A quantitative approach to the dike intrusion process inferred from a joint analysis of geodetic and seismological data for the 1998 earthquake swarm off the east coast of Izu Peninsula, central Japan
A quantitative approach to the dike intrusion process inferred from a joint analysis of geodetic and seismological data for the 1998 earthquake swarm off the east coast of Izu Peninsula, central Japan
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DOI：
10.1029/2005jb003860
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发表时间：
2006-06-20
影响因子：
3.9
通讯作者：
Hayashi, Yoshinari
中科院分区：
文献类型：
--
作者：
Morita, Yuichi;Nakao, Shigeru;Hayashi, Yoshinari
日本中部伊豆半岛东海岸的一系列地震群与活火山周围的岩脉侵入有关。在该地区的许多研究中，记录了地震活动和地面变形，但没有完全解决堤坝入侵的过程。这项研究涉及联合分析的大地测量和地震数据，从最近的主要活动在该地区，发生在1998年，以揭示的过程中，堤防入侵的数量。我们结合了联合收割机的数据，从一个密集的GPS阵列，包括10个临时站，与地震分析以前发表的。我们估计的位置的岩脉地震数据和体积的侵入岩浆大地测量数据。通过对这两组资料的综合分析，揭示了与1998年震群有关的岩脉侵入运动学过程。堤防入侵的过程中，定量模拟记录的堤防体积的时间演变和使用的地震震源作为指示器的瞬时堤防入侵的网站。根据这些观察，我们提出了以下过程的岩脉侵入：岩浆上升通过一个通道垂直排列，并创建一个岩脉时，它失去了浮力。我们还评估了岩脉侵入过程定量使用一个模型的圆形岩脉，从深岩浆库的连续岩浆供应下增长。根据观测资料，我们推断了岩墙形状、压力分布和岩浆粘度的时间演化。获得的粘度随着时间的推移而增加，这可能是合理的，因为岩浆逐渐冷却。然而，与该地区预期的典型玄武岩浆相比，其值太大。它可能代表岩脉内几乎凝固的岩浆。另外，岩浆的供给是间歇性的，岩墙的生长主要受深部储层岩浆供给速率的控制。在这项研究中所描述的自然界中的堤防入侵过程的定量描述是非常罕见的，我们的研究结果提供了一些参数，还没有解决在许多以前的理论研究的堤防入侵过程的约束。
A series of earthquake swarms off the east coast of Izu Peninsula, central Japan, is typically associated with dike intrusion around active volcanoes. Numerous studies in this region have documented the seismic activity and ground deformations without fully resolving the process of dike intrusion. This study involves a joint analysis of geodetic and seismic data from the most recent major activity in this region, occurring in 1998, to reveal the process of dike intrusion quantitatively. We combine data from a dense GPS array, including 10 temporary stations, with seismic analysis published previously. We estimate the location of the dikes from seismic data and the volume of intruded magma from geodetic data. Combined analysis of both data sets enables us to reveal the kinematic process of dike intrusion associated with the 1998 earthquake swarm. The process of dike intrusion is quantitatively modeled using the time evolution of recorded dike volume and the use of seismic hypocenters as an indicator of the site of instantaneous dike intrusion. On the basis of these observations, we propose the following process of the dike intrusion: The magma rose upward through a pathway aligned vertically and created a dike when it lost buoyancy. We also evaluate the dike intrusion process quantitatively using a model of a circular dike that grows under a continuous magma supply from a deep magma reservoir. From the observational data, we infer the time evolution in the dike shape, pressure distribution, and magma viscosity in the dike. The acquired viscosity increases over time and it may be reasonable because magma cools gradually. However, its value is too large compared to typical basaltic magma expected in this region. It may represent magma within the dike that is nearly solidified. Otherwise, the magma is supplied intermittently and the dike growth is mainly controlled by the magma supply rate from a deep reservoir. The quantitative description of the dike intrusion process in nature described in this study is very rare, and our results provide constraints on several parameters that have not been solved in many previous theoretical studies on the dike intrusion process.