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Filippucci, Marilena
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Filippucci, Marilena
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- PublicationOpen AccessSeismogenic Structure Orientation and Stress Field of the Gargano Promontory (Southern Italy) From Microseismicity Analysis(2021-04)
; ; ; ; ; ; ; ; ; ; ; Historical seismic catalogs report that the Gargano Promontory (southern Italy) was affected in the past by earthquakes with medium to high estimated magnitude. From the instrumental seismicity, it can be identified that the most energetic Apulian sequence occurred in 1995 with a main shock of MW = 5.2 followed by about 200 aftershocks with a maximum magnitude of 3.7. The most energetic earthquakes of the past are attributed to right-lateral strike-slip faults, while there is evidence that the present-day seismicity occur on thrust or thrust-strike faults. In this article, we show a detailed study on focal mechanisms and stress field obtained by micro-seismicity recorded from April 2013 until the present time in the Gargano Promontory and surrounding regions. Seismic waveforms are collected from the OTRIONS Seismic Network (OSN), from the Italian National Seismic Network (RSN), and integrated with data from the Italian National Accelerometric Network (RAN) in order to provide a robust dataset of earthquake localizations and focal mechanisms. The effect of uncertainties of the velocity model on fault plane solutions (FPS) has been also evaluated indicating the robustness of the results. The computed stress field indicates a deep compressive faulting with maximum horizontal compressive stress, SHmax, trending NW-SE. The seismicity pattern analysis indicates that the whole crust is seismically involved up to a depth of 40 km and indicates the presence of a low-angle seismogenic surface trending SW-NE and dipping SE-NW, similar to the Gargano–Dubrovnik lineament. Shallower events, along the eastern sector of the Mattinata Fault (MF), are W-E dextral strike-slip fault. Therefore, we hypothesized that the seismicity is locally facilitated by preexisting multidirectional fractures, confirmed by the heterogeneity of focal mechanisms, and explained by the different reactivation processes in opposite directions over the time, involving the Mattinata shear zone.59 63 - PublicationOpen AccessSeismicity of the Gargano promontory (Southern Italy) after 7 years of local seismic network operation: Data release of waveforms from 2013 to 2018(2021-04)
; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ;; ; ; ;; The University of Bari (Italy), in cooperation with the National Institute of Geophysics and Volcanology (INGV) (Italy), has installed the OTRIONS micro-earthquake network to better understand the active tectonics of the Gargano promontory (Southern Italy). The OTRIONS network operates since 2013 and consists of 12 short period, 3 components, seismic stations located in the Apulian territory (Southern Italy). This data article releases the waveform database collected from 2013 to 2018 and describes the characteristics of the local network in the current configuration. At the end of 2018, we implemented a cloud infrastructure to make more robust the acquisition and storage system of the network through a collaboration with the RECAS-Bari computing centre of the University of Bari (Italy) and of the National Institute of Nuclear Physics (Italy). Thanks to this implementation, waveforms recorded after the beginning of 2019 and the station metadata are accessible through the European Integrated Data Archive (EIDA, https://www.orfeus-eu.org/data/eida/nodes/INGV/).295 32 - PublicationOpen AccessIntrinsic Qp at Mt. Etna from the inversion of rise times of 2002 microearthquake sequence(2006-12)
; ; ; ; ;de Lorenzo, S.; Dipartimento di Geologia e Geofisica, Università degli Studi di Bari, Italy ;Filippucci, M.; Centro Interdipartimentale per la Valutazione e Mitigazione del Rischio Sismico e Vulcanico, Bari, Italy ;Giampiccolo, E.; Istituto Nazionale di Geofisica e Vulcanologia, Catania, Italy ;Patanè, D.; Istituto Nazionale di Geofisica e Vulcanologia, Catania, Italy; ; ; About three-hundred microearthquakes, preceeding and accompanying the 2002-2003 Mt. Etna flank eruption, were considered in this study. On the high-quality velocity seismograms, measurements of the first half cycle of the wave, the so-called rise time τ, were carried out. By using the rise time method, these data were inverted to infer an estimate of the intrinsic quality factor Qp of P waves and of the source rise time τ0 of the events, which represents an estimate of the duration of the rupture process. Two kind of inversions were carried out. In the first inversion τ0 was derived from the magnitude duration of the events, assuming a constant stress drop and Qp was inferred from the inversion of reduced rise times τ−τ0. In the second inversion both τ0 and Qp were inferred from the inversion of rise times. To determine the model parameters that realize the compromise between model simplicity and quality of the fit, the corrected Akaike information criterion was used. After this analysis we obtained Qp=57±42. The correlation among the inferred τ0 and Qp, which is caused by some events which concomitantly have high τ0 (>30 ms) and high Qp (>100) indicates that the technique used is able to model rise time versus travel time trend only for source dimensions less than about 80 m.220 231 - PublicationOpen Access3D-Kernel Based Imaging of an Improved Estimation of (Qc) in the Northern Apulia (Southern Italy)(2021)
