Sunday, April 17, 2016

Ecuador's Subduction Earthquake

A massive earthquake struck the Ecuador coast, northwest of Quito, yesterday evening.  Triggered by pressure release between the South American and Nazca Plates, the magnitude 7.8 quake was 20 times more powerful than the most recent 7.0 earthquake on Kyushu Island, Japan.

The Nazca Plate, a remnant of the Farallon oceanic Plate, is subducting beneath the South American Plate along the western coast of that Continent; the volcanic Andes Mountain Range formed (and continues to form) as the leading edge of the Nazca Plate melts near the outer surface of the Earth's mantle.  As the Nazca Plate advances (about 2 inches per year), friction builds between the Plates; this may release as a series of small quakes or as a mega-thrust event as occurred this weekend.

Numerous aftershocks typically follow such mega-thrust subduction earthquakes and have done so in this case.  To date, more than 260 persons have been killed and more than 2500 have been injured; considering the power and extent of this earthquake, one can expect both figures to rise significantly.  As with the recent Japan quakes, this earthquake was centered over land (16 miles SSE of Muisne) and a destructive tsunami did not develop.