[Crib-list] Speaker: Phoebe Robinson DeVries (Harvard) Computational Research in Boston and Beyond Seminar (CRIBB) -- TIME: 12:00 Noon in Building 34, Room 401A (Grier Room) -- Friday, Oct. 2, 2015

[Shirley Entzminger]

 		   COMPUTATIONAL RESEARCH in BOSTON and BEYOND SEMINAR



DATE:		Friday, October, 2, 2015

TIME:		12:00 Noon

NEW LOCATION:	Building 34, Room 401A  (Grier Room A)
 		(50 Vassar Street, Cambridge)
 		http://whereis.mit.edu/?mapterms=34-401A&mapsearch=go

 	[Refreshments (Pizza) will be served at 11:45 AM inside the Room 34-401A]


SPEAKER:	Phoebe Robinson DeVries  (Harvard University)


TITLE:		Geodetically constrained models of viscoelastic stress
 		transfer and earthquake triggering along the
 		North Anatolian Fault


ABSTRACT:


Over the past 75 years, $8 M_w >6.7$ strike-slip earthquakes have ruptured 
the North Anatolian fault (NAF) from east to west. The series began with 
the 1939 Erzincan earthquake in eastern Turkey, and the most recent $1999 
M_w=7.4$ Izmit earthquake extended the pattern of ruptures into the Sea of 
Marmara in western Turkey. The mean time between seismic events in this 
westward progression is 8.5 years, with a standard deviation of 11 years, 
much greater than the timescale of seismic wave propagation (seconds). The 
delayed triggering of these earthquakes may be explained by the 
propagation of earthquake-generated diffusive viscoelastic fronts within 
the upper mantle that slowly increase the Coulomb failure stress (CFS) at 
adjacent hypocenters. Here, we develop a three-dimensional viscoelastic 
block model of the greater NAF region to simultaneously explain geodetic 
observations from both before and after the Izmit earthquake. With a 
two-layer structure (crust and mantle) and a Burgers rheology (with 
Maxwell viscosity \eta _M \approx 10^18.6-10^19.0 and Kelvin viscosity 
\eta _M \approx 10^18.0 -10^19.0), a block model that incorporates 
tectonic plate motions, interseismic elastic strain accumulation, 
transient viscoelastic perturbations, and internal strain can explain 
these pre- and post- earthquake observations with a single unified model. 
We combine this geodetically constrained rheological model with the 
observed sequence of large earthquakes since 1939 to calculate the 
time-evolution of CFS changes along the North Anatolian Fault due to 
viscoelastic stress transfer. Based on the median and mean of these 
critical stress values, we infer that the NAF strand in the northern 
Marmara Sea near Istanbul, which previously ruptured in 1509, may reach a 
critical stress level between 2015 and 2032.

****************************************************************************

Massachusetts Institute of Technology
Cambridge, MA


For information about the Computational Research in Boston and Beyond 
Seminar (CRIBB), please visit...


 			http://math.mit.edu/crib/
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