Wednesday, June 23, 2010

USGS Aerial Magnetic Survey

I received what struck me as very rapid, polite and helpful responses from several people regarding my post yesterday, "News You Can't Use." The first was a comment from reader Skinny Dennis, who sent me a link to the Goldak Airborne Survey website, explaining that the aircraft that would be used were Piper Navajos. The page also indicated the nature of the project: a magnetic survey. Here's a photo of the plane:
That doodley-bob sticking off the back is called a stinger. No seriously, that what the site calls it. Now if I saw one of these guys flying low, with an apparent "stinger" (though I have to say it looks more like an ovipositor to me), I might very well do a double-take and wonder just what was going on. More so if I noticed them doing multiple, closely-spaced passes...

The second was from Marisa Lubeck, a public affairs specialist with USGS, who also sent me a link to the Goldak Page, and explained she was forwarding my question to a project scientist.

Finally, only a couple of hours after receiving Ms. Lubeck's note, I received the following from Richard Blakely:
Eric Anderson (Denver USGS) forwarded me your inquiry about our ongoing geophysical studies of eastern Washington. I am the scientist in charge of the airborne survey, and perhaps I can answer some of your questions.

We are currently flying an airborne magnetic survey of two areas: One is a swath over the Columbia River, from east of Walla Walla to Mt. Adams. The other is a smaller patch north of Hyak. Once completed, these data will be merged with similar surveys acquired in 2008 and 2009; together these data will cover all or large parts of Kittitas, Yakima, Benton, Klickitat and Grant Counties. We have contracted this year's effort to Goldak, a Canadian Company headquartered in Saskatoon.

We are flying this year's surveys along closely spaced (1/4 mile) flight lines as close to the ground as safely possible. The aircraft carries a cesium-vapor magnetometer, an instrument that measures the total magnetic field of the earth. This device is completely passive; i.e., it measures the static magnetic field without introducing any electromagnetic energy of its own. After a fair amount of data processing, we eventually obtain maps that indicate the magnetic field caused by rocks in the upper crust. Because different lithologies have differing magnetic properties, magnetic maps help us determine the near-surface geology, even though the area might be covered by young geologic deposits or vegetation. Our main motivation is to learn about the tectonic setting, geologic history, and earthquake hazards of the greater Yakima region. This year's survey is funded by the U.S. Geological Survey and the Department of Energy. It is our policy to release our data to the public within months of completion, and we intend to publish our scientific findings soon thereafter.
In the spirit of honesty, I have to say I might have been able to pick out Yakima County on an unlabeled Washington map... but I might not have. And I certainly didn't recognize the other four, so here is a quick'n'dirty graphic to show the area of concern. (original map from here)So there might be some incursion into Oregon as they turn around and line up for the next pass, but by and large, the fly-overs will be restricted to south-central Washington State. (Clarification: the flights will extend into Oregon; see the followup at the end.) So to the extent I'm likely to be startled by planes resembling parasitic wasps stalking me, this is not relevant to my interests.

In terms of geology though, different story entirely...
In the above image, from a USGS Tapestry page, the orange arrow highlights what I suspect is the structure of interest: the somewhat enigmatic Olympic-Wallowa lineament.I have mentioned this... thing... in a previous post, labeled "OWL?" in my hand-drawn schematic above. Is it a real structural feature, or is it an illusion? As far as I can tell, that question hasn't been definitively answered yet.
There are plenty of tectonic, potentially seismogenic, features in the study area, as shown in an illustration from the Wikipedia link, above. Whether the OWL is a real feature or not, it is very interesting to note how many structures either align with it, or dramatically change orientation on opposite sides of it. And if you want to at least qualify the seismic potential of an area, it would be a good thing to know what features are and aren't real.

Whether or not the OWL is a target of this study, it does look as if the survey will clarify the nature of the geologic structures in the area. Not only is Yakima an important community (metro population about 230,000- I hadn't realized it was that large), but the Hanford nuclear reservation lies within the study area.
It's in the area south of that northward hook in the Columbia River, in northern Benton County.

So this pair of posts started off as yet another episode of exasperation with the incuriosity and, frankly, laziness of journalists- "science journalists" in particular. And what do you know? There really is quite a bit of really interesting information here, and it was quite easy for me to get at. I now have a better idea of the geography of the project beyond "northern Oregon and southern Washington," I have a better idea of the purpose of the study and what USGS hopes to achieve (incidentally, more than calming any concerns I might have over my tax dollars being used for something called "earthquake monitoring"), and I'm now quite convinced that seeing 11 or 12 meter mechanical ichneumonid wasps flying closely over my head would probably be quite startling to me, possibly even traumatizing. Citizens of south-central Washington, take heed.

Followup, 3:41: I received the following feedback from Blakely:
Nice job. It all looks accurate to me except for one statement: Our swath over the Columbia River will extend well into Oregon rather than terminating at the border. That wasn't clear from my email to you, and I apologize. You correctly surmised that the OWL is a major target of our investigations.
So residents of north central Oregon, you too may have the opportunity to be startled by low-flying magnetic surveyors.


Garry Hayes said...

Boy, tell some conspiracy nuts that those planes are carrying "stingers", they'll go even more nuts, and start looking for the black helicopters...

Silver Fox said...

Nice reporting! I thought you'd get some answers.