Instrumental intensity scales for geotechnical and structural damage

The purpose of an earthquake intensity scale is to express the severity of ground shaking at different locations. Intensity values can be used to compare one area with another for a given earthquake, as well as to compare shaking in the same area in different earthquakes. Intensity measures are useful for providing a historical record of the effects of an earthquake; for seeing an aerial distribution of ground shaking which can be correlated to the geology of the site; in understanding historical earthquakes in areas with no instruments; for rapid response purposes; and to correlate observed "damage" to ground shaking. Earthquake damage may consist of structural damage due to ground shaking (e.g. buildings, bridges, etc.) and/or damage due to ground movement (e.g. liquefaction, landslides, etc.).; New instrumental intensity scales that correlate well with structural and geotechnical damage have been developed. Five primary damage mechanisms were identified as important potential contributors to earthquake damage in a typical urban environment: structures, slope instability, lateral spreading, post-liquefaction settlement, and damage to lifelines. Damage states for each mechanism were identified to create comparable measures of damage and to combine damage potential for the individual mechanisms into a single instrumental intensity scale. Physical damage to each of these mechanisms was related to performance levels of appropriate response parameters. Ground motion parameters that were strongly correlated to different damage states for a wide variety of earthquakes were identified. These parameters were used to develop a set of structural and geotechnical instrumental intensity scales capable of estimating damage potential based on recorded ground motions.; The instrumental intensity scales were used to estimate the spatial distribution of damage potential to areas affected by the Loma Prieta and Northridge earthquakes using a GIS framework. For selected pairs of records, intensity values computed from the structural and geotechnical instrumental intensity scales were compared with intensity values computed from the instrumental intensity scale of Wald et al., which is currently used to create real-time ShakeMaps. It was shown that the intensity values computed by the scales developed in this research provide a better indication of damage potential than the latter.