A jumbled section of Vine Road, south of Wasilla, also made news, but what Alaskans remarked upon most was the speed with which roads were repaired. Rob Witter wanted photos of the slumped Minnesota off-ramp, seeking clues to the ground failure. “The next day I was in a helicopter and I was kind of bummed,” Witter laughs. “We couldn’t get a good shot of that off-ramp; it had already been pretty much fixed.”

Anchorage and Mat-Su valley schools nearly all suffered damage, from tumbled books and dropped ceiling panels to water damage and structural problems. Three schools—two in Eagle River and one in Houston—remain closed, pending at least a year of repairs. Students in Alaskan schools regularly perform earthquake drills to “Drop, Cover and Hold!” Practice and luck paid off last November. In over 100 area schools, among 50,000 students and staff, there were almost no serious injuries.

Huge boulders and snapped trees, remnants of the 2018 magnitude 7.1 quake, line the Turnagain Arm hiking trail near Anchorage. Debris from above shook loose and bounced hundreds of feet down the mountainside, cutting a swath through the forest. SUSAN SOMMER

In the Earthquake Lab

Alaska has three kinds of earthquakes. The most powerful and least frequent are megathrust monsters, arising where massive plates of Earth’s crust collide in slow, inexorable motion, with one plate sliding beneath the other in a process called subduction. In Alaska’s Aleutian Trench, subduction occurs where the Pacific Plate sinks and slips under North America. The 1964 megathrust quake started 15 miles deep under Prince William Sound; at M9.2, it remains the second largest earthquake ever recorded.

The quake that cracked Sonya Senkowsy’s chimney also came from subduction, but it wasn’t a megathrust. It was an intra-slab quake, 27 miles deep, inside the descending Pacific Plate. Unleashed where the plate bends and cracks as it dives under North America, it radiated seismic energy in waves that rolled and shook the surface.

Intra-slab quakes happen daily, many too small to notice. “Most little bumps and shocks that we feel are these types,” Witter says. Intra-slab quakes as large as the November M7.1 shake, or larger, occur less often.

Men who worked at the Hilton Hotel in downtown Anchorage stand in Town Square immediately after the quake, saying they didn’t want to be inside during aftershocks. ; ANN RAUP/ADN

Crustal earthquakes are a third type, produced by movement on shallow faults or cracks in the crust. The power of any quake depends on the size of the fault patch ruptured, and most crustal faults are relatively small. The 2002 Denali Fault earthquake ruptured a patch 200 miles long, however. The resulting M7.9 quake shifted ground 14 feet under the Trans-Alaska Pipeline, without causing a leak.

The Great Alaskan Earthquake of 1964 rang planet Earth like a bell, but Anchorage had no seismograph to record it. Today, over 30 seismographs monitor Anchorage 24/7. Six tall buildings and one bridge are also fitted with sensitive devices. The 20-story Atwood Building boasts 21 instruments alone, with seven more a block away buried in holes drilled up to 200 feet deep to record seismic waves in underground layers, revealing how different soils and materials can shape surface shaking.

“Essentially, we live in an earthquake laboratory,” says John Thornley, who chairs Anchorage’s Geotechnical Advisory Commission. “This is one of the most dense seismic networks in the U.S. The big story of this earthquake is, depending on where you were, you felt it differently. Everyone has a different story.”

The earthquake damaged many houses in the region—from minor cracks in drywall to major structural ruin such as the chimney at Sonya Senkowsky’s and Chris Floyd’s house. Here, demolition is underway to ready the building for renewal. COURTESY SONYA SENKOWSKY

Damage can strike anywhere during a major quake, but it is not random. Geology, soils, and topography can amplify shaking, increasing the risk of landslides and giving people a scarier ride.

During the November quake, Eagle River (15 miles north of Anchorage) seemed to fare worse than Anchorage. According to building safety guru Noffsinger, both inspection reports of serious damage and emergency relief applications were proportionately higher in Eagle River. Early speculation was that Eagle River was closer to the quake. “But the epicentral distance is pretty much the same,” John Thornley says. Instead, he outlines three things “working against Eagle River,” starting with topography, which can focus seismic waves like a lens.

