This standard is intended for use at light water-cooled, land-based nuclear power plants and may be used for guidance, where appropriate, at other types of nuclear power plants. Included is an Earthquake Decision Tree and specific associated procedures for evaluating records obtained from seismic instrumentation specified in American National Standard "Earthquake Instrumentation Criteria for Nuclear Power Plants, ANSI/ANS-2.2-1978. This standard does not include specific operator functions to be accomplished in the event of an earthquake. The standard does, however, define the type and timing of plant owner activities to be accomplished in the event of an earthquake. These activities relate to shutdown requirements of Title 10, Code of Federal Regulations, Part 100, Appendix A, "Seismic and Geologic Siting Criteria for Nuclear Power Plants," and evaluation of seismic data obtained from seismic instrumentation. The activities described should be accomplished in a timely fashion to satisfy the regulatory requirements of promptness in reporting information and determining the seismic response of the plant. Instructions are provided in this standard for treatment of data from a variety of seismic instruments not all of which may be required. The procedures set forth herein may be used where applicable, or when considered desirable by the plant owner for instrumentation other than specified in ANSI/ANS-2.2-1978.