Search Results (19)

Assessing the seismic performance of buildings from various epochs is essential for guiding retrofitting policies and educating occupants about their homes’ conditions. However, limited resources pose challenges. Some approaches focus on detailed analyses of a limited number of buildings, while others favor broader coverage with less precision. This paper presents a seismic risk assessment method that balances and integrates the strengths of both, using a comprehensive building survey. We propose a low-cost indicator for evaluating the structural resilience of individual buildings, designed to inform both authorities and property owners, support building rankings, and raise awareness. This indicator classifies buildings by their taxonomy and uses analytical capacity curves (2D or 3D studies) obtained from consulting hundreds of studies to determine the ultimate acceleration (agu) that each building type can withstand before collapse. It also considers irregularities found during the survey (to the exterior and interior) through structural modifiers Δ, and adjusts the peak ground acceleration the building can withstand, agu, based on macroseismic data from past events and based on potential retrofitting, Δ+. Although this method may not achieve high accuracy, it provides a significant approximation for detailed analysis with limited resources and is easy to replicate for similar constructions. The final agu value, considered as resistance, is then compared to the seismic demand at the foundation of the building (accounting for hazard and soil conditions at the building location), resulting in a final R-value. This paper provides specificities to the methodology and applies it to selected areas of the City of Lisbon, clearly supporting the advancement of a more sustainable society. Full article

Predicting macroseismic intensity from instrumental ground motion parameters remains a complex task due to the nonlinear relationship with observed damage patterns. An explainable machine learning model based on the XGBoost algorithm was developed to address the challenge. The model is trained on data from Italian earthquakes recorded between 1972 and 2016, linking ground motion recordings to MCS observations located within 3 km. The dataset has been enhanced with site-specific correction factors to better capture local amplification effects. Key input features include Arias Intensity, spectral accelerations at four representative periods (0.15 s, 0.4 s, 0.6 s, and 2 s), and site condition proxies, such as slope and Vs30. The model achieves strong predictive performance (RMSE = 0.73, R² = 0.76), corresponding to a 33% reduction in residual standard deviation compared to traditional GMICE-based regression methods. To ensure transparency, Shapley Additive Explanations (SHAPs) are used to quantify the contribution of each feature. Arias Intensity emerges as the dominant predictor, followed by spectral ordinates in line with structural response mechanics. As damage severity increases, feature importance shifts from PGA to PGV, while site-specific variables (slope, Vs30) act as refiners rather than amplifiers of shaking. The proposed approach enables near real-time prediction of local damage scenarios and supports data-driven decision-making in seismic emergency management. Full article

Macroseismic intensity data are the only source of information for historical earthquakes; it is therefore necessary to devise methods that allow us to retrieve as many source parameters as possible on the basis of these data. We present the inversion of macroseismic data as a first validation of an improved version of the kinematic function, KF. Following the previous results of some earthquakes on Italian territory and several validations by Californian events provided with instrumental solutions, we have now simplified the KF by reducing some degrees of freedom of the parameters and rearranging the code for parallel calculation. This approach will allow for a more extensive application of the KF technique. We present the inversion of the macroseismic intensity pattern of the M_wp6 earthquake of 27 March 1928 (8:32 GMT), which occurred in Northeastern Italy (Carnia), and we retrieved source parameters that are compatible with the solutions of other authors who independently treat instrumental data. The 1928 event is located a few tens of kilometers west of the more destructive M_w6.5 of 6 May 1976 and northeast of the subsequent earthquake M_wp6.1 of 18 October 1936. The inversion was performed as a blind test, without prior knowledge for fault plane solutions and tectonic information; it resulted in a minimum variance model with a strike of 62°, a dip of 10°, and a rake of 101°. This solution is not consistent with the entire tectonic framework of the eastern Southalpine chain, but it is in agreement with the But-Chiarsò line. This result encourages us to test further improvements to the KF method and to treat other cases from the Italian macroseismic catalog. Full article

