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Objectives With the improvement of geodetic observation accuracy, higher requirements are put forward for the seismic inversion algorithm.Methods In view of this problem, we successfully develop a novel grey wolf optimizer (GWO) algorithm to invert the seismic source parameters. The weighted distance GWO (wdGWO) algorithm with the strategy of the nonlinear decreasing convergence factor based on the cosine law is proposed to instead that of the original linear decreasing. Subsequently, a combination approach with the improved wdGWO algorithm and the simplex algorithm is configured and the introduction of the latter algorithm is to stabilize the performance of the proposed wdGWO algorithm. Thus, the combination algorithm has better advantages for both convergence and stability. Finally, we achieve synthetic tests to evaluate the performance of the basic wdGWO algorithm, the genetic algorithm and the combination algorithm.Results The simulated experimental results show that the estimation of seismic source parameters via the proposed algorithm is superior to the wdGWO algorithm, which expresses excellent stability and accuracy. On the other hand, the stability of seismic source parameters is validated between the combination algorithm and the genetic algorithm, and we find the superiority of the combination algorithm. Furthermore, the availability of the combination algorithm is tested by the 2014 Napa earthquake and the 2017 Bodrum-Kos earthquake. The results show that the combination algorithm can achieve the inversion precision of genetic algorithm, and exhibit better parameters stability.Conclusions Considering the accuracy and stability of the inversion results is particularly important for the accurate determination of seismic source parameters, the combination algorithm has potential applications in the inversion of seismic source parameters. [ABSTRACT FROM AUTHOR]

Studying the source characteristics of doublet or multiple earthquake sequences presents significant challenges in seismology, especially with short time intervals between events. On November 14, 2021, a doublet earthquake (Mw 6.0 and Mw 6.1) occurred near Fin city, southern Iran, within a span of less than two minutes and 10 km apart. We employed the Kinematic Waveform Inversion (KIWI) procedure to determine the point and extended source parameters of these events, using a multistep inversion approach for stable solutions. Our analysis highlighted the directivity of the earthquakes: the first event exhibited bilateral directivity, causing a rupture area that reached the surface, while the second event showed unilateral westward directivity, supported by waveform amplitude differences observed at various stations. This directivity analysis plays an essential role in seismic hazard studies. Our findings regarding the source parameters of these recent doublet earthquakes in the Fin region align well with regional geological trends and fault patterns. However, retrieving the main fault plane for the second earthquake was challenging due to the complexities of the waveform. Moment tensor decomposition revealed significant non-double-couple components for the second event, indicating the complexity inherent in analyzing doublet events. This study underscores the critical role of precise waveform analysis and robust inversion techniques in understanding complex seismic events. [ABSTRACT FROM AUTHOR]

Seismic source locations are fundamental to many fields of Earth and planetary sciences, such as seismology, volcanology and tectonics. However, seismic source detection and location are challenging when events cluster closely in space and time with signals tangling together at observing stations, such as they often do in major aftershock sequences. Though emerging algorithms and artificial intelligence (AI) models have made processing high volumes of seismic data easier, their performance is still limited, especially for complex aftershock sequences. In this study, we propose a novel approach that utilizes three‐dimensional image segmentation—a computer vision technique—to detect and locate seismic sources, and develop this into a complete workflow, Source Untangler Guided by Artificial intelligence image Recognition (SUGAR). In our synthetic and real data tests, SUGAR can handle complex, energetic earthquake sequences in near real time better than skillful analysts and other AI and non‐AI based algorithms. We apply SUGAR to the 2016 Kaikōura, New Zealand sequence and obtain five times more events than the analyst‐based GeoNet catalog. The improved aftershock distribution illuminates a continuous fault system with extensive fracture zones beneath the segmented, discontinuous surface ruptures. Our method has broader applicability to non‐earthquake sources and other time series image data sets. Plain Language Summary: Detecting and locating earthquakes is fundamental to seismology, volcanology, and tectonics. A number of emerging algorithms, including some based upon artificial intelligence (AI), have made processing large volumes of seismic data much easier. However, their performance is still limited, especially in clustered aftershock sequences whose signals overlap at observing seismographs. We propose a new, AI computer vision‐based approach to this problem, and develop it into a complete earthquake detection and location workflow, named SUGAR. Tests on synthetic and real earthquake data sets show that SUGAR characterizes complex earthquake sequences better than other AI and non‐AI algorithms or professional analysts. We apply SUGAR to the complex aftershock sequence of the 2016 Mw 7.8 Kaikōura, New Zealand earthquake, detecting five times more events than the analyst‐based GeoNet catalog. Whereas surface breaks of the Kaikōura earthquake are highly discontinuous, our improved aftershock distribution supports a continuous fault system surrounded by extensive fracture zones at depth. Our method has broader potential for other types of seismic sources and image series. Key Points: We propose a new seismic source detection and location approach based on the source‐scanning algorithm and 3D image segmentationThis approach outperforms human analysts and popular artificial intelligence (AI) and non‐AI based methods in characterizing intense aftershock sequencesThe resulting catalog of the 2016 Kaikōura earthquake sequence suggests a continuous fault system surrounded by extensive fracturing [ABSTRACT FROM AUTHOR]

