• Volume 44,Issue 1,2022 Table of Contents
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    • >地震工程
    • Research progress of friction dampers

      2022, 44(1):1-16. DOI: 10.20000/j.1000G0844.20200909001

      Abstract (493) HTML (0) PDF 10.89 M (1136) Comment (0) Favorites

      Abstract:Friction damper is a kind of damping device that uses the principle of friction damping to dissipate the energy input into the structure from vibration. Compared with traditional damping dampers, friction dampers have the following advantages: the convenience of engineering structure installation, ease of construction and assembly, large initial stiffness, and stability in performance. This paper summarized a large number of research achievements on friction dampers made by domestic and foreign scholars, including the types of friction dampers, performance influencing factors, experimental research, and engineering applications of friction dampers at home and abroad, then discusses the development process and research status of friction dampers in the field of shock absorption. Through an introduction to the development context and current status of friction dampers, it provides theoretical guidance and design reference for the application and selection of friction dampers in structural energy dissipation and shock absorption, thus promoting the development of friction dampers in research and engineering.

    • Peak particle velocity of adjacent residential buildingsinfluenced by blasting construction of subway tunnel

      2022, 44(1):17-21. DOI: 10.20000/j.1000-0844.20200617002

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      Abstract:The blasting construction of subway tunnel seriously endangers the structural safety of adjacent residential buildings. Therefore, it is necessary to propose blasting control measures based on the peak blasting vibration velocity. Based on the simplified model of milti-hole load, the cylindrical wave theory, and the traditional stress wave attenuation theory, the formula of peak particle velocity considering the effect of elevation was derived in this paper. The blasting construction response of an adjacent six-story residential building to the Metro Line 1 in Urumqi City was monitored, and the measured peak particle velocity was compared with the vibration velocity predicted by the modified formula and the traditional Sadov's formula. The results show that the distribution of peak particle velocity predicted by the modified formula is inconsistent with the measured value, showing a trend of gradually increasing with the elevation. Moreover, the relative error between the measured value and the predicted value is small, indicating that the modified formula considering the elevation factor is feasible.

    • A safe entrance scheme of shallow buried biastunnels on high-speed railways

      2022, 44(1):22-28. DOI: 10.20000/j.1000-0844.20201215001

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      Abstract:In this paper, the selection of reasonable construction scheme for shallow buried bias tunnels with partially exposed surface was discussed. Combined with the on-ite engineering geology and construction environmental conditions, a technical scheme with the arch tunneling method was proposed: steel grating concrete retaining arches were preinstalled on the exposed surface side, then the earth rock was backfilled as back pressure, finally the tunnel portal was constructed by the tunneling method. The comparison results between the proposed scheme and the open-cut construction schemes showed that, although the open-cut construction scheme is technically mature, it is faced with some problems, i.e., large quantities of excavation and protection, wide range of ecological environment disturbance, high construction and operation risks, etc. The arch tunneling construction scheme can not only overcome these problems, but also ensure the safe and rapid entrance of shallow buried bias tunnels. The research results can provide a reference for tunnel construction under similar conditions.

    • Residual seismic behavior of precast hollow slabs based onreinforcement tension and pressure transfer

      2022, 44(1):29-35. DOI: 10.20000/j.1000-0844.20210817002

      Abstract (191) HTML (0) PDF 4.04 M (435) Comment (0) Favorites

      Abstract:To improve the building quality and analyze the overall seismic performance of precast hollow slabs under cyclic loading, the residual seismic performance of precast hollow slabs based on reinforcement tension and pressure transfer was studied. Different types of test pieces of the precast hollow slab without reinforcement were prepared, and the performance changes of each test piece were recorded under cyclic loading. The test results showed that, compared with the precast hollow slab with shear\|compression failure, the hysteresis curve of the precast hollow slab with compression bending failure is fuller, and the safety margin of bearing capacity and seismic bearing capacity are higher. Under cyclic loading, the buckling stiffness and peak stiffness of each specimen are only 50% and 20% of the original stiffness, respectively. However, the stiffness degradation of the specimen with reinforcement tension and pressure transfer and prefabricated boundary elements is the smallest, and its residual deformation distribution and residual seismic performance are better.

