Historical Seismicity Research Articles

Volcano‑tectonic seismicity and related hazard: a component of the multi‑hazard assessment in the highly exposed region of Mt. Etna (Italy)

In this study, seismic hazard, a component of the multi‑hazard assessment studied in the framework of the PANACEA project, was performed following the probabilistic approach (PSHA) based on historical macroseismic data. This approach uses intensity site observations to compute the seismic history for each investigated locality. Site seismic histories completeness are improved the integrating observed intensities with “virtual” values calculated according to attenuation laws, starting from the earthquake parameters (epicentre and epicentral intensity). The probability distribution of the expected intensities at a given site is calculated for exposure times of 10, 30 and 50 years. Results are given as reference intensity and peak ground acceleration for a chosen exceeding probability. In order to obtain hazard also in terms of expected peak ground acceleration (PGA) a relation between macroseismic intensity and ground acceleration calibrated for Mt. Etna was also developed. A PGA value was predicted for each intensity site observation using a specific ground motion model for Mt. Etna shallow events, assuming a soil class A. We tested the performance of the obtained relationship through synthetic and observed PGAs associated with the most energetic seismic event instrumentally recorded at Etna. Finally, the probability distribution for PGA at the site for a given exposure time results from the combination of the corresponding seismic hazard curve for the macroseismic intensity and the specific local intensity‑PGA relationship.

Seismic Signatures of Fluctuating Fragmentation in Volcanic Eruptions

AbstractFragmentation plays a critical role in eruption explosivity by influencing the eruptive jet and plume dynamics that may initiate hazards such as pyroclastic flows. The mechanics and progression of fragmentation during an eruption are challenging to constrain observationally, limiting our understanding of this important process. In this work, we explore seismic radiation associated with unsteady fragmentation. Seismic force and moment tensor fluctuations from unsteady fragmentation arise from fluctuations in fragmentation depth and wall shear stress (e.g., from viscosity variations). We use unsteady conduit flow models to simulate perturbations to a steady‐state eruption from injections of heterogeneous magma (specifically, variable magma viscosity due to crystal volume fraction variations). Changes in wall shear stress and pressure determine the seismic force and moment histories, which are used to calculate synthetic seismograms. We consider three heterogeneity profiles: Gaussian pulse, sinusoidal, and stochastic. Fragmentation of a high‐crystallinity Gaussian pulse produces a distinct very‐long‐period seismic signature and associated reduction in mass eruption rate, suggesting joint use of seismic, infrasound, and plume monitoring data to identify this process. Simulations of sinusoidal injections quantify the relation between the frequency or length scale of heterogeneities passing through fragmentation and spectral peaks in seismograms, with velocity seismogram amplitudes increasing with frequency. Stochastic composition variations produce stochastic seismic signals similar to observed eruption tremor, though computational limitations restrict our study to frequencies less than 0.25 Hz. We suggest that stochastic fragmentation fluctuations could be a plausible eruption tremor source.

Tectonic implications of raised Quaternary relative sea‐level indicators along the NE border of the Campania Plain (southern Italy)

