2024
Gulf of Corinth Groundwater – Is the deep offshore freshened, groundwater body within the Gulf of Corinth actively recharging? Cruise No. M196, 5.12.2023 – 27.12.2023, Piraeus (Greece) – Limassol (Cyprus)
https://doi.org/10.48433/cr_m196
Jegen, Marion, Haroon, Amir, Schwalenberg, Katrin, Müller, Thomas H, Schmidt, Mark, Pandolpho, Bruna, Bucci, Monica, Horozal, Senay, Sakkelariou, Dimitris
Characterizing Offshore Freshened Groundwater Salinity Patterns Using Trans-Dimensional Bayesian Inversion of Controlled Source Electromagnetic Data: A Case Study From the Canterbury Bight, New Zealand
https://doi.org/10.1029/2023WR035714
Zahra Faghih, Amir Haroon, Marion Jegen, Romina Gehrmann, Katrin Schwalenberg, Aaron Micallef, Jan Dettmer, Christian Berndt, Joshu Mountjoy, Bradley A. Weymer
Geophysical methods that measure the electromagnetic properties of the Earth are effective in investigating freshwater sources beneath the seafloor. By combining the geophysical and geological information, we can better assess the quality of this groundwater. In this study, we develop a workflow that uses statistical methods to integrate electromagnetic observations with borehole and acoustic measurements along the eastern coast of the South Island of New Zealand. We aim to improve our understanding of the groundwater quality beneath the seafloor. Our research confirms the presence of freshened groundwater within the sandy seafloor up to 60 km from the coastline. Importantly, our observations indicate that the groundwater quality increases toward the coast. These findings are significant as they enhance the hydrogeological modeling of the groundwater system and suggest its potential as a source of freshwater.
2023
Automated Seafloor Massive Sulfide Detection Through Integrated Image Segmentation and Geophysical Data Analysis: Revisiting the TAG Hydrothermal Field
Amir Haroon, Hendrik Paasche, Sebastian Graber, Sven Petersen, Eric Attias, Marion Jegen, Romina Gehrmann, Sebastian Hölz, Meike Klischies
Accessible seafloor minerals located near mid-ocean ridges are noticed to mitigate the projected metal demands of the net-zero energy transition, promoting growing interest in quantifying the global distributions of seafloor massive sulfides (SMS). Mineral potentials are commonly estimated using geophysical and geological data that lastly rely on additional confirmation studies using sparsely available, locally limited, seafloor imagery, grab samples, and coring data. We introduce an automated two-step machine learning approach that integrates the mound detection through image segmentation with geophysical data. Our study focuses on the Trans-Atlantic Geotraverse area, which is among the most explored SMS areas worldwide and includes 15 known SMS sites. The automated workflow classifies 14 of the 15 known mounds as exploration targets of either high or medium priority. This reduces the exploration area to less than 7% of the original survey area from 49 to 3.1 km2.
SWAN: A surface-towed modular controlled-source electromagnetic system for mapping submarine groundwater discharge and offshore groundwater resources
Anna Eliana Pastoressa, Amir Haroon, Mark E. Everett, Lea Rohde, Thies Bartels, Martin Wollatz-Vogt, Zahra Faghih, Gesa Katharina Franz, Aaron Micallef
Controlled-source electromagnetic (CSEM) techniques have emerged as a promising noninvasive method for identifying and characterizing OFG and SGD. We present the initial theoretical and practical developments of SWAN — a low-cost, modular, surface-towed hybrid time-frequency domain CSEM system capable of detecting resistivity structures in the seafloor at water depths of up to 100 m. A field test of the system is presented from the central Adriatic Sea at water depths between several tens to approximately 160 m. The study demonstrates that the resulting data coverage enables the system to detect variations in subsurface resistivity to depths of approximately 150–200 m below seafloor.
