Search results for "GEOPHYSICS"
showing 10 items of 2645 documents
Evidence of a recent input of magmatic gases into the quiescent volcanic edifice of Panarea, Aeolian Islands, Italy
2004
- Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Vesuviano, Naples, Italy. - Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Palermo, Palermo, Italy. - Dipartimento Chimica e Fisica della Terra ed Applicazioni, Palermo, Italy.
Acoustic detection of neutrinos in bedrock
2019
We propose to utilize bedrock as a medium for acoustic detection of particle showers following interactions of ultra-high energy neutrinos. With the density of rock three-times larger and the speed of sound four-times larger compared to water, the amplitude of the generated bipolar pressure pulse in rock should be larger by an order of magnitude. Our preliminary simulations confirm that prediction. Higher density of rock also guarantees higher interaction rate for neutrinos. A noticeably longer attenuation length in rock reduces signal dissipation. The Pyh\"asalmi mine has a unique infrastructure and rock conditions to test this idea and, if successful, extend it to a full-size experiment.
Development of topography in 3-D continental-collision models
2015
Understanding the formation and evolution of high mountain belts, such as the Himalayas and the adjacent Tibetan Plateau, has been the focus of many tectonic and numerical models. Here we employ 3-D numerical simulations to investigate the role that subduction, collision, and indentation play on lithosphere dynamics at convergent margins, and to analyze the conditions under which large topographic plateaus can form in an integrated lithospheric and upper mantle-scale model. Distinct dynamics are obtained for the oceanic subduction side (trench retreat, slab rollback) and the continental-collision side (trench advance, slab detachment, topographic uplift, lateral extrusion). We show that sla…
Subduction of the Nazca Ridge and the Inca Plateau: Insights into the formation of ore deposits in Peru
2005
A large number of ore deposits that formed in the Peruvian Andes during the Miocene (15-5 Ma) are related to the subduction of the Nazea plate beneath the South American plate. Here we show that the spatial and temporal distribution of these deposits correspond with the arrival of relatively buoyant topographic anomalies, namely the Nazca Ridge in central Peru and the now-consumed Inca Plateau in northern Peru, at the subduction zone. Plate reconstruction shows a rapid metallogenic response to the arrival of the topographic anomalies at the subduction trench. This is indicated by clusters of ore deposits situated within the proximity of the laterally migrating zones of ridge subduction. It …
Late Quaternary slip rates for the southern Elsinore fault in the Coyote Mountains, southern California from analysis of alluvial fan landforms and c…
2019
Abstract Offset alluvial fans along the Elsinore fault in the south-central Coyote Mountains were studied to resolve an average late Quaternary slip rate for this major western strand of the San Andreas fault system in southern California. Alluvial fans and their offsets were mapped using high-resolution DEMs combined with field observations of fan-surface morphology and the character of the soils developed in each fan remnant. Clast assemblage data was used to determine the source of each alluvial fan upstream of the fault, and U-series dating of pedogenic carbonate was used to estimate minimum ages of the alluvial fan surfaces. Forty U-Th dates on pedogenic carbonate confirm the utility o…
Detrital footprint of the Mozambique ocean: U–Pb SHRIMP and Pb evaporation zircon geochronology of metasedimentary gneisses in eastern Madagascar
2003
Abstract The southern East African Orogen is a collisional belt where the identification of major suture zones has proved elusive. In this study, we apply U–Pb isotopic techniques to date detrital zircons from a key part of the East African Orogen, analyse their possible source region and discuss how this information can help in unravelling the orogen. U–Pb sensitive high-mass resolution ion microprobe (SHRIMP) and Pb evaporation analyses of detrital zircons from metasedimentary rocks in eastern Madagascar reveal that: (1) the protoliths of many of these rocks were deposited between ∼800 and 550 Ma; and (2) these rocks are sourced from regions with rocks that date back to over 3400 Ma, with…
Modelling of piping collapses and gully headcut landforms: Evaluating topographic variables from different types of DEM
2021
Abstract The geomorphic studies are extremely dependent on the quality and spatial resolution of digital elevation model (DEM) data. The unique terrain characteristics of a particular landscape are derived from DEM, which are responsible for initiation and development of ephemeral gullies. As the topographic features of an area significantly influences on the erosive power of the water flow, it is an important task the extraction of terrain features from DEM to properly research gully erosion. Alongside, topography is highly correlated with other geo-environmental factors i.e. geology, climate, soil types, vegetation density and floristic composition, runoff generation, which ultimately inf…
The Proterozoic P–T–t Evolution of the Kemp Land Coast, East Antarctica; Constraints from Si-saturated and Si-undersaturated Metapelites
2007
Integrated metamorphic and geochronological data place new constraints on the metamorphic evolution of a Neoproterozoic orogen in east Antarctica. Granulite-facies rocks from a 150 km stretch of the Kemp Land coast reflect peak conditions involving T � 870^9908 Ca t P� 7� 4^10 kbar, with pressure increasing westward towards an Archaean craton. Electron microprobe-derived (Th þ U)^Pb monazite ages from metapelitic assemblages indicate that the major mineral textures in these rocks developed during the c. 940 Ma Rayner Orogeny. Complex compositional zoning in monazite suggests high-T recrystallization over c. 25 Myr. Diversity in metapelitic reaction textures reflects silica and ferromagnesia…
Speculations on the impact of catastrophic subduction initiation on the Earth System
2016
Abstract The physics of subduction initiation can be studied with numerical models of lithosphere dynamics, to the extent where we can now test the potential consequences of a catastrophic subduction initiation event on the Earth System. The South American Atlantic passive margin is here used to show that, once subduction has catastrophically initiated there, a major geodynamic reconfiguration of the South American plate (SAm) is likely to take place: (1) compression in the east will be inverted to extension, because ridge push will be replaced by subduction rollback and trench retreat; (2) compression in the west will be inverted to extension due to absolute rollback; and (3) without buttr…
Spatial response spectra and site amplification effects
2002
A simplified analysis of local site amplification effects on the seismic response of multi-support structures is presented. The site effects are modeled by considering reflections and transmission of vertically propagating shear waves from bedrock to the surface through a soil layer. A random vibration-based response spectrum of a simple oscillator on two supports, one of which is founded on rock outcrop and the other on soil layer, is formulated in order to study the influence of non-uniform excitations on multi-support structures. Joint inertial and pseudo-static effects in the overall response are studied in detail. The resulting response spectra are formulated as displacement and force …