The geophysics, geology and mechanics of slow fault slip

Abstract

Modern geodetic and seismologic observations describe the behavior of fault slip over a vast range of spatial and temporal scales. Slip at sub-seismogenic speeds is evident from top to bottom of lithospheric faults and plays an important role throughout the earthquake cycle. Where earthquakes and tremor accompany slow slip, they help illuminate the spatiotemporal evolution of fault slip. Geophysical subsurface imaging and geologic field studies provide information about suitable environments of slow slip. In particular, exhumed fault and shear zones from various depths reveal the importance of multiple deformation processes and fault-zone structures. Most geologic examples feature frictionally weak and velocity-strengthening materials, well-developed mineral fabrics, and abundant veining indicative of near-lithostatic fluid pressure. To produce transient slow slip events and tremor, in addition to the presence of high-pressure fluids a heterogeneous fault-zone structure, composition, and/or metamorphic assemblage may be needed. Laboratory and computational models suggest that velocityweakening slip patches smaller than a critical dimension needed for earthquake nucleation will also fail in slow slip events. Changes in fluid pressure or slip ratecan cause a fault to transition between stable and unstable fault slip behavior. Future interdisciplinary investigations of slow fault slip, directly integrating geophysical, geological and modeling investigations, will further improve our understanding of the dynamics of slow slip and aid in providing more accurate earthquake hazard characterizations.

The Transient and Intermittent Nature of Slow Slip

“…We now know that some faults are locked up to the surface while others slip aseismically down to seismogenic depth (e.g., Cetin et al, ; Jolivet et al, ). Finally, growing evidence suggests the nucleation, propagation, and arrest of seismic rupture are mediated by slow slip, which in turn directly affects the seismic hazard in tectonically active regions (e.g., Avouac, ; Bürgmann, ; Obara & Kato, ).…”

Shallow Creep Along the 1999 Izmit Earthquake Rupture (Turkey) From GPS and High Temporal Resolution Interferometric Synthetic Aperture Radar Data (2011–2017)

“…Aseismic slip can occur with various temporal behaviors: it can be steady (e.g., Fialko, 2006;Motagh et al, 2007), as observed during the interseismic period, or transient (e.g., Hayes et al, 2014), either triggered by a major earthquake and decaying with time (postseismic relaxation known as afterslip, e.g., Lienkaemper et al, 2001) or spontaneously generated by processes still poorly understood. Frictional properties, fault geometry and lithology, as well as pore fluid pressure variations were proposed to explain creep behavior (Avouac, 2015;Bürgmann, 2018). For example, the presence of clay-rich gouges and high fluid pressure appear as key factors for the presence of creep (Carpenter et al, 2011, Kaduri et al, 2017, 2018.…”

“…Frictional properties, fault geometry and lithology, as well as pore fluid pressure variations were proposed to explain creep behavior (Avouac, 2015;Bürgmann, 2018). For example, the presence of clay-rich gouges and high fluid pressure appear as key factors for the presence of creep (Carpenter et al, 2011, Kaduri et al, 2017, 2018. Recent development and widespread use of advanced space-based techniques, particularly interferometric synthetic aperture radar (InSAR), has revealed that steady or transient surface creep behavior along major continental faults is more common than previously thought.…”

Testing the Influence of Static and Dynamic Stress Perturbations On the Occurrence of a Shallow, Slow Slip Event in Eastern Taiwan

“…Stress perturbations from a mainshock rupture can trigger spontaneous or delayed SSEs (over hours to months; e.g., Hayes et al, 2014;Hirose et al, 2012;Rolandone et al, 2018), which release stress that had built up during the previous inter-SSE interval (Bürgmann, 2018), and can also trigger transient creep (Lienkaemper et al, 1997;Wei et al, 2015) or modulate surface creep rate (Xu et al, 2018). In general, dynamic triggering of SSEs remains a rare phenomenon, and only a few cases are documented (Araki et al, 2017;Itaba & Ando, 2011;Wallace et al, 2017;Zigone et al, 2012).…”