[1] While it is widely recognized that highly permeable ‘large‐scale' fractures dominate chemical migration in many fractured aquifers, recent studies suggest that the pervasive ‘small‐scale’ fracturing once considered of less significance can be equally important for characterizing the spatial extent and residence time associated with transport processes. A detailed examination of chemical migration through fracture‐controlled aquifers is used to advance this conceptual understanding. The influence of fracture structure is evaluated by quantifying the effects to transport caused by a systematic removal of fractures from three‐dimensional discrete fracture models whose attributes are derived from geologic and hydrologic conditions at multiple field sites. Results indicate that the effects to transport caused by network simplification are sensitive to the fracture network characteristics, degree of network simplification, and plume travel distance, but primarily in an indirect sense since correlation to individual attributes is limited. Transport processes can be ‘enhanced’ or ‘restricted’ from network simplification meaning that the elimination of fractures may increase or decrease mass migration, mean travel time, dispersion, and tailing of the concentration plume. The results demonstrate why, for instance, chemical migration may not follow the classic advection‐dispersion equation where dispersion approximates the effect of the ignored geologic structure as a strictly additive process to the mean flow. The analyses further reveal that the prediction error caused by fracture network simplification is reduced by at least 50% using the median estimate from an ensemble of simplified fracture network models, and that the error from network simplification is at least 70% less than the stochastic variability from multiple realizations.
This paper reports on the analysis of the highest spatial resolution hyperspectral images acquired by the Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft during its prime mission. A bright area matches a flow-like feature coming out of a caldera-like feature observed in Synthetic Aperture Radar (SAR) data recorded by the Cassini radar experiment [Lopes et al., 2007. Cryovolcanic features on Titan's surface as revealed by the Cassini Titan Radar Mapper. Icarus 186, 395–412, doi:10.1016/j.icarus.2006.09.006]. In this SAR image, the flow extends about 160 km east of the caldera. The contrast in brightness between the flow and the surroundings progressively vanishes, suggesting alteration or evolution of the composition of the cryolava during the lifetime of the eruptions. Dunes seem to cover part of this flow on its eastern end. We analyze the different terrains using the Spectral Mixing Analysis (SMA) approach of the Multiple-Endmember Linear Unmixing Model (MELSUM, Combe et al., 2008). The study area can be fully modeled by using only two types of terrains. Then, the VIMS spectra are compared with laboratory spectra of known materials in the relevant atmospheric windows (from 1 to 2.78 μm). We considered simple molecules that could be produced during cryovolcanic events, including H2O, CO2 (using two different grain sizes), CH4 and NH3. We find that the mean spectrum of the cryoflow-like feature is not consistent with pure water ice. It can be best fitted by linear combinations of spectra of the candidate materials, showing that its composition is compatible with a mixture of H2O, CH4 and CO2.
