A matlab-based frequency-domain electromagnetic inversion code (FEMIC) with graphical user interface

Abstract

We present a new Matlab-based 1 frequency-domain electromagnetic (EM) inversion code (FEMIC) for analysis of datasets collected using multi-frequency EM-induction instruments. The code includes routines for data filtering and calibration, forward modeling, inverse modeling, image appraisal (i.e., calculation of the depth of investigation), and visualization. A one-dimensional forward model is assumed, but two or three dimensional lateral regularization constraints can be applied during the inversion. The code can take advantage of the parallel-processing capabilities of multi-processor computers, thus facilitating efficient inversion of large datasets. Synthetic and field examples demonstrate the operation of the FEMIC code and showcase its capabilities. Source code is provided as material supplementary to this paper to allow modifications and extensions by others.

Wetland‐Scale Mapping of Preferential Fresh Groundwater Discharge to the Colorado River

“…Although this type of analysis can be quite useful, when average apparent bulk EC patterns were used to inform new monitoring well installation (Figures and ), the full potential of the EMI data may not be realized. New software allows for rapid processing and inversion of large EMI datasets (Auken et al ; Elwaseif et al ), and reveals highly resolved patterns of shallow aquifer bulk EC (Figures and ). Estimates of groundwater SpC derived from the inverted EMI data using Equation (1) compare favorably to that measured directly in wells within the preferential groundwater discharge zone through the southwestern wetland area at approximately 500 to 2500 µS/cm.…”

“…EMI can be associated with certain depths below ground surface using various frequency domain‐ or time domain‐based methods and/or varying the transmitter‐receiver coil separation. As with VES, all depth‐specific data associated with a single measurement are made relative to a common point on the land surface, but as measurement times are on the order of seconds or less, data can be collected quickly across the terrain to build comprehensive 2‐ and 3‐D spatial models of bulk electrical conductivity (EC) (Auken et al ; Elwaseif et al ), which is the inverse of bulk resistivity, and more intuitively related to pore water fluid EC.…”

EMagPy: Open-source standalone software for processing, forward modeling and inversion of electromagnetic induction data

“…(Auken et al, 2015), or EM4Soil (Monteiro Santos, 2004). In addition, several open source software codes exist, such as the Matlab-based open-source GUI for EMI data, FEMIC (Elwaseif et al, 2017), or the Python-based open-source codes SimPEG (Heagy et al, 2017) and pyGIMLI (Rücker et al 2017). Open-source software has several benefits over commercial software, for instance it has better reproducibility, it is free and allows the user to interrogate the source code and, where necessary, adapt and customize for their own application.…”

MoisturEC: A New R Program for Moisture Content Estimation from Electrical Conductivity Data

“…These values were converted to bulk EC through Archie's law assuming the following soil properties: σ w = 2 S/m, φ =0.3, φ int =0.3, m =2, and n =2. Horizontal coplanar frequency domain EMI data were simulated using the 1D forward modeling functions available in frequency‐domain electromagnetic inversion code (FEMIC, Elwaseif et al ) for seven frequencies ranging from 1530 to 93,090 Hz. Data were generated assuming a 1‐m instrument elevation over a 1‐m grid on the surface of the soil block.…”