curie isotherm depth from aeromagnetic data constraining shallow heat source depths in the central aeolian ridge southern tyrrhenian sea italy the salina lipari and vulcano volcanic ridge and the surrounding sea sectors aeolian archipelago southern tyrrhenian sea italy are characterized by vents responsible for a recent 40 ka 1889 1890 ad effusive and explosive subareal activity and repeated 56 to 7 ka in age submarine explosive eruptions from source areas located between lipari and vulcano a spectral depth estimation of the magnetic bottom using a fractal method on aeromagnetic data from vulcano lipari and salina volcanic ridge allows us to constrain the curie isotherm depth the elevated portion of the isotherm is between 2 and 3 km below salina and vulcano and about 1 km below lipari the curie depth results in the context of other geological and geophysical evidence suggest that the rise of the curie isotherm is mainly due to the occurrence of shallow heat sources such as magma ponds and associated hydrothermal systems the short wavelength magnetic anomaly field reflects magnetic contrasts from highly magnetized volcanic bodies low magnetization sediments and hydrothermally altered rocks borehole temperature data verify the curie temperature derived from the magnetic methods on the island of vulcano we conclude that the whole vulcano lipari and salina volcanic ridge is active and should be monitored

on the origin and post depositional history of widespread massive ash deposits the case of intermediate brown tuffs ibt of lipari aeolian islands italy abstract we analysed a widespread massive ash unit outcropping on the island of lipari which belongs to the intermediate brown tuffs ibt succession of the aeolian islands italy the use of a multidisciplinary approach that integrates textural petrological and pedological methods allows us to discriminate between syn eruptive and post depositional features the deposits are dominated by uncrystallised blocky glass fragments of homogeneous shoshonitic composition confirming a provenance from hydromagmatic eruptions on the island of vulcano many glass fragments are surrounded by a coating separated by a thin void of syn eruptive origin due to alteration by aggressive acid gases in the eruptive cloud the lack of this coating in the northern part of lipari can be explained as a progressive dispersion of the gases far from the vent and or to post depositional processes the degree of soil development significantly increases from south soil profiles p1 and p2 at valle muria to north p3 and p4 at madoro and chiesa vecchia sites respectively as a response to a decrease in slope steepness which has brought about a progressive deepening of the pedogenetic front on gentler landforms and conversely its rejuvenation on steep slopes the relatively poor to moderate degree of pedogenic evolution of the studied ibt unit is consistent with its emplacement during part of the last glacial period

control of rupture by fault geometry during the 1966 parkfield earthquake a reanalysis of the available data for the 1966 parkfleld california earthquake mr 5 suggests that although the ground breakage and aftershocks extended about 40 km along the san andreas fault the initial dynamic rupture was only 20 to 25 km in length the foreshocks and the point of initiation of the main event locate at a small bend in the mapped trace of the fault detailed analysis of the p wave first motions from these events at the gold hill station 20 km southeast indicates that the bend in the fault extends to depth and apparently represents a physical discontinuity on the fault plane other evidence suggests that this discontinuity plays an important part in the recurrence of similar magnitude 5 to 6 earthquakes at parkfield analysis of the strong motion records suggests that the rupture stopped at another discontinuity in the fault plane an en echeion offset near gold hill that lies at the boundary on the san andreas fault between the zone of aseismic slip and the locked zone on which the great 1857 earthquake occurred foreshocks to the 1857 earthquake occurred in this area sieh 1978 and the epicenter of the main shock may have coincided with the offset zone if it did a detailed study of the geological and geophysical character of the region might be rewarding in terms of understanding how and why great earthquakes initiate where they do

relations between surface deformation fault geometry seismicity and rupture characteristics during the el asnam algeria earthquake of 10 october 1980 abstract the el asnam earthquake of october 10 1980 ms 7 3 produced surface faulting on a northeast trending thrust fault of 30 km length with displacements of up to 6 5 m though average displacements were about 3 m in addition widespread tensional features were formed some in clear association with folding above the thrust and others in an area beyond the exposure of the thrust at the surface which may be related to buried reverse faults the observed thrust fault is split into southern central and northern segments local and teleseismic data are examined to show that the main shock nucleated at the southwest end of the fault and propagated 12 km northeast where a second rupture of approximately equal moment occurred continuing the faulting a further 12 km northeast along the central segment both ruptures nucleated at about 8 10 km depth displacements were largest on the central segment where they were probably enlarged by aftershocks including one of mb 6 1 three hours after the main shock the northern segment was much shorter than the other two and showed smaller displacement the junctions between fault segments are marked by distinct geomorphological characteristics and a change in strike of the faulting as well as a sudden drop in the observed displacement it appears that the rupture development is influenced by the changes in fault geometry between segments and that such junctions or barriers have persisted through much of the late quaternary

seismicity normal faulting and the geomorphological development of the gulf of corinth greece the corinth earthquakes of february and march 1981 three major destructive earthquakes of m s 6 7 6 4 6 4 occurred in the eastern part of the gulf of corinth in february and march 1981 associated normal faulting was observed on both the north and the south sides of the gulf examination of teleseismic local seismic surface faulting and geomorpbological data suggests that the first and second of these shocks activated major north dipping normal faults these faults control the topography and bathymetry and are related to the recent uplift and subsidence of the coastline it is probable that the first earthquake occurred on a faultwhich outcrops underwater and the second on a fault which is visible on land it appears that the third shock activated an antithetic normal fault dipping southwards on the north side of the gulf and that the overall structure of the gulf of corinth graben is asymmetric the northern antithetic fault clearly demonstrates the geomorphological changes associated with developing young normal faulting in addition we suggest that observations of recent coastline movement provide a powerful tool for identifying major active fault systems and predicting their historical role in the paleogeography of an area

musings over sedimentary basin evolution field geologists and explorationists are of necessity immersed in numerous very detailed surface and subsurface observations they are often perplexed by the choice of relatively simple geophysical models that so elegantly explain the origin and evolution of sedimentary basins geophysicists on the other hand search for a simple theme to explain the origin of sedimentary basins and much like managers are often impatient with lengthy detailed geological discourse that often uses fancy jargon to hide the very real difficulty that geologists have in separating important evidence from mere encyclopaedic description the following musings address the quality and limitations of geologic and geophysical evidence that may be used to evaluate the relative roles of stress thermal effects and gravity loading which have been so lucidly summarized by m h p bott in the preceding summary the fine papers presented during this meeting of course have led to significant modifications of some of my earlier thoughts because these have been previously published elsewhere bally snelson 1980 bally 1980 they are summarized here only for the convenience of the reader

wet surge deposits at la fossa di vulcano depositional and eruptive mechanisms abstract wet surge deposits of different volcanic cycles of the recent fossa activity at vulcano have been measured on a bed by bed basis with data recorded to millimeter detail the wet surge layers are varicoloured with variable thickness with the most recurrent thickness being about 1 cm the beds consist of fine ash without internal structures textural features include a accretionary lapilli of maximum size of 0 5 cm dispersed thoroughout the layer or forming continuous layers of submillimeter size b vesiculated layers which represent 10 to 65 of the total deposit vesicles have different shapes and smooth walls varying in volume from 1 to 15 20 c soft sediment types of bedding deformation such as gravity flowage ripples load cast and slumps the slope angle has not influenced either the concentration and size of the accretionary lapilli or the shape size and distribution of vesicles only the thickness of the layers decreases with distance from the vent sem investigations show features indicating the hydromagmatic origin of the deposits and stressing the role of the fluid phase noteworthy is the presence of vesiculated grains produced by magmatic exsolution which show chilling effects on the internal walls of the broken bubbles grain size analyses reveal that the layers are not graded and most of the samples have a median size finer than 50 m the grain size distributions are frequently polymodal suggesting several closely timed explosions as all the beds exhibit the same textures grain size and particle morphology a single mechanism can explain their deposition the depositional unit formed at the base of the cloud through the lateral expansion on the ground of a sticky muddy medium consisting of ash and fluid in general each layer lost its plasticity before the deposition of the next layer the deposition occurred in a nearly continuous sequence without periods of rest long enough to permit erosional discontinuity the eruptions are hydromagmatic and occur where magma at least partially fragmented comes into effective contact with subsurface water the process follows a model suggested by wohletz 1983b 1986 developing in more than one fragmentation event in the turbulent surge cloud both severe hydration and alteration of glassy grains and the formation of accretionary lapilli occur

