The 14th Symposium on Accelerator Science and Technology, Tsukuba, Japan, November 2003

CHARACTERISTICS OF MICRO TREMOR IN KEKB (TSUKUBA)
Y.Nakayama, T.Ito, Electric Power Development Co.,Ltd., Kanagawa, Japan
R.Sugahara, S.Takeda, M.Yoshioka, H.Yamaoka, KEK, Ibaraki, Japan
S.Yamashita, ICEPP, University of Tokyo, Tokyo, Japan
Abstract
Stability of ground is preferable for accelerator beam
operation. We have measured micro tremor of ground atthe KEKB site.
In this paper, some of analysis results are shown, andthe characteristics of the ground motion at the KEKB site
are discussed.

INTRODUCTION
Stability of ground is preferable for accelerator beam
operation. For example, position errors of quadrupole
magnets are required to be less than 5nm in theacceleration area and even 1nm at the collision point in
GLC (Global Linear Collider)[1]. In general, the hard rockbed is stable and has less seismic noise. It is very
important to know the characteristics of the groundmotion to select the site for an accelerator facility such asGLC. We have measured micro tremor of ground part andunderground part at the KEKB site. The KEKB is locatedon the diluvium ground in Kanto plain, and the KEKB
tunnel is buried 10m deep in the ground.
Measurement executed in the KEKB tunnel is reported.
Some analysis results on vertical ground motion are
shown, and the characteristics of the ground motion at theKEKB site are considered. Effect of traffic noise to theground motion is also discussed.

The measurement points in each facility are listed inTable 1. Some examples of the measurement points areshown in Figure 2 and Figure 3.
Table 1: List of measurement points
Measurement

BaseFacility

PointsCondition

D09

D03

OhoUndergroundOn concrete

Set upSet upSet upGround (1)On concrete

Set upSet upSet upGround (2)On soil

Set upSet up-Ground (3)On soil

Set upSet up-Ground (1)(concrete)
10m
UndergroundFigure 2: Measurement points in the Oho exp. hall
Underground

OUTLINE OF MEASUREMENT
Measurement points
The measurement was individually executed in threefacilities of KEKB. The facilities where the measurement
was executed are shown in Figure 1. The measurement
facilities were selected to understand the influence fromutilities and traffic. Three facilities were selected along
the KEKB ring, one of which is close to the main street,
Higashi-odori, and the others are far from it.

D03(Power supplybuilding)

D09(Power supplybuilding)Higashi-odori

OHO(ExperimentalHall)

Figure 1: Measurement facilities in KEKB

Ground (2)(Soil)

Higashi-Oodori

Ground (1)(concrete)

Ground (3)(Soil)

Figure 3: Measurement points in the D03 building

Condition of Measurement
The measurement was executed during the machine
shutdown period. The sampling frequency was set to be
100Hz in all measurements. The condition ofmeasurement is listed in Table 2.
Table 2: Condition of measurement
FacilityPoints

Measuring periodD09

4

13:00 Jan 5,2003∼12:10 Jan 6,2003

D03

4

13:00 Jan 8,2003∼12:10 Jan 9,2003

OHO

2

13:00 Jan 15,2003∼12:10 Jan 16,2003*10 minutes duration in every hour for 24 hours

The 14th Symposium on Accelerator Science and Technology, Tsukuba, Japan, November 2003

0.0050

00:10
01:10

02:10
03:10

04:10
05:10

06:10
07:10

08:10
09:10

10:10
11:10

12:10

00:00
01:00

02:00
03:00

04:00
05:00

06:00
07:00

08:00
09:00

10:00
11:00

12:00

Figure 6: RMS of vertical velocity of ground motion
at the Oho experimental hallComparison with the results of traffic census
In the measurement at the D03 building, the traffic
census was executed in Higashi-odori. The results of thetraffic census are shown in Figure 7, and the comparison
between the RMS and traffic is shown in Figure 8.
500
450
Number of traffic (number)

The obtained data is time history in velocity. We
calculated the RMS of them, and observed the variationaccording to time of the day. We pay attention to thevertical component. Results for the D09 building areshown in Figure 4, and those for the D03 building inFigure 5, and those for the Oho hall in Figure 6.
From these results, the RMS in the underground isgenerally lower than that on the ground. The RMS in theunderground of the D03 building is about two times larger
than that of the D09 building at daytime. By the way, it
can be seen that there is the correlation between the RMS
and the wind at the D09 building. It is thought that thiscorrelation is due to some towers for power line near theD09 building. But we have to pay attention to that thetraffic and the data of wind have the same variationaccording to time of the day.

