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Anomalous surface waves from Lop Nor nuclear explosions: Observations and numerical modeling

Pedersen, Helle A. and Avouac, Jean-Philippe and Campillo, Michel (1998) Anomalous surface waves from Lop Nor nuclear explosions: Observations and numerical modeling. Journal of Geophysical Research B, 103 (B7). pp. 15051-15068. ISSN 0148-0227. doi:10.1029/98JB00027.

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Surface waves from the Chinese test site of Lop Nor are analyzed using long-period and broadband stations located at regional and teleseismic distances and at different azimuths. For most azimuths, strong Love waves between 0.02 and 0.045 Hz are observed with an amplitude of up to 10 times that of the Rayleigh waves. In addition, an anomalous early Rayleigh wave train is observed at some stations in western Europe. Due to a particularly favorable station and source configuration, it is possible to isolate the areas where the anomalies are created. The high-amplitude Love waves must be attributed to either source effects or path effects immediately north of Lop Nor. The early wave train is shown to be due to a partial energy conversion between Love and Rayleigh waves, probably at the Tornquist Zone. To estimate the possible contribution from surface wave conversions to the observed anomalies, numerical simulations are carried out with the indirect boundary element method. The simulations show that a relatively small variation of crustal thickness can induce Rayleigh to Love wave conversions between 0.02 and 0.1 Hz frequency. The calculated amplitudes of the Love waves are significant (up to 35% of the amplitude of the incoming Rayleigh waves), but they are too small to fit the observed amplitude anomaly. The observed converted waves and the numerical results nevertheless indicate that surface wave conversions can be significant across strong lateral crustal heterogeneities. In particular, the conversions due to changes in crustal thickness are located in the period interval which is routinely used for estimation of Ms.

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Avouac, Jean-Philippe0000-0002-3060-8442
Additional Information:© 1998 American Geophysical Union. Received 14 March 1997; accepted 26 December 1997; published 10 July 1998. Data from the LDG, GEOSCOPE, and GRSN networks were used, and supplementary data were obtained through the IRIS data management center. Discussions with J. -L. Plantet. and Y. Menechal are gratefully acknowledged. We thank P. Benoist. and E. Thauvin for drawing the maps. The numerical simulations were carried out at the Centre de Calcul Intensif of the Observatoire de Grenoble, France. We thank the associate editor, A. Levshin, and two anonymous reviewers for constructive comments to the original manuscript.
Group:Seismological Laboratory
Issue or Number:B7
Record Number:CaltechAUTHORS:20120919-115715043
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Official Citation:Pedersen, H. A., J.-P. Avouac, and M. Campillo (1998), Anomalous surface waves from Lop Nor nuclear explosions: Observations and numerical modeling, J. Geophys. Res., 103(B7), 15,051–15,068, doi:10.1029/98JB00027.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:34212
Deposited On:19 Sep 2012 23:55
Last Modified:09 Nov 2021 23:07

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