backward erosion monitored by spatial temporal pore pressure changes during field experiments abstractthis paper focuses on understanding the temporal behavior of backward erosion using measurements from densely spaced piezometers during large scale field experiments in october 2009 and september 2012 at ijkdijk in the netherlands observations and data originate from nearly continuous monitoring of pore water pressure and visual observations of seepage and sand boils in 2009 the test progressed to breach release of reservoir while in 2012 the test included a vertical geotextile in the foundation to mitigate backward erosion such that the embankment did not breach study of pore water pressure provides indicators of backward erosion also known as piping detectable in instrument readings temporally and spatially dense pore water pressure measurements detect two pore water pressure transitions characteristic to the development of internal erosion even in piezometers located away from the backward erosion activity first the backward erosion causes anomalous pressure decrease in piezometers

geomorphologic index validation by dinsar technique in the andean orogenic front 32 33 s abstract this paper deals with a morphotectonic characterization of the mendoza piedmont located in the south edge of the andean precordillera 32 33 s very close to mendoza city where at least 800 000 people habits marked tectonic geomorphological expressions exist in this area associated with the andean orogenic active front showing historical earthquakes with magnitudes from 6 0 to 7 0 the main objective of this work is the understanding of current deformation on the study area by two indirect and complementary methods analysis of classic morphometric parameter h index and calculation of deformation fields by dinsar technique applying morphometric analysis of drainage basins of the mendoza piedmont heterogenetic hypsometric values h were found as probable response to different dynamic relations with base level of the fluvial drainage system this segmentation on piedmont behaviour allows us to discriminate three different areas northern central and southern on the basis of morphological criteria the southern area reveals a greater tectonic activity matching with a greater vertical deformation inferred by dinsar technique these findings improve the knowledge about regional seismic hazard allowing release where main deformation is currently being accumulated in the andean active front

southern california permanent gps geodetic array continuous measurements of regional crustal deformation between the 1992 landers and 1994 northridge earthquakes the southern california permanent gps geodetic array pgga was established in 1990 across the pacific north america plate boundary to continuously monitor crustal deformation we describe the development of the array and the time series of daily positions estimated for its first 10 sites in the 19 month period between the june 28 1992 mw 7 3 landers and january 17 1994 mw 6 7 northridge earthquakes we compare displacement rates at four site locations with those reported by feigl et al 1993 which were derived from an independent set of global positioning system gps and very long baseline interferometry vlbi measurements collected over nearly a decade prior to the landers earthquake the velocity differences for three sites 65 100 km from the earthquake s epicenter are of order of 3 5 mm yr and are systematically coupled with the corresponding directions of coseismic displacement the fourth site 300 km from the epicenter shows no significant velocity difference these observations suggest large scale postseismic deformation with a relaxation time of at least 800 days the statistical significance of our observations is complicated by our incomplete knowledge of the noise properties of the two data sets two possible noise models fit the pgga data equally well as described in the companion paper by zhang et al this issue the pre landers data are too sparse and heterogeneous to derive a reliable noise model under a fractal white noise model for the pgga data we find that the velocity differences for all three sites are statistically different at the 99 significance level a white noise plus flicker noise model results in significance levels of only 94 43 and 88 additional investigations of the pre landers data and analysis of longer spans of pgga data could have an important effect on the significance of these results and will be addressed in future work

influence of initial fines content on fabric of soils subjected to internal erosion seepage induced internal erosion often happens in earth structures this paper presents experimental investigations on the influence of initial fines content on fabric of soils subjected to interna

experimental investigation of initiation of backward erosion piping in soils experiments were conducted on field and laboratory mixed soils in a new true triaxial test apparatus to assess factors that influence initiation of piping in non cohesive and cohesive soils three modes of piping behaviour were recognised concentrated leak erosion backward erosion and suffusion the amount and type of the fines present in the soils significantly influenced the initiation and mode of piping the presence of non plastic fines significantly reduced the required seepage velocity to initiate piping critical seepage velocity whereas the presence of plastic fines greatly increased the hydraulic gradient required to initiate piping concentrated leak erosion occurred along the soil apparatus interface in soils with plastic fines at very low seepage velocity but required very high hydraulic gradients backward erosion was the primary mode of failure in non cohesive soils and this mode required a seepage velocity of 0 8 1 1 cm s to initiate piping in uniform sand the critical seepage veloc

prospects for larger or more frequent earthquakes in the los angeles metropolitan region far too few moderate earthquakes have occurred within the los angeles california metropolitan region during the 200 year long historic period to account for observed strain accumulation indicating that the historic era represents either a lull between clusters of moderate earthquakes or part of a centuries long interseismic period between much larger moment magnitude m w 7 2 to 7 6 events geologic slip rates and relations between moment magnitude average coseismic slip and rupture area show that either of these hypotheses is possible but that the latter is the more plausible of the two the average time between m w 7 2 to 7 6 earthquakes from a combination of six fault systems within the metropolitan area was estimated to be about 140 years

experiments on piping in sandy gravels tests on internally unstable sandy gravels show that a significant proportion of the sand content is washed out by piping at hydraulic gradients far lower than the critical gradient given by a classical theory the probable explanation is that a major part of the overburden load is carried on a framework of gravel particles leaving the sand under relatively small pressures by contrast piping of the sand from stable sandy gravels occurs at approximately the full theoretical gradient the tests broadly confirm kenney s criterion for the internal stability of granular materials des essais realises sur des graves sableuses a instabilite interne importante montrent qu une proportion non negligeable du sable est lessivee pour des gradients hydrauliques bien inferieurs au gradient critique donne par les theories classiques l explication la plus probable est que la majeure partie de la surcharge des couches subjacentes est transmise au reseau des particules graveleuses le sable n etant alors plus soumis qu

investigation of the yellow river buried fault in the wuhai basin northwestern ordos block china using deep shallow seismic reflection and drilling techniques abstract studying the faults in wuhai basin which is located in the northwestern corner of the ordos block in china can not only guide earthquake safe construction in the region but also provide a greater understanding of the structure of the wuhai basin and the dynamic environment of northwestern ordos block in this study we effectively detected the yellow river buried fault yrf which we believe currently presents a risk to human life in the area first we laid out a deep seismic reflection profile dsrp in the north of the wuhai basin and found that the yrf is composed of two subparallel faults the east branch of the yellow river buried fault eyf and the west branch of the yellow river buried fault wyf which formed a y type graben in the section we then used 25 shallow seismic exploration profiles to find out how the faults are distributed finally we used drillings and quaternary dating methods to certify their existence and obtain their activity parameters we used the sequence stratigraphy method to compare sediment strata and identified paleo earthquake events by finding the unequal thickness layers utls on both sides of the fault the drillings revealed that four earthquakes occurred on the yrf around 25 6 0 11 ka bp 39 5 0 45 41 7 0 57 ka bp 58 25 7 13 ka bp and 111 1 21 ka bp since the last activity on the yrf occurred much longer ago than its estimated recurrence cycle we believe that the fault yrf currently presents a dangerous risk our study confirms that the yrf is a normal fault graben and that the wuhai bain is an extensional basin formed by the relative movement of the tibetan plateau the alashan block and the ordos block