","language":"English","publisher":"Elsevier","doi":"10.1016/j.pss.2009.03.005","usgsCitation":"Le Corre, L., Le Mouelic, S., Sotin, C., Combe, J.#., Rodriguez, S., Barnes, J.W., Brown, R.H., Buratti, B.J., Jaumann, R., Soderblom, J., Soderblom, L., Clark, R., Baines, K.H., and Nicholson, P.D., 2009, Analysis of a cryolava flow-like feature on Titan: Planetary and Space Science, v. 57, no. 7, p. 870-879, https://doi.org/10.1016/j.pss.2009.03.005.","productDescription":"10 p.","startPage":"870","endPage":"879","numberOfPages":"10","costCenters":[{"id":131,"text":"Astrogeology Science Center","active":true,"usgs":true}],"links":[{"id":243606,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"otherGeospatial":"Titan","volume":"57","issue":"7","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"5059eb02e4b0c8380cd48b58","contributors":{"authors":[{"text":"Le Corre, L.","contributorId":92874,"corporation":false,"usgs":false,"family":"Le Corre","given":"L.","email":"","affiliations":[],"preferred":false,"id":446969,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Le Mouelic, S.","contributorId":92786,"corporation":false,"usgs":false,"family":"Le Mouelic","given":"S.","affiliations":[],"preferred":false,"id":446968,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Sotin, Christophe","contributorId":53924,"corporation":false,"usgs":false,"family":"Sotin","given":"Christophe","email":"","affiliations":[],"preferred":false,"id":446963,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Combe, J. #NAME?","contributorId":37982,"corporation":false,"usgs":false,"family":"Combe","given":"J.","email":"","middleInitial":"#NAME?","affiliations":[],"preferred":false,"id":446961,"contributorType":{"id":1,"text":"Authors"},"rank":4},{"text":"Rodriguez, S.","contributorId":54329,"corporation":false,"usgs":false,"family":"Rodriguez","given":"S.","email":"","affiliations":[],"preferred":false,"id":446964,"contributorType":{"id":1,"text":"Authors"},"rank":5},{"text":"Barnes, J. W.","contributorId":14554,"corporation":false,"usgs":false,"family":"Barnes","given":"J.","email":"","middleInitial":"W.","affiliations":[],"preferred":false,"id":446958,"contributorType":{"id":1,"text":"Authors"},"rank":6},{"text":"Brown, R. H.","contributorId":19931,"corporation":false,"usgs":false,"family":"Brown","given":"R.","email":"","middleInitial":"H.","affiliations":[],"preferred":false,"id":446959,"contributorType":{"id":1,"text":"Authors"},"rank":7},{"text":"Buratti, B. J.","contributorId":69280,"corporation":false,"usgs":false,"family":"Buratti","given":"B.","email":"","middleInitial":"J.","affiliations":[],"preferred":false,"id":446966,"contributorType":{"id":1,"text":"Authors"},"rank":8},{"text":"Jaumann, R.","contributorId":81232,"corporation":false,"usgs":false,"family":"Jaumann","given":"R.","email":"","affiliations":[],"preferred":false,"id":446967,"contributorType":{"id":1,"text":"Authors"},"rank":9},{"text":"Soderblom, J.","contributorId":52699,"corporation":false,"usgs":false,"family":"Soderblom","given":"J.","affiliations":[],"preferred":false,"id":446962,"contributorType":{"id":1,"text":"Authors"},"rank":10},{"text":"Soderblom, L.A. 0000-0002-0917-853X","orcid":"https://orcid.org/0000-0002-0917-853X","contributorId":6139,"corporation":false,"usgs":true,"family":"Soderblom","given":"L.A.","affiliations":[],"preferred":false,"id":446957,"contributorType":{"id":1,"text":"Authors"},"rank":11},{"text":"Clark, R.","contributorId":100780,"corporation":false,"usgs":true,"family":"Clark","given":"R.","affiliations":[],"preferred":false,"id":446970,"contributorType":{"id":1,"text":"Authors"},"rank":12},{"text":"Baines, K. H.","contributorId":37868,"corporation":false,"usgs":false,"family":"Baines","given":"K.","email":"","middleInitial":"H.","affiliations":[],"preferred":false,"id":446960,"contributorType":{"id":1,"text":"Authors"},"rank":13},{"text":"Nicholson, P. D.","contributorId":54330,"corporation":false,"usgs":false,"family":"Nicholson","given":"P.","email":"","middleInitial":"D.","affiliations":[],"preferred":false,"id":446965,"contributorType":{"id":1,"text":"Authors"},"rank":14}]}} ,{"id":70034685,"text":"70034685 - 2009 - Assessment of water quality trends in the Minnesota River using non-parametric and parametric methods","interactions":[],"lastModifiedDate":"2012-03-12T17:21:39","indexId":"70034685","displayToPublicDate":"2009-01-01T00:00:00","publicationYear":"2009","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":2262,"text":"Journal of Environmental Quality","active":true,"publicationSubtype":{"id":10}},"title":"Assessment of water quality trends in the Minnesota River using non-parametric and parametric methods","docAbstract":"Excessive