Seismic Scenarios Research Articles

Mechanical‐probabilistic formulation of the soil–structure interaction, accounting for the average shear wave velocity

SummaryThis work proposes a mechanical‐probabilistic formulation of the soil–structure interaction, taking into account the variability of the mean velocity of shear wave seismic load. This work aims at studying the sensitivity of the seismic response of a reinforced concrete frame structure by accounting for different seismic scenarios. For this purpose, the simplified model of a two‐story structure system has been developed. This model is based both on a macro‐element approach and on a stochastic collocation method. The sensitivity of the maximum displacement of the structure under different average shear wave velocities is studied. This aim in view, Gaussian or lognormal random variables are arbitrarily chosen to model this velocity. Analysis of the seismic vulnerability of the soil–structure system leads to cumulative distribution functions, which sometimes show significant differences for the same soil class in the sense of the European standard for the design of structures for earthquake resistance.

Seismic vulnerability analysis of medieval rammed earth fortifications in southeastern Spain

This paper analyses the seismic vulnerability of various rammed earth medieval fortifications situated in Southeastern Spain, where seismic events with intensity over VII have taken place in the last millennium, using the vulnerability index method. This method begins with the choice of a certain initial value, V0, of the vulnerability index, which is obtained from a preset range between maximum, $${\text{V}}_{0}^{ {\rm max} }$$ , and minimum, $${\text{V}}_{0}^{ {\rm min} }$$ , values, which are likely for vulnerability indices, according to the constructive material characteristics and based on expert judgments. Rammed earth structures have not yet been studied using the vulnerability index method, despite the fact that they are quite common medieval structures in Spain and other countries in the Mediterranean region, many of which are also heritage sites, and hence are legally protected. Intervention priorities on them have been determined from the results in this paper with the aim of reducing their seismic vulnerability. For the different rammed earth techniques, a proposed primary value Vp = 0.76 together with some other material modifiers (construction typology and quality, current material porosity and density, and superficial deterioration) make the range of values V0 vary between 0.58 and 1.02. Moreover, structural behavior modifiers (MK) have been adapted to the various defensive rammed earth structural typologies used for these fortifications allowing us to obtain individualized vulnerability index values. Three rammed earth fortifications damaged by historical earthquakes and located in SE Spain have been used to validate the method, in which values of V0med range between 35.2 and 89.1% and upwards and the vulnerability index IVmed may vary between 27.9 and 70.7% and upwards as compared to those used by other authors for castles. Besides, the proposed method has been used by carefully choosing six rammed earth fortifications (two towers, two walls and two castles) in SE Spain which are representative of different construction systems, structural typologies and topographies. Furthermore, the mean damage grade and the probability of its occurrence is determined for each fortification based on PGA data and site effects, taking into account a probabilistic seismic scenario for a 975 year return period, in accordance with existing legislation. In the end, direct relations are established between the seismic vulnerability and the types of material and the typology of the fortifications. We have carried out a sensibility analysis in order to learn about the influence of the constructive technique, the material condition and the structural typology on the damage grade value. The results show that lime-crusted rammed earth technique and tower typologies are the most vulnerable structures while topography is somehow less important. The results suggest that for half of the structures analyzed for the given scenario the probabilities are above 80% for damage grade 4 and 5 (EMS-98).

Newmark displacement data for low to moderate magnitude events in the Betic Cordillera.

Land-use decisions in relation to seismic-induced landslide hazard are usually made through the preparation of hazard maps. The rigid-block method is probably the most used for this purpose. Under this method, Newmark displacement is computed for each slope unit and this displacement is used as a guide for establishing categories of hazard. At present, most relations used for computing Newmark displacement are established from moderate-to-high magnitude earthquakes (Mw ≥ 6.5). This data article provides Newmark displacements computed from accelerograms recorded in the Betic Cordillera for low-to-moderate magnitude earthquakes (Mw = 3.5–6.3). Records come from the Spanish Strong Ground Motion database (Instituto Geográfico Nacional). Newmark displacements were computed focusing on yield accelerations frequently recorded in such scenarios (0.02, 0.03, 0.04, 0.05, 0.06, 0.08 and 0.10), although higher accelerations were also considered (0.125, 0.15, 0.20, 0.25 and 0.30 g's). These data are useful for the study of the hazard in seismic scenarios of low-to-moderate magnitude, very frequent in practice. These data have been used in the study by Delgado et al. [1].

