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Abstract Oceanic transform faults connect spreading centers and are imprinted with previous tectonic events. However, their tectonic interactions are not well understood due to limited observations. The Discovery transform fault system at 4°S, East Pacific Rise (EPR), represents a young transform system, offering a unique opportunity to study the interplay between faulting and other tectonic events at an early phases of an oceanic transform system. Discovery regularly hostsM5–6 characteristic earthquakes, and the seafloor north of Discovery includes a 35 km‐long rift zone that records a complex history of rifting, faulting and volcanism, suggesting that the transform faults likely interact with regional tectonic activity. We apply a machine‐learning enabled workflow to locate 21,391 earthquakes recorded during a 1‐year ocean bottom seismometer experiment in 2008. Our results indicate that seismicity on the western Discovery fault is separated into seven patches with distinct aseismic and seismic slip modes. Additionally, we observe a patch of off‐fault seismicity near where seafloor abyssal hills intersect the rift zone. This seismicity may have been caused by varying opening rates as spreading rate decreases from north to south in the rift zone. Our findings suggest that the Discovery system is still evolving, and that system equilibrium has not been reached between rifting and faulting. These results reflect the complex yet rarely observed interactions between fault slip, plate rotation, and rifting which are likely ubiquitous at oceanic transform systems.
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Microseismicity Indicates Atypical Small‐Scale Plate Rotation at the Quebrada Transform Fault System, East Pacific Rise
Abstract Closely spaced, multi‐strand ridge transform faults (RTFs) accommodate relative motions along fast spreading mid‐ocean ridges. However, the relations between RTFs and plate spreading dynamics are poorly understood. The Quebrada system is one of the most unique RTF systems at the East Pacific Rise, consisting of four transform faults connected by three short intra‐transform spreading centers (ITSCs). We use seven‐months of ocean bottom seismograph data to study the Quebrada system, and find abundant earthquakes unevenly distributed among three active faults. We identify two deep, diffuse seismicity clouds at the inside corners of the ITSC‐transform fault intersections, and one seismically active fracture zone. The observations suggest a complex regional plate‐motion pattern, including possible heterogeneous rotations within the Quebrada system. Evolution of multi‐strand RTFs may have resulted from a strong three‐dimensional local thermal and fluid effects, while the RTFs may have also regulated regional tectonics, forming an intricate feedback system.
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- Award ID(s):
- 1833279
- PAR ID:
- 10490883
- Publisher / Repository:
- Geophysics Research Letters
- Date Published:
- Journal Name:
- Geophysical Research Letters
- Volume:
- 49
- Issue:
- 3
- ISSN:
- 0094-8276
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1029/2021GL097000