loading of sediment and nutrients to rivers is a major problem in many parts of the United States. In this study, we tested the non-parametric Seasonal Kendall (SEAKEN) trend model and the parametric USGS Quality of Water trend program (QWTREND) to quantify trends in water quality of the Minnesota River at Fort Snelling from 1976 to 2003. Both methods indicated decreasing trends in flow-adjusted concentrations of total suspended solids (TSS), total phosphorus (TP), and orthophosphorus (OP) and a generally increasing trend in flow-adjusted nitrate plus nitrite-nitrogen (NO3-N) concentration. The SEAKEN results were strongly influenced by the length of the record as well as extreme years (dry or wet) earlier in the record. The QWTREND results, though influenced somewhat by the same factors, were more stable. The magnitudes of trends between the two methods were somewhat different and appeared to be associated with conceptual differences between the flow-adjustment processes used and with data processing methods. The decreasing trends in TSS, TP, and OP concentrations are likely related to conservation measures implemented in the basin. However, dilution effects from wet climate or additional tile drainage cannot be ruled out. The increasing trend in NO3-N concentrations was likely due to increased drainage in the basin. Since the Minnesota River is the main source of sediments to the Mississippi River, this study also addressed the rapid filling of Lake Pepin on the Mississippi River and found the likely cause to be increased flow due to recent wet climate in the region. Copyright ?? 2009 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. All rights reserved.","largerWorkType":{"id":2,"text":"Article"},"largerWorkTitle":"Journal of Environmental Quality","largerWorkSubtype":{"id":10,"text":"Journal Article"},"language":"English","doi":"10.2134/jeq2008.0250","issn":"00472425","usgsCitation":"Johnson, H., Gupta, S., Vecchia, A.V., and Zvomuya, F., 2009, Assessment of water quality trends in the Minnesota River using non-parametric and parametric methods: Journal of Environmental Quality, v. 38, no. 3, p. 1018-1030, https://doi.org/10.2134/jeq2008.0250.","startPage":"1018","endPage":"1030","numberOfPages":"13","costCenters":[],"links":[{"id":243852,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"},{"id":216013,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.2134/jeq2008.0250"}],"volume":"38","issue":"3","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"5059ee85e4b0c8380cd49dd0","contributors":{"authors":[{"text":"Johnson, H.O.","contributorId":13796,"corporation":false,"usgs":true,"family":"Johnson","given":"H.O.","email":"","affiliations":[],"preferred":false,"id":447028,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Gupta, S.C.","contributorId":58863,"corporation":false,"usgs":true,"family":"Gupta","given":"S.C.","email":"","affiliations":[],"preferred":false,"id":447030,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Vecchia, A. V.","contributorId":23533,"corporation":false,"usgs":true,"family":"Vecchia","given":"A.","email":"","middleInitial":"V.","affiliations":[],"preferred":false,"id":447029,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Zvomuya, F.","contributorId":82942,"corporation":false,"usgs":true,"family":"Zvomuya","given":"F.","email":"","affiliations":[],"preferred":false,"id":447031,"contributorType":{"id":1,"text":"Authors"},"rank":4}]}} ,{"id":70034686,"text":"70034686 - 2009 - Deposition and flux of sediment from the Po River, Italy: An idealized and wintertime numerical modeling study","interactions":[],"lastModifiedDate":"2012-03-12T17:21:39","indexId":"70034686","displayToPublicDate":"2009-01-01T00:00:00","publicationYear":"2009","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":2667,"text":"Marine Geology","active":true,"publicationSubtype":{"id":10}},"title":"Deposition and flux of sediment from the Po River, Italy: An idealized and wintertime numerical modeling study","docAbstract":"Recent studies of sediment dynamics and clinoform development