Negative repeating doublets' in an aftershock sequence

Abstract

We observed some 'negative repeating doublets', with nearly opposite three-component waveforms, in the aftershock sequence of the 2008 Wenchuan earthquake. The 'negative repeaters' are identified by using the broadband seismic record (with frequency range from 1 to 10 Hz) of the Wenchuan station (WCH) with a near epicenter distance from 19.7 to 26.6 km. These opposite three-component waveforms are not due to the changing of polarities of the seismic station.