SS-precursors Imaging of the Mantle Transition Zone based on Finite-Frequency Theory

Olivine, the most abundant mineral in mantle rock, undergoes a sequence of pressure-induced phase changes. Given the opposite signs of the Clapeyron slopes, estimates of the depths of the 400-km and 660-km phase changes can be used to constrain temperature variations in the transition zone. SS-precursor analysis is a classic tool to map the depths of the 410-km and 660-km phase changes. A number of researchers have argued that finite-frequency theory is necessary to accurately model SS-precursors since the sensitivity of SS reflections extends several thousands kilometers beyond the ray-theoretical reflection point. Using a new global data set of SS precursors, we will make a preliminary comparison of 410-km and 660-km maps derived using ray and finite-frequency theories.