Transoceanic Tsunami Research Articles

Records of the 5 March 2021 Raoul Island transoceanic tsunami around the Pacific Ocean

ABSTRACT At 19:28 AM on 4 March 2021 (UTC), a Mw 8.1 megathrust earthquake occurred close to Raoul Island, New Zealand, on the Kermadec Subduction Zone. Closely following two other tsunamigenic ruptures, it triggered a tsunami that was quickly recorded by oceanic and coastal gauges. Analysis of 158 filtered sea-level records revealed that the tsunami had not only a regional impact but was recorded by most gauges in the Pacific Ocean and eight gauges in the Indian and the southern Atlantic Oceans, in good agreement with modelling results of tsunami propagation. Careful determination of tsunami arrival times and first and largest waves amplitude for each station support the fact that the first wave is almost never the highest one. The maximum amplitude is about three times higher than the first wave amplitude and the largest wave is recorded with a median value of ∼3 h after the first arrival. In addition, recordings of the largest wave of this small but transoceanic tsunami are not related to the distance to the earthquake epicentre. Finally, this tsunami which occurred simultaneously with several localised storms in the Pacific Ocean is an opportunity to highlight the difficulty in distinguishing between the different types of waves.

Simulation of Tsunami Inundation for the Island of Martinique to Nearby Large Earthquakes

ABSTRACT In this article, we estimate the tsunami hazard in Martinique due to tsunamis generated by earthquakes associated with the Lesser Antilles subduction zone. Using a deterministic approach based on reliable earthquake scenarios, we use high-resolution bathymetric and topographic data to model tsunami propagation and inundation with Cornell Multi-grid Coupled Tsunami model. An extreme earthquake subduction scenario of magnitude Mw 8.0 is tested, and a further realistic scenario of lower magnitude Mw 7.5, thus of different tsunami frequency content, is also processed to test the possible appearance of bay resonances. We find that the western coast of the island is relatively sheltered, because it represents a shadow area to diffraction, in particular, for the major city of Fort de France. Because of its very gentle slope, the eastern coast is prone to numerous floodings with meter scale wave amplitudes; most of the inundated zones consist of mangroves and geological depressions t are naturally regularly flooded by tides or storm surges. Hence such areas are often not exploited, the mangroves being let in their natural state, enhancing the protection of the surrounding communities. However, some strategic inhabited areas are subject to severe inundation. Finally, comparing our results with studies of the 1755 Lisbon transoceanic tsunami reveals a tsunami hazard close to our local Mw 7.5 scenario. It suggests the possibility to generalize our local tsunami hazard assessment in Martinique to other tsunami contexts and enlarge its validity. This issue is crucial for minimizing the efforts and increasing the efficiency of tsunami preparedness.

The near-field tsunami generated by the 15 January 2022 eruption of the Hunga Tonga-Hunga Ha’apai volcano and its impact on Tongatapu, Tonga

On 15 January 2022 at 04:15 UTC, the Hunga Tonga-Hunga Ha’apai (HTHH) volcano in Tonga produced a massive eruption that triggered a transoceanic tsunami generated by the coupled ocean and atmospheric shock wave produced during the explosion. The tsunami first reached the coast of Tonga and eventually reached many coasts around the world. This volcano previously underwent a massive eruption in 1100 AD, and an eruption occurs approximately every 1000 years. The 2022 HTHH event provides an opportunity to study a major volcanically generated tsunami that caused substantial damage. In this study, we present a numerical simulation of a tsunami with a state-of-the-art numerical model based on a submarine explosion scenario. We constrain the geometry and magnitude of the explosion energy source based on analyses of pre- and post-event satellite images, which demonstrate that the explosion magnitude varied from 1 to 90 megatons of trinitrotoluene (Mt). Estimated submarine explosion geometries result in a suitable explosion magnitude of approximately 25 Mt, as determined with the waveform from the tide gauge in the time and frequency domains. The tsunami wave first reached the northwestern part of Tonga’s Tongatapu within 10 min, with a maximum runup height of approximately 15 m, and covered the whole of Tongatapu within 30 min. Finally, the numerical simulation provides deep insights into the physical volcanic explosion processes and improves our understanding and forecasting capabilities of frequent and catastrophic tsunamis caused by submarine volcanic explosions.

Tsunami Effects on the Coast of Mexico by the Hunga Tonga-Hunga Ha'apai Volcano Eruption, Tonga.

