Earthquake microzonation and site effects

Hu, Y.X.; Sun, P.S.

Proceedings of the Third International Microzonation Conference, Seattle, June 28-July 1, 1982 2: 587-597


In the first part of the paper, the authors' opinion on microzonation is presented; ie, zonation is the study of primarily large scale factors such as earthquake occurrence, while microzonation is the study of primarily small scale factors such as local conditions. Main findings on effect of site conditions at the Institute of Engineering Mechanics (IEM) in 1962-1978 are then summarized: (1) Ground failure should be taken care of by site selection or foundation treatment; (2) Soil condition changes, primarily the spectral shape and single parameter adjustment method such as Medvedev's, are criticized; (3) Causative faults are dangerous, non-causative faults are not; (4) Under special conditions, liquefaction may act as a cushion to structures. The first four findings have been accepted in the 1974 and the current Chinese codes. In the last part, authors recommend a two-sets-of-maps microzonation principle, one for ground failures such as liquefaction, land slide, differential settlement and ground breakages, and one for ground motion parameters such as acceleration, velocity, displacement, and spectrum.