Did you feel last week’s earthquake? I did. It was my third one.
Back in 1968 Nixon was running for president, I was a sophomore in high school, and Indiana experienced an earthquake measuring 5.3 on the Richter scale. I didn’t feel it. But almost everyone else did.
Back then, the Indianapolis Star ran is daily quip on the front page by a cartoon bird called Joe Crow. In the edition following the quake, I clearly remember Joe Crow’s political wisecrack: “Nixon said he had some earthshaking ideas, but this is ridiculous!”
Fast forward to 1980. It was in the summer and I was sitting in a swivel rocker on the back porch of my parents’ house on Kyle St. when I thought I noticed the chair quivering just a tad. I looked around to see if the dog had brushed against it, but he was lying on the floor across the room. About 10 seconds later, the chair started rocking. I’d never felt an earthquake before, but I thought perhaps I was in one. It turns out, I was.
Then, in 1987, I was sitting on a bench on my deck in Hobart, Indiana. Again, I felt a very slight jolt. I looked out at the kids’ swing set. I felt it again, like I was in a boat. The swings started swinging on their own. It was my second earthquake experience.
I know we had an earthquake five or six years ago, but I didn’t feel that one. But the one last Friday, I felt. I was lying in bed on my back, fully awake. Again I felt a very subtle shaking of the bed, and again I blamed it on the dog. But she was nowhere near the bed. Then, as the first time, 10 seconds later the bed started heaving, the bottles on the dresser started shaking loudly, I heard pops and crackles from downstairs. I just lay their and enjoyed the ride because I knew what it was.
Earthquakes in Indiana are not frequent. And for the most part, they are not severe or damaging. But there are clear exceptions. Southwest Indiana lies on the Wabash fault zone. It is a northward extension of the famed New Madrid fault system.
One of the biggest earthquakes in U.S. history happened here in the Midwest in 1812. The epicenter was in New Madrid, Missouri, just across the Mississippi River from Tennessee. It changed the course of the river and added a new lake in eastern Missouri. It was the largest of a series of quakes running from late 1811 into January of 1812.
When earthquakes happen in the Midwest, they are felt for hundreds of miles around the epicenter. That’s for two reasons. One is that the fault lines are deep within the bedrock. Primarily, though, it is because most of the Midwest and the Northeast lie on a hard, continuous sheet of bedrock. The surface waves from an earthquake carry for long distances uninterrupted by unconformities in the rock layers.
Contrast that to California. That state has many more earthquakes, and usually they are more severe. But the bedrock of California is a hodgepodge of younger rock formations that have been tacked on to the West Coast as the entire continent slowly moves westward.
When an earthquake happens in California, it usually isn’t as deep, and the bedrock that carries the waves is discontinuous. So even a larger earthquake than the one most of us felt last week will be very localized. It typically won’t travel more than a hundred miles or so.
Unfortunately, since Midwestern earthquakes are so infrequent, and typically not as strong as those in the West, most buildings here are not designed to withstand a major shock. But as the big one of 1812 has shown, we here in the nation’s midsection are not immune from catastrophic earth shaking.