[Skywise]

http://www.usgs.gov/blogs/features/usgs_...from=title

Full story at link.

[Island Chris]

Hi Brian,

I did not go to the link but did look at the map. They still have a huge bull's-eye hazard around New Madrid; this is questionable. They have an area of hazard in Oklahoma, but not where most of the recent, presumably induced quakes have been. The actual hazard is likely where the quakes are now occurring, including for larger quakes (larger than the 4s that have been occurring).

Chris

[Skywise]

(07-18-2014, 11:05 AM)Island Chris Wrote: Hi Brian,

I did not go to the link but did look at the map. They still have a huge bull's-eye hazard around New Madrid; this is questionable. They have an area of hazard in Oklahoma, but not where most of the recent, presumably induced quakes have been. The actual hazard is likely where the quakes are now occurring, including for larger quakes (larger than the 4s that have been occurring).

Chris

And, what's with the thin little arcing line in Alaska along the Denali fault? It's a narrow band of high hazard that cuts through low hazard areas? Like the shaking drops off that much in so little distance from such a fault capable of large quakes? "Yeah, you're 20 miles from the fault and screwed, but I'm 30 so I'm ok." errrrr.....

Brian

[Island Chris]

Brian,
actually, I'll agree with the Denali fault one. If there are not deep sedimentary basins (like Los Angeles basin), the shaking does drop off sharply with distance from strike-slip faults, at least in California. This was demonstrated by Jim Brune's work on precariously-balanced rocks in southern California: they are seen something like >20 km from the distributed strike-slip faults.You don't see such a narrow strip in California because there are too

many faults: for example, thrust faults east of the San Andreas along the west side of the Central Valley (think Coalinga, vs, San Andreas at Parkfield).

Hmm, might there be such faults in Alaska that have been missed (or at least their activity?).

Chris

[Skywise]

(07-19-2014, 11:50 AM)Island Chris Wrote: Hmm, might there be such faults in Alaska that have been missed (or at least their activity?).

Well, considering how many offshoots and parallel faults there are around the San Andreas, I think it's reasonable to suppose that any large strike/slip system is going to be similar, especially around the kinks and bends.

But, there's probably not enough people and infrastructure (ie $$$$) to worry about in Alaska to make finding them all worth the effort.

Brian