International Tsunami Day

5 November 2016 marks the first International Tsunami Day!

This special blog covers tsunamis today!

What are tsunamis and what causes them?

The name tsunami originates from the Japanese word for ‘harbour wave’, they are also referred to as seismic waves. The word tidal wave has in the past been used to describe tsunamis, which is incorrect since tsunamis are not tidal waves and are produced by different mechanisms.

Tsunamis involve the vertical or horizontal displacement of water and propagate long distances from source travelling at speeds of over 500 km per hour in the open ocean. The speed is dependent on the depth of the water body in which the tsunami has been generated.

Tsunamis are generated by earthquakes, landslides (surface or subsurface), volcanoes (including edifice collapse and pyroclastic flows) and near earth objects. They occur in oceans or other enclosed water bodies such as lakes.

When tsunamis are generated in the open ocean they are undetectable, characterised by long wavelengths and short amplitudes (1 metre or less) and as they approach the coast this changes; the wavelength decreases and amplitude increases, therefore increasing the runup distance and height. This is dependent on various factors such as bathymetry, topography, coastal characteristics and tsunami characteristics such as speed.

Landslide generated tsunami (Source: SOEST, 2003)

Characteristics of a tsunami (Source: NOAA)

Generation of a tsunami by an earthquake at a subduction zone (Source: NOAA)

Generation of a tsunami

Tsunami Facts

• 95% of tsunamis are cause by earthquakes of magnitudes greater than 7.0 and depths less than 30 km. The majority of these tsunamigenic earthquakes occur in subduction zones where a large vertical movements occurs on the fault.
• Tsunamis generated by earthquakes have caused the largest fatalities and greatest damage. They also propagate the furthest from source.
• 81% of tsunamis are generated by earthquakes, 6% by volcanoes, 3% by landslides and 10% from unknown sources.
• 81% Based on 13,000 runup locations of where tsunami effects were observed; 82% have occurred in the Pacific Ocean, 9% in the Indian Ocean, 4% in the Mediterranean Sea, 3% in the Atlantic Ocean and 2% in the Caribbean Sea. 
• 21% of volcano fatalities have been a result of volcanogenic tsunamis.
• Between 1900 to present, over 700 fatalities have occurred from Tsunamis in the Pacific Ocean.
• 2000 B.C was the first recorded tsunami which occurred on the coast of Syria. Tsunamis have been well documented especially in Japan and the Mediterranean areas.
• 42 deadly tsunamis have occurred since 1975. 70% of these occurred in the Pacific Ocean.
• Between 1610 BC to AD 2016, 1235 confirmed tsunamis have occurred of which 249 were deadly. 76% of these occurred in the Pacific Ocean and 87% were caused by earthquakes.
• Tsunamis have caused over 500,000 fatalities over the world. The Indian Ocean tsunami in 2004 is responsible for 227,898 of these fatalities.
• Between 1900 to 1990 an estimated 33,500 fatalities have occurred from tsunamis. Between 1990 to 2004, over 230,00 fatalities have occurred due to tsunamis.
• The September 2009 American Samoa tsunami, February 2010 Chile tsunami and October 2010 Indonesia tsunami in combination have caused over 400 fatalities.
• The highest recorded tsunami was nearly 525 metres high (1720 feet). It was caused by an earthquake in Lituya Bay, south east of Alaska in 1958. Two fatalities resulted from this tsunami.
• In the Mediterranean Sea, 84% of tsunamis have been caused by earthquakes and 4% by volcano eruptions.
• According to EM-DAT, between 1900 to 2009, 240,959 fatalities have occurred as a result of tsunamis. 2.48 million others have been affected. This is an underestimate as the Indian Ocean tsunami itself affected millions.
• An average of one damaging tsunami event per year takes place.
• 95% of the most damaging take place in the Pacific Ocean.
•  On average tsunamis cause 300 deaths per year.
• Millions of coastal population are at risk from tsunamis. 1.2 million are on the western coast of U.S alone.
• Tsunamis are a significant hazard in the Caribbean Sea where 77 tsunami events have been recorded. An example is the magnitude 8.1 earthquake which generated a tsunami in 1946 killing 1800 people.