the 1971 may 12 burdur earthquake sequence sw turkey a synthesis of seismological and geological observations summary it is now widely accepted that the rapid extension observed in western turkey is mainly accommodated by large active normal faults which control the geomorphology the ne sw trending burdur acigol and baklan basins bounded by large faults form a system of half graben whose orientation is evident in both the topography and the tilting of neogene sediments adjacent to them we used long period p and sh waveforms to determine the source parameters of the two largest earthquakes of the 1971 may 12 sequence that occurred in the burdur region the main shock was followed by many aftershocks which were distributed in a broad zone elongated ne sw parallel to the long axes of the basins in the region documented surface breaks of the 1971 event suggest that the northwest dipping faults along the southern margin of the burdur basin are those which moved well exposed fault planes are found dominantly to the south of burdur lake the surface dips of these faults are greater than that of the nw dipping nodal plane obtained for the main shock combined seismological and geological observations suggest that these faults have listric geometries

magnetic fabric and remanent magnetization of pyroclastic surge deposits from vulcano aeolian islands italy abstract tufi di grotte dei rossi inferiori are unwelded fine grained pyroclastic deposits of hydromagmatic origin emplaced between 21 and 11 8 6 ka at vulcano aeolian islands italy by deposition through surges spreading laterally from inside the la fossa caldera in this study the deposit s magnetic properties were investigated and interpreted in terms of eruptive and emplacement dynamics rock magnetism data were supplemented by grain size and textural characteristic analyses as well as scanning electron microscope sem investigations curie point measurements isothermal remanent magnetization and microprobe analyses showed that magnetization is carried by low ti titanomagnetite the size of the grains ranges from about 20 to 300 micrometres their shape from equidimensional to highly elongated the magnetic fabric is typical of fine grained pyroclastics foliation is well developed and in most sites lineation is directed towards the source area of the la fossa caldera the remanent magnetization consists of two components whose blocking temperature spectra partially overlap the direction of the low temperature component is close to that of the axial dipole and consistent with the palaeosecular variation curve for the aeolian islands the high temperature component is systematically shallowed and close to the direction of the magnetic lineation the overall results suggest that the high temperature component was acquired before and the low temperature component after the actual deposition of grains immediately after eruption the grains cooled and moved as free particles in the turbulent cloud during the expansion of the surge flows those particles with high blocking temperatures acquired a thermal remanence they were then deposited and shear at the very base of the flow oriented them and imprinted the rock s fabric and high temperature magnetization component volcanological and magnetic data suggest turbulent transportation and traction deposition of particles finally the rock cooled down and acquired the low temperature magnetization according to this model remanence acquisition in pyroclastic rocks deposited at temperatures lower than the curie point of their ferromagnetic grains depends on both the fluid dynamic forces and cooling history and must therefore be more complex than in pyroclastics deposited at higher temperatures such as welded ignimbrites

the 1978 earthquake sequence near thessaloniki northern greece summary this paper presents a detailed study of teleseismically and locally recorded foreshocks and aftershocks of the 1978 thessaloniki earthquake sequence and discusses the relations between the locations and mechanisms of these shocks and the three dimensional geometry of faulting in the source region sixteen teleseismically recorded events were relocated using a relative relocation method and positioned geographically using the accurate locally determined location of the largest aftershock all these shocks had depths shallower than 15 km the spatial distribution of the foreshocks showed that the activity was initiated at the central part of the epicentral region progressed westwards and for about 20 days clustered in the region of the imminent mainshock no teleseismically recorded foreshock was located west of the mainshock location in less than 1 hr after the mainshock large aftershocks occurred west of it and in later stages spanned the entire western part of the epicentral region no teleseismically recorded aftershocks were located east of the mainshock locally recorded aftershocks were accurately located and provided a more detailed picture of the seismic deformation they occurred at depths between 3 and 12 km and in three distinct clusters separated by well defined gaps the largest foreshock on may 23 had a moment of 5 6 1024dyne cm and a mean displacement of 31cm the mainshock on june 20 had a moment of 5 2 1025dyne cm a strain drop of 4 0 10 5 static stress drop of 12 bar and a mean displacement of 64 cm these values are for one of the two possible interpretations of the aftershock distribution which suggests that the largest earthquakes of the sequence occurred on two different but adjacent fault segments the first event 1 on may 23 occurred along the central fault segment and was followed 28 days later by the second event 2 on june 20 along a western fault segment finally 61 days later another smaller earthquake event 3 occurred along another fault east of event 1

volcanic geomorphology and tectonics of the aeolian archipelago southern italy based on integrated dem data the geomorphological and morphometric analysis of the sea floor topography surrounding the aeolian islands south tyrrhenian sea italy provides insights into the relationships between the volcanological evolution of the islands and their tectonic features we constructed geomorphological maps of the submarine portions of the seven large edifices constituting the islands on the basis of a dem with a 5 m resolution step these maps include constructional and destructional landforms such as submarine volcanic vents located west of lipari and north of alicudi and hummocky surfaces recognised north of lipari and salina the latter landforms together with the occurrence of large scars affecting the main edifices on land suggest that sector collapses affected some islands geomorphological data indicate that the location of subaerial and submarine vents is strongly controlled by local tectonic structures striking wnw ese alicudi filicudi sector nnw sse salina lipari vulcano sector and ne sw panarea stromboli sector the islands can be divided into two groups on the basis of some morphometric parameters a first group with a pancake like shape dp d abrasion platform diameter basal diameter higher than 0 40 and h d total height basal diameter lower than 0 13 and a second group with a conical shape characterised by dp d lower than 0 34 and h d higher than 0 14 these ratios and other morphometric parameters reflect the different volcanological and structural evolution of the aeolian islands the pancake like shaped complexes have been created in addition to their submarine stage by extrusive and highly explosive activity whereas the cone shaped edifices have been characterised by effusive or moderate explosive activity

an approach for investigating the depositional mechanism of fine grained surge deposits the example of the dry surge deposits at la fossa di vulcano abstract fine grained thinly laminated surge deposits have been studied in order to understand the physical properties of pyroelastic deposits with a large tractional component and to investigate on type and number of laminae deposited from a single surge cloud the examples are taken from the dry surge deposits of the fossa cone vulcano island where there is a good knowledge of the stratigraphy good exposures of the deposits and an absence of secondary structures analysis of texture and structure allows all the bed facies to be grouped into 4 principal types type 1 is made up of a loose coarse and medium ash in dark grey gently undulating laminae sometimes with cross laminae that alternate with pale grey laminae type 2 consists of grey ash in beds characterized by limited lateral continuity normal grading and a flat non erosive base type 3 is made up of submillimeter ochreous laminae plane parallel or gently undulating type 4 consists of massive beds of fine ash ochre in colour characterized by notably lateral continuity and constant thickness determination of the nature morphology and size of the grains shows that a close relationship exists between the relative abundance and shape of components and the textural and grain size characteristics of the bed facies the results suggest that a single surge event could deposit either a set of plane parallel to transverse laminae as type 1 and type 3 or a pair of laminated beds as type 2 and 4 depending on the flow velocity the effective grain size and density of the solid phase and the particle concentration in the eruptive cloud the almost complete lack of lithics suggests that magma water interaction occurred in sub surface conditions across a fragmented magma surface the efficiency of the interaction was primarily controlled by the ascent velocity of the magma in the conduit and its physical properties

