Last earthquake broadcast over the air


Since 2011, J1 Radio has been monitoring earthquake activity in Japan and using our systems to report them to our listeners, both on our website and over our programming streams.  For many around the world, J1 may be the first source for finding out when an earthquake takes place.  Within Japan, J1 is a secondary source for receiving earthquake alerts.  

How it works.  J1 has designed programs that monitor the Japan Meteorological Agency (JMA) Earthquake Early Warning (EEW) system as well as XML data in order to get early and then detailed information on earthquakes and tsunami that takes place throughout Japan.  We also use some third party software to assist in the monitoring process.  We deliver this information to the public:

  • over the air on our audio streams (temporarily unavailable),
  • display on the website,
  • display on the J1 Radio Ticker on the J1 webplayer and mobile app,
  • display on the J1 Earthquake Website (

You may feel shaking before getting the alert over the air.  If you are in Japan, depending on how far you are from the hypocenter of the earthquake, it is very possible that shaking will start before you hear the alert tones on the audio streams.  Because of the nature of the internet with how audio streams are sent, there may be a delay of up to 30 seconds or longer from when the program originates at J1 to the time you hear the alerts.  Therefore, if you are in Japan, you should not use J1 as your primary source of receiving alerts.  Everyone in Japan should have an emergency alert app installed on their phone.  Local television and radio, desktop apps (like Jquake) as well as dedicated EEW receiver units are the best way to receive alerts in a more expedient manner.

It is important to remember that J1 monitors EEW for the entire country.  This means that you may hear an EEW message where you are not anywhere near the earthquake (such as an earthquake near Kagoshima and the listener is in Aomori).  Earthquake mobile apps and local media are the best way to receive EEW for your local area.

The Shindo Scale of Intensity

In Japan, the intensity of shaking is measured on the Shindo scale that ranges from 0 to 7.  Readings are taken all the way down to the town level.  Here's an explanation of each level:

  • Intensity 1: Some people indoors may feel a slight quake.
  • Intensity 2: Many people indoors may feel the quake, and items suspended from the ceiling such as lamps may sway slightly.
  • Intensity 3: Most people indoors may feel the quake, ceiling lamps will sway and dishes may clatter.
  • Intensity 4: People may get awaken.  Unstable objects may move or fall.  Some people may feel the quake when walking.
  • Intensity 5 Lower (5-): Furniture moves, plates and books may fall off of shelves and windows may shatter.
  • Intensity 5 Upper (5+): The falling of heavy furniture such as chests and vending machines may occur.  Driving may be difficult.
  • Intensity 6 Lower (6-): People will have difficulty standing still.  Shattering of wall tiles and windows is observed.  Doors may be damaged to the point where they can't be opened.
  • Intensity 6 Upper (6+): People are not able to stand up and are forced to crawl to move around.  The falling of most heavy furniture is observed and doors will be thrown in the air.
  • Intensity 7: People lose total control of their physical actions.  Massive cracks appear in the ground and landslides occur.

The Shindo Intensity that is displayed on the J1 website and other sources, including local media, is the peak intensity for this episode.  Those further away from the earthquake's hypocenter will not feel the quake as strong as someone who is closer to the center.  J1 does list more granular detail of intensity in different parts of Japan by visiting our dedicated Earthquake Website.

When the shaking starts

Protect yourself!  Make sure you protect your head and seek shelter under a table or desk.  Don't rush outside.  Don't worry about turning off the gas in the kitchen.  

If outside: Watch for collapsing brick walls, falling debris and broken glass.  If on a train or bus, hold on to a handstrap or handrail.  If driving, don't slow down suddenly.  Turn on your hazards and then slow down smoothly.  

J1 Loves You!

This is more than just a cute slogan. We value our listeners and we want all of you to be safe.  Please follow this advice, even if you are not in Japan.  For more information, see these English language resources:

Earthquake Early Warnings from the JMA

Explaining the Shindo Intensity Scale from the JMA

ShakeAlert EEW for California, Oregon and Washington

United States Geological Survey Earthquake Information Page


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