The Granada Basin (Depresión de Granada) is located in the Central Betic Cordillera of Southern Spain. It is bounded by active normal faults (e.g., Santa Fe, Atarfe, Chauchina, Sierra Elvira) undergoing active NW-SE to NE-SW extensional crustal stress.
Why Seismic Swarms? Unlike classic mainshock-aftershock sequences with a single dominant rupture, the Granada Basin frequently experiences seismic swarms characterized by hundreds to thousands of shallow (< 10 km) moderate earthquakes clustered in space and time over days or weeks (e.g., the notable 2021 Santa Fe – Atarfe swarm). These swarms are driven by pore-fluid overpressures interacting with high fracture-density fault gouge.
Key Seismological Metrics in this Workbench:
- Gutenberg-Richter b-value: Swarm sequences typically exhibit high b-values (> 1.1–1.4) indicating smaller average magnitude events and low effective normal stress with fluid migration.
- Modified Omori-Utsu Law: Models aftershock temporal decay:
n(t) = K / (t + c)^p, where p ~ 0.9–1.2.
- EMS-98 & Soil Amplification: The soft alluvial sediments of the Vega de Granada basin cause pronounced resonant amplification of S-waves and surface waves, leading to sharp localized shaking felt strongly overnight.