unveiling the sources of the catastrophic 1456 multiple earthquake hints to an unexplored tectonic mechanism in southern italy we revisited data related to the 1456 seismic crisis the largest earthquake to have ever occurred in peninsular italy in search of its causative source s data about this earthquake consist solely of historical reports and their intensity assessment because of the age of this multiple earthquake the scarcity and sparseness of the data and the unusually large damage area no previous studies have attempted to attribute the 1456 events to specific faults existing analytical methods to identify a likely source from intensity data also proved inappropriate for such a sparse dataset since historical evidence suggests that the cumulative damage pattern contains at least three widely separated events we subdivided the 1456 damage pattern into three independent mesoseismal areas each of these areas falls onto east west tectonic trends previously identified and marked by deep 10 km right lateral slip earthquakes based on this evidence we propose 1 that the 1456 events were generated by individual segments of regional east west structures and are evidence of a seismogenic style that involves oblique dextral reactivation of east west lower crustal faults 2 that each event may have triggered subsequent but relatively distant events in a cascade fashion as suggested by historical accounts hence 3 that the 1456 sequence reveals a fundamental but unexplored mechanism of tectonic deformation and seismic release in southern italy this style dominates the region that lies between the northwest southeast system of large extensional faults straddling the crest of the southern apennines and the buried outer front of the chain although the quality of the available information concerning the 1456 earthquake is naturally limited we show that the overlap of the damage distribution the orientation and characteristics of regional tectonic structures the seismicity patterns and the focal mechanisms all concur with our interpretations and would be difficult to justify otherwise

a soft linkage between major seismogenic fault systems in the central southern apennines italy evidence from low magnitude seismicity abstract we investigate the transfer zone and linkage between divergent extensional seismogenic fault systems on the border amid the central and southern apennines central italy these regional nw se striking sets include large seismogenic sources that caused major historical earthquakes m w 7 the faults in the northern part of the study area dip to the southwest those in the southern part dip to the northeast the sw dipping system abruzzi apennines terminates with the aremogna cinque miglia source the ne dipping system southern apennines terminates with the boiano basin source to test whether the transfer zone model applies to the central southern apennines border we analyzed and relocated seismicity that occurred from 2007 to 2011 between the aremogna cinque miglia and boiano basin sources where we expect the transfer zone seismicity is made of independent events md the spatial distribution of seismicity the geometry and kinematics of active faulting in the region and the results from previous geophysical studies allow us to contend the existence of a transfer zone between these seismogenic normal fault systems our data also allow us to recognize the activity of such transfer along the central part of the ortona roccamonfina line we infer that reverse in dip polarity between the two normal fault systems could also result from the passage between the diverse tectonic units composing the border between central and southern apennines

automatic detection of atmospheric boundary layer height using ceilometer backscatter data assisted by a boundary layer model this work tackles the problem of the automated detection of the atmospheric boundary layer bl height h from aerosol lidar ceilometer observations a new method the bayesian selective method bsm is presented it implements a bayesian statistical inference procedure which combines in a statistically optimal way different sources of information firstly atmospheric stratification boundaries are located from discontinuities in the ceilometer backscattered signal the bsm then identifies the discontinuity edge that has the highest probability to effectively mark the bl height information from the contemporaneous physical boundary layer model simulations and a climatological dataset of bl height evolution are combined in the assimilation framework to assist this choice the bsm algorithm has been tested for 4 months of continuous ceilometer measurements collected during the base alfa project and is shown to realistically diagnose the bl depth evolution in many different weather conditions a standard one dimensional processing of the ceilometer signal without the a priori support of the dynamical and climatological bl models often fails to correctly detect h with the greatest inaccuracies occurring at night time when residual layers can generate very strong signals which are then classified by an automated application of the gradient or of the wavelet analysis as the most probable bl height the bsm approach instead carries information on the low climatological probability to find elevated bl depths at night and penalizes the selection of these points moreover this method is able to correctly convey information along the temporal dimension thus filling data gaps using earlier and subsequent ceilometer information for the retrieval copyright 2011 royal meteorological society

the puglia uplift se italy an anomaly in the foreland of the apenninic subduction due to buckling of a thick continental lithosphere the apenninic foreland shows two distinct structural signatures comparing the central adriatic sea and the puglia region during the pliocene pleistocene the central adriatic underwent high subsidence rates due to the eastward rollback of the hinge of the west dipping apenninic subduction the puglia region and the bradanic foredeep are located southward along strike in the same foreland but in contrast with the central adriatic after pliocene early pleistocene subsidence they underwent uplift since the middle pleistocene the geometry and the kinematics of the frontal accretionary wedge and related foreland changed from that moment on between the two areas at the front of the central northern apennines off scraping and subsidence continued whereas the foredeep and foreland of the southern apennines were buckled those differences are interpreted as being due to the larger subduction hinge rollback rate since middle pleistocene of the central adriatic lithosphere 70 km thick with respect to the thicker puglia 110 km the different thicknesses of the continental crust and lithosphere were inherited from the mesozoic rifting that disrupted the adriatic plate the different thicknesses appear to have controlled the variable degree of flexure of the lithosphere and its asthenospheric penetration rate the tremiti e w alignment is the right lateral lithospheric transfer zone of those different tectonic regimes the consequent different dip of the subduction in the two sections steeper west of puglia could also explain the lower elevation of the southern apennines compared to their central northern sector

spatial variation in stresses in peninsular italy and sicily from background seismicity abstract we have retrieved the stress tensor orientation in the italian region applying the fmsi technique gephart j 1990b fmsi a fortran program for inverting fault slickenside and earthquake focal mechanism data to obtain the regional stress tensor comput geosci 16 953 989 to fault plane solutions of 298 small earthquakes 2 5 m d istituto nazionale di geofisica in the period 1988 1995 first we verified that the stress inversion procedure generally applied to a large number of focal mechanisms of earthquakes recorded in a local seismic network could be successfully used in italy using background seismicity recorded over large 100 200 km regions then comparing the stress inversion results with other stress indicators we find that they are geologically sound for many regions in italy even if the misfit values are relatively large we also find that the largest misfit values are determined by a few earthquakes only 10 20 of the total number excluding these earthquakes from inversion the average misfit becomes much lower by 30 40 the results obtained in this study confirm the large variations of the stress field over a relatively short distance in italy but also confirm the existence of regions extending for a few hundred kilometres within which the stress is homogeneous among these most of the apennines are dominated by extension perpendicular to the trend of the mountain belt only in the northern apennines is there any clear distinction between an area of extension in the inner portion of the belt and an area under horizontal compression along the adriatic margin of the belt more rapid variations occur around calabria and sicily as expected because of the complexities linked with the tyrrhenian subduction and with active volcanism in the ionian calabrian coastal region there are hints of active nw se compression although constrained by a few data whereas in the messina strait we observe e w extension and a vertical 1 in northern and western sicily our results indicate n s to nw se compression roughly consistent with the general convergence between the european and the african plates

