modulation de l'énergie sismique par la marée - resif.fr · modulation de l’énergie...

Modulation de l’énergie sismique par la marée

Éric Beucler, Antoine Mocquet, Martin Schimmel, SébastienChevrot, Jérôme Vergne, Matthieu Sylvander, Pierrick Gernigon &

Olivier Quillard†

[email protected]

Laboratoire de Planétologie et GéodynamiqueObservatoire des Sciences de l’Univers Nantes Atlantique

/data/eric/img/logo/logoresifquadri.jpgPYROPE

Éric Beucler (LPG) Tidal modulation of the seismic energy JST RESIF (13 oct. 2015) 1 / 17

The seismic signal, the seismic noise and vice-versa

2015 Oct 06 20:41:49

4˚W

4˚W

2˚W

2˚W

0˚

0˚

46˚N

47˚N

48˚N

49˚N

50˚N

−400

−350

−300

−250

−200

−150

−100

−50

0

50

100

150

200

250

300

350

400

Alti

tude

(m

)

NANTES

LA ROCHELLE

BREST

RENNES

CAEN

LA ROCHE/YON

SAINT−BRIEUC

LE MANS

SAINTESANGOULÊME

ANGERS

NIORT

POITIERS

LORIENT

VANNES

CARHAIX

PY41

PY42

PY43

PY44

PY45

PY45A

PY46

PY47

PY48

PY49

CEA/DASE (LB+CP)

RESIF−CLB

PYROPE/VIBRIS

24 h of the Earth’s surface displacement (Feb. 26th, 2012) at PY43 (ANR PYROPE).



24 h of the Earth’s surface displacement (Feb. 26th, 2012) at PY43. Which part of the seismic signal is interesting?



The seismic signal/noise: temporal vs spectral.



Spectral estimate of the continuous seismic energy over 24h at TAM (http://geoscope.ipgp.fr).

The microseismic noise

Wiechert (1904)Linke (1909)Gutenberg (1931)Bernard (1941)

Longuet-Higgins (1950)Hasselmann (1963)Burg & Burrell (1967)Haubrich & Mc Camy (1969)



Primary peak (PM)period ∼11-16 soceanic waves on the shoresless energetic comparatively



Secondary peak (SM)period ∼2-12 sconstructive interferences ofalmost opposing wavesmuch more energetic

a In the open ocean(moving storm)

b Near the coastlines

c In the open ocean(simultaneous storms)

Ardhuin et al. (2011)


Short-duration PSD

Coastal and continental seismic stations (+buoy data +tidal ranges)

window length 360 s (with overlap 60 s)→ SR @ 0.8333 mHz (1 point every 20’)

PY48

PY41


Short-duration PSD

Coastal and continental seismic stations (+buoy data +tidal ranges) - vertical component


Short-duration PSD

Coastal and continental seismic stations (+buoy data +tidal ranges) - North/South component


Short-duration PSD variations

PY41 vertical component



PY41 vertical component PY41 vertical component. a. Time PSD variations, b. SpectralPSD variations.



Sea level near PY41. PY41 vertical component. a. Time PSD variations, b. SpectralPSD variations.



M2 modulations are computed for all components at PY41, PY48, VAL and ECH between 0.014 and 0.2 Hz (2-70 s period).


Tracking SM sources

Short-duration PSD vs numerical wave models (http://www.previmer.org).


Tracking SM sources


Summary

North Atlantic seismic noise sources


Summary

Coastal and inland stations


Summary

The SM energy (∼2-12 s)is generated in shallow waters (shores) and in the deep ocean;can be due to multiple and simultaneous sources;is time/frequency dependent due to the swell period variations(over a day/week/year?);is location dependent due to attenuation;depends on the coupling efficiency between water depth columnand solid ground;depends on the site quality (geology) beneath the receivers.

Very simple process indeed. . . work in progress

More details in Beucler, É., A. Mocquet, M. Schimmel, S. Chevrot, O. Quillard, J. Vergne & M.

Sylvander (2014). Observation of deep water microseisms in the North Atlantic Ocean using tide

modulations. Geophys. Res. Lett., 2014GL062347.


Summary

Coastal and continental seismic stations (+buoy data +tidal ranges) - East/West component



Buoy data



Normalized M2 modulations for all components at PY41, PY48, VAL and ECH between 0.014 and 0.2 Hz (2-70 s period).


Tracking SM sources

Short-duration PSD vs numerical wave models (http://www.previmer.org).


Microseism sources


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