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[J01-P-01] Classification of ice tremor recorded at Syowa Station in Antarctica
Tectonic earthquakes and tremors related to ice (ice tremor) have been observed by seismic stations in Antarctica. Ice tremors are the tremors which are originates in some ice motion (Kanao et al., 2012). Purposes of this study are to classify ice tremors and to reveal the spatio-temporal variation in the distribution of ice tremors.
We use the waveform data recorded by seismometer at coastal stations. The analysis period is from January to December in 2014. We define here an ice tremor as the tremor of which P-waves and S-waves are not clear and the duration is longer than five minutes.
We find the total of 148 ice tremors in 2014. The monthly number of the ice tremors correlates well with the monthly mean temperature from April to December. We classify the ice tremors into three types based on a temporal variation in their spectrum features. Type A is the ice tremor which shows that the duration is long (about ten thousands seconds) and the amplitude is small over the waveform. Type B is that of which dominant frequency changes irregularly over the waveform. Type C is that of which dominant frequency continuously decreases and the overtone is recognized. The hypocenters of 47 ice tremors are determined in this study. There are 26 ice tremors, six in the coastal area, six on the sea area and 14 on the land area, within ~ 150 km from the stations.
In summer, both the seismic and microbaroms amplitudes are large and the shape of the waveform of type A is excited by sea wave. In winter, the amplitude of microbaroms is large, while that of the ice tremor is not recorded well because of growing coastal ice (Grob et al, 2011). The hypocenters of type C are located on the sea area ~ 150 km away from Syowa station. Eckstaller et al. (2006) and MacAyeal et al. (2008) reported ice tremors related to iceberg and the spectral feature of them are similar to that of type C. Therefore, we suggest that the source of the type C is related to the iceberg motion.
We use the waveform data recorded by seismometer at coastal stations. The analysis period is from January to December in 2014. We define here an ice tremor as the tremor of which P-waves and S-waves are not clear and the duration is longer than five minutes.
We find the total of 148 ice tremors in 2014. The monthly number of the ice tremors correlates well with the monthly mean temperature from April to December. We classify the ice tremors into three types based on a temporal variation in their spectrum features. Type A is the ice tremor which shows that the duration is long (about ten thousands seconds) and the amplitude is small over the waveform. Type B is that of which dominant frequency changes irregularly over the waveform. Type C is that of which dominant frequency continuously decreases and the overtone is recognized. The hypocenters of 47 ice tremors are determined in this study. There are 26 ice tremors, six in the coastal area, six on the sea area and 14 on the land area, within ~ 150 km from the stations.
In summer, both the seismic and microbaroms amplitudes are large and the shape of the waveform of type A is excited by sea wave. In winter, the amplitude of microbaroms is large, while that of the ice tremor is not recorded well because of growing coastal ice (Grob et al, 2011). The hypocenters of type C are located on the sea area ~ 150 km away from Syowa station. Eckstaller et al. (2006) and MacAyeal et al. (2008) reported ice tremors related to iceberg and the spectral feature of them are similar to that of type C. Therefore, we suggest that the source of the type C is related to the iceberg motion.