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Projekte der AG Tezkan

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DFG – Projekt

Entwicklung und Anwendung eines neuen Inversionsprogramms für die Induzierte Polarisation im Zeitbereich in drei Dimensionen

Im Rahmen des von der Deutschen Forschungsgemeinschaft finanzierten Projekts „ Entwicklung und Anwendung eines neuen Inversionsprogramms für die Induzierte Polarisation im Zeitbereich in drei Dimensionen“ wird zur Interpretation der Induzierten Polarisation im Zeitbereich die gesamte Zeitreihe genutzt.

Ziel ist die Entwicklung eines Algorithmus zur Inversion ganzer Zeitreihen in ein 3D Cole – Cole Leitfähigkeitsmodell.
Hierzu werden die Transienten zu jedem Zeitpunkt mit einer 3D Geoelektrik – Inversion in ein Widerstandsmodell invertiert. Der so erhaltene zeitabhängige Widerstand für jede Zelle lässt sich anschließend für jede Zelle in ein Cole – Cole Modell invertieren.

Um der benötigten hohen Datenqualität gerecht zu werden, kommt in diesem Projekt erstmals der neue Empfänger RIP 924 in Kombination mit dem Sender VIP 3000 zum Einsatz. Dies ermöglicht die Aufzeichnung des gesamten Transienten.
Das neue Messsystem wird auf zwei Testflächen angewandt. Die Daten werden mit dem neuen Inversionsalgorithmus ausgewertet.

DFG Project                                                                                            

 

CRC 806 - Our Way To Europe: Culture Environment Interaction and Human Mobility in the Late Quaternary

Multidimensional Joint Interpretation of TEM and ERT Measurements in the East-African Rift Valley

In the framework of the Collaborative Research Centre (CRC) 806 „Our way to Europe“, a geophysical survey was conducted on sedimentary basins in southern and central Ethiopia. Combining geoscientific and archeological methods, the CRC 806 is designed to reconstruct the passageway of Modern Man from eastern Africa to central Europe over the last 200,000 years. The CRC is a multidisciplinary project and investigates archaeological sites, terrestrial and aquatic archives in the source region of Modern Man, along trajectories of dispersal and in sink areas.
In Nov./Dec. 2014 and in Feb./Mar. 2015, scientists of the work group of Applied Geophysics conducted two geophysical field campaigns in Ethiopia investigating three different sedimentary basins with 2-dimensional Transient-Electromagnetics (TEM) assisted by Electrical Resistivity Tomography (ERT). The vertical TEM component is used for the estimation of sediment thicknesses and stratigraphic layers. The horizontal TEM component will be used to study 2D effects generated by lateral resistivity variations. The ERT measurements assist with the investigation of sediment thicknesses by jointly interpreting them with the TEM data.
The Geophysical measurements and data analyses assist with the identification and definition of possible paleoenvironmental archives such as sedimental deposits with the aim of reconstructing the paleoclimate, the determination of sediment thicknesses and the location of possible borehole sites.

Acknowledgements: We thank the Institute of Geophysics, Space Science and Astronomy (IGSSA) of the University of Addis Ababa, Ethiopia, for the collaboration and the great assistance during our fieldwork.

DESMEX (Deep Electromagnetic Sounding for Mineral Exploration)

The overall objective of the BMBF funded DESMEX (Deep Electromagnetic Sounding for Mineral Exploration) project is the development of an electromagnetic exploration system which can be used for the exploration of mineral resources for depths up to 1000 m. In order to obtain a high coverage as well as an high resolution, air borne and ground based methods are combined. In the framework of DESMEX, the University of Cologne will carry out ground based (long offset) transient-electromagnetic (LOTEM) measurements in an old mining area in eastern Thuringia. Within the LOTEM validation study, an independent resistivity model of the survey area will be derived, which serves as reference model for the semi airborne concept and will eventually be integrated in a final mineral deposition model.

To define the geometry, grid and the transmitter/receiver settings of the LOTEM survey beforehand, one and two dimensional modeling studies are carried out, for which a good conducting ore vein embedded in more resistive host rocks is assumed. Within the modeling study, the thickness and the dipping angle of the ore vein as well as the resistivity of the neighboring rocks are varied. Ground based TEM and RMT measurements deliver first insights in the conductivity distribution of the survey area and are included in the modeling study.

In order to interprete the LOTEM dataset jointly, the inversion algorithm EMUPLUS will be extended with the forward calculation of the air borne EM data. The joint inversion will first be validated on synthetic data and subsequently applied to the dataset of the main experiment. In order to derive a realistic model of the subsurface with respect to the source geometry of the LOTEM configuration and the expected geometry of the mineral deposition formation, a multi dimensional inversion tool will be applied to the dataset.


