an orthopyroxene biotite geothermometer and its application in crustal granulites and mantle derived rocks using the experimental data on fe mg exchange between orthopyroxene and biotite of fonarev konilov 1986 an orthopyroxene biotite geothermometer is developed the thermometer is corrected for mixing of ti and al in octahedral sites in biotite and also for non ideal mixing of fe and mg in orthopyroxene the thermometer is applied to several amphibolite granulite transition facies and granulite facies rocks and also to mantle xenoliths it yields consistent results in rocks of widely varying bulk composition and highly magnesian mantle xenoliths this thermometer removes the difficulty of estimating temperature in garnet free rocks in high grade terrains and also provides independent estimates of temperature in garnet bearing assemblages

gis based landslide susceptibility mapping using bivariate statistical analysis in devrek zonguldak turkey devrek town with increasing population is located in a hillslope area where some landslides exist therefore landslide susceptibility map of the area is required the purpose of this study was to generate a landslide susceptibility map using a bivariate statistical index and evaluate and compare the results of the statistical analysis conducted with three different approaches in seed cell concept resulting in different data sets in geographical information systems gis based landslide susceptibility mapping applied to the devrek region the data sets are created from the seed cells of a crowns and flanks b only crowns and c only flanks of the landslides by using ten different causative parameters of the study area to increase the data dependency of the analysis all parameter maps are classified into equal frequency classes based directly on the percentile divisions of each corresponding seed cell data set the resultant maps of the landslide susceptibility analysis indicate that all data sets produce fairly acceptable results in each data set analysis elevation lithology slope aspect and drainage density parameters are found to be the most contributing factors in landslide occurrences the results of the three data sets are compared using seed cell area indexes scai this comparison shows that the crown data set produces the most accurate and successful landslide susceptibility map of the study area

metamorphic p t paths and zircon u pb ages of archean ultra high temperature paragneisses from the qian an gneiss dome east hebei terrane north china craton

swarm satellite and eiscat radar observations of a plasma flow channel in the auroral oval near magnetic midnight we present swarm satellite and eiscat radar observations of electrodynamical parameters in the midnight sector at high latitudes the most striking feature is a plasma flow channel located equatorw

statistical models for slope instability classification abstract statistical models for reliable hazard assessment of landslides in a given area are presented the models are based on information theory and regression analysis information theory is a branch of probability in which the most significant feature is unpredictability and regression analysis is based on simple statistical theory both methods of statistical prediction have been applied to slope instability to provide cross validation of the results a fortran 77 program for computer aided assessment of the landslide hazard has been developed the program considers the factors affecting the slope instability and history of past landslides of the area as its input the program also calculates the information and regression value in a given area and classifies the area into different grades of instability a case study of landslide hazard assessment of a 66 km2 area in parts of the alkananda valley the gharwal himalaya is presented the factors considered in the analysis are angle and height of the slope rock type and geological structures such as faults and thrusts the results obtained are illustrated in the form of landslide hazard maps the predicted results are compared by the above methods

neoarchean and paleoproterozoic events in the minnesota river valley subprovince with implications for southern superior craton evolution and correlation abstract the lithologic diversity and protracted geologic history of the minnesota river valley mrv gneiss terrane at the southern margin of the archean superior province provide key perspectives on the growth and modification of this craton innovations in geochronology specifically the application of the chemical abrasion technique to remove pb loss domains in zircon and the tandem use of in situ geochemistry and precise isotope dilution age analysis for establishing the petrologic context of radioisotopic ages are yielding new insights into these old rocks first u pb geochronology on a variety of plutonic to mesoscale intrusive rocks from the morton and montevideo blocks of the mrv provide precise constraints on the neoarchean 2603 2584 ma sacred heart orogeny which sutured the mesoarchean gneisses of the mrv to the southern margin of the superior craton in an episode of contractional deformation high grade metamorphism and voluminous plutonism second we report the first radioisotopic age constraints on the st leo and taunton belts of greenstone and supracrustal rocks within the yellow medicine shear zone an inferred lithosphere scale structure juxtaposed between the morton and montevideo gneisses titanite from a metadiorite intrusion into the st leo belt yields igneous 2539 ma and metamorphic 2510 ma ages confirming the archean provenance of the host greenstones and revealing a latest neoarchean episode of magmatism and deformation focused along and within the shear zone third a new 1781 ma u pb zircon age for one of a number of small granitic plugs in the southern montevideo block confirms its correlation to the more voluminous east central minnesota batholith and its origin in the yavapai orogeny again later magmatism was focused along the yellow medicine shear zone suggesting the lithosphere scale significance of that structure this more resolved history for the neoarchean to proterozoic evolution of the southern superior craton provides new opportunities to test archean craton correlations and reconstructions including links to the wyoming and slave cratons

relation of landslides triggered by the kiholo bay earthquake to modeled ground motion abstract the 2006 kiholo bay hawaii earthquake triggered high concentrations of rock falls and slides in the steep canyons of the kohala mountains along the north coast of hawaii within these mountains and canyons a complex distribution of landslides was triggered by the earthquake shaking in parts of the area landslides were preferentially located on east facing slopes whereas in other parts of the canyons no systematic pattern prevailed with respect to slope aspect or vertical position on the slopes the geology within the canyons is homogeneous so we hypothesize that the variable landslide distribution is the result of localized variation in ground shaking therefore we used a state of the art high resolution ground motion simulation model to see if it could reproduce the landslide distribution patterns we used a 3d finite element analysis to model earthquake shaking using a 10 m digital elevation model and slip on a finite fault model constructed from teleseismic records of the mainshock ground velocity time histories were calculated up to a frequency of 5 hz dynamic shear strain also was calculated and compared with the landslide distribution results were mixed for the velocity simulations with some areas showing correlation of landslide locations with peak modeled ground motions but many other areas showing no such correlation results were much improved for the comparison with dynamic shear strain this suggests that 1 rock falls and slides are possibly triggered by higher frequency ground motions velocities than those in our simulations 2 the ground motion velocity model needs more refinement or 3 dynamic shear strain may be a more fundamental measurement of the decoupling process of slope materials during seismic shaking

scapolite phase equilibria and carbon isotopes constraints on the nature and distribution of co2 in the lower continental crust abstract recent applications of scapolite phase equilibria and carbon isotopes are reviewed in order to evaluate the role played by co2 in the genesis of granulites in the lowermost crust scapolite occurs mainly in mafic granulites from exposed high grade terranes most of which have had a prior upper crustal history before equilibration at 9 10 kbar and in high pressure 11 15 kbar xenoliths and orthogneisses which likely represent mantle derived material that has not interacted with supracrustal lithologies calculated equilibrium co2 activities are sufficiently high 0 7 to be consistent with the presence of a co2 rich fluid phase accounting for the low h2o activities in scapolite bearing granulites and some xenoliths co2 activities less than ca 0 5 or the absence of scapolite are consistent with fluid absent metamorphism the measured isotopic composition of carbon 13cpdb in scapolite is only a tight constraint on the source of carbon in scapolite for mafic xenoliths and high pressure orthogneisses carbon isotope values for these lithologies 7 to 2 overlap the range of values for co2 dissolved in or exsolved from basalts and are consistent with a magmatic origin for the co2 the carbon isotope composition of scapolite in granulites from exposed terranes 10 to 4 is more equivocal and may instead be related to pregranulite facies carbonate present in the rock minimum values of volumetric fluid rock calculated to account for the modal abundance and composition of scapolite in granulites on the order of 0 001 to 0 1 are much lower than those required for the desiccation of amphibolites to granulites 0 1 to 0 5 thus scapolite should form in response to infiltration of such large volumes of co2 if p t and bulk compositional constraints are met however only seven of twenty granulite occurrences contain primary carbonate bearing scapolite in mafic granulites it appears that co2 occurs in the lower crust only locally in a co2 rich fluid phase or dissolved in mafic melts and not on a pervasive scale or at the high volumetric fluid rock required the model of carbonic metamorphism

the fossil theory of nighttime high latitude f region troughs observations of f region electron density electron and ion temperatures and ion drift velocity over the latitude interval 40 70 have been made from millstone hill by means of incoherent scatter radar we conclude that the f region density trough that forms on the nightside of the earth may have more than one cause current computer models indicate that it can be produced as a consequence of the competing effects of convection and corotation that cause some flux tubes to remain for long periods in darkness in the premidnight sector thereby allowing the ionisation in them to decay our observations show that troughs often are first seen in the late afternoon sector in regions of fast sunward convective flow and can move in latitude in association with substorms we suggest that these troughs are produced by convection of low density regions from the nightside into daylight and the increased recombination rate that occurs in regions where the o ions are forced through the neutral air at high speed 1 km s troughs created in the dusk sector by this mechanism during substorms can be left as the ionospheric signature of the substorm or fossil when the region of fast convective flow moves poleward following the substorm these extended e w troughs then are carried across the nightside of the earth by corotation relative to the surrounding regions the trough changes little with time and finally is destroyed only when it is carried into sunlight on the dawnside

block and shear zone architecture of the minnesota river valley subprovince implications for late archean accretionary tectonics the minnesota river valley subprovince of the superior province is an archean gneiss terrane composed internally of four crustal blocks bounded by three zones of east northeast trending linear geophysical anomalies two of the block bounding zones are verified regional scale shears the geological nature of the third boundary has not been established potential field geophysical models portray the boundary zones as moderately north dipping surfaces or thin slabs similar in strike and dip to the morris fault segment of the great lakes tectonic zone at the north margin of the subprovince the central two blocks of the subprovince morton and montevideo are predominantly high grade quartzofeldspathic gneiss some as old as 3 6 ga and late tectonic granite the northern and southern blocks benson and jeffers respectively are judged to contain less gneiss than the central blocks and a larger diversity of syntectonic and late tectonic plutons a belt of moderately metamorphosed mafic and ultramafic rocks h

the characteristics of the landslides triggered by the wenchuan ms 8 0 earthquake from anxian to beichuan abstract this paper presents a quantitative analysis of the number and area of the landslides triggered by the wenchuan ms 8 0 earthquake from anxian to beichuan in this study the controlling factors of landslides are obtained from geological maps relief amplitude slope and topographic roughness calculated from dem data in arcgis 9 2 a total of 4134 landslides are identified from digital aero image of 1 m resolution covering 19 7 km2 that accounts for 6 4 of the study area the number of landslides with areas less than 5000 m2 is up to 85 22 the smallest landslide is 6 m2 and the largest 1515 000 m2 the number of landslides which have occurred is 1 6 times more prevalent at hanging walls as opposed to foot walls also the relationship between the numbers of landslides and the distances to an earthquake rupture at a hanging wall is linear but exponential at a footwall these results prove that landslide activity is more severe at hanging walls than at foot walls the outcrop area of geologic unit is proportional to the number of landslides except the jurassic triassic and quaternary units r2 0 952 in the study area and landslide density is 19 meanwhile the area of a landslide is linearly proportional to outcrop area of geologic unit except jurassic lower cambrian and quaternary unit r2 0 8279 in the study area and appear to indicate that the lithology does not play an important role in landslides in the study area earthquake triggered landslides tend to be concentrated in specific zones associated with the event controlling parameters such as reliefs slopes and topographic roughness the landslides occurred particularly in the range of 600 1293 m relief amplitudes and the number in this range amounts to 90 of total slides in the studied region moreover landslides easily occurred in the curvature 1 15 with slope between 5 and 55 in addition landslides also usually occurred in the range of 1 1 5 topographic roughness therefore these correlations provide a way to assess regional landslide hazards and are of great significance to regional geohazard planning and prediction

first observations of the temporal spatial variation of the sub auroral polarization stream from the superdarn wallops hf radar 1 in this letter we present the first two dimensional observations of sub auroral ion drift said variability within the sub auroral polarization stream saps using a new mid latitude superdarn radar located at wallops island va the radar data are complemented with observations from the dmsp f15 timed and noaa 18 spacecraft to confirm that a backscatter feature observed at the equatorward edge of the auroral oval is a manifestation of saps said during a several hour long period on august 6 2005 the velocity data indicate that significant changes in the saps flow occurred on time scales of a few minutes the wallops hf radar observations demonstrate that the saps phenomenon is a source of small scale irregularities extending over many hours of mlt and that the electric fields associated with said in particular are highly variable

multiradar observations of the polar tongue of ionization 1 we present a global view of large scale ionospheric disturbances during the main phase of a major geomagnetic storm we find that the low latitude auroral and polar latitude regions are coupled by processes that redistribute thermal plasma throughout the system for the large geomagnetic storm on 20 november 2003 we examine data from the high latitude incoherent scatter radars at millstone hill sondrestrom and eiscat tromso with superdarn hf radar observations of the high latitude convection pattern and dmsp observations of in situ plasma parameters in the topside ionosphere we combine these with north polar maps of stormtime plumes of enhanced total electron content tec derived from a network of gps receivers the polar tongue of ionization toi is seen to be a continuous stream of dense cold plasma entrained in the global convection pattern the dayside source of the toi is the plume of storm enhanced density sed transported from low latitudes in the postnoon sector by the subauroral disturbance electric field convection carries this material through the dayside cusp and across the polar cap to the nightside where the auroral f region is significantly enhanced by the sed material the three incoherent scatter radars provided full altitude profiles of plasma density temperatures and vertical velocity as the toi plume crossed their different positions under the cusp in the center of the polar cap and at the midnight oval polar cap boundary greatly elevated f peak density 1 5e12 m 3 and low electron and ion temperatures 2500 k at the f peak altitude characterize the sed toi plasma observed at all points along its high latitude trajectory for this event sed toi f region tec 150 1000 km was 50 tecu both in the cusp and in the center of the polar cap large upward directed fluxes of o 1 e14 m 2 s 1 were observed in the topside ionosphere

development of the archean crust in the medina mountain area wind river range wyoming u s a abstract evidence for an extensive archean crustal history in the wind river range is preserved in the medina mountain area in the west central part of the range the oldest rocks in the area are metasedimentary mafic and ultramafic blocks in a migmatite host the supracrustal rocks of the medina mountain area mms are folded into the migmatites and include semi pelitic and pelitic gneisses and mafic rocks of probable volcanic origin mafic dikes intrude the older migmatites but not the mms suggesting that the mms are distinctly younger than the supracrustal rocks in the migmatites the migmatites and the mms were engulfed by the late archean granite of the bridger louis lake and bears ears batholiths which constitutes the dominant rock of the wind river range isotopic data available for the area include nd crustal residence ages from the mms which indicate that continental crust existed in the area at or before 3 4 ga but the age of the older supracrustal sequence is not yet known the upper age of the mms is limited by a 2 7 ga rb sr age of the bridger batholith which was emplaced during the waning stages of the last regional metamorphism the post tectonic louis lake and bears ears batholiths have ages of 2 6 and 2 5 ga respectively stuckless et al 1985 at least three metamorphic events are recorded in the area 1 an early regional granulite event m 1 that affected only the older inclusions within the migmatites 2 a second regional amphibolite event m 2 that locally reached granulite facies conditions and 3 a restricted contact granulite facies event m 3 caused by the intrusion of charnockitic melts associated with the late archean plutons results from cation exchange geobarometers and geothermometers yield unreasonablu low pressures and temperatures suggesting resetting during the long late archean thermal evenn

