Earthquake Early Warning System





PHYSICAL CONSTRUCTION

QuakeAlert is encased in a sleek 2" x 7" x 1¾", pewter colour sturdy aluminum and steel case, which is well designed and high-tech in appearance. The shipping weight is .72Kg. The unit is wall mounted, on a cushion of 651 Closed Cell Neoprene pressure-sensitive adhesive foam. Two screws (supplied) affix the device to a wall. There are two separate alarm signals, one high and the other, low frequency. Each alarm employs a separate driver so as to create a distinctive alarm rhythm. The combination of harmonics and rhythm provide for an exceptionally distinctive alarm sound that would not be mistaken with other appliances or alarms. 

DESCRIPTION

QuakeAlert is an electronic earthquake early warning device that will provide the user with a warning of up to 2 minutes of an impending earthquake. With research and development funding from the National Research Council of Canada and rigorous testing by the University of British Columbia, QuakeAlert is the first line defense in accurate warning of imminent earthquake activity.

QuakeAlert reacts to vertical ground movements caused by vibrations in the form of motion waves from an earthquake. The QuakeAlert detector senses the arrival of primary (P) waves, the first waves to reach the detector, and so provides adequate time to react before the arrival of more destructive shear (S) and rally (R) waves. This warning is possible by the use of a transducing element set, adjusted to the frequency of the (P) waves. The detector is extremely accurate and will sound only when a vertical displacement above a critical level occurs.

OPERATING PRINCIPLE

The findings relating to the testing show conclusively that the product and technology is scientifically sound. The results are summarized in the series of four field and lab tests conducted to date under a Canadian National Research Council Grant for research and development. The principle of P and S wave separation follows: Since the P waves travel 1.68 times faster than the S waves, the greater the distance from the focus of an earthquake one is, the greater would be the time elapsed between the P and S waves. In a deep earthquake situation a significant warning time is possible, especially when an extremely large magnitude earthquake occurs at 65-80 km in depth and at a distance of 300-475 km. Generally P and S separation is 1 second for each 8 km of distance traveled. Therefore, if an earthquake occurred at a depth of 80 km and the epicenter was a distance of 475 km from the detector, a 60 second warning would be possible. It is apparent, of course, that if the earthquake was substantially deeper, larger in terms of magnitude and further away, an even longer warning time would follow. We have only discussed P (primary vertical waves) and S (shear horizontal) waves above. There are also R waves to consider. R waves differ from P and S waves because they begin on the surface of the earth (the epicenter) as compared to P and S waves which originate at the source to the earthquake underground (focus). R waves travel even slower than S waves and are extremely dangerous because they posses both vertical and horizontal components. In practical terms, if a building has suffered structural damage as a result of the arrival of S waves, it will probably not withstand the final volley of R waves. In the context of the previous example, QuakeAlert may give the user a warning time up to 130 seconds before the arrival of R waves. 

In conclusion:

  "The results of the tests showed, in general, that QuakeAlert is sensitive enough to detect small vertical ground motions, thereby providing a warning time before the arrival of more damaging horizontal motions produced by earthquakes. Warning time will allow users enough time to take precautionary action in the event of an upcoming seismic shaking. The warning time will depend, of course, on the earthquake type, the epicentral and focal distances, and the geological conditions of the site where the device is to be installed. A careful consideration of these aspects would ensure an effective performance of the device and will help to prevent or minimize undesirable false-alarm triggers caused by ground motions with similar characteristics to those produced by earthquakes." Dr. Carlos E. Ventura, Earthquake Research Laboratories, University of British Columbia.