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21.
An early warning system forewarns an urban area of the forthcoming strong shaking, normally with a few seconds to a few tens
of seconds of early warning time before the arrival of the destructive S-wave part of the strong ground motion. For urban
and industrial areas susceptible to earthquake damage, where the fault rupture system is complex and the fault-site distances
are short, there is usually insufficient time to compute the hypocenter, focal parameters and the magnitude of an earthquake.
Therefore, simpler and robust early warning algorithm is needed. The direct (engineering) early warning systems are based
on algorithms of the exceedance of specified threshold time domain amplitude levels. The continuous stations’ data are processed
to compute specific engineering parameters robustly and compared with specified threshold levels. The parameters can be chosen
as band-pass filtered peak ground accelerations and/or the bracketed cumulative absolute velocity (BCAV). In this paper, an
enhancement to bracket cumulative absolute velocity for the application of online urban early warning systems results in a
new parameter called window based bracketed cumulative absolute velocity (BCAV-W). The BCAV-W allows computation of cumulative
absolute velocity in a specified window size and to include the vertical component of the motion. The importance of choosing
optimum window size for the cumulative absolute velocity BCAV-W is discussed and the correlations between BCAV-W and the macro-seismic
intensity are studied for three combinations of horizontal and vertical components of the motion. Empirical relationship is
developed to estimate BCAV-W as a function of magnitude, distance, fault mechanism, and site category based on 1,208 recorded
ground motion data from 75 earthquakes in active plate-margins. 相似文献
22.
In this study, geochemical and biogeochemical investigations by means of organic carbon (Corg) and element chemistry were
performed on deposits in the Miocene Himmeto lu basin which is represented by various depositional characteristics. As a result
of Corg and element analyses conducted on more than 50 samples, precious and rare metals such as Ag, Hg, Bi, In and U were
found to have wide accumulation ranges. The average concentrations of these metals in bitumen-rich sediments in the area are
0.9, 1.17, 0.9, 0.85 and 10.0 ppm, respectively. Enrichment coefficients (EC) of these metals are 12.86, 58.5, 4.5, 14.2 and
3.7 times greater than the earth crust. However, in some sediment units enrichment coefficients are much higher such as 34.3
for Ag, 100 for Hg, 13.3 for Bi, 33.3 for In and 12.44 for U. The average Corg values of sediments studied is 37.21%. Except
for two samples (2.78 and 2.65%), Corg values range from 11.09 to 80.03 wt % indicating that this part of Miocene basin has
unique paleobionomic and paleogeographic characteristics. The main source of OM is algal/amorphous Type I and also Type II
kerogens consisting of vegetal sources such as spore-pollen and leaf cuticle. Results show that region under investigation
is important by means of energy and metal sources. 相似文献
23.
Minna V?liranta Jan Weckstr?m Susanna Siitonen Heikki Sepp? Jyri Alkio Sari Juutinen Eeva-Stiina Tuittila 《Journal of Paleolimnology》2011,45(3):339-352
We studied multiple variables in a sediment core from Lake Kipojärvi, northern Finland, to investigate Holocene ecosystem changes in relation to catchment characteristics and known climate variations. We focused on a forested catchment because previous paleolimnological studies conducted in Fennoscandia focused mainly on subarctic lakes within a range of shifting treeline(s). Data on aquatic macrophytes, diatoms, Cladocera, C:N ratio, organic matter (LOI) and regional vegetation (pollen), revealed a three-phase limnological development. The early Holocene, species-rich, mesotrophic lake was transformed into an oligotrophic, species-poor aquatic ecosystem by the early middle Holocene, ca. 7,500 cal years BP, earlier than has generally been reported. The transition involved considerable changes in aquatic macrophytes. Changes in the Cladocera and diatom communities appear to have been linked to aquatic macrophyte development, which in turn, was probably regulated by catchment development and hydrology, and a consequent decrease in nutrient input from the catchment. During the more humid late Holocene, surface flow from the catchment probably increased, but the lake??s nutrient status remained oligotrophic. Possible reasons for low nutrient concentration in the late Holocene include: 1) slower biogeochemical cycling due to cooler climate, 2) a new hydrologic outlet and associated shorter water-retention times, and 3) accelerated peatland development in the catchment that affected water flow patterns and nutrient cycling. 相似文献
24.
