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11.
The prediction of critical frequency foF2 is of great importance in the area of short-wave telecommunication and ionospheric modelling. The test study of foF2 data should enable the validity of data used in
PRIME
map generating and testing to be checked. The preliminary results show that some data should not be used because they could affect the latest results of
PRIME
map generating, testing and improving. 相似文献
12.
Chuanrong Zhang Tian Zhao E. Lynn Usery Dalia Varanka Weidong Li 《Transactions in GIS》2020,24(2):508-525
Disaster response operations require fast and coordinated actions based on real‐time disaster situation information. Although crowdsourced geospatial data applications have been demonstrated to be valuable tools for gathering real‐time disaster situation information, they only provide limited utility for disaster response coordination because of the lack of semantic compatibility and interoperability. To help overcome the semantic incompatibility and heterogeneity problems, we use Geospatial Semantic Web (GSW) technologies. We then combine GSW technologies with Web Feature Service requests to access multiple servers. However, a GSW‐based geographic information system often has poor performance due to the complex geometric computations required. The objective of this research is to explore how to use optimization techniques to improve the performance of an interoperable geographic situation‐awareness system (IGSAS) based on GSW technologies for disaster response. We conducted experiments to evaluate various client‐side optimization techniques for improving the performance of an IGSAS prototype for flood disaster response in New Haven, Connecticut. Our experimental results show that the developed prototype can greatly reduce the runtime costs of geospatial semantic queries through on‐the‐fly spatial indexing, tile‐based rendering, efficient algorithms for spatial join, and caching, especially for those spatial‐join geospatial queries that involve a large number of spatial features and heavy geometric computation. 相似文献
13.
Dalia Bach Kirschbaum Robert Adler Yang Hong Sujay Kumar Christa Peters-Lidard Arthur Lerner-Lam 《Environmental Earth Sciences》2012,66(6):1683-1696
The increasing availability of remotely sensed data offers a new opportunity to address landslide hazard assessment at larger
spatial scales. A prototype global satellite-based landslide hazard algorithm has been developed to identify areas that may
experience landslide activity. This system combines a calculation of static landslide susceptibility with satellite-derived
rainfall estimates and uses a threshold approach to generate a set of ‘nowcasts’ that classify potentially hazardous areas.
A recent evaluation of this algorithm framework found that while this tool represents an important first step in larger-scale
near real-time landslide hazard assessment efforts, it requires several modifications before it can be fully realized as an
operational tool. This study draws upon a prior work’s recommendations to develop a new approach for considering landslide
susceptibility and hazard at the regional scale. This case study calculates a regional susceptibility map using remotely sensed
and in situ information and a database of landslides triggered by Hurricane Mitch in 1998 over four countries in Central America.
The susceptibility map is evaluated with a regional rainfall intensity–duration triggering threshold and results are compared
with the global algorithm framework for the same event. Evaluation of this regional system suggests that this empirically
based approach provides one plausible way to approach some of the data and resolution issues identified in the global assessment.
The presented methodology is straightforward to implement, improves upon the global approach, and allows for results to be
transferable between regions. The results also highlight several remaining challenges, including the empirical nature of the
algorithm framework and adequate information for algorithm validation. Conclusions suggest that integrating additional triggering
factors such as soil moisture may help to improve algorithm performance accuracy. The regional algorithm scenario represents
an important step forward in advancing regional and global-scale landslide hazard assessment. 相似文献
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Migl&#x; Stan
ikait&#x; Valentinas Baltr nas Petras &#x;ink nas Dalia Kisielien&#x; Tomas Ostrauskas 《Quaternary International》2006,150(1):113
Palaeoenvironmental studies combining 14C dating, palaeobotanical and archaeological data provide information about the human reaction to Holocene environmental changes registered in the surroundings of Biržulis Lake in northwest Lithuania.Responding to water regression, early Mesolithic communities were established on the lower lake terraces, which were overgrown by predominantly birch and pine forest. The formation of a mixed forest with Ulmus (immigrated at 8100–7500 cal yr BC), Corylus (7600–7200 cal yr BC) and Alnus (7300–6900 cal yr BC) provided plenty of natural resources, which led to the increase in population during the late Mesolithic. The expansion of Tilia (6400–5900 cal yr BC) and Quercus (5900–5700 cal yr BC), as well as the subsequent flourishing of broad-leaved forest, provided inhabitants with suitable living conditions.The reduction of broad-leaved woodland and the expansion of Picea (4400–3700 cal yr BC), which suggest changing temperature and moisture conditions as well as increasing erosion activity, could have negatively influenced the early-middle Neolithic population, as evidenced by the partial abandoning of the land. The lowering of the water level and thinning of the forest structure possibly related to some dry episode, positively influenced late Neolithic groups, as intensive exploitation of the area, including the earliest attempts at agriculture, has been registered. Since 1770–1490 cal yr BC, when intensive bogging began, evidence of periodic inhabitation around the lake has been registered. 相似文献
18.
