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A maximum rupture model for the central and southern Cascadia subduction zone—reassessing ages for coastal evidence of megathrust earthquakes and tsunamis

A new history of great earthquakes (and their tsunamis) for the central and southern Cascadia subduction zone shows more frequent (17 in the past 6700 yr) megathrust ruptures than previous coastal chronologies. The history is based on along-strike correlations of Bayesian age models derived from evaluation of 554 radiocarbon ages that date earthquake evidence at 14 coastal sites. We reconstruct a
Alan Nelson, Christopher DuRoss, Robert C. Witter, Harvey M. Kelsey, Simon E. Engelhart, Shannon A. Mahan, Harrison J. Gray, Andrea D. Hawkes, Benjamin P. Horton, Jason S. Padgett

Toward an integrative geological and geophysical view of Cascadia subduction zone earthquakes

The Cascadia subduction zone (CSZ) is an exceptional geologic environment for recording evidence of land level changes, tsunamis, and ground motion that reveals at least 19 great megathrust earthquakes over the past 10 kyr. Such earthquakes are among the most impactful natural hazards on Earth, transcend national boundaries, and can have global impact. Reducing the societal impacts of future event
Maureen A. L. Walton, Lydia M. Staisch, Tina Dura, Jessie K. Pearl, Brian L. Sherrod, Joan S. Gomberg, Simon E. Engelhart, Anne Trehu, Janet Watt, Jonathan P. Perkins, Robert C. Witter, Noel Bartlow, Chris Goldfinger, Harvey Kelsey, Ann Morey, Valerie J. Sahakian, Harold Tobin, Kelin Wang, Ray Wells, Erin Wirth

In‐situ mass balance estimates offshore Costa Rica

The Costa Rican convergent margin has been considered a type erosive margin, with erosional models suggesting average losses up to −153 km3/km/m.y. However, three‐dimensional (3D) seismic reflection and Integrated Ocean Drilling Program data collected offshore the Osa Peninsula images accretionary structures and vertical motions that conflict with the forearc basal erosion model. Here we integrate
Joel Edwards, Jared W. Kluesner, Eli Silver, Rachel Lauer, Nathan Bangs, Brian Boston

Limited mantle hydration by bending faults at the Middle America Trench

Seismic anisotropy measurements show that upper mantle hydration at the Middle America Trench (MAT) is limited to serpentinization and/or water in fault zones, rather than distributed uniformly. Subduction of hydrated oceanic lithosphere recycles water back into the deep mantle, drives arc volcanism, and affects seismicity at subduction zones. Constraining the extent of upper mantle hydration is a

Nathaniel C. Miller, Danile Lizarralde, John A. Collins, Steven Holbrook, Harm van Avendonk

Systematic characterization of morphotectonic variability along the Cascadia convergent margin: Implications for shallow megathrust behavior and tsunami hazards

Studies of recent destructive megathrust earth­quakes and tsunamis along subduction margins in Japan, Sumatra, and Chile have linked forearc mor­phology and structure to megathrust behavior. This connection is based on the idea that spatial varia­tions in the frictional behavior of the megathrust influence the tectono-morphological evolution of the upper plate. Here we present a comprehen­sive exa
Janet Watt, Daniel S. Brothers

Localized fluid discharge by tensile cracking during the post-seismic period in subduction zones

It is thought that extensional structures (extensional cracks and normal faults) generated during the post-seismic period create fluid pathways that enhance the drainage of the subducting plate interface, thus reducing the pore pressure and increasing fault strength. However, it remains to be elucidated how much pore fluid pressure decreases by the extension crack formation. Here we examined i) th
Makoto Otsubo, Jeanne L. Hardebeck, Ayumu Miyakawa, Asuka Yamaguchi, Gaku Kimura

Segmentation and supercycles: A catalog of earthquake rupture patterns from the Sumatran Sunda Megathrust and other well-studied faults worldwide

After more than 100 years of earthquake research, earthquake forecasting, which relies on knowledge of past fault rupture patterns, has become the foundation for societal defense against seismic natural disasters. A concept that has come into focus more recently is that rupture segmentation and cyclicity can be complex, and that a characteristic earthquake model is too simple to adequately describ
Belle E. Philibosian, Aron J. Meltzner

Submarine canyons, slope failures and mass transport processes in southern Cascadia

The marine turbidite record along the southern Cascadia Subduction Zone has been used to interpret paleoseismicity and suggest a shorter recurrence interval for large (>M7) earthquakes along this portion of the margin; however, the sources and pathways of these turbidity flows are poorly constrained. We examine the spatial distribution of sediment storage, downslope transport, and slope failures a
Jenna C. Hill, Janet Watt, Daniel S. Brothers, Jared W. Kluesner

The role of seismic and slow slip events in triggering the 2018 M7.1 Anchorage earthquake in the Southcentral Alaska subduction zone

The M 7.1 2018 Anchorage earthquake occurred in the bending part of the subducting North Pacific plate near the geometrical barrier formed by the underthrusting Yakutat terrane. We calculate the triggering potential related with stress redistribution from deformation sources including the M 9.2 1964 earthquake coseismic slip, postseismic deformation, slip from regional M  > 5 earthquakes, and the
Margarita Segou, Thomas E. Parsons

Subduction megathrust heterogeneity characterized from 3D seismic data

Megathrust roughness and structural complexity are thought to be controls on earthquake slip at subduction zones because they result in heterogeneity in shear strength and resolved stress. However, because active megathrust faults are difficult to observe, the causes and scales of complexity are largely unknown. Here we measured the in situ properties of the megathrust of the Middle America subduc
James D. Kirkpatrick, Joel H. Edwards, Alessandro Verdecchia, Jared W. Kluesner, Rebecca M. Harrington, Eli Silver

Structural control on megathrust rupture and slip behavior: Insights from the 2016 Mw 7.8 Pedernales Ecuador earthquake

The heterogeneous seafloor topography of the Nazca Plate as it enters the Ecuador subduction zone provides an opportunity to document the influence of seafloor roughness on slip behavior and megathrust rupture. The 2016 Mw 7.8 Pedernales Ecuador earthquake was followed by a rich and active postseismic sequence. An internationally coordinated rapid response effort installed a temporary seismic netw
Lillian Soto-Cordero, Anne Meltzer, Eric A. Bergman, Mariah Hoskins, Joshua C. Stachnik, Hans Agurto-Detzel, Alexandra Alvarado, Susan L. Beck, Philippe Charvis, Yvonne Font, Gavin P. Hayes, Stephen Hernandez, Sergio Leon-Rios, Colton Lynner, Jean-Mathieu Nocquet, Marc Regnier, Andreas Rietbrock, Frederique Rolandone, Mario Ruiz

The 30 November 2018 Mw7.1 Anchorage Earthquake

The Mw 7.1 47 km deep earthquake that occurred on 30 November 2018 had deep societal impacts across southcentral Alaska and exhibited phenomena of broad scientific interest. We document observations that point to future directions of research and hazard mitigation. The rupture mechanism, aftershocks, and deformation of the mainshock are consistent with extension inside the Pacific plate near the d
Michael E. West, Adrian Bender, Matthew Gardine, Lea Gardine, Kara Gately, Peter J. Haeussler, Wael Hassan, Franz Meyer, Cole Richards, Natalia Ruppert, Carl Tape, John Thornley, Robert Witter