Search Results (183)

In this study, we analyzed the lithospheric seismic background of the Tianshan and adjacent areas by combining various geophysical methods (effective elastic thickness, time-varying gravity, apparent density, and InSAR), and explored the genesis mechanism of the Wushi Ms7.1 earthquake as an example, which led to the following conclusions: (1) The effective elastic thickness (Te) of the Tianshan lithosphere is low (13–28 km) and weak, while the Tarim and Junggar basins have Te > 30 km with high intensity, and the loads are all mainly from the surface (F < 0.5). Earthquakes occur mostly in areas with low values of Te. (2) Medium and strong earthquakes are prone to occur in regions with alternating positive and negative changes in the gravity field during the stage of large-scale reverse adjustment. It is expected that the risk of a moderate-to-strong earthquake occurring again in the vicinity of the survey area between 2025 and 2026 is relatively high. (3) Before the Wushi earthquake, the positive and negative boundaries of the apparent density of the crust at 12 km shifted to be approximately parallel to the seismic fault, and the earthquake was triggered after undergoing a “solidification” process. (4) The Wushi earthquake is a leptokurtic strike-slip backwash type of earthquake; coseismic deformation shows that subsidence occurs in the high-visual-density zone, and vice versa for uplift. The results of this study reveal the lithosphere-conceiving environment of the Tianshan and adjacent areas and provide a basis for regional earthquake monitoring, early warning, and post-disaster disposal. Full article

The Mw 7.8 Gorkha Earthquake of 25 April 2015 triggered over 25,000 landslides across central Nepal, with 4775 events concentrated in Gorkha District alone. Despite substantial advances in landslide susceptibility mapping, existing studies often overlook the compound role of post-seismic rainfall and lack robust spatial validation. To address this gap, we validated an ensemble machine learning framework for co-seismic landslide susceptibility modeling by integrating seismic, geomorphological, hydrological, and anthropogenic variables, including cumulative post-seismic rainfall. Using a balanced dataset of 4775 landslide and non-landslide instances, we evaluated the performance of Logistic Regression (LR), Random Forest (RF), and eXtreme Gradient Boosting (XGBoost) models through spatial cross-validation, SHapley Additive exPlanations (SHAP) explainability, and ablation analysis. The RF model outperformed all others, achieving an accuracy of 87.9% and a Receiver Operating Characteristic (ROC) Area Under the Curve (AUC) value of 0.94, while XGBoost closely followed (AUC = 0.93). Ensemble models collectively classified over 95% of observed landslides into High and Very High susceptibility zones, demonstrating strong spatial reliability. SHAP analysis identified elevation, proximity to fault, peak ground acceleration (PGA), slope, and rainfall as dominant predictors. Notably, the inclusion of post-seismic rainfall substantially improved recall and F1 scores in ablation experiments. Spatial cross-validation revealed the superior generalizability of ensemble models under heterogeneous terrain conditions. The findings underscore the value of integrating post-seismic hydrometeorological factors and spatial validation into susceptibility assessments. We recommend adopting ensemble models, particularly RF, for operational hazard mapping in earthquake-prone mountainous regions. Future research should explore the integration of dynamic rainfall thresholds and physics-informed frameworks to enhance early warning systems and climate resilience. Full article

Tall-pier girder bridges with fluid viscous dampers (FVDs) are widely used in earthquake-prone mountainous areas. However, the influence of higher-order modes and near-field earthquakes on tall piers has rarely been studied. Based on an asymmetric tall-pier girder bridge, a finite element model is established, and the parameters of FVDs are optimized using SAP2000. The higher-order mode effects on tall piers are explored by proportionally reducing the pier heights. The pulse effects of near-field earthquakes on FVD mitigation and higher-order modes are analyzed. The optimal FVDs can coordinate the force distribution among tall piers, effectively reducing displacement responses and internal forces. Due to higher-order modes, the internal force envelopes of tall piers exhibit concave-convex distributions. As pier heights decrease, the internal force envelopes gradually become linear, implying reduced higher-order mode effects. Long-period pulse-like motions produce the maximum seismic responses because the slender tall-pier bridge is sensitive to high spectral accelerations in medium-to-long periods. The higher-order modes are more easily excited by near-field motions with large spectral values in the high-frequency range. Overall, FVDs can simultaneously reduce the seismic responses of tall piers and diminish the influence of higher-order modes. Full article