AbstractTectonically raised paleoshorelines have been recently identified along the southern fault scarps of the Mt. Fellino and Roccarainola horst blocks, which are part of the northeastern border of the Campania Plain coastal basin (southern Apennines, Italy). Such horst blocks are bounded to the south by the Polvica Fault, a roughly E‐W trending normal fault. The sequence of uplifted paleoshorelines has been studied in detail by integrating geomorphological, structural and stratigraphical analyses to assess the Quaternary uplift of the Mt. Fellino and Roccarainola horst blocks. Yet, the staircase of paleoshorelines is still not chronologically well constrained.Aimed at constraining the uplift history of Mt. Fellino and Roccarainola horst blocks and the rate of activity of the Polvica fault, in this study, we integrate former knowledge on paleoshorelines with a geomorphological analysis to map erosional terraces, that we interpret as remnants of shore platforms. We apply the synchronous correlation method, driven by new and a former 230Th/234U dating of calcite veins cutting marine sands, to infer the age of the paleoshorelines and terraces. Based on the synchronous correlation, the mapped paleoshorelines and terraces are correlated with sea‐level peaks of the late Early to Late Pleistocene. In particular, the paleoshorelines along the Mt. Fellino ridge are correlated with the Marine Isotope Stage (MIS) 7e and 9c or 11, while the oldest terrace is correlated with the sea‐level peak of 980 ka. Using inferred paleoshorelines ages, we estimate the uplift rate of the Polvica Fault footwall. The uplift rate varies from c. 0.2 mm/yr close to the western fault tip up to c. 0.5–0.6 mm/yr in the East, in the Roccarainola block. We combine surface evidence with subsurface data from a shallow well to constrain the vertical throw of the Polvica Fault. A mean fault throw rate of c. 0.4 mm/yr in the last c. 1 Ma is estimated for the central part of the PF. Assuming that the Polvica Fault is still active, we estimate the maximum expected earthquake by means of empirical relationship and obtain a Mw ~ 6.2 value and recurrence interval value of c. 1,200 yr. Historical seismicity activity of the PF has not been acknowledged to date. However, our results raise the crucial question of an in‐depth assessment of the seismic hazard for the densely populated Campania Plain.

Influence of a non-free field subsurface seismic history on the liquefaction resistance of sandy soils

Influence of a non-free field subsurface seismic history on the liquefaction resistance of sandy soils

Strategies for Teaching Natural Hazards to Children in Rural Communities

This research focuses on teaching strategies for natural hazards in rural educational communities, centring on El Abanico, a seismic region in Argentina with a history of destructive earthquakes. Geomorphological, tectonic, and climatic processes amplify hazards, while socio-economic factors, including a predominantly agricultural economy, informal housing, reliance on irrigation, and limited services, increase community vulnerability.The Tierra del Fuego School serves students from diverse socio-economic backgrounds, and its structure was severely affected by seismic and flood events in 2021. An assessment revealed deficiencies in disaster risk management within the community. In response, an intervention was implemented at the school using educational strategies focused on natural hazards, distinct from formal classroom learning and adapted to the rural context. This intervention engaged children aged 9 to 11 over a year.The objective was to explore children’s understanding of hazards in their territory, develop knowledge through interaction with the physical environment, encourage children’s expression and experiential knowledge, formulate disaster response strategies, foster resilience and preparedness, and analyse the potential for replicating these initiatives in other rural communities.The findings revealed a significant increase in knowledge of natural hazards and risk prevention among both students and teachers. The project culminated in the creation of a book that amplified the children's voices and disseminated the seismic history of the region, fostering improved seismic risk management. The educational strategies are replicable in other rural schools and can positively influence disaster risk reduction strategies while enhancing community resilience.

EARTHQUAKES FELT in the NORTH CAUCASUS in 2020: VERKHNE-FIAGDON EARTHQUAKE on JANUARY 26, 2020 with KR=11.2, I0=5 and JEYRAKH EARTHQUAKE on MAY 24, 2020 with KR=10.6, I0=4

In 2020, two significant earthquakes were registered in the south of the Republics of North Ossetia-Alania and Ingushetia: on January 26 with KR=11.2 and on May 24 with KR=10.6. The earthquakes occurred in different seismotectonic conditions. The source of the first event was formed within the Adaykom Kazbek fault, and the source of the second event – within the Karmadon zone of occurrence of earthquake sources. The January 26 earthquake, named the Verkhne-Fiagdon, became the strongest instrumentally recorded earthquake in North Ossetia since the beginning of seismological observations on this territory. It was felt in 19 settlements with the intensity from 2 to 4–5. The calculated intensity in the epicenter is estimated as I0=5. According to the focal mechanism solution, the Verkhne-Fiagdon earthquake occurred under the influence of prevailing compres sive stress. The type of movement in the focus is reverse fault with significant strike-slip component. The earth quake on May 24, named the Jeyrakh earthquake, was felt in 12 settlements with intensity from 2 to 4. Tensile stresses oriented in a south-west direction prevailed in the focus. The type of movement is a normal fault on both planes, with minor strike-slip components. Information on historical seismicity in the focal zones of both earth quakes is given for the last 150 years.