seismic profiling of archean crust crustal structure in the morton block minnesota river valley subprovince abstract a 58 km seismic reflection profile recorded by the university of wyoming over the early archean gneisses 3 6 3 8 ga of the minnesota river valley subprovince superior province shows more complicated structure and rock variation with depth than the limited surface geology suggests wide angle data show a high average velocity of 6 8 0 1 km s and a crustal thickness of 49 1 km from a zero offset time of 14 2 0 2 s upper crustal 0 10 km reflections are consistent with the gentle dips from surface folding while middle crustal 10 24 km reflections are interpreted as a 40 km long se dipping thrust or fold structure 6 km thick lower crustal 24 48 km reflections are short and low amplitude consistent with small reflection coefficients and short reflectors modeling suggests that this reflectivity is consistent with small

relationship between polar cap patches and field aligned irregularities as observed with an all sky airglow imager at resolute bay and the polardarn radar at rankin inlet 1 simultaneous two dimensional observations of airglow enhancement and radar backscatter from field aligned irregularities fais associated with polar cap patches were conducted the spatial structure of 630 nm airglow from polar cap patches was imaged using an all sky airglow imager at resolute bay canada while backscatter echoes from decameter scale fais were observed using the newly constructed hf polar dual auroral radar network polardarn radar at rankin inlet canada both the airglow enhancement and the radar backscatter appeared within a structured region with the spatial extent of about 500 1000 km the decameter scale fais were found to extend over the entire region of airglow enhancement associated with polar cap patches indicating that the polar patch plasma became almost fully structured soon after initiation within approximately 20 25 min these findings imply that some rapid structuring process of the entire patch area is involved in addition to the primary gradient drift instabilities

coordinated stable auroral red arc observations relationship to plasma convection during the march 20 22 1990 magnetic storm millstone hill radar and dmsp satellite observations detailed the conditions surrounding the occurrence of a sar arc which was observed continuously through an 8 hour interval from dusk till past midnight in the north american sector all sky imaging with a 630 0 nm imager continually monitored the two dimensional position and magnitude of the sar arc emission while radar scans and satellite overflights measured magneto spheric inputs and ionospheric response the arc was colocated with a deep narrow plasma trough and a region of enhanced westward plasma convection of similar width simate3 immediately equa torward of the low latitude extent of plasma sheet particle precipitation a region of low energy ion precipitation was observed at the equatorward edge of the sar arc during a period of spatial tem poral coincident satellite radar observations near the millstone hill longitude the width of the sar arc and related phenomena was of the order of 2 o and the 200 r emission was associated with an electron temperature of 3500ok and a 10x reduction of plasma density at an altitude of 450 kin the best fit model for the emission intensities of both the sar arc and the background airglow suggests that either the electron temperature at the center of the sar arc was somewhat higher than observed by the radar 4000ok or the neutral densities 0 2 and o were increased by factors of 2 and 4 respectively with respect to the msis values the ionospheric trough and a colocated region of enhancext sunward convection 500 1700 m s 1 were observed in conjugate hemispheres through out the local time range 18 02 mlt the convection feature seen in association with the sar arc had many of the characteristics of a subauroral ion drifts said event we report here the first long duration observations of a colocated said sar arc event a narrow ionospheric trough developed during the interval when the said velocity was 1000 m s and was accompanied by a weak 100 r 630 0 nm emission as the velocity fell to 700 m s 1 the density in the trough recovered some what and the arc intensity rose to 300 r above background this brighter period of the sar arc occurred within a fossil trough said we conclude that there is a close spatial and temporal associ ation among these three types of subauroral low altitude phenomena the sar arc the said even and the fossil convection related trough and that this is indicative of the interrelationship of the

landslide hazard zonation using analytical hierarchy process along national highway 3 in mid himalayas of himachal pradesh india landslide zonation studies emphasize on preparation of landslide hazard zonation maps considering major instability factors contributing to occurrence of landslides this paper deals with geographic information system based landslide hazard zonation in mid himalayas of himachal pradesh from mandi to kullu by considering nine relevant instability factors to develop the hazard zonation map analytical hierarchy process was applied to assign relative weightages over all ranges of instability factors of the slopes in study area to generate landslide hazard zonation map layers in geographic information system were created corresponding to each instability factor an inventory of existing major landslides in the study area was prepared and combined with the landslide hazard zonation map for validation purpose the validation of the model was made using area under curve technique and reveals good agreement between the produced hazard map and previous landslide inventory with prediction accuracy of 79 08 the landslide hazard zonation map was classified by natural break classifier into very low hazard low hazard moderate hazard high hazard and very high landslide hazard classes in geographic information system depending upon the frequency of occurrence of landslides in each class the resultant hazard zonation map shows that 14 30 of the area lies in very high hazard zone followed by 15 97 in high hazard zone the proposed model provides the best fit classification using hierarchical approach for the causative factors of landslides having complex structure the developed hazard zonation map is useful for landslide preparedness land use planning and social economic and sustainable development of the region

garnet orthopyroxene plagioclase quartz barometry refinement and application to the english river subprovince and the minnesota river valley recent experimental theoretical and thermodynamic studies permit better calibration of two reactions for geobarometry grossular pyrope quartz anorthite enstatite grossular almandine quartz anorthite ferrosilite if both reactions are applied using the same thermodynamic data and activity models they should yield the same pressure for a given garnet pyroxene plagioclase quartz assemblage application to a variety of high grade terrains generally yielded excellent results however poor results have been obtained for high fe rocks which can be traced to errors in activity models for garnet and or pyroxene either a two site ideal mixing model for orthopyroxene cf wood and banno 1973 underestimates enstatite activity for high fe orthopyroxenes or the ganguly and saxena 1984 model overestimates pyrope activity in low mg garnets

direct observations of the role of convection electric field in the formation of a polar tongue of ionization from storm enhanced density 1 we examine the relationship of convection electric fields to the formation of a polar cap tongue of ionization toi from midlatitude plumes of storm enhanced density sed observations from the geomagnetic storm on 26 27 september 2011 are presented for two distinct sed events during an hour long period of geomagnetic activity driven by a coronal mass ejection a channel of high density f region plasma was transported from the dayside subauroral ionosphere and into the polar cap by enhanced convection electric fields extending to middle latitudes this toi feature was associated with enhanced hf backscatter indicating that it was the seat of active formation of small scale irregularities after the solar wind interplanetary magnetic field conditions quieted and the dayside convection electric fields retreated to higher latitudes an sed plume was observed extending to but not entering the dayside cusp region this prominent feature in the distribution of total electron content tec persisted for several hours and elongated in magnetic local time with the rotation of the earth no ionospheric scatter from superdarn radars was observed within this sed region the source mechanism enhanced electric fields previously drawing the plasma from midlatitudes and into the polar cap as a toi was no longer active resulting in a fossil feature we thus demonstrate the controlling role exercised by the convection electric field in generating a toi from midlatitude sed

