Causes Of The 2009 Miami Earthquake

2009 Samoan Earthquake and Tsunami Report

Stage one: Cause

The 2009 Samoan Tsunami that occurred on the 29th of September was a major earth science event, caused by two significant earthquakes. Generally, with most earthquakes it’s a single earthquake which is followed by few or several aftershocks. However, the 2009 Samoan earthquake was one earthquake which triggered the second earthquake to occur. This event was called a ‘triggered doublet’. As a consequence of these two earthquakes, the 2009 Samoan Tsunami was created which lead to the destruction of the main coasts in Samoa, American Samoa and Tonga. These earthquakes occurred around 6:48am (Samoan local time) with the second earthquake occurring seconds after the first and were measured

Tsunamis are different to normal waves because the energy doesn't come from wind, because wind affects the surface and doesn't significantly increase the size or speed of waves. Instead, tsunamis are created by energy that originates from underwater. Tsunamis can occur from volcanic eruptions or submarine landslides, but the 2009 Samoan tsunami was caused by a submarine earthquake, generated from the initial fault rupture. The sudden movement of the seafloor rising around 7 meters, caused by the second earthquake, led to a massive amount of energy in the water. This energy then travels up to the surface which then displaces water, raising it above the normal sea level. Gravity then pulls the water down which makes the energy ripple out. This results in the formation of a tsunami, moving around 500 miles per hour. From shores, tsunamis aren't noticeable because it’s too far to see due to the distance, and that it’s constantly moving through the whole depth of the water. That means that the tsunami hasn’t yet created high waves and is mostly travelling within the water before reaching the shore. When reaching the shallower parts of the water, a process called wave shoaling happens. This means, that due to less water being available for the tsunami to move through, a substantial amount of energy is compressed. This causes the waves speed to slow down, consequently the tsunamis height can rise to as high as 100 feet. With the 2009 Samoan Tsunami, waves were recorded to have reached around 46 feet (14-15m) easily sweeping people, homes and facilities away.(8) The trough of a tsunami usually reaches the shore first, the water withdraws further than normal before the wave actually hits the shore, this is dangerous because it is one of the major