Seismic risk analysis of high-speed railway bridges based on new seismic hazard model

The 2017 (Mw=5.3) and 2019 (Mw=5.0) Ayvacık earthquakes in northwestern Türkiye generated significant structural damage in rural settlements despite their moderate magnitudes. This study presents a comprehensive empirical damage assessment based on post-earthquake field surveys covering 4740 structures after the 2017 event and 288 structures after the 2019 event. Buildings were classified by structural type and damage grade. Results indicate remarkably high heavy damage ratios for rural masonry buildings. Following the 2017 event, 25.3% of residential buildings and 41.9% of agricultural structures were classified as collapsed or heavily damaged. Similar patterns were observed in 2019, where 43% of residential and 89% of agricultural buildings experienced heavy damage. The spatial distribution of damage reveals strong correlation with epicentral proximity and local site conditions. The findings highlight the structural vulnerability of non- engineered masonry buildings in rural Anatolia under moderate ground shaking levels (MMI V–VI). Damage ratios derived from this dataset provide valuable empirical input for regional vulnerability modeling and seismic risk assessment studies. The Ayvacık earthquake sequence demonstrates that moderate-magnitude earthquakes can produce disproportionately high damage in areas dominated by low-strength masonry construction and inadequate seismic detailing. This study contributes to the development of region-specific vulnerability parameters for rural building stock in western Türkiye and supports improved seismic risk mitigation strategies.

Photogrammetry of architectural heritage amid climate change and seismic risk: Adobe, rock, and brick structures in the Andes Mountain Range and plains of Mendoza, Argentina

Seismic failure analysis and risk assessment framework for masonry-slab arch bridges considering comprehensive seismic intensity measures

Seismic traffic risk assessment method for high-speed railway bridge networks based on multi-level running reliability

Seismic failure and risk estimation of reinforced concrete bridges considering fatigue and seismic intensity measures

Dynamic ensemble-learning model for seismic risk assessment of masonry infilled steel structures incorporating soil-foundation-structure interaction

Probabilistic seismic risk analysis models for building portfolios considering ground motion intensities and duration sequences

In seismic probabilistic safety assessment (SPSA), ongoing efforts to reduce core damage frequency (CDF) encounter fundamental limitations due to modeling saturation, epistemic uncertainties, and the diminishing contribution of extremely low-probability events. This paper introduces and develops the concept of "inherent CDF"-a residual risk floor that persists when further reductions in CDF become practically or physically unattainable despite best-estimate modeling and conservative design. Drawing from recent literature, regulatory philosophy, and structural fragility modeling, the paper synthesizes the rationale for formalizing this floor within seismic PSA methodology. A conceptual framework is proposed to identify, justify, and declare the inherent CDF based on hazard-fragility convolution, uncertainty bounds, and plateauing risk behaviour at high ground motions. The implications for licensing, risk-informed decision-making, and safety optimization are examined, along with potential extensions to multi-hazard PSA domains. This study advocates for the integration of residual risk acknowledgment into modern safety frameworks, providing a technically grounded and transparent foundation for defining acceptable seismic risk in nuclear power plants.

