iron in plagioclase as a monitor of the differentiation of the skaergaard intrusion several recent publications suggest that the appearance of fe ti oxides terminates iron enrichment and starts pronounced silica enrichment the bowen trend during the differentiation of tholeiitic basalt however this does not appear to hold for the skaergaard intrusion new data from a 950 m long drill core 90 22 through its upper zone reveal that 1 iron in plagioclase increases from 0 25 to 0 45 wt feot with fractionation of evolved oxide ferrodiorites an46 32 and 2 the evolving liquid which is modelled by incremental bulk rock summation increased its iron content from 20 1 to 26 5 wt feot and its silica content from 47 4 to 49 6 wt sio2 with fractional crystallisation the fenner trend positive correlation between modelled iron content of the magmas and measured iron content of plagioclase confirms that iron enrichment is petrologically feasible even with fe ti oxides in the fractionating assemblage as suggested by previous authors fractional crystallisation closed to oxygen exchange is the likely reason why some layered intrusions diverge from the bowen mechanism of differentiation it is emphasised that both trends seem to exist in nature

metasomatic replacement in the skaergaard intrusion east greenland preliminary observations abstract several unusual types of replacement structures in the layered series and marginal border series of the skaergaard intrusion indicate that metasomatic changes have altered the modal proportions and in places the mineral composition of the gabbro the geometrical forms and compositional patterns of these features indicate that they result from reactive fluids moving through the rocks at high temperatures shortly after the magma had reached an advanced stage of crystallization the principal effect of metasomatism has been to produce strongly contrasting mafic and felsic rocks

the skaergaard layered series part vi excluded trace elements in contrast to the smooth trends of major elements and mineral principal minerals of the skaergaard layered series my purpose here is to examine the corresponding excluded compositions the excluded trace elements in the skaergaard layered series have an irregular distribution that does not conform to the elements and their relations to progressive differentiation of the skaergaard magma the principal conclusion that normal trends of rayleigh type fractionation their concentrations are about constant or even decline through the lower and middle will emerge is that the trends of enrichment of these elements differ markedly from those of the major elezones before increasing sharply to reach maximum concentrations 100 200 m above the sandwich horizon as in the case of ments possibly because their distribution was affected by a build up and eventual exsolution of volatile comincluded elements the relative concentrations of excluded elements in coexisting phases deviate widely from those predicted by exponents in the magma it will also be shown that the observed partition coefficients differ widely from those perimentally determined partition coefficients under presumed magmatic conditions this is seen most clearly in the immiscible predicted from experimental studies several earlier studies addressed various aspects of the melanogranophyres and conjugate ferrogabbros although the major elements conform to the experimentally determined relations for skaergaard trace elements haskin and his co workers haskin haskin 1968 paster et al 1974 were the first immiscible liquids the trace elements do not they follow a totally independent trend the abrupt increase in the concentrations of to attempt to reconcile the distribution of excluded trace elements with earlier interpretations of trace element excluded elements in the upper part of the intrusion could plausibly be attributed to an addition of new magma or to a density inversion behavior during crystallization and differentiation of the layered series other previous work has been sumthat resulted in upward migration of a late liquid or fluid but these possibilities are inconsistent with the compositional and spatial marized by wager brown 1968 and more recently by mcbirney 1996 1998a relations of the upper parts of the intrusion although a late residual liquid certainly migrated upward the most likely explanation for the structural form of the intrusion and its principal units illustrated in simplified form in fig 1 have already the observed distribution of excluded elements is that the partition coefficients were altered by volatile components which gradually been described at length mcbirney 1989 1995 1996 boudreau mcbirney 1997 mcbirney nicolas 1997 increased during the early stages of crystallization then began to exsolve near the top of the middle zone sonnenthal mcbirney 1998 and need not be repeated apart from minor differences noted in the appendix the distribution and selection of samples as well as the methods by which they have been analyzed are essentially the same as those described in part v of this

on the skaergaard intrusion and forward modeling of its liquid line of descent a reply to principles of applied experimental igneous petrology by morse 2008 lithos 105 pp 395 399 abstract forward modeling based on an experimental investigation successfully duplicated main features of the gabbros in the skaergaard layered series thy p lesher c e nielsen t f d and brooks c k 2006 experimental constraints on the skaergaard liquid line of descent lithos 92 154 180 the foundation for the modeling was equilibrium melting experiments that were controlled by temperature and oxygen fugacity at low pressure conditions the experimental techniques and methods were chosen to represent a reasonable approximation to the inferred emplacement and crystallization conditions of the skaergaard intrusion the dike rocks used as starting materials define a strong differentiation trend that represents the skaergaard liquid line of descent this suite of dikes allowed liquidus conditions to be defined for a range of composition and temperature the initial redox conditions were chosen based on measured and calculated estimates for the gabbros of interest the melting experiments defined liquidus and subliquidus conditions that were used to understand crystallization of the lower and middle zones of the skaergaard layered series and can be extrapolated to the upper zone gabbros assuming perfect fractional crystallization the forward modeling reproduces the cryptic variation seen in the main gabbro minerals olivine augite plagioclase well into the upper zone and provides reasonable liquidus temperatures and compositions it can be shown that based on the assumption of fe ti oxide modes in the middle and upper zones a range of oxygen fugacity trends can be obtained we repeat our previous conclusion that iron depletion and strong reduction in oxygen fugacity in the upper zone are only feasible for very high fe ti oxide modes that exceed the experimental evidence as well as the observations from the gabbros a strong drop in oxygen fugacity in the upper zone requires a significant sink for fe ti oxides that so far has not been identified we thus reject morse s morse s a 2008 principles of applied experimental igneous petrology a comment on experimental constraints on the skaergaard liquid line of descent by thy lesher nielsen and brooks 2006 lithos 92 154 180 lithos 105 pp 395 399 contention that we violated in our original study established principles of applied experimental igneous petrology such principles dictate that experimental and forward models are carefully tested against field observations before petrologic processes can be verified

crystallization of interstitial liquid and latent heat buffering in solidifying gabbros skaergaard intrusion greenland new compositional profiles across plagioclase grains from the layered series ls marginal border series mbs and upper border series ubs of the skaergaard intrusion are used to understand the mechanisms of cumulate rock solidification and the fate of the interstitial liquid the data show that plagioclase crystals display three types of compositional profile over the whole intrusion as follows 1 grains with normal zoning which dominate the mbs and ubs these are interpreted as having formed at the top of a crystal mush and then buried in the cumulate pile crystallization of the interstitial melt resulted in liquid differentiation and produced normally zoned rims on plagioclase cores 2 unzoned crystals which dominate the upper part of the ls also crystallized at the top of the mush and were then buried in mush with a low interstitial liquid fraction or one experiencing convective movements that kept the liquid to a constant composition 3 crystals with a mantle of decreasing an content followed by a rim of constant composition grains showing this complex zoning mostly occur in the lower parts of the ls depending on the stratigraphic position within the intrusion the composition of the rim can be an56 an51 or an40 in the main magma body these compositions an contents correspond to those of plagioclase primocrysts e g cores at the appearance of cumulus clinopyroxene an56 fe ti oxides an51 and apatite an40 compositional buffering of plagioclase rims is interpreted as being a consequence of enhanced release of latent heat of crystallization at the appearance of new interstitial phases in the crystal mush when a new phase saturates the latent heat contribution to the global enthalpy budget of the system becomes sufficiently high to keep the interstitial melt at its liquidus temperature for a period of time that could exceed thousands of years under these conditions equilibrium adcumulus growth together with diffusion and possibly advection of chemical components result in the formation of plagioclase rims of constant composition an content efficient thermal buffering of the mush liquid depends on the porosity i e fraction of liquid within the mush and the degree of compositional homogeneity of the mush in a heterogeneous and highly porous mush saturation of the new phase occurs in the coldest part of the mush and the enhanced latent heat release at the saturation of this phase is quickly dissipated to the whole volume of liquid including the warmest part that is not yet saturated in a new phase as a consequence no thermal buffering occurs and interstitial crystallization produces grains with normal zoning the distribution of the various types of plagioclase grains throughout the skaergaard intrusion can therefore be used to infer the spatial variability in the physical properties of the crystal mush such as the residual porosity both at an intrusion wide scale and at a millimetre to centimetre scale

seismic and infrasonic eruption tremors and their relation to magma discharge rate a case study for sub plinian events in the 2011 eruption of shinmoe dake japan

the skaergaard liquid line of descent revisited there is a fundamental conflict between the suggestion that the iron content of skaergaard liquids increases during fe ti oxide fractionation and the observation that at the same time oxygen fugacity f text o text 2 drops by two log units below the fayalite magnetite quartz oxygen buffer fmq a new petrographic study of average skaergaard gabbros shows that the total modal content of fe ti oxides is about 22 in the early lzc and markedly decreases to below 5 in the uzc forward modeling based on these modal constraints as well as experimental results on skaergaard related dikes predicts that fractionation of troctolitic lza gabbros drives the derivative liquid towards a high iron content strong iron enrichment continues together with a small decline in silica during lzb crystallization due to the appearance of augite as a fractionating phase the fractionation of fe ti oxides in the lzc initially suppresses iron enrichment and reverses the silica trend to one of slight enrichment however continued evolution into the uz produces liquids with maximum uzc feo content of 23 25 wt and sio2 content of 53 wt feo is total iron as feo the maximum in feo is dependent on several factors of which the fe ti oxide mode has the strongest effect the f text o text 2 during crystallization of the lzc is widely thought to have been at or slightly below the fayalite magnetite quartz oxygen buffer fmq under closed system evolution incorporation of ferric iron into augite during formation of the lzb restricts the increase in f text o text 2 to about 0 1 log units above fmq 0 1 fmq likewise crystallization of the lzc through the uza involving fe ti oxide minerals leads to a decline in f text o text 2 of less than 0 1 fmq crystallization of the uzb c gabbros results in oxidation to a maximum of 0 5 fmq this behavior can account for the iron rich character of the uz gabbros as well as the low modal content of fe ti oxides thus evolved skaergaard liquids are high in iron and contain a modest amount of sio2 our modeling result do not account for a strong drop in f text o text 2 through the layered series such a drop would require an unacceptably high proportion of fe ti oxides and high magnetite content in the fractionating assemblage

