Biomarkers as a tool to measure coseismic temperature rise

Genevieve L. Coffey, Heather M. Savage, Pratigya J. Polissar, Brett M. Carpenter, & Cristiano Collettini

Submitted September 2, 2016, SCEC Contribution #6811, 2016 SCEC Annual Meeting Poster #025 (PDF)

Poster Image: 
During earthquake slip, frictional resistance within a fault can lead to the generation of extremely high temperatures. As a consequence, investigating temperature rise within fault zones provides a promising mechanism for the detection of past large earthquakes. Evidence of frictional heating is often sparse, but a variety of techniques have been successfully applied to identify past heating events, these include vitrinite reflectance, pseudotachylytes, and fission track thermochronology.
Here we explore the use of biomarkers as an alternative approach to identification and quantification of temperature rise in faults and apply it to different faults.

Biomarkers offer significant advantages as a tool to measure temperature rise as they are abundant in the rock record, undergo systematic structural changes as they are heated, and are stable over a range of different time-temperature windows. Specifically, we are interested in methylphenanthrenes, a polycyclic aromatic hydrocarbon that is formed during the diagenesis of organic material. As temperature increases we see that the abundance of thermally stable methylphenanthrene isomers also increases, while the abundance of thermally unstable isomers decreases. Thermal maturity is quantified using the modified methylphenanthrene index (MPI-3), which increases with increasing maturity and is dependent both on the temperature and duration of heating.

We present preliminary results from the Muddy Mountain thrust in Nevada and the Spoleto thrust in the Northern Apennines of Italy, both locations which demonstrate clear fault zone architecture with well-defined principal slip zones (PSZ). High-resolution sampling of these locations was completed to construct temperature profiles across the fault zone and gain an understanding of how small-scale complexity may influence earthquake rupture.

Key Words
Biomarkers, coseismic slip, frictional heating

Citation
Coffey, G. L., Savage, H. M., Polissar, P. J., Carpenter, B. M., & Collettini, C. (2016, 09). Biomarkers as a tool to measure coseismic temperature rise. Poster Presentation at 2016 SCEC Annual Meeting.


Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)