Seismic Vulnerability Research Articles

Development of Seismic microzonation for Rancaekek Sub-District using microtremor method

Abstract Rancaekek sub-district located in the Bandung Regency is geologically characterized by soft and loose sediment layers such as clays, silts, and sands associated with the old Bandung Lake. Due to the existence of the Sesar Lembang Fault, the Rancaekek area is also vulnerable to seismic disasters. To provide knowledge on seismic vulnerability, therefore, a seismic microzonation study was conducted at 25 locations in the Rancaekek area using the microtremor method. Based on the available microtremor measurement data, the seismic vulnerability of the Rancaekek sub-district varies from one area to another. Amongst other areas Northern part of Bojongloa, Northern part of Rancaekek Wetan and Northern part of Jelegong areas are the most vulnerable to seismic damage because these areas have low dominant frequencies with medium amplification zones, and low Vs30 values ranging from 90 to 127 m/s. Thus, any building and infrastructure development in these areas should follow the national building code to reduce damage due to earthquake shaking.

Seismic response and ambient vibrations of a Mediaeval Tower in the Mugello area (Italy)

AbstractThis paper describes the experimental campaigns on the Tower of the Palazzo dei Vicari in Scarperia, a village in the Mugello area (Tuscany) exposed to high seismic hazards. The first campaign was carried out from December 2019 to January 2020, and the Tower underwent the so-called Mugello seismic sequence, which featured an M 4.5 earthquake. Other ambient vibration tests were repeated in June 2021 and September 2023 when another seismic sequence struck the area near Scarperia. These tests aimed to characterise the Tower’s dynamic behaviour under ambient and seismic excitations and check the response of the Tower over time. The experimental results were then used to calibrate a finite-element model of the Tower and estimate its seismic vulnerability. Several numerical simulations were conducted on the calibrated model using the NOSA-ITACA code for nonlinear structural analysis of masonry buildings. The dynamic behaviour of the Tower subjected to a seismic sequence recorded in 2023 by a seismic station at the base was investigated by comparing the velocities recorded along the Tower’s height with their numerical counterparts. Furthermore, several pushover analyses were conducted to investigate the collapse of the Tower as the load’s distribution and direction varied.

Active tectonic evolution of two adjoining thrust sheets in the Indo-Myanmar fold-thrust belt, Northeast India

The active tectonic aspects of the Indo-Myanmar Range (IMR) have not yet been studied in detail in spite of the fact that it’s seismically active. In the present study qualitative and quantitative geomorphic analyses have been carried out to understand the active tectonic evolution of Nungba, and Barak-Makru thrust sheets (NBTS and BMTS) in the central part of IMR. The focus of the study is on understanding the active spatial growth pattern of adjacent thrust sheets in an evolving mountain range and providing baseline data for further detailed seismotectonic and seismic hazard vulnerability analyses. Drainage characteristics, disposition of landforms and statistical analyses of Normalized Steepness Index (ksn), Hypsometric Integral (HI) and Transverse Topography Symmetry Factor (T), computed for a total of 164 4th-order drainage basins, reveal that both of these adjoining thrust sheets are actively uplifting. Higher values of ksn (mode = 111) and HI (mode = 0.46) in NBTS suggest its faster uplift than the BMTS, which has comparatively lower values of ksn (mode = 56) and HI (mode = 0.43). Moreover, the northern parts of the both the thrust sheets are uplifting faster than their southern parts due to along-strike variations in the movement on their basal thrusts, as a result of which the NBTS has been south-southeastwardly down-tilting and the BMTS is south-southwestwardly down-tilting. The study reveals that both the adjacently lying NBTS and BMTS have almost the same spatial growth patterns that are mainly controlled by the movements on their basal thrusts.

