Last week (December 6), a powerful 7.2 magnitude earthquake, centered in Turkmenistan near the southeastern coast of the Caspian Sea, shook parts of central Asia. The epicenter of the quake (the point on the ground directly above the focus of the earthquake) was about mid way between Baku, the capital of Azerbaijan, and Ashkhabad, the capital of Turkmenistan. Though damage from last week's quake was likely severe, thus far there have been few reports of casualties. Fortunately, the area near the epicenter is sparsely populated. The Turkmenistan quake shook the ground for 2 minutes, and it was felt as far away as Moscow, about 1,200 miles (2,000 km) to the northwest of the epicenter, where residents could feel their house shake and see household items trembling. Across the Caspian Sea in Baku, people fled into the streets as soon as the ground began to shake. They were understandably jumpy, especially since just the week before (November 25), Baku was hit by a 6.5 magnitude earthquake, killing 31 people.

Between December 4 and December 11 there were 11 earthquakes somewhere around the globe that registered at least a 5.0 magnitude on one of three seismic scales commonly used (the Richter Scale, the body and surface wave magnitude and the moment magnitude). Two of these shakers were in Alaska. A 7.0 magnitude quake is considered to the marker or threshold for a major earthquake. Here in the US, a quake of this magnitude would likely be a big news story for several days, providing some lives were lost, buildings were destroyed and no election was being contested. However, worldwide, a 7.0 quake occurs on average more than once a month.

Last year (1999) there were 23 quakes with at least a 7.0 magnitude, including two that struck the US - one was in southern California and another in Alaska. The "big one" was a devastating 7.8 shocker that hit Turkey in August. More than 17,000 people lost their lives as a result of this quake. This year, it has been relatively quiet, nonetheless, fifteen 7.0 or greater magnitude earthquakes have shook some part of the world during the past 11 months. Thankfully, there have been no major quakes this year that have struck North America, Europe, Australia, or Africa. Antarctica was also spared.

From one year to the next, a map of the world showing where major earthquakes have occurred looks pretty much the same. Most of the action is centered around the rim of the Pacific Ocean, sometimes referred to as the "ring of fire," a name derived from the large number of active volcanoes found here. Earthquakes, like volcanoes, occur where and when crustal plates push against each other. For example, the Pacific Plate is pushing against or subducting beneath the lighter American Plate. In general, where the plates are rubbing the hardest, the seismic activity is greatest.

This year, the majority of the major quakes occurred about the western portion of the "ring of fire." What was different about the earthquake in Turkmenistan last week, compared to other major quakes this year, was that it occurred so far inland. The epicenter was about 1,000 miles (1,600 km) from the Indian Ocean (Arabian Sea) and was hundreds of miles from where two large plates are juxtaposed. Not all earthquakes occur where continental plates and oceanic are colliding. Smaller sub plates or micro plates are also frequently the focus for major earthquakes. For instance, last year's quake in Turkey occurred at the conjunction of the Eurasian Plate and the Anatolian Plate, and the killer quake that rocked parts of western Columbia, South America early in 1999 occurred where the South American Plate meets the Nazca Plate.

In addition, though most major quakes happen along fault lines, such as the San Andreas Fault in California, some powerful quakes have occurred even when no surface expression of a fault is visible. Two such quakes occurred in the US during the 19th century; one along the east coast, the Charleston, SC earthquake, and one deep in our country's mid section, the New Madrid, MO earthquake.