TECTONIC GEOMORPHOLOGY AND EARTHQUAKE HAZARD OF LARGE NORMAL FAULTS: AKSEHIR FAULT, SW TURKEY
Tectonic geomorphology of 32 drainage basins and mountain front facets suggests: 1) Mountain front facets (~100-900 m high) are triangular (34%) with slopes of 6-30°; trapezoidal (25%) with slopes of 31-38°; and combination (lower trapezoidal and upper triangular (41%) with slopes of 15-30°. Facets at the NW and SE segments ends are larger than the intervening facets. Steepest facets are along the central segments; 2) Mountain front sinuosity varies from about 1.1 on the NW segment to 2.4 on SE segment suggesting that the 6 northern segments are more active than the southernmost segment. Ratio of valley floor width to valley height varies from 0.2 to 0.6 consistent with tectonically active mountain fronts; and 3) Alluvial fans along the 4 northernmost segments are back-tilted to the south.
Large normal faults with a similar slip rate of 0.2-0.3 m/ka typically have strong earthquakes every few thousand years. Therefore, the many moderate to strong earthquakes on the Aksehir fault in the past few hundred years may be misleading. A paleoseismic evaluation could answer questions concerning the area’s earthquake hazard. Tectonic geomorphology suggests that the Aksehir fault is active, and larger earthquakes than those of the historic period are a potential threat.