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We investigate the rupture process of the 2016, Mw6.1 Amatrice earthquake, the first shock of a seismic sequence characterized by three damaging earthquakes occurred in central Italy between August and October. We jointly invert strong motion, High‐Rate GPS data, GPS, and DInSAR displacements and we adopt ad hoc velocity profiles of the crust below each station. The retrieved source model reveals a high degree of complexity, characterized by a prominent bilateral rupture with low slip at the hypocenter, two well‐separated slip patches and a rupture front accelerating when breaking the largest patch. The rupture of the main asperity features a slip‐velocity pulse that is impeded ahead of its current direction and splits into two pulses. In this fault section we find clues of structural and rheological control of the rupture propagation due to the fault system segmentation. This work provides relevant information for Seismology community and the results may have important implications for earthquake hazard assessment. Indeed, indication of the role played by the fault segmentation in limiting the size of single earthquake in Central Italy is gained.In particular, we retrieve the source process of the 2016 Amatrice, central Italy, earthquake by jointly invert for a comprehensive dataset (strong motion, HRcGPS, GPS and DInSAR measurements).The main outcome of our study is that the rupture process has been characterized by a strong geometrical and rheological control due to the presence of important segmentation of the thrust fault system, distinctive of the central Apennines. Indeed, our results provide a complete description of the rupture propagation and inhibition due to the presence of inherited tectonic structures, which role in the seismic sequence evolution could be due to the favourable or unfavourable orientation within the active stress regime geometries and rheological variations between fault blocks. We believe that, in this context, our results are of potential impact for a broad readership because the interaction between new and/or inherited faults, strongly influences the fault segmentation and fault lengths, determining the maximum magnitude of individual earthquakes and consequently the seismic hazard. Full kinematic rupture process of the 2016 Amatrice earthquake was retrieved from nonlinear joint inversion of Strong Motion, HRcGPS, GPS, and DInSAR dataThe complexity of the rupture history has been investigated by means of a rupture velocity and rupture mode propagation detailed analysisThe rupture process of the 2016 Amatrice earthquake has been characterized by a strong geometrical and rheological control due to the fault system segmentation in the central Apennines

We present the first rupture models of the two mainshocks of the 2012 northern Italy sequence, determined by jointly inverting seismic and geodetic data. We aim at providing new insights into the mainshocks for which contrasting seismotectonic interpretations are proposed in literature. Sources' geometric parameters were constrained by seismic reflection profiles, 3‐D relocations and focal mechanisms of mainshocks/aftershocks. Site‐specific velocity profiles were used to model accelerograms affected by strong propagation effects related to the Po basin. Our source models differ significantly from previous ones relying on either seismic or geodetic data. Their comparison against geological sections and aftershock distribution provides new insights about the ruptured thrust faults. The May 20th Mw6.1 mainshock activated the Middle Ferrara thrust‐ramp dipping ∼45° SSW‐wards, breaking a main eastern slip patch 4–15 km deep in Mesozoic carbonates (maximum slip 0.7–0.8 m) and Paleozoic‐Triassic basement rocks, and a small western patch in the basement. The May 29th Mw6.0 mainshock featured two separated asperities along the Mirandola thrust‐ramp dipping ∼42° S‐wards: an eastern asperity 4–15 km deep in Mesozoic carbonates and basement rocks (maximum slip 0.7 m) and a deeper western one (7–16 km depth) mainly in the basement (slip peak 0.8 m). On‐fault aftershocks were concentrated within the basement and Mesozoic carbonates, devoiding high‐slip zones. Slip and aftershock distribution was controlled by the rheological transition between Mesozoic carbonates and Cenozoic sediments. Unlike previous thin‐skinned tectonic interpretations, our results point to a complex rupture process along moderately dipping (40°–45°) thrust‐ramps deeply rooted into the Paleozoic crystalline basement. The two M6 mainshocks of the 2012 Italy sequence are the strongest earthquakes ever observed in the Po Plain, a strategic region for the Italian economy. The mainshocks ruptured blind thrust‐faults, however their source models and seismotectonic interpretation are still debated because the thrust‐system architecture is controversial. Contrasting thick‐skinned and thin‐skinned tectonic models are proposed. In thick‐skinned interpretations, shortening is accommodated by thrust‐ramps rooted into the crystalline basement that represent main seismogenic structures, whereas in thin‐skinned interpretations, shortening and seismicity are controlled by listric faults splaying out from dècollement levels in the sedimentary crust. A comprehensive analysis of the mainshocks' source represents an opportunity to provide new insights into the seismogenesis in northern Italy and on a broader scale into seismotectonics of thrust‐and‐fold belts. We get a complete picture of the mainshocks kinematics by jointly inverting, for the first time, seismic and geodetic data, and unravel rupture heterogeneities not resolved by previous studies. By integrating source models with aftershock locations and geological models, we propose a comprehensive seismotectonic interpretation of the sequence. We conclusively identify the ruptured faults that correspond to thrust‐ramps rooted into the crystalline basement and evidence the key role played by lithological changes in the rupture process. Rupture models of the 2012 northern Italy mainshocks obtained by inverting the most comprehensive geodetic and strong motion data set to dateBoth mainshocks ruptured two asperities along moderately dipping thrusts rooted into the Paleozoic crystalline basement down to ∼15 km depthAsperities located in Mesozoic carbonates and Paleozoic basement and slip distribution controlled by lithological and structural barriers Rupture models of the 2012 northern Italy mainshocks obtained by inverting the most comprehensive geodetic and strong motion data set to date Both mainshocks ruptured two asperities along moderately dipping thrusts rooted into the Paleozoic crystalline basement down to ∼15 km depth Asperities located in Mesozoic carbonates and Paleozoic basement and slip distribution controlled by lithological and structural barriers

