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981.
Natural Hazards - Earthquakes as a natural hazard have caused substantial economic losses and human life loss in many countries. Taiwan, which is located on the western Circum-Pacific seismic belt,... 相似文献
982.
Asten Michael W. Yong Alan Foti Sebastiano Hayashi Koichi Martin Antony J. Stephenson William J. Cassidy John F. Coleman Jacie Nigbor Robert Castellaro Silvia Chimoto Kosuke Cornou Cécile Cho Ikuo Hayashida Takumi Hobiger Manuel Kuo Chun-Hsiang Macau Albert Mercerat E. Diego Molnar Sheri Pananont Passakorn Pilz Marco Poovarodom Nakhorn Sáez Esteban Wathelet Marc Yamanaka Hiroaki Yokoi Toshiaki Zhao Don 《Journal of Seismology》2022,26(4):757-780
Journal of Seismology - Site response is a critical consideration when assessing earthquake hazards. Site characterization is key to understanding site effects as influenced by seismic site... 相似文献
983.
National Weather Service issues deterministic warnings in a tornado event. An alternative system is being researched at National Severe Storms Laboratory to issue Probabilistic Hazard Information (PHI). This study investigated how providing the uncertainty information about the tornado occurrence through PHI changes people’s protective actions. In an experiment, visual displays of the probabilistic information and deterministic warnings were presented to fifty participants to report their expected protective actions in different scenarios. It was found that the percentage of people who expected to immediately take shelter right after receiving the weather information increased exponentially as their proximity to the threat decreased. When there was more chance that the information about occurrence of a particular tornado was false rather than true, in scenarios that the likelihood of the threat occurrence was less than 50%, providing it through PHI lowered the percentage of people who immediately took shelter. The ordinal logistic regression models showed that the probability of taking protective actions significantly changes by providing the uncertainty information when people have less than 20 min lead time before getting impacted by the threat. When the lead time is less than 10 min, the probability of immediately taking shelter increases to 94 from 71%, and when the lead time is more than 10 but less than 20 min, that probability increases from 53 to 70%, if they are provided with the probabilistic information. Presenting the likelihood of any tornado formation in the area did not have significant effect on the people’s protective actions. 相似文献
984.
985.
Impact melting of the largest known enstatite meteorite: Al Haggounia 001, a fossil EL chondrite 下载免费PDF全文
Alan E. Rubin 《Meteoritics & planetary science》2016,51(9):1576-1587
Al Haggounia 001 and paired specimens (including Northwest Africa [NWA] 2828 and 7401) are part of a vesicular, incompletely melted, EL chondrite impact melt rock with a mass of ~3 metric tons. The meteorite exhibits numerous shock effects including (1) development of undulose to weak mosaic extinction in low‐Ca pyroxene; (2) dispersion of metal‐sulfide blebs within silicates causing “darkening”; (3) incomplete impact melting wherein some relict chondrules survived; (4) vaporization of troilite, resulting in S2 bubbles that infused the melt; (5) formation of immiscible silicate and metal‐sulfide melts; (6) shock‐induced transportation of the metal‐sulfide melt to distances >10 cm; (7) partial resorption of relict chondrules and coarse silicate grains by the surrounding silicate melt; (8) crystallization of enstatite in the matrix and as overgrowths on relict silicate grains and relict chondrules; (9) crystallization of plagioclase from the melt; and (10) quenching of the vesicular silicate melt. The vesicular samples lost almost all of their metal during the shock event and were less susceptible to terrestrial weathering; in contrast, the samples in which the metal melt accumulated became severely weathered. Literature data indicate the meteorite fell ~23,000 yr ago; numerous secondary phases formed during weathering. Both impact melting and weathering altered the meteorite's bulk chemical composition: e.g., impact melting and loss of a metal‐sulfide melt from NWA 2828 is responsible for bulk depletions in common siderophile elements and in Mn (from alabandite); weathering of oldhamite caused depletions in many rare earth elements; the growth of secondary phases caused enrichments in alkalis, Ga, As, Se, and Au. 相似文献
986.
The Basement Sill is part of the Ferrar Large Igneous Provinceexposed in the McMurdo Dry Valleys, Antarctica. The sill is330 m thick in the Bull Pass area and 450 + m thick in the Daisarea, 12 km to the west, and is characterized by phenocryst-freelower and upper margins and an orthopyroxene-rich central tongue(opx 15 mm in size). Halogen variations in apatite froma suite of samples collected along vertical transects throughthe sill were examined to evaluate the process of crystallization-induceddegassing (i.e. second boiling) and its effects on magma chemistry.Apatite grains from any given sample are generally unzoned withrespect to Cl and F concentrations, but may vary by 2030mol% in the halogen site between grains. Overall average Cl/Fmass ratios increase with height from the lower margin to thecenter of the sill, and then decrease to near zero towards thetop margin where the rocks are relatively oxide-rich. The Cl/Ftrend parallels those of bulk MgO and grain size. The uppermargin contains abundant mafic pegmatoids and the apatite inthese segregations has lower Cl/F ratios compared with thatin the host-rocks, although REE show no measurable difference.Numerical modeling illustrates that a cooling and crystallizingsill initially develops two separate vapor-saturated zones atthe lower and upper margins owing to the irreversible heat lossto the cooler country rock. Vapor separating from the lowerzone migrates upward into hotter silicate liquid, where it isresorbed, thus increasing the Cl/F mass ratio of the liquid.This process leads to saturation and precipitation of apatitefrom the liquid with a higher Cl/F ratio than would otherwiseoccur. Volatile enrichment can also aid compaction and graingrowth in the central part of the sill. In contrast, the relativelyFe-rich, Cl-poor nature of the upper zone rocks suggests thatthese rocks may have crystallized from more evolved, degassedsilicate liquid, possibly compacted out of the underlying crystalmush. In addition, as vapor sourced from the lower and centralparts of the sill ascends into the cooler upper zone of thesill, the vapor may be localized (along with late interstitialsilicate liquid) to form pegmatoids at temperatures at whichCl is less favored in apatite and can be leached from existingapatite by the ascending vapor, the latter causing the observeddecrease in the Cl/F mass ratio of apatite in the (evolved)pegmatoids. KEY WORDS: Ferrar Igneous Province; halogens; fluid; apatite 相似文献
987.
