This session is devoted to the advancement of methods and techniques that may contribute to the compilation, storage, and elaboration of impact data sets useful for the intensity characterization of historical earthquakes as well as for seismic hazard and risk assessment purposes. Also welcomed to this session are similar studies focusing on the collection and elaboration of impact data sets for other earthquake-related natural hazards, e.g., tsunamis and landslides, with the aim to help the assessment of hazards and risks.
Coastal lagoons are dynamic, semi-enclosed sedimentary environments highly susceptible to high-energy disturbances, such as storms and tsunamis. Their sedimentary archives are critical for reconstructing paleoseismic activity. This study aims to identify the lithostratigraphic imprints of historical seismic events in the sedimentary record of Kumlubent Lagoon (Gallipoli Peninsula, adjacent to the Sea of Marmara, NW Türkiye) using two sediment cores (KLB-S1 and KLB-S2). However, the lagoon’s high-energy hydrodynamic regime resulted in a discontinuous biogenic carbonate record, preventing a conventional radiocarbon-based age-depth model for the entire sequence. A chronology for recent sedimentation was instead established using 210Pb radioisotopes on the upper 20 cm, indicating a background sedimentation rate of ~ 3.6 mm/year.
To characterize rapid lithological transitions, we integrated targeted radiocarbon dating with high-resolution ITRAX XRF core scanning. Remote sensing analysis also reveals a phase of rapid geomorphological evolution, with approximately half a meter of sediment accreted over five-years. This rapid infill is expressed as stratigraphic reversals and the presence of reworked, anomalously-aged allochthonous material in the upper core sections. In contrast, within the lower, lower-energy facies -particularly in core KLB-S1- distinct event horizons were identified. ITRAX geochemical analysis shows that the elemental profiles and scattering ratios of these horizons are consistent with a marine sediment provenance, suggesting a sudden marine incursion. Radiocarbon dating of these specific event layers yields calibrated ages clustering within the 1912–1919 AD. This temporal constraint correlates strongly with the 1912 Şarköy-Mürefte earthquake (Mw 7.4), a major seismic event in the Sea of Marmara known to have triggered submarine landslides and tsunamis. These findings suggest that the sedimentary succession of Kumlubent Lagoon preserves a distinct record of the 1912 tsunamigenic event, thereby validating the site's potential for archiving historical seismic activity in the Western Marmara region.
How to cite: Tülümen, E. B., Tarı, U., Kıyak, N. O., Avşar, U., and Kapan Ürün, S.: Tracking the 1912 Tsunamigenic Earthquake: A Multi-Proxy Study of Rapid Coastal Evolution and Event Stratigraphy in Kumlubent Lagoon, NW Türkiye, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1120, https://doi.org/10.5194/egusphere-egu26-1120, 2026.
In intraplate domain, active faults mostly have slow slip rates (<mm/year). The Vuache Mountain Fault (MVF) is one of the few active faults in mainland France with a recent event (Epagny, Mw 5.3, 1996). Its northwestern section crosses the archeological site of Villards d'Héria (Jura, France), which was occupied between 50 BCE and 400 CE. In the Jura massif, the cumulative displacements linked to the activity of the MVF since ~65 Ma are easily identifiable in the morphology. However, due to the scarcity of quaternary geomorphological structures, it is difficult to characterize the recent activity of the MVF. We use a multidisciplinary approach focused on archeoseismological analysis to overcome this. This is based on the quantification of deformations in archeological objects according to the EAE classification. It differentiates i) direct deformation markers, which are colocalized with surface fault rupture and synchronous with the earthquake, and ii) markers of induced deformation, linked to an earthquake causing transient ground motion beneath the object concerned, and various deformations within it.
Analysis of these EAE has identified two seismic events that took place on and in the immediate vicinity of the archeological site. To chronologically constrain these seismic events, a stratigraphic section was made near a wall impacted by two EAE. This indicates a first seismic event, EQ1, occurring between ~50 BCE and 100 CE. This earthquake caused a coseismic rupture that reached the surface and directly shifted the foundations. These were subsequently reconsolidated by Gallo-romans. A second earthquake, EQ2, occurred between ~70 CE and the abandonment of the site (400 CE). This earthquake impacted the wall indirectly, causing it to tilt and creating a cone-shaped collapse level, that we assimilate to a earthquake-related colluvial wedge. If we apply the Environmental Seismic Intensity (ESI) Scale, one could derive intensities between VII and IX, because of the amplitude of surface rupture.
