magmatic evolution of a volcano studied by 230th 238u disequilibrium and trace elements systematics the etna case age determinations of several lava flows from etna through 230th 238u disequilibrium internal isochrons yield a precise chronology of the volcano s history for the last 200 000 years and emphasize the main episodes in the formation of this huge complex strato volcano study of 230th232th 0 initial ratios of lavas together with their trace element compositions yields a consistent model of magmatic evolution implying the existence for 200 000 years of a deep reservoir of alkalic magma periodically mixed with magmas of tholeiitic affinity these short periods of mixing appear to be related to the formation of the large calderas of etna in addition to these processes affecting the deep reservoir fractional crystallization also occurred in more superficial levels of the volcanic edifice thereby yielding several series of differentiation of relatively short duration as for its geochemistry etna s volcanism is of oceanic type but with its own characteristics and in a peculiar geodynamic context at the edge of the african plate

ground deformation patterns on mount etna 1992 to 1994 inferred from gps data in this paper ground deformation that occurred on mount etna from 1992 1994 is studied using gps data first problems relating to data processing of the 1993 and 1994 surveys carried out on the whole of the mount etna gps network are considered care has been paid to the network adjustment step particularly in evaluating effects of the reference frame stability in finding final solutions comparison between survey results allows us to invert the strain tensor and to compute displacement vectors the latter when fully constrained solutions are available the comparisons lead to the conclusion that during the 1992 1994 period at least two sources were active the first was related to a shallow dyke that produced the 1991 1993 eruptive fissures the second deeper source was depleted during the 1991 1993 eruption and recharged between 1993 and 1994 local ground movements correlate spatially and temporally with seismic phenomena

geometry and kinematics of the fault systems controlling the unstable flank of etna volcano sicily abstract an updated tectonic framework of etna s unstable flank has been defined as a result of multidisciplinary analyses carried out by integrating geological and geophysical data the different typologies of datasets have been analyzed and correlated in order to constrain the geometry and kinematics of the fault systems controlling the unstable flank of etna volcano and to better understand their complex relationship with the offshore morphostructures of the continental margin in particular we have considered as the main structural elements the following four fault systems pernicana ragalna tremestieri trecastagni and timpe slip rates and kinematics have been estimated in both long and short terms respectively from geological and seismotectonic geodetic data data integration has allowed defining five kinematic domains in the sliding flank of etna 1 the ne block bordered by the pernicana fault and characterised by the highest deformation velocities ground velocity progressively diminishes toward south with a clockwise rotation of the vectors defining 2 the block embracing the central part of the timpe system 3 the giarre wedge 4 the medium east block bounded by the s tecla and trecastagni faults and 5 the se block bordered by the hidden belpasso ognina tectonic lineament the dynamics of these blocks takes place through discontinuous movements sudden short term accelerations related to the magma intrusion are superimposed to a fairly constant mid term ese sliding the proposed comprehensive model of the unstable flank provides the basic input parameters for applying analytical models to flank dynamics of etna volcano

influence of calcite decarbonation on the frictional behavior of carbonate bearing gouge implications for the instability of volcanic flanks and fault slip abstract the impact of heat readily provided by magma circulating hot fluids or rapid fault slip on carbonate substrata is an important factor in determining the flank stability of volcanoes and the mechanical behavior of faults in areas where carbonate lithologies are prevalent the mineralogy and mechanical properties of carbonate rocks are demonstrably altered by thermally induced decarbonation while previous studies have considered the role of decarbonation in bulk strength loss at subvolcanic conditions and dynamic weakening during coseismic fault slip little is known about the effects of decarbonation on the frictional properties of carbonate rocks during both the nucleation and inter seismic phases here we present results from experiments performed on a portlandite rich material a typical hydrous product of the decarbonation reaction to evaluate frictional strength stability and healing at shallow crustal conditions we sheared gouge layers of this material under saturated conditions at room temperature and at velocities comparable to those involved in earthquake nucleation our data indicate that the reaction of calcite to portlandite results in a distinct change in the mechanical behavior of the gouge decarbonated shear zones are 1 frictionally weaker at higher normal stresses 2 more frictionally unstable and 3 likely to regain their frictional strength more quickly than unaltered calcite rich zones the occurrence of portlandite could be key for interpreting the stability of volcanic flanks that root into carbonate substrata and for seismogenic normal faults located within thick sedimentary sequences and thus provide a better understanding of the hazards they pose

very shallow earthquakes and brittle deformation in active volcanic areas the eatnean region as an example abstract some aspects of the stress field acting in active volcanic areas were investigated by studying the relationship between surficial seismicity h 1 2 km and the brittle deformation pattern of the etna volcano the magmatic composition and structural character of mt etna are described together with its geodynamic regional context after a discussion of the problem of the state of stress in active volcanoes and a definition of very shallow seismicity the high level of surficial seismicity the morphology of the sedimentary basement and the kinematic behaviour of the faults suggest that the eastern flank of mt etna is a shallow seismotectonic domain structurally decoupled from the rest of the volcanic body this flank shows a tendency to slide in an eastern direction and is bound to the north by a left lateral oblique slip normal fault trending e w and in the south by an arcuate fault system with right lateral features right lateral oblique slip normal faults

long term stress strain analysis of volcano flank instability the eastern sector of etna from 1980 to 2012 1 we investigated the evolution of seismicity and deformation in the unstable eastern flank of etna volcano over a 30 year period from 1980 to 2012 a significant temporal correlation has been revealed between periods of flank acceleration and intensified seismic activity by comparing seismicity along the northern border pernicana fault system of the sliding flank and the deformation of the eastern flank two marked phases have been observed in 1984 1986 and in the years following 2002 these two phases are separated by an intermediate phase from 1987 to 2001 in which the flank sliding slowed down and the seismicity dropped drastically this common temporal evolution in the deformation rate and seismic release supports the hypothesis that the seismicity in the northern border can be viewed as a marker of the response to accommodate the stress exerted by the traction of the eastern flank sliding this interplay has also been corroborated by finite element method numerical computations that highlight a good correlation between the seismicity pattern and areas of positive stress changes induced by the sliding surface the two intense phases of flank acceleration are representative of two main different sources volcano flank instability stretching the eastern sector in the first 1984 1986 phase and magmatic intrusions pushing the eastern flank seaward since the 2002 2003 eruption establishing the relationship between flank acceleration and seismic activation therefore contributes to understanding etna s mechanical behavior and provides insights into the processes regulating the unstable flank response

new evidence for the form and extent of the pernicana fault system mt etna from structural and soil gas surveying a multidisciplinary study based on structural and soil gas surveys was carried out in order to investigate the relationship between soil co2 degassing and the tectonic setting of the lower northeastern flank of mt etna volcano the results show that anomalous soil co2 emissions occur mainly along faults trending wnw ese and also where these faults intersect the other main fault set trending ne sw that displaces the study area in particular anomalies in co2 degassing were revealed both along the pernicana fault and along another fault fiumefreddo fault which may represent the prolongation of the former towards the ionian sea coast in the areas where these structures show evident surface faulting they are all characterised by left lateral displacements and aseismic creep behaviour furthermore the geochemical survey revealed that these faults join in an area devoid of geological evidence of surface faulting and continue underneath an apparently unfaulted alluvial cover near the coastline in the light of these findings we suggest that the pernicana and fiumefreddo faults are discrete segments of a near continuous left lateral shear zone affecting the whole north eastern flank of mt etna as far as the ionian coast

