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Roselli, Pamela
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Roselli, Pamela
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pamela.roselli@ingv.it
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- PublicationOpen AccessMoho-depth and subglacial sedimentary layer thickness in the Wilkes Basin from Receiver Function Analysis(2005-10)
; ; ; ; ;Piana Agostinetti, N.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Roselli, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Cattaneo, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Amato, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; ; ; Wilkes Basin lies to the east of the Transantarctic Mountains. The origin of this sub-glacial basin is still controversial. Flexural uplift of the Transantarctic Mountains has been suggested as the geophysical process which generated the basin (Stern & ien Brink, 1989). Other studies proposed a continental rift structure for this region (Ferraccioli et al., 2001). The two models differ mainly in the crustal structure predicted beneath the basin. In the former, crustal thickning is expected to be originated from the high rigidity of the East Antarctic Craton lithosphere. Otherwise, the rift structure hypothesis is consistent with a broad crustal thinning. During the WIBEM 2003 campaign, we deployed five broadband seismic stations across the basin. We selected high signal/noise teleseismic recording to compute a data-set of receiver functions. We applied a classical inversion scheme, the Neighbourhood Algorithm, to our data-set. Here, two different and complementary studies are presented. We constrain the Moho geometry beneath the Wilkes Basin from the analysis of low-frequency P-to-S conversion at the base of the crust. Also, we investigate the nature of the basin mapping the presence of subglacial sediments using the P-to-S conversion at the ice-bedrock interface.254 362 - PublicationRestrictedAnalysis of small magnitude seismic sequences along the Northern Apennines (Italy)(2009-10-15)
; ; ; ; ; ;Piccinini, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Piana Agostinetti, N.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Roselli, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Ibs-von Seht, M.; Federal Institute for Geosciences and Natural Resources, Hannover, Germany ;Braun, T.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; ; We analyze the seismicity of a small sector of the Northern Apennines merging data from the Italian seismic bulletin with original data collected by temporary seismic networks. Our attention is focused on the region enclosed between the Apenninic watershed and the Adriatic Sea. This portion of belt is interested by the occurrence of diffuse crustal seismicity and small-to-moderate earthquakes. In this paper we study the five small sequences with mainshock having Mw < 4.7 that in the past 15 years hit the area. Our interest is addressed to better understand the relationship between these events and the regional seismotectonic setting in terms of seismicity distribution and stress field. Two regions with different behavior in the seismic release can be distinguished: (i) along the watershed where seismicity is clustered at shallow depths (< 15 km) and where strong earthquakes occurred in the past, (ii) an eastern portion where the seismicity is distributed across all of the crustal volume, locally reaching depths down to 30 km. The focal mechanism of the seismic sequences shows mainly normal fault kinematics coherent with the regional stress field. Detailed stress field analysis suggests a rotation of the principal stress axis moving from the axial part of the chain toward the Adriatic Sea to the east.312 32 - PublicationOpen AccessAnalysis of non-double-couple source mechanisms in an area of induced seismicity, West Texas (USA)In the scope to investigate the possible interactions between injected fluids, subsurface geology, stress field and triggering earthquakes, we investigate seismic source parameters related to the seismicity in West Texas (USA). The analysis of seismic moment tensor is an excellent tool to understand earthquake source process kinematics; moreover, changes in the fluid volume during faulting leads to existence of non-double-couple (NDC) components (Frohlich, 1994; Julian et al., 1998; Miller et al., 1998). The NDC percentage in the source constitutes the sum of absolute ISO and CLVD components so that %NDC= % ISO + %CLVD and %ISO+%CLVD+%DC=100%. It is currently known that the presence of NDC implies more complex sources (mixed shear-tensile earthquakes) correlated to fluid injections, geothermal systems and volcano-seismology where induced and triggered seismicity is observed. With this hypothesis, we analyze the micro-earthquakes (M <2 .7) recorded by the Texas Seismological Network (TexNet) and a temporary network constituted by 40 seismic stations (equipped by either broadband or 3 component geophones). Our study area is characterized by Northwest-Southeast faults that follow the local stress/field (SHmax) and the geological characteristic of the shallow basin structure of the study area. After a selection based on signal-to-noise ratio, we filter (1-50 Hz) the seismograms and estimate P-wave pulse polarities and the first P-wave ground displacement pulse in time domain. Then, we perform the full moment tensor analysis by using hybridMT technique (Andersen, 2001; Kwiatek et al., 2016) with a detailed 1D velocity model. The key parameter is the polarity/area of the first P-wave ground displacement pulse in time domain. Uncertainties of estimated moment tensors are expressed by normalized root-mean-square (RMS errors) between theoretical and estimated amplitudes (Vavricuk et al., 2014). We also evaluate the quality of the seismic moment tensors by bootstrap and resampling. In our preliminary results we obtain NDC percentage (in terms of %ISO and %CLVD components), Mw, seismic moment, P, T and B axes orientation for each source inverted.
