Transcript Slide 1

Lecture - contents
1. Introduction
- Activity; data processing; approach
2. Radon and earthquakes in
the DSR
3.
Rn as a proxy of subtle
geodynamics - other indicators
4. Conclusions and implications
1
Radon - as a geophysical tracer
• Ultra trace gas in geogas
(== “air” in subsurface porosity)
• Noble gas
• Radioactive
• Easily measurable with high sensitivity using
electronic systems
• Extremely large variations in space and in time
• A unique combination  a unique tool
Local stress/strain,
inducing minute changes
in rocks (source),
enhances release of
radon into the geogas
environment.
T0
This radon is available
for transfer from source
to detector
DL/L = 0
T1
Detector
s
s
Advection
DL/L=
10-7-10-10
3
Source
Measurement principles
U-238 radioactive decay series
Decay → recoil → Rn emanation
Detection
g
a
a
Solid
Geogas
3.82 days
4
1620 years
Earthquakes
1900-1990
Monitoring sites
along Dead Sea
Transform
5
Radon monitoring arrays along the Dead
Sea Rift (DSR)
NW Dead Sea
• Array of stations covering a 20km sector
• Next to main western DSR active fault trace
• 1.5m deep in unconsolidated gravel
• Monitoring since 1994
Intraplate
• Depth: 1.2m & 90m
• Massive syenite
Southern sector of DSR
• Array of stations covering a 20km sector
• Precambrian basement rocks of uplifted
boundary blocks of DSR
6
NW Dead Sea
19W – 19E
17W
23W – 23E
21W
Ramon
Arava margin
BGO
Roded
E1, E2, E3
7
IUI
C
High Rn zone
Monitoring
Rn (gamma) sensor
Integration time: 15 min
1994-2005
8
9
E
W
Rn monitoring
at 1.2 meter in gravel
Dead Sea
Graben fill
U bearing
phosphorite
10
u
u
Rn on
carrier gas
u
u
u
u
Alpha and gamma co-registration
17W - time series
140
1600
120
1400
100
80
1200
60
40
1000
20
0
800
4700
4720
4740
4760
Days since 1.1.1992
• Radon !
• Geophysical sensitivity - High
4780
1800
Alpha (counts /15-minutes)
Alpha (counts /15-minutes x10)
Barasol (alpha)
PM-11(gamma)
Gamma (Counts/15-minutes, x1000)
1800
160
17W - hour resolution
Reference: Day 4690-->
1600
1400
1200
1000
800
600
400
200
0
800
1000
1200
1400
1600
Gamma (Counts/15-minutes, x1000)
11
1800
Multi-year, seasonal (and multi-day [MD]) variation signatures and signals
400
17-west, Daily average
Counts x 1000
300
200
100
0
1000
1500
2000
2500
3000
Days
1.1.92
Days
sincesince
1.1.1992
Radon time series of (gamma radiation) in geogas in gravel at main monitoring
site, NW Dead Sea, DSR.
1. Multi-year decrease (relative to stable background originating from solid gravel)
2. Seasonal variation
3. 12
Multi-day variations (MD) - statistically correlated to earthquakes in the Dead Sea Rift (Steinitz et
al., 2003; see below).
Seasonal, Multi-day (MD) and Diurnal Radon Signals (DRS)
Concordance & correlation of signals
140
45
40
35
30
25
20
Rn concentration, K-counts (19)
• Sites 12 km apart
• Next to the main
western boundary
fault of DSR
Rn concentration, K-counts (23)
50
A
120
100
80
60
1935
1940
1945
23
19
A
40
1800
1850
1900
1950
2000
Days since 1.1.1992
13
2050
2100
NW Dead Sea -15 km sector
Correlation of MD radon signals among three sites
• Depth:
2 meters
• Lithology:
gravel
300
17-W
19-W
23-W
58
36
34
200
56
19W
17W
38
150
32
54
30
100
52
28
50
50
1935
14
1940
Day since 1.1.1992
1945
26
23W
250
60
200
A
Counts/15-minutes (x1000)
Radon signal at site 17W
• 30 days
• varying gamma signal in
the geogas.
• composed of a multi-day
variation (MD) and a
superimposed diurnal
signal (DRS).