The massive explosion by the January 15, 2022 Hunga Tonga-Hunga Ha’apai volcano in Tonga triggered a trans-oceanic tsunami generated by coupled ocean and atmospheric shock waves during the explosion. The tsunami reached first the coast of Tonga, and later many coasts around the world. The shock wave went around the globe, causing sea perturbations as far as the Caribbean and the Mediterranean seas. We present the effects of the January 15, 2022 Tonga tsunami on the Mexican Pacific Coast, Gulf of Mexico, and Mexican Caribbean coast, and discuss the underrated hazard caused by great volcanic explosions, and the role of early tsunami warning systems, in particular in Mexico. The shock wave took about 7.5 h to reach the coast of Mexico, located about 9000 km away from the volcano, and the signal lasted several hours, about 133 h (5.13 days). The shock wave was the only cause for sea alterations on the Gulf of Mexico and Caribbean Sea, while at the Mexican Pacific coast both shock wave and the triggered tsunami by the volcano eruption and collapse affected this coast. The first tsunami waves recorded on the Mexican Pacific coast arrived around 12:35 on January 15, at the Lázaro Cárdenas, Michoacán tide gauge station. The maximum tsunami height exceeded 2 m at the Ensenada, Baja California, and Manzanillo, Colima, tide gauge stations. Most tsunami warning advisories, with two exceptions, reached communities via social media (Twitter and Facebook), but did not clearly state that people must stay away from the shore. We suggest that, although no casualties were reported in Mexico, tsunami warning advisories of far-field tsunamis and those triggered non-seismic sources, such as landslides and volcanic eruptions, should be included and improved to reach coastal communities timely, explaining the associated hazards on the coast.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00024-022-03017-9.

Deterministic tsunami hazard assessment and zoning approach using far-field and near-field sources: Study of Cixi County of Zhejiang Province, China

Investigating the potential tsunami hazard for coastal regions is helpful for urban development and emergency evacuation. In this paper, we present a deterministic method for tsunami hazard assessment (DTHA) in terms of tsunami amplitude and tsunami-induced currents. 21 extreme far-field transoceanic tsunami sources located in the Pacific Rim and, 14 near-field sources in Ryukyu Trough and Manila Trench are suggested. The Digital Elevation Model (DEM) data of 50 m combined with coastal breakwater data is adopted. The tsunami hazard is analyzed based on tsunami amplitude and tsunami-induced velocity. The coastal risk of Cixi County is presented and discussed. The results highlight the necessity of combining the tsunami amplitude and tsunami-induced currents in hazard assessment with the protective role of breakwaters. Further study manifests the effects of astronomical tide on tsunami hazard. The submarine topography consisted of ridges and trenches could trap tsunami energy and change propagation direction. The heterogeneous effect of slip distribution on tsunami hazard assessment is investigated, indicating the feasibility of using uniform slip source in DTHA. This study provides a comprehensive and quantitative assessment method incorporating tide, DEM, breakwater, and multiple sources to evaluate the tsunami risk for hazard reduction and urban planning.

Accelerating an Adaptive Mesh Refinement Code for Depth‐Averaged Flows Using GPUs

AbstractSolving the shallow water equations efficiently is critical to the study of natural hazards induced by tsunami and storm surge, since it provides more response time in an early warning system and allows more runs to be done for probabilistic assessment where thousands of runs may be required. Using adaptive mesh refinement speeds up the process by greatly reducing computational demands while accelerating the code using the graphics processing unit (GPU) does so through using faster hardware. Combining both, we present an efficient CUDA implementation of GeoClaw, an open source Godunov‐type high‐resolution finite volume numerical scheme on adaptive grids for shallow water system with varying topography. The use of adaptive mesh refinement and spherical coordinates allows modeling transoceanic tsunami simulation. Numerical experiments on the 2011 Japan tsunami and a local tsunami triggered by a hypothetical Mw 7.3 earthquake on the Seattle Fault illustrate the correctness and efficiency of the code, which implements a simplified dimensionally split version of the algorithms. Both numerical simulations are conducted on subregions on a sphere with adaptive grids that adequately resolve the propagating waves. The implementation is shown to be accurate and faster than the original when using Central Processing Units (CPUs) alone. The GPU implementation, when running on a single GPU, is observed to be 3.6 to 6.4 times faster than the original model running in parallel on a 16‐core CPU. Three metrics are proposed to evaluate relative performance of the model, which shows efficient usage of hardware resources.