in the northern Adriatic Sea focused on winter 2002-2003 and provided the data and motivation for development of a detailed sediment-transport model for the area near the Po River delta. We used both idealized test cases and more realistic simulations to improve our understanding of seasonal sediment dynamics there. We also investigated the relationship between physical processes and the observed depositional products; e.g. the accumulation of sediment very near the Po River distributary mouths. Sediment transport near the Po River was evaluated using a three-dimensional ocean model coupled to sediment-transport calculations that included wave- and current-induced resuspension, suspended-sediment transport, multiple grain classes, and fluvial input from the Po River. High-resolution estimates from available meteorological and wave models were used to specify wind, wave, and meteorological forcing. Model results indicated that more than half of the discharged sediment remained within 15??km of the Po River distributary mouths, even after two months of intensive reworking by winter storms. During floods of the Po River, transport in the middle to upper water column dominated sediment fluxes. Otherwise, sediment fluxes from the subaqueous portion of the delta were confined to the bottom few meters of the water column, and correlated with increases in current speed and wave energy. Spatial and temporal variation in wind velocities determined depositional patterns and the directions of sediment transport. Northeasterly Bora winds produced relatively more eastward transport, while southwesterly Sirocco winds generated fluxes towards both the north and the south. Eastward transport accounted for the majority of the sediment exported from the subaqueous delta, most likely due to the frequent occurrence of Bora conditions. Progradation of the Po River delta into the Adriatic Sea may restrict the formation of the Western Adriatic Coastal Current, increasing sediment retention at the Po delta and reducing the supply of sediment to the Apennine margin. A positive morphodynamic feedback may therefore be present whereby the extension of the delta into the Adriatic increases sediment accumulation at the delta and facilitates further progradation. ?? 2009 Elsevier B.V.","largerWorkType":{"id":2,"text":"Article"},"largerWorkTitle":"Marine Geology","largerWorkSubtype":{"id":10,"text":"Journal Article"},"language":"English","doi":"10.1016/j.margeo.2009.01.007","issn":"00253227","usgsCitation":"Bever, A., Harris, C.K., Sherwood, C.R., and Signell, R.P., 2009, Deposition and flux of sediment from the Po River, Italy: An idealized and wintertime numerical modeling study: Marine Geology, v. 260, no. 1-4, p. 69-80, https://doi.org/10.1016/j.margeo.2009.01.007.","startPage":"69","endPage":"80","numberOfPages":"12","costCenters":[],"links":[{"id":243853,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"},{"id":216014,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1016/j.margeo.2009.01.007"}],"volume":"260","issue":"1-4","noUsgsAuthors":false,"publicationStatus":"PW","scienceBaseUri":"5059feb6e4b0c8380cd4eea6","contributors":{"authors":[{"text":"Bever, A.J.","contributorId":48766,"corporation":false,"usgs":true,"family":"Bever","given":"A.J.","email":"","affiliations":[],"preferred":false,"id":447033,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Harris, C. K.","contributorId":80337,"corporation":false,"usgs":true,"family":"Harris","given":"C.","email":"","middleInitial":"K.","affiliations":[],"preferred":false,"id":447034,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Sherwood, C. R.","contributorId":48235,"corporation":false,"usgs":true,"family":"Sherwood","given":"C.","email":"","middleInitial":"R.","affiliations":[],"preferred":false,"id":447032,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Signell, R. P.","contributorId":89147,"corporation":false,"usgs":true,"family":"Signell","given":"R.","email":"","middleInitial":"P.","affiliations":[],"preferred":false,"id":447035,"contributorType":{"id":1,"text":"Authors"},"rank":4}]}} ,{"id":70034688,"text":"70034688 - 2009 - Plant toxicity, adaptive herbivory, and plant community dynamics","interactions":[],"lastModifiedDate":"2012-03-12T17:21:42","indexId":"70034688","displayToPublicDate":"2009-01-01T00:00:00","publicationYear":"2009","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":1478,"text":"Ecosystems","active":true,"publicationSubtype":{"id":10}},"title":"Plant toxicity, adaptive herbivory, and plant community dynamics","docAbstract":"We model effects of interspecific plant competition, herbivory, and a plant's toxic defenses against herbivores on vegetation dynamics. The model predicts that, when a generalist herbivore feeds in the absence of plant toxins, adaptive foraging generally increases the probability of coexistence of plant species populations, because the herbivore switches more of its effort to whichever plant species is more common and accessible. In contrast, toxin-determined selective herbivory can drive plant succession toward dominance by the more toxic species, as previously documented in boreal forests and prairies. When the toxin concentrations in different plant species are similar, but species have different toxins with nonadditive effects, herbivores tend to diversify foraging efforts to avoid high intakes of any one toxin. This diversification leads the herbivore to focus more feeding on the less common plant species. Thus, uncommon plants may experience depensatory mortality from herbivory, reducing local species diversity. The depensatory effect of herbivory may inhibit the invasion of other plant species that are more palatable or have different toxins. These predictions were tested and confirmed in the Alaskan boreal forest. ?? 2009 Springer Science+Business Media, LLC.","largerWorkType":{"id":2,"text":"Article"},"largerWorkTitle":"Ecosystems","largerWorkSubtype":{"id":10,"text":"Journal Article"},"language":"English","doi":"10.1007/s10021-009-9240-x","issn":"14329840","usgsCitation":"Feng, Z., Liu, R., DeAngelis, D., Bryant, L.C., Kielland, K., Stuart, C.F., and Swihart, R., 2009, Plant toxicity, adaptive herbivory, and plant community dynamics: Ecosystems, v. 12, no. 4, p. 534-547, https://doi.org/10.1007/s10021-009-9240-x.","startPage":"534","endPage":"547","numberOfPages":"14","costCenters":[],"links":[{"id":215570,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1007/s10021-009-9240-x"},{"id":243382,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"12","issue":"4","noUsgsAuthors":false,"publicationDate":"2009-03-10","publicationStatus":"PW","scienceBaseUri":"505a7c02e4b0c8380cd79744","contributors":{"authors":[{"text":"Feng, Z.","contributorId":84991,"corporation":false,"usgs":true,"family":"Feng","given":"Z.","email":"","affiliations":[],"preferred":false,"id":447046,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Liu, R.","contributorId":23731,"corporation":false,"usgs":true,"family":"Liu","given":"R.","email":"","affiliations":[],"preferred":false,"id":447042,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"DeAngelis, D.L. 0000-0002-1570-4057","orcid":"https://orcid.org/0000-0002-1570-4057","contributorId":32470,"corporation":false,"usgs":true,"family":"DeAngelis","given":"D.L.","affiliations":[],"preferred":false,"id":447044,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Bryant, Lee C.","contributorId":62045,"corporation":false,"usgs":false,"family":"Bryant","given":"Lee","email":"","middleInitial":"C.","affiliations":[{"id":12698,"text":"Northern Arizona University","active":true,"usgs":false}],"preferred":true,"id":447045,"contributorType":{"id":1,"text":"Authors"},"rank":4},{"text":"Kielland, K.","contributorId":98932,"corporation":false,"usgs":true,"family":"Kielland","given":"K.","affiliations":[],"preferred":false,"id":447048,"contributorType":{"id":1,"text":"Authors"},"rank":5},{"text":"Stuart, Chapin