Measure of the energy released in an earthquake, obtained from interpretation of seismograms. For technical reasons several different magnitude scales are in common use. At PNSN we use the following: Md (Duration Magnitude) - based on the duration of shaking. Ml (Local Magnitude) - based on the peak amplitudes of high frequency seismograms, and Mw (Moment Magnitude) - based on matching waveforms of the lowest frequency ground motions in broad-band seismograms. More information at: https://earthquake.usgs.gov/learn/glossary/?term=magnitude and http://neic.usgs.gov/neis/phase_data/mag_formulas.html