan Basin is higher than that of the surrounding blocks. The surface expansion and maximum shear strain rates in the basin also show strong tensile and shear deformations. The Yellow River fault and the eastern piedmont fault of Helanshan show strong strain accumulation, which indicates a relatively strong seismic risk.

Abstract:In this study, we collected the P-wave first motion data of small earthquakes that have occurred in the middle-southern segment of the Tan-Lu fault zone since 2009. We used the grid point test method to obtain the integrated mechanism solutions of small earthquakes recorded by 51 stations and the focal mechanical solutions of 167 moderate and small earthquakes. The results show that the direction of the principal compressive stress is close to NEE and nearly EW in the study area and that there are local differences in the crustal deformation in the middle-southern segment of the Tan-Lu fault zone. The segmental characteristics of the regional deformation, as reflected by composite mechanism solutions for different station types, have a close correlation with the tectonic background and stress field in the study area..

Abstract:The activity of the NWW striking South Guinan fault that developed in the Keririgang mountain and northeast boundary of the Xinghai-Tongde basin is studied using Google Earth image data. Through remote sensing interpretation and field geological investigation, the fault was found to be mainly a thrust fault with a length of 157 km. Research on microlandform offsets indicates that the fault was last active during the late Pleistocene era and there have been no signs of movement since the Holocene era.

Abstract:According to geological section data for the Tongbai fault and the seismic survey line LFZS1 arranged by the Geophysical Exploration Center of the China Earthquake Administration, we determined the Tongbai fault to be the northern boundary fault of the Langgu Sag, which is composed of two parallel faults-a main fault and a branch fault. We then conducted a shallow seismic exploration of the Tongbai fault. The shallow seismic exploration profiles reveal that the main fault strikes nearly EW and the buried depth of the upper break point is about 200 m. The latest activity of the main fault occurred in the early Pleistocene. The buried depth of the upper break point of the branch fault is about 150 m and the latest activity occurred in the middle Pleistocene. This conclusion provides reference information for seismic safety considerations of important buildings and urban construction planning around the Tongbai fault.

Abstract:Detection of the radon concentration in fault gas is the method commonly employed in the study of active faults, but this method has been seldom applied in plateau areas. In the detection and evaluation of the active faults in Shigatse City, Tibet, we determined the fault-gas radon anomaly characteristics by comparing the fault gas detection results with those from shallow artificial seismic detection. Our analysis results show the detection of radon gas to be an effective method for determining the location of buried faults in a plateau area, and that the fault activity could be preliminarily determined based on abnormal changes in the radon concentration in addition to other exploration methods.

Abstract:In this study, we review the Jiuzhaigou M_S7.0 earthquake occurred on August 8, 2017, in Sichuan Province, by using four methods——the "quasi-activity in quiescence" method, the triplet method, the rhythm of multiplied nine days in different years, and the method of earthquake precursor co-migration. The results show that the prediction of the four methods are all in agreement with the practice to a certain extent.

Abstract:In this paper, we investigate the Tangshan M7.8, Datong M5.9, and Zhangbei M6.2 earthquake groups, each of which includes three to four earthquakes of the same magnitude. The case study results of these earthquake groups in north China show that stations near earthquake epicenters can record a significant rate of earth resistivity anomalies, which are characterized by a wide spatial distribution and long duration. We applied the wavelet transform method to analyze the geo-resistivity data observed prior to the occurrence of the earthquake groups to study the wavelet power geo-resistivity spectrum and its relative variation. The results suggest that the wavelet power spectrum can well reflect changes in the geo-resistivity, and is an effective method for extracting short-term geo-resistivity anomalies. In the mid-term stage prior to earthquakes, the wavelet power spectra of geo-resistivity are abnormal. The relative wavelet power spectra show obvious increases prior to moderate earthquakes or an earthquake group, which can well identify short-term and impending changes in geo-resistivity.

