The development of reliable design procedures for the design of earthquake resistant structures requires an understanding of the manner in which the surrounding earth material at the site of a structure responds to seismic loading. However, due to the infrequent nature of earthquakes, and to the variability in the geology and physical properties of the soil at different locations, it is virtually impossible to provide such records for every proposed site. This action is to provide equipment to measure the long period microtremors in the entire Los Angeles basin. Microtremors, or microseisms, are small tremors or vibrations of the earth that are generated by natural occurrences such as the pounding of surf on the shore, or road traffic. They are not associated with earthquakes, but may be used, as is proposed here, to understand better the process of ground shaking due to earthquakes. The measured microtremors in the Los Angeles basin will be compared with existing strong ground motion measurements in the basin. Previous studies of microtremor data in Japan strongly suggests that microtremor data can be used to understand the strong motion response at a particular site to a damaging earthquake. The principal investigators are recognized for their expertise in earthquake engineering studies, and have the institutional resources to use effectively the equipment to be purchased.
