Jan 13 (Reuters) - Operations remained halted for a second day on Wednesday at a remote Repsol Oil and Gas site in the Canadian province of Alberta as regulators investigated the cause of the area's largest earthquake in more than a year.
Repsol, a unit of Spanish energy company Repsol S.A. said it was conducting hydraulic fracturing at the site at time of the earthquake, which occurred on Tuesday morning. It registered magnitude 4.8, according to the Alberta Energy Regulator.
Repsol operations "will remain suspended until we have approved their plans to resume operations without inducing further seismicity," said Carrie Rosa, a spokeswoman for the regulator.
Rosa said she did not know how long the investigation would take, adding it was too early to say if the quake was caused by fracking, which involves injecting water, sand and chemicals deep underground to break up rock formations.
Many people have associated fracking with earthquakes. But the U.S. Geological Survey (USGS) said last year that the actual fracking process is only occasionally the direct cause of felt earthquakes. (on.doi.gov/1KGiLzy)
The earthquake occurred 18 km (11 miles) north of the town of Fox Creek in northwestern Alberta, a preliminary USGS report said. No injuries or damage was reported.
A Repsol spokeswoman said the company had nothing to add to a Tuesday statement that confirmed the quake and said it had been fracking at the site at the time. Repsol, whose site is about 30 km (19 miles) west of Fox Creek, immediately shut down operations, it said.
The quake was the second time in less than a year that the area has experienced an earthquake with a magnitude of more than 4.0, the level at which the regulator requires operations to be halted pending further investigation, Rosa said.
On June 13, 2015 Chevron Canada, a unit of Chevron Corp, shut down operations at its site near Fox Creek, where it had been fracking, after an earthquake measuring 4.3, according to the regulator's database.
"Chevron's operations at the site near Fox Creek were not affected by the earthquake (on Tuesday) and were up and running," spokesman Leif Sollid said.
There were more than 300 seismic events in Alberta, Canada's main oil-producing province, last year, Rosa said. (Reporting by Nicole Mordant in Vancouver; Editing by Frances Kerry)