; ; ; ; ; ; ; ; ; ; ; We investigate crustal seismic attenuation by the coda quality parameter (Qc) in the Gargano area (Southern Italy), using a recently released dataset composed of 191 small earthquakes (1.0 ≤ ML ≤ 2.8) recorded by the local OTRIONS and the Italian INGV seismic networks, over three years of seismic monitoring. Following the single back-scattering theoretical assumption, Qc was computed using different frequencies (in the range of 2–16 Hz) and different lapse times (from 10 to 40 s). The trend of Qc vs. frequency is the same as that observed in the adjacent Umbria-Marche region. Qc at 1 Hz varies between 11 and 63, indicating that the area is characterized by active tectonics, despite the absence of high-magnitude earthquakes in recent decades. The 3D mapping procedure, based on sensitivity kernels, revealed that the Gargano Promontory is characterized by very low and homogeneous Qc at low frequencies, and by high and heterogeneous Qc at high frequencies. The lateral variations of Qc at 12 Hz follow the trend of the Moho in this region and are in good agreement with other geophysical observations.49 36 - PublicationOpen AccessQβ, Qc, Qi, Qs of the Gargano Promontory (Southern Italy)(2023-08)
; ; ; ; ; ; ; ;; ;; ; ;We have provided the first estimate of scat- tering and intrinsic attenuation for the Gargano Prom- ontory (Southern Italy) analyzing 190 local earthquakes with M L ranging from 1.0 to 2.8. To separate the intrin- sic Q i and scattering Q s quality factors with the Wen- nerberg approach (1993), we have measured the direct S waves and coda quality factors ( Q 𝛽 , Q c ) in the same volume of crust. Q 𝛽 parameter is derived with the coda normalization method (Aki 1980) and Q c factor is derived with the coda envelope decay method (Sato 1977). We selected the coda envelope by performing an automatic picking procedure from T start = 1.5T S up to 30 s after origin time (lapse time T L ). All the obtained quality factors clearly increase with frequency. The Q c values correspond to those recently obtained for the area. The estimated Q i are comparable to the Q c at all frequencies and range between 100 and 1000. The Q s parameter shows higher values than Q i , except for 8 Hz, where the two estimates are closer. This implies a pre- dominance of intrinsic attenuation over the scattering attenuation. Furthermore, the similarity between Q i and Q c allows us to interpret the high Q c anomaly previ- ously found in the northern Gargano Promontory up to a depth of 24 km, as a volume of crust characterized by very low seismic dumping produced by conversion of seismic energy into heat. Moreover, most of the earth- quake foci fall in high Q i areas, indicating lower level of anelastic dumping and a brittle behavior of rocks.39 10 - PublicationOpen AccessNature and origin of an undetected seismic phase in waveforms from Southern Tyrrhenian (Italy) intermediate-depth and deep earthquakes: First evidence for the phase-A in the subducted Uppermost Lithospheric Mantle?(2023-08-05)
; ; ; ; ; ; ; ; ; ; ;We have found a previously unreported later seismic phase in seismograms of European seismic stations from intermediate-depth and deep earthquakes of the Southern Tyrrhenian subduction zone. We observe this phase at stations from 6 to 9◦ from the epicentre, towards north. Only seismograms of earthquakes located in a welldefined region of the slab, in the depth range of 215–320 km, show the later x-phase. In this work, we describe the nature and possible origin of this phase, and we provide a simple 2D model to explain the observed arrival times. Our analyses reveal that the x-phase propagates downward in a high velocity layer, possibly located within the deepest part of the slab. We suggest that this layer reveals the presence of the dense hydrous magnesium silicate phase A, introduced from petrological laboratory experiments, inferred to carry water in the upper mantle and predicted to be found in cold subduction zones.87 58 - PublicationOpen AccessSeismic Envelopes of Coda Decay for Q-coda Attenuation Studies of the Gargano Promontory (Southern Italy) and Surrounding RegionsHere, we describe the dataset of seismic envelopes used to study the S-wave Q-coda attenuation quality factor Qc of the Gargano Promontory (Southern Italy). With this dataset, we investigated the crustal seismic attenuation by the Qc parameter. We collected this dataset starting from two different earthquake catalogues: the first regarding the period from April 2013 to July 2014; the second regarding the period from July 2015 to August 2018. Visual inspection of the envelopes was carried out on recordings filtered with a Butterworth two-poles filter with central frequency fc = 6 Hz. The obtained seismic envelopes of coda decay can be linearly fitted in a bilogarithmic diagram in order to obtain a series of single source-receiver measures of Qc for each seismogram component at different frequency fc. The analysis of the trend Qc(fc) gives important insights into the heterogeneity and the anelasticity of the sampled Earth medium.