Genuine non‐double‐couple (non‐DC) components of a seismic source, defined here as the non‐DC components that are not due to summation of pure double‐couple (DC) components, provide important insight into special physical processes in non‐earthquake sources such as explosion, volcano eruption and collapse etc. Yet they remain challenging to be resolved. To address the issue and explore the physical mechanism of those special events, we develop a waveform‐polarity‐based moment tensor (WPMT) inversion method and employ it to study physical process in the 2014–2015 Bárðarbunga volcano event sequence. The WPMT method incorporates P‐wave polarity data and seismic waveforms in the source inversion, designs a source simplicity test to check possible complex rupture in the seismic source, and employs a simulated annealing algorithm to search the best source solution. The simplicity test checks consistency of the source processes in the initiation stage of the event and the major energy release process of the event, thus ensuring that the inferred non‐DC components are genuine to the seismic source. Real event and synthetic tests indicate that the WPMT method can identify and resolve genuine non‐DC components in a seismic source. The WPMT inversions of the Bárðarbunga sequence yield many genuine non‐DC source components and reveal that the eruptions are accompanied by seismic activities in depths of 1–5 km with magma migrations out of chambers, collapses of conduits, failures of normal faults, and a magma recharge at a depth of 9 km accompanied by a failure on a nearby normal fault. Plain Language Summary: Special seismic events such as explosion, collapse and volcanic eruption possess source components that are different from fault solutions used to represent a typical tectonic earthquake of simple shear. The identification and quantification of the source components of those special seismic sources thus play an important role in deciphering the physical process during those events. Yet, it remains challenging to resolve the source components of special seismic events due to the ambiguity of distinguishing them from an apparent one due to complex earthquake rupture. We develop a waveform‐polarity‐based moment‐tensor inversion to resolve the source components of a special seismic source and employ the method to study the physical process in the 2014–2015 Bárðarbunga volcano event sequence in Iceland. Real event and synthetic tests confirm method's capability of identifying and constraining the source components of special non‐earthquake events. The study of the Bárðarbunga sequence reveals that the eruptions are accompanied by seismic activities in depths of 1–5 km with magma migrations out of chambers, collapses of conduits, failures of normal faults, and a magma recharge at a depth of 9 km accompanied by a failure on a nearby normal fault. Key Points: We propose a waveform‐polarity‐based moment tensor inversion method to extract non‐double‐couple components of moderate seismic eventsReal event and synthetic tests show the method is effective in distinguishing and resolving genuine non‐double‐couple componentsMethod application reveals magma activities, conduit collapses and induced earthquakes during the 2014–2015 Bárðarbunga eruptions [ABSTRACT FROM AUTHOR]

Archaeoseismological research often deals with two unresolved questions: the magnitude and level of damage caused by past earthquakes, and the precise location of the seismic source. We propose a comprehensive review of an integrated approach that combines site effects with the analysis of geochemical data in the field of archaeoseismology. This approach aims to identify active buried faults potentially related to the causative seismic source and provide insights into earthquake parameters. For each integrated method, we report the foundational principles, delineation of theoretical field procedures, and exemplification through two case studies. Site effects analysis in archaeoseismology assumes a pivotal role in unraveling historical seismic occurrences. It enables estimating the earthquake magnitude, assessing the seismotectonic patterns, and determining the resulting damage level. Valuable data related to earthquake parameters can be extracted by analyzing vibration frequencies and acceleration measurements from structures within archaeological sites. This information is instrumental in characterizing seismic events, evaluating their impact on ancient structures, and enhancing our understanding of earthquake hazards within the archaeological context. Geochemical investigations supply indispensable tools for identifying buried active faults. The analysis of fluids and gases vented in proximity to faults yields valuable insights into their nature, activity, and underlying mechanisms. Faults often manifest distinctive geochemical imprints, enabling the differentiation between tectonically active and volcanically related fault systems. The presence of specific gases can further serve as indicators of the environmental conditions surrounding these fault networks. Integrating site effects analysis and geochemical investigations within archaeoseismological research is crucial to improving our understanding of unknown past earthquakes. Moreover, it enhances the seismic hazard assessment of the region under study. [ABSTRACT FROM AUTHOR]

Earthquake is one of the main factors causing structural disasters in current buildings. Under earthquake action, adjacent building structures are generally in different vibration stages, and collisions may occur in the structures, which may cause serious damage to the structure. In order to prevent certain earthquakes from damaging the designed buildings, this article mainly introduced the design and analysis of a numerical algorithm for seismic nonlinear structural dynamic response based on the HVSR algorithm. This article evenly divided the acceleration response time series into 15 time periods and then selected the position corresponding to the peak point of instantaneous amplitude within each period as the selected data point position. The same seismic load can be applied at the bottom of the established nonlinear model to extract the dynamic response data of the top layer of the structure, and then, the instantaneous amplitude and corresponding instantaneous phases and frequencies of the main components of the structural dynamic response can be extracted through the time-varying filter and Hilbert transform based on the discrete analytic mode decomposition. Under the influence of these four ground motions, the collision force within the range of 0-50 kN accounted for over 87% of the total number of collisions. In the comparison results of collision response to peak displacement, the four ground motions all led to structural collision, and the collision inhibited the positive peak displacement response of node 1512. Compared with noncollision, the peak displacement was reduced by 27.273, 33.675, 27.727, and 37.248%, respectively. The peak displacement of 1512 nodes was suppressed and reduced by 18.856%. The results indicate that the HVSR algorithm can obtain the instantaneous characteristic parameters of nonlinear structural dynamic response and achieve model correction., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

In this research we estimated the slip distribution of the 1966 Huacho Peru earthquake, by inverting tsunami waveforms. This event took place offshore the central Peru region and produced severe ground shaking in the cities of Supe and Huacho, with intensities of VIII MM, leading to 100 fatalities. The coseismic seabed deformation produced by the earthquake triggered a regional tsunami that inundated some coastal areas, with major effects in Casma and Tortugas. We used the tsunami waveforms from three tidal stations located in Chimbote, Callao and Marcona, to obtain the parameters of the seismic source through an inversion process, whereby we compared the simulated and observed waveforms using the non-negative least square approach. Our results show a dislocation with a maximum slip of 5.5 m located around the epicentre. This implies that the asperity with maximum energy release was located offshore Barranca city. The seismic moment was calculated as 2.05 × 10 21 Nm, which is equivalent to a moment magnitude of 8.1 Mw. We suggest that there is a high potential for the generation of a tsunamigenic earthquake in the central region of Peru, despite the occurrence of the 1966 Peruvian earthquake, because this earthquake (together with the 1940, 1974 and 2007 earthquakes) has only released around the 20% of the energy accumulated from the 1746 earthquake (Mw9.0). [ABSTRACT FROM AUTHOR]