atmospheric effects and spurious signals in gps analyses improvements in the analyses of global positioning system gps obser vations yield resolvable mm to sub mm di erences in coordinate estimates thus provid ing su cient resolution to distinguish subtle di erences in analysis methodologies here we investigate the e ects on site coordinates of using di erent approaches to modelling atmospheric loading deformation atml and handling of tropospheric delays the rig orous approach of using the time varying vmf1 mapping function yields solutions with lower noise at a range of frequencies compared with solutions generated using empiri cal mapping functions this is particularly evident when atml is accounted for some improvement also arises from using improved a priori zenith hydrostatic delays zhd with the combined e ect being site speci c importantly inadequacies in both mapping functions and a priori zhds not only introduce time correlated noise but signi cant pe riodic terms at solar annual and semi annual periods we nd no signi cant di erence between solutions where non tidal atml is applied at the observation level rather than as a daily averaged value but failing to model diurnal and semi diurnal tidal atml at the observation level can introduce anomalous propagated signals with periods that closely match the gps draconitic annual 351 4 d and semi annual period 175 7 d ex acerbated by not xing ambiguities these signals are evident in both stacked and sin gle site power spectra with each tide contributing roughly equally to the dominant semi annual peak the amplitude of the propagated signal reaches a maximum of 0 8 mm with a clear latitudinal dependence that is not correlated directly with locations of maximum tidal amplitude this is the first evidence of aliased signals being produced from tidal atml deformations

rock magnetism and compositional investigation of brown tuffs deposits at lipari and vulcano aeolian islands italy abstract a rock magnetic investigation was carried out on the nonwelded ash deposits of the brown tuffs aeolian islands southern tyrrhenian sea to improve the stratigraphic correlation between the deposits cropping out on lipari and vulcano islands and locate their source area the study was supplemented by petrographical and geochemical analyses on selected strata with the intent to compare the brown tuffs to other rocks emplaced at vulcano in the same time span more than 30 levels were sampled in the intermediate 56 4 ka ibt 21 22 ka and upper 21 22 ka ubt parts of the brown tuffs sequences on the two islands their characteristic remanent magnetization chrm directions were derived from stepwise thermal demagnetization and the magnetic fabric from measurements of the anisotropy of magnetic susceptibility the levels with indistinguishable chrm directions were regarded as coeval and to form an individual stratigraphic unit the units were referred to the brown tuffs sequence of lucchi et al 2008 on the grounds of their emplacement age provided by comparison of their mean paleomagnetic direction with the paleosecular variation curves of the southern tyrrhenian region as well as the field constraints the closer correlation between the sequences of lipari and vulcano contributes to a better understanding of the volcanic activity that produced the brown tuffs and shows that most of the ibt and the oldest ubt levels were emplaced in a short time span between 24 and 20 17 ka the magnetic fabric is typically well developed but at most sites the magnetic foliation is very close to horizontal and no imbrication is defined the source area of the brown tuffs parent pyroclastic flows as constrained from the intersection of the magnetic lineations falls in the northeastern part of la fossa caldera structure although limited to major elements compositional data provide further indication about the parent plumbing system and its behaviour magma batch es involved in the ibt eruptions have homogeneous features and underwent frequent refilling and tapping processes conversely those involved in the early ubt eruptions are compositionally more variable this suggests more complex evolution and plumbing system activity the ubt eruptions represent either residual mafic magmas from the previous eruptions or the arrival of new fresh shoshonitic magma in the system

palaeomagnetism of holocene and late pleistocene sediments from lago di mezzano and lago grande di monticchio italy initial results abstract palaeomagnetic records of the geomagnetic secular variation reaching back to 31 and 102 kyr cal bp respectively were obtained from two sediment cores from lago di mezzano central italy and two cores from lago grande di monticchio southern italy intra lake correlation was based on continuous high resolution susceptibility measurements and discrete dry density samples characteristic remanent magnetization chrm of all 4800 samples was determined by analysis of the results of progressive alternating field af demagnetization intra lake comparison of the resulting chrm directions confirms that the inclination and declination records reflect the palaeosecular variation of the local geomagnetic field composite curves of geomagnetic palaeosecular variations psv were created for each lake in order to compare the reconstructed psv records with those from lac du bouchet massif central france and lac de joux switzerland the good agreement in the general patterns of the inclination and declination records of all lakes mentioned above confirms the reconstructed psv records of the italian lakes investigated

a procedure for modelling shallow dislocation sources summary expressions for displacements on the surface of a layered half space due to an arbitrary oriented shear dislocation are given in terms of generalized ray expansions useful approximations of these expressions for shallow events as recorded at teleseismic distances for realistic earth models are presented the results of this procedure are used to generate synthetic p sv and sh waveforms for various assumptions of stress drop

noise in gps displacement measurements from southern california and southern nevada 1 time series of position changes estimated from data from 236 continuously recording gps receivers operating in southern california and southern nevada are evaluated for noise models that characterize their temporal correlations the lengths of the time series range between 3 5 and 10 years after adjusting these data for postseismic deformation offsets and annual periodicities i find that about one half of the time series have temporal correlations that are categorized as either flicker or random walk noise the remaining time series can be best categorized as either a combination of flicker and random walk power law noise first order gauss markov plus random walk noise or power law plus broadband seasonal noise a variety of geodetic monuments are used in southern california and nevada including deeply braced designs cement piers pins drilled in outcrop and buildings when i evaluate the noise for each time series in terms of an estimate of the standard error in velocity i find that the sites with the smallest errors are those located in nevada using deeply braced monuments sites that are installed within regions of active pumping both for groundwater and oil had the largest standard errors in velocity comparison of monument stability as measured by standard error in rate with average annual rainfall nearby indicates a marginally significant correlation in addition even though regional filtering removed much of the common mode signals in these time series there still remains a common mode seasonal signal which can and should be removed

slip re orientation in oblique rifts oblique extension is expected to result in a combination of dip slip and strike slip displacement along faults with strike orthogonal and oblique to the extension direction respectively this general concept is in disagreement with observations from natural oblique rifts where faults show dip slip kinematics indicating pure extension irrespective of the fault strike with respect to the regional extension direction consequently along oblique structures slip is re oriented and oblique to the applied extension direction besides at fault scale slip is re oriented along strike such that it is dip slip at the fault center and becomes highly oblique slip toward the fault tips here we use analogue experiments to show that this discrepancy can be resolved when a preexisting weak zone wz is present in the crust at the onset of oblique extension the wz is implemented within the lower crust and strikes oblique to the extension direction our experimental results show that an inherited wz within the ductile crust favors the re orientation of slip such that oblique extension results in pure dip slip displacement on faults that strike oblique with respect to the extension direction furthermore we show that slip is re oriented along strike of major faults such that the fault center shows dip slip kinematics whereas its tips display strike slip kinematics these findings call into question the use of paleostress reconstructions to constrain plate kinematics in oblique extensional tectonic settings

monte carlo ssa to detect time variable seasonal oscillations from gps derived site position time series abstract we explore the capability of singular spectrum analysis ssa to extract time variable seasonal oscillations from continual gps observations and demonstrate the statistical assessment on the colored noise in particular the first order autoregressive ar 1 noise using monte carlo ssa mcssa methodology we provide example applications to 15 year vertical coordinate time series for 36 globally distributed international gnss service igs sites we find the ssa filtered seasonal signals can easily pass the confidence interval and hypothesis tests of mcssa however maximum likelihood estimate mle results show that 72 of sites have their flicker noise amplitudes reduced after removing ssa filtered annual signal implying that the ssa filtered seasonal signals may contain an artificial signal driven by colored noise therefore the ar 1 null hypothesis noise model may be misleading in surrogate data tests for gps seasonal signals moreover comparison between ssa filtered gps annual signals and joint geophysical model predictions non tidal atmospheric loading non tidal ocean loading hydrological loading confirms that seasonal signals are resulting from a combination of mass loading and systematic error

