Detection of high-frequency tensile vibrations of a fault during shear rupturing: Observations from the 2008 West Bohemia swarm

Abstract

The analysis of 12 earthquakes of magnitudes between 1.7 and 3.7 that occurred in 2008 in West Bohemia, Czech Republic reveals that shear rupturing along a fault is accompanied by weak tensile vibrations of the fault. The vibrations are of a narrow frequency band with frequencies distinctly higher than those of shear rupturing. The tensile vibrations decay slowly in time and often resemble resonant waves. They complicate the radiated P waveforms and the P-wave radiation pattern. The tensile vibrations can be observed in waveforms in directions near the nodal lines where the dominance of shear-faulting radiation is lost. The tensile vibrations are probably generated by opening of the fault during shear rupturing or by creating a wing tensile crack at the tip of the fault when shear fracturing stops. © 2011 The Author Geophysical Journal International © 2011 RAS.