Tatsuto Aoki

Identification of an active fault in the Japanese Alps from DEM-based hill shading

Shaded-relief images created from digital elevation models (DEMs) are helpful in identifying faults in rugged mountains. Unlike airphoto interpretation, the method enhances lineaments by simulating topographic illumination under varied light directions. Interpretation of shaded-relief images of the Japanese Alps led to the discovery of a lineament unrelated to bedrock structure. Field surveys and analysis of large-scale maps and airphotos reveal the lineament to be a fault with high rates of vertical and lateral slip. The new fault is the southernmost segment of a known adjacent fault, and the rate and direction of its slip provide fresh insight into the late Quaternary history of the fault system. Because previous research mistook the fault scarp for a fluvial terrace scarp, discovery of the fault also changed the correlation of river terraces in the Northern Japanese Alps. The new corrections affect Pleistocene glacial chronology in the upstream area.

Satellite-derived equilibrium lines in Northern Patagonia Icefield, Chile, and their implications to glacier variations.

Abstract The Northern Patagonia Icefield (NPI), covering 3953 km2, is the second largest temperate ice body in South America. Despite its importance as a climate change indicator because of its location and size, data on ground-based mass balance and meteorological records for the analysis of glacier (snout) variations are still lacking. The use of multitemporal satellite images to estimate equilibrium line altitude variations could be a surrogate for such analyses. Since late-summer snowlines of temperate glaciers coincide with the equilibrium line, we analyzed five Landsat images spanning 1979–2003 and an ASTER-derived digital elevation model to reveal oscillations in the equilibrium line altitude (ΔZELA). The average ELAs range between 870 m and 1529 (± 29 m), with lower altitudes on the west side. Winter snow cover accumulation indicates higher elevations (relative to the glacier snout) of the transient snowlines in the west. Thus, one of the reasons for the higher retreating rates observed on the west side is that the lower part of the ablation area is likely exposed to year-round ablation. Glacier sensitivity to ΔZELA oscillations would depend upon the topographic condition of the accumulation area (gentle or steep). In outlet glaciers with gentle accumulation areas such as San Rafael and San Quintin, ΔZELA of up to 65 and 70 m at the central flow part and bare ice area variations > 5 km2 and > 13 (± 0.6 km2) were observed, respectively.

Timings and causes of glacial advances across the PEP-II transect (East-Asia to Antarctica) during the last glaciation cycle

A comparison of glacial advances through the last glacial cycle between Northern and Southern Hemispheres in the PEP 2 transect (East Asia and Australasia) revealed (1) a relatively good synchrony of glacial advances during the LGM across the whole transect except Antarctica, (2) a rough synchrony in glacial advances in the Karakorums, Himalayas, Japan, and New Zealand during Marine Isotope Stages (MIS) 3 and 4, although the age control is still poor, and (1) a greater glacial extent in MIS 3 and 4 than in MIS 2. The LGM advances are driven by Northern Hemisphere temperature forcing, but the MIS 3 and/or MIS 4 advances appear to be dominantly controlled by the effects of moisture availability or lack of thereof. In mainland Australia and Antarctica glaciers advanced only in the most humid phases. In Himalaya and Karakorum, where the moisture is supplied both by a Summer monsoon and the westerlies, timings of glacier advance coincide with both Summer monsoon enhancement and westerly intensification. In Japan the glacier extent is controlled by monsoon changes, sea-surface temperatures (SSTs) in the Japan Sea (moisture source) and by zonal shifts in westerly circulation. In New Zealand, either insolalion changes or changes in the intensity of westerly circulation are invoked, Lis the main track of the westerlies did not change greatly during glacial times

Late Quaternary glaciations in Japan

A general introduction to the Quaternary glaciations in the Japanese high mountains is presented. Particular attention is paid to the two most significantly-glaciated mountain ranges, and recent knowledge of the glacial history in the Japanese Alps and Hidaka Mountains is presented. Six glacial advances are recognised in the Japanese Alps that occurred during the penultimate glacial cycle, the Last Glaciation, and the Holocene. In the high Japanese mountains, the maximum advance during the Last Glaciation is commonly recognised during Marine Isotope Stage (MIS) 4 with subsequent advances occurring just before 24 ka BP, 18–20 ka PB, 11–10 ka BP and in the early Holocene. In the Hidaka Mountains, recent tephrochronological investigations have revealed the age and extent of the maximum glacier advance during MIS 5a, MIS 3, MIS 2 and MIS 6. Mountain glaciers in Japan were less extensive during the Last Glacial Maximum. This is out of phase with the continental ice sheets in the northern hemisphere.

A GIS-based study toward forecast of suburban forest change

At a time when the concept of ‘human and environmental symbiosis’ has taken on much significance, protection of suburban forests (i.e. forests adjacent to or near developed areas) is a topic that has drawn much attention. Suburban forests have, since ancient times, been places where people have gathered firewood and cultured trees. As a result, the vegetation of suburban forests is only partially natural and continues to change as the forms of human activity in and around them changes. Accurate forecasts of how suburban forests will change are, therefore, an important element in the debate over how to protect them. In this study, a suburban forest was analyzed with laser radar sensing, multi-spectrum scanning, digital photogrammetry analysis, aerial photograph interpretation, and a field survey. Data gathered using these techniques were compiled on a GIS to forecast future changes in the forest. Aerial photographs taken over the past 50 years were analyzed to illuminate changes in the forest over that period. Specifically, comparisons of precise Digital Elevation Models (DEMs) measured by using digital photogrammetry workstations made it possible to estimate growth in forest height. The possible future conversion of such results to estimates of amounts of carbon dioxide consolidated by forests should be very significant for discussions of global environmental problems.

Chapter 72 - Late Quaternary Glaciations in Japan

The Taiwanese high mountain range is not glaciated at present, and the modern theoretical equilibrium line altitude (ELA) was calculated at about 3950 ± 100 m. Large erosional glacial landforms are evidence for a high glacier surface elevation in the central parts of the mountain massifs at the maximum stage of the last glacial cycle, but corresponding glacial terminal deposits are still sparsely known and age control is weak. Luminescence dating from Hsueh Shan suggests the widest glacier extent during MIS 4 with an ELA depression of > 1000 m. Surface exposure and luminescence ages of glacial deposits in Nanhuta Shan above 3100 m a.s.l. indicate a subsequent late glacial to early Holocene glacier advance with an ELA depression of 510–610 m.