The Himachal Pradesh and Uttarakhand areas are known for their high seismic activity in India. According to the Bureau of Indian Standards, the areas are situated in seismic zones IV and V, and have the potential to produce small to large earthquakes. These areas have also seen significant seismic events in the past. To accurately and reliably estimate the seismic hazard and simulate the characteristics of strong ground motion in the region, it is essential to evaluate the source characteristics of earthquakes and their scaling relationships. Our investigation involved the estimation of earthquake source parameters and high-frequency spectrum decay parameters using 1059 seismograms, corresponding to 247 earthquake events with magnitudes ranging from 3.0 to 5.5 that occurred in the Himachal Pradesh and Uttarakhand regions of the Northwest Himalaya between 2010 and 2020. The classic Brune’s model is used to estimate source parameters. The relationship can be expressed as M0=2×1015fc-2.316\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${M}_{0} = 2 \times {10}^{15}{{f}_{c}}^{-2.316}$$\end{document} for Himachal Pradesh and M0=2×1016fc-3.445\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${M}_{0} = 2 \times {10}^{16}{{f}_{c}}^{-3.445}$$\end{document} for Uttarakhand region, which agrees with previous studies given for the study region, providing vital insights into tectonics and structural heterogeneity beneath the respective regions of Northwest Himalaya. Our analysis revealed that for earthquakes in Himachal Pradesh, the source radius of circular fault ranges from 42 to 771 m, whereas, for events in the Uttarakhand region, it varies from 48 to 437 m. Additionally, the seismic moment ranged from 2 × 1011 N-m to 9.93 × 1015 N-m for Himachal Pradesh and 1.11 × 1011 N-m to 1.40 × 1016 N-m for Uttarakhand events. An increasing trend in stress drop is observed, varying from 0.0026 MPa to 8.66 MPa for Himachal Pradesh and 0.0014 MPa to 9.51 MPa for Uttarakhand, within the similar range of seismic moment. Moreover, the study highlighted that the estimation of κ and fmax\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$${f}_{max}$$\end{document} is influenced by both source characteristics and propagation path, with the source exerting a significant impact. A detailed analysis of the data suggests that the differences in how earthquakes start and fade in Himachal Pradesh and Uttarakhand are due to the complex geological structures and the intricate earthquake processes in these regions. [ABSTRACT FROM AUTHOR]

In this study, a multi-source data fusion method was proposed for the development of a Hybrid seismic hazard model (HSHM) in China by using publicly available data of the 5th Seismic Ground Motion Parameter Zoning Map (NSGM) and historical seismic catalogues and integrating with modern ground motion prediction equations (GMPEs). This model incorporates the characteristics of smoothed seismicity and areal sources for regional seismic hazard assessment. The probabilistic seismic hazard for the North China Plain earthquake belt was investigated through sensitivity analysis related to the seismicity model and GMPEs. The analysis results indicate that the Hybrid model can produce a consistent result with the NSGM model in many cases. However, the NSGM model tends to overestimate hazard values in locations where no major events have occurred and underestimate hazard values in locations where major events have occurred. The Hybrid model can mitigate the degree of such biases. Compared to the modern GMPEs, the GMPE with epicentral distance measures significantly underestimate the seismic hazard under near-field and large-magnitude scenarios. In addition, a comparison of the uniform hazard spectra (UHS) obtained by the models, with China's design spectrum, shows that the current design spectrum is more conservative than the calculated UHS. [ABSTRACT FROM AUTHOR]

The fast individuation and modeling of faults responsible for large earthquakes are fundamental for understanding the evolution of potentially destructive seismic sequences. This is even more challenging in case of buried thrusts located in offshore areas, like those hosting the 9 November 2022 Ml 5.7 (Mw 5.5) and ML 5.2 earthquakes that nucleated along the Apennines compressional front, offshore the northern Adriatic Sea. Available on- and offshore (from hydrocarbon platforms) geodetic observations and seismological data provide robust constraints on the rupture of a 15 km long, ca. 24° SSW-dipping fault patch, consistent with seismic reflection data. Stress increase along unruptured portion of the activated thrust front suggests the potential activation of longer portions of the thrust with higher magnitude earthquake and larger surface faulting. This unpleasant scenario needs to be further investigated, also considering their tsunamigenic potential and possible impact on onshore and offshore human communities and infrastructures. [ABSTRACT FROM AUTHOR]

On June 21, 2022, a shallow earthquake of Mw 6.0 struck southeastern Afghanistan at the interaction of the Eurasian and Indian Plates. The earthquake was VIII (severe) intensity. It drew the attention of many seismologists and earth scientists. The presented work brings satellite-based detection of pre-earthquake transient thermal anomaly, co-seismic ground deformations estimation using InSAR (SAR Interferometry) and inversion of InSAR deformations results to estimate focal solution parameters. Near the Afghanistan earthquake, a rise of 5–7 °C from the normal temperature in both day and night Land Surface Temperature (LST) time series along the SW, NW, NE and east parts of the fault is observed using MODIS satellite thermal data. Sentinel-1A microwave satellite data with the InSAR technique is used to analyze co-seismic ground deformations for both passes, and the estimation of source parameters of the fault and slip distribution of the earthquake using the Bayesian inversion approach is carried out. InSAR-based ground deformations estimate upliftment of about 325 mm and subsidence of –160 mm. The inversion results of ground deformations show that the event might be occurred due to the left lateral slip mechanism. The fault seems to be steeply dipping in eastward with NE–SW trends at a depth of 7 km. A number of aftershocks have occurred till now in the regions as evident by the Coulomb static stress along the NE, east side of the fault. The correlation between high-stress regions using thermal anomaly before the occurrence of event and coulomb static stress map after the occurrence of event have been also observed. The total seismic moment for the event using the inversion result yields a value of 1.08 × 1025 dyne-cm, which is equivalent to Mw 5.99. [ABSTRACT FROM AUTHOR]

Large-magnitude earthquakes in northern Chile and southern Peru occur every 108 years on average. It should be noted that over 143 years since the catastrophic earthquake of May 9, 1877, any similar events were completely absent. In 2007, a 7.7 Mw earthquake occurred near Tocopilla, and in 2014 a catastrophic M = 8.1 earthquake hit Pisagua. It is believed that only part of the energy accumulated over 143 years has been released during those events, while most of it is yet to be released. Thus, we can conclude that a serious tsunami hazard exists for all coastal cities of southern Peru and northern Chile. In this paper, on the basis of the available historical data and geodynamic studies, numerical simulation of the historical catastrophic earthquake and tsunami of May 9, 1877 is carried out assuming the blockwise earthquake source configurations. We implemented 23 simulation scenarios for different kinematic behavior patterns of such a source, sequentially updating the source fragmentation to reduce the misfit between the simulated and observed wave height data. Using the proposed methodology, for each scenario, the generation of a tsunami source is simulated and the computation of wave fields up to the 5-m isobath is carried out. The results obtained are compared with historical data. Analysis of the entire set of simulated earthquake scenarios makes it possible to choose a tsunamigenic earthquake scenario with the most adequate characteristics of tsunami waves in the coastal zone. [ABSTRACT FROM AUTHOR]

