Earthquakes and Redwood Forests

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#1)  Earthquakes and Redwood Forests

Postby MarkGraham » Wed Feb 17, 2016 10:35 pm

There has been a lot of research over the past couple decades on giant (around 9.0) magnitude earthquakes which apparently occur a couple hundred miles offshore where the Juan de Fuca plate subducts the North American plate along a line west of Vancouver island down to offshore of Mendocino county. The incidence of these quakes is about every 500 years, with the last giant quake (8.7 to 9.2 magnitude) in 1700.   There are tsunamis associated with these earthquakes, thus the tsunami evacuation zone signs seen when driving along 101 from Eureka northward.

Obviously the greatest concern for these quakes revolve around people and structures.  However these quakes could have impacts on forests.  The coastal cedar and spruce trees could be impacted by the associated tsunamis versus the redwood and fir forests could be impacted by subsidence and landslides.   I read an article concerning the 1989 6.9 magnitude Loma Prieta earthquake whose epicenter was underneath the Forest of Nisene Marks state park near Santa Cruz.  Apparently there was so much lateral shaking in certain areas ALL the tops of trees snapped off.  The author of this article (M Humenik) notes it must have looked like it was raining Christmas trees during the quake.

Older long lived trees, such as redwoods, have survived three to five giant quakes over their lifetimes.  Do you feel these large quakes, such as the one in 1700, had some effects on the redwood forest that can still be noted or identified today.   For example, is there a cluster of reiterations in redwood crowns that tie back to the 1700 earthquake.  Based on what happened in Nisene Marks, maybe the next big Cascadia earthquake will take the heights of the tallest trees, many of them, from 350-370 feet to 320-340 feet.  Are there are lot of logs on the ground that fell in 1700?  Is the slight twisting seen in many older redwoods due to the reorientation of the tree as a whole or the reorientation of the trunk in relation to the roots, with the reorientation due to rapid subsidence and lateral shaking during the earthquakes?

Can the study of the redwood forest assist in the study of earthquake impacts?

Let me know you thoughts.

Mark
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#2)  Re: Earthquakes and Redwood Forests

Postby edfrank » Mon Feb 06, 2017 10:35 pm

Not a bad question, but I really think the answer is no.  Trees sway in the wind and sway during earthquakes, but I don't see any reason why they would affect the forests in any meaningful way.  The only thing I can think of would be if they earthquake started a landslide or mudslice that impacted the forest, but then it really isn't the earthquake directly affecting the forest, but a secondary factor doing the impacting.
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#3)  Re: Earthquakes and Redwood Forests

Postby Don » Tue Feb 07, 2017 12:33 pm

Mark-
Interesting thoughts!
While I basically agree with Ed, I grew up in "Shake and Bake California", and during a time when several earthquakes took place. Attending a community college, taking a geology class, I recall locally an account of a "lateral, slip, dip fault movement" that so befuddled a rancher's cattle that they would never afterwards cross the fault (though lengthy, the drop was only several feet (and these were mountain ranging cattle), and the slip somewhat more).
And a few years later, while taking another geology class from the local state university, on the fifth floor of the new science building designed and spec-ced by another geology prof, we experienced a 5.7 earthquake during class...the prof went "hmmmm..." I believe that was an earthquake, but don't be alarmed, just dive under your table (very sturdy chemistry lab quality desks) for a minute of so, it would be foolhardy to go down the elevator, or stairs as there's usually an aftershock within the first thirty seconds.

Move ahead to the late '60s, when I went to Humboldt State University (very northwestern California), we were very aware of the impact of the 1964 Alaska earthquake.  Now considered the second most powerful every recorded at 9.2 on today's standards, the following attachment rounds up some facts and figures:
http://www.livescience.com/44412-1964-a ... facts.html

Perhaps not mentioned, was the tsumami it caused...it first hit the Alaska coast and in particular Valdez and Seward (both have memorable accounts), and some hours later, the north coast of California, at Crescent City (very northernmost corner of California), running rampant across the rather flat shallow shoreline there, washing cars inland, and destroying much of the town.

In 1992, near the small town of Landers in the southeastern desert of California, a 7.3 earthquake occurred less than 10 miles from the country residence of my parents. the paved county road leading into their place, shifted north and south horizontally 18', displacing the whole road (centerline matched up with the road's edge, post quake)

Best for last?  In 1958, at Lituya Bay in Southeastern Alaska, a 7.3 earthquake occurred that loosened accumulating land mass (from lesser, prior earthquakes) that slid into the Bay with such force that the  highwater lines are still visible more than 100 feet up both sides, as the tsunami raced out the narrow fjord.  A Forest Service ranger happened to be out with his son fishing and records the story of riding that wave out, "looking down on the tops of hundred foot high trees..."   Facts and figures and other accounts abound. Especially the "boulder" detailed in this account:
http://www.wsspc.org/resources-reports/ ... y-tsunami/

What is it that they say?  "Stranger things have happened!"
-Don
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#4)  Re: Earthquakes and Redwood Forests

Postby MarkGraham » Sat Feb 11, 2017 2:36 pm

Yes that 1964 Alaska earthquake is a good example of what will happen when the next Cascadia quake occurs off the northern California / Oregon / Washington coast.   I have the July 1964 National Geographic, the one that has the article on finding the "world's tallest tree" in what was subsequently named Tall Trees Grove.  The same issue has extensive write ups and photography from the Alaska earthquake which occurred earlier in the year.    There were lots of land upthrusts and there are pictures of conifers standing on shifted ground at 45 degree angles.  The control tower at the airport snapped, killing the controller working there at the time.  There were big landslides that raked the hillsides clear of trees.  And of course the big tsunamis.

