I recently discovered that one of our residents has unknowingly helped debunk a UFO conspiracy theory.
Someone noticed an underwater structure off the Malibu coast using Google Earth, and decided it was an underwater UFO base because it couldn't possibly be a natural formation. It's too perfectly oval and flat topped, and has supporting columns on one side, and it's too close to a military naval base.
Fact is, the columns are an artifact of the low resolution bathymetry data being interpolated by the software. I recognized it immediately from my own experience playing with GIS software and digital elevation models.
But what does Chris have to do with all of this? I was listening to the Coast to Coast AM show the other night and one of the guests is a newspaper journalist who wrote about the theory. He pointed out a paper published by GSA that shows the area was studied and already known. And named... Sycamore Knoll.
A link to the paper was provided and it turned out to be,
Potential earthquake faults offshore Southern California,
from the eastern Santa Barbara Channel south to Dana Point
- Fisher, Sorlien, Sliter, 2009.
In the article is a link to the paper. In the paper, the authors conducted seismic reflection surveys, and one survey line runs right across the knoll. Clearly, it's a natural structure.
So is Chris going add "UFO Theory Debunker" to his CV?
I had nothing to do with the debunking except having worked on this structure much earlier (so others used this work to debunk). The reference to my earlier paper is below, and JGR is an AGU publication so should be Open Access now.
Yes, I get similar artifacts gridding sparse data, depending on how I grid it. Some of the Google Earth sea floor is based on dense sampling by multibeam bathymetry and does not have these artifacts: you can see a lot of detail on these data, including Dume (?) Canyon. Where there is no multibeam, the sea floor is based on point data including 100 year old data. This can be dense in shallow water, but surprisingly sparse in the deep offshore bathymetric basins, with as much as 1 km between points (enough to hide a 1 km-wide spaceship!). I have a figure of faults between San Diego and about San Clemente where I gridded faults differently; some are very smooth with few artifacts but not much precision, with others are completely bumpy etc.
OK: Sycamore Knoll, the giant UFO base in question, is an anticline above the Santa Monica-Dume fault, which dips about 45 deg north. Santa Monica Basin to its south is subsiding because of post-rift thermal contraction and the weight of sediment loading. Relative to the basin, Sycamore knoll is uplifting relative to the basin because of a reverse component of slip on this left-lateral fault. There is a reverse component because of bends in the fault strike there. The rock uplift at Sycamore knoll is just enough to make a little island during glacial times of low sea level, so it is eroded by waves and makes a relatively smooth sea floor, same as the rest of the continental shelf. Not so mysterious!
Reference below,
Chris
Sorlien, C. C., M. J. Kamerling, L. Seeber, and K. G. Broderick (2006), Restraining segments and reactivation of the Santa Monica–Dume–Malibu Coast fault system, offshore Los Angeles, California, J. Geophys. Res., 111, B11402, doi:10.1029/2005JB003632.
Thanks for the additional info, Chris. I haven't looked yet, but am hoping the 2006 paper is online somewhere NOT behind a pay wall.
I have a question about the seismic reflection maps. The vertical axis is labeled as round trip time, which makes sense. Is there any way to correlate that to a depth? Or is it not possible due to too many unknowns in the rock?
OK, to answer your question, yes, I/we convert our two-way time work to depth. The stills from the supplemental animation below are in depth, 5 km scale, no vertical exaggeration. These days, I/we have been making 3D velocity models so that we can convert everything to depth, including the seismic reflection data. For Santa Barbara Channel and offshore south-central California, there are a lot of petroleum test wells with velocity surveys. For offshore Istanbul, there was dense seismic refraction. For offshore San Diego, we used the Community velocity model, Harvard U., which there must be based on processing of multichannel seismic reflection data. I will use the last for Ross Sea.
P.S, forgot to joke that there are a couple of 1 1/2 km-deep petroleum test wells into Sycamore Knoll from the 1960s. Must have been the CIA checking for aliens or Soviets.
Again, the wells exist but am joking about the rest.
(01-01-2015, 02:11 PM)Island Chris Wrote: P.S, forgot to joke that there are a couple of 1 1/2 km-deep petroleum test wells into Sycamore Knoll from the 1960s. Must have been the CIA checking for aliens or Soviets.
Again, the wells exist but am joking about the rest.
Chris
Thanks, Chris. Got the paper. I also found a few others online. One I like in particular because it has a detailed cross-section of the knoll itself:
Recent Deformation Along the Offshore Malibu Coast, Dume, and Related Faults West of Point Dume ,Southern California - Fisher, Langenheim, Sorlien, et al
Unfortunately the copy I found is a scan of a paper document so the diagrams don't come across that well.
A question for you Chris, the "MCS section WG85-394", when was that taken? I'd almost guess 1985 due to the number. I wonder because it helps to push back the chronology of when the knoll was studied, and can show how long the knoll was understood before the recent... ahem... "theory".
I appreciate your help in this. It'll come in handy if I ever decide to weigh in on the subject myself.
Hi Brian, is probably "WC85", and yes, was acquired in 1985. This is Western Geophysical Company data. Western Geco and the USGS more or less saved my career by making all or most their 2D seismic reflection data available for the west coast, Alaska, and other places including the east coast USA, Haiti, etc. Google USGS NAMSS and you will find the site where these data are available.
The knoll probably has been known for 100 years or more because depth sounding have been done for a long time. I'm not sure when it was first understood that the knoll was an anticline associated with the Dume fault. I'm guessing 1960s because the petroleum test wells are, I think, from the 1960s.
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