Tuesday, May 31, 2011

Exploring the Website - ChCh Aftershock Forecasts

As its been in the news a bit today i thought we could look at the aftershock forecast map for Canterbury.

In the Canterbury Quakes section of our website (here) there is a tab called aftershocks.

Aftershock Forecast Map
Here you will be able to see an aftershock forecast map. This map is updated hourly, covers a 24-hour period and shows the probability of experiencing slight damage or MM6 shaking. (MMI Scale)

 Probabilities are calculated using a background of geological and earthquake information and all of the earthquakes that GeoNet records are looked at. For each event the probability that it will be followed by an earthquake large enough to cause strong shaking is calculated from the known behavior of aftershocks. The shaking that would be produced by such an earthquake is then predicted from the known relations between earthquake size and shaking patterns. The likelihood of that shaking is then added to the background probability on the map.

 More detailed info here

Below the map are a few tables:

The top show the number of afershocks that have occured (vs how many were expected) and then there is a
table that shows a one month forecast of expected aftershocks of magnitude 4.0-4.9, and 5.0 +.

Dr Matt Gerstenberger produces these aftershock probabilities for one month ahead and they cover the entire aftershock zone, which extends from Sheffield in the west to Rangiora in the north to Lincoln in the south, and right across Banks Peninsula.

Forecast Table

NB: We are currently looking into extending these forecasts (covering a few months, rather than just one) on our website, shortly.
These longer range forecasts are where the figures in todays news came from. And as far as today's news, the figures for Christchurch metropolitan area are roughly one quarter of the figures given to CERA. So 23% probability for Canterbury becomes 6% probability for Christchurch.

In rough terms, it means the quake probability for Christchurch has become similar to many other parts of NZ such as Wellington, Hawke's Bay, Wanganui, and Poverty Bay where quakes are more frequent. The initial driver of this increased activity was the September M7.1 quake. It started an aftershock sequence that will continue for many months, these aftershocks will gradually get less frequent, but there is still a small chance of a larger aftershock for a while yet.

And....  Its not saying there will be another large event, its saying what the probabilities of one occurring are - there is a difference, and they may not happen. All you can do is be prepared, it is the earth we are talking about here!

Friday, May 20, 2011

Friday - The end of the world is nigh...

This year has really been the year of 'predictions'!  End of the world, large earthquakes, large tsunami etc. have all come at us. (we won't even go into the Moon!) The most recent is the May 21st where .. well its confusing but something to do with rapture and doomsday and then the 'end of days'.  But don't forget we also have the big world end on December 2012 (tis very confusing keeping up with them all)!

So in light of this i thought the above song would fit in great for this weekend - REM 'The end of the world'.

PS - No one can predict earthquakes, tsunami, nor the end of the world!!  So have a great weekend!

Saturday, May 7, 2011

Network - Exploring our website data - Part three

Ever wondered where all of our instruments are located around NZ?  Its all on our website here!

ROPS - Strong-Motion site at Rotorua Police Station

*  DELTA - is our database that has detailed information about each of our sites (tsunami, seismic and strong-motion) Including maps, coordinates and photos of the instruments.

You can search by name, location or use the map. 


Network Maps - There are two options here, the first page is an interactive map that allows you to choose what you want to see (different networks, operational, under construction etc.) and zoom around on the map on NZ.

The second option is to view the static network maps (the tab is up on the left). Here you can see full maps of NZ showing our seismograph, cGPS, strong-motion and tsunami sites.  Underneath is a map of NZ where you can click on regions and see a more detailed view in each area.   All of these maps are automatically updated daily.
ScreenShot of the interactive map.

Auckland Region Network Map