IDA DCC staff routinely review data segments including the teleseismic P-arrival from moderate earthquakes to make certain that the timing is grossly correct and that the instruments are behaving properly. In the plot below, the trace of the primary seismometer (an STS1) is shown in blue, and the trace of the secondary sensor (an STS2) is shown in red. The horizontal data from the secondary sensor is rotated into the frame of the primary sensor to permit a direct comparison.
