Open AccessStress distribution at the transition from subduction to continental collision (northwestern and central Betic Cordillera)
Author(s) -
RuizConstán A.,
GalindoZaldívar J.,
Pedrera A.,
Célérier B.,
MarínLechado C.
Publication year - 2011
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2011gc003824
Subject(s) - geology , subduction , continental crust , continental collision , convergent boundary , continental shelf , seismology , collision zone , transition zone , crust , slab , continental margin , induced seismicity , oceanic crust , eclogitization , underplating , compression (physics) , tectonics , geophysics , oceanography , materials science , composite material
We analyze focal mechanisms of shallow‐intermediate earthquakes in a NW‐SE transect along the western Betic Cordillera and Alboran Sea, and deep earthquakes located in the central Betics to constrain the state of stress at the Gibraltar Arc slow convergence area. Shallow earthquakes (< 40 km) are preferably clustered at the mountain front. A general NW‐SE horizontal compression is compatible with the convergence, and NW plunging compression axes are in agreement with frontal thrust activity. Toward the Alboran Sea the earthquakes are progressively deeper, reaching intermediate depths (40–120 km) near the coast and supporting the present‐day activity of subduction only in this area. The Iberian continental crust concentrates most of the intermediate seismicity and is forced to partially sink into the mantle, probably through the pull of the oceanic slab. This downdip pull together with the buoyancy of the Iberian continental crust produces the slab curvature, downdip extension in the external arc of the continental slab, and downdip compression in the inner arc. T axes highly dipping to the southeast at 90–120 km depth occur at the oceanic/continental transition. Deep earthquakes (>620 km) show very similar focal mechanisms, fitting the general slab behavior of resistance to further descent at the 660 km discontinuity. Seismicity features evidence the present‐day stress distribution in a context of transition from subduction to continental collision.