2023(1):1-11. DOI: 10.20000/j.1000-0844.20210712001
Abstract:A coupled discrete element model for two degree of freedom subgrade and pavement was established in this paper to study the settlement problem caused by the red beds filling material in the Lanzhou-Haishiwan section of the G6 Beijing-Tibet Expressway. Through iterative calculation, the meso parameters of each layer of the material were obtained. The Fish function was compiled, and the impact load and half sine load were used to simulate the traffic load. On this basis, the displacement and stress time history curves of the subgrade and pavement under traffic load were analyzed. Research results show that displacement stratification occurs at the interface between the base layer and the red layer filler, and the base layer, subjected to horizontal tensile stress, is a high risk area for crack development. Therefore, there should be regular monitoring for cracks in this area during periods of highway operation. The PFC model realizes cooperative deformation coupling of subgrade soil and pavement structure layer in the discrete element software, provides a research idea for road disease problems and settlement deformation calculations in poor subgrade areas, and lays a theoretical foundation for subsequent subgrade disease remediation in this area.
2023(1):12-19,42. DOI: 10.20000/j.1000-0844.20220829001
Abstract:A model of equipment structure coupling isolation system was first established in this paper, then fifty near fault pulse like and fifty near fault non pulse like seismic waves were selected to determine the dynamic responses of the isolation system. The analysis results show that the effect of near fault pulse like ground motions on the coupling isolation system is greater than that of near fault non pulse like ground motions, and the effect on the main structure is greater than that on equipment. Average responses of the displacement of isolation layer, story drift, floor acceleration, equipment acceleration, and equipment displacement under near fault pulse like ground motions are 2.25 times, 2.17 times, 2.24 times, 1.17 times, and 1.20 times of those under near fault non pulse like ground motions, respectively. In the design of the equipment structure coupling isolation system, the impact of pulse characteristics of near fault ground motions should be considered. Meanwhile, it should be noted that ground motions causing the maximum response of the main structure and equipment may not be the same.
2023(1):20-26. DOI: 10.20000/j.1000-0844.20220811005
Abstract:Since the damper is widely used nowadays, traditional friction dampers with no self centering function cannot adapt to different vibration intensities and will be seriously damaged after the earthquake. In this paper, a new type of self centering variable friction damper is proposed based on the superelasticity of shape memory alloy. The structure and basic working principle of the damper were introduced, and its mechanical model was then established. Through the mechanical test of the damper, the following conclusions are obtained: (1) The damper can not only meet the requirements of energy dissipation under different earthquake intensities but also has a good self centering ability. (2) The hysteretic curve obtained from the mechanical experiment is in good agreement with the derived mechanical model, which confirms the correctness of the model. (3) The energy dissipation capacity of the damper increases with the increase in the diameter of alloy wire, bolt preload, and slope gradient. The residual displacement decreases with the increase in the diameter of alloy wire and slope but increases with the increase in bolt preload.
2023(1):27-33. DOI: 10.20000/j.1000-0844.20200601005
Abstract:A slope at the Bingchang mining area was taken as an example to investigate the fracturing effect of extra thick coal seam mining on the overlying loess slope. The occurrence and mechanical characteristics of fractures in the loess slope were analyzed by using the physical model test and numerical simulation method. The test results show that fractures caused by coal mining in the overlying loess slope can be divided into two groups: fractures approximately perpendicular to the slope surface and fractures approximately parallel to the slope surface, indicating obvious spatial differentiation and orderly appearance. Fractures approximately perpendicular to the slope surface appear first and have characteristics of tensile cracks; they play an important role in cutting slopes. The fractures approximately parallel to the slope surface are derived gradually from the fractures perpendicular to the slope surface; they have characteristics of shear cracks and control the formation of potential sliding surfaces in the loess slope. In a word, the two groups of fractures cut the slope in a net shape, inducing the soil structure of the slope to break and fragment.
