HR: 0830h
AN: S31E-0813    [PDF]
TI: Travel Time Tomography of the Uppermost Mantle Beneath Europe
AU: * Amaru, M
EM: amaru@geo.uu.nl
AF: Faculty of Earth Sciences Utrecht University, Postbus 80021, Utrecht, 3508 TA Netherlands
AU: Villasenor, A
EM: antonio@geo.uu.nl
AF: Faculty of Earth Sciences Utrecht University, Postbus 80021, Utrecht, 3508 TA Netherlands
AU: Spakman, W
EM: wims@geo.uu.nl
AF: Faculty of Earth Sciences Utrecht University, Postbus 80021, Utrecht, 3508 TA Netherlands
AB: We have obtained high-resolution P-wave and S-wave velocity models of the uppermost mantle beneath Europe using travel time tomography. The main purpose of this study was to create a model that accurately predicts regional travel times and also images the main tectonic features in Europe so that it can be used as background for more detailed local studies. To obtain this model we have applied a tomographic inversion method using a subset of well located events from the ISC bulletin which contains significantly more regional data than previous global data sets. Furthermore, improvements have been done in the methodology, including the use of a 3D ray-tracer, and an irregular grid parameterization, with cell sizes that depend on the ray density. In addition, a 3D reference model containing regional features is used, instead of a standard 1D reference velocity model. Because of the data selection and the ray path distribution, our results are comparable to Pn tomography but without the usual approximations required by that method. Synthetic tests show that anomalies with wavelengths of 45 km and 90 km horizontally can be reconstructed by the P and S model respectively. To investigate the influence of the new regional data alone, the inversion is first carried out using a 1D model (ak135) as reference/starting model. The results agree well with previous studies but more details are imaged. Next the inversion is performed using a 3D reference model. In the resulting model, tectonic features are not only imaged for the uppermost mantle but also for the crust. For example, structures like the Alps or the Pyrenees are imaged as prominent low-velocity features. To test the ability of the obtained model to predict travel times, travel time residuals are computed for well located earthquakes that are not part of the used data set. Generally, the model predicts the travel times better than the 1D reference model, particularly for regions of good ray coverage like Italy, where the travel time residuals computed with the new model are smaller than the residuals computed with the 1D reference model ak135.
DE: 7203 Body wave propagation
DE: 7218 Lithosphere and upper mantle
DE: 7294 Instruments and techniques
SC: Seismology [S]
MN: 2003 Fall Meeting