Research

27 pages, 9290 KiB

Open AccessEditor’s ChoiceArticle

SEM3D: A 3D High-Fidelity Numerical Earthquake Simulator for Broadband (0–10 Hz) Seismic Response Prediction at a Regional Scale

by Sara Touhami, Filippo Gatti, Fernando Lopez-Caballero, Régis Cottereau, Lúcio de Abreu Corrêa, Ludovic Aubry and Didier Clouteau

Geosciences 2022, 12(3), 112; https://doi.org/10.3390/geosciences12030112 - 02 Mar 2022

Cited by 11 | Viewed by 4186

Abstract

In this paper, we present SEM3D: a 3D high-fidelity numerical earthquake simulator that is tailored to predict the seismic wave field of complex earthquake scenarios from the fault to the epicenter site. SEM3D solves the wave-propagation problem by means of the spectral element [...] Read more.

In this paper, we present SEM3D: a 3D high-fidelity numerical earthquake simulator that is tailored to predict the seismic wave field of complex earthquake scenarios from the fault to the epicenter site. SEM3D solves the wave-propagation problem by means of the spectral element method (SEM). The presented demonstrative test case was a blind

M_{W}

6.0 earthquake scenario at the European experimental site located in the sedimentary basin of Argostoli on the island of Kefalonia (Western Greece). A well-constrained geological model, obtained via geophysical inversion studies, and seismological model, given the large database of seismic traces recorded by the newly installed ARGONET network, of the site were considered. The domain of interest covered a region of 44 km × 44 km × 63 km, with the smallest grid size of 130 m × 130 m × 35 m. This allowed us to simulate the ground shaking in its entirety, from the seismic source to the epicenter site within a 0–10 Hz frequency band. Owing to the pseudo-spectral nature of the numerical method and given the high polynomial order (i.e., degree nine), the model featured 1.35·10

^{10}

DOFs (degrees of freedom). The variability of the synthetic wave field generated within the basin is assessed herein, exploring different random realizations of the mean velocity structure and heterogeneous rupture path. Full article

(This article belongs to the Special Issue Engineering Analysis of Near-Source Strong Ground Motion)

► Show Figures

Figure 1

18 pages, 5356 KiB

Open AccessArticle

Site Amplification during Strong Earthquakes Investigated by Vertical Array Records

by Takaji Kokusho and Tomohiro Ishizawa

Geosciences 2021, 11(12), 510; https://doi.org/10.3390/geosciences11120510 - 14 Dec 2021

Cited by 3 | Viewed by 2612

Abstract

A number of vertical array records during eight destructive earthquakes in Japan are utilized, after discussing criteria for desirable requirements of vertical arrays, to formulate seismic amplification between ground surface and outcrop base for seismic zonation. A correlation between peak spectrum amplification and [...] Read more.

A number of vertical array records during eight destructive earthquakes in Japan are utilized, after discussing criteria for desirable requirements of vertical arrays, to formulate seismic amplification between ground surface and outcrop base for seismic zonation. A correlation between peak spectrum amplification and V_s (S-wave velocity) ratio (base V_s/surface V_s) was found to clearly improve by using V_s in an equivalent surface layer wherein predominant frequency or first peak is exerted, though the currently used average V_s in top 30 m is also meaningful, correlating positively with the amplification. We also found that soil nonlinearity during strong earthquakes has only a marginal effect even in soft soil sites on the amplification between surface and outcrop base except for ultimate soil liquefaction failure, while strong nonlinearity clearly appears in the vertical array amplification between surface and downhole base. Its theoretical basis has been explained by a simple study on a two-layered system in terms of radiation damping and strain-dependent equivalent nonlinearity. Full article

(This article belongs to the Special Issue Engineering Analysis of Near-Source Strong Ground Motion)

► Show Figures

Figure 1

27 pages, 4327 KiB

Open AccessArticle

Efficiency of Intensity Measures Considering Near- and Far-Fault Ground Motion Records

by Yeudy F. Vargas-Alzate and Jorge E. Hurtado

Geosciences 2021, 11(6), 234; https://doi.org/10.3390/geosciences11060234 - 30 May 2021

Cited by 10 | Viewed by 2384

Abstract

This paper focuses on the identification of high-efficiency intensity measures to predict the seismic response of buildings affected by near- and far-fault ground motion records. Near-fault ground motion has received special attention, as it tends to increase the expected damage to civil structures [...] Read more.

