1935 – Helena, MT (series) – M 6¼

Intermountain Seismic Belt Historical Earthquake Project

October 18, 1935 – Helena, MT (series) – M 6¼

October 12, 1935 – Foreshock (M 5.9)

This early morning earthquake (12:50 a.m. local time) caused many frightened residents to run from their homes. It was reported that despite the alarm people felt, many maintained a sense of humor about the event as they gathered in the streets and swapped stories of their experiences. No deaths resulting from the foreshock were reported.

Reports described damage as severe and widespread throughout the city. Windows were broken, stock was shaken from store shelves, pipes and wires were broken, chimneys toppled, furniture overturned, walls were cracked and plaster was shaken from walls and ceilings. It was reported that City Engineer Oscar Baarson estimated total damages between $50,000 and $75,000.

Following the foreshock, two officials advised taking measures to make buildings more earthquake resistant. Suggested measures included bracing chimneys, deeper foundations especially on loose soils, fastening brick veneers to walls, discontinuing the use of veneers altogether. Other suggestions included revising the building codes to make structures more earthquake resistant.

The earthquake was reported felt in Great Falls, Butte and Dillon, MT. Additional smaller earthquakes continued to be felt. In a news article published on October 17 it was reported that the Helena Weather Bureau had recorded a total of 52 earthquakes as of October 16 with the latest two quakes being 12 hours and 45 minutes apart. The article concluded that, “The fact that the quivers are so far apart indicates that the ‘earthquake season’ is drawing to a conclusion.”

October 18, 1935 – Main Shock (M 6¼)

At 9:48 p.m. (local time) the city was rocked by the magnitude 6¼ main shock. Some individuals screamed and ran from buildings. One person was reported killed when he was crushed under a brick wall that fell into the street. Another died from injuries sustained from a building collapse. A score or more individuals were seriously injured, most from being struck by falling debris as they ran out of buildings. As terrified people fled the city by car, a number of automobile accidents occurred resulting in additional injuries.

The earthquake knocked out lights and power for approximately an hour causing further terror, and difficulty for doctors attempting to treat the injured.

Significant damage occurred to many buildings with some entirely destroyed. Approximately 300 homes were damaged so badly as to be uninhabitable. One report described the streets being strewn with debris. Telephone service was interrupted for more than two hours.

City Engineer Oscar Baarson estimated damages from the earthquake at a minimum of $2,500,000. A report on October 21 indicated that Mr. Baarson requested patience as he and a crew of seven worked their way through several hundred requests for damage inspections.

The American Red Cross, Federal Emergency Relief Administration (FERA) and National Guard, assisted in providing first aid stations, sleeping quarters and kitchens for the hundreds of people rendered homeless by the earthquake. The local Y.M.C.A. invited homeless individuals to shower at their facilities for no cost. Authorities estimated it would be a week before people were allowed to resume normal affairs in the city.

The Red Cross reported 100 requests (representing approximately 400 individuals) for emergency food and medical care. The Red Cross also prepared to assist with a home rebuilding program for families in need. Local banks pledged resources for making home repair loans as approved by the Federal Housing Administration.

Surface cracks 150 feet long, three feet deep and several inches wide were reported at one location in the Helena Valley.

The earthquake was reported felt over a wide area of western Montana, but no damage outside the city of Helena was reported. Additional felt reports were received from Washington and Idaho.

October 31, 1935 – Aftershock (M 6)

At 11:37 a.m. (local time) a significant aftershock occurred near East Helena, MT. One report noted that the shock surprised Helena residents, who had believed the worst of the shaking had occurred earlier in the month. The report also noted that aside from some fainting spells, little panic was observed. However, some individuals evacuated the city by car.

Cracked plaster and broken windows were reported. Two school buildings suffered significant damage. On the west side of the city, there were reports of fallen chimneys. However, on Helena’s east side, some buildings that had been only partly damaged by the main shock were completely destroyed when the aftershock occurred. It appeared that most of the damage was to structures already weakened by the main shock. Damage to buildings that had been unaffected by the main shock consisted mostly of cracks in plaster and exterior walls and damaged chimneys.

