@article {mark_constraints_2023,
	title = {Constraints on Bend-Faulting and Mantle Hydration at the Marianas Trench From Seismic Anisotropy},
	journal = {Geophysical Research Letters},
	volume = {50},
	number = {10},
	year = {2023},
	note = {_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2023GL103331},
	month = {05/2023},
	pages = {e2023GL103331},
	abstract = {Subduction zones are a key link between the surface water cycle and the solid Earth, as the incoming plate carries pore water and hydrous minerals into the subsurface. However, water fluxes from surface to subsurface reservoirs over geologic time are highly uncertain because the volume of water carried in hydrous minerals in the slab mantle is poorly constrained. Estimates of slab mantle hydration based on seismic tomography assume bulk serpentinization, representing an upper bound on water volume. We measure azimuthal seismic anisotropy near the Marianas Trench, use spatial variations in anisotropy to constrain the extent and geometry of bend-related faulting, and place a lower bound on slab mantle water content for the case where serpentinization is confined within fault zones. The seismic observations can be explained by a minimum of \~{}0.85 wt\% water in the slab mantle, compared to the upper bound of \~{}2 wt\% obtained from tomography.},
	keywords = {anisotropy, Marianas Trench, serpentinization, solid-Earth water cycle, subduction},
	issn = {1944-8007},
	doi = {10.1029/2023GL103331},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2023GL103331},
	author = {Mark, Hannah F. and Lizarralde, Daniel and Wiens, Douglas A.}
}
@article {brunsvik_mantle_2021,
	title = {Mantle Structure and Flow Across the Continent-Ocean Transition of the Eastern North American Margin: Anisotropic S-Wave Tomography},
	journal = {Geochemistry, Geophysics, Geosystems},
	volume = {22},
	number = {12},
	year = {2021},
	note = {_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2021GC010084},
	pages = {e2021GC010084},
	abstract = {Little has been seismically imaged through the lithosphere and mantle at rifted margins across the continent-ocean transition. A 2014{\textendash}2015 community seismic experiment deployed broadband seismic instruments across the shoreline of the eastern North American rifted margin. Previous shear-wave splitting along the margin shows several perplexing patterns of anisotropy, and by proxy, mantle flow. Neither margin parallel offshore fast azimuths nor null splitting on the continental coast obviously accord with absolute plate motion, paleo-spreading, or rift-induced anisotropy. Splitting measurements, however, offer no depth constraints on anisotropy. Additionally, mantle structure has not yet been imaged in detail across the continent-ocean transition. We used teleseismic S, SKS, SKKS, and PKS splitting and differential travel times recorded on ocean-bottom seismometers, regional seismic networks, and EarthScope Transportable Array stations to conduct joint isotropic/anisotropic tomography across the margin. The velocity model reveals a transition from fast, thick, continental keel to low velocity, thinned lithosphere eastward. Imaged short wavelength velocity anomalies can be largely explained by edge-driven convection or shear-driven upwelling. We also find that layered anisotropy is prevalent across the margin. The anisotropic fast polarization is parallel to the margin within the asthenosphere. This suggests margin parallel flow beneath the plate. The lower oceanic lithosphere preserves paleo-spreading-parallel anisotropy, while the continental lithosphere has complex anisotropy reflecting several Wilson cycles. These results demonstrate the complex and active nature of a margin which is traditionally considered tectonically inactive.},
	keywords = {anisotropy, continent-ocean transition, eastern North American margin, shear wave splitting, tomography},
	issn = {1525-2027},
	doi = {10.1029/2021GC010084},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2021GC010084},
	author = {Brunsvik, Brennan R. and Eilon, Zachary C. and Lynner, Colton}
}
@article {heath_relationship_2021,
	title = {Relationship Between Active Faulting/Fracturing and Magmatism Around Santorini: Seismic Anisotropy From an Active Source Tomography Experiment},
	journal = {Journal of Geophysical Research: Solid Earth},
	volume = {126},
	number = {8},
	year = {2021},
	note = {_eprint: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2021JB021898},
	month = {07/2021},
	pages = {e2021JB021898},
	abstract = {In extending volcanic arcs such as the Aegean, tectonic processes exert a significant control on magmatism. Spanning scales from 1 to 10s of km, volcanic vents, edifices, and eruptive centers follow the orientation of, and are located near, fault zones. Whether this tectonic control on magmatism results from individual faults/fractures weakening the crust or because regional stresses control magma input into the crust is debated. Here we investigate the scales of tectonic and magmatic interactions, specifically focusing on the role of local-scale (<10 km) faults/fractures in controlling magmatism. We infer local-scale fault/fracture orientations from anisotropic active-source P-wave travel-time tomography to investigate tectonic and magmatic interactions in the upper crust of Santorini Volcano, Greece, and the actively deforming region to the east. We use the anisotropy magnitude and seismic velocity reduction to model the relative distribution of both consistently oriented and randomly oriented faults/fractures. Our results show that oriented faulting/fracturing resulting from regional-scale (>10 km) tectonic stresses is distributed broadly across the region at 2{\textendash}3 km depth, approximately paralleling volcanic/magmatic features. On a local-scale, magmatism is neither localized in areas of higher oriented fault/fracture density, nor is it accommodating enough extensional strain to inhibit oriented faulting/fracturing of host rock. The alignment of magmatic features shows strong tectonic control despite the lack of correlation with local oriented fault/fracture density. These results suggest that magmatic processes are strongly influenced by regional-scale, not local-scale, tectonic processes. We infer regional processes have a greater impact on magmatism than local features due to their greater effect at depth.},
