Seismic sources and attenuation properties at the Campi Flegrei volcanic area
Hypocenter distribution and the size of the seismic zone do not change with time and do not depend on the ground uplift rate. Events occurred clustered in time with no simple causal relations between the cluster occurrences and their energy.
Anelastic attenuation does not depend strongly on frequency, showing a constant pattern at high frequencies. The observed values of low and high frequency attenuation, due to the short source receiver distances, do not seriously affect the spectral content of signals radiated by the sources.
A constant Brune stress drop pattern (∼4–5 bars) as a function of seismic moment is observed. This indicates that the manner of fracturing is almost independent on magnitude of earthquakes (hypothesis of self-similarity (Aki, 1967)). Seismic processes in a prefractured medium can explain the observed small stress drop values.
Focal mechanisms from moment tensor estimates show that radiation patterns are mostly well interpreted in terms of double couple source models.
The scaling of peak ground motion parameters (Amax andVmax vs seismic moment) can be explained by an ω2 source model (constant stress drop) multiplied by an exponential function with a small decay parameter, which takes into account the measured attenuation.
These results support the hypothesis of earthquakes generated by simple shear fractures along prefractured structures as a response to changes in the stress field due to the ground deformation.
Key wordsCampi Flegrei Volcanic earthquakes Attenuation Source parameters Moment tensor
Unable to display preview. Download preview PDF.
- Aki, K. (1967),Scaling law of seismic spectrum. J. Geophys. Res.72, 1217–1231.Google Scholar
- Aki, K. (1986),Physical theory of earthquakes. Proceedings of Strasbourg, 1986 Summer School on ‘Seismic hazard in mediterranean regions’ (in press).Google Scholar
- Aki, K. andChouet, B. (1975),Origin of coda waves: source, attenuation, and scattering effects. J. Geophys. Res.80, 3332–3342.Google Scholar
- Aki, K., andRichards, P. G. (1980),Quantitative seismology: theory and methods. (W. H. Freeman and Co., S. Francisco, CA).Google Scholar
- Anderson, J. G. andHough, S. (1984),A model for the shape of the Fourier amplitude spectrum of acceleration at high frequencies. Bull. Seism. Soc. Am.74, 1969–1994.Google Scholar
- Archuleta, R. J., Cranswick, E., Mueller, C. andSpudich, P. (1982),Source parameters of the 1980 Mammoth Lakes, California earthquake sequence. J. Geophys. Res.87, 4595–4607.Google Scholar
- Aster, R. (1987),Hypocenter locations and velocity structure in Phlegraean Fields, Italy. Master Sc. (Geophysics) Thesis, U. Wisconsin, Madison USA.Google Scholar
- Barberi, F., Innocenti, F., Lirer, L., Munno, R., Pescatore, T. andSantacroce, R. (1978),The campanian ignimbrite: a major prehistoric eruption in the neapolitan area (Italy). Bull. Volc.41, 1–22.Google Scholar
- Berrino, G., Corrado, G., Luongo, G. andToro, B. (1984),Ground deformation and gravity changes accompanying the 1982 Pozzuoli uplift. Bull. Volc.47 (2), 187–200.Google Scholar
- Boatwright, J. (1978),Detailed spectral analysis of two small New York State earthquakes. Bull. Seism. Soc. Am.68, 1117–1131.Google Scholar
- Boatwright, J. (1980),A spectral theory for circular seismic sources: simple estimates of source dimension, dynamic stress drop and radiated energy. Bull. Seism. Soc. Am.71, 69–94.Google Scholar
- Boore, D. M. (1983),Stochastic simulation of high frequency ground motions based on seismological models of the radiated spectra. Bull. Seism. Soc. Am.73, 1865–1894.Google Scholar
- Boore, D. M. andBoatwright, J. (1984),Average body wave radiation coefficients. Bull. Seism. Soc. Am.74, 1615–1621.Google Scholar
- Brune, J. N. (1970),Tectonic stress and the spectra of seismic shear waves from earthquakes. Bull. Seism. Soc. Am.60, 4997–5009.Google Scholar
- Castellano, M., Del Pezzo, E., De Natale, G. andZollo, A. (1984).Seismic coda Q and turbidity coefficient at the Phlegraean Fields volcanic area: preliminary results. Bull. Volc.47, 219–224.Google Scholar
- Chouet, B., Aki, K. andTsujura, M. (1978),Regional variation of the scaling law of earthof earthquake source spectra. Bull. Seism. Soc. Am.68, 49–80.Google Scholar
- Chouet, B. (1979),Sources of seismic events in the cooling lava lake of Kilauea Iki, Hawaii. J. Geophys. Res.84, 2315–2330.Google Scholar
- Clearbout, J. (1976),Fundamentals of geophysical data processing (McGraw Hill, S. Francisco, 1976).Google Scholar
