On 29 July 2025, global monitoring systems detected a large earthquake offshore of the Kamchatka Peninsula, Russia, and widespread tsunami warnings were issued across the Pacific region. With a magnitude of 8.8, it was all too easy to think back to the 9.0 to 9.1 magnitude event that devastated Japan in 2011, or the 9.2 to 9.3 magnitude event on Boxing Day in 2004. Thankfully, on this occasion, the impact is believed to be relatively small by comparison.

However, the Kamchatka event did reveal impact of a different nature. Almost as soon as news broke of the earthquake, tsunami warnings were issued and millions of people were told to evacuate across locations at risk, 2 million in Japan alone. This was the result of two decades of research on hazard mitigation following the Boxing Day earthquake in 2004, which claimed the lives of more than 220 000 people in one of the largest disasters, in terms of loss of life, in modern history.

Immediately after the Indian Ocean event in 2004, BGS scientists participated in responsive marine research expeditions that resulted in increased knowledge of sea-bed deformation resulting from the earthquake. Longer-term responses resulted in major advances in understanding earthquake tsunami mechanisms, which have further contributed to disaster risk reduction efforts.

Most significant, in terms of public safety, has been the installation of improved tsunami warnings for coastal communities. Tsunami early warning systems (TEWS) are based on identifying earthquake magnitudes (usually larger than magnitude 7 to 8) that could result in hazardous tsunamis. The Indian Ocean tsunami took two hours to reach the coasts of India, Sri Lanka and Thailand, where around 80 000 people lost their lives. Many of them could potentially have been saved if there had been an operational TEWS in place.

In the wake of the catastrophic 2011 Great East Japan Earthquake and Tsunami, further advancements were made in our understanding of tsunami mechanisms, which ultimately led to improved mitigation measures around the world.

Our knowledge base today to plan for and respond to tsunamis is far beyond anything considered possible before the turn of the century.

Following the devastating events of 2004, research has allowed us to be more prepared than ever before to mitigate the threat of this formidable phenomenon. This was highlighted during the Kamchatka earthquake and subsequent tsunamis. TEWS were activated, which led to the evacuation of millions to safety and has ultimately led to a relatively minimal impact being reported.

Prof David Tappin, BGS marine geologist and leading tsunami expert.

Whilst warning systems for earthquake tsunamis are now effectively implemented for major events, there is still the major challenge of designing warning systems for other tsunami mechanisms, such as landslides and volcanic eruptions. Hopefully, with new approaches potentially available through applications such as artificial intelligence, these will become a reality.

On Boxing Day, 26 December 2004, a magnitude 9.2 to 9.3 earthquake struck off the west coast of northern Sumatra in Indonesia. It triggered a tsunami with waves reaching 30 m in height that claimed the lives of more than 220 000 people in one of the largest disasters, in terms of loss of life, in modern history. Local residents and tourists in countries including Thailand, Sri Lanka and India would all face a fight for survival as giant walls of water swept through coastal communities and far inland.

Known by the scientific community as the 2004 Sumatra-Andaman Earthquake, we now know more about the underlying reasons that led to the disaster: the unexpected occurrence of a gigantic earthquake in the region, the lack of a tsunami warning system, and a lack of awareness amongst local inhabitants and visitors about the hazard and how to respond.

There have been other devastating tsunami events over the past 30 years, aside from the Sumatra-Andaman Earthquake, including in Papua New Guinea in 1998 and the Great East Japan Earthquake and Tsunami of 2011. The tsunami events of 1998, 2004 and 2011 were catastrophic and it seems that we are now living in an β€˜age of tsunamis’. The events have resulted in better understanding of tsunami mechanisms and improved mitigation measures around the world.

