During the duration of the FRICTION project I carried out field geological studies, novel rock deformation experiments, and Petrographical, Mechanical, Chemical, and Microstructural Analyses.
The field geological studies included the production of high-resolution structural maps quantifying the spatial distribution of the distinct deformation stages and their characteristic hydrothermal signature. The fieldwork allowed me to describe the first pseudotachylytes recognized in the Atacama Fault System (AFS) in Northern Chile, characterized by the presence of amygdales both, spatially and temporally associated with foliated hydrothermally altered fault-core rocks in a strong fluid-rock interaction environment. Also to constrain the formation of pseudotachylytes (by long time thought to be unique to certain water-deficient seismogenic environments) to hydrothermal fluid-rich environments. The details of these findings are detailed in Gomila et al., GGG (2021).
Prior to the realization of the rock deformation experiments, I successfully installed, implemented and started-up a new hydrothermal vessel unique of its type in Europe (with only a couple more around the world), which allowed me to perform novel deformation experiments in rotary configuration (shear velocity of 10 µm/s) under hydrothermal conditions (temperature of 300°C and fluid pressure of 25 MPa). The analyses of the experimental products (both mechanical data and the “post mortem” microstructures of experimental samples) showed a change in fault healing rates from positive to negative, which was a mayor discovery of this project, with potential implications in our understanding on earthquakes nucleation and recurrency. These findings would suggest that under hydrothermal conditions, total shear displacement and duration of the fluid-rock interaction enhance mineral reactions that promote negative healing rates in faults during the seismic cycle. This would imply that during the life-span of an evolving fault, as it matures, it would be possible to (1) lower the fault yield strength due to and increasing fluid-rock interaction, henceforth (2) increase the recurrence but decrease the intensity of the seismic activity.
Part of the findings of this project have been disseminated in presentations at different conferences (as posters and as an invited speaker), in 2 open-access publications in ISI journals and publication of data in open-access repositories, in addition to several outreach activities.
