Article,
Direct observation of rupture propagation during the 2011 off the Pacific coast of Tohoku earthquake (Mw 9.0) using a small seismic array
Earth, Planets and Space, 63 (7): 589--594 (Sep 27, 2011)
DOI: 10.5047/eps.2011.06.002
Abstract
A great earthquake of Mw 9.0 occurred on March 11, 2011 off the coast
of Tohoku region, Northeast Honshu, Japan. Strong ground motions
from the earthquake were recorded at 4 stations of a small seismic
array, with an aperture of about 500 m, located 120 km away from
the epicenter. Peak ground acceleration exceed the full scale of
2 g on the horizontal components, and was larger than 1 g even on
the vertical component. Two prominent bursts and at least two following
smaller bursts are identified on the strong-motion records which
lasted for longer than 200 s. We have performed semblance analysis
to estimate the rupture propagation during the earthquake using coherent
seismograms at frequencies of 0.5-2 Hz. The rupture seems to consist
of at least four stages. Rupture propagated in a northerly direction
in the beginning 50 s forming the first burst, then proceeded to
the southwest from the epicenter in the next 50 s during the second
burst. The rupture further extended southwests in the following 40
s, and finally migrated to the south for about 30 s. A small seismic
array makes it possible to observe rupture propagation during a large
earthquake even with a small number of stations.