interlaminated ice proximal glacimarine sediments in muir inlet alaska muir inlet in glacier bay alaska is a glacial fjord receiving a tremendous volume of sediment annually the rate of sediment accumulation is greatest proximal to muir glacier about 9 m yr 1 and decreases away from the glacier the primary sediment sources are meltwater streams discharging at subglacial and ice marginal positions to form overflows interflows and underflows continuous turbidity currents overflows and interflows interact with diurnal tidal currents and their volume and sediment concentration varies diurnally and annually with meltwater discharge these effects produce cyclic deposits of a thin fine grained sand or silt lamina that grades normally to a thicker poorly to very poorly sorted mud lamina this lamina couplet is termed a cyclopel underflows are suggested to occur in this glacimarine environment because of conditions unique to subglacial fluvial systems underflow deposits occur only in proximal positions 0 5 km from glacier face and are coarse grained reverse to normal graded and exhibit an increase in sorting and sand content up layer ice rafted debris identified as particles 177 m is ubiquitous though low 5 by weight and occurs as isolated particles frozen pellets or as lenses that in cores may have a lamina appearance proximally ice rafted debris is difficult to identify because proximal sediment is often as coarse grained deposited sediment may be reworked by tidal currents and sediment gravity flows depositional processes operating in muir inlet produce interlaminated sand silt clay that characterizes sediment proximal to a glacier and fines seaward to mud sediment is classified into one of three sediment types 1 1 type i sediment is very fine grained mean 8 65 7 17 o low in sand 0 1 11 2 and very poorly to poorly sorted it is the dominant sediment type in muir inlet and is transported by plumes and deposited by suspension settling 2 2 type ii sediment is fine to coarse grained mean 6 70 3 12 o low to high in sand 5 1 86 6 and very poorly to moderately sorted it represents reworked sediment proximal plume deposits or coarse grained laminae of cyclopels 3 3 type iii sediment is coarse grained mean 3 89 2 38 o high in sand 58 0 100 0 and poorly to well sorted it is deposited by sediment gravity flows or underflows

laboratory modeling of the mechanisms of piping erosion initiation a laboratory modeling program has been conducted to assess the mechanics of initiating the piping erosion process in sandy soils the models were performed on several soils differing in gradation grain size grain shape and specific gravity observations and monitoring of pore pressures within the samples during the modeling identified four stages in the development of piping initiation initial movement progressive heave boil formation and total heave by linking the observed behavior with the measured pore pressure regime in the sample a model for the mechanics of piping development has been developed finite element seepage analyses were performed to model the progression of piping development in the laboratory models and corroborate the developed model of mechanics the findings of the study identified a new model for the initiation of piping development that can be applied to the assessment of piping in the field

kinematics of fault related folding derived from a sandbox experiment we analyze the kinematics of fault tip folding at the front of a fold and thrust wedge using a sandbox experiment the analog model consists of sand layers intercalated with low friction glass bead layers deposited in a glass sided experimental device and with a total thickness h 4 8 cm a computerized mobile backstop induces progressive horizontal shortening of the sand layers and therefore thrust fault propagation active deformation at the tip of the forward propagating basal decollement is monitored along the cross section with a high resolution ccd camera and the displacement field between pairs of images is measured from the optical flow technique in the early stage when cumulative shortening is less than about h 10 slip along the decollement tapers gradually to zero and the displacement gradient is absorbed by distributed deformation of the overlying medium in this stage of detachment tip folding horizontal displacements decrease linearly with distance toward the foreland vertical displacements reflect a nearly symmetrical mode of folding with displacements varying linearly between relatively well defined axial surfaces when the cumulative slip on the decollement exceeds about h 10 deformation tends to localize on a few discrete shear bands at the front of the system until shortening exceeds h 8 and deformation gets fully localized on a single emergent frontal ramp the fault geometry subsequently evolves to a sigmoid shape and the hanging wall deforms by simple shear as it overthrusts the flat ramp system as long as strain localization is not fully established the sand layers experience a combination of thickening and horizontal shortening which induces gradual limb rotation the observed kinematics can be reduced to simple analytical expressions that can be used to restore fault tip folds relate finite deformation to incremental folding and derive shortening rates from deformed geomorphic markers or growth strata

regional propagation characteristics and source parameters of earthquakes in northeastern north america abstract the vertical components of the s wave trains recorded on the eastern canadian telemetered network ectn from 1980 through 1990 have been spectrally analyzed for source site and propagation characteristics the data set comprises some 1033 recordings of 97 earthquakes whose magnitudes range from m 3 to 6 the epicentral distances range from 15 to 1000 km with most of the data set recorded at distances from 200 to 800 km the recorded s wave trains contain the phases s s m s s n and l g and are sampled using windows that increase with distance the acceleration spectra were analyzed from 1 0 to 10 hz to separate the source site and propagation characteristics an inversion for the earthquake corner frequencies low frequency levels and average attenuation parameters is alternated with a regression of residuals onto the set of stations and a grid of 14 distances ranging from 25 to 1000 km the iteration between these two parts of the inversion converges in about 60 steps the average attenuation parameters obtained from the inversion were q 1997 10 and 0 998 0 003 the most pronounced variation from this average attenuation is a marked deamplification of more than a factor of 2 at 63 km and 2 hz which shallows with increasing frequency and increasing distance out to 200 km the site response spectra obtained for the ectn stations are generally flat the source spectral shape assumed in this inversion provides an adequate spectral model for the smaller events m o 21 dyne cm in the data set whose brune stress drops range from 5 to 150 bars for the five events in the data set with m o 10 23 dyne cm however the source spectra obtained by regressing the residuals suggest that an 2 spectrum is an inadequate model for the spectral shape in particular the corner frequencies for most of these large events appear to be split so that the spectra exhibit an intermediate behavior where u is roughly proportional to

mechanism of the progressive failure of non cohesive natural dam slopes abstract progressive failure which begins in the downstream slopes of dams is one of the main failure modes for natural dams in the field however this failure mode lacks attention in the scientific literature especially regarding its formation mechanism in this paper flume tests were conducted to simulate the progressive failure of a natural dam the results show that the progressive failure process is induced by seepage water discharging on the downstream slope including the erosion of individual soil particles repeated minor slip failures upward head cutting erosion of the dam crest and finally the collapse of the dam when the processes have evolved sufficiently this study focuses on analyzing the initiation mechanism of soil particle migration the influence of seepage and interflow stresses on the incipient erosion of soil particles is analyzed in addition the buoyancy of soil particles on the downstream slope surface is not considered in the vertical direction in this paper but in the direction perpendicular to the downstream slope surface the paper also discusses how to estimate the occurrence of the progressive failure of a natural dam in the estimation method the stress of the interfacial flow the seepage flow stress and the friction stress of the soil particles are considered when the phreatic line reaches the downstream slope surface

