Structural engineers have measured a building’s response to strong motion from civil structures that have been instrumented with accelerometers, such as the Robert A. Millikan Library of the California Institute of Technology. The attenuation of the motion of this building has been measured using seismic interferometry techniques in the past. We use the breaking of the temporal symmetry of the wave equation by attenuation, in combination with seismic interferometry, to estimate attenuation. These estimates are made from fitting the differences in acausal and causal waveforms obtained from different deconvolution processes. We apply the method to the motion recorded at the Millikan Library and obtain estimates of intrinsic attenuation that compare well with past measurements. This technique has more precision for higher frequencies than earlier measurements that are based on seismic interferometry, and it is not dependent on radiation losses at the base of the building.