When we walk along the street, we most likely feel like we’re walking on solid ground. Actually, according to figures published by USGS, our world is constantly moving under our feet.
Figures published by the United States Geological Survey show that in the 7 days from March 31 to April 6, 2012, 240 earthquakes of magnitudes from 2.5 to 6.2 occurred around the world. 207 of those earthquakes (87%) took place somewhere on the Pacific Ring of Fire, the arc of converging tectonic plate boundaries that ring the Pacific basin, from New Zealand to Fiji, to Indonesia, to Japan, to Alaska, and down the west coast of North America to the tip of South America.
However, there are few places on earth that are completely earthquake free. 33 of those 240 earthquakes occurred in such diverse places as Oklahoma, Texas, Idaho, Virginia, Puerto Rico, the Caribbean, Algeria, Turkey, Pakistan, Tristan da Cunha, Tajikistan, Italy, Greece, and Poland.
Even if an earthquake struck somewhere near you, you may not have felt the earth move because most of the 240 quakes registered in the magnitude 2.5 to 4.0 range, many of those with epicenters deep underground. There were two magnitude 6.0 or greater quakes in the 7-day period. One took place near New Guinea, and the other near Oaxaca, Mexico, an aftershock to the magnitude 7.4 that struck that region on March 20, 2012. A magnitude 5.8 earthquake off Japan’s main island, Honshu, was an aftershock to the 9.0 earthquake that hit that area in March, 2011, and triggered the tsunami that took 19,000 lives.
Earthquakes — large or small, shallow or deep underground– are produced by the constant pressure of the world’s oceanic tectonic plates pushing against and sliding under the world’s continental plates. This process of one plate thrusting into the other goes on day after day, year after year. Fault line tension builds higher and higher. Minor fault line slippages cause small earthquakes that serve to relieve some of the stress; but from time to time, a large fault line section undergoes a sudden release of the pent-up strain, causing a major rupture or fault line slippage that results in a destructive earthquake and in some cases, a killer tsunami.
Seismologists have been working on ways to predict the location and time of the next major fault line slippage and great earthquake, but the science has not yet been perfected. We know that devastating earthquakes will continue to strike. But we still don’t know when and where.