Upper mantle of the Bohemian Massif (Central Europe) studied by surface waves from

Kurile Islands M8.1 and M8.3 earthquakes

Petr Kolinsky

Jiri MalekInstitute of Rock Structure and Mechanics

Academy of Sciences of the Czech Republic

AGU 2007 Fall MeetingDecember 10 – 14

San Francisco, CA, USA

Kolinsky and Malek: Upper mantle of the Bohemian Massif 2

contents

motivation

data

surface waveanalysis

polarization

phasevelocity

dispersioncurves

structure

conclusion

contents

motivation

data

surface wave analysis

polarization

phase velocity

dispersion curves

structure

conclusion

Kolinsky and Malek: Upper mantle of the Bohemian Massif 3

contents

motivation

data

surface waveanalysis

polarization

phasevelocity

dispersioncurves

structure

conclusion

motivation- structural: Bohemian Massif

- former project on crustal velocity estimation 9 – 36 s, 40 km depth- can we look at the deeper structure of the same region?

area of inverted S -w ave velocities average S-wave ve locity

a b

average of d isp. curv. estim ated by the freq.-tim e analysisd isp. curv. corresponding to inverted S -w ave ve locityd isp. curv. corresponding to the average S-w ave ve locity

KH CNKC

TBRKH U

phas

e ve

loci

ty (

km/s

)

10 20 30 40 506070

per iod (s)

3 .0

3.4

3.8

4.2

4.6

5.010 20 30 40 506070

phase velocity (km/s)

10 20 30 40 506070

10 20 30 40 506070

per iod (s)

2.5 3.0 3.5 4.0 4.5 5.0 5.5

50

45

40

35

30

25

20

15

10

5

0

2.5 3.0 3.5 4.0 4.5 5.0 5.5

S-w ave velocity (km /s)

2.5 3.0 3.5 4.0 4.5 5.0 5.5

S-w ave veloc ity (km /s)

50

45

40

35

30

25

20

15

10

5

0

50

45

40

35

30

25

20

15

10

5

0

de

pth

(km

) depth

(km)

2 .5 3.0 3.5 4.0 4.5 5.0 5.5

halfspace

halfspace

Kolinsky and Malek: Upper mantle of the Bohemian Massif 4

contents

motivation

data

surface waveanalysis

polarization

phasevelocity

dispersioncurves

structure

conclusion

motivation- methodological

surface wavestudies areincluded inthe PASSEQproject

surface wave phase velocity analysis"long" period phase velocitymeasured at "short" distances

"long" period: up to 200 s"short" distances: around 150 km

Kolinsky and Malek: Upper mantle of the Bohemian Massif 5

contents

motivation

data

surface waveanalysis

polarization

phasevelocity

dispersioncurves

structure

conclusion

Kurile IslandsM 8.1 and M 8.38.600 km

Scotia SeaM 7.013.000 km

Kolinsky and Malek: Upper mantle of the Bohemian Massif 6

contents

motivation

data

surface waveanalysis

polarization

phasevelocity

dispersioncurves

structure

conclusion

Kolinsky and Malek: Upper mantle of the Bohemian Massif 7

contents

motivation

data

surface waveanalysis

polarization

phasevelocity

dispersioncurves

structure

conclusion

STS-2

170 km

STS-2

Guralp

150 km

Guralp

Kolinsky and Malek: Upper mantle of the Bohemian Massif 8

contents

motivation

data

surface waveanalysis

polarization

phasevelocity

dispersioncurves

structure

conclusion

STS-2 (natural period 120 s)

60 s

150 s

Guralp (natural period 30 s)

60 s

150 s

Kolinsky and Malek: Upper mantle of the Bohemian Massif 9

contents

motivation

data

surface waveanalysis

polarization

phasevelocity

dispersioncurves

structure

conclusion

multiple filteringGaussian filters

constant relative resolution filteringinstantaneous period estimation

0.0 0.1 0.2 0.3 0.4 0.5 0.6frequency (H z)

ampl

itude

pow er spectrumG aussian filte rsfilte red pow er spectra

surface wave analysis

Kolinsky and Malek: Upper mantle of the Bohemian Massif 10

contents

motivation

data

surface waveanalysis

polarization

phasevelocity

dispersioncurves

structure

conclusion

frequency-time spectrogram

and

truncated fundamental mode spectrogram

period (s) period (s)

velo

city

(km

/s)

velo

city

(km

/s)

Kolinsky and Malek: Upper mantle of the Bohemian Massif 11

contents

motivation

data

surface waveanalysis

polarization

phasevelocity

dispersioncurves

structure

conclusion

set ofharmonic signals

Kolinsky and Malek: Upper mantle of the Bohemian Massif 12

contents

motivation

data

surface waveanalysis

polarization

phasevelocity

dispersioncurves

structure

conclusion

R

T

2400 2800 3200 3600 4000

t im e from orig in (s)

RT

R

2400 2800 3200 3600 4000

t im e from orig in (s)

R

2500 3000 3500 4000

t im e from orig in (s)

R

2500 3000 3500 4000

t im e from orig in (s)

R

2400 2800 3200 3600 4000

t im e from orig in (s)

30 s 60 s 90 s 120 s 150 s

R

T

1600 2000 2400 2800

tim e from orig in (s)

