Geophysicists are ramping up their efforts to monitor major undersea faults | Hacker News Reader

Geophysicists are ramping up their efforts to monitor major undersea faults

nature.com

65 pointssohkamyung14 comments

I found this really interesting. I was curious about the Japanese realtime sea-floor sensors they mentioned so I went hunting.

The data appears to be available here:

http://www.jamstec.go.jp/scdc/top_e.html

After registration [1] you can download data in some funky binary format. Looks like there's a 10min delay on data. It looks like an interesting dataset, and I hope to play with it a bit.

[1] includes such joys as password being set to username, and the seeming inability to change your password citing "invalid chars: 1" error.

Did you find any documentation about the data format?

Yes, it's documented. Doesn't look to bad. They appear to do some custom delta compression but nothing too bad.

I used to work at an exploration geophysics firm, these data formats less scary than you'd often encounter in that world. There are a number of interchange formats in geophysics, notably SEG-Y, which date back a long way – most vendors then have their custom formats that they ingest that interchange format into:

https://en.wikipedia.org/wiki/SEG_Y

Fundamentally you've usually got one to three dimensional data, metadata for the entire file, and then metadata for (potentially) each column along some axis of the file. It's interesting that CDF, etc have had zero traction: I guess it's just that each field has its little data format subculture and there's not much incentive for collaboration?

I currently work at an exploration geophysics firm and was just talking to my boss about this yesterday. His comment was that data acquisition had an arms race to the bottom in the late 80s and has become complete commodity object. This has results in data from the 80s through today being no different as they're still using the (mostly) same tools and techniques.

There is no incentive to better your seismic surveying since stuff from the 80s is "good enough" for all the processing shops.

Yep, that sounds about right, at least on the data formats. A survey now is gathering orders of magnitude more data than it would have in the 80s (especially 3d/4d surveys), but I guess the formats didn't really need to change.

I don't miss writing code to guess whether a file has traces encoded in IBM floating point or IEEE; or handling SEG-Y headers which ought to be EBCDIC but are sometimes ASCII :-)

A sci-fi apocalyptic story starting with the underwater monitoring of the Juan De Fuca fault: Peter Watt's Starfish.

http://www.goodreads.com/book/show/66479.Starfish

Free in various formats on the author's web site

http://www.rifters.com/real/STARFISH.htm

Really dense hard sci-fi. Peter Watts' book come with massive appendixes detailing the scientific motivation and references for his work.

Great stuff!

I highly recommend his Blindsight & Echopraxia duo, too. Also with dense appendixes at the end.

I wonder if US military takes part in the project: ultra-precise pressure gauges may be exactly what's needed to detect subs

Somewhat related to this, the US Navy did operate the SOSUS[1] network at one point.

[1]https://en.wikipedia.org/wiki/SOSUS

Actually, you wouldn't get a signal from a sub going overhead with these.

They're focused on recording relatively low-frequency response, so they don't pick up sound (hydrophones do a great job of that, and they're dirt cheap). Subs are neutrally buoyant, so there's no pressure anomaly. There will be a tiny one from the bow wake, but that's the sort of thing you're trying not to detect.

Part of the entire point of these is to sum out things like waves (and possible minor blips like the bow wake from a nearby sub). You're summing over time to get a very precise average height of the water above the sensor. You're deliberately designing the sampling system to not be sensitive to small temporal blips and filtering the data to remove any that show up.

Basically, if you want to detect subs, there are far cheaper and easier ways to do it. These tools are designed to do something very different.

Yeah, I was thinking about bow wake as it's probably very hard to hide that (as opposed to silencing the sound).

Thanks for your explanation, it makes ton of sense!

you may not need to hide it so much as disguise it. There are lots of things swimming in the oceans, some of them big. None as big as a sub, but a well designed sub can potentially present that wake signature. (maybe not all the time, but a sub can choose to go at a slow hiding pace or a fast but visible pace)

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