Bulletin of the Seismological Society of America; December 2004; v. 94; no. 6B;
p. S202-S213; DOI: 10.1785/0120040601
© 2004 Seismological Society of America
Dynamic Slip Transfer from the Denali to Totschunda Faults, Alaska: Testing Theory for Fault Branching
Harsha S. Bhat1,
Renata Dmowska2,
James R. Rice3 and
Nobuki Kame4
1 Harvard University
Division of
Engineering and Applied Sciences
29 Oxford Street
Cambridge, Massachusetts
02138
bhat{at}esag.harvard.edu
(H.S.B.)
2 Harvard University
Division of
Engineering and Applied Sciences and
Department of Earth and Planetary
Sciences
29 Oxford Street
Cambridge, Massachusetts
02138
(R.D.)
3 Harvard University
Division of
Engineering and Applied Sciences and
Department of Earth and Planetary
Sciences
29 Oxford Street
Cambridge, Massachusetts
02138
(J.R.R.)
4 Kyushu University
Department of
Earth and Planetary Sciences
Faculty of Sciences
6-10-1
Hakozaki
Higashi-ku
Fukuoka 812-8581
Japan
(N.K.)
We analyze the observed dynamic slip transfer from the Denali to Totschunda
faults during the Mw 7.9 3 November 2002 Denali fault
earthquake, Alaska. This study adopts the theory and methodology of
Poliakov et al.
(2002) and
Kame et al.
(2003), in which it was shown that the propensity of the rupture
path to follow a fault branch is determined by the preexisting stress state,
branch angle, and incoming rupture velocity at the branch location. Here we
check that theory on the Denali-Totschunda rupture process using 2D numerical
simulations of processes in the vicinity of the branch junction. The maximum
compression direction with respect to the strike of the Denali fault near the
junction has been estimated to range from approximately 73° to 80°. We
use the values of 70° and 80° in our numerical simulations. The rupture
velocity at branching is not well constrained but has been estimated to average
about 0.8 cs throughout the event. We use 0.6
cs , 0.8
cs , 0.9
cs , and even 1.4
cs as parameters in our simulations. We simulate
slip transfer by a 2D elastodynamic boundary integral equation model of mode II
slip-weakening rupture with self-chosen path along the branched fault system.
All our simulations except for 70° and 0.9 cs
predict that the rupture path branches off along the Totschunda fault without
continuation along the Denali fault. In that exceptional case there is also
continuation of rupture along the Denali fault at a speed slower than that along
the Totschunda fault and with smaller slip.
Copyright © 2004 by the Seismological Society of America.