What happens when the Big One hits?

Tuesday, August 31, 2010

By Jake Nichols

Jackson Hole, Wyoming - Jackson Hole residents tend to believe the end of the world will come when a dormant supervolcano beneath Yellowstone NP awakens from its 600,000-year-old slumber. At least when that happens there will be warning, a chance to pack a few things for a doomsday vacay. But other things go bump in the night – sudden events with no forewarning. A catastrophic earthquake in Jackson Hole might be the true end of the world for many valley residents, and it might go something like this …

Hank pulls into the driveway at his East Jackson rental, gets off his bike and falls down. He biked home from the Tavern because he knew he had too much to drink. Still, he didn’t think he was this drunk. He rises, but loses his balance again. His bike headlight dances all over the place. Hank feels sick.

At Dornan’s, Beth dreams she is kayaking. Waves roll under her touring Dagger and she paddles to stay upright. She wakes in her employee cabin surprised at how real the dream felt, then watches as a riffle rolls under her entertainment console and knocks her TV to the floor that seems to be flowing like liquid. She sees the Grand to the west where a wall used to be, and the roof begins to rain pieces of plaster. Beth crawls under her bed.

eanne bolts upright and looks at her husband Gerry beside her. The California couple is spending their second day of a week’s stay in a quaint condo in the Aspens. Jeanne knows right away what it is and it’s a big one. The two race downstairs, grabbing nothing. Gerry pauses for a moment – “I should shut off the gas” – but he has no idea where it is. They spill out into the parking area with a dozen other frightened vacationers …

Then, The Sirens Go Off.
A noticeable jump in seismic activity lately has got valley residents asking the question, “What if?” A patch of activity in the Gros Ventre followed a unique earthquake swarm in Yellowstone at the beginning of the year. If a magnitude 4-point-something earthquake, as measured on the Richter Scale, epicentered 20 miles away rattled the windows in Jackson, what kind of destruction would a 7.5 earthquake wreak if it were centered in the heart of the valley on the Teton, East Gros Ventre or Hoback faults?

Quick Geology Lesson
The Teton landscape is a tectonic battleground, with numerous active faults showing the scars of the geological tug-o-war. The young Teton Range is one of the world’s finest examples of an upfaulted mountain block. As the Tetons continue to rise – at the rate of one inch every 10 years – they pull at the fabric of the sinking valley floor. The result is what geophysicists call a “normal fault,” as opposed to a “strike-slip” fault like Southern California’s San Andreas.

“The Teton fault formed because of extension,” said John Willott, the president of Geologists of Jackson Hole. GJH is a group of active and retired geoscientists who enjoy studying the fascinating behavior still taking place underneath our feet. “The rocks found two miles up at the top of Moran, for instance, are also the same type found miles deep beneath the surface of the valley. In the last two million years, this valley has been slowly pulling apart. When you start doing the math you realize the Teton Fault has had a number of very large earthquakes.”

All Quiet on the Western Fault
Scientists have been studying Teton Fault since the turn of the century. David Love is responsible for most of the definitive work on the valley’s crooks and crannies through his studies in the 1960s. Still, no one has ever been able to answer the million-dollar question: When? They’re also uncertain of the warnings. Can solar flares cause earthquakes? Weather? Time of year? Time of day? Will my dog behave oddly before an earthquake?

“Nobody knows,” Willott said. “Much has been speculated but nobody has ever been able to prove anything. In California, quakes tend to happen in the morning so people thought it might be the heating of the sun. There are lots of theories.”
All scientists can do is extrapolate data from layers of rock and sediment – data stored on Earth’s hard drive. A 2000 study by Ivan Wong and others estimates that the Teton Fault is capable of generating a magnitude 6.9 to 7.5 earthquake.

Research has shown a 7.5 event has a recurrence interval of 800 to 3,600 years. The last major earthquake on the Teton Fault was somewhere between 4,800 and 7,000 years ago, suggesting, according to a J.C. Case Earthquakes in Wyoming study (1997) that “the Teton Fault may be overdue for a magnitude 7.5 earthquake.”

