[NOTE: Waiting to hear from speaker before publishing online.]Taking the temperature of earthquakes
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Heather Savage
UC Santa Cruz
- Date & Time
- Location
- Online via Microsoft Teams and Moffett Field Yosemite Room
- Host
- Nick Beeler
- Summary
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. However, we have had little information on whether faults produce some amount of heat (enough for faults to weaken during earthquakes but not enough to melt) from the rock record. 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 occur in a fault zone? Can creeping faults host earthquakes? Does lithology control rupture propagation? and How is energy partitioned during earthquakes? Finally, we have paired these biomarker measurements with K-Ar dating techniques to establish the age of earthquakes on the San Andreas fault at the San Andreas Fault Observatory at Depth (SAFOD).