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Monday, December 17

Global "Adjoint Tomography" on Titan

Jeroen Tromp, Princeton University, Princeton, N.J.
National Center for Computational Sciences Seminar
2:00 PM — 3:00 PM, Joint Institute for Computational Sciences (Building 5100),
Auditorium (Room 128)
Contact: Judy Hill (, 865.576.8453


Precise information about the structure of the Earth comes from seismograms recorded at the surface of a highly heterogeneous lithosphere. Seismic imaging based on spectral-element and adjoint methods can assimilate this information into three-dimensional models of elastic (seismic wavespeeds) and anelastic structure (Q). These methods fully account for the physics of wave excitation, propagation, and interaction by numerically solving the inhomogeneous equations of motion for a heterogeneous anelastic solid. Such methods require the execution of complex workflows, requiring extensive pre- and post-processing of observed and simulated seismograms.

After successful applications of "adjoint tomography" in southern California and Europe, we are moving toward "adjoint tomography" of the entire planet. The goal is to image Earth's global interior based on full waveform inversion, thereby facilitating a deeper understanding of its physics and chemistry. To start with, we selected 255 earthquakes and gathered data from global seismographic networks. Our strategy is to invert for crust and mantle structure jointly, thereby avoiding any bias introduced into upper-mantle images due to commonly used "crustal corrections". Our ultimate goal is to harness more than 6,000 magnitude 5.5-7.2 earthquakes digitally recorded over the past 20 years.