The Malta Horst is a NW-SE trending, 30 km-wide structural high situated on the southern Hyblean-Malta Plateau, which is an African continental indenter in collision with Eurasia. Sediments consist of a shallow marine carbonate platform succession (Mesozoic to Oligocene) capped by Miocene pelagic carbonates and marl. Utilizing seismic profiles, well data, and outcrop observations, this study provides the first description of kilometre-scale contractional structures within the horst and analyses the reactivation of normal faults by transcurrent movement under NW compression. The tectonic evolution of this foreland region is defined by five distinct phases (A through E), alternating between extension and compression. This cyclicity reflects the interplay between the migrating Calabrian Arc and the converging African craton. Initial NE-SW trending faults (Phases A and B) developed during the Late Oligocene to Early Miocene, coinciding with platform drowning. Following Tortonian uplift (Phase C), accelerated migration of the Calabrian Arc during Phase D triggered N-S extension, establishing the NW-SE and NE-SW normal faults that bound the Malta Horst. The neotectonic regime (Phase E) marks a return to dominance of the NW-directed compression by the African craton as the Calabrian Arc migration decelerated. This regional stress field has reactivated the NW-SE marginal normal faults through strike-slip motion. The combination of transcurrent drag and regional compression has inverted Phase A NE-SW normal faults into oblique reverse faults. These thrusts sole along a weak top Eocene evaporite décollement, producing a series of folds and inverted basins within 10 km of the horst's northeast margin. Onshore, these structures are manifest as en echelon, non-cylindrical, and doubly plunging folds that define the topography of Malta's northeast coast. These shear zone structures are thin-skinned deformations in Oligo-Miocene sediments controlled by thick-skinned, W-E transcurrent movement in the crust and Mesozoic sediments. Ongoing compression suggests an increase in seismic risk proximal to the Maltese Islands, with significant implications for local geohazard frequency and magnitude.

Estimating the level of earthquake-induced liquefaction settlements in shallow foundations is essential for assessing seismic risk and designing effective soil improvement strategies. Reliable predicting methods of vertical deformations and tilting in buildings founded on shallow liquefiable soils enable the development of seismic-resilient and cost-effective foundation solutions while supporting informed decision-making in earthquake insurance and mitigation planning. This study presents a comparative analysis of machine learning and deep learning models for classifying liquefaction-induced building settlements using a systematically compiled database of documented case studies. The dataset integrates building characteristics, geotechnical parameters, and seismic intensity indicators. Different kinds of resampling methods working at data level, cost-sensitive learning strategies, and algorithm-level advancements were studied in detail to treat extremely skewed class distribution. A SHAP-based feature selection method was applied as an extension to identify the most influential predictors, optimizing model efficiency without sacrificing predictive performance. Moreover, to improve classification reliability, dynamic threshold tuning and ensemble learning with weighted voting was employed. The result points out that data-driven feature selection and threshold optimization can better classify seismic damage, thus offering geotechnical earthquake engineering applications a methodology that is both interpretable and computationally efficient.

Background: Bangladesh is located within a seismically active region influenced by the interactions of the Indian, Eurasian, and Burmese tectonic plates, making the country vulnerable to potentially damaging earthquakes. Despite this geological risk, earthquake preparedness in Bangladesh has historically received limited attention, largely due to the country’s greater exposure to floods and cyclones and the absence of a catastrophic earthquake in recent decades. This relative seismic quiescence has contributed to low public risk perception and inadequate prioritization of earthquake-specific preparedness. In contrast, neighboring South Asian countries have experienced multiple devastating earthquakes, resulting in substantial mortality and a high burden of long-term disability.Materials and Methods: This article is a narrative review synthesizing existing evidence on earthquake risk and preparedness in Bangladesh, with emphasis on the role of Rehabilitation Medicine in disaster management. Relevant literature was identified through searches of PubMed, Google Scholar, and selected grey literature from national and international disaster management and health agencies. Search terms included earthquake, Bangladesh, South Asia, disaster preparedness, rehabilitation, and physiatry. Sources were selected based on relevance to seismic risk, injury patterns, rehabilitation needs, and disaster rehabilitation models, and findings were synthesized thematically. Formal systematic review procedures were not applied.Results: Evidence from South Asia consistently demonstrates that earthquakes result in significant long-term disability, predominantly due to musculoskeletal trauma, spinal cord injuries, and neurological impairments. However, current preparedness frameworks in Bangladesh insufficiently integrate rehabilitation services, workforce planning, and continuity of care across the disaster management continuum.Conclusion: Rehabilitation must be recognized as a core component of earthquake preparedness in Bangladesh. Systematic integration of physiatrist-led rehabilitation teams within disaster management systems is essential to reduce long-term disability, optimize functional outcomes, and strengthen national health system resilience against future seismic events.

