@article {gong_constraints_2021,
	title = {Constraints on the Geometry of the Subducted Gorda Plate From Converted Phases Generated by Local Earthquakes},
	journal = {Journal of Geophysical Research: Solid Earth},
	volume = {126},
	number = {2},
	year = {2021},
	note = {_eprint: https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2020JB019962},
	month = {01/2021},
	pages = {e2020JB019962},
	abstract = {The largest slip in great megathrust earthquakes often occurs in the 10{\textendash}30 km depth range, yet seismic imaging of the material properties in this region has proven difficult. We utilize a dense onshore-offshore passive seismic dataset from the southernmost Cascadia subduction zone where seismicity in the mantle of the subducted Gorda Plate produces S-to-P and P-to-S conversions generated within a few km of the plate interface. These conversions typically occur in the 10{\textendash}20 km depth range at either the top or bottom of a \~{}5 km thick layer with a high Vp/Vs that we infer to be primarily the subducted crust. We use their arrival times and amplitudes to infer the location of the top and bottom of the subducted crust as well as the velocity contrasts across these discontinuities. Comparing with both the Slab1.0 and the updated Slab2 interface models, the Slab2 model is generally consistent with the converted phases, while the Slab1.0 model is 1{\textendash}2 km deeper in the 2{\textendash}20 km depth range and \~{}6{\textendash}8 km too deep in the 10{\textendash}20 km depth range between 40.25{\textdegree}N and 40.4{\textdegree}N. Comparing the amplitudes of the converted phases to synthetics for simplified velocity structures, the amplitude of the converted phases requires models containing a \~{}5 km thick zone with at least a \~{}10\%{\textendash}20\% reduction in S wave velocity. Thus, the plate boundary is likely contained within or at the top of this low velocity zone, which potentially indicates a significant porosity and fluid content within the seismogenic zone.},
	keywords = {converted phases, seismic imaging, subduction zone plate boundary},
	issn = {2169-9356},
	doi = {10.1029/2020JB019962},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2020JB019962},
	author = {Gong, Jianhua and McGuire, Jeffrey J.}
}
@article {Gong2018,
	title = {Interactions between strike-slip earthquakes and the subduction interface near the Mendocino Triple Junction},
	journal = {Earth and Planetary Science Letters},
	volume = {482},
	year = {2018},
	month = {jan},
	pages = {414{\textendash}422},
	issn = {0012821X},
	doi = {10.1016/j.epsl.2017.11.022},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0012821X17306581},
	author = {Gong, Jianhua and McGuire, Jeffrey J.}
}
@article {Cattania2017,
	title = {Dynamic triggering and earthquake swarms on East Pacific Rise transform faults},
	journal = {Geophysical Research Letters},
	volume = {44},
	number = {2},
	year = {2017},
	month = {jan},
	pages = {702{\textendash}710},
	issn = {0094-8276},
	doi = {10.1002/2016GL070857},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/2016GL070857},
	author = {Cattania, Camilla and McGuire, Jeffrey J. and Collins, John A.}
}
@article {Flores2017,
	title = {Observations of Seismicity and Ground Motion in the Northeast U.S. Atlantic Margin from Ocean-Bottom Seismometer Data},
	journal = {Seismological Research Letters},
	volume = {88},
	number = {1},
	year = {2017},
	month = {jan},
	pages = {23{\textendash}31},
	issn = {0895-0695},
	doi = {10.1785/0220160079},
	url = {https://pubs.geoscienceworld.org/srl/article/88/1/23-31/314313},
	author = {Flores, Claudia H. and ten Brink, Uri S. and McGuire, Jeffrey J. and Collins, John A.}
}
@article {Chen2016a,
	title = {Measuring earthquake source parameters in the Mendocino triple junction region using a dense OBS array: Implications for fault strength variations},
	journal = {Earth and Planetary Science Letters},
	volume = {453},
	year = {2016},
	month = {nov},
	pages = {276{\textendash}287},
	issn = {0012821X},
	doi = {10.1016/j.epsl.2016.08.022},
	url = {https://linkinghub.elsevier.com/retrieve/pii/S0012821X16304459},
	author = {Chen, Xiaowei and McGuire, Jeffrey J.}
}
@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 {gouedard_correction_2014,
