Seismic Ground Response Research Articles

Seismic Ground Response Prediction Based on Multilayer Perceptron

Earthquake disasters can cause enormous social and economic damage, and therefore the sustainability of infrastructure requires the mitigation of earthquake consequences. In seismic design of infrastructures, it is essential to estimate the response of the site during earthquake. Geotechnical engineers have developed quantitative methods for analyzing the seismic ground response. This study proposes a multilayer perceptron (MLP) model to evaluate the seismic response of the surface based on the seismic motion at the bedrock (or 100 m level), and compares its performance with that of a conventional model. A total of 6 sites, with 100 earthquake events at each site, were selected from the Kiban Kyoshin Network (KiK-net) and used as datasets. The acceleration response spectra were calculated from the predicted and measured (baseline) acceleration histories and compared. The proposed MLP model predicted the magnitudes of response and the natural periods where the response amplifies closely with the measured ground motions (baseline). The MLP model outperformed the conventional model for seismic ground response analysis. However, the proposed model did not perform as well for earthquakes whose response spectra exceed 2 g due to a deficiency in large earthquake measurements in the training datasets.

Seismic Response of Flat Ground and Slope Models through 1 g Shaking Table Tests and Numerical Analysis

In order to verify the reliability of numerical analysis, a series of 1 g shaking table tests for flat ground and slope were conducted using a laminar shear box subjected to different seismic waves. Firstly, numerical analyses, using the DEEPSOIL and ABAQUS software, were done to compare the results of flat ground experiments. After that, finite element analyses with ABAQUS were conducted to compare the results of slope experiments. For numerical analyses, considering the influence of the boundary, the concept of adjusted elastic modulus was proposed to improve the simulation results. Based on the analyses, it is found that in terms of acceleration-time history and spectral acceleration, the numerical analysis results are in good agreement with the experiment results. This implies that numerical analysis can capture the dynamic behavior of soil under 1 g shaking table test conditions.

Numerical modeling of seismic ground response considering the coupled effect of slope and soil layering

Seismic waves change as they pass through the soil layers. This change can be due to soil layering or existence of surface topography, which is estimated by ground response analysis. In this study, the coupled effect of soil layering and topographic irregularity is considered to evaluate the interaction of these two factors. In the first part, using two-dimensional finite element method (FEM) and viscous boundaries, the Gilroy region is simulated and one of the devastating earthquakes in this area, Loma Prieta (1989), applied to the model as an incident wave. The results are compared with those of recorded data to evaluate the performance of the model. In the second part, different slopes are assumed to exist in the Gilroy region and the seismic site response considering the coupled effect of soil layering and topographic irregularity is estimated using a nonlinear approach. In this part, characteristics of the soil layers are considered as same as the Gilroy region. Obtained results show that the amplification generally increases with increasing the slope angle. Comparing the results of free field condition with those of slope region reveals that the coupled effect of soil layering and topographic irregularity cannot be ignored and should be evaluated using accurate and practical approach.

Ground Response and Historical Buildings in Avellino (Campania, Southern Italy): Clues from a Retrospective View Concerning the 1980 Irpinia-Basilicata Earthquake

Cultural heritage represents our legacy with the past and our identity. However, to assure heritage can be passed on to future generations, it is required to put into the field knowledge as well as preventive and safeguard actions, especially for heritage located in seismic hazard-prone areas. With this in mind, the article deals with the analysis of ground response in the Avellino town (Campania, Southern Italy) and its correlation with the effects caused by the 23rd November 1980 Irpinia earthquake on the historical buildings. The aim is to get some clues about the earthquake damage cause-effect relationship. To estimate the ground motion response for Avellino, where strong-motion recordings are not available, we made use of the seismic hazard disaggregation. Then, we made extensive use of borehole data to build the lithological model so being able to assess the seismic ground response. Overall, results indicate that the complex subsoil layers influence the ground motion, particularly in the lowest period (0.1–0.5 s). The comparison with the observed damage of the selected historical buildings and the maximum acceleration expected indicates that the damage distribution cannot be explained by the surface geology effects alone.

