EQHazard: max sources for ERF

[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.

[elhaddad]

This is now implemented, it is available in the latest preview release (v1.1.1) here:
https://github.com/NHERI-SimCenter/GroundMotionUtilities/releases/tag/v1.1.1

This is a direct download link to the jar file:
https://github.com/NHERI-SimCenter/GroundMotionUtilities/releases/download/v1.1.1/EQHazard.jar

To exclude background seismicity you need to specify a parameter to the ERF as follows:

   "EqRupture": {
      "Type": "ERF",
      "RuptureForecast": "...",
      "Parameters":{
         "Background Seismicity": "Exclude"
      }
   }

Other possible values for this parameter are "Include" which is the default or "Only Background".

Let me know if this does not work as expected or does not satisfy your requirements.

[Anne Hulsey]

Great, thank you! I am really looking forward to trying this out.

My first attempt gave me the following error:
Error: A JNI error has occurred, please check your installation and try again
Exception in thread "main" java.lang.UnsupportedClassVersionError: org/designsafe/ci/simcenter/EQHazardCalc has been compiled by a more recent version of the Java Runtime (class file version 56.0), this version of the Java Runtime only recognizes class file versions up to 52.0

I am currently using Java 8. Before I upgrade and risk having trouble using the older EQHazard.jar file, could you confirm whether the older EQHazard file will still work with later Java versions?

[elhaddad]

I will test it and let you know.
I think it should work fine with newer versions.
I can also try to build it with an older version.
We moved away from older Oracle jdk versions because their license changed and their long term support expired.
The current version I am using is 12.

[elhaddad]

I tested it, older EQHazard build worked well for me with OpenJDK 12.0.1

[elhaddad]

I also built a version with OpenJDK 1.8, available here:
https://github.com/NHERI-SimCenter/GroundMotionUtilities/releases/download/v1.1.1/EQHazard-v1.8.jar

[Anne Hulsey]

Thanks for recompiling in OpenJDK 1.8 - that reduced the level effort for me to get it working.

This is a huge improvement - both with respect to correctly retrieving symmetric background sources for a low max_sources value and for specifying background vs fault sources. Thank you!