@article {wang_fluids_2024,
	title = {Fluids control along-strike variations in the Alaska megathrust slip},
	journal = {Earth and Planetary Science Letters},
	volume = {633},
	year = {2024},
	month = {may},
	pages = {118655},
	abstract = {Interseismic and coseismic slip on the subduction zone megathrust show complex along-strike variations and the controlling factors remain debated. Here we image seismic velocity anomalies to infer fluid distribution in the Alaska subduction zone (Alaska Peninsula section) with seismic tomography. The weakly locked Shumagin segment is characterized by abundant fluids on the plate interface and in the overriding plate, whereas the moderately-to-highly locked Chignik and Chirikof segments that hosted M > 8 earthquakes are relatively dry. The Kodiak segment, which was ruptured by the 1964 M9.2 Great Alaska earthquake and is presently fully locked near the trench, is characterized by a fluid-rich plate interface but a fluid-poor and inferred low-porosity overriding plate. Multiple large earthquakes have nucleated in fluid-rich regions at the plate interface. Our study highlights the important roles of fluids, particularly in the overriding plate, in controlling interseismic slip deficit and earthquake rupture. We propose that a fluid-rich overriding plate means that there has been a high sustained flux of fluids across the plate interface, which enhances the formation of clay minerals that promote fault creep.},
	keywords = {Alaska peninsula, Body-wave tomography, fluids, Megathrust earthquakes, Slip behavior, subduction zone},
	issn = {0012-821X},
	doi = {10.1016/j.epsl.2024.118655},
	url = {https://www.sciencedirect.com/science/article/pii/S0012821X24000888},
	author = {Wang, Fan and Wei, S. Shawn and Drooff, Connor and Elliott, Julie L. and Freymueller, Jeffrey T. and Ruppert, Natalia A. and Zhang, Haijiang}
}
@article {acquisto_evidence_2022,
	title = {Evidence of Strong Upper Oceanic Crustal Hydration Outboard the Alaskan and Sumatran Subduction Zones},
	journal = {Journal of Geophysical Research: Solid Earth},
	volume = {127},
	number = {10},
	year = {2022},
	note = {_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2022JB024751},
	pages = {e2022JB024751},
	abstract = {The hydration state of subducting oceanic crust has been proposed to influence subduction zone processes like seismic coupling at the megathrust interface and arc magmatism downdip. Plate bending in the outer rise region is thought to help rehydrate the incoming oceanic lithosphere before subduction. Although numerous seismic refraction studies provide constraints on the amount of water stored in the lower crust and uppermost mantle, little information exists about how much free water is present in the upper 1{\textendash}2 km of oceanic crust. Here, we present results from the application of advanced techniques to long-offset multi-channel seismic data acquired outboard the Alaskan and South Sumatran subduction zones. Our results show that the incoming upper crustal seismic layer, layer 2A, is significantly hydrated in both areas. Favorable conditions offshore the Alaska Peninsula promote the creation of a dense system of bending-related faults, facilitating the infiltration of fluids that increases average water estimates to \~{}3.9 wt.\% H2O in the outer rise. As the crust subducts and temperature increases, some free water may react with the host rocks to form mineral-bound water that is carried to greater depths, in agreement with elevated water contents found in arc lavas of Shumagin Gap volcanoes. Offshore Sumatra, we propose that similar layer 2A water estimates (\~{}3.2 wt.\% H2O average) and heterogeneous hydration within 2B are associated with the ongoing, slow, complex deformation occurring in the Wharton Basin and thus potentially contribute to the presence of a long-lived slow slip event recently inferred there at seismogenic depths.},
	keywords = {Alaska, hydration, subduction zone, Sumatra, upper crust},
	issn = {2169-9356},
	doi = {10.1029/2022JB024751},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2022JB024751},
	author = {Acquisto, Tanner and B{\'e}cel, Anne and Singh, Satish C. and Carton, H{\'e}l{\`e}ne}
}