Willott, too, said no news is bad news. “Here in the valley there have been several thousand earthquakes since the mid-80s,” he said. “Three weeks ago, we experienced one of the largest in the last 20 years. Almost all of those earthquakes have been in the Gros Ventre, virtually none on the Teton Fault itself and that has us a little worried. You would like to see some small ones there. There is a sense that it’s still kind of locked up.”

Many geoscientists ascribe to the theory that numerous smaller quakes relieve pressure and help stave off the ‘big one.’ The recent burst of activity in the Gros Ventre near Red Rock Ranch is business as usual for an area Willott calls “a pivot point” for the valley. Similar swarms rocked the Gros Ventre Wilderness in 1925, 1996 and 2004. Willott also joins the camp of experts that think there may be correlations between tremblers worldwide.

“My personal opinion is that what we are seeing right now is a result of the Easter Sunday earthquake in Baja,” Willott said. “There have been thousands of earthquakes since then along the San Andreas Fault and smaller ones in Nevada and Utah. In that earthquake, basically a chunk of California got pulled away from the rest of the continent. The effect rippled right up the Western U.S.”

Shake, Rattle and Roll
When the big one hits, what seems like the end will only be the beginning. Landslides will obliterate hillside vacation homes. Misinformation and panic will beget poor decisions that could accelerate disaster. Fires will rage throughout the valley, occupying firefighters until a wall of water rumbling south makes them a lesser concern. Once held at bay by the Jackson Dam, the Snake River will return to its natural state, reclaiming its original name – the Mad River.

There will be nowhere to run after a major tremor shocks the valley. Bridges will wash out – WYDOT estimates 80 percent of them in Teton County will crumble – and canyon walls will ooze like soft snow, plugging exits to the south. Mountain passes won’t be much better. Decisions made in the first few hours following a major earthquake, combined with a preconceived plan of action, could mean the difference between life and death.

A M7+ earthquake will trigger a series of events. Communication, between authorities and the public, will be essential. Seven air raid-type sirens are positioned at Teton Village, the airport, Teton Pines, Wilson Fire station, Jackson Fire station on Pearl, Adams Canyon and Hoback Fire station. A three-minute wail will signal an emergency.

The sirens at the Village and in downtown Jackson are confirmed voice-capable (others may also be). The message will blast: “Your attention please! An emergency situation has occurred or is imminent. Repeat! An emergency situation has occurred or is imminent. Tune to local radio, TV, or all-hazards weather radio for further information.”

EAS broadcasts will interrupt local radio programming. Bresnan will broadcast message scroll information on all of its channels. In the event that power outages or other circumstances cause local radio and television to cease, battery-powered NOAA Weather Radio will keep citizens informed with messages relayed from their Riverton base.

Area bridges carry phone and power lines underneath them. Rich Ochs – head of Teton County Emergency Management, formerly known as the FEMA-sponsored Project Impact – said that there is a good chance normal lines of communication will be down and scattered power outages will be experienced. With 911 jammed with local calls, families will be better off using someone out of state as a designated contact, Ochs said.

“Typically following a disaster, if phone lines are still intact, making local calls is next to impossible,” Ochs said. “Long distance calls are usually much easier because those lines work on separate circuits and will probably not be jammed.”
Ochs said that emergency responders in Teton County have the ability to override normal landline activity and can usually get a dedicated free line. If not, or if phone lines are severed, many first responders have satellite phones or ham radio options.

In the event of widespread destruction, state aid will be made available almost immediately – a Wyoming National Guard unit stationed in Afton specializes in bridge repair and bridge building. Federal resources would also be available even before the area is officially declared a national disaster thanks to the unique relationship with Wyoming’s national parks and forests.

If Jackson Hole is shut off from the outside world for an extended period of time, Smith’s and Albertsons – whose staff say they have a three-day supply of food and water in-store – would be commandeered by local authorities for rationing and two state-owned C-130 cargo planes could airdrop supplies.

The Damned Dam
Rescue efforts and survivability after a major quake will depend on the likelihood of the dam at Jackson Lake holding up. A Bureau of Reclamation study prepared in the mid-1980s claims the dam can take a M7 hit. Some experts aren’t so sure.

