Technical Note of the National Research Institute for Earth Science and Disaster Prevention, No. 380 ; July, 2013
* Institute of Geology and Geoinformation, National Institute of Advanced Industrial Science and Technology (AIST) 1. Introduction
The National Institute of Advanced Industrial Science and Technology (AIST) produces and compiles geological information to enhance our society’s safety and security.
AIST also works on technological development to create solutions to various problems. These solutions include mitigation of damage by natural disasters, preservation of the global environment, and development of resources and energy on the basis of the compiled information. Among these fields, geological research to mitigate damage by volcanic disasters is the major research theme. To reduce volcanic damage it is indispensable to evaluate and predict changes in volcanic activity and eruptions. In this respect, AIST conducts geological surveys to understanding and evaluating past eruption history, frequency of eruption, and changes in volcanic activity and modeling of magma supply systems, magma ascent and eruption sequences, which are the causes of the activity changes, by using geophysical observations and materials science analyses of rocks and volcanic gas with the aim to refine the techniques to predict volcanic activity changes. This paper focuses on the three research activities currently conducted by AIST: (2) geological maps of volcanoes; (3) researches for prediction of volcanic activity changes; and (4) database of active volcanoes.
2. Geological Maps of Volcanoes
Each volcano has its own characteristics, and eruptions often follow a similar pattern. Study of the history of past activity of a volcano is therefore important to infer the style and scale of possible future eruptions. AIST conducts regular detailed field surveys and compiles the results into geological maps to reveal the past histories of volcanic activity. These geological maps are useful to understand the possible eruption sites, eruptions styles and areas affected by the future eruptions (Fig. 1). There are two series of geological map of volcanoes. The Geological Map of Volcanoes focuses on active volcanoes and the 1:50,000-scale Quadrangle Series covers the entire country. The first Geological Map of Volcanoes was published in 1981 for Sakurajima, issued for 16 volcanoes and was revised. Since 2000, seven maps have been added
Technical Note of the National Research Institute for Earth Science and Disaster Prevention, No. 380 ; July, 2013
the melt inclusions in the phenocrysts in volcanic rock or the microstructures of the phenocrysts. Because these samples are very small, they are analyzed by using an electron microprobe or secondary ion mass analyzer. In addition, magma reaction experiments are conducted with an internally heated gas pressure temperature high-pressure apparatus to quantitatively evaluate the results obtained. This analysis provides us with various findings such as follows;
For an example, the magma ejected by the eruption of Kirishimayama (Shin-Moedake) in 2011 was mixed repeatedly for a long time in the magma chamber and underwent another mixing immediately before eruption, and this final mixing triggered the eruption.
Volatile components in the magma are the major driving force of explosive eruption. At the same time, the emission of volcanic gas onto the ground reflects the degassing process of the magma underground.
Fig. 1 Geological map of Tokachidake Volcano (Ishizuka et al., 2010).
Fig. 2 Melt inclusions of basaltic magma in an olivine phenocryst in Miyakejima ejecta emitted on 18 August 2000 (photo taken by Genji Saito).
AIST’s Research on Volcanology — H. SHINOHARA and Y. ISHIZUKA
We observe the gases from active volcanoes to monitor volcanic gas discharge activity and analyze the degassing process of magma and changes in hydrothermal systems.
Conventionally, the major means of observing volcanic gas components is direct sampling and analysis; the subject of observation is therefore limited to fumarolic activity. However, we have newly developed an apparatus and method for observations of volcanic smoke to measure volcanic gas components (Fig. 3). This system enables us to observe the gases from various volcanoes within and outside Japan. It also allows us to quantify the components of large-scale volcanic gas discharges, such as that in the case of Miyakejima. Thanks to this new technique, advances are being made in evaluating changes in the process of volcanic gas supply as a result of changes in volcanic activity. As the apparatus is designed to conduct automatic measurements, it can be installed on a volcano for long-term observations. Various improvement of the apparatus and techniques are being performed to realize continuous observation of volcanic gas.
