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  1. Abstract

    The evolution of fault friction during the interseismic period affects the mechanics of a future earthquake on the same fault patch. Frictional aging has been previously tied to time‐dependent contact area growth through observations made on rock analogs. However, our understanding of the processes that control frictional aging is limited and is dependent on experiments that explore only numerous mechanisms. We conduct slide‐hold‐slide experiments with a dual‐axis nanoindenter on single‐crystal surfaces of quartz and calcite. Our results show that frictional aging in diamond‐quartz contacts is independent of time and contact area, in stark contradiction to past experiments done on quartz‐quartz contacts in rocks. Diamond‐calcite contacts show modest frictional aging, but still well below previous reported values from calcite‐calcite contacts. These results suggest that frictional aging of like‐on‐like minerals may be of chemical origin, as suggested in recent studies with atomic force microscopy and molecular dynamics simulations.

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