GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.1 GNGTS 2024 On-fault earthquake energy density parttoning from an exhumed seismic mid-crustal fault G. Tofol 1 , G. Pennacchioni 1 , L. Menegon 2 , D. Wallis 3 , M. Faccenda 1 , A. Camacho 4 , M. Bestmann 5 1 Department of Geosciences, University of Padova, Padva, Italy 2 Department of Geosciences, University of Oslo, Oslo, Norway 3 Department of Earth Sciences, University of Cambridge, Cambridge, UK 4 Department of Geological Sciences, University of Manitoba, Winnipeg, Canada 5 Department of Geology, University of Vienna, Wien, Austria The energy released during an earthquake is mostly dissipated in the fault zone and subordinately as radiated seismic waves. The on-fault energy budget is parttoned into frictonal heat, generaton of new grain surface by microfracturing, and crystal-latce distorton associated with dislocaton defects. The energy parttoning strongly infuences earthquake mechanics; however, the relatve contributon of the on-fault components is debated and difcult to assess. Exhumed fault rocks bearing pseudotachylytes (quenched coseismic frictonal melts, the geological record of earthquake failure) represent a fundamental source of informaton to understand earthquake mechanics. We used high-resoluton scanning-electron-microscopy techniques to analyse shocked garnets in a fault wall-rock, to provide the frst estmate of all three energy components for a seismic fault patch exhumed from midcrustal conditons. Fault single-jerk seismicity is recorded by the presence of pristne quenched frictonal melt. The estmated value of energy per unit fault surface is ~ 13 MJ/m2 for heat, which is predominant with respect to both surface energy (up to 0.29 MJ/m2) and energy associated with crystal latce distorton (0.02 MJ/ m2). Corresponding author: giovanni.tofol@unipd.it