Frequency-dependent energy radiation and fault coupling for the 2010 Mw8.8 Maule, Chile, and 2011 Mw9.0 Tohoku, Japan, earthquakes



[1] 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.