Ideas and perspectives: Land–ocean connectivity through groundwater
Damian L Arévalo-Martínez, Amir Haroon, Hermann W Bange, Ercan Erkul, Marion Jegen, Nils Moosdorf, Jens Schneider von Deimling, Christian Berndt, Michael Ernst Böttcher, Jasper Hoffmann, Volker Liebetrau, Ulf Mallast, Gudrun Massmann, Aaron Micallef, Holly A Michael, Hendrik Paasche, Wolfgang Rabbel, Isaac Santos, Jan Scholten, Katrin Schwalenberg, Beata Szymczycha, Ariel T Thomas, Joonas J Virtasalo, Hannelore Waska, Bradley A Weymer
Here, we present our perspectives on future research directions to better understand land–ocean connectivity through groundwater, including the spatial distributions of the essential hydrogeological parameters, highlighting technical and scientific developments and briefly discussing the societal relevance of that connectivity in rapidly changing coastal oceans.
2022
The coastal transition zone is an underexplored frontier in hydrology and geoscience
Bradley A. Weymer, Mark E. Everett, Amir Haroon, Marion Jegen-Kulcsar, Aaron Micallef, Christian Berndt, Holly A. Michael, Rob L. Evans & Vincent Post
The transition zone deep beneath and crossing the coastline is a very poorly studied frontier resulting from limitations of technology and logistical barriers. Here, we point out the significance of this region for understanding fundamental geologic processes, geohazards, and especially coastal aquifers. One prominent example is the increasing awareness of the importance of groundwater exchange between land and sea. This Perspective defines the region beneath the coastal transition zone, or coastal white ribbon as an underexplored frontier, and highlights the need for characterization of this critical region to depths of tens of km. We discuss available geophysical methods and their limitations with coastal groundwater used as the primary illustration. Advances in geophysical and drilling technology, coupled with numerical modeling, are needed to enable better accounting of this poorly understood component of the geosphere.
2-D joint inversion of semi-airborne CSEM and LOTEM data in eastern Thuringia, Germany
Ji Cai, Pritam Yogeshwar, Wiebke Mörbe, Maria Smirnova, Amir Haroon, Michael Becken & Bülent Tezkan
The novel frequency-domain semi-airborne controlled source electromagnetic (semi-AEM) method takes advantages of both ground and airborne techniques. It combines ground-based high-power electrical dipole sources with large-scale and spatially densely covered magnetic fields measured via airborne receivers. The method can survey the subsurface down to approximately 1000 m and is particularly sensitive towards conductive bodies (e.g. mineralized bodies) in a more resistive host environment. Our study shows that LOTEM and semi-AEM data have complementary subsurface resolution capabilities, we present a 2-D joint inversion algorithm to simultaneously interpret frequency-domain semi-AEM data and transient electric fields using extended dipole sources. Additionally, our synthetic study suggests that more flexible land-based configurations with sparse receiver locations are possible in combination with semi-AEM without a significant loss of target resolution, which is promising for accelerating data acquisition and for survey planning and logistics, particularly when measuring in inaccessible areas.
The Digital Earth Smart Monitoring Concept and Tools
Uta Koedel, Peter Dietrich, Philipp Fischer, Jens Greinert, Ulrich Bundke, Ewa Burwicz-Galerne, Antonie Haas, Isabel Herrarte, Amir Haroon, Marion Jegen, Thomas Kalbacher, Marcel Kennert, Tobias Korf, Ralf Kunkel, Ching Yin Kwok, Christoph Mahnke, Erik Nixdorf, Hendrik Paasche, Everardo González Ávalos, Andreas Petzold, Susanne Rohs, Robert Wagner & Andreas Walter
Reliable data are the base of all scientific analyses, interpretations and conclusions. Evaluating data in a smart way speeds up the process of interpretation and conclusion and highlights where, when and how additionally acquired data in the field will support knowledge gain. An extended SMART monitoring concept is introduced which includes SMART sensors, DataFlows, MetaData and Sampling approaches and tools. In the course of the Digital Earth project, the meaning of SMART monitoring has significantly evolved. It stands for a combination of hard- and software tools enhancing the traditional monitoring approach where a SMART monitoring DataFlow is processed and analyzed sequentially on the way from the sensor to a repository into an integrated analysis approach. The measured values itself, its metadata, and the status of the sensor, and additional auxiliary data can be made available in real time and analyzed to enhance the sensor output concerning accuracy and precision. Although several parts of the four tools are known, technically feasible and sometimes applied in Earth science studies, there is a large discrepancy between knowledge and our derived ambitions and what is feasible and commonly done in the reality and in the field.
