Modelling the seismic velocity structure beneath Indonesia: a comparison with tomography

Studies of the geodynamic evolution of Southeast Asia have resulted in a nu mber of tectonic reconstructions that exhibit a broad consensus as well as significant differences. In this contribution we apply a method to further test these surface reconstructions, using independent seismic tomography re sults. Our kinematic modelling procedure comprises the calculation of three -dimensional forward models of the seismic velocity structure beneath Indon esia. From information contained in the tectonic reconstructions, the effec t of the proposed surface motions on the thermal structure of the underlyin g mantle is modelled. This results in a prediction of the present-day tempe ratures which are converted into seismic (P-wave) velocity anomalies. By co mparing the predicted velocity models with recent tomography results of the area, the quality of the tectonic reconstructions can be evaluated. The mo dels presented in this paper are based on the reconstructions of Rangin et al. (Bull. Sec. Geol. France, 8 (1990a) 889; Bull. Sec. Geol. France, 8 (19 90b) 907) and Lee and Lawyer (Tectonophysics, 251 (1995) 85). In general, w e conclude that the calculated positive velocity anomalies beneath the Sund a and Banda are show strong similarities with the tomography results. The m odelled patterns of high velocities beneath southern Sulawesi are not found in the tomographic images. The model predicted from Rangin et al. (1990a,b ) does not show the double-sided subduction under the Molucca Sea region th at can be seen in the model predicted from Lee and Lawyer (1995) and in the tomographic model. Our results indicate the potential of the method for in vestigating the geodynamic evolution of the Indonesian region. (C) 2001 Els evier Science B.V. All rights reserved.