Examples of historical tsunamis

·   Indian Ocean Tsunami 2004 (also known as the Boxing Day tsunami and Sumatra-Andaman earthquake): This tsunami event bought the hazard into the public eye and demonstrated the vulnerability of the world's coastal population and the lack of warning and preparedness in the Indian Ocean.

It was caused by a magnitude 9.1 earthquake on the west coast of Sumatra, Indonesia, with a focus of 30 km and duration of approximately 10 minutes. This earthquake is the third largest recorded earthquake in the world. The magnitude of the earthquake has been controversial with estimates ranging from 9.1 to 9.3. The tsunami generated, had runup heights of between 15 to 30 metres and the maximum runup height recorded was 50.9 metres in Lhoknga, Indonesia.

The tsunami caused devastation in numerous countries including Indonesia, which was the worst affected country followed by Sri Lanka, India and Thailand. Entire coastal villages and towns were wiped out. The economic losses are estimated to be over $10 billion.

According to Reliefweb, the tsunami claimed an estimated 227,898 lives, left 1,126,900 homeless and affected 14 countries including Indonesia, Thailand, India, Sri Lanka, Maldives, Somalia, Malaysia, Tanzania, Myanmar, Seychelles, Bangladesh, Madagascar, South Africa and Kenya. The number of death toll is underestimated and the true death toll of this tsunami may never be known as thousands were swept away into the ocean.

Before this tsunami event, warning systems which could have saved thousands of lives were not in place. Today, a tsunami warning system is in place for the Indian Ocean and numerous risk reduction methods are also taking place such as exercises.

Extensive research, data, images, videos and documentaries can be found on this event.

Estimated first arrival times in hours (Source: NOAA)

Maximum computed tsunami amplitudes (Source: NOAA)

Tsunami propagation (Source: NOAA)

Please note the videos below contain upsetting footage

Impact of the tsunami (Source: NASA)

Impact of the tsunami

Impact of the tsunami

Impact of the tsunami

·   Japan 2011 (Tōhoku earthquake and tsunami): On 11 March 2011 at 2:46 pm local time, an earthquake measuring 9.0 struck 231 miles (373 km) north east of the capital Tokyo and 80 miles (130 km) east of Sendai on the island of Honshu, causing total devastation in numerous regions. The earthquake was the highest magnitude to hit the country and one of the largest recorded in the world. Large aftershocks measuring magnitude 6 and above followed the earthquake. The poster by USGS below shows more details on the earthquake.

Japan 2011 earthquake poster (Source: USGS)

The tsunami generated had a maximum runup height of 38 metres. The destruction was unprecedented and widespread; buildings and properties were destroyed or washed away by the lethal power of the tsunami, if not damaged and crushed by the earthquake already. Entire towns and villages were also washed away. Miles of roads and other infrastructure were destroyed, trains carrying passengers went missing; assumed to be washed away as well and fires caused further destruction.

According to Reliefweb, more 15,882 people were confirmed dead, 400,000 were displaced, 2668 were left missing. The tsunami destroyed 130,000 houses, severely damaged 260,000 more and inundated 500 km2 of land.

Tsunami defenses in place failed during this event. According to the USGS, the defenses were built for tsunamis generated by a magnitude 8.0 earthquake and not a magnitude 9.0, i.e. they were not prepared for a 1 in 1000-year tsunami event.

Another phenomenon that occurred as a result of the displacement of the water during the earthquake was the creation of a whirlpool. Astonishing footage captured showed how boats were being pulled into the whirlpool. 

The Fukushima Nuclear Power Plant put authorities on high alert leading to the evacuation of an estimated 3000 people when the cooling system failed to shut down during the earthquake. On 12 March an explosion occurred at the power plant, injuring 4 workers and releasing radioactive material. The population within 20 km of the power plant were evacuated immediately. The nuclear accident is well documented and further information on this can be widely found. Extensive research, data, images, videos and documentaries can be found on this event.

Summary of damage and fatalities caused by the earthquake and tsunami (Source: Reliefweb)

The images below show examples of the devastation caused by the tsunami in Japan. You can also view videos of the tsunami and the damage on YouTube.

 

(Source: AP)

(Source: AP)

(Source: AP)

(Source: AP)

(Source: AP)

·       The eruptions of Santorini in Greece (1650BC) and Krakatoa in Indonesia (1883) caused tsunamis reaching heights of over 46 meters and 40 meters, caused either by edifice collapse or/and pyroclastic flows. These events wiped out the entire Minoan population in the Santorini case and claimed 36,000 lives in Indonesia. 