Signal
Smoothed
150
100
50
B – Separated diurnal
variation
2050
2055
2060
2065
2070
2060
2065
2070
X Data
10
0
-10
2040
15
2045
B
Counts/15-minutes (x1000)
A – Measured signal and the
smoothed signal
representing the multi-day
variation (MD)
2040
2045
2050
2055
Days since 1.1.1992
Average annual Rn concentration vs. Earthquakes
400
17-west, Daily average
Counts x 1000
300
200
100
0
1000
1500
2000
2500
3000
Days
1.1.92
Days
sincesince
1.1.1992
Multi-year time series of radon (gamma radiation) in geogas in
gravel at main monitoring site, NW Dead Sea, DSR.
16
35 0
300
5
250
90
90
150
Number of earthquakes
in Dead Sea rift
200
4
32 0
150
100
3
85
85
80
80
100
75
75
70
70
Radon
Radon
Earthquakes
65
65
50
50
31
0
60
60
1996
1996
2
Conclusion (1994-2004)
1998
1998
and
-100
2
3
4
5
to
to
to
to
3
4
5
5.3
50 km
100
150
200
250
Annual
number
of EQ along
DSR
17
(IJES 2005)
2004
2004
90
Annual average Rn concentration
counts/15-minutes / 1000
at monitoring station 17W
-50
Relationship
found between:
Magnitude
Annual average
1 Rn level
2002
2002
Year
Year
0
30 0
2000
2000
85
80
75
70
65
60
40
60
80
100
120
140
Annual number of earthquakes
in the Dead Sea rift
160
Annual
Annualaverage
averageRn
Rnconcentration
concentration
counts/15-minutes
counts/15-minutes//1000
1000
at
atmonitoring
monitoringstation
station17W
17W
33 0
NW Dead Sea, 1995-2004:
• Average annual Rn concentration
• Annual number of earthquakes in the DSF
For (1994-2004)
Relationship found between:
Annual average Rn level
and
Annual number of EQ along DSR
The relation between
400 km
• MD radon signals (at site
17W)
&
200 km
18
• earthquakes along the
Dead Sea Transform
Earthquake
Catalog
TECTONIC
SEGMENTS
Seismological
Div., GII
1994-2002
Arabian
plate
Israel-Sinai
plate
Dead Sea
rift valley
19
1075
earthquakes,
4.2≥ ML ≥ 0
M>2
M<2
Extraction “start” of MD Rn signal, time windows, Earthquakes
Start-time of MD radon signal
140
120
100
80
60
1900
1950
2000
2050
2100
Counts/15 minutes X1000
Counts/15 minutes X1000
Smoothing: 25-hour sliding average
Threshold: Relative amplitude > 1.9
100
90
80
70
60
50
1950
Days since 1.1.1992
1960
1970
1980
1990
Days since 1.1.1992
100
(40 Days)
90
minima
80
70
60
50
1950
1960
1970
1980
Days since 1.1.1992
20
1990
Counts/15 minutes X1000
Counts/15 minutes X1000
Bin = time window
100
90
80
70
60
50
1950
1960
1970
1980
Days since 1.1.1992
1990
Correlation between Rn MD signals and EQ in DSR
(Geology 2003)
40
0.01%
For:
ML>=2
RA = 1.9
Number of earthquakes
0.1%
1%
30
5%
Expected
20
10
8 Years: 1995-2002
0
-15 -12 -9
-6
-3
0
3
6
9
12 15
Days after start-time of MD radon signal
21
No. EQ(ML≥2): 165
Steinitz et al 2003
Earthquakes are
clustered in the 0-3
days after the starttime of MD Rn signal
40 C
of earthquakes
Number
Number
of earthquakes
Statistical significance Probability (%) of random
occurrence
Probability (%) of
random occurrence
0.01
0.1
1.0
5.0
30
20
10
Dead Sea, Kinneret
and Hula pull-apart
grabens
0
-15-12 -9 -6 -3 0 3 6 9 12 15
after Start-time
Days Days
after start-time
of radon event
Timing of 165 earthquakes (ML2) in the pull-apart grabens of the Dead
Sea Rift (Dead Sea, Hula+Kinneret) – relative to the start-time of a radon
MD signal.
