On the stress drop in North Eurasia earthquakes source-sites versus specific seismic energy

Abstract

A generalization of the results on the stress drop and the specific seismic energy for the earthquakes in Northern Eurasia has been made. The relationship of these parameters with the seismic moment and the magnitude has been analyzed. Detailed studies for the Northern Tien Shan (Bishkek geodynamic polygon) were carried out, the values of the dynamic parameters of the sources for 183 earthquakes of various energy classes (K = 8.7–14.8) were obtained: angular frequency, spectral density parameter, scalar seismic moment, source radius, stress drop level, seismic energy and specific seismic energy. Two models have been used to compute the source radius and the stress drop – the Brune approach and the improved Madariaga–Kaneko–Shearer model. For relatively weak events, a power-law dependence (regression) of the stress drop on the scalar seismic moment M0 has been identified, that complies with the results on the power-law dependence of the specific seismic energy on M0 in a number of other regions of Northern Eurasia. The relationship between the type of source movement and the stress drop level has been noted as well.

Keywords

• earthquake source
• magnitude
• seismic moment
• stress drop
• specific seismic energy
• scaling dependence