Oregon tsunamis

This article on Bend.com is interesting, about the occurence (and likelihood of) tsunamis off the coast of Oregon.

Some time between 9 and 10 p.m. on Jan. 26, 1700, a similar great earthquake, with the same estimated magnitude as the one in Asia, struck the Northwest, rocking the region with strong shaking for several minutes. The specific time can be told through a variety of evidence closely studied by scientists in recent years, such as land levels, sand deposits, the rings of ancient trees and historic records….

 

Geological evidence indicates that mega-quakes have occurred in the zone at least seven times over the past 3,500 years, meaning they happen, on average, every 400 to 600 years.

With a little digging, I found out this was the Cascadia Earthquake (thank you, Wikipedia), a magnitude 9 megathrust earthquake that slammed the Pacific Northwest. I also found this page which has a somewhat more consequential description:

The earthquake collapsed houses of the Cowichan people on Vancouver Island and caused numerous landslides. The shaking was so violent that people could not stand and so prolonged that it made them sick. On the west coast of Vancouver Island, the tsunami destroyed the winter village of the Pachena Bay people, leaving no survivors. These events are recorded in the oral traditions of the First Nations people on Vancouver Island.

Freaky. I knew the area was geologically active—volcanoes and such—but I had no idea it was this active.

South Sister Quakes

Sweeping the local news this evening is the South Sister earthquakes: more than 100 shook the area three miles west of the South Sister today, with a magnitude of up to 1.5 on the Richter scale. Bend.com has the best writeup on the story I’ve seen online.

The quakes were occurring in the northeast part of an area centered three miles west of South Sister, in which the ground has undergone what scientists call “crustal uplift” (but others have called “the bulge”) by as much as 25 centimeters (about 10 inches) since late 1997….

The magma appears to be accumulating at a depth about four miles below the ground surface, and measures about 50 million cubic yards in volume.

Interesting stuff; of course the entire Cascade Range is geologically active, so it’s not really a surprise, but with the South Sister about, oh, 30 miles away, this news has more than a few people worried, I’m sure.

Personally, I’d expect Mount Hood to be the one to erupt first, of all of them.