Site Characterization and Shallow Shear Velocity through HVSR Measurements around the Hyderabad Metropolitan Region, India

ABSTRACT We investigate the site characterization and shallow shear velocity profiles from the analysis of the Horizontal to Vertical Spectral ratio (HVSR) around the Hyderabad metropolitan region (HMR), which falls under the southern Indian shield. This work uses both the ambient noise and microearthquake data to compute the HVSR, and additionally the Random Decrement technique to compute the HVSR of extracted Rayleigh waves. This study indicates comparable HVSR curves at each station with the three different datasets, from which we obtain the average dominant frequency (f0) and amplification value (A0). They are further used to calculate the seismic vulnerability index value (Kg). We observe that the value of f0 around the HMR is not fixed, but is varying in the range of 3.4 to 18 Hz, whereas the value of A0 is in the range of 1.7 to 12 approximately and Kg in the range of 0.16 to 1.68 approximately, with an exception of ∼ 33 at VKB (Vikarabad) station, which may be due to a local unconsolidated sub-surface structure. Based on the Diffused Field Assumption (DFA), we invert the average HVSR curves and average dispersion curves of Rayleigh waves, and provide the shallow shear velocity profiles up to 300 m, along with an approximate estimate of VS30 (in upper 30 m depth). The estimated VS30 values vary between 911 to 3143 m/s, falling under the classifications A and B (mostly Hard Rock and Rock type) of National Earthquake Hazards Reduction Program (NEHRP) (BSSC, 2001). However, our study shows some stations with shear velocity inversions at shallow depths within 300 m, indicating layers of low velocity, needing further study. In the absence of detailed near-surface findings, these findings are valuable inputs for geotechnical engineering studies and urban-city planning around the HMR, and emphasizes the effectiveness the HVSR method to determine sub-surface topography and/or unknown soil structures as an economical investigation viability.

Fragility Assessment of Single Concrete Pier and Pile-Soil Interaction Impact under Near and Far-Fault Earthquakes

Civil engineers face a significant challenge in assessing seismic vulnerability due to the complex of soil-pile-structureinteraction system. This research aims to evaluate the seismic vulnerability of individual piers under various seismicground motions. Factors like sand type, pile diameter, pier height, and mass placed were investigated for their impacton the seismic fragility of concrete piers. Using incremental dynamic analysis with a beam on a nonlinear Winklerfoundation model, the study compared the effects of near and far ground motions. Results from the dynamic analysisand fragility assessment demonstrated the effects of the parameters above-mentioned on the design of fragilitycurves, as well as its relationships to fundamental period of structural system.

Seismic Vulnerability Analysis of Multistorey Base Isolated RC Building

Seismic Vulnerability Analysis of Multistorey Base Isolated RC Building

Out-of-plane non-intrusive seismic retrofitting of in-plane damaged masonry infill through 3D printed recycled plastic devices

The current techniques used for strengthening existing buildings made out of masonry infilled frames are characterized by high impact on the daily internal activities, as people living or working in the building need to move out while the retrofitting activities take place.The seismic vulnerability of infilled concrete frames is related to their high stiffness that, being due to the presence of masonry infills, induces a very brittle failure mechanism. The available retrofitting techniques do not allow to decrease the frames stiffness without making demolitions, especially for what concerns the double layer infills, a typology that characterizes a large part of the Italian buildings built from 1970s. For such infills only traditional techniques are available, mostly lime/cement-based mortars strengthened with various fibers that increase the frame stiffness. This study proposes an innovative technique for the out-of-plane strengthening of masonry double layer infills. The system is based on a 3D printed system made of recycled plastic, placed between the two masonry layers composing the infill and acts: i) triggering preferential in-plane sliding surfaces for reducing stiffness and therefore damaging, ii) warranting out-of-plane stability avoiding the snap-through mechanism, iii) ensuring low environmental impact by using recycled materials and, iv) no disrupting the daily internal activities. The full scale out of plane test is carried out on an infill specimen previously damaged in the in plane direction, by using a hydraulic jack placed at mid-height of the infill. The experimental results are compared with analytical models available in literature combined with a model specifically developed for the resistant mechanism provided by the plastic devices. The obtained results suggest that plastic joints are effective in preventing instability and can be used as effective strengthening system for concrete frames with masonry infills.

