Quaternary strike-slip crustal deformation around an active fault based on paleomagnetic analysis: a case study of the Enako fault in central Japan
Quaternary strike-slip crustal deformation around an active fault based on paleomagnetic analysis: a case study of the Enako fault in central Japan
复制标题
DOI：
10.1016/j.epsl.2004.08.003
复制
发表时间：
2004-10
影响因子：
5.3
通讯作者：
H. Kimura;Y. Itoh;H. Tsutsumi
中科院分区：
文献类型：
--
作者：
H. Kimura;Y. Itoh;H. Tsutsumi
为了评价活动断裂周围的累积走滑变形，我们对日本中部的右行走滑活动断裂Enako进行了构造地貌调查，并对分布在该断裂周围的Kamitakara火山碎屑流沉积(KPFD；0.6 Ma焊接凝灰岩)进行了古地磁调查。构造地貌研究表明，该断裂600ka以来的走滑位移约为150m。对火山碎屑流沉积中的古地磁方向和磁化率各向异性(AMS)进行了测量。各采样点稳定的主磁方向聚集良好，AMS组构非常扁平。然后，我们利用由AMS性质和真移构造取向获得的倾斜数据，对15个地点的古地磁方向进行了倾斜校正。在距断层约500m的范围内，观测到了不同的顺时针旋转，且距离断层越近，旋转角度越大。由于这种联系和块体边界断裂的缺失，用连续形变模型解释了研究区的地壳形变。在剪切带内探测到的与这种变形有关的走滑位移的计算最小值为210m，与Enako断层上的偏移量之和为360m，滑动速率估计为0.6 mm/年。
To evaluate cumulative strike-slip deformation around an active fault, we carried out tectonic geomorphic investigations of the active right-lateral strike-slip Enako fault in central Japan and paleomagnetic investigations of the Kamitakara pyroclastic flow deposit (KPFD; 0.6 Ma welded tuff) distributed around the fault. Tectonic geomorphic study revealed that the strike-slip displacement on the fault is ca. 150 m during the past 600 ka. We carried out measurements of paleomagnetic directions and anisotropy of magnetic susceptibility (AMS) within the pyroclastic flow deposit. Stable primary magnetic directions at each sampling site are well clustered and the AMS fabric is very oblate. We then applied tilt correction of paleomagnetic directions at 15 sites using tilting data obtained by the AMS property and orientations of eutaxitic structures. Within a distance of about 500 m from the fault trace, differential clockwise rotations were detected; the rotation angle is larger for zones closer to the fault. Because of this relation and absence of block boundary faults, a continuous deformation model explains the crustal deformation in the study area. The calculated minimum value of strike-slip displacement associated with this deformation detected within the shear zone is 210 m. The sum of this and offset on the Enako fault is 360 m and the slip rate is estimated at 0.6 mm/year.