Sunday, June 6, 2021

Earthquake Swarm Hits Mt Hood, Oregon

After Salton Buttes, now Mt. Hood is swarming too: M3.9 earthquake and series of quakes on June 5, 2021

At 20:51 PDT on June 5 (0351 UTC on June 6) a M3.9 earthquake occurred about 2.5 mi (~4 km) south of the summit of Mount Hood, Oregon, at a depth of 2.7 mi (4.3 km) below sea level. The earthquake was felt in areas around Mount Hood.

The swarm was preceded by several earthquakes in the hour prior to the M3.9, and tens of aftershocks have occurred with event rates declining in a manner typical of mainshock-aftershock sequences.

The mainshock characteristics and location are consistent with past swarms in the Mount Hood area, including a M 4.5 on June 29, 2002, that was located ~1 mi (~1.6 km) east of the M 3.9. Aftershocks will likely continue for hours or days, some of which may be felt.

The quake got the attention of some who live nearby. “The living room chair I was sitting in moved somehow, like a slight swaying side to side,” said Jane Bowker, of Rhododendron. “My brother is visiting with us and said he felt it as well. I thought it may have been one of the huge Douglas firs falling, since we live in such a wooded area, but you would usually hear a thud along with that.

At this time, seismologists at the Cascades Volcano Observatory and Pacific Northwest Seismic Network do not believe this swarm signifies a change in volcanic hazard at Mount Hood, but will continue to monitor the swarm and will issue further updates as the situation warrants.

Salton Sea earthquake swarm

Just a few hundreds of miles south, another earthquake swarm is rattling the Salton Buttes area in southern California.

The Salton Buttes geothermal system is fueled by heat emanating from zones of partially molten rock (magma) deep below the Earth’s surface.

Eruptions occurring about 400,000 years ago were followed by a long lull in volcanic activity until about 18,000 years ago. The most recent eruptions, which took place about 1,800 years ago, started explosively, then progressed to relatively gentle effusion of dense, glassy-looking (obsidian) lavadomes.

The Salton Sea Geothermal Field, which currently produces enough power to supply about 325,000 homes, has persistent small to moderate earthquakes related to the geothermal system and to movement along regional faults.

The available data are insufficient to establish a pattern of volcanic activity to determine the likelihood of eruption. The high heat flow from the area and relatively young age of Salton Buttes, however, attest to the potential for future eruptions.

So what’s going on on the West Coast of the US? Are all volcanoes going to erupt together?

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