frequent activity on vulcano italy spanning the last 80 ky new insights from the chemo stratigraphy of the brown tuffs abstract the brown tuffs bt are widespread reddish brown to grey ash rich pyroclastic deposits recognized in the stratigraphic sequences of the aeolian islands and capo millazzo peninsula sicily that span the last 80 ky they have very homogeneous lithological textural and sedimentological features which make it difficult to reliably correlate units on the islands to proximal units in the source areas here we carefully re interpret the stratigraphic profiles of the bt on vulcano and lipari where the deposits are thickest and present the most complete succession the investigation is based on a large dataset of major and minor element geochemistry of juvenile glass components for the majority of the recognized bt depositional units whilst also providing new radiocarbon ages the distinctive chemical groupings observed within the glass analyses both temporally and spatially allow us to fingerprint the three main stratigraphically defined macro units in which the bt succession can be sub divided using prominent tephra marker beds the ischia tephra monte epomeo green tuff 56 ky and monte guardia pyroclastics from lipari herein radiocarbon dated to 27 26 ky the lower 80 56 ky lbt intermediate 56 27 ky ibt and upper bt here dated at 24 6 ky ubt macro units display k series volcanic glasses ranging from basaltic trachy andesites through trachy andesites to more evolved trachytes all consistent with an origin on vulcano the ubt are clearly distinguished from the lower macro units by their higher sio2 trachy andesite to trachytic glasses which extend to noticeably lower tio2 cao and mgo contents these features make it possible to re define the geochemical evolutionary boundary between ibt and ubt as corresponding to the 24 ky spiaggia lunga scoria bed on vulcano which is stratigraphically higher and younger than the previous boundary marker monte guardia the glass compositions of the lbt ibt and ubt are used to 1 assess links to known proximal eruption units outcropping on vulcano 2 validate medial distal bt occurrences across the aeolian archipelago salina filicudi and panarea and on capo millazzo 3 confirm that the bt are responsible for distal volcanic ash layers preserved in central mediterranean marine sedimentary archives interestingly the glass compositions of the ubt are very similar to those of the punte nere unit the earliest pyroclastic products erupted from the currently active la fossa cone on vulcano indicating the corresponding magmatic system has likely erupted similar melts and products over the last 24 ky and thus extending its life cycle such information is crucial for evaluating the long term eruption scenarios underpinning hazard assessment of the la fossa caldera magmatic system

numerical simulations of global scale high resolution hydrological crustal deformations 1 high resolution load induced crustal deformations calculated from numerical models are tested for their ability to predict hydrologically induced station height variability as they are known to be large enough to affect epoch wise parameters obtained from the analysis of global geodetic networks loading contributions due to terrestrial water storage as given by global hydrological models are calculated on a 0 5 global regular grid with daily temporal resolution apart from the dominant seasonal variations the hydrological loading signal discloses also rapid changes exceeding 1 mm in several regions that can be associated with major precipitation events and river floods locally strong loading signals with exceptionally high amplitudes in many cases even with nonseasonal nature occur along the major river channels only high resolution loading calculations considering also the water mass anomalies stored in the model river flow can resolve the correct amplitudes in the surrounded area up to 100 km distance the comparison of the modeled hydrological surface deformation with gps station time series shows that high resolution hydrological loading estimates based on global scale models are able to explain a considerable fraction up to 54 of the observed vertical station movements caused by continental water storage variations

crustal displacements due to continental water loading the effects of long wavelength 100 km seasonal variability in continental water storage on vertical crustal motions are assessed the modeled vertical displace ments arm have root mean square rms values for 1994 1998 as large as 8 mm with ranges up to 30 mm and are predominantly annual in character regional strains are on the order of 20 nanostrain for tilt and 5 nanostrain for hori zontal deformation we compare arm with observed global positioning system gps heights aro which include ad justments to remove estimated effects of atmospheric pres sure and annual tidal and non tidal ocean loading for 147 globally distributed sites when the aro time series are ad justed by arm their variances are reduced on average by an amount equal to the variance of the arm of the aro time series exhibiting a strong annual signal more than half

evolution of the fossa cone vulcano abstract in decreasing order of abundance the principal emplacement mechanisms for deposits of the fossa edifice of vulcano include dry surge wet surge pyroclastic fall lahar lava flow pyroclastic flow and epiclastic processes most samples from pyroclastic beds on fossa contain two grain size populations the coarser mode at 0 5 1 5 resulted from modified ballistic transport whereas the finer mode at 2 5 3 5 is related to surge transport reconstruction of the entire stratigraphy of the cone permits the beds to be grouped into five principal eruptive cycles all of which postdate the lower pilato ash of lipari dated at 11 000 to 8 500 y b p pte nere cycle palizzi cycle commenda cycle pietre cotte cycle and the modern cycle additional cycles may be present but exposures on the cone are insufficient for their adequate definition all cycles follow a similar stochastic pattern starting with surge eruptions and ending with effusion of lava from the crater rim the frequency of pyroclastic fall events increases with time throughout each cycle this progressive decrease in the efficiency of water melt interaction through the duration of each cycle may be due to a gradual rise of each new magma column coupled with an increase in magmatic volatiles tectonism and magma mixing both play a role in triggering eruptions on fossa the present crater lies at the intersection of two prominent tectonic trends a nnw fracture system parallels the main eruptive centers and an ene set aligns with the migration of minor vents the silicic lavas of fossa contain a mixture of two components xenocrysts of plagioclase augite and olivine surrounded by a dark glass are intimately dispersed into an evolved rhyolitic matrix

unexpected earthquake hazard revealed by holocene rupture on the kenchreai fault central greece implications for weak sub fault shear zones this work forms part of the nercand esrc funded project earthquakes without frontiers and was partly funded by the nerc grant looking inside the continents from space

atmospheric pressure loading corrections applied to gps data at the observation level 1 space geodetic techniques can detect elastic deformation of the earth caused by atmospheric pressure loading atml however it has not yet been demonstrated whether these surface displacements should be accounted for at the time of reduction of the observations or by applying time averaged values to the coordinates after the analysis of the observations an analysis of the power spectral density of the atml predicted vertical deformation shows that aside from the diurnal and semi diurnal periods there is very little power in the sub daily frequencies the present tidal atml models improve the analysis at sites near the equator but seem to degrade the height estimates elsewhere the majority of the non tidal deformation can be modelled by applying a daily averaged correction to daily estimates of coordinates but a greater improvement in height rms is found if non tidal atml is applied at the observation level

magnitude assessment for the historical earthquake based on strong motion simulation and liquefaction analysis case of the 1894 atalanti earthquake greece abstract the historical earthquake of the 1894 in atalanti greece produced widespread liquefaction effects on the broader coastal area although this earthquake has been extensively studied in the past its magnitude still remains controversial in the present study we propose an indirect method for assessing its magnitude by simulating the ground motion and liquefaction effects caused by a scenario earthquake with the characteristics of the 1894 event at several sites located at the coastal zone of atalanti bay for this purpose we utilize information about the near surface soil conditions obtained by geophysical tools data of recent seismic events and results of stochastic simulation of strong ground motion for the scenario earthquake of the 1894 event we confirm the high liquefaction potential of the investigated sites and establish that the low limit of magnitude m w for the 1894 earthquake is equal to 7 0 electronic supplement results of liquefaction analysis

instantaneous deformation from continuous gps contributions from quasi periodic loads summary continuous gps cgps coordinate time series are known to experience repeating deformation signals with seasonal and other periods it is unlikely that these signals represent perfect sinusoids with temporally constant amplitude we develop an analysis method that accommodates temporal variations in the amplitudes of sinusoidal signals we apply the method to simulated coordinate time series to numerically explore the potential consequences of neglecting decadal variation in amplitude of annual motions on the residual error spectra of cgps measurements as well as potential bias in estimates for secular site velocity we find that secular velocity bias can be appreciable for shorter time series and that residual error time series of longer duration may contain significant power in a broad band centred on semiannual frequency if temporal variation in the amplitude of annual motions is not accounted for in the model used to reduce the observations to residuals it may be difficult to differentiate the bandpass filtered signature of mismodelled loading signals from power law noise using residual error spectra for shorter time series we provide an example application to a 9 yr coordinate time series for a cgps station located in southern california at carbon creek control structure cccs which is known to experience large amplitude seasonal motions associated with the santa ana aquifer system

