Variable detachment strength along the Peruvian margin estimated from Critical Taper Analysis

Along the Peruvian margin, the subduction of the Nazca Plate beneath the South American Plate shows significant along-strike variability, including changes in slab dip and the subduction of major bathymetric features such as the Nazca Ridge and several fault zones. Seismic behavior along the Peruvian margin is likewise highly variable, ranging from frequent large megathrust earthquakes in southern Peru to comparably low seismicity in the north, where tsunami earthquakes have nevertheless caused significant historical damage.

To investigate the mechanical strength of the Peruvian forearc, we perform an areal critical taper analysis based on gridded surface slope and slab dip data. The results reveal significant spatial variations in detachment strength along the margin. South of the Nazca Ridge (~15°S), the forearc is characterized by a relatively strong detachment. The central segment (15°S–10°S) shows moderate to weak detachment strength, with particularly weak conditions near the trench. In northern Peru (10°S–4°S), the detachment is generally weak across the entire forearc. Overall, detachment strength tends to decrease toward the trench, except in the region affected by the subducting Nazca Ridge, where an increase in strength is observed.

The long-time-scale spatial variability in detachment strength correlates fairly well with interseismic coupling patterns derived from short-time-scale geodetic observations, with locked portions of the subduction interface generally characterized by higher detachment strength. In our study, we address the question of whether and how short-term seismic behavior is controlled by the long-term mechanical properties of the Peruvian forearc.