TADJIKABAD EARTHQUAKE of JULY 4, 2020 with Мs=5.2, I0=7 (TAJIKISTAN)

Instrumental and macroseismic data are presented for the Tadjikabad earthquake on July 4, 2020 with intensity in the epicenter I0=7 and surface wave magnitude Ms=5.2, which has happened in the eastern part of Tajikistan, in the crest area of Peter the Great Ridge. This seismic event has been accompanied by numerous aftershocks (NΣ=137), which spread area has the form of ellipse stretched in sub-meridional direction with axes 83 and 96 km. The information about the earthquake perceptibility has been collected in 32 settlements and the map with isoseist of I=7, 6, 5, 4 has been created. Description of seismotectonic position of the origin and historical seismicity of the area is given. The areas of the strongest shaking in the focal zone from earthquakes in the study area were determined and a probabilistic model of the earthquake isoseist map of the earthquake of May 4, 2020 was compiled.

Sedimentary record of historical seismicity in a small, southern Oregon lake

Abstract. We compare event deposits from the historical portion of the sedimentary record from lower Acorn Woman Lake, Oregon, to historical records of regional events to determine if the lake records Cascadia megathrust earthquakes. We use the sedimentological characteristics and X-ray fluorescence (XRF) provenance of disturbance deposits (labeled A–J) from the historical portion (∼1650 CE and younger) of the record to discriminate between deposit types. We show that earthquake-triggered deposits can be differentiated from flood deposits, and Cascadia megathrust earthquake deposits can be differentiated from other types of earthquake deposits. Event deposit J dates close to 1700 CE (1680–1780 CE) through multiple approaches, suggesting it was the result of shaking from the M8.8–9.2 1700 CE Cascadia megathrust earthquake. Event deposits H and I are interpreted to be the result of the ∼M7.0 1873 CE Brookings earthquake, which is explained here to be a crustal earthquake immediately followed by a subduction earthquake. These results demonstrate the usefulness of lake sediments to infer earthquake hazards in Cascadia.

Performance evaluation of high ductility class RC framed structure by seismic event time histories

Abstract The seismic performance of new designed to high ductility class, mid-rise RC framed structure is numerically tested by non-linear dynamic time history analysis using records adjusted to represent events with different periods of recurrence. The earthquake performance assessment employs the code-defined limit states criteria. The results of the numerical non-linear studies are indicative of the seismic performance of mid-rise RC framed structures designed to Eurocode ductility classes.

Earthquake Environmental Effects: The Case of Late Classical-Hellenistic Helike, Gulf of Corinth, Greece

Human habitat is much controlled by the landscape and its ongoing processes overtime. Some of these processes occur instantaneously and are often triggered by seismic events with a major destructive impact on the human-built environment. Helike, on the southwest shore of the Gulf of Corinth, is a characteristic case of an ancient habitation site bearing witness to repetitious natural disasters from the Early Bronze Age to the Late Antiquity. The Late Classical-Hellenistic site, revived in the Helike plain after the 373 BC earthquake, has been systematically investigated thanks to the multidisciplinary research and excavations of the Helike Project in the last 35 years. This work has significantly enriched the historical seismicity of the region and shed light on past human-environment relationships. The study of the architectural remains excavated by the Helike Project, coupled with geological and soil micromorphological analysis on archaeological soils and sediments of the settlement, demonstrates a constant effort of the Helike people to reconcile with the elements of nature. Our results underline the destruction of a flourishing textile dyeworks operated at the settlement, due to a strong earthquake which triggered extensive morphological changes in a broader area. These changes include co-seismic liquefaction and lateral spreading, and post-seismic changes in the gradient of river channels. The former changes attest to an uplift in the headwater area and subsidence in the lowland plain of the ravine flowing near the ancient site.

