Long-period seismic waves will be added to the emergency earthquake alert.

The criteria for issuing emergency earthquake alerts announced by the Japan Meteorological Agency have been changed, and starting from February 1, 2023 (Wednesday), a long-period seismic motion classification will be added to the criteria for issuing emergency earthquake alerts.

Change Details

Until now, emergency earthquake alerts have been issued based on the predicted seismic intensity, but starting from February 1, 2023 (Wednesday), the criteria for issuing alerts will include predictions for long-period seismic motion levels. Emergency earthquake alerts will be issued even if long-period seismic motion level 3 or higher is predicted.

The level announced as an emergency earthquake alert is 3 or higher

Long-period seismic motion

Long-period seismic waves refer to large tremors (seismic motion) that occur during a major earthquake, characterized by a long period (the time it takes for the shaking to complete one cycle).

[Targets of caution are high-rise floors above the 14th floor or buildings with seismic isolation structures]

Related Information

• Regarding the Change in the Criteria for Issuing Emergency Earthquake Alerts (Japan Meteorological Agency)(External Link)