Open-slope, translational submarine landslide in a tectonically active volcanic continental margin (Licosa submarine landslide, southern Tyrrhenian Sea)

The southern Tyrrhenian continental margin is the product of Pliocene-Recent back-arc extension. An area of approximately 30 km of gentle (about 1.5°) lower slope of the last glacial outer shelf sedimentary wedge in water depths of between 200 and 300 m failed between 14 and 11 ka BP. We approached the landslide by multibeam and sub-bottom profiler surveying, high-resolution multichannel seismics, and coring for stratigraphic and geotechnical purposes. With regard to a slope-stability analysis, we carried out an assessment of the stratigraphic and structural setting of the area of the Licosa landslide. This analysis revealed that the landslide detached along a marker bed that was composed of the tephra layer Y-5 (c. 39 ka). Several previously unknown geological characteristics of the area are likely to have affected the slope stability. These are the basal erosion of the slope in the Licosa Channel, a high sedimentation rate in the sedimentary wedge, earthquake shaking, the volcanic ash nature of the detachment surface, subsurface gas/fluid migration, and lateral porewater flow from the depocentre of wedge to the base of the slope along the high-permeability ash layers. A newly discovered prominent structural discontinuity is identified as the fault whose activity may have triggered the landslide

Propagation of frontally confined subaqueous landslides: Insights from combining geophysical, sedimentological, and geotechnical analysis

Subaquatic mass movements are common in marine and lacustrine environments, but due to their barely pre- dictable nature, direct observations of these processes are limited so that knowledge is only indirectly obtained by investigating the resulting mass-transport deposits (MTDs). Most research focuses on the most common fron- tally emergent slides, fast-moving events able to generate turbidity currents and tsunamis. Geohazards of fron- tally confined slides and mechanisms behind their typical fold-and-thrust deformation structures are however still poorly understood. We investigate frontally confined MTDs in Lake Lucerne (Switzerland) by integrating bathymetric and high-res- olution seismic data with geotechnical information derived from in situ Cone Penetrometer Tests and short core analysis. Investigated MTDs consist of three units: i) a mass-slide deposit, located at the base of the slope consisting of a coherent slope sequence, ii) a fold-and-thrust system developed in basin sediments, and iii) an overrunning mass flow deposit, consisting of remolded slope sediments. The deformed and thrusted basin sed- iments show higher undrained shear strength compared to the undisturbed basin sequence. We propose that this strengthening is caused by lateral compression leading to fluid expulsion in the high-plasticity basin sedi- ments by the bulldozing sliding mass. Relative kinematic indicators document that the fold-and-thrust deforma- tion structures occur rapidly. Thus, they should be considered in tsunami hazard analysis. Furthermore, our data highlight that the slope angle of the gliding surface and basin topography are key controlling factors for slope sta- bility and propagation of basin-plain deformations, respectively. Our integrated study supports and refines prop- agation models proposed in marine environments, revealing the potential of investigating smaller-scale easier- to-access MTDs in lakes

Performance at Cryogenic Temperatures of an Ultra Low Noise CMOS Front-end for Fano-limited X-ray Spectroscopy

We qualified the noise performance of Sirio CMOS Charge Sensitive Preamplifier as a function of temperature down to -92 °C. The goal is twofold: i) quantify the improvement of the ENC and ii) disentangle the temperature dependence of the individual noise contributions and identify critical design issues. The intrinsic noise of the preamplifier, without connection to any detector, has been measured by injecting charge pulses through a test capacitance. The main noise contributions (series white, series flicker, parallel white) have been extracted from the experimental data. The lowest measured ENC at the optimal peaking time is around 1 el. rms

From catastrophic collapse to multi-phase deposition: flow transformation, seafloor interaction and triggered eruption following a volcanic-island landslide

The current understanding of tsunamis generated by volcanic-island landslides is reliant on numerical models benchmarked against reconstructions of past events. As the largest historical event with timed tsunami observations, the 1888 sector collapse of Ritter Island, Papua New Guinea provides an outstanding opportunity to better understand the linked process of landslide emplacement and tsunami generation. Here, we use a combination of geophysical imaging, bathymetric mapping, seafloor observations and sampling to demonstrate that the Ritter landslide deposits are spatially and stratigraphically heterogeneous, reflecting a complex evolution of mass-flow processes. The primary landslide mass was dominated by well-bedded scoriaceous deposits, which rapidly disintegrated to form an erosive volcaniclastic flow that incised the substrate over much of its pathway. The major proportion of this initial flow is inferred to have been deposited up to 80 km from Ritter. The initial flow was followed by secondary failure of seafloor sediment, over 40 km from Ritter. The most distal part of the 1888 deposit has parallel internal boundaries, suggesting that multiple discrete units were deposited by a series of mass-flow processes initiated by the primary collapse. The last of these flows was derived from a submarine eruption triggered by the collapse. This syn-collapse eruption deposit is compositionally distinct from pre- and post-collapse eruptive products, suggesting that the collapse immediately destabilised the underlying magma reservoir. Subsequent eruptions have been fed by a modified plumbing system, constructing a submarine volcanic cone within the collapse scar through at least six post-collapse eruptions. Our results show that the initial tsunami-generating landslide at Ritter generated a stratigraphically complex set of deposits with a total volume that is several times larger than the initial failure. Given the potential for such complexity, there is no simple relationship between the volume of the tsunamigenic phase of a volcanic-island landslide and the final deposit volume, and deposit area or run-out cannot be used to infer primary landslide magnitude. The tsunamigenic potential of prehistoric sector-collapse deposits cannot, therefore, be assessed simply from surface mapping, but requires internal geophysical imaging and direct sampling to reconstruct the event

