The study, published in Frontiers in Environmental Science, began with a 30-meter-resolution ASTER digital elevation model and built every thematic layer from scratch within ArcGIS Pro. The researchers derived slope and landform maps from the elevation data, produced a drainage density map by modeling flow direction and drainage networks, and estimated groundwater depth by overlaying soil, precipitation, and drainage intensity data. Because high water tables increase the fluidity of loose alluvial sediments, groundwater depth was included as a proxy for liquefaction potential, the phenomenon in which saturated soil temporarily loses its strength and behaves like a liquid during strong shaking. Active fault maps and a catalog of historical earthquakes with magnitudes greater than 3.0, retrieved from Turkey’s disaster management agency AFAD for the period 2000 to 2025, completed the dataset.

At the heart of the analysis lies the Analytic Hierarchy Process, a multi-criteria decision-making framework developed by Thomas Saaty that breaks complex problems into pairwise comparisons. Experts in seismotectonics, geomorphology, GIS, and disaster management judged the relative importance of each risk factor on Saaty’s nine-point scale, and the judgments were aggregated using the geometric mean method. The resulting weights were then applied to the spatial layers through weighted overlay analysis to produce the final earthquake risk map. A consistency ratio of 0.0324 confirmed that the expert judgments were internally coherent, well below the 0.10 threshold that AHP methodology requires for scientific validity.

The two dominant factors shaping earthquake risk in Çemişgezek turned out to be distance from fault lines, which accounted for 39.53 percent of the total risk weighting, and lithology, the rock and soil type underlying the surface, which contributed 30.41 percent. Together these two criteria explain nearly 70 percent of the overall seismic threat. Groundwater potential carried a weight of 17.98 percent, while slope contributed 12.08 percent. The findings underscore a fundamental principle of seismic hazard assessment: where a structure sits relative to an active fault, and what kind of ground it stands on, matter far more than the steepness of the terrain or the amount of rainfall the area receives.

When the weighted overlay was complete, the risk map revealed a district divided into five classes. Very low-risk terrain covers 17.87 percent of the district’s 821 square kilometers, while low-risk areas encompass 43.92 percent. Medium-risk zones account for 36.74 percent, high-risk areas for 1.34 percent, and very high-risk zones for a mere 0.07 percent, equivalent to just one square kilometer. That single square kilometer of extreme danger clusters around the villages of Tekeli and Cihangir, where the active fault line runs directly beneath the settlements and where the highest-magnitude earthquakes in the regional record have been recorded. The alignment between the model’s predicted hot spots and the historical earthquake catalog provides strong validation of the approach.

By contrast, 61.81 percent of the district falls into the low or very low risk categories, largely because it lies far from the active fault segments and rests on geologically older, more consolidated formations. The town center of Çemişgezek itself sits within the low and medium risk classes. This spatial concentration of hazard presents both a challenge and an opportunity for planners: rather than distributing limited resources uniformly across the entire district, disaster management equipment, structural reinforcement programs, and emergency preparedness initiatives can be targeted precisely at the small but critical corridor where the fault line passes.

Yet the researchers emphasize that physical hazard is only part of the story. Çemişgezek’s population has declined steadily over recent decades, with rural villages emptying faster than the district center, leaving behind an aging population with reduced physical mobility and diminished capacity for self-organized emergency response. Many buildings in the district are old, poorly maintained, and constructed without modern seismic engineering standards. The ferry line crossing the Keban Dam Lake, which serves as the region’s primary connection to the outside world, passes through high-risk geological units, meaning that a significant earthquake could sever the district’s only transportation link and leave residents isolated from external aid.

The study frames earthquake risk not as a purely tectonic phenomenon but as a socio-spatial vulnerability shaped by the interaction of natural conditions and demographic change. Continuous emigration of younger residents has eroded local economic investment and institutional capacity, while the remaining elderly population is less able to evacuate or rebuild after a disaster. The researchers argue that effective risk reduction requires a combination of measures: relocating new settlements to safer ground, reinforcing existing structures in the high-risk corridor, raising public awareness of earthquake hazards, and developing alternative evacuation routes, including helicopter landing areas and water-based transport options, to compensate for the district’s dependence on a single vulnerable crossing.