apparent stability of gps monumentation from short baseline time series 1 long running short 1 km gps baselines offer an insight into the accuracy budget of geophysical estimates inferred from gps coordinate time series in this paper we report on analysis of 10 short baselines using data spanning several years and examine deviations from a constant baseline length annual signals with amplitude 0 5 mm are evident in various coordinate components at 6 of the 10 sites with amplitudes exceeding 2 5 mm on two baselines these signals are largely invariant to elevation cutoff angle multipath and phase center model errors are shown to probably have negligible effects at most sites at annual periods they are therefore likely real monument motions although linear thermal expansion is negligible at most sites linear trends 0 25 mm yr 1 are evident on four baselines in at least one coordinate component subdaily signals are present at all sites at k1 and its higher harmonics time correlated noise possibly in the form of flicker noise dominates despite many common signals being eliminated as a result of the small baseline lengths although it is around 1 order of magnitude smaller than for single site ppp solutions we constrain monument random walk motion to be no more than 0 5 mm yr 1 2 if these baseline motion results were representative of the 300 currently active igs sites 180 would have annual signals 0 5 mm in at least one coordinate component 120 would have linear rates 0 25 mm yr 1 and almost all sites would have subdaily k1 k2 signals of 0 1 mm each solely due to local site effects

magnetic fabric flow directions and source area of the lower miocene peach springs tuff in arizona california and nevada we have used anisotropy of magnetic susceptibility ams to define the flow fabric and possible source area of the peach springs tuff a widespread rhyolitic ash flow tuff in the mojave desert and great basin of california arizona and nevada the tuff is an important stratigraphic marker from the colorado plateau to barstow california a distance of 350 km however the location of its source caldera is unknown dated at 18 5 ma by 40ar 39 ar the tuff erupted during the early stages of miocene extension along the lower colorado river the thicker accumulations 100 m occur at kingman arizona and in the piute mountains california on opposite sides of the colorado river extensional corridor our ams studies produced well defined magnetic lineations in 30 of 42 sites distributed throughout the tuff typical ratios of the principal ams axes are 1 01 for the magnetic lineation kmax kint and 1 02 for the foliation kint kmin the bulk magnetic susceptibility of the peach springs tuff averages 2 0 10 3 in the si unit system the subhorizontal lineations which presumably parallel the flow directions form a pattern radiating outward from the approximate center of the outcrop area magnetic foliations define an imbrication that generally dips away from the distal margins and toward the center of the outcrop of the tuff the lineation and imbrication indicate a source region near the southern tip of nevada defining the best intersection of the ams lineations required restoration of major extension strike slip faulting and associated tectonic rotation in the disrupted tuff the optimum intersection of magnetic lineations lies in the southern black mountains of arizona on the eastern side of the colorado river extensional corridor no caldera structures are known from that area but the area contains thick sections of the peach springs tuff above a silicic volcanic center the caldera may be buried under younger deposits in the mohave valley of arizona tertiary granite in the newberry mountains may represent a deeper level of the peach springs tuff vent that has been exhumed by detachment faulting

three dimensional model of hellenic arc deformation and origin of the cretan uplift 1 the hellenic arc of greece is the most seismically active part of europe but little is know about its mechanics we modeled deformation along the arc using a finite element model the model was intended to capture large scale 3 d structure of nubian plate subduction beneath the aegean block and its deformational consequences the shape of the interface was developed using mapped traces at the surface and earthquake hypocenters at depth model block motions were constrained by recent compilations of gps velocity vectors we simulated a 10 ka period of convergence between nubia and the aegean and calculated the strain field in the overriding plate as well as the spatial distribution and orientation of differential stress 1 3 from these calculations we derived testable quantities such as the expected seismic moment rate on the interplate contact uplift pattern and distribution of strain modes our relatively simple model broadly reproduced observed uplift patterns earthquake activity and loci of extension and contraction the model showed a localization of uplift near the island of crete where the fastest aegean uplift rates are well documented comparison of calculated expected seismic moment and observed earthquake catalogs implies a nearly fully coupled interplate contact on the basis of our modeling results we suggest that south aegean deformation is driven primarily by the fast moving 33 mm a 1 aegean upper plate overriding a nearly stalled 5 mm a 1 nubian lower plate this tectonic setting thus more closely resembles a continental thrust than it does a typical oceanic subduction zone

reply to comments to volcanic geomorphology and tectonics of the aeolian archipelago southern italy based on integrated dem data by favalli et al bull volcanol 68 157 170 2005 doi 10 1007 s00445 005 0429 3 by calanchi et al 2007 bull volcanol doi 10 1007 s00445 007 0134 5

a method for correcting geographically separated remanence directions for the purpose of archaeomagnetic dating summary spatial variations in the geomagnetic field must be taken into account if secular variation master curves and directional magnetic dates are to be optimized two methods for relocating remanence vectors have been proposed and in this paper their relative accuracies are compared using a numerical model based on the present day field a method which converts archaeomagnetic directions via a virtual geomagnetic pole is shown to be the more efficient transformation for an archaeomagnetic region the size of the british isles 900 km radius the maximum error in relocating vectors to a central location is predicted to be of the order of 1 2

paleomagnetic secular variation at vulcano aeolian islands during the last 135 kyr abstract paleosecular variation psv of the earth s magnetic field during the last 135 kyr has been investigated in lavas scoriae and pyroclastic rocks of vulcano aeolian islands about 1000 samples have been collected at 77 sites from 25 distinct volcanic units whose age is either known from published isotopical data or constrained on the grounds of statigraphical relationships magnetic mineralogy investigation shows that ti magnetite is the main ferromagnetic mineral at most sites secondary magnetization components are either absent or easily removed by stepwise thermal or alternating field demagnetization the mean site direction of the characteristic remanent magnetization is usually well defined since the semi angle of confidence is greater than 5 at only four sites the mean paleomagnetic direction over the last 135 kyr d 9 4 i 53 2 95 3 5 differs from the geocentric axial dipole gad at vulcano d 0 i 57 8 and might be interpreted as the effect of a long term non axial dipolar component the psv record from vulcano agrees well with those from the lacustrine sediments of lago grande di monticchio 100 kyr bp and lago di mezzano 30 kyr bp located in the italian peninsula brandt et al quat sci rev 18 1999 961 976 the inclination anomaly i found at vulcano corresponds to about half of the shallowing observed in the sediments of the two lakes and the declination anomaly d may be used to tie the declination values derived from azimuthally unoriented cores to the geographical reference system in order to find the optimum site to be used as reference for psv studies in italy the angular values of the earth s magnetic field measured at the 113 repeat stations of the italian geomagnetic network coticchia et al boll geod sci aff 40 2001 277 291 have been analyzed with the relocation via pole method noel and batt geophys j int 102 1990 753 756 the viterbo station lat 42 27 n long 12 02 e proved the best since the mean error is 0 3 for both declination and inclination wherever the original psv site is located in italy a preliminary composite psv curve for the last 30 kyr bp is thus proposed merging and relocating to viterbo the data from vulcano and the curve from lago di mezzano corrected for the gad deviation found at vulcano

meandering flow of a pyroclastic density current documented by the anisotropy of magnetic susceptibility ams in the quartz latite ignimbrite of the pleistocene monte cimino volcanic centre central italy abstract a pattern of shifting current direction is revealed by the anisotropy of magnetic susceptibility ams in the quartz latite ignimbrite associated with the pleistocene cimini dome complex in central italy high field ams documents that both paramagnetic and ferrimagnetic minerals contribute to the magnetic fabric of the ignimbrite the results of low field ams studies suggest that the pyroclastic density current changed both direction and character during deposition of each flow unit that makes up the ignimbrite the meandering behaviour of the currents can be observed on the scale of 15 cm increments in the fine grained basal layer 2a of one flow unit in an area lacking significant palaeotopography ams data from 1 2 and 4 metre increments through the flow units also show complex changes in flow direction throughout the deposition of each unit studied the most closely aligned ams fabrics occur near the bases of flow units and dispersion increases upward this trend may represent decreased shear between the flow and the substrate or increased turbulence in the upper depositional zone of the pyroclastic density current or both suggesting a progressively waning current in terms of capacity or particle concentration the phenomena observed in this study have broad implications for the general methodology of ams studies detailed vertical profiles made up of several individual sample sites within 1 metre thickness intervals can reveal small scale current flow variations that may not be evident if sampling is done more sparsely