wavefield polarization in fault zones of the western flank of mt etna observations and fracture orientation modelling ambient noise measurements performed on the western flank of mt etna are analyzed to infer the occurrence of directional amplification effects in fault zones the data were recorded along short 500 m profiles crossing the ragalna fault system ambient noise records were processed to compute the horizontal to vertical noise spectral ratio as a function of frequency and direction of motion wavefield polarization was investigated in the time frequency domain as well peaks of the spectral ratios generally fall in the frequency band 1 0 6 0 hz pointing out directional amplifications that are also confirmed by the results of the time frequency analysis the largest amplification occurring with high angle to the fault strike a variation of the frequency of the spectral peak is observed between the two sides of the fault possibly related to a damage fault asymmetry measurements performed several kilometers away from the fault zone do not show behavior that is as systematic as in the fault zone and this suggests that the observed directional effects can be ascribed to the fault fabric we relate the polarization effect to compliance anisotropy in the fault zone where the presence of predominantly oriented fractures makes the normal component of ground motion larger than the transversal one in order to test the direction and the type of fractures that are expected in the fault zone we modeled the brittle deformation pattern of the investigated fault theoretical results are in good agreement with field observations of the fracture strike

geometric and kinematic variations along the active pernicana fault implication for the dynamics of mount etna ne flank italy abstract geological and structural analyses and ground deformation measurements performed along the eastern portion of the pernicana fault system and its splay segments allow the structural setting and the kinematic behaviour of the fault to be defined in addition the interrelationship between the deformation style of fault segments and the variations of the volcanic pile thickness along the fault strike are investigated using detailed sedimentary basement data brittle deformation dominates the n105 fault segment where the volcanic pile is more than 200 m thick with the development of a well defined fault plane characterised by main left lateral kinematics the transtensive deformation of the n105 fault is partitioned eastward at rocca campana to a main n120 segment here this segment crosses a culmination of the sedimentary basement close to vena village where the deformation pattern of the thin volcanic pile less than 100 m thick is influenced by the more ductile behaviour of the basement generating local short structures with different orientation and kinematics in the southern block of the fault on the northern one short e w trending faults show left lateral displacements with a minor reverse component on south dipping planes this kinematics is related to the oblique orientation of the n120 segment with respect to the seaward motion of the ne flank of etna on the whole the compressive component of the deformation affecting the n120 segment of the pernicana fault system generates a positive flower structure

dynamics of the eastern flank of mt etna volcano italy investigated by a dense gps network abstract mount etna has developed at the intersection of two regional tectonic lineaments the nnw sse trending hybleo maltese escarpment which separates the thick inland continental crust of the african platform from the ionian mesozoic oceanic crust and the ne sw messina fiumefreddo fault that marks a rift zone between south calabria and north eastern sicily extending as far as the mt etna area all tectonic features affect with outstanding surface features the eastern side of the volcano the eastern flank of the volcano is affected by a long term motion toward ese in 1997 in order to increase the detail of the ground deformation pattern on the lower eastern flank of mt etna a new gps network the ionica network was installed on this sector of the volcano this gps network consists of 24 stations and covers the lower eastern flank of the volcano from the town of catania to taormina and from the coastline up to an altitude of about 1300 m all the new stations consist in self centring benchmarks this kind of benchmark allows all station set up errors to be avoided before the merging of the ionica network to the frame of the global gps network of mt etna in june 2001 three surveys were carried out on this network in september 1997 august 1998 and january 2001 from the ground deformation pattern it is possible to distinguish two different sectors showing different characteristics of deformation the southern part of the network shows a more uniform distribution of the vertical motion with a mean se ward horizontal component while the northern one shows an heterogeneous vertical motion with a ese ward horizontal component furthermore a higher velocity is detected between 1997 and 1998 due to the additional stress induced by a shallow intrusion on the nw flank of the volcano the model resulting from data inversions defines a wide sliding plane beneath the entire eastern flank of the volcano with a low dip angle the expected velocity vectors fit well the observed ones even if the measured velocities are still quite higher than expected at lowermost stations the vertical inclination of the velocity vectors measured during the 1998 2001 period gradually decreases from west to east suggesting a sort of rotational movement of the south eastern flank interrupted by some anomalous vectors on the lower part that show higher vertical velocities these anomalies being located on a wedge defined by the intersection of the main nnw sse and ne sw fault systems and near the timpe faults are probably due to the activity of the vertical faults cutting the lower eastern flank of mt etna stations lying on the hanging wall and on the footwall of the timpe fault system are affected by similar horizontal displacements meaning that these structures are moving eastwards together with the sliding flank this evidence suggests that the timpe faults are probably second order structures with respect to the detachment surface these results depict a structural framework of the eastern flank of mt etna in which the low angle dislocation can be considered as a first order approximation of an actual listric plane and the current active part of the timpe fault system is confined above the detachment surface

evidences for strong directional resonances in intensely deformed zones of the pernicana fault mount etna italy 1 in this paper we investigate ground motion properties in the western part of the pernicana fault this is the major fault of mount etna and drives the dynamic evolution of the area in a previous work rigano et al 2008 showed that a significant horizontal polarization characterizes ground motion in fault zones of mount etna both during earthquakes and ambient vibrations we have performed denser microtremor measurements in the ne rift segment and in intensely deformed zones of the pernicana fault at piano pernicana this study includes mapping of azimuth dependent horizontal to vertical spectral ratios along and across the fault frequency wave number techniques applied to array data to investigate the nature of ambient vibrations and polarization analysis through the conventional covariance matrix method our results indicate that microtremors are likely composed of volcanic tremor spectral ratios show strong directional resonances of horizontal components around 1 hz when measurements enter the most damaged part of the fault zone their polarization directions show an abrupt change by 20 to 40 at close measurements between the northern and southern part of the fault zone recordings of local earthquakes at one site in the fault zone confirm the occurrence of polarization with the same angle found using volcanic tremor we have also found that the directional effect is not time dependent at least at a seasonal scale this observation and the similar behavior of volcanic tremors and earthquake induced ground motions suggest that horizontal polarization is the effect of local fault properties however the 1 hz resonant frequency cannot be reproduced using the 1 d vertically varying model inferred from the array data analysis suggesting a role of lateral variations of the fault zone although the actual cause of polarization is unknown a role of stress induced anisotropy and microfracture orientation in the near surface lavas of the pernicana fault can be hypothesized consistently with the sharp rotation of the polarization angle within the damaged fault zone

evidence for ground motion polarization on fault zones of mount etna volcano 1 during local and regional earthquakes an evident amplification of horizontal ground motion is observed at two seismological stations near the tremestieri fault on the southeastern flank of mount etna volcano rotated component spectral ratios show a narrow spectral peak around 4 hz along a n40 e direction a conventional polarization analysis using the eigenvectors of the covariance matrix confirms the very stable directional effect enhancing the approximately ne sw elongation of the horizontal ground motion in the fault zone the effect is evident during the entire seismogram and independent of source back azimuth as well as distance and depth of earthquakes the same polarization is observed in ambient noise as well this consistency allowed us to use microtremors for checking ground motion polarization along and across the tremestieri fault zone with a high spatial resolution the result is a stable polarization of horizontal motion in the entire area that can be observed in a broad frequency band to check whether this ground motion property is recurrent and to understand a possible relationship with fault strike faulting style or orientation of fractures ambient noise was recorded on other mapped faults of the mount etna area the moscarello acicatena and pernicana faults the latter in particular is characterized by different strike and faulting style a systematic tendency of ambient noise to be polarized is found in all of the faults a picture emerges where normal faults of the eastern flank show an e w to ne sw polarization that changes on the pernicana fault which develops approximately e w and is characterized by a prevailing nw se to n s polarization directions of polarization were never parallel to the fault strike moreover polarization persists too far away from the fault trace excluding an effect limited to a narrow low velocity zone hosted between harder wall rocks both these observations rule out an interpretation in terms of fault trapped waves the cause of observed polarizations will be the subject of future studies however the consistency with recent results of velocity anisotropy in a part of the investigated area suggests a possible role of attenuation anisotropy on horizontal amplitude variations versus azimuth

the influence of correlations in computing crustal strains from trigonometric network results abstract a variance covariance analysis is made concerning the crustal strain parameters deduced from triangulation results the coordinate difference method is treated the algorithm of the analysis being valid for either free or constrained network adjustments the importance of the correlations entering into the calculation of the standard deviations of strains is emphasized showing how even poor geodetic results can be sometimes useful in crustal strain analyses