	title = {Correction of Ocean-Bottom Seismometer Instrumental Clock Errors Using Ambient Seismic Noise},
	journal = {Bulletin of the Seismological Society of America},
	volume = {104},
	number = {3},
	year = {2014},
	month = {apr},
	pages = {1276{\textendash}1288},
	abstract = {Very accurate timing of seismic recordings is critical for modern processing techniques. Clock synchronization among the instruments constituting an array is, however, difficult without direct communication between them. Synchronization to Global Positioning System (GPS) time is one option for on-land deployments, but not for underwater surveys as electromagnetic signals do not propagate efficiently in water. If clock drift is linear, time corrections for ocean-bottom seismometer (OBS) deployments can be estimated through GPS synchronization before and after the deployment, but this is not sufficient for many applications as the nonlinear component of the drift can reach tens to hundreds of milliseconds for long-duration experiments. We present two techniques to retrieve timing differences between simultaneous recordings at ocean-bottom instruments after deployment has ended. Both techniques are based on the analysis of the cross correlation of ambient seismic noise and are effective even if clock drift is nonlinear. The first, called time symmetry analysis, is easy to apply but requires a proper illumination so that the noise cross-correlation functions are symmetric in time. The second is based on the doublet analysis method and does not have this restriction. Advantages and drawbacks of both approaches are discussed. Application to two OBS data sets shows that both can achieve synchronization of recordings down to about five milliseconds (a few percent of the main period used).},
	issn = {0037-1106},
	doi = {10.1785/0120130157},
	url = {https://doi.org/10.1785/0120130157},
	author = {Gou{\'e}dard, Pierre and Seher, Tim and McGuire, Jeffrey J. and Collins, John A. and van der Hilst, Robert D.}
}
@article {wolfson-schwehr_relationship_2014,
	title = {The relationship between seismicity and fault structure on the Discovery transform fault, East Pacific Rise},
	journal = {Geochemistry, Geophysics, Geosystems},
	volume = {15},
	number = {9},
	year = {2014},
	note = {_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/2014GC005445},
	pages = {3698{\textendash}3712},
	abstract = {There is a global seismic moment deficit on mid-ocean ridge transform faults, and the largest earthquakes on these faults do not rupture the full fault area. We explore the influence of physical fault structure, including step-overs in the fault trace, on the seismic behavior of the Discovery transform fault, 4S on the East Pacific Rise. One year of microseismicity recorded during a 2008 ocean bottom seismograph deployment (24,377 0 ML 4.6 earthquakes) and 24 years of Mw 5.4 earthquakes obtained from the Global Centroid Moment Tensor catalog, are correlated with surface fault structure delineated from high-resolution multibeam bathymetry. Each of the 15 5.4 Mw 6.0 earthquakes that occurred on Discovery between 1 January 1990 and 1 April 2014 was relocated into one of five distinct rupture patches using a teleseismic surface wave cross-correlation technique. Microseismicity was relocated using the HypoDD relocation algorithm. The western fault segment of Discovery (DW) is composed of three zones of varying structure and seismic behavior: a zone with no large events and abundant microseismicity, a fully coupled zone with large earthquakes, and a complex zone with multiple fault strands and abundant seismicity. In general, microseismicity is reduced within the patches defined by the large, repeating earthquakes. While the extent of the large rupture patches on DW correlates with physical features in the bathymetry, step-overs in the primary fault trace are not observed at patch boundaries, suggesting along-strike heterogeneity in fault zone properties controls the size and location of the large events.},
	keywords = {earthquakes, East Pacific Rise, fault structure, transform fault},
	issn = {1525-2027},
	doi = {10.1002/2014GC005445},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/2014GC005445},
