Archive for ‘New Zealand Historical’

July 23, 2012

Canterbury Series, NZ 2010 to 2012

Probably the longest running and largest numbered earthquake aftershock series recorded in New Zealand.
There have been 4 main strong events, which had their own sub series of aftershocks, these have been named Darfield, Port Hills, Taylors Mistake and New Brighton.
The earthquakes are a consequence of release of accumulated stress on geological faults deep (about 6 – 8 km) in the earth’s crust that have been perturbed by the initial earthquake in September 2010, and the more recent sequences. It is most likely that the current earthquakes were triggered by stress readjustment driven by the February and June 2011 earthquakes.

It is near impossible to isolate each series of aftershocks by location, as many of the later earthquakes (aftershocks) were still on the earlier Faults, so the following data has been sorted by the timeline. Perhaps the series of maps showing the “moderate” main events near the end of this page best shows how the earthquakes progressed west to east.
Data for the main large aftershock maps was downloaded on 16/07/2012, the M5+ smaller maps data was downloaded on 24/07/2012 and the large M5+ map data downloaded on 06/08/2012.

7.1Mw, Darfield (Canterbury), Saturday, September 4 2010 at 4:35 am NZST

Maximum Intensity: MM 9
The magnitude 7.1 earthquake occurred at 4:35 am on September 4 NZST, the epicentre was 40 km west of Christchurch city, and the depth of the quake was at 10 km. The epicentre was close to the town of Darfield. There was no tsunami resulting from this earthquake as it had occurred on land. It was the most damaging earthquake in New Zealand since the Hawke’s Bay earthquake in 1931, but there was no loss of life. It was fortunate the earthquake occurred when the central city streets were deserted, as there would almost certainly have been many deaths and serious injuries had it happened during a busy time of the day.
The mainshock has a reverse faulting mechanism. Most of the aftershocks located near the epicentre have strike-slip mechanisms.

GCMT MTS

GCMT MTS DARFIELD 7.0MW 15-07-2009

Global Displacement Wavefields Graph

Understanding Global Displacement Wavefields Graphs
Darfield 7.0Mw GDWclick on image for full size version, opens in new tab/window
In the 171 day period Sept 3 UTC until the next strong damaging quake in the series on 21 February UTC, Geonet recorded 4240 aftershocks;
24 aftershocks of between 5.022 and 5.867ML
154 aftershocks of between 4.0 and 4.999ML
1139 aftershocks of between 3.0 and 3.998ML
2908 aftershocks of between 2.001 and 2.999ML
14 aftershocks of between 1.53 and 1.984ML
The main 7.1 shock released 673,609.687 TTNT and the other aftershocks released 62,035.387 TTNT for a total of 735,645.074 TTNT, or equal to a single 7.125 magnitude event.
the map below shows the locations of these, colour coded by magnitude, clicking on the “view larger map” text below the map will open the file in Google Maps with a decending list by time from the main shock on the left hand side.

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6.343ML, Port Hills (Canterbury), Tuesday, February 22 2011 at 12:51 pm NZDT

Maximum Intensity: MM 9
On Tuesday 22 February 2011 at 12.51 p.m. NZDT Christchurch was badly damaged by a magnitude 6.343ML
earthquake, which killed 185 people and injured several thousand. The earthquake epicentre was near Lyttelton, just 10 kilometres south-east of Christchurch’s central business district. The earthquake occurred more than five months after the 4 September 2010 earthquake, but is considered to be an aftershock of the earlier quake.

The earthquake was caused by the rupture of a 15-kilometre-long fault along the southern edge of the city, from Cashmere to the Avon-Heathcote estuary. The fault slopes southward beneath the Port Hills and didn’t break the surface.
The 6.343 mainshock and a couple of other events in the aftershock sequence are reverse (thrust) faulting mechanisms. Most of the remaining mechanisms are strike-slip.

GCMT MTS

GCMT MTS PORT HILLS 6.1 21-02-2011

In the 112 day period February 21 UTC until the next strong damaging quake in the series on 13 June UTC, Geonet recorded a total of 3654 aftershocks;
8 aftershocks of between 5.042 and 5.906ML
92 aftershocks between 4.004 and 4.982ML
798 aftershocks between 3.0 and 3.993ML
2599 aftershocks between 2.0 and 2.999ML
and 161 aftershocks between 1.06 and 1.99ML
The main 6.343 shock released 49,306.971 TTNT and the other aftershocks released 45,433.935 TTNT for a total of 94,740.906 TTNT, or equal to a single 6.532 magnitude event.
the map below shows the locations of these, colour coded by magnitude, clicking on the “view larger map” text below the map will open the file in Google Maps, with a descending order list by time from the main shock, on the left hand side.

