Aftershock Blue Cool Citrus Liqueur, 70 cl

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Tanioka, Y. & Satake, K. Tsunami generation by horizontal displacement of ocean bottom. Geophys. Res. Lett. 23, 861–864 (1996). The specific geometry of the inferred slow thrust faulting, with along-trench compression in the upper plate, is surprising, and if this model is correct, it comprises an unexpected tsunami hazard in the region. The presence of weak sediments near the shelf break may have influenced slow-slip rupture with 15 m of slip over ~300 s, as found for this successful model, which has fault dimensions of 20 km × 20 km. Such large slip over localized area has been observed in shallow megathrusts environments, typically involving a tsunami earthquake 23 or aseismic transient slip 24. Transpressional environments have been observed to have large slow thrust faulting along with dominant strike-slip faulting as well 25. Models with a larger fault area (30 km × 30 km; 40 km × 40 km) and lower slip (7 m, 4 m) that have similar total moment may be viable, but it is challenging to fit all of the tsunami data as well as in Fig. 8 (e.g., Supplementary Figs. 16, 17). While lower slip is appealing, larger fault dimensions imply more observable faulting in the wedge, for which available bathymetry and reflection profiling now provide independent evidence. The non-unique modeling suggests slow slip of from 4 to 15 m on the westward-dipping upper plate thrust fault. Okal, E. A. & Hébert, H. Far-field simulation of the 1946 Aleutian tsunami. Geophys. J. Inter. 169, 1229–1238 (2007). Liu, C., Lay, T., Xiong, X. & Wen, Y. Rupture of the 2020 M W 7.8 earthquake in the Shumagin gap inferred from seismic and geodetic observations. Geophys. Res. Lett. 47, e2020GL090806 (2020). Bai, Y., Ye, L., Yamazaki, Y., Lay, T. & Cheung, K. F. The 4 May 2018 M W 6.9 Hawaii Island earthquake and implications for tsunami hazards. Geophys. Res. Lett. 45, 11,040–11,049 (2018).

Bécel, A. et al. Tsunamigenic structures in a creeping section of the Alaska subduction zone. Nat. Geosci. 10, 609–613 (2017).Four levels of telescopic grids are needed to model the tsunami from the sources with increasing resolution to the Kahului tide gauge. An additional level is needed to resolve the more complex waterways leading to Hilo, King Cove, and Sand Point. Supplementary Fig. 7 shows the layout of the computational grid systems. The level-1 grid extends across the North Pacific at 2-arcmin (~3700 m) resolution, which gives an adequate description of large-scale bathymetric features and optimal dispersion properties for modeling of trans-oceanic tsunami propagation with NEOWAVE 35. The level-2 grids resolve the insular shelves along the Hawaiian Islands at 24-arcsec (~740 m) and the continental shelf of the Alaska Peninsula at 30-arcsec (~925 m), while providing a transition to the level-3 grids for the respective islands or coastal regions at 6-arcsec (~185 m) resolution. The finest grids at levels 4 or 5 resolve the harbors where the tide gauges are located at 0.3-arcsec (9.25 m) or 0.4 arcsec (12.3 m). A Manning number of 0.025 accounts for the sub-grid roughness at the harbors. The digital elevation model includes GEBCO at 30-arcsec (~3700 m) resolution for the North Pacific, multibeam and LiDAR data at 50 m and ~3 m in the Hawaii region, and NCEI King Cove 8/15-arcsec dataset and Sand Point V2 1/3-arcsec dataset, which also covers the Shumagin Islands. Long-period spectral analysis Xiao, Z. et al. The deep Shumagin gap filled: Kinematic rupture model and slip budget analysis of the 2020 M W 7.8 Simeonof earthquake constrained by GNSS, global seismic waveforms, and floating InSAR. Earth Planet. Sci. Lett. 576, 117241 (2021). An upper plate splay-fault model for the additional source of tsunami waves involves a compact 20 km × 30 km slip patch with an upper edge 3 km deep, and strike 250°, dip 35°, and rake 90°, with 12 m of pure thrust slip. The slow-fault ruptures at the same time as the initiation of the earthquake and lasts for 5 min. Assuming a rigidity of 30 GPa, appropriate for the shallow megathrust environment, the seismic moment is 2.16 × 10 20 Nm ( M W 7.49). The computed seafloor deformations for the two-fault coseismic rupture and the slow thrust slip on the splay patch are shown in Supplementary Fig. 10, separately and combined. The thrust splay patch is located near the shelf break and similar to the dipole fitting has about 20 km absolute uncertainty, but cannot locate significantly out onto the continental slope, as the tsunami excitation changes rapidly along the slope and incompatible waveforms are produced at the DART stations. The resulting seafloor deformation again resembles a scaled-up version of the 2-fault model with uplift and subsidence straddled across the shelf break. Comparisons of the observed and computed tsunami signals for the three-fault model are shown in Supplementary Fig. 11, with clear uniform improvement relative to the two-fault solution in Fig. 4. The fits are slightly improved in comparison to those for the optimal megathrust slow-slip model in Supplementary Fig. 9. The large second arrival and the following trough in the DART waveforms are matched well by the slow-slip event. The computed tsunami waves from the two sources are out-of-phase in Hawaii waters and the matching with the tide gauge records through destructive interference is remarkable (Supplementary Fig. 11). Again, we reject this specific model despite its ability to match the tsunami data because it predicts larger dynamic displacements at GNSS stations AC12 and AC28 (Supplementary Fig. 10), which are not observed after the motions from the fast rupture. Coulomb failure stress Fukao, Y. et al. Detection of “Rapid” aseismic slip at the Izu-Bonin trench. J. Geophys. Res.: Solid Earth 126, e2021JB022132 (2021).

