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601.
Curvature analysis as a tool for subsidence-related risk zones identification in the city of Tuzla (BiH) 总被引:1,自引:0,他引:1
Shallow Miocene salt deposits located below the city of Tuzla (BiH) have been exploited during the last 60 years by means of wells extracting salt-saturated groundwater brines. The massive extraction activities have led to severe subsidence accommodated by collapse and strain localization. Surface topography and geomorphology have been influenced and modified by several faults and fractures.A series of sequential topographical survey data collected during the last 50 years have been used to obtain the total subsidence envelope surface. In order to analyze the salt dissolution-related morphological development of the Tuzla topography and to identify the location of faults and fractures in the deformed area, we applied curvature analysis to the subsidence surface by means of two different analytical methods: the directional, two-dimensional curvature and the analytic Gaussian curvature. The comparison of the curvature maps with those of surface fractures visible in the area shows a good spatial agreement between the directional curvature and fracture intensity, whereas the subsurface normal faults are more evident in the Gaussian curvature maps. 相似文献
602.
Morpho-structural setting of Stromboli volcano revealed by high-resolution bathymetry and backscatter data of its submarine portions 总被引:1,自引:0,他引:1
Alessandro Bosman Francesco L. Chiocci Claudia Romagnoli 《Bulletin of Volcanology》2009,71(9):1007-1019
The first high-resolution bathymetric and backscatter maps of offshore Stromboli Island are presented, together with an interpretation
of its volcanic, structural and sedimentary features. The volcanic edifice is characterized by a sub-conical shape with a
quasi-bilateral symmetry with respect to a NE-SW axis. The dimensions of the Strombolicchio volcanic centre, to the NE of
Stromboli, have been restored by redrawing its morphology before wave action that eroded it in Late Quaternary time. On the
NE submarine flank of Strombolicchio, a N64°E structural trend controls the shape of Strombolicchio Canyon. On the southern
side of Stromboli, the submarine flank has a radial structural trend, possibly reflecting a volcanic stress regime. Landslide
scars at various scales are ubiquitous on the submarine slopes of Stromboli. Repeated large-scale lateral collapses have affected
both the northwestern and southeastern unbuttressed flanks of the volcano, producing large debris avalanche deposits. 相似文献
603.
Andrew J. L. Harris Massimiliano Favalli Francesco Mazzarini Christopher W. Hamilton 《Bulletin of Volcanology》2009,71(4):459-474
We use a kinematic GPS and laser range finder survey of a 200 m-long section of the Muliwai a Pele lava channel (Mauna Ulu,
Kilauea) to examine the construction processes and flow dynamics responsible for the channel–levee structure. The levees comprise
three packages. The basal package comprises an 80–150 m wide ′a′a flow in which a ∼2 m deep and ∼11 m wide channel became
centred. This is capped by a second package of thin (<45 cm thick) sheets of pahoehoe extending no more than 50 m from the
channel. The upper-most package comprises localised ′a′a overflows. The channel itself contains two blockages located 130 m
apart and composed of levee chunks veneered with overflow lava. The channel was emplaced over 50 h, spanning 30 May–2 June,
1974, with the flow front arriving at our section (4.4 km from the vent) 8 h after the eruption began. The basal ′a′a flow
thickness yields effusion rates of 35 m3 s−1 for the opening phase, with the initial flow advancing across the mapped section at ∼10 m/min. Short-lived overflows of fluid
pahoehoe then built the levee cap, increasing the apparent channel depth to 4.8 m. There were at least six pulses at 90–420 m3 s−1, causing overflow of limited extent lasting no more than 5 min. Brim-full flow conditions were thus extremely short-lived.