Assessing the interaction of seismically loaded adjacent valleys using time-domain approach

Amplification or attenuation of seismic waves while passing through the soil medium can be due to soil type and its stratification or local topographic effects. Such aspects have been theoretically explained in many researches by means of ground response analysis. The results of seismic ground response analysis provide the necessary and realistic information for seismic design of structures and soil-structure interaction problems. In present study, two-dimensional finite element method is applied to evaluate the ground response of valley environments and estimation their interaction effects using time-domain approach. In this regard different cases include free field condition, single valley and double valleys environments are considered. Numerical simulations of seismic wave propagation for these cases are carried out and compared with each other. The results show that irregular topography can greatly amplify the seismic waves. On the other hand, if there are adjacent topographies, due to interaction of them, the amplification effect can be substantially increased. This amplification can be attenuated by moving away from the valley center to free field conditions.

The Implementation of Ground Response Analysis to Quantify Liquefaction Potential Index (LPI) in Bengkulu City, Indonesia

Bengkulu City is one of the areas vulnerable to earthquakes in Indonesia and several studies have shown the city experienced a unique phenomenon called liquefaction during the Mw 8.6 Bengkulu-Mentawai Earthquake. This event has initiated a step by step intensive study on earthquake in the area but previous studies are generally limited by the use of site investigation data to empirically analyse liquefaction potential and those that used advance method such as the seismic wave propagation model are rare. This means the level of liquefaction damage in the study area is not totally understood, therefore, this research focused on implementing the ground response analysis to quantify the Liquefaction Potential Index (LPI) using several areas in Bengkulu City in order to determine their vulnerability. The process involved the collection of several site investigation data including boring log and shear wave velocity profile as well as a desk study to determine the geological condition of the observed sites. Moreover, a non-linear seismic ground response analysis was conducted to obtain maximum ground surface acceleration (amax) parameter which was further used to analyse the liquefaction potential in the study area. The results showed several sites have the potential to experience liquefaction during earthquakes. The method applied was considered successful and the results are expected to be implemented for city development. Furthermore, the framework is recommended for adoption in investigating the liquefaction in other areas.

Site Effects Analysis of Shallow Subsurface Structures at Mashiki Town, Kumamoto, Based on Microtremor Horizontal-to-Vertical Spectral Ratios

ABSTRACTIn this study, we conducted a series of microtremor surveys to understand the contribution of soil amplifications to the heavy structural damage of wooden houses in downtown Mashiki, Kumamoto, Japan, during the 2016 Kumamoto earthquake. We analyzed the microtremor horizontal-to-vertical spectral ratios (MHVRs) of each observation site. A few previous studies have demonstrated the applicability of the earthquake horizontal-to-vertical spectral ratios (EHVRs) to identify velocity structures. Therefore, we transformed the MHVRs into pseudo-EHVRs (pEHVRs) using the EHVR-to-MHVR ratio (EMR) method. We identified the velocity structures in Mashiki, according to the diffuse field concept (DFC) for earthquake, using the pEHVRs. We also estimated the seismological bedrock motions during the mainshock based on the DFC. We then performed the seismic ground response analyses of subsurface structures, using a 1D linear analysis and an equivalent linear analysis (ELA). Finally, we obtained the distribution maps of peak ground acceleration (PGA) and peak ground velocity (PGV) for Mashiki town. We obtained the following results: (a) the thickness of the soft sediment under the southwestern part of Mashiki is deeper than that under the northeastern part; (b) the thickness of the soft sediments was a primary cause of the heavy damage to buildings of Mashiki; (c) the ground motions estimated by the ELA method seemed to be close to the observed seismic ground motions in Mashiki; (d) the distribution of the estimated PGV in Mashiki had a close relationship with the damage ratio distribution of buildings; (e) the EMR method, along with the DFC for earthquake and the 1D ELA method, successfully simulated the strong motions that occurred during the mainshock in Mashiki.

