SPP 1257 Modelling of the Dynamic Earth from an Integrative Analysis of Potential Fields, Seismic Tomography and other Geophysical Data M. Kaban, A. Baranov and M. Rothacher GFZ Potsdam and H. Schmeling J. W. Goethe University, Frankfurt/M First Steps Towards 3D Global Density and Dynamic Model of the Crust and Mantle

SPP 1257 Modelling of the Dynamic Earth from an Integrative Analysis of Potential Fields, Seismic Tomography and other Geophysical Data Main Goals of the Project 1. Integrative density model of the crust and upper mantle. a. Improvement of the existing global crustal compilation (Central & South Asia). b. Global determination of the lithosphere thickness (Sodoudi and Kind). b. Global determination of the lithosphere thickness (Sodoudi and Kind). c. Modelling of the lithosphere and upper mantle density structure and c. Modelling of the lithosphere and upper mantle density structure and computation of the non-isostatic geoid anomalies and dynamic topography. computation of the non-isostatic geoid anomalies and dynamic topography. 2. Construction of a new “snap-shot” dynamic model of the mantle. Key issues: Key issues: a. Modelling of effects of the transition zone boundaries on the geoid and a. Modelling of effects of the transition zone boundaries on the geoid and dynamic topography. dynamic topography. b. Considering strong lateral viscosity variations in the mantle. b. Considering strong lateral viscosity variations in the mantle. 3. Modelling temporal geoid variations and effects of sublithospheric convection.

SPP 1257 Modelling of the Dynamic Earth from an Integrative Analysis of Potential Fields, Seismic Tomography and other Geophysical Data Integrative Model of the Mantle and the Lithosphere (existing background and main problems) Some of the Key Problems: 1. 1.Crust is the most heterogeneous layer in the Earth. It is principal to determine its effect beforehand using available information Impact of compositional and temperature variations in the upper mantle is unclear Gravity effect of the transition zone (potentially very strong) has not identified in the observed gravity field/geoid.

SPP 1257 Modelling of the Dynamic Earth from an Integrative Analysis of Potential Fields, Seismic Tomography and other Geophysical Data Improvement of the Global Crustal Model 1. 1.Quality of the existing global crustal models do not meet present-day requirements The new global crustal model is principally improved based on high resolution regional data. North America (Kaban and Mooney in prep.) EuCRUST-07 (Tesauro, Kaban and Cloetingh, 2007 subm.) Main focus of this study

SPP 1257 Modelling of the Dynamic Earth from an Integrative Analysis of Potential Fields, Seismic Tomography and other Geophysical Data Collection of new data for Central & South Asia

SPP 1257 Modelling of the Dynamic Earth from an Integrative Analysis of Potential Fields, Seismic Tomography and other Geophysical Data Moho depth - China Based on the data from (Li, Mooney and Fan ; Sodoudi et al., 2006, 2006; Huanga & Zhaob, 2004; Chunju et al. 2005; Mangino et al., 1999) and more …

SPP 1257 Modelling of the Dynamic Earth from an Integrative Analysis of Potential Fields, Seismic Tomography and other Geophysical Data Moho depth – Middle East

SPP 1257 Modelling of the Dynamic Earth from an Integrative Analysis of Potential Fields, Seismic Tomography and other Geophysical Data Moho depth - India

SPP 1257 Modelling of the Dynamic Earth from an Integrative Analysis of Potential Fields, Seismic Tomography and other Geophysical Data Modelling of the effect of the transition zone on the geoid and dynamic topography 1. 1.How significant is the impact of the transition zone on the dynamic geoid? 2. 2.Up to now, most of the combined gravity-seismic models are based on the tomography data, in which the effects of velocity variations and phase boundaries are mixed. This can lead to strong artificial seismic velocity anomalies and, consequently, to false inferences on the mantle structure Artificial “dynamic” reconstructions of the transition boundaries give the topography, which is remarkably different from observations (e.g. Cadek and Fleitout, 1999; Steinberger, 2007) We use the new tomography model of Gu et al. (2003), in which mantle velocities have been estimated in a joint inversion with the transition zone discontinuities.

SPP 1257 Modelling of the Dynamic Earth from an Integrative Analysis of Potential Fields, Seismic Tomography and other Geophysical Data “Effective” velocity and density variations in the TZ based on traditional tomography models Parametrization, Gu et al., 2003 In fact, the observed Vs variations could be either negative or positive in the vicinity of the 660 discontinuity depending on many variable factors! Z

SPP 1257 Modelling of the Dynamic Earth from an Integrative Analysis of Potential Fields, Seismic Tomography and other Geophysical Data “Effective” velocity-density scaling factor in the TZ for traditional tomography models Vertical resolution of the model, km “Effective” velocity-to-density scaling factor

SPP 1257 Modelling of the Dynamic Earth from an Integrative Analysis of Potential Fields, Seismic Tomography and other Geophysical Data New global seismic model based on a simultaneous inversion (660 km) Ekström and Dziewonski, 1998 Gu et al., 2003

SPP 1257 Modelling of the Dynamic Earth from an Integrative Analysis of Potential Fields, Seismic Tomography and other Geophysical Data Inversion Scheme To calculate the effect of density variations on the geoid we use a direct method for solution of the differential equation system, which provides a possibility to model arbitrary distributions of density and viscosity with depth (Kaban et al., 2007).

SPP 1257 Modelling of the Dynamic Earth from an Integrative Analysis of Potential Fields, Seismic Tomography and other Geophysical Data Results of the Simultaneous Inversion (scaling factor)

SPP 1257 Modelling of the Dynamic Earth from an Integrative Analysis of Potential Fields, Seismic Tomography and other Geophysical Data Variations of the Model Parameters

SPP 1257 Modelling of the Dynamic Earth from an Integrative Analysis of Potential Fields, Seismic Tomography and other Geophysical Data Variations of the Model Parameters

SPP 1257 Modelling of the Dynamic Earth from an Integrative Analysis of Potential Fields, Seismic Tomography and other Geophysical Data Observed and Calculated Geoid

SPP 1257 Modelling of the Dynamic Earth from an Integrative Analysis of Potential Fields, Seismic Tomography and other Geophysical Data Impact of the transition zone boundaries

SPP 1257 Modelling of the Dynamic Earth from an Integrative Analysis of Potential Fields, Seismic Tomography and other Geophysical Data Summary and Perspectives 1. 1.The global model of the crust is principally improved in several key regions. This model provides a basis for construction of a global integrative density model of the crust and upper mantle Considering the transition zone provides much better similarity of the calculated and observed geoid relative to the previous tomography models. a. The calculated scaling factor and density jump for the 400-km discontinuity are very close to the mineral physics prediction. b. The effective density contrast for the 660, which characterizes its depth variations, is 4 times less than the PREM value. We analyze possible mineral physics applications of this result. c. In agreement with previous GIA studies, viscosity of the layer right above 660 is remarkably less than of the neighboring layers. 3. More results coming soon!

SPP 1257 Modelling of the Dynamic Earth from an Integrative Analysis of Potential Fields, Seismic Tomography and other Geophysical Data Thank you!