KARAKTERISTIK VISUAL DARI ERUPSI GUNUNG LUMPUR BLEDUG KUWU, GROBOGAN, JAWA TENGAH BERDASARKAN VOLUME LETUPAN MATERIAL; VISUAL CHARACTERISTICS OF A MUD VOLCANO IN BLEDUG KUWU, GROBOGAN, CENTRAL JAVA BASED ON THE VOLUME OF THE ERUPTED MATERIAL

Widiyatun, Fita, suryanto, Wiwit

2015 | Disertasi | FMIPA UGM

Bledug Kuwu is one an active mud volcano in the world. Research using seismic method and visual recording has not been done in Bledug Kuwu. The aim of this research is to find the characteristics of eruption based on seismic data and visual data. Seismic and video monitoring have been carried out at Bledug Kuwu Mud Volcano, Grobogan, Central Java to study the characteristics of the eruptions. The seismic data acquisition has been done by using three short period seismometers TDV – 23 S with a triangular array configuration. The surface manifestation of eruption is located at the center of the array. One camcorder was installed near the Eastern seismometer to record the eruption visually. From the analysis of the visual recording, we observed four types of eruptions which are frequently happen in Bledug Kuwu. The types of the eruptions is the strong eruption, the row eruptions, the double eruption, and the common eruptions. Each of the eruptions have a varying diameters. The largest diameter is (3.1 ± 0.1) m and the frequently eruptions diameters are (1.0 - 2.0) m. The total volume of gas during 47 minutes and 27 seconds is (5.0 ± 1.0) x102 m3. because the majority of the material eruption is a gas phase. The seismic signal analysis shows that the activity started beneath the surface erupting at the surface and recorded by the camcorder. The frequency range of the eruption seismic signal is (1.6 – 4.2) Hz and the dominant frequency is 2.0 Hz. The analysis of the amplitude for the West station and the East station showed that the medium below Bledug Kuwu is heterogen. From data analysis there is no correlation between the amplitude and the volume of eruption. Differences concentrations of the gas and the liquid phase contributes to density of the material eruption.

Kata Kunci : Mud volcano; Bledug Kuwu; time-frequency analysis; characteristics of the eruption