HOUSTON, Jan. 31 (Xinhua) -- A 4.5-magnitude earthquake hit the U.S. state of Oklahoma on Monday, local media reported.
The U.S. Geological Survey said it recorded the earthquake around 11:10 a.m. local time (1910 GMT). The epicenter is about 4.5 miles (7.2 km) northwest of Medford, a city with a population of about 1,000 in northern Oklahoma.
Following the earthquake, the Oklahoma Corporation Commission shut down three oil and gas wastewater disposal wells within 6 miles (9.6 km) of the epicenter.
State seismologist Jake Walter said in north-central Oklahoma, wastewater from hydro-carbon extractions is injected deep underground which can unintentionally reactivate faults and cause earthquakes.
"This is an area in Oklahoma where in the past we've attributed a lot of the seismicity to wastewater disposal practices," Walter said.
Authorities are investigating the cause of the quake. ■
