资源环境科技发展态势分析平台

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 100km north of the IDS to similar to 130km 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.