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Welcome to the ‘IkeWai Marine CSEM survey! 

‘Ike Wai, means in Hawaiian “knowledge” and “water”, respectively. The mission of the IkeWai project is to ensure Hawaiʻi’s future water security through multidisciplinary research (e.g., geophysics, microbiology, biochemistry, hydrological modeling) to elucidate the groundwater systems in the island of Hawaiʻi. This large-scale project is funded by the National Science Foundation (NSF) EPSCoR program.

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The marine geophysics component of this project will use a newly developed surface-towed marine electromagnetic (EM) system and 2D/3D inversion algorithms to study the spatial distribution and interconnectivity of the Hualalai groundwater system offshore the Kona coastline, the island of Hawai‘i. The surface-towed controlled-source EM (CSEM) data will be acquired to image the electrical resistivity structure of these submarine groundwater reserves, likely embedded within complex volcanic geology that includes buried dike, fault systems, and lava tubes.

Download the full project description: IkeWaiMarineCSEM

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An example of a lava tube located adjacent to the Kona coastline, perpendicular to the offshore CSEM survey area.

The Survey Team:
Dr. Eric Attias – Chief scientist
Hawaiʻi Institute of Geophysics & Planetology
School of Ocean and Earth Science and Technology, University of Hawaiʻi

Dr. Dallas Sherman – Scientist
Scripps Institution of Oceanography
Frontier Geosciences, Inc.

Dr. Khaira Ismail – Scientist
Universiti Malaysia Terengganu

Jake Perez – Sr. Marine Mechanician
Electromagnetic laboratory
Scripps Institution of Oceanography

James Barry – P.E. Ocean Engineer, Hydrographer
Sea Engineering, Inc.

Jason Magalen – P.E. Hydrographer
Solmar Hydro

Brendan Hunter – Ocean Engineer
Sea Engineering, Inc.

Patrick Anderson – Ocean Engineer
Sea Engineering, Inc.

Max Sudnovsky – Huki Pono Captain
Sea Engineering, Inc.

Scientific Collaborations:
This marine study will foster collaborations to harness the knowledge of leading scientists in the fields of marine EM, seafloor mapping, and rock physics modeling, including universities and research institutions from USA, Europe, and Southeast Asia. The marine EM laboratory at Scripps Institution of Oceanography (UCSD) will provide the CSEM system and support the data processing workflow. 2D and 3D CSEM forward and inverse modeling, as well as interpretation, will be conducted in collaboration with researchers from the Lamont-Doherty Earth Observatory (Columbia University), and Woods Hole Oceanographic Institution. Joint inversion of electric and magnetic data will be run in collaboration with scientists from the GEOMAR Helmholtz Centre for Ocean Research Kiel. The multi-beam and backscatter datasets will be processed and analyzed in collaboration with researchers from the National Oceanography Centre (Southampton), and the Universiti Malaysia Terengganu. For submarine groundwater quantification, a rock physics modeling scheme will be applied in collaboration with scientists from the Jackson School of Geosciences, the University of Texas at Austin.

 

About

Controlled-source EM (CSEM) is an active-source electromagnetic technique that employs a deep or surface-towed horizontal electric dipole to generate electric and magnetic fields at low frequencies. The transmitted CSEM fields diffuse through the seafloor whereas the returning secondary fields are recorded by either ocean-bottom or fixed-towed electric receivers. The CSEM method is primarily sensitive to resistive structures at crustal depths.

Porpoise Array is a surface-towed CSEM system that comprises an onboard EM transmitter, horizontal electric dipole (HED) antenna, and an array of electric field receivers. This marine project will utilize the Porpoise array to produce a resistivity tomography of the sub-seafloor, down to a depth of ~500-600 mbsf. The Porpoise CSEM system was developed and owned by the EM laboratory at the Scripps Institution of Oceanography.

Porpoise_Array_Sketch
Schematic illustration of the Porpoise surface-towed CSEM system.

Additional marine geophysical datasets will be acquired using a high-resolution R2Sonic2024 multi-beam system and a G-882 marine magnetometer. These additional datasets will help us to map the seabed bathymetry and detect strong magnetic features such as dike systems. Additionally, backscatter data will provide information regarding the seafloor texture, whereas multi-beam data derived from the water column might detect localized regions of prominent freshwater influx to the sea.

The CSEM survey will encompass the entire offshore region that is parallel to the Hualalai terrestrial aquifer, acquiring data using 5 parallel survey lines (48 km each), and 5 perpendicular survey lines (1-3 km each). The total survey length is approximately  250 km.

Map_FINAL
The marine CSEM survey layout: The red lines denote the parallel survey towlines, whereas the black lines represent the survey crosslines. Right inset: Bathymetry/elevation map of the island of Hawaiʻi. The survey area is indicated by black rectangular.

The CSEM results to be derived from this study will be analyzed in a joint interpretation framework that will include the additional marine geophysical datasets (multi-beam, backscatter, and magnetometer). The interpretation scheme will also consider land-based geophysical information (MT and seismic), as acquired from the area adjacent to the Kona coastline. Such an integrative approach will lead to a broad understanding of the groundwater system in western Hawai‘i island, both inland and in offshore submarine regions. Ultimately, the resulting submarine resistivity models will be available to the Hawai‘ian community, the board of water supply, and local stakeholders via the Ike Wai project web-based Gateway platform.

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Contact

Please send me a message with your thoughts and impressions! Give me a call or email if you have any questions. I’ll be delighted to hear from you!

Eric
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Dr. Eric Attias
Postdoctoral Researcher
Hawaiʻi Institute of Geophysics & Planetology
School of Ocean and Earth Science and Technology
University of Hawaiʻi at Mānoa
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Tel: +1 (808) 829-6559
Email: attias@hawaii.edu
Website: www.ericattias.com

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