Mostly aftershocks
Of 27,900 magnitude 3+ quakes since 2012, only 24% are mainshocks. Remove the aftershocks and the yearly count holds at about 400–500. 2016 had 4,816 M3+ quakes but just 424 mainshocks.
Data analysis · GeoNet earthquake catalogue · 2000 to Oct 2026
Three in four New Zealand earthquakes are aftershocks.
GeoNet locates around 20,000 earthquakes a year in and around New Zealand. I modelled 175,000 of them, every magnitude 2.5 or larger since 2000, to find out where they strike, how often the big ones come, and how quickly the shaking dies away. Strip out the aftershocks and the country's background rate is remarkably steady. The catalogue also hides a trap: in 2012 the way magnitudes were measured changed.
Live from GeoNet
Right now
The latest quakes GeoNet has located, loaded straight from its public API when you open this page.
Latest quakes
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Quakes located per day, past year
Key findings
Each step up is about 7.6 times rarer
The magnitude–frequency slope (b-value) is 0.88. New Zealand averages about 26 M5+ quakes a year, two M6+, and an M7+ every few years.
Kaikōura faded fast
The M7.8 produced 522 aftershocks of M3.5+ in its first day. Its decay exponent of 1.31 means that a month later, the daily rate was under 2% of day one.
The ruler changed in 2012
Before 2012, GeoNet's old system recorded twice as many M3+ quakes a year, but the same number of M5+. The country didn't get calmer: small quakes were rated about 0.35 magnitude lower after the switch.
Where they strike
Every quake of magnitude 4 or more since 2000, coloured by depth. Circle size shows magnitude.
Shallow quakes (lightest) follow the plate boundary from East Cape to Fiordland. The deep ones (darkest) under the central North Island sit on the Pacific plate as it dives westward. The dashed line marks the cross-section.
The plate diving under the North Island
Quakes within 50 km of the dashed line on the map, 2012–2025, by distance from the Hikurangi trench and depth.
Quakes line up along a sloping band: the top of the Pacific plate, sinking from the trench off Hawke's Bay to more than 200 km deep west of Taupō, before the quakes stop short of Taranaki.
The largest since 2000
NZ dates. Location as described by GeoNet.
How often each size comes
Average quakes a year at or above each magnitude, 2012–2025, on a log scale. The dashed line is the Gutenberg–Richter fit.
How aftershocks fade
Aftershocks of M3.5+ per day after the mainshock, both axes on a log scale. The dashed line is the fitted Omori law.
Take out the aftershocks and the background is steady
Quakes of M3+ per month, all events and mainshocks only (Gardner–Knopoff declustering), 2012 to Sep 2026.
What's normal near you
Shallow quakes (under 40 km deep) within 100 km of each city, 2012–2025. Mainshocks only, so one big sequence doesn't swamp the count.
A magnitude 5 quake 100 km away is usually felt but rarely damaging. These are observed rates over 14 years, not a hazard forecast; for that, see GNS Science's National Seismic Hazard Model.
Data-quality note
The ruler changed in 2012
Quakes a year at M3+ and M5+, each indexed to its own 2000–2011 average (= 100).
Data-quality note
Quakes ignore the clock. The catalogue doesn't.
Events by hour of day, NZ time.
Small quakes (M2.5–3), 2012–2025
Quarry blasts, 2000–2026
Not everything in an earthquake catalogue is an earthquake
Every event of M2.5+ that GeoNet recorded since 2000, by type, with the largest of each. Only earthquakes (and events of unknown type) in the New Zealand region are analysed here.
How this was built
Data
The GeoNet FDSN event service: every event of M2.5+ since January 2000, fetched a year at a time (busy years in halves, as the service caps requests at 10,000 events). The study region is 34–48°S, 165–180°E. The live panel calls GeoNet's public quake API from your browser.
Model
Loaded, typed and de-duplicated in DuckDB with SQL, then analysed in Python. Declustering uses Gardner–Knopoff windows, which are generous, so some independent quakes count as aftershocks. The b-value is Aki's maximum-likelihood estimate above M3.0 with a 500-sample bootstrap; Omori fits are maximum likelihood from 1.2 hours to the end of each window.
Checks
Rates and the b-value use 2012–2025 only, after the 2012 magnitude change. The b-value is stable (0.88–0.93) for cut-offs from M2.6 to M3.6. The first 1.2 hours after a big quake are left out of aftershock fits, because small aftershocks are missed in the coda of large ones.
Source: . Coastline: Natural Earth. Code: SQL model, pipeline and dashboard on GitHub · analysis notebook.