The Mendocino Triple Junction is located in the Pacific Ocean near Cape Mendocino in northern California. This area is the most seismically active active regions of the San Andreas transform system . Seismologists have measured over 80 earthquakes each year since 1983 that are magnitude 3.0 or greater. This seismic activity is due to the plate motions between the three plates of the lithosphere that form the Mendocino Triple Junction.
What is a Triple Junction?
A triple junction is the intersection of three plate boundaries. Plates are either ridges (R), trenches (T), or transform faults (F).
The Three Plates of the Mendocino Triple Junction
The concentration of earthquakes at Cape Mendocino is known as the Mendocino Triple Junction. This junction is where the Gorda plate (a south section of the Juan de Fuca Plate), the North American plate, and the Pacific plate meet.
This map shows the triple junction (red arrow) off the coast of Oregon in the United States.
This animation shows the movement of the three plates.
Download GIS tectonic plates and boundaries data
The GIS tectonic plates and boundaries data used to create the map showing the three plates that form the Mendocino Triple Junction was downloaded from Github and is a conversion of the dataset originally published in the paper An updated digital model of plate boundaries by Peter Bird (Geochemistry Geophysics Geosystems, 4(3), 1027, doi:10.1029/2001GC000252, 2003).
References Oppenheimer, D. (2014). Mendocino Triple Junction Offshore Northern California. Retrieved from https://woodshole.er.usgs.gov/operations/obs/rmobs_pub/html/mendocino.html