two m5 earthquakes in corinth gulf, january 2010
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Two M5 earthquakes in Two M5 earthquakes in Corinth Gulf, January 2010Corinth Gulf, January 2010
J. Janský, O. Novotný, J. ZahradníkJ. Janský, O. Novotný, J. Zahradník - Prague - PragueE. Sokos - PatrasE. Sokos - Patras
2
Outline
• Records
• Hypocenter
• Centroid and moment tensor
• Finite source
• Faults ?
3
4
5
Stations and records
6
7
8
9
peak accel.1.7 m/s2
Intensity6 to 7
acceleration velocity
displacement
the near-field ramp
10Pre-shock
11
Possible signal from hypocenter (P)before signal from asperity (P’).
This is not the anti-alias filter effect !
12
Thisis thefiltereffect.
13
8 9 10 11 12
-0.0004
-0.0002
0
0.0002
Jan 18SER raw _Z
8 12 16 20
-0.03
-0 .02
-0 .01
0
0.01
0.02
0.03
Jan 18SER raw _Z
11 11.1 11.2 11.3 11.4
0.000108
0.000112
0.000116
0.00012
0.000124
0.000128
0.000132
Jan 18SERraw _Z
Zooming the first arrival.
14
60 62 64 66 68 70tim e (se c)
-0 .012
-0 .008
-0 .004
0
0.004
dis
pla
cem
en
t (m
)
Jan 18SER filf> 0.01 H zblack: EW
The near-field ramp. Where is S ?
S?
S?
15
60 62 64 66 68 70tim e (se c)
-0 .012
-0.008
-0.004
0
0.004
dis
pla
cem
en
t (m
)
Jan 18SER filf> 0.01 H zblue: Zblack: EW
16
Stations and records – a summary:
Clipping of CMG-3T, double P arrival (P, P’?), unclear S onset,
a clear near-field ramp at SER (thanks to CMG-5T)…
17
Location
18
19
21.8 21.9 22 22.1Lon E (deg)
38.3
38.35
38.4
38.45
38.5
Lat
N (
deg)
SEREFP
U PR
plus: 11circ le : 14square: 16cross: 17
One event located by many methods.
21
-100000 0 100000
EW re lative d isp lacem ent
-100000
0
100000
NS
rel
ativ
e di
spla
cem
ent
10.43 sec
9.96 sec
Jan 18, 2010EFP
clip 10.60 sec
-100 0 100
EW re lative d isp lacem ent
-100
0
100
NS
rel
ativ
e di
spla
cem
ent
12.90 sec 11.41 sec
Jan 18, 2010SER 5T
(clip on 3T at 13.1 sec)
-100000 0 100000
EW re la tive d isp lacem ent
-100000
0
100000
NS
rel
ativ
e di
spla
cem
ent
12.95 sec
11.41 sec
Jan 18, 2010SER 3T
(clip at 13.1sec)
-10000 0 10000
EW re la tive d isp lacem ent
-10000
0
10000
NS
rel
ativ
e d
isp
lace
me
nt 13.40 sec
12.61 sec
Jan 18, 2010UPR
22
21.8 21.9 22 22.1Lon E (deg)
38.3
38.35
38.4
38.45
38.5
Lat
N (
deg)
SEREFP
U PR
23
24
4 6 8 1 0 1 2 1 4
z ( k m )
0
1 0
2 0
3 0
4 0
Grid-search location.
25
38.38 38.4 38.42 38.44 38.46 38.48
0
10
20
30
Jan 18depth 8.1 km
21.84 21.88 21.92 21.96 22 22.04
0
5
10
15
20
25
Jan 18depth 8.1 km
26
Grid search combined with station-differences; trade off between depth and origin time is eliminated.
27
21.8 21.9 22 22.1Lon E (deg)
38.3
38.35
38.4
38.45
38.5
Lat
N (
deg)
SEREFP
U PR
plus: 11circ le : 14square: 16cross: 17
EM SC (5 km )
TH E (0.8 km )N O A (20.38 km )
U PSL (9.24 km )G SnoSD (10.5 km )
ATH (7.15 km )
Jan 18
One event located by many methods,agencies included.
28
21.8 21.9 22 22.1Lon E (deg)
38.3
38.35
38.4
38.45
38.5
Lat
N (
deg)
SEREFP
U PR
square: 13triangle: 15plus: 18circ le : 19
Jan 22
One event located by many methods
29
21.8 21.9 22 22.1Lon E (deg)
38.3
38.35
38.4
38.45
38.5La
t N
(de
g)
SEREFP
U PR
30
21.8 21.9 22 22.1Lon E (deg)
38.3
38.35
38.4
38.45
38.5
Lat
N (
deg)
SEREFP
U PR
black: Jan 18blue: Jan 22
The two eventsslightly shiftedone to another.