flume scale experiments on suffusion at the bottom of cutoff wall in sandy gravel alluvium this paper presents a series of flume scale experiments to investigate suffusion at the bottom of a cutoff wall in an internally unstable sandy gravel alluvium the initiation progression and potential failure of suffusion and the interactive effects of geomechanical and hydraulic conditions with the evolution of suffusion were investigated in this particular application temporal and spatial development of pore pressure earth pressure and settlement demonstrated suffusion was a multi phase involving pore water fine and coarse fractions and multi field involving seepage seepage induced fine fraction variation and stress deformation coupling phenomenon suffusion initiated at the downstream side of the tip of the cutoff wall and then generally progressed backward to the upstream side the monitored earth pressure provided an evidence of the heterogeneous stress distribution in internally unstable soil two linear empirical formulas for average hydraulic gradients at the initiation of suffusion a

spatial and temporal progression of internal erosion in cohesionless soil permeameter tests were performed on four widely graded cohesionless soils to study their susceptibility to in ternal erosion test specimens were reconstituted as a saturated slurry consolidated and then subjected to multi stage seepage flow under increasing hydraulic gradient the occurrence of internal instability is described qualitatively from vis ual observations through the wall of the permeameter during a test and from post test observations it is also described quantitatively from change of hydraulic gradient within the specimen and from axial displacement during a test the re sults provide a novel insight into the spatial and temporal progression of seepage induced internal instability this insight yields an improved characterization of suffusion and suffosion in cohesionless soils the progression of which appears gov erned by a critical combination of hydraulic gradient and effective stress resume des essais en permeametre ont eterealises sur quatre sols sans cohesion et agranulometrie etalee afin d etudier leur susceptibilitea l erosion interne les echantillons ont etereconstitues sous forme de pulpe saturee consolidee et en suite soumise aun ecoulement multi etapes sous un gradient hydraulique qui augmente l apparition de l instabiliteinterne est decrite de facon qualitative a partir d observations visuelles a travers la paroi du permeametre durant l essai ainsi que par des observations post essai l instabiliteinterne est aussi decrite quantitativement apartir des variations du gradient hydraulique al interieur des echantillons et du deplacement axial durant l essai les resultats offrent une vision nouvelle de la progression spatiale et temporelle de l instabiliteinterne causee par l infiltration ces resultats apportent une meil

seismicity and shape of the subducted nazca plate an updated compilation of earthquake locations and focal mechanism solutions from the international seismological centre and preliminary determination of earthquakes is the basis of a comprehensive study of the geometry of the wadati benioff zone beneath western south america the new data support previous mapping of a sharp flexure rather than a tear in the subducted nazca plate beneath southern peru and provide evidence for a similar flexure in the southward transition from nearly horizontal subduction to a slab with 30 dip at latitude 33 s in contrast the transition from 30 slab dip beneath bolivia to a nearly horizontal dip in the region between 28 s 32 s is more gradual occurring over several hundred kilometers of along strike distance between 20 s and 32 s this southward flattening corresponds to a broadening of a horizontal benchlike part of the subducted plate formed between 100 and 125 km depth the transition in continental tectonic style near 27 s 28 s from a wide volcanically active plateau to a narrow nonvolcanic cordillera appears not to be associated with the main slab flattening which begins to the north of these latitudes but with a more abrupt change in curvature of the subducted slab from convex upward to concave upward immediately below the plate boundary interface the concept of gaussian curvature is applied to slab bending to explain how subduction geometry is affected by the shape of the south american plate we hypothesize that the polarity of vertical curvature in the subducting slab is governed by the orientation of lateral curvature of the plate margin focal mechanism solutions for intermediate and deep earthquakes are grouped by geographic region and inverted for the orientation and relative magnitudes of the principal stresses results of the inversion indicate that downdip extension dominates in the slab above 350 km while downdip compression dominates at greater depths

the relationship between the geometry of normal faults and that of the sedimentary layers in their hanging walls abstract we derive an analytical expression that relates the shape of a fault in cross section to the shape of the bedding horizons in its hanging wall block the expression assumes that the hanging wall deforms by simple shear and that the footwall remains undeformed throughout although this paper concentrates on normal faults the expression is equally valid and applicable to thrust faults the direction of simple shear in the hanging wall block is arbitrary and has a dramatic effect on the predicted fault or bedding geometry there is no reason to believe that the simple shear occurs on vertical planes as is commonly assumed in graphical approaches to this problem and ignoring the presence of inclined simple shear is likely to lead to considerable underestimates of the amount of extension across normal faults and in the amount of shortening across thrusts similar though more complicated expressions can be obtained when compaction within the hanging wall block is taken into account for a planar normal fault such compaction may result in the development of a hanging wall syncline

critical hydraulic gradients of internal erosion under complex stress states abstractinternal erosion involves selective loss of fine particles within the matrix of coarse soil particles under seepage flow which affects the hydraulic and mechanical behavior of the soil in this research extensive laboratory internal erosion tests were conducted under complex stress states following three stress paths isotropic drained triaxial compression and triaxial extension stress paths these tests were designed to investigate the initiation and development of internal erosion and the effect of stress state on critical hydraulic gradients the entire erosion process can be divided into four phases stable initiation development and failure accordingly three critical gradients termed as initiation skeleton deformation and failure hydraulic gradients can be defined these critical gradients correspond to the onset of erosion of the fine particles filling the large pores of the skeleton the buckling of the strong force chains formed by the coarse particles and the soil failure re

visualisation of seepage induced suffusion and suffosion within internally erodible granular media a rigid walled transparent soil permeameter has been developed to study visually the mechanisms occurring during seepage induced internal erosion in susceptible granular media under upward flow

crustal deformation in the south central andes backarc terranes as viewed from regional broad band seismic waveform modelling summary the convergence between the nazca and south america tectonic plates generates a seismically active backarc region near 31 s earthquake locations define the subhorizontal subducted oceanic nazca plate at depths of 90 120 km another seismic region is located within the continental upper plate with events at depths 1 80 th 45 55 km than those of the eastern sierras pampeanas vp 6 0 6 2 km s 1 vp vs 1 70 th 27 35 km in addition we observed an apparent distribution of reverse crustal earthquakes along the suture that connects those terranes finally we estimated average p and t axes over the charge period the entire region showed p and t axis orientations of 275 and 90 plunging 6 and 84 respectively

