2017 Annual Report

2017 Annual Report Cover Page

2017 Annual Report

I am happy to report the University of Utah Seismograph Sta- tions (UUSS) had another exciting and productive year in 2017. Thanks to all of you who support and promote our mission of reducing the risk of earthquakes in Utah through research, edu- cation, and public service.

An Mw 5.3 earthquake on Sept. 2, 2017, in southeastern Idaho reminded us that we absolutely do live in earthquake country. Thankfully, this earthquake caused little damage, but its shaking was felt throughout northern Utah, as far south as Provo. UUSS responded to the earthquake by partnering with the U.S. Geo- logical Survey and the Idaho Geological Survey to deploy a tem- porary array of seismographs in the source region. Using these data, we detected and located over 1,000 aftershocks in the two months following the mainshock. This allowed us to map out a previously unknown fault system.

UUSS also recorded enhanced seismicity in Yellowstone Na- tional Park during 2017. Between June 12 and Sept. 30, a swarm of over 2,400 earthquakes was recorded in the Maple Creek re- gion of Yellowstone. The largest event in the swarm was an Mw 4.4 earthquake on June 15 that was widely felt throughout the park. Although earthquake swarms in Yellowstone are common, this was the second longest swarm ever recorded. Yellowstone earthquake swarms are often related to the movement of fluids in the crust and usually do not portend a volcanic eruption; howev- er, it remains important to monitor them closely.

In 2017, UUSS continued working with the University of Utah team vying to host the Frontier Observatory for Research in Geo- thermal Energy (FORGE). This project is sponsored by the U. S. Dept. of Energy and aims to build a facility for developing tech- nologies related to enhanced geothermal energy production. The UUSS FORGE effort is led by Prof. Kris Pankow and is focused on quantifying the seismic hazard near the proposed FORGE site in Milford, Utah. Utah is one of two finalists for this project, and the winner will be announced in 2018.

We look forward to another exciting year in 2018. I encourage you to visit our web page at quake.utah.edu to stay up-to-date on our initiatives and products as well as to find out about the lat- est seismic activity in Utah and Yellowstone. You can also follow UUSS on Twitter with the handle @UUSSquake.

Best wishes, Keith D. Koper

1959 – Hebgen Lake, MT – M 7.5

Intermountain Seismic Belt Historical Earthquake Project

August 17, 1959 – Hebgen Lake, MT – M 7.5

The Hebgen Lake earthquake—the largest and deadliest earthquake recorded in Montana and the Intermountain West—occurred at 11:37 p.m. (local time) on Monday, August 17, 1959. The epicenter of the magnitude 7.5 earthquake was approximately 15 miles north of West Yellowstone, Montana (later revised by the U.S. Geological Survey to magnitude 7.3 and located 6.5 miles northwest of West Yellowstone). The earthquake was reported felt as far north as Banff, Canada; as far south as Provo, Utah; as far east as Dickinson, North Dakota; and as far west as Seattle, Washington (Stover and Coffman, 1993). Seven significant aftershocks ranging in magnitude from 5½ to 6½ occurred in the three months following the mainshock.

The greatest number of reported injuries and deaths occurred in the Madison River Canyon where the earthquake triggered an 85-million-ton landslide on a mountain five miles west of Hebgen Lake. The landslide roared down over a popular recreation area where an estimated 200 people were camping. The earthquake also caused a northward tilt of the Hebgen Lake bed. This triggered a reported 20-foot wall of water that overtopped Hebgen Dam followed by several 3-4 foot surges. Eyewitnesses reported seeing camping trailers swept down into the Madison River, cars and their occupants buried in dirt and rock, and trees flying through the air. There were reports of screams and cries for help. Twenty-eight individuals died from their injuries or were presumed buried in the slide.

The landslide dammed the Madison River, creating what became known as “Quake Lake.” Montana Highway 287, the primary route through the Madison River Canyon, was rendered impassable due to slide debris, fault scarps (as high as 18 feet) and sections of the highway that fell into Hebgen Lake.

Emergency responders parachuted into the area to establish communication and to provide first-aid. The injured were evacuated by helicopter to an aid station in West Yellowstone and then on to nearby hospitals by airplane. Deceased were airlifted to a morgue in the town of Ennis, Montana. Remaining survivors were able to evacuate later on roads that had been cleared or newly constructed.

According to one report, the ground shaking produced sixteen cracks in the Hebgen Dam. In spite of the damage it was determined the dam would hold. However, precautions were taken to evacuate the town of Ennis 45 miles away and to warn residents in the Madison Valley. The Army Corps of Engineers moved quickly to construct a spillway at Quake Lake before the rising waters topped the landslide dam. Additional earthquake tremors slowed work on roads and dams as well as search and rescue efforts.

When it was determined that no other victims would be recovered from the landslide, a brief memorial service was held near the mouth of the Madison River Canyon. Officiators from several denominations led the group of approximately 50 attendees in prayer. They also consecrated the slide as the final resting place for those who had perished.

The West entrance to Yellowstone National Park was closed with no travel possible along the park’s west side due to landslides, rockfalls and bridge damage. One individual in West Yellowstone at the time of the earthquake reported hearing an awful roar, felt his cabin shaking and lost electrical power. No buildings collapsed but many were severely cracked or damaged. Thousands of frightened tourists left the park, while curious onlookers arrived to survey the damage.

In Billings, Montana, the earthquake awakened hundreds of residents who reported swinging light fixtures, rattling dishes, rolling beds, swinging doors and shaking houses. One person reported that his swimming pool completely overflowed onto the patio.

In Bozeman, Montana, damage included downed chimney tops and store merchandise shaken from shelves.

For additional information about this earthquake:

Earthquake Summary 3D Newspaper Articles 3D Photos 3D Blank Thumbnail
Personal Accounts 3D Additional Resources 3D Blank Thumbnail Blank Thumbnail

For more information about this project:

ISB Hist EQ Proj