A mega tsunami is possible and most particularly those that can be caused by massive underwater landslides or volcanic collapses which can generate waves that are much higher than typical tsunamis.
The most well known example of a mega tsunami is the 1958 Lituya Bay tsunami in Alaska that is often cited as a mega tsunami due to it's extreme wave height that is caused by a landslide.
Although the term mega tsunami does not have any strict scientific definition and is also often used to describe exceptionally large tsunami events.
Tsunamis have hit the United States including in locations such as the West Coast, Alaska and Hawaii.
Some Notable Tsunamis that have hit the United States include.
The 1964 Gulf of Alaska Tsunami.
The 1964 Gulf of Alaska Tsunami was generated by a 9.2 magnitude earthquake that caused extensive damage in Hawaii, Alaska, California, Oregon and Washington.
The 1964 Gulf of Alaska Tsunami was the largest Tsunami recorded in United States History.
A 1946 Aleutian Islands Tsunami was generated by an 8.6 magnitude earthquake and killed 167 people and caused $322 million in damage.
Another tsunami that hit the US was a Tsunami that was generated by a 7.3 magnitude earthquake which reached as far south as South Carolina and occurred in 1929 and is known as the 1929 Grand Banks earthquake.
The states in the United States that are at the greatest risk of Tsunamis are California, Oregon, Washington, Alaska and Hawaii.