Slip distribution of the 1952 Tokachi‐Oki earthquake (M 8.1) along the Kuril Trench deduced from tsunami waveform inversion

Abstract

[1] We inverted 13 tsunami waveforms recorded in Japan to estimate the slip distribution of the 1952 Tokachi-Oki earthquake (M 8.1), which occurred southeast off Hokkaido along the southern Kuril subduction zone. The previously estimated source area determined from tsunami travel times [Hatori, 1973] did not coincide with the observed aftershock distribution. Our results show that a large amount of slip occurred in the aftershock area east of Hatori's tsunami source area, suggesting that a portion of the interplate thrust near the trench was ruptured by the main shock. We also found more than 5 m of slip along the deeper part of the seismogenic interface, just below the central part of Hatori's tsunami source area. This region, which also has the largest stress drop during the main shock, had few aftershocks. Large tsunami heights on the eastern Hokkaido coast are better explained by the heterogeneous slip model than previous uniform-slip fault models. The total seismic moment is estimated to be 1.87 Â 10 21 N m, giving a moment magnitude of M w = 8.1. The revised tsunami source area is estimated to be 25.2 Â 10 3 km 2 , $3 times larger than the previous tsunami source area. Out of four large earthquakes with M $ 7 that subsequently occurred in and around the rupture area of the 1952 event, three were at the edges of regions with relatively small amount of slip. We also found that a subducted seamount near the edge of the rupture area possibly impeded slip along the plate interface.

Surface latent heat flux and nighttime LF anomalies prior to the M<sub>w</sub>=8.3 Tokachi-Oki earthquake

“…The epicenter is located in the same region where the earlier 1952 Tokachi-Oki earthquake M w =8.1 occurred Hirata et al, 2003). Figure 1 shows a map of the epicentral region with the plate boundaries and major fault lines, as well as the location of the epicenters of earthquakes that occurred within six months after the main earthquake of 25 September 2003.…”

Spatial pattern in stress drops of moderate-sized earthquakes on the Pacific Plate off the south-east of Hokkaido, Japan: implications for the heterogeneity of frictional properties

“…However, the afterslip area of the 2003 Tokachi-oki earthquakes could be also included in the coseismic area of the 1952 Tokachi-oki earthquake (e.g., Hirata et al 2003). The spatial resolution of the slip distribution of the 1952 earthquake would be lower than that of the 2003 sequence, which implies that the frictional properties in the region might exhibit significant temporal change.…”

New study on the 1941 Gloria Fault earthquake and tsunami

“…These studies can be broadly divided into two categories: with a priori assumptions on the fault model (e.g. Satake, 1987Satake, , 1993Hirata et al, 2003;Titov et al, 2005), and without a priori assumptions on the source, namely , Satake et al (2005), Tsushima et al (2009), Wu andHo (2011) and Yasuda and Mase (2012).…”

“…Among these events are those that occurred on 25 November 1941 (Udias et al, 1976;Lynnes and Ruff, 1985), 9 June 1969 (Argus et al, 1989), 26 May 1975(Buforn et al, 1998Argus et al, 1989;Kaabouben et al, 2008) and 17 October 1983 (Argus et al, 1989). Some of these earthquakes generated tsunamis, described in historical documents and recorded by tide stations, namely on 31 March 1761, 25 November 1941and 26 May 1975(Baptista et al, 2006Kaabouben et al, 2008;Baptista and Miranda, 2009).…”