An automated cross‐validation method to assess seismic time‐to‐depth conversion accuracy: a case study on the Cooper and Eromanga basins,Australia          下载免费PDF全文

David Kulikowski  Catherine Hochwald  Khalid Amrouch 《Geophysical Prospecting》2018,66(8):1521-1534

Selecting a seismic time‐to‐depth conversion method can be a subjective choice that is made by geophysicists, and is particularly difficult if the accuracy of these methods is unknown. This study presents an automated statistical approach for assessing seismic time‐to‐depth conversion accuracy by integrating the cross‐validation method with four commonly used seismic time‐to‐depth conversion methods. To showcase this automated approach, we use a regional dataset from the Cooper and Eromanga basins, Australia, consisting of 13 three‐dimensional (3D) seismic surveys, 73 two‐way‐time surface grids and 729 wells. Approximately 10,000 error values (predicted depth vs. measured well depth) and associated variables were calculated. The average velocity method was the most accurate overall (7.6 m mean error); however, the most accurate method and the expected error changed by several metres depending on the combination and value of the most significant variables. Cluster analysis tested the significance of the associated variables to find that the seismic survey location (potentially related to local geology (i.e. sedimentology, structural geology, cementation, pore pressure, etc.), processing workflow, or seismic vintage), formation (potentially associated with reduced signal‐to‐noise with increasing depth or the changes in lithology), distance to the nearest well control, and the spatial location of the predicted well relative to the existing well data envelope had the largest impact on accuracy. Importantly, the effect of these significant variables on accuracy were found to be more important than choosing between the four methods, highlighting the importance of better understanding seismic time‐to‐depth conversions, which can be achieved by applying this automated cross‐validation method.  相似文献   

SSIIM: Sediment simulation in intakes with multiblock option. A model for free surface flows     

Catherine A.M.E Wilson 《水文研究》2000,14(14):2619-2622

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The sediment-fill of Pago Pago Bay (Tutuila Island,American Samoa): New insights on the sediment record of past tsunamis     

Brieuc Riou  Eric Chaumillon  Jean-Luc Schneider  Thierry Corrège  Catherine Chagué 《Sedimentology》2020,67(3):1577-1600

Extensive bathymetric and two-dimensional seismic surveys have been carried out and cores collected in Pago Pago Bay (Tutuila, American Samoa) in order to describe and gain a better understanding of the sediment fill of the bay, which was affected by the 2009 South Pacific Tsunami. Eight sedimentary units were identified over the volcanic bedrock. The basal transgressive unit displays retrograding onlaps towards the shore, whereas the overlying seven aggradational layers alternate between four draping units and three pinching out seaward units. ‘Core to seismic’ correlation reveals that draping units are composed of homogeneous silts, while pinching out units are dominated by very coarse coral fragments showing fresh cuts, mixed with Halimeda plates. The basal unit is attributed to transgressive sedimentation in response to flooding of the bay after the last glacial maximum, followed by the upper aggradational units corresponding to highstand sedimentation. The changeovers in these upper units indicate an alternation between low-energy silt units and high-energy coral debris units interpreted as tsunami-induced deposits. The ¹⁴C dating reveals that high-energy sedimentation units can last up to approximately 2000 years while low-energy sedimentation units can last up to approximately 1000 years. This alternation, deposited during the last highstand, may be explained by cycles of tectonic activity and quiescence of the Tonga Trench subduction, which is the main source of tsunamigenic earthquakes impacting the Samoan archipelago. In the uppermost silt unit, only the geochemical signature of the terrestrial input of the 2009 SPT backwash deposits was detected between 7 cm and 9 cm depth. Hence, Pago Pago Bay offers a unique sediment record of Holocene bay-fill under the impact of past tsunamis intermittently during the last 7000 years.  相似文献   

New coring study in Augusta Bay expands understanding of offshore tsunami deposits (Eastern Sicily,Italy)     

Alessandra Smedile  Flavia Molisso  Catherine Chagué  Marina Iorio  Paolo Marco De Martini  Stefania Pinzi  Philip E. F. Collins  Leonardo Sagnotti  Daniela Pantosti 《Sedimentology》2020,67(3):1553-1576

