SANTA CRUZ -- A new UC Santa Cruz study concludes that a CalEnergy geothermal field near the Salton Sea is triggering small earthquakes very close to the San Andreas Fault, a finding with potentially big implications.

Published Thursday in the journal Science, the study draws a straight line between pulling water out of the ground and increasing numbers of temblors. The conclusion is sure to add to a growing debate about whether a new generation of energy production methods could have unintended effects with potentially serious consequences.

"We're not the first people to ever say that pulling fluid out of the ground is causing earthquakes, but the demonstration here is much clearer," said the study's chief author, UC Santa Cruz geophysicist Emily Brodsky. "It's a very strong signal. This is not subtle."

This March 12, 2011 file photo a man walks by a collapsed house and debris at Sendai Port in Sendai, northeastern Japan, following Friday’s
This March 12, 2011 file photo a man walks by a collapsed house and debris at Sendai Port in Sendai, northeastern Japan, following Friday's 8.9-magnitude quake. New research appearing Thursday July 11, 2013 in the journal Science suggests that such powerful distant quakes can trigger minor shaking around wastewater injection sites in the U.S. Midwest. ((AP Photo/Koji Sasahara,File))

The study examined more than 30 years of data from CalEnergy production facilities near Brawley, but it could have broader implications. Tinkering with subterranean pressure dynamics is a staple of modern oil and gas production, and if they cause earthquakes it could prove a sensitive topic in California, where lawmakers are grappling with new regulations for the emerging technologies.

At CalEnergy's Imperial Valley operation, the company taps into naturally heated deep-water reservoirs located thousands of feet below the surface. That water then is flash-steamed to help produce geothermal energy before being pumped back into the ground.

But some of the water is lost during the process, a net loss that seems to be the source of the problem. CalEnergy's facilities are located in a seismically active area, and the vast majority of the earthquakes are not large enough to pose a threat to human life or property.

"There are many more little earthquakes in this world than big earthquakes, and this is no exception," said Brodsky, though she added that her data included a magnitude 5.1 quake, and that the risk of triggering a large one was more than zero.

A CalEnergy representative declined to comment. The San Andreas Fault ends across the Salton Sea from CalEnergy's facilities, and the Imperial Fault is also nearby. CalEnergy is a subsidiary of MidAmerican Energy Holdings, which is controlled by Berkshire Hathaway.

Scientists at Lawrence Berkeley Laboratory said "induced seismicity" is an accepted phenomenon within the scientific community. As far back as the 1930s, oil workers near Long Beach noticed they needed to replace oil with salt water or the ground would shake, said Ernest Majer, a senior adviser in the lab's geophysics department.

"Reinjecting water and taking water out of the ground has been long known to cause seismicity," said Majer, an authority on the topic.

The phenomenon is only new to the general public, said his colleague, Stefan Finsterle, a hydrogeologist.

"It just boiled to the top of the public's perception in recent years because of fracking," Finsterle said.

Hydraulic fracturing, or fracking, is a process that taps previously unrecoverable oil resources. But it is a water-intensive process, and federal officials and advocacy groups are concerned about the disposal water, which contains chemicals and is often injected back into the ground.

In a state riven with fault lines and vast, untapped oil potential -- particularly beneath the Monterey Shale, a geologic formation that expands east into the Central Valley from Monterey County -- there has been surprisingly little debate about the earthquake risks from fracking. There are 88,000 active wells in California, helping make the state the fourth-largest oil producer in the U.S, California also tops the nation in geothermal production.

This year, various state lawmakers proposed a series of fracking-related bills, but just one survives. It now includes the remnants of a bill proposed by Assemblyman Mark Stone, D-Scotts Valley, which establishes standards governing fracking wastewater.

But that omnibus bill does not address seismic concerns. Stone said the link is "seen as a myth" in Sacramento, adding that the state needs to take a harder look at the issue.

"If they're potentially causing earthquakes in areas that don't have earthquakes" such as the Midwest, Stone said, "what's going to happen in areas that are susceptible to earthquakes?"

Last year, the U.S. Geological Survey concluded that a new prevalence of Midwest earthquakes had to be man-made -- with a sixfold increase over the previous century -- but stopped short of saying that human activity was causing the earthquakes.

A 2012 University of Texas study cited fracking for a series of small earthquakes near the Barnett Shale in North Texas. And in March, scientists published a study blaming a 2011 magnitude 5.6 quake in Oklahoma on fracking, saying a relatively small wastewater injection triggered a cascade of small earthquakes that became a larger one.

Jason Marshall, the California Department of Conservation's chief deputy director, said more than a million fracking wells have been drilled nationally without evidence they cause earthquakes. The state recently studied available data from California wells and found they are drilled to an average of nearly 3,000 feet and use an average of 143,000 gallons of water, which is much less than in other states.

However, it is the associated process of reinjecting wastewater into the ground that has been the focus of seismic studies. Marshall said the state has "Underground Injection Control" regulations keeping oil producers from increasing underground water pressure beyond normal circumstances, which have kept induced earthquakes from becoming an issue here.

Majer said some changes are on the horizon after a recent court ruling over fracking on federal lands. There, a San Jose federal magistrate said the Bureau of Land Management must update its oversight of fracking wells, a process Majer said could include a look at seismic regulations.