The science behind an earthquake
“Southern Africa is known to be tectonically stable. A 5.3 magnitude quake is really big for South Africa,” said geologist, Mr John Sparrow.
The most common standard of measurement for an earthquake is the Richter scale, developed in 1935 by Charles F. Richter of the California Institute of Technology.
The Richter scale is used to rate the magnitude of an earthquake.
This is calculated using information gathered by a seismograph.
The Richter scale is logarithmic, meaning that whole-number jumps indicate a tenfold increase.
A wave amplitude in a level 6 earthquake is 10 times greater than in a level 5 earthquake.
The amplitude increases 100 times between a level 7 earthquake and a level 9 earthquake.
The amount of energy released increases 31.7 times between whole number values.
Most earthquakes are small with the majority of quakes registering less than three on the Richter scale.
These tremors, called microquakes, are not even felt by humans.
Only a small portion (15 or so) of the 1.4 million quakes that register above 2, also register at 7 or above, which the threshold for a quake being considered major.
The biggest quake in recorded history was the 9.5 quake that struck Chile in 1960.
It killed nearly 1,900 people.
“Southern Africa is known to be tectonically stable. A 5.3 magnitude quake is really big for South Africa,” said geologist, Mr John Sparrow.
“There is always a chance after an earthquake strikes that there will be additional seismic activity. The ground will compensate for the energy released,” said Mr Sparrow.
He added that the activity would more than likely be limited to the Orkney and surrounding areas.
Mr Sparrow also said that the longer an earth quake lasts, the more energy is released.
