Intense friction-generated heat occurs along thin, localized slip layers during an earthquake. Heat facilitates dynamic fault weakening, rupture propagation, and transformation of the mechanical and chemical rock properties that influence subsequent deformation. However, documenting temperature rise in the rock record is challenging, as many chemical reactions are dependent on the magnitude and duration of heating. We are directly comparing two different fault slip paleotemperature proxies: thermal maturation of organic material and low-temperature thermochronometry to accurately quantify earthquake temperature rise in exhumed faults. Conventional low-temperature thermochronometry systems, analogous to biomarker systems, can serve as fault slip thermometers because they are reset by transient high temperatures. We are applying this combined approach to the well-characterized Punchbowl fault (PF), CA, where recent SCEC-supported work applying biomarkers demonstrates past temperature rise along localized principal slip zones (PSZs).
This work is collaborative with Heather Savage and Pratigya Polissar (UCSC), Kelly Bradbury (USU), and Stuart Thompson (University of Arizona) and issupported by SCEC (award - 20153). Publications (denotes * graduate mentee) *Armstrong, E.M., Ault, A.K., Bradbury, K.K., Savage, H.M., Thomson, S.N., Polissar, P., 2022, A multi-proxy approach to robustly capture earthquake temperature rise on the Punchbowl fault, CA, Geochemistry, Geophysics, Geosystems, 23, e2021GC01029, doi: 10.1029/2021GC010291. |