Raspberry shake app GMPE

General Questions
1

Hello All,

Just a quick question, for the predicted ground velocity in the raspberry shake mobile app, which GMPE equation is used? And what parameters are used for it?

I’m planning on setting up an alert for earthquakes that meet a specific threshold based on the ground motion prediction. Sadly I can’t set up an earthquake trigger as I get a lot of anthropogenic noise on my raspishake, which confuses various triggers.

Thanks in advance,
Cheers,
Alex

1 Like
2

Hello Alex, and welcome back to the community! I always follow your interesting plots on social media.

Could you expand on your GMPE query a bit more?

This is because the only model used in the ShakeNet App is the iasp91 reference model, which, as you surely already know, is

a parameterized velocity model that has been constructed to be a summary of the travel time characteristics of the main seismic phases.
(NSF SAGE: Data Services Products: EMC-iasp91 )

For all readers, this model takes into account the location of your Shake relative to the earthquake data it has and automatically computes the P and S pickers that are displayed on the screen.

As our Mobile App does not include the generation of ShakeMaps, for which the GMPE equation is used, I am not sure how I can be of help.

Thanks!

3

Hello Giuseppe,

Thanks for the welcome back and I’m glad you enjoy my posts, I enjoy yours too :smile:.

Yes, I make use of the velocity model for looking at my waveforms sometimes, it’s very useful for emphasising the peaks in the waveform as well, especially when it’s a noisy one.

For added context, on the Mobile App on the relevance sorting, it’s sorted by ground motion in m/s. For example, on 5th December when the M7.0 happened in California, it appeared as a “below 1e-5 m/s” before it had arrived.

I assumed there was a simple GMPE that calculates the PGV (for those unaware: predicted ground motion) based on distance and magnitude in the Mobile App, or am I wrong in thinking this? If so, could you give me some details on where the PGV in the app comes from?

Hope this helps,
Thanks,
Alex

1 Like
4

Hello Alex,

Your additional details un-confused me, and now I understand better what you were getting to. Thanks for that!

I have passed your query to the Mobile App developers so that I can get more details and let you know.

5

Hello again Alex,

From the Mobile App developer, I got this (they received the formula from one of their seismologists):

double distance = this->location().distanceTo(otherLocation) / 1000; // in km
double relevance= pow(10, this->magnitude() - 3.9720 - 2.1577 * log10(sqrt(pow(distance, 2) + pow(4.6403,2))));

The final calculation of the estimated ground movement is thus based on both distance and magnitude.

I hope this can be of help. If you have any more questions, just let me know.