Pair of early-morning earthquakes rattle Glenwood Springs
December 11, 2018
Richter scale
The Richter magnitude scale was developed in 1935 by Charles F. Richter of the California Institute of Technology as a mathematical device to compare the size of earthquakes. The magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs. Adjustments are included for the variation in the distance between the various seismographs and the epicenter of the earthquakes. On the Richter Scale, magnitude is expressed in whole numbers and decimal fractions. For example, a magnitude 5.3 might be computed for a moderate earthquake, and a strong earthquake might be rated as magnitude 6.3. Because of the logarithmic basis of the scale, each whole number increase in magnitude represents a tenfold increase in measured amplitude; as an estimate of energy, each whole number step in the magnitude scale corresponds to the release of about 31 times more energy than the amount associated with the preceding whole number value.
Source: U.S. Geological Survey
A pair of small-magnitude earthquakes struck north of Glenwood Springs early Tuesday morning, according to the U.S. Geological Survey's Earthquake Hazards Program reporting center website.
The first quake hit about 3:02 a.m. just a little over a mile north of Glenwood Springs and at a depth of 3.2 miles beneath the earth's surface. It registered at a magnitude 3.4 quake.
The second quake was about 3.7 miles north of town at 4:13 a.m., also at a depth of 3.2 miles, and registered 3.6 magnitude, according to the earthquake information site.
According to the educational website UPSeis, an earthquake of 2.5 to 5.4 magnitude on the Richter scale is often felt, but only causes minor damage. About 30,000 such quakes are reported worldwide each year, according to the site.
Several area residents reported similar experiences to the reporting website Earthquake-Report.com.
"Walls shook for 3 seconds at 3 a.m. and then two more tremors about a half hour apart. You could see walls move shake and the floor shake," one person reported to the site from Glenwood Springs regarding the later quake.
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"At around 3 a.m., I suddenly woke up to a strange shaking like sensation that was clearly felt around all my apartment," another Glenwood resident wrote regarding the initial quake. "A second shake occurred about one hour later, this time stronger with smaller ones following it for about 5 seconds."
And another commenter wrote, "House was shaking enough my china was clinking. Second quake was stronger and woke up everybody who all came running out of the bedrooms."
A media representative for the USGS was not immediately available for comment.
Richter scale
The Richter magnitude scale was developed in 1935 by Charles F. Richter of the California Institute of Technology as a mathematical device to compare the size of earthquakes. The magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs. Adjustments are included for the variation in the distance between the various seismographs and the epicenter of the earthquakes. On the Richter Scale, magnitude is expressed in whole numbers and decimal fractions. For example, a magnitude 5.3 might be computed for a moderate earthquake, and a strong earthquake might be rated as magnitude 6.3. Because of the logarithmic basis of the scale, each whole number increase in magnitude represents a tenfold increase in measured amplitude; as an estimate of energy, each whole number step in the magnitude scale corresponds to the release of about 31 times more energy than the amount associated with the preceding whole number value.
Source: U.S. Geological Survey
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