·     A magnitude 7.0 earthquake in 1998 of the coast of Papua New Guinea caused a submarine landslide measuring an estimated 4 km cubed. A 15 metre tsunami was generated by this landslide, killed 2200 people. 12,000 were made homeless and extensive damage was caused. Three villages were entirely wiped out and four were extensively damaged.

·        1955 Lisbon earthquake: An earthquake measuring a magnitude 8.5 in the Atlantic Ocean generated a tsunami with an estimated height of between 5 to 15 metres. This tsunami impacted the coasts of Portugal and Morocco. An estimated 60,000 people died, although this may be an overestimate since the majority of fatalities occurred as a result of the earthquake itself.

·     Storegga Landslide: 8200 years ago, a landslide generated a tsunami affecting the coasts of west Norway (10-13 metres high), Shetland (20-30 metres high), north east Scotland (3-6 metres high) and Faroe Islands (10 metres high).

Risk Management

It is currently impossible to accurately predict when and where a tsunami will occur, however it is possible to identify areas which are susceptible to tsunamis. This being said, it is possible to accurately forecast the tsunami arrival times and areas of impact once the tsunami has been generated and measured by ocean sensors. Once issued, warnings can allow minutes or hours to prepare and evacuate to higher ground. Effective communication of warnings and alerts is also essential to meet the purpose of early warning systems successfully.

For local tsunamis, warnings are generally not sufficient as the first wave can arrive within minutes. This makes preparedness, including education and raising awareness essential to successfully reduce fatalities.

Today, technology such as GIS, Remote Sensing and complex numerical models exist to detect, monitor, predict, forecast and mitigate or assess the propagation and impacts of tsunamis.

Tsunami Monitoring and Warning Centres/Organisations:

·         Pacific Tsunami Warning Centre (PTWC)

·         International Group for Tsunami Warnings in the Pacific

·         National Tsunami Warning Centre

·        Tsunami and other Coastal Hazards Warning System for the Caribbean and Adjacent Regions

·         Japan Tsunami Warning Centre (part of Japan Meteorological Agency)

·         The Joint Australian Tsunami Warning Centre

·         Indian Ocean Tsunami Warning and Mitigation System (ICG/IOTWMS)

·         North-Eastern Atlantic, Mediterranean and connected seas Tsunami Information Centre

Tsunami Warning/Alert Messages:

Below are the definitions of the Tsunami Warning/Alerts message issued by the PTWC.

Tsunami Warning - A tsunami warning is issued when a tsunami with the potential to generate widespread inundation is imminent, expected, or occurring. Warnings alert the public that dangerous coastal flooding accompanied by powerful currents is possible and may continue for several hours after initial arrival. Warnings alert emergency management officials to take action for the entire tsunami hazard zone. Appropriate actions to be taken by local officials may include the evacuation of low-lying coastal areas, and the repositioning of ships to deep waters when there is time to safely do so. Warnings may be updated, adjusted geographically, downgraded, or canceled. To provide the earliest possible alert, initial warnings are normally based only on seismic information.

Tsunami Advisory - A tsunami advisory is issued when a tsunami with the potential to generate strong currents or waves dangerous to those in or very near the water is imminent, expected, or occurring. The threat may continue for several hours after initial arrival, but significant inundation is not expected for areas under an advisory. Appropriate actions to be taken by local officials may include closing beaches, evacuating harbors and marinas, and the repositioning of ships to deep waters when there is time to safely do so. Advisories are normally updated to continue the advisory, expand/contract affected areas, upgrade to a warning, or cancel the advisory.

Tsunami Watch - A tsunami watch is issued to alert emergency management officials and the public of an event which may later impact the watch area. The watch area may be upgraded to a warning or advisory - or canceled - based on updated information and analysis. Therefore, emergency management officials and the public should prepare to take action. Watches are normally issued based on seismic information without confirmation that a destructive tsunami is underway.