seismological features of the pernicana provenzana fault system mt etna italy and implications for the dynamics of northeastern flank of the volcano abstract the pernicana provenzana fault system is one of the most active tectonic systems of mt etna and it plays an important role in the dynamic of the eastern flank of the volcano earthquakes occurring close to this structural trend have reached magnitudes up to 4 2 sometimes with coseismic surface faulting and have caused severe damages to tourist resorts and villages in the vicinity of this structure in the last decade a large number of shocks sometimes in the form of swarms linked to pernicana provenzana fault system movements have been detected by the permanent local seismic network operating in eastern sicily in this paper we report on the detailed study of the seismic activity occurring during the 2000 2009 time span in the pernicana provenzana fault system area firstly we located 407 earthquakes using a standard location code and a 1d crustal velocity model we then applied two different approaches to calculate precise hypocenter locations of the events in particular a non linear code was adopted to obtain an estimate of the a posteriori probability density function in 3d space for the hypocenter location moreover a relative location of correlated event pairs was performed using the double difference method these two different location approaches allowed defining with good accuracy the most active and hazarding sectors of the structure the results of these precise locations showed a tighter clustering in the epicenters and in focal depths in comparison with standard locations earthquakes are located along the pernicana provenzana fault system and are mainly clustered in two zones separated by an area with very low rate of earthquakes occurrence but characterized by the highest energy release depths of the foci are very shallow ranging between the surface and about 3 km b s l kinematics of the pernicana provenzana fault system revealed by the fault plane solutions computed for the most energetic earthquakes highlights a predominant dip slip and left strike movements along e w oriented fault planes in agreement with field observations

evidence of multiple strain fields beneath the eastern flank of mt etna volcano sicily italy deduced from seismic and geodetic data during 2003 2004 we carried out a study of the seismicity and ground deformation occurring on mt etna volcano after the end of the 2002 2003 eruption and before the onset of the 2004 2005 eruption data were recorded by the permanent local seismic network run by istituto nazionale di geofisica e vulcanologia sezione di catania and by geodetic surveys carried out in july 2003 and july 2004 on the gps network most earthquakes were grouped in two main clusters located in the northeastern and southeastern sectors of the volcano the areal distribution of seismic energy associated with the recorded earthquakes allowed us to highlight the main seismogenic areas of mt etna in order to better understand the kinematic processes of the volcano 3d seismic locations were used to compute fault plane solutions and a selected dataset was inverted to determine stress and strain tensors the focal mechanisms in the northeastern sector show clear left lateral kinematics along an e w fault plane consistent with events occurring along the pernicana fault system the fault plane solutions in the southeastern sector show mainly right lateral kinematics along a nne and ene fault plane and left lateral kinematics along nw fault planes that together suggest roughly e w oriented compression surface ground deformation affecting mt etna measured by gps surveys highlighted a marked inflation during the same period and exceptionally strong seawards motion of its eastern flank the 2d geodetic strain tensor distribution was calculated and the results show mainly ene wsw extension coupled with wnw ese contraction indicating right lateral shear along a nw se oriented fault plane the different deformation of the eastern sector of the volcano as measured by seismicity and ground deformation must be interpreted by considering the different depths of the two signals seismic activity in the southeastern sector of volcano is located between 3 and 8 km b s l and can be associated with a very strong additional e w compression induced by a pressurizing source just westwards and at the same depth located by inverting gps data ground deformation in contrast is mainly affected by the shallower dynamics of the fast moving eastern flank which produces a shallower opposing e w extension the entire dataset shows that two different processes affect the eastern flank at the same time but at different depths the boundary is clearly located at a depth of 3 km b s l and could represent the decollement surface for the mobile flank

early permian cisuralian global brachiopod palaeobiogeography abstract palaeobiogeography of four consecutive early permian cisuralian stages is quantitatively analyzed based on a global database of brachiopods consisting of 9131 occurrences 3003 species of 515 genera of brachiopods from 2757 localities all over the world our analyses reveal three distinct largely palaeolatitude related palaeobiogeographical realms developed during the cisuralian like the other stages of the permian six distinct provinces are distinguished during the asselian the asselian brachiopod faunas from gondwanaland and its surrounding areas in general are not well differentiated at the provincial level and characterized an indoralian province a large transitional zone southern transitional zone stz between the palaeoequatorial and gondwanan realms and another distinct austrazean province in the eastern margin of gondwanaland were formed from sakmarian contemporaneous with the largest peak of the late palaeozoic ice age in contrast to the stz the palaeogeographical stations in the northern temperate transitional zone are not differentiated before kungurian instead they are grouped with the stations in the palaeoequatorial region thus collectively constituting a large asymmetrical cathaysian province stretching from south china iran in the western palaeotethys to the mongolian continent in the north the northeast european province mainly consisting of the stations in the ural fold belt and eastern and northeastern parts of the european platform shows a closer palaeobiogeographical relationship with the cathaysian province when the ural seaway opened to the palaeotethys in the southern end before the kungurian but became more distinguished during the kungurian after the closure of the ural seaway and showed a relationship with the faunas of the boreal realm and the northern transitional zone ntz the stations in texas western north america constitute a distinct grandian province based on the high diversity brachiopod faunas with abundant endemic taxa and became distinguishable even at the realm level during the kungurian three high latitude provinces the verkolyman province with characteristic boreal brachiopod faunas the paratinan province with some bipolar and cosmopolitan genera in south america and the austrazean province in eastern australia and new zealand were present from the sakmarian further principal co ordinate analysis pco and minimum spanning tree mst analysis suggest that palaeolatitude related thermal gradient was the major controlling determinant for the cisuralian provincialism and brachiopod distribution in addition geographic barriers and regional eustatic changes also played some roles in the brachiopod distribution and cisuralian marine palaeobiogeography the transition from an icehouse to greenhouse stage led to a steady increase in brachiopod diversity and provincialism during the cisuralian and guadalupian

early detection of eruptive dykes revealed by normalized difference vegetation index ndvi on mt etna and mt nyiragongo abstract flank fissure eruptions involve lateral injection and propagation of magma in a volcanic edifice along pre existing fractures in the direction of the rift zones where magma intrusion and lava flow production are concentrated over time thus the identification and mapping of active fractures and faults is a fundamental aspect of studies of active volcanic systems however gradual dyke wedge emplacement at depth in well fractured zones on volcano flanks and in volcanic rift zones does not necessarily trigger large amplitude deformation signals susceptible to be recorded months or even years before the actual eruption here we show that active and potentially eruptive areas can be detected up to 2 yrs before the arrival to the surface of the final eruptive dyke and venting of lava flows by processing satellite images applying a normalized difference vegetation index ndvi algorithm a posteriori analysis of satellite images indeed reveals that the surficial effects of dyke wedge injection and ascent on plant growth were apparent for mt etna from 2000 to 2002 and for mt nyiragongo in 2001 thus months to years before they erupted

rock and mineral transformations in a fault zone leading to permanent creep interactions between brittle and viscous mechanisms in the san andreas fault creep processes may relax part of the tectonic stresses in active faults either by continuous or episodic processes the aim of this study is to obtain a better understanding of these creep mechanisms and the manner in which they change in time and space results are presented from microstructural studies of natural samples collected from san andreas fault observatory at depth borehole drilled through the san andreas fault which reveal the chronology of the deformation within three domain types i a relatively undeformed zone of the host rock reflects the first step of the deformation process with fracturing and grain indentations showing the coupling between fracturing and pressure solution ii shear deformation development that associates fracturing and solution cleavage processes leads to profound changes in rock composition and behavior with two types of development depending on the ratio between the amount of dissolution and deposition abundant mineral precipitation strengthens some zones while pervasive dissolution weakens some others iii zones with mainly dissolution trended toward the present day creeping zones thanks to both the passive concentration of phyllosilicates and their metamorphic transformation into soft minerals such as saponite this study shows how interactions between brittle and viscous mechanisms lead to widespread transformation of the rocks and how a shear zone may evolve from a zone prone to earthquakes and postseismic creep to a zone of steady state creep in parallel the authors discuss how the creeping mechanism mainly controlled by the very low friction of the saponite in the first 3 4 km depth may evolve with depth

