CAREER: Along-Strike Variation: A Comparative Study of Subduction Zones at Multiple Scales Using Joint Receiver Function and Tomographic Inversion

University Of Massachusetts Amherst, Amherst MA

Investigators

Abstract

Subduction zones are where two tectonic plates converge, and one plate is thrusting beneath the other. Subduction zones play a major role in driving plate tectonics and host great earthquakes, volcanic eruptions, tsunamis, and landslides, many of which have significant impacts on natural systems and society. A recent study showed that most subduction zones can generate earthquakes with magnitude equal to or greater than 8.5 over a 250-year interval. The location and magnitude of subduction earthquakes are strongly influenced by many factors, which vary significantly within a single subduction zone and among global subduction systems. However, the causes, effects, and relationships among the widely observed variations are not well understood. The objective of the CAREER project is to develop a new understanding of the characteristics at five representative subduction zones with advanced methods of seismic modeling. A large collection of geophysical datasets now provides us with an excellent opportunity to construct comparative models of the subduction system. By creating high-quality models of subduction systems, the project will provide new insights into understanding of fundamental subduction processes. This project will involve the development of young scientists at different early career stages, including an early-career female geoscientist, undergraduate and graduate students. More broadly, this project aims to develop teaching tools for undergraduate students, to provide opportunities for K-12 education, and to increase public knowledge of the importance of subduction research. Three fundamental questions are at the core of this research: What are the scales of along-strike variations (segmentation) of subduction properties and to what degree are they correlated from one subduction zone to another? How do various scales of mantle flow interact with each other and control along-strike variation in, e.g., melt productivity and magmatism? And how do properties of the downgoing and overriding plates contribute to along-strike variation within the upper mantle? To fully understand segmentation, high-resolution tomographic models of multiple subduction zones are critically necessary in order to compare the characteristics and scales of segmentation. This project will investigate the structure of five subduction environments, using a joint receiver function (RF) and full-wave tomography (FWT). RFs will identify and delineate sharp velocity discontinuities. An advanced FWT will provide a powerful way to image the structure of the crust and upper mantle. Combination of RFs and FWT will detect a variety of seismic features. The outcomes of this project will help answer questions in the two following areas: 1) A new understanding of the types and scales of along-strike variations in subduction system. What structural correlations from crust to upper mantle can be imaged that may give insight to along-strike variations? What are the dimensions of segmentation? What are the relationships of subduction parameters with along-strike variations? What are the influences of segmentation on surface tectonomagmatism? 2) A key understanding of multi-scale mantle flow and the influences on along-strike variations. What seismic features are related to large-scale subduction-driven processes? What are the roles of regional geology and tectonic processes? How do interactions between plate-driven flow and regional convection relate to segmentation? Does small-scale convection control the spacing of segmented features? The research component will be complemented by an education and outreach effort, which will focus on developing a summer seismology education workshop for the Five-College undergraduate students. The PI will also introduce Earth science to underserved 8th-12th grade girls through the Girls Inc. Eureka! Program. Furthermore, the PI will establish a mechanism for public outreach using the adopted Transportable Array seismic station. Through the integrated work, the PI aims to devote to research, teaching, and outreach activities that will positively impact the subduction community and general public. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.