Peak Ground Motion Acceleration Research Articles

Research on landslide susceptibility prediction model based on LSTM-RF-MDBN.

The occurrence of landslide disasters causes huge economic losses and casualties. Although many achievements have been made in predicting the probability of landslide disasters, various factors such as the scale and spatial location of landslide geological disasters should still be fully considered. Further research on how to quantitatively characterize the susceptibility of landslide geological disasters is necessarily important. To this end, taking the Wenchuan earthquake as the research area and extracting eight influencing factors, including terrain information entropy (Ht), lithology, distance from rivers, distance from faults, vegetation coverage (NDVI), distance from roads, peak ground motion acceleration (PGA), and annual rainfall, a landslide susceptibility prediction model was hereby established based on LSTM-RF-MDBN, a landslide susceptibility prediction map was drawn, and the spatial distribution characteristics of landslide disasters were analyzed. The results showed that (1) LSTM had good prediction results for the eight influencing factors, with an average prediction accuracy of 85%; (2) compared with models such as DNN and LR for predicting landslide disaster points, the AUC value of RF for predicting landslide point positions reached 0.88, presenting a higher accuracy compared to other models; (3) the AUC value of the landslide susceptibility prediction model based on LSTM-RF-MDBN reached 0.965, which had a high accuracy in predicting landslide susceptibility. Overall, the research results can provide a scientific basis for selecting the best strategy for landslide disaster warning, prevention, and mitigation.

A numerical study of 3D topographic site effects considering wavefield incident direction and geomorphometric parameters

The topographic site effect plays a vital role in controlling the characteristics of earthquake ground motions. Due to its complexity, the factors affecting topographic amplification have not been fully identified. In this study, 100 ground motion simulations generated by double-couple point sources in the homogeneous linear elastic half-space are performed based on the 3D (three-dimensional) Spectral Element Method, taking the Menyuan area of Qinghai Province, China as a local testbed site. A relationship between incident direction and the strength of topographic amplification has been observed. The horizontal ground motion is affected by the back-azimuth, which is typically chosen to be the direction from seismic station to seismic source measured clockwise from north. Specifically, the east-west PGA (Peak Ground-motion Acceleration) is significantly amplified when back-azimuth is about 90° or 270°, and the north-south PGA is significantly amplified when back-azimuth is around 0° or 180°. The vertical ground motion is affected by the dipping angle, which is the angle from vertical at which an incoming seismic wave arrives. The vertical PGA is strongly amplified when the seismic wave is almost horizontally incident (e.g., dipping angle = 78°). A correlation study between geomorphometric parameters and frequency-dependent topographic amplification indicates that relative elevation and smoothed curvature contain similar information, both of which are closely related to the topographic amplification of horizontal components, but not the vertical component. Our study reveals the influence of source and propagation path on topographic amplification and provides a reference for considering the topographic site effect in real engineering sites.

Earthquake Risk Probability Evaluation for Najin Lhasa in Southern Tibet

The probabilistic seismic hazard analysis (PSHA) method is effectively used in an earthquake risk probability evaluation in seismogenic regions with active faults. In this study, by focusing on the potential seismic source area in Najin Lhasa, southern Tibet, and by incorporating the PSHA method, we determined the seismic activity parameters and discussed the relationship of ground motion attenuation, the seismic hazard probability, and the horizontal bedrock ground motion acceleration peak value under different transcendence probabilities in this area. The calculation results show that the PSHA method divides the potential source area via specific tectonic scales and detailed tectonic markers, which reduces the scale of the potential source area and better reflects the uneven spatial distribution of seismic activity in the vicinity of Najin. The corrected attenuation relationship is also in line with the actual work requirements and is suitable for earthquake risk analysis. In addition, the major influences on the peak acceleration of ground motion in the study area are mainly in the potential source areas of Qushui (M7.5), Dangxiong (M8.5), and Kangma (M7.5). The peak horizontal ground motion acceleration (PGA) with a transcendence probability of 10% in 50 years is 185.9 cm/s2, and that with a transcendence probability of 2% in 50 years is 265.9 cm/s2.

Spatial-Temporal Evolution and Driving Forces of NDVI in China's Giant Panda National Park.