USGS geologist Haeussler agrees. “If you have a nice view home along a steep bluff, that topography may have contributed to damage. Along the bluff right next to Eagle River itself, there’s a lot more red-tagged homes,” marked unsafe to occupy.

The November 30 shaker wasn’t Alaska’s largest for 2018. A magnitude 7.9 occurred off the coast of Kodiak in January that had people heading for high ground in their pajamas. This graph shows just how seismically active Alaska is. COURTESY ALASKA EARTHQUAKE CENTER

Second, just as ocean waves nearing a beach slow but steepen in shallow water, loose soil slows but amplifies seismic waves near the surface. Inspections showed some damaged Eagle River homes rested on unsafe, loose fill.

The third piece of the puzzle is building code. Anchorage requires building permits, Eagle River does not.

A permit buys two things, Noffsinger explains. First, “a detailed review” of building plans to ensure structural safety and code compliance. Then, during construction, “detailed inspections to make sure it’s being built per the approved plans. If you think about it, the plan review and inspection process is really cheap earthquake insurance.”

Most people in earthquake country don’t have earthquake insurance. Sonya Senkowsky and Chris Floyd did.

Days after the quake, a contractor decapitated the jumbled top of their chimney. When an engineer deemed the remainder unsafe, they tore that down, too, leaving a two-story hole in their house with no fireplace to offset heating needs boosted by building damage. Having spent $13,000 on demolition, they needed a like amount for a new chimney. They were not halfway to their 15 percent deductible, some $60,000. Their insurance would pay nothing.

The largest earthquake in North America, at magnitude 9.2, was the March 27 Good Friday shaker in 1964 that devastated Anchorage and triggered deadly tsunamis as far away as California. Pictured is 4th Avenue; today, it is still a main artery through the city’s downtown. COURTESY U.S. ARMY CORPS OF ENGINEERS

Approaching the Federal Emergency Management Agency, “at first, we were completely denied any funding, due to having earthquake insurance,” Senkowsky says. Armed with a letter stating insurance wouldn’t cover their damage, they returned to FEMA. Back and forth, talking with contractors, juggling inspections, meeting with FEMA. “The process, and the allocation of funds, was confusing and mind-boggling.” Regulations seemed arbitrary, often “designed for people in flooding situations or down south…Finally, we got around $6,200 for home repair and another couple thousand for living expenses during construction.” Praising “a very friendly supervisor,” Senkowsky concludes, “FEMA can definitely be helpful, but it breaks my heart and hurts my head to see how they actually work.”

One good result of the earthquake was a Facebook group Senkowsky created. “Neighbors Helping Neighbors” let people share experiences, advice, and support in navigating what she calls the bureaucratic aftershocks.

“Emotionally, I’m drained,” she admits. “I feel bad saying this, because I know how lucky we were, and I’m very, very glad it wasn’t worse. I’m also proud of us and our neighbors for pushing through. I got to see the best in many people as we reached out to and helped one another.”

An overwhelming amount of paperwork loomed for Sonya Senkowsky and Chris Floyd in dealing with fixing their house.

Earthquake Coda

Resilience is a common theme when earthquake experts speak of the quake, too. Ross Noffsinger reflects on how well Anchorage building codes performed. “It’s just basic science, basic engineering. But we can build buildings to resist earthquakes.”

John Thornley is grateful there were no deaths and few injuries, especially in schools. “It really speaks to the training that these kids receive,” he says. “I mean, there’s structural design to avoid collapse, but items like ceiling tiles can kill, too. So it’s pretty amazing there were so few injuries. I find it phenomenal.”

“I was really proud of our community,” Rob Witter adds, “proud of the way the city and Alaska Department of Transportation got together and started fixing road failures. The thing I take away from this is how resilient Anchorage is. There are still things to do, but yeah, I was just jazzed at how the community responded.”

Richard Emanuel is a science and nature writer who came to Alaska as a geologist 40 years ago. He loves volcanoes and earthquakes and lives in Anchorage with his wife and daughter.

1 2

Write A Comment