Plot of all well-located earthquakes (quality factor BB or better) occurring directly beneath Mount Rainier between 1989 and 1996. All of these earthquakes are high-frequency (or "volcano-tectonic") events. Low-frequency events are frequently observed, but are attributable to ice movement on the volcano. This plot extends back only to 1989 because no stations existed on Mount Rainier's edifice before 1989. Installation of two stations (RER and RCS) in 1989 and a third (RCM) in 1993 directly on the edifice resulted in a significant increase in the number of earthquakes recorded.

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