Small-aperture Array for Seismic Monitoring of Mt. Vesuvius

Abstract

Mt. Vesuvius is potentially one of the most dangerous volcanoes in the world. It is located practically within the urban area of Naples and its activity is characterized by strong explosive eruptions, such as the Plinian eruption that destroyed Pompeii in A.D. 79. This volcano has been monitored by the Vesuvius Observatory (V.O.), which has conducted geophysical and geochemical monitoring since 1841. Since that time, Mt. Vesuvius has experienced only open conduit eruptions, with some effusive eruptions (see http://www.ov.ingv.it/), the last of which (in 1944) was followed by conduit closure and return to an apparently dormant state. From the long historical record it can be hypothesized that Mt. Vesuvius might erupt the next time with a new sub-Plinian eruption. If an eruption is considered imminent an evacuation plan will be activated for more than 700,000 people living in the “red” zone at the base of this volcano. The start of the evacuation plan is based on a conceptual eruptive model essentially based on the sub-Plinian eruption of 1631, which is well described in many historical chronicles and recent publications (e.g. , Nazzaro, 1998). The essence of this model is the hypothesis that the next sub-Plinian eruption will be preceded by significant precursors, including seismicity, ground deformation, and geochemical changes. Possible seismological precursors include increasing volcanic tremor and/or LP events that could accompany pressure changes caused by rising magma. Monitoring effects are followed closely by the Government Commission, which is responsible for making the decision to evacuate. Arrays (also known as seismic antennas) are used in seismology when it is necessary to track sources generating nonimpulsive signals, such as those of volcanic tremor and LP events. An antenna samples the wavefield in time and space, allowing the decomposition of the observed signal into one or more incident plane waves characterized by …