    • Seismic performance of high-rise control towerof airport under strong earthquake

      2022, 44(1):36-45. DOI: 10.20000/j.1000-0844.20210512003

      Abstract (246) HTML (0) PDF 10.27 M (699) Comment (0) Favorites

      Abstract:To improve the seismic performance and safety of high-rise control towers of airports under severe earthquake, the damage distribution mechanism of the tower structure under strong earthquake was studied by using the nonlinear time-history analysis method. Performance levels of structural key components were determined with the performance-based seismic design method, then the performance-based seismic design and damage control of the tower structure were carried out. Finally, the influence of vertical earthquake on the damage of tower was analyzed. The results indicated that the story drift ratio of the control tower with frequent earthquake design can meet the specification requirements under the action of rare earthquake, while the local area of tower tube is seriously damaged. Compared with upper frame members, the weak part of tower structure under rare earthquake is tower tube. The damage state of local area of the tower tube is reduced from severe damage to moderate damage by using the performance design of non-yielding under fortification earthquakes. The influence of vertical earthquake action on the tensile damage of tower tube is greater than that of compression damage.

    • A method of ground motion selection for base-isolatedstructures based on vulnerability analysis

      2022, 44(1):46-53. DOI: 10.20000/j.1000-0844.20200209001

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      Abstract:As the selection of seismic records is very important for dynamic elasto-plastic time-history analysis of base isolated structures, a method for selecting seismic records based on the elasto-plastic dynamic amplification factor spectrum of base-isolated structures was proposed. The dynamic elasto-plastic time-history analysis method was first used to analyze the two degree of freedom simplified model of the base-isolated structure, and the dynamic amplification coefficient spectrum of the structure was obtained. Then, the seismic records were selected by the spectral matching method, and used to carry out the incremental dynamic analysis, seismic vulnerability analysis, and collapse capacity analysis of an 8-story base isolated structure. Finally, the two selection methods of seismic records were compared from the accuracy and discreteness of the analysis results. The results showed that the calculation accuracy of the proposed method for selecting seismic records is not much different from that of traditional methods, but it shows some advantages in reducing the discreteness of structural seismic response and the number of seismic records.

    • A comprehensive method for rapid assessment ofseismic stability of loess slopes: a case studyof Xiji County in Ningxia

      2022, 44(1):54-61. DOI: 10.20000/j.1000-0844.20200831001

      Abstract (216) HTML (0) PDF 18.15 M (860) Comment (0) Favorites

      Abstract:In this paper, a detailed field investigation was carried out on 347 loess seismic landslides in Xiji County, Ningxia induced by the Haiyuan MS8.5 earthquake in 1920. Based on the detailed basic data and the interpretation of remote sensing images, the distribution characteristics of the loess seismic landslides in the study area were summarized. Then, a macroscopic and qualitative rapid discrimination method for the seismic stability of loess slopes was proposed. Based on the distribution characteristics, the slope height, slope angle, slope direction, and ground motion intensity were selected as basic parameters. A quantitative rapid discrimination model for the seismic stability of loess slopes was proposed by using the MLP neural network model. The comprehensive discrimination method proposed in this paper, which integrates the qualitative and quantitative fast judgment methods, is of great significance to the site selection before earthquake, as well as the rapid evaluation of seismic stability of loess slopes in the emergency rescue after earthquake.

    • Dynamic response and spectrum characteristics ofanti-dip rock slopes under earthquake

      2022, 44(1):62-71. DOI: 10.20000/j.1000-0844.20210206001

      Abstract (226) HTML (0) PDF 9.79 M (636) Comment (0) Favorites

      Abstract:Taking the Gongza landslide in Changdu City, Sichuan Province as the prototype, a 1:1 000 shaking table test model was designed, and the shaking table model tests of anti-dip rock slopes with weak lithologic association and a penetrating structural plane were carried out. Considering the engineering geological conditions and site characteristics, the dynamic response law of the anti-dip rock slope under artificial seismic waves with various frequencies was discussed, and then compared with the amplification effect law under the input of sine wave. Based on the spectrum analysis of the data obtained from vertical monitoring points under different types of seismic waves, the dynamic response of anti-dip rock slope was studied. The results show that under the action of artificial seismic wave, the acceleration amplification coefficient shows obvious elevation amplification effect both along the slope surface and the vertical direction, and shows obvious skin effect along the horizontal direction. Under the action of artificial seismic wave, the slope and in-slope responses are similar to those under the action of sine wave, but the skin effect is not the same. Under the action of sine wave, the spectra of slope monitoring points show a vertical straight line, and the derived characteristic frequency is an integral multiple of the input sine wave frequency. The artificial and natural waves have more complex frequency distribution, so the amplification effect of the slope on the high frequency band is obviously higher than that on the low frequency band. However, the closer the predominant frequency of sine wave and artificial wave is to the natural frequency of the slope, the more obvious the slope dynamic response is. By comparing the frequency spectra of different types of seismic waves, it is found that due to the simple waveform of sine wave, the frequency spectrum of each measuring point does not change obviously after propagating through the slope, so it can not accurately reflect the influence of rock slope on the input seismic wave. Therefore, the sine wave is not recommended to be used as the dynamic input wave when studying the spectral characteristics of rock slopes.

