Archives typically contain a wider variety of primary source materials. As you do research on the catastrophe you are investigating, it's always a good strategy to see which materials have been digitized in national, state, or local archives.
Here are a few examples to get you started:
Books in Primo are assigned Library of Congress Subject Headings. In many ways, subject headings are a form of tagging, in that they represent the content of the material and provide ways for you to efficiently locate more materials that are conceptually related.
Library of Congress Subject Headings are also quite useful for discovering primary sources. The following subheadings usually are added to indicate that the material is a primary source: sources, personal narratives, correspondence, diaries, manuscripts, or notebooks. Once you've discovered the subject heading for secondary sources, try adding one of the primary source subheadings to see what you find.
Another good strategy to try is to sort your results by "Date--oldest." For example, here's the Library of Congress Subject Heading for the San Francisco Earthquake:
After clicking on this link, use the navigation bar on the right hand side to switch from "relevance" to "date--oldest." You'll see that there are a handful of books in the Collins Library collection that were published in 1906 or shortly thereafter!
Collins Library includes the print copies of many 20th-century news magazines. You can use these databases to find citations, and then go downstairs to find the magazines, or, if we do not have them, order them through interlibrary loan.