Geoscientists compiled three centuries of magnitude-5 and larger earthquakes across the Taichung-Changhua-Nantou region, documenting 31 events whose epicenters concentrate in Nantou County and recur on irregular timers that frustrate simple forecasting models.
Central Taiwan universities are already citing the catalog in grant applications for dense seismic arrays along the Jhuoshuei River, hoping finer instrumentation can reduce uncertainty in the modern interval where quakes arrive closer together.
What the catalog shows
The study published in Terrestrial, Atmospheric and Oceanic Sciences merges historical accounts with instrumental records from 1795 through 2025. Epicenters map tightly into Nantou, while temporal clustering divides the series into three intervals with average gaps between major shocks ranging from 2.3 years to more than 18 years depending on the window.
Seasonal analysis found slightly higher activity in September, November, and December, and roughly twice as many Ms≥5 events during local nighttime hours than daytime, a pattern authors link to tidal stresses rather than industrial triggers.
Link to recent shaking
Separate work in Applied Geophysics examined directivity effects from the April 2024 Mw 7.4 Hualien offshore quake, showing long-period ground motions amplified along the rupture’s forward direction relative to northeastern Taiwan attenuation models. While Hualien lies outside the Taichung-Changhua-Nantou box, emergency planners use both studies to stress-test building codes in central Taiwan’s soft basins.
NCREE researchers are also updating site-characterization databases for Taiwan Strong Motion Instrumentation Program stations, pairing ambient noise with earthquake HVSR curves so new instruments inherit soil classifications faster.
Policy relevance
Interior Ministry reviewers cited the catalog during autumn briefings on school seismic retrofits, noting Nantou campuses still on legacy lists even after 2016 Mei-nong repairs. County officials want prioritized grants where recurrence intervals shorten to multi-year scales in the modern interval.
Insurance actuaries may incorporate the nighttime tidal signal into commercial premiums for mountain tourism lodges, though authors caution the effect is statistical rather than deterministic for any single season.
Limits of the data
Pre-instrumental magnitudes rely on historical damage descriptions, introducing uncertainty bands that widen before 1900. Still, the merged timeline gives civil engineers a shared reference when debating whether new industrial parks in Changhua should adopt stricter liquefaction surveys.
Scientists plan to release an interactive map through Academia Sinica’s geophysics portal later this year, letting township planners overlay epicenters with active fault traces published by the Central Weather Administration.