Migration of pulsations after earthquakes

The analysis of the records from IRIS broadband seismic stations revealed wave trains with a period of ~129.5 min emerging after the strong earthquakes. These wave trains are simultaneously observed at the stations shifted by 180° in longitude in the form of the oscillations with opposite polarity. The occurrence time of the wave trains at the different stations testify to their westward migration by 2.5° per hour. The wave trains are earlier recorded at the stations that are close to the earthquake’s epicenter and to its antipode; they become less manifest with the increase in the distance from the station to the line connecting the epicenter with its antipode. The amplitude of the oscillations in the wave trains is estimated at a few mm and μGal. The wave trains presumably reflect the emergence of an area of free postseismic flexural oscillations of the lithosphere.