Deep sea oil drilling raises concern as experts predict another big jolt in next 7 days, New Zealand

Deep sea oil drilling raises concern as experts predict another big jolt in next 7 days, New Zealand

According to Geonet's computer models another large shake on both sides of Cook Strait, New Zealand, is highly likely over the next week. The chance for an earthquake of magnitude 5.0 - 5.9 in next 24 hours is 30%, in next 7 days 76%, and in next 12 months more than 99%. Chance for an earthquake of magnitude 6.0 and above in next 24 hours is 3.5%, in next 7 days 14%, and in next 12 months 46%.

Seismologists warn people to be vigilant and expect another large shake. Since M6.6 on August 16 - August 19th, there had been 932 earthquakes with magnitudes ranging from 2.0 - 6.9, and a total of 2582 earthquakes with the same magnitude range since this sequence started on July 19, 2013 with M5.7 earthquake. This makes a total of 3514 earthquakes in 30 days.

Map showing the region for which earthquake probabilities have been calculated, indicated by the white box. Source: GNS Science - GEONET

The table below summarizes the expected probabilities of further earthquakes anywhere in the central New Zealand region shown on the accompanying map (above). This is an increase over and above what is normal seismicity for this part of New Zealand. The figures are based on the behavior 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 M≥6

 

Average
number

Range

Probability

Average
number
Range

Probability

Average
number
Range

Probability

Within 24 hours 3.8 1 - 8 98% 0.35 0 - 2 30% 0.04 0 - 1 3.5%

Within 7 days

15

8 - 23

>99%

1.4 0 - 4

76%

0.15 0 - 1

14%

Within 1 year

63

48 - 79

>99%

5.9 2 - 11

>99%

0.61 0 - 2

46%*

Issued at 12:00pm (NZT), Monday, August 19, 2013. Source: GEONET

*On August 19, the probability of a magnitude 6 or above in the next year in this region is approximately seven times greater than what we would normally expect from our National Seismic Hazard model due to this sequence. As the aftershock rates decrease, this difference will decrease as well.

Deep sea oil drilling concerns

After the M6.5 earthquake on July 21, 2013, and hundreds of aftershocks that followed, environmental group Oil Free Wellington said the recent series of earthquakes should be enough to stop plans for deep sea oil drilling in the Pegasus Basin which lies south east of Wellington and the Cook Strait.

Their spokesperson Jessie Dennis said there are massive risks when drilling at unproven depths in an area with obvious seismic activity. Calling Wellingtonians to join together, she said there is a chance for an oil spill caused by seismic activity should the drilling go ahead.

Environmental group Greenpeace is also trying to stop deep sea oil drilling plans. The catastrophic disaster in the Gulf of Mexico showed us all the terrible risks of deep sea drilling. We do not want to take that risk with the coastlines and oceans on which we depend for our economy, our culture and our way of life... ​We are strong willed, determined and persistent and we will defend our unspoiled waters by all peaceful means available to us...

On Sunday, August 18th, TVNZ series Marae Investigates brought a show on Kaikoura, an internationally recognized eco-tourism town fighting for their survival from oil and gas exploration:

Featured image: GNS SCIENCE - GEONET

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