The Whittier Narrows, California Earthquake of October 1, 1987—Evaluation of Strengthened and Unstrengthened Unreinforced Masonry in Los Angeles City

On November 15, 1987, the City of Los Angeles' Earthquake Division, launched a study of the performance of its strengthened unreinforced masonry buildings during the Whittier Narrows Earthquake. The objective of the study was twofold: (1) To analyze the damage to unstrengthened as well as to strengthened and tension-anchored-only buildings, and from that analysis (2) to determine the most effective ways of improving the design standards for strengthening unreinforced masonry buildings. The initial part of that objective has been completed, and the findings of that study are the primary basis for this article. Observed damage demonstrated a clear-cut need to improve certain aspects of the Code design standards for strengthened buildings; more importantly, however, it sent out warning signals to owners of unstrengthened buildings and only to a slightly lesser extent to owners of tensioned-anchors-only buildings, of the very serious need to fully strengthen their buildings and to improve on the low probability of those buildings surviving a major earthquake. The second part of the study's objective will require additional work, and the combined effort of the City of Los Angeles and the SEAOSC.