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

本研究项目的目标是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+深拖测量系统和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活动断层的偏移率和大地震的重现时间。在最初的两年里，我们花了很多时间构建新的测量方法。2001年，我们利用白凤丸将我们的新方法应用于位于熊野盆地的远州断层系统。远州断层系以右旋断层为特征，具有垂直位移，泥沃卡诺在断层上排列。我们可以识别断层运动引起的泥火山位移。第一步，我们利用高分辨率水下定位系统+深拖测量系统对远州断层系进行遥感调查，获得了2m计数器的高分辨率测深图、海底后向散射图像以及远州断层系的海底剖面。接下来，我们根据遥感数据选择了两个可能计算位移率的位置进行采样，并利用活塞取芯器上安装的响应器进行了活塞芯采样。在活塞芯上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采样点，需要较高的船舶导航技术。但白凤丸号船员的高航海技术使得他们能够从预定地点采集样本。岩心样本分析结果显示，我们无法估计大地震的复发时间，因为从两个地点获得的岩心中没有识别出相关层。因此，我们试图根据泥浆沃卡诺喷发的事件时间来估计大地震的复发时间，假设泥浆喷发与引起断层位移的地震事件相对应。各向同性年龄测定表明，泥浆喷发事件的最小年龄为23KMa。因此，我们无法估计地震的复发时间。我们将3D叠前深度偏移过程应用于从Kodaiba断层系获得的3D MCS数据集，以阐明Kodaiba断层系的表面表现与深层滑脱（发震带？）之间的结构关系。该过程的结果表明：1）滑脱的特征是在距小台场断层系与滑脱融合点（地震核？）5km范围内具有高反射率；2）滑脱不是连续的而是间歇性的；3）在下斜坡下方识别出俯冲脊（古泽尼苏脊）。较少的

项目成果

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）。

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。

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）。