A Brief Review of Vulnerability, Preparedness and Resilience Measures of Anticipated Istanbul Earthquake

This review examines the seismic vulnerability of Istanbul, a city uniquely positioned at the crossroads of Asia and Europe and exposed to significant earthquake risks due to the North Anatolian Fault (NAF). By synthesizing data on historical seismic events, urban development patterns, and current building and infrastructure resilience, the paper highlights the complexities of disaster management in a densely populated and rapidly growing metropolis. It critically evaluates the effectiveness of existing preparedness and mitigation strategies, including legislative frameworks, urban planning policies, and community-based resilience efforts. The review also identifies gaps in the current approach to earthquake risk reduction and suggests areas for improvement, emphasizing the need for an integrated, multi-sectoral approach to enhance the city's capacity to withstand and recover from future seismic events. The findings underscore the importance of proactive planning and the adoption of innovative technologies in building a resilient Istanbul.

Damage‐informed ground motion and semi‐empirical fragility assessment

AbstractCalibrating parametric fragility curves via empirical damage data is one of the standard approaches to derive seismic structural vulnerability models. Fragilities based on empirical data require the characterization of the ground motion (GM) intensity at the building sites in the area affected by the earthquake producing the observed damages. This is commonly conducted via ShakeMap, that is, a map of the expected values of a Gaussian random field (GRF) of the logarithms of a GM intensity measure conditional to magnitude, location, and possibly a set of recordings of the earthquake. Once that intensity and damage data at the same sites are available, the typical approach calibrates a two‐parameter fragility model. However, ShakeMap estimates are affected by uncertainty deriving from that of the GM model used to characterize it. Furthermore, such an uncertainty can be reduced by building damage data, which provide information on the shaking intensity at the sites where damage is observed. It is shown herein that if this uncertainty is not addressed, also considering the shaking information provided by damage, the estimates of the fragility parameters obtained using a median ShakeMap only can be biased, and a recommended maximum likelihood estimation procedure – which exploits the expectation maximization algorithm – is provided. These arguments are illustrated via an application considering damage data from the 2009 L'Aquila earthquake in central Italy.

Assessing seismic hazard and uncertainty in Büyükçekmece using ground motion simulations

This study presents a comprehensive seismic hazard assessment for Büyükçekmece, a district in Istanbul, Turkey, situated near the seismically active North Anatolian Fault (NAF). The study utilizes stochastic ground motion simulations with the validated EXSIM algorithm to understand the potential impact of medium to large-magnitude earthquakes (ranging from MW 6.3 to 7.42) on this vulnerable community. The research employs a site-specific approach, considering unique amplification factors for each location. By conducting 50 scenario-based simulations, the study assesses the seismic hazard, highlighting the importance of comprehending variations in ground motion, even when they are small, for a more precise hazard assessment. Furthermore, this study addresses the critical issue of uncertainty, particularly concerning stress parameters and hypocenter locations. The researchers demonstrate that variability in these factors can introduce substantial uncertainty in ground motion predictions. The study provides insights into the range of potential ground motion outcomes through probabilistic assessments involving multiple scenarios and stress drop values. Notably, the results indicate that ground motion levels vary with earthquake magnitudes and underscore the significance of accounting for this variability. This research emphasizes the seismic vulnerability of Büyükçekmece and the importance of accurate ground motion simulations, offering valuable insights for earthquake preparedness and mitigation efforts in the region.

