dike deflection modelling for inferring magma pressure and withdrawal with application to etna 2001 case abstract we studied the stress effects of the topography load on dike propagation by considering the results from analogue experiments in addition we refined the results by applying numerical simulations using the finite element method fem in order to also consider the medium rheology and real topography we investigated the dike deflection observed during the final dike emplacement accompanying etna s 2001 eruption we cross related the information on the position of the dike from ground deformation modelling with the numerical simulation results with the aim of estimating the final excess pressure of the dike when it started to deflect which proved to be about 4 8 mpa assuming that the pressure decreases linearly with the volume of magma moving from the chamber into the dike we estimated 7 15 mpa as the initial overpressure accumulated at the intermediate magma chamber before its breakout although the previous modelling overestimated the stress the approach presented here leads to infer a compatible stress with the strength of the rocks

recent dyke induced large scale block movement at mount etna and potential slope failure here we report the results of a geodetic survey undertaken on mount etna between 1981 and 1988 observed horizontal ground movements in the vicinity of the valle del bove caldera demonstrate that dyke emplacement during 1983 and 1985 resulted in the 2 8 m eastward displacement of a block of western caldera rim a history of past instability and collapse along the rim is indicated by the presence of large back rotated blocks of prehistoric volcanics1 furthermore the unusually linear form of the present western rim indicates past slope failure along north south aligned surfaces and therefore that dyke induced collapse may have been an important agent in caldera enlargement we suggest a self sustaining mechanism whereby the stress regime generated as a consequence of the caldera s existence results in the repeated injection of north south orientated dykes adjacent to the western rim2 3 dilation associated with magma intrusion leads in turn to periodic phases of slope instability and failure of the cliff wall causing a progressive westward migration of the western rim

effect of source depth correction on the estimation of earthquake size the relationship between surface wave magnitude ms and seismic moment mo of earthquakes is essential for the estimation of seismic risk in any region in the hypothesis of constant stress drop theoretical models predict that log mo and ms are related by a linear law the slope most commonly found in the literature is around 1 5 here we show that the application to the ms values of the necessary correction for the focal depth gives a general increment of the correlation coefficient and that a slope around 1 0 is consistent with the global data while for regionalized data it can vary from about 1 0 to 2 0

how mechanical layering affects local stresses unrests and eruptions of volcanoes 1 in most active volcanoes unrest periods with dike injections are much more common than eruptions while widely recognized this simple observation has not been satisfactorily explained surface deformation in volcanoes is commonly attributed to dikes injected from shallow magma chambers that fail to reach the surface field observations of dike tips many of which are blunt indicate arrest that is primarily controlled by the local stresses in the layers through which the dikes propagate numerical models on the stress fields around magma chambers located in an anisotropic heterogeneous layered crust indicate that for uniform loading a layered crust normally develops stress fields that are unfavorable for feeder dike formation in particular the models together with the field observations indicate that an essentially homogeneous stress field along the potential pathway of a dike is a necessary condition for its reaching the surface to supply magma to a volcanic eruption

a microtremor survey to define the subsoil structure in a mud volcanoes area the case study of salinelle mt etna italy a microtremor survey aiming to obtain information on subsoil structure was performed in the lower southwestern etnean flank sicily italy the area is characterized by emissions of muddy and salty water which create specific pseudo volcanic edifices recording sites were both randomly selected in the area and along two profiles horizontal to vertical noise spectral ratio polarization and surface wave prospecting techniques were used the spectral ratios results set into evidence different frequency ranges that appear interesting to infer information on the subsoil structure the depth of the hydrocarbon reservoir was inferred through 1d modeling by using the information coming from the literature and experimental surveys moreover a strongly directional effect suggests the existence of a nnw sse oriented mud feeding dike

neotectonics in central mexico regional neotectonic activity in central mexico was mapped through analysis of eleven landsat thematic mapper images the study area stretches from mexico city on the east to the gulf of california on the west between 17 and 21 n latitude fault scarps of plio quaternary age define several large scale tectonic features within the mexican volcanic belt dominated by rifting transtension and shear with probable sinistral components three large crustal blocks south of the mexican volcanic belt are separated from the north american plate and from each other by zones of neotectonic activity that express the relative motions between the adjacent blocks a simple vector diagram for plates and crustal blocks in central mexico has been constructed using information from the literature combined with the orientations of fault zones as mapped in this study the relative motion between the blocks varies from about 2 5 to 8 mm year 1 which is comparable to motions of crustal blocks in areas of active rifting in other parts of the world in the mexican volcanic belt there is a clear relationship between volcanism and neotectonic activity fault zones that traverse nearly the entire region have the same location and orientation as the volcanic belt this may indicate that deformation within the crust of the overriding slab plays a significant role in determining the unusual orientation of the mexican volcanic belt relative to the trench the ultimate factor controlling the location of plio quaternary volcanism and tectonism in central mexico may be large zones of crustal weakness formed during major mesozoic and cenozoic tectonic events

