Tsunami Runup and Inundation in Tonga from the January 2022 Eruption of Hunga Volcano.

On January 15th, 2022, at approximately 4:47 pm local time (0347 UTC), several weeks of heightened activity at the Hunga volcano 65 km northwest of Tongatapu, culminated in an 11-h long violent eruption which generated a significant near-field tsunami. Although the Kingdom of Tonga lies astride a large and tsunamigenic subduction zone, it has relatively few records of significant tsunami. Assessment activities took place both remotely and locally. Between March and June 2022, a field team quantified tsunami runup and inundation on the main populated islands Tongatapu and Eua, along with several smaller islands to the north, including the Ha'apai Group. Peak tsunami heights were ~ 19 m in western Tongatapu, ~ 20 m on south-eastern Nomuka Iki island and ~ 20 m on southern Tofua, located ~ 65 km S and E and 90 km N from Hunga volcano, respectively. In western Tongatapu, the largest tsunami surge overtopped a 13-15 m-high ridge along the narrow Hihifo peninsula in several locations. Analysis of tide gauge records from Nukualofa (which lag western Tongatapu arrivals by ~ 18-20 min), suggest that initial tsunami surges were generated prior to the largest volcanic explosions at ~ 0415 UTC. Further waves were generated by ~ 0426 UTC explosions that were accompanied by air-pressure waves. Efforts to model this event are unable to reproduce the timing of the large tsunami wave that toppled a weather station and communication tower on a 13 m-high ridge on western Tongatapu after 0500 UTC. Smaller tsunami waves continued until ~ 0900, coincident with a second energetic phase of eruption, and noted by eyewitnesses on Tungua and Mango Islands. Despite an extreme level of destruction caused by this tsunami, the death toll was extraordinarily low (4 victims). Interviews with witnesses and analysis of videos posted on social media suggest that this can be attributed to the arrival of smaller 'pre tsunami' waves that prompted evacuations, heightened tsunami awareness due to tsunami activity and advisories on the day before, the absence of tourists and ongoing tsunami education efforts since the 2009 Niuatoputapu, Tonga tsunami. This event highlights an unexpectedly great hazard from volcanic tsunami worldwide, which in Tonga's case overprints an already extreme level of tectonic tsunami hazard. Education and outreach efforts should continue to emphasize the 'natural warning signs' of strong ground shaking and unusual wave and current action, and the importance of self-evacuation from coastal areas of low-lying islands. The stories of survival from this event can be used as global best practice for personal survival strategies from future tsunami. Supplementary Information: The online version contains supplementary material available at 10.1007/s00024-022-03215-5.

Tsunami currents in ports.

Tsunami-induced currents present an obvious hazard to maritime activities and ports in particular. The historical record is replete with accounts from ship captains and harbour masters describing their fateful encounters with currents and surges caused by these destructive waves. Despite the well-known hazard, only since the trans-oceanic tsunamis of the early twenty-first century (2004, 2010 and 2011) have coastal and port engineering practitioners begun to develop port-specific warning and response products that accurately assess the effects of tsunami-induced currents in addition to overland flooding and inundation. The hazard from strong currents induced by far-field tsunami remains an underappreciated risk in the port and maritime community. In this paper, we will discuss the history of tsunami current observations in ports, look into the current state of the art in port tsunami hazard assessment and discuss future research trends.

Modeling the transport and accumulation floating debris generated by the 11 March 2011 Tohoku tsunami.

A global ocean circulation model is coupled to a particle-tracking model to simulate the transport of floating debris washed into the North Pacific Ocean by the Tohoku tsunami. A release scenario for the tsunami debris is based on coastal population and measured tsunami runup. Archived 2011/2012 hindcast current data is used to model the transport of debris since the tsunami, while data from 2008 to 2012 is used to investigate the distribution of debris on timescales up to 4years. The vast amount of debris pushed into ocean likely represents thousands of years worth of 'normal' litter flux from Japan's urbanized coastline. This is important since a significant fraction of the debris will be comprised of plastics, some of which will degrade into tiny particles and be consumed by marine organisms, thereby allowing adsorbed organic pollutants to enter our food supply in quantities much higher than present.

Tsunami inundation modeling for western Sumatra.

A long section of the Sunda megathrust south of the great tsunamigenic earthquakes of 2004 and 2005 is well advanced in its seismic cycle and a plausible candidate for rupture in the next few decades. Our computations of tsunami propagation and inundation yield model flow depths and inundations consistent with sparse historical accounts for the last great earthquakes there, in 1797 and 1833. Numerical model results from plausible future ruptures produce flow depths of several meters and inundation up to several kilometers inland near the most populous coastal cities. Our models of historical and future tsunamis confirm a substantial exposure of coastal Sumatran communities to tsunami surges. Potential losses could be as great as those that occurred in Aceh in 2004.

Field data and satellite imagery of tsunami effects in Banda Aceh.

After the 26 December 2004 earthquake and tsunami, field data on the extent of the inundation in Banda Aceh, Sumatra, were combined with satellite imagery to quantify the tsunami effects. Flow depths along the shores of Banda Aceh exceeded 9 meters, with inundation reaching 3 to 4 kilometers inland. To the southwest, at Lhoknga, flow depths were more than 15 meters at the shoreline and runup exceeded 25 meters. Erosion and subsidence moved the shoreline of Banda Aceh inland up to 1.5 kilometers, and 65 square kilometers of land between Banda Aceh and Lhoknga were flooded.