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  • 1
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    Attenuation study in the Straits of Messina area (southern Italy) (2007)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: The attenuation of seismic waves is one of the basic physical parameters used in seismological studies and earthquake engineering, which is closely related to the seismicity and regional tectonic activity of a particular area. In this work, the seismic attenuation in the Straits of Messina, affected by several and strong historical earthquakes, was studied using waveforms recorded by a local seismic network composed of seven stations. We measured: the coda quality factor (Qc) in the Single Scattering model hypothesis; the direct quality factor (Qd) applying the Coda Normalization method for S-waves; and the intrinsic and scattering quality factor (Qi and Qs) by the Multiple Lapse Time Window Analysis (MLTWA) method. Coda Q values were obtained using different lapse times (40, 60 and 80 s) for the frequency bands centred at 1.5, 3, 6 and 12 Hz. Our findings indicate that Qc increases with increasing lapse time and that Qc is frequency dependent. This behaviour is usually correlated to the degree of tectonic complexity and to the presence of heterogeneities at several scales. In fact, by using the Coda Normalization method we obtained low Qd values, as expected for a heterogeneous and active zone. Finally, by the MLTWA method we observe that the contribution of the scattering attenuation (Qs −1) prevails on the intrinsic absorption (Qi −1) until 3 Hz. Conversely, Qi −1 and Qs −1 seem to be of the same order in the higher frequency bands.
    Description: Published
    Description: 173-185
    Description: reserved
    Keywords: Coda waves ; Intrinsic attenuation ; S-waves ; Scattering attenuation ; Straits of Messina ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Format: 897169 bytes
    Format: application/pdf
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  • 2
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    Seismic tomography of Central Sao Miguel, Azores (2008)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: We determine the three-dimensional distribution of P- and S-wave velocities for Central São Miguel Island (Azores, Portugal) by tomographic inversion of local earthquake arrival times. We use P- and S-phases from 289 earthquakes recorded by a network of 20 seismometers. The model shows good resolution in the shallowest 5–6 km, as illustrated by different resolution tests. There are several velocity anomalies, interpreted as pyroclastic deposits, intrusive bodies, geothermal fields, and the effects of tectonics. A low Vp zone marks Furnas caldera, probably evidencing volcaniclastic sediments with development of intense geothermal activity. Another low Vp zone extends in correspondence of the highly fractured area between Fogo and the north coast. Conversely, strong positive anomalies are found south of Fogo and northwest of Furnas. They are interpreted in terms of high-density deposits and remnants of a plutonic intrusion. These interpretations are supported by the distribution of Vp/Vs, and are consistent with previous geological, geochemical, and geophysical data.
    Description: Published
    Description: 8-18
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: Seismic tomography ; Volcano seismology ; Crustal structure ; Azores ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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