morphometry of scoria cones located on a volcano flank a case study from mt etna italy based on high resolution lidar data abstract by using new high resolution 2 m digital elevation model derived from the 2005 lidar survey of mt etna volcano italy our study measured the classical morphometrical parameters for scoria cones i e w co cone width w cr crater diameter h cone height as well as volume inclination of cone slope and substrate and a number of other parameters for 135 scoria cones of mt etna volume and age distribution of cones shows that there is no direct structural control on their emplacement in terms of etna s rift zones the cones are progressively smaller in size toward summit which can be explained by the large volcano s feeding system and progressively frequent lava burial toward top a careful analysis of h w co ratio determined as 0 18 for other volcanic fields worldwide shows that this ratio strongly depends on 1 the calculation method of h and 2 lava burial of cone for etnean cones applying an improved method for calculating h relative to the dipping substrate results in a significantly lowered standard h w co ratio 0 137 which in turn questions the validity of the classical value of 0 18 in the case of large central volcanoes the reduction of the ratio is not only due to methodology but also to the common lava burial this can be expressed even better if h mean is used instead of h max h mean w co 0 098 using this measure at etna well formed cones have higher ratios than structurally deformed e g double or rifted cones furthermore although the sampled scoria cones at etna have formed in a relatively narrow time interval h w co corresponding to erosional changes detected globally h w co 0 143 0 135 and 0 115 for three age classes of etna s scoria cones corresponding to average slopes of 26 6 23 9 and 23 7 because the morphometrical effect of position on a dipping substrate as well as lava burial exceeds the effect of erosion we call attention to use caution in simply using the h w co ratio of scoria cones for detecting age especially on large active volcanoes

climatic and tectonic sea level gauge for midcontinent pennsylvanian cyclothems new sedimentological determinations suggest that pennsylvanian sea level change ranged from as little as 40 m to as much as 160 m depending on which model establishes the deepest water facies of a midcontinent cyclothem average sedimentological estimates of sea level change for models of heckel and gerhard are 96 4 m and 86 0 m respectively in the midcontinent tectonic subsidence contributed 5 to 20 of the total pennsylvanian sea level change in platform areas and basin depocenters additional change in sea level was controlled by short term glacial eustasy nearly 70 of sea level change and long term climate change nearly 15 of sea level change these findings suggest that away from orogenic belts climatic change is the principal driving mechanism controlling sea level change whereas within orogenic belts climate becomes more subordinate to tectonic processes that influenced pennsylvanian sea level change even though indicators of climatic change reportedly are preserved

ambient vibration measurements to support morphometric analysis of a pyroclastic cone pyroclastic cones are a typical feature on volcanoes characterized by flank activity their distribution and orientation are important markers to obtain information on the maximum horizontal compressional stress acting on a volcano a geophysical survey was performed on the pyroclastic cone of mt vetore mt etna volcano southern italy to obtain information on its internal structural setting and to support the standard morphometric analysis results highlighted evident frequency peaks at 1 0 hz inside the cone which are attenuated away from it the random decrement method was applied to this peak to compute damping and then to exclude links with anthropogenic sources moreover time frequency polarization analysis revealed that ambient vibrations are strongly polarized in a narrow frequency band centered at a frequency of 1 0 hz with a preferred oscillation azimuth of 70 90 n array measurement of ambient vibrations was also used to obtain a shear wave velocity profile and then to retrieve the main interfaces with high seismic impedance results suggest a cone structure having a feeder dike consisting of fractured rocks with thickness of about 50 m surrounded by pyroclastic material lying on a high velocity substrate finally a 3d model of mt vetore cone was built employing the finite element method to reproduce an experimental modal frequency of the cone itself the numerical results successfully reproduced the experimental ones collected by the geophysical survey

empirical evidence of orthogonal relationship between directional site effects and fracture azimuths in an active fault zone the case of the mt etna lower eastern flank abstract mt etna in eastern sicily is a composite active volcano whose eastern flank is affected by several normal and strike slip active faults in this study geological structural field survey and ambient vibration measurements are performed in the lower eastern flank of mt etna in order to define the role of the tectono stratigraphic setting in the seismic site response the sites of measurements are mainly distributed inside the few hundreds of meters long s caterina graben which is located between two main seismogenic active faults of this volcano sector the acireale and the fiandaca faults our study aims at defining the contribution of the fault related active deformation in determining the local ground motion amplification also providing a subsoil geological model based on the integration of geological and geophysical investigation therefore structural measurements were made in seven sites revealing coseismic and aseismic extensional fractures mainly striking nnw the seismic site response was studied processing the ambient vibration measurements through horizontal to vertical spectral ratio the measured fundamental frequency falls in the range 1 0 4 0 hz that we linked to the presence of a velocity contrast at depth of 80 200 m by calibrating a frequency depth function moreover the seismic site effect is due to the stratigraphic setting and is markedly directional showing maximum amplification along the direction orthogonal to the strike of the observed isooriented extensional fracture field produced by the activity of the s caterina graben it is noteworthy that far from the graben on sites of measurements located near the fiandaca fault we observed directional effects parallel to the direction of maximum extension inferred for this tectonic lineament our results suggest a linkage between directional site effects and local stress tensors and fractures field orientation