Rigorous versus less-demanding fragility relations for RC high-rise buildings

Analytical seismic scenario-based probabilistic fragility relations form the spine of earthquake risk assessment and mitigation of RC high-rise wall buildings. In this study, a framework is proposed to develop both rigorous (refined) and less-demanding (cheaper) fragility relations for such structures. Multi-record incremental dynamic analysis is employed using a new scalar intensity measure and net inter-storey drift as a consistent global damage measure for varying heights of buildings. To illustrate the framework, a 30-storey wall building located in a multiple-scenario earthquake-prone region is analysed. The refined fragility sets are derived using 40 real earthquake records representing two seismic scenarios, while the proposed methodology to develop less-demanding seismic scenario-based fragility relations employs a considerably lower number of earthquake records. In this methodology, a new record selection criterion and a fragility curve tolerance factor are introduced. Finally, the two fragility relation sets for the reference structure are developed, assessed, and compared to provide insights into their features and accuracy. Using the proposed methodology, the study revealed that fairly reliable seismic scenario-based fragility sets can be developed for RC high-rise buildings with a significant reduction in computational time and efforts. The proposed framework is generic and can be implemented to deriving refined and less-demanding fragility relations for RC high-rise buildings of different configurations and structural systems.

A Macro Seismic Hazard Zonation for Sri Lanka

This paper describes the outcome of a comprehensive study carried out to analyse the seismic hazards affecting Sri Lanka. The main seismic threat is from oceanic earthquakes originating at failed Mannar rift zone and Comorin ridge off the west to south west coast with some secondary influence from South Indian crustal earthquakes. The analyses were performed using Deterministic Seismic Hazard Assessment, Probabilistic Seismic Hazard Assessment and seismic wave propagation using FLAC software ignoring the overburden attenuation within the landmass. The seismic scenario included 100 years earthquake catalogue with an characteristic earthquake of magnitude 6.9 at a distance 90 km from the west coast. Historical records of earthquakes in the vicinity of Sri Lanka indicate that 1615 earthquake was the most significant earthquake that affected Sri Lanka. The analyses show that South West to North West coastal areas are the most vulnerable to seismic hazards. There is also reflection of seismic waves leading to amplification of seismic waves in the central highland. Based on the analyses described above, a seismic hazard map for Sri Lanka dividing the country into two zones of seismic intensity and response spectrum is provided accordingly. The study was constrained by the lack of recorded data of past earthquake responses within the country and a network of seismic stations are proposed in the paper for future data collection.

Physical stratigraphy and geotechnical properties controlling the local seismic response in explosive volcanic settings: the Stracciacappa maar (central Italy)

Nowadays, policies addressed to prevention and mitigation of seismic risk need a consolidated methodology finalised to the assessment of local seismic response in explosive volcanic settings. The quantitative reconstruction of the subsoil model provides a key instrument to understand how the geometry and the internal architecture of outcropping and buried geological units have influence on the propagation of seismic waves. On this regard, we present a multidisciplinary approach in the test area of the Stracciacappa maar (Sabatini Volcanic District, central Italy), with the aim to reconstruct its physical stratigraphy and to discuss how subsoil heterogeneities control the 1D and 2D local seismic response in such a volcanic setting. We first introduce a new multidisciplinary dataset, including geological (fieldwork and log from a 45-m-thick continuous coring borehole), geophysical (electrical resistivity tomographies, single station noise measurements, and 2D passive seismic arrays), and geotechnical (simple shear tests performed on undisturbed samples) approaches. Then, we reconstruct the subsoil model for the Stracciacappa maar in terms of vertical setting and distribution of its mechanical lithotypes, which we investigate for 1D and 2D finite element site response analyses through the application of two different seismic scenarios: a volcanic event and a tectonic event. The numerical modelling documents a significant ground motion amplification (in the 1–1.5 Hz range) revealed for both seismic scenarios, with a maximum within the centre of the maar. The ground motion amplification is related to both 1D and 2D phenomena including lithological heterogeneity within the upper part of the maar section and interaction of direct S-waves with Rayleigh waves generated at edges of the most superficial lithotypes. Finally, we use these insights to associate the expected distribution of ground motion amplification with the physical stratigraphy of an explosive volcanic setting, with insights for seismic microzonation studies and local seismic response assessment in populated environments.