Characterization of a novel pixelated Silicon Drift Detector (PixDD) for high-throughput X-ray astrophysics

Multi-pixel fast silicon detectors represent the enabling technology for the next generation of space-borne experiments devoted to high-resolution spectral-timing studies of low-flux compact cosmic sources. Several imaging detectors based on frame-integration have been developed as focal plane devices for X-ray space-borne missions but, when coupled to large-area concentrator X-ray optics, these detectors are affected by strong pile-up and dead-time effects, thus limiting the time and energy resolution as well as the overall system sensitivity. The current technological gap in the capability to realize pixelated silicon detectors for soft X-rays with fast, photon-by-photon response and nearly Fano-limited energy resolution therefore translates into the unavailability of sparse read-out sensors suitable for high throughput X-ray astronomy applications. In the framework of the ReDSoX Italian collaboration, we developed a new, sparse read-out, pixelated silicon drift detector which operates in the energy range 0.5\u201315 keV with nearly Fano-limited energy resolution ( 64150 eV FWHM @ 6 keV) at room temperature or with moderate cooling (~0\ub0C to +20\ub0C). In this paper, we present the design and the laboratory characterization of the first 16-pixel (4 7 4) drift detector prototype (PixDD), read-out by individual ultra low-noise charge sensitive preamplifiers (SIRIO) and we discuss the future PixDD prototype developments

A new large solid angle multi-element silicon drift detector system for low energy X-ray fluorescence spectroscopy

Low-energy X-ray fluorescence (LEXRF) is an essential tool for bio-related research of organic samples, whose composition is dominated by light elements. Working at energies below 2 keV and being able to detect fluorescence photons of lightweight elements such as carbon (277 eV) is still a challenge, since it requires in-vacuum operations to avoid in-air photon absorption. Moreover, the detectors must have a thin entrance window and collect photons at an angle of incidence near 90 degrees to minimize the absorption by the protective coating. Considering the low fluorescence yield of light elements, it is important to cover a substantial part of the solid angle detecting ideally all emitted X-ray fluorescence (XRF) photons. Furthermore, the energy resolution of the detection system should be close to the Fano limit in order to discriminate elements whose XRF emission lines are often very close within the energy spectra. To ensure all these features, a system consisting of four monolithic multi-element silicon drift detectors was developed. The use of four separate detector units allows optimizing the incidence angle on all the sensor elements. The multi-element approach in turn provides a lower leakage current on each anode, which, in combination with ultra-low noise preamplifiers, is necessary to achieve an energy resolution close to the Fano limit. The potential of the new detection system and its applicability for typical LEXRF applications has been proved on the Elettra TwinMic beamline

Pixel Drift Detector (PixDD) \u2013 SIRIO: an X-ray spectroscopic system with high energy resolution at room temperature

An X-ray spectroscopic system composed of a novel Pixel Drift Detector (PixDD) and SIRIO charge sensitive preamplifier is presented. The PixDD prototype is a 4 × 4 matrix of 500 μm × 500 μm pixels, manufactured on a 450 μm thick, 9 kΩcm silicon wafer. The anode current of a pixel is 0.7 pA at +20 ◦C and decreases down to tens of fA for temperatures lower than 0 ◦C. The low current together with the low pixel capacitance (30 fF independent of the pixel area), make PixDD an extremely low noise detector. When PixDD is coupled to the ultra-low noise SIRIO CMOS preamplifier, intrinsic spectral line widths (pulser) of 51 eV FWHM (5.9 electrons r.m.s.) and 130 eV FWHM at 5.9 keV (55Fe) are obtained at +20 ◦C. If the system is slightly cooled down to 0 ◦C, the FWHMs decrease down to 38.5 eV (4.5 electrons r.m.s) and 127 eV for the pulser and the 5.9 keV line respectively. The high energy resolution of PixDD joined with its intrinsic position sensitivity and the possibility to sustain high photon fluxes open new perspectives in X-ray spectroscopic imaging in the 0.1 keV–20 keV energy range