Assembly Algorithms for Seismic Vulnerability Estimation in Confined Masonry Dwellings

Assembly Algorithms for Seismic Vulnerability Estimation in Confined Masonry Dwellings

Reliability-Based Seismic Safety Assessment of the Metropolitan Cathedral of Brasília

Recent destructive earthquakes in Turkey (2023) with devastating effects have reawakened the discussion about seismic activity in Brazil and the vulnerability of the Brazilian buildings. Despite the lower magnitudes, national records should not be disregarded, as earthquakes with a magnitude below five may still cause loss of life and property damage. The assessment of existing RC buildings allows us to understand the performance of a structure during an earthquake and the adoption of mitigating measures. This paper preliminarily investigates the seismic vulnerability of the Metropolitan Cathedral in Brasilia, which was recognized as a World Heritage Site by ONU in 1987. The Rapid Visual Screening (RVS) procedure has been adopted for qualitative vulnerability assessment through the guidelines of the Japan Building Disaster Prevention Association at the procedure updated in accordance with the Brazilian reality. This research examined the structure under horizontal acceleration defined by national seismic code, and various scenarios are assumed as time aging, structural irregularities, and the level of importance of the structure. In this study, the Monte Carlo simulation is carried out to evaluate the level of safety. A performed analysis has shown that the examined building possesses the seismic capacity required against the expected earthquake motions. Even with reliability analysis, the structure achieves an acceptable level of safety. The results highlight the importance of a probabilistic approach to make reliable decisions on the conservation and rehabilitation of architectural heritage buildings.

Dynamic response and seismic vulnerability assessment of the near-fault steep slope

Existing field data demonstrates that structures situated near faults, such as slopes, dams, and bridges, are particularly vulnerable to damage. Near-fault ground motions exhibit marked disparities from their far-field counterparts, necessitating thorough investigation. This study conducts a comprehensive analysis of ground motion characteristics utilizing response spectra, Hilbert-Huang Transform (HHT), and marginal spectra to discern near-fault pulse-like ground motions (PLGMs), near-fault non-pulse-like ground motions (NPGMs), and far-fault ground motions (FFGMs). PLGMs distinguished by their heightened energy content, typically induce more pronounced amplification effects compared to NPGMs and FFGMs. Employing an efficacy criterion, optimal intensity measures (IMs) are identified and linked to dynamic response, referred to as engineering demand parameters (EDPs). Velocity-based IMs demonstrate substantial correlations across diverse ground motion types for both plastic volume ratio (PVR) and crest displacement (Dc). Lastly, probabilistic seismic demand models are leveraged to establish seismic vulnerability curves for steep slopes exposed to PLGMs and NPGMs. Notably, with Dc as the EDP, the exceedance probabilities associated with the three IMs under PLGMs generally surpass those under NPGMs. This underscores the propensity of PLGMs to trigger larger displacements in slopes, rendering them more prone to failure.

Seismic fragility of unbraced industrial steel pallet racks

Past Italian earthquakes revealed the high seismic vulnerability of steel pallet racks designed for gravity loads only, which are still the most widespread industrial storage system. This study aims to derive the seismic fragility of these structures to enable more refined estimates of enterprise risk and the definition of effective retrofit solutions. For this purpose, 3D non-linear models of 27 unbraced pallet racks, representative of the Italian context, were analysed in Time-History under 268 bidirectional events, representative of Italian seismicity. Multiple fragility models were then derived, based on various engineering demand parameters and seismic intensity measures, through a cloud approach.

Investigation of Structural Seismic Vulnerability Using Machine Learning on Rapid Visual Screening