Source Estimate for the 1960 Chile Earthquake From Joint Inversion of Geodetic and Transoceanic Tsunami Data

AbstractThe slip distribution of the 1960 Chile earthquake was estimated using geodetic data, local tsunami data, and newly usable transoceanic tsunami data. The large slips triggered a significant tsunami which was recorded by the tide gauges around the Pacific Ocean. We performed a two‐step inversion to estimate the slip distribution. In the first step, we jointly inverted the tsunami waveforms and local geodetic data to recover the ground and seafloor vertical displacement. The transoceanic tsunami data could not be used for waveform inversions until the wave phase and arrival time discrepancies were recently reconciled by improving the long‐wave theory with the phase correction method. The random arrival time discrepancy due to inaccurate local bathymetry and/or instrumental problems was considered by the optimal time alignment. In the second step, we estimated the slip distribution on the plate interface by inverting the vertical displacement obtained in the first step. Checkerboard tests showed that our method and data can resolve displacement at a spatial resolution of at least ~100 km but cannot estimate the rupture velocity. The result for actual data shows a rupture extended about 800 km with a width of about 150 km and three asperities. The large slips are concentrated in the offshore shallow plate interface. Our results indicate that the central and south patches contribute to the large coastal elevation changes at southern source area and high tsunami waves at far field. The estimated moment ranges 1.3–1.9 × 1023 Nm (Mw 9.3–9.4) for rake angles of 90–140°.

Far-Field Tsunami Hazard Assessment Along the Pacific Coast of Mexico by Historical Records and Numerical Simulation

Historical records of the Chile (22 May 1960), Alaska (27 March 1964), and Tohoku (11 March 2011) tsunamis recorded along the Pacific Coast of Mexico are used to investigate the goodness of far-field tsunami modeling using a focal mechanism consisting in a uniform slip distribution on large thrust faults around the Pacific Ocean. The Tohoku 2011 tsunami records recorded by Deep ocean Assessment and Reporting of Tsunami (DART) stations, and at coastal tide stations, were used to validate transoceanic tsunami models applicable to the harbors of Ensenada, Manzanillo, and Acapulco on the coast of Mexico. The amplitude resulting from synthetic tsunamis originated by Mw ~ 9.3 earthquakes around the Pacific varies from ~ 1 to ~ 2.5 m, depending on the tsunami origin region and on the directivity due to fault orientation and waveform modification by prominent features of sea bottom relief.

Improved Phase Corrections for Transoceanic Tsunami Data in Spatial and Temporal Source Estimation: Application to the 2011 Tohoku Earthquake

AbstractSystemic travel time delays of up to 15 min relative to the linear long waves for transoceanic tsunamis have been reported. A phase correction method, which converts the linear long waves into dispersive waves, was previously proposed to consider seawater compressibility, the elasticity of the Earth, and gravitational potential change associated with tsunami motion. In the present study, we improved this method by incorporating the effects of ocean density stratification, actual tsunami raypath, and actual bathymetry. The previously considered effects amounted to approximately 74% for correction of the travel time delay, while the ocean density stratification, actual raypath, and actual bathymetry, contributed to approximately 13%, 4%, and 9% on average, respectively. The improved phase correction method accounted for almost all the travel time delay at far‐field stations. We performed single and multiple time window inversions for the 2011 Tohoku tsunami using the far‐field data (>3 h travel time) to investigate the initial sea surface displacement. The inversion result from only far‐field data was similar to but smoother than that from near‐field data and all stations, including a large sea surface rise increasing toward the trench followed by a migration northward along the trench. For the forward simulation, our results showed good agreement between the observed and computed waveforms at both near‐field and far‐field tsunami gauges, as well as with satellite altimeter data. The present study demonstrates that the improved method provides a more accurate estimate for the waveform inversion and forward prediction of far‐field data.

