T. MacDonald, J. Kissel

Initial measurements of the H1EX piers and floor were taken on 8-15-14 to establish that the B&K system and accelerometers were functioning as expected. These were done with a B&K 4506 
accelerometer on each north edge of the top of north side piers, and another on the north side of the chamber about 5 ft from the top. The B&K 8340 accelerometer was centered under the beam tube 
and 1 ft north of the center line between the north piers. During these measurements, no features were found near 8 Hz.

There were some concerns about the coherence of the 4506 accelerometers at 8 Hz, which was generally below 0.5. The 8340 accelerometer coherence was much better, so on 8-16-15 it was mounted on the 
top of the northeast pier next to one of the 4506s. Measurements were taken again at several points on the ground and the pier, with still no features at 8 Hz. However, an impact on the crossbeam
showed a clear feature in the frequency response at 8 Hz. To characterize this response, a full set of measurements was taken around the floor and along the pier and crossbeam. Results were
consistent and key measurements are outlined. Full results and files are also available on the SVN at https://svn.ligo.caltech.edu/svn/seismic/Common/PierMotionStudy/EXH1/20140816.

Following these measurements, the 8340 was moved to the crossbeam and a measurement sequence covering the full north side was created to examine floor motion and mode shapes of the structure. These measurements
were completed and further analysis will follow. More extensive measurements of all four piers will also be completed.