Abstract:In this study, we used an analytic hierarchy process (AHP) to establish a prediction index system model for medium-strong earthquakes in middle-eastern Tianshan, Xinjiang, based on better predictors of earthquakes in that region. On this basis, we built a judgment matrix with a 1~9 ratio scale and then calculated the weight of each index. The results indicate that among the better predictors reflecting earthquakes, those with relatively large weight values reflect deformation anomalies and some seismometry parameters can be used as short-term prediction indicators. The AHP model also provides a comprehensive prediction index Y for medium-strong earthquakes in middle-eastern Tianshan, whereby the Y value can better reflect the strength or weakness of the earthquake precursor and abnormality reliability. When the value of Y is no less than 1.15, medium-strong earthquakes are likely to occur in middle-eastern Tianshan, Xinjiang in the short term.

Abstract:In this study, we analyzed observation data recorded prior to the occurrence of an M5.2 earthquake in Cangshan county, Shandong province, which were recorded by eight deep-well geoelectric stations within a 100 km radius of the epicenter. The results reveal varying degrees of anomalies at all stations. Further analysis of these anomalies indicates that the anomalies appeared synchronously 26 months prior to the earthquake at three stations located at the cross section of the Yishu and Cangni faults; 16 months prior to the earthquake at two stations located between the two faults; and 13 months prior to the earthquake at two stations located several faults away from the epicenter. Our analysis of the anomaly features shows that their times of appearance and changes are related to the epicentral distance, tectonic position of the station, tectonic setting, and the direction of the principal compressional stress of the regional stress field. The research suggests that observations of deep-well geoelectricity networks are extracted directly from the internal bedrock and are significant for earthquake monitoring and prediction.

Abstract:Based on systematic analysis of repeatedly measured gravity data in the Linfen-Shanxi border area combined with deep crustal structure data, evolution characteristics of the gravity field in the Yuncheng Saline Lake, Shanxi province before and after the M_L4.9 earthquake on March 12, 2016 are discussed. The dynamic patterns of the gravity field clearly reflect the dynamic change of gravity field and the evolution process of M_L4.9 earthquake, that is quasi-homogeneous state-non homogeneous state-earthquake occurrence-post-quake recovery. In addition, gravity variation characteristics and their relation to the earthquake are analyzed.

Abstract:In this paper, we summarize the characteristics of the typical underground fluid anomalies associated with the Sheyang M_S4.4 earthquake that occurred on Oct. 20, 2016, and discuss the precursor mechanisms. Our analysis results show that the underground fluid anomalies prior to the earthquake can be divided into medium-and short-term anomalies. The medium-term anomalies are distributed within a 300-km radius of the epicenter and initially migrated from the epicenter to the outer area and then near to the epicenter. Compared to the medium-term anomalies, the short-term anomalies are located much closer to the epicenter, being distributed within 100-200 km of the epicenter and migrate close to the epicenter. The spatial properties and distribution characteristics of the anomalies show that the change in the water-temperature anomalies, which occurred prior to the Sheyang earthquake, may be caused by regional stress variations.

Abstract:With respect to the Tangshan, Hebei M4.2 earthquake that occurred on March 6, 2010, in this study, we analyzed the changes in the observed daily and monthly average deformation values recorded at the Yixian seismic station in Hebei Province. Based on our anomaly extraction results, we discuss the ability of the Yixian station to reflect earthquake activity. Our results show that during the formation and evolution of the source, there are stress and strain sensitivity points at a certain distance from the source area. Prior to the earthquake, several instruments at the same station either showed abnormal activity or different aspects of the same observation showed simultaneous abnormality. These anomalies may be related to the M4.2 earthquake and are more credible than the anomalies of single aspects. Anomalies in the same observation indicate that differences may occur prior to different earthquakes. These differences must be carefully considered when analyzing data.