The 2011 Tohoku Tsunami on the Coast of Mexico: A Case Study

The Tohoku (East Japan) earthquake of 11 March 2011 (M w 9.0) generated a great trans-oceanic tsunami that spread throughout the Pacific Ocean, where it was measured by numerous coastal tide gauges and open-ocean DART (Deep-ocean Assessment and Reporting of Tsunamis) stations. Statistical and spectral analyses of the tsunami waves recorded along the Pacific coast of Mexico have enabled us to estimate the principal parameters of the waves along the coast and to compare statistical features of the tsunami with other tsunamis recorded on this coast. We identify coastal “hot spots”—Manzanillo, Zihuatanejo, Acapulco, and Ensenada—corresponding to sites having highest tsunami hazard potential, where wave heights during the 2011 event exceeded 1.5–2 m and tsunami-induced currents were strong enough to close port operations. Based on a joint spectral analysis of the tsunamis and background noise, we reconstructed the spectra of tsunami waves in the deep ocean and found that, with the exception of the high-frequency spectral band (>5 cph), the spectra are in close agreement with the “true” tsunami spectra determined from DART bottom pressure records. The departure of the high-frequency spectra in the coastal region from the deep-sea spectra is shown to be related to background infragravity waves generated in the coastal zone. The total energy and frequency content of the Tohoku tsunami is compared with the corresponding results for the 2010 Chilean tsunami. Our findings show that the integral open-ocean tsunami energy, I 0, was ~2.30 cm2, or approximately 1.7 times larger than for the 2010 event. Comparison of this parameter with the mean coastal tsunami variance (451 cm2) indicates that tsunami waves propagating onshore from the open ocean amplified by 14 times; the same was observed for the 2010 tsunami. The “tsunami colour” (frequency content) for the 2011 Tohoku tsunami was “red”, with about 65% of the total energy associated with low-frequency waves at frequencies 35 min). The “red colour” (i.e., the prevalence of low-frequency waves) in the 2011 Tohoku, as well as in the 2010 Chile tsunamis, is explained by the large extension of the source areas. In contrast, the 2014 and 2015 Chilean earthquakes had much smaller source areas and, consequently, induced “bluish” (high-frequency) tsunamis.

Trapping mechanism of submerged ridge on trans-oceanic tsunami propagation

Based on the linear shallow water equations, an analytic solution of trapped waves over a symmetric parabolic- profile submerged ridge is derived. The trapped waves act as propagating waves along the ridge and as standing waves across the ridge. The amplitude gets the maximum at the ridge top and decays gradually towards both sides. The decaying rate gets more gently with higher modes. Besides, an explicit first-order approximate dispersion relation is derived to simplify transcendental functions in the exact solution, which is useful to describe trapped waves over shallowly submerged ridges in reality. Furthermore, the trapping mechanism of the submerged ridge waveguides on the trans-oceanic tsunami propagation can be explained by the ray theory. A critical incident angle exists as a criterion to determine whether the wave is trapped. Besides, a trapped parameterγis proposed to estimate the ratio of the energy trapped by the oceanic ridge if a tsunami is generated at its top.

A possible transoceanic tsunami directed toward the U.S. west coast from the Semidi segment, Alaska convergent margin

AbstractThe Semidi segment of the Alaska convergent margin appears capable of generating a giant tsunami like the one produced along the nearby Unimak segment in 1946. Reprocessed legacy seismic reflection data and a compilation of multibeam bathymetric surveys reveal structures that could generate such a tsunami. A 200 km long ridge or escarpment with crests >1 km high is the surface expression of an active out‐of‐sequence fault zone, recently referred to as a splay fault. Such faults are potentially tsunamigenic. This type of fault zone separates the relatively rigid rock of the margin framework from the anelastic accreted sediment prism. Seafloor relief of the ridge exceeds that of similar age accretionary prism ridges indicating preferential slip along the splay fault zone. The greater slip may derive from Quaternary subduction of the Patton Murray hot spot ridge that extends 200 km toward the east across the north Pacific. Estimates of tsunami repeat times from paleotsunami studies indicate that the Semidi segment could be near the end of its current inter‐seismic cycle. GPS records from Chirikof Island at the shelf edge indicate 90% locking of plate interface faults. An earthquake in the shallow Semidi subduction zone could generate a tsunami that will inundate the US west coast more than the 1946 and 1964 earthquakes because the Semidi continental slope azimuth directs a tsunami southeastward.

Stratigraphic evidence for earthquakes and tsunamis on the west coast of South Andaman Island, India during the past 1000 years

