Monday, December 31, 2007

Earthquake Risk

It is well known that California is laced with earthquake faults and is likely to slide off into the sea someday, and that southern Alaska has earthquakes - they are part of the Pacific Ring of Fire. Less well known is that there is a small area of high seismic risk far to the north, around Yellowstone National Park. On the USGS seismic danger map, there is a bright red dot on the border of Montana and Wyoming, with a trail extending down through Wyoming to Utah. Yellowtone National Park and Big Sky, Montana, are in seismic zone 4 - just like San Francisco (and much of California); the only other place in the US with zone 4 ratings is southern Alaska. Bozeman is in zone 3, along with much of the northern Rockies, the rest of California, the area around Puget Sound (Seattle), much of Alaska, Puerto Rico, the main island of Hawaii, and a portion along the Mississippi River, in Arkansas, Tennessee, and Missouri (over the New Madrid fault).

Just to make the point, there was a magnitude 3.6 earthquake in Yellowstone National Park last night, followed by 13 aftershocks. It didn't do any damage, but it was larger than usual.

No comments: