broadband waveform inversion of moderate earthquakes in the messina straits southern italy abstract we report the first application of the cut and paste cap method to compute earthquake focal mechanisms in the messina straits area by waveform inversion of pnl and surface wave segments this application of cap has furnished new knowledge about low magnitude earthquake mechanics that will be useful for improved understanding of the local geodynamics this is possible because the cap inversion technique can be applied to small earthquakes for which traditional moment tensor inversion methods are not appropriate and p onset focal mechanisms in the study area fail because of a lack of sufficient observations we estimate the focal mechanisms of 23 earthquakes with local magnitudes in the range of 3 4 occurring in the 2004 2008 time period and recorded by the broadband stations of the italian national seismic network and the mediterranean very broadband seismographic network mednet run by the istituto nazionale di geofisica e vulcanologia ingv the solutions show that normal faulting is the prevailing style of seismic deformation in the northern part of the study area while co existence of normal faulting and strike slip has been detected in the southern part in the whole area of investigation the t axes of focal mechanisms display a preferential northwest southeast direction of extension combined with the findings of previous investigations this improved database of focal mechanisms allows us to better detail the transitional area between the extensional domain related to subduction trench retreat southern calabria and the compressional one associated with continental collision western central sicily the observed spatial change of seismic deformation regime offers new data to current seismotectonic and seismic hazard investigations in the area of messina straits where a magnitude 7 2 earthquake caused more than 60 000 casualties on 28 december 1908

magma storage and ascent at lipari island aeolian archipelago southern italy at 223 81 ka the role of crustal processes and tectonic influence fluid inclusion studies together with volcanological and petrochemical data allow reconstruction of the magma feeding system of basaltic andesitic to andesitic activity during the oldest and intermediate stages of development of lipari island 223 81 ka a major magma storage zone is active during the overall investigated time span at depths of 22 km close to the crust mantle moho transition at which mantle derived mafic magmas tend to accumulate due to neutral buoyancy conditions beneath central type volcanoes m mazzacaruso m s angelo m chirica costa d agosto a shallower magma reservoir is located within the upper crust at 5 5 3 5 km associated with a major lithological discontinuity for fissural type volcanoes timpone ospedale monterosa m chirica tectonic structures are suggested to influence further magma ascent and storage at mid crustal depths 14 km with no ponding at shallower levels partial crustal melting processes at the roofs of the deep magma reservoirs 17 km are invoked to explain the origin of cordierite bearing lavas beneath m s angelo and m chirica costa d agosto volcanoes which were active during the intermediate stages of development of lipari 105 81 ka the generation of felsic anatectic melts in the lower crust could have created density and rheologic barriers to impede the passage of mafic melts and promote their ponding with influence on the subsequent evolution of lipari volcano

modeling the magma plumbing system of vulcano aeolian islands italy by integrated fluid inclusion geobarometry petrology and geophysics an integrated petrological geophysical and fluid inclusion model is presented for the internal structure of the active vulcano island southern tyrrhenian sea the present structure of the magma storage system in the crust consists of two major deep accumulation zones located at 17 21 km and 8 13 km depth plus a minor one at 1 5 km depth beneath fossa cone the deepest magma accumulation zone contains mafic melts and is located at the transition between the upper mantle and a granulitic lower crust this reservoir has been active since the onset of the exposed volcanism and has undergone continuous fractional crystallization crustal assimilation and mixing with primary melts from the mantle slightly differentiated magmas from the deep reservoir feed a shallower accumulation zone in the middle and upper crust or erupt directly to the surface through lateral vents deep melts probably enter the shallowest reservoir shortly before magma outbreak at the surface and may represent the trigger of eruptions according to our model magmatic eruptions at vulcano are related to deep magma dynamics whereas most of the changes in the geochemical and geophysical parameters observed at the active cone in the last century could be due to shallow depth modification of rock permeability possibly as a result of cone gravitative instability and or tectonic events implications for strategies of volcano monitoring and for forecasting eruptions are briefly discussed

lithospheric p and s wave velocity models of the sicilian area using wam tomography procedure and assessments we present 3 d models of the p and s wave velocity distributions in the crust and uppermost mantle beneath sicily calabria southern italy and surrounding submerged areas obtained by tomographic inversion of traveltimes of regional body waves phases our method combines double difference tomographic inversion with a post processing procedure weighted average model method wam this procedure was applied to a set of models consistent with the experimental data we tested the ability of the wam procedure to mitigate the uncertainty associated with the arbitrary nature of the many input parameters required for each inversion the local reliability and resolution of the obtained models have been assessed through syn thetic tests experimental tests carried out with independent data sets and unconventional tests based on the analysis of the internal consistency of the p and s velocity models the tomo graphic images provide a detailed sketch of p and s wave velocity anomalies these clearly show the shape of the sicilian maghrebian belt beneath sicily and calabrian arc at different depths low vp and vs bodies are imaged beneath stromboli and marsili volcanoes in the southern tyrrhenian whereas high and low seismic velocities alternate beneath the etna giving inferences on the possible depth of the mantle melting feeding the volcano in the upper crust the main sedimentary basins and tectonic features are also well imaged finally tomographic cross sections show the trend of the moho in the study area where its depth ranges between 35 and 40 km beneath the sicilian belt and between 15 and 22 km in the southern tyrrhenian basin and ionian sea

seismotomography of the crust in the transition zone between the southern tyrrhenian and sicilian tectonic domains 1 a crustal tomography of seismic wave velocity was performed in the contact zone between the southern tyrrhenian sicilian and ionian tectonic units a zone where the lithospheric structure can be expected to furnish evident signatures of dynamics related to the tyrrhenian subduction process a dataset of 10241 p and 5597 s readings from 932 local earthquakes recorded between 1978 and 2001 by stations operating in sicily and calabria was inverted by the simulps12 algorithm for simultaneous computation of hypocenter parameters and vp and vp vs three dimensional distributions the study brought significant improvement in the knowledge of the local velocity structure furnishing new information useful to better identify the local tectonic units the results appear to be compatible with the most recent hypotheses regarding the geodynamics of the study region

