National Seismic Data Act of 1985 - Amends the Earthquake Hazards Reduction Act of 1977 to direct the President, through the Director of the U.S. Geological Survey, to establish two national seismic data centers to conduct research into the basic causes and mechanisms of earthquakes. Requires that one of the centers be at an institution of higher learning east of the Continental Divide, and the other at such an institution west of the Continental Divide.

Sets forth provisions relating to such centers' functions. Sets forth guidelines for the Director's selection of such centers' sites.

Requires the regional seismic data networks to assist such centers.

Authorizes appropriations by the Secretary of the Interior for FY 1986 and 1987 to carry out, through the Director, the responsibilities that may be assigned to the Director under the Act, earmarking specified amounts for purposes of this Act.