Volume 4 Issue 2: December 2025

In February 2023, a devastating earthquake sequence struck southern Tü rkiye, marking one of the most destructive seismic disasters in the region’s modern history. The MW 7.8 mainshock, followed by several large aftershocks, produced catastrophic consequences, including extensive structural collapse, widespread ground failure, and severe liquefaction that collectively left millions displaced and caused tens of thousands of fatalities. The extraordinary intensity of the shaking was reflected in the recorded ground motion parameters, particularly spectral accelerations, which significantly exceeded the design thresholds stipulated in the Turkish Earthquake Code (2018). Such exceedances provide critical insights into the limitations of existing design provisions and underscore the urgent need to revisit seismic hazard and risk assessments. Field investigations documented severe manifestations of liquefaction, lateral spreading, and ground subsidence, especially in Holocene sedimentary basins where loose, water‑saturated soils amplified shaking and induced ground instability. Structural surveys further revealed recurring vulnerabilities in the built environment, including weak or soft‑story configurations, non‑ductile reinforcement, and inadequate foundation practices, all of which amplified damage levels. The disaster highlights the urgent need for stricter enforcement of seismic building codes, the integration of resilient design methodologies, and the deployment of technologies such as base isolation systems and energy‑dissipating devices to enhance structural safety. In addition, systematic performance audits and proactive urban planning are recommended to mitigate similar future catastrophes. This study integrates geological evidence with engineering perspectives, offering targeted strategies to strengthen earthquake preparedness and foster long‑term urban resilience across Tü rkiye’s high‑risk seismic zones.

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Lorca town (southeast Spain) is on the trace of the southwest-northeast Alhama de Murcia fault. This fault splits into several branches in Lorca, which are hidden under the urban area. Most of the branches were identified in excavation sites and deformed houses at the surface. The formerly hypothesized Alburquerque branch is here confirmed, with the discovery of two closely spaced faults in the 6 Selgas street excavation site. This branch, coated with fibrous gypsum, cut and verticalized middle Miocene lutites during the Plio-Quaternary, creating a breccia and fracture cleavage. It also produced surface rupture, disturbing both Late Antiquity burials and a XIII century red gravel unit, most probably accompanied by earthquakes in the town between the 5th century and the house construction date (1775 AD). The preserved southwest Aguado alley facade of that house appears nowadays bent, with the vertical edge of the dihedral angle located directly above the Alburquerque fault. This implied both 2.5° of rotation and 0.2 m of horizontal displacement in the southeast corner of the facade, along the last 250 years. Series disruption, breccia, fracture cleavage, surface rupture, and recent rotation, all features together suggest left-lateral oblique-slip action of the Alburquerque fault.

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The Wasatch Fault Corridor in northern Utah (USA) faces increasing seismic risks due to rising population density. V_s30 is a vital parameter for understanding how a site will respond to earthquake shaking; however, obtaining V_s30 can be costly or impractical because of infrastructure or access challenges. The horizontal-to-vertical spectral ratio (HVSR) enables rapid assessment, provided a relationship between V_s30 and the resonant frequency (f₀) of the shallow subsurface can be established. Previously surveyed V_s30 sites in the Provo segment of the Wasatch Fault Zone were measured with a three-component seismometer to obtain f₀. These sites are located on the hanging wall of the fault zone, within alluvial and lacustrine Quaternary sediments. For each of the 20 sites, ambient noise was recorded for 30 minutes and amplitude-frequency spectra computed for each component. A rubric was applied to select site results most suitable for analysis and forward modelling, based on uncertainty of f₀, uncertainty of H/V response, and peak quality. The H/V response was then derived for 15 selected sites. The strongest low-frequency peak identified the f₀, which ranged from 0.28 to 1.38 Hz. Experimenting with linear regression helps guide understanding of the potential for estimating V_s30 from HVSR in this region. 

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