seismotectonics of the loma prieta california region determined from three dimensional v p v p v s and seismicity three dimensional vp and vp vs velocity models for the loma prieta region were developed from the inversion of local travel time data 21 925 p arrivals and 1 116 s arrivals from earthquakes refraction shots and blasts recorded on 1700 stations from the northern california seismic network and numerous portable seismograph deployments the velocity and density models and microearthquake hypocenters reveal a complex structure that includes a san andreas fault extending to the base of the seismogenic layer a body with high vp extends the length of the rupture and fills the 5 km wide volume between the loma prieta mainshock rupture and the san andreas and sargent faults we suggest that this body controls both the pattern of background seismicity on the san andreas and sargent faults and the extent of rupture during the mainshock thus explaining how the background seismicity outlined the along strike and depth extent of the mainshock rupture on a different fault plane 5 km away new aftershock focal mechanisms based on three dimensional ray tracing through the velocity model support a heterogeneous postseismic stress field and can not resolve a uniform fault normal compression the subvertical or steeply dipping san andreas fault and the fault surfaces that ruptured in the 1989 loma prieta earthquake are both parts of the san andreas fault zone and this section of the fault zone does not have a single type of characteristic event

the dynamics of back arc extension an experimental approach to the opening of the tyrrhenian sea the e w opening tyrrhenian sea developed after the cretaceous palaeogene alpine collision nearly perpendicular to the motion of the african plate as a back arc of the adria ionian westward subduction three driving mechanisms have been proposed to explain the dynamic evolution of the tyrrhenian apennine system 1 the northward indentation of the african plate 2 the retreating subduction of the adria ionian lithosphere and 3 the gravitational collapse of the alpine post collisional wedge in order to define the relative contribution of each of these mechanisms in the neogene dynamic of the tyrrhenian apennine system we performed 3 d laboratory experiments in which we simulated a retreating subduction process in a compressional regime oriented perpendicularly to the direction of subduction in this framework we also tested the influence of the gravitational collapse of the overriding plate experiments were constructed using dry sand and silicone putties to simulate brittle upper crust and ductile lower crust upper mantle respectively these layers floated on a high density low viscosity glucose syrup which simulated the asthenosphere the main conclusion of our experiments is that large scale continental extension similar to that observed in the tyrrhenian area could be reproduced perpendicular to the shortening direction induced by the indentation of the african plate in this framework extensional processes are indeed possible if the trench retreat velocity is higher than the rate of shortening induced by the advancing african plate our experimental results indicate that this high trench retreat velocity could be explained by the coexistence of the gravitational collapse of the post alpine wedge with a slab pull process linked to the retreating subduction of the adria ionian plate while the first mechanism is predominant in the northern tyrrhenian area the second one seems to be important in the latest stage of extension and oceanic accretion of the southern tyrrhenian area

crustal structure and seismicity of southern tyrrhenian basin abstract in this paper all the travel time data from crustal earthquakes that occurred in the period 1978 1991 along the southern tyrrhenian sea have been re examined in particular 410 local earthquakes recorded at a minimum number of seven seismic stations and 52 shots fired on sea have been utilized to infer a tomographic image of the velocity model beneath a region located in the domain 37 41 39 10 n and 14 10 16 44 e these earthquakes are selected from a database containing about 1000 local earthquakes the results from the inversion of about 9000 travel times confirm the strong lateral variations of the velocity model relative to compressional and shear waves below the volcanic center of the aeolian islands in the upper crust several low velocity bodies are found in agreement with features inferred from seismicity and other geophysical data the 3 d velocity images also show a thickening of the crust from the center of the tyrrhenian sea towards the coasts of sicily and calabria finally hypocenter locations derived from inversion which appear to be significantly less scattered than using 1 d velocity models help to identify with some accuracy two notable fault systems of the southern tyrrhenian basin

the ionian and alfeo etna fault zones new segments of an evolving plate boundary in the central mediterranean sea highlights plate boundary re organization in the central mediterranean sea segmentation of the subduction complex along lithospheric transverse faults step faults in the ionian sea pleistocene active faulting and mt etna formation abstract the calabrian arc is a narrow subduction rollback system resulting from africa eurasia plate convergence while crustal shortening is taken up in the accretionary wedge transtensive deformation accounts for margin segmentation along transverse lithospheric faults one of these structures is the nnw sse transtensive fault system connecting the alfeo seamount and the etna volcano alfeo etna fault aef a second nw se crustal discontinuity the ionian fault if separates two lobes of the ca subduction complex western and eastern lobes and impinges on the sicilian coasts south of the messina straits analysis of multichannel seismic reflection profiles shows that 1 the if and the aef are transfer crustal tectonic features bounding a complex deformation zone which produces the downthrown of the western lobe along a set of transtensive fault strands 2 during pleistocene times transtensive faulting reactivated structural boundaries inherited from the mesozoic tethyan domain which acted as thrust faults during the messinian and pliocene 3 the if and the aef and locally the malta escarpment accommodate a recent tectonic event coeval and possibly linked to the mt etna formation regional geodynamic models show that whereas aef and if are neighboring fault systems their individual roles are different faulting primarily resulting from the ese retreat of the ionian slab is expressed in the northwestern part of the if the aef on the other hand is part of the overall dextral shear deformation resulting from differences in africa eurasia motion between the western and eastern sectors of the tyrrhenian margin of northern sicily and accommodating diverging motions in the adjacent compartments which results in rifting processes within the western lobe of the calabrian arc accretionary wedge as such it is primarily associated with africa eurasia relative motion

continental heat anomalies and the extreme melting of the greenland ice surface in 2012 and 1889 recent decades have seen increased melting of the greenland ice sheet on 11 july 2012 nearly the entire surface of the ice sheet melted such rare events last occurred in 1889 and prior to that during the medieval climate anomaly studies of the 2012 event associated the presence of a thin warm elevated liquid cloud layer with surface temperatures rising above the melting point at summit station some 3212 m above sea level here we explore other potential factors in july 2012 associated with this unusual melting these include 1 warm air originating from a record north american heat wave 2 transitions in the arctic oscillation 3 transport of water vapor via an atmospheric river over the atlantic to greenland and 4 the presence of warm ocean waters south of greenland for the 1889 episode the twentieth century reanalysis and historical records showed similar factors at work however markers of biomass burning were evident in ice cores from 1889 which may reflect another possible factor in these rare events we suggest that extreme greenland summer melt episodes such as those recorded recently and in the late holocene could have involved a similar combination of slow climate processes including prolonged north american droughts heat waves and north atlantic warm oceanic temperature anomalies together with fast processes such as excursions of the arctic oscillation and transport of warm humid air in atmospheric rivers to greenland it is the fast processes that underlie the rarity of such events and influence their predictability

