paleoseismology along the 1980 surface rupture of the irpinia fault implications for earthquake recurrence in the southern apennines italy the irpinia fault was the source of the ms 6 9 1980 irpinia earthquake and produced the first unequivocal historical surface faulting in italy trenching of the 1980 fault scarp at piano di pecore a flat intermontane basin about 5 km south of the 1980 instrumental epicenter provides the first data on earthquake recurrence intervals slip per event and slip rate on a major normal fault in the southern apennines fault zone the trenches exposed evidence of four pre 1980 paleoearthquakes that occurred during the past 8600 years a best estimate average recurrence interval is 2150 years although the time interval between individual events varies by as much as a factor of 2 each paleo earthquake is similar to the 1980 surface rupture in amount of slip and style of deformation which suggests that the 1980 event is characteristic for the irpinia fault slip per event values average 61 cm the net vertical displacement of 2 12 2 36 m since 8600 cal year b p observed in the trenches gives a vertical slip rate of 0 25 0 35 mm yr a dip slip rate of 0 29 0 40 mm yr and an extension rate of 0 14 0 20 mm yr although fault behavior data are only available for the irpinia fault they provide a starting point for evaluating earthquake recurrence and rates of deformation in southern apennines they suggest that 1 fault specific earthquake recurrence intervals based on the historical seismic record overestimates the occurrence of large magnitude m7 earthquakes and 2 the holocene rate of extension across the apennines is 1 mm yr the 1980 earthquake and the paleoseismologic observations show that repeated and localized surface faulting occurs in southern apennines and leaves subtle but distinct geomorphic evidence that can be detected with detailed and careful investigation

evidence for postseismic viscoelastic relaxation following the 1959 m 7 5 hebgen lake montana earthquake a 1983 releveling survey conducted by the national geodetic survey combined with previous surveys in 1923 1960 1967 and 1975 provides evidence for ongoing vertical deformation of a broad region diameter of 150 km surrounding the site of the 1959 hebgen lake earthquake deformation consists of relative uplift centered roughly on the coseismic fault and a smaller amplitude zone of relative subsidence south of the fault maximum observed elevation change during the postseismic period 1960 1983 exceeds 30 cm assuming that the entire uplift i e 1923 1983 occurred following the 1959 earthquake i e uplift measured between 1923 and 1960 was entirely postseismic the rate of vertical deformation appears to have decreased exponentially with a characteristic decay time of about 10 years the spatial pattern and time behavior of the observed movements are consistent with simple models of postseismic deformation following normal faulting in an elastic layer thickness of 30 40 km overlying a viscoelastic half space viscosity of 1019 pa s this model may also account for the anomalously large horizontal strain around the hebgen lake region measured by repeated trilateration surveys during the period 1973 1984 the releveling measurements in the hebgen lake region appear to provide the first observations of viscoelastic relaxation in the asthenosphere following an intraplate earthquake in the united states

the evolution of regional seismicity between large earthquakes 1 we describe a simple model that links static stress coulomb modeling to the regional seismicity around a major fault unlike conventional coulomb stress techniques which calculate stress changes we model the evolution of the stress field relative to the failure stress background seismicity is attributed to inhomogeneities in the stress field which are created by adding a random field that creates local regions above the failure stress the inhomogeneous field is chosen such that when these patches fail the resulting earthquake size distribution follows a gutenburg richter law immediately following a large event the model produces regions of increased seismicity aftershocks where the overall stress field has been elevated and regions of reduced seismicity where the stress field has been reduced stress shadows the high stress levels in the aftershock regions decrease due to loading following the main event combined with the stress shadow from the main event this results in a broad seismically quiet region of lowered stress around the epicenter pre event seismicity appears as the original stress shadows finally fill as a result of loading the increase in seismicity initially occurs several fault lengths away from the main fault and moves inward as the event approaches as a result of this effect the seismic moment release in the region around the future epicenter increases as the event approaches synthetic catalogues generated by this model are virtually indistinguishable from real earthquake sequences in california and washington

the minimalist model of characteristic earthquakes as a useful tool for description of the recurrence of large earthquakes renewal models are usually applied to seismic regions where large earthquakes occur repeatedly at approximately regular time intervals in most cases these models lack a seismological basis and are just well known statistical distributions rooted in reliability theory here we show the good properties of the recently introduced minimalist model of characteristic earthquakes to describe the recurrence of these large earthquakes several examples in japan italy and the united states are shown manuscript received 20 november 2003

temporal gravity and height changes of the yellowstone caldera 1977 1994 this paper describes the longest record of gravity measurements in the area of the yellowstone caldera wyoming the temporal gravity changes at the 12 gal 10 8 ms 2 precision level are compared with changes in heights from leveling and gps the gravity field decreased across the caldera from 1977 to 1983 during the uplift and attained a maximum decrease of up to 60 2 gal along the caldera axis the gravity field then reversed polarity to increasing values of up to 60 12 gal between 1986 and 1993 the ratio between height and gravity changes varied during the entire time but converged over the latter period following the free air gravity gradient general ground deformation deduced from leveling showed caldera wide uplift of 15 mm a during the period of gravity decrease then from leveling and gps subsidence of 25 mm a during the gravity increase

paleoceanographic change during the last deglaciation east sea of korea foraminiferal assemblage and stable isotopic data are presented for three quaternary piston cores from ulleung basin east sea of korea esk japan sea near the korean peninsula major changes in both temperature and salinity strongly affected surface and deep waters of the esk during the transition from the last glacial maximum lgm to the middle holocene local environmental effects dominated during the lgm and the bolling allerod b a when the esk became semi isolated from the pacific ocean regional global influences dominated following the b a after sufficient reconnection with the pacific this is reflected in the foraminiferal 18o record which was largely salinity controlled before the younger dryas yd and temperature controlled after the yd paleoceanographic changes in the esk during the last deglaciation reflect sequential reconnection with the pacific ocean through gateways first b a in the north tsugaru strait and later holocene in the south korea strait

morphodynamic modelling for a tidal inlet in the wadden sea abstract a dynamic model for morphological development in a tidal inlet het friesche zeegat in the wadden sea along the northern coast of the netherlands is set up to obtain a better understanding of the behaviour of the morphological system around tidal inlets the model is based on delmor a program package for morphological changes developed at delft hydraulics computations of the flow the sediment transport the initial bed level change rate as well as long term morphological development have been carried out the model has proven to be a useful research tool even though it does not yet reproduce reality in detail

p wave attenuation of the yellowstone caldera from three dimensional inversion of spectral decay using explosion source seismic data using explosion source seismic refraction data recorded in the 1978 and 1980 yellowstone snake river plain seismic experiments a three dimensional inversion of differential p wave attenuation was used to assess the relative variations in q 1 in and around the volcanically active 45 km by 70 km yellowstone caldera northwestern wyoming differential attenuation was derived from spectral decay of upper crustal pg phases observed from six explosions and recorded at 90 temporary stations because of the relatively short time windows used to determine the spectral content a maximum entropy technique was employed to estimate the spectra that yielded an optimally small variance differential p wave attenuation was calculated from least squares determinations of the spectral ratios corrected for source and path effects the observed differential attenuation parameters were then inverted using a weighted least squares technique for a discretized 70 105 km three dimensional surface and upper crustal q 1 model of the yellowstone caldera and surrounding region results showed that the surface layer to depths of 2 km within the yellowstone caldera is characterized by relatively high attenuation with low q values less than 30 compared to values of 38 to 50 outside the caldera the higher attenuation in the caldera s surface layer is thought to be associated with quaternary lake sediments highly altered rhyolites and the possible influence of steam in areas of hydrothermal activity in the crystalline upper crust at depths of 2 km to 12 km q values of 40 to 70 were observed in areas of thick sedimentary fill northwest of the caldera and in areas of hydrothermal activity within the caldera upper crustal attenuation generally corresponded to q of 200 in areas that are interpreted to be associated with hot but now solidified granitic material in comparison relatively high attenuation q 40 was observed in the upper crust of the northeastern yellowstone caldera in an area that also corresponds to a 20 reduction in pg velocity a prominent negative bouguer gravity low of 20 mgal near yellowstone s largest area of hydrothermal activity and near a quaternary volcanic resurgent dome on the basis of constitutive models of velocity and density this zone of high attenuation is likely a product of unusual hydrothermal activity highly altered upper crustal rocks a shallow magmatic source or a highly porous steam saturated body outside the caldera the upper crust is relatively unaffected by high temperatures and thermal alteration and the corresponding attenuation is low with q values greater than 200

tetraether lipids from the southern yellow sea of china implications for the variability of east asia winter monsoon in the holocene to better understand the origin and distribution of organic matter om in the yellow sea ys and to delineate potential interactions between the atmosphere and the marine system during the holocene we reconstructed terrestrial input and temperature variation for the last 8 8 ka bp using glycerol dialkyl glycerol tetraethers gdgts obtained from a 4 4 m sediment core ysc 1 from the southern ys the archaea derived isoprenoid gdgts igdgts were dominated by gdgt 0 and crenarchaeol the igdgts and bacteria derived branched gdgts bgdgts correlated well and varied in opposition to the bit branched vs isoprenoid tetraether index this may be due to varying river runoff and influence of the ys coastal current yscc and ys warm current yswc related to the east asia winter monsoon eawm which made the bit proxy less suitable for tracing soil om input to the ys tex86 tetraether index of tetraethers consisting of 86 carbons derived sea surface temperature values sst varied from 9t o 16c close to the sst in the ys cold season the mbt cbt methylation of branched tetraethers and cyclization of branched tetraethers derived continental temperature ranged from 10 to 19 c indicating an annual mean air temperature for the middle and low drainage basin of the ys these two temperature records were decoupled but both correlated with the variation in the eawm suggesting an intimate link between eawm and temperature variation in east asia

a model of characteristic earthquakes and its implications for regional seismicity regional seismicity i e that averaged over large enough areas over long enough periods of time has a size frequency relationship the gutenberg richter law which differs from that found for some seismic faults the characteristic earthquake relationship but all seismicity comes in the end from active faults so the question arises of how one seismicity pattern could emerge from the other the recently introduced minimalist model of vazquez prada et al of characteristic earthquakes provides a simple representation of the seismicity originating from a single fault here we show that a characteristic earthquake relationship together with a fractal distribution of fault lengths can accurately describe the total seismicity produced in a region the resulting earthquake catalogue accounts for the addition of both all the characteristic and all the non characteristic events triggered in the faults the global accumulated size frequency relationship strongly depends on the fault length fractal exponent and for fractal exponents close to 2 correctly describes a gutenberg richter distribution with a b exponent compatible with real seismicity

