National Aeronautics and Space Administration Jet Propulsion Laboratory

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National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Post-large earthquake

National Aeronautics and Space Administration Jet Propulsion Laboratory California Institute of Technology Post-large earthquake seismic activities mediated by aseismic deformation processes Zhen Liu, Jet Propulsion Laboratory, Caltech (a) (b) Spatio-temporal dominant independent components (IC) from vb. ICA associated with (a) viscoelastic relaxation and (b) afterslip processes. Top panel: GPS IC temporal evolution and standard deviation (black) versus model prediction (Green) and cumulative number of earthquakes non-clustered (set NC) and clustered (set C) (Magenta). Bottom panel: Map view of the corresponding spatial distributions (black) overlaid with model prediction (red). Notice the excellent correlation between the temporal evolution of the geodetically derived IC and respective set of earthquake activity. Gualandi, A. , Z. Liu, C. Rollins (2020). Post-large earthquake seismic activities mediated by aseismic deformation processes, Earth and Planet. Sci. Lett. , 530, 115870, https: //doi. org/10. 1016/j. epsl. 2019. 115870. Science Question: Post-seismic deformation processes (afterslip and viscoelastic relaxation) induce time-dependent stress variations, affecting aftershock occurrence. One outstanding question is how to separate relative contribution of each mechanism to surface deformation and seismicity in space and time? Data & Results: A novel variational Bayesian independent component analysis (vb. ICA) approach was applied to GPS data following the 2010 Mw 7. 2 El Mayor-Cucapah earthquake. The authors find afterslip likely drove clustered seismicity after the earthquake. The long-range earthquake interactions were modulated by viscoelastic relaxation at large scales in space and time (>7 yr). Significance: For the first time the study illustrates post-seismic deformation related to a single Mw 7. 2 earthquake can affect interseismic velocities and regional seismicity rates for more than a decade. This has important implications for the study of the “seismic cycle” and for seismic hazard estimation. This work was supported by NASA’s Earth Surface Interior program 1