In a little more than an hour, they would start detonating their explosives, generating seismic waves that would be recorded by seismometers buried throughout these sandy hills and positioned on the floor of the
A geophysicist with the United States Geological Survey, Fuis is overseeing an ambitious project to create an underground image of one of the most seismically active and geologically complex regions of the country, a triangle of land extending from Palm Springs to the Mexico border.
This work, he believes, will change current assumptions about the earthquakes that originate here, especially the Big One expected on the
Fuis, 67, sat on the top of a ridge and took out his dinner, a ham and jalapeno sandwich. From here, he would be able to stay in touch with the crew by two-way radio and cellphone in case any problems or confusion arose during the night.
A voice broke over the radio.
A freight speeding along the shore of the lake would interfere with the readings from the detonations, and they'd have to wait until it passed.
Fuis looked south toward Bombay Beach, a community of small homes and double-wide trailers on the edge of the Salton Sea, where the
Three years ago, seismologists imagined the effect of a magnitude 7.8 earthquake with an epicenter less than a mile from where he sat. Their scenario had the full force of the temblor reaching the
The released energy would be approximately 30 times less than the Japanese earthquake. Still, landslides, fires, collapsed buildings and roadways, severed communication lines, cracked runways, derailed trains, broken aqueducts and dams were projected, along with nearly 2,000 deaths, 50,000 injuries and $200 billion in damage.
The model was based on the last rupture of the San Andreas in this region, dated more than 300 years ago by recent geological studies. Because this stretch of the fault — from
Fuis describes the fault with dispassionate conviction. It is "near failure," he says, though he believes the seismologists' predictions may not be accurate. Whether the destruction will be worse or not, he's not certain. He just knows that some conclusions have been drawn without enough information.
"Neither the shape of the
The chatter on his radio picked up.
He checked the time — 21:59:07 — less than a minute before the first blast.
Earlier that morning, just as the sun was rising, the day crew gathered at a warehouse in
John Hole paced with clipboard and pen in hand. Hole, 48, is an associate professor of geophysics at Virginia Tech and is managing the study along with Fuis and Joann Stock, 51, professor of geology and geophysics at Caltech.
The Salton Seismic Imaging Project is funded with a $1.2-million grant from the National Science Foundation. Additional money comes from the
Similar research in the 1990s looked at the
By detonating explosives and measuring the speed of the seismic waves as they move horizontally and vertically underground, seismologists can assemble images of the crust of the Earth, capturing structures like fault lines.
The project was three years in the planning, and the field work got underway late February. During public hearings, Fuis had fielded concerns from residents and local officials who worried that the explosions might set off earthquakes. Rock quarries, he told them, conduct similar blasts without any consequence.
Then less than 24 hours after the earthquake in
Now with only six days left, Hole wanted to make sure everyone stayed focused. So far, they had put out more than 4,000 seismometers, and the night crew had set off more than 100 explosions.
"This is huge," he reminded them, "the largest project of its kind."
On the wall behind him was a map of
Penetrated by volcanoes and cut by the San Andreas and Imperial faults, the region is part of the Salton Trough, one of the few rift valleys in the world not covered by an ocean, a place where geologists can see the continent coming apart and a new crust of the Earth being formed.
These processes are the result of the Pacific and North American plates sliding against each other for nearly 6 million years, an action that triggers the earthquakes in the region.
Toting 40-pound packs in 80-degree heat, the day crew covered a five-mile route. About every 50 yards, they stopped at mapped locations, dug a trench about a foot deep and buried a seismometer and geophone.
By mid-afternoon, the night crew parked their SUVs, pick-ups and an enclosed truck between the Union Pacific tracks and
Fuis stuffed three boxes of detonators and a bottle of water into his day pack and headed out. He began working for the
"What got a lot of us into the earthquake business," he says, "was the hope we could predict earthquakes — and we still have this hope. In the meantime we have had to start working on something that's practical to the public, namely how to predict earthquake effects."
Standing roadside, Fuis talked easily about "planar distributions of hypocenters," "sedimentary velocities," P waves and S waves. When he described the
"The San Andreas fault actually appears to be propeller shaped," he said, drawing a pirouette in the air and describing how the fault tilts to the northeast in this basin, then tilts in the opposite direction father north, past the Mojave Desert.
Many seismologists, he explained, assume the fault in this region is largely vertical, a configuration that places the Pacific plate squarely up against the North American plate. Fuis and a few colleagues, however, believe that the Pacific plate here is wedged beneath the North American plate.
The implications for
But a greater threat, according to Fuis, is the sedimentary structure of the Salton Trough itself. Excavate this basin of the rocks and soil swept down over the millenniums from the Rocky Mountains and you'd have a canyon larger than the
This formation — sediment nearly nine miles deep — can trap earthquake energy and amplify the seismic waves, resulting in longer and more intense shaking. No one has measured the wave speeds throughout the basin until now.
By midnight, Fuis was chilled. Orion angled behind the Santa Rosa Mountains, and a cool breeze came in from the east.
For the last hour he had been following the progress of his explosives handlers as they moved from one blast site to the next. Each team had to follow a rigorous schedule that kept them from firing at the same time and distorting the readings.
Coyn Criley and Joe Svitek were running late for their 1 a.m. detonation. Their first blast had taken longer than expected, and Svitek spooled out 200 feet of wire to the clearing where the explosives were buried. He and Criley spliced it to the detonators, connecting the circuit.
With two minutes remaining, they retreated to the shooting box, a small yellow briefcase that contained a clock and the battery that would initiate the explosion. At 25 seconds, Criley pushed the charge button. An orange light started flashing. At 15 seconds, he pushed the arm button.
"Five, four, three, two, one."
A sharp jolt and a fast undulation raced through the sandy soil.
Fuis heard the blast from the ridge. By then the seismic waves, racing at three miles a second, had already passed beneath him and were dissipating in the distance. The geophones had captured the ground motion; the seismometers recorded the impulse; and soon the information would join the rest of the data, one piece in the larger puzzle.
One day, Fuis knew, another sort of wave would start from this place, and it wouldn't fade so quickly.