T- phase
T-phase, also known as “T-waves”, are low frequency sound waves that are transmitted very efficiently through the ocean and are recorded on seismographs. They can be generated by earthquakes or large landslides near or beneath the sea, or by submarine explosions such as eruptions.

The rock-deforming processes and resulting structures that occur over large sections of the lithosphere.

Tectonic plates
The tectonic plates are the large, thin, relatively rigid plates that move relative to one another on the outer surface of the Earth.

The set of instruments and communications that send a data signal from their source to a distant data acquisition system.

Earthquakes at distances greater than 1000 km for the measurement site.

A tsunami originating from a far-away source, usually more than 1000 km or more than three hours from its source.

Materials of all types and sizes that are erupted from a crater or a volcanic vent and deposited from the air.

A period of geologic time extending from 65 million years ago to the present.Tilt
The angle between the slope of a part of a volcano and some reference point.

A sensor that detects the ‘tilt’ of the ground, and which is used for measuring ground deformation at volcanoes

Transform fault
A special variety of strike slip faults that accommodates relative horizontal slip between other tectonic elements.

Travel time
Time required for the first tsunami to propagate from its source to a given point on a coastline.

Japanese term meaning wave (“nami”) in a harbour (“tsu”). A series of travelling waves of extremely long length and period, usually generated by disturbances associated with earthquakes occurring below or near the ocean floor. (Also called seismic sea wave and, incorrectly, tidal wave). Volcanic eruptions, submarine landslides, and coastal rock falls can also generate tsunamis, as can a large meteorite impacting the ocean. These waves may reach enormous dimensions and travel across entire ocean basins with little loss of energy. They proceed as ordinary gravity waves with a typical period between 10 and 60 minutes. Tsunamis steepen and increase in height on approaching shallow water, inundating low-lying areas, and where local submarine topography causes the waves to steepen, they may break and cause great damage. Tsunamis have no connection with tides; the popular name, tidal wave, is entirely misleading.

Earthquakes commonly along major subduction zones that can create tsunamis.

Tsunami All-Clear
After a warning is cancelled, an All-Clear condition is issued by local authorities to the public when it is safe for them to return to the evacuated zones. As local conditions can cause wide variations in tsunami wave action, the All-Clear will depend on the degree of damage.

Tsunami damage
Loss or harm caused by a destructive tsunami. More specifically, the damage caused directly by tsunamis can be summarized into the following: 1) Deaths and injuries; 2) houses destroyed, partially destroyed, inundated, flooded, or burned; 3) other property damage and loss; 4) boats washed away, damaged or destroyed; 5) lumber washed away; 6) marine installations destroyed, and; 7) damage to public utilities such as railroads, roads, bridges, power plants, water or fuel storage tanks, or wastewater facilities, etc. Indirect secondary tsunami damage can be: 1) Damage by fire of houses, boats, oil tanks, gas stations, and other facilities; 2) environmental pollution or health hazards caused by drifting materials, oil, and hazardous waste spillages; 3) outbreak of disease of epidemic proportions, which could be serious in densely populated areas.

Tsunami Warning
A tsunami warning is an alert, usually issued by a National Tsunami Warning Centre (NTWC), to indicate that a tsunami threat is expected and imminent. A tsunami warning may be issued for different levels of tsunami threat.

Tsunami Watch
The second highest level of tsunami alert. Watches are issued by the Tsunami Warning Centres (TWCs) based on seismic information without destructive tsunami confirmation. The watch is issued as a means of alerting the affected populations located, for example, one to three hours tsunami travel time beyond the warned area. Subsequent text products are issued at least hourly to expand the watch and warning area, upgrade all areas to a warning, or cancel the watch and warning.

A general name for consolidated ash or tephra, usually with clasts less than 2 cm