Amr S. Elnashai is the director of the Mid-America Earthquake Center at the University of Illinois.
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Amr S. Elnashai (pronounced Ah-MURR El-NOSH-eye) is the director of the Mid-America Earthquake Center at the University of Illinois. The Bill and Elaine Hall Professor of Civil Engineering, he has reported on most of the damaging earthquakes around the world since the mid-1980s. He has been on field missions to 17 earthquake sites around the world. Before joining the faculty at Illinois, he was the head of the Engineering Seismology and Earthquake Engineering Section at Imperial College in London.
How widespread was the April 18 earthquake, and did it occur on an active fault?
The earthquake nucleated from the well-known Wabash Valley seismic zone, a zone of relatively active seismic activity that has generated many earthquakes in the range of 4-5 over the past years. The geology of our region is such that an earthquake here would be felt in approximately 10 times the area that an equal magnitude earthquake would be felt in, had it been in the western U.S. In other words, the earthquake motion here dies very, very slowly compared to earthquake motion in California. The famous 1811-1812 earthquakes were felt all the way to Washington, D.C. The shaking this morning woke me and my family up, and also woke most of my CEE572 earthquake engineering course students. We exchanged many e-mails and phone calls at 5 a.m., even with our dean of engineering. I even have reports from Iowa, where the shaking was felt, albeit slightly.
Are aftershocks expected. If so, when?
Aftershocks always occur, and they may continue for a few days after such a relatively low-magnitude earthquake. Usually, with some exceptions, aftershocks are one magnitude unit below the main event, so perhaps we will get a few magnitude 4 aftershocks. From what we know, it is unlikely that this earthquake is a foreshock for a larger event, since we do not have evidence of great earthquakes being caused by the Wabash Valley region.
What should a homeowner check after an earthquake?
The first thing to do is to switch off the gas, and then sniff around for leaks. Homeowners should also check the utility networks in general, and be watchful of any signs of underground leakage, especially if they know that their properties are on soft ground.