sedimentation control on growth of stromatoporoid reefs in the silurian of gotland sweden silurian stromatoporoid dominated reefs of gotland sweden are bioherms and biostromes formed during phases of reduced clastic supply well exposed examples are in the early wenlock hogklint formation and middle ludlow hemse group reef development culminated in shallow water biostromes laterally expanded over a stabilized substrate and associated with frequent erosion surfaces hogklint reefs began as bioherms to be replaced by biostromal phases as water shallowed with vertically zoned communities biostromal phases are considered equivalent to the whole of individual stromato poroid biostromes without biohermal phases of the hemse group which developed in shallow low to moderate energy water on stabilized substrate low clastic supply associated with these reefs reduced not only the clay input which is otherwise common in most non reef environments on gotland but also is interpreted to have lowered available nutrient levels modern reefs develop best in conditions of low nutrients and also show a suppressed bioerosion and b increased symbiosis between corals and algae which conserves nutrients in the reef biota hogklint reefs show reduced bioerosion while hemse reefs show almost complete lack of bioerosion symbiosis between stromatoporoids and corals interpreted as a response to the need for nutrient conservation occurs in the reefs but is much more common in hemse reefs both hogklint and hemse reefs are regarded as having grown in nutrient deficient conditions in line with modern reefs although the effect on hemse reefs is believed to have been greater because they appear to have grown in quieter conditions on a broad shelf and may have had reduced access to nutrients in a regressive regime throughout the ludlow reduced clastic supply while the gotland reefs grew could have been due to regional tectonism controlling local sea level change however the hogklint formation and hemse group reef phases coincide with times of proposed eustatic sea level falls reef growth on gotland could therefore relate to eustatic tectonism by subduction related or plate flexure processes or climatic control an oceanographic model for the silurian proposed alternating wet and dry episodes interpreted as co 2 driven and could have controlled clastic input permitting the development of fossiliferous reefs and the carbonate platforms on which they formed these interpretations provide a revised framework for examining the reef growth

complex polarization analysis of particle motion knowledge of particle motion polarization aids in identifying phases on three component seismograms the scheme of montalbetti and kanasewich 1970 is extended to analytic three component seismograms where the imaginary part of the signal is the hilbert transform of the real part this scheme has only one free parameter the length of the time window over which the polarization parameters are estimated so it can be applied in a routine way to three component data the azimuth and dip of the direction of maximum polarization and the degree of elliptical polarization as a function of time for the seismograms are obtained polarization analysis of strong motion data from the 1971 san fernando earthquake aids in the discrimination between wave types which is important for the understanding of the complicated earthquake induced shaking observed in basins most arrivals are incident on the receivers in the direction of the back azimuth to the epicenter which suggests that despite the complicated motions two dimensional finite difference methods are sufficient to understand the effect on seismic waves of the los angeles and san fernando basins vidale and helmberger 1986b

site frequency response characterisation of the maltese islands based on ambient noise h v ratios abstract the maltese islands in the central mediterranean are composed of a simple 4 layer sedimentary sequence of oligocene miocene limestones and clays highly disturbed by synsedimentary to recent tectonic activity so that the surface outcrops present a variety of lithologies as well as complex geomorphology the seismic history of the islands includes a number of damaging earthquakes the largest intensity since 1500 being ems 98 vii viii in 1693 in this study a first seismic site response survey was undertaken over the whole archipelago by recording ambient noise and applying the h v horizontal to vertical spectral ratio technique the results show a clear correlation between site response and outcrop geology in general where the two oldest layers the lower coralline limestone and the globigerina limestone outcrop the h v is flat above 0 5 hz a thick layer of clays and marls blue clay deposited originally on top of the globigerina limestone is preserved in the western half of the archipelago and this strongly influences the site response where the clay outcrops at the surface it produces the highest amplitudes and peak frequencies ranging between 2 and 5 hz whereas all sites on the hard upper coralline limestone which overlies the clay in many regions still exhibit h v peaks at a consistent frequency between 1 and 2 hz which we attribute to the presence of the underlying clay results were validated by a second measurement survey and numerical modelling the site effect induced by the clay layer has implications for the assessment of seismic risk as well as for the validity of using v s30 as a proxy for site class and site amplification

fracture control on type morphology and distribution of parasitic volcanic cones an example from mt etna italy abstract this paper uses a coupled morphometric and stratigraphic analysis of several tens of parasitic pyroclastic cones of the se flank of mt etna volcano italy to explain the structure of a poorly understood actively deforming zone of the volcano moreover we present a new general classification of pyroclastic cones based on the parameterisation of coeval eruption points along the same magma feeding fracture each cone has been studied in detail in order to define its stratigraphic position morphometric characteristics growth evolution in relation to fracture distribution and orientation stress field and morphology of the substratum end members of this classification are at one side a simple circular or elongated edifice that grew around a single eruption point and can be related to a magma feeding fracture constrained by a relatively high confining stress in the substratum or a low magma pressure the other end member is a multiple rifted strongly elongated cone formed along multiple eruption points of a magma feeding fracture constrained by a relatively low confining stress or a high magma pressure lithostratigraphic and historical analyses demonstrate that the cones in this area developed between 15 ka bp and historical times the most recent one in 1669 ad testifying to a high rate of lateral eruption occurrence in the area these cones show n s elongated maximum crater axes n s trending axis of the depressed points of the crater rim and southward and southeastward breaching directions while coeval cones are n s aligned these morphometric characteristics reflect the geometry of n s magma feeding fractures the area can be regarded as a transitional weakness zone between the n s rift and the releasing system represented by the transtensional trecastagni and mascalucia faults indicating an e w oriented local component of extension possibly related to the interplay between the regional timpe fault system and the eastward gravitational spreading of the volcano the azimuth of breaching is controlled by magma feeding fracture orientation and substrate morphology especially in the eastern part of the area where it is influenced by the scarps related to the timpe regional fault system but it is also sensitive to cone development

