VI. National Project for Prediction of Volcanic Eruptions
1. Outlines of National Project for Prediction of Volcanic Eruptions
Brief History of the First, Second, Third and Fourth 5-year Plans
National Project for Prediction of Volcanic Eruptions was initiated in 1974, on the recommendation of the Geodetic Council of Ministry of Education, Science and Culture. Since then, the subsequent 5-year plans have been carried out by the relating governmental institutions and observatories. The aims of the plan are to grasp the state of volcanic activity, predict the time of eruption and to forecast the subsequent eruptive stages. For these purposes, basic researches to understand the volcanic phenomena as well as detailed and comprehensive observations have been conducted.
During the first plan (1974-1978), the volcano observatories of Japan Meteorological Agency (JMA) and national universities were strengthened and modernized by introducing new techniques of telemetering and computer processing of data. The newly established mobile observation teams of JMA and universities contributed to frequent field observations at active and potentially active volcanoes. A new observatory was established in 1976 in Hokkaido, in time for the 1977 eruption of Usu volcano. The comprehensive joint observations were also conducted at two specified volcanoes every year since 1976. The Coordinating Committee for prediction of Volcanic Eruptions (CCPVE) was founded in 1974 in order to exchange information and to evaluate the volcanic activity in Japan.
During the second plan (1979-1983), volcano observation was expanded and strengthened, especially routine observation at the most active 6 volcanoes by JMA and the local to regional station coverage by universities. The Hydrographic Department, the Geographical Survey Institute, the Center of Science and Technology on Disaster Prevention, and the Geological Survey also participated in the observations and the related basic researches.
During the third plan (1984-1988), 12 volcanoes were selected as the active volcanoes with highest priority for observations and researches. Observation networks were reinforced and improved step by step to more extensive, dense, and accurate systems. Izu-Oshima volcano observatory was established in 1984 two years before the recent eruption. A special volcano observatory for geochemical researches was established in 1988 at Kusatsu-Shirane volcano.
Continuous monitoring of ground deformation with improved S/N ratio was started at three volcanoes (Sakurajima, Tokachi and Aso), using newly constructed observation vaults. At Sakurajima, a personal computer system to predict summit eruptions was successfully developed to practical use, by detecting the precursory tilt and strain changes due to magma/gas pressure increase in the shallow vent-gas chamber system. Similar precursory changes were also detected during the 1988-1989 eruption of Tokachidake.
In addition to seismic and geodetic methods, the geochemical, electromagnetic and gravimetric observations, marine experiments by self-navigation buoy, and satellite imagery of eruption clouds gave new contributions to comprehensive and fundamental researches of volcanic activity.
The 1986 eruption of Izu-Oshima occurred 2 years after the establishment of a volcano observatory. So, valuable fundamental data on long- and short-term precursors and on prediction of development in volcanic activities were obtained, based on extensive, dense and accurate monitoring networks. The CCPVE organized the comprehensive observation team and the Izu-Oshima sub-committee, for a quick and comprehensive information to public.
Basic researches on subsurface structure were conducted at several volcanoes; eruption dynamics and its relation to subsurface structure of a vent-chamber system (Sakurajima), time history of physical properties of lava dome Showa-Shinzan (Usu), detection of magma storage zones (Sakurajima and Aso), sub-crust low velocity zone under the volcanic front in Tohoku district.
Comprehensive joint observations were made at two volcanoes each year. Joint observations had been conducted eight times at Sakurajima during 1974-1988. One of the main conclusions of the joint observations was the detection of a density increase at the magma chamber beneath the summit crater that had been continuously erupting since 1955.
During the fourth plan (1989-1993), seismic and geodetic observations were reinforced and improved by using borehole instruments at some of the most active 12 volcanoes. Comprehensive observations were conducted at many volcanoes and real-time monitoring of active craters was also made at some volcanoes. Precursors to the recent activity of Unzen volcano were detected 2 years before the beginning of the eruption in 1990. Since then, comprehensive observations were made to realize the present state and to predict the future activity. The CCPVE organized the Unzen WG for a deep discussion of observational data to give a comprehensive information to public.
At other volcanoes, monitoring networks were also expanded, and mobile observation teams and the research vessels contributed to better grasping and understanding of a wide range of activities and a greater number of volcanoes. The 1989 submarine eruption off east Izu peninsula and related earthquake swarm activity were comprehensively observed, in an intimate collaboration with the Project for Prediction of Earthquakes. An unmanned radio-controlled research boat had been developed and tested before the 1989 submarine eruption, and its usefulness was proven during the eruption. Comprehensive joint observations were made at two volcanoes each year during the fourth plan.
