Earthquakes ‘steadily increasing’ under Mount St. Helens

A series of small earthquakes under Mount St. Helens are believed to be “volcano-tectonic in nature,” the United State Geological Survey reports.

The minor quakes have occurred beneath Helens over the last eight weeks. They began March 14, the USGS reports.

More than 130 earthquakes have been recorded. Many more are believed to have occurred, but were too small to pick up by Pacific Northwest Seismic Network monitors, according to the USGS.

“Earthquake rates have been steadily increasing since March, reaching nearly 40 located earthquakes per week,” information from USGS reads.

The nature of the quakes under Helens are indicative of a slip along a small fault, and the events are “commonly seen in active hydrothermal and magmatic systems.”

“The magma chamber is likely imparting its own stresses on the crust around and above it, as the system slowly recharges,” information from USGS reads “The stress drives fluids through cracks, producing the small quakes.”

The activity is similar to that seen under Helens in 2013 and 2014. “Recharge” swarms in the 1990s had higher quake rates and released more energy, according to the USGS. The activity beneath Helens is “likely associated with the recharge of the volcano.”

In short, Helens is slowly re-pressurizing, much like it did after the end of the eruption in the 1980s.

The USGS reports there are no signs of an imminent eruption.

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