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A dense seismic array was deployed at a 2 km spacing to record the aftershocks of the Mw (moment magnitude) 5.8 Mineral, Virginia (USA), earthquake in 2011. The three-component seismometers, installed on a 60-km-long profile, recorded 40 aftershocks over 9 days of deployment. Based on manual picking of P-wave (primary, compressional) and S-wave (secondary, shear) arrival times of 15 aftershocks, we find that the P-wave propagates with a velocity of 6.15 km/s through the upper crust, and the direct S-wave travels with a velocity of 3.66 km/s within the first 20 km (Vs<20km) and decreases slightly to 3.54 km/s (Vs>20km) for distances >20 km. Hence, the aftershock data show a Vp/Vs ratio of 1.68 within the first 20 km of hypocentral distance, and a ratio of 1.73 for distances >20 km. We attribute the small decrease in Vs with increased distance to the complex geologic setting: the recording array was deployed across the geologic boundary between the Quantico Formation and the Ta River Metamorphic Suite. Near-source attenuation of S-waves (amplitude decay with hypocentral distance R) was measured using ~1200 digital seismograms (north-south and east-west components) from 40 aftershocks. The decay of amplitude was extracted using a nonlinear least-squares regression for different frequency bands: 1–2, 2–4, 4–8, and 8–16 Hz. For 1–2 Hz the decay can be described as a function of distance (R) as R−0.8, for 2–4 Hz as R−0.9, for 4–8 Hz as R−1.05, and for 8–16 Hz as R−1.15. The decay exponents, or b values, increase ~9%–15% from a lower to the next higher analyzed frequency band. These values are valid to a distance of as much as ~45 km from the aftershocks.

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