Probabilistic seismic hazard analysis in Northern Algeria using the Parametric-Historic method

AbstractIn this study the seismic hazard in Northern Algeria is analyzed by using a probabilistic approach, and specifically the parametric-historic method. This method enables the incorporation of the entire accessible seismic history into the analysis and effectively addresses both the spatial heterogeneity and temporal variability of the seismicity parameters. The recently compiled earthquake catalog covering the region and spanning the period from 1658 to 2018 was used for estimating the seismicity parameters. The seismic hazard maps in terms of peak ground acceleration (PGA) were calculated for return period of 475 years for rock, stiff soil, and soft soil conditions. The uniform hazard spectra (UHS) for the major cities in Northern Algeria were calculated for the same conditions. The largest PGA values are observed near the cities of Chlef, Algiers, Blida, Medea, and Tipasa. Arguably the most important obtained result is evident in the seismic hazard estimates for the capital city of Algiers, which significantly exceed previously published estimates.

Carbonate rock physics model using different approaches to estimate rock frame stiffness

Deepwater carbonate reservoirs in the Brazilian pre-salt have emerged as significant hydrocarbon plays in the region and globally. Seismic monitoring of these reservoirs is crucial to provide information for well placement assessments, to reduce uncertainty in reservoir models, and to enhance model-based decision making. To integrate seismic data quantitatively, a petroelastic model (PEM) is required to estimate elastic properties. The modeling of the rock frame stiffness is an essential part in the study of PEM. However, this becomes more complex for carbonate rocks given their diverse pore-types. One way for estimating stiffness is to model each distinct pore-type and include them into the overall rock frame (different inclusion models). In this research, an alternative approach is explored to estimate the rock frame stiffness. A proxy model is employed, and its coefficients are subsequently calibrated with well-log information. Two PEMs were developed using different approaches for rock frame stiffness modeling. The first was inspired by inclusion models and incorporated two pore types (compliant and stiff pores) for the modeling process. The second considered a mathematical regression model as a proxy to relate reservoir porosity to the rock frame stiffness. These two PEMs were tested on the Brazilian pre-salt carbonate rocks of the Barra Velha (BVE) formation using well-log data from three wells and core sample measurements for one well. The accuracy of the PEMs’ performances was assessed by measures (such as, mean absolute error and root mean square error) and visual comparisons of their predictions. The results showed that both PEMs predicted velocities (compressional and shear) within an acceptable match with the actual well-log data. Similarly, when tested on the core samples, the PEMs produced comparable results, which indicates the validity of the proxy, not only at the well-log scale but at the core scale. The visual comparison and the accuracy analyses of the results for all three wells confirmed that the two PEMs had comparable predictions. This is significant given that the proxy simplifies the modeling process and facilitates the representation of various pore-types in the prediction of elastic properties in carbonate rocks. Overall, the proxy for the rock frame stiffness modeling is a computationally less expensive model compared to the inclusion models which involve modeling of various pore-types. It also offers a straightforward model which enables the quantitative integration of seismic data in a multidisciplinary team of geosciences and petroleum engineers (for instance, early engagement of petroleum engineers in 3D/4D seismic history matching).

