Given I wasn't going to shoot the #LunarEclipse #BloodMoon last night, but then eventually got to bed at 3am & despite the incoming cloud, I got a start to finish sequence & am happy with the results.
MuaΕ«poko Otago Peninsula, Εtepoti Dunedin, NZ
#Nikon Z7ii
@stardome-nz.bsky.social
Aftershock decay for the Canterbury earthquake sequence showing an increase in aftershock activity following each of the main earthquakes in the sequence (top). Middle and bottom plots show the numbers of earthquakes and magnitudes beginning two years prior to the Darfield earthquake and two years following the February Christchurch earthquake. It demonstrates the low seismicity in the region prior to Darfield and the reinvigoration of the sequence following each large earthquake.
(top) Number of earthquakes per day in the Canterbury region starting five years before the Darfield earthquake up to February 2026. (Bottom) Earthquake magnitude per day starting five years before Darfield up to February 2026. Canterbury seismicity is still substantially elevated compared with pre-Darfield.
Over the first ~18 months following the Darfield earthquake the aftershock sequence would continue to evolve as each large earthquake reinvigorated the sequence. To this day the seismicity of the Christchurch/Canterbury region remains much higher than pre-Darfield. 13/
Aftershocks for the period 21 February 2011 β 31 January 2012. Stars show the epicentres of the Darfield earthquake, Christchurch earthquake, and later large aftershocks. Aftershock symbols are colour coded to correspond to each of the main earthquakes and before the next earthquake. Aftershocks preceding the Christchurch earthquake are not shown. Bottom are focal mechanisms derived from regional moment tensor solutions for the period 21 February 2011 β 20 November 2013.
The earthquake initiated a rejuvenated aftershock sequence, mainly near Christchurch and the Pegasus Bay offshore region. Most significant were a M 6.0 in June 2011, ~4 km east of the February epicentre, and a sequence of M 5.4-5.9 aftershocks in December 2011 in Pegasus Bay. 12/
The historic Christchurch Cathedral in the city centre before the Christchurch earthquake and after.
Damage to the Cathedral of the Blessed Sacrament (top left), damaged building (top right), and building damage in the central business district (bottom).
Damage to unreinforced masonry and concrete structures was considerable, but timber homes and modern reinforced buildings performed better. Most significant was the almost complete collapse of the Canterbury Television (CTV) and Pyne Gould buildings where most of the fatalities occurred. 11/
Liquefaction area behind the Catholic Basilica and car trapped by liquefaction. Photos are from the GNS Science library archive.
Map showing the distribution of mass movements caused by the Christchurch earthquakes. Photo shows an example of earthquake induced mass movement and the proximity of homes and the top and base of the cliff.
Widespread liquefaction caused extensive damage with ~15 000 homes damaged, more than half beyond repair. Numerous landslides were triggered causing widespread damage, weakened slopes, and at least 5 deaths. 10/
Vertical acceleration waveforms from strong-motion sites showing larger positive accelerations than negative. Many of the negative acceleration troughs are also broader than the narrow positive spikes.
Strong-motion recordings showed a high degree of asymmetry with upward accelerations exceeding downward. This is caused by a free-fall of near-surface material over deeper material during vertical motion, called a βtrampolineβ and βslap-downβ effect. 9/
Kinematic solution showing the slip distribution. Inset shows the vertical projection of the slip distribution with the slip direction indicated by the white vectors, showing energy directed updip towards Christchurch. Red dots are aftershocks, yellow star is the Christchurch epicentre, and black diamonds are strong-motion instruments.
Observed (blue) and modelled (red) displacements at GPS sites and the three fault slip model derived from GPS and InSAR data. The eastern section has oblique reverse/right-lateral faulting and the western section mainly right-lateral faulting.
A kinematic source model showed a high rupture velocity and energy directed towards the city centre. Kinematic and geodetic data are consistent with multiple fault segments, 2 or 3, with both reverse and strike-slip faulting involved. 8/
Map of the Christchurch urban area showing maximum PGA (vertical and horizontal components). Epicentre is shown by the green star.
High peak ground accelerations (PGA) were observed up to 2.2 g vertically and 1.7 g horizontally near the epicentre, and 0.8 g vertical and 0.7 g horizontal in the city centre. These were among the highest recorded worldwide. 7/
In the 5 Β½ months following the Darfield earthquake most aftershocks were focused in the Canterbury Plains, west of Christchurch. Activity also extended east towards Christchurch, notably a cluster on 25-26 Dec 2010 near the city centre. 6/
Seismograph and strong-motion network in the Canterbury region at the time of the Christchurch earthquake. Darfield epicentre is marked by the orange star and Christchurch by the yellow star. Mapped faults are the orange lines and inferred subsurface faults the dashed blue lines. Black triangles are broadband seismometers and inverted magenta triangles are strong-motion accelerometers. Below are focal mechanisms and parameters from the GeoNet regional moment tensor solution, USGS W-phase solution, and Global CMT Project CMT.
