Strong-motion simulation for the 1944 Tonankai earthquake based on the statistical green’s function method and stochastic representation of complex source process

• Published in: Earth, planets, and space planets, and space, 2023-12, Vol.75 (1), p.97-27, Article 97
• Main Authors: Ito, Eri, Nakano, Kenichi, Sekiguchi, Haruko, Nagashima, Fumiaki, Kawase, Hiroshi
• Format: Article
• Language: English
• Subjects: 1944 Tonankai earthquake; 4. Seismology; Amplitudes; Broadband; Earth and Environmental Science; Earth Sciences; Earthquake prediction; Earthquakes; Effects of Surface Geology on Seismic Motion (ESG): General State-of-Research; Frequency ranges; Geology; Geophysics/Geodesy; Green's function; Green's functions; Ground motion; Heterogeneous source model; Japan; Kinematics; Methods; Motion simulation; Perturbation; Representations; Seismic activity; Seismic waves; Slip; Statistical Green’s function; Stochastic processes
• ISSN: 1880-5981; 1343-8832; 1880-5981
• DOI: 10.1186/s40623-023-01847-y

Precisely evaluating the source, path, and site terms in a broadband frequency range is indispensable for quantitatively predicting strong motions. We conducted a generalized spectral inversion of strong motion in Japan to delineate both the spectral amplitude and phase characteristics for statistical Green’s functions. To predict ground motion from future megathrust earthquakes, we also need to model a kinematic source with a stochastic representation of the slip and rupture velocities on the fault surface. In this fundamental study, we first reported the basic features of statistical Green’s functions used for summation. We then demonstrated the construction of a kinematic source with distinctive strong-motion-generation areas with spatially random slip and rupture velocity variations. After the summation of statistical Green’s functions following the constructed kinematic source, we found that the peak ground accelerations and peak ground velocities of synthetics for the Mw8.2 1944 Tonankai earthquake are in good agreement with those of the well-established empirical formula in Japan because the medians of the synthetic values are well within the average plus/minus one standard deviation of the formula. Based on the simulation results of conducted parametric studies, we observed relatively small but meaningful effects of random slip distribution, as well as relatively small effects of random rupture velocity perturbation. In conclusion, our implementation of the complex source model and the empirically obtained statistical Green’s function used as an element source can be a viable combination for broadband (0.1 to 20 Hz) strong-motion simulations, realistic in terms of the amplitude and duration, without any hybrid scheme. Graphical Abstract