M5.5 Earthquake 21 km S of Hualien City, Taiwan — April 18, 2021
2021-04-18 14:11:38 UTC (2021-04-18) · approx. 10:11 PM UTC+8 local
Felt by 30 people across nearby locations. Maximum shaking intensity MMI 6.7 (very strong).
On April 18, 2021 at 14:11 UTC, a magnitude 5.5 shallow crustal earthquake struck 21 km S of Hualien City, Taiwan, at a depth of 10.0 km and coordinates 23.7895°, 121.5649°. The earthquake was reported felt by 30 peopleacross nearby locations, with a maximum shaking intensity of Modified Mercalli Intensity (MMI) 6.7 (very strong). The USGS PAGER system issued a green alert level for this event, indicating no significant casualties or damage expected. The nearest populated place is Hualien City (population 350,468).
Physical scale: An earthquake of magnitude 5.5 releases seismic energy equivalent to roughly 3 kilotons of TNT. Empirical fault-scaling laws (Wells & Coppersmith, 1994) estimate the subsurface rupture length at approximately 3.8 km — a useful intuition for the size of the slip patch on the fault.
The epicenter is located in Taiwan, a region characterized by the collision of the Luzon volcanic arc with the Eurasian continental margin, where the Philippine Sea Plate converges at 80 mm per year. View all earthquakes in Taiwan.
Learn more: Magnitude scale · Aftershock sequences
Nearest Populated Places
ShakeMap — predicted shaking intensity
Modeled ground-motion intensity contoured on the Modified Mercalli scale (MMI). Computed by the USGS from the moment-tensor solution and regional ground-motion prediction equations.
Source: U.S. Geological Survey ShakeMap. View interactive ShakeMap on USGS
Did You Feel It? — community-reported shaking
Aggregated felt-report intensity from 30 citizen responses to the USGS Did You Feel It? system. Each colored zone represents the average MMI from reports in that area.
Source: U.S. Geological Survey Did You Feel It?. View on USGS · submit your own report
Population exposure (USGS PAGER)
Estimated population that experienced each level of shaking. Based on the USGS PAGER rapid impact assessment, which combines ShakeMap output with global population grids.
| Shaking intensity (MMI) | Description | Population exposed |
|---|---|---|
| MMI 3 | weak | 21,186,843 |
| MMI 4 | light | 2,552,702 |
| MMI 5 | moderate | 177,219 |
| MMI 6 | strong | 65,365 |
| MMI 7 | very strong | 2,155 |
Earthquake Details
121.5649°E
Technical Information
Nearby Earthquakes (Last 7 Days)
Common Questions
How strong was the magnitude 5.5 earthquake near Hualien City, Taiwan?
The magnitude 5.5 earthquake that struck 21 km S of Hualien City, Taiwan on April 18, 2021 at 14:11 UTC had a depth of 10.0 km. It was felt by 30 people with maximum shaking intensity of MMI 6.7 (very strong). For context, this was a moderate earthquake that could be widely felt.
Where did the earthquake occur?
The earthquake epicenter was located at 23.7895°, 121.5649°, which is 21 km S of Hualien City, Taiwan. The nearest populated place is Hualien City (population 350,468). View all earthquakes in Taiwan.
Were there aftershocks?
Aftershock activity is monitored continuously by the USGS. Aftershock sequences from magnitude 5.5 earthquakes can continue for days to weeks and gradually diminish over time.
Has Taiwan had earthquakes this big before?
The largest recorded earthquake in Taiwan was the M7.6 Chi-Chi earthquake of September 21, 1999. Today's magnitude 5.5 event is significantly smaller than that historical record.
Authoritative source: USGS event page (event ID: us6000e2mt). All scientific values on this page are sourced verbatim from the USGS feed.
Cite this page: EarthquakeTracker.org. (2021, April 18, 2021). M5.5 Earthquake 21 km S of Hualien City, Taiwan — April 18, 2021. Retrieved December 22, 2025 from https://www.earthquaketracker.org/earthquakes/event/us6000e2mt/