Sea Beam/Deep‐Tow Investigation of an active oceanic propagating rift system, Galapagos 95.5°W

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Abstract
We have tested and corroborated the propagating rift hypothesis with high‐resolution Sea Beam and Deep‐Tow data collected over the Galapagos 95.5°W propagating rift system. The propagating rift is continuously breaking through the Cocos plate at a velocity of about 50 km/m.y. with an azimuth of about 273°, away from the Galapagos hotspot. This process transfers Cocos lithosphere to the Nazca plate, including the preexisting spreading center which fails as it is gradually preempted by the propagating rift. The spreading center azimuth is being changed by about 8° clockwise by this rift propagation. The active propagating and failing rift axes overlap by about 15 km and are joined by a broad and anomalously deep zone of nonrigid plate deformation rather than by a transform fault. Although rift propagation is continuous on a scale of a few kilometers (50,000 years), and lithospheric transferral from one plate to the other occurs mostly continuously, as the preexisting rift fails, it breaks into discrete segments. The geometry of seafloor fabric and tectonic elements such as active and failed rifts, the V‐shaped pattern of pseudofaults, and the oblique tectonic fabric in the sheared zone of transferred lithosphere are observed as predicted. This quantitative verification provides strong support for the propagating rift hypothesis.