Source rupture processes of the 1944 Tonankai earthquake and the 1945 Mikawa earthquake derived from low-gain seismograms
Source rupture processes of the 1944 Tonankai earthquake and the 1945 Mikawa earthquake derived from low-gain seismograms
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DOI：
10.1186/bf03351745
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发表时间：
2003-01-01
影响因子：
3
通讯作者：
Yoshikawa, K
中科院分区：
文献类型：
--
作者：
Kikuchi, M;Nakamura, M;Yoshikawa, K
在20世纪40年代，日本西部发生了几次破坏性的地震。这一时期的地震图通常记录在烟熏纸上，与现代数字数据相比，质量很差。但是，近年来图像处理技术的发展使我们能够重建可行的波形数据，据此，我们研究了两个破坏性地震的震源破裂过程：1944年12月7日的托南海地震（M7.9）和1945年1月13日的三川地震（M6.8）。对东南海地震的研究结果表明，震源大致由一个长度为100 km的单凸体组成，不存在长度较小的分段结构。这一特征似乎反映在源区以上的海底地形上。主要震源参数如下：地震矩= 1.0 × 10（21）Nm（Mw=7.9），断层面积=140 km × 80 km，（走向、倾向、倾角）=（225度、15度、79度），最大位错量和平均位错量分别为4.4 m和3.0 m。对三川地震的地震记录分析表明，震源是一个逆断层，具有轻微的左旋分量。气压轴指向东北偏西，与日本西部的东西向气压轴略有旋转。这条断层可以被认为是Nobi地震断层系统的南延。主要震源参数为：地震矩= 1.0 × 10 ~（19）Nm（Mw=6.6），断层面积=20 km × 15 km，（走向、倾向、倾角）=（135 °，30 °，65 °），最大位错量为2.1 m，平均位错量为1.1 m。滑动分布主要由两个微凸体组成，一个位于震中附近，另一个位于震中西北10-15 km处，严重破坏区与西北部的微凸体有较好的对应关系。
In the 1940's, several destructive earthquakes occurred in western Japan. Seismograms in this period were usually recorded on smoked paper and the quality was poor compared to modern digital data. But the recent development of image processing technology enabled us to reconstruct feasible waveform data, whereby we investigated source rupture processes of two devastating earthquakes: the Tonankai earthquake (M7.9) of December 7, 1944, and the Mikawa earthquake (M6.8) of January 13, 1945. The results for the Tonankai earthquake show that the source roughly consists of a single asperity with a length scale of 100 km, having no segment structure with a smaller length-scale. Such a feature seems to be reflected to the sea bottom topography above the source region. The main source parameters are as follows: the seismic moment=1.0x10(21) Nm (Mw=7.9); the fault area=140 km x 80 km;, (strike, dip, rake)=(225degrees, 15degrees, 79degrees); the maximum and averaged dislocations=4.4 m and 3.0 m, respectively. The analysis of the seismograms for the Mikawa earthquake shows that the source is a reverse fault with a slight left-lateral component. The pressure axis is directed to ENE-WSW, which is a little rotated from the EW compression axis prevailing in western Japan. This fault can be regarded as the southern extension of the Nobi earthquake fault system. The main source parameters are as follows: the seismic moment=1.0x10(19) Nm (Mw=6.6); the fault area=20 km x 15 km; (strike, dip, rake)=(135degrees, 30degrees, 65degrees); the maximum and averaged dislocations are 2.1 m and 1.1 m, respectively. The slip distribution mainly consists of two asperities: the one near the hypocenter and the other 10-15 km northwest from it. The heavily damaged area is well correlated with the northwestern asperity.