comments on some permian conodont faunas reported from southeast asia and adjacent areas and their global correlation abstract some important conodont faunas reported from southeast asia excluding south china and japan are re evaluated on the basis of the improved taxonomy and resulting newly established provincialism these faunas are representative of either the equatorial warm water province ewwp or the peri gondwana cool water province gcwp except that the fauna from jilin north china represents the north cool water province ncwp the gcwp is marked by vjalovognathus and or merrillina in the cisuralian vjalovognathus merrillina and mesogondolella in the guadalupian and vjalovognathus and mesogondolella sheni or merrillina in the lopingian the ewwp is characterized by the absence of gondolelloides and vjalovognathus in the early and middle cisuralian abundance of sweetognathus and pseudosweetognathus in the kungurian late cisuralian dominance of jinogondolella and sweetognathus in the guadalupian and dominance of clarkina and iranognathus in the lopingian mixed faunas are recognized in regions on the border between the ewwp and gcwp including western timor during the artinskian southeast pamirs during the kungurian and the salt range during the guadalupian and lopingian

tectonic evolution of the qiangtang block northern tibet during the late cisuralian late early permian evidence from fusuline fossil records abstract the tectonic evolution of the qiangtang block in the qinghai tibetan plateau has been a controversial subject for a long time in this paper the discovery of new stratigraphic and fusuline fossil evidence from the permian sequences qudi and lugu formations of the qiangtang block is reported and the palaeogeographical position and tectonic history of this block during the late cisuralian late early permian are discussed the qudi formation is typified by thick turbidite deposits and contains artinskian fusulines such as pseudofusulina and chalaroschwagerina the fusulines were deposited as grains involved in debris flow deposits suggesting a synchronicity with the depositional time of the turbidites the subsequent lugu formation is dominated by seamount type carbonates with an irregular basalt base fusulines cancellina pseudodoliolina and parafusulina in the base of the carbonates confirm its age as middle kungurian the transition from the turbidite qudi formation to the seamount lugu formation is here interpreted to be a continuous depositional process recording the qiangtang block s separation from the indian plate this separation signaled the opening of the neotethys ocean between the qiangtang block and the indian plate palaeogeographically the qiangtang block s separation is comparable with the baoshan block s separation in the east and central pamir s separation in the west by contrast the ultimate opening of the neotethys ocean by the separation of india pakistan and northern oman is apparently much later than this event recorded in the qiangtang block consequently it is interpreted that the opening of the neotethys ocean in the whole northern gondwanan margin is a diachronous series of events

ground deformation patterns at mt etna from 1993 to 2000 from joint use of insar and gps techniques abstract combined gps measurements and radar interferometry insar have been applied at mt etna to study the ground deformation affecting the volcano both over the long 1993 2000 and short term 1997 1998 and 1998 2000 the aim was to better understand the dynamics of the volcano during the magma recharging phase following the 1991 93 eruption since 1993 insar and gps data indicate that mt etna has undergone an inflation a deep intrusion was detected by insar on the western flank of the volcano between march and may 1997 in the following months this intrusion rose up leading to a seismic swarm occurring in january 1998 in the western sector this now shallow intrusion is confirmed by gps data from 1998 to 2000 a general deflation affecting the upper part of the volcano was detected over the whole study period a continuous eastward to south eastward motion of the eastern sector of the volcano was also evidenced the analytical inversions of gps data inferred a plane dipping about 12 ese located beneath the eastern flank of the volcano at a depth of 1 4 km b s l the movement along this plane is able to reproduce the observed south eastward motion of a sector bounded northward by the pernicana fault westward by the north east rift and the south rift and southward by the mascalucia tremestieri trecastagni fault system insar data have validated this model

fault creep and kinematics of the eastern segment of the pernicana fault mt etna italy derived from geodetic observations and their tectonic significance abstract aseismic fault displacements related to numerous fast slipping active faults are frequently observed on mt etna but the characteristics and the rate of displacements along with the behaviour of individual fault segments are poorly constrained to resolve this we installed two local geodetic networks in 1997 along the eastern segment of the pernicana fault one of the most active structures in the geodynamic framework of the volcano the networks are based on the electroptical distance measurements edm and global positioning system gps techniques and consist of four and six benchmarks respectively geodetic data confirm that the tectonic activity of the eastern pernicana fault is controlled by fault creep i e a near continuous stable sliding at a mean slip rate of 2 8 cm yr punctuated by aseismic displacement episodes the analysis of the strain tensor calculated from the edm and gps data indicates that deformation in the fault zone is related to a clear sinistral strike slip movement a more complete picture is obtained from the gps measurements for the rocca campana area where the main structure branches out eastward into a splay fault the inversion of 3d displacement vectors suggests a deformation model consisting of two principal sinistral strike slip faults with an oblique component of movement the maximum observed displacement 6 1 cm measured in the period april 1997 february 1999 is accommodated by the splay fault this finding corroborates the hypothesis that as proposed by the tectonic models in the literature the movement of the eastern segment of the pernicana fault is transferred easterly towards structures at a lower altitude along the same strike e g the fiumefreddo fault as a consequence the pernicana fault may constitute part of a continuous left lateral trans current zone which displaces the whole north eastern flank of mt etna

fem based inversion for heterogeneous fault mechanisms application at etna volcano by dinsar data summary a procedure based on the finite element method fem for high resolution geodetic data inversion was developed to estimate non uniform slip distribution during the 2002 september 22 m3 7 earthquake rupture occurring only one month before the 2002 2003 eruption of etna volcano fem generated synthetic green s functions are combined with an inverse algorithm to simulate deformation of the earthquake for a 3 d problem domain that takes into account heterogeneity of material properties in the volcanic edifice the inversion of dinsar data shows complex kinematics of the northeastern flank of the etna volcano involving the pernicana fault system we detailed the coseismic shear rupture mechanism and highlighted a tensile mechanism never observed before related to a first attempt of magma intrusion which preceded the following october 26 eruption

ground deformation modeling of flank dynamics prior to the 2002 eruption of mt etna on 22 september 2002 1 month before the beginning of the flank eruption on the ne rift an m 3 7 earthquake struck the northeastern part of mt etna on the westernmost part of the pernicana fault in order to investigate the ground deformation pattern associated with this event a multi disciplinary approach is presented here just after the earthquake specific gps surveys were carried out on two small sub networks aimed at monitoring the eastern part of the pernicana fault and some baselines belonging to the northeastern edm monitoring network of mt etna were measured the leveling route on the northeastern flank of the volcano was also surveyed furthermore an investigation using sar interferometry was performed and also the continuous tilt data recorded at a high precision sensor close to the epicenter were analyzed to constrain the coseismic deformation the results of the geodetic surveys show a ground deformation pattern that affects the entire northeastern flank of the volcano clearly shaped by the pernicana fault but too strong and wide to be related only to an m 3 7 earthquake leveling and dinsar data highlight a local strong subsidence up to 7 cm close to the pernicana fault significant displacements up to 2 cm were also detected on the upper part of the ne rift and in the summit craters area while the displacements decrease at lower altitude suggesting that the dislocation did not continue further eastward three dimensional gps data inversions have been attempted in order to model the ground deformation source and its relationship with the volcano plumbing system the model has also been constrained by vertical displacements measured by the leveling survey and by the deformation map obtained by sar interferometry

dynamics of mount etna before during and after the july august 2001 eruption inferred from gps and differential synthetic aperture radar interferometry data we acknowledge the istituto nazionale di geofisica e vulcanologia the italian dipartimento per la protezione civile and the european community contract ingv dpc ur v3 6 36 and volume project for their economic contribution to this research the sar data are provided by esa esrin

