scraped from the walls of the deep trench showed unmistakable evidence that massive earthquakes had ruptured the fault no less than six times during the last fifteen hundred years. The horizontal layers of clay, sand, silt, and gravel were riddled with the trace marks of those disturbances. The sequence was striking. The shortest period between quakes was roughly two hundred years. Most occurred at intervals of anywhere from five hundred to eight hundred years.
The zone had been incredibly active over the centuries. The vertical displacements varied from several inches to as much as forty feet.
“They’re textbook examples of severe faulting,” Holleran said. She showed a blowup of a photograph she’d taken about a hundred feet down into the fissure.
Even to the president’s untrained eye, the thick scarring and darkening of the soil stood out clearly.
Using a pointer, Holleran outlined the telltale signs of repeated faulting. The small room was stuffy and crowded, but no one moved or fidgeted. They were all listening intently, jotting down notes.
“The quake that left those footprints dates from just after the time of Columbus’ voyage of discovery,” she said.
The jagged crack in the exposed soil was striking. But the most distinctive aspect was the clear indication that the fault had repeatedly produced great earthquakes. The evidence appeared in each of the different strata, which were separated by bands of lighter-colored soil.
“I take it this wasn’t caused by just one earthquake,” Ross said.
Here it comes, Atkins thought.
“As best we can tell, there were at least four major earthquakes,” Holleran said, outlining their tracings. “They were probably concentrated over a very short span of time.”
“How short?” Ross asked.
“That’s difficult to say,” Holleran said.
“Give me a range.”
“At the longest end, months.”
“And at the shortest?”
Holleran’s reply was quietly stated: “Weeks.”
With a possible error of no more than thirty years, the carbon-14 tests had shown major earthquakes around A.D. 200 then again in 631, about the time of Mohammed. Mega quakes had also occurred when the ancestors of the American Indian were migrating to North America in the 1100s and, again, during the Black Death that depopulated much of Europe in the 1650s.
The sedimentary patterns Holleran had found in the deep fissure indicated that the big quakes often came in groups of three, but at least one sequence had four, possibly five major earthquakes. The best evidence of a huge earthquake was a sharp, twenty-five-foot offset that dated roughly to the mid-1600s.
Only an extraordinary quake could have done that. Atkins thought. The growing body of data increasingly indicated that the American heartland was prime earthquake country to a degree no one had ever imagined before. And much of the credit for nailing this definitively had to go to Holleran. He had no doubt, none, that she was right in her analysis. It was highly likely they were going to get rocked again.
“So we could be looking at maybe two or three more major quakes?” Ross asked. Casually dressed in jeans and a blue pullover, he was taking notes on a yellow legal pad.
“It’s possible. Mister President,” Holleran said. “If the fault follows the usual pattern.”
“How possible?” Ross persisted.
Holleran said, “I can’t give a percentage. I’d say at least one more big quake in the magnitude 8 range is likely.”
Weston, who’d been biding his time, objected. He’d managed to find a clean suit and tie for the trip to the White House, even a set of cufflinks. He launched into an attack on the whole field of paleoseismology. He wasn’t alone in his argument. Several of the USGS scientists were also leery of basing seismic projections on the physical evidence of past quakes. There were simply too many exceptions, too many gaps in the chain, too many inconsistencies.
“At best it’s interesting data that needs more interpretation,” one of them said. “It would be a mistake to use it now to try to project for future earthquakes, especially under present circumstances.”
Atkins had expected their objections, which echoed Weston’s. He had a serious problem with Weston over the cracks at Kentucky Dam, a problem they still needed to resolve. But he understood that Weston expressed what most of the seismologists working on the crisis were thinking. Weston had been an effective spokesman for their viewpoints. Argumentative and opinionated, he had history on his side. Back-to-back earthquakes of magnitude 8 or greater were incredibly rare.
Holleran let the remark pass without comment. She knew she had the support of most of the seismologists in the room. But on another level, she no longer cared what others thought. Her job, as she understood it, was to examine the physical evidence and try to draw meaningful conclusions while keeping speculation to a minimum. She’d done just that. The evidence was rich. The clues, buried deep in the ground, told them a great deal about the area’s violent seismic history.
Walt Jacobs had information to report—if not as dramatic, equally as troubling.
The man looked awful, Atkins thought. The bags under his eyes were dark and puffy. He hadn’t shaved or changed clothes in days. Atkins noticed his old friend was still wearing the rumpled blue denim shirt he’d had on two days earlier. He resolved to talk to him, see if he could help him pull out of it.
“The latest GPS sweep shows continued deformation along a line running roughly northeast of the Caruthersville Fault about two hundred miles into Kentucky.”
The satellite data had just been harvested by the GPS Master Control Station near Colorado Springs. It had been analyzed and enhanced at the Jet Propulsion Laboratory at Cal Tech before it was relayed by satellite to Memphis. The data was projected on a map.
“How much uplift are we getting?” Weston asked. Like the others, he was seeing the data for the first time. Thompson had only recently processed it.
“Twenty inches along most of the fault. A little more than that at the point of axis with the main New Madrid segment. It’s roughly thirty inches there.”
Even Ross knew enough geology by then to realize an uplift of that magnitude was serious, an unmistakable signal that tremendous amounts of seismic energy continued to build along the fault lines.
Jacobs had another satellite-generated detail to add to the analytical mix.
Earthquakes were known to produce strong energy currents or pressure waves in the earth’s upper atmosphere, the ionosphere. This connection had been first noticed after the Northridge quake of 1994.
Jacobs said, “We saw then that for two days before the earthquake, the GPS 10-3mn frequency band began to pick up a train of strong pressure waves. The waves were generated by a change in electrons. The greatest waves appeared within minutes after the first strong tremors.”
“What’s your point?” snapped the president, exasperated by the unrelenting complexity of the science.
“We’re starting to see some significant electronic disturbances in the atmosphere at distances of five hundred to six hundred kilometers above the fault line,” Jacobs said. “The waves are intensifying in strength.”
Guy Thompson hadn’t changed his Western look for the visit to the White House. He wore his usual attire— jeans, expensive cowboy boots, and a gaudy Western shirt. He’d braided his black hair in the back.
“I’d like to talk about the P velocity data.” Thompson explained that the velocities of the P waves had dropped by about 10 percent since that magnitude 8.4 event. “In the last twenty-four hours those velocities have started climbing again,” he said.
Ross asked him to explain.
“The theory was developed from observations in Russia,” Thompson said. “It holds that P velocities decrease after a precursor quake, then start to return to more normal levels just before a major event.”
“That’s only a theory,” Weston said, making no effort to conceal his anger. His view was shared by several others.
“I want to hear this,” Ross said, silencing Weston.
Thompson explained that his team had prepared a map of the entire seismic zone based on geomagnetic data gathered by satellite. Shifts in magnetic fields were recognized indicators of seismic activity. The recent readings showed a major change in the zone’s magnetic field.
