P and S wave velocity measurements of water‐rich sediments from the Nankai Trough, Japan
P and S wave velocity measurements of water‐rich sediments from the Nankai Trough, Japan
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DOI：
10.1002/2013jb010290
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发表时间：
2014-02
期刊：
影响因子：
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通讯作者：
K. Schumann;M. Stipp;J. Behrmann;D. Klaeschen;D. Schulte‐Kortnack
中科院分区：
文献类型：
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作者：
K. Schumann;M. Stipp;J. Behrmann;D. Klaeschen;D. Schulte‐Kortnack
在南开俯冲带粉质粘土和粘质粉质岩心样品的三轴变形试验(综合海洋钻探计划第315、316和333次)中测量了声速。我们提供了一个新的数据集，在压力增加和随后的轴向变形过程中连续测量。提出了一种利用地震时间序列分析进行数据处理的新方法。纵波速度Vp约为1450~2200m/S，横波速度Vs约为150~800m/S，Vp随有效围压和有效轴向应力的增大而略有增大。增积棱柱状脚趾样品的Vp最高，而弧前斜坡沉积物的Vp较低。来自新来板块的样品，粘土矿物略丰富，Vp值最低。VS随有效围压和有效轴向应力的增大而增大，与成分和构造环境无关。剪切模数和体积模数分别在0.2~1.3 Gpa和3.85~8.41 Gpa之间。巨型断裂增积棱柱趾部和下盘的弹性模量值(1.50和3.98 Gpa)高于上盘和进料板的弹性模量值(0.59和0.88 Gpa)。这使得可以区分正常和过度固结的沉积物。数据表明，在只有微小成分差异的构造沉积环境中，声学特性可用于区分较强的(增生棱柱状脚趾)和较弱的(弧前斜坡、来水板块)沉积物。特别是，Vp/VS比值可能有助于探测低有效应力和高孔隙流体压力的区域。
Acoustic velocities were measured during triaxial deformation tests of silty clay and clayey silt core samples from the Nankai subduction zone (Integrated Ocean Drilling Program Expeditions 315, 316, and 333). We provide a new data set, continuously measured during pressure increase and subsequent axial deformation. A new data processing method was developed using seismic time series analysis. Compressional wave velocities (Vp) range between about 1450 and 2200 m/s, and shear wave velocities (Vs) range between about 150 and 800 m/s. Vp slightly increases with rising effective confining pressure and effective axial stress. Samples from the accretionary prism toe show the highest Vp, while fore‐arc slope sediments show lower Vp. Samples from the incoming plate, slightly richer in clay minerals, have the lowest values for Vp. Vs increases with higher effective confining pressures and effective axial stress, irrespective of composition and tectonic setting. Shear and bulk moduli are between 0.2 and 1.3 GPa, and 3.85 and 8.41 GPa, respectively. Elastic moduli of samples from the accretionary prism toe and the footwall of the megasplay fault (1.50 and 3.98 GPa) are higher than those from the hanging wall and incoming plate (0.59 and 0.88 GPa). This allows differentiation between normal and overconsolidated sediments. The data show that in a tectonosedimentary environment of only subtle compositional differences, acoustic properties can be used to differentiate between stronger (accretionary prism toe) and weaker (fore‐arc slope, incoming plate) sediments. Especially Vp/Vs ratios may be instrumental in detecting zones of low effective stress and thus high pore fluid pressure.