An earthquake is caused by a sudden movement of tectonic plates which collide, split, or slide past each another. Earthquakes occasionally occur in volcanically active areas or along fault lines, and can occur both on land and beneath the sea. When tectonic movement occurs beneath the sea, they result in earthquakes that trigger tsunamis. A tsunami is a giant wave caused by a volcanic eruption or an earthquake under the sea. The effects are hardly felt in the deep sea, but as the waves travel to the shore, they increase in height. Earthquakes under the sea cause an earthquake tsunami. Earthquake tsunamis originate from distant locations in the sea but the tsunamis cause more damage along the coastline than if an earthquake of the same magnitude occurred on land. Tsunami earthquakes are dangerous because they are unpredictable and often occur abruptly.
Characteristics of an Earthquake Tsunami
Tsunami earthquakes release low-frequency seismic energy over long periods. They do not show the peak of energy release like the earthquakes on land, but tsunami earthquakes can generate twice the amount of energy as tsunamigenic earthquakes of the same magnitude on land. The rupture velocity of a tsunami earthquake is about one kilometer per second, while a normal earthquake has a rupture velocity of 2.5–3.5 km per second. The slow speed results in a series of waves that build up along the coastline.
Effects of Tsunami Earthquakes
The effects of tsunamis depend on the energy released during the seismic event, the magnitude, and the distance from the point of origin to the point of impact. The effects range from unnoticeable to devastating. The effects are also impacted by the geography of the bathymetry along the coast. Small tsunamis occur frequently, are undetectable, and non-destructive. When approaching the coastline, small tsunamis are often felt as fast-moving but strong tides. Large tsunamis, on the other hand, cause severe property damage, death, destruction of the environment, floods, and displacement.
Predicting Tsunami Earthquakes
Scientists are yet to develop a reliable method of forecasting tsunami earthquakes. However, animals are reputed to sense the vibrations of earthquakes, although research has not yet proved this theory. The inability to detect earthquakes and tsunamis is the major reason why so many people die when they occur. However, geologists can map areas that are likely to experience earthquakes that could result in tsunamis. These areas include the western shore of South America and the Ring of Fire. Indonesia, which is located in the Ring of Fire, has been identified as an earthquake territory because of the volcanic activities in the region and the presence of fault lines. In December 2004, an earthquake of magnitude 9.0 struck the coast of Sumatra, resulting in a tsunami that left more than 200,000 dead and billions of dollars of property damage.