optimal tropical sea surface temperature forcing of north american drought abstract the optimal anomalous sea surface temperature sst pattern for forcing north american drought is identified through atmospheric general circulation model integrations in which the response of the palmer drought severity index pdsi is determined for each of 43 prescribed localized sst anomaly patches in a regular array over the tropical oceans the robustness and relevance of the optimal pattern are established through the consistency of results obtained using two different models and also by the good correspondence of the projection time series of historical tropical sst anomaly fields on the optimal pattern with the time series of the simulated pdsi in separate model integrations with prescribed time varying observed global sst fields for 1920 2005 it is noteworthy that this optimal drought forcing pattern differs markedly in the pacific ocean from the dominant sst pattern associated with el nino southern oscillation enso and also shows a large sensitivity of north american drought to

seismotectonics of the nubia plate compressive margin in the south tyrrhenian region italy clues for subduction inception 1 seismological and structural data are used to constrain the active tectonics of the nubia plate compressive margin in southern italy in this region compressional displacements have resumed at the rear of the maghrebian orogenic wedge since about 700 500 ka and are presently accommodated along a seismic belt in the south tyrrhenian area where a passive margin has developed during late neogene quaternary times earthquake data from the south tyrrhenian belt are analyzed with bayloc a probabilistic nonlinear location method results show that the seismic belt is segmented and involves a series of ne sw and nw se elongated clusters the ne sw clusters are interpreted as high angle reverse fault zones verging toward the southeast whereas the perpendicular clusters are interpreted as possible strike slip fault zones transferring the contractional displacements to advanced segments of the belt in the southeast brittle deformations observed in the quaternary volcanic island of ustica are consistent with the geometry and kinematics of the seismic belt deduced from the seismological data the south tyrrhenian active belt may constitute an early stage of subduction of the tyrrhenian oceanic crust beneath sicily a similar scenario has been hypothesized also for the westward prolongation of the south tyrrhenian belt off the algerian coast by integrating instrumental and historical seismic data with tectonic evidences we infer that the south tyrrhenian belt is probably capable of producing earthquakes with a maximum size close to magnitude 7 the analyzed data suggest a multifault system behavior for the studied compressional belt this inference is important to estimate and mitigate the seismic and tsunamic hazards in such a densely populated region

geophysical investigations of the plumbing system of stromboli volcano aeolian islands italy abstract in this work we report the results of an integrated approach using both seismological and geodetic data provided by the ingv ct istituto nazionale di geofisica e vulcanologia sezione di catania stromboli volcano monitoring systems in order to improve the knowledge of its plumbing system in particular we investigated the relationships between the june 1999 seismic swarm occurring in the area of stromboli and the possible activation of the ne sw oriented volcano tectonic structure we analyzed this seismic swarm proposing new locations and a morphological analysis of the waveforms this approach allowed us to demonstrate that there are relationships between the tectonic activity near stromboli and the rising of magma this evidence supports the hypothesis that during the 1999 swarm an intrusive process started from a crustal level where earthquakes were located about 10 15 km b s l as already testified by other similar episodes deformation anomaly recorded between december 1994 and march 1995 after the november 1994 swarm months after the 1999 seismic activity the tiltmeters and the gps permanent stations deployed in stromboli showed slow variations over three months may july 2000 we performed an analytical inversion of these geodetic observations and found that the modelled sources are characterized by ne sw trend compatible with the regional faults cutting the volcano the modelled sources could represent the rising pathway connecting the deep plumbing system about 10 15 km b s l to the shallow one located in the body of the stromboli volcano about 500 m a s l these new evidences support the hypothesis of the existence of a simple plumbing system with different levels of magma storage where batches of magma are periodically pushed up along the main ne sw tectonic trend

travel time residuals and three dimensional velocity structure of italy jeffreys bullen p and pkp travel time residuals observed at more than 50 seismic stations distributed along italy and surrounding areas in the time interval 1962 1979 indicate the complex velocity pattern of this region strong lateral velocity inhomogeneities and low velocity zones are required to explain the observed pattern of residuals in particular late arrivals of about 1 sec are observed in the apenninic mountain range requiring both greater crustal thickness and low velocity layers coherent with seismic refraction data and surface wave dispersion measurements the seismic stations located in the western and eastern alps indicate the presence of high velocities in the western alps the strong azimuthal variation of residuals and the high values of early arrivals have a close relationship to the ivrea body an intrusive crustal complex characterized by a velocity as high as 7 7 2 km sec a travel time inversion performed with theaki et al 1977 block model confirms the peculiar characteristics and the sharp variations in the lithosphere of the whole italian region with values of velocity perturbations between many adjacent blocks ranging in size from 50 to 100 km and independent from the earth parametrization chosen reaching values up to 10 in the lithospheric part and 5 in the asthenosphere 3 d inversion requires also high velocity along the tyrrhenian coastal margin equivalent to an uprise of major crustal and lithospheric discontinuities along this part of the italian peninsula moreover low velocity material must be present in the northern part of the adriatic foreland in the lithosphere asthenosphere system closely related to the stress and seismicity pattern and the lateral bending of the lithosphere in the same region

regional deformation and offshore crustal local faulting as combined processes to explain uplift through time constrained by investigating differentially uplifted late quaternary palaeoshorelines the foreland hyblean plateau se sicily

factors determining the extratropical response to equatorial diabatic heating anomalies abstract the steady linear response of a spherical baroclinic atmosphere to an equatorial diabatic heat source having a simple horizontal and vertical structure is examined this source is imposed upon representative zonally symmetric as well as zonally varying flows during the boreal winter two climatologies are considered one is a 6 year average of global observations analyzed at the european centre for medium range weather forecasts ecmwf the other is a 30 year average taken from a general circulation model gcm run at the geophysical fluid dynamics laboratory in princeton the extratropical response is found to be very sensitive to the basic state around which the governing primitive equations are linearized and in the case of the ecmwf climatology to the longitudinal position of the source with respect to the climatological waves there is also some sensitivity to the vertical level of maximum heating although again this is more evident in the case of the ecmwf basic state these results ar