During a dominant period of below-bank flow, flow depth was ∼2 m with an effusion rate of ∼35 m3 s−1, consistent with the mean output rate (obtained from the total flow bulk volume) of 23–54 m3 s−1. During pulses, levee chunks were plucked and floated down channel to form blockages. In a final low effusion rate phase,
lava ponded behind the lower blockage to form a syn-channel pond that fed ′a′a overflow. After the end of the eruption the
roofed-over pond continued to drain through the lower blockage, causing the roof to founder. Drainage emplaced inflated flows
on the channel floor below the lower blockage for a further ∼10 h. The complex processes involved in levee–channel construction
of this short-lived case show that care must be taken when using channel dimensions to infer flow dynamics. In our case, the
full channel depth is not exposed. Instead the channel floor morphology reflects late stage pond filling and drainage rather
than true channel-contained flow. Components of the compound levee relate to different flow regimes operating at different
times during the eruption and associated with different effusion rates, flow dynamics and time scales. For example, although
high effusion rate, brim-full flow was maintained for a small fraction of the channel lifetime, it emplaced a pile of pahoehoe
overflow units that account for 60% of the total levee height. We show how time-varying volume flux is an important parameter
in controlling channel construction dynamics. Because the complex history of lava delivery to a channel system is recorded
by the final channel morphology, time-varying flow dynamics can be determined from the channel morphology. Developing methods
for quantifying detailed flux histories for effusive events from the evidence in outcrop is therefore highly valuable. We
here achieve this by using high-resolution spatial data for a channel system at Kilauea. This study not only indicates those
physical and dynamic characteristics that are typical for basaltic lava flows on Hawaiian volcanoes, but also a methodology
that can be widely applied to effusive basaltic eruptions. 相似文献
604.
Theoretical and practical issues concerning the multi-faceted task of mitigating the latero-torsional seismic response of a prototypal frame structure with asymmetric mass distribution are approached.Chevron braces with embedded magnetorheological dampers acting on the interstory drift are used to ensure additional energy dissipation.The semi-active control strategy employed to govern the modifi cation of the damper characteristics via feedback is based on the selection of optimal forces according to a H2/L... 相似文献
605.
Massimiliano Favalli Andrew J. L. Harris Alessandro Fornaciai Maria Teresa Pareschi Francesco Mazzarini 《Bulletin of Volcanology》2010,72(1):119-127
Etna’s 2001 basaltic lava flow provided a good example of the distal flow segment between the flow front and stable channel,
across which the flow evolves from channel-contained to dispersed. This zone was mapped with meter precision using LIDAR data
collected during 2004 and 2005. These data, supported by field mapping, show that the flow front comprised eight lobes each
10 to 20 m high. The flow front appears to have advanced not as a single unit, but as a series of lobes moving forward one
lobe at a time. Primary lobes were centered on the channel axis and marginal lobes were off-axis. The lobes advanced as breakouts
of low-yield-strength lava from the flow core of the stalled flow front. Marginal lobes were abandoned and contributed to
marginal levees flanking the transitional channel. For Etna’s 2001 flow, the transitional channel is 140 m wide, 700 m long
and fed a 240-m-long zone of dispersed flow; the change from stable to transitional channel occurred at a major reduction
in slope. Above this, the stable channel is 5.2 km long, 55 to 105 m wide and bounded by 15- to 25-m-high levees, and the
stable channel is located over a previous channel. In a final stage of activity, lava ponding at the break-in-slope that marks
the terminus of the stable channel put pressure on the eastern levee, causing it to fail. Liberated lava then fed a final
break-out to the east. Similar flow front-features occur at other volcanoes, indicating that similar processes are characteristic
of dispersed flow zones. 相似文献
606.
