Question

identify the type of observational study. historical records are searched to find magnitudes of earthquakes prior to 1970. retrospective. prospective. cross - sectional.

Explanation:

A retrospective study looks back at past events. Here, historical records of earthquake magnitudes before 1970 are being examined, which is characteristic of a retrospective study. A prospective study would look forward in time, and a cross - sectional study examines a population at a single point in time.

Answer:

Retrospective