Detecting Microseismicity in Jammu and Kashmir Himalaya Using Template Matching Technique

We study microseismicity in the Kashmir seismic gap from broadband data of the Jammu and Kashmir Seismological NETwork (JAKSNET) using the template-matching technique. Template-matching is done by the Python routine ‘PyMPA’ (Vuan et al. 2018) to detect new events. For templates, we use 189 earthquakes, taken from the ISC reviewed catalogue, which occurred between 2013 and 2018. We use 5 second long waveform templates by taking 2.5 s before and after the S-wave arrival. Normalized cross-correlations are calculated for each template earthquake, recorded at different channels, with continuous data from their respective recording channels. The individual cross-correlation traces are shifted according to the travel times of the template earthquake, calculated using a local 1D velocity model, and stacked to get a Network Stack Function (NSF). A detection is declared if the NSF crosses a threshold value eight times the Median Absolute Deviation. We assign the location of the template, corresponding to the detection, as the location of the newly detected event. If multiple templates detect one event, we consider the one with the maximum NSF value. After running the process, we obtain a catalog of 935 events, an immediate 5-fold increase in the number of events. We also observe two clear sequences of events in the middle of 2013 and in the start of 2016. We intend to perform a probabilistic and relative relocation of all the events to get a detailed seismotectonics of the region.