On 22 May 2012, a magnitude Mw 5.6 earthquake struck the Pernik region of western Bulgaria, causing structural damage in nearby cities, including Sofia. This study assesses the seismic response of a six-story reinforced concrete building in central Sofia, utilizing real accelerogram data recorded at the basement (SGL1) and sixth floor (SGL2) levels during the earthquake. Using the Kanai–Yoshizawa (KY) model, the study estimates inter-story motion and assesses amplification effects across the structure. Analysis of peak ground acceleration (PGA), velocity (PGV), displacement (PGD), and spectral ratios reveals significant dynamic amplification of peak ground acceleration and displacement on the sixth floor, indicating flexible and dynamic behavior, as well as potential resonance effects. The analysis combines three spectral techniques—Horizontal-to-Vertical Spectral Ratio (H/V), Floor Spectral Ratio (FSR), and the Random Decrement Method (RDM)—to determine the building’s dynamic characteristics, including natural frequency and damping ratio. The results indicate a dominant vibration frequency of approximately 2.2 Hz and damping ratios ranging from 3.6% to 6.5%, which is consistent with the typical damping ratios of mid-rise concrete buildings. The findings underscore the significance of soil–structure interaction (SSI), particularly in sedimentary basins like the Sofia Graben, where localized geological effects influence seismic amplification. By integrating accelerometric data with advanced spectral techniques, this research can enhance ongoing site-specific monitoring and seismic design practices, contributing to the refinement of earthquake engineering methodologies for mitigating seismic risk in earthquake-prone urban areas. Full article

This study examines urban expansion, coastal erosion, and extreme wave events in Licantén, Maule Region, following the 2010 earthquake and tsunami. Using multi-source data—Landsat and Sentinel-2 imagery, ERA5 reanalysis, high-resolution Maxar images, UAV surveys, and the CoastSat algorithm—we detected significant urban growth in tsunami-prone areas: Iloca (36.88%), La Pesca (33.34%), and Pichibudi (20.78%). A 39-year shoreline reconstruction (1985–2024) revealed notable changes in erosion rates and shoreline dynamics using DSAS v6.0, influenced by tides, storm surges, and wave action modeled in R to quantify storm surge events over time. Results underscore the lack of urban planning in hazard-exposed areas and the urgent need for resilient coastal management under climate change. Full article

In earthquake-prone areas such as Tokyo, accurate estimation of bearing stratum depth is crucial for foundation design, liquefaction assessment, and urban disaster mitigation. However, traditional methods such as the standard penetration test (SPT), while reliable, are labor-intensive and have limited spatial distribution. In this study, 942 geological survey records from the Tokyo metropolitan area were used to evaluate the performance of three machine learning algorithms, random forest (RF), artificial neural network (ANN), and support vector machine (SVM), in predicting bearing stratum depth. The main input variables included geographic coordinates, elevation, and stratigraphic category. The results showed that the RF model performed well in terms of multiple evaluation indicators and had significantly better prediction accuracy than ANN and SVM. In addition, data density analysis showed that the prediction error was significantly reduced in high-density areas. The results demonstrate the robustness and adaptability of the RF method in foundation soil layer identification, emphasizing the importance of comprehensive input variables and spatial coverage. The proposed method can be used for large-scale, data-driven bearing stratum prediction and has the potential to be integrated into geological risk management systems and smart city platforms. Full article