The earthquake occurred on an unmapped NE-SW striking fault in the Port Hills area of the outer suburbs where temporary instruments were already installed. Focal mechanisms indicated primarily reverse faulting with a strike-slip component. 5/
Building damage, including collapse of some office buildings, was severe. Liquefaction was widespread, and numerous rockfalls and slope failures caused further damage. This was the deadliest earthquake to occur in New Zealand since the 1931 Hawkes Bay earthquake (Mw 7.4-7.6). 4/
Although much smaller than the Darfield earthquake, the Christchurch earthquake was far more devastating. The epicentre was much closer to Christchurch and occurred at midday on a weekday when the city centre was highly populated (Darfield occurred at 04:35 AM on a Saturday). 3/
The South Island of New Zealand showing the location of the Canterbury region (rectangle) and Christchurch. Mapped active faults and plate boundaries and shown by the black lines. 10 years of M 3+ seismicity prior to the 2010 M 7.1 Darfield is plotted showing the low level of seismicity in the Canterbury region prior to the Darfield earthquake.
15 years ago, 22 February 2011 at 12:51 PM local time, the M 6.2 Christchurch earthquake struck, an aftershock to the M 7.1 Darfield earthquake. The epicentre was ~6 km SE of the city centre and the impact was severe, most notably 185 fatalities. 2/ www.geonet.org.nz/earthquake/3...
A thread for the 15-year anniversary of the 2011 Christchurch earthquake. I wonβt have a chance to post it on the day, so Iβm doing it a couple days early. Note that the work Iβm posting was carried out by many brilliant people. 1/
And you get to live in a great city!
The most widely felt earthquake was a Mw 4.5/ML 5.1 west of Wellington with more than 29 000 felt reports www.geonet.org.nz/earthquake/2.... There was also a Mw 5.0/ML 5.4 with more than 23 000 felt reports www.geonet.org.nz/earthquake/2.... 4/
The largest earthquake was Mw 6.6/ML 6.8 in the Puysegur region, south of the South Island. It was widely felt over the southern South Island and was closely monitored for a tsunami threat. www.geonet.org.nz/earthquake/2.... 3/
Locations of M 4+ earthquakes across New Zealand and the Kermadec region.
Focal mechanisms from regional moment tensor solutions.
More than 440 earthquakes with M 4+, most located in the Kermadec region and south of the South Island, but many scattered across the country. Nearly 190 regional moment tensor solutions with Mw 3.0 β 6.6 and depth 2 β 278 km. 2/
Locations of more than 21 000 earthquakes located across New Zealand and the Kermadec region in 2025 with a wide range of magnitudes and depths.
Histogram of the number of earthquakes and magnitudes with most in the M 1.5 - 2.5 range.
A quick summary of 2025 New Zealand earthquakes. GeoNet located more than 21 000 earthquakes in New Zealand and the Kermadec region. Magnitudes range from -0.3 β 6.8 and depth from 0 (just below the surface) β 750 km. 1/ π§ͺ
The 2010 Darfield earthquake involved the unmapped Greendale fault (half the energy release) and several other unmapped faults which we named. But to my knowledge we never named any of the faults in the 2011 Christchurch earthquake. The main fault was a blind thrust fault on the city outskirts.
On 26 Dec. 2004, an M9.1 quake struck Sumatra, generating a tsunami that killed >220,000 people from >50 countries. A regional tsunami warning system wasn't in place then. There are now more extensive global warning systems, including DART buoys developed by NOAA. π§΅βοΈπ§ͺ www.youtube.com/watch?v=B0Mj...
Yes, subsurface structure, the type of building you're in, what you're doing at the time, how the energy propagates through the ground from the epicentre, will all affect your experience of the shaking, or if you even feel it at all!
A little early morning Boxing Day shake for the lower North Island, New Zealand.
Strong earthquake occurred 10 km south-west of Pongaroa: geonet.org.nz/quakes/2025p...
A non-earthquake post - the annual Christmas turkey smoke is underway.
I'm glad you enjoy the posts! I lived in Victoria for 7 years doing my doctorate and with the Geological Survey of Canada. I thought it would nice to share some seismology/tectonics of New Zealand with the world.
Focal mechanisms from moment tensor solutions for the first year after the Kaikoura earthquake. The mainshock solution is from the USGS as the earthquake was too large to calculate a regional moment tensor solution.
Focal mechanisms were mainly strike-slip or reverse faulting, consistent with shallow crustal faults in the region. The mainshock is shown as reverse faulting, but the entire rupture was much more complex than this. 16/
Seismicity in the Kaikoura region in the year prior to the Kaikoura earthquake.
Aftershocks for the first year following the Kaikoura earthquake. Orange stars are M 6+ aftershocks and the Kaikoura epicentre.
Before the earthquake there was regular seismicity in the region with ~700 earthquakes recorded in the previous year. In the first year post-KaikΕura, more than 18 000 aftershocks were recorded, six with M 6+ (orange stars). 15/
A more far-reaching effect was the triggering of several large slow-slip earthquakes off the east coast of the North Island. East coast slow-slip earthquakes are a regular occurrence; however, several at the same time was unprecedented. 14/
Many buildings were damaged in the Wellington region, some beyond repair, along with docks in the harbour. Roads and railways in the region were significantly damaged affecting transportation for months, and extensive landslides, more than 10 000, occurred throughout the KaikΕura region. 13/
Kaikoura tide gauge (KAIT) showing a maximum amplitude of ~2 metres and peak-to-trough of ~3 metres.
Among the faults that ruptured were several offshore faults which caused a tsunami along the NE coast of the South Island with a run-up of up to 6.9 m. The KaikΕura tide gauge recorded a tsunami with a max amplitude of ~2 m and peak-to-trough of ~3 m. 12/