Our analysis shows two earthquakes very close together, which we believe to be a period of seismic activity with probably a main earthquake and an aftershock. The next step in our study is to characterise a return period for the MVF. To do this, we carried out a paleoseismological trench 3 km south of the archeological site. This 3-meter-deep trench reveals several stratigraphic horizons dating from ~1220 BCE to the present day. These horizons show disturbances that result in an apparent vertical shift of ~20 cm between horizons. One horizon seals these events. Here, we characterise two seismic events of the MVF with a recurrence period of ~2000 years.
Magnitude of identified events can be inferred from various empirical relationships. If we rely on classical ones, established from worldwide database and containing a heterogenous set of earthquakes, the ~20 cm right-lateral offsets would mean events with magnitude ~6.3-6.4. However, we stress that the Jura seismotectonics are mainly confined within the Mesozoic cover above the Triassic decollement level, meaning that the above-mentioned relationship could be inapplicable. In such shallow tectonic regime, magnitude ~5 events could actually cause this range of surface rupture.
How to cite: Lallemand, T., Audin, L., Quiquerez, A., Baize, S., Grebot, R., Brousse, T., and Saqui, D.: Archeoseismological and paleoseismological approach to characterizing recent tectonic activity of the Montagne du Vuache fault, a slow fault in an intraplate domain (Jura Mountains, France)., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1230, https://doi.org/10.5194/egusphere-egu26-1230, 2026.
Earthquakes in intraplate regions pose significant seismic hazards since they can occur close to populated areas. In particular, large intraplate earthquakes tend to have long recurrence intervals, making it difficult to identify potential source regions prior to their occurrence. Understanding the mechanisms of earthquake nucleation is therefore crucial for seismic hazard assessment in low-seismicity regions. Historical earthquakes provide valuable constraints on such assessments. To address this issue, we investigate a magnitude ~6 earthquake that occurred in December 1952 in the southwestern suburban area of Pyongyang, North Korea, the largest instrumentally recorded event on the Korean Peninsula. We constrain its poorly known source parameters from analysis of long-period analog seismic records. The event is identified as a normal-faulting earthquake with a moment magnitude of Mw 6.3 and a focal depth of approximately 28 km. The source region is located along the eastern margin of the paleo-collision zone between the North China and South China blocks, where crustal-scale seismogenic structures are inferred to have developed. Beyond this large-event nucleation example, we further examine seismicity associated with other paleotectonic structures in the Korean Peninsula. We find persistent seismicity within reactivated paleo-rifting structures in East Sea (Sea of Japan). Mid- to lower-crustal earthquakes continue to occur offshore along the eastern coast of the Korean Peninsula, where laterally progressive variations in focal depth suggest ongoing neotectonic thrust evolution across inherited rift-related structures. In addition, paleovolcanic structures also host significant earthquakes.The 14 December 2021 Mw 4.9 Jeju offshore earthquake ruptured an aseismic paleovolcanic structure that responded sensitively to changes in the regional stress field and crustal properties. This mid-crustal moderate-sized event generated strong ground motions and local stress perturbations, triggering aftershocks on adjacent, preferentially oriented subparallel (NE–SW) faults. These observations indicate that paleotectonic structures act as preferred sites for earthquake nucleation in intraplate regions. We suggest that systematic monitoring of seismic activity associated with paleotectonic inheritance is essential for assessing the potential for future large earthquakes. This study presents seismic evidence for earthquake nucleation along paleotectonic structures surrounding the Korean Peninsula.
How to cite: Hong, T.-K., Lee, J., Kim, B., Lee, J., and Kim, D. G.: Paleotectonic controls on earthquake nucleation in stable intraplate regions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2094, https://doi.org/10.5194/egusphere-egu26-2094, 2026.
This study re-evaluates the historical earthquake sequence that struck southern Turkey in 1114/5 CE as one of the most damaging sequences in that region during the last millennium. We use the February 2023 Turkey doublet as a modern analogue to shed light on the spatial and temporal dynamics of the 12th century sequence. By applying geospatial analysis to Intensity Data Points (IDPs) derived from historical sources, we identify persistent damage hotspots associated with the 1114/5 sequence in the Kahramanmaraş–Elbistan and Antakya regions. This damage pattern aligns closely with the 2023 rupture zones, suggesting a repeated scenario of similar fault segments nearly 900 years apart. A rich historical record, including two eyewitness accounts at different endpoints of the fault rupture, is combined with paleoseismic evidence and insights from the February 2023 Turkey doublet to propose that the 1114/5 events likely involved multiple large-magnitude earthquakes, probably triggered in close succession. The study presents a ‘reverse-approach’ differing from traditional historical seismology by using patterns of modern seismicity to constrain pre-instrumental earthquake events. The implications reinforce the East Anatolian Fault Zone’s (EAFZ) capacity for cascading, high-magnitude ruptures and are important for understanding the seismic history of southern Turkey.
