scholarly journals Seismic Response of Coupled Long-Period Structures with Maxwell-Type Dampers Subjected to Long-Period Ground Motions observed in the 2011 off the Pacific Coast of Tohoku earthquake

2012 ◽  
Vol 12 ◽  
pp. 4_414-4_431 ◽  
Author(s):  
Gaku SHOJI ◽  
Shintaro KADO ◽  
Qiang HANG
Keyword(s):  
Seismic Response ◽  
Pacific Coast ◽  
Ground Motions ◽  
Tohoku Earthquake ◽  
Long Period ◽  
The Pacific

Long-Period Ground Motions Observed in the Northern Part of Kanto Basin, During the 2011 off the Pacific Coast of Tohoku Earthquake, Japan

2013 ◽  
Vol 8 (sp) ◽  
pp. 781-791 ◽  
Author(s):  
Seiji Tsuno ◽  
◽  
Andi Muhamad Pramatadie ◽  
Yadab P. Dhakal ◽  
Kosuke Chimoto ◽  
...  
Keyword(s):  
Wave Velocity ◽  
Love Wave ◽  
Pacific Coast ◽  
Velocity Structure ◽  
Ground Motions ◽  
Tohoku Earthquake ◽  
S Wave ◽  
Long Period ◽  
The Pacific ◽  
Kanto Basin

During the 2011 off the Pacific coast of Tohoku earthquake (Mw 9.0), strong ground motions were observed at many seismic stations in the Tokyo Metropolitan Area located about 200 km away from the southern edge of the earthquake source fault. Large earthquake responses in high-rise buildings having long natural periods of several seconds were also observed. The largest ground responses for a period of 4 to 5 seconds were observed locally in Oyama (K-NET TCG012) and Koga (K-NET IBR009) on the border between Tochigi and Ibaraki Prefectures in the northern part of Kanto basin. Geophysical information in these areas was not accurate enough, however, to evaluate these ground motions. To understand S-wave velocity structures, we performed array microtremors observations at TCG012 seismic station in Oyama. We applied the Spatial Autocorrelation (SPAC) method to array microtremors data for vertical components. Rayleigh wave phase velocity from 0.3 to 1.6 km/s was obtained for a period of 0.25 to 3 seconds. We inverted phase velocity to a S-wave velocity structure reaching to bedrock at a depth of 1.6 km, using a Genetic Algorithm. The estimated structure explained the first peak of the H/V spectral ratio of microtremors well by the ellipticity of fundamentalmode Rayleigh wave. To evaluate long-period ground motions observed around Oyama during the main shock, we estimated earthquake ground motions by 1-D analysis, showing agreements with and the differences from those observed. As a result, velocity calculated at IBR008 located midway between the Tsukuba Mountains and Oyama, explained that observed for main phases and later phases. However, velocity calculated at TCG012 did not explain that observed for later phases. According to the emphasis of airy phases for group velocity of Love wave using the estimated S-wave velocity structure and the principal axis for later phases obtained by PCA corresponding to the vibration direction of Love wave propagating from the earthquake source fault and through the Tsukuba Mountains, long-period ground motions of a period of 3 to 5 seconds observed at TCG012 lasting for 200 seconds after the arrival of main phases, consist of Love wave.

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