Center for Earthquake Research and Information (CERI)
University of Memphis, Memphis, Tenessee
The New Madrid Earthquakes Two Hundred Years Later:
What Have We Learned About Earthquakes at the Center of Tectonic Plates?
One of the pillars of plate tectonics is the rigidity of major plates, and one of the corollaries of this assumption is that most of the seismicity on our planet occurs at plate boundaries. Along those boundaries, strain steadily accumulates due to the relative movement of tectonic plates and is periodically released during large earthquakes. By contrast, the interiors of continents, far away from plate boundaries, are mostly stable.
The New Madrid seismic zone (NMSZ), located in the heart of the North American continent (over 2,000 km away from the nearest plate boundary) is a notorious exception to this generally observed behavior. The NMSZ has generated large magnitude earthquakes (M>7.0). Understanding the NMSZ is the focus of scientific research. Scientists are debating whether the NMSZ faults have been unloaded, and therefore will not produce additional large earthquakes for thousands of years, or whether the faults remain close to failure and are ready to slip. If so the series of catastrophic earthquakes that have been occurring approximately every 500 years will continue to occur at that rate.
This talk will discuss the existing data, the models proposed to reconcile them and the implications for seismic hazard in the Central U.S. The lecture will also present the results of a new study along the Mississippi River suggesting that the NMSZ is not the only fault system that has been active in this region. The study images the sedimentary layers beneath the Mississippi River for more than 600 km and reveals that a widespread network of faults has been active throughout the Mesozoic and the Cenozoic until today, accommodating the deformation in the interior of the North American continent.
About Dr. M. Beatrice Magnani
M. Beatrice Magnani is a seismologist whose overarching research theme is the formation and evolution of continents (a.k.a. continental dynamics). Dr. Magnani received her Ph.D. in 2000 at the University of Perugia, in Italy, where she worked on the tectonics of the Northern Apennines mountain belt. Shortly after completing her Ph.D., she moved to the U.S. and was a post-doc at Rice University before joining the faculty of the Center for Earthquake Research and Information (CERI) at the University of Memphis in 2006.
Dr. Magnani employs controlled-source seismology to image continents at a wide range of scales and resolutions, from the lithosphere to the near surface. In 2000 she was part of a team that investigated the legacy of Archean and Proterozoic assembly structures in the evolution of the North American continent in the Western U.S., and in 2004 she studied the growth of the South American continent at the southeast Caribbean plate boundary using a combination of offshore and onshore data. More recently she has become interested in the puzzling topic of intraplate deformation and the resulting seismic hazard. In 2007 she started studying the New Madrid seismic zone in the Central U.S. and, together with her colleagues, she designed an innovative application of conventional marine reflection seismology to data acquisition along the Mississippi River. This new method allowed her to map known and unknown faults hidden beneath the river, and to begin unmask the network of faults that have been shaking the Midcontinent.