    • Stability analysis of high-slope loess subgradewith hidden holes under earthquake

      2022, 44(1):72-78. DOI: 10.20000/j.1000-0844.20200601001

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      Abstract:As a kind of adverse geological phenomenon developed in the Loess Plateau, hidden holes in loess have become one of the main causes of highway damage in loess areas of China. On the basis of a deep study on the development characteristics of hidden holes in loess, the collapse mechanism under earthquake was simulated by the finite element method. The dynamic responses of three types of high-slope loess subgrade (subgrade without hidden hole, subgrade with arched hidden hole, and subgrade with triangle hidden hole) under seismic load were obtained, and the ground motion amplification effect of hidden holes on the high-slope loess subgrade was analyzed. The results showed that the hidden holes in loess has the effect of ground motion amplification. With the same hole diameter and buried depth, the amplification effect of arched hidden holes on the peak horizontal acceleration of high-slope loess subgrade is more obvious than that of triangular hidden holes, especially on the slope shoulder and hole roof. It is suggested that due to the existence of hidden holes in loess, the high-slope loess subgrade is prone to collapse and destroy under earthquake.

    • Seismic vulnerability of urban overpasses under active ground fissures

      2022, 44(1):79-85. DOI: 10.20000/j.1000-0844.20201208002

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      Abstract:Urban overpasses and other linear structures can not completely avoid the impact of ground fissure activities. Considering the amplification effect of hanging wall on the ground motion in ground fissure sites and the intersection angle between the ground fissure and the bridge structure, the hanging wall magnification factor of the structure used for nonlinear dynamic time-history analysis under non-uniform ground motions was obtained. The differential settlement on both sides of the ground fissure causes significant change of internal force of the continuous bridge, resulting in the increase of axial force of the pier and the increase of horizontal force at the pier top under earthquake. According to the characteristics of ground fissure activities and ground fissure sites in Xi'an, a three-span urban overpass was taken as an example to carry out the vulnerability analysis of the overpass under different site conditions. The uncertainty of the structure and ground motions were considered, and the Park model was adopted as the damage index of bridge pier. The results showed that the ground fissure activity makes the failure probability of urban overpass pier crossing the ground fissure significantly higher than that in non ground fissure sites, and the failure probability of pier is related to its location.

    • Influence of near-fault ground motion characteristics on the seismicresponse of isolated continuous curved girder bridges

      2022, 44(1):86-92. DOI: 10.20000/j.1000-0844.20201026001

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      Abstract:To study the seismic response and pounding effect of curved continuous girder bridges under near-fault ground motions, the nonlinear time history analysis method was used to analyze the influence of velocity pulse effect, hanging wall effect, and directivity effect on the bearing displacement, the internal force of pier, and the pounding force between girders of a three-span continuous curved girder bridge. Through a comparative analysis of bearing isolation ratio, the reasons for the difference between seismic responses of the bridge under different types of near-fault ground motions were explored. The results showed that the impulse effect, the hanging wall effect, and the directional effect will all increase the seismic response of the curved continuous beam bridge, especially the impulse effect. The impulse effect and directivity effect weaken the seismic isolation performance of the high-damping rubber bearing, while the influence of hanging wall effect on the bridge response is only related to the characteristics of hanging wall ground motion. Overall, the impulse effect has the most obvious impact on the pounding effect of the curved girder, and the hanging wall effect can be neglected.

    • Influence of curvature radius on the seismic response of small radiuscurved girder bridges in large temperature difference area

      2022, 44(1):93-99. DOI: 10.20000/j.1000-0844.20200714001

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      Abstract:The seismic response and pounding effect of small radius curved girder bridges considering the curvature radius and the near-fault pulse-impulse effect in areas with large temperature difference were analyzed in this paper. Taking a curved gird bridge in large temperature difference area of Northwest China as an project example, different nonlinear finite element models of the whole bridge with different radius of curvature were established. The influence of thermal load on the bearing stiffness and beam expansion deformation was considered. The influence of curvature radius on the seismic response of the curved girder bridge was studied based on the internal force of pier and the pounding effect of adjacent girders. The results showed that with the increase of curvature radius of main beam, both the internal force response of pier bottom and the pounding effect between adjacent beams increase gradually. The internal force of pier bottom at extreme low temperature is much greater than that at extreme high temperature. The internal force of pier bottom under the action of near-fault pulse-like ground motion is larger than that under the action of gar-field ground motion.

