Morphotectonic fabric of the Orozco Transform Fault: Results From a Sea Beam investigation

Abstract

We have used data collected with the Sea Beam system to produce a detailed regional bathymetric map of the medium to fast slipping (90 mm/yr) Orozco Transform Fault. The morphotectonic fabric of the 90 × 50 km transform domain is spatially heterogeneous and is composed of relatively shallow areas (<2800 m) bounded by E‐W and N‐S trending troughs and basins (>3200 m). The plate boundary geometry is clearly identified morphologically and is characterized by a series of linked basins and troughs that approximate a zed pattern in plan view. East‐west trending basins define the northern and southern boundaries of the transform domain, and these troughs are thought to mark the location of strike‐slip tectonism. A central, north‐south trending ridge with an axial valley, called here the Mid‐Orozco spreading center, is thought to represent a short (30 km) ridge segment that links two transform faults. Morphotectonic relationships developed along the southeastern flank of the survey area suggest that this plate boundary geometry has recently become unstable and is presently undergoing a transformation as the tip of the East Pacific Rise axis propagates northward across the transform domain bypassing the Mid‐Orozco spreading center. If the southern ridge axis continues to propagate northward it will link with the aseismic extension of the northern strike‐slip strand and the present‐day plate boundary will evolve into a simple ridge‐transform‐ridge (R‐T‐R) geometry with an offset of approximately 70 km.