Development of paleoseismic trench logging and dating techniques: a case study on the Central North Anatolian Fault

The North Anatolian Fault (NAF) is a dextral strike slip fault zone extending ~1400km in an arc across northern Turkey. This study seeks to further constrain the timing of ground rupturing earthquakes of the NAF while developing the techniques used in paleoseismology. A paleoseismic trench was opened ~2.7km NW of Destek on a segment which ruptured (for ~280km) in the 1943 Tosya Earthquake (Mw:7.7). The trench site comprises a pop-up structure formed by a small releasing step-over at a restraining bend which has caused progressive growth of an upslope facing scarp. The trench is situated across the main fault trace and a trapped sedimentary sequence that includes several paleosoils. The stratigraphy is expected to be Late Holocene and historic in age due to the high level of activity on the NAF, although this has yet to be confirmed by radiometric dating. Preliminary interpretation of the trench stratigraphy indicates a record of up to 6 paleoearthquake events, the presence of an angular unconformity suggests the record may be incomplete beyond the 3 most recent events on this strand.Subtle contrasts in stratigraphy made conventional face logging difficult and was therefore augmented by mapping the magnetic susceptibility (MS) of the west wall. Approximately 6000 measurements were made using a Bartington MS2 Magnetic Susceptibility Meter with a MS2E (point) Sensor with a 5cm vertical spacing and a 20cm horizontal spacing predominantly on one side of the trench. A pilot test led to development of a strategy of moving the sensor to the nearest exposure of coarse sand or finer grained material where possible to minimize the noise generated by individual clasts. To negate the sensitivity of the MS logging method to variations in temperature the survey was conducted at night. Plotted data clearly shows the contact between rock units, the rock-soil interface (reflecting fault juxtaposition), anthropogenic influence and some soil stratigraphy. Other paleoseismic investigations on this section of the NAF (Hartleb R. et al 2003 and Yoshioka T. et al 2000) have encountered out-of-stratigraphic-order ranges in 14C ages. They attributed this to reworking, in addition to which the effects of long term human occupation are likely to be similar. The trench yielded a large amount of datable material including 158 charcoal and 140 minute gastropod samples, and some ceramic, bone and slag samples. Unlike charcoal and bone fragments, fragile minute gastropods are unlikely to have been transported, reworked or used by humans, ultimately providing improved accuracy of temporal constraints on paleoearthquakes. Using both charcoal and gastropod samples, the trench chronology can be established and the use of minute gastropods for dating paleoearthquakes can be critiqued

Indonesian earthquake: Earthquake risk from co-seismic stress.

Following the massive loss of life caused by the Sumatra-Andaman earthquake in Indonesia and its tsunami, the possibility of a triggered earthquake on the contiguous Sunda trench subduction zone is a real concern. We have calculated the distributions of co-seismic stress on this zone, as well as on the neighbouring, vertical strike-slip Sumatra fault, and find an increase in stress on both structures that significantly boosts the already considerable earthquake hazard posed by them. In particular, the increased potential for a large subduction-zone event in this region, with the concomitant risk of another tsunami, makes the need for a tsunami warning system in the Indian Ocean all the more urgent.John McCloskey, Suleyman S.Nalbant, Sandy Steac

Radionuclide profiles and recent earthquakes history of Lake Hazar Pull-apart basin (East Anatolian Fault, Turkey)

In Turkey, the continuous Pull-apart sediment records constitute powerful chronometers for tracking environmental perturbations such as earthquakes. In South-east Turkey, the East Anatolian Fault (EAF) is a major strike-slip fault along which large earthquakes (Ms > 7) occurred in the 19e century. According to chronicles, the seismicity of this area has been minimal for most of the last century; the latest surface rupturing earthquakes may be the Ms = 7.1 in AD 1874 and the Ms = 6.7 in AD 1875. The EAF consists of two large surface rupturing segments interrupted by a pull-apart basin at Lake Hazar (the Sincik/Lake Hazar and the Lake Hazar/Palu segments). In this geological context, the present project seeks to assess: 1) the recent sedimentation rates of Lake Hazar main Pull-apart system located on the EAF; 2) the occurrence of recent past earthquakes along the EAF. For these purposes, we use a diverse array of complementary techniques involving sediment coring, and radionuclide profiles of sediment cores. Here, we present the first results obtained within the framework of a EU-project focusing on the “seismic cycles” in Turkey (“Understanding the irregularity of seismic cycles: A case study in Turkey”). We present 210Pb and 137 Cs age models obtained from a series of short sediment cores. The radionuclide profiles are utilized for both, annual sediment rates estimates, and for tracking the historic earthquakes. The correlation between several cores and the comparison between radionuclide profiles and preliminary sedimentological data shows that sedimentary structures induced by the last AD 1874 and 1875 earthquakes can be detected by ultra-high resolution X-ray radiographies. However, our results show the presence of an additional hypothetic event in the early 20e century. These first results will be further utilized for tracking past earthquakes in longer Lake Hazar sediment time series

