Seismic Moment from Regional Surface-Wave Amplitudes: Applications to Digital and Analog Seismograms

Authors

Fabrizio Bernardi, Institute of Geophysics
Jochen Braunmiller, Institute of GeophysicsFollow
Domenico Giardini, Institute of Geophysics

Document Type

Article

Publication Date

4-2005

Digital Object Identifier (DOI)

https://doi.org/10.1785/0120040048

Abstract

Accurate, consistent earthquake size estimates are fundamental for seismic hazard evaluation. In central Europe, seismic activity is low and long-term seismicity, available as intensities from written historical records, has to be included for meaningful assessments. We determined seismic moments M₀ of 25 stronger twentieth-century events in Switzerland from surface-wave amplitude measurements. These M₀ can be used to calibrate intensity-moment relations applicable to preinstrumental data. We derived the amplitude-moment relation using digital data from 18 earthquakes in and near Switzerland where independent M₀ estimates exist. The surface-wave amplitudes were measured at empirically determined distance varying reference periods T_Δ. For amplitudes measured at T_Δ, the distance attenuation term of the surface-wave magnitude relation S(Δ) = log (A/T)_max + 1.66 log Δ is independent of distance. For log M₀ = M_S + C_E, we get log M₀ = S(Δ) + 14.90. Uncertainties of ±0.3 for the 14.90-constant correspond to a factor of 2 M₀ uncertainty, which was verified with independent data. Our relation allows fast, direct M₀ determination for current earthquakes, and after recalibration of the constant, the relation can be applied anywhere. We applied our relation to analog seismograms from early-instrumental earthquakes in Switzerland that were collected from several European observatories. Amplitude measurements from scans were performed at large amplifications and corrected for differences between T_Δ and actual measurement periods. The resulting magnitudes range from M_w = 4.6 to 5.8 for the largest earthquake in Switzerland during the twentieth century. Uncertainties for the early-instrumental events are on the order of 0.4 magnitude units.

Was this content written or created while at USF?

No

Citation / Publisher Attribution

Bulletin of the Seismological Society of America, v. 95, issue 2, p. 408-418

Scholar Commons Citation

Bernardi, Fabrizio; Braunmiller, Jochen; and Giardini, Domenico, "Seismic Moment from Regional Surface-Wave Amplitudes: Applications to Digital and Analog Seismograms" (2005). School of Geosciences Faculty and Staff Publications. 809.
https://digitalcommons.usf.edu/geo_facpub/809