Immediately after the 2004 event, the Hyogo Framework of Action for 2005 to 2015 was adopted at the World Disaster Reduction Conference and later endorsed by the UN General Assembly. It was created for building the resilience of nations and communities to disasters, and consists of five action items:

β€’ make disaster risk reduction a national and local priority
β€’ identify, assess and monitor disaster risks and enhance early warning
β€’ use knowledge, innovation and education to build understanding and awareness
β€’ reduce risk factors
β€’ be prepared and ready to act

Immediately after the Indian Ocean event, BGS scientists participated in responsive marine research expeditions that resulted in increased knowledge of sea-bed deformation resulting from the earthquake. Of particular importance was whether submarine landslides triggered by the earthquake could have contributed to the tsunami. The surprising result was that, despite the massive earthquake magnitude, the landslides identified were numerous but small, so did not contribute to the tsunami.

Longer-term responses to the Indian Ocean event have resulted in major advances in understanding earthquake tsunami mechanisms, which have further contributed to disaster risk reduction efforts. Most important was improved tsunami warnings for coastal communities. Before 2004, the only tsunami early warning system (TEWS) was in the Pacific Ocean. TEWS are based on identifying earthquake magnitudes (usually larger than magnitude 7 to 8) than could result in hazardous tsunamis. With the Indian Ocean tsunami, around 80 000 people died along the coasts of India, Sri Lanka and Thailand that could have been saved if there was an operational TEWS, because the tsunami took two hours to reach these locations.

The 2004 event resulted in the establishment of TEWS in the Indian and Atlantic oceans and the Mediterranean and Caribbean seas. These can now identify earthquakes that could generate hazardous tsunamis and provide warnings to local coastal populations, resulting in evacuation from threatened locations.

Other practical developments in earthquake and tsunami mitigation include:

β€’ early detection of potentially or tsunami generating earthquakes
β€’ identification of tsunami magnitudes and their likely impacts
β€’ more accurate modelling of different tsunami mechanisms, such as earthquakes and submarine landslides
β€’ improved instrumental measurements of offshore and deep-ocean tsunamis
β€’ global studies of recurrence intervals of large earthquakes in subduction zones, enabling improved statistical analysis of past events, better assessments of probable maximum size and long-term forecasting of great subduction zone earthquakes

Our knowledge base today, to plan and respond to tsunamis, is far beyond anything considered possible 30 years ago. Devastating tsunami events are, fortunately, quite rare, but as the last few decades have proved, can happen with devastating consequences.

The 20th anniversary of the Boxing Day Indian Ocean earthquake and tsunami is critically important for both honouring the victims of this tragedy and reminding ourselves that it will happen again in the future. Thanks to research undertaken over last twenty years, we are now more prepared than ever before to mitigate the threat of this formidable phenomenon.

Prof David Tappin, lead marine tsunami expert at BGS.

The tsunami from Hunga Tonga-Hunga Ha’apai volcano in Tonga on 15 January 2022 was the first from a violent eruption for over 130 years, the last being the Krakatau volcanic eruption in Indonesia in 1883. Hunga Tonga-Hunga Ha’apai was also the first dual eruption tsunami since the Krakatau event and the first recorded by modern technology. The resulting shockwave was the most significant ever recorded and the volcano plume was the highest on record.

The Hunga Tonga-Hunga Ha’apai event was comparable to the Papua New Guinea submarine landslide tsunamis of 1998, which resulted in 2200 fatalities, and the Indian Ocean earthquake tsunami of 2004 when over 250 000 people died. Although the mechanisms are different, all identify a previously unrecognised tsunami hazard. The Papua New Guinea submarine landslide generated massively destructive tsunamis, while the Indian Ocean event saw great-magnitude earthquake tsunamis striking along convergent margins outside the Pacific Ocean.

Volcanic activity along the Tonga convergent margin is not unexpected. Hunga Tonga-Hunga Ha’apai last erupted in 2015, but the magnitude and violence of the 2022 eruption was a complete surprise. The unexpected nature of the eruption reveals that the global hazard from large volume volcanic eruptions is underestimated and identifies a global unpreparedness for the effects of these events.