seismic character and progression of explosive activity during the 2016 2017 eruption of bogoslof volcano alaska bogoslof volcano in the central aleutian arc experienced a major eruption between december 2016 and august 2017 that was characterized by explosive activity volcanic explosivity index 2 to 3 and the extrusion of lava domes the alaska volcano observatory tracked the activity in real time using seismicity observed on distant stations as well as infrasound lightning satellite data and occasional visual observations in this study we measure the duration of seismic signals associated with individual explosive events to track their progression during the two explosive phases of the eruption seismic recordings of bogoslof explosions show complex waveforms that suggest both individual explosive events and sequences of several explosions separated by lower amplitude tremor the lack of local seismic monitoring stations at distances of 1 km to 15 km distance unfortunately limits our ability to closely observe seismicity and to interpret changing conditions at the vent such as position the presence of a lava dome or plug and the role of seawater associated with the eruption we use the rate of explosive activity seismic waveform character and repose time between explosions to infer the conditions within the conduit

on the mesozoic ionian basin summary new seismic reflection profiles of the italian deep crust project crop provide new insights on the structure of the ionian sea in spite of the apennines and hellenides neogene subduction zones two conjugate passive continental margins are preserved at the margins of the ionian sea along the malta escarpment to the southwest and the apulian escarpment to the northeast the ionian sea is likely to be a remnant of the mesozoic tethys ocean confined by these two conjugate passive continental margins the transition from continental to oceanic crust appears sharper to the northeast than to the southwest the basin between southeast sicily and southwest puglia was about 330 km wide and suggests a low spreading rate the inferred oceanic ridge should have been flattened by thermal cooling and buried by later sediments based on stratigraphic and structural constraints to the north in the apennines belt the ocean continued to the northwest this palaeogeography is supported by the seismicity of the apennines slab underneath the southern tyrrhenian sea which implies downgoing oceanic lithosphere the adjacent absence or paucity of deep seismicity does not imply absence of subduction but rather it can be interpreted as due to the more ductile behaviour of the subducted continental lithosphere surprisingly we note that where the oceanic inherited basin is subducting underneath the apennines in the hangingwall of the subduction hinge there are outcropping slices of continental crystalline basement previously deformed by the alpine orogen

global atmospheric sensitivity to tropical sst anomalies throughout the indo pacific basin abstract the sensitivity of the global atmospheric response to sea surface temperature sst anomalies throughout the tropical indian and pacific ocean basins is investigated using the ncep mrf9 general circulation model gcm model responses in january are first determined for a uniform array of 42 localized sst anomaly patches over the domain results from the individual forcing experiments are then linearly combined using a statistically based smoothing procedure to produce sensitivity maps for many target quantities of interest including the geopotential height response over the pacific north american pna region and regional precipitation responses over north america south america africa australia and indonesia perhaps the most striking result from this analysis is that many important targets for seasonal forecasting including the pna response are most sensitive to sst anomalies in the nino 4 region 5 n 5 s 150 w 160 e of the central tropical pacific with lesser and sometimes opposite s

p wave deep velocity structure of the southern tyrrhenian subduction zone from nonlinear teleseismic traveltime tomography a new 3 d model for the p wave velocity structure of the southern tyrrhenian subduction zone stsz is determined from nonlinear inversion of relative arrival times of teleseismic events the data used in the imaging are the travel time residuals of both direct p and pk p df and secondary pp sp pcp pkp bc phases computed with respect to the global 1 d velocity model ak135 2308 teleseismic waveforms were collected for this study from 109 events recorded by the italian national seismic network rsnc during 1988 1998 the velocity perturbation field is reconstructed gradually by means an iterative sequence of linearized inversions incorporating a 3 d minimum travel time ray tracing the tomographic images reveal a broad high velocity zone dominating the pattern of lateral variations beneath the southern tyrrhenian sea and calabria this fast structure extends laterally for a maximum of 350 km from northern sicily to southern campania and vertically for at least 400 km from the uppermost mantle down to 500 km depth below 350 km the geometry of the depicted slab is characterized by horizontal deflection of the subducting lithosphere towards the central tyrrhenian basin

estimation of an optimum velocity model in the calabro peloritan mountains assessment of the variance of model parameters and variability of earthquake locations summary accurate earthquake locations are of primary importance when studying the seismicity of a given area they allow important inferences on the ongoing seismo tectonics both for standard as well as for earthquake relative location techniques the velocity parameters are kept fixed to a priori values that are assumed to be correct and the observed traveltime residuals are minimized by adjusting the hypocentral parameters however the use of an unsuitable velocity model can introduce systematic errors in the hypocentre location precise hypocentre locations and error estimate therefore require the simultaneous solution of both velocity and hypocentral parameters we perform a simultaneous inversion of both the velocity structure and the hypocentre location in ne sicily and sw calabria italy since the density of the network is not sufficient for the identification of the 3 d structure with a resolution of interest here we restrict ourselves to a 1 d inversion using the well known code velest a main goal of the paper is the analysis of the stability of the inverted model parameters for this purpose we carry out a series of tests concerning the initial guesses of the velocity structure and locations used in the inversion we further assess the uncertainties which originate from the finiteness of the available data set carrying out resampling experiments from these tests we conclude that the data catalogue is sufficient to constrain the inversion we note that the uncertainties of the inverted velocities increases with depth on the other hand the inverted velocity structure depends decisively on the initial guess as they tend to maintain the overall shape of the starting model in order to obtain an improved starting model we derive a guess for the probable depth of the moho for this purpose we exploit considerations of the depth distribution of earthquake foci and of the shear strength of rock depending on its rheological behaviour at depth in a second step we derive a smooth starting model and repeated the inversion strong discontinuities tend to attract hypocentre locations which may introduce biases to the earthquake location using the smooth starting model we obtaine again a rather smooth model as final solution which gives the best traveltime residuals among all models discussed in this paper this poses severe questions as to the significance of velocity discontinuities inferred from rather vague a priori information besides this the use of those smooth models widely avoids the problems of hypocentre locations being affected by sudden velocity jumps an effect which can be extremely disturbing in relative location procedures the differences of the velocity structure obtained with different starting models is larger than those encountered during the bootstrap test this underscores the importance of the choice of the initial guess fortunately the effects of the uncertainties discussed here on the final locations turned out as limited that is less than 1 km for the horizontal coordinates and less than 2 km for the depth

are the source models of the m 7 1 1908 messina straits earthquake reliable insights from a novel inversion and a sensitivity analysis of levelling data

