[S01-P] Poster

[S01-P-05] Rupture process of the 1979 Tumaco, Colombia, earthquake using teleseismic body waves

^○Masahiro Yoshimoto¹, Hiroyuki Kumagai¹, Nelson Pulido² (1.Nagoya University, Nagoya, Japan, 2.National Research Institute for Earth Science and Disaster Resilience, Tsukuba, Japan)

We investigated the rupture process of the 1979 Tumaco earthquake using the teleseismic P-wave records at WWSSN stations with epicentral distances between 30 and 100 degrees. The records consist of six vertical and three horizontal seismograms. We used the fault geometry model of Yoshimoto and Kumagai [AGU fall meeting, 2016], which was constructed from slab model Slab 1.0 [Hayes et al., JGR, 2012]. We calculated Green's functions using the method of Kikuchi and Kanamori [BSSA, 1991] and applied the waveform inversion scheme of Kikuchi et al. [EPS, 2003] to determine the spatial and temporal slip distribution. Our analysis indicated Mw 8.3 and the total rupture duration of about 120 s. The rupture propagated northeast from the rupture initiation point with a rupture velocity of 2.0 km/s. The large slip area was estimated in the northeastern part of the source region with the maximum slip of 3.5 m. This large slip area is consistent with reported regions of large tsunami height and strong shaking intensity. White et al. [EPSL, 2003] estimated the average plate coupling ratio in the 1979 earthquake source region to be only 30 %. From this coupling ratio and the average slip of 2.4 m in our slip model, the recurrence interval of the 1979 earthquake was estimated to be 174 years. This suggests that the 1906 Ecuador-Colombia earthquake did not rupture the source region of the 1979 Tumaco earthquake. This interpretation is consistent with that proposed by Yoshimoto and Kumagai [2016].