EXPLORATION - Controlled chemical explosions in Lake Superior UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICAL SURVEY WATER RESOURCES DIVISION WASHINGTON, D. C. 20242 October 7, 1964 GROUND WATER BRANCH MEMORANDUM NO. 65.6 To: District Chiefs and Staff Officials (GW) From: Chief, Ground Water Branch Subject: EXPLORATION - Controlled chemical explosions in Lake Superior A series of controlled chemical explosions were made in Lake Superior during the first week of October, 1964. Detonations were made on five successive days during the period October 1 through October 8. The purpose of the explosions is to obtain data relative to the structure of the earth underneath the Great Plains and to study the effects of this structure on the seismic waves generated. Geologists hope to obtain a profile of a portion of the earth's crust from Minnesota to Arizona from studies of resultant shock waves which should be detected on seismographs as far away as California. We anticipate that the shock waves may cause water-level changes in some of our observation wells. Each district is requested to check recorder charts carefully when they are changed and to send a picture copy of charts showing an effect to Mr. R. C. Vorhis, U.S. Geological Survey (GW), 19 Hunter Street SW, Atlanta, Georgia. If no changes in water levels are noted, you should send this information also to Mr. Vorhis. (s) Gerald Meyer for O. M. Hackett WRD Distribution: A, B3, S3, FOL3, SL