Crustal Structure Beneath the Malawi and Luangwa Rift Zones and Adjacent Areas from Ambient Noise Tomography
Abstract
Crustal shear wave velocity structure beneath the Malawi and Luangwa Rift Zones (MRZ and LRZ, respectively) and adjacent regions in southern Africa is imaged using fundamental mode Rayleigh waves recorded by 31 SAFARI (Seismic Arrays for African Rift Initiation) stations. Dispersion measurements estimated from empirical Green's functions are used to construct 2-D phase velocity maps for periods between 5 and 28 s. The resulting Rayleigh wave phase velocities demonstrate significant lateral variations and are in general agreement with known geological features and tectonic units within the study area. Subsequently, we invert Rayleigh wave phase velocity dispersion curves to construct a 3-D shear wave velocity model. Beneath the MRZ and LRZ, low velocity anomalies are found in the upper-most crust, probably reflecting the sedimentary cover. The mid-crust of the MRZ is characterized by an ~3.7% low velocity anomaly, which cannot be adequately explained by higher than normal temperatures alone. Instead, other factors such as magmatic intrusion, partial melting, and fluid-filled deep crustal faults might also play a role. Thinning of the crust of a few kilometers beneath the rifts is revealed by the inversion. A compilation of crustal thicknesses and velocities beneath the world's major continental rifts suggests that both the MRZ and LRZ are in the category of rifts beneath which the crust has not been sufficiently thinned to produce widespread syn-rifting volcanisms.
Recommended Citation
T. Wang et al., "Crustal Structure Beneath the Malawi and Luangwa Rift Zones and Adjacent Areas from Ambient Noise Tomography," Gondwana Research, vol. 67, pp. 187 - 198, Elsevier Inc., Mar 2019.
The definitive version is available at https://doi.org/10.1016/j.gr.2018.10.018
Department(s)
Geosciences and Geological and Petroleum Engineering
Research Center/Lab(s)
Center for High Performance Computing Research
Keywords and Phrases
Ambient noise tomography; Crustal structure; Luangwa Rift Zone; Malawi Rift Zone
International Standard Serial Number (ISSN)
1342-937X
Document Type
Article - Journal
Document Version
Citation
File Type
text
Language(s)
English
Rights
© 2019 International Association for Gondwana Research, All rights reserved.
Publication Date
01 Mar 2019