Subducting Slab Thermo‐Petrologic Structure and Intermediate‐Depth Supra‐Slab Earthquakes Beneath Southern Colombia

Abstract We develop 2‐D thermo‐petrologic models for two transects through southern Colombia and compare the model‐predicted temperature distributions and depths of slab dehydration with seismological observations. Along the northern transect, earthquakes occur above the relatively young subducting Nazca slab at 80–160‐km depths. However, these intermediate‐depth supraslab earthquakes are largely absent along the southern transect. Our thermo‐petrologic models indicate that the maximum depth of decoupling (MDD) between the subducting slab and the overriding mantle is anomalously deep, at ∼180‐ and ∼130‐km depths for the northern and southern transects, respectively, likely due to the presence of an accreted oceanic terrane. With these MDDs, the model‐predicted thermal fields result in slightly deeper peak dehydration in the subducting slab along the northern transect compared to the southern transect, affecting the distribution of slab‐derived fluids, which may explain their contrasting distributions of supraslab and intraslab seismicity and Vp/Vs ratios.