the gargano promontory an important italian seismogenic tsunamigenic area abstract gargano is a small mountainous promontory protruding into the southern adriatic and from a structural point of view it is part of the apulia foreland deformative structures both inland and offshore the promontory are quite common and can partially be associated with a substantial quaternary uplifting seismogenically this area is well known because several historical strong earthquakes have been reported to occur here and recent important seismic sequences have been recorded this paper is a contribution to evaluate the seismogenic as well as the tsunamigenic potential of this region particular attention has been given to study the major events some of which were able to produce tsunamis the epicenter location of some of these earthquakes computed solely on the basis of macroseismic data would point to focal regions on land but this is questionable if tsunami generation is taken into account as regards the tsunamigenic potential statistical analysis is used to evaluate the local geographical distribution of expected tsunamis and the mean return periods it is found that large events are expected on average every 228 years while a tsunami of any size is generated every about 84 years which is in good agreement with the experimental observations

volatile fluxes through the big bend section of the san andreas fault california helium and carbon dioxide systematics abstract to investigate the source of volatiles and their relationship to the san andreas fault system safs 18 groundwater samples were collected from wells near the big bend section of the safs in southern california and analyzed for helium and carbon abundance and isotopes concentrations of 4 he corrected for air bubble entrainment vary from 4 15 to 62 7 10 8 cm 3 stp g 1 h 2 o 3 he 4 he ratios vary from 0 09 to 3 52 r a where r a air 3 he 4 he consistent with up to 44 mantle helium in samples a subset of 10 samples was analyzed for the major volatile phase co 2 the hypothesized carrier phase of the helium in the mantle crust system co 2 3 he ratios vary from 0 614 to 142 10 11 and 13 c co 2 values vary from 21 5 to 11 9 vs pdb 3 he 4 he ratios and co 2 concentrations are highest in the wells located in the mil potrero and cuddy valleys adjacent to the safs the elevated 3 he 4 he ratios are interpreted to be a consequence of a mantle volatile flux though the safs diluted by radiogenic he produced in the crust samples with the highest 3 he 4 he ratios also had the lowest co 2 3 he ratios the combined helium isotope he co 2 elemental relationships and 13 c co 2 values of the groundwater volatiles reveal a mixture of mantle and deep crustal metamorphic fluid origins the flux of fluids into the seismogenic zone at high hydrostatic pressure may cause fault rupture and transfer volatiles into the shallow crust we calculate an upward fluid flow rate of 147 mm a 1 along the safs up to 37 times higher than previous estimates kennedy et al 1997 however using newly identified characteristics of the safs we calculate a total flux of 3 he along the safs of 7 4 10 3 cm 3 stp a 1 0 33 mol 3 he a 1 and a co 2 flux of 1 5 10 13 cm 3 stp a 1 6 6 10 8 mol a 1 1 of previous estimates lower fluxes along the big bend section of the safs suggest that the flux of mantle volatiles alone is insufficient to cause the super hydrostatic pressure in the seismogenic zone however results identify crustal metamorphic fluids as a major component of the co 2 volatile budget which may represent the additional flux necessary for fault weakening pressure in the safs

diffuse emission of carbon dioxide methane and helium 3 from teide volcano tenerife canary islands diffuse emission of co2 ch4 and he was investigated in the summit crater of teide volcano tenerife canary islands the results indicate that teide volcano releases abundant co2 not only from its active crater but also from its flanks as diffuse soil emanations the spatial distribution of these emanations correlates quite closely with that of geothermal anomalies and manifestations our flux measurements indicate a total output of 380 ton day 1 of co2 and 1 6 on day 1 of ch4 by diffuse degassing from the he co2 ratios and the co2 flux we estimate a diffuse he flux of 0 052 mol year 1 isotopic analysis of carbon in soil gas samples from sites of high soil co2 flux indicates a magmatic origin for the co2 also reported by high he 4he ratios of 5 50 and 5 87 ra the origin of methane is more uncertain with low 13c values suggesting a biogenic contribution

paleoseismic evidence of legendary earthquakes the apparition of archangel michael at monte sant angelo italy abstract the gargano promontory a carbonate massif belonging to the adria microplate the foreland of both the apenninic and dinaric mountain chains is a well known seismogenic area with historic earthquake up to i max x mcs july 30 1627 m 6 7 nevertheless paleoseismic data on the region are still scarce and no trench fault stratigraphy has been analysed along the major e w trending right lateral strike slip fault system that cuts through the whole massif the south gargano line sgl the over 60 km long on shore trace of the sgl the mattinata fault is clearly segmented this study focused on the eastern active fault segment the monte sant angelo fault msa to verify the associated seismic potential analysis of contemporary descriptions of the august 10 1893 earthquake m 5 2 coupled with field work allowed identification of surface faulting along the msa along the fault there is paleoseismic evidence of the occurrence of larger earthquakes after collecting geomorphic evidence of paleo earthquakes we selected two trench sites at the base of two prominent fault escarpments where the msa is characterized by significant vertical components of fault displacement the preliminary results demonstrate that i the recent vertical slip rate of the msa range between 0 2 0 3 and 0 7 mm yr ii the msa moves with incremental slip episodes with vertical surface offset up to several decimeters iii based on the stratigraphic and geomorphic evidence of surface faulting observed and assuming a rupture length of around 20 km the seismic potential of the msa segment would be similar to that displayed by the western sgl segment during the 1627 event a large earthquake on the msa is reported only in ancient legends the most relevant of which being the one describing the apparition of archangel michael at monte sant angelo traditionally dated ad 493 using a multidisciplinary approach combining paleoseismic and historical data it has been possible to interpret the legend and hereby identify an event of surface faulting before 8th century ad a recent scarplet up to 1 m high on the msa can be seen to be related to this legendary earthquake which in turn seems to correspond to the maximum possible magnitude geologic phenomena observed during the earthquake at the site of the sanctuary appear to lie at the very origin of the veneration of the place

