The village of Anna in Shelby County once had seismic distinction.

A map of U.S. seismic risk created in the 1960s showed a series of concentric circles landing atop the western Ohio town, making it the most recognizable region of earthquake risk in the state.

In eastern Ohio, nothing. From the look of the map, things were quiet there. Nothing shook. Nothing rumbled.

If that map were drawn today, it might look quite different. This year, northeast Ohio had 13 small earthquakes, all centered near Lake County, many in Lake Erie. Meanwhile, western Ohio has been relatively quiet, with only two small earthquakes, both in Lima.

Has something changed about the state's geology?

Probably not, said Mike Hansen, director of the Ohio Seismic Network.

"A lot of these quakes that we're seeing today, if we didn't have instruments recording them," no one would ever know about them, Mr. Hansen said. The tremors are often small, and take place under Lake Erie.

"Secondly, people up here [in northeast Ohio] are very tuned in to earthquakes. I get e-mails several times a week that someone felt something. Before, people would feel them and wonder what it was. Now, they think it's an earthquake."

Two events sensitized people in the northeast corner of the state to the slight rumble of a small earthquake.

The first took place minutes before noon on a chilly January day in 1986. A magnitude 5 earthquake struck Lake County, just north of the Geauga County line, knocking stock off store shelves, separating chimneys from houses, and cracking plaster walls. The quake epicenter was 11 miles from the Perry Nuclear Power Plant, which was preparing to go on line.

That helped draw some 30 earthquake experts to Lake County to study the event.

The following year brought even more tremors into eastern Ohio. On a single day in July, 1987, Ashtabula County, just east of Lake County, rumbled with nine small earthquakes, the largest a magnitude 3.8. There was no record of Ashtabula County ever being struck by an earthquake before.

The next day, July 14, two more small quakes hit Ashtabula. In 1989, the county had three more. In all, Ashtabula County has experienced 41 earthquakes since that first one. Although most were smaller than magnitude 3, a quake in 2001 hit 4.5, the most powerful in the county.

But unlike most seismic activity, many of the quakes in Ashtabula County are man-made, Mr. Hansen said.

The culprit: A class 1 injection well that in July, 1986, began pumping 215 cubic yards of liquid waste into the Earth every day.

"They started the injection well in July, and the first earthquake popped off in 1987. The epicenter was 700 meters [765 yards] away from the well," Mr. Hansen said.

"The idea was that the pressure front of the fluid moving out from the well moved 700 meters in a year, hit a fault, and, boom, it triggered the earthquake."

In 2001, the 4.5 magnitude quake took place about three miles from the well.

"It had taken from 1986 to 2001 for the pressure front of that fluid to move 4 kilometers south, and it hit another fault," he said.

The Ashtabula County quakes are the only ones in the state known to be caused by injection wells, Mr. Hansen said.

Lima, where two quakes have occurred this year, has injection wells in the vicinity, but Mr. Hansen said there is reason to believe the wells have no connection to the earthquakes.

First, Lima has experienced earthquakes before, although most recently in 1937, when five struck the city in three months. The most powerful of those was magnitude 3.2. In 1884, the Allen County city was hit by a 4.8 magnitude earthquake.

"We know where all the injection wells are. After Ashtabula, we started to keep an eye on this stuff," Mr. Hansen said. The Lima wells have been in place for 15 years with no associated disturbances, and the two recent quakes appear to have nothing to do with their placement.

But Ohio is in danger of losing its ability to track the state's seismic activity and to answer these kinds of questions in the future.

There are 25 monitoring sites in the state, most run by volunteers at colleges and universities.

Mr. Hansen, who is retired from the Ohio Geological Survey, is paid for eight hours a week to operate the network - a task that takes significantly more time than he's paid for. The whole operation runs on about $12,000. Next year, even that small amount of funding will disappear.

"At first, all of our funding was cut back to half, which is what we're operating the system on now," said State Geologist Tom Berg, who runs the Ohio Geological Survey. "In the next budget cycle, that will be zeroed out."

Mr. Berg, who retires at the end of October after 18 years leading the agency, said he intends to lobby legislators after his retirement to come up with continued funding for the seismic network.

"My presence will be known," he said.

"I'd sure hate to see the system go down, because it does provide information that we need to carry out geological mapping of deep structures in the state," Mr. Berg said.

Among other things, knowing what lies beneath the ground helps companies locate power plants, particularly nuclear power plants, in regions of lowest risk.

Ohio has often been without blanket seismic surveillance. While there's been some seismic monitoring since at least 1900 when a seismic station was established in Cleveland, by 1992 the University of Toledo was the only station remaining. It wasn't until 1998 that funding became available to make a real network.

The network started in 1999, and it has already allowed geologists to solve some puzzles.

"As we began to get a lot of earthquakes recorded, and located very accurately, this stuff starts to make sense," Mr. Hansen said.

For instance, by plotting earthquake occurrences on a recently created map showing the magnetic properties of the state's bedrock, a pattern formed among some of the northeast Ohio quakes.

"I've been looking at these [earthquake locations] for 30 years, and nothing made sense. Everything looked like a shotgun scatter," Mr. Hansen said. "Now we have these things located quite accurately. We see clusters of seismicity coinciding with features in the magnetic basement."

Many of the earthquakes were lining up along what is now referred to as the Akron magnetic boundary, which may be a fault that extends into Lake Erie and is responsible for some of this year's quakes.

"We're at a very early stage of the research," Mr. Hansen said. "I'm not welling to say, yes, there's a fault out there."

Contact Jenni Laidman at: jenni@theblade.com or 419-724-6507.

First Published August 20, 2006, 3:14 p.m.