Question about earthquakes -trying to expand my knowledge on the area (Portland: 2015, house)

[Desperado09]

So please be kind in regards to my post. I admit I'm a tad ignorant in regards to earthquake knowledge since I haven't been around them or to the Pacific Coast. I recently watched a movie that had an earthquake in it and I started doing research as a result out of curiosity. I see that obviously Portland is at risk and have looked at the fault lines. Then I came across an article that said if a bad earthquake hit that the Bend area would be the "safe zone." I see from some history reports that Bend has around 2.3 rating for earthquakes, do they go beyond that or have the possibility to get up to a 6 or 7 in Bend?

Also, what about the Eugene area of Oregon is it around the same as Bend?

[Thom52]

Bend is a designated staging area for disaster relief when the Big One hits. I figure that is a pretty good statement for backing up its stability.

You can google "earthquake zone maps" or similar to get some good resources for evaluating risk at specific locations. There are some real surprises if you look at the USA map in general.

Now if the pools of magma barely under the surface of Central Oregon decide to "leak", that is a whole other concern. There is a reason there are so many hot springs in Central Oregon.

[oregonwoodsmoke]

Seriously, the topic of earthquakes in Oregon gets beaten to death frequently. Do a search for the topic and you can see plenty of information on the topic plus all of "the sky is falling" paranoia.



I suppose I should mention in passing that Bend has three live volcanoes, one of which has been very recently active.

[PNW-type-gal]

There are a lot of earthquake discussions in the forums about "the big one", the Cascadia Subduction Zone earthquake. It'll be felt in Bend, but it isn't likely to be a large-scale event there. However, there are a number of local faults (mostly NW trending) that can produce earthquakes. Remember the that Cascades, which run from Canada to Northern California, are a chain of active volcanoes and earthquakes are strongly associated with volcanoes - Newberry Crater's last lava eruption was only 1,300 years ago, which is pretty recent in volcanic terms.

The upshot is - yes, earthquakes are possible. Probably not the large earthquakes that are associated with other areas, but enough that you need to take a look at the connection between house walls and foundation, unreinforced masonry and the like.

A general guide:
https://www.oregon.gov/OEM/hazardspr...rthquakes.aspx

[BendLocal]

Originally Posted by oregonwoodsmoke

I suppose I should mention in passing that Bend has three live volcanoes, one of which has been very recently active.

Which volcanoes in Bend are live? Which was recently active?

[Desperado09]

Oh okay, interesting. Thanks for the info I was just curious. I didn't know earthquakes were a big topic in this forum as some others mentioned. I don't live there or even close to the Oregon/Pacific Coast so I'm personally not concerned, I was just trying to have a better understanding. I was confused when I read some articles about Bend being the safe zone, but Thom52 cleared that up for me, I didn't realize it was in regards to if a big one hit. So thank you! I also didn't know about the volcanoes (active ones) in that area as some commented on, so that's interesting, learned something new.

[PNW-type-gal]

Originally Posted by BendLocal

Which volcanoes in Bend are live? Which was recently active?

I suspect she is thinking of the Sisters "bulge" which has been pretty active over the last couple decades.

In geologic terms "active" doesn't mean currently erupting, it means capable of some type of volcanic event (not necessarily erupting like Mt St Helens). Volcanoes are considered "dormant" if it's been 10,000 years since the last event. An "event" can be detection of internal magma movement, steam explosions, lava explosions, pyroclastic (hot and cold) flows.

[oregonwoodsmoke]

Originally Posted by BendLocal

Which volcanoes in Bend are live? Which was recently active?

All three sisters are live and it's possible that some of the others are too.


One of the Sisters, I don't remember if it was Middle Sister or South Sister has been building a lava bulge. That means magma is right up near the surface.


(A quick Google says it is South Sister)

[oregonwoodsmoke]

It's very possible to have Earthquakes in the Bend area. I think that it gets called "safe" because ther is very little danger of Central Oregon falling into the ocean or of being drowned with a tsunami.

[Terryj]

This is a very well put together assessment on what to expect when the Cascadia subduction zone quake does happen.

http://wleog.org/wp-content/uploads/...astructure.pdf