Subsurface Weathering Revealed in Hillslope-Integrated Porosity Distributions

Russell P. Callahan , Clifford S. Riebe , Sylvain Pasquet (1) , Ken L. Ferrier , Dario Grana , Leonard S. Sklar , Nicholas J. Taylor , Brady A. Flinchum , Jorden L. Hayes , Bradley J. Carr , Peter C. Hartsough , Anthony T. O'Geen , W. Steven Holbrook

1 IPGP (UMR_7154) - Institut de Physique du Globe de Paris

Subsurface weathering has traditionally been measured using cores and boreholes to quantify vertical variations in weathered material properties. However, these measurements are typically available at only a few, potentially unrepresentative points on hillslopes. Geophysical surveys, conversely, span many more points and, as shown here, can be used to obtain a representative, site-integrated perspective on subsurface weathering. Our approach aggregates data from multiple seismic refraction surveys into a single frequency distribution of porosity and depth for the surveyed area. We calibrated the porosities at a site where cores are coincident with seismic refraction surveys. Modeled porosities from the survey data match measurements at the core locations but reveal a frequency distribution of porosity and depth that differs markedly from the cores. Our results highlight the value of using the site-integrated perspective obtained from the geophysical data to quantify subsurface weathering and water-holding capacity.

Domains: Sciences of the Universe [physics]

Russell P. Callahan, Clifford S. Riebe, Sylvain Pasquet, Ken L. Ferrier, Dario Grana, et al.. Subsurface Weathering Revealed in Hillslope-Integrated Porosity Distributions. Geophysical Research Letters, 2020, 47, ⟨10.1029/2020GL088322⟩. ⟨insu-03584745⟩