Earthquakes were widely misunderstood until the year 1906. It was in April of this year that the Great San Francisco earthquake occurred. At this time, a scientist named H.F. Reid came up with his own hypothesis about what caused these tremors on the earth’s surface. He followed the movement created around the fault (a fracture in the earth’s crust) after the 1906 earthquake and realized that it followed a pattern. These studies led him to believe that a strain built up in the earth’s crust, and at some point, this strain could hold no more. The result was a breaking or shifting that caused the phenomenon of an earthquake.
The only piece of the puzzle that Reid was unable to decipher was what caused this intense build-up of pressure. Scientists later realized that the earth’s tectonic plates are in constant motion, a fact that inevitably leads to an occasional clash. Two plates meet and get stuck together, where they continue to remain stuck together. After years of constant stretching and pulling, the plates suddenly shift, causing an earthquake.
The sudden shifting of tectonic plates releases seismic energy waves so strong that they rock the earth. Earthquakes are measured with a seismometer or seismograph. The severity of an earthquake runs from 0 to 9 on this scale. Those with a magnitude under 3 are generally imperceptible, while a magnitude of 7 or more can cause significant and life-threatening damage. The epicenter is the point at which an earthquake is felt the strongest, and it is at this point where the most damage can be usually expected.
The USGS Earthquake Hazards Program reports that the world actually experiences around 500,000 earthquakes each year, while only a fraction of these (approximately one-fifth) have a high enough magnitude to be felt. The largest recorded earthquake in human history took place in Cañete, Chile in 1960. This earthquake reached a 9.5 magnitude on the seismograph.
Scientists are constantly searching to discover new ways to predict earthquakes. However, their predictions are not always accurate. They have realized that one earthquake can trigger another. This is one of the reasons that aftershocks are common after a large earthquake, and sometimes these aftershocks can be even larger than the original quake.
Geologists have also found that quakes occur most commonly around faults, which potentially represent areas of weakness in the earth’s crust. Just because an earthquake occurs around a fault does not mean that another will not occur there. In fact, this should be a warning sign that another will likely follow at some point.
Often it is the aftermath of earthquakes that is more destructive and generally feared than the quakes themselves. Landslides, floods, or avalanches triggered by a quake can wipe out an entire town. Tsunamis are another serious concern for areas near large bodies of water.
A tsunami is a series of very long wave lengths that typically move at frightening speeds, traveling for thousands of miles, and growing taller as they near shallow water, wiping out everything in their path. They generally cause widespread devastation, especially to small islands and coastal regions. According to a Geological Survey at Maine.gov, the largest recorded tsunami occurred in Lituyah Bay, Alaska, in 1958. It was the result of an 8.3 magnitude earthquake and reached an astounding 1,720 feet in height.
An earthquake is one of the most frightening natural phenomena that humans experience. It is frightening because we have no control over it; however, rather than being fearful, authorities encourage the world to be prepared. Prepare.org is a site dedicated to offering earthquake safety information. Earthquakes can occur at any time without warning, so it is best to plan ahead of time.
- USGS Earthquake Hazards Program: An extensive list of response agencies and other helpful links dedicated to helping increase awareness and encourage earthquake preparedness. Especially helpful for those who live in areas that are more susceptible to these quakes.
- Latest Earthquakes in the World: Want to know when the last earthquake occurred? Get real-time information on the latest earthquakes around the world.
- Earthquake Engineering Research Institute: This is a national nonprofit group of geologists, engineers, and other professionals. Here you can find the latest news about earthquakes.
- Welcome to Earthquake: A fun and educational resource. Take part in an interactive exercise that explains how seismologists pinpoint the epicenter of an earthquake.
- Earthquakes: A basic look at earthquakes. Learn how they happen, as well as how they are measured and predicted.
- Savage Earth: A PBS article with an in-depth look at earthquakes. It is complete with an interesting earthquake animation that helps readers better visualize the phenomenon.
- Welcome to Tsunami: The University of Washington’s Department of Earth and Space Sciences maintains this website. It is updated with tsunami warnings and features pictures and videos from past tsunamis. Take note of the informative resource on “Surviving a Tsunami” found here.