Bookshelf faulting in Nicaragua

Oblique subduction at a high rate of convergence along much of the Middle America Trench results in northwest-directed trench-parallel block motion. Accomodation of this motion along northwest-striking dextral strike-slip faults has been postulated; however, in Nicaragua such faults are not well developed. We suggest instead that this motion is accomodated by bookshelf faulting that includes northeast-striking left-lateral faults. We present earthquake epicenter and focal mechanism data and mapped fracture and fault data consistent with this model. Trenchward migration of the volcanic arc since the Miocene and reactivation of northeast-striking Miocene structures may have led to the development of this arc- and trench-normal fault system.