Joint Deconvolution of Building and Downhole Strong‐Motion Recordings: Evidence for the Seismic Wavefield Being Radiated Back into the Shallow Geological Layers

Abstract

In this study, the strong‐motion recordings collected by a vertical array of borehole sensors and a network of accelerometers installed in a nearby building (distance between borehole and building ∼10 m) are innovatively jointly analyzed through wavefield‐deconvolution analysis. The analysis shows complicated patterns in the deconvolved wavefield of the borehole sensors that are interpreted by taking advantage of synthetic seismograms generated considering vertically propagating plane waves in the soil and building. Using a constrained deconvolution approach, we show that it is possible to separate the different components of the wavefield and, in particular, to retrieve the input ground motion and the wavefield radiated back by the building at different levels in the borehole, without a priori information about the attenuation structure (and velocity) of the building and soil. This therefore allows the energy radiated back by the structure at different depth to be estimated, which, in the case of the bottom of the borehole (at −145 m), is of the order of 10% of the energy of the input wavefield in the 1–10 Hz frequency band.