We constructed an integrated rupture model of the 2021 M w 7.1 Fukushima earthquake, an intraplate earthquake, by resolving both its spatiotemporal distribution of slip-rate and high-frequency (∼1 Hz) radiations. We analysed near-field seismic observations using a novel finite-fault inversion method that allows automatic parametrization and teleseismic data from multiple arrays using the MUSIC backprojection (BP) method that enhances imaging resolution. The inverted slip distribution obtained from waveforms filtered in the frequency band of 0.02–0.2 Hz showed that the kinematic rupture propagated along both the strike (∼35 km) and dip directions (∼85 km), and that the large-slip area was located southwest to the hypocentre with a maximum slip of ∼1.03 m. Overall, no obvious frequency-dependent rupture behaviours occurred during the rupture process due to the deep nucleation of the Fukushima earthquake on a heterogeneous fault where sizes of asperities do not monotonically increase with depth, which sheds light on understanding the rupture dynamics of intraplate earthquakes in subduction zones. Both the slip inversion and BP revealed the general rupture feature of this earthquake with southwestward and updip directivity. A comparison of BPs between multiple arrays indicates that the source–receiver geometry and the directivity effect of an earthquake may cause critical discrepancies in BPs of different arrays. From the temporal change of stress around the hypocentre of the 2021 Fukushima earthquake due to the 2011 Tohoku-Oki M w 9.1 earthquake, the long-term dominance of viscoelastic relaxation increased the Coulomb failure function (CFF) by 0.3–0.7 MPa, indicating that the occurrence of the Fukushima earthquake has been likely promoted by the post-seismic deformation due to the Tohoku-Oki earthquake. [ABSTRACT FROM AUTHOR]

After 43 years of repose, Taal Volcano (Philippines) erupted on 12 January 2020 with plumes reaching 17 km above sea level. To investigate Taal's magma system before, during, and after the 2020 eruption, we performed detailed analyses of local seismic data using the amplitude source location (ASL) method to estimate sources of volcano-tectonic (VT) earthquakes and tremor. Our ASL estimates indicate that magma intruded beneath the northern flank of Taal Volcano Island (TVI) before the main sustained eruption, which started at 06:40 UTC on 12 January 2020 and continued for about 14 h. Within one hour after the start of the eruption, magma emplacement along an inclined magmatic dike from a magma reservoir initiated. Seismically estimated plume heights during the eruption show that plumes were initially almost continuously higher than 10 km, then intermittently fluctuated while the base-level height of the sustained plume gradually decreased. After the eruption, tremor episodes occurred at depths down to 8.5 km beneath TVI along the northern end of a dike. Our study highlights the drastic change of Taal's magmatic system from a closed to an open system during the 2020 eruption. Before the eruption, Taal had been a closed system, and the increased pressure caused by renewed magma supply to a magma reservoir produced heightened VT activity within the edifice. The eruption opened the vent–conduit system, and CO 2 and/or SO 2 degassing within the conduit may have generated gas flows through shear-induced fractures in the conduit margins, triggering tremor episodes at various depths. • Local seismic data were analyzed to investigate the 2020 Taal eruption. • Magma emplacement initiated within one hour after the start of the eruption. • Plume height estimates indicated repetitive occurrences of pulsatory eruptions. • Tremor episodes occurred at depths down to 8.5 km after the eruption. • Taal's magmatic system changed from a closed to an open system during the eruption. [ABSTRACT FROM AUTHOR]

On May 26, 2019, an unusual depth-intermediate focus earthquake, in the interior of the Nazca plate, shook the northern Peruvian jungle and caused the death of two victims. This earthquake was felt in almost all of Peru as well as Brazil, Ecuador and Colombia. The focal mechanism calculated is of the normal fault type (strike = 353∘, dip = 57∘, rake = − 99∘) for a focal depth of 114 km. The slip distribution was obtained through an inversion process of teleseismic waveforms. The maximum slip was 6.3 m, located around the central side of the fault plane. The moment magnitude calculated was Mw 8.0; the spectral analysis indicated a similar magnitude of Mw 8.0. The source time function indicates a multiple rupture earthquake, with the presence of several pulses of seismic energy release, with a total duration around 80 s. The rupture directivity was from the south to the north; we have assumed a propagation rupture velocity of 2.8 km/s. The modeled fault plane geometry has dimensions of 208×105 km2. The predicted vertical coseismic deformation field shows a pattern of mostly subsidence. [ABSTRACT FROM AUTHOR]

Earthquake source parameters are important for understanding earthquake physics and crustal fault properties. However, strong trade‐offs between parameters (e.g., depth and origin time) and a lack of accurate velocity models and near‐field seismic stations could cause large uncertainties of these parameters in seismic catalogs, particularly for shallow events. To further improve the resolution of earthquake source parameters, we use Interferometric Synthetic Aperture Radar (InSAR) images to derive source solutions of 33 moderate‐size (Mw 4.1–6.6) earthquakes that occurred at shallow depths (<20 km) from November 2014 to July 2020 in western China. After evaluating the uncertainties of the InSAR solutions, we systematically compare the location, centroid depth, focal mechanism and magnitude from InSAR models with that from seismic catalogs. We find that all seismic catalogs generally report deeper (4–10 km) hypocenters or centroid depths. The uncertainties of moment tensor solutions are partially related to the percentage of the non‐double‐couple components in the seismic catalogs. The InSAR solutions indicate that considerable seismic moments (i.e., ∼2×1018 ${2\times 10}^{18}$ Nm) were released in the uppermost crust (i.e., <5 km) in a period of ∼6 years, which is not resolvable in the seismic catalogs. The smooth seismic moment distribution along depth indicates a gradual change of the frictional properties from the surface to the middle crust. As most of the studied earthquakes are located on secondary and/or unmapped faults, these findings imply a considerable portion of velocity‐weakening friction in the uppermost crust along immature, secondary fault systems, which should be included in the seismic hazard evaluation. Plain Language Summary: Uncertainties of parameters that describe earthquake location, fault geometry, and fault slip are generally poorly known in the seismological catalogs. Due to these unknown uncertainties, the distribution of earthquakes in the shallow crust (e.g., <10 km) is not well understood, hindering our understanding of its seismic capacity. Here, we study the moderate‐size earthquakes that occurred in western China from November 2014 to July 2020. We use Interferometric Synthetic Aperture Radar (InSAR) data to obtain surface deformations caused by earthquakes in the shallow crust. We find 33 events (Mw 4.1–6.6) out of 310 earthquakes that have clear InSAR signals, which are used to constrain the source parameters of these earthquakes. We estimate the uncertainties of these InSAR solutions and systematically compare them with the solutions in the seismic catalogs. Our analysis shows that all seismic catalogs report deeper source depth and the horizontal mislocations of the Global Centroid Moment Tensor catalog show geographic correlation features. InSAR solutions also show fault geometry and rupture complexity more precisely than the seismic catalogs. Our results indicate considerable earthquake energy released in the uppermost crust that is not resolvable in the seismic catalogs, which raises additional concerns on the seismic hazard possessed by the shallow earthquakes. Key Points: Coseismic deformations and source solutions of 33 shallow moderate‐size earthquakes (Mw 4.1–6.6) derived from Interferometric Synthetic Aperture Radar (InSAR) dataSource parameters from InSAR solutions and seismic catalogs are systematically compared to estimate their uncertaintiesInSAR solutions show considerable moments released in the uppermost crust, revealing the seismogenic capacity of the shallow crust [ABSTRACT FROM AUTHOR]

