5:15 PM - 6:30 PM
[SVC47-P33] Volcanic tremor recorded on two seismic arrays at Kirishima volcano, Japan
Keywords:Kirishima volcano, volcanic tremor, seismic array
It is difficult to locate tremor sources by conventional methods using travel times because we cannot pick the arrival time correctly. One useful method of estimating the source locations is array analysis, which uses data from a dense seismic network in small area. Generally, a seismic array can decompose waves approaching from many directions and determine the slowness of each wave. Although location of the source cannot be uniquely determined by only one seismic array, multiple array enable us to estimate the source location. We deployed two seismic array on August 30, 2014. One consisted of 7 seismometers located near Ohata pond 5 km away from Shinmoedake crater, and the other consisted 7 seismometers located at Shinyu hot springs 3km away from the crater. They were installed with a sensor interval of 200-350 m, and signals from the seismometers were recorded by a data logger with 250 Hz sampling frequency. We use the combination of two array to determine the tremor sources. Moreover, we can also detect temporal change by array analysis.
From August 30, 2014 to October 5, 2015, two volcanic tremor were recorded at our site. We analyzed the tremor which occurred on July 26 at 9:23, 2015 and its duration was about 150 seconds. Peak frequency of the tremor was about 2-3 Hz. As the result of semblance analysis with 2-4 Hz band-pass filter, we found that the tremor was radiated from WSW direction to Ohata array and from north direction to Shinyu array, corresponding to Ioyama area.