Dike-fault interaction during the 2004 Dallol intrusion at the northern edge of the Erta Ale Ridge (Afar, Ethiopia)

During continental rifting the interaction between faulting and magmatic intrusions is not well understood. Using InSAR and seismicity, we show that a ∼0.06 km³ dike was intruded along the Dallol segment, Ethiopia and was accompanied by a M_w 5.5 earthquake and associated fault slip along the western flank of the rift. The intrusion was fed by a previously unidentified magma chamber under Dallol. The total seismic moment release was ∼2.3 × 10¹⁷ Nm, ∼10% of the geodetic moment. This is a higher proportion than during the 2005-2009 Dabbahu rifting episode, which ranged between 1-4% of the geodetic moment. A larger component of faulting occurs at Dallol than at Dabbahu segment, a feature we interpret to be related to the proximity (10 km) of the Dallol segment to the rift margin, where well-developed faults facilitate slip.