Abstract:In this paper, in combination with the analysis of tectonic activities in the Ningxia region, we use 2011-2013 gravity observation data to investigate the gravity anomaly variation before and after the 2012 Yongning M_S4.6 earthquake. We used LG-ADJ software to process the data, which has been generalized by the China Earthquake Administration. The research results show that the gravity field in the measurement area underwent good medium-term precursory variation before the 2012 Yongning M_S4.6 earthquake, after which the impending anomalies suddenly increased. The gravity field showed a sharp rise in both area and quantity. The variation tendency of the gravity point value before the earthquake showed a descent-ascent-accelerative ascent-earthquake occurrence style, which is an anomaly of widely recognized concern.

Abstract:Initially, this study discusses the relation between seismic quiescence and moderately strong earthquakes in northern Qinghai and its adjacent areas from 1980 to 2015. Further, we obtain the distribution characteristics of strong earthquakes in Chaidam seismic belt and Qilian seismic belt and the main seismogenic pattern of M_S ≥ 4.9 earthquakes in these two belts. This study provides a reference for short-term prediction of earthquakes in northern Qinghai and its adjacent areas.

Abstract:In recent years, broadband seismographs have shown the obvious superposition of abnormal seismic observation signals a few days prior to large earthquakes. These signals can be distinguished in the frequency domain by frequency spectrum analysis. Study results show that broadband digital signals contain rich information related to crustal movement and damage. In this study, based on the fatigue damage theory, we computed and analyzed the broadband digital signals from the ENH, KMI, and LSA stations three days prior to the 2008 Wenchuan MS8.0 earthquake. The results show that the relative equivalent stress indicated by the signals increased significantly in the three days prior to the earthquake.

Abstract:During the Tohoku M9.0 great earthquake of March 11th, 2011, the digital observation data on underground fluids in the Gansu area showed different degrees of co-seismic response. In this study, we analyzed the co-seismic change characteristics and response ability of the digital water levels and water temperature in the Gansu area during the earthquake. It was found that the co-seismic response of the water level had two main patterns:oscillation and mutation. The water level of most wells returned to the initial state a short time after the earthquake. The recorded water temperature data showed a lower response capacity than the water level data. Only one of the measurement instruments recorded the co-seismic response of the water temperature, but this was just a short-term fluctuation and it easily recovered.

Abstract:In this study, an inversion of the inelastic attenuation in the Taiwan region and the site response of 12 stations are investigated. We used 92 seismic waveform data recorded at 16 stations in the Taiwan area, linked up to the Fujian seismic network, The inversion results indicate that the inelastic attenuation is Q(f)=271.6f^0.381. The low frequency part of the site response is~1 and the high frequency part decreases quickly. This study can help improve calculation accuracy while deriving source parameters of earthquakes in the Taiwan Strait; this enriches the data service of the Fujian seismic network. It has some reference significance for correcting earthquake magnitude, selecting and evaluating station sites, and assessing earthquake engineering and disasters.

Abstract:The cross-fault deformation observation data from the Yixian seismic station from 2007 to 2012 show that the surface fluid changes caused by rainfall and underground water level change will cause the subsidence and rise of point positions. This effect is seasonal and related to the amount of rainfall (or change in the underground water level). When the rainfall changes seasonally, the leveling observation values show corresponding seasonal changes. When the surface fluid shows low or irregular values, the fault deformation behavior will not exhibit cyclical change. As such, changes in the surface fluid will cause fault deformation behavior. The qualitative and quantitative analyses of these shallow layer anomalies are important for the determination of impending anomalies.

Abstract:Based on the earthquake activities recorded by the Hetian small-aperture seismic array from January 1 to June 30, 2015, in this study, we analyzed the waveforms and positioned the source of these events using the linear inversion method and the software swa to obtain a complete artificial earthquake catalog. Next, we used MSDP software and the simplex location method to compute and analyze the earthquake activities recorded by the Xinjiang Seismic Network. Then, we analyzed the seismic record of the Xinjiang Seismic Network within 200 km around the Hetian small-aperture seismic array and compared our results with those recorded by the array to determine the monitoring capacity of the Hetian small-aperture seismic array. Based on our results, we conclude that the low limit of the earthquake monitoring capacity in the Hetian array has a magnitude of -2.19, within a 500 km range its magnitude is less than 1; and within a 800 km range its magnitude is less than 2.

