Non-volcanic Areas Research Articles

Development of a trip time for bit exchange simulator for drilling time estimation

The development of geothermal power generation technologies for applications in non-volcanic areas, based on artificial reservoir creation, has prompted numerous studies on the efficient and economic execution of costly deep subsurface drilling operations. However, the difficulties in predicting the duration and cost of boring work with acceptable reliability make the efficient and organized management of drilling operations very difficult. The trip time for drill bit (i.e., the time taken to withdraw the drill stem to replace bits worn-out, followed by its re-entry into the borehole) that is required because of the abrasion and replacement of bits has a large impact on drilling time and performance. Therefore, a methodology for predicting the time required for a trip for bit exchange at a given depth will enable reliable drilling time and cost estimation for better drilling production management. This study divided the abrasion condition of roller bits into eight steps and used bit life expectancy time for developing a simulation algorithm for Trip Time for Bit Exchange (TTBE). A methodology that can classify the depth of drilling well based on the characteristics of the formation and drilling parameters has also been suggested based on the Bourgoyne and Young model to forecast drilling rates and the extent of bit abrasion.

Thyroid Cancer in the Pediatric Age in Sicily: Influence of the Volcanic Environment.

Pediatric thyroid cancer (TC) is rare but its incidence is increasing. We analyzed incidence and characteristics of pediatric TC in Sicily and comparatively evaluated data from the volcanic and non-volcanic areas. All incident pediatric (0-19 years) TCs in Sicily between 2002-2009 were analyzed for the area of residence and compared to data for adults. A total of 54 differentiated TCs (DTC) and nine medullary TCs were diagnosed in Sicily in children between 2002-2009. DTC age standardized rate for the world population (ASRw) was 0.8/105 in females and 0.2/105 in males, with a higher incidence in the volcanic area (ASRw=1.4/105 in females, 0.5/105 in males) vs. the rest of Sicily (ASRw=0.6/105 in females, 0.1/105 in males). Pediatric TCs were larger in size and more frequently with extrathyroid extension and lymph-node involvement in comparison to TCs in adults. In the volcanic environment of Sicily, TC incidence is markedly increased in children, suggesting a short-term effect of unidentified carcinogens of volcanic origin.

Stochastic ground-motion simulations for the 2016 Kumamoto, Japan, earthquake

On April 15, 2016, Kumamoto, Japan, was struck by a large earthquake sequence, leading to severe casualty and building damage. The stochastic finite-fault method based on a dynamic corner frequency has been applied to perform ground-motion simulations for the 2016 Kumamoto earthquake. There are 53 high-quality KiK-net stations available in the Kyushu region, and we employed records from all stations to determine region-specific source, path and site parameters. The calculated S-wave attenuation for the Kyushu region beneath the volcanic and non-volcanic areas can be expressed in the form of Q s = (85.5 ± 1.5)f 0.68±0.01 and Q s = (120 ± 5)f 0.64±0.05, respectively. The effects of lateral S-wave velocity and attenuation heterogeneities on the ground-motion simulations were investigated. Site amplifications were estimated using the corrected cross-spectral ratios technique. Zero-distance kappa filter was obtained to be the value of 0.0514 ± 0.0055 s, using the spectral decay method. The stress drop of the mainshock based on the USGS slip model was estimated optimally to have a value of 64 bars. Our finite-fault model with optimized parameters was validated through the good agreement of observations and simulations at all stations. The attenuation characteristics of the simulated peak ground accelerations were also successfully captured by the ground-motion prediction equations. Finally, the ground motions at two destructively damaged regions, Kumamoto Castle and Minami Aso village, were simulated. We conclude that the stochastic finite-fault method with well-determined parameters can reproduce the ground-motion characteristics of the 2016 Kumamoto earthquake in both the time and frequency domains. This work is necessary for seismic hazard assessment and mitigation.