F.","contributorId":23781,"corporation":false,"usgs":true,"family":"Stuart","given":"Chapin","email":"","middleInitial":"F.","affiliations":[],"preferred":false,"id":447043,"contributorType":{"id":1,"text":"Authors"},"rank":6},{"text":"Swihart, R.K.","contributorId":90560,"corporation":false,"usgs":true,"family":"Swihart","given":"R.K.","email":"","affiliations":[],"preferred":false,"id":447047,"contributorType":{"id":1,"text":"Authors"},"rank":7}]}} ,{"id":70034690,"text":"70034690 - 2009 - Sources of uncertainty in flood inundation maps","interactions":[],"lastModifiedDate":"2014-07-08T15:42:25","indexId":"70034690","displayToPublicDate":"2009-01-01T00:00:00","publicationYear":"2009","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":2289,"text":"Journal of Flood Risk Management","active":true,"publicationSubtype":{"id":10}},"title":"Sources of uncertainty in flood inundation maps","docAbstract":"Flood inundation maps typically have been used to depict inundated areas for floods having specific exceedance levels. The uncertainty associated with the inundation boundaries is seldom quantified, in part, because all of the sources of uncertainty are not recognized and because data available to quantify uncertainty seldom are available. Sources of uncertainty discussed in this paper include hydrologic data used for hydraulic model development and validation, topographic data, and the hydraulic model. The assumption of steady flow, which typically is made to produce inundation maps, has less of an effect on predicted inundation at lower flows than for higher flows because more time typically is required to inundate areas at high flows than at low flows. Difficulties with establishing reasonable cross sections that do not intersect and that represent water-surface slopes in tributaries contribute additional uncertainties in the hydraulic modelling. As a result, uncertainty in the flood inundation polygons simulated with a one-dimensional model increases with distance from the main channel.","largerWorkType":{"id":2,"text":"Article"},"largerWorkTitle":"Journal of Flood Risk Management","largerWorkSubtype":{"id":10,"text":"Journal Article"},"language":"English","publisher":"Wiley-Blackwell Publishing Ltd.","publisherLocation":"Oxford, England","doi":"10.1111/j.1753-318X.2009.01029.x","usgsCitation":"Bales, J., and Wagner, C.R., 2009, Sources of uncertainty in flood inundation maps: Journal of Flood Risk Management, v. 2, no. 2, p. 139-147, https://doi.org/10.1111/j.1753-318X.2009.01029.x.","productDescription":"9 p.","startPage":"139","endPage":"147","numberOfPages":"9","costCenters":[],"links":[{"id":476446,"rank":10000,"type":{"id":40,"text":"Open Access Publisher Index Page"},"url":"https://doi.org/10.1111/j.1753-318x.2009.01029.x","text":"Publisher Index Page"},{"id":215601,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1111/j.1753-318X.2009.01029.x"},{"id":243415,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"2","issue":"2","noUsgsAuthors":false,"publicationDate":"2009-05-26","publicationStatus":"PW","scienceBaseUri":"505b9397e4b08c986b31a59d","contributors":{"authors":[{"text":"Bales, J. D.","contributorId":21569,"corporation":false,"usgs":true,"family":"Bales","given":"J. D.","affiliations":[],"preferred":false,"id":447051,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Wagner, C. R.","contributorId":102881,"corporation":false,"usgs":true,"family":"Wagner","given":"C.","email":"","middleInitial":"R.","affiliations":[],"preferred":false,"id":447052,"contributorType":{"id":1,"text":"Authors"},"rank":2}]}} ,{"id":70034691,"text":"70034691 - 2009 - Inducing in situ, nonlinear soil response applying an active source","interactions":[],"lastModifiedDate":"2012-03-12T17:21:42","indexId":"70034691","displayToPublicDate":"2009-01-01T00:00:00","publicationYear":"2009","noYear":false,"publicationType":{"id":2,"text":"Article"},"publicationSubtype":{"id":10,"text":"Journal Article"},"seriesTitle":{"id":2314,"text":"Journal of Geophysical Research B: Solid Earth","active":true,"publicationSubtype":{"id":10}},"title":"Inducing in situ, nonlinear soil response applying an active source","docAbstract":"[1] It is well known that soil sites have a profound effect on ground motion during large earthquakes. The complex structure of