• Volume 41,Issue 4,2019 Table of Contents
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    • >结构抗震
    • Study on the Seismic Resilience of Substations

      2019, 41(4):827-833. DOI: 10.3969/j.issn.1000-0844.2019.04.827

      Abstract (945) HTML (0) PDF 3.58 M (881) Comment (0) Favorites

      Abstract:In this study, a grading method of the seismic resilience of substations is presented. The quantitative indicator "resilience index" is proposed to evaluate the seismic resilience of substations. A formula for computing the resilience index based on seismic intensity and the weighting coefficients of buildings and high-voltage electrical equipment is also proposed. The corresponding relationship between the resilience index and resilience grades is determined. The substation resilience matrix is also established through the study of actual seismic damage and recovery samples. The result shows that the seismic resilience of substation becomes weaker as the resilience index decreases. Once the index drops to less than 0.45, the substation would reach a threshold beyond recoverability. Generally, the higher the seismic intensity is, the weaker the substation resilience will be, and a longer restoration time will be needed. Most of the substations are conditionally restorable and hard to be restored in the area of 9-degree seismic intensity, and will be almost unrestorable in the area of 10-degree seismic intensity.

    • Experimental Study on the Dynamic Response of Vertical Pile-Group Structure in Saturated Sand with Different Thicknesses under Earthquake Action

      2019, 41(4):834-839,852. DOI: 10.3969/j.issn.1000-0844.2019.04.834

      Abstract (730) HTML (0) PDF 9.42 M (947) Comment (0) Favorites

      Abstract:Based on the shaking table test, in this study, we designed a similar model of a 2×2 vertical pile-group structure. By inputting the Qian'an seismic wave with a certain peak acceleration, the lateral dynamic response characteristics of a vertical pile-group cap in non-liquefied, saturated sand with different thicknesses of 300 mm and 380 mm were studied by the shaking table test. The results showed that under the Qian'an wave input, the acceleration and displacement time histories of the pile-group cap in non-liquefied sand were not significantly different from those at the platform; for the two sand thicknesses, the acceleration amplification of the pile-group cap in the saturated sands was enlarged, but the peak displacements of the pile-group cap were not much different from those at the platform. In 300 mm and 380 mm saturated sands, the peak acceleration of the pile-group cap was amplified by 1.35 times and 1.42 times, respectively, compared with that of the platform input, which shows that under the same input condition, the dynamic response of the pile-group cap was more remarkable in the thicker saturated sand after the liquefaction.

    • A Dynamic Elastoplastic Damage Model of Building Structures under Moderate and Strong Earthquakes

      2019, 41(4):840-844. DOI: 10.3969/j.issn.1000-0844.2019.04.840

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      Abstract:The anti-seismic performance is an important index in building design; therefore, analyzing the elastoplastic damage of a building structure under earthquake is necessary. In this paper, an elastic-plastic damage model of building structures under moderate and strong earthquakes is proposed. The basic principle of the elastic-plastic damage model is analyzed from the aspects of the effective stress, the Cauchy stress tensor, and the damage evolution equation of building materials. Based on this, the relationship between the strain rate of the building material and the damage energy release rate of the structure is analyzed. The damage index of failure of a building material is obtained through the Bonara damage model, and the damage index of the building structural component is calculated. On this basis, the dynamic-plastic damage model of the building structure under moderate and strong earthquakes is constructed. When the seismic acceleration value is 0.3g, the relative displacement time history curve of the building structure is fitted with the actual displacement curve, and the dynamic elastic-plastic damage simulation accuracy of the building structure is good. The results show that the model is feasible to a certain extent.

    • A Comparison between Vibration and Wave Methods in Seismic Analysis of Underground Structures

      2019, 41(4):845-852. DOI: 10.3969/j.issn.1000-0844.2019.04.845

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      Abstract:The wave and vibration methods of seismic analysis are widely employed with underground structures. Comparisons between the two approaches were conducted in the paper. First, the wave method, i.e., the viscoelastic artificial boundary and pertinent equivalent nodal force method, is introduced briefly. Second, the governing equation and finite element formulation of the problem are presented to clarify the interrelation and distinction between the two methods. On the basis of standard numerical tests, it was proved that the vibration method is only applicable to degraded cases, with assumptions of a rigid base and an SV propagating vertically upward. Then, the comparison between the rigid base and the elastic base was conducted. The rigid base was simulated through the vibration method, while the elastic base was simulated using the equivalent nodal force method. The results showed that there are significant differences between elastic and rigid bases in terms of ground surface displacement response and internal force response of tunnel structures. Therefore, the influence of different site conditions was far from negligible, and the analysis method should be carefully selected based on site conditions and whether a rigid or elastic base is incorporated into the seismic design of underground structures.

    • Roof Design for Large-span Steel-Wood Hybrid Structures and the Seismic Performance Based on Actual Cases

      2019, 41(4):853-859. DOI: 10.3969/j.issn.1000-0844.2019.04.853

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      Abstract:To effectively improve the seismic performance of roofs in buildings and save the construction cost, the seismic performance of the roof of a long-span steel-wood hybrid structure is deeply studied based on an engineering case. The seismic response and tension control stress of pre-stressed cables are determined according to five test parameters, namely, the lateral stiffness ratio, the estimation of seismic action, the setting of bearing capacity, the checking of seismic deformation, and the connection and foundation design. The hybrid roof designed in this study ensures that the roof structure can be subjected to frequent and rare earthquakes. Based on an engineering example, the seismic performance test of a long-span steel-wood hybrid structure roof is carried out according to the effective work. The experimental performance test results show that the seismic performance of the long-span steel-wood hybrid structure roof is stronger than that of a single-structure roof. Moreover, the case study shows that the seismic performance of the inner column is weaker than those of other members of the long-span steel-wood hybrid structure under multidimensional earthquakes.

