Earthquake Properties in Georgia and Armenia of the Caucasus Constrained by Regional Waveform Modeling
Abstract
Caucasus mountain belts mark the northern terminus of the continental collision between Arabia and Eurasia. The plate convergence is predominantly in north-south direction at a rate of approximately 10-20 mm/yr across the Iranian Plateau and Caucasus region. The collision also causes the Anatolian block to extrude laterally. In the Caucasus region, earthquakes are usually in lower magnitudes (M<4). However, a few historical events are found with magnitude approaching 7 since the nineteenth century. Over the past 40 years, three large earthquakes occurred: the 1970 Dagestan (Ms= 6.5) and the 1991 Racha-Dzhava (Ms = 7.0) Georgian earthquakes in the foothill of the Greater Caucasus and the 1988 Spitak Armenian earthquake (Ms = 6.9) near the Lesser Caucasus. Due to limited stations in this area, focal mechanisms are estimated using global waveform data for primarily large earthquakes. In contrary, small earthquakes are less studied and poorly constrained. In this study, we use regional waveforms to constrain the focal mechanisms and depths of the earthquakes in the major seismic zones in the Greater Caucasus and Lesser Caucasus. Through international collaboration since 2008, we collect the data from broadband stations deployed by Institute of Earth Sciences, Academia Sinica of Taiwan, permanent stations of Global Seismographic Network and the Georgian local broadband stations for superior coverage. We examine earthquakes with magnitude above 3.5 in the study region. Preliminary results of the analyzed focal mechanism for small earthquakes are generally consistent with the large events constrained by earlier studies and the corresponding faults. We will improve the solutions with suitable parameters through systematic tests and including more available stations. With well determined focal mechanisms, we aim to better understand the stress distribution, the relation with fault system nearby and the detail tectonic structure in the Caucasus.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.S41B2436H
- Keywords:
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- 7230 SEISMOLOGY / Seismicity and tectonics