Earthquake Tiltmeter (Telemetry) Frequencies

[madscanner]

A decade ago, when scanning the 160-174 MHz and 400-420 MHz bands in the greater Los Angeles area, one would often encounter numerous USGS "tiltmeter" telemetry signals. They were easily identifiable as they each consisted of a continuous steady tone. That tone would warble (flutter in pitch) with the slightest hint of ground motion, and during actual quakes, they went positively nuts. (You could often also hear them continuing to warble for minutes after an earthquake stopped, as they continued sensing microscopic amounts of ground motion undiscernable to human senses.)

Years back, the ones I could receive in my area disappeared, and after inquiring about them, I was told that all the analog tiltmeters had been decomissioned in favor of digital units not receivable by scanners.

Well, while recently scanning the aforementioned bands, I found two that weren't receivable in my area in the old days. Checking my old list of tiltmeter frequencies (below), the frequencies of the two I found just happened to match two of the frequencies on that list. (163.6062 MHz and 164.8437 MHz -- I'm receiving them in the eastern San Gabriel valley.) So apparently, some analog tiltmeters have been "brought back." Now I'm curious if there might be others, receivable in other areas of L.A. Anyone interested in scanning 160-174 and 400-420 for these things, and reporting on where they're audible (and on what frequencies)?

162.5943
162.8062
162.8093
163.3500
163.3937
163.3968
163.6031
163.6062
163.6093
163.7937
163.7968
164.0062
164.0093
164.8406
164.8437
164.8468
165.5375
165.8062
165.8093
166.4052
166.4187
166.4203
166.4218
166.6562
166.6593
167.1937
167.1968
167.8031
167.8062
167.8093
167.9900
168.0000
168.4690
171.2156
171.2187
171.2218
171.3947
171.4062
171.4203
171.4297
173.1906
173.1937
173.1968
408.5062
408.9837
409.8762
419.9931

 

[Teotwaki]

necromancing an old topic.

I hear tones on

162.8093
163.7968
171.4062

Jim
Orange County, CA

 

[Alain]

Earthquake Tiltmeter

I still continue to monitor the San Sevaine Seismometer on 163.795 MHz [FM]. Yes, I do, on occasion, hear the "warble"! This info comes from the Orange County A.R.C. Newsletter of 5/3/17 OCARC: http://www.w6ze.org/IXN-NET-NEWS/NETNEWS-2017-05.html

Specifically, note the "2 m Phone Net" paragraph, as well as from the RR link below, from 2009, sorta on topic.

https://forums.radioreference.com/california-radio-discussion-forum/159058-earthquake-freqs.html

 

[madscanner]

Thanks for the replies. Better late than never, I guess! I'll check those frequencies out when I get home next week.

 

[zz0468]

Is anyone aware of any software that will process the telemetry and provide a form of seismograph?

 

[madscanner]

Software that plots the varying pitch of an audio frequency sinewave as a visual graph trace is probably going to be hard to find. It's a fairly specialized task.

The closest substitute I can suggest would be using the spectral graphing feature in software like CoolEdit or Audition, or even in free software like SoX (SoX - Sound eXchange | HomePage). However, software like this, when used for such an application, would only produce visually low resolution plots, useful only for curiosity-satiating eye candy purposes and not for anything scientific. But it can still produce interesting results. For example, when run against http://www.musicradio77.com/images/ing11-9-65blackout.mp3 -- a recording of WABC 770 AM during the great 1965 power blackout, SoX generates https://i.imgur.com/j1ZKVqJ.png, which reveals the 60 Hz power grid waveform that was going into WABC's downtown New York City studio building as the power grid slowly collapsed (WABC probably had a mixing console without perfect AC hum induction shielding). The recording was made in a portion of the northeast whose power grid was unaffected, so you'll also see a locally-inducted (and much stronger) 60 Hz waveform that is perfectly stable in pitch over time (as well as some other weird but also stable harmonics and subharmonics). The warbling, faint trace which starts at about 58 Hz at the recording's onset, and ends by crashing beneath 50 Hz at its end, is the one you want to look at, as it is a bona fide, amazingly accurate visual record of precisely how the northeastern power grid's power plant generators all simultaneously destabilized and sagged in their rotational speeds before everything tripped off. (FYI, https://en.wikipedia.org/wiki/File:Northeast_Blackout_of_1965.svg shows the areas affected by the blackout. Judging by the strength of the recordist's AM reception versus the fact his recorder wasn't affected by the blackout, I'd guess he was probably in a state like Pennsylvania.)