seismicity and geometry of a 110 km long blind thrust fault 2 synthesis of the 1982 1985 california earthquake sequence during 1982 1985 three 5 4 mw 6 5 earthquakes migrated 65 km along the north half of a string of quaternary folds at the east front of the california coast ranges there is no surface fault associated with these earthquakes but the fold chain oriented parallel to the san andreas fault 30 km to the west takes up contraction normal to the san andreas fault identification of active blind thrust faults is hindered by the absence of a fault trace but may be revealed by the presence of growing folds at the surface and by earthquakes at depth because of excellent seismic geodetic and geologic data this earthquake sequence illuminates the geometry of the blind faults and enables us to probe their mechanics we relocate seismicity and compute focal mechanisms in a three dimensional velocity space and model the vertical deformation associated with the 1983 m 6 5 coalinga earthquake the aftershock zones abut at echelon offsets in the fold axes and the mainshocks display reverse slip perpendicular to the axes suggesting that the folds conceal a contiguous segmented thrust fault background seismicity concentrates at bends and breaks in the fold chain sites that may correspond to tears and ramps in the thrust fault at depth seismic reflection profiles reveal thrust and reverse faults dipping toward the san andreas fault at depths of 5 10 km with several kilometers of cumulative slip and high angle reverse faults in the anticlines with several hundred meters cumulative slip coseismic fold uplift accompanied the coalinga and kettleman hills north dome earthquakes suggesting that fold growth is episodic and coupled closely to repeated earthquakes on the underlying thrusts the north half of the fold chain has been the site of several 6 m 6 5 earthquakes since 1885 thus kettleman hills middle dome the next fold segment to the south has an elevated seismic potential the aftershock zones of the three main shocks are diffuse and occupy a region much larger than the site of seismic slip aftershocks occur 5 7 km from the fault regions where on the basis of a boundary element model the shear strain increase caused by the fault slip exceeds 20 ppm equivalent to about 0 7 mpa we argue that the broad aftershock zone is a product of high sustained off fault stress caused by repeated displacement on faults that do not cut the earth s surface the fault tip stresses lead to the formation of secondary faults which can become sites of aftershocks and postseismic creep

an automatic method for determining three dimensional normal fault geometries we describe a general kinematic method for automatically determining the three dimensional 3 d geometry of normal faults at depth from the 3 d geometry of deformed hanging wall horizons the method should be applicable to normal faults which do not change shape as deformation proceeds it is a generalization of two dimensional models and assumes that the hanging wall deforms by arbitrarily inclined bulk simple shear deformation in three dimensions is parameterized by the three euler angles which describe the horizontal slip vector the rake angle and the inclination of shear planes as in two dimensions differential compaction can be included by assuming that the axis of shortening is parallel to the direction of shear three dimensional fault geometry and the three euler angles can all be automatically determined provided the geometries of two or more hanging wall horizons are known here the method is tested on both synthetic data and on 3 d sand box models synthetic modeling shows that unique solutions can be found and more importantly that the horizontal slip vector can be constrained solutions obtained from sand box models are also encouraging in most cases the method can predict automatically the correct direction of extension and a 3 d fault geometry close to the fault geometry used hence arbitrarily inclined bulk simple shear appears to be a good approximation of hanging wall deformation in three dimensions this general method will allow 3 d palinspastic analysis to be undertaken on 3 d seismic reflection data sets

the seasonal circulation of the glacier bay alaska fjord system the seasonal circulation in glacier bay an alaskan fjord system with active tidewater glaciers is derived from oceanographic data collected on 13 cruises from june 1964 to september 1967 the fjord bottom waters were renewed annually between november and april by saline intrusion over the 69 m deep entrance sill in february the inlet waters were homogeneous with temperature of 3 c and salinity of 31 0 freshwater runoff derived from melting glacial ice stored runoff and precipitation led to a pycnocline formation in april or may the deepening pycnocline cut off the saline intrusion at the entrance sill the period from april to november was characterized by the downward mixing of brackish surface waters some evidence is presented for mixing by tidally induced internal waves these waves oscillate at twice the tidal frequency and have amplitudes of at least 50m vertical diffusion coefficients of the order of 5 0 cm2s 1 are reported the topographic influence of the glaciated terrain and retreating glaciers on the fjord circulation is demonstrated

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

high rates of late cenozoic crustal shortening in the andean foreland mendoza province argentina at least 16 km of pliocene shortening occurred beneath the la pilona anticline an oil producing structure that lies along the east flank of the argentine andes near the city of mendoza balanced cross sections show that the anticline which is expressed at the surface by late cenozoic strata overlies imbricated paleozoic and triassic strata that are bounded above and below by detachment surfaces with opposing vergence local and regional geochronologic data dictate that shortening occurred during an interval that was less than 2 7 m y and probably less than 1 0 m y shortening rates therefore must have exceeded 0 6 cm yr and probably exceeded 1 6 cm yr shortening rates in ancient foreland fold and thrust belts are generally between 0 2 and 0 5 cm yr but these long term averages probably incorporate periods of tectonic inactivity as well as pulses of deformation this study suggests that rates of motion on major structures at the deformation front may be five to ten times greater than shortening rates averaged over the entire history of a thrust belt dynamic models of foreland shortening must be able to account for these deformation pulses

coseismic growth of basement involved anticlines the northridge laramide connection seismogenic thrust faults in the transverse ranges of southern california may provide analogues for interpreting kinematic data from some laramide anticlines in the southern rocky mountains the 1994 northridge earthquake m w 6 7 occurred on a southwest dipping blind thrust fault beneath the transverse ranges and resulted in incremental growth of a basement involved fault propagation fold analyses of geodetic data and aftershock focal mechanisms show that deformation of the hanging wall block consisted of two major components 1 a large scale elastic strain characterized by horizontal shortening normal to the fault and horizontal lengthening parallel to the fault that was imposed by reverse slip on the underlying blind thrust during the main shock and 2 postseismic cataclastic flow with a geometry comparable to the coseismic strain including horizontal fault parallel lengthening of the hanging wall block which was accommodated at least in part by distributed aftershock activity fault and fold parallel lengthening strains similar to those observed during the northridge earthquake have been obtained by inversion of fault slip data from some laramide basement involved anticlines the northridge analogue suggests that distributed brittle faulting of the crystalline basement may reflect aftershock deformation during incremental growth of the laramide folds if so then the laramide structures provide examples now exposed by erosion of the mature internal structure of the active basement involved folds in the transverse ranges

an elusive blind thrust fault beneath metropolitan los angeles seismic reflection profiles petroleum wells and relocated earthquakes reveal the presence of an active blind thrust fault beneath metropolitan los angeles a segment of this fault likely caused the 1987 whittier narrows magnitude 6 0 earthquake mapped sizes of other fault segments suggest that the system is capable of much larger magnitude 6 5 to 7 and more destructive earthquakes

comparison of two criteria for internal stability of granular soil internal instability describes the loss of soil particles as a result of seepage two criteria are commonly used to determine the potential for such instability within a granular soil that is subje