	author = {Wolfson-Schwehr, Monica and Boettcher, Margaret S. and McGuire, Jeffrey J. and Collins, John A.}
}
@article {mcguire_millimeter-level_2013,
	title = {Millimeter-level precision in a seafloor geodesy experiment at the Discovery transform fault, East Pacific Rise},
	journal = {Geochemistry, Geophysics, Geosystems},
	volume = {14},
	number = {10},
	year = {2013},
	note = {_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1002/ggge.20225},
	pages = {4392{\textendash}4402},
	abstract = {Direct-path acoustic ranging is a promising seafloor geodetic technique for continuous high-resolution monitoring of geodynamical process such as fault slip and magma intrusion. Here we report on a yearlong acoustic ranging experiment conducted across the discovery transform fault at \~{}4{\textdegree}S on the East Pacific Rise. The ranging instruments utilized a novel acoustic signal designed to enhance precision. We find that, after correcting for variations in sound speed at the path end-points, the ranging measurements have a precision of \~{}1 mm over baselines approaching 1 km in length. The primary difficulty in this particular experiment was with the physical stability of the benchmarks, which were deployed free fall from a ship. Despite the stability issues, it appears that the portion of the transform fault that the array covered was locked during the year of our survey. The primary obstacle to continuous, high sample rate, high-precision geodetic monitoring of oceanic ridges and transform faults is now limited to the construction of geodetic monuments that are well anchored into bedrock.},
	keywords = {oceanic transform fault, seafloor geodesy},
	issn = {1525-2027},
	doi = {10.1002/ggge.20225},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/ggge.20225},
	author = {McGuire, Jeffrey J. and Collins, John A.}
}
@article {roland_seismic_2012,
	title = {Seismic velocity constraints on the material properties that control earthquake behavior at the Quebrada-Discovery-Gofar transform faults, East Pacific Rise},
	journal = {Journal of Geophysical Research: Solid Earth},
	volume = {117},
	number = {B11},
	year = {2012},
	note = {_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2012JB009422},
	abstract = {Mid-ocean ridge transform faults (RTFs) vary strongly along strike in their ability to generate large earthquakes. This general observation suggests that local variations in material properties along RTFs exert a primary control on earthquake rupture dynamics. We explore these relationships by examining the seismic structure of two RTFs that have distinctly different seismic coupling. We determine the seismic velocity structure at the Gofar and Quebrada faults on the East Pacific Rise (EPR) using P wave traveltime tomography with data from two active-source wide-angle refraction lines crossing the faults. We image low-velocity zones (LVZs) at both faults, where P wave velocities are reduced by as much as 0.5{\textendash}1.0 km/s (\~{}10{\textendash}20\%) within a several kilometer wide region. At the Gofar fault, the LVZ extends through the entire crust, into the seismogenic zone. We rule out widespread serpentinization as an explanation for the low velocities, owing to the lack of a corresponding signal in the locally measured gravity field. The reduced velocities can be explained if the plate boundary region is composed of fault material with enhanced fluid-filled porosity (1.5{\textendash}8\%). Local seismic observations indicate that the high-porosity region lies within a \~{}10 km long portion of the fault that fails in large swarms of microearthquakes and acts as a barrier to the propagation of large (M \~{} 6.0) earthquakes. Tomographic images of fault structure combined with observed earthquake behavior suggest that EPR transform segments capable of generating large earthquakes have relatively intact gabbro within the seismogenic zone, whereas segments that slip aseismically or via earthquake swarms are composed of highly fractured, >=2 km wide damage zones that extend throughout the crust.},
	keywords = {fault structure, marine seismology, rupture dynamics, tomography, transform fault},
	issn = {2156-2202},
	doi = {10.1029/2012JB009422},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2012JB009422},
