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Pompano
Elite Nomad
Posts: 8194
Registered: 11-14-2004
Location: Bay of Conception and Up North
Member Is Offline
Mood: Optimistic
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I believe this diagram describes the wave caused by water displacement?
Tsunamis were historically referred to as tidal waves because as they approach land they take on the characteristics of a violent onrushing tide,
rather than the sort of cresting waves that are formed by wind action upon the ocean (with which people are more familiar). However, as they are not
actually related to tides, the term is considered misleading, and its use is deprecated by oceanographers.
I do what the voices in my tackle box tell me.
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Taco de Baja
Super Nomad
Posts: 1913
Registered: 4-14-2004
Location: Behind the Orange Curtain, CA
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Mood: Dreamin' of Baja
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| Quote: | Originally posted by OCEANUS
"Thanks for your report... So, no concern of an under-sea landslide or fault upthrust creating a tsunami?"
You need to have water displacement in order to generate a tsunami. Underwater landslides will not, because they are already underwater. Thrust
faulting is not common along this region of the plate boundary, as lateral or transform faulting is the norm, thus considerably reducing any potential
tsunami threat. |
I beg to differ. Underwater slides can cause Tsunamis. Even slides a long way from the actual epicenter, and possibly slides not even associated
with an earthquake event.
Here's a paper from my Alma mater:
| Quote: |
Landslide Tsunami
Steven N. Ward
Institute of Geophysics and Planetary Physics
University of California at Santa Cruz
Santa Cruz, CA 95064 USA
Abstract
In the creation of “surprise tsunami”, submarine landslides head the suspect list. Moreover, improving technologies for seafloor mapping continue to
sway perceptions on the number and size of surprises that may lay in wait offshore. At best, an entirely new distribution and magnitude of tsunami
hazards has yet to be fully appreciated. At worst, landslides may pose serious tsunami hazard to coastlines worldwide, including those regarded as
immune.
To raise the proper degree of awareness, without needless alarm, the potential and frequency of landslide tsunami have to be assessed quantitatively.
This assessment requires gaining a solid understanding of tsunami generation by landslides, and undertaking a census of the locations and extent of
historical and potential submarine slides. This paper begins the process by offering models of landslide tsunami production, propagation and shoaling;
and by exercising the theory on several real and hypothetical landslides offshore Hawaii, Norway and the United States eastern seaboard.
Introduction
Earthquakes generate most tsunami. Rightly so, tsunami research has concentrated on the hazards posed by seismic sources. The past decade however, has
witnessed mounting evidence of tsunami parented by submarine landslides. In fact, submarine landslides have become prime suspects in the creation of
“surprise tsunami” from small or distant earthquakes. As exemplified by the wave that devastated New Guinea's north
coast in 1998......
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http://es.ucsc.edu/~ward/papers/single.pdf
Edit: Here's a visual of what happens to generate the wave.
[Edited on 4-17-2012 by Taco de Baja]
Truth generally lies in the coordination of antagonistic opinions
-Herbert Spencer
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Barry A.
Select Nomad
Posts: 10007
Registered: 11-30-2003
Location: Redding, Northern CA
Member Is Offline
Mood: optimistic
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Every time we think we know something, we find out we don't.
Thanks, Taco.
Barry
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Bugman
Nomad
Posts: 143
Registered: 9-20-2006
Location: Escondido
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I was with my wife and 3 kids at Raquel and Larry's when that thing hit. I went through the big quake in San Francisco back in 89 and this one felt
nearly as strong. That hotel was really shaking and the bed one of my kids was sleeping in had a leg collapse so he freaked out and jumped in bed
with me. 2 seconds later his little brother was in bed with me two. We considered running outside but I was more worried about the deck collapsing
so made the call to hold up inside. It took awhile for everyone to settle down to go back to sleep and all the aftershocks did not make it any
easier. As scary as it was there really did not seem to be any major damage at the hotel or around town. One of the chairs on the deck moved several
feet (glad I was not up there when it hit!). We just got back Sunday night and not sure which was worse, the quake or the 3 hour wait at the border.
By the way, fishing does not seem to improve right after a major quake 
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OCEANUS
Nomad
Posts: 139
Registered: 10-11-2008
Location: Dana Point; L.A. Bay
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Taco:
That is an interesting paper. It would be nice to know how much of it actually applies to the geology/faulting of the sea floor in the Sea Cortez.
