Near-surface attenuation using traffic-induced seismic noise at a downhole array

Abstract

A novel approach is developed for estimating the near-surface attenuation using seismic noise recordings at a downhole array. The amplitude spectrum of the traffic-induced seismic noise at the engineering bedrock level exhibits a high-frequency decay between 10 and 40 Hz. Subsequently, it yields a Kappa value of 14 ± 3 ms and a quality factor of 45 ± 10 for the profile between the highway and the sensor. Likewise, using the earthquake recordings made at the surface and the engineering bedrock levels, the Kappa values are calculated as 60 and 45 ms, respectively. The difference was attributed to near-surface attenuation where the upgoing earthquake waves and the downgoing traffic-induced seismic waves traverse similar soil profiles resulting in similar Kappa values. Hence, the near-site geology attenuation properties can be derived using the seismic noise data induced by a known source at a close distance recorded at engineering bedrock level.