Globally, there are 42 volcanoes with the potential to erupt on a similar scale to Krakatau and Hunga Tonga-Hunga Ha’apai, so the events of 15 January 2022 should serve as a wake-up call to the potential hazards from other violent eruptions. Many of these volcanoes, unlike Hunga Tonga-Hunga Ha’apai, are close to high-density coastal populations.

So far there has been little published on the eruption or on local tsunami mechanisms. Over one hundred papers on the event have been published, but most focus on the satellite data recordings of the atmospheric disturbances generated from the shockwave, and ‘far field’ tsunamis. Both were due to changes in atmospheric pressure on the ocean surface, which initially generated small waves that increased through a process called ‘resonance’, which is determined by the relationship between the speed of the shockwave and the speed of the tsunami.

There are still fewer papers on the local, or near, tsunamis. The mechanism of these is still uncertain. There are several possibilities as to what generated these tsunamis, including collapsing pyroclastic density currents, caldera collapse and phreatomagmatic explosions, where magma interacts with sea water.

One fear from the eruption was an effect on climate, possibly from sulphur dioxide (SO₂), but measurements showed that SO₂ was quite low in volume. More surprisingly was the volume of water pumped into the atmosphere; recent research shows this to be a high volume that could possibly affect the climate.

Regarding the wake-up call from the effects of the event, so far there has been little reaction. This could be attributed to the volume of unpublished papers (such as sea-bed mapping of the area). These as-yet unpublished papers could well affect the uncertainty over the local tsunami mechanism. The source of the cataclysmic culminating explosion is also yet to be determined, whether it was mixing of magmas beneath the caldera or the entry of cold water into the edifice during the final phase.

There is still much research to do and many lessons to take from the Hunga Tonga-Hunga Ha’apai eruption and following events, but once the results are in, hopefully the real mitigation work will begin.

Further reading

• Cassidy, M, and Mani, L. 2022. . Nature, Vol. 608, 469–471. DOI: https://doi.org/10.1038/d41586-022-02177-x
• Lynett, P, et al. 2022. . Nature, Vol. 609, 728–733. DOI: https://doi.org/10.1038/s41586-022-05170-6
• Newhall, C, Self, S, and Robock, A. 2018. . Geosphere, Vol. 14(2), 572–603. DOI: https://doi.org/10.1130/GES01513.1
• Witze, A. 2022. . Nature, Vol. 602, 376–378. DOI: https://doi.org/10.1038/d41586-022-00394-y

About the author

For the first time,β€―soon after an event, scientists have been able to study the marine deposits of a deadly volcanic island landslide-tsunami at Anak Krakatau, Indonesia, using modern hydroacoustic equipment. 

Professor David Tappin, Principal Scientist at the 51ΑΤΖζ (BGS), contributed to the research led by Dr James Hunt from the National Oceanography Centre (NOC).  

Together, with their international team, they have just published the survey results of the submarine landslide, which in December, 2018 created the devastating β€˜silent’ tsunami flooding miles of the of the Sunda Strait coastlines of Sumatra and Java that killed over 400 people and injured more than 14,000. 

Using the detailed seafloor mapping data, together with satellite images of the subaerial collapse scar, the scientists have been able to better understand the volcanic processes in the months before the event which ultimately contributed to the collapse.   

Their results reveal the landslide was large enough (0.214 km³) to bury the City of London to around the height of St Paul Cathedral.  The findings, titled β€˜β€™ are published in the journal Nature Communications.

Major tsunamis from the collapse of volcanic islands are rare. We were fortunate to have the opportunity to study this event, and improve our understanding of their hazard.

Professor David Tappin, BGS Principal Scientist & Visiting Professor at University College

It is a time for remembrance; on the 11^th March 2011 at 2.46 in the afternoon, a 9.1 magnitude earthquake off the east coast of Honshu Island, Japan caused a tsunami up to 40 metres high that flooded local coastlines, causing over 18,500 fatalities and over 280 billion dollars’ worth of damage. This was the most recent devastating tsunami, and its magnitude was a major surprise. Seven years previously, in 2004, in the Indian Ocean, another surprise earthquake generated tsunami resulted in over 220,000 deaths. Afterward, there was still some uncertainty over where these events would strike, and Japan demonstrated that the hazard was global but, also, that their mechanisms (earthquake or submarine landslide) might not be as clear cut as first observations might suggest.

