Southeastern Section - 61st Annual Meeting (1–2 April 2012)

Paper No. 11
Presentation Time: 11:40 AM


DIECCHIO, Richard J., Department of Atmospheric, Oceanic and Earth Sciences, George Mason University, 4400 University Drive, Fairfax, VA 22030-4444,

Earthquakes have been occurring for billions of years, ever since there has been a thick solid crust. Crude seismographs have only existed for 2 thousand years. We have been observing and accurately measuring earthquakes for only a century or two. The reality is that we have been collecting accurate seismic data for less than 1 ten millionth of the time during which earthquakes have been occurring.

The Richter scale is open-ended. The longer we measure earthquakes, the higher the magnitudes we observe. In 2011 alone, the 9.0 magnitude Japan earthquake, and the 5.8 magnitude Virginia earthquake were the worst recorded in their region. The highest magnitude earthquake recorded globally was a 9.5 in southern Chile in 1960. These are the worst we have measured, not the worst that have ever occurred.

We do not know, and cannot predict the worst case scenario. We do not know what the highest possible magnitude earthquake is, globally or regionally. We know which areas are more prone to earthquakes of various magnitudes, but we do not know where or when an earthquake of any magnitude will occur. The problem is that the general public is not fully aware of the limits of our knowledge. When we engineer our cities and infrastructures, we engineer for the worst we have observed, or something less than that. With a false sense of security, we then rely on these structures, and build our communities accordingly. Then when a big earthquake hits, we are always caught off guard, and the disaster is worse because of structures and infrastructures we have created.

We geologists are responsible for alerting the public not just about what we know, but also that our knowledge is limited. This is especially crucial for societies that exist in earthquake-prone areas. It should be expected that an earthquake will occur with a higher magnitude than has ever been recorded in a given region or globally. It’s just a matter of time.