Modern Methods of Estimating Local Effects of Earthquakes

Local effects pertain to the main factors determining the ground motion parameters during earthquakes. The local effects associated with seismic ground response have always been paid much attention in the practice of engineering seismology since most urban regions in the world are situated in river valleys, on the soft young sedimentary deposits. The river valleys in the earthquake-prone areas host a number of large cities of the world such as Tokyo, Osaka, Kobe, Los Angeles, San Francisco, San Salvador, Caracas, Lima, Bogota, Kathmandu, Manila, Thessaloniki, Mexico City, etc. The abundance and significance of these effects stimulated numerous instrumental, theoretical, and numerical studies aimed at better understanding and quantifying these effects. To date, the methods have been developed in seismology for reliable assessment of these effects. In this paper, the methods of assessing the local effects of the earthquakes that were used at the early stages of seismology and their evolution up to the modern level are described.

Numerical simulations of LEAP centrifuge tests for seismic response of liquefiable sloping ground

This paper presents numerical simulations of a liquefiable sloping ground related to LEAP-UCD-2017 and LEAP-Asia-2019 (Liquefaction Experiments and Analysis Projects) dynamic centrifuge model tests (Type-C phase) conducted by various institutions. The numerical simulations are performed using a pressure-dependent constitutive model implemented with the characteristics of dilatancy, cyclic mobility and associated shear deformation. The soil parameters are determined based on a series of available stress-controlled cyclic triaxial and torsional shear tests for matching the liquefaction strength curves of Ottawa F-65 sand with relative densities Dr. = 65% and 60% in calibration phase of LEAP-UCD-2017 and LEAP-Asia-2019, respectively. The computational framework for the dynamic response analysis is discussed and the computed results are presented for the selected centrifuge experiments during Type-C phase. Measured time histories (e.g., displacement, acceleration and excess pore pressure ratio) of these experiments are reasonably captured. Comparisons between the numerical simulations and measured results showed that the pressure-dependent constitutive model as well as the overall employed computational framework have the potential to predict the response of the liquefiable sloping ground, and subsequently realistically evaluate the performance of an equivalent soil system subjected to seismically-induced liquefaction.

Seismic hazard microzonation of ground response parameters in Bengkulu City, Indonesia

This paper presents the seismic hazard microzonation of ground motion parameters on the basis of earthquakes events in Bengkulu City. Geotechnical site investigation and geophysical survey were performed in Bengkulu City. Furthermore, data were used to observe the geological condition. The local seismic design code for soft soil was used to generate spectral acceleration, which was later used as the scaling factor to generate ground motion for earthquake simulation. One-dimensional seismic ground response analysis was conducted to simulate earthquake wave propagating through soil layers. Several parameters, such as peak ground acceleration (PGA), spectral accelerations (SA) at 0.2 s and 1 s, and seismic wave amplification factor were observed. Those parameters were also depicted in seismic microzonation maps and addressed to identify potential impact during the earthquake. The results showed that the possibility of structural building responses along coastal area of Bengkulu City is relatively high. Therefore, a local seismic design code is important to propose as the alternative for reliable seismic design code. In general, the results of this study could give a recommendation to local government to consider seismic resistance design for buildings in Bengkulu City.

Seismic Hazard Vulnerability of Bengkulu City, Indonesia, Based on Deterministic Seismic Hazard Analysis

Bengkulu City is one of cities in Indonesia, which is located on the west coastline of Sumatra. Within last two decades, Bengkulu City had undergone at least two large earthquakes with magnitudes ≥ Mw 7.0. This paper presents a study of deterministic seismic hazard for Bengkulu City. The hazard analysis is initiated by determining the controlling earthquake. Site investigation results are also studied for seismic ground response analysis. Analysis is performed by propagating seismic wave to investigate seismic behaviour during earthquake. Three parameters including peak ground acceleration, spectral acceleration at 0.2 s (SA at 0.2 s), and spectral acceleration at 1 s (SA at 1 s) are analysed to generate seismic hazard maps. In general, this study could help people to understand seismic hazard in Bengkulu City. The results also could recommend local engineers to consider earthquake in structural design and spatial plan in Bengkulu City.