The SW Iberian margin is one of the most seismogenic and tsunamigenic areas in W‐Europe, where large historical and instrumental destructive events occurred. To evaluate the sensitivity of the tsunami impact on the coast of SW Iberia and NW Morocco to the fault geometry and slip distribution for local earthquakes, we carried out a set of tsunami simulations considering some of the main known active crustal faults in the region: the Gorringe Bank (GBF), Marquês de Pombal (MPF), Horseshoe (HF), North Coral Patch (NCPF) and South Coral Patch (SCPF) thrust faults, and the Lineament South strike‐slip fault. We started by considering for all of them relatively simple planar faults featuring with uniform slip distribution; we then used a more complex 3D fault geometry for the faults constrained with a large 2D multichannel seismic dataset (MPF, HF, NCPF, and SCPF); and finally, we used various heterogeneous slip distributions for the HF. Our results show that using more complex 3D fault geometries and slip distributions, the peak wave height at the coastline can double compared to simpler tsunami source scenarios from planar fault geometries. Existing tsunami hazard models in the region use homogeneous slip distributions on planar faults as initial conditions for tsunami simulations and therefore underestimate tsunami hazard. Complex 3D fault geometries and non‐uniform slip distribution should be considered in future tsunami hazard updates. The tsunami simulations also support the finding that submarine canyons attenuate the wave height reaching the coastline, while submarine ridges and shallow shelves have the opposite effect. Deformation along the present‐day plate boundary between Africa and Eurasia off SW Iberia is distributed over a 200‐km‐wide and 600‐km‐long area, and is mainly accommodated by thrusts and strike‐slip faults. The region hosts frequent seismic activity of moderate magnitude punctuated by higher magnitude events, which have also originated major historical and pre‐historical tsunamis. The run‐up and coastal area affected by these tsunamis depend on the characteristics and location of the seismic source, bathymetry, and morphology of the coasts. Previous tsunami hazard assessments in the region used simplified fault models for tsunami simulations, ignoring the detailed 3D fault geometry and slip distribution. To investigate the sensitivity of the tsunami impact and eventually of the hazard to these complexities, we have carried out a series of tsunami simulations using planar and 3D fault surfaces, as well as homogeneous and heterogeneous slips. To build the fault surfaces, we used a large dataset of 2D multichannel seismic profiles that images the active faults in the region. Our study indicates that using the more complex fault models produce significantly larger tsunamis with the modeled wave heights at the coastline that can be several times bigger than those generated using planar fault sources. The tsunami is sensitive to both the fault geometry and the slip distributionIntroducing complexity into the fault geometry and slip distribution can strongly enhance the simulated wave height at the coastOversimplified source models may hinder the prediction of the tsunami intensity, hence the tsunami hazard analysis The tsunami is sensitive to both the fault geometry and the slip distribution Introducing complexity into the fault geometry and slip distribution can strongly enhance the simulated wave height at the coast Oversimplified source models may hinder the prediction of the tsunami intensity, hence the tsunami hazard analysis

