Method for prediction of off Ibaraki M7 characteristic earthquakes based on seismicity change
description
Transcript of Method for prediction of off Ibaraki M7 characteristic earthquakes based on seismicity change
Method for prediction of off Ibaraki M7 characteristic earthquakes based o
n seismicity change
Shozo Matsumura
(NIED)
Recent Characteristic Earthquakes off Ibaraki Prefecture
A: 1982M7.0
B: 2008M7.0
Seamount discovered by Mochizuki et al. (2008)
27.4y 19.9y 22.4y 16.8y 25.8y
a
cd1
d2
A Bb
?
C2027 - 2035
One Century History of Characteristic Earthquakes Sequence off Ibaraki Prefecture
Micro-seismicity observed by NIED for 30 years
Event AEvent B
Micro-earthquake Density Maps before event B
Ratio of Density Maps
2007.7.8. – 2007.12.7. 2007.12.8. – 2008.5.7.
Before event B
Correlation coefficient
r(A:B) = 0.577
Degree of freedom
n = 22
Significance level
e = 0.16 %
Before event
Before event
- 0.5
- 0.4
- 0.3
- 0.2
- 0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
1980 1985 1995 2000 20051990
A: 1982.7.23. B: 2008.5.8.
Cor
rela
tion
coef
ficie
nt (
r)
Pacific Plate
asperities
The point of this method is existence of “Preparing stage”
• Distribution of inhomogeneous asperities
• Quasi-static slipping
• Stress redistribution
- 0.5- 0.4
- 0.3- 0.2
- 0.10
0.10.2
0.30.4
0.50.6
0.70.8
0.91
B: 2008.5.8.
Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
2007 2008
Cor
rela
tion
coef
ficie
nt (
r)
3.5 months before
4 days before
r0 = 0.53
2008 2009
- 0.4
- 0.3
- 0.2
- 0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
B: 2008.5.8.
Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb
Cor
rela
tion
coef
ficie
nt (
r)
rA
rB