1. Evidence for low Vp/Vs ratios along the eastern Romanche ridge-transform intersection in the equatorial Atlantic Ocean.
- Author
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Yu, Zhiteng, Singh, Satish C., and Maia, Marcia
- Subjects
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EARTHQUAKE zones , *SEISMOLOGY , *SEISMIC tomography , *SEISMIC arrays , *EARTHQUAKES , *SEISMOMETERS - Abstract
Very long oceanic transform faults do not just offset mid-oceanic ridges by hundreds of kilometers, but they also induce variations in the lithospheric structure and affect mantle melting, and hence the crustal accretion at the ridge-transform intersection (RTI). However, the deep structure of large offset RTIs remains unknown. Here, we present three-dimensional seismic tomography results (P- and S-wave velocities, Vp, Vs) in the vicinity of the eastern Romanche transform and the Mid-Atlantic Ridge in the equatorial Atlantic Ocean, using arrival times from microearthquakes recorded by a recent temporary array of seafloor seismometers. We find that normal to low Vp/Vs ratios (∼1.7) are observed at the Mid-Atlantic Ridge, representing weak serpentinization and the dominant magmatic processes, whereas high Vp/Vs ratios (∼1.8-1.95) are observed west of the RTI, at the eastern termination of the 2016 M w 7.1 earthquake. However, unusually low Vp/Vs ratios (∼1.6-1.7) are observed at 0-15 km depth and in the region of the 2016 M w 7.1 earthquake rupture zone. We suggest that the unusually low Vp/Vs ratios result from the presence of thick cracks at shallow depths (0-8 km) and/or the enrichment of orthopyroxene in the deep mantle (8-15 km). • 3-D Vp and Vs models for the Romanche eastern ridge-transform intersection. • Low Vp/Vs ratios (∼1.6-1.7) at depths of <15 km along the transform are observed. • The low ratios may be due to thick cracks and/or orthopyroxene enrichment. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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