Recent studies show that fault zone weakening processes can occur/operate over a range of different timescales during fault activity.
In the long term, the influx of fluids into fault zones can enhance fluid rock interactions favouring the replacement of strong anhydrous mineral assemblages by weaker hydrated minerals. The development of continuous networks of weak mineral phases results in a strong decrease in friction coefficient and is thought to promote stable sliding and fault creep. In addition, elevated temperatures in hydrothermal systems are known to affect the permeability of fault zones with time, and the dynamic evolution of structural permeability in the seismogenic zone may induce fault zone weakening through the generation of elevated pore pressures which can act as nucleation sites which trigger earthquakes.
In the short term, during sliding at seismic slip rates (m/s), thermally activated processes (e.g. thermal pressurization, flash heating, melt lubrication) may dramatically reduce the frictional strength of the slip zone and facilitate rupture propagation. Recent advances in high-velocity friction experiments now allow such processes to be tested in the laboratory. However, the operation of short term dynamic weakening processes under natural conditions is still debated due to the paucity of field evidence.
Understanding short and long term fault zone weakening processes is of paramount importance as their interplay may result in complex slip behaviour, which ultimately controls the potential seismogenic behaviour of major shear zones.
We welcome multidisciplinary, innovative contributions addressing long and short term fault zone weakening processes through the integration of field, laboratory and seismological data. We also welcome discipline-specific studies on those topics.