We describe the space-time pattern of seismicity occurring on Campi Flegrei Caldera (CFC), Italy, where ground deformations and seismicity represent the drivers of its current bradyseismic crisis, well known and extensively studied at an international level. In detail we consider the seismicity in the time interval starting on 1.1.2000 and ending on 31.12.2023. We revise the statistics of the earthquake occurrence, focusing at possible precursory time changes of the b-parameter of the Gutenberg and Richter (G&R b − value) distribution and at the time distribution of the total seismic moment inside any swarm. To estimate the G&R b − value we use a Monte Carlo method instead of the ordinary Least Squares or Maximum likelihood methods, to easily measure the uncertainty on the b − value taking into account uncertainties on the magnitude estimates. Results show that G&R a − value and b − value calculated for cumulative and discrete distributions of M w , the moment-magnitude, and M d , the so-called duration-magnitude, are the same inside the uncertainties; a − value and b − value for M d are significantly different from the same parameters estimated for M w , being b − value for M w close to the value of 1.0 and b − value for M d close to 0.8. The "bounded" G&R distribution fits the data yielding a − value and b − value close to those for the unbounded distribution. The mean annual rate of exceedance, calculated for the entire catalogue, results to be 0.033 ± 0.015 (years−1) corresponding to a return period of 30 ± 14 years for M w = 4.5. The time dependence of G&R b-parameter show a b − value time pattern characterized by variations slightly outside 1- σ uncertainty bar, tending to the value of 1 approaching present. As evidenced by several past studies, earthquakes in CFC occur in space-time clusters, with a mean time duration of 1 day. We selected the swarms with a selection algorithm, based on the joint estimation of inter-arrival times and inter-event distance for the consecutive event couples. The plot of the event number in each cluster vs the time of occurrence, clearly show that in CFC the number of cluster occurrences and the event number in each cluster accelerates during time starting from 2010. The time-pattern of the total seismic moment in each cluster shows that, contrarily to the event number, there is no evident striking increase of the total swarm moment as a function of time. We also consider distribution of the Energy Space Density of the CFC earthquakes, ESD. This quantity shows a clearly visible enlargement of the fractured rock volumes in the last 15 months, toward West, at a depth around 3000 m below sea level. The most fractured zone coincides with the greatest contrasts in seismic attenuation. The present study confirms that the current unrest phase is still ongoing, with an enlargement of the rock fracturing zone which extends southward and westward as compared with that measured 22 months before. [Display omitted] • Statistical analyses on the whole seismological data set shows time acceleration of the seismic swarm occurrence. • Energy Space Density shows time enlargement of the fracturing volumes. • The rock fracturing zone at 3000 m of depth, matches the elliptical inner caldera rim evidenced by geology. [ABSTRACT FROM AUTHOR]

Because of the scarcity of recorded seismic ground motions from Vrancea intermediate-depth source that can be used in designing a structure, engineers are bound to use scaled, artificial, or simulated accelerograms. Out of these options, the first two might incompletely account for the phenomena that may appear. Although complicated, simulated accelerograms provide one of the best options for defining the seismic demand in engineering design, but further research is needed to adapt the simulation methods to the source, path, and site-specific characteristics. As some parameters used in simulations were not addressed yet specifically for the Vrancea-intermediate seismic source, the specific path duration is investigated in this paper. Using a database with the recorded ground motions from March 4, 1977, August 30, 1986, May 30 and May 31, 1990, October 27, 2004 Vrancea earthquakes (the only five recorded earthquakes with moment magnitudes at least equal to 6), the path and magnitude dependent duration specific to Vrancea intermediate-depth seismic source to be used in the stochastic simulation is developed. [ABSTRACT FROM AUTHOR]

The source parameters of earthquakes (stress drop, corner frequency, seismic moment, source size, radiant energy, etc.) provide important information about the source features, the state of stress, and the mechanism of earthquake rupture dynamics. Using the digital observation data obtained from a high-density seismic monitoring network deployed in the Baihetan reservoir area of the lower Jinsha River, we obtained Brune source parameters of the 459 earthquakes ranging in magnitude ML 1.50~4.70. The results revealed seismic moments M0 within the range of 2.03 × 1012~1.45 × 1016 N·m, corner frequencies f c between 2.00 and 10.00 Hz, and source dimensions varying from 130.00 to 480.00 m, with stress drops spanning from 0.12 to 61.24 MPa. It is noteworthy that the majority of the earthquakes had stress drops less than 10.00 MPa, with as much as 73.30% of these events having stress drops within the range of 0.10 to 2.00 MPa. We found that stress drop, corner frequency, and source size in the study area exhibited positive correlations with earthquake magnitude. Earthquakes occurring at shallower depths for the same magnitude tended to have smaller stress drops and corner frequencies, but larger rupture scales. During the first 2 years of impoundment with significant water level fluctuation, earthquakes beneath or near the reservoir released higher stress drops relative to pre-reservoir conditions, with average stress drops significantly elevated from 5.52 to 13.562 Mpa for events above ML3 since the impoundment. The radiated energy released by earthquakes with magnitudes below ML3.0 are significantly more than before impoundment, indicating that earthquakes of similar magnitudes in the reservoir area may produce greater intensity and perceptibility following the impoundment. According to our result, the triggered seismicity will continue to be active under annual regulation changes in the water level of the Baihetan Dam at high elevations in future years. [ABSTRACT FROM AUTHOR]

