کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
6430339 | 1634789 | 2013 | 9 صفحه PDF | دانلود رایگان |
Mantle flow in Earth's interior has been inferred from a variety of geo-disciplines. Two continental-scale, nearly antipodal, large low shear velocity provinces (LLSVPs) at the base of the mantle, thought to be dense and chemically distinct likely play a significant role in mantle dynamics and plume generation, and hence are targeted in a high-resolution seismic study. We analyze broadband SPdKS waveforms using a 2.5D axi-symmetric finite difference wave propagation algorithm PSVaxi. Here we find patches of greatly reduced seismic wave speeds at the core-mantle boundary, i.e., ultra-low velocity zones (ULVZs), within the Pacific LLSVP, including the largest ULVZ detected to date, roughly 250Ã800Â km in lateral dimension and 10-15Â km thick, in an apparent hole in the LLSVP. The presence of this ULVZ in the LLSVP hole is well explained by dynamically merging, chemically-distinct piles containing ULVZs at their margins. The consequence of these merging piles may be to initiate anomalously large, infrequent plumes, as well as to provide a means to transfer isotopes to the surface.
⺠Mapped the largest and most extensive ultra-low velocity zone (ULVZ) found to date. ⺠Modeled seismic waveforms using newly developed 2.5D PSVaxi synthetic seismogram simulation code. ⺠Discovered two new seismic phases including the precursor phase SPKS which is present for large ULVZs. ⺠Location of the mega ULVZ discovered can be explained by the merging of two or more thermochemical piles. ⺠The Pacific LLSVP is dynamically evolving.
Journal: Earth and Planetary Science Letters - Volume 364, 15 February 2013, Pages 59-67