Mona Passage - Structure and Seismicity

Structure and Seismicity

The Passage was also the site of a devastating earthquake and resulting tsunami that hit western Puerto Rico in 1918. It is the site of frequent small earthquakes. The passage is underlain by a seismically active rift zone that overprints an older partly eroded tilted-block structure. Desecheo Island sits on the Desecheo ridge, a narrow east - west ridge that extends west from the northwest corner of Puerto Rico. The ridge forms the southern boundary of the 4000 m deep Mona rift which extends toward the north to the strike slip fault zones which bound Puerto Rico and Hispanola. The east face of the rift has a sharp relief of 3 km and is controlled by the N - S trending Mona Rift Fault. The epicenter of the 1918 earthquake was located along the east or southeast edge of the Mona Rift.