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Seismographic array observation in and around Iceland by use of ocean bottom seismographs and land seismometers.

利用海底地震仪和陆地地震仪对冰岛及其周边地区进行地震阵列观测。

基本信息

批准号：
02044003
负责人：
SHIMAMURA Hideki
金额：
$ 8.64万
依托单位：
Hokkaido University
依托单位国家：
日本
项目类别：
Grant-in-Aid for international Scientific Research
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1991
项目状态：
已结题

项目摘要

Mid-Atlantic Ridge is the place where plate is being born. Iceland is situated immediately on the Ridge. There was no detailed study on crustal and upper mantle structure of any ridge. Also there was no detailed seismicity study around ridge. This study has revealed a very detailed seismicity in and around Iceland which made use of sensitive ocean bottom Seismograph (OBS) array.Also, crustal structure off north of Iceland was obtained in this study.Twenty OBS were transported from Japan to Iceland twice in 1990 and 1991. The OBS were deployed by an Icelandic Coast Guard Ship, for both years. In 1990, the OBS array was along Reykjanes Ridge, whose length is 150 km, and width is 40 km. The dense array observation was operated for one month continuously.The result shows that earthquake hypocenters are distributed only along the very crest area of the ridge, and no earthquake was observed outside of the ridge crest. We found some patches of concentrations of earthquakes along the ridge axis, which show a good correspondence to the past submarine volcanic activities. The depth distributions of observed earthquakes were nearly vertical, and the maximum depth was 12 km. Two microearthquake swarms were caught during the observation period, which shows a very concentrated epicenters with vertical chimney-like distribution of hypocenters.In 1991 similar OBS expeditions were made to the north off Iceland, where tectonics is more complicated than usual mid-oceanic ridges. 21 OBS as well as 15 land-based seismographs were deployed for the observation. Explosions were made for controlled source study of crust and upper mantle. The expedition was quite successful, and obtained data are now being processed.As a results of this study in 1990 and 1991, microseismicity of mid-oceanic ridge in Icelandic region has been clearly revealed, which is for the first time in any ridge. Also, a detailed crustal structure of the ridge has been obtained.

大西洋中脊是板块形成的地方。冰岛就坐落在海脊上。没有对任何脊的地壳和上地幔结构进行详细的研究。也没有详细的地震活动研究。本研究利用灵敏的海底地震仪（OBS）阵列揭示了冰岛及其周边地区非常详细的地震活动。此外，本研究还获得了冰岛北部的地壳结构。1990年和1991年两次从日本向冰岛运送了20架OBS。OBS由冰岛海岸警卫队的一艘船部署了两年。1990年，OBS阵列沿着雷克雅内斯山脊，其长度为150公里，宽度为40公里。密集阵列观测连续运行1个月。结果表明，震源仅分布在脊顶区域，脊顶外未发生地震。我们在山脊轴线上发现了一些地震集中的斑块，这与过去的海底火山活动有很好的对应关系。观测到的地震深度分布接近垂直，最大深度为12 km。观测期间捕捉到两个微震群，震源非常集中，震源呈垂直烟囱状分布。1991年，OBS在冰岛北部进行了类似的考察，那里的构造比通常的洋中脊更为复杂。部署了21台OBS和15台陆基地震仪进行观测。对地壳和上地幔进行了控制源研究。这次考察相当成功，获得的数据正在处理中。1990年和1991年的研究结果清楚地揭示了冰岛地区洋中脊的微震活动，这在所有洋中脊中尚属首次。此外，还得到了该脊的详细地壳结构。