2021
Magnetic and Gravity Surface Geometry Inverse Modeling of the TAG Active Mound
C. Galley, P. Lelièvre, A. Haroon, S. Graber, J. Jamieson, F. Szitkar, I. Yeo, C. Farquharson, S. Petersen, R. Evans
As the exploration and exploitation of seafloor polymetallic deposits appears to be the next frontier in mineral exploration, developing and optimizing remote sensing methods to locate and study these deposits is becoming increasingly important for understanding the resource potential and environmental implications of mining from the deep seafloor. Drilling SMS deposits is expensive, and unless drill cores are collected in large numbers, and to sufficient depth, they will offer limited geometric information of the deposit. Alternatively, magnetic and gravity data collected over SMS deposits can be modeled to derive 3D deposit models. This study presents magnetic and gravity models of the Trans-Atlantic Geotraverse active mound, updating its tonnage estimate to 2.17 ± 0.44 Mt.
Electrical Resistivity Anomalies Offshore a Carbonate Coastline: Evidence for Freshened Groundwater?
Amir Haroon, Aaron Micallef, Marion Jegen, Katrin Schwalenberg, Jens Karstens, Christian Berndt, Xavier Garcia, Michel Kühn, Enzo Rizzo, Nicoletta Chiara Fusi, Chibuzo Valeria Ahaneku, Lorenzo Petronio, Zahra Faghih, Bradley A. Weymer, Michele De Biase, Francesco Chidichimo
Coastal regions with freshened groundwater beneath the seafloor are found worldwide. Here, we report on a geophysical study conducted off the eastern coastline of the Maltese Islands, where a number of resistivity anomalies are observed in limestone. The anomalies located offshore southeast Malta are likely associated with freshened groundwater. Hydrogeological modeling suggests that this groundwater was deposited during lower sea levels and preserved in fine-grained units. Our study indicates that offshore freshened groundwater may be found offshore limestone coastline in dry climates, but its potential to be used as a source of freshwater is likely low.
Offshore Freshened Groundwater in Continental Margins
Aaron Micallef, Mark Person, Christian Berndt, Claudia Bertoni, Denis Cohen, Brandon Dugan, Rob Evans, Amir Haroon, Christian Hensen, Marion Jegen, Kerry Key, Henk Kooi, Volker Liebetrau, Johanna Lofi, Brian J. Mailloux, Renée Martin-Nagle, Holly A. Michael, Thomas Müller, Mark Schmidt, Katrin Schwalenberg, Elizabeth Trembath-Reichert, Bradley Weymer, Yipeng Zhang, Ariel T. Thomas
This review paper considers offshore freshened groundwater (OFG), which is water hosted in sediments and rocks below the seafloor, with a total dissolved solid concentration lower than seawater. We have compiled >300 records to demonstrate that freshened groundwater occurs offshore on most continents around the world and has a global volume of 106 km3. The majority of OFG was deposited when sea level was lower than today and is hosted in sandy sub-seafloor layers that are located within 55 km of coasts in water depths less than 100 m. We present a range of geochemical, geophysical, and modeling approaches that have successfully been used to investigate OFG systems. We also propose approaches to address key scientific questions related to OFG, including whether it may be used as an unconventional source of potable water in coastal areas.
2020
Step-on versus step-off signals in time-domain controlled source electromagnetic methods using a grounded electric dipole
Amir Haroon, Andrei Swidinsky, Sebastian Hölz, Marion Jegen, Bülent Tezkan
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. 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.
