2:30 PM - 2:45 PM
[SSS10-04] Similarity of the regional PL waves in the crustal waveguide and the teleseismic W-phase in the upper-mantle waveguide
Keywords:PL-wave, W-phase, wave propagation
Similar PL-type waves propagation processes can occur in the waveguide formed by the entire upper-mantle in a much longer period band (100-1,000s period). This signal observed at teleseismic distances (1,000 – 10,000 km) is well recognized as the “W-phase” (Kanamori, 1983). We demonstrated by observations and numerical simulations of the wave propagation for the 2011 Off Tohoku earthquake, Japan (Mw=9.0; h=20 km) that the W-phase is produced by multiple PP-type reflections from the upper-mantle, reinforced by the Earth’s sphericity. Thus, the propagation of the PL wave and the much longer-period W-phase have common features at different space and time scales; The PL wave travels in the crustal waveguide and the W-phase travels in the waveguide formed by the lower wavespeeds in the upper-mantle. The W-phase has been used extensively for the CMT source inversion for large (Mw>7.5) earthquakes, and recently, it is extended to apply for much smaller events. The continuity of behavior between PL and W indicates the possibility of further extension of W-phase style source inversion to much smaller events (i.e., to Mw < 5-6) exploiting dense observation networks at regional distances, with the use of regional structural models.