article: Nov 2 2007 - Bringing you the "shaky isles"

The GeoNet website home page now features a near real-time shaking intensity map. Within minutes of feeling an earthquake you can see which parts of the country were affected and the impact it's had upon the community.

How the map would have looked after a 30 km deep magnitude 5.5 earthquake near Wellington.

For a number of years the GeoNet project has been bringing you details about the earthquakes you feel: the time, the location and the magnitude. It takes our Duty Officer about 20 minutes to establish these and get them onto the website. In the meantime you've been experiencing the frustration of waiting for these to appear.

Now we can make that wait a bit more interesting with ShakeNZ, our near real-time shaking intensity map of New Zealand. It can't tell you where the earthquake was, but it can tell you how widely and to what extent it has affected the country. And that is important information in the first few minutes after any large, damaging earthquake.

We receive continuous seismic data within seconds from about 100 seismographs throughout New Zealand. If the ground is subject to strong shaking, we can supplement that by data from another network of 200 strong motion instruments. We convert the shaking into the expected Modified Mercalli Intensity and colour-code it on a map of New Zealand.

Data on the map remain current for one hour. You can use the slider to turn the clock back over the previous sixty minutes to see when and where significant shaking first appeared. There will even be occasions when two or more earthquakes occur within an hour, and using the slider will help unscramble the intensity patterns. Please take time to click on the i button for more information and the e.g. button for examples of what you can expect to see.

We are sure that ShakeNZ will help answer that all-important question, "What was that I felt?".