The Main Ethiopian Rift (MER) captures the transition from embryonic fault-controlled continental rifting in the south to more evolved magma-rich continental rifting in the north (e.g., .In the relatively mature central and northern MER, the locus of strain has largely shifted from 60 kmlong Miocene border faults to narrower (20 km-wide), Quaternary magmatic zones of short length-scale (1 km), small-offset faults (the Wonji Fault Belt, WFB:

<p>Continental rifting is currently active in East Africa, where breakup of the African continent is generally occurring in relatively focused rift zones within two uplifted plateaus, with magma intrusions the primary mechanism for strain accommodation throughout the crust and mantle lithosphere. Linking the two narrow rift valleys is the low-lying, and as-yet poorly studied Turkana Depression - an unusually broad 300km-wide region of diffuse faulting, seismicity and magmatism. How the East African Rift has developed here remains elusive and is complicated by the fact the Depression was variably stretched by several superposed episodes of failed rifting since the Mesozoic.</p> <p> </p> <p>Utilising data from the NSF-NERC-funded TRAILS seismic network, we produce the first detailed crustal and uppermost-mantle shear-wave velocity model below the Turkana Depression, illuminating Moho and lithosphere-asthenosphere boundary topography that ultimately shed light on rift development in a multiply-rifted region. We find Turkana’s lithosphere is relatively melt-poor, unlike the Ethiopian rift and Plateau further north, which have undergone extensive lithospheric modification by voluminous Cenozoic flood-basalt magmatism and magma-assisted rifting. The lower crust below rift zones in Turkana is not associated with markedly slow (melt) or fast (cooled gabbroic intrusions) wavespeeds suggesting magmatic extension has not dominated rift development in Turkana. Throughout the Depression, the thinnest crust resides within failed Mesozoic rift zones which the present-day East African Rift appears to circumnavigate, not exploit. Fast uppermost mantle wavespeeds below the thinnest crustal regions indicate post-Mesozoic rifting, re-equilibrated and possibly melt-depleted mantle lithosphere, which now renders the plate stronger and more refractory than regions not previously rifted. Refractory Proterozoic lithosphere also present in southern Ethiopia may have influenced strain localisation and the broad, complex rift zone between Ethiopia and Kenya.</p>

<p>Cyprus sits at the plate boundary between Anatolia in the north and Africa in the south, at a transition from oceanic subduction in the west to continental strike-slip and collision tectonics in the east. The nature of the plate boundary at Cyprus has been historically controversial and poorly understood, in part due to a lack of constraints on local seismicity. Ongoing subduction of either oceanic or continental African lithosphere is argued, with some invoking subduction of the Eratosthenes Seamount, a continental fragment to the south of Cyprus rising 2km above the sea floor, as a driver of uplift in Cyprus. At the centre and highest point of the Troodos ophiolite, which dominates the island, is the Mt Olympus mantle sequence, an outcrop of heavily serpentinised peridotite that is associated with a localised gravity low and proposed to be the top of a rising serpentinite diapir. Geophysical constraints to test these hypotheses at depth are lacking. </p> <p> </p> <p>We analyse data from a two-year deployment of five broadband seismometers along with the existing permanent network to create a new earthquake catalogue for Cyprus. We use our catalogue to constrain the first formalised 1-D velocity model for the island, improving earthquake locations. Earthquake hypocentres clearly delineate a northward-dipping African slab beneath Cyprus at 20-60 km depth. The most seismically active part of the island is at 15-20 km depth beneath the southern edge of the ophiolite, approximately the expected depth to the plate interface; thrust faulting focal mechanisms here are consistent with ongoing subduction. Hypocentral depths suggest a topography of the slab top, with the shallowest depths in the centre of the island, coincident with the greatest uplift in the overlying plate, supporting hypotheses of uplift driven by subduction of the Eratosthenes Seamount. A lack of seismicity in a 20km-wide zone at this ‘peak’ coincides with the outcropping Mt Olympus mantle sequence, and may be associated with the deep root of the proposed serpentinite diapir. </p>

<p>The island of Cyprus sits at the boundary between the Anatolian and African plates, at a transition between oceanic subduction and incipient continental collision. Seismicity has been recorded here for millenia, with at least 12 town-destroying earthquakes recorded over the last 2,000 years. However, the instrumental coverage on the island has remained poor until relatively recently, and there is no bespoke velocity model or local magnitude scale, meaning that local seismicity is relatively poorly understood. Larger earthquakes, mainly to the south and west of the island, have revealed a mix of strike-slip and reverse faulting mechanisms. More enigmatic is the onshore seismicity, and questions remain over deformation within the Cyprus slab and uplift mechanisms of the Troodos ophiolite. We investigate seismicity in and around the island, in order to better understand these processes and their associated seismic hazard. We combine records of a temporary deployment of five broadband seismometers with the 13 permanent broadband seismometers on the island, as well as two accelerometers, to create a two-year local earthquake catalogue. We locate earthquakes both within the overriding Cyprus crust and the underthrusting African plate, and identify previously unrecognised seismically active regions on the island, especially around the Troodos ophiolite. We use this earthquake catalogue to constrain a new 1-D velocity model and local magnitude scale for the region. We also constrain new focal mechanisms and interpret these in the context of the regional tectonics.</p>