Tsunami deposits present an important archive for understanding tsunami histories and dynamics. Most research in this field has focused on onshore preserved remains, while the offshore deposits have received less attention. In 2009, during a coring campaign with the Italian Navy Magnaghi, four 1 m long gravity cores (MG cores) were sampled from the northern part of Augusta Bay, along a transect in 60 to 110 m water depth. These cores were taken in the same area where a core (MS06) was collected in 2007 about 2·3 km offshore Augusta at a water depth of 72 m below sea level. Core MS06 consisted of a 6·7 m long sequence that included 12 anomalous intervals interpreted as the primary effect of tsunami backwash waves in the last 4500 years. In this study, tsunami deposits were identified, based on sedimentology and displaced benthic foraminifera (as for core MS06) reinforced by X-ray fluorescence data. Two erosional surfaces (L1 and L2) were recognized coupled with grain-size increase, abundant Posidonia oceanica seagrass remains and a significant amount of Nubecularia lucifuga, an epiphytic sessile benthic foraminifera considered to be transported from the inner shelf. The occurrence of Ti/Ca and Ti/Sr increments, coinciding with peaks in organic matter (Mo incoherent/coherent) suggests terrestrial run-off coupled with an input of organic matter. The L1 and L2 horizons were attributed to two distinct historical tsunamis (ad 1542 and ad 1693) by indirect age-estimation methods using ²¹⁰Pb profiles and the comparison of Volume Magnetic Susceptibility data between MG cores and MS06 cores. One most recent bioturbated horizon (Bh), despite not matching the above listed interpretative features, recorded an important palaeoenvironmental change that may correspond to the ad 1908 tsunami. These findings reinforce the value of offshore sediment records as an underutilized resource for the identification of past tsunamis.  相似文献   

Consequences of changed water management for Aboriginal Australians in the Murrumbidgee catchment,NSW     

Catherine Conroy  Skye Wassens  Catherine Allan 《The Australian geographer》2019,50(2):169-184

In the Murrumbidgee catchment of the Murray-Darling Basin, wetlands, rivers and other waterscapes are important features of Country for Aboriginal peoples. The Murrumbidgee River is the most heavily regulated river system in the Murray-Darling Basin. Discussion around the use of Murrumbidgee water is framed as a conflict between sustaining rural communities and using water to support ecological values, yet the voices of Aboriginal custodians are relatively unheard in this discussion. Using culturally important wetland plants as a starting point, this paper explores the understanding and perception of some Aboriginal people in relation to their Country and water. The grief of participants as they experience the degradation of their Country was palpable. The strong message that Country should be considered in its entirety—including ecological, social and cultural aspects—contrasts with current ownership and other institutional arrangements. Improving opportunities for communities and water managers to share knowledge and information, an openness to use Aboriginal wisdom, and careful ongoing management of environmental and cultural water have the potential to achieve positive cultural and ecological outcomes in the Murrumbidgee.  相似文献   

JPEG2000 Image Compression on Solar EUV Images     

Catherine E. Fischer  Daniel Müller  Ineke De Moortel 《Solar physics》2017,292(1):16

For future solar missions as well as ground-based telescopes, efficient ways to return and process data have become increasingly important. Solar Orbiter, which is the next ESA/NASA mission to explore the Sun and the heliosphere, is a deep-space mission, which implies a limited telemetry rate that makes efficient onboard data compression a necessity to achieve the mission science goals. Missions like the Solar Dynamics Observatory (SDO) and future ground-based telescopes such as the Daniel K. Inouye Solar Telescope, on the other hand, face the challenge of making petabyte-sized solar data archives accessible to the solar community. New image compression standards address these challenges by implementing efficient and flexible compression algorithms that can be tailored to user requirements. We analyse solar images from the Atmospheric Imaging Assembly (AIA) instrument onboard SDO to study the effect of lossy JPEG2000 (from the Joint Photographic Experts Group 2000) image compression at different bitrates. To assess the quality of compressed images, we use the mean structural similarity (MSSIM) index as well as the widely used peak signal-to-noise ratio (PSNR) as metrics and compare the two in the context of solar EUV images. In addition, we perform tests to validate the scientific use of the lossily compressed images by analysing examples of an on-disc and off-limb coronal-loop oscillation time-series observed by AIA/SDO.  相似文献   

Decadal evolution of anthropogenic CO₂ in the northwestern Mediterranean Sea from the mid-1990s to the mid-2000s     

Franck Touratier  Catherine Goyet 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(10):1708-1716

