Earthquake Early Warning: How can an earthquake alert
be announced before tremors are felt?

How the Earthquake Early Warning WorksBroadcast to the public

Propagation of seismic
waves (P-waves)

Broadcast tothe public
Media and disasterprevention organizations

Propagation of seismic
waves (S-waves)
Instantaneous datatransmission
Seismograph

Earthquake Early Warning

After a tremor (P-wave) is detected the earthquake
early warning will be transmitted immediately. This isessentially a race against the seismic wave.

Anearthquake
occursP-waveobservation

Severalseconds later

Information cannot beprovided in time

Announcement ofearthquake

0 second

5 seconds

P-waves (initial tremors)S-waves (main tremors)
10 seconds

15 seconds

Window of time from the announcement
until the arrival of the main tremor
Information can be provided before strong tremors begin(those further from the seismic focus will have more time toprepare for the quake)

Tremors extend out from the seismic focus in a wave-like motion.
There are two main types of seismic waves: P-waves, or initial tremors, and Swave, or main tremors.
P-waves are the first to travel outward. They are followed by S-waves, whichcause stronger tremors. Most earthquake-induced damage results from these Swaves.
--- Traveling speed of seismic waves --P-waves (cause rattling tremors):around 7km/s
S-waves (cause larger, more powerful tremors): around 4km/s

The purpose of the earthquake early warning is to quickly announce to the publicthat an earthquake has occurred and to inform them of the estimated seismic
intensity several seconds or more before the arrival of strong tremors caused bythe quake. In those areas close to the focus of the earthquake, however, theearthquake early warning may not be transmitted before the tremors hit.

Hundreds of seismographs are installed inlocations all around Japan, with the Japan
Meteorological Agency maintaining around 200 of
the devices and the National Research Institute for
Earth Science and Disaster Prevention some 800.
Using theses devices, the location and size of anearthquake can be estimated immediately,
followed by an approximation of the extent of thetremors (seismic intensity) expected to result fromthe quake.
Prompt warnings delivered
using the latest information technology(Earthquake Early Warning)

How to Use the Information
In order to make effective use of the earthquake early warning, it is important tohold emergency response training so that you can take appropriate action as soon
as you receive the warning.
--- Examples of appropriate actions --Most important of all is to remain calm and not panic.
¾ If inside a home, move away from large appliances or pieces offurniture that could fall over and take cover under a sturdy table orother object that provides similar protection.
¾ When in other types of buildings, do not panic and do not rush for theexit or stairs.
For more information about the earthquake early warning system, please contact
the Administration Division of the Japan Meteorological Agency’s Seismological andVolcanological Department or visit the agency’s website.
Administration Division, Seismological and Volcanological Department
Japan Meteorological Agency
1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122
Phone: (03) 3212-8341
Website: http://www.jma.go.jp/jma/indexe.html

Earthquake earlywarning
Strong tremors arecoming!
(Tremor forecast)

The JapanMeteorological Agency
is currently preparing tostart the earthquake
early warning system inorder to warn the public
as widely and as quickly
as possible. The
agency is also
developing a planned
course of action whenpeople receive an alert
in the variety ofsituation.

Take cover!

October 2006