Spatiotemporal variations of characteristic repeating earthquake sequences along the Middle America Trench in Mexico

Searching for repeating earthquakes allows the examination of spatiotemporal variation of slip budget in the subduction of the Cocos plate in the Guerrero‐Oaxaca region of Mexico. As different transient phenomena continuously load and unload stresses around asperities in an area where megathrust earthquakes nucleate, repeating earthquakes act as track markers for slip on the plate interface. We systematically examined 14 years of waveform records from 2001 through 2014 to identify repeating earthquakes along the subducting segment of the Cocos plate. An analysis of waveform similarity resulted in a significant number (224) of earthquake sequences with highly correlated waveforms (correlation coefficient cc ≥ 0.95 and spectral coherency coh ≥ 0.95). The reported set of correlated waveforms shows a well‐defined clustering in space and substantial temporal variability. We find a significant increase of repeating earthquake activity after the 20 March 2012 Ometepec (Mw 7.4) and 18 April 2014 Tecpan (Mw 7.2) earthquakes as a result of the postseismic relaxation. In contrast, the rupture zone of the 1985 (Mw 8.1) Michoacán earthquake is completely devoid of repeating sequences, suggesting a strongly coupled segment. Examining the temporal behavior of repeating earthquake activity provides a new tool to better understand how creeping of the subduction thrust controls stress release and postseismic relaxation. Key Points We identified 224 characteristic repeating earthquake sequences occurring between 2001 and 2014 Estimates of Coulomb stress changes suggest that characteristic repeating earthquakes cluster preferably near the edges of large ruptures The lack of characteristic repeating sequences along the 1985 M8.1 earthquake rupture area suggests that this segment is fully locked