lusi hydrothermal structure inferred through ambient vibration measurements abstract the spectacular lusi mud eruption started in northeast java indonesia the 29th of may 2006 following a m6 3 strike slip seismic event after the earthquake several mud pools aligned along a ne sw direction appeared in the sidoarjo district the most prominent eruption site was named lusi lusi is located 10 km to the ne of the northernmost cone of the arjuno welirang volcanic complex with which it is connected by the watukosek fault system in this study we applied the hvsr method which is a common tool used for site effect investigations as well as to infer buried structures and reconstruct sub surface geology the method is based on the ratio of the horizontal to vertical components of ground motion and it generally exhibits a peak corresponding to the fundamental frequency of the site spectral ratio results highlight a fundamental frequency band between 0 4 and 1 0 hz in the lusi neighborhood we interpret these peaks as related to the velocity lithological contrast at depth between alluvial deposits and bluish grey clay our analysis also highlights the presence of a depocenter characterized by fundamental frequency up to 0 3 hz which is interpreted as the subsidence caused by withdrawal of mud and fluids from depth as also shown by the comparison of the hvsr results with gravimetry data moreover in the area of the lusi vent a broad band frequency range is related to the lusi conduit in this paper we show that detailed microtremor surveys could be used as a preliminary and fast approach to locate mud conduits with sufficient precision

persistence of late carboniferous tropical vegetation during glacially driven climatic and sea level fluctuations abstract the late carboniferous glaciation reached its peak during the latter part of the westphalian late desmoinesian in the tropical illinois basin this was the time of deposition of the carbondale and lower modesto formations characterized by the cyclic repetition of major coal deposits black shales limestones gray shales and sandstones these lithological changes evidence repeated major fluctuations in climate and sealevel fossil floras from the tropical ever wet to seasonally wet terrestrial lithofacies coals and shales above coals remain compositionally similar throughout the 1 1 5 m y time interval floras from coals known from coal balls and palynology characteristically were composed of three major plant communities the wettest sites were dominated by monocarpic lycopsids intermediate sites were dominated by polycarpic lycopsids and areas subject to fires and intermittent flooding were dominated by medullosans and the small lycopsid paralycopodites clastic substrate environments were dominated by ferns and pteridosperms and conform to a single biozone indicating their compositional unity and distinctness from earlier and later assemblages the composition of lowland floras is poorly known from times between the deposition of coals and associated terrestrial rocks intervals during which most of the lowlands were flooded and marine rocks were being deposited consequently the temporally intermittent recurrence of lowland floras despite repeated widespread environmental disruption may be explained either by vegetational persistence and migration of floras or repeated disruption and reassembly several lines of evidence suggest persistence as a likely explanation

anthropogenic sources stimulate resonance of a natural rock bridge the natural modes of vibration of bedrock landforms as well as the sources and effects of stimulated resonance remain poorly understood here we show that seismic energy created by an induced earthquake and an artificial reservoir has spectral content coincident with the natural modes of vibration of a prominent rock bridge we measured the resonant frequencies of rainbow bridge utah using data from two broadband seismometers placed on the span and identified eight distinct vibrational modes between 1 and 6 hz a distant induced earthquake produced local ground motion rich in 1 hz energy stimulating a 20 db increase in measured power at the bridge s fundamental mode moreover we establish that wave action on lake powell an artificial reservoir generates microseismic energy with peak power 1 hz also exciting resonance of rainbow bridge these anthropogenic sources represent relatively new energy input for the bridge with unknown consequences for structural fatigue

morphology of pyroclastic cones and tectonics the relationships between morphology and spatial distribution of 1315 quaternary pyroclastic cones and coeval faulting of the volcanic substrate are analyzed in the following regions with different structural settings tepic rift mexico ethiopian rift mexican volcanic belt canary archipelago and mount etna field data and analog experiments of tephra cone emplacement and collapse enable the definition of a number of parameters which can be used to infer the geometry of the fracture feeding the magma to a pyroclastic cone the strike of the feeding plane is directly related to 1 the elongation of cone base and crater 2 the location of depressions on the crater rim and 3 the alignment of pyroclastic cones in relation to a given vent spacing in addition the strike and dip of faults affect the direction of cone breaching these relationships are valid for volcanic substrate topographic surfaces with an inclination of less than 9 and are especially sensitive to fault escarpment and cone height lava and cone density and fault orientation with respect to the dip of the volcanic substrate topography relations 1 and 2 become more pronounced for regions undergoing extensional tectonics where edifices also have a larger dimension whereas breaching in the direction of the fault dip is more widespread in regions under extension breaching along the fault strike as well as the coincidence between fault strike and vent alignment are more frequent in regions with transcurrent or transtensional tectonics

ambient resonance of mesa arch canyonlands national park utah we analyzed the resonance characteristics of a prominent natural arch in canyonlands national park mesa arch as measured from ambient seismic data evaluating spectral and polarization attributes we distinguished the first four resonant frequencies of the arch 2 9 6 0 6 9 and 8 5 hz as well as basic properties of the associated mode shapes we then affirmed experimental data using 3 d numerical modal analysis providing estimates of material properties and clarifying vibrational mode shapes monitoring resonant frequencies over time we searched for shifts associated with changing environmental conditions and long term progressive damage we measured 3 direct daily variation in resonant frequency associated with changing rock temperature thermal stress and stiffening of the rock matrix independent tilt data showed similar diurnal cycles associated with thermoelastic stresses and deformation of the arch we observed no permanent resonant frequency shifts related to irreversible damage of mesa arch during our study period

