EGU1001 - Fault-controlled geomorphology and paleoseismology of Fethiy

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Presented at the 2010 European Geosciences Union General Assembly, Vienna, Austria, 2-7 May 2010. Reference: Chatzipetros A., Pavlides S., Yağmurlu F., Özgür N., Kamaci Z. and Şentürk M. (2010). Fault-controlled geomorphology and paleoseismology of Fethiye fault and gulf, European Geosciences Union General Assembly, Vienna, Austria, 2-7 May 2010,Geophysical Research Abstracts, 13, EGU2010-9045-1.

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Fault-Controlled Geomorphology and Paleoseismology of Fethiye Fault and Gulf:

Fault-Controlled Geomorphology and Paleoseismology of Fethiye Fault and Gulf A. Chatzipetros , S. Pavlides , F. Ya ğ murlu , N. Özgür , Z. Kamaci , and M. Sentürk

Fethiye – Burdur fault zone (FBFZ):

Fethiye – Burdur fault zone (FBFZ) FBFZ is the mainland extension of the Aegean Arc in southwestern Turkey EGU General Assembly 2010, Vienna, Austria 2

Fethiye fault:

Fethiye fault EGU General Assembly 2010, Vienna, Austria 3

FET-1 trench site geophysics:

FET-1 trench site geophysics EGU General Assembly 2010, Vienna, Austria 4

Fethiye trenching (FET-1 site):

Fethiye trenching (FET-1 site) EGU General Assembly 2010, Vienna, Austria 5 FET-1 trench has dimensions of 10x2.7 m, is directed N-S and was excavated at the edge of a large alluvial fan that has a northward flow direction. The Fethiye fault at the site forms a high limestone scarp that feeds the alluvial fan with large blocks of three units were recognized. Log of the eastern wall of FET-1 trench 1. Recent soil and lateral scree. This is the upper layer that is probably reworked and consists of the same alluvial fan deposits as layer 4, only of smaller size. 2. The upper, more weathered part of layer 4. It is the same material as layer 4, but it appears lighter in colour and less coherent. 3. This unit is interpreted as a colluvial wedge, comprised of loose and undifferentiated material that came from layer 2. Its chaotic structure indicates that this unit has been deposited during a sudden event, most probably an earthquake. 4.This is the main deposit of the trench. It is coherent alluvial fan deposits with angular pieces and coarse matrix. There is no traceable layering in this unit. The latest event is the one that ruptured the southernmost fault zone and reached the surface. It is probably related with the 1957 earthquake, but is certainly postdates the age of FET-1/5 sample. The penultimate event is associated with the northernmost fault zone and the small colluvial wedge. It doesn’t reach the surface, and it signifies an earthquake that happened before FET-1/1 and after FET-1/2 and FET-1/3 ages.

FET-1 trench calibration:

FET-1 trench calibration 6 EGU General Assembly 2010, Vienna, Austria

FET-1 dating and interpretation:

FET-1 dating and interpretation EGU General Assembly 2010, Vienna, Austria 7 AD 556 - 642 BC 511 - 388 AD 1950 4110 ± 70 BP The last event is the one rupturing the southern fault branch, as is shown by the AD 1950 dating of the overlying colluvium. The penultimate event at the northern branch of the fault zone caused the deposition of the respective colluvial wedge aged AD 556-642 and postdates the age of the colluvial cover 2 (BC 511-388). This earthquake should be dated by the age of the colluvial wedge, due to the geomorphic processes leading to the formation of a wedge over a fault free face. BC 16700

FET-1 trench details:

FET-1 trench details EGU General Assembly 2010, Vienna, Austria 8 View of the penultimate surface rupture.

FET-1 trench details:

FET-1 trench details EGU General Assembly 2010, Vienna, Austria 9 Contact between two different colluviums.

Seismic profiling results (FET-2 site):

Seismic profiling results (FET-2 site) EGU General Assembly 2010, Vienna, Austria 10 745 m/sec 485 m/sec 2,995 m/sec

FET-2 trench site:

FET-2 trench site EGU General Assembly 2010, Vienna, Austria 11

Fethiye trenching (FET-2 site):

Fethiye trenching (FET-2 site) EGU General Assembly 2010, Vienna, Austria 12 FET-2 trench was excavated at the only possible site in Fethiye urban area. Its strike is SW – NE and its dimensions are 10x2.80 m. Its stratigraphy consists of slope deposits and alluvial deposits. The structure of the layers observed in the trench are abruptly discontinued by a fault zone. This fault zone seems to be reverse, but it is considered to be a pseudo-reverse structure, changing its dip direction at depth. The stratigraphy includes the topmost layer 1 that appears to be disturbed and a sequence of layers (2-6) that are successive generations of colluvial and alluvial deposits. Since the original surface was altered by human activities, the observed stratigraphy corresponds to a previous dynamic state of the site. The assumed normal displacement is at least 2 m, corresponding to several events (not too recent). Radiocarbon dating will help us be more precise on the timing of the events. Log of the western wall of FET-1 trench

FET-2 trench calibration:

FET-2 trench calibration 13 EGU General Assembly 2010, Vienna, Austria

FET-2 dating and interpretation:

FET-2 dating and interpretation EGU General Assembly 2010, Vienna, Austria 14 AD 619 - 678 BC 1047 - 918 BC 329 - 203 BC 5480 - 5343 In this trench, the 1957 event is not evident, but a previous one rupturing the AD 619 – 678 dated layer has deformed the entire sequence. This event is well correlated with the one traced in FET-1 trench. BC 9000 BC 1900

FET-2 trench details:

FET-2 trench details EGU General Assembly 2010, Vienna, Austria 15 Rotated block of colluvium due to faulting.

Combined calibration dating results for Fethiye trenches:

Combined calibration dating results for Fethiye trenches Pemultimate event (AD 619-642) Probable antepenultimate event 16 EGU General Assembly 2010, Vienna, Austria

Conclusions:

Conclusions EGU General Assembly 2010, Vienna, Austria 17 Fethiye fault is a known active fault, associated with the large1957 earthquake. Trenching shows one recent and at least two older events along the same fault zone. Gökova fault is not associated with any significant historical earthquake, and the geological / geomorphological evidence suggest that there have been no recent reactivations. However, steep offshore seafloor morphology indicates that the most recent strands should have migrated seawards. Apart from the recent 1957 event, Fethiye fault has ruptured during a large, ground rupturing earthquake dated at about AD 619-642, based on palaeoseismological info from two trenches.

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