The 2015 M7.1 Earthquake on the Northern Mid-Atlantic Ridge

The northern Mid-Atlantic Ridge forms a divergent tectonic boundary separating the North American and Eurasian plates. This segment of the global mid-ocean ridge system extends from the Azores triple junction northward toward Iceland and is characterized by slow seafloor spreading rates of approximately 20–25 mm per year. The ridge axis lies at depths of 2,000–3,000 m below sea level and is marked by a central rift valley where new oceanic crust is continuously generated through basaltic volcanism and normal faulting. On 13 February 2015 at 18:59 UTC, a magnitude 7.1 earthquake occurred directly on the northern Mid-Atlantic Ridge at a focal depth of 16.6 km. The event was centered at the ridge axis and produced no reported damage or tsunami because of its remote oceanic location. It remains the sole M7+ earthquake recorded along this segment since 2000. Seismic activity along the Mid-Atlantic Ridge is driven by extensional stresses that create steeply dipping normal faults parallel to the ridge axis. Although most ridge earthquakes are smaller than magnitude 6, larger events such as the 2015 shock can occur when longer fault segments rupture. The moderate focal depth of 16.6 km is consistent with the brittle–ductile transition zone in young oceanic lithosphere. Geologically, the Mid-Atlantic Ridge was first systematically mapped during the 1950s through bathymetric surveys that revealed its continuous axial valley and fracture-zone offsets. These observations provided key evidence for seafloor spreading and the theory of plate tectonics. Magnetic anomaly stripes symmetric about the ridge axis further documented the history of crustal accretion extending back tens of millions of years. The 2015 earthquake underscores the persistent tectonic forces operating at this divergent boundary. Continued monitoring by global seismic networks contributes to refined models of ridge segmentation and the mechanics of oceanic faulting.

References

USGS Earthquake Catalog (event parameters).
NOAA National Centers for Environmental Information (ridge bathymetry and spreading rates).
Macdonald, K. C. (2001). Mid-ocean ridge tectonics. Encyclopedia of Ocean Sciences.