2023(1):34-42. DOI: 10.20000/j.1000-0844.20210703003
Abstract:Super high rise building has become an important structure type in urban development, and the seismic performance of the complex out of code high rise structure system is currently a critical concern. The actual project of an international trade center in a city was taken as an example in this paper, and a finite element model of the complex super high rise structure was established through the performance based seismic analysis and calculation platform OpenSees. The reliability of the model was verified by the identification of dynamic parameters based on the in seismic analysis vibration detection technique. Dynamic response analysis of the structure under earthquake was then carried out, taking into consideration the base shear force, story drift ratio, displacement of structure top, and structural damage. The research results can provide technical support for the seismic design of complex super high rise building structures.
2023(1):43-49,57. DOI: 10.20000/j.1000-0844.20211017001
Abstract:In this work, the statistical distribution characteristics of peak acceleration ratios in the horizontal, vertical, and horizontal directions were studied on the basis of 156 783 groups of ground motion records from 2 129 destructive earthquakes, and the acceleration records were classified and analyzed in accordance with epicentral distance, magnitude, and focal depth. Results showed that the overall average value of the acceleration ratio peak in the horizontal direction was 0.83, and the cumulative probability of the acceleration peak ratio in the horizontal direction≤0.85 was 63%. The ratio of vertical to horizontal peak accelerations generally presented an extreme type II distribution with an average value of 0.44, and the cumulative probability of the ratio of vertical to horizontal peak accelerations ≤0.65 was 92%. With the increase in epicentral distance, the horizontal peak acceleration ratio increased, whereas the ratio of vertical to horizontal peak accelerations decreased. The ratio of vertical to horizontal peak accelerations increased with the increase in magnitude, and this increasing trend was more obvious under large (7＜M≤8) near field (0＜R≤60) earthquakes. Meanwhile, the correlation between the horizontal peak acceleration ratio and magnitude was not obvious. Within 0-100 km from the epicenter, the peak acceleration ratios in the horizontal, vertical, and horizontal directions increased with the increase in focal depth.
2023(1):50-57. DOI: 10.20000/j.1000-0844.20210516001
Abstract:Some continuous rigid frame bridges are constructed adjacent to active faults in western China, but the influence of the angle between the fault strike and the longitudinal bridge direction on the seismic response of rigid frame bridges is usually ignored in the seismic design. Four long span continuous rigid frame bridge models with different pier heights were established by Midas Civil software in this paper. Ten groups of near fault ground motions were selected for time history analysis to study the influence of the fault strike on seismic responses of the displacement and ending moments in rigid frame bridges. Results show that under horizontal bidirectional near fault ground motions, the longitudinal seismic response of main piers and main girders is the largest when the angle between the fault strike and the longitudinal bridge direction varies from 75° to 135°, while the maximum transverse seismic response occurs when the angle is in the ranges 0°-30° or 120°-180°. Compared with the seismic response of bridges under horizontal bidirectional ground motions, the vertical ground motion has a great influence on the vertical bending moment response of the main girder under three directional near fault ground motions. Specifically, the seismic response can be multiplied two or more times, especially at the junction of the main pier and the main girder of the rigid frame bridge. It is possible to underestimate the seismic response of the four bridges selected in this paper if analyzed without considering the angle between the fault strike and the longitudinal bridge direction; the underestimated error is about 15%-40%.
2023(1):58-64. DOI: 10.20000/j.1000-0844.20220804005
Abstract:The elastoplastic response of a new type of gravity column core tube structure system was studied by considering comprehensive adversary conditions of pulse like ground motion and structural mass eccentricity. Ten pulse like and ten non pulse like ground motion acceleration records were selected as bidirectional seismic input. The structural nonlinear analysis software CANNY was used to conduct a finite element numerical analysis, and the effects of pulse like ground motion and structural mass eccentricity on the elastoplastic seismic response of the new structure were investigated. The analysis results indicate that the story drift ratio, shear force, and inter story torsion angle under pulse like ground motions are remarkably higher than those under non pulse like ground motions. Besides, mass eccentricity apparently affects the elastic plastic seismic demand of the structure. With the increase in eccentricity, the story drift ratio and inter story torsion angle increase while the inter story shear decreases. It is recommended that attention should be paid to coupling adversary influence of pulse like ground motion and structural mass eccentricity during the design of the gravity column core tube structure.
