Glossary of Terms

Below are terms of reference used within the TsunamiSafe website

All Clear

An advice that danger to life and property has passed.

Combat Agency

Means the agency identified in the State EMPLAN as the agency primarily responsible for controlling the response to a particular emergency.

Distant tsunami

A tsunami generated from a distant source, generally outside the south-west pacific region. This type of tsunami may also be referred to as ‘far field tsunami’.

Deep Ocean Tsunami Buoys (Deep Ocean Tsunameter)

A tsunami detection instrument capable of detecting tsunami in the deep ocean.

Effective Warning Time

The time likely to be available after a tsunami warning is issued and in which people at-risk can take action to leave an at-risk area or find a safe refuge.

Evacuation Order

Advice to the community authorised by the SES when the intent of an Operations Controller is to instruct a community to immediately evacuate in response to an imminent threat.

Evacuation Warning

Advice to the community authorised by the SES when the intent of an Operations Controller is to warn a community of the need to prepare for a possible evacuation.

Hazardous Material (HAZMAT)

Means anything that when produced, stored, moved, used or otherwise dealt with without adequate safeguards to prevent it from escaping, may cause injury or death or damage to property (Source: Fire Brigades Act 1989 (as amended).

Inland Waters

All riverine and estuary systems within NSW not included in State Waters (see State Waters).

Inundation

The maximum horizontal penetration of the tsunami from the shoreline measured in tens of metres or  kilometres.

Joint Australian Tsunami Warning Centre

The Joint Australian Tsunami Warning Centre (JATWC), jointly operated 24 hours a day by the Bureau of Meteorology (Bureau) and Geoscience Australia (GA) detects, monitors, verifies and warns of any tsunami threat to the coastline of Australia and its offshore territories.

Local Tsunami

A tsunami that is generated close to the areas it floods, for example a tsunami generated by a continental shelf collapse off the NSW coast. This type of  tsunami may also be referred to as ‘near-field’ tsunami.

Marine Rescue Agencies

Agencies involved in marine rescue include the Australian Volunteer Coast Guard, Marine Rescue NSW, NSW Police Force (Marine Area Command), Surf Life Saving NSW, and the Volunteer Rescue Association.

National Tsunami No Threat Bulletin

Notification that there is no tsunami threat to the Australian mainland or islands after an undersea earthquake has occurred. The Bulletin is issued after the JATWC has detected a large undersea earthquake and based upon an evaluation of the magnitude and location of this earthquake it has been determined that there is no threat  of dangerous tsunami to the Australian mainland, islands or territories. Bulletins are issued by the Bureau to all  media and emergency services.

National Tsunami Warning Summary

Provides a national summary of all Tsunami Warnings, Tsunami Watches and cancellations issued by the  Bureau of Meteorology.

Regional Tsunami

Tsunami generated within the South West Pacific Region.

Run-up

The maximum vertical height, above mean sea level, that the sea attains during a tsunami (measured in  metres).

Tidal Wave

A common term for tsunami used in older literature, historical descriptions and popular accounts. Tides, caused by the gravitational attractions of the sun and moon, may increase or decrease the impact of a tsunami, but have nothing to do with their generation or propagation. However, most tsunami (initially) give the appearance of a fast rising or fast-ebbing tide as they approach shore, and only rarely appear as a near vertical wall of water.

Travel Time

Time that it takes the tsunami to travel from its source to a particular location that it floods.

Tsunami

A series of travelling waves generated by the sudden displacement of the sea by submarine earthquakes, volcanic eruptions, landslides or asteroid impacts. The word ‘tsunami’ is Japanese for ‘harbour wave’.

Tsunami Warning

A Tsunami Warning may be issued once there is high degree of confidence that a tsunami threat exists based  upon detection that a tsunami has been generated; or if there is a potential threat (unconfirmed) to NSW within the next 90 minutes. This warning will outline the areas under threat using coastal waters forecast districts and the actions that should be taken by the community. Warnings are stratified to give some indication of tsunami magnitude. Tsunami warnings may be issued for the NSW mainland coast and/or Lord Howe Island. Tsunami Warnings are issued by the Bureau of Meteorology and are distributed to all media outlets and emergency management agencies. The following specific warning classes exist:

Marine Environment and Immediate Foreshore Threat

– The tsunami is expected to mainly affect the marine environment for specified coastal areas. Although major land inundation is not expected, there may be local amplification of the tsunami in some areas leading to land inundation in limited low-lying coastal areas. Significant sea level variations, may continue for many hours and even days along the affected coastal areas. Strong rips and currents may result in extreme danger to people in the water. Potential for damage to marine facilities and craft in marinas and harbours. Potential for sea water intrusions to the top of the beach, minor overtopping of sea walls and even over very low lying foreshore areas –paths, roads, beachfront car parks etc.

Major Land Inundation Threat

– Major sea level variations along the affected coastal areas. Significant over-topping of foreshore dunes and sea walls, with areas of inundation beyond the immediate foreshore. Extreme danger extending beyond the water to low lying coastal areas. Probable extensive damage to ports, marina and small boats. Potential damage to buildings and infrastructure near the shore. Extremely dangerous affects in the water continuing for many hours and even days. Tsunami Warnings can be cancelled if the situation is reassessed as having no threat, or at a point following an event at which the situation is assessed as posing no further threat.

Tsunami Watch

- A Tsunami Watch is a notification of a possible tsunami threat after an undersea earthquake has been detected and analysed. When the threat is confirmed or the potential tsunami may impact on NSW in less than 90 minutes a Tsunami Warning will be issued. A Tsunami Watch will typically be issued less than 30 minutes after an earthquake. Three types of Tsunami Watches exist; all have the same technical meaning but differ in the areas they apply to:

  • National Tsunami Watch – issued in the context of Australian region
  • NSW Tsunami Watch – issued in the context of NSW only. Issued when there is a warning for some part of the Australian region
  • Lord Howe Island Tsunami Watch - issued in the context of Lord Howe Island only. Issued when there is a warning for some part of the Australian region
National No Threat Bulletin

- To advise people that the earthquake has been assessed and that no tsunami threat exists

Tsunami Watches can be cancelled if the situation is reassessed as no threat Tsunami Watches are issued by the Bureau of Meteorology and are distributed to all media outlets and emergency management agencies.

Wave Height

Height of a tsunami wave is most important at shore and refers to the depth of water under the wave crest

Wave Period

The length of time between two successive tsunami wave peaks or troughs. May vary due to complex interference of waves. Is usually measured in minutes.