rapid exhumation at 8 ma on the liupan shan thrust fault from apatite fission track thermochronology implications for growth of the northeastern tibetan plateau margin abstract the liupan shan mountain is one of the outermost ranges in northeastern tibetan plateau the onset of its uplift provides insight on whether the plateau grew sequentially outward or broad areas of the plateau deformed simultaneously the apatite fission track method can be used to date rapid cooling as the result of unroofing of rocks in response to tectonically induced vertical motion fission track data from apatite in early cretaceous sedimentary strata exposed on the hanging wall of liupan shan thrust fault in northeastern tibet suggest that a late cenozoic rapid cooling events occurred at 7 3 8 2 ma or 8 ma this age apparently dates fault activity of the liupan shan thrust in response to northeastward growth of the tibetan plateau uplift and lateral growth which continues today numerous studies of the tibetan plateau suggest that the onset of deformation in eastern and northern margin of tibetan plateau occurred in the latest miocene

an experimental investigation of the influence of water and oxygen fugacity on differentiation of morb at 200 mpa crystallization experiments were performed at 200mpa in the temperature range 1150 950 c at oxygen fugacities corresponding to the quartz fayalite magnetite qfm and mno mn3o4 buffers to assess the role of water and fo2 on phase relations and differentiation trends in mid ocean ridge basalt morb systems starting from a primitive mgo 9 8 wt and an evolved morb mgo 6 49 wt crystallization paths with four different water contents 0 35 4 7 wt h2o have been investigated in primitive morb olivine is the liquidus phase followed by plagioclase clinopyroxene amphibole is present only at water saturated conditions below 1000 c but not all fluid saturated runs contain amphibole magnetite and orthopyroxene are not stable at low fo2 qfm buffer residual liquids obtained at low fo2 show a tholeiitic differentiation trend the crystallization of magnetite at high fo2 mno mn3o4 buffer results in a decrease of melt feo mgo ratio causing a calc alkaline differentiation trend because the magnetite crystallization temperature is nearly independent of the h2o content in contrast to silicate minerals the calc alkaline differentiation trend is more pronounced at high water contents residual melts at 950 c in a primitive morb system have compositions approaching those of oceanic plagiogranites in terms of sio2 and k2o but have ca na ratios and feo contents that are too high compared with the natural rocks implying that fractionation processes are necessary to reach typical compositions of natural oceanic plagiogranites

late cenozoic tectonic evolution of the ningxia hui autonomous region china part of the transition from active crustal shortening and strike slip faulting in northwestern china to active extension in northeastern china takes place within the ningxia autonomous region four arcuate zones of both strike slip faults and thrust faults with associated ramp anticlines dominate the structures in southern ningxia deformation in these zones indicates that a component of left slip displacement is transferred into crustal shortening on north south trending folds and thrust faults the average quaternary slip rate along the haiyuan liupan shan fault zone is 5 10 mm yr and that along the tianjin shan mibo shan fault zone is about 1 5 2 7 mm yr the amount of offset and rate of slip along the yanton shan and the niushou shan daluo shan fault zones are unknown but the topography of the mountains suggests that the rates of slip along these zones is lower than that of the haiyuan liupan shan fault zone deformation in northern ningxia is dominated by normal faulting and extension the helan shan rise about 2 000 m above the yinchuan basin reportedly filled with a few kilometers of cenozoic sediments the average rate of vertical separation in quaternary time along the east helan shan fault is estimated to be at least 0 5 0 8 mm yr opening of the yinchuan graben is probably partly related to left lateral slip on the niushou shan and daluo shan fault zone the northeastern margin of tibetan plateau is probably being elevated by the irregular growth of convergent and left slip structural zones the evolution of deformation along the haiyuan liupan shan structural zone probably foreshadows the future deformation in the ranges north of it left slip and shortening within the ningxia region appears to accommodate less than 20 25 km of east or northeast displacement of crustal fragments of the northern tibetan plateau large magnitude lateral transport of crust with respect to the area to the east has not taken place within the part of the ningxia region covered by this study

experimental constraints on the low pressure evolution of transitional and mildly alkalic basalts the effect of fe ti oxide minerals and the origin of basaltic andesites one atmosphere melting experiments controlled at the fayalite magnetite quartz oxygen buffer on mildly alkalic and transitional basalts from iceland show that these begin to crystallize fe ti oxide minerals magnetite and or ilmenite at 1105 5 c apparently independently of bulk composition and the order of silicate and oxide mineral crystallization most samples crystalline plagioclase and olivine as the first two crystalline phases augite as the third phase and an fe ti oxide mineral as the fourth phase the main effects of fe ti oxide crystallization are a marked decrease in feo and tio2 in the liquid and a notable increase in sio2 and al2o3 and the minor oxides k2o and p2o5 with decreasing temperature the most silicic glasses are compositionally mugearitic and shoshonitic basaltic andesites because the smallest amount of glass that could be analyzed with the microprobe represents 20 55 percent liquid remaining it can be expected that more silicic liquids will occur at lower temperatures on normative pseudoternary projections the general effect of fe ti oxide crystallization for mildly alkalic and transitional basalts is a marked increase in normative quartz this is caused by a strong systematic convergence with the appearance of fe ti oxides of the bulk solid precipitates toward the liquid compositions as projected on the triangle plagioclase diopside olivine for alkalic basalts the bulk solid precipitate shows an increase in normative diopside with falling temperature and fe ti oxide crystallization this causes the liquids to move toward decreasing normative diopside and relatively little variation in nepheline the experimental observations imply that mildly alkalic and transitional magmas without stabilizing a fe ti oxide mineral will not evolve toward early silica saturation

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

the cenozoic lower rhine basin rifting sedimentation and cyclic stratigraphy in the cenozoic the lower rhine basin formed as a rift at the southeastern terminus of the dutch german central graben while the rhenish massif was uplifted the study focusses on the marginal marine and fluvial fill of the lower rhine basin a basin model is developed support for this study was given by extensive industry outcrop and well data by new stratigraphical and sedimentological observations the ingression and subsequent regression of the cenozoic north sea is analysed using the concept of base level cyclicity as the geohistory of the basin was complex a subsidence curve is constructed furthermore an attempt is made to trace the simultaneous uplift of the rhenish massif

the pliocene and quaternary fluvial archives of the rhine system abstract the river rhine is one of the few major fluvial systems that connect the areas of the alpine glaciers and scandinavian ice sheet and so provides a key for correlating the two glacial areas in northern and middle europe the fluvial sequences of the rhine valley include at least 11 pleistocene terraces in the lower rhine area 2 pliocene and 12 pleistocene terraces in the middle rhine area resulting in 15 different pliocene and pleistocene terraces based on the correlation between lower and middle rhine the formation of fluvial terraces is significantly influenced by climatic and tectonic processes the terrace staircases are a result of uplift in the middle rhine area and the southern part of the lower rhine area whereas subsidence in the northern part of the lower rhine area resulted in buried stacked sequences magnetostratigraphic data provide chronological constraints for the terrace deposits in the lower rhine embayment and middle rhine region the matuyama brunhes boundary is a reliable marker horizon for the upper terrace fluvial deposits exposed in the karlich clay pit in the middle rhine area the first appearance of volcanic heavy mineral grains in the terrace sediments in loess and soils can be correlated from the middle rhine area through the lower rhine embayment to the netherlands the first occurrence of nordic components in terrace sediments of the lower rhine area is known from gravel on top of the kempen krefeld beds and so are younger than the holsteinian but older than the penultimate glaciation in the lower middle rhine area 40ar 39ar dating of tephra layers intercalated in the aeolian and fluvial sediments provide age constraints the upper pleistocene aeolian sediments overlying the terrace deposits have been dated by luminescence methods and the tephra from the laacher see eruption 12 860 bp is present in the younger lower terrace deposits

geological and geomorphological evidence for active faulting of the southern liupanshan fault zone ne tibetan plateau abstract the southern liupanshan fault zone slfz has been active during the holocene and accommodates complex deformation between the compressional liupanshan mountain and the extensional weihe graben we characterized the active faulting of the slfz using interpretations of high resolution satellite images digital elevation models derived from structure from motion models combined with field investigations the presence of well preserved linear fault troughs scarps knickpoints offset streams and ridges and landslides along the slfz indicate that surface rupturing earthquakes have occurred along the slfz in the holocene evidence from paleoseismic trenching indicates that the most recent earthquake occurred between 1607 77 bce and 1070 90 ce and thus may have been the 600 ce historical earthquake the estimated magnitude of this earthquake is mw 6 7 radiometric dating of an offset fluvial terrace indicates a late pleistocene to holocene left lateral slip rate of 1 5 0 3 mm yr our geologic and geomorphic observations show that the slfz may extend into the weihe graben where the slip is transferred onto other active faults within the weihe graben

crustal deformation in the india eurasia collision zone from 25 years of gps measurements the india eurasia collision zone is the largest deforming region on the planet direct measurements of present day deformation from global positioning system gps have the potential to discriminate between competing models of continental tectonics but the increasing spatial resolution and accuracy of observations have only led to increasingly complex realizations of competing models here we present the most complete accurate and up to date velocity field for india eurasia available comprising 2576 velocities measured during 1991 2015 the core of our velocity field is from the crustal movement observation network of china i ii 27 continuous stations observed since 1999 56 campaign stations observed annually during 1998 2007 1000 campaign stations observed in 1999 2001 2004 and 2007 260 continuous stations operating since late 2010 and 2000 campaign stations observed in 2009 2011 2013 and 2015 we process these data and combine the solutions in a consistent reference frame with stations from the global strain rate model compilation then invert for continuous velocity and strain rate fields we update geodetic slip rates for the major faults some vary along strike and find that those along the major tibetan strike slip faults are in good agreement with recent geological estimates the velocity field shows several large undeforming areas strain focused around some major faults areas of diffuse strain and dilation of the high plateau we suggest that a new generation of dynamic models incorporating strength variations and strain weakening mechanisms is required to explain the key observations seismic hazard in much of the region is elevated not just near the major faults

