On January 30, 1973, at 15:01 (UTC–6), a magnitude 7.6 earthquake struck 35.3 km (21.9 mi) beneath the Sierra Madre del Sur range in the Mexican states of Colima, Jalisco and Michoacán.

The January 30 earthquake ruptured a shallow-angle section of the megathrust near a triple junction with the Rivera plate.

[9] Around 330 aftershocks were recorded over a two-and-a-half week period following the deployment of seismographs four days after the mainshock.

Most of the aftershocks measured 1.5–4.5 on the local magnitude scale with focal depths of 2–30 km (1.2–18.6 mi).

Severe shaking and heavy damage were limited to the states of Colima, Jalisco and Michoacán.

[13] A highway which connected Manzanillo with Salagua and Santiago in Colima suffered major damage including large fissures which opened in the asphalt.