[J02-1] Recent large earthquakes I

[J02-1-02] Detailed crustal deformation and fault ruptures of the 2016 Kumamoto Earthquake revealed by ALOS-2 SAR data

^○Tomokazu Kobayashi, Hiroshi Yarai, Yu Morishita, Satoshi Kawamoto, Satoshi Fujiwara, Takayuki Nakano (GSI of Japan, Tsukuba, Japan)

We report ground displacement associated with the 2016 Kumamoto Earthquake obtained by ALOS-2 SAR data. For the SAR analyses, we applied InSAR and pixel offset methods, which has successfully provided a 3D displacement field showing the widely- and locally-distributed deformation. The obtained displacement field shows clear displacement boundaries linearly along the Futagawa, the Hinagu, and the Idenokuchi faults across which the sign of displacement component turns to be opposite, suggesting that the fault ruptures reached the ground surface or subsurface. The known fault trace of the Futagawa fault terminates at the western edge of Aso caldera, but the displacement discontinuity clearly extends into the caldera with a position slightly shifting northward. Our fault model suggests that the main rupture occurred on the Futagawa fault with a right-lateral motion including a slight normal fault motion. The rupture on the Futagawa fault extends into the Aso caldera with slightly shifting the position northward. Of note, the fault plane oppositely dips toward southeast. It may be a conjugate fault against the main fault. For the Idenokuchi fault, a normal fault motion is dominant at the depth of around 5 km. The Idenokuchi faults runs near the Futagawa fault in parallel, and they have different slip components separately. It maybe suggest a slip partitioning, which supports the idea proposed by Toda et al. (2016). In the western side of the source region, the slip on the Hinagu fault, in which the Mj6.5 and Mj6.4 foreshocks occurred with a pure right-lateral motion, is also deeply involved with the main shock.

Acknowledgements: ALOS-2 data were provided from the Earthquake Working Group under a cooperative research contract with JAXA (Japan Aerospace Exploration Agency). The ownership of ALOS-2 data belongs to JAXA.