Two brick masons, part of a crew from Salt Lake City, were killed from falling bricks as they were removing a smokestack at the local brewery. There were at least nine individuals who suffered serious injuries during the aftershock.

The north wing of the new Helena High School, already badly damaged from the main shock, completely collapsed during the October 31 aftershock. It was reported that 25-30 men who were working in the building escaped without injury thanks in part, to their foreman who shouted reminders for them not to run out of the structure.

Plans to open city schools following the main shock were cancelled when the aftershock occurred. It was later decided that schools would not open until after the new year.

November 28, 1935 – Aftershock (M 5.5)

Less than a month later, the city experienced another significant aftershock that struck at 7:41 a.m. (local time). The earthquake did not cause significant new damage in the city of Helena. It was, however, reported to be among the strongest of the series felt outside the area in locations such as Great Falls, Butte, Missoula, Kalispell and Deer Lodge among others. Bozeman reported only light shaking.

Following the earthquake, City Engineer Oscar Baarson revised his estimate of total damages from the earthquake series to $5,000,000.00 or more.

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1902 – Pine Valley, UT – M 6±

Intermountain Seismic Belt Historical Earthquake Project

November 17, 1902 – Pine Valley, UT – 6 ±

In the early afternoon of November 17, 1902 residents of Pine Valley, UT were startled by a magnitude 6 (+/-) earthquake. The shaking caused individuals to flee their homes, some being hit by swaying doors and jambs as they ran. Most of the chimneys in town were reportedly damaged. Clocks stopped. Some individuals reported seeing clouds of dust in nearby canyons as rocks weighing many tons came crashing down. Poultry and domestic animals were frightened. Some individuals reported that upon putting an ear to the ground, they could hear a low roar like a stove burning. Though residents were on edge day and night, no one was reported to have evacuated the area.

To the south, in St. George and Santa Clara, there were reports of considerable damage to many buildings. The shaking was strong enough in some buildings to flip hanging pictures completely over. Terrified children and adults ran from homes and other buildings, some experiencing the sensation of seasickness. Many residents were afraid to reenter their homes. Clouds of dust were seen in many directions from falling rocks as far as 25 miles away. It was reported that in some places, hot and cold springs were increased in their flows and waters became muddy.

The earthquake was reported felt in other cities and towns in the surrounding area including Bloomington, Pinto, Cedar City and Toquerville. Individuals in these areas reported damage such as toppled chimneys, falling ceiling plaster, cracked walls, items toppling from shelves, frightened people rushing from buildings and huge boulders rolling down causing clouds of dust. The communities of Lund, Notom, Parowan, Marysvale and Tropic reported feeling the earthquake but suffering no damage.

Felt reports from Salt Lake City mentioned stopped clocks and jarred nerves but no damage. One establishment reported a substance that appeared to be volcanic ash on its windowsills, causing some to question whether the earthquake had activated extinct volcanoes in the southern part of the state. Some individuals speculated that ash from such a volcano could have been carried northward by strong winds. Closer to the epicenter, a few individuals reported seeing smoke above the Pine Valley Mountains and some reported seeing a flash of fire lasting a few seconds, though others reported detecting no evidence of volcanic activity in the area.

On December 4, it was reported that not a day had passed since the initial shock without one or two earthquakes being felt in Pine Valley. A report from St. George on the same day noted that residents there were rejoicing in the belief that the earthquakes had finally ceased – at that point it had been four days since a shock had been felt.

 

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1928 – Helena, MT – M 5½ ±

Intermountain Seismic Belt Historical Earthquake Project

February 29, 1928 – Helena, MT – M 5½ ±

The 1928 Helena, Montana earthquake had no reported injuries or damage. The shaking startled people throughout the city of Helena and was more noticeable on upper floors of buildings with two or more stories above ground. The shaking was severe enough to disrupt a trial in one city courthouse. Without taking time to formally adjourn the proceedings, the judge and others fled the courtroom as the shaking began.

