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The Scientific Value of Internet Macroseismic Data in Operational Seismology

Description: 

The advent of the internet has had a profound impact on the field of macroseismology, with the EMSC now routinely collecting thousands of felt reports following a widely felt earthquake. In 2023, its LastQuake multi-component system (websites, app, social media & messaging app bots) amassed 470k felt reports (8.5 min median time). After a decade of operation, three principal conclusions can be drawn. Firstly, a data collection system is effective if it also functions as an information system that meets the information needs of witnesses in the immediate aftermath of an earthquake and if it is deployed on multiple platforms. Secondly, in the absence of dense real-time accelerometric networks, a reliable and rapid assessment of the impact of global earthquakes cannot be achieved without the integration of macroseismic data. Finally, for operational seismology, this data represents an effective and affordable complement to dense accelerometric data, particularly in urban areas where the density of crowdsourced data is highest and where the risk is increasingly concentrated as a result of global urbanisation.

In order to illustrate these conclusions, a number of cases are presented. For example, the joint analysis of seismic and crowdsourced data enabled the precise location of the M4.8 New Jersey earthquake to be determined, (within 2km of USGS one). The public was promptly informed, and a total of 3,000 felt reports were crowdsourced in just 20 min in a region where LastQuake was previously unknown. Furthermore, the incorporation of felt reports into ShakeMaps serves to mitigate the inherent uncertainties associated with such models. Even when employed in isolation, without the requisite earthquake parameters, they can effectively identify destructive global earthquakes. In the case of large-magnitude earthquakes, felt reports can be used to rapidly (10 min) determine a line source model. When integrated into the ShakeMap of the M7.8 Turkey 2023 earthquake, the combination of felt reports and the line model provides a reliable estimate of the human impact within 10 min when using the PAGER method (USGS).

Session: Macroseismic Intensity: Past, Present and Future - I

Type: Oral

Date: 4/17/2025

Presentation Time: 02:00 PM (local time)

Presenting Author: Remy

Student Presenter: No

Invited Presentation: 

Poster Number: 17

Authors