That distinctive alert tone from your smartphone or TV — that’s the Earthquake Early Warning. From the moment it sounds to when the strong shaking arrives, you have only a few seconds, or at most a few tens of seconds. There’s almost no time to think, so the only real preparation is training your body to move on its own.

What the Earthquake Early Warning actually is

The Japan Meteorological Agency (JMA) describes the Earthquake Early Warning as follows:

Information that, immediately after an earthquake occurs, forecasts the arrival time and seismic intensity of strong shaking at each location, along with the long-period ground motion class, and announces it as quickly as possible

It does not predict the earthquake itself. It’s a system that, immediately after an earthquake begins, calculates the arrival of the larger shaking (S-waves) from the smaller shaking that arrives first (P-waves), trying to give you warning before the strong shaking hits.

The threshold for the “warning” to sound

The loud alert on your smartphone is the Earthquake Early Warning’s Warning tier. According to JMA, a Warning is issued when a maximum seismic intensity of lower-5 or greater, or a long-period ground motion class of 3 or higher, is forecast, and is delivered to areas where strong shaking is forecast, plus areas where a seismic intensity of 4 is forecast.

In other words, if the Warning sounds, it means “strong shaking may be coming.” It’s easy to freeze in surprise at how loud it is, but those few seconds are what count.

When it sounds, first protect yourself

There is only one thing to do: secure your own safety first. JMA also states that the top priority is to “stay calm and secure your own safety first.” With only a few seconds of lead time, there’s no room for complicated actions. Train your body to remember just these three things.

  1. Protect your head
  2. Get low
  3. Get somewhere nothing will fall on you, tip over onto you, or slide into you — such as under a sturdy desk

This is exactly where securing your furniture pays off. Whether you can move to safety in a few seconds comes down to whether the room is already set up so furniture won’t fall. There’s no point taking cover somewhere furniture can still topple onto you.

Things worth keeping in the back of your mind, by location:

  • Indoors — stay away from window glass, tall furniture, and anything that could fall; don’t rush outside in a panic
  • In the kitchen — if you’re near a flame, don’t push it; secure yourself first (deal with the fire once the shaking stops)
  • Outdoors — stay away from block walls, vending machines, signs, and utility poles; protect your head
  • While driving — slamming the brakes invites a rear-end collision. Turn on your hazard lights and slowly slow down, then pull over to the left
  • Near the ocean — once the shaking stops, head for high ground in case of a tsunami

Know that “it sometimes won’t arrive in time”

This is the most important limitation to understand. The Earthquake Early Warning is not foolproof. JMA states this plainly:

In areas close to the epicenter, the warning will not arrive in time.

With an earthquake whose hypocenter is close to directly beneath you, strong shaking can arrive before the warning, or at the same time. Okinawa can experience earthquakes near Miyako Island and near the main island of Okinawa itself, so you should assume that if the epicenter is nearby, the warning may not sound at all, or may sound too late to help.

That’s exactly why the basic rule is: don’t wait for the warning — the moment you feel shaking, move. As covered in Tsunamis Do Reach Okinawa, the Great Meiwa Tsunami followed an earthquake that caused no shaking damage at all. “It didn’t shake much, so we’re fine” does not hold.

JMA is also candid about the accuracy of the warning itself:

Because the warning uses only a very short window of data, it carries limitations, including margins of error in the forecast seismic intensity.

The actual shaking can turn out weaker or stronger than forecast. Hold onto both of these: if it sounds, don’t worry about a false alarm — protect yourself anyway. If it doesn’t sound but you feel shaking, move anyway.

Check your phone’s settings in advance

A compatible smartphone receives the Earthquake Early Warning automatically. Even so, it’s worth checking once whether it’s set to sound even in silent mode, and whether notifications are switched off on a budget SIM plan or certain devices.

If you have family visiting as tourists, it’s also worth sharing If an Earthquake or Tsunami Strikes During Your Trip with them.

What this article does not cover

This site does not cover whether an earthquake or an Earthquake Early Warning is currently occurring. For the latest information, check JMA and other official sources. Follow JMA’s warnings and the evacuation information issued by your municipality when deciding whether to evacuate after the shaking stops.