Abstract:The 2014-2016 geoelectric field observation data from the Changli station, Hebei province, are analyzed in this study. Results indicate that the daily variation in NS components of the geoelectric field exhibits double peaks and a single valley, similar to that of geomagnetic fields. In contrast, the daily variation in EW components of the geoelectric field has double peaks and double valleys with obvious, semi-diurnal waves, which are affected by the earth tide. The geoelectric field at Changli station is a tidal geoelectric field.

Abstract:In this study, we collected the geological, electrical strata, and electrical sounding data from the Linfen seismic station in the Shanxi Province, China. According to this information, the electrical structure of the medium beneath the Linfen station was simplified as a two dimensional electric section. On this basis, a three-dimensional inhomogeneous finite element model was constructed, and the electrical structure of the strata in the study area was analyzed. The results show that the earth resistivity will increase with rainfall, which explains why the georesistivity in the Linfen station shows a high feature in the summer and a low one in the winter. In addition, the impact of rainfall on earth resistivity increases with depth, which is also concerned with media uniformity and geological factors. The rise of the water level in surrounding canals has little effect on the earth resistivity; therefore, it is believed that the gradual decrease of georesistivity since 2010 is not related to canals. The study has great significance to the interference factors of earth resistivity and possible earthquake precursors.

Abstract:In this study, a survey of the newly built deep-well earth resistivity observation station in Changji prefecture, Xinjiang and its site test results are introduced. According to the various requirements of observation, research, experiment, and comparison, corresponding observation components were set. The test function of some technical indexes of specific observation equipment in the deep well is discussed, and a test method for grounding resistance and circuit insulation is presented. Therefore, two realistic requirements of deep-well earth resistivity observation are met. In addition, a near-field source interference experiment was performed using the site conditions of the station.

Abstract:Most precursor observation stations are unattended and are mainly affected by temperature and humidity. When the temperature or the humidity is continuously beyond a certain range, the instruments tend to get damaged, which subsequently affects continuity and integrity of the observation data. In this study, design of a simple temperature and humidity monitoring equipment, which can continuously monitor the temperature and humidity, is proposed. A temperature and humidity data acquisition system was designed based on the STC89C52 single chip. The digital temperature and humidity sensor DHT11 was used to gather the environmental temperature and humidity values, which were displayed on the LCD12864 with Chinese font. The temperature and humidity values were sent to the host computer through the serial port, and the VC 6.0 was used to program the temperature and humidity display interface on the computer. The hardware and software design methods were given, which was validated by experiments. The experimental results show that the system has the advantage of simple structure and can acquire and display the environmental temperature and humidity values in real time. When any of the values are out of range, the system will send messages to handlers for timely processing to ensure that observations are steady and continuous. In conclusion, our temperature and humidity monitoring equipment is successful and has a range of potential applications. This equipment can be highly useful for obtaining environmental parameters in working sites that are extremely far away or considerably difficult for physical access.

Abstract:As a radioactive gas geochemical survey method, soil radon measurement can be affected by a lot of interference. If we do not pay attention to these interference factors while testing, interference and abnormal phenomena will be observed; these present great difficulties while analyzing the data. The P2000 is portable, battery-powered, and easily operable. It can be used for field observation, anomaly verification, and the measurement of soil radon concentration for seismic subsurface fluid observation. In this study, based on soil radon concentration measurements using the AlphaGUARD P2000 portable radon monitor, we analyze the gas recovery conditions and influencing factors, discuss the soil radon determination method, and try to identify related factors that influence soil radon measurement.

