Energy dissipation in a simulated fault system

Abstract

Abstract: The energy dissipation in an earthquake can be partitioned into three components Wtot = Wradiated +Wexpansion +Wfriction, where Wradiated is the seismic radiated energy, Wexpansion is the energy consumed propogating the fault and producing new surfaces, and Wfriction is the energy used to resist the frictional strength of the fault. Characterizing each of these components in order to estimate this total energy budget and the energy dissipated during fault dynamics is essential for getting a better understanding of earthquake physics. Even though there have been great advancements in the physics of earthquakes in the recent decades there is still not complete agreement on the role of the different energy components. In this thesis we simulate a fault system by sliding an indenter (glass bead) across the surface of a halite crystal. Since halite is transparent in the mid infrared range (3-5 micro meters) we can monitor the radiation emission at the sliding surface (coated with black anti-reflective paint) through the crystal with an infrared camera and quantify the temperature increase caused by the frictional sliding at the surface. Using an analytical model describing the thermal di usion of a 2D point heat source inside the crystal we estimate the thermal energy generated in the frictional sliding experiment from the temperature data acquired with the infrared camera. From this analysis we get that the energy dissipated in heat is 26% of the total work applied in the experiment. Analysing the sur face of the crystal after a frictional sliding experiment we observe a breakage pattern inside the groove, and from this pattern we estimate an upper limit of the energy spent creating new surfaces in the plastically deformed region of the crystal. The upper estimation we get for the energy spent creating new surfaces in an experiment is 12% of the total work applied during sliding. The contribution from the friction of the rig and the acoustic emission could not yet be estimated.