A devastating earthquake took place on 8 April 1893, close to the town of Svilajnac, central Serbia. Over the past decade, significant historical data on the effects of this earthquake has been collected from a variety of sources, including books, scientific publications, reports, newspapers, and coeval chronicles. Additionally, this earthquake was recorded 750 km from the epicenter at the seismological station Rocca di Papa in Rome, Italy. Based on critical review and analysis of the historical data, we demonstrate that the epicentral area of this earthquake was 531 km², and the macroseismic effects were recorded at epicentral distances up to 600 km towards the west (Vienna, Austria) towards the north, up to 500 km (Košice–Michalovce, Slovakia), towards the east up to 460 km (Brašov–Borsec, Romania); and towards the south up to about 300 km (Radoviš, North Macedonia). Finally, we show that the key parameters of the 1893 Svilajnac earthquake are as follows: (1) epicentral intensity, I₀ = IX EMS-98, (2) the estimations of the moment magnitude and focal depth based on the observed intensities, M_W = 6.8 and h = 13 km, respectively, and (3) the epicenter coordinates, 44.160° N and 21.354° E. Full article

This study presents an updated view of the effects of the 1940 Vrancea earthquake. Recently compiled studies in the literature from the time of the event, as well as other studies, present the opportunity to gain additional and relevant information regarding this large-magnitude event. The effects of this earthquake on various locations in Romania are compared to those observed after the subsequent large Vrancea earthquake of 1977. An assessment of the economic losses caused by the seismic event is also attempted. The seismic vulnerability of some building typologies commonly used before 1940 is assessed by employing the earthquake damage data and the well-known macroseismic method. The impact of this event on the design and construction practices in Romania is evaluated using the collected information as well. Finally, the policy of repair and strengthening of buildings applied after the event is also discussed, and case studies are presented. Full article

During the 2021 La Palma strombolian and fissure eruption, two faults were identified that controlled the spatial distribution of earthquake hypocenters and effusive eruptive vents. One of these faults has a NW-SE trend (Tazacorte Fault: TZF) and the other one shows an ENE-WSW trend (Mazo Fault: MZF). Previous works on fault structural analysis in La Palma indicated that the eruption zone was compatible with an extensional tectonic strain ellipsoid which activated normal-strike-slip directional faults at the confluence of TZF and MZF. These fractures were activated during the 2021 Tajogaite eruption, determining the NW-SE and WSW-ENE spatial distribution of vents. Both faults were mapped in real time during the volcanic eruption from fieldwork and remote sensing imagery (aerial drone images). We have collected more than 300 fracture data associated with the effusive vents and post-eruption seismic creep. Since the affected area was densely inhabited, most of these fractures affect houses and infrastructures. Some of the houses affected by the TZF were damaged 9 months after the eruption, although they were not damaged during the eruption. Surprisingly, these houses already had repairs made to the same fractures since 1980, giving information of previous fault creep movement. During the 2021 Tajogaite eruption, shallow seismicity was spatially related to both faults, suggesting a seismic behavior instead of the precedent creep movement. However, the lack of seismicity after the eruption indicates that the faults went back to creep aseismic behavior, similarly to 1980. The mapping and monitoring of these faults (TZF and MZF) is relevant bearing in mind that they have been active since 1980 and the post-eruptive phase of the 2021 volcanic eruption, which has to be included in the land use planning in areas affected by the volcanic eruption and creep movement. Furthermore, both faults could act as seismogenic sources triggering volcanic earthquakes with potential high macroseismic intensities and mass movements. The data presented here show the importance of having this type of study before the onset of the eruption, thus allowing a better interpretation of seismic data during volcanic unrest. Full article