Abstract:The effect of barometric pressure on well water levels is well recognized in continuous observations of seismic ground water fluid, especially in deep confined water. The response of the underground water level to barometric pressure is called the water-level-barometric-pressure effect. The main research emphasis on the water-level-barometric-pressure effect has shifted from how to eliminate the influence of barometric pressure on the water level to the calculation and determination of the well-water-level-barometric-pressure coefficient, and then to the exploration of abnormal changes of the water level in response to the barometric pressure prior to earthquakes. However, there has been little research on the response lag changes of the well-water level to barometric pressure. In this paper, we use three methods, including correlation analysis, convolutional regression, and harmonious analysis, to calculate the response lag time of the water level of the Baodi and Gaocun wells to barometric pressure. Then, we compare the regularity and differences in the calculation results of the three methods to clarify the advantages and disadvantages of each. The study results provide a reference for the selection of methods in the future.

Abstract:In this paper, we present the EPDAPS system, which was originally dedicated to the data processing and automatic mapping of a borehole strain and gravity time series based on the MATLAB platform. EPDAPS follows the design code of the earthquake precursor database and configures and manages the basic information of the database, such as the database information, station code, and item components. The system can perform data pre-processing, and can also integrate many common deformation data analysis methods, including time-frequency analysis, wavelet analysis, and frequency spectrum analysis, among others. In this paper, we first describe the main frame structure of the system, and then we present the correcting tools dealing with raw data. Finally, we present an example of spectral analysis based on the software. In conclusion, it was found that the system had strong expansibility and compatibility; therefore, the efficiency of daily deformation data analysis and processing can be improved and thus provide powerful support to an earthquake emergency consultation.

Abstract:In this paper, the water temperature data of the Xiuyan No.1 well in the Liaoning Province during the 9th and 10th five-year plan were analyzed and summarized. In addition to earthquake activity and precursory anomalies in the Liaoning Province, we focused on the increase of digital water temperature in the well since September, 2013. The results show that, during the 10th five-year plan, the daily dynamic stability of water temperature in the Xiuyan No.1 well is rather poor, and not correlated well with the small earthquakes. The mid-term anomaly of water temperature since September, 2013 was distributed northwestwards in the form of a belt; thus, it was evident that we should continue to strengthen tracking and research on the high value of the Xiuyan water temperature.

Abstract:In this study, we collected and analyzed water-level data of the Huanghua well in Hebei Province observed since 2005. We then combined the water-level data of the surrounding Hejian and Hengshui wells to analyze the water-level step-variation anomaly of the Huanghua well, taking the Changli M4.2 earthquake in Hebei as an example. The results show that the earthquake reflection ability of the water level of the Huanghua well is good. Since 2015, the water-level step-variation anomaly of the Huanghua well and the water-level anomalies in the Hejian and Hengshui wells have shown a certain correspondence. As a short-term precursor anomaly, water-level change is caused by tectonic activity, which is related to the Changli M4.2 earthquake.

Abstract:In recent years, lightning has increasingly caused significant losses to seismic observation equipment in seismic stations of China. Lightning hazard has become the main security risk for the stations' seismic observation equipment, which plays a critical role in the continuity, stability, and reliability of observation data. Therefore, preventing lightning damage and ensuring the normal operation of observation systems are particularly important. Given the characteristics of instantaneous overvoltage generation, hazard routes, and seismic station monitoring systems, we believe that it is necessary to adopt systematic and comprehensive lightning protection measures to reduce losses caused by lightning. This study first analyzes the formation of lightning, the types of lightning strikes, and the hazards of lightning to digital earthquake precursor stations; further, it explores lightning protection measures from six different angles:power distribution system protection, signal line protection, shielding measures and wiring protection, grounding and equipotent bonding, lightning warning, and equipment maintenance and management. These lightning protection technologies can achieve better results in earthquake monitoring, which can effectively reduce the loss of data. In particular, these protective measures can reduce the amount of lightning-inflicted damage on seismic observation system equipment.

