Marine controlled-source electromagnetic survey for deep imaging of submarine groundwater systems
Author: Eric Attias
My research focus on utilizing state-of-the-art marine remote sensing electromagnetic ocean technologies to explore and image shallow and deep Earth structures.
I recently presented the results of this project in the Friday seminar (TGIF) of Hawaiʻi Institute of Geophysics & Planetology, School of Ocean and Earth Science Technology, University of Hawaiʻi.
The results of the IkeWai marine CSEM project were presented for the first time at AGU Annual Fall Meeting that was held in San Fransico this year. The results include 2-D CSEM isotropic/anisotropic inversions and magnetic data that image the electrical resistivity and magnetic signature of submarine groundwater structures extending up to ~4 km offshore. Our poster attracted attention from Earth scientists and hydrologists.
Dr. Attias presenting the poster to his colleagues from Lamont-Dorothy Earth Observatory (Columbia University), associate professor Kerry Key, and postdoctoral research fellow Julen Alvarez-Aramberri.
The backbone of the surface-towed CSEM system used in this survey are the Porpoise electric field receivers. We used a 1 km array with 4 Porpoises; each named after a fish that starts with the letter P: Parrotfish, Pike, Pompano, and Perch.
Data loggers of the Porpoise surface-towed receivers, and their associated fish.
The packing & demobilization of the CSEM system took us 6 hours, primarily because of the extreme heat at the honokohau harbor.
Khaira disassembles the Porpoises.
CSEM system gear.
CSEM system packing & demobilization.
CSEM system demobilization.
CSEM system demobilization.
CSEM system demobilization.
With the help of Max, Brenden, Khaira and Keven, we got the CSEM system all packed before sunest, and even managed to celebrate the succesful completion of the survey at “thebar without a Poproise”.
Yes, there is actually a bar by that name in Kona.
Our last day of operation was dedicated for surveying 3 crosslines (perpendicular to the Kona coastline) situated in the northern section of the survey area, inline with the offshore trajectories of the Kiholo Bay and the Hualalai volcano. These crosslines will help us to (a) validate the data acquired from 7 inlines in this area, and (b) detect any localized submarine lava tubes that extend offshore from the Hualalai volcano.
This completes our successful survey! where we collected multiple datasets from ~250 km of towlines (total of 15 survey lines) encompassed within the boundaries of the Hualalai aquifer. This data will be utilized to detect, delineate, and understand both the spatial distribution and interconnectivity of deep submarine groundwater deposits, offshore Kona, the Island of Hawai’i.
Survey Area 1: North section of the Hualalai groundwater system. Includes 7 survey inlines and 3 crosslines. The color bar represents bathymetric depth that ranges from 10 m (red) to 100 m (blue).
Survey Area 2: Middle section of the Hualalai groundwater system. Includes 2 survey inlines. The color bar represents bathymetric depth that ranges from 10 m (red) to 100 m (blue).
Survey Area 3: South section of the Hualalai groundwater system. Includes 3 survey inlines. The color bar represents bathymetric depth that ranges from 10 m (red) to 100 m (blue).
Total survey coverage along the Hualalai groundwater system. Total of 15 survey lines. The color bar represents bathymetric depth that ranges from 10 m (red) to 100 m (blue).
Porpoise array alignment along crossline 1. Our chase boat is positioned at the end of the 1 km array of Porpoise E-field receivers.
A failed attempt to take a photo of the Porpoise array through a pair of binoculars.
The team before the last recovery of the Porpoise array.
Quoting Brenden: “we’re blonde, we’re making science, nothing can stop us!”.
Quoting Max: “Well, maybe just blonde “.
Eric & Dallas in a moment of joy after the final recovery of the CSEM system.
Crew group photo, from front to back: Khaira, Jake, Dallas, Max, Jason, and Eric.
As shown above, a family of dolphins escorted us during our last transit back to the Honokohau harbor at Kona, the island of Hawai’i.
Finally, I wish to thank all the wonderful people that made this marine project possible: Gwen Jacobs, Steve Constable, Dallas Sherman, Khaira Ismail, Kevin Kelly, Michelle Choe, Ellen Koppenheffer, Jake Perez, Chris Armerding, John Souders, Jacques Lemire, James Barry, Jason Magalen, Brendan Hunter, Patrick Anderson, Max Sudnovsky, Steve Kennedy, Jason Hasler, Emily Wilson, Keith Olsen, Jan C War, Dean Towle, Keven Rinkenbach.
