Fault-magma interactions during early continental rifting: Seismicity of the Magadi-Natron-Manyara basins, Africa

Simple item page
dc.contributor.authorWeinstein, A., C. J. Ebinger, S. J. Oliva, S. Roecker, C. Tiberi, M. Aman, C. Lambert, E. Witkin, J. Albaric, S. Gautier, A. Muzuka, G. Mulibo, G. Kianji, R. Hadfield, F. Illsley-Kemp, M. Msabi, R. Ferdinand-Wambura, S. Perrot, J. Muirhead, A. Rodzianko, T. Fischer
dc.date.accessioned2021-04-20T14:09:26Z
dc.date.available2021-04-20T14:09:26Z
dc.date.issued2017-11-16
dc.description.abstractAlthough magmatism may occur during the earliest stages of continental rifting, its role in strain accommodation remains weakly constrained by largely 2-D studies. We analyze seismicity data from a 13 month, 39-station broadband seismic array to determine the role of magma intrusion on state-of-stress and strain localization, and their along-strike variations. Precise earthquake locations using cluster analyses and a new 3-D velocity model reveal lower crustal earthquakes beneath the central basins and along projec- tions of steep border faults that degas CO2. Seismicity forms several disks interpreted as sills at 6–10 km below a monogenetic cone field. The sills overlie a lower crustal magma chamber that may feed eruptions at Oldoinyo Lengai volcano. After determining a new ML scaling relation, we determine a b-value of 0.87 6 0.03. Focal mechanisms for 65 earthquakes, and 13 from a catalogue prior to our array reveal an along-axis stress rotation of 􏰉608 in the magmatically active zone. New and prior mechanisms show pre- dominantly normal slip along steep nodal planes, with extension directions 􏰉N908E north and south of an active volcanic chain consistent with geodetic data, and 􏰉N1508E in the volcanic chain. The stress rotation facilitates strain transfer from border fault systems, the locus of early-stage deformation, to the zone of magma intrusion in the central rift. Our seismic, structural, and geochemistry results indicate that frequent lower crustal earthquakes are promoted by elevated pore pressures from volatile degassing along border faults, and hydraulic fracture around the margins of magma bodies. Results indicate that earthquakes are largely driven by stress state around inflating magma bodies.en_US
dc.description.sponsorshipNSF . Grant Numbers: EAR‐1113355 , ANR‐12‐JS06‐000401en_US
dc.identifier.citationWeinstein, A., et al. (2017), Fault-magma interactions during early continental rifting: Seismicity of the Magadi-Natron-Manyara basins, Africa, Geochem. Geophys. Geosyst., 18, 3662– 3686, doi:10.1002/2017GC007027.en_US
dc.identifier.doidoi:10.1002/2017GC007027
dc.identifier.urihttp://hdl.handle.net/20.500.11810/5639
dc.language.isoenen_US
dc.publisherWileyen_US
dc.titleFault-magma interactions during early continental rifting: Seismicity of the Magadi-Natron-Manyara basins, Africaen_US
dc.typeJournal Article, Peer Revieweden_US
Files
Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
Name:
Weinstein_etal-GJI2017-Gcubed.pdf
Size:
9.73 MB
Format:
Adobe Portable Document Format
Description:
Main article
Download
License bundle
Now showing 1 - 1 of 1
No Thumbnail Available
Name:
license.txt
Size:
1.71 KB
Format:
Item-specific license agreed upon to submission
Description:
Download
Collections
Department of Geology
Department of Geosciences