geomorphology and surface tilting in an active extensional basin sw montana usa the valley and alluvial cone of the antecedent madison river in the missouri flats area of sw montana lie in a half graben bounded by a prominent prehistoric fault scarp footwall sourced alluvial fans and fans derived from a major transfer zone have prograded onto the oldest of a prominent suite of three paired terraces of holocene age which bound the modern braided floodplain of the river the terraces have been cut into the pleistocene alluvial cone and are cut by the prehistoric fault scarp levelling studies on the terrace surfaces in the hangingwall reveal that movement on the fault has caused surface tilting erosion and deposition a suite of terraces present in the footwall of the fault shows backtihing consistent with footwall uplift having occurred

age and petrology of the late pleistocene brown tuffs on lipari italy late pleistocene volcanic products on lipari consist mainly of pyroclastic surge deposits monte guardia sequence and fine grained brown tuffs radiometric age determination on carbon from thin soils at the top of the tuffs indicate that they have several ages of emplacement ranging from more than 35 000 to 16 800 years ago chemical and microprobe data on glass and mineral fragments from these tuffs show that they belong to a shoshonite or high k series this composition is compatible with an origin related to the magma system of vulcano but not with the magma system on lipari

volcanic history of lipari aeolian islands italy during the last 10 000 years abstract examination of the volcanic stratigraphy of deposits younger than 10 000 years on lipari indicates four principal periods of volcanic activity related to specific centers the products from each different volcanic center are defined as volcano stratigraphic unit vsu from the oldest these are the canneto dentro gabellotto fiume bianco forgia vecchia and monte pilato rocche rosse vsus the study of textures and dispersal of the deposits permitted the vents to be localized and the recent volcanic history of lipari to be reconstructed the oldest event formed a small explosion breccia cone with a final obsidian lava in the canneto dentro area immediately afterward a complex series of explosions produced the widespread dry surge deposits of the gabellotto fiume bianco sequence this activity ended with the extrusion of a domical lava flow the renewal of activity occurred in the pirrera area with an explosive eruption that produced explosion breccia deposits the last eruptions from this vent were coeval with the first eruption of m pilato the rim of the explosion breccia cone was partially destroyed by the forgia vecchia lava flow m pilato cone grew in a very short period of time due to a continuous swarm of explosive events after a short repose time a series of more energetic and superficial explosions occurred through a vent slightly to the south the extrusion of the rocche rosse lava flow about 729 a d ended this cycle of activity all the volcanic centers follow a quite similar stochastic pattern starting with a fall or surge eruption and ending with effusion of viscous rhyolitic lavas the four centers are aligned along either nw se or ne sw fault systems according to the structural pattern of the island they can be placed into two groups the canneto dentro gabellotto centers and the forgia vecchia m pilato centers a long quiescence 3 500 years separates the activity of these two groups while inside of each the activities were nearly contemporaneous or in rapid succession

monte guardia sequence a late pleistocene eruptive cycle on lipari italy this paper documents a complex sequence of interbedded lapilli fall base surge and pyroclastic flow deposits here named the monte guardia sequence that erupted from volcanic centers in the southern part of lipari aeolian island arc radiocarbon data from ash flow tuffs above and below this sequence bracket its eruption between 22 600 and 16 800 years ago geologic evidence however suggests that this single eruptive cycle had a more restricted duration of years to tens of years the basis for our interpretations comes from data measured at 38 detailed sections located throughout the island the monte guardia sequence rests on a series of lower rhyolitic endogenous domes in the southern part of lipari and it covers the oldest lavas lahars and pyroclastic flows in the north only in the northeast part of the island is it covered by younger deposits which there consist of lapilli tuffs and lavas of the monte pilato rhyolitic cycle the deposit ranges in thickness from more than 60 m surrounding the vents in the south to less than a few decimeters at 10 km distance in the north throughout most of the island the monte guardia sequence overlies a thin andesitic lapilli fall layer which is a key bed for correlation this lapilli tuff probably erupted from a volcanic center on another island of the aeolian arc possibly salina the principal activity of the monte guardia sequence started with an explosion that formed a continuous breccia blanket covering most of the island some pumiceous blocks within this breccia are composed of alternating bands of acidic and andesitic composition suggesting that the initiation of pyroclastic activity could have been triggered by magma mixing typical monte guardia sequence consists of explosive products that grade from magmatic pumice fall to phreatomagmatic base surge character the eruptive cycle is characterized by a number of energy decreasing megarhythms that start with a lapilli fall bed and end with a base surge set that progresses through sand wave massive and planar beds isopach maps of the fall and surge deposits indicate that both types were directed to the northwest by prevailing winds existing topographic relief was an additional factor that affected the emplacement of surge products at the end of the cycle andesitic pyroclastic flows and rhyolitic endogenous domes were emplaced above the monte guardia deposits near the vent

temporal evolution of a three component system the island of lipari aeolian arc southern italy the volcanic products from lipari define an evolutionary trend with a high gradient of k enrichment similar to the calc alkaline to potassic volcanism of other islands in the aeolian arc stratigraphic reconstruction of the island based on field and geochronological data indicate that the volcanic activity can be subdivided in two stages the first stage from 223 to 42 ka consists of six eruptive cycles and is characterized by basalts and basalt andesites showing progressive increase in both sio2 and k2o contents with time the second stage consists of four cycles erupted since 42 ka and is marked by an apparent rejuvenation of the geochemical system with the appearance of the first rhyolitic products fractional crystallization assimilation and mixing models suggest that the geochemistry of lipari volcanism evolved with time by a complex interplay between two mantle derived components one sub alkaline and the other alkaline in addition to crustal melts and or crustally derived materials a petrogenetic model in which fractional crystallization was subordinate to mixing best fits the geochemical data and petrographic observations of macro and microscopic features melts from the crustal and mantle end members are almost always present in the system but the relative proportions appear to vary with time the sub alkaline mantle component source of tyrrhenian tholeiites is an important contributor to the early evolution of the volcanism in lipari input from the alkaline mantle component source of the roman comagmatic province increases with time and the crustal component becomes dominant in the later activity the preferred petrogenetic model for the temporal evolution of the volcanic system in lipari involves melting initially caused by an increase in the thermal input related to the opening of the tyrrhenian sea and or to subduction processes the quick rise of the isotherms and almost contemporaneous melting of source materials with different compositions favored complex mixing during ascent of the melts

active folding in the algerian earthquake of 10 october 1980 a fold controlling the form of the local topography near el asnam algeria increased in amplitude at the time of the earthquake of 10 october 1980 the deformation occurred rapidly in an elastic brittle manner and not in the gradual ductile fashion in which folds are normally thought to develop

effect of annual signals on geodetic velocity 1 our analysis of global positioning system gps site coordinates in a global reference frame shows annual variation with typical amplitudes of 2 mm for horizontal and 4 mm for vertical with some sites at twice these amplitudes power spectrum analysis confirms that gps time series also contain significant power at annual harmonic frequencies with spectral indices 1 2 which indicates the presence of repeating signals van dam et al 2001 showed that a major annual component is induced by hydrological and atmospheric loading unless accounted for we show that annual signals can significantly bias estimation of site velocities intended for high accuracy purposes such as plate tectonics and reference frames for such applications annual and semiannual sinusoidal signals should be estimated simultaneously with site velocity and initial position we have developed a model to calculate the level of bias in published velocities that do not account for annual signals simultaneous estimation might not be necessary beyond 4 5 years as the velocity bias rapidly becomes negligible minimum velocity bias is theoretically predicted at integer plus half years as confirmed by tests with real data below 2 5 years the velocity bias can become unacceptably large and simultaneous estimation does not necessarily improve velocity estimates which rapidly become unstable due to correlated parameters we recommend that 2 5 years be adopted as a standard minimum data span for velocity solutions intended for tectonic interpretation or reference frame production and that we be skeptical of geophysical interpretations of velocities derived using shorter data spans