Changes in volcanic activity—including increased underground thermal activity, increased supply of volcanic gas, and intrusion of magma—initially cause changes in the underground hydrothermal system. These changes
can be detected on the surface as the changes in thermal activity on the ground surface or in spontaneous potential or resistance in the volcanic edifice. AIST conducts continuous observations of spontaneous potential and repeated observations of surface temperature distribution to detect changes in volcanic activity by observing hydrothermal activity. We also conduct hydrothermal system simulations to quantitatively evaluate these changes. Based particularly on comparisons between the simulation results and observation results, we develop quantitative models of hydrothermal systems that can reproduce those of actual volcanoes to quantitatively predict changes in hydrothermal systems under various conditions caused by magma intrusion or supply of volcanic gas.
4. Database of Active Volcanoes
The histories, the scales and styles of eruption of active Japanese volcanoes are compiled and published as a database to facilitate the understanding and usage of the geological information. The database includes 10,000-year eruption event data, geological maps of volcanoes, detailed volcano data, and researches on active volcanoes.
Collection and editing of information is still under way.
Battery Pump
Data Logger Barometer H
2Sensor
Infrared H
2O/CO
2Analyzer
H
2S/SO
2Gas Sensors
Fig. 3 Multi-GAS (multi-component gas analyzer system).
Technical Note of the National Research Institute for Earth Science and Disaster Prevention, No. 380 ; July, 2013 The 10,000-year eruption event data contains the eruption
date, eruption styles, types of sediments, sources of supply, and scale of eruption, taken from the documents so far published, and those data are chronologically compiled in standardized format. The geological maps of volcanoes and detailed volcano data explain in detail the relevant geology of particularly active volcanoes with the aid of drawings and photos. Researches on active volcanoes overviews the studies on a volcano from an interdisciplinary viewpoint covering geology, geophysics,
and geochemistry, so that readers can obtain a general understanding of volcanoes and is published for Satsuma-Iojima and Usuzan.
Reference
1) Ishizuka, Y., Nakagawa, M., and Fujiwara, S. (2010):
Geological Map of Tokachidake Volcano. Geological Map of Volcanoes, no.16, Geological Survey of Japan, AIST, p. 8.
Technical Note of the National Research Institute for Earth Science and Disaster Prevention, No. 380 ; July, 2013
* The last position; Former fire and Disaster Management Agency, Civil Protection and Disaster Management Department, Disaster 1. Fire and Disaster Management Agency Volcanic
Disas-ter CounDisas-termeasures
Today there are 110 active volcanoes in Japan. A diverse range of volcanic phenomena have high risk for destruction of life and property including volcanic cinders, pyroclastic flows, lahars, lava flows, falling ash, debris flows, volcanic gas, landslides, and are sometime accompanied by tsunami tidal waves. Various measures have been taken in line with Act on Special Measures for Active Volcanoes and other statutes to minimize the impact of volcanic hazards, and the Fire and Disaster Management Agency is charged with administering government support to defray the infrastructure costs of maintaining evacuation facilities in towns and cities in areas where volcanoes are present. In light of volcanic disasters that occurred in 2000—one at the base of Usuzan and the other involving Miyakejima—the Fire and Disaster Management Agency began holding Volcano Disaster-related Prefectural Liaison Council meeting in 2001 to promote sharing of the latest information regarding volcano disaster countermeasures and information held by the various council member organizations.
Then in March 2008, the Cabinet Office, the Fire and Disaster Management Agency, the Ministry of Land, Infrastructure, Transport and Tourism (MLIT), and the Japan Meteorological Agency drafted the “Volcano Disaster Prevention Guidelines for Evacuation when Eruptions Occur” based on discussions of volcano-related information and evacuation plans with the aim of constructing an effective volcano disaster management system. The agencies called on all affected prefectures and municipalities to hold council meetings during normal times in order to set up Joint Countermeasure Headquarters to deal with abnormal situations that arise when eruptions occur, to develop specific and practical evacuation plans, to educate their local populations, and to formulate volcano management countermeasures based on the guidelines.