Collaborative Research: Investigation of Sources of Intraplate Volcanism Using PASSCAL Broadband Instruments in Madagascar, The Comores, and Mozambique (MACOMO)

该项目将涉及从安装在马达加斯加、科摩罗群岛和莫桑比克的宽带地震仪网络获取和分析地震数据，以确定该地区板内火山活动的起源。对于马达加斯加这个世界第四大岛，至今还没有进行过现代地震调查，火山活动的源头也是未知的，不在任何板块边界附近。这项研究试图确定火山活动是否与巨大的下地幔大的低剪切速度省(LLSVP)或任何上地幔热点有关，如阿法尔或留尼汪岛下的热点。从IRIS PASSCAL仪器池借来的地震仪将部署在两个设施中：2011年夏天18个(马达加斯加、科摩罗和莫桑比克)，2012年夏天15个(全部在马达加斯加)。所有地震仪将在2013年夏天收回。宽带地震数据将使用几种技术进行分析，以确定该地区的地下结构。面波和体波数据将用于生成地壳和地幔的3D层析图像；横波分裂将用于检查各向异性组构；P波到S波的转换将用于生成用于确定莫霍面和其他次表面不连续面地形的接收函数。非洲LLSVP是地球内部最大的地震异常，作为地幔和核之间的巨大热化学边界层，它在控制地幔内垂直质量通量的性质，从而控制地幔对流及其在地表的板块构造表现方面发挥着至关重要的作用。非洲LLSVP被认为在非洲板块热点火山活动的大量发生中发挥了重要作用，但由于南半球这一位置可获得的数据样本极其有限，这种情况发生的机制尚不清楚。许多学科的地球科学家将对非洲次区域LLSVP的进一步研究感兴趣，因为这将提供对马达加斯加地下地质的第一次研究。该项目将有助于培训美国研究生以及马达加斯加和莫桑比克的科学家，并将有助于加强这三个国家之间的科学联系。该项目还将成为非洲阵列的科学伙伴，非洲阵列一直是非洲科学和善意的一股统一的积极力量。该奖项由美国国家科学基金会国际科学与工程办公室共同资助。

This project will involve the acquisition and analysis of seismic data from a network of broadband seismometers installed in Madagascar, the Comores Islands, and Mozambique in order to determine the origin of intraplate volcanism in the region. No modern seismic investigation of Madagascar, the world?s 4th largest island, has ever been made, and the source of the volcanism, not near any plate boundary, is unknown. This study seeks to determine if the volcanism is connected with either the giant lower mantle large low-shear velocity province (LLSVP) or with any of the upper mantle hot spots such as those beneath Afar or Reunion. The seismometers, borrowed from the IRIS PASSCAL pool of instruments, will be deployed in two installations: 18 in the summer of 2011 (in Madagascar, the Comores, and Mozambique), and 15 in the summer of 2012 (all in Madagascar). All seismometers will be retrieved in the summer of 2013. The broadband seismic data will be analyzed using several techniques in order to determine the sub-surface structure of the region. Both surface and body wave data will be use to generate 3D tomographic images of the crust and mantle; shear-wave splitting will be used to examine anisotropic fabric; P-to-S-wave conversions will be used to generate receiver functions for determining topography on the Moho and other sub-surface discontinuities. The African LLSVP is the largest seismic anomaly within the earth; as an enormous thermochemical boundary layer between the mantle and core, it plays a vitally important role in controlling the nature of vertical mass flux within the mantle, and therefore of both mantle convection and its manifestation at the surface as plate tectonics. The African LLSVP is thought to play an important role in the abundant occurrence of hot spot volcanism on the African plate, but the mechanism by which this occurs is not known due to the extremely limited data sampling available at this location in the Southern Hemisphere. Further study of the sub-African LLSVP will be of interest to earth scientists in many disciplines, as will providing the first study of the sub-surface geology of Madagascar. This project will help in the training of U.S. graduate students as well as scientists in Madagascar and Mozambique, and will help strengthen the scientific ties between these three countries. This project will also be a scientific partner with AfricaArray, which has been a unifying positive force of science and good will in Africa. This award is co-funded by NSF's Office of International Science and Engineering.