The Java Island, Indonesia with abundant amount of pyroclastic deposits is located in the very active and dynamic Pacific Ring of Fires. Studying the geochemical weathering indices of these pyroclastic deposits is imp...The Java Island, Indonesia with abundant amount of pyroclastic deposits is located in the very active and dynamic Pacific Ring of Fires. Studying the geochemical weathering indices of these pyroclastic deposits is important to get a clear picture about weathering profiles on deposits resulting from the eruption of Mt. Merapi. Immediately after the first phase of the eruption （March to June 2006）, moist and leached pyroclastic deposits were collected. These pyroclastic deposits were found to be composed of volcanic glass, plagioclase feldspar in various propoitions, orthopyroxene, clinopyroxene, olivine, amphibole and titanomagnetite. The total elemental composition of the bulk samples （including trace elements and heavy metals） was determined by wet chemical methods and X-ray fluorescence （XRF） analyses. Weathering of the pyroelastic deposits was studied using various weathering indices. The Ruxton ratio, weathering index of Parker, Vought resudual index and chemical index of weathering of moist pyroclastic deposits were lower than those of the leached samples, but the alteration indices （chemical and plagioclase） were slightly higher in the moist compared to the leached pyroelastic deposits.展开更多
To characterize the magma that gave rise to explosive eruptions of Merapi volcano in October-November 2010, melt inclusions and juvenile components fiom the eruption deposits have been analyzed. Major-element composit...To characterize the magma that gave rise to explosive eruptions of Merapi volcano in October-November 2010, melt inclusions and juvenile components fiom the eruption deposits have been analyzed. Major-element compositions of whole-rocks were analyzed by X-ray fluorescence and trace elements, including the Rare Earth Elements by inductively coupled plasma mass spectrometry. Melt inclusions and the host minerals were analyzed using energy-dispersive X-ray spectroscopy and CO2 and H20 in melt inclusions, and their associated bubbles, were analyzed using laser Raman spectrometry. The compositions of the whole-rock eruption products are basaltic and esite that slightly sifting of SiO2 and K20 composition to previous eruption products, whereas the melt inclusions in pyroxene, plagioclase and hornblende are dacite to rhyolite, likely trapped mainly during late stages of crystallization of the magma. The most high volatile content in the melt inclusion are CO2 and H2O which appear strong Raman peaks for CO2 in the gas bubbles indicate abundances on high levels of CO2. Interpretation of result from a long-term flux of CO2 into the reservoir, either derived from more mafic magmas at depth or from reaction of magma in the reservoir with limestone and it may indicate that volcanic outgassing rates far exceed the amounts that can be supplied magmas.展开更多
Debris flow triggered by rainfall that accompanies a volcanic eruption is a serious secondary impact of a volcanic disaster.The probability of debris flow events can be estimated based on the prior information of rain...Debris flow triggered by rainfall that accompanies a volcanic eruption is a serious secondary impact of a volcanic disaster.The probability of debris flow events can be estimated based on the prior information of rainfall from historical and geomorphological data that are presumed to relate to debris flow occurrence.In this study,a debris flow disaster warning system was developed by applying the Na?¨ve Bayes Classifier(NBC).The spatial likelihood of the hazard is evaluated at a small subbasin scale by including high-resolution rainfall measurements from X-band polarimetric weather radar,a topographic factor,and soil type as predictors.The study was conducted in the Gendol River Basin of Mount Merapi,one of the most active volcanoes in Indonesia.Rainfall and debris flow occurrence data were collected for the upper Gendol River from October 2016 to February 2018 and divided into calibration and validation datasets.The NBC was used to estimate the status of debris flow incidences displayed in the susceptibility map that is based on the posterior probability from the predictors.The system verification was performed by quantitative dichotomous quality indices along with a contingency table.Using the validation datasets,the advantage of the NBC for estimating debris flow occurrence is confirmed.This work contributes to existing knowledge on estimating debris flow susceptibility through the data mining approach.Despite the existence of predictive uncertainty,the presented system could contribute to the improvement of debris flow countermeasures in volcanic regions.展开更多
