Episodic Buckling and Collapse -- An alternative to the Slow Slip hypothesis

The Slow-Slip hypothesis is postulated on two observations – existence of tectonic tremors and their spatio-temporal correlation with anomalous ‘slow’ reversals in horizontal geodetic measurements. The above observations have led geoscientists to believe that the down-dip portion of the plate interface is slowly shearing and releases energy gradually in the form of tremor. However, numerous observations and scientific findings are poorly explained by the Slow-Slip hypothesis. Here, we show that periodic seismic activity and geodetic changes, result from the episodic buckling of the overriding continental crust and its rapid collapse on the subducting oceanic slab. According to the Episodic Buckling and Collapse hypothesis, geodetic measurements, previously inferred as slow slip, are the surficial expressions of slowly-evolving buckling and rapid collapse of the overriding plate, while tremor swarms result from the striking of the collapsing overriding plate on the subducting slab (as opposed to slipping or shearing). All existing scientific observations and findings are resonably explained by the proposed model. In addition, we provide additional evidence in the form of numerical studies of static deformation and analysis of vertical and horizontal GPS measurements in Cascadia and Alaska. We also show how subduction zones all around the world exhibit a beautiful relationship between the tremor interval and the slenderness ratio of the overriding plate – a relationship that closely resembles that between critical stress and slenderness ratio that is characteristic of Euler’s buckling.