Following in the steps of Japan’s Meteorological Agency, the U.S. Geological Survey have agreed in upgrading the shattering earthquake that hit Japan on March 11 to a magnitude 9. This means that the earthquake was approximately 1.5 times stronger than originally thought.
According to the USGS, “this magnitude places the earthquake as the fourth largest in the world since 1900 and the largest in Japan since modern instrumental recordings began 130 years ago.”
From the USGS:
The USGS often updates an earthquake’s magnitude following the event. Updates occur as more data become available and more time-intensive analysis is performed. There are many methods of calculating the energy release and magnitude of an earthquake. Some methods give approximate values within minutes of the earthquake, and others require more complete data sets and extensive analysis. Due to inherent uncertainties in the modeling of energy and magnitude, the results from different agencies often vary slightly. These magnitude discrepancies arise from the use of different data and techniques.