Over the past 20 years there have been a number of devastating tsunamis, which suggests that we are living in the β€˜Age of Tsunamis’. Perhaps the first of these important recent events was in 1998, in Papua New Guinea, where 2,200 people died in tsunami up to 15 metres high. Here the earthquake magnitude 7.1 was too small to explain the tsunami height, and for the first time, a submarine sediment failure, termed a slump was proved to explain the tsunami. At that time submarine landslides were not considered effective at causing hazardous tsunamis; and the landslide was identified by new technology available to map the seabed, with the surveys mainly funded by Japan. Six years after the Papua New Guinea tsunami, in December 2004 over 220,000 people died in the devastating tsunami that struck the eastern Indian Ocean. Then in March 2011 the Japan tsunami struck. Here, although the earthquake generated most of the tsunami along the low-lying Sendai Plain, the very high, up to 40 metre elevations, father north along the β€˜Sanriku’ coast have been proposed as being from a secondary, submarine landslide. This is still not completely certain, but without the Papua New Guinea tsunami of 1998, it would have been an impossible idea.

The tsunami events of 1998, 2004 and 2011 were catastrophic, with many hundreds of thousands of fatalities, but they all resulted in improved understandings of tsunami mechanisms and tsunami hazard which led to improved mitigation; there are now tsunami warning systems in all the world major oceans, whereas in 2004, only the Pacific was covered. The recent earthquake event in New Zealand testifies to the importance of these global warning systems; here there was no dangerous tsunami, but if there had been many lives would have saved.

Our knowledge base today, to plan and respond to tsunamis is far beyond anything considered possible 20 years ago. The result is that all the major ocean basins have warning systems. Devastating tsunami events are, fortunately, quite rare, but not impossible. In this context rather than letting time subdue our memories of these devastating events, anniversaries are important, both in remembering and honouring those who died and suffered in them, but also in reminding us that they will happen again in the future, and when they do we will be aware and prepared. Today anniversary of the Japan 2011 tsunami is critically important in this respect.

References:

Tappin, D.R., Evans, H.M., Jordan, C.J., Richmond, B., Sugawara, D., Goto, K., 2012. Coastal changes in the Sendai area from the impact of the 2011 Tōhoku-oki tsunami: Interpretations of time series satellite images, helicopter-borne video footage and field observations. Sedimentary Geology 282, 151-174.

Tappin, D.R., Grilli, S.T., Harris, J.C., Geller, R.J., Masterlark, T., Kirby, J.T., Shi, F., Ma, G., Thingbaijam, K.K.S., Mai, P.M., 2014. Did a submarine landslide contribute to the 2011 Tohoku tsunami? Marine Geology 357, 344-361

David Tappin is a BGS scientist, and Visiting Professor at University College, London, who has researched tsunamis for over 20 years, including those in Papua New Guinea, the Indian Ocean and Indonesia. After the Japan 2011 tsunami struck, he participated in a number of post-tsunami field surveys in Japan and published on the possibility that the tsunami was in part caused by a submarine landslide. Most recently he has researched the Indonesian tsunamis of 2018 in Palu, Sulawesi and the Sunda Strait.

Prof David Tappin, a tsunami expert at the BGS and UCL, was part of a research team led by Heriot-Watt University that used seismic data to map underneath the sea floor of the Makassar Strait, the narrow seaway between the islands of Borneo and Sulawesi.

The team say their findings mean that coastal communities currently without tsunami warning systems or mitigation systems could be at risk.

They found evidence of 19 ancient submarine landslides. Submarine landslides have triggered tsunami waves before, such as the 2018 event on Sulawesi in Indonesia, although most tsunamis are caused by large earthquakes.

Dr Rachel Brackenridge, now at University of Aberdeen, said:

β€œWe found evidence of submarine landslides happening over 2.5million years.

