Outside earthquake countries, the idea of earthquake warnings probably seems alien. In Japan it's an embedded part of the infrastructure. On our mobile phones we have earthquake alerts that usually (not always) go off about 10 seconds before a high magnitude earthquake. It's not much time, but time to put down a boiling pot or get down from a ladder. Sometimes they go off and there is no perceptible quake - but better to be forewarned. Since there have been so many earth tremors lately, from time to time TV shows are interrupted by the alerts. On live shows (of which there are many) the announcer will read from autocues to prepare for a quake. No one jumps under tables... people just sit still and wait... and usually it's nothing to be very concerned about.
It's hard to overstate the importance of earthquake information & tsunami alerts though. Every time there is a tremor above 3 on the Japanese scale news about it is broadcast on television. The size of the earthquake and the perceived danger determine the prominence that it is given. Along the coast lines there are tsunami siren and without doubt the tsunami alerts that followed the earthquake on the 11th saved the lives of many thousands of people - I have not seen any attempt to quantify this though.
The following are from a tremor tonight. It was a 6.4 magnitude earthquake off Fukushima.
On the TV screen in the pictures below, you can see the writing across the top which informs which places experienced which level on the Japanese seismic scale and whether there is any danger of tsunami. The character in the top left - 震度３- means it was three on the Japanese scale. Three means -
|3) / 2.5–3.4||Felt by most people indoors. Some people are frightened.||Dishes in a cupboard rattle occasionally.||Electric wires swing slightly.|
Wikipedia gives a good explanation of the Japanese seismic scale. http://en.wikipedia.org/wiki/Japan_Meteorological_Agency_seismic_intensity_scale
The writing on top of the TV screens notes that the earthquake was rated 3
on the Japanese shaking scale in
Natori City, Kakuda City, Iwanuma City,
Zao Town, Shichigama Town, Ogahara Town.
Also 3 in parts of Akita and Yamagata.
Akita City, Daisen City, Kamiyama City,
Murayama city Tendo City, Nakayama City.
Also 3 in much of Ibaraki and Tochigi prefectures. Ibaraki prefecture- south,
Tochigi prefecture - north, Tochigi south,
Chiba prefecture north east
Shindo 3 in Higashi Matsushima, Matsushima, Rifu, Daigo,
Tomiya, Ohira (Miyagi)
A warning that it may change sea levels but there is no
danger from this earthquake.
Or the list of the previous 10 or so.