the applicability of microbially induced calcite precipitation micp for internal erosion control in gravel sand mixtures seepage induced internal erosion in earth filled embankment dams has been attracting the attention of civil engineering researchers and practitioners for decades microbially induced carbonate prec

does calving matter evidence for significant submarine melt abstract during the summer in the northeast pacific ocean the alaska coastal current sweeps water with temperatures in excess of 12 c past the mouths of glacierized fjords and bays the extent to which these warm waters affect the mass balance of alaskan tidewater glaciers is uncertain here we report hydrographic measurements made within icy bay alaska and calculate rates of submarine melt at yahtse glacier a tidewater glacier terminating in icy bay we find strongly stratified water properties consistent with estuarine circulation and evidence that warm gulf of alaska water reaches the head of 40 km long icy bay largely unaltered a 10 20 m layer of cold fresh glacially modified water overlies warm saline water the saline water is observed to reach up to 10 4 c within 1 5 km of the terminus of yahtse glacier by quantifying the heat and salt deficit within the glacially modified water we place bounds on the rate of submarine melt the submarine melt rate is estimated at 9 m d 1 at least half the rate at which ice flows into the terminus region and can plausibly account for all of the submarine terminus mass loss our measurements suggest that summer and fall subaerial calving is a direct response to thermal undercutting of the terminus further demonstrating the critical role of the ocean in modulating tidewater glacier dynamics

capillary tube model for internal stability of cohesionless soil abstractkovacs criterion to assess the potential for internal instability of cohesionless soils that was proposed but never tested experimentally is verified with reference to a database of laboratory test results the inherent margin of safety is described and a threshold boundary between stable and potentially unstable gradations is established a variation on the method is then presented termed the simplified kovacs criterion

geometric models of listric normal faults and rollover folds existing geometric models allow master fault shapes to be constructed given the shape and heave or displacement of a deformed marker horizon in the hanging wall these models assist in projecting normal faults to depth where the fault geometry is poorly constrained by available seismic data currently it is unclear which model best predicts the actual relation between rollover and fault geometries to address this deficiency the relative accuracies of the constant heave constant displacement constant bed length slip line and inclined shear constructions are evaluated using clay model analogs and seismic examples each of the geometric models predicts a different fault shape and depth to detachment for the same rollover shape because different hanging wall deformat on mechanisms are assumed a construction is developed for determining the hanging wall geometry from a known fault geometry this construction is based on the inclined shear model and geometric constraints imposed by material displacement paths viewed from different reference frames fixed to the hanging wall and footwall blocks in clay models the inclined shear antithetic shear greek alpha 20 degrees and slip line constructions produce the best agreement between actual and modeled fault and marker bed shapes in rollovers for subsurface examples the inclined shear model antithetic shear greek alpha 20 40 degrees and the constant displacement model predict fault trajectories that are the most similar to the positions and shapes of the master fault segments interpreted fr m offshore norway and gulf of mexico seismic lines the shear angle required in the inclined shear model can often be estimated from the orientation of minor faults in the hanging wall the shear angle may also be determined through iterative modeling in which the shear angle is systematically varied and the resultant model fault shape is compared to the shape of the shallow segment of the master fault interpreted from the seismic record

assessing uncertainties in balanced cross sections abstract balanced structural cross sections are models that are fit to incomplete data the models are under constrained with respect to any particular two dimensional line length model but enough data generally exists to yield a well constrained area balance solution furthermore the area balance encompasses all possible line length solutions therefore where the primary objective of section balancing is the determination of horizontal shortening magnitude area balancing provides an analytical solution we use this analytical solution to develop a comprehensive robust analysis of the uncertainty in shortening estimates resulting from cross section balancing the analytical solution allows us to propagate errors formally on the input parameters stratigraphic thicknesses depth to decollement eroded hanging wall cutoffs through the equations and produce the resulting uncertainty on the magnitude of shortening balanced cross sections from the subandean belt of the central andes are used to demonstrate the relative importance of stratigraphy and eroded hanging wall cutoffs in the contribution to the overall error

the dynamic controls on carbonate mineral saturation states and ocean acidification in a glacially dominated estuary abstract recently a number of studies have shown that the intrusion of anthropogenic carbon dioxide co2 into the ocean has created an acidification effect leading to the reduction in carbonate mineral saturation states however the uptake of atmospheric co2 is not the only climate induced phenomenon that leads to a reduction of in marine environments over the past 250 years glacier bay ak glba has experienced rapid deglaciation leading to an increase in the amount of freshwater entering the marine ecosystem this excess freshwater discharge is low in total alkalinity and reduces the buffering capacity of surface waters and enhances the vulnerability of the estuary to further reductions in ph the corresponding reduction in may cause these waters to become corrosive to shell building organisms to better understand these processes we collected monthly samples within glba that show the variability in throughout the water column low values were well correlated with the timing of maximum glacial discharge events and most prominent within the two regions where tidewater glacial discharge was highest the saturation state with respect to aragonite reached a minimum of 0 40 at the surface during the summer of 2011 before rebounding to a maximum value of 3 26 in the spring of 2012 aragonite was undersaturated at the surface throughout the entire bay during fall months sept and oct here we present results from a year long study designed to constrain the effects of glacial freshwater discharge on the marine carbonate system and discern the primary controls on in this pristine estuarine environment 1

hydromechanical modeling of granular soils considering internal erosion this paper attempts to formulate a coupled practical model in the framework of continuum mechanics to evaluate the phenomenon of internal erosion and its consequences on the mechanical behavior of

a study of a flowslide with significant entrainment in loess areas in china flowslides are a frequent type of natural disaster in loess areas and may result in the significant loss of properties and or casualties the dagou flowslide is a typical event in a loess area and is accompanied by significant sediment entrainment to analyze the mechanisms responsible for flowslides and to obtain the parameters for a runout analysis a field investigation was conducted specimens were sampled on site to carry out laboratory tests including a triaxial test sieve analysis and chemical component analysis the parameters were used in the runout study employing an energy based runout model an analytical entrainment model was adopted to calculate the entrainment after considering physical properties and the mechanism of the entrainment process of the loess finally the entrainment model was incorporated into the runout model to simulate the post failure process of this case energy dissipation due to the deformation of slices was considered as it was thought to be important for a slide with a significant deformation the simulation results were compared with the measurements including runout distance total volume erosion depth deposition height at different sections and velocities at specific locations the results indicate that the energy based runout model together with the entrainment model can capture the kinematic characteristics of the dagou flowslide therefore it is feasible to use this model to predict the runout characteristics of flowslides in similar areas copyright c 2017 john wiley sons ltd

