Earthquake Warning System in Japan

Earthquake is an event when two main plates collide each other in their boundaries for strong shaking, small level of earthquake are even felt by mining, volcanic activities too. Moderate level of earthquake may cause due to inter plate(when in boundary of two major plates) or intra-plate (in between small plates with in major plate). Earthquake produces major waves that they called P-wave and S-wave from the source which travel through the body of earth and reach up to ground surface. In ground it changes in to surface waves and cause tremors on ground so we feel shaking.
Velocity of P-wave is higher than S-wave when they produces in same time during earthquake but they reach to surface in lag of time. S-wave which is slower in its velocity is main responsible for damage to structures. If we can beware before few seconds then we can manage possible safety in any situation. Up to now scientists could not achieve the accurate results of forecasting earthquake but the research is in progress from different aspects  may be in near future they can be able to save lives. Now a days, Japan Meteorological Agency (JMA) has earthquake warning system launched on October 1st 2007. This is based on the phenomenon that P and S waves have different velocities. 

How it works?

When earthquake happens in certain depth of ground then P and S waves propagates but P-wave reach to ground surface earlier than S-wave, tremor by P-wave then recorded by the sensors that are placed near the epicenter area. They send automatically to central unit of JMA that it analyze and send the information to different media about the earthquake is happening. Time difference of two waves are in just seconds or tens of seconds. Even we know before 5 seconds or 10 seconds we can take prevention suddenly.

In Japan all railways companies, hospitals, construction companies, factories, transport companies set alarm systems which automatically active after they receive message from JMA system. Televisions, radios of possible affected area, cell phones gets emergency alerts. All the railways will emergency stop with in few seconds, sensitive equipment suddenly shutdown, warning lights and sounds are active then all people can be safe nearby them. This system is good enough in practice and it has better efficiency that saved many lives up to now from when it is in practice.

You can see video produced by NHK and provided by JMA website (Sources of picture: JMA)(Due to copyright claim of JMA i have to remove this video from my youtube account. But i found the same on youtube later so you can have a short look)

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