Special One Time Event: Alison Malcolm

Abstract:

High-order surface integral methods are powerful modeling tools for problems involving isolated variations in sound speed.  The challenge in these methods lies in designing discretizations that appropriately account for the singularities in the Green's functions.  I will discuss a method for doing this and will illustrate its applicability with two examples: (i) Modelling ultrasound vibro-acoustography, a nonlinear medical imaging technique that uses two different frequencies of ultrasound, combining the resolution of high-frequency ultrasound with the clean images possible when imaging at low frequencies.  (ii) Understanding wavefront healing, a phenomena observed in seismic tomography where traveltime delays are reduced as waves propagate further from an isolated anomaly.  I will also briefly discuss a related method for modeling seismic data near topography; our method allows us to quickly estimate a rough structure that can then be used as a starting model for full-waveform inversion techniques.