This data set was acquired with the LDEO Multi-Channel Seismic system during Marcus G. Langseth expedition MGL1211 conducted in 2012 (Chief Scientist: Dr. Suzanne Carbotte). These data files are of UKOOA P1/90 format and include Seismic Navigation data and were processed after data collection. Data were acquired as part of the projects: Collaborative Research: Imaging the Cascadia Subduction Zone: A Ship-to-shore Opportunity and Collaborative Research: Evolution and hydration of the Juan de Fuca crust and uppermost mantle: A plate-scale seismic investigation from ridge to trench, and funding was provided by NSF grants: OCE10-29305, OCE10-29411, EAR11-47622, and EAR11-47975.