Crustal structure of the Main Ethiopian rift inferred from ambient noise tomography
Abstract
In this study, we estimate three-dimensional shear wave velocity model of the Main Ethiopian rift (MER) using the combined analyses of the ambient noise tomography and the depth inversion of the group velocity dispersion curves for Rayleigh waves. Considering the coverage of our data set, the estimated model is reliable over upper-to-lower crustal depths of the MER and surrounding plateaus. Our major findings are: (1) magma structures of the MER are dislocated in the boundary between the northern and the central MERs, (2) the magmatic body of the central MER is widespread and slants to the east, while its northern boundary contacts with the southern boundary (Ambo fault) of a NW-SE elongated high velocity zone beneath the northwestern plateau, and (3) low velocity structures are intruded to the region beneath the northwestern plateau surrounding the NW-SE high velocity zone. Our observations along with results from previous studies suggest that the northern and central MERs have propagated in opposite directions from the north and south, respectively. The high velocity structure beneath the northwestern plateau might play an important role in evolving the dislocated rift structure. This rift propagation model corresponds to the recent tomography result which suggests the existence of the separated upper mantle plumes in the Afar and the Kenya. The low velocity zone beneath the northwestern plateau indicates that the crust beneath plateau is modified by crustal magma activities, and the remaining high velocity zone may be a heterogeneous structure which formed before the MER initiation.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.T33D2445K
- Keywords:
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- 7205 SEISMOLOGY / Continental crust;
- 8123 TECTONOPHYSICS / Dynamics: seismotectonics;
- 8180 TECTONOPHYSICS / Tomography