Mercury indicating inflow zones and ruptures along the Wenchuan Ms 8.0 earthquake fault

Abstract

During the Wenchuan Fault Scientific Drilling Project, we determined the values of total mercury (HgT) and gaseous elemental mercury (GEM) from drilled cores and drilling mud, respectively. Geochemical analysis shows HgT values ranging from 0.24 to 6.45 ng/g for the Penguan complex and from 2.90 to 137.54 ng/g for T3 sediment. The average levels of HgT for the Penguan complex and T3 sediments are 1.81 ± 0.26 ng/g and 23.96 ± 4.80 ng/g, respectively. Major anomalous peaks of HgT appear at depth of 614,731,993 and 1,107 m, which correspond to the long-term high seismic activity during crustal deformation in response to tectonic stresses. Gaseous elemental mercury dissolved in drilling mud was also analyzed. We found fluid inflow zones with high GEM at depths of 590-750 m, suggesting that fluid-filled ruptures exist in the LMS fault zone. It indicates that mercury provides geochemical evidence for inflow zones and ruptures/fault zones in the Wenchuan Ms 8.0 earthquake fault.