Research in Natural Hazards Engineering > Regional Hazard Simulation (R2D, rWhale)

EQHazard: max sources for ERF

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Anne Hulsey:
The MaxSources limit in the UCERF2 ERF causes odd behavior in the background seismicity. I believe that it searches the sources by index until it reaches the maximum number. However, the index seems to be order South to North, such that the background seismicity is not centered around the site.

I have handled this by increasing the number of sources to a value that does not control the selection. However, it would be preferable to have the background seismicity radiate out from the site, no matter what the distance is.

elhaddad:
Thanks for posting your question!
You are correct, the current version of EQHazard scans the sources in the ERF using the source index as defined in OpenSHA.
The resulting ruptures won't be ordered based on closest distance to the site.
To be able to implement that, it will require calculating distances for all the ruptures, which may hinder performance as the distance calculation is more time consuming.
If a combination of increasing the number of sources to a higher value and reducing the distance achieves the purpose then we may leave the current implementation as it is.

Anne Hulsey:
Sounds good, thanks. It might be good to mention this issue and the solution in the documentation. I never would have realized it if I hadn't mapped the sources.

Speaking of which, when mapping the sources, I differentiate between ruptures vs background seismicity based on the index. The background sources start somewhere around 500. I often only need the ruptures so, it would be nice to have a flag that indicates whether the catalog should include background sources or not.

elhaddad:
We started implementing this feature, it will be available in the next preview version in the next few days.
Just to confirm we satisfy your requirements, we will change the ERF export code to sort the sources based on proximity to the provided site and export the sources in that order.
We will also provide a way to control background seismicity, either by including it, excluding it or only process background sources.

Anne Hulsey:
This is excellent. Thank you for addressing both features.

If, in addition to sorting the sources by proximity to site, you could further sort each rupture index by the rupture proximity to site, that would be a great bonus.

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