differentiation and compaction in the skaergaard intrusion igneous differentiation processes are constrained from bulk compositions densities and mineral modes of 116 cumulate gabbro samples in a new reference profile through the layered series of the skaergaard intrusion east greenland the stratigraphic distribution of p u and rb in cumulates and residual magma modeled by rayleigh fractionation constrains the final porosities or trapped liquid contents to 30 52 in lza troctolites decreasing to 4 12 at the top of lzb olivine gabbros and remaining low 1 13 4 middle dot 6 on average in the oxide gabbros of lzc mz and uz local variations in trapped liquid content are associated with modal layering leucocratic low density rocks have higher proportions of trapped melt than adjacent melanocratic high density rocks these observations are explained by varying degrees of compaction compaction was most important after the onset of fe ti oxide crystallization because of the high densities of the crystal matrix here computed rates of compaction exceed the rate of crystal accumulation in layers that are metres to a few tens of metres thick in the basal section lza the crystal pile was too thin and the density of the crystal matrix too low to drive the rate of compaction above the high rate of crystal accumulation promoted by initial cooling through the intrusion floor in the overlying section lzb the efficiency of compaction gradually increased as a result of thickening of the crystal pile and lowering of the rate of crystal accumulation the modeling constrains the p2o5 content of the residual magma to 1 middle dot 7 wt at the level of apatite in suggesting that the magma contained 49 wt sio2 and followed a trend of iron enrichment compaction of the uppermost metres to tens of metres of crystal mush at the top of the cumulate pile was an efficient means of differentiation and resulted in layers with variable final porosities and trace element contents depending on the mineralogy and density of the crystal matrix

the roman eifel aqueduct archaeoseismological evidence for neotectonic movement at the transition of the eifel to the lower rhine embayment the lower rhine embayment and adjacent areas are characterised by neotectonic deformation resulting in differential crustal movement slip rates along the fault systems are very low 0 1 mm a significant earthquakes are known to have occurred in the past but the faulting behaviour is not adequately known which hampers the risks assessment we analysed the archaeological record of the largest roman aqueduct north of the alps this so called eifel aqueduct is 95 4 km long has its source in the eifel mountains and supplied the ancient city of cologne with calcareous fresh water the aqueduct crosses major faults of the lower rhine embayment perpendicular analyses of the aqueduct s gradient gives weak evidence for creep along the kirspenich fault resulting in differential movement of hanging and foot wall in the order of a few centimetres vertical offsets of 15 and 35 cm are documented exactly where the aqueduct crosses the holzheim fault system close to the city of mechernich here also structural damage of the aqueduct is recorded and archaeological evidence exists for repair works on the aqueduct we interpret these observations as well as the construction of a 4 km long deviation as necessary measures to keep the aqueduct operational after earthquake damage the timing of the event falls within the period of aqueduct operation which is reconstructed to be between 80 10 and 270 10 ce supporting evidence for earthquake activity within this period is seen in the roof collapse of the nearby kakus cave

trace element constraints on the differentiation and crystal mush solidification in the skaergaard intrusion greenland new major and trace element analyses of plagioclase and clinopyroxene in gabbros from the skaergaard intrusion are used to understand the mechanisms of crystallization in the main magma body and in the crystal mush crystal cores show a continuous chemostratigraphic evolution in the layered series with compatible elements e g cr and ni in clinopyroxene being progressively depleted from the bottom up whereas incompatible elements e g sr ba ree in plagioclase and clinopyroxene become progressively enriched we performed numerical models and showed that these trends can be explained by a simple process of fractional crystallization except for the upper 20 of the intrusion where plagioclase and clinopyroxene trace element compositions depart from fractional crystallization trends at this stage of magma chamber solidification fractional crystallization becomes less efficient and is replaced by a major proportion of in situ equilibrium crystallization trace elements also show significant variations in interstitial overgrowths on plagioclase and clinopyroxene cumulus crystals they result from crystallization of the interstitial liquid in the liquid crystal mush however incompatible elements and especially ree show a degree of enrichment in plagioclase rims 20 ppm ce that strongly exceeds the highest concentrations observed in plagioclase cores up to 4 ppm ce at the top of the layered series such a strong enrichment is difficult to reconcile with a simple process of fractional crystallization of the interstitial liquid in the crystal mush but may be related to the development of silicate liquid immiscibility in the crystal mush or to delayed nucleation of apatite after the crystallization of plagioclase and clinopyroxene overgrowths diffusive re equilibration during a period of 0 1 0 25 myr significantly changed the original zoning profiles ce flux from clinopyroxene into the plagioclase lattice of adjacent crystals could also have contributed to the strong ce enrichment observed in plagioclase rims

applications in geomorphology abstract geomorphology is a pure science with the goal of understanding earth surface processes and landscape evolution and it is also an applied science with the goal of addressing the needs of society with many new high resolution methods of depicting topography and much improved numerical dating geomorphologists are working on problems involving rates of surface processes landscape evolution and applications to areas of concern to society that were impossible to address a few decades ago some of the areas of enquiry where geomorphology has been applied include natural hazards landslides floods earthquakes and tsunamis ecosystem management site anthropology land use planning engineering geology expert witness testimony and hazard reduction assessment and perception how people perceive and respond to potential hazards how their vulnerability can increase their risk and how preparedness and response can be improved depends as much on the social sciences as on physical science

california integrated seismic network cisn local magnitude determination in california and vicinity determining local magnitude m l in a manner that is uniform and internally consistent for earthquakes throughout california and the vicinity is an important component of the california integrated seismic network cisn we present a new local magnitude attenuation function and corresponding station adjustments that are valid throughout california the new attenuation function is an analytic function of the radial hypocentral distance between 1 and 500 km associated station adjustments are also available for 1185 horizontal seismometer and accelerometer channels from five seismic networks operating in california the new attenuation function and adjustments provide several advantages to cisn they allow a more robust m l computation the m ls are more consistent between northern and southern california than they have been in the past and because adjustments are now available for more station network channel location codes sncls m ls can be computed for small earthquakes in more locations than was previously possible in addition to describing our method for calibrating the new cisn m l we also present a tool for adding adjustments for new or upgraded stations

a discussion of hunter and sparks contrib mineral petrol 95 451 461 silica poor iron rich liquids like those estimated for skaergaard by wager and brown are preserved in labrador as chilled pillows iron rich rocks in the kiglapait intrusion have likewise been produced by liquids poor in silica there is no reason to expect such liquids in volcanoes so their absence as lavas means nothing about their possible plutonic occurrence successful tests of the siliceous liquid hypothesis would include showing that the proposed rhyolitic liquids can produce the observed olivines in the range fo 10 40 they would require showing that the observed low f o 2 oxide mineral assemblages can occur at the high silica contents proposed and that the silicate mineral assemblages and compositions can represent high silica liquids i doubt very much that these critical tests can be met

present day crustal deformation in china constrained by global positioning system measurements global positioning system gps measurements in china indicate that crustal shortening accommodates most of india s penetration into eurasia deformation within the tibetan plateau and its margins the himalaya the altyn tagh and the qilian shan absorbs more than 90 of the relative motion between the indian and eurasian plates internal shortening of the tibetan plateau itself accounts for more than one third of the total convergence however the tibetan plateau south of the kunlun and ganzi mani faults is moving eastward relative to both india and eurasia this movement is accommodated through rotation of material around the eastern syntaxis the north china and south china blocks east of the tibetan plateau move coherently east southeastward at rates of 2 to 8 millimeters per year and 6 to 11 millimeters per year respectively with respect to the stable eurasia

an experimental study of the influence of oxygen fugacity on fe ti oxide stability phase relations and mineral melt equilibria in ferro basaltic systems

geology of the haiyuan fault zone ningxia hui autonomous region china and its relation to the evolution of the northeastern margin of the tibetan plateau the haiyuan area located along the northeastern margin of the tibetan plateau in north central china provides a laboratory for studying how the plateau has grown in late cenozoic time rocks in the area range from pre silurian precambrian to recent the pre silurian and cenozoic rocks form the most extensive outcrops the pre silurian rocks consist of amphibolite and greenschist grade metasedimentary and metaigneous rocks unconformably overlain by silurian and devonian red beds all of these rocks are intruded by granodiorite of unknown age cenozoic rocks consist of 2 6 3 0 km of eocene to miocene red beds that were deposited over an extensive area in this part of china pliocene conglomerate contains clasts from all older formations and is interpreted to have been derived from highlands developed during the beginning of cenozoic deformation in the haiyuan area except for the widespread loess deposits quaternary rocks reflect deposition in local tectonic environments the oldest cenozoic structures in the haiyuan area are folds and small thrust faults that generally strike n30 45 w and involve mostly pre quaternary rocks these structures and all the quaternary rocks are cut by the haiyuan left lateral strike slip left slip fault zone that generally trends n60 65 w and is nearly vertical at the western end of the mapped area a fault zone which strikes n75 90 w forms a left stepping transfer zone that connects with another segment of the haiyuan fault zone which continues n60 65 w west into gansu province a small basin the salt lake basin is marked by active faults in the area of the transfer zone and is interpreted as a pull apart basin along the left slip haiyuan fault zone at its eastern end the haiyuan fault zone has an irregular surface trace east of luzigou an active fault striking n35 45 w branches to the south this southern branch appears to be a younger fault and now accommodates most of the left slip deformation that formerly occurred on the easternmost part of the haiyuan fault zone this younger fault connects through a left stepping transfer zone to a parallel fault the xiaokou fault that can be traced into the liupan shan about 60 km to the southeast the laohuyaoxian basin is interpreted as a very young pull apart basin in the area of the transfer zone matching different geological features across the haiyuan fault zone yields a total left slip offset of between 10 5 and 15 5 km and the best constrained offsets yield 12 9 14 8 km if left slip began near the end of the pliocene time or earliest pleistocene time it indicates an average slip rate between 5 and 10 mm yr progressively smaller offsets can be determined on progressively younger geological features but dates for these younger features are too imprecise to constrain slip rates through time surface ruptures that formed during the 1920 haiyuan earthquake m 8 7 show mostly left slip displacement with magnitudes of more than 10 m in some places active faulting in the region suggests the tibetan plateau may be extending to the northeast in time in the haiyuan area deformation probably began in pliocene time compared with a likely earlier initiation to the southwest thus deformation began about 40 45 m y after collision between india and asia formation of the low ranges to the northeast of the haiyuan area however may have developed at different times and deformation may not have propagated regularly to the northeast a total displacement of 10 5 15 5 km on the haiyuan fault zone indicates that this fault zone does not accommodate large scale eastward lateral transfer of continental fragments in the northern tibetan plateau

