A. Delorme

September 2005 Manda Hararo‐Dabbahu rifting event, Afar (Ethiopia): Constraints provided by geodetic data

faults. The volume of the 2005 dike (1.5–2.0 km 3 ) is not balanced by sufficient volume loss at Dabbahu and Gabho volcanoes (0.42 and 0.12 km 3 , respectively). Taking into account the deflation of a suspected deep midsegment magma chamber simultaneously to dike intrusion produces a smoother opening distribution along the southern segment. Above the dike, faults slipped by an average 3 m, yielding an estimated geodetic moment of 3.5 � 10 19 Nm, one order of magnitude larger than the cumulative seismic moment released during the earthquake swarm. Between Dabbahu and Ado’Ale volcanic complexes, significant opening occurred on the western side of the dike. The anomalous location of the dike at this latitude, offset to the east of the axial depression, may explain this phenomenon. A two-stage intrusion scenario is proposed, whereby rifting in the northern Manda Hararo Rift was triggered by magma upwelling in the Dabbahu area, at the northern extremity of the magmatic segment. Although vigorous dike injection occurred during the September 2005 event, the tectonic stress deficit since the previous rifting episode was not fully released, leading to further intrusions in 2006–2009.

Geological structures control on earthquake ruptures: The Mw7.7, 2013, Balochistan earthquake, Pakistan

The 2013 Mw 7.7 Balochistan earthquake, Pakistan, ruptured the Hoshab fault. Left-lateral motion dominated the deformation pattern, although significant vertical motion is found along the southern part of the rupture. Correlation of high-resolution (2.5 m) optical satellite images provided horizontal displacement along the entire rupture. In parallel, we mapped the ground rupture geometry at 1:500 scale. We show that the azimuth of the ground rupture distributes mainly between two directions, N216° and N259°. The direction N216° matches the direction of pre-existing geologic structures resulting from penetrative deformation caused by the near-by Makran subduction. Hence, during a significant part of its rupture, the 2013 Balochistan rupture kept switching between a long-term fault front and secondary branches, which existence and direction are related to the compressional context. It shows unambiguous direct interactions between different pre-existing geologic structures, regional stress, and dynamic-rupture stress, which controlled earthquake propagation path.