The tsunami source of the 2021 MW8.1 Raoul Island earthquake in the Kermadec subduction zone was estimated by inverting the tsunami signals recorded by Deep‐ocean Assessment and Reporting of Tsunamis (DART) bottom pressure sensors and coastal tide‐gauges. The main asperity of up to 5 m of slip is located northeastward from the hypocenter, with features compatible with the aftershock distribution and rapid back‐projection analysis. Three earthquakes of MW∼8 or larger which also produced moderate tsunamis happened in the 20th century in the same portion of the subduction zone. This is the first great tsunamigenic event captured by the new New Zealand DART network in the South West Pacific, which proved valuable to estimate a robust image of the tsunami source. We also show a first proof of concept of the capability of this network to reduce the uncertainty associated with tsunami forecasting and to increase the lead time available for evacuation for future alerts. We estimated the tsunami source for the 4 March 2021 Raoul Island earthquake (MW8.1), obtained by inverting tsunami data from tide‐gauges and open ocean Deep‐ocean Assessment and Reporting of Tsunamis (DART) stations. The main asperity of up to 5 m of slip is located northeastward from the hypocenter, with features compatible with the aftershock distribution and rapid back‐projection analysis. This event is important because it was the strongest one of three earthquakes that occurred within hours during the same day. Moreover, it caused the largest of three tsunami that altogether represent a great test for the New Zealand DART new network. The results demonstrate the potential importance of this new DART network for resolving the tsunami source and for early warning purposes as it can reduce the uncertainty of the tsunami forecasts and at the same time increase the lead time available for evacuation. Tsunami source of the 2021 MW8.1 Raoul Island earthquake by inverting tsunami waveformsThe main slip peaks at 5 m and is located at a depth of ∼20–30 and ∼100 km north of the epicenterNew Deep‐ocean Assessment and Reporting of Tsunamis network was crucial for characterizing the source and will significantly reduce the uncertainty and speed up future warnings Tsunami source of the 2021 MW8.1 Raoul Island earthquake by inverting tsunami waveforms The main slip peaks at 5 m and is located at a depth of ∼20–30 and ∼100 km north of the epicenter New Deep‐ocean Assessment and Reporting of Tsunamis network was crucial for characterizing the source and will significantly reduce the uncertainty and speed up future warnings

Abstract—On October 4, 1994, an earthquake of magnitude Mw = 8.2 occurred in the western part of the Kurile Islands, generating a tsunami that has been well recorded along the entire coast of Japan. Previous works have shown that this earthquake does not represent a low angle thrust event, normally expected in a subduction zone, rather an intra-plate event rupturing through the slab. On the basis of the accepted mechanism, two fault models, representative of the nodal plane ambiguity, have been suggested. The goal of this work is to verify whether the tsunami simulations are able to rule out one of the two proposed fault models. Taking into account both fault models together with a heterogeneous slip along the fault, we have performed numerical simulations of the tsunami. All source models produce tide-gauge records in agreement with the observed ones. The limit of resolution of the performed simulations, estimated by means of a perturbed bathymetry, does not allow us to distinguish the best source model.

