Zurab Javakhishvili

Avian Influenza Virus Surveillance in Wild Birds in Georgia: 2009-2011

The Caucasus, at the border of Europe and Asia, is important for migration and over-wintering of wild waterbirds. Three flyways, the Central Asian, East Africa-West Asia, and Mediterranean/Black Sea flyways, converge in the Caucasus region. Thus, the Caucasus region might act as a migratory bridge for influenza virus transmission when birds aggregate in high concentrations in the post-breeding, migrating and overwintering periods. Since August 2009, we have established a surveillance network for influenza viruses in wild birds, using five sample areas geographically spread throughout suitable habitats in both eastern and western Georgia. We took paired tracheal and cloacal swabs and fresh feces samples. We collected 8343 swabs from 76 species belonging to 17 families in 11 orders of birds, of which 84 were real-time RT-PCR positive for avian influenza virus (AIV). No highly pathogenic AIV (HPAIV) H5 or H7 viruses were detected. The overall AIV prevalence was 1.6%. We observed peak prevalence in large gulls during the autumn migration (5.3–9.8%), but peak prevalence in Black-headed Gulls in spring (4.2–13%). In ducks, we observed increased AIV prevalence during the autumn post-moult aggregations and migration stop-over period (6.3%) but at lower levels to those observed in other more northerly post-moult areas in Eurasia. We observed another prevalence peak in the overwintering period (0.14–5.9%). Serological and virological monitoring of a breeding colony of Armenian Gulls showed that adult birds were seropositive on arrival at the breeding colony, but juveniles remained serologically and virologically negative for AIV throughout their time on the breeding grounds, in contrast to gull AIV data from other geographic regions. We show that close phylogenetic relatives of viruses isolated in Georgia are sourced from a wide geographic area throughout Western and Central Eurasia, and from areas that are represented by multiple different flyways, likely linking different host sub-populations.

Relict basin closure and crustal shortening budgets during continental collision: An example from Caucasus sediment provenance

Comparison of plate convergence with the timing and magnitude of upper-crustal shortening in collisional orogens indicates both shortening deficits (200-1700 km) and significant (10-40%) plate deceleration during collision, the cause(s) for which remain debated. The Greater Caucasus Mountains, which result from post-collisional Cenozoic closure of a relict Mesozoic back-arc basin on the northern margin of the Arabia-Eurasia collision zone, help reconcile these debates. Here we use U-Pb detrital zircon provenance data and the regional geology of the Caucasus to investigate the width of the now-consumed Mesozoic back-arc basin and its closure history. The provenance data record distinct southern and northern provenance domains that persisted until at least the Miocene. Maximum basin width was likely ~350-400 km. We propose that closure of the back-arc basin initiated at ~35 Ma, coincident with initial (soft) Arabia-Eurasia collision along the Bitlis-Zagros suture, eventually leading to ~5 Ma (hard) collision between the Lesser Caucasus arc and the Scythian platform to form the Greater Caucasus Mountains. Final basin closure triggered deceleration of plate convergence and tectonic reorganization throughout the collision. Post-collisional subduction of such small (102-103 km wide) relict ocean basins can account for both shortening deficits and delays in plate deceleration by accommodating convergence via subduction/underthrusting, although such shortening is easily missed if it occurs along structures hidden within flysch/slate belts. Relict-basin closure is likely typical in continental collisions in which the colliding margins are either irregularly shaped or rimmed by extensive back-arc basins and fringing arcs, such as those in the modern South Pacific.

Influenza A virus evolution and spatio-temporal dynamics in Eurasian wild birds: a phylogenetic and phylogeographical study of whole-genome sequence data.