An 8.5 - 9.2 magnitude earthquake is apart from the earthquake experience since the Pacific Northwest was settled.  A magnitude 9 earthquake releases 1,000 times more energy than a magnitude 7 earthquake.   Based on what happened during the 1989 Loma Prieta earthquake and the 1964 Alaska earthquake these events will surely occur with the next Cascadia earthquake:

Tall redwood trees, with their long axes, will have their tops snapped off by centrifugal force.
Groves of redwood trees will be destroyed by landslides, pushing a lot of timber into creeks.
Other groves of redwoods will by "dead trees standing" due to land shifts cutting roots and inducing leans
Tsunamis will scrub clean existing natural features at the coast such as Fern Canyon.

It may not happen in our lifetimes, but it will happen, certainly sometime in the next 200 years.
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#5)  Re: Earthquakes and Redwood Forests

Postby AndrewJoslin » Fri Feb 17, 2017 2:17 pm

I remember reading that people in small towns and villages in Japan would go to bamboo groves during and after (aftershock potential) earthquakes. The interwoven rhizome root systems form a strong but flexible mat that would essentially float over and survive severe land shifts/movement and even ground liquification. In the PNW old-growth I suspect there could be a similar effect, depending on slope and other variables the root "infrastructure" might dampen destructive effects on the land surface. It does make sense that a bunch of wood would fall out of the sky.

I've only climbed a PNW Coast Redwood once, it was a second-growth tree in an obscure canyon south of San Francisco. It was a substantial tree, taller than the biggest white pines I've been in on the east coast. At a point approximately 2 thirds up the tree I felt a jolt through the entire tree. It was a very minor quake. On the ground I may not have felt it, the tree amplified the effects of the shock wave. I had to pause for a moment after that and consider the interconnectedness of geology and forest ecology ;-)
-AJ
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#6)  Re: Earthquakes and Redwood Forests

Postby AndrewJoslin » Fri Feb 17, 2017 4:09 pm

This is fairly boring documentation of the climb, unless you're a student of conifer climbing but... at 8:35 into the video the tremor happens, interesting event to experience. I suspect that this happens to PNW tree climbing researchers relatively often:
Tremor in Coast Redwood at 8:35 into the video clip

-AJ

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#7)  Re: Earthquakes and Redwood Forests

Postby Don » Fri Feb 17, 2017 5:43 pm

Andrew-
Your post reminds me of an account by Richard Preston's The Wild Trees, where if memory serves me, Steve Sillett, his better half, and somebody else were up in one of the larger redwoods when one of the iterations they had decided to 'camp on' had an adjustment of significant jostle, and they decided to stay the night. The next time they returned to the area, the iteration or maybe even the whole tree had fallen.
It seems we can't always take for granted that these thousands of year old trees are stable...
Your comment about land shifts/movements/ground liquification could be a factor in the coastal redwoods, especially those that have shown 'permanence' on the flood plains...water moving across the bottom 5 foot of a redwood will have much less leverage exerted on it than floodwaters moving across the bottom 25' of the redwood. I haven't seen any studies on the inter-relationships between adjacent redwood root systems, but there could sure be some synergy there.
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#8)  Re: Earthquakes and Redwood Forests

Postby Rand » Fri Feb 17, 2017 5:49 pm

Heres a clip of smallish open grown trees shaking in the parkfield earthquake a few years ago.


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#9)  Re: Earthquakes and Redwood Forests

Postby AndrewJoslin » Sat Feb 18, 2017 6:57 pm

Don wrote:Andrew-
Your post reminds me of an account by Richard Preston's The Wild Trees, where if memory serves me, Steve Sillett, his better half, and somebody else were up in one of the larger redwoods when one of the iterations they had decided to 'camp on' had an adjustment of significant jostle, and they decided to stay the night. The next time they returned to the area, the iteration or maybe even the whole tree had fallen.


Yes, starting pg 126, the chapter is "Detonation Zone". Sillett was with a climb team in a mainly double leader redwood that had significant lean. Sillett named it Telperion. They were in it overnight and were hit by an unexpected autumn storm. At the height of the wind they heard and felt structural roots popping, I believe they were up over 300' at the time. Much much more dramatic and life threatening than my fairly subtle experience!
-AJ
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#10)  Re: Earthquakes and Redwood Forests

Postby Don » Sat Feb 18, 2017 7:39 pm

AJ
I suspect that maximum 'glute' clenching forces were attained by those in both scenarios!
DB
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