Effects of metallic system components on marine electromagnetic loop data
Konstantin Reeck, Hendrik Müller, Sebastian Hölz, Amir Haroon, Katrin Schwalenberg, Marion Jegen
While data analysis and geological interpretations benefit vastly from each added instrument and multidisciplinary approaches, this introduces a systematic and platform-immanent bias in the measured electromagnetic data. In this scope, we present two comparable case studies targeting loop-source electromagnetic applications in both time and frequency domains: the time-domain system trades the compact design for a clear separation of 15 m between an upper fiberglass frame, holding most critical titanium system components, and a lower frame with its coil and receivers. In case of the frequency-domain profiler, the compact and rigid design is achieved by a circular fiberglass platform, carrying the transmitting and receiving coils, as well as several titanium housings and instruments. In this study, we analyze and quantify the quasi-static influence of conductive objects on time- and frequency-domain coil systems by applying an analytically and experimentally verified 3D finite element model. Moreover, we present calibration and optimization procedures to minimize bias inherent in the measured data.
3D Characterization of a Coastal Freshwater Aquifer in SE Malta (Mediterranean Sea) by Time-Domain Electromagnetics
Potpreecha Pondthai, Mark E. Everett, Aaron Micallef, Bradley A. Weymer, Zahra Faghih, Amir Haroon, Marion Jegen
Electromagnetic (EM) geophysical methods are well equipped to distinguish electrical resistivity contrasts between freshwater-saturated and seawater-saturated formations. Beneath the semi-arid, rapidly urbanizing island of Malta, offshore groundwater is an important potential resource but it is not known whether the regional mean sea-level aquifer (MSLA) extends offshore. To address this uncertainty, land-based alongshore and across-shore time-domain electromagnetic (TDEM) responses were acquired and used to map the onshore structure of the aquifer. We present 2D and 3D electromagnetic forward modeling based on finite-element (FE) analysis to further constrain the subsurface geometry of the onshore freshwater body. We interpret the high resistivity zones that as brackish water-saturated bodies are associated with the mean sea-level aquifer. Generally, time-domain electromagnetic (TDEM) results provide valuable onshore hydrogeological information, which can be augmented with marine and coastal transition-zone measurements to assess potential hydraulic continuity of terrestrial aquifers extending offshore.
3D characterization and quantification of an offshore freshened groundwater system in the Canterbury Bight
Aaron Micallef, Mark Person, Amir Haroon, Bradley A. Weymer, Marion Jegen, Katrin Schwalenberg, Zahra Faghih, Shuangmin Duan, Denis Cohen, Joshu J. Mountjoy, Susanne Woelz, Carl W. Gable, Tanita Averes & Ashwani Kumar Tiwari
Although offshore freshened groundwater (OFG) systems have been documented in numerous continental margins worldwide, their geometry, controls and emplacement dynamics remain poorly constrained. Here we integrate controlled-source electromagnetic, seismic reflection and borehole data with hydrological modelling to quantitatively characterize a previously unknown OFG system near Canterbury, New Zealand. The OFG system consists of one main, and two smaller, low salinity groundwater bodies. The main body extends up to 60 km from the coast and a seawater depth of 110 m. We attribute along-shelf variability in salinity to permeability heterogeneity due to permeable conduits and normal faults, and to recharge from rivers during sea level lowstands. A meteoric origin of the OFG and active groundwater migration from onshore are inferred. However, modelling results suggest that the majority of the OFG was emplaced via topographically-driven flow during sea level lowstands in the last 300 ka. Global volumetric estimates of OFG will be significantly revised if active margins, with steep coastal topographies like the Canterbury margin, are considered.
Seafloor massive sulfide exploration using deep-towed controlled source electromagnetics: navigational uncertainties
Romina A S Gehrmann, Amir Haroon, McKinley Morton, Axel T Djanni, Timothy A Minshull
Deep-towed geophysical surveys require precise knowledge of navigational parameters such as instrument position and orientation because navigational uncertainties reflect in the data and therefore in the inferred geophysical properties of the sub-seafloor. We address this issue for the case of electrical conductivity inferred from controlled source electromagnetic data. We show that the data error is laterally variable due to irregular motion during deep towing, but also due to lateral variations in conductivity, including those resulting from topography. To address this variability and quantify the data error prior to inversion, we propose a 2-D perturbation study. Our workflow enables stable and geologically reliable results for multi-component and multi-frequency inversions. An error estimation workflow is presented, which comprises the assessment of navigational uncertainties, perturbation of navigational parameters, and forward modelling of electric field amplitudes for a homogeneous and then a heterogeneous sub-seafloor conductivity model.
