Rate of displacement and recurrence time of earthquake of the submarine active fault off Tokai

东海海域海底活动断层的位移速率和地震重现时间

• 批准号: 11309002
• 负责人: TOKUYAMA Hidekazu
• 金额: $ 26.29万
• 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 (A)
• 财政年份: 1999
• 资助国家: 日本
• 起止时间: 1999 至 2002
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11309002/
• 关键词: Submarine active fault; Deep Tow survey; Enshu Fault system; High resolution underwater positioning system; Piston core; Responder; decollement; the paleo-Zenisu ridge; 遠州断層; 高精度水中測位法; ピストン・コアラー; リニアメント; 巨大地震; 活断層; 3次元・マルチチャンネル音波探査; 海底音響画像

The objectives of this research program is 1)to establish the method of deep-sea active fault surveying system(integration of high resolution underwater positioning system + deeptow surveying system, and high resolution underwater positioning system + pinpoint sampling system from oceanfloor),and 2) to determine the rate of offset of the active faults off Tokai and the recurrence time of great earthquake using the method of deep-sea active fault surveying system. In the first two years, we spent our time to construct new survey method.In 2001, we applied our new method to the Enshu fault system located in Kumano Basin using Hakuho-maru. The Enshu fault system is characterized by dextral fault with vertical displacement and mudvokanoes are aligned on the fault. We can identify displacements on the mudvolcanoes induced by fault movement.As a first step, we performed remote sensing survey across the Enshu fault system using a high resolution underwater positioning system + deeptow surveyi … More ng system, and obtained high resolution bathymetric map with a 2m counter, backscattering image of ocean floor, and subbottom cross section across the Enshu Faults system. Next, we selected two position for sampling where the rate of displacement is likely to be calculated based on the remote sensing data, and performed piston core sampling using responders attached on piston corer.The operation to make the piston core approach to the intended sampling point with high accuracy requires a high ship navigation technique in case of no remote operation capability installed on the piston core. But the high ship navigation technique of the crew members of Hakuho-maru enable to take samples from the intended points.The results of core sample analysis revealed, we can not estimate the recurrence time of great earthquake, becausecorrelated layers are not identified hi the cores obtained from the two sites. So, we tried to estimate the recurrence time of great earthquake based on the event time of mud vokano eruption, assuming that the mud eruption corresponds with the earthquake event inducing the displacement of fault. Isotropic age determination revealed that the youngest age of the mud eruption event is 23KMa. So, we can not estimate the recurrence time of earthquake.We applied 3D pre-stack depth migration process to the 3D MCS data sets obtained from Kodaiba fault system in order to clarify the structural relationship between surface manifestation of the Kodaiba fault system and the deep seated decollement(seismogenic zone? ). The results of the process suggests that 1)the decollement is characterized by high reflectivity in a range of 5km from the point where the Kodaiba fault system merges with decollement(seismic nuclear? ), 2) the decollement is identified not continuously but intermittently, and 3)subducted ridge(the paleo-Zenisu ridge) is identified beneath the lower slope. Less

本课题的研究目标是：1)建立深海活动断层测量系统方法（高分辨率水下定位系统+深拖曳测量系统集成，高分辨率水下定位系统+海底精确采样系统集成）；2)利用深海活动断层测量系统方法确定东海外活动断层偏移速率和大地震重现时间。在前两年，我们花时间构建新的调查方法。2001年，我们利用Hakuho-maru将新方法应用于熊野盆地恩树断裂系统。恩树断裂系以右向断裂为特征，纵向位移，泥火山岩在断层上排列。我们可以识别由断层运动引起的泥火山位移。首先，利用高分辨率水下定位系统+深度拖带测量系统对恩舒断裂系统进行了遥感调查，获得了高分辨率2米计测深图、海底后向散射图像和恩舒断裂系统海底剖面。接下来，我们选择了两个可能根据遥感数据计算位移率的位置进行采样，并使用附着在活塞盖上的响应者进行活塞芯采样。在活塞芯没有安装远程操作能力的情况下，要使活塞芯高精度地接近预定的采样点，需要很高的船舶导航技术。但白湖丸号船员的高船舶导航技术使他们能够从预定的地点采集样本。岩心样品分析结果表明，由于两个地点的岩心没有识别出相关层，我们无法估计大地震的复发时间。因此，我们尝试根据泥火山喷发的事件时间，假设泥火山喷发与引起断层位移的地震事件相对应，来估计大地震的重复时间。各向同性年龄测定表明，泥喷发事件的最年轻年龄为23KMa。因此，我们无法估计地震的复发时间。为了明确Kodaiba断裂系统的地表表现与深部滑脱（发震带）之间的结构关系，对Kodaiba断裂系统的三维MCS数据集进行了三维叠前深度偏移处理。。结果表明：1)离Kodaiba断裂系统与滑脱体合并处5km范围内的滑脱体具有高反射率的特征（地震核？）(2)滑脱不是连续的，而是间歇性的；(3)下斜坡下确定俯冲脊（古泽尼苏脊）。少

项目成果

Wonn Soh, Hidekazu Tokuyama: "Rejuvenation of submarine canyon associated with ridge subduction, Tenryu Canyon, off Tokai, central Japan"Marine Geology. 187(1-2). 203-220 (2002)

Wonn Soh、Hidekazu Tokuyama：“与山脊俯冲有关的海底峡谷的复兴，日本中部东海附近的天龙峡谷”海洋地质学。

芦 寿一郎: "熊野沖南海トラフ付加プリズムの地質と構造と冷湧水"深海研究. 20(in press). (2002)

Juichiro Ashi：“熊野附近南海海槽增生棱镜的地质和结构以及冷泉水”深海研究 20（出版中）。

Juichiro Ashi: "Mass Balance of the subduction zone in relation to methane hydrate and cold seepage activity"Chikyu Monthly. 32(Special Volume). 122-129 (2001)

Juichiro Ashi：“俯冲带的质量平衡与甲烷水合物和冷渗活动的关系”地球月刊。

徳山 英一: "相模湾・駿河湾の湧水活動"海洋と生物. 141. 290-293 (2002)

德山荣一：“相模湾和骏河湾的春季活动”海洋和生物学 141. 290-293 (2002)。

氏家由利香: "琉球海溝・南海トラフ域におけるマッドダイアピルの活動,プレート沈み込み帯における物質循環-付加体の役割-"月刊地球. 号外(32). 206-213 (2001)

Yurika Ujiie：“琉球海沟/南海海槽地区的泥底辟活动，板块俯冲带的物质循环——增生体的作用”月刊特刊（32）（2001）。