Researchers from NASA’ Jet Propulsion Laboratory (JPL) and the Ohio State University (OSU) used satellite altimeters to observe “merging tsunamis”. The image comes from a data-based computer model that shows Tohoku-oki tsunami waves propagation. Waves peaks are depicted in red-brown, while depressions in sea surface appear in blue-green. Grayscale outlines show the location of mid-ocean ridges, peaks, and islands. Image: NASA.


A tsunami is a series of travelling waves of extremely long length and period, generated when a large volume of ocean water is rapidly displaced by a sudden displacement of the seabed. These series of waves are generated by a displacement of massive amounts of water through underwater earthquakes, volcanic eruptions or landslides. Tsunami waves travel at very high speed across the ocean but as they begin to reach shallow water they slow down and the wave grows steeper (IRDR Glossary).

The majority of tsunami are generated by shallow large earthquakes in subduction zones. Tsunami is also known as seismic sea waves because it is most often generated by earthquakes (UNESCO).

Facts and figures

The word tsunami is derived from the Japanese word “tsu” and “nami”, meaning “Harbor” and “Wave” respectively.

The speed of tsunami waves depends on ocean depth rather than the distance from the source of the wave. Scientists can predict when a tsunami will arrive at various places by knowing the source characteristics of the earthquake that generated the tsunami and the characteristics of the seafloor along the paths to those places. When the ocean is over 19,685 feet (6,000 m) deep, unnoticed tsunami waves can travel over 500 mph (804.67 kmh). One coastal community may see no damaging tsunami wave activity while in another nearby community destructive waves can be large and violent. Reefs, bays, entrances to rivers, undersea features and the slope of the beach help to modify the tsunami as it approaches the coastline (NOAA).

Dependent on the distance of the tsunami from its source, it may be classified as a:

  • Local/near field tsunami A tsunami from a nearby source for which its destructive effects are confined to coasts less than 1 hour tsunami travel time or typically within about 100 km from its source.
  • Regional tsunami A tsunami that is capable of destruction in a particular geographic region.
  • Destructive tsunami Happens when tsunami waves become extremely large in height, they savagely attack coastlines, causing devastating property damage and loss of life. A small wave only 30 cm high in the deep ocean may grow into a much larger wave 30 m high as it sweeps over the shore.
  • Non-Destructive Tsunami Mostly happens as a result of minor earthquakes and/or other events. It can be due to the source being far away from land or the earthquake being too small to have any effect when approaching the shore. When a small tsunami comes to the shoreline it is often seen as a strong and fast-moving tide (Caribbean Tsunami Information Center).

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Publishing institution: Radiant Earth Foundation
The website: https://www.radiant.earth Help and Tutorials: https://help.radiant.earth/ Demos & Use Cases: https://demos.radiant.earth/
Publishing institution: NASA Earth Science Disasters Program
NASA's Earth Observing System Data and Information System (EOSDIS) is a program for archiving and distributing Earth science data from multiple missions to users.
Publishing institution: OceanDataLab
The Ocean Virtual Laboratory is a web platform making satellite and in-situ data for ocean monitoring accessible. It presents one of multiple Syntool Web portals that promote the synergistic use of Ocean Remote Sensing data in a wider context of Oceanic and Atmospheric models or in-situ data. , ESA/SEOM Ocean Virtual Laboratory portal: SAR roughness Sentinel 1: Ocean Color: From Sentinel-2, Sentinel-3 and Meteosat. Chlorophyll: From VIIRS and MODIS Sea Surface Temperature, Sea level, Salinity, Wind, Current, Rain, Mean Square Slope, Sea ice concentration , ESA/DUE GlobCurrent portal: SAR roughness, Ocean Color, Chlorophyll, Sea surface temperature, Sea level, Salinity, Wind, Wave, Current, Rain, ESA SMOS Storm portal: Significant Wave height (SWH) Jason 2 and ALTIKA, SAR roughness Sentinel-1, Wind speed SMOS, SMAP, AMSR2 and ASCAT, wind barbs ASCAT, CNES Aviso'VIZ altimetry portal: Sea Surface Height Anomaly (SSHA) Jason-2 and SARAL, Sea Level Anomaly (SLA) Jason-2 and SARAL, Absolute Dynamic Anomaly (ADT) Jason-2 and SARAL, Mean Sea Level RIse, Sea Level Anomaly, Geostrophic current vectors and streamlines., ESA Sentinel3 Viewer: products from OLCI, SLSTR and SRAL sensors., CNES PEPS Sentinel-1 Ocean Viewer: SAR roughness Sentinel-1, ESA Sea Surface Salinity portal: SMOS salinity, SMAP salinity
Publishing institution: European Organization for the Exploitation of Meteorological Satellites (EUMETSAT)
Map Viewer that allows downloading and time series creation of meteosat products.


The Asia and Oceania regions are frequently affected by severe natural phenomena such as tropical cyclones, torrential monsoons, volcanic eruptions, yellow sandstorms, floods, sea ice, and wildfires. The importance of monitoring the climate and the environment is also increasing, which has prompted enhanced global interest in the field.

In this area, the new generation of meteorological and earth observation satellites provide frequent and extensive observational information for use in disaster prevention and climate monitoring/diagnostics; they are indispensable in today’s world. The Asia/Oceania Meteorological Satellite Users’ Conferences provide an excellent forum for satellite operators and users within the Asia/Oceania community to meet and enhance their joint efforts in the utilization of satellite data and products for better weather, climate, and disaster mitigation services.


Copernicus Emergency Management Service (© 2018 European Union), [EMSR317] Palu - Indonesia, Grading Map.

The International Charter “Space and Major Disasters” and the Copernicus Emergency Management Service Mapping have been activated on 29 September after a 7.5 magnitude earthquake in the central Indonesian Island of Sulawesi.

At least 844 people have been killed and 64,000 displaced according to reports.

The cities of Palu and Donggala are the worst affected areas by the earthquake and a tsunami with waves as high as six metres.

The International Charter was activated by the Asian Disaster Reduction Centre (ADRC) on behalf of the Indonesian National Institute of Aeronautics and Space (LAPAN). Both institutions are UN-SPIDER Regional Support Offices (RSO). Mapping products made available under the activation are available on the... read more

Publishing date: 01/10/2018

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