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NMSU scientists prepare for next phase of research on Tibetan Plateau

Researchers from New Mexico State University will join other scientists from around the world this month in the fourth phase of a project on the Tibetan Plateau that intends to unlock more secrets of continent building.

A seismic sensor is buried during the INDEPTH III project on the Tibetan Plateau. (Courtesy photo)

Supported by a $755,000 grant from the National Science Foundation, the NMSU team, along with researchers from the University of Missouri-Columbia, Peking University and Cambridge University, will establish a network of 91 buried, broadband seismic sensors that will cover an area 600 miles long and 400 miles wide, larger than New Mexico and southern Colorado combined. This network of sensors will record earthquake activity around the world from seismic signals that travel beneath northern Tibet, which will help reveal the structure of the earth's lithosphere - the crust and uppermost mantle.

"An earthquake goes through the earth carrying information," said James Ni, physics professor at NMSU.

Each sensor and digital recorder will be powered by an above-ground solar panel, and will collect data for two years. These temporary stations will be checked on six-month to one-year intervals.

Leading the NMSU team are Ni and physics professor Thomas Hearn. Hearn will spend about two months in Tibet during the summer of 2007. Ni will be there about a month. Also participating from NMSU will be graduate students Xinling Wang and Gerardo Leon-Soto. Ni also hopes to involve some undergraduate students.

Also involved in the Tibetan Plateau research are the Qinghai Seismological Bureau in China and researchers from Cornell University.

Ni, who has studied the Tibetan Plateau for more than 30 years, will be participating for the third time in the four-phase INDEPTH project. The International Deep Profiling of Tibet and Himalaya began in 1992 to study the Tibetan Plateau, considered to be the best place in the world to observe the ongoing process of continent-to-continent collision.

Although numerous Chinese and international studies of the plateau have been conducted over the past two decades, INDEPTH is the first to use deep seismic reflection profiling to explore the continental lithosphere beneath the Himalayas and Tibet.

INDEPTH I studied the High Himalayas and recorded echoes from the mid-crustal detachment fault where the Indian plate slides, or even penetrates, beneath the Himalayas and southern Tibet, as well as the world's deepest moho, which indicates the boundary between the earth's crust and its mantle.

Ni became involved in 1994 during INDEPTH II, which studied the southern and middle Tibetan Plateau. Ni and Hearn participated in 1998 in INDEPTH III, which studied the extent of crustal melting below the central Tibetan Plateau as well as the northern extent of the Indian plate. Data from that phase are still being analyzed.

Work on INDEPTH IV, also known as Project ASCENT (Array Seismology Collaborative Experiments of Northern Tibet), is designed to study the northern boundary of the Tibetan Plateau and is expected to last until 2012.

Thanks to the first three phases of the project, scientists have a much better idea of what is happening below the surface of the earth. The collision of India and Asia, which began about 55 million years ago and created the Himalayas and the Tibetan Plateau, is still under way. Scientists believe that the leading edge of the Indian plate broke off and became lodged between the still-advancing Indian plate and the Asian plate, resulting in the greater thickness of the crust beneath the Tibetan Plateau.

"India underthrusts its own leading edge," Ni said. The presence of water is lubricating the interface, Ni said, enabling one plate to slide by the other.

"If there's no water, there would be no Himalaya, no Tibet," Ni said. The formation of granites that eventually are pushed southward to the surface along the High Himalayas also indicated the presence of water, since it takes heat and water to form the rock. This was established in INDEPTH II.

And like the incremental process of continent-building, the researchers are learning more and making progress, one step at a time. "We're just gradually solving mysteries," Ni said. "The endeavor is never complete. We try to understand a little bit at a time."