Mount St Helens: More than 400 earthquakes recorded since mid-July. It is a threat?

A report by the US Geological Survey (USGS) revealed that around 400 earthquakes have been recorded under Mount St Helens since mid-July this year.

The latest quakes are the longest series of tremors since the volcano's last eruption ended in 2008. However, there are no indications of an imminent eruption.

In an update posted to its website, the USGS said: "Mount St Helens has had a slight uptick in earthquakes, have you noticed? Most are small (less than M1.0) & not felt at the surface."

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"No cause for concern right now - no significant changes in ground deformation or gases. Volcano remains at normal (green) background levels," it added.

The USGS added that since mid-July this year, over 400 EQs have been located by the Pacific Northwest Seismic Network (PNSN), which monitors earthquakes and volcanoes.

"Most recently, there have been about 30 located EQs per week. To compare, since 2008, on average about 11 earthquakes have been located per month at Mount St. Helens.

In 1980, 57 people were killed when Mount St Helens erupted on May 18 in southwest Washington state. When a 5.1 earthquake hit, the north flank of the volcano collapsed. It blasted more than 1,300 feet off the top and rained volcanic ash for miles around. The eruption led to the largest landslide in recorded history.

Most of the quakes over a three-month span beginning in mid-July were less than magnitude 1.0, USGS recently reported, adding that the quakes were apparently too small to be felt at the surface.

Meanwhile, Wes Thelen, who is a volcano seismologist with the agency's Cascade Volcano Observatory told The Columbian newspaper that small magnitude earthquakes detected with sensitive equipment signal a volcano is "recharging" as magma flows through chambers and cracks deep underground.

(With inputs from agencies)