Oklahoma hit by its third-strongest earthquake ever - USGS

OKLAHOMA CITY (REUTERS) - Oklahoma was struck by a magnitude 5.1 earthquake on Saturday morning, the third-strongest quake ever recorded in the state, which has experienced a surge in seismic activity in recent years, the US Geological Survey reported.

The quake at 11.07am local time (1.07am on Sunday, Singapore time) was followed by several aftershocks in the next 90 minutes, including one with a magnitude of 3.9, the USGS said.

The first quake was felt from Kansas City, Missouri, to Dallas, Texas, but no damage or injuries were reported..

Oil fields have boomed in Oklahoma over the past decade thanks to advances in hydraulic fracturing and horizontal drilling, and seismologists have said the state’s frequent earthquakes may be linked to disposal wells that inject saltwater, a natural byproduct of oil and gas work, into deep underground caverns.

Earthquakes in Oklahoma in January led to calls for the governor to make changes to oil and gas drilling regulations.

Saturday’s quake was centered about 153km north-west of Oklahoma City, and at an estimated depth of 7km, the USGS said.

The epicentre is near the East Campbell Gas Field and about 121km west of Cushing, Oklahoma, which is one of the largest oil storage hubs in the world and is known as the Pipeline Crossroads of the World.

Only two previous earthquakes in Oklahoma were stronger than Saturday’s: a magnitude 5.6 quake in 2011 and a 5.5 magnitude quake in 1952, said Robert Williams, a geophysicist with USGS.

USGS initially said that Saturday’s quake was probably the second-biggest in the state’s history but then revised it after reviewing records.

The USGS said it was not known if Saturday’s quake was related to oil and gas production activities.

The state has been recording about two-and-a-half earthquakes a day of a magnitude 3 or greater, a rate 600 times greater than observed before 2008, the Oklahoma Geological Survey said in a report last year.