Earthquakes: How Much Do You Know About the Aftershocks in Christchurch?

The media normally reports only the major earthquakes that occur around the world, even though there are dozens each day, many of which are insignificant and cause no damage.

The earthquake that struck Christchurch in New Zealand on Wednesday 22^nd February 2011 however was just one of a large number of aftershocks that had hit the area since a large earthquake on 4^th September 2010.

The main earthquake, which had a magnitude of 7.1, did far less damage than the big aftershock on 22^nd February, and for two reasons. Firstly, the depth was greater at 10km, and the epicenter was 40km west of Christchurch. Secondly, it occurred at 4:35am, when most people were in bed and sleeping.

The aftershock that hit Christchurch on 22^nd February 2011 was by comparison only 6.3 in magnitude, but was much shallower and the epicenter was only 10km southeast of the city.

The effect of that shock, like all the other shallow aftershocks, had the effect of liquefying the ground, rather like shaking a bowl of jelly. It also occurred shortly after midday, when people were at work, or having lunch, and the streets and office buildings were crowded.

Having seen all about the horrific earthquake in Christchurch, aside from knowing that it was an aftershock, do you have any idea how many aftershocks there have been in the Christchurch area since the big earthquake on 4^th September 2010?

How many aftershocks do you think there have been?

100? 200? 500?

How about more than 5,100 aftershocks, many of which were close to the city, and also at a shallow depth.

That is more than 5,100 significant tremors in 5 months. Assuming that they were all spread evenly over that period of time, that's roughly 1,000 a month, or 30 a day, certainly more than 1 every hour.

I don't know about you, but I would certainly have been very concerned to have been living in the Christchurch area, and with hindsight, I think a lot more people probably now wish that they had left sooner.

5,100 however is still just a number, and numbers are hard to visualize. Paul Nicholls of the University of Canterbury's Digital Media Group has put together a time-lapse map of the earthquakes and tremors that have taken place since the 7.1 earthquake on 4^th September 2010, which you can see HERE .

It's quite an amazing plot, especially if you look at the number of aftershocks around the 22^nd February 2011. There were 65 aftershocks on that day, including the one that caused all the damage, 79 aftershocks on the 23^rd February, and 70 on the 24^th February.

I think that only those who have been in a situation like this can fully understand what it is like to experience the earth shaking below your feet more or less constantly.

I think you will agree with me though, that putting statistics like this into a time lapse image, really paints a far more impressive picture of what was happening in the Christchurch area over the last few months.

I can just see those of you who live in the Los Angeles area or any other zone that is prone to earthquake activity, Googling to see if there are any time lapse maps available.

Sources:

Christchurch Quake Map

New Zealand Herald

See Also:

Should We Be Concerned About Increased Major Earthquakes Around The World