The Sanzugawa Caldera had formed through Neogene to Quaternary in south-east part of Akita Prefecture, Northeast Japan. The southern part of the caldera has been investigated for understanding geothermal energy potentiality. We carried out geological survey as a geothermal exploration, and behaviors of thermoluminescence (TL) of quartz were also applied to evaluate thermal effects. According to natural geothermal activities, TL intensity was decreased as a function of time and temperature.
Three types of hydrothermal alteration were identified in this area, which were neutral pH alteration consisted of montmorillonite, sericite and their mixed layered clay minerals, acid sulfate alteration composed of kaolinite and alunite, and alkaline alteration characterized by laumontite and wairakite. The latter two types of hydrothermal alterations were observed sporadically and correlated to low TL intensity.
Additionally, TL intensities of samples at high elevation showed relatively high and those of low elevation samples were decreased. Some samples including specific alteration minerals such as laumontite and wairakite showed relatively low TL intensity against general relation between TL intensity and elevation. On the other hand, neutral pH hydrothermal alteration distributed through whole area and showed no clear relation to TL behaviors.
Those facts strongly suggested that two stages of geothermal activity occurred in this area. First, a neutral pH alteration happened contemporaneous with the Torage-yama formation within the southern part of the Sanzugawa Caldera, and then both of alkaline and acid sulfate hydrothermal alterations were formed by later geothermal activities, showing low TL intensities.
General trends of TL behaviors which were related to elevation of surface suggest that potential heat source maybe widely distributed in subsurface, and sporadic hydrothermal alteration during later stage hydrothermal alteration associating with relatively low TL intensities was enhanced by upwelling flow through fractures. The latest geothermal activities were related to a discrete magma emplacement, which also indicates potential formation of deep-seated geothermal reservoirs.
2010 年と2012 年に県内4 ヵ所のブドウ園で，クビアカスカシバを対象にしてフェロモントラップによる成虫の発生消長と幼虫の加害時期を調査した．成虫は6 月上旬頃から8 月中旬頃にかけて発生し，誘殺盛期は年次により30 日程度のずれを生じた．幼虫の加害による虫糞排出は7 月中旬頃から見られ始め，10 月中旬頃まで樹上で幼虫の寄生が確認できたが，11 月中旬頃には幼虫は土中へ移動して土繭を形成していた．また，ブドウ園で採取した雌成虫13 頭（飼育中の土繭から羽化した個体2 頭を含む）に，蜜源として市販のスポーツドリンクを給餌しながら25℃恒温自然日長条件で飼育したところ，採取後の生存日数は未交尾雌で7～13 日，既交尾雌は7～11 日であった．産卵総数は未交尾雌が176～792 個，既交尾雌は73～481 個でふ化率は28.0～88.9％とバラツキが大きかった．これらのバラツキは成虫日齢や飛来後の経過日数によるものと考えられた．