SMU Geophysicists Discover Large Blob Deep In The Earth

The concentrated matter, located more than 500 miles under the western Caribbean Sea, is about 80 miles thick by 380 miles tall, almost vertical, and is believed to be slowly descending vertically like the colored substance in a lava lamp. Scientists believe it may be an old subductive slab, but they are not certain how it moves.

SMU's Ileana Madalina Tibuleac made the surprising discovery while analyzing data gathered by sophisticated seismic equipment designed to detect underground nuclear tests. The equipment, which is being developed at SMU, is used to verify compliance with the international Nuclear Non-Proliferation Treaty now pending in Congress.

Tibuleac's findings were published in the Sept. 10 edition of Science magazine, the weekly journal of the American Association for the Advancement of Science.

Tibuleac is a post doctorate researcher in the Department of Geological Science in SMU's Dedman College of Humanities and Sciences. Co-author of the Science article is Dr. Eugene T. Herrin, Shuler-Foscue Professor of Geological Sciences at SMU, who headed development of computer programs and seismic monitoring technology used in detecting and analyzing seismic events.

Discovery of the concentration of anomalous matter involved analyzing parameters related to the geometrical path taken by rays from seismic events in the Caribbean's Windward Islands, Venezuela and the Mid-Atlantic Ridge to SMU's seismic monitoring station in Texas' Big Bend area and the Yellowknife station in northwestern Canada.

Scientists have long believed that the earth's lower mantle (about 450 to 1,800 miles below the earth's surface) was a homogeneous substance surrounding the earth's core. The new discovery raises questions about the composition of the lower mantle and the role it may play in seismic events close to the earth's surface, Tibuleac said.

Herrin has been involved in the development of seismic stations to detect underground nuclear explosions since 1987 with grants from the Defense Advanced Research Projects Agency. He has developed computer software and operating standards for the system and coordinated installation of seismic stations in the U.S. and several other countries.

The system prioritizes seismic data, distinguishing between signals related to nuclear testing, chemical explosions, earthquakes and shuttle quakes (quakes produced by the passing of the space shuttle). The system provides a nonintrusive method of verifying compliance with terms of bans and limitations on underground nuclear testing. The goal of the research is to develop an international network to monitor nuclear explosions anywhere in the world.