This paper comprehensively reviews structural vibration control systems for earthquake mitigation in civil engineering structures. Structural vibration control is vital for enhancing the resilience and safety of infrastructure subjected to seismic activity. This study examines various control strategies, including passive, active, and hybrid methods, with a focus on the advantages of semi-active systems, which offer a balance of energy efficiency and adaptive capabilities. Semi-active devices, such as magnetorheological dampers, are highlighted for their ability to offer adaptive control without the high energy demands of fully active systems. The review discusses challenges like time delays, sensor placement, and model uncertainties that can impact the practical implementation of these systems. Experimental studies and real-world applications demonstrate the effectiveness of semi-active systems in reducing seismic responses. This paper emphasizes the need for further research into optimizing control algorithms and addressing practical challenges to enhance the reliability and robustness of these systems. It concludes that semi-active control systems are a promising solution for enhancing structural resilience in earthquake-prone areas, offering a practical alternative that strikes a balance between performance and energy requirements. Full article

This paper evaluates the time-dependent fragility and post-earthquake residual seismic performance of existing steel frame columns in offshore atmospheric environments. Based on experimental research, the seismic failure mechanism and deterioration laws of the seismic behavior of corroded steel frame columns were revealed. A finite element analysis (FEA) method for steel frame columns, which considers corrosion damage and ductile metal damage criteria, is developed and validated. A parametric analysis in terms of service age and design parameters is conducted. Considering the impact of environmental erosion and aging, a classification criterion for damage states for existing steel frame columns is proposed, and the theoretical characterization of each damage state is provided based on the moment-rotation skeleton curves. Based on the test and numerical analysis results, probability distributions of the fragility function parameters (median and logarithmic standard deviation) are constructed. The evolution laws of the fragility parameters with increasing service age under each damage state are determined, and a time-dependent fragility model for existing steel frame columns in offshore atmospheric environments is presented through regression analysis. At a drift ratio of 4%, the probability of complete damage to columns with 40, 50, 60, and 70-year service ages increased by 18.1%, 45.3%, 79.2%, and 124.5%, respectively, compared with columns within a 30-year service age. Based on the developed FEA models and the damage class of existing columns, the influence of characteristic variables (service age, design parameters, and damage level) on the residual seismic capacity of earthquake-damaged columns, namely the seismic resistance that can be maintained even after suffering earthquake damage, is revealed. Using the particle swarm optimization back-propagation neural network (PSO-BPNN) model, nonlinear mapping relationships between the characteristic variables and residual seismic capacity are constructed, thereby proposing a residual seismic performance evaluation model for existing multi-aged steel frame columns in an offshore atmospheric environment. Combined with the damage probability matrix of the time-dependent fragility, the expected values of the residual seismic capacity of existing multi-aged steel frame columns at a given drift ratio are obtained directly in a probabilistic sense. The results of this study lay the foundation for resistance to sequential earthquakes and post-earthquake functional recovery and reconstruction, and provide theoretical support for the full life-cycle seismic resilience assessment of existing steel structures in earthquake-prone areas. Full article

Research on the relationship between structural characteristics and vibration periods in concrete buildings is crucial to ensure the safety and efficiency of these structures, especially in earthquake-prone areas. This article aims to analyze and compare the impact of structural stiffness of different elements, such as beams, columns and shear walls, on vibration periods, through a systematic review of existing models and formulas in the literature, identifying their applications and limitations. The methodology used consists of a systematic review that integrates recent and relevant studies, providing a solid basis for analysis. The results indicate that an increase in the stiffness of structural elements can reduce vibration periods by 20–50%, implying a faster response to external forces. Even in low-rise buildings, the fundamental period can be reduced by 53% to 70%. These findings are significant for the design and construction of concrete buildings, as they suggest that incorporating rigid structural elements can improve seismic resistance and reduce the risk of damage. In addition, the research contributes to the field of structural dynamics by highlighting the need to integrate different methods of analysis and evaluation. It is recommended that engineers and architects adopt innovative approaches, such as the use of emerging technologies and monitoring methods, to improve damage detection and optimize structural design. Finally, it identifies areas where more research is required, suggesting that future studies should explore the interaction between structural characteristics and environmental conditions for a more complete understanding of the vibrational behavior of buildings. Full article

