Monday, January 30, 2012

Drums - not the musical kind!

Now i did a blog last year on how to read the earthquake drums on our website (you can read it here) but we have had quite a few queries recently about the scale and things showing up on various drums - so i thought I'd have another look!

Some key points:
- The drums have scales (top right)
- The scales automatically change depending on the current activity (we don't change them to 'hide activity', if they didn't change you wouldn't be able to see anything!
- The drums often show noise -wind, stock, traffic etc. as the instruments are very sensitive (although we do try and put them in quiet areas).
- If you see an event on the drum and its not on the 'recent quakes' page, it probably wasn't felt.
- There are several different kinds of seismometer in use, so you cannot directly compare them.

And we don't use these drum images to locate the earthquakes, they are just there for you to look at!

The drums on the left, are in the 'Canterbury Quakes' tab here, they will have different scales and you can't directly compare quakes.

 Under our earthquake tab you can find Quake Drums, these show instruments from all over NZ. The picture on the right is from December 23 2011, as you can see it clearly shows how widely events were picked up across the country.

Edgecumbe 1987 event on  Hicks Bay drum

Here is an example of what the earthquakes looked like on the old drums. This picture (left) is off a drum in Hicks Bay and shows the March 1987 Edgecumbe earthquake and aftershocks, as you can see - its a mess!

Friday, January 20, 2012

Earthquakes - A competitive sport?

New Zealanders are well know for their competitive nature when it comes to sport, which is great as we are pretty good at it! But it has come of a bit of a surprise lately at the 'mine was bigger than yours' mentality people seem to be getting regarding earthquakes.

I'm sure most people remember the small earthquake in Auckland last year, yes everyone had a bit of a laugh and there were plenty of 'oh no my latte has fallen over' jokes! But in all seriousness Auckland does not get a large amount of felt earthquakes, and living on top of over 50 volcanoes we should let them worry a bit when they do feel shaking - as this is often a precursor to eruptive activity!
Fence crossing the Hope Fault - it was straight until 1888!
Back to the rest of NZ - at GeoNet we record over 15000 earthquakes every year - luckily most are not felt!  We do however, get a few 'biggies' every now and then, here is a wee jaunt through our earthquake history::

North Canterbury 1888 ~ 7.1
This earthquake had a shaking intensity of MM9, it occurred on September 1st 1888. As you can see in the picture on the right - it created a fair amount of land movement, there were also numerous landslides, liquefaction and broken chimneys.

Wairarapa 1855 ~ 8.2
With a maximum intensity of MM10 this earthquake was felt all over NZ,  around 7-9 people were killed and 5 injured. This is also the famous event that uplifted many areas in Wellington including: the Basin Reserve (sports ground) which used to be under water, as well as the harbor ( Lampton quay used to be the waterline), and even the land our airport is on.
Fault Scarp in Buller Gorge.

Buller/Murchison 1929 ~ 7.8
On June 17 this large event occurred, luckily in an area sparsely populated, though it still killed 15 people and injured 1. The quake had an max intensity of MM10 and was felt all over NZ, and damaged many roads, bridges and buildings. The quake also created 38 new lakes after slips blocked rivers (21 still exist today). If you look at the picture on the left, the wee man on the bike is on the other side of the road, now 4m higher than the rest!

Severely damaged road - Hawkes Bay

Hawke's Bay 1931 ~ 7.8
This earthquake caused the largest loss of life and most damage of any quake in NZ history (prior to the Canterbury events) The MM10 event killed 256 people and injured thousands, the earthquake was followed by devastating fires that were unable to be stopped as the water mains were broken. This event also changed the coastline and deformed much land in the area.

Rift in a paddock - Edgecumbe.

Edgecumbe 1987 ~ 6.5
This event is  well remembered in NZ history, it occurred on March 2nd and had a max shaking intensity of MM9. 25 people were injured, and although many buildings collapsed - fortunately they had been evacuated following a large foreshock.

Dusky Sound 2009 ~ 7.8
This event is the largest in New Zealand since Marlborough 1848 and Buller 1929. With a max. of MM7 it triggered numerous landslides and even a small tsunami.

And of course we have the 2011 Christchurch ~6.3 earthquake, with MM9, 181 people killed and 164 seriously injured. For more info on the canterbury events, see our pages here

Although the size of these earthquakes vary, it is interesting to see how the maximum shaking intensity(MMI) is pretty similar. Looking at the maximum shaking intensity is a much better indicator of how earthquakes effect people and the environment, rather than just the magnitude. You can read more on the MMI scale here

Now this is just a few of the major historic earthquakes in NZ, for  more info on these events and others go to our 'historic quakes' page here

And back to my original point(s)
*All of New Zealand gets earthquakes, both small and damaging. So stick together - offer help and words of support, rather than tell people to 'get over it' as it was 'only a baby one'. We are only a small country, stick together!
* and remember to look at the MM shaking intensity of an earthquake before you judge on its size, it may have been small but strongly/widely felt!

Tuesday, January 10, 2012

2012 - A taste of things to come!

As most of you know, we announced a while back that we were working on some exciting new things for the website, these will be out for user testing in a few months, in the meantime here is a sneak peak...

Introducing the GeoNet smart-phone App... 

It has some really cool features and our team of geeks are adding new things all the time!  As you can see on the pic to the right ->
it is showing earthquakes from as little as '9 minutes ago' - so yes that means you can find out (roughly) how big etc an earthquake was within a few minutes. It generally takes between 2-5minutes for a preliminary result and as more data becomes available the figures can change slightly (its similar to the system USGS use at the moment).

This pic on the left <--  shows some older events, but also the color coding, the higher the intensity the darker shade of red the event will be. So white = small, light red = felt, deep red = the big ones!

You can also click on each event for more info (links to the www), map, refresh the event and share it.

There is a map button so you can see all of the recently located events and click on each for more info, and you see have 'all' events or select  'my' which allows you to choose events of a certain intensity, from a certain place and even (using your GPS or wireless) quakes near your current location.

So i hope you all enjoy this sneak peak, by the time it is released it will probably have even more neat functions!

NB: at the moment it will just be Android, but we do want / and will be working on an 'i' friendly App.