“The issue with the dam makes many of us nervous,” Willott admitted. “The Bureau of Reclamation said [in the event of a M7.5 quake on the Teton Fault] the concrete portion of the bridge that you drive across would be subject to 90 seconds of shaking at an equivalent of a magnitude eight. The earthy part underneath it would be subject to an M9 for three minutes. Think about that. Three minutes of shaking at magnitude nine. It might hold, it might not.”

Founder of GJH, Wallace Ulrich, who was named State Geologist last month, explained that the generally accepted formula means valley tremors are felt with more intensity at Jackson Lake dam.

“A 7.5 release could create 8 to 9.5 magnitude at the dam site because of the energy release,” Ulrich said. “The Bureau of Reclamation said the dam might settle a little but didn’t think it would fail. Another geologist on that study said that’s incorrect.”

In some cases, earth turns to mush in a process called ‘soil liquefaction.’ “Water gets expelled from rocks with a lot of water in them when you shake them,” Willott said. “The rock underneath the lake has been there for a long time carved by glaciers with a lot of water-filled sediment.”

Liquefaction was first evidenced in Alaska in 1964 when a M9.2 earthquake ‘melted’ the ground beneath Anchorage buildings causing them to sink out of sight.
“If we have a catastrophic failure of the dam, people in Moose will have five hours to evacuate for higher ground,” Ochs said. “Water will reach Wilson and Jackson eight hours after the dam manager phones in with the word that there has been a dam breach.”

Downtown Jackson will likely not experience flood waters, but areas like Teton Village, the Aspens, Teton Pines, Wilson and the West Bank will be submerged. Ochs said that a collapse at Jackson Lake dam can mean additional failures along the way including Palisades and American Falls. Floodwaters will reach Idaho Falls 24 hours after releasing from Jackson Lake.

Earthquake Prep
In the minutes following any natural disaster, Ochs can be found juggling a two-way radio and satellite phone.

“Essentially, I have a really big rolodex and I can get people to do things for us,” Ochs said. For instance, minutes after the massive slide at the Headwall at Jackson Hole Mountain Resort on December 29, 2008, Ochs was headed to the scene with the Wyoming Office of Homeland Security on the line. “Initially there was a potential 10 to 15 people buried. We mobilized FEMA’s Search and Rescue team and they were on the tarmac in Denver ready to be here in 45 minutes. That’s the kind of thing that we can do.”

September begins National Preparedness month. Like all public safety agencies, Ochs stressed that preparedness begins with a ‘ready kit.’ In the event of a disaster like a major earthquake, it may be days or weeks before help arrives. Check www.tetonwyo.org/em to see what essentials could help ensure survival. In Jackson, all buildings are required to meet International Building Code. Most public buildings exceed seismic safety guidelines for this area. Casualties often come in the hours and days after a quake.

“We use an earthquake often as our ultimate disaster scenario because an earthquake will produce what we call cascading effects,” Ochs said. “An earthquake will potentially cause landslides and avalanches which then can rupture gas lines and cause fires. Then there is always the potential that the dam could be damaged which could in turn cause flooding. Our mindset in emergency management is that if we plan for the earthquake, we are essentially planning for every other disaster too.”

Willott and Ulrich are just two of the seismic experts keeping an eye on the valley. Both are quick to assure residents that Jackson Hole has one of the most sophisticated and extensive monitoring networks in place in America thanks to groundwork laid by Bob Smith at the University of Utah.

After the Teton Dam failed in Teton Valley, Idaho on June 5, 1976, the Bureau of Reclamation installed an extensive seismic monitoring system in 1986 which remained in place until 2001 when it was removed due to budget restraints. Ulrich and the GJH worked with the state to get a new system put in place in 2003. It includes six real time seismogram stations scattered throughout the valley, monitored through the University of Utah (www.quake.utah.edu/helicorder/).
As a retired geophysicist, Willott said that Jackson Hole is a fascinating place to spend his twilight years. “We have everything here: the active tectonics that made our mountains, volcanism from Yellowstone, glaciations right over the top. You can all see it from the road. It’s a geologist’s heaven.” JHW

Image by Ben Carlson

PERMALINK:
What happens when the Big One hits? | Planet JH News Article: Cover Stories

Leave a Comment