Friday Earthquake Blogging: M7.9 Southeast Alaska
Well, technically this is Friday tsunami blogging, but sometimes it’s hard to tell the difference. Yesterday was the 50th anniversary of the 1958 Southeast Alaska earthquake and ensuing Lituya Bay megatsunami, a half-kilometer high wave which killed only a handful of people.
The earthquake happened on the Fairweather fault, a strike-slip fault which forms the main boundary between the Pacific and North American plates on the Alaska panhandle. Strike-slip earthquakes don’t typically cause tsunamis directly – in a strike-slip event, the ground moves mostly horizontally, not vertically, so it doesn’t displace any water to speak of. This tsunami was caused by a large chunk of mountain that fell into the ocean as a result of the earthquake.
The same structure which generates strong tidal currents within Lituya Bay also funneled the tsunami into a super-high wave. There’s not much in this photo for scale, but wave damage was found at altitudes of up to 1,720 feet (524m).