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| 1 | Rockfall seismic features analysis based on in situ tests:frequency, amplitude, and duration显示文摘In the seismic event classification,determining the seismic features of rockfall is significantly important for the automatic classification of seismic events because of the huge amount of raw data recorded by seismic stations in continuous monitoring. At the same time, the rockfall seismic features are still not completely understood.This study concentrates on the rockfall frequency content, amplitude(ground velocity), seismic waveform and duration analysis, of an artificial rockfall test at Torgiovannetto(a former quarry in Central Italy). A total of 90 blocks were released in the test, and their seismic signals and moving trajectories were recorded by four tri-axial seismic stations and four cameras, respectively. In the analysis processing,all the artificial rockfall signal traces were cut separately and the seismic features were extracted individually and automatically. In this study, the relationships between a) frequency content and impacted materials, b) frequency content and the distance between block releasing position and seismic station(source-receiver distance) were discussed. As a result, we found that the frequency content of rockfall focuses on 10-60 Hz and 80-90 Hz within a source-receiver distance of 200 m, and it is well correlated with impacted material and source-receiver distance. To evaluate the difference between earthquake and rockfall, 23 clear earthquake signals recorded in a seven month-long continuous seismic monitoring, carried out with the four seismic stations, were picked out, according to the Italian national earthquakes database(INGV). On these traces we performed the same analysis as in the artificial rockfall traces, and two parameters were defined to separate rockfall events from earthquake noise. The first one, the amplitude ratio, is related to the amplitude variation of rockfall between two stations and is greater than that of earthquakes, because of the higher attenuation occurring for rockfall events, which consists in high frequencies whereas for earthquakes it consists in low frequencies. The other parameter, the shape of waveform of signal trace, showed a significant difference between rockfall and earthquake and that could be a complementary feature to discriminate between both. This analysis of artificial rockfall is a first step helpful to understand the seismic characteristics of rockfall, and useful for rockfall seismic events classification in seismic monitoring of slope. | Liang FENG Veronica PAZZI Emanuele INTRIERI Teresa GRACCHI Giovanni GIGLI | 2019 | Journal of Mountain Science2019，16，5： | 2 |
| 2 | Long-term renal function under plasma exchange in atypical hemolytic uremic syndrome 显示文摘 | Davin JC Groothoff J Gracchi V | 2011 | Pediatr Nephrol2011，26，10： | 1 |
| 3 | Long-term renal function underplasma exchange in atypical hemolytic uremic syndrome显示文摘 | Davin JC Groothoff J Gracchi V | 2011 | PediatrNephrol2011，26，10： | 1 |
| 4 | Renal infarction in a child with henoch-schtinlein purpura显示文摘 | Gracchi V van Lienden KP Groothoff JW | 2014 | Kidney Int2014，85，2： | 1 |
| 5 | Renal infarction in a child with Henoch - Schonlein purpura 显示文摘 | Gracchi V van Lienden KP Groothoff JW | 2014 | Kidney Int2014，85，2： | 1 |
| 6 | Renal infarction in a child with Henoch-Schonlein pulpura 显示文摘 | Gracchi V van Lienden KP Groothoff JW | 2014 | Kidney Int2014，85，2： | 1 |
| 7 | Re-nal infarction in a child with Henoch-Schonlein purpura显示文摘 | Gracchi V van Lienden KP Groothoff JW | 2014 | Kidney Int2014，85，2： | 1 |
| 8 | Maintenance of kidney function following treatment with eculizumab and discontinuation of plasma exchange after a third kidney transplant for atypical hemolytic uremic syndrome associated with a CFH Mutation显示文摘 | Davin JC Gracchi V Bouts A | | 0，，： | 1 |
| 9 | Rockfall localization from seismic polarization considering multiple triaxial geophones and frequency bands显示文摘Boulder/rock mass movements generate ground vibrations that can be recorded by geophone networks.Generally,there are two methods applied to rockfall trajectory reconstruction or rockfall seismic localization.One method uses seismic wave arrival times and is achieved by minimizing the differences in signal arrival times between multiple stations by grid map searching.The other method uses seismic polarization and is achieved by calculating eventsource back azimuths from the seismic polarizations of rockfall signals.In this study,we proposed the use of an overdetermined matrix for joint localization based on the polarization method.The overdetermined matrix considers the contributions of all geophones in the network,and at each geophone is assigned a different weight according to the recorded signal qualities and the reliability of the calibrated back azimuths.This method shows a great advantage relative to the case in which only two sensors are employed.Besides,we suggested three marker parameters for proper frequency band selection in back azimuth calculations:energy,rectilinearity,and a special permanent frequency band(SPF).We found that the back azimuths calculated with energy and an SPF are generally close to the real back azimuths measured in the field,while the SPF is limited by seismic attenuation due to a long-distance propagation.The localization results of rockfalls were validated by using field camera videos and in situ calibrations.Three typical cases and 43 artificially released rockfalls are presented in this paper.The proposed method provides an interesting way to locate rockfall events and track rockfall trajectories and avoids the difficulties of obtaining accurate arrival times,as required by the arrival times method. | Liang FENG Veronica PAZZI Emanuele INTRIERI Teresa GRACCHI Giovanni GIGLI Grazia TUCCI | 2020 | Journal of Mountain Science2020，17，7： | 0 |
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