The Red Sea, Coastal Landscapes, and Hominin Dispersals

This chapter provides a critical assessment of environment, landscape and resources in the Red Sea region over the past five million years in relation to archaeological evidence of hominin settlement, and of current hypotheses about the role of the region as a pathway or obstacle to population dispersals between Africa and Asia and the possible significance of coastal colonization. The discussion assesses the impact of factors such as topography and the distribution of resources on land and on the seacoast, taking account of geographical variation and changes in geology, sea levels and palaeoclimate. The merits of northern and southern routes of movement at either end of the Red Sea are compared. All the evidence indicates that there has been no land connection at the southern end since the beginning of the Pliocene period, but that short sea crossings would have been possible at lowest sea-level stands with little or no technical aids. More important than the possibilities of crossing the southern channel is the nature of the resources available in the adjacent coastal zones. There were many climatic episodes wetter than today, and during these periods water draining from the Arabian escarpment provided productive conditions for large mammals and human populations in coastal regions and eastwards into the desert. During drier episodes the coastal region would have provided important refugia both in upland areas and on the emerged shelves exposed by lowered sea level, especially in the southern sector and on both sides of the Red Sea. Marine resources may have offered an added advantage in coastal areas, but evidence for their exploitation is very limited, and their role has been over-exaggerated in hypotheses of coastal colonization

Gas seepage and seismogenic structures along the North Anatolian Fault in the eastern Sea of Marmara

We carried out a combined geophysical and gas-geochemical survey on an active fault strand along the North Anatolian Fault (NAF) system in the Gulf of İzmit (eastern Sea of Marmara), providing for the first time in this area data on the distribution of methane (CH4) and other gases dissolved in the bottom seawater, as well as the CH4isotopic composition. Based on high-resolution morphobathymetric data and chirp-sonar seismic reflection profiles we selected three areas with different tectonic features associated to the NAF system, where we performed visual and instrumental seafloor inspections, including in situ measurements of dissolved CH4, and sampling of the bottom water. Starting from background values of 2–10 nM, methane concentration in the bottom seawater increases abruptly up to 20 nM over the main NAF trace. CH4 concentration peaks up to ∼120 nM were detected above mounds related probably to gas and fluids expulsion. Methane is microbial (δ13CCH4: −67.3 and −76‰ versus VPDB), and was found mainly associated with pre-Holocene deposits topped by a 10–20 m thick draping of marine mud. The correlation between tectonic structures and gas-seepages at the seafloor suggests that the NAF in the Gulf of İzmit could represent a key site for long-term combined monitoring of fluid exhalations and seismicity to assess their potential as earthquake precursors

Kinematic behavior of southern Alaska constrained by westward decreasing postglacial slip rates on the Denali Fault, Alaska

Long-term slip rates for the Denali Fault in southern Alaska are derived using ^(10)Be cosmogenic radionuclide (CRN) dating of offset glacial moraines at two sites. Correction of ^(10)Be CRN model ages for the effect of snow shielding uses historical, regional snow cover data scaled to the site altitudes. To integrate the time variation of snow cover, we included the relative changes in effective wetness over the last 11 ka, derived from lake-level records and δ^(18)O variations from Alaskan lakes. The moraine CRN model ages are normally distributed around an average of 12.1 ± 1.0 ka (n = 22, ± 1σ). The slip rate decreases westward from ~13 mm/a at 144°49′W to about 7 mm/a at 149°26′W. The data are consistent with a kinematic model in which southern Alaska translates northwestward at a rate of ~14 mm/a relative to a stable northern Alaska with no rotation. This suggests progressive slip partitioning between the Denali Fault and the active fold and thrust belt at the northern front of the Alaska range, with convergence rates increasing westward from ~4 mm/a to 11 mm/a between ~149°W and 145°W. As the two moraines sampled for this study were emplaced synchronously, our suggestion of a westward decrease in the slip rate of the Denali Fault relies largely upon the measured offsets at both sites, regardless of any potential systematic uncertainty in the CRN model ages

The Flux-Line Lattice in Superconductors

Magnetic flux can penetrate a type-II superconductor in form of Abrikosov vortices. These tend to arrange in a triangular flux-line lattice (FLL) which is more or less perturbed by material inhomogeneities that pin the flux lines, and in high-$T_c$ supercon- ductors (HTSC's) also by thermal fluctuations. Many properties of the FLL are well described by the phenomenological Ginzburg-Landau theory or by the electromagnetic London theory, which treats the vortex core as a singularity. In Nb alloys and HTSC's the FLL is very soft mainly because of the large magnetic penetration depth: The shear modulus of the FLL is thus small and the tilt modulus is dispersive and becomes very small for short distortion wavelength. This softness of the FLL is enhanced further by the pronounced anisotropy and layered structure of HTSC's, which strongly increases the penetration depth for currents along the c-axis of these uniaxial crystals and may even cause a decoupling of two-dimensional vortex lattices in the Cu-O layers. Thermal fluctuations and softening may melt the FLL and cause thermally activated depinning of the flux lines or of the 2D pancake vortices in the layers. Various phase transitions are predicted for the FLL in layered HTSC's. The linear and nonlinear magnetic response of HTSC's gives rise to interesting effects which strongly depend on the geometry of the experiment.Comment: Review paper for Rep.Prog.Phys., 124 narrow pages. The 30 figures do not exist as postscript file

Purinergic signalling and immune cells

This review article provides a historical perspective on the role of purinergic signalling in the regulation of various subsets of immune cells from early discoveries to current understanding. It is now recognised that adenosine 5'-triphosphate (ATP) and other nucleotides are released from cells following stress or injury. They can act on virtually all subsets of immune cells through a spectrum of P2X ligand-gated ion channels and G protein-coupled P2Y receptors. Furthermore, ATP is rapidly degraded into adenosine by ectonucleotidases such as CD39 and CD73, and adenosine exerts additional regulatory effects through its own receptors. The resulting effect ranges from stimulation to tolerance depending on the amount and time courses of nucleotides released, and the balance between ATP and adenosine. This review identifies the various receptors involved in the different subsets of immune cells and their effects on the function of these cells