Imaging deep structures of Makran subduction zone by 3D joint inversion of gravity data and Rayleigh wave group velocities
عنوان دوره: نوزدهمین کنفرانس ژئوفیزیک ایران
نویسندگان
1موسسه ژئوفیزیک دانشگاه تهران
2استاد، دانشکدة علوم زمین، دانشگاه پاریس-سود، فرانسه
3استاد، موسسه ژئوفیزیک دانشگاه تهران
4دانشیار، مؤسسه ژئوفیزیک دانشگاه تهران
چکیده
In this study, we developed a method to invert jointly gravity anomalies and Rayleigh wave group velocities for velocity and density structure of the crust and upper mantle. We applied the method to the Makran region, SE Iran. The reason for using different data sets is that each of these data sets is sensitive to different parameters. Surface wave group velocities are sensitive mainly to shear wave velocity distribution in depth but do not well resolve density variations. Therefore, joint inversion with gravity data increases the resolution of density distribution. Our approach differs from others mainly in the model parameterization: Instead of subdividing the model into a large number of thin layers, we invert for the properties of only four layers: thickness, P- and S-wave velocities and densities and their vertical gradients in sediments, upper-crust, lower-crust and upper mantle. The method is applied first to synthetic models in order to demonstrate its usefulness. We then applied the method to real data to investigate the lithosphere structure beneath the Makran. The resulting model shows that Moho depth increases from Oman Sea and Makran fore-arc to the volcanic-arc. The crustal density is high in the Oman Sea as should be expected for the oceanic crust.
کلیدواژه ها
 
Title
Imaging deep structures of Makran subduction zone by 3D joint inversion of gravity data and Rayleigh wave group velocities
Authors
Somayeh Abdollahi, Hermann Zeyen, Vahid Ebrahimzadeh Ardestani, Zaher Hossein Shomali
Abstract
In this study, we developed a method to invert jointly gravity anomalies and Rayleigh wave group velocities for velocity and density structure of the crust and upper mantle. We applied the method to the Makran region, SE Iran. The reason for using different data sets is that each of these data sets is sensitive to different parameters. Surface wave group velocities are sensitive mainly to shear wave velocity distribution in depth but do not well resolve density variations. Therefore, joint inversion with gravity data increases the resolution of density distribution. Our approach differs from others mainly in the model parameterization: Instead of subdividing the model into a large number of thin layers, we invert for the properties of only four layers: thickness, P- and S-wave velocities and densities and their vertical gradients in sediments, upper-crust, lower-crust and upper mantle. The method is applied first to synthetic models in order to demonstrate its usefulness. We then applied the method to real data to investigate the lithosphere structure beneath the Makran. The resulting model shows that Moho depth increases from Oman Sea and Makran fore-arc to the volcanic-arc. The crustal density is high in the Oman Sea as should be expected for the oceanic crust.
Keywords
Rayleigh wave group velocity, Gravity, Joint Inversion, Moho Depth, Shear velocity