Rupture process of the largest aftershock of the M 9 Tohoku-oki earthquake obtained from a back-projection approach using the MeSO-net data

Abstract

The largest aftershock (M w 7.8) of the giant M 9.0 Tohoku-oki earthquake occurred near the coast of Ibaraki Prefecture about thirty minutes after the main shock. We have imaged the rupture process of the M w 7.8 earthquake by back-projection of waveform data from the Metropolitan Seismic Observation network (MeSOnet). Original acceleration seismograms were integrated. They were then band-pass filtered in the frequency range of 0.1-1.0 Hz. We assumed a fault plane on the plate boundary with a dimension of 115 km × 175 km, and this was divided into 112 subfaults. Travel times from each of the subfaults to observation sites were calculated by using a 3-D velocity structure model. Applying the restrictions that the rupture velocity is smaller than 4 km/s and the rupture duration on each subfault is less than 25 s, we obtained a rupture propagation image by projecting the power of the stacked waveforms. Propagation of the rupture toward north and east was suppressed by the existence of those areas that had radiated a large seismic energy at the main shock occurrence, or at the occurrence of the M 7.0 earthquake in 2008. The westward propagation of the rupture stopped at the area where the Philippine Sea plate lies over the Pacific plate.

Changes in seismicity before and after the 2011 Tohoku earthquake around its southern limit revealed by dense ocean bottom seismic array data

“…[] and Honda et al . [] proposed that the subducting seamount played an important role in rupture termination of the M w 7.8 largest aftershock of the Tohoku earthquake by estimating its rupture process from an inversion analysis and from a backprojection analysis, respectively. Although theoretical [e.g., Cloos , ; Scholz and Small , ; Wang and Bilek , ] and computational [e.g., Yang et al ., ] studies investigated the effect of subduction of seamounts on plate coupling and earthquake rupture propagation, it still remains controversial.…”

Along‐Dip Variation in Seismic Radiation of the 2011 Ibaraki‐Oki, Japan, Earthquake (Mw 7.9) Inferred Using a Multiple‐Period‐Band Source Inversion Approach

“…It was the largest aftershock of the 2011 Tohoku earthquake (M w 9.1) and occurred ~30 min after the mainshock. Previous studies have reported on the source process of this earthquake (e.g., Honda et al, 2013;Kubo et al, , 2016. However, the estimated source model differs among those studies.…”

“…The source model in the period band of 5-50 s is similar to those in the period bands of 10-25 and 25-50 s, indicating that the source model obtained in the period band of 5-50 s strongly reflected the rupture process relating to the generation of long-period (10-50 s) waveforms. The radiation image of short-period seismic waves in the period band of 1-10 s (Honda et al, 2013) is also consistent with our source model in the period band of 5-10 s, suggesting that it is difficult to derive information on seismic-wave generation in the short-period band (5-10 s) from the source inversion results in the period band of 5-50 s. Thus, we infer that the multiple-period-band source inversion approach is useful for revealing the broadband seismic-radiation characteristics of a large earthquake.…”

“…On the other hand, Honda et al (2013) investigated the seismic‐wave radiation process in the short‐period band of 1–10 s for this earthquake with a back‐projection technique using strong‐motion data and found that the radiation source of the short‐period seismic‐waves predominantly propagated from the hypocenter to the west. The contrast in the source models between Kubo et al (2013) and Honda et al (2013) is expected to be due to the difference in the period range of the waveform data used in these studies. This implies the spatial variation in the dominant period of seismic radiation during the 2011 Ibaraki‐oki earthquake.…”

Relationship between Heterogeneity of Plate Interface and Seismicity at Subduction Zones: The Japan Trench and Hikurangi Subduction Zones as Examples

“…Large and small green stars are epicenters of the largest aftershock, which occurred 30 minutes after the 2011 Tohoku-oki main shock, and its foreshock, which occurred seven minutes before the largest aftershock, respectively. Green shaded areas are regions of large slip of the largest aftershock of the 2011 Tohoku-oki earthquake (Kubo et al, 2013;Honda et al, 2013) . White and black dashed lines are as in Fig.…”