importance of gravitational spreading in the tectonic and volcanic evolution of mount etna the interaction between gravity and thermal effects largely determines the structural and magmatic evolution of volcanic constructs at scales spanning several orders of magnitude from small cones to the oceanic crust1 3 although gravitational spreading is a direct consequence of this interaction and a fundamental process in volcano growth it is rarely recognized as such here we describe a striking example of this process at etna volcano in italy the volcano and its clay rich substratum are slowly spreading towards the east and south driven by gravity spreading produces extensional structures in the summit region and contpressional structures at the base of the volcano eastward movement of the volcanic edifice over a stationary magma supply may be the cause of an apparent westward migration of volcanic activity as gravitational spreading seems to control the location and magnitude of shallow seismicity and flank eruptions an appreciation of its effects could become an essential element of future volcanic hazard evaluation our model proposed here for etna may also be relevant to a reinterpretation of the geological history of a number of other volcanoes

time dependent deformation of the eastern flank of mt etna after slip or viscoelastic relaxation abstract major results of post intrusive gps monitoring of the 5 months encompassing and following the onset of 2002 03 mt etna eruption are presented and discussed here the overall ground deformation pattern is characterized by a time dependent relaxation function we evaluated two different parametrizations of relaxation functions each one linked to a different relaxation process i viscoelastic relaxation and ii after slip mechanism the former indicated that the process occurred within a weak layer characterized by viscosity values ranging between 7 1 1014 pa s and 1 3 1015 pa s the latter evidenced that frictional processes occurred beneath a layer of velocity strengthening having a thickness with values ranging between 0 4 km and 1 7 km either model may explain the observed time dependent deformation both from the statistical point of view and the comparison with geologic and seismic information although we are unable to favour one model rather than the other these results indicate that the mechanism responsible for the observed post intrusive deformation occurs within a sliding zone located inside the clayey sedimentary basement

magma faults and gravitational loading at mount etna the 2002 2003 eruptive period 1 mount etna is characterized by a complex structural setting that influences its evolution in order to understand how the interaction between dike forming intrusions and faulting influences the kinematics of the volcanic edifice we developed a numerical model it takes account of the topography the medium heterogeneities the gravitational loading and the most active crustal discontinuities a parameterization of the apparent coefficient of friction as a function of the depth has been considered in the range from 0 01 to 0 5 the density values used young s modulus and poisson s ratio range from about 1700 to 3200 kg m3 8 5 to 140 gpa and 0 15 to 0 35 respectively the model was applied to the 2002 2003 etna eruption the resulting deformation pattern was in agreement with the data provided by the continuous gps stations and the seismological knowledge obtaining displacements up to 1 m some discrepancies between the recorded ground deformation field and the modeled displacements allowed us to make some hypotheses on the volcano tectonic e g for the pernicana fault or regional tectonic origin acireale s alfio fault system of the crustal discontinuities moreover our results suggested that the pernicana fault is characterized by a very low apparent coefficient of friction less than 0 1 furthermore we evaluated the contribution of the gravitational loading and found that it implies a variation of about 10 of the overall deformation pattern our results clearly showed that the weight of the volcanic edifice acts in opposition to the magmatic intrusions conversely we found that the presence of medium heterogeneities may favor the eastern flank movements toward the se and the spreading of the summit area playing a fundamental role in ascending magma finally we investigated the shallow sliding model and found that dike forming intrusions produce negligible displacements less than 1 mm along the subhorizontal detachment surface therefore the gravitational loading during dike forming intrusions is not able to trigger sliding processes along this plane

stick slip vs stable sliding fault behaviour a case study using a multidisciplinary approach in the volcanic region of mt etna italy abstract in active volcanic zones fault dynamics is considerably fast but it is often difficult to separate the pattern of nearly continuous large scale volcanic processes inflation deflation processes flank instability from impulsive episodes such as dyke intrusions or coseismic fault displacements at etna multidisciplinary studies on active faults whose activity does not strictly depend on volcanic processes are relatively few here we present the case study of the san leonardello fault an active structure located in the eastern flank of mt etna characterised by a well known seismic history this fault saw renewed activity in may 2009 when pre seismic creeping along the southern segment preceded an mw 4 0 earthquake in the northern segment followed by some twenty five aftershocks later in march april 2016 creep events reactivated the southern section of the same fault both the seismic and aseismic phenomena were recorded by the seismic and gnss networks of ingv osservatorio etneo and produced surface faulting that left a footprint in the pattern of ground deformation detected by the insar measurements we demonstrate that the integration of multidisciplinary data collected for volcano surveillance may shed light on different aspects of fault dynamics and allow understanding how coseismic slip and creep alternate in space and time along the strike moreover we use findings from our independent datasets to propose a conceptual model of the san leonardello fault taking into account behaviour and previous constraints from fault based seismic hazard analyses although the faulting mechanisms described here occur at a very small scale compared with those of a purely tectonic setting this case study may represent a perfect natural lab for improving knowledge of seismogenic processes also in other fault zones characterised by stick slip vs stable sliding fault behaviour

inferences drawn from two decades of alinement array measurements of creep on faults in the san francisco bay region we summarize over 20 years of monitoring surface creep on faults of the san andreas system in the san francisco bay region using alinement arrays the san andreas fault is fully locked at five sites northwest from san juan bautista the southern end of the 1906 earthquake rupture that is no creep 1 mm yr is observed likewise the san gregorio rodgers creek and west napa faults show no creep the measured creep rate on the calaveras paicines fault from hollister southward is either 6 or 10 mm yr depending on whether the arrays cross all of the creeping traces northward of hollister the central calaveras creep rate reaches 14 2 mm yr but drops to 2 mm yr near calaveras reservoir where slip transfers to the southern hayward fault at a maximum creep rate of 9 mm yr at its south end however the hayward fault averages only 4 6 mm yr over most of its length the northern calaveras fault now creeping at 3 4 mm yr steps right to the concord fault which has a similar rate 2 5 3 5 mm yr which is slightly slower than the 4 4 mm yr rate on its northward continuation the green valley fault the maacama fault creeps at 4 4 mm yr near ukiah and 6 5 mm yr in willits the central and southern segments of the calaveras fault are predominantly creeping whereas the hayward northern calaveras and maacama faults are partly locked and along with the rodgers creek and san andreas have high potential for major earthquakes manuscript received 6 november 2002

large scale ground deformation of etna observed by gps between 1994 and 2001 we have processed thirty global positioning system gps campaigns carried out at etna from 1994 to early 2001 between the last two main flank eruptions of the mt etna sicily italy this rest period allowed us to investigate the deep magma plumbing system of the mt etna the temporal dynamics of twenty three points observed three times or more were analyzed all the time series show a first order linear trend during the five years period it suggests that the volcano was continuously deformed by the action of a deep source while a discrete activity of the volcano was observed at the summit we have interpreted the residual deformation field as the result of an major eastward motion of the eastern flank of the volcano

seismo tectonic behavior of the pernicana fault system mt etna a gauge for volcano flank instability 1 flank instability at basaltic volcanoes is often related to repeated dike intrusions along rift zones and accompanied by surface fracturing and seismicity these processes have been mostly studied during specific events and the lack of longer term observations hinders their better understanding here we analyze 20 years of deformation of the pernicana fault system pfs the key structure controlling the instability of the eastern flank of mt etna we exploit east west and vertical components of mean deformation velocity as well as corresponding time series computed from ers envisat 1992 2010 and cosmo skymed 2009 2011 satellite radar sensors via synthetic aperture radar interferometry techniques we then integrate and compare this information with field seismic and leveling data collected between 1980 and 2012 we observe transient displacements accompanied by seismicity overprinted on a long term background eastward motion 2 cm yr in the last decades these transient events were preceded by a constant amount of accumulated strain near the pfs the time of strain accumulation varies between a few years and a few decades also depending on magma emplacement within the nearby north east rift which may increase the strain along the pfs these results suggest that the amount of deformation near the pfs may be used as a gauge to forecast the occurrence of instability transients on the eastern flank of etna in this context the pfs may provide an ideal small scale structure to test the relations between strain accumulation stress loading and seismic energy release

