P-wave seismic interferometric profile within the Granada Basin (Southern-Spain)

Abstract

A detailed seismic imaging profile of the subsurface beneath the Granada Basin (southern Spain) has been generated using P-wave seismic interferometry applied to local microseismicity. The analysis, conducted along a 44 km long, SW–NE trending transect, used 117 well-located earthquakes (12–17 km depth) recorded by only three local stations between 1984 and 2024. Our imaging methodology applies Common Interferometry Points (CIPs), a geometric construction that approximates the stationary phase points for impulsive seismic sources. CIPs provide a robust spatial organization of the interferometric traces, enabling improved stacking, enhanced reflector continuity, and extensive subsurface illumination despite the sparse station coverage. The resulting seismic section reveals the complex crustal architecture in the central part of the basin, including a mid-crustal reflector at 10–15 km depth. This low-angle structure is interpreted as being part of the basal detachment of the basin, decoupling the brittle upper crust from the ductile part. The detachment roots major normal faults that generate horst-and-graben structures within the basin. Integration with four decades of instrumental seismicity supports this structural interpretation and demonstrates the potential of the method to recover deep crustal structure in tectonically active and logistically challenging regions.