Abstract

Among the multitude of magnitude scales developed to measure the size of an earthquake, the surface wave magnitude MS is the only magnitude type that can be computed since the dawn of modern observational seismology (beginning of the 20th century) for most shallow earthquakes worldwide. This is possible thanks to the work of station operators, analysts and researchers that performed measurements of surface wave amplitudes and periods on analogue instruments well before the development of recent digital seismological practice. As a result of a monumental undertaking to digitize such pre-1971 measurements from printed bulletins and integrate them in parametric data form into the database of the International Seismo- logical Centre (ISC, www.isc.ac.uk, last access: August 2021), we are able to recompute MS using a large set of stations and obtain it for the first time for several hundred earthquakes. We summarize the work started at the ISC in 2010 which aims to provide the seismological and broader geoscience community with a revised MS dataset (i.e., catalogue as well as the underlying station data) starting from December 1904 up to the last complete year reviewed by the ISC (currently 2018). This MS dataset is available at the ISC Dataset Repository at https://doi.org/10.31905/0N4HOS2D.

Highlights

  • Since its introduction, the surface wave magnitude Ms has been very popular, and for a long period of time, before the moment magnitude Mw was introduced by Kanamori (1977) and Hanks and Kanamori (1979), it was considered the most reliable magnitude to estimate an earthquake size

  • Storchak: One hundred plus years of recomputed Ms in degrees of the seismic station from the earthquake epicentre. This is the so-called Moscow–Prague formula, and it was accepted as the standard for Ms computation by the International Association of Seismology and Physics of the Earth’s Interior (IASPEI, http://www.iaspei.org/, last access: August 2021) at the 1967 Zurich meeting (Bormann et al, 2012; IASPEI, 2013)

  • Considering the whole ISC Ms dataset, major features can be discussed using Fig. 10, where we show the magnitude timeline, number of earthquakes per year for various magnitude thresholds and annual magnitude of completeness (Mc) computed with the maximum curvature method of Wiemer and Wyss (2000)

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Summary

Introduction

The surface wave magnitude Ms has been very popular, and for a long period of time, before the moment magnitude Mw was introduced by Kanamori (1977) and Hanks and Kanamori (1979), it was considered the most reliable magnitude to estimate an earthquake size. In degrees of the seismic station from the earthquake epicentre (distance and period limits will be discussed ) This is the so-called Moscow–Prague formula, and it was accepted as the standard for Ms computation by the International Association of Seismology and Physics of the Earth’s Interior (IASPEI, http://www.iaspei.org/, last access: August 2021) at the 1967 Zurich meeting (Bormann et al, 2012; IASPEI, 2013). Hereafter we refer to the catalogue and underlying station data as the ISC Ms dataset (International Seismological Centre, 2021d) To create this product we benefit from the work done by Di Giacomo et al (2015b, 2018) to digitize (i.e., converted from printed to computer accessible format) a large volume of surface wave parametric data prior to 1971 and by Storchak et al (2017, 2020) to rebuild the ISC Bulletin from 1964 onwards. We briefly discuss the largest earthquakes ever recorded and outline further activities that could improve this dataset in different time periods

Reporters and Ms recomputation
Station data
Catalogue properties
On the Ms saturation and large differences with Mw
Future developments
Findings
Conclusions
Full Text

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