Abstract
Abstract The sequence of dyke intrusions between 2005 and 2010 in the Manda Hararo rift segment, Ethiopia, provided an opportunity to test conceptual models of continental rifting. Based on trends up to dyke 13 in the sequence, it was anticipated that, should magma supply continue, dykes would shorten in length and eruptions would increase in size and decrease in distance from the segment centre as extensional stress was progressively released. In this paper we revisit these predictions by presenting a comprehensive overview of the May 2010 dyke and fissure eruption, the 14th and last in the sequence, from InSAR, seismicity, satellite thermal data, ultraviolet SO 2 retrievals and multiple LiDAR surveys. We find the dyke is longer than other eruptive dykes in the sequence, propagating in two directions from the segment centre, but otherwise fairly typical in terms of opening, propagation speed and geodetic and seismic moment. However, though the eruption is located closer to the segment centre, it is much smaller than previous events. We interpret this as indicating that either the Manda Hararo rifting event was magma limited, or that extensional stress varies north and south of the segment centre.
Highlights
Erupted at the surface in extensional settings (Head et al 1996; Delaney et al 1998)
The earthquake swarms associated with the dykes originated at the segment centre in a region approximately 5 km in radius and .6 km depth (Belachew et al 2011): satellite geodesy revealed little to no deformation during intrusion except for the November 2007 and October 2008 intrusions, where a Mogi source cannot account for the volume intruded (Hamling et al 2009), while between intrusion deformation has been modelled as being consistent with re-inflation of a shallow composite sill –dyke magma body and a deeper body (Grandin et al 2010b; Hamling et al 2014)
The interferometric synthetic aperture radar (InSAR) and seismicity data show the dyke was intruded along the same axis as the earlier dykes in the sequence, with the seismicity lying mostly within the axial graben-bounding faults of the deformation model used by Hamling et al (2009, 2010) to model fault slip associated with earlier intrusions (Fig. 1)
Summary
Erupted at the surface in extensional settings (Head et al 1996; Delaney et al 1998). The current Manda Hararo rifting event began with the intrusion of an 80 km-long, 10 km-deep and 8 m-wide dyke running the full length of the segment between 20 September and 4 October 2005 (Wright et al 2006; Ayele et al 2007). This began with seismicity beneath Dabbahu at the segment tip, which jumped to the segment centre and subsequently propagated north and south along the rift, indicating the involvement of both central and satellite magma chambers (Ayele et al 2009). In this paper we test this prediction by integrating interferometric synthetic aperture radar (InSAR), seismicity, light detection and ranging (LiDAR) and thermal and ultraviolet satellite observations of the May 2010 dyking event
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