Scaling Fossil Earthquakes from the Lab to the Field
Abstract
Recent experimental and field results described high-pressure pseudotachylytes that formed in peridotite at mantle depth in similar pressure-temperature conditions. The pseudotachylyte is the rock originating from the solidification of the rupture-induced magma, often referred to as "frictional" melt, which transiently forms on the fault plane and aids sliding.
The pseudotachylyte thickness scales with the relative displacement. The scaling law seems continuous over eight orders of magnitude from the laboratory to the field scale, for measured sliding varying from some microns to hundreds of meters. When the rupture mechanism is not affected by the size of the sample, i.e. when the fault is smaller than the sample it forms within, experimental and natural high-pressure faults show amazing similarities. A kink is observed in the scaling law and could be due to scale-depend impacts of both thermal diffusion and magma mobility. A similar kink was observed in seismological estimations of the fracture energy G as a function of slip, which has been attributed to thermal pressurization leading to lower fracture density at larger scale. Our results suggest the same evolution of G as a function of fault thickness at small and large scale, despite a steep jump (two orders of magnitude) when the thickness approaches a critical value (≈ 1 mm). In addition, experimental micro-pseudotachylytes and experimental faults due to transformational faulting follow the same scaling law, which brings into light that transformational faulting could hide a transient melting stage.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.S42A..03F
- Keywords:
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- 7209 Earthquake dynamics;
- SEISMOLOGYDE: 7215 Earthquake source observations;
- SEISMOLOGYDE: 7230 Seismicity and tectonics;
- SEISMOLOGYDE: 7260 Theory;
- SEISMOLOGY