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Subseismic to Seismic Slip in Smectite Clay Nanofoliation
Author(s) -
Aretusini S.,
Plümper O.,
Spagnuolo E.,
Di Toro G.
Publication year - 2019
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1029/2019jb017364
Subject(s) - slip (aerodynamics) , geology , clay minerals , slipping , geotechnical engineering , landslide , seismology , mineralogy , geometry , physics , mathematics , thermodynamics
Smectite clays are the main constituent of slipping zones found in subduction zone faults at shallow depth (e.g., <1‐km depth in the Japan Trench) and in the decollements of large landslides (e.g., 1963 landslide, Vajont, Italy). Therefore, deformation processes in smectite clays may control the mechanical behavior from slow creep to fast accelerations and slip during earthquakes and landslides. Here, we use (1) laboratory experiments to investigate the mechanical behavior of partly water‐saturated smectite‐rich gouges sheared from subseismic to seismic slip rates V and (2) nanoscale microscopy to study the gouge fabric. At all slip rates, deformation localizes in volumes of the gouge layer that contain a “nanofoliation” consisting of anastomosing smectite crystals. “Seismic” nanofoliations produced at V = 0.01, 0.1, and 1.3 m/s are similar to “subseismic” nanofoliations obtained at V = 10 −5 m/s. This similarity suggests that frictional slip along water‐lubricated smectite grain boundaries and basal planes may occur from subseismic to seismic slip rates in natural smectite‐rich faults. Thus, if water is available along smectite grain boundaries and basal planes, nanofoliations can develop from slow to fast slip rates. Still, when nanofoliations are found highly localized in a volume, they can be diagnostic of slip that occurred at rates equal or larger than 0.01 m/s. In such a case, they could be markers of past seismic events when found in natural fault rocks.