An emendation of elastic rebound theory: Main rupture and adjacent belt of right-lateral distortion detected by Viaduct at Kaynash, Turkey 12 November 1999 Duzce Earthquake

摘要

The fault trace of the 12 November 1999 earthquake in the Duzce-Bolu region in Anatolia crossed the alignment of a 2.4 km viaduct in Kaynash that had been carefully surveyed. The builders of the viaduct, the ASTALDI-BAYINDIR Co., resurveyed the viaduct after the earthquake. We repeated the survey for approximately one kilometre of the eastern end of the viaduct and obtained essentially identical results. Though it was unfortunate that the earthquake damaged the new structure, the piers did produce a very rare record of ground deformation of an earthquake. In effect, the viaduct was a giant strain gage that yielded reliable data about ground movement and distortion near a fault. This paper describes the survey data and their evaluation leading to convincing evidence that (a) the fault trace must be considered, not as a fault line or plane, but as a fault zone with a finite width and that (b) the structural damage within the zone was caused, not primarily by ground acceleration, but by ground distortion. Along the right-lateral fault at Kaynash, the fault zone consists of right-lateral movement at the main trace, a zone of right-lateral distortion near the trace, bounded by left-lateral distortion. The 12 November 1999 event in Turkey, like the ground deformation and fracturing at Landers, California (Johnson et al., 1994, 1996), thus affirmed a forgotten conclusion from the studies by Lawson (1908), Gilbert and Reid (1910) of the 1906 San Francisco earthquake that earthquake ruptures typically occur throughout zones or belts, rather than along linear traces or planes.