 

Geoscientists Without Borders

Integration of geophysical, hydrogeological and geotechnical methods to aid monitoring landslide in Nordic countries: A 4D approach for landslide risk assessment

Landslides are one of the most commonly occurring natural disasters. Global damages range in the billions of dollars and cost hundreds of lives each year. This project will study one particular kind, a quick clay or rapid earth flow landslide. Undisturbed quick clay resembles a water-saturated gel. When a mass of quick clay undergoes sufficient stress, however, it instantly turns into flowing ooze, a process known as liquefaction. A small block of quick clay can liquefy from a stress as simple as a modest blow from a human hand, while a larger deposit is mainly vulnerable to greater stresses such as earthquake vibrations or saturation by excess rainwater. Through the partners and transfer of the information, the humanitarian impact of this project will go beyond national borders.
Our approach to study clay landslides is the application of multidisciplinary geophysical methods with integration of ground magnetics, geo-electrics, Controlled Source/Radio magnetotellurics, as well as seismic reflection/refraction; borehole pore pressure monitoring and analytical modeling.

During a survey in September 2011 the Radiomagnetotelluric (RMT) method as well as the Very Low Frequency method (VLF) were utilized in order to study the structures of quick clay found on a reference site near Göteborg.

Partners: Uppsala University, Geological Survey of Sweden, Leibniz Institute for Applied Geophysics, Syiah Kuala University, and Swedish Geotechnical Institute

Links:
http://www.seg.org/web/foundation/misc/geoscientists-without-borders/projects/current#SW
http://www.seg.org/documents/53703/63387/Uppsala_fact_sheet_042011.pdf

Marie Curie project: IGSEA – Integrated Nonseismic Geophysical Studies to Assess the Site Effect of the EUROSEISTEST Area in Northern Greece

Multidimensional Interpretation of Near Surface Electromagnetic Data Measured in Volvi Basin, Northern Greece

The Volvi basin is located in an alluvial valley 45 km northeast of the city of Thessaloniki in Northern Greece. It is a neotectonic graben (6 km wide) structure with increasing seismic activity where the large 1978 Thessaloniki earthquake occurred. The seismic response at the site is strongly influenced by local geological conditions. Therefore, the European test site “Euroseistest” for studying site effects of seismically active areas was installed in Volvi-Mygdonian Basin. The ambient noise measurements from the area east of Euroseistest give strong implication for a complex 3-D tectonic setting. Hence, near surface EM (electromagnetic) measurements are carried out to understand the location of the local active fault and the top of the basement structure of the study area.

The RMT (radiomagnetotelluric) and TEM (transient electromagnetic) measurements were carried out along eight profiles, which include 500 RMT and 104 TEM soundings. The correlation between the borehole data and the interpreted TEM and RMT data generally shows a four layer model. The layers are identified as sediment and metamorphic rocks, which are in detail: silty sand (10 -30 ?m ), sandy clay ( 30 – 50 ?m ), marly sand with clay (50 – 100 ?m ) and marly sand with gravel ( >>100 ?m ) with varying thicknesses. Due to the high resistivity of the top layer, the skin depths of the RMT soundings are approximately 35 m. The TEM data give detailed information about the deeper structure up to the depth of 200 m. The joint and sequential inversion of RMT and TEM data proves to be an effective tool to investigate complex geological structure. The 1-D and 2-D interpretation of RMT and TEM data, respectively, indicate a local fault structure and helps in explaining the direction of the fault structure. In order to understand the local geological background and the impact of the 3-D effects in the area, 3-D modeling of RMT data was realized. According to the analyses, a normal fault is located next to the Euroseistest site, with a strike direction of N 70 ° E.

For more information see the poster.

Volkswagenstiftung

Electromagnetic (EM) methods to study the inner structure of mud volcanoes in Perekishkul, Azerbaijan

Three different electromagnetic methods were applied to study the inner structure of mud volcanoes at various depths in the Perekishkul region of Azerbaijan. The methods are capable of detecting geotectonic boundaries and fault zones and are able to confine and improve structural models of the mud volcanoes in the region.

Mud volcanoes have relevance to climate processes by means of methane out gassing that is likely to contribute significantly to the global methane budget and therefore impacts the climate dynamics. In addition, mud volcanoes are often related to anticline uplifts and to large deposits of hydrocarbons.

