definition of tsunami

Definition of tsunami

Tsunamis are ocean waves caused by earthquakes, landslides or volcanic eruptions that occur at sea. The tsunami waves move at speeds of hundreds of kilometers per hour at sea, and can hit the mainland with the wave height reaches 30 m or more. Tsunami magnitude that occurred in Indonesia ranges from 1.5 to 4.5 Imamura scale, with a high maximum tsunami wave that reached the coast ranges from 4-24 meters and reach of the waves to the mainland ranged from 50 to 200 meters from the coastline.

Based on the earthquake catalog (1629 - 2002) never happened Tsunami in Indonesia as much as 109 times, which is 1 times the result of landslides (landslide), 9 times due to volcanoes and 98 times the result of tectonic earthquake.
[tsunami mechanism]
The earthquake that caused the tsunami most of the earthquake that has a focus mechanism with dip-slip component, the vast majority were thrust type (Flores 1992) and a small normal type (Sumba, 1977). Earthquakes with focal mechanisms of strike slip is very small chance to cause a tsunami.

The signs of the coming tsunami in coastal areas are:

1. Sea water receded abruptly.
2. Salty smell was terrible.
3. From a distance appear white waves and a very loud rumbling sound.

Tsunamis occur when:

1. Earthquake major earthquake with a strength of> 6.3 SR
2. The location of the epicenter in the sea
3. Shallow depth <40 km
4. Vertical deformation occurred seabed