Studies of recent seismo-volcanic activity in the Gegham volcanic ridge (Armenia)

Armenia, SE Turkey and NW Iran are located in the central part of the Arabian lithosphere collision zone, a region, which experiences N–S shortening and E–W extension accompanied by intense faulting, strong earthquakes and active volcanism. The Gegham volcanic ridge (GVR) is located in the center part of the Neogene-Quaternary volcanic belt formed within the territory of the Armenian Highland. The duration of volcanism within the Gegham Ridge spans from the Late Miocene to the Holocene. The GVR in central Armenia represents one of the densest clusters of individual monogenetic volcanoes in the world.

The study area of the Gegham Volcanic Ridge is located between the system of the Gegham Ridge Fault (GF1) and the Gavaraghet Fault (GF2).

The faults in the axial part of the Gegham ridge (GF1) represent structures of fracturing related to eruptions of numerous Quaternary volcanoes. The Gavaraghet Fault (GF2) related to a few historical and recent earthquakes is the most active one in the Gegham Fault system.

During the period of 2014-2018, earthquake swarms were recorded in the area of the Gegham Volcanic Ridge. Further studies of the relationship between tectonic and volcanic processes will contribute to the assessment of the volcanic hazard for this area. Beyond its importance for natural hazard assessment, the volcanically young Gegham Ridge also holds great potential as a source of geothermal energy.

Seismic activity in the study area was recorded using data from the advanced and dense seismic network installed recently. This network equipped by full-broad band (permanent and temporary) stations has been developed since 2012 and covers both the study region and adjacent areas.

Seismic activity of this area is manifested in the form of small-size earthquakes. Earthquake epicenters tend to concentrate in volcanic vents, as well as near active faults areas. The depths of earthquakes are up to 25 km.

In this study, source mechanisms of earthquakes were investigated using digital waveform data recorded by seismic stations of the Armenian seismic networks (included the 3 temporary seismic stations). The focal mechanisms of a set of earthquakes that occurred within 2022-2023 were constructed with high reliability, based on the polarity of the first motion of the P-wave.

All data were relocated using local and regional seismic network data with the aim to reduce main parameter uncertainties in the catalogue, used in the current study.