HR: 09:45h
AN: S31B-08    [Abstracts]
TI: Geomorphic Signals for Preferred Propagation Direction of Earthquake Ruptures on North Anatolian Fault System, TURKEY
AU: * Yildirim, C
EM: cengizyildirim@mta.gov.tr
AF: General Directorate of Mineral Research and Exploration of TURKEY (MTA), General Directorate of Mineral Research and Exploration of TURKEY (MTA), Balgat, Ankara, 06520 Turkey
AU: Dor, O
EM: dor@usc.edu
AF: University of Southern California, USC, Department of Earth Sciences, Trousdale Ave. 90089, Los Angeles, CA 90089 United States
AU: Rockwell, T
EM: trockwell@geology.sdsu.edu
AF: San Diego State University, Dept. Geological Sciences, MC-1020, 5500 Campanile Dr. San Diego State University, San Diego, CA 92182 United States
AU: Emre, O
EM: emre@mta.gov.tr
AF: General Directorate of Mineral Research and Exploration of TURKEY (MTA), General Directorate of Mineral Research and Exploration of TURKEY (MTA), Balgat, Ankara, 06520 Turkey
AU: Ben-Zion, Y
EM: benzion@usc.edu
AF: University of Southern California, USC, Department of Earth Sciences, Trousdale Ave. 90089, Los Angeles, CA 90089 United States
AU: Sisk, M
EM: MatthewMB77@aol.com
AF: San Diego State University, Dept. Geological Sciences, MC-1020, 5500 Campanile Dr. San Diego State University, San Diego, CA 92182 United States
AU: Duman, T
EM: tduman@mta.gov.tr
AF: General Directorate of Mineral Research and Exploration of TURKEY (MTA), General Directorate of Mineral Research and Exploration of TURKEY (MTA), Balgat, Ankara, 06520 Turkey
AB: The North Anatolian Fault ruptured in a sequence of large earthquakes between 1939 and 1999, generally progressing from east to west. The 1943 and 1944 ruptures propagated unilateraly in opposite directions. Preliminary analysis of the geomorphology along these ruptures shows distinct differences that may reflect repeated ruptures with similar propagation directions. A persistent preferred propagation direction should produce asymmetric damage across the fault that may have goemorphic manifestations. Here we analyze geomorphic signals along the 43 and 44 ruptures to test whether correlative rock bodies across the fault have similar or distinct expression. We made observations at three scales: 1) small scale (< 100m) damage zone, generally expressed as localized badlands due to extremely high drainage density; 2) medium scale data of standard morphometric analyses (drainage density, stream frequency, ruggednes number, bifurcation ratio, landslide density, stream power index, slope length index, curvature and longitudinal profiles) on basins with same lithology; and 3) large scale on major rivers that display different adjustments. At two locations along the 43 rupture, highly eroded badlands south of the rupture have a higher gully density and frequency compared to the north. Drainage density gradually decreases as a function of distance from fault. On the 44 rupture, two sites near Ismetpasa were compared with one north and one south of the fault in the same lithology and with similar morphometric controls (elevation, relief and climate are very similar). Bifurcation ratios are 3.7 for the S side and 3.4 for the N, revealing the general homogeniety of the lithology. Morphometric analysis shows that the N area has higher drainage density, stream frequency, ruggedness number and landslide density. Stream power index , slope length index and curvature analysis are erosion-related parameters that indicate distinctive differences between the two sides of the fault. Finally, the longitudinal profiles of the major streams and rivers also show differences between the northern and southern sides of the fault. The 43 and 44 ruptures follow several major river valleys. Along the 43 rupture, most of the thalwegs are S of the rupture (Kizilirmak, Eksik, Mavga and Destek rivers) whereas along the 44 rupture, most of the river thalwegs are N of the rupture (Abant, Goynuk, Mudurnusuyu, Kuzeren, Karanlik and Gerede Rivers). Our observations include various expressions for more erosion (geomorphic work) on the S side of the 43 rupture, and the N side of the 44 rupture, presumabely due to higher levels of rock damage. These results are consistent with a preferred direction of rupture of west to east for the 43 segment, and east to west for the 44 segment, as occurred in these historical earthquakes. The observations from the 43 rupture are compatible with smaller scale data of damage asymmetry (Dor et al., this meeting).
DE: 1242 Seismic cycle related deformations (6924, 7209, 7223, 7230)
DE: 1815 Erosion
DE: 1819 Geographic Information Systems (GIS)
SC: Seismology [S]
MN: Fall Meeting 2005