Documenting Earthquakes in the United States of the Ionian Islands, 1815–1864

Abstract The seven islands of Corfu, Paxoi, Kephalonia, Ithaca, Lefkada, Zakynthos, and Cythera (Ionian Sea, offshore western Greece) were a British protectorate with the name of “United States of the Ionian Islands” between 1815 and 1864. Although many earthquake studies have already examined the past seismicity of this area, they contain only a few data for a handful of earthquakes, for an area known to be characterized by a high level of seismicity. Against this fragmentary seismological knowledge stands a 50 yr abundant production of local documentary sources of different types and in diverse languages. For this reason and because most of the available sources had not been yet nor systematically looked into in the search for testimonies of earthquake effects, an ad hoc and comprehensive investigation was carried out. The number of records on earthquake effects is huge as well as unexpected, and the quality of the collected records is high. The 147 new macroseismic European Macroseismic Scale 1998 intensity values, accurately assigned on the basis of independent contemporary records only, are presented in the form of timelines of earthquake effects for the main towns of the four islands of Corfu, Kephalonia, Lefkada, and Zakynthos. Besides partially amending the gaps of the knowledge of these 50 yr of seismicity in the Ionian Islands, the great amount of freshly collected data suggests that historical seismological research may effectively contribute to improving the seismic scenarios of past earthquakes in many areas of the world.

A Simplified Mechanical Approach for a Large-Scale Seismic Vulnerability Assessment of the Algerian Masonry Buildings

ABSTRACT Hitherto, considerable research has been developed on the city scale to estimate the seismic hazard in terms of peak ground acceleration (PGA), which could be a valuable tool for the assessment of the building vulnerability using mechanical approaches. However, as material properties and dynamic characteristics are commonly unavailable to define detailed models for large-scale analysis, mechanical methods cannot be applied building-by-building. The only way to perform this task is by correlating the mechanical method with a macroseismic approach, which can be highly useful when only structural and geometrical surveys are available. In this context, this research aims to develop a simplified mechanical approach to assess the seismic vulnerability and the probability of damage of the Algerian masonry buildings at a large scale using a general structural data survey and in the presence of the seismic hazard in terms of PGA or spectral values. Accordingly, an existing macroseismic method derived from the GNDT II approach was correlated with the mechanical N2 method, which is herein adapted and applied to fit the features of the Algerian masonry buildings. This nonlinear method identifies the performance of buildings by means of “performance point,” referred to as the intersection between the earthquake demand curve, built here according to the Algerian seismic code (RPA 99/version 2003), and the capacity curve of an equivalent nonlinear S.D.O.F. system. For the implementation of the proposed approach, a total of 380 masonry buildings located in Annaba City (North-east in Algeria) were assessed. The fragility and the probability of damage results of the building stock were obtained through a comparison between the application of the vulnerability index method and the simplified mechanical approach for different seismic scenarios.

Seismic vulnerability assessment and loss estimation in Cephalonia and Ithaca islands, Greece, due to earthquake events: A case study

In this paper an estimation of seismic losses for various seismic scenarios of the Cephalonia and Ithaca islands, Greece, is proposed. The area under consideration is located in one of the most seismically active regions with the most damage and human casualties in recent history. Seismic losses were estimated at buildings, economic and human level. The estimation method is based on the assumption that seismic risk depends on vulnerability and seismic hazard. Vulnerability estimation was done by detailed fragility curves representing the structures in the area. Subsequently, losses in the wider area were estimated for various seismic risk scenarios. Parametric scenarios for different earthquake level and retrofit strategy were performed. The earthquake loss estimation software ELER (Earthquake Loss Estimation Routine) was used for the calculations. The numerical results extracted and their comparison with results from actual earthquake loss showed that losses can be estimated in the same order of magnitude as the real data and thus enable the state to be better prepared to deal with future earthquakes more effectively.

