A shallow M 4.7 quake struck today on the Septentrional Fault off Cap-Hatien in northern Haiti. Though small, two great quakes likely ruptured the fault in 1842 and 1887. The epicenter of the 1842 M~8 quake appears to coincide with today’s quake. While there is nothing that marks the M 4.7 as a foreshock, the possibility of an M 7 there is quite real.
With a fault slip rate of ~12 mm/yr and with 179 elapsed years (Ali, Freed, Calais, Manaker, and McCann Geophys. J. Int., 2008), more than 2 m of slip has since accumulated, enough to release a M~7 quake. The 2010 M 7.0 Leogane quake killed more than 200,000 people, demonstrating Haiti’s extreme vulnerability.