The 1st day of spring started with a bang here on the Big Island of Hawaii. We had a cute little 4.6 magnitude earthquake just after dawn. Rattled the windows and made a nice Bang!
What really intrigues me is that so many earthquakes like this start with a low rumble, a rumble that makes me think "Big Truck", then the shaking starts. What is that rumble? I mean what frequency? It's low, but not super low.
I've obtained some seismographic data from the nearest monitoring station on Mauna Kea. It' in 2 column ASCII format, with date and time in the left column, magnitude in the right column. I want to work on the data a little to see if I can convert it to audio, or other data for spectrum analysis. Anyone done this before? How did you do it? I'm thinking that some of my wave editors could import it, if it's in the right format.
What really intrigues me is that so many earthquakes like this start with a low rumble, a rumble that makes me think "Big Truck", then the shaking starts. What is that rumble? I mean what frequency? It's low, but not super low.
I've obtained some seismographic data from the nearest monitoring station on Mauna Kea. It' in 2 column ASCII format, with date and time in the left column, magnitude in the right column. I want to work on the data a little to see if I can convert it to audio, or other data for spectrum analysis. Anyone done this before? How did you do it? I'm thinking that some of my wave editors could import it, if it's in the right format.
There are professionals monitoring all those, why not contact them and ask these things? They I am sure know the frequencies of the tremors and such. There may be some resources that already have the data in a more convenient format for your needs.
I was thinking of you this morning. I keep an eye on the USGS site and saw the 4.6 and wondered if you fell out of bed. Maybe contact them?
I got data form the USGS. It's sampled at 30Hz, which is really too low for my needs, but I'm giving it a try anyway.
No falling out of bed, Cal. Just a mild one, nice shake. You must get those too.
Yep, I'll try to contact some local seismologists to find out if they already have what I need. They probably do. But I did kinda want to Do It Yourself 🙂
No falling out of bed, Cal. Just a mild one, nice shake. You must get those too.
Yep, I'll try to contact some local seismologists to find out if they already have what I need. They probably do. But I did kinda want to Do It Yourself 🙂
Twice in my lifetime. Last one was 2001. It was fun to watch the water in the fishpond splash over the sides.
https://en.wikipedia.org/wiki/2001_Nisqually_earthquake
I am interested in what others might have to offer.
My problem seem to be importing the data. I can actually export audio files as text with Audacity, but it has no function to import them. Importing as RAW does not work, as that expects a binary file.
Might need a MATLAB script to convert from the text to RAW.
Might need a MATLAB script to convert from the text to RAW.
You can probably walk to the local USGS office, I mean how big is that little island you live on anyway? Just take them a slice of pineapple coconut pie and maybe they can help you.
Bigger than you think. The main office is 100 miles from here (160km). But pie is always welcome.
I did find some earthquake sound files on the USGS site. Not Hawaii, but it's something.
Seems most of the rumble is around 40-50Hz. Or like an open E or open A string on a bass.
Of course there is plenty of infrasonic energy, but the main audible parts of the files I got was in the bass E,F,G,A range. Rumble, without many audible harmonics.
I did find some earthquake sound files on the USGS site. Not Hawaii, but it's something.
Seems most of the rumble is around 40-50Hz. Or like an open E or open A string on a bass.
Of course there is plenty of infrasonic energy, but the main audible parts of the files I got was in the bass E,F,G,A range. Rumble, without many audible harmonics.
Yes Michael, I was having a spot of fun with you.
Show me a man who doesn't like pie and I'll show you a hairdresser.
Now you're just confusing me, stop it.
We posted at the same time. Them's some pretty interesting graphs. The 2001 quake here was like a every subwoofer on the block turned up to clipping, and around 40 hz, like your graphs show. Pretty impressive and no other noises like falling buildings to interfere. Is that what you got?
@ Pano
I've only experienced 1 earthquake here in the UK about 5 years ago. It woke me up & felt Very wierd. Not a 4.6 though !
I didn't know you could export an audio file to .txt with Audacity ? I just tried it and saw no option to do that ?
Anyway i experimented on my desktop by changing the extension of a .WAV file to .txt I was able to drag/drop that into Audacity perfectly. I know there's a difference in what you want to convert, but thought you might like a heads up to experiment in various ways to try & get it to work.
I've only experienced 1 earthquake here in the UK about 5 years ago. It woke me up & felt Very wierd. Not a 4.6 though !
I didn't know you could export an audio file to .txt with Audacity ? I just tried it and saw no option to do that ?
Anyway i experimented on my desktop by changing the extension of a .WAV file to .txt I was able to drag/drop that into Audacity perfectly. I know there's a difference in what you want to convert, but thought you might like a heads up to experiment in various ways to try & get it to work.
Thanks Zero. 
The export to text is in an odd place, it's under the Analyze menu.
So far no luck with the spreadsheet style text file. The sample rate is too low for me anyway.
The export to text is in an odd place, it's under the Analyze menu.So far no luck with the spreadsheet style text file. The sample rate is too low for me anyway.
I did some work on very cheap industrial monitors. While testing I had to look at the British monitoring stations.
These have real time graphs that update each time you hit the refresh button.
These have real time graphs that update each time you hit the refresh button.
"one of these things is not like the other..."
How does one represent 40 to 50 hz signals using a 30 hz sampling rate?
John
Completely different data and file formats. I should have explained it better, sorry. The files I analyzed are in .wav format with a 8k sample rate. They are from some quakes on the mainland. The files I got from the local monitoring station are in a text table form, time and amplitude, 30 times per second. Good to see the shakes, not good to analyze sound.
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