Abstract:In this paper, we mainly investigate the seismic characteristics of the antenna servo system. When a large earthquake occurs, the antenna deviates from the satellite and the system can automatically correct the antenna attitude to re-align the satellite and resume communication in a short time. To overcome the possible azimuth, we have added two calibration devices to this system:the inclinometer and electronic compass. We fixed the inclinometer at the back of antenna surface along the beam direction. Because its output value is absolute, even in the case of antenna tilt or structural distortion, the accuracy will not be affected. We fixed the electronic compass on the antenna base, and its output value can be set as the reference azimuth angle for normal work. This system can ensure the normal use of the fixed satellite communication earth station following any initial accident, and can thus play a positive role in our emergency rescue ability.

Abstract:The intensity rapid report and earthquake early warning network in the Wuhan city circle, which connects the seismic data of the Three Gorges Reservoir and the Danjiangkou Reservoir network, could realize the function of the intensity rapid report and early earthquake warning. The network would greatly improve the ability for earthquake prevention and disaster reduction in the Wuhan city circle. In this study, we present a preliminary discussion on the construction of the network, introduce the distribution of stations, performance index, installation, debugging, and trial operation situation of the instruments in the network. During the trial operation of the network, a M3.2 earthquake occurred at Shayang county, in Jingmen city, on Nov. 1, 2015, and was monitored by the network; thereby a warning was issued successfully. Finally, we offer various suggestions for the development of the network.

Abstract:Earthquakes can directly damage rail transit facilities, thereby leading to train derailment, overturning, and other major accidents that can threaten the safety of train operations. In this study, we compared the development and current status of earthquake monitoring and early warning systems with respect to rail transit in China and other countries. Based on our results, we highlight the urgency and necessity of the construction of earthquake monitoring and early warning systems for rail transportation.

Abstract:Based on statistical data on rural houses in Shiyan City, we estimated their potential earthquake damage using probabilistic analysis of building earthquake disaster vulnerability. The results indicate that the seismic capacity of the existing three types of housing structure in the city is poor, particularly in the houses with a civil structure. If an earthquake of Ⅵ degree intensity does occur, a large area would be damaged and local areas with a concentration of civil-and brick-wood structural buildings would be damaged to a medium degree. If an earthquake of Ⅶ degree intensity occurred, it would cause damage to a medium degree; however, local areas such as Yunxi, Zhushan, Zhuxi, and Fangxian would experience damage above this level.

Abstract:In this paper, using the on-site investigation data on seismic damage induced by the Junlian M_S4.9 earthquake of January 28, 2017, we determine the earthquake hazard characteristics of different buildings and the typical seismo-geological hazards in this region. The distribution and mechanism of earthquake damage are discussed based on the geological structure, focal mechanism, and aftershock sequence. The results indicate that buildings in the quake-hit region are mainly of brick-concrete structure, and their destruction is more serious than the buildings with a masonry-timber or a civil structure. The distribution of seismo-geological hazards is affected by many factors, such as height difference, slope gradient, and lithology. The critical factors that affected the seismic damage in this area are summarized as follows:(1) weak seismic performance and unreasonable building structures in the seismic area; (2) prominent uneven settlement because of the weak foundations and free faces in the epicentral area; (3) complicated geological structure, including the obvious hanging wall/footwall effect of a reverse fault; (4) frequent occurrence of small earthquakes in a short time before the Junlian M_S4.9 earthquake caused remarkable accumulation of earthquake damage and increased the possibility of seismic damage; and (5) restricted by the human geographical environment, water stored on roofs intensified any asymmetric loading of the brick-concrete buildings.

Abstract:Based on the construction of earthquake simulation experimental and experiential platforms in Shandong Province, in this paper, we analyze the basic principles and key technologies of these platforms, compare their similarities and differences, and discuss the feasibility of combining them. We analyze in detail several key problems in project construction, including the load, acceleration, maximum displacement, and maximum speed. The study results show that an earthquake simulation that combines experimental and experiential platforms can not only provide reliable technical parameters and valuable construction experience for similar projects, but also play a demonstration role in earthquake research.

