Aigulak Focal Area as a Result of the Impact of the 2003 Chuya Earthquake on Gorny Altai

Abstract

Abstract —Years after the Chuya earthquake of 2003, geological structures adjacent to the focal area of the Chuya earthquake are still seismically active. The Aigulak focal area is one of them, but energetically the most pronounced. Detailed studies have been carried out with the network of stations of the Altai seismological testing site, supplemented by temporary stations. The region activated in the form of a local and compact structure measuring 10 × 10 km with focal depths from the first 100 m to 20 km. The focal area is not a subsequent activation along the same fault with the Chuya earthquake, but is located on a subparallel fault in the nodal region with its branching into three faults. The seismic activation of the Aigulak focal area is not an aftershock process after a major earthquake, but is an activated structure with a dynamically changing seismic process. An intensive process has formed since the earthquake in 2012 with ML = 6.1 with a gradual decrease in the number of earthquakes, and in 2019 the Aigulak earthquake with ML = 5.5 occurred with a very strong aftershock process after it. Our results of an area study of earthquake density in the focal zone indicate a change in the regime over time: from chaotic to self-organizing along short faults. We conclude that the focal area has not reached the maximum level of seismic energy release.