Pub Date : 2002-03-25DOI: 10.3313/JLS1964.38.4_318
Wen-Neng Wang, Hiroyuki Nakamura, S. Tsuchiya, Chih Chen
An earthquake (M7. 3) took place in central Taiwan on the early morning of September 21, 1999. This disastrous ground shaking is called the Chi-chi earthquake, with its hypocenter about 10km below land surface. Earthquake-induced landslides were surveyed in order to mitigate secondary hazards. The area studied is about 375, 000 ha, in which landslides were identified by aerial photo interpretation accompanied by SPOT images and field surveys. The color aerial photos used in this study are on the scale of 1/17, 000 and were taken between September 22-26, 1999.More than twenty thousand Chi-chi earthquake-induced landslides have been recognized by aerial photo interpretation. The average landslide density and landslide rate are 0.1 pieces/ha and 4.7%, respectively. Over 90% of the landslides were less than one hectare in average and categorized as shallow landslides and rock falls. Most of the landslides occurred in a region between the Chelungpu active fault to the west and the Lishan fault to the east or in regions with a horizontal peak-ground acceleration (PGA) of more than 300 gal. Of the four geological regions in the area studied, the inner foothill zone had the greatest average landslide rate (11.6%) and the greatest number of landslides (9, 090 landslides).The occurrence of earthquake-induced landslides has a close relation to their geology and distances from the earthquake fault. As to geologic formation and PGA, the Ptk2 (Plio-Pleistocene period) formation has the greatest landslides rate, 20% in a 501-600 gal area, and the Pcl formation (Pliocene period) has a landslide rate, 9.2% in a 401-500 gal area. By dividing into six 5-km-wide belts paralleling the Chelungpu fault, the landslide amount and its rate in the Pcl formation area have the greatest value in the 5-10km belt (about 6, 000 amount) and the 10-15km belt (12.7%), respectively. In the Mkc formation area, the landslide amount and its rate have the greatest value in the 0-5km belt, about 1, 400 amount, 4.7%, respectively, and then generally decrease with an increase of 5km.
{"title":"Distributions of landslides triggered by the Chi-chi Earthquake in Central Taiwan on September 21, 1999 [E] : Mountains and slopes(GEOMORPHOLOGICAL ABSTRACTS (2001)From scientific papers published in Japan)","authors":"Wen-Neng Wang, Hiroyuki Nakamura, S. Tsuchiya, Chih Chen","doi":"10.3313/JLS1964.38.4_318","DOIUrl":"https://doi.org/10.3313/JLS1964.38.4_318","url":null,"abstract":"An earthquake (M7. 3) took place in central Taiwan on the early morning of September 21, 1999. This disastrous ground shaking is called the Chi-chi earthquake, with its hypocenter about 10km below land surface. Earthquake-induced landslides were surveyed in order to mitigate secondary hazards. The area studied is about 375, 000 ha, in which landslides were identified by aerial photo interpretation accompanied by SPOT images and field surveys. The color aerial photos used in this study are on the scale of 1/17, 000 and were taken between September 22-26, 1999.More than twenty thousand Chi-chi earthquake-induced landslides have been recognized by aerial photo interpretation. The average landslide density and landslide rate are 0.1 pieces/ha and 4.7%, respectively. Over 90% of the landslides were less than one hectare in average and categorized as shallow landslides and rock falls. Most of the landslides occurred in a region between the Chelungpu active fault to the west and the Lishan fault to the east or in regions with a horizontal peak-ground acceleration (PGA) of more than 300 gal. Of the four geological regions in the area studied, the inner foothill zone had the greatest average landslide rate (11.6%) and the greatest number of landslides (9, 090 landslides).The occurrence of earthquake-induced landslides has a close relation to their geology and distances from the earthquake fault. As to geologic formation and PGA, the Ptk2 (Plio-Pleistocene period) formation has