upper crustal structure of the yellowstone caldera from seismic delay time analyses and gravity correlations the 1978 yellowstone snake river plain seismic experiment provided detailed refraction data that were recorded across a two dimensional array of seismographs in yellowstone national park a delay time analysis was applied to 173 crystalline basement pg arrivals from these data to determine the three dimensional distribution of velocities and the layer configuration of the upper crust beneath the yellowstone caldera the p wave velocity structure of the caldera is characterized by a surface layer of combined sediments and rhyolite flows averaging 2 8 km s that range in thickness from 1 5 to 2 0 km adjacent to the caldera the crystalline upper crustal layer has a velocity of 6 05 0 01 km s but this layer decreases by 6 to 5 70 km s beneath the caldera and extends northeast 15 km beyond the caldera smaller zones of very low p velocity 4 0 km s a 30 velocity reduction compared to the 6 05 km s layer occur in the upper crust beneath the northeastern caldera rim and beneath the southwest caldera in the vicinity of the upper and midway geyser basins a three dimensional gravity interpretation based upon densities derived from the seismic model suggests that the regional gravity low of 60 mgal over the caldera correlates directly with 1 the surface layer of combined sediments and rhyolite flows 2 the low velocity 5 7 km s upper crustal layer and 3 the 4 0 km s low velocity zone beneath the northeastern caldera rim an interpretation of the seismic velocities and densities based on experimental data and theoretical models suggests that the 6 05 km s 2 70 g cm3 regional pg velocity is characteristic of crystalline basement rocks such as the precambrian granitic gneisses that are exposed north and south of the yellowstone caldera the 5 7 km s velocity layer 2 65 g cm3 is interpreted to be a 10 km thick hot body of granitic composition the 4 0 km s low velocity body 2 40 g cm3 beneath the northeastern caldera rim is associated with a local 20 mgal gravity anomaly with a range of interpretations from a large steam dominated system to a felsic body of 10 to 50 partial melt the postulated 4 0 km s low velocity layer beneath the southwestern caldera does not have a corresponding gravity signature and may reflect a zone of high seismic attenuation attributed to a saturated fracture zone this seismic velocity model of the yellowstone caldera suggests that the source of the quaternary silicic volcanic rocks corresponds to the 5 7 km s layer in the upper crust that appears to contribute the principal source of heat to the yellowstone hydrothermal systems the anomalous low velocity body in the northeastern caldera rim area may be a cupola of partial melt with an overlying vapor dominated carapace and may represent the waning stages of the third cycle of quaternary volcanism or the beginning of a new cycle of volcanism that will continue the northeastward progression of the silicic volcanism of the yellowstone snake river plain propagating system

a way to synchronize models with seismic faults for earthquake forecasting insights from a simple stochastic model abstract numerical models are starting to be used for determining the future behaviour of seismic faults and fault networks their final goal would be to forecast future large earthquakes in order to use them for this task it is necessary to synchronize each model with the current status of the actual fault or fault network it simulates just as for example meteorologists synchronize their models with the atmosphere by incorporating current atmospheric data in them however lithospheric dynamics is largely unobservable important parameters cannot or can rarely be measured in nature earthquakes though provide indirect but measurable clues of the stress and strain status in the lithosphere which should be helpful for the synchronization of the models the rupture area is one of the measurable parameters of earthquakes here we explore how it can be used to at least synchronize fault models between themselves and forecast synthetic earthquakes our purpose here is to forecast synthetic earthquakes in a simple but stochastic random fault model by imposing the rupture area of the synthetic earthquakes of this model on other models the latter become partially synchronized with the first one we use these partially synchronized models to successfully forecast most of the largest earthquakes generated by the first model this forecasting strategy outperforms others that only take into account the earthquake series our results suggest that probably a good way to synchronize more detailed models with real faults is to force them to reproduce the sequence of previous earthquake ruptures on the faults this hypothesis could be tested in the future with more detailed models and actual seismic data

the impact of refraction correction on leveling interpretations in southern california recent investigations show that the refraction corrections in leveling are large but can be adequately modeled the corrections are proportional to the temperature differences and the square of the sight lengths changes in sight length with time have resulted in apparent crustal movements when non refraction corrected data were used applying refraction corrections to leveling data in southern california significantly alters the size and configuration of the southern california uplift uplift at palmdale and gorman lebec relative to los angeles bm v32 during the 1953 1978 time period is no greater than 10 cm the bulk of the motion about 6 cm occurs as localized motion along the san gabriel fault during the 1953 1964 time period this motion along the san gabriel fault and uplift of 8 cm directly north of the san fernando fault between 1955 and 1968 may represent precursors to the 1971 san fernando earthquake

water level records used to evaluate deformation within the yellowstone caldera yellowstone national park abstract water level records from gages on the shore of yellowstone lake and at its outlet are used to evaluate deformation year by year since 1923 on the southeastern flank of yellowstone caldera there is good agreement with deformation as measured by precise benchmark leveling surveys in 1923 1976 1983 1984 and 1985 the water level record provides documentation of historical deformation of a large dynamic silicic caldera available by no other means and it gives detail lacking from benchmark leveling prior to 1983 when annual surveys began the data from southwest of fishing bridge suggest that this portion of the caldera has undergone relatively monotonic inflation since 1923 0 4 radian a up to the northeast with a small quasi oscillatory variation superimposed north of fishing bridge the data suggest a higher rate with onset of quasi oscillatory uplift ca 1940 and a leveling off since ca 1965 of particular importance are the suggestion of episodic uplift and subsidence the apparent lack of significant devation at the time of the m 7 5 hebgen lake earthquake 1959 and the apparent subsidence of the intra caldera area north of fishing bridge at the time of the m 6 1 norris earthquake 1975 with concurrent inflation of the flank of the caldera to the southwest

paleoenvironmental changes associated with the holocene marine transgression yellow sea hwanghae benthic foraminiferal and stable isotopic data from two radiocarbon dated cores from the yellow sea record paleoenvironmental changes largely associated with the holocene marine transgression the holocene marine transgression began significantly earlier 12 9 ka in the central part of the yellow sea as recorded in 278 cm long core cc 02 water depth 77 5 m compared with 7 9 ka in a tidal flat on west coast of korea as recorded in 350 cm long vibra core dh4 1 water depth 1 8 m the benthic foraminiferal assemblages in the lower part of cc 02 and the entire marine sequence of dh4 1 are dominated by assemblages characteristic of shallow 50 m waters ammonia ketienziensis ishizaki astrononion italicum cushman and edwards and hanzawaia nipponica asano after 7 5 ka in the central yellow sea much higher 18o 1 6 to 1 8 and 13c 0 1 to 0 7 values of a ketienziensis reflect a change to more open ocean higher salinity environments with deeper waters dominated by the hwanghae cold water as in the present day

inversion for sources of crustal deformation and gravity change at the yellowstone caldera the 3100 km2 yellowstone caldera yellowstone national park was formed in the latest of three explosive eruptions of rhyolites and ash flow tuffs totalling 3700 km3 at 2 1 2 and 0 6 m y before present its youthful volcanic history widespread hydrothermal activity intense seismicity and extremely high heat flow in excess of 30 times the continental average marks the yellowstone volcanic system as a giant caldera at unrest orthometric height increases of the caldera of up to 76 cm measured from precise leveling surveys from 1923 to 1975 1977 were inverted to determine volume expansion source models for the caldera wide deformation for the 1923 to 1977 uplift episode two regions of expansion were found 1 in the northern part of the caldera near the sour creek resurgent dome of 0 37 km3 and 2 in the southern part of the caldera near the mallard lake resurgent dome of 0 41 km3 both bodies occur in the upper crust from near surface depths to 6 0 km but the largest volume expansions were found in the 3 0 6 0 tan depth range the southern caldera source volume near the mallard lake dome may extend down to 9 0 km the data are however unable to resolve if these two resurgent domes separated laterally by 40 km are connected prom 1976 to 1987 nearly simultaneous measurements of elevation and gravity changes were made on a profile across the northern caldera during a period of net uplift models of the temporal gravity variation infer that the volume increase for the northern caldera source must lie above 9 0 km and involved a density perturbation greater than 0 002 g cm3 the modeled volumetric sources are in the same general locations as bodies of low p wave velocities high seismic attenuation and large negative bouguer gravity anomalies in view of the intense quaternary volcanism the anomalously high heat flow and the correlation of the source volumes with the regional geophysical anomalies it is likely that the modeled volumetric increases were caused by migration of magmas and or the introduction of large volumes of hydrothermal fluids into the upper crust

crustal deformation and source models of the yellowstone volcanic field from geodetic data 1 geodetic observations comprising interferometric synthetic aperture radar insar global positioning system gps and precision leveling measurements are used to infer volume change in the subsurface associated with the dynamics of the yellowstone volcanic system we focus primarily on the yellowstone caldera and its related magmatic hydrothermal and fault systems it appears that known faults play a significant role in controlling crustal volume increases and decreases due to the migration of volcanic and hydrothermal fluids for example over 5 cm of subsidence from 1992 to 1995 is associated with source volume changes 6 10 km beneath the nw trending elephant back fault zone and a north trending fault cutting across the caldera furthermore we are able to image an episode of fluid intrusion near the northern edge of the caldera the intrusion is elongated in the north south direction and is parallel to the north trending volume decrease the primary intrusion and related hydrothermal activity occurred between 1996 and 2000 though the volume changes appear to have continued shallowed and changed shape between 2000 and 2002 there is evidence that the intrusive activity influenced extensional faults to the north of the caldera

comparison of probabilistic seismic hazard estimates in italy abstract macroseismic intensity has recently attracted attention as a tool for validating probabilistic seismic hazard assessment psha studies or as an alternative method for psha in countries where the historical catalog is much longer than the instrumental one in italy the new seismic hazard map was recently produced using the cornell mcguire approach in terms of the peak ground acceleration characterized by a 10 exceedance probability for an exposure time of 50 yr a max we compare this map with an alternative one produced using a different approach based on a nonparametric and zonation free statistical analysis of local seismic histories in this case results are expressed in terms of the maximum intensity corresponding to an exceedance probability of not less than 10 for an exposure time of 50 yr i ref in order to compare the two maps we selected 1401 control sites where local seismic history includes at least 10 intensity values relative to felt effects documented during past earthquakes the values of a max and i ref at these sites have been ranked in the respective domains the spatial distribution of rank differences of a max and i ref values shows a strong correlation with the seismogenic zoning used in the calculation of psha following the cornell mcguire approach this suggests that the adopted zoning could be incomplete some further hidden sources may exist and too rough to capture actual seismogenic sources because more detailed zoning is prevented by the amount of data available the results obtained suggest the preference of zonation free approaches for seismic hazard assessment in italy furthermore among the possible zonation free approaches those that offer better exploitation of local information about the effects of past earthquakes would be preferred