determination of critical head in soil piping one of the main mechanisms of failure of levees is a phenomenon called piping which generally begins with the formation of a sand boil at the leeward side of the levee and has been frequently observed to proceed upstream along the base of the levee through a slit formation the issue of most important concern is to estimate the critical head that could promote the occurrence of piping considering the flow through porous media and coupling it with bernoulli s equation and a critical tractive stress condition a model is developed for the critical head using appropriate transformations the proposed model takes on a form which supports bligh s empirical findings another model based on critical velocity is also developed to estimate the critical head the functional form of these two models is evaluated using the critical head versus porosity data from a number of laboratory studies conducted in the netherlands these models were found to perform better than did terzaghi s model

influence of porosity on piping models of levee failure a piping model based on darcy s law is developed an analysis of data pertaining to different soil particle sizes and varying porosity shows that the choice of the permeability function is critical for the piping model the permeability relations which depend only on the grain size are of limited value

escape tectonics in the los angeles metropolitan region and implications for seismic risk recent damaging earthquakes in california including the 1971 san fernando1 1983 coalinga2 1987 whittier narrows3 and 1994 northridge4 events have drawn attention to thrust faults as both potentially hazardous seismic sources and as a mechanism for accommodating shortening in many regions of southern california consequently many geological studies5 6 have concluded that thrust faults in southern california pose the greatest seismic hazard and also account for most of the estimated 5 7 mm yr 1 of contraction across the greater los angeles metropolitan area7 8 indicated by global positioning system geodetic measurements9 our study demonstrates however that less than 50 of the geodetically observed contraction is accommodated on the principal thrust systems across the los angeles region we integrate the most recent geological geodetic and seismological data to assess the spatial distribution of strain across the los angeles metropolitan region we then demonstrate that a significant component of seismic moment release and shortening in this region is accommodated by east west crustal escape extrusion along known strike slip and oblique slip faults

observations on internal stability of cohesionless soils introduction internal stability refers to the ability of the coarser fraction of a soil to prevent migration of its finer fraction as a result of seepage flow skempton brogan 1994 report findings from piping tests on four well graded to gap graded sandy gravels flow was imposed in an upward direction without surcharge loading and without vibration an abrupt transition was noted from stable to unstable states defined by the ratio d9 15 d9 85 1 4 4 as postulated by kezdi 1979 and attributed to work published in 1969 the latter concept was conceived independently by de mello 1975 advocated by sherard 1979 for a ratio 4 to 5 and recommended by lowe 1988 for a ratio of 5 it involves splitting the gradation at arbitrary points along the curve to yield d9 15 of the coarse fraction and d9 85 of the fine fraction as illustrated in fig 1 for gradation g3 c in this study we further evaluate the kezdi 1979 criterion through laboratory permeameter testing of five soils fig 1 and table 1 and compare the results with a dataset of 34 gradations extracted from kenney lau 1985 1986 and honjo et al 1996

crustal motion in the southern andes 26 36 s do the andes behave like a microplate 1 a new global positioning system gps derived velocity field for the andes mountains 26 36 s allows analysis of instantaneous partitioning between elastic and anelastic deformation at the orogen s opposing sides adding an andes microplate to the traditional description of nazca south america plate convergence provides the kinematic framework for nearly complete explanation of the observed velocity field the results suggest the oceanic nazca boundary is fully locked while the continental backarc boundary creeps continuously at 4 5 mm yr the excellent fit of model to data 1 7 mm yr rms velocity misfit and the relative aseismicity of the upper crust in the interior andean region in comparison with its boundaries supports the notion that the mountains are not currently accruing significant permanent strains additionally the model implies permanent deformation is not accumulating throughout the backarc contractional wedge but rather that the deformation is accommodated only within a narrow deformational zone in the backarc

analysis of the january 26th 1985 mendoza argentina earthquake effects and of their possible correlation with the recorded accelerograms and soil conditions abstract an analysis was made of the distribution of effects produced by mendoza argentina earthquake of january 26 1985 mb 6 0 which affected one of the most important urban agglomerates of western argentina housing more than 800 000 inhabitants the epicenter was located at distances of 15 and 50 km from the closest and farthest ends of the urban area respectively damage distribution was not uniform some small areas reached a maximum intensity of viii mm damage indexes were defined from the information provided by damage surveying these indexes relate the degree of damage suffered by adobe constructions with respect to the total number of them also the distribution of damaged constructions as a function of their age was analyzed many strong motion records were obtained during this earthquake five accelerograms were recorded at sites located in the highly populated area several seismoscope records were also obtained some of them at the same sites as the accelerograms peak ground accelerations in gran mendoza varied between 0 10 and 0 41 g the analysis of all these records gave information on spectral acceleration spectral amplification and prevailing periods two types of subsoil conditions prevail in the area studied shallow stiff soils and deep soils the former are soils with less than 20 m of depth to the high shear wave velocity materials while the latter have more than 20 m to that material the spatial distribution of both types of soils was accurately known from the information provided by many drillings and several surface geophysical measurements this knowledge allowed the soil types to be relate with damage distribution and strong motion record parameters the results obtained show no relation between damage intensities and subsoil conditions the best example of this conclusion was observed in the two places where higher intensities were recorded in agreement with the higher values of peak accelerations while the subsoil conditions were completely different however a fairly good relation was obtained between intensity of damage and age of the construction

experimental investigation of global backward erosion and suffusion of soils in embankment dams many embankment dams constructed with a core of nonplastic or very low plasticity silt sand gravel typically of glacial fluvioglacial or alluvial origin have experienced internal erosion this h

erosion of silty sand tailings through a geomembrane defect under filter incompatible conditions at tailings storage facilities a geomembrane may be used to contain tailings from relatively more permeable foundation or embankment materials a filter incompatible condition may arise between the tailings and underliner materials in this study potential for piping erosion of tailings through a 1 cm diameter geomembrane defect was evaluated in a series of physical experiments the geomembrane defect was sandwiched between silty sand tailings and various underliners df15 db85 5 6 to 13 5 not meeting typical retention criteria for filtration the leakage rates and visual findings revealed that a critical stress condition existed where erosion continuously occurred for up to 24 hours this stress condition could be encountered during early deposition or development of a reclaim pond at a tailings storage facility when allowed to occur erosion during this stress condition resulted in subsequent leakage rates that were 2 to 3 orders of magnitude higher than previously observed with filter compatible c

sill processes related to deep water renewal in a fjord observations of the gravitational circulation over the sill at the entrance to puget sound indicate a fortnightly modulation of the two layer flow with a corresponding variation in stratification gravitational circulation and stratification reach a maximum during neap tides and a minimum during spring tides the modulation appears to be a function of the turbulence generation by tidal flow over the sill which varies as a function of tidal amplitude the enhanced gravitational circulation during neap tides augments the flux of dense water across the sill region and episodes of bottom water renewal in puget sound result intrusions of dense water in the main basin of the sound show a fortnightly periodicity with a phase lag appropriate for the propagation of an internal bore from the sill region commencing at the neap tide observations indicate that the intrusions take the form of gravity currents propagating at approximately 20 cm s 1 down the main basin the detailed dynamics of the turbulent mixing processes that modulate the onset of inflow were not resolved in this study but the integrated effect of tidal mixing on the low frequency circulation is clearly demonstrated