36 15 - PublicationOpen AccessSource mechanisms and induced seismicity in the Val d'Agri Basin (Italy)(2023-04-11)
; ; ; ; ; ; ; ; ; ;; We present the results from a fully unconstrained moment tensor inversion of induced seismic events in a complex and high seismic hazard region (Val d’Agri basin, Southern Italy). The study area hosts two well-documented cases of induced microseismicity linked to (i) a wastewater injection well of a giant oilfield (the largest in onshore Europe), and (ii) severe seasonal level changes of an artificial lake. In order to gather information on the non-doublecouple components of the source and to better understand the rupture mechanisms, we analyse seismic events recorded during daily injection tests in the disposal well. The computed moment tensors have significant non-double-couple components that correlate with the well-head injection pressure. The injection parameters strongly influence the rupture mechanism that can be interpreted as due to the opening/closing of a fracture network inside a fault zone of a pre-existing thrust fault. For the case of the reservoir-induced seismicity, no direct correlations are observed with the loading/unloading of the reservoir.66 9 - PublicationOpen AccessNon-Double-Couple Seismic Sources and Active Intrusions in Mountain Chains: an Example from a Moderate Seismic Sequence in Southern Apennines, Italy(American Geophysical Union, Fall Meeting 2019, abstract #S23E-0689, 2019-12)
; ; ; We investigate an anomalous deep seismic sequence characterized by low-frequency bursts of earthquakes (maximum magnitude 5) that occurred between December 2013 and January 2014 in the southern Apenninic chain, Italy. Previous studies (Di Luccio et al., 2018) have shown evidences of fluid involvement in the earthquake nucleation process and identified thermal anomaly in nearby aquifers where CO2 of magmatic origin dissolves. Seismic source parameters reveal important information about the rupture mechanisms and stress field and their relation with the geological-tectonics processes. It is commonly assumed seismic source as pure shear dislocation described by a double-couple model. When volumetric changes occur, we need to consider the non-double couple source component in the description of the rupture process, as in geothermal and volcanic systems where fluids play an important role. In this study we analyze the 2013-2014 seismic sequence (earthquakes larger than 3) through a full moment tensor (FMT) inversion by using the HybridMT code (Kwiateck et al., 2016). The FMT is based on computing the integral of the first P-wave ground displacement pulse that is proportional to the seismic moment. Uncertainties of estimated FMTs are expressed by the normalized root-mean-squares between theoretical and observed amplitudes. The FMT technique is done on the vertical components of the seismograms, using a detailed 1D velocity model and accurate locations of the events. After a visual inspection of the waveforms based on the signal-to-noise ratio, we compute the displacement to estimate P-wave pulse polarities and the area beneath the P-pulse for each event and each station within epicentral distance comparable to the focal depth. The inversion procedure provides Mw, seismic moment and P, T and B axis orientation. Our results show high percentages of non-double couple components that vary over time and do not depend on earthquake magnitude. The stress axis orientations are in agreement with the regional crustal stress regime. The comparison of the obtained source parameters with petrological and geological data will allow us to better understand the emplacement mechanisms of intrusive bodies and the seismicity in mountain chains.52 2 - PublicationOpen AccessAnalisi strutturale di crosta e mantello in prossimità dell’alta Val di Chiana (Toscana orientale)(2006-11)
; ; ; ;Roselli, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Piana Agostinetti, N.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Braun, T.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; L’Appennino Settentrionale è una catena montuosa NE-vergente ed è il risultato dell’affioramento del prisma di accrezione originato in seguito alla subduzione della litosfera adriatica sotto il mar Tirreno ed ancora in atto (Faccenna et al., 2001). Dall’Oligocene ad oggi, l’Appennino Settentrionale è stato interessato da due fasi deformative: inizialmente compressiva con la formazione di thrusts e più recentemente distensiva (Elter et al., 1975). Attualmente è caratterizzato da un regime crostale distensivo con una velocità stimata circa 2.5 mm/anno (Hunstad et al., 2003). Gli effetti e le conseguenze di questi episodi deformativi sono ben visibili attraverso un’analisi geologica e geofisica. L’area in studio è posta in corrispondenza della transizione tra la successione Toscana ed il settore Tirrenico del dominio Umbro-Marchigiano, quindi, una zona particolarmente dibattuta da un punto di vista geodinamico, a causa della presenza di diverse tipologie crostali, flusso di calore e anomalie gravimetriche.163 143 - PublicationOpen AccessPreliminary earthquake focal mechanism forecasts for the Amatrice sequence (Central Italy)We compare the moment tensor solutions data of the last Amatrice seismic sequence with the corresponding forecasts computed with independent information for the same territory derived from both focal mechanism catalogue and the present-day stress data (latest release). The knowledge of expected focal mechanism at the site is important to reduce the uncertainty of the Ground Motion Prediction Equation models used. For this purpose, we apply a procedure to compute, for each spatial cell, the probability to observe in the future a Normal, Reverse, and Strike-Slip event, the average distribution of the P, T, B axes and the related SHmax, for each of these types of earthquake.
