Erosion-driven uplift of the modern Central Alps

We present a compilation of data of modern tectono-geomorphic processes in the Central European Alps which suggest that observed rock uplift is a response to climate-driven denudation. This interpretation is predominantly based on the recent quantification of basin-averaged Late Holocene denudation rates that are so similar to the pattern and rates of rock uplift rates as determined by geodetic leveling. Furthermore, a GPS data-based synthesis of Adriatic microplate kinematics suggests that the Central Alps are currently not in a state of active convergence. Finally, we illustrate that the Central Alps have acted as a closed system for Holocene redistribution of sediment in which the peri-Alpine lakes have operated as a sink for the erosional products of the inner Central Alps.While various hypotheses have been put forward to explain Central Alpine rock uplift (e.g. lithospheric forcing by convergence, mantle processes, or ice melting) we show with an elastic model of lithospheric deformation, that the correlation between erosion and rock uplift rates reflects a positive feedback between denudation and the associated isostatic response to unloading. Thus, erosion does not passively respond to advection of crustal material as might be the case in actively converging orogens. Rather, we suggest that the geomorphic response of the Alpine topography to glacial and fluvial erosion and the resulting disequilibrium for modern channelized and associated hillslope processes explains much of the pattern of modern denudation and hence rock uplift. Therefore, in a non-convergent orogen such as the Central European Alps, the observed vertical rock uplift is primarily a consequence of passive unloading due to erosion.     

ESEEM of industrial quartz powders: insights into crystal chemistry of Al defects

A set of raw industrial materials, that is, pure quartz and quartz-rich mixtures, were investigated through electron paramagnetic resonance and electron spin echo-envelope modulation spectroscopies, with the aim of evaluating the effective role played by defect centres and of assessing whether they can be used to monitor changes in the physical properties of quartz powders with reference to their health effects. The obtained results point to two interactions of the Al defect centres with H⁺, hosted in sites within the channels parallel and perpendicular to the c axis of quartz, respectively. These two Al/H⁺ (h_Al) centres exhibit a weak chemical bond, and their relative amounts appear to be modified/controlled by the thermo-mechanical processes underwent by powders. Indeed, a mechanically promoted inter-conversion between the two kinds of site is suggested. As a consequence, the h_Al centres are effective in monitoring even modest activations of powders, through thermal or mechanical processes, and they are also supposed to play a specific, relevant role in quartz reactivity during the considered industrial processes.     

Axisymmetric Simulations of Pulsar Wind Nebulae with a New Central-Type Scheme for Relativistic MHD

A third-order shock-capturing numerical scheme for three-dimensional special relativistic magnetohydrodynamics (3-D RMHD) is presented. Due to the difficulties in developing exact or even approximate Riemann solvers in RMHD, a simple two-speed central-type solver that requires the knowledge of only the local fast magnetosonic velocities is employed. First results from axisymmetric simulations of Pulsar Wind Nebulae (PWNe) are finally presented. We show that when the wind magnetization is high enough, magnetic hoop stresses at work downstream of the termination shock are able to collimate a polar jet-like outflow, with velocities similar to those observed in the Crab and Vela Nebulae (v ≈ 0.5-0.7c).     

A simplified vulnerability model for the extensive liquefaction risk assessment of buildings

Bulletin of Earthquake Engineering - The quantitative assessment of natural risks offers a rational strategy to protect communities, undertake cost effective mitigation and plan the organic and...     

PCBs in Central Vietnam coastal lagoons: levels and trends in dynamic environments

PCBs were analysed in surficial sediments and selected sediment cores collected between 2002 and 2008 in Central Vietnam coastal lagoons. The aim was to determine contamination levels and trends, and to evaluate the effects of anthropogenic pressures and natural events. Samples were mostly fine-grained with low total PCB concentrations (0.367-44.7 μg kg⁻¹). Atmospheric transport and post depositional processes modify to some degree the fingerprint of PCB inputs to the environment favouring the predominance of 3, 4 and 5 chlorinated congeners. The similarity of congener distributions in contemporary surficial samples also suggests the presence of a unique source over the entire study area, probably connected to mobilisation and long range transports from land-based stocks. The removal of consistent sediment layers is hypothesised based on repeated samplings of the same area. Natural meteorological events (such as typhoons) are suspected to be responsible for these sediment losses.     

First study of fault trench stratigraphy at Mt. Etna volcano, Southern Italy: understanding Holocene surface faulting along the Moscarello fault