2023(1):65-73. DOI: 10.20000/j.1000-0844.20210629001
Abstract:The standardized design method of nuclear power plants is an important means to save the cost of nuclear power construction. It is of great significance to carry out the analysis on the standardized foundation model of nuclear power plants in non rock foundation site. In this paper, based on the investigation data of dynamic parameters of typical sites with soft rock and hard soil at home and abroad, the variation law of dynamic parameters with depth was first summarized. The profile characteristic curves of the foundation shear wave velocity was obtained through normalized analysis, thus determining the preliminary standardized foundation model. Furthermore, the seismic response analysis of the preliminary standard foundation model was carried out using the SuperFLUSH/2D Ver6.0 software. The influence of dynamic parameters on the seismic response was explored by two consideration indexes: the variation of maximum acceleration with depth and the acceleration response spectrum. Finally, according to the similarity and envelope of shear wave velocity profiles of the preliminary foundation model, the standardized foundation model of nuclear power plant in the case of soft rock and hard soil sites was defined, and the reasonable values of corresponding dynamic parameters were given. The model and research results in this paper can provide important references for the standardized design of nuclear power plants in China.
2023(1):74-85,93. DOI: 10.20000/j.1000-0844.20211107003
Abstract:Numerical analysis is widely used to study the excavation deformation of deep foundation pits in complex environment, but the constitutive model and the selection of model parameters have great influence on the rationality of calculation results. By comparing and analyzing the characteristics of various constitutive models, it is found that the constitutive model of hardening soil with small strain (HSS) can well predict the deformation caused by excavation of foundation pit in soft soil sites, but the parameters of HSS model are difficult to take values. The lacustrine sedimentary soft soil is widely distributed in Kunming area, but there are no relevant studies on how to select the parameters of HSS model for such soil, especially peaty soil with high organic matter content and water content. To solve these problems, data of many geotechnical tests and indoor tests of undisturbed samples were analyzed, and the relationship among empirical values of several stiffness parameters were obtained, then the HSS model parameters of typical lacustrine sedimentary soft soil were obtained. To examine the rationality of HSS model and related parameter values, numerical models for two subway foundation pits in soft soil site were established using the numerical analysis software PLAXIS 2D. The deformation of foundation pits under different excavation conditions were calculate and compared with the monitoring value of actual deformation. Results show that they are in good agreement, indicating that the calculated results are reasonable and reliable. The research results have important reference value for the support design of deep foundation pit and the geotechnical engineering research and investigation.
2023(1):86-93. DOI: 10.20000/j.1000-0844.20220809003
Abstract:The eddy current damper (ECD) has the characteristics of no contact and friction with the structure; unlike viscous damper, ECD has no problems, such as liquid leakage. First, the theory of planar ECD was introduced to investigate the performance of a planar ECD. Then, the reliability of the simulation method and the model for the planar ECD based on the software COMSOL was verified in accordance with the test on ECD coefficients. Finally, COMSOL was used to analyze the parameters of the planar ECD, such as conductive clearance, conductor thickness, conductor’s back iron thickness, and magnet’s back iron thickness. The planar ECD basically conforms to the assumption of viscous damping theory, and the results of damping coefficient simulation using COMSOL are also authentic. Thus, the conductive clearance and thickness of conductors have considerable influence on the damping coefficient, while the back iron thickness of the conductor and magnet has minimal influence.
