GNGTS 2022 - Atti del 40° Convegno Nazionale

GNGTS 2022 Sessione 2.2 377 EARTHQUAKE MONITORING NETWORKS: A COMPARISON BETWEEN HIGH SEISMIC RISK COUNTRIES S. Scudero, A. D’Alessandro Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Nazionale Terremoti, Rome, Italy Introduction. A country-scale earthquake monitoring network usually extends over areas in the range of 10 5 - 10 6 km 2 (D’Alessandro et al. , 2019) and, from its initial planning to its final configuration may be necessary several years to decades. Throughout this process, the final geometrical arrangement of the nodes could turn remarkably different from the initial, planned configuration. As a counterpart, in some cases, the long time span necessary to build up the networks turned into a benefit because of the concurrent technological improvements of sensors, transmission systems, etc. In all the cases, it is always opportune to verify periodically whether the distribution of nodes within a given network satisfies its final needs and objectives, also because the knowledge about the seismicity of a given area may evolve over time. In this work, we propose the application of the statistical approach proposed by Siino et al. , (2020) for the evaluation of the earthquake monitoring networks in three countries characterized by high seismic hazard, namely Italy, New Zealand, and Taiwan. This approach considers the spatial distribution of the nodes of the network together with the ancillary information related to the aims of the network itself (e.g. earthquakes’ distribution, seismic hazard, population). Data are analysed by means of descriptive spatial statistics and point process methods following the approach proposed by Siino et al. , (2020) and also employed by Scudero and D’Alessandro ( submitted ) to get insights about the distribution of the earthquake networks with respect to the related data sets. Fig. 1 - Maps of Italy, New Zealand, and Taiwan. The instrumental seismicity is represented with grey dots, while the M>5.5 earthquakes with green squares. The triangles indicate the seismic (in red) and strong motion (in blue) networks. Details about the data are provided also in Tab. 1. Results. The data considered for this study are displayed in Fig. 1. Technical details about the earthquake monitoring networks can be retrieved for Italy (Dolce, 2009; Michelini et al. , 2016), New Zealand (Patterson et al. , 2007; Uma et al. , 2011), and Taiwan (Tsai and Lee, 2005; Hsiao et al. , 2009; Chang et al. , 2012; Shin et al. , 2013). A comparison between the networks and the earthquake catalogues is provided in Tab.1. In particular, concerning the earthquake monitoring networks, we distinguish the broad-band, or in general, the velocimetric sensors, from the strong-motion sensors (i.e. accelerometers). While the former