Low pathogenic avian influenza A viruses (IAVs) have a natural host reservoir in wild waterbirds and the potential to spread to other host species. Here, we investigated the evolutionary, spatial and temporal dynamics of avian IAVs in Eurasian wild birds. We used whole-genome sequences collected as part of an intensive long-term Eurasian wild bird surveillance study, and combined this genetic data with temporal and spatial information to explore the virus evolutionary dynamics. Frequent reassortment and co-circulating lineages were observed for all eight genomic RNA segments over time. There was no apparent species-specific effect on the diversity of the avian IAVs. There was a spatial and temporal relationship between the Eurasian sequences and significant viral migration of avian IAVs from West Eurasia towards Central Eurasia. The observed viral migration patterns differed between segments. Furthermore, we discuss the challenges faced when analysing these surveillance and sequence data, and the caveats to be borne in mind when drawing conclusions from the apparent results of such analyses.

Uncertainties in Teleseismic Earthquake Locations: Implications for Real-Time Loss Estimates

Abstract For estimating fatalities and injured within minutes after an earthquake worldwide, we rely on real-time teleseismic determinations of epicenters. To estimate the teleseismic location errors, we computed the difference between the local epicenters of the dense seismograph networks of Japan, Italy, and Taiwan with those given by the PDE, those distributed in real time by the U.S. Geological Survey (USGS), and the European Mediterranean Seismological Center (EMSC). The average difference is 16 and 8 km between PDE teleseismic epicenters and those by the local networks for Japan/Taiwan and Italy, respectively. For EMSC epicenters, the average difference is 13 km for Italy. The average difference between real-time USGS parameters and those listed in the PDE is 12 km (median 9 km) for 30 earthquakes in Japan. Comparisons of real-time USGS epicenters and the Japan Meterological Agency (JMA) locations yield an average difference of 31 km (median 26 km). Estimates indicate that the epicenter errors in the local catalogs are typically 1 and 3 km for Japan/Italy and Taiwan, respectively. Assuming that the differences in earthquake locations are mostly due to teleseiseismic errors, we conclude that the mean errors in real-time epicenter solutions are in the range of 25 to 35 km. This implies that for earthquakes of M ≈ 6:7 in the vicinity of a medium-sized city (80,000), the fatality estimates using QLARM in real time have to range from near 0 to 10,000 in the developing world and from 0 to 500 in an industrialized country. These results were verified by comparison with observed numbers of fatalities in the cases of the 2003 M 6.7 Bam, Iran, and the 2008 M 6.9 Iwate–Miyagi, Japan, earthquakes.

Detecting differences in temporal distribution of small earthquakes before and after large events

We have evaluated the dynamical properties of the temporal distribution of the small earthquakes. Two main goals of the investigation were: (a) a qualitative evaluation of the nonlinear structure of the time distribution of earthquakes, taking place before and after the strongest Caucasian events; (b) a quantitative discrimination of the dynamics (of time distribution of earthquakes) preceding and following the largest regional earthquakes.The dynamical characteristics of seismicity before and after four recent large earthquakes in the Caucasian region have been investigated. Nonlinear time-series analysis techniques, such as calculation of the correlation dimension for sliding windows and surrogate data analysis tests have been used; inter-event time-interval sequences have been considered as a time series.It was determined that the dynamics of lithospheric processes, generating the temporal distributions of earthquakes, do not change qualitatively before and after the largest Caucasian earthquakes. Inter-event time-interval sequences reveal low-dimensional nonlinear structure in both situations.On the other hand, quantitative analysis shows that the low-dimensional nonlinear structure of the temporal distributions of earthquakes after the largest events is significantly different than those before the largest events.

Discrimination between stochastic dynamics patterns of ambient noises (Case study for Oni seismic station)

Investigation of complex dynamics of ambient seismic noise remains as an important scientific research challenge. In this work we investigated dynamical features of the ambient noises at Oni seismic station, Georgia. We used stochastic model reconstruction method from measured data sets. Seismic records for different time periods around Oni seismic station have been analysed.It was shown that the dynamics of fluctuations of seismic noise vertical component undergoes essential changes for considered time period from 2005 to 2012. These changes are more noticeable for time periods of preparation and aftershock activity of strong M6.0 earthquake occurred in 2009 in the vicinity of Oni seismic station.