Dynamic soil properties and seismic ground response analysis for North Indian seismic belt subjected to the great Himalayan earthquakes

The paper highlights the importance of using site-specific shear modulus reduction (G/Gmax versus shear strain, γ) curves and damping ratio (D versus shear strain, γ) curves for ground response analysis. In order to develop comprehensive G/Gmax–γ and D–γ curves (i.e. over a wide range of strain level), two types of apparatus, viz. resonant column and cyclic simple shear, have been used. The case study considered the geological deposits from the river beds of Yamuna River originating from the Himalayan seismic zone of North India. The tests results have been analysed to develop G/Gmax–γ and D–γ curves and compared with standard curves. It has been observed that upper and lower boundaries for the standard curves are remarkably different for the geological deposit under consideration. In order to assess the impact of using standard curves rather than site-specific curves, ground response analysis has been carried out at five sites along the Yamuna River using two types of curves (standard and site-specific developed in this study). The study showed that the amplification of shear waves at these sites based on the experimentally derived curves is much higher as compared to the standard curves. The proposed curves better represent dynamic behaviour of the soil deposits of the region and will provide a realistic response as far as practically possible, for the structures constructed in the states of Haryana and Delhi and nearby areas. It is anticipated that the data presented in this paper will have wide application and usage.

Seismic Response of Sri Lanka using DSHA Technique

Deterministic seismic hazard assessment developed in 1960s is the oldest method of analysis of seismic ground response. This paper describes the application of seismic hazard assessment to obtain the Peak Ground Acceleration at major cities in Sri Lanka due to an oceanic earthquake. Two earthquakes, occurred in 2011 and 2012 in the above region, were chosen for the validation of suitable attenuation relationships for the region. The comparison shows that, out of the two attenuation relationships investigated, Gitterman et al. (1993) relationship gives the bestprediction.

Shear wave velocity profiling by inverse analysis of array microtremors for two cities in Iran: conventional derivative-based versus genetic algorithm inversion methods

GA-based and conventional derivative-based inversion methods were employed to determine Vs profile of subsurface soil layers from array microtremors for two cities in Iran. The applied methods were verified against geotechnical and geophysical data. The results obtained by both GA-based and conventional inversions were in acceptable agreement with results of other Vs profiling techniques. However, the variability of obtained Vs data was smaller at deeper depths indicating more reliability of predictions. Comparison between seismic ground response based on Vs profiles of different methods showed that both GA-based and conventional inversion methods agree more with the seismic downhole method than the seismic refraction technique.

Verification of Liquefaction Potential during the Strong Earthquake at the Border of Thailand-Myanmar

ABSTRACT The study presents a liquefaction potential analysis for the Thailand-Myanmar border area due to the earthquake. Three sites reported liquefaction during Tarlay earthquake in 2011 were investigated including a microtremor to obtain the shear wave velocity profile and depth of engineering bedrock. Next-generation attenuation model was used to estimate the peak ground acceleration at the liquefied sites. A seismic ground response analysis was then conducted, and the result revealed that the shallow sand layers were very vulnerable to undergo liquefaction. The results also showed a similar tendency to the predictions based on the empirical methods.

