P-wave upper mantle structures beneath the Ontong Java Plateau
Abstract
We obtained a three dimensional P-wave velocity structure with a focus on the mantle beneath the Ontong Java Plateau (OJP) using data from the seismological experiment on the OJP and its vicinity from late 2014 to early 2017. More than 120 events during the 2-years long OBS deployment yielded precious measurements. We measured more than ~170,000 relative travel times of P-wave between any two stations using the cross-correlation method, in pass-bands between 30 s and 2.7 s dominant period. We also measured more than 500 PP - P differential travel times of which PP rays bounce at the surface around the OJP. We inverted these data in addition to more than 15 million first arrival data of ISC and our own data set for the whole mantle using the multifrequency tomography technique. The tomographic result shows high velocity anomalies at the middle of the OJP and low velocity anomalies in the northwest part of the OJP in the depth ranges of 100 - 350 km. Massive Fast anomalies are observed at 600 km depth. These anomalies are considered as stagnant Pacific slabs related to the trench migration as well as seafloor-spreading in the Santa Cruz Basin and Melanesia Basin during the Eocene and Oligocene. Slow anomalies along Caroline islands ridge are observed down to about 500 km depth. Although Caroline Islands are considered as a hotspot chain, the slow anomalies are elongated like a sheet along the islands rather than a plume toward a spot. These slow anomalies are located at the northern edge of the stagnant slab, suggesting the mantle upwelling affected by the stagnant slabs.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMDI13C0024O
- Keywords:
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- 3006 Marine electromagnetics;
- MARINE GEOLOGY AND GEOPHYSICS;
- 3025 Marine seismics;
- MARINE GEOLOGY AND GEOPHYSICS;
- 7208 Mantle;
- SEISMOLOGY;
- 8120 Dynamics of lithosphere and mantle: general;
- TECTONOPHYSICS