EPS Colloquium: Heather Savage

How Hot Do Faults Get During Earthquakes?

During earthquakes, faults heat up due to their frictional resistance. Sometimes, the temperature rise during earthquakes makes the rocks hot enough to melt. However, solidified frictional melt (pseudotachylyte) is not very common in the rock record, and other paleoseismic temperature proxies have only recently been established. The dearth of pseudotachylyte led researchers to hypothesize that faults get very weak during earthquakes, and hence do not produce much heat. If faults dramatically weaken during slip, there are important implications for how earthquakes propagate, and hence why some earthquakes grow to be very large. Here, we use a new sub-solidus temperature proxy, biomarker thermal maturity, to identify temperature rise on faults in a variety of tectonic settings. With this new temperature proxy we revisit some outstanding questions in fault mechanics such as: Where does earthquake slip occurs in a fault zone? Can creeping faults host earthquakes? Does lithology control rupture propagation? and How is energy partitioned during earthquakes? How strong are faults during earthquakes?