It is one of the largest earthquakes ever recorded in the Rocky Mountains. Located just outside the northwestern boundary of Yellow-stone National Park, the Hebgen Lake M 7.5 earthquake occurred at 11:37 pm, August 17, 1959, and registered shaking intensities of X on the Modified Mercalli scale (a relative intensity rating from 1-12 shown in Roman numerals).

The quake caused several landslides and rock falls, including one enormous slide that temporarily blocked the Madison River Canyon, creating a lake nearly 175 feet deep.

Spectacular fault offsets occurred along the north shore of Lake Hebgen with maximum displacements of 21 vertical feet.

Most of the 28 people killed were due to landslides and rock falls within the mountainous areas.

Purchase a poster-sized map of earthquakes in the United States here.

Purchase a poster-sized map of California/Nevada Earthquakes here.

Track weekly earthquake activity with the comprehensive Seismo-Watch Earthquake Reports.

• Global
• Northern California
• Southern California
• Western Basin and Range

You can also track local activity maps from

• Central California
• Eastern Sierra (Western Basin and Range)
• Mammoth Lakes
• Coachella Valley
• Pacific Northwest

Seismo-Watch EQ Flash! Alert Bulletins are a great way to be informed right away when significant earthquakes occurs.