Aurélia Hubert-Ferrari

A 3400 year lacustrine paleoseismic record from the North Anatolian Fault, Turkey: Implications for bimodal recurrence behavior

High-resolution physical, geochemical, and geochronological analyses on the sedimentary sequence of Yenicaga Lake, located in a fault-bounded basin along the North Anatolian Fault, reveal fingerprints of paleoearthquakes. A robust sediment chronology, spanning the last 3400 years, is constructed by radiocarbon dating and time-stratigraphical correlation with the precisely dated Sofular Cave speleothem record. Yenicaga sedimentary sequence contains 11 seismically induced event deposits characterized by siliciclastic-enriched intervals. Some of the event deposits are also associated with implications of sudden lake deepening, which may be related to coseismic subsidence. The paleoearthquake series having an average recurrence interval of ca. 260 years are interrupted by two possible seismic gaps of ca. 420 and 540 years.

A 3000-year record of ground-rupturing earthquakes along the central North Anatolian fault near Lake Ladik, Turkey

The North Anatolian fault (NAF) is a similar to 1500 km long, arcuate, dextral strike-slip fault zone in northern Turkey that extends from the Karliova triple junction to the Aegean Sea. East of Bolu, the fault zone exhibits evidence of a sequence of large (M(w) > 7) earthquakes that occurred during the twentieth century that displayed a migrating earthquake sequence from east to west. Prolonged human occupation in this region provides an extensive, but not exhaustive, historical record of large earthquakes prior to the twentieth century that covers much of the last 2000 yr. In this study, we extend our knowledge of rupture events in the region by evaluating the stratigraphy and chronology of sediments exposed in a paleoseismic trench across a splay of the NAF at Destek, similar to 6: 5 km east of Lake Ladik (40.868 degrees N, 36.121 degrees E). The trenched fault strand forms an uphill-facing scarp and associated sediment trap below a small catchment area. The trench exposed a narrow fault zone that has juxtaposed a sequence of weakly defined paleosols interbedded with colluvium against highly fractured bedrock. We mapped magnetic susceptibility variations on the trench walls and found evidence for multiple visually unrecognized colluvial wedges. This technique was also used to constrain a predominantly dip-slip style of displacement on this fault splay. Sediments exposed in the trench were dated using both charcoal and terrestrial gastropod shells to constrain the timing of the earthquake events. While the gastropod shells consistently yielded (14)C ages that were too old (by similar to 900 yr), we obtained highly reliable (14)C ages from the charcoal by dating multiple components of the sample material. Our radiocarbon chronology constrains the timing of seven large earthquakes over the past 3000 yr prior to the 1943 Tosya earthquake, including event ages of (2 sigma error): A. D. 1437-1788, A. D. 1034-1321, A. D. 549-719, A. D. 17-585 (1-3 events), 35 B. C.-A. D. 28, 700-392 B. C., 912-596 B. C. Our results indicate an average interevent time of 385 +/- 166 degrees yr (1 sigma).

Submarine Earthquake History of the Çınarcık Segment of the North Anatolian Fault in the Marmara Sea, Turkey

The North Anatolian fault (NAF) in the Marmara Sea is a significant hazard for the city of Istanbul. The use of paleoseismological data to provide an accurate seismic risk assessment for the area is constrained by the fact that the NAF system is submarine; thus a history of paleoearthquakes can be inferred only by using marine sediment cores. Here, a record of turbidites was obtained in two cores and used to reconstruct the earthquake history along the Cinarcik segment, a main branch of the NAF. Klg04 was collected from a berm north of the fault, and Klg03 was positioned in the Cinarcik basin, south of the fault. The cores were correlated using long-term geo-chemical variations in the sediment, and turbidites deposited simultaneously at both sites were then identified. Radionuclide measurements suggest the most recent turbi-dite was triggered by the 1894 C.E. M w 7.3 earthquake. We conclude that the turbidites identified at both sites are earthquake generated, based on their particular sedimento-logical and geochemical signatures; the correlation of turbidites at berm and basin sites; and the match of the most recent turbidite with a nineteenth century historical earthquake. To date older turbidites, we used carbon-14 and paleomagnetic data to build an OxCal model with a local reservoir correction of 400 50 yr. The Cinarcik segment is found to have ruptured in 1509 C.E., sometime in the fourteenth century, in 989 C.E., and in 740 C.E., with a mean recurrence interval in the range of 256–321 years. Finally, we used the earthquake record obtained to review the rupture history of the adjacent segments over the past 1500 years.

Inter-technique comparison of PIXE and XRF for lake sediments

In this paper we describe a validation procedure for the chemical analysis of major elements and some minor elements such as Sr, Cr, Ni, Zn and Zr in heterogeneous geological sediments. The procedure applies two distinct techniques (PIXE and XRF) for the analysis of sediments. In this work an inter-technique comparison of heterogeneous lacustrine sediments from Amik Lake in the vicinity of the Roman city of Antioch (SE, Turkey) was carried out. Dried raw samples and samples with linking powder added were analyzed using PIXE performed at the “Arkeo” beamline of the University of Liege AVF cyclotron and XRF (University of Liege). The aim of this work was to compare PIXE and XRF analysis with set-ups routinely in use in the two laboratories. The purpose was also to determine the best combination of techniques and sample preparation protocols to be applied for heterogeneous sediments and the main elements of interest for each specific technique. The results are in agreement among the two techniques, with discrepancies concerning lighter and minor elements. These differences are mainly related to the texture of the sediments and the intrinsic features of the XRF and PIXE techniques. Major and selected minor elements are sensitive to the grain size and porosity of the samples. However, the accuracy of both XRF and PIXE requires the reduction of the grain size or addition of a linking powder to the sediments to fill the voids in order to increase the intensities of both lighter and minor elements. The results demonstrate the critical importance of sample treatment prior to analysis as well as the necessity of several measurement points and replicates to ensure the accuracy of PIXE results.