Source mechanism of very-long-period signals accompanying dome growth activity at Merapi volcano, Indonesia

[1] Very-long-period (VLP) pulses with period of 6-7s, displaying similar waveforms, were identified in 1998 from broadband seismographs around the summit crater. These pulses accompanied most of multiphase (MP) earthquakes, a type of long-period event locally defined at Merapi Volcano. Source mechanisms for several VLP pulses were examined by applying moment tensor inversion to the waveform data. Solutions were consistent with a crack striking similar to70degrees and dipping similar to50degrees SW, 100m under the active dome, suggest pressurized gas transport involving accumulation and sudden release of 10-60 m(3) of gas in the crack over a 6s interval.