OCE-PRF: Quantifying Magmatic Influences on the Longevity of Segmented Transform Fault Systems

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).

The project will use numerical modeling to study the processes that control the geometry of oceanic transform faults. Oceanic transform faults are large faults that occur throughout the global mid oceanic ridge system. Transform faults are known to split, segment, and give rise to new volcanic spreading centers.

These shifts can alter the locations where earthquakes are likely to occur on the seafloor. The proposed study will focus on the influence of magma supply on the longevity and geometry of transform faults. New 2-D and 3-D models will be developed, and results compared with observations of crustal thickness.

Project results will improve the understanding of the controls on formation of new ocean crust on mid ocean ridges, and on the processes that drive seafloor earthquakes. The project will support an early career scientist (the PI/postdoc). It will also help broaden participation by underrepresented scientists in marine geosciences through an introductory seminar series that will introduce marine geoscience research to undergraduates at both host institutions.

The proposed work hypothesizes that magmatic supply to an intra-transform spreading center is the primary control on spreading center longevity in a segmented transform system. As magmatic supply wanes, spreading in the intra-transform region will cease, and previously-segmented strike slip faults will unify, regardless of imposed tectonic compression or extension due to changing plate motions.

The hypothesis will be investigated with a series of finite difference, marker-in-cell, 2-D and 3-D numerical tectonic models, constrained by

seafloor bathymetry soundings and gravity anomaly observations. Changing magmatic proportions of spreading at both inactive fracture zones and active transform faults along mid-oceanic ridges in the case studies (Clarion FZ, St. Paul TF, and Gofar TF) will be estimated from fault and seafloor fabric measurements, coupled with crustal thickness estimates derived from gravity anomaly observations.

Magmatic supply in the numerical simulations will be systematically decreased over time according to observational constraints and the responding changes in transform fault morphology will be recorded. Parameters varied will include the spreading rate, length of original transform fault offset, and the proportion of magmatic to tectonically-accommodated spreading within the intra-transform region.

The 3-D model produced by this work will be publicly available for use by other researchers to expand upon this work.

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.