Magnetic inference of in situ open microcracks in sandstone samples from the Taiwan Chelungpu Fault Drilling Project (TCDP)

This paper presents a thorough magnetic study of centimeter-sized rock samples from Hole B of the Taiwan Chelungpu Fault Drilling Project (TCDP). Fabrics were obtained from magnetic susceptibility and anhysteretic remanent magnetization are interpreted using whole rock and magnetic mineralogy characterization. We infer the presence in the sandstone lithology of secondary magnetite coating a dense network of microcracks. Using other evidence from ferrofluid saturation experiments, we conclude that this network of microcracks is not sealed but open in situ, and should therefore be incorporated in the interpretation of seismic and borehole scale studies in the TCDP area. (C) 2011 Elsevier Ltd. All rights reserved.