22
(Steinitz, Begin, Gazit-Yaari, Geology 2003)
Previous approach focused on:
Counting earthquakes within
multi-day Rn anomalies
(Steinitz et al., 2003, Geology 31: 505-508)
New approach focuses on:
Counting days of
earthquakes and Rn anomalies
(unpublished)
23
MD-Starts and EQ correlation
Rn time series at 1-hour resolution
Smoothing: 25-hour sliding average
Residual time series
EQ Catalog
Regional sets
24
Smoothed time series
Extraction of MD starts,
Amplitude and RA
MD-starts  EQ
queries
Rn Start-times
4
3
160000
120000
2
80000
1
40000
0
1600
0
1610
1620
1630
1640
Days since 1.1.92
25
1650
1660
1670
Relative amplitude
Rn counts/15 min
200000
3 days
Rn Start-times for Relative Amplitude > 1.9
Earthquakes
4
3
160000
120000
2
80000
1
40000
0
1600
0
1610
1620
1630
1640
Days since 1.1.92
26
1650
1660
1670
Relative amplitude
Rn counts/15 min
200000
Flowchart for MD-Starts and EQ correlation
Radon time-series
Tectonic segment
Number of EQ
in tectonic
segment
Extraction of significant “starts”
(n ~ 150)
Number of
measurement
days
(1995-2004)
3 & 4 -day time window
(bin), Relative to “start”
Expected number of EQ per:
a) (1-day)
b) 3 & 4 -day time window
(bin)
All
“starts”
Count: number of EQ
in time window
(EQ in time-bin)n starts
Histogram: number of EQ in 3 & 4 -day bin
27
All
bins
Definition of “Rn anomaly days” for a time bin of n=3
after the start time of Rn anomalies
Rn anomaly
starts a.m
Rn anomaly days
1
2
3
623
624 625 626 627
Days since 1.1.92
628
629
Rn anomaly
starts p.m
Rn anomaly days
1
2
3
623
28
624 625 626 627
Days since 1.1.92
628
629
A day is characterized by two attributes:
Y N
1) It is a day in which
at least one earthquake (of
magnitude ≥ML) occurred (or not)
2) It is a day which occurred
n days after the start time of a Rn
anomaly,
with a certain Relative Amplitude
(or not)
29
Y
N
Y N
Y
N
Are these two attributes
independent ?
Use the 2 test to
determine the probability of
random occurrence
(One degree of freedom)
Did at least one
earthquake
occur in day?
Yes
No
Observed
count
day-start
Was day within Yes
Expected
n days after
Observed
start of
No
Rn anomaly?
Expected
Total number of days
30
Total
number
of days
(diff)
count
EQ
(diff)
Ntotal
Analyzing the Rn-EQ connection
1. For earthquakes out
of the Dead Sea rift valley
Rn monitor
Arabian
plate
Sinai
plate
Dead Sea
rift valley
31
0 to 2
2 to 4.601
For earthquakes 1994-2004, ML >0
Out of the Dead Sea rift valley,
Rn anomaly cutoff of Rel. Amp: 2.0
Did at least one
earthquake
occur in day?
Yes
No
Was day within Yes
3 days after
start of
No
Rn anomaly?
Total number of days
32
Total
number
of days
342
3094
607
2829
3436
For earthquakes 1994-2004, ML >0
Out of the Dead Sea rift valley,
Rn anomaly cutoff of Rel. Amp: 2.0
Did at least one
earthquake
occur in day?
Yes
Was day within Yes
3 days after
start of
No
Rn anomaly?
Observed
Expected
Observed
Expected
Total number of days
33
57
60.4
No
Total
number
of days
285
281.6
342
550
2544
546.6 2547.4
3094
607
3436
2829
For earthquakes 1994-2004, ML >0
Out of the Dead Sea rift valley,
Rn anomaly cutoff of Rel. Amp: 2.0
Σ [2] = 0.19
*
One degree of freedom
Was day within Yes
3 days after
start of
No
Rn anomaly?
Observed
Expected
Observed
Expected
Total number of days
35
Did at least one
earthquake
occur in day?
Yes
57
60.4
No
Total
number
of days
285
281.6
342
550
2544
546.6 2547.4
3094
607
3436
2829
* Including the Yates continuity correction
For earthquakes 1994-2004, ML >0
Out of the Dead Sea rift valley,
Rn anomaly cutoff of Rel. Amp: 2.0
Σ [2] = 0.19
Probability of
random occurrence = 0.66
No significant connection
Observed
Yes
Was day within
Expected
3 days after
start of
Observed
No
Rn anomaly?