S wave attenuation structure on the western side of the Nankai subduction zone: Implications for fluid distribution and dynamics

AbstractWe estimated the S wave attenuation structure in southwestern Japan and the western Nankai Trough by analyzing maximum S wave amplitudes at 4–8, 8–16, and 16–32 Hz with a correction term for apparent amplitude attenuation due to multiple forward scattering. Because the estimated attenuation (Q−1) in our tomographic study was much larger than Q−1 due to wide‐angle scattering, our estimated Q−1 was composed mainly of intrinsic attenuation. High‐attenuation areas (Q−1 > 1/300 at 4–8 Hz) were imaged beneath Quaternary volcanoes and south off Shikoku. Low (<1/1500 at 4–8 Hz) or moderate Q−1 (1/500–1/1000 at 4–8 Hz) was imaged beneath Shikoku and nonvolcanic areas of Chugoku. High and moderate Q−1 in and around Shikoku are located near the top of subducting Philippine Sea Plate. This correspondence implies that these high and moderate Q−1 reflect fluid in the subducting slab. By applying a theoretical model of attenuation in water‐saturated porous random media, we examined wave‐induced fluid flow induced by lower frequency (<1 Hz) seismic waves that may be related with triggering of nonvolcanic tremor by surface waves. Even though Q−1 structure in this study cannot fully explain the tremor triggering by wave‐induced fluid flow, large uncertainties of Q−1 in tremor zone suggest that high resolution imaging of Q−1 and random inhomogeneities would give some constraints for the spatial variation of permeability and other medium properties.

Diffuse soil CO_2 degassing from Linosa island

<!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:HyphenationZone>14</w:HyphenationZone> <w:PunctuationKerning/> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <w:DontGrowAutofit/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--><p class="MsoNormal" style="text-align: justify; line-height: 200%;"><!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:TrackMoves/> <w:TrackFormatting/> <w:HyphenationZone>14</w:HyphenationZone> <w:PunctuationKerning/> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:DoNotPromoteQF/> <w:LidThemeOther>IT</w:LidThemeOther> <w:LidThemeAsian>X-NONE</w:LidThemeAsian> <w:LidThemeComplexScript>X-NONE</w:LidThemeComplexScript> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <w:DontGrowAutofit/> <w:SplitPgBreakAndParaMark/> <w:DontVertAlignCellWithSp/> <w:DontBreakConstrainedForcedTables/> <w:DontVertAlignInTxbx/> <w:Word11KerningPairs/> <w:CachedColBalance/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> <m:mathPr> <m:mathFont m:val="Cambria Math"/> <m:brkBin m:val="before"/> <m:brkBinSub m:val="--"/> <m:smallFrac m:val="off"/> <m:dispDef/> <m:lMargin m:val="0"/> <m:rMargin m:val="0"/> <m:defJc m:val="centerGroup"/> <m:wrapIndent m:val="1440"/> <m:intLim m:val="subSup"/> <m:naryLim m:val="undOvr"/> </m:mathPr></w:WordDocument> </xml><![endif]--></p><p>Herein, we present and discuss the result of 148 measurements of soil CO<span><sub>2</sub></span> flux performed for the first time in Linosa island (Sicily Channel, Italy), a Plio-Pleistocene volcanic complex no longer active but still of interest owing to its location within a seismically active portion of the Sicily Channel rift system. The main purpose of this survey was to assess the occurrence of CO<span><sub>2</sub></span> soil degassing, and compare flux estimations from this island with data of soil degassing from worldwide active volcanic as well as non-volcanic areas. To this aim soil CO<span><sub>2</sub></span> fluxes were measured over a surface of about 4.2 km<span><sup>2</sup></span> covering ~80% of the island. The soil CO<span><sub>2</sub></span> degassing was observed to be mainly concentrated in the eastern part of the island likely due to volcano-tectonic lineaments, the presence of which is in good agreement with the known predominant regional faults system. Then, the collected data were interpreted using sequential Gaussian simulation that allowed estimating the total CO<span><sub>2</sub></span> emissions of the island. Results show low levels of CO<span><sub>2</sub></span> emissions from the soil of the island (~55 ton d<span><sup>-1</sup></span>) compared with CO<span><sub>2</sub></span> emissions of currently active volcanic areas, such as Miyakejima (Japan) and Vulcano (Italy). Results from this study suggest that soil degassing in Linosa is mainly fed by superficial organic activity with a moderate contribution of a deep CO<span><sub>2</sub></span> likely driven by NW-SE trending active tectonic structures in the eastern part of the island.</p>

Provenance and proximity: a technological analysis of Late and Final Neolithic ceramics from Euripides Cave, Salamis, Greece

