Seismic Observations Indicating That the 2015 Ogasawara (Bonin) Earthquake Ruptured Beneath the 660 km Discontinuity

Seismic evidence for accumulated oceanic crust above the 660-km discontinuity beneath southern Africa

[1] High-pressure assemblages of subducted oceanic crust are denser than the normal upper mantle but less dense than the uppermost lower mantle. Thus subducted oceanic crust may accumulate at the base of the upper mantle. Direct observational evidence for this hypothesis, however, remains elusive. We present an analysis of a negativepolarity shear wave converted from compressional wave at a sei...

SH velocity and compositional models near the 660-km discontinuity beneath South America and northeast Asia

[1] We constrain SH wave velocity structures near the 660-km discontinuity beneath South America and northeast Asia, using triplicated phases near the discontinuity recorded in the epicentral distance range of 10 –35 for three deep events. We then explore mineralogical and compositional models appropriate for explaining the inferred seismic structures between the two regions. SH velocity struct...

Bent-shaped plumes and horizontal channel flow beneath the 660 km discontinuity

a r t i c l e i n f o Keywords: mantle plumes phase transitions temperature dependent viscosity thermal expansivity lattice thermal conductivity Recent high-resolution seismic imaging of the transition zone topography beneath the Hawaiian archipelago shows strong evidence for a 1000 to 2000 km wide hot thermal anomaly ponding beneath the 660 km boundary west of Hawaii islands [Q. Cao et al. Sei...

The Flora of the Bonin (Ogasawara) Islands

The nature of the 660-kilometer discontinuity in Earth's mantle from global seismic observations of PP precursors.

The 660-kilometer discontinuity, which separates Earth's upper and lower mantle, has been detected routinely on a global scale in underside reflections of precursors to SS shear waves. Here, we report observations of this discontinuity in many different regions, using precursors to compressional PP waves. The apparent absence of such precursors in previous studies had posed major problems for m...