This paper focuses on the identification of high-efficiency intensity measures to predict the seismic response of buildings affected by near- and far-fault ground motion records. Near-fault ground motion has received special attention, as it tends to increase the expected damage to civil structures compared to that from ruptures originating further afield. In order to verify this tendency, the nonlinear dynamic response of 3D multi-degree-of-freedom models is estimated by using a subset of records whose distance to the epicenter is lower than 10 km. In addition, to quantify how much the expected demand may increase because of the proximity to the fault, another subset of records, whose distance to the epicenter is in the range between 10 and 30 km, has been analyzed. Then, spectral and energy-based intensity measures as well as those obtained from specific computations of the ground motion record are calculated and correlated to several engineering demand parameters. From these analyses, fragility curves are derived and compared for both subsets of records. It has been observed that the subset of records nearer to the fault tends to produce fragility functions with higher probabilities of exceedance than the ones derived for far-fault records. Results also show that the efficiency of the intensity measures is similar for both subsets of records, but it varies depending on the engineering demand parameter to be predicted. Full article

(This article belongs to the Special Issue Engineering Analysis of Near-Source Strong Ground Motion)

► Show Figures

Figure 1

19 pages, 4788 KiB

Open AccessArticle

Near-Source Simulation of Strong Ground Motion in Amatrice Downtown Including Site Effects

by Alessandro Todrani and Giovanna Cultrera

Geosciences 2021, 11(5), 186; https://doi.org/10.3390/geosciences11050186 - 25 Apr 2021

Cited by 3 | Viewed by 2511

Abstract

On 24 August 2016, a Mw 6.0 earthquake started a damaging seismic sequence in central Italy. The historical center of Amatrice village reached the XI degree (MCS scale) but the high vulnerability alone could not explain the heavy damage. Unfortunately, at the time [...] Read more.

On 24 August 2016, a Mw 6.0 earthquake started a damaging seismic sequence in central Italy. The historical center of Amatrice village reached the XI degree (MCS scale) but the high vulnerability alone could not explain the heavy damage. Unfortunately, at the time of the earthquake only AMT station, 200 m away from the downtown, recorded the mainshock, whereas tens of temporary stations were installed afterwards. We propose a method to simulate the ground motion affecting Amatrice, using the FFT amplitude recorded at AMT, which has been modified by the standard spectral ratio (SSR) computed at 14 seismic stations in downtown. We tested the procedure by comparing simulations and recordings of two later mainshocks (Mw 5.9 and Mw 6.5), underlining advantages and limits of the technique. The strong motion variability of simulations was related to the proximity of the seismic source, accounted for by the ground motion at AMT, and to the peculiar site effects, described by the transfer function at the sites. The largest amplification characterized the stations close to the NE hill edge and produced simulated values of intensity measures clearly above one standard deviation of the GMM expected for Italy, up to 1.6 g for PGA. Full article

(This article belongs to the Special Issue Engineering Analysis of Near-Source Strong Ground Motion)

► Show Figures

Figure 1

21 pages, 7275 KiB

Open AccessArticle

Case Study of a Heavily Damaged Building during the 2016 M_W 7.8 Ecuador Earthquake: Directionality Effects in Seismic Actions and Damage Assessment

by Luis A. Pinzón, Luis G. Pujades, Irving Medranda and Rodrigo E. Alva

Geosciences 2021, 11(2), 74; https://doi.org/10.3390/geosciences11020074 - 09 Feb 2021

Cited by 3 | Viewed by 2067

Abstract

In this work, the directionality effects during the M_W 7.8 earthquake, which occurred in Muisne (Ecuador) on 16 April 2016, were analyzed under two perspectives. The first one deals with the influence of these effects on seismic intensity measures (IMs), while the [...] Read more.