a deep low velocity body under the yellowstone caldera wyoming delineation using teleseismic p wave residuals and tectonic interpretation in previously published papers iyer 1975 iyer and stewart 1977 iyer 1979 evidence was presented for the presence of a large body of anomalous material with compressional velocities considerably lower than normal from the surrounding rock in the crust and upper mantle under yellowstone national park wyoming in this paper we give a detailed analysis of p residual data from the 26 element telemetered seismic array and three groups of portable stations operated by the u s geological survey in the yellowstone region using a variety of analytical techniques we delineate the shape of the low velocity body determine the velocity structure inside the body and interpret the nature of the material that constitutes the body we will also outline some tectonic implications of our model the spectacular surface geothermal phenomena for which yellowstone is famous result from deep seated volcanism the volcanic evolution of yellowstone is discussed by christiansen and blank 1972 and summarized by eaton and others 1975 briefly the geothermal manifestations in yellowstone are results of three cycles of quaternary volcanism each culminating in a devastating pyroclastic eruption and resulting in large collapse calderas and predominantly rhyolitic flows the oldest cycle ended about 1 9 m y ago forming a caldera from island park to perhaps the central part of the present yellowstone caldera the second cycle climaxed about 1 2 m y ago and was confined to the island park caldera the third cycle began soon after the second and is responsible for the 75 by 45 km yellowstone caldera as it is outlined today this caldera is the result of a catastrophic eruption approximately 600 000 yr ago the most recent episode of volcanism probably began about 150 000 yr ago in the western half of the caldera near old faithful geyser and the youngest flows in yellowstone about 70 000 yr old are probably associated with this episode

depositional development of an isolated mound and adjacent area in the southern yellow sea during the last postglacial sea level rise abstract a detailed analysis of the chirp 2 7 khz profiles core sediments and 14c ages from an isolated mound and adjacent area in the southern yellow sea off the jiangsu coastal area reveals a highly complex development of transgressive and highstand deposits during the last postglacial sea level rise in water depths of 50 60 m the terrace consists of thin transgressive sediments directly above transgressive surface the isolated mound 40 7 km long and 29 6 km wide occurs above 40 50 m in water depth and is detached from the jiangsu and east china sea tidal sand ridges it comprises the sse ward prograding sandy unit pu and the overlying muddy flank unit fu at the outer margin the terrace with thin transgressive sediments was most likely formed when sea level rose rapidly from 58 to 45 m around about 11 6 ka as rate of sea level rise was attenuated from 45 to 36 m between ca 11 6 and 9 6 ka the nearly flat lower boundary of the pu was produced at water depths of 37 42 m by a ravinement process subsequent rapid sea level rise from 36 to 16 m between ca 9 6 and 9 1 ka created accommodation for deposition of the pu sea level rise stagnated from 16 to 10 m between ca 9 1 and 7 5 ka during which the huanghe river apparently shifted south of the shandong peninsula and discharged directly into the western yellow sea the combination of slow sea level rise and sediment supply from the early holocene huanghe delta by the southward flowing coastal currents most likely favoured the formation of the sse ward prograding transgressive sandy pu the highstand muddy fu overlying the pu was accumulated after ca 7 5 when sea level approached its present position and the huanghe river shifted back to the north development of transgressive and highstand deposits in the study area during the last postglacial sea level rise was highly variable in time and space in response to changes in rate of sea level rise together with variations in sediment supply caused by the shifting of the huanghe river

uplift across long valley caldera california the results of levelings along u s highway 395 between lee vining and toms place california in 1957 1975 1980 1982 and 1983 define the development of a dome shaped uplift across the long valley caldera these levelings indicate that toms place remained virtually invariant with respect to lee vining during the full interval 1957 1983 implying that the end points of the survey route lie beyond the range of the developing dome no significant uplift occurred before 1975 but by october 1980 the uplift near casa diablo hot springs reached 0 25 m and the half width of the dome was of the order of 25 km the uplift of casa diablo hot springs increased to 0 35 m by august 1982 and to about 0 40 m by august 1983 without any appreciable increase in the lateral extent of the dome the august 1982 to august 1983 uplift apparently occurred before february 1983 with little or no uplift during the period february august 1983 the 1975 1983 uplift is attributed to the injection of 0 19 km3 of magma into a spherical chamber at a depth of 10 km beneath the southern quadrant of the ancient resurgent dome within the caldera examination of the full vertical control record through the long valley area indicates that the 1975 1983 uplift is unique within the period 1905 1983 although comparisons of the results of a 1932 leveling against a 1914 datum disclose a 1914 1932 down to the northwest tilt of about 10 rad over the reach between toms place and lee vining this tilt if real is more reasonably attributed to regional tectonic deformation than it is to the movement of magma at depth

recent plate motions and crustal deformation reports by u s workers on geodetic measurements of recent plate motions or crustal deformation published in 1987 1990 are reviewed the review begins with global plate motions proceeds through plate boundaries in california alaska and the pacific northwest and finishes with volcanic phenomena monument stability and longevity and gps relative position measurements 184 refs

climatic solar oceanic and geomagnetic influences on late glacial and holocene atmospheric 14c 12c change late glacial and holocene 14c12c ratios of atmospheric co2 vary in magnitude from a few per mil for annual decadal pertubations to more than 10 for events lasting millennia a data set illuminating 10 to 104 yr variability refines our understanding of oceanic climatic versus geomagnetic or solar forcing of atmospheric 14c12c ratios most of the variance in the holocene atmospheric 14c12c record can be attributed to the geomagnetic millennia time scale and solar century time scale influence on the flux of primary cosmic rays entering the atmosphere attributing the observed atmospheric 14c12c changes to climate alone leads to ocean circulation and or global wind speed changes incompatible with proxy records climate ocean related 14c redistribution between carbon reservoirs while evidently playing a minor role during the holocene may have perturbed atmospheric 14c12c ratios measurably during the late glacial younger dryas event first order corrections to the radiocarbon time scale 12 000 30 000 14c yr b p are calculated from adjusted lake sediment and tree ring records and from geomagnetically defined model 14c histories paleosunspot numbers 100 9700 cal yr b p are derived from the relationship of model 14c production rates to sunspot observations the spectral interpretation of the 14c12c atmospheric record favors higher than average solar activity levels for the next century minimal evidence was found for a sun weather relationship

hydrothermal and tectonic activity in northern yellowstone lake wyoming yellowstone national park is the site of one of the world9s largest calderas the abundance of geothermal and tectonic activity in and around the caldera including historic uplift and subsidence makes it necessary to understand active geologic processes and their associated hazards to that end we here use an extensive grid of high resolution seismic reflection profiles 450 km to document hydrothermal and tectonic features and deposits in northern yellowstone lake sublacustrine geothermal features in northern yellowstone lake include two of the largest known hydrothermal explosion craters mary bay and elliott9s mary bay explosion breccia is distributed uniformly around the crater whereas elliott9s crater breccia has an asymmetric distribution and forms a distinctive 2 km long hummocky lobe on the lake floor hydrothermal vents and low relief domes are abundant on the lake floor their greatest abundance is in and near explosion craters and along linear fissures domed areas on the lake floor that are relatively unbreached by vents are considered the most likely sites of future large hydrothermal explosions four submerged shoreline terraces along the margins of northern yellowstone lake add to the holocene record of postglacial lake level fluctuations attributed to heavy breathing of the yellowstone magma reservoir and associated geothermal system the lake hotel fault cuts through northwestern yellowstone lake and represents part of a 25 km long distributed extensional deformation zone three postglacial ruptures indicate a slip rate of 0 27 to 0 34 mm yr the largest 3 0 m slip and most recent event occurred in the past 2100 yr although high heat flow in the crust limits the rupture area of this fault zone future earthquakes of magnitude 5 3 to 6 5 are possible earthquakes and hydrothermal explosions have probably triggered landslides common features around the lake margins few high resolution seismic reflection surveys have been conducted in lakes in active volcanic areas our data reveal active geothermal features with unprecedented resolution and provide important analogues for recognition of comparable features and potential hazards in other subaqueous geothermal environments

a 12 000 year record of vertical deformation across the yellowstone caldera margin the shorelines of yellowstone lake the 600 ka yellowstone caldera exhibits several signs of unrest the most evident of which is historic ground deformation including both uplift and subsidence we document deformation in the area of the southeastern caldera across 12 000 years using the postglacial shoreline terraces of yellowstone lake raised shoreline elevations were interpreted from 230 leveling profiles surveyed across flights of terraces with an accuracy of 0 5 m of about 11 recognizable terraces the five most continuous raised shorelines were correlated around the lake basin to reveal deformation patterns shoreline ages are based on minimum and maximum limiting radiocarbon and obsidian hydration dates each terrace is interpreted as representing an episode of uplift 1 kyr 1 of the caldera interior and subsequent subsidence with little net volume change this cyclic behavior may result from magma emplacement and subsequent withdrawal or cooling and crystallization and or episodic trapping and release of magmatic fluids evolved during cooling and crystallization in a self sealing reservoir as hypothesized by dzurisin et al 1990 early postglacial shoreline deformation reveals substantial intracaldera subsidence possibly reflecting cooling and loss of trapped hydrothermal fluids extension along north south trending normal faults and related structures is also apparent in early to middle postglacial deformation both inside and outside of the caldera margin including downwarping and local faulting of hot weak intracaldera crust net deformation over the past 3 kyr has been dominantly up within the caldera interior and slightly down along the caldera rim relative to the extracaldera region this uplift is roughly similar to the historic pattern and may largely represent the effects of the most recent inflation episode subtraction of the total estimated magnitude of inflation in this episode suggests that the overall trend of postglacial deformation has been subsidence the cause of this trend is undetermined but is most likely related to the effects of regional extension and long term cooling within the yellowstone caldera

