HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Full Text (PDF) Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Vassallo, M. Articles by Iannaccone, G. Search for Related Content GeoRef GeoRef Citation

A Comparison of Sea-Floor and On-Land Seismic Ambient Noise in the Campi Flegrei Caldera, Southern Italy

Dipartimento di Scienze Fisiche, Università di Napoli Federico II, Napoli, Italy vassallo{at}na.infn.it

Antonella Bobbio and Giovanni Iannaccone

Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Vesuviano, Napoli, Italy

^* Current address: Analisi e Monitoraggio del Rischio Ambientale (AMRA) Scarl, via Nuova Agnano, 11-80125 Napoli, Italy.

The Campi Flegrei (southern Italy) is one of the most active calderas in the world. This caldera is characterized by episodes of slow vertical ground movement, called bradyseism. With several hundred thousand people living within its borders, this area is in a high-risk category should there be an eruption. The seismological monitoring system in the Campi Flegrei is based on nine seismic stations, eight of which are equipped with short-period seismometers (1 Hz), and one with a broadband seismometer (60 sec–50 Hz). While all of the seismic stations are located on land, part of the seismic activity occurs in the undersea area of the Pozzuoli Gulf (Campi Flegrei), where there are no seismic stations. This gap in the data coverage produces a biased and incomplete image of the volcanic area. We carried out an experiment in the Pozzuoli Gulf with the installation of two broadband seismic stations on the seafloor with remote and continuous data acquisition for a duration of 31 days between January and March 2005. Using the data acquired, we have computed the power spectral density (PSD) to characterize the background seismic noise, and to evaluate the true noise variation, we have generated the seismic noise probability density functions from the computed PSD curves. The results of our analysis show that the broadband seismic noise is high when compared with the Peterson noise model (land model), but for periods less than 0.3 sec, the seismic noise on the seafloor is lower than the recordings on land over the same period range. The last bradyseismic crisis (1982–1984) highlights the importance of this frequency range, where most of the spectral content of the recorded earthquakes was observed. Finally, we evaluate the detection threshold of a new seismic station located on the seafloor of the Campi Flegrei caldera considering the characteristics of the local seismicity. This analysis shows that the detection threshold for the sea-floor stations (M_w0.2) is less than that for land stations (M_w0.8).

This article has been cited by other articles:

				G. Iannaccone, S. Guardato, M. Vassallo, L. Elia, and L. Beranzoli A New Multidisciplinary Marine Monitoring System for the Surveillance of Volcanic and Seismic Areas Seismological Research Letters, March 1, 2009; 80(2): 203 - 213. [Full Text] [PDF]