Identifying the ecological evolution trends and vegetation driving mechanisms of giant panda national parks can help to improve the protection of giant panda habitats. Based on the research background of different geomorphological zoning, we selected the MODIS NDVI data from 2000 to 2020 to analyze the NDVI trends using a univariate linear model. A partial correlation analysis and multiple correlation analysis were used to reveal the influence of temperature and precipitation on NDVI trends. Fourteen factors related to meteorological factors, topographic factors, geological activities, and human activities were selected, and the Geographically Weighted Regression model was used to study the mechanisms driving NDVI change. The results were as follows: (1) The NDVI value of Giant Panda National Park has fluctuated and increased in the past 21 years, with an annual growth rate of 4.7%/yr. Affected by the Wenchuan earthquake in 2008, the NDVI value fluctuated greatly from 2008 to 2012, and reached its peak in 2018. (2) The NDVI in 94% of the study area improved, and the most significant improvement areas were mainly distributed in the northern and southern regions of Southwest Subalpine and Middle Mountain and the Xiaoxiangling area. Affected by the distribution of fault zones and their local activities, vegetation degradation was concentrated in the Dujiangyan–Anzhou area of Hengduan Mountain Alpine Canyon. (3) The Geographically Weighted Regression analysis showed that natural factors were dominant, with climate and elevation having a double-factor enhancement effect, the peak acceleration of ground motion and fault zone having a superimposed effect, and river density and slope having a double effect, all of which had a significant impact on the NDVI value of the surrounding area. To optimize the ecological security pattern of the Giant Panda National Park, we recommended strengthening the construction of ecological security projects through monitoring meteorological changes, preventing, and controlling geo-hazards, and optimizing the layout and intensity of human activities.

The study of soft soil seismic subsidence based on the 3D OpenSees model

AbstractSoft soils are characterized by high sensitivity, low strength, and susceptibility to seismic subsidence. In this study, nonlinear dynamic finite element analysis was performed using the OpenSees numerical simulation method to evaluate the seismic subsidence response of soft soil sites to ground motions. Higher peak acceleration of ground motion was found to enhance the degree of uneven seismic subsidence, depth of the seismic depression, and damage to the horizontal surface. The frequency characteristic of ground motion is another factor that influences the seismic subsidence of soft soil. Ground motions with low-frequency contents or high amplitudes lead to a more pronounced seismic subsidence of soft soil, particularly in the case of ground motion that exhibits frequency predominantly close to one of the soil sites. The findings of this study expand the current understanding of seismic subsidence of soft soil.

Study on the influence of the seafloor soft soil layer on seismic ground motion

Abstract. In the complex medium system of the sea area, the overlying seawater and the surface soft soil have a significant impact on the seafloor ground motion, which brings great seismic risk to the safety of offshore-engineering structures. In this paper, four sets of typical free-field models are constructed and established, comprising a land model, land model with surface soft soil, sea model and sea model with surface soft soil. The dynamic finite-difference method is used to carry out two-dimensional seismic response analysis of a typical free field based on the input forms of P and SV waves. By comparing the seismic response analysis results of four groups of calculation models, the effects of overlying seawater and soft soil on the peak acceleration and acceleration response spectrum are studied. The results show that when an SV wave is input, the peak acceleration and response spectrum of the surface of soft soil on the surface and the seabed surface can be amplified, while the overlying seawater can significantly reduce the ground motion. When the P wave is used, the effect of overlying seawater and soft soil on the peak acceleration and response spectrum of the surface and seabed can be ignored. The peak acceleration decreases first and then increases from the bottom to the surface, and the difference of peak acceleration calculated by four free-field models is not obvious. The results show that the overlying seawater and the surface soft soil layer have little effect on the peak acceleration of ground motion below the surface.