The earthquake was reported felt in areas southeast of Helena including: Trident, Three Forks, Manhattan, Logan, Lombard, and Sixteen-Mile Canyon. White Sulphur Springs, to the east of Helena, also reported earthquake shaking.

There were reports of shaken buildings, windows rattling, furniture moving, and goods being shaken from shelves.

 

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1947 – Virginia City, MT – M 6¼

Intermountain Seismic Belt Historical Earthquake Project

November 23, 1947 – Virginia City, MT – M 6¼

The Virginia City earthquake was reported felt in several communities in Montana, including: Billings, Missoula, Lewistown, Livingston, Helena, Harlowton, Malta, Havre, Glasgow, Kalispell, and Bozeman; and as far south as Idaho Falls, Idaho.

In most areas, the earthquake rocked buildings with, what was described in Helena as, a “long and easy” motion. There were widespread reports of swaying light fixtures, stopped clocks, dishes rattling, and window blinds and curtains moving back and forth. Cracks in plaster were observed and a plaster ceiling fell in a café in Hamilton.

Near the epicenter, in Virginia City, bricks and plaster were shaken loose from buildings, windowpanes were shattered, walls were cracked, and chimneys damaged. There were also reports of pictures being shaken off walls and dishes falling from cupboards.

In some locations sleeping residents were awakened as the shaking dislodged icicles from rooftops. Strange noises were reportedly heard during the shaking, and some residents fled their homes in fear. However, there were no reports of injuries or significant damage resulting from the earthquake.

 

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1934 – Hansel Valley, UT – M 6.6

Intermountain Seismic Belt Historical Earthquake Project

March 12, 1934 – Hansel Valley, UT – M 6.6

Believed to be the most severe earthquake in Utah’s recorded history, the 1934 Hansel Valley earthquake was reportedly felt as far west as Elko, Nevada and as far east as Rawlins, Wyoming. Felt reports were also issued from as far north as Boise, Idaho and as far south as Richfield, Utah.

The main shock occurred approximately 30 miles north of the Great Salt Lake at 8:05 a.m. local time. Five significant aftershocks were recorded over a nearly eight-week period from March 12 to May 6, 1934.

Some of the most severe damage was reported in Logan, Utah and surrounding communities. At least two public buildings in the area had to be abandoned. A three-story brick building on the campus of the Utah State Agricultural College was, reportedly, split from top to bottom. In Preston, Idaho, the shaking dislodged a 150-pound capstone from the top of the local high school building, separating the west wall from the rest of the building.

Other reports of damage included falling chimneys, broken windows, cracked walls and falling plaster. Swinging light fixtures were observed during the earthquake. Furniture rocked back and forth or rolled across floors. Dishes and goods fell from shelves and clocks stopped. Near the epicenter, in Snowville, Utah, the water main was broken and out of service for 10 hours. In some locations schools were evacuated and closed, particularly following the first aftershock.

Near the epicenter of the earthquake the appearance of several fissures or cracks in the ground surface were observed. Witnesses reported hearing loud roars as the fissures ruptured. A geologist who later examined the area reported one of the fissures to be about eight miles in length. He found a maximum fissure width of 14 inches, with a maximum drop of the ground on one side measuring 19 inches. Other reports noted a downward displacement of the ground on the east of the larger, predominantly north-south trending fissures.

Phenomena described as sand or mud cones were observed near the epicenter. There were also sightings of new springs and streams changing course. Artesian wells that had been long dry began flowing with water. Other wells, active prior to the earthquake, ceased to flow for several hours.

In many locations, shaking from the earthquake sent people running out of doors. There were also reports of people fainting from fright. In areas of intense shaking, people were unable to stand during the earthquake.

