A completeness analysis of the national seismic network of Italy

We present the first detailed study of earthquake detection capabilities of the Italian National Seismic Network and of the completeness threshold of its earthquake catalog. The network in its present form started operating on 16 April 2005 and is a significant improvement over the previous networks. For our analysis, we employed the PMC method as introduced by Schorlemmer and Woessner (2008). This method does not estimate completeness from earthquakes samples as traditional methods, mostly based on the linearity of earthquake-size distributions. It derives detection capabilities for each station of the network and synthesizes them into maps of detection probabilities for earthquakes of a given magnitude. Thus, this method avoids the many assumptions about earthquake distributions that traditional methods make. The results show that the Italian National Seismic Network is complete at M=2.9 for the entire territory excluding the islands of Sardinia, Pantelleria, and Lampedusa. At the M=2.5 level, which is the reporting threshold level of the Italian Civil Protection, the network may miss events in southern parts of Apulia and the western part of Sicily. The stations are connected through many different telemetry links to the operational datacenter in Rome. Scenario computations show that no significant drop in completeness occurs if one of the three major links fail, indicating a well-balanced network setup.

Amato, A., and F. M. Mele (2008), Performance of the INGV National Seismic Network from 1997 to 2007, Ann. Geophys., 51(2-3), 417-431.

Amato, A., L. Badiali, M. Cattaneo, A. Delladio, F. Doumaz, and F. M. Mele (2006), The real-time earthquake monitoring system in Italy, Geosciences, 4, 70-75.

Amorese, D. (2007), Applying a change-point detection method on frequency-magnitude distributions, Bull. Seismol. Soc. Am., 97, 1742-1749, doi:10.1785/0120060181.

Augliera, P., et al. (2001), Catalogo Strumentale dei Terremoti Italiani dal 1981 al 1996 (CSTI), Versione 1.0 [CD-ROM], Inst. Naz. di Geofis. e Vulcanol., Rome.

Baer, M., P. Zweifel, and D. Giardini (2000), The Swiss Digital Seismic Network (SDSNet), ORFEUS Newsl., 2(2), 10.

Bindi, D., D. Spallarossa, C. Eva, and M. Cattaneo (2005), Local and duration magnitudes in northwestern Italy, and seismic moment versus magnitude relationships, Bull. Seismol. Soc. Am., 95, 592-604.

Bono, A., and L. Badiali (2005), PWL Personal Wavelab 1.0, an objectoriented workbench for seismogram analysis on Windows systems, Comput. Geosci., 31(1), 55-64.

Bragato, P. L., and A. Tento (2005), Local magnitude in northeastern Italy, Bull. Seismol. Soc. Am., 95, 579-591.

Cao, A., and S. S. Gao (2002), Temporal variation of seismic b values beneath northeastern Japan island arc, Geophys. Res. Lett., 29(9), 1334, doi:10.1029/2001GL013775.

Castello, B., M. Olivieri, and G. Selvaggi (2007), Local and duration magnitude determination for the Italian earthquake catalog, 1981-2002, Bull. Seismol. Soc. Am., 97, 128-139.

Chiarabba, C., L. Jovane, and R. D. Stefano (2005), A new view of Italian seismicity using 20 years of instrumental recordings, Tectonophysics, 395, 251-268.

Enescu, B., J. Mori, and M. Miyazawa (2007), Quantifying early aftershock activity of the 2004 mid-Niigata Prefecture earthquake (Mw 6.6), J. Geophys. Res., 112, B04310, doi:10.1029/2006JB004629.

Enescu, B., J. Mori, M. Miyazawa, and Y. Kano (2009), Omori-Utsu law c values associated with recent moderate earthquakes in Japan, Bull. Seismol. Soc. Am., 99, 884-891.

Gasperini, P. (2002), Local magnitude revaluation for recent Italian earthquakes (1981-1996), J. Seismol., 6(4), 503-524.

Gomberg, J. (1991), Seismicity and detection/location threshold in the outhern Great Basin seismic network, J. Geophys. Res., 96(16), 16,401-16,414.

Granet, M. (2001), The French National Network of Seismic Survey (ReNaSS), ORFEUS Newsl., 3(1), 2.

Gutenberg, B., and C. F. Richter (1944), Frequency of earthquakes in California, Bull. Seismol. Soc. Am., 34, 185-188.

Helmstetter, A., Y. Y. Kagan, and D. D. Jackson (2006), Comparison of short-term and long-term earthquake forecast models for southern California, Bull. Seismol. Soc. Am., 96, 90-106.

Huber, P. J. (1981), Robust Statistics, John Wiley, New York.