    • Extraction of IMF time-domain features based on EMD andits application to recognition of vibration event source type

      2022, 44(1):100-107. DOI: 10.20000/j.1000-0844.20200110002

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      Abstract:In this paper, the seismic waveform was decomposed by the empirical mode decomposition (EMD) method, and the time-domain features of the decomposed intrinsic mode function (IMF) were extracted.The two types of event sources (natural earthquake and artificial explosion) were classified and identified by the extracted features.The results showed that the time-domain features extracted from IMF have good discrimination and recognition ability.The original waveform signal was decomposed into 7.IMFs and residual functions by the EMD, and 2 6.time-domain statistical features were extracted from the original waveform, each IMF, and each residual function, respectively, to form 9.feature groups (named Q0, Q1,…, Q8).Then 7.energy ratio features were calculated from the amplitude-energy ratio of 7.IMFs, and 3 2.features were selected from the time-domain features of the first 4.IMFs, which formed a feature group with 3 9.features (named Q9).A series of identification experiments were conducted on single group or various combinations of the 1 0.feature groups by using the symmetrical Kullback-Leibler (KL) divergence.In each experiment, the training and testing samples were the same, but were randomly selected from the corresponding feature groups of all waveform of some events (30%, 60%, 70, or 90%).The experiments were repeated many times, and the results showed that the time domain features extracted by the second IMF have the best recognition effect, and the correct recognition rate is above 90%.It suggests that the IMF, which has better ability to distinguish event types than the original waveform, can provide more effective features for the recognition of event source type.

    • A method for seismic response analysis ofcoral island sites based on UPFS

      2022, 44(1):108-118. DOI: 10.20000/j.1000-0844.20210123005

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      Abstract:The key technical problem for seismic safety analysis of coral islands is to reasonably and efficiently simulate the nonlinear dynamic characteristics of coral sand, the radiation damping of far-field infinite foundation, and the influence of hydrodynamic pressure of sea islands. Based on the characteristics of UPFs, a time-domain calculation model for analyzing the seismic response of island sites with coral sand foundation was established by using the general finite element software ANSYS. A new equivalent linear element of coral sand was created to describe the nonlinear dynamic characteristics of coral island sites, and a viscous artificial boundary element was derived and developed. Based on Westergaard's added mass formula, the hydrodynamic pressure of the channel was simulated with mass21 element, and the FORTRAN interface program was established to realize the free-field response. Furthermore, the rationality and effectiveness of the proposed model were verified by the free-field analysis of a typical coral island site. Finally, an actual coral island site in China was taken as an example, and the nonlinear seismic response of coral island sites was discussed from the aspects of surface peak acceleration and response spectrum. Thus, the dynamic response analysis of various complex island sites can be carried out by using the large-scale solution and analysis ability of ANSYS.

    • Seismic optimization design of combined layout springturbine foundations based on ANSYS

      2022, 44(1):119-127. DOI: 10.20000/j.1000-0844.20200714002

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      Abstract:The combined layout spring foundation structure of a 1 000 MW coal\|fired power plant was selected as the research object, and a finite element model including the foundation structure and the main power house structure was established. Then the seismic time history analysis was carried out on the combined layout type spring foundation structure with the large mass method. According to the analysis results, the optimization algorithm provided by the finite element software ANSYS was adopted in this paper. Taking the size and position of the foundation column as design variables and the seismic response acceleration at the node of turbine bearing center as the objective function, the seismic design of the turbine foundation and the main powerhouse structure were optimized. After optimization, the value of objective function was significantly reduced under varying design variables and the optimization structure can effectively improve the structural seismic performance. The algorithm proposed in this paper breaks through the tradition of only comparing a few solutions for this type of structure, and provides a new idea of optimization.

