January 11, 2013
by Steve Malone
Several news reports, for example from KREM and from KHQ, describe a bright flash in the sky with colors and in some cases followed by a boom or series of booms. Reviewing seismograms around 6:30 AM PST we find weak signals on several stations (fairly strong signal on station, DAVN). By picking the arrival times (marked with blue arrows on the attached seismograms) of these signals and knowing that sound travels about 325 meters/second in air we can invert the arrival times for a common source location and origin time.
The specific parameters are as follows:
Origin time: 2013/01/11 14:25:19.6 Z (06:25:19.6 AM PST)
Latitude: 47.437, Longitude: -117.145
Height: ???? (Because we have no stations within 90 km of the location we have no control on how far above the earth's surface the source was but assume it probably was in the range of 5 to 25 km.
Thus we think the bolide entered the atmosphere somewhere above the town of Rockford southeast of Spokane probably at a fairly high angle.
While the generation of seismic energy from such an event is not exactly known, we think the way this works is that the bolide, as it enters the atmosphere generates a shock similar to that generated by a supersonic aircraft. This "sonic boom" travels through the air until it hits the ground where it can be heard by people and, for some seismograph station shake the instrument well enough to be recorded. Seismograph stations are usually installed in a place and in such a way to minimize shaking that comes from the air. After all we are mostly interested in vibrations of the ground and so try to minimize the "noise" from other sources. Of course, we fail in some cases and thus we make lemonade from this noise and locate sources in the air.
The attached map shows PNSN stations in eastern Washington and western Montana. The blue underline is for stations that have a weak but recognizable signal. The red circle indicates the approximate location of this event. Unfortunately station, SFER is currently down because of reconstruction work at the site.
- Great ShakeOut, Great success!
- The Great ShakeOut 2014 is Tomorrow!
- Three Cascadia ETS events in past month??
- Is Mount St. Helens seismicity increasing?
- Warm weather triggers snow avalanches at St. Helens
- Seismic recordings of a gas explosion in North Bend, WA
- Seismic signals generated by the March 22nd Oso Landslide
- Legacy web site content returns
- Ice avalanches on Cascade volcanoes
- A New View On What's Shaking on the Cascade Volcanoes
- October (2)
- September (1)
- July (1)
- May (1)
- April (1)
- March (2)
- February (3)
- January (4)
- October (1)
- September (1)
- August (1)
- June (1)
- April (3)
- March (4)
- February (1)
- January (2)
- December (1)
- November (2)
- October (3)
- September (1)
- August (3)
- July (2)
- June (4)
- May (4)
- April (2)
- The wech-o-meter takes over all of Cascadia
- Keystone Cops: Italy prosecutes seismologists for failure to predict deadly quake
- UFOs in eastern Washington? No, rather UTEs (Unidentified Terrestrial Events)
- New Sodo Seattle Liquefaction Array Installed
- Why we should constantly watch the deformation of the seafloor
- Mystery chirp near Newberry Volcano
- Planting seismographs causes earthquakes? or maybe ice-quakes?
- Tunneling rumbles south under Capitol Hill
- 15 years of mostly silent magma inflation near Three Sisters, Oregon
- Mount Hood earthquake swarm of Feb 23, 2012
- Web glitches: duplicate (and even triplicate!) earthquakes
- How earthquake magnitude scales work
- Mine blast masquerades as volcanic tremor
- The Spokane Swarm about 10 years ago
- Another hum around Mount St. Helens
- Slow slip: A new kind of earthquake under our feet
- PNSN and social media
- 3am M3.4 earthquake in St. Helens Seismic Zone
- The wrong kind of volcano noise
- Fast chatter on Rainier an hour ago
- Can slush-mageddon trigger earthquakes?
- Rainier Repeating Earthquakes Update and Comparison with Weather Patterns
- 22-minutes drumbeat icequakes(?)
- Mount Rainier popping away
- Repeating Earthquakes on Mount Rainier - are glaciers the culprit?
- Debunking another SEC football myth by the PAC-12
- One year ago, Seattle Seahawks 12th Man Earthquake
- The odds this year of a megaquake on the Pacific Northwest coast
- Is the plague of great earthquakes this decade a sign of increased danger?
- Nile Valley landslide talks to PNSN seismologists
- Good vs evil in central US earthquake hazard analysis
- Why does a volcano scream?
- Predicting big quakes from patterns of little ones
- 1-hour warning for Japanese M9 earthquake?
- Sound Transit train under Interlaken keeps a rollin'
- Invisible changes under the hood at the PNSN
- Sound Transit Tunneling Noise
- "Visionary" toads
- Earthquake early warning in the PNW
- November (1)
- December (13)