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Closing‐up structures, alternatives to pull‐apart basins; the effect of bends in the North Anatolian Fault, Turkey
Author(s) -
Neugebauer Joachim
Publication year - 1994
Publication title -
terra nova
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.353
H-Index - 89
eISSN - 1365-3121
pISSN - 0954-4879
DOI - 10.1111/j.1365-3121.1994.tb00508.x
Subject(s) - geology , transtension , seismology , north anatolian fault , fault (geology) , structural basin , slip (aerodynamics) , fault trace , strike slip tectonics , kinematics , extensional fault , extensional definition , tectonics , geomorphology , sinistral and dextral , engineering , physics , classical mechanics , aerospace engineering
Fault blocks passing bends or stepovers in a fault zone must adapt their margins to the uneven fault trace. Two cases of adaption are distinguished for extensional bends or stepovers (transtension): (1) The fault margins close up behind a single bend ('knickpoint') of a strike‐slip fault and a ‘closing‐up structure’ (new term) arises or (2) fault‐block margins are extended behind a releasing bend (double bend) or stepover parallel to the displacement and a pull‐apart basin originates. The dosing up described here is accomplished by acute‐angled synthetic strike‐slip faults that dissect the straight fault in front of a knickpoint to form a zig‐zag block boundary behind it. Crustal extension is also involved in the closing‐up structure, but in a different way from typical pull‐apart basins. The closing‐up structure illustrated was developed behind an extensional knickpoint in the North Anatolian Fault west of Lake Abant, NW Turkey, where the process of closing up continues to this day. The kinematic model of this closing‐up structure is supported by displacements and ruptures observed during the 1967 Mudurnu valley earthquake and the 1957 Abant earthquake.