The Transient and Intermittent Nature of Slow Slip

• Published in: AGU advances 2020-03, Vol.1 (1), p.n/a
• Main Authors: Jolivet, R., Frank, W. B.
• Format: Article
• Language: English
• Subjects: Earth Sciences; geodesy; Geophysics; Sciences of the Universe; seismology; slow slip
• ISSN: 2576-604X; 2576-604X
• DOI: 10.1029/2019AV000126

To first order, faults are locked while stress builds up to a devastating earthquake. However, we know that faults also slip slowly. After decades of geophysical observation, slow slip is now recognized as part of a continuum of transient deformation ranging from the dynamic propagation of seismic rupture to aseismic events over a wide range of durations and sizes. A growing body of evidence suggests that large‐scale slow slip events can be decomposed into a multitude of smaller, temporally clustered events. Slow slip is more frequent and more dynamic than is suggested by conceptual models of rate‐strengthening, stable slip. The relative motion of tectonic plates on Earth leads to the accumulation of elastic energy at plate boundaries. Tectonic faults can release this energy, either suddenly by rapid (m/s) slip that generates seismic shaking (i.e., during earthquakes) or gently by slow (mm/year to m/year) slip. Subseismic slip can release just as much energy as fast slip, implying slow slip plays an important role in the earthquake cycle. Following decades of discoveries fueled by technological improvements in geophysical observation methods, we argue that the main difference between various slow slip phenomena is, for now, semantics. Diving into the details of time series of geodetic and seismological observations suggests slow slip is made up of many subevents that interact with each other, just like the aftershocks that always follow the triggering earthquake mainshock. We thus conclude that slow slip is simply the release of elastic energy by slip along faults, just at much slower rates than regular earthquakes. Slow slip happens at all spatial and temporal scales Slow slip is an intrinsically intermittent and clustered process There is no observational evidence for different physical mechanisms for slow slip in different tectonic contexts