Monthly observations accumulated over more than a decade at the DYFAMED time-series station allow us to estimate the temporal evolution of anthropogenic CO₂ in the western Mediterranean Sea. This objective is reached by using recognized interpolation procedures to reconstruct the incomplete distributions of measured total dissolved inorganic carbon and total alkalinity. These reconstructed fields, associated with those available for dissolved oxygen and temperature, are used to estimate the distribution of anthropogenic CO₂. This is done with the recently developed Tracer combining Oxygen, inorganic Carbon, and total alkalinity (TrOCA) approach. The main results indicate that (1) the concentrations of anthropogenic CO₂ are much higher than those found in the Atlantic Ocean (the minimum concentration at the DYFAMED site is 50 μmol kg⁻¹), and (2) the temporal trend for anthropogenic CO₂ is decreasing, especially in the intermediate and the deep layers of the water column at the DYFAMED site. This decrease in anthropogenic CO₂ is significantly correlated with a decrease in the dissolved oxygen and with an increase in both salinity and temperature. These trends are discussed in the light of recent published works that propose explanations for the observed increases in salinity and temperature that occurred in the western basin since the 1950s. We conclude that the decrease in anthropogenic CO₂ probably resulted from an invasion of old water masses. Different hypotheses on the origin of these water masses are considered and several arguments indicate that the eastern Mediterranean transient (EMT) could have played an important role in the observed decrease in anthropogenic CO₂ concentrations at the DYFAMED site.  相似文献   

Semipermeable membrane devices link site-specific contaminants to effects: PART II - A comparison of lingering Exxon Valdez oil with other potential sources of CYP1A inducers in Prince William Sound, Alaska   总被引：1，自引：1，他引：0  

Short JW  Springman KR  Lindeberg MR  Holland LG  Larsen ML  Sloan CA  Khan C  Hodson PV  Rice SD 《Marine environmental research》2008,66(5):487-498

We deployed semipermeable membrane devices (SPMDs) on beaches for 28 days at 53 sites in Prince William Sound (PWS), Alaska, to evaluate the induction potential from suspected sources of cytochrome P450 1A (CYP1A)-inducing contaminants. Sites were selected to assess known point sources, or were chosen randomly to evaluate the region-wide sources. After deployment, SPMD extracts were analyzed chemically for persistent organic pollutants (POPs) and polycyclic aromatic hydrocarbons (PAH). These results were compared with hepatic CYP1A enzyme activity of juvenile rainbow trout injected with the same extracts prior to clean-up for the chemical analyses. Increased CYP1A activity was strongly associated with PAH concentrations in extracts, especially chrysene homologues but was not associated with POPs. The only apparent sources of chrysene homologues were lingering oil from Exxon Valdez, asphalt and bunker fuels released from storage tanks during the 1964 Alaska earthquake, creosote leaching from numerous pilings at one site, and PAH-contaminated sediments at Cordova Harbor. Our results indicate that PWS is remarkably free of pollution from PAH when nearby sources are absent as well as from pesticides and PCBs generally.  相似文献   

Sedimentation within and among mangrove forests along a gradient of geomorphological settings     

María Fernanda Adame  David Neil  Sara F. Wright  Catherine E. Lovelock 《Estuarine, Coastal and Shelf Science》2010

Coastal wetlands provide important ecological services to the coastal zone, one of which is sediment retention. In this study we investigated sediment retention across a range of geomorphological settings and across vegetation zones comprising coastal wetlands. We selected six coastal wetlands dominated by mangroves over a gradient from riverine to tidal settings in Southeast Queensland, Australia. Each site was comprised of three distinct vegetation communities distributed as parallel zones to the coast line: seaward fringe mangroves, landward scrub mangroves and saltmarsh/ cyanobacteria mat of the high intertidal zone. We measured suspended sediment retention and sedimentation rates. Additionally, in order to assess the origin of sediment transported and deposited in the mangroves, glomalin, a novel terrestrial soil carbon tracer, was used. Our results show a mean average sedimentation of 0.64 ± 0.01 mg cm⁻² spring tide⁻¹, which was variable within sites, regardless of geomorphological setting. However, geomorphological setting influenced spatial patterns of sediment deposition. Riverine mangroves had a more homogeneous distribution of sediments across the intertidal zone than tidal mangroves, where most sedimentation occurred in the fringe zone. Overall, the fringe zone retained the majority of sediment entering the coastal wetland during a tidal cycle with 0.90 ± 0.22 mg cm⁻² spring tide⁻¹, accounting for 52.5 ± 12.5% of the total sedimentation. The presence of glomalin in suspended sediments, and thus the relative importance of terrigenous sediment, was strongly influenced by geomorphological setting, with riverine mangroves receiving more glomalin in suspended solids than tidal mangroves. Glomalin was also differentially deposited within the vegetation zones at different geomorphological settings: primarily at the fringe zone of tidal mangroves and within the scrub zone of riverine mangroves. The differences we observed in the spatial distribution of sedimentation and the difference in the origin of the sediment deposited in riverine and tidal mangroves are likely to have an impact on ecological processes.  相似文献