Details

Autor(en) / Beteiligte

• Wysession, Michael E.
• Langenhorst, Amy
• Fouch, Matthew J.
• Fischer, Karen M.
• Al-Eqabi, Ghassan I.
• Shore, Patrick J.
• Clarke, Timothy J.

Titel

Lateral Variations in Compressional/Shear Velocities at the Base of the Mantle

Ist Teil von

• Science (American Association for the Advancement of Science), 1999-04, Vol.284 (5411), p.120-125

Ort / Verlag

Washington, DC: American Society for the Advancement of Science

Erscheinungsjahr

1999

Quelle

Science Online_科学在线

Beschreibungen/Notizen

• Observations of core-diffracted P (P$_{diff}$) and SH (SH$_{diff}$) waves recorded by the Missouri-to-Massachusetts (MOMA) seismic array show that the ratio of compressional (P) seismic velocities to horizontal shear (SH) velocities at the base of the mantle changes abruptly from beneath the mid-Pacific (V$_P$/V$_S$ = 1.88, also the value predicted by reference Earth models) to beneath Alaska (V$_P$/V$_S$ = 1.83). This change signifies a sudden lateral variation in material properties that may have a mineralogical or textural origin. A textural change could be a result of shear stresses induced during the arrival at the core of ancient lithosphere from the northern Pacific paleotrench.