In this work, the directionality effects during the M_W 7.8 earthquake, which occurred in Muisne (Ecuador) on 16 April 2016, were analyzed under two perspectives. The first one deals with the influence of these effects on seismic intensity measures (IMs), while the second refers to the assessment of the expected damage of a specific building located in Manta city, Ecuador, as a function of its azimuthal orientation. The records of strong motion in 21 accelerometric stations were used to analyze directionality in seismic actions. At the closest station to the epicenter (R_Rup = 20 km), the peak ground acceleration was 1380 cm/s² (EW component of the APED station). A detailed study of the response spectra ratifies the importance of directionality and confirms the need to consider these effects in seismic hazard studies. Differences between IMs values that consider the directionality and those obtained from the as-recorded accelerograms are significant and they agree with studies carried out in other regions. Concerning the variation of the expected damage with respect to the building orientation, a reinforced concrete building, which was seriously affected by the earthquake, was taken as a case study. For this analysis, the accelerograms recorded at a nearby station and detailed structural documentation were used. The ETABS software was used for the structural analysis. Modal and pushover analyses were performed, obtaining capacity curves and capacity spectra in the two main axes of the building. Two advanced methods for damage assessment were used to obtain fragility and mean damage state curves. The performance points were obtained through the linear equivalent approximation. This allows estimation and analysis of the expected mean damage state and the probability of complete damage as functions of the building orientation. Results show that the actual probability of complete damage is close to 60%. This fact is mainly due to the greater severity of the seismic action in one of the two main axes of the building. The results are in accordance with the damage produced by the earthquake in the building and confirm the need to consider the directionality effects in damage and seismic risk assessments. Full article

(This article belongs to the Special Issue Engineering Analysis of Near-Source Strong Ground Motion)

► Show Figures

Figure 1

14 pages, 39349 KiB

Open AccessArticle

An Empirical Model to Account for Spectral Amplification of Pulse-Like Ground Motion Records

by Sara Sgobba, Giovanni Lanzano, Francesca Pacor and Chiara Felicetta

Geosciences 2021, 11(1), 15; https://doi.org/10.3390/geosciences11010015 - 29 Dec 2020

Cited by 8 | Viewed by 2305

Abstract

Near-source effects can amplify seismic ground motion, causing large demand to structures and thus their identification and characterization is fundamental for engineering applications. Among the most relevant features, forward-directivity effects may generate near-fault records characterized by a large velocity pulse and unusual response [...] Read more.

Near-source effects can amplify seismic ground motion, causing large demand to structures and thus their identification and characterization is fundamental for engineering applications. Among the most relevant features, forward-directivity effects may generate near-fault records characterized by a large velocity pulse and unusual response spectral shape amplified in a narrow frequency-band. In this paper, we explore the main statistical features of acceleration and displacement response spectra of a suite of 230 pulse-like signals (impulsive waveforms) contained in the NESS1 (NEar Source Strong-motion) flat-file. These collected pulse-like signals are analyzed in terms of pulse period and pulse azimuthal orientation. We highlight the most relevant differences of the pulse-like spectra compared to the ordinary (i.e., no-pulse) ones, and quantify the contribution of the pulse through a corrective factor of the spectral ordinates. Results show that the proposed empirical factors are able to capture the amplification effect induced by near-fault directivity, and thus they could be usefully included in the framework of probabilistic seismic hazard analysis to adjust ground-motion model (GMM) predictions. Full article

