Earthquake warning system
Encyclopedia
An earthquake warning system is a system of accelerometer
s, communication, computer
s, and alarms that is devised for regional notification of a substantial earthquake
while it is in progress. This is not the same as earthquake prediction
, which is currently incapable of producing decisive event warnings.
in each direction along the fault surface. The speed of the progression of this fault tear is slower than and distinct from the speed of the resultant pressure
and shear
waves, with the pressure wave traveling faster than the shear wave. The pressure wave will generate an abrubt shock while the shear waves can generate a periodic motion (at about one cycle per second) that is the most destructive in its effect upon structures, particularly buildings that have a similar resonant period, typically buildings around eight floors in height. These waves will be strongest at the ends of the slippage, and may project destructive waves well beyond the fault failure. The intensity of such remote effects are highly dependent upon local soils conditions within the region and these effects are considered in constructing a computer model
of the region that determines appropriate responses to specific events.
The earliest automated earthquake pre-detection systems, named QuakeGuard, were installed in the 1990's by the company now known as Seismic Warning Systems of Scotts Valley, California. QuakeGuard technology currently protects over 40 locations, mostly across California, and has successfully detected multiple earthquakes with no false positive triggers, which is crucial to the effectiveness of such early warning devices. California's Calistoga fire station QuakeGuard installation automatically triggers a city-wide siren to alert the entire area's residents the moment any forewarning p-wave
signature of a potentially dangerous quake is detected. Japan's Earthquake Early Warning
system was put to practical use in 2006. Its scheme to warn the general public was installed on October 1, 2007. It was modeled partly on the Urgent Earthquake Detection and Alarm System (UrEDAS) of Japan Railways
, which was designed to enable automatic braking of bullet train
s.
Accelerometer
An accelerometer is a device that measures proper acceleration, also called the four-acceleration. This is not necessarily the same as the coordinate acceleration , but is rather the type of acceleration associated with the phenomenon of weight experienced by a test mass that resides in the frame...
s, communication, computer
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
s, and alarms that is devised for regional notification of a substantial earthquake
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...
while it is in progress. This is not the same as earthquake prediction
Earthquake prediction
An earthquake prediction is a prediction that an earthquake of a specific magnitude will occur in a particular place at a particular time . Despite considerable research efforts by seismologists, scientifically reproducible predictions cannot yet be made to a specific day or month...
, which is currently incapable of producing decisive event warnings.
Time lag and wave projection
An earthquake is caused by the release of stored elastic strain energy during rapid sliding along a fault. The sliding will start at some location and progress away from this hypocenterHypocenter
The hypocenter refers to the site of an earthquake or a nuclear explosion...
in each direction along the fault surface. The speed of the progression of this fault tear is slower than and distinct from the speed of the resultant pressure
P-wave
P-waves are a type of elastic wave, also called seismic waves, that can travel through gases , solids and liquids, including the Earth. P-waves are produced by earthquakes and recorded by seismographs...
and shear
S-wave
A type of seismic wave, the S-wave, secondary wave, or shear wave is one of the two main types of elastic body waves, so named because they move through the body of an object, unlike surface waves....
waves, with the pressure wave traveling faster than the shear wave. The pressure wave will generate an abrubt shock while the shear waves can generate a periodic motion (at about one cycle per second) that is the most destructive in its effect upon structures, particularly buildings that have a similar resonant period, typically buildings around eight floors in height. These waves will be strongest at the ends of the slippage, and may project destructive waves well beyond the fault failure. The intensity of such remote effects are highly dependent upon local soils conditions within the region and these effects are considered in constructing a computer model
Computer simulation
A computer simulation, a computer model, or a computational model is a computer program, or network of computers, that attempts to simulate an abstract model of a particular system...
of the region that determines appropriate responses to specific events.
Configuration
Earthquake warning systems consist of arrays of seismic motion sensors arranged throughout a region. High speed communications systems and computers collect the sensor readings and the computers are programmed to detect the likely strength and progression of the seismic event. If a dangerous event is detected then alarms can be signalled through the region likely to be affected, allowing warnings before local ground motion of up to and beyond twenty seconds. While short, such warnings would be sufficient to allow many people to move to safer areas or to take shelter under substantial furnishings.Transit safety
Such systems are currently implemented to determine appropriate real-time response to an event in determining train operator response for urban rail systems such as BART (Bay Area Rapid Transit). The appropriate response will be highly dependent upon the warning time, the local right–of–way conditions, and the current speed of the train.Deployment
Japan, Taiwan, Mexico and limited regions of Romania (the Basarab bridge in Bucharest) and the United States are protected by earthquake early-warning systems.The earliest automated earthquake pre-detection systems, named QuakeGuard, were installed in the 1990's by the company now known as Seismic Warning Systems of Scotts Valley, California. QuakeGuard technology currently protects over 40 locations, mostly across California, and has successfully detected multiple earthquakes with no false positive triggers, which is crucial to the effectiveness of such early warning devices. California's Calistoga fire station QuakeGuard installation automatically triggers a city-wide siren to alert the entire area's residents the moment any forewarning p-wave
P-wave
P-waves are a type of elastic wave, also called seismic waves, that can travel through gases , solids and liquids, including the Earth. P-waves are produced by earthquakes and recorded by seismographs...
signature of a potentially dangerous quake is detected. Japan's Earthquake Early Warning
Earthquake Early Warning (Japan)
The is a warning issued just after an earthquake in Japan is detected. The warnings are issued mainly by the Japan Meteorological Agency , and they issue tips on how to react to the warnings.-Introduction:...
system was put to practical use in 2006. Its scheme to warn the general public was installed on October 1, 2007. It was modeled partly on the Urgent Earthquake Detection and Alarm System (UrEDAS) of Japan Railways
Japan Railways
The Japan Railways Group, more commonly known as , consists of seven for-profit companies that took over most of the assets and operations of the government-owned Japanese National Railways on April 1, 1987...
, which was designed to enable automatic braking of bullet train
Shinkansen
The , also known as THE BULLET TRAIN, is a network of high-speed railway lines in Japan operated by four Japan Railways Group companies. Starting with the Tōkaidō Shinkansen in 1964, the network has expanded to currently consist of of lines with maximum speeds of , of Mini-shinkansen with a...
s.
See also
- Earthquake engineeringEarthquake engineeringEarthquake engineering is the scientific field concerned with protecting society, the natural and the man-made environment from earthquakes by limiting the seismic risk to socio-economically acceptable levels...
- P-waveP-waveP-waves are a type of elastic wave, also called seismic waves, that can travel through gases , solids and liquids, including the Earth. P-waves are produced by earthquakes and recorded by seismographs...
- Hayward fault - a typical slip-strike fault within a highly urbanized region
- Earthquake preparedness
- Seismic retrofitSeismic retrofitSeismic retrofitting is the modification of existing structures to make them more resistant to seismic activity, ground motion, or soil failure due to earthquakes. With better understanding of seismic demand on structures and with our recent experiences with large earthquakes near urban centers,...
External links
- Seismic Warning Systems
- CREWS: Coachella Valley Regional Earthquake Warning System
- European-Mediterranean Sismological Center, real-time earthquake information website.