seismic signals associated with landslides and with a tsunami at stromboli volcano italy in this article we analyze the seismic signals produced by two landslides that occurred at the stromboli volcano on 30 december 2002 recorded by both broadband and short period seismic stations located in the 2 5 22 km distance range from the source for both landslides the characteristics of the low frequency seismograms indicate a complex time history in the release of seismic energy the first landslide occurred over the submerged part of the northwest sector of the volcano and had associated a large amplitude low frequency pulse representative of the abrupt detachment of a large mass lower amplitude phases in the following 3 minutes possibly indicate minor detachment events the highest amplitude low frequency signals are well described by a single force source model the second mass failure episode is also characterized by a complex source and can be interpreted as a multiple event with a less abrupt onset and at least four detachments occurring during 4 5 minutes and producing low frequency signals synthetic seismograms generated by a shallow single force located in the submerged area of sciara del fuoco and directed upslope fit well the first low frequency seismic pulse recorded at stromboli and panarea by three component stations from this simulation we estimated the force exerted by the first mass failure the estimate of the volume through two different procedures gives values in the range of 1 0 1 5 million m3 and about 14 million m3 respectively the landslides which involved both the submarine and the subaerial northwest flank of the volcano produced a tsunami that struck the coast of stromboli island and in a few minutes reached the other islands of the aeolian archipelago three broadband seismic stations installed on land about 100 m from the coastline at panarea island located 20 km southwest of stromboli recorded very long period seismic signals produced by the tsunami waves analysis of these signals gives invaluable information on the spectral content and propagation properties of tsunami waves and on their interaction with the ground at a short distance from the coast synthetic tsunami waves obtained by a landslide source model and taking into account the bathymetry of the sea surrounding stromboli and panarea islands fit the observed phenomena and the experimental data very well manuscript received 19 november 2003

new insights on volcanic and tectonic structures of the southern tyrrhenian italy from marine and land seismic data 1 we present results from the first crustal seismic tomography for the southern tyrrhenian area which includes ocean bottom seismometer obs data and a bathymetry correction this area comprises mt etna the aeolian islands and many volcanic seamounts including the marsili seamount the seismicity distribution in the area depends on the complex interaction between tectonics and volcanism the 3 d velocity model presented in this study is obtained by the inversion of p wave arrival times from crustal earthquakes we integrate travel time data recorded by an obs network tyrrhenian deep sea experiment the sn 1 seafloor observatory and the land network our model shows a high correlation between the p wave anomaly distribution and seismic and volcanic structures two main low velocity anomalies underlie the central aeolian islands and mt etna the two volumes which are related to the well known active volcanism are separated and located at different depths this finding in agreement with structural petrography and gps data from literature confirms the independence of the two systems the strongest negative anomaly is found below mt etna at the base of the crust and we associate it with the deep feeding system of the volcano we infer that most of the seismicity is generated in brittle rock volumes that are affected by the action of hot fluids under high pressure due to the active volcanism in the area lateral changes of velocity are related to a transition from the western to the central aeolian islands and to the passage from continental crust to the tyrrhenian oceanic uppermost mantle

seismotectonics of northeastern sicily and southern calabria italy new constraints on the tectonic structures featuring in a crucial sector for the central mediterranean geodynamics

interpretation of heat flow density of the apennine chain italy the apennine chain is a consequence of the continental collision between europe and africa characterized by several compressive phases with events of intense shortening during one of these phases from early oligocene to early miocene the continental crust broke into various segments which became packed one over the other forming an adriatic verging structure of imbricated listric wedges this event is thermally modeled in the southern apennines by the successive overthrust of two slabs of 7 km total thickness and explains the low heat flow density hfd 40 mw m 2 observed there in the northwestern apennines modeling is on the basis of the overthrusting of a slab 10 km thick which reduced the hfd of the steady lithosphere 63 mw m 2 observed on the iblean platform to 50 4 mw m 2 from the late miocene onwards tensional tectonism developed in the internal areas of the chain application of mckenzie s simple stretching model shows that the high regional heat flow 100 mw m 2 obtaining by filtering the observed data is explained by a stretching of the lithosphere of a factor 3 1

relocation of microearthquake swarms in the peloritani mountains implications on the interpretation of seismotectonic patterns in ne sicily italy summary the peloritani mountains in northeastern sicily make part of the appennine maghrebian chain which forms the highly deformed southern margin of the european continent in this zone the nw se striking aeolian tindari giardini system atg separates two areas of seismicity to the west of the atg fault system seismic activity below a depth of 40 km is essentially absent to the east of this fault system we note a significant presence of intermediate depth and deep events which mark the subduction zone in the calabrian arc between 1994 and 2003 300 microearthquakes could be located with fair accuracy near the atg fault system their depths range from less than 5 to 40 km with greater depths occurring to the east of the atg we examined the resolution capability of the standard location by applying a grid search location for typical events the distribution of the residuals shows trends recognizable in the standard locations that are in part an artefact of a non ideal conditions of the standard locations such as the station configuration the use of an unsuitable velocity model and inconsistencies of arrival time pickings by applying relative location techniques the double difference method and a master event technique we were able to reduce the scatter of hypocentres significantly we focused in particular on earthquake families with similar waveforms and estimated the geometrical extent of hypocentre clusters compared to the standard location the dispersion of hypocentres decreased by an amount of over 90 per cent and the volume occupied by the foci contracted to 1 per cent the significance of these geometries was tested with monte carlo experiments and by interchanging the master events the cluster geometries are consistent with the dislocation patterns as inferred from fault plane solutions but do not show a simple relation to the atg the role of fluid flow of plutonic origin may be invoked as a possible trigger mechanism this hypothesis is supported by the presence of geothermal anomalies in the vicinity as well as by an upward migration trend in foci

episodic back arc extension during restricted mantle convection in the central mediterranean abstract in the central mediterranean during the last 80 myr africa has been slowly converging toward eurasia with an average relative velocity of less than 1 cm yr 1 for 50 myr this slow convergence led to the build up of the alpine orogenic belt and to the initiation of consumption of the former tethys ocean in the last 30 myr however the whole central western mediterranean has been swept by rapid episodes of trench migration up to 6 cm yr 1 and back arc opening which consumed the whole former tethys ocean we combine plate tectonic history geological timing and laboratory modelling to reconstruct the subduction history and the evolution of the central mediterranean over the last 80 myr we find that the dynamic evolution of the subducting oceanic lithosphere can reconcile the rapid episodic back arc migration with the slow african convergence but only if the subduction process is restricted to the upper mantle

