Paola Vannoli

The structural architecture of the northern Apennines is dominated by NE-verging arc-shaped folds and thrusts that developed through progressive migration of the contractional process combined with regional uplift. Migration and shortening of the Apennine fold-and-thrust system appear to be constant over space (from SW to NE) and time (since the Burdigalian; ca. 19 My), indicating that the two major frontal thrusts are active. The coastal area of the northern Marche - one of the most densely populated regions in central Italy - extends between the axes of these two structures. We reconstructed the deep geometry, size, and style of deformation of these youngest folds and blind thrusts by using seismic reflection lines. Anomalously behaving river courses and warped coastal and fluvial terraces provided insights on the rates of their recent activity. The occurrence of several historical and instrumental earthquakes suggests that these structures can also be seismogenic. The results of ...

The northern Apennines thrust belt has an arcuate trend made up of several fronts progressively younger to the NE. The youngest are buried in the southern Po Plain, and deform the Marche and the northern Abruzzi coastal regions. Instrumental and historical seismicity, fault plane solutions, and a large dataset of seismic exploration lines testify that blind thrust faults produce significant deformation and moderate-size earthquakes up to M=6.0. In spite of their size, earthquakes can still be damaging and pose a substantial hazard to the population and to the civil and industrial facilities. Slip rates lower than depositional rates, blindness of thrust faults and subtle topographic expression of the active anticlines hinder the identification of individual seismic sources. The detection of the active structures is also made difficult by the low seismic release and by the small number of well constrained instrumental earthquakes. However the drainage network and river and coastal ter...

ABSTRACT On 30 October 1930, an Mw 5.8 earthquake hit the northern Marche coastal area (central Italy), causing significant damage (I0 VIII–IX degree Mercalli–Cancani– Sieberg) along a 40 km stretch of the Adriatic coast between Pesaro and Ancona, centered on the town of Senigallia. This area is characterized by relatively infrequent and moderate-sized earthquakes and by elusive active faults. In spite of the presence of wellknown northwest–southeast-trending, northeast-verging fault-propagation folds forming the outer thrusts of the Apennines, the current level of activity, and the kinematics of these coastal structures are still controversial. We present a multidisciplinary analysis of the source of the 30 October 1930 Senigallia earthquake, combining instrumental and macroseismic data and elaborations with available evidence from geological and tectonic investigations.We determine the main seismic parameters of the source, including the earthquake location, its magnitude, and, for the first time, its focal mechanism, providing the first instrumental evidence for thrust faulting along the northern Marche coastal belt. Our findings provide conclusive evidence for the current activity of the northern Marche coastal thrusts. As such they have significant implications for the seismic hazard of the area, a densely populated region that hosts historical heritage, tourism facilities, industrial districts, and key transportation infrastructures.

The backbone of the Southern Apennines is perhaps the largest seismic moment release area in Italy. The region is dominated by an extensional regime dating back to the Middle Pleistocene, with maximum extension striking SW-NE (i.e. orthogonal to the mountain belt). The full length (~ 200 km) of the mountain range has been the locus of several destructive earthquakes occurring

