May 13, 2016
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion

Evaluation of the 2016 Kumamoto Earthquakes
(View of Earthquake Research Committee Chairman)

* Based on the Kumamoto Earthquakes, considering the necessity of intensifying transmission of information from Earthquake Research Committee, in addition to the traditional evaluation of seismic activity, hereafter, we announce "view of chairman" in case of necessity and transmit the related information.

* The recent Kumamoto Earthquakes reminded the earthquake risk in our country.

* Although the series of seismic activity is decaying as a whole, the activity in the Kumamoto region, Kumamoto prefecture and Aso region is still rather high. The activity in the central Oita prefecture is decaying.
In cases of the Mid Niigata prefecture Earthquake in 2004 (M6.8) and earthquake in Hamadori, Fukushima prefecture in 2011 (M7.0), aftershocks of M5.0 or so occurred 1 to 2 months after the main shocks. Also in Kyushu region, as is the case for the earthquake in Aso region, Kumamoto prefecture (M6.1) and earthquake in central Oita prefecture (M6.4), both in 1975, and for the 1997 seismic activity in Satsuma region, Kagoshima prefecture (M6.6 and M6.4), the second earthquake of M6 or so in neighboring region, 2 or 3 months after the first. Therefore in the region of the series of seismic activity of Kumamoto earthquake and in the neighboring regions, we should be prepared with attention to the possibility of earthquakes with strong shaking.
In the adjacent area to the series of recent seismic activity, there are the Hinagu fault zone (Hinagu segment, Yatsushirokai segment), Futagawa fault zone (Uto segment, north coast of Uto peninsula segment), and Beppu-Haneyama fault zone where no sign of active seismicity is observed at present. We should routinely be prepared for a future earthquake, remembering the existence of active faults. We continue the monitoring of seismic activity.
In addition, although we cannot say that the probability of earthquake occurrence along the Median tectonic line and plate boundary along the Nankai trough has raised by the series of recent seismic activity, we should pay attention to these areas of inherent high earthquake risk.

* Based on the Kumamoto Earthquakes, Earthquake Research Committee promptly reinvestigates active faults for the Futagawa fault zone and the Hinagu fault zone, and use the results for the long-term evaluation of seismic activity.

* Based on the Kumamoto Earthquakes, we think to revise "On probabilistic evaluation of aftershocks" (1998 Report of Earthquake Research Committee). After the examination in the "Subcommittee on examination of predictive evaluation method of seismic activity" for about 3 months, we want to get the conclusion.

* It is important that local governments and residents, in the regions not suffering damage from the recent Kumamoto earthquakes, based on the announced investigation results by Earthquake Research Committee, make progress in knowledge and understanding of earthquake risk, and reconsider the routine preparation for earthquakes, such as the earthquake resistance of buildings and immobilization of furniture, and active participation in disaster prevention training, and take a concrete disaster prevention action.

* Earthquake Research Committee continues to revise the transmission of information, such as the examination of expression easy to understand of earthquake occurrence probability and so on, and results of seismic research and investigation contributing to earthquake disaster prevention and disaster mitigation measures.