β€œThey happened every 160,000 years or so and ranged greatly in size. The largest of the landslides comprised 600km3 of sediment, while the smallest we identified were five km3. There will be many smaller events that we have yet to identify.”

Dr Brackenridge explained how they identified the ancient landslides.

β€œSeismic data allows us to image the subsurface. The different characteristics of rocks below the seabed allow us to reconstruct the conditions they were deposited in.

β€œWe can see a layered and orderly seabed, then there are huge bodies of sediment that appear chaotic.

β€œWe can tell from the internal characteristics that these sediments have spilled down a slope in a rapid, turbulent manner. It like an underwater avalanche.”

The researchers say that the strong ocean current that flows through the Makassar Strait could be behind the prehistoric events and any potential submarine landslides.

Dr Uisdean Nicholson, who led the research at Heriot-Watt University, said:

β€œThe Makassar Strait is an important oceanic gateway. It through there the main branch of the Indonesian Throughflow transports water – over 10 million cubic metres a second – from the Pacific to the Indian Ocean.

β€œThe current acts as a conveyor belt, transporting sediment from the Mahakam Delta and dumping it on the upper continental slope to the south, making the seabed steeper, weaker and more likely to collapse.

β€œWe estimate the largest, tsunamigenic events – those that displace 100 km3 – occurred every 500,000 years.

β€œIndonesia has mitigation and early warning measures in place in different parts of the country, but not the area that would be affected by a tsunami wave generated from these landslides. This includes the cities of Balikpapan and Samarinda, which have a combined population of over 1.6 million people.

β€œSuch an event could be concentrated and amplified by Balikpapan Bay, the site selected for the new capital city of Indonesia.

β€œOur next step is to quantify the risk in this area by building various numerical models of landslide events and tsunami generation. This could help us predict a threshold size that causes dangerous tsunamis and help inform any mitigation strategies.

β€œWe also plan to visit the coastal areas of Kalimantan to look for physical evidence for historic or prehistoric tsunamis, to test the model outcomes and further improve our understanding of this hazard.”

Prof Tappin is studying the Sulawesi tsunami which struck the opposite side of the Makassar Strait in September 2018.

Prof Tappin said:

β€œThe new study on submarine landslides is important in demonstrating that the tsunami hazard in this region of Indonesia is possibly greater than previously thought, but more research is necessary to confirm this.”

Dr Nicholson recently in a separate research project.

The report was published in a special publication on by the Geological Society, London.

The Falkland Islands are at risk from tsunamis caused by underwater landslides, according to new research by scientists from the 51ΑΤΖζ and Heriot-Watt University.

They found evidence of prehistoric submarine landslides in the Falkland Trough, 150km south of the Falkland Islands. The landslides are all in the same location, caused by one of Earth strongest currents, the Subantarctic Front. This current pushed sediment high up on the continental slope causing a drift, named Burdwood Drift by the researchers. Over time, a tipping point would then occur and cause a landslide.

Sediment has been accumulating again at the site and the seabed is so steep and unstable it will collapse – but scientists can’t tell when.

Professor David Tappin, a tsunami specialist at the 51ΑΤΖζ said:

β€˜Tsunamis from submarine landslides are still an underrated hazard, despite increasing recognition of their presence along most ocean margins. This new work identifies a previously unforeseen series of submarine landslides in the South Atlantic.

β€˜These landslides are thousands of years old, so the present day risk to local coastal regions from them is very low. However if a landslide happened today, it would be a different story. The present day submarine landslide tsunami hazard was highlighted at the end of 2018, when coastal landslides and volcanic collapse in Indonesia resulted in tsunamis which claimed numerous lives.’

Most large tsunamis, such as the Indian Ocean event Boxing Day tsunami in 2004, or the 2011 event in Japan, were caused by large earthquakes. However, landslides have also triggered tsunami waves, including the 1998 Papua New Guinea tsunami, the prehistoric Storegga landslide that inundated Scotland around 8000 years ago and most recently in 2018, on Sulawesi in Indonesia.

