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Macerola, Luca
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Macerola, Luca
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Macerola, L.
6 results
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- PublicationRestrictedA late Cretaceous contamination episode of the European–Mediterranean mantle(2008-01-10)
; ; ; ; ;Piromallo, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Gasperini, D.; Dipartimento di Scienze della Terra, Universita' di Pisa, Pisa, Italy ;Macera, P.; Dipartimento di Scienze della Terra, Universita' di Pisa, Pisa, Italy ;Faccenna, C.; Dipartimento di Scienze Geologiche, Università di Roma 3, Rome, Italy; ; ; One of the most challenging issues about the Tertiary–Quaternary alkaline magmatism spreading across the Euro-Mediterranean region is the assessment of both the nature of its mantle source and the mechanism responsible for the common HIMU-like (High μ=high 238U/204Pb) character of erupted lavas, enduring over about 100 million years in diverse tectonic environments. In this paper we try to reconcile geochemical and geophysical data through a multidisciplinary investigation on geochemistry, timing and locations of the main Na-rich alkaline volcanic centers, seismic tomographic images and plate kinematics. We propose that the common component of the Euro-Mediterranean mantle derives from a contamination episode triggered by the rise of the Central Atlantic Plume (CAP) head. Plate reconstruction shows that at late Cretaceous- Paleocene time the oldest magmatic centers of the Euro-Mediterranean region were located more than 2000 km SW of their present day position, in proximity of the CAP hot spot location, where seismic tomography detects a broad low seismic velocity region in the lower mantle. The northeastward migration of the Eurasian and African plates could have involved also part of the CAP contaminated mantle, which moved in the same direction being coupled to the lithospheric plates, thus explaining the presence of geochemically-uniform material spread in the sub-lithospheric Euro-Mediterranean mantle. During the Tertiary, regional-scale convection and related processes such as rifting, back-arc spreading, slab detachment/windows, may have favored upwelling and partial melting of the frayed plume head material via adiabatic decompression, shaping the spatial and temporal distribution of HIMU-like volcanics. The growing supply of subducted lithosphere may explain as well the increase of crustal isotopic signatures of alkaline magmas with time. In our opinion, the Euro-Mediterranean upper mantle contamination can be eventually related to a global event occurred during the Cretaceous as a consequence of a mantle avalanche caused by the Tethys closure.261 527 - PublicationRestrictedThe 1-D and 2-D Seismic Modeling of Deep Quaternary Basin (Downtown L'Aquila, Central Italy)(2019-11)
; ; ; ; ; ; ; ; ; We compare the results of one-dimensional (1-D) and two-dimensional (2-D) modeling of the up-to-date geological section of downtown L'Aquila. The section transects a 300-m-deep Quaternary graben assumed as a “deep basin.” It is placed in the southern zone of downtown L'Aquila and is mainly filled up by silt and clay. The northern zone of downtown L'Aquila is conversely characterized by stiff rock (breccia superposed onto limestone). The study's aim is to validate this upgraded subsoil model and to investigate possible 2-D seismic effects. Considering both the experimental and simulated data, all the sites exhibit a clear resonance frequency (F0:0.4–0.6 Hz), and its amplitude (A0) decreases northward. The linear modeling is in good agreement with experimental data, confirming the subsoil model. In the southern zone, the A0 of the 2-D transfer function is higher than the A0 of the 1-D transfer function, which can be attributed to a bidimensional deep basin effect.220 10 - PublicationRestrictedGeodynamic implications of deep mantle upwelling in the source of Tertiary volcanics from the Veneto region (South-Eastern Alps)(2003)
; ; ; ; ; ; ; ;Macera, P.; Dipartimento di Scienze della Terra, Universita’ di Pisa ;Gasperini, D.; Dipartimento di Scienze della Terra, Universita’ di Pisa ;Piromallo, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Blichert-Toft, J.; Ecole Normale Superieure, Lyon ;Bosch, D.; Universite ‘‘Montpellier 2", Montpellier ;Del Moro, A.; Istituto di Geoscienze e Georisorse, C.N.R., Pisa ;Martin, S.; Dipartimento di Chimica Fisica Matematica, Universita` Insubria, Como; ; ; ; ; ; Major and trace element and Sr–Nd–Hf–Pb isotopic data for the most primitive Tertiary lavas from the Veneto region (South-Eastern Alps, Italy) show the typical features of HIMU hotspot volcanism, variably diluted by a depleted asthenospheric mantle component (87Sr/86Sri=0.70306–0.70378; "Ndi=+3.9 to +6.8; "Hfi=+6.4 to +8.1, 206Pb/204Pbi=18.786–19.574). P-wave seismic tomography of the mantle below the Veneto region shows the presence of low-velocity anomalies at depth, which is consistent with possible upwellings of plume material. Between the depths of 100–250 km the velocity anomalies are approximately 2–2.5% slower than average, implying a temperature excess of about 220–280 K, in agreement with estimates for other mantle plumes in the world. In this context, the Veneto volcanics may represent the shallow expression of a mantle upflow. The presence of a HIMU-DM component in a collision environment has significant geodynamic implications. Slab detachment and ensuing rise of deep mantle material into the lithospheric gap is proposed to be a viable mechanism of hotspot magmatism in a subduction zone setting.242 23 - PublicationOpen AccessSite response analyses for complex geological and morphological conditions: relevant case-histories from 3rd level seismic microzonation in Central Italy(2020)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ; ;The paper presents the results of 5 case studies on complex site e ects selected within the project for the level 3 seismic microzonation of several municipalities of Central Italy dam- aged by the 2016 seismic sequence. The case studies are characterized by di erent geo- logical and morphological con gurations: Monte San Martino is located along a hill slope, Montedinove and Arquata del Tronto villages are located at ridge top whereas Capitignano and Norcia lie in correspondence of sediment- lled valleys. Peculiarities of the sites are constituted by the presence of weathered/jointed rock mass, fault zone, shear wave veloc- ity inversion, complex surface and buried morphologies. These factors make the de ni- tion of the subsoil model and the evaluation of the local response particularly complex and di cult to ascertain. For each site, after the discussion of the subsoil model, the results of site response numerical analyses are presented in terms of ampli cation factors and acceleration response spectra in selected points. The physical phenomena governing the site response have also been investigated at each site by comparing 1D and 2D numerical analyses. Implications are deduced for seismic microzonation studies in similar geological and morphological conditions.303 8 - PublicationRestrictedA multidisciplinary approach to the seismic characterization of a mountain top (Monteluco, central Italy)This study provides a seismic characterization of the flat top area of Monteluco carbonate mountain using a multidisciplinary approach. Recordings of ambient vibrations and local earthquakes, geophysical and borehole data, detailed geological surveys and rock mass characterizations were used to investigate the ground-motion amplification observed on the flat top of Monteluco. Weak motion measurements carried out on the top area gave resonance frequency (f0) in the range of 2–4 Hz, likely due to the occurrence of fractured rocks, tens of meters thick. In this frequency range and in the same target area, it was also possible to observe a nearly NW-SE polarization of the seismic signal, which we have tentatively correlated with the main mapped fault systems. Nevertheless, a topographic effect on noise polarization cannot be excluded.
126 5 - PublicationRestrictedNew insights into earthquake precursors from InSAR(2017-09-20)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; We measured ground displacements before and after the 2009 L’Aquila earthquake using multitemporal InSAR techniques to identify seismic precursor signals. We estimated the ground deformation and its temporal evolution by exploiting a large dataset of SAR imagery that spans seventy-two months before and sixteen months after the mainshock. These satellite data show that up to 15 mm of subsidence occurred beginning three years before the mainshock. This deformation occurred within two Quaternary basins that are located close to the epicentral area and are filled with sediments hosting multi-layer aquifers. After the earthquake, the same basins experienced up to 12 mm of uplift over approximately nine months. Before the earthquake, the rocks at depth dilated, and fractures opened. Consequently, fluids migrated into the dilated volume, thereby lowering the groundwater table in the carbonate hydrostructures and in the hydrologically connected multi-layer aquifers within the basins. This process caused the elastic consolidation of the fine-grained sediments within the basins, resulting in the detected subsidence. After the earthquake, the fractures closed, and the deep fluids were squeezed out. The pre-seismic ground displacements were then recovered because the groundwater table rose and natural recharge of the shallow multi-layer aquifers occurred, which caused the observed uplift.417 5