Two deaths were attributed to the earthquake. Ida Atkinson died instantly from a heart attack upon hearing that the shaking she felt was due to an earthquake. Salt Lake City waterworks employee Charles Bithel was injured when a six-foot trench in which he was working at the time of the earthquake caved in. Bithel died from his injuries the following day in a local hospital.

 

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1959 – Kanab, UT – M 5.7

Intermountain Seismic Belt Historical Earthquake Project

July 21, 1959 – Kanab, UT – M 5.7

This earthquake was felt over an area of 21,000 square kilometers, primarily in southern Utah and northern Arizona, according to newspaper accounts. Dishes and canned goods were knocked to the floor, cars were jostled on roads, and minor rockslides occurred. Felt reports were received from as far south as Flagstaff, Arizona–approximately 195 miles from the epicenter.

Near the epicenter, in the Kanab-Fredonia area, there were also reports of windows and dishes breaking, as well as canned goods tumbling from market shelves. In Kanab, the police chief reported bricks falling from at least one chimney. And plaster in the county courthouse was shaken from the walls. A truck driver traveling through the area at the time of the earthquake related that he “thought his steering had gone haywire.”

The earthquake, which occurred at 10:39 am local time, sent frightened Kanab residents scurrying from their homes–but no injuries or significant damage was reported.

 

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1915 – Provo, UT – M 5.0

Intermountain Seismic Belt Historical Earthquake Project

July 15, 1915 – Provo, UT – M 5.0

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According to newspaper accounts this earthquake was felt throughout the Utah, Salt Lake, and Bear River Valleys, and also in Provo Canyon, Tooele, Parley’s Canyon, and Park City, Utah.  The felt area measured 13,000 square kilometers.

In parts of Utah Valley buildings swayed, chimneys toppled, building walls were cracked, and individuals were knocked from chairs and couches. Wallpaper was split over doors and plaster was cracked and shaken loose. Dishes and pans rattled. In Provo Canyon shaking from the earthquake caused rockslides which blocked at least one road. At Utah Lake an upheaval of water, like a small tidal wave, was sighted.

In the Salt Lake Valley clocks stopped, windows and dishes rattled, and furniture was knocked over. Cans and packages were shaken from grocery store shelves.

Shaking appeared to be more pronounced in the upper floors of taller buildings both in Provo and Salt Lake City. In some locations both in the Utah and Salt Lake Valleys, the shaking caused individuals to rush out of buildings. This was the case throughout Provo where people hurried into the streets wondering what had happened. It was reported that more than an hour passed before the city resumed normal activities.

There were no reports of injuries or significant damage from the earthquake.

 

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1975 – Yellowstone National Park, WY – M 6.1

Intermountain Seismic Belt Historical Earthquake Project

June 30, 1975 – Yellowstone National Park, WY – M 6.1

map-june30_1975
This earthquake was located approximately 5 miles ESE of Norris Junction, in Yellowstone National Park. According to newspaper accounts, no casualties resulted from the earthquake and damage was minor. Near the epicenter, telephone service was temporarily knocked out. The earthquake also dislodged boulders that temporarily blocked a road between Norris and Madison Junction – however, campgrounds and park facilities remained open.

A park service employee reported, “There wasn’t any noise; no dishes rattled. There was just a gentle rolling of the floor.”

The earthquake shook buildings and rattled windows 200 miles away from the epicenter, and was reported felt both in Great Falls and Billings, Montana. The total felt area of the earthquake was 50,000 square kilometers.

A significant aftershock (magnitude 5.5) occurred just over 17 months later on December 8, 1976, approximately 5 miles W of Norris Junction. This earthquake was the largest since the June 30, 1975 main shock, and was felt over an area of 5,000 square kilometers.

Park officials noted that the aftershock shook buildings, but no damage was reported. One park official believed that damage to the terrain would likely be limited to rockslides. The earthquake occurred after the close of the summer tourist season – the park service received no inquiries about the earthquake from individuals inside park boundaries.

 

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