Soil characterization using patterns of magnetic susceptibility versus effective radium concentration

F Girault (1) , C Poitou (1) , F Perrier (1) , B. P. Koirala (2) , M Bhattarai (2)

1 IPGP - Institut de Physique du Globe de Paris
2 National Seismic Centre, Nepal

Low-field magnetic susceptibility χ m and effective radium concentration EC Ra , obtained from radon emana-tion, have been measured in the laboratory with 129 soil samples from Nepal. Samples along horizontal profiles in slope debris or terrace scarps showed rather homogeneous values of both χ m and EC Ra. One sample set, collected vertically on a lateritic terrace scarp, had homogeneous values of EC Ra while χ m increased by a factor of 1 to 10 for residual soils and topsoils. However, for a set of samples collected on three imbricated river terraces, values of EC Ra , homogeneous over a given terrace, displayed a gradual increase from younger to older terraces. By contrast, χ m showed more homogeneous mean values over the three terraces, with a larger dispersion, however, for the younger one. Similarly, Kathmandu sediments exhibited a large increase in EC Ra from sand to clay layers, while χ m increased moderately. The combination of χ m and EC Ra , thus, provides a novel tool to characterize quantitatively various soil groups and may be of interest to distinguish modes of alteration or deposition histories.

Domaines: Planète et Univers [physics]

F Girault, C Poitou, F Perrier, B. P. Koirala, M Bhattarai. Soil characterization using patterns of magnetic susceptibility versus effective radium concentration. Natural Hazards and Earth System Sciences, 2011, 11, pp.2285-2293. ⟨10.5194/nhess-11-2285-2011⟩. ⟨insu-01298112⟩