206 36 - PublicationOpen AccessSpatial and temporal seismicity clustering in Central-Northern Apennines: fluids and seismicity(2007-11-13)
; ; ; ; ; ;Roselli, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Piccinini, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Braun, T.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Piana Agostinetti, N.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Ibs-von Seht, M.; BGR, Hannover, Germany; ; ; ; The Northern Apennines (NAs) are composed by a NE verging thrust-fold belt formed as result of the collision (Oligo-Miocene) between the European plate (Sardinia-Corsica block) and the Adriatic microplate, once the westward subduction of the Tethyan oceanic lithosphere was completed (Alvarez, 1972; Reutter et al., 1980; Argnani, 2002). This mountain chain is dominated by concomitant extension and compression in two adjacent areas: inner zone of the belt and outer zone (Frepoli and Amato, 1997; Collettini and Barchi, 2002). Our study area is located in the inner zone characterised by Pliocene-Quaternary sedimentation developed in grabens and half-grabens borded by normal faults. This tectonic extension process is associated whith diffuse CO2 degassing (Chiodini et al., 2004). The question whether the CO2 has a metamorphic and/or magmatic upper crust origin is more debated (Minissale et al., 2000; Chiodini et al., 2004; Minissale, 2004; Heinicke et al., 2006). Instrumental seismicity is concentrated in a relatively shallow layer that deepens from the internal to external areas (Chiarabba and Amato, 2003). High fluid pressures (85% of the lithostatic pressure) encountered at shallow crustal depth suggest that deep fluids from deeper layers could play a key role in triggering earthquakes (Chiodini et al., 2004; Antonioli et al., 2005) and seem to control also the spatio-temporal evolution of the seismicity (Piccinini & Antonioli, 2007). Our study area is confined by the Upper Tiber Valley (NSE), Casentino (W), Mugello (NW) and the Montefeltro seismic area (NE). We analysed the seismic events recorded both by the National Seismic Network (1981-2001, CSI 1.1; data-set was extracted online, http://www.ingv.it/CSI/) and by two temporal local seismic networks installed by INGV-Arezzo Observatory (OSCAR) during 2002-2003 (CAESAR experiment) and 2005-2006 (M88-2005 experiment). In order to obtain a better azimuthal coverage we integrated this data-set with on-line database of the Rete Sismometrica Marchigiana (DBRSM, http://protezionecivile.regione.marche.it/dbrsm/) and the monthly seismic bulletin of the INGV. We extracted the events located inside the area of interest in order to retrieve a detailed local 1D velocity model used for successive location with VELEST-code (Kissling et al., 1994) and relocation using HYPOELLIPSE (Lahr, 1989). We discuss the main seismicity patterns of several seismic clusters by integrating the results of previous studies with newly determined hypocentral locations and focal mechanisms. Our results are interpreted as a function of the historical seismicity, the structural and geodynamic setting and the carbon dioxide degassing.144 118 - PublicationOpen AccessUn array lineare fra Sansepolcro e Anghiari (Alta Valtiberina): acquisizione dati e prime analisi da terremoti e microtremore(2006-11)
; ; ; ; ; ; ; ; ; ; ; ;Azzara, R. M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Augliera, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Bergamaschi, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Braun, T.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;D'Alema, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Di Giacomo, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Marzorati, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Massa, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Piana Agostinetti, N.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Piccinini, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Roselli, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; ; ; ; ; ; ; ; La Valtiberina è da alcuni anni una delle principali aree dell'Appennino Centro-Settentrionale sottoposta ad indagini mirate alla definizione della geometria del bacino e alla descrizione in termini di geometria e meccanismo della faglia AltoTiberina, principale responsabile dell'attività sismica dell'area. Al fine di contribuire con dati sismometrici alla ricostruzione della risposta sismica del bacino, nella seconda metà del 2005 è stato realizzato un esperimento temporaneo consistito nell'installazione di un array lineare di 8 stazioni sismiche fra Sansepolcro e Anghiari. L'array era disposto lungo una direzione NE-SW, approssimativamente ortogonale all'asse della valle per una lunghezza di circa 8 km con una spaziatura fra le stazioni di circa 1 km. Le stazioni sismiche, equipaggiate con sismometri Lennartz LE3D-5s e Guralp CMG40T accoppiati a sistemi di acquisizione Reftek 130 e Reftek 72A/07, hanno acquisito in continua per circa 5 mesi (da Maggio 2005 a Novembre 2005), registrando alcune centinaia di eventi sismici locali, regionali e telesismi.249 182 - PublicationOpen AccessReply to comment on "Assessing CN earthquake predictions in Italy"(2018-01-16)
; ; ; ; ; Molchan et al. [2018] raised concerns on the reliability of the main Taroni et al.’s [2016] conclusion that reads “Considering the data available so far, the Molchan Test does not show that CN prediction performance is significantly better than predictions based on the stationary Poisson model.” In particular, Molchan et al. [2018] discuss two main issues: 1) the Taroni et al.’s [2016] results are based on too few data to achieve robust conclusions, and 2) the parimutuel gambling score (PGS) produce unfair results in comparing predictive models. We thank Molchan et al. [2018] to give us this opportunity to clarify further some aspects of our paper, but we anticipate that we do not see any compelling reason to modify our original conclusion.209 27