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Constraints on the long-period moment-dip tradeoff for the Tohoku earthquake

Tsai, Victor C. and Hayes, Gavin P. and Duputel, Zacharie (2011) Constraints on the long-period moment-dip tradeoff for the Tohoku earthquake. Geophysical Research Letters, 38 (7). Art. No. L00G17. ISSN 0094-8276. doi:10.1029/2011GL049129.

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Since the work of Kanamori and Given (1981), it has been recognized that shallow, pure dip-slip earthquakes excite long-period surface waves such that it is difficult to independently constrain the moment (M_0) and the dip (δ) of the source mechanism, with only the product M_0 sin(2δ) being well constrained. Because of this, it is often assumed that the primary discrepancies between the moments of shallow, thrust earthquakes are due to this moment-dip tradeoff. In this work, we quantify how severe this moment-dip tradeoff is depending on the depth of the earthquake, the station distribution, the closeness of the mechanism to pure dip-slip, and the quality of the data. We find that both long-period Rayleigh and Love wave modes have moment-dip resolving power even for shallow events, especially when stations are close to certain azimuths with respect to mechanism strike and when source depth is well determined. We apply these results to USGS W phase inversions of the recent M9.0 Tohoku, Japan earthquake and estimate the likely uncertainties in dip and moment associated with the moment- dip tradeoff. After discussing some of the important sources of moment and dip error, we suggest two methods for potentially improving this uncertainty.

Item Type:Article
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Tsai, Victor C.0000-0003-1809-6672
Additional Information:© 2011 American Geophysical Union. Received 1 August 2011; revised 19 September 2011; accepted 22 September 2011; published 25 October 2011. We thank L. Rivera for providing scripts and other support, and two anonymous reviewers for comments that lead to improvements in the paper. This work was partially supported by a Mendenhall Postdoctoral Fellowship to VCT. The Editor wishes to thank two anonymous reviewers for their assistance evaluating this paper.
Group:Seismological Laboratory
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Issue or Number:7
Record Number:CaltechAUTHORS:20111114-110515606
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Official Citation:Tsai, V. C., G. P. Hayes, and Z. Duputel (2011), Constraints on the long-period moment-dip tradeoff for the Tohoku earthquake, Geophys. Res. Lett., 38, L00G17, doi:10.1029/2011GL049129
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:27770
Deposited By: Tony Diaz
Deposited On:23 Nov 2011 17:53
Last Modified:09 Nov 2021 16:51

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