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"Long-period ground motion" will be added to the Earthquake Early Warning System

Update date: January 25, 2023

The announcement standards for Earthquake Early Warnings issued by the Japan Meteorological Agency have been changed, and from Wednesday, February 1, 2020, long-period ground motion classes will be added to the announcement standards for Earthquake Early Warnings.

Change details

Until now, Earthquake Early Warnings have been announced based on seismic intensity predictions, but from Wednesday, February 1, 2020, predicted values ​​of long-period ground motion classes will be added to the announcement criteria. , an earthquake early warning will be issued even if a long-period ground motion class 3 or higher is predicted.

Image Class Overview

[Classes announced as earthquake early warnings are 3 or higher]

What is long-period ground motion?

The large shaking (seismic motion) that occurs during a large earthquake and has a long period (the time it takes for the shaking to make one round trip) is called long-period ground motion.

Image Short period earthquake motion
Short period earthquake motion Long period earthquake motion

[Warning targets are high floors above 14th floor or buildings with seismic isolation structure]

Inquiries regarding this page

Inagi City Fire Department Headquarters Disaster Prevention Division
2111 Higashi-Naganuma, Inagi-shi, Tokyo (Inagi Fire Department)
Phone: 042-377-7119 Fax: 042-377-0119

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Inagi City's official mascot, Inagi Nashinosuke
2111 Higashinagumanuma, Inagi City, Tokyo 206-8601
Office hours: 8:30 a.m. to 5:00 p.m. Main phone: 042-378-2111 Fax: 042-377-4781
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