a dynamical model of high latitude convection derived from superdarn plasma drift measurements 1 a discrete set of climatological patterns of high latitude ionospheric convection are derived using line of sight plasma drift data from the super dual auroral radar network superdarn the patterns are derived independently for the northern hemisphere and southern hemisphere and for varying solar wind interplanetary magnetic field imf and dipole tilt angle conditions by interpolating between discrete patterns a dynamical model of convection is obtained which can uniquely specify the high latitude electrostatic potential distribution for a wide range of solar wind imf and dipole tilt parameter values accounting for solar wind velocity dependencies in convection leads to better resolving the large scale convection pattern as compared to previous statistical models based on superdarn data it is shown that the mesoscale features of the climatological model compare favorably to the features seen in instantaneous patterns of convection observed with superdarn comparison of the model to other statistical or empirical models derived from ground and space based measurements shows good agreement with most models

thermometry and barometry of some amphibolite granulite facies rocks from the otter lake area southern quebec grenville rocks from a 2500 km2 area centered on otter lake quebec some 75 km northwest of ottawa are in the uppermost amphibolite to lower granulite facies orthopyroxene occurs occasionally in both metabasic and charnockitic rocks the temperature of metapmorphism was approximately 675 c based upon oxide feldspar and garnet clinopyroxene thermometry little thermal gradient could be detected across the area carbonate thermometry using reintegrated calcite compositions yielded lower temperatures of 600 c maximum while garnet biotite and other kd thermometers yielded scattered and for the most part unreasonable results metamorphic pressure calculated from the reaction anorthite grossular sillimanite quartz was 5 0 0 5 kbar 500 50 mpa similar calculations based upon the reactions garnet quartz anorthite orthopyroxene and garnet quartz anorthite clinopyroxene yielded pressures of 5 5 7 0 kbar 550 700 mpa pressure calculations based upon assemblages of cordierite g

distribution and characteristics of loess landslides triggered by the 1920 haiyuan earthquake northwest of china abstract on december 16 1920 an earthquake with a magnitude of 8 5 occurred in haiyuan county ningxia hui autonomous region northwest of china this earthquake triggered several thousand loess landslides which resulted in thousands of deaths and blockages of rivers the distribution and characteristics of the landslides triggered by the haiyuan earthquake in loess areas were studied using satellite images and field investigation a total of about 3700 landslides with a cumulative area of about 177 km2 were interpreted over an area of 21 000 km2 it was found that landslides triggered by the earthquake were concentrated in a western of 40 55 km from the haiyuan fault landslides were concentrated near ridge crests with 65 7 of the landslides originating in the upper quadrant of slopes the aspects of the landslides triggered by the haiyuan earthquake were parallel to the faults and there is no back direction effect in landslides triggered by haiyuan earthquake these landslides have long run out distances travel distance l height different h 0 6 and deposited materials in river channels forming 51 dammed lakes that still exist the relationship between the area a and volume v of the landslides is v 4 170 a1 086 based on the relationship between number and volume of landslide and the magnitude of earthquake 100 000 landslides with a cumulative volume of 0 5 1010 m3 were triggered by the haiyuan earthquake as loess is sensitive to liquefaction during an earthquake and tends to produce landslides with long travel distances hence the loess depth slope and geological stresses are the primary factors responsible for the high density of landslides in this region

spatial variability and attenuation of arias intensity during the 1999 chi chi mw 7 6 earthquake taiwan arias intensity is a measure of earthquake intensity that captures the potential destructiveness of an earthquake using the strong ground motion records of the m w 7 6 chi chi earthquake taiwan we analyze the spatial distribution of the vertical horizontal fault parallel and fault normal components of the arias intensity we investigate the effects of the hanging wall and footwall on ground motions and develop a relationship between arias intensity and peak ground acceleration pga incorporating the influence of local site conditions we also evaluate the applicability of some widely used arias intensity attenuation relationships by comparing the observed values with empirical estimates our results show the vertical arias intensity is generally lower than the horizontal component with nearly 90 of the vertical to horizontal ratios between 0 1 and 0 6 during this typical reverse mechanism earthquake the fault normal component of the arias intensity is approximately 20 higher than the fault parallel component for sites within 40 km of the fault arias intensities on the hanging wall are systematically higher than those on the footwall indicating clear hanging wall effects site conditions influence the correlation between arias intensity and pga arias intensity shows a good correlation with pga and v s 30 arias intensity increases with increasing pga and decreasing v s 30 the arias intensities observed within 40 km of site class c locations and within 80 km of site class d locations are generally lower than the mean estimates from empirical predictions in contrast at distances of 80 km from site class d locations the observed arias intensities are much larger than the empirical predictions as a result of site amplification considering the variability of ground motion between earthquakes the attenuation model of travasarou et al 2003 model 4 of stafford et al 2009 and the model of lee et al 2012 provide a good fit with observations from the chi chi earthquake online material table of station coordinates fault distances footwall hanging wall indicator site classes v s 30 and measured arias intensities

comparing the cross polar cap potentials measured by superdarn and amie during saturation intervals 1 assimilative mapping of ionospheric electrodynamics amie and super dual auroral radar network superdarn are two commonly used techniques to measure cross polar cap potential pc in this study i compare pc inferred from amie with that inferred from superdarn during saturation intervals measurements from defense meteorological satellite program dmsp and polar cap pc index are also used to help estimate true pc seven saturation events in 2000 were selected for each event i ran the amie software driven by magnetometer data only by magnetometer data and superdarn data and by superdarn data only then i compared pc obtained from amie with that from superdarn i found that 1 pc inferred from superdarn is significantly lower than that inferred from other techniques including amie when pc is large e g greater than 150 kv 2 pc inferred from amie with superdarn input is much higher than pc inferred from superdarn 3 pc inferred from amie with magnetometer input tends to give the same results as that inferred from amie with magnetometer and superdarn input 4 pc inferred from amie with magnetometer input is in general in agreement with pcinferred from amie with superdarn input it is suggested that reason for the low values of superdarn derived pc during saturation intervals is that the superdarn algorithm to compute pc from measurements is not applicable to such intervals

a gis based automated procedure for landslide susceptibility mapping by the conditional analysis method the baganza valley case study italian northern apennines among the many gis based multivariate statistical methods for landslide susceptibility zonation the so called conditional analysis method holds a special place for its conceptual simplicity in fact in this method landslide susceptibility is simply expressed as landslide density in correspondence with different combinations of instability factor classes to overcome the operational complexity connected to the long tedious and error prone sequence of commands required by the procedure a shell script mainly based on the grass gis was created the script starting from a landslide inventory map and a number of factor maps automatically carries out the whole procedure resulting in the construction of a map with five landslide susceptibility classes a validation procedure allows to assess the reliability of the resulting model while the simple mean deviation of the density values in the factor class combinations helps to evaluate the goodness of landslide density distribution the procedure was applied to a relatively small basin 167 km2 in the italian northern apennines considering three landslide types namely rotational slides flows and complex landslides for a total of 1 137 landslides and five factors namely lithology slope angle and aspect elevation and slope bedding relations the analysis of the resulting 31 different models obtained combining the five factors confirms the role of lithology slope angle and slope bedding relations in influencing slope stability

