Speaker: Associate Research Professor Heather Savage (Lamont Columbia University)

Title: Fault Zone Temperature Rise During Earthquakes

Abstract: Earthquakes dissipate some amount of energy as frictional heat. Therefore at the most fundamental level, evidence of a large temperature gradient between the fault zone and the surrounding rock tells us definitively that the fault has experienced earthquake slip, as heat diffusion prevents significant temperature rise at slower slip rates.  Identifying seismic signatures in the rock record is important for several reasons. First, exhumed fault zones are rich in structural detail, and localized features within thicker gouge layers are common. In order to understand earthquake mechanics, it is vital to be able to distinguish which structures within a fault zone are due to seismic slip and which are from slower processes.  Second, quantifying earthquake temperature rise can constrain characteristics of the earthquake such as shear stress along the fault and/or frictional work.  Finally, increased temperature is required for faults to weaken during slip, and estimates of absolute temperature allow us to constrain what thermal weakening mechanisms are possible during earthquake slip. Using thermal maturity of biomarkers as a new proxy for earthquake temperature rise, we will discuss temperature rise on several faults including the Japan trench at the site of maximum slip during the 2011 Tohoku earthquake, the San Andreas fault, and several exhumed, ancient faults. [Background reading]