Submarine groundwater contained in continental shelves may be a significant global phenomenon, yet little is known about its distribution. Off the US Atlantic coast, boreholes have revealed low salinity groundwater far offshore but are unable to characterize the aquifer’s lateral extent. We conducted a pilot study of large-scale electromagnetic (EM) surveying to map offshore groundwater at locations off New Jersey and Martha’s Vineyard. The high conductivity contrast between resistive fresh or brackish water and the surrounding conductive seawater saturated sediments makes offshore aquifers good targets that are electrically analogous to resistive hydrocarbon reservoirs. We used a combination of seafloor magnetotelluric (MT) and surface-towed controlled-source electromagnetic (CSEM) instrumentation originally developed for hydrocarbon exploration to map the lateral extent of the aquifers. Joint inversion of the MT and CSEM data reveals the aquifers extend about 80 km offshore in both locations. Off New Jersey, the EM results agree well with borehole data that show a shallow low salinity aquifer in the upper 400 m that is underlain by a deeper saline brine.
Presentation Date: Thursday, October 18, 2018
Start Time: 8:30:00 AM
Location: 213A (Anaheim Convention Center)
Presentation Type: Oral