The geochemical methods of gas and ground water monitoring were repeatedly applied to evaluate the volcanic activity. Remarkable variations in SO2 discharge were observed in relation to changes in the activity of many volcanoes. The GPS technique was successfully applied for ground deformation surveys during the activities off east Izu peninsula and at Unzen volcano.
The automatic data processing and integration system was developed for the rapid and accurate evaluation of volcanic activities. We also developed an intelligent observation and telemetering system for remote volcanoes and a detection method of explosive eruptions at remote volcanoes based on low frequency airwaves.
Basic researches were conducted on many aspects of volcanic eruptions: characteristics of explosive eruptions (Tokachidake, Sakurajima and Suwanosejima), generation mechanisms of pyroclastic flows (Tokachidake and Unzen), a mechanism of explosion earthquakes and its relation to a magma chamber-conduit system (Sakurajima). Modeling of eruption mechanisms was also made based on extensive observational data of several volcanoes (Sakurajima, Izu-Oshima, off east Izu peninsula, and Unzen).
The controlled-source seismic experiments revealed the high velocity zone at depths shallower than a few km beneath several volcanoes (Bandai, Iwaki and Izu-Oshima). Tomographic studies of 3-D velocity structure indicated the low velocity zone at the lower crust and upper mantle beneath active volcanoes in Tohoku district. Unusual low frequency earthquakes are observed around the LV zone. Later phases reflected at mid-crustal depths are also detected around active volcanoes. Magnetotelluric soundings revealed the low resistivity layers beneath volcanoes, and the shallow layer was found to be the aquifer.
Some basic materials of precise topographic maps, volcanic geology maps, submarine bathymetric maps were published. For a more effective utilization of the abundant basic data, they have been compiled to construct databases.
Organizations of volcano sections were reinforced at JMA, National Research Institute for Earth Science and Disaster Prevention, Geographical Survey Institute, and Hydrographic Department. Several university observatories extended their observation and research to cover volcanoes and earthquakes (Shimabara, Tohoku and Nagoya).
At the 1989 eruption off east Izu peninsula (Teishi Knoll), the Coordinating Committee made collaboration with the organizations involved in Earthquake Prediction Plan, and formed a subcommittee for the submarine eruption. Those were examples of reinforcement of the functions of the Coordinating Committee.
Various international collaborations over a wide range of volcanic activities and exchange of experiences were made (e.g., Philippine, Zaire and Indonesia). They could also contribute to the development of eruption prediction.
Achievement of the Fifth (1994-1998) 5-year Plan
The fifth plan emphasized that, in order to further improve the precision of prediction, basic researches, including the elucidation of the internal structure and state within volcanic bodies as well as the modeling of eruption processes, had to be promoted, and volcanic structure explorations began to be carried out in a full scale.
(1) Expansion and reinforcement of observational research on volcanoes
At some of the most active 12 volcanoes, seismic and geodetic observations were reinforced and improved by using newly constructed observation wells and vaults. Comprehensive observations were conducted at many volcanoes and a satellite-aided system (ARGOS) expanded the monitoring of active craters at some volcanoes.
At other volcanoes, monitoring networks were also expanded, and mobile observation teams and the research vessels contributed to better grasping and understanding of a wide range of activities and a greater number of volcanoes. A new research vessel equipped with an unmanned radio-controlled research boat was constructed to reinforce the extensive surveys of submarine volcanoes.
In the fifth plan, the joint observation was divided into two parts. One is the similar comprehensive observation as before, and another is the basic research experiment on subsurface structure of volcanoes. Each joint observation was made at one volcano every year. Since 1998, comprehensive joint observations have been repeated to monitor the increased activity of Iwate volcano.
(2) Promotion of basic research for the elucidation of eruption mechanisms -with an emphasis on the understanding of volcanic structures
Dense seismic explorations with artificial sources were carried out at Kirishima, Unzen, Bandai and Aso volcanoes, using excellent data loggers equipped with GPS timing devices that became practicable shortly after the launching of the fifth plan. Gravity and electromagnetic explorations were also conducted at these volcanoes.
