11.01.2014: A team with Prof. Dr. Michael Weber, head of GFZ-Section Geophysical Deep Sounding, found evidence for a to date unknown stagnant slab in the mantle transition zone in ca. 400 km depth, close to Mariana Trench.
About ca. 550 kilometers west of the present Mariana subduction zone (at 20°N, 140°E) a steeply dipping reflector was identified in the mantle transition zone, using array seismology. The discovery of this anomaly helps in understanding the evolution of the Mariana margin. The stagnant slab may be the remnant of the North New Guinea plate, which was subducted ca. 50 million years ago.
Compared to conventional tomography the array method is even sensitive to impedance contrast of thin tabular anomalies. The array method, in combination with new tomographic imaging techniques, can thus help to reconstruct the history of subduction and plate tectonics much more detailed than previously.
Paper: Michael Weber, Charles Wicks Jr., Yves Le Stunff, Barbara Romanowicz, Frank Kruger, 2015. Seismic evidence for a steeply dipping reflector-stagnant slab in the mantle transition zone - Geophysical Journal International, 2015, 200 (2): 1237-1253 doi: 10.1093/gji/ggu438