the greatest landslides rate, 20% in a 501-600 gal area, and the Pcl formation (Pliocene period) has a landslide rate, 9.2% in a 401-500 gal area. By dividing into six 5-km-wide belts paralleling the Chelungpu fault, the landslide amount and its rate in the Pcl formation area have the greatest value in the 5-10km belt (about 6, 000 amount) and the 10-15km belt (12.7%), respectively. In the Mkc formation area, the landslide amount and its rate have the greatest value in the 0-5km belt, about 1, 400 amount, 4.7%, respectively, and then generally decrease with an increase of 5km.","PeriodicalId":35821,"journal":{"name":"Chikei","volume":"23 1","pages":"695"},"PeriodicalIF":0.0,"publicationDate":"2002-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3313/JLS1964.38.4_318","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69504350","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Timing of large-scale ridge-moving landslides around Aigawa, Northern Nagano Prefecture, central Japan, and their tectonic implications [JE] : Mountains and slopes(GEOMORPHOLOGICAL ABSTRACTS (2001)From scientific papers published in Japan) :","authors":"T. Ueki","doi":"10.4116/JAQUA.40.393","DOIUrl":"https://doi.org/10.4116/JAQUA.40.393","url":null,"abstract":"糸魚川-静岡構造線活断層系の北部セグメントの東に位置する長野県北部八坂村相川周辺において認められる大規模な尾根移動型地すべり地形を記載・火山灰編年し,中期更新世の断層活動との関連性について考察した.そこでは,大規模な尾根移動型地すべりの地すべり堆を構成する破砕された大峰溶結凝灰岩の凹部を,大峰溶結凝灰岩と大町Apmテフラ群(APm)のブロックが混在するローム層が埋め,その上位には立山Dテフラ(Tt-D)をはさむローム層が斜面を覆っている.このことから,APm降下以後でTt-D降下以前,すなわち約30～40万年前から12万年前の間に大規模な尾根移動型の地すべりが発生したと考えられる.このような大規模な地すべりの発生は,相川周辺の主稜線が当時比高の大きな山地になっていたことを示唆し,それは糸魚川-静岡構造線活断層系の運動によると考えられる.","PeriodicalId":35821,"journal":{"name":"Chikei","volume":"23 1","pages":"699"},"PeriodicalIF":0.0,"publicationDate":"2001-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70875271","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Late Holocene Environmental Changes at Kuninaka Plain, Sado Island, Central Japan, Deduced from Sediment Facies and Diatom Assemblages [JE] : Plains and basins(GEOMORPHOLOGICAL ABSTRACTS (2001) From scientific papers published in Japan )","authors":"Keiko Matsunaga, Y. Ota","doi":"10.4116/JAQUA.40.355","DOIUrl":"https://doi.org/10.4116/JAQUA.40.355","url":null,"abstract":"佐渡島の国中平野における沖積層の掘削調査から得たコア,および既存のコアの層相と珪藻分析,14C年代測定によって,完新世海成層の上限を認定した.真野湾側の国中平野南西部では,海成層上限高度はほぼ標高2.6m以下で,その年代は4,000～5,000yrs BPである.本地区では,それ以降に海が侵入したことはない.一方,両津湾側の北東部では,国中南断層上盤延長部での標高2～4mを除くと,同じ時代の堆積物はほぼ現海面下にあり,本地区の相対的沈降を示す.両津湾岸では,それ以降も海進と海退を繰り返したが,これはユースタティックな現象ではなく,砂州による閉塞や開口の結果現れた見かけ上のものと思われる.さらに,完新世海進高頂期以降の3時期における古地理の変化を,堆積物と考古遺跡に基づいて復元した.","PeriodicalId":35821,"journal":{"name":"Chikei","volume":"23 1","pages":"708-709"},"PeriodicalIF":0.0,"publicationDate":"2001-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70875255","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Feasibility of Land Use Control along Active Faults for Hazard Mitigation Some Considerations Derived from the Questionnaire Survey of Local Government Staffs in Japan [JE] : Applied geomorphology(GEOMORPHOLOGICAL ABSTRACTS (2001) From scientific papers publised in Japan )","authors":"Y. Murayama, Satoru Matsuda","doi":"10.5190/TGA.53.34","DOIUrl":"https://doi.org/10.5190/TGA.53.34","url":null,"abstract":"筆者らは, 防災を念頭に置いた建築規制や, 移転・構造強化へのインセンティブ付与, 情報公開等を含む計画手法を防災型土地利用規制と呼び, 活断層上の土地利用規制についての受容可能性を仙台市民アンケートを通じて検討してきた。本論では, 政策実施主体である自治体の職員 (防災と都市計画担当者) への調査結果を紹介し上と比較する。第一に自治体職員よりも市民の方が, 規制全般に積極的な傾向が確認できた。次に行政内では, 防災より都市計画担当者の方が活断層上の規制支持が低く市民意向との差も大きいが, 自治体職員 (特に都市計画) も市民同様に, 災害関連の情報獲得が多いほど規制実施への支持は高まる。第三に市民・職員ともその過半数が, 危険物施設, 公共・集客施設, 集合住宅の活断層上立地は避けるべきとしている。最後に活断層を持つ自治体の職員は, 厳しい土地利用規制には消極的な一方, 開発時の断層調査義務化には積極的である。現在, 防災型土地利用規制の適用例は少ないが, 採用可能な法的手法 (災害危険区域・地区計画等) も存在する。事前的防災対策の充実に向け, 都市計画と地域防災の連携強化や計画メニューの豊富化・柔軟化等の制度改革が求められる。","PeriodicalId":35821,"journal":{"name":"Chikei","volume":"23 1","pages":"722"},"PeriodicalIF":0.0,"publicationDate":"2001-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70847665","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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