Hurricanes Irma and Maria caused catastrophic damages across the Caribbean Islands during the 2017 hurricane season. After the storms, a joint United States–Japanese team investigated coastal impacts in the US Virgin Islands, which are composed of the islands of St. Thomas, St. John, Water Island, and St. Croix. Coastal inundation was dominated by wave run-up in almost all locations, with many locations showing inundation exceeding 4-m elevation from mean sea level. In contrast, maximum elevations recorded at tide gauges did not exceed 1 m at any location. Coastal damage was relatively minor for such strong hurricanes because of the lack of heavy development at low elevations on the most exposed coastlines. Many moored vessels were destroyed, and coastal structures and infrastructure within the inundation region suffered significant damage. However, few large structures experienced catastrophic losses from coastal inundation. In contrast, strong winds caused extensive structural damage throughout the US Territory. Evidence was seen for past inundation of the coastline, but could not be conclusively linked to any particular events.

We investigated ship navigation records known as Automatic Identification System (AIS) data near the source region of the 2011 Tohoku, Japan, tsunami. The AIS data of 16 ships in the offshore navigation could be compiled by about 40 min after the tsunami generation. Most of the AIS data showed notable deviation of the ship heading from the course over ground during the tsunami passage. There was good agreement in terms of amplitude/phase between the ship velocity and the simulated tsunami velocity in the direction normal to the ship heading. An equation of motion due to wave drag and inertia forces was examined for an offshore movable floating body. We explain that the ship movement in the direction normal to the heading immediately responds to the tsunami current, and relative velocity between the ship and the tsunami current asymptotically become zero. This indicates the movement velocity of navigating ships in the direction normal to the heading derived from AIS data will work as an offshore tsunami current meter. We examined the AIS data during the 2011 Tohoku tsunami and showed these data could be useful for tsunami source estimation and forecast. The AIS data in the current framework will possibly be a crowd-sourced tool for monitoring offshore tsunami current and tsunami forecast.

Ocean bottom pressure (OBP) observations are a powerful tool for determining vertical crustal displacements, especially due to earthquakes and slow earthquakes, with centimeter‐level resolution. In these studies, removal of oceanographic noise (tens of centimeters) is required to identify centimeter‐level crustal deformation. We undertake barotropic modeling to remove oceanographic signals from data from an OBP array deployed offshore New Zealand in 2014/2015. We show that removing the nontidal component calculated from a barotropic ocean model reduces the variance in the data by about 66% and provides a feasible means to resolve pressure changes due to crustal deformation during the slow slip events. We also discuss the vertical displacements from slow slip events that occurred in late September to mid‐October 2014, and we outline our procedure for processing OBP data.

A tsunamigenic earthquake with a moment magnitude of 7.3 occurred near the Japan Trench, off Tohoku, northeast Japan, on 7 December 2012. Operational seismic monitoring inferred that the earthquake was composed of doublet sources of comparable magnitudes: the first event was reverse faulting and the second event, which occurred 10–20 s later, was normal faulting. An associated tsunami was observed at offshore stations, having an amplitude of 10⁻¹to 10¹cm. Inverse modeling using the observed tsunami records reveals possible vertical seafloor deformations. We can then constrain, in terms of the source location, that the tsunamigenic earthquake involves two subfaults across the Japan Trench: one is the outer trench reverse faulting as the first event and the second is the inner trench normal faulting. The present study shows that tsunami analysis with seismograph analyses effectively constrains the epicenter locations, even in the case of complex earthquakes like doublets.

Recent studies have shown that ocean‐bottom pressure gauges (OBPs) can record seismic waves in addition to tsunamis and seafloor permanent displacements, even if they are installed inside the focal area where the signals are extremely large. We developed a method to extract dynamic ground motion waveforms from near‐field OBP data consisting of a complex mixture of various signals, based on an inversion analysis along with a theory of tsunami generation. We applied this method to the OBP data of the 2011 Tohoku‐Oki earthquake. We successfully extracted the low‐frequency vertical seismograms inside the focal area (f < ∼0.05 Hz), although those of the Mw ∼9 megathrust earthquake had never previously been reported. The seismograms suggested two dominant energy releases around the hypocenter. The seismic wave signals recorded by the near‐field OBP will be important not only to reveal earthquake ruptures and tsunami generation processes but also to conduct real‐time tsunami forecasts.