Lawrence J. Jackson Christopher Ellis Alan V. Morgan John H. McAndrews 《Geoarchaeology》2000,15(5):415-440
This article investigates changing lake levels in the late Pleistocene eastern Great Lakes in order to gain insights into the Early Palaeo‐Indian occupations. Significant new information bearing on lake level history is provided, notably the first well‐documented deposits of a high water level above modern in the ca. 11,000–10,300 B.P. period in the southern Lake Huron basin. The lake level information, along with paleoenvironmental and site data, reinforces site age estimates to the 11th millennium B.P.; suggests significant numbers of sites have been inundated by rising water levels; provides specific information on the setting of archaeological sites such as placing the Parkhill site adjacent to a large lake estuary; indicates reasons for the attractiveness of shorelines to Palaeo‐Indians including persistence of more open areas conducive to higher game productivity; and points to ideal areas for future archaeological site survey, particularly in the Lake Erie drainage. © 2000 John Wiley & Sons, Inc. 相似文献
988.
Integer ambiguity resolution in precise point positioning: method comparison 总被引:24,自引:10,他引:14
Integer ambiguity resolution at a single receiver can be implemented by applying improved satellite products where the fractional-cycle
biases (FCBs) have been separated from the integer ambiguities in a network solution. One method to achieve these products
is to estimate the FCBs by averaging the fractional parts of the float ambiguity estimates, and the other is to estimate the
integer-recovery clocks by fixing the undifferenced ambiguities to integers in advance. In this paper, we theoretically prove
the equivalence of the ambiguity-fixed position estimates derived from these two methods by assuming that the FCBs are hardware-dependent
and only they are assimilated into the clocks and ambiguities. To verify this equivalence, we implement both methods in the
Position and Navigation Data Analyst software to process 1 year of GPS data from a global network of about 350 stations. The
mean biases between all daily position estimates derived from these two methods are only 0.2, 0.1 and 0.0 mm, whereas the
standard deviations of all position differences are only 1.3, 0.8 and 2.0 mm for the East, North and Up components, respectively.
Moreover, the differences of the position repeatabilities are below 0.2 mm on average for all three components. The RMS of
the position estimates minus those from the International GNSS Service weekly solutions for the former method differs by below
0.1 mm on average for each component from that for the latter method. Therefore, considering the recognized millimeter-level
precision of current GPS-derived daily positions, these statistics empirically demonstrate the theoretical equivalence of
the ambiguity-fixed position estimates derived from these two methods. In practice, we note that the former method is compatible
with current official clock-generation methods, whereas the latter method is not, but can potentially lead to slightly better
positioning quality. 相似文献
989.
Lauren E. Hay 《水文研究》1998,12(4):613-634
In this study a stochastic approach to calibration of an orographic precipitation model (Rhea, 1978) was applied in the Gunnison River Basin of south-western Colorado. The stochastic approach to model calibration was used to determine: (1) the model parameter uncertainty and sensitivity; (2) the grid-cell resolution to run the model (10 or 5 km grids); (3) the model grid rotation increment; and (4) the basin subdivision by elevation band for parameter definition. Results from the stochastic calibration are location and data dependent. Uncertainty, sensitivity and range in the final parameter sets were found to vary by grid-cell resolution and elevation. Ten km grids were found to be a more robust model configuration than 5 km grids. Grid rotation increment, tested using only 10 km grids, indicated increments of less than 10 degrees to be superior. Basin subdivision into two elevation bands was found to produce ‘optimal’ results for both 10 and 5 km grids. © 1998 John Wiley & Sons, Ltd. 相似文献
990.
Piero Bellanova Mike Frenken Bruce Richmond Jan Schwarzbauer Seanpaul La Selle Frances Griswold Bruce Jaffe Alan Nelson Klaus Reicherter 《Sedimentology》2020,67(3):1230-1248
Far-field tsunami deposits observed in the Kahana Valley, O‘ahu, Hawai‘i (USA), were investigated for their organic-geochemical content. During short high-energy events, (tsunamis and storms) organic and chemical components are transported with sediment from marine to terrestrial areas. This study investigates the use of anthropogenic based organic geochemical compounds (such as polycyclic aromatic hydrocarbons, pesticides and organochlorides) as a means to identify tsunami deposits. Samples were processed by solid–liquid extraction and analyzed using gas chromatography–mass spectrometry. A total of 21 anthropogenic marker compounds were identified, of which 11 compounds were selected for detailed analysis. Although the tsunami deposits pre-date industrial activity in Hawai‘i by several hundred years, distinct changes were found in the concentrations of anthropogenic marker compounds between sandy tsunami deposits and the surrounding mud/peat layers, which may help in identifying tsunami deposits within cores. As expected, low overall concentrations of anthropogenic markers and pollutants were observed due to the lack of industrial input-sources and little anthropogenic environmental impact at the study site. This geochemical characterization of tsunami deposits shows that anthropogenic markers have significant potential as another high-resolution, multi-proxy method for identifying tsunamis in the sedimentary record. 相似文献