There is concern that the number of catastrophic earthquakes worldwide may be increasing not only in number, but also intensity. In fact, there are many unfounded beliefs circulating the phenomena.
The United States Geological Survey (USGS) is among many scientific agencies that researches earthquakes. According to its website, the USGS is “a science organization that provides impartial information on the health of our ecosystems and environment, the natural hazards that threaten us, the natural resources we rely on, the impacts of climate and land-use change, and the core science systems that help us provide timely, relevant, and useable information.”
In a bid to counter misinformation or long-held misconceptions, the USGC published list of most “Frequently Asked Questions” (FAQ).
First of all, how many earthquakes are there? The USGC’s National Earthquake Information Center (NEIC) currently registers about 20,000 earthquakes worldwide each year – or about 55 each day
As far as whether there has been an increase in earthquakes, the USGC points out that the public now learns about earthquakes more quickly than ever before due to improvements in communications and the increased interest in natural disasters. Some 16 major earthquakes can be expected annually, including 15 with a magnitude 7 range and one at M8.0 or greater. Long-term historical records kept since around 1900 reveal that the over average number of major earthquakes was exceeded only 8 times: in 1976, 1990, 1995, 1999, 2007, 2009, 2010, and 2011. The year with the largest total was 2010, which experienced 24 earthquakes greater than or equal to magnitude 7.0. Other years saw fewer that the 16 annual average for major earthquakes; for example, there were only 6 in 1989 and 7 during the previous year.
Many people believe that the lack of a significant earthquake might be indicative that “pressure is building up and a big one is coming, but the USGS says this is untrue. Temporary increases and decreases in seismicity is “part of the normal fluctuation of earthquake rates,” says the official government agency, adding that, “Neither an increase or decrease worldwide is a positive indication that a large earthquake is imminent.”
There is also concern over so-called “Mega Quakes,” which could theoretically possible but realistically unlikely. The magnitude of an earthquake is related to the length of the fault on which it occurs – meaning that “the longer the fault, the larger the earthquake.” Faults are breaks in the rocks that compose the Earth’s crust, along which rocks on either side have moved past one another; and no fault long enough to generate a magnitude 10 earthquake is known to exist. ‘Mega Quakes still can’t be ruled out entirely due to a lack of research beyond the last century over which earthquakes have been measured, and science has still not placed a limit on how powerful they could potentially become. Historically, the greatest earthquake ever recorded was an M9.5 on 22 May 1960 in Chile, on a fault that is almost 1,610 kilometers in length.
On the topic of faults, it is important to know that they do not suddenly “open up” during earthquakes, as feared by some. “Shallow crevasses can form during earthquake-induced landslides, lateral spreads, or other types of ground failures” as movement occurs along the plane of a fault, but not perpendicular to it. Interestingly, the theoretical opening of faults would actually stop the occurrence of an earthquake “because there would be no friction to lock them together.”
It is also impossible to predict earthquakes. While “neither the USGS nor any other scientists have ever predicted a major earthquake. They do not know how, and they do not expect to know how any time in the foreseeable future,” it is possible to calculate the probabilities of potential future earthquakes based on scientific data. Research does puts 60% – 67% chance a major quake will occur in the San Francisco Bay area of Southern California over the next 30 years. The USGS emphasizes that it is critical to focus efforts on the “long-term mitigation of earthquake hazards by helping to improve the safety of structures, rather than by trying to accomplish short-term predictions.”
On that note, the USGS also rules out the long-held tale that animals can predict earthquakes, even though the earliest reference to such behavior dates back to Greece in 373 BC when rats, weasels, snakes, and centipedes were said to have abandoned their nests to seek safety elsewhere ahead of a destructive earthquake. Despite such anecdotal evidence that animals, fish, birds, reptiles, and insects exhibit strange behavior anywhere from weeks to seconds before an earthquake, the USGC says that “consistent and reliable behavior prior to seismic events, and a mechanism explaining how it could work, still eludes us. Most, but not all, scientists pursuing this mystery are in China or Japan.”
Nor is it true, as often heard that California eventually fall into the ocean. Interestingly though, the USGC believes that far in the future, two major cities in the North American state, Los Angeles and San Francisco, “will one day be adjacent to one another!” This is due to the 46-millimeter annual shift of the Pacific Plate northwest with respect to the North American Plate, which occurs about the same “rate your fingernails grow.”
Another commonly held belief in “earthquake weather” can be traced back in the 4th Century B.C., when Aristotle postulated that earthquakes were caused by winds trapped in underground caves. It was thought at that time that small tremors were the result of pressure below ground and larger ones when this trapped air escaped to the surface. Above-terrain conditions would be “hot and calm” just before these events. Later theories also held that earthquakes take place in similar calm, cloudy conditions, with the additional proposition that they were “usually preceded by strong winds, fireballs, and meteors.” None of this is scientifically factual, however. Citing Dr. Malcolm Johnston, the USGC definitively states that, “statistically, there is approximately an equal distribution of earthquakes in cold weather, hot weather, rainy weather, etc. Very large low-pressure changes associated with major storm systems (typhoons, hurricanes, etc.) are known to trigger episodes of fault slip (slow earthquakes) in the Earth’s crust and may also play a role in triggering some damaging earthquakes. However, the numbers are small and are not statistically significant.”
On a related topic, some speculate that “space weather” can cause earthquakes, which the USGC says “has never been demonstrated,” even though these technological systems and the activities of modern civilization can be affected by changing conditions caused by events such as solar flares and magnetic storms. Citing Dr. Jeffrey Love, the USGC explains that the occurrence of flares and magnetic storms wax and wane over the course of the Sun’s 11-year variable cycle, while earthquakes happen without any such 11-year variability. “Since earthquakes are driven by processes in the Earth’s interior, they would occur even if solar flares and magnetic storms were to somehow cease occurring,” concludes the USGC.
Last, but certainly not least, are the best means of self-protection during earthquakes. A so-called “Triangle of Life” method has been circulating largely on email. This unsubstantiated plan advocates that residents seek shelter from potentially-collapsing structures near solid items, and advocates against doing so under tables. The USGC dismisses the “Triangle of Life” as “a misguided idea,” and strongly recommends adhering to the recommendation of the American Red Cross to “Drop, cover, and hold under a table or desk.”
The American Red Cross also rejects the “Triangle of Life” notion, and insists that research continues to demonstrate that, in the U.S., “Drop, Cover, and Hold On!” not only saves lives, but is also “the simplest, reliable, and easiest method to teach people, including children.
The Agency points out that it “has not recommended use of a doorway for earthquake protection for more than a decade. The problem is that many doorways are not built into the structural integrity of a building, and may not offer protection. Also, simply put, doorways are not suitable for more than one person at a time.” Also consistent with information published in “Talking About Disaster: Guide for Standard Messages,” (visit http://www.disastereducation.org/guide.html ), the American Red Cross advocates remaining in bed when an earthquake happens. Rolling out of bed and lying prone to it, as posited by the “Triangle of Life,” could lead to greater injury from falling debris.
If residents are based in nations which observe proper building codes, the very best thing to do, says the Red Cross, is try to move at all during the tremors, as “the more and the longer distance that someone tries to move, the more likely they are to become injured by falling or flying debris, or by tripping, falling, or getting cut by damaged floors, walls, and items in the path of escape.”
— By Erin Viner