TY  - JOUR
A1  - Streich, R.
A1  - Becken, Michael
T1  - Sensitivity of controlled-source electromagnetic fields in planarly layered media
JF  - Geophysical journal international
N2  - The study of electromagnetic (EM) field sensitivities is useful for assessing the feasibility of controlled-source electromagnetic (CSEM) surveys. Sensitivity calculations are also a principal building block of EM inversion schemes. Sensitivities are formally given by the derivatives of the EM field components with respect to conductivity. For horizontally layered media, these derivatives can be evaluated analytically, offering advantages in computational efficiency and accuracy over numerical evaluation. We present a complete set of explicit analytic expressions for the EM field sensitivities in 1-D VTI-anisotropic media for horizontal and vertical electric and magnetic dipole sources, and also for finite horizontal electric sources. Since our derivations are based on a formulation for EM fields that is quite general in allowing for sources and receivers at any depth, our sensitivity expressions exhibit the same generality. We verify our expressions by comparison to numerical solutions, and finally present application examples that demonstrate the utility and versatility of these expressions for CSEM feasibility studies.
KW  - Electromagnetic theory
Y1  - 2011
U6  - https://doi.org/10.1111/j.1365-246X.2011.05203.x
SN  - 0956-540X
VL  - 187
IS  - 2
SP  - 705
EP  - 728
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Kübler, Simon
A1  - Streich, R.
A1  - Lück, Erika
A1  - Hoffmann, M.
A1  - Friedrich, A. M.
A1  - Strecker, Manfred
T1  - Active faulting in a populated low-strain setting (Lower Rhine Graben, Central Europe) identified by geomorphic, geophysical and geological analysis
JF  - Seismicity, fault rupture and earthquake hazards in slowly deforming regions
N2  - The Lower Rhine Graben (Central Europe) is a prime example of a seismically active low-strain rift zone characterized by pronounced anthropogenic and climatic overprint of structures, and long recurrence intervals of large earthquakes. These factors render the identification of active faults and surface ruptures difficult. We investigated two fault scarps in the Lower Rhine Graben, to decipher their structural character, offset and potential seismogenic origin. Both scarps were modified by anthropogenic activity. The Hemmerich site lies c. 20 km SW of Cologne, along the Erft Fault. The Untermaubach site lies SW of Duren, where the Schafberg Fault projects into the Rur River valley. At the Hemmerich site, geomorphic and geophysical data, as well as exploratory coring reveal evidence of repeated normal faulting. Geophysical analysis and palaeoseismological excavation at the Untermaubach site reveal a complex fault zone in Holocene gravels characterized by subtle gravel deformation. Differentiation of tectonic and fluvial features was only possible with trenching, because fault structures and grain sizes of the sediments were below the resolution of the geophysical data. Despite these issues, our investigation demonstrates that valuable insight into past earthquakes and seismogenic deformation in a low-strain environment can be revealed using a multidisciplinary approach.
Y1  - 2017
SN  - 978-1-86239-745-3
SN  - 978-1-86239-964-8
U6  - https://doi.org/10.1144/SP432.11
SN  - 0305-8719
VL  - 432
SP  - 127
EP  - 146
PB  - The Geological Society
CY  - London
ER  -