Tsunami Information Statement - A tsunami information statement is issued to inform emergency management officials and the public that an earthquake has occurred, or that a tsunami warning, watch or advisory has been issued for another section of the ocean. In most cases, information statements are issued to indicate there is no threat of a destructive tsunami and to prevent unnecessary evacuations as the earthquake may have been felt in coastal areas. An information statement may, in appropriate situations, caution about the possibility of destructive local tsunamis. Information statements may be re-issued with additional information, though normally these messages are not updated. However, a watch, advisory or warning may be issued for the area, if necessary, after analysis and/or updated information becomes available.

Tsunami Warning/Alerts message definitions (Source: NOAA)

Example of tsunami risk mitigation (Source: NOAA)

Tsunami Databases:

·         EU GITEC, GITEC-Two –Genesis and Impact of Tsunamis on the EU Coasts

·         The Novosibirsk Tsunami Laboratory

·         NCEI (NGDC/WDC) – National Centre for Environmental Information NOAA

Useful Link:

·    Tsunami Database: NCEI (NGDC/WDC) – National Centre for Environmental Information (NOAA) Tsunami Database: NCEI (NGDC/WDC)

·  North-Eastern Atlantic, Mediterranean and connected seas Tsunami Information Center NEARMTIC

·         Indian Ocean Tsunami Information Center IOTIC

·         ESSO - Indian National Centre for Ocean Information Services INCOIS

·         TsunamiReady Program, NOAA TsunamiReady

·         Tsunami, NOAA NOAA Tsunamis

·         International Tsunami Information Center ITIC

·        The Tsunami story, NOAA The tsunami story

·        Reliefweb, Japan earthquake and tsunami 24 month report Japan earthquake/tsunami 24 month report

·  Reliefweb, Great East Japan Earthquake, Learning from Megadisasters Learning from megadisasters

·    Reliefweb, Great East Japan Earthquake, Learning from Megadisasters report Learning from megadisasters

2016 Tsunami Day videos:

References:

·        NOAA, Tsunami, Available online at: www.tsunami.noaa.gov/index.html

·        Rougier J., Sparks S. and Hill L., (2013), Risk and Uncertainty Assessment for Natural Hazards, Cambridge University Press.

·       Alexander, D. (2002) Natural Disasters, London, Routledge.

· USGS, (n.d), Tsunami and earthquake research at USGS, Available online at: http://walrus.wr.usgs.gov/tsunami

·      Mehdiyev M., Smarakoon L., Kyaw S.O. and Jagath Rajapaksha (2005) Tsunami disaster damage detection and assessment using high resolution satellite data, GIS and GPS- Case study in Sri Lanka. Asian Institute of Technology, Geoinformatics Center Available online at: www.geoinfo.ait.ac.th/publications/ACRS_2005_Tsunami_Paper_vf.pdf  http://www.apng.org/9thcamp/Slide/Rittick.pdf Accessed 11/02/2008

·        Koshmura S., Oie T., Yanagisawa H. and Imamura F. (n.d), Vulnerability estimation in Banda Aceh using the tsunami numerical model and the post-tsunami survey data. Available online at: http://www.arct.cam.ac.uk/curbe/RSWS_Koshimura.pdf

·       Papathoma M. and Dominey D. (2003), Tsunami vulnerability assessment and its implications for coastal hazard analysis and disaster management planning, Gulf of Corinth, Greece. Natural Hazards and Earth System Sciences. Volume 3, pp. 733–747

·      Venturato A. J., Titov V. V., Arcas D., Gonzalez F. I. and Chamberlin C.D. (2005), Reducing the Impact: U.S. Tsunami Forecast Modeling and Mapping Efforts. ESRI International User Conference Proceedings. Available online at: http://gis.esri.com/library/userconf/proc05/papers/pap2471.pdf

·  Esri (2007) GIS for disaster recovery. Available online at: http://www.esri.com/library/brochures/pdfs/gis-for-disaster-recovery.pdf

·    Papathamo M., Dominey-Howes D., Zong Y. and Smith D. (2003), Assessing tsunami vulnerability, an example from Herakleio, Crete. Natural Hazards and Earth System Sciences. Volume 3, pp. 377–389

·         Helal M.A. and Mehanna M.S. (2008), Tsunamis from nature to physics, Chaos, Solitons & Fractals, Volume 36, Issue 4, pp. 787-796

