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Tsunami coastal hazard is modeled along the US East Coast (USEC), at a coarse regional (450 m) resolution, from coseismic sources located in the Açores Convergence Zone (ACZ) and the Puerto Rico Trench (PRT)/Caribbean Arc areas. While earlier work only considered probable maximum tsunamis, here we parameterize and simulate 18 coseismic sources, with magnitude M8-9 and return periods ∼ 70–2000 year, using seismo-tectonic and historical data. The largest sources in the ACZ are repeats of the 1755 M8.6-9 Lisbon earthquake and tsunami; other sources are hypothetical. In the ACZ, due to the limited data on faults, each source is parameterized with a single fault plane, while in the PRT, coseismic sources are parameterized based on fault segmentation established during a 2019 USGS workshop of experts, using 10–26 SIFT subfault planes (Gica et al. in NOAA Tech. Memo., OAR PMEL-139, 2008). Tsunamis are simulated for each source using the fully nonlinear and dispersive model FUNWAVE-TVD, in two levels of nested grids. At the considered scales, dispersion is shown to affect tsunami propagation. Coastal hazard is quantified by four metrics computed at many save points (∼ 20–30 thousand) defined along the 5-m isobath (due to the coarse resolution), i.e., maximum (1) surface elevation, (2) current, (3) momentum force; and (4) travel time, representing flooding, navigation, structural, and evacuation hazards. Overall, the first three metrics are larger, the larger the source magnitude, and their alongshore variation shows similar patterns of higher/lower values, due to the shelf bathymetric control (refraction). The fourth metric mostly differs between sources from each area, but less so among sources from the same area; its inverse quantifies evacuation hazard. A 1–5 score is given to results for each metric, based on five intensity classes representing low, medium low, medium, high, and highest tsunami hazard. A novel tsunami intensity index is computed as a weighted average of these scores, allowing both a comparison among sources and a quantification of tsunami hazard as a function of their estimated return periods. In the most impacted areas of the USEC, the highest tsunami hazard in the 250–500-year return period range is commensurate with that posed by 100-year category 3–5 tropical cyclones, taking into account the larger current velocities and forces caused by tsunami waves. Results of this work could serve as a basis for a future regional Probabilistic Tsunami Hazard Analysis for the USEC, considering additional source types such as underwater landslides, volcanic flank collapse, and meteotsunamis, that were studied elsewhere. [ABSTRACT FROM AUTHOR]

We perform numerical simulations to assess how coastal tsunami hazard from submarine mass failures (SMFs) is affected by slide kinematics and rheology. Two types of two-layer SMF tsunami generation models are used, in which the bottom (slide) layer is depth-integrated and represented by either a dense Newtonian fluid or a granular flow, in which inter-granular stresses are governed by Coulomb friction (Savage and Hutter model). In both cases, the upper (water) layer flow is simulated with the non-hydrostatic 3D σ-layer model NHWAVE. Both models are validated by simulating laboratory experiments for SMFs made of glass beads moving down a steep plane slope. In those, we assess the convergence of results (i.e., SMF motion and surface wave generation) with model parameters and their sensitivity to slide parameters (i.e., viscosity, bottom friction, and initial submergence). The historical Currituck SMF is simulated with the viscous slide model, to estimate relevant parameters for simulating tsunami generation from a possible SMF sited near the Hudson River Canyon. Compared to a rigid slump, we find that deforming SMFs of various rheology, despite having a slightly larger initial acceleration, generate a smaller tsunami due to their spreading and thinning out during motion, which gradually makes them less tsunamigenic; the latter behavior is controlled by slide rheology. Coastal tsunami hazard is finally assessed by performing tsunami simulations with the Boussinesq long wave model FUNWAVE-TVD, initialized by SMF tsunami sources, in nested grids of increasing resolution. While initial tsunami elevations are very large (up to 25 m for the rigid slump), nearshore tsunami elevations are significantly reduced in all cases (to a maximum of 6.5 m). However, at most nearshore locations, surface elevations obtained assuming a rigid slump are up to a factor of 2 larger than those obtained for deforming slides. We conclude that modeling SMFs as rigid slumps provides a conservative estimate of coastal tsunami hazard while using a more realistic rheology, in general, reduces coastal tsunami impact. [ABSTRACT FROM AUTHOR]

The seismic crisis that hit Calabria (South Italy) since the beginning of 1783, lasted 3 years with strong earthquakes concentrated in the first 2 months, causing many fatalities and great destruction, as reported by several detailed historical reports. Following an earthquake that occurred on February 6, 1783, a mass with volume of about 6 Mm detached from the flank of Mount Pacì and collapsed into the sea. In 1 min, huge waves attacked the nearby village of Scilla and killed most of the people that had gathered in the wide shore named Marina Grande to escape from seismic danger. More than 1500 people died due to the tsunami, many buildings were destroyed. In the paper, such catastrophic event is studied by means of numerical models. First we reconstruct the initial sliding mass and compute its motion through a Lagrangian model; then, we simulate the tsunami generation, propagation and flooding on the coast of Scilla by means of a nonlinear shallow-water equations model. The results of the simulation are compared against the detailed description of the tsunami effects available from several historical accounts and are found to be in a very satisfactory agreement with the 6-8 m inundation height reported in the Marina Grande beach. [ABSTRACT FROM AUTHOR]

