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Relation between Seismic Moment M0 and Surface Wave Magnitude Ms.

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The relation between MS and logM0 is examined using Harvard CMT M0, with both MPrague S and the improved surface wave magnitude scale Mt S [1] applied to ISC data. Although Mt S shows less scatter than MPrague S , neither dataset supports a slope of MS against logM0 which tends to 1.0 towards smaller magnitudes. Instead, a good linear fit of slope 0.76 using tS M is found throughout the fitted range of M0 (2.0×10^24 to 1.26×10^27 dyne-cm), and this linearity extends down to M0=2.5×10^23 dyne-cm. This suggests that previous proposals that MS data support a theoretical slope of 1.0 in the low range of magnitude which may be expected from established relationships, is not justified.

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