Preliminary reports on Canterbury Quake Live stated that the 5.1 aftershock in Christchurch ranks as the 19th equal largest shake since the 7.1 earthquake on September 4th 2010. Although it was centred 38 kilometers from the CBD, it was widely felt across the city.
Aftershock Wakens Christchurch
The 5.1 aftershock on the 22nd July appears to be related to the Greendale fault that caused the September earthquake in Christchurch. It was pinpointed as being in Dunsandel at a depth of just under 12 kilometers.
The amount of energy released was 646 tons and it measured VI on the Mercalli Scale. This defines the movement as follows: 'Felt by everyone. Difficult to stand. Some heavy furniture moved, some plaster falls. Chimneys may be slightly damaged.' Early reports stated that it was also felt in Ashburton and Hokitika.
Comments on Facebook
Within minutes of the shake, people were commenting on Facebook, describing the motion in the area and their feelings about the shake which was the biggest one since a 5.4 on the 21st June 2011.
Some of the comments included;
- ‘Morning South Island! Do you think we can go back to sleep now, no didn't think so! Heart was fluttering again after a night of nightmares then that to wake me up.’
- ‘Woke up the entire family from a deep sleep here in Rolleston!’
- ‘Was a sway one so probably came out the city (we get jolted and shaken if they're close to us). Hope everyone's OK down Chch way!’
- ‘Weird slow shaking in Phillipstown. Once again doesn't she know it is rude to wake me up early on my day off!’ ‘All the utensils above the oven were swinging big time.’
- ‘That was a very long wobble. Yuck yuck yuck. Thought it was going to keep going and get bigger. First one the cockatiels have reacted to for a while in the dark. That's enough of that thank you MN!’ ‘Wow that was big Here in Dunsandel. Thanks MN I have 4 kids in my bed, hope everyone's ok.’
- ‘Set off the alarm next door and gave our bed a good shake.’
Seismologists Warned Christchurch Aftershocks not Over Yet
The aftershock forecast map on Geonet warned that up to two more aftershocks of over 5.0 could be expected between July 13 and August 12 2011. In addition to this, 1 to 10 shocks between 4.0 and 4.9 could also be expected. An estimated average of five is forecast for this period. The probability of an earthquake measuring 6.0 or above currently stands at 25 percent.
While aftershocks are expected to continue for many months, people still react in alarm when a large shake strikes. However Cantabrians are known for their resilience and in spite of the shaking ground, life continues as they pick up the pieces and continue with the process of repairing their broken city.
Debbie Roome - Debbie Roome is an award-winning freelance writer, journalist and novelist with over 25 years experience.
