A Decade of Data-Driven Analysis (2016-2026) | 206 Earthquakes M5.0+ | 2026-04-05
USGS Earthquake Database
Open-Meteo Weather API
Claude Opus 4.6 Analysis
Disclaimer: This is an exploratory data analysis, not a rigorous academic paper. Sample size is limited (only 18 M6.0+ events), and conclusions are for reference only and do not constitute prediction criteria.
*2026 data through April 5. The 2024 spike is primarily from the April 3 Hualien earthquake and its numerous aftershocks.
The April spike (71 events) is primarily from the 2024 April 3 Hualien earthquake sequence. Excluding April 2024, the monthly distribution is more even, though winter-spring (Dec-Apr) still shows slightly higher counts.
| Date | Mag | Depth | Location | Notes |
|---|---|---|---|---|
| 2024-04-02 | 7.4 | 40 km | Hualien | Decade's largest, April 3 Hualien earthquake |
| 2022-09-18 | 6.9 | 10 km | Taitung | Sep 18 Chishang earthquake |
| 2022-03-22 | 6.7 | 24 km | Hualien | — |
| 2025-12-27 | 6.6 | 63 km | Yilan | — |
| 2022-09-17 | 6.5 | 10 km | Taitung | Sep 18 foreshock |
| 2016-02-05 | 6.4 | 23 km | Tainan | Feb 6 Meinong earthquake |
| 2018-02-06 | 6.4 | 17 km | Hualien | Feb 6 Hualien earthquake |
| 2024-04-03 | 6.4 | 14 km | Hualien | April 3 aftershock |
| 2021-10-24 | 6.2 | 69 km | Yilan | Deep earthquake |
| 2022-01-03 | 6.2 | 19 km | Hualien | — |
| 2022-05-09 | 6.2 | 21 km | Hualien offshore | — |
| 2018-02-04 | 6.1 | 12 km | Hualien | Feb 6 foreshock |
| 2019-04-18 | 6.1 | 20 km | Hualien | — |
| 2020-12-10 | 6.1 | 71 km | Yilan | Deep earthquake |
| 2024-04-22 | 6.1 | 10 km | Hualien | April 3 aftershock sequence |
| 2024-04-22 | 6.1 | 9 km | Hualien | Same-day double quake |
| 2024-08-15 | 6.1 | 14 km | Hualien | — |
| 2025-01-20 | 6.0 | 16 km | Tainan | — |
| 2025-12-24 | 6.0 | 8 km | Taitung | — |
Below is the weather summary for the 15 days (day -15 to day -1) preceding each M6.0+ earthquake:
| Quake Date | Mag | Location | Avg Temp °C | Total Rain mm | Rainy Days | Heavy Rain | Avg Press hPa | Press Range hPa | Avg Humid % |
|---|---|---|---|---|---|---|---|---|---|
| 2016-02-05 | 6.4 | Tainan | 15.1 | 125.4 | 10 | 2 | 1022.2 | 12.2 | 91.1 |
| 2018-02-04 | 6.1 | Hualien | 18.6 | 120.1 | 15 | 0 | 1018.9 | 10.2 | 84.7 |
| 2018-02-06 | 6.4 | Hualien | 17.5 | 138.7 | 15 | 0 | 1020.0 | 10.7 | 83.5 |
| 2019-04-18 | 6.1 | Hualien | 24.6 | 74.1 | 13 | 0 | 1014.1 | 7.0 | 85.3 |
| 2020-12-10 | 6.1 | Yilan | 20.6 | 254.9 | 15 | 5 | 1022.0 | 5.8 | 85.2 |
| 2021-10-24 | 6.2 | Yilan | 25.8 | 319.8 | 12 | 5 | 1014.4 | 15.6 | 84.9 |
| 2022-01-03 | 6.2 | Hualien | 20.1 | 29.3 | 5 | 0 | 1022.3 | 13.7 | 80.7 |
| 2022-03-22 | 6.7 | Hualien | 23.1 | 33.0 | 5 | 0 | 1014.5 | 10.7 | 80.3 |
| 2022-05-09 | 6.2 | Hualien | 26.8 | 75.0 | 8 | 1 | 1012.7 | 8.4 | 84.9 |
| 2022-09-17 | 6.5 | Taitung | 22.9 | 155.9 | 13 | 2 | 1009.0 | 17.8 | 91.5 |
| 2022-09-18 | 6.9 | Taitung | 22.8 | 142.9 | 12 | 2 | 1009.5 | 17.8 | 91.3 |
| 2024-04-02 | 7.4 | Hualien | 23.3 | 16.7 | 7 | 0 | 1017.0 | 13.6 | 82.2 |
| 2024-04-03 | 6.4 | Hualien | 23.8 | 14.2 | 6 | 0 | 1016.6 | 13.6 | 81.4 |
| 2024-04-22 | 6.1 | Hualien | 26.9 | 27.1 | 6 | 0 | 1013.0 | 8.6 | 82.3 |
| 2024-08-15 | 6.1 | Hualien | 31.1 | 28.6 | 7 | 0 | 1007.1 | 5.9 | 79.5 |
| 2025-01-20 | 6.0 | Tainan | 15.9 | 13.1 | 5 | 0 | 1020.7 | 9.5 | 79.3 |
| 2025-12-24 | 6.0 | Taitung | 19.3 | 11.3 | 3 | 0 | 1019.1 | 3.0 | 79.8 |
| 2025-12-27 | 6.6 | Yilan | 20.9 | 68.6 | 9 | 0 | 1020.3 | 9.2 | 81.9 |
The control group consists of 18 randomly selected "no major earthquake" dates (evenly distributed across 2016-2025 seasons), using the same 15-day weather window.
