Since Sunday, March 23, a quake swarm of at least 31 small quakes so far has been recorded on Mt. Hood. This quake swarm not only captured the attention of geologists, but it also rattled the nerves of nearby residents. Mount Hood in northern Oregon is an active stratovolcano, about 50 miles E-SE (80km) from Portland.
Is Oregon experiencing earth wobble symptoms?
Could be. In a little over a month, there have been loud booms and shaking heard and felt from Lincoln to Tillamook Counties, a sinkhole in Portland, and landslides near Portland and in the Columbia river Gorge, and now earthquake swarms at Mount Hood.
The earthquakes started on Sunday evening and have been rumbling directly under Government Camp, a community within five miles of Mount Hood. Even though the largest quake recorded was only a magnitude 2.3, but it's not the size of the quakes that intrigues the scientists like Ian Madin, Chief Scientist at the Oregon Department of Geology and Mineral Industries. It's the location where they're happening – along a recently discovered fault.
Other recent plate movement/earth wobble incidents in Oregon includes several mid-February events: Large landslides, loud booms and ground shaking, and a sinkhole to be exact.
- Two large landslides – one in the Columbia River Gorge dumped about 2,000 cubic yards of rock and debris on highway I84 just 3 miles west of the Hood River, and another blocked US30 near Portland.
- Loud booms and ground shaking reported by people from Lincoln to Tillamook Counties; some reported hearing a rumble, as well (No earthquakes recorded by the USGS in the area at the time.)
- A 20 ft. deep sinkhole swallowed a woman and her dog in her Portland backyard.
Stratovolcanoes like Mount Hood are common in subduction zones. Some other stratovolcanoes of note include:
- Mount Fuji in Japan
- Mount Vesuvius in Italy, known for its destruction of Pompeii and Herculaneum in 79 AD
- Krakatoa in Indonesia, best known for its catastrophic eruption in 1883
- Mount St. Helens in Washington State.
Before Mount St. Helens erupted in May 1980, small earthquakes rattled the area, an indication that magma may have been moving below the volcano. A gradual build up of quake swarms saturated area seismographs for several days, during which 174 shocks of magnitude 2.6 or greater were recorded.
With regard to Mount Hood, Madin says the earthquakes are defining a fault, which means that fault is active. He also says that if it can cause a 2.3 quake, it is capable of a magnitude 6 or stronger quake. Now that geologists know there may be active fault close to Government Camp, they will keep a closer eye on it.
Won’t we all!