The northern Aegean is the place where two different geologies hand off to each other. To the east, the North Anatolian Fault runs through the Sea of Marmara as a long strike-slip wound, the Anatolian plate sliding westward against the Eurasian plate. To the south and west, the Hellenic arc rules - the African plate plunging beneath Greece, generating extensional tectonics, the slow stretching apart of the Aegean basin. The May 2014 epicenter sat right in the transition. Aftershock distribution and the focal mechanism showed dextral, right-lateral strike-slip motion on a roughly west-southwest to east-northeast trending fault, which seismologists interpret as the western continuation of the North Anatolian system, still pushing west, still cutting through the seabed. Earlier earthquakes had hinted at this geometry - a magnitude-6.6 in 1975, a 5.7 in 2003 - but 2014 was the clearest signal yet.

Backprojection analysis of strong-motion waveforms showed that the earthquake actually involved two separate fault segments. A shorter section ruptured first, west of the hypocenter. Then the rupture jumped east and tore along a longer, 65-kilometer segment - and on this longer segment, propagation occurred at speeds well in excess of the local shear-wave velocity. That detail matters more than it sounds. Supershear ruptures focus seismic energy in narrow Mach cones, can produce unusually intense ground motion in directions ahead of the rupture front, and are rare enough that each documented case adds significantly to what we know about how faults break. The 2014 Aegean event joined a small club: only a handful of earthquakes worldwide have been confirmed as supershear, including the 2001 Kunlun event in Tibet and parts of the 2002 Denali rupture in Alaska. For a fault under fifty meters of seawater between two NATO countries, that was unexpected company.

The shock did real harm even if the magnitude was modest. On the Turkish island of Imbros - now officially Gökçeada, off Turkey's northern Aegean coast - old houses cracked and walls fell. Thirty people were taken to hospitals with minor injuries. In Çanakkale on the mainland Turkish coast, the governor reported 324 injuries in his province alone, and three deaths confirmed in the broader earthquake area. Eleven houses collapsed across Greek territory; on the island of Lemnos, plaster fell from walls. Two churches and thirteen mosques were damaged to varying extents - a tally that captures something about the ethnic geography of this corner of the Aegean, where Greek and Turkish populations have been pulled apart and stirred together for centuries. The shaking was felt in Bulgaria, in southern Romania, on the Greek mainland. For a few minutes that morning, an enormous swath of southeastern Europe stopped what it was doing and looked at the lights swaying.

The death toll is small enough to be easy to skip past, and that is exactly the wrong instinct. Three people died in the broader earthquake area, according to Çanakkale officials - real human beings whose families that morning had not expected to be making funeral arrangements. Early reports also noted at least one heart attack in the affected zone, though the connection to the earthquake was never formally confirmed. The 324 injured on the Turkish side and the patients in Imbros's hospital had stories of their own: walls that fell on them in their kitchens, glass that came out of windows, panic that drove them into stairwells where the shaking did the rest. A magnitude-6.9 earthquake in a populated region is never just a seismological event. The supershear physics will end up in a research paper. The funerals were privately held. Both are part of what 24 May 2014 means.