crustal structure and deformation across a mature slab tear zone the case of southern tyrrhenian subduction italy we compute s velocity profiles of the crust across the messina strait italy the tear zone at the southern end of the ionian subduction zone separating sicily from calabria the messina strait hosted some of the strongest earthquakes to ever occur in italy here the motion of the ionian slab with respect to sicily creates a complex tectonic setting characterized by lithospheric tearing we show velocity models of the crust computed from teleseismic receiver function inversion outlining the differences between sicily and calabria strong deformation across the messina strait between 10 15 and 30 km depth is expressed by strong anisotropy up to 10 developed in a ductile shear zone of the crust the top of these ductile weaker layers could limit the depth extent of future ruptures

seismic strain and seismogenic stress regimes in the crust of the southern tyrrhenian region abstract an investigation has been performed to identify and characterize the seismic deformation zones active over the last decades in the region of italy that has experienced the strongest seismicity during the last centuries the study is based on the estimate of hypocenter locations fault plane solutions seismogenic stress and seismic strain tensor orientations carried out using the entire dataset of the national and local seismic networks and the recently improved three dimensional 3d crustal velocity model of the study area a series of simulation tests have been performed to evaluate the significance of the earthquake space distribution obtained and whether it was influenced by network geometry problems related to the sea and the lack of ocean bottom seismometers in the sectors where hypocentral location was synthetically proved to be reliable space distributions of earthquakes located with epicenter and focal depth errors less than 3 and 4 km respectively have been compared with local geology in order to identify seismogenic faults the dataset of 32 fault plane solutions estimated with fault parameter errors less than 20 has been used to investigate space variations of seismogenic stress and seismic strain orientations over the study area stress was found to be uniform in the messina strait and southern calabria where inversion of the available set of 11 fault plane solutions showed clear evidence of an extensional regime the different orientations of the minimum compressive stress and strain found in this sector together with the information available on local geology and tectonics lead us to propose that the seismicity occurring over the last decades in the messina strait and southern calabria was not in general produced at the main faults but at minor faults activated by the main tectonic stress field acting in the area to the west in the sector including western etna the nebrodi chain and the western aeolian islands analysis of the available set of 16 fault plane solutions revealed a certain degree of stress heterogeneity with an apparent prevalence of north south compression this east to west change of stress strain regimes is evaluated in the light of current hypotheses regarding the geodynamics of the study region

sensitivity of asian summer monsoon precipitation to tropical sea surface temperature anomalies sensitivity of asian summer monsoon asm precipitation to tropical sea surface temperature sst anomalies was estimated from ensemble simulations of two atmospheric general circulation models gcms with an array of idealized sst anomaly patch prescriptions consistent sensitivity patterns were obtained in both models sensitivity of indian summer monsoon ism precipitation to cooling in the east pacific was much weaker than to that of the same magnitude in the local indian western pacific over which a meridional pattern of warm north and cold south was most instrumental in increasing ism precipitation this indicates that the strength of the enso ism relationship is due to the large amplitude east pacific sst anomaly rather than its sensitivity value sensitivity of the east asian summer monsoon easm represented by the yangtze huai river valley yhrv also known as the meiyu baiu front precipitation is non uniform across the indian ocean basin yhrv precipitation was most sensitive to warm sst anomalies over the northern indian ocean and the south china sea whereas the southern indian ocean had the opposite effect this implies that the strengthened easm in the post nino year is attributable mainly to warming of the northern indian ocean the corresponding physical links between these sst anomaly patterns and asm precipitation were also discussed the relevance of sensitivity maps was justified by the high correlation between sensitivity map based reconstructed time series using observed sst anomaly patterns and actual precipitation series derived from ensemble mean atmospheric gcm runs with time varying global sst prescriptions during the same period the correlation results indicated that sensitivity maps derived from patch experiments were far superior to those based on regression methods

a model of vulcanian eruptions at galeras volcano colombia abstract a series of six vulcanian eruptions at galeras volcano colombia occurred during 1992 1993 these eruptions followed the emplacement of a lava dome in late 1991 which was accompanied by cooling crystallizing and partial solidification of the column of magma plugging the conduit five of the eruptions were preceded by episodes of monochromatic long period seismicity suggesting cyclic pressurization of the magma the quiescent intervals between eruptions generally decreased with each successive eruption we propose a model of gas release from magma into confined stationary pore spaces by 5 10 crystallization of anhydrous minerals causing repeated overpressurization of the magmatic system using initial lithostatic pressures of 20 100 mpa 800 3900 m depth gas buildup by crystallization indicates overpressures of 3 17 mpa which is the approximate fracture criterion for a magma chamber our galeras data suggest two models of pressurization 1 gas exsolution may have occurred at similar depths but with progressively smaller overpressures being developed before each successive eruption according to this model the comparatively long quiescent periods between the first eruptions resulted in relatively large amounts of gas exsolution from the magma and accumulation in pore spaces whereas the shorter quiescent periods for the later eruptions exsolved less gas the decrease in overpressure with time may have resulted from progressive fracturing of partly solidified magma during the eruptions which progressively decreased the tensile strength and increased the permeability of the magma 2 since overpressures are smaller at shallower depths for a given amount of crystallization the first eruptions of 1992 1993 were caused by gas exsolution at shallow depths while the last eruptions having shorter quiescent intervals resulted from a greater amount of gas exsolution at greater depths in this case the rate of gas exsolution varied as a function of depth the two scenarios for pressurization may be combined into a more general model involving edifice weakening and the development of a shallow hydrothermal system from continued degassing of the magma plug as weakening of the edifice formed an extensive system of fractures the shallow hydrothermal system deepened due to meteoric water input and magmatic degassing with time a greater number of fractures were filled and partly sealed by hydrothermal minerals at progressively deeper levels as a result the source of the overpressure also deepened with time