Since the devastating earthquake of 2010 in Haiti, significant efforts have been devoted to estimating future seismic and tsunami hazard in Hispaniola. In 2013, following a workshop of experts, UNESCO commissioned an initial modeling study to assess tsunami hazard, essentially from seismic sources, along the North shore of Hispaniola (NSOH), which is shared by the Republic of Haiti (RH) and the Dominican Republic (DR). The scope of this study included detailed tsunami inundation mapping for two selected critical sites, Cap Haitien in RH and Puerto Plata in DR. Results of this effort are reported here, and, although still limited in scope, they are within the framework and contribute to the advancement of the UNESCO IOC Tsunami and other Coastal Hazards Warning System for the Caribbean and Adjacent Regions (CARIBE EWS; von Hillebrandt-Andrade in Science 341:966-968, ). In similar work done for critical areas of the US east coast (under the auspice of the US National Tsunami Hazard Mitigation Program), the authors have modeled the most extreme far-field tsunami sources in the Atlantic Ocean basin, including: (1) a hypothetical $$M_w$$ 9 seismic event in the Puerto Rico Trench (PRT); (2) a repeat of the historical 1755 $$M_w$$ 9 earthquake in the Azores convergence zone (LSB); and (3) a hypothetical extreme $$450\,\hbox {km}^3$$ flank collapse of the Cumbre Vieja Volcano (CVV) in the Canary Archipelago. Here, tsunami hazard assessment is performed along the NSOH for these three sources, plus two additional near-field coseismic tsunami sources: (1) a $$M_w$$ 8 earthquake in the western segments of the nearshore Septentrional fault (SF), as a repeat of the 1842 event; and (2) a $$M_w$$ 8.7 earthquake occurring in selected segments of the North Hispaniola Thrust Fault (NHTF). Initial tsunami elevations are modeled based on each source's parameters and propagated with FUNWAVE-TVD (a nonlinear and dispersive long-wave Boussinesq model) in a series of increasingly fine-resolution nested grids (from 1 arc-min to 205 m) using a one-way coupling methodology. For the two selected sites, coastal inundation is computed with TELEMAC (a Nonlinear Shallow Water wave model), in finer-resolution (12-30 m) unstructured nested grids. While for the EC, PRT is a far-field source, for RH and DR, this would be local source as some of the NSOH would be affected within 1 h or is within 200 km of the PRT. This is per definitions of UNESCO IOC. Regional goes from 200 to 1000 km and within 1 and 3 h, and distant is greater than 3 h and more than 1000 km. We find that among the far-field sources CVV causes the largest impact, with up to 20-m runup at the critical sites while PRT, which is a local source for the NSOH, only causes up to 4-m runup due to its directionality; PRT, however, has both a much shorter return period and would impact the NSOH within 30 min of the earthquake. Among near-field sources, the SF event, as could be expected from a strike-slip fault, only causes a small tsunami, but the NHTF event causes up to 12-m runup in the critical sites, with the tsunami arriving within minutes of the earthquake. Hence, the latter event can be considered as the 'Probable Maximum Tsunami' (PMT; following, e.g., the US Nuclear Regulatory Commission terminology) for the NSOH. Results of detailed coastal modeling for this PMT can be used to develop maps of vulnerability for the critical sites and prepare for mitigating measures and evacuation; a few examples of such maps are given in the paper. Although a number of earlier studies have dealt with each of the far-field tsunami sources, the modeling of their impact on the NSOH and that of the near-field sources, presented here as part of a comprehensive tsunami hazard assessment study, are novel. Future work should model additional coastal sites and may consider effects of tsunamis generated by near-field submarine mass failures. [ABSTRACT FROM AUTHOR]

We present the seismic energy, strain energy, frequency-magnitude relation ( b-value) and decay rate of aftershocks ( p-value) for the aftershock sequences of the Andaman-Sumatra earthquakes of December 26, 2004 ( M 9.3) and March 28, 2005 ( M 8.7). The energy released in aftershocks of 2004 and 2005 earthquake was 0.135 and 0.365% of the energy of the respective mainshocks, while the strain release in aftershocks was 39 and 71% for the two earthquakes, respectively. The b-value and p-value indicate normal value of about 1. All these parameters are in normal range and indicate normal stress patterns and mechanical properties of the medium. Only the strain release in aftershocks was considerable. The fourth largest earthquake in this region since 2004 occurred in September 2007 off the southern coast of Island of Sumatra, generating a relatively minor tsunami as indicated by sea level gauges. The maximum wave amplitude as registered by the Padang, tide gauge, north of the earthquake epicenter was about 60 cm. TUNAMI-N2 model was used to investigate ability of the model to capture the minor tsunami and its effect on the eastern Indian Coast. A close comparison of the observed and simulated tsunami generation, propagation and wave height at tide gauge locations showed that the model was able to capture the minor tsunami phases. The directivity map shows that the maximum tsunami energy was in the southwest direction from the strike of the fault. Since the path of the tsunami for Indian coastlines is oblique, there were no impacts along the Indian coastlines except near the coast of epicentral region. [ABSTRACT FROM AUTHOR]

Hindcasting of a tsunami by numerical simulations is a process of lengthy and complicated deductions, knowing only the final results such as run-up heights and tide records, both of which are possibly biased due to an insufficient number of records and due to hydraulic and mechanical limitation of tide gauges. There are many sources of error. The initial profile, determined with seismic data, can even be different from the actual tsunami profile. The numerical scheme introduces errors. Nonlinearity near and on land requires an appropriate selection of equations. Taking these facts into account, it should be noted that numerical simulations produce satisfactory information for practical use, because the final error is usually within 15% as far as the maximum run-up height is concerned. The state-of-the-art of tsunami numerical simulations is critically summarized from generation to run-up. Problems in the near future are also stated. Fruitful application of computer graphics is suggested. [ABSTRACT FROM AUTHOR]