Some neotectonic and paleosismological features of the Fethiye-Burdur fault zone, SW-Anatolia

The purpose of this investigation is to explain some neotectonic and paleoseismolojical features of Fethiye-Burdur Fault zone that is located in SW- Turkey between gulf of Fethiye and Burdur Lake. This zone, which is about 300 km. in length, is characterized as a combination of a number of normal faults which has generally left lateral oblique-slip in feature. It is, also, charecterized as beeing the most active fault system in Southwest Anotolia. Burdur fault zone, normally, extends in NE-SW direction, but it was segmented in various lengths by several faults tilted in NW direction. Burdur and Tefenni segments, that are 60-70 km. in length, are considered as the most active lines of these segments. It has been reported that two major earthquakes in 1914 and 1971 took place on these segments with a magnitude of 7.1 and 6.2, respectively. Trench studies have been conducted on Yass?güme and Burdur locations to investigate deformations caused by the vertical displacements following the 1914 and 1971 earthquakes. The Burdur fault in the Yass?güme location is characterized as a single line fault structure in the field. Its visible fault plane clearly reflects the left lateral oblique - slip moving and related sliding lines. As a result of the trench study performed on this segment a vertical displacement of 70 cm. in length has been identified as belong the 1971 earthquake. On the other hand, Burdur segment, which is one of the most important branch of Burdur fault zone, consists of four different stepwise oblique fault systems within the south of Burdur Lake which extends in NE direction. These fault systems pass through the city center of Burdur and caused the stepwise topographical features. The unconsolidated sediments within the trench section consists dominantly of cross-bedded sands, mudstones and present slope-debris deposits. Also, fault plane and kolluvial sediments with muddy dike structures were found as most important structural constituents in the trenches. These structures are thought to be developed as a result of 1914 earthquake. Several faults located on the hills show vertical displacements of 90-250 cm. These faults are seen in discordant with the colluvial developments. Thus, the youngest faults located in the trenches and hills can be considered having the highest vertical displacements. Observations of some folds and local discontinuties can be considered as typical in this type of settings. Two recent earthquekes, which took place in 3rd and 5th April, 2002 with a magnitude of 3,9 and 4,0 respectively, can be considered significant since they highlight the exsistence of sismic activity on this segment. Futhermore, they help us to prove that this segment can be identified as obliquely left tilted normal fault.