This information needs to be completed with back azimuth usually derived from P-wave polarization or S-wave polarization (Eisner et al.
Note that the back azimuth measured from the P-wave particle polarizations has constrained the locations of the perforations relatively well with a small scatter corresponding to several degrees.
To determine the back azimuth of the events we used only the P-wave arrivals.
In this stimulation the fracture probably grew twice as long to the east then to the west, although this observation is based on the least certain back azimuth observation.
We analyzed eleven teleseismic earthquakes recorded by USArray (a transportable seismic array) for back azimuth
The hypocentral area of swarm 2000 was relatively small and values of back azimuth
did not vary to much for used stations (but for NKC station--due to its position directly in the epicentral area).
The epicentral distance and the time difference is needed to estimate the absolute value of group velocity and the back azimuth was used to transform the horizontal components of the record.
According to the back azimuth [alpha] the north-south (N) and the east-west (E) components were transformed using
The presence of surface waves at "wrong" component could be explained by lateral heterogeneity (Levshin, 2002) due to which the waves do not propagate along the great circle path and they come to the station from another direction than the geometrical back azimuth predicts.
The back azimuth assigns the direction from the Praha seismic station to the epicenter.
The ingenuity and flexibility of TACPs, whether serving with special forces on horseback in Afghanistan or using bomb-crater analysis to establish back azimuths
to enemy firing locations, demonstrate their role as the vital nexus of the emerging air-ground dynamic.