Investigating the dynamical features of the time distribution of the reservoir-induced seismicity in Enguri area (Georgia)

We analyzed the fractal and multifractal properties of the earthquake time series occurred around the Enguri dam in West Georgia by applying the methods of detrended fluctuation analysis and multifractal detrended fluctuation analysis. We examined the interevent time series in two periods: (1) 1960–1980, in which the investigated area was characterized by the natural seismicity; and (2) 1981–2012, in which the quasi-periodic change of the reservoir water level affected the earthquake generation. Our findings show that the water level variation may influence the fractal properties of earthquake temporal distribution in the local area around the Enguri dam. In particular, it is observed that the time distribution features of seismicity occurred in the second period are more persistent than the natural seismicity occurred in the first period. Furthermore, the seismic process of the second period shows a lower multifractal degree than that of the first period, indicating that the influence of quasi-periodic fluctuation of water level features the seismicity as more regular compared to the natural seismicity.

Scaling features of ambient noise at different levels of local seismic activity: A case study for the Oni seismic station

Investigation of dynamical features of ambient seismic noise is one of the important scientific and practical research challenges. We investigated scaling features of the ambient noises at the Oni seismic station, Georgia, using detrended fluctuation analysis method. Data from this seismic station, located in the epicentral zone of Oni M6.0, 2009, earthquake, were selected to include time periods with different levels of local seismic activity.It was shown that the investigated ambient noise is persistent long-range correlated at calm seismic conditions in the absence of earthquakes. Fluctuation features of the analyzed ambient noises were affected by local earthquakes, while remote seismic activity caused just slight quantitative changes. Processes related to the preparation of a strong local earthquake may cause quantifiable changes in fluctuation features of ambient noises. Fluctuation features of seismic noise for periods of increased local seismic activity cease to be long-range correlated and appear to become a complicated mixture of random and correlated behaviours.

Assessment of uncertainties related to seismic hazard using fuzzy analysis

Seismic hazard analysis in the last few decades has become a very important issue. Recently, new technologies and available data have been improved that have helped many scientists to understand where and why earthquakes happen, the physics of earthquakes, etc. Scientists have begun to understand the role of uncertainty in seismic hazard analysis. However, how to handle existing uncertainty is still a significant problem. The same lack of information causes difficulties in quantifying uncertainty accurately. Usually, attenuation curves are obtained in a statistical manner: regression analysis. Statistical and probabilistic analyses show overlapping results for the site coefficients. This overlapping takes place not only at the border between two neighboring classes but also among more than three classes. Although the analysis starts from classifying sites using geological terms, these site coefficients are not classified at all. In the present study, this problem is solved using fuzzy set theory. Using membership functions, the ambiguities at the border between neighboring classes can be avoided. Fuzzy set theory is performed for southern California in the conventional way. In this study, standard deviations that show variations between each site class obtained by fuzzy set theory and the classical manner are compared. Results of this analysis show that when we have insufficient data for hazard assessment, site classification based on fuzzy set theory shows values of standard deviations less than those obtained using the classical way, which is direct proof of less uncertainty.

Analysis of the Complexity of Seismic Data Sets: Case Study for Caucasus

Abstract The investigation of the dynamics of complex seismic processes remains a major scientific challenge. Presently this problem is viewed in the light of modern concepts of the spatiotemporal behaviour of highly nonlinear or complex natural systems. The significant progress in this direction achieved over recent decades has paved a new avenue of research in the investigation of qualitative and quantitative aspects of the dynamics of seismic processes. Special attention has been paid to the elaboration of new methods of measuring the complexity of both global and local dynamics from seismic data sets. In this chapter, we present examples using several modern data analysis approaches on data sets related to seismic activity in the Caucasus. These data analysis methods are often used for the qualitative and quantitative evaluation of the complexity of natural processes, including seismic processes in different parts of globe.