4.2 magnitude earthquake jolts WA. What are the chances of an aftershock?
Earthquake in WA: 9,100 people feel 4.2 magnitude quake
More than 9,000 people in western Washington reported feeling Tuesday's 4.2-magnitude earthquake centered in the Kitsap Peninsula.
KITSAP COUNTY, Wash. - More than 9,200 people in western Washington reported feeling Tuesday's 4.2-magnitude earthquake centered in the Kitsap Peninsula. After reviewing the data, scientists with the United States Geological Survey (USGS) have released a forecast for potential aftershocks.
(USGS)
Earthquake in Washington: 4.2 magnitude felt by thousands in western WA
What we know:
On Tuesday at 2:05 p.m., a 4.2-magnitude earthquake struck about 3.7 miles west-northwest of Wauna, Washington in Kitsap County. Scientists with the Pacific Northwest Seismic Network (PNSN) initially recorded a magnitude of 4.3, but it was quickly revised after review – which is common for measuring earthquakes.
Within an hour of the quake, PNSN received thousands of "Did You Feel It?" reports. As of 9 a.m. on Wednesday, more than 9,200 reports have been received and the number is steadily climbing. People mostly felt weak shaking in areas near the epicenter on the Kitsap Peninsula, including Seattle, Tacoma and Bremerton. Many did not feel it at all.
USGS "Did You Feel It?" map. (USGS)
According to the USGS 'Did You Feel It?' map, people reportedly felt the quake from distances as far as Salem, Oregon; Union, Oregon; Carlton, Washington; Nanaimo, B.C.; and Vancouver, B.C.
What you can do:
Anyone who felt the earthquake is encouraged to report it on the USGS website.
What are the chances of an aftershock earthquake in WA?
The United States Geological Survey (USGS) released an aftershock forecast following the 4.2-magnitude quake, indicating that there is an 11% chance of another earthquake at magnitude 3.0 or higher within the next 24 hours and a 25% chance of a magnitude-3.0 or higher aftershock within the next week.
USGS Aftershock Forecast Map. (USGS)
By the numbers:
Here's a detailed aftershock forecast:
- Magnitude 3 or higher: 11% chance within 24 hours, 25% chance within a week, 35% chance within a month, 50% chance within a year.
- Magnitude 4 or higher: 1% chance within 24 hours, 4% chance within a week, 6% chance within a month, 12% chance within a year.
- Magnitude 5 or higher: 1 in 700 chance within 24 hours, 1 in 200 chance within a week, 1 in 100 chance within a month, 2% chance within a year.
- Magnitude 6 or higher: 1 in 7,000 chance within 24 hours, 1 in 2,000 chance within a week, 1 in 1,000 chance within a month, 1 in 600 chance within a year.
- Magnitude 7 or higher: 1 in 70,000 chance within 24 hours, 1 in 20,000 chance within a week
Recent earthquakes: PNW sees notable cluster of earthquake activity in last 48 hours
A series of three sizable earthquakes with magnitudes near 5.0 struck off the coast of Vancouver Island late Sunday and early Monday. (USGS)
Timeline:
Over the last 48 hours, multiple earthquakes were recorded by the USGS. Here's a timeline:
- Sunday, Sept. 27 at 5:12 p.m.: A 2.6-magnitude earthquake was recorded on the western flank of Mount Adams.
- Sunday, Sept. 27 at 7:53 p.m.: A 4.9-magnitude earthquake was recorded west of Vancouver Island.
- Sunday, Sept. 27 at 9:41 p.m.: A 5.4-magnitude earthquake was recorded in the same general area.
- Monday, Sept. 28 at 2:13 a.m.: A 5.2-magnitude earthquake was recorded in the same general area.
- Tuesday, Sept. 29 at 2:05 p.m.: A 4.2-magnitude earthquake was recorded in the Kitsap Peninsula in Washington's Puget Sound.
A 2.6-magnitude earthquake struck a shallow depth on the western flank of Washington's Mount Adams on Sunday evening. (USGS)
When was the last earthquake in Seattle?
Dig deeper:
Not counting Tuesday's 4.2-magnitude earthquake in Kitsap County, other notable earthquakes felt heavily in Seattle in modern history include the 2001 Nisqually earthquake (6.8 magnitude), the 1965 Puget Sound earthquake (6.5 magnitude), and the 1949 Olympia earthquake (6.8 magnitude). While all three caused significant shaking and damage in Seattle, their epicenters were located miles away in the South Sound, deep beneath the earth's surface.
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The Source: Information in this story comes from the United States Geological Survey, the Pacific Northwest Seismic Network, original reporting by FOX 13 Seattle reporter Lauren Donovan, and recent earthquake reporting by the FOX 13 Seattle Digital Team.
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