laboratory model tests on water inrush in foundation pit bottom numerous deep foundation pits were constructed in china in the course of urbanization water inrush is one of the most important causes of foundation pit accidents at present few images and detail courses of the water inrush have been recorded and reported the evidences for the hypothesis of water inrush calculation are not enough in this study model tests were performed to verify the water inrush course in foundation pit bottom the water inrush modes of foundation pits were analyzed for the aquitards that included clay and silty clay in shanghai china the deformation and failure characteristics of the layers under different water pressures were obtained the deformation course without water inrush was divided into three stages continuous deformation progressive deformation and equilibrium stages the deformation course with water inrush was divided into four stages continuous deformation progressive deformation shear failure and water inrush and sinking stages the course included creep deformation and micro cracks development before failure it was not an instantaneous phenomenon but a time depending one the pore water pressure was the response of aquitard to boundary water pressure which indicated the seepage in low permeable aquitard and the development of micro cracks the water inrush formula was verified and tested using the model test results the limit equilibrium method had larger safe reserves and the prestressed homogeneous continuous beam method was relatively accurately

seasonal variability of the circulation system in a west greenland tidewater outlet glacier fjord godthabsfjord 64 n many tidewater outlet glacier fjords surround the coast of greenland and their dynamics and circulation are of great importance for understanding the heat transport toward glaciers from the ice sheet thus fjord circulation is a critical aspect for assessing the threat of global sea level rise due to melting of the ice sheet however very few observational studies describe the seasonal dynamics of fjord circulation here we present the first continuous current measurements april november from a deep mooring deployed in a west greenland tidewater outlet glacier fjord four distinct circulation phases are identified during the period and they are related to exchange processes with coastal waters tidal mixing and melt processes on the greenland ice sheet during early summer warm intermediate water is transported toward the glacier at an average velocity of about 7 cm s 1 in late summer the average velocity decreases to 3 cm s 1 during a period with significant subglacial freshwater discharges during this period a large variability in current velocities is also observed the associated average heat transport in an intermediate depth range corresponds to 568 gw in early summer and is reduced to 287 gw in late summer these heat fluxes are at the higher end of previously reported fluxes our measurements show that the intermediate heat transport varies over time and during summer provides a major contribution to the heat budget and thereby potentially to glacial melt we suggest that intermediate heat transport may play a similar important role in other fjords around greenland

evaluation analysis and prediction of geologic structures abstract balanced cross sections claim to be better because they apply a rigorous set of rules to develop the conceptual model of the structures present in an area balanced cross sections can be further improved and become more useful to understanding real physical problems by collection of additional data such as seismic reflection surveys collection of additional stratigraphic data or collection of rock fabric information the additional information validates the initial model and provides details on deformation conditions and on local rock responses to the deformation although individual cross sections are two dimensional the objective of evaluation and analysis of deformed regions should be three dimensional whenever possible to recognize the challenges of the real world subsurface system analysis derived from the hydrologic community emphasizes conceptual model development through model verification validation uncertainty quantification benchmarking and meta analysis their approach includes many steps informally used by the structural geology community but in a much more explicit way newer geological applications of structural geology would benefit from this more rigorous approach for designing and doing performance predictions as technological needs become more socially sensitive such as for carbon storage sites new areas of energy exploration in higher population density areas or for nuclear waste storage facilities

glacier calving a numerical model of forces in the calving speed water depth relation empirical data suggest that the rate of calving of grounded glaciers terminating in water is directly proportional to the water depth important controls on calving may be the extent to which a calving face tends to become oversteepened by differential flow within the ice and the extent to which bending moments promote extrusion and bottom crevassing at the base of a calving face numerical modelling suggests that the tendency to become oversteepened increases roughly linearly with water depth in addition extending longitudinal deviatoric stresses at the base of a calving face increase with water depth these processes provide a possible physical explanation for the observed calving rate water depth relation

quaternary tectonics and seismic potential of the andean retrowedge at 33 34 s the andean retrowedge located between 338s and 348s lies in the transition region of the pampean flat slab subduction zone to the north and a normal subduction zone to the south neo tectonic structures and shallow seismicity are very common north of this segment and become pro gressively less frequent southwards the frontal cordillera and the cerrilladas pedemontanas are the main morphostructures involved in the quaternary deformation of this region the frontal cor dillera is a thick skinned fold and thrust belt uplifted since late miocene time the cerrilladas pedemontanas are low relief hills that represent the mild inversion of the cuyo triassic rift depo centre since pliocene time middle miocene holocene synorogenic strata cover the cuyo basin and surrounding foreland areas the quaternary tectonic evolution of this area has been established through integration of new data from fieldwork in the frontal cordillera piedmont with subsurface information and previously published data mean late pleistocene uplift rates ranging between 0 21 and 0 92 mm a 21 and earthquake minimum moment magnitudes mw o fc 6 4 6 7 have been estimated for the morphostructural units analysed in this manuscript

the 1987 whittier narrows earthquake sequence in los angeles southern california seismological and tectonic analysis the october 1 1987 whittier narrows earthquake m l 5 9 was located at 34 2 96 n 118 4 86 w at a depth of 14 6 0 5 km in the northeastern los angeles basin the focal mechanism of the mainshock derived from first motion polarities shows pure thrust motion on west striking nodal planes with dips of 25 5 and 65 5 respectively the aftershocks define an approximately circular surface that dips gently to the north centered at the hypocenter of the mainshock with a diameter of 4 6 km hence the spatial distribution of the mainshock and aftershocks as well as the focal mechanisms of the mainshock indicate that the causative fault was a 25 north dipping thrust fault striking west and is confined to depths from 10 to 16 km although most of the 59 aftershock focal mechanisms presented here document a complex sequence of faulting they are consistent with deformation of the hanging wall caused by the thrust faulting observed in the mainshock a cluster of reverse faulting events on north striking planes occurred within hours after the mainshock 2 km to the west of the mainshock the largest aftershock m l 5 3 occurred on october 4 and showed mostly right lateral faulting on the same north northwest striking plane within the hanging wall similarly several left lateral focal mechanisms are observed near the eastern edge of the mainshock rupture the earthquake and calibration blast arrival time data were inverted to obtain two refined crustal velocity models and a set of station delays when relocating the blast using the new models and delays the absolute hypocentral location bias is less than 0 5 km the mainshock was followed by nearly 500 locatable aftershocks which is a small number of aftershocks for this magnitude mainshock the decay rate of aftershock occurrences with time was fast while the b value was low 0 67 0 05 for a los angeles basin sequence

