Earthquakes rattle our psyches as well as our structures. We Californians can crack jokes about jumpy East Coast types, but the truth is, our blood pressure also rises precipitously when the Earth suddenly springs to life, without so much as a warning.
Events such as this past week’s magnitude-5.8 earthquake centered in Virginia, which shook up lots of people without inflicting tremendous damage, offer a good wake-up call: They provide a chance to consider our response and preparedness plans, and to reconsider what we really know and don’t know about earthquakes.
A feature from The Post’s Outlook section that dismantles myths, clarifies common misconceptions and makes you think again about what you thought you already knew.
Washington-area residents and workers crowded the streets near the White House on Tuesday following a 5.8-magnitude earthquake in Virginia. (Aug. 23)
1. Animals sense impending earthquakes.
A golden oldie. The notion that animals anticipate impending earthquakes predates the birth of Christ, with documented references to unusual animal behavior as early as the 4th century B.C. This belief was fueled recently by accounts, including one in The Washington Post, that some animals at the National Zoo had their knickers in a knot just before Tuesday’s quake.
This notion could contain a kernel of truth: Being generally squat, four-legged, close to the ground and inclined to sit still, an animal might feel an initial weak shaking that goes unnoticed by humans until stronger waves arrive. But also, it is an example of a natural human tendency to look back in time for anomalies, or precursors, that supposedly heralded the coming quake. Every pet owner understands that, say, cats and dogs sometimes behave strangely for no apparent reason; that’s what cats and dogs do. And if an earthquake had not subsequently struck, you can bet we would not be talking about strange animal behavior this week — because we wouldn’t have noticed anything out of the ordinary. As far as we understand, animals, like humans, have no ability to predict earthquakes.
2. The frequency of large-scale earthquakes has spiked.
With so many earthquakes in the news recently — such as those in Haiti, Chile and Japan — it seems that the frequency of big temblors is on the rise. Here again, there is an element of truth: Since the magnitude-9.3 Sumatra-Andamans earthquake struck just after Christmas in 2004 and unleashed a tsunami in the Indian Ocean, the Earth has experienced more great quakes, with magnitudes near or above 9.0, than the historical average.
Yet the frequency of tremors across the world always fluctuates considerably from year to year. And the energy released by big earthquakes since the end of 2004 was less than the energy released by the two biggest recorded earthquakes: the 1960 temblor in Chile and the 1964 Good Friday quake in Alaska. The number of earthquakes greater than magnitude 7.0has been somewhat high in recent years but well within the range throughout the 20th century.
A more concerning trend is illustrated by the 2010 Haiti earthquake: This one had a devastating toll despite its relatively modest magnitude because of a prevalence of poorly built structures and a densely packed population. As both population and urbanization expand in developing nations, many more people are in harm’s way. So even if the frequency of quakes is not expected to change significantly, the toll they exact is likely to keep rising.