Monitoring seismic wave velocity changes associated with the Mw 7.9 Wenchuan earthquake: increasing the temporal resolution using curvelet filters

L. Stehly 1, 2 B. Froment 3 M. Campillo 2 Q. Y. Liu 4 J. H. Chen 4
1 GEOAZUR 7329 - Géoazur
2 ISTerre - Institut des Sciences de la Terre
3 EAPS - Department of Earth, Atmospheric and Planetary Sciences [MIT, Cambridge]
4 State Key Laboratory of Earthquake Dynamics
Abstract : The aim of this study is to improve the temporal resolution of seismic wave velocity variations measured using ambient noise correlations. We first reproduce the result obtained by Chen et al. using a network of 21 broad-band stations ideally located around the fault system activated during the Wenchuan earthquake.We measure a velocity drop of 0.07 per cent that was associated with the main shock, with a temporal resolution of 30 days. To determine whether this velocity drop is co-seismic or post-seismic, we attempt to increase the temporal resolution of our observations. By taking advantage of the properties of the curvelet transform, we increase the signal-to-noise ratio of the daily correlations computed between each station pair. It is then possible to measure the velocity drop associated with the Wenchuan earthquake with a temporal resolution of 1 day. This shows that the velocity drop started on 2008 May 12, which was the day of the earthquake, and the velocity reached its lowest value 2 days after the main shock. Moreover, there was a second velocity drop on 2008 May 27, which might relate to strong aftershocks.
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https://hal.archives-ouvertes.fr/hal-01381373
Contributeur : Publications Géoazur <>
Soumis le : vendredi 14 octobre 2016 - 13:57:37
Dernière modification le : mercredi 18 décembre 2019 - 10:52:09

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L. Stehly, B. Froment, M. Campillo, Q. Y. Liu, J. H. Chen. Monitoring seismic wave velocity changes associated with the Mw 7.9 Wenchuan earthquake: increasing the temporal resolution using curvelet filters. Geophysical Journal International, Oxford University Press (OUP), 2015, 201 (3), pp.1939 - 1949. ⟨10.1093/gji/ggv110⟩. ⟨hal-01381373⟩

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