the yellowstone hebgen lake geoid obtained through the integrated geodesy approach the 1987 crustal deformation survey of the yellowstone hebgen lake region produced accurate geodetic measurements in an area unique for its rugged topography and volcanic processes using the integrated geodesy approach global positioning system gps baseline vectors geodetic leveling and gravity measurements were combined in a simultaneous least squares adjustment using 30 30 digital terrain data and an airy model isostatically corrected complete bouguer gravity disturbances highlight both the yellowstone caldera and a second gravity low near hebgen lake a linear relationship between these disturbances and the departures of geoid height from the airy isostatic model have been found r 0 84 adjusting the covariance function while incorporating the gps contribution yields a function whose correlation length is significantly longer than that predicted by autocorrelation statistics of the gravity disturbances alone the integrated adjustment produced a geoid whose low frequency components are in good agreement with osu86f formal statistics indicate precision of 2 5 cm gps residuals for 35 leveled points in the adjustment have a root mean square value of 2 9 cm and a standard error estimate of 4 6 cm in comparison a free adjustment of 152 gps vectors yields a differential height standard error of 3 8 cm

an episodic creep slip event detected by precise levelling surveys in the central part of the longitudinal valley fault eastern taiwan in 2011 2012 abstract precise levelling surveys were conducted across the central longitudinal valley fault eastern taiwan to understand the deformation of the transition zone between the stable fault creep area and the asperity area in order to investigate the surface relationship between the fault creep area and the geological condition of the transition zone we established levelling routes in the yuli chike san and reishuei areas the yuli area forms the geological boundary of the lichi melange formation which is composed of chaotic mudstones containing numerous exotic blocks of various sizes and lithologies along the yuli route located on the lichi melange an uplift rate of 30 mm yr was detected during the period 2010 2012 suggesting that aseismic fault creep might be continuing with long term stability along the chike san route a vertical deformation rate of 8 mm yr was detected in the period 2010 2011 however a large deformation with an uplift rate of 40 mm yr was detected in the period 2011 2012 along the reisuei route we detected a deformation of 8 mm yr in the period 2011 2012 a two dimensional single fault model was developed to discuss the slip distributions in the periods 2010 2011 and 2011 2012 relatively large slip rates were estimated at two parts of the fault plane one at a depth of 1 5 km and another at a depth of 4 km in both periods because both parts of the fault plane show approximately the same slip distribution we believe that the detected deformation resulted from an episodic acceleration event of creeping slip the northern limit of the stable creep area may be the yuli area the episodic creep event occurred in the transition zone between the stable fault creep area and the asperity area the boundary between the stable creep area and the episodic creep area is consistent with the geological boundary of the lichi melange formation

strain accumulation in the rocky mountain states strain accumulation in trilateration networks in montana utah and new mexico has been measured for over a decade the network in new mexico spans the rio grande rift near socorro the absence of any observed strain accumulation in that network places an upper limit 2 standard deviations of 3 mm a on east west spreading across the 100 km wide rift the network in utah spans the wasatch fault near ogden although the 1972 1984 average rate of strain accumulation in that network is not significant at a 2 standard deviation detection threshold of 0 03 strain a short term strain fluctuations of marginal significance have been detected in the network the network in montana spans the epicentral area of the 1959 hebgen lake earthquake magnitude 7 1 the principal strain rates observed in that network for the 1973 1984 interval were e 1 0 28 0 02 strain an14 e 1 and e 2 0 05 0 02 strain an76 w 1 extension reckoned positive the principal extension is perpendicular to the 1959 rupture trace the deformation of this network suggests rather rapid reloading of the 1959 rupture zone but whether this is steady strain accumulation or still postseismic relaxation is not known the strain rate does appear to be constant over the 1973 1984 interval

denudation vertical crustal movements and sedimentary basin infill denudation and vertical crustal movements are linked through the isostatic equation for conservation of lithospheric mass recent empirical results from a wide range of sources are presented on the rates of these processes denudation alone can cause non tectonic isostatic surface uplift of the right magnitude predicted by theory a case is made following ahnert for a single linear relationship although with much scatter between denudation rate and mean drainage basin relief for large basins some recent determinations of denudational time constants have neglected to include tectonic and isostatic terms which oppose the reduction of relief by denudation application of diffusional transport models to determine the rate of sediment deposition are severely limited by inherent one dimensionality and neglect of suspended and washload contributions basin infill sequences may be used to determine past sediment transfer coefficients from a hinterland but problems arise in the apportionment of the various hinterland fluxes that occur in real world three dimensional basins sediment yields in smaller half graben and growth fold basins must reflect the magnitude of drainage basins and the complex local controls upon sediment yields examples are given from extensional basins in the western usa and greece the length of tectonic relief produced in tilt blocks and growth folds will control the area of drainage basin developed through the fractal form of hack s law and hence the magnitude of deposition in sedimentary basins adjoining tectonic uplands

slip rate variations on faults during glacial loading and post glacial unloading implications for the viscosity structure of the lithosphere abstract many active faults in extensional and contractional tectonic settings experienced a slip rate increase after the last glacial period when the volume of nearby glaciers and lakes decreased this post glacial slip rate increase is caused by transient stresses that are generated by the unloading induced rebound and superimposed on the tectonic background stress field as the latter is different for normal and thrust faults the response to loading and unloading should depend on the fault type here we use finite element models including a fault in rheologically layered lithosphere to explore the conditions under which both normal and thrust faults experience a post glacial slip rate increase the results show that a post glacial slip rate increase occurs on normal faults if the lower crust is stronger than the lithospheric mantle whereas thrust faults accelerate if the lower crust is weaker than the lithospheric mantle these findings imply that the response of faults to mass fluctuations on the earth9s surface may provide constraints on the rheological stratification of the lithosphere we use our results to make predictions on the viscosity structure of the basin and range province and northern scandinavia where palaeoseismological data document a pronounced increase in seismicity as a result of post glacial unloading and rebound

sediment supply and channel morphology in mountain river systems 1 relative importance of lithology topography and climate 1 quantifying landscape scale variations in sediment supply to streams and rivers is fundamental to our understanding of both denudational processes and stream channel morpho dynamics previous studies have linked a variety of sediment supply proxies to climatic topographic or geologic factors but few have connected these directly to the characteristics of fluvial systems draining these landscapes here we correlate landscape controls on sediment supply to observed sedimentology and channel patterns through direct measurements of water and sediment fluxes in over 80 drainage basins ranging in area from 1 4 to 35 000 km2 in the northern rocky mountains usa these data show that the relative sediment supply defined by the bankfull sediment concentration is dominated by basin lithology while exhibiting little correlation to factors such as relief mean basin slope and drainage density bankfull sediment concentrations bed load and suspended load increase as much as 100 fold as basin lithology becomes dominated by softer sedimentary and volcanic rocks relative to basins with more resistant lithologies as bed load concentrations increase stream beds become less armored and bed load grain size coarsens at very high sediment concentrations bed surface subsurface and bed load grain sizes converge and a transition from single thread to to braided channel patterns is commonly observed

magma and fluid migration at yellowstone caldera in the last three decades inferred from insar leveling and gravity measurements we studied the yellowstone caldera geological unrest between 1977 and 2010 by investigating temporal changes in differential interferometric synthetic aperture radar insar precise spirit leveling and gravity measurements the analysis of the 1992 2010 displacement time series retrieved by applying the sbas insar technique allowed the identification of three areas of deformation i the mallard lake ml and sour creek sc resurgent domes ii a region close to the northern caldera rim ncr and iii the eastern snake river plain srp while the eastern srp shows a signal related to tectonic deformation the other two regions are influenced by the caldera unrest we removed the tectonic signal from the insar displacements and we modeled the insar leveling and gravity measurements to retrieve the best fitting source parameters our findings confirmed the existence of different distinct sources beneath the brittle ductile transition zone which have been intermittently active during the last three decades moreover we interpreted our results in the light of existing seismic tomography studies concerning the sc dome we highlighted the role of hydrothermal fluids as the driving force behind the 1977 1983 uplift since 1983 1993 the deformation source transformed into a deeper one with a higher magmatic component furthermore our results support the magmatic nature of the deformation source beneath ml dome for the overall investigated period finally the uplift at ncr is interpreted as magma accumulation while its subsidence could either be the result of fluids migration outside the caldera or the gravitational adjustment of the source from a spherical to a sill like geometry

an assessment of the accuracy of the geodetic measurements that define the southern california uplift examination of the charge that the geodetic measurements which define the southern california uplift are seriously flawed by height dependent systematic errors indicates that this charge is unfounded our review of those factors designed to minimize the effects of rod error shows that systematic errors attributable to rod miscalibration are trivial and would tend to cancel during the particularly pertinent period 1955 1965 comparisons between the results of measurements in which the correlation between topography and signal is generally poor reveal large aseismic tilts in a number of places within and around the margins of the uplift especially significant in this context are the results of preuplift and postuplift levelings over routes characterized by diverse length topography and atmospheric conditions that produce closely matching temporally equivalent heights for a representative bench mark within the uplift statistical analyses of the short wavelength components of uplift signal and elevation along a frequently repeated survey line indicate variable correlations between the two however the spatial and temporal patterns of these correlations are inconsistent with their attribution to height dependent systematic errors statistically significant short wavelength correlations along this survey line are reasonably explained in part as due to real movement associated with differentially subsiding bench marks and there is a strong likelihood that this movement tends to dominate many of the correlations

mineralogical and isotopic evidence for the sediment provenance of the western south yellow sea since mis 3 and implications for paleoenvironmental evolution abstract changing sediment provenance and related paleoenvironmental evolution since marine isotope stages mis 3 have been investigated based on accelerator mass spectrometry ams 14c and optically stimulated luminescence osl dating of core csdp 01 recovered from the western south yellow sea sys based on our results sea level fluctuations and monsoonal climate variations are identified as the principal factors driving these changes sea level fluctuations determined the accommodation space in the shelf area while the monsoonal climate controlled the sediment supply capacity from river to sea mineral and sr nd isotopic records reveal the major contribution of the paleo changjiang river yangtze river to the study core area during the early mid mis 3 which likely defined the northern limit of the paleo changjiang delta at that time high sediment supply and limited accommodation space led to the development of sediment fed systems on the sys shelf resulting in a high preservation potential for thick stacking and overlapping deltaic sediments along with deltaic progradation core sediment provenance gradually transformed from the paleo changjiang river to the paleo huanghe river yellow river near the late mis 3 implying that the paleo huanghe river likely emptied into the sys and built a large delta during the mis 3 interval a strong summer monsoon during the early mis 1 interval was favorable for the changjiang to deliver abundant sediments to the study core area a weak summer monsoon during the mid late mis 1 when the coastline had retreated to nearly its present day position decreased the changjiang and huanghe supply to the study area low sediment supply and sufficient accommodation space gave rise to the development of sediment starved systems during this period nd values fluctuated between the changjiang and huanghe sources at that time suggesting that sea bed erosion materials are the main sediment contribution to the study area in general sedimentary evolution in the western sys since mis 3 is a good example of river sea interaction in the marginal seas of southeast asia in which sea level and monsoonal climate changes should play an important role

