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Earthquake S-Meter Comparison

There was recent documentary called “Mega quake 10.0.” With my apologies to the seismologists here is a little comparison to our more familiar dB scale measurements.

In some respects we all live in Earthquake Country not just California. The program described the effects of an earthquake in various magnitudes. Some of the bigger quakes have occurred in the middle of the country such as the “New Madrid Quakes” around 1809 and 1810. They rang church bells in Boston!

The presenter tried to explain the earthquake scale using stacked quarters. A magnitude one quake was 1 quarter and magnitude 2 quake was 31 (square root of 1,000) quarters and magnitude 3 was a stack of 1,000 quarters and so on.

The old Richter scale has been revised several times. Now the earthquakes are measured in “Moment Magnitudes.” It measures more directly the amount of energy released by a quake. The scale is logarithmic, so that a magnitude 5 quake releases a 1,000 times more energy than a “3.” If you are walking, you may not notice a magnitude 4 but a magnitude 5 definitely will get your intention.

What would our Earthquake S-meter readings look like? Let’s say a magnitude 5 was “S-9”. A magnitude 7 would be a 1,000 times more energetic than a “5” So converted into dB, it would 30 dB greater than S-9 or we would say “30 dB over S-9.” A magnitude 9 would be 30 dB greater than a “7” or “S-9 plus 60 dB.”

The largest recorded quake was a “9.6”, which would have pegged our mythical earthquake S-meter.

So may all your earthquakes be little ones but do not count on it.

73 Jim N6TP

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