1966 Truckee earthquake was a real earth mover | SierraSun.com

1966 Truckee earthquake was a real earth mover

The Tahoe-Truckee area is always on the verge of the next earthquake. Minor quakes occur frequently throughout the region, but the 1966 shaker was one of the larger ones in the past century. Moderate earthquakes have been felt in the Truckee-Tahoe region since mankind has occupied the area.

The calm and quiet of the region northeast of Truckee was shattered at 9:41 a.m. on Sept. 12, 1966, when the Dog Valley fault running from Dog Valley to Donner Lake ruptured, causing an earthquake that registered from 5.5 to 6.25. The epicenter itself was located west of Boca Reservoir.

In 1948 an earlier quake struck the northern end of this fault causing a 6.0 temblor that was centered in Dog Valley. That one caused little damage except rocks rolling down onto US 40 near Verdi and Floriston.

The shallow quake lasted from 20 seconds up to a minute, depending on the soil under the people feeling the quake. Those on hard bedrock felt two sharp jolts, those on alluvium or sandy soils felt a longer rolling motion. Close to Truckee it was felt as two distinct shocks . The temblor was felt in Reno, San Francisco, and Modesto.

All over the Truckee area, damage was found from just 30 seconds worth of shaking. The mountains shook furiously unleashing rockslides from Donner Summit to the Floriston area.

The worst damage was in the Boca area.

The dam keeper’s house, occupied by the Kirby family, suffered the most damage. It had the chimney knocked off, landing a good 20 feet from the house. Twelve feet of the foundation crumbled into the basement, causing the death of four pet chinchillas the Kirby’s were raising. The interior was a shambles with belongings scattered everywhere. Mrs. Kirby and her year-old daughter happened to be in a closet at the time and were not inured.

In nearby Hirschdale and Floriston, chimneys were damaged or toppled over. Merchandise in stores and household goods in homes wee tossed to the floor. All of the residents were nervous waiting for the thousands of aftershocks to subside.

A boulder as big as a car was loosened above Interstate 80, rolled over the road at Farad. The rock wrecked a section of the wooden flume, passed on by and landed against the concrete powerhouse, knocking a nine-foot diameter hole in the wall.

Ten-foot diameter rocks came down on the freeway, causing traffic delays but no injuries occurred. Below Boca the outside lanes of the highway slumped toward the Truckee River 10 inches for over a thousand feet long.

The Interstate 80 bridges in the area had the most noticeable damage. The Union Mills Bridges suffered minor to moderate cracking and joints that shifted by greater than an inch. Other minor highway damage was noted.

In Truckee merchandise fell of the shelves at Z’s Market in Gateway, and groceries splattered to the floor in downtown in the Ponderosa Grocery. An off-duty deputy had a shelf full of frozen foods pummel him.

In the Truckee schools, students and desks were flung across the room. A few windows were broken and items fell from shelves. The fire alarm was sounded and the school was evacuated in an orderly way and students were sent home. No immediate serious injuries occurred, though a falling window after school resumed resulted in a broken arm of student Mark Sullivan.

The Prosser Reservoir dam sustained cracking in the exterior fill section about 2 inches wide. Only very cracks appeared on Boca Dam. A report of small cracks in the Tahoe City Dam at Lake Tahoe was never verified by researchers.

The Southern Pacific Railroad had numerous rock slides between Boca and Verdi that halted all westbound trains for a few days. The grade suffered so many slumps and slipouts along the river canyon, that re-grading and relaying of new track was required for a few days after the quake.

The wave motion was recorded in the US Geological Survey river gauging stations as a sharp wave in the levels of the river. At the Lake Tahoe Dam the water rose about five inches. A windstorm was blowing up big waves on the lake so reports of a three foot plus wave could not be substantiated.

Springs north of Truckee increased their flows and turned muddy for several days after. Small wells either filled up or dried up, depending on where they were in relation to the fault. The Truckee public utility district quickly repaired a broken six-inch water line, but murky water remained flowing in the pipes for a few days all over Truckee.

On the North Shore, merchandise fell on a man in Tahoe City, shelves full of glass jarred food crashed to the floor in a gigantic mess. Chimneys were also cracked on a few homes.

Reno felt the quake very sharply. Phone lines jammed with calls, as people feared that major damage had occurred. Merchandise in many stores strewn over the floors, plaster cracked in some buildings. The main Reno fire station suffered moderate cracking and was out of service for a month.

Gamblers and office workers in the downtown multi-story buildings all felt moderate swaying that sent the workers scrambling for cover, but the gamblers just played on. A crane operator building the 275-foot high Arlington Towers was thrown from his cab onto the roof, coming within four feet of being tossed to the ground.

This magnitude of earthquake have been occurring in the Truckee-Tahoe area for the last few million years. As the Carson Range on the east and the Sierra Nevada on the west rise, a long block of rock has slipped down, forming the depressions that are now the Martis Valley and Lake Tahoe. This block is fractured with multiple faults, most running north to south.

Every year, hundreds of micro and small quakes occur as these blocks slip past each other. But every decade or so, a large enough movement occurs that startles humans and causes minor damage. So the next time we have a real heart stopping quake you can blame the forces that created the mountains and valleys themselves.

Gordon Richards is the research historian for the Truckee Donner Historical Society. Please visit the Truckee Donner Historical Society Web site at http://truckeehistory.tripod.com. The e-mail address is tdhs@inreach.com. Past articles by Gordon Richards are available at http://www.sierrasun.com in the archives.

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