    • Comparison of four constitutive models for sand based on OpenSees

      2022, 44(1):128-135. DOI: 10.20000/j.1000-0844.20200910001

      Abstract (337) HTML (0) PDF 5.31 M (725) Comment (0) Favorites

      Abstract:As one of the most common engineering geological phenomena caused by earthquake, the liquefaction of saturated sand is also one of the main causes of major earthquake disasters. Due to the complexity of causes and the severity of disasters, the liquefaction of saturated sand has always been an important subject in the field of soil dynamics and geotechnical earthquake engineering. In this paper, based on the platform OpenSees, the numerical simulation were carried out on four constitutive models for sand. The response results of the four models in terms of acceleration, displacement, excess pore water pressure, shear stress-strain, and mean effective stress path under the action of cyclic dynamic load were analyzed and compared. The research results showed that: (1) Sand shows a certain amplification effect on the input acceleration, and there are some differences in the amplification effect for different models; (2) Stress Density model is prone to permanent deformation under cyclic dynamic load; (3) Under cyclic dynamic load, the strength of PDMY model and CycLiqCPSP model gradually decreases until it completely lost; (4) Stress Density model and Manzari Dafalias model show obvious dilatancy effect under cyclic dynamic load. The research results have important theoretical value for the numerical simulation of sand liquefaction, thus providing a reference for the liquefaction simulation of saturated sand and the selection of constitutive models for sand.

    • Difference between dynamic and static liquefactionmechanisms of saturated loess

      2022, 44(1):136-144. DOI: 10.20000/j.1000-0844.20210608003

      Abstract (749) HTML (0) PDF 8.81 M (864) Comment (0) Favorites

      Abstract:The liquefaction mechanism of saturated loess varies significantly under different external loads. To study the difference between dynamic and static liquefaction mechanisms of saturated loess, a series of dynamic and static triaxial tests were conducted. The relationship between dynamic stress and dynamic strain, dynamic pore water pressure ratio and dynamic strain of saturated loess in Yongguang Village, Minxian County after dynamic liquefaction were analyzed. The relationship between deviatoric stress and axial strain, pore water pressure ratio and axial strain of the saturated loess after static liquefaction were also discussed. Based on the SEM test results before and after liquefaction, the effects of dynamic and static liquefaction on the structural characteristics of saturated loess were studied, and the difference of the two liquefaction mechanisms was discussed. The results showed that under cyclic dynamic loading, the strength of loess skeleton gradually loses and the pore deformation develops, resulting in the rise of pore water pressure until the dynamic liquefaction with flow slip characteristics occurs. However, under monotonic static load, the overhead pores in the loess are gradually compressed, and the soil particles falling into the pores are rearranged and combined, resulting in the increase of pore water pressure until static liquefaction occurs. Compared with static liquefaction, the apparent pore area of saturated loess after dynamic liquefaction is smaller, the pore uniformity is better, the pore arrangement is more disordered, and the pore structure is more complex. The difference between the two liquefaction mechanisms is mainly manifested in different growth modes of pore water pressure caused by the difference of meso-structure change process under different loads. The results may provide a theoretical basis for the prevention and control of liquefaction in loess area.

    • >Earthquake Research
    • Analysis of seismic ambient noise before and after the prevention andcontrol of COVID\|19 pandemic at Enshi station, Hubei Province

      2022, 44(1):145-151. DOI: 10.20000/j.1000-0844.20211207004

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      Abstract:Based on the continuous waveform data recorded by Enshi seismic station in Hubei Province from January 2018 to March 2020, we obtained the distribution of PSD in different frequency bands by calculating the power spectral density (PSD) and probability density function (PDF), and then compared and analyzed the variation characteristics of seismic ambient noise before and after the COVID-19 pandemic. Meanwhile, we compared the vertical acceleration amplitudes of seismic noise in 2018, 2019, and 2020, and found that the acceleration amplitude variation curves were highly consistent in the days before the Spring Festival, indicating that the operation of high-frequency noise sources and seismometers around Enshi seismic station were very stable in these three years. The results showed that during the prevention and control period of COVID-19 in Enshi area, the high-frequency noise caused by human activities rapidly decreased, and the noise in the high frequency band (~10 Hz) decreased by 1-20 dB. The amplitude decreased significantly during the day and the low value of noise decreased slightly at night. The calculation and analysis of seismic ambient noise can provide a powerful means for human activity monitoring and urban public management.

    • Characteristics of 2017 Chengduo, Qinghai earthquakeswarm and its implications for moderate earthquakes

      2022, 44(1):152-157. DOI: 10.20000/j.1000-0844.20200811001

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      Abstract:Chengduo earthquake swarm of 2017, an ML<3.0 earthquake swarm recorded for the first time in Chengduo Country, Qinghai Province, occurred under the background that the calm of MS5.0 earthquakes in Tanggula seismic belt was broken and ML>4.0 earthquakes were active. To study the influence of the Chengduo earthquake swarm on subsequent earthquakes in Qinghai and its adjacent areas, the activity characteristics, swarm parameters, focal mechanism, and apparent stress of the swarm were calculated and analyzed. The results showed that the earthquake swarm is a precursor swarm, in which the earthquakes are mainly strike-slip. By comparing with historical swarm activities in Tanggula seismic belt, it is considered that the occurrence of this swarm indicates that the occurrence signs of medium and strong earthquakes in Tanggula seismic belt in the future are enhanced, and attention should be paid to strengthening the earthquake tracking research.