Seismic vulnerability assessment is one of the most impactful engineering challenges faced by modern societies. Thus, authorities require a reliable tool that has the potential to rank given structures according to their seismic vulnerability. Various countries and organizations over the past decades have developed Rapid Visual Screening (RVS) tools aiming to efficiently estimate vulnerability indices. In general, RVS tools employ a set of structural features and their associated weights to obtain a vulnerability index, which can be used for ranking. In this paper, Machine Learning (ML) models are implemented within this framework. The proposed formulation is used to train binary classifiers in conjunction with ad hoc rules, employing the features of various Codes (e.g., the Federal Emergency Management Agency, New Zealand, and Canada). The efficiency of this modeling effort is evaluated for each Code separately and it is clearly demonstrated that ML-based models are capable of outperforming currently established engineering practices. Furthermore, in the spirit of the aforementioned Codes, a linearization of the fully trained ML model is proposed. ML feature attribution techniques, namely SHapley Additive exPlanations (SHAP) are employed to introduce weights similar to engineering practices. The promising results motivate the potential applicability of this methodology towards the recalibration of the RVS procedures for various types of cases.

Spatial mapping of the seismic vulnerability index in Kathmandu Valley: insight from dominant frequency and amplification factor

Abstract Kathmandu Valley situated in Nepal has experienced several earthquakes in the past. The expanding population of Kathmandu Valley is driving a significant acceleration in building construction reaching record levels and posing risks to both human lives and the economy, despite this surge in development. This study aimed to spatially map the dominant frequency, amplification factor, and vulnerability index map of Kathmandu Valley, Nepal using ArcGIS. This paper presents the nonlinear response analysis of 225 boreholes using the Gorkha earthquake as input motion and DEEPSOIL software for determining the amplification ratio and dominant frequency. The results revealed a range of values for dominant frequency from 0.08 to 7.65 Hz and soil amplification ratio from 0.13 to 8.14. Furthermore, the seismic vulnerability index was derived from the dominant frequency and soil amplification ratio ranging from 0.22 to 21.84. The resulting maps acquired through this study enable the decision-makers and stakeholders, to prioritize resources and implement targeted measures for enhancing seismic resilience in the region.

Seismic vulnerability assessment of Venetian façades and artistic assets: Historical Digital Twin approach

The seismic vulnerability assessment of monumental façades and of their valuable artistic assets, along with considerations for protection and valorisation, requires the development of an integrated, multidisciplinary procedure able to enhance the accessibility, promotion and management of cultural heritage as well as to effectively model and simulate the structural performances of each artistic element. The multi-step methodology presented in this paper starting from an advanced survey and an appropriate tridimensional (3D) restitution, leads to the development of an Historical Digital Twin useful to create a detailed finite element model able to carry out structural simulations of both the historic façade and the artistic assets. To illustrate this methodology, the paper delves into a real case study involving a typical Venetian monumental façade, focusing on the seismic vulnerability assessment of two statues located at different levels. Emphasis is given to the importance of the 3D models to support vulnerability analysis, and to evaluate the seismic action at the points of the façade where the statues are placed. To this aim different methods are used and compared, showing on the one hand a strong dependence of the amplification of the seismic acceleration on earthquake frequency content and on the other hand the precautions to take using design-oriented predictive formulations.

Prediction of local site influence on seismic vulnerability using machine learning: A study of the 6 February 2023 Türkiye earthquakes

This study uses machine learning to analyze local seismic features' influence on damage from the 6 February 2023 Türkiye Earthquakes.The input features include Vs30 (the average shear wave velocity to a depth of 30 m), f0 (the predominant frequency of the site), A0 (HVSR ratio for the site), and EBd (engineering bedrock depth), along with the target feature of damage status for 44 locations. Machine learning involves Random Forest (RF), K-nearest Neighbor (KNN), Logistic Regression (LR), Decision Trees (DT), Support Vector Machines (SVM), Stochastic Gradient Descent (SGD), and Multilayer Perceptron (MP) algorithms. Also, five-fold cross-validation is employed to acquire suitable hyperparameters, enhancing its efficacy in modeling small sample sets. RF emerged as the most effective in whole performance metrics, presenting recall scores for damage and no damage conditions respectively by a 94% and 92% ratio and achieving a damage status prediction accuracy of 93%. All remaining algorithms also exhibited remarkable performance, reaching a minimum accuracy of 89% by DT, and recall score for no damage condition with 80% by MP and damage condition with 88% by SVM and SGD. The outcomes definitively designate EBd as the most crucial parameter, attributing 52% importance to its role in building damage occurrence within the study area. In contrast, significance values were determined as 24%, 18%, and 6% for f0, Vs30 and A0 respectively. These findings underscore the importance of demonstrating that initial damage estimation in high seismic hazard zones can be effectively carried out using machine learning approaches through seismic-based local site parameters.