How to cite: Zohar, M. and Williams, J.: Revisiting the 1114/5 CE earthquake sequence in southern Turkey through modern lens, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2176, https://doi.org/10.5194/egusphere-egu26-2176, 2026.
Throughout history, the Mediterranean basin has experienced the occurrence of several large tsunamigenic events due to the active geodynamics of the existent plate boundaries and associated seismogenic structures. These events were documented by the many civilizations that have settled in northern Africa, eastern Mediterranean, and southern Europe. The tsunamis were generated either through seafloor rupture during offshore earthquakes, or through submarine landslides that were triggered by onshore earthquakes. In addition, some tsunamis were triggered by volcanic-eruption landslides. In this paper, the authors review the large tsunamis that took place in the Mediterranean basin, and they relate the sources and locations of those tsunamis to specific structures throughout the Mediterranean basin. They underline that the coasts with tsunami hazards can be near or far from the tsunamigenic sources, and that the near- and far-source effects of any tsunami that follows a major event can be equally critical as it propagates for short or long distances across the basin. They recommend that all Mediterranean countries should coordinate their efforts to handle their basin-wide tsunami hazards, and to undergo the required preparations ahead of the next big tsunami.
How to cite: Nemer, T., Sarieddine, K., and Faysal, R.: Is the Mediterranean ready for the next big tsunami?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2211, https://doi.org/10.5194/egusphere-egu26-2211, 2026.
Historical earthquake catalogs are essential for understanding long-term seismic patterns. Yet many events are based on sparse and spatially biased damage reports, which can lead to a significant underestimation of hazard levels. This research addresses the problem of undocumented damage by employing spatial data imputation techniques that represent distinct approaches to modelling spatial relationships: Linear Distance-Gradient assumes a relationship between variance and neighbour’s distance, k-Nearest Neighbors (KNN) relies on similarity between nearby observations, and averages the values from k nearest sites or within a fixed radius, and Kriging applies a complex geostatistical model that refines the spatial pattern through autocorrelation. These methods were used to generate synthetic reports that estimate the intensity value of earthquake damage at undocumented sites, referred to as "negative evidence".
By comparing two historical events with relatively large dataset from the Dead Sea Transform system (the 1837 South Lebanon and 1927 Jericho earthquakes) and six well-documented instrumental earthquakes such as South Napa (2014) and Ridgecrest (2019), the study evaluates model performance through Mean Squared Error (MSE) and success rates, measuring the ratio of synthetic data where predictions fall within ±0.5 and ±1.0 intensity units of true observations. The results show that seismic intensity can be estimated at undocumented locations within boundaries of uncertainty, and that simpler models, such as Fixed-K KNN and Linear regression, achieve higher accuracy than complex statistical approaches, like Kriging models. For example, for the two historical events, Linear regression and KNN models achieved average success rates of 79% and 75% respectively within ±0.5 intensity units, compared to 58% average success rates for Kriging model.
While Kriging models are widely used to create continuous intensity surfaces for historical earthquakes, this research shows that they often lack accuracy for predicting intensity at specific sites. The findings provide a reproducible framework for researchers working with sparse historical datasets, offering an alternative to complex geostatistical methods. By filling gaps in the historical record, this research may improve seismic hazard assessments and ensures that undocumented damage are accurately accounted for in future research.
How to cite: Ofir, A. and Zohar, M.: Spatial imputation techniques for identifying historical earthquake damage that probably occurred but was not reported in the historical sources., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3415, https://doi.org/10.5194/egusphere-egu26-3415, 2026.