residual topography lithospheric structure and sunken slabs in the central mediterranean abstract the central mediterranean comprises subduction collision and backarc extension all in a relatively small area in this paper we analyze the topography of this region examining the influence of subducting slabs on overriding plates we take the observed surface elevation remove the contribution of the crust to it and use the residual topography to identify regions that are unusually low unusually high or normal then we calculate lithospheric thickness where local isostasy applies the results provide information about the structure of the lithosphere in this complex region and about the vertical tectonics in particular we found a difference between the south tyrrhenian subduction zone and the apennines consistent with the processes of slab rollback and slab break off respectively in the south tyrrhenian the edge of the oceanic plate is strongly pulled down whereas the edge of the overriding plate the calabrian peninsula is uplifted this opposite trend indicates weak plate coupling that is the subducting slab which is rapidly rolling back hangs almost entirely on the oceanic plate and the overriding plate is free in contrast in the apennines high residual topography and uplifting are detected on both sides of the mountain belt consistent with complete break off of the subducted lithosphere

crustal structure of the ionian margin of sicily etna volcano in the frame of regional evolution abstract crustal imaging could be achieved on normal incidence reflection profiles offshore eastern sicily by using industrial grade reflection seismic with improved marine sources thick recent sediments a reflective pile including the mesozoic deposits a transparent upper crust and a band of low frequency reflections attributed to the lower crust are imaged in the seismic sections the structure of the crust and its thickness show features inherited from the mesozoic evolution as a passive margin by which ionian basin crust was formed around the hyblean continental promontory of africa to constitute the southern plate in the later convergence with europe the seismic images are also marked by the lithospheric deformation due to the neogene overriding of the northern part of this paleomargin by the calabro peloritan block of european continental crust this transpressive motion may have been guided along the northern part of this paleomargin where the seismic profiles evidence a hinge line between the northward upslope of the moho of that old passive margin and its downslope to the present slab under the tyrrhenian sea etna volcano is located at the intersection of this mantle upwarp by a zone of active sea bottom normal faults which cut across the formerly constructed compressional belt the onset of its volcanic activity is roughly coeval with that of the cessation of interplate thrusting and could hence be related to a change of the coupling of the ionian slab this slab is now probably disconnected from the overriding plate and rolled back in front of the expanding hot tyrrhenian asthenospheric dome with the mobilisation of a viscous mantle material at depth an active lithospheric fault is here imaged which cuts over more than 100 km into the ionian basin the fault runs from the tyrrhenian margin in the sse direction of etna updip of the southwestern lateral edge of this slab leaving north eastward the extruded calabrian block and on its south westward edge the uplifted crust and mantle structures of etna along it the crust including the mesozoic and deeper layers has sagged vertically in the segment in front of the slab with a finite throw across the fault increasing from the basin towards etna

relocation and focal mechanisms of earthquakes in the south central sector of the aeolian archipelago new structural and volcanological insights abstract to recognize possible spatial clusters and identify active seismogenic zones and structures in the aeolian archipelago in the south of italy we analyzed the spatial pattern of seismicity between 1993 and 2010 in a selected area comprising vulcano lipari salina and filicudi and calculated 22 fault plane solutions fpss for shocks with magnitude greater than 2 7 first we computed a 1 d velocity model for this area including information from recorded earthquakes by a joint hypocenter velocity inversion kissling et al 1994 successively we applied the double difference approach of waldhauser and ellsworth 2000 finding that a certain part of the scattered epicenter locations collapse in roughly linear features relocated seismicity evidenced three main alignments oriented nnw sse and ne sw at different depths that concur well with the known tectonic lineaments and focal mechanisms a detailed discussion is focused on a seismogenetic structure ne sw oriented 3 8 km deep located in the northern area of vulcano island this recognized element could represent a link between magma accumulation zones thus representing a possible preferential pathway along which magma may intrude two earthquake clusters located south west and east of vulcano with their focal mechanisms highlight the aeolian tindari letojanni fault system seismic activity and the existence of a transitional zone going from the n s compressive domain that dominates the aeolian islands to the nw se extensional domain characterizing the south eastern tyrrhenian

crustal image of the ionian basin and its calabrian margins abstract previous seismic investigation of the crustal structure in the ionian basin has been limited to shallow penetration seismics of the 1970 s characterized by inadequate source power and low fold earlier obs and esp seismic refraction experiments have not been able to firmly resolve one of the principal scientific problems for this region which is whether the ionian basin is floored by oceanic crust or by highly attenuated continental crust a second elusive problem is the nature of the transition of the boundaries between the ionian basin and its margins in this paper we describe and interpret new deep seismic reflection and wide angle data collected in the western ionian sea and the calabria region of italy one of the principal features of our multichannel reflection data beneath the ionian basin is a band of layered high amplitude reflections near the base of the crust this band shows a quasi monochromatic ca 8 to 10 hz frequency and a traveltime thickness of 1 to 1 5 s these images contrast with the well known reflection patterns of mesozoic oceanic crust investigated in the atlantic ocean there is evidence that the low frequency band dips down towards the edge of the malta escarpment me where landward dipping reflectors separate continental and intermediate type crust in the central tract of the me the increased traveltimes of the lower crustal reflectors and moho from the basin towards the southern and eastern margins of southern calabria could be partially due to the velocity pull down effect of the sedimentary pile of the arc although a true dip of 15 to 18 over 60 km distance can be substantiated moreover the reflecting band maintains its reflectivity and thickness until its abrupt termination beneath the ionian continuation of the calabrian compressional crustal structures the coincident acquisition of wide angle seismic data and marine reflection seismic data provided a landward extension of the survey which will complement existing geologic information on the deep framework of the ionian basin and its calabrian margin

tomographic constraints on the geodynamic evolution of the italian region in this paper we present p wave tomographic images of the mantle beneath italy obtained by inverting 6000 teleseismic p and pkp wave arrival times accurately repicked recorded in the time period 1988 1994 by the stations of the national seismic network of the istituto nazionale di geofisica we pay great attention in the data selection and picking procedure of seismic phases to obtain a very high quality data set the data were inverted with the well established aki christofferson husebye tomographic technique different reference models and residuals computation have been tried to verify the stability of the results the high quality of the repicked arrival times allows us to enhance the definition of the deep structures beneath both the alps and the apennines looking for their lateral and vertical continuity down to 800 km depth the main finding of this study is a continuous high velocity body located between 250 and 670 km depth beneath the entire apenninic system dipping toward the tyrrhenian area which continues upward segmented in two main anomalies in the northern apenninic and the calabrian arcs we interpret this high velocity feature as the subducted oceanic lithosphere between the eurasian and african plates dipping down to the upper lower mantle boundary beneath the tyrrhenian sea the retrieved images of the lithosphere subducting beneath apennines are reliable in terms of thickness about 80 90 km and p wave velocity contrast 2 4 higher than the normal mantle furthermore our tomographic images which focus on the deep geometry and continuity of the velocity structures provide new keys to understanding the geodynamic evolution of the italian region the segmentation of the high velocity slab upward suggests a complex evolution of the arc trench system and the initially continuous subduction of the ionian adriatic plate progressively developed in subordinate arcs probably due to lateral heterogeneity of the subducting lithosphere