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6.411ML (6.0Mw),Taylors Mistake (Canterbury), Monday, June 13 2011 at 2:20 pm NZST

On June 13, another strong 6.411 ML magnitude quake located a few kilometres east of the February 22 event caused serious damage in Canterbury and was felt from Southland to Taranaki. There were no casualties and damage was not as severe as that caused by the February 22 event.
Further analysis of the waveforms show that the focal mechanism for the June 13 M6.3 earthquake is a strike-slip mechanism and is different from the February 22 M6.3 earthquake which had a reverse (thrust) faulting mechanism.

GCMT MTS

GCMT MTS TAYLORS MISTAKE 6.0 13-06-2011

Global Displacement Wavefields Graph

Understanding Global Displacement Wavefields Graphs
TAYLORS MISTAKE 6.0 GDWclick on image for full size version, opens in new tab/window

In the 193 day period June 13 UTC until the next strong damaging quake in the series on 23 December UTC, Geonet recorded a total of 1,879 aftershocks;
8 aftershocks between 5.147 and 5.85ML
70 aftershocks between 4.003 and 4.943ML
536 aftershocks between 3.001 and 3.998ML
1245 aftershocks between 2.02 and 2.998ML
19 aftershocks between 1.407 and 1.994ML
The main 6.411 shock released 62,360.318 TTNT and the other aftershocks released 28,550.977 TTNT for a total of 90, 911.295 TTNT or equal to a single 7.186 magnitude event.
the map below shows the locations of these, colour coded by magnitude, clicking on the “view larger map” text below the map will open the file in Google Maps, with a descending order list by time from the main shock, on the left hand side.

6.0ML, New Brighton (Canterbury), December 23 at 3:18pm 2011 NZDT

On December 23 at 3:18pm NZST, a magnitude 6.0 earthquake centred offshore from New Brighton at a depth of 5 km caused moderate damage in Canterbury and was felt from Southland to Taranaki. It was preceded by a 5.8 at 1:58pm and a 5.3 at 2:06pm.
As with other earthquakes of this shaking intensity, liquefaction occurred in the eastern suburbs of Christchurch. This new sequence of earthquakes is further east again from the June 13 set of quakes. Being further from people, and coupled with the slightly lower magnitudes of the biggest shakes, the effects have been less damaging to structures than on previous occasions.

GCMT MTS

GCMT MTS NEW BRIGHTON 5-8MW 23-12-2011

In the 196 day period 23 December 2011 UTC until 6 July 2012 UTC, Geonet recorded a total of 1,304 aftershocks;
7 aftershocks between 5.05 and 5.478ML
64 aftershocks between 4.001 and 4.955ML
473 aftershocks between 3.0 and 3.993ML
751 aftershocks between 2.022 and 2.999ML
8 aftershocks between 1.775 and 1.951ML
The main 6.0 shock released 15,080.242 TTNT and the other aftershocks released 13,154.546 TTNT for a total of 28,234.788 TTNT, or equal to a single 6.184 magnitude event.
the map below shows the locations of these, colour coded by magnitude, clicking on the “view larger map” text below the map will open the file in Google Maps, with a descending order list by time from the main shock, on the left hand side.

Main Events

The maps below show the “moderate” sized aftershocks of each part of the series, magnitude 5 and up.

Darfield

Port Hills

Taylors Mistake

New Brighton

Mag 5+

The map below shows the earthquakes above magnitude 5.0 in the Canterbury series, colour coded as follows;
Darfield – orange
Port Hills – grey
Taylors Mistake – green
New Brighton – aqua
This map has been updated with data as at 6/08/2012, several M5’s have been downgraded below 5.0 and several New Brighton aftershocks have been relocated, so may not match the individual preliminary data maps above.

All Quakes

The map below shows the complete Canterbury series, colour coded as follows;
Darfield – orange
Port Hills – grey
Taylors Mistake – green
New Brighton – aqua
(best viewed by clicking “view larger map” as there are too many icons for all the tiles to load in the i-frame.)


The map below shows the entire series of 11,092 aftershocks colour coded by magnitude

Remarks

I haven’t bothered putting the location addresses on the popup tags, except on the Mag5+ maps, as this would make the files too big to load smoothly for most internet connections.
If all the icons don’t show try refreshing the page with your browser, there are over 33,000 icons shown in the maps. Alternatively click the “view larger map” text below each map which will open the file in Google Maps. Right clicking “view larger map” text and selecting “Open Link in New Tab” or “Open Link in New Window” will keep this page open saving time reloading if you click “back” when you are finished with the Google Map.
These are all issues with ISP speed, what type of connection you have and what time of day it is ( if the Internet is busy), the maps and files and data ARE there.
The search area covered by the maps is a box West 171.81584, South -43.93907, East 173.17656, North -42.96192.
The period covered is the 672 days (96 weeks) September 3rd 2010 to July 6th 2012.
Acknowledgements to Te Ara, GeoNet, GNS Science and GPS Visualiser