Spatially continuous characterization of the bedrock – regolith interface at the Rio Icacos Watershed (Luquillo Critical Zone Observatory) Puerto Rico

Abstract:

Joint processing of geophysical data can enhance data interpretation. This study focuses on spatially continuous multifrequency electro-magnetic (EM) data for near subsurface characterization. Recent advances in EM data processing allow for efficient inversion of multi-frequency data, utilization of calibration routines and additional constrains for better subsurface imaging. For this work the newly developed FEMIC (Frequency-Domain Electromagnetic Inversion Code) code was used to invert the EM data. High resolution electrical resistivity (ER) data were used to calibrate the EM process; additionally, available data from ground penetrating radar (GPR) and field observations were used to better constrain the inversions.

The multistep EM processing allowed for improving characterization of the subsurface over long (i.e. Km scale) 2D transects. The aim of this work was to better understand the lateral extent of the bedrock-regolith interface in the Rio Icacos watershed of the Luquillo Critical Zone Observatory (LCZO), while providing evidence for changes in regolith thickness as related to proximity to the nickpoint. This research highlights the advantages of geophysical methods for critical zone studies and their potential for improving spatial characterization of the subsurface at multiples scales. Furthermore it shows the potential of EM methods for translating high resolution spatially limited point measurements (e.g. boreholes) to large (km) scales.