The 1908 Messina Straits tsunami is the last catastrophic event that hit the Italian coast. The parent earthquake may be considered one of the strongest shocks reported in Italian seismic catalogues. Several source models have been; proposed in the literature that are quite different with regard to almost all the fault parameters. The aim of this work is to evaluate whether tsunami data can add reliable inforiration for the identification of the fault mechanism of this earthquake. Tsunamis generated by two of the faults proposed in the literature were simulated via finite-element modelling in a former work (see Piatanesi et al., 1998): the results were in good agreement with the observations as regards the polarity of the first wave, whereas a relevant disagreement was found as far as run-up data were concerned. In this paper, that may be considered the continuation of the previous work, we focus on a particular fault, the one proposed by Capuano et al. (1988), and simulate the consequent tsunami adding two new features to possibly improve the agreement with run-up observations: i) an algorithm allowing for the effect of the sea bottom bathymetry on the tsunami initial condition, and ii) a heterogeneous slip distribution on the fault.

Finite-element methods are often used to compute the evolution of tsunami waves over a grid suitably adapted to the selected basin. In this article it is shown that the finite-element space discretization of the shallow-water wave equations leads to a set of differential equations that are first order in time, and that, after linearization, admit a solution in terms of a linear operator we call the wave propagator. The initial perturbation is decomposed over the basis of the wave propagator eigenvectors, modified according to factors suitably depending on time and eventually synthesized as a superposition of the grid eigenmodes. The properties of the solution can therefore be analyzed in terms of the spectral components of the initial fields and of the spectral properties of the wave propagator. It is shown that a wave propagator can be defined even when the problem is constrained by means of the conditions imposed on the grid boundaries, which is indeed what occurs in all practical applications. Free and constrained wave propagator spectra are analyzed and discussed. The theory is applied to compute tsunami wave propagation in two simple cases: aflat-bottom channel and a flat-bottom, closed, rectangular basin. These examples are instructive since they permit us to introduce two simple methods for improving the numerical solution by controlling the numerical noise: annihilation of the exponentially growing spectral components and cutting of the high-frequency eigenmodes.

The earthquake we are dealing with occurred on December 28, 1908: because of the number of victims (about 60,000) and the extension of the destroyed area (6,000 km2), this earthquake with the epicentral MCS intensity XI may be considered the strongest event ever reported for Italy along with the 1693 eastern Sicily earthquake. The shock produced a large tsunami that caused severe damage and many victims. In all places the first sea movement was a withdrawal for a few minutes, followed by a flooding of the coast with at least three big waves. A post-event survey allowed to estimate flooding and run-up heights (more than 10 m in some places). In this work we perform some numerical simulations of the tsunami generation and propagation, taking into account different source faults: the model is based on the shallow water equations, solved numerically by means of a finiteelement method. The computational domain, covered by a mesh consisting of triangular elements, includes the Messina Straits and the sea facing the northeastern coast of Sicily and southern Calabria.

Tsunami waveform inversion is often used to retrieve information about the causative seismic tsunami source. Tide gauges record tsunamis routinely; however, compared to deep‐ocean sensor data, tide‐gauge waveform modeling is more difficult due to coarse/inaccurate local bathymetric models resulting in a time mismatch between observed and predicted waveforms. This can affect the retrieved tsunami source model, thus limiting the use of tide‐gauge data. A method for nonlinear inversion with an automatic optimal time alignment (OTA), calculated by including a time shift parameter in the cost function, is presented. The effectiveness of the method is demonstrated through a series of synthetic tests and is applied as part of a joint inversion with interferometric synthetic aperture radar data for the slip distribution of the 2015 Mw8.3 Illapel earthquake. The results show that without OTA, the resolution on the slip model degrades significantly and that using this method for a real case strongly affects the retrieved slip pattern. Optimal time alignment (OTA) overcomes known modeling issues of tsunami tide‐gauge records for source inversionSynthetic tests are used to illustrate and validate the new method showing how OTA significantly improves the retrieved source modelWith OTA method the tsunami source of the Illapel earthquake is displaced trenchward