Studies on the Causes of Unique Strong Ground Motions Observed during the 1993 Hokkaido-Nansei-Oki Earthquake Sequence

1993年北海道南西冲地震序列中观测到的独特强烈地面震动的成因研究

• 批准号: 06452409
• 负责人: SASATANI Tsutomu
• 金额: $ 2.75万
• 依托单位: HOKKAIDO UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (B)
• 财政年份: 1994
• 资助国家: 日本
• 起止时间: 1994 至 1995
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06452409/
• 关键词: Unique strong ground motion; The 1993 Hokkaido-Nansei-Oki earthquake; Site response; Unusually high peak acceleration; Soil-structure interaction; Liquefaction; Soft sedimentary basin; Basin-induced surface waves; 地盤と建物の相互作用; 加速度スペクトル

We carried out a temporal strong motion observation in the southwestern part of Hokkaido after the 1993 Hokkaido-Nansei-Oki earthquake (M7.8). Unusually high peak acceleration (-1.6g) was observed at OTB during the largest aftershock (8/8/1993 ; M6.3). The OTB station is located at the foot of a small cape (Shibino-Misaki) and its site response shows a sharp peak (a factor of about 80) at about 4 Hz. The unique site response was observed at KNK,located on a small, soft sedimentary basin in Kaminokuni, where liquefaction was observed during the main shock : the amplification factors are large (10to20) at low frequencies (-1 Hz), while they are less than l at high frequencies (>10 Hz). In order to clarify the causes of the above unique strong ground motions, we carried out the following geotechnical measurements near the observation sites : P-S logging, microtremore array observations, and geoelectrical soundings. The following results were obtained :(1) The causes of the unique site response at OTB are combined effects of amplification due to shallow sediments overlaying very hard rock and soil-structure interaction.(2) The causes of the unique site response at KNK are combined effects of amplification at low frequencies and deamplification at high frequencies due to very soft surface sediments. A part of the amplification at low frequencies is attributed to the basin-induced surface waves generated at the basin edge.

1993年北海道南关7.8级地震后，我们在北海道西南部进行了一次时间强震观测。在最大余震(1993年8月8日；M6.3)期间，OTB观测到异常高的峰值加速度(-1.6g)。OTB站位于一个小海角(柴野-三崎)的脚下，其场地响应在大约4赫兹处显示出一个尖锐的峰值(系数约为80)。在KNK观测到了独特的场地响应，KNK位于Kaminokuni的一个小型软沉积盆地，在主震期间观察到了液化：在低频(-1赫兹)下，放大倍数很大(10到20)，而在高频(&gt；10赫兹)时，放大倍数小于L。为了弄清上述独特强地面运动的原因，我们在观测点附近进行了以下岩土工程测量：P-S测井、Microtremore阵列观测和地电测深。研究结果表明：(1)复盖非常坚硬岩石的浅层沉积物的放大效应和土-结构相互作用的共同作用是造成OTB独特场地反应的原因。(2)KNK场地独特的场地反应是由于表层沉积物很软而产生的低频放大和高频去放大的综合效应。低频放大的一部分归因于盆地边缘产生的盆地诱发面波。

项目成果

大島 弘光: "北海道上の国地域における電気探査" 北海道大学地球物理学研究報告. 58. 137-150 (1996)

大岛宏光：《北海道上游地区的电法勘探》北海道大学地球物理研究报告 58. 137-150 (1996)。

工藤 一嘉: "1993年北海道南西沖地震の余震群の強震記録-最大余震による大加速度記録を中心にして-" 月刊海洋. 号外No.7. 95-101 (1994)

工藤一义：“1993年北海道南西大地震余震的强运动记录——关注最大余震的大加速度记录——”月刊特刊第7期95-101（1994年）。

Sasatani, T.and H.Nagumo: "Seismic response of a small, soft sedimentary basin : The Kaminokuni basin in Hokkaido." Proc. of the International Workshop on Site Response Subjected to Strong Earthquake Motions, January 16-17,1996, Yokosuka, Japan.(in press)

Sasatani, T. 和 H.Nagumo：“小型软沉积盆地的地震响应：北海道的 Kaminokuni 盆地。”

T.Sasatani: "Seismic response of a small,soft sedimentary basin:The Kaminokuni basin in Hokkaido" Proceedings of the International Workshop on Site Response Subjected to Strong Earthquake Motions,January 16-17,1996,Yokosuka,Japan. (in press). (1996)

T.Sasatani：“小型软沉积盆地的地震响应：北海道的 Kaminokuni 盆地”强地震现场响应国际研讨会论文集，1996 年 1 月 16-17 日，日本横须贺。

K.Kudo: "Effects of surface soil and earthquake source radiation on the ground motion of 1.6g acceleration, observed during the August 8, 1993, South-West Off Hokkaido earthquake, Japan -A preliminary analysis-" Proceedings of the International Workshop o

K.Kudo：“在 1993 年 8 月 8 日日本北海道西南海域地震期间观测到的表层土壤和地震源辐射对 1.6g 加速度地面运动的影响 - 初步分析 -” 国际研讨会论文集