Stratigraphic records from west coast of South Andaman Island revealed evidence of three historical earthquakes and associated transoceanic tsunamis during past 1000yrs, in addition to the Mw 9.3 tsunamigenic earthquake of 26 December, 2004. Our finding suggests that along with Sumatran arc segment the Andaman–Arakan segment is also capable of generating mega-subduction zone earthquakes and transoceanic tsunamis. To study the near sub-surface stratigraphic succession we excavated shallow trenches and obtained geoslices from two sites around Collinpur (sites 1 and 2). The exposed succession comprised 11 lithounits (Unit a — youngest and k — oldest) of alternating sequence of coarser units overlain by peaty soils and some of these are indicative of deposition during paleo-tsunami events.Event I that predated AD 800, and is marked by a 35–40cm thick deposit of fine gravel to coarse sands along with broken shell fragments (Unit k). Event II dated around AD 660–800, is represented by 20–25cm thick coarse sand and broken shell fragments (Unit i). Based on stratigraphic evidences of land-level changes, this event is attributed to a near source rupture along Andaman–Arakan segment, accompanied by a transoceanic tsunami. Event III, occurred around AD 1120–1300, is marked by a 50cm thick sand deposit (Unit g). The 2004 tsunami resulted in deposition of 15cm thick medium to coarse sand at the same location. We infer that the 2004 tsunami and Event III resulted in different styles of sedimentation at the same site.Four events at Collinpur along with the record of a subsidence event of AD 1679 from the east coast of Andaman, close-to, Port Blair (Malik et al., 2011), suggest that mega-subduction zone earthquakes and associated tsunamis recur at an interval of 300–500 years at variable locations along the Sumatra–Andaman subduction zone.

Tsunami propagation over varying water depths

The linear Boussinesq equations are an ideal model for transoceanic propagation of tsunamis. However, they are impractical for real-time application because Boussinesq-type equation models rely on a fine grid system and therefore require a huge computational domain. Thus, shallow-water equations models are the preferred method of predicting propagation and run-up of near- and far-field tsunamis since they produce fairly accurate results with a much smaller computational requirement. There may be an additional benefit in including physical dispersion effects in numerical models since shallow-water equations theoretically neglect the effect of dispersion on the transoceanic propagation of tsunamis. In this study, a modified finite difference scheme was proposed that adds terms to the linear shallow-water equations in order to account for varying water depths. The proposed model was verified by applying it to tsunami propagation over a submerged shoal and the results were compared with those of the well-known Boussinesq equations model, FUNWAVE. The proposed model was further tested by simulating transoceanic tsunami propagation on real topographies and comparing the numerical results with available observed data.

NUMERICAL AND PHYSICAL MODELING OF LOCALIZED TSUNAMI-INDUCED CURRENTS IN HARBORS

Based on the observations on the recent transoceanic tsunami events, it has been seen that severe damage may still occur in ports and harbors as a result of the strong tsunami-induced currents, even if there is no or limited inundation. Dynamic currents induced by tsunami waves, while regularly observed and known to cause significant damage, are poorly understood. In this paper, it will be discussed that the strongest currents in a port are governed by horizontally sheared and rotational shallow flow with imbedded turbulent coherent structures, and without proper representation of the physics associated with these phenomena; predictive models may provide drag force estimates that are an order of magnitude or more in error. Such an error can mean the difference between an unaffected port and one in which vessels 300 meters in length drift and spin chaotically through billions of dollars of infrastructure. This paper also focuses on tsunami induced currents and seeks to define the relative hazard in specific ports and harbors as a result of these currents.

On Some Aspects of Tsunami Waves Propagation in Ocean

Interest in transoceanic tsunami wave propagation has been revived recently. By adopting the World Geodetic System 1984 Earth model, this article presents a method to solve shallow-water long-wave equations on an ellipsoidal surface. Method of characteristics on a regular grid coupled with Strang-type splitting results in finite difference schemes with order (2, 2) accuracy both in space and time. Discontinuous solution (traveling shock wave) which may represent one kind of tsunami bore-propagating bore front step is discussed.

Excitation of Basin-Wide Modes of the Pacific Ocean Following the March 2011 Tohoku Tsunami

This study is an attempt towards understanding the sources of long oscillations observed within the Pacific Ocean following the 11 March 2011 Tohoku earthquake. We present evidence that extremely long modes of the Pacific Ocean in the range of 2–48 h were excited by this giant tsunami. A numerical approach was employed to calculate the basin-wide modes of the Pacific Ocean, resulting in 49 modes in the range of 2–48 h. We studied 15 tide-gauge records around the Pacific Ocean in order to extract basin-wide modes of the Pacific Ocean excited by this transoceanic tsunami. Spectral analysis of these tide-gauge records showed that some of the calculated basin-wide modes were indeed excited by the Tohoku tsunami. The observed modes ranged from 2 to 49.8 h. We attributed the long oscillations of the Pacific Ocean during the 2011 Tohoku tsunami to the excitation of these basin-wide modes, which can be grouped into global modes (15–48 h) and regional modes (2–15 h). We classified the signals on the tide gauges into three groups: (1) basin-wide modes (>1.5 h), (2) the tsunami source periods (20–90 min), and (3) local bathymetric effects (<20 min). The average contributions to the total tsunami energy were 6.4 % for the basin-wide mode, 64.1 % for the tsunami source, and 29.5 % for the local bathymetry, although the ratios varied from station to station. Simulations suggest that the amount of contribution of basin effects to the total tsunami energy depends on the location of the tsunami source.

