The Hebgen Lake Fault lies in southwestern Montana just northwest of Yellowstone National Park, along the margin of the Hebgen Lake basin in the Rocky Mountains. It is a normal fault, where the valley block drops down relative to the surrounding highlands as the crust of the region is pulled apart.
This fault sits within the tectonically active zone surrounding the Yellowstone volcanic system, where extension and hot crust drive frequent seismicity. Movement on such faults progressively deepens the basins and raises the flanking ranges.
The fault ruptured in the 1959 Hebgen Lake earthquake (magnitude ~7.3), the largest historical quake in the Rocky Mountains region. The shaking tilted the lake, dropped ground by several metres, and triggered the Madison Canyon rockslide that buried a campground and killed 28 people.