%0 Journal Article %T Constraining Jumps in Density and Elastic Properties at the 660 km Discontinuity Using Normal Mode Data via the Backus Gilbert Method %+ Collège de France (CdF (institution)) %+ Institut de Physique du Globe de Paris (IPGP (UMR_7154)) %A Lau, Harriet C. P. %A Romanowicz, Barbara %< avec comité de lecture %@ 0094-8276 %J Geophysical Research Letters %I American Geophysical Union %V 48 %P pp.97-110 %8 2021 %D 2021 %Z 2021GeoRL..4892217L %R 10.1029/2020GL092217 %K mantle phase transitions %K normal modes %K transition zone %Z Sciences of the Universe [physics]Journal articles %X We apply the Backus Gilbert approach to normal mode center frequency data, to constrain jumps in P, S, bulk sound speed and density at the "660" discontinuity in the earth's mantle (∼650-670 km depth). Different 1 D models are considered to compute sensitivity kernels. When using model PREM (Dziewonski & Anderson, 1981, Physics of the Earth and Planetary Interiors, 25, 297-356. doi:10.1016/0031 9201(81)90046 7) as reference, with a "660" at 670 km depth, the best fitting jumps in density, P and S wave speeds range from (5.1-8.2)%, (5.3-8.0)%, (5.0-7.0)%, respectively, so the PREM values lie outside the ranges of acceptable density and P wave speed jumps. When shifting the depth of "660" to 660 km, the density and S wave speed jumps increase, while the P wave speed jump decreases. Normal mode data do not support a global transition at 650 km depth. The density jumps are closer to those of pyrolite than PREM, while our bulk sound wave speed jumps suggest a larger garnet proportion at "660." %G English %2 https://insu.hal.science/insu-03590053/document %2 https://insu.hal.science/insu-03590053/file/Geophysical%20Research%20Letters%20-%202021%20-%20Lau%20-%20Constraining%20Jumps%20in%20Density%20and%20Elastic%20Properties%20at%20the%20660%20km.pdf %L insu-03590053 %U https://insu.hal.science/insu-03590053 %~ INSU %~ AFRIQ %~ CNRS %~ CDF %~ IPGP %~ PSL %~ UNIV-PARIS %~ UNIVERSITE-PARIS %~ CDF-PSL