contemporary vertical surface displacements in yellowstone national park relative vertical displacements and average relative vertical velocities have been determined for bench marks located throughout yellowstone national park ynp by comparing geodetic leveling measurements made in 1923 second order 1936 third order 1941 third order 1955 third order 1960 first order and 1975 1977 first order the 1923 1975 data indicate uplift greater than 400 mm 7 7 mm yr of an area approximately 15 20 km wide and at least 40 km long which is centered along the northeast trending axis of the 600 000 year old yellowstone caldera the maximum 1923 1975 vertical displacement in this area is 726 mm 14 0 mm yr the existence of a well defined and untilted yellowstone lake terrace implies that the 1923 1975 average vertical velocities cannot have been maintained for more than a few hundred years the 1955 1977 data from central ynp indicate that the northeastern caldera half has risen relative to the southwestern half at an average velocity of about 8 mm yr a similar bias is present in the 1923 1975 data but it is less pronounced the 1923 1960 and 1960 1975 data from northwestern ynp and a 200 mm depression in the 1923 1975 data near norris junction may be interpreted in terms of deformation associated with the 1959 hebgen lake earthquake and the 1975 yellowstone park earthquake a composite profile of the 1936 1977 and 1941 1977 average vertical velocity data which skirts the edge of the yellowstone caldera in northeastern ynp is most easily explained as the result of random leveling error and or bench mark instabilities the apparent youth of the 1923 1975 yellowstone uplift and its close association with the yellowstone caldera suggest that the most likely cause of the uplift is a recent not more than 500 years ago influx of molten material into the upper crust beneath the caldera

results of repeated leveling surveys at newberry volcano oregon and near lassen peak volcano california personnel from the u s geological survey s cascades volcano observatory conducted first order class ii leveling surveys near lassen peak california in 1991 and at newberry volcano oregon in 1985 1986 and 1994 near lassen peak no significant vertical displacements had occurred along either of two traverses 33 and 44 km long since second order surveys in 1932 and 1934 at newberry however the 1994 survey suggests that the volcano s summit area had risen as much as 97 22 mm with respect to a third order survey in 1931 the 1931 and 1994 surveys measured a 37 km long east west traverse across the entire volcano the 1985 and 1986 surveys on the other hand measured only a 9 km long traverse across the summit caldera with only one benchmark in common with the 1931 survey comparison of the 1985 1986 and 1994 surveys revealed no significant differential displacements inside the caldera a possible mechanism for uplift during 1931 1994 is injection of approximately 0 06 km3 of magma at a depth of approximately 10 km beneath the volcano s summit the average magma supply rate of approximately 1 10 3 km3 year would be generally consistent with the volcano s growth rate averaged over its 600 000 year history 0 7 1 7 10 3 km3 year

the dry holocene megathermal in inner mongolia the paleoclimate since 14 kyr bp 14c age was reconstructed based on a 16 22 m long sediment core collected from lake yanhaizi a saline lake located near the northern limit of the east asian summer monsoon in inner mongolia coarse sediments were deposited there during a shrinkage phase of the lake when sand dunes reactivated these sediments have low organic carbon contents but high maturity indices indicating that they were deposited in an arid environment by contrast based on high organic contents and low maturity indices fine sediments were deposited during periods of high lake stand in a humid environment it was in general dry between 8 0 and 4 3 kyr bp the above dry and wet phases are consistent with those recovered from the arid semiarid transition zone elsewhere but are unlike the widely perceived humid holocene megathermal reported in east china and the newly reconstructed record in the alpine retreat lake in taiwan the discrepancy may be due to a relative insensitivity to humidity changes in these two areas since they have both been under the total influence of the summer monsoon on the other hand much enhanced evaporation over higher monsoon precipitation at lake yanhaizi reduces the effective humidity in the warm climate near the northern boundary of the summer monsoon this also accounts for the fact the high temperature holocene megathermal as revealed in the okinawa trough and the northern south china sea is correlated to the dry phases at lake yanhaizi conversely the 4 2 kyr bp coldest period in the holocene corresponds to a wet phase at lake yanhaizi

deformation near the casa diablo geothermal well field and related processes long valley caldera eastern california 1993 2000 abstract regional first order leveling lines which extend from lee vining ca to tom s place ca have been surveyed periodically since 1957 by the u s geological survey usgs the national geodetic survey ngs and caltrans two of the regional survey lines or leveling networks intersect at the casa diablo geothermal well field these leveling networks referenced to a distant bench mark c916 near lee vining provide time series vertical control data of land surface deformation that began around 1980 these data are also useful for delineating localized subsidence at casa diablo related to reservoir pressure and temperature changes owing to geothermal development that began in 1985 a comparison of differences in bench mark elevations for five time periods between 1983 and 1997 shows the development and expansion of a subsidence bowl at casa diablo the subsidence coincides spatially with the geothermal well field and temporally with the increased production rates and the deepening of injection wells in 1991 which resulted in an increase in the rate of pressure decline the subsidence superimposed on a broad area of uplift totaled about 310 mm by 1997 the usgs established orthogonal tilt arrays in 1983 to better monitor deformation across the caldera one tilt array dbr was established near what would later become the casa diablo geothermal well field this array responded to magmatic intrusions prior to geothermal development tilting away from the well field with the start of geothermal fluid extraction in 1985 tilt at the dbr array reversed direction and began tilting into the well field in 1991 geothermal power production was increased by a factor of four and reservoir pressures began a period of steep decline these changes caused a temporary three fold increase in the tilt rate the tilt rate became stable in 1993 and was about 40 lower than that measured in 1991 1992 but still greater than the rates measured during 1985 1990 data from the local leveling networks spanning the well field and the bounding graben were analyzed for several 2 year periods 1993 1995 1995 1997 and 1997 1999 annual rates of change across the normal faults bounding the graben have steadily decreased for each 2 year period between 1993 and 1999 reflecting the slowing decline in geothermal reservoir pressure horizontal control data from a two color electronic distance meter edm defined the lateral extent of subsidence at casa diablo the edm and leveling data elucidate the localized effect of the shallow source of subsidence and the broader effect of the deeper magmatic inflation source data from bench marks common to both the vertical and the horizontal control networks were used to assess the effect of subsidence on the edm base station casa modeling of geodetic data collected during periods of little or no magmatic inflation indicated that the casa two color edm station is being drawn toward the well field at a rate of 3 5 mm yr

geodynamics of the yellowstone hotspot and mantle plume seismic and gps imaging kinematics and mantle flow abstract integration of geophysical and geological data show that the yellowstone hotspot resulted from a mantle plume interacting with the overriding north america plate a process that has highly modified continental lithosphere by magmatic and tectonic processes and produced the 16 17 ma 700 km long yellowstone snake river plain ysrp silicic volcanic system accessibility of the ysrp allowed large scale geophysical projects to seismically image the hotspot and evaluate its kinematic properties using geodetic measurements seismic tomography reveals a crustal magma reservoir of 8 to 15 melt 6 km to 16 km deep beneath the yellowstone caldera an upper mantle low p wave velocity body extends vertically from 80 km to 250 km beneath yellowstone but the anomalous body tilts 60 wnw and extends to 660 km depth into the mantle transition zone we interpret this conduit shaped low velocity body as a plume of up to 3 5 vp and 5 5 vs perturbation that corresponds to a 1 2 partial melt models of whole mantle convection reveal eastward upper mantle flow beneath yellowstone at relatively high rates of 5 cm yr that deflects the ascending plume into its west tilted geometry a geodynamic model of the yellowstone plume constrained by vp and vs velocities and attenuation parameters suggests low excess temperatures of up to 120 k corresponding to a maximum 2 5 melt and a small buoyancy flux of 0 25 mg s i e properties of a cool weak plume the buoyancy flux is many times smaller than for oceanic plumes nonetheless plume buoyancy has produced a 400 km wide 500 m high topographic swell centered on the yellowstone plateau contemporary deformation derived from gps measurements reveals sw extension of 2 3 mm yr across the yellowstone plateau one fourth of the total basin range opening rate which we consider to be part of basin range intraplate extension locally decadal episodes of subsidence and uplift averaging 2 cm yr characterize the 80 year yellowstone caldera monitored history and are modeled as hydrothermal magmatic sources moreover a recent episode 2004 2009 of accelerated uplift of the yellowstone caldera at rates up to 7 cm yr has been modeled as resulting from magmatic recharge of a 10 km deep sill at the top of the crustal magma reservoir regionally gravitational potential energy of the yellowstone swell drives the lithosphere southwest and downhill from the yellowstone plateau 400 km where it coalesces with basin range province wide westward extension based on the geometry and its assumed 660 km depth we extrapolate the plume source southwest to its original location at 17 ma and 600 km southwest and 200 km north of the ysrp importantly this location is beneath the southern part of the columbia plateau flood basalt field of the same age and implies that the yellowstone mantle plume may be the common source for both of these large volcanic fields our time progression model suggests that the original plume head rose vertically behind the juan de fuca plate but at 12 ma it lost the protection of the subducting plate from eastward mantle flow and encountered cooler thicker continental lithosphere becoming entrained in eastward upper mantle flow these results reveal that yellowstone plume plate processes have had a profound effect on late cenozoic geologic evolution and topography of a large part of the western u s

the effect of collapse structures on ground deformations in calderas ground deformations related to unrest episodes in calderas are generally interpreted like in other volcanic environments in terms of increased pressure within a magma chamber embedded in a continuous elastic medium in this framework the depth of the pressure source is inferred from the size of the deformed area this scheme works quite well for individual volcanoes for instance hawaiian shields where a good correspondence between inflation events and eruptive episodes has been observed ground deformation in calderas however show unusual features that are difficult to interpret within such a scheme because considerable positive deformation in the order of several meters and microfracturing i e intense seismicity may occur without eruptions altough the estimated depth for the magma source is sometime very shallow less than 1 2 km it has been recently suggested that the contact zones at the border of collapsed calderas could act as stress strain discontinuity zones and thus bias modeling results obtained for continuous elastic media we use both observations and theoretical modeling based on 3 d finite element techniques to show that ground deformations in collapsed calderas are strongly influenced by the caldera structure giving a new perspective in related geological and geophysical observations in such areas