fault plane solutions and seismicity of the italian peninsula abstract a new fault plane solution map of the italian peninsula is presented in this paper the earthquakes analyzed are included in the period 1905 1980 with magnitudes ranging 4 7 75 earthquakes are located in the crust while 31 are related to the deep and intermediate zone of the calabrian arc the large seismic events of the italian peninsula are generally associated with normal faulting while strike slip motion is mostly related to small earthquakes located along lateral segments of the mountain chain the deep and intermediate earthquakes of the tyrrhenian sea indicate predominant down dip compression and strike slip motion at the boundaries of this benioff zone this last is interpreted as a remnant of a subduction zone active since oligocene extending to 500 km depth with a very small lateral size about 300 km the present tectonics of this benioff zone is strongly conditioned by the lateral bending more so than the gravitational sinking process the coexistence of thrust and normal faulting motion associated to the earthquakes within a few tens of kilometers of each other seems to be explained by the strong lateral inhomogeneities of the crustal rocks present in this region more so than to the depth of the seismogenetic zone and the nature of the faulting process

global emissions of helium 3 by subaerial volcanism the emission rate of helium 3 by subaerial volcanism is re evaluated by coupling 3he co2 ratios in volcanic gases with new estimate of the flux of carbon dioxide from both arc and non arc volcanoes steady volcanic plume emissions are computed to supply 240 310 mole 3he yr most of which is due to non arc volcanoes major eruptions represent minor additions on average whereas diffuse 3he emanations through volcanic piles may be important sources although not including this contribution the above figure is equivalent to 20 40 of the 3he flux from mid ocean ridges and thus suggests that primordial 3he degassing from subaerial volcanic regions may be larger than expected

sedimentary features influencing the occurrence and spatial variability of seismites late messinian gargano promontory southern italy abstract seventeen layers characterized by soft sediment deformation structures ssds were identified within the calcari di fiumicello an upper messinian miocene stratigraphic unit 30 m thick cropping out in the northern sector of the gargano promontory apulia southern italy facies analysis was performed on the whole outcrop and detailed sedimentological investigations were carried out on the deformed beds in order to interpret the deformation mechanism the driving mechanism and the possible trigger agent deformed layers occur in some thin bedded ooidal limestones skeletal calcarenite as well as in some pebble size conglomerate alternated with marls deposited in a protected embayment or barrier island lagoon system possibly characterized by high salinity and tidal influx ssds can be classified as load and slump slide structures the continuous exposures allow us to follow a single deformed layer along tens of meters hence several types of lateral variations were observed that can be summarised as follows 1 ssds disappear within a few meters with a decreasing pattern of their deformation or in an abrupt way 2 deformed layers laterally change in thickness and morphology and 3 a single deformed bed can laterally correspond to two deformed beds most of the soft sediment deformation features were identified as liquefaction and or fluidization features related to seismic shocks seismites seismites are often used as an indicator of seismic events especially along small outcrops trench excavation and core analysis this study highlights the value of the sedimentological analysis for paleoseismic investigations with the aim of improving criteria for identifying seismites in the sedimentary record and their suitability as marker of seismic events

an active margin across the adriatic sea central mediterranean sea abstract new seismological and structural data from the central adriatic gargano promontory area demonstrate that the current models of an aseismic and slightly deformed adriatic block have to be revised a seismically active deformational belt is mapped along two main fault systems the tremiti islands and mattinata faults moreover geologic and geophysical evidence suggests that a more extensive lithospheric boundary may cut across the central italian peninsula to the tyrrhenian basin

new empirical relationships among magnitude rupture length rupture width rupture area and surface displacement source parameters for historical earthquakes worldwide are compiled to develop a series of empirical relationships among moment magnitude m surface rupture length subsurface rupture length downdip rupture width rupture area and maximum and average displacement per event the resulting data base is a significant update of previous compilations and includes the additional source parameters of seismic moment moment magnitude subsurface rupture length downdip rupture width and average surface displacement each source parameter is classified as reliable or unreliable based on our evaluation of the accuracy of individual values only the reliable source parameters are used in the final analyses in comparing source parameters we note the following trends 1 generally the length of rupture at the surface is equal to 75 of the subsurface rupture length however the ratio of surface rupture length to subsurface rupture length increases with magnitude 2 the average surface displacement per event is about one half the maximum surface displacement per event and 3 the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface displacement thus for most earthquakes in this data base slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface log linear regressions between earthquake magnitude and surface rupture length subsurface rupture length and rupture area are especially well correlated showing standard deviations of 0 25 to 0 35 magnitude units most relationships are not statistically different at a 95 significance level as a function of the style of faulting thus we consider the regressions for all slip types to be appropriate for most applications regressions between magnitude and displacement magnitude and rupture width and between displacement and rupture length are less well correlated and have larger standard deviation than regressions between magnitude and length or area the large number of data points in most of these regressions and their statistical stability suggest that they are unlikely to change significantly in response to additional data separating the data according to extensional and compressional tectonic environments neither provides statistically different results nor improves the statistical significance of the regressions regressions for cases in which earthquake magnitude is either the independent or the dependent parameter can be used to estimate maximum earthquake magnitudes both for surface faults and for subsurface seismic sources such as blind faults and to estimate the expected surface displacement along a fault for a given size earthquake

helium isotope systematics at nevado del ruiz volcano colombia implications for the volcanic hydrothermal system abstract we have collected 14 water and gas samples from 9 thermal springs and gas vents near nevado del ruiz volcano colombia the 3 he 4 he and 4 he 20 ne ratios vary significantly from 0 98 r atm where r atm is the atmospheric 3 he 4 he ratio of 1 4 10 6 to 6 30 r atm and from 0 37 to 7 0 respectively the 3 he 4 he ratio corrected for air contamination decreases with increasing distance from the central crater of the volcano to the sampling site the trend is very similar to that observed at ontake volcano japan a hydrodynamic porous media dispersion model can explain the 3 he 4 he trend the temporal variations in the 3 he 4 he ratio at four sites provide useful information on the apparent velocity of the magmatic fluid flow brought on by a volcanic eruption the estimated value of several tens m day 1 agrees well with the inferred velocity of flow in oshima volcano japan and is comparable to the largest rate of groundwater movement in a deep sedimentary basin

seismicity of the adriatic microplate abstract the adriatic microplate was previously considered to be a unique block tectonically active only along its margins the seismic sequences that took place in the basin from 1986 to 1990 give new information about the geodynamics of this area three subsets of well recorded events were relocated by the joint hypocentre determination technique on the whole this seismic activity was concentrated in a belt crossing the southern adriatic sea around latitude 42 in connection with regional e w fault systems some features of this seismicity similar to those observed in other well known active margins of the adriatic plate support a model of a southern adriatic lithospheric block detached from the northern one other geophysical information provides evidence of a transitional zone at the same latitude