experimental equilibrium tested by plagioclase loop widths are solid and liquid respectively and an is the mole fraction or per cent an an ab it is measured from the plagioclase composition and an estimate of the liquid composition based on standard assumptions rooted in the norm recalculation routine a survey of a large new database allows study of the 1 atm experimental literature involving 819 experiments the approach to equilibrium is tested empirically by the loop width and its transform the linear partitioning function kd this function is the exchange coefficient formed as the intercept at pure an s from the array over all x s of the partition coefficient d when defined as x s x l w herex is the mole fraction d and kd are thus limited to lie between zero and 1 0 the results show a 1atm loop width ranging from 0 2t o 68 mol a n with associated kd 0 03 0 98 these extrema represent loops both far too small and far too large to represent stable equilibrium between plagioclase and liquid some of the higher values lie near the persodic limit because the an component of the liquid is scarce and the liquid composition is ab rich the loops from ne normative liquids span the range from 40 to 90 mol an in the crystal with loops 2 50 mol wide a baseline for loop width is derived from the precise synthetic study of the system di an ab at 1atm and an array of high pressure data that extrapolates to the same value of kd 0 26 at 1atm many of the 1atm experimental data fall far outside any reasonable uncertainty limits on the baseline causes of departure include crystal disequilibrium that can lead to errors in both directions and compositional problems comparison of the values of kd with liquid compositions in silica oxygen fugacity temperature kinetics and sodium reveals the common presence of sodium deficiency a crystallinity study shows a definite decrease in sodium content with liquid evolution whereas the sodium content should increase or at least remain nearly constant with evolution of the melt a selection of self consistent 1atm data from a few laboratories shows a close correspondence to the standard distribution of loop widths and indeed most literature data lie within the limited range of kd 0 26 0 4 experiments known to be hydrous show very low values of kd and corresponding large loop widths as previously understood from literature data when data limited to nearbaseline kd values are plotted against temperature they yield expected thermal slopes and concave up curves of temperature plotted against plagioclase composition literature data show a positive correlation of kd with dry pressure and a separate database from 2 to 15 kbar shows that more than half the data comport with this pressure effect a different group ranges down to kd as low as 0 2 with increasing loop widths some of these are alkalic and hence rich in the ab component of the liquid others were obtained in fe containers that control the oxygen fugacity to low values and convert the fayalite component of the liquid to iron oxygen and silica this reaction increases the activity of silica and in turn the activity of ab in the melt thus widening the loop thermodynamic studies concerned with plagioclase melt equilibria will profit from an awareness of these effects

plagioclase in the skaergaard intrusion part 1 core and rim compositions in the layered series the anorthite content of plagioclase grains xan in 12 rocks from the layered series of the skaergaard intrusion has been studied by electron microprobe typically 30 core and 70 rim analyses per thin section mean core compositions vary continuously from an66 at the base of the layered series lza to an32 30 at the top on the other hand crystal rims are of approximately constant composition an50 1 from the lza to the lower middle zone mz above the mz core and rim compositions generally overlap profiles across individual plagioclase grains from the lower zone show that most crystals have an external zone buffered at xan 50 1 the simplest explanation for these features is that during postcumulus crystallization in the lower zone interstitial liquids passed through a density maximum this interpretation is consistent with proposed liquid lines of descent that predict silica enrichment of the liquid associated with the appearance of cumulus magnetite

source parameter estimation for large bermed surface chemical explosions abstract near source accelerograms 0 2 to 2 0 km range were acquired from a series of bermed surface charges 0 075 to 1 65 kilotons detonated in alluvium at a test site near yuma arizona the areal extent of the explosion test beds radii from 18 to 54 m affords the unique opportunity to study wave propagation from and source parameters of large surface explosions at near source ranges p and sv rayleigh phases are identified using particle motions rayleigh waves at an intermediate range transition to a combination of higher mode and fundamental mode rayleigh waves at the farthest range the power law decay rates for body waves radial at r 1 8 and vertical at r 1 4 and surface waves radial at r 1 0 and vertical at r 0 8 are further indication of complex propagation effects in the shallow alluvial geology as a result of this complexity and the two orders of magnitude range of explosive yields available seismic source parameters are obtained with full waveform spectral ratios source corner frequency is proportional to the radius of the explosion test beds and long period level relative moment scales linearly with yield spectral ratio yield estimates using smaller explosions as standard or calibration events gave absolute yield estimates within 6 to 35 of the true yield with a linear scaling law the precision of individual yield estimates is reflected by multiplicative errors of 1 11 to 1 17 full waveform spectral ratio corner frequency estimates compare favorably with reglonal p wave corner frequencies and validate the use of the spectral ratio technique for near source seismic data

toward a thermal model for the skaergaard liquidus after a review of history it is shown that in a comprehensive 1 atm study by mcbirney and naslund 1990 the skaergaard liquidus temperature is linear from lza to uza on stratigraphic height when corrected to pressure the augite saturation point at lza b has the same liquid composition in terms of plagioclase an content as the corresponding point in the kiglapait intrusion studied at 5 kbar by morse et al 2004 this temperature 1203 c at 5 kbar is transformed to the skaergaard pressure at lza b to a value of 1173 c from this fixed point all other liquidus temperatures at skaergaard are scaled to mean plagioclase core compositions from a detailed study by toplis et al 2007 all such points from lzb to uza lie within experimental error on the regression from mcbirney and naslund and the further points in uzb and uzc also agree plagioclase based temperatures at the base of lza exceed the earlier estimates by 24 c and imply a possible temperature of 1210 c in the hidden zone these results provide a good interim model for the skaergaard liquidus pending further experimental study at the liquidus

liquidus temperatures of the skaergaard magma the liquidus temperatures of the skaergaard intrusion can be estimated for the layered series from plagioclase compositions plagioclase saturation in one atmosphere melting experiments on evolved north atlantic basalts is a function of an content mol and can be described by an empirical linear relationship t c 899 3 6 an 1 20 c this relationship predicts a total crystallization interval for the intrusion of 150 c plagioclase crystallized in the hidden zone an 71 at 1155 c at the base of the lower zone an 66 at 1137 c and finally in the sandwich horizon an 30 at 1007 c these temperatures are in good agreement with previous estimates based on melting studies of suitable chilled margin rocks and gabbros from the skaergaard intrusion and liquid line of descent modeling our temperature estimates however are markedly lower by up to 60 c than recent temperature estimates based on an extrapolation of high pressure experimental data for the kiglapait intrusion to skaergaard emplacement conditions proposed variations in magmatic pressure during skaergaard evolution and reasonable estimates of magmatic water contents do not alter these conclusions

microstructures and late stage magmatic processes in layered mafic intrusions symplectites from the sept iles intrusion quebec canada replacive symplectites vermicular intergrowths of two or more minerals are an important feature of layered igneous intrusions recording evidence of late stage reactions between interstitial liquid and crystals they are common throughout the layered series of the 564 ma sept iles layered intrusion in quebec canada and fall into three types oxy symplectites type i symplectites and type ii symplectites oxy symplectites are comprised of magnetite and orthopyroxene nucleate on olivine primocrysts and form via the reaction olivine o2 orthopyroxene magnetite type i symplectites of which there are 3 distinct categories are comprised of anorthitic plagioclase with pyroxene amphibole or olivine vermicules grow from primocryst oxide grains and replace primary plagioclase and type ii symplectites of which there are 2 distinct categories are comprised of anorthitic plagioclase with orthopyroxene amphibole vermicules grow from primocryst olivine

block like versus distributed crustal deformation around the northeastern tibetan plateau abstract it has been debated for decades whether crustal deformation in and around the tibetan plateau is distributed or block like we model crustal deformation in northeastern tibet using a deformable block motion model in which kinematic parameters of block motion and internal deformation and the associated boundary slip rates are inverted for using gps velocity data the f test is used to screen out station velocity outliers justify independence of neighboring blocks and determine the significance of block internal strains through an iteration process as a result fifteen blocks are identified with their boundary faults slipping at rates of 1 10 mm a blocks located east and north of the plateau have large sizes 10 4 km 2 in area in general with little internal deformation six blocks within the plateau in contrast are smaller in sizes with internal strain rates on the order of 1 10 nanostrain a five blocks sitting at the northeast borderland of the plateau have small block sizes but no significant internal deformation our results show sinistral slip rates of 4 3 1 6 and 4 6 1 8 mm a across the western and eastern segments of the haiyuan fault and 10 8 2 3 4 6 2 6 and 3 8 2 1 mm a across the western central and eastern segments of the east kunlun fault respectively the southwestern central and northeastern segments of the longmenshan fault slip right laterally at rates of 1 7 1 1 1 1 0 8 and 1 1 0 8 mm a with shortening rates of 1 1 1 2 0 4 0 8 and 0 8 1 1 mm a respectively we also develop a scheme to convert geodetic strain rate into seismic moment accumulation rate within blocks and at block boundaries and estimate the two rates as 8 40 10 18 and 2 06 10 19 n m a respectively in comparison the corresponding seismic moment release rates are estimated as 6 06 10 18 and 2 44 10 19 n m a using an contemporary earthquake catalog of 1920 2015 such results indicate that the seismic moment accumulation and release rates are comparable for the latest 95 years when the earthquake catalog is complete for strong to large events both geodetic and seismic estimates suggest that a major portion 70 80 of the total seismic moment is accumulated and released at block boundaries and a minor but still significant portion 20 30 is accumulated and released within blocks

determination of earthquake energy release and ml using terrascope we estimated the energy radiated by earthquakes in southern california using on scale very broadband recordings from terrascope the method we used involves time integration of the squared ground motion velocity and empirical determination of the distance attenuation function and the station corrections the time integral is typically taken over a duration of 2 min after the p wave arrival the attenuation curve for the energy integral we obtained is given by q r cr n exp kr r 2 2 h ref 2 with c 0 49710 n 1 0322 k 0 0035 km 1 and h ref 8 km where is the epicentral distance a similar method was used to determine m l using terrascope data the station corrections for m l are determined such that the m l values determined from terrascope agree with those from the traditional optical wood anderson seismographs for 1 5 6 5 m l saturates the ratio e s m 0 m 0 seismic moment a measure of the average stress drop for six earthquakes the 1989 montebello earthquake m l 4 6 the 1989 pasadena earthquake m l 4 9 the 1990 upland earthquake m l 5 2 the 1991 sierra madre earthquake m l 5 8 the 1992 joshua tree earthquake m l 6 1 and the 1992 landers earthquake m w 7 3 are about 10 times larger than those of the others that include the aftershocks of the 1987 whittier narrows earthquake the sierra madre earthquake the joshua tree earthquake and the two earthquakes on the san jacinto fault the difference in the stress drop between the mainshock and their large aftershocks may be similar to that between earthquakes on a fault with long and short repeat times the aftershocks which occurred on the fault plane where the mainshock slippage occurred had a very short time to heal hence a low stress drop the repeat time of the major earthquakes on the frontal fault systems in the transverse ranges in southern california is believed to be very long a few thousand years hence the events in the transverse ranges may have higher stress drops than those of the events occurring on faults with shorter repeat times such as the san andreas fault and the san jacinto fault the observation that very high stress drop events occur in the transverse ranges and the los angeles basin has important implications for the regional seismic potential the occurrence of these high stress drop events near the bottom of the seismogenic zone strongly suggests that these fault systems are capable of supporting high stress that will eventually be released in major seismic events characterization of earthquakes in terms of the e s m 0 ratio using broadband data will help delineate the spatial distribution of seismogenic stresses in the los angeles basin and the transverse ranges

