"I've only been in one or two, but those were felt and not heard."
"Puny ones just rattled the dishes, but larger quakes can sound like a string of locomotives running by," Pitt said.
"There is a great deal of tectonic activity under Lake Baikal," Sarghov added. "Earthquakes occur frequently in this region."
"Personally, I can do without them," Gunn said sheepishly, retaining his seat by the monitor bank. "I hope they don't disrupt our data collection of the lake's currents."
The Vereshchagin was engaged in a joint Russian-American scientific survey of Lake Baikal's uncharted current flows. Not one to stay confined in NUMA's Washington headquarters, Pitt was leading a small team from the government research agency in collaboration with local scientists from the Limnological Institute at Irkutsk. The Russians provided the ship and crew, while the Americans provided high-tech sonobuoys and monitoring equipment which would be used to paint a three-dimensional image of the lake and its currents. The great depth of Lake Baikal was known to create unique water-circulation patterns that often behaved unpredictably. Tales of swirling vortexes and fishing boats getting pulled underwater by their nets were common stories among the local lakeside communities.
Starting at the northern tip of the lake, the scientific team had deployed dozens of tiny sensors, packaged in orange colored pods that were ballasted to drift at varying depths. Constantly measuring temperature, pressure, and position, the pods relayed the data instantaneously to a series of large underwater transponders that were positioned in fixed locations. Computers onboard the Vereshchagin processed the data from the transponders, displaying the results in 3-D graphic images. Gunn glanced at a bank of the monitors in front of his seat, then focused on one in particular, which depicted the midsection of the lake. The image resembled a pack of orange marbles floating in a bowl of blue ice cream. Nearly in unison, a vertical string of the orange balls suddenly jumped rapidly toward the top edge of the screen.
"Whoa! Either one of our transponders is going tilt or there's a significant disturbance at the bottom of the lake," he blurted.
Pitt and Sarghov turned and studied the monitor, watching as a flood of orange dots raced toward the surface.
"The current is uplifting, at a dramatic rate," Sarghov said with a raised brow. "I find it difficult to believe the earthquake was severe enough to produce that kind of effect."
"Perhaps not the earthquake itself," Pitt said, "but a resulting side effect. A submarine landslide set off by a minor quake might create that sort of uplift."
A hundred and thirty miles north of the Vereshchagin and two thousand feet beneath the surface, Pitt was exactly right. The rumblings that first echoed across the lake were the shock waves from a strong earthquake, measuring 6.7 on the Richter scale. Though seismologists would later determine that the quake's epicenter was near the lake's northern shore, it created a devastating effect midway down the western flank, near Olkhon Island. A large, dry, barren landmass, Olkhon sat near the center of the lake. Directly off the island's eastern shoreline, the lake floor dropped like an elevator down a steep slope that ran to the deepest part of the lake.
Seismic studies had revealed dozens of fault lines running beneath the lake floor, including a cut at Olkhon Island. Had an underwater geologist examined the fault line before and after the quake, he would have measured a movement of less than three millimeters. Yet those three millimeters was sufficient enough to create what the scientists call a "fault rupture with vertical displacement," or an underwater landslide.
The unseen effects of the quake sheared off a mountain-sized hunk of alluvial sediments nearly twenty meters thick. The runaway chunk of loose sediments slid down a subterranean ravine like an avalanche, accumulating mass and building momentum as it went. The mountain of rock, silt, and mud fell a half mile, obliterating underwater hills and outcroppings in its path before colliding with the lake bottom at a depth of fifteen hundred meters.
In seconds, a million cubic meters of sediment was dumped on the lake floor in a dirty cloud of silt. The muffled rumble of the massive landslide quickly fell away, but the violent energy produced by the slide was just unleashed. The moving sediment displaced a massive wall of water, driving it first to the bottom ahead of the landslide and then squeezing it up toward the surface. The effect was like a cupped hand pushing under the surface of a bathtub. The force from millions of gallons of displaced water had to be redirected somewhere.
The submarine landslide had fallen in a southerly direction off Olkhon Island and that was the direction that the mounting swell of water began to move. To the north of the slide, the lake would remain relatively undisturbed, but to the south a rolling wave of destructive force was released. At sea, the moving force of water would be labeled a tsunami, but in the confines of a freshwater lake it was called a seiche wave.
An upsurge of water punched the surface in a ten-foot-high rolling wave that drove south along the lake's lower corridor. As the wave pushed into shallower depths, the upswell squeezed higher, increasing the size and speed of the surface wave. To those in its path, it would be a liquid wall of death.
On the bridge of the Vereshchagin, Pitt and Gunn tracked the development of the killer wave with growing alarm. An enlarged three-dimensional map of the lake south of Olkhon Island showed a swirl of orange dots jumping in rapid succession across an expanding line.
"Dial up the surface pods only, Rudi. Let's find out exactly what's going on up top," Pitt requested.
Gunn typed a short command into the computer and a two-dimensional image suddenly appeared on the monitor, showing an array of surface pods bobbing over a five-mile stretch of the lake. All eyes on the bridge focused on the screen as one orange pod after another visibly jumped in a slow line of progression from north to south.
"It's a rolling wave, all right. The sensors are getting kicked up almost five meters as it passes," Gunn reported. He double-checked his measurements, then nodded silently to Pitt and Sarghov with a grim look on his face.
"Of course, a landslide would produce such a wave," Sarghov said, comprehending the electronic images. The Russian pointed to a map of the lake pinned to the bulkhead. "The wave will pass through the shallow delta of the Selenga River as it moves south. Perhaps that will dilute its force."
Pitt shook his head. "As the wave moves into shallower water, it will likely have the opposite effect and increase its surface force," he said. "How fast is she moving, Rudi?"
Gunn toggled the computer mouse and drew a line between two pods, measuring their distance apart. "Based on the spikes in the sensors, the wave looks to be traveling about one hundred twenty-five miles per hour."
"Which will put it upon us in about fifty minutes," Pitt calculated. His mind was already racing in overdrive. The Vereshchagin was a stout and stable vessel, he knew, and stood a good chance of steaming through the wave with minimal damage. The greater harm would be to the lake's prevailing marine traffic, small fishing boats and transport vessels not designed to withstand the onslaught of a ten-foot wave. Then there were the shoreline inhabitants, who would be subject to an unexpected flooding of the low-lying areas around the lake.
"Dr. Sarghov, I sugge
st you have the captain issue an immediate emergency warning to all vessels on the lake. By the time anyone catches sight of the wave, it will be too late to get out of its way. We'll need to contact the authorities on shore to evacuate all residents at risk to flooding. There's no time to lose."
Sarghov beat a path to the ship's radio and issued the warning himself. The radio hummed with chatter as a myriad of respondents called back to confirm the emergency. Though Pitt didn't speak Russian, he could tell by the tone of skepticism in the replying voices that at least some thought Sarghov was either drunk or crazy. Pitt could only smile when the normally jovial scientist turned red and spat a series of obvious obscenities into the microphone.
"Idiot fishermen! They're calling me a fool!" he cursed.
The warnings took heed when a fishing boat in the protected cove of Aya Bay barely survived capsizing as the fringe of the wave passed by and its captain hysterically reported the event. Pitt scanned the horizon with a pair of binoculars and could make out a half dozen black fishing boats motoring toward the safety of Listvyanka, in addition to a small freighter and a hydrofoil ferry.
"I guess you got their attention, Alex," Pitt said.