tracing magma sources in an arc arc collision zone helium and carbon isotope and relative abundance systematics of the sangihe arc indonesia 1 the sangihe arc is presently colliding with the halmahera arc in northeastern indonesia forming the world s only extant example of an arc arc collision zone we report the first helium and carbon isotopic and relative abundance data from the sangihe arc volcanoes as a means to trace magma origins in this complicated tectonic region results of this study define a north south trend in 3he 4he co2 3he and 13c suggesting that there are variations in primary magma source characteristics along the strike of the arc the northernmost volcanoes awu and karangetang have higher co2 3he and 13c up to 179 109 and 0 4 respectively and lower 3he 4he 5 4 ra than the southernmost volcanoes ruang lokon and mahawu resolving the arc co2 into component structures mantle derived plus slab derived organic and carbonate co2 the northern volcanoes contain an unusually high 90 contribution of co2 derived from isotopically heavy carbonate associated with the subducting slab sediment and altered oceanic basement furthermore the overall slab contribution co2 of carbonate and organic origin relative to carbon of mantle wedge origin is significantly enhanced in the northern segment of the arc these observations may be caused by greater volumes of sediment subduction in the northern arc along strike variability in subducted sediment composition or enhanced slab derived fluid melt production resulting from the superheating of the slab as collision progresses southward

stratigraphy and tectonics offshore of puglia italy southern adriatic sea abstract the structural and stratigraphic framework of puglia offshore between the gargano promontory and the town of brindisi southern adriatic sea has been analysed based on 1700 km of multichannel seismic profiles and 10 exploratory wells the area includes two different geodynamic settings 1 part of the undeformed apenninic foreland apulian carbonate platform consisting mainly of shallow water mesozoic carbonates and 2 part of the southern adriatic basin which represents the foredeep of the hellenic thrust system a mesozoic slope buried by tertiary clastics and corresponding to the edge of the apulian carbonate platform is observed on seismic data the present physiography of the escarpment is the result of an erosional retreat mainly developed during the tertiary and related to the subsidence of the south adriatic basin at the same time carbonate facies belts as evidenced by well data seem to suggest that in some sectors of the margin the original mesozoic physiography has been preserved and fossilized three seismostratigraphic units separated by regional or local unconformities have been distinguished in the neogene clastic sequence of the south adriatic basin significant deformations in the sedimentary cover are represented by various antiforms one of these antiforms named the gondola ridge is an elongated positive structure deforming the pre tertiary basement the western sector of the gondola ridge belongs to a major e w strike slip lineament extending on land in the gargano promontory in the eastern part of the area in question some tectonic features resembling pop up like and thrust antiforms are arranged along an arcuate pattern named here grifone trend the grifone trend structures indicate a post pliocene tectonism probably related to the late stages of the dinaric hellenic orogenesis the recent westward migration of the hellenic fold and thrust belt can be demonstrated by the south adriatic foredeep shift during the last 5 6 million years

observation of convection initiation processes with a suite of state of the art research instruments during cops iop 8b in the afternoon of 15 july 2007 a thunderstorm was initiated within a line of cumulus clouds which formed parallel to the crest of the black forest mountains during the intensive observation period iop 8b of the convective and orographically induced precipitation study cops this paper extends the analysis of processes that led to convection initiation ci i e the transition from shallow to deep convection on this day with the data from several cops instruments that have not been considered in previous studies in particular the boundary layer structure lids and the water vapour field in the pre convective environment of the event are discussed for this purpose we investigated measurements of water vapour lidars temperature lidars and wind lidars profiles from radiosondes in situ aircraft data and gridded data of weather stations as well as gps integrated water vapour data and satellite imagery thermally driven circulation systems formed over both the black forest and the vosges mountain ranges which resulted in local convergence zones these superimposed with the large scale convergence in the black forest area in the presence of sufficient moisture and updraught clouds formed close to the mountain crests the related latent heat release allowed larger thermals to be produced which may have had a positive feedback on stabilizing these convergence zones as a whole we believe that differences in the moisture field explain why convection remained shallow and sparse over the vosges mountains because these differences were responsible for differences in convective inhibition cin the stationary location of the convergence zone over the southern black forest was probably decisive for ci because it constantly transported sensible and latent heat into the area in which ci took place

helium emission at cumbre vieja volcano la palma canary islands abstract we report herein the results of three soil helium surveys undertaken at cumbre vieja volcano la palma island canary islands helium content analyses at the surface environment of the volcano were carried out in the summers of 2002 2003 and 2004 to estimate the diffusion contribution of helium emission soil porosity was estimated indirectly from the granulometry data measured on a previous soil survey carried out in 1997 helium enrichments in the soil layer with respect to the air concentration measured on cumbre vieja indicate a strong structural control in the degassing processes of the volcano and the excess helium seems to be emitted mainly along both n s and n w rifts of the volcano 4 he flux values calculated following a pure diffusive model ranged between non detectable values and 1 0 mg m 2 d 1 in 2002 2003 and 2004 surveys total 4 he emission rate at cumbre vieja was estimated in the range of 18 38 kg d 1 isotopic composition of helium measured in soil gases along the n s volcanic rift of cumbre vieja showed small contributions of morb type helium increasing towards the southern part of the volcano a 3 he 4 he ratio of 9 95 0 12 r a was measured at a cold spring geothermal sample showing a 7 2 contribution of plume type helium 3 he emission results in the range of 0 6 0 7 mol yr support the hypothesis of contemporary degassing at cumbre vieja coming from magmas stored at different depths under la palma island

strike slip fault propagation cleavage in carbonate rocks the mattinata fault zone southern apennines italy disjunctive spaced solution cleavage in carbonate rocks is genetically associated with the propagation of the left lateral strike slip mattinata fault in the gargano promontory italy typical cleavage development is restricted within the 200 300 mwide fault zone which is bounded by virtually unfractured wall rocks the cleavage consists of sub parallel solution surfaces which are often reactivated as sheared solution planes geometrical and kinematic relationships exist between the fault and the associated cleavage planes thus 1 cleavage fault intersection lines lie parallel to the fault and the sheared cleavage rotational axes and 2 the cleavage fault angle is almost constantly equal to 408 a model for the development of the mattinata fault is proposed in which the cleavage surfaces are interpreted as fault propagation deformations cleavage nucleates as solution planes at the front of the advancing fault as the result of stress concentration in this region two distinct time sequential processes are shown to operate during the fault propagation 1 typical millimetre to centimetre spaced solution surfaces form in the distal tip zone of the advancing fault plane 2 as the tip advances the fault plane breaks through the cleavage as minor shear displacements reactivate some of these nascent surfaces these observations may prove useful in understanding mechanisms for fault controlled enhanced reduced permeability and fluid pathways 1999 elsevier science ltd all rights reserved

