3:00 PM - 3:15 PM
[SIT28-06] Determination of Intrinsic Attenuation in the Oceanic Lithosphere-Asthenosphere System
Keywords:seismology, lithosphere, asthenosphere, attenuation
For this end, we simulated energy transportation of higher frequency seismic waves (~3 Hz) in scattering media and compared the simulated and observed envelopes. The envelopes observed in the NW Pacific are characterized by larger amplitudes especially in S and quasi-exponential amplitude decay with distance. We showed that such features can be explained if and only if we have high intrinsic Q in the lithosphere and low intrinsic Q in the asthenosphere.
The strong intrinsic attenuation in the asthenosphere obtained in this study (~3 Hz) is comparable to that constrained at lower frequency (~100 s) by surface waves and suggests frequency-independent anelasticity, while that in the lithosphere is frequency dependent. This difference in frequency dependence indicates that the strong and broad peak dissipation recently observed in the laboratory exists only in the asthenosphere and sheds new light on what distinguishes the asthenosphere from the lithosphere.