Identifying teleseisms

I’ve had my 1-D Raspberry Shake for a few months now and since I live in a relatively active zone (Southern California) I’ve been able to identify local earthquakes (<200 km) down to about magnitude 1.8, they’re pretty easy. However I’m pretty clueless about how i would go about spotting a teleseismic event. Presumably it should be a lower frequency, less noisy signal with a big P and S separation, but over longer time intervals there are almost always spiky events that occur. I have no idea where the spiky events come from, but it would seem like they would interfere with identifying the teleseismic phases. Anyway, if someone experienced in identifying teleseisms could point me in the right direction, I’d appreciate it.

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Hello jmeans,

Yes, it easy to understand this difficulty, because the approach is, albeit quite similar, a bit different from the one used to identify local earthquakes.

The first thing I can recommend you is (if you haven’t already) to download our ShakeNet App, you can find links for both iOS and Android here: Mobile and Web Apps — Instructions on Setting Up Your Raspberry Shake

You are right that teleseismic events appear at lower frequencies, and, unless very strong, they will remain “hidden” inside the unfiltered signal that your Shake is recording. You will need to filter the out, a bit like hide and seek, and find the data inside the stream.

That’s why, with the App, you will be able to see them already filtered (since the App will do it for you) and then you can go to DataView and replicate the same filtering settings (an usual good one is the 0.7Hz to 2.0Hz) to see what you can find.

It’s a whole new dimension of earthquake data analysis, but it can be a very interesting one.

Resources can be found online, for example here: A Teleseismic Event and here: Seismogram of a Teleseismic Earthquake- Incorporated Research Institutions for Seismology