The methodology has clear limitations. The model relies on open-access data with a spatial resolution that limits micro-level accuracy, and it does not incorporate building-level structural parameters such as construction age, number of floors, or load-bearing materials. Seismic engineering parameters like peak ground acceleration and Vs30 shear-wave velocity measurements were also absent. The researchers acknowledge that the resulting map is better described as a physical susceptibility assessment than a comprehensive risk model, and they recommend that future work integrate dynamic datasets, building inventories, and machine learning approaches to refine predictions further.

Nevertheless, the Çemişgezek study offers a replicable template for other small, isolated districts across Turkey and beyond. By demonstrating that earthquake risk can be spatially quantified with freely available satellite data and a transparent weighting procedure, the research provides local governments with a practical decision-support tool aligned with the United Nations Sustainable Development Goal 11 on sustainable cities and communities. The message is clear: even in places far from major population centers, the ground beneath one’s feet can be mapped, measured, and planned for, long before the next earthquake arrives.

Subject of Research: GIS-based multi-criteria earthquake risk assessment in Çemişgezek District, Tunceli, Türkiye

Article Title: Multi-criteria GIS analysis of earthquake risk and spatial resilience in Eastern Anatolia

Article References: Engin, F., Giyik, C., Şengün, M. T., & Kaya, A. Y. (2026). Multi-criteria GIS analysis of earthquake risk and spatial resilience in Eastern Anatolia. Frontiers in Environmental Science, 14, Article 1800445. https://doi.org/10.3389/fenvs.2026.1800445

Image Credits: AI Generated

DOI: 10.3389/fenvs.2026.1800445

Keywords: earthquake risk, GIS, AHP, Çemişgezek, Tunceli, fault proximity, lithology, liquefaction, disaster planning, spatial analysis, Eastern Anatolia, risk mapping

The research, carried out by Muqit Ajmain Shahriyar of the Department of Geology and Mining at the University of Rajshahi, pits two established techniques against each other across the same landscape. The first is Probabilistic Seismic Hazard Analysis, or PSHA, the quantitative backbone of modern building codes worldwide. PSHA treats earthquakes as a statistical problem: it combines a catalogue of past events, a recurrence relationship describing how often quakes of each size occur, and an equation predicting how strongly the ground will shake at a given distance from a rupture. The second approach is the Analytic Hierarchy Process, or AHP, a multi-criteria decision-making method that weighs contributing factors, such as fault proximity and geological conditions, against one another to produce a susceptibility ranking. Because the two methods rest on entirely different assumptions, agreement between them carries real weight.

The probabilistic half of the study was built on a grid-based framework covering the entire corridor from Sylhet to the Chittagong hill districts. Shahriyar compiled a regional earthquake catalogue and fitted it with a Gutenberg-Richter recurrence analysis, the classic logarithmic relationship that links the frequency of earthquakes to their magnitude. Ground shaking was then estimated using the Ground Motion Prediction Equation developed by Sharma and colleagues in 2009, which draws on strong-motion data from the Himalayan and Zagros regions, tectonic environments broadly comparable to Bangladesh’s. The analysis was run for two standard hazard levels: a 10 percent probability of exceedance in 50 years, corresponding to a return period of roughly 475 years, and a more stringent 2 percent probability, corresponding to roughly 2,475 years, the level typically used for critical infrastructure design.

The numbers that emerged are striking. At the 475-year return period, predicted peak ground acceleration values range from 0.084 g to 1.53 g across the study area, where g is the acceleration due to gravity. At the 2,475-year level, the range widens to between 0.10 g and 1.89 g. For context, shaking above roughly 0.2 g is generally strong enough to cause damage to vulnerable buildings, and values approaching 1 g and beyond imply violent ground motion capable of devastating even well-constructed structures. The upper end of these estimates is concentrated in a specific location: Barkal Upazila in Rangamati District, in the Chittagong Hill Tracts, emerges from the PSHA as the single highest seismic hazard zone in the entire study corridor.

