Mt. Hood Activity

[dgavin]

There was a rather significant avalanch looking like reading on Siesmographgs at Mt. Hood today. However nothing reported on the Avalanch warning networks yet, or from SkiHood.com.

[dgavin]

Still no news, but the skihood blog does indicate they are working on preparing a currently avalanch prone area for skiing. It was probably a manmade triggered avalanch.

They are also reporting 10 feet of new snow in last nine days.

[Gillianren]

Yeah, there's probably avalanche risk at a lot of the local mountains.

[dgavin]

From USGS:

An earthquake swarm at Mount Hood began Thursday, February 23, at 12:36 p.m. As many as 23 small earthquakes, with magnitudes ranging from 1.7 down to minus 0.3 had occurred by 7:30 Thursday evening. Focal depths ranged from 4 to 8 km. Although quiet overnight, the swarm has resumed this morning. This and previous swarms like it are thought to result from the regional tectonic forces affecting north-central Oregon. They recur at Mount Hood 1-2 times a year and then may go absent, occurring only once every few years. When underway, a Mount Hood swarm may be brief or may persist over a few days.

[dgavin]

There was another micro-swarm located just 8km south of Mt. Hood, at Clear Lake area. It was Comprosed of 27 Quakes, starting at 5am until 11am Sunday PDT, with magnitudes ranging from .5 to 2.9, and depths varying greatly from 13.7km to just 1.8km.

My somewhat amatuerish training is telling me this might just be magmatic in origin, possibly uplift related, as opposed to tectonic.

[danscope]

Doesn't tectonic activity generate the potential for increased uplift within areas of weaker rock or rock which has been previously or newly fractured as a function of increased magma plume activity? Curious.

Best regards,
Dan

[dgavin]

USGS posted a brief on this swarm saying it's tectonic not magma related. However that report ignored the two deepest events that were in the known area of the Mt. Hood area's magma chamber. (one almost in the dead center of the magma) I'm not sure why they didn't include the two deeper events in the report.

I think i'll stick by my amaturish assesment for now about it beign a magmatic related swarm due to uplift (or subsidence).

Doesn't tectonic activity generate the potential for increased uplift within areas of weaker rock or rock which has been previously or newly fractured as a function of increased magma plume activity? Curious.

Best regards,
Dan

Far as I know you are correct.

[danscope]

Thank you,Sir. I'm an amateur as well, but interested. Thanks again for your reports and observations as always.
Dan

[dgavin]

Two possible harmonic tremors at Mt. Hood. Before anyone worries these were very-very weak, and not very long duration.

The folloing URL will be good for about a week, it shows the weak tremors at 21:03 and at 00:31 hours.

http://www.ess.washington.edu/SEIS/P...012041700.html

[dgavin]

Nothing since those two tremors. From the depth of them, short duration and weak signals, my best guess would be gas pockets moving through magma or rock. Nothing really out of the ordinary , and still considered background activity in a volcanic region.

[dgavin]

This is not well known about, but since the 80's when St. Helens erupted, there has been Fumeral activity at Mt. Hood. Some days strong enough you can see steam in the emissions. USGS has been monitoring these fumerals and while there is some minor SO2, and rock discolorations, it's not been increasing in S02 content at all.

Here is a cool picture of one of the fumerals.

http://volcanoes.usgs.gov/vsc/images...499/img439.jpg

[Ara Pacis]

That's one of the reasons we moved from Portland, I think. I've never climbed to the top, but I got halfway there once before deciding I probably needed something more than a t-short and shorts.

[dgavin]

A minor earthquake swarm at Mt hood on the 19th, of 15 event sa rounf 3.6km depth. Still considered background activity.