| Author/s: | B. Bolzon, L. Brunetti, M. Esposito, A. Jeremie, U. Rotundo, S. Tomassini
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| Title: | Ground Motion Measurements at LNF
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Report: | LNF - 09 / 13(P)
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| Date: | 19-11-2009 |
| PACS: | 07.10.-h, 46.40.-f |
| Pubblished on: | Submitted to the IPAC10 Conference, Kyoto, Japan, 23-28 May 2010 |
| PDF File: | LNF-09-13(P).pdf |
| Abstract: | Preliminary measurements of ground motion have been done at the LNF for Super B site characterization. Measurements done during 18 hours in the vertical direction near a main road on surface show that earth motion (from 0.2Hz to 1Hz) is around 70nm, and that cultural noise (from 1Hz to 100Hz) varies from about 12nm to 35nm between 17h40 and 8h00 and from 38nm to 65nm between 09h40 and 11h40 on average, but highly increases between 8h00 and 09h40 due to traffic of rush hours ([3; 30] Hz) up to 240nm. However, measurements done during 20 minutes simultaneously on the surface and a 50m depth hole show that cultural noise is well attenuated in depth on its entire bandwidth (from 1Hz up to at least 100Hz). Vertical ground motion measured for 20 minutes in three other points located near various vibration sources during non rush hours the day was shown to be almost the same, about 70-80nm from 0.2Hz to 100Hz and about 30-35nm from 1Hz to 100Hz on average. Also, ground motion measurements done during 20 minutes simultaneously in the three directions at two points (located also near different vibration sources) show that horizontal motion is not much higher than vertical motion compared to horizontal tolerances which should be much less strict than the vertical one. To finish, measurements of ground motion coherence has been done for different distances on two different floors close to each other at LNF (soft and rigid) and compared to the one of ATF2 where a special floor was built for stability. Results confirm that a rigid floor keeps the coherence at higher frequencies, and that the LNF floor is much better than the one of ATF2 although it was not built for stability. |