The seismic shaking observed around Delhi and the surrounding region due to near-field and far-field earthquakes is a matter of concern for the seismic safety of the national capital of India, as well as the historical monuments of the region. Historical seismicity indicates that the Delhi region has been affected by several damaging earthquakes originating from the Himalayan region as far-field events, as well as due to near-field earthquakes with epicenters close to Delhi. The historical records, along with recent archeoseismological studies, suggest that Qutab Minar, a UNESCO World Heritage Site, was damaged by the earthquake of 1803 CE. This event represents the only evidence of seismic damage from the region, as there has been no detailed study of other historical monuments in the area or earthquakes that have caused damage. In this context, the earthquake damage to other monuments might have been overlooked to some extent around the Qutab Minar due to the lack of proper earthquake damage surveys and documentation in historical times. The main goal of this study is to identify evidence of earthquake archeological effects around the Qutab Minar and to shed new light on the occurrence and characteristics of ancient earthquakes while providing data to inform seismic risk assessment programs. With this aim, we describe different earthquake-related damage (EAE, earthquake archeological effects) at the Isa Khan Tomb and Humayun’s Tomb, built between 1548 CE and 1570 CE, respectively, as well as the older Tomb of Iltutmish (built in 1235 CE) along with the Qutab Minar, which was built between 1199 CE and 1220 CE. The damage was probably caused by seismic events with intensities between VIII and IX on the European Macroseismic Scale (EMS). Based on the methodology of paleo ShakeMaps, it is most likely that the 1803 CE earthquake was the causative earthquake for the observed deformation in the Isa Khan Tomb, Tomb of Iltutmish, and Humayun’s Tomb. More detailed regional paleoseismological studies are required to identify the responsible fault. In conclusion, the impressive cultural heritage of Delhi city and the intraplate region is constantly under seismic threats from near-field earthquakes and far-field Himalayan earthquakes. Full article

In tectonically active areas, such as the Italian peninsula, studying the faults responsible for strong earthquakes is often challenging, especially when the earthquakes occurred in historical times. In such cases, geoscientists need to integrate all the available information from historical reports, surface geology, and geophysics to constrain the faults responsible for the earthquakes from a seismotectonic point of view. In this paper, we update and review, according to the EMS-98 scale, the macroseismic fields of the five main events of the 1783 Calabria sequence (5, 6, and 7 February, 1 and 28 March, M_w 5.9 to 7.1), two other destructive events within the same epicentral area of the 1783 sequence (1791, M_w 6.1 and 1894, M_w 6.1), plus the Messina Strait 1908 earthquake (M_w 7.1). For the 1783 seismic sequence, we also elaborate an updated and new catalog of coseismic effects. The new macroseismic fields were analyzed using a series of MATLAB algorithms to identify (1) the unitarity of the field or its partitioning in sub-sources and (2) the field and sub-fields’ main elongation. A collection of earthquake scale laws from literature was used to compute the average source parameters (length, width, and area) with their range of variability, and an elliptical map-view representation of the source geometry was calculated and made available. The analyses of such data allow us to speculate on the earthquakes/faults association, as well as propose new interpretations and reconstruct the space–time evolution of the significant southern Calabria seismic sequences in the last five centuries. Full article

Studies on earthquakes that occurred in the early instrumental period of seismology are of importance for the seismic hazard assessment and are still under investigation since new data are being increasingly revealed. We study the case of a moderate-to-strong earthquake that occurred on 15 July 1909 in NW Peloponnese, Greece. Although the earthquake event was quite destructive, it remains little-known so far in the seismological tradition. We compiled a variety of documentary sources and showed that the earthquake caused extensive building destruction in Chavari and in many other villages with an estimated maximum intensity IX (in EMS-98 scale) and a death toll as high as 55. We also assigned macroseismic intensities in several observation points and drew isoseismal lines by applying the nearest-neighbor technique. From empirical relationships between magnitude and intensities, we estimated the macroseismic magnitude of proxy M_s5.9. Our examination also revealed a variety of earthquake associated phenomena including several types of precursors and abundant co-seismic hydrological changes and ground failures, such as soil liquefaction, surface ruptures, and rock falls. Since no surface fault-trace was reported, the determination of the causative blind fault remains an open issue for future investigation. Full article