    • Dynamic Performance Analysis of Hybrid Structures with Different Vertical Stiffnesses under Near-field Earthquakes

      2019, 41(4):860-865. DOI: 10.3969/j.issn.1000-0844.2019.04.860

      Abstract (673) HTML (0) PDF 8.08 M (857) Comment (0) Favorites

      Abstract:The dynamic characteristics of near-field earthquakes are different from those of far-field earthquakes; therefore, it is necessary to analyze the seismic performance of structures under near-field ground motion in actual projects. In this paper, a hybrid structure with different vertical stiffnesses of the upper steel structure-lower concrete structure is taken as the research object. The dynamic responses of the structure under the action of near-field pulse-like ground motions, near-field non-pulse-like ground motion, and far-field ground motion are respectively studied. The results show that the near-field pulse-like earthquake will amplify the dynamic response of the story drift ration, interlayer shear force, and acceleration under frequent, designed, and rare earthquakes. Under the rare earthquake, the structural response increases the most. Because the near-field impulse effect will bring unsafe factors to the structure, it is necessary to study the applicability of the hybrid structure with different vertical stiffnesses in the design and construction of layered hybrid frame structures in near fields.

    • Seismic Response Analysis of Curved Bridges Considering Pile-Soil Interaction under Multi-dimensional Earthquakes

      2019, 41(4):866-872. DOI: 10.3969/j.issn.1000-0844.2019.04.866

      Abstract (758) HTML (0) PDF 6.71 M (933) Comment (0) Favorites

      Abstract:To study the seismic response characteristics of curved bridges considering the pile-soil dynamic interaction under a multi-dimensional seismic excitation, a nonlinear theoretical analysis model of pile-soil interaction was established in this paper. To simplify the calculation process, the nonlinear spring model was linearized, and a simulation model of curved bridges on a loess site was established based on the finite element ANSYS analysis platform. A multi-dimensional and multi-condition numerical analysis of curved bridges, in the context of pile-soil interaction, was carried out. Analysis included the seismic response of the midspan bending moment of curved girder, the shear force and bending moment at the bottom of the pier, and the displacement at the top of the pier. The results showed that the midspan internal force of the main girder of the curved bridge, under given pile-soil interaction, was closely related to the direction of seismic wave input, and the internal force of the girder was the largest under three-dimensional seismic action. The radial shear force response at the bottom of the bridge pier was much larger than the tangential shear force response under the seismic load, while the radial bending moment of the bridge pier was slightly smaller than the tangential bending moment. Under the same loading condition, the top tangential displacement responses of different piers were the same, while the radial displacements were quite different. In the seismic design of irregular curved bridges, the input conditions of multi-dimensional and single-dimensional seismic excitation should be fully considered.

    • A Flexible Mechanical Model with Variable Cross-Section in Prestress of Beam and Column of Prefabricated Steel Structure

      2019, 41(4):873-879. DOI: 10.3969/j.issn.1000-0844.2019.04.873

      Abstract (648) HTML (0) PDF 3.10 M (561) Comment (0) Favorites

      Abstract:To improve the seismic performance of fabricated steel beams and columns, a flexible mechanical model with variable cross-section was designed to evaluate the prestress of the cross-section seismic performance. In this method, ultimate bearing capacity constraints were used for seismic analysis and flexural stiffness softening coefficient was introduced to correct the error and then the load moment of the steel beam and column was obtained. Through stress assessment and structural decoupling design, seismic evaluation of steel beam and column was realized. The seismic performance analysis function having steel strength, ductility index, and seismic vulnerability of steel frame as constraint parameters was constructed, and the prediction method of initial prestressing for thin waist cracking of prefabricated steel structure was established to realize the accurate evaluation of prestress of beam and column in prefabricated steel structure. The test results showed that the proposed model can accurately calculate the stress-strain relation, yield strength, and ultimate bearing capacity of beam and column in prefabricated steel structure, thereby improving the seismic performance of beam and column in prefabricated steel structure.

    • Seismic Performance Evaluation of Typical Modern Brick-Wood Structures in Tianjin Based on Safety Assessment

      2019, 41(4):880-886. DOI: 10.3969/j.issn.1000-0844.2019.04.880

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      Abstract:Considering the older buildings in Tianjin that have survived to modern times, particularly the brick and wood structure, considerable safety assessments and actual inspection work were carried out in this paper. The structural dimensions of a typical brick and wood building in modern times were obtained, and the strength of the load-bearing body was tested. The hidden risks of the structures were identified, and the seismic performance of the structure was analyzed. Finally, suggestions and measures for seismic reinforcement of such buildings are given. This study offers guiding in the safety assessment and seismic reinforcement of typical modern brick and wood structures.

    • Time-Dependent Seismic Fragility Analysis of OffshoreBridge Piers under Mainshock and Aftershocks

      2019, 41(4):887-894. DOI: 10.3969/j.issn.1000-0844.2019.04.887

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      Abstract:With the increase of service time, the durability damage caused by environmental corrosion has a greater influence on the seismic performance of offshore bridges. A pier is the main energy-consuming component of a bridge to resist earthquake. In this study, an offshore rigid bridge pier was taken as an example. Based on the OpenSees platform, seismic waves that meet the site conditions were selected to construct the mainshock-aftershock sequence according to the seismic records. Using the capacity demand ratio method, the seismic vulnerability curves of pier control sections in different service time points under different damage states were drawn, and the influences of chloride ion erosion and mainshock-aftershock sequence on the seismic performance of bridge piers were studied. The results show that the exceeding probability increases with the increase of service time and PGA, but decreases with the increase of damage grade. In the state of slight damage, the mainshock-aftershock sequence has a limited influence on the seismic fragility of the bridge pier. However, under moderate damage, serious damage, and complete collapse, in the same service time, the mainshock-aftershock sequence has a greater influence on the seismic fragility of the bridge pier than the mainshock.