Adjusting the local magnitude scale to match the regional tectonic characteristics is crucial to enhance studies focused on evaluating seismic risk and measuring seismic activity in geologically dynamic zones. In this study, we developed a local magnitude scale for Mongolia. Using the Mongolia earthquake catalog for the period from 2012 to 2019, we analyzed 261 earthquakes with magnitudes ˃3.5 that occurred within a 1000 km epicentral distance and were recorded by at least five broadband stations. The compiled data set includes 8616 horizontal peak amplitude measurements from 144 broadband stations. We performed a detailed linear regression analysis to develop the local magnitude formula in accordance with the guidelines of the International Association of Seismology and Physics of the Earth’s Interior. As a result, the new local magnitude formula is expressed as: M L =log10( A )+0.9287log10( R )+0.0012 R −1.66. In addition, we determined the correction factors S for each station.

Türkiye is a country at high seismic risk due to its location on active tectonic zones. Therefore, regional-scale studies to reduce earthquake risk are of great importance. In this study, the soil-geotechnical properties, existing building stock, settlement patterns, and historical earthquake records of the Saraydüzü district of Sinop province, located close to the North Anatolian Fault Zone, were examined in detail. Seismic hazard assessment, Vs(30)-based soil classification, building inventory analysis, and earthquake scenario modeling were performed during the analysis. ELER v3.0 software was used in scenario development, and the Erdik and Eren (1983) model was applied as an empirical attenuation relation specific to Turkish conditions. In the scenario developed based on the February 6, 2023, Kahramanmaraş-centered earthquake, calculations based on 14588 residences projected to suffer severe or collapsed damage indicate that approximately 1508 people could lose their lives, with a loss of life rate of approximately 10335 for every 100 structures. Using an injury/death ratio of 2.019 for the same earthquake, it was estimated that approximately 3044 people could be injured. Multiplying the total of 17197 moderately and severely damaged residences by the 2024 average household size of 2.61 people in Turkey and subtracting the number of deaths, it was determined that approximately 43377 people would be in need of shelter. In the second scenario, using the parameters of the August 17, 1999 Izmit Gulf Earthquake, the number of residences with severe/collapsed damage was calculated as 322. Applying a 26% loss of life ratio, it was estimated that approximately 84 people could lose their lives. Similarly, using an injury/death ratio of 2.515, it was determined that 211 people could be injured, and based on household size, approximately 3155 people would need shelter. The results demonstrate that medium-sized settlements can be as high a seismic risk as large cities, clearly demonstrating the importance of disaster preparedness in such regions. It is evaluated that these analyses, specifically conducted in Saraydüzü, will be instructive for other settlement areas with similar characteristics and will contribute to Türkiye's earthquake response processes at a local scale.

Paleolandslides, paleoshorelines and lacustrine sediment deformation structures in the midstream Tashkurgan River, Chinese Pamir and implications on regional seismic risk

Owing to the increasing frequency and magnitude of earthquakes, it is necessary to improve the seismic capacity of nuclear power plants (NPPs) by strengthening systems, structures, and components (SSCs). Seismic probabilistic safety assessment is a widely used method for evaluating seismic performance, but it often does not consider correlations between component failures. In this study, a method to enhance seismic safety by considering such correlations is proposed. First, a seismic risk model that includes failure correlations between components was developed. Then, key components that have a significant impact on seismic risk were identified through sensitivity analysis. Multiobjective optimization was performed using the strengthening cost and seismic risk as objective functions. The OPR1000, a Korean standard NPP model, was used for the case study because it is the most widely used reactor type in Korea. The multiobjective gray wolf optimizer was applied for the multioptimization. The results show that the key components were the same regardless of whether correlations were considered. However, when correlations were included, greater risk reduction was achieved with less strengthening. This is because the loss of essential power, which accounts for the largest portion of the seismic risk in OPR1000, is primarily structured with OR gates. These findings indicate that while the selection of important SSCs is not affected by the inclusion of correlations, incorporating them is crucial for accurate seismic risk assessment, enabling more effective strategies for seismic performance enhancement.

