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  • 1
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 15 (2014): 4692–4711, doi:10.1002/2014GC005563.
    Description: A multifaceted study of the slow spreading Mid-Atlantic Ridge (MAR) at 16.5°N provides new insights into detachment faulting and its evolution through time. The survey included regional multibeam bathymetry mapping, high-resolution mapping using AUV Sentry, seafloor imaging using the TowCam system, and an extensive rock-dredging program. At different times, detachment faulting was active along ∼50 km of the western flank of the study area, and may have dominated spreading on that flank for the last 5 Ma. Detachment morphologies vary and include a classic corrugated massif, noncorrugated massifs, and back-tilted ridges marking detachment breakaways. High-resolution Sentry data reveal a new detachment morphology; a low-angle, irregular surface in the regional bathymetry is shown to be a finely corrugated detachment surface (corrugation wavelength of only tens of meters and relief of just a few meters). Multiscale corrugations are observed 2–3 km from the detachment breakaway suggesting that they formed in the brittle layer, perhaps by anastomosing faults. The thin wedge of hanging wall lavas that covers a low-angle (6°) detachment footwall near its termination are intensely faulted and fissured; this deformation may be enhanced by the low angle of the emerging footwall. Active detachment faulting currently is limited to the western side of the rift valley. Nonetheless, detachment fault morphologies also are present over a large portion of the eastern flank on crust 〉2 Ma, indicating that within the last 5 Ma parts of the ridge axis have experienced periods of two-sided detachment faulting.
    Description: This work was supported by the National Science Foundation grant OCE-1155650.
    Description: 2015-06-05
    Keywords: Oceanic detachment faults ; AUV Sentry ; Mid-Atlantic Ridge
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 14 (2013): 4667–4680, doi:10.1002/ggge.20278.
    Description: Catastrophic collapses of submarine volcanoes have the potential to generate major tsunami, threatening many coastal populations. Recognizing the difficulties surrounding anticipations of these events, quantitative assessment of collapse-prone regions based on detailed morphological, geological, and geophysical mapping can still provide important information about the hazards associated with these collapses. Rumble III is one of the shallowest, and largest, submarine volcanoes found along the Kermadec arc, and is both volcanically and hydrothermally active. Previous surveys have delineated major collapse features at Rumble III; based on time-lapse bathymetry, dramatic changes in the volcano morphology have been shown to have occurred over the interval 2007–2009. Furthermore, this volcano is located just ∼300 km from the east coast of the North Island of New Zealand. Here, we present a geophysical model for Rumble III that provides the locations and sizes of potential weak regions of this volcano. Shipborne and near-seafloor geological and geophysical data collected by the AUV Sentry are used to determine the subsurface distribution of weak and unstable volcanic rocks. The resulting model provides evidence for potentially unstable areas located in the Southeastern flank of this volcano which should be included in future hazard predictions.
    Description: This contribution was funded by the Royal Society of New Zealand by theMarsden Fund (grant GNS1003).
    Description: 2014-04-18
    Keywords: Rumble III ; Geophysical modeling ; Flank collapse ; AUV mapping
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 3
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 41 (2014): 7080–7088, doi:10.1002/2014GL061555.
    Description: Long-lived detachment faults play an important role in the construction of new oceanic crust at slow-spreading mid-oceanic ridges. Although the corrugated surfaces of exposed low-angle faults demonstrate past slip, it is difficult to determine whether a given fault is currently active. If inactive, it is unclear when slip ceased. This judgment is crucial for tectonic reconstructions where detachment faults are present, and for models of plate spreading. We quantify variation in sediment thickness over two corrugated surfaces near 16.5°N at the Mid-Atlantic Ridge using near-bottom Compressed High Intensity Radar Pulse (CHIRP) data. We show that the distribution of sediment and tectonic features at one detachment fault is consistent with slip occurring today. In contrast, another corrugated surface 20 km to the south shows a sediment distribution suggesting that slip ceased ~150,000 years ago. Data presented here provide new evidence for active detachment faulting, and suggest along-axis variations in fault activity occur over tens of kilometers.
    Description: This work was supported by the National Science Foundation grant number OCE-1155650.
    Description: 2015-04-23
    Keywords: Mid-ocean ridge ; Detachment faulting
    Repository Name: Woods Hole Open Access Server
    Type: Article
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