Still struggling to recognise a quake

There were a couple of big quakes in the Philippines on the 13th at about 21.00. From what I can workout from the great Google, it should take about 12 minutes for the p-waves to travel the 11000km from there to my Shake in Spain. I’ve looked at my traces but I can’t work it out.

If some kind soul could spoon feed me this one thing then I’m sure I would be more self sufficient. My station is:

https://dataview.raspberryshake.org/#/AM/R7B23/00/EHZ?streaming=on

Ideally, I need someone to point to the spot on the trace and say “That’s an earthquake”. I’ve read lots but at my age I don’t think I’ll live long enough to learn this stuff :slight_smile:

Thank you in advance
Andy

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Hello Andy,

Yes, the first times it can be a bit frustrating trying to score around and around to find some traces that resemble the ones from an actual earthquake.

Let’s start from a local quake first. This M4.0 near the Strait of Gibraltar on March 13th is a perfect example of a local quake: Earthquake - Magnitude 4.0 - STRAIT OF GIBRALTAR - 2022 March 13, 20:08:02 UTC

You can see how the P-wave arrives, when the vibrations immediately start from a “calm” background noise, and then the more high-amplitude S-waves arrive, just around 10 seconds later. You can use this as a reference, both the waveform and the spectrogram. If what you see resembles this, then it could likely be a quake.

Regarding the Philippines’ ones, I think that you are in, or very close by, at your distance, to the P-waves shadow-zone. This is an area where no P-waves will reach your seismometer, unless the earthquake is strong enough to allow detection of core waves from your location. The matter becomes a bit more complicated, but I’m sure these pages can get you started:

Earthquake Glossary)%20by%20the%20liquid%20core.

In any case, if a distant strong or major earthquake waves (let’s say from magnitude M6, 6.5 and above) reach your location, you will likely see high-amplitude waveform from the start of the event, like a wall rising up from the calm trace before it.

You can also use our ShakeNet App Mobile and Web Apps — Instructions on Setting Up Your Raspberry Shake to help you with arrival times and checking out the waveforms. Trust me, after a bit you will easily be able to distinguish what you are seeing.

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This is brilliant! Thank you so much! Now I’ve seen one, I will continue my reading. This is really, really helpful and very much appreciated.

Best regards
Andy

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Hello Andy, no problem, you’re absolutely welcome!

Remember, if you have any other questions, just write here, and we will do our best to answer them!

Enjoy your Shake!

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A bit more info for you, which may or may not be helpful.

This morning (my time - West Coast USA) I saw this:

It looks pretty much like an earthquake … Checked surrounding RS devices, and most showed something but really not as big or clearly defined as I was seeing on mine. I almost wrote it off as something purely local. Then saw that there was a 7.3 earthquake just off the coast of Japan.

Checked the timing, and this is roughly in the right area. Not a nice clean P-S trace, but 7,500Km away, it is pretty likely that.

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Yes, I got the Japan one too. The app is the game changer for me as you click on a quake and it takes you straight to the right point on your station. Then you can cross reference that with the browser version.

Loving this!

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Yes, the app is good for that. I am hoping that some of that makes its way into the website version (DataView) one day – easier to read my Mac screen than my cellphone :slight_smile:

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