Conspiracy advocates and 2012 doomsdayers just got more fodder for their predictions with an unusual 4.0 earthquake shaking Ohio this past weekend.

The earthquake itself isn't what's raising eyebrows, though; it's the apparent cause: pressure from a wastewater injection well used by fracking companies.

This isn't the first time we've heard this is possible, but it's grabbing headlines now.

Just the facts
It seems that the problems aren't necessarily from the fracking process per se, but the disposal of the fluids used in the process. According to The Christian Science Monitor, "At issue is the effect fluids injected at high pressure can have on faults. The billion-year-old 'basement' rock that underlies much of the eastern US is laced with faults."

At the request of the state of Ohio, Northstar Disposal Services -- the operator -- has closed the well  while the situation is studied more closely.

This situation isn't limited to Ohio. Earthquakes shook Oklahoma last year, and with major players Chesapeake Energy (NYSE: CHK) and SandRidge Energy (NYSE: SD) headquartered in Oklahoma City, it doesn't take the layperson too long to connect the dots.

Here's where our nation's largest natural gas shales are being developed right now. As you might expect, community members in these states will be very interested to see what professionals conclude.

Duffyoil

Source: Energy Information Association.

What this means
For those invested heavily in natural gas, there may be some solace in the fact that the fracking process itself isn't to blame. It seems that the fluid being used in fracking -- which itself has raised environmental concerns -- needs to be disposed of in ways that won't cause the earth to rumble.

It remains to be seen whether simply adjusting disposal methods can solve this, or if it will require a more intensive solution.

Because certain chemicals are added to the water being used in fracking, disposal itself can present a sticky situation. Though some companies -- such as Range Resources (NYSE: RRC) -- reveal what chemicals are in its fracking solutions, many do not. These organizations claim that fracking solutions must be kept secret for proprietary reasons.

Whom this effects
Let me be clear, it's far too early for anyone to start proclaiming that the sky is falling for natural gas companies. But if the recent quakes, questions about fracking solutions, and the effects of their disposal continue, this could create a real problem for both investors and the larger energy industry in America.

Beyond the obvious natural gas extractors such as Chesapeake and SandRidge, there are several peripheral companies that are counting on natural gas to power our future. Westport Innovations (Nasdaq: WPRT) develops engines for cars, trucks, semis, and locomotives that can run solely on natural gas.

Likewise, Clean Energy Fuels' (Nasdaq: CLNE) goal is to build out natural-gas-filling stations to support new fleets of natural gas vehicles. If natural gas extraction were to screech to a halt before it even begins to really hit its stride, it could set these two companies and the movement in general back by years.

What's a Fool to do?
As I said, it's way too early to run for the hills over this. But the fact remains that if you want to make sure your investments are safe, you'd be well served to add these companies to your watchlist to make sure you're up to date on all the latest developments.

If, on the other hand, these developments have convinced you to focus your energy portfolio outside of natural gas, I suggest you take a look at our special free report, "3 Stocks for $100 Oil." With oil having crossed that threshold lately, the report is more pertinent than ever. Get your copy today, absolutely free!