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!