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We propose a procedure for uncertainty quantification in Probabilistic Tsunami Hazard Analysis (PTHA), with a special emphasis on the uncertainty related to statistical modelling of the earthquake source in Seismic PTHA (SPTHA), and on the separate treatment of subduction and crustal earthquakes (treated as background seismicity). An event tree approach and ensemble modelling are used in spite of more classical approaches, such as the hazard integral and the logic tree. This procedure consists of four steps: (1) exploration of aleatory uncertainty through an event tree, with alternative implementations for exploring epistemic uncertainty; (2) numerical computation of tsunami generation and propagation up to a given offshore isobath; (3) (optional) site-specific quantification of inundation; (4) simultaneous quantification of aleatory and epistemic uncertainty through ensemble modelling. The proposed procedure is general and independent of the kind of tsunami source considered; however, we implement step 1, the event tree, specifically for SPTHA, focusing on seismic source uncertainty. To exemplify the procedure, we develop a case study considering seismic sources in the Ionian Sea (central-eastern Mediterranean Sea), using the coasts of Southern Italy as a target zone. The results show that an efficient and complete quantification of all the uncertainties is feasible even when treating a large number of potential sources and a large set of alternative model formulations. We also find that (i) treating separately subduction and background (crustal) earthquakes allows for optimal use of available information and for avoiding significant biases; (ii) both subduction interface and crustal faults contribute to the SPTHA, with different proportions that depend on source-target position and tsunami intensity; (iii) the proposed framework allows sensitivity and deaggregation analyses, demonstrating the applicability of the method for operational assessments. [ABSTRACT FROM AUTHOR]

Probabilistic tsunami hazard analysis (PTHA) relies on computationally demanding numerical simulations of tsunami generation, propagation, and non-linear inundation on high-resolution topo-bathymetric models. Here we focus on tsunamis generated by co-seismic sea floor displacement, that is, on Seismic PTHA (SPTHA). A very large number of tsunami simulations are typically needed to incorporate in SPTHA the full expected variability of seismic sources (the aleatory uncertainty). We propose an approach for reducing their number. To this end, we (i) introduce a simplified event tree to achieve an effective and consistent exploration of the seismic source parameter space; (ii) use the computationally inexpensive linear approximation for tsunami propagation to construct a preliminary SPTHA that calculates the probability of maximum offshore tsunami wave height (HMax) at a given target site; (iii) apply a two-stage filtering procedure to these 'linear' SPTHA results, for selecting a reduced set of sources and (iv) calculate 'non-linear' probabilistic inundation maps at the target site, using only the selected sources. We find that the selection of the important sources needed for approximating probabilistic inundation maps can be obtained based on the offshore HMax values only. The filtering procedure is semi-automatic and can be easily repeated for any target sites. We describe and test the performances of our approach with a case study in the Mediterranean that considers potential subduction earthquakes on a section of the Hellenic Arc, three target sites on the coast of eastern Sicily and one site on the coast of southern Crete. The comparison between the filtered SPTHA results and those obtained for the full set of sources indicates that our approach allows for a 75-80 per cent reduction of the number of the numerical simulations needed, while preserving the accuracy of probabilistic inundation maps to a reasonable degree. [ABSTRACT FROM AUTHOR]

SUMMARY In this study, we investigate the rupture history of the 2009 April 6 ( Mw 6.1) L'Aquila normal faulting earthquake by using a non-linear inversion of strong motion, GPS and DInSAR data. Both the separate and joint inversion solutions reveal a complex rupture process and a heterogeneous slip distribution. Slip is concentrated in two main asperities: a smaller shallow patch of slip located updip from the hypocentre and a second deeper and larger asperity located southeastwards along-strike direction. The key feature of the source process emerging from our inverted models concerns the rupture history, which is characterized by two distinct stages. The first stage begins with rupture nucleation and with updip propagation at relatively high (∼4.0 km s−1), but still subshear, rupture velocity. The second stage starts nearly 2.0-2.5 s after nucleation and it is characterized by the along-strike rupture propagation. The largest and deeper asperity fails during this stage of the rupture process. The rupture velocity is larger in the updip than in the along-strike direction. The updip and along-strike rupture propagation are separated in time and associated with a Mode II and a Mode III crack, respectively. The comparison between the source models inferred in this study with the Poisson ratio anomalies in the crustal volume containing the fault plane allows the interpretation of the delay in along-strike rupture propagation in terms of a structural control of the rupture history. Our results show that the L'Aquila earthquake featured a very complex rupture, with strong spatial and temporal heterogeneities suggesting a strong frictional and/or structural control of the rupture process. [ABSTRACT FROM AUTHOR]

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 introduce a rapid and robust, energy-duration procedure, based on the Haskell, extended-source model, to obtain an earthquake moment and a moment magnitude, MED. Using seismograms at teleseismic distances (30°–90°), this procedure combines radiated seismic energy measures on the P to S interval of broadband signals and source duration measures on high-frequency, P-wave signals. The MED energy-duration magnitude is scaled to correspond to the Global Centroid-Moment Tensor (CMT) moment-magnitude, MCMTw, and can be calculated within about 20 min or less after origin time (OT). The measured energy and duration values also provide the energy-to-moment ratio, Θ, used for identification of tsunami earthquakes. The MED magnitudes for a set of recent, large earthquakes match closely MCMTw, even for the largest, great earthquakes; these results imply that the MED measure is accurate and does not saturate. After the 2004 December 26 Sumatra-Andaman mega-thrust earthquake, magnitude estimates available within 1 hr of OT ranged from M= 8.0 to 8.5, the CMT magnitude, available about 3 hr after OT, was MCMTw= 9.0, and, several months after the event, Mw= 9.1–9.3 was obtained from analysis of the earth normal modes. The energy-duration magnitude for this event is MED= 9.2, a measure that is potentially available within 20 min after OT. After the 2006 July 17, Java earthquake, the magnitude was evaluated at M= 7.2 at 17 min after OT, the CMT magnitude, available about 1 hr after OT, was MCMTw= 7.7; the energy-duration results for this event give MED= 7.8, with a very long source duration of about 160 s, and a very low Θ value, indicating a possible tsunami earthquake. [ABSTRACT FROM AUTHOR]

Presents a study of the tsunami following the disastrous earthquake that occurred on September 8, 1905 in Calabria, southern Italy. Analysis by means of numerical modelling; Source fault of the earthquake; Failure of the study to discriminate between Capo Vaticano and Vibo Valentia sources; Macroseismic data; Seismotectonic knowledge of the region.

Examines the numerical modelling of tsunami generation and propagation from submarine slumps in Papua New Guinea. Comparison of the destructive force between tsunamis of submarine slumps and of tectonic origin; Efficiency of deep slumps in producing tsunamis; Generation of water waves by sea-bottom displacements caused by landslides.