	author = {Roland, Emily and Lizarralde, Dan and McGuire, Jeffrey J. and Collins, John A.}
}
@article {collins_seismicity_2012,
	title = {Seismicity of the Atlantis Massif detachment fault, 30{\textdegree}N at the Mid-Atlantic Ridge},
	journal = {Geochemistry, Geophysics, Geosystems},
	volume = {13},
	number = {10},
	year = {2012},
	note = {_eprint: https://onlinelibrary.wiley.com/doi/pdf/10.1029/2012GC004210},
	abstract = {At the oceanic core complex that forms the Atlantis Massif at 30{\textdegree}N on the Mid-Atlantic Ridge, slip along the detachment fault for the last 1.5{\textendash}2 Ma has brought lower crust and mantle rocks to the seafloor. Hydroacoustic data collected between 1999 and 2003 suggest that seismicity occurred near the top of the Massif, mostly on the southeastern section, while detected seismicity along the adjacent ridge axis was sparse. In 2005, five short-period ocean bottom seismographs (OBS) were deployed on and around the Massif as a pilot experiment to help constrain the distribution of seismicity in this region. Analysis of six months of OBS data indicates that, in contrast to the results of the earlier hydroacoustic study, the vast majority of the seismicity is located within the axial valley. During the OBS deployment, and within the array, seismicity was primarily composed of a relatively constant background rate and two large aftershock sequences that included 5 teleseismic events with magnitudes between 4.0 and 4.5. The aftershock sequences were located on the western side of the axial valley adjacent to the Atlantis Massif and close to the ridge-transform intersection. They follow Omori{\textquoteright}s law, and constitute more than half of the detected earthquakes. The OBS data also indicate a low but persistent level of seismicity associated with active faulting within the Atlantis Massif in the same region as the hydroacoustically detected seismicity. Within the Massif, the data indicate a north-south striking normal fault, and a left-lateral, strike-slip fault near a prominent, transform-parallel, north-facing scarp. Both features could be explained by changes in the stress field at the inside corner associated with weak coupling on the Atlantis transform. Alternatively, the normal faulting within the Massif might indicate deformation of the detachment surface as it rolls over to near horizontal from an initial dip of about 60{\textdegree} beneath the axis, and the strike-slip events may indicate transform-parallel movement on adjacent detachment surfaces.},
	keywords = {Atlantis Massif, hydroacoustic, Mid-Atlantic Ridge, oceanic detachment fault, seismicity, T-phase},
	issn = {1525-2027},
	doi = {10.1029/2012GC004210},
	url = {https://onlinelibrary.wiley.com/doi/abs/10.1029/2012GC004210},
	author = {Collins, John A. and Smith, Deborah K. and McGuire, Jeffrey J.}
}
@article {mcguire_variations_2012,
	title = {Variations in earthquake rupture properties along the Gofar transform fault, East Pacific Rise},
	journal = {Nature Geoscience},
	volume = {5},
	number = {5},
	year = {2012},
	note = {Number: 5 Publisher: Nature Publishing Group},
	month = {may},
	pages = {336{\textendash}341},
	abstract = {Mid-ocean ridge transform faults experience more foreshocks than continental faults, yet the mainshock rarely ruptures the entire fault. Analysis of seismic data from the Gofar transform fault at the East Pacific Rise indicates that the foreshock region has different material properties from the mainshock region, and acts as a barrier to rupture propagation.},
	keywords = {seismology},
	issn = {1752-0908},
	doi = {10.1038/ngeo1454},
	url = {https://www.nature.com/articles/ngeo1454},
	author = {McGuire, Jeffrey J. and Collins, John A. and Gou{\'e}dard, Pierre and Roland, Emily and Lizarralde, Dan and Boettcher, Margaret S. and Behn, Mark D. and van der Hilst, Robert D.}
}
@article {yao_structure_2011,
	title = {Structure of young East Pacific Rise lithosphere from ambient noise correlation analysis of fundamental- and higher-mode Scholte-Rayleigh waves},
	journal = {Nouveaux d{\'e}veloppements de l{\textquoteright}imagerie et du suivi temporel {\`a} partir du bruit sismique},
	volume = {343},
	number = {8},
