TY - JOUR
T1 - InSAR Observations of 2007 Tanzania Rifting Episode Reveal Mixed Fault and Dyke Extension in an Immature Continental Rift
AU - Biggs, Juliet
AU - Amelung, Falk
AU - Gourmelem, Noel
AU - Dixon, Timothy H.
AU - Kim, Sang-Wan
PY - 2009/10/1
Y1 - 2009/10/1
N2 - In the early stages of continental rifting, extension takes place by normal faulting, while in mature continental rifts dyke intrusion dominates. Little is known about the nature of the transition between fault-controlled and dyke-controlled extension or about the processes in an intermediate setting. Here, we present observations of the temporal and spatial evolution of surface displacements during the 2007 July 14–August 4 rifting episode in Northern Tanzania, an immature section of the East African Rift. The ground deformation initiated with subsidence that can be attributed to ∼40 cm of normal motion on a NE striking fault. Following July 17, deformation was dominated by the intrusion of ∼7-km-long dyke. Dyke opening increased gradually to a total of ∼2.4 m. From July 21, the collapse of a shallow graben above the fault dominated the near-field displacements. Comparison to the 2007 Dabbahu dyke, Afar, which occurred in a more mature rift, shows an order-of-magnitude scale difference in dyke length. Using numerical models of dyke propagation, we attribute this to the size and depth of the magma chamber; in immature rifts the thick crust and slow spreading rate favour small, deep magma chambers, forming short, buried dykes, whereas in mature rifts the thinner crust and faster spreading rate favour large, shallow magma chambers and long, erupting dykes. Observing the pattern of active processes in the East African Rift is key to understanding the development of rift systems and passive margins elsewhere.
AB - In the early stages of continental rifting, extension takes place by normal faulting, while in mature continental rifts dyke intrusion dominates. Little is known about the nature of the transition between fault-controlled and dyke-controlled extension or about the processes in an intermediate setting. Here, we present observations of the temporal and spatial evolution of surface displacements during the 2007 July 14–August 4 rifting episode in Northern Tanzania, an immature section of the East African Rift. The ground deformation initiated with subsidence that can be attributed to ∼40 cm of normal motion on a NE striking fault. Following July 17, deformation was dominated by the intrusion of ∼7-km-long dyke. Dyke opening increased gradually to a total of ∼2.4 m. From July 21, the collapse of a shallow graben above the fault dominated the near-field displacements. Comparison to the 2007 Dabbahu dyke, Afar, which occurred in a more mature rift, shows an order-of-magnitude scale difference in dyke length. Using numerical models of dyke propagation, we attribute this to the size and depth of the magma chamber; in immature rifts the thick crust and slow spreading rate favour small, deep magma chambers, forming short, buried dykes, whereas in mature rifts the thinner crust and faster spreading rate favour large, shallow magma chambers and long, erupting dykes. Observing the pattern of active processes in the East African Rift is key to understanding the development of rift systems and passive margins elsewhere.
KW - satellite geodesy
KW - radar interferometry
KW - continental margins: divergent
KW - physics of magma and magma bodies
KW - Africa
UR - https://digitalcommons.usf.edu/geo_facpub/439
UR - https://doi.org/10.1111/j.1365-246X.2009.04262.x
U2 - 10.1111/j.1365-246X.2009.04262.x
DO - 10.1111/j.1365-246X.2009.04262.x
M3 - Article
VL - 179
JO - Geophysical Journal International
JF - Geophysical Journal International
ER -