@article {ashraf_high-resolution_2025,
	title = {A High-Resolution 3-D P-Wave Velocity Structure of the South-Central Cascadia Subduction Zone From Wide-Angle Shore-Crossing Seismic Refraction Data},
	journal = {Journal of Geophysical Research: Solid Earth},
	volume = {130},
	number = {2},
	year = {2025},
	note = {_eprint: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2024JB029525},
	pages = {e2024JB029525},
	abstract = {Abstract This study addresses a significant gap in understanding the features of the south-central Cascadia subduction zone, a region characterized by complex geologic, tectonic, and seismic transitions both offshore and onshore. Unlike other segments along this margin, this area lacks a 3-D velocity model to delineate its structural and geological features on a fine scale. To address this void, we developed a high-resolution 3-D P-wave velocity model using active source seismic data from ship-borne seismic shots recorded on temporary and permanent onshore seismic stations and ocean-bottom seismometers. Our model shows velocity variations across the region with distinct velocity-depth profiles for the Siletz, Franciscan, and Klamath terranes in the overlying plate. We identified seaward dipping high-velocity static backstops associated with the Siletz and Klamath terranes, situated near the shoreline and further inland, respectively. Regions of reduced crustal velocity are associated with crustal faults. Moreover, there is significant along-strike depth variation in the subducting slab, which is about 4 km deeper near the thick, dense Siletz terrane and becomes shallower near the predominantly less-dense Franciscan terrane. This highlights a sudden tectonic and geologic transition at the southern boundary of the Siletz terrane. Our velocity model also indicates slightly increased hydration, though still minimal, in both the oceanic crust and the upper mantle of the subducting plate compared to other parts of the margin.},
	doi = {https://doi.org/10.1029/2024JB029525},
	author = {Ashraf, Asif and Hooft, Emilie E. E. and Toomey, Douglas R. and Tr{\'e}hu, Anne M. and Nolan, Sarah and Wirth, Erin A. and Ward, Kevin M.}
}
@article {trehu_deformation_2023,
	title = {Deformation of the Juan de Fuca Plate Beneath the Central Cascadia Continental Margin (44{\textdegree}-45{\textdegree}N) in Response to an Upper Plate Load},
	journal = {Earth Science, Systems and Society},
	volume = {3},
	year = {2023},
	note = {Publisher: Frontiers},
	month = {11/2023},
	pages = {10085},
	abstract = {A 3D crustal model for the central Cascadia continental shelf and Coast Range between 44{\textdegree}N and 45{\textdegree}N shows that the crystalline crust of the forearc wedge beneath the coastline is characterized by a NW-trending, vertical slab of high-velocity rock interpreted to represent the dike complex that fed the Yachats basaltsBasalt, which werewas intruded into the forearc approximately 3637 million years ago. A spatial correlation is observed between downward deflection of the crust of the subducting Juan de Fuca plate, inferred from inversion of PmP arrivals to image the Moho surface, and the high velocity (and consequently high density) dike complex.anomaly underlying the Yachats Basalt. Apparent subsequent rebound of the subducting plate at greater depth suggests a primarily elastic response of the subducting plate to this load. Calculations for a range of plausible values for the magnitude of the load and the width and depth of the depression indicate that that the effective elastic thickness of the subducted Juan de Fuca plate is \textasciitilde2-<6 km. Although our simple analytical models do not include partial support of the load of the slab by the adjacent upper plate crust or time dependence to account for the motion of the slab beneath the load, incorporation of those effects should decrease rather than increase the apparent strength of the subducted plate. We conclude that the subducted Juan de Fuca plate beneath the central Oregon margin is elastically thin and has the potential to store elastic strain energy before rupturing. Our model of a well-defined, focused and static upper plate load that locally deforms the subducted plate within the nominally seismogenic or transitional part of the Cascadia plate boundary may be unique in providing a relatively straightforward scenario for estimating the mechanical properties of the subducted Juan de Fuca plate. We extrapolate from these results to speculate that elastic deformation of the subducting plate may contribute to the low level of seismicity throughout much of the Cascadia forearc in inter-seismic period between great earthquakes but note that our local results do not preclude faulting or elasto-plastic deformation of a thin and weak plate as it subducts.},
