They appear as a result of earthquakes that occurred far from the intended settlement. The ocean ridges themselves do little to protect the coast. Most of the tsunami energy passes over the ridge to the coastline. The most famous tsunami of remote origin occurred in 1960. It formed along the coast of Chile, and its waves reached the coast of Japan.
In 2013, the US Geological Survey initiated a project in Alaska dedicated to such a tsunami. In the course of the work, experts discovered that an earthquake of magnitude 9.1 could cause a tsunami of a distant origin with a height of about a meter in the ports of Los Angeles and not only. According to preliminary estimates, this could lead to losses of $ 4.2 billion.
Scientists have found that by the beginning of the next century, according to forecasts of sea level rise, an earthquake with a much lower magnitude, 8 points, could cause a distant tsunami with a height of more than 1 m.