William Menke Hannah Abend Dalia Bach Kori Newman Vadim Levin 《Surveys in Geophysics》2006,27(6):603-613
The December 26, 2004 Sumatra–Andaman Island earthquake, which ruptured the Sunda Trench subduction zone, is one of the three largest earthquakes to occur since global monitoring began in the 1890s. Its seismic moment was M
0 = 1.00 × 1023–1.15 × 1023 Nm, corresponding to a moment-magnitude of M
w
= 9.3. The rupture propagated from south to north, with the southerly part of fault rupturing at a speed of 2.8 km/s. Rupture propagation appears to have slowed in the northern section, possibly to ∼2.1 km/s, although published estimates have considerable scatter. The average slip is ∼5 m along a shallowly dipping (8°), N31°W striking thrust fault. The majority of slip and moment release appears to have been concentrated in the southern part of the rupture zone, where slip locally exceeded 30 m. Stress loading from this earthquake caused the section of the plate boundary immediately to the south to rupture in a second, somewhat smaller earthquake. This second earthquake occurred on March 28, 2005 and had a moment-magnitude of M
w
= 8.5. 相似文献
19.
Landslide susceptibility mapping is most effective if detailed surface and subsurface information can be combined with authoritative landslide catalogs or a deep understanding of local conditions. However, these types of homogeneous input data and catalogs are frequently not available over large areas. In this study, we model landslide susceptibility in Central America and the Caribbean islands by combining three globally available datasets and one regional dataset with fuzzy overlay. This primarily heuristic model provides the flexibility to test a range of different contributing variables and the capability to compare landslide inventories within the model framework that vary greatly in their size, spatiotemporal scope, and collection methods. We create a regional susceptibility map and evaluate its performance using receiver operating characteristics for both continuous and binned susceptibility values. This susceptibility map forms the basis for a near-real-time landslide hazard assessment system that couples susceptibility with rainfall and soil moisture triggers to estimate potential landslide activity at a regional scale. The application of this susceptibility model at the regional scale provides a foundation for transferring the methodology to other geographic areas. 相似文献
20.
Zonghu Liao Yang Hong Dalia Kirschbaum Robert F. Adler Jonathan J. Gourley Rick Wooten 《Natural Hazards》2011,58(1):325-339
The key to advancing the predictability of rainfall-triggered landslides is to use physically based slope-stability models
that simulate the transient dynamical response of the subsurface moisture to spatiotemporal variability of rainfall in complex
terrains. TRIGRS (transient rainfall infiltration and grid-based regional slope-stability analysis) is a USGS landslide prediction
model, coded in Fortran, that accounts for the influences of hydrology, topography, and soil physics on slope stability. In
this study, we quantitatively evaluate the spatiotemporal predictability of a Matlab version of TRIGRS (MaTRIGRS) in the Blue
Ridge Mountains of Macon County, North Carolina where Hurricanes Ivan triggered widespread landslides in the 2004 hurricane
season. High resolution digital elevation model (DEM) data (6-m LiDAR), USGS STATSGO soil database, and NOAA/NWS combined
radar and gauge precipitation are used as inputs to the model. A local landslide inventory database from North Carolina Geological
Survey is used to evaluate the MaTRIGRS’ predictive skill for the landslide locations and timing, identifying predictions
within a 120-m radius of observed landslides over the 30-h period of Hurricane Ivan’s passage in September 2004. Results show
that within a radius of 24 m from the landslide location about 67% of the landslide, observations could be successfully predicted
but with a high false alarm ratio (90%). If the radius of observation is extended to 120 m, 98% of the landslides are detected
with an 18% false alarm ratio. This study shows that MaTRIGRS demonstrates acceptable spatiotemporal predictive skill for
landslide occurrences within a 120-m radius in space and a hurricane-event-duration (h) in time, offering the potential to
serve as a landslide warning system in areas where accurate rainfall forecasts and detailed field data are available. The
validation can be further improved with additional landslide information including the exact time of failure for each landslide
and the landslide’s extent and run out length. 相似文献