the hardwood gneiss evidence for high p t archean metamorphism in the southern province of the lake superior region the hardwood gneiss is an areally small unit of precambrian granulite grade rocks exposed in the archean gneiss terrane of the southern lake superior region the rocks are located in the southwestern portion of the upper peninsula of michigan and consist of a structurally conformable package of quartzitic metapelitic amphibolitic and metabasic units three texturally distinct garnet types are present in the metabasites and are interpreted to represent two metamorphic events geothermobarometry indicates conditions of 8 2 11 6 kbar and 770 c for ml and conditions of 6 0 10 1 kbar and 610 740 c for m2 it is proposed that ml was archean and contemporaneous with a high grade metamorphic event recorded in the minnesota river valley the m2 event was probably early proterozoic and pre penokean with metamorphic conditions more intense than those generally ascribed to the penokean orogeny in michigan but similar to the conditions reported for the kapuskasing zone of ontario the high paleopres sures a

average characteristics and activity dependence of the subauroral polarization stream 1 data from the millstone hill incoherent scatter radar taken over two solar cycles 1979 2000 are examined to determine the average characteristics of the disturbance convection electric field in the midlatitude ionosphere radar azimuth scans provide a regular database of ionospheric plasma convection observations spanning auroral and subauroral latitudes and these scans have been examined for all local times and activity conditions we examine the occurrence and characteristics of a persistent secondary westward convection peak which lies equatorward of the auroral two cell convection individual scans and average patterns of plasma flow identify and characterize this latitudinally broad and persistent subauroral polarization stream saps which spans the nightside from dusk to the early morning sector for all kp greater than 4 premidnight the saps westward convection lies equatorward of l 4 60 invariant latitude spans 3 5 of latitude and has an average peak amplitude of 900 m s in the predawn sector saps is seen as a region of antisunward convection equatorward of l 3 55 spanning 3 of latitude with an average peak amplitude of 400 m s

superdarn assimilative mapping 1 an assimilative mapping procedure is developed to optimally combine information from super dual auroral radar network superdarn plasma drift observations and a background statistical convection model to derive global distributions of electrostatic potential this procedure takes into account statistical properties of the background model errors obtained through the empirical orthogonal function analysis technique described in a companion paper the assimilative mapping procedure is evaluated quantitatively using cross validation and is found to reduce median prediction errors by up to 43 as compared to the existing linear regression based superdarn mapping procedure furthermore the mapped results from the assimilative procedure show a greater dynamic range in convection strength than do those of the regression based procedure i e the cross polar cap potential is smaller for weak driving conditions and larger for strong driving conditions the application of the assimilative procedure is demonstrated for a case study containing a geomagnetic storm it is shown that qualitatively the results of the assimilative procedure appear more smooth and consistent across both data dense and data sparse regions than do those of the regression based procedure

landslide hazard zoning using the gis approach a case study from the ramganga catchment himalayas abstract this paper deals with the development of a technique for risk assessment of landslide hazards using the geographic information system gis approach the method has been applied to the ramganga catchment lying in the lower himalayas and the investigations are based on multi data sets the landslide activity is related to a number of parameters viz lithology land use distance from major tectonic shear zone and azimuth direction based on the data for 522 landslides in four selected sub basins an index value called landslide nominal risk factor lnrf is defined and developed for each of the important factors different weights have been assigned to the terrain depending upon the lnrf and integrated in an ordinal scale to help locate areas of high moderate and low landslide risk

comment on spatial distribution analysis of landslides triggered by 2008 5 12 wenchuan earthquake china by shengwen qi qiang xu hengxing lan bing zhang jianyou liu engineering geology 116 2010 95 108

probabilistic landslide hazard assessment at the basin scale abstract we propose a probabilistic model to determine landslide hazard at the basin scale the model predicts where landslides will occur how frequently they will occur and how large they will be we test the model in the staffora river basin in the northern apennines italy for the study area we prepare a multi temporal inventory map through the interpretation of multiple sets of aerial photographs taken between 1955 and 1999 we partition the basin into 2243 geo morpho hydrological units and obtain the probability of spatial occurrence of landslides by discriminant analysis of thematic variables including morphological lithological structural and land use for each mapping unit we obtain the landslide recurrence by dividing the total number of landslide events inventoried in the unit by the time span of the investigated period assuming that landslide recurrence will remain the same in the future and adopting a poisson probability model we determine the exceedance probability of having one or more landslides in each mapping unit for different periods we obtain the probability of landslide size by analysing the frequency area statistics of landslides obtained from the multi temporal inventory map assuming independence we obtain a quantitative estimate of landslide hazard for each mapping unit as the joint probability of landslide size of landslide temporal occurrence and of landslide spatial occurrence

a gis based potential analysis of the landslides induced by the chi chi earthquake the chi chi earthquake struck central taiwan in 1999 triggering many landslides over a broad area a large amount of information was obtained from the field reconnaissance conducted by national center for research on earthquake engineering ncree 2000 investigation report of the geotechnical hazard caused by chi chi earthquake taiwan and other follow up investigations the objective of this research was to analyze the landslide data for assessment of the potential for landslides triggered by the chi chi earthquake and a predictive model was constructed accordingly the analysis was conducted under a geographic information system gis environment and the landslide potential was defined by the information value proposed by jade and sarkar eng geol 36 1993 91 seven factors were selected and the structural equation model was used to describe the relationship among the factors and building of the predictive model verifications of the model were conducted using an independent set of field investigation data and results were satisfactory with the field investigation data displaying higher potential

fluvial response to rapid episodic erosion by earthquake and typhoons tachia river central taiwan abstract analysis of typhoon and earthquake triggered landsliding and fluvial response in the tachia river central taiwan documents highly episodic sediment supply over decade to century timescales landslide data from the chi chi earthquake 1999 and subsequent typhoons 2001 2004 and 2005 quantify the sediment supply from these events fluvial response was investigated by decadal scale and century scale longitudinal river profile data spanning 1904 to 2008 and by sediment delivery recorded in suspended sediment load and reservoir sedimentation data our results show that the different time periods of satellite images and aerial photographs used in previous studies make it difficult to unambiguously identify the causes of landslides previously attributed by some studies to the effects of the chi chi earthquake rather than subsequent high intensity precipitation in response to significant variability in sediment delivery from hillslopes century scale profile variation data indicate substantial bed surface elevation change of 2 6 6 7 m and decade scale bed surface elevation change of 1 1 3 3 m since 1993 the downstream reaches incised in response to bedload sediment trapping by reservoirs while headwater reaches aggraded in response to increased sediment delivery from uplands a tremendous increase in reservoir sedimentation after 2000 likely reflects the effects of the highest decade average daily rainfall since 1900 suspended sediment load data indicate a post chi chi earthquake increase in sediment concentration in low flow events but do not exhibit the clear influence on sediment yields at higher flows as e g typhoons reported by others for fluvial response in the epicentral region

development of shallow seismic landslide potential map based on newmark s displacement the case study of chi chi earthquake taiwan with the development of the geographic information system gis the analysis of regional slope stability under seismic loading has evolved rapidly in recent years in many studies the newmark s method is used for the computation of displacements triggered by an earthquake on a single slope while for regional analysis the infinite slope theory is frequently used due to its simplicity when large amount of computations are required in this research the infinite slope theory was examined considering various seismic conditions material properties and slope geometry to verify the suitability of the method when applied to regional analysis and development of potential shallow landslide maps the landslide cases induced by chi chi earthquake in central taiwan were used in this study for verification it was found that the infinite slope theory is valid for regional analysis when used with discretion based on the calculated newmark s displacement and combining the gis technique procedures for the potential map development are established in this study