Barkal does not stand alone. The probabilistic maps also flag elevated hazard across surrounding parts of Rangamati, as well as in Chandpur, Cumilla, Sylhet, and Moulavibazar. This spatial pattern reflects the geometry of the underlying fault systems, particularly the active structures of the Tripura Fold Belt and the Chittagong-Tripura Boundary Fault, which thread through the region and accumulate strain as the plates continue their slow collision. The hazard values are not predictions of when an earthquake will strike, but statements about the level of shaking that has a defined probability of being exceeded within a given window of time, a distinction that matters greatly for engineers and planners who must translate the numbers into design requirements.

The second half of the study took a different route to the same question. Using the Analytic Hierarchy Process, first formalized by mathematician Thomas Saaty in the 1970s, the assessment assigned relative weights to the factors that control seismic susceptibility and combined them into a single index for each location. The AHP-based susceptibility map shows a distribution that is broadly comparable to the PSHA result but with subtle differences in where the highest categories fall. In this model, high-susceptibility zones cluster in parts of Sylhet, Sunamganj, Moulavibazar, Feni, Cumilla, and Chittagong. The differences between the two maps are instructive: PSHA is driven primarily by earthquake recurrence and ground-motion physics, while AHP responds to the weighted combination of susceptibility criteria, so each method illuminates aspects of the hazard picture the other may understate.

Where the two approaches overlap is where the findings become most consequential. Sylhet, Moulvibazar, Sunamganj, Chandpur, Cumilla, Rangamati, and Chittagong are all identified as areas of elevated seismic potential by both methods independently. That convergence is significant because these are not empty hinterlands. Sylhet and Chittagong are major urban centers with rapidly growing populations and building stocks of widely varying quality, and the intervening districts contain millions of residents. When two techniques with different theoretical foundations point to the same places, the case for prioritizing those areas in seismic risk mitigation and land-use planning becomes difficult to ignore.

The study arrives at a moment when Bangladesh’s seismic exposure is drawing increasing scientific attention. Previous work has applied the Gutenberg-Richter relationship and spectral analysis to national seismicity, updated probabilistic hazard assessments for the country as a whole, and used GIS-based AHP methods to assess earthquake risk in other tectonically active regions, such as Bitlis Province in Türkiye. The comparative approach taken here adds a layer of robustness that single-method studies cannot provide. It also highlights a practical challenge for a country whose building codes have been revised to address geotechnical earthquake engineering concerns: hazard maps are only useful if they are trusted, and demonstrating that independent methods converge on the same high-risk zones helps build that trust among the officials who must act on them.

For residents of the region, the practical message is that the earthquake threat is not evenly distributed, and the areas of greatest concern are now mapped with two independent lines of evidence. The highest modeled shaking, approaching 1.9 g in the most extreme scenario, is centered on the hill tracts of Rangamati, while a broad band of elevated hazard runs through the Sylhet region and the central districts along the fold belt. Translating these hazard levels into safer communities will require region-specific mitigation measures, from enforcing seismic design provisions in new construction to retrofitting vulnerable buildings and steering future development away from the most susceptible ground. The study’s author notes that the data generated and analyzed are available from the corresponding author upon reasonable request, and the work was carried out with academic support from the Department of Geology and Mining at the University of Rajshahi, without external funding. As the plates beneath Bangladesh continue their inexorable convergence, maps like these, tested against each other and grounded in decades of seismological theory, offer one of the few tools available for looking ahead to the next great earthquake before it arrives.

