The 2019 M7.5 Earthquake Near Palora, Ecuador: Geological Setting and Seismic History

On February 22, 2019, at 10:17 local time, a magnitude 7.5 earthquake struck 115 km east-southeast of Palora, Ecuador, at a depth of 145 km. This intermediate-depth event was the strongest recorded in the country since 2000 and originated within the subducting slab beneath the Andean margin. Ecuador sits at a convergent plate boundary where the Nazca Plate descends beneath the South American Plate at rates of approximately 5–7 cm per year. This subduction drives the formation of the Ecuadorian Andes and produces both shallow crustal earthquakes and deeper intraslab events. The February 2019 hypocenter lies within the steeply dipping portion of the slab, consistent with the region’s characteristic seismicity at depths between 100 and 200 km. The tectonic regime also features the Carnegie Ridge, an oceanic plateau that influences slab geometry and contributes to along-strike variations in seismicity. East of the volcanic arc, the sub-Andean zone accommodates shortening through thrust faults, although the 2019 rupture occurred well below this shallow deformation belt. Ecuador has a long record of destructive earthquakes. Notable events include the 1797 Riobamba earthquake (estimated M 7.5–8.0), the 1949 Ambato earthquake (M 6.8), and the 2016 Pedernales earthquake (M 7.8). Intermediate-depth events similar to the 2019 quake have occurred historically but rarely exceed magnitude 7.0 in the modern catalog. The 2019 earthquake produced felt shaking across much of eastern and central Ecuador, with peak intensities reaching VI on the Modified Mercalli scale near the epicentral region. Because of its depth, surface damage was limited compared with shallow events, though minor landslides and rockfalls were reported in the rugged Andean foothills. No fatalities were directly attributed to the mainshock. Seismic monitoring by the Instituto Geofísico at the Escuela Politécnica Nacional recorded numerous aftershocks, all smaller than magnitude 5.0 and clustered near the mainshock depth. These aftershocks confirmed the intraslab nature of the rupture and helped delineate the geometry of the downgoing Nazca Plate. Ongoing research integrates data from the 2019 sequence with regional tomography to refine models of slab hydration and dehydration reactions that control intermediate-depth seismicity. Such studies support improved seismic hazard assessments for Ecuador’s populated inter-Andean valleys.

References

USGS Earthquake Catalog (event page for 2019-02-22 M 7.5 Ecuador)
Instituto Geofísico, Escuela Politécnica Nacional – Informe Sísmico 2019
Global CMT Catalog – Centroid-moment tensor solution for 2019 Ecuador event