Volcanic Earthquakes at Merapi (Central Java) During the Lava Dome Building Beginning in October 1986
This study presents results of seismic measurements on Merapi volcano from August 1986 to July 1987. This time period includes the volume increase of the magma dome by about 2 million m3 in October 1986. The seismic data were recorded by three stations which are located within 5 km distance from the summit, (KLT: 1.5 km from the summit. north-west; LBH and KKN: 2.2km and 5 km, south).
With the beginning of the lava doming, the following changes in the seismicity were observed: the number of shocks per hour increased, with an increase in the ratio of recorded shocks between the stations LBH to KLT and KKN to KLT. Before the building of the lava dome, a significant periodicity at 24 and 12 h in the occurrence of the shocks was noted. This phenomenon was greatly reduced with the accumulation of outcoming magma. The diurnal and semidiurnal occurrence possibly follows barometric pressure fluctuations acting on the volcano.
Furthermore, the dominant frequencies in the seismic shocks shifted to lower values. As the first onset of the shocks can not be accurately determined (Minakami B-type), epicentres and source depths were estimated using the maximum amplitude ratios found at the different stations. The locations of the shocks with respect to the lava dome building are discussed.
KeywordsSeismic Data Discrete Fourier Transform Amplitude Ratio Barometric Pressure Earth Tide
Unable to display preview. Download preview PDF.
- Emter D, Zuern W, Schick R, Lombardo G (1986) Search for tidal effects on volcanic activities at Mt. Etna and Stromboli. Proc Int Symp Earth Tides, Madrid, pp 765-774.Google Scholar
- Fadeli A (1987) An Analysis of seismic data from Merapi volcano (central Java). 1987 Contrib Merapi Volcano Res Group. Gadjah Mada Univ, Sekip Unit III, PO Box Bls 21, Yogyakarta, Indonesia.Google Scholar
- Fadeli A, Kirbani SB, Mugiono R, Schick R (1987) First Results on a new seismic station network on Merapi volcano (central Java, Indonesia). 1987 Contrib Merapi Res Group. Gadjah Mada Univ, Sekip Unit III, PO Box Bls 21, Yogyakarta, Indonesia.Google Scholar
- Heaton TH (1975) Tidal triggering of earthquakes. Geophys J R Astr Soc 43:307–326.Google Scholar
- Kirbani SB (1987) Seismicity (Tremors) of Merapi volcano (central Java, Indonesia). 1987 Contrib Merapi Volcano Res Group. Gadjah Mada Univ, Sekip Unit III, PO Box Bls 21, Yogyakarta, Indonesia.Google Scholar
- Klein FW (1976) Earthquakes swarm and semidiurnal solid earth tide. Geophys J R Astr Soc45:245–295.Google Scholar
- Knopoff L (1964) Earth tides as triggering mechanism for earthquakes. Bull Seismol Soc Am54:1865–1870.Google Scholar
- Lenat JF, Bachelery P (1988) Dynamics of magma transfer at Piton de la Fournaise volcano (Reunion island, Indian ocean). In: Yu King C, Scarpa R (eds) Modeling of volcanic processes. Vieweg, Braunschweig, pp 57–72.Google Scholar
- Nicolis G (1987) Bifurcation and stochastic Analysis of nonlinear systems: an introduction. In: Nicolis C, Nicolis G (eds) Irreversible phenomena and dynamical systems analysis in geosciences. NATO ASI Ser C: Mathematical and physical sciences, vol 192, pp 3-29.Google Scholar
- Oppenheim AV, Schafer RW (1975) Digital signal processing. Prentice Hall, Englewood Cliffs, New Jersey.Google Scholar
- Sassa K (1936) Micro-seismometric study on eruptions of the volcano Aso. Mem Coll Sci, Kyoto Imp Univ, Ser A 19:11–56.Google Scholar
- Schick R, Mueller W (1988) Volcanic activity and eruption sequences at Stromboli during 1983–1984. In: Yu King C, Scarpa R (eds) Modelling of volcanic processes. Vieweg, Braunschweig, pp 120–139.Google Scholar
- Ulbrich U, Ahorner L, Ebel A (1987) Statistical investigations on diurnal and annual periodicity and on tidal triggering of local earthquakes in central Europe. J Geophys Res 61:150–157.Google Scholar
- Van Bemmelen (1950) The geology of Indonesia, vol 1A. General Geology Government Printing office, The Hague.Google Scholar
- Young D, Zuern W (1979) Tidal triggering of earthquakes in the Swabian Jura? J Geophys45:171–182.Google Scholar