deep water basins within the mesozoic carbonate platform of argolis greece in the past the classic argolis area of the central southern hellenides was interpreted as comprised of essentially in situ carbonate platforms and basins or alternatively of far travelled thrust sheets derived from a mesozoic ocean basin sited well to the east vardar ocean our fieldwork however demonstrates that at two key localities an important unit of middle triassic early jurassic deep water redeposited carbonates asklipion unit passes laterally into shallow water platform carbonates pantakrator unit the deep water limestones represent basins within the platform rather than far travelled thrust sheets while other slices of deep water limestone record a platform margin further east the basins originated during middle triassic ladinian rifting of the neotethys and are floored by extrusive rocks of intermediate composition highly condensed ammonitico rosso pelagic limestones accumulated on an inferred volcanic seamount during the mid late triassic anisian carnian the platforms slowly subsided in early jurassic time while the basins partly filled with redeposited carbonates adhami limestone shallow water carbonates locally transgressed the margins of the deeper water basins the platforms were submerged in the mid jurassic toarcian bathonian with the deposition of pink pelagic ammonitico rosso followed by marked subsidence and ribbon radiolarite deposition below the carbonate compensation depth e g koliaki chert in early late jurassic time kimmeridgian the area was regionally compressed eohellenic phase and the intraplatform basins founded on thinned continental crust were inverted and thrust up to several kilometres over the adjacent platform units the deformed continental margin then flexurally subsided ahead of emplacing jurassic ophiolites largely olistostromes migdhalitsa unit after taking account of up to 90 degrees clockwise palaeorotation of assumed neotectonic age kinematic indicators and facies trends suggest the ophiolite was derived from a pindos ocean basin originally sited to the west early cretaceous transgression resulted in the deposition of shallow water limestone and was followed by late cretaceous deep water limestone then terrigenous flysch accumulation in a foreland basin related to final suturing of the neotethyan ocean later the area was dissected by a series of mainly e w trending high angle neotectonic normal faults related to the aegean back arc extensional system

stratigraphy and significance of brown tuffs on the aeolian islands southern italy abstract brown tuffs bt are volcaniclastic ash deposits prominently represented in the stratigraphic profiles of all the aeolian islands and capo milazzo on the northern coast of sicily detailed stratigraphy and tephrochronology together with available radiometric ages suggest that they were emplaced over a long time interval spanning from the end of the last interglacial period ca 80 ka bp up to 4 5 ka bp age of the overlying punte nere pyroclastic products on vulcano the most complete bt succession is documented on lipari where 14 distinct and successive units are subdivided by the interbedding of widespread tephra layers local volcanic products paleosols and epiclastic deposits and the occurrence of local erosive surfaces inter island occurrence of ischia tephra a widely known tephra layer in the aeolian archipelago dated at 56 ka bp and monte guardia pyroclastics from lipari dated at 22 20 ka bp subdivides the bt succession in upper ubt intermediate ibt and lower bt units lbt which can be correlated at regional level the lbt was emplaced between 80 and 56 ka bp the ibt between 56 and 22 ka bp and the ubt between 20 and 4 5 ka bp on the basis of stratigraphy similarity in lithology and textural features morphology of glass fragments composition and consistency of thickness and grain size variations ubt units correlate with piano grotte dei rossi tuffs on vulcano island they were generated by pulsating hydromagmatic explosive activity giving rise to pyroclastic density currents spreading laterally from a source located inside the la fossa caldera on vulcano island composition is in agreement with this hypothesis since ubt compositional features match those of vulcano magmas erupted in that period the effect of co ignimbrite ash clouds or associated fallout processes from sustained eruptive columns is seen to explain the presence of ubt in areas further away from the suggested source e g salina and lipari islands and capo milazzo the origin of ubt exposed on panarea island is still a matter of debate due to contrasting compositional data due to large uniformity of lithological textural and componentry characters with respect to the ubt the lower portions of the bt succession lbt ibt are considered to be the result of recurrent large scale hydromagmatic eruptions of similar type moreover for the ibt units the correlation with monte molineddo 3 pyroclastics of vulcano island on the basis of lithological compositional and stratigraphic matching again suggests source s related to the vulcano plumbing system and located within the la fossa caldera

fractal characteristics of active normal faults an example of the eastern gulf of corinth greece abstract we present a model proposing the evolution of segmented normal faults in a currently extended area allowing an explanation of strong earthquakes hosted by short faults active normal faults accommodating the current extension in the gulf of corinth result from the linkage of smaller component faults well exposed fault zones in the sofiko range are arranged as pairs of graben bounding faults and thus our structural analysis has implications for the evolution of active normal faults as well as graben evolution a basal strip of fresh bedrock at the base of fault scarps suggests continuous seismic or aseismic creep thus the structural analysis of component faults that show a power law length distribution describes an evolved fault zone of particular interest is that faulting in this region is self similar between limits distribution is characterized by a fractal dimension of d 1 and the limits in our study are between 10 m mapping resolution and double the maximum displacement of each fault zone component segments of any compartmentalized fault show a length to maximum displacement ratio of two basin architecture and structural analysis suggest that the nucleation points of faults are detectable over the entire evolution of the fault zone all analyzed faults evolved by an independent nucleation model morphotectonic and kinematic data as well as fractal dimension of trace length population plots all suggest that fault zones defining north and south dipping conjugates are active at least over the late stages of basin evolution although this study was focused on a relatively small area this pattern of fault growth appears to be applicable to the entire fault population in the gulf of corinth and is thus an important model for normal faults

a source study of the thessaloniki northern greece 1978 earthquake sequence summary the thessaloniki northern greece earthquake sequence appears to have occurred along faults forming a graben structure this graben situated in the border region between the serbomacedonian massif and the vardar zone is bounded to the south west by clearly exposed north west striking north east dipping normal faults relative hypocentre determinations fault plane solutions surface faulting and the aftershock distribution suggest that some of these faults have been reactivated during the 1978 earthquakes the source parameters of the mainshock mb 6 1 ms 6 4 were determined by computing body wave synthetic seismograms in the time domain and comparing them with the observed this modelling constrained the orientation of faulting determined by the p wave fault plane solution it also constrained the source depth to 6 mp 2 km similar depths were calculated by a relative relocation method for the other three large events of the sequence the dislocation time function required for the far field had a total duration of 9 mp 1 5 s the body wave moment was 5 2 mp 1 8 times 1025 dyne cm for a fault length of 35 km and a fault width of 17 km both estimated from the aftershock distribution the static stress drop was found to be 4 bar an accelerograph record of the mainshock shows two distinct events 3 4 s apart these two events were unresolved by the long period data in the far field but the unusually long duration of the mainshock time function suggests an overall slow energy release which probably occurred as a sequence of events close in space and time seismic energy released in this fashion can account for waveform complexities observed at some stations

basement faulting and the focal depths of the larger earthquakes in the zagros mountains iran summary the present day seismicity of the zagros seems to occur on high angle reverse faults distributed across the whole width of the belt it does not indicate activity on a single inclined thrust surface and there do not seem to have been any well located events at intermediate depths modelling of the long period teleseismic body waves of seven large earthquakes presented here shows their focal depths to be in the range 8 15 km this is thought to indicate faulting in the uppermost basement beneath the sedimentary cover though the absence of published seismic refraction results renders the sediment thickness uncertain faulting of this type and depth may occur on inherited normal faults which have subsequently been reactivated as thrusts such reactivation allows considerable shortening to take place in the early stages of continental collision without the subduction or excessive thickening of continental crust

