Abstract: Provisional Seismic Zonation of Portions of Los Angeles, Ventura, and Orange Counties, California Following the January 17, 1994 Northridge Earthquake

Charles R. Real, Mark D. Petersen, Michael S. Reichle

Following the devastating Northridge Earthquake the Federal Emergency Management Agency, Governor's Office of Emergency Services, and California Seismic Safety Commission requested CDMG to prepare provisional seismic hazard zone maps for sixteen 7 1/2 minute quadrangles (scale 1:24,000) to help prioritize the distribution of post-earthquake mitigation funds and to facilitate immediate earthquake resistant reconstruction. The analysis included an assessment of ground motion hazard for a 10% exceedance in 50 years using published attenuation curves and an adaptation of the Southern California Earthquake Center's source model. Ground failure hazard was evaluated by classifying geology using independent strength criteria for liquefaction and landslide hazard, and then spatial y intersecting these areas with locations of shallow ground water and steep slope gradient respectively.

An advanced geotechnically-oriented geographic information system having functionality in remote sensing, photogrammetry, subsurface stratigraphic correlation, and terrain analysis was used for data integration and spatial analysis. Because simplified criteria were used to enable preparation of the hazard maps in less than 7 months, they are not Official Seismic Hazard Zones as defined under the Seismic Hazard Mapping Act. Continuing work will incorporate subsurface geotechnical data and higher resolution terrain data which will provide for a more thorough analysis of hazard, and permit designation of Official Seismic Hazard Zones.

AAPG Search and Discovery Article #90958©1995 AAPG Pacific Section Meeting, San Francisco, California