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51.
The purpose of this study is to develop a technique to discriminate artificial explosions from local small earthquakes ( M ≤ 4.0) in the time–frequency domain. In order to obtain spectral features of artificial explosions and earthquakes, 3-D spectrograms (frequency, time and amplitude) have been used. They represent a useful tool for studying the frequency content of entire seismic waveforms observed at local and regional distances (Kim, Simpson & Richards 1994). P and S(L g ) waves from quarry blasts show that the frequency content associated with the dominant amplitude appears above 10 Hz and Rg phases are observed at close distances. P and S(L g ) waves from the Tongosan earthquake have strong amplitudes below 10 Hz. For the Munkyong earthquake, however, a broader frequency content up to 20 Hz is found.
For discrimination between small earthquakes and explosions, Pg/L g spectral ratios are used below 10 Hz, and through spectrogram analysis we can see different frequency contents of explosions and earthquakes. Unfortunately, because explosion data recorded at KSRS array are digitized at 20 sps, we cannot avoid analysing below 10 Hz because of the Nyquist frequency. In order to select time windows, the group velocity was computed using multiple-filter analysis (MFA), and free-surface effects have been removed from all three-component data in order to improve data quality. Using FFT, a log-average spectral amplitude is calculated over seven frequency bands: 0.5 to 3, 2 to 4, 3 to 5, 4 to 6, 5 to 7, 6 to 8 and 8 to 10 Hz. The best separation between explosions and earthquakes is observed from 6 to 8 Hz. In this frequency band we can separate explosions with log ( Pg/L g ) above −0.5, except EXP1 recorded at SIHY1-1, and earthquakes below −0.5, except the Munkyong earthquake record at station KMH. 相似文献
For discrimination between small earthquakes and explosions, Pg/L g spectral ratios are used below 10 Hz, and through spectrogram analysis we can see different frequency contents of explosions and earthquakes. Unfortunately, because explosion data recorded at KSRS array are digitized at 20 sps, we cannot avoid analysing below 10 Hz because of the Nyquist frequency. In order to select time windows, the group velocity was computed using multiple-filter analysis (MFA), and free-surface effects have been removed from all three-component data in order to improve data quality. Using FFT, a log-average spectral amplitude is calculated over seven frequency bands: 0.5 to 3, 2 to 4, 3 to 5, 4 to 6, 5 to 7, 6 to 8 and 8 to 10 Hz. The best separation between explosions and earthquakes is observed from 6 to 8 Hz. In this frequency band we can separate explosions with log ( Pg/L g ) above −0.5, except EXP1 recorded at SIHY1-1, and earthquakes below −0.5, except the Munkyong earthquake record at station KMH. 相似文献
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Tourist farms in Lower Silesia, Poland 总被引:1,自引:0,他引:1
Stanisław Grykień 《GeoJournal》1998,46(3):279-281
In view of the small size of most Polish farms, attempts have been made to encourage diversification into rural tourism. The
paper examines the progress made in Lower Silesia which has good resources for domestic and international tourism. Thanks
to the promotional work of the Agricultural Consultative Centres over a hundred farms are now providing services. They do
not generate a large share of the farm income but business is expanding and some areas are becoming very popular. Thus a base
has been established for future expansion. Further development depends on easier access to credit and government support for
ecological agriculture. Better promotion is also needed to increase interest in rural tourism in Poland and attract more visitors
from abroad.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
55.
Invasion of mud filtrate from the borehole into the surrounding formation can significantly alter the response of logging tools.In this paper the neutron tool response was calculated for a gas-bearing rock crossed by the borehole.The invaded zone is characterized by variable fluid and gas saturation and is defined by a specific hyperbolic function. The saturation function is based on the characteristics of Polish Carpathian Foredeep Miocene formations reached in gas-bearing rocks. The whole system including neutron tool equipped with Am-Be neutron source and a set of neutron detectors, borehole, invaded zone, and virgin zone, was numerically modeled and used as the input to the Monte-Carlo neutron transport code. The response of each detector was calculated for different combinations of porosity and saturation of invaded zone and virgin zone. 相似文献
56.
M. Ćwiok W. Dominik K. Małek L. Mankiewicz J. Mrowca-Ciułacz K. Nawrocki L. W. Piotrowski P. Sitek M. Sokołowski G. Wrochna A. F. Żarnecki 《Astrophysics and Space Science》2007,309(1-4):531-535
Experiment “Pi of the Sky” is designed to search for prompt optical emission from GRB sources. 32 CCD cameras covering 2 steradians will monitor the sky continuously. The data will be analysed on-line in search for optical flashes. The prototype with 2 cameras operated at Las Campanas (Chile) since 2004 has recognised several outbursts of flaring stars and has given limits for a few GRB. 相似文献
57.
Hans-Uwe Dahms Hyoung-Min Joo Jae Hyung Lee Mi Sun Yun So Hyun Ahn Sang Heon Lee 《Ocean Science Journal》2015,50(4):639-648
Demersally drifting organisms were collected at Ny Ålesund (Svalbård–Arctic Ocean) to study the taxon composition and relative abundances in the Arctic summer. Catch potentials of two collection devices for demersal drift were compared. A lowvolume submersible drift-pump and a drift-net unit were employed for the collection of demersally drifting biota, particularly for shallow aquatic habitats. With the exception of Appendicularia, Chaetognatha, Coelenterata, and Ctenophora, which were damaged at times, the pump catches were in good condition and sufficient for identification and quantification of less mobile fauna. A comparison of the two devices revealed that the drift-pump collected more specimens than the drift-net. However, the drift-net may have caused an underestimation of the abundances of invertebrates. No differences in identified taxon number and indices of richness, evenness and diversity were found. However, the proportion of invertebrate animals in the two devices was different for the three groups: zooplankton, macrofauna and meiofauna. At Svalbård, zooplankton, larvae of macrofauna, and meiofauna were successfully collected by the two collecting devices. However, the catchibility of the two devices in collecting various invertebrate taxa was different and, therefore, a sound ‘Device Effect’ was revealed. 相似文献
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Kuster-Toksöz and Biot-Gassmann models for estimating velocities of longitudinal and shear waves on the basis of well-logging data were analysed. P-wave and S-wave velocity models are crucial for interpretation of seismic data. Discussed models enable determination with quite good accuracy, in some cases higher than the acoustic full wavetrains interpretation. Because velocity strongly depends on lithology and saturation of pore space, the selection of parameters of rock matrix, hydrocarbons and formation waters has a strong effect on the quality of velocities estimation. 相似文献