This paper examines application of the provenance hypothesis in areas of complex regional geology, where all potential sources of raw materials cannot be isolated or taken into account. With a few notable exceptions most pottery of the Late and Final Neolithic in Central and Southern Mainland Greece is considered to be locally produced by non-specialist household potters. Nevertheless small quantities of pottery with fresh volcanic fabrics have been found in largely non-volcanic areas and interpreted as imports. This interpretation has been questioned and alternative local sources proposed either in isolated palaeovolcanic units amongst otherwise non-volcanic rocks or through reuse of imported artefacts such as millstones made from fresh volcanic rock. In this study we examine evidence for pottery exchange at the Cave of Euripides, located opposite the island of Aegina, a potential source of imported volcanic materials in the region. The analysis uses petrography to identify raw materials, production technologies and provenance of the pottery. Results show that most pottery at the cave was produced locally. It is argued that grog and sparry calcite tempered fabrics are indicative of shared technological knowledge amongst potters in different communities. Pottery imports are identified based on their fresh volcanic inclusions. They are consistent with pottery fabrics from Aegina and distinguished from the local palaeovolcanic rocks that occur in close proximity to the cave.

P wave attenuation structure beneath the Kanto district and surrounding area, Japan

Spectral ratios of teleseismic P waves for 15 deep (>200 km) earthquakes recorded at 146 High-Sensitivity Seismographic Network stations in the Kanto district and its surrounding area, eastern Japan, were inverted for attenuation parameter \( t_P^{ * } \). The dataset consisted of good-quality vertical-component seismograms, whose P phases were handpicked. The P wave spectral ratios with high signal-to-noise ratios were calculated up to 1 Hz for all the station pairs, linear regressed, and then inverted for \( t_P^{ * } \) using the technique of least squares . The result showed that the active volcanic areas were clearly characterized by high \( t_P^{ * } \). In contrast, \( t_P^{ * } \) varied in the nonvolcanic areas. The present result on the \( t_P^{ * } \) distribution was roughly consistent with the shallow part (<30 km) of an attenuation structure, which has been previously obtained based on 3-D tomography by using records of high-frequency (around 5 Hz) P waves from local earthquakes. This suggested that the present method of \( t_P^{ * } \) estimation is valid. The advantage and possible application to other areas were also discussed.

日本列島の非火山地域における深層地下水水質と地質との関係について

日本列島の非火山地域における深層地下水水質と地質との関係について

The Tancitaro Debris Avalanche: Characterization, propagation and modeling

The Tancitaro volcano (3860 m) is an andesitic–dacitic stratovolcano located in the western portion of the Trans-Mexican Volcanic Belt within the state of Michoacán (Mexico). The tectonic activity of this area has likely contributed to a large sector collapse of the volcano. The first findings of a multidisciplinary investigation into this debris avalanche are presented here. Geomorphological analyses, based on the interpretation of orthophotos, satellite imagery and on GIS elaborations, had the objective of determining the main morphometric features of the landslide. The collapse structure is an east-facing horseshoe-shaped crater (4 km wide and 5.3 km long), while the deposit forms a large fan that is 66 km long, covers an area of approximately 1155 km 2 and has an estimated volume of 18 km 3. Event volume was established by reconstructing the paleo-edifice in a GIS and taking into account volumetric expansion. Cross sections measured in the field were also used for this purpose. Field investigations also highlighted the presence of two texturally distinct units, which are referred to as the “block facies” and the “matrix facies”, respectively. The first is responsible for the typical hummock morphologies found in the proximal area. A transitional zone contains a “mixed block and matrix facies” while in the distal portion blocks and megablocks, some of which have a jigsaw puzzle texture, gradually decrease in size until they disappear entirely. A number of matrix samples were collected to conduct direct shear tests, granulometric analyses and classification of the materials. The data and analyses described above were used to discuss the mechanism controlling the long runout of the avalanche. Based on the comparison between the Tancitaro debris avalanche and similar events we propose that mechanical fluidization was the mechanism responsible for the remarkable mobility of the landslide. The predisposing factors leading to the collapse were also considered. Field observations suggest that these are mainly related to weakening processes operating both in volcanoes and in non-volcanic areas. The runout of the Tancitaro debris avalanche was numerically modeled using DAN-W. The geotechnical parameters determined in the field and from the laboratory analyses were used as input. The DAN-W code models longitudinal spreading and the thickness and velocity of the failed mass by opportunely selecting a specific rheological model (Voellmy, Frictional, Bingham). Thus, it was determined that the two-parameter “Voellmy model” provided the best simulation of the Tancitaro debris avalanche movement, and the best fitting rheological parameters have been found through back analysis.

