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Tromp, J.
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Tromp, J.
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- PublicationRestrictedForward and adjoint simulations of seismic wave propagation on fully unstructured hexahedral meshes(2011)
; ; ; ; ; ; ; ; ; ; ; ; ; ;Peter, D.; Princeton University, Department of Geosciences, 318 Guyot Hall, Princeton, NJ 08544, USA ;Komatitsch, D.; Université de Pau et des Pays de l’Adour, CNRS & INRIA Magique-3D, Laboratoire de Modélisation et d’Imagerie en Géosciences UMR 5212, Avenue de l’Université, 64013 Pau Cedex, France. Institut universitaire de France, 103 boulevard Saint-Michel, 75005 Paris, France ;Luo, Y.; Princeton University, Department of Geosciences, 318 Guyot Hall, Princeton, NJ 08544, USA ;Martin, R.; Université de Pau et des Pays de l’Adour, CNRS & INRIA Magique-3D, Laboratoire de Modélisation et d’Imagerie en Géosciences UMR 5212, Avenue de l’Université, 64013 Pau Cedex, France ;Le Goff, N.; Université de Pau et des Pays de l’Adour, CNRS & INRIA Magique-3D, Laboratoire de Modélisation et d’Imagerie en Géosciences UMR 5212, Avenue de l’Université, 64013 Pau Cedex, France ;Casarotti, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Le Loher, P.; Université de Pau et des Pays de l’Adour, CNRS & INRIA Magique-3D, Laboratoire de Modélisation et d’Imagerie en Géosciences UMR 5212, Avenue de l’Université, 64013 Pau Cedex, France ;Magnoni, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Liu, Q.; Department of Physics, University of Toronto, Ontario, Canada ;Blitz, C.; Université de Pau et des Pays de l’Adour, CNRS & INRIA Magique-3D, Laboratoire de Modélisation et d’Imagerie en Géosciences UMR 5212, Avenue de l’Université, 64013 Pau Cedex, France ;Nissen-Meyer, T.; Institute of Geophysics, ETH Zurich, Sonneggstr. 5, CH-8092 Zurich, Switzerland ;Basini, P.; Institute of Geophysics, ETH Zurich, Sonneggstr. 5, CH-8092 Zurich, Switzerland ;Tromp, J.; Princeton University, Department of Geosciences, 318 Guyot Hall, Princeton, NJ 08544, USA. Princeton University, Program in Applied & Computational Mathematics, Princeton, NJ 08544, USA; ; ; ; ; ; ; ; ; ; ; ; We present forward and adjoint spectral-element simulations of coupled acoustic and (an)elastic seismic wave propagation on fully unstructured hexahedral meshes. Simulations benefit from recent advances in hexahedral meshing, load balancing and software optimization. Meshing may be accomplished using a mesh generation tool kit such as CUBIT, and load balancing is facilitated by graph partitioning based on the SCOTCH library. Coupling between fluid and solid regions is incorporated in a straightforward fashion using domain decomposition. Topography, bathymetry and Moho undulations may be readily included in the mesh, and physical dispersion and attenuation associated with anelasticity are accounted for using a series of standard linear solids. Finite-frequency Fre ́chet derivatives are calculated using adjoint methods in both fluid and solid domains. The software is benchmarked for a layercake model. We present various examples of fully unstructured meshes, snapshots of wavefields and finite-frequency kernels generated by Version 2.0 ‘Sesame’ of our widely used open source spectral-element package SPECFEM3D.239 28 - PublicationRestrictedCUBIT and seismic wave propagation based upon the Spectral-Element Method: An advanced unstructured mesher for complex 3D geological media(2008)
; ; ; ; ; ; ;Casarotti, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Stupazzini, M.; Department of Earth- and Environmental Sciences, Ludwig-Maximilians-Universitat, Munich, Germany ;Lee, S. J.; Institute of Earth Science, Academia Sinica. Taipei, Taiwan ;Komatitsch, D.; Laboratoire de Modlisation et d’Imagerie en Gosciences UMR 5212, Universit de Pau et des Pays de l’Adour., Pau, France ;Piersanti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Tromp, J.; Seismological Laboratory, California Institute of Technology, Pasadena, California, USA; ; ; ; ; ; ; ; ;Brewer, M. L.Marcum, D.Unstructured hexahedral mesh generation is a critical part of the model- ing process in the Spectral-Element Method (SEM). We present some ex- amples of seismic wave propagation in complex geological models, automati- cally meshed on a parallel machine based upon CUBIT (Sandia Laboratory, cubit.sandia.gov), an advanced 3D unstructured hexahedral mesh genera- tor that offers new opportunities for seismologist to design, assess, and improve the quality of a mesh in terms of both geometrical and numerical accuracy. The main goal is to provide useful tools for understanding seismic phenomena due to surface topography and subsurface structures such as low wave-speed sedimentary basins. Our examples cover several typical geophysical problems: 1) “layer-cake” volumes with high-resolution topography and complex solid- solid interfaces (such as the Campi Flegrei Caldera Area in Italy), and 2) models with an embedded sedimentary basin (such as the Taipei basin in Taiwan or the Grenoble Valley in France).236 31 - PublicationRestrictedSpectral‐Element Simulations of Seismic Waves Generated by the 2009 L’Aquila Earthquake(2014)