The results of velocity tomography revealed the 3-D structure at depths shallower than 3km, and delineated higher velocity bodies beneath the volcanoes. Electromagnetic exploration has identified a low-resistivity layer at a depth of about 10km beneath the northwestern part of the Kirishima Volcano Group. A reflection analysis of seismic data also indicated a remarkable reflective layer at a depth of 10km. A 3-D seismic tomography, based on data from permanent observations, also identified a low-velocity layer and high attenuation zones in much the same area. A new method of diffraction tomography was developed and applied to the teleseismic waves observed by dense array to obtain the distribution of scatterers beneath Izu-Oshima. A comparison of the distribution of scatterers, hypocenter distribution and the location of the magma chamber as estimated from continuing inflation of the volcano, has suggested that the zone of strong scatterers corresponds to the location of magma chamber. Drilling of a 1km-deep observation well was completed in 1998 near the summit crater of Izu-Oshima volcano. Major objectives include 3-D array seismic observation and the exploration of subterranean structure, studies of thermal interaction of hot magma/gas with ground water around the summit conduit, the elucidation of caldera structure and formation mechanism, history of volcanic activity, and magma plumbing system.
To elucidate the mechanisms of phreatic explosions, experimental studies have been launched to specify the conditions for destabilization of the interactions between magma and ground water. A theoretical approach to reconstruct the dynamics of diffusion of ejected smoke on the basis of grain size analysis of tephra was developed, and was applied to the 1991 eruption of Pinatubo.
(3) Development of prediction techniques and the assembling of basic database
Various remote sensing techniques have been developed: detection of ground deformations around volcanoes by interferometric processing of SAR data from satellites and airplanes and laser altimeters mounted on airplanes, quantitative observations of the smoking activities by microwave radiometers and high-resolution microwave radars, measurements of the SO2 discharge rate from satellites, monitoring of submarine volcanoes by hydrophones.
Various observation equipments have been developed: intelligent data loggers with GPS timing devices, throw-down type seismograms for volcanoes, precisely-controlled source devices for subsurface exploration, monitoring of active craters by using a satellite-aided ARGOS system, and a system for continuous measurements of volcanic gases.
The automatic data processing and integration systems have been under continual upgrading for the rapid and accurate evaluation of volcanic activities.
Some basic materials of precise topographic maps around volcanoes, volcanic geology maps, submarine bathymetry, geology and geophysical maps were published. For a more effective utilization of the abundant basic data, they have been compiled to construct databases.
(4) Reinforcement of the organizations for the prediction of volcanic eruptions
In order to conduct more effective monitoring and researches of volcanic activity, it is necessary to reinforce the facilities and personnel of concerned agencies. The volcano section of JMA was reinforced to Volcanological Division. Organizations of volcano sections were also reinforced at Geological Surveys and Geographical Survey Institute. Communications Research Laboratory has joined the national project since its fifth plan. The volcano section at Earthquake Research Institute was reorganized into Volcano Research Center to promote more efficient collaborative observation and researches of volcanic activity. Sakurajima Volcano Observatory was also reorganized into Sakurajima Volcano Research Center. Several university observatories extended their observations and researches (Hokkaido, Hirosaki, Tohoku, Kusatsu-Shirane and Tokyo).
Various international collaborations over a wide range of volcanic activities and exchange of experiences were made (e.g., Indonesia, Philippine, Zaire and USA). They could also contribute to the development of eruption prediction.
Review of the National Project for Prediction of Volcanic Eruptions and the Sixth 5-year Plan (1999-2004)
The entire past history (from first to fifth) of the National Project for Prediction of Volcanic Eruptions was reviewed in 1997. The review confirmed, based on the achievements to date, that it was possible to detect short-term eruption precursors if observations were carried out to match each individual volcano's characteristics, while problems to be tackled in the future for a practicable eruption prediction were pointed out. It pointed out that, in order for the eruption prediction to become practicable, it was indispensable to elucidate mechanisms of eruption and of the manifestation of precursory phenomena, as well as to have a detailed knowledge of the current state of activity at each volcano. It also suggested that, in order to promote long-term forecasting, a precise understanding of the eruption history of active volcanoes and the study of eruptive potential evaluation were necessary.
The recommendation for the sixth 5-year plan (1999-2004), which appeared in 1998, suggested that, in order to achieve qualitative improvements in eruption prediction, a physico-chemical model had to be constructed for a precise understanding of the subsurface state beneath volcanoes and for a quantitative forecasting of the eruption processes, and that a method of eruptive potential evaluation had to be established for long-term forecasting. With these notions in mind, the sixth plan is to be carried out along the following lines: (1) Amplification of observational research on volcanoes, (2) Promotion of basic research for a higher-grade prediction of volcanic eruptions, (3) Strengthening of the scheme for the prediction of volcanic eruptions.
Coordinating Committee for Prediction of Volcanic Eruptions
The CCPVE was established in 1974 when National Project for Prediction of Volcanic Eruptions in Japan started. The aim is to execute the National Project by a tight cooperation in research and duty of all organizations concerned.