2019
RV POSEIDON Cruise Report POS535 – Loki2GrimseyEM: Geophysical and geological investigations of massive sulfides at and in the vicinity of Loki?s Castle (Norway) and similar experiments around the Grimsey Hydrothermal Field (Iceland) for the assessment of the geothermal potential and the exploration for potential mineralizations within the seafloor, Akureyri (Iceland) – Bremerhaven (Germany), 09.06 – 03.07.2019
2018
Marine dipole–dipole controlled source electromagnetic and coincident-loop transient electromagnetic experiments to detect seafloor massive sulphides: effects of three-dimensional bathymetry
Amir Haroon, Sebastian Hölz, Romina A S Gehrmann, Eric Attias, Marion Jegen, Timothy A Minshull, Bramley J Murton
In 2016, CSEM and TEM experiments were carried out at several locations near the Trans-Atlantic Geotraverse hydrothermal field to investigate shallow occurrences of massive sulfides below the seafloor. Measurements were conducted in an area that contains distinct SMS sites located several kilometers off-axis from the Mid-Atlantic ridge, some of which are still connected to hydrothermal activity and others where hydrothermal activity has ceased. Based on the quality of the acquired data, both experiments were operationally successful. However, the data analysis indicates bias caused by three-dimensional (3D) effects of the rough bathymetry in the study area and, thus, data interpretation remains challenging. Therefore, we study the influence of 3D bathymetry for marine CSEM and TEM experiments, focusing on shallow 3D conductors located beneath mound-like structures. We analyze synthetic inversion models for attributes associated with 3D distortions of CSEM and TEM data that are not sufficiently accounted for in conventional 1D (TEM) and 2D (CSEM) interpretation schemes.
High-resolution resistivity imaging of marine gas hydrate structures by combined inversion of CSEM towed and ocean-bottom receiver data
Eric Attias, Karen Weitemeyer, Sebastian Hölz, Samer Naif, Tim A Minshull, Angus I Best, Amir Haroon, Marion Jegen-Kulcsar, Christian Berndt
We present high-resolution resistivity imaging of gas hydrate pipe-like structures, as derived from marine controlled-source electromagnetic (CSEM) inversions that combine towed and ocean-bottom electric field receiver data, acquired from the Nyegga region, offshore Norway. 2.5-D CSEM inversions applied to the towed receiver data detected four new prominent vertical resistive features that are likely gas hydrate structures, located in proximity to a major gas hydrate pipe-like structure, known as the CNE03 pockmark. The resistivity model resulting from the CSEM data inversion resolved the CNE03 hydrate structure in high resolution, as inferred by comparison to seismically constrained inversions. Our results indicate that shallow gas hydrate vertical features can be delineated effectively by inverting both ocean-bottom and towed receiver CSEM data simultaneously. The approach applied here can be utilized to map and monitor seafloor mineralization, freshwater reservoirs, CO2 sequestration sites and near-surface geothermal systems.
First application of the marine differential electric dipole for groundwater investigations: A case study from Bat Yam, Israel
Amir Haroon, Klaus Lippert, Vladimir Mogilatov, Bülent Tezkan
The marine differential electric dipole (DED) is applied for the first time to study a subseafloor groundwater body in the coastal region of Bat Yam, Israel. Previous marine long-offset transient electromagnetic applications detected this freshwater body underneath the Mediterranean seafloor. We have applied the novel DED method for the first time in the marine environment to further investigate this natural phenomenon.