    • Wave velocity ratio of the Minxian-Zhangxian MS6.6 earthquakefrom source spectral parameters of P-wave and S-wave

      2022, 44(1):158-165. DOI: 10.20000/j.1000-0844.20190825001

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      Abstract:In this paper, the source spectral parameters of 183 ML≥2.5 earthquakes from January 2010 to June 2014 in southeastern Gansu were calculated by using the seismic waveform in the regional seismic network of Gansu Province. The variation characteristics of the ratio of P-wave corner frequency to S-wave and the ratio of P-wave long-period spectral level to S-wave before and after the Minxian MS .6 earthquake on July 22, 2013 were analyzed, as well as the change of wave velocity ratio. The results indicate that: (1) The average value of corner frequency ratio is about 1.32, and the average value of wave velocity ratio calculated from the long-period spectral level ratio is about 1.55, higher than the former. (2) The time variation trends of the wave velocity ratios obtained by the two source spectral parameters are basically the same: “obvious rise-decline-sharp decline before the earthquake-slow recovery after the earthquake”; (3) The spatial distribution of wave velocity ratios are basically the same: low value anomalies appeared near the epicenter of Minxian earthquake before the earthquake, and the wave velocity ratio near the epicenter rebounded after the main shock.

    • Quality detection and comparative experimentof a novel water radon detector

      2022, 44(1):166-171. DOI: 10.20000/j.1000-0844.20200729003

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      Abstract:The simulated observation of water radon in China is cumbersome and has many interference factors. To overcome this drawback, a novel radon detector instrument was introduced in this paper, and a comparative experimental study was carried out with the FD-125 radon detector. The two water radon detectors were calibrated in the standard radon chamber of the emanometer measurement platform for earthquake monitoring, and a comparative measurement with the same water samples and environment was carried out at Jiujiang seismic station. The results show that the repeatability, relative error, relative inherent error, and inherent background of the novel radon detector can meet the technical requirements with a standing time of 1 h. The observation data has good consistency with those of FD-125 radon detector, but the sensitivity index needs to be improved. The overall design of the proposed instrument can basically meet the development needs of analog water radon observation and reduce the measurement error caused by manual operation, thus improving the measurement efficiency and data quality.

    • Earthquake damage simulation of urban buildings based onground motion parameters: a case study ofChengguan District in Lanzhou City

      2022, 44(1):172-182. DOI: 10.20000/j.1000-0844.20210514001

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      Abstract:The spatial distribution of ground motion parameters of two earthquakes was simulated by using the intensity attenuation model based on the shortest fault method, and the reliability of the model was verified through a comparison with the meizoseismal area of actual earthquakes. Then, based on the simulated spatial distribution of seismic intensity and the information of building structure type and story height in Chengguan District of Lanzhou City, a three\|dimensional seismic damage simulation of buildings was carried out with the elastoplastic time\|history method. The results showed that the proposed model could well simulated the spatial distribution of historical earthquake intensity. When the seismic intensity reaches Ⅷ degree, the overall seismic performance of buildings in Chengguan District of Lanzhou City is good; When the seismic intensity reaches Ⅸ degree, the buildings with 3-7 stories is seriously damaged by the earthquake. The seismic performance of buildings in the mountainous areas of southern Chengguan District and the urban villages is weak. The results of this paper can not only provide an important technical support for the survey of earthquake disaster risk and key hidden dangers, but also help government to investigate, repair, and reinforce hidden danger of urban buildings. It can also help to improve the accuracy of earthquake disaster risk assessment, which is of great significance for earthquake disaster emergency rescue in large and medium-sized cities.