2023(1):94-102. DOI: 10.20000/j.1000-0844.20210717001
Abstract:To study the dynamic response characteristics of loess slopes under dynamic seismic action, a 1:20 scaled loess slope test model was established based on a natural loess slope along the Baoji-Lanzhou passenger dedicated line. Through large scale shaking table test and other methods such as time history analysis, wavelet packet analysis, and response spectrum analysis, we analyzed the variation rules of the first frequency band energy proportion (E1), second frequency band energy proportion (E2), characteristic period, response spectrum amplitude, peak acceleration (PGA), and amplification factor of acceleration (AFA) of the loess slope structure under seismic load . Results show that according to the transformation law of E1 and E2,the maximum value of E1+E2 is located at the top of the slope. In the elastoplastic stage, the time for the same seismic wave to reach the characteristic period under different seismic intensities is basically the same; the time for the El Centro wave to reach the characteristic period lags behind that of the Wenchuan Tangyu wave, and the amplitudes of its acceleration and velocity response spectrum are slightly smaller. The PGA and AFA amplification effects in the horizontal direction of the model are in the order of their magnitudes: failure stage＞plastic stage＞elastic stage. During the earthquake, the location closer to the slope surface is more likely to be destroyed and to be destroyed first, which proves the existence of the“whiplash effect.”It is recommended that anti seismic protection measures should be conducted at the surface and top position of the loess slope in actual projects.
2023(1):103-111. DOI: 10.20000/j.1000-0844.20220708004
Abstract:Based on theoretical derivation and numerical simulation methods, a systematic study was carried out on the seismic stability of a series isolation system after isolation retrofitting, which is composed of laminated rubber isolation bearings and the lower pillar of the basement. The laminated rubber bearing was simplified to a special hinge bearing with horizontal stiffness and flexural rigidity, while the RC column was simplified to a curved vertical rod. Then a theoretical model of the series isolation system was established, and the equation for the critical bearing capacity of the lower pillar of the basement was derived. The concrete expression of the critical bearing capacity was solved based on practical cases, and the influences of typical parameters were analyzed. Six kinds of column top isolation models with different lower pillar section dimensions were established by the numerical simulation method. Then the overall displacement response of the system and the response of the story drift ratio in the superstructure were compared and analyzed. Results show that the variation of deduced expression for the critical bearing capacity was consistent with the numerical simulation results of the column top isolation model. The increase in the cross section of the lower pillar has no obvious effect on the dynamic response of the superstructure and the isolation bearing, but it could remarkably reduce the displacement of the lower pillar. In the actual seismic isolation reconstruction project for existing buildings, increasing the lower pillar section size is a simple and effective method for ensuring that the seismic capacity of the lower structure is higher than that of the upper structure. However, in practical projects, the section increment is generally large and conservative, resulting in some waste.
2023(1):112-119,129. DOI: 10.20000/j.1000-0844.20220803003
Abstract:The new staggered story isolation structure is a novel seismic isolation structure developed from the base isolation structure and the inter story isolation structure. A large mainshock may trigger numerous aftershocks, which may cause greater damage to the structure. In this paper, the deformation and damage of the new staggered story isolation structure under the action of a single mainshock and mainshock aftershock sequences were analyzed. The finite element software ETABS for nonlinear time history response analysis was used to establish a 24 story frame core tube structure model. Results show that the damage on the core tube of the structure under mainshock aftershock sequences is concentrated between the frame isolation layer and the core tube isolation layer. The plastic hinge of the frame is concentrated below the frame isolation layer. The hysteretic curve of the corner column bearing of the frame isolation layer is full, and its energy dissipation effect is better than that of the core tube isolation layer. The maximum displacement of the isolation layer of the new staggered story isolation structure occurs in the frame isolation layer. Under the aftershocks, there is a significant increase in the damage to the new staggered floor isolation structure. Under aftershocks, the damage of the new staggered story isolation structure obviously increases. The damage to the frame part above and below the frame isolation layer increases by 8% and 10%, respectively, and the damage to the core tube increases by 19.80%. Aftershocks have a greater impact on the isolation layer, and the inter story displacement of the frame isolation layer and the core tube isolation layer increases by 78.70% and 60.54%, respectively.