Safety Analysis of the Running Train under Earthquake Dynamic Disturbance

Focusing on the safe operation of rail transit during earthquakes, the finite element method is used to construct a wheel-track-subgrade dynamics model in this study. Through spring-damper units, the relationship between the rail and the track slab and the connection between the track slab and the subgrade are established. A method for establishing a viscoelastic artificial boundary is proposed. Four seismic waves—the Tianjin wave, the El Centro wave, the Taft wave, and the Qian’an wave—are selected as the seismic input waveforms, and only the impact of the lateral ground motion on the wheel-track-subgrade system is considered. In this paper, the ground motion problem is transformed into a wave source problem, the seismic input is transformed into an equivalent load acting on the artificial boundary, and the wave input of the viscoelastic artificial boundary is realized. The normalization method is used to process the seismic waves, and a method that converts the input of the seismic waves into equivalent loads is proposed. The changing laws of different dynamic response indexes under the influence of the four waveforms are studied. Under the action of the Tianjin wave, the wheel-rail dynamic response is very violent near the acceleration peak, whereas, after the peak, all dynamic response indexes are within a safe range. Under the effect of the El Centro wave, the collision between the wheel and the track is relatively violent, and the train is already in a dangerous state. Under the action of the Taft wave, due to the sudden action of the peak ground motion acceleration, the displacement between the wheel and the track increases instantaneously, causing the train to derail. Under the action of the Qian’an wave, the force between the wheel and rail changes approximately linearly with respect to the frequency of the ground motion, and all dynamic response indexes are within a safe range. The vibration intensity of the four seismic waves is amplified by an intensity expansion factor. Except for the Tianjin wave, the amplified seismic wave has a greater impact on safe train operations. This paper can provide a reference for research on the running safety of trains under similar dynamic disturbance conditions.

DAMAGE INVESTIGATION AND RE-ANALYSIS OF DAMAGED BUILDING AFFECTED BY THE GROUND MOTION OF THE 2009 PADANG EARTHQUAKE

The purpose of this paper is to introduce a complete assessment to damaged buildings due to earthquake event in earthquake-prone areas. Padang city is located on the western part of the island of Sumatra, Indonesia, an earthquake-prone area. One of the largest earthquake events (Mw 7.6) occurred on 30 September 2009, striking the west coast of Sumatra. A total of 106,658 houses and 4,000 other buildings suffered damage classified from slight to severe, and a reported 1,117 people were killed. Some large-scale reinforced concrete buildings in Padang, as the capital of West Sumatra province, were also damaged. In order to determine the antiseismic deficiencies of these buildings, the authors assessed three buildings (BPKP, UNP and PU building) on soft soil (the predominant period is greater 2s and Vs30 400m/s) to the BPKP building (Vs30<150m/s), the peak ground motion acceleration at BPKP was found to have amplified 1.47 times. This result enables us to conclude that the soil characteristics (rock to soft) influence ground motion amplification and affect the degree to which buildings suffer damage.

Investigation into the Nonlinear Time-History Analysis of CNT-Reinforced Concrete Column by a Multiscale Approach

Many concrete structures have been damaged during recent earthquakes due to the low ductility of their columns. Hence, several recent research contributions have been dedicated to producing high-performance concrete materials. Among these contributions, carbon nanotubes (CNTs) are of superior mechanical properties and can be used as additive in concrete. In this research, a sequential multiscale method, including nano-, micro-, meso- and macro-scales, is used to investigate the cyclic and seismic responses of concrete columns through numerical simulations. The aim of this research is to investigate the load-carrying capacity and energy absorption of CNT-reinforced concrete columns under cyclic loading. The results of the current research indicate that both of these properties improve significantly in the presence of CNTs. Furthermore, the results of fragility analysis reveal that for similar damage states, a CNT-reinforced column reaches the specified damage state at higher peak ground motion acceleration than an ordinary concrete column. Hence, the use CNTs in concrete structures may prove beneficial for high-seismic risk areas.

Seismic Response Characteristics of Stabilizing Pile Based on Elastic-Plastic Analysis

Stabilizing pile is widely used in the landslide controlling projects and shows excellent seismic performance under the action of earthquake. Therefore, in order to improve seismic design theory, it is of importance to study the seismic response characteristics of stabilizing pile based on elastic-plastic analysis. In view of this, elastic-plastic constitutive model was established to deduce the plastic zone of stabilizing pile. Based on elastic-plastic analysis, the seismic response characteristics and the influence of different section sizes, material strengths, and peak ground motion acceleration (PGA) were analyzed by ANSYS 3D. Resultantly, the elastic-plastic fourth-order tensor Cijklep was deduced, which can be used to calculate plastic strain of stabilizing pile under loading. Compared with Chinese code, the material of stabilizing pile working with elastic-plastic state will be decreased under the same section size and the same property. Furthermore, stabilizing pile is in the elastic stage at the beginning under the action of earthquake. With the increase of ground motion time, the section starts to exhibit elastic-plastic state and then the plastic zone expands gradually. Finally, the plastic zone runs through the whole section, resulting in the performance loss of the pile. In addition, under the different design parameters, pile shows different seismic response characteristics; namely, changing these parameters reasonably can improve the seismic design.