Fault-controlled magma pathways driving seismicity and eruption risk in Eastern Turkey

New Zealand, located along the boundary between the Pacific and Australian plates, is among the most seismically active regions in the world. In such an area, reliable short-term forecasting of strong aftershocks is essential for seismic risk mitigation. In this study, we apply NESTORE (NExt STrOng Related Earthquake), a machine learning probabilistic forecasting algorithm, to the New Zealand earthquake catalogue to evaluate the probability that a mainshock of magnitude Mm will be followed by an event of magnitude ≥ Mm − 1 within a defined space–time window. NESTORE uses nine features describing early post-mainshock seismicity and outputs the probability that a cluster is Type A (i.e., containing a strong aftershock) or not (Type B). We assess performance using two testing strategies: chronological training–testing splits and k-fold cross-validation and refine the training set using the REPENESE outlier-detection procedure. The k-fold approach proves more robust than the chronological one, despite changes in catalogue characteristics over time. Eighteen hours after the mainshock, NESTORE correctly classified 88% of clusters (75% for Type A and 92% for Type B; Precision = 0.75). Notably, the highly destructive 2010–2011 Canterbury–Christchurch sequence was correctly identified as Type A. These findings support the applicability of NESTORE for short-term aftershock forecasting in New Zealand.

Urban environments face heightened seismic risks due to dense infrastructure and population concentration. Traditional seismic methods often face significant practical limitations in cities due to space constraints, traffic disruption, and acoustic noise, necessitating reliable alternative geophysical approaches for fault screening. This study evaluates the efficacy and practical utility of the opposing-coils transient electromagnetic method (OCTEM) as an effective alternative to conventional seismic techniques for detecting shallow-fault-like resistivity signatures under complex urban electromagnetic noise. By employing dual coaxial coils with opposing currents, the OCTEM suppresses primary-field interference, enabling high-resolution imaging of subsurface structures at depths of 0–200 m. A case study in Tiancheng Chengyuan, Cangzhou City, China, demonstrates the OCTEM’s capability to reliably delineate stratigraphic interfaces and resistivity anomalies under challenging electromagnetic background conditions. Field data exhibited a mean square relative error of 4.01%, validating its data quality and measurement stability. The survey successfully identified stratigraphic continuity and localized heterogeneity features within the investigation zone. These results establish the OCTEM as a robust and efficient tool for urban fault screening, particularly in environments where traditional high-resolution seismic methods are impractical or economically unfeasible.

Romania is highly exposed to seismic risk, with significant implications for residential earthquake insurance and risk-transfer mechanisms, due to the Vrancea intermediate-depth seismic source and a vulnerable building stock. This paper presents a harmonised seismic exposure model for the Romanian residential sector, developed to support probabilistic seismic risk assessment and catastrophe modelling for (re)insurance applications. The model integrates official data from the 2021 Population and Housing Census with the nationally adopted RTC-10 structural typology, height classification, seismic code level, and standardised reconstruction cost indicators. The results indicate that nearly 70% of residential dwellings were constructed before 1990 under pre-code or low- to moderate-code seismic design provisions. Although individual houses dominate the dwelling stock, multi-family apartment buildings concentrate approximately 40% of the total residential replacement cost, particularly in urban areas. The total replacement cost of the residential building stock is estimated at approximately EUR 709 billion, exceeding values derived from global exposure models. Comparison with existing insurance coverage highlights a substantial protection gap between potential seismic losses and insured values. The proposed exposure model provides a transparent, nationally calibrated basis for seismic loss estimation, portfolio accumulation analysis, and evidence-based risk management in both engineering and (re)insurance contexts.