	issn = {2634-730X},
	doi = {10.3389/esss.2023.10085},
	url = {https://www.escubed.org/articles/10.3389/esss.2023.10085/full},
	author = {Tr{\'e}hu, Anne M. and Davenport, Kathy and Kenyon, Christopher B. and Carbotte, Suzanne M. and N{\'a}b{\v e}lek, John L. and Toomey, Douglas R. and Wilcock, William S. D.}
}
@article {trehu_post-seismic_2019,
	title = {Post-seismic response of the outer accretionary prism after the 2010 Maule earthquake, Chile},
	journal = {Geosphere},
	volume = {16},
	number = {1},
	year = {2019},
	month = {dec},
	pages = {13{\textendash}32},
	abstract = {To investigate the dynamic response of the outer accretionary prism updip from the patch of greatest slip during the 2010 Mw 8.8 Maule earthquake (Chile), 10 ocean-bottom seismometers (OBSs) were deployed from May 2012 to March 2013 in a small network with an inter-instrument spacing of 7{\textendash}10 km. Nine were recovered, with four recording data from intermediate-band three-component seismometers and differential pressure gauges, and five recording data from absolute pressure gauges (APGs). All instruments were also equipped with fluid flow meters designed to detect very low rates of flow into or out of the seafloor. We present hypocenters for local earthquakes that have S-P times \&lt;17 s (i.e., within \~{}125 km of the network), with a focus on events located beneath or near the network. Most of the seismicity occurred either near the boundary between the active accretionary prism and continental basement or in the outer rise seaward of the trench. For many outer-rise earthquakes, the P and S arrivals are followed by a distinctive T-phase arrival. Very few earthquakes, and none located with hypocenters deemed {\textquotedblleft}reliable,{\textquotedblright} were located within the active accretionary prism or on the underlying plate boundary. Nonvolcanic tremor-like pulses and seafloor pressure transients (but no very-low-frequency earthquakes or fluid flow) were also detected. Many of the tremor observations are likely T-phases or reverberations due to soft seafloor sediments, although at least one episode may have originated within the accretionary prism south of the network. The transient seafloor pressure changes were observed simultaneously on three APGs located over the transition from the active prism to the continental basement and show polarity changes over short distances, suggesting a shallow source. Their duration of several hours to days is shorter than most geodetic transients observed using onshore GPS networks. The results demonstrate the need for densely spaced and large-aperture OBS networks equipped with APGs for understanding subduction zone behavior.},
	issn = {1553-040X},
	doi = {10.1130/GES02102.1},
	url = {https://doi.org/10.1130/GES02102.1},
	author = {Tr{\'e}hu, Anne M. and de Moor, Alexander and Madrid, Jos{\'e} Mieres and S{\'a}ez, Miguel and Chadwell, C. David and Ortega-Culaciati, Francisco and Ruiz, Javier and Ruiz, Sergio and Tryon, Michael D.}
}
@article {Weirathmueller2017a,
	title = {Spatial and temporal trends in fin whale vocalizations recorded in the NE Pacific Ocean between 2003-2013},
	journal = {PLOS ONE},
	volume = {12},
	number = {10},
	year = {2017},
	month = {oct},
	pages = {e0186127},
	issn = {1932-6203},
	doi = {10.1371/journal.pone.0186127},
	url = {https://dx.plos.org/10.1371/journal.pone.0186127},
	author = {Weirathmueller, Michelle J. and Stafford, Kathleen M. and Wilcock, William S. D. and Hilmo, Rose S. and Dziak, Robert P. and Tr{\'e}hu, Anne M.},
	editor = {Li, Songhai}
}
@article {Wang2016,
	title = {Invited review paper: Some outstanding issues in the study of great megathrust earthquakes{\textemdash}The Cascadia example},
	journal = {Journal of Geodynamics},
	volume = {98},
	year = {2016},