Intrinsic and scattering attenuation of the Mt Fuji Region, Japan

Mount Fuji is the focus of intense study because of its potential hazard signaled by seismic, geologic and historical activity. Based on extensive seismic data recorded in the vicinity of Mt Fuji, coda quality factor (Q−1C) using a single scattering model hypothesis, and intrinsic and scattering quality factor (Q−1i and Q−1S) using the Multiple Lapse Time Window (MLTW) method were measured. To focus the study on the magmatic structure below Mt Fuji, the data were separated into two groups: a near-Fuji region of rays traversing an area with radius 5 km around the summit (R < 5 km), and a far-Fuji region of rays beyond a radius of 20 km around the summit (R > 20 km). This classification shows the largest discrepancy of Q−1C at a range of sampling volumes corresponding to overlapped sampling depth of about 80 km. Further, the spatial division shows significant difference of Q−1i and Q−1s at hypocentral distance of 80 km. The large difference of Q−1s in bandwidths 2–4, and 4–8 Hz indicates lithospheric heterogeneity beneath Mt Fuji with a characteristic heterogeneity scale length of about 1 km. The results have a small error range due to the large data sample, showing that all Q−1 values in the near-Fuji area are greater than those of the far-Fuji area, and Q−1i for both the near and far-Fuji areas is higher than Q−1s at high frequencies. The Q−1i and Q−1s values for far-Fuji are in the range of values for typical non-volcanic areas. The Q−1i values of the near-Fuji area are lower than those of other volcanic areas considered, where as values of Q−1s are not. The low Q−1i for the volcanic region of near-Fuji suggests that the magmatic activity, indicated by percent partial melt, in the vicinity of Mt Fuji is not as active as hot spot volcanoes, such as Kilauea, Hawaii.

Statistical Analysis of Landslide Events in Central America and their Run-out Distance

Statistical analyses of landslide deposits from similar areas provide information on dynamics and rheology, and are the basis for empirical relationships for the prediction of future events. In Central America landslides represent an important threat in both volcanic and non-volcanic areas. Data, mainly from 348 landslides in Nicaragua, and 19 in other Central American countries have been analyzed to describe landslide characteristics and to search for possible correlations and empirical relationships. The mobility of a landslide, expressed as the ratio between height of fall (H) and run-out distance (L) as a function of the volume and height of fall; and the relationship between the height of fall and run-out distance were studied for rock falls, slides, debris flows and debris avalanches. The data show differences in run-out distance and landslide mobility among different types of landslides and between debris flows in volcanic and non-volcanic areas. The new Central American data add to and seem consistent with data published from other regions. Studies combining field observations and empirical relationships with laboratory studies and numerical simulations will help in the development of more reliable empirical equations for the prediction of landslide run-out, with applications to hazard zonation and design of optimal risk mitigation measures.

A landslide database for Nicaragua: a tool for landslide-hazard management

A digital landslide database has been created for Nicaragua to provide the scientific community and national authorities with a tool for landslide-hazard assessment, emergency management, land-use planning, development of early warning systems, and the implementation of public and private policies. The Instituto Nicaraguense de Estudios Territoriales (Nicaraguan Geosciences Institute, INETER) began to compile the database in a digital format in 2003 as part of a comprehensive geographical information system for all types of geohazards. Landslide data have been obtained from a variety of sources including newspapers, technical reports, and landslide inventory maps. Inventory maps are largely based on fieldwork and aerial-photo analyses conducted by foreign development agencies in collaboration with INETER and other Nicaraguan institutions. This paper presents the sources of landslide information, introduces the database, and presents the first analyses of the data at national and regional scales. The database currently contains spatial information for about 17,000 landslides that occurred in mountainous and volcanic terrains. Information is mainly recorded for the period 1826–2003, with a large number of events that occurred during the disastrous Hurricane Mitch in October 1998. The oldest historical event is dated at 1570, some events are recorded as prehistorical, and other events have unknown dates of occurrence. Debris flows have been the most common types of landslides, both in volcanic and nonvolcanic areas, but other types, including rockfalls and slides, have also been identified. Intense and prolonged rainfall, often associated with tropical cyclones, and seismic and volcanic activity represent the most important landslide triggers. At a regional scale, the influence of topographic (elevation, slope angle, slope aspect) and lithologic parameters on the occurrence of landslides was analyzed. The development of the database allowed us to define the state of knowledge on landslide processes in the Nicaragua and to provide a preliminary identification of areas affected by landslides.