Using the specific satellite line of sight geometry and station location with respect to the source, Thomas et al. [Scientific Reports, 10.1038/s41598-018-30476-9] developed a method to infer the detection altitude of co-seismic ionospheric perturbations observed in Global Positioning System (GPS) – Total Electron Content (TEC) measurements during the Mw 7.4 March 9, 2011 Sanriku-Oki earthquake, a foreshock of the Mw 9.0, March 11, 2011 Tohoku-Oki earthquake. Therefore, in addition to the spatio-temporal evolution, the altitude information of the seismically induced ionospheric signatures can also be derived now using GPS-TEC technique. However, this method considered a point source, in terms of a small rupture area (~90 km) during the Tohoku foreshock, for the generation of seismo-acoustic waves in 3D space and time. In this article, we explore further efficacy of GPS-TEC technique during co-seismic ionospheric sounding for an extended seismic source varying simultaneously in space and time akin to the rupture of Mw 9.0 Tohoku-Oki mainshock and the limitations to be aware of in such context. With the successful execution of the method by Thomas et al. during the Tohoku-Oki mainshock, we not only estimate the detection altitude of GPS-TEC derived co-seismic ionospheric signatures but also delineate, for the first time, distinct ground seismic sources responsible for the generation of these perturbations, which evolved during the initial 60 seconds of the rupture. Simulated tsunami water excitation over the fault region, to envisage the evolution of crustal deformation in space and time along the rupture, formed the base for our model analysis. Further, the simulated water displacement assists our proposed novel approach to delineate the ground seismic sources entirely based on the ensuing ionospheric perturbations which were otherwise not well reproduced by the ground rupture process within this stipulated time. Despite providing the novel information on the segmentation of the Tohoku-Oki seismic source based on the co-seismic ionospheric response to the initial 60 seconds of the event, our model could not reproduce precise rupture kinematics over this period. This shortcoming is also credited to the specific GPS satellite-station viewing geometries. [ABSTRACT FROM AUTHOR]

In this investigation, we have conducted a long period teleseismic and tsunami waveform inversion to obtain the slip distribution of the 1974 Lima-Perú earthquake occurred in the central region of Peru. According to teleseismic inversion, the rupture process was complex with a duration of 90 s approximately and the main asperity was located in the northern side of the rupture geometry, offshore Lima and Callao. According to tsunami waveform inversion the main asperity was located in the southern side of the fault plane, offshore Cañete. However, a joint inversion of teleseismic and tsunami waveforms averaged the contribution of the two datasets and could give a better result. The maximum slip from the joint inversion was 7.25 m, and the moment magnitude was Mw 8.1. Despite the occurrence of this earthquake (almost 50 years ago), there is a high seismic potential to trigger a tsunamigenic earthquake in the central region of Peru. According to the interseismic coupling the next earthquake in the central region of Peru is ready to occur and it would be of 8.5–8.8 Mw. [ABSTRACT FROM AUTHOR]

On June 23, 2001 at 15:33 local time (20:33 UTC), a strong earthquake of magnitude Mw 8.2 shook the southern region of Peru, causing considerable material damage and the loss of 74 human lives. The epicenter was located in the sea near the city of Atico (Arequipa). As a coseismic effect, a local tsunami was generated, which after 15 min, caused the flood and destruction of the beach resorts of Camana and resulted in the death of 25 people and 62 missing persons. Another coseismic effect was the subsidence of the coastal zones in the source region, evidenced by geodetic observations. We have conducted a joint inversion of tsunami and geodetic data with a fault plane of variable dip to obtain the slip distribution. The main asperity (slip = 12.6 m) was located offshore Camana, this explains the great damage in this city. The seismic moment was calculated in 2.72 × 10 21 Nm and the corresponding moment magnitude was Mw 8.2. The subfaults near the trench have a null slip, therefore there is a high potential for the generation of a tsunamigenic earthquake in the updip of the fault plane near the trench. [ABSTRACT FROM AUTHOR]

On 14 May 2019, a major (Mw 7.6) earthquake struck eastern Papua New Guinea, causing a tsunami warning that was later canceled. The last major rupture in the region was a 2000 Mw 8.0 event, which resulted in massive horizontal land movements of up to several meters and a series of aftershocks with primarily thrust mechanisms, and caused a damaging tsunami. Seismic methods for characterizing the source process were applied. Vertical components of the long-period P-waves from 35 stations of the Global Seismic Network with even azimuthal coverage were adopted in the inversions. First, the focal mechanism solution was retrieved after the earthquake. From the inverted results as well as aftershock distribution, the causative fault of the great PNG earthquake was confirmed to be a fault of strike = 316°, dip = 84°, and rake = 0°, indicating that the earthquake was a left-lateral strike-slip event. Then, to clearly understand the spatiotemporal evolutionary process of the source rupture of the earthquake, far-field body wave data were collected, and the source rupture process of this earthquake was studied using the finite fault inversion method. A finite-fault model was estabished with length and width of 152 and 32 km, respectively, and we set the initial seismic source parameters referring to the center of the focal mechanism solution. This was estimated by the focal mechanism solutions of defferent studies referring to different focal mechanism solutions. We found that the focal mechanism solution determined by Global Centroid Moment Tensor Catalog was not appropriate. Inversion results indicated that the seismic moment was 3.63 × 1020 Nm (Mw 7.6), and the source duration was ~ 40 s. The rupture propagated mainly toward the northwest in an asymmetrical bilateral mode, with a maximum slip of ~ 13.2 m, and a large-scale slip patch strongly ruptured to the surface. The study of Coulomb stress changes suggested that the PNG earthquake may trigger a thrust-type rupture in the New Britain Trench, which has the potential to trigger a tsunami. [ABSTRACT FROM AUTHOR]