Abstract:Based on 26 scenes of Sentinel 1 ascending data from October 22, 2014, to April 11, 2019, the deformation monitoring test of the Jiyunhe fault, a buried fault, was carried out using the PS InSAR technology. Results show the following:(1)The Ninghe area in the south of the study area is strongly disturbed by land subsidence, which leads to gradual weakening toward the north and basically disappears in the north of the northern segment of the Jiyunhe fault.(2)The deformation rate of the northern part of the study area in the direction of the line of sight(LOS)is about 0 mm/a in the northern segment of the Jiyunhe fault and increases northward with the distance from the fault, indicating that the northern part of the study area controlled by the nearly EW trending Yanshan uplift has a trend of tilting toward the south.(3)The movement mode in the northern segment of Jiyunhe fault is stick slip. The difference in LOS relative deformation rate between the two sides is about 1.83 mm·a-1,while that between the two sides of the southern segment of the Jiyunhe fault is less than 2.96 mm·a-1,which is close to the leveling results from 2005 to 2012, indicating that since 2005, the Jiyunhe fault has been relatively stable.(4) Under the influence of land subsidence, the InSAR deformation field of buried fault contains a lot of non structural information, so the specific deformation rate of a fault cannot be obtained. However, the aquifers on the two sides of the fault have different thicknesses due to the fault activity. The land subsidence amplitude caused by groundwater overdraft is also different. Correspondingly, the InSAR deformation field changes abruptly on the two sides of the fault, which is of certain significance in determining the location of hidden faults.
2023(1):130-137,180. DOI: 10.20000/j.1000-0844.20210223001
Abstract:The Northern Jiangsu-South Yellow Sea is underlain by the Yangtze Craton continental lithosphere. Based on the collected phase velocity data of Rayleigh surface wave, a depth inversion of the underground three dimensional S wave velocity structure in the Northern Jiangsu-South Yellow Sea area was carried out. Based on the data, the relationship between the geological structure and seismotectonics of the Northern Jiangsu-South Yellow Sea Basin was discussed. The surface wave tomography results show that the regional velocity structure model is basically consistent with the geological characteristics of the study area, and the velocity structure clearly depicts the main sedimentary structure range and basement fluctuation of the Northern Jiangsu-South Yellow Sea Basin. The inversion results also reveal that there is a remarkable low velocity layer in the middle crust of the Northern Jiangsu-South Yellow Sea Basin, which is consistent with the concentrated distribution area of historically strong earthquakes, indicating that the activity of shallow strong earthquakes is closely related to the low velocity layer in the crust.
2023(1):138-144. DOI: 10.20000/j.1000-0844.20210720004
Abstract:Approximately two days prior to the Ningqiang MS5.7 earthquake (May 27,2008), a large amount of cave strain anomalies were recorded in the NS and EW components at Baoji station. A previous study showed that these phenomena were short imminent earthquake precursors of the Ningqiang MS5.7 earthquake.By means of repeated earthquake tests and empirical statistics, the attribution of these anomalies was analyzed systematically to objectively verify the authenticity of this conclusion. Results showed that rainfall interference was the main cause of the remarkable strain anomalies.
2023(1):145-152. DOI: 10.20000/j.1000-0844.20220812001
Abstract:As an important part of earthquake early warning(EEW)systems,the EEW service system is the key protection target and object of network security.Given the wide impact of EEW information, ensuring its authenticity, integrity, and high timeliness is necessary. Therefore,a tamper proof framework for EEW service systems based on domestic cryptographic algorithms is designed in this study. The digital certificate and cosignature technique were used to optimize the verification process of identity authentication and message integrity,thus minimizing time consumption by the cryptographic algorithm.After the design was completed, the time consumed by the above operations was less than 0.2s, considering the safety and high timeliness of EEW information.
