The response of shallow sites, with depth to bedrock less than 100 feet, in the geologic and tectonic setting of the Eastern United States (EUS) cannot generally be captured with code-based site factors. The need to address this issue on a regional basis became even more evident with the 2011 Mineral, Virginia earthquake. The difference in site response of EUS shallow soil profiles are mainly due to: (i) the sharp stiffness contrast between overburden soils and very hard underlying bedrock, and (ii) the bedrock ground motions that are typically of short duration, low intensity, and have high frequency content.