3. EQcorrscan FAQs¶
This is a developing list of frequently asked questions. If you find yourself experiencing a problem similar to one of these, then try the solution here first!
If your problem/question isn’t answered here then check the issues on the github page and, if there isn’t an issue related to your problem/question then open a new one and we will try to help.
3.1. Usage Questions¶
3.1.1. No output to terminal¶
EQcorrscan uses Logging to handle output. If you are seeing no output to screen you probably haven’t set up your logging settings. A simple way to do this is to run code like:
You can set different levels to get more or less output (DEBUG is the most output, then INFO, then WARNNG, then ERROR, then CRITICAL). You will need to run this before any calls to EQcorrscan’s functions to get logging output.
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3.1.2. No correlations computed¶
Frequently the cause of no correlations being computed is that the SEED ID (network.station.location.channel) for your template do not match your continuous data. Check that they match, and try increasing the logging output (above) to help you find the issue.
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3.1.3. Everything is done multiple times!¶
EQcorrscan uses multiprocessing under the hood, which will spawn multiple processes when called. To ensure that programs do not run multiple times you should always write your scripts with a form:
def main():
# Do the mahi
if __name__ == "__main__":
main()
See the multiprocessing note on “Safe importing of main module” for more info.
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3.1.4. Making templates from SAC files¶
While there is support for making templates from SAC, it generally isn’t a good idea, unless you have SAC waveforms of the length that you want to correlate with. This is for two reasons: 1. Because templates and continuous data must be processed the same, including using the same length FFT, for correlations to be accurate. If you make your template from short data you will be forced to correlate with short chunks of data, which is not very efficient 2. The programming team are not SAC users, and do not understand the nuances of where picks can be saved in SAC headers.
Instead: you might find it better to convert your SAC picks into another obspy readable pick/event format. You can try EQcorrscan’s basic sac_utils to do this, but not everything will be retained.
3.2. Design Questions¶
3.2.1. Can I use different lengths for different channels in a template?¶
Not yet in EQcorrscan - we want this as well, but haven’t had time to implement it. If you want this then we would really appreciate the contribution! There are two main issues with this that require some thought: 1) How correlations are computed, and 2) how correlations are weighted in the correlation sum.
3.2.2. Why doesn’t EQcorrscan have a GUI?¶
This would be cool, and it would be great if someone wants to contribute this, however, the developers thus far have been focused on other things and don’t have unlimited time.
If you want this, and know how to program GUIs then please do contribute, it would open EQcorrscan up to more users, which would be great!
3.2.3. Why do you have a functional and object-oriented API?¶
Simply legacy, when Calum started writing EQcorrscan he didn’t know anything about classes. The functional API is retained so that old codes can still be run, but if you are starting from scratch please use the OO API where possible.