The Cook Strait earthquake sequence is generating hundreds of aftershocks, although most of them are not felt. What are the numbers so far?
What are the probabilities of future significant earthquakes?
The table below summarises the expected probabilities of further earthquakes anywhere in the central New Zealand region shown on the accompanying map. This is an increase over and above what is normal seismicity for this part of New Zealand. The figures are based on the behaviour of aftershock sequences worldwide and the specific knowledge that scientists have of the Cook Strait sequence so far. The figures are generated from computer models that are updated as the sequence continues. It shows that as time passes these probabilities become smaller, but any further significant earthquakes that do occur will cause these probabilities to change. The magnitude categories illustrate clearly how the probability falls away as magnitude increases.
| M4.0-4.9 | M5.0-5.9 | M6.0-6.9 | M ≥7.0 | ||||||||
Average | Range* | Probability of | Average number | Range* | Probability of | Average number | Range* | Probability of | Average | Range* | Probability of | |
Within 30 days | 1 | 0 - 4 | 75% | 0.1 | 0 - 1 | 12% | 0.01 | 0 - 1 | 1% | 0.001 | 0 - 1 | <1% |
Within 1 year | 11 | 5 - 18 | >99% | 1 | 0 - 3 | 65% | 0.1 | 0 - 1 | 9% | 0.01 | 0 - 1 | 1% |
Issued on 1 June 2014 for the coming month. * 95% confidence bounds. |
What are the ten largest earthquakes so far?
Magnitude | Depth (km) | Date |
6.6 | 8 | 2013-08-16 14:31 |
6.5 | 13 | 2013-07-21 17:09 |
6.0 | 14 | 2013-08-16 17:31 |
5.8 | 20 | 2013-07-21 07:17 |
5.7 | 17 | 2013-07-19 09:06 |
5.6 | 19 | 2013-08-16 15:51 |
5.5 | 8 | 2013-08-16 15:09 |
5.5 | 20 | 2013-08-16 18:55 |
5.5 | 20 | 2013-08-17 20:58 |
5.4 | 9 | 2013-08-16 14:37 |
This table was last confirmed on 6 August 2014 AM |
How many have there been?
Numbers of Cook Strait region earthquakes | |||
Magnitude range | 7 am, 19 July 2013 to 2:30 pm, 16 August 2013 | 2:30 pm, 16 August 2013 to 11:40 am, 6 August 2014 | Total |
---|---|---|---|
6.0 - 6.9 | 1 | 2 | 3 |
5.0 - 5.9 | 6 | 15 | 21 |
4.0 - 4.9* | 73 | 74 | 147 |
3.0 - 3.9* | 450 | 460 | 910 |
2.0 - 2.9* | 2115 | 3515 | 5630 |
TOTAL | 2645 | 4066 | 6711 |
* Due to the complexity of the bigger earthquakes, numbers of these smaller earthquakes will be underestimated | |||
This table was last updated on 6 August 2014 AM |