During the first survey in April 2010 the Radiomagnetotelluric (RMT) method as well as the Transient Electromagnetic (TEM) method were utilized in order to study the inner structures of the mud volcanoes up to a depth of about 130 meters. The Long Offset Transient Electromagnetic (LOTEM) method was then applied during a second survey in September 2011. Resistivity structures up to a depth of 5 km were resolved.

For more information see poster EMTF 2011.

 

BMBF/TÜBITAK project

Two-Dimensional Joint Interpretation of Radiomagnetotelluric, Direct Current Resistivity and Induced Polarization Data; an example from an ore exploration

A new 2D algorithm will be developed for the joint interpretation of direct current resitivity (DCR), Radiomagnetotelluric (RMT) and Induced Polarization (IP) data during this project. The developed algorithm will be applied on geophysical data observed on a mining test area in the South of Turkey.

We are confident to show at the end that conductive and resitive structures can be better resolved by a 2D joint inversion result rather than by individual inversions of RMT and DCR data sets. The RMT method is sensitive to conductive structures while the DCR method is sensitive to resistive structures. While the DCR and RMT methods investigate the resitivity distribution, the IP method is used to resolve the chargeability properties of the subsurface. Therefore, all three methods are supporting each other and they will increase the overall significance of the subsurface model derived from their common physical parameter, i.e. electrical conductivity.

The main idea to be realized in our code is to do a 2D joint inversion of DCR and RMT data and then use the calculated 2D resistivity model in the 2D inversion of IP data. The first steps will be to develop a 2D DC/IP and a 2D RMT forward modeling algorithm with finite element method using unstructured mesh. This approach should help to incorporate surface topography and to consider sensitivity analysis and depth of investigation.

After the newly developed code was successfully tested on synthetic data, we will interpret real data, which we are going to acquire in field surveys on some mining areas from exploring Cu-Pb-Zn ±Ag ±Au mineralizations in Turkey.

AIDA: From airborne data inversion to in-depth analysis

Unmanned Aerial System

In addition to RMT ground data and existing TEM and helicopter-borne EM-data, we propose a new deployment of the so called Unmanned Aerial System (UAS), an innovative platform for airborne VLF/LF-measurements on
a regional scale. An UAS shall be utilized to perform geophysical surveys on a flying measuring platform. The utilization of UAS enables the performance of a time and cost-effective measuring platform to acquire high resolution images of geophysical parameters of electrical conductivity. Since many decades, VLF-measurements are a well established method in exploration geophysics on the ground as well as in airborne geophysics. These qualitatively provide an indication about lateral changes of the electrical conductivity of the ground. 

An innovative electromagnetic induction coil system will also be applied, which measures the EM field of VLF/LF and radio transmitters over a broad range of frequencies (10 kHz to 250 kHz). In 2008, METRONIX GmbH released an induction coil triple, the so called Super High Frequency Triple (SHFT)-sensor, which enables sensing the radiated magnetic field of VLF/LF-transmitter stations. This sensor was already deployed in a Swedish airborne geophysical survey performed by Pedersen und Dynesius (2008). This method allows determination of the electromagnetic impedance tensor over a large depth range and yields images of complex 3D conductivity structures. Finally, a transform function is used to derive the electrical conductivity from the magnetic field measured at different evaluation frequencies. According to the number of radio stations, many evaluation frequencies are available at a site, which considerably improves the depth resolution and is a significant advantage of this method. In addition, UAS's have the potential to open new possibilities concerning the organisation and performance of geophysical exploration.

For more information please see the poster-emtf-2011.

 

 

 

DFG-project

CRC 806 - Our Way To Europe: Culture Environment Interaction and Human Mobility in the Late Quaternary

Multidimensional Interpretation of Geoelectrical Data: Exploring the Structure of Sedimentary Basins in the Eastern Desert of Jordan

