A REVIEW OF THE LITERATURE ON SITE EFFECTS AND STRUCTURAL FOCUSING IN THE LOS ANGELES BASIN AND THE SAN FERNANDO VALLEY FROM THE JANUARY 17, 1994 NORTHRIDGE EARTHQUAKE IN THE LOS ANGELES REGION, CALIFORNIA

We reviewed numerous subsurface geological/geophysical published studies in the BSSA, GSA and other scientific publications from 1996 to February 2003, on site effects and structural focusing of earthquake energy from the 1994 Northridge Earthquake and aftershocks in the Sherman Oaks area of the San Fernando Valley. It was the consensus of these researchers that there were subsurface structural features in the San Fernando Valley that focused and, or amplified the January 17, 1994, earthquake waves and the aftershocks causing heavily damage zones that were controlled by these geological structures. We found in these published geological and geophysical studies that were written within the last six years there were numerous references of focusing of earthquake energy due to the local geology in basins located in other areas such as the Santa Clara Valley in northern California, the European test site in Greece, the structural focusing in folds along faults in Santa Monica, and the site response and basin effects in Seattle for the M 6.8 Nisqually, Washington, Earthquake. There was a consensus among these researchers on the earthquake damage due to site effects during major earthquakes. This lead us to review published studies that caught our attention on site effects and structural focusing; and earthquake damage first to the CSUN campus located in Northridge and a second study of the damage due to focusing in Santa Monica and Sherman Oaks in the 1994 Northridge Earthquake. We then reviewed the subsurface geology of the San Fernando Valley with respect to the structural geologic features that are located below the known red tag areas of the San Fernando Valley both in the 1994 Northridge Earthquake and also in the1971 San Fernando/Sylmar Earthquake to look for similar patterns of earthquake damage due to structural focusing of earthquake waves.