Scattering‐to‐Intrinsic Transition Governing Coda Attenuation in the US Continental Crust

Abstract

Seismic attenuation is a key indicator of crustal heterogeneity and energy dissipation, yet the physical mechanism of coda‐wave attenuation remains unclear due to the combined influence of scattering and intrinsic absorption. In this study, we analyze multi‐frequency S‐wave coda attenuation using the seismic recordings from USArray. Our results reveal that S‐wave coda attenuation exhibits pronounced frequency dependence, with distinct dominant mechanisms across different frequency bands. At lower frequencies (1.5 and 3 Hz), attenuation is primarily controlled by scattering associated with crustal heterogeneities and velocity contrasts, whereas at higher frequencies (6 and 12 Hz), intrinsic absorption becomes the dominant mechanism and exhibits a strong correlation with surface heat flow, consistent with temperature‐dependent viscoelastic dissipation. Comparisons with attenuation models derived from other seismic phases highlight their different sensitivities to depth and frequency, indicating that no single approach can fully capture the complexity of attenuation. These findings underscore the diagnostic value of multi‐frequency coda‐wave attenuation and highlight the importance of integrating various attenuation measurement methods to better constrain crustal heterogeneity and thermal state, with implications for improved crustal imaging and geodynamic interpretation.