Independently supportedby a relative location of Jan 22 with respect to Jan 18.
31
Location - summary:
Conjugate gradients, grid search, relative location, all providing a
stable epicenter location. Two events close to each other. Depth ~10 km.
32
Centroid and moment tensor
33
Distances < 100 km
34
Even date-time: 20100122 15:56:00Displacement (m). Inversion band (Hz) 0.05 0.06 0.10 0.2
ObservedSynthetic
Gray waveforms weren't used in inversion.
Blue numbers are variance reduction
-101
x 10-3 NS
SE
R
-0.00-10-505
x 10-4 EW
0.64-4-202
x 10-4 Z
0.45
-2-101
x 10-4
MA
M
0.68-4-2024
x 10-4
0.87 -2
0
2x 10
-4
0.77
-1
0
1x 10
-4
DS
F
0.48 -505
x 10-5
0.28-1
0
1x 10
-4
0.44
-202
x 10-4
DR
O
0.53-2
0
2x 10
-4
0.48 -1012
x 10-4
0.69
-2
0
2x 10
-4
GU
R
0.82 -202
x 10-4
0.60 -505
10x 10
-5
0.55
-1
0
1x 10
-4
PD
O
-0.02 -101
x 10-4
0.46 -505
x 10-5
0.55
50 100 150-2
02
x 10-4
Time (sec)
LT
K
0.92
50 100 150
-505
10x 10
-5
Time (sec)
0.60
50 100 150
-202
x 10-5
Time (sec)
0.12
Specific role of thenearest station.Excluded from inversion.
Jan 18
Frequency < 0.2 Hz
35
Even date-time: 20100122 15:56:00Displacement (m). Inversion band (Hz) 0.05 0.06 0.10 0.2
ObservedSynthetic
Gray waveforms weren't used in inversion.
Blue numbers are variance reduction
-505
x 10-4 NS
SE
R
0.17 -101
x 10-3 EW
0.77 -505
x 10-4 Z
0.45
-101
x 10-4
MA
M
0.70 -202
x 10-4
0.70 -101
x 10-4
0.80
-505
x 10-5
DS
F
0.04-1
0
1x 10
-4
0.65-10-505
x 10-5
0.65
-202
x 10-4
DR
O
0.75 -1012
x 10-4
0.68-2-101
x 10-4
0.72
-2-101
x 10-4
GU
R
0.90 -101
x 10-4
0.41 -505
x 10-5
0.66
-101
x 10-4
PD
O
0.58 -505
x 10-5
0.47-505
x 10-5
0.63
50 100 150-2
0
2x 10
-4
Time (sec)
LT
K
0.88
50 100 150-1
01
x 10-4
Time (sec)
0.81
50 100 150-6-4-2024
x 10-5
Time (sec)
0.33
strike, dip, rake Jan 18: Plane 1: 108 57 -74 Plane 2: 260 37 -113Jan 22: Plane 1: 76 38 -108 Plane 2: 279 54 -76
Jan 22
36
(Lat 38.4250, Lon 21.9187, model ON)
Centroidal depth ~ 3-5 km,independent of crustal models.
37
Uncertainty ofthe centroid position
38
Centroid and moment tensor - summary
Two normal events, slightly different positions and mechanisms, small
centroid depths (~ 4 km).
39
Fault plane
40
-20
0
20-15 -10 -5 0 5 10 15
-20
-15
-10
-5
0
5
10
North-South (km)
jan18
East-West (km)
Dep
th
Jan 18: H-C consistency; fault dipping to South
4121.92 21.94 21.96 21.98 22 22.02
38.38
38.4
38.42
38.44
38.46
38.48
No
Yes !
Jan 18
4221.92 21.94 21.96 21.98 22 22.02
38.38
38.4
38.42
38.44
38.46
38.48
21.92 21.94 21.96 21.98 22 22.02
38.38
38.4
38.42
38.44
38.46
38.48
No
Yes !
Jan 18 Jan 18, Jan 22
??
44
-20
0
20
-20 -15 -10 -5 0 5 10 15 20
-20
-15
-10
-5
0
5
10 jan22
North-South (km)
Dep
th
East-West (km)
Jan 22: H-C consistency achieved when C shifted by 0.02° to North.