The 1668 M8.5 Tancheng earthquake is one of the largest historical intraplate earthquakes in eastern China, yet its rupture length, particularly the southward extent across the Yaoshang area, remains debated. We investigate the dynamic rupture process of this event using four fault geometry models and compare the simulated seismic intensity with field observations, constraining the rupture length of the 1668 M8.5 Tancheng earthquake. The models consist of six near‐parallel fault segments with rupture nucleation on the central segment near Tancheng. Yaoshang is located near the southern end of this segment and is separated from the adjacent southern fault by a ~13 km gap, which is a strong barrier to the rupture based on our simulations. With a linking fault, rupture can cross this gap and extend southward to the adjacent segment but terminates there. Further southward propagation requires enhanced weakening such as the thermal pressurization effect. However, models involving rupture of the southernmost segments generate a seismic intensity X zone southeast of Bengbu, which is inconsistent with historical intensity records. The preferred model suggests that the 1668 Tancheng earthquake was dominated by northward rupture propagation, including supershear rupture on northern segments, with limited southward extension beyond Yaoshang. Thermal pressurization played a minor role in the overall rupture process. These results provide new constraints on the rupture extent of large intraplate earthquakes and highlight the complexity of cascading rupture dynamics.
How to cite: Qiu, H. and Hu, F.: Unconstrained Rupture Length of the 1668 M8.5 Tancheng Earthquake: Insights from dynamic rupture simulation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4356, https://doi.org/10.5194/egusphere-egu26-4356, 2026.
On 9 July 1956 at 05:11 local time, a Mw7.5 earthquake struck the southeastern Cyclades (Greece), followed thirteen minutes later by a second event of magnitude Mw7.1–7.2. The combined effects of these two earthquakes, whose epicentres were located between the islands of Amorgos and Santorini, resulted in 54 fatalities and caused severe damage on Santorini, leading the Greek authorities to declare the island a “large-scale local disaster.” In contrast, the situation on Amorgos is less well documented. Although reported macroseismic intensities (EMS98) on the island range between VI and IX, recent field surveys and interviews conducted with local inhabitants, within the framework of the ANR-Amorgos project, suggest that the actual impact was limited. This discrepancy raises a key question: how can such markedly different seismic responses be explained between Amorgos and Santorini, given that Amorgos lies less than 30 km from the rupture zone? While several geophysical studies have focused on Santorini to characterise its geological structure and site response, no comparable investigations had previously been carried out on Amorgos. To address this gap, we conducted a large geophysical survey combining HVSR, MAM (Microtremor Array Measurements) and MASW (Multichannel Analysis of Surface Waves). The aim was to characterise site response in the island’s main inhabited areas and to compare these results with the unexpectedly high macroseismic intensities reported for the 1956 earthquakes. A comparative analysis with existing data from Santorini was also performed to identify the factors responsible for the contrasting seismic responses observed between the two islands.
Our results provide a geophysical site characterisation of the main urbanised sectors of Amorgos (Aegiali, Katapola, Chora and Arkesini). No significant site amplification effects have been identified to date, neither within sedimentary basins nor along topographic highs. Moreover, the fundamental ground frequencies obtained are significantly lower than the relatively high resonance frequencies typical of traditional Cycladic buildings (>10 Hz), suggesting limited double resonance effects. At this stage, the available geophysical data do not account for the strong spatial variability of macroseismic intensities reported on Amorgos Island and call into question the reliability of these historical observations. By contrast, the presence of thick volcanic formations (first and second explosive cycles: 2-300 kyr) combined with steep topography appears to be the primary factor explaining the much more severe damage observed on Santorini during the 1956 seismic sequence.
How to cite: Combey, A., Mercerat, E. D., Langlaude, P., Pernoud, M., Kouskouna, V., Sakellariou, N., Galanos, N., and Leclerc, F.: Divergent Responses of Cyclades Islands to a Major Aegean Earthquake: A geophysical perspective from Amorgos Island, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6603, https://doi.org/10.5194/egusphere-egu26-6603, 2026.
Posters virtual: Mon, 4 May, 14:00–18:00 | vPoster spot 3
EGU26-1467 | Posters virtual | VPS12
Using geoid height changes to study the thermal evolution of a sedimentary basin and possible relation with earthquake occurrence in the regionMon, 04 May, 14:27–14:30 (CEST) vPoster spot 3
Geoid height values obtained in 1984, 1996 and 2008 were used to study the thermal evolution (considering density variations caused by temperature alterations) of a sedimentary basin located in the central eastern part of the Atlantic Ocean region. Historical and registered earthquakes have been detected in this basin.
The results obtained show a heterogeneous basin with increases/decreases in density (temperature) values occurring in the time interval between measurements and points with identical values in different years, separating regions of warming from regions of cooling. It is also observed that the maximum values obtained increase from 1984 to 1996 and 2008, occurring at different latitudes.
