Source complexity of the 1988 Armenian earthquake: evidence for a slow after-slip event

Abstract

Teleseismic P and S waves were analysed using a multiple-event deconvolution method to investigate the source process of the Spitak, Armenia, earthquake of December 7, 1988. Teleseismic long-period body waves exhibit complex waveforms. Two groups of subevents were identified. One is a group of strike-slip events during the first 20s. The other is a dip-slip event initiating at about 30s after the initial rupture. The tensor sum of all the subevents is essentially strike-slip with a scalar moment of 1.47×1019Nm. The seismic moment of the dip-slip event is 5.6×1018Nm, nearly 40% of the total, and the moment release rate is slower than the other subevents with a strike-slip mechanism. The mechanism of the after-slip event is consistent with the present-day deformation pattern in the Caucasus where north-south compression is predominant due to the continental collision between the Arabian plate and the Russian platform. -from Authors