    • An Invulnerability Estimation Model of High-rise Buildings under Strong Earthquake Based on Least Squares Support Vector Machine Algorithm

      2019, 41(4):895-900. DOI: 10.3969/j.issn.1000-0844.2019.04.895

      Abstract (896) HTML (0) PDF 1.13 M (631) Comment (0) Favorites

      Abstract:The existing estimation model as a method to estimate the invulnerability of concrete building structures is characterized by some problems, such as low estimation accuracy and long time consumption. Therefore, for high-rise buildings under strong earthquakes, an invulnerability estimation model based on least squares support vector machine is proposed. The least squares support vector machine is used to train the training samples of concrete structures damaged by strong earthquakes; then, an invulnerability estimation model of concrete structures is established. To reduce the possible model errors, the KLASSO parameter adjustment model is used to adjust and optimize the parameters of the invulnerability estimation model. The simulation results show that the model has a high estimation accuracy, and thus, the estimation time can be saved. The study can provide a good basis for improving the safety inspection efficiency of the construction industry.

    • >岩土抗震
    • Accumulative Plastic Strain Model of Soft Clay Considering Temperature Effect and Its Verification

      2019, 41(4):901-907,961. DOI: 10.3969/j.issn.1000-0844.2019.04.901

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      Abstract:According to the cyclical triaxial tests for the stress control of saturated soft clay in Ningbo area, the effects of the same temperature, dynamic stress, initial deviatoric stress, and confining pressure on the cyclic softening characteristics of saturated soft clay were studied. Based on the test, the data were normalized by introducing comprehensive influence parameters. A hyperbolic model of the cumulative plastic strain in saturated soft clay was established. Based on the assumption of dynamic equilibrium, the normalized cumulative plastic strain prediction model considering the temperature effect under the action of the long-term dynamic load was established, and the predicted values of the model agree well with the experimental results. The proposed model can provide a reference for the design and construction of rail transit.

    • Structural Plane Effect on the Deformation and Failure of the Heifangtai Tableland Slope

      2019, 41(4):908-915. DOI: 10.3969/j.issn.1000-0844.2019.04.908

      Abstract (771) HTML (0) PDF 7.29 M (979) Comment (0) Favorites

      Abstract:The structural plane effect on the deformation and failure of the Heifangtai tableland slope has been well studied; however, such studies mainly focus on a single side, and only few systematic studies have been conducted. Therefore, based on the analysis of the structural plane types and the combination characteristics, the deformation and failure types, and the characteristics of the slope, in this work, it was found that the structural surface types in the study area mainly include joint fissures, layers, interfaces, faults, and free face; the combination types of structural planes are divided into two classes and eight subclasses, and each type has its own structural characteristics and distribution characteristics. The slope deformation and failure types and the spatial distribution selection of Heifangtai tableland slopes are significantly affected by the structural planes and their combination.

    • Characteristics of Dynamic p-y Curves for Large-DiameterBelled Piles in Liquefiable Sites

      2019, 41(4):916-924. DOI: 10.3969/j.issn.1000-0844.2019.04.916

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      Abstract:The p-y curve of the dynamic pile-soil interaction of large-diameter belled piles in liquefiable sites is of great significance for seismic design. Based on the finite-difference program FLAC3D, a three-dimensional finite-difference model of the large-diameter belled pile and the equal-diameter pile is established. By inputting a sine wave at the bottom of the model, the p-y curve of pile-soil dynamic interaction between the large-diameter belled pile and the conventional equal-diameter pile in the liquefiable site is obtained. The dynamic p-y curve characteristics of the large-diameter pile are analyzed, and the characteristics of the dynamic p-y curve are compared between the large-diameter pile and the conventional equal-diameter pile under different buried depths. The results show that the p-y curve of the belled pile under the sinusoidal input is mostly an inverted "S" shape. With the increase of the burial depth, the hysteresis loop area and the area growth rate of the dynamic p-y curve gradually decrease, and the slope gradually increases. The large-diameter belled piles are similar to the dynamic p-y curves of the equal-diameter piles. The slopes of both p-y curves gradually increase with the increase of buried depth. The hysteresis loop area and the area growth rate of the dynamic p-y curve of the large-diameter belled pile are larger than those of the equal-diameter pile in each buried depth, which is conducive to energy dissipation and better seismic performance.

    • Measurement of the Seismic Behavior of Bedding Slopes Based on Uncertainty Analysis

      2019, 41(4):925-930. DOI: 10.3969/j.issn.1000-0844.2019.04.925

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      Abstract:Seismic indexes of bedding rock slopes are mostly uncertain and cannot be measured by a fixed threshold. An uncertain analysis-based method of measuring the seismic behavior of bedding rock slopes is proposed. The bedding rock slope is regarded as several superimposed thin plates. The dynamic safety factor and the dynamic limit state equation of each thin plate are calculated by an uncertain analysis method, and the dynamic limit of bedding rock slope is calculated. The relationship between the dynamic reliability index and failure probability of the bedding slope under earthquake can be obtained by solving the dynamic limit state equation, and the overall stability of the bedding slope can be evaluated under seismic force. The minimum average safety factor and average failure probability of the bedding slope can be comprehensively considered, and the evaluation results can be obtained. The experimental results show that the height, angle, and dip angle of the bedding slope have a significant influence on the seismic performance of the bedding slope under seismic force, and the evaluation results are consistent with the actual results.

