Journal Article

Seismological Observations on Amplitude‐Dependent Energy Dissipation in the Crust and Uppermost Mantle

Nakajima, Junichi, Tero, Hayato

2025

Overview

The amplitude‐dependent seismic attenuation in the crust and uppermost mantle was investigated using spectral analysis of crustal and intraslab earthquakes that occurred in two areas in northeastern Japan. P‐wave attenuation (Q−1${Q}^{-1}$ ) was found to be weakly proportional to amplitude (A$A$ ) in both areas, following the relationship, Q−1∝An${Q}^{-1}\\mathit{\\propto }{A}^{n}$ . Quantitative analysis reveals that amplitude‐dependent attenuation is more pronounced in the uppermost mantle (n ∼ 0.16) than in the crust (n ∼ 0.05). This depth‐dependent behavior of attenuation may be attributed to increasing temperature and pressure, which enhance dislocation density and mobility. Our findings challenge the common assumption of amplitude‐independent attenuation. Although we infer dislocation mechanisms as the primary cause of the amplitude‐dependent energy dissipation, further experimental studies under high temperature and pressure conditions are necessary for better understanding of the complex nature of seismic attenuation and the underlying processes. Plain Language Summary Seismic attenuation, the energy loss per one cycle as seismic waves propagate through the Earth, has traditionally been considered amplitude independent. Our research challenges this assumption, revealing a weak amplitude dependence of attenuation. We found this effect is more pronounced in the uppermost mantle than in the crust. This depth‐dependent behavior likely results from increasing temperature and pressure affecting the microstructure of rocks. These findings will improve the accuracy of seismic wave propagation models and enhance our understanding of Earth's internal structure, contributing to advancements in seismology. Key Points We revealed amplitude‐dependent attenuation in both the crust and the uppermost mantle using a spectral analysis Amplitude‐dependent attenuation is more dominant in the uppermost mantle than in the crust We quantified amplitude‐dependent attenuation with an exponent of about 0.05 for the crust and 0.16 for the uppermost mantle

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: Amplitude / Amplitudes / Dislocation / Dislocation density / Dislocation mobility / Earth / Earth mantle / Earthquakes / Energy dissipation / Energy exchange / Energy loss / Energy losses / High temperature / Microstructure / P-waves / Pressure / Pressure dependence / Pressure effects / Quantitative analysis / Seismic activity / Seismic attenuation / Seismic propagation / Seismic response / Seismic wave propagation / Seismic waves / Seismology / Spectral analysis / Spectrum analysis / Temperature dependence / Wave attenuation / Wave propagation