MAPPING RESIDENTIAL PROPERTY DAMAGE RESULTING FROM THE AUGUST 23, 2011 EARTHQUAKE IN LOUISA COUNTY, VIRGINIA TO SUPPORT RECOVERY, RESEARCH, AND MITIGATION EFFORTS

The magnitude 5.8 earthquake that occurred near Mineral, VA on August 23, 2011 impacted more than 1,500 residences in Louisa County and surrounding areas. Reported damage was to chimneys, brick veneer siding, building foundations, building frames, interior walls, porches, carports, and water lines. In Louisa County, repair and replacement costs for residential property exceeded 21 million U.S. dollars. Preliminary maps showing the distribution of property damage and the geology of the epicentral area were created by the Virginia Department of Mines, Minerals, and Energy shortly after the earthquake to assist in recovery and aftershock monitoring efforts. Improved damage maps have been developed in collaboration with James Madison University to assist with recovery, research, and mitigation efforts including locating the causative fault(s) and determining which geologic conditions affect the intensity of property damage in this region. The creation of a damage map for this earthquake was challenging because of the low density and irregular spacing of residences and the variability in structure size, style, age, and method of construction. In addition, damage reports from inspectors did not specify the type of damage that occurred and are not available for all residences reporting damage. Our approach uses data for more than 100 structures that were collected by geologists from the Virginia Department of Mines, Minerals and Energy and the U.S. Geological Survey immediately after event in combination with residential property damage reported by property owners in Louisa, Fluvanna, Goochland, and Spotsylvania Counties, and damage rankings assigned by county and FEMA inspectors. Damage is mapped as zones of intensity based on the predominant type and level of damage observed or reported in a given area and the percentage of total homes in that area reporting damage.