seismotectonics of the southern apennines and adriatic foreland insights on active regional e w shear zones from analogue modeling 1 the active tectonics at the front of the southern apennines and in the adriatic foreland is characterized by e w striking right lateral seismogenic faults interpreted as reactivated inherited discontinuities the best studied among these is the molise gondola shear zone the interaction of these shear zones with the apennines chain is not yet clear to address this open question we developed a set of scaled analogue experiments aimed at analyzing 1 how dextral strike slip motion along a preexisting zone of weakness within the foreland propagates toward the surface and affects the orogenic wedge 2 the propagation of deformation as a function of displacement and 3 any insights on the active tectonics of southern italy our results stress the primary role played by these inherited structures when reactivated and confirm that regional e w dextral shear zones are a plausible way of explaining the seismotectonic setting of the external areas of the southern apennines

the chemistry of fumarolic vapor and thermal spring discharges from the nevado del ruiz volcanic magmatic hydrothermal system colombia on the basis of three sets of gas samples taken during the three months preceding the november 13 1985 eruption of nevado del ruiz from fumaroles on the crater floor the composition of the vapors discharged following minor eruptive activity in september corresponded to that of an essentially magmatic gas during the subsequent quiet period in october the proportion of a hydrothermal component in the vapor discharge increased steadily up until the major eruption the gases were found to be exceptionally high in total sulfur and are super saturated with respect to elemental sulfur their thermodynamic equilibration temperatures range from 200 to 600 c gases and waters from fumaroles and thermal springs on the flanks of the volcano are likely to be derived from a two phase vapor brine envelope surrounding the magmatic system the chemistry of the fumarole discharges is compatible with the assumption of an eruptive mechanism involving the build up of pressure in an extensive vapor zone by gas released from an essentially stagnant already extensively degassed body of magmatic material at depth production of such a residual gas over extended periods may account for the large amount of so2 discharged from the volcano in relation to the small amount of ejected solids

water saturated oceanic lavas from the manus basin volatile behaviour during assimilation fractional crystallisation degassing afcd we have analysed volatiles h 2 o he ar co 2 in differentiated basaltic andesite dacite volcanic glasses dredged at a depth of ca 2000 m in the eastern part of the manus basin between 151 20 and 152 10 e these samples have sr o b isotopic ratios that show that they most likely represent lavas evolved from a common magma source since these glasses are very fresh they provide a unique opportunity to study the behaviour of magmatic volatiles during assimilation fractional crystallisation degassing afcd the samples are highly vesicular up to 18 and the volatiles trapped in vesicles consist predominantly of h 2 o with minor amounts of co 2 and the concentration of water in the glasses indicates that h 2 o saturation was attained rare gases except helium are atmospheric in origin and the 3 he 4 he ratios and the co 2 3 he ratios are respectively lower and higher than those typical of mid ocean ridge basalt morb and appear to correlate with the degree of differentiation afcd allows efficient degassing of mantle derived volatiles and contribution of crust derived and atmosphere derived volatiles given the widespread occurrence of differentiated magmatism at arcs we suggest that afcd is responsible for large scale occurrence of 3 he rich crustal fluids and of atmospheric like rare gases in arc emanations and that most of the volatiles are lost continuously during fractional crystallisation rather than catastrophically during eruptions

geological events in the bible the books of the bible contain numerous frequently very exact descriptions of geological events some of these are discussed here earthquakes and their accompanying landslides the crossing of the river jordan seiches and tsunamis the flood flooding sodom and gomorrah faulting burning gas seepages the burning bush and volcanism mount sinai these geological events appear in the biblical text mainly for artistic reasons they serve as a suitable background to dramatize the biblical account they create a supernatural atmosphere for the main stories but the time and place at which they occurred are of no importance to the narrator and might be shifted freely

evaluating earth degassing in subduction zones by measuring helium fluxes from the ocean floor abstract volatiles are lost from the earth s mantle to the atmosphere hydrosphere and the crust through subaerial and submarine volcanism quantifying the volatile sources bears fundamental information on a number of issues in earth sciences from the evolution of the atmosphere and oceans to the nature of chemical heterogeneity of the earth s mantle the primordial noble gas isotope 3he provides an unambiguous measure of the volatile flux from the mantle yet so far in the ocean region it has been only measured at a mid ocean ridge here we present original measurements of the 3he flux at the mid okinawa trough back arc basin the 3he flux was estimated from 3he 20ne vertical profiles measured in deep sea sediment pore water diffusive 3he fluxes vary from 1 6 3he atoms cm 2 s 1 at the hydrothermally active izena cauldron to 0 57 3he atoms cm 2 s 1 at the background site 13 km away these values are about 20 of the 3he flux measured at the east pacific rise supporting the never proven hypothesis that 3he mantle flux from subduction zones is a quarter of that at mor measured ocean floor 4he flux ranges from 3 3 105 to 4 8 105 4he atoms cm 2 s 1 higher than that measured worldwide suggesting that 4he flux at subduction zones might have been previously underestimated

chemical variations in fumarolic gases at vulcano island southern italy seasonal and volcanic effects abstract because of increasing in fumarolic activity at vulcano since september 1987 regular sampling and analysis is conducted on the well known f5 crater fumarole t 330 5 c significant chemical variations have been recorded over the period 1987 1989 variations of water vapour in the fumarolic fluid follow seasonal pattern and can be related to both external seasonal and internal volcanic influences suggesting a control by a shallow water aquifer significant variations of h 2 o and of some species in the anhydrous gas phase h 2 so 2 hcl hf n 2 he probably result from chemical or dynamic changes in the feeding system at depth several mechanism are considered for explaining the chemical trends results in relationship to the recent increase in activity a growing input of deep magmatic fluids is not supported by the low co content and the apparent constancy of the 3 he 4 he ratio apparent equilibrium temperatures close to the fumarolic outlet temperature 350 400 c were calculated suggesting isothermal expansion of the gas from a shallow equilibration zone comparison with the fumaroles at sea level porto di levante suggests that these latter may be fed a different hydrothermal systems variable interaction between both systems may account for some of the chemical variations observed at f5 fumarole

recasting historical earthquakes in coastal areas gargano promontory italy insights from marine paleoseismology uf was financially supported by miur italian ministry of education and research firb project airplane this research has also benefited from funding provided by the italian presidenza del consiglio dei ministri dipartimento della protezione civile dpc scientific papers funded by dpc do not represent its official opinion and policies this is ismar bologna contribution n 1720

