Constraining Short Scale Core-Mantle Boundary Topography with Amplitudes of Core-Reflected ScP Wave

Abstract:

The coupling mechanisms at core-mantle boundary (CMB) play critical roles in mantle convection and geomagnetic evolution. The topography of CMB provides fundamental information to understanding of the coupling processes. Previous observations with short period core-reflected phases PcP reported rapid amplitude variation and suggested small scale variation of core-mantle boundary topography. 3D synthetic seismograms based on the seismic ray theory have been adopted to constrain CMB topography beneath Alaska which features a few kilometers topography variation across horizontal length scale of a few hundred km. We developed a similar algorithm for computing short period synthetic ScP seismograms based on the representation theorem and ray theory. We then explore the quantitative relationships between the synthetic ScP seismograms’ amplitude variation and CMB topography depression or jump, and compare the synthetics with array observations of ScP data. We will discuss the algorithm’s limitation and possible extension so that it may work in more complicated mantle structures.