    • Stability Limit Analysis of Bedding Rock SlopesBased on Pseudo-dynamic Method

      2019, 41(4):931-938. DOI: 10.3969/j.issn.1000-0844.2019.04.931

      Abstract (667) HTML (0) PDF 5.38 M (1035) Comment (0) Favorites

      Abstract:A limit analysis model for the stability of bedding rock slopes with a tensile fracture is established based on the upper bound limit analysis method and pseudo-dynamic method after considering the influences of earthquake, water pressure, and surcharge, and the corresponding formula of slope safety factor is derived. The facts of whether the front edge of the slope is blocked and the influences of the horizontal and vertical earthquake coefficients, the depth of water in the tension crack, and the surcharge on the slope safety factor are analyzed in detail by employing a reasonable form of water pressure distribution on the structure plane and non-proportional strength reduction. The results indicate that the blocked front edge of the slope, the increment of the horizontal earthquake coefficient, the depth of water in the tension crack, and the surcharge will reduce the slope stability, whereas the increment of the vertical earthquake coefficient will increase the slope stability. In addition, with the increase of non-proportional strength reduction coefficient, the safety factor of slope stability will significantly increase. Consequently, it is important to consider the strength parameter of the structure plane.

    • Seismic Slope Stability Analysis of Earth-Rockfill Dams Considering Spatial Variability of Rockfill Materials via Random Finite Element Method

      2019, 41(4):939-948. DOI: 10.3969/j.issn.1000-0844.2019.04.939

      Abstract (700) HTML (0) PDF 2.86 M (664) Comment (0) Favorites

      Abstract:The influence of spatial variability of rockfill materials on the dynamic stability of dam slope of rockfill dams was studied. Under the framework of Monte Carlo method, the random finite element method (RFEM) based on the local average subdivision method was adopted to simulate the seismic response and analyze the slope stability of a high concrete face rockfill dam in Xinjiang, China. By comparing the calculation results using the RFEM and conventional deterministic finite element method, it is determined that (1) when the spatial variability of the rockfill materials is considered, the number and dimension of sliding bodies, together with sliding movements and duration increased; therefore, the overall risk of the dam slope is significantly higher than that when the spatial variability of rockfill materials is not considered and (2) the dynamic safety indexes of dam slope are sensitive to the spatial variability of rockfill materials and show high degree of discretion consequently.

    • Resonance Column Tests on the Dynamic Characteristics of Remolded Loess in Guyuan

      2019, 41(4):949-956. DOI: 10.3969/j.issn.1000-0844.2019.04.949

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      Abstract:Dynamic shear modulus and damping ratio are important indicators in characterizing the mechanical properties of soil under the action of an earthquake. The influences of dry density and consolidation pressure on the dynamic shear modulus and damping ratio of remolded loess in Guyuan, and the basic rule of the error of test data were studied by the GCTS resonant column apparatus. The comparative analysis results under different test conditions indicated that the maximum dynamic shear modulus increases with increasing consolidation pressure and dry density under constant moisture content. Under the same dry density, the dynamic shear modulus ratio of loess increases and the damping ratio decreases with increasing confining pressure. Under the same confining pressure, the dynamic shear modulus ratio of loess increases and the damping ratio decreases with increasing dry density. The test data of dynamic shear modulus ratio and damping ratio of different shear strain points showed a certain discreteness, and the discrete degree of the damping ratio was obviously higher than that of the dynamic shear modulus ratio. The research results can provide basic information for local seismic response analysis and engineering construction.

    • >地震科学研究
    • Reviewing Discussion on the Prediction of Jiuzhaigou MS7.0 Earthquake in 2017 Based on the Resistivity Precursor Anomalies of Pingliang Remote Station and the Method of Earthquake Precursor Co-migration

      2019, 41(4):957-961. DOI: 10.3969/j.issn.1000-0844.2019.04.957

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      Abstract:The short-impending anomalies of geo-resistivity recorded by the Pingliang seismic station before Jiuzhaigou MS7.0 earthquake in 2017 is very obvious. Pingliang station is 360 km from the epicenter of Jiuzhaigou earthquake, so the epicenter of the Jiuzhaigou MS7.0 earthquake can only be predicted by the method of "earthquake precursor co-migration" in this paper.

    • A Preliminary Study of Seismogenic Structure for the Hutubi,Xinjiang MS6.2 Earthquake on December 8, 2016

      2019, 41(4):962-969. DOI: 10.3969/j.issn.1000-0844.2019.04.962

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      Abstract:On December 8, 2016, an MS6.2 earthquake occurred in Hutubi County, Xinjiang. Given the large uncertainty in initial earthquake location, the aftershock sequence was discrete, and the causative fault of Hutubi earthquake remains unknown. In this study, the CAP method was used to invert the focal mechanism solutions of the main earthquake and aftershocks (MS ≥ 3.5). Aftershocks were relocated by double-difference location algorithm. We obtained the source parameters of 637 earthquakes. The results show that the focal mechanism solution of Hutubi earthquake featured a strike, dip, and rake of 82°, 18°, and 61°, respectively, on the first nodal plane and 292°, 74°, and 98° on the second nodal plane. The earthquake involved a nodal surface Ⅱ rupture of. After relocation, the Hutubi earthquake was relocated at 86.36° E, 43.79° N, with a depth of 14 km. According to the distribution characteristics, focal mechanism solution characteristics, and regional structure characteristics of aftershocks, we inferred that the seismogenic fault of the Hutubi earthquake was not the southern Junggar fault but a back thrust fault on the Huoerguosi-Manas-Tugulu fault. In the northern Tianshan, structural inversion causes the formation of numerous faults in the north dip with inclination angles between 45° and 55°. According to Global Positioning System data, stress in the northern part of Tianshan accumulated in the Late Cenozoic, thus increasing the probability of earthquakes.