2023(1):153-160. DOI: 10.20000/j.1000-0844.20200525005
Abstract:On the basis of thermal infrared data from China’s geostationary meteorological satellite, the wavelet transform and power spectrum estimation method were used in this study to analyze thermal infrared brightness temperature anomalies before the 2018 Chengduo earthquake, and the prediction process was reviewed and summarized. Results showed that the evolution of thermal infrared brightness temperature anomalies before the Chengduo earthquake was characterized by four stages: emergence, enhancement, weakening, and disappearance. The anomalies were distributed in strips and were basically consistent with the fault strike. Some characteristic parameters describing the anomaly were within the reference range of previous earthquake cases. Comparison with the anomalies in the thermal infrared brightness temperatures of other earthquakes with similar magnitudes in the same region revealed that the anomalies before the Chengduo earthquake may be related to the double earthquake type of the Chengduo earthquake. The prediction process of the Chengduo earthquake is summarized as the four stages of analysis judgment prediction test and can provide a new experience for the determination of regional earthquake situations
2023(1):161-168. DOI: 10.20000/j.1000-0844.20210723004
Abstract:HVDC transmission faults, geoelectric storms, geoelectric resistivity observations, artificial power supplies, and subways usually interfere significantly with geoelectric field observations, thus causing great trouble to the application of observation data and the extraction and identification of seismic anomaly information. Thirteen geoelectric field stations with good observation systems, such as Lingyang and Guazhou stations, were selected for analysis in this paper. Based on the seepage(movement)model of rock fissure water (charge) in the telluric field, the change of dominant azimuth α of the telluric field at each station under typical interference was calculated. Results show that the effect of usual interference on the calculated value of α is not obvious. However, severe interference with large amplitude lasting for many days may have impacts on some sites. The analysis results of the Ningqiang MS5.3 earthquake in Shaanxi Province on September 2018 show that the anomaly of α in the surrounding sites may be remarkable before a strong earthquake under complex conditions. The results of this research may have some reference significance for the application of geoelectric field data.
2023(1):169-180. DOI: 10.20000/j.1000-0844.20220502002
Abstract:btaining earthquake source information quickly and accurately soon after the occurrence of a large earthquake is very important. However, it is often challenging to simultaneously obtain the distribution characteristics of rupture space. In this paper, a multiple point source based W-phase inversion method was developed based on the traditional W-phase inversion technology. The new method can quickly determine the energy release characteristics and focal mechanism of a large earthquake rupture on the spatial scale. The effectiveness of the program was tested by taking the 2004 Sumatra MW9.1 earthquake as an example. We set up 1, 2, 3, 4, 5, and 6 point sources to determine the energy release characteristics and focal mechanism of the earthquake. Results show that the change of focal mechanism from south to north is consistent with the striking change of the subduction surface, which is also highly consistent with the focal mechanisms of historical earthquakes near the point sources. Therefore, the multiple point source based W-phase inversion method can effectively result in spatial energy release characteristics of large earthquakes, thus providing scientific support for post earthquake emergency response and tsunami warning.
2023(1):181-190. DOI: 10.20000/j.1000-0844.20210805001
Abstract:To predict the distribution of instrumental seismic intensities around the epicenter immediately after an earthquake, we selected 2 331 triggered strong motion stations from 632 earthquakes and extracted the epicentral distance, magnitude, and seven effective ground motion parameters within 20 seconds after the triggers to the stations. The selected data samples were trained using an artificial neural network, and three effective prediction models were established. The results show the following:(1)Model one, which selects seven ground motion parameters without epicentral distance and magnitude, has good timeliness in prediction. From 1 to 20 s, the average intensity difference in prediction gradually reduces to 0.45.(2)Model two selects eight ground motion parameters, including the epicentral distance; it can be used to ensure early earthquake warning through the prediction of magnitude. The average intensity difference in prediction gradually reduces to 0.36.(3)Model three selects nine ground motion parameters and has the best prediction result among the three models; its average intensity difference in prediction reduces to 0.31, and it can be used to predict the post earthquake intensity field in real time. The three models were used to predict the intensity of two real earthquakes, and the difference in predicted intensity is greater than 95% and 76%, within 1, indicating that the models can be applied in earthquake early warning.
