A note on the power of strong ground motion during the January 17, 1994 earthquake in Northridge, California

• Average and maximum power of strong earthquake ground motion.
• Attenuation of power in terms of the distances measured along the wave paths.
• Sedimentary basins act as wave-guides of strong motion energy.
• Flow of the power of strong motion energy through sedimentary waveguides.

Variations of average and maximum power of strong earthquake ground motion during the 1994 Northridge, California earthquake were gradual and smooth over distances as large as tens of kilometers. Correlation of the contours of recorded power with the depth of sediments and vertical offsets of the basement rocks along the faults in the Los Angeles basin implies a horizontal flow of earthquake wave energy through the deep waveguides of this basin. If the fault-to-station distances were to be measured along the three-dimensional wave paths through these sedimentary waveguides, rather than along straight lines emanating from the source, as is common in empirical studies of strong motion amplitudes, the accuracy of empirical-scaling equations for the prediction of the power of strong shaking could improve significantly.