Soil response characteristics to earthquakes based on deconvolution interferometry

Seismic interferometry technique was used to extract the shear wave velocity and damping ratio of the soil at the Delaney Park, Anchorage Alaska from the measured soil response to ten earthquakes. The soil response is record-ed by a geotechnical array. This array consists of a surface and six borehole stations equipped with a tri-axial accelerometer each. Deconvolution of the waveforms recorded by the borehole accelerometers at various depths with the waveform recorded at the surface accelerometer manifests an upward and a downward travelling wave in the soil. The arrival times to each accelerometer are obvious so that the entire travel time and time differences are extracted from the deconvolved waveforms. The shear wave velocity and its profile estimated from the deconvolution analysis agree reasonably well with in-situ measurements. The predominant frequencies are also inferred from the shear wave velocity and they are basically consistent for the ten earthquakes. The damping ratio is similarly investigated from the amplitude attenuation of the upward and the downward travelling waves. The value of damping ratio coincides with the empirical damping ratio of the soft clay as well. Analysis indicates that wave deconvolution can be used to extract the soil response and its characteristics.