Niu wins NSF support to probe quake zones, Earth’s core

Niu wins NSF support to probe quake zones, Earth’s core
Seismologist earns CAREER award for wide-ranging research

BY JADE BOYD
Rice News staff

Seismologist Fenglin Niu has received a prestigious Early CAREER Development Award from the National Science Foundation (NSF) to probe the structure of the Earth — from seismically active zones just a kilometer or so beneath the surface to the center of the planet, the innermost inner core.

CAREER grants support research and education development plans of junior faculty. They are among the most competitive grants awarded by the NSF, which gives out only about 400 per year across all disciplines. The five-year grants range from $400,000 to $500,000 and are designed to support transformative research activities of scholars who are likely to become leaders in their field.

Niu, assistant professor of Earth science, won CAREER support from the NSF Earthscope Program for a wide-ranging research program that will probe the Earth’s crust for telltale signs of impending earthquakes, look for patterns in 3-D velocity maps of the Earth’s mantle and search for clues about the early formation of the Earth’s core.

“Almost everything we know about the deep interior structure of the Earth comes from seismic waves, the elastic waves of energy that are released during earthquakes,” Niu said. “Today’s state-of-the-art sensors and computers are allowing us look at these waves with greater precision than ever before.”

One track of Niu’s research is conducted on California’s famed San Andreas fault, which runs through San Francisco and around Los Angeles. About halfway between the cities lies the small town of Parkfield, where the U.S. Geological Survey has been collecting seismic data for almost 40 years. Using a new generation of sensors, Niu and colleagues are measuring slight changes in the time — sometimes just tens of billionths of a second — that it takes seismic waves to travel through the rock along a fixed pathway beneath Parkfield. Ultimately, they hope to detect changes in the rock structure that precede earthquakes — something scientists could use to make early warning systems for quakes.

In a second area of research, Niu is probing the mantle, the largest portion of the Earth. The mantle stretches from just beneath the Earth’s crust, about 25 miles below ground, to the boundary of the Earth’s core, about 1,800 miles beneath the surface. Heat from the planet’s core drives convection of the mantle, which behaves — over hundreds of million years — like a thick sauce left simmering on a stove. Niu is using new methods to analyze data to make 3-D maps of the mantle in a manner similar to medical CAT scans. The goal is to determine precisely how seismic energy moves through the mantle and thus develop a clearer picture of the forces that drive our planet.

Deeper still, about 3,100 miles below the Earth’s surface, lies the inner core, a ball of crystalline iron about two-thirds the size of the moon. In a third track of research, Niu has developed a new method to probe the seismic waves that travel through the inner core. In prior research, he and his colleagues showed that seismic waves travel about 1 percent faster through the uppermost inner core in the eastern hemisphere of the inner core than they do in the Western Hemisphere.

“We don’t know when the inner core was formed, how the atoms of iron are arranged inside it or whether it formed continuously or episodically,” Niu said. “Answering these questions and others can help us better understand how the Earth evolved and how it will change in the future.”