What is the Mendocino Triple Junction ?

The Mendocino triple junction (MTJ) is the intersection of three tectonic plates in Western North America: The Pacific, North American and Gorda Plates (the Gorda plate is a subplate of the Juan de Fuca plate). The trench associated with the Cascadian Subduction Zone meets two right lateral transform faults: The Mendocino Fracture Zone and the San Andreas Fault (figure 1).

Figure 1. Map view of the plates converging in Northern California. The MTJ is the Northern end of the San Andreas fault, were the Pacific, North American and Juan de Fuca plates meet (from http://pubs.usgs.gov/publications/text/understanding.html ).

General Configuration:

- Gorda Plate is subducting beneath North America

- Right – lateral strike-slip along the San Andreas Fault (SAF)

- Right - lateral strike-slip along the Mendocino Fault Zone.

- Translation of the MTJ towards the north, pushed by the northward moving Pacific Plate.

Figure 2. Three-dimensional view of the plates converging at the MTJ (from http://geo.arizona.edu/researchers/tinker/research/MTJ/Evolution ).

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