The use of QLARM to estimate seismic risk in Kirghizstan at the regional and city scales

An analysis of seismic risk using our tool QLARM has been performed for the Batken region including the cities of Aidarken and Kadamjay, 100 km SW of Osh. The damage to residential buildings and induced casualties has been estimated for a set of seismic scenarios of typical and maximum magnitude considering the existing seismicity data. Population and building datasets have been built based on up-to-date information, and for the two cities, satellite photographs and a field survey have been used. A preliminary soil response zonation is proposed using seismic ambient noise analyses. In the investigated region, the probability of damaging earthquakes with M > 6 is judged to be low because the slip accumulation rate along individual faults is only in the range of 0.01–0.3 cm/year. The amplification of seismic waves by soil deposits is estimated to be low; however, the proposed zonation needs to be complemented by additional seismic measurements. The calculations indicate that the combined fatalities of Kadamjay and Aidarken in a hypothetical earthquake of magnitude between 6.0 and 6.6 are fewer than 100.

Seismic vulnerability assessment methodology for historic masonry buildings in the near-field areas

Timisoara is the biggest city located in the Banat seismic area, the second most important seismic zone of Romania. The specificity of the area is represented by shallow earthquakes of crustal type, with small focal depths and a PGA = 0.20 g.Because Timisoara was declared the European Capital of Culture 2021, it is mandatory to assess the seismic vulnerability of its most sensitive areas and to design potential losses scenario. This study also provides useful data for the local authorities, helping them develop/improve the prevention and intervention plans.The paper focusses on the analysis of two historical urban districts, likely to be among the most attractive tourist areas. The study aims to assess the seismic vulnerability of the districts in a quick and simplified way, seeks to identify the exposure of the city, and also to provide losses statistics for a specific seismic scenario. The empirical seismic vulnerability assessment methodology is based on European studies and is applied for more than 100 historic buildings.Our assessment analysis aims to adapt the existing seismic assessment methodologies to the near-field earthquake’s effects. That is why a new formula is proposed to correlate the empirical vulnerability curves with the actual damage level. The real damage state was observed on similar historical masonry buildings during the site inspection and after the past earthquakes in nearby areas. Besides, a new failure mechanism is highlighted based on the investigation of the effects of previous near-field earthquakes in the Banat seismic region. The new methodology proposes original vulnerability curves, particularly for the near-field earthquakes specific to Banat seismic area.

Probabilistic assessment of an earth dam stability design using the adaptive polynomial chaos expansion

Assessment of the stability for an earth dam under seismic loadings is presented in a probabilistic framework. The geotechnical parameters measured at the dam site permit a realistic description of the soil variability for the dam and the superficial foundation. An active learning sparse polynomial chaos expansions (A-bSPCE) combined with Monte Carlo simulation is employed to quantify the uncertainty propagation. The proposed dam design is assessed within two seismic scenarios: the first one considers a constant pseudo-static acceleration while the second one accounts for the uncertainties in seismic loadings by modeling the pseudo-static acceleration as a random variable. The probabilistic assessments for variation of the amplitude and standard deviation of the seismic loading are performed. In addition, the effects of the correlation coefficient between the soil’s shear strength parameters and the soil spatial variability are discussed. It is found that these effects are more significant in the first scenario. The obtained results permit an evaluation of the preliminary dam design and to provide guidance on seismic safety enhancement for the final design phase. The present study also highlights the accuracy and efficiency of the employed reliability method. It is shown that the total computational time of a probabilistic analysis can be reduced from several days to only 20 min by using the A-bSPCE.