; ; ; ; ; ; ; ;Magnoni, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Casarotti, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Michelini, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Piersanti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Komatitsch, D.; LMA, CNRS UPR 7051, Aix‐Marseille University, Centrale Marseille, 13402 Marseille Cedex 20, France ;Peter, D.; Institute of Geophysics, ETH Zurich, NO H1.2, Sonneggstrasse 5, 8092 Zurich, Switzerland ;Tromp, J.; Department of Geosciences and Program in Applied & Computational Mathematics, Princeton University, Princeton, New Jersey 08544; ; ; ; ; ; We adopt a spectral-element method (SEM) to perform numerical simulations of the complex wavefield generated by the 6 April 2009 Mw 6.3 L’Aquila earthquake in central Italy. The mainshock is represented by a finite-fault solution obtained by inverting strong-motion and Global Positioning System data, testing both 1D and 3D wavespeed models for central Italy. Surface topography, attenuation, and the Moho discontinuity are also accommodated. Including these complexities is essential to accurately simulate seismic-wave propagation. Three-component synthetic waveforms are compared to corresponding velocimeter and strong-motion recordings. The results show a favorable match between data and synthetics up to ∼0:5 Hz in a 200 km × 200 km × 60 km model volume, capturing features mainly related to topography or low-wavespeed basins. We construct synthetic peak ground velocity maps that, for the 3D model, are in good agreement with observations, thus providing valuable information for seismic-hazard assessment. Exploiting the SEM in combination with an adjoint method, we calculate finite-frequency kernels for specific seismic arrivals. These kernels capture the volumetric sensitivity associated with the selected waveform and highlight prominent effects of topography on seismic-wave propagation in central Italy.384 54 - PublicationRestrictedImaging lateral heterogeneity in the northern Apennines from time reversal of reflected surface waves(2009-05)
; ; ; ; ;Stich, D.; Instituto Andaluz de Geofisica, Universidad de Granada, Campus Universitario de Cartuja s/n, 18071 Granada, Spain ;Danecek, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Morelli, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia ;Tromp, J.; Department of Geosciences, Princeton University, Princeton, NJ 08544, USA; ; ; Prominent arrivals in the coda of seismograms from the wider Alpine area can be associated with lateral reflections of Love waves at the northern Apennines mountain chain (Italy), where structural heterogeneity causes an abrupt contrast in phase velocity. We discuss an approach to image lateral heterogeneity from reflected surface waves using intermediate-period, three- component coda waveforms as sources for an adjoint wavefield that propagates the reflections backward in time. We numerically compute three-dimensional sensitivity kernels for the dependence of coda waveforms on P velocity, S velocity and density, based upon correlations between the adjoint and the regular forward wavefields. We consider synthetic coda waveforms for a simplified model of the northern Apennines, as well as real coda observations from five moderate magnitude earthquakes (M W 4.6–5.6) in the southern Alps. Wave propagation is simulated using the spectral-element method, for which a 3-D regional earth model is used in the case of real data. Single and combined event sensitivity kernels provide clear images of the reflectivity associated with the northern Apennines in kernels for density and S-wave speed. The kernels show that surface wave reflections occur near the axial zone of the mountain chain. Apart from the Apennines, the approach is able to image other smaller reflectivity patches from the coda waveforms, like the Ivrea zone in the southern Alps. Our coda misfit kernels can be integrated in a gradient-based waveform tomography, where they could enhance the shar pness of the model at lateral discontinuities.179 29