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

Geophysical Research Letters
By: , , and 
https://doi.org/10.1029/2011GL049129

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Abstract

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 (M0) and the dip (δ) of the source mechanism, with only the product M0 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.

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Publication type Article
Publication Subtype Journal Article
Title Constraints on the long‐period moment‐dip tradeoff for the Tohoku earthquake
Series title Geophysical Research Letters
DOI 10.1029/2011GL049129
Volume 38
Issue 7
Year Published 2011
Language English
Publisher American Geophysical Union
Publisher location Washington, D.C.
Contributing office(s) Geologic Hazards Science Center
Description L00G17, 6 p.
Country Japan
State Tohoku
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