Small Earthquakes Deviate from the Omega‐Square Model as Revealed by Multiple Spectral Ratio Analysis
Small Earthquakes Deviate from the Omega‐Square Model as Revealed by Multiple Spectral Ratio Analysis
复制标题
多谱比分析揭示小地震偏离欧米伽方模型
DOI：
10.1785/0120150322
复制
发表时间：
2016
影响因子：
3
通讯作者：
K. Imanishi
中科院分区：
文献类型：
--
作者：
T. Uchide;K. Imanishi
我们通过使用多重谱比分析估计日本茨城县北部和福岛县滨通地区 196 M w 3.2-4.0 浅源地震的震源谱来检验欧米茄方模型。目标事件的地震图与附近多个小事件（经验格林函数 [EGF] 事件）的地震图的频谱比允许否定路径和场地效应，并通过欧米伽平方模型进行拟合。不同 EGF 事件的残差光谱表现出相似的曲线，表明目标事件的源光谱如何偏离欧米伽方模型。许多地震明显偏离，而其他事件则吻合良好。这些发现的可能含义是破裂过程中的不连贯性、双角频率模型以及略高于 2 的高频衰减指数值，尽管这仍然是一个悬而未决的问题。这项研究将有助于改进震源谱模型，不仅增强震源研究，而且增强强震评估和其他地震学研究。
在线材料：显示具有最大和最小峰峰值幅度的事件的频谱分析结果的图。
We examine the omega‐square model by estimating the source spectra of 196 M w 3.2–4.0 shallow earthquakes in the northern Ibaraki prefecture and the Fukushima prefecture Hamadori area of Japan using multiple spectral ratio analysis. Spectral ratios of the seismograms of target events to those of multiple nearby small events (empirical Green’s function [EGF] events) allow for negation of path and site effects and are fitted by the omega‐square model. The residual spectra for different EGF events exhibit similar curves, indicating how the source spectra of the target events deviate from the omega‐square model. Many earthquakes deviate remarkably, whereas other events fit well. The possible implications of these findings are incoherencies in the rupture process, the double‐corner‐frequency model, and a high‐frequency falloff exponent value slightly higher than 2, although this is still an open question. This study will help to improve the source spectrum model, enhancing not only source studies, but strong motion assessments and other seismological studies.
Online Material: Figures showing results of spectral analysis of the events with the largest and smallest peak‐to‐peak amplitudes.