Structure of Tertiary and Pleistocene normal faults in Iceland

摘要: Normal faults were measured in three selected areas of the late Tertiary and Pleistocene lava pile Iceland. The arithmetic mean throw 315 is 8.2 m, minimum being 0.5 m maximum 150 m. About 93% have throws less than 20 strike N31°E, but mode N45°E. dip from 42° to 89°, nearly 80% between 65° 79°, 73°. Fault breccia common varies thickness 0.05 2 There a positive linear relation throw, correlation coefficient 0.78. It proposed that normal Iceland form by two basic mechanisms. One development sets inclined joints pile. initially vertical columnar lavas gradually decrease with depth crust because regional increases about 1° for every 150–170 depth. en echelon cracks may link up through tension propagate near ends joints. other mechanism involves formation growth coalescence smaller fractures. great majority fractures within active rift zone are fractures, when they attain length several hundred meters normally change into faults. concluded fault commonly starts at depths 1 km crust.