Tsunami

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.

Definition

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).

Related content on the Knowledge Portal

Noticias

This map shows the ground motion during the six months following the earthquake that struck the Indonesian Island of Sulawesi on 28 September 2018, and was obtained by processing Copernicus Sentinel-1 images acquired between October 2018 and April 2019. Image: ESA/contains Copernicus Sentinel data (2018–19), processed by Planetek Rheticus Service.

In September 2018, the Indonesian island of Sulawesi was hit by a 7.5 magnitude earthquake. The impact, combined with the tsunami, landslides, and soil liquefaction that followed, “... claimed well over 2000 lives, destroyed homes, buildings, infrastructure and farmland in several districts,” according to the European Space Agency (ESA)

Ten months later, response efforts are now moving into the recovery and rebuilding phase, with satellite information offering important insights to local officials. For example, through a collaboration with the Asian Development Bank, ESA is providing Indonesian officials with hazard-mapping tools derived from Earth observation data, and training in how to most effectively use these resources. “The main purpose of sharing these information products is to help the... read more

Publishing date: 06/08/2019
Damage from a 7.4 earthquake and a tsunami that hit the Indonesian island of Sulawesi on 28 September 2018. Image: European Union/Pierre Prakash/Flickr.

In the past year, “there were 315 natural disaster events recorded with 11,804 deaths, over 68 million people affected, and US$131.7 billion in economic losses around the world.” This is according to the Centre for Research on the Epidemiology of Disasters (CRED) in its recently released 2018 Natural Disasters Report

While these 2018 natural disaster values represent a decrease when compared with the annual averages from 2008 to 2017, some geographic areas still experienced great losses of life and damages due to natural hazards. Indonesia was most adversely impacted in terms of lives claimed, with earthquakes in August and September 2018 that left a total of 4,904 people dead or missing, according to the CRED. Earthquakes also accounted for the greatest number of deaths among natural disasters worldwide in 2018. And among all types of natural hazards, floods affected the greatest number of people during the past... read more

Publishing date: 01/07/2019

As part of it advisory support activities, UN-SPIDER is carrying out out a Technical Advisory Mission (TAM) to Peru from 1 to 5 April to evaluate the current and potential use of space-based information in all aspects of disaster management. Based on exchanges with a wide range of stakeholders, UN-SPIDER will provide recommendations as to how to strengthen the use of space-based information in disaster risk management and emergency response in the country.

The team of experts led by UN-SPIDER is conducting multiple activities and institutional visits in Lima. The team is comprised of eight experts from UN-SPIDER; the German Aerospace Centre (DLR); the Argentinian National Space Activities Commission (CONAE); the Mexican Space Agency (AEM); the Agustin Codazzi Geographic Institute of Colombia (IGAC); the Santa... read more

Publishing date: 01/04/2019
In September 2018, an earthquake and tsunami hit the island of Sulawesi in Indonesia, leaving thousands dead and injured. Image: European Union 2018 / CC BY-NC-ND 2.0.

Following a tsunami that hit coastal areas around the Sunda strait between the Indonesian islands of Sumatra and Java on 22 December, the United Nations Office for Outer Space Affairs (UNOOSA) has requested the activation of the International Charter Space and Major Disasters on behalf of the National Institute of Aeronautics and Space (LAPAN) of Indonesia. LAPAN is a UN-SPIDER Regional Support Office (RSO).

According to the Indonesian National Disaster Management Agency (BNPB), 281 people have been killed, 1,016 people injured, and an estimated 11,700 people displaced as a result of the tsunami. The waves struck after volcanic activity from the Anak Krakatau volcano likely set off undersea landslides than in turn caused the surges.

... read more

Publishing date: 24/12/2018
Regional Support Offices mentioned:

Data Source

Screenshot of Global Tsunami Model
Publishing institution: Geoscience Australia
The input tsunami hazard data are based on the global hazard analysis of Davies et al. (2017), developed jointly by Geoscience Australia and NGI, formatted for use in ThinkHazard!. The data serves as data for Global Tsunami Model (GTM, http://globaltsunamimodel.org/). The global tsunami dataset contains maximum inundation heights, calculated at offshore hazard points and projected to shoreline by simple interpolation. Tsunami Maximum Inundation Height (MIH) is defined as the largest elevation the tsunami reaches above still water level, consistent with IOC-UNESCO terminology. The MIH hazard data are at global level for return periods: 10, 50, 100, 200, 500, 1000, and 2500 year. Values above and below extreme values, are referred to as >=20 m and <=0.1 m, respectively.
Publishing institution: European Space Agency (ESA)
ESA's Earth Observation Thematic Exploitation Platform (TEP) is a browser for satellite imagery and specific products on an environmental topic. The TEP platforms are divided into 7 categories: Coastal; Forstry; Geohazards; Hydrology; Polar; Urban; and Food Security. Each platform is a collaborative, virtual work environment providing access to EO data and the tools, processors and Information and Communication Technology resources required to work with them. TEP aims to bridge the gap between the users and the data and tools.
Publishing institution: Airbus Defence & Space
Pleidas, TerraSar-X, SPOT and Elevation data available commercially from airbus, certain sample data sets at various locations available for free.
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/

Evento

In the intermediate webinar Remote Sensing for Disasters, participants learn the usage of NASA products to monitor three kinds of disasters. The webinar takes place in three sessions on each Tuesday from 16 until 30 April 2019, starting 10 to 12 am and 2 to 4 pm. It is taught in English and Spanish and is free of charge.

Learning Objectives

By the end of this training, attendees will be able to:

  • Identify NASA data products to characterize and monitor the disasters, Tropical Storms, Flooding, Landslides and Earthquakes, and support decision-making

  • Understand the different data products available and their shortcomings

  • Access and interpret data covered in the different sessions

Course Format

  • Three, two-hour sessions that include a 30 min Q&A period

  • Session A will be... read more

Pages

Hazard group

Terms in the same hazard group

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