water characteristics and movements of the yellow sea warm current in summer water characteristics of the yellow sea warm current and its movement in summer are examined from the analysis of the recent hydrographic data collected in adjacent seas of cheju island it is suggested that the yellow sea warm current water in the northeastern china sea is a mixture of western north pacific central water and the yellow sea bottom cold water in the ratio of 7 to 3 it is characterized by salinities of 34 2 s 34 5 and temperatures of 13 t 15 c at depths below 50 m the yellow sea warm current does not seem to extend into the yellow sea as previously believed at least in summer but instead it turns eastward around cheju

vertical surface displacements at yellowstone caldera wyoming 1976 1986 between first order leveling surveys in 1976 and 1986 the east central floor of yellowstone caldera rose 15 4 1 4 mm yr and the west central floor rose 17 0 2 0 mm yr with respect to points on the south caldera rim the same pattern has prevailed since an initial survey in 1923 except that the western caldera rose 30 faster during 1976 1986 than during 1923 1976 the 1976 1986 uplift extends beyond the northwest caldera rim near the adjacent hebgen lake fault zone site of a magnitude 7 3 earthquake in august 1959 marginally significant displacements in the eastern caldera suggest that uplift continued during 1983 1984 stopped during 1984 1985 and reversed to subsidence during 1985 1986 thus long term uplift may accumulate episodically historical uplift is especially noteworthy because regional crustal extension and thermal contraction during cooling would cause the caldera floor to subside if other processes were not acting to warp it upward the pattern and dimensions of the uplift indicate a source in the upper crust beneath yellowstone caldera probably a reservoir of rhyolite magma within a cooling granitic pluton a simple point source model would suggest a source 10 15 km deep but the reservoir is probably lens shaped and closer to the surface uplift may be caused by basaltic intrusions near the base of the reservoir or accumulation of magmatic fluids during cooling and crystallization within the reservoir subsidence might be a response to regional tectonic extension or release of trapped magmatic fluids magmatic inflation volatile accumulation and crustal extension may culminate eventually in renewed eruptive activity but there is no evidence of an imminent volcanic hazard

recent uplift of the alban hills volcano italy evidence for magmatic inflation first order leveling surveyed in 1951 and 1994 along a line across the alban hills volcano reveals maximum vertical uplift of 30 cm average of 7 mm yr in the region of geologically recent 0 020 0 030 ma explosive activity the uplifted region corresponds to an area where seismic activity is concentrated at depths of 3 6 km uplift exceeding 10 cm is observed over a 14 km wide zone in the center of a 40 km long line with the deformation tapering to zero at both ends of the line data from a few sparse older benchmarks measured in 1891 and 1927 suggest that the deformation in the first half of this century was very small compared to the period 1951 1994 the observed uplift together with increased seismic activity suggest that recent magma injection has occurred in the upper crust beneath the alban hills volcano

sediment accumulation in a modern epicontinental shelf setting the yellow sea sediment accumulation in the yellow sea epicontinental shelf environment is investigated on 100 yr and 1000 yr time scales using 210pb and 14c geochronologies the distribution of modern 210pb accumulation rates in the yellow sea reveals that the loci of modern huanghe sediment accumulation are the topset 1 2 mm yr foreset 4 9 mm yr and proximal bottomset deposits 2 4 mm yr of the shandong subaqueous delta which extends south from the shandong peninsula 210pb rates in the distal bottomset deposits of the subaqueous delta in the central and southern yellow sea are generally low 0 3 0 9 mm yr a sediment budget demonstrates that between 9 15 of the annual huanghe discharge is accumulating in the yellow sea about two thirds of this sediment is accumulating in the topset foreset and proximal bottomset deposits of the shandong subaqueous delta with the remaining third accumulating as widespread distal bottomset deposits 14c age dates of subaqueous delta sediments indicate that the thick 40m clinoform structure formed predominantly between 6200 and 4060 yrs b p at rates approaching 20 mm yr observations in the yellow sea as well as on the amazon and ganges brahmaputra shelves demonstrate that subaqueous deltaic stratigraphy is the general rule where major rivers enter energetic shelves whether epicontinental or pericontinental the development of extensive bottomset deposits may be restricted to epicontinental shelf environments and may be diagnostic of sedimentation in this type of setting

a unique yellow river derived distal subaqueous delta in the yellow sea abstract newly acquired high resolution chirp sonar profiles reveal a unique yellow river derived alongshore distributed bidirectional landward and seaward across shelf transported omega shaped distal subaqueous deltaic lobe deposited around the eastern tip of the shandong peninsula in the yellow sea this clinoform deposit directly overlies the postglacial transgressive surface featured by convex up seafloor morphology up to 40 m thick locally radiocarbon 14 dates from the underlain pre holocene and transgressive sediments indicate this distal lobe has formed since the middle holocene highstand under a relatively stable sea level this along shelf distributed distal clinoform has been deposited mainly by the resuspended yellow river sediments carried down by the coastal current interacting with the local waves tides and upwelling collectively over the past 7000 years nearly 30 of the yellow river derived sediment has been re suspended and transported out of the bohai sea into the yellow sea overall the yellow river derived sediment could reach the 80 m water depth in the central south yellow sea about 700 km from the river mouth in contrast a very small fraction of the modern riverine sediment could escape the outer shelf or reach the okinawa trough

models of lithosphere and asthenosphere anisotropic structure of the yellowstone hot spot from shear wave splitting 1 teleseismic shear wave splitting measured at 56 continuous and temporary seismographs deployed in a 500 km by 600 km area around the yellowstone hot spot indicates that fast anisotropy in the mantle is parallel to the direction of plate motion under most of the array the average split time from all stations of 0 9 s is typical of continental stations there is little evidence for plume induced radial strain suggesting that any contribution of gravitationally spreading plume material is undetectably small with respect to the plate motion velocity two stations within yellowstone have splitting measurements indicating the apparent fast anisotropy direction is nearly perpendicular to plate motion these stations are 30 km from stations with parallel to plate motion the 70 rotation over 30 km suggests a shallow source of anisotropy however split times for these stations are more than 2 s we suggest melt filled stress oriented cracks in the lithosphere are responsible for the anomalous orientations within yellowstone stations southeast of yellowstone have measurements of oriented nnw to wnw at high angles to the plate motion direction the archean lithosphere beneath these stations may have significant anisotropy capable of producing the observed splitting

development of depositional systems in the southeastern yellow sea during the postglacial transgression this study focuses on the development of depositional systems in the southeastern yellow sea during the postglacial transgression based on the analysis of closely spaced high resolution seismic profiles chirp and piston cores transgressive deposits comprise the paralic component of estuarine channel fills seaward prograding wedge and along shore prograding mound and the marine component of sand veneer mud blanket and offshore ridge these transgressive deposits were developed through three distinctive stages in terms of possible sea level position during the early stage tidal sand ridges and sand veneer formed south of jeju island resulting from shoreface erosion associated with a relatively slow transgression the following transgression in the middle stage inundated subaerially formed interfluves along the central part of the sea and affected development of estuarine environments with increasing tidal regime in the eastern part of the sea combined with the strong tidal reworking insufficient sand supply enhanced the formation of erosional ridges short period increase in fluvial discharge affected the deposition of coastal wedge in the western part fine grained sediments from either fluvial discharge or tidal reworking were dispersed seaward to form mud blanket the late stage was characterized by the deposition of veneered sands off the jiangsu coast which was due to relatively slow rise in sea level further offshore along shore prograding mound was constructed by huanghe derived sediment influx and subsequently eroded and redeposited by wave and tide activities thus detached from the proximal source the depositional processes and variability of the transgressive deposits in the southeastern yellow sea were largely controlled by changes in rate of sea level rise during the transgression most likely related to the global flooding events triggered by melt water pulses the changes in shoreline configuration and oceanographic regime have also influenced the distribution and morphology of the transgressive deposits a short period increase in riverine discharge caused the temporal sediment progradation off the jiangsu coast

evaluation of the evolving stress field of the yellowstone volcanic plateau 1988 to 2010 from earthquake first motion inversions abstract although the last rhyolite eruption occurred around 70 ka ago the silicic yellowstone volcanic field is still considered active due to high hydrothermal and seismic activity and possible recent magma intrusions geodetic measurements document complex deformation patterns in crustal strain and seismic activity likewise reveal spatial and temporal variations in the stress field we use earthquake data recorded between 1988 and 2010 to investigate these variations and their possible causes in more detail earthquake relocations and a set of 369 well constrained double couple focal mechanism solutions were computed events were grouped according to location and time to investigate trends in faulting the majority of the events have normal faulting solutions subordinate strike slip kinematics and very rarely reverse motions the dominant direction of extension throughout the 0 64 ma yellowstone caldera is nearly ene consistent with the perpendicular direction of alignments of volcanic vents within the caldera but our study also reveals spatial and temporal variations stress field solutions for different areas and time periods were calculated from earthquake focal mechanism inversion a well resolved rotation of 3 was found from nne ssw near the hebgen lake fault zone to ene wsw near norris junction in particular the 3 direction changed throughout the years around norris geyser basin from being ene wsw as calculated in the study by waite and smith 2004 to nne ssw while the other 3 directions are mostly unchanged over time the presence of chocolate tablet structures with two sets of nearly perpendicular normal faults was identified in many stages of the deformation history both in the norris geyser basin area and inside the caldera

volcano hydrothermal activity detected by precise levelling surveys at the tatun volcano group in northern taiwan during 2006 2013 abstract precise levelling surveys were conducted from 2006 to 2013 on three levelling routes in the tatun volcano group tvg located approximately 15 km northeast of taipei to detect deformation in relation to the volcano hydrothermal activities of the tvg uplift was detected around the most active fumarole tayoukeng fumarole throughout the period 2007 to 2011 the uplift rate throughout the period from march 2009 to march 2011 was reduced in comparison to the rate between 2007 and 2009 following this a dormant state or a small amount of subsidence was detected in the period march 2011 to march 2013 and throughout the period from june 2006 to march 2013 subsidence was centred on an area 0 5 km east of the summit of mt cising the highest peak in the tvg a model of two spherical sources was therefore estimated from the deformation recorded from august 2007 to march 2011 using a genetic algorithm a deflation source was obtained about 0 5 km northeast of mt cising at a depth of 2 km and an inflation source was situated approximately 1 km south of the tayoukeng fumarole at a depth of 0 7 km based on previous seismic and amt studies the estimated sources are interpreted as being hydrothermal reservoirs because almost all the benchmarks around mt cising show subsidence at a constant speed we conclude that the deeper hydrothermal reservoir at a depth of 2 km may have been releasing hydrothermal fluid at a constant rate throughout the period from 2006 to 2013 however it was suggested that in 2011 the shallower hydrothermal reservoir at a depth of 0 7 km changed from an inflation state to a dormant state or small deflation based on temporal vertical changes around tayoukeng fumarole a possible model for the volcano hydrothermal system is therefore proposed it is considered that the hydrothermal fluid may be supplied intermittently from the magma chamber to the deeper hydrothermal reservoir at a depth of 2 km although this type of fluid input event may not have occurred during our research period and that the hydrothermal fluid upwelling between mt cising and tayoukeng fumarole flows transversally into a highly cracked and fluid saturated area that continues to tayoukeng fumarole the existence of a shallower hydrothermal reservoir at a depth of 0 7 km in the highly cracked and fluid saturated area is therefore plausible

