11:45 〜 12:00
[SSS04-11] Spectral analysis for precise estimation of seismic attenuation
Spectral analyses of seismic waveforms have been used to estimate source parameters of earthquakes (corner frequency and stress drop) and medium heterogeneity (direct and coda attenuation). However, we often have a strong tradeoff, for example, between corner frequency and attenuation because both parameters control the high-frequency fall-off of each spectrum. We developed a new method to avoid the trade-off using two-step approaches and was able to estimate seismic attenuation with high resolution in space and time (Nakajima et al., JGR, 2013; Nakajima and Uchida, Nature Geoscience, 2018). In this talk, we will present two spectral analysis methods and show that they were able to reveal high-resolution 3D seismic attenuation model and temporal variation in attenuation. The former method will improve our understanding sub-surface attenuation structures associated with magmatism and fault heterogeneity, while the latter one will highlight the migration of fluids along the megathrust boundary and immediately below active volcanoes.