Japan Geoscience Union Meeting 2019

Presentation information

[E] Oral

S (Solid Earth Sciences ) » S-IT Science of the Earth's Interior & Techtonophysics

[S-IT20] Property and role of liquids inside terrestrial planets

Sun. May 26, 2019 10:45 AM - 12:15 PM A09 (TOKYO BAY MAKUHARI HALL)

convener:Tatsuya Sakamaki(Department of Earth Science, Tohoku University), Yoichi Nakajima(Kumamoto University, Priority Organization for Innovation and Excellence), Chairperson:Tatsuya Sakamaki(Tohoku University), Yoichi Nakajima(Kumamoto University )

11:15 AM - 11:30 AM

[SIT20-02] Scaling pseudotachylytes from the lab to the field

*Thomas P. Ferrand1, Alexandre Schubnel2, Nadège Hilairet3, Loïc Labrousse4, Stefan Nielsen5 (1.Earthquake Research Institute, 2.Ecole Normale Supérieure, Paris, France, 3.Unité Matériaux et Transformations, Université de Lille, France, 4.Sorbonne Université, Institut des Sciences de la Terre Paris, France, 5.Department of Earth Sciences, Durham University, United Kingdom)

Keywords:pseudotachylytes, melt, earthquakes, scaling, lubrication, laboratory analogues

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 and aids sliding on the fault plane.
The pseudotachylyte thickness a 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 microns to meters. For magnitudes between -6 and 9, experimental and natural high-pressure faults show striking similarities.
In most lithologies, a kink is observed in the scaling law when the sliding and thickness reach 1 mm and 100 µm, respectively, i.e. Mw >1. This saturation of the pseudotachylyte thickness is due to the scale-depend efficiency of thermal diffusivity, and may also be affected by variations in magma mobility.
Previous studies show a similar kink in seismological estimations of the fracture energy G as a function of D, for D > 10cm. The saturation of both a and G for large magnitudes would mark the transition from adiabatic to diffusive rupture propagation.
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.