Seismicity, fault architecture, and slip mode of the westernmost Gofar
transform fault
Abstract
Oceanic transform faults accommodate plate motions through both seismic
and aseismic slips. However, deformation partition and slip mode
interaction at these faults remain elusive mainly limited by rare
observations. We use one-year ocean bottom seismometer data collected in
2008 to detect and locate earthquakes at the westernmost Gofar transform
fault. The ultra-fast slipping rate of Gofar results in
~30,000 earthquakes during the observational period,
providing an excellent opportunity to investigate interrelations between
the slip mode, seismicity, and fault architecture at an unprecedented
resolution. Earthquake distribution indicates that the ∼100 km long
Gofar transform fault is distinctly segmentated into five zones,
including one zone contouring a M6 earthquake that was captured by the
experiment. Further, a barrier zone east of the M6 earthquake hosted
abundant foreshocks preceding the M6 event and halted its active
seismicity afterwards. The barrier zone has two layers of earthquakes at
depth, and they responded to the M6 earthquake differently.
Additionally, a zone connecting to the East Pacific Rise had
quasi-periodic earthquake swarms. The seismicity segmentation suggests
that the Gofar fault has multiple slip modes occurring in adjacent fault
patches. Spatiotemporal characteristics of the earthquakes suggest that
complex fault architecture and fluid-rock interaction play primary roles
in modulating the slip modes at Gofar, possibly involving multiple
concurrent physical processes.