determining the source characteristics of explosions near the earth s surface we present a method to determine source characteristics of explosions near the earth s surface the technique accounts for the reduction in amplitudes as the explosion depth approaches the free surface and less energy is coupled into the ground we apply the method to the humming roadrunner series of shallow explosions in new mexico where the yields and depths are known knowledge of the material properties is needed for both source coupling excitation and the free surface effect although there is the expected trade off between depth and yield the estimated yields are close to the known values when the depth is constrained to the free surface we then apply the method to a regionally recorded explosion in syria we estimate an explosive yield less than the 60 t claimed by sources in the open press the modifications to the method allow us to apply the technique to new classes of events

evidence of active tectonics on a roman aqueduct system ii iii century a d near rome italy abstract in this paper we describe evidence of strong tectonic deformation affecting two aqueducts of roman age ii iii century a d the channels are located approximately 20 km northeast of rome along the ancient via tiburtina brittle and ductile deformation affects these two structures including extensional joint systems ne oriented faults and horizontal distortion this deformation is consistent with right lateral movement on major n striking faults and represents the first evidence that tectonic deformation took place in historical times in the vicinity of rome with local strike slip movement superimposed on a regional extensional fault system

differentiation of ferro basaltic magmas under conditions open and closed to oxygen implications for the skaergaard intrusion and other natural systems because processes such as fractional crystallization and crystallization under conditions closed to oxygen are difficult to simulate in the laboratory there is a need for quantitative models of magma crystallization behaviour comparison of experimental data on an iron rich basaltic composition with predictions of the melts free energy minimization algorithm shows that although liquidus temperatures and silicate mineral equilibria are predicted relatively well the saturation of fe ti oxides is not we have used the same experimental data to construct an alternative crystallization model based on known equilibrium phase relations mineral melt partitioning of major elements and mass balance constraints the model is used to explore the consequences of equilibrium and fractional crystallization in systems open and closed to oxygen liquid lines of descent for perfect equilibrium and perfect fractional crystallization are predicted to be very similar in a system open to oxygen the model predicts that magnetite saturation leads to strongly decreasing iron and increasing silica contents of residual liquids whereas systems closed to oxygen crystallize less abundant magnetite leading to a less pronounced iron depletion in the liquid predicted bulk solid compositions and variations offo with falling temperature agree well with those observed or inferred from the cumulates of the skaergaard intrusion but none of the predicted liquid lines of descent are consistent with the extreme iron enrichment proposed for this intrusion based on mass balance calculations compositional factors such as water and phosphorus are not thought to be the source of the discrepancy as the cumulates of the basistoppen sill which closely resemble those of skaergaard may be used to calculate a liquid line of descent in agreement with that predicted by the model for fractional crystallization closed to oxygen a comparison of the predicted t io paths and liquid lines of descent with those inferred from natural systems suggests that volcanic centres such as iceland and hawaii evolve under conditions open to oxygen whereas evidence from plutonic environments e g skaergaard and kiglapait layered intrusions suggests that they evolved under conditions more closed to oxygen the compositional evolution of the melt phase in volcanic and plutonic systems may therefore be different although the results of this study suggest that magnetite saturation will limit fe enrichment in all environments to 20wt feo consistent with enrichments reported for volcanic glasses

parental liquids of the skaergaard intrusion cumulates petrogenetic relationships between compositions advocated as possible liquids parental to the skaergaard layered series cumulates have been investigated using equations for the prediction of liquidus temperature and liquid path followed during fractional crystallization given a suitably defined sequence of primocryst mineral assemblages a variation of the fractionation scheme provides a new method for the calculation of the parent liquid composition

experimental constraints on the low pressure evolution of transitional and mildly alkalic basalts multisaturated liquids and coexisting augites basaltic liquids saturated at one atmosphere in augite olivine and plagioclase show a strong linear trend in pseudo quaternary projections from nepheline to slightly quartz normative compositions coexisting augites show a corresponding variation from slightly nepheline to hypersthene normative compositions consequently alkalic and mildly alkalic liquids coexist with nepheline normative augites tholeiitic liquids coexist with hypersthene normative augites and transitional liquids coexist with augites compositionally intermediate between those crystallizing in alkalic and tholeciitic melts the variation in augite composition is due to a decrease in wollastonite and non quadrilateral components going from mildly alkalic to transitional and tholeiitic augites the observed liquid and augite trends lack correlations between normative composition and crstallization temperature this is an artifact of plotting unrelated liquid lines of descent individual liquid lines of descent in contrast display good correlation between normative composition and crystllization temperature which for both liquids and coexisting augites are highly oblique to nearly perpendicular to the general trend because the composition of the first augite to appear on the liquidus varies as a function of the bulk system the location of the thermal divide shows corresponding variations as a consequence unifying cotectics and pseudo quaternary normative projections should not without specific experimental knowledge be used to address liquid lines of descent and common magmatic parentages

kiglapait mineralogy iii olivine compositions and rayleigh fractionation models olivints present throughout the layered cumulates of the kiglapait intrusion record extreme iron enrichment during fractional crystallization mn is less compatible than fe the exchange coefficient kd for mn fe ol liq has values near 0 95 but they drop to 0 7 near the lower one upper one boundary ca is depleted by more than a factor of 30 relative to experimental values at 5 kbar pressure attempts to find a sink for ca in the lower zone without invoking liquid as a reactant are unconvincing and questions of metastability arise cumulus olivines vary systematically to lower fo contents with stratigraphic height using equilibrium values for the exchange coefficient kd fe mg ol ljq j and the observed mode of olivine and residual porosity a rayleigh fractionation calculation reproduces the observed lower zone trend without recourse to multiple injections of magma an anomalously fe rich region above the main ore band in the upper zone ascribed to ponding of fe rich magma at the floor of the intrusion until later buoyant residual magma entrained the fe rich residua such fe rich ponds probably account for the abnormal fe enrichment shown by some other fenner trend layered intrusions summation over the observed crystal compositions yields values of xjug that do not represent the equilibrium liquid but that reduce to it by a simple multiplier p 0 78 this result means that if ko is known the high temperature liquidus olivine compositions can be retrieved or vice versa because the observed olivine compositions are supported by realistic forward models there is no need to invoke evolved boundary layer liquids to explain the in situ crystallization of kiglapait cumulates classical cumulate theory suffices

phase relations and liquid lines of descent in hydrous ferrobasalt implications for the skaergaard intrusion and columbia river flood basalts crystallization experiments using a hydrous ferrobasalt as starting material conducted at 200mpa 940 12008c at a wide range of water activities 0 1 1 and redox conditions qfm 3 to qfm 4 where qfm is the quartz fayalite magnetite oxygen buffer show that h2o influences significantly the differentiation history of ferrobasaltic magmas a combination of our data with published experiments on dry ferrobasalt at 1atm provides an extensive experimental database for modeling and quantifying crystallization and differentiation processes within a typical fe rich tholeiitic system under both dry and hydrous conditions the addition of h2o decreases liquidus temperatures and changes significantly the proportions temperature range and sequence of crystallizing mineral phases the dry liquidus is at about 11708c whereas the liquidus for h2o saturated melts is at 10608c the main phases crystallizing from h2o bearing ferrobasalt at the investigated conditions are olivine ol clinopyroxene cpx plagioclase pl magnetite mt hematite hm ilmenite ilm and amphibole am the phase assemblage is similar to that of the dry system except for the presence of hm at extremely oxidizing conditions and am at low temperatures 59508c and h2o saturated conditions the important observation made in this study is that the stability of fe ti oxides and in particular mt as well as the simultaneous coprecipitation of mtand ilm are almost independent of the activity of h2o ah2o in the system whereas the liquidus temperatures of the silicate minerals are dramatically depressed by increasing ah2o the stabilities of oxides are controlled mainly by the redox conditions prevailing in the system the most pronounced effect of ah2o on the liquidus temperatures of silicates is observed for pl which shows a considerable delay in crystallization with progressive magma differentiation early crystallization of fe ti oxides in h2o bearing ferrobasaltic compositions precludes any significant fe enrichment during differentiation as fe enrichment is a characteristic feature of the skaergaard intrusion it implies that the skaergaard parental magma did not contain considerable amounts of water on the other hand our experiments indicate that the differentiation of some ferrobasaltic series from the columbia river flood basalt province might have occurred in magmatic systems containing significant amounts of volatiles 0 5 3 wt h2o

seismo acoustic energy partitioning at near source and local distances from the 2011 sayarim explosions in the negev desert israel the january 2011 calibration explosions at the sayarim military range in the negev desert israel provide a unique dataset to study seismic and acoustic partitioning for surface sources at near source and local distances we present an analysis of the seismic and overpressure acoustic signals generated from two explosions which included 10 240 and 102 080 kg of mainly anfo with some composition b detonated on the surface on 24 and 26 january respectively at different times of the day a temporary seismo acoustic overpressure network was deployed at distances between 0 1 and 39 km to supplement data from permanent stations in israel the near source data confirm the explosions produced overpressure signals consistent with complete and simultaneous surface detonation of 7 4 and 76 8 metric tons of tnt equivalent explosives we observe acoustic amplification at local distances 5 km south of the larger explosion that can be explained by a low altitude southward flowing wind at the detonation time for the smaller shot the southward flow was not present and amplification was not observed in the pressure data we present results of modeling these overpressure data with blast pressure scaling models with and without meteorological data seismic phases generated by the surface shots include p waves fundamental and higher mode rayleigh waves and love waves that appear to have been generated at or very near the explosion source the seismic ground motion is less than would be expected for fully coupled explosions of 7 6 and 76 8 tons and at near source distances 10 km can be modeled well by reducing ground motion predictions from the fuis et al 2001 model by a factor of 4 the results from the sayarim explosions combined with past and future experimental datasets will lead to an improved understanding of the seismo acoustic source function for explosions and energy partitioning between seismic and acoustic waves

