Aseismic strike–slip associated with the 2007 dike intrusion episode in Tanzania
Aseismic strike–slip associated with the 2007 dike intrusion episode in Tanzania
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与 2007 年坦桑尼亚堤坝入侵事件相关的抗震走滑
DOI：
10.1016/j.tecto.2015.06.005
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发表时间：
2015
期刊：
影响因子：
2.9
通讯作者：
M. Furuya
中科院分区：
文献类型：
--
作者：
Y. Himematsu;M. Furuya
2007年7月，坦桑尼亚北部纳特龙湖附近发生震群，持续了大约两个月。Mt.Mt.位于震群西南部的Oldoinyo Lengai在震群前一个月左右开始喷发，并在9月份震群几乎停止时增加了喷发强度。以前的几项研究已经利用干涉合成孔径雷达(InSAR)报告了与震群有关的地壳形变信号。然而，几乎所有已发表的数据都是基于仅从下降路径获取的C波段ENVISAT/ASAR图像。我们使用了L波段的ALOS/PALSAR图像，这使得我们能够更详细地研究形变信号。除了InSAR数据外，我们还使用了偏移跟踪技术来检测沿方位方向的信号。利用干涉合成孔径雷达和炮检距跟踪数据，我们得到了与该幕相关的完整的3D位移场。除了已报道的堤防入侵引起的水平伸展和下沉信号外，推断的全三维位移进一步表明，沉降带向SSW方向水平移动了约480亿厘米。为了解释位移，我们进行了断层源模拟，假设为弹性半空间。断层滑动分布表明，走滑分量的贡献约占力矩释放总量的20%。由于2007年地震期间几乎所有的地震震源机制都表明了几乎纯粹的正常断层活动，因此非地震走滑一定是导致下沉带水平运动的原因。最浅层的走滑表明了扭动应力的存在，这似乎是产生东非裂谷中广泛观察到的接力带的合理原因。我们还证实了堤防入侵引起的应力变化与推断的断层滑动分布是一致的。
In July 2007, an earthquake swarm initiated in northern Tanzania near Lake Natron and lasted for about two months. Mt. Oldoinyo Lengai, located to the southwest of the swarm, began to erupt effusively about a month prior to the swarm, and increased its eruption intensity on September when the swarm almost ceased. Several previous studies have already reported the crustal deformation signals associated with the swarm using Interferometric Synthetic Aperture Radar (InSAR). However, nearly all the published data are based on the C-band ENVISAT/ASAR images acquired only from the descending path. We use the L-band ALOS/PALSAR images acquired from both ascending and descending paths, which allow us to examine the deformation signals in more detail. In addition to the InSAR data, we employ the offset-tracking technique to detect the signals along the azimuth direction. Using InSAR and offset-tracking data, we obtain the full 3D displacement fields associated with the episode. Besides the horizontal extension and subsidence signals due to the dike intrusion as already reported, the inferred full 3D displacements further indicate that the subsiding zone was horizontally moving by ~ 48 cm toward SSW. To explain the displacements, we performed fault source modeling, assuming an elastic half space. The fault slip distribution indicates that the contribution of the strike–slip component is about 20% of total moment release. Because almost all the focal mechanisms of earthquakes during the 2007 event indicate nearly pure normal faulting, aseismic strike–slip must have been responsible for the horizontal movement of the subsiding zone. The strike–slip at the shallowest depths suggests the presence of transtensive stress, which seems to be reasonable to generate the relay zones that are widely observed in the East African Rift. We also confirmed that the stress changes due to the dike intrusion were consistent with the inferred fault slip distributions.
对正在进行的达巴胡裂谷事件的大地测量观测：2006 年和 2007 年新的堤坝入侵
影响因子：
2.8
作者：
Hamling I
通讯作者：
Hamling I