twenty years of paleoseismology in italy abstract italy has one of the most complete and historically extensive seismic catalogues in the world due to a unique and uninterrupted flow of written sources that have narrated its seismic history since about the end of the iron age seismic hazard studies have therefore always been mainly based upon this huge mass of data nevertheless the italian catalogue probably lacks many m 6 5 events the seismogenetic structures responsible for which are characterized by recurrence times that are longer than the time span covered by our historical sources for these reasons and as in other countries earthquake data that in italy have been derived from paleoseismological studies should finally become a necessary ingredient in seismic risk assessment indeed over the past 20 years some hundred trenches have been excavated supplying reliable and conclusive data on the recent activities of many faults through to many robust datings of surface fault events these studies have provided the ages of several unknown or poorly known m 6 5 earthquakes here we summarize the state of the art of paleoseismology in italy and present a first catalogue of 56 paleoearthquakes pci that occurred mainly in the past 6 kyr the pci integrates the historical instrumental seismic catalogue and extends it beyond the recurrence time of the seismogenetic faults 2000 1000 yr we feel confident that the use of the pci will enhance future probabilistic seismic hazard assessment and thus contribute to more reliable seismic risk mitigation programs

analysis of satellite and in situ ground deformation data integrated by the sistem approach the april 3 2010 earthquake along the pernicana fault mt etna italy case study abstract etna is known worldwide as one of the most studied and monitored active volcanoes flank instability along the eastern and southern portions of mt etna has been observed and measured thanks to geodetic networks and insar data analysis the spreading area is bordered to the north by the east west pernicana fault system pfs whose dynamics is often linked with the eruptive activity as recently observed during the 2002 2003 eruption a seismic sequence occurred from april 2 3 2010 along the pfs with very shallow a few hundred meters mainshocks of magnitude 4 3 and 3 6 explosions and ash emissions at the summit craters followed this swarm culminating a few days later april 7 8 despite their small magnitude the earthquakes caused damage and significant surface fracturing along the pfs in order to investigate and measure the deformations in the near field of the earthquakes the sistem integration approach has been exploited the sistem enabled integrating geodetic in situ ground deformation measurements gps and leveling with satellite interferometric measurements envisat and alos in order to obtain high resolution 3d displacement maps allowing to overcome the limitations of each technique and take advantage of the particular features of each of them the integrated ground deformation field evidenced that the medium behave elastically we inverted the sistem results using an optimization algorithm based on the genetic algorithm ga in order to model the kinematics of the pfs associated to seismic swarm the results are in good agreement with the field evidence and improved the knowledge on the kinematics of the pfs and mt etna s unstable flank

dynamics of fault creep observations along the surface traces of active faults in california and elsewhere indicate that tectonic displacement can occur as seismic slip or as aseismic fault creep fault creep occurs as secular displacement and as displacement episodes called creep events which last a few hours to days and include from a millimeter or less to a few tens of millimeters of displacement instrumental measurements of displacement versus time during creep events show that many events have a characteristic simple form including a steep beginning followed by a gradual decay in the rate of displacement some creep events display small amounts of precursory slip and many seem to be composed of several discrete simple events propagation of creep events along the san andreas calaveras and imperial faults in california has been inferred from the nearly simultaneous observation of creep events at nearby creepmeters and from kinematic modeling of continuous measurements of strain during creep events fault creep can be viewed as arising from the interplay of three factors stress applied to the fault from external sources stress caused by the geometry and distribution of displacement on the fault arising from the elastic response of the surrounding medium to the displacements within the anelastic fault zone itself and the constitutive relations characterizing the resistance to slip on the fault analytic solutions are presented for a simple rectangular dislocation quasi static model of nonpropagating fault creep assuming viscous and quasi plastic power law creep fault zone rheology and for a multi element composed of several rectangular or striplike dislocation surfaces quasi static model assuming a viscous rheology viscous rheology implies solutions composed of exponentials that decay with time the simple one element quasi plastic model is in agreement with the form of creep events observed at melendy ranch california a matrix formulation is presented to calculate dislocation stresses on a fault zone in a half space or plate the formulation involves the division of the dislocation surface into strips or rectangles and the use of published solutions to calculate the stress resulting from displacement on each individual element results from the matrix method agree with analytic results for equilibrium displacements on stress free cracks the matrix formulation is then used as the basis for a numerical method to simulate one and two dimensional propagating creep assuming a quasi plastic rheology on the fault zone results from this method agree reasonably well with observations of afterslip from the 1966 parkfield 1975 oroville and 1979 imperial valley california earthquakes and of a propagating creep event observed along the southern calaveras fault central california during july 1977 this method of analysis and the assumption that creep at each point on the fault zone follows a power law rheology after the applied stress reaches a spatially varying yield stress can explain the secular and episodic nature of fault creep afterslip the simple shape of some individual events and the multiple composite shape of others and the propagation of creep events on the southern calaveras fault observations of propagating creep indicate a yield stress near zero at the surface and throughout much of the fault zone however they also indicate the presence of a zone at a depth of about 0 5 km and about 5 km long with a yield stress of about 15 bars 1 5 mpa the methods of solution presented here should be applicable to many problems in the dynamics of faulting

late palaeozoic global changes affecting high latitude environments and biotas an introduction abstract the late palaeozoic ice age lpia spanning approximately from 320 ma serpukhovian late mississippian to 290 ma mid sakmarian early permian represents the vegetated earth s largest and most long lasting regime of severe and multiple glaciations involving processes and patterns probably comparable to those of the last ice age accompanying the lpia occurred a number of broadly synchronous global environmental and biotic changes these global changes as briefly reviewed and summarized in this introductory paper comprised but are not limited to the following massive continental reorganization in the lead up to the final assembly of pangea resulting in profound changes in global palaeogeography palaeoceanography and palaeobiogeogarphy substantially lowered global atmospheric carbon dioxide concentrations p co 2 coupled with an unprecedented increase in atmospheric oxygen concentrations reaching earth s all time high in its last 600 million year history sharp global temperature and sea level drops albeit with considerable spatial and temporal variability throughout the ice age and apparently a prolonged period of global sluggish macro evolution with both low extinction and origination rates compared to other times in the aftermath of the lpia the world s climate entered into a transitional climate phase through the late early to middle permian before its transformation into a greenhouse state towards the end permian in recent years considerable amount of data and interpretations have been published concerning the physical evidence in support of the lpia its broad timeframe and eustatic and ecosystem responses from the lower latitudes but relatively less attention has been drawn to the impact of the ice age on late palaeozoic high latitude environments and biotas it is with this mission in mind that we have organized this special issue with the central focus on late palaeozoic high latitude regions of both hemispheres that is gondwana and northern eurasia our aim is to gather a set of papers that not only document the physical environmental changes that had occurred in the polar regions of gondwana and northern eurasia during the lpia but also review on the biotic responses at different taxonomic ecological and spatial scales to these physical changes in a refined chronological timeframe this introductory paper is designed to provide a global context for the special issue with a brief review of key late palaeozoic global environmental changes including changes in global land sea configurations atmospheric chemistry global climate regimes global ocean circulation patterns and sea levels and large scale biotic biogeographic and evolutionary responses followed by a summary of what we see as unresolved scientific issues and various working hypotheses concerning late palaeozoic global changes and in particular the lpia as a possible reference to future research