    • Quaternary activity characteristics of the Jiyunhe fault revealedby shallow seismic prospecting data

      2022, 44(1):183-191. DOI: 10.20000/j.1000-0844.20200222002

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      Abstract:As is an important fault in the northeast of Tianjin,Jiyunhe fault is a component of the Zhangjiakou-Bohai tectonic belt.Due to the lack of special exploration and research on its activity,the spatial distribution and Quaternary activity of the Jiyunhe fault is always in dispute.Through extensive data collection,the general distribution of Jiyunhe fault was determined.Then 9 artificial seismic lines were arranged in the study area,and the vibrator was used to detect the fault.The results showed that the Jiyunhe fault is not a north-south fault,but roughly divided into two segments:the northwest segment and the southeast segment.The northwest section of Jiyunhe fault is mainly characterized by fault depression with deep cutting and large fault distance.It is an early fault of late Pleistocene and also the boundary fault of Yanshan fold belt and Cangxian uplift.The fault in the southeast section is not obvious,and it is speculated to be an early\|middle Pleistocene fault which is dominated by strike slip movement.

    • Review of precursor anomalies and coseismic responsecharacteristics in Ningxia area before WenchuanMS8.0 earthquake

      2022, 44(1):192-202. DOI: 10.20000/j.1000-0844.20200807001

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      Abstract:This paper made a retrospective analysis on the precursory observation anomalies in Ningxia area before the Wenchuan MS 8.0 earthquake on May 12, 2008. From the seismogenic range of large earthquakes and the development stage of earthquake precursory, it is considered that these observation anomalies may be related to the Wenchuan MS 8.0 earthquake. The data of digital fluid and deformation observation in Ningxia area occurred different degrees of coseismic response changes. The characteristics of coseismic response were compared and analyzed, and the results indicated that the precursory observation of the Wenchuan MS 8.0 earthquake in Ningxia have north-south regional features. The precursory observation anomalies and morphological characteristics of coseismic response in this study reflect the change process of stress\|strain state in Ningxia area from the preparation stage to the occurrence of Wenchuan MS8.0 earthquake.

    • Dynamic ground deformation and coseismic deformation field duringthe Alaska MW7.8 earthquake in 2020 by GPS data

      2022, 44(1):203-209. DOI: 10.20000/j.1000-0844.20200916001

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      Abstract:The GPS 1 Hz and 30 s sampling observation data published by UNVAVCO were processed and analyzed with the double difference position method, then the dynamic ground deformation and coseismic three-dimensional deformation field during the Alaska MW 7.8 earthquake on July 22, 2020 were obtained. The results showed that the seismic waveform of high-rate GPS within 270 km of epicenter is obvious, and the maximum amplitude is 600 mm. The amplitude and response time of dynamic deformation waveform of each GPS station are greatly affected by the rupture propagation direction of earthquake and site effect. The static coseismic displacement vector points to the epicenter, and the coseismic displacement basically decreases with the increase of epicenter distance. Except for station AC13, the maximum horizontal displacement of the station nearest to the epicenter is 26.7 cm.

    • Seismogenic fault study of the 1654 M8 Lixianearthquake in Gansu Province

      2022, 44(1):210-217. DOI: 10.20000/j.1000-0844.20211021002

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      Abstract:The 1654 Lixian M8 earthquake occurred in the northeastern margin of the Qinghai-Tibet Plateau with strong Neotectonic activity. The earthquake stricken area is located in the mid-north segment of the South-North seismic belt, where many active faults are developed. The M8 earthquake occurred in the loess area about 370 years ago. Affected by natural erosion and human activities, its surface rupture zone and secondary disasters are now difficult to distinguish. Many seismologists have done a lot of research work on the earthquake, and there are different understandings and opinions on its seismogenic fault. Therefore, based on the observation data of seismic network and mobile network since 1970, this paper studied the seismogenic structure of the Lixian M8 earthquake in 1654 by using the seismic tomography method and joint inversion calculation. According to the distribution of small earthquake activities along the Minxian-Lixian-Liangdang line, it was speculated that the "Minxian-Lixian-Liangdang fault" may be the seismogenic fault of the Lixian M8 earthquake in 1654, but further study of field geological work is still needed.

    • Precise location and focal mechanism solutions of the 2021 Maduo,Qinghai MS7.4 earthquake sequence

