Question

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

Explanation:

Retrospective studies look back in time using existing data such as historical records. Here, historical records are used to find earthquake magnitudes prior to 1970. Prospective studies look forward in time, and cross - sectional studies examine a population at a single point in time.

Answer:

Retrospective