the 1978 yellowstone eastern snake river plain seismic profiling experiment crustal structure of the yellowstone region and experiment design in 1978 a major seismic profiling experiment was conducted in the yellowstone eastern snake river plain region of idaho and wyoming fifteen shots were recorded that provided coverage to distances of 300 km in this paper travel time and synthetic seismogram modeling was used to evaluate an average p wave velocity and apparent q structure of the crust from two seismic profiles reversed across the yellowstone national park region this area includes the well known hydrothermal features of yellowstone national park geysers fumeroles etc a large collapse caldera and extensive silicic volcanism of quaternary age features attributed to shallow crustal sources of magma the averaged crustal structure for this region as interpreted from the seismic data consists of 1 a highly variable near surface layer approximately 2 km thick with variable velocities of 3 0 to 4 8 km s and a low apparent q of 30 that is interpreted to be composed of weathered rhyolites and sedimentary infill 2 an upper crustal layer 3 to 4 km thick with variable velocities of 4 9 to 5 5 km s and apparent q of 50 to 200 that is thought to represent the accumulation of the pleistocene quaternary rhyolite flows ash flow tuffs and possible paleozoic and precambrian metamorphic equivalents 3 the crystalline upper crust that is characterized by a laterally inhomogeneous layer that varies in velocity from 4 0 to 6 1 km s averaging 5 km thick with a q of 300 this layer appears to be a cooling but still hot body of granitic composition beneath the yellowstone caldera it is thought to be a remnant of the magma chambers that produced the quaternary silicic volcanic rocks of the yellowstone plateau and may still be a major contributor to the high heat flow 4 a laterally homogeneous intermediate crustal layer 8 to 10 km thick with a velocity of 6 5 km s and apparent q of 100 to 300 5 a homogeneous 25 km thick lower crust with a velocity of 6 7 to 6 8 km s and an apparent q of 300 and 6 a total crustal thickness of 43 km the upper crustal layer 5 5 to 6 0 km s is thought to be the thermally altered equivalent of the continental crystalline basement that is normally 15 to 20 km thick in the surrounding thermally undisturbed archean crust an interpretation from these results suggests that mafic melts from the mantle have penetrated the lower crust without significant variations in the velocity structure but produce the main source of heat that drives the volcanic and hydrothermal systems of yellowstone the high apparent attenuation and large lateral velocity variations in the upper crust are consistent with a model in which partial fractionation partial melting and metamorphism differentiate the original upper crust to produce silicic melts that were extruded as rhyolites and ash flow tuffs across the yellowstone plateau this seismic model is consistent with the evidence for a systematic northeastward propogation of silicic volcanic centers along the eastern snake river plain to their present location beneath the yellowstone hydrothermal system while these findings do not bear directly on the origin and source of the heat i e mantle lumes lithospheric fractures mantle radiogenetic heat basal lithospheric shearing etc they provide a constraint on the configuration and lateral extent of crustal layers that reflect thermal and compositional boundaries

oxygen and carbon isotope study of the holocene oyster reefs and paleoenvironmental reconstruction on the northwest coast of bohai bay china abstract the northwest coast of bohai bay supports large areas of holocene crassostrea gigas oyster reefs their huge size and the fact that the shells are composed of consecutive microgrowth layers consisting of primary calcite make them an ideal object for a stable isotope study the 18o and 13c compositions of the oysters reveal a number of interesting features the most important are annual cycles related to seasonal variations the regional 18o water versus salinity ratio and a stop in shell secretion below a water temperature of 11 5 1 5 c a positive correlation covariance between 18o and 13c values is present in most specimens the 18o and 13c values of single specimens are believed to be mainly controlled by water temperature and the occurrence of phytoplankton blooms and decomposition however correlation among oysters of different ages indicate that the 18o and 13c values are mainly dependant of three variables water temperature salinity and phytoplankton blooms decomposition between ca 6500 yrs cal b p and 2300 yrs cal b p the salinity in bohai bay increased from less than 20 to 30 based on geological data combined with ecological data from c gigas we suggest that precipitation decreased during this period while the input of fluvial sediments increased the sediment load of rivers increased markedly after ca 4000 yrs cal b p possibly due to a change in climate in our study area this resulted in the development of the oyster plain

numerical modelling of caldera dynamical behaviour summary the study of the mechanics of caldera formation can yield valuable insight into the behaviour of near surface magma chambers and their mechanical interaction with the crust we have addressed the problem of physical processes responsible of long term ground deformation from the emplacement of magma in the crust to a final resurgent stage a mechanical model based on a thermally coupled elastovisco plastic rheology and a finite deformation formulation has been used and solved via a finite element approximation the history of an ideal caldera is modelled in the following two stages 1 a doming phase corresponding to the growth of the magma chamber this stage is constrained by values of amplitude half width and time constant of regional doming and by a range of realistic over pressures this uplift is linked to the plastic strain field within the crust which strongly depends upon the pressure and temperature fields 1 a resurgence phase which results from a collapse stage with an instantaneous change in shape of the topography the magma chamber is passive and this stage is basically similar to a crater relaxation process the rebound amplitude and half width are controlled by the length scale of the collapse a gravitational rebound is a very likely mechanism explaining large caldera uplift without over pressure mechanisms for most intracrustal loading processes the crustal deformation is critically influenced by the relative importance of the upper crustal rheology pressure dependent plasticity versus the lower crustal rheology temperature dependent viscosity because the upper part of the crust can deform without time dependent dissipation it may be responsible for large uplift variations that can occur for moderate loading variations by contrast the creep of the middle crust acts as a regulating medium

evolution of the yellow sea warm current and the yellow sea cold water mass since the middle pleistocene abstract the yellow sea warm current yswc and the yellow sea cold water mass yscwm are the most significant hydrological characteristics of the yellow sea as they strongly influence the matter transportation sedimentation and the benthic and pelagic environments of the region previous studies focused mostly on formation and evolution of the yswc and the yscwm on shorter time scales e g since the holocene and studies on longer time scales are rather sparse this study conducted a high resolution magnetostratigraphic investigation on core dlc70 3 with a water depth of 71 2 m in the northern part of the south yellow sea results show that the brunhes matuyama polarity reversal boundary is located at a depth of 59 08 m constrained by both magnetostratigraphy and 14c dating three sedimentation episodes revealed by the benthic foraminifera content correspond to high sea level periods of marine isotope stage mis 5 mis9 mis11 mis17 and mis19 mis21 respectively cold water benthic foraminifera species total organic carbon total sulfur molybdenum element and long chain unsaturated alkenones index of the studied sediments show that both the yswc and the yscwm have evolved since the middle pleistocene mainly due to combined effects of fluctuations of sea level and local tectonic subsidence more specifically both the yswc and the yscwm were intensified during high sea level periods of mis5e mis9 mis19 and mis21 in addition occurrence of the yswc and the yscwm are not always coeval as in the mis5a 5d period which is characterized by relatively stronger yscwm but absence of the yswc these studies significantly improve our understanding of the evolution mechanism of both the yswc and the yscwm in this region

anomalous shear wave delays and surface wave velocities at yellowstone caldera wyoming to investigate the effects of a geothermal area on the propagation of intermediate period 1 30 s teleseismic body waves and surface waves a specially designed portable seismograph system was operated in yellowstone caldera wyoming travel time residuals relative to a station outside the caldera of up to 2 s for compressional phases are in agreement with short period residuals for p phases measured by other investigators travel time delays for shear arrivals in the intermediate period band range from 2 to 9 s and decrease with increasing dt d delta measured rayleigh wave phase velocities are extremely low ranging from 3 2 km s at 27 s period to 2 0 km s at 7 s period the estimated uncertainty associated with these values is 15 we propose a model for compressional and shear velocities and poisson s ratio beneath the yellowstone caldera which fits the teleseismic body and surface wave data it consists of a highly anomalous crust with an average shear velocity of 3 0 km s overlying an upper mantle with average velocity of 4 1 km s the high average value of poisson s ratio in the crust 0 34 suggests the presence of fluids there poisson s ratio in the mantle between 40 and approximately 200 km is more nearly normal 0 29 than inmore the crust a discrepancy between normal values of poisson s ratio in the crust calculated from short period data and high values calculated from teleseismic data can be resolved by postulating a viscoelastic crustal model with frequency dependent shear velocity and attenuation less

the possible contribution of circumferential fault intrusion to caldera resurgence in the geological record the intrusion of substantial amounts of magma into circumferential faults and ring fractures is commonly observed finite element modelling is used here to investigate the strain field that may be expected from such intrusive events two simple vertical scenarios are explored one for a caldera with a central block of thickness to diameter ratio of 1 1 similar to rabaul and one with a ratio much less than 1 1 similar to the valles type surface deformation in both cases is similar with central uplift the development of a moat or trough like feature just outside of the intersection of the azimuth of the intruded ring fault and the free surface and broader scale tumescence at a scale several times larger than the caldera s radius the response of the block and sub caldera magma chamber for the two scenarios however is different the blocks are in effect squeezed the high aspect ratio one deforms upwards at the surface and downwards at its base whereas the low aspect ration one experiences up arching or bending of the central part of the caldera block central uplift still occurs when only a short arc of a ring fracture system or a circumferential fault is intruded in both models tumescence in the centre of the caldera from single ring dyke intrusion can only account for decimetres to metres of surface uplift repeated intrusions over tens to hundreds of thousands of years however may cause incremental up doming of the caldera block leading to larger scale resurgent features the amount of uplift possible due to squeezing of a high aspect ratio block is limited it is proposed however that where bending of plate like blocks occur above a decompressible and or malleable magma body ring fault intrusion may be a significant contributor to resurgence in the simple conceptual models shown here the amount of ring dyke induced central uplift will be 40 50 of the width of the ring complex in the geological record the accumulation of intrusions into some ring fractures has led to annular or arcuate plutons of hundreds of meters to several kilometres in thickness at certain calderas such intrusions may be a control on the marked concentration of uplift within the restricted area defined by the caldera faults the complex nature of the horizontal displacements associated with the intrusion of ring and arcuate dykes is also explored intrusion into ring fracture zones will tend to take place into those sectors of the annular zone which are perpendicular to the least compressive stress vector this may be a factor in the observed difference for caldera evolution in extensional and compressional areas the unrest at several modern calderas is tentatively related to circumferential fault intrusion