To match the observed tsunami waveforms, an additional stronger source of tsunami excitation is required, but the two-fault fast-slip model alone already adequately accounts for the full set of seismic and geodetic data. This holds even for 256 s period Rayleigh and Love waves from global stations, for which the two-fault model predicts the four-lobed radiation patterns well (Supplementary Fig. 6). From the DART waveform comparisons, the additional source must have a 4–5 min delay relative to the initial compound faulting to account for the larger second peak, yet the nearby geodetic ground motions show no deformation after the first 60 s. The earlier deformation is well accounted for by the two-fault fast-slip model (Fig. 3c). Because the tsunami wave period is inversely proportional to the square root of the source water depth, the excitation most likely includes uplift of the sea surface over the continental slope to account for the impulsive peak along with some drawdown near the shelf break to match the wide trough that follows immediately.

Horowitz, W. L., Steffy, D. A. & Hoose, P. J. Geologic report for the Shumagin Planning Area, Western Gulf of Alaska. (U.S. Department of the Interior, Minerals Manages Services, Alaska OCS Region, 1989). OCS Report, MMS 89-0097. For the intraslab fast-slip strike-slip fault, computations use seismic moment M 0 = 2.43 × 10 20 Nm, strike 350°, dip 50°, rake 173°, and depth 35.5 km. For the upper plate fast-slip oblique normal fault, computations use M 0 = 0.29 × 10 20 Nm, strike 260°, dip 35°, rake 225°, and depth 15 km. For the upper plate slow-slip thrust fault, computations use M 0 = 1.8 × 10 20 Nm, W = 20 km, L = 20 km, slip 15 m, strike 190°, dip 30°, rake 90°, and depth 8 km. The rigidity used for the strike-slip faulting was 5.4 GPa, and it was 3.2 GPa for the oblique faulting and 3.0 GPa for the thrust faulting. Slow megathrust rupture Shillington, D. J., Bécel, A. & Nedimovíc, M. R. Upper plate structure and megathrust properties in the Shumagin Gap near the July 2020 M7.8 Simeonof event. Geophys. Res. Lett. 49, e2021GL096974 (2022). Niazi, M. & Chun, K. Y. Crustal structure in the southern Bering Shelf and the Alaska Peninsula from inversion of surface-wave dispersion data. Bull. Seism. Soc. Amer. 79, 1883–1893 (1989). Ye, L. et al. Rupture model for the 29 July 2021 M W 8.2 Chignik, Alaska earthquake constrained by seismic, geodetic, and tsunami observations. J. Geophys. Res.: Solid Earth 127, e2021JB023676 (2022).