      2022, 44(1):218-226. DOI: 10.20000/j.1000-0844.20210705001

      Abstract (703) HTML (0) PDF 13.41 M (695) Comment (0) Favorites

      Abstract:In this paper, 1 434 earthquakes of the Maduo MS .4 earthquake sequence on May 22, 2021 were relocated using the double-difference location method, and the focal mechanism solutions of M≥ 4.5 earthquakes were also obtained by TDMT inversion method. Through a comprehensive analysis, following conclusions were obtained: (1) The overall trend of the Maduo earthquake sequence is NWW-SEE, which is consistent with the orientation of Kunlun Pass-Jiangcuo fault. There is a NW-trending band on the northwest side of the main shock, and a sparse segment of aftershocks and a distribution zone across the Maduo-Gande fault on the southeast side, which may be caused by the difference of underground velocity structure. (2) The seismic sequence is mainly left-lateral strike-slip type, with the dominant direction of NWW, NE tendency, and high dip angle. Combined with the aftershock positioning results, it is inferred that the Kunlun Pass-Jiangcuo fault is the seismogenic fault of this earthquake. (3) The average azimuth of P axis near the main shock is 237°; the average dip angles of P axis and T axis are 15° and 16°, respectively; the average dip angle of N axis is 65°. Combined with the structural characteristics of the study area, it is inferred that the earthquake is caused by the left-lateral strike-slip dislocation of the NWW-SEE trending fault driven by the NEE-SWW horizontal compressive stress.

    • Thermal infrared anomaly detection of the MS5.8 earthquake in thejunction area between Jiashi and Atushi based on MODIS data

      2022, 44(1):227-235. DOI: 10.20000/j.1000-0844.20201215003

      Abstract (627) HTML (0) PDF 19.16 M (546) Comment (0) Favorites

      Abstract:An MS .8 earthquake occurred at the junction area between Jiashi and Atush on August 11, 2011. In this paper, the annual variation trend and the periodic influence of seasonal factors in the spatio-temporal data of surface temperature were effectively removed by using the LST product data of MODIS and STL decomposition method. The GESD test was carried out on the remaining residual terms for anomaly detection, and the LST anomaly and data of other earthquakes from January 1, 2008 to January 1, 2013 were analyzed. The results showed that: (1) The surface temperature has an obvious change trend in time and space; It can be seen that there was an obvious thermal infrared anomaly before the earthquake by using the STL decomposition method, and the temperature increase phenomenon experienced several stages: "appearance-expansion-dispersive temperature increasing-temperature increase to extreme value-disappearance-earthquake occurrence". (2) There were obvious thermal infrared anomalies around the study area four months before the earthquake. Widespread anomalies appeared around the seismologic fault on February 10 and lasted for two months. The earthquake occurred four months later, and there was a long time interval between the peak value and the occurrence time of earthquake. (3) The distribution of aftershocks is related to the fault zone and the distribution characteristics of thermal infrared anomalies. After the earthquake, most of the aftershocks are mainly distributed near the fault zone where thermal infrared anomaly appeared before the main shock. (4) By comparing similar earthquake events in the same area, it is found that the thermal anomaly characteristics of the MS5.8 earthquake have much in common with the MS5.5 earthquake in Jiashi County on September 4, 2018. The significant thermal infrared anomalies of the MS5.8 earthquake further verify the role of satellite thermal infrared anomaly in earthquake prediction.

    • Apparent stress characteristics of small and mediumearthquakes in northern Qinghai Province

      2022, 44(1):236-243. DOI: 10.20000/j.1000-0844.20200901001

      Abstract (235) HTML (0) PDF 7.66 M (752) Comment (0) Favorites

      Abstract:In this paper, based on the Brune model, the apparent stress and other focal source parameters of ML≥3.0 earthquakes in northern Qinghai Province from January 2010 to May 2020 were calculated by using the waveform data recorded by Qinghai digital seismic network. The spatial-temporal variation characteristics of apparent stress were studied. The relationship between apparent stress anomalies and moderate strong earthquakes was discussed based on M≥5.0 earthquakes occurred in northern Qinghai Province, and the prediction efficiency was tested. The results showed that high value of apparent stress occurred prior to most of M≥5.0 earthquakes, indicating that obvious anomaly of high apparent stress in northern Qinghai Province has certain indication significance for moderate strong earthquakes.

    • EMSEV and 2016 international workshop in Lanzhou:commemoratingthe initiation of geoelectric earthquake prediction for more thanhalf a century by Lanzhou Institute of Seismology

      2022, 44(1):244-250. DOI: 10.20000/j.1000-0844.20190807005

      Abstract (251) HTML (0) PDF 8.35 M (655) Comment (0) Favorites

      Abstract:To commemorate the initiation of earthquake monitoring and prediction with geoelectric methods for more than half a century by Lanzhou Institute of Seismology, CEA, this paper first briefly introduced the international Electromagnetic Studies of Earthquakes and Volcanoes (EMSEV), then described in detail the international workshop of EMSEV, which was held in Lanzhou, China during August 25-29, 2016. The international workshop, which was mainly hosted by Lanzhou Institute of Seismology, was held in China for the first time. Finally, the progress of seismo-electromagnetics in China in the past few years after the workshop was introduced.

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