Impact of the soil-foundation-structure interaction in the seismic behaviour of a heritage masonry tower: The Giralda of Seville

The seismic safety of heritage buildings may be affected by the interaction between the soil, the foundation and the structure, which is usually neglected in conventional seismic assessments. These factors are particularly important in the case of slender constructions, such as masonry towers, over soft strata. Hence, this work deals with the influence of the soil-foundation-structure interaction in the seismic behaviour of complex heritage masonry towers. The investigations have been carried out considering the case study of the Giralda tower in Seville, Spain. The region is an earthquake-prone area, characterised by far away very large earthquakes with long-return periods. The Giralda tower is a slender brick unreinforced masonry tower, 95 m high and about 13 m wide. It features a high artistic value and popularity as it has been the historical symbol of the city. It was declared a UNESCO Word Heritage Site of Outstanding Universal Value in 1987. Apart from its slenderness, the tower presents some other seismic vulnerabilities: openings irregularities, material heterogeneity and the position of a belfry on the top. Furthermore, the building is placed on soft alluvial strata and has a shallow foundation. Likewise, the tower has a considerable weight, which has caused large settlements. A thorough evaluation of the soil, the foundation and the structure has been carried out to develop a complex and detailed finite element model. Macro mechanical elements and the direct method have been used to develop the numerical model of the tower in the OpenSees framework. Free ambient vibration tests and non-destructive experiments have been used to calibrate the model. Its dynamic behaviour has been evaluated considering the seismic action suggested by the Spanish Code and those determined through a seismic response analysis, bearing in mind different return periods and considering real ground motions. Finally, the numerical results showed that the effect of the soil and the foundation have a significant impact on the seismic behaviour of the bell tower, amplifying the acceleration and its damage at the top.

Integrated study on buried pipelines, co-seismic landslides, and magnitude conversion for 2023 Türkiye earthquake

Türkiye is known for its intricate tectonic structure and high seismic activity, which makes in-depth research on earthquakes necessary. This research paper presents a multifaceted examination of earthquake impact in Türkiye, encompassing critical elements of seismic vulnerability with a special focus on the latest twin earthquake of February 6, 2023. Firstly, a three-dimensional finite element (FE) analysis has been conducted to explore the buried pipeline behavior under left-lateral strike-slip faults. Secondly, making use of the earthquake data from 1976 to 2023, a new Newmark displacement-based model has been proposed which predicts co-seismic landslide displacement. Finally, new magnitude conversion relations are developed in the generalized moment magnitude scale (Mwg) for Türkiye using three statistical regression techniques. The maximum tensile strain was found to be around 2.0% based on the findings of the 3D numerical study of an underground pipe that was subjected to left-lateral strike-slip fault movement. The proposed co-seismic landslide displacement model was developed based on moment magnitude, yield acceleration, and peak ground acceleration, which yields an R-squared value of 0.93. Outcomes of the magnitude conversion study depicted that the improved general orthogonal regression (IGOR) relationships developed in this study performed better than the other conventional methods of regression. Also, the proposed regional relations based on Mwg scale perform better than global relations as they provide closer values to the observed ones. By offering a comprehensive perspective on seismic impact, the research lays the groundwork for upgraded predictive methods and refined seismic design considerations. The proposed models and conversion relations contribute to the strengthening of critical infrastructures, providing a forward-looking approach to enhance preparedness and resilience against earthquake disasters in Türkiye.