volatile emissions from the crater and flank of oldoinyo lengai volcano tanzania as a comparison to airborne infrared ir flux measurements ground based sampling of fumarole and soil gases was used to characterize the quiescent degassing of co2 from oldoinyo lengai volcano aerial and ground based measurements are in good agreement 75 of the aerially measured co2 flux at lengai 0 05 0 06 1012 mol yr 1 or 6000 7200 tonnes co2 d 1 can be attributed to seven large crater vents in contrast to etna and vulcano island where 15 50 of the total co2 flux emanates diffusely through the volcanic flanks diffuse emissions were measured only within 500 m of the crater rim at lengai contributing 2 of the total flux the lack of extensive flank emissions may reflect the dimensions of the magma chamber and or the lack of a shallow fluid flow system thermodynamic restoration of fumarole analyses shows that gases are the most co2 rich and h2o poor reported for any volcano containing 64 74 co2 24 34 h2o 0 88 1 0 h2 0 1 0 4 co and 0 1 h2s hcl hf and ch4 volatile emissions of s cl and f at oldoiyno lengai are estimated as 4 5 1 5 and 1 0 107 mol yr 1 respectively accuracy of the airborne technique was also assessed by measuring the c emission rate from a coal burning power plant co2 fluxes were measured within 10 near the plant however poor resolution at increased distances caused an underestimation of the flux by a factor of 2 the relatively large co2 fluxes measured for alkaline volcanoes such as oldoinyo lengai or etna may indicate that midplate volcanoes represent a large yet relatively unknown natural source of co2

the effects of volatile recycling degassing and crustal contamination on the helium and carbon geochemistry of hydrothermal fluids from the southern volcanic zone of chile abstract we report new helium and carbon isotope 3he 4he 13c and relative abundance co2 3he characteristics of a suite of hydrothermal gases and fluids fumaroles hot springs geothermal wells from 18 localities in the central southern volcanic zone csvz of chile the csvz is characterized by a wide range of 3he 4he ratios from 1 50 to 6 47 ra where ra air 3he 4he 13c co2 values from 2 9 to 17 7 vs pdb and co2 3he ratios which vary over 5 orders of magnitude 3 1 105 to 2 3 1011 one hydrothermal locality aguas calientes has combined he co2 characteristics remarkably similar to other arc related systems worldwide implying that the underlying subduction zone complex and mantle wedge supplies volatiles to the volcanic front with little or no modification en route to the surface the mechanism controlling helium isotope ratios of other hydrothermal systems appears to be mixing between mantle derived helium and a radiogenic component derived from 4he rich country rock the variable he co2 elemental relationships and 13c co2 values at these localities are consistent with gas separation gas samples or temperature dependent calcite precipitation water samples in shallow level hydrothermal systems both processes result in co2 loss which exacerbates the effects of contamination by crustal gases whereas the aguas calientes locality is useful for understanding the role of the underlying mantle wedge and subducting slab in supplying volatiles to the andean volcanic front the value of the majority of hydrothermal samples in the present study lies with discerning the potentially complicating effects of degassing and or crustal contamination on the resulting he co2 record

the 1717 eruption of volcan de fuego guatemala cascading hazards and societal response assessing and communicating the risks posed by natural hazards requires not only a thorough understanding of the hazards themselves but also an understanding of the spatial and temporal impact of successive events from the same source s this approach is enhanced by the lens of time which is often missing from modern responses to recent hazards archaeological studies in contrast examine the longterm consequences of hazardous events but often lack details of the event chronology and immediate human impact that are available for recent events here we show ways in which historical records can bridge the gap between modern and prehistoric studies we focus on the volcanically and seismically active region that hosts the capital city of guatemala a city that has been relocated twice in response to hazardous events since its original founding in 1527 more specifically we examine documents e autos hechos sobre el lastimoso estrago y ruina que padecio esta ciudad de guatemala autos e that were collected in response to a cascading sequence of volcanic seismic and mudflow events in 1717 to support a request to the spanish government to relocate the capital city for a second time these documents provide exceptional detail about the location of the witnesses the nature of the hazardous activity and the response of local communities this detail allows us not only to reconstruct the sequence of events

environment human relationships in historical times the balance between urban development and natural forces at leptis magna libya abstract the relationships between human modification of the environment and natural events in the roman city of leptis magna unesco world heritage western libya are analyzed for the first time the history of leptis magna is tested against a geomorphological and stratigraphical reconstruction and radiocarbon dating historical and archaeological interpretations or analyses indicate the occurrence of different extreme natural events as the cause of the town s decline earthquakes flooding and tsunami geological and geomorphological surveys investigated the dynamics of the nearby wadi lebda a major dryland stream that forms the depositional and erosional systems of the settlement area alluvial phases were studied by applying traditional stratigraphic analyses of outcrops and hand cores additionally the mapped flights of inset terrace surfaces provided insights into the human modifications of the natural depositional erosional environment during historical times and the following alluvial phases affecting the leptis magna harbor the results integrate the archaeological knowledge by providing some independent chronological constraints and indicate that leptis magna history was tightly linked to the wadi lebda aware of the hazards related to devastating flooding the romans were able to cope with the threat posed by the wadi by performing engineering defensive hydraulic works around the town dam and artificial channels once the economic decay began and the society could no longer guarantee the ongoing maintenance of these structures the decline of the settlement started and the occurrence of destructive floods reclaimed the populated areas conversely the occurrence of a large earthquake 365 ce or of a tsunami that caused the disruption of the hydraulic systems and the infill of the harbor has been discarded as primary cause of the decline of leptis magna

a critical revision of the seismicity of northern apulia adriatic microplate southern italy and implicationsfor the identification of seismogenic structures abstract northern apulia is an emerged portion of the adriatic microplate representing the foreland foredeep area of a stretch of the apennine chain in southern italy the interaction between the relatively rigid microplate and the contiguous more deformable domains is responsible for the intense seismicity affecting the chain area however strong sometimes even disastrous earthquakes have also hit northern apulia on several occasions the identification of the causative faults of such events is still unclear and different hypotheses have been reported in literature in order to provide guidelines and constraints in the search for these structures a comprehensive re examination and reprocessing of all the available seismic data has been carried out taking into consideration 1 the characteristics of historical events 2 the accurate relocation of events instrumentally recorded in the last 20 years 3 the determination of focal mechanisms and of the regional stress tensor the results obtained bring to light a distinction between the foreland and foredeep areas in the first region there is evidence of a regional stress combining nw compression and ne extension thus structures responsible for major earthquakes should be searched for among strike slip faults possibly with a slight transpressive character these structures could be either approximately n s oriented sinistral or e w dextral faults in the foredeep region there is a transition toward transtensive mechanisms with strikes similar to those of the previous zone or maybe also towards nw oriented normal faults more similar to those prevailing in the southern apennine chain in relation to a dominant ne extension this appears to be the effect of a reduction of the nw compression probably due to a decrease in efficiency of stress transmission along the more tectonised border of the adriatic microplate

