[U-15] The 2024 Noto Peninsula Earthquake (1:J)

[U15-P33] Waveform inversion with empirical Green's functions for the rupture process of the Noto Peninsula earthquake

*Atsushi Nozu¹, Yosuke Nagasaka¹ (1.Port and Airport Research Institute)

Keywords:2024 Noto Peninsula earthquake, rupture process, waveform inversion, empirical Green's function

The spatiotemporal slip distribution of the January 1, 2024, Noto Peninsula earthquake was estimated by an waveform inversion with empirical Green's functions. Ground motion records of the January 7 14:38 (M_J4.6), the January 7 15:26 (M_J4.5) and the February 15 15:29 (M_J5.0) aftershocks were used as empirical Green's functions. Conventional least-squares linear waveform inversion (Hartzell and Heaton, 1983) was adopted. The GSI geodetic fault model was extended and used. The JMA hypocenter was projected to this fault model and used as the rupture starting point. The first-time-window triggering front was assumed to start from there and to propagate radially at a constant velocity of 3.4 km/s. However, the second fault was assumed to rupture earlier by 10 s. At each subfault, the moment rate function after passage of the rupture front was expressed as a convolution of an impulse train with the moment rate function of the aftershock (Nozu, 2007). The impulse train spanned for 6.0 s and consisted of 12 impulses at equal time intervals of 0.5 seconds. Thus the height of each impulse corresponds to the ratio of the moment release during each 0.5 second at each subfault with respect to the moment of the aftershock. The ratio was determined through the inversion. Conventional corrections for the geometrical spreading and time shifts (Irikura, 1983) were applied to the empirical Green's functions to represent arrivals from different subfaults. The shear wave velocity in the source region was assumed to be 3.55 km/s. Absolute time information for both the mainshock and the aftershock recordings was used.