Creating a trigger to detect low amplitude earthquakes using cross correlation

Question

Hello I am new to python and obspy community. I have been using obspy and have managed to cross correlate to known earthquake signals to find a suitable correlation coefficient to then use on unknown seismic signals to detect earthquakes. I have used the obspy function correlate(a,b,shift_len) to correlate these two signals. But I am having trouble implementing this to correlate an entire trace of seismic data against a single known earthquake signal to detect similar earthquakes (by cross correlating) and finding at what times in the seismic trace these similar signals are found.

Answer 1

We actually already have some cross correlation detection functionality on ObsPy. Take a look at the "event_templates" option in function "obspy.signal.trigger.coincidence_trigger", see ObsPy documentation and tutorial:

• http://docs.obspy.org/packages/autogen/obspy.signal.trigger.coincidence_trigger.html?highlight=event_templates
• http://docs.obspy.org/tutorial/code_snippets/trigger_tutorial.html?highlight=trigger#advanced-network-coincidence-trigger-example-with-similarity-detection

Furthermore there is currently a Pull Request for new functionality of this kind and it will likely be in the upcoming release version 1.2.0, see https://github.com/obspy/obspy/pull/2315.