·        Pietrzak Julie, Socquet Anne, Ham David, Wim Simons, Vigny Christophe, Labeur Robert Jan, Schrama Ernst, Stelling Guus and Vatvani Deepak (2007), Defining the source region of the Indian Ocean Tsunami from GPS, altimeters, tide gauges and tsunami models, Earth and Planetary Science Letters, Volume 261, Issues 1-2, 15, pp. 49-64

·        Obura David (2006), Impacts of the 26 December 2004 tsunami in Eastern Africa Ocean &Coastal Management, Volume 49, Issue 11, pp. 873-888

·         Kharif Christian and Pelinovsky Efim (2005), Asteroid impact tsunamis Comptes Rendus Physique, Volume 6, Issue 3,  Pages 361-366

·         McAdoo B.G and Watts P. (2004), Tsunami hazard from submarine landslides on the Oregon continental slope, Marine Geology, Volume 203, Issues 3-4, pp. 235-245

·        Cita M.B and Aloisi G. (2000), Deep-sea tsunami deposits triggered by the explosion of Santorini (3500 y BP), eastern Mediterranean, Sedimentary Geology, Volume 135, Issues 1-4, pp. 181-203

·        Monaghan J.J., Bicknell P.J.  and Humble R.J. (1994), Volcanoes, Tsunamis and the demise of the Minoans Physica D: Nonlinear Phenomena, Volume 77, Issues 1-3, 1 October 1994, pp. 217-228

·         Yokoyama I. (1987), A scenario of the 1883 Krakatau tsunami, Journal of Volcanology and Geothermal Research, Volume 34, Issues 1-2, pp. 123-132

·         Francis P.W (1985), The origin of the 1883 Krakatau tsunamis, Journal of Volcanology and Geothermal Research, Volume 25, Issues 3-4, pp. 349-363

·       Pari Y., Ramana Murthy N.V, Jaya kumar S, Subramanian B.R. and Ramachandran S. (2007), Morphological changes at Vellar estuary, India—Impact of the December 2004 tsunami, Journal of Environmental Management.

·        Thanawood Chanchai, Yongchalermchai Chao and Densrisereekul Omthip (2006), Effects of the December 2004 tsunami and disaster mitigation in southern Thailland, Science of Tsunami Hazards, Volume 24, No. 3, pp. 206

·       Environmental Waikato (2008), How tsunamis develop. Available online at: http://www.ew.govt.nz/enviroinfo/hazards/naturalhazards/coastal/images/tsunami1.jpg

·         SOEST Communications & Outreach (2003), Modern threat of tsunamis. Available online at: www.soest.hawaii.edu/.../SOESTinthenews2004.htm 

·      Alquist A.E. (2007), The tsunami wave. Available online at: www.seismic.ca.gov/tsunami.html  

·        Tappin D.R, Watts P., McMurtry G.M., Lafoy Y. and Matsumoto T. (2001), The Sissano, Papua New Guinea tsunami of July 1998 - offshore evidence on the source mechanism. Marine Geology, Volume 175, Issues 1-4, 15, pp. 1-23

·        Tsunami Database: NCEI (NGDC/WDC) – National Centre for Environmental Information (NOAA) https://www.ngdc.noaa.gov/hazard/tsu_db.shtml

·        North-Eastern Atlantic, Mediterranean and connected seas Tsunami Information Center http://neamtic.ioc-unesco.org/

·        Indian Ocean Tsunami Information Center http://iotic.ioc-unesco.org/

·       ESSO - Indian National Centre for Ocean Information Services http://www.incois.gov.in/Incois/tsunami/eqevents.jsp

·       TsunamiReady Program, NOAA http://www.tsunamiready.noaa.gov/

·        Tsunami, NOAA http://www.tsunami.noaa.gov/

·        International Tsunami Information Center http://itic.ioc-unesco.org/index.php

·       The tsunami story, NOAA http://www.tsunami.noaa.gov/tsunami_story.html

·        Reliefweb, Japan earthquake and tsunami 24 month report http://reliefweb.int/report/japan/japan-earthquake-and-tsunami-24-month-report

·        Reliefweb, Great East Japan Earthquake, Learning from Megadisasters http://reliefweb.int/report/world/great-east-japan-earthquake-learning-megadisasters

·        Reliefweb, Great East Japan Earthquake, Learning from Megadisasters report http://reliefweb.int/sites/reliefweb.int/files/resources/drm_exsum_english.pdf