The earthquake of July 22, 2011 (Mw = 4.5) in a low-seismicity area of the Argun region

Abstract

The paper considers the Argun earthquake of July 22, 2011 (M_w = 4.5), which occurred in the Argun River valley in a low-seismicity territory in China. The focal parameters of the earthquake (depth of the hypocenter, moment magnitude, scalar seismic moment, and focal mechanism) were determined by calculating the seismic moment tensor from the amplitude spectra of surface waves and the data on the signs of the first arrivals of body waves at regional stations. The solution of the focal mechanism makes it possible to assume a relationship between the earthquake focus and a fault with a northeastern strike bordering the southeastern side of the Argun Basin (in Chinese territory). The Argun earthquake was felt in Russia with an intensity of II–III to V at the epicentral distances up to 255 km. The intensity of shaking did not exceed values suggested by new GSZ-2012 and GSZ-2014 seismic zoning maps of Russian territory. Nevertheless, the question on the possible occurrence of stronger earthquakes in the studied region remains open.