Title

Imaging the mantle flow field beneath the Atlantic Ocean using seismic waves

Presenter Information

Danielle Wang

Department

Geosciences and Geological and Petroleum Engineering

Major

Geology and Geophysics

Research Advisor

Gao, Stephen S.

Advisor's Department

Geosciences and Geological and Petroleum Engineering

Funding Source

Opportunities for Undergraduate Research (OURE)

Abstract

The mid-ocean ridge in the Atlantic Ocean, which is also called Mid-Atlantic Ridge (MAR), is a divergent tectonic plate boundary and part of the longest mountain range in the world. It separates the Eurasian Plate and North American Plate in the North Atlantic, and the African Plate from the South American Plate in the South Atlantic. MAR is caused by sea floor spreading and can also be an indication of plate motion. Studying the mechanism of plate motion in this area is meaningful for giving an idea of continental drift which is being discussed for a long time. We studied the mechanism of plate motion in the Atlantic Ocean by imaging the mantle flow field using seismic waves, which is called “shear wave splitting”(SWS). SWS is a robust tool to infer the direction and strength of seismic anisotropy in the lithosphere and underlying asthenosphere. Measurements of the splitting or birefringence of seismic shear waves that have passed through the Earth’s mantle yield constraints on the strength and geometry of elastic anisotropy in various regions. In turn, information about the occurrence and character of seismic anisotropy allows us to make inferences about the style and geometry of mantle flow because anisotropy is a direct consequence of deformational processes. Splitting of P-to-S converted phases at the core-mantle boundary (XKS, including SKS, PKS, and SKKS) is a direct manifestation of seismic anisotropy, which is mostly the result of deformational processes in the Earth’s lithosphere and asthenosphere. As demonstrated by hundreds of XKS splitting studies, spatial distribution of two splitting parameters (ɸ, which is the polarization direction of the fast shear wave, and δt which is the splitting delay time between the fast and slow shear waves) has played an essential role in the investigation of anisotropic structure and associated mantle dynamic processes of the Earth. We required and processed the broadband XKS data recorded in the Atlantic Ocean area at the Incorporated Research Institutions for Seismology (IRIS) Data Management Center (DMC).

Biography

He has been a lab/research assistant of geophysics lab for almost three years. In fall 2012, he was involved in a large project to measure seismic anisotropy beneath 700 broadband stations in Asia and Australia, and mastered the complicated codes and procedures. At the present time the manuscript is being written. He is also a teaching assistant for seismic interpretation and physical mineralogy & Petrology courses. He is the former vice president of Chinese Student and Scholar Association.

Research Category

Sciences

Presentation Type

Poster Presentation

Document Type

Poster

Location

Upper Atrium/Hall

Presentation Date

16 Apr 2014, 9:00 am - 11:45 am

Comments

Joint project with Chunyu Liu, Chenyi Mao

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Apr 16th, 9:00 AM Apr 16th, 11:45 AM

Imaging the mantle flow field beneath the Atlantic Ocean using seismic waves

Upper Atrium/Hall

The mid-ocean ridge in the Atlantic Ocean, which is also called Mid-Atlantic Ridge (MAR), is a divergent tectonic plate boundary and part of the longest mountain range in the world. It separates the Eurasian Plate and North American Plate in the North Atlantic, and the African Plate from the South American Plate in the South Atlantic. MAR is caused by sea floor spreading and can also be an indication of plate motion. Studying the mechanism of plate motion in this area is meaningful for giving an idea of continental drift which is being discussed for a long time. We studied the mechanism of plate motion in the Atlantic Ocean by imaging the mantle flow field using seismic waves, which is called “shear wave splitting”(SWS). SWS is a robust tool to infer the direction and strength of seismic anisotropy in the lithosphere and underlying asthenosphere. Measurements of the splitting or birefringence of seismic shear waves that have passed through the Earth’s mantle yield constraints on the strength and geometry of elastic anisotropy in various regions. In turn, information about the occurrence and character of seismic anisotropy allows us to make inferences about the style and geometry of mantle flow because anisotropy is a direct consequence of deformational processes. Splitting of P-to-S converted phases at the core-mantle boundary (XKS, including SKS, PKS, and SKKS) is a direct manifestation of seismic anisotropy, which is mostly the result of deformational processes in the Earth’s lithosphere and asthenosphere. As demonstrated by hundreds of XKS splitting studies, spatial distribution of two splitting parameters (ɸ, which is the polarization direction of the fast shear wave, and δt which is the splitting delay time between the fast and slow shear waves) has played an essential role in the investigation of anisotropic structure and associated mantle dynamic processes of the Earth. We required and processed the broadband XKS data recorded in the Atlantic Ocean area at the Incorporated Research Institutions for Seismology (IRIS) Data Management Center (DMC).