Earthquake in Illinois 5.2 on Richter Scale

After reviewing the USGS website at www.earthquake.gov, and speaking with Gutierrez, aftershocks are still trembling throughout the seismic zone.  Gutierrez says that aftershocks are common, but it is hard to tell how many or how long the Midwest will continue to feel them, although he does not expect them to last long.  To bring things into perspective, Gutierrez mentioned the earthquake that triggered a tsunami in 2004.  That earthquake was measured at a 9.0 magnitude, of which aftershocks are still felt today.

The Richter magnitude scale, or the local magnitude M_L scale measures the amount of seismic energy released by an earthquake.  It was developed in 1935 by Charles F Richter of the California Institute of Technology to compare the size of earthquakes.  According to the USGS, “The magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs.”

2.0 magnitude earthquakes and smaller are not felt, but can occur up to 8,000 times per day.  2.-3.9 magnitudes are minor earthquakes, but occurrences range from 1,000 per day (for 2.0-2.9 magnitudes) to 49,000 per year (for 3.0-3.9 magnitudes).  4.0-4.9 are considered light tremors, but can cause indoor items to shake.  These happen about 6,200 times per year.  The Illinois earthquake falls within the 5.0-5.9 area, which can cause significant damage to buildings.    Anything higher than a 6.0 magnitude spans across large areas and are very destructive.