22:10
23:10

Comparison by RMS value in time history

22:00
23:00

020:10
21:10

10.0000

20:00
21:00

20.0005
18:10
19:10

30.0010

18:00
19:00

40.0015

16:10
17:10

50.0020

14:10
15:10

60.0025

16:00
17:00

70.0030

13:10

80.0035

14:00
15:00

RESULTS OF MEASUREMENT

90.0040

13:00

RMS in velocit y (kine)

In this measurement, we used the servo type velocity
meter VSE355G2 (Resolution: 10e-6 gal, Frequency
band: 0.012-70Hz) and the data logger SAMTAC802H.
These are manufactured by Tokyo Sokushin Co.,Ltd.
Before accumulating data, VSE355G2 and STS-2 werecompared on the same granite block, and the comparison
authorization was executed.

10OHO Underground of KEKB t unnel
OHO Ground➀ on concret e
Wind Speed Tsukuba AMeDAS point )0.0045Wind velocity m/ sec

Measurement instruments

400350full-sized car
large-sized car[Special note]➀It is not possible to measure it at 18:00-18:10.
➁5:00-5:10 is measured only for 7.5 minutesThe conversion value is indicated.

300
250
200
150
1000.0050

1008
70.0030

60.002550.002040.001530.001020.0005

1

Figure 7: Results of traffic census in Higashi-Oodori
0.00500.0040RMS in velocity (kine)

12:00~12:10
12:00~12:10

10:00~10:10
11:00~11:10

Figure 5: RMS of vertical velocity of ground motion
at the D03 power supply building

Wind velocity (m/sec)

0
08:00~08:10
09:00~09:10

0.000006:00~06:10
07:00~07:10

1

04:00~04:10
05:00~05:10

20.0005

02:00~02:10
03:00~03:10

30.001000:00~00:10
01:00~01:10

0.001522:00~22:10
23:00~23:10

4

20:00~20:10
21:00~21:10

50.0020

18:00~18:10
19:00~19:10

60.0025

16:00~16:10
17:00~17:10

7

12:00~12:10

0

8

09:00~09:10
10:00~10:10
11:00~11:10

0.000006:00~06:10
07:00~07:10
08:00~08:10

0.02

9

04:00~04:10
05:00~05:10

0.000501:00~01:10
02:00~02:10
03:00~03:10

0.04

10

22:00~22:10
23:00~23:10
00:00~00:10

0.06

0.0010

20:00~20:10
21:00~21:10

0.08

0.001517:00~17:10
18:00~18:10
19:00~19:10

0.1

0.00200.0030

14:00~14:10
15:00~15:10

0.14
0.120.0035

13:00~13:10

RMS in velocity (kine)

0.00400.160.0025

14:00~14:10
15:00~15:10
16:00~16:10

D03 Underground of KEKB tunnel
D03 Ground➀ (on concrete )D03 Ground➁ (soil)
D03 Ground➂ (soil : near Higashi-Oodori)Wind Speed Tsukuba AMeDAS point

0.00450.18

0.0030Figure 4: RMS of vertical velocity of ground motion
at the D09 power supply building
0.00500.003513:00~13:10

11:00~11:10

09:00~09:10
10:00~10:10

07:00~07:1008:00~08:10

06:00~06:10

04:00~04:10
05:00~05:10

03:00~03:10

01:00~01:10
02:00~02:10

23:00~23:10
00:00~00:10

22:00~22:10

20:00~20:10
21:00~21:10

19:00~19:10

17:00~17:10
18:00~18:10

15:00~15:10
16:00~16:10

14:00~14:10

0
13:00~13:10

0.00000.2

D03:Underground of KEKB tunnel
D03:Ground➀ (on concrete)
D03:Ground➁ (soil)
D03:Ground➂ (soil : near Higashi-Oodori)
Normalized Traffic (full-sized car)
Normalized Traffic (large-sized car)0.0045

Amount of normalized traffic(Total traffic is assumed 1 per day (each size))

