Abstract
Abstract. Seismologists and geoscientists often need earthquake catalogues for various types of research. This input usually contains basic earthquake parameters such as location (longitude, latitude, depth, and origin time), as well as magnitude information. For the latter, the moment magnitude Mw has become the most sought after magnitude scale in the seismological community to characterize the size of an earthquake. In this contribution we provide an informative account of the Mw content for the newly rebuilt Bulletin of the International Seismological Centre (ISC, http://www.isc.ac.uk, last access: May 2021), which is regarded as the most comprehensive record of the Earth's seismicity. From this data, we extracted a list of hypocentres with Mw from a multitude of agencies reporting data to the ISC. We first summarize the main temporal and spatial features of the Mw provided by global (i.e. providing results for moderate to great earthquakes worldwide) and regional agencies (i.e. also providing results for small earthquakes in a specific area). Following this, we discuss their comparisons, by considering not only Mw but also the surface wave magnitude MS and short-period body wave magnitude mb. By using the Global Centroid Moment Tensor solutions as an authoritative global agency, we identify regional agencies that best complement it and show examples of frequency–magnitude distributions in different areas obtained both from the Global Centroid Moment Tensor alone and complemented by Mw from regional agencies. The work done by the regional agencies in terms of Mw is fundamental to improve our understanding of the seismicity of an area, and we call for the implementation of procedures to compute Mw in a systematic way in areas currently not well covered in this respect, such as vast parts of continental Asia and Africa. In addition, more studies are needed to clarify the causes of the apparent overestimation of global Mw estimations compared to regional Mw. Such difference is also observed in the comparisons of Mw with MS and mb. The results presented here are obtained from the dataset (Di Giacomo and Harris, 2020, https://doi.org/10.31905/J2W2M64S) stored at the ISC Dataset Repository (http://www.isc.ac.uk/dataset_repository/, last access: May 2021).
Highlights
Among the different magnitude scales developed over the years to measure an earthquake’s size, the moment magnitude Mw, introduced by Kanamori (1977) and Hanks and Kanamori (1979), has a fundamental role in seismology
The moment magnitude Mw has become the most sought after magnitude scale in the seismological community to characterize the size of an earthquake. In this contribution we provide an informative account of the Mw content for the newly rebuilt Bulletin of the International Seismological Centre (ISC, http://www.isc.ac.uk, last access: May 2021), which is regarded as the most comprehensive record of the Earth’s seismicity
With the completion in early 2020 of the Rebuild project (Storchak et al, 2017, 2020) of the ISC Bulletin, here we provide an overview of the Mw content in the rebuilt ISC Bulletin and discuss some of its features
Summary
Among the different magnitude scales developed over the years to measure an earthquake’s size, the moment magnitude Mw, introduced by Kanamori (1977) and Hanks and Kanamori (1979), has a fundamental role in seismology. Other techniques instead use spectral analysis (Andrews, 1986) to obtain M0 and other source parameters (e.g. stress drop, corner frequency; Brune, 1970). Such techniques are useful for earthquakes recorded in the local distance range as they allow M0 computation for small earthquakes. Some seismological agencies systematically compute Mw on a global scale and in recent years at regional scale (i.e. magnitude 5 and below in a specific area). We discuss the feasibility of complementing regional Mw to global ones by showing the Gutenberg–Richter distribution in some areas where regional Mw is available for a long period of time We discuss the feasibility of complementing regional Mw to global ones by showing the Gutenberg–Richter distribution in some areas where regional Mw is available for a long period of time (Sect. 5)
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