The study area is encompassed by the 33.59-34.93°N latitudes and 45.44-46.39°E longitudes and divided into four groups with respect to earthquake event locations. We determined fault plane solutions, moment magnitudes, focal depths, and trend of slip with the direction of the moment stress axes (P, N, and T) for 102 earthquakes. These earthquakes had a local magnitude in the range between 4.0 and 6.4 for the time period from January 2018 to the end of August 2019, with focal depths ranged between 6 and 17 km. Waveform moment tensor inversion technique was used to analyze the database constructed from seismic stations on local and neighboring country networks (Iraq, Iran, and Turkey). We separated the studied events into four regional subsets (circles). The types of the obtained fault plane solutions are predominantly thrust fault and strike-slip, with the focal depths ranging from 8 to 21 km. A new scaling relation between local magnitude (Ml) and the estimated moment magnitude (Mw) has been developed utilizing a linear regression. Good match results obtained in the present research good match with both seismic trends concluded from earthquake locations and mapped faults. Generally, direction shows NW–SE striking focal planes corresponding with the tectonic framework of the Arabian–Eurasian continental collision zone. The anticlockwise rotation of the Arabian plate that appears accountable for strike-slip displacements on fault surfaces. [ABSTRACT FROM AUTHOR]

Inversion of the parameters characterising the seismic source of the instraslab 2017 Chiapas Mexico earthquake (Mw 8.2) shows a simple rupture process with a unidirectional propagation and directivity towards the North-West and a duration of the rupture process around 75 s. The initial point source values of strike, dip and rake are 316°, 80° and −91° respectively. The focal mechanism indicates a normal fault type within the oceanic Cocos plate, with an almost vertical fault plane for a focal depth of 59 km. The seismic data was obtained from 51 seismic stations of the global seismic network IRIS for the epicentral distances between 30° and 90°. In the finite-fault inversion, 75 seismic signals between P and SH waves were used. The epicenter is on the southeast margin of the large slip zone which extends 75 km to the northwest, this large slip zone is located to the south of the city of Arriaga. The scalar seismic moment was estimated at 2.55 × 10 21 N m , equivalent to a moment magnitude of Mw 8.2. The maximum dislocation or slip is 14.5 m. As a coseismic effect, a local tsunami was generated, recorded by several tidal gauges and offshore buoys. The deformation pattern shows a coastal uplift and subsidence. [ABSTRACT FROM AUTHOR]

We use data from a small aperture array in southern California to quantify variations in source parameter estimates at closely spaced stations (distances ranging from ~7 to 350 m) to provide constraints on parameter uncertainties. Many studies do not consider uncertainties in these estimates even though they can be significant and have important implications for studies of earthquake source physics. Here, we estimate seismic source parameters in the frequency domain using empirical Green's function (EGF) methods to remove effects of the travel paths between earthquakes and their recording stations. We examine uncertainties in our estimates by quantifying the resulting distributions over all stations in the array. For coseismic stress drop estimates, we find that minimum uncertainties of ~30% of the estimate can be expected. To test the robustness of our results, we explore variations of the dataset using different groupings of stations, different source regions, and different EGF earthquakes. Although these differences affect our absolute estimates of stress drop, they do not greatly influence the spread in our resulting estimates. These sensitivity tests show that station selection is not the primary contribution to the uncertainties in our parameter estimates for single stations. We conclude that establishing reliable methods of estimating uncertainties in source parameter estimates (including corner frequencies, source durations, and coseismic static stress drops) is essential, particularly when the results are used in the comparisons among different studies over a range of earthquake magnitudes and locations. [ABSTRACT FROM AUTHOR]

Finite seismic source parameters were determined for a set of 91 selected events of the West Bohemia year 2008 earthquake swarm ( M from 0.6 to 3.7) using the stopping phases method. According to the theory, two stopping phases are generated along the source border where the rupture process terminates. These two phases form a Hilbert transform pair; it is also a criterion for their identification. Circular and elliptical source models were considered and their parameters were recovered using the differences in arrival times between the identified stopping phases. Generalization of the circular to elliptical model was found to be statistically significant only for a minority of the events; consequently, only circular source models were investigated in detail. Individual source parameter errors were estimated with the use of the jackknife method. Our results are in good agreement with a previously published theoretical formula relating source radius and magnitude and also with the relation derived in the year 2000 swarm. Our results also confirm rather well the general theoretical assumption about the constant stress drop (with median value of 2.4 MPa and with the majority of values ranging from 1 to 10 MPa). [ABSTRACT FROM AUTHOR]

The article reports on using machine learning methods to identify patterns in time-dependent spectral properties of seismic signals and enable detection of changes in faulting processes. These methods characterize subtle changes in seismic source properties, with applications to tectonic and geothermal seismicity. The study examined 46,000 earthquakes from the Geysers geothermal field (CA).

The September 16, 2015, M w 8.4 Illapel, Chile earthquake is the first large event occurring in north-central Chile after the 1943 earthquake, filling a known seismic gap in the region. The earthquake took place in a complex tectonic region, nearby an area where transition from erosive to accretionary margin occurs due to the collision of Juan Fernandez Ridge (JFR) along the Chilean margin. We inverted the kinematic rupture process of the 2015 Mw 8.4 Illapel earthquake from the joint inversion of teleseismic body waves and near-field data. The relative weighting between datasets and the weighting of spatial/temporal constraints are objectively estimated by applying the Akaike's Bayesian Information Criterion. The coseismic slip model yields a total seismic moment of 4.92 × 1021 Nm occurred over ~120 s. The rupture shows both downdip and updip propagation with slip extending along the thrust interface from ~50 km depth to shallow near-trench depths (<15 km), with maximum slip of ~9 m located at shallow depths, where low average rupture speeds ~1.8–2 km/s are estimated. Outer-rise events, triggered within the oceanic Nazca plate after the mainshock, did not penetrate into the mantle and are related to preexisting faults due to both bending of Nazca plate and JFR uplift, which promotes a tensional stress regime in the surrounding area. This seismicity was triggered by static stress transfer from near-trench slip revealed by our source rupture modelling, suggesting outer-rise seismicity as a proxy for near-trench coseismic slip. Crustal seismicity within continental South American plate is observed prior to, and after, the mainshock, mainly related to extensional faulting within eroded and fractured wedge due to tectonic processes along erosive margins. We also show evidence of shallow seismicity after the mainshock associated with a long-lived crustal fault, which can represent a high seismic hazard for La Serena-Coquimbo conurbation. • The 2015 Mw 8.4 Illapel earthquake triggered shallow intraplate seismicity. • Low average rupture speeds were estimated in the main coseismic slip patch. • Crustal seismicity was detected after the mainshock near La Serena city. [ABSTRACT FROM AUTHOR]

