In a guest piece at Scientific American, David Ropeik argues that an Italian court's decision to charge scientists and a government official with manslaughter isn't about quake prediction per se, but a failure to communicate science effectively. Snip:

But, contrary to the majority of the news coverage this decision is getting and the gnashing of teeth in the scientific community, the trial was not about science, not about seismology, not about the ability or inability of scientists to predict earthquakes. These convictions were about poor risk communication, and more broadly, about the responsibility scientists have as citizens to share their expertise in order to help people make informed and healthy choices.

An editorial from Nature, a publication that covered the case extensively in 2011, echoes this sentiment. "It is important to note that the seven were not on trial for failing to predict the earthquake," but...

The verdict is perverse and the sentence ludicrous. Already some scientists have responded with warnings about the chilling effect on their ability to serve in public risk assessments.

The National Research Council published a report today, reviewing and analyzing peer-reviewed literature, federal and state documents, data requested from private companies, and more ... all in an effort to better understand the link between earthquakes and natural gas fracking techniques.

Because this is the National Research Council, you can read the whole thing online for free. But here are the three key takeaways:

First: The actual process of hydraulic fracturing—injecting fluid into the ground to break rocks and release trapped natural gas—doesn't seem to come with a serious seismic risk. This process has been definitively linked to small earthquakes—no greater than 2.8 magnitude—at one location.

Second: Injecting wastewater from fracking back into the ground has a much more noticeable seismic effect. What's more, this effect goes far beyond fracking. Injecting liquids into the ground is part of advanced recovery for oil, conventional drilling for oil and gas, carbon capture and storage, and geothermal electricity generation. This should not be a surprise. We've known that human can induce small earthquakes since the 1920s and injecting large amounts of liquids into a space that previously didn't hold much liquid—what the NRC calls a fluid imbalance—is part of that.

The strongest induced earthquakes are related to hydrocarbon withdrawl—basically, oil drilling—in California, Illinois, Oklahoma, Texas, and Nebraska. Some of those events have reached magnitudes of 6.5.

But the highest frequency of events seems to be associated with a California geothermal site called The Geysers, which has experienced 300-400 events a year since 2005, some of them reaching a magnitude of 4.6.

Basically, whether we should be really worried about this effect or not is up for debate. None of these human-induced earthquakes have led to significant property damage or loss of life and, historically, human-induced earthquakes have been on the small side, magnitude wise. Also, we've been injecting liquid into the Earth for decades and the overall number of induced earthquakes remains small. But, if we are going to be concerned, we have to understand that this is not just a fracking problem. It's going to come into play any time you're extracting or injecting a large quantity of liquid from the earth without counterbalancing that liquid loss or gain.

Finally: The thing to keep your eye on is carbon capture and storage. There's only one commercial scale project in the whole world right now. So we really don't have enough data to know what's going on here. But, the paper points out, CCS involves injecting very large quantities of liquid. Larger than the quantities involved in, say, storage of wastewater from fracking. So while we don't know what will happen with CCS, there's definitely a potential for those sites to cause some earthquakes at the larger end of the human-induced-earthquake scale.

Read the full report (Executive Summary and Summary are particularly useful if you want a quick overview.)

Read a summary at Scientific American

Read a story I wrote last year about human-induced earthquakes

Last year, the Eastern coast of Japan was struck by a massive 9.0 earthquake and tsunami. Since that happened, you've heard researchers talk about how it was not the first time that region had experienced an earthquake that large. Although the 2011 Tohoku earthquake has been called the biggest earthquake in Japan's recorded history, that's really only describing the relatively short history of scientifically measured earthquakes. The Japanese have kept written records, describing earthquakes that sound as though they could have been every bit as destructive. And those records date back 1600 years.

But written records aren't the only way of preserving local memories, or warning future generations about the destructive power of the Earth.

Geologic evidence shows that North America's Pacific Coast has experienced earthquakes on the scale of the Tohoku earthquake. (In fact, the Pacific Northwest is probably due for one of these large quakes. It's not an "if", but a "when".) The last time it happened, nobody in the area was keeping written documents. Instead, the story of a massive earthquake and a devastating tsunami—which probably occurred around the year 1700—have become a part of oral storytelling traditions. Ruth Ludwin, a seismologist at the University of Washington, has been collecting these stories since the early 1990s.

"There was a shaking, jumping up and trembling of the earth beneath, and a rolling up of the great waters."

So says an ancient tale told to generations of Quilleute and Hoh Indians. Variations of this saga of an epic battle between the Thunderbird and the Whale are found among Pacific Northwest Tribes from Vancouver Island to Oregon's Tillamook tribe.

The Whale was a monster, killing other whales and depriving the people of meat and oil. The Thunderbird, a benevolent supernatural being, saw from its home high in the mountains that the people were starving. The great bird soared out over the coastal waters, then plunged into the ocean and seized the Whale.

A struggle ensued first in the water, the tribal tale says. "The waters receded and rose again. Many canoes came down in trees and were destroyed and numerous lives were lost."

The Thunderbird eventually succeeds in lifting the evil Whale out of the ocean, carrying it "high into the air (and then) dropping it to the land surface at Beaver prairie. Then at this place there was another great battle."

"A picture began to emerge that looked a lot like what you'd expect from a major quake," she said. One tribe even had what sounds like an explanation for aftershocks, noting Whale had a son, Subbus, who took Thunderbird several more days to locate and kill. The earth-rumbling struggle persisted, but eventually Subbus was subdued.

"I can't say for certain this was the 1700 event, but it sure sounds like it," Ludwin said. "You hear the same story from tribes all along the coast."

Read more about how Ruth Ludwin connected the story of the Whale and the Thunderbird to the 1700 Pacific Coast earthquake.