ABSTRACT Gaseous and liquid hydrocarbons are seeping from sandy sea bottom ∼10 m deep, about 2.4 km NNE of Civitanova Marche harbour, in central Adriatic Sea (Italy). We investigated the origin of the gas, the presence of a wide range of aromatic and aliphatic hydrocarbons and trace metals in shallow sediments, as well as the stable carbon and oxygen isotope composition of benthic foraminifera. In absence of detailed seismic images and subsurface geochemical data, we tried to estimate the source rock type and maturity based only on seep gas geochemistry. Molecular and isotopic composition of gas bubbles showed that the CH4-rich gas is thermogenic (δ13C4CHδ13CCH4∼ −55‰; δ2H4CHδ2HCH4∼ −280‰; C1/(C2 + C3) < 100) with isotopic features that are compatible with low maturity source rocks belonging to the Emma-Scaglia (carbonate source rocks) Petroleum System (Upper Trias to Paleocene). Gas could then be stored in a biodegraded hydrocarbon pool, as suggested by 13C enrichment in propane (δ13C3: −24‰) and CO2 (δ13C2COδ13CCO2: +12‰). Fluid seepage might be due to a local fracture zone corresponding to the intersection of NNW–SSE thrust faults with a NE–SW regional transversal deformation belt. Compared to other shallow marine seeps in Europe, the amount of methane released into the atmosphere is negligible (102–103 kg of CH4 per year); but the seep also releases ethane and propane (103–104 L per year), which are photochemical pollutants and are not emitted by microbial gas seeps. Compared to a reference site one nautical mile far from the seep, the seabed sediments show higher concentrations of various classes of chemicals, such as benzene, toluene and ethylbenzene, semivolatile and non volatile aliphatic hydrocarbons (C10–C40), and phenols (2-methylphenol and 2,4-dichlorophenol). These compounds likely derive from the oil seepage. The sediments at the seepage site and those at the reference site have similar concentrations of trace metals (arsenic, barium, cadmium, chromium, copper, iron, manganese, nickel, lead, vanadium, zinc, mercury), typical of uncontaminated and shallow coastal areas. Finally, we provided the first data on foraminifera associated to thermogenic hydrocarbons. No endemic foraminifera species or authigenic carbonates occur in the sediments. Carbon isotopic composition of Quinqueloculina padana where oil slick prevails is less variable than in the gas bubbling site. However, thermogenic methane and oil do not apparently decrease the δ13C value of foraminifera carbonate shell.

Abstract For decades, alluvial plains have been the areas of the fastest population growth over most of the globe. Modern societies demand growing extensions of flat and easily accessible land to accommodate the swelling urban areas, booming industrial districts, ...

ABSTRACT We investigate fault-trapped waves observed at a permanent broad-band station (FAGN) installed on the San Demetrio Fault, about 20 km southeast of L'Aquila. This fault has the same strike of the Paganica Fault which was responsible for the MW 6.3, 6 April 2009 earthquake. The two faults display an en-echelon pattern with a few km offset. We have found that events causing efficient trapped waves are clustered at the northwestern and southeastern bottom ends of the ruptured Paganica fault plane. The efficiency of trapped waves at FAGN, which is located about 5 km far from the ruptured fault plane, indicates that the two faults are linked at depth. This suggests that fault segments in the study area can be part of a longer and continuous fault system which controls the seismic hazard of the region. Moreover, we have found that the two earthquake clusters generating the most efficient trapped waves occur in portions of the fault system with the highest fluid pressure.

ABSTRACT A methodology aimed at selecting sites characterized by directional resonances is applied to a sample of 226 rock stations of the Italian Telemeterd Seismic Network. The procedure consists in calculating the horizontal-to-vertical spectral ratio for rotation angles of the horizontal components from 0 to 180° using one hour of ambient noise recordings. In a second step, the covariance matrix method is applied both to ambient noise and earthquake records, in order to select only stations showing a strong horizontal polarization independently on the signal nature. As a result, 66 stations show a marked directional amplification consistently in ambient noise and earthquake records. They represent the 29% of the entire sample, which is a significant percentage, whereas rock sites are supposed not to be affected by local amplification in the hazard practice. Using this subset of 66 stations we investigated the role of topography on directional amplification. The station topography was determined through morphometric analyses of high resolution digital elevation models (DEM), with the support of Geographic Information Systems (GIS). The aim was to identify isolated or complex-shaped reliefs, calculate ridge orientations and evaluate the relative location of the recording station in respect to the elevation (hilltop, hillside, base). Exploiting the Neighborhood Statistics GIS application, the elevation of each pixel is compared with those of the adjacent ones in proper buffer zones, according to the Topographic Position Index procedure; successively a landform classification is performed by a 30x30 m resolution Global Digital Elevation Model. The identification of ridges is achieved through the development of a proper RIDGE application that combine sequences of GIS tools (mainly curvature, slope, flow accumulation and focal statistics) and automate the identification process. The relief is fully characterized by identifying its base as a simple and regular polygon framing all the pixels higher than the valley zones; once the base is defined, the transversal/longitudinal dimensions, height difference, average slope and other morphometric parameters are consequently outlined. The comparison between the polarization direction at station lying on topography and hill morphology showed that that ground motion on polarization is recurrent on elongated ridges, and the azimuth of amplification is transversal to the ridge orientation.