Vegetation restoration in seismically active regions involves complex interactions between geological hazards and ecological processes. Understanding the spatiotemporal patterns of vegetation recovery is critical for assessing disaster evolution, evaluating mitigation effectiveness, and guiding ecological resilience planning. This study investigates post-earthquake vegetation dynamics in the Chutou Gully watershed, located in the 12 May 2008 Wenchuan earthquake zone, using NDVI data from 2000 to 2022. Results reveal a sharp decline in vegetation cover following the earthquake, followed by a steady recovery trend, with NDVI values projected to return to pre-earthquake levels by 2030. Degradation was concentrated in debris flow channels, while more stable adjacent slopes exhibited stronger recovery. Over time, the area of poorly restored vegetation significantly declined, indicating increased ecosystem resilience. The findings highlight the need for site-specific ecological restoration strategies tailored to localized recovery conditions. This study provides valuable insights for disaster mitigation agencies, ecological planners, and local governments working in mountainous hazard-prone regions, and contributes to the long-term sustainability of ecosystems in disaster-prone areas. Full article

On 6 February 2023, two major earthquakes struck southeastern Türkiye along the East Anatolian Fault, causing widespread structural damage, including the partial collapse of the historic Habibi Neccar Mosque in Antakya. This study presents a simulation-based approach to rapidly assess the seismic vulnerability of this partially damaged historic masonry structure. Due to the complexity and urgent condition of such heritage buildings, a simplified finite element (FE) modeling methodology is employed to evaluate structural behavior and support immediate stabilization decisions. Response spectrum analysis is applied to simulate and interpret stress distribution and deformation patterns in both undamaged and damaged states. The simulation results highlight significant tensile stress concentrations exceeding 0.2 MPa at dome–arch joints and vaults—primary indicators of localized failures. Additionally, the analysis reveals increased out-of-plane deformations and the influence of soil amplification in the remaining walls, both of which further compromise the structural integrity of the building. The findings demonstrate that simplified FE simulations can serve as practical and efficient tools for early seismic assessment of historic structures, contributing to rapid decision making, risk mitigation, and cultural heritage preservation in earthquake-prone areas. Full article

From 1940 to the present, Turkish seismic standards for masonry building have gradually evolved, culminating in the performance-based TBEC (2018). Unregulated tenant expansions and informal construction, especially in rural areas, continue to be a significant cause of seismic risk despite developments in ring beam design, mortar categorization, and capacity-based criteria. This paper critically examines the structural flaws caused by such expansions in partly built unreinforced masonry homes, focusing in particular on areas of moderate-to-high seismicity. The research shows that occupant changes often ignore necessary seismic protections by means of post-earthquake field observations, comparative code analysis, and recorded failure patterns. Among them are wall slenderness ratios, ring beam continuity, and masonry unit and mortar quality checks. Common ensuing failures include corner disintegration, roof–wall separation, and diagonal shear cracking. Relying on qualitative analysis of reoccurring damage mechanisms seen during field investigations, the results come from post-disaster evaluations of 2568 masonry dwellings after the 2023 Kahramanmaraş earthquakes. This paper emphasizes a continual gap between seismic rules and informal building practice and contends that without official acknowledgment of owner-built changes, code efficacy stays constrained. These results are also of worldwide importance for earthquake-prone areas struggling to control informal or self-built buildings. Full article