Subject of Research: Comparative seismic hazard and susceptibility mapping in northeastern to southeastern Bangladesh

Article Title: Comparative seismic hazard assessment using PSHA and AHP-based susceptibility mapping in northeastern to southeastern Bangladesh

Article References: Shahriyar, M. A. (2026). Comparative seismic hazard assessment using PSHA and AHP-based susceptibility mapping in northeastern to southeastern Bangladesh. Bulletin of Earthquake Engineering. https://doi.org/10.1007/s10518-026-02672-w

Image Credits: AI Generated

DOI: 10.1007/s10518-026-02672-w

Keywords: seismic hazard, PSHA, Analytic Hierarchy Process, Bangladesh, peak ground acceleration, Gutenberg-Richter, ground motion prediction, Dauki Fault, Chittagong-Tripura Boundary Fault, Sylhet, Rangamati, earthquake risk

The project, titled Earthquake Risk Assessment of the City of Zagreb, was conceived in 2014 but only approved and funded two days after the March 2020 earthquake. Researchers from the University of Zagreb Faculty of Civil Engineering, working with the Croatian Centre for Earthquake Engineering, city departments, seismologists, geologists and geotechnical experts, carried out the work between 2021 and 2023 as part of a broader EU-financed aerial survey programme for disaster risk reduction. The team describes the initiative as a pilot intended to serve as a template for earthquake risk assessments across Croatia and as a foundation for changes to national regulations expected in 2026.

Zagreb’s hazard profile is serious. The city lies along the southeastern edge of Medvednica mountain, and its seismic threat comes mainly from the Medvednica epicentral area, particularly two seismogenic sources: the Reverse Northern Medvednica boundary fault and the nearly perpendicular Kašina strike-slip fault. Historical records recall the Great Zagreb earthquake of 1880, assessed at magnitude 6.1, whose epicentre lay very near the 2020 event and which caused widespread damage and emigration. The official Croatian hazard map assigns the city area a reference peak ground acceleration on rock of 0.20 to 0.28 grams for a 475-year return period, and investigations so far indicate that Eurocode 8 ground types B and C predominate, although a full seismic microzonation of the city remains unfinished.

The greatest technical achievement of the project, according to its authors, was the creation of a comprehensive geographic information system building inventory database. Croatia has no national building registry, so the team overlapped three official data sources: the Digital Cadastral Plan, the Register of Spatial Units and the Existing Land Use 2020 dataset. Of more than 300,000 objects examined, roughly 230,000 proved to be buildings and auxiliary structures, while about 70,000 were stairways and terraces that were excluded. Engineers then collected 35 required attributes for each building, covering geographic position, site category, year of construction, material and type of the lateral load-resisting system, number of storeys, structural regularity, position within a block, interaction with adjacent buildings, floor and roof systems, foundations, occupancy, cultural heritage status and physical condition, among others. Additional attributes consistent with the Global Earthquake Model building taxonomy, including system ductility and seismic code level, were added.

Populating the database proved laborious. Post-earthquake damage assessment databases from Zagreb and Petrinja, cadastral records, aggregated census data, design documentation, and LiDAR recordings from the national aerial survey all fed into the model. Ten experts spent two years collecting, verifying and entering data, combining field surveys with remote desktop work. Public participation, tested through an online questionnaire, yielded fewer than 300 responses, with residents citing privacy concerns, lack of time and anxieties about illegally constructed or modified buildings. The resulting exposure model covers approximately 136,000 residential buildings. More than half of them, 52 percent, are unreinforced masonry structures, 39 percent are confined masonry, 8 percent reinforced concrete and about 1 percent timber. Among unreinforced masonry buildings, roughly three quarters have rigid floor diaphragms. The replacement value of the residential stock is estimated at about 86 billion euros.

The risk model itself rests on three components: hazard, exposure and vulnerability. Two hazard models were used, one developed within the project from eleven seismic area sources within 200 kilometres of the city’s main square, built on the Croatian Earthquake Catalogue, and the European model ESHM20. The project-specific model generated 100,000 stochastic event sets through Monte Carlo sampling, each representing one year of seismicity, and used six ground motion prediction equations in a logic tree. Notably, the local model proved considerably more conservative than the European one for weaker, more frequent earthquakes, producing higher average annual losses. In accordance with the project methodology, the reported results rely on the project-specific hazard model. On the vulnerability side, because locally derived fragility curves were lacking, the team used the Global Earthquake Model database of roughly 500 building classes, applying 98 vulnerability curves to Zagreb’s residential typologies, with consequence models for collapse, fatalities, injuries, displacement and financial loss.