The Committee exchanges observational results and other information on volcanic activity periodically. At the time of emergency or increased volcanic activity, the Committee, the Secretary Meeting or the Sub-committee will be held, and official comments are issued if necessary. During 1994-1998, the Committee was held 15 times (No. 65-No. 79).
The CCPVE organized the Sub-Committee for submarine volcano off east Izu Peninsula in 1989. This area was located at the margin of the expected M8 class Tokai Earthquake, and extensively monitored by the National Project of Earthquake Prediction. Many observational data detected by those networks were also valuable for volcano studies. Some members working in the Earthquake Prediction Project were asked to join the Sub-Committee for the submarine eruption, and the Sub-Committee worked efficiently to collect all the observational data and to issue a necessary information to public. The CCPVE organized a working group in 1993 for an intensive evaluation of the activity of Unzen volcano that started the eruption in 1990. The CCPVE could point out a possible outflow of lava, prior to the emergence of a lava dome at the erupting Unzen. The CCPVE also organized a special working group within itself to discuss authorization of new active volcanoes, long-term forecasting and the dispatching of volcanic information. This has pushed the number of authorized active volcanoes in Japan to 86, up from 77 at the time of inauguration of the National Project. Categorization of the activity level is also under consideration.
The executive office of the CCPVE is placed at Japan Meteorological Agency. The CCPVE published a report, Report of Coordinating Committee for Prediction of Volcanic Eruptions. During 1994-1998, 15 issues (No. 58-No. 72) were published. The reports are written in Japanese but figure captions are both in Japanese and in English (since 1982).
The Joint Experiment on Subsurface Structure of Volcanoes, Comprehensive Joint Volcano Observation and Other Joint Observations
During 1994-1998, the university volcanologists made the scheduled joint experiments on subsurface structure of volcanoes and comprehensive joint volcano observations at 11 volcanoes on the National Project for Prediction of Volcanic Eruptions.
Structure exploration Comprehensive observation
1994 Kirishima Unzen (2nd)
1995 Unzendake Miyakejima (4th)
1996 Kirishima (2nd) Sakurajima (9th)
1997 Bandai Hokkaido-Komagatake (2nd), Tarumai (2nd)
1998 Aso Suwanosejima (3rd)
Other joint volcano observations were made at Kuju and Iwate volcanoes.
(Appendix)
List of institutions and observatories that participate in observations for the National Project for Prediction of Volcanic Eruptions in Japan (as of 1998).
(1) Japan Meteorological Agency
Volcanological Division (with related observatories)
Meteorological Research Institute
Magnetic Observatory
(2) Hydrographic Department, Maritime Safety Agency
(3) Geographical Survey Institute, Ministry of Construction
(4) Geological Survey of Japan, Agency of Industrial Science and Technology
(5) National Research Institute for Earth Science and Disaster Prevention, Science and Technology Agency
(6) Communications Research Laboratory, Ministry of Post and Communications
(7) National Universities (Ministry of Education, Science, Sports and Culture)
1) Institute of Seismology and Volcanology (Usu Volcano Observatory), Graduate School of Science, Hokkaido University
2) Earthquake and Volcano Observatory, Faculty of Science, Hirosaki University
3) Research Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku University
4) Kusatsu-Shirane Volcano Observatory, Tokyo Institute of Technology
5) Volcano Research Center, Earthquake Research Institute, University of Tokyo
Asama Volcano Observatory
Izu-Oshima Volcano Observatory
Kirishima Volcano Observatory
6) Laboratory for Earthquake Chemistry, Graduate School of Science, University of Tokyo
7) Research Center for Seismology and Volcanology, Graduate School of Science, Nagoya University
8) Shimabara Earthquake and Volcano Observatory, Faculty of Science, Kyushu University
9) Aso Volcanological Observatory, Graduate School of Science, Kyoto University
10) Sakurajima Volcano Research Center, Disaster Prevention Research Institute, Kyoto University
11) Nansei-Toko Observatory for Earthquakes and Volcanoes, Faculty of Science, Kagoshima University
(Hidefumi Watanabe)
References
**The Geodesy Council of the Ministry of Education, Science, Sports and Culture, Japan (1993):
The Fifth National Plan for Prediction of Volcanic Eruptions (proposal). 16p.
**The Geodesy Council of the Ministry of Education, Science, Sports and Culture, Japan (1997): State-of-the-art review of the National Project for Prediction of Volcanic Eruptions. 88p.
**The Geodesy Council of the Ministry of Education, Science, Sports and Culture, Japan (1998): The Sixth National Plan for Prediction of Volcanic Eruptions (proposal), 15p.
(** In Japanese)