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Study of Crustal Activity in the East African Rift Valley

东非大裂谷地壳活动研究

基本信息

批准号：
08041092
负责人：
HAMAGUCHI Hiroyuki
金额：
$ 9.54万
依托单位：
Faculty of Science, Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for international Scientific Research
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08041092/
关键词：
Africa Rift Valley Volcanic Activity Earthguake Seismic Wave Earth's Interior GPS Earth's Core 地溝帯火山活動地震地震波内核

项目摘要

(1) After the initial episode of eruption of Volcano Nyiragongo, eastern Zaire, we monitored the temporal levnl changes of lava lake in the summit crater by using the electro-optical distance measuring (EDM) deuce. The surface of lava lake elevated 118 meter in the period from August, 1994 to September 1996. The lava volume supplied in this period was 86 mmllion cubic meter.(2) We observed at least 37 eruptive episodes in the period from June, 1994 to February, 1995, during which volcanic tremors were intermittently recorded at the nearby stations. The A-type volcanic earthquakes were located at the depth ranges of 10 - 15km beneath the summit and around the NE flank. We found the reverse correlation between the occurence of earthquake and that of tremors.(3) We summarized the volcanic and seismic activities at the Virunga volcanic area, based on the geophysical, geochemical and geological published data.(4) We cooperated with Kenya Institute of Surveying and mapping and made the GPS networks crossing the Rift Valley at the northern Kenya. We measured the seven locations in 1997 and 1998.(5) We analyzed PKP,S and ScS seismic phases recorded by the GDSN networks in order to clarify the lateral heterogeneity in the mantle ant the core : (A) We found that large positive residuals of ScS-S differential travel times greater than 10 seconds locate 2 % low-velocity regions beneath south and northwest Africa : (B) The geographical pattern of the PKP differential travel time (BC-DF) residuals was found to be a manifestation of degree one heterogeneity in the outermost 100 to 500km of the inner core. The P velocities in the inner core are fast in the quasi-eastern hemisphere with a peak value of +0.29 sec and slow in the quasi-western hemisphere with that of -0.66 sec.

(1)扎伊尔东部尼拉贡戈火山首次喷发后，利用电光测距仪(EDM)对山顶火山口熔岩湖的时间水平变化进行了监测。 1994年8月至1996年9月期间，熔岩湖表面抬高118米，该时期熔岩供应量为86百万立方米。（2）1994年6月至1995年2月期间，我们观测到至少37次喷发事件，在此期间，附近站点间歇性记录到火山地震。 A型火山地震发生在顶峰以下10-15公里深度范围内和东北侧翼周围。我们发现地震的发生与地震的发生之间存在反向相关性。（3）根据地球物理、地球化学和地质公布的数据，总结了维龙加火山区的火山和地震活动。（4）与肯尼亚测绘研究所合作，制作了跨越肯尼亚北部裂谷的GPS网络。我们在 1997 年和 1998 年测量了这 7 个位置。(5) 我们分析了 GDSN 网络记录的 PKP、S 和 ScS 地震相位，以澄清地幔和地核的横向异质性：(A) 我们发现大于 10 秒的 ScS-S 差分走时时间的大正残差位于非洲南部和西北部下方的 2% 低速区域：(B) 地理格局 PKP差分走时（BC-DF）残差的变化被发现是内核最外层100至500公里一级异质性的表现。准东半球内核P速度快，峰值为+0.29秒；准西半球内核P速度慢，峰值为-0.66秒。