Watching the ground move

Who watches the ground

The CWA is responsible for meteorological, seismological, and weather-related marine and astronomical operations in Taiwan. Its earthquake work is done by the Seismological Center, formally established on 1 July 1989.

The centre monitors seismic activity in the Taiwan area, issues felt earthquake reports and tsunami warnings, runs the Taiwan Strong Motion Instrumentation Program, studies possible earthquake precursors and provides earthquake information and safety education.

It does not work alone. Academia Sinica’s Institute of Earth Sciences, whose geophysics is particularly strong in seismology, runs its own island-wide geophysical and geodetic networks alongside those of the CWA. Its researchers have also used instruments inside Taipei 101 to study how the tower moves; that work is described on A pendulum in a skyscraper.

More than a century of records

Earthquake observation in Taipei is much older than the centre. The CWA traces it to 1896, when a temporary weather station opened in Taipei and earthquakes were recorded by what people felt. On 19 December 1897 the station received Taiwan’s first seismograph, a Gray-Milne instrument, and by 1900 Omori seismographs, including strong-motion instruments, formed a first small network.

In 1963 a station at Ansiu (Hsinpu) joined the World-Wide Standardized Seismograph Network, which linked Taiwan to a global system of comparable instruments. The modern era began in 1990, when a real-time seismic network was built and a complete Taiwan earthquake catalogue was compiled. From 1991 a strong-motion programme set up 689 free-field strong-motion stations and monitoring systems in 61 structures. The CWA notes that their records are among the most important inputs for the seismic design codes that engineers use.

The following decades added layer after layer: a GPS network for measuring how the crust deforms (from 1993), real-time strong-motion stations with automatic location of earthquakes (1995), broadband seismometers (2001), work on a modern tsunami warning system (from 2003), geomagnetic observation (2006) and seismometers in boreholes (2008), about 300 metres deep or close to bedrock, where they are shielded from the noise of the surface.

Sensors on land, under the sea and in volcanoes

Today the CWA reports more than 400 real-time stations sending velocity and acceleration signals to the centre, and an archive of more than 300,000 earthquake records (status as of 3 November 2026). A GNSS network of satellite positioning stations tracks slow movements of the ground and changes in the ionosphere.

Stations on land cannot sit above earthquakes that begin at sea. To watch the sea floor, the CWA runs a cable system off eastern Taiwan with a total length of 735 kilometres and nine observation devices on the seabed; the sites laid in 2017 lie at depths of 5,796 and 5,554 metres. The system was activated in 2020, and the CWA’s strategic plan foresees a similar submarine cable system off southern Taiwan.

Closer to the city, the Taiwan Volcano Observatory-Tatun, established on 17 October 2011, monitors volcanic seismicity in the hills on Taipei’s northern edge, with some broadband stations linked to the centre in real time. More about those hills is on City & Region.

Magnitude and intensity

A news report about an earthquake often gives two numbers. Magnitude describes the earthquake itself: how much energy it released. Intensity describes the shaking at a particular place, so one earthquake has a single magnitude but different intensities in different towns.

The CWA’s intensity scale is built on measured ground motion. A version issued in 2000 set level 7 for ground acceleration of 400 gal or more (one gal is one centimetre per second squared). In 2020 a new scale split levels 5 and 6 into “weak” and “strong” grades, so that reports describe strong shaking more precisely, and the way intensity is calculated for earthquakes of magnitude 5 and above was revised.

This is why a felt earthquake report from the CWA looks like a map rather than a single figure: alongside the origin time, epicentre, depth and magnitude, it lists the intensity observed in each region.

Seconds of warning

Earthquake early warning does not predict earthquakes. It detects one that has already started, estimates where it will shake strongly, and sends an alert before the slower, damaging waves reach places further away. The CWA describes the aim as winning ten or twenty seconds of warning for metropolitan areas far from the epicentre, and gives the average warning time as about 20 seconds.

Taiwan’s first prototype system was tested in 1994, and the CWA launched its early warning service in 2013. Since 2016 strong-motion alerts have also been sent to phones through the Public Warning System cell broadcast and shown on television. For a large earthquake on the island, the centre says it can issue a warning and a rapid report within 15 seconds and publish the felt earthquake report within 5 minutes.

The CWA is open about the limits. Its earthquake app sends notifications to users in areas where the estimated intensity is above 3, about 10 to 15 seconds after the earthquake begins. Close to the epicentre there is a blind zone that cannot be alerted before strong shaking starts, and because the first estimate uses only a few stations near the epicentre, what people feel may differ from the alert. A six-year project for 2022 to 2027 aims to make the system faster and smarter, including with machine learning.

What arrives, and when

After a strong earthquake, information reaches the public in several waves, each slower but more complete than the one before. The CWA app describes them as follows:

• Early warning: about 10 to 15 seconds after the start, for areas with an estimated intensity above 3; based on a few stations, so it is fast but rough.
• Felt earthquake report: about 5 to 10 minutes after the start, sent to all users for significant earthquakes; it uses all the data, so it takes longer.
• Tsunami information: about 20 minutes after an earthquake that could cause a tsunami, only for users near coasts where the estimated wave height reaches the CWA’s threshold.

The app also keeps an archive of CWA earthquake reports going back to 1995 and lists recent large earthquakes and tsunami messages worldwide, using data from the US Geological Survey and the Pacific Tsunami Warning Center.

Where to find official advice

For current earthquake reports, tsunami information and advice on what to do during an earthquake, use the CWA’s own pages and app. This site explains how the system works; it does not replace official guidance. How Taipei’s tallest building copes with shaking and wind is described on A pendulum in a skyscraper, and the research institute behind much of Taiwan’s seismology on Taiwan’s national academy.