dynamic temporal evolution of polar cap tongue of ionization during magnetic storm 1 during a magnetic storm on 14 16 december 2006 a polar cap tongue of ionization toi was detected by an all sky imager asi at resolute bay canada 74 73 n 265 07 e we investigate the temporal evolution and spatial structure of the toi in detail by combining the optical data with other observations e g solar wind gps total electron content superdarn and dmsp and noaa poes satellites the toi was observed as a bright and elongated 630 nm airglow plume for 4 h during the main phase of the storm this interval corresponded to a period of prolonged stable large amplitude southward imf during a coronal mass ejection cme one to one and a half hours before the appearance of toi the polar cap boundary expanded rapidly far equatorward and a positive ionospheric storm occurred this implies that both the expansion of the high latitude plasma convection and build up of the source plasma in the midlatitudes are necessary conditions for the formation of a toi because both of them were triggered by a major southward turning of the imf the prolonged large amplitude southward imf orientation in the trailing part of the cme was primarily responsible for the generation of toi after its appearance the toi exhibited dynamic motion in the dawn to dusk direction simultaneous superdarn data suggest that a longitudinal progression of subauroral polarization stream controlled this dynamic motion the optical toi was found to be a continuous stream elongated in the noon midnight direction although it contained some mesoscale patterns absence of large scale temporal changes in the cusp plasma flow during the stable imf period allowed the toi to remain continuous without being broken into polar cap patches the mesoscale structures within the toi were probably produced by small scale velocity fluctuations in the cusp plasma flow the toi as visualized with the all sky airglow imager was found to be much more dynamic and much more complicated than we ever thought the current study indicates that such a behavior of the toi was presumably caused by a combination of temporal variations in the global scale plasma circulation system expansion and contraction of the polar cap area and plasma density changes in the dayside low to midlatitudes

large scale observations of a subauroral polarization stream by midlatitude superdarn radars instantaneous longitudinal velocity variations 1 we present simultaneous measurements of flow velocities inside a subauroral polarization stream saps made by six midlatitude high frequency superdarn radars the instantaneous observations cover three hours of universal time and six hours of magnetic local time mlt from velocity variations across the field of view of the radars we infer the local 2d flow direction at three different longitudes we find that the local flow direction inside the saps channel is remarkably constant over the course of the event the flow speed however shows significant temporal and spatial variations after correcting for the radar look direction we are able to accurately determine the dependence of the saps velocity on magnetic local time we find that the saps velocity variation with magnetic local time is best described by an exponential function the average velocity at 00 mlt was 1 2 km s and it decreased with a spatial e folding scale of two hours of mlt toward the dawn sector we speculate that the longitudinal distribution of pressure gradients in the ring current is responsible for this dependence and find these observations in good agreement with results from ring current models using tec measurements we find that the high westward velocities of the saps are as expected located in a region of low tec values indicating low ionospheric conductivities

topographic locations and size of earthquake and typhoon generated landslides tachia river taiwan analysis of mapped landslide locations using a high resolution 5 m grid digital elevation model dem in the tachia river basin taiwan finds distinct differences in the topographic locations and size of landslides during the 1999 chi chi earthquake and the 2001 toraji typhoon our analysis supports densmore and hovius hypothesis that earthquake induced landslides cluster near ridgetops due to topographic amplification of ground shaking and that typhoon induced landslides occur with greater frequency lower on slopes in addition the differing topographic locations of seismically induced and subsequent typhoon induced landslides shows no evidence of residual post earthquake influences on landslides during typhoon toraji previously hypothesized for drainage basins closer to the earthquake epicenter our results support the interpretation that in this tectonically active landscape seismically induced landslides help shatter and erode ridgetops but typhoon triggered landslides concentrate erosion farther downslope with the combination acting to more uniformly lower upland terrain than either process does individually copyright 2013 john wiley sons ltd

high precision u pb geochronology in the minnesota river valley subprovince and its bearing on the neoarchean to paleoproterozoic evolution of the southern superior province high precision u pb ages have been obtained for high grade gneisses late kinematic to postkinematic granitic plutons and a crosscutting mafic dike of the archean minnesota river valley tectonic subprovince at the southern ramparts of the superior craton of north america the antiquity of the minnesota river valley terranes is confirmed by a high precision u pb zircon age of 3422 2 ma for a tonalitic phase of the morton gneiss voluminous late kinematic monzogranites of the benson ortonville granite and morton sacred heart granite blocks yield identical crystallization ages of 2603 1 ma illustrating the synchrony and rapidity of deep crustal melting and plutonism throughout the minnesota river valley terranes postkinematic 2591 2 ma syenogranites and aplitic dikes in both blocks effectively constrain the final penetrative deformation of the minnesota river valley subprovince monazite growth from 2609 to 2595 ma in granulitic paragneisses of the benson and montevideo blocks is interpreted to record prograde to peak granulite facies metamorphic conditions associated with crustal thickening and magmatism neoarchean metamorphism and plutonism are interpreted to record the timing of collisional accretion and terminal suturing of the mesoarchean continental minnesota river valley terranes to the southern margin of the superior province along the western great lakes tectonic zone subsequent paleoproterozoic rifting of this margin is recorded by voluminous basaltic dike intrusion expressed in the minnesota river valley by major wnw trending tholeiitic diabase dikes dated at 2067 1 ma only slightly younger than the structurally and geochemically similar 2077 4 ma fort frances kenora kabetogama dike swarm of northern minnesota and adjoining canada

causes of the longitudinal differences in the equatorial vertical e b drift during the 2013 ssw period as simulated by the time gcm during stratospheric sudden warming ssw periods large changes in the low latitude vertical drift have been observed at jicamarca as well as in other longitudinal sectors in general a strengthening of the daytime maximum vertical drift with a shift from prenoon to the afternoon is observed during the january 2013 stratospheric warming significant longitudinal differences in the equatorial vertical drift were observed at jicamarca the previously reported ssw behavior prevails however no shift of the daytime maximum drift was exhibited in the african sector using the national center for atmospheric research thermosphere ionosphere mesosphere electrodynamics general circulation model time gcm the possible causes for the longitudinal difference are examined the timing of the strong ssw effect in the vertical drift 15 20 january coincides with moderate geomagnetic activity the simulation indicates that approximately half of the daytime vertical drift increase in the american sector may be related to the moderate geophysical conditions kp 4 with the effect being negligible in the african sector the simulation suggests that the wind dynamo accounts for approximately 50 of the daytime vertical drift in the american sector and almost 100 in the african sector the simulation agrees with previous findings that the migrating solar tides and the semidiurnal westward propagating tide with zonal wave number 1 sw1 mainly contribute to the daytime wind dynamo and vertical drift numerical experiments suggest that the neutral wind and the geomagnetic main field contribute to the presence absence of a local time shift in the daytime maximum drift in the american african sector

