Illuminating the near-sonic rupture velocities of the intracontinental
Kokoxili Mw 7.8 and Denali fault Mw 7.9 strike-slip earthquakes with
global P wave back projection imaging
The Denali and Kokoxili strike-slip earthquakes are two of the longest
recent intracontinental ruptures. Previous studies report a range
of rupture velocities. Here we image these earthquakes by reverse
time migration of the intermediate-frequency P wave train recorded
by global broadband seismometers. This technique permits a relatively
direct measure of rupture velocity (speed and direction) as constrained
by the radiated seismic energy, free from restrictive assumptions
or rupture speed bounds placed on the solution. We compare our results
with published seismic, GPS displacement, and surface slip inversion
results. Both ruptures were initially subshear and transitioned over
a distance no longer than 40 km to supershear speeds close to the
P wave speed of \~5.6 km/s. We investigate the accuracy of our
results with synthetic data and experiment with using different imaging
parameters and seismic subnetworks. These tests allow us to rule
out the possibility of subshear speeds along the supershear segments.
Although we cannot exclude supershear speeds of 4.5-6.5 km/s, our
most reliable rupture velocities of \~5.6 km/s are close to the
local P wave speeds. We hypothesize that these intracontinental faults
have weak shear strengths or high breakdown slips or crustal rigidities
and experience at least moderate slip or slip rate weakening. Our
observations and previous published results lead us to speculate
that very long, surface-extending faults with general homogeneity
in prestress and fault strength, together with smaller adjacent fault
segments to provide triggering, may be necessary ingredients for
the sub-Rayleigh to supershear rupture speed transition in strike-slip
earthquakes.
%0 Journal Article
%1 walker_shearer:2009
%A Walker, Kristoffer T.
%A Shearer, Peter M.
%D 2009
%J Journal of Geophysical Research
%K geophysics seismology
%N B2
%P B02304+
%R 10.1029/2008JB005738
%T Illuminating the near-sonic rupture velocities of the intracontinental
Kokoxili Mw 7.8 and Denali fault Mw 7.9 strike-slip earthquakes with
global P wave back projection imaging
%U http://dx.doi.org/10.1029/2008JB005738
%V 114
%X The Denali and Kokoxili strike-slip earthquakes are two of the longest
recent intracontinental ruptures. Previous studies report a range
of rupture velocities. Here we image these earthquakes by reverse
time migration of the intermediate-frequency P wave train recorded
by global broadband seismometers. This technique permits a relatively
direct measure of rupture velocity (speed and direction) as constrained
by the radiated seismic energy, free from restrictive assumptions
or rupture speed bounds placed on the solution. We compare our results
with published seismic, GPS displacement, and surface slip inversion
results. Both ruptures were initially subshear and transitioned over
a distance no longer than 40 km to supershear speeds close to the
P wave speed of \~5.6 km/s. We investigate the accuracy of our
results with synthetic data and experiment with using different imaging
parameters and seismic subnetworks. These tests allow us to rule
out the possibility of subshear speeds along the supershear segments.
Although we cannot exclude supershear speeds of 4.5-6.5 km/s, our
most reliable rupture velocities of \~5.6 km/s are close to the
local P wave speeds. We hypothesize that these intracontinental faults
have weak shear strengths or high breakdown slips or crustal rigidities
and experience at least moderate slip or slip rate weakening. Our
observations and previous published results lead us to speculate
that very long, surface-extending faults with general homogeneity
in prestress and fault strength, together with smaller adjacent fault
segments to provide triggering, may be necessary ingredients for
the sub-Rayleigh to supershear rupture speed transition in strike-slip
earthquakes.
@article{walker_shearer:2009,
abstract = {The Denali and Kokoxili strike-slip earthquakes are two of the longest
recent intracontinental ruptures. Previous studies report a range
of rupture velocities. Here we image these earthquakes by reverse
time migration of the intermediate-frequency P wave train recorded
by global broadband seismometers. This technique permits a relatively
direct measure of rupture velocity (speed and direction) as constrained
by the radiated seismic energy, free from restrictive assumptions
or rupture speed bounds placed on the solution. We compare our results
with published seismic, GPS displacement, and surface slip inversion
results. Both ruptures were initially subshear and transitioned over
a distance no longer than 40 km to supershear speeds close to the
P wave speed of \~{}5.6 km/s. We investigate the accuracy of our
results with synthetic data and experiment with using different imaging
parameters and seismic subnetworks. These tests allow us to rule
out the possibility of subshear speeds along the supershear segments.
Although we cannot exclude supershear speeds of 4.5-6.5 km/s, our
most reliable rupture velocities of \~{}5.6 km/s are close to the
local P wave speeds. We hypothesize that these intracontinental faults
have weak shear strengths or high breakdown slips or crustal rigidities
and experience at least moderate slip or slip rate weakening. Our
observations and previous published results lead us to speculate
that very long, surface-extending faults with general homogeneity
in prestress and fault strength, together with smaller adjacent fault
segments to provide triggering, may be necessary ingredients for
the sub-Rayleigh to supershear rupture speed transition in strike-slip
earthquakes.},
added-at = {2012-09-01T13:08:21.000+0200},
author = {Walker, Kristoffer T. and Shearer, Peter M.},
biburl = {https://www.bibsonomy.org/bibtex/2d97ff7194f7c9668ebd3c721d77213d6/nilsma},
day = 13,
doi = {10.1029/2008JB005738},
interhash = {5f172045b38971aad22b33884adb0e08},
intrahash = {d97ff7194f7c9668ebd3c721d77213d6},
issn = {0148-0227},
journal = {Journal of Geophysical Research},
keywords = {geophysics seismology},
month = feb,
number = {B2},
pages = {B02304+},
timestamp = {2021-02-09T13:25:16.000+0100},
title = {Illuminating the near-sonic rupture velocities of the intracontinental
Kokoxili Mw 7.8 and Denali fault Mw 7.9 strike-slip earthquakes with
global P wave back projection imaging},
url = {http://dx.doi.org/10.1029/2008JB005738},
volume = 114,
year = 2009
}