Fig. 4. Regression analysis of estimated H concentration in percentage (w/w) vs. neutron log response in API-N units for saturated massive basalt. Hydrogen concentration was estimated by assuming that 100% of total porosity was filled with unbound pore water. Neutron log data used for the regression analyses was averaged over 30 cm. The analyses were confined to massive saturated basalt to minimize the effects of infiltrated sediments, alteration minerals, and water in unquantified and/or unidentified fracture porosity, since these are rare in the massive interiors of basalt flows. Outliers associated with infiltrated sediments in the C1A cores were eliminated from the data set. Some of the correlations established were subsequently used to calculate the percentage (w/w) H curves shown in Fig. 5.