Michele Saroli Michele Lancia Matteo Albano Anna Casale Gaspare Giovinco Marco Petitta Francesco Zarlenga Marco dell’Isola 《Hydrogeology Journal》2017,25(6):1811-1832
A hydrogeological conceptual model has been developed that describes the hydrothermal system of Suio Terme (central Italy). The studied area is located along the peri-Tyrrhenian zone of the central Apennines, between the Mesozoic and Cenozoic carbonate platform sequences of the Aurunci Mountains and the volcanic sequences of the Roccamonfina. A multi-disciplinary approach was followed, using new hydrogeological surveys, the interpretation of stratigraphic logs of boreholes and water wells, and geophysical data—seismic sections, shear-wave velocity (Vs) crustal model and gravimetric model. The collected information allowed for construction of a conceptual hydrogeological model and characterization of the hydrothermal system. The Suio hydrothermal system is strongly influenced by the Eastern Aurunci hydrostructure. Along the southeastern side, the top of the hydrostructure sinks to ?1,000 m relative to sea level via a series of normal faults which give origin to the Garigliano graben. Geological and hydrogeological data strongly suggest the propagation and mixing of hot fluids, with cold waters coming from the shallow karst circuit. The aquitard distribution, the normal tectonic displacements and the fracturing of the karst hydrostructure strongly influence the hydrothermal basin. Carbon dioxide and other gasses play a key role in the whole circuit, facilitating the development of the hydrothermal system. The current level of knowledge suggests that the origin of the Suio hydrothermalism is the result of interaction between the carbonate reservoir of the Eastern Aurunci Mountains and the hot and deep crust of this peri-Tyrrhenian sector, where the Roccamonfina volcano represents the shallowest expression. 相似文献
607.
The External Tanger Unit (Intrarif sub-Domain,External Rifian Zones,Morocco): an interdisciplinary study 总被引:1,自引:0,他引:1
Soufian Maaté Francisco Javier Alcalá Francesco Guerrera Rachid Hlila Alí Maaté Manuel Martín-Martín Giuliana Raffaelli Francisco Serrano Mario Tramontana 《Arabian Journal of Geosciences》2017,10(24):556
The External Tanger Unit represents one of the most complete Cretaceous-Miocene successions in the central areas of the Internal Intrarif sub-Domain (External Rif Zones, Morocco). An interdisciplinary study has been carried out to propose a new characterization of this unit which would allow a better comprehension of the confused and complex relationships among different units of the same sub-domain. The results achieved can be summarized as follows: (1) redefinition of the stratigraphic (litho-, bio-, and chrono-) record and introduction of a new, informal lithostratigraphic terminology; (2) recognition of two main depositional sequences (lower-middle Eocene p.p. and lower Oligocene p.p.-lower Miocene p.p.) separated by extended gaps (latest Cretaceous-early Eocene p.p. and middle Eocene p.p.-early Oligocene p.p.); (3) reconstruction of the evolution of the sedimentary realm, and of the relationships between tectonics and sedimentation; and (4) comparison between the upper Cretaceous-Miocene stratigraphic record and tectonic events of the Intrarif, which is located in the western external portion of the Maghrebian Flysch Basin, and the equivalent sedimentary record of the eastern portion of this basin in the Tunisian Tell. More in general, our results allowed (i) a first reconstruction of the Cretaceous-Miocene main tectono-sedimentary events; (ii) a more detailed location of the sedimentary suite in the external African Margin in the context of a wider palaeogeographic framework; and (iii) the definition of the main stages of the geological evolution of the area. 相似文献
608.
Tommaso De Pippo Carlo Donadio Micla Pennetta Carmela Petrosino Francesco Terlizzi Alessio Valente 《Geomorphology》2008,97(3-4):451-466
In the Northern Campanian coastal zone, over 150 km long, three geomorphic units are recognised: (1) sandy beaches that are well developed in the northern area, where a prominent river mouth (Volturno River) is also present; (2) steep and rocky shores, often with gravelly beaches or debris cones at their base, are mainly diffuse in the southern area (Sorrentine Peninsula); and, lastly, (3) “techno coast”, shorelines stabilized with revetments and seawalls as well as former natural environments no longer clearly operational because of urbanization, as is visible in Naples and in the Vesuvian coast. Six primary hazards are considered in this investigation: shoreline erosion, riverine flooding, storms, landslides, seismicity and volcanism, and man-made structures. These hazards do not have a uniform distribution along this coast in terms of their frequency and intensity; moreover both their interaction and the intensive action of humans, often uncontrolled, makes it difficult to assess the overall coastal hazard. In this paper a semi-quantitative method with which to quantify, rank and map the distribution of hazard is applied along this particular stretch of coast. In such a stretch, previously characterized in terms of types and processes and compartmentalized into geomorphic units, the effect of individual hazards, based on their magnitude and recurrence, is evaluated. Dominant and subordinate hazards for each geomorphic unit are identified, assigning a rank that is also a weighting. Comparison of each weighting through an interaction matrix permits the calculation of a resultant, which is the overall hazard assessment and which can be expressed cartographically. The results obtained for a coastal zone with one of the highest pressures from urbanization in the world, help us to recognise that this approach could become a useful tool to aid decision-making regarding coastal land-use and planning. 相似文献
609.
