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Abstract:
The intermediate-depth seismicity (IDS) beneath the Gibraltar Arc is enigmatic. So far, there is no
general consensus on its relationship with the ongoing tectonic processes. We analyzed S wave receiver
functions (SRFs) with data recorded by a dense N-S seismic profile deployed across the Sierra Nevada in
southern Spain. SRF piercing points at depths of the lithosphere-asthenosphere boundary (LAB) sample an
area of the IDS zone, providing an ideal opportunity to study the lithospheric structure at the IDS zone. We
observe an abrupt change in the LAB depth along a profile from north to south across the northern
branch of the IDS. The LAB depth changes from 90 to 100 km north of the IDS to ~130 km south of it. We
propose that the IDS marks a tear in the Iberian mantle lithosphere along its entire length, implying an
ongoing lithospheric delamination process that produces the seismicity at its onset.
