An automated method for TT detection

Abstract:

A TT (Tectonic Tremor) catalog spanning 2009-2012 has been created using data from the GGAP network located in the central part of Guerrero state in southwest Mexico. Using a method that compares 54 second window spectrums in the 2-8 Hz bandwidth range against a predetermined TT pattern selected from the best bare-eyed noticeable TTs, we were able to detect them in time. It is possible to lower the time window for TT to only 54 seconds which is much smaller than previous TT detection in Guerrero which used a 20 minute window. This allowed for many more detections. Moreover, it is possible to do single station detections with this method, as shown in the figure attached (Light blue above is a single station detection from the permanent SSN network. Dark blue below is the detection from a temporary “GGAP” array). The error in the detection was lowered by means of setting the high and low spectral amplitudes in which TTs could be seen, allowing a more robust detection. No increase of the TT activity was seen at the beginning of the long term 2009-2010 SSE, but tremor bursts were recorded with each short term SSEs. An energy based inversion was applied to get TT epicenters. Low error inversions (horizontal error less than 20 km) could only be obtained for about 20% of the total of the catalog. The large majority of TT's were found in the Sweet Spot, with fewer in the Transient Zone as had been seen in previous studies.