Spatial analysis for an evaluation of monitoring networks: examples from the Italian seismic and accelerometric networks

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ORIGINAL ARTICLE

Spatial analysis for an evaluation of monitoring networks: examples from the Italian seismic and accelerometric networks Marianna Siino · Salvatore Scudero Luca Greco · Antonino D’Alessandro

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Received: 9 August 2019 / Accepted: 21 June 2020 © The Author(s) 2020

Abstract In this work, we propose a statistical approach to evaluate the coverage of a network based on the spatial distribution of its nodes and the target information, including all those data related to the final objectives of the network itself. This statistical approach encompasses descriptive spatial statistics in combination with point pattern techniques. As case studies, we evaluate the spatial arrangements of the stations within the Italian National Seismic Network and the Italian Strong Motion Network. Seismic networks are essential tools for observing earthquakes and assessing seismic hazards, while strong motion (accelerometric) networks allow us to describe seismic shaking and to measure the expected effects on buildings and infrastructures. The capability of both networks is a function of an adequate number of optimally distributed stations. We compare the seismic network with the spatial distributions of historical and instrument seismicity and with the distribution of M. Siino () · S. Scudero · L. Greco · A. D’Alessandro Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Nazionale Terremoti, Rome, Italy e-mail: [email protected] S. Scudero e-mail: [email protected] L. Greco e-mail: [email protected] A. D’Alessandro e-mail: [email protected]

well-known seismogenic sources, and we compare the strong motion station distribution with seismic hazard maps and the population distribution. This simple and reliable methodological approach is able to provide quantitative information on the coverage of any type of network and is able to identify critical areas that require optimization and therefore address areas of future development. Keywords Point process · Spatial correlation · Spatial statistics · Seismic network · Accelerometric network

1 Introduction Country-scale seismic networks usually extend over an area of 105 –106 km2 (D’Alessandro et al. 2019) and, from planning to completion, can require several years to decades. In addition, the final spatial distribution of the nodes can be remarkably different from the planned configuration for a multitude of reasons. As some examples, the Italian National Seismic Network, (D’Alessandro et al. 2011a, 2019) the Red S´ısmica Nacional in Spain (D’Alessandro et al. 2013), the Romanian network, and the Global Seismographic Network (GSN) took on average 20– 30 years (or more) to reach their present-day configuration, and they are still developing (Nacional and Rodr´ıguez 1995; Gee and Leith 2011; Popa

J Seismol

et al. 2015; Michelini et al. 2016; D’Alessandro et al. 2011b, 2012; D’Alessandro and Ruppert 2012; D’Alessandro and Stickney 2012). The development process for most seismic (or strong motion) networks is often analogous to that for these