effects of seismic anisotropy and geological characteristics on the kinematics of the neighboring jiufengershan and hungtsaiping landslides during chi chi earthquake abstract the chi chi earthquake mw 7 6 of september 21 1999 triggered many landslides in central taiwan two of these landslides hungtsaiping htp and jiufengershan jfes were situated as close as 2 km from each other but had significant differences in their kinematics jfes landslide was a catastrophic rockslide avalanche and the htp landslide was relatively slow moving the authors conducted a study to explore the reasons for such differences factors such as the characteristics of strong ground motion sliding direction of landslide and friction angle of the sliding surface were considered in the study an analysis of 12 strong motion records collected in the study area showed that the distribution of horizontal pseudostatic coefficients earthquake energy ratio and permanent sliding block displacements newmark displacement were anisotropic with their predominant direction mostly in the e w ese wnw trending this direction is perpendicular to the axis of the main geological structures of the studied area the computed newmark displacement in the sliding direction of the jfes landslide is larger 44 than that of the htp landslide with sliding surface inclination of 21 and friction angle of 28 we can conclude that the seismic anisotropy and the corresponding sliding direction are important contributing factors to the kinematics of studied landslides the back calculated friction angle of the sliding surface that corresponds to a critical newmark displacement for the jfes landslide is about 3 5 higher than that of htp landslide the material colluvium on the sliding surface in htp should be less velocity dependent than that of the jfes landslide rock according to the back calculations the importance of seismic anisotropy sliding direction and mechanical properties of sliding surface on the kinematics of deep seated landslides is demonstrated

dynamic subauroral ionospheric electric fields observed by the falkland islands radar during the course of a geomagnetic storm ion drift said located between 53 and 58 magnetic south and lasting 6 5 hours was observed by the falkland islands radar in the pre midnight sector coincident flow data from the dmsp satellites and the magnetically near conjugate northern hemisphere blackstone hf radar reveal that the said was embedded within the broader subauroral polarization streams saps dmsp particle data indicate that the said location closely followed the equatorward edge of the auroral electron precipitation boundary while remaining generally poleward of the equatorward boundary of the ion precipitation the latitude of the said varied throughout the interval on similar timescales to variations in the interplanetary magnetic field and auroral activity while variations in its velocity were more closely related to ring current dynamics these results are consistent with said electric fields being generated by localized charge separation in the partial ring current but suggest that their location is more strongly governed by solar wind driving and associated large scale magnetospheric dynamics

charnockite geobarometers based on coexisting garnet pyroxene plagioclase quartz numerous geothermometers based on compositions of coexisting minerals have been calibrated experimentally or theoretically during the past 10 yr in contrast few continuous reaction geobarometers exist which have had wide application one based on the reaction of cordierite to garnet sillimanite and quartz is limited by a relatively narrow pressure range of application and also by conflicting calibrations1 2 because the mixing relations of mg and fe and the role of h2o in cordierite3 are not understood another successful barometer uses the assemblage garnet plagioclase al2sio5 and quartz4 5 continuous geobarometers based on the reaction of orthofer rosilite to fayalite plus quartz6 and on the aluminium content of enstatite in equilibrium with garnet7 have been used to a lesser extent the former barometer is limited by rarity of the requisite assemblage and the latter by uncertain experimental calibration for crustal rocks we calibrate here two mineralogical geobarometers from measured thermodynamic data the participating minerals pyroxenes garnet plagioclase and quartz are frequently associated in high grade metamorphic rocks calculation of pressures for several terrains show that the geobarometers yield reasonable and consistent results for the entire range of crustal pressures

observations of ionospheric convection from the wallops superdarn radar at middle latitudes 1 during geomagnetic storms the ability of the super dual auroral radar network superdarn to measure ionospheric convection becomes limited when the radars suffer from absorption and the auroral disturbance expands equatorward of the radar sites to overcome these shortcomings it was decided to construct a superdarn radar at middle latitudes on the grounds of the nasa wallops flight facility this paper presents the first comprehensive analysis of doppler measurements from the wallops radar which commenced operations in may 2005 wallops measurements are compared with the goose bay radar during the onset of a geomagnetic storm on 31 august 2005 goose bay measured the onset of geomagnetic activity at high latitude while wallops monitored the expansion of convection to middle latitudes average convection patterns binned by the kp geomagnetic index are also presented during weak moderate geomagnetic activity kp 3 the wallops radar observes ionospheric irregularities between 50 and 60 magnetic latitude drifting westward across much of the nightside when these measurements are incorporated into the calculation of an average superdarn convection pattern the streamlines of polar cap outflow on the nightside become kinked in a manner reminiscent of the harang discontinuity this morphology arises quite naturally when the two cell convection at high latitudes merges with the prevailing westward convection at middle latitudes during increased geomagnetic activity kp 3 wallops is able to measure the expansion of auroral electric fields to middle latitudes and the average superdarn cross polar cap potential is increased by 25

storm time plasma transport at middle and high latitudes associated with the large scale enhancement of the ionospheric convection electric field during disturbed geomagnetic conditions solar produced f region plasma is transported to and through the noontime cleft from a source region at middle and low latitudes in the afternoon sector as a result of the offset between the geomagnetic and geographic poles the afternoon sector region of strong sunward convection is shifted to increasingly lower geographic latitude throughout the interval between 12 ut and 24 ut a snowplow effect occurs in which the convection cell continually encounters fresh corotating ionospheric plasma along its equatorward edge producing a latitudinally narrow region of storm enhanced plasma density sed and increased total electron content which is advected toward higher latitudes in the noon sector the millstone hill incoherent scatter radar regularly observes sed as a spatially continuous large scale feature spanning local times between noon and midnight and at latitudes between the polar cap and its mid or low latitude source region for local times away from noon the latitude of most probable sed occurrence moves equatorward by 6 for an increase of 2 in the kp index during strong disturbances the topside sed is observed to be convecting sunward at 750 m s 1 with a flux of 1014 m 2 s 1 this feature accounts for the pronounced enhancement of ionospheric density near dusk at middle latitudes observed during the early stages of magnetic storms called the dusk effect and constitutes a source for the enhanced f region plasma observed in the polar cap during disturbed conditions

statistical patterns of high latitude convection obtained from goose bay hf radar observations we have derived patterns that describe the statistical interplanetary magnetic field imf dependencies of ionospheric convection in the high latitude region of the northern hemisphere the observations of plasma motion were made with the hf coherent backscatter radar located at goose bay labrador over the period september 1987 to june 1993 the area covered by the measurements extended poleward of 65 to a working limit of about 85 distributions of electrostatic potential have been derived and expressed as series expansions in spherical harmonics the patterns are the first derived from direct ground based observations of ionospheric convection that approach in completeness and level of detail the patterns derived in recent satellite studies rich and hairston 1994 weimer 1995 we show the dependence of the convection on imf angle in the gsm y z plane for three intervals of imf magnitude in this plane except for predominantly northward imf the convection is primarily two cell the dusk cell is larger in terms of both spatial extent and potential variation the effect of imf by is apparent in the global shaping of the cells and the orientation of the overall pattern in mlt for by by the dusk dawn cell is more round crescent shaped and the pattern more rotated toward earlier mlts the by effect on the nightside convection is pronounced and is hemispherically antisymmetric like the well known day side by effect for imf increasingly northward the convection trajectories on the dayside become increasingly distorted evolving through a three cell to a four cell circulation the additional cells appear on either side of the noon meridian and result in sunward flow the overall agreement with the results of the satellite studies is good and extends to quite fine detail in the case of the comparison with weimer 1995 there are significant differences with the statistical patterns derived from magnetometer measurements which tend to show domination by the dawn rather than the dusk cell

statistical analysis of an earthquake induced landslide distribution the 1989 loma prieta california event the 1989 loma prieta california earthquake moment magnitude m 6 9 generated landslides throughout an area of about 15 000 km2 in central california most of these landslides occurred in an area of about 2000 km2 in the mountainous terrain around the epicenter where they were mapped during field investigations immediately following the earthquake the distribution of these landslides is investigated statistically using regression and one way analysis of variance anova techniques to determine how the occurrence of landslides correlates with distance from the earthquake source slope steepness and rock type the landslide concentration defined as the number of landslide sources per unit area has a strong inverse correlation with distance from the earthquake source and a strong positive correlation with slope steepness the landslide concentration differs substantially among the various geologic units in the area the differences correlate to some degree with differences in lithology and degree of induration but this correlation is less clear suggesting a more complex relationship between landslide occurrence and rock properties