Subsurface thermal and hydrothermal characterization based on geothermal resources map, drill hole thermal gradients, Curie point depths and hypocenter distribution — Examples of Tohoku district, Japan

Subsurface thermal structure in Tohoku district are characterized by existing data such as geothermal resources maps, drill hole thermal gradients, Curie point depths and hypocenters distribution maps. The collected data are registered in a database system, then, compared in plan view, cross-section and bird's-eye pictures. The comparison indicates that subsurface temperatures extrapolated from drill hole thermal gradients are generally concordant to the Curie point depth, assumed to be 650 °C. Tohoku district is generally divided into 5 type areas; fore arc lowland, fore arc mountain country, Quaternary volcanic terrain, back arc lowland and back arc mountain country. The surface thermal manifestations in Quaternary volcanic terrain are mainly controlled by the magma chambers as heat sources, while, surface thermal features such as hot springs in non-volcanic areas are controlled by degrees of heat flows, and hydrothermal flows in permeable Cenozoic formations and along permeable fault zones.

Seismic Energy for Shallow Earthquakes in Southwest Japan

We estimated the radiated energy for 88 earthquakes with M w ≥4.0 that occurred in southwest Japan by analyzing direct S waves recorded by the Freesia broadband seismic network (F-net) at local/regional distances. The attenuation factors for each source–receiver group are estimated by the coda method using the recently established high-sensitivity and high-density seismic network (Hi-net) data. The site amplification for each F-net station is calculated by using the coda normalization method. We find good agreement between the source spectra calculated by using these propagation effects and those determined by using an empirical Green’s function method for 4 M w >5 earthquakes. The station variance of the energy estimates is a factor of 2 for earthquakes with M w ≥5, and it is a factor of 3 for the smaller ones. The resultant energy estimations show that: (1) The overall ratios between the radiated energy and seismic moment ( E s / M 0 ) lie in a band of 5 × 10 −7 to 5 × 10 −5 for 88 earthquakes with M w 3.9–6.8. For the Tottori, 2000, earthquake and its 16 aftershocks with M 0 10 14 –10 19 N m, we found a very slight increase of E s / M 0 with increasing seismic moment. For the rest of earthquakes E s / M 0 are almost constant for earthquakes occurring in the same source area. The constants corresponding to each source area are slightly but systematically different, indicating a location dependence of E s / M 0 . Earthquakes that occur in volcanic areas show lower E s / M 0 values relative to earthquakes occurring in nonvolcanic areas. However, the weak to non-scaledependence is not certain because of the scantiness of large earthquakes in the data set. (2) For earthquakes in the volcanic source areas, there appears to be a trend of increasing E s / M 0 with focal depth. We believe this trend is a result of, at least in part, the decreasing attenuation with depth in volcanic areas. For the nonvolcanic area earthquakes, however, E s / M 0 tends to be a constant in a depth range of 12–50 km. Since the Akinada earthquake, 2001 ( M w 6.8), took place in the western part of subducting Philippine Sea slab and the two deeper earthquakes occurred in the upper mantle below the same subducting slab in its eastern part, the constancy of E s / M 0 may indicate that the apparent stress at the brittle patches in the ductile zone can be as high as in the brittle part of the crust. (3) Estimated E s / M 0 are inversely related to the surface heat flow, approximately. Such a relationship suggests that the geothermal structure may be the dominating tectonic factor that controls the level of apparent stress.

