The Magnetic Depths

The emerging sub-genre of public service announcements about geological surveys—apparently offered not just due to FAA regulations, but to quell the growth of potential conspiracy theories—continues with this heads-up about a “low-flying airplane” over parts of Virginia and North Carolina.

[Image: USGS map of eastern Virginia, altered by BLDGBLOG.]

Of course, beyond the idea of simply preempting the development of new conspiracy theories, the work being done by the project is fascinating in and of itself: “Instruments on the airplane will measure variations in the Earth’s magnetic field and natural low-level radiation created by different rock types near and up to several miles beneath the surface. This information will help researchers develop geologic maps of the area that will be used to better understand sand resources and underground faults in the region.”

While we’re on the topic of the Virginia/North Carolina border region, I’m reminded of why there’s a strange “notch” in the state line, a story “that mostly involves collecting taxes and avoiding swamps”: “The rough and rowdy inhabitants living close to the border told North Carolina tax collectors they lived in Virginia, [Gates County historian Linda Hofler] said. When the Virginia tax man came, they said North Carolina was their home.”

In any case, check out the USGS for more on the low-flying geomagnetic airplane and The Virginian-Pilot for more on VA/NC border history.

(Related: Geomedia, or What Lies Below.)

2 thoughts on “The Magnetic Depths”

  1. In 2001 the Spokane, Washington, area had a couple of swarms of very small, very shallow earthquakes, centered more or less on downtown. They sounded, and felt, like a big truck had hit the side of the building. In 2017 or so, USGS flew aeromagnetics to see if there is evidence in the magnetics of a fault. The PI is a colleague, and he would send me maps of the progress as they completed the survey. One afternoon, the day after he’d sent me a map with a big data hole over my house, I was riding my bike home from work, and low and behold, there was a small aircraft with along “stinger” out the tail, obviously the survey plane, right over my neighborhood. I sent him an email, saying, “They’re not making it up!”
    The aeromag data was inconclusive as to pinning down a fault, but another researcher was intrigued and investigated the Spokane area via InSAR, basically, satellite radar interferometry, to identify changes in the earth’s surface over time. It identified a “bulge” of about 10 mm. and a southeastward shift in the ground surface of about 15 mm (I may have transposed the values). Anyway, this data proved that the earthquakes were real tectonic responses to near surface crustal stress, and not just due to groundwater withdrawal, or construction, or some other recent causes.
    Nothing like what California experiences, but it was pretty cool.

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