Flatland: Moving Beyond 1D Waveform Models to Examine Earth’s Mantle Structure
IPGP - Îlot Cuvier
Séminaires de Sismologie
University of Leeds
Ultra-low velocity zones (ULVZs) are thin patches of strongly reduced seismic velocities and likely increased density at the core-mantle boundary (CMB). A common phase to detect ULVZs is SPdKS (SKPdS). The characterization of ULVZ properties typically uses waveform modeling through wave propagation through 1D (radial) Earth models. Within the past few years advances in computational waveform modeling and the significant increase of available data from large scale networks such USArray allow much better insight into the structure of the Earth’s interior. With the advent of large scale parallel processing we can now start moving beyond 1D models into minimally the 2D case. To explore the affects of moving into the 2D world this seminar will examine high frequency (up to ~0.5Hz) synthetic results generated by the axisymmetric finite difference code PSVaxi with respect to the interaction of the SP¬dKS with ULVZs. Significantly, the 2D models behave vastly differently from the 1D case including features such as the generation of a rogue reflected phase. This new library of 2D waveforms can be used to image the location and critically the geometry of global ULVZs providing valuable insight into the dynamic state of the Earth’s lowermost mantle.