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A Citizen’s Eye View of Public Preparedness

Are Earthquakes Becoming More Frequent? No, But Our Exposure To Them Is Increasing

April 14th, 2010 · 1 Comment

With today’s 7.1 earthquake in western China on the heels of the quakes in Haiti and China as well as those last week in Baja California and Indonesia, seismologist Roger Musson has a timely op-ed in the New York Times addressing the question: “Are earthquakes becoming more frequent?” His answer: “no.”

It’s true that more earthquakes are recorded than used to be the case, but that’s simply because there are more monitoring stations that are able to pick up minor earthquakes that once went undetected. If we compare the average global rates of large earthquakes, we find that these are stable as far back as we can trace them. On average, we record an earthquake with a magnitude over 6 every three days or so, and over 7 at least once a month.

Basic geology explains why the number of earthquakes remains relatively constant. Quakes release a lot of energy, and that energy has to come from somewhere. Ultimately, the source of it is heat released by the steady decay of radioactive material deep inside the earth. For a real long-term increase in earthquake activity, there would have to be an increase in that energy supply, and it’s hard to see how that could happen.

But he explains why the concern if not the volume is now greater:

One problem that we do have to face is that our exposure to earthquakes is increasing. As the world becomes more populated and cities grow ever bigger, the potential for quakes to become disasters rises. Tehran, for instance, has been destroyed by earthquakes several times, but it was still quite small at the time of its last damaging quake, in 1830. Now the city is home to millions, and when the next major quake hits, the results will be catastrophic.

Unless we devote more effort to protecting communities, the number of earthquake disasters will grow, even if the number of earthquakes stays the same.

Thanks to the Red Cross Oregon Trail Chapter’s Twitter feed for flagging this story. The United States Geological Survey today also put out a release on the subject of earthquake frequency.

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Tags: Earthquake Preparedness

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