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Author Topic: Do Earthquakes Happen Under Mountains ?  (Read 42254 times)

Offline Bass

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Do Earthquakes Happen Under Mountains ?
« Reply #50 on: 23/09/2007 05:59:44 »
Are you all anywhere close to Libby Montana!
near Missoula, 2 1/2 hour drive to Libby
I live in the beautiful Bitterroot Valley
« Last Edit: 23/09/2007 06:01:33 by Bass »
 

Offline Karen W.

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Do Earthquakes Happen Under Mountains ?
« Reply #51 on: 23/09/2007 06:01:31 »
Hee Hee! LOL Yes it does, But I have none and it's not from not being old enough.. me kids don't want kids anytime in the near future!
 

Offline Karen W.

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« Reply #52 on: 23/09/2007 06:05:10 »
Are you all anywhere close to Libby Montana!
near Missoula, 2 1/2 hour drive to Libby
I live in the beautiful Bitterroot Valley

My husbands Aunt Uncle and cousins all live in Libby and that neck of the woods I have only been there 1 time on our honeymoon. It was beautiful!

His Uncles name is Jon Person, harvey, Stan, Karen, and Sue Person.
 

Offline Karen W.

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« Reply #53 on: 23/09/2007 06:07:23 »
I don't remember seeing it on our way! I was 21 years old so it has been 26 years ago! LOL!
« Last Edit: 23/09/2007 17:51:19 by Karen W. »
 

Offline Bass

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Do Earthquakes Happen Under Mountains ?
« Reply #54 on: 23/09/2007 20:02:27 »
Seismic shake hazards for northern California, from CA Bureau of Mines and Geology

looks like you're in one of the most intense areas
« Last Edit: 23/09/2007 20:10:23 by Bass »
 

Offline Karen W.

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« Reply #55 on: 23/09/2007 20:08:51 »
Nice map! That is a good shot!

Yep Thats what I understand.. LOL I always thought it would be a Quake that would take me out here! LOL
« Last Edit: 23/09/2007 20:14:45 by Karen W. »
 

Offline Karen W.

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« Reply #56 on: 23/09/2007 20:18:50 »
I do not have a single thing anchored bolted down or otherwise stablized in me house.

 I have a large crack in me wall from the quake in 1989 I have numerous cracks in my foundation I cannot afford to fix and my head is constantly at a downhill sloe in my bedroom because thats where the foundation cracked and it drops downhill there! LOL It looks fine until you walk on it and go down hill! LOL
 

Offline Bass

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Do Earthquakes Happen Under Mountains ?
« Reply #57 on: 23/09/2007 22:15:07 »
I do not have a single thing anchored bolted down or otherwise stablized in me house.

Not too late to start!
 

Offline Bass

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Do Earthquakes Happen Under Mountains ?
« Reply #58 on: 24/09/2007 01:04:25 »
Hopefully this works- from USGS site

This is a geologic map of your area




lots of thrust faults- black lines with sawteeth (due to the size of the map- only the major faults are shown- there are likely to be many, many more smaller faults).  We call these imbricate thrust zones, where there are lots of thrust faults stacked one on top of another.  Sort of like cards in card deck sliding over the top of each other.  Sawteeth are on the upper plate that gets pushed up over the lower plate:



Rocks are mostly "melanges" - (cb1 and cm2 units on map) which means mixture.  A geologic melange is a mixture of different rocks caused by extensive faulting.  The faults break up the rocks and the fault movements jumble them together.  the blocks in your area are are mainly made up of sandstones and mudstones.  Overlying this are recent marine sediments QTw (pushed up out of the ocean), river deposits Qal,Qt and too many landslides (Qls).

The root cause of most of the faulting is that you live adjacent to a subduction zone, and the North American tectonic plate is trying to push up over the top of the Juan de Fuca oceanic plate, and you just happen to be on the leading edge- where the biggest stresses are. 

In plain english- get used to a "whole lot of shakin' going on".  I think it would be prudent to stabalize your house and anchor heavy objects to the extent of what's affordable.  I know there are some things that can be done fairly cheaply.  There's probably a county department that might be able to help out or at least make suggestions.  Also check in with the geology dept at Humblodt State- they can give you alot more detail.
« Last Edit: 24/09/2007 01:08:58 by Bass »
 

Offline Karen W.

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« Reply #59 on: 24/09/2007 05:55:51 »
Thanks for the information. It is interesting about the rocks and things in this area. here where I am when we dug our wells we found our property full of clay around 4 ft one well was 2 feet down into the clay! but very wet with a real high water line.. We have two 100 ft wells and one 25ft well, but it always went dry in the summer so we closed it. It was dug and put in by a professional.. The other wells we witched for ourselves and have never had a problem with the water since. Except for broken pumps we love our water. do these faults ever effect the underground streams that supply our water?
 

Offline Bass

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« Reply #60 on: 29/09/2007 03:11:10 »
Most definitely.  Your water supply depends on several factors, but two important factors are porosity and permeability- porsosity being the amount of available (void) space for water and permeability being the ease with which that water can move through the rocks.  Earthquakes do change these conditions, especially permeability.  After a good shake, your water may be more abundant, less abundant, but commonly will be a bit muddy or silty.
 

Offline Karen W.

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« Reply #61 on: 01/10/2007 06:08:56 »
I have noticed that once after the 7.2 quake several years ago. It only lasted a few hours and we turned on evry fawcit on the property to rallow the mud to run its course it was a bout three days of flushing before it was perfectly clear. we have very good well water. They test it every year. Its the best water around here. I need to fix the pump again!

I did not notice that any of the smaller quakes effected it but was suspicious of the big one and wondered if that had been the cause!
 

Offline Bass

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« Reply #62 on: 30/12/2008 22:40:58 »
Karen- an excellent book on California Geology, written by a non-professional for ordinary folks, but still full of information that even I didn't know:

"Assembling California" by John McPhee. 

"Rising from the Plains", McPhee's story of Dave Love and Wyoming geology is also a good read.

I'm sure you can find these in the local library, or any good bookstore.
 

Offline Karen W.

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« Reply #63 on: 18/01/2009 08:22:03 »
Thanks bass.. I missd this post and just found it!
I will check it out and try to find it!

I am amazed at all the sizemic action when you look at all those lines...
 

Offline Bass

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« Reply #64 on: 21/01/2009 03:07:51 »
de nada

enjoy the book!
 

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Do Earthquakes Happen Under Mountains ?
« Reply #64 on: 21/01/2009 03:07:51 »

 

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