crystallization sequence of the upper border series of the skaergaard intrusion revised subdivision and implications for chamber scale magma homogeneity although it is one of the best studied layered mafic intrusions in the world the crystallization sequence of the skaergaard intrusion east greenland remains in debate in particular it has been argued that the crystallization sequence in the upper border series which crystallized downwards from the roof of the magma chamber differs from that in the layered series formed at the floor the proposed deviation would require chemical stratification of the magma and a reexamination of the crystallization sequence therefore has important implications for understanding the dynamics of the system here we examine a new sample set from the upper border series combining field observations petrography and anorthite contents of plagioclase with bulk rock ti v p cu and mn concentrations we demonstrate that the first phases on the liquidus were plagioclase and olivine followed by augite then ilmenite and magnetite simultaneously sulfides apatite and finally ferrobustamite now inverted to hedenbergite this crystallization sequence represents extreme differentiation along the tholeiitic trend and it mirrors those at the floor layered series and walls marginal border series we therefore propose a revised subdivision of the upper border series into equivalents of the subzones in the layered series denoted by apostrophes lza lzb etc moreover the first appearance of each of the cumulus phases occurs at similar plagioclase core anorthite contents the mirror images of the crystallization sequences and the anorthite contents of plagioclase cores in the three series imply that the skaergaard magma chamber solidified by in situ crystallization along the floor walls and roof from one largely homogenous convecting magma body

the campsite dykes a window into the early post solidification history of the skaergaard intrusion east greenland the skaergaard intrusion of east greenland is cut by several generations of dykes the earliest of which is thought to have intruded shortly after solidification of the skaergaard two 6 m wide doleritic dykes from the earliest generation are exposed in the campsite area near homestead bay of the skaergaard peninsula one of the dykes the campsite dyke locally contains abundant xenoliths of troctolitic cumulate the other the plagioclase phyric dyke contains abundant large plagioclase phenocrysts cross cutting relationships between the two dykes are not exposed the median clinopyroxene plagioclase plagioclase dihedral angle cpp in the campsite dyke is 88 89 5 whereas that of the plagioclase phyric dyke is 79 using an empirical relationship between cpp and the duration of crystallisation derived from dolerite sills the observed cpp suggests that the campsite dyke is the older of the two intruding the skaergaard when it had cooled to 920 970 c the plagioclase phyric dyke intruded later once the skaergaard had cooled below 670 c the troctolitic xenoliths divide into two separate groups type a xenoliths have microstructures similar to those of the skaergaard layered series although mineral compositions are generally more primitive than those of the exposed cumulates this type of xenolith is likely to have been derived from either deeper levels in the skaergaard intrusion or from a closely related underlying magma chamber one type a xenolith has mineral compositions and cpp consistent with an origin in lzb of the layered series this xenolith contains partially inverted pigeonite suggesting that inversion of low ca pyroxene in the lower part of the layered series took place after the intrusion had completely solidified type b xenoliths are characterized by plagioclase containing large and abundant melt inclusions comparison with the microstructures of glassy crystalline nodules from iceland points to a multi stage cooling history for type b xenoliths consistent with step wise entrainment of partially crystallised material from a deep chamber type b xenoliths are very unlikely to have been derived from deeper levels in the skaergaard chamber

apatite hosted melt inclusions from the panzhihua gabbroic layered intrusion associated with a giant fe ti oxide deposit in sw china insights for magma unmixing within a crystal mush the 2 km thick panzhihua gabbroic layered intrusion in sw china is unusual because it hosts a giant fe ti oxide deposit in its lower zone the deposit consists of laterally extensive net textured and massive fe ti oxide ore layers the thickest of which is 60 m to examine the magmatic processes that resulted in the fe enrichment of parental high ti basaltic magma and the formation of thick fe ti oxide ore layers we carried out a detailed study of melt inclusions in apatite from a 500 m thick profile of apatite bearing leucogabbro in the middle zone of the intrusion the apatite hosted melt inclusions are light to dark brown in color and appear as polygonal rounded oval and negative crystal shapes which range from 5 to 50 m in width and from 5 to 100 m in length they have highly variable compositions and show a large and continuous range of sio2 and feot with contrasting end members one end member being fe rich and si poor 40 2 wt feot and 17 7 wt sio2 and the other being si rich and fe poor 74 0 wt sio2 and 1 20 wt feot this range in composition may be attributed to entrapment of the melt inclusions over a range of temperature and may reflect the presence of m scale and immiscible fe rich and si rich components in different proportions simulating results for the motion of si rich droplets within a crystal mush indicate that si rich droplets would be separated from fe rich melt and migrate upward due to density differences in the interstitial liquid when the magma unmixed migration of the si rich immiscible liquid component from the interstitial liquid caused the remaining fe rich melt in the lower part to react with plagioclase primocrysts an59 60 as evidenced by fine grained lamellar intergrowth of an rich plagioclase an79 84 clinopyroxene in the oxide gabbro of the lower zone therefore magma unmixing within a crystal mush combined with gravitationally driven loss of the si rich component resulted in the formation of fe rich melagabbro and major fe ti oxide ores in the lower part and si rich leucogabbro in the upper part of the intrusion

empirical dependence of seismic ground velocity on the weight of explosives shotpoint site condition and recording distance for seismic refraction data in this study we have constructed an empirical least squares model for maximum seismic ground velocity vertical component as a function of source size and distance from explosions in drillholes and bodies of water this model is intended in part for use in designing explosion seismic experiments in order to produce acceptable signal to noise ratios at larger distances 10 km and to avoid damaging human structures at smaller distances 1 km data consist of velocities recorded by 120 portable seismographs from 159 shots fired by the u s geological survey in alaska and arizona results show that maximum ground velocity amplitude not necessarily first arrival amplitude decreases with distance and the functional dependence changes with distance for example at 3 km amplitudes decrease as r 2 but at 73 km they decrease as r 1 results also show a strong dependence on site conditions at the shotpoint for example a drillhole shot in wet alluvium produces amplitudes that are four times larger than a drillhole shot in dry alluvium ground velocities are proportional to the square root of the weight of explosives

kinematics of late quaternary slip along the qishan mazhao fault implications for tectonic deformation on the southwestern ordos china

european cenozoic rift system abstract the european cenozoic rift system extends from the coast of the north sea to the mediterranean over a distance of some 1100 km it finds its southern prolongation in the valencia trough and a plio pleistocene volcanic chain crossing the atlas ranges development of this mega rift was paralleled by orogenic activity in the alps and pyrenees major rift domes accompanied by subsidence reversal of their axial grabens developed 20 40 ma after beginning of rifting uplift of the rhenish shield is related to progressive thermal lithospheric thinning the vosges black forest and the massif central domes are probably underlain by asthenoliths emplaced at the crust mantle boundary evolution of this rift system is thought to be governed by the interaction of the eurasian and african plates and by early phases of a plate boundary reorganization that may lead to the break up of the present continent assembly

further work on experimental plagioclase equilibria and the skaergaard liquidus temperature equilibria between plagioclase and ferrobasaltic melt in low pressure dry melting experiments can be demonstrated near the liquidus further analyses of melting experiments using optimized beam conditions reveals that previous data for understanding the skaergaard intrusion potentially suffered from the analytical inclusion of non equilibrated components in the average plagioclase compositions new reversal experiments demonstrate convergence between plagioclase rim compositions in melting and crystallization products for a ferrobasaltic melt and thus support equilibrium relations the new data set provides tighter bounds on experimental plagioclase composition and documents composition dependent partitioning of na and ca between plagioclase and melt application of the results to modeling the skaergaard requires only minor adjustments to the previously proposed liquidus temperatures and liquid line of descent

lithospheric memory state of stress and rheology neotectonic controls on europe s intraplate continental topography abstract to date research on neotectonics and related continental topography development has mostly focused on active plate boundaries characterized by generally high deformation rates the intraplate sedimentary basins and rifts of the northern alpine foreland are associated with a much higher level of neotectonic activity than hitherto assumed seismicity and stress indicator data combined with geodetic and geomorphologic observations demonstrate that europe s intraplate lithosphere is being actively deformed this has major implications for the assessment of its natural hazards and environmental degradation the lithosphere of the northern alpine foreland has undergone a polyphase evolution with an intense interplay between upper mantle thermal perturbations and stress induced intraplate deformation that points to the importance of lithospheric folding of the thermally weakened lithosphere in this paper we address relationships between deeper lithospheric processes neotectonics and surface processes in the northern alpine foreland with special emphasis on tectonically induced topography the objectives are to quantify the effects of ongoing alpine collision and atlantic ridge push on the intraplate deformation in europe and its impact on topography evolution and related natural hazards this paper reviews the four dimensional topographic evolution of the european lithosphere through a multi disciplinary approach linking geology geophysics and geotechnology until now research on neotectonics and related topography development of intraplate regions has received little attention our study examines a number of selected natural laboratories in continental europe from orogen through platform to continental margin these natural laboratories include the carpathians pannonian system the northwest european platform iberia and the atlantic continental margin we focus on lithosphere memory and neotectonics with special attention to the thermo mechanical structure of the lithosphere mechanisms of large scale intraplate deformation late neogene anomalies in subsidence and uplift and links with surface processes and topography evolution

a critical comment on thy et al 2009b liquidus temperatures of the skaergaard magma the study by thy tegner and lesher thy et al 2009b is based on whole rock compositions in batch melting experiments at one atmosphere that have a very large temperature variation for a very small plagioclase compositional variation their steep t x slopes of up to 14 c an contrast with the overall regression for the intrusion of 4 c an this paradox can be evaluated by using separate tests for equilibrium in temperature and composition the issue of temperature is clouded by the presence of low temperature components in the beginning of melting experiments compositions of plagioclase and liquid are too close to each other compared to expectations from other experiments at 1 atm and at pressure a ruling hypothesis is perceived here to the effect that every t xpair represents a valid equilibrium between a liquidus composition and a solidus composition therefore by inversion each solidus composition defines a valid temperature its corollary is that all such pairs receive equal weight and can therefore be legitimately regressed together the thy et al 2009b regression is passed through the center of gravity of the data rather than through the extrapolated maximum liquidus points if the ruling hypothesis is falsified these approaches lose their validity upon testing it is falsified in temperature testing leads to consequences known to be false in composition a test for reproducibility in results also fails thereby falsifying the principle of stable equilibrium the falsifications are repeated in at least three ways the study results cannot furnish a valid thermal path for the fractional crystallization of skaergaard magma a selection of the highest temperature results comes closer to a realistic result based on comparison with earlier experiments that melted out the trapped liquid component of the skaergaard cumulates new experimental approaches at the liquidus are needed to help define temperatures and fractionation progress in the skaergaard intrusion