32 23 - PublicationRestrictedAn EGF technique to infer the rupture velocity history of a small magnitude earthquake(2008)
; ; ; ;de Lorenzo, S.; Dipartimento di Geologia e Geofisica and Centro Interdipartimentale per la Valutazione e Mitigazione del Rischio Sismico e Vulcanico, Università di Bari, Bari, Italy. ;Filippucci, M.; Dipartimento di Geologia e Geofisica and Centro Interdipartimentale per la Valutazione e Mitigazione del Rischio Sismico e Vulcanico, Università di Bari, Bari, Italy. ;Boschi, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione AC, Roma, Italia; ; An empirical Green’s function (EGF) technique has been developed to detect the rupture velocity history of a small earthquake. The assumed source model is a circular crack that is characterized by a single and unipolar moment rate function (MRF). The deconvolution is treated as an inverse problem in the time domain, which involves an assumed form of the moment rate function (MRF). The source parameters of the MRF are determined by adopting a global nonlinear inversion scheme. A thorough synthetic study on both synthetic and real seismograms allowed us to evaluate the degree of reliability of the retrieved model parameters. The technique was applied to four small events that occurred in the Umbria-Marche region (Italy) in 1997. To test the hypothesis of a single rupture process, the inversion results were compared with those arising from another EGF technique, which assumes a multiple rupture process. For each event, the best fit model was selected using the corrected Akaike Information Criterion. For all the considered events the most interesting result is that the selected best fit model favors the hypothesis of a single faulting process with a clear variability of the rupture velocity during the process. For the studied events, the maximum rupture speed can even approach the P-wave velocity at the source, as theoretically foreseen in studies of the physics of the rupture and recently observed for high-magnitude earthquakes.195 26 - PublicationOpen AccessCooling of a channeled lava flow with non-Newtonian rheology: crust formation and surface radiance(2011)
; ; ; ; ; ; ;Tallarico, A. ;Dragoni, M. ;Filippucci, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Piombo, A. ;Santini, S. ;Valerio, A. ; ;; ; ;We present here the results from dynamical and thermal models that describe a channeled lava flow as it cools by radiation. In particular, the effects of power-law rheology and of the presence of bends in the flow are considered, as well as the formation of surface crust and lava tubes. On the basis of the thermal models, we analyze the assumptions implicit in the currently used formulae for evaluation of lava flow rates from satellite thermal imagery. Assuming a steady flow down an inclined rectangular channel, we solve numerically the equation of motion by the finite-volume method and a classical iterative solution. Our results show that the use of power-law rheology results in relevant differences in the average velocity and volume flow rate with respect to Newtonian rheology. Crust formation is strongly influenced by power-law rheology; in particular, the growth rate and the velocity profile inside the channel are strongly modified. In addition, channel curvature affects the flow dynamics and surface morphology. The size and shape of surface solid plates are controlled by competition between the shear stress and the crust yield strength: the degree of crust cover of the channel is studied as a function of the curvature. Simple formulae are currently used to relate the lava flow rate to the energy radiated by the lava flow as inferred from satellite thermal imagery. Such formulae are based on a specific model, and consequently, their validity is subject to the model assumptions. An analysis of these assumptions reveals that the current use of such formulae is not consistent with the model.164 179 - PublicationRestrictedConditions for crust and tube formation in lava flows with power-law rheology(2011)
; ; ; ;Filippucci, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Tallarico, A. ;Dragoni, M.; ;We studied the conditions of crust and tube formation of a lava flow moving under the effect of gravity in a rectangular cross-section channel and assumed a power-law rheology for lava. We followed the work of Valerio et al. (2008), who studied the effect of surface cooling on the formation and accretion of the crust in the central region of the channel, assuming for lava a Newtonian rheology. According to these authors, tube formation is influenced by topography and channel morphology. In this work, we extended this study to a non-Newtonian rheology, in particular to the power-law rheology. Results indicate that a power-law rheology strongly influences the condition of crust formation but does not produce significant differences as a function of topographical or morphological variations.209 25