soil deposits and the highly nonlinear constitutive behavior of soils largely control nonlinear site response at soil sites. Measurements of nonlinear soil response under natural conditions are critical to advancing our understanding of soil behavior during earthquakes. Many factors limit the use of earthquake observations to estimate nonlinear site response such that quantitative characterization of nonlinear behavior relies almost exclusively on laboratory experiments and modeling of wave propagation. Here we introduce a new method for in situ characterization of the nonlinear behavior of a natural soil formation using measurements obtained immediately adjacent to a large vibrator source. To our knowledge, we are the first group to propose and test such an approach. Employing a large, surface vibrator as a source, we measure the nonlinear behavior of the soil by incrementally increasing the source amplitude over a range of frequencies and monitoring changes in the output spectra. We apply a homodyne algorithm for measuring spectral amplitudes, which provides robust signal-to-noise ratios at the frequencies of interest. Spectral ratios are computed between the receivers and the source as well as receiver pairs located in an array adjacent to the source, providing the means to separate source and near-source nonlinearity from pervasive nonlinearity in the soil column. We find clear evidence of nonlinearity in significant decreases in the frequency of peak spectral ratios, corresponding to material softening with amplitude, observed across the array as the source amplitude is increased. The observed peak shifts are consistent with laboratory measurements of soil nonlinearity. Our results provide constraints for future numerical modeling studies of strong ground motion during earthquakes.","largerWorkType":{"id":2,"text":"Article"},"largerWorkTitle":"Journal of Geophysical Research B: Solid Earth","largerWorkSubtype":{"id":10,"text":"Journal Article"},"language":"English","doi":"10.1029/2008JB005832","issn":"01480227","usgsCitation":"Johnson, P., Bodin, P., Gomberg, J., Pearce, F., Lawrence, Z., and Menq, F., 2009, Inducing in situ, nonlinear soil response applying an active source: Journal of Geophysical Research B: Solid Earth, v. 114, no. 5, https://doi.org/10.1029/2008JB005832.","costCenters":[],"links":[{"id":215602,"rank":9999,"type":{"id":10,"text":"Digital Object Identifier"},"url":"https://dx.doi.org/10.1029/2008JB005832"},{"id":243416,"rank":0,"type":{"id":24,"text":"Thumbnail"},"url":"https://pubs.usgs.gov/thumbnails/outside_thumb.jpg"}],"volume":"114","issue":"5","noUsgsAuthors":false,"publicationDate":"2009-05-21","publicationStatus":"PW","scienceBaseUri":"505a3aace4b0c8380cd61e93","contributors":{"authors":[{"text":"Johnson, P.A.","contributorId":91220,"corporation":false,"usgs":true,"family":"Johnson","given":"P.A.","email":"","affiliations":[],"preferred":false,"id":447057,"contributorType":{"id":1,"text":"Authors"},"rank":1},{"text":"Bodin, P.","contributorId":29554,"corporation":false,"usgs":true,"family":"Bodin","given":"P.","email":"","affiliations":[],"preferred":false,"id":447054,"contributorType":{"id":1,"text":"Authors"},"rank":2},{"text":"Gomberg, J.","contributorId":95994,"corporation":false,"usgs":true,"family":"Gomberg","given":"J.","email":"","affiliations":[],"preferred":false,"id":447058,"contributorType":{"id":1,"text":"Authors"},"rank":3},{"text":"Pearce, F.","contributorId":73322,"corporation":false,"usgs":true,"family":"Pearce","given":"F.","email":"","affiliations":[],"preferred":false,"id":447055,"contributorType":{"id":1,"text":"Authors"},"rank":4},{"text":"Lawrence, Z.","contributorId":12962,"corporation":false,"usgs":true,"family":"Lawrence","given":"Z.","email":"","affiliations":[],"preferred":false,"id":447053,"contributorType":{"id":1,"text":"Authors"},"rank":5},{"text":"Menq, F.-Y.","contributorId":90024,"corporation":false,"usgs":true,"family":"Menq","given":"F.-Y.","email":"","affiliations":[],"preferred":false,"id":447056,"contributorType":{"id":1,"text":"Authors"},"rank":6}]}} ]}