Preprints
https://doi.org/10.5194/essd-2020-371
https://doi.org/10.5194/essd-2020-371

  13 Jan 2021

13 Jan 2021

Review status: this preprint is currently under review for the journal ESSD.

Complementing regional moment magnitudes to GCMT: a perspective from the rebuilt ISC Bulletin

Domenico Di Giacomo, James Harris, and Dmitry A. Storchak Domenico Di Giacomo et al.
  • International Seismological Centre (ISC), Pipers Lane, Thatcham, Berkshire, RG19 4NS, United Kingdom

Abstract. Seismologists and geoscientists in general 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 became 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/), which is regarded as the most comprehensive record of the Earth's seismicity. From it, we extracted a list of hypocentres with Mw from a multitude of agencies reporting data to the ISC. We first summarize the main temporal-spatial features of the Mw provided by global agencies (i.e., providing results for moderate to great earthquakes worldwide) and regional ones (i.e., also providing results or small earthquakes in a specific area). Then we discuss their comparisons, not only by considering Mw but also the surface wave magnitude MS and short-period body wave magnitude mb. By using the Global Centroid Moment Tensor solutions as 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/).

Domenico Di Giacomo et al.

Status: open (until 10 Mar 2021)

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Domenico Di Giacomo et al.

Domenico Di Giacomo et al.

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Short summary
We provide a comprehensive overview of the content in terms of moment magnitude Mw in the Bulletin of the International Seismological Centre (ISC). Mw is the preferred magnitude to characterize earthquakes in various research topics (e.g., Earth seismicity rates) and other applications (e.g., seismic hazard). We describe first the contribution of global agencies and then of agencies operating at regional scale, and then discuss features of Mw via different sets of comparisons.