Re: Finding Fault in Wrightwood

The new

> "bonus photo" on my Web site,
formatting link
, shows the > tree ring signature of the 1812 San Andreas fault earthquake!

Appropos of nothing in particular I was wondering what factors cause the notable changes in the way a tree grows rings.

Obviously climate differences, the cycles used to calibrate tree ring dating.

Local water table changes as would probably occur in an area where the ground is heaved up or down.

Local building and water abstraction requirements.

Felling other trees; planting other things.

Balance of the tree, as mentioned, the tree lost branches. Gravity will affect the way the tree needs to produce branches. (Note the shapes of trees growing on hills vs those on flat land.)

Covered in the above but not normally noticed even by tree huggers is the effect of aerodynamics.

Trees and bushes in an untended coppice will form an overall curve to minimise the effects that gales will have on a tree. The same way that the individual trees grow out to maximise the light available to them.

Remove some and the environment is either better or worse, depending on the competiton.

Have you got a full picture of the cross section and can you highlight the rings involved please?

I believe (I can't back it up but) the way a tree pumps up water depends on the twisting motion imparted by the wind on its branches.

Reply to
Michael Mcneil
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There is an abrupt slowing of tree ring growth in the purple area. Unless other trees in the area showed the same slowing, the cause can be attributed to damage to the tree caused by the eq.

Reply to
asetnil

Sometimes an answer is deceptively easy: the tree was growing almost directly atop the main fault trace, so presumably when it moved (abruptly) by 4-5 meters, it didn't bring 100% of its root system along for the ride!

Susan

Reply to
susan hough

SNIP

For a tree in the area of ground movement one could expect some serious damage to the root system. This could possibly takes years to restore.

Bob

Reply to
Robert Flory

I can remember the xmas tree of a neighbour when I lived in a place that had suffered from a sea flood.

The tree was rooted and planted out each year after xmas. Until the flood came in February and turned all the needles brown but they kept it for several years. One day faint traces of green at the tips of the branches could be seen.

Very unusual.

Reply to
Michael Mcneil

The earthquake-induced innundation of trees, by either fresh or salt water, allows another kind of tree-ring study. Up in Cascadia, some of the earliest/most compelling evidence for the 1700 megathrust quake came from "ghost forests"--trees along the coast that had been innundated by sea water and died, but whose trunks were still standing. And baldcypress trees standing in Reelfoot Lake provide evidence of an abrupt creation of the lake, because the trees can grow but not germinate in standing water. Clever stuff, these tree-ring studies.

Susan

Reply to
susan hough

snipped-for-privacy@gps.caltech.edu (susan hough) wrote in news: snipped-for-privacy@posting.google.com:

I lived up in Bremerton Washington in 90-91 and had a chance to go hiking on the outskirts of the Olympic Forrest. The place we went to is called Lena Lake and was formed by a massive landslide that blocked the river. You could still see the forest standing in the lake.

Later on as my interest in seismology grew I learned that there are dozens of these lakes in the area, all probably caused by the 1700 event.

It's amazing to think back on those memories and realize those submerged trees have been there for 300 years.

BTW, Susan, I was watching a program on The Science Channel today about 'earthquake storms' in which you made the little walk across the San Andreas fault from the Pacific Plate to the North American.

Brian

Reply to
Skywise

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