This investigation examines the contemporary documentation of a sequence of low-magnitude earthquakes at the fringes of the Kingdom of Sweden, today Southeastern Finland, in 1751–1752. A total of 11 pages of original correspondence sent from the target village of Svenskby to the Swedish capital Stockholm are reviewed. Newspaper accounts from Sweden and Russia are included in the analysis, and a timeline of the reporting is constructed. A newly created catalog shows over 30 distinct events between the end of October and December 1751 (Julian calendar). The assignment of macroseismic intensity to the earthquakes is hampered by loud acoustic effects that accompany and/or constitute the observations. Maximum intensities are assessed at IV–V (European Macroseismic Scale 1998), and maximum macroseismic magnitudes in the range of M_M1.9–2.4, and were probably observed at short epicentral distances close to the ground surface. Comparisons to macroseismic data related to instrumentally recorded earthquakes in the region support the notion of low magnitudes. The data from 1751 provide an analog to modern macroseismic observations from geothermal stimulation experiments. Such experiments have acted as a spur for considering seismic risk from low-magnitude earthquakes whose consequences have seldom previously been a matter for concern. Full article

This paper presents a multi-level methodology for near real-time seismic damage assessment of multi-story buildings, tailored to the available level of knowledge and information from sensors. The proposed methodology relates changes in the vibratory characteristics of a building—evaluated via alternative dynamic identification techniques—to the European Macroseismic Scale (EMS-98) damage grades. Three distinct levels of knowledge are considered for the building, with damage classification made through (i) empirical formulation based on quantitative ranges reported in the literature, (ii) analytical formulation exploiting the effective stiffness concept, and (iii) numerical modelling including a simplified equivalent single-degree-of-freedom model or a detailed finite element model of the building. The scope of the study is twofold: to construct a framework for integrating structural health monitoring into seismic damage assessment and to evaluate consistencies/discrepancies among different identification techniques and model-based and model-free approaches. The experimental data from a multi-story building subject to sequential shaking are used to demonstrate the proposed methodology and compare the effectiveness of the different approaches to damage assessment. The results show that accurate damage estimates can be achieved not only using model-driven approaches with enhanced information but also model-free alternatives with scarce information. Full article

Seismic risk assessment has become a crucial issue for optimal management of economic resources allocated to mitigation. For this purpose, in the last decades, several research activities were aimed to update hazard, exposure, and vulnerability models that contribute to seismic risk assessment. From this perspective, the present work focuses on developing new empirical damage fragility curves for census-based typological unreinforced masonry buildings. In particular, damage data observed after the 2009 L’Aquila earthquake, Italy, related to almost 57,000 residential buildings, were used to calibrate the fragility functions. These data were complemented with the census data with the aim of obtaining an accurate estimation of the number of undamaged buildings. Damage fragility curves were identified for typological building classes, defined considering parameters present in both post-earthquake observations and census data with the aim of extending the results to the whole national territory. Six typological classes were defined considering the categories of the construction timespan and of the state of repair parameters. Then, a further distinction of the typological classes considering the number of stories parameter was included where relevant. The fragility curves were defined as a function of peak ground acceleration for five damage states, defined according to the European macroseismic scale. The results confirmed that older buildings are more vulnerable than newer ones and highlighted the crucial role of the state of repair on the damage fragility curves. Finally, the new set of damage fragility functions was uploaded in the Italian Risk Maps information technology platform, used by the Civil Protection Department for risk evaluation, as an exemplification of the potential application of the fragility curves. Full article

