The earthquake that rocked Youngstown, OH, late last year has been blamed on practices associated with natural gas drilling, leading many observers to wonder if the earth will start to shake under the Marcellus Shale.

The short answer, scientists say, is that it's unlikely. The Youngstown earthquake has been blamed on injecting large quantities of wastewater into a deep well - a practice widespread in Ohio but hardly done at all in Pennsylvania.

Ohio has 177 deep-water injection wells used for the disposal of waste, which the state regulates. Pennsylvania only has eight, and one of them is no longer active. Three are in the northwestern part of the state; of the remaining four, two are in Clearfield County and two are in Somerset County. Those counties are on the periphery of the Chesapeake watershed, although the rivers that run through them do reach the Susquehanna.

In Pennsylvania, the EPA has regulated the deep-water injection wells since the mid-1980s. More deep-water injection wells have been proposed in Pennsylvania, but with the process controlled by the EPA, it will be harder to get them approved.

Pennsylvania's lack of injection wells, coupled with its drilling boom, has resulted in more waste going to Ohio. Pennsylvania recently asked state wastewater treatment plants to stop accepting drilling waste. Much of that waste was trucked to Ohio. Last year, the Buckeye State disposed of 11 million barrels of drilling waste in those wells, according to the Cleveland Plain Dealer. That was a 30 percent increase from the year before. State officials in Ohio estimate more than half of that waste is trucked there from Pennsylvania and West Virginia, where the pace of drilling in the Marcellus Shale has reached Gold Rush proportions.

Ohio does not require seismic testing before drilling; its governor, John Kasich, said that the state pretty much knows where the fault lines are. Pennsylvania doesn't require seismic testing before drilling, either, though it is a common practice.

The National Science Foundation has been studying the phenomenon of "induced seismicity" in energy development and expects to have a report completed in the spring. The committee began the work in 2010 at the request of New Mexico Sen. Jeff Bingaman, chair of the Committee on Energy and Natural Resources. In 2011, a series of earthquakes that rocked Arkansas were blamed on deep-water injection processes. Texas, too, has suffered earthquakes that scientists believe are related to the fracking process.

Even if earthquakes are unlikely in Pennsylvania, drilling continues to be a divisive issue. In January, the EPA began providing water to four homes in Dimock, a Northeastern Pennsylvania hamlet where drilling has destroyed water supplies and led to several toxic spills in streams. The EPA said it would provide the water as well as sample 61 wells after residents complained they did not have any faith in the state's Department of Environmental Protection.

A Texas company, Cabot Oil & Gas, drilled about 70 wells in Dimock in 2008 and 2009. Soon after, several residents reported methane and other contaminants in their water. The DEP declared Cabot responsible and ordered the company to provide them with water, but in December it released the company from that obligation.

Dimock residents, many of whom are suing Cabot, asked the EPA to provide water and also test their current supplies. They said they did not trust the gas company or the DEP to give them objective results. The EPA agreed to do the testing and is analyzing the water supply of about 60 homes. It may supply water to more homeowners depending on the results.

In January, Cabot sent a letter to EPA Administrator Lisa Jackson objecting to the testing, saying that the state DEP had it covered. EPA officials said they felt the testing was necessary, though. Residents cheered the EPA's arrival and said they were glad that the federal government was stepping in where the DEP had failed them.

In other state Marcellus news, New York's moratorium on drilling continues, despite the governor's interest in resuming the practice. Drilling advocates are expected to lobby the Maryland legislature for a quicker timetable to begin drilling in the Western part of the state. Maryland's study on drilling safety won't be completed for at least a year.

USGS warns fracking could contaminate NY drinking water

As New York officials consider lifting the state's ban on hydrofracking for natural gas, a federal agency is questioning whether enough safeguards are in place to protect the Empire State's water.

A U.S. Geological Survey assessment warned that fracking in the Marcellus Shale, which overlays much of upstate New York, could contaminate private wells, municipal aquifers and even New York City's water supply. Specifically, the assessment said the state's plan to put 500-foot buffers around municipal water supplies before drilling may not protect them. It also warned of a one-size-fits-all approach, as hydrological conditions vary from place to place. It said a five-mile buffer might be more appropriate in some places.

The assessment follows an earlier warning from the EPA that the state is ill-equipped to enforce all the new regulations that come with drilling, including the treatment and disposal of fracking wastewater. Regular wastewater plants can't remove the fracking chemicals through their treatment processes.

New York hasn't issued any new drilling permits since 2008, when then-Gov. David Paterson ordered his staff to conduct an environmental review and, ultimately, come up with stronger regulations to protect waterways. That decision led to a de-facto moratorium. Gov. Andrew Cuomo, who like Paterson is a Democrat, has not directly said he'd like to lift the moratorium and has usually referred reporters to his Department of Environmental Conservation and its regulations. New York lawmakers are considering legislation to extend the moratorium for another year.

Several towns in New York have taken their own actions to stop drilling. The town of Dryden recently won a ruling from a New York court allowing it to keep its ban on drilling. So did Middletown, a small village just outside Cooperstown near the Susquehanna River. Officials in other towns are agitating to remove the ban, arguing it will create jobs in hard-luck areas of the state.