The geophysical research takes place in the frame of the DFG funded Collaborative Research Centre 806 (CRC 806/ Sonderforschungsbereich 806) "Our Way to Europe: Culture Environment Interaction and Human Mobility in the Late Quaternary"
The CRC-806 concerns the history of mankind. It is designed to capture the complex nature of dispersal of Modern Man from Africa to Western Eurasia, and particularly to Europe. The CRC concentrates on the time span between the dispersal of Modern Man from Africa (190,000 B.P.) and the permanent establishment of Man in Central Europe (40,000 B.P.). The CRC is a multidisciplinary project and investigates archaeological sites, terrestrial and aquatic archives in the source region of Modern Man, along trajectories of dispersal and in sink areas.
The Eastern Mediterranean has been the passageway for human migration between Africa, the Middle East, the Balkans and Europe. The Azraq area, around the former oasis Qa' Al Azraq, in the eastern desert of Jordan has been a major spot for prehistoric settlements since the middle Pleistocene. Very promising archives for paleoclimatical reconstruction are sediment successions accumulated in dry clay lakes (Playa lakes).
We utilized the Transient Electromagnetic (TEM), the Direct Current Resistivity (DCR) and the Radiomagnetotelluric (RMT) methods to identify the most complete sedimentary sequences inside the mud?at Qa' Al Azraq and to derive suitable borehole locations for the paleoclimatical reconstruction.
Twodimensional interpretation of TEM-data ist not very common, as the computation of transient electromagnetic fields is very time expensive. However, to improve the geoelectrical models the TEM data will be interpreted in 2D.

For more information please visit: www.sfb806.uni-koeln.de or poster-emtf-2011

 

 

Deutsch-Israelische Wassertechnologie-Kooperation

Detection of fresh groundwater bodies within the Mediterranean submarine aquifers offshore Israel using marine geoelectric methods

Vorhabensbeschreibung - Zusammenfassung:

Die Erkundung von Süßwasseraquiferen unter den Flachmeeren stellt weltweit ein aktuelles Forschungsgebiet dar. Solche untermeerischen Süßwasservorkommen von einigen Metern bis hin zu einigen Kilometern vor der Küste- existieren weltweit (z. B. vor den Küsten der Niederlande, New Jerseys, der USA usw.).

Der Küstenaquifer am Mittelmeer in Israel ist eine wichtige Grundwasserquelle. Neue elektromagnetische Messungen auf dem Land zeigen die Existenz einer relativ schlecht leitenden Schicht unter dem mit Meerwasser kontaminierten Aquifer. Die vorhandenen Bohrungen zeigen, dass diese Schicht Süßwasser beinhaltet und es ist anzunehmen, dass sie sich untermeerisch fortsetzt. Ihre Tiefe und ihre laterale Dimension können mit marinen elektromagnetischen Methoden detektiert werden.

Das Hauptziel des Vorhabens ist die Erkundung des Aquifers unter dem Mittelmeer an der israelischen Küste mit elektromagnetischen Verfahren. Dabei wird die Long-Offset-Transient-Elektromagnetik- (LOTEM-) Methode in diesem Projekt erstmalig für marine Untersuchungen eingesetzt. Auf dem Land werden die Messungen mit einer Kombination von LOTEM und Short-Offset-Transient-Elektromagnetik (SHOTEM) durchgeführt, damit die Fortsetzung des Aquifers vom Land zum Meeresgrund erkundet werden kann. Mit Hilfe der erzielten geophysikalischen Ergebnisse wird eine optimale hydrogeologische Modellierung durchgeführt, um das Wassermanagement in der untersuchten Region zu verbessern.

DFG

Deutsch-Indische Kooperation

Groundwater contamination due to waste disposal and aquifer characterization around Roorkee using integrated Geoelectrical techniques

Objectives of the Project:

The objective of the proposal is to apply the radiomagneto-telluric (RMT) technique by using a recently developed device integrated with Electrical resistivity tomography (ERT), and Time domainelectromagnetic (TEM) methods for the first time in India for environmental studies. The impact of current practice forwaste disposal used in Roorkee area on roundwater will be accessed. This will lead to the development of efficient and economic tools for monitoring the groundwater conta-mination and delineation of flow path of contaminants. Quantitative interpretation of resistivity data and its correlation with the lithological formation in the area will be used to define a water table elevation map and will be used as an indicator for the local groundwater flow direction.

There is a risk of groundwater contamination due to surface runoff from landfills around waste disposal site. Present proposal will focus on the determination of impact of contaminant in groundwater, geological medium underlying the landfill site, hydrological condition of the area and the effect of irrigation return-flow. A detailed planned systematic geophysical investigation will be carried out at selected sites in the vicinity of waste disposal site and a far uncontaminated remote site.
Aquifer model relating the electrical parameters and hydraulic parameters (transmissivity) of the aquifer will be developed for the Roorkee area using the results of the investigations and available pumping test data.