Paleoseismology, the study of past earthquakes based on their geological record in the stratigraphy and landscape, is a successful newly developing field of research. The application of fault trench studies in volcanic environments is one of the youngest branches of paleoseismology. In this paper, we present the results of the first exploratory trenches excavated at Mt. Etna in Sicily, the largest European volcano. Modern surface faulting at Etna is a very well known feature, which poses significant hazard to the local community, both in terms of ground displacement of essential lifelines and ground shacking from frequent damaging earthquakes. However, while the geomorphology and the seismicity of the active fault in the Etna region consistently show very high rates of tectonic activity, the Holocene cumulative throw and slip-rates, along with the nature (coseismic vs. creeping fault slip), dimension and timing of the displacement events, are still poorly constrained. For this purpose, we selected as a sample area the Moscarello fault, one of the most outstanding segment of the Timpe system of active normal faults in the volcano’s lower eastern flank. Displaced landforms and volcanic units at the Fondo Macchia basin, in the central sector of this fault, indicate some hundreds of meters of vertical offset in the last ca. 80 kyr, with a long-term slip-rate substantially higher than 1.5–2.0 mm/yr. According to the historical sources and instrumental observations, the Moscarello fault ruptured four times in the last 150 years during shallow (H < 5 km) and moderate magnitude (M < 4.8) earthquakes. These events were associated with severe damage in a narrow epicentral area (macroseismic intensities up to the IX–X grade of the MSK scale) and extensive surface faulting (end-to-end rupture length up to 6 km, vertical offsets up to 90 cm). This clearly indicates very high modern rates of deformation along this fault. We conducted trench investigations at the Fondo Macchia site, in a point where eyewitnesses observed ca. 20 cm of coseismic vertical displacement after the April 21, 1971, M_s=3.7, earthquake. The excavated sections provided direct stratigraphic evidence for a vertical slip-rate of 1.4–2.7 mm/yr in the last ca. 6 kyr. This should be regarded as a minimum slip-rate for the central section of the fault. We explored a single scarp at a single site, while we know from recent historical observations that several parallel scarps may rupture coseismically at Fondo Macchia. Thus, the relevant deformation rate documented for the modern period might be likely extended back in the past to a time-span of some thousands of years at least. As expected, for such a volcanic environment, the activity rates of the Moscarello fault are also significantly higher than for the Apennines normal faults, typically showing slip-rates lower than 1 mm/yr. The agriculturally reworked trench hangingwall stratigraphy did not allow to recognize individual displacement events. Nevertheless, the sedimentary structures observed in the trench footwall strongly suggest that, as for the last 150–200 years of detailed historical record, fault behavior at Fondo Macchia is governed by coseismic surface displacement rather than fault creep. This research confirms that paleoseismology techniques can be effectively applied also in active volcanic environments, typically characterized by rheology and, consequently, seismicity and fault dynamics very different from those of other tectonic environments in which paleoseismology has been firstly developed and is today extensively applied.     

Periodic Behavior and Stochastic Fluctuations of Solar Activity: Proper Orthogonal Decomposition Analysis

We use the Proper Orthogonal Decomposition (POD) to investigate the spatiotemporal features of the solar activity. Daily observation in the period 1949–1996 of the green coronal emission line at 530.3 nm are used as indicators of the activity behavior. We show that few POD modes suffice in describing both the space and time main periodicities. In particular, being affected by a strongly energetic stochastic behavior, daily data are described by five POD modes, while two POD modes are enough to describe the butterfly diagram in monthly averaged data. Apart from the basic period T₀ = 11 years, using daily data we found evidences for intercycle temporal periodicities.     

Exhumation patterns along shallow low‐angle normal faults: an example from the Altotiberina active fault system (Northern Apennines,Italy)

A multi‐method approach (palaeothermal and thermochronological analyses; thermal modelling) is applied to reconstruct the exhumation history of the Altotiberina Fault (ATF), a representative example of crustal‐scale active low‐angle normal faulting in the Northern Apennines (Italy). Thermal maturity and thermochronological data yield similar burial histories but different exhumation patterns for the sedimentary successions in the hangingwall and the footwall of the ATF. Since 3.8 Ma, the ATF footwall has exhumed at rates of 0.90 mm a^?1. Exhumation led to bending and deactivation of the ATF uppermost portion as a result of tectonic unloading and isostatic adjustment, followed by migration of extension and the development of a set of domino‐like, east‐dipping normal faults, rooting on the buried portion of the ATF. ATF activity and isostatic rebound exhumed Triassic rock units from depths of about 4 km. We suggest that isostatic instability is accommodated at shallow crustal levels, in a similar way to what is observed on larger structures at mid‐low crustal levels.     

Near-bankfull floods in an Alpine stream: Effects on the sediment mobility and bedload magnitude

In a mountain environment, the transport of coarse material is a key factor for many fields such as geomorphology, ecology, hazard assessment, and reservoir management. Despite this, there have been only a few field investigations of bedload, in particular using multiple monitoring methods. In this sense, attention has frequently focused on the effects of “high magnitude/low frequency floods” rather than on “ordinary events”. This study aims to analyze the sediment dynamics triggered by three high-frequency floods (recurrence interval “RI” between 1.1 and 1.7 yr) that occurred in the Rio Cordon basin during 2014. The flood events were investigated in terms of both sediment mobility and bedload magnitude. The Rio Cordon is an Alpine basin located in northeastern Italy. The catchment has a surface area of 5 km², ranging between 1763 and 2763 m above sea level. The Rio Cordon flows on an armored streambed layer, with a stable step-pool configuration and large boulders. Since 1986, the basin has been equipped with a permanent station to continuously monitor water discharge and sediment flux. To investigate sediment mobility, 250 PIT-tags were installed in the streambed in 2012. The 2014 floods showed a clear difference in terms of tracer displacement. The near-bankfull events showed equal mobility conditions, with mean travel distance one order of magnitude higher than the below-bankfull event. Furthermore, only the near-bankfull events transported coarse material to the monitoring station. Both events had a peak discharge up to 2.06 m³ s^-1, but the bedload transport rates differed by more than one order of magnitude, proving that under the current supply-limited condition, the bedload appears more related to the sediment supply than to the magnitude of the hydrological features. In this sense, the results demonstrated that near-bankfull events can mobilize large amounts of material for long distances, and that floods of apparently similar magnitude may lead to different sediment dynamics, depending on the type and amount of sediment supply.