the differentiation of the skaergaard intrusion we find no support for the claim that the skaergaard magma followed the trend of common tholeiitic volcanic magmas such as those of iceland and the scottish tertiary the end product of differentiation was not a large mass of rhyolite but an iron rich silica poor liquid not unlike that deduced by wager in 1960 the proposal that a large mass of rhyolitic liquid occupied the upper levels of the intrusion finds no support in the field the thick series of ferrogabbos which became richer in iron and poorer in silica until they reached a field of immiscibility cannot be reconciled with crystallization of a large mass of felsic magma mass balance calculations that indicate otherwise are invalid because they fail to take into account large volumes of rocks that differ in composition from those assumed in the calculations while ignoring the existence of major units of the intrusion hunter and sparks propose that lavas in scotland and iceland are more relevant to the liquid compositions than rocks that are intimately associated with the intrusion their argument that the skaergaard intrusion followed a trend of silica enrichment that is universal to tholeiitic magmas is based on an incomplete knowledge of the rocks and faulty calculations of mass balance relations we agree that much remains to be learned about the skaergaard intrusion and the basic mechanisms of magmatic differentiation in this case however we are ready to hang our case on well established field relations and a mass of laboratory data for what must be the most intensely studied body of rock on earth

seismic phases and scaling associated with small high explosive surface shots abstract an analysis of seismic field data from surface shots in two radically different geologic environments shows significantly different seismic phases at the two sites at the first site which has a layered sedimentary section five distinct phases are observed the p wave first arrival a complex wave train consisting of higher mode rayleigh waves a precursor to air blast wave the air blast wave and the air coupled rayleigh waves records from the second site overlying an unlayered mass of igneous rocks show only three distinct seismic phases the p wave first arrival a simple wave train of fundamental mode rayleigh and love waves and an air blast wave peak ground velocity based on the average of the three largest amplitudes in the surface waves preceding the air blast wave scales well with yield for both sites measurements of peak ground velocity may be used to estimate yields of explosive charges at either site within a factor of about 2 if the source distance is known the scaling relationship appears to be valid over a wide range of yields and site geological conditions

sulphide melt and aqueous fluid saturation in the pge au mineralisation of the skaergaard intrusion evidence from melt inclusions the skaergaard intrusion in east greenland hosts mineralisation of platinum group elements and gold that is characterised by a remarkably low amount of sulphides about 0 02 wt sulphide and a very high metal sulphur ratio here we present the first quantitative analyses of sulphur s copper cu lithium li and other trace elements from melt inclusions in plagioclase to trace their evolution in the magma and to constrain the formation of the mineralisation the concentration of these elements in the melt inclusions varies considerably within each sample the s content in melt inclusions ranges from 165 to 320 ppm in the lower part of the intrusion but increases to 349 512 ppm immediately below the mineralisation interval in the same interval the li content increases from 22 43 to 40 69 ppm and cu ranges from 118 to 1586 ppm with no systematic variations across the mineralisation the li content drops an order of magnitude to 4 7 ppm and s drops to 250 326 ppm we explain these compositional changes as reflecting the magmatic evolution as the result of fractional crystallisation below and coinciding aqueous fluid exsolution and sulphide saturation across the mineralisation normally the s content of basaltic magmas is much higher at sulphide saturation we propose that sulphide saturation is possible nevertheless mostly due to the high cu content and high cu fe in the evolved ferrobasaltic melt resulting in a lowering of the s concentration required for sulphide saturation the relationship between exsolutions of aqueous fluids and sulphides remains unknown

importance of iron rich tholeiitic magmas at divergent plate margins a reappraisal when a tholeiitic liquid differentiates it may give rise to either iron poor silica rich rhyolitic differentiates or to iron rich silica poor differentiates as found in the skaergaard intrusion iron rich differentiated liquids are rare among erupted rocks but are found in small quantities from several localities at divergent plate margins among the tertiary basalts and intrusions in east greenland normal erupted basalts may be mixtures of primitive liquid and differentiated iron rich liquid which exists at depth but normally does not reach the surface because of its high density the evolved liquids of the skaergaard intrusion were of this kind data from mid oceanic ridges confirm this view we believe that iron rich differentiated liquids despite their scarcity on the surface are much more voluminous at depth as picrites at the other side of the density minimum attained during liquid evolution are thought to be the trend toward iron enrichment develops when the tholeiitic magma differentiates in a closed system at a relatively low oxidation state whereas the trend toward silica enrichment and iron depletion occurs when the magma has interacted with the oxidized and hydrated surroundings in the crust

magma chamber processes in the formation of the low sulphide magmatic au pge mineralization of the platinova reef in the skaergaard intrusion east greenland

amount and style of late cenozoic deformation in the liupan shan area ningxia autonomous region china the structures of the liupan shan area are characterized by numerous active thrust and strike slip faults that suggest thin skinned deformation the structural history of this area can be divided into three phases that probably overlap one another in time and are parts of a single protracted deformation the oldest cenozoic deformational phase occurred probably between late pliocene and early quaternary time and produced some of the folds and thrust faults in the liupan shan and yueliang shan during this phase deformation was the result of approximately n50 e shortening and the amount of shortening seems to have been about 1 2 km the second phase of deformation was dominated by left lateral strike slip faulting left slip on the n60 w striking haiyuan fault zone and shortening on north south trending structures shortening was associated with a transfer of the left slip displacement on the haiyuan fault zone to shortening in areas farther east shortening occurred by thrust faulting in the liupan shan and xiaoquan shan and by folding in the madong shan during this phase the orientation of shortening changed to n60 w the average amount of shortening on the north south trending folds in the madong shan is about 6 3 7 8 km most of the shortening on the liupan shan and xiaoguan shan thrust faults also occurred during this phase and amounted to a minimum of 4 8 6 3 km and 6 6 7 6 km respectively also with an orientation of n60 w during the third phase of deformation about 1 1 5 km of late pleistocene to recent left slip occurred on the xiaokou fault which was transferred into oblique left slip thrusting in the liupan shan at this time deformation in the madong shan and xiaoguan shan ceased or was reduced to a very slow rate the present active left slip on the haiyuan fault zone is accommodated by shortening in the liupan shan area the total displacement along the haiyuan fault is essentially the same as the total amount of shortening in the liupan shan area the sequence and interaction of strike slip and thrust faults in the liupan shan area seem to apply to the folds and thrust faults farther north in the southern ningxia region thus the northeastern margin of the tibetan plateau appears to grow by shortening oriented northeast and by left slip faulting that transfers material from farther to the west the total left slip in the entire southern ningxia region probably is less than 20 25 km and may be absorbed by shortening within this region thus the eastward translation of crustal fragments in the northern part of the tibetan plateau may not extend east of southern ningxia and if large scale eastward displacement has occurred it must lie farther south

structure from motion photogrammetry a low cost effective tool for geoscience applications abstract high resolution topographic surveying is traditionally associated with high capital and logistical costs so that data acquisition is often passed on to specialist third party organisations the high costs of data collection are for many applications in the earth sciences exacerbated by the remoteness and inaccessibility of many field sites rendering cheaper more portable surveying platforms i e terrestrial laser scanning or gps impractical this paper outlines a revolutionary low cost user friendly photogrammetric technique for obtaining high resolution datasets at a range of scales termed structure from motion sfm traditional softcopy photogrammetric methods require the 3 d location and pose of the camera s or the 3 d location of ground control points to be known to facilitate scene triangulation and reconstruction in contrast the sfm method solves the camera pose and scene geometry simultaneously and automatically using a highly redundant bundle adjustment based on matching features in multiple overlapping offset images a comprehensive introduction to the technique is presented followed by an outline of the methods used to create high resolution digital elevation models dems from extensive photosets obtained using a consumer grade digital camera as an initial appraisal of the technique an sfm derived dem is compared directly with a similar model obtained using terrestrial laser scanning this intercomparison reveals that decimetre scale vertical accuracy can be achieved using sfm even for sites with complex topography and a range of land covers example applications of sfm are presented for three contrasting landforms across a range of scales including an exposed rocky coastal cliff a breached moraine dam complex and a glacially sculpted bedrock ridge the sfm technique represents a major advancement in the field of photogrammetry for geoscience applications our results and experiences indicate sfm is an inexpensive effective and flexible approach to capturing complex topography

yield and emplacement depth effects on acoustic signals from buried explosions in hard rockyield and emplacement depth effects on acoustic signals from buried explosions in hard rock

pressure conditions for the solidification of the skaergaard intrusion eruption of east greenland flood basalts in less than 300 000 years abstract primary granophyres are differentiated from olivine tholeiitic magma and occur interstitially throughout the cumulus stratigraphy of the skaergaard intrusion east greenland samples from the lower zones a c lza c the middle zone mz and the sandwich horizon sh are included in the present study together with granophyric accumulations in gabbroic pegmatite from lza c fluid inclusions in quartz and the mineral assemblage in the granophyres record the pressure under which the skaergaard intrusion crystallised pegmatitic granophyre from lza c consists mainly of quartz plagioclase an 4 7 and alkali feldspar or 40 80 enclosing an earlier formed assemblage of ferrohastingsitic and ferroedenitic hornblende fayalite fo 4 5 titanite biotite and fluor apatite granophyric quartz albite and alkali feldspar crystallised from water saturated granitic melts near eutectic minimum conditions between 680 and 660 c the pressure of granophyre crystallisation was modelled by the intercept between fluid inclusion isochores and the minimum melt solidus for granitic compositions pressures recalculated to the roof pendant of the intrusion are 0 7 0 5 for lza 2 0 0 2 for lzb c 2 3 0 8 for mz the triple group level and 3 3 1 3 kb for sh amphibole geobarometry independently confirm the pressure estimates for pegmatitic granophyres in lza c the granophyres formed as the intrusion cooled through the minimum melt solidus in lza lzb lzc mz and sh respectively the pressure increase from lza to sh granophyres is explained by progressive burial during cooling of the intrusion and contemporaneous outpouring of 5 3 6 3 2 7 km of flood basalts during the initial opening of the northeast atlantic ocean accordingly the skaergaard intrusion evolved from a subvolcanic magma chamber at emplacement to a more deep seated igneous system during terminal crystallization when the majority of the intercumulus phases formed the present cooling history suggests the intrusion cooled through the temperature of granophyre formation in less than 300 000 years the increase in the pressure of granophyre formation therefore implies that 5 3 6 3 2 7 km of flood basalts were emplaced within this time window

