权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Do the gravity and geoid height changes accumulate during the course of earthquake cycle?

重力和大地水准面高度的变化是否在地震周期过程中累积？

基本信息

批准号：
13440130
负责人：
OKUBO Shuhei
金额：
$ 7.42万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2003
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-13440130/
关键词：
Viscoelasticity Gravity Fault motion Active faults

项目摘要

We formulated the gravity, geoid height and elevation changes due to fault motoin in a Maxwell viscoelastic earth. The formulation is implemented to a FORTRAN computer code, which enables us to compute interseismic gravity/elevation changes during an earthquake cycle based on the Savage's backslip model. We applied the technique to the interseismic deformation around the Tokai area where the Philippine Sea plate is subducting beneath the Eurasian plate.The model successfully reproduces the steady subsidence when we assume reasonable viscosity profile and asperity distribution. On the contrary, we find the computed gravity change rate is significantly larger than the observed one. The result casts profound doubt on the validity of the Savage's supposition that no deformation accumulates over repeated seismic cycles.We applied the formulation to the analysis of gravity change before and after the Tokachi-oki Earthquake (M8.1, September 26, 2003). To be more specific, we calculated the interseismic gravity change rate to reduce the absolute gravity value taken several years before the earthquake to the one just before the earthquake. When compared with the absolute gravity value just after the earthquake, it enables us to estimate the coseismic gravity change. The change agrees well with the theoretically predicted one.

给出了麦克斯韦粘弹性地球中断层运动引起的重力、大地水准面高度和高程变化的公式。该公式已在FORTRAN计算机程序中实现，它使我们能够根据Savage的背滑模型计算地震周期期间的震间重力/高程变化。我们将该技术应用于菲律宾板块俯冲到欧亚板块之下的东海地区周围的震间变形，当我们假设合理的粘性剖面和粗糙度分布时，模型成功地再现了稳定的下沉。相反，我们发现计算的重力变化率明显大于观测的重力变化率。这一结果对Savage关于在重复的地震周期中不积累形变的假设的正确性提出了严重的质疑。我们将该公式应用于2003年9月26日东京8.1级地震前后的重力变化分析。更具体地说，我们计算了震间重力变化率，将地震前几年的绝对重力值降至地震前几年的绝对重力值。与地震后的绝对重力值相比，它使我们能够估计同震重力变化。这一变化与理论上预测的变化非常吻合。