Hydrothermal Effects on calcite in faults

Earthquakes result from the repeated buildup and release of stress along faults in the Earth’s crust. These processes are controlled by friction between rocks. The way rocks change between earthquakes governs when and how slip initiates and propagates. Water’s effect is widely recognized in fault processes. The complexity of natural fault systems makes it difficult to isolate individual factors. This project will address a central gap in earthquake science by examining how temperature, fluid chemistry, and surface roughness influences frictional strength along a common material in faults. By conducting laboratory experiments, the research will isolate the processes that govern how contacts between mineral surfaces evolve over time. These experiments will clarify how fault surfaces strengthen or weaken under conditions that are difficult to observe in natural settings. The gained knowledge will thus contribute to developing more reliable prediction of seismic processes to support national welfare, security, and resilience. The project will strengthen the STEM workforce by training a graduate student and several undergraduate students. This project will determine how interfacial properties, pressure solution, and plastic creep influence friction, adhesion, and wear in nanoscale contacts as a function of temperature and fluid chemistry. The project hypothesis is that elevated temperature and specific fluid chemistries promote contact aging and velocity-weakening friction. To bridge the gap between nano- and macroscale frictional behavior, this project determines the contribution of roughness to the frictional characteristics of single calcite crystals under selected hydrothermal conditions. The project will develop a model for kinetic friction, informed by experimental results and existing microphysical theory to capture both contact quality and quantity. Experimental studies of the interfacial properties and measurements of friction, adhesion, deformation, and wear will be carried out using Atomic Force Microscopy and a Surface Forces Apparatus in a temperature-controlled fluid cell. A modeling framework will also be also developed to describe friction in single- and multi-asperity contacts using microphysics-based parameters. By linking these insights to rate and state friction equations, the work will bridge microscale mechanisms and macroscale fault behavior. Collectively, the project will generate new knowledge on hydrothermal effects in calcite friction with broad implications for earthquake physics and geomechanics. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria. NSF Award ID: 2539930 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Rosa Espinosa-Marzal | Institution: University of Illinois at Urbana-Champaign, URBANA, IL | Award Amount: $425,179 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2539930 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2539930.html