Erin Spencer

PREPARING FOR THE FUTURE BY LOOKING TO THE PAST: Could ancient rocks help predict earthquakes? Dr. Chuck Bailey wants to find out.

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Bailey demonstrates how to tell if a rock is likely to cause an earthquake. 

An hour into the Fall 2011 Geology Faculty meeting, the building shook. As his colleagues yelled frantically, Dr. Chuck Bailey whipped out his cell phone and hurriedly filmed the swaying classroom furniture, as if to prove that the earthquake was real. Thirty seconds later, longer than Bailey or his colleagues expected for a Virginia earthquake, the building settled to a halt. It was clear the staff meeting was over. The William & Mary Geology professors rushed back to their offices where the phones rang with confused Virginians looking for answers about the startlingly large earthquake.

“We certainly knew it was an earthquake, but we weren’t sure where it came from,” Bailey recalls. “But I thought ‘Wow, this is a big deal’.”

The clues to earthquake origins lie in rocks, making Bailey somewhat of a ‘Sherlock Holmes’ of geology. Bailey studies tectonics, or the movements of Earth’s hard outer plates. These plates interlock like puzzle pieces and move along a conveyor belt of hot molten rock bubbling up from deep inside the Earth. Like slow-motion bumper cars creeping along the Earth’s surface at a few centimeters per year, the plates shift and grind against each other, creating geologic formations like mountains, volcanoes, and valleys.

Scientists use tectonics to predict approximately 90% of earthquake locations worldwide. Although it’s nearly impossible to predict exactly where an earthquake will hit, scientists can detect general locations of plate movements and warn people living in at-risk areas to take precautions.

To predict future earthquakes, Dr. Bailey looks to the past. Every slight variation on a rock face is a prehistoric riddle. “We can learn about the process that lead to earthquakes by studying ancient faults” he explains. Bailey focuses on “deformed” rocks – those that are bent or broken from being under high stress. One discolored ridge or break in the rock could reveal a chapter in the history of ancient tectonic movements and provide insight into future shifts brewing beneath our feet. To find these ancient faults, Bailey heads to the field. Bailey and his students conduct research in the Appalachian Mountains of Virginia. Although not as large or famous as the Rockies to the west, the Appalachians contain over a billion years of tectonic history. To identify faults, Bailey measures cracks in the rock surface. By determining the orientation of the cracks, he can infer which way the rocks were squeezed, pushed, or pulled. From there, he can predict where the pressure was coming from and whether an earthquake occurred when the crack formed.

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Bailey displays the tool used to measure the orientation of cracks on a rock. By holding it next to a crack, he can determine the crack’ s location in terms of North or South, as well as to other cracks.

“[As] geologists we have this sort of
dualism: the present is the key to the past. If we can understand the present world and how it works, we can use it to understand how things worked in the ancient past,” he explains. By studying cracks in rocks today, geologists get a glimpse of the processes that formed those cracks thousands or millions of years ago.

Over the last 15 years, Bailey has painstakingly accumulated a massive database of the orientation and abundance of cracks in rock outcroppings all over Virginia. Bailey’s colleagues weren’t certain of the value of the database outside the study of specific rock formations. Until the 2011 earthquake.

Dr. Bailey is as much a teacher as he is a scientist, and is dedicated to involving students in his research. His office is littered with rocks — dozens and dozens of them, scattered over every imaginable surface, creating a colorful array of textures and patterns. In his meetings with students, he frequently pauses and jumps up from his chair excitedly, scanning the room for a rock or tool that will help him explain whatever geological concept they are discussing.

Bailey’s expertise, as well as his patient yet enthusiastic way of explaining geological processes, made him the obvious person to turn to after the earthquake. Following the quake, Bailey’s phone rang incessantly with media outlets and scared citizens searching for an explanation. In between phone calls, he poured over data collected by seismic monitors that measure tectonic activity, looking for clues to the earthquake’s origin.

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Dr. Bailey’s office is piled high with rocks and geology books.

The 5.8 magnitude earthquake was the strongest to hit the region in over 110 years and the tremors were felt as far north as New York City. A mass exodus of people clogged Washington D.C. roads and the Metro was at a standstill due to concerns of possible tunnel damage. The Capital Building was evacuated, causing the Senate to meet in the nearby Postal Square Building—the first time the Senate has officially met outside of the Capitol since the British burned the building 200 years ago. Nearly two tons of stone damaged by the earthquake were removed from the Washington National Cathedral, at a cost of over $20 million. Damage intensified closer to the epicenter, costing $28 million worth of repairs to the Louisa County School District alone. Two schools had to be closed permanently. Ultimately, the earthquake caused over $200 million in damage and released half the energy of a World War II-era atomic bomb.

The earthquake was a startling reminder that the east coast is not immune to seismic activity. Researchers determined the epicenter was located about five miles south of Mineral, Virginia and was caused by a fault no geologist had ever discovered. Bailey was shocked. “Even in eastern North America where there are lots of geologists on the ground, there are still things we don’t understand very well. If you had asked me what faults were likely [to cause an earthquake], I wouldn’t have said some random place north of Richmond,” he explained.

As Bailey dug deeper into the origins of the earthquake, he realized the consequences could have been much more severe. The epicenter was located less than 15 miles from the North Anna Nuclear Power Plant. The plant generates 1,892 megawatts of power, creating enough electricity to power 450,000 homes in Northern Virginia and the greater Richmond area. When the plant was constructed in the 1970s, the plans incorporated estimates regarding the amount of shaking the reactor might experience in its lifetime. The 2011 earthquake was twice as big as any the reactor was built to withstand. Another strong quake near the reactor could have deadly consequences.

Shortly after the earthquake, Bailey traveled to North Anna to see if the power plant was at risk for an earthquake close to the reactor. He studied the faults deep under the power plant and determined they were different than the fault that caused the earthquake, meaning it’s not likely there will be a quake under the reactor anytime soon. The plant is safe—for now.

Next, Bailey turned to the rock database. “Once you know the orientation of fractures, you can play a game. We can say ‘I know which way the rocks are squeezed. Would they be reactivated and move?” This movement could result in another earthquake. By studying the orientation of the cracks in the fault that caused the earthquake, he could find other cracks in Virginia that had similar measurements.

After combing through the database, Bailey identified a handful of fractures that have similar measurements to the one that caused the earthquake. Using this information, he is compiling a hotspot map of Virginia, highlighting areas that are susceptible to an earthquake like that in 2011. This information can warn people in at-risk areas to take precautions, such as securing furniture, assembling emergency kits, and practicing earthquake safety procedures.

The ultimate goal is to not only determine where earthquakes will occur, but when. Bailey contends that currently scientists can’t, in real time, predict when earthquakes will occur. “And that, you could argue, is a reason to keep studying these things,” he explained. “If you knew five minutes beforehand that we were going to have a magnitude 7 earthquake outside of Los Angeles— you could save lives.”

Bailey doesn’t think we’ll be able to accurately predict the timing of earthquakes within his scientific career. But that doesn’t mean it’s not a possibility. The more scientists learn about how faults work, the closer they are to establishing a set of parameters that would indicate an earthquake is imminent. To get there, it’s going to take lots of geologists like Chuck Bailey, patiently piecing together clues uncovered in the earth’s surface towards an understanding of our planet’s tectonic past.

* This article was written as part of William and Mary’s Environmental Science & Policy course, ENSP 249: Science Communication. For more information, please contact the course instructor, Dr. Ibes at dcibes@wm.edu.

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