(This article belongs to the Special Issue Engineering Analysis of Near-Source Strong Ground Motion)

► Show Figures

Figure 1

Review

Jump to: Research, Other

28 pages, 15192 KiB

Open AccessReview

Energy Demand in Surface Soils for Earthquake Engineering by Vertical Array Strong Motion Records

by Takaji Kokusho

Geosciences 2022, 12(2), 102; https://doi.org/10.3390/geosciences12020102 - 21 Feb 2022

Viewed by 2019

Abstract

In earthquake engineering, acceleration has played a major role, while wave energy has rarely been considered as a demand in design. In order to understand earthquake damage mechanism in terms of energy, the demand in terms of wave energy in surface soil layers [...] Read more.

In earthquake engineering, acceleration has played a major role, while wave energy has rarely been considered as a demand in design. In order to understand earthquake damage mechanism in terms of energy, the demand in terms of wave energy in surface soil layers is studied here, assuming one-dimensional SH wave propagation by using a number of vertical array records during nine strong earthquakes in Japan. A clear decreasing trend of the energy demand with decreasing ground depth and decreasing surface soil stiffness has been found as well as a propensity of incident energies calculated at bedrocks being roughly compatible with empirical formulas. How the energy demand is correlated with structural damage is also discussed in simplified models to show that induced structural strain is governed by upward energy flux, degree of structural resonance, and impedance ratio between structure and ground and structural stiffness. In low-damping brittle superstructures, wave energy flux in resonance and associated predominant frequency are decisive in determining the damage, while cumulative wave energy determines the damage in high damping ductile soil and massive concrete structures. The trend of lower energy demand in softer soil sites may not be contradictory, with a widely accepted perception that softer soil sites tend to suffer heavier earthquake damage as far as geotechnical damage is concerned. Full article

(This article belongs to the Special Issue Engineering Analysis of Near-Source Strong Ground Motion)

► Show Figures

Figure 1

Other

Jump to: Research, Review

22 pages, 8944 KiB

Open AccessTechnical Note

Fling-Step Recovering from Near-Source Waveforms Database

by Erika Schiappapietra, Chiara Felicetta and Maria D’Amico

Geosciences 2021, 11(2), 67; https://doi.org/10.3390/geosciences11020067 - 04 Feb 2021

Cited by 5 | Viewed by 2478

Abstract

We present an upgraded processing scheme (eBASCO, extended BASeline COrrection) to remove the baseline of strong-motion records by means of a piece-wise linear detrending of the velocity time history. Differently from standard processing schemes, eBASCO does not apply any filtering to remove the [...] Read more.

We present an upgraded processing scheme (eBASCO, extended BASeline COrrection) to remove the baseline of strong-motion records by means of a piece-wise linear detrending of the velocity time history. Differently from standard processing schemes, eBASCO does not apply any filtering to remove the low-frequency content of the signal. This approach preserves both the long-period near-source ground-motion, featured by one-side pulse in the velocity trace, and the offset at the end of the displacement trace (fling-step). The software is suitable for a rapid identification of fling-containing waveforms within large strong-motion datasets. The ground displacement of about 600 three-component near-source waveforms has been recovered with the aim of (1) extensively testing the eBASCO capability to capture the long-period content of near-source records, and (2) compiling a qualified strong-motion flat-file useful to calibrate attenuation models for peak ground displacement (PGD), 5% damped displacement response spectra (DS), and permanent displacement amplitude (PD). The results provide a more accurate estimate of ground motions that can be adopted for different engineering purposes, such as performance-based seismic design of structures. Full article

(This article belongs to the Special Issue Engineering Analysis of Near-Source Strong Ground Motion)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Engineering Analysis of Near-Source Strong Ground Motion

Share This Special Issue

Special Issue Editors

Special Issue Information

Keywords

Published Papers (8 papers)

Research

Review

Other

Further Information

Guidelines

MDPI Initiatives

Follow MDPI