Real-Time Substructure Tests and Numerical Simulation of Mechanical Characteristics of Natural Rubber-Laminated Bearings

Natural rubber lamination is a kind of seismic isolation of bearings often used in civil engineering. The advantage of laminated bearings is large vertical stiffness and small lateral stiffness. In seismic regions, structural periods would be extended and the effect of seismic forces can be lowered using bearings. In previous tests, the static cyclic loading method was mainly used that failed to take account of the loading rate. The real-time substructure testing is proposed to simulate true seismic loads. This testing and test setup were first introduced, and the effect of the loading rate was studied. Then the effects of vertical pressure and peak acceleration of ground motion were studied. At last the test results were simulated by the finite element method, and an accurate method to calculate seismic responses of bridges with laminated bearings was proposed.

Analysis of Dynamic Coupling Characteristics of the Slope Reinforced by Sheet Pile Wall

Large deformation of slope caused by earthquake can lead to the loss of stability of slope and its retaining structures. At present, there have been some research achievements about the slope reinforcement of stabilizing piles. However, due to the complexity of the structural system, the coupling relationship between soil and pile is still not well understood. Hence it is of great necessity to study its dynamic characteristics further. In view of this, a numerical model was established byFLAC3Din this paper, and the deformation and stress nephogram of sheet pile wall in peak ground motion acceleration (PGA) at 0.1 g, 0.2 g, and 0.4 g were obtained. Through the analysis, some conclusions were obtained. Firstly, based on the nephogram of motion characteristics and the positions of the slip surface and the retaining wall, the reinforced slope can be divided into 6 sections approximatively, namely, the sliding body parts of A, B, C, D, and E and the bedrock part F. Secondly, the deformation and stress distributions of slope reinforced by sheet pile wall were carefully studied. Based on the results of deformation calculation from time history analysis, the interaction force between structure and soil can be estimated by the difference of peak horizontal displacements, and the structure-soil coupling law under earthquake can be studied by this approach.

Hazard-consistent ground motions generated with a stochastic fault-rupture model

Conventional seismic probabilistic risk assessments (PRAs) of nuclear power plants consist of probabilistic seismic hazard and fragility curves. Even when earthquake ground-motion time histories are required, they are generated to fit specified response spectra, such as uniform hazard spectra at a specified exceedance probability. These ground motions, however, are not directly linked with seismic-source characteristics.In this context, the authors propose a method based on Monte Carlo simulations to generate a set of input ground-motion time histories to develop an advanced PRA scheme that can explain exceedance probability and the sequence of safety-functional loss in a nuclear power plant. These generated ground motions are consistent with seismic hazard at a reference site, and their seismic-source characteristics can be identified in detail.Ground-motion generation is conducted for a reference site, Oarai in Japan, the location of a hypothetical nuclear power plant. A total of 200 ground motions are generated, ranging from 700 to 1100cm/s2 peak acceleration, which corresponds to a 10−4 to 10−5 annual exceedance frequency. In the ground-motion generation, seismic sources are selected according to their hazard contribution at the site, and Monte Carlo simulations with stochastic parameters for the seismic-source characteristics are then conducted until ground motions with the target peak acceleration are obtained. These ground motions are selected so that they are consistent with the hazard. Approximately 110,000 simulations were required to generate 200 ground motions with these peak accelerations.Deviations of peak ground motion acceleration generated for 1000–1100cm/s2 range from 1.5 to 3.0, where the deviation is evaluated with peak ground motion accelerations generated from the same seismic source. Deviations of 1.0 to 3.0 for stress drops, one of the stochastic parameters of seismic-source characteristics, are required to obtain these acceleration deviations. A similar tendency can be found for some other seismic-source characteristics, meaning that ground motions obtained in this study cannot be generated by simulations of deterministic fault-rupture models with averaged seismic-source characteristics. Generated ground motions incorporate differences between each seismic-source characteristic, and they are effectively available for PRAs of structures.

