[SIO GP Seminars] Tomorrow: Allan Rubin, Princeton University

[Matt Wei]

Join us tomorrow for this week's Geophysics Seminar.


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Friday, Feb.9, 3:00 PM
   (refreshments served at 2:45 PM)
   Munk Conference Room

Allan Rubin

"Theoretical earthquake nucleation:  Implications for slow slip  
events, and possibly more"

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Abstract:
Recent advances in our understanding of rate- and state-dependent  
friction have proven to be quite useful in understanding
periodic slow slip events and accompanying tremor along subduction  
zones in Cascadia and Japan.  Using the most common form of the rate- 
and-state equations, three length scales arise naturally.  Periodic  
slow slip events occur when the region of fault capable of slip is  
intermediate in size between the larger two length scales - that is,  
large enough to nucleate an event, but too small to allow  
acceleration to instability.  The ratio of these two length scales  
increases as neutral stabilty (the transition from velocity-weakening  
to velocity-strengthening behavior) is approached, implying that  
"typical" subduction zones might reasonably host periodic slip  
events.  Unfortunately, the large ratio of these length scales is  
attributable to an aspect of the most common friction law that has no  
support from lab experiments.  I use what we have learned about  
nucleation to suggest plausible alternatives.  Regardless of the  
precise form of the friction law, several lines of reasoning derived  
from rate-and-state friction suggest that the pore pressure in the  
slip-slow source zone is close to lithostatic, including the  
existence of periodic slip events, their small slip, and their  
observed propagation speeds.  This adds to an accumulating body of  
geologic and seismic evidence for large pore pressures in these regions.

Have a good day.

Matt

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Meng Wei ( Matt )
Institute of Geophysics and Planetary Physics
Scripps Institution of Oceanography
University of California, San Diego
La Jolla, CA 92093-0225
mwei at ucsd.edu
(858) 822-4347
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