Miyakejima Eruption in 2000 ABSTRACTS VOLUME CITIES ON VOLCANOES 5 CONFERENCE Shimabara, Japan November 19-23, 2007 Hosted by Volcanological Society of Japan, The City of Shimabara Co-hosted by International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) Faculty of Sciences, Kyushu University Earthquake Research Institute, The University of Tokyo Kyushu Regional Development Bureau, Ministry of Land, Infrastructure and Transport Nagasaki Prefecture The City of Unzen The City of Minamishimabara Mount Unzen Disaster Memorial Foundation Supported by Japan Society for the Promotion of Science (JSPS) The Commemorative Organization for the Japan World Exposition ('70) Tokyo Geographical Society CONTENTS Orals Posters Conference Lectures ..CL Symposium 1: Knowing volcanoes 1-1. Recent developments in volcano research ..11-O ..11-P 1-2. Volcano observation research and eruption forecast and alert programs ..12-O ..12-P 1-3. Health hazards of coexisting with active volcanoes ..13-O ..13-P Symposium 2: Volcanoes and cities 2-1a. Responding to Natural Disasters: Case Histories with Lessons for Volcano ..21a-O ..21a-P Crises 2-1b. Assessing long term volcanic hazards and risks ..21b-O ..21b-P 2-2. Impacts of volcanic activity on infrastructure and effective risk reduction ..22-O ..22-P strategies 2-3. Long-term land-use planning that mitigates volcanic risk ..23-O ..23-P Symposium 3: Living with volcanoes 3-1. Linkage for reducing volcanic risks: Cooperation and mutual support among ..31-O ..31-P researchers, administrators, mass media, inhabitants, local organization and volunteers 3-2. Education and Outreach--Strategies that Improve Community Awareness about ..32-O ..32-P Volcanoes 3-3. Communities and volcanism - archaeology, tradition and recovery ..33-O ..33-P Author Index ____________________________________________ Copyright 2007 by the Volcanological Society of Japan ABSTRACTS VOLUME, CITIES ON VOLCANOES 5 Conference Lectures prepared for more than 30 volcanoes covering most of those on the black list. The swarms of long-period CL 1 earthquakes beneath Fuji volcano in 2000-2001 gave a finishing touch. The impact of possible major eruption like The 1990-1995 Eruption of Unzen Volcano –Spectacle the one occurred in 1707 gave good enough incentive to of Lava Dome Growth and Menace of Pyroclastic the national government which launched a Flows and Lahar– comprehensive investigation. The time is now ripe to take further steps to elaborate well coordinated disaster Kazuya Ohta1 mitigation plans involving many government agencies 1. SEVO, Kyushu Univ. / Japan and citizens-communities. The most needed agenda for Japan is not to implement more hardwares but to strongly Session 1-1 enhance software expertise in science, technology, and Studies Volcano Mt. Fugen had erupted after the 198 years dormancy and administration. formed lava dome at interval of bout 5000 years from previous document. We could observe the formation process in detail for forty-five months by air observations. 3 When magma supply was active more than 5 - 10 m /day, Session 1-1 fluidal lava were extruded and formed lobes. Lava effused showing the form like a flower with several petals. They 11-O-01 grew into mounds on the top of the dome, and on the other hand, they grew into tongue shape on the slope, Recent Developments In Volcano Research: Diversity showing bisecting-crease-structure initially. Some lobes In Volcanism of them were buried by the following ones, and most of them were destroyed by pushing of following lava and Bruce F. Houghton1 generated pyroclastic flows. Lava extrusion site was 1. Geology & Geophysics, University of Hawaii / USA changed 13 times inside the 300 m in diameter through e-mail: [email protected] the whole lava extrusion period, and lava was piled up to a big lava dome. The 11th-B lobe is remained only on the We have yet to explain all aspects of diversity in eastern slope. Formation type of lava dome like these volcanology which limits our ability to forecast the path of corresponded to the squeeze-type offered by Yokoyama future eruptions. Reducing eruption impacts critically (2006). When magma supply was decreased less than 5 - needs better knowledge of what controls the style and 10 m3/day, solidified or semi-solidified lava were uplifted intensity of eruptions. Sudden shifts in the style or just above the conduit and formed fragmented lava cone intensity of eruption are particularly difficult to deal with in with spines. We can see them now at the top of lava the environment of an escalating volcanic crisis. Recent dome. Formation type of lava dome like these history suggests that variations in eruptive intensity during corresponded to the spine-type offered by Yokoyama a single eruption may be as large as 7 orders of (2006). Falling sediments from the lava dome flowed magnitude. Shifts in eruptive style can be equally abrupt, down as lahars and promoted the development of fan e.g. stable Plinian plumes may give way abruptly to dome deposits at the foot in coast area. growth, or