Small Earthquakes Deviate from the Omega‐Square Model as Revealed by Multiple Spectral Ratio Analysis

摘要: We examine the omega‐square model by estimating source spectra of 196 M w 3.2–4.0 shallow earthquakes in northern Ibaraki prefecture and Fukushima Hamadori area Japan using multiple spectral ratio analysis. Spectral ratios seismograms target events to those nearby small (empirical Green’s function [EGF] events) allow for negation path site effects are fitted model. The residual different EGF exhibit similar curves, indicating how deviate from Many remarkably, whereas other fit well. possible implications these findings incoherencies rupture process, double‐corner‐frequency model, a high‐frequency falloff exponent value slightly higher than 2, although this is still an open question. This study will help improve spectrum enhancing not only studies, but strong motion assessments seismological studies. Online Material: Figures showing results analysis with largest smallest peak‐to‐peak amplitudes.