基金supported by the Directorate of Higher Education Department of National Education of Republic of Indonesia under Fundamental Research Grant no: 005/SP3/PP/ DP2M/II/2006-2007, granted to the first authorthe Ministry of Research and Technology of the Republic Indonesia (Fundamental Research Intensive Program with grant no. 97/M/Kp/XI/ 2007) granted to first and second authors
文摘The Java Island, Indonesia with abundant amount of pyroclastic deposits is located in the very active and dynamic Pacific Ring of Fires. Studying the geochemical weathering indices of these pyroclastic deposits is important to get a clear picture about weathering profiles on deposits resulting from the eruption of Mt. Merapi. Immediately after the first phase of the eruption （March to June 2006）, moist and leached pyroclastic deposits were collected. These pyroclastic deposits were found to be composed of volcanic glass, plagioclase feldspar in various propoitions, orthopyroxene, clinopyroxene, olivine, amphibole and titanomagnetite. The total elemental composition of the bulk samples （including trace elements and heavy metals） was determined by wet chemical methods and X-ray fluorescence （XRF） analyses. Weathering of the pyroelastic deposits was studied using various weathering indices. The Ruxton ratio, weathering index of Parker, Vought resudual index and chemical index of weathering of moist pyroclastic deposits were lower than those of the leached samples, but the alteration indices （chemical and plagioclase） were slightly higher in the moist compared to the leached pyroelastic deposits.
文摘To characterize the magma that gave rise to explosive eruptions of Merapi volcano in October-November 2010, melt inclusions and juvenile components fiom the eruption deposits have been analyzed. Major-element compositions of whole-rocks were analyzed by X-ray fluorescence and trace elements, including the Rare Earth Elements by inductively coupled plasma mass spectrometry. Melt inclusions and the host minerals were analyzed using energy-dispersive X-ray spectroscopy and CO2 and H20 in melt inclusions, and their associated bubbles, were analyzed using laser Raman spectrometry. The compositions of the whole-rock eruption products are basaltic and esite that slightly sifting of SiO2 and K20 composition to previous eruption products, whereas the melt inclusions in pyroxene, plagioclase and hornblende are dacite to rhyolite, likely trapped mainly during late stages of crystallization of the magma. The most high volatile content in the melt inclusion are CO2 and H2O which appear strong Raman peaks for CO2 in the gas bubbles indicate abundances on high levels of CO2. Interpretation of result from a long-term flux of CO2 into the reservoir, either derived from more mafic magmas at depth or from reaction of magma in the reservoir with limestone and it may indicate that volcanic outgassing rates far exceed the amounts that can be supplied magmas.
基金supported by the Science and Technology Research Partnership for Sustainable Development(SATREPS)Japan Science and Technology Agency(JST)the Japan International Cooperation Agency(JICA)
文摘Debris flow triggered by rainfall that accompanies a volcanic eruption is a serious secondary impact of a volcanic disaster.The probability of debris flow events can be estimated based on the prior information of rainfall from historical and geomorphological data that are presumed to relate to debris flow occurrence.In this study,a debris flow disaster warning system was developed by applying the Na?¨ve Bayes Classifier(NBC).The spatial likelihood of the hazard is evaluated at a small subbasin scale by including high-resolution rainfall measurements from X-band polarimetric weather radar,a topographic factor,and soil type as predictors.The study was conducted in the Gendol River Basin of Mount Merapi,one of the most active volcanoes in Indonesia.Rainfall and debris flow occurrence data were collected for the upper Gendol River from October 2016 to February 2018 and divided into calibration and validation datasets.The NBC was used to estimate the status of debris flow incidences displayed in the susceptibility map that is based on the posterior probability from the predictors.The system verification was performed by quantitative dichotomous quality indices along with a contingency table.Using the validation datasets,the advantage of the NBC for estimating debris flow occurrence is confirmed.This work contributes to existing knowledge on estimating debris flow susceptibility through the data mining approach.Despite the existence of predictive uncertainty,the presented system could contribute to the improvement of debris flow countermeasures in volcanic regions.
