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Absorption of P- and S-waves Above Subduction Zones

Y. F. Temme, M. Weber and C. Wicks

Paper reference: Y. F. Temme, M. Weber and C. Wicks, 2000, Absorption of P- and S-waves Above Subduction Zones, Geophys. Res. Let., 27, 1327-1330

We investigate local variations of absorption above the subduction zones of the northwest Pacific. Teleseismic broad-band (BB) recordings at German arrays from 59 earthquakes in this area allow the determination of the quality factor QP and QS. The method to determine Q is the phase pair method. Here, for the first time, P-wave BB-recordings at dense arrays are used, extending the frequency range studied and increasing the reliability of the QP determination for the northwest Pacific. 1-D Earth models have typical QP values of 200 to 800 (QS: 100 to 400) in the upper 200 km. QP under the Kuriles, the Kurile Basin and Japan is about 100, i.e. significantly lower than average. QS under Japan is also only about 1/3 of the value of 1-D models. No frequency dependence of QP and QS could be detected for the broad frequency range studied [0.05 to 1 Hz].