ML (local magnitude (or Richter - k)) was not designed to be applied to data with distances to the hypocenter of the earthquake greater than 600 km (373 mi). For national and local seismological observatories the standard magnitude scale is today still ML. Unfortunately this scale saturates at around ML = 7, because the high frequency waves recorded locally have wavelengths shorter than the rupture lengths of large earthquakes.
To express the size of earthquakes around the globe, Gutenberg and Richter later developed a magnitude scale based on surface waves, surface wave magnitude Ms; and another based on body waves, body wave magnitude mb. These are types of waves that are recorded at teleseismic distances. The two scales were adjusted such that they were consistent with the ML scale. This succeeded better with the Ms scale than with the mb scale. Both of these scales saturate when the earthquake is bigger than magnitude 8 and therefore the moment magnitude scale, Mw, was invented.
http://en.wikipedia.org/wiki/Richter_magnitude_scale
The table at the bottom of this page shows 3 out of 9 instances where the Richter rating was higher than the moment magnitude scale.
http://en.wikipedia.org/wiki/Moment_magnitude_scale#Comparison_with_Richter_scale
Together with early reporting uncertainty this could explain the discrepancy without having to question the quality of your recollections.
When we returned from Japan, we were both attracted to the Pacific NW but ruled it out early because of the quakes. Having been on the East Coast and away from quakes for a while now, though, we are presently reconsidering that decision; but it still figures in our thinking.
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