RT

R

1600 2000 2400 2800

tim e from orig in (s)

R

1600 2000 2400 2800

tim e from orig in (s)

R

1600 2000 2400 2800

tim e from orig in (s)

R

1600 2000 2400 2800

tim e from orig in (s)

30 s 60 s 90 s 120 s 150 s

KurilIslands

continentalpath

8700 km

Scotia Sea

oceanicpath

13000 km

particle motion in horizontal plane

Kolinsky and Malek: Upper mantle of the Bohemian Massif 13

contents

motivation

data

surface waveanalysis

polarization

phasevelocity

dispersioncurves

structure

conclusion

set ofcoherentharmonic signalsat two stations

(time shift = 41 s)

Kolinsky and Malek: Upper mantle of the Bohemian Massif 14

contents

motivation

data

surface waveanalysis

polarization

phasevelocity

dispersioncurves

structure

conclusion

43.51 s

41.71 s

39.95 s

T = 50 s

T = 100 s

T = 150 s

Kolinsky and Malek: Upper mantle of the Bohemian Massif 15

contents

motivation

data

surface waveanalysis

polarization

phasevelocity

dispersioncurves

structure

conclusion

20 40 60 80 100 120 140 160 180 20030 50 70 90 110 130 150 170 190p e rio d (s)

2.6

3.0

3.4

3.8

4.2

4.6

gro

up

ve

loci

ty (

km/s

)

Love continental

Rayleigh continental

Love oceanic

Rayleigh oceanic

group velocity

Love PREM

Rayleigh PREM

Kolinsky and Malek: Upper mantle of the Bohemian Massif 16

contents

motivation

data

surface waveanalysis

polarization

phasevelocity

dispersioncurves

structure

conclusion

20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200p e rio d (s)

2.6

3.0

3.4

3.8

4.2

4.6

5.0

ph

ase

ve

loci

ty (

km/s

)

blue = Z componentgreen = R component

phase velocity

Kolinsky and Malek: Upper mantle of the Bohemian Massif 17

contents

motivation

data

surface waveanalysis

polarization

phasevelocity

dispersioncurves

structure

conclusion

- the dispersion curves are computed by matrix method

Proskuryakova et al. (1981)

- it uses modified Thomson – Haskell matrices

- Isometric Method (IM) was developed for solving weakly non-linear inverse problems with many parameters

Malek et al. (2005 and 2007)

structure – inversion problem

Kolinsky and Malek: Upper mantle of the Bohemian Massif 18

contents

motivation

data

surface waveanalysis

polarization

phasevelocity

dispersioncurves

structure

conclusion

- similar dispersion curves may correspond to different velocity models

- measured dispersion points can be fitted by different smooth dispersion curves

inversion non-uniqueness

Kolinsky and Malek: Upper mantle of the Bohemian Massif 19

contents

motivation

data

surface waveanalysis

polarization

phasevelocity

dispersioncurves

structure

conclusion

- during Love wave phase velocity inversion we look for vS model

- during Rayleigh wave phase velocity inversion we look for vS and vP/vS ratio

- depths of interfaces are fixed during the inversion

parameters

Kolinsky and Malek: Upper mantle of the Bohemian Massif 20

contents

motivation

data

surface waveanalysis

polarization

phasevelocity

dispersioncurves

structure

conclusion

inversions

20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200p e rio d (s)

2.6

3.0

3.4

3.8

4.2

4.6

5.0

ph

ase

ve

loci

ty (

km/s

)

Kolinsky and Malek: Upper mantle of the Bohemian Massif 21

2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0velocity (km /s)

210

200

190

180

170

160

150

140

130

120

110

100

90

80

70

60

50

40

30

20

10

02.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0

210

200

190

180

170

160

150

140

130

120

110

100

90

80

70

60

50

40

30

20

10

0

de

pth (km)d

ep

th (

km)

contents

motivation

data

surface waveanalysis

polarization

phasevelocity

dispersioncurves

structure

conclusion

velocitydistribution

Z - component

R - component

T - component

Kolinsky and Malek: Upper mantle of the Bohemian Massif 22

2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0velocity (km /s)

210

200

190

180

170

160

150

140

130

120

110

100

90

80

70

60

50

40

30

20

10

02.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0

210

200

190

180

170

160

150

140

130

120

110

100

90

80

70

60

50

40

30

20

10

0

de

pth (km)d

ep

th (

km)

contents

motivation

data

surface waveanalysis

polarization

phasevelocity

dispersioncurves

structure

conclusion

Kolinsky and Malek: Upper mantle of the Bohemian Massif 23

contents

motivation

data

surface waveanalysis

polarization

phasevelocity

dispersioncurves

structure

conclusion

conclusions

- phase velocities in the period range of 30 – 200 s were studied at the short station distances of 150 and 170 km

- Rayleigh wave phase velocity dispersion curves are well pronounced in the whole period range

- Love wave phase velocity dispersion curves are well pronounced only in limited period range of 30 – 110 s

- continental path gives clearer Rayleigh wave fundamental mode while oceanic path gives clearer Love wave fundamental mode

- Rayleigh waves from Z and R components give slightly different results (anisotropy?)

- S-wave velocity in the upper mantle of the Bohemian Massif reaches minimum around the depth of 130 km