M0.1 Quarry Blast (my Closest and Smallest)

I spotted a small local earthquake signature on the helicorder of my Shake and Boom this morning. I checked the next closest Shake (6kms away) it was there too, and then checked the next closest but the signal was not obvious at all. That’s unusual… it’s obviously small… so I ran my localstations.py code to work out where it was.

Only having a good signal at two locations wasn’t good, so I took and educated guess that the location would be Oberon Quarries - not far away. The result of the section plot:

I decided to ring the quarry to confirm they did a blast. After they put some effort into comforting me that it wasn’t an earthquake, I told them I had a seismograph and could see by the signal it wasn’t an earthquake, and explained I just wanted to confirm my observation. That relaxed them a bit ;o) and before I knew it, I’ve been invited to go up and get inducted so I can push the button on a blast! I’m happy with that! lol!

The spectrograms and FFT plots on the signals show strong spikes at about 24Hz and 48Hz which correspond to detonation intervals of 0.042s and 0.021s.



Al.

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And here’s the infrasound arrivals from the blast:


Al.

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Always a great presentation and… wow, that was a mighty small event you’ve managed to capture!

I think the smallest I was able to see on a Shake was an M0.6.

Station density matters!

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