    • Application of the Ant Colony Algorithm on the Identification of Surface Buried Faults: A Case Study of Jiuzhaigou Scenic Spot

      2019, 41(4):970-977. DOI: 10.3969/j.issn.1000-0844.2019.04.970

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      Abstract:In a seismic area, the accurate identification of the surface fault zone can provide basic data for geological and seismic disaster prediction. In this paper, the recognition of the buried section of a surface fault is studied using the ant colony algorithm. Based on remote sensing image and aerial survey data, the terrain, geomorphological elements, and other elements are obtained. The improved shortest diagonal method is used to extract the image feature of the fault surface. All the triangular patches of the fault zone are matched and connected into tetrahedral in turn; then, the ant colony algorithm is used to carry out the spatial identification of the surface buried fault. Taking the Jiuzhaigou scenic spot as a case study, we discuss the fault identification of Jiuzhaigou earthquake in 2017. It is considered that this method can be used as a reference for the auxiliary identification of surface faults. Meanwhile, the proposed method is analyzed and compared with the other two identification methods.

    • Crustal Shear Wave Velocity Structure beneath Shaanxi Province and Its Adjacent Region Inverted from Ambient Noise Tomography

      2019, 41(4):978-990. DOI: 10.3969/j.issn.1000-0844.2019.04.978

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      Abstract:In this study, we applied seismic ambient noise tomography technology to process the continuous ambient noise data of 257 broadband stations in Shaanxi province and its adjacent regions, and used the surface-wave-dispersion direct inversion method based on ray tracing to obtain the high-resolution shear wave velocity structure of the crust (6-39 km) beneath Shaanxi province and its adjacent regions. The results demonstrate the following:(1) The thick sedimentary layer covering the top of the Weihe Basin is the cause of the low-velocity anomaly in its shallow crust, and the middle and upper crusts of the basin feature low-velocity structures. There is a high-speed and low-speed combination belt beneath the boundary area between the Weihe Basin and geological tectonic units on both the northern and southern sides and under the interaction of blocks. Moreover, there may be a strong exchange of material and energy within the block, especially in the deep part of the boundary zone, which provides a deep environment for the preparation and generation of the earthquakes in the Weihe Basin and its adjacent areas. (2) The southern Ordos block is not a uniform whole; the low-velocity structure of the shallow crust in the block is thin in the east and thick in the west, which may be related to the overall tilting of the Ordos block in the Phanerozoic eon and the strong differential denudation of the eastern uplift and western fall since the Late Cretaceous. The velocity of the middle crust beneath the Ordos block is higher than those of the upper and lower crusts. There is no significant low-velocity structure in the crust of the block, which shows that the low-velocity structure in the crust does not penetrate the whole Ordos block. We speculate that the southern Ordos block still maintains a stable craton property, and its crustal structure may reflect the structural characteristics of the early formation of the craton, but so far, the craton has not been significantly reformed. (3) The deep structure beneath the eastern and western Qinling orogenic belt is different and is characterized by segmentation and the presence of a subarea. The reason for the higher velocity of the middle crust beneath the orogenic belt may be that in the processes of plate collision and orogeny, the material of the lower crust rises into the middle crust, leading to the higher velocity of middle crust.

    • A Comparative Study of Focal Mechanism Solutions of Earthquakes in Taiwan Region Calculated by Fujian Seismic Network and Other Seismic Networks

      2019, 41(4):991-998. DOI: 10.3969/j.issn.1000-0844.2019.04.991

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      Abstract:Based on the seismic waveform data recorded by 16 seismic stations in Fujian seismic network, the CAP method and an appropriate crustal model were used to calculate the focal mechanism solutions of 4 M>6.0 earthquakes that occurred in the Hualien sea area of Taiwan in February 2018. To verify the reliability and effectiveness of the calculation results, the results were compared with those from the Taiwan Central Weather Bureau, US Geological Survey, and Global GMT. The comparison results show that the focal mechanism solutions from Fujian seismic network are basically consistent with those from other seismic networks. Through this research, the dynamic tectonic environment of Taiwan region is further clarified. Moreover, the study lays the foundation for routine products of focal mechanism solutions of Taiwan region from Fujian seismic network.

    • An Information Intelligent System for Seismic Observation at Unattended Stations

      2019, 41(4):999-1005. DOI: 10.3969/j.issn.1000-0844.2019.04.999

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      Abstract:To ensure the normal operation of seismic observation stations and solve the problems existing in the current system, such as the weak observation anti-interference ability, the inconsistency between the observation and actual results, the inefficient utilization of resources, and the inadequate working efficiency, using the combination of various techniques, an intelligent seismic observation system of unattended station information is designed. The system integrates equipment management, information collection, information communication, information management, and application. Considering the particularity of the working task of seismic observation stations, the required functions of the observation system are analyzed. To realize real-time monitoring, timely repair, and remote control, a 12 V stabilized DC power supply and a UPS with two channels are used as the power supply equipment of the observation system. A network communication system is integrated by adopting a wired and wireless dual-line backup mode, and a man-machine interaction design is realized. On this basis, the system software, including user management, on-duty work management, station equipment management, station operation state observation, fault early warning, and fault emergency repair are mainly designed. The performance test results show that the design system can maintain a continuous rate of information transmission when the network is interrupted, and the work efficiency is high. It has a strong anti-interference ability, stability, and reliability, and does not cause a large waste of resources.