Seismic vibration suppression of a building with an adaptive nonsingular terminal sliding mode control

This study investigates the control performance of a structural building system during a seismic scenario using an adaptive nonsingular terminal sliding mode control. To realize the structural integrity of a building, it is necessary to equip the building with a structural control device. This research is focused on a hybrid control device that has excellent characteristics of passive and active control devices and implemented in a three degree-of-freedom system. The system, actuator, and controllers are designed by using the mathematical model developed in MATLAB/Simulink. The input excitation to the structure is taken from the El Centro earthquake that occurred in the 1940s with a magnitude of 6.9 Mw and the Southern Sumatra earthquake that occurred in 2007 with a magnitude of 8.4 Mw. Adaptive nonsingular terminal sliding mode control is the new proposed control strategy to be applied in structural control field is investigated in terms of controller performance in suppressing the vibrations, and then, compared with sliding mode control and fuzzy logic controller strategies. Sliding mode control is chosen to be compared with adaptive nonsingular terminal sliding mode control because of its advantages of robust performance, whereas fuzzy logic controller is chosen because of its intelligent control base. The effectiveness of the proposed controllers is evaluated based on the displacement response, performance indices, and the probability of building damage. The results have shown that the new proposed controller, an adaptive nonsingular terminal sliding mode control, reduced vibrations better and has superior performance compared with fuzzy logic controller and sliding mode control.

A near-fault vertical scenario earthquakes-based generic simulation framework for elastoplastic seismic analysis of light rail vehicle-viaduct system

This paper focuses on the rapid elastoplastic analyses of light rail vehicle (LRV)- benchmark viaduct system to different seismic scenarios considering the dynamic substructuring method (DSM). Combining the energy-variational principle with the vehicle-bridge interaction (VBI) system, a new framework of train-track system space dynamics is constructed. The present study has established the train-track-bridge coupled system (TTBCS) model, calculated the elastic-plastic seismic responses of the light rail transit bridge (LRTB) subjected to the combined effect of vertical and horizontal earthquakes. Considering three ground motion ensembles, i.e. pulse-like near-fault ground motions (NFGMs), non-pulse-like NFGMs, and far-field ground motions (FFGMs). Results indicate that the large vertical ground motions (VGMs) type NFGMs greatly impact the seismic response of the running safety of the LRV in the low-frequency band compared to the non-pulse-like NFGMs and FFGMs. The results underscore the significance of distinguishing velocity pulses of different types when selecting NFGMs for assessing the nonlinear dynamic response of the VBI system.

An improved method of Newmark analysis for mapping hazards of coseismic landslides

Abstract. Coseismic landslides can destroy buildings, dislocate roads, sever pipelines, and cause heavy casualties. It is thus important but challenging to accurately map the hazards posed by coseismic landslides. Newmark's method is widely applied to assess the permanent displacement along a potential slide surface and model the coseismic response of slopes. This paper proposes an improved Newmark analysis for mapping the hazards of coseismic landslides by considering the roughness and effect of the size of the potential slide surfaces. This method is verified by data from a case study on the 2014 Mw 6.1 (the United States Geological Survey) Ludian earthquake in Yunnan Province, China. Permanent displacements due to the earthquake ranged from 0 to 122 cm. The predicted displacements were compared with a comprehensive inventory of landslides triggered by the Ludian earthquake to map the spatial variation in the hazards of coseismic landslides using the certainty factor model. The confidence levels of coseismic landslides indicated by the certainty factors ranged from −1 to 0.95. A hazard map of the coseismic landslide was generated based on the spatial distribution of values of the certainty factor. A regression curve relating the predicted displacement and the certainty factor was drawn, and can be applied to predict the hazards of coseismic landslides for any seismic scenario of interest. The area under the curve was used to compare the improved and the conventional Newmark analyses, and revealed the improved performance of the former. This mapping procedure can be used to predict the hazards posed by coseismic landslides, and provide guidelines for decisions regarding the development of infrastructure and post-earthquake reconstruction.

Sea surface network optimization for tsunami forecasting in the near field: application to the 2015 Illapel earthquake

SUMMARYWe propose a method for defining the optimal locations of a network of tsunameters in view of near real-time tsunami forecasting using sea surface data assimilation in the near and middle fields, just outside of the source region. The method requires first the application of the empirical orthogonal function analysis to identify the potential initial locations, followed by an optimization heuristic that minimizes a cost-benefit function to narrow down the number of stations. We apply the method to a synthetic case of the 2015 Mw8.4 Illapel Chile earthquake and show that it is possible to obtain an accurate tsunami forecast for wave heights at near coastal points, not too close to the source, from assimilating data from three tsunameters during 14 min, but with a minimum average time lag of nearly 5 min between simulated and forecasted waveforms. Additional tests show that the time lag is reduced for tsunami sources that are located just outside of the area covered by the tsunameter network. The latter suggests that sea surface data assimilation from a sparse network of stations could be a strong complement for the fastest tsunami early warning systems based on pre-modelled seismic scenarios.