fife atmospheric boundary layer budget methods the budget methods and the mixed layer model used to analyze the aircraft data from the first islscp field experiment fife are outlined the separation of the temporal and horizontal derivatives is discussed vector budgets for the mixed layer are presented on conserved variable diagrams theoretical solutions are given for the critical surface bowen ratio which produces no boundary layer moistening or equivalent potential temperature rise as a function of the bowen ratio at the inversion improved measurement strategies are suggested

rate of diffuse carbon dioxide earth degassing estimated from carbon balance of regional aquifers the case of central apennine italy central italy is characterized by an anomalous flux of deeply derived co2 in the western tyrrhenian sector of central italy co2 degassing occurs mainly from focused emissions vents and strong diffuse degassing and thermal springs whereas in the eastern apennine area deep co2 is dissolved in cold groundwaters of regional aquifers hosted by mesozoic carbonate evaporite formations influx of deep co2 into 12 carbonate aquifers 12 500 km2 of the central apennine is computed through a carbon mass balance that couples aquifer geochemistry with isotopic and hydrogeological data mass balance calculations estimate that 6 5 1010 mol yr 1 of inorganic carbon are dissolved in the studied aquifers approximately 23 of this amount derives from biological sources active during the infiltration of the recharge waters 36 comes from carbonate dissolution while 41 is representative of deep carbon sources characterized by a common isotopic signature 13c 3 the calculated deep co2 influx rate ranges from 105 to 107 mol yr 1 km 2 increasing regionally from east to west in the study area

global co2 emission from volcanic lakes the global co 2 discharge from subaerial volcanism has been estimated at 300 mt yr 1 however estimates of co 2 emissions from volcanic lakes have not been considered in order to improve this information extensive research on co 2 emissions of volcanic lakes worldwide has been performed the observed normalized average co 2 emission rates increase from alkaline 5 5 t km 2 d 1 to neutral 201 2 t km 2 d 1 to acid 614 2 t km 2 d 1 in volcanic lakes taking into account 1 normalized co 2 emission rates 2 the number of volcanic lakes in the world 769 and 3 the fraction and average areas of the investigated alkaline neutral and acid volcanic lakes the estimated global co 2 emission from volcanic lakes is 117 19 mt yr 1 with 94 17 mt yr 1 as deep seated co 2 this study highlights the importance of a revision of the actual global co 2 discharge from subaerial volcanism

structure of the entrainment zone capping the convective atmospheric boundary layer the authors use large eddy simulation les to investigate entrainment and structure of the inversion layer of a clear convectively driven planetary boundary layer pbl over a range of bulk richardson numbers ri the les code uses a nested grid technique to achieve fine resolution in all three directions in the inversion layer extensive flow visualization is used to examine the structure of the inversion layer and to illustrate the temporal and spatial interaction of a thermal plume and the overlying inversion it is found that coherent structures in the convective pbl that is thermal plumes are primary instigators of entrainment in the ri range 13 6 ri 43 8 at ri 5 13 6 strong horizontal and downward velocities are generated near the inversion layer because of the plume interface interaction this leads to folding of the interface and hence entrainment of warm inversion air at the plume s edge at ri 5 34 5 the inversion s strong stability prevents folding of the interface but strong horizontal and downward motions near the plume s edge pull down pockets of warm air below the nominal inversion height these pockets of warm air are then scoured off by turbulent motions and entrained into the pbl the structure of the inversion interface from les is in good visual agreement with lidar measurements in the pbl obtained during the lidars in flat terrain field experiment a quadrant analysis of the buoyancy flux shows that net entrainment flux or average minimum buoyancy flux wu min is identified with quadrant iv w2u1 0 motions that is warm air moving downward plumes generate both large negative quadrant ii w1u2 0 and positive quadrant iii w2u2 0 buoyancy fluxes that tend to cancel the maximum vertical gradient in potential temperature at every x y grid point is used to define a local pbl height zi x y a statistical analysis of zi shows that skewness of zi depends on the inversion strength spectra of zi exhibit a sensitivity to grid resolution the normalized entrainment rate we w where we and w are entrainment and convective velocities varies as ari21 with a 0 2 in the range 13 6 ri 43 8 and is in good agreement with convection tank measurements for a clear convective pbl the authors found that the finite thickness of the inversion layer needs to be considered in an entrainment rate parameterization derived from a jump condition

active faulting at delphi greece seismotectonic remarks and a hypothesis for the geologic environment of a myth historical data are fundamental to the understanding of the seismic history of an area at the same time knowledge of the active tectonic processes allows us to understand how earthquakes have been perceived by past cultures delphi is one of the principal archaeological sites of greece the main oracle of apollo it was by far the most venerated oracle of the greek ancient world according to tradition the mantic proprieties of the oracle were obtained from an open chasm in the earth delphi is directly above one of the main antithetic active faults of the gulf of corinth rift which bounds mount parnassus to the south the geometry of the fault and slip parallel lineations on the main fault plane indicate normal movement with minor right lateral slip component combining tectonic data archaeological evidence historical sources and a reexamination of myths it appears that the helice earthquake of 373 b c ruptured not only the master fault of the gulf of corinth rift at helice but also the antithetic fault at delphi similarly to the corinth earthquake of 1981 moreover the presence of an active fault directly below the temples of the oldest sanctuary suggests that the mythological oracular chasm might well have been an ancient tectonic surface rupture