paroxysmal pyroclastic density currents, or phreatomagmatic explosions, or an abrupt cessation of activity. Eruption intensity, duration and style are CL 2 determined either during magma storage, which provides the overpressure driving an eruption, or in the volcanic Last 30 Years of Volcanic Hazard Mitigation in Japan conduit, where magma decompresses, loses volatiles, and sometimes partially crystallizes. These environments Shigeo Aramaki1 cannot be observed directly and must be inferred from 1. Yamanashi Inst. Environ. Sci. / Japan geophysical data, theoretical models, analog experiments, e-mail: [email protected] and the textures preserved in the eruptive products. Recent models have sought to explain gradual and abrupt In the last 30 years, Japan has witnessed an average of 3 shifts in eruptive style/intensity in volcanic systems in volcanic eruptions as well as many more volcanic crises terms of changing conduit/vent dimensions, unsteady each year. Out of 50 deaths occurred during this period, non-linear behavior during conduit flow and in eruption 44 were caused by the pyroclastic flows of Unzen volcano plumes, shifts in mass flux, onset of permeability and in 1991. Except this Unzen case, the low death rate and outgassing of ascending magma, or pressure shifts in the large number of evacuated residents during the crises shallow magma chambers causing transitions from (ca. 40,000 people in 7 events) may indicate steady to unsteady conduit flow. Much of our current effectiveness of recent preventive measures. In a few understanding of the dynamics of ascent and eruption of cases, including the 2000 eruption of Usu, forecasting magma has come from the studies of Mount St Helens, was so successful that large number of residents had Unzen and Soufrière Hills for silicic volcanoes and Etna, been evacuated before the eruption actually started. The Stromboli and Kilauea for basaltic systems. For these most regrettable was the loss of 43 people in the recent eruptions the disciplines above have combined to peripheral part of pyroclastic surge during the 1991 June offer models based on very broad data sets. The 3 eruption of Unzen, The victims were not sufficiently remaining challenge is to bring these linkages between warned of the danger, which in the hindsight, could have geology, hydrology, geochemistry, geophysics, analog been done by the volcanologists, including myself, and experimentation and numerical modeling together to offer the authority. Thanks to this event, no question was reliable forecasts on reasonable time scales. asked when 16,000 people followed the evacuation advisory in fear of the pyroclastic flow during the 2000 Usu eruption. During the last 30 years, hazard maps were 11-O-02 1 ABSTRACTS VOLUME, CITIES ON VOLCANOES 5 recorded, then followed by occurrence of 55 LF events in Seismic Imaging of Magma Chambers Under Active October, and HF events reached 450 events in Arc Volcanoes and Hotspots November. HF events are dominated by high-frequency Dapeng Zhao1 component in range of 6-25 Hz. LF events have . Research Center for Prediction of Earthquakes & Volcanic lower-frequency content of 1-5 Hz. Monochromatic Eruptions, Tohoku University, Sendai / Japan events have an unique waveform, especially at coda part e-mail: [email protected] which shows a slowly decaying amplitude of coda part. Based on their frequency content, monochromatic events We have used multi-scale seismic tomography methods are sub-divided into two types, low-frequency to image the detailed three-dimensional velocity monochromatic (LFMC) and high-frequency structures of the crust and mantle beneath active arc monochromatic (HFMC) events. LFMC events have volcanoes in Japan, intraplate volcanoes in the continents, dominant frequency of 1-5 Hz and show some peaks of and hotspot volcanoes in the oceanic regions. subdominant frequencies. HFMC events show higher Applications of local and teleseismic tomography dominant frequency at 6-15 Hz and some peaks of methods to high-quality data recorded by the dense subdominant frequencies also appeared. Subdominant seismic networks on the Japan Islands have resulted in peaks have varied frequency content from low-frequency, clear images of the subducting Pacific and Philippine Sea less than 5 Hz, to higher-frequency more than 5 to 30 Hz. slabs and magma chambers in the crust and upper Associated with increase of monochromatic events, mantle wedge beneath active arc volcanoes, indicating inflation of ground around the crater was observed by that geodynamic systems associated with arc magmatism GPS observation and it was followed by increase in and back-arc spreading are related to deep processes, fumarolic activity. Monochromatic events at Papandayan such as convective circulation in the mantle wedge and volcano recorded in June-July 1998, which was related to dehydration reactions of the subducting slab (Zhao, 2001). the increase in seismicity and the anomalous gas Evidence also shows that arc magma and slab emission from the active crater.