The minimum values obtained in 1984 are clearly higher than values obtained in 1996 and 2008 at same latitudes. The minimum values obtained in 2008 are higher than those of 1996 in latitudes between 35.8 and 36.2 N and also for latitudes equal to or greater than 36.6 N. At intermediate latitudes, the values obtained in 2008 are lower than those obtained in 1996.
Climate data presented on IPMA website show high values of precipitation data occurring in 1996 in months with lowest temperature values in Mainland Portugal, suggesting that the low values of temperature found may be related with infiltration of cold water and to an increase of water pressure in depth.
In the present work, special attention is given to the western boundary of the basin, where it is possible to observe high temperature values associated with lateral cooling of seamounts linked to cooling in the sedimentary basin, and a consequent increase in temperature in the inner part of the seamount. The location of 3 earthquakes recorded in May, July, and August 2005 showed that they occurred near points without changes, separating a warming area (on the West side) from a cooling area (on the East side). The earthquakes are located in the warming area.
The analyzed data show that the region under study experienced warming in the past and is now in a heterogeneous cooling phase. Areas in a warming phase can be identified with the 2008 geoid height values, after been cooled in 1996.
Climate data was used to identify temporal relationships between geoid height values and precipitation and temperature values in mainland Portugal.
Earthquakes with magnitude greater than 4.0 were identified in the region in 2005. They are located close to the crossing points of geoid height values between 1996 and 2008, which separate areas under heating from areas under cooling, giving rise to different horizontal thermal and pressure gradients in the western and eastern side of the point with no changes in density (temperature) and possible contribution to the occurrence of earthquakes.
How to cite: Duque, M. R.: Using geoid height changes to study the thermal evolution of a sedimentary basin and possible relation with earthquake occurrence in the region, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1467, https://doi.org/10.5194/egusphere-egu26-1467, 2026.
EGU26-905 | Posters virtual | VPS12
Reconstructing rupture dynamics of historical Alpine–Marlborough Fault earthquakes, Aotearoa–New ZealandMon, 04 May, 14:39–14:42 (CEST) vPoster spot 3
Forecasting seismic hazard on complex fault systems remains a global challenge, particularly where ruptures can cascade across structural transitions. Aotearoa–New Zealand’s (A–NZ) central transition zone exemplifies this, where the Alpine Fault (AF) and Marlborough Fault System (MFS) connect the Puysegur and Hikurangi subduction zones and pose a major seismic risk to A–NZ communities. The Alpine Fault is late in its interseismic cycle, with a 75% probability of rupture on its central segment within the next 50 years, and a high likelihood of this cascading into a Mw>8 multi-fault rupture onto the MFS. Understanding the behaviour of past earthquake sequences in this region is therefore a national priority to better estimate the extent and dynamics of future shaking. Instrumental records only span a fraction of an earthquake cycle, leaving critical gaps in recurrence patterns and rupture behaviour, which paleo-seismic archives can help to resolve.
We address this gap by integrating lake-sediment paleo-shaking records with calibrated ground-motion modelling and empirical source inversion. Using South Island lakes as binary seismometers, we reconstruct rupture scenarios for historical earthquakes in the central A–NZ transition zone. For each event, we define the probable fault planes and forward-model potential peak ground velocities at each lake site using a suite of ground-motion models that have been extensively tested and adopted in the New Zealand National Seismic Hazard Model. These modelled ground motions are then compared with age-dated mass-transport deposits, which record earthquake-induced shaking and allow calibration of the sequence and timing of events at each site. Finally, a source-inversion technique is used to identify rupture extents and magnitudes that satisfy both rupture-scaling constraints and the binary shaking evidence preserved in the sedimentary record.
In this presentation, we will demonstrate how our integrated approach constrains the magnitudes, rupture locations, and recurrence histories of eight historical earthquakes in central Aotearoa–New Zealand at unprecedented spatial and temporal resolution. The methodology reduces epistemic uncertainty associated with conventional intensity-based methods and is transferable to other complex fault systems, including subduction zones. Crucially, our research provides essential empirical inputs for time-dependent seismic hazard models in Aotearoa–New Zealand.
How to cite: OKane, A., Howarth, J., Fitzsimons, S., Moody, A., and Clark, K.: Reconstructing rupture dynamics of historical Alpine–Marlborough Fault earthquakes, Aotearoa–New Zealand, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-905, https://doi.org/10.5194/egusphere-egu26-905, 2026.
