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）建立深海活断层探测方法体系（高分辨率水下定位系统+深拖测量系统、高分辨率水下定位系统+海底定点采样系统的集成），（2）用深地震法确定东海活动断裂的错动速率和大震复发时间。海洋活断层探测系统2001年，我们利用Hakuho-maru对位于熊野盆地的恩州断层系统进行了调查。恩舒断裂系以垂直位移的右旋断裂为特征，断裂上排列着泥火山岩。我们可以识别断层运动引起的泥火山位移。作为第一步，我们使用高分辨率水下定位系统+深水测量对恩州断层系统进行了遥感测量。 ...更多信息 ng系统，并获得了高分辨率的测深图与一个2 m计数器，海底的后向散射图像，和海底横截面的恩州断裂系统。其次，我们选择了两个采样点，这两个采样点都是根据遥感数据可能计算位移速率的位置，并使用活塞取样器上的响应器进行活塞岩心采样，在活塞岩心上没有安装远程操作能力的情况下，使活塞岩心高精度地接近预定采样点的操作对船舶导航技术要求很高。但由于博宝丸船员的高超航海技术，可以在预定地点取样，岩心分析结果表明，由于两个地点的岩心中没有识别出相关层，因此无法估计大地震的重现时间。因此，我们试图根据火山泥喷发的事件时间来估计大地震的复发时间，假设火山泥喷发与引起断层位移的地震事件相对应。各向同性年龄测定结果表明，泥流喷发事件的最年轻年龄为23 KMa。为了弄清高台场断裂系统的地表表现与深部滑脱构造（孕震区）之间的构造关系，对高台场断裂系统的三维MCS数据集进行了三维叠前深度偏移处理。).结果表明：①从高台场断裂系统与滑脱层的交汇点起，5 km范围内滑脱层具有高反射率的特征（地震核？滑脱构造不是连续的，而是间断的;俯冲脊（古Zenisu脊）位于下斜坡之下。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）。