    • Exploration of the Mechanism of Earthquake Triggering by Coulomb Stress Change Based on a Case Analysis

      2019, 41(4):1006-1016,1052. DOI: 10.3969/j.issn.1000-0844.2019.04.1006

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      Abstract:In many cases of seismic triggering, several scholars have studied the effects of Coulomb stress changes caused by large earthquakes on subsequent earthquakes. In this study, based on the Coulomb stress change theory and through the statistics of the Coulomb stress results in the study of some earthquake sequences and typical events, we carried out the analysis from four aspects:magnitude, triggering distance, Coulomb stress change, and triggering time. The results show that the optimal influence range of static Coulomb stress is 5-50 km, and the stress condition of triggering earthquakes is usually 0.01-0.4 MPa; however, the triggering magnitude has no clear correlation with the distance and the magnitude of the main shock. The range of dynamic triggering is mostly 100-2 500 km; the magnitude of the main shock is always high, and the magnitudes of the triggered earthquakes are all smaller than that of the main shock. The magnitude of the main earthquake is positively correlated with the triggering distance, but the triggering times are independent of other factors in the analysis of several typical remote triggering events. The phenomenon of delay triggering in a long-term scale is reasonably explained by three mechanisms of post-earthquake stress transfer, but the accurate calculation of stress transfer may have a positive effect on the reasonable interpretation of the relationship between Coulomb stress change and earthquake triggering.

    • >工程地震
    • Dynamic Characteristics of Sawdust-mixed Clay Site Model under Bidirectional Seismic Actions

      2019, 41(4):1017-1025. DOI: 10.3969/j.issn.1000-0844.2019.04.1017

      Abstract (676) HTML (0) PDF 12.85 M (819) Comment (0) Favorites

      Abstract:A series of shaking table tests on free-field sawdust-mixed clay site model under uniform earthquake excitation was conducted at the multiple shaking table testing systems in Beijing University of Technology. These tests were performed using a rigid prefabricated continuous model box. The test system was subjected to strong ground motions from El Centro record, Taft record, and Tianjin record. In this paper, we focused on the dynamic characteristics of the sawdust-mixed clay site model under bidirectional seismic actions, including the peak ground accelerations and their amplification factors, acceleration time histories, and their Fourier spectra for the site responses. The test results indicated that the increase in the intensity of ground motions increases the peak ground acceleration at the same test point; however, its acceleration amplification factor generally decreases and the main frequency components move from high to low frequency. The dynamic change rule of the sawdust-mixed clay site model under bidirectional seismic actions is consistent with that of one-directional seismic action.

    • Characteristics of Strong Motion Records from Minxian-Zhangxian MS6.6 Earthquake and Aftershock

      2019, 41(4):1026-1034. DOI: 10.3969/j.issn.1000-0844.2019.04.1026

      Abstract (714) HTML (0) PDF 17.17 M (953) Comment (0) Favorites

      Abstract:On July 22, 2013, an MS6.6 earthquake and its aftershock occurred at the border area between Minxian and Zhangxian Counties, Gansu Province. In this study, 273 items of acceleration records from the MS6.6 mainshock and the MS5.6 aftershock were processed, and the characteristics of the amplitudes, response spectra, and duration of the records were compared. The peak ground acceleration range of the main earthquake was 0.728-177.5 gal, and that of the aftershock was 0.732-69.3 gal. According to the comparison among observation data, the attenuation relationship of Huo Junrong, and the ground motion attenuation relationship in the fifth Chinese seismic zonation map, it was found that the attenuation relationship of Huo Junrong is more suitable for the acceleration attenuation of the two earthquakes; the 5%-95% significant duration distribution of the two earthquakes was calculated and plotted. The response spectrum of the main earthquake at 62 MXT was compared with the design spectrum and the response spectra of major strong earthquakes in China in recent years. Finally, the response spectrum characteristics of typical soil stations, bedrock stations, and the same station with different magnitudes were analyzed.

    • Influence of Urban Intensive Building Groups on the Ground Motion Amplification Effect of an Alluvial Valley

      2019, 41(4):1035-1045. DOI: 10.3969/j.issn.1000-0844.2019.04.1035

      Abstract (563) HTML (0) PDF 19.08 M (1018) Comment (0) Favorites

      Abstract:A two-dimensional model of a buildings-alluvial valley system is established using the finite-element method, and the viscoelastic artificial boundary is applied on the truncated boundary of the soil body. By comparing and analyzing the seismic responses of the buildings-alluvial valley system and the single alluvial valley both in the frequency domain and the time domain, the dynamic interaction between alluvial valley and buildings under earthquake is studied. The results show that because of the resonance effect under low-frequency incident waves, the surface displacement response amplitude of the buildings-alluvial valley system is larger than that of the single alluvial valley in some areas. As the frequency of the incident wave increases, the buildings will have a significant weakening effect on the seismic response. In addition, the impact of the buildings on the valley is also related to the building height and building spacing, and the responses at different locations are significantly different. The numerical results can provide a theoretical basis for the setting of fortification intensity in alluvial valleys and the seismic design of projects.