southern california permanent gps geodetic array error analysis of daily position estimates and site velocities we analyze time series of daily positions estimated from data collected by 10 continuously monitoring global positioning system gps sites in southern california during the 19 month period between the june 28 1992 mw 7 3 landers and january 17 1994 mw 6 7 northridge earthquakes each time series exhibits a linear tectonic signal and significant colored noise spectral power at frequencies in the range 5 yr 1 to 0 5 d 1 is dominated by white noise or possibly fractal white noise and is several orders of magnitude higher than what would be expected from random walk noise in this short period range attributed by others to geodetic monument motions estimating a single slope for the time series power spectra suggests fractal white noise processes with spectral indices of about 0 4 site velocity uncertainties assuming this fractal white noise model are 2 4 times larger than uncertainties obtained assuming a purely white noise model a combination white noise plus flicker noise spectral index of 1 model also fits the data and suggests that the velocity uncertainties should be 3 6 times larger than for the white noise model we cannot adequately distinguish between these two noise models nor can we rule out the possibility of a random walk signal at the lowest frequencies these questions await the analysis of longer time series in any case reducing the magnitude of low frequency colored noise is critical and appears to be best accomplished by building sites with deeply anchored and braced monuments otherwise rate uncertainties estimated from continuous gps measurements may not be improved significantly compared to those estimated from infrequent campaign mode measurements

composite detrital and thermal remanent magnetization in tuffs from aeolian islands southern tyrrhenian sea revealed by magnetic anisotropy this paper reports on the complex relation between rock emplacement and remanence acquisition in tuffs deposited by pyroclastic density currents disclosed by systematic measurements of the anisotropy of magnetic susceptibility and natural remanent magnetization nrm thermal demagnetization shows that the nrm consists of two components with different blocking temperature spectra the direction of the low temperature component is consistent with the geocentric axial dipole value whereas the high temperature component has dispersed directions the magnetic fabric is oblate the magnetic foliation is close to the bedding and the lineations are generally dispersed along a girdle within the foliation plane the directions of the magnetic lineation and the high temperature remanence component of individual specimens are close to each other this correspondence suggests that the high blocking temperature grains acquired a remanence aligned to their long dimension before deposition while cooling within the explosive cloud and the moving pyroclastic current thereafter during deposition the traction processes at the base of the current oriented the grains along the flow direction and affected both fabric and high temperature remanence this nrm component results from mechanical orientation of previously magnetized grains and is thus detrital in origin a second thermal component was then acquired during the cooling of the low blocking temperature grains after deposition these results show that nrm in fine grained pyroclastic rocks is affected by the earth s magnetic field as well as the emplacement processes and that magnetic fabric data are essential to unravel its complex nature

eruptive and emplacement mechanisms of widespread fine grained pyroclastic deposits on vulcano island italy tufi di grotte dei rossi inferiori are thick ash deposits representing the most voluminous stratigraphic unit on vulcano island the deposits are related to hydromagmatic eruption which occurred under shallow water inside a caldera depression grain size data and results of sem investigation allow the character of the transporting medium solid material concentration in the cloud during the lateral expansion and the nature and role of the fluids present at the time of deposition to be constrained we suggest that the eruption was characterized by closely timed hydromagmatic pulses giving rise to eruption clouds rich in water vapor and steam the coarser material was not significantly transported in the eruptive cloud and it probably deposited in the caldera depression area the finer material was extensively transported in the cloud creating turbulent flows which surmounted the caldera rim barrier and dispersed in a southward direction forming widespread deposits in the piano area lower concentrated flows produced laminated deposits of more limited dispersion whereas higher concentrated flows formed more dispersed thicker massive layers

reflection refraction seismics in the gulf of corinth hints at deep structure and control of the deep marine basin abstract the gulf of corinth is a natural laboratory for the study of seismicity and crustal deformation during continental extension seismic profiling along its axis provides a 24 fold normal incidence seismic reflection profile and wide angle reflection refraction profiles recorded by sea bottom seismometers obs and land seismometers at wide angle incidence the land receivers document the moho at 40 km depth under the western end of the gulf north of aigion rising to 32 km depth under the northern coast in the east of the gulf both refraction and normal incidence reflection sections image the basement under the deep marine basin that has formed by recent extension the depth to the base of the sedimentary basin beneath the gulf constrained by both methods is no more than 2 7 km with 1 km of water underlain by no more than 1 7 km of sediment less than what was expected from past modeling of uplift of the south coast in the east of the gulf unlike the flat sea bottom the basement and sedimentary interfaces show topography along this axial line several deeps are identified as depocenters which suggest that this axial line is not a strike line to the basin it appears instead to be controlled by several faults oblique to the s60 e overall trend of the south coast of the gulf their more easterly strikes being consistent with the instantaneous direction of extension measured by earthquake slip vectors and by gps

palaeoenvironmental evolution of the ancient harbor of lechaion corinth gulf greece were changes driven by human impacts and gradual coastal processes or catastrophic tsunamis abstract the corinth gulf central greece is one of the most rapidly widening tectonic rifts on earth where large earthquakes with magnitudes of up 7 0 have been documented not only by instrumental records but also assessed from historical reports extending back to the 5th century bce several of these earthquakes were associated with tsunamis particularly in the western part of the gulf of particular interest is the ancient harbor of lechaion in the eastern side of corinth gulf we reexamine the hypothesis that lechaion was hit by high energy tsunami waves in the 8th 6th century bce 1st 2nd century ce and during the 6th century ce on the basis of sedimentological seismotectonic archaeological and historical data completed with field observations we support that there is no evidence for tsunami impact in lechaion local stratigraphy and environmental changes are rather interpreted by human impacts and gradual coastal processes such interpretations confirm that the tsunami potential in the east corinth gulf is relatively low

complex remanent magnetization in the kizilkaya ignimbrite central anatolia implication for paleomagnetic directions abstract pyroclastic flow deposits known as ash flow tuffs or ignimbrites are invaluable materials for paleomagnetic studies with many applications for geological and tectonic purposes however little attention has been paid to evaluating the consistency and reliability of the paleomagnetic data when results are obtained on a single volcanic unit with uneven magnetic mineralogy in this work we investigate this issue by concentrating on the kizilkaya ignimbrite the youngest large volume unit of the neogene ignimbrite sequence of the central anatolian volcanic province in turkey bringing evidence of significant magnetic heterogeneities in ignimbrite deposits magnetic mineralogy susceptibility magnetic remanence coercivity etc and emphasizing the importance of a stratigraphic sampling strategy for this type of volcanic rocks in order to obtain reliable paleomagnetic data six sections were sampled at different stratigraphic heights within the devitrified portion of the ignimbrite isothermal remanence measurements point to low ti titanomagnetite as the main magnetic carrier at all sites at some sites the occurrence of oxidized ti magnetite and hematite is disclosed the bulk susceptibility k m decreases vertically at two out of six sections its value for the topmost samples is commonly one order of magnitude lower than that of the samples at the base in most cases low k m values relate to high coercivity of remanence b cr values which range from 25 to 400 mt and to low s ratios measured at 0 3 t between 0 28 and 0 99 these data point to the occurrence of oxidized magnetic phases we therefore consider the k m parameter as a reliable proxy to check the ignimbrite oxidation stage and to detect the presence of oxidized ti magnetite and hematite within the deposit the characteristic remanent magnetization is determined after stepwise thermal and af demagnetization and clearly isolated by principal component analysis at most sites for these sites the site mean paleomagnetic direction is consistent with data from the literature at a few other sites the remanence is more complex the direction moves along a great circle during demagnetization and no stable end point is reached the occurrence of oxidized ti magnetite or hematite as well as two remanence components with overlapping coercivity and blocking temperature spectra suggest that the kizilkaya ignimbrite acquired first a thermal remanent magnetization and then during the final cooling or a short time later a secondary remanent magnetization component which is interpreted as a crm acquired during post emplacement devitrification processes notwithstanding the kizilkaya ignimbrite is a single cooling unit its magnetic properties suffered substantial variations laterally and vertically within the deposit the kizilkaya case shows that thick pyroclastic deposits should be sampled using a stratigraphic approach at different sites and different stratigraphic heights at each individual sampling location otherwise under sampling may significantly affect the paleomagnetic results when sampling is performed on a short duration or on very poorly preserved deposits we recommend drilling the lower central portion in the most strongly welded and devitrified facies such sampling strategy avoids complications arising from the potential presence of a pervasive secondary crm masking the original chrm