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Dataset related to: La Rosa, A., Raggiunti, M., Pagli, C., Keir, D., Wang, H. and Ayele, A (2023).Extensional Earthquakes in the Absence of Magma in Northern Afar: Insights from InSAR. Geophysical Research Letters, 50, e2023GL102826. https://doi.org/10.1029/2023GL102826 The dataset contains the unwrapped interferograms, incidence angles and related resource files, along with the distributed slip model presented in the paper.

The roughly 3000 km long East Africa Rift system (EARS) is one of the striking features of the African continent that captures all stages of rift development from the most juvenile to nascent seafloor spreading in Okavango delta and Afar depression, respectively. It provides a natural laboratory for studying a fundamental, and yet enigmatic, component of plate tectonics. A mechanism for rupturing thick, cold, continental lithosphere is not readily apparent in conventional models of mechanical stretching. However, magma production weakens the plate and serve to localize strain, thus better facilitating rifting. Studies of seismicity and volcanism provide insights into this problem and a variety of geophysical, geochemical and geological studies can be used to better understand the role of the crust and mantle in continental breakup. Permanent seismic station distribution is sparse in the continent but some focused and detailed studies have been conducted using temporary broad seismic networks in collaboration with overseas researchers. Earthquakes of magnitude M > 7.0 are observed in EARS from instrumentally recorded seismicity (the 1910 Rukwa earthquake in Tanzania, the 1990 earthquake in South Sudan and the 2006 Machase earthquake in Mozambique) which is a wakeup call for the fast growing construction industry in the region. It is also inferred that the EARS is more active than we think, from recently recorded seismicity, which requires collaborative efforts to enhance studies in the region both for basic science research and disaster risk management purposes., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Geophysical Research Abstracts, 21, ISSN:1029-7006, ISSN:1607-7962

The Boset-Bericha Volcanic Complex (BBVC) is one of the largest stratovolcanoes of the northern Main Ethiopian Rift (MER). However, very little is known about its eruptive history, despite the fact that approximately 4 million people live within 100 km of the complex. Here, we combine field observations, morphometric analysis using high-resolution LiDAR data, geochemistry and 40Ar/39Ar geochronology to report the first detailed account of the geological evolution of the BBVC, with a focus on extensive young lava flows covering the two edifices, Gudda and Bericha. These lavas exhibit a bimodal composition ranging dominantly from basaltic rift floor lavas and scoria cones, to pantelleritic trachytes and rhyolite flows at Gudda, and comenditic rhyolites at Bericha. Further, several intermediate compositions are associated with fissure vents along the Boset-Kone segment that also appear to link the silicic centres. We divide the BBVC broadly into four main eruptive stages, comprising: (1) early rift floor emplacement, (2) formation of Gudda Volcano within two main cycles, separated by caldera formation, (3) formation of the Bericha Volcano, and (4) sporadic fissure eruptions. Our new 40Ar/39Ar geochronology, targeting a representative array of these flows, provides evidence for episodic activity at the BBVC from ~ 120 ka to the present-day. We find that low-volume mafic episodes are more frequent (~ 10 ka cyclicity) than felsic episodes (~ 100 ka cyclicity), but the latter are more voluminous. Over the last ~ 30 ka, mafic to intermediate fissure activity might have reinvigorated felsic activity (over the last ~ 16 ka), manifested as peralkaline lava flows and pyroclastic deposits at Gudda and Bericha. Felsic episodes have on average a higher eruption rate (2–5/1000 years) and productivity at Gudda compared to Bericha (1–2/1000 years). The young age of lavas and current fumarolic activity along the fault system, suggest that the BBVC is still potentially active. Coincident episodic activity within the BBVC and at several rift segments in the MER is observed, and facilitates continental rifting.

The Boset-Bericha Volcanic Complex (BBVC) is one of the largest stratovolcanoes of the northern Main Ethiopian Rift (MER). However, very little is known about its eruptive history, despite the fact that approximately 4 million people live within 100 km of the complex. Here, we combine field observations, morphometric analysis using high-resolution LiDAR data, geochemistry and 40Ar/39Ar geochronology to report the first detailed account of the geological evolution of the BBVC, with a focus on extensive young lava flows covering the two edifices, Gudda and Bericha. These lavas exhibit a bimodal composition ranging dominantly from basaltic rift floor lavas and scoria cones, to pantelleritic trachytes and rhyolite flows at Gudda, and comenditic rhyolites at Bericha. Further, several intermediate compositions are associated with fissure vents along the Boset-Kone segment that also appear to link the silicic centres. We divide the BBVC broadly into four main eruptive stages, comprising: (1) early rift floor emplacement, (2) formation of Gudda Volcano within two main cycles, separated by caldera formation, (3) formation of the Bericha Volcano, and (4) sporadic fissure eruptions. Our new 40Ar/39Ar geochronology, targeting a representative array of these flows, provides evidence for episodic activity at the BBVC from ~ 120 ka to the present-day. We find that low-volume mafic episodes are more frequent (~ 10 ka cyclicity) than felsic episodes (~ 100 ka cyclicity), but the latter are more voluminous. Over the last ~ 30 ka, mafic to intermediate fissure activity might have reinvigorated felsic activity (over the last ~ 16 ka), manifested as peralkaline lava flows and pyroclastic deposits at Gudda and Bericha. Felsic episodes have on average a higher eruption rate (2–5/1000 years) and productivity at Gudda compared to Bericha (1–2/1000 years). The young age of lavas and current fumarolic activity along the fault system, suggest that the BBVC is still potentially active. Coincident episodic activity within the BBVC and at several rift segments in the MER is observed, and facilitates continental rifting.

Continental rifting is a fundamental component of plate tectonics. Recent studies have highlighted the importance of magmatic activity in accommodating extension during late-stage rifting, yet the mechanisms by which crustal thinning occurs are less clear. The Red Sea rift in Northern Afar presents an opportunity to study the final stages of continental rifting as these active processes are exposed subaerially. Between February 2011 and February 2013 two seismic networks were installed in Ethiopia and Eritrea. We locate 4,951 earthquakes, classify them by frequency content, and calculate 31 focal mechanisms. Results show that seismicity is focused at the rift axis and the western marginal graben. Rift axis seismicity accounts for ∼64% of the seismic moment release and exhibits a swarm-like behavior. In contrast, seismicity at the marginal graben is characterized by high-frequency earthquakes that occur at a constant rate. Results suggest that the rift axis remains the primary locus of seismicity. Low-frequency earthquakes, indicative of magmatic activity, highlight the presence of a magma complex ∼12 km beneath Alu-Dalafilla at the rift axis. Seismicity at the marginal graben predominantly occurs on westward dipping, antithetic faults. Focal mechanisms show that this seismicity is accommodating E-W extension. We suggest that the seismic activity at the marginal graben is either caused by upper crustal faulting accommodating enhanced crustal thinning beneath Northern Afar or as a result of flexural faulting between the rift and plateau. This seismicity is occurring in conjunction with magmatic extension at the rift axis, which accommodates the majority of long-term extension.