Below the EM data are low and high sampled seismic data. On the right plot are EM data from PKD1 shown in the top five traces and seismic data from both PKD1 and PKD, shown below. The mechanism for such an EM field is presently unknown. One explanation for these signals could be local ground motion at PKD1 since there is no corresponding signal on seismic traces 9 and 10 from PKD which is 12 km away. Hollister data on the left and Parkfield data on the right.
Vertical scale is counts and horizontal scale is time.
The lower five traces are seismic data. From Parkfield the 1 Hz seismic data comes from both PKD1, traces 6-8, and PKD, traces 9 and 10. Note, the first EM channel from Parkfield, Ex, is down. The extraction of such information from the array data is another indication of the high sensitivity to anomalous EM fields. Under Frank Morrison's general supervision, Sierra Boyd, Bill Karavas, John Friday, Dave Rapkin, and Doug Neuhauser contribute to the operation of the MT observatories.