- Corrado, G., Guerra, I., Lo Bascio, A., Luongo, G. andRampoldi, R. (1976),Inflation and microearthquake activity at Phlegraean Fields, Italy. Bull. Volc.40, 1–20.Google Scholar
- Crosson, R. S. (1981),LQUAKE: a computer program for hypocenter locations. Techn. Rep. Univ. Wash. (Seattle).Google Scholar
- Crosson, R. S. andBame, D. A. (1986),A spherical source model for low frequency volcanic earthquakes. J. Geophys. Res.92, 10237–10247.Google Scholar
- Dainty, A. M. (1981),Scattering model to explain seismic Q observations in the litosphere between 1 and 30 Hz. Geophys. Res. Lett.8, 1126–1128.Google Scholar
- Del Pezzo, E., De Natale, G. andZollo, A. (1984),Space-Time distribution of small earthquakes at Phlegraean Fields. Bull. Volc.47, 201–207.Google Scholar
- Del Pezzo, E., De Natale, G., Scarcella, G. andZollo, A. (1985),Q c of three component seismograms of volcanic microearthquakes at Campi Flegrei volcanic area, Southern Italy. PAGEOPH123, 683–696.Google Scholar
- Del Pezzo, E., De Natale, G., Martini, M. andZollo, A. (1987),Source parametersoof microearthquakes at Phlegraean Fields (Southern Italy) volcanic area. Phys. Earth Pla. Int.47, 25–42.Google Scholar
- De Natale, G., Iannaccone, G. andZollo, A. (1986),Un metodo per la determinazione del meccanismo focale dal tensore momento. Boll. Soc. Geol. It. (in press).Google Scholar
- De Natale, G., Madariaga, R., Scarpa, R. andZollo, A. (1987a),Source parameter analysis from strong motion records of the Friuli (Italy) earthquake sequence (1976–1977). Bull. Seism. Soc. Am.77, 1127–1146.Google Scholar
- De Natale, G., Faccioli, E. andZollo, A. (1987b),Scaling of peak, ground motions from digital recordings of small earthquakes at Campi Flegrei, Southern Italy. PAGEOPH (in press).Google Scholar
- De Natale G. andZollo, A. (1986),Statistical analysis and clustering features of the Phlegraean Fields earthquake sequence (May 1983–May 1984). Bull. Seism. Soc. Am.76, 801–814.Google Scholar
- Di Vito, M., Lirer, L., Mastrolorenzo, G., Rolandi, G. andScandone, R. (1985),Volcanological map of Campi Flegrei (Edited by Dipartimento di Geofisica e Vulcanologia, Universitá di Napoli).Google Scholar
- Fehler, M. andChouet, B. (1982),Operation of digital seismic network on Mt. St. Helens volcano and observations of long period seismic events that originate under the volcano. Geophys. Res. Letters9, 1017–1020.Google Scholar
- Gao, L. S., Lee, L. C., Biswas, N. N. andAki, K. (1983),Comparison of the effects between single and multiple scattering on coda waves for local earthquakes. Bull. Seism. Soc. Am.74, 337–389.Google Scholar
- Gaudiosi, G. andIanaccone, G. (1984),Preliminary study of stress pattern at Phlegraean Fields as inferred from focal mechanisms. Bull. Volcan.47, 225–231.Google Scholar
- Hanks, T. C. (1982),F max. Bull. Seism. Soc. Am.72, 1867–1879.Google Scholar
- Julian, B. R. andSipkin, S. (1985),Earthquake processes in the Long Valley Caldera area, California. J. Geophys. Res.90, 11155–11170.Google Scholar
- Keilis-Borok, V. I. (1959),On estimation of the displacement in an earthquake source dimensions. Ann. Geophys.12, 205–214.Google Scholar
- Lawson, C. L. andHanson, R. J. (1974),Solving least squares problems (Prentice Hall, Englewood Cliff, New Jersey, 1974).Google Scholar
- Madariaga, R. (1976),Dynamics of an expanding circular fault. Bull. Seism. Soc. Am.66, 639–666.Google Scholar
- Oncescu, M. C. (1986),Relative seismic moment tensor determination for Vrancea intermediate depth earthquakes. PAGEOPH (in press).Google Scholar
- Quareni, F., Bonafede, M. andDragoni, M. (1985),A viscoelastic model for ground deformation and seismic activity at Campi Flegrei, Italy. Geophys. J.R. Ast. Soc. (submitted).Google Scholar
- Rautian, T. G. andKhalturin, V. I. (1978),The use of coda for determination of the earthquake source spectra. Bull. Seism. Soc. Am.68, 49–80.Google Scholar
- Rosi, M., Sbrana, A. andPrincipe, C. (1983),The Phlegraean Fields: structural evolution, volcanic history and eruptive mechanisms. J. Volc. Geoth. Res.17, 237–288.Google Scholar
- Scarcella, G. (1984),Metodi di inversione di dati sismici: applicazione nel Basso Tirreno e nei Campi Flegrei. Degree in Physics, Thesis University of Naples, Italy.Google Scholar
- Strelitz, R. A. (1978),Moment tensor inversions and source models. Geophys. J.R. Astr. Soc.52, 359–364.Google Scholar
- St. Laurence, W. andQamar, A. (1979),Hydraulic transients: a seismic source in volcanoes and glaciers. Science203, 654–656.Google Scholar