Anatomy of the late Pennsylvanian to early Triassic failed rift system of the Cooper Basin, eastern Australia

The onshore intracratonic Cooper Basin of eastern Australia developed during the Late Pennsylvanian to Middle Triassic periods at paleolatitudes of approximately 50°S within the Gondwanan sector of Pangea. Despite the wealth of data available, including the drilling of over 4,800 boreholes, there is limited knowledge about the Cooper Basin’s origins and evolution. To better understand the basin’s geological history, legacy data sets, including composite 2D seismic sections, well logs, measured sections, and 1D burial history models from the west of the basin, are integrated to reinterpret the basin’s tectonic and sedimentary evolution. Interpretation of the seismic sections and calculated subsidence rates indicates an earlier active rift phase with grabens and half-grabens that transitioned, in the latest Permian, into a regional sag phase. The evolution of tectonic styles heavily influenced the paleogeographic evolution of the basin fill and resulting depositional architecture. The basin sediments are entirely terrestrial in nature and facies reflect a transition from glacial environments in the late Pennsylvanian to warmer and drier conditions in the early Triassic. During much of the Permian the basin was underfilled and the relative low influx of fluvial sediment did not keep pace with creation of accommodation, allowing the development of extensive mire and lake systems. Coal beds are up to 30 m thick. By contrast, the basin appears to have been overfilled during the latest Permian to Triassic with rivers flowing along the central axis of the basin. The synchroneity of commencement of rifting, termination of rifting, and commencement of a sag phase within the failed rift systems of the Cooper Basin, the East Gondwana Interior Rift, and the East Australian Rift strongly suggests a continent-wide period of extension related to significant changes in plate motions during the Late Pennsylvanian to Middle Triassic.

Rupture behaviors of the southern Xianshuihe fault and seismicity around Mt. Gongga: Insights from the 2022 MW 6.6 Luding (China) earthquake sequence

The 2022 MW 6.6 Luding earthquake occurred on the Moxi segment of the Xianshuihe fault at the southeast margin of Tibetan Plateau, China. To assess the seismic potential of the Moxi segment, we examine the rupture process of the mainshock and aftershock sequence, along with historical seismicity. Our preferred slip model inverted from teleseismic body waves and regional GNSS static displacements shows a dominant southeastward rupture consisting of two distinct, prominent slip patches along strike extending by ∼15 km, with a peak slip of ∼2.8 m, approximately balancing the slip deficit since the last major earthquake in 1786. The northern section of the Moxi segment experienced minor coseismic slip, which, together with the significant slip deficits and positive Coulomb failure stress change induced by the 2022 mainshock indicates a high seismic potential. Several aftershock clusters are distributed along or near the Moxi segment, with strike-slip focal mechanisms around the downdip edge of the coseismic slip area at ∼8‐12 km. At the eastern flank of Mt. Gongga, another cluster of normal faulting aftershocks is located at shallower depths of ∼3‐7 km, with high seismicity rate over ∼9 months including two other M5 sequences in January and February 2023. Similar intense shallow normal faulting activity had occurred after the impoundment of the nearby Dagangshan reservoir in 2015. We speculate that some NW-SE trending normal faults were initially developed by the gravitational collapse of Mt. Gongga underneath the eastern flank, further weakened by fluid flow, as supported by the existence of hot springs and water impoundment, and reactivated by the tensional stress change induced by the 2022 mainshock. These results have important implications for assessing the seismic hazard in and around the Moxi segment, and the potential interplay between strike-slip fault and nearby mountain areas.

Unveiling crustal deformation patterns along the north Tabriz fault from 2015 to 2022 using multi-temporal InSAR analysis

