“I was working under contract in the northeast Indian Ocean,” he said, “helping map underwater topography near the Sunda Trench, what used to be called the Java Trench, just prior to the catastrophic Sumatra-Andaman quake and tsunami in 2004. I had come home, back to Oregon, for Christmas vacation. The disaster struck the day after Christmas, Boxing Day. Virtually all of the Indonesian friends I’d made over there—I hung out a lot on the Sumatran coast—lost their lives, along with over two hundred thousand others . . .” His voice trailed off.
“I’m sorry,” Cassie said, her words soft and coated with compassion. “I understand loss.” She reached out and touched his arm.
“Thank you. Anyhow, the point I was driving at is that the Sumatran tragedy mirrored what happened here over three centuries ago.”
“In 1700, right?” Cassie asked.
Rob nodded.
“Really?” Tim said. “How could you know the exact year? The Indians’ stories”—he inclined his head toward Cassie—“seem kind of, well, vague.”
Rob gestured at an old deadfall lying in repose in the thick marsh grass. “Let’s sit. We’ve got a little while before the tide reaches us.”
The heron whose territory they’d invaded studied their movements briefly, then dipped its beak into one of the sluggish streams braiding the marsh. It grabbed a squirming fish, flapped its wings in graceful slow motion, and took flight.
The trio seated itself on the decaying, moss-covered log, Tim to Rob’s right, Cassie on the other side. Rob turned to Cassie. “You’re from U-Dub?” he said.
“Oh, this.” She patted her ball cap. “No, I guess I just like purple and gold. I bought it at a University of Washington bookstore. I’m actually from Troy.” She offered an inscrutable smile, something that suggested she might harbor some sort of secret, but Rob found himself unable to decipher what might be involved.
Instead he said, “Troy University? Good school. What’s your field?”
“Strategic Communication, but I guess I’ve morphed into more of a cultural anthropologist. You know, studying the history of Native American tribes in the Northwest. How about you?”
“from the University of Washington, then got my doctorate from Oregon State in geology with a specialization in geophysics and plate tectonics. Have my own company in Portland now.”
“Then you really are an expert in all of this?” She moved her gaze over the marsh.
“As much as one can be, I suppose.”
She didn’t respond right away, but appeared to study him intently, a non-threatening appraisal.
After several moments she said, “You’re apprehensive about something. I sense it.”
He stared at her, puzzled, and a little surprised.
She shrugged. “It’s a gift I have.” She looked into the middle distance, seeming to focus on nothing. “Or maybe a curse.”
He nodded. “Here’s the thing, Cassie. What took place here is not just an interesting geological study of something that happened in the past. It’s a canary in a coal mine.”
“The past as prologue to the future?”
“Exactly.”
“If you’ve got time, I’d like to hear about it.”
“Sure, but bear with me for moment. I have to start with a quick lesson in something called plate tectonics.”
A smile crept across her face. “I’ve been learning all my life. Go ahead.”
“Over the past century, we’ve discovered that the outer shell of the Earth consists of rigid plates, kind of like the cracked-but-not-completely-broken shell of an egg. These plates, seven or eight huge slabs and many smaller ones, ‘float’ on a viscous mantle beneath them.”
“Continental drift,” Tim piped up, recognition of the concept flashing in his eyes.
“Well, maybe you got some of your old man’s genes after all,” Rob exclaimed, raising his gaze skyward in a gesture of praise. “At least it’s good to know you haven’t been spending all your time thinking about babes in bikinis.”
Tim’s cheeks flushed again. “Come on.” He flicked his gaze in Cassie’s direction. She isn’t family.
Cassie laughed, something melodious and timeless. “Hey, you think babes don’t ever think about guys, too?” She redirected the conversation. “So, we’ve got continental drift which, I gather, isn’t always smooth.”
