Abstract
We carried out back-projections of teleseismic data filtered in different
frequency bands for the 2010 Maule, Chile and the 2011 Tohoku, Japan
earthquakes. For the Maule earthquake, there were differences along
strike of the fault, with the high-frequency energy mainly originating
from an area 200 km northeast of the epicenter, whereas low-frequency
energy came from a location closer to the epicenter. The Tohoku earthquake
shows strong frequency dependence in the dip direction. High-frequency
sources were located about 100 km west of the epicenter, while low-frequency
sources were around epicenter, near the Japan Trench. We compare
the spatial distributions of energy with estimates of seismic coupling
before the earthquakes. Areas of high-frequency radiation seem correlated
with regions that were strongly coupled before the earthquakes. Areas
of high coupling, may be associated with fault properties that are
more heterogeneous and/or have overall higher stress, producing higher
frequency seismic waves.
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