By their very nature, earthquakes are unpredictable. When large ones occur close to densely populated urban areas, however, the potential for loss of human life is large. Two of the most recent earthquakes in the 21st century were also the most catastrophic in terms of casualties: the Indonesian tsunami of 2004 and the Japanese tsunami of 2011.
What Causes Earthquakes?
Every child in California learns about the shifting earth and the tectonic "plates" that make up the surface of the world we live in. Though it seems unchanging and solid, the ground you walk on is actually part of a complex system of interlocking slabs of rock that push against each other with tremendous force. Occasionally, one of these slabs slides or slips a bit, which is what we know as an earthquake. Although it's possible to trigger an earthquake through things like volcanic eruptions and even human causes like nuclear testing, the vast majority of earthquakes are simply the result of built up tension in the earth's crust, or surface.
Earthquakes Facts
The next thing most people want to know besides what causes earthquakes is whether or not they have to worry about one. The Federal Emergency Management Agency has produced maps that show the likelihood of experienced "damaging earthquake effects" for all locations in the United States, including Alaska, Hawaii, Puerto Rico, and the U.S. Virgin Islands. Although folks in the Midwest have less to worry about than those on the West Coast (unless they live in Chicago), the very nature of the earthquakes is that they are unpredictable. Haiti was considered a very unlikely spot for a major earthquake—until January 12, 2010.
Some Famous Earthquakes
Besides the aforementioned quakes in recent memory, there have been a number of major tremors that have remained in popular culture.
- 1906 San Francisco Earthquake. The 1906 earthquake that destroyed San Francisco is probably one of the most famous earthquakes in many ways, and has become a cultural legend in many ways. The damage was real enough, however; modern estimates put it as high as $6.08 billion.
- 1989 Loma Prieta Earthquake. The more recent quake in 1989 caused far less damage than its predecessor, but received significant media coverage when the Cypress Structure freeway overpass collapsed in Oakland.
- 1976 Tangshan, China, Earthquake. The communist regime in China makes it difficult to get exact numbers, but one of the deadliest disasters in recent history occurred in China in 1976. Loss of life due to the quake has been roughly estimated between 242,000 to 779,000 people.
Quakes In History
Before modern science, a quake was considered an act of the gods, with wildly varying explanations from a giant catfish thrashing about (Japan) to a bizarre torture ritual outlined in Norse mythology. What is clear from ancient literature is that earthquakes have been a part of human life from the beginning, and although the causes were not as well understood as they are today, certainly the effects have always been the same.
How Are Earthquakes Measured?
In spite of attempts to alter the method used to measure quakes to the Mercalli scale (amongst others), the Richter scale continues to be the way most people understand earthquakes. Quakes are reported in the news with a number rating, usually in the format of 3.1 or 5.6, to indicate the strength of the tremors. The majority of quakes are minor, with a rating of 3.0 or less on the Richter scale. Anything greater than 7.0, however, is considered a major quake by the U.S. Geological Survey, the branch of the Federal government charged with measuring them.
Some Other Earthquakes Facts
Unlike hurricanes or even tornadoes, the science of predicting earth's quakes continue to evade scientists. Even the idea that a quake on one part of a fault releases pressure on the rest of the fault has been called into question, making even the vaguest of predictions unreliable. Meanwhile, nature's creatures continue to predict these events with remarkable accuracy. The common toad, for example, will abandon his home days in advance of a quake—and no one knows how he knows one is coming. Future possibilities for a prediction science center around the relationship between magnetism and electrical charges deep within the earth's surface. For now, however, the only reliable method remains rather, well, jumpy.
Earthquake Preparation
Although the most recent earthquakes in Haiti and Japan garnered tremendous media attention, the vast majority of Americans remain completely unprepared for a major quake, even those living in earthquake-prone areas. Even having a plan in advance for how to communicate with other family members if an earthquake happens puts you in the top 20% of prepared community members. Actually making an emergency kit, complete with food, water, and basic medical supplies, puts you in the top 10%; and more importantly gives you the assurance of having something to fall back on when earthquakes do strike.
