Muography in Usu
Taro KUSAGAYA1, Hiroyuki TANAKA1, Akimichi TAKETA1,
Hiromistsu OSHIMA2, Tokumitsu MAEKAWA2,
Izumi YOKOYAMA3
1. Earthquake Research Institute, University of Tokyo
2. Usu Volcano Observatory, Hokkaido University
3. The Japan Academy
Table of Contents
• Introduction
– Motivation: why development ?
– The issue of noise in conventional detector
• Methods
– Linear cut method with multilayer detector
• Results and discussion
– Improved data of test measurement in Usu volcano
• Summary
1
Introduction
Method
Result
Discussion
Summary
Motivation: why development?
cosmic ray muons penetrate
a volcano
• If昭和新山[Tanaka
et al., 2007]
a thickness of > 1 km, muography is difficult.
–with
火道構造
↓Because et al., 2009a]
• 薩摩硫黄島硫黄岳[Tanaka
More
thickness of rock results in less muons(signal),
– 脱ガス現象
• 浅間山[Tanaka
et al.,
2009b]
that is, worse
signal-to-noise(S/N)
ratio.
– 2009年噴火前後の変化
↓Then
• La
Soufrière（フランス）[Lesparre
et of
al.,a large
2012]
In order
to obtain a real density structure
– 溶岩ドーム密度異方性
volcano, muography needs improvements.
• Puy de Dôme（フランス）[Cârloganu et al., 2012]
↓So
– Puy de Dome上部の密度
We developed a low noise muon detection system.
2
Introduction
Method
Result
Discussion
Summary
The issue of Background(BG) noise
in conventional detector
EM shower particle
(electron, positron, gamma ray)
Conventional
detector
μ?
A fake track is generated by accidental coincidence of
electromagnetic(EM) shower particles
3
Introduction
Method
Result
Discussion
Summary
Noise reduction by software
-Linear cut methodUse multilayer detector
→Check the linearity of a detection pattern by software.
μ?
4
Introduction
Method
Result
Discussion
Summary
Noise reduction by software
-Linear cut method-
μ
5
Introduction
Method
Result
Discussion
Summary
Noise reduction by software
-Linear cut methodText data of WHEN and WHERE muons passed in each position
sensitive detector is recorded.
Time, X1,Y1, X2,Y2, X3,Y3, …
Then process the text data with our AWK code.
X_i_min = linearcut1_slopeX * (plane_combination[i]-1)
X_i_max = linearcut1_slopeX * (plane_combination[i]-1)
gridX_i_min = $(4*(plane_combination[i]-1)+3)
gridX_i_cen = gridX_i_min + 0.5*width_of_scintillator
gridX_i_max = gridX_i_min + width_of_scintillator
. . . . . .
μ
6
Introduction
Method
Result
Discussion
Summary
Verification test
Usu Volcano, Hokkadio, Japan
Measurement range（±30°）
1 km
Negative azimuth
−φ
Positive azimuth
+φ
Oo-Usu
Showa-Shinzan
Lake Toya
Ko-Usu
Usu-Shinzan
Installed place
（Usu Volcano Observatory, Hokkaido Univ.）
Meiji-Shinzan
7
Introduction
Method
Result
Discussion
Summary
Verification test
Detector configuration
From Oct. 20, 20121 km
7 layers, effective area 1.21 m2
10x10 cm2/segment
）Negative
azimuth ±3°
Angular resolution
Measurement range（±30°）
Positive azimuth
+φ
−φ
Oo-Usu
Showa-Shinzan
76
54 3
2 1
Lake Toya
Ko-Usu
Usu-Shinzan
Installed place
（Usu Volcano Observatory, Hokkaido Univ.）
Meiji-Shinzan
1.21 m2
Oo-Usu
8
Introduction
Method
Result
Discussion
Summary
Verification test
Usu-Shinzan
Oo-Usu
300
Open sky
2000
200
100
-600
3000
> 1 km
-400
-200
South
Path
Length
0
200
azimuth φ [mrad]
1000
400
600
0
Path length[m]
elevation θ [mrad]
Muon path length distribution
Oo-Usu Usu-Shinzan
θ
φ
©Google Earth
9
Introduction
Method
Result
Discussion
Summary
Results
elevation θ [mrad]
raw data from conventional 2-layer detector
Oo-Usu
Usu-Shinzan
1276 2684 4447 6713 9269 11917 15472 18533 21306 23942 26814 24178 21213 18148 15206 11891 9275 6477 4338 2662 1329
300 1263
200
2715 4585 6807 9828 12426 16215 19241 20589 20657 17832 17003 16278 12989 10572 7952 5653 3895 2928 1754
869
1376 2709 4563 6631 9374 11605 14262 12670 8207 6069 5748 5055 4713 3651 3368 2658 2163 1428 1092
799
329
1068 2036 3175 3972 4640 4938 5016 3604 3617 3877 4488 3837 3452 2681 2381 1998 1645 1138
976
712
266
1390 1686 2129 2338 3045 3227 3831 4328 5056 4468 3951 3032 2600 2131 1759 1291 1098
780
299
100 462
-600
The data do NOT reflect the
distribution of path length.