A multidisciplinary work integrating structural, geodetic and seismological data was performed in the Catanzaro Trough (central Calabria, Italy) to define the seismotectonic setting of this area. The Catanzaro Trough is a structural depression transversal to the Calabrian Arc, lying in-between two longitudinal grabens: the Crati Basin to the north and the Mesima Basin to the south. The investigated area experienced some of the strongest historical earthquakes of Italy, whose seismogenic sources are still not well defined. We investigated and mapped the major WSW–ENE to WNW–ESE trending normal-oblique Lamezia-Catanzaro Fault System, bounding to the north the Catanzaro Trough. Morphotectonic data reveal that some fault segments have recently been reactivated since they have displaced upper Pleistocene deposits showing typical geomorphic features associated with active normal fault scarps such as triangular and trapezoidal facets, and displaced alluvial fans. The analysis of instrumental seismicity indicates that some clusters of earthquakes have nucleated on the Lamezia-Catanzaro Fault System. In addition, focal mechanisms indicate the prevalence of left-lateral kinematics on E–W roughly oriented fault plains. GPS data confirm that slow left-lateral motion occurs along this fault system. Minor north-dipping normal faults were also mapped in the southern side of the Catanzaro Trough. They show eroded fault scarps along which weak seismic activity and negligible geodetic motion occur. Our study highlights that the Catanzaro Trough is a poliphased Plio-Quaternary extensional basin developed early as a half-graben in the frame of the tear-faulting occurring at the northern edge of the subducting Ionian slab. In this context, the strike-slip motion contributes to the longitudinal segmentation of the Calabrian Arc. In addition, the high number of seismic events evidenced by the instrumental seismicity, the macroseismic intensity distribution of the historical earthquakes and the scaling laws relating to earthquakes and seismogenic faults support the hypothesis that the Lamezia-Catanzaro Fault System may have been responsible for the historical earthquakes since it is capable of triggering earthquakes with magnitude up to 6.9. Full article

We report a geophysical study across an active normal fault in the Southern Apennines. The surveyed area is the “Il Lago” Plain (Pettoranello del Molise), at the foot of Mt. Patalecchia (Molise Apennines, Southern Italy), a small tectonic basin filled by Holocene deposits located at the NW termination of the major Quaternary Bojano basin structure. This basin, on the NE flank of the Matese Massif, was the epicentral area of the very strong 26 July, 1805, Sant’Anna earthquake (I0 = X MCS, Mw = 6.7). The “Il Lago” Plain is bordered by a portion of the right-stepping normal fault system bounding the whole Bojano Quaternary basin (28 km long). The seismic source responsible for the 1805 earthquake is regarded as one of the most hazardous structures of the Apennines; however, the position of its NW boundary of this seismic source is debated. Geological, geomorphological and macroseismic data show that some coseismic surface faulting also occurred in correspondence with the border fault of the “Il Lago” Plain. The study of the “Il Lago” Plain subsurface might help to constrain the NW segment boundary of the 1805 seismogenic source, suggesting that it is possibly a capable fault, source for moderate (Mw < 5.5) to strong earthquakes (Mw ≥ 5.5). Therefore, we constrained the geometry of the fault beneath the plain using low-frequency Ground Penetrating Radar (GPR) data supported by seismic tomography. Seismic tomography yielded preliminary information on the subsurface structures and the dielectric permittivity of the subsoil. A set of GPR parallel profiles allowed a quick and high-resolution characterization of the lateral extension of the fault, and of its geometry at depth. The result of our study demonstrates the optimal potential of combined seismic and deep GPR surveys for investigating the geometry of buried active normal faults. Moreover, our study could be used for identifying suitable sites for paleoseismic analyses, where record of earthquake surface faulting might be preserved in Holocene lacustrine sedimentary deposits. The present case demonstrates the possibility to detect with high accuracy the complexity of a fault-zone within a basin, inferred by GPR data, not only in its shallower part, but also down to about 100 m depth. Full article

Being a country exposed to strong seismicity, the estimation of seismic hazard in Tajikistan is essential for urbanized areas, such as the rapidly growing capital city Dushanbe. To ensure people’s safety and adequate construction work, a detailed seismic microzonation is the key to proper hazard planning. Existing estimations of seismic hazard date back to 1978; they are based on engineering geological investigations and observed macroseismic data. Thereupon relies the Tajik Building Code, which considers seismic intensities according to the Medvedev–Sponheuer–Karnik Scale, MSK-64. However, this code does not accurately account for soil types, which vary considerably in Dushanbe—not only by their nature, but also due to increasing anthropogenic influences. In this study, we performed a series of analyses based on microtremor array measurements, seismic refraction tomography, and instrumental data recording from permanent stations for standard spectral ration and from mobile seismic stations for the horizontal to vertical spectral ratio in order to provide a comprehensive full-cover microzonation of Dushanbe accounting for soil types. Our results identify several critical areas where major damage is likely to occur during strong earthquakes. Full article