The Des Moines Seismograph Station started operation December 20, 1934, using a single component to record east-west motion. On March 15, 1935, a second instrument was placed in operation to record north-south motion.
Proceedings of the Iowa Academy of Science
©1935 Iowa Academy of Science, Inc.
Seeburger, Mrs. M. M.
"Teleseismic Recording in Iowa,"
Proceedings of the Iowa Academy of Science, 42(1), 133-138.
Available at: https://scholarworks.uni.edu/pias/vol42/iss1/53