Of the 18 M6.0+ earthquakes, 8 occurred in winter (44%) and 6 in spring (33%), totaling 78%. Only 1 occurred in summer (6%).
This implies that differences in temperature, pressure, and rainfall may simply reflect seasonal effects rather than independent weather factors.
However, the seismological community remains divided on whether earthquakes exhibit seasonality. Some studies suggest the crust is influenced by tidal forces and atmospheric pressure loading, and winter high-pressure systems may impose additional stress on shallow faults.
Average rainfall in the 15 days before earthquakes was 91.6mm, 54% higher than the control group's 59.3mm. This is the most prominent difference.
Even accounting for seasonal factors, some cases had exceptionally high rainfall: 254.9mm before the Dec 2020 Yilan M6.1 and 319.8mm before the Oct 2021 Yilan M6.2.
Academic context: "Rainfall-induced seismicity" is a known geophysical phenomenon. Heavy precipitation infiltrating the ground increases pore water pressure, potentially reducing the effective normal stress on faults and making faults already near critical state more likely to slip. This effect is more pronounced for shallow earthquakes (<20km).
83% (15/18) of major earthquakes had average humidity above 80% in the preceding 15 days, compared to only 56% in the control group.
However, Taiwan is inherently a high-humidity environment, and the northeast monsoon brings moisture in winter-spring, so a larger sample is needed to confirm significance.
The 15-day pressure range (max-min) averaged 10.7 hPa before earthquakes vs. 9.3 hPa for controls. The gap isn't large, but several major earthquakes showed notably high pressure ranges:
Academic context: The hypothesis that atmospheric pressure changes can trigger earthquakes has a long history. Rapid pressure changes (such as passing typhoon low-pressure systems) can theoretically exert small but measurable forces on the crust. The Sep 2022 Taitung earthquake was preceded by a typhoon approaching Taiwan.
Among the 18 M6.0+ earthquakes, not a single one had less than 10mm of total rainfall in the preceding 15 days. The control group also had none (Taiwan rarely goes 15 days without rain), but the driest pre-earthquake periods still recorded 11-16mm.
From another angle: Taiwan's major earthquakes never occur during completely dry periods. This "absence" itself is a pattern worth noting.
15-day pre-quake rainfall of 319.8mm (highest of 18 events), including 5 days of heavy rain (>20mm/day). Pressure range 15.6 hPa. This is the case most consistent with the "rainfall-induced earthquake" hypothesis.
However, this earthquake had a depth of 69km (deep), and rainfall infiltration theoretically cannot affect such depths.
15-day rainfall 155.9mm, pressure range 17.8 hPa (highest), humidity 91.5% (highest). During this period, a typhoon system was approaching Taiwan, causing dramatic pressure and weather changes. Two M6+ earthquakes occurred within two days.
15-day pre-quake rainfall was only 16.7mm, with relatively calm weather. Pressure range 13.6 hPa was slightly elevated but not extreme. This is the best counterexample for weather-earthquake independence — the decade's largest earthquake occurred during the calmest weather.
The observed differences (54% more rainfall, 3.8% higher humidity, 4.3°C lower temperature) are most likely primarily due to seasonal bias — Taiwan's major earthquakes statistically prefer winter-spring, which naturally features low temperatures, high humidity, and more rainfall.
The strongest counterevidence is the 2024 Hualien M7.4 (decade's strongest) occurring during extremely calm weather, demonstrating that weather is not a necessary condition for major earthquakes.
Data sources: USGS Earthquake Catalog API | Open-Meteo Historical Weather API | Central Weather Administration Seismological Center