Rapid dike intrusion into Sakurajima volcano on August 15, 2015, as detected by multi-parameter ground deformation observations
Rapid dike intrusion into Sakurajima volcano on August 15, 2015, as detected by multi-parameter ground deformation observations
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DOI：
10.1186/s40623-016-0450-0
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发表时间：
2016-04-27
影响因子：
3
通讯作者：
Tameguri, Takeshi
中科院分区：
文献类型：
--
作者：
Hotta, Kohei;Iguchi, Masato;Tameguri, Takeshi
为了解释2015年8月15日的快速变形事件，我们提出了2015年8月樱岛的地面变形观测结果，并使用GNSS、倾斜和应变数据组合对变形进行了建模。2015年8月14 - 16日水平位移呈西北西东向扩展，表明有堤防打开。利用遗传算法得到了位错源的位置、倾角、走向长度、宽度和开口。在昭和陨石坑下方海平面以下1.0公里处发现了一条几乎垂直的北北-南南南走向的堤。长度和宽度分别为2.3公里和0.6公里，1.97米的堤口使体积增加2.7 × 10(6)米(3)。887次火山构造（VT）地震表明，岩脉的快速打开引起了围岩应变的积累，而VT地震是为了释放这种应变而产生的。总变形量的一半集中在8月15日10:27 ~ 11:54之间。估计该时期岩浆侵入速率为1 × 10(6) m(3)/h。这是2012年7月24日南达克山顶火山口最大一次喷发前岩浆侵入速率的200倍，是2011年10月至2012年3月期间平均岩浆侵入速率的2200倍。以往的莫吉型地表变形被认为是岩浆在已存在的球形储层中聚集的过程。相反，2015年8月的事件是一次堤防入侵，发生在与先前存在的水库不同的位置。岩脉开口方向与t轴和断层方向一致，形成地堑构造。
We present observations of ground deformation at Sakurajima in August 2015 and model the deformation using a combination of GNSS, tilt and strain data in order to interpret a rapid deformation event on August 15, 2015. The pattern of horizontal displacement during the period from August 14 to 16, 2015, shows a WNW-ESE extension, which suggests the opening of a dike. Using a genetic algorithm, we obtained the position, dip, strike length, width and opening of a dislocation source based on the combined data. A nearly vertical dike with a NNE-SSW strike was found at a depth of 1.0 km below sea level beneath the Showa crater. The length and width are 2.3 and 0.6 km, respectively, and a dike opening of 1.97 m yields a volume increase of 2.7 x 10(6) m(3). 887 volcano-tectonic (VT) earthquakes beside the dike suggest that the rapid opening of the dike caused an accumulation of strain in the surrounding rocks, and the VT earthquakes were generated to release this strain. Half of the total amount of deformation was concentrated between 10:27 and 11:54 on August 15. It is estimated that the magma intrusion rate was 1 x 10(6) m(3)/h during this period. This is 200 times larger than the magma intrusion rate prior to one of the biggest eruptions at the summit crater of Minami-dake on July 24, 2012, and 2200 times larger than the average magma intrusion rate during the period from October 2011 to March 2012. The previous Mogi-type ground deformation is considered to be a process of magma accumulation in preexisting spherical reservoirs. Conversely, the August 2015 event was a dike intrusion and occurred in a different location to the preexisting reservoirs. The direction of the opening of the dike coincides with the T-axes and direction of faults creating a graben structure.