Noise due to surface wind and temperature is a problem in infrasound. Efficiency of IMS network concerns scientists. It is obvious to find the causes of deficiencies of detection of infrasound station by studying back...Noise due to surface wind and temperature is a problem in infrasound. Efficiency of IMS network concerns scientists. It is obvious to find the causes of deficiencies of detection of infrasound station by studying background noise power with respect to the surface wind and the temperature. Data measured by MB2000 microbarometer of infrasound station I33MG are used for the study. Infrasound records are separated into 4 frequency bands centered respectively at: 1 Hz, 0.25 Hz, 0.0625 Hz and 0.0156 Hz. Effects of surface wind and temperature are studied by plotting the variations of the background noise power with respect to the temperature or wind speed in the four considered frequency bands and compared with the median of background noise power. The influence of temperature is manifested by a reduction in the number of low-frequency detection. The surface wind reduces the number of detection at a high frequency. An exponential function is proposed to predict the variations of the noise power in different observation frequencies and temperature and wind conditions. The views expressed herein are those of the authors and do not necessarily reflect the views of the CTBTO Preparatory Commission.展开更多
Spot Them All,is the first localization software developed by the Laboratoire de Seismologie et Infrason Madagascar.The objective of this study is to validate results obtained from the software by comparing them with ...Spot Them All,is the first localization software developed by the Laboratoire de Seismologie et Infrason Madagascar.The objective of this study is to validate results obtained from the software by comparing them with bulletin published by GFZ and the revised event bulletin of the CTBTO from April 2018 to November 2019.On May 15th,2018 around 15:48,an unusual seismic event of magnitude 5.9 was detected in northwest of Madagascar with thousands of aftershocks.The program Spot Them All collects data from IRIS,GEOFON,DASE,IMS,Africa Array network on request.Results showed that earthquake location obtained using STA is consistent with the other two international bulletins.Moreover,199 earthquakes of magnitude greater than 4 were detected by the IMS,39 by the GEOFON network while 937 by STA.Depth is fixed at 10 km in the GFZ’s bulletin and at 0 km in the CTBTO’s REB.STA’s bulletin shows more constrain on events’depth,ranging from 0 to 135 km and they are located between latitudes 11.84°S and 14.18°S,and longitudes 44.8°E and 46.78°E.Information collected from different researches showed that a magma is propagating from Moho depth to the surface.Consequently,a new mountain of about 800 m high and 5 km wide is raising above the seafloor.展开更多
文摘Noise due to surface wind and temperature is a problem in infrasound. Efficiency of IMS network concerns scientists. It is obvious to find the causes of deficiencies of detection of infrasound station by studying background noise power with respect to the surface wind and the temperature. Data measured by MB2000 microbarometer of infrasound station I33MG are used for the study. Infrasound records are separated into 4 frequency bands centered respectively at: 1 Hz, 0.25 Hz, 0.0625 Hz and 0.0156 Hz. Effects of surface wind and temperature are studied by plotting the variations of the background noise power with respect to the temperature or wind speed in the four considered frequency bands and compared with the median of background noise power. The influence of temperature is manifested by a reduction in the number of low-frequency detection. The surface wind reduces the number of detection at a high frequency. An exponential function is proposed to predict the variations of the noise power in different observation frequencies and temperature and wind conditions. The views expressed herein are those of the authors and do not necessarily reflect the views of the CTBTO Preparatory Commission.
基金We thank the staff of the Laboratoire de Seismologie et Infrason for providing constructive comments and suggestions in their review of the present document.We would like to acknowledge the GFZ,the CTBTO,DASE,IRIS,Africa Array,for supplying the resource needed in order to complete this work.We are very grateful to all IOGA(NDC Madagascar)staff for giving a productive environment.
文摘Spot Them All,is the first localization software developed by the Laboratoire de Seismologie et Infrason Madagascar.The objective of this study is to validate results obtained from the software by comparing them with bulletin published by GFZ and the revised event bulletin of the CTBTO from April 2018 to November 2019.On May 15th,2018 around 15:48,an unusual seismic event of magnitude 5.9 was detected in northwest of Madagascar with thousands of aftershocks.The program Spot Them All collects data from IRIS,GEOFON,DASE,IMS,Africa Array network on request.Results showed that earthquake location obtained using STA is consistent with the other two international bulletins.Moreover,199 earthquakes of magnitude greater than 4 were detected by the IMS,39 by the GEOFON network while 937 by STA.Depth is fixed at 10 km in the GFZ’s bulletin and at 0 km in the CTBTO’s REB.STA’s bulletin shows more constrain on events’depth,ranging from 0 to 135 km and they are located between latitudes 11.84°S and 14.18°S,and longitudes 44.8°E and 46.78°E.Information collected from different researches showed that a magma is propagating from Moho depth to the surface.Consequently,a new mountain of about 800 m high and 5 km wide is raising above the seafloor.