a model for calculating eruptive volumes for monogenetic volcanoes implication for the quaternary auckland volcanic field new zealand abstract monogenetic basaltic volcanism is characterised by a complex array of behaviours in the spatial distribution of magma output and also temporal variability in magma flux and eruptive frequency investigating this in detail is hindered by the difficulty in evaluating ages of volcanic events as well as volumes erupted in each volcano eruptive volumes are an important input parameter for volcanic hazard assessment and may control eruptive scenarios especially transitions between explosive and effusive behaviour and the length of eruptions erosion superposition and lack of exposure limit the accuracy of volume determination even for very young volcanoes in this study a systematic volume estimation model is developed and applied to the auckland volcanic field in new zealand in this model a basaltic monogenetic volcano is categorised in six parts subsurface portions of volcanoes such as diatremes beneath phreatomagmatic volcanoes or crater infills are approximated by geometrical considerations based on exposed analogue volcanoes positive volcanic landforms such as scoria spatter cones tephras rings and lava flow were defined by using a light detection and ranging lidar survey based digital surface model dsm finally the distal tephra associated with explosive eruptions was approximated using published relationships that relate original crater size to ejecta volumes considering only those parts with high reliability the overall magma output converted to dense rock equivalent for the post 250 ka active auckland volcanic field in new zealand is a minimum of 1 704 km3 this is made up of 1 329 km3 in lava flows 0 067 km3 in phreatomagmatic crater lava infills 0 090 km3 within tephra tuff rings 0 112 km3 inside crater lava infills and 0 104 km3 within scoria cones using the minimum eruptive volumes the spatial and temporal magma fluxes are estimated at 0 005 km3 km2 and 0 007 km3 ka the temporal volumetric evolution of auckland is characterised by an increasing magma flux in the last 40 ky which is inferred to be triggered by plate tectonics processes e g increased asthenospheric shearing and backarc spreading of underneath the auckland region

detecting short term evolution of etnean scoria cones a lidar based approach the 2001 and 2002 2003 flank eruptions on mount etna italy were characterized by intense explosive activity which led to the formation of two large monogenetic scoria cones one from each eruption on the upper southern flank of the volcano continuous monitoring of etna especially during flank eruptions has provided detailed information on the growth of these cones they differ in genesis shape and size a set of high resolution 1 m digital elevation models dems derived from light detection and ranging lidar data collected during four different surveys 2004 2005 2006 and 2007 has been used to map morphology and to extract the morphometric parameters of the scoria cones by comparing lidar derived dems with a pre eruption 1998 10 m dem the volume of the two scoria cones was calculated for the first time comparison of the lidar derived dems revealed in unprecedented detail morphological changes during scoria cone degradation in particular the morphologically more exposed and structurally weaker 2002 2003 cone was eroded rapidly during the first few years after its emplacement mainly due to gravitational instability of slopes and wind erosion

continuous tracking of volcanic tremor at mount etna italy summary using data from two dense array of short period seismometers we analyse the kinematic properties of volcanic tremor preceding and accompanying the 2004 2005 eruption of etna volcano italy results from slowness analyses indicate the action of at least two distinct sources the first dominates the pre eruptive period and is likely associated with the main plumbing system feeding the summit and southeast craters following the onset of the eruption secondary directions of wave arrival encompass the eruptive fissures located on the lower eastern flank of the southeast crater nonetheless significant energy radiation from this latter source was also occurring prior to the onset of the lava effusion likely suggesting the presence of a resident magma batch in agreement with independent petrologic and geochemical data