a global merged land air sea surface temperature reconstruction based on historical observations 1880 1997 abstract a merged land air sea surface temperature reconstruction analysis is developed for monthly anomalies the reconstruction is global and spatially complete reconstructed anomalies damp toward zero in regions with insufficient sampling error estimates account for the damping associated with sparse sampling and also for bias uncertainty in both the land and sea observations averages of the reconstruction are similar to simple averages of the unanalyzed data for most of the analysis period for the nineteenth century when sampling is most sparse and the error estimates are largest the differences between the averaged reconstruction and the simple averages are largest sampling is always sparse poleward of 60 latitude and historic reconstructions for the polar regions should be used with caution

tectonics and seismicity of the tindari fault system southern italy crustal deformations at the transition between ongoing contractional and extensional domains located above the edge of a subducting slab 1 the tindari fault system southern tyrrhenian sea italy is a regional zone of brittle deformation located at the transition between ongoing contractional and extensional crustal compartments and lying above the western edge of a narrow subducting slab onshore structural data an offshore seismic reflection profile and earthquake data are analyzed to constrain the present geometry of the tindari fault system and its tectonic evolution since neogene including the present seismicity results show that this zone of deformation consists of a broad nnw trending system of faults including sets of right lateral left lateral and extensional faults as well as early strike slip faults reworked under late extension earthquakes and other neotectonic data provide evidence that the tindari fault system is still active in the central and northern sectors and mostly accommodates extensional or right lateral transtensional displacements on a diffuse array of faults from these data a multiphase tectonic history is inferred including an early phase as a right lateral strike slip fault and a late extensional reworking under the influence of the subduction related processes which have led to the formation of the tyrrhenian back arc basin within the present regional geodynamic context the tindari fault system is interpreted as an ongoing accommodation zone between the adjacent contractional and extensional crustal compartments these tectonic compartments relating to the complex processes of plate convergence occurring in the region the tindari fault system might also be included in an incipient oblique extensional transfer zone linking the ongoing contractional belts in the calabrian ionian and southern tyrrhenian compartments

earthquake locations and three dimensional crustal structure in the coyote lake area central california previous work on the simultaneous inversion method has been improved and extended to incorporate iterative solution for earthquake locations and laterally heterogeneous structure approximate ray tracing and parameter separation are important elements of the improved method application of the method to p wave arrival time data recorded by stations of the u s geological survey central california network yields a three dimensional model for the velocity structure of the upper crust in an area encompassing the rupture zone of the coyote lake earthquake of august 1979 very strong correlations between the velocity model and the geology and gravity and magnetic anomalies are observed improved estimates of the locations of earthquakes in the study area are also determined the relocation of explosions indicates epicentral accuracies of the order of a kilometer or better based on the revised hypocentral locations it is concluded that the san andreas fault is vertical in this area with no actual offset between the epicenters and the fault trace in contrast the calaveras has two or more active fault surfaces one nearly vertical and another dipping 75 to the northeast

geochemistry of the submarine gaseous emissions of panarea aeolian islands southern italy magmatic vs hydrothermal origin and implications for volcanic surveillance the marine sector surrounding panarea island aeolian islands south italy is affected by widespread submarine emissions of co2 rich gases and thermal water discharges which have been known since the roman age on november 3rd 2002 an anomalous degassing event affected the area probably in response to a submarine explosion the concentrations of minor reactive gases co ch4 and h2 of samples collected in november and december 2002 show drastic compositional changes when compared to previous samples collected from the same area in the 1980s in particular the samples collected after the november 3rd phenomenon display relative increases in h2 and co and a strong decrease in the ch4 contents while other gas species show no significant change the interaction of the original gas with seawater explains the variable contents of co2 h2s n2 ar and he which characterize the different samples but cannot explain the large variations of co ch4 and h2 which are instead compatible with changes in the redox temperature and pressure conditions of the system two models both implying an increasing input of magmatic fluids are compatible with the observed variations of minor reactive species in the first one the input of magmatic fluids drives the hydrothermal system towards atypical more oxidizing redox conditions slowly pressurizing the system up to a critical state in the second one the hydrothermal system is flashed by the rising high t volcanic fluid suddenly released by a magmatic body at depth the two models have different implications for volcanic surveillance and risk assessment in the first case the november 3rd event may represent both the culmination of a relatively slow process which caused the overpressurization of the hydrothermal system and the beginning of a new phase of quiescence the possible evolution of the second model is unforeseeable because it is mainly related to the thermal baric and compositional state of the deep magmatic system that is poorly known

3d crustal structure from local earthquake tomography around the gulf of arta ionian region nw greece during summer of 1995 local seismicity was recorded in the area around the gulf of arta in northwestern greece by a dense temporary seismic network of the 441 local events observed at 37 stations 232 well locatable events with a total of 2776 p phase readings were selected applying the criteria of a minimum of 6 p observations and an azimuthal gap less than 180 this data set is used to compute a minimum 1d velocity model for the region several tests are conducted to estimate model stability and hypocenter uncertainties leading to the conclusion that relative hypocenter location accuracy is about 500 m in latitude and longitude and 1 km in depth the minimum 1d velocity model serves as initial model in the non linear inversion for three dimensional p velocity crustal structure by iteratively solving the coupled hypocenter velocity problem in a least squares sense careful analysis of the resolution capability of our data set outlines the well resolved features for interpretation the resulting 3d velocity model shows generally higher average crustal velocities in the east and the well resolved area of the eastern gulf of arta exhibits a homogeneous velocity around 6 km s for the whole upper crust a pronounced north south trending zone of low velocities in the upper 5 10 km is observed in the area of the katouna fault zone kfz at greater depths below 10 km the kfz is underlain by high velocity material e w profiles suggest a horst graben structure associated with the kfz