Deputy Director of the Seismological Center Central Weather Bureau (CWB) in Taiwan, Nai-Chi Hsiao, explains how the country’s quick earthquake alert system provides notification when it comes to ensuring disaster risk reduction
Taiwan is located on the boundary between the Philippine plate and the Eurasian Plate. The convergence of these two tectonic plates activity causes about 100 obvious felt earthquakes per year and 100 minor non-felt events per day around Taiwan. Several hazard earthquakes have occurred during our history. The most famous one was the 1999 Chi-Chi earthquake with Richter magnitude 7.3 in the middle of Taiwan, which killed more than 2,000 and caused mass building damage as well. The threat of an earthquake is, therefore, a serious issue today in Taiwan.
The Central Weather Bureau (CWB) is the government agency responsible for earthquake monitoring and relevant warning issues in Taiwan. More than 700 seismic sensors were deployed in and around Taiwan, including some on the ocean floor in the East Offshore Marine Area. About a quarter of these stations communicate in real-time with the headquarters at CWB at any given time. Depending on these precious ground motion signals, an automatic detection system was developed which can locate an earthquake at any time.
Besides the automated system in place, there are at least three persons on duty in the Seismological Center of CWB. They have ensured the healthy operation of the Seismic Network and the computer systems all the time, and their most important mission is to verify the correctness of all information and to issue felt earthquake reports as quickly as possible. The report is disseminated to hazard-rescue agencies, hazard assessment organisations, earthquake research institutions, important infrastructure systems (such as power supply, communication, and transportation), and mass media. Besides the initiative disseminated, these reports will also be published on the website of the CWB to inform the general public simultaneously. For instance, 139 obvious felt-earthquake reports were issued in 2018, and the average performance of auto detect and location takes place in about 60 seconds and issues are reported within the space of around five minutes.
Based on the millions of earthquake data recorded and the monitoring experience in place for over 25 years, the CWB had been conscious that felt-earthquake reports are useful, but only in the hazard-rescue stage after earthquake shaking occurs. Therefore, we developed the Earthquake Early Warning System (EEW) to detect significant earthquakes quickly in order to issue a warning about 10-15 seconds after the earthquake occurs. That means we can issue alerts for the area about 60 km away from the epicentre and provide seconds to 10s of seconds warning time for an urgent response before the destructive shaking occurs.
Since 2014, CWB has provided the EEW warning directly to all the public schools, hazard-rescue agencies and other government departments in Taiwan. Since 2016, CWB has issued EEW warnings through the Public Warning System (PWS) to wireless devices of the general public. The PWS was developed and constructed by the government and communication Corp., which is based on the Cell Broadcast Service (CBS) on the 4G network. This means that all the people in a high-risk area can receive an EEW warning at the same time! CWB also collaborates with TV companies to deliver instant live pop-up messages during the transmission of programmes.
However, the warning can only help people taking action to protect themselves (Drop, Cover, and Hold on) because the warning time is limited. The main benefit of an EEW is the application of industrial auto control, slowing down high-speed communication vehicles, suspending or halting the gas-line or powerline system, auto protection for a dangerous system such as power plants, hi-tech equipment, and so on. CWB had promoted the application of the EEW, recruited more than 10 private companies and research institutes in different domains to collaborate in order to develop warning message forwarding and customised application for requirements for any hazard mitigation purpose.
No matter what the earthquake report or the EEW warning is, we focus on improving the availability, accuracy, and efficiency of earthquake monitoring. There are several tasks that need to be promoted eagerly in the future. These include expanding the coverage of the Seismic Network and installing more advanced and robust ocean bottom seismographs on the east-south ocean of Taiwan where it is most likely that an earthquake will occur. To enhance the density of the Seismic Network: upgrading more off-line to real-time stations is required – improving the algorithm of computer modules so that it will take less time for the EEW to be issued. The ultimate goal of earthquake monitoring in Taiwan is to provide useful EEW and earthquake reports to whoever needs them, to achieve practical earthquake hazard mitigation, helping to secure the civil life and properties in the country.
Nai-Chi Hsiao, PhD
Center Central Weather Bureau (CWB)
Tel: +886 2 234 91 162