Marine geophysical study of the Solomon Arc convergent zone

所罗门弧汇聚带的海洋地球物理研究

基本信息

批准号：
05044041
负责人：
SUYEHIRO Kiyoshi
金额：
$ 5.76万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for international Scientific Research
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1994
项目状态：
已结题

项目摘要

The Solomon island arc area is a complex plate convergence zone. On the northern side is the North Solomon Trench at which the Pacific plate is being consumed. Another trench on the southern side is the San Cristobal Trench, where the Indo-Australian plate and the Solomon Sea plate seem to be subducting beneath the Solomon arc. The San Cristobal Trench becomes less conspicuous west of Guadalcanal.A plate subduction zone is usually best described by the seismic data, that is by the determination of hypocenters that define the geometry of the subducting slab. However, in a complex region like the Solomon area, the worldwide seismic network dataset is unable to resolve the complexity unless one assumes the tectonics operating in the region. Only less than 10 events are determined each year west of Guadalcanal.The only way to obtain high spatial resolution in hypocenter determination is to conduct an on-site seismic observation with very high sensitivity. We have improved our digital ocean bottom seismograph (OBS) in 1993 and made a temporary microseismicity observation west of Guadalcanal using 5 OBS's for the period of Aug.28 through Sep.7 in 1994.Our preliminary results indicate (1) about 200 times higher seismic detectability compared to the International Seismological Center determinations, (2) subduction of the Indo-Australian plate to about 50 km with a surprisingly large dip angle of about 50 degrees, (3) almost no seismicity in the small basin between the double arc, (4) 60 to 90 km deep events probably associated with the Pacific plate subduction.We are planning an arc transect to obtain the whole crustal structure of the arc system, which will help to link the above findings with the structure and tectonics.

所罗门岛弧区是一个复杂的板收敛区。在北侧，是北所罗门沟，太平洋板块正在消耗。南侧的另一个沟渠是San Cristobal沟渠，那里的印度澳大利亚板块和所罗门海板似乎在所罗门弧下方俯冲。 San Cristobal的沟渠变得不那么显着，在瓜达尔卡纳尔山脉以西。板俯冲带通常是通过地震数据来描述的，即通过确定定义俯冲板几何形状的低中心者。但是，在像所罗门地区这样的复杂地区，除非有人假设在该地区运作的构造，否则全球地震网络数据集无法解决复杂性。每年在瓜达尔卡纳尔岛（Guadalcanal）以西的每年仅确定少于10个事件。获得高空间确定的高空间分辨率的唯一方法是进行现场地震观察，并具有很高的灵敏度。我们在1993年改善了数字海洋底部地震仪（OBS），并在1994年8月28日至9月7日的瓜达尔卡纳尔山脉以西进行了暂时的微观震丝性观察。您的初步结果表明（1）与国际地震学中心的确定相比，（2）Indip aftip to to tosip to to to to Indip（2）较高的地震可检测性，（2）大约50度的角度，（3）双弧之间的小盆地几乎没有地震性，（4）60至90 km深的事件可能与太平洋板块的俯冲相关。我们正在计划ARC样带，以获得弧系统的整个地壳结构，这将有助于与上述发现与结构和构造的结构和构造链接。