Frequency-Dependent Seismic Attenuation in the Eastern United States as Observed from the 2011 Central Virginia Earthquake and Aftershock Sequence

摘要

Ground shaking due to earthquakes in the eastern United States (EUS) is felt at significantly greater distances than in the western United States (WUS) and for some earthquakes it has been shown to display a strong preferential direction. Shaking intensity variation can be due to propagation path effects, source directivity, and/or site amplification. In this paper, we use S and Lg waves recorded from the 2011 central Virginia earthquake and aftershock sequence, in the Central Virginia Seismic Zone, to quantify attenuation as frequency-dependent Q(f). In support of observations based on shaking intensity, we observe high Q values in the EUS relative to previous studies in the WUS with especially efficient propagation along the structural trend of the Appalachian mountains. Our analysis of Q(f) quantifies the path effects of the northeasttrending felt distribution previously inferred from the U.S. Geological Survey (USGS) "Did You Feel It" data, historic intensity data, and the asymmetrical distribution of rockfalls and landslides.