Evidence for ascending upper mantle‐derived melt beneath the Cheb basin, central Europe

We present new 3He/4He data of CO2‐rich gas exhalations of three presently nonvolcanic areas in Europe. The 3He/4He ratios from the Cheb basin (Czech Republic) are clearly higher than data obtained ten years ago, whereas the 3He/4He ratios from the other areas (Laacher See/Germany and Mariánské Lázně/CR) have remained nearly constant. No other locality showing such high 3He/4He ratios in free gases supplied by continental mantle degassing is known in the European Cenozoic rift system. At the northeastern edge of the Cheb basin swarm earthquakes repeatedly occur. In the context of contemporaneous periods of seismicity the increased 3He/4He ratios are interpreted as the first geochemical evidence for ascending mantle‐derived melt beneath the Cheb basin, which is related to the triggering of earthquake swarms.

Hydrogeochemistry of the Campania region in southern Italy

A geochemical study of thermal springs, cold springs, stream waters and natural gas emissions has been carried out in the Campania region of southern Italy. This region hosts four Quaternary volcanic areas, and thermal springs and gas emissions occur in three of them. Most thermal springs discharge Na-Cl composition waters of connate origin derived from post-orogenic volcanic and sedimentary formations. Although high-enthalpy systems are present in two of the four volcanic areas, there appear to be no magmatic contributions to the thermal springs. Solute geothermometers are unreliable as spring waters are strongly affected by mixing with “shallow” brines before discharging. Thermal springs and gas emissions also occur in non-volcanic areas, where an extensive carbonate unit acts as a regional aquifer for cold, low-salinity, bicarbonate waters. Thermal features in these areas occur in fractured zones associated with active faults. Their compositions are determined only by the type of rock encountered by solutions before surface discharge. As in other areas of north-central Italy, the widespread occurrence of hot and cold CO 2-rich springs, and gas emissions in both volcanic and non-volcanic zones, suggests a deep origin for the CO 2.

Scaling of peak ground motions from digital recordings of small earthquakes at Campi Flegrei, southern Italy

The dependence of peak ground acceleration and velocity on seismic moment is studied for a set of small earthquakes (0.7<ML<3.2) recorded digitally at distances of a few km in the Campi Flegrei volcanic area near Naples, Italy, during the ground uplift episode of 1982–1984. Numerical simulations, using the ω-square spectral model with constant stress drop and ane−πkf high frequency decay, fit well both the velocity and acceleration data for an averagek=0.015. The observed ground motions in the 1–24 Hz frequency band appear to consist of radiation from simple sources modified only slightly by attenuation effects. Moreover, the scaling of peak values agrees closely with those determined in nonvolcanic areas, once the difference in stress drop is taken into account.

Characterization of debris avalanche deposits in Japan

Seventy-one debris avalanche deposits are identified from 52 Japanese Quaternary volcanoes. The structures of these volcanoes are mostly stratovolcanoes and lava domes. No avalanche deposit is found in calderas, pyroclastic cones or maar volcanoes. Debris avalanche deposits are found in 18% of all Quaternary volcanoes or 25% of Quaternary stratovolcanoes and lava domes. The ratio rises to 49% when considering only active stratovolcanoes and lava domes. At least five debris avalanche deposits have formed since 9th century. The maximum height difference of sliding ( H) for each debris avalanche ranges from 200 to 2400 meters and the maximum runout distance of sliding ( L) ranges from 1.6 to 32 km. The ratio H/ L ranges from 0.2 to 0.06, and becomes smaller in larger debris avalanches. They are more mobile than landslides in non-volcanic areas. Volume is within a range of 0.03 and 9 km 3. There is no relation between the direction of sliding and the regional horizontal compressional stress axis at the site of a volcano. Two-dimensional computer simulations of avalanches using a simplified physical model are made. The maximum velocity is mainly controlled by the length of steep slope.

Some aspects of exploration in non-volcanic areas

Geothermal exploration in non-volcanic areas must above all rely on geophysical techniques to identify the reservoir, as it is unable to resort to volcanological methodologies. A brief description is therefore given of the contribution that can be obtained from certain types of geophysical prospectings.

47. Tectonic characteristics of the non-volcanic areas along the East Japan volcanic belt.(Abstracts of Papers Submitted for the Meeting of Society)

47. Tectonic characteristics of the non-volcanic areas along the East Japan volcanic belt.(Abstracts of Papers Submitted for the Meeting of Society)