a review of permian stratigraphy palaeobiogeography and palaeogeography of the qinghai tibet plateau the permian marine lithostratigraphy biostratigraphy and faunal compositions among all the major tectonic blocks in the qinghai tibet plateau are synthesised based on published literature authors unpublished data and field observations palaeobiogeographically the permian marine faunas in the qinghai tibet plateau can be assigned to four biotic provinces cathaysian indoralian cimmerian and himalayan provinces as well as a broad south transitional zone for parts of the permian the qamdo block clearly belongs to the cathaysian province as it is characterised by a lack of glacial deposits and a dominance of warm water faunas during the whole permian the qiangtang block lhasa block and the himalaya tethys zone in southern tibet can be grouped into the south transitional zone during the cisuralian which is characterised by the combination of the bivalve eurydesma the brachiopods cimmeriella bandoproductus and the fusuline monodiexodina the south transitional zone gave birth to the cimmerian province as shown in the qiangtang and lhasa blocks from roadian to capitanian during which its faunas were characterised by an admixture of cold and warm water elements supplemented by a limited number of endemic taxa such as the fusuline eopolydiexodina the non fusuline foraminifer shanita hemigordiopsis assemblage and the coral thomasiphyllum the formation and development of the south transitional zone and the cimmerian province is interpreted to be closely linked to and driven by the northward drift of the cimmerian continent superimposed with a gradual global warming in the wake of gondwanan deglaciation the consequently combined effects of these events forced the climate of the drifting peri gondwana blocks to ameliorate and its marine faunas to transform from an essentially cold water gondwanan type in the early cisuralian through a transitional stage to a predominantly warm water cathaysian type by the lopingian the himayala tethys zone in southern tibet is assigned to the himalayan province from late guadalupian to lopingian and identified by persistent occurrences and dominance of cold water brachiopods and corals both the permian sedimentary sequences and faunal successions are strongly different between the qamdo block and the qiangtang block this is taken to suggest that the longmu co shuanghu lancangjiang suture between the two blocks most likely represents the main branch of the palaeotethys suture in tibet a comparison and correlation of permian sequences and faunas between tibetan blocks and adjacent blocks in western yunnan indicates that the qiangtang block should be aligned with the baoshan block whereas the lhasa block more closely related to the tengchong block further comparison and correlations of permian stratigraphy and faunas of all major peri gondwana blocks suggest that they probably constituted three different continental slices rather than one as perceived in some previous literature the first slice is composed of central pamir the qiangtang block and the baoshan block the second slice consists of south pamir karakorum south afghanistan central iran and turkey these two continental slices are both characterised by a continuously active rifting event from artinskian to guadalupian by contrast the third slice is interpreted to consist of the lhasa block the tengchong block and the sibumasu block none of which has late cisuralian rift related basalts the baoshan block and the lhasa block are thought to have initially early cisuralian intersected probably at a triple junction point close to western australia and were then rifted off from gondwana at different times during the permian

fast deformation processes and eruptive activity at mount etna italy the seismic and deformation patterns observed on mount etna before and during the 1991 1993 eruption the third largest since the seventeenth century in terms of lava volume are consistent with the regional tectonic framework of eastern sicily the pattern of the stress field acting on the intermediate and lower crust was defined at the local scale by focal mechanisms of microearthquakes occurring at depths between 10 and 25 km beneath the volcano they provide evidence for a strike slip compressional stress regime with the maximum compressive component acting approximately n s the fault plane solutions and the spatial and temporal distribution of seismicity indicate that usually sinistral shear ruptures occur along approximately ne sw trending fault zones while dip slip ruptures affect approximately nnw sse trending fault zones the latter include the avenues along which magma ascended during the 1991 1993 eruption seismic observations indicate a local inversion of the stress field acting on the upper crust depth 10 km underlying mount etna which was initiated less than 2 months before the eruptive event and disappeared with its end this is consistent with a local tensile regime that favored the magma ascent through the shallow crust the events preceding the eruption and accompanying its onset tilt anomalies and seismic swarms and those occurring shortly after its beginning a mainshock aftershock seismic sequence and associated coseismic tilts provide important evidence for understanding the dynamics of the two main volcano tectonic structures ne sw and nnw sse trending fault zones and associated intrusive mechanisms on etna the shape and location of the eruption feeding dike have been modeled from ground deformation data this approximately nnw sse modeled dike the seismicity and the position of the fractures are consistent with the regional stress field characterized by 1 oriented approximately n s the geophysical data presented and analyzed in the present paper strongly suggest an overall regional tectonic control as well as an active role for the intruding magma in the dynamics of the volcano

control of rock rheology on deformation style and slip rate along the active pernicana fault mt etna italy abstract the already known part of the active left lateral strike slip pernicana fault on the eastern flank of mt etna volcano has a holocene high slip rate of 1 5 2 7 cm yr but its surface trace abruptly disappears eastward approaching the lower slope of the volcano using geological geomorphological and structural surveys we found that the pernicana deformation zone extends 8 km further to the east beyond this point through a different mechanism as the thickness of the volcanic pile decreases the single e w to ese striking main fault plane gives way to a set of faults arranged in a splay structure which partitions the fault motion here slip rates are 0 4 to 1 4 cm yr on each fault further east where the lava succession is very thin and unfaulted we suggest that lavas are decoupled from plastic deforming sub etnean clay deposits which absorb the strain or that lavas have a too low mass to slide on the very lowest slope of the volcano i e further east lavas are once again thicker and the pernicana deformation zone behaves at the surface once again in a brittle manner locally known as the fiumefreddo fault with a low slip rate of

age of initiation of collision between india and asia a review of stratigraphic data abstract the collision of india with asia is perhaps the most profound tectonic event to have occurred in past 100 ma it is responsible for the uplift of the himalayas and tibetan plateau and has been argued to have been responsible for geological geochemical and climatological consequences of global extent yet the age of initiation of this collision remains poorly constrained the literature is replete with estimates that range from the late cretaceous 65 ma to latest eocene

modeling of alos and cosmo skymed satellite data at mt etna implications on relation between seismic activation of the pernicana fault system and volcanic unrest abstract we investigate the displacement induced by the 2 3 april 2010 seismic swarm the largest event being of ml 4 3 magnitude by means of dinsar data acquired over the volcano by the cosmo skymed and alos radar systems satellite observations combined with leveling data allowed us to perform a high resolution modeling inversion capable of fully capturing the deformation pattern and identifying the mechanism responsible for the pfs seismic activation the inversion results well explain high gradients in the radar line of sight displacements observed along the fault rupture the slip distribution model indicates that the fault was characterized by a prevailing left lateral and normal dip slip motion with no fault dilation and hence excludes that the april 2010 seismic swarm is a response to accommodate the stress change induced by magma intrusions but it is due to the tectonic loading possibly associated with sliding of the eastern flank of the volcano edifice these results provide a completely different scenario from that derived for the 22 september 2002 m3 7 earthquake along the pfs where the co seismic shear rupture was accompanied by a tensile mechanism associated with a first attempt of magma intrusion that preceded the lateral eruption occurred here a month later these two opposite cases provide hints into the behavior of the pfs between quiescence and unrest periods at etna and pose different implications for eruptive activity prediction and volcano hazard assessment the dense pattern of ground deformation provided by integration of data from short revisiting time satellite missions together with refined modeling for fault slip distribution can be exploited at different volcanic sites where the activity is controlled by volcano tectonic interaction processes for a timely evaluation of the impending hazards

tethyan uppermost permian dzhulfian and dorashamian foraminiferal faunas and their paleogeographic and tectonic implications abstract the foraminiferal faunas and biostratigraphic correlation of the tethyan uppermost permian dzhulfian and dorashamian provide important paleogeographic and tectonic data for the interpretation of the palaeofusulina bearing terranes in east and southeast asia these interpretations have a significant bearing on understanding japanese pre cretaceous tectonostratigraphic and micropaleontologic data as well as the geodynamic evolution of the japanese palaeofusulina bearing terranes the tethyan foraminiferal fauna in the uppermost permian is characterized by the occurrence of provincial and endemic schubertellid genera and the absence of neoschwagerinids and verbeekinids which had characterized the rapidly evolving middle permian tethyan marine faunas until their extinction at the end of the midian difficulties in world wide correlation of the uppermost permian have resulted because of different geographic faunal compositions and the geographic patterns of extinction of permian marine faunas the palaeofusulina fauna is one of the most reliable indicators of the uppermost permian its presence or absence serves as paleogeographic constraints on east and southeast asian terranes for example the absence of palaeofusulina fauna and the presence of late midian lepidolina multiseptata faunas in the lhasa terrane in tibet and the wolya terrane in sumatra the third continental sliver north of gondwana are important particularly for identifying the rift drift collision process of the gondwana affinity terranes they suggest a late permian separation of the two terranes from gondwana tethyan palaeofusulina occur in the latest permian tropical to subtropical latitudinal belt and along with other geologic data assist in paleogeographic reconstructions and in interpreting the possible movement and emplacement of the palaeofusulina bearing terranes such as the maizuru south kitakami kurosegawa and chichibu terranes in japan they reveal that 1 the upper permian maizuru group was deposited on the eastern continental margin of south china 2 the occurrence of the lower permian cathaysian flora and a number of geologic data in the south kitakami kurosegawa suggest an arc trench system setting and the late permian deposition in a shallow open marine environment in proximity to south china 3 foraminiferal biogeograpic data and the reconstructed oceanic plate stratigraphy in the chichibu terrane constrain the location of the chichibu seamount chains to the western part of the panthalassan domain as they moved westwards against the cathaysian continent until their jurassic accretion

