Source rupture process of the 2016 central Tottori, Japan, earthquake (M JMA 6.6) inferred from strong motion waveforms

Abstract

The source rupture process of the 2016 central Tottori, Japan, earthquake (M JMA 6.6) was estimated from strong motion waveforms using a multiple-time-window kinematic waveform inversion. A large slip region with a maximum slip of 0.6 m extends from the hypocenter to the shallower part, caused by the first rupture propagating upward 0-3 s after rupture initiation. The contribution of this large slip region to the seismic waves in the frequency band of the waveform inversion is significant at all stations. Another large slip region with smaller slips was found in northnorthwest of the hypocenter, caused by the second rupture propagating in the north-northwest direction at 3-5 s. Although the contribution of this slip region is not large, seismic waveforms radiating from it are necessary to explain the later part of the observed waveforms at several stations with different azimuths. The estimated seismic moment of the derived source model is 2.1 × 10 18 Nm (M w 6.1). The high-seismicity area of aftershocks did not overlap with largeslip areas of the mainshock. Two wave packets in the high frequency band observed at near-fault stations are likely to correspond to the two significant ruptures in the estimated source model.

Going to Any Lengths: Solving for Fault Size and Fractal Slip for the 2016, Mw 6.2 Central Tottori Earthquake, Japan, Using a Transdimensional Inversion Scheme

“…Ross et al () find a concentrated slip patch of ∼5‐m slip with 93% of the seismic moment released below 8 km, which would leave the surface at risk from further faulting and considerable seismic hazard. Ross et al () also estimate a much higher peak slip (maximum of 5 m of slip), whereas we estimate a peak slip of 1.8 m. Kubo et al (), however, find two distinct slipping patches of 0.6‐m slip from 3‐km depth down to 12‐km depth, supporting our view that most of the seismogenic zone ruptured, though the peak slip magnitude is only 0.6 m. The InSAR data also encompass several days to weeks of activity after the earthquake (up to 4 days for the four ALOS‐2 scenes and 15 days for Sentinel‐1), which means there could be postseismic and aftershock signal included in our data. All of the InSAR scenes include the 70 foreshocks in the preceding 12 hr, but the largest foreshock, with magnitude M w 4.2 (Ross et al, ), represents only 5 ×10 15 Nm of moment, which is less than 1% of the moment of the M w 6.2 event.…”

Dissipative Intraplate Faulting During the 2016 Mw6.2 Tottori, Japan Earthquake

“…Kubo et al () also derived a slip model for the 2016 Tottori earthquake using the closest strong‐motion records and a traditional finite‐fault inversion. Their model has a main asperity located generally in the same place as ours but is distributed over an area that is more than 4 times as large.…”

Coseismic and Postseismic Deformation of the 2016 Central Tottori Earthquake and its Slip Model

“…In this study, we analyze coseismic and postseismic deformation of the 2016 Central Tottori earthquake. To date, two coseismic slip distributions based on seismic data have been published for this event (Kubo et al, ; Ross et al, ). Kubo et al () analyzed near‐field strong motion data using a multiple time window linear kinematic waveform inversion.…”

“…To date, two coseismic slip distributions based on seismic data have been published for this event (Kubo et al, ; Ross et al, ). Kubo et al () analyzed near‐field strong motion data using a multiple time window linear kinematic waveform inversion. They calculated Green's functions with the discrete wavenumber method in a 1‐D layered velocity structure model and delimited two areas of concentrated slip on the fault plane and maximum slip of 0.6 m. On the other hand, Ross et al () inverted near‐ and far‐field strong motion data using an empirical Green's function method.…”