This is a proposal to carry out an active source EM experiment on the sea floor on 25-40 my. old lithosphere. A number of receivers will be deployed at a site off the coast of California and the source will be towed through the array along various paths. Data will be collected over many ranges and directions of propagation and over a range of frequencies. Thus the electrical conductivity structure over a depth range of 2 to 50 km will be determined, and also the lateral anisotropy and heterogeneity of that structure. The data will complement that obtained in an earlier experiment on lithosphere of different age, so that an initial estimate of the electrical conductivity- age dependence of the lithosphere can be obtained. This is a unique experiment; the information cannot be obtained by any other electrical methods experiment and should provide important information about a fundamental physical property of the oceanic lithosphere.