	year = {2011},
	month = {sep},
	pages = {571{\textendash}583},
	abstract = {Inter-station Green{\textquoteright}s functions estimated from ambient noise studies have been widely used to investigate crustal structure. However, most studies are restricted to continental areas and use fundamental-mode surface waves only. In this study, we recover inter-station surface (Scholte-Rayleigh) wave empirical Green{\textquoteright}s function (EGFs) of both the fundamental- and the first-higher mode using one year of continuous seismic noise records on the vertical component from 28 ocean bottom seismographs deployed in the Quebrada/Discovery/Gofar transform faults region on the East Pacific Rise. The average phase-velocity dispersion of the fundamental mode (period band 2{\textendash}30s) and the first-higher mode (period band 3{\textendash}7s) from all EGFs are used to invert for the 1-D average, shear-velocity structure in the crust and uppermost mantle using a model-space search algorithm. The preferred shear-velocity models reveal low velocities (4.29km/s) between Moho and 25km depth below sea-surface, suggesting the absence of a fast uppermost mantle lid in this young (0{\textendash}2Myr) oceanic region. An even more pronounced low-velocity zone, with shear velocities \~{}3.85km/s, appears at a depth between 25{\textendash}40km below sea-surface. Along with previous results, our study indicates that the shear velocity in the uppermost oceanic mantle increases with increasing seafloor age, consistent with age-related lithospheric cooling. R{\'e}sum{\'e} Les fonctions de Green estim{\'e}es {\`a} partir de l{\textquoteright}analyse du bruit ambiant ont beaucoup {\'e}t{\'e} utilis{\'e}es pour {\'e}tudier la structure de la cro{\^u}te terrestre. La plupart de ces travaux sont toutefois limit{\'e}s aux zones continentales, et ne consid{\`e}rent que le mode fondamental des ondes de surface. Dans cette {\'e}tude, les fonctions de Green empiriques (EGFs) du mode fondamental et du premier mode sup{\'e}rieur des ondes de surface (Scholte-Rayleigh) sont reconstruites {\`a} partir d{\textquoteright}une ann{\'e}e d{\textquoteright}enregistrements continus de la composante verticale du bruit sismique sur 28 ocean bottom seismometers (OBSs) d{\'e}ploy{\'e}s dans la r{\'e}gion des failles transformantes Quebrada/Discovery/Gofar, le long de la dorsale oc{\'e}anique du Pacifique Est. La dispersion moyenne des vitesses de phase du mode fondamental (dans la bande de p{\'e}riode 2{\textendash}30s) et du premier mode sup{\'e}rieur (dans la bande 3{\textendash}7s), issus des EGFs, est utilis{\'e}e pour d{\'e}terminer un mod{\`e}le moyen 1D de la vitesse des ondes de cisaillement dans la cro{\^u}te et le manteau sup{\'e}rieur {\`a} partir d{\textquoteright}un algorithme de recherche dans l{\textquoteright}espace mod{\`e}le. Le mod{\`e}le de vitesse des ondes de cisaillement r{\'e}sultant pr{\'e}sente une couche de faible vitesse (4,29km/s) entre le Moho et 25km sous le niveau de la mer, ce qui sugg{\`e}re l{\textquoteright}absence de couche superficielle rapide dans le manteau sup{\'e}rieur de cette jeune r{\'e}gion oc{\'e}anique (0{\textendash}2millions d{\textquoteright}ann{\'e}es). Une zone de faible vitesse encore plus prononc{\'e}e, avec une vitesse de cisaillement de \~{}3,85km/s, appara{\^\i}t entre 25 et 40km sous le niveau de la mer. Combin{\'e}e avec des r{\'e}sultats ant{\'e}rieurs, notre {\'e}tude montre que la vitesse de cisaillement dans le manteau oc{\'e}anique sup{\'e}rieur augmente avec l{\textquoteright}{\^a}ge du fond oc{\'e}anique, ce qui est en accord avec le refroidissement dans le temps de la lithosph{\`e}re.},
	keywords = {ambient noise, Bruit ambiant, Dorsale Est Pacifique, East Pacific Rise, Fundamental- and higher-mode Scholte-Rayleigh waves, Lithosphere, Low-velocity zone, Manteau oc{\'e}anique sup{\'e}rieur, Modes fondamental et sup{\'e}rieur des ondes de Scholte-Rayleigh, Oceanic Uppermost Mantle, Zone de faible vitesse},
	issn = {1631-0713},
	doi = {10.1016/j.crte.2011.04.004},
	url = {https://www.sciencedirect.com/science/article/pii/S1631071311000952},
	author = {Yao, Huajian and Gou{\'e}dard, Pierre and Collins, John A. and McGuire, Jeffrey J. and van der Hilst, Robert D.}
}