The 6 April 2009 MW 6.3 L'Aquila earthquake, central Italy, has been recorded by the Irpinia Seismic Network (ISNet) about 250 km southeast of the epicenter. Up to 19 three-component accelerometer stations could be used to infer the main source parameters with different seismological methods. We obtained an approximate location of the event from arrival times and array-based back-azimuth measurements and estimated the local magnitude (6.1) from an attenuation relation for southern Italy. Assuming an omega-square spectral model, we inverted S-wave displacement spectra for moment magnitude (6.3), corner frequency (0.33 Hz), stress drop (2.5 MPa), and apparent stress (1.6 MPa). Waveform modeling using a point source and an extended-source model provided consistent moment tensors with a centroid depth around 6 km and a prevalently normal fault plane solution with a dominant directivity toward the southeast. The relatively high corner frequency and an overestimated moment magnitude of 6.4 from moment tensor inversions are attributed to the rupture directivity effect. To image the rupture geometry, we implemented a beamforming technique that back-projects the recorded direct P-wave amplitudes into the earthquake source region. A northwest-southeast striking rupture of 17 km length is imaged, propagating with an average velocity up to 3 km/s. This value is significantly higher than our estimate of 2.2 km/s from S-wave spectra. Our case study demonstrates that the use of array techniques and a dense accelerometer network can provide quick and robust estimates of source parameters of moderate-sized earthquakes located outside the network. [ABSTRACT FROM AUTHOR]

We studied 62 normal-faulting inslab earthquakes in the Mexican subduction zone with magnitudes in the range of 3.6 ≤ M ≤ 7.3 and hypocentral depths of 30 ≤ Z ≤ 108 km. We used different methods to estimate source parameters to observe differences in stress drop, corner frequencies, source dimensions, source duration, energy-to-moment ratio, radiated efficiency, and radiated seismic energy. The behavior of these parameters is derived. We found that normal-faulting inslab events have higher radiated seismic energy, energy-to-moment ratio, and stress drop than interplate earthquakes as expected. This may be explained by the mechanism dependence of radiated seismic energy and apparent stress reported in previous source parameter studies. The energy-to-moment ratio data showed large scatter and no trend with seismic moment. The stress drop showed no trend with seismic moment, but an increment with depth. The radiated seismic efficiencies showed similar values to those obtained from interplate events, but higher than near-trench events. We found that the source duration is independent of the depth. We also derived source scaling relationships for the mentioned parameters. The low level of uncertainties for the seismic source parameters and scaling relationships showed that the obtained parameters are robust. Therefore, reliable source parameter estimation can be carried out using the obtained scaling relationships. We also studied regional stress field of normal-faulting inslab events. Heterogeneity exists in the regional stress field, as indicated by individual stress tensor inversions conducted for two different depth intervals ( Z < 40 km and Z > 40 km, respectively). While the maximum stress axis ( σ ) appears to be consistent and stable, the orientations of the intermediate and minimum stresses ( σ and σ ) vary over the depth intervals. The stress inversion results showed that the tensional axes are parallel to the dip direction of the subducted plate. At depths greater than 40 km, the maximum horizontal stresses are oblique to the dip direction following the general trend of the slab geometry. [ABSTRACT FROM AUTHOR]

We present a new seismic source zone model for the seismic hazard assessment of Slovakia based on a new seismotectonic model of the territory of Slovakia and adjacent areas. The seismotectonic model has been developed using a new Slovak earthquake catalogue (SLOVEC 2011), successive division of the large-scale geological structures into tectonic regions, seismogeological domains and seismogenic structures. The main criteria for definitions of regions, domains and structures are the age of the last tectonic consolidation of geological structures, thickness of lithosphere, thickness of crust, geothermal conditions, current tectonic regime and seismic activity. The seismic source zones are presented on a 1:1,000,000 scale map. [ABSTRACT FROM AUTHOR]

A next generation ground motion model for the prediction of spectral accelerations both in the fore-arc and back-arc regions of the Carpathians Mountains is developed in this research for the Vrancea intermediate depth seismic source in Romania. This ground motion prediction equation (GMPE) is an updated version of the model given in Vacareanuet al.[2014] and is applicable in both the fore-arc and the back-arc regions. The strong ground motion database from which the prediction model is derived consists of over 700 triaxial accelerograms from Vrancea subcrustal seismic events, as well as from other intermediate-depth earthquakes produced in other seismically active regions in the world. The applicability of this ground motion prediction model in both the fore-arc and the back-arc region is tested using the analysis of residuals. Moreover, the appropriateness of this GMPE for soil classes B and C defined in EN 1998-1, as well as for average soil conditions is investigated. All results suggest that this model is an improvement of the previous versions of ground motion prediction equations for Vrancea intermediate-depth seismic source and its use in both the fore-arc and the back-arc regions make it a reliable candidate for more accurate seismic hazard studies of Romania. [ABSTRACT FROM AUTHOR]

The disastrous earthquake of 1693 AD caused over 60,000 causalities and the total destruction of several villages and towns in south-eastern Sicily. Immediately after the earthquake, a tsunami struck the Ionian coasts of Sicily and the Messina Strait and was probably recorded even in the Aeolian Islands and Malta. Over the last few decades, the event has been much debated regarding the location of the seismogenic source and the possible cause of the associated tsunami. The marine event has been related to both a submarine landslide and a coseismic displacement at the seafloor. To better define the most reliable sources and dynamics of the tsunami, we couple high-resolution marine seismic survey data with hydrodynamic modelling to simulate various scenarios of tsunami generation and propagation. Results from the simulations are compared with geomorphological evidence of past tsunami impacts, described in previous work along the coast of south-eastern Sicily, and within historical chronicles and reports. The most reliable scenario considers the 1693 event composed by two different tsunami waves: a first wave generated by the coseismic fault displacement at the seafloor and a second wave generated by a submarine landslide, triggered by the earthquake shaking. Tsunami modelling shows that a simultaneous movement between fault displacement and submarine mass movement could determine a destructive interference on the tsunami waves, resulting in a reduction in wave height. For this reason, the second tsunami wave probably occurred with a maximum delay of few minutes after the one generated by the earthquake and induced a greater flooding. The double-source model could explain the observation because in the course of other destructive earthquakes in south-eastern Sicily, such as that of 1169 AD, the associated tsunami caused less damages. This implies the need to better map, define and assess the hazard responsible for this type of tsunami events., (© 2022. The Author(s).)