One hundred plus years of recomputed surface wave magnitude of shallow global earthquakes

Abstract

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 Seismological Centre (ISC, http://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 (International Seismological Centre, 2021d).

Rupture Model for the 29 July 2021 MW 8.2 Chignik, Alaska Earthquake Constrained by Seismic, Geodetic, and Tsunami Observations

“…The 1938 event occurred when seismic stations with limited bandwidth and dynamic range were operational, and there were no geodetic or deep-sea ocean bottom pressure measurements to constrain the ground deformation. Surface-wave magnitude, M S , measurements for about 20-s period are available (Di Giacomo & Storchak, 2022), and these are compared with M S measurements from global broadband stations for the 2021 event (Figure 8). The azimuthal distribution for modern instruments is good and demonstrates that there can be substantial variations in magnitudes with azimuth, so one must be cautious in interpreting the sparse data for 1938.…”