    • An Adaptive Baseline Correction Method for Strong Motion Records: Application in the Wenchuan Earthquake

      2019, 41(4):1046-1052. DOI: 10.3969/j.issn.1000-0844.2019.04.1046

      Abstract (683) HTML (0) PDF 9.10 M (737) Comment (0) Favorites

      Abstract:Baseline correction is one of the most critical procedures for data processing of strong motion records. Most of the current methods depend on personal experience and cannot be automatically implemented, which results in large uncertainties of permanent displacement. In this regard, an adaptive baseline correction method for strong motion records is proposed. The strong motion records obtained at Wolong station (051WCW) were used as an example to describe each step of the proposed method. Subsequent permanent displacement was consistent with a value provided by another method, which verified the accuracy of the proposed method. Finally, the proposed method was applied to the Wenchuan earthquake, and permanent displacement field of 37 strong motion stations was achieved. Compared to the results given by Wang, et al. (2011), this result shows that maximum permanent displacement of 24 stations given by the proposed method is almost the same as those given by the other method. The comparison indicates that the proposed method is able to correct the baseline drift in strong motion records, but has some limitations that require further improvement.

    • >震灾防御
    • Field Investigation and Failure Characteristics of Buildings Damaged by the 7.0-Magnitude Earthquake in Jiuzhaigou

      2019, 41(4):1053-1059. DOI: 10.3969/j.issn.1000-0844.2019.04.1053

      Abstract (616) HTML (0) PDF 19.37 M (889) Comment (0) Favorites

      Abstract:The 7.0-magnitude earthquake that occurred in Jiuzhaigou on August 8, 2017, which featured a focal depth of 20 km, caused damage to a large number of houses. Analysis of seismic damage characteristics of 337 buildings with different types of structures in areas VⅢ and IX revealed the failure mechanism of each type of building. Statistics indicated 3.3% well-kept buildings, 19.9% slightly damaged buildings, 51.3% moderately damaged buildings, 21.1% severely damaged buildings, and 4.5% destroyed building. Field investigation suggested that reinforced concrete frame structures, large-span spatial structures, steel-frame structures, and Chuandou-type timber structures with infilled walls of wood present good seismic performance. The analysis results indicated that the structures surveyed basically fulfill the seismic fortification criterion of "repairable under moderate earthquake," and, thus, the lives and personal property of residents may be considered to be greatly protected.

    • A Novel Suitability Planning Model for Rural Earthquake Disaster Prevention Based on ANSYS

      2019, 41(4):1060-1065. DOI: 10.3969/j.issn.1000-0844.2019.04.1060

      Abstract (461) HTML (0) PDF 1.17 M (557) Comment (0) Favorites

      Abstract:At present, the analysis of the suitability of earthquake resistance and disaster prevention in new rural areas usually adopts the geological zoning method for the survey points. The complexity of the GIS space is neglected in the analysis process, and the weighted analysis of the evaluation indicators is not carried out, resulting in the low fitting degree of the calculated and actual results. Based on this, a new rural earthquake disaster prevention suitability planning model based on ANSYS is proposed. Considering the spatial complexity of GIS, the ANSYS is used to modify the finite-element structure field in GIS space. Combined with the logistic nonlinear regression model, a nonlinear regression analysis is carried out on the binary variable data in the earthquake disaster prevention suitability planning of rural land. To prevent the calculation value from being too subjective, the combined entropy coefficient model is used to weight the evaluation index calculated by the logistic equation, and the new rural earthquake disaster prevention suitability planning model based on ANSYS is completed. The case study proves that the calculated results obtained by the proposed method have a high degree of fitting with the actual results, can successfully complete the quantification of the evaluation indicators, and can objectively complete the rural earthquake disaster prevention suitability planning analysis.

    • Design of the Population Casualty Acquisition and Evaluation System in Earthquake Disaster Areas Based on Mobile Communication Big Data

      2019, 41(4):1066-1071,1097. DOI: 10.3969/j.issn.1000-0844.2019.04.1066

      Abstract (583) HTML (0) PDF 1.61 M (662) Comment (0) Favorites

      Abstract:To solve the problems in the existing evaluation system, i.e., low evaluation accuracy, long time consumption, and poor stability, a seismic disaster casualty assessment system based on mobile communication big data is proposed and designed. The overall system architecture is first given; then, combined with the mobile communication big data, hardware modules, including systems for seismic damage data acquisition, data transmission, population injury assessment, and data statistical analysis, are designed. Finally, the acquisition and data statistics of the population casualties of earthquake disasters are completed. The first positioning data are compared with the seismic data after the correction of the epicenter intensity and local population density coefficient. If the positioning data remain unchanged, the casualty can be regarded as injured or trapped, or even dead. According to the key-value pattern, the second positioning data are arranged in a table to store and analyze the big data. Using the principle of linear regression, the earthquake casualty assessment model is constructed, and the earthquake disaster population casualty assessment system is designed. The experimental results show that the system evaluation result is accurate, and the fitting degree with the actual evaluation results is high, indicating that the system has a certain feasibility.

