To isolate effects of the laterally varying lithosphere on regional seismograms, we geographically smoothed source- and distance-corrected amplitudes from 853 events recorded at station LZH in central China. This procedure was applied to Pn, Pg, Sn and Lg phases and various coda windows for eight bands between 0.5 and 8 Hz. We assume smoothing reduces effects such as source radiation, leaving an estimate of the path effect that can be used to correct data. A cross-validation procedure showed that path corrections performed best with low-frequency Lg data, reducing variance up to 39% for 1 Hz Lg, and up to 57% for 0.75 Hz P/Lg ratios, compared to correction for distance alone. These corrections reduce scatter in magnitude estimates and discriminant ratios without needing to know detailed geological structure and will be important for effective test-ban monitoring. ¿ 1998 American Geophysical Union