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Adjoint Tomography for the Middle East
Daniel Peter (Princeton University), Brian Savage (University of Rhode Island), Arthur Rodgers (Lawrence Livermore
National Laboratory), Jeroen Tromp (Princeton University)
We evaluate 3D models of the Middle East by computing full waveforms for a set of regional earthquakes [Savage et al., 2009].
We measure traveltime shifts between observed broadband data obtained from IRIS and synthetic seismograms for distinct seismic
phases within selected time windows using a recently developed, automated measurement algorithm [Maggi et al., 2009].
Based on the measurements for our study region, we selected a best model to feature as the starting seismic model for a fully
numerical 3D seismic tomography approach.
In order to improve the initial 3D seismic model, the sensitivity to seismic structure of the traveltime measurements for all
available, regional network recordings is computed. As this represents a computationally very intensive task, we take advantage
of an adjoint method combined with spectral-element simulations [Tromp et al., 2005]. We calculate such sensitivity kernels
for all seismic events and regional records and use them in a conjugate-gradient approach to iteratively update the 3D seismic
model. This will lead to various improvements of the initial seismic structure in order to better explain regional seismic waveforms
in the Middle East for nuclear monitoring.
References
Maggi, A., C. Tape, M. Chen, D. Chao and J. Tromp, 2009. An Automated time-window selection algorithm for seismic tomography, Geophys.
J. Int., 178, 257–281.
Savage, B., D. Peter, B. Covellone, A. Rodgers and J. Tromp, 2009. Progress towards next generation, waveform based three-dimensional
models and metrics to improve nuclear explosion monitoring in the Middle East, Proceedings of the 31th Monitoring Research Review of
Ground-Based Nuclear Explosion Monitoring Technologies, LLNL-PROC-414451, 9 pages.
Tromp, J., C. Tape and Q. Y. Liu, 2005. Seismic tomography, adjoint methods, time reversal and banana-doughnut kernels, Geophys. J. Int.,
160, 195–216.
Acknowledgements: This research is sponsored by Air Force Research Laboratory and by National Nuclear Security Administration, Contract
No. FA8718-08-C-0009.
Shear-velocity event kernel for an earthquake in the strait of Hormuz recorded 2005 by several regional stations. Sensitivities are shown on a horizontal cross-section
at 5 km depth and a vertical cross-section through the source and a station location down to a depth of 670 km.
II-200 | 2010 IRIS Core Programs Proposal | Volume II | Upper Mantle Structure and Dynamics