Delineation of Subsea Freshwater Extension by Marine Geoelectromagnetic Soundings (SE Mediterranean Sea)

Levi, E.; Goldman, M.; Tibor, Gideon; Herut, Barak

doi:10.1007/s11269-018-2018-1

Cited by 14 publications

(9 citation statements)

References 25 publications

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“…Occam and Marquardt inversions produce a similar resistivity value of approximately 80 Ωm for this layer. This layer is associated with the marine groundwater layer and is in good agreement with the results of Levi et al (2018) and Haroon et al (2018). The left example in Figure 16 does not show a high resistive layer in the depth: the aquifer is not present at this station.…”

Section: A R I N E L O N G -O F F S E T T R a N S I E N T E L E C Tsupporting

confidence: 86%

“…() and Levi et al . () prove the extension of the aquifer under the Mediterranean Sea in this region. For this survey, the authors used a grounded dipole emitting TE and TM mode and recorded the vertical magnetic field at a short offset (e.g.…”

Section: Introduction and The Long‐offset Transient Electromagnetic Mmentioning

confidence: 62%

“…This layer is associated with the marine groundwater layer and is in good agreement with the results of Levi et al . () and Haroon et al . ().…”

Section: Marine Long‐offset Transient Electromagnetic Measuring Systementioning

confidence: 87%

“…The area from the cities of Ashdod in the south to Bat Yam in the north, the so-called Palmahin disturbance, has to be highlighted: Here, resistivity values show constant high values, which argues against lateral seawater intrusion. Offshore measurements by Goldman et al (2011) and Levi et al (2018) prove the extension of the aquifer under the Mediterranean Sea in this region. For this survey, the authors used a grounded dipole emitting TE and TM mode and recorded the vertical magnetic field at a short offset (e.g.…”

Section: Figurementioning

confidence: 99%

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On the exploration of a marine aquifer offshore Israel by long‐offset transient electromagnetics

Lippert

Tezkan

2019

Geophysical Prospecting

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The existence of aquifers extending from land beneath the sea floor up to a distance of several kilometres has been observed and examined all over the world. The coastal aquifer of Israel is a heavily used groundwater reservoir which has to be constantly monitored to ensure the drinking water supply. Former land‐based electromagnetic measurements show that it is, in several places, blocked to seawater intrusion and is consequently a candidate for submarine extension. Multicomponent long‐offset transient electromagnetic measurements were carried out offshore on the coast of Israel. We deployed a 400‐m‐long grounded dipole as transmitter and several electric and magnetic receivers on the sea floor up to a distance of 4.8 km from the coast. Altogether, we deployed 8 transmitter positions and received data sets at 14 receiver stations onshore and offshore, with offsets of mostly 400 and 800 m. In this paper, we present the survey and 1D Occam and Marquardt inversions of the offshore horizontal electric components in the broadside and inline configuration. In addition, the vertical magnetic component in the broadside position is also considered. Only single inversions, both single offset and single component, were used to detect the aquifer under sea sediments. We prove the submarine existence of the Israeli coastal aquifer up to a distance to the coast of approximately 3.2 to 3.6 km using all measured long‐offset transient electromagnetic components. In addition, we present modelling studies with synthetic data derived from a subsurface model adjusted to our survey area with very shallow water from 10 to 50 m. As part of the planning before the survey, a parameter study of the expected subsurface, the examination of the airwave phenomenon and the justification for our 1D inversion strategy are shown. More detailed eigen parameter analyses are added to explain the measured data.

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Section: A R I N E L O N G -O F F S E T T R a N S I E N T E L E C Tsupporting

confidence: 86%

Section: Introduction and The Long‐offset Transient Electromagnetic Mmentioning

confidence: 62%

“…This layer is associated with the marine groundwater layer and is in good agreement with the results of Levi et al . () and Haroon et al . ().…”

Section: Marine Long‐offset Transient Electromagnetic Measuring Systementioning

confidence: 87%

Section: Figurementioning

confidence: 99%

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On the exploration of a marine aquifer offshore Israel by long‐offset transient electromagnetics

Lippert

Tezkan

2019

Geophysical Prospecting

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“…Haroon et al ., 2015; Hölz et al ., 2015) or offshore groundwater studies (e.g. Haroon et al ., 2018b; Levi et al ., 2018; Micallef et al ., 2018; Gustafson et al ., 2019; Lippert and Tezkan, 2020). In a CSEM survey, current is injected into the subsurface via a grounded horizontal electrical dipole (HED) antenna, and the response of the Earth is measured by one or more electric and/or magnetic field receivers located at various distances from the source.…”

Section: Introductionmentioning

confidence: 99%

Step‐on versus step‐off signals in time‐domain controlled source electromagnetic methods using a grounded electric dipole

Haroon

Swidinsky

Hölz

et al. 2020

Geophysical Prospecting

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The time-domain controlled source electromagnetic method is a geophysical prospecting tool applied to image the subsurface resistivity distribution on land and in the marine environment. In its most general setup , a square-wave current is fed into a grounded horizontal electric dipole, and several electric and magnetic field receivers at defined offsets to the imposed current measure the electromagnetic response of the Earth. In the marine environment, the application often uses only inline electric field receivers that, for a 50% duty-cycle current waveform, include both step-on and step-off signals. Here, forward and inverse 1D modelling is used to demonstrate limited sensitivity towards shallow resistive layers in the step-off electric field when transmitter and receivers are surrounded by conductive seawater. This observation is explained by a masking effect of the direct current signal that flows through the seawater and primarily affects step-off data. During a step-off measurement, this direct current is orders of magnitude larger than the inductive response at early and intermediate times, limiting the step-off sensitivity towards shallow resistive layers in the seafloor. Step-on data measure the resistive layer at times preceding the arrival of the direct current signal leading to higher sensitivity compared to step-off data. Such dichotomous behaviour between step-on and step-off data is less obvious in onshore experiments due to the lack of a strong overlying conductive zone and corresponding masking effect from direct current flow. Supported by synthetic 1D inversion studies, we conclude that time-domain controlled source electromagnetic measurements on land should apply both step-on and step-off data in a combined inversion approach to maximize signal-to-noise ratios and utilize the sensitivity characteristics of each signal. In an isotropic marine environment, step-off electric fields have inferior sensitivity towards shallow resistive layers compared to step-on data, resulting in an increase of non-uniqueness when interpreting step-off data in a single or combined inversion.

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Dynamic Bayesian Networks to Assess Anthropogenic and Climatic Drivers of Saltwater Intrusion: A Decision Support Tool Toward Improved Management

Rachid

Alameddine

Najm

et al. 2020

Integr Envir Assess & Manag

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Delineation of Subsea Freshwater Extension by Marine Geoelectromagnetic Soundings (SE Mediterranean Sea)

Cited by 14 publications

References 25 publications

On the exploration of a marine aquifer offshore Israel by long‐offset transient electromagnetics

On the exploration of a marine aquifer offshore Israel by long‐offset transient electromagnetics

Step‐on versus step‐off signals in time‐domain controlled source electromagnetic methods using a grounded electric dipole

Dynamic Bayesian Networks to Assess Anthropogenic and Climatic Drivers of Saltwater Intrusion: A Decision Support Tool Toward Improved Management

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