Expected
Total number of days
36
Did at least one
earthquake
occur in day?
Yes
57
60.4
No
Total
number
of days
285
281.6
342
550
2544
546.6 2547.4
3094
607
3436
2829
Analyzing the Rn-EQ connection
2. For earthquakes within
the Dead Sea rift valley
Rn monitor
Arabian
plate
Sinai
plate
Dead Sea
rift valley
37
0 to 2
2 to 4.601
For earthquakes 1994-2004, ML >0
Within the Dead Sea rift valley,
Rn anomaly Relative Amplitude > 2.0
Did at least one
earthquake
occur in day?
Yes
Was day within Yes
3 days after
start of
No
Rn anomaly?
Observed
Expected
Observed
Expected
Total number of days
38
66
49.2
No
Total
number
of days
276
292.8
342
428
2666
444.8 2649.2
3094
494
3436
2942
For earthquakes 1994-2004, ML >0
Within the Dead Sea rift valley,
Rn anomaly Relative Amplitude > 2.0
Σ [2] = 7.03
Did at least one
earthquake
occur in day?
Yes
Was day within Yes
3 days after
start of
No
Rn anomaly?
Observed
Expected
Observed
Expected
Total number of days
39
66
49.2
No
Total
number
of days
276
292.8
342
428
2666
444.8 2649.2
3094
494
3436
2942
For earthquakes 1994-2004, ML >0
Within the Dead Sea rift valley,
Rn anomaly Relative Amplitude > 2.0
Probability of
random occurrence = 0.008
Significant connection
Was day within Yes
3 days after
start of
No
Rn anomaly?
Observed
Expected
Observed
Expected
Total number of days
40
Did at least one
earthquake
occur in day?
Yes
66
49.2
No
Total
number
of days
276
292.8
342
428
2666
444.8 2649.2
3094
494
3436
2942
Analyzing the Rn-EQ connection
We now test a Rnearthquake connection
within the Dead Sea rift
valley
for
3 days before the start
time of Rn anomalies
Rn monitor
41
Arabian
plate
Sinai
plate
Dead Sea
rift valley
0 to 2
2 to 4.601
For earthquakes 1994-2004, ML >0
Within the Dead Sea rift valley,
Rn anomaly Relative Amplitude > 2.0
Σ [2] = 0.98
Did at least one
earthquake
occur in day?
Yes
Was day within Yes
3 days before
start of
No
Rn anomaly?
Observed
Expected
Observed
Expected
Total number of days
42
55
48.5
No
Total
number
of days
282
288.5
337
439
2660
445.5 2653.5
3099
494
3436
2942
For earthquakes 1994-2004, ML >0
Within the Dead Sea rift valley,
Rn anomaly Relative Amplitude > 2.0
Probability of
random occurrence = 0.32
No significant connection
Was day within Yes
3 days before
start of
No
Rn anomaly?
Observed
Expected
Observed
Expected
Total number of days
43
Did at least one
earthquake
occur in day?
