1. Earthquake Early Warning – An Overview
One often hears that hurricanes can be very destructive but at least citizens can get some warning of their approach and intensity, while earthquakes are unpredictable. While earthquake prediction is still an inexact science the early warning of earthquakes is possible and systems are being deployed across the globe. This ability to provide early warning is based on the fact that the energy from an earthquake is released through different kinds of motion that create different waves of energy that move through the earth. Fortunately for us the most destructive waves are slower than some others, and the early sensing of these faster and earlier waves gives us the ability to have some warning of the arrival of the more destructive ones.
Much of the early work began in Japan and as a result that country has the most advanced network operating in the world. However, Earthquake Early Warning (EEW) is still a young science; the Japanese system was first used only 10 years ago in 2006. It is used to provide early warning on earthquakes and associated tsunami, important for an island nation. Other countries that have EEW systems are Canada, Mexico and Italy, plus the United States.
There are four key elements of any large scale Earthquake Early Warning system :
• The sensor network
• Processing and analysis system
• The alerting and notification system
• Public education and coordination with key public and private organizations.
All of these elements are needed for the overall system to achieve its goal of saving lives and reducing damage to key infrastructure. While EEWS’s can at best provide only a few minutes of warning (and often less) even this short time can permit trains to slow or stop, key manufacturing equipment can be secured, individuals can get to safer locations and prepare for the shocks of the quake, and emergency responders can prepare. These early responses can save innumerable lives when the system as a whole works.
Most systems use large scale and geographically distributed commercial sensors with a central computer processing system and then work with government and communications carriers on the alerting and notification systems. However, some systems are being trialed that use small scale and inexpensive sensors and local processing; some even use smartphones to sense the different waves and help provide warning to the person carrying the phone, as well as others in the sensor network (http://myshake.berkeley.edu)