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Abstract The 2021 shallow plate‐boundary thrust‐faulting and 2023 outer rise normal‐faultingM_W7.7 earthquakes southeast of the Loyalty Islands produced significant, well‐recorded tsunamis around the North and South Fiji Basins. The two earthquakes occurred in close proximity on opposing sides of the Southern Vanuatu Trench with similar seismic moments and east‐west rupture lengths but different faulting mechanisms. This provides a basis to examine tsunami sensitivity to source geometry and location for paths in the complex southwest Pacific region. Finite‐fault models of the source processes for both events were inverted from teleseismic body wave data with constraints from forward, nonhydrostatic modeling of regional tide gauge and seafloor pressure sensor recordings. The wave motions are reversed in sign, with a leading crest generated by 1.31 m uplift on the upper plate slope for the 2021 tsunami and a leading trough from 2.37 m subsidence on the subducting plate near the trench for the 2023 tsunami. The more recent outer rise normal faulting produces narrower seafloor deformation beneath deeper water resulting in shorter period tsunami waves that shoal and refract more effectively along seamounts and island chains to produce a more elaborate radiation pattern. The source location relative to seamounts and small islands in the near field influences the energy lobes and directionality of the far‐field tsunami to the north. In contrast, both events have very similar radiation patterns to the south due to absence of major bathymetric features immediately southward of the sources. 

Abstract The 1938M_S8.3 and 2021M_W8.2 earthquakes both ruptured within the Semidi segment of the Aleutian‐Alaska subduction zone. The large‐slip distribution of the 2021 event is well constrained within the depth range 25–45 km, with seaward tsunami observations excluding significant shallower coseismic slip. The 1938 event slip distribution is more uncertain. Regional and far‐field tide gauge observations for the 1938 event are modeled to constrain the location of large coseismic slip. The largest slip (2.0 m) is located below the continental shelf on a 180‐km‐long portion of the rupture extending further northeast than the 2021 rupture, to near Sitkinak Island. Minor slip (1.0 m) extends seaward under the continental slope to 8 km deep, where large slip may have occurred in 1788. The megathrust shallower than 25 km depth to the southwest experienced many small aftershocks and aseismic slip following the 2021 event, and has limited slip deficit. 

Abstract The El Niño‐Southern Oscillation (ENSO) influences ocean wave activity across the Pacific, but its effects on island shores are modulated by local weather and selective sheltering of multi‐modal seas. Utilizing 41 years of high‐resolution wave hindcasts, we decipher the season‐ and locality‐dependent connections between ENSO and wave patterns around the Hawaiian Islands. The north and west‐facing shores, exposed to energetic northwest swells during boreal winters, experience the most pronounced ENSO‐related variability, with increased high‐surf activity during El Niño years. While the year‐round trade wind waves exhibit moderate correlation with ENSO, the basin‐wide climate influence is masked by locally accelerated trade winds in channels and around large headlands. The remarkable global‐to‐local pathway through the high‐resolution hindcast enables development of an ENSO‐based semi‐empirical wave model to statistically describe and predict severe wave conditions on vulnerable shores with potential application in coastal risk management and hazard mitigation for Pacific Islands and beyond.