0.0035

13:0
0
14 ~13::0
0 10
15 ~ 14:0
0 :10
16 ~ 1:0 5:1
00
17 ~ 1:0 6:1
00
18 ~ 1:0 7:1
00
19 ~ 1:0 8:100
20 ~ 1:0 9:1
0
021 ~ 2:0 0:100
22 ~ 2:0 1:100
23 ~ 2:0 2:1
0000 ~ 23:0
0 :10
01 ~ 0:0 0:1
0002 ~ 01:0
0 :10
03 ~ 0:0 2:1
0004 ~ 0:0 3:1
0005 ~ 0
4:0
0 :10
06 ~ 0:0 5:1
0
007 ~ 0:0 6:10008 ~ 0:0 7:1
0009 ~ 0:0 8:100
10 ~ 0:0 9:1
0011 ∼ 10:00 :1012 ∼11::00∼ 10
12:1
00.0040

9Wind velocity (m/sec)

0.0045
RMS in velocity (kine)

50

D09:Underground of KEKB tunnel
D09:Ground➀ (on concrete)
D09 Ground➁ (soil)
D09 Ground➂ (soil : near the tower for power line)
Wind Speed (Tsukuba AMeDAS point)

Figure 8: Comparison between the RMS and traffic
at the D03 power supply building
According to these results, it is clear that the variationfor traffic according to time of the day has the correlation
with the RMS in velocity. Even if the KEKB tunnel isburied 10m deep in the ground, the energy of traffic
vibration is transmitted into the direction of theunderground.

The 14th Symposium on Accelerator Science and Technology, Tsukuba, Japan, November 2003

Spectral analysis
The spectra for 24 measurements were analysed. The
duration of measurement is 10 minutes. Those spectra
were averaged. The averaged spectra of vertical groundmotion over 24 hours are shown. The spectra at the D09
are shown in Figure 9, and those at the D03 in Figure 10,
and those at the Oho experimental hall in Figure 11.

Figure 9: Spectra of vertical ground motion at the D09

Figure 10: Spectra of vertical ground motion at the D03

on the ground part and the underground part look almost
the same on the low frequency side from about 3Hz. It isconsidered that the ground motion around this frequency
band is a vibration based on the position that is deeper
than the KEKB tunnel. But the difference in the amplitude
between the ground part and the underground part isremarkable on the high frequency side from about 3Hz.
Comparing the spectra at the D09 building, those at theD03 building and those at the Oho experimental hall, thespectra at the D03 building are most remarkable. When
we pay attention to the gentle peaks around 10-20Hz, wecan find two characteristics. One is that the gentle peaks
around 10-20Hz can be seen at the D03 building. The
other is that the difference between the underground partand the concrete part is seen at the D03 building, but thatis not seen at the others. It is indicated that there weresome influences from the traffic near the D03 building. Itis considered that the vibration due to heavy traffic istransmitted from the ground toward the direction of theunderground through the concrete structure.

SUMMARY
The micro tremor measurement was executed in the D09
building, the D03 building, and the Oho experimental hallin KEKB. The followings are observed in the analysis ofthe data.
• The peak around 0.2Hz and 2Hz-3Hz can be seenin all measurement points.
• The amplitude of the vertical ground motion
around 10-20Hz is remarkable at the D03 building.
It is thought that there are some influences fromthe heavy traffic.
• If there are some vibration sources in surroundings,
the vibration is transmitted from the groundtoward the direction of the underground.
• There is a possibility that the level of the groundmotion grows up due to some high structures insurroundings when the wind is strong.

ADDRESS OF THANKS
We thank to the staff of Electric Power Development Co.,
Ltd. who helped us in setting instruments andaccumulating data during the measurement period.

REFERENCES

Figure 11: Spectra of vertical ground motion at the Oho
In all spectra, two peaks are observed clearly. One isaround 0.1-0.2Hz, which is said to be caused by somenatural phenomena such as ocean swells and the wind.
The other is around 3Hz, which is said to be caused bysome artificial noise such as traffic noise and utility noisein factories. At the each measurement point, the spectra[1] ACFA, JHEPC and KEK, “JLC Project, Linear Collider for
Tev Physics”, JLC Project Report, March 2003.
[2] Y. Nakayama, et al., Characteristics of micro tremor in
SPring-8 (Harima), Proceedings of the 14th Symposium ofAccelerator Science and Technology, Tsukuba, Nov. 11-13,
2003.
[3] Y. Nakayama, et al., Comparison of micro tremor between
KEKB and SPring-8, Proceedings of the 14th Symposium ofAccelerator Science and Technology, Tsukuba, Nov. 11-13,
2003.