Planning the improvement of a seismic network for monitoring active volcanic areas: the experience on Mt. Etna

A D'Alessandro,S Rapisarda,A Scaltrito,S Di Prima,L Scarfì

doi:10.5194/adgeo-36-39-2013

A D'Alessandro, S Rapisarda + Show 3 more

Open Access

https://doi.org/10.5194/adgeo-36-39-2013

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Abstract

Abstract. Seismology and geodesy are generally seen as the most reliable diagnostic tools for monitoring highly active or erupting volcanoes, like Mt. Etna. From the early 1980's, seismic activity was monitored at Mt. Etna by a permanent seismic network, progressively improved in the following years. This network has been considerably enhanced since 2005 by 24-bit digital stations equipped with broad-band (40 s) sensors. Today, thanks to a configuration of 33 broad-band and 12 short-period stations, we have a good coverage of the volcanic area as well as a high quality of the collected data. In the framework of the VULCAMED project a workgroup of Istituto Nazionale di Geofisica e Vulcanologia has taken on the task of developing the seismic monitoring system, through the installation of other seismic stations. The choice of optimal sites must be clearly made through a careful analysis of the geometry of the existing seismic network. In this paper, we applied the Seismic Network Evaluation through Simulation in order to evaluate the performance of the Etna Seismic Network before and after the addition of the stations in the candidate sites. The main advantage of the adopted method is that we can evaluate the improvement of the network before the actual installation of the stations. Our analysis has permitted to identify some critical issues of the current permanent seismic network related to the lack of stations in the southern sector of the volcano, which is nevertheless affected by a number of seismogenic structures. We have showed that the addition of stations at the candidate sites would greatly extend the coverage of the network to the south by significantly reducing the errors in the hypocenter parameters estimation.

Highlights

A new impulse for seismic observations came in 1978 when a short-period telemetered network was set up permanently by the University of Catania. It is only from the early 1990’s, thanks to the Istituto Internazionale di Vulcanologia and the Poseidon Project, which merged into the Istituto Nazionale di Geofisica e Vulcanologia (INGV) in 2001, that seismic data have been available in digital format for a sufficient number of stations, increased in time as well as for three-component sensors
Before installing the seismic stations in the candidate sites (CS), it should be opportune to quantify the improvement in terms of coverage, decrease in magnitude detection threshold and improvement www.adv-geosci.net/36/39/2013/
This would allow to identify in advance changes in the network geometry that would ensure a better coverage in the area to be monitored

Summary

Introduction

In this paper we applied the Seismic Network Evaluation through Simulation (SNES) method (D’Alessandro et al, 2011a) to ESN, in order to evaluate the location performance, along with the magnitude detection threshold of the network, before and after the addition of the stations in the candidate sites. The SNES method allows determining, as a function of magnitude, hypocentral depth and confidence level, the spatial distribution of the following parameters: magnitude detection threshold, number of active stations in the location procedure, azimuthal gap and confidence levels of hypocentral parameters.

Results

Conclusion