surface rupture geomorphology and vertical slip rates constrained by terraces along the wulashan piedmont fault in the hetao basin china abstract the wulashan piedmont fault is a typical normal fault in the northern ordos block and has exhibited intense activity since the late pleistocene it is located among the ordos block alashan block yanshan block and north china block and between the ne expansion of the tibetan plateau and the subduction of the pacific plate this area is important as a key location to study the remote effects of the tibetan plateau ne expansion historical m 8 earthquakes in 7 bce and 849 ce occurred near this fault and thus the fault poses a potential earthquake threat but has received little research attention we observed the surface ruptures measured the heights of terraces created by fault offsets excavated trenches and used optically stimulated luminescence osl dating of samples to study the late quaternary fault activity this study shows that the fault is divided into three segments three levels of terraces were produced by movement on the fault the t1 terrace formed at approximately 10 ka the t2 terrace formed between 30 and 40 ka and the t3 terrace formed between 40 and 50 ka based on the average terrace heights along the fault we calculate that the vertical fault slip rates have been approximately 1 12 1 34 mm a in the holocene and 2 2 2 28 mm a since 50 ka our analysis shows that the daqingshan piedmont fault has the highest vertical slip rate the wulashan piedmont fault has an intermediate slip rate and the sertengshan piedmont fault has the lowest vertical slip rate the area between the wulashan and daqingshan piedmont faults readily accumulates seismic stress and represents a potential future earthquake site trenches provide visible evidence of vertical rupture and slip movement in subsurface profiles revealing six events on the gongmiaozi segment since 25 ka and 14 events on the baotou segment since 120 ka the analysis shows that the ordos peripheral fault system formed due to the subduction of the pacific plate the northward expansion of the tibetan plateau and the movement of the ordos block have caused fault activity in the northern part of the hetao basin since the late pleistocene the modern tectonic stress field and the upwelling of asthenospheric material east of the hetao fault zone have resulted in an increase in the slip rate on the hetao fault zone from west to east

a new osl chronology for dust accumulation in the last 130 000 yr for the chinese loess plateau abstract a sensitivity corrected multiple aliquot regenerative dose protocol has been developed for fine grained quartz osl dating of chinese loess its reliability has been assessed on the basis of the methodology and by dating reference samples of known age close to the transition from the last interglacial paleosol s 1 to the last glacial loess l 1 which corresponds to the marine oxygen isotope stage mis 5 4 transition on the basis of the fine grained quartz osl age estimates for 33 loess samples from the upper part of the luochuan profile a detailed chronostratigraphy of continuous dust accumulation in the past 130 ka has been proposed changes in the accumulation rate occurred during the last glacial period mis 4 to mis 2 unexpectedly high accumulation rates were found in the weakly developed l 1 2 s paleosol of the last interstadial mis 3 rather than in the classic l 1 1 and l 1 3 loess of the cold dry glacial condition mis 2 and 4 the osl ages show some disagreement with the previous numerical chronology for the loess paleosol sequence based on correlation of variations in grain size with sedimentation rate the latter method resulted in an almost constant accumulation rate from 72 to 12 ka

seismic models for near surface explosion yield estimation in alluvium and sedimentary rock author s templeton dc rodgers aj ford sr harben pe ramirez al foxall w reinke re abstract 2018 seismological society of america all rights reserved seismic ground motion data provide valuable constraints on explosion characteristics such as yield and height of burst depth of burial hob dob this study investigated a range of seismic amplitude features and their efficacy in minimizing errors associated with yield estimation using a set of explosion recordings from experiments conducted in alluvium and sedimentary rock geologies we investigated the effectiveness of three different seismic feature types over a range of different frequencies using both velocity and displacement data we investigated the zero to peak ztp amplitude of the first arriving p wave the peak to peak ptp amplitude of the first arriving p wave and the prms amplitude over various time windows starting with the p wave these three basic features were measured on both vertical component only data and the vertical radial vector sum in total there were 56 different combinations investigated our seismic models combine the effects of scaled range and scaled hob dob on the observed seismic features the results show that the vertical radial vector sum of the ztp amplitudes measured on displacement seismograms most consistently produce models with the smallest difference between predicted amplitude values and observed amplitude values when accounting for both alluvium and sedimentary rock lithology the improvement in fit to the data when incorporating the difference in source lithology is significant if an alluvium lithology is assumed for a sedimentary rock lithology the difference in yield could be up to 3 0 times the appropriate yield in the far field

assessment of relative active tectonics southwest border of the sierra nevada southern spain abstract we present a new method for evaluating relative active tectonics based on geomorphic indices useful in evaluating morphology and topography indices used include stream length gradient index sl drainage basin asymmetry af hypsometric integral hi ratio of valley floor width to valley height vf index of drainage basin shape bs and index of mountain front sinuosity smf results from the analysis are accumulated and expressed as an index of relative active tectonics iat which we divide into four classes from relatively low to highest tectonic activity the study area along the southwest border of the sierra nevada in southern spain is an ideal location to test the concept of an index to predict relative tectonic activity on a basis of area rather than a single valley or mountain front the study area has variable rates of active tectonics resulting from the collision of africa with europe that has produced linear east west anticlinal forms as well as extension with variable vertical rates of normal faulting to about 0 5 m ky we test the hypothesis that areas of known relatively high rates of active tectonics are associated with indicatives values of iat

transformation of displacement between strike slip and crustal shortening in the northern margin of the tibetan plateau evidence from decadal gps measurements and late quaternary slip rates on faults abstract studies of late quaternary geological slip rates and the gps decadal slip rates along the major strike slip faults in the northern margin of the tibetan plateau show that slip rates remain relatively constant along the middle sections of each fault and decrease rapidly toward the ends our recent studies suggest that the slip rates are low

partitioning of seismoacoustic energy and estimation of yield and height of burst depth of burial for near surface explosions explosions near the earth s surface excite both seismic ground motions and atmospheric overpressure the energy transferred to the ground and atmosphere from a near surface explosion depends on yield w as well as the height of burst depth of burial hob dob for above belowground emplacements we report analyses of seismic and overpressure motions from the humble redwood series of low yield near surface chemical explosions with the aim of developing quantitative models of energy partitioning and a methodology to estimate w and hob dob the effects of yield hob and range on amplitudes can be cast into separable functions of range and hob scaled by yield we find that displacement of the initial p wave and the integral of the positive overpressure impulse are diagnostic of w and hob with minimal scatter an empirical model describing the dependence of seismic and air blast measurements on w hob dob and range is determined and model parameters are found by regression we find seismic amplitudes for explosions of a given yield emplaced at or above the surface are reduced by a factor of 3 relative to fully contained explosions below ground air blast overpressure is reduced more dramatically with impulse reduced by a factor of 100 for deeply buried explosions relative to surface blasts our signal models are used to invert seismic and overpressure measurements for w and hob and we find good agreement w errors 30 hob within meters with ground truth values for four noncircular validation tests although there is a trade off between w and hob for a single seismic or overpressure measurement the use of both measurement types allows us to largely break this trade off and better constrain w and hob however both models lack resolution of hob for aboveground explosions

displacement and geometrical characteristics of earthquake surface ruptures issues and implications for seismic hazard analysis and the process of earthquake rupture there now exist about three dozen historical earthquakes for which in vestigators have constructed maps of earthquake rupture traces accompanied by de scriptions of the coseismic slip observed along the fault strike the maps and slip distributions are compiled here to place observational bounds on aspects of seismic hazard analysis and fault mechanics analysis leads to an initial statistical basis to predict the end points of rupture and the amount of surface slip expected at sites along the strike during earthquakes on mapped faults the observations also give support to the ideas that there exists a process zone or volume of about 3 4 km in dimension at the fronts of large laterally propagating earthquake ruptures within which stress changes may be sufficient to trigger slip on adjacent faults and that the ultimate length of earthquake ruptures is controlled primarily by the geometrical complexity of fault traces and variations in accumulated stress levels along faults that arise due to the location of past earthquakes to this may be added the observation that the form of earthquake surface slip distributions is better described by asymmetric rather than symmetric curve forms and that earthquake epicenters do not appear to correlate in any systematic manner to regions of maximum surface slip observed along strike online material maps of surface ruptures digitized values and curve fits to surface slip distributions and notes and references for tables 1 and 2

contemporary kinematics of the ordos block north china and its adjacent rift systems constrained by dense gps observations abstract the detailed kinematic pattern of the ordos block north china and its surrounding rift systems remains uncertain mainly due to the low signal to noise ratio of the global positioning system gps velocity data and the lack of gps stations in this region in this study we have obtained a new and dense velocity field by processing gps data primarily collected from the crustal motion observation network of china and from other gps networks between 1998 and 2014 the gps velocities within the ordos block can be interpreted as counterclockwise rotation of the block about the euler pole with respect to the eurasia plate velocity profiles across the graben bounding faults show relatively rapid right lateral strike slip motion along the yinchuan graben with a rate of 0 8 2 6 mm a from north to south in addition a right lateral slip rate of 1 1 1 6 mm a is estimated along the central segment of the shanxi rift however strike slip motion is not detected along the northern and southern margins of the ordos block conversely significant extension motion is detected across the northwestern corner of the block with a value of 1 6 mm a and along the northern segment of the shanxi rift where an extensional rate of 1 3 1 7 mm a is measured both the daihai and datong basins are experiencing crustal extension on the southwestern margin of the block deformation across the compressional zone of the liupanshan range is subtle however the far field shorting rate is as high as 3 0 mm a implying that this region is experiencing ongoing compression the results reveal that present day fault slip occurs mainly along the block bounding faults with the exception of faults along the northern and southern margins of the block these results provide new insights into the nature of tectonic deformation around the ordos block and are useful for assessing the seismic activity in this region

an analysis of the effects of site geology on the characteristics of near field rayleigh waves abstract an approximate analytical model is presented for describing the effects of site geology on the near field rayleigh wave ground motions induced by atmospheric explosions the model is based on an airy phase approximation to the time domain displacement corresponding to the exact frequency domain solution results of numerical simulations are presented which indicate that the amplitude duration and dominant frequency of the rayleigh wave ground motions are strongly dependent on the variation of shear wave velocity with depth at the site the approximate model is tested over a range of site conditions and it is demonstrated that the dependence of the rayleigh wave characteristics on site geology predicted by the more complex exact model can be accurately described by a remarkably simple set of analytic approximations