The 2018 Hokkaido Eastern Iburi Earthquake (Distribution of hypocenters determined by 3 dimensional velocity structure)

* The main shock and the aftershocks occurred near the boundary between the low velocity region in the east and the high velocity region in the west.
* By using the 3 dimensional velocity structure with surface station corrections, re-determined hypocenters become about 4 km shallower.
* The seismic activity is high mainly in the region with P wave velocity being smaller than 7.5 km/s and earthquakes occur within the crust.

National Research Institute for Earth Science and Disaster Resilience
[Evaluation of the 2018 Hokkaido Eastern Iburi Earthquake (October 12, 2018)]