“It’s not,” Rob said. “Around the globe there are a number of ‘subduction zones’ where one plate is sliding beneath another—subducting. Usually this happens where a heavier oceanic slab is knifing underneath a lighter continental plate. If the plates get locked, that is, stuck together with the subducting plate dragging the edge of the upper plate along with it, then they sometimes ‘unlock’ in a single, violent event. The result is what geologists call a megathrust earthquake. I was telling my son about that earlier.”
“Is that what happened here?” Cassie asked.
“It happened here. It happened in Sumatra in 2004. In Japan in 2011. It’ll happen here again. And when I say ‘here,’ I mean in the Pacific Northwest. That’s because there’s something called the Cascadia Subduction Zone just offshore. It extends from southern Vancouver Island to northern California. It’s where the Juan de Fuca Plate is sliding underneath the North American Plate.”
“How far offshore?” Cassie asked.
“From where we are, the leading edge of the zone is maybe fifty miles west. But for all practical purposes, we’re standing on it.”
Tim stood, tugged the brim of his stocking cap up, and surveyed the area again. “So there was a big quake—”
“Monstrous quake. The shaking would have felt like ocean swells rippling through the earth and probably lasted for several minutes. It would have been difficult to stand. The ground deformed, cracks yawned open, portions of the land suddenly subsided by as much as eight or ten feet. Then the sea invaded, rushing in like a forty-or fifty-foot-high storm surge—the tsunami. The dense grove of trees that had lived here for centuries suddenly found itself swamped in saltwater. They died. Only the skeletons of the cedar trees remained standing to remind us of what happened.”
“Don’t forget the Native American legends,” Cassie said. “They’re reminders, too, not just folklore.”
Rob nodded.
“So, 1700,” Tim said. “How can you be sure?”
“I can narrow it down even more than that. How about January 26th, 1700, at 9 p.m.?”
“Come on, Dad, that’s BS. The Indians didn’t have calendars or clocks, they didn’t write anything down, and apparently weren’t very precise in dating their stories.” He glanced at Cassie who bobbed her head in agreement.
“Actually, determining the exact date and time of the event is a fascinating detective story. It’s one that involves tree growth rings, radiocarbon dating, and knowing how fast a tsunami moves through the ocean. To summarize the tale, by carbon dating the plant material in the mud layer I showed you, scientists were able to narrow down the time frame to between 1690 and 1720. The technique is imprecise.
“But, by studying tree growth rings of these dead trees”—he gestured at the Ghost Forest—“and trees that were still living at the time, ‘witness trees,’ researchers pinned the time down to late 1699 or early 1700. It was like reading a barcode from Mother Nature.”
“So, 1700. And the rest you kinda guessed at?” Tim asked.
“Not at all. Enter the Japanese. They’ve been keeping written records of earthquakes and tsunamis since the 5th Century.”
“During the last years of the Roman Empire,” Cassie noted.
Rob shrugged. He didn’t know. “Anyhow, the Japanese recorded what they termed an ‘Orphan Tsunami’ in early 1700. ‘Orphan’ because it struck without a local earthquake as a precursor. So no one could understand where the tsunami came from. It washed over the Japanese
coast around midnight on January 27th.
“Investigators have since determined the ‘orphan’ could only have been triggered by the same monster quake that created this Ghost Forest and all the others along the coasts of the Northwest.”
“How could they know that?” Tim asked, appearing to be fully engaged by the story.
“Good question,” Rob said. “Forget being a writer. Work on being a scientist.”
Tim smiled and waited for his father to continue.
“Well,” Rob said, “given the size of the waves that smashed into Japan, around twelve feet, researchers calculated they must have been spawned by at least a magnitude-nine earthquake. Since there’s no evidence of any other megaquake from around 1700, it left only the one that struck here. Then, since scientists also knew it would take about ten hours for a tsunami to race from here to Japan, it pinpointed the time of the quake as 9 p.m. on January 26th.”
“That’s pretty cool, Dad.”
Rob stifled a chuckle. A breakthrough. My teenaged son thinks science is cool.
