Adjoint tomography employing 3D wavefield simulations for 72 well recorded regional earthquakes in the western U.S. yields spectacular improvements to waveform fits.
Fundamental questions on subsurface properties are robustly addressed through probabilistic assessment of multiple forward/inverse modelling formalisms using interrogation theory.
Waveform inversion of regional earthquakes reveals velocity anomalies interpreted as subducting seamounts that control an enigmatic segmentation in plate coupling along the Hikurangi margin.
Seismic waveform inversion is inherently non-linear. New objective functions based on optimal transport theory mitigate nonlinearity yielding stable solutions without need for accurate initial models.