Taiwan’s earthquake early warning system will soon experience a significant boost to its monitoring and forecasting capability. New technology will be able to send alert messages more quickly after an earthquake is detected by seismometers, giving warning to residents of an island that is highly susceptible to destructive tremors.
The construction of submarine electric cables will also help the island to better monitor deep sea plate movement, with 580km of new undersea cables due for completion next year. Taiwan sits on the western edge of the Philippine Sea Plate, part of the seismically active Pacific Ring of Fire.
The current response time for the island’s alarm system operated by the Central Weather Bureau is 15 to 16 seconds. The bureau has land-based stations and undersea cables to detect earthquakes. It is also improving the facilities of earthquake detection stations and updating related software.
The enhanced system is designed to more quickly warn people when an earthquake has been detected. This should give people a few more seconds to seek shelter somewhere safer, like under a stairwell or even under a table.
For earthquakes whose epicenters are on land, alerts can be sent within 15 to 16 seconds after a tremor is detected. However, if an earthquake occurs offshore, it can take 25 to 30 seconds for the system to transmit an alert.
The early warning system, however, will still not be able to provide timely alerts for so-called “earthquake blind spots,” which are areas that are too close to an earthquake’s epicenter, according to the Central News Agency.
When an earthquake occurs, seismographs are able to record primary (P) waves and shear (S) waves. P waves travel faster than S waves. The former cause very little damage, whereas S waves shake the ground perpendicular to the direction in which the wave is moving.
The bureau said that if an earthquake were to occur 100km from a city, P waves would arrive at the city 15 seconds after the earthquake, whereas S waves would arrive in 25 seconds. If a device that detects seismic waves is installed in a city, it would issue an alert when it detects P waves, giving residents 10 seconds to prepare themselves before S waves arrive.
The time that a person has to react to an earthquake depends on their distance from its epicenter, the bureau said, adding that if an earthquake happened in Hualien, the early warning system might not be of use to them, but it could help those in Yilan County or Taipei to seek shelter.