2023(1):191-198. DOI: 10.20000/j.1000-0844.20210128001
Abstract:Based on the mobile geomagnetic observation data of Hebei and its adjacent areas in 2018, 2019, and 2020, the annual variation model of the lithospheric magnetic field in “2018-2019”and“2019-2020”was obtained. In combination with the epicenter distribution of the Fengnan M4.5 earthquake in December 2019 and the Guye M5.1 earthquake in July 2020 in Tangshan, the spatial distribution and time evolution characteristics of changes in the lithospheric magnetic field of the epicentral area were systematically analyzed. Results show that there is no consistency or inheritance in the spatial distribution of annual changes of the 2 term lithospheric magnetic field. Compared with the“2018-2019” lithospheric magnetic field, there has been a decreasing trend in the annual change of various elements of the“2019-2020”lithospheric magnetic field. Before the two earthquakes above, there have been obvious anomalies in the lithospheric magnetic field near the epicenter. Specifically, the horizontal vector of the lithospheric magnetic field appears as a local weakening and results in direction changes with a zero value line and high cascade zone through the epicenter area, which may be the preceding anomalies for the two earthquakes.
2023(1):199-208. DOI: 10.20000/j.1000-0844.20220107001
Abstract:The Jiangjunshan-Baishui fault is a branch of the eastern section of the northern margin fault of the Weihe Basin. It is located in front of Jiangjun Mountain and East Taibai Mountain and extends northeast to Baishui County. The existing data and research results suggest that the Jiangjunshan-Baishui fault is an active fault in the Late Pleistocene. In this paper, the distribution and activity of the fault were studied based on some methods such as geomorphological and geological surveys, shallow seismic exploration, composite drilling section exploration, and Quaternary sediment dating. The results show that the Jiangjunshan-Baishui fault, with an overall trend of NE dipping S,is a piedmont buried fault. The latest active age of the fault is the late Middle Pleistocene. No evidence of activity has been found since the Late Pleistocene. It is therefore concluded that the Jiangjunshan-Baishui fault is an active fault in the Middle Pleistocene.
2023(1):209-219,243. DOI: 10.20000/j.1000-0844.20220831002
Abstract:The mantle velocity structure provides crucial information regarding the thermal and chemical states and tectonic evolutionary history of the Earth’s interior. The study of mantle discontinuities can provide a clearer understanding of the temperature distribution characteristics and chemical structure of the Earth’s interior. Moreover, it is important for determining geodynamic issues, such as the cause of mantle discontinuities and mantle convection models. Seismological observation data show that velocity discontinuities are commonly found at the depths of 410 and 660 km, as well as in the upper mantle (220,300-350,520,and560km) and lower mantle(800-900,1100-1200,1800,and2400km) in specific regions of the world. The topography of mantle discontinuities in different regions may be influenced by temperature, water content, mineral phase transformation, and subducting plates. The use of precursors to study mantle discontinuities has a unique advantage: Precursors arrive at the observation station earlier than the reference phase, thus avoiding the interference of other phases and detecting the weak discontinuity of the mantle more accurately. In this study, we collected and compiled research results on mantle discontinuities obtained by using precursors in recent years. The precursors used included precursors of long period reflection phases SS or PP, of deep phases sP and pP, and of the Earth surface reflection phase PKPPKP. In addition, we summarized the characteristics of different precursors and related research results of mantle discontinuities. Methods for the use of precursors to study mantle discontinuities have matured. The timely collection and summarization of relevant research results are important for understanding various scientific problems, i.e., the internal structure of the Earth, material composition of the mantle, influence of slab subduction on the mantle structure, and mantle convection mode.