    • A Quantized Control Model for Safety Management of Repair of Collapsed Walls of High-Rise Buildings

      2019, 41(4):1072-1078. DOI: 10.3969/j.issn.1000-0844.2019.04.1072

      Abstract (608) HTML (0) PDF 2.34 M (528) Comment (0) Favorites

      Abstract:To ensure safety during the process of repairing of collapsed walls of the high-rise buildings after an earthquake, some safety management guidance measures are given. In addition, a safety management method for repair of collapsed walls of high-rise buildings after an earthquake was proposed. Combined with principal component analysis and information entropy method, the controlled characteristic variables for the repair of collapsed wall of high-rise buildings post earthquake were extracted to determine the weight of the model evaluation index. The quantized control for the management of collapsed wall restoration based on weighted learning method was conducted. A security management control model was constructed by constrained parametric analysis through grayscale quantitative evaluation. The construction safety management control was realized by adopting the fuzzy scheduling algorithm and the optimization decision was completed. The management benefit and cumulative evaluation percentage for the restoration construction management control for the collapsed wall were verified via simulation experiments. The case analysis results showed that the management benefit of this method can reach 95.34%, and the cumulative evaluation percentage was about 98.65%. The method can considerably improve the safety management efficiency of the construction process and ensure construction safety.

    • >其他
    • Nondestructive Testing Method for Steel Structures Based on Building Information Modeling and Surface Image Analysis

      2019, 41(4):1079-1085. DOI: 10.3969/j.issn.1000-0844.2019.04.1079

      Abstract (605) HTML (0) PDF 1.36 M (634) Comment (0) Favorites

      Abstract:Using the method of quality vulnerability assessment to detect the steel structure of green construction buildings in the earthquake area easily leads to noise disturbance. Moreover, the detection depth is shallow; therefore, the damage of the steel structure cannot be detected comprehensively. Herein, a nondestructive detection method for steel structure based on building information modeling (BIM) and surface image analysis is proposed. The wavelet decomposition method is used to denoise the detection image of the steel structure. Further, the expansion and corrosion processings are used to enhance the clarity of the detection image. According to the change rate of image restoration at defect edges, the infrared image technology, and rotation tracking method are adopted to extract the defect edge. The detection model of green construction steel structure based on BIM in seismic area was constructed to comprehensively control the material, nondestructive testing, and management of green construction steel structure in the seismic area. Additionally, the whole life cycle of steel structure is controlled, and the nondestructive testing of steel structure is completed. The experimental results show that the effective detection rate of the proposed method, detection depth, and relative error of the detection results are 100%, 1 499 mm, and 0.000 7%, respectively.

    • Inclination Measurement of Buildings after Earthquake Based on Three-Dimensional Measurement Using Optical Flow Recovery Algorithm and Building Information Modeling

      2019, 41(4):1086-1091. DOI: 10.3969/j.issn.1000-0844.2019.04.1086

      Abstract (510) HTML (0) PDF 1.30 M (507) Comment (0) Favorites

      Abstract:After an earthquake occurs, the moving measurement of the inclination of dangerous buildings is complex, and the conventional measurement methods present a symmetrical deviation. Therefore, to improve the accuracy of the measurement of inclination, a three-dimensional (3D) measurement through optical flow recovery algorithm combined with building information modeling (BIM) was designed. The BIM technology is used to collect and integrate all the building inclination information and thereafter the dangerous building information model is constructed. The 3D measurement through optical flow recovery algorithm was used to obtain the target feature points in the constructed building information model. Based on this, a three-dimensional measurement model of inclination of dangerous buildings after the earthquake was designed. The simulation results showed that the error rate of 3D coordinate values of dangerous building, measured by the proposed method, is less than 0.4% and the average evaluation time is only 2.5 s, which indicates that this method can improve the evaluation effect of building inclination.

    • An Optimal Scheduling Method of Emergency Signal in Post-earthquake Traffic Wireless Communication System Based on Genetic Algorithm

      2019, 41(4):1092-1097. DOI: 10.3969/j.issn.1000-0844.2019.04.1092

      Abstract (541) HTML (0) PDF 1.67 M (592) Comment (0) Favorites

      Abstract:To solve the problems in the traditional emergency signal optimization scheduling method, such as the long task time and low reliability, a genetic algorithm-based emergency signal optimization scheduling method for traffic wireless communication system after a strong earthquake is proposed. The communication occupation time of different sub-nodes of a traffic wireless communication system after a strong earthquake is segmented, and an emergency signal scheduling model based on the genetic algorithm is constructed by judging whether the task scheduling table can be updated. According to the related characteristics of the model, the genetic algorithm is used to solve the emergency signal scheduling model, and the optimal emergency signal scheduling scheme is obtained. The simulation results show that the proposed method can shorten the task scheduling time and adjust the reliability of emergency signal scheduling.

    • Mobile Phone Signal Location Analysis of Trapped People after Earthquake Based on Satellite Navigation

      2019, 41(4):1098-1104. DOI: 10.3969/j.issn.1000-0844.2019.04.1098

      Abstract (692) HTML (0) PDF 3.43 M (695) Comment (0) Favorites

      Abstract:Aiming at the problems in the current method of mobile phone signal location, i.e., the limitation of location distance and the great influence of the change of signal propagation loss on the determination of signal source direction, a mobile phone signal location analysis method based on satellite navigation is proposed. From four aspects of the suddenness, destructiveness, social influence, and defensive difficulty of the earthquake, a portable mobile station is designed to extract the residual signal of the mobile phone through the GPS single difference model. Then, the average residual of mobile phone signals in the appointed area is calculated, and the root mean square of the mobile phone signals of each area is obtained. The mean square deviation is substituted into the two-difference equations of all seismic events, and the mobile phone signal intensity is solved. The positioning of mobile phone signals based on satellite navigation is realized by the angle of arrival measurement method. The collected data were analyzed to verify the ability of the system for searching in large-scale earthquake ruins. The experimental results show that the proposed method can search and locate a large range of mobile phones, and the signal source direction is stable.

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