Analysis Carrying Capacity of Hydraulic Concrete Dam

This paper makes analysis on accelerated speed overload and hydraulic pressure after earthquake, as well as the relationship between the ground motion peak acceleration and the dam body displacement, dam body damage volume ratio, and dam facing damage volume ratio. According to dam body partition, this paper takes the ratio of over stress accumulative duration and stress required capacity as parameters, and studies arch local earthquake damage evaluation of dam body partition. After analysis, it is found that after arch dam experiences different geological process, there are damages in both sides of dam abutment and upper part of dam body, overstressed area expands continuously and local damages take place.

Large-scale two-dimensional nonlinear FE analysis on PGA amplification effect with depth and focusing effect of Fuzhou Basin

Based on the explicit finite element (FE) method and platform of ABAQUS, considering both the inhomogeneity of soils and concave-convex fluctuation of topography, a large-scale refined two-dimensional (2D) FE nonlinear analytical model for Fuzhou Basin was established. The peak ground motion acceleration (PGA) and focusing effect with depth were analyzed. Meanwhile, the results by wave propagation of one-dimensional (1D) layered medium equivalent linearization method were added for contrast. The results show that: 1) PGA at different depths are obviously amplified compared to the input ground motion, amplification effect of both funnel-shaped depression and upheaval areas (based on the shape of bedrock surface) present especially remarkable. The 2D results indicate that the PGA displays a non-monotonic decreasing with depth and a greater focusing effect of some particular layers, while the 1D results turn out that the PGA decreases with depth, except that PGA at few particular depth increases abruptly; 2) To the funnel-shaped depression areas, PGA amplification effect above 8 m depth shows relatively larger, to the upheaval areas, PGA amplification effect from 15 m to 25 m depth seems more significant. However, the regularities of the PGA amplification effect could hardly be found in the rest areas; 3) It appears a higher regression rate of PGA amplification coefficient with depth when under a smaller input motion; 4) The frequency spectral characteristic of input motion has noticeable effects on PGA amplification tendency.

Analysis on intensity zonation in thick loess region

The earthquakes, which occurred in Haiyuan, Tangshan and Wenchuan, have caused serious damages in the loess area and the abnormal intensity sites are commonly found during the earthquakes. The investigation of the actual earthquake damages and character analysis on sites shows that the topography, loess overburden and underground water level and many other factors affect the intensity. In this paper, the thickness of loess overburden of Tianshui City is achieved by inversion algorithm based on site exploration and microtremor test; the amplification effect of peak ground motion acceleration is calculated using numerical method; a complete formula is obtained through summarizing previous achievements and is used to calculate the abnormal intensity under the multifactorial influence. Finally, a seismic intensity anomaly distribution map is plotted applying the graphic information system (GIS) software in Maiji District, Tianshui City. Through the practical investigation of earthquake disaster, it is found that the figure fits the distribution of actual intensity anomaly very well.

GIS-Information Method Based Risk Evaluation for Debris Flow in Chencang District

This study chooses chencang district in Baoji city as the study area.To use ArcGIS combination information method, slected engineering geological lithologic, ground motion peak acceleration, geological structure, elevation, geomorphological types, slope, annual rainfall, human engineering activities and land use type as the main evaluation factors,for debris flow risk assessment. Debris flow risk is divided into an extreme high risk,high risk,moderate risk,low risk and extreme low risk levels,The evaluation result show that 11.01% of area is extreme high risk,include 12 debris flows; 24.94% of area is high risk,include 9 debris flows; 20.78% of area is moderate risk,include 4debris flows; 26.35% of area is low risk,include 3 debris flows;16.92% of the area is extreme low risk areas,there is no debris flows.