2023(1):220-227. DOI: 10.20000/j.1000-0844.20210325001
Abstract:A large number of earthen sites are found in arid and semi arid regions of Northwest China. Based on the field investigation of earthen sites in Northwest China, this paper summarizes the diseases of these sites in the study area according to the types of disease causes. The quantitative fitting analysis of survey data revealed an internal relationship between four typical diseases, namely cracks, erosion, gullies, and collapse, and a sequence and promotion relationship between the formation and development of various diseases. Linear fitting results show a positive correlation among the four aforementioned diseases in varying degrees; cracks, erosion, and gullies will eventually lead to the collapse of earthen sites. The correction coefficient indicates that the most significant factors leading to the collapse of earthen sites are the development of gullies and erosion. Thus, the reinforcement and protection of earthen sites should consider a variety of diseases, and comprehensive treatment of multiple diseases should be performed to delay the destruction of earthen sites to the largest extent.
2023(1):228-234. DOI: 10.20000/j.1000-0844.20220716002
Abstract:Based on small earthquake catalog data from 2000 to 2008 in the Longmenshan fault zone and its neighboring areas, we apply the idea of impact“superposition”of global earthquake activity(M＞7)in systematically analyzing the anomalous activity characteristics of remotely and dynamically triggered small earthquakes in the neighboring areas before a major earthquake. Results show that before the Wenchuan MS8.0 earthquake, the small earthquake activity in the Longmenshan fault zone and adjacent areas was influenced by global earthquake activity(M＞7). About one year before the MS8.0 earthquake, there were significant abnormal characteristics of small earthquake activity triggered by remote earthquakes. The reliability of calculation results was verified by using the random test method and changing the statistical parameters. The method can effectively highlight the anomalous activity characteristics of small earthquakes that are remotely and dynamically triggered on the seismogenic fault before a major earthquake, thus having some reference significance for regional strong earthquake risk assessment.
2023(1):235-243. DOI: 10.20000/j.1000-0844.20210714003
Abstract:In recent years, the development of deep learning has opened up a new idea for researchers examining earthquake locations. Deep learning technology has been applied to earthquake locations with good results. The paper first introduces the classification of deep neural networks according to the coding and decoding of neural networks, then summarizes the basic process of deep learning. Finally, it reviews the methods of deep learning widely used in seismic locations and summarizes the characteristics and practical applications of each method. The results show that deep learning methods can help in the automatic determination of the locations of seismic events, with high accuracy of location identification, which greatly shortens the time required for the seismic location. They also have obvious advantages in processing seismic big data and can overcome some shortcomings of traditional geophysical methods in earthquake locations. It is believed that with the further development of deep learning technology, it will be more widely used in seismic location research.
Abstract:The popularization of the scientific knowledge of earthquake prevention and disaster mitigation is conducive to enhancing public awareness of earthquake prevention and disaster reduction. Reducing social and economic losses and human casualties when earthquakes occur is of great significance. This work analyzes the public cognition and demand for earthquake disaster prevention and mitigation science popularization by means of a questionnaire survey and draws the following conclusions.(1)The overall level of public cognition of earthquake science popularization in Shandong Province is low, and the level of mastery of basic earthquake knowledge is limited. The ability to recognize earthquake rumors is insufficient, and the ability for earthquake emergency avoidance needs to be strengthened. The level of mastery of emergency rescue skills and the cognition of principles of earthquake avoidance are low.(2)The public in Shandong Province has a high demand for science popularization content on earthquake emergency avoidance and skills, earthquake forecasting and warning, and earthquake rumor recognition, as well as the earthquake resistance of buildings.(3)The most expected way for the public in Shandong Province to obtain popular science information on earthquake prevention and disaster reduction is through mobile apps or websites, and the respondents are more willing to participate in offline activities, i.e., earthquake emergency drills, popular science lectures, and popular science museum visits. In view of the above actual situation, this work provides some suggestions for improving the work of earthquake science popularization.
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