Coseismic slip distribution of the 2011 Tohoku MW9.0 earthquake inferred from GPS and InSAR data
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摘要: 本文首先对Envisat/ASAR数据进行干涉处理， 获取2011年日本东北MW9.0地震的地表InSAR同震形变场； 然后通过对InSAR同震形变数据重采样方法的深入分析， 选择条纹率法结合干涉图的空间相干性对InSAR同震形变数据进行重采样； 最后基于弹性半空间位错模型， 联合InSAR与GPS形变数据， 采用最小二乘法反演发震断层的滑动分布. 研究结果表明： 考虑相干性的条纹率重采样方法， 更适用于形变场中存在除断层外的有限边界、 且形变场范围较大的InSAR数据重采样处理； 断层滑动主要发生在地表以下50 km范围内， 最大滑动量为49.9 m， 矩张量为4.89×1022 N·m， 所对应的矩震级为MW9.1， 与地震学反演的结果比较吻合.
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关键词:
- 日本东北MW9.0地震 /
- 合成孔径雷达干涉测量 /
- 数据重采样 /
- 同震滑动分布
Abstract: To determine the causative fault slip distribution of the Tohoku MW9.0 earthquake in Japan， the coseismic deformation field of this earthquake was obtained with synthetic aperture radar interferometry (InSAR) technique based on Envisat/ASAR data. With detailed analysis and comparison of different methods used to resample InSAR deformation data， the fringe rate method taking into account spatial coherence of the interferogram was chosen for data resampling. Based on the elastic half-space dislocation model， the slip distribution of causative fault was inverted from InSAR and GPS data using the least squares method. The research results show that the fringe rate with coherence method is more suitable for data resampling of wider range InSAR deformation field, within which there are finite boundaries except fault. The majority of the fault slips occurred mainly in the range of 50 km below the surface， and the maximal slip on the fault is 49.9 m， meanwhile， the moment tensor is 4.89×1022 N·m， the corresponding moment magnitude is MW9.1. All these are consistent well with the results from seismological inversion， suggesting this inversion result in this study is reliable. -
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图 1 GPS测站位置(三角形)及InSAR覆盖范围(矩形框)
Figure 1. GPS sites (triangles) and InSAR coverage areas (rectangles)
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图 2 GPS测定的日本东北MW9.0地震的水平(a)和垂直(b)同震位移场
Figure 2. Horizontal (a) and vertical (b) coseismic displacements of the Tohoku MW9.0 earthquake inferred from GPS data
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图 3 日本东北MW9.0地震的同震形变干涉图(星号代表震中位置，下同)
Figure 3. Coseismic interferogram of the Tohoku MW9.0 earthquake where the star represents the epicentral location (the same below)
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图 4 四叉树方法重采样示例图
(a) 原始形变图; (b) 四叉树方法重采样后的形变图
Figure 4. Example of quadtree method for resampling
(a) Original deformation map; (b) Deformation map after quadtree method is used for resampling
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图 6 条纹率法(a)和平均选点法(b)重采样InSAR数据点分布图
Figure 6. Distribution of InSAR data resampled by fringe rate method (a) and uniform method (b)，respectively
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图 8 日本东北MW9.0地震的模拟形变干涉图(a)和残差干涉图(b)
Figure 8. Simulated deformation interferogram (a) and residual interferogram (b) of the Tohoku MW9.0 earthquake
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图 9 水平方向(a)和垂直方向(b)的实测(蓝色箭头)和模拟(红色箭头)GPS形变
Figure 9. Observed (blue arrows) and simulated (red arrows) GPS deformations in horizontal (a) and vertical (b) direction
表 1 Envisat/ASAR数据信息
Table 1 Details of Envisat/ASAR data
数据名称 轨迹 主影像时间 辅影像时间 时间基线/d 垂直基线/m T189 2011-03-10 2011-04-09 30 -315 Envisat/ASAR T347 2011-02-19 2011-03-21 30 -174 T74 2011-03-02 2011-04-01 30 -120 
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ARIA. 2011. ARIA GPS displacement data provided by JPL and Caltech[EB/OL]. [2011-08-01]. ftp://sideshow.jpl.nasa.gov/pub/usrs/ARIA/.
doi: 10.1029/2005RG000183 doi: 10.1029/2009GL041213 doi: 10.1029/2012GL051628 Supersites. 2011. Supersites Tohoku-Oki: GEO's Tohoku-Oki event Supersite website[EB/OL]. [2013-07-31]. http://supersites.earthobservations.org/sendai.php.
doi: 10.1029/2011GL048701
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