Site specific prediction equations for peak acceleration of ground motion due to earthquakes induced by underground mining in Legnica-Głogów Copper District in Poland

Ground motion database from the region of Żelazny Most tailings pond, the largest in Europe ore-flotation waste repository, is used to identify ground motion prediction equations (GMPE-s) for peak horizontal and peak vertical acceleration. A GMPE model including both geometrical spreading and anelastic damping terms cannot be correctly identified and the model with only spreading term is accepted. The analysis of variance of this model’s residuals with station location as grouping variable indicates that station locations contribute significantly to the observed ground motion variability. Therefore, a site specific GMPE model with relative site amplifications is assessed. Despite short distances among stations, the amplification considerably vary from point to point, up to 1.8 times for the horizontal and 3.5 times for the vertical peak amplitude. The model including site effects enhances GMPE-s fit to observations, explains more than 60% dependent variables variability and correctly accounts for site effects.

신속 지진피해통보를 위한 지반가속도의 초당 최대값 구간적산 방법의 활용에 관한 연구

지반가속도의 초당 최대값은 최근 제정된 지진재해대책법에 따라 지진기록계로부터 통신망을 통해 소방방재청으로 실시간 제공되어야 한다. 본 연구에서는 현재 PGA를 기반으로 한 신속한 지진피해통보 용도로만 고려되고 있는 지반가속도의 초당 최대값의 추가적인 활용성을 검토하고자, 국내외 강진자료 및 중소규모 지진자료에 대한 초당 100 샘플링된 지반가속도 자료의 1초 구간내 최대 절대값을 30초 동안 적산한 결과(<TEX>$BSPGA_k$</TEX>)를 CAV(Cumulative Absolute Velocity) 및 진도 등과 비교하였다. CAV는 진도와의 높은 상관성으로 지진발생시 원자력발전소의 운전초과기준으로 사용되고 있으나, 계산시 초당 100 샘플링 이상의 많은 양의 지진파형 디지털 자료를 필요로 하는 단점이 있다. 비교 결과 <TEX>$BSPGA_k$</TEX>는 지진규모에 따른 지진동 수준과 상관없이 CAV와 전 범위에서 높은 상관성을 나타내었으며, 다수의 관측소가 연계된 지진관측망 운영시 유용하게 활용될 수 있는 신속 지진피해평가 지진동 파라미터로 확인되었다. 국내 중소규모 유감지진자료에 대한 지진진도 자료와의 비교결과, <TEX>$BSPGA_k$</TEX>-진도 상관식을 이용한 진도추정 오차는 CAV-진도 상관식의 진도추정 오차와 유사하였으며, PGA-진도 상관식보다 진도를 신뢰성 있게 추정하였다. In an effort to further exploit the peak ground-motion acceleration (PGA) information per second available in real time by the enacted law, bracketed summations of the PGA per second (<TEX>$BSPGA_k$</TEX>) for 30 seconds based on the records with a rate of 100 samples were compared with the cumulative absolute velocity (CAV) and earthquake intensities based on a worldwide database of records from small-to-large earthquakes. The CAV, currently in use as an earthquake damage indicator for nuclear power plants due to its strong correlation with the earthquake intensity, has the disadvantage of requiring a massive amount of digital data with a rate of more than 100 samples per second. The comparative study shows that the <TEX>$BSPGA_k$</TEX> is well correlated with the CAV over the wide range of strong ground-motion levels, which suggests that the <TEX>$BSPGA_k$</TEX> is one of the new promising ground-motion parameters especially useful for rapid earthquake alert notifications through an earthquake monitoring network. Based on the domestic database of records from small-to-moderate earthquakes with felt reports, it is also observed that the <TEX>$BSPGA_k$</TEX> is comparable to the CAV and better than the PGA in predicting the intensity by using the correlation relation.

Analysis of Tunnel Rock’s Dynamic Stress with Input of Different Peak Ground Motions

The changes of tunnel rock stress caused by dynamic load is a hot point in geotechnical engineering. The paper introduces seismic methods of seismic design codes in China. The paper select state road 318(Huangcaoping part)as an example. Using finite difference software to analyze the rock pressure changes around the lining-tunnel with different seismic inputs. Comparing the results the rock static pressure and find the relative amplification factor between dynamic pressure and static pressure. Based on the results of analysis, we can obtain the following conclusions: As the peak ground motion acceleration increases, the peak value of tunnel rock increases, too. The amplifications change in a small range. The oblique parts of tunnel are the weakest parts of the tunnels. In different areas, the amplifications change a lot. The maximum ones are in the area of oblique.