Pre-, Post-, and Independent Slow Slip
Many large earthquakes are preceded by foreshock sequences that are key to short-term forecasting. Using matched-filter detection and repeating-earthquake analysis, we study pre-seismic, post-seismic, and independent slow slip. Before the 2015 Gorkha earthquake we found a significant increase in seismicity rate a few days before the mainshock; before the 2015 Illapel earthquake, seismicity and aseismic slip progressively accelerated around the epicenter. After Illapel, we identified distinct early-aftershock expansion and afterslip consistent across methods. We also model episodic slow-slip events at the brittle–ductile transition as occurring within a viscoplastic shear zone, reproducing the observed linear-then-exponential slip evolution.