The probabilistic results, computed with the OpenQuake Engine, are sobering. For an earthquake with a 500-year return period, the assessment predicts around 900 collapsed buildings, approximately 600 fatalities, about 2,000 injured people and roughly 79,000 residents requiring temporary shelter, with direct financial losses of about 9.6 billion euros. Around 9,000 buildings would reach complete damage, about 7 percent of the stock, while a further 5,100 would be heavily damaged. Average annual losses amount to roughly 215 million euros, an average annual loss ratio of 0.25 percent that the authors consider high. Financial losses concentrate in the historic centre, where cultural heritage protection raises replacement costs, while the largest numbers of collapsed buildings and fatalities are expected in the northeastern districts, driven mainly by the amount of exposed built-up area. Unreinforced masonry buildings account for about half of all expected financial losses.

Two deterministic scenarios sharpen the picture. A repeat of the 1880 earthquake, modelled at magnitude 6.3 on the Reverse Northern Medvednica boundary fault, would collapse around 1,460 buildings, kill about 1,050 people, injure roughly 3,400 and displace approximately 126,000, with losses near 14.6 billion euros. A repeat of the 2020 magnitude 5.4 event would produce about 300 collapsed buildings, 170 fatalities, 630 injuries, 25,000 displaced residents and losses of about 3.5 billion euros. When the modelled 2020 scenario was compared with actual observed impacts, agreement was good at both city-wide and district scales: the districts that suffered the heaviest losses in reality, led by Donji Grad and Gornji Grad-Medveščak, match the model’s predictions, although the post-earthquake government report estimated higher total financial losses, partly reflecting different unit prices and market changes.

The project’s results have already found practical application. In collaboration with the Zagreb City Office, researchers evaluated the city’s official evacuation routes for potential blockage by debris from collapsed buildings. Following Croatian regulations, which assume debris reaches a distance equal to half the building height, the team created GIS buffers around building footprints, intersected them with road surfaces, and ranked buildings by their probability of collapse in the 1880-type scenario. The analysis identified safer access zones for civil protection forces but showed that problems are expected in the central part of the city, prompting a subsequent detailed study of the Lower Town using discrete element simulations of masonry façade collapse. The authors caution that current fragility models do not capture non-structural elements such as chimneys, parapets and gables, which caused many road blockages in the 2020 earthquake.

The team is candid about the model’s limitations and future needs. There is no microzonation for the entire city, secondary hazards such as landslides and liquefaction were not considered, many building attributes relied on expert judgement, and locally specific fragility and vulnerability functions remain a critical gap, although Croatian research projects are now developing them. Indirect losses and retrofit scenarios are not yet included, and the building database has not been established as an officially maintained data source. Even so, the authors conclude that earthquake risk for Zagreb is high and that the model provides a robust foundation for prioritising retrofitting and preparedness. Masonry buildings, responsible for about 80 percent of expected damage and losses, emerge as the clear priority. With national regulatory changes expected in 2026, the pilot marks a decisive shift from general awareness to data-driven risk management, offering a methodological and data-rich framework that other seismic-prone cities in the region and beyond can adapt.

Subject of Research: Building-level earthquake risk assessment of Zagreb, Croatia, using GIS exposure data and OpenQuake probabilistic modelling

Article Title: Earthquake risk assessment of the city of Zagreb, Croatia: recent advances

Article References: Šavor Novak, M., Uroš, M., Baniček, M., Demšić, M., & Atalić, J. (2026). Earthquake risk assessment of the city of Zagreb, Croatia: recent advances. Bulletin of Earthquake Engineering. https://doi.org/10.1007/s10518-026-02662-y

Image Credits: AI Generated

DOI: 10.1007/s10518-026-02662-y

Keywords: earthquake risk, Zagreb, Croatia, seismic hazard, exposure model, OpenQuake, unreinforced masonry, building inventory, vulnerability, evacuation routes, GIS database, disaster risk reduction