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In this study, we aim to understand the dependence of the critical slip weakening distance on the final slip during the propagation of a dynamic rupture and the consistency of their inferred correlation. To achieve this goal we have performed a series of numerical tests suitably designed to validate the adopted numerical procedure and to verify the actual capability in measuring . We have retrieved two kinematic rupture histories from spontaneous dynamic rupture models governed by a slip weakening law in which a constant distribution on the fault plane as well as a constant ratio are assumed, respectively. The slip velocity and the shear traction time histories represent the synthetic ‘real’ target data which we aim to reproduce. We use a 3-D traction-at-split nodes numerical procedure to image the dynamic traction evolution by assuming our modelled slip velocity as a boundary condition on the fault plane. We assume a regularized Yoffe function as source time function in our modelling attempts and we measure the critical slip weakening distance from the inferred traction versus slip curves at each point on the fault. We compare the inferred values with those of the target dynamic models. Our numerical tests show that fitting the slip velocity functions of the target models at each point on the fault plane is not enough to retrieve good traction evolution curves and to obtain reliable measures of . We find that the estimation of is very sensitive to any small variation of the slip velocity function. An artificial correlation between is obtained when a fixed shape of slip velocity is assumed on the fault (i.e. constant rise time and constant time for positive acceleration) which differs from that of the target model. We point out that the estimation of fracture energy (breakdown work) on the fault is not affected by biases in measuring . [ABSTRACT FROM AUTHOR]

We propose a new source-time function, to be used in kinematic modeling of ground-motion time histories, which is consistent with dynamic propagation of earthquake ruptures and makes feasible the dynamic interpretation of kinematic slip models. This function is derived from a source-time function first proposed by Yoffe (1951), which yields a traction evolution showing a slip-weakening behavior. In order to remove its singularity, we apply a convolution with a triangular function and obtain a regularized source-time function called the regularized Yoffe function. We propose a parameterization of this slip-velocity time function through the final slip, its duration, and the duration of the positive slip acceleration (Tacc). Using this analytical function, we examined the relation between kinematic parameters, such as peak slip velocity and slip duration, and dynamic parameters, such as slip-weakening distance and breakdown-stress drop. The obtained scaling relations are consistent with those proposed by Ohnaka and Yamashita (1989) from laboratory experiments. This shows that the proposed source-time function suitably represents dynamic rupture propagation with finite slip-weakening distances. [ABSTRACT FROM AUTHOR]

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. Plain Language Summary: 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. Key Points: 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 [ABSTRACT FROM AUTHOR]

The westernmost Mediterranean hosts part of the plate boundary between the European and African tectonic plates. Based on the scattered instrumental seismicity, this boundary has been traditionally interpreted as a wide zone of diffuse deformation. However, recent seismic images and seafloor mapping studies support that most of the plate convergence may be accommodated in a few tectonic structures, rather than in a broad region. Historical earthquakes with magnitudes M w > 6 and historical tsunamis support that the low-to-moderate instrumental seismicity might also have led to underestimation of the seismogenic and tsunamigenic potential of the area. We evaluate the largest active faults of the westernmost Mediterranean: the reverse Alboran Ridge, and the strike-slip Carboneras, Yusuf and Al-Idrissi fault systems. For the first time, we use a dense grid of modern seismic data to characterize the entire dimensions of the main fault systems, accurately describe the geometry of these structures and estimate their seismic source parameters. Tsunami scenarios have been tested based on 3D-surfaces and seismic source parameters, using both uniform and heterogeneous slip distributions. The comparison of our results with previous studies, based on limited information on the fault geometry and kinematics, indicates that accurate fault geometries and heterogeneous slip distributions are needed to properly assess the seismic and tsunamigenic potential in this area. Based on fault scaling relations, the four fault systems have a large seismogenic potential, being able to generate earthquakes with M w > 7. The reverse Alboran Ridge Fault System has the largest tsunamigenic potential, being able to generate a tsunami wave amplitude greater than 3 m in front of the coasts of Southern Spain and Northern Africa. • We identify the largest active fault systems of the Alboran Basin. • Characterization of faults is key for accurate tsunamigenic potential estimations. • Alboran largest fault systems may generate M w > 7 earthquakes. • These earthquakes have the potential to generate significant tsunami waves approaching the coast. [ABSTRACT FROM AUTHOR]

We calculated the expected impact on the Italian coast of the Adriatic Sea of a large set of tsunamis resulting from potential earthquakes generated by major fault zones. Our approach merges updated knowledge on the regional tectonics and scenario-like calculations of expected tsunami impact. We selected six elongated potential source zones. For each of them we determined a Maximum Credible Earthquake and the associated Typical Fault, described by its size, geometry and kinematics. We then let the Typical Fault float along strike of its parent source zone and simulated all tsunamis it could generate. Simulations are based on the solution of the nonlinear shallow water equations through a finite-difference technique. For each run we calculated the wavefields at specified simulation times and the maximum water height field (above mean sea level), then generated travel-time maps and maximum water height profiles along the target coastline. Maxima were also classified in a three-level code of expected tsunami threat. We found that the southern portion of Apulia facing Albania and the Gargano promontory are especially prone to the tsunami threat. We also found that some bathymetric features are crucial in determining the focalization-defocalization of tsunami energy. We suggest that our results be taken into account in the design of early-warning strategies. [ABSTRACT FROM AUTHOR]

Tsunami warning centres face the challenging task of rapidly forecasting tsunami threat immediately after an earthquake, when there is high uncertainty due to data deficiency. Here we introduce Probabilistic Tsunami Forecasting (PTF) for tsunami early warning. PTF explicitly treats data- and forecast-uncertainties, enabling alert level definitions according to any predefined level of conservatism, which is connected to the average balance of missed-vs-false-alarms. Impact forecasts and resulting recommendations become progressively less uncertain as new data become available. Here we report an implementation for near-source early warning and test it systematically by hindcasting the great 2010 M8.8 Maule (Chile) and the well-studied 2003 M6.8 Zemmouri-Boumerdes (Algeria) tsunamis, as well as all the Mediterranean earthquakes that triggered alert messages at the Italian Tsunami Warning Centre since its inception in 2015, demonstrating forecasting accuracy over a wide range of magnitudes and earthquake types., (© 2021. The Author(s).)

The 2015/11/17 Lefkada (Greece) earthquake ruptured a segment of the Cephalonia Transform Fault (CTF) where probably the penultimate major event was in 1948. Using near-source strong motion and high sampling rate GPS data and Sentinel-1A SAR images on two tracks, we performed the inversion for the geometry, slip distribution and rupture history of the causative fault with a three-step self-consistent procedure, in which every step provided input parameters for the next one. Our preferred model results in a ~70° ESE-dipping and ~13° N-striking fault plane, with a strike-slip mechanism (rake ~169°) in agreement with the CTF tectonic regime. This model shows a bilateral propagation spanning ~9 s with the activation of three main slip patches, characterized by rise time and peak slip velocity in the ranges 2.5-3.5 s and 1.4-2.4 m/s, respectively, corresponding to 1.2-1.8 m of slip which is mainly concentrated in the shallower (<10 km) southern half of the causative fault. The inferred slip distribution and the resulting seismic moment (M 0  = 1.05 × 10 19 N m) suggest a magnitude of M w 6.6. Our best solution suggests that the occurrence of large (M w  > 6) earthquakes to the northern and to the southern boundaries of the 2015 causative fault cannot be excluded.