Ohio earthquake was not a natural event, expert says CLEVELAND (Reuters) - A 4.0 magnitude earthquake in Ohio on New Year's Eve did not occur naturally and may have been caused by high-pressure liquid injection related to oil and gas exploration and production, an expert hired by the state of Ohio said on Tuesday. Ohio's Department of Natural Resources on Sunday suspended operations at five deep well sites in Youngstown, Ohio, where the injection of water was taking place, while they evaluate seismological data from a rare quake in the area. The wells are about 9,000 feet deep and are used to dispose of water from oil and gas wells. The process is related to fracking, the controversial injection of chemical-laced water and sand into rock to release oil and gas. Critics say that the high pressure injection of the liquid causes seismic activity. Won-Young Kim, a research professor of Seismology Geology and Tectonophysics at the Lamont-Doherty Earth Observatory at Columbia University, told Reuters in an interview on Tuesday that circumstantial evidence suggests a link between the earthquake and the high-pressure well activity. "We know the depth (of the quake on Saturday) is two miles and that is different from a natural earthquake," said Kim, who is advising the state of Ohio. Data collected from four seismographs set up in November in the area confirm a connection between the quakes and water pressure at the well, Kim said. "There is circumstantial evidence to connect the two -- in the past we didn't have earthquakes in the area and the proximity in the time and space of the earthquakes matches operations at the well," he said. A spokesman for Ohio Republican Gov. John Kasich, a strong supporter of oil and gas exploration in the state, said Ohio could announce a preliminary decision whether to continue the suspension of the wells as early as Wednesday. The state was already looking into the cause of earlier seismic activity from 10 previous earthquakes, beginning in March, 2011. According to Kim, this is not the first time Ohio tremors have been linked to human activities. "We have several examples of earthquakes from deep well disposal in the past," Kim said. A quake of 4.2 magnitude in Ashtabula, Ohio, on January 26, 2001, was believed to be due to deep-well injection, he said. And in 1987 there was an incident with a correlation to high pressure deep well injection, he said. There are 177 so-called "class two" deep wells in Ohio, according to Tom Stewart, executive vice president of Ohio Oil and Gas Association. They all operate under federal guidelines spelled out by the Clean Water Act. There is no evidence that the wells in Youngstown were operating at higher pressures than allowed, Stewart said. "We haven't seen anything from anyone at (the state agency) that would lead us to believe that the well was not operating properly," he said. Kim said that even though the wells have stopped pumping water into the rock, the area might not have experienced its last earthquake. It could take a couple of years for the earthquakes to go away. The migration of the fluid injected into the rock takes a long time to leave," Kim said. Ohio's Democratic Senator, Sherrod Brown, said the quick response by the state shows it is a serious issue. "There are things we need to know about drilling and earthquakes," Brown told Reuters on Tuesday. Brown said he supports new energy exploration that brings jobs to the state but has questions about how companies will handle fracking and wastewater disposal. "They have got to answer the question of what they are going to do with the waste just like nuclear power," Brown said. Editing by Greg McCune and Jim Marshall