Microseismicity Indicates Atypical Small-Scale Plate Rotation at the Quebrada Transform Fault System, East Pacific Rise

Closely spaced, multi-strand ridge transform faults (RTFs) accommodate relative motions along fast spreading mid-ocean ridges. However, the relations between RTFs and plate spreading dynamics are poorly understood. The Quebrada system is one of the most unique RTF systems at the East Pacific Rise, consisting of four transform faults connected by three short intra-transform spreading centers (ITSCs). We use seven-months of ocean bottom seismograph data to study the Quebrada system, and find abundant earthquakes unevenly distributed among three active faults. We identify two deep, diffuse seismicity clouds at the inside corners of the ITSC-transform fault intersections, and one seismically active fracture zone. The observations suggest a complex regional plate-motion pattern, including possible heterogeneous rotations within the Quebrada system. Evolution of multi-strand RTFs may have resulted from a strong three-dimensional local thermal and fluid effects, while the RTFs may have also regulated regional tectonics, forming an intricate feedback system.