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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。冰岛位于山脊上。没有对任何海脊的地壳和上地幔结构进行详细研究。此外，没有详细的地震活动性研究周围的山脊。利用灵敏的海底地震仪（OBS）台阵，对冰岛及其周边地区的地震活动进行了详细的研究，并获得了冰岛北部近海的地壳结构。这两年，OBS都是由冰岛海岸警卫队的一艘船只部署的。1990年，OBS阵列沿着雷克雅内斯海脊，长150 km，宽40 km。连续进行了一个月的密台观测，结果表明，地震震源仅沿脊顶沿着分布，脊顶以外未观测到地震。我们发现，沿脊轴沿着有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。观测地震的深度分布接近垂直，最大深度为12 km。1991年，在冰岛北部海域进行了类似的OBS考察，那里的构造比通常的洋中脊复杂。为进行观测，部署了21个OBS和15个陆基地震仪。爆炸是为了研究地壳和上地幔的受控源。这次考察相当成功，所获得的数据正在处理中，作为1990年和1991年研究的结果，清楚地揭示了冰岛地区洋中脊的微震活动，这在任何洋中脊中尚属首次。此外，还获得了海脊的详细地壳结构。