Report on Campi Flegrei (Italy) — April 1984
Scientific Event Alert Network Bulletin, vol. 9, no. 4 (April 1984)
Managing Editor: Lindsay McClelland.
Campi Flegrei (Italy) Seismic energy release and uplift slow after 1 April earthquake swarm
Please cite this report as:
Global Volcanism Program, 1984. Report on Campi Flegrei (Italy). In: McClelland, L (ed.), Scientific Event Alert Network Bulletin, 9:4. Smithsonian Institution. http://dx.doi.org/10.5479/si.GVP.SEAN198404-211010.
40.827°N, 14.139°E; summit elev. 458 m
All times are local (unless otherwise noted)
"Seismic activity at Campi Flegrei decreased in April. Following the earthquake swarm of 1 April and a M 3.5 event that occurred on 3 April, the cumulative seismic strain energy release had a smaller slope than in the previous three months (figure 5).
|Figure 5. Daily number of earthquakes at Campi Flegrei (vertical lines) and cumulative strain release (curve), January 1983-April 1984.|
"The distribution of epicenters for the best-located events (number of stations >8, RMS <0.16) until 15 January shows an interesting feature (figure 6). Three different clusters are evident. The first, which includes the events with highest energy, is located around the S border of Solfatara Crater. The events that occur during swarms are located on the W edge of the active seismic region. The third cluster includes a few events located in the Gulf of Pozzuoli.
|Figure 6. Epicentral distribution of best-located events at Campi Flegrei through 15 January 1984. Courtesy of OV.|
"The mean velocity of uplift during April, as measured by the tide gauge located in Pozzuoli harbor, was 1.6 mm/day. This value is definitely smaller than the previous month. Temperatures of the two fumaroles within Solfatara Crater remained at constant values of 110° and 157-159°C.
"The decrease in activity observed after the swarm of 1 April is similar to the decrease observed during November 1983. In that case, a diminuition in seismic activity and a decrease in the uplift velocity were observed after a M 4.0 earthquake, and a swarm that occurred 13 October 1983."
Geologic Background. Campi Flegrei is a large 13-km-wide caldera on the outskirts of Naples that contains numerous phreatic tuff rings and pyroclastic cones. The caldera margins are poorly defined, and on the south lie beneath the Gulf of Pozzuoli. Episodes of dramatic uplift and subsidence within the dominantly trachytic caldera have occurred since Roman times. The earliest known eruptive products are dated 47,000 yrs BP. The caldera formed following two large explosive eruptions, the massive Campanian ignimbrite about 36,000 BP, and the >40 cu km Neapolitan Yellow Tuff (NYT) about 15,000 BP. Following eruption of the NYT a large number of eruptions have taken place from widely scattered subaerial and submarine vents. Most activity occurred during three intervals: 15,000-9500, 8600-8200, and 4800-3800 BP. Two eruptions have occurred in historical time, one in 1158 at Solfatara and the other in 1538 that formed the Monte Nuovo cinder cone.
Information Contacts: G. Luongo and R. Scandone, OV; F. Barberi, Univ. di Pisa.