The team of researchers used seismic data to assess the density of sediments in three dimensions. The landslides deposited huge volumes of mud, sand and rocks on the ocean floor, much as an onshore landslide does.

Dr Uisdean Nicholson, a sedimentary geologist at Heriot-Watt University, said:

β€˜The large landslides shifted around 100 km³ of sediment – that enough to bury a city the size of Edinburgh under 400m of material. The large landslides happened once every million years or so. But we also found evidence of smaller landslides that generated tens of cubic kilometres of material and happened more frequently. These would still provide a real hazard.’

The team modelled the landslides to test whether they could have generated hazardous tsunamis and calculate whether future landslides would pose a risk to the Falkland Islands.

Dr Nicholson said:

β€˜The models show that, for a 100 km³ landslide event, the resultant wave would be up to 40 m high, and reach the Falklands about an hour after the event. Smaller and more frequent 10 km³ events could still cause a significant hazard, with likely wave heights of several metres affecting the capital Stanley.

β€˜We must understand more about these processes and the likelihood of another landslide, and whether it will cause a tsunami that could affect the nearby Falkland Islands.’

The research was funded by the Carnegie Institute and used seismic data and well data provided by Borders and Southern Petroleum and Rockhopper Exploration and the Falkland Island Government.

The report was published in Marine Geology:

The volcano Anak Krakatau (β€˜Child of Krakatoa’), located between Java and Sumatra, collapsed in December 2018, causing a devastating tsunami that killed hundreds of people and displaced tens of thousands more living on the coasts of Indonesia. Recent scientific research has found that the tsunami was caused by an eruption-triggered landslide generated as the volcano collapsed into the Sunda Strait.

Anak Krakatau is a small volcano that formed in the caldera of Krakatau (Krakatoa) following its cataclysmic eruption in 1883, which was the deadliest in recorded history with over 36000 deaths and led to global climactic effects. Anak Krakatau first emerged above the waves in 1930 and reached a pre-collapse height of 327 m above sea level. On 22 December 2018, an eruption led to the collapse of the south-western flank of the volcano, with the resulting landslide generating a tsunami that caused devastation along the nearby coasts of southern Sumatra and west Java.

The major factors that led to the collapse of Anak Krakatau were:

• its location on the north-eastern flank of a 220 m-deep submarine trough
• the migration of the volcano itself closer to the edge of the trough
• the very weak base of the volcano, which was formed of older volcanic deposits

In addition, the volcano had grown very quickly over the last 90 years to form a steep-sided cone of unstable volcanic material.

The results of modelling indicate that the landslide consisted of between 0.2 and 0.4km³ of volcanic material. Initial numerical simulations of tsunami generation and propagation match to a high degree the recordings from tide gauges on the coasts of Sumatra and Java, as well as observations recorded from eye witnesses.

• Watch a video of a

This is the first major eruption-generated tsunami since the devastating Krakatau event of 1883 which killed over 36 000 people – it demonstrates yet again the lack of preparedness of countries threatened by tsunamis and highlights the urgent need for better mitigation and warning.

Prof David Tappin, BGS Marine Geologist and visiting professor at University College, London.

Numerical modelling of eruption generated tsunamis is far less developed than for other tsunami mechanisms – such as earthquakes and landslides. The Anak Krakatau event is timely in that it should stimulate the development of new models that will underpin improved mitigation strategies.

Prof Stephan Grilli, numerical modeller at the University of Rhode Island.

Prof Tappin will present the findings of this research at the (EGU) in Vienna, Austria, on 10 April 2019.

This research was a collaboration between

• 51ΑΤΖζ, UK
• Institut Teknologi Bandung, Indonesia
• University College London, UK
• University of Birmingham, UK
• University of Rhode Island, USA
• University of Santa Cruz, USA

Funding for the research was provided by BGS, the Natural Environment Research Council (NERC) and US National Science Foundation (NSF).