Ocean Bottom Seismometer Clock Correction using Ambient Seismic Noise

Ocean-bottom seismometers (OBSs) are equipped with seismic sensors that record acoustic and seismic events at the seafloor, which makes them suitable for investigating tectonic structures capable of generating earthquakes offshore. One critical parameter to obtain accurate earthquake locations is the absolute time of the incoming seismic signals...

Sensitivity analysis of inverted model parameters from transient electromagnetic measurements affected by induced polarization effects

We investigate the application of the distance-based global sensitivity analysis (DGSA) to evaluate the sensitivity of electrical model parameters obtained from transient electromagnetic (TEM) data including induced polarization (IP) effects. We propose novel open-source forward modeling and inversion routines for single-loop TEM data...

Shaping Geobodies by Joint Inversion of CSEM and Gravity Data with a Modular Framework

To optimize geological structures a multi-physics inversion of electromagnetic and gravity data is carried out. With the TERRASYS’ Joint Inversion Framework JIF and its modules for 3D EM (here CSEM) and for 3D GRAV (gravity and gradients) the geometry of a salt body located in the Nordkapp Basin is optimized. The physical effects of a complex...

Determining clock errors of ocean-bottom seismometers: an ambient-noise based method designed for large-scale ocean bottom deployments

The timing of the recordings of ocean-bottom seismometers (OBSs) is critical for accurate earthquake location and Earth model studies. GNSS signals, however, cannot reach OBSs deployed at the ocean bottom. This prevents their clocks from being synchronized with a known reference time. To overcome this, we developed OCloC, a Python package that...

Feasibility Study of Controlled-Source Electromagnetic Method for Monitoring Low-Enthalpy Geothermal Reservoirs

Tracking temperature changes by measuring the resulting resistivity changes inside low-enthalpy reservoirs is crucial to avoid early thermal breakthroughs and maintain sustainable energy production. The controlled-source electromagnetic method (CSEM) allows for the estimation of sub-surface resistivity. However, it has not yet been proven that...

An Introduction to the Application of Marine Controlled-Source Electromagnetic Methods for Natural Gas Hydrate Exploration

Natural gas hydrates have been an unconventional source of energy since the beginning of this century. Gas-hydrate-filled reservoirs show higher resistivity values compared with water-filled sediments. Their presence can be detected using marine controlled-source electromagnetic methods. We classify acquisition configurations into stationary and...

Feasibility Study of Monitoring Delft Geothermal Project Using Land Controlled- Source Electromagnetic Method

Delft geothermal project (DAPwell) is a planned geothermal well doublet, where relatively cold water is going to be injected through one well into a low enthalpy geothermal reservoir to produce hot water from the other well. The volume of the cold water around the injection well will increase over time and, in the end, result in a thermal...

Time-Domain Modeling of Three-Dimensional Earth's and Planetary Electromagnetic Induction Effect in Ground and Satellite Observations

Electric currents induced in conductive planetary interiors by time-varying magnetospheric and ionospheric current systems have a significant effect on electromagnetic (EM) field observations. Complete characterization of EM induction effects is difficult owing to nonlinear interactions between the three-dimensional electrical structure of a...

Fast Fourier transform of electromagnetic data for computationally expensive kernels

3-D controlled-source electromagnetic data are often computed directly in the domain of interest, either in the frequency domain or in the time domain. Computing it in one domain and transforming it via a Fourier transform to the other domain is a viable alternative. It requires the evaluation of many responses in the computational domain if...

Towards an open-source landscape for 3-D CSEM modelling

Large-scale modelling of 3-D controlled-source electromagnetic (CSEM) surveys used to be feasible only for large companies and research consortia. This has changed over the last few years, and today there exists a selection of different open-source codes available to everyone. Using four different codes in the Python ecosystem, we perform...

Examples of Seismic Shallow Subsurface Characterisation and Deep Electromagnetic Monitoring

Difficulties in detecting and characterising shallow objects close the surface with seismic shear waves are often problematic because of dominant surface waves. By sequencing a specific combination of two data driven processing steps followed by diffraction tomography can overcome these problems. Small scattering objects become visible in the...

Time-Domain CSEM Modelling Using Frequency- and Laplace-Domain Computations

Modelling time-domain electromagnetic data with a frequency-domain code requires the computation of many<br/>frequencies for the Fourier transform. This can make it computationally very expensive when compared with timedomain codes. However, it has been shown that frequency-domain codes can be competitive if frequencydependent modelling grids...

emg3d: A multigrid solver for 3D electromagnetic diffusion

Controlled-source electromagnetic (CSEM) surveys are a common geophysical investigationtool in the search for, amongst other, groundwater, hydrocarbons, and minerals. The nu-merical modelling of CSEM data requires the solution of the Maxwell equations. These canbe simplified in the particular case of CSEM, as the frequencies used in surveys are...

A tool for designing digital filters for the Hankel and Fourier transforms in potential, diffusive, and wavefield modeling

The open-source code fdesign makes it possible to design digital linear filters for the Hankel and Fourier transforms used in potential, diffusive, and wavefield modeling. Digital filters can be derived for any electromagnetic (EM) method, such as methods in the diffusive limits (direct current, controlledsource EM [CSEM]) as well as methods...

Inversion of multi-transient EM data from anisotropic media

Forward modelling demonstrates that resistivity anisotropy has a huge effect on Multi-Transient ElectroMagnetic step and impulse responses. The earth is never isotropic – even a stack of isotropic layers behaves anisotropically – and there is a great need to ccount for resistivity anisotropy in order to delineate the true target depth and target...