Abstract This study aims to predict the daily precipitation from meteorological data from Turkey using the wavelet—neural network method, which combines two methods: discrete wavelet transform (DWT) and artificial neural networks (ANN). The wavelet—ANN model provides a good fit with the observed data, in particular for zero precipitation in the summer months, and for the peaks in the testing period. The results indicate that wavelet—ANN model estimations are significantly superior to those obtained by either a conventional ANN model or a multi linear regression model. In particular, the improvement provided by the new approach in estimating the peak values had a noticeably high positive effect on the performance evaluation criteria. Inclusion of the summed sub-series in the ANN input layer brings a new perspective to the discussions related to the physics involved in the ANN structure. 相似文献
25.
26.
Yasin Dursun Sari 《Marine Georesources & Geotechnology》2013,31(6):567-571
The biologically induced cementation (BioGrout) method has been used in this study to improve engineering properties of soil. Laboratory tests have been carried out to quantify the effect of BioGrout treatment on the strength of two types of sand by using Sporosarcina pasteurii bacteria. Bearing strength and other parameters, such as colony forming units (number of bacteria), pH level, temperature, and amount of CaCO3, have also been studied. Calcification (cementation) through precipitation of CaCO3 on the mineral surfaces has been clearly observed from the images of a scanning electron microscope (SEM). Finally, the effect of sand material on the effectiveness of biocementation was investigated via employement of different sand types. 相似文献
27.
The interannual precipitation variability in the southern part of Iran as linked to large-scale climate modes 总被引:1,自引:0,他引:1
Farnaz Pourasghar Tomoki Tozuka Saeed Jahanbakhsh Behrooz Sari Sarraf Hooshang Ghaemi Toshio Yamagata 《Climate Dynamics》2012,39(9-10):2329-2341
The interannual variation of precipitation in the southern part of Iran and its link with the large-scale climate modes are examined using monthly data from 183 meteorological stations during 1974–2005. The majority of precipitation occurs during the rainy season from October to May. The interannual variation in fall and early winter during the first part of the rainy season shows apparently a significant positive correlation with the Indian Ocean Dipole (IOD) and El Ni?o-Southern Oscillation (ENSO). However, a partial correlation analysis used to extract the respective influence of IOD and ENSO shows a significant positive correlation only with the IOD and not with ENSO. The southeasterly moisture flux anomaly over the Arabian Sea turns anti-cyclonically and transport more moisture to the southern part of Iran from the Arabian Sea, the Red Sea, and the Persian Gulf during the positive IOD. On the other hand, the moisture flux has northerly anomaly over Iran during the negative IOD, which results in reduced moisture supply from the south. During the latter part of the rainy season in late winter and spring, the interannual variation of precipitation is more strongly influenced by modes of variability over the Mediterranean Sea. The induced large-scale atmospheric circulation anomaly controls moisture supply from the Red Sea and the Persian Gulf. 相似文献
28.
An empirical attenuation relationship for Northwestern Turkey ground motion using a random effects approach 总被引:2,自引:0,他引:2
Cem
zbey Ali Sari Lance Manuel Mustafa Erdik Yasin Fahjan 《Soil Dynamics and Earthquake Engineering》2004,24(2):115-125
Using a random effects model that takes into consideration the correlation of data recorded by a single seismic event, a database consisting of 195 recordings from 17 recent events is employed to develop empirical attenuation relationships for the geometric mean of horizontal peak ground acceleration and 5-percent damped spectral acceleration (Sa). The recordings employed are obtained from strong motion stations operating in Northwestern Turkey and resulted from events that include the Kocaeli (Mw=7.4) and the Düzce (Mw=7.1) earthquakes and their aftershocks as well as other events. By studying differences in standard errors, the random effects model is compared with a fixed effects model that does not account for distinctions between intra- and inter-event variability. Effects of local site conditions are included in the empirical relationships developed. The dependence on frequency of the various model parameters is also studied. Frequency-dependent attenuation coefficients for the proposed random effects models developed are summarized in tables to facilitate their use. 相似文献
29.
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