This paper presents a comprehensive study on the recognition of crustal deformation patterns surrounding the North Tabriz Fault in Northwestern Iran, utilizing Multi-Temporal InSAR analysis. The fault, despite its seismic inactivity for over two centuries, has a long history of ancient seismicity, with earthquake recurrence intervals exceeding two centuries. This makes it highly susceptible to future activity and the generation of significant and devastating earthquakes. However, limited research has been conducted on extracting and modeling deformation patterns of the North Tabriz Fault to identify its active segments. The primary objective of this study is to derive a general trend for fault displacement and investigate regions under pressure in terms of abnormal crustal movements. The results indicate that the Earth's crust in the surrounding regions of the central and northwest segments of the fault exhibits an upward movement ranging from approximately 2 to 10 millimeters per year from 2015 to 2022. In contrast, neighboring areas of the northwestern fault, as well as the northwestern, western, and southwestern parts of Tabriz County, experience ground subsidence with rates ranging from approximately 5 to 40 millimeters per year. These findings are consistent with GNSS-derived line-of-sight measurements obtained from some IPGN stations around the fault with an RMSE of 1.72 mm/yr. Furthermore, the study identifies critical points near the fault that exhibit varying and diverse displacement patterns over time, suggesting significant strain and notable stress within the subsurface environment. According to the analysis of time series data on crustal movements at the identified critical points, it has been found that the prevailing motion pattern of the Earth's crust within the fault zone largely conforms to a sinusoidal descending pattern. Additionally, recent earthquakes in the northwest vicinity of the fault have been observed to occur close to these critical points. Using line-of-sight (LOS) data acquired at these critical points, the study estimates a slip rate of 7.71 ± 0.01 mm/year and a locking depth of 11.27 ± 0.01 km, contributing to a better understanding of the fault's seismogenic behavior. These findings provide valuable insights into the crustal deformation patterns around the North Tabriz Fault, highlighting active segments and regions under pressure.

Tectonic-Paleoseismological Characteristics and Quaternary Activity of Maymundağı Fault (Northern Acıgöl Graben)

The Aegean region and its graben system constitute one of Turkey’s most significant seismic zones. The faults within the Aegean graben generate numerous earthquakes, leading to various human and economic losses. To better understand the seismicity of western Anatolia, it is necessary to obtain concrete findings regarding the seismic history of earthquake-producing graben faults. This can be achieved through paleoseismological studies and other relevant disciplines. This study focuses on paleoseismological investigations along the northern boundary fault of the Acıgöl graben, located east of the Aegean graben system. The Maymundağı fault zone has been examined in two separate segments: east and west. The Dazkırı segment to the east shows evidence of movement dating back at least 10,000 years, with subsequent intensified activity observed later on the western Bozkurt segment. An earthquake occurred approximately 2370 years ago east of the Bozkurt segment, followed by movements migrating westward, resulting in earthquakes approximately 1322 and 598 years ago. Further analysis of the western segment indicates an average recurrence interval of 724 years for earthquakes, with a slip rate of 0.58 mm/year. Based on these findings, a future earthquake can be expected in this region around 2028–2129 AD.

Historical earthquakes in the Holy Cross Mountains, Poland, true or false? Unveiling insights through archaeoseismology

The Holy Cross Mountains are an intraplate range with a limited historical seismicity record. The only documented earthquakes include the February 6, 1837 M 4.3 event, which caused ground cracks, and swarm events from February 1932 (M ∼ 3.5), likely triggered by the Holy Cross Fault (HCF) or sub-perpendicular faults. The apparent lack of older destructive earthquakes in historical catalogs motivated us to conduct archaeoseismological research to improve seismic hazard assessment, risk mitigation, and urban planning strategies, ultimately benefiting local communities. We focused on the 12th-century Collegiate church of Saint Martin in Opatów, located near the Holly Cross Fault (HCF). We report numerous damage features, such as leaning, bulging, and twisted walls, dropped keystones in Romanesque and Gothic portals, strike-slip displacements of these portals, surplus, oversized buttresses, and walled-up portals. While some deformations may result from humid loess instability and war destructions, our data, combined with historical records, suggest two to three seismic events in the past 800 years as a cause. We argue these deformations were co-seismically triggered by either large far-field events, like the 1259 AD earthquake, or local, shallow small-magnitude events significantly amplified by site effects. This indicates potential seismic activity in the Holy Cross Mountains during Medieval times. The absence of historical records does not imply the absence of earthquakes.

