The U.S. Geological Survey upgraded Saturday's earthquake near Pawnee to a magnitude 5.8, the largest in state history.
The U.S. Geological Survey upgraded the official magnitude of Saturday's earthquake near Pawnee to a magnitude 5.8, making the tremblor Oklahoma’s largest recorded to date.
According to a Wednesday news release, the magnitude revision was based on further in-depth analysis of seismic recordings. Saturday's quake was previously estimated to be a magnitude 5.6.
The USGS said changes in estimated magnitude for an earthquake are common immediately following the shake-up, as more data are analyzed in greater detail than is possible in the first minutes after the earthquake occurs.
Additionally, the USGS also upgraded the official magnitude of the Nov. 6, 2011 tremor near Prague from a magnitude 5.6 to a 5.7. The USGS said questions were raised about the size-relationship between the two quakes prompted the agency to re-evaluate previous estimates.
“USGS analyses indicate that the two earthquakes are very similar in size - to within typically-cited uncertainties of 0.1 magnitude units,” USGS research geophysicist Gavin Hayes said. “However, the 2016 Pawnee event is slightly larger than the Prague earthquake in 2011."
The USGS said magnitude estimates can vary for a variety of reasons, including differences in methods used to compute magnitude, differences in data used, uncertainties in that data, differences in how that data is processed, and differences in assumptions about the Earth structure through which seismic waves travel.