Abstract:The 72-hour post-earthquake rescue period have been a matter of priority in recent major earthquakes. The communication and network environments at the earthquake site are extremely complicated, so the conventional network access mode has difficulty guaranteeing real-time data and communication transmission from the site to the rear command center. In this study, based on the post-disaster relief work and damage caused by several destructive earthquakes in recent years, and the Wenchuan and Yushu earthquakes in particular, we analyzed several key emergency communication technologies for application to earthquake rescue sites and make recommendations on how to ensure effective communication at earthquake sites. We also studied the emergency communication system with respect to information flow at the rescue site, the emergency communication network, and the command center.

Abstract:Based on field investigation,we have new historical data of 1609 Hongyabu earthquake;1352 Huining Earthquake;1785 Huihui earthquake,and get new understanding of three earthquakes.

Abstract:With the rapid development of urban rail transit in China, a number of large underground structures have been built and have drawn growing concern regarding the adequacy of their earthquake resistance. Approaching large underground structures from the engineering perspective, in this paper, we investigate the seismic characteristics of large underground structures with respect to their design in response to high-level earthquake activity. First, we established three-dimensional dynamic models using the finite element program MIDAS/GTS. Using the time history analysis method, we obtained the deformation and internal forces responses of a large underground structure. We analyzed the relative displacements and drift angles of the floors of this structure and compared the mechanical properties of the main structural components under earthquake and non-earthquake conditions. Our research results show that, during the design phase, the seismic performance of large underground urban rail transit structures should be analyzed. We recommend that designers undertake three-dimensional dynamic time history analyses to more fully understand future seismic performance. Under earthquake loads, the internal forces at some parts of the top plates, base plates, and side walls are greater than those in static conditions. The openings of the main structure of large underground spaces are inherently weak, so appropriate reinforcement measures should be considered during the design process.

Abstract:On the basis of the wave equation analysis program, the driving process of a large-diameter steel pipe pile in a huge cross-sea bridge project was simulated and analyzed in this paper. The drivability analysis of the pile was performed to determine the performance of a pile-soil-hammer system and the force condition of pile movement during driving and to provide feasible technical parameters for designers and piling contractors. Successful application of wave equation drivability analysis in this project resulted in significant advantages in the design and construction of offshore piles. Various hammers can be used to simulate various piling conditions and obtain a series of parameters such as blow counts, bearing capacity, soil resistance to driving, compressive stress, and tensile stress. The best suited hammer can be chosen using this analysis and a rational installation criterion can be formulated. The total driving time can also be estimated.

Abstract:Changzhou City is located on the alluvial plain of the Yangtze River Delta, which is covered by relatively thick Quaternary strata. Combining geological origin of transgression, 2 691 test data on shear wave velocities of soils from 358 boreholes in Changzhou City were collected for statistical analysis. Using the linear V_S=a+bH, the polynomial formula V_S=a+bH+cH², and the power function V_S=cH^d, regression analysis was performed on the variation in shear wave velocity in different soil types with different soil depths. Three relations between the type of soil and shear wave velocity variation with depth and the corresponding regression parameters are presented. The shear wave velocities were estimated and tested using actual data from engineering boreholes. The results show that the shear wave velocity and soil depth in Changzhou City exhibit a reliable empirical relation. The formulas can be used to predict the shear wave velocity in the study area and provide reliable values for use in future seismic engineering analyses of Changzhou City.

Abstract:Seismological standardization is of great significance for earthquake prevention and disaster reduction. Therefore, the review of seismological standards is a key aspect in effective seismological standardization. In this paper, we analyze reviews of seismic national standards and trade standards and propose some countermeasures, make suggestions for addressing certain problems, and recommend further work.