DFG

Entwicklung und Anwendung eines Inversionsprogramms zur dreidimensionalen Rekonstruktion der Leitfähigkeit aus mehrkomponentigen TEM-Daten

Transientelektromagnetische (TEM) Verfahren werden zur Erforschung des Untergrundes, wie beispielsweise zur Erkundung von Lagerstätten oder Frischwasser aber auch zur Beantwortung geologischer Fragestellungen und im Umweltbereich zunehmend eingesetzt. Die rasch fortschreitende Entwicklung im Bereich der elektromagnetischen Tiefenforschung erlaubt es, dass TEM Messungen verstärkt auf dreidimensionale Fragestellungen angewandt werden. Für eine dreidimensionale Interpretation der gewonnenen TEM-Daten fehlt jedoch bislang eine geeignete Inversionssoftware. Das primäre Ziel dieses Forschungsvorhabens ist es, die vom vorgesehenen Projektbearbeiter bereits erstellte aber noch experimentelle Interpretationssoftware fertig zu stellen, um mittels moderner Inversionstechniken eine dreidimensionale Leitfähigkeitsverteilung aus TEM-Daten zu rekonstruieren. Das Interpretationswerkzeug soll auf reale Daten eines TEM-Verfahrens zur oberflächennahen Erkundung des Untergrundes eingesetzt werden, welches am Institut für Geophysik und Meteorologie der Universität zu Köln entwickelt wird.

Marie Curie Reintegration Grant

Integrated nonseismic geophysical studies to assess the site effect of the EUROSEISTEST area in Northern Greece

Acronym: IGSEA, PERG03-GA-2008-230915 {REF RTD REG/T.2 (2008)D/596232}

Host: Institute of Geophysics and Meteorology (IGM), University of Cologne - Germany
Partner: Institute of Engineering Seismology and Earthquake Engineering (ITSAK), Thessaloniki - Greece

Abstract:

IGSEA addresses primarily topics out of the main scientific area such as Geophysics, Tectonics, and Seismology in combination with Earthquake Engineering, Engineering Seismology and building-soil & soil-water processes through the interaction between geophysicists and civil engineers. This project aims to assess site effects in the surrounding area of the EUROSEISTEST site by means of low-cost integrated nonseismic geophysical methods that are capable of detecting vertical geotectonic boundaries and fault zones with high accuracy and are able to confine and improve one of the first 3D resistivity inversion models of the area. The project will benefit from the use of state of the art devices and techniques which allow for a comprehensive view inside the inner structure of the basin. Through the implementation of hydrogeophysical and hydrogeological aspects we believe to significantly support the waveguide propagation modelling process of researcher and civil engineers in Greece and Europe who are working on strong motion data.

Geotechnologien

Aero-Ground-Joint-Inversion

In this sub-project it is intended to enhance the resolution of model parameters through the development of a joint inversion algorithm for helicopter-borne electromagnetic (HEM), transient electromagnetic (TEM), and radiomagnetotelluric (RMT) data sets. The proposed concept of the joint inversion takes advantage of each single method, which in most cases consists of a dense measuring grid (HEM and RMT) and on the other hand provides the capability to resolve near surface (RMT) and deeper electrical conductivity structures (TEM). HEM-, TEM-, and RMT-measurements are widely used in practical environmental, geotechnical, and exploration problems.

Helicopter-borne electromagnetic (HEM) measurements are an effective way to map the electrical conductivity of large areas. The typical scenario is first to identify the geophysical property that is diagnostic of the sought geological structure or buried object. The map, however, presents no information about the depth of the object or details regarding its shape. The depth of investigation of HEM-data is rather limited compared to EM sounding methods on the ground. In order to improve the accuracy of model parameters of shallow depth as well as of the deeper crust, we plan to combine HEM, TEM, and RMT measurements by using numerical joint inversion methodology. However, in most cases, the measuring grids of each single method will not overlap with each other. Therefore a reduction of all measuring grids to one grid requires either an interpolation algorithm or the introduction of smoothing conditions in the parameter space. Such algorithms are not available at present and shall be realized in this project. At the moment, there is no inversion method which enables the joint interpretation of HEM-, TEM-, and RMT-data.

Application of a novel marine EM Method to study sub-seafloor freshwater bodies

In the framework of a DFG funded project, a novel marine electromagnetic method called Differential Electrical Dipole (DED) was developed and subsequently applied to study a sub-seafloor freshwater body. A measurement campaign was realized in April 2016 using the R/V Mediterranean Explorer from EcoOcean measuring at different stations along a 4 km profile near Bat Yam, Israel. The aim of the study is to test the feasibility of the marine DED method and to gain valuable information regarding the saltwater/freshwater interface at the western boundary of the sub-seafloor aquifer. The obtained data set is processed and interpreted in the framework of doctoral studies at the University of Cologne.