The temblor on that date was the largest of a series of earthquakes that also included a large aftershock on October 31 of magnitude 6.0 and a maximum intensity of VIII.

[6] The ISB is characterized by normal faulting of late Quaternary age, indicating active extensional tectonics, as recognized throughout the Basin and Range province to the south.

The most extensively damaged building was the Helena High School, which was completed in August 1935[2] and had just been dedicated in early October.

The first night, 400 people stayed there, but most had found space with friends or family outside of the damaged area by the end of the week.

[11] A computer simulation performed for the Lewis and Clark County office of Disaster and Emergency Services estimated that a 6.3 magnitude earthquake today would result in property damage over $500 million.