	keywords = {anisotropy, faulting, magmatism, seismology, tectonism, tectono-magmatism},
	issn = {2169-9356},
	doi = {10.1029/2021JB021898},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2021JB021898},
	author = {Heath, B. A. and Hooft, E. E. E. and Toomey, D. R. and Paulatto, M. and Papazachos, C. B. and Nomikou, P. and Morgan, J. V.}
}
@article {collins_pn_2014,
	title = {Pn anisotropy beneath the South Island of New Zealand and implications for distributed deformation in continental lithosphere},
	journal = {Journal of Geophysical Research: Solid Earth},
	volume = {119},
	number = {10},
	year = {2014},
	note = {_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/2014JB011233},
	pages = {7745{\textendash}7767},
	abstract = {Pn travel times from regional earthquakes recorded both by stations on New Zealand and by ocean bottom seismographs deployed offshore indicate anisotropy in the uppermost mantle beneath the region. The largest anisotropy of 8\% ({\textpm}2\%, 1σ) lies beneath the deforming part of the South Island to just off its West Coast, a zone roughly 100{\textendash}200 km wide. The fastest propagation is aligned N60{\textdegree}E ({\textpm}3{\textdegree}), essentially parallel to the largely strike-slip relative plate motion since 20 Ma, also N60{\textdegree}E. The magnitude of anisotropy decreases abruptly northwest and southeast of this zone, and on the southeast side of the island, the orientation of fastest propagation is between N32{\textdegree}W and N-S. The N60{\textdegree}E orientation of fast propagation is consistent with finite strain within the uppermost part of the mantle lithosphere if the measured 850 km of displacement of the Pacific plate past the Australia plate is spread over a region with a width of 100{\textendash}200 km. The agreement of this orientation of fast propagation with the orientation or relative plate motion suggests the possibility of but does not require some dynamic recrystallization in rock as cold as 500{\textendash}800{\textdegree}C, where Peierls creep seems to be the likely deformation mechanism. Such a strain distribution matches deformation of a thin viscous sheet that obeys a constitutive relationship of the form , where is the average strain rate and τ is the operative deviatoric stress, with an average value of n ≈ 3{\textendash}10. Presumably, the NW-SE fast propagation in the region southeast of the island results from strain that precedes the Cenozoic deformation that has shaped the island.},
	keywords = {anisotropy, Lithosphere, New Zealand, Pn},
	issn = {2169-9356},
	doi = {10.1002/2014JB011233},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/2014JB011233},
	author = {Collins, John A. and Molnar, Peter}
}
@article {shintaku_pn_2014,
	title = {Pn anisotropy in Mesozoic western Pacific lithosphere},
	journal = {Journal of Geophysical Research: Solid Earth},
	volume = {119},
	number = {4},
	year = {2014},
	note = {_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/2013JB010534},
	pages = {3050{\textendash}3063},
	abstract = {Pn is the high-frequency, scattered P phase guided for great distances within the old oceanic lithosphere. Two arrays of ocean bottom seismometers were deployed on old (150{\textendash}160 Ma) seafloor in the northwestern Pacific south of Shatsky Rise for the Pacific Lithosphere Anisotropy and Thickness Experiment. We use Pn phases from 403 earthquakes during the 1 year of deployment to measure apparent velocities across the arrays. Each array was deployed on a separate limb of a magnetic bight, formed near a fast-spreading, ridge-ridge-ridge triple junction. Using high-frequency waves (5{\textendash}10 Hz), we look at variations of Pn velocities as a function of azimuth. In the western array, we find Pn anisotropy with velocities ranging from 8.7 km/s in the back azimuth (θ) direction of 310{\textdegree} to 7.7 km/s at 350{\textdegree}. In the eastern array, the velocity ranges from 8.5 km/s in back azimuth direction of 210{\textdegree} to 7.7 km/s at 260{\textdegree} and 310{\textdegree}. We observe rapid velocity changes with azimuth in the both arrays requiring sinusoidal variations of roughly equal amplitude as a function of both 2θ and 4θ, which is not expected for the orthorhombic symmetry of olivine or orthopyroxene. The fastest directions on the two limbs are roughly orthogonal to each other suggesting the dominance of fossil anisotropy, but the fast directions of the 2θ components are skewed counterclockwise from the spreading directions. We speculate that the rapid azimuthal variations may be caused by vertical stratification with changing anisotropy with depth in the oceanic lithosphere.},
	keywords = {anisotropy, asthenosphere, mantle, oceanic lithosphere, Pn waves, western Pacific},
	issn = {2169-9356},
	doi = {10.1002/2013JB010534},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/2013JB010534},
	author = {Shintaku, Natsumi and Forsyth, Donald W. and Hajewski, Christina J. and Weeraratne, Dayanthie S.}
}
