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SKS splitting beneath Mount St. Helens: Constraints on subslab mantle entrainment

Observations of seismic anisotropy can provide direct constraints on the character of mantle flow in subduction zones, critical for our broader understanding of subduction dynamics. Here we present over 750 new SKS splitting measurements in the vicinity of Mount St. Helens in the Cascadia subduction zone using a combination of stations from the iMUSH broadband array and Cascades Volcano Observator
Authors
Caroline M Eakin, Erin A. Wirth, Abraham Wallace, Carl W Ulberg, Kenneth C Creager, Geoffrey A Abers

Volcanic hazards in the Pacific U.S. Territories

The Commonwealth of the Northern Mariana Islands, Guam, and American Samoa lie along the western side of the famed Pacific Ring of Fire. Here, the processes of active island and submarine volcanoes produce activity both underwater and in the atmosphere that poses potential hazards to the daily lives of residents and travelers. Since 2000, CNMI volcanoes have erupted six times, and one submarine vo
Authors
Gabrielle Tepp, Brian Shiro, William W. Chadwick

Isotopic and petrologic investigation, and a thermomechanical model of genesis of large-volume rhyolites in arc environments: Karymshina Volcanic Complex, Kamchatka, Russia

The Kamchatka Peninsula of eastern Russia is currently one of the most volcanically active areas on Earth where a combination of >8 cm/yr subduction convergence rate and thick continental crust generates large silicic magma chambers, reflected by abundant large calderas and caldera complexes. This study examines the largest center of silicic 4-0.5 Ma Karymshina Volcanic Complex, which includes the
Authors
Ilya N. Bindeman, Vladimir L. Leonov, Dylan P. Colòn, Aleksey N. Rogozin, Niccole Shipley, Brian Jicha, Matthew W. Loewen, Taras V. Gerya

Unravelling the complexity of magma plumbing at Mount St. Helens: A new trace element partitioning scheme for amphibole

Volcanoes at subduction zones reside above complex magma plumbing systems, where individual magmatic components may originate and interact at a range of pressures. Because whole-rock compositions of subduction zone magmas are the integrated result of processes operating throughout the entire plumbing system, processes such as mixing, homogenisation and magma assembly during shallow storage can ove
Authors
Madeleine C. S. Humphreys, George F. Cooper, Jing Zhang, Matthew W. Loewen, Adam J. R. Kent, Colin G. Macpherson, Jon P. Davidson

The Shumagin seismic gap structure and associated tsunami hazards, Alaska convergent margin

The potential for a major earthquake in the Shumagin seismic gap, and the tsunami it could generate, was reported in 1971. However, while potentially tsunamigenic splay faults in the adjacent Unimak and Semidi earthquake segments are known, such features along the Shumagin segment were undocumented until recently. To investigate margin structure and search for splay faults, we reprocessed six lega
Authors
Roland E. von Huene, John J. Miller, Anne Krabbenhoeft

Holocene surface rupture history of an active forearc fault redefines seismic hazard in Southwestern British Columbia, Canada

Characterizing the hazard associated with Quaternary‐active faults in the forearc crust of the northern Cascadia subduction zone has proven challenging due to historically low rates of seismicity, late Quaternary glacial scouring, and dense vegetation that often obscures fault‐related geomorphic features. We couple lidar topography with paleoseismic trenching across the Leech River Fault on southe
Authors
K. D. Morell, C. Regalla, C. Amos, S. Bennett, L. Leonard, A. Graham, T. Reedy, V. Levson, A. Telka

Wetland stratigraphic evidence for variable megathrust earthquake rupture modes at the Cascadia subduction zone

Although widespread agreement that the Cascadia subduction zone produces great earthquakes of magnitude 8 to 9 was reached decades ago, debate continues about the rupture lengths, magnitudes, and frequency of megathrust earthquakes recorded by wetland stratigraphy fringing Cascadia’s estuaries. Correlation of such coastal earthquake evidence along the subduction zone has largely relied on relative
Authors
Alan R. Nelson, Robert C. Witter, Simon Englehart, Andrea Hawkers, Benjamin P. Horton

Incorporating teleseismic tomography data into models of upper mantle slab geometry

Earthquake-based models of slab geometry are limited by the distribution of earthquakes within a subducting slab, which is often heterogeneous. The fast seismic velocity signature of slabs in tomography studies is independent of the distribution of earthquakes within the slab, providing a critical constraint on slab geometry when earthquakes are absent. In order to utilize this constraint, researc
Authors
Daniel E. Portner, Gavin P. Hayes

Crustal inheritance and a top-down control on arc magmatism at Mount St Helens

In a subduction zone, the volcanic arc marks the location where magma, generated via flux melting in the mantle wedge, migrates through the crust and erupts. While the location of deep magma broadly defines the arc position, here we argue that crustal structures, identified in geophysical data from the Washington Cascades magmatic arc, are equally important in controlling magma ascent and defining
Authors
Paul A. Bedrosian, Jared R. Peacock, Esteban Bowles-Martinez, Adam Schultz, Graham Hill

Slab2, a comprehensive subduction zone geometry model

Subduction zones are home to the most seismically active faults on the planet. The shallow megathrust interfaces of subduction zones host our largest earthquakes and are likely the only faults capable of magnitude 9+ ruptures. Despite these facts, our knowledge of subduction zone geometry—which likely plays a key role in determining the spatial extent and ultimately the size of subduction zone ear
Authors
Gavin P. Hayes, Ginevra Moore, Daniel E. Portner, Mike Hearne, Hanna E. Flamme, Maria Furtney, Gregory M. Smoczyk

Effect of dynamical phase on the resonant interaction among tsunami edge wave modes

Different modes of tsunami edge waves can interact through nonlinear resonance. During this process, edge waves that have very small initial amplitude can grow to be as large or larger than the initially dominant edge wave modes. In this study, the effects of dynamical phase are established for a single triad of edge waves that participate in resonant interactions. In previous studies, Jacobi elli
Authors
Eric L. Geist

Pleistocene vertical motions of the Costa Rican outer forearc from subducting topography and a migrating fracture zone triple junction

Understanding the links between subducting slabs and upper-plate deformation is a longstanding goal in the field of tectonics. New 3D seismic sequence stratigraphy, mapped within the Costa Rica Seismogenesis Project (CRISP) seismic-reflection volume offshore southern Costa Rica, spatiotemporally constrains several Pleistocene outer forearc processes and provides clearer connections to subducting p
Authors
Joel H. Edwards, Jared W. Kluesner, Eli A. Silver, Nathan L. Bangs