Anthony?FinizolaEmail author Francesco?Sortino Jean-Fran?ois?Lénat Maurice?Aubert Maurizio?Ripepe Mariano?Valenza 《Bulletin of Volcanology》2003,65(7):486-504
Accurate and precisely located self-potential (SP), temperature (T) and CO2 measurements were carried out in the summit area of Stromboli along 72 straight profiles. SP data were acquired every metre and T data every 2.5 m. CO2 concentrations were acquired with the same density as T, but only along seven profiles. The high density of data and the diversity of the measured parameters allows us to study structures and phenomena at a scale rarely investigated. The shallow summit hydrothermal activity (Pizzo–Fossa area) is indicated by large positive SP, T and CO2 anomalies. These anomalies are focused on crater faults, suggesting that the fracture zones are more permeable than surrounding rocks at Stromboli. The analysis of the distribution of these linear anomalies, coupled with the examination of the geologic, photographic and topographic data, has led us to propose a new structural interpretation of the summit of Stromboli. This newly defined structural framework comprises (1) a large Pizzo circular crater, about 350 m in diameter; (2) a complex of two concealed craters nested within the Pizzo crater (the Large and the Small Fossa craters), thought to have formed during the eruption of the Pizzo pyroclastites unit; the Small Fossa crater is filled with highly impermeable material that totally impedes the upward flow of hydrothermal fluids; and (3) The present complex of active craters. On the floor of the Fossa, short wavelength SP lows are organized in drainage-like networks diverging from the main thermal anomalies and converging toward the topographic low in the Fossa area, inside the Small Fossa crater. They are interpreted as the subsurface downhill flow of water condensed above the thermal anomalies. We suspect that water accumulates below the Small Fossa crater as a perched water body, representing a high threat of strong phreatic and phreatomagmatic paroxysms. T and CO2 anomalies are highly correlated. The two types of anomalies have very similar shapes, but the sensitivity of CO2 measurements seems higher for lowest hydrothermal flux. Above T anomalies, a pronounced high frequency SP signal is observed. Isotopic analyses of the fluids show similar compositions between the gases rising through the faults of the Pizzo and Large Fossa craters. This suggests a common origin for gases emerging along different structural paths within the summit of Stromboli. A site was found along the Large Fossa crater fault where high gas flux and low air contamination made gas monitoring possible near the active vents using the alkaline bottle sampling technique. 相似文献
610.
A syn-eruptive ground deformation episode measured by GPS,during the 2001 eruption on the upper southern flank of Mt Etna 总被引:4,自引:0,他引:4
Alessandro?BonforteEmail author Francesco?Guglielmino Mimmo?Palano Giuseppe?Puglisi 《Bulletin of Volcanology》2004,66(4):336-341
Ground deformation occurring on the southern flank of Mt Etna volcano during the July–August 2001 eruption was monitored by GPS measurements along an E–W profile crossing the fissure system. This profile was measured eight times during the eruption, using the 'stop and go' semi-kinematic technique. Horizontal and vertical displacements between GPS surveys are reported for each station. The most significant event is a deformation episode occurring during the first week of the eruption, between 25–27 July. Displacements were measured on benchmarks close to the eruptive fissure and the tensile 1989 fracture. Data inversions for measured displacements were performed using the Okada model. The model shows the narrowing of the 2001 dyke accompanied by a dextral dislocation along an east-dipping fault, parallel to the 1989 fracture.Editorial responsibility: T. Druitt 相似文献