New geological insights from Legacy Seismic Sections: Decoding the
Granada Basin (Spain)
Abstract
Seismic surveys are crucial for investigating subsurface geological
formations and require significant logistical and economic resources.
This study explores the reuse of legacy seismic surveys from the Granada
Basin conducted by the Chevron Oil Company in the mid-1980s to gain new
geological insights. In a previous paper, data from two deep boreholes
and 30 epochal seismic sections were recovered and reprocessed using
Machine Learning, and this work interprets the results to generate three
complete pseudo-three-dimensional models of the entire basin: a P-wave
velocity model, a sedimentary sequences model, and a fault systems
model. The sedimentary sequence model identified five distinct
depocenters with varying sediment compositions throughout the basin. The
study found a progressive decline in sediment accumulation rates over
time, from 0.18 mm/yr in the Tortonian to 0.10 mm/yr in the
Pliocene-Quaternary. This trend reflects changes in the sedimentary
system, moving from transitional platforms to regression and
transgression episodes and finally to a stable continental state. The
differences in sediment accumulation rates suggest that greater
disparities are linked to intense tectonic activity, while lower
differences indicate reduced tectonic activity and a consistent
sedimentary ratio since the Pliocene. Additionally, 17 new faults were
detected. Using the fault model and seismic activity data from 1984 to
2023 provided by the Andalusian Institute of Geophysics (IAG), a hazard
analysis was performed based on the maximum magnitude supported by each
fault, demonstrating the value of reusing vintage seismic data to update
geological models and improve our understanding of subsurface formations
and seismic hazards