Another earthquake swarm hits Mount Hood stratovolcano in Oregon

By Strange Sounds -Jan 21, 2021

On Sunday afternoon, January 17, 2021, a swarm of small earthquakes started rattling the south side of Mount Hood with several dozen small quakes happening withing a few hours.

The swarm has yet slowed down and stopped on January 20, 2021. 

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About 45 earthquakes struck near Mt. Hood within a few hours. The swarm lasted unti January 20, 2021.

The figure below summarizes the timeline of earthquakes that occurred off-summit (i.e. not centered under the volcano, but within 2.5 km of it).

During the time period in the figure (1980-2017), occasional earthquakes have occurred beneath the summit as well, but most of the seismic action in recent decades has taken place in swarms near or on faults close to the volcano.

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Is this January 2021 earthquake swarm at Mt. Hood actually normal? Graph shows timeline of earthquakes that occurred off-summit. Picture: USGS

Today’s swarm is also located close to the Twin Lakes Fault. But this is not the only fault around the volcano. Back in 2019 a new dangerous seismic line was discovered in the vicinity of the stratovolcano in Oregon.

CVO recently installed three more seismic stations near Mt. Hood that we can now use to better constrain exactly where these small earthquakes occur.

The figure below is a screenshot on one of Jan 17th little earthquakes on recordings from the three new stations.

Each station measures the shaking in three directions, up-down (Z), north-south (N), and east-west (E).

Picks on new CVO stations near Mount Hood, Jan 17 2021

Scientists at the Cascades Volcano Observatory (CVO) aren’t too worried about an impending volcanic eruption because similar swarms of small tectonic, not volcanic, earthquakes have happened in the past in this area. (Click to Source)

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