Hutton, L. K., and D. M. Boore (1987), The ML scale in southern California, Bull. Seismol. Soc. Am., 77, 2074-2094.

Ishimoto, M., and K. Iida (1939), Observations of earthquakes registered with the microseismograph constructed recently, Bull. Earthquake Res. Inst. Tokyo Univ., 17, 443-478.

Kanamori, H., and P. C. Jennings (1978), Determination of local magnitude, ML, from strong-motion accelerograms, Bull. Seismol. Soc. Am., 68, 471-486.

Kobal, M., J. Kolar, J. Pahor, and M. Z¡ ivc¡ic´ (2007), Performance of the seismic network of the Republic of Slovenia, first results, ORFEUS Newsl., 7(2), 6.

Kvaerna, T., F. Ringdal, J. Schweitzer, and L. Taylor (2002a), Optimized seismic threshold monitoring: Part 1. Regional processing, Pure Appl. Geophys., 159(5), 969-987.

Kvaerna, T., F. Ringdal, J. Schweitzer, and L. Taylor (2002b), Optimized seismic threshold monitoring: Part 2. Teleseismic processing, Pure Appl. Geophys., 159(5), 989-1004.

Lenhardt, W., and P. Melichar (2000), The Austrian Seismic Network, ORFEUS Newsl., 2(3), 20.

Lombardi, A. M., and W. Marzocchi (2007), Evidence of clustering and nonstationarity in the time distribution of large worldwide earthquakes, J. Geophys. Res., 112, B02303, doi:10.1029/2006JB004568.

Marsan, D. (2003), Triggering of seismicity at short timescales following Californian earthquakes, J. Geophys. Res., 108(B5), 2266, doi:10.1029/ 2002JB001946.

Marzocchi, W., L. Sandri, and E. Boschi (2003), On the validation of earthquake-forecasting models: The case of pattern recognition algorithms, Bull. Seismol. Soc. Am., 93, 1994- 2004.

Mazza, S. (1996), Magml, Programma per il Calcolo della Magnitudo ML da dati broad-band, Open File Rep., Inst. Naz. di Geofis., Rome.

Mazza, S., A. Morelli, and E. Boschi (1998), Near real-time data collection and processing at MEDNET, Eos Trans. AGU, 79, 569.

Mazza, S., M. Olivieri, A. Mandiello, and P. Casale (2008), The Mediterranean Broad Band Seismographic Network Anno 2005/06, in Earthquake Monitoring and Seismic Hazard Mitigation in Balkan Countries, NATO Sci. Ser., vol. 81, edited by E. S. Husebye, pp. 133- 149, Springer, Dordrecht, Netherlands.

Melis, N. S., and K. I. Konstantinou (2006), Real-time seismic monitoring in the Greek region: An example from the 17 October 2005 east Aegean Sea earthquake sequence, Seismol. Res. Lett., 77(3), 364-370.

Richter, C. F. (1958), Elementary Seismology, W. H. Freeman, San Francisco, Calif.

Rydelek, P. A., and I. S. Sacks (1989), Testing the completeness of earthquake catalogues and the hypothesis of self-similarity, Nature, 337, 251-253.

Schorlemmer, D., and J. Woessner (2008), Probability of detecting an earthquake, Bull. Seismol. Soc. Am., 98, 2103 - 2117, doi:10.1785/0120070105.

Selva, J., and W. Marzocchi (2005), Variations of southern California seismicity: Empirical evidence and possible physical causes, J. Geophys. Res., 110, B11306, doi:10.1029/2004JB003494.

Taccetti, Q., F. M. Mele, and R. Buland (1989), Il sistema automatico per la rilevazione, il processamento e l’archiviazione dei dati della rete sismica nazionale italiana I. N. G., in Aree Sismogenetiche e Rischio Sismico in Italia - II, edited by E. Boschi and M. Dragoni, pp. 1 - 7, Il Cigno Galileo Galilei, Lausanne, Switzerland.

Tinti, S., and F. Mulargia (1985), Completeness analysis of a seismic catalog, Ann. Geophys., 3(3), 407-414.

Wessel, P., and W. H. F. Smith (1991), Free software helps map and display data, Eos Trans. AGU, 72(441), 445-446.

Wiemer, S., and M. Wyss (2000), Minimum magnitude of completeness in earthquake catalogs: Examples from Alaska, the western United States and Japan, Bull. Seismol. Soc. Am., 90, 859-869.

Woessner, J., and S. Wiemer (2005), Assessing the quality of earthquake catalogues: Estimating the magnitude of completeness and its uncertainty, Bull. Seismol. Soc. Am., 95, 684-698, doi:10.1785/0120040007.

An edited version of this paper was published by AGU. Copyright (2010) American Geophysical Union.