Sociodemographic analysis of unbraced unbolted cripple wall retrofits in the City of Los Angeles

Disparities in seismic risk mitigation programs can lead to uneven impacts during an earthquake and an increased burden on socially vulnerable and underserved communities. This article examines the extent to which the distribution of cripple wall retrofits in residential buildings (primarily one- and two-family units) located within the City of Los Angeles (LA), varies based on the sociodemographics of the affected populations. Utilizing multiple data sources including the LA Department of Building and Safety (LADBS) and LA Open Data Portal (LAOPD), a combination of spatial and statistical approaches are implemented at the regional, neighborhood, and census-tract scales. At each scale, the number of retrofitted buildings normalized by the total number of pre-1980 one- and two-family residential buildings (or retrofit rate) is the primary dependent variable. The effect of the Earthquake Brace and Bolt (EBB) program on the disparities in the retrofit rate distribution is also assessed. Despite having relatively older one- and two-family residential buildings, those neighborhoods with the highest representation of Black and Hispanic households are generally associated with lower retrofit rates. We also found that the neighborhoods with the lowest median income have retrofit rates that are less than the average for the entire City of LA. The rate among Black, Hispanic, and low-income households was found to increase significantly after the EBB program was instituted in 2013, suggesting that the initiative may have served as a mechanism to reduce the demographic and economic disparities in the cripple wall retrofits. However, to date, the average retrofit rate in the ten neighborhoods with the highest representation of Hispanic households is roughly one-third that of the rest of LA City.