“I’m not sure I know what a magnitude-nine earthquake means,” Cassie said. Something caught her eye and interrupted her thoughts. She sprang from the log where they’d been seated and pointed toward the thick forest bordering the marsh. “Look,” she exclaimed. A herd of about a dozen elk, females and youngsters, wandered along the verge of the evergreens, grazing on grass and leaves and giving Rob, Tim, and Cassie only a cursory examination.
Rob stood, too. “That’s why I love field work. Not too many other jobs have an office environment like this.” He glanced at the river. “We’d better be heading back. The tide’s coming up quickly now.”
They trudged toward their moored canoes. “You asked about magnitude,” Rob said to Cassie. “The old Richter Scale has been put out to pasture. We now measure earthquakes with something called the moment magnitude scale. The Richter and moment magnitude are basically similar for smaller convulsions, the quakes in the three to seven range, but for larger ones, the megaquakes, moment magnitude is much better at capturing the total energy released. That’s because monster quakes don’t necessarily shake harder, they shake longer.”
“Could you put this whole idea of magnitude into a context for me?” Cassie asked. “That would help me understand better.”
“Me, too,” Tim chimed in.
“Sure,” Rob said. “The Sumatran megathrust quake was a nine-point-one. The 2011 monster off the coast of Japan was a nine.”
“What was the biggest ever?” Tim asked.
“After the advent of the seismograph, that is, when we were actually able to measure the intensity of ground shaking, that would have been a nine-point-five off the coast of Chile in 1960. It claimed over sixteen hundred lives.”
“Wasn’t there a major quake in Alaska around that same time?” Cassie asked.
“Prince William Sound, 1964, a nine-point-two. Did an immense amount of damage in Anchorage and launched a tsunami that killed a dozen people as far south as Crescent City, California.”
“How about quakes in the Lower 48?” Cassie asked.
They reached their canoes. The incoming tide had lifted them almost to the level of the marsh.
“Well, among the more famous, or infamous, the quake that destroyed San Francisco in 1906 was a seven-point-seven. The Bay Area earthquake that occurred during the World Series in 1989 registered a six-point-nine. More recently, the Northridge quake in Southern California in ’94 checked in at six-point-eight. None of those, by the way, was a megathrust earthquake. They didn’t occur near subduction zones.”
“Is there really that much difference between, say, a six-point-eight like Northridge, and a nine-point-one like Sumatra?” Tim asked. “The numbers don’t seem very far apart.”
“The moment magnitude scale is logarithmic,” Rob said. “Have you studied logarithms in school yet?”
“Yeah.”
“So you know that each whole-number increase on the scale represents a factor of—”
“Ten,” Tim interjected.
“You’re right. See, you really do have the makings of a scientist. But here’s the deal, for total energy released—that’s taking into account how long the shaking goes on—each full step in the scale represents a thirty-fold increase.”
“Still a bit abstract,” Cassie said.
“Okay, think of it this way. Weight aside, consider something the diameter of a large pearl. Let that represent the energy in a six-point-eight tremor. Like for Northridge. A lot of damage there, right? Now consider a nine-point-one megathrust. Sumatra. You’re talking about something the size of a bowling ball. There’s a big difference between the diameter of a pearl and a bowling ball.”
“That helps,” Cassie said. She stooped to tug her canoe closer. Tim stepped forward to help. “Thank you,” she said. She turned to Rob. “So what’s the thinking about the magnitude of the 1700 quake?”
“At least a nine. But it wasn’t just 1700. I don’t have time to go into detail now, but by examining sediments cored from the seafloor off the Pacific coast, researchers have determined there probably have been at least nineteen megathrust earthquakes over the past ten thousand years, and at least that many ‘smaller’ ones.”
“What’s the difference?” Tim said, whacking his hands together to get the mud off.