holocene paleoenvironmental changes in mud area southwest off cheju island east china sea evidence from benthic foraminiferal assemblages and stable isotope records abstract a sediment core retrieved from the mud area southwest off cheju island masci was analysed for benthic foraminifera grain size and stable isotopes and constrained by ams14c dating holocene paleoenvironmental changes in this broad shallow shelf were investigated with special focus on the evolution of the masci and its related ocean eddy system the results indicate that the east china sea shelf has undergone four major environmental evolution stages during the holocene prior to 9 8 cal kyr bp the benthic foraminiferal assemblages were dominated by low salinity shallow water species ammonia beccarii linnaeus elphidium advenum cushman and cribrononion subincertum asano reflecting a near coast deposit environment a noticeable transition of the benthic foraminifera from an a beccarii dominated to ammonia compressiuscula brady dominated assemblage taking place at approximately 9 8 cal kyr bp together with a contemporaneous increase in 18o and 13c provides evidence that a rapid rise in sea level occurred at this time in the east china shelf a gradual increase in 18o between 9 8 and 6 cal kyr bp indicates a steady strengthening influence of open ocean water on the area under study a sudden increase in the abundance of benthic foraminifera along with a decrease in the coarse fraction imply that an early eddy circulation system was established since almost 6 cal kyr bp in the masci this eddy circulation system was quite weak but gradually strengthened between 6 and 3 cal kyr bp possibly due to the intrusion of the yellow sea warm current yswc a more stable mud deposition period characterised by a high sedimentation rate of fine grained sediment and lighter value of 13c starting at approximately 3 cal kyr bp indicates that the masci was formed mainly during the late holocene we believe that the strengthened yswc since 3 cal kyr bp might increase the trap efficiency of the eddy system thereby accounting for the high sedimentation rate of mud deposits during this period

hydrothermal changes related to earthquake activity at mud volcano yellowstone national park wyoming the mud volcano hydrothermal area in yellowstone national park is near the intersection of a 20 km long zone of northeast trending normal faults with the eastern resurgent dome within the 600 000 year old yellowstone caldera recent crustal uplift along the northeast trending axis of the caldera is at a maximum 700 mm since 1923 near the mud volcano area from 1973 through april 1978 less than 10 earthquakes largest m 2 4 were located within 3 km of the mud volcano area in may 1978 earthquakes began occurring beneath the hydrothermal area at depths of 1 to 5 km the seismic activity continued until the end of november with intense swarms 100 events per hour occurring on october 23 and november 7 the largest event m 3 1 occurred on november 14 and at least 8 events were m 2 5 or larger in december 1978 heat flux in the mud volcano hydrothermal features began increasing along a 2 km long northeast trending zone existing mud cauldrons became more active new mud cauldrons and fumeroles were formed and vegetation primarily lodgepole pine was killed by increased soil temperature the increase in heat flux continued through july 1979 then gradually declined reaching the early 1978 level by june 1980 the spatial and temporal association of earthquakes and increased hydrothermal activity at mud volcano suggests that the seismic activity expanded preexisting fracture systems premitting increased fluid flow from depths of several kilometers

high resolution aeromagnetic mapping of volcanic terrain yellowstone national park high resolution aeromagnetic data acquired over yellowstone national park ynp show contrasting patterns reflecting differences in rock composition types and degree of alteration and crustal structures that mirror the variable geology of the yellowstone plateau the older eocene absaroka volcanic supergroup a series of mostly altered andesitic volcanic and volcaniclastic rocks partially exposed in mountains on the eastern margin of ynp produces high amplitude positive magnetic anomalies strongly contrasting with the less magnetic younger latest cenozoic yellowstone plateau group primarily a series of fresh and variably altered rhyolitic rocks covering most of ynp the yellowstone caldera is the centerpiece of the yellowstone plateau part of its boundary can be identified on the aeromagnetic map as a series of discontinuous negative magnetic anomalies that reflect faults or zones along which extensive hydrothermal alteration is localized the large volume rhyolitic ignimbrite deposits of the 0 63 ma lava creek tuff and the 2 1 ma huckleberry ridge tuff which are prominent lithologies peripheral to the yellowstone caldera produce insignificant magnetic signatures a zone of moderate amplitude positive anomalies coincides with the mapped extent of several post caldera rhyolitic lavas linear magnetic anomalies reflect the rectilinear fault systems characteristic of resurgent domes in the center of the caldera peripheral to the caldera the high resolution aeromagnetic map clearly delineates flow unit boundaries of pre and post caldera basalt flows which occur stratigraphically below the post caldera rhyolitic lavas and are not exposed extensively at the surface all of the hot spring and geyser basins such as norris upper and lower geyser basins west thumb and gibbon are associated with negative magnetic anomalies reflecting hydrothermal alteration that has destroyed the magnetic susceptibility of minerals in the volcanic rocks within yellowstone lake which is mostly within the yellowstone caldera aeromagnetic lows also are associated with known hydrothermal activity in the lake many of the magnetic lows extend beyond the areas of alteration and hot springs suggesting a more extensive currently active or fossil hydrothermal system than is currently mapped steep magnetic gradients suggesting faults or fractures bound the magnetic lows this implies that fractures localize the hot springs magnetic gradient trends reflect the mapped basin and range structural trends of north and northwest as well as northeasterly trends that parallel the regional trend of the snake river plain and the track of the yellowstone hot spot which follow the precambrian structural grain these trends are found both at small scales such as in hydrothermal basins and at more regional fault scales which suggests that the regional stress field and reactivated

summertime hydrographic features in the southeastern hwanghae abstract ctd casts in the southeastern hwanghae yellow sea were made in august 1983 and 1984 to describe the spatial structure of the summertime hydrographic features cold coastal water appeared around the southwestern coast of korea which was formed by strong tidal stirring tidal mixing in the study area seems to have been enhanced by the presence of many small islands in the deeper region beyond the tidal front stratification became much stronger and the bottom layer below seasonal thermocline was occupied mostly by the hwanghae cold water characterized by a temperature lower than 10 c and salinity of 32 5 33 0 the northeastward extension of the changjiang diluted water was shown by a tongue like plume of relatively warm fresh water confined to the thin surface layer 10 m thick there was no evidence for the hwanghae warm current carrying high salinity water into the eastern hwanghae along the korean coast the warm current was found to flow in a narrow band close to the west and north coast of chejudo cheju island and then to pass eastward through the cheju strait thus the eastern part of the cyclonic circulation in the surface layer cannot be considered to be a northward continuation of the hwanghae warm current the local salinity maximum in the lower layer off kunsan and the higher salinity on the west side of the central trough than on the east side would imply a northward flow on the west flank of the trough to compensate for the southward intrusion of the hwanghae cold water from which an anticyclonic circulation could be expected in the lower layer

the parkfield california earthquake prediction experiment five moderate magnitude 6 earthquakes with similar features have occurred on the parkfield section of the san andreas fault in central california since 1857 the next moderate parkfield earthquake is expected to occur before 1993 the parkfield prediction experiment is designed to monitor the details of the final stages of the earthquake preparation process observations and reports of seismicity and aseismic slip associated with the last moderate parkfield earthquake in 1966 constitute much of the basis of the design of the experiment

crustal deformation of the yellowstone caldera from first gps measurements 1987 1989 a global positioning system gps network was established in 1987 in order to measure crustal deformation across the yellowstone plateau centered on the yellowstone caldera and adjacent teton wyoming and hebgen lake montana fault zones forty four gps stations in the yellow stone network were re surveyed in 1989 and station coordinates using broadcast orbits were obtained these results were used to assess the precision and accuracy of the gps surveys and to identify areas of rapid crustal deformation on the yellowstone plateau the gps measured displacements between 1987 and 1989 were calculated relative to a station at the eastern edge of the 100 km wide network the relative horizontal displacements have an average magnitude of 15 10 mm the relative vertical displacements are generally less than 25 mm about an average near zero and with an uncertainty of 20 mm comparisons with leveling and trilateration measurements taken nearly simultaneously suggest that the accuracy of these gps measurements is at the level of the above uncertainties gps measured vertical displacements across the northern part of the yellowstone caldera and 1st order leveling results show up to 20 mm of subsidence between 1987 and 1989 this subsidence is part of a six year period of caldera deflation that began in 1985 in addition up to 66 mm of uplift is observed with gps at the northwest edge of the yellowstone caldera and may be associated with processes following an intense earthquake swarm in 1985 86 and with caldera subsidence

sediment trapping in deltas of small mountainous rivers of southwestern taiwan and its influence on east china sea sedimentation abstract taiwan s setting of high mountains steep gradients frequent earthquakes erodible lithology and heavy rainfall represents an ideal site to focus on sedimentary processes of the deltas of small mountainous rivers smrs several smrs in southwestern taiwan have deposited a thick sedimentary succession in the composite southwest taiwan delta swtd since the middle holocene evidence from the swtd can help to determine its trapping efficiency and assess the role of smrs in sediment transport to the sea we used historical nautical charts bathymetric data satellite radar data and 14c dates to calculate the sediment volume of the swtd on millennial and decadal scales the 14c dates of core samples indicate deposition of thick deltaic sediment in subsiding areas since the time of the maximum flooding surface about 7 cal ka bp the paleo shoreline changes of the swtd suggest a steady westward progradation since 7 cal ka bp in contrast the nautical charts suggest minor volume reduction of the offshore part of the swtd with a deepening trend and retreating shorelines during the last seven decades the results show that at least 201 72 13 90 km3 3 23 105 mt of sediment has been trapped in the swtd since 7 cal ka bp and that the delta has shifted to a destructive phase during the past seven decades as human influences such as construction of reservoirs dams and weirs in the hills have reduced the sediment supply the birth of the taiwan warm current and following continuous sediment supply from the western rivers of taiwan to the east china sea since 7 3 cal ka bp have played a crucial role in the sedimentation of the east china sea particularly in the okinawa trough and the japan sea through the tsushima warm current