On 11 October 1918, the western coast of Puerto Rico was hit by a major earthquake which caused a tsunami. The 1918 earthquake was caused by an old left-lateral strike-slip fault near the Mona Passage. In 1953, Santo Domingo, Dominican Republic, was affected by the Santo Domingo earthquake. The actual subduction zone (Puerto Rico Trench) has not ruptured in over 200 years, which is a major concern to geophysicists, as they believe it may be due for a major event.