Comprehensive ambient noise analyses for seismic microzonation of sarpol-e-zahab after the Mw 7.3 2017 Iran earthquake

This study is intended to investigate ambient noise recordings in form of array and single-station measurements at Sarpol-e-zahab city after the destructive Mw = 7.3 earthquake of 12 November 2017 in Kermanshah province, Iran. The ESPAC, f-k, HVTFA, and HVSR methods are applied to analyze the ambient noise and obtain useful information on three key factors of site seismic properties, i.e. the geometry of ground layers, their mechanical characteristics and site resonance frequencies. The results of this study are presented as maps of the fundamental frequency of the ground, depth of bedrock, the thickness of top cover materials, as well as the average shear wave velocity (Vs)700 and (Vs)30 for Sarpol-e-zahab. The analyses show that the single value of (Vs)30 does not represent seismic ground response, and the depth of competent bedrock, which dominates the low-frequency seismic response amplifications is located far beyond 30 m in this city. The most effective grade II seismic microzonation of Sarpol-e-zahab is provided by combining the results of these analyses.

Seismic ground response analyses at an international airport in northern Italy by using a stochastic-based

Seismic ground response analyses at an international airport in northern Italy by using a stochastic-based

Evaluation of one-dimensional seismic site response due to liquefiable sub-layer

Although seismic site response is affected by liquefiable soil, the issue is complex and there are few comprehensive studies in this area. It is rare for seismic codes to consider attenuation or amplification of seismic waves due to the presence of liquefied sub-layers. In the research reported in this paper, the seismic behaviour of liquefiable sub-layers and their effect on seismic ground response were evaluated. The initial patterns of seismic response along the height of a soil profile containing a liquefiable sub-layer were extracted using physical modelling and shaking table tests. Afterwards, a series of one-dimensional effective stress numerical models was employed to verify the results and the seismic amplification patterns were processed. The roles of liquefiable sub-layers are discussed from different perspectives as they relate to attenuation or amplification of the seismic ground response at the surface. Overall, the experimental and numerical studies showed that the liquefaction of sub-layers, in addition to the usual settlement, can effectively attenuate the intensity of seismic waves and reduce earthquake-induced force.

Seismic response analysis of soil profile: comparison of 1D versus 2D models and parametric study

One of the most important parts of geotechnical earthquake engineering is evaluation of the ground motion due to incident earthquake. Seismic ground response evaluation can be categorized into time and frequency domain methods. In this study, an applied method is proposed to evaluate 2D ground response analysis in frequency domain. The results are presented in terms of peak acceleration and velocity diagrams as well as the diagrams of 2D/1D results using four real earthquakes, two in the far field and two in the near field as an incident waves. The accuracy of the proposed method is shown by comparison of results obtained using current method with those of 1D method in free field condition. Then, to evaluate the effect of irregular topographies on seismic ground response, parametric study is carried out on empty valleys and diagrams of amplification factors have been presented. The obtained results confirm the necessity of 2D modeling and the use of precise and applied methods in the case of irregular topography. The superiority of the proposed 2D method than 1D method is elimination of limiting assumption of 1D method such as horizontal bedrock and parallel soil layer despite its simplicity and practicality.

Dynamic properties of two historically liquefiable sands in the Lisbon area

The stiffness properties of soils, particularly shear modulus and damping ratio, play a fundamental role in predicting the ground deformation during cyclic and dynamic loading. The dynamic properties can be used for the assessment of seismic ground response and the analysis of soil–structure interaction. This study provides a detailed dynamic characterisation of two liquefiable sandy soils, which have experienced earthquake-induced liquefaction, as historically documented. The soils were collected in the greater Lisbon area, in the south of Portugal. For this purpose, a comprehensive laboratory testing programme, which included a series of bender-element and resonant-column tests, was conducted. During the study, the effects of void ratio and mean effective stress on the soil stiffness were examined, focusing on the small-strain response. Results show shear modulus degradation and damping ratio curves, at small and intermediate shear strain levels, for saturated reconstituted samples under different stress conditions. Data obtained in the laboratory of both materials were fitted into normalised models to estimate the dynamic properties for different stress and state conditions. In addition, damping ratio curves were compared against the typical bounds of quartz materials. Stress-dependent models for estimating the maximum shear modulus and threshold shear strain amplitudes of both sands are proposed in this paper. The data provided in this study are useful for numerical analyses and geotechnical design, particularly when involving dynamic or seismic approaches.