	month = {aug},
	pages = {1{\textendash}18},
	issn = {02643707},
	doi = {10.1016/j.jog.2016.03.010},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S026437071530017X},
	author = {Wang, Kelin and Tr{\'e}hu, Anne M.}
}
@article {toomey_cascadia_2014,
	title = {THE CASCADIA INITIATIVE: A Sea Change In Seismological Studies of Subduction Zones},
	journal = {Oceanography},
	volume = {27},
	number = {2},
	year = {2014},
	note = {Publisher: Oceanography Society},
	pages = {138{\textendash}150},
	abstract = {ABSTRACTIncreasing public awareness that the Cascadia subduction zone in the Pacific Northwest is capable of great earthquakes (magnitude 9 and greater) motivates the Cascadia Initiative, an ambitious onshore/offshore seismic and geodetic experiment that takes advantage of an amphibious array to study questions ranging from megathrust earthquakes, to volcanic arc structure, to the formation, deformation and hydration of the Juan De Fuca and Gorda Plates. Here, we provide an overview of the Cascadia Initiative, including its primary science objectives, its experimental design and implementation, and a preview of how the resulting data are being used by a diverse and growing scientific community. The Cascadia Initiative also exemplifies how new technology and community-based experiments are opening up frontiers for marine science. The new technology{\textemdash}shielded ocean bottom seismometers{\textemdash}is allowing more routine investigation of the source zone of megathrust earthquakes, which almost exclusively lies offshore and in shallow water. The Cascadia Initiative offers opportunities and accompanying challenges to a rapidly expanding community of those who use ocean bottom seismic data.},
	issn = {1042-8275},
	doi = {10.5670/oceanog.2014.49},
	url = {https://www.jstor.org/stable/24862164},
	author = {Toomey, Douglas R. and Allen, Richard M. and Barclay, Andrew H. and Bell, Samuel W. and Bromirski, Peter D. and Carlson, Richard L. and Chen, Xiaowei and Collins, John A. and Dziak, Robert P. and Evers, Brent and Forsyth, Donald W. and Gerstoft, Peter and Hooft, Emilie E.E. and Livelybrooks, Dean and Lodewyk, Jessica A. and Luther, Douglas S. and McGuire, Jeffrey J. and Schwartz, Susan Y. and Tolstoy, Maya and Tr{\'e}hu, Anne M. and Weirathmueller, Michelle and Wilcock, William S.D.}
}
@article {williams_seismicity_2011,
	title = {Seismicity at the Cascadia Plate Boundary beneath the Oregon Continental Shelf},
	journal = {Bulletin of the Seismological Society of America},
	volume = {101},
	number = {3},
	year = {2011},
	pages = {940{\textendash}950},
	abstract = {Since 2003, 39 small earthquakes have been detected off the coast of central Oregon in the nominally locked part of the Cascadia subduction zone, where very little seismic activity has been recorded in spite of a paleoseismic record of great subduction events. Although the regional earthquake bulletin reports depths of 29 and 28~km for the two largest events (Mw~4.9 and Mw~4.7, which occurred in 2004), analysis by Tr{\'e}hu et~al. (2008) indicates that they were low-angle thrust events that occurred on the plate boundary at depths of 9{\textendash}11 and 16~km, respectively. Because of sparse onshore station coverage, most of the smaller events have large location uncertainties. Double-difference relative location of 30 of these earthquakes reveals two tight clusters approximately 30~km apart; each cluster is associated with one of the two larger events. Within each cluster, relocation reduces the hypocenter depth spread from \&gt;15 km to \&lt;3 km, with uncertainties on the order of 0.1~km. The relocations, combined with independent absolute hypocenter locations for two 2008 events using a deployment of land and ocean-bottom seismometers, suggest that the seismicity occurred at plate boundary depths, possibly on the Cascadia megathrust. This concentrated activity in the seismogenic zone may represent patches on the fault plane with anomalous frictional characteristics, possibly caused by subducted topographic features, which can affect the propagation of a large megathrust rupture.},
	issn = {0037-1106},
	doi = {10.1785/0120100198},
	url = {https://doi.org/10.1785/0120100198},
	author = {Williams, Mark C. and Tr{\'e}hu, Anne M. and Braunmiller, Jochen}
}