scour protection of partially embedded pipelines using sloping curtains abstracta geotextile mattress with sloping curtain gmsc was introduced to protect underwater pipelines from scour in steady currents gmsc is a newly developed countermeasure against river and es

fold style inversion placing probabilistic constraints on the predicted shape of blind thrust faults we develop a new methodology which compares quantitatively styles of folding from seismic reflection data the goal of the fold style inversion fsi method is to provide an objective choice of the most appropriate model used when solving for the shape of an unimaged blind fault from folded layer geometry fsi is a discretization of the dip isogon fold classification scheme reformulated as simple vector transformations a data set s goodness of fit to parallel class 1c or similar class 2 fold geometry is assessed by calculating misfit between the predicted and observed bed geometries through a grid search of the parameter space specific to each transformation the two fold types correspond to the constant bed length and arbitrarily inclined simple shear aiss fault solution routines respectively for seismic reflection data confidence estimates may be placed on the preference of fold style and its corresponding fault solution by monte carlo simulations of depth correlative spatially limited depth conversion errors for synthetic geometric examples fsi determines fold style preference and parameters exactly at low fold limb dips 15 the actual geometric difference between parallel and similar folds is very small and the difference between fold styles cannot be resolved highlighting a general difficulty in the analyses of young blind thrust structures for a synthetic seismic line of an aiss fault related fold the method chooses the correct folding style and leads to the correct fault geometry at depth in examples of real data from the barrancas lunlunta carrizal anticlinal complex in mendoza argentina fsi analysis determines 71 and 54 probability of similar preference for two seismic lines on separate structures the corresponding fault solutions for the first example are well constrained whereas for the second example the solutions are widely variant this analysis helps to quantify the relationship between the predicted sub surface fault trajectories and hypocenter and aftershock data of the 1985 mw 5 9 mendoza earthquake showing that the earthquake and the fault causing the barrancas lunlunta carrizal anticlinorium are most likely unrelated

uncertainty quantification in section balancing using pseudo 3d forward modeling example of the malargue anticline argentina abstract quantifying uncertainty in balancing cross sections is an insufficiently resolved challenge we present a new workflow to assess uncertainty of selected modeling parameters in contrast to conventional restoration we focus on forward modeling and mapping uncertainty in solution space we test the approach by applying trishear as the most appropriate mechanism reproducing associated fault fold systems we present a new structural model of the exceptionally well exposed thick skinned malargue anticline located in the malargue foldbelt neuquen basin argentina several structural models of varying quality have been published by oil explorers and researchers but lack detailed kinematic assessment to minimize uncertainty we systematically vary the key modeling parameters shortening and ramp angle to reduce the cross sectional area difference the misfit between model and observation we find that the misfit is highly sensitive to these two parameters the total uncertainty for a single structure w r t these values rarely undercuts 7 apparently dependencies exist between these parameters we recommend this method be extended to other parameter combinations and tectonic settings our analysis results in new shortening rates for the ma up to 1 57 mm yr and a refined genetic model whereby the anticline was generated during andean contraction rather than evolving from a pre existing structure

assessing the potential of internal instability and suffusion in embankment dams and their foundations suffusion is the process by which finer soil particles are moved through constrictions between larger soil particles by seepage forces soils susceptible to suffusion are described as internally unstable this technical note describes a method for assessing the potential of internal instability of silt sand gravel or clay silt sand gravel soils based on their particle size distribution based on laboratory tests carried out by the writers and results published by others it is shown that some commonly used methods are conservative for these soils

meltwater and tidal currents controls on circulation in a small glacial fjord mcbride inlet is a small glacial fjord that receives freshwater from a submarine tunnel at the base of a tidewater glacier at its head the upwelling buoyant plume mixes with basin water lowering the salinity throughout the ice proximal basin freshwater also upwells from the melting ice face but the effects are only important in winter when discharge is low deep water renewal occurs in summer because the water mass crossing the sill inward is denser than the deep basin water the thick low velocity surface layer is affected by tides and wind producing a slow moving gyre near the glacier meltwater discharge from a submarine position and the resultant circulation in mcbride inlet result in extremely high ice proximal sedimentation rates

multibend fault bend folding this paper shows how slightly complex but angular fault shapes with only a few bends lead to broadly curved and or highly complex folds a common perception exists that simple angular fold geometries are a necessary consequence of the normal assumptions of fault bend fold theory namely angular fault bends straight faults and flexural slip to the contrary it is shown here that exact application of these low level assumptions produces great complexity from simple fault shapes this complexity is caused by the combination of 1 generation of new axial surfaces by displacement of hangingwall cut offs past successive fault bends and 2 fragmentation of axial surfaces by mutual interference the result is entwined arrays of fold axial surfaces that produce quasi curved and or complex folds from discrete angular fault bends fold complexity grows in a highly non linear way in the most extreme case the number of fold axial surface segments grows as the fourth power of the number of fault bends this paper presents examples of the immense variety of complex fold geometries that are thus generated 0 1997 elsevier science ltd all rights reserved

experimental parametric study of suffusion and backward erosion within hydraulic earth structures dikes levees or dams internal seepage flows can generate the entrainment of the soil grains grain transportation affects both particle size distributions and porosity and changes the mechanical and hydraulic characteristics of the earth s structure the occurrence of failures in new earth structures due to internal erosion demonstrates the urgency of improving our knowledge of these phenomena of erosion with this intention a new experimental device has been developed that can apply hydraulic stresses to reconstituted consolidated cohesive soils without cracks in order to characterize the erosion evolution processes that might be present a parametric study was conducted to examine the influence of three critical parameters on clay and sand erosion mechanisms when the hydraulic gradient was low it was concluded that the erosion of the structure s clay fraction was due to suffusion when the hydraulic gradient increased it was concluded that the sand fraction erosion initiation was due to backward erosion the extent of the erosion was dependent on the clay content the study underlines the complexity of confinement stress effects on both erosion phenomena

cenozoic tectonics of the high andes of west central argentina 30 36 s latitude abstract the structure of the central andes shows three distinctive segments characterized by different geometries these geometries are superimposed on the present large scale plate tectonic setting characterized by distinct subduction segments the northern la ramada segment is a thick skinned fold and thrust belt formed by tectonic inversion of a late triassic rift the central aconcagua segment consists of a thin skinned fold and thrust belt while the southern malargue segment like the first one is a thick skinned fold and thrust belt developed by tectonic inversion of a late triassic early jurassic rift system during late cenozoic times the amount of shortening gradually decreases from north to south as indicated by the crustal roots of the central andes the different geometries along the principal cordillera controlled the abrupt changes in the shortening among segments the structure of precordillera and sierras pampeanas has also been considered in order to account for the total shortening in the la ramada segment the main shortening occurred in the precordillera in the aconcagua segment in the principal cordillera while in the malargue segment the shortening is widely distributed in a broader principal cordillera because south of the flat slab subduction segment the precordillera and sierras pampeanas are missing