Yes
55
48.5
No
Total
number
of days
282
288.5
337
439
2660
445.5 2653.5
3099
494
3436
2942
10 years; 1994-2004
Earthquakes,
4.2≥ ML ≥ 0
Arabian
plate
Israel-Sinai
plate
TECTONIC SEGMENTS
Dead Sea
rift valley
44
Twelve 4-day time bins
around “start”
OUT-ofDSR
M>2
M<2
DSR
Testing for correlation between Rn MD signals and EQ in DSR
DSR
OUT-of-DSR
Observed no. of earthquakes & Expected number
Enrichment of earthquakes
Testing the statistical significance of enrichment
Or
Probability that correlation is a random one
(using the 2 criterion)
10 Years
(1995-2004)
45
RA = 1.8; 2.0
bins: 4 days
span: -24 to +24 days
relative to “start”
Earthquakes:
ML≥0;
ML≥2
Observed - Expected
Observed/Expected no. of EQ in DSR, ML >=2
Observed/Expected no. of EQ in OUT-of-DSR, ML >=2
50
RA > 1.8
RA > 2
Expected 1.8
Expected 2
40
RA > 1.8
RA > 2
Expected >1.8
Expected >2
40
Number
Number
30
30
20
10
10
ML >=2
ML >=2
0
0
-24
-20
-16
-12
-8
-4
0
4
8
12
16
20
-24
24
-20
-16
-12
-8
-4
0
4
8
12
16
20
Time bin relative to START
Time bin relative to START
Observed/Expected no. of EQ in OUT-of-DSR, ML >=0
Observed/Expected no. of EQ in DSR, ML >=0
RA > 1.8
RA > 2
Expected >1.8
Expected >2
140
120
100
80
60
40
20
24
RA > 1.8
RA > 2
Expected >1.8
Expected >2
140
Observed number
120
Number
20
100
80
60
40
20
ML >=0
0
-24
46
-20
-16
-12
0
-8
-4
0
4
8
12
Time bin relative to START
16
20
24
ML >=0
-24
-20
-16
-12
-8
-4
0
4
8
12
Time bin relative to START
16
20
24
Enrichment
Enrichment of EQ OUT-of-DSR, ML >=2
Enrichment of EQ in DSR, ML >=2
80
RA > 1.8
RA > 2
RA >1.8
RA >2
40
Enrichement (%)
Enrichement (%)
60
20
0
-20
40
20
0
-20
-24
-20
-16
-12
-8
-4
0
4
8
12
16
20
24
-24
-20
-16
Time bin relative to START
-12
-8
-4
0
4
8
12
16
20
24
Time bin relative to START
Enrichment of EQ OUT-of-DSR, ML >=0
Enrichment of EQ in DSR, ML >=0
50
RA > 1.8
RA > 2
20
RA > 1.8
RA > 2
Enrichement (%)
Enrichement (%)
40
10
0
-10
30
20
10
0
-20
-10
-24
47
-20
-16
-12
-8
-4
0
4
8
12
Time bin relative to START
16
20
24
-24
-20
-16
-12
-8
-4
0
4
8
12
Time bin relative to START
16
20
24
Statistical significance
Probability for random correlation in DSR, ML >=2
Probability for random correlation in OUT-of-DSR, ML >=2
RA >1.8
RA > 2
14
14
RA > 1.8
RA > 2
12
12
0.1%
0.1%
10
0.5%
2
8
Chi
Chi
2
10
1%
1%
6
6
4
0.5%
8
5%
5%
4
2
2
0
0
-24
-20
-16
-12
-8
-4
0
4
8
12
16
20
-24
24
-20
-16
-12
-8
-4
0
4
8
12
16
20
24
Time bin relative to START
Time bin relative to START
Probability for random correlation in OUT-of-DSR, ML >=0
Probability for random correlation, in DSR, ML >=0
14
12
12
0.1%
0.1%
10
2
0.5%
8
Chi
2
10
Chi
RA > 1.8
RA > 2
14
RA > 1.8
RA > 2
1%
6
0.5%
1%
6
5%
4
8
4
2
5%
2
0
0
-24
48
-20
-16
-12
-8
-4
0
4
8
12
Time bin relative to START
16
20
24
-24
-20
-16
-12
-8
-4
0
4
8
12
Time bin relative to START
16
20
24
Conclusions:
Earthquakes within the Dead Sea rift valley
(but not out of it)
• significantly occur within several days after the start
of Radon anomalies,
as recorded in the Dead Sea 17W monitor,
(but not before them)
[ The daily probability of earthquake occurrence
in “Rn-Anomaly days”
increases with the increase in the cutoff value
of Relative Amplitude of the Rn anomalies ]
49
Preliminary explanation
1. A transient strain causes increase in Rn flux
near the 17W monitor.
2. This strain may cause an earthquake to occur
several days later, somewhere within the Dead
Sea rift valley.
3. The higher the strain, the higher is the transient
Rn flux, and the higher is the probability of an
earthquake occurrence in “Rn anomaly” days,
relative to other days.
50
Summary of results of 10 years
of high-resolution Rn monitoring:
51
1. This study presents
a significant statistical relationship
between Rn flux and earthquakes
that occur within the same tectonic province
on an annual basis.
2. This study also presents a significant
statistical relationship
between Rn anomalies and earthquakes
that occur after the start time of the
anomalies
within the same tectonic province.
52
END
Thank You
53