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Research on the tectonics of the southeastern Philippine Sea based on GPS observations

基于GPS观测的菲律宾海东南部构造研究

基本信息

批准号：
14403003
负责人：
KATO Teruyuki
金额：
$ 7.36万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14403003/
关键词：
GPS The Northern Marian Islands back-arc back-arc spreading plate motion Philippine Sea Anatahan Island eruption フィリピン海プレート

项目摘要

We have repeated GPS observations for darifying tectonic motion in the Northern Mariana Islands, Commonwealth of the Northern Mariana Islands. Moreover, we investigated the volcanic activity of Anatahan Island that began eruption in May 2003 for the first time in the human history. GPS observations were conducted in January 2003, July 2003 and May-Jun 2004. The obtained data were analyzed taking earlier data into consideration. Considering that the northernmost three islands were not been observed more than once, we extensively made observations in those three islands, namely, Asencion, Maug and Uracus. Results show that the effect of back-arc spreading in the Mariana Trough is eminent in the region. However, at the northern three islands, residual vectors that indicate effects of back-arc spreading show somewhat diverging vectors. The effect of back-arc spreading is not very eminent. This is probably due to short observation time of only one year. We should make more detailed analysis … More of the data. In addition, we may have to repeat GPS observations in the future to obtain more reliable results.Anatahan volcano began erupting in May-Jun 2003. A series of subplinian explosive eruptions of andesite magma began at the Eastern Crater in the eastern part of the summit caldera on the evening of 10 May. Brown tephra was sent mainly westward by strong winds. Small-scale pyroclastic surges were discharged eastward outside the caldera in late May. An andesite lava dome that had once filled the inner crater was fragmented by phreatomagmatic explosions in the middle of June. The phreatomagmatic explosions probably occurred due to interaction of the magma lead with ground water around the crater, and abundant very fine ash ("gray tephra") was discharged within the caldera and over most of the island. The volume of eruption products of the May-June eruption was estimated to be 1.4x10^7 m^3 dense-rock-equivalent. Erupted pumices and lava are aphyric andesite and are variously colored depending on their vesicularity. The SiO2 contents of erupted materials decreased slightly with time. The fine gray ash is depleted in alkalies, probably due to leaching by acid hydrothermal fluids during explosions. Seismic activity resumed in late March 2004, and small strombolian-like explosions were repeated in May and June 2004. About hard of the inner crater was filled with new scoria and lava. Less

我们在北方马里亚纳群岛联邦的北方马里亚纳群岛进行了重复的GPS观测，以研究构造运动。此外，我们还调查了人类历史上第一次于2003年5月开始喷发的阿纳塔汉岛火山活动。GPS观测于2003年1月、2003年7月和2004年5月至6月进行。考虑到早期数据，对获得的数据进行了分析。考虑到最北端的三个岛屿没有被观察过一次以上，我们在这三个岛屿，即Asencion，Maug和Uracus进行了广泛的观察。结果表明，马里亚纳海槽弧后扩张作用在该区域具有显著的作用。然而，在北方的三个岛屿，残余矢量，表明弧后扩张的影响，显示有点发散的矢量。弧后扩展的影响不是很显著。这可能是由于观察时间短，只有一年。我们应该做更详细的分析 ...更多信息的数据。此外，我们可能必须在未来重复GPS观测，以获得更可靠的结果。5月10日晚，在山顶破火山口东部的东部火山口，安山岩岩浆开始了一系列的次布里尼亚爆炸性喷发。棕色火山灰主要被强风吹向向西。5月下旬，小规模的火山碎屑潮向东排出破火山口外。一个曾经充满内部火山口的安山岩熔岩圆顶在6月中旬被蒸汽岩浆爆炸破碎。蒸汽岩浆爆炸可能是由于岩浆铅与火山口周围的地下水相互作用而发生的，大量非常细的火山灰（“灰色火山灰”）被排放到火山口内和岛屿的大部分地区。5月至6月的喷发产物体积估计为1.4x10^7 m^3致密岩石当量。喷出的浮岩和熔岩是隐晶质安山岩，根据它们的泡状而呈现各种颜色。随着时间的推移，喷发物的SiO2含量略有下降。灰色细灰缺乏碱，可能是由于爆炸期间酸性热液流体的沥滤。2004年3月下旬，地震活动重新开始，2004年5月和6月又发生了类似斯特龙博利式的小爆炸。大约硬的内部陨石坑充满了新的火山渣和熔岩。少