[Crib-list] TODAY: 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

[daisymae]

T O D A Y . . .


      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.

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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/