For the first couple of days after the quake, the theory persisted that the slide must have happened quite some time after the first shock—as late as 5:00 A. M., according to some theorists.
But, as the facts, and the testimony of folks trapped near the slide—the Osts, Fredericks, Smiths, and Mrs. Bennett—became available, it was apparent that the slide must have closely followed the initial shock. Even if you discount the disrupted time sense of people under stress—when a minute can seem like an hour, and vice versa—it’s difficult to imagine that more than 20 minutes elapsed between the first shock and the slide.
According to one set of calculations, big waves could have swept from the dam to the slide site in 18 minutes or so.
A man stands in the gap left by the earthquake-caused simple fault scarp.(U. S. Geological Survey)
Something slipped here! Before the quake caused the ground drop, creating this magnificent scarp, the ground surface shown here was continuous.(U. S. Forest Service)
Hebgen Lake Hebgen Fault Red Canyon Fault