Reverse Engineering a Fully Collapsed Ancient Roman Temple through Geoarchaeology and DEM

ABSTRACT The imperial Temple at the ancient Roman site of Antiochia ad Cragum has been excavated and studied by an interdisciplinary team since 2005. The temple was found in a collapsed state. Since there were no full-height columns and wall segments left standing, the vertical dimensions of the structure were unknown. After detailed drawings and investigations, the original design of the façade, as well as the key dimensions of the Temple, were established. The cause of the collapse was another unknown. As there is documentation about major seismic events about 500 km to the east of this site during the 5th century, collapse due to earthquakes is highly likely. This paper has three important contributions: First, it is the first reveal of a scaled 3D structural representation of this collapsed Temple. Second, it uses unique interdisciplinary collaboration to determine whether seismic events could be the cause of the initial collapse of the Temple. Finally, it investigates the original Temple’s behavior under various forms of seismic loading through discrete element modeling. The results of these interdisciplinary investigations confirm an earthquake as a highly plausible cause of the initial collapse of this structure and demonstrate the complex behavior of the structure under various seismic event scenarios.

Seismic Hazard Analysis of Vadodara Region, Gujarat, India: Probabilistic & Deterministic Approach

ABSTRACT The seismic scenario of the peninsular India has been changed due to many devastating earthquakes in the past few decades. The present paper discusses the hazard analysis with deterministic and probabilistic approaches for Vadodara region. Homogeneous seismic catalogue has been prepared covering the longitude 68° E to 77° E and latitude 18° N to 26° N for the study region and seismotectonic model has been developed for the different moment magnitude range of the earthquake events. Four ground motion prediction relationships have been used to evaluate the peak ground acceleration value at rock level for the Vadodara region.

Probabilistic life-cycle seismic resilience assessment of aging bridge networks considering infrastructure upgrading

This paper presents a probabilistic framework for life-cycle seismic resilience assessment of aging bridges and transportation road networks subjected to infrastructure upgrade. The proposed framework accounts for the uncertainties in damage occurrence of vulnerable deteriorating bridges and restoration rapidity of the overall system functionality. The time-variant bridge fragilities and the damage combinations probability are evaluated considering different earthquake magnitudes and epicenter locations that define the seismic scenario. Traffic analyses are carried out to assess in probabilistic terms the network functionality profiles, the corresponding resilience levels, and a damage-based measure of life-cycle resilience. The effects of structural deterioration, seismic damage, and post-event repair actions under uncertainty are related to traffic restrictions applied over the network. The framework is applied to reinforced concrete bridges exposed to chloride-induced corrosion and simple road networks with a single bridge or two bridges in series under different earthquake scenarios. The effect of network upgrading is also investigated by adding road segments with a vulnerable bridge to strengthen the network connectivity and improve the lifetime system resilience. The results show the capability of the proposed resilience framework in quantifying the detrimental effects of structural deterioration at the network scale and the beneficial consequences of infrastructure investments, such as enhancing the network redundancy with the construction of an additional highway branch.

The investigation into the effect of consecutive earthquakes on the strongback bracing system

This paper examines a newly developed seismic-force-resisting system technically known as Strongback. To achieve improved seismic performance, this system combines characteristics of a traditional concentric braced frame (CBF) with a mast to form a hybrid system; the strongback system aims to promote uniform story drifts over the height of a structure. In seismically prone areas, structures are not always subjected to a single earthquake and they are likely to experience seismic events sequentially. Accordingly, this paper deals with design method as well as the nonlinear dynamic behavior of structures equipped with strongback system (SBS). In this regard, three buildings with 3, 6 and 12 stories configured in three diverse forms at the intersection of the braces to the beam were studied. For the sake of dynamic analysis, different earthquake records and 18 various consecutive seismic scenarios were accounted for. Finally, it is concluded that SBS can effectively deconcentrate deformations using the proposed design strategy and prevent the occurrence of the soft-story phenomenon.