 

[zz0468]

The closest substitute I can suggest would be using the spectral graphing feature in software like CoolEdit or Audition, or even in free software like SoX (SoX - Sound eXchange | HomePage). However, software like this, when used for such an application, would only produce visually low resolution plots, useful only for curiosity-satiating eye candy purposes and not for anything scientific.

That's really the idea, something that can produce visible activity on a 1.5 Richter scale event would be kind of neat. I suppose any audio spectrum analyzer software with a waterfall display would suffice.

Thanks for the ideas.

Are these tiltmeter transmitters on continuously, or only when they've detected something? Time to dig in the garage for a few dedicated receivers, I guess.

 

[pinballwiz86]

Thank you for giving me something else to search for on the scanner bands!

 

[RichardKramer]

Here in Berks County, PA on 409.825 there is a continuous tone on; started after we had a 4.4 quake here back in '94.

 

[ecps92]

409.8250 is/was generally assigned for the FAA - drive-by your local Airport see if it gets stronger

Here in Berks County, PA on 409.825 there is a continuous tone on; started after we had a 4.4 quake here back in '94.

 

[KB7MIB]

Many years ago in Pop' Comm' or MT magazine, there was a review of a speaker that had an audio frequency notch feature.
The author, (Gordon West?), suggested using it to monitor a tiltmeter frequency.
You could notch out the steady tone, but if the ground started moving, the tone would warble above and below the notch, and you'd know if something was happening, perhaps giving you several seconds heads up before you started feeling anything.

Obviously, you'd need a dedicated receiver sitting on a tiltmeter frequency to do that.

John
Peoria, AZ

 

[xilix]

I remember the VHF freqs from more than a decade ago. I don't know if this still holds true, but back then the transmitter antennas were horizontally polarized.

- KG6DOQ

 

[madscanner]

Many years ago in Pop' Comm' or MT magazine, there was a review of a speaker that had an audio frequency notch feature.
The author, (Gordon West?), suggested using it to monitor a tiltmeter frequency.
You could notch out the steady tone, but if the ground started moving, the tone would warble above and below the notch, and you'd know if something was happening, perhaps giving you several seconds heads up before you started feeling anything.

Obviously, you'd need a dedicated receiver sitting on a tiltmeter frequency to do that.

Neat. I too had that idea once. Only in my version, I foresaw the receiver's reception not being 100% full quieting and the notch's output audio amounting to an unintentional white noise generator during periods of no shaking. So I envisioned following the notch with an old noise gate whose threshold was set a few dB above the background noise to guarantee dead silence between earthquakes. Also, imagine modifying the gate, retrofitting it with a contact closure connector of some kind that makes it possible for external stuff to tell when the processor's gate is open/closed. With that, and some additional circuitry, you could do neat things like wiring battery backed-up emergency lights to turn themselves on upon ground motion. Would be very handy when it's 3 AM and you need to see where you're going the instant the loud warbling tone jolts you out of bed!

Are these tiltmeter transmitters on continuously, or only when they've detected something? Time to dig in the garage for a few dedicated receivers, I guess.

They transmit continuously. When there's no ground shaking, they sound like a stuck morse code key: a steady tone at a perfectly fixed pitch. And the pitch can be anything, so don't necessarily only listen for something around 1 kHz or whatever. I've heard tiltmeters that sounded like they were idling as low as 300 Hz.

 

[bryan_herbert]

Back in the day I dedicated a scanner to my local tiltmeter. I ran the audio to my oscilloscope which would show a sine wave until an earthquake occurred, depending on the magnitude the sine wave would go from fuzzy to jiggly. When I needed my oscilloscope I would use oscilloscope software, it works just as good, I recommend Winscope.

https://windowsreport.com/oscilloscope-software-pc-laptop/

 

[Alain]

Off the telemetry topic...sorta

My wife and I teach the "disaster preparedness" module for our local C.E.R.T. team. Earthquake "prediction" has been going on a lot longer than most folks would think.

Consider Zhang Heng's invention, the seismoscope:

Zhang Heng Seismograph Could Record Earth's Dangerous Movements | Ancient Pages

Without going into too much detail, his "seismoscope" was about 6 foot in diameter. As soon as an earthquake struck, his "machine" could accurately indicate in which direction the "P" & "S" waves originated.

Although the instrument was unable to show hypocenter/epicenter or magnitude, it did show direction...not bad for 1,900 years ago!

Fast-forward 1,900 years to a "sand pendulum" tracing the waves of a 6.8 earthquake, in Washington State, in 2001:

https://inhabitat.com/a-beautiful-and-mysterious-rose-created-by-an-earthquake-and-a-pendulum/