Türkiye, a country that suffers significant structural damage from earthquakes, was struck by two major quakes on 6 February 2023, centered in Pazarcık (M_w = 7.7) and Elbistan (M_w = 7.6) in Kahramanmaraş. These earthquakes caused extensive damage and destruction to urban concrete structures, significantly contributing to the loss of life. Inadequate designs in columns, which are meant to maintain structural integrity and transfer forces, were a primary cause of the structural damage. This study provides information about these catastrophic earthquakes, focusing on the detailed examination of damages in reinforced-concrete (RC) columns. Structural analyses were conducted on a selected RC building, taking into account the primary causes of column damage: low-strength concrete and insufficient transverse reinforcement. Five different concrete classes and two transverse reinforcement spacing options were considered to analyze the impact of concrete strength. To address the exceeded shear forces in the columns, a fiber-reinforced polymer (FRP) wrapping method was employed for strengthening. Initially, a reinforcement analysis was performed on a single column that exceeded shear force limits, followed by strengthening applications on all columns exceeding the limit shear force. The results demonstrated that carbon fibers have a significant impact on the shear forces in columns. The conclusion of the research is that FRP increases the ductility of concrete columns, enabling them to withstand seismic forces more effectively. This is vital in ensuring the integrity of structures in earthquake-prone areas. Using FRP materials can also significantly reduce the carbon footprint associated with concrete construction by minimizing the need for maintenance and extending the lifespan of structures. FRP presents a sustainable and effective solution for addressing failures in reinforced concrete columns. Its unique properties not only enhance strength and durability but also significantly improve the resilience of structures against corrosion, seismic events, and overload conditions. Full article

Cities face growing challenges from climate change, including rising temperatures, extreme rainfall, and intensifying urban heat islands, resulting in significant socio-cultural costs. Urban areas are increasingly vulnerable to food insecurity during disasters, yet the potential of urban agriculture (UA) to address this challenge remains underexplored. This study focuses on Wellington, New Zealand (NZ), a region highly prone to earthquakes, to evaluate the role of UA in enhancing post-disaster food security. The study calculates vegetable self-sufficiency by mapping potential productive land, estimating vegetable yields, and assessing post-disaster food demands across multiple scenarios. Potential productive land was quantified using a reproducible GIS-based method, considering three soil-based UA types: private yards, communal gardens, and urban farms. Due to Wellington’s mountainous topography, slopes and aspects were used to select four land scenarios. Three yield scenarios were estimated using aggregated data from previous studies and cross-checked with local UA and NZ conventional farming data. Food demands were based on NZ’s recommended vegetable intake and three targeted population scenarios: the entire population, displaced populations, and vulnerable populations. Results indicate that potential productive land is primarily evenly distributed in the eastern part within the city boundary, accounting for 0.3% to 1.5% of the total area. Vegetable self-sufficient rates for Wellington through UA range from 3% to 75%, with higher rates for displaced and vulnerable populations. These figures significantly exceed the current self-sufficiency rate estimated in the authors’ preliminary research, indicating Wellington’s considerable potential to enhance post-disaster food security through expanding UA and promoting related initiatives. However, realizing this potential will require stronger policy support, integrating UA with urban planning and disaster preparedness. Full article

Conventional buildings made of reinforced concrete (r/c) or steel are practically encountered daily in common construction practice. Current regulations offer complete guidance on the seismic design and dimensioning of typical structures made of the same structural material throughout. Nevertheless, in the case of a structure constructed with r/c structural elements at the lower part and steel structural elements at the upper part, forming a so-called hybrid steel–r/c building is common. The present regulations do not address hybrid buildings in design or dimensioning. This study aims to fill this gap in the literature by comparing the seismic performance of 3D hybrid buildings to conventional r/c and steel buildings. Three sets of buildings are designed and dimensioned, namely r/c buildings, steel ones, and hybrid steel–r/c ones. The considered r/c, steel, and hybrid models are subjected to the same strong ground excitations using a nonlinear time history analysis, considering the potential impact of the excitation orientation. Especially for hybrid models, two limit interconnection conditions are dealt with, characterized here as a “fixed” or “fixed-pinned” support of the steel part upon the r/c one. Unitless parameters are selected to compare the seismic response diagrams to determine the most detrimental structural effect. The advantages and disadvantages of r/c, steel, and hybrid buildings are comparatively discussed in terms of seismic resilience, noting that a hybrid configuration provides a promising alternative for seismic performance compared to typical constructions, thus providing enhanced possibilities in structural design. The analysis results show that fewer structural failures occur for hybrid buildings compared to conventional ones when subjected to the same earthquake excitations. The findings suggest that hybrid buildings could be a viable solution for practical construction projects, particularly in seismic-prone areas. Full article