Precariously Balanced Rocks in Northern New York and Vermont, U.S.A.: Ground-Motion Constraints and Implications for Fault Sources

ABSTRACT Precariously balanced rocks (PBRs) and other fragile geologic features have the potential to constrain the maximum intensity of earthquake ground shaking over millennia. Such constraints may be particularly useful in the eastern United States (U.S.), where few earthquake-source faults are reliably identified, and moderate earthquakes can be felt at great distances due to low seismic attenuation. We describe five PBRs in northern New York and Vermont—a region of elevated seismic hazard associated with historical seismicity. These boulders appear to be among the most fragile PBRs in the region, based on reports from hobbyists. The PBRs are glacial erratics, best evidenced by glacial striations on bedrock pedestals. The pedestals themselves are locally high knobs, often situated on regionally high topography; this setting limits soil development and indicates that any outwash deposits were likely ephemeral. As a result, PBR ages can be reliably established by the retreat of the last continental ice sheet, ∼15–13 ka. To quantify the fragility of the PBRs, we surveyed them with ground-based light detection and ranging and calculated geometric parameters from the point clouds, field observations, and seismic responses. Preliminary validation of the 2023 time-independent U.S. National Seismic Hazard Model (NSHM) shows that the existence of PBRs is generally consistent with the median site-specific hazard curves. Only the Blue Ridge Road site suggests a modest reduction in hazard. To visualize the ensemble of data, we mapped the minimum permissible distance to potential source faults around each PBR site as a function of source magnitude by using the ground-motion models from the 2023 NSHM. Viewed in this manner, our data are consistent with potential M∼6.5 earthquake-source faults in many parts of the Lake Champlain Valley and northern Adirondack Mountains. Our work illustrates a potential pathway for better constraining earthquake-source faults in regions of cryptic faults.

Seismic Fragility Analysis of a Multi-Tower Super High-Rise Building Under Near-Fault Ground Motions

ABSTRACT Earthquake damage to engineering structures often occur in near-fault areas. Near-fault ground motion is characterized by high-energy velocity pulses, long action period, and strong destructiveness. This paper forces on the seismic analysis of a multi-tower super high-rise building that subjected to near-fault ground motions. The interactions between each tower makes the internal forces and dynamic responses much complex and totally different from single-tower super high-rise buildings. However, currently, multi-tower buildings in China are usually regarded as multiple single-tower buildings, and then separately designed based on the relevant provisions in seismic code for single-tower buildings. The mutual influence between the towers is almost not taken into account. Seismic response history analysis was carried on a three-tower super high-rise building using finite element method. Various near-fault and far-fault ground motions and high-energy velocity pulses were used as inputs. Through calculation of inter-story drift ratio and maximum displacement, the quantitative seismic fragility analysis was conducted for the main tower and sub-tower structures. The results show that the responses from near-fault ground motions to the structure are much greater than those from far-fault ground motions. The damage probabilities of various damage levels for near-fault ground motions are 12.5% higher than far-fault ground motions averagely. A further analysis reveals that the velocity pulses are the main factor causing structural damage in near-fault ground motions.

Behind the Italian catalogues: overlooked but far from negligible earthquakes

The Italian parametric earthquake catalogue is the result of several decades of historical seismological research, based in its turn on a centuries-long tradition of descriptive earthquake compilations. Thanks to historical seismological research undertaken since the mid-1980s, knowledge of the major historical earthquakes in Italy has hugely improved. These studies, however, focused mainly on earthquakes already recorded in Mario Baratta’s extensive compilation I terremoti d’Italia (a summary of earlier descriptive earthquake studies, published in 1901), rather than on the identification of earthquakes still ‘unknown’ to the Italian seismological tradition. As the results of a systematic perusal of ‘serial’ historical sources show, it is still possible to discover locally significant earthquakes (i.e. important for improving seismic history and hazard assessment of given localities or areas) that no previous studies had ever considered. Initiating new research projects specifically aimed at the identification of earthquakes unknown to the seismological tradition is therefore essential to improve hazard assessments on a subregional and local level.