2016
Exploration of resistive targets within shallow marine environments using the circular electrical dipole and the differential electrical dipole methods: a time-domain modelling study
Amir Haroon, Vladimir Mogilatov, Mark Goldman, Rainer Bergers, Bülent Tezkan
Two novel transient controlled source electromagnetic methods called circular electrical dipole (CED) and differential electrical dipole (DED) are theoretically analysed for applications in shallow marine environments. 1-D and 3-D time-domain modelling studies are used to investigate the detectability and applicability of the methods when investigating resistive layers/targets representing hydrocarbon-saturated formations. The results are compared to the conventional time-domain horizontal electrical dipole (HED) and vertical electrical dipole (VED) sources. The applied theoretical modelling studies demonstrate that CED and DED have higher signal detectability towards resistive targets compared to TD-CSEM, but demonstrate significantly poorer signal amplitudes. Future CED/DED applications will have to solve this issue prior to measuring. Furthermore, the two novel methods have very similar detectability characteristics towards 3-D resistive targets embedded in marine sediments as VED while being less susceptible towards non-verticality. Due to the complex transmitter design of CED/DED the systems are prone to geometrical errors. Modelling studies show that even small transmitter inaccuracies have strong effects on the signal characteristics of CED making an actual marine application difficult at the present time. In contrast, the DED signal is less affected by geometrical errors in comparison to CED and may therefore be more adequate for marine applications.
2015
Joint inversion of long-offset and central-loop transient electromagnetic data: Application to a mud volcano exploration in Perekishkul, Azerbaijan
A. Haroon, J. Adrian, R. Bergers, M. Gurk, B. Tezkan, A. L. Mammadov, A. G. Novruzov
Mud volcanism is commonly observed in Azerbaijan and the surrounding South Caspian Basin. This natural phenomenon is very similar to magmatic volcanoes but differs in one considerable aspect: Magmatic volcanoes are generally the result of ascending molten rock within the Earth’s crust, whereas mud volcanoes are characterized by expelling mixtures of water, mud, and gas. The majority of mud volcanoes have been observed on ocean floors or in deep sedimentary basins, such as those found in
Azerbaijan. Furthermore, their occurrences in Azerbaijan are generally closely associated with hydrocarbon reservoirs and are therefore of immense economic and geological interest. The broadside long-offset transient electromagnetic method and the central-loop transient electromagnetic method were applied to study the inner structure of such mud volcanoes and to determine the depth of a resistive geological formation that is predicted to contain the majority of the hydrocarbon reservoirs in the survey area.
Signal detectability of marine electromagnetic methods in the exploration of resistive targets
Mark Goldman, Vladimir Mogilatov, Amir Haroon, Eldad Levi, Bülent Tezkan
We compare selected marine electromagnetic methods for sensitivity to the presence of relatively thin resistive targets (e.g., hydrocarbons, gas hydrates, fresh groundwater, etc.). The study includes the conventional controlled-source electromagnetic method, the recently introduced transient electromagnetic prospecting with vertical electric lines method, and the novel marine circular electric dipole method, which is still in the stage of theoretical development. The comparison is based on general physical considerations, analytical (mainly asymptotic) analysis, and rigorous one-dimensional and multidimensional forward modelling. It is shown that transient electromagnetic prospecting with vertical electric lines and marine circular electric dipole methods represent an alternative to the conventional controlled-source electromagnetic method at shallow sea, where the latter becomes less efficient due to the air-wave phenomenon. Since both former methods are essentially short-offset time-domain techniques, they exhibit a much better lateral resolution than the controlled-source electromagnetic method in both shallow sea and deep sea.
2013
Investigation of the Azraq sedimentary basin, Jordan using integrated geoelectrical and electromagnetic techniques
P. Yogeshwar, B. Tezkan and A. Haroon
The Eastern Mediterranean has been used as a passageway for human migration from Africa to the Middle East, the Balkans and Europe. The Azraq basin contains a mudflat with thick sequences of alluvial sediments that are promising archives used for reconstructing a paleoclimate. In order to identify geological structures and to derive suitable borehole locations in the area for a paleoclimatical reconstruction, the Transient Electromagnetic (TEM) and the Electrical Resistivity Tomography (ERT) methods were utilized. Two transects were investigated from the edge of the basin to the basin centre, crossing three geological formations. The data sets of both methods are interpreted by 1D and 2D inversion algorithms and appraised by inversion statistics. Previously uncertain geological boundaries are determined from geoelectrical models along both transects. Furthermore, a transition zone from fresh to saline groundwater is clearly detected.
