We present a method of calibrating a regional network of seismographic stations for Lg-wave site responses. Characterized by remarkable simplicity and practicality, the calibration procedure involves merely the determination of what we call calibration curves, defined as the frequency-dependent station site responses relative to that of a reference station. The method is used to calibrate a group of twelve stations belonging to the Eastern Canada Telemetered Network (ECTN), with an SRO-type station (GAC) serving as a reference station. The calibration curves are employed in a test application to Lg amplitude data from 50 small- to moderate-sized earthquakes (mLg (f) between 1.4 and 5.3). We found that use of the calibration curves leads to a systematic reduction in the variance of the station magnitude estimates of 37 per cent. A calibrated network minimizes station-specific systematic biases between the network magnitudes and those determined at any given station. As a result, it allows meaningful applications of empirically developed magnitude/yield relationship for stimulation of underground nuclear explosion yields, even when they are well recorded at very few stations of an in-country monitoring network.