the CauSIN Project
The Caucasus lie between the Black and Caspian Seas, within a broad zone of deformation, which forms part of Alpine-Himalayan collision belt. The present day tectonics of the area is dominated by the motion of Arabian plate northward relative to the Eurasian plate. In the last decades several major earthquakes of magnitude M~6.5-7 occur in the region (Spitak 1988, Racha 1991, Barisakho 1992, Eastern Turkey, 1976, 1983, 1992, Northern Iran, 1990, 1997), with catastrophic consequences both to the population and economies of the region.
One of the most recent tragic seismic events in the history of Caucasus was the Spitak earthquake occurring in Armenia on December 7, 1988. More than 25,000 died, 20,000 were injured and 515,00 were left homeless.
The relatively high geodynamic activity within the region, expressed as both seismic and aseismic deformations, are the result of ongoing convergence of lithospheric plates and northward propagation of Afro-Arabian continental block at a rate of several cm/year. This has been identified through numerous paleoseismodislocations, contrasting neotectonic movements and related seismic activity. Consequently the occurrence of a strong earthquake (with intensity 9 MSK) is quite probable in the near future. This could cause significant loss of life as well as significant economic difficulties for the governments of the Caucasian republics, including catastrophic ecological consequences (through the reconstruction and development of new industrial and transportation infrastructures). In these countries with fragile economies , i.e. Azerbaijan, Armenia and Georgia a large earthquake could in fact lead to economic collapse. The reliable assessment of seismic hazard, which requires comprehensive study of seismic processes, structure of earth crust, active faulting and surface geology is necessary in order to mitigate the earthquake impact; including loss of life, loss of public trust, economic loss, or socio-psychological and political disruption
In spite of long-standing investigations in the field of geology and seismology in the Caucasus, a number of problems still remain unclear or insufficiently studied because of the complicated mosaic of geologic structures of the region. There are several publications, aiming at explaining the mechanism of seismic process in the Caucasus region (Philip et al, 1989; Jackson, 1992; McCormack, 1994; Triep et al, 1995) which suggest different tectonic models. In order to access the validity of these models it is necessary to conduct a substantial investigation of existing data using modern methods of processing and interpretation as well as to obtain new field data.
New GPS measurements in the Caucasus are providing tectonic deformation rates in the region (Reilinger et al., 1997), (McClusky et al., 2000). These data are important for seismic hazard assessment. They complement modern and historical earthquake data for determining seismicity rates, they identify regions of greatest strain accumulation that will be the likely locations of future earthquakes, and they provide quantitative information on deformation rates necessary to estimate earthquake repeat times (Reilinger and Barka, 1997).
In order to obtain additional data on seismic events digitization of old analog recordings is needed. Of course, as digitization is a time-consuming procedure, only selected events will be digitized, in particular, old recordings dating from the beginning of the 20th century, which will provide new important quantitative measures of these events will be analyzed.
It must be emphasized that the western collaborators play a crucial role in this project. The collaborators have been intimately involved with the development of the project and will continue to help in guiding the development of the regional database and ensuring quality control of the data. They will help to identify, and implement new approaches and methodologies to hazard and risk assessment, as well as identify needed training and access to useful materials. Finally they will provide consultation and independent assessment and expertise for the reinterpretation of existing data.
To address the problem of seismic hazard it is also necessary to establish a modern regional monitoring network comprised of highly-sensitivity digital seismographs. The Caucasus are tectonically complicated, containing many structural formations: thrusts, tectonic nappes, buried folds, normal, reverse, and strike-slip faults and other seismoactive structures. This complexity is most likely responsible for the widespread diffuse character of seismicity in the Caucasus region. It has been demonstrated, for example, that the Racha event of 1991 was most probably a hidden earthquake, realized on a buried strained fold. Thus, the precise location of hypocenters is necessary to relate a given earthquake to a specific fault and thus assess its type and activity rate and finally, give more accurate assessment of seismic hazard of region. In addition, the appearance of the new nuclear countries (India, Pakistan) and the potential of other Near-East states to produce nuclear weapons make the seismic monitoring an important task for the CTBT. Thus, creation of a modern seismic network and calibration of the region are urgent problems both for seismic hazard assessment and CTBT. The regional network developed through this project will support future sustainable functioning of this infrastructure for follow-on activities.
The likelihood of new earthquakes as well as large scale secondary hazards related to these events (landslides, fires, floods, etc) directly resulting from urbanization and population growth in the region contributes to an increase in the seismic risk. Taking into consideration the tragic lessons of the Spitak, Racha and other seismic catastrophes in the region and the continuing activation of seismic processes, the problem of reduction of seismic impact in the Caucasus countries is vital for the protection of the population. It should be noted that one of the main reasons for the grave consequences of the Spitak and other seismic catastrophes in the region (namely, very high value of ratio of number of deaths to the number of injured) is the lack of state policy in seismic risk reduction. One direct goal of this project is to share with the decision-makers the seismic hazard, the resulting expected impact on the and economy population to identify the vulnerabilities, as well as demonstrate the necessity to have a scientifically grounded program of protection against this impact. Thus it is necessary to conduct studies, aimed at further detailing the geologic structures in the region, better understanding the seismic process, determining the spatial and temporal distribution of seismicity and mitigating earthquake effects. Scientific and practical results obtained under the realization of the project will be transferred, in a usable format, as recommendations to appropriate state and private institutions, organizations and companies interested in or responsible for managing and mitigating the effects of natural hazards.
Seismic faults and the ensuing hazards due to these fault zones have no state boundaries and a catastrophe in the region could easily damage two neighboring countries. Taking this into consideration as well as the great interest of each state in the region to protect their own population and sustainable economic development, the problem of earthquake hazard assessment and risk reduction in the Caucasus countries is essential to all the countries of the region and will be best achieved through regional collaboration. The impact of an earthquake is not only limited to direct losses, such as the loss of life, building damages and business disruption. Earthquakes also cause indirect losses by producing supply shortages and demand reductions in various economic sectors that do not sustain direct damage. Indirect losses have a ripple effect that is transmitted throughout the regional economy and social fabric. In a country with a fragile economy such as Armenia or Georgia, a large earthquake can actually contribute to an economic or governmental collapse.