active oblique extension in the central apennines italy evidence from the fucino region the fucino basin is a flat quaternary depression within the central apennines it is surrounded by active normal faults with small oblique slip components surface faulting was observed along the east side of the basin during the ms 7 0 avezzano earthquake of 1915 in order to understand the kinematics of recent strain better and to assess the seismic hazard of this region we carried out a detailed geomorphic and structural study of the faults around the basin fault scarp heights were accurately measured with total station profiles and vertical slip rates were estimated assuming slope offsets to post date the end of periglacial abrasion 14 4 kyr bp to the north the most prominent fault the magnola fault appears to have an average postglacial throw rate of 0 7 0 3 mm yr 1 and together with the velino fault to be capable of generating earthquakes of maximum magnitudes of 6 9 7 3 with recurrence intervals of 1000 3000 yr east of the basin the serrone parasano and ventrino faults form a right stepping horsetail of the giovenco fault current vertical slip rates on the three former faults appear to be between 0 5 and 1 4 0 5 and 1 0 and 0 3 and 1 1 mm yr 1 respectively infrequent maximum magnitude earthquakes on them may also exceed 7 particularly in the case of coupled rupture with loosely constrained recurrence intervals up to several thousand years the right lateral slip components implied by the most recent slickensides and by geomorphic offsets on the nw se trending normal faults of the area suggest that the blocks they bound rotate counterclockwise consistent with oblique left slip on the nnw sse trending giovenco and ovindoli faults to the east sinistral shear parallel to the latter faults the maximum relief across the magnola fault and the postglacial slope offsets measured suggest that the extension rate across the central apennines might be of the order of 6 3 mm yr 1 in a n20 10 e direction more northerly than hitherto inferred

soil gas emanations as precursory indicators of volcanic eruptions field measurements conducted on several active volcanoes in italy the lesser antilles and indonesia demonstrate the common occurrence of diffuse soil gas emanations from the volcanic piles at distances from active craters or fumarolic zones these emanations consist essentially of carbon dioxide and rare gases and their genetic link with crater fumaroles and or magma degassing at depth can be verified both chemically and isotopically we emphasize here the potential use of these fluids for continuous volcano monitoring and eruption forecasting

major and rare gases at white island volcano new zealand origin and flux of volatiles analyses of fumarolic gases at white island new zealand are reported with special emphasis on rare gases he ne ar kr and xe normalization of major species to rare gases have lead to the identification of several sources air saturated meteoric or marine water a magma body the crust and or sediments when compared to mid ocean ridge discharges the white island gas discharge represents about 3 0 7 0 1 and 0 05 of the global water carbon sulfur and helium 3 discharges respectively this balance shows that except for 3he which derives from the mantle practically all rare gases water and carbon and part of sulfur derive from originally superficial sources

evaluation of gases condensates and so2 emissions from augustine volcano alaska the degassing of a cl rich volcanic system after the march april 1986 explosive eruption a comprehensive gas study at augustine was undertaken in the summers of 1986 and 1987 airborne cospec measurements indicate that passive so2 emission rates declined exponentially during this period from 380 45 metric tons day t d on 7 24 86 to 27 6 t d on 8 24 87 these data are consistent with the hypothesis that the augustine magma reservoir has become more degassed as volcanic activity decreased after the spring 1986 eruption gas samples collected in 1987 from an 870 c fumarole on the andesitic lava dome show various degrees of disequilibrium due to oxidation of reduced gas species and condensation and loss of h2o in the intake tube of the sampling apparatus thermochemical restoration of the data permits removal of these effects to infer an equilibrium composition of the gases although not conclusive this restoration is consistent with the idea that the gases were in equilibrium at 870 c with an oxygen fugacity near the ni nio buffer these restored gas compositions show that relative to other convergent plate volcanoes the augustine gases are very hcl rich 5 3 6 0 mol hcl s rich 7 1 mol total s and h2o poor 83 9 84 8 mol h2o values of d and 18o suggest that the h2o in the dome gases is a mixture of primary magmatic water pmw and local seawater part of the cl in the augustine volcanic gases probably comes from this shallow seawater source additional cl may come from subducted oceanic crust because data by johnston 1978 show that cl rich glass inclusions in olivine crystals contain hornblende which is evidence for a deep source 25km for part of the cl gas samples collected in 1986 from 390 642 c fumaroles on a ramp surrounding the inner summit crater have been oxidized so severely that restoration to an equilibrium composition is not possible h and o isotope data suggest that these gases are variable mixtures of seawater fmw and meteoric steam these samples are much more h2o rich 92 97 h2o than the dome gases possibly due to a larger meteoric steam component the 1986 samples also have higher cl s s c and f cl ratios which imply that the magmatic component in these gases is from the more degassed 1976 magma thus the 1987 samples from the lava dome are better indicators than the 1986 samples of degassing within the augustine magma reservoir even though they were collected a year later and contain a significant seawater component future gas studies at augustine should emphasize fumaroles on active lava domes condensates collected from the same lava dome fumarole have enrichments ot 107 102 in cl br f b cd as s bi pb sb mo zn cu k li na si and ni lower temperature 200 650 c fumaroles around the volcano are generally less enriched in highly volatile elements however these lower termperature fumaroles have higher concentration of rock forming elements probably derived from the wall rock

marine palaeoseismology from very high resolution seismic imaging the gondola fault zone adriatic foreland we present a marine palaeoseismology analysis of a dense network of very high resolution seismic profiles along the gondola fault zone gfz a right lateral e w striking active fault system in the adriatic foreland this case study aims to show how time and space variations in the activity of a dominantly right lateral fault system can be assessed using the vertical component of slip the gfz has been investigated for a length of 50 km it includes two parallel subvertical fault sets and two main anticlines the late middle pleistocene to holocene vertical component of displacement along the fault is bell shaped suggesting that in the long term the fault zone acts as a single kinematically coherent structure slip rates are 0 0 18 mm a 1 and vary temporally on individual segments this variability is consistent with a model in which individual fault segments rupture independently during earthquakes with magnitudes up to 6 4 and 1 3 1 8 ka recurrence intervals

fumarolic emissions from mount st augustine alaska 1979 1984 degassing trends volatile sources and their possible role in eruptive style gas samples were collected from high temperature rooted summit vents at mount st augustine in 1979 1982 and 1984 all of the gas samples exhibit various degrees of disequilibrium thermodynamic restoration of the analyzed gases permits partial or complete removal of these disequilibrium effects and allows inference of equilibrium gas compositions long term 1979 1984 degassing trends within resampled or adjacent vents are characterized by increases from 97 4 to 99 8 mole in the h2o fraction and major decreases in the residual gases over this same period total gas hcl contents decreased by a factor of 3 to 10 while dry gas h2o free recalculated hcl contents increased by a factor of 1 6 to 3 dry gas mole proportions at these sites changed from being co2 dominated 46 co2 24 h2 in 1979 to h2 dominated 49 h2 22 co2 in 1984 the overall trends in gas chemistry and the stable isotope patterns in gases and condensates from the summit fumaroles can be explained by progressive magmatic outgassing coupled with increasing proportions of seawater in the fumarole emissions