spatial and temporal distribution of microbial carbonates skeletal and non skeletal grains in a pennsylvanian carbonate platform valdorria northern spain abstract the valdorria carbonate platform in northern spain features a well preserved and continuous outcrop of a bashkirian platform to basin transect during the asatauian late bashkirian the platform growth changed gradually from a progradational to an aggradational mode recording 10 most likely short eccentricity controlled cyclothems the facies of the platform top and slope have been mapped and the architecture of each cyclothem schematically reconstructed the distribution of microbial carbonates microbially mediated precipitates skeletal grazers burrowers corals filter feeders algae foraminifera osagia like oncoids and thartarella terebella worm tubes and non skeletal grains faecal pellets has been quantified for the transgressive regressive periods of deposition transgressive maximum flooding early and late regressive intervals of each cyclothem this study shows that the distribution of microbial carbonates skeletal and non skeletal grains along a carbonate platform transect is variable through time and mainly governed by a set of measurable interconnected factors regulating the local palaeoenvironments the water depth and the wave energy facies along the platform profile inner outer break slope during periods of sea level fluctuations transgressive to regressive intervals of deposition auloporid corals siliceous sponges phylloid algae and osagia like oncoids are characteristic of a low energy environment situated from estimated palaeo water depths of 25 to 80 metres below sea level mbsl onward that formed in the outer platform during the maximum flooding intervals anthracoporella archaeolithoporella boundstone is characteristic of the moderate energy environments created in the horizontal inner platform during the transgressive intervals microbially mediated precipitates are reliable indicators of the slope and masloviporidium indicator of low energy environments of the upper slope on the platform top ungdarella and donezella are more abundant during the early regressive intervals than during any other interval stacheoids are mainly present in the water depth range of 10 to 60 mbsl tournayellids from 15 to 35 mbsl and archaediscids from 15 to 75 mbsl all in low to moderate energy conditions rugose corals are common in the water depth range of 5 to 35 mbsl either during the transition from the early to the late regressive intervals as solitary forms or forming boundstone or during periods of higher sea level stand as solitary forms in floatstone fenestellids fistuliporids and trilobites occur mainly in the slope but are also common in the platform top during the maximum flooding and or the early regressive intervals archaeolithoporella is a reliable indicator of the platform top deposits but its abundance is closely linked to the presence of adequate substrates a high abundance in the assemblage of gastropods endothyrids palaeotextulariids bradyinids and fusulinids characterizes the platform top shallow water coated grain grainstones formed under high energy currents during the late regressive intervals tetrataxids act as encrusters on microbial precipitates of the slope or on phylloid algae and archaeolithoporella of the platform top but are also observed as nuclei of coated grains brachiopods are more abundant in low to moderate energy and 35 to 55 mbsl environments that prevailed during the transgressive intervals faecal pellets were commonly observed in low energy environments from 50 to 325 mbsl at the platform break and in the slope and the same applies for thartarella terebella worm tubes that are virtually absent in high energy deposits finally crinoids lasiodiscids and tuberitinids are randomly distributed and are not indicative of any specific environment the here well constrained distribution patterns of microbial carbonates skeletal and non skeletal grains in valdorria outcrop hold the potential to serve as a reference for interpretation of depositional environments of other platforms using biota associations and depositional texture particularly in regions where the platform geometry is not preserved or is not fully exposed

instrumental evidence of normal mode rock slope vibration summary a unique field experiment was performed to constrain the seismic response of a large potentially unstable rock slope in the southern swiss alps small aperture seismic arrays were deployed to record ambient vibrations both inside and outside of the mapped instability boundary the recordings were analysed by means of the high resolution f k method site to reference spectral ratios and time frequency dependent polarization analysis all three methods indicated that the wavefield within the potentially unstable rock mass is dominated by normal mode motion standing waves rather than horizontal propagation of seismic waves both fundamental frequency and relative amplification could be recovered from ambient noise data the observed amplification is strongly directional and the maximum amplification is oriented perpendicular to open tension cracks mapped at the ground surface our results highlight site response characteristics relevant for analysis of earthquake triggered rock slope failures

magma emplacement into the lemptegy scoria cone chaine des puys france explored with structural anisotropy of magnetic susceptibility and paleomagnetic data the lemptegy volcano is a small monogenetic scoria cone located in the chaine des puys auvergne france which erupted about 32 000 years ago a first edifice lemptegy 1 formed during a trachybasalt eruption as a group of satellite vents of the puy de gouttes scoria cone a second trachyandesitic edifice lemptegy 2 formed soon after and completely covered lemptegy 1 with an 80 m high breached cone since 1946 the lemptegy volcano has been quarried for scoria and today offers unprecedented three dimensional exposure of the subvolcanic plumbing system to map the internal flow architecture of the plumbing system and to study the subvolcanic deformation of lemptegy 2 structural mapping petrographic observations anisotropy of magnetic susceptibility ams rock magnetic and paleomagnetic data were collected field structural mapping and thin section study of tension gashes riedel shears striations as well as ductile shear zones and bubbles allow the direction and sense of the magma flow to be determined twenty ams sites were established in ten dikes one to four sites in each dike with 504 specimens analyzed and 479 specimens used to infer magma flow patterns structural data the maximum susceptibility axis k 1 and the imbrication of the magnetic foliation k 1 k 2 planes indicate both upward and downward sense of flow as well as flow toward and away from the central vent rock magnetic experiments reveal that a cubic fe ti oxide phase likely low ti titanomagnetite is the principal magnetic phase carrying both the remanence and anisotropy paleomagnetic data from some sites yield statistically distinct at the 95 confidence level remanence directions while at other sites the data are indistinguishable at the 95 confidence level the paleomagnetic results observed steeply tilted scoria layers internal unconformities and faults show that as each dike was emplaced it displaced earlier dikes evidencing subvolcanic deformation the lemptegy 2 volcano shares similarities in terms of inferred eruption style and structures with other scoria cones such as cerro negro nicaragua and thus provides an excellent field laboratory to investigate active scoria cones world wide

monogenetic volcanism personal views and discussion monogenetic volcanism produces small volume volcanoes with a wide range of eruptive styles lithological features and geomorphic architectures they are classified as spatter cones scoria or cinder cones tuff rings maars maar diatremes and tuff cones based on the magma water ratio dominant eruption styles and their typical surface morphotypes the common interplay between internal such as the physical chemical characteristics of magma and external parameters such as groundwater flow substrate characteristics or topography plays an important role in creating small volume volcanoes with diverse architectures which can give the impression of complexity and of similarities to large volume polygenetic volcanoes in spite of this volcanic facies complexity we defend the term monogenetic volcano and highlight the term s value especially to express volcano morphotypes this study defines a monogenetic volcano a volcanic edifice with a small cumulative volume typically 1 km3 that has been built up by one continuous or many discontinuous small eruptions fed from one or multiple magma batches this definition provides a reasonable explanation of the recently recognized chemical diversities of this type of volcanism