46
-200
20-20 -15 -10 -5 0 5 10 15 20
-20
-15
-10
-5
0
5
10
East-West (km)
North-South (km)
jan18 green, jan22 red (same C)
Dep
th
If the H depths are 8 km, both H’s are in the same planedetermined by the strike and dip of Jan 22.
47
-20
-10
0
10
20 -20
-10
0
10
20
-20
-15
-10
-5
0
5
10
North-South (km)
jan18 green, jan22 red (same C)
East-West (km)
Dep
th
Caution: These are the two likely fault planes, not the conjugate nodal planes !
48
49
Fault plane - summary
Jan 18 fault plane dipping to South,
Jan 22 a bit more problematic
(a Northward 0.02° shift of C would be needed, but allowed within the
uncertainty limits).
Relation to surface faults is unclear.
50
Fault plane – additional data ?
51
Preliminary location of the sequence (Patras Univ.)
5250 60 70 80 90 100
tim e (s)
-0 .008
-0 .004
0
0.004
0.008
0.012
dis
pla
cem
en
t (m
)
SER _EWblack: dataco lor: synt
blue: fin ite_25pink: fin ite_43green: fin ite_hypred: po in t source
-1.5 -1 -0.5 0 0.5 1 1.5
-1
-0.5
0
0.5
1
2543
Finite-fault modeling(forward simulation for SER)
Finite-source effectsare evident, but no simple preferencecan be made.
53
-1.5 -1 -0.5 0 0.5 1 1.5
-1
-0.5
0
0.5
1
50 60 70 80 90 100tim e (s)
-0 .008
-0 .004
0
0.004
0.008
0.012
dis
pla
cem
en
t (m
)
SER _EWblack: datacolor: synt
blue: fin ite_25pink: fin ite_49green: fin ite_hypred: po in t source
54
50 60 70 80 90 100tim e (s)
-0 .004
-0 .002
0
0.002
0.004
dis
pla
cem
en
t (m
)
SER _Zblack: datacolor: synt
blue: fin ite_25pink: fin ite_43green: fin ite_hypred: po in t source
50 60 70 80 90 100tim e (s)
-0 .004
-0 .002
0
0.002
0.004
dis
pla
cem
en
t (m
)
SER _Zblack: datacolor: synt
blue: fin ite_25pink: fin ite_49green: fin ite_hypred: po in t source
-1.5 -1 -0.5 0 0.5 1 1.5
-1
-0.5
0
0.5
1
-1.5 -1 -0.5 0 0.5 1 1.5
-1
-0.5
0
0.5
1
55
Finite fault (additional data) – summary
Relocation of the sequence by relative methods would be useful.
Finite-source effects were found but their interpretation is non-unique.
The near stations are few, only forward simulation is possible.
56
Interesting observation
Fast long-period waves were observed at many stations for these events, perhaps leaking modes PL. How to use them in the source and
crustal structure studies?
57
58
Even date-time: 20100122 15:56:00Displacement (m). Inversion band (Hz) 0.05 0.06 0.9 1.0
ObservedSynthetic
Gray waveforms weren't used in inversion.
Blue numbers are variance reduction
-5
0
5x 10
-3 NS
SE
R
-1.92 -4-20
x 10-3 EW
0.61-4-20
x 10-3 Z
-0.76
-505
x 10-4
MA
M-1.90 -10
-505
x 10-4
-1.68 -505
10x 10
-4
-4.58
-202
x 10-4
DS
F
-0.60-4-2024
x 10-4
-0.07-5
0
5x 10
-4
-0.51
-505
x 10-4
DR
O
0.07-4-2024
x 10-4
0.03 -505
x 10-4
-1.18
-4-20246
x 10-4
GU
R
-0.71 -505
x 10-4
-2.04 -50
5x 10
-4
-2.26
-4-202
x 10-4
PD
O
-0.46-2
0
2x 10
-4
0.10 -202
x 10-4
-1.00
60 80 100
-2024
x 10-4
Time (sec)
LT
K
-0.31
60 80 100-202
x 10-4
Time (sec)
-0.25
60 80 100-202
x 10-4
Time (sec)
-1.99
Source depth 5.5 km, source duration 1 sec: ableto simulate the 5-sec waves. It is a structural effect.
59
Concluding remarks
• Routine epicenter location is surprisingly good.• Details needed for local tectonic interpretation are ‘on the
edge’ of the available data. • It seems possible to formulate an H-C consistent model of
both events. • How to produce the whole class of possible (non-unique)
models automatically?• Combining the geometry constrains and finite-source
effects is a good strategy. • The near-filed effects and the long-period waves (PL?)
provide interesting additional data.
60
Thanks for your attention !
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