SCEC Award Number 14112 View PDF
Proposal Category Collaborative Proposal (Data Gathering and Products)
Proposal Title Organic Thermal Maturity of SAFOD Fault Rocks
Investigator(s)
Name Organization
Pratigya Polissar Columbia University Heather Savage Columbia University
Other Participants one undergraduate research assistant (TBD)
SCEC Priorities 3a, 3b, 3e SCEC Groups FARM, Seismology, Geology
Report Due Date 03/15/2015 Date Report Submitted 11/18/2015
Project Abstract
 An important question for understanding seismic potential along faults is whether creeping sections can rupture in large earthquakes. The creeping section of the San Andreas Fault appears to be moving at tectonic plate rate,
and therefore may not be accumulating elastic strain. Such a region of low strain may prohibit rupture through this region, disconnecting the seismogenic northern and southern ends of the fault. Understanding the earthquake
history of the creeping section would allow for a clearer picture of the seismic hazard for California.

One way to determine whether a paleoearthquake has occurred on the creeping section is the presence of a thermal anomaly from frictional resistance during earthquakes, which could be significantly hotter than background temperatures. The aim of this proposal was to make organic thermal maturity measurements on samples from the SAFOD core. The SCEC portion of our SAFOD work covered funds to analyze the non-extractable organic compounds using hydropyrolysis. One major question that we are addressing with this project is the role of migrated fluids overprinting the in situ extractable molecular signature. To date, we see strong lithological differences in the concentration of extractable compounds (high concentrations in mudstones, low in sandstones) that suggest there has not been strong overprinting of the SAFOD rocks from migrating fluids. We are continuing with extraction of organics and will be conducting hydropyrolysis analyses at the University of Nottingham in the next few months. Results will provide a clearer estimate of seismic activity in the creeping section of the
fault.
Intellectual Merit The intellectual merit and broad impact of this analysis is to help determine whether the creeping section of the San Andreas Fault ever hosted large earthquakes. If the creeping section has been shown to rupture, the implication is that the San Andreas can potentially host an earthquake along its entire length, rather than the rupture being halted by an area with lower stress accumulation. A further significance is the development of a new method for studying frictional heating on faults that could be used where migrated petroleum has contaminated the extractable organic molecules. This is a common occurrence on sediment-hosted faults in southern California, therefore this new technique could allow analysis on faults hosted within petroleum source rocks such as the Monterey Formation (e.g. Borderland Faults) or contaminated by petroleum migration
Broader Impacts The societal impact of this analysis is to help determine whether the creeping section of the San Andreas Fault ever hosted large earthquakes. If the creeping section has been shown to rupture, the implication is that the San
Andreas can potentially host an earthquake along its entire length, rather than the rupture being halted by an area with lower stress accumulation. This has important societal implications for seismic hazards along the San Andreas
Fault.
Exemplary Figure Not yet available.
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