an evaluation of garnet clinopyroxene geothermometry in granulites four new formulations of the garnet clinopyroxene geothermometer ellis and green 1979 ganguly 1979 saxena 1979 dahl 1980 have been evaluated in the adirondacks and five other granulite terranes using results from 94 mineral pairs the saxena and ganguly formulations give temperatures that are generally 100 150 c above those constrained by phase equilibria and other independent thermometry while the empirical calibration of dahl gives widely scattered erratic results despite some scatter in the data the ellis and green calibration appears to be more accurate and precise than the others and is the most useful garnet clinopyroxene thermometer currently available for quantitative thermometry in granulites all four formulations are sensitive to large variations 70 80 c in temperature suggesting that problems with accuracy and precision can be improved with further refinement of model based aspects of the thermometers

large scale imaging of high latitude convection with super dual auroral radar network hf radar observations the hf radars of the super dual auroral radar network superdarn provide measurements of the e b drift of ionospheric plasma over extended regions of the high latitude ionosphere with the recent augmentation of the northern hemisphere component to six radars a sizable fraction of the entire convection zone approximately one third can be imaged nearly instantaneously 2 min to date the two dimensional convection velocity has been mapped by combining line of sight velocity measurements obtained from pairs of radars within common volume areas we describe a new method of deriving large scale convection maps based on all the available velocity data the measurements are used to determine a solution for the distribution of electrostatic potential expressed as a series expansion in spherical harmonics the addition of data from a statistical model constrains the solution in regions of no data coverage for low order expansions the results provide a gross characterization of the global convection we discuss the processing of the radar velocity data the factors that condition the fitting and the reliability of the results we present examples of imaging that demonstrate the response of the global convection to variations in the interplanetary magnetic field imf in the case of a sudden polarity change from northward to southward imf the convection is seen to reconfigure globally on very short 6 min timescales

mixing behavior in quaternary garnet solid solution and an extended ellis and green garnet clinopyroxene geothermometer applications of the different formulations of garnet clinopyroxene geothermometers to crustal granulites and particularly to metamorphosed manganese formations show a wide scatter of estimates this is primarily related to the uncertainty associated with the formulation of the activity composition relationship in garnet solid solution besides that in the clinopyroxene solid solution the largest uncertainty appears to have resulted from the adopted mg mn interaction parameter in garnet which is yet to be experimentally determined a fresh statistical regression of eleven pairs of garnet and clinopyroxene equilibrated at identical p t conditions from a manganese formation in india yields wmg mngt wmn mg value of 1600 500 cal mols an extension of the ellis and green 1979 geothermometer known to work well in normal granulites incorporating terms associated with the activity coefficients of the exchangeable cations now yields consistent temperature estimation from normal granulites as well as from metamorphosed manganese formations the geothermometer however will not work well for garnet having xfe 0 65 and clinopyroxenes containing appreciable na al and or fe3

modeling typhoon and earthquake induced landslides in a mountainous watershed using logistic regression landslides can be caused by storms and earthquakes most logistic regression models proposed in recent years have been targeted at rainfall induced landslides in areas such as taiwan where landslides can be triggered by typhoons tropical cyclones and earthquakes a rainfall induced model is insufficient because it provides only a partial explanation of landslide occurrence and overlooks the potential effect of earthquakes on typhoon triggered landslides this study used landslides triggered by a major earthquake and a typhoon prior to the earthquake to develop an earthquake induced model and a typhoon induced model the models were then validated by using landslides triggered by three typhoons after the earthquake according to the results typhoon triggered landslides tended to be near stream channels and earthquake triggered landslides were more likely to be near ridge lines moreover a major earthquake could still affect the locations of typhoon triggered landslides 6 years after the earthquake this study therefore demonstrates that an earthquake induced model both sheds light on the environmental factors for triggering landslides and augments a rainfall induced model in its predictive capability in areas such as taiwan

calculation and application of clinopyroxene garnet plagioclase quartz geobarometers recently published thermodynamic and experimental data in a variety of chemical systems have been evaluated to derive gibbs free energies for hedenbergite and pyrope these were used to calculate the geobarometric equilibria

empirical high latitude electric field models electric field measurements from the dynamics explorer 2 satellite have been analyzed to extend the empirical models previously developed from dawn dusk ogo 6 measurements j p heppner 1977 the analysis embraces large quantities of data from polar crossings entering and exiting the high latitudes in all magnetic local time zones paralleling the previous analysis the modeling is based on the distinctly different polar cap and dayside convective patterns that occur as a function of the sign of the y component of the interplanetary magnetic field the objective which is to represent the typical distributions of convective electric fields with a minimum number of characteristic patterns is met by deriving one pattern model bc for the northern hemisphere with a y interplanetary magnetic field imf and southern hemisphere with a y imf and two patterns models a and de for the northern hemisphere with a y imf and southern hemisphere with a y imf the most significant large scale revisions of the ogo 6 models are 1 on the dayside where the latitudinal overlap of morning and evening convection cells reverses with the sign of the imf y component 2 on the nightside where a westward flow region poleward from the harang discontinuity appears under model bc conditions and 3 magnetic local time shifts in the positions of the convection cell foci the modeling above was followed by a detailed examination of cases where the imf z component was clearly positive northward neglecting the seasonally dependent cases where irregularities obscure pattern recognition the observations range from reasonable agreement with the new bc and de models to cases where different characteristics appeared primarily at dayside high latitudes the analysis of these differences for strong bz conditions using passes through different mlt zones led to finding that the deviations from both the bc and de models could be modeled by extending the evening cell foci toward and beyond noon with a deformation that roughly resembles a rotational twist of the extended evening cell the morning cell accommodation to the model bc deformation produces a narrow tongue of eastward convection near 75 invariant latitude on the dayside the model de deformation compresses the morning cell toward the night hours such that the sunward convection in the morning cell is diverted to polar latitudes in the 0400 to 0700 mlt sector in both cases the deformations of the two cell patterns lead to sunward convection in dayside polar regions while maintaining the integrity of the nightside convection pattern thus the nightside dilemmas that plague three and four cell models designed to explain sunward convection in polar regions under bz conditions do not appear

metamorphic conditions of late archean high grade gneisses minnesota river valley u s a a detailed comparative geothermobarometric analysis for the minnesota river valley mrv archean gneiss and migmatite terrane yields temperature and pressure ranges of 650 750 c and 4 5 7 5 kbar 450 750 mpa based on garnet biotite two feldspar garnet clinopyroxene garnet cordierite orthopyroxene clinopyroxene and magnetite ilmenite thermometry and garnet cordierite sillimanite quartz and garnet orthopyroxene plagioclase quartz barometry the temperature variation observed is interpreted to be primarily a result of varying degrees of re equilibration of assemblages with falling temperature but may include real temperature variations between areas exhibiting granulite facies versus upper amphibolite facies migmatitic lithologies the large pressure range is primarily a result of differences among the pressure calibrations applied but may also record variations in pressure within the terrane lower pressures are consistent with the occurrence of cordierite bearing assemblages at granite falls and d