christchuch new zealand earthquake 6.3
Magnitude 5.6 at 1:00 pm*
Magnitude 6.3 at 2:20 pm*

Peak Ground Accelerations for the magnitude 5.6 earthquake.
The two diagrams to the right show Peak Ground Accelerations for the earthquakes.

The diagram at the left shows both earthquakes as recorded at the McQueens Valley (MQZ) seismograph.

* The Richter magnitudes for these earthquakes were revised to 5.6 and 6.3 upon receipt of further data and analysis.

Our initial estimates are based on the data received at the time of website update, generally 15 minutes after the earthquake. The magnitude 6.3 earthquake was detected on over 250 New Zealand seismographs, and not all of the necessary waveforms used for working out the most accurate Richter magnitude were present then. Rather than wait any longer, the website is updated with the best estimate we can make at that time.