Global study of the seismic discontinuities in the mantle
Time: 10:30 a.m., August, 7, 2014
Location: Meeting Room, LCG-CAS
Speaker: Xueqing Li
Abstract：Receiver functions of a few hundred global permanent stations exhibit the upper mantle stratification and topography of the upper mantle discontinuities. We detected a negative global discontinuity at a depth of ~600 km, indicating a low velocity layer at the base of the mantle transition zone. The X-discontinuity at ~300 km depth is also observed in our global stacks, which can be explained by the coesite-stishovite phase transformation. The mantle transition zone thickness, measured by differential times of the 410 and 660 km discontinuity phases, deviates by -35 km to +20 km from that predicted by the IASP91 model and changes according to mantle temperature, e.g., the transition zone is thick in subduction zones and thin within mantle plumes. According to the Clapeyron slopes of the 410 and 660 km discontinuities, temperature anomaly in the mantle transition zone is in a range of -200º to 350º. The correlation of the arrival times of the 410 and 660 km discontinuity phases are closely related to the upper mantle velocities above them, therefore, reflecting the tectonic features in the upper mantle. Averaged temperature anomalies at the shallow 400 km depth can be estimated based on petrological expectations. We found a good correlation between the arrival times of the 410 km discontinuity phase and the thickness of the lithosphere, derived by surface wave inversion, implying that the variation of the lithospheric thickness is the most significant heterogeneity in the upper mantle.
Curriculum Vitae：
Xueqing Li
Academic Training
2000: Ph.D., Seismology, Freie Universität Berlin
1989: M.Sc., Seismology, Institute of Geophysics, Chinese Earthquake Administration
1986: B.Sc., Geophysics, University of Science and Technology of China
Professional Experience
2008-present: System adminstrator, GFZ
2001-2007: Scientist, GFZ
1996-2000: PhD student, GFZ
1989-1995: Research assistant, Institute of Geophysics, Chinese Earthquake Administration
|