The 2004 Sumatra tsunami effect on the Itajaí-Açu estuary water level, Santa Catarina, Brazil

December, 2004 off the coast of Sumatra, in the Indian Ocean, was generated by a megathrust earthquake of magnitude 9.3 on the Richter scale, and felt worldwide (Fig. 1A; TITOV et al., 2005). It was the longest-lasting ever recorded in history, of around 600 seconds, giving rise to a 1,500 km long failure in the seabed (NIO, 2011). The earthquake produced the largest trans-oceanic tsunami in over 40 years, and killed more people than any other tsunami in recorded history (NOAA, 2010), in Indonesia, Sri Lanka, India, Thailand, Myanmar and Somalia. According to Titov et al. (2005), the recorded worldwide effects revealed the unprecedented, truly global reach of the waves generated on 26

Waveform and Spectral Analyses of the 2011 Japan Tsunami Records on Tide Gauge and DART Stations Across the Pacific Ocean

We studied the 11 March 2011 Tohoku tsunami through analysis of the sea level records from 21 tide gauge and 16 DART (Deep-ocean Assessment and Reporting of Tsunamis) stations from across the Pacific Ocean. The extreme power of this trans-oceanic tsunami was indicated by the trough-to-crest heights of 3.03 m at Arena Cove on the western coast of the USA and 3.94 m at Coquimbo on the southern coast of Chile. The average value of the maximum amplitude was 163.9 cm for the examined tide gauge records. At many coastal tide gauge stations the largest wave arrived several hours after the first arrival of the tsunami wave, and the tsunami lasted for a long time with an average duration of 4 days. On the contrary, at most of the DART stations in the deep ocean, the first wave was the largest, the tsunami amplitudes were smaller with an average maximum of 51.2 cm, and the durations were shorter with an average of 2 days. The two dominant tsunami periods on the DART records were 37 and 67.4 min, which are possibly attributed to the width and length of the tsunami source fault, respectively. The dimensions of the tsunami source was estimated as 233 km × 424 km. Wavelet analyses of tide gauge and DART records showed that most of the tsunami energy was distributed at the wide period band of around 10–80 min during the first hour after the tsunami arrival, then it was concentrated in a relatively narrower band. The frequency-time plots showed the switches and lapses of tsunami energy at the 35- and 65-min period bands.

The 2010 Chilean Tsunami Off the West Coast of Canada and the Northwest Coast of the United States

The major (M w = 8.8) Chilean earthquake of 27 February 2010 generated a trans-oceanic tsunami that was observed throughout the Pacific Ocean. Waves associated with this event had features similar to those of the 1960 tsunami generated in the same region by the Great (M w = 9.5) 1960 Chilean Earthquake. Both tsunamis were clearly observed on the coast of British Columbia. The 1960 tsunami was measured by 17 analog pen-and-paper tide gauges, while the 2010 tsunami was measured by 11 modern digital coastal tide gauges, four NEPTUNE-Canada bottom pressure recorders located offshore from southern Vancouver Island, and two nearby open-ocean DART stations. The 2010 records were augmented by data from seven NOAA tide gauges on the coast of Washington State. This study examines the principal characteristics of the waves from the 2010 event (height, period, duration, and arrival and travel times) and compares these properties for the west coast of Canada with corresponding properties of the 1960 tsunami. Results show that the 2010 waves were approximately 3.5 times smaller than the 1960 waves and reached the British Columbia coast 1 h earlier. The maximum 2010 wave heights were observed at Port Alberni (98.4 cm) and Winter Harbour (68.3 cm); the observed periods ranged from 12 min at Port Hardy to 110–120 min at Prince Rupert and Port Alberni and 150 min at Bamfield. The open-ocean records had maximum wave heights of 6–11 cm and typical periods of 7 and 15 min. Coastal and open-ocean tsunami records revealed persistent oscillations that “rang” for 3–4 days. Tsunami energy occupied a broad band of periods from 3 to 300 min. Estimation of the inverse celerity vectors from cross-correlation analysis of the deep-sea tsunami records shows that the tsunami waves underwent refraction as they approached the coast of Vancouver Island with the direction of the incoming waves changing from an initial direction of 340° True to a direction of 15° True for the second train of waves that arrived 7 h later after possible reflection from the Marquesas and Hawaiian islands.