817
-400
-200
0
200
azimuth φ [mrad]
400
> 1km
thickness
600
μ
10
Introduction
Method
Result
Discussion
Summary
Results
elevation θ [mrad]
raw data from 7-layer with software analysis
Usu-Shinzan
Oo-Usu
300
200
827
1809 2981 4715 6414 8707 10135 11863 13133 14141 17705 14020 12820 11517 9597 7633 5516 3884 2283 1425
886
777
1802 2969 4572 6573 8848 10306 11943 12334 11671 10652 9092 9060 7417 6042 4504 3046 2092 1300
797
532
848
1757 2878 4387 6197 8009 8906 7422 3697 1943 1321 1156 1190 1000
602
149
100
-600
466
339
141
101
66
1126 1721 2139 2379 2510 2032
143
89
47
33
18
181
80
85
33
22
13
195
217
216
-400
277
827
699
The
data reflect the
826 435 373 395 305 271 217 201 200
distribution of path length.
238 241 240 280 295 224 181 143 142 103
-200
0
200
azimuth φ [mrad]
400
> 1km
thickness
600
μ
11
Introduction
Method
Result
Discussion
Summary
Results
Noise reduction rate
Data(2-layer) - Data(7-layer)
´100
Data(2-layer)
100
90
400
300
50
200
100
-600
> 1km
thickness
-400
-200
0
200
azimuth φ [mrad]
400
600
0
Noise reduction rate[%]
elevation θ [mrad]
Noise reduction rate[%] =
12
Introduction
Method
Result
Discussion
Summary
Results
Density distribution
Usu-Shinzan
Oo-Usu
A
Showa-Shinzan
B
Usu Volcano
Lake Toya
13
Introduction
Method
Result
Discussion
Summary
Results
Density distribution on AB cross section
Measurement
duration
1977 hours
2.4
Altitude Elevatio
n[mrad]
[m]
1185 600
836 400
AA
BB
Oo-Usu
(φ=0 mrad)
662 300
Usu-Shinzan
(φ=398 mrad)
2.1
1.8
488 200
density [g/cm3]
1011 500
314 100
140
1.5
0
−600 −500 −400 −300 −200 −100 0
−1044 −871 −696 −522 −348 −174 0
100 200 300
174 348 522
400 500 600 Azimuth[mrad]
696 871 1044 Distance[m]
14
Introduction
Method
Result
Discussion
Summary
Discussion
Comparison with resistivity
Oo-Usu
SW
A
Showa-Shinzan
B
Usu Volcano
NE
Usu-Shinzan
Lake Toya
15
Introduction
Method
Result
Discussion
Summary
Discussion
Altitude (m)
Comparison with resistivity
Fault UsuShinzan
SW
500
NE
250
(Ωm)
10000
SW
100
0
A
-250
-1
0
1
Distance (km)
After Ogawa et al.(1998)
10
1
Fault zone
Usu Volcano
NE
Lake Toya
16
Introduction
Method
Result
Discussion
Summary
Summary
• We developed a discrimination method with
multilayer muon detector.
• We obtained a density distribution with a path
length of more than 1 km in Usu volcano.
• We found high- and low-density anomalies
beneath between Oo-Usu and Usu-Shinzan
• We’re planning to apply our new detection system
to other active volcanoes (e.g., Shinmoe-dake).
17