Barry:
There are many examples of faults throughout the BOLA and Animas region. I've read that much of it is very old, and occurred before the land was moved
to its current position via tectonics. Many of the rocks too, are igneous in origin (basalts, granites, pumice, tufts, etc.) which suggest a very rich
history of formation. I've been out with geologists before who have a difficult time piecing together a story that explains the region - they just
summarize the area as being very "complex" geologically.
David K: Ever since I read your lost mission post focusing on the Animas region, I've been meaning to get over there to check it out. I've been able
to see the walls for years from a boat, but this year we ventured out to walk the site. We had an archaeologist with us who, aside from the man made
walls, was very interested in checking out the two mesas that stretched south from the peak containing the circular "rock rooms." He seemed to think
that it would be the most likely place to find more evidence of human activity because of the relatively flat and hospitable terrain. We surveyed the
location extensively for artifacts (pottery, etc.) and could not come up with any good explanations for the apprent human activity. The dead palm tree
was significant because it definitely appeared to be an introduced variety (possibly a date palm?) that had no business being in that part of the
gulf. In any case, it was a fun activity that gave us an excuse to go out and play. Thank you for the adventure.
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DavidE
Ultra Nomad
Posts: 3814
Registered: 12-1-2003
Location: Baja California México
Member Is Offline
Mood: 'At home we demand facts and get them. In Mexico one subsists on rumor and never demands anything.' Charles Flandrau,
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I took three semesters of geology, and when I expressed an interest in both seismology and vulcanology the professor took me under her wing. My father
later convinced me that geologists earn about as much as a car wash employee...
Anyway, it is helpful to understand (simplified) that subduction events close to a shoreline that are of significant magnitude coupled with shallow
depth of event center can generate substantial tsunami as well. A significant magnitude event seems to be in the Richter 7.0 and higher range.
Most of the current fracturing events seem to indicate slip-strike fault activity. But one has to wonder about the obvious upthrust seen along this
coastline. It is certainly the product of subduction events.
A Lot To See And A Lot To Do
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David K
Honored Nomad
Posts: 65278
Registered: 8-30-2002
Location: San Diego County
Member Is Offline
Mood: Have Baja Fever
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| Quote: | Originally posted by OCEANUS
Taco:
That is an interesting paper. It would be nice to know how much of it actually applies to the geology/faulting of the sea floor in the Sea Cortez.
Barry:
There are many examples of faults throughout the BOLA and Animas region. I've read that much of it is very old, and occurred before the land was moved
to its current position via tectonics. Many of the rocks too, are igneous in origin (basalts, granites, pumice, tufts, etc.) which suggest a very rich
history of formation. I've been out with geologists before who have a difficult time piecing together a story that explains the region - they just
summarize the area as being very "complex" geologically.
David K: Ever since I read your lost mission post focusing on the Animas region, I've been meaning to get over there to check it out. I've been able
to see the walls for years from a boat, but this year we ventured out to walk the site. We had an archaeologist with us who, aside from the man made
walls, was very interested in checking out the two mesas that stretched south from the peak containing the circular "rock rooms." He seemed to think
that it would be the most likely place to find more evidence of human activity because of the relatively flat and hospitable terrain. We surveyed the
location extensively for artifacts (pottery, etc.) and could not come up with any good explanations for the apprent human activity. The dead palm tree
was significant because it definitely appeared to be an introduced variety (possibly a date palm?) that had no business being in that part of the
gulf. In any case, it was a fun activity that gave us an excuse to go out and play. Thank you for the adventure. |
Glad you liked it...
Finding that site has been a goal of mine for many years (first read about it in 1973). I got to meet Choral Pepper before she died (10 years ago) and
she wished me well to find it, as she couldn't remember the location. I also talked with Bruce Barron, J.W. Black and Ricardo Castillo by phone... no
luck. I made a few searches for it with other Nomads... and it was a Nomad at home on Google Earth that saw the wall... I went south to confirm, and
yes, it was the same!
As a follow up to my Magdalena Mystery article in BajaBound.com's Baja Travel Adventures page last month, I have the story on the 'other' Magdalena
mystery submitted for this month...
Anyone interested in the lost mission discovery by Choral Pepper and the Gardner expedition of 1966, and how it looked over 40 years later: http://vivabaja.com/109/
[Edited on 4-17-2012 by David K]
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Pompano
Elite Nomad
Posts: 8194
Registered: 11-14-2004
Location: Bay of Conception and Up North
Member Is Offline
Mood: Optimistic
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Tuesday night, April 17. Mulege.
Another shaker late last night felt in Mulege area? Anybody else notice this?
I do what the voices in my tackle box tell me.
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