Investigation of Earthquake and Microtremor Ground Motions.

摘要

The nature of strong earthquake ground shaking was studied in 15accelerograms recorded at El Centro,Calif. No local site periodicities could be clearly identified,and it was concluded that the characteristics of the source mechanism and transmission path overshadow the influence of local site conditions in determining details of strong ground shaking at the site. The method of using microtremor measurements to determine local site characteristics was tested by direct comparison with strong motion measurements. The microtremors were measured at 5locations in the El Centro area and some were repeated after 24hours. These low amplitude ground motions differed widely from the motions caused by strong earthquake ground shaking and their nonstationarity render interpretations difficult and unreliable. It was concluded that they are forced oscillations of the ground caused by nearby sources of excitation,and that the use of microtremor measurements to define local subsoil conditions was not feasible. (Author)