@article {nakai_near_2021,
	title = {Near Trench 3D Seismic Attenuation Offshore Northern Hikurangi Subduction Margin, North Island, New Zealand},
	journal = {Journal of Geophysical Research: Solid Earth},
	volume = {126},
	number = {3},
	year = {2021},
	note = {_eprint: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2020JB020810},
	month = {02/2021},
	pages = {e2020JB020810},
	abstract = {We image seismic attenuation near the Hikurangi trench offshore New Zealand, using ocean bottom and land-based seismometers, revealing high attenuation above a recurring shallow slow-slip event and within the subducting Hikurangi Plateau. The Hikurangi subduction margin east of the North Island, New Zealand is the site of frequent shallow slow slip events. Overpressured fluids are hypothesized to lead to slow slip at shallow depths close to the oceanic trench. Seismic attenuation, energy loss of seismic waves, can be used to detect high temperatures, melt, the presence of fluids, and fractures. We use local earthquake P- and S-waves from 180 earthquakes to invert for t*, and subsequently invert for Qp and Qs, offshore the North Island directly above the area of slow slip. We image Qp and Qs to \~{}25 km depth, increasing resolution of previously identified coastal low Q (100{\textendash}300), and finding a new region of even higher attenuation (Qp and Qs < 50{\textendash}100) directly above the shallow slow slip event of 2014{\textendash}2015, beneath the offshore seismic array. This highest attenuation is downdip of a subducting seamount, and is spatially correlated with a high seismic reflectivity zone and Vp/Vs > 1.85, all of which provide evidence for the presence of fluids. The Qp and Qs is low at the trench (<50{\textendash}100) and in the subducting plate (100{\textendash}200), suggesting that seismic wave scattering due to faults, fractures, and the inherent heterogeneous composition of the Hikurangi Plateau, a large igneous province, plays a role in seismic attenuation.},
	keywords = {fluids, seismic attenuation, subduction zone},
	issn = {2169-9356},
	doi = {10.1029/2020JB020810},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2020JB020810},
	author = {Nakai, Jenny S. and Sheehan, Anne F. and Abercrombie, Rachel E. and Eberhart-Phillips, Donna}
}
@article {lata_uppermost_2020,
	title = {Uppermost crustal structure across the eastern Lau spreading center from P-to-S converted waves},
	journal = {Marine Geophysical Research},
	volume = {41},
	number = {4},
	year = {2020},
	month = {11/2020},
	abstract = {P and S wave data from the L-SCAN active-source wide-angle reflection/refraction experiment are modelled to investigate upper crustal structure in the Lau backarc basin. A combination of ray tracing and finite difference numerical wavefield simulation is used to identify P and P-to-S converted seismic phases. The phases primarily arise from two shallow interfaces, one at \textasciitilde 80~m depth or less, and the other at 500{\textendash}650~m depth. The shallower interface is deeper than the sediment base, is observed across the study area, and is interpreted as a {\textquoteleft}layer 2Aa{\textquoteright} boundary, proposed to result from a rapid change in crack density. The deeper interface is interpreted as the layer 2A{\textendash}2B boundary, corresponding to a transition from lavas to sheeted dykes. Layer 2A, on average, is 150~m thicker in crust that formed at the spreading center when spreading was located near the arc (< 50~km away), as compared to when spreading was located farther away from the arc (> 70~km away). Layer 2A thickness and Vp/Vs values indicate that a thicker and more porous lava layer, dominated by basalts to basalt-andesites, cap near-arc crust, while a thinner and less-porous, mostly basaltic, volcanic layer caps the far-arc crust. These results are consistent with the waning influence of slab-derived volatiles on crustal formation as seafloor spreading moves away from the active arc.},
	keywords = {Backarc spreading center, oceanic crust, S-waves, subduction zone},
	issn = {1573-0581},
	doi = {10.1007/s11001-020-09419-5},
	url = {https://doi.org/10.1007/s11001-020-09419-5},
	author = {Lata, Charu and Dunn, Robert A.}
}