“The megathrust quakes represent a full-length rupture of the Cascadia Subduction Zone, from Vancouver Island to northern California, almost seven hundred miles. The smaller ones, still monsters by any standards, occur when only a portion of Cascadia rips, usually the southern half, from southern Oregon to northern California. Even those quakes probably check in between eight-point-two and eight-point-six.”
“Nice,” Cassie said. “So there’s a sleeping giant under us?”
“Interestingly enough,” Rob responded, “Cascadia is essentially a Doppelgänger of the Sunda Trench, the subduction zone that triggered the Sumatran disaster.” He let the statement hang. The television and YouTube images of the tsunami surging through Thailand’s resort areas and Banda Aceh flashed through his mind. A tiny dart of terror knifed into his psyche. He blinked and drew a deep breath, willing the vision to disappear.
“You okay, Dad?” Tim asked, resting a hand on Rob’s shoulder.
“Sure. Just a bit tired. Time we get back to Portland. Mom will be worried if we’re late.”
“We shoulda brought the plane.”
“I’m not instrument qualified, remember?” He pointed at the lowering cloud deck. “This is strictly IFR weather.” A splatter of rain emphasized his point.
Cassie retrieved her paddle from the canoe, ready to depart. “So I guess the real question is not how bad things might get here, we kind of know that, but when?”
“That’s the long pole in the tent. We don’t know. We do know the full-length rips in Cascadia, the ones that trigger the biggest quakes, come along every five hundred years or so. But if you tally all the quakes, including the so-called smaller ones, the interval is around two hundred and fifty years.
“Here’s the catch, though, there’s no real rhythm in the intervals. The marsh records and sea sediment cores suggest there have been gaps as short as a hundred years, but also as long as a thousand. There’s no predictive value in that. If you look at just the last five megaquakes, the intervals have averaged around three hundred and twenty-five years. So does that mean we’re due? Or does that mean the stress in the locked plates may have been relieved enough by the more recent convulsions we don’t have to worry for another millennium?” He paused. “No one knows for sure.”
A seagull coasted overhead and issued a sharp cry.
Cassie prepared to step into her boat. “And even if you knew, who would listen?” Her gaze seemed to drift away again to something distant and unseen. “Oracles of doom never see
m to fare well. People don’t want to believe dire news. Think about the Old Testament prophets. Isaiah, by some accounts, was sawn in half. Jeremiah, who was reviled and ridiculed, lamented his own birth. Zechariah was murdered.”
Rob steadied Cassie as she seated herself in her canoe. “Yeah,” he said, “I should probably stay out of the soothsaying business.”
“Well, perhaps we’ll run into each other again,” Cassie said. I’ll be working on the Oregon coast through the summer.”
“We’ve got a beach house in Manzanita. So maybe.”
With Cassie in the lead and Rob and Tim following, they moved off, paddling against the incoming tide, but riding the lazy seaward drift of the Copalis.
Rob allowed his thoughts to wander. Back to a dark winter night along the Pacific Coast of North America when the earth shook and dogs yowled and seawater surged and people died—the wrath of what must have seemed a mythological beast, angry and fierce and relentless. He looked around and shuddered slightly, knowing it still lurked.
“In medieval times,” he said, raising his voice to be heard over the steady slap of their paddles, “maps often carried sketches of dragons to represent the guardians of unexplored territories. In fact, some ancient mapmakers entered the inscription ‘Here Be Dragons,’ to warn of such dangers.”
Cassie looked back.
Rob stopped paddling. “We could stamp that on modern maps of the Pacific Northwest.”
Chapter Three
Nightmare
Lake Oswego, Oregon
A Portland Suburb
Wednesday, May 27
“I HAD THAT DREAM again last night,” Rob said. Seated at the breakfast table, his hand trembled as he lifted a mug of coffee to his lips. His stomach roiled as he sipped the hot liquid. He considered spitting the coffee back into the mug, but dismissed the idea. Instead, in an unsteady motion, he placed the large ceramic cup back on the tiled table. A dollop of the mug’s contents splashed out.
Cascadia Page 3