compared geochemical signatures and the evolution of menez gwen 37 50 n and lucky strike 37 17 n hydrothermal fluids south of the azores triple junction on the mid atlantic ridge during the diva 1 cruise in may 1994 a series of 19 dives was conducted using the french submersible nautile at the topographic highs of three volcanic segments centered at 37 17 n 37 50 n and 38 20 n respectively south of the azores triple junction atj on the mid atlantic ridge mar hydrothermal fluids were collected at the lucky strike ls hydrothermal field discovered at 37 17 n in 1993 and at a new hydrothermal site called menez gwen mgw discovered at 37 50 n during this cruise both systems are relatively shallow compared to other mar systems with seafloor depths of 1700 and 850 m respectively characteristics which make them unique among the already known sites on the mar the characteristics of the ls fluids are the same as in 1993 and include temperatures ranging from 170 c to 324 c variable chlorinities lower than seawater low hydrogen sulfide 3 0 mmol kg high ba concentrations up to 80 mol kg low metal concentrations and high gas contents and distinct chemical end members indicative of significant geographic control of the venting system in contrast the very clear mgw fluids at 37 50 n show a rather uniform exit temperature 285 c and chemical compositions with chlorinities 360 380 mmol kg lower than at ls and corresponding lower concentrations of cations h2s 1 8 mmol kg metals and silica 8 11 5 mmol kg due to the lower temperature t and pressure p of the system in the two systems fluid chemistry is strongly affected by phase separation at the low pressure conditions of these sites phase relations in the nacl h2o system dictate production of an extremely low salinity the higher salinities observed in fluids thus indicate that mixing of extremely low salinity vapor with single phase hydrothermal seawater is the dominant process controlling cl concentrations depletions and enrichments of elements in solutions are also explained by the involvement of fluid rock reactions the enrichment of ba k cs and rb in the fluids is linked to the enriched character of these elements in basalts relatively high ph and ca low li sr and metals are related to the highly altered basaltic substrate in the reaction zone low sr ca and high ca na ratios are explained by albitization within the crust the increase of degassing when approaching the azores may be related to the carbon enriched basaltic crust near the azores hot spot isotopic ratios show that co2 ch4 and helium gases have a magmatic signature compared to other deeper sites on the mar all fluids collected at ls and mgw are gas enriched except for h2s and helium whose both concentration and isotopic ratio compare well with other hydrothermal fluids the high ch4 concentration associated with unsaturated hydrocarbons and the high ch4 3he ratios also suggest a contribution of ch4 generated by serpentinization of ultramafic rocks by fischer tropsch catalysis of co2 reduction

the permian antitropical fusulinoidean genus monodiexodina distribution taxonomy paleobiogeography and paleoecology all the documented occurrences with illustration of specimens of the permian fusulinoidean genus monodiexodina from a total of 33 areas in 11 regions are reviewed and their taxonomic positions are reexamined in this paper among 17 species including two subspecies of monodiexodina in the current taxonomy the following 10 species are recognized as valid m kattaensis m wanneri m caracorumensis m sutchanica m shiptoni m kumensis m wanganensis m neimongolensis m delicata and m rhaphidoformis in addition species once referred to monodiexodina but now should be excluded from the genus are also investigated in terms of their generic positions in reconstructed mid permian paleomap monodiexodina bearing areas can be restored to either northern or southern middle latitudes between high latitudinal cool cold water climatic realm and paleo tropical warm water realm these two middle latitudinal areas each corresponding to the northern and southern transitional zones respectively can be best interpreted climatologically as mesothermal warm temperate belts in both hemispheres thus suggesting the genus to be a paleobiogeographically typical antitropical fusulinoidean taxon moreover the genus is generally found in a monotypic crowded manner in sandy sediments with their shells being often aligned uni directionally this mode of occurrence of monodiexodina strongly suggests that it was adapted to shallow marine high energy environments which would probably be essentially maintained by the acquisition of highly elongated fusiform subcylindrical shells with well developed polar torsion this morphological feature is adapted to increase septal pores per unit area in polar regions thus increasing possibility to develop more pseudopodia on both sides of test it probably has a functional significance for not only locomotion but also anchoring their tests on the surface of bottom sediments in agitated water conditions the genus itself is considered to be a rather long ranging taxon from the late yakhtashian artinskian to the early midian capitanian it is therefore concluded that monodiexodina had an opportunistic character occurring repeatedly only when favorable high energy conditions such as sand shoal appeared in warm temperate climatic belts in both hemispheres monodiexodina originated in the southern transitional zone from an elongated eoparafusulina stock at late early permian around late artinskian time it flourished in southern middle latitudinal areas in latest early and early middle permian time the genus then migrated to the northern hemisphere northern transitional zone by some dispersion mechanism at around the early middle permian and prevailed there during the remaining period of the middle permian

thermal weakening of the carbonate basement under mt etna volcano italy implications for volcano instability abstract the physical integrity of a sub volcanic basement is crucial in controlling the stability of a volcanic edifice for many volcanoes this basement can comprise thick sequences of carbonates that are prone to significant thermally induced alteration these debilitating thermal reactions facilitated by heat from proximal magma storage volumes promote the weakening of the rock mass and likely therefore encourage edifice instability such instability can result in slow gravitational spreading and episodic to continuous slippage of unstable flanks and may also facilitate catastrophic flank collapse understanding the propensity of a particular sub volcanic basement to such instability requires a detailed understanding of the influence of high temperatures on the chemical physical and mechanical properties of the rocks involved the juxtaposition of a thick carbonate substratum and magmatic heat sources makes mt etna volcano an ideal candidate for our study we investigated experimentally the effect of temperature on two carbonate rocks that have been chosen to represent the deep heterogeneous sedimentary substratum under mt etna volcano this study has demonstrated that thermal stressing resulted in a progressive and significant change in the physical properties of the two rocks porosity wet i e water saturated dynamic poisson s ratio and wet vp vs ratio all increased whilst p and s wave velocities bulk sample density dynamic and static young s modulus dry vp vs ratio and dry dynamic poisson s ratio all decreased at temperatures of 800 c the carbonate in these rocks completely dissociated resulting in a total mass loss of about 45 and the release of about 44 wt of co 2 uniaxial deformation experiments showed that high in situ temperatures 500 c significantly reduced the strength of the carbonates and altered their deformation behaviour above 500 c the rocks deformed in a ductile manner and the output of acoustic emissions was greatly reduced we speculate that thermally induced weakening and the ductile behaviour of the carbonate substratum could be a key factor in explaining the large scale deformation observed at mt etna volcano our findings are consistent with several field observations at mt etna volcano and can quantitatively support the interpretation of 1 the irregularly low seismic velocity zones present within the sub volcanic sedimentary basement 2 the anomalously high co 2 degassing observed 3 the anomalously high vp vs ratios and the rapid migration of fluids and 4 the increasing instability of volcanic edifices in the lifespan of a magmatic system we speculate that carbonate sub volcanic basement may emerge as one of the decisive fundamentals in controlling volcanic stability