evaluation of seismic site response nearby underground cavities using earthquake and ambient noise recordings a case study in catania area italy abstract the influence of underground cavities in assessing local seismic response was studied in some test sites in the urban area of catania the investigations were performed both in a natural cavity and in artificial tunnels taking into account the near surface geological features earthquake and ambient noise records were processed through spectral ratio techniques investigating also on the possible directional effects a set of 70 local and regional earthquakes was recorded by seismic stations deployed nearby a grotto located in the northern part of the town as well as in a reference site on the bedrock as regards ambient noise measurements about 30 recording sites were selected locating the mobile stations inside the cavities as well as along short profiles crossing them spectral ratios coming out from performed measurements show that spectral peaks in the frequency range 3 0 7 0 hz appear stable nearby the cavity and show a tendency to be less pronounced at increasing distance from it moreover the natural period of buildings erected nearby and over the considered cavity was evaluated to investigate on possible soil structure interactions the results so far obtained point out that the height of the cavities plays an important role it appears evident that only cavities having height greater than about 4 m show significant h v amplification peaks moreover spectral ratios deriving from measurements performed inside the cavities show less pronounced spectral peaks than those obtained from measurements over and outside the cavities investigations about the interaction with nearby edifices show slight increments in the amplitude of spectral peaks representing the fundamental period of buildings located over the investigated grotto finally our observations set into evidence a tendency toward a pronounced polarization of the ground motion that is parallel to the main axis of the grotto

volcanic tremor location during the 2004 mount etna lava effusion 1 a lava emission started at mt etna italy on 7 september 2004 neither earthquake seismicity heralded or accompanied the opening of the fracture field from which the lava poured out nor volcanic tremor changed in amplitude and frequency content at the onset of the effusive activity to highlight long term changes we propose a method for the location of the tremor source based on a 3d grid search using the amplitude decay of the seismic signal from january to november 2004 we find the centroid of the tremor source within a zone close to and partially overlapped with the summit craters pre effusive phase which extended up to 2 km south of them effusive phase the depths are of between 1698 and 2387 m a s l we hypothesize the lava effusion stemmed from a degassed magma body although we find evidence of temporary magma overpressure conditions such as those documented on 25 september

inversion of surface wave data for subsurface shear wave velocity profiles characterized by a thick buried low velocity layer the study formed part of the simit project integrated italy malta cross border system of civil protection b1 2 19 11 part financed by the european union under the italiamalta cross border cooperation programme 2007 2013

shallow high resolution geophysical investigation along the western segment of the victoria lines fault island of malta abstract the victoria lines fault island of malta is a 15 km long and n260 striking segmented normal fault system which is probably inactive since the late pliocene in the westernmost part the fomm ir rih segment displays comparable geologic throw and escarpment height 150 170 m moreover its hangingwall hosts thin patches of middle pleistocene clastic continental deposits red beds which are poorly preserved elsewhere we acquired two seismic transects by collecting ambient vibration recordings processed by using horizontal to vertical spectral ratios complemented by one high resolution 2 d refraction tomography survey crossing this fault where it is locally covered by red beds and recent colluvial deposits we found a resonance peak at 1 0 hz in the hangingwall block whereas clear peaks in the range 5 0 10 0 hz appear when approaching the subsurface fault and we relate them to the fractured bedrock within the fault zone the best fit tomographic model shows a relatively high vp shallow body vp 2200 2400 m s that we relate to the weathered top of the miocene upper coralline limestone fm bounded on both sides by low vp regions 230 m s above the weathered top bedrock our results depict a clear seismic signature of the victoria lines fault characterized by low seismic velocity and high amplification of ground motion we hypothesize that during the middle pleistocene faulting may have affected the basal part of the red beds so that this part of the investigated complex fault system may be considered inactive since 0 6 myr ago

a fractal analysis of quaternary cenozoic mesozoic and late pennsylvanian sea level changes sea level changes are related to both climatic variations and tectonic movements the fractal dimensions of several sea level curves were compared to a modern climatic fractal dimension of 1 26 established for annual precipitation records a similar fractal dimension 1 22 based on 18o 16o in deep sea sediments has been suggested to characterize climatic change during the past 2 m y our analysis indicates that sea level changes over the past 150 000 to 250 000 years also exhibit comparable fractal dimensions sea level changes for periods longer than about 30 m y are found to produce fractal dimensions closer to unity and missourian late pennsylvanian sea level changes yield a fractal dimension of 1 41 the fact that these sea level curves all possess fractal dimensions less than 1 5 indicates that sea level changes exhibit nonperiodic long run persistence the different fractal dimensions calculated for the various time periods could be the result of a characteristic overprinting of the sediment record by prevailing processes during deposition for example during the quaternary glacio eustatic sea level changes correlate well with the present climatic signature during the missourian however mechanisms such as plate reorganization may have dominated resulting in a significantly different fractal dimension

geological and geomorphological evolution of the etna volcano ne flank and relationships between lava flow invasions and erosional processes in the alcantara valley italy abstract in this paper the interrelationships between volcanic activity and fluvial events in the alcantara valley are investigated based on the correlation between the stratigraphy of the ne flank of mt etna and subsurface data the geological and geomorphological evolutions of the valley are reconstructed new 1 10 000 scale geological mapping shows that the bulk of this sector of the volcano is made up of the ellittico volcano lava flows though they are widely covered by the products of the eruptive activity of the last 15 ka the present day morphological setting of the alcantara valley is the result of two main evolutionary phases initiated during the activity of the ellittico volcano only one lava flow invasion of the valley floor occurred in the first phase this phenomenon was followed by a long period of erosional processes leading to the entrenchment of the drainage pattern and the erosion of the ellittico lava flow about 20 25 ka ago an important change in the frequency of the lava flow invasions into the valley occurred associated with the final stage of the ellittico volcano activity marking the beginning of the second phase during this phase volcanic processes became predominant with respect to other morphogenetic processes in the alcantara valley lava flows coming from the ne flank of the ellittico volcano caused a radical modification of the morphological setting of this area even though only one lava flow emitted by an eruptive fissure located within the valley partially filled the riverbed during the eruptive activity of the last 15 ka the complete filling of the alcantara valley floor occurred in particular between 15 and 7 ka a lava flow originated from the mt moio scoria cone filled the valley floor for a distance of about 9 km following a short period of erosion an eruptive fissure located within the valley generated a 20 21 km long lava flow that was channelled along the full extent of the alcantara valley and stretches for about 3 km offshore in the ionian sea in the last 7 ka lava flows originating from the ne rift zone produced only temporary damming of the riverbed without any important contribution to the filling of the alcantara valley

the role of climate in stratigraphic patterns exhibited by late palaeozoic rocks exposed in kansas abstract late palaeozoic cyclothems of the midcontinental u s cannot be represented by a single ideal facies sequence rather they encompass a wide range of cycle types depending on their stratigraphic position the exposed late palaeozoic pennsylvanian and permian rocks of kansas as compiled by zeller 1968 can be divided into nine major lithofacies these lithofacies were ordered based on their times of greatest abundance through the section from oldest to youngest they attain their peak abundance in the following order 1 coal 2 gray mudrocks and sandstones 3 black mudrocks 4 limestones 5 cherty limestones 6 fossiliferous mudrocks 7 variegated mudrocks 8 evaporites and 9 variegated dolomitic siliciclastics climatically these nine lithofacies suggest a change from generally wetter at the base to generally drier at the top of the section this climatic trend was probably generated by a complex interaction of factors primarily driven by global tectonics climatic changes can be used to explain the five generally recognized types of lithofacies cyclothems in kansas and thus are a potential explanation for the changing stratigraphic patterns of the entire late palaeozoic time interval of kansas and perhaps elsewhere

mapping the structure and depth of lava tubes using ground penetrating radar 1 the formation of lava tubes is one of the most significant factors controlling the emplacement of lava flows however extents and structures of lava tubes are typically not precisely known due to the difficulty in finding lava tubes in the field we developed a new stepped frequency ground penetrating radar gpr system with shielded antennas which allows measurements that have both high spatial resolution and large penetration depth we performed two types of measurements over an inactive lava flow and show that this method can easily detect the existence of a lava tube importantly phase reversals of the reflection signals can help identify reflections from a lava tube using these reflection patterns we estimate the vertical dimension and the depth of a lava tube at fuji volcano which are validated by survey measurements the presented method may be the most practical way to map terrestrial and perhaps extraterrestrial lava tubes

the cryptic summit graben of mt etna volcano abstract previous studies have inferred the likelihood of a summit graben at mt etna but until now there has been no direct observation or evidence of such a feature here the results of 43 years of deformation measurements at the summit are reported in which the presence of an actively forming north south graben 1 5 km wide is evident with a maximum subsidence of nearly 4 m in 43 years its bounding faults have in most places been hidden by the eruptive deposits of 190 summit eruptions but horizontal measurements across these faults show a maximum value of nearly 9 m of east west extension most of the subsidence and extension has taken place during the injection of eruption feeder dykes with extreme values for single events of 1 7 m subsidence during the injection of the 2002 2003 dyke and 4 4 m extension across the 1989 feeder dyke but subsidence and extension continues to take place slowly during inter eruptive periods analogue modelling indicates that its origin is probably a consequence of the gravitational spreading and downslope sliding of the etna edifice on its clay rich substrate aided by magmatic pressure from feeder dykes intruded into individual faults and by downward pressure from surface loading of erupted lava this study clarifies the way in which the mechanism of gravitational spreading is maintained throughout the lifetime of this and other spreading volcanoes and rifts on earth and mars

buoyancy controlled eruption of magmas at mt etna buoyancy controls the ability of magma to rise its ascent rate and the style of the eruptions geophysical geological and petrological data have been integrated to evaluate the buoyancy of magmas at mt etna the density difference between host rocks and magmas is mainly related to the amount of h2o dissolved in the magma and to the bubble liquid separation processes in the depth interval 22 2 km b s l highly hydrated h2o 3 basaltic magmas or mixtures of bubbles liquid have positive buoyancy and rise rapidly conversely bubble depleted liquids with an intermediate h2o content 1 5 having neutral buoyancy will spread out and form magmatic reservoirs at different depths until cooling crystallization further modify composition and density these different processes account for the magma compositions location of magmatic reservoirs as determined by geophysical methods and the complex eruptive cycles slow effusions fire fountains and plinian eruptions that have been observed in the history of the volcano