Earthquake Source Dynamics and High-Frequency Decal Characteristics of Japanese Arc Region

Abstract

The shape of the seismic frequency spectrum and its relationship to the magnitude of earthquakes have been a significant focus. This pursuit aims to extract valuable information about the nature of earthquake source mechanisms. Additionally, it serves as a valuable reference for generating accurate simulations of strong ground motion, which is crucial for engineering applications. A data set of 10 sites, each site having 20 data of surface and well of magnitude equal to 3.8 or greater than 3.8 Japan (Kik), has been used in this study. A MATLAB script was employed to calculate key spectral parameters. These parameters include the corner frequency (fc), which designates the point beyond which the spectrum’s decline follows a specific rate of 2. Furthermore, the high-cut frequency (fmax) was determined, signifying the frequency above which the spectrum’s decay occurs, along with the rate of this decay (p) for frequencies beyond fmax. Previous research conducted by Kumar et al. demonstrates that the relationship involving fmax is not influenced by factors such as focal depth, distances from the epicenter, and the conditions of recording sites. Both fmax and fc exhibited a comparable correlation with seismic moments or magnitudes, indicating that fmax is likewise influenced by the characteristics of the earthquake source process. Across various recording locations, the observed values of fmax consistently exhibit a rise in conjunction with seismic moment or magnitudes. This trend suggests that the primary influencing factor is the seismic source itself, rather than the conditions at the recording sites. Within this particular study, it has been observed that fmax is found independent of site conditions, seismic moment is directly proportional to power (−3) of cornering frequency. Also variation of fmax with epicenter and the Average value of kappa is estimated. The exploration of this field was initiated by Aki (J Geophys Res 72:1217–1231, 1967), who delved into the relationship between the seismic wave’s amplitude spectrum and the dimensions pertaining to the origin of the earthquake. He achieved this by analyzing a pair of fault displacement models for an earthquake, extending his research until 1970. Aki conceived of the origin of an earthquake as an immediate horizontal strain surge acting on a